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@@ -63,3 +63,5 @@ Law/cyclopedia_of_law_and_procedure_vol_25_1907.md filter=lfs diff=lfs merge=lfs
 Law/current_law-a_complete_encyclopedia_of_new_law_vol_10_1904.md filter=lfs diff=lfs merge=lfs -text
 Law/current_law-a_complete_encyclopedia_of_new_law_vol_2_1904.md filter=lfs diff=lfs merge=lfs -text
 Law/current_law-a_complete_encyclopedia_of_new_law_vol_9_1904.md filter=lfs diff=lfs merge=lfs -text
+Law/cyclopedia_of_law_and_procedure_vol_34_1910.md filter=lfs diff=lfs merge=lfs -text
+Law/current_law-a_complete_encyclopedia_of_new_law_vol_7_1904.md filter=lfs diff=lfs merge=lfs -text

Aeroplanes/piper_cub_airframe.md

@@ -0,0 +1,65 @@
+<img>A detailed technical drawing of a Piper Cub aircraft.</img>
+**Piper Cub**
+**Special**
+(Model 1941)
+**Piper Aircraft Corporation**
+**Lake Erie, Pennsylvania & Co.**
+
+**SCALE**
+5 IN. = 1 FT.
+
+<img>A stylized illustration of a Piper Cub with "NG0000" on the fuselage.</img>
+
+<img>A stylized illustration of a Piper Cub with "NG0000" on the fuselage.</img>
+
+<img>A stylized illustration of a Piper Cub with "NG0000" on the fuselage.</img>
+
+<img>A stylized illustration of a Piper Cub with "NG0000" on the fuselage.</img>
+
+<img>A stylized illustration of a Piper Cub with "NG0000" on the fuselage.</img>
+
+<img>A stylized illustration of a Piper Cub with "NG0000" on the fuselage.</img>
+
+<img>A stylized illustration of a Piper Cub with "NG0000" on the fuselage.</img>
+
+<img>A stylized illustration of a Piper Cub with "NG0000" on the fuselage.</img>
+
+<img>A stylized illustration of a Piper Cub with "NG0000" on the fuselage.</img>
+
+<img>A stylized illustration of a Piper Cub with "NG0000" on the fuselage.</img>
+
+<img>A stylized illustration of a Piper Cub with "NG0000" on the fuselage.</img>
+
+<img>A stylized illustration of a Piper Cub with "NG0000" on the fuselage.</img>
+
+<img>A stylized illustration of a Piper Cub with "NG0000" on the fuselage.</img>
+
+<img>A stylized illustration of a Piper Cub with "NG0000" on the fuselage.</img>
+
+<img>A stylized illustration of a Piper Cub with "NG0000" on the fuselage.</img>
+
+<img>A stylized illustration of a Piper Cub with "NG0000" on the fuselage.</img>
+
+<img>A stylized illustration of a Piper Cub with "NG0000" on the fuselage.</img>
+
+<img>A stylized illustration of a Piper Cub with "NG0000" on the fuselage.</img>
+
+<img>A stylized illustration of a Piper Cub with "NG0000" on the fuselage.</img>
+
+<img>A stylized illustration of a Piper Cub with "NG0000" on the fuselage.</img>
+
+<img>A stylized illustration of a Piper Cub with "NG0000" on the fuselage.</img>
+
+<img>A stylized illustration of a Piper Cub with "NG0000" on the fuselage.</img>
+
+<img>A stylized illustration of a Piper Cub with "NG0000" on the fuselage.</img>
+
+<img>A stylized illustration of a Piper Cub with "NG0000" on the fuselage.</img>
+
+<img>A stylized illustration of a Piper Cub with "NG0000" on the fuselage.</img>
+
+<img>A stylized illustration of a Piper Cub with "NG0000" on the fuselage.</img>
+
+<img>A stylized illustration of a Piper Cub with "NG0000" on the fuselage.</img>
+
+<img>A stylized illustration of a Piper Cub with "NGOOGO" on the nose section. The nose section has three circular dials, possibly indicating speed, altitude, and other flight parameters. The word "CUB" is written below these dials. The word "CUB" is also written at the bottom right corner of this image. The word "CUB" is also written at the top left corner of this image. The word "CUB" is also written at the bottom left corner of this image. The word "CUB" is also written at the top right corner of this image. The word "CUB" is also written at the bottom right corner of this image. The word "CUB" is also written at the top left corner of this image. The word "CUB" is also written at the bottom left corner of this image. The word "CUB" is also written at the top right corner of this image. The word "CUB" is also written at the bottom right corner of this image. The word "CUB" is also written at the top left corner of this image. The word "CUB" is also written at the bottom left corner of this image. The word "CUB" is also written at the top right corner of this image. The word "CUB" is also written at the bottom right corner of this image. The word "CUB" is also written at the top left corner of this image. The word "CUB" is also written at the bottom left corner of this image. The word "CUB" is also written at the top right corner of this image. The word "CUB" is also written at the bottom right corner of this image. The word "CUB" is also written at the top left corner of this image. The word "CUB" is also written at the bottom left corner of this image. The word "CUB" is also written at the top right corner of this image. The word "CUB" is also written at the bottom right corner of this image. The word "CUB" is also written at the top left corner of this image. The word "CUB" is also written at the bottom left corner of this image. The word "CUB" is also written at the top right corner of this image. The word "CUB" is also written at the bottom right corner of this image. The word "CUB" is also written at the top left corner of this image. The word "CUB" is also written at the bottom left corner of this image. The word "CUB" is also written at the top right corner of this image. The word "CUB" is also written at the bottom right corner of this image. The word "CUB" is also written at the top left corner of this image. The word "CUB" is also written at the bottom left corner of this image. The word "CUB" is also written at the top right corner of this image. The word "CUB" is also written at the bottom right corner of this image. The word "CUB" is also written at the top left corner of this image. The word "CUB" is also written at the bottom left corner of this image. The word "CUB" is also written at the top right corner of this image. The word "CUB" is also written at the bottom right corner of this image. The word "CUB" is also written at the top left corner of this image. The word "CUB" is also written at the bottom left corner of this image. The word "CUB" is also written at the top right corner of this image. The word "CUB" is also written at the bottom right corner of this image. The word "CUB" is also written at the top left corner of this image. The word "CUB" is also written at the bottom left corner of this image. The word "CUB" is also written at the top right corner of this image. The word "CUB" is also written at the bottom right corner of this image. The word "CUB" is also written at the top left corner of this image. The word "CUB" is also written at the bottom left corner of this image. The word "CUB" is also written at the top right corner of this image. The word "CUB" is also written at the bottom right corner of this image. The word "CUB" is also written at the top left corner of this image. The word "CUB" is also written at

Airships/commercial_aviation_in_germany-past_and_future_1921.md

@@ -0,0 +1,472 @@
+MAR - 6 1921
+
+APR 17 1925
+
+NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS.
+
+<signature>Copy</signature>
+
+Technical Memoandum No. 5
+
+COMMERCIAL AVIATION IN GERMANY
+PAST AND FUTURE.
+By
+W. Wronsky.
+
+Translated by Paris Office, N. A. C. A.
+
+February, 1921.
+
+FILE COPY
+To be returned to
+the files of the Langley
+Memorial Aeronautical
+Laboratory.
+
+<img>barcode</img>
+3117601439896
+
+COMMERCIAL AVIATION IN GERMANY
+PAST AND FUTURE.*
+By W. Wronsky.
+
+Translated by Paris Office, N. A. C. A.
+
+"A million kilometers covered in flight! Is it really much or little?" I have frequently been asked by the unin-
+tiated; and even when I explained that a railway train would
+need to rush 89 times to Gibraltar, Berlin, Constantinople
+and back in order to travel a million kilometers, I could
+see that my statement made but little impression. As a ma-
+ter of fact, a concrete idea of the meaning of a flight of a
+million kilometers can be gained only by retracing the path
+developed.
+
+The D.L.R. (German Aerial Navigation Board) was estab-
+lished in 1917 in order to study the question of civil aeri-
+nal transport in all its phases. At that time, when the
+world-war was at the height of its fury and numerous tens
+of thousands of英勇 souls plunged in the thick of the
+fight on all the fronts, the investigation of aerial trans-
+port - which will form a link between different nations-
+was certainly a far-seeing project.
+
+The unfortunate termination of the war altered the even
+tenor of the work. No time could be lost if anything were
+to be rescued from the general smash for civil aviation;
+rapid action and continuous energy were called for if civil
+aviation were destined to be a factor - even though a small
+one - in the scheme of economical reconstruction.
+
+Until the end of January, 1919, the D.L.R. possessed
+an extensive aerodrome with mail and giant airplanes, and
+an adequate number of pilots and observers. Then it was
+that the Government issued the decree which soon enabled
+the "grey theory" to be replaced by the "Green Tree of Life".
+
+The much-desired opportunity was presented by the open-
+ing of the National Congress. Preliminary negotiations
+with the Government postal authorities easily led to a fav-
+orable understanding, and a regular aerial postal service
+was established between Weimar and Berlin on February 5th.
+
+*(From *Der Luftweg*, Nos. 50-51, pp. 6-9).
+
+L 2 A
+
+The results obtained were so encouraging from an aero-tech-
+nical viewpoint, and the new means of transit met with such
+high approval on the part of the public, the postal authori-
+ties and the Press that a second aerial postal line was opened
+to Hamburg in March, 1919. In April, these lines were extend-
+ed by further services between Berlin, Hanover, the Rhine Pro-
+vinces, Berlin and Warnemünde. The Aerial Naval Station of
+the U. P. S. C. Wannsee and airmail service to Berlin being
+only in special flights. The following summer, mail services
+(summer resort services) were established to Swinemünde
+and Westerland, and the entire mail was delivered by airplane in
+various regions when railway traffic was suspended. Besides
+these numerous special flights, special mention should be
+made of an aerial service to Ukraine, organized on behalf of
+the Government.
+
+It was quite evident to the D.L.R., from the outset,
+that all these undertakings were to be looked upon as mere
+tests, carried out first and foremost with a view to convin-
+ing the public hitherto extremely sceptical about such un-
+dertakings that "a thing can be done" and that "it did get on."
+The figure of safety attained during the whole
+service was 95% to 98%, which exceeded the most optimistic
+expectations.
+
+The success of these flights led to the necessity for
+bringing the idea of flight to popular acceptance. The fol-
+lowing instance will prove that this has also been achieved
+to some extent:
+
+Our airplanes were utilized at Stolp, this summer, as
+a means of transporting East Prussian voters over Polish
+territory. Some hundreds of people of the poorer working
+class crowded about our machines, and old men with white
+beards, grandmothers turned 70 and nursing mothers got into
+them with perfect confidence and self-assurance.
+
+It has been one of the dreams of mankind, for thousands
+of years, to fly through the air, and the vision has now
+been realized.
+
+Such aerial transport as this cannot, however, be con-
+sidered as foreboding the final aim to be attained. The
+airplane has a higher destiny than that of competing with ex-
+press trains over short distances. It is now an everyday
+occurrence to meet a flying film-star, a merchant or banker
+going to a conference, a government official on his way to a
+meeting or a physician hastening to a sickbed, and an aerial
+transport association must eventually reach a higher stand-
+ard than this ordinary routine.
+
+<page_number>- 3 -</page_number>
+
+Aerial communication should be the means of uniting na-
+tions from a political as well as from an economical point of
+view, for no country in the world is such a link more es-
+sential, at the present time, than for us.
+
+Thousands of Germans are now living in occupied terri-
+tory, exposed to outside influences and incurring the danger
+of getting out of close touch with the mother country. This
+should be prevented by all possible means, and methods
+should be found which will afford a certain measure of indif-
+ference to us if the German living in occupied territory or in
+other countries received his German newspaper half a day ear-
+lier or later, and with it his ideas with regard to his native
+land, or he may even be able to obtain a foreign newspaper
+earlier than a German one. More again, the air-post service
+must and should intervene. Besides this, German national
+news and money market reports will enable to reach foreign
+countries in advance of information from other lands or will
+at least arrive as soon as any other news. German business
+letters will be delivered abroad as speedily as telegrams in
+bygone days; stamps, parcels, goods etc., can now be taken
+days by air from Hamburg to New York within few hours.
+And all this opens up a fine prospect for the collaboration
+of the airplane in reconstructing the economical life of our
+country, which has always been one of our noblest aims.
+
+The field of action of the airplane consists in opening
+up communication with distant lands and in making oversea
+flights and flights across districts where railway facilities
+are poor or non-existent. Our maxim must be that of our be-
+loved Hapag: "The World is my Field".
+
+But there were many preliminaries to be gone through;
+not until dozens of typewriters had filled sheet upon sheet
+with written matter did we finally reach the goal, when a
+general agreement enabled us to make our first special flight
+over the frontiers of Germany and we thereby climbed another
+step on the ladder.
+
+When the North-West European flight was undertaken this year, - the line that links up five countries and along which our airplanes fly side by side with those of other coun-
+tries, over Sweden, Denmark and Germany to Holland - few people who read the simple red posters had any idea of the work that had paved the way for the new enterprise. It has been crossed with such difficulty however, and the first step has been taken along the high road.
+
+The night passenger can now settle into his sleeping-
+car at Stockholm with his flight pass for London in his pock-
+et, and when he awakes at Malmö in the morning and rubs his
+
+<page_number>- 4 -</page_number>
+
+sleepy eyes, he sees his airplane in readiness on the quay; the afternoon of the same day may see him wandering through the old-world streets of Amsterdam. The Londoner posting a letter to a business friend at Copenhagen knows that it will be handed to the recipient on the following day; and our airplanes have several times carried more than one-tenth of the entire Scandinavian mail over to Germany.
+
+A step has thus been taken forward, but though it is only a step, no prophet is needed to foretell that aerial transport is bound to develop with a rush, and in ever-increasing proportions, during the next few years.
+
+All over the world, comfortable, up-to-date transport airplanes are ousting inconvenient and wasteful war machines, and one of the newest airplane types has already covered 300 km. in one hour. There can be no great difficulty in combining and adapting them both, nor will much time be taken up in the work.
+
+A veritable Wonderland will then lie before us. We shall be able to take breakfast at 7 a.m. in Berlin, to get into a comfortable airplane cabin at Johannisthal at 8 a.m. and sit there in a luxurious club chair, smoking a cigar and reading the morning paper while we glance from time to time at the world below us as we fly by at the rate of 300 km. p.h. We shall then proceed without interruption to the land of Gasparo, the smiling fields of Italy and the blue waters of the Mediterranean, all appearing like so many maps drawn beneath us; and the clock will barely have struck two before we shall be sitting at lunch at Tunis, under the burning sun of Africa.
+
+All this probably sounds like one of Jules Verne's romances, yet we may say with Faust that "so much has already been done that little remains for us to do".
+
+There are nevertheless many reasons that will prevent our Dreamland Flight from being realized too soon or too completely. French political obstacles are constantly arising out of the Peace Treaty and its execution, and they will all require to be overcome.
+
+The ban on construction has but recently been prolonged, the export and import of airplanes forbidden, and the utilization of the airplanes left to us by the Allies for flights abroad has also been prohibited. So it is that new difficulties confront us day by day; but we have ample proof that the development of aerial transport cannot be permanently handicapped by such voluntary impediments, and we learn from reliable sources among our late enemies that they make no headway in their efforts to impede the progress of German aerial transport.
+
+<page_number>- 5 -</page_number>
+
+Aerial transport is nothing more or less than a UNIVERSAL MEDIUM OF COMMUNICATION BY AIR, which can only be based, in all parts of the world, on solidarity, mutual confidence and mutual aid. The first step has already been taken in the right direction. About a year and a half ago, the D.L.R. formed an aerial transport association with the leading aerial companies of Sweden, Norway, Denmark, Holland and England since that time known as the International Aerial Transport Association (Iata). The first result of this association was the North-West European flight previously mentioned, and other plans will be followed up in common. A glance at the map of the World will show great stretches of country as yet uncrossed by any sort of line of communication or transport, such as, for instance, the enormous tract of land in the East and South-East, almost like North and South America.
+
+All these lands are rich in treasure that has never been exploited, chiefly owing to such lack of transport; and it is in regions like these that the airplane will act as a pioneer and avoid the problem of undesirable competition between the different countries.
+
+The airplane will also assert its rights as a means of communication in the most frequented parts of Europe. The utilization of the speed of the airplane, and the substitution of transport planes of improved construction for existing types are all that is now to bring the whole of Europe within the scope of a day's journey from Germany.
+
+It must not, however, be supposed that the only difficulties to be overcome with regard to air traffic are of a political nature; they are not so formidable as some emotional ones, far from being satisfactory, in the present time much need to be coped with. The next thing to be undertaken will be the REPLACEMENT OF airplanes developed during the war, by MODERN TRANSPORT AIRPLANES, which will give results in respect of speed and economy and will also render the highest possible degree of comfort to the working-class. This high grade work will have to arise and must be overcome. The number of transport airplanes utilized in a year, in Germany, will probably amount only to about one-tenth or one-twentieth of the former monthly figure of some 2000 machines at the outset. For this very reason, the construction of transport airplanes should be undertaken by none but the most efficient of firms.
+
+It does not seem to be of advantage to fix on any partic- ular type. Aerial transport is so many-sided that it calls for as much latitude as possible as regards type, though this does not exclude any possibility of close cooperation between the different parties concerned in building new machines with a view to attaining greater economical success. Safety in working depends upon the ENGINES, and there is no doubt but that
+
+- 6 -
+
+our technicians will make considerable headway in that branch.
+The COMFORT of the passengers must also be considered, as it is important that their capacity for work should not be diminished after an aerial journey of several hours, through fatigue.
+
+It has already been stated that the SPEED of airplanes has been raised to more than 300 km/h in test flights. With modern machines, we shall therefore soon be able to count on an average speed of 200 to 250 km/h., though we now have, on the other hand, speeds of about 130 km/h. We shall, eventually have differentiated speeds for flight and for landing, and the tests already planned on this line give every promise of satisfactory results.
+
+Flight by night and in fog will also be facilitated in the near future, and this point is essential to enable us to compete with night trains. A systematic ground organization will here be necessary, to light up the routes with flares; shipping-line methods might serve as a model in this case. More difficulty is to be expected from the economical than from the technical side of the question.
+
+It is a well-known fact that all aerial traffic companies have-as yet been working at a heavy loss. In certain countries as, for instance, France and Germany, these losses were somewhat diminished by Government subsidies. In other countries, an effort has been made to stimulate through prizes in money. The subvention system is unsatisfactory, and it can only be regarded as a transition stage. A reduction of expenditure must be achieved by the use of more economical machines, and by an organization extending to the smallest details. And at the same time, the receipts must be increased by judicious propagation of the idea of travelling by air.
+
+The economical question is a particularly difficult one owing to the fact of its being SCARCELY POSSIBLE to make any EXACT CALCULATION beforehand; there are certain items on the account of which the rates cannot be definitely fixed. Such are, for instance, the length of existence of the airplane, the rates of insurance, the consumption and cost of fuel,-all of which are subject to variation.
+
+The question of economical usage depends chiefly on the choice of suitable MACHINES. A survey of existing technical conditions opens up the prospect of the possibility of improvement in this respect, as may be seen by the following data.
+
+<page_number>- 7 -</page_number>
+
+FIVE HOURS' FLIGHT.
+
+Present Day Mail Airplane, 200 H.P.
+1918-1920. 250 liters of fuel were needed for every 100 kg. useful load, and a distance of 650 km was covered at a cost of 1500 M, (130 km/h). A freight of 150 kg could be transported.
+
+Modern Transport Airplane, 185 H.P.
+1921 - 56 liters of fuel are needed per 100 kg useful load, and a distance of 800 km is covered for 336 Marks. (160 km/h). A freight of 400 kg. can be transported.
+
+Giant Airplane with 4 engines of 185 H.P.
+1922. 50 liters needed per 100 kg useful load; a dis-
+tance of 1100 km will be covered for 300 Marks,
+1800 kg. freight can be transported
+
+The above table above that the airplanes formerly used in our transport service consumed five times as much fuel as an up-to-date airplane, constructed for transport.
+
+It is also most important for economical working results to be obtained by the favorable and accurate disposition of the crew, upon which the possibility of attaining the highest possible efficiency is dependent, both for the airplane and the crew.
+
+The question of INCREASED RECEIPTS is probably the most difficult to be met - Such receipts are the joint outcome of the transport of MAILS, PARCELS, GOODS AND PASSENGERS.
+
+The postal service has now been regulated by an agreement with the POSTAL AUTHORITIES, whereby the transport of a certain quantity of mail is obligatory in return for payment of a tax per kilometer. In the case of goods and passengers, the comparatively high tariffs charged on account of the high cost of living have done a good deal towards frightening people. The day is bound to come when we shall manage to have greater traffic at somewhat lower fares.
+
+The greatest attraction of all will always lie in the working safety, the punctuality and the comfort of aerial journeys.
+
+The list of accidents is a very low one: three cases of slight injuries, one of severe injury.
+
+<page_number>- 5 -</page_number>
+
+The European-North-West Flight gives a distinct picture of the present lack of favorable economical conditions.
+
+In the course of 304 flights, a distance of 82,000 km was traversed, and only 8,115 kg. carried, whereas 45,500 kg. might have been transported; or if we express it in figures of energy, 7.4 H.P. was expended on every kilogram transported. Had the freight room been utilized to the full, the figures would have been only 1.3 H.P. per kilogram. In the modern transport airplane, the figure of energy expended would have been only 0.3 H.P.
+
+All this clearly shows that though all that has been done in the domain of civil aerial transport is certainly to be considered as a good step forwards, many problems remain to be solved. And this task can only be achieved by a close collaboration on the part of all those interested in the matter.
+
+It may be suggested that CONFERENCES should be held regularly, once or twice a year; they might be summoned by the Air Board, and their object would be that of having all questions connected with aerial traffic discussed by aeronautical experts.
+
+From all that has been written above, the following main points may be summarized:
+
+1. Aerial transport cannot possibly be carried out in Germany alone; its activities must be extended beyond the frontiers, and particularly in districts where there is a lack of communication by transport.
+
+2. Specially constructed machines are necessary for aerial transport; safety in working is the first requirement for such airplanes, speed and economy are the next essentials.
+
+3. The great outlay consequent on aerial transport can only be met by means of efficient undertakings founded on a strong financial basis. Unnecessary division should be avoided.
+
+4. During the next few years, aerial transport will need the support of State subsidies, but it will gradually be enabled to stand on its own feet by progress in the technics of aeronautics and through the enlistment of the sympathy of the economical classes.
+
+- 9 -
+
+The objection might possibly be raised, that "all these prospects of development are extremely good in their way, but we are not in a position, here in Germany, to devote our attention to them, because there are so many more urgent things to be done that we surely ought to leave to richer countries the task of solving the problem of aerial transport".
+
+There can be but one reply to such an attitude: "If we were to adopt and follow up that view, we should see, sooner or later, that we had made a grave mistake, and that we had failed to capture an opportunity that can never be regained". And it is very certain that mankind, having once obtained the command of the Air, will never relinquish that victory.
+
+The airplane represents extraordinary progress in the lines of transport, and it is consequently a progressive movement from an economical and industrial viewpoint. For the very reason that we are laboring under such economical oppression through the War and its after-results, we ought not to exclude ourselves from participating in the development of Aerial Transport.
+
+---
+
+W. WRONSKY.
+A MILLION KILOMETERS COVERED IN FLIGHT.
+
+NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS PARIS OFFICE
+
+DESIGNED DRAWN CHECKED APPROVED
+
+A 20
+
+Increase in Transport
+
+<table>
+<thead>
+<tr>
+<td>Month</td>
+<td>Km</td>
+<td>No. of Passengers</td>
+<td>Km of Mail</td>
+<td>Total Load</td>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>Oct 1920</td>
+<td>301/678</td>
+<td>7354</td>
+<td>1235</td>
+<td>27</td>
+<td>3707</td>
+<td>52821</td>
+</tr>
+<tr>
+<td>Oct 1921</td>
+<td>301/678</td>
+<td>7354</td>
+<td>1235</td>
+<td>27</td>
+<td>3707</td>
+<td>52821</td>
+</tr>
+<tr>
+<td>Oct 1922</td>
+<td>301/678</td>
+<td>7354</td>
+<td>1235</td>
+<td>27</td>
+<td>3707</td>
+<td>52821</td>
+</tr>
+<tr>
+<td>Oct 1923</td>
+<td>301/678</td>
+<td>7354</td>
+<td>1235</td>
+<td>27</td>
+<td>3707</td>
+<td>52821</td>
+</tr>
+<tr>
+<td>Oct 1924</td>
+<td>301/678</td>
+<td>7354</td>
+<td>1235</td>
+<td>27</td>
+<td>3707</td>
+<td>52821</td>
+</tr>
+<tr>
+<td>Oct 1925</td>
+<td>301/678</td>
+<td>7354</td>
+<td>1235</td>
+<td>27</td>
+<td>3707</td>
+<td>52821</td>
+</tr>
+<tr>
+<td>Oct 1926</td>
+<td>301/678</td>
+<td>7354</td>
+<td>1235</td>
+<td>27</td>
+<td>3707</td>
+<td>52821</td>
+</tr>
+<tr>
+<td>Oct 1927</td>
+<td>301/678</td>
+<td>7354</td>
+<td>1235</td>
+<td>27</td>
+<td>3707</td>
+<td>52821</td>
+</tr>
+<tr>
+<td>Oct 1928</td>
+<td>301/678</td>
+<td>7354</td>
+<td>1235</td>
+<td>27</td>
+<td>3707</td>
+<td>52821</td>
+</tr>
+<tr>
+<td>Oct 1929</td>
+<td>301/678</td>
+<td>7354</td>
+<td>1235</td>
+<td>27</td>
+<td>3707</td>
+<td>52821</td>
+</tr>
+<tr>
+<td colspan="6">Total Load Carried:</table>
+
+FLIGHT RESULTS - January October 1920 for the month
+
+Number of Flights made
+
+<table border="0">
+<thead><tr><th></th><th>Allies<br>Kilometers flown<br>Km<br>Passengers<br>Km<br>Total Load<br>Kg<br>Total Load<br>Kg<br>Total Load<br>Kg<br>Total Load<br>Kg<br>Total Load<br>Kg<br>Total Load<br>Kg<br>Total Load<br>Kg<br>Total Load<br>Kg<br>Total Load<br>Kg<br>Total Load<br>Kg<br>Total Load<br>Kg<br>Total Load<br>Kg<br>Total Load<br>Kg<br>Total Load<br>Kg<br>Total Load<br>Kg<br>Total Load<br>Kg<br>Total Load<br>Kg<br>Total Load<br>Kg<br>Total Load<br>Kg<br>Total Load<br>Kg<br>Total Load<br>Kg<br>Total Load<br>Kg<br>Total Load<br>Kg<br>Total Load<br>Kg<br>Total Load<br>Kg<br>Total Load<br>Kg<br>Total Load<br>Kg<br>Total Load<br>Kg<br>Total Load<br>Kg<br>Total Load<br>Kg<br>Total Load<br>Kg<br>Total Load.<br></th></tr></thead><tbody><tr><th colspan="6">Quantity of Mail Transported:</th></tr><tr><th colspan="6">Total Load Carried:</th></tr></tbody></table>
+
+<watermark>Safety in Flight Results - January October 1920 for the month.</watermark>
+
+<watermark>National Advisory Committee for Aeronautics Paris Office.</watermark>
+
+<watermark>Increase in Transport.</watermark>
+
+<watermark>Briefing Sheet.</watermark>
+
+<watermark>Tourist Report.</watermark>
+
+<watermark>Safety in Flight Results - January October 1920 for the month.</watermark>
+
+<watermark>National Advisory Committee for Aeronautics Paris Office.</watermark>
+
+<watermark>Increase in Transport.</watermark>
+
+<watermark>Briefing Sheet.</watermark>
+
+<watermark>Tourist Report.</watermark>
+
+<watermark>Safety in Flight Results - January October 1920 for the month.</watermark>
+
+<watermark>National Advisory Committee for Aeronautics Paris Office.</watermark>
+
+<watermark>Increase in Transport.</watermark>
+
+<watermark>Briefing Sheet.</watermark>
+
+<watermark>Tourist Report.</watermark>
+
+<watermark>Safety in Flight Results - January October 1920 for the month.</watermark>
+
+<watermark>National Advisory Committee for Aeronautics Paris Office.</watermark>
+
+<watermark>Increase in Transport.</watermark>
+
+<watermark>Briefing Sheet.</watermark>
+
+<watermark>Tourist Report.</watermark>
+
+<watermark>Safety in Flight Results - January October 1920 for the month.</watermark>
+
+<watermark>National Advisory Committee for Aeronautics Paris Office.</watermark>
+
+<watermark>Increase in Transport.</watermark>
+
+<watermark>Briefing Sheet.</watermark>
+
+<watermark>Tourist Report.</watermark>
+
+<watermark>Safety in Flight Results - January October 1920 for the month.</watermark>
+
+<watermark>National Advisory Committee for Aeronautics Paris Office.</watermark>
+
+<watermark>Increase in Transport.</watermark>
+
+<watermark>Briefing Sheet.</watermark>
+
+<watermark>Tourist Report.</watermark>
+
+<watermark>Safety in Flight Results - January October 1920 for the month.</watermark>
+
+<watermark>National Advisory Committee for Aeronautics Paris Office.</watermark>
+
+<watermark>Increase in Transport.</watermark>
+
+<watermark>Briefing Sheet.</watermark>
+
+<watermark>Tourist Report.</watermark>
+
+<watermark>Safety in Flight Results - January October 1920 for the month.</watermark>
+
+<watermark>National Advisory Committee for Aeronautics Paris Office.</水印></p></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div/></p><p style="text-align: center;"><strong><u><span style="font-size: large;">W. WRONSKY-</span><br/></u><span style="font-size: large;">A MILLION KILOMETERS COVERED IN FLIGHT-</span><br/><span style="font-size: large;">NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS PARIS OFFICE-</span><br/></p><p style="text-align: center;"><strong>A 20-</strong><br/></p><p style="text-align: center;"><strong>Increase in Transport:</strong><br/></p><p style="text-align: center;"><strong>January October 1920 compared to Aug. Oct. 1919:</strong><br/></p><p style="text-align: center;"><strong>Mileage:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><p style="text-align: center;"><strong>P.O.D.:</strong><br/></p><hr/>
+
+<img>barcode 3 1176 01439 9696</img>
+MBA Technical Library

Airships/principle_of_the_boerner_airship_1905.md

@@ -0,0 +1,125 @@
+NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS.
+<page_number>154</page_number>
+
+PRINCIPLE OF THE BOERNER AIRSHIP.
+By A. Kapteyn.
+
+From Premier Congres International de la Navigation Aerienne,
+Paris, November, 1921, Vol. II.
+
+COPY
+Returned to
+of the Langley
+National Aeronautical
+Laboratory,
+
+November, 1923.
+
+<page_number>173</page_number>
+<img>A stamp with "U.S." and "NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS" written on it.</img>
+
+<img>NASA Technical Library barcode</img>
+3 1176 01437 3329
+
+**PPINCIPIE OF THE BOERNER AIRSHIP.***
+
+By A. Kapteyn.
+
+The Boerner airship is built on entirely different principles from ordinary airships, of which the Zeppelin is the best known type. Mr. Boerner has abandoned the rigid body of the Zeppelin and has adopted a body with a double keel forming a rigid platform for attaching the gas balloonets, which must support the whole in the air.
+
+The body is provided with two rigid arched ends capable of withstanding the pressure of the wind (Figs. 3 and 4).
+
+The gas bags are arranged above the metal platform (Fig. 1) in three rows of 17 each, as indicated in Fig. 4, by simple squares. There are therefore always three balloonets abreast, forming a section. Fig. 1 represents a transverse cut through such a section, which consists not of three simple balloonets but rather of compartments with flexible walls. The middle compartment $A_1$ contains hydrogen, but the side compartments are subdivided by double partitions, forming three compartments $A_2$, $B_1$ and $C$. The double partition $B_1$ is made very slack, so it can be inflated or deflated at will, like a balloon.
+
+This whole series of compartments of a single series is enclosed in an envelope forming another shallow compartment $B_2$ surrounding all the others.
+
+The compartments marked $A_1$ and $A_2$ contain hydrogen. The ones marked $B_1$ and $B_2$ contain nitrogen. Those marked $C$ contain air. They are under a pressure of 10 mm of water above the normal. Thus
+
+* From Premier Congrès International de la Navigation Aérienne, Paris, November, 1921, Vol. II, pp. 54-57.
+
+<page_number>1</page_number>
+
+- 2 -
+
+all the hydrogen compartments are surrounded by a layer of nitrog
+in order to prevent the formation of an explosive mixture, so ex-
+tremely dangerous in airships.
+
+There are various valves and communicating tubes not shown in
+the diagrams. Compartments A₁ and A₂ communicate freely through
+a tube. Compartment C communicates with the outside air through
+a valve under a pressure of 10 mm of water. Compartments B₁ and
+B₂ communicate with each other. All the compartments are subject
+ed to the same pressure of 10 mm of water above that of the sur-
+rounding air.
+
+Functioning. - After being charged with gas at the proper pre-
+sure, the airship rises. The gas in the compartments A₁ and A₂
+expands and exerts a pressure on the double partition B₁. The
+nitrogen contained in the latter transmits this pressure to the
+air in compartment C, some of which is discharged into the at-
+mosphere through the safety valve already mentioned.
+
+On starting, the air compartments C contain about 25% of th
+volume of the hydrogen carried, whence it follows that the airship
+can ascend 3000 meters before the expansion of the hydrogen drives
+all the air from the compartments C. The latter are provided
+with blowers, by means of which atmospheric air may be again for-
+ed in, in order to make the airship descend.
+
+In this manner, the vertical movements of the airship are pr.
+duced without the loss of hydrogen, nor a single kilogram of bal-
+last, which constitutes one of the great advantages of the Boerner.
+airship.
+
+- 3 -
+
+**Engines.** - On either side of the airship there is a series of engines, each engine driving a propeller whose axis of rotation can be placed at any angle of inclination desired, thereby rendering it possible to exercise with each engine individually a force on the airship tending to make it advance, back, ascend or descend at will (Figs. 1 and 2). This disposition is important in case the airship should suddenly enter a colder, and consequently denser, layer of air. The airship would then immediately climb in a pronounced manner, which movement, in the case of a Zeppelin, could only be arrested by releasing hydrogen, but which may be easily arrested, in the case of the Boerner, by placing the axes of some of the propellers in a vertical position (Fig. 2), so as to offset by dynamic force the climbing tendency produced by the difference of temperature of the surrounding air.
+
+But this is not all. In the case of the Zeppelin, the temperature of the hydrogen in the ballonets falls to that of the surrounding air and consequently the airship grows heavier and begins to descend with a motion that can only be arrested by promptly releasing ballast. In the case of the Boerner, if there is a descending tendency which it is desired to stop, it is only necessary to exert, by means of propellers, a dynamic lifting force. In a word, the movements of the Boerner airship are under absolute control.
+
+**Carrying Capacity.** - The Zeppelin or rigid type is greatly handicapped by its metal hull, which is so heavy that it is hardly possible to carry passengers or merchandise. It goes without say-
+
+- 4 -
+
+ing that the Boerner airship, with its strong metal body, is both stronger to withstand all stresses which can be brought to bear upon it and leaves at the same time a much wider margin for carrying a large number of passengers and large quantities of freight.
+
+Only the principle and the general lines of the Boerner airship have been given above. The completed project, which has been carefully worked out and computed, contains modifications of special parts, but the principle remains as here described.
+
+Translated by the National Advisory Committee for Aeronautics.
+
+<img>A technical drawing showing a transverse sectional elevation of a structure.</img>
+<page_number>L</page_number>
+
+Fig. 3
+
+C B A₁ A₂ B₁ C
+
+x x x x
+
+126.31 ft.
+
+y y y y
+
+x x x x
+
+Fig. 1.
+
+a = 6.583 ft.
+b = 9.843 ft.
+c = 11.483 ft.
+v = 13.123 ft.
+w = 34.776 ft.
+x = 49.312 ft.
+y = 30.347 ft.
+z = 65.816 ft.
+
+Fuel Blower Engine
+
+Figs. 1 and 2. Transverse sectional elevation.
+
+<img>A diagram showing three views of a boat's sectional plan. The top view shows the overall length of 1082.73 ft. The middle view shows the transverse section with dimensions 49.215 ft x 49.215 ft x 49.215 ft. The bottom view shows the longitudinal section with dimensions 147.645 ft.</img>
+Fig. 4. Sectional plan.
+
+<img>WAPA Technical Library barcode</img>
+3 1176 01437 3329

Airships/procedure_for_determining_speed_and_climbing_performance_of_airships_1936.md

@@ -0,0 +1,1141 @@
+FILE COPY
+NO. I-W
+
+# CASE FILE
+COPY
+
+TECHNICAL NOTES
+NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
+
+No. 564
+
+PROCEDURE FOR DETERMINING SPEED AND CLIMBING
+PERFORMANCE OF AIRSHIPS
+By F. L. Thompson
+Langley Memorial Aeronautical Laboratory
+
+FILE COPY
+To be returned to
+the files of the National
+Advisory Committee
+for Aeronautics
+Washington, D.C.
+
+Washington
+April 1936
+
+NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
+
+TECHNICAL NOTE NO. 564
+
+PROCEDURE FOR DETERMINING SPEED AND CLIMBING
+PERFORMANCE OF AIRSHIPS
+
+By F. L. Thompson
+
+SUMMARY
+
+The procedure for obtaining air-speed and rate-of-climb measurements in performance tests of airships is described. Two methods of obtaining speed measurements, one by means of instruments on the airship and the other by flight over measured courses, are explained. Instruments, their calibrations, necessary correction factors, observations, and calculations are detailed for each method, and also for the rate-of-climb tests.
+
+A method of correction for the effect on density of moist air and a description of other methods of speed-course testing are appended.
+
+INTRODUCTION
+
+The procedure required to obtain accurate measurements of air speed and rate of climb in performance tests of airships is described herein for the instruction and guidance of those who, without having had the benefit of previous experience, are required to conduct such tests. Since it is important that those who conduct the tests should appreciate the necessity of following the correct procedure in all details, the basis for the recommended procedure, as well as an outline of it, is briefly given. The paper is written in an elementary form and is to be followed in considerable detail so as to minimize as far as possible the necessity for previous knowledge of the factors involved and to avoid the possibility of error in following the correct procedure.
+
+The general methods of measuring the air speed in flight are: by means of instruments attached to the air-ship and by means of timed flight over a measured course.
+
+<img>A scanned page from a technical note.</img>
+
+<page_number>2</page_number>
+N.A.C.A. Technical Note No. 564
+
+on the ground. The instrument method may employ one of the numerous types of air-speed head that measure the dynamic pressure, from which instantaneous values of the true air speed can be calculated when the air density is known, or a windmill type of instrument independent of the air density to give measurements both of the instantaneous or the average true air speed directly, depending on the type of mechanism. Various types of air-speed instruments are described in reference 1. The speed-course method may employ a straight or a triangular course. In either case an average value of true air speed is deduced from the results; the accuracy of the measurements is largely dependent on wind conditions. The procedure outlined herein will be confined to cases in which the instrument method with a pitot-static head is employed and in which the speed-course method with either a straight or a triangular course is used.
+
+Rate-of-climb measurements are made by recording the rate of change of barometric pressure with time, which is then converted to a rate of change of altitude with time in accordance with the change of pressure with altitude for observed air densities.
+
+It will frequently be necessary in describing the procedure for determining air speed and rate of climb to refer to "standard atmosphere," "pressure altitude," and "density altitude." The standard atmosphere is defined in reference 3, and represents approximately average atmospheric conditions as regards relations between true altitude, pressure, temperature, and density. In any actual case there may be a considerable departure from these average conditions. The term "pressure altitude" is the altitude in the standard atmosphere corresponding to an observed barometric pressure; "density altitude" is the altitude in the standard atmosphere corresponding to an observed density. Since altimeters are instruments actuated solely by pressure changes, they can be used to obtain pressure altitude directly. Density altitude can be calculated when the pressure and temperature at a given height are known. For convenience in relating the calculations subsequently described, figures 1 and 2, showing the relations between pressure and density in the standard atmosphere, are included. The true altitude, which is of practically no importance in the present case, can be determined accurately only when the pressure at a given height and the temperatures at all altitudes below this height are known. (See reference 3.)
+
+N.A.C.A. Technical Note No. 564 <page_number>3</page_number>
+
+AIR-SPEED MEASUREMENTS
+
+Instrument Method
+
+Effect of velocity field.- The velocity of the air relative to an airship in flight is influenced over a wide field by the presence of the airship and control car or other protuberances. The local velocity at any point is dependent on the shape of the airship and protuberances, on the location of this point relative to the body or bodies causing the disturbance, and on the direction of the relative wind. In addition to this general velocity field, which extends to a great distance in all directions, there is the so-called "boundary layer" of air close to the body in which the velocity is retarded by friction. Although this boundary layer increases in thickness from bow to stern, it is relatively thin and easily avoided in making measurements of air speed.
+
+The general nature of the velocity field close to the hull is indicated by the distribution of normal pressure on the hull. At the bow and stern the normal pressures are higher than true static, and the velocities in these regions are correspondingly lower than the true air speed by as much as 100 percent. Amidships the normal pressures are less than true static and the velocities are correspondingly higher than the true air speed by as much as about 10 percent. Between these regions of low and high velocity there are marginal regions in which the true air speed prevails but they are of small practical significance as regards air-speed measurements. The location of these marginal regions is dependent on the trim of the airship and local irregularities of contour and, furthermore, tests would be required to establish the location for any given trim condition.
+
+In order to avoid the effect of the velocity field, it is necessary to place the air-speed head used in speed trials at a considerable distance from the airship. An indication of the distance that is recommended is shown in figure 3. The values shown in this figure apply to calculated values for the U.S.S. Akron hull at zero pitch and although they do not apply exactly to other airships, they can be regarded as approximately representative of the general case. As shown in the figure, beyond the distance of 1-1/2 diameters from the midship section the error in local velocity becomes very small. Thus with an
+
+<page_number>4</page_number>
+N.A.C.A. Technical Note No. 564
+
+airship such as the TC-13 (maximum diameter of 54 feet), a suspension length of 75 to 100 feet, which is a practica- ble length, seems to insure satisfactory results. It should be noted that the actual distance from the airship to the suspended instrument will be appreciably reduced by a curvature of the cable in flight.
+
+**Pitot-static head.** Theoretically the pitot-static head has two openings, one of which is normal to the air stream and is subjected to the total or impact pressure $P$ caused by bringing the air to rest, whereas the other opening is parallel to the air stream and is subjected to the static pressure $p$. The relation between these two pressures is $P = p + \frac{1}{2} \rho V^2$, where $\rho$ is the mass density of the air and $V$ is the true air speed. The two openings in the pitot-static head are connected to a pressure gage that records the difference between these pressures,
+
+$$\frac{1}{2} \rho V^2 = q,$$
+
+which is defined as the dynamic pressure.
+
+This ideal condition is seldom exactly realized, owing to the structural details of the head itself, so that the recorded pressure is actually an erroneous value $q'$ which for practical purposes can be regarded as proportional to $q$ regardless of the slope. It is therefore necessary to calibrate the pitot-static head after it is constructed in order to establish the correction factor $K = q'/q$. Knowledge of pitot-static heads is sufficient to permit designing a head for which this factor is very close to unity.
+
+There are an infinite number of possible forms for pitot-static head. A satisfactory design based on convenience of use and ruggedness is shown in figures 4 and 5. A straight tube with a rounded nose has an opening in the nose to obtain the total pressure $P$ at a point around its circumference at a distance of 8 inches from the nose to obtain the static pressure $p$. The curvature of the nose portion is in accordance with the equation
+
+$$r = \frac{4}{3} \sqrt{\frac{x - x_0}{d}} + \frac{1}{6} \left( \frac{x}{d} \right)^2$$
+
+where $d$ is the maximum diameter of the tube and $r$ is the radius of a section at any distance $x$ measured from the extremity. The curvature terminates at $x_0$. The tube, which has a diameter of 2 inches, is loaded with lead to make it heavy enough for satisfactory suspension and is equipped with stabilizing surfaces to keep it point-
+
+J.A.C.A. Technical Note No. 564 <page_number>5</page_number>
+
+ed in the direction of flight. The head weighs about 16 pounds, this weight being necessary in order to reduce the tendency for the suspension cable to swing back owing to its drag.
+
+**Method of suspension.** The pitot-static head is suspended on a small flexible cable (1/8-inch diameter is satisfactory) and the static and dynamic pressures are conducted through a pair of rubber tubes. The tubes and cable are tightly encased in a longitudinal strip of adhesive tape having a width considerably greater than the circumference of the enclosed tubes and cable so that a generous overlap of the edges of the tape is obtained. This type of suspension replaces the single-duct cable shown in figure 1 which is used only when the static pressure is to be measured in order to avoid excessive drag of the pipe. The outside diameter of these tubes should not exceed 1/4 inch and, owing to the possibility of lag in the transmission of varying pressures through these tubes, they should have an internal diameter of at least 3/32 inch. The recommended size of tubing is 3/16 inch with a wall thickness of 1/32 inch, which gives an outside diameter of 1/4 inch.
+
+**Pressure gage or manometer.** The pressure difference at the ends of the tube can be observed by means of a commercial type air-speed indicator, at least for the upper end of the speed range or by means of a liquid manometer. The air-speed meter should be checked for leaks and to determine whether its calibration is affected by temperature or position error (effect of changes in the direction of the gravitational force with respect to the instrument) and whether there is any hysteresis. A liquid manometer should be so designed that it is not materially influenced by changes in attitude by providing it with two reservoirs symmetrically placed on either side of the glass tube in which the height of the liquid is observed. The error due to deviation of the manometer attitude from the vertical will then be represented by the deviation of the line of equal pressure level. The design should be such that surging of the liquid from one reservoir to the other does not develop an appreciable fluctuation at the juncture of the tube with the reservoir system, which would tend to lower the reading in the glass tube. Whether or not such an effect exists can readily be detected by observing the manometer reading as the manometer is tilted slowly from side to side. The reservoirs should be large in comparison with the volume of the glass tube so that the change of level
+
+<img>A diagram showing a pitot-static head suspended on a small flexible cable.</img>
+
+<page_number>6</page_number>
+N.A.C.A. Technical Note No. 564
+
+in them is small as compared with that in the glass tube. Such an arrangement tends to provide the maximum sensitivity. The sensitivity is also improved by the use of a relatively light liquid such as alcohol rather than water. The density of alcohol or any other light liquid changes considerably with temperature, however, and alcohol also tends to absorb moisture so that the density may change with time. If alcohol is used, the density must therefore be carefully checked at the time the tests are made. Alcohol is recommended in preference to any other light liquid that might be used in place of water. The manometer must be calibrated.
+
+When air speeds are varying rapidly, as in descent tests for which it is necessary to obtain a close relation between air speed and time, it is advisable to use a recording instrument such as the N.A.C.A. recording air-speed meter. This instrument gives a continuous photographic record of the dynamic pressure with a time scale, but requires attention by an operator who is thoroughly familiar with it. For most airship tests visual observations are sufficient.
+
+**Lag error due to change of altitude.** One additional point that must be considered when measurements are made while climbing or descending is that erroneous readings may be obtained unless precautions are taken to eliminate lag effects in the pressure lines. Owing to the change of static pressure with height in this case there is a change of static pressure with time. One side of the air-speed system is subjected simply to the static pressure $p$ and the other side to the total pressure $P$ which is the sum of the static pressure and the dynamic pressure $q$. Actually $p$ is very large compared with $q$ so that for purposes of this argument the pressure in the two sides of the system can be regarded as approximately equal. Then, since $p$ varies with time, both sides of the system are subjected to the effect of the varying pressure. Owing to the difference in the volume of air in the two sides of the line there is a difference in the resistance to this force, the effect of this varying pressure may not be the same in both lines, with the result that the recorded dynamic pressure will be in error. A simple test shows whether or not the lag effects are equal. A small pressure is applied simultaneously at both openings of the pitot-static head and as this pressure is released so as to vary the pressure rapidly at the same rate in each side of the system, the reading of the pressure gage is observed. If the
+
+N.A.C.A. Technical Note No. 564 <page_number>7</page_number>
+
+gage shows an appreciable deflection from zero, the system requires modification. This modification consists simply in adding additional volume at the gage end of the side of the system that shows the least lag, that is, the more rapid drop in pressure. It may only be necessary to add a small length of tubing to provide the additional volume required. For an ordinary air-speed meter, however, there is a large difference in the volume on the two sides of the gage so that it may be necessary to add a large volume to compensate for this inequality.
+
+Errors due to wind gradient.- It is possible that under certain conditions there may be a sufficient gradient of wind velocity with altitude so that the suspended head and the airship may be traveling at different velocities relative to the air. In order to avoid the possibility of an appreciable error from this source it seems advisable to use the average of readings obtained by flights in opposite directions.
+
+Calculation of air speed from observed data.- From the basic relation $q = \frac{1}{2} \rho V^2$, two expressions are derived, namely,
+
+$$V_1 = 45.08 \sqrt{q}$$
+
+and
+
+$$V = V_1 \sqrt{\delta}$$
+
+where $V_1$ is the indicated air speed in miles per hour
+
+$q$, the dynamic pressure in inches of water
+
+$V$, the true air speed in miles per hour
+
+$\delta = \frac{\rho_o}{\rho}$, the ratio of air density at standard sea-level conditions to the density at which tests are made. At standard sea-level conditions the air is assumed to be dry, the barometric pressure $\rho_o$ is 29.92 inches of mercury, and the temperature $T_o$ is 59° F. The density $\rho_o$ for these conditions is 0.002378. The density $\rho$ for any other condition of temperature and pressure for dry air can be found from the relation
+
+$$\rho = \rho_o \times \frac{p + T_o}{p_o + T}$$
+
+<page_number>8</page_number>
+N.A.C.A. Technical Note No. 564
+
+which, upon substitution of the above-mentioned standard values of temperature and pressure, reduced to
+
+$$p = 0.04120 \times \frac{P}{459.4 + T}$$
+
+where $p$ is the observed pressure in inches of mercury and $T$, the observed temperature in degrees Fahrenheit.
+
+For the density ratio we can write
+
+$$\delta = \frac{p_0}{p} = 0.05772 \times \frac{459.4 + T}{P}$$
+
+Moisture in the air reduces the value of $p$ slightly and, if the effect of the moisture is neglected, the result is a small negative error in the calculated velocity. This error can generally be neglected but for extreme precision, humidity should be taken into account as shown in Appendix I. The pressure $p$ in inches of mercury may be found from the observed pressure altitude in feet by reference to standard altitude tables or charts. (See fig. 1.) A more convenient method is to have the calibration of the altimeter used in the tests plotted against pressure in inches of mercury.
+
+The observed data obtained in flight tests cannot be used in the foregoing equation without some initial steps. The first step in any case is to correct the observed readings in accordance with the calibration of the pressure gage used in the tests. The subsequent steps depend upon the type of instrument used and the nature of the calibra- tions. Two cases are assumed:
+
+a. The dynamic pressure is expressed as $q'$ in terms of the height of a liquid.
+
+b. Dynamic pressure is expressed as $V_i'$ in mile-per-hour units.
+
+For case (a) the next step is to find $q' = q' r K$ where $r = \frac{\text{specific weight of liquid}}{\text{specific weight of water}}$ and $K$ is the pitot correction factor. For case (b) the next step is to find $V_i' = V_i' \sqrt{K}$.
+
+<img>A page from a technical note, discussing corrections for humidity and altitude in calculating dynamic pressure.</img>
+
+N.A.C.A. Technical Note No. 564 <page_number>9</page_number>
+
+**Speed-Course Method**
+
+*Flight observations.* Measurements of true air speed can be obtained by flying over a straight speed course in opposite directions or over a triangular course. (See also Appendix II for other methods.) The deduction of true air speed from the results of such tests presupposes that the course is closely followed, that the wind speed is constant as regards both its magnitude and direction, and that the timing is accurate. For satisfactory results the wind should be steady and of low velocity relative to the speed of the aircraft. Large errors in the computations are likely to introduce difficulty in following the required ground course. Accurate timing demands care in determining the exact instant a specified point is passed. The observer's line of sight should be directed normal to the flight path and, in order to insure accuracy, the landmark should be a line at right angles to the direction of flight or two points on such a line.
+
+*Calculations.* If a straight course is used the proper method of evaluation is to find
+
+$$V_a = \frac{S}{t_1 + t_2} \times \frac{1}{1.457}$$
+
+where $S$ is the length of the course in feet, $t_1$ and $t_2$ are the times in seconds for runs in opposite directions, $V_a$ is the true air speed in miles per hour uncorrected for the effect of a cross wind.
+
+In general, it is not desirable to attempt to fly such a course unless the wind is approximately parallel to the course but, if there is an appreciable cross-wind component, a correction can be made by the most convenient of the two following methods:
+
+$$V = \frac{V_a}{\cos \alpha}$$
+
+or
+
+$$V = \sqrt{V_a^2 + (V_w \sin \theta)^2}$$
+
+<page_number>10</page_number>
+M.A.C.A. Technical Note No. 564
+
+where $V$ is the true air speed in miles per hour
+$\alpha$, the angle of drift
+$V_w$, the wind speed in miles per hour
+and $\theta$, the angle between the direction of the wind and the speed course.
+
+If the triangular course is used, the true air speed can best be determined graphically, the analytical solution being too laborious and inconvenient for ordinary use. One point should be mentioned in this connection that the average of the ground speeds for the three legs does not give the correct result. The error is dependent on the shape of the triangle, the magnitude of the wind velocity as a percentage of the speed of the aircraft, the direction of the wind relative to the orientation of the triangle, and, unless the triangle is equilateral, on the direction of flight around the course.
+
+The graphical solution is illustrated in figure 6. The geographical orientation of the three legs of the triangle is required. Vectors representing the ground speeds $V_1$, $V_2$, and $V_3$ along each of these three legs from a common point $X$ are laid out in directions corresponding to the orientation of the appropriate legs. The extremities A, B, and C of these vectors determine a circle, the center O of which can be found by a geometrical construction. This construction consists simply of finding the mutual intersection of the perpendicular bisectors of the three sides of the triangle A, B, and C. The radius of the circle represents the true air speed $V$ and a vector drawn from $X$ to $O$ represents the magnitude and direction of the wind speed $V_w$. If drift angles were observed during the flights over the speed course, an indication of the steadiness of the wind can now be obtained by drawing air-speed vectors OA, OB, and OC and comparing the drift angles thus indicated with those observed.
+
+It may sometimes be necessary to interpret data obtained in runs during which the engine speed was not maintained constant for the three legs of the triangle. A fairly satisfactory correction may be possible in such a case; for example, suppose that the engine speed is held constant for two legs of the triangle but is reduced for the third leg. The average speed deduced from the vector diagram will lie between that corresponding to the two ex-
+
+N.A.C.A. Technical Note No. 564
+
+<page_number>11</page_number>
+
+gine speeds. The air-speed meter readings for the three legs, even though they are considerably in error, can be used to establish an approximate correction factor, by means of which the air speed corresponding to a higher (or the lower) desired engine speed can be found. If, from the air-speed meter readings for the three legs, it is deduced that the air speeds were roughly $V_{a_1}$, $V_{a_2}$, and $V_{a_3}$, then, since $V_{a_1} = V_{a_2}$, the correction factor by which the average air speed deduced from the vector diagram must be multiplied is
+
+$$\frac{3V_{a_1}}{2V_{a_1} + V_{a_3}}$$
+
+If the air speed corresponding to a lower engine speed is desired, the factor becomes
+
+$$\frac{3V_{a_3}}{2V_{a_1} + V_{a_3}}$$
+
+After $V$ has been found, the correct indicated air speed may be calculated from the relation $V_1 = \sqrt{\frac{8}{\delta}}$, where $\delta$ is the density ratio as previously defined.
+
+Condition of Airship for Speed Trials
+
+Trim or pitch angle (defined as the inclination of the longitudinal axis to the flight path) is an important consideration in speed trials. The drag of the airship increases to a marked extent with increasing angle of attack and, in order to obtain maximum speed, the airship must be at approximately zero pitch. In order to illustrate the effect of pitch, figure 7, which applies to a model of the U.S.S. Akron hull (reference 4), is shown. A pitch angle of $3^\circ$ causes an increase in drag and power required of 9 percent with elevator neutral and 25 percent with elevator deflected to overcome the pitching moment of the hull; whereas for $6^\circ$ pitch the increase is 33 percent or 71 percent, depending upon whether or not the elevators are deflected to obtain balance. The angle of pitch equals the inclination of the hull in level flight, and hence can readily be observed in speed trials. In any speed trials,
+
+<img>A diagram showing the relationship between airspeed and pitch angle.</img>
+
+<page_number>12</page_number>
+N.A.C.A. Technical Note No. 564
+
+conditions of heaviness or lightness, the average pitch angle for different speeds, and any other items that might influence the speed, such as unusual protuberances of any sort, modifications of protuberances, condition of engine, etc., should be noted.
+
+It is apparent from the foregoing remarks that if, in normal operation, the airship is to be flown heavy, it would be advisable to determine the speed characteristics for the range of loads likely to be carried by dynamic lift. The effect of the heaviness on the engine speed and fuel consumption required to fly at a given air speed is likely to be very marked, particularly at low cruising speeds with correspondingly large pitch angles.
+
+**Interpretation of Speed Data**
+
+It is advisable to plot readings of the air-speed meter of the airship against correct indicated air speed $V_1$ in order to obtain a calibration curve for the complete air-speed installation. This curve will show the combined effect of all errors, the principal one probably being that due to the location of the fixed air-speed head. The magnitude of this error is likely to be dependent to some extent on the angle of pitch, so that the curve thus obtained does not necessarily apply to all conditions of trim. Thus, if the curve is obtained with the airship in static buoyant equilibrium, some deviation can be expected when the airship is heavy or light, and also when it is turning.
+
+True speed $V$ should be plotted against correct engine speed $K$. This curve has important characteristics. If the airship is in static buoyant equilibrium so that it flies at zero pitch, and hence constant drag coefficient at all speeds, and if there is but one propeller or multiple propellers synchronized to act as one propeller at all speeds, this curve will be very close to a straight line passing through zero. The slope will depend on the drag coefficient of the airship and the propeller characteristics but will be independent of altitude or mechanical condition of the engine. The maximum air speed will depend, of course, on the maximum engine speed obtainable and hence on the altitude and mechanical condition of the engine but the slope will remain constant. The slope of the curve will be altered if there are alterations to the airship that change either the propeller characteristics or the drag coefficient.
+
+<img>A page from a technical note discussing airship performance.</img>
+
+N.A.C.A. Technical Note No. 564
+
+If the airship is not in equilibrium during the speed trials, the curve of $V$ against $W$ should show a varying slope with the ratio of $V/W$ increasing with increasing speed. This type of variation will occur because of the reduction in pitch angle, and since this coefficient with increasing speed decreases, the plot of the speed results shows this type of variation. It serves, therefore, as an indication that the airship was not in equilibrium and that the measured speeds at the various engine speeds were not as great as could have been obtained with zero pitch. The curve will approach the curve corresponding to zero pitch at high speed.
+
+Summary of Test Procedure for Speed Trials
+
+I. Suspended-head method:
+
+A. Observations:
+   1. Dynamic pressure from suspended head.
+   2. Air speed from air-speed meter of airship.
+   3. Outside air temperature.
+   4. Inside temperature in control car (unless water manometer is used so that change of density of manometer liquid with temperature is negligible).
+   5. Pressure altitude (altimeter reading).
+   6. Inclination.
+   7. Engine speeds (tachometer readings).
+   8. Make note of such things as the buoyant condition of the airship, protuberances or openings, behavior of synchronization of the engines, and other conditions which are likely to involve bearing wear, the speed results. It might also be of assistance in interpreting results, to obtain records of control position and to observe the compass readings at short regular intervals.
+
+<page_number>13</page_number>
+
+<page_number>14</page_number>
+N.A.C.A. Technical Note No. 564
+
+B. Calculations:
+
+1. Correct readings of dynamic pressure for calibration of instrument to obtain $q'$ (or $V_1$' if air-speed meter is used).
+
+2. (a) Liquid manometer.- Multiply $q'$ by p-i-tot correction factor $K$ and manome- ter liquid-density factor $r$ to obtain $q$, and then find correct indi- cated air speed from $V_1 = 45.08 \sqrt{q}$.
+
+(b) Air-speed meter.- Find correct indicated air speed $V_1$ from
+$$V_1 = V_1' \sqrt{\frac{K}{p}}$$
+
+3. Correct altimeter readings in accordance with calibration to obtain correct barometric pressure $p$.
+
+4. Same for thermometer to obtain $T$.
+
+5. Calculate $\delta$ from relation
+$$\delta = 0.05772 \times \frac{459.4 + T}{p}$$
+
+6. Calculate true air speed from relation
+$$V = V_1 \sqrt{\delta}$$
+
+7. Correct tachometer readings in accordance with calibration to find correct engine speed.
+
+C. Plot:
+1. True air speed $V$ against engine speed.
+2. Correct indicated air speed $V_1$ against read- ing of air-speed meter of airship.
+
+N.A.C.A. Technical Note No. 564 <page_number>15</page_number>
+
+II. Speed-course method - straight course:
+
+A. Observations:
+1. Time to traverse course in opposite directions.
+2. Angle of drift $\alpha$ or magnitude $V_w$ and direction $\theta$ of wind relative to course.
+3. Items 2, 3, 5, 6, 7, and 8 of IA.
+
+B. Calculations:
+1. Find $V_a$ from relation
+$$V_a = \frac{S_1 + S_2}{t_1 + t_2} \times \frac{1}{1.467}$$
+2. Correct $V_a$ for effect of cross wind to find true air speed $V$ from
+$$V = \frac{V_a}{\cos \alpha}$$
+or
+$$V = \sqrt{V_a^2 + (V_w \sin \theta)^2}$$
+3. Items 3, 4, and 5 of IB to find $\delta$.
+4. Calculate correct indicated air speed $V_1$ from $$V_1 = \frac{V}{\sqrt{\delta}}$$
+5. Item 8 of IB to find correct engine speed.
+
+C. Plots:
+Same as IC.
+
+<page_number>16</page_number>
+N.A.C.A. Technical Note No. 564
+
+III. Speed-course method - triangular course:
+
+A. Observations:
+1. Time for each log.
+2. Items 2, 3, 5, 6, 7, and 8 of IA.
+
+B. Calculations:
+1. Find average true air speed by graphical method (fig. 6).
+2. Items 3, 4, and 5 of IB to find $S$.
+3. Find correct indicated air speed $V_1$ from
+$$V_1 = \frac{V}{\sqrt{S}}$$
+4. Item 7 of IB to find correct engine speed.
+
+C. Plots:
+Same as IC.
+
+RATE-OF-CLIME MEASUREMENTS
+
+General Method
+
+Under average atmospheric conditions represented by the standard atmosphere there is a definite pressure, temperature, and density corresponding to any given altitude. In actual cases there is some departure from the average so that the relations that hold for the standard conditions can be regarded as only approximate in any given case. Altimeters, which are graduated by pressure changes, are graduated in feet in accordance with the variation of pressure with altitude in the standard atmosphere. Hence the reading of an accurate altimeter may be regarded as an exact indication of pressure and an approximate indication of height or true altitude. In general, however, pressure and density, or pressure altitude $h_p$ and density altitude $h_d$, are the quantities desired. These items can readily be obtained, the former being given directly by
+
+N.A.C.A. Technical Note No. 564 <page_number>17</page_number>
+
+the altimeter reading and the latter being obtained from calculations based on readings of the altimeter and the thermometer.
+
+Although the true altitude may not be known, the true rate of climb can readily be obtained by utilizing the basic relation between altitude change and pressure change.
+
+$$\Delta h = - \Delta p \frac{1}{g \rho}$$
+
+where $\Delta h$ is an increment of altitude
+$\Delta p$, the corresponding increment in pressure
+$\rho$, the average air density for the altitude increment being considered
+$g$, the acceleration of gravity ($g = 32.17$ ft./sec.$^2$).
+
+Thus, the altitude change corresponding to a given pressure change depends on the average density $\rho$, which is determined by the average pressure and temperature for the increment. From the preceding calculation there is obtained for the true rate of climb $V_c$, the expression
+
+$$V_c = \frac{\Delta h}{\Delta t} = - \frac{\Delta p}{\Delta t} \frac{1}{g \rho}$$
+
+$\Delta t$ being the time interval required for the observed pressure change $\Delta p$. Then the angle of climb is obtained from
+
+$$\theta = \sin^{-1} \frac{V_c}{V}$$
+
+where $\theta$ is the angle of climb
+$V$, the true air speed
+
+The units of velocity, time, height, etc., must be consistent as explained later under Calculations.
+
+It now becomes necessary to consider which of the various items are finally desired. An analogy with heavier-than-air craft offers little assistance, since the airship is essentially sustained by static buoyancy rather than by
+
+<page_number>18</page_number>
+N.A.C.A. Technical Note No. 564
+
+dynamic forces. Ceiling is determined by volumes and weights in relation to density, rather than by engine power, and is a height which it is not safe to exceed rather than one which it is impossible to exceed. The ceiling of an airship can probably be determined better from calculations than from actual tests. Below the ceil- ing no more power is required to climb than to fly level as long as no dynamic lift is required. The factors that limit the ability to ascend or descend are essentially the pitch control or maximum inclination permitted by the de- sign, and the condition for maintaining a correct gas pres- sure when the atmospheric pressure is varying. The alti- tude at which the ascent or descent is made is generally of no great importance. It appears, therefore, that we are concerned chiefly with the rate at which the pressure varies $\Delta p/\Delta t$, or the equivalent rate of change of pre- sure altitude $h_p/dt$, and the angle of climb $\theta$. If climbs were to be made with dynamic lift the climbing abil- ity would tend to become definitely dependent on engine performance, in which case it appears that the true rate of climb $V_c$ should be obtained as a function of altitude, the pressure altitude $h_p$ probably being better for this purpose than density altitude $h_d$, although there is some doubt as to which should be used.
+
+Instruments
+
+Some instruments indicate rate of climb directly, the reading of the instruments being dependent on the rate of change of pressure. Such instruments are not recommended for test work, although they are useful in determining at a glance whether one is ascending or descending, and the ap- proximate rate. The standard types of Kollsman altimeters for airplanes are small compact instruments that are gen- erally satisfactory and can be recommended for climb tests. These instruments have an appreciable friction and must be lightly tapped to insure accuracy of the readings, unless they are vibrated by other means. When thus vibrated there should be no perceptible hysteresis.
+
+The altitude scale is divided into feet in accordance with the change of pressure with altitude in the standard atmosphere. The instrument, of course, should be cali- brated before it is used for test purposes, and it may be convenient to have the calibration show the scale reading in feet against pressure in inches of mercury. The Kolls-
+
+N.A.C.A. Technical Note No. 564 <page_number>19</page_number>
+
+man instrument, like most other altimeters, has an adjust-
+able zero but, in order that one calibration shall suffice,
+it is desirable that this adjustment be locked in position
+before the calibration is made. The instrument then becomes
+essentially a simple aneroid barometer reading barometric
+pressures in foot units.
+
+The Kellerman instruments are usually equipped with a
+fitting on the back of the case that permits the pressure
+chamber to be connected to a source of true static pres-
+sure. For airships this connection can be ignored since
+at the relatively low speeds obtainable with airships the
+pressure in the control car will not differ from the true
+static pressure by an amount sufficient to introduce a se-
+rious error into the barometric pressure. It seems prob-
+able that the error in pressure altitude from this source
+would not be more than about 40 feet at a speed of 70 miles
+per hour, and less at lower speeds. The error will proba-
+bly depend to some extent upon whether windows are open or
+closed. If absolute precision were desired, it would be
+necessary to connect the instrument to a suspended static
+head.
+
+Any type of calibrated thermometer will probably be
+satisfactory for determining the free-air temperature if
+it is freely exposed to the outside air. Some considera-
+tion should, however, be given to the lag characteristics
+of the thermometer because for extreme rates of ascent or
+descent the lag may introduce an appreciable error. The
+error for any given type of thermometer will be propor-
+tional to the rate or change of temperature and hence, in
+general, to the rate or change of altitude. The tempera-
+ture ordinarily varies with altitude at the rate of about
+3° F. per thousand feet, so that if the rate of ascent or
+descent were 2,000 feet per minute the temperature would
+vary 0.1° F. per second. According to data given in refer-
+ence 5, the errors in reading with different thermome-
+ters for this case would be approximately as follows:
+
+<table>
+  <tr>
+    <td>Laboratory thermometer, mercury in glass</td>
+    <td>1° F.</td>
+  </tr>
+  <tr>
+    <td>Laboratory thermometer, liquid in glass</td>
+    <td>12° F.</td>
+  </tr>
+  <tr>
+    <td>Strut thermometer, liquid in glass, flat bulb</td>
+    <td>18° F.</td>
+  </tr>
+  <tr>
+    <td>Strut thermometer, liquid in metal helical bulb</td>
+    <td>1½° F.</td>
+  </tr>
+  <tr>
+    <td>Strut thermometer, liquid in glass, large cylindrical bulb</td>
+    <td>3° F.</td>
+  </tr>
+</table>
+
+<page_number>20</page_number>
+N.A.C.A. Technical Note No. 564
+
+Since an error of $1^{\circ}$ F. introduces an error of only about 0.2 percent in the calculated density, it appears that the error due to the air usually being neglected over for the high rate of ascent or descent assumed in this case. If greater precision is desired, however, the relation between temperature and altitude can be established immediately before or after the tests by readings made under steady conditions, or at least while the variation in altitude is slow.
+
+When timing the ascent or descent, the increments of altitude for which the time is taken should not exceed 1,000 feet and smaller increments should be used if feasible. The time for equal increments of altitude change or the altitude difference for a given increment of time may be observed depending upon which method is more convenient with the apparatus available. Probably the best accuracy will be obtained by the former method with two or more stop watches being used so that one watch can be started and the other stopped at each interval, and the time readings noted between intervals. Another satisfactory method is to use a bank of stop watches mounted on a single board and so arranged that they can be simultaneously started and independently stopped, one watch being stopped for each increment of altitude observed.
+
+CALCULATIONS
+
+It will be assumed that the flight observations give observed altimeter readings $h_{p_1}'$, $h_{p_2}'$, etc., and times $t_1$, $t_2$, etc., corresponding to those altitudes. Air temperatures $T_1$, $T_2$, etc., must also be known, of course, before the rates of climb can be calculated. Furthermore, it is assumed that the air speed is observed so that the true air speed can be found.
+
+The first step is to find the barometric pressures corresponding to the observed altimeter readings. If the calibration of the instrument is plotted against pressure in inches of mercury as previously suggested, pressures $p_1$, $p_2$, etc., will be obtained directly from the calibration. If the calibration is plotted only against correct pressure altitude $h_c$, it will be necessary first to find $h_{p_1}'$, $h_{p_2}'$ etc., and then, by reference to standard altitude tables or charts (see fig. 1) to find $p_1$, $p_2$, etc.
+
+N.A.C.A. Technical Note No. 564
+
+The next step is to find the air densities $\rho_1$, $\rho_2$, etc., corresponding to the observed pressures and temperatures.
+
+$$\rho_1 = 0.04120 \times \frac{P_1}{459.4 + T_1}$$
+
+where $P_1$ is in inches of mercury and $T_1$ is in degrees Fahrenheit. Subsequent values of $\rho$ are calculated in a similar manner. Thus, for the first increment of altitude $\Delta p = P_2 - P_1$, the corresponding increment of time is $\Delta t = t_2 - t_1$, and the rate at which the pressure varies is
+
+$$\frac{\Delta p}{\Delta t} = \frac{P_2 - P_1}{t_2 - t_1}$$
+
+in inches of mercury per second when $\Delta p$ is in inches of mercury and $\Delta t$ is in seconds or
+
+$$\frac{\Delta p}{\Delta t} = \frac{P_2 - P_1}{T_2 - T_1} \quad 13.59$$
+
+in inches of water per second.
+
+The average value of $\rho$ is
+
+$$\frac{\rho_1 + \rho_2}{2}$$
+
+Then, with pressure still expressed in inches of mercury, the rate of climb in feet per second is
+
+$$v_c = -70.7 \frac{(P_2 - P_1)}{t_2 - t_1} \frac{1}{(\rho_1 + \rho_2)/2} \quad 32.17$$
+
+the constant 70.7 being the conversion factor for reducing pressure in inches of mercury to pounds per square foot.
+
+The angle of climb $\theta$ is given by
+
+$$\theta = \sin^{-1} \frac{v_c (f.p.s.)}{1.467 V (m.p.k.)}$$
+
+<page_number>22</page_number>
+N.A.C.A. Technical Note No. 564
+
+For example, assume the following data to have been observed in a climb:
+
+Altitude:
+$$h_{P_1} = 3,000 \text{ feet}$$
+$$h_{P_2} = 4,000 \text{ feet}$$
+
+Time:
+$$t_1 = 0$$
+$$t_2 = 62 \text{ seconds}$$
+
+Temperature:
+$$T_1 = 75^\circ \text{F}.$$
+$$T_2 = 73^\circ \text{F}.$$
+
+Indicated air speed:
+$$V_1 = 50 \text{ miles per hour (average)}$$
+
+After the altimeter calibration has been consulted, which it is assumed has been plotted so as to show both the correct pressure altitude and actual pressure corresponding to a given altimeter reading, suppose it is found that
+
+$$h_{P_1} = 3,250 \text{ feet}$$
+$$h_{P_2} = 4,475 \text{ feet}$$
+
+the corresponding pressures being
+$$p_1 = 26.57 \text{ inches mercury}$$
+$$p_2 = 25.39 \text{ inches mercury}$$
+
+Similarly, from the thermometer and air-speed meter calibration is obtained
+
+N.A.C.A. Technical Note No. 564.
+<page_number>23</page_number>
+
+$$T_1 = 77^\circ F.$$  
+$$T_2 = 75^\circ F.$$  
+$$V_1 = 47 \text{ miles per hour}$$
+
+The densities are
+
+$$\rho_1 = 0.04120 \times \frac{26.57}{459.4 + 77} = 0.002040$$  
+$$\rho_2 = 0.04120 \times \frac{26.39}{459.4 + 75} = 0.001957$$
+
+Then, the rate of change of pressure altitude is
+
+$$\frac{\Delta h_p}{\Delta t} = \frac{4475 - 3250}{62} = 19.75 \text{ f.p.s. (1185 f.p.m.)}$$
+
+and the rate of change of pressure
+
+$$\frac{\Delta p}{\Delta t} = \frac{26.39 - 26.57}{62 - 0} \times 13.59 = -0.259 \text{ in. of water/sec. (-16.54 in. of water/min.)}$$
+
+The true rate of climb
+
+$$V_c = \frac{-70.7(25.39 - 26.57)}{62 - 0} \times \frac{1}{(0.002040 + 0.001957) / 32.17}$$  
+$$= 20.92 \text{ f.p.s. (1285 f.p.m.)}$$
+
+Since the average indicated air speed is 47 miles per hour and the average value of $\rho$ is 0.00200, the true air speed is
+
+$$V = 47 \sqrt{\frac{0.002378}{0.00200}} = 51.2 \text{ m.p.h.}$$
+
+Then, for the angle of climb,
+
+$$\sin \theta = \frac{20.92}{51.2 \times 1.487} = 0.278$$
+
+or  
+$$\theta = 16.2^\circ$$
+
+<page_number>24</page_number>
+N.A.C.A. Technical Note No. 564
+
+Condition of Airship for Climb Tests
+
+The condition of the airship for climb tests may or may not be important depending upon what factors limit the rate at which an ascent or descent can be made. It does not seem feasible, therefore, to attempt stipulate in general what the condition of the airship should be. If the ability to maintain proper gas pressure limits the performance, as is usually the case for a descent, the condition of buoyancy and trim would probably be unimportant. If the pitch control limits performance, the condition of buoyancy and trim might be important. For example, assume that the airship is heavy so that a positive pitch angle is required in order to maintain a certain dynamic lift. Aside from the fact that the climbing performance now tends to become dependent on horsepower available, the heaviness will have an important bearing on the pitch control. Airship design has been such that a negative angle of pitch introduces a positive pitching moment tending to increase the pitch. A negative trimming moment must be applied. If this negative moment is applied by the elevator the result will be that, in maintaining the positive pitch angle, the average elevator position will be down. The net effect is somewhat as though the neutral position of the elevator were shifted downward so that the range of downward elevator movement is diminished and the range of upward motion correspondingly increased. This change in the effective elevator range may have considerable bearing on the ability to ascend or descend.
+
+Interpretation of Climb Data
+
+The results of the climb tests should show maximum values for angle and rate of ascent and descent. They should also show, so far as is possible, what characteristics of the airship limit the ability to ascend or descend, as for example, controllability, valve capacity, or blower capacity. In connection with items pertaining to valve and blower capacity, rate of change of atmospheric pressure, as well as the corresponding rate of change of altitude, could well be shown.
+
+N.A.C.A. Technical Note No. 564 <page_number>25</page_number>
+
+Summary of Test Procedure for Climb Tests
+
+A. Observations:
+1. Altimeter at regular intervals.
+2. Time interval between successive altimeter readings.
+3. Outside air temperature corresponding to each altimeter reading.
+4. Air-speed meter.
+5. Inclinometer.
+6. Note amount of elevator control required, condition of static buoyancy, and other items that appear to be significant.
+
+B. Calculations:
+(Note: In each of the following equations pressures p are in inches of mercury, times t are in seconds, and temperatures T are in degrees Fahrenheit.)
+
+1. Correct altimeter, thermometer, and air-speed meter readings in accordance with calibration to find correct pressure altitudes h₁, h₂, etc., and pressures P₁, P₂, etc.; correct temperatures T₁, T₂, etc.; and correct indicated air speed V₁.
+
+2. Find rate of change of pressure for successive intervals in inches of water per second from
+$$\frac{\Delta P}{\Delta t} = \frac{(p_2 - p_1)}{(t_2 - t_1)} \times 13.59.$$  
+If desired, also find rate of change of pressure altitude in feet per second from
+$$\frac{\Delta h_p}{\Delta t} = \frac{(h_{p_2} - h_{p_1})}{(t_2 - t_1)}.$$
+
+<page_number>26</page_number>
+
+N.A.C.A. Technical Note No. 564
+
+3. Find successive values of density $\rho_1$, $\rho_2$, etc., from
+$$\rho_1 = 0.04120 \times \frac{P_1}{460 + T_1}, \quad \text{etc.}$$
+
+4. Find true rates of climb for successive intervals in feet per second from
+$$V_c = \frac{-70.7 (\rho_2 - \rho_1)}{t_2 - t_1} \cdot \frac{1}{\rho_1 + \rho_2} \cdot 32.17$$
+
+5. Find average true air speed $V$ in miles per hour for successive intervals from
+$$V = \sqrt{\frac{0.002378 V_1}{\rho_1 + \rho_2}} \quad \text{m.p.h.}$$
+
+6. Find the sine of angle of climb $\theta$ in degrees from
+$$\sin \theta = \frac{V_c (f.p.s.)}{1.467 V (m.p.h.)}$$
+
+and $\theta$ from trigonometric tables.
+
+C. Plot:
+
+It is apparent that no plotting is required. If climbs with dynamic lift were made, however, there might be some point in plotting rate of climb against air speed for different amounts of dynamic lift at a given altitude or rate of climb against altitude (preferably pressure altitude) for given amounts of dynamic lift.
+
+Langley Memorial Aeronautical Laboratory,
+National Advisory Committee for Aeronautics,
+Langley Field, Va., March 28, 1936.
+
+N.A.C.A. Technical Note No. 564 <page_number>27</page_number>
+
+APPENDIX I
+
+Density of Moist Air
+
+Moist air is slightly lighter than dry air because it is a mixture of air and a small quantity of water vapor (steam), and the latter is lighter than air. The first step required to determine the density of the mixture is to find the partial pressure of the water vapor so that the total barometric pressure $p$ may be divided into two parts;
+
+$$p = p_a + p_w$$
+
+where $p_a$ is the partial pressure of air and $p_w$ is the partial pressure of the water vapor.
+
+Wet-bulb and dry-bulb temperature readings are required in order to calculate $p_w$ by means of Carrier's equation
+
+$$p_w = p'_w - \frac{(p - p'_w) (T - T_w)}{2755 - 1.28 T_w} \text{ inches of mercury}$$
+
+where $T$ is the dry-bulb temperature in degrees Fahrenheit
+
+$T_w$, the wet-bulb temperature in degrees Fahrenheit
+
+$p'_w$, vapor pressure in inches of mercury corresponding to the temperature $T_w$
+
+$p$, barometric or total pressure in inches of mercury. (See standard textbooks of thermodynamics for a more complete explanation; for example, reference 6.)
+
+In order to find $p'_w$ it is necessary to refer to standard steam tables for saturated steam (reference 7). Table I, which has been copied from reference 7, has been included for convenience. The density $\rho_w$ of the water vapor can then be found from
+
+$$\rho_w = \frac{0.0286 p'_w}{459.4 + T}$$
+
+<page_number>28</page_number>
+
+N.A.C.A. Technical Note No. 564
+
+The density of the dry air is.
+
+$$\rho_a = \frac{0.04120 \, p_a}{459.4 + T}$$
+
+and the density $\rho$ of the mixture is the sum of the two,
+
+or
+
+$$\rho = \frac{0.0256 \, p_w + 0.04120 \, p_a}{459.4 + T}$$
+
+In order to show the error involved by neglecting the humidity, the ratio of the densities of humid and dry air at any given temperature and pressure can be written
+
+$$\frac{\rho(\text{humid})}{\rho(\text{dry})} = (1 - 0.378 \frac{p_w}{p})$$
+
+Example:
+
+$$T = 80^\circ F.$$  
+$$T_w = 70^\circ F.$$  
+$$p = 29.42 \, \text{inches of mercury}$$
+
+From table I the vapor pressure $p_w$ corresponding to the wet-bulb temperature of $70^\circ$ is found to be $0.739$ inch of mercury. Then
+
+$$p_w = 0.739 - \frac{(29.42 - 0.739)(80 - 70)}{2755 - 1.28 \times 70} = 0.628$$
+
+and $$p_a = 29.42 - 0.63 = 28.79$$
+
+so that
+
+$$\rho = \frac{(0.0256 \times 0.63) + (0.04120 \times 28.79)}{459.4 + 80} = 0.002228$$
+
+The ratio
+
+$$\frac{\rho(\text{humid})}{\rho(\text{dry})} = 1 - 0.378 \times \frac{0.63}{29.42} = 0.992$$
+
+Y.A.C.A Technical Note No. 564 <page_number>29</page_number>
+
+which shows that the error in density due to neglecting humidity would have been 0.8 percent. The results of this error as regards the conversion of indicated air speed to true air speed would have been an error of -0.4 percent in true air speed.
+
+APPENDIX II
+
+Additional Speed-Course Methods
+
+In addition to the speed-course methods discussed in the main body of the text, Dr. Arnstein of the Goodyear-Zeppelin Corporation has recommended two additional methods. For one of them two neighboring but not necessarily adjoining straight courses arranged in the shape of an L or T are used. The two legs are followed in one direction and then retraced. The evaluation can be made for the triangular course except that there are four instead of three vertices from which to determine the circle, so that to some extent a check on the accuracy is obtained. The other method is limited in its application to parts of the country where long parallel landmarks such as roads are available. When such landmarks are available, the method appears to have considerable advantage over other speed-course methods. A summary of the method as described in a Goodyear-Zeppelin Corporation report by Dr. Elemenperer follows:
+
+From an accurate map two parallel roads, say 5 miles apart, are selected as the parallel landmarks. A compass course is set exactly at right angles to these roads and held without regard to the ground path as the crossing is made from one road to the other. (See fig. 8.) The compass course is then reversed and a return is made. It can readily be proved that, from the two crossing times, the true air speed $V$ in miles per hour is obtained without graphical analysis by means of the equation
+
+$$V = \frac{1}{2} \left( \frac{L}{t_1} + \frac{L}{t_2} \right) \times \frac{1}{1.437}$$
+
+where $L$ is the perpendicular distance in feet between the landmarks and $t_1$ and $t_2$ are the crossing times for the two directions of flight.
+
+30
+N.A.C.A. Technical Note No. 564
+
+REFERENCES
+
+1. Beij, K. Bilding: Aircraft Speed Instruments. T.R. No. 420, N.A.C.A., 1932.
+
+2. Diehl, Walter S.: Standard Atmosphere - Tables and Data. T.R. No. 318, N.A.C.A., 1925.
+
+3. Brombacher, W. G.: Altitude-Pressure Tables Based on the United States Standard Atmosphere. T.R. No. 538, N.A.C.A., 1935.
+
+4. Freeman, Hugh B.: Force Measurements on a 1/40-Scale Model of the U.S. Airship Akron. T.R. No. 432, N.A.C.A., 1932.
+
+5. Hanrickson, H. B.: Thermometric Lag of Aircraft Thermometers, Thermographs, and Barographs. Research Paper No. 222, Bur. Standards Jour. Res.. September 1930, pp. 695-709.
+
+6. Enswiler, J. E.: Thermodynamics. McGraw-Hill Book Co., Inc., 1921.
+
+7. Marks, Lionel S., and Davis, Harvey L.: Tables and Diagrams of the Thermal Properties of Saturated and Superheated Steam. Longmans, Green and Co., 1923.
+
+W.A.C.A. Technical Note No. 584 <page_number>31</page_number>
+
+**TABLE I. RELATION BETWEEN TEMPERATURE AND VAPOR PRESSURES OF SATURATED STEAM**
+
+<table>
+  <thead>
+    <tr>
+      <th>Temperature</th>
+      <th>Pressure</th>
+      <th>Temperature</th>
+      <th>Pressure</th>
+    </tr>
+  </thead>
+  <tbody>
+    <tr>
+      <td>° F.</td>
+      <td>in. Hg</td>
+      <td>° F.</td>
+      <td>in. Hg</td>
+    </tr>
+    <tr>
+      <td>32</td>
+      <td>0.1904</td>
+      <td>70</td>
+      <td>0.739</td>
+    </tr>
+    <tr>
+      <td>33</td>
+      <td>.1878</td>
+      <td>71</td>
+      <td>.764</td>
+    </tr>
+    <tr>
+      <td>34</td>
+      <td>.1955</td>
+      <td>72</td>
+      <td>.790</td>
+    </tr>
+    <tr>
+      <td>35</td>
+      <td>.2034</td>
+      <td>73</td>
+      <td>.817</td>
+    </tr>
+    <tr>
+      <td>36</td>
+      <td>.2117</td>
+      <td>74</td>
+      <td>.845</td>
+    </tr>
+    <tr>
+      <td>37</td>
+      <td>.2202</td>
+      <td>75</td>
+      <td>.873</td>
+    </tr>
+    <tr>
+      <td>38</td>
+      <td>.2290</td>
+      <td>76</td>
+      <td>.903</td>
+    </tr>
+    <tr>
+      <td>39</td>
+      <td>.2382</td>
+      <td>77</td>
+      <td>.933</td>
+    </tr>
+    <tr>
+      <td>40</td>
+      <td>.2477</td>
+      <td>78</td>
+      <td>.964</td>
+    </tr>
+    <tr>
+      <td>41</td>
+      <td>.2575</td>
+      <td>79</td>
+      <td>.996</td>
+    </tr>
+    <tr>
+      <td>42</td>
+      <td>.2671</td>
+      <td>80</td>
+      <td>.1029</td>
+    </tr>
+    <tr>
+      <td>43</td>
+      <td>.2762</td>
+      <td>81</td>
+      <td>.1063</td>
+    </tr>
+    <tr>
+      <td>44</td>
+      <td>.2890</td>
+      <td>82</td>
+      <td>.1098</td>
+    </tr>
+    <tr>
+      <td>45</td>
+      <td>.3002</td>
+      <td>83</td>
+      <td>.1134</td>
+    </tr>
+    <tr>
+      <td>46</td>
+      <td>.3118</td>
+      <td>84</td>
+      <td>.1171</td>
+    </tr>
+    <tr>
+      <td>47</td>
+      <td>.3238</td>
+      <td>85</td>
+      <td>.1209</td>
+    </tr>
+    <tr>
+      <td>48</ td><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><<br></table>
+
+<table cellspacing="0" cellpadding="0">
+  <!-- Table data -->
+  <!-- Row 51 to 60 -->
+  <!-- Row 61 to 69 -->
+  <!-- Row 70 to 79 -->
+  <!-- Row 80 to 89 -->
+  <!-- Row 90 to 99 -->
+  <!-- Row 100 to 109 -->
+  <!-- Row 110 to 119 -->
+  <!-- Row 120 to 129 -->
+  <!-- Row 130 to 139 -->
+  <!-- Row 140 to 149 -->
+  <!-- Row 150 to 159 -->
+  <!-- Row 160 to 169 -->
+  <!-- Row 170 to 179 -->
+  <!-- Row 180 to 189 -->
+  <!-- Row 190 to 199 -->
+  <!-- Row 200 to 209 -->
+  <!-- Row 210 to 219 -->
+  <!-- Row 220 to 229 -->
+  <!-- Row 230 to 239 -->
+  <!-- Row 240 to 249 -->
+  <!-- Row 250 to 259 -->
+  <!-- Row 260 to 269 -->
+  <!-- Row 270 to 279 -->
+  <!-- Row 280 to 289 -->
+  <!-- Row 290 to 299 -->
+  <!-- Row 300 to 309 -->
+  
+<table cellspacing="0" cellpadding="0">
+<tr style="background-color: #f5f5f5;">
+<td colspan="4">*Reference*<sup>7.</sup></table>
+
+<table cellspacing="0" cellpadding="0">
+<tr style="background-color: #f5f5f5;">
+<td colspan="4">*Reference*<sup>7.</sup></table>
+
+<table cellspacing="0" cellpadding="0">
+<tr style="background-color: #f5f5f5;">
+<td colspan="4">*Reference*<sup>7.</sup></table>
+
+<table cellspacing="0" cellpadding="0">
+<tr style="background-color: #f5f5f5;">
+<td colspan="4">*Reference*<sup>7.</sup></table>
+
+<table cellspacing="0" cellpadding="0">
+<tr style="background-color: #f5f5f5;">
+<td colspan="4">*Reference*<sup>7.</sup></table>
+
+<table cellspacing="0" cellpadding="0">
+<tr style="background-color: #f5f5f5;">
+<td colspan="4">*Reference*<sup>7.</sup></table>
+
+<table cellspacing="0" cellpadding="0">
+<tr style="background-color: #f5f5f5;">
+<td colspan="4">*Reference*<sup>7.</sup></table>
+
+<table cellspacing="0" cellpadding="0">
+<tr style="background-color: #f5f5f5;">
+<td colspan="4">*Reference*<sup>7.</sup></table>
+
+<table cellspacing="0" cellpadding="0">
+<tr style="background-color: #f5f5f5;">
+<td colspan="4">*Reference*<sup>7.</sup></table>
+
+<table cellspacing="0" cellpadding="0">
+<tr style="background-color: #f5f5f5;">
+<td colspan="4">*Reference*<sup>7.</sup></table>
+
+<table cellspacing="0" cellpadding="0">
+<tr style="background-color: #f5f5f5;">
+<td colspan="4">*Reference*<sup>7.</sup></table>
+
+<table cellspacing="0" cellpadding="0">
+<tr style="background-color: #f5f5f5;">
+<td colspan="4">*Reference*<sup>7.</sup></table>
+
+<table cellspacing="0" cellpadding="0">
+<tr style="background-color: #f5f5f5;">
+<td colspan="4">*Reference*<sup>7.</sup></table>
+
+<table cellspacing="0" cellpadding="0">
+<tr style="background-color: #f5f5f5;">
+<td colspan="4">*Reference*<sup>7.</sup></table>
+
+<table cellspacing="0" cellpadding="0">
+<tr style="background-color: #f5f5f5;">
+<td colspan="4">*Reference*<sup>7.</sup></table>
+
+<table cellspacing="0" cellpadding="0">
+<tr style="background-color: #f5f5f5;">
+<td colspan="4">*Reference*<sup>7.</sup></table>
+
+<table cellspacing="0" cellpadding="0">
+<tr style="background-color: #f5f5f5;">
+<td colspan="4">*Reference*<sup>7.</sup></table>
+
+<table cellspacing="
+
+N.A.C.A. Technical Note No. 564
+
+Fig. 1
+
+<table>
+  <tr>
+    <td rowspan="2">Altitude, thousands of feet</td>
+    <td colspan="3">Figure 1. - Variation of pressure with altitude in N.A.C.A. standard atmosphere. (Reference 2)</td>
+  </tr>
+  <tr>
+    <td>Atmospheric pressure, inches of mercury</td>
+    <td>feet</td>
+    <td>feet</td>
+  </tr>
+  <tr>
+    <td>4</td>
+    <td>10</td>
+    <td>20</td>
+    <td>28</td>
+  </tr>
+  <tr>
+    <td>3</td>
+    <td>9</td>
+    <td>21</td>
+    <td>29</td>
+  </tr>
+  <tr>
+    <td>2</td>
+    <td>8</td>
+    <td>22</td>
+    <td>30</td>
+  </tr>
+  <tr>
+    <td>1</td>
+    <td>7</td>
+    <td>23</td>
+    <td>31</td>
+  </tr>
+  <tr>
+    <td>0</td>
+    <td>6</td>
+    <td>24</td>
+    <td>32</td>
+  </tr>
+  <tr>
+    <td>-1</td>
+    <td>5</td>
+    <td>25</td>
+    <td>33</td>
+  </tr>
+  <tr>
+    <td>-2</td>
+    <td>4</td>
+    <td>26</td>
+    <td>34</td>
+  </tr>
+  <tr>
+    <td>-3</td>
+    <td>3</td>
+    <td>27</td>
+    <td>35</td>
+  </tr>
+  <tr>
+    <td>-4</td>
+    <td>2</td>
+    <td>28</td>
+    <td>36</td>
+  </tr>
+  <tr>
+    <td>-5</td>
+    <td>1</td>
+    <td>29</td>
+    <td>37</td>
+  </tr>
+  <tr>
+    <td>-6</td>
+    <td></table><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/>.<div style="text-align:center;">Figure 1. - Variation of pressure with altitude in N.A.C.A. standard atmosphere. (Reference 2)</div><div style="text-align:center;">Atmospheric pressure, inches of mercury<br/></div><div style="text-align:center;">Altitude, thousands of feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><div style="text-align:center;">Feet<br/></div><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/><hr/>.
+
+M.A.C.A. Technical Note No. 564
+
+Fig. 2
+
+<table>
+  <tr>
+    <td rowspan="2">Figure 2 - Variation of density with altitude in standard atmosphere.</td>
+    <td rowspan="2">N.A.C.A. Standard Atmosphere (Reference 2)</td>
+    <td colspan="3" style="text-align:center;">4000 feet</td>
+  </tr>
+  <tr>
+    <td>3000</td>
+    <td>to</td>
+    <td>4000</td>
+  </tr>
+  <tr>
+    <td rowspan="2">Air density p · slugs per cubic foot</td>
+    <td rowspan="2"></td>
+    <td>10,000</td>
+    <td>feet</td>
+    <td>.0023</td>
+    <td>.0024</td>
+  </tr>
+  <tr>
+    <td>10,000</td>
+    <td>to</td>
+    <td>.0021</td>
+    <td>.0022</td>
+  </tr>
+  <tr>
+    <td rowspan="2">Altitude in thousands of feet</td>
+    <td rowspan="2"></td>
+    <td>1</td>
+    <td>feet</td>
+    <td>.0018</td>
+    <td>.0019</td>
+  </tr>
+  <tr>
+    <td>1</td>
+    <td>to</td>
+    <td>.0021</td>
+    <td>.0022</td>
+  </tr>
+  <tr>
+    <td>-1</td>
+    <td></td>
+    <td>-2</td>
+    <td></td>
+    <td></td>
+  </tr>
+</table>
+
+<img>A graph showing the variation of air density with altitude in the standard atmosphere, according to N.A.C.A. Reference 2. The x-axis represents altitude in thousands of feet, ranging from -1 to +4. The y-axis represents air density in slugs per cubic foot, ranging from .0018 to .0024. Two lines represent the variation of air density at different altitudes: one line extends from approximately .0018 at -1 thousand feet to .0024 at +4 thousand feet, and another line extends from approximately .0019 at -1 thousand feet to .0022 at +4 thousand feet.</img>
+
+V_{o}, true air speed
+V_{o}, local air speed
+y, distance from hull
+D_{max}, maximum diameter
+
+<img>
+A graph showing velocity ratio, V/V_{o} against y/D_{max}.
+The x-axis ranges from 0 to 3.
+The y-axis ranges from 1.00 to 1.04.
+A curve is plotted that decreases slightly as y increases.
+</img>
+
+y/D_{max}, distance from hull in terms of maximum diameter
+
+Figure 3.- Calculated variation of air velocity with distance from the hull at maximum diameter for the U.S.S. Akron.
+
+N.A.C.A. Technical Note No. 594
+<page_number>P14-3</page_number>
+
+B.A.C.A. Technical Note No. 564
+
+<img>A technical drawing of a suspended air-speed head.</img>
+<page_number>FIG. 4</page_number>
+
+8 1/2" 3 3/8" 4"
+15 7/8"
+
+6" 3/4" 1/4" 1/4"
+
+Dynamic opening
+3/16 inch diameter
+
+Static orifices
+36 holes
+0.05 inch diameter
+equally spaced
+
+Figure 4.- Suspended air-speed head.
+
+N.A.C.A. Technical Note No. 564
+
+Fig. 5
+
+Figure 5 - Suspended air-speed head with single duct cable.
+
+N.A.C.A. Technical Note No. 564
+
+Fig. 6
+
+<img>
+A triangle with labels "Leg 1", "Leg 2", and "Leg 3" pointing clockwise. The top vertex is labeled "N". Below the triangle, the text "Orientation of speed course" is written.
+</img>
+
+V₁, V₂, V₃, measured ground speeds
+Vw, wind speed
+V, true air speed
+
+<img>
+A diagram showing three points B, X, and C on a circle. Point X is connected to B by a line labeled V₁ and to C by a line labeled V₂. A line from X to the center of the circle is labeled Radius V. Another line from X to point D on the circumference is labeled V₃. The text "Figure 6.- Graphical method of finding true air speed from flights over a triangular speed course." is written below the diagram.
+</img>
+
+Figure 6.- Graphical method of finding true air speed from flights over a triangular speed course.
+
+M.A.C.A. Technical Note No. 564
+
+Fig. 7
+
+320
+Elevator deflected to obtain zero pitching moment
+Elevator neutral
+
+280
+240
+200
+160
+120
+80
+40
+
+Pitch angle, degrees
+
+Figure 7.- Increase in drag coefficient due to pitch as a percentage of the minimum drag coefficient for U.S.S. Akron model.
+
+<img>A graph showing the increase in drag coefficient due to pitch as a percentage of the minimum drag coefficient for U.S.S. Akron model.</img>
+
+V, true air speed
+V<sub>w</sub>, wind velocity
+V<sub>1</sub>, V<sub>2</sub>, ground velocities
+
+<img>A diagram showing a speed course with parallel landmarks. The diagram includes labels for various vectors and angles.</img>
+
+Figure 8.- Diagram of speed course with parallel landmarks.
+
+W.A.C.A. Technical Note No. 564
+
+<page_number>718-8</page_number>

Airships/spherical_ballooning-some_of_the_requirements_1917.md

@@ -0,0 +1,975 @@
+SPHERICAL
+BALLOONING
+
+Price
+One Dollar
+
+By P. J. McCULLOUGH
+Saint Louis
+
+LIBRARY
+UNIVERSITY OF THE
+MICHIGAN
+
+DEPARTMENT
+OF
+ENGINEERING
+
+East Engla
+13
+TL
+600
+M133
+
+<img>Google Books logo</img>
+
+<watermark>Google</watermark>
+
+SPHERICAL
+BALLOONING
+
+SOME OF THE
+REQUIREMENTS
+
+By P. J. McCULLOUGH
+
+THE MANGAN PRINTING COMPANY, Publishers
+325 Olive Street
+SAINT LOUIS
+U.S.A.
+
+<page_number>1917</page_number>
+
+<img>A small black and white image of a balloon.</img>
+<watermark>Google</watermark>
+
+Cart Engin
+TH
+600
+M13B
+
+<watermark>
+Corrected
+F. J. McGUILOUGH
+Barr Louis
+1917
+</watermark>
+
+<img>A scanned page with handwritten notes and a watermark.</img>
+
+THIS VOLUME
+IS RESPECTFULLY DEDICATED TO
+OUR BOYS IN FRANCE
+WHOSE DEVOTION TO THE BEST INSTINCTS
+OF MANHOOD WILL MAKE THE
+WORLD SAFE FOR
+DEMOCRACY
+
+327258
+
+<watermark>Google</watermark>
+
+<img>A floral design with three large leaves.</img>
+
+# Foreword
+
+**MODERN** works on theory and practice in the art of ballooning, not being sufficiently primary to satisfy the average student, this compilation was suggested as a means to assist in an effort to become competent to successfully assemble and pilot the spherical balloon.
+
+Description of equipment herein should not be regarded as covering all methods of design and construction, but is offered as an example of one popular type and system as used at the present day, the object being to impress the fact that in addition to keen observation as to detail in regard to both work and equipment, self-reliance is much to be preferred in preference to theory or suggestions from any other source, in deference as to just what should be done to maintain control; i. e., problems cannot be solved until presented for solution.
+
+<watermark>Google</watermark>
+
+<watermark>Google</watermark>
+
+Gas Ballooning
+
+Some of the Requirements
+
+C
+ONSULT the weather man. Arrange for a supply of gas of the proper specific gravity and sand to fill each bag. Secure a complete balloon outfit and check the equipment, making sure that each part examined is in serviceable condition.
+
+One balloon assembly as follows:
+One Ground Cloth.
+One Balloon Cover.
+One Balloon Cover Lace or Rope.
+One Balloon Envelope.
+One Balloon Appendix.
+One Appendix Ring (two parts).
+One Appendix Rope Assembly.
+One Filling Hose.
+One Filling Hose Thimble.
+One Rip Cord (red).
+One Valve Cord (white).
+One Load-Ring Assembly.
+One Passenger Basket or Car Assembly.
+One Drag Rope.
+One Anchor.
+One Anchor Rope.
+
+<img>Google logo</img>
+
+<page_number>10</page_number>
+SPHERICAL BALLOONING
+
+One Sand Bag for each mesh in the circumference of the balloon net, plus six or eight sand bags to hold down the appendix rope cords and the corners of the ground cloth.
+Recording Barograph. Barometer. Stasoscope. Thermometer. Compass. Watch. Knife. Flash Lamps. Camera. Megaphone. Matches. Pencil. Log. Maps. Money.
+
+Ground Cloth
+Place one corner of ground cloth about five feet from end of gas supply pipe in such position that pipe points diagonally across center of cloth.
+
+Envelope
+Unroll balloon envelope so that it will lie diagonally across the center of the ground cloth with the opening for the appendix about four feet from the ground cloth corner which is nearest to the gas filling pipe. The valve end of the envelope should be near the corner of the ground cloth diagonally opposite to that of the gas filling pipe. Pull the folds of the envelope in such way that it will form a cylinder, with its side sloping on the under side and upper side of the envelope, is evenly distributed in the outer part of the disc thus formed.
+
+Appendix Rings And Appendix
+Place appendix rings on the ground cloth with bolt heads down and remove upper ring. Place bolt holes in the cloth of the appendix over the bolts in the lower appendix ring in such way that the inside of the appendix cloth will be next to the lower ring. Place the appendix and lower ring in to the balloon. Place bolt holes (which are near each other) on the ground cloth over the bolts in the ring. Put the upper appendix ring in place, making sure that the markers register, as bolt holes are not interchangeable.
+
+<img>Google logo</img>
+
+SOME OF THE REQUIREMENTS <page_number>11</page_number>
+
+Appendix Cord and Loop Nuts
+
+A loop nut is secured to each of the appendix cords which should be twisted five or six times in the opposite direction to that required to tighten the nuts. Turn appendix loop nuts down firmly on the appendix ring bolts, but don't use a wrench or pliers, a small nail or key furnishes quite enough leverage. Both the balloon cloth and the appendix cloth should be impregnated with glue so that no folds of the cloth have been clamped between the two appendix rings. Carry the appendix, appendix ring and the folds of the balloon fabric on each side of the appendix ring about half way to the valve opening in the balloon. Place a bag of sand on each side of the ground cloth, keeping in line with the gas supply pipe. Stretch the appendix so that it points toward the gas supply pipe. Place lower edge of appendix ring on ground cloth with upper edge inclined toward the gas supply pipe at an angle of thirty to sixty degrees.
+
+Anchor for Appendix Ring
+
+Place a bag of sand on the appendix ropes at each side of the appendix ring and see that appendix cords on which the sand bags rest are tight between bag and loop nuts on appendix ring.
+
+Filling Hose and Thimble
+
+Place thimble or a joint of stove pipe in end of filling hose, and place both of these into the end of the appendix, making a gas tight joint by binding with a strap or cord. Place other end of filling hose over gas supply pipe and attach it in same way. Place bags of sand on each side of the appendix and filling hose so that the flow of gas is not restricted by the weight of the balloon fabric. Carry folds of envelope on either side of the appendix ring back so that it is again in the form of a disc.
+
+Slack on Under Side Fabric
+
+While doing this, be sure that all of the slack has been taken up on the under side, and that the appendix ring and bags of sand have not been pulled out of position. Pull the cloth or fabric over
+
+<img>Google logo</img>
+
+<page_number>12</page_number>
+SPHERICAL BALLOONING
+
+to that half of the disc or circle nearest to the gas supply pipe until the fabric at the bottom of the appendix ring has been stretched up over the top of the ring and back to the edge of the balloon nearest to the gas filling pipe. This gives the envelope the appearance, in shape, of the moon in its first quarter. From the inside of the crescent thus formed pull the balloon fabric in the opposite direction until a disc is again formed, the fabric being distributed such way that the center of the hole for the balloon valve is located directly below that from the gas filling pipe than is the appendix ring.
+
+Shape the balloon fabric so that it forms a disc about two-thirds as large in diameter as that of the balloon when inflated. Be sure that all folds in the balloon fabric are evenly distributed, within two or three feet of each side of the disc. Remove bunches of loose when walking with balloon fabric. Pull end of rip panel flap and rip cord support flap out through the valve hole.
+
+Roll the rip cord into a compact ball and tie one end to the flap on the rip panel. At a point on the rip cord, about twelve inches from the rip cord hole in the rip panel flap, tie a piece of cotton stringing, twisting it around the rip cord support flap which is immediately above the rip panel. Pull the balloon fabric back into place so that its disc-like shape is restored. Hold balloon fabric up at rip panel so that rip cord ball can be thrown through the valve hole and caused to lodge near the outer edge on the inside of the envelope.
+
+Roll valve cord into a compact ball. Hold one end of cord and throw ball through valve hole in envelope so that it lodges on the inside opposite to the rip cord ball.
+
+<img>Google logo</img>
+
+SOME OF THE REQUIREMENTS <page_number>13</page_number>
+
+Nat
+
+Lay rope ring at valve end of net over the valve hole in the balloon envelope. Separate the net ropes by three feet apart and pull upper part of net over lower part of net until net ropes have been moved to proper locations. Ropes should be placed as many degrees apart as the number representing double net ropes is contained times in 360; i. e., there should be a distance of 30 degrees between the ropes of a twelve-ropes net. Evenly distribute the net over the surface of the envelope and see that the cords of the net—which connect to the rope valve ring—point to the center of the ring. Make a coil of about ten inches diameter of each rope, and place surplus net under the balloon envelope near the edge, making sure that rope coils have not been placed through any of the meshes in the net.
+
+Valve
+
+Remove clamp ring from the valve. Tie valve rope to valve cords, and if there is a pair of cords to limit the opening of the valve be sure that they are properly adjusted, otherwise the valve might be rendered unsafe. Place the valve in position with threaded ends of bolts up, feel or look around each of valve to see that valve cords and rope are not looped around the bolts or caught in the valve doors. Place the bolt holes in the envelope over the bolts in the valve and put on the valve clamp ring, observing that location marks register, as bolt holes are not interchangeable. Screw wing nuts down firmly, but do not use wrench or pliers. See that balloon forms a perfect circle with the valve ring. Stretch the balloon fabric and pleats around it so that no thread folds have been caught under the valve clamp ring. Strap or tie with a string the net rope ring to the valve clamp ring or wing nuts, leaving about one inch slack.
+
+<img>Image of a page from a manual.</img>
+<watermark>Google</watermark>
+
+<page_number>14</page_number>
+SPHERICAL BALLOONING
+
+Sand Bag: Hook a bag of sand on every other mesh of the net, each bag being the same number of meshes from the valve or net rope. See that bags are located an equal distance apart on the ground cloth so as to form a circle around the balloon. Roll the drag rope into a compact ball with the loop end out.
+
+Inflating: Eliminate all fire. Turn on the gas. As soon as the net begins to tighten pull down on the balloon fabric to remove all large folds or wrinkles near the valve; this should be observed until the balloon is about one-eighth inflated. As soon as the balloon fabric has been forced out against the net by the pressure of the gas, to within one or two feet of the ground cloth opposite each sand bag, the sand bag hooks should be changed so that they are one mesh farther from the top of the net. If there is a wind velocity of over fifteen miles per hour, it is best to make a change of one-half mesh only. After bal-
+loon is one-eighth inflated, hook a bag of sand on every mesh in a single row of meshes around the balloon. The necessity of hanging a bag of sand on every mesh increases as the velocity of the wind increases; that is, it might be necessary to hang a bag of sand on every mesh before the balloon is one-third inflated.
+
+Danger to Fabric: Remove all bags of sand from appendix ropes before inflation causes undue stress on balloon fab-
+ric near appendix ring. When inflation is complete, stop the flow of gas at the supply pipe. Hook all bags of sand on the net so that appendix ring is about three to five feet from the ground cloth.
+Remove filling hose and thimble from appendix.
+The next operation requires that you hold your breath to prevent inhaling gas, therefore it is im-
+portant to concentrate on the following things to be done:
+
+<img>Google logo</img>
+
+SOME OF THE REQUIREMENTS <page_number>15</page_number>
+
+Look up through the appendix. Inspect the valve, valve-cords, valve-ropes, rip-cord or rope and rip panel. Locate the rip cord ball and the valve-cord ball. Remove the rip cord ball through the appendix. Unroll and take out all kinks or knots.
+
+Take hold of the end of the rip cord, reach up through the appendix and push end of cord down from the inside of the balloon through the rip cord hole. Pull through until there is no slack in the rope on the inside of the balloon, then pull about six or eight feet of back into the balloon and fasten securely to the rip cord ring through the hole or small appendix, which is about two feet radially from the outside of the appendix ring and directly under the rip panel.
+
+If there is a small eyellet the rope can be secured with a piece of lead pencil or any similar substance used as a wedge. If there is just a hole in the fabric without any arrangement for securing the rip cord, a lead pencil or short stick may be tied to the end of the rope and allowed to turn at right angles to the rope while inside of the balloon, in which position it will act as an anchor. If there is a short piece of fabric hose or appendix integral with the envelope, the rope may be tied to the lower end of this with a piece of cotton wrapping twine, forming a pocket into which the slack that part of the cord which is inside of the balloon may be placed.
+
+String for Rip Cord Support
+
+Any string used to support the rip cord at the rip cord support flap, and at the lower part of the envelope, should be so low in tensile strength that a pull of five or six pounds will cause it to break. Let the valve rope ball down through the appendix and see that the rope hangs properly. Place a string of white cotton wrapping twine—once only—through the loop in the end of the balloon cover lace or rope, and tie it around the appendix. Hold
+
+<img>Google logo</img>
+
+<page_number>16</page_number>
+
+SPHERICAL BALLOONING
+
+loosely the appendix rope, balloon cover rope or lace, valve rope and rip cord in a position under the place where the rip cord comes down through the balloon.
+
+Placing Basket or Car in Position
+
+Change position of sand bag hooks in net until there is room to place the basket under the appendix ring. Connect the basket ropes to the load ring in such way that the drag rope toggle is on one side of the basket and outside of the basket ropes. If there is a door or gate in the side of the basket, the drag rope toggle should be on that side. Fold and secure all excess ropes around the basket. Remove temporarily a sufficient number of sand bags from the net so that basket can be placed under appendix ring with the drag rope toggle directly under the place where the rip cord comes through the balloon.
+
+Connecting Basket Ropes
+
+Toe Ropes
+
+Connect all net ropes or toe ropes to the load ring. Tie end of rip cord to load ring and place slack into the red bag loosely, beginning near the end which is tied. Tie end of valve cord also, and place it into the white bag in the same way. Change bags of sand onto mesh at a time until no free double is left. After each change put on the last double, the pilot takes his place in the basket. Hook all bags of sand on toe ropes. The buoyancy of the gas in the balloon should be sufficient to cause the bags of sand to slowly slide over the ground cloth to the basket; if not, remove bags of sand from basket and hook them on toe ropes again. Remove all bags of sand from toe ropes and hook them on the basket ropes. Keep load ring level until basket ropes are tight, to prevent the net slipping out of position on the envelope. Place the loop end of the drag rope over the drag rope toggle, and tie the drag rope ball to one of the basket ropes with a cord which should be secured to one of the inner coils of the ball. Aids or students enter
+
+SOME OF THE REQUIREMENTS <page_number>17</page_number>
+
+basket and see that instruments and supplies are ready. Remove a sufficient amount of sand to secure an equilibrium. Pull the balloon cover lace or rope and break the string which holds the appendix closed. See that appendix opens before leaving the ground. The balloon appendix rope loosesly around the load ring, opposite to the drag toggle. Release the balloon, after which the pilot should have complete control.
+
+Temperature Assuming the temperature of the atmosphere, and the gas in balloon to be constant and that no escape of gas takes place, except through the appendix and the valve when it is being held open, the task of piloting a balloon is very simple. After striking an equilibrium at any altitude, that altitude would be maintained indefinitely and the balloon would never ascend or descend unless some material substance were added or removed. In this range of temperature requires the release of ballast, the amount of which cannot be determined unless conditions are known. The amount of ballast required to recover equilibrium does not depend on the capacity of the balloon, but on the number of cubic feet of gas lost or gained. For specific cases of the gas e. c., if, at the start, one half of ballast is required to make a correction, it would require but one-half bag to produce the same result if one-half of the gas were lost. This quite often happens after having been in the air for something like 48 hours.
+
+Method of Piloting The most successful method of piloting a balloon is to constantly observe the statoscopes and release a few ounces of sand as soon as the descent starts, provided the descent is due to reduction in the ascending power of the gas. If the rate of fall increases more ballast must have been released. Momentum will continue to carry the balloon down after the proper amount of ballast has been re-
+
+<img>Google logo</img>
+
+<page_number>18</page_number>
+SPHERICAL BALLOONING
+
+leased. This sometimes deceives the pilot into re-
+leasing too much ballast, after which the balloon
+will ascend to an altitude greater than the previous
+maximum altitude. Close observation will assist
+in preventing a repetition of the same mistake dur-
+ing future flights, but as no two flights are
+alike, an "aiming shot" - two is generally required
+unless conditions are ideal.
+
+Landing
+
+Having selected a field in which to land, tie the
+appendix rope to the load ring opposite to the drag
+rope, which should be unrolled any time at an alti-
+tude greater than its length. The rate of descent
+should be governed by releasing ballast or by open-
+ing the valve, remembering that that portion of the
+drag rope which is on the ground represents the
+release of that much ballast.
+
+Some persons may jump from the top of a
+twenty-foot wall without injury, while two feet
+would be the limit for another, so let this fact be
+borne in mind when deciding on the rate of fall
+with which the basket is allowed to come to earth.
+
+Rate of Fall
+
+The work of landing is much simplified by pull-
+ing down the rip panel. This is absolutely neces-
+sary if the velocity of the wind is over fifteen miles
+per hour, and should be completed by the time the
+basket is within ten feet of the ground.
+
+Rippling
+
+If there is assistance sufficient to hold the bal-
+loon basket so it does not drag over the ground,
+deflation may be made by valve, which requires much
+longer. After deflation is four-fifths complete, the
+valve, valve rope, appendix assembly and rip cord
+should be removed. When completed, that part of
+the basket which has been exposed should be covered
+by pulling the toe ropes over to the valve side of
+the balloon. Fold balloon envelope by straighten-
+ing one seam or row of panels from valve opening
+
+SOME OF THE REQUIREMENTS <page_number>19</page_number>
+
+to appendix opening and fold each row of panels over this until they form a strip of fabric about two or three feet wide, depending on size of balloon.
+
+The net should be straightened out by placing all of the ropes together. Straighten out one row of meshes from the top to the bottom and place each corresponding row with these, after which twist it like a rope and tie with a string at intervals of about ten feet. Load basket should be placed against one side of the basket slats. Carefully drag rope loosely in basket, also the net. Hang appendix ring and valve to load ring. Put in appendix, appendix rope and sand bags and put on basket cover. Beginning at the valve end of the balloon (to protect top of envelope from railroad employees) roll up compact roll and lace or tie cover in such way that no part of the balloon fabric can become exposed.
+
+Instruments should be carried and not shipped with the balloon outfit, unless they are well protected by packing in separate boxes.
+
+<table>
+  <tr>
+    <td>How to Roll Net</td>
+    <td>Care of Instruments</td>
+  </tr>
+</table>
+
+<img>Google logo</img>
+
+<page_number>20</page_number>
+SPHERICAL BALLOONING
+
+DIMENSIONS OF SPHERICAL BALLOON
+
+<table>
+  <thead>
+    <tr>
+      <th>Volume<br>in<br>Cubic Feet</th>
+      <th>Diameter<br>in<br>Feet</th>
+      <th>Surface<br>in<br>Square Yards</th>
+    </tr>
+  </thead>
+  <tbody>
+    <tr>
+      <td>10,000</td>
+      <td>26.75</td>
+      <td>249.77</td>
+    </tr>
+    <tr>
+      <td>15,000</td>
+      <td>30.58</td>
+      <td>326.42</td>
+    </tr>
+    <tr>
+      <td>20,000</td>
+      <td>33.68</td>
+      <td>384.75</td>
+    </tr>
+    <tr>
+      <td>25,000</td>
+      <td>36.28</td>
+      <td>459.14</td>
+    </tr>
+    <tr>
+      <td>30,000</td>
+      <td>38.54</td>
+      <td>518.52</td>
+    </tr>
+    <tr>
+      <td>35,000</td>
+      <td>40.58</td>
+      <td>575.34</td>
+    </tr>
+    <tr>
+      <td>40,000</td>
+      <td>42.43</td>
+      <td>627.55</td>
+    </tr>
+    <tr>
+      <td>50,000</td>
+      <td>45.71</td>
+      <td>731.11</td>
+    </tr>
+    <tr>
+      <td>60,000</td>
+      <td>48.57</td>
+      <td>832.55</td>
+    </tr>
+    <tr>
+      <td>70,000</td>
+      <td>51.26</td>
+      <td>917.30</td>
+    </tr>
+    <tr>
+      <td>80,000</td>
+      <td>53.46</td>
+      <td>997.62</td>
+    </tr>
+  </tbody>
+</table>
+
+<img>A partial image of a balloon.</img>
+
+<watermark>Brought to you by Google</watermark>
+
+SOME OF THE REQUIREMENTS <page_number>21</page_number>
+
+**OSCILLATION**
+
+Vertical oscillation of a balloon is generally caused by variation in temperature of the gas. At night the temperature of the air generally diminishes as the altitude becomes greater, this condition remaining relatively constant throughout the night.
+
+<img>A diagram showing a balloon with a line indicating oscillation.</img>
+Dotted line shows normal oscillation.
+FIG. 1
+
+Assume that at an altitude of 1,000 feet the equilibrium is perfect, after which, due to some irregular air movement, the balloon rises to an altitude of lower temperature, the gas will, of course, contract, causing a descent. However, it will not stop at the 1,000-foot altitude, unless it were possible to stop it from rising indefinitely. Some means of stopping the vertical movement at the 1,000-foot mark and holding it there until the temperature of the gas and air equalizes. This not being possible, what really happens is that the momentum and reduction in buoyancy carries the sphere down into the warmer air, where expansion of gas takes place and causes a change in direction become the descending momentum and produce ascending momentum which will not cease until an altitude greater than the 1,000-foot mark has been reached.
+
+The range of oscillation is governed mostly by momentum, and the rapidity with which heat is transmitted between the gas in the balloon and the air in which it floats.
+
+<watermark>Google</watermark>
+
+<page_number>22</page_number>
+
+SPHERICAL BALLOONING
+
+The greater the difference in temperature of the air at different altitudes the more sudden will be the change in the temperature of the gas, which means a smaller range in oscillation. Also, if the balloon fabric is very thin it responds to tempera-
+ture changes much quicker and acts more sensitive when oscillating than would a heavy fabric, which would, perhaps, oscillate in a range two or three times as great.
+
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+Oscillation of a heavy balloon.
+A constant fall in temperature will cause the same movement.
+
+FIG. 2
+
+Range of Oscillations
+500 feet, and will not begin until the temperature of the gas has very nearly approached that of the average of the air. Very close attention is required of the pilot to determine just when oscillation takes place, as the balloon acts identically as it would if it were necessary to release gas or ballast to make the correction.
+
+How to Determine Oscillations
+As a rule, when a balloon begins to oscillate,
+the maximum rate of fall will not be greater than two or three feet per second. Therefore, after
+the balloon has been released—the pressure of
+the gas has become normal, the rate of descent should be allowed to increase considerably above three feet per second before releasing ballast. One should be able to "feel out" these conditions be-
+fore the altitude has been reduced more than one hundred or two hundred feet.
+
+Leaky Balloon
+If a balloon leaks gas, oscillation will represent a movement describing stair steps unless ballast be
+
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+<img>A diagram showing a circular balloon with an arrow indicating oscillation.</img>
+
+SOME OF THE REQUIREMENTS <page_number>23</page_number>
+
+released to compensate for leakage as rapidly as it takes place. Rainfall, even though it be heavy, does not prevent oscillation, it being necessary only to release an amount of ballast equal in weight to that of the water which adheres to the balloon.
+A steady fall in the temperature of the atmosphere will cause oscillation due to the same cause as that due to a leakage of gas. A rise in the temperature of the atmosphere will cause oscillation describ-
+ing stair steps ascending and can be corrected by valving or by the use of the blower.
+
+<img>fleur-de-lis</img>
+<watermark>Google</watermark>
+
+<page_number>24</page_number>
+SPHERICAL BALLOONING
+
+AIR POCKETS
+
+A term denoting a condition which causes a vehicle of the air to rapidly descend out of control. Vertical movement of the air, due to rapid change of great difference in temperature, is one cause very impressively illustrated by cyclonic conditions.
+
+FIG. 3
+
+Influence of earth's contour on vertical movement of balloon
+
+Near the leeward side of hills and mountains, or other large objects, will be found a downward movement of air which becomes more decided with an increase in wind velocity. This condition is due to the tendency of the wind to follow the contour of the earth's surface.
+
+Variety in Air Currents
+
+Another condition which mostly affects the heavier-than-air type of air craft may be explained by assuming an aeroplane to be moving at the rate of fifty miles per hour in a stratum of still air, and that the air immediately below forms a stratum which is moving at the same speed as that of the aeroplane, and in the same direction; it is obvious that if the craft comes down into the low stratum that relative to the air it has no horizontal movement and will at once begin to fall.
+
+Relative Movement
+
+If the stratum of air is moving in the opposite direction it will produce the same effect as though
+
+SOME OF THE REQUIREMENTS <page_number>25</page_number>
+
+the aeroplane had suddenly increased its speed to 100 miles per hour, a condition demanding wide margin of safety in strength of material and workmanship employed in its construction.
+
+Stratum of air moving west fifty miles per hour.
+
+Stratum of air with no movement
+
+Plane speed 30 mi. per hr.
+
+Stratum of air moving east, velocity fifty miles per hour.
+
+FIG. 4
+
+<page_number>36</page_number>
+SPHERICAL BALLOONING
+
+EXPANSION
+
+All gases expand at a uniform rate (co-efficient of expansion) for equal increment of heat: 1-273 increase in volume for every degree above zero C.
+So that, assuming an 80,000 cubic feet capacity balloon, with a lifting capacity of 40 pounds per 1,000 cubic feet, and that a 1-degree C. rise in temperature has taken place, the expansion would be 1-273 of 80,000, or 293.05 cubic feet, with a lifting capacity of 11.92 pounds.
+
+If it were possible to raise the temperature of the gas to something like 240 degrees C., there would be enough gas flow out at the appendix, due to expansion, to fill another balloon of the same capacity. One thousand cubic feet of air weighs 80.73 pounds; 1,000 cubic feet of gas that would lift 40 pounds of ballast would have to be exactly twice this weight. Hence, we could replace the ballast and air, 80.73 + 40 = 40.73, the exact weight of 1,000 cubic feet of gas that would lift 40 pounds.
+
+The above figures apply at sea level only. For every degree C. drop in temperature of the gas, there would have to be discharged 11.5+ pounds of ballast to maintain an equilibrium. As a rule, temperature conditions are most variable between the hours of 10:00 A. M. and 7:00 P. M., so that these hours of the day are the most difficult time for piloting a balloon. The conditions at night are much more desirable because of temperature conditions remaining practically constant. If the sky is clear
+
+Temperature Conditions
+<img>Google logo</img>
+
+SOME OF THE REQUIREMENTS <page_number>27</page_number>
+
+from sunrise until eleven o'clock A. M., as a rule the temperature expansion is sufficient to maintain altitude without releasing ballast.
+
+Release of Gas
+
+If the balloon is to be kept at an equilibrium, a sufficient amount of gas must be released at the valve compensated for the difference in weight betwen the gas in its envelope and a higher temperature i. e., if at an altitude of 1,000 feet the balloon is at an equilibrium, after which, due to a rise in temperature, 1,000 cubic feet of gas flows out at the appendix, there remains in the balloon the same number of cubic feet of gas, but the lifting power has been increased. This would not be true if we could liquify and freeze the 1,000 cubic feet of gas released, and put it in a sand bag to be used as ballast, but this cannot be done, but as this cannot be done, the only thing to do is to release enough gas at the valve to maintain the equilibrium, after which it will be noticed that the lower part of the envelope is somewhat wrinkled because not so much of the warmer gas is required to lift the same load.
+
+Maintaining Equilibrium
+
+Under these conditions it is very difficult to maintain an equilibrium, because unless the valve is used when too much ballast has been released—regardless of how small the excess may be—the balloon will ascend to an altitude where the atmosphere is sufficiently rare to allow the gas to expand and flow out at the appendix sufficient to offset the excess ballast, plus enough to overcome ascending momentum, after which it will at once return to earth unless ballast is released.
+
+Air Blower
+
+The use of a blower (similar to that used by the blacksmith) is often resorted to to keep the envelope fully inflated by introducing air, so that
+
+<page_number>38</page_number>
+SPHERICAL BALLOONING
+
+any increase in altitude will cause gas to flow from the appendix, which eliminates the necessity of opening the valve. The blower is secured to the inside of the basket or car and connected to the balloon with a fabric tube or hose about six inches in diameter. If there is no connection at the balloon for the hose, a thimble should be secured to the inside of the appendix ring, to which the hose may be fastened.
+
+<img>fleur-de-lis</img>
+
+Google Books
+
+SOME OF THE REQUIREMENTS <page_number>29</page_number>
+
+**VERTICAL MOVEMENT**
+
+When descending from one stratum of air to another, which is moving in a different direction or in the same direction at a different velocity, or not moving, on the surface of the earth, the decrease of pressure on the surface of its lower hemisphere sufficient to reduce the rate of fall or cause it to ascend.
+
+<img>(A) Diagram showing buoyant effect of contrary air currents.</img>
+<watermark>Foto Register of Statesman</watermark>
+
+Great differences in the velocity of air strata will sometimes cause a balloon to seem to oscillate when in fact the gas is contracting. In this event the surprise will come when the excess ballast becomes sufficient to overcome the upward "kick" of the lower stratum and pull the balloon down into it, requiring the discharge of the excess ballast, plus a sufficient amount to overcome momentum after which it will generally appear that the balloon has fallen into an 'air pocket.'
+
+Faro irregularity, as described above, is generally accompanied by one in the reading of the stasoscope which will register very small differences in air pressure. This indication is produced by wind pressure against the diaphragm or liquid in the instrument.
+
+<img>(B) Diagram showing direction of movement of upper stratum of air.</img>
+<img>(C) Diagram showing direction of movement of middle stratum of air.</img>
+
+<page_number>30</page_number>
+SPHERICAL BALLOONING
+
+When ascending from one stratum of air into another the opposite effect is produced due to the upper surface of the sphere striking the lower side of the opposite stratum. This effect is most evident when a balloon is released in still air and ascends to a stratum of high velocity at low altitude.
+
+All variable horizontal air currents are favorable to landing, so far as checking a fall is concerned, inasmuch as the lower surface of the balloon being spherical has a tendency to glance up or away from each stratum which is not moving in the same direction at the same rate of speed. This accounts for the fact that quite often a balloon will act very erratically at first but on landing it seems to take its life and exhibit a remarkable ability to drop and land beautifully without any coaching or assistance from the pilot, so that—other things being equal—the more contrary the air currents the less difficult it is to keep a balloon at a given altitude, because of the energy displayed by strata No. 1 and No. 5 in keeping the balloon in its stratum No. 2, Fig. 5.
+
+<img>Google logo</img>
+
+SOME OF THE REQUIREMENTS <page_number>31</page_number>
+
+**A FALSE START**
+
+When a balloon is being "weighed off", its horizontal speed is less than the velocity of the wind which strikes the sphere, divides at its equator and passes over and under, producing a downward pressure on the surface of the upper hemisphere and an upward pressure on the surface of the lower hemisphere. The resultant forces which are equal when the balloon is at a considerable altitude; but when it is near the earth the pressure on the surface of the lower hemisphere is greater, due to the air becoming compressed between the lowest part of the sphere and the surface of the earth, producing a pneumatic effect sufficient to lift considerable ballast, the amount depending on the velocity of the wind.
+
+If there be no movement of air, the chance of making a false start is very remote. The time required for a balloon to attain its maximum horizontal velocity or zero velocity relative to the wind may be determined by hanging a long string fifty or one hundred feet in length from the basket. The lowest end of the string will be in the basket until the balloon "catches" with the wind, then after which the string will hang perfectly straight if the velocity of the wind is uniform. This difference may also be determined by releasing tissue paper.
+
+As soon as the balloon is released the pneumatic effect will disappear for two reasons. First: The velocity of the wind relative to that of the balloon reduces. Second: The distance between the earth's surface and balloon is so great that the wedging effect of the wind is no longer apparent, therefore the balloon will fall if the excess ballast is not at once released.
+
+To Determine Relative Speed of Wind and Balloon
+
+<img>A diagram showing a balloon being weighed off, with arrows indicating wind direction and pressure differences.</img>
+
+<page_number>32</page_number>
+SPHERICAL BALLOONING
+
+AIR WEDGE AND THE "PENGUIN"
+
+A striking example of the wedging effect of the wind may be observed in the action of the "Pen-
+guin," a type of aeroplane used for training pur-
+poses. It has just sufficient power to attain an alti-
+tude of a few feet only, which is the critical altitude
+for its maximum speed.
+
+<img>A Penguin Airplane showing comparison of air
+speed under wing and body
+and the earth.</img>
+
+Leakage
+
+The altitude is limited by a reduction in air
+pressure between the wings and the earth by what
+might be termed leakage. That is, assume the
+earth to represent one side of an air tank which will
+be filled air under pressure. The plane of the aer-
+oplane representing the upper part of the tank, and
+the opening at the rear, and at both ends between
+the plane and the earth representing leakage, and
+the opening between the front edge of the plane
+and the earth representing the supply opening. It
+will be observed that if the plane is near the earth
+that the rear edge will be so near the earth that
+the leakage would be small compared to the inlet
+represented by the large opening between the front
+edge of the plane and the earth due to this edge
+being much farther from the earth. If the plane
+were one inch from the earth at the rear edge and
+ten inches from the earth at the front, or entering
+edge, the ratio of leakage to that of supply would
+be one to ten, or 10 per cent, but if the plane
+
+SOME OF THE REQUIREMENTS <page_number>33</page_number>
+
+were one hundred inches from the earth the ratio would be one hundred one to one hundred ten, or more than 90 per cent; this comparative leakage being so great that the pressure in the "tank" could not be kept sufficiently high to sustain the weight.
+
+<img>fleur-de-lis</img>
+<watermark>Google</watermark>
+
+<page_number>34</page_number>
+SPHERICAL BALLOONING
+
+AIR RESISTANCE TO VERTICAL MOVEMENT
+
+For example, if an 80,000 cubic feet balloon full of gas at an altitude of 1,608 feet were not supported by the atmosphere or any other substance,
+i. e., had nothing in which to float, it would fall in accord with the law of the acceleration of freely falling bodies. The first second it would fall 32.16 feet;
+the second second it would fall a total distance of
+64.32 feet, continuing in acceleration until, after having fallen a distance of 1,608 feet, it would have attained a velocity of 32.16 feet per second, or nearly by the mile in two minutes. The little pressure of the gas and amount of ballast on the weight would make no difference, as it would be falling in a vacuum where, if two balloons—one filled with hydrogen gas and the other filled with lead—were released at the same time and same altitude, they would strike the earth at the same instant and at the same velocity.
+
+However, these are not existing conditions, as we have the atmosphere which is only not buoyant but also offers resistance to the relative movement of all substances so that a balloon containing 80,- 000 cubic feet of gas weighing 1,000 pounds or 40 pounds per 1,000, would be at rest vertically or at an equilibrium with a total load of 3,200 pounds; assuming that 1,000 cubic feet of gas has been released and that no expansion has taken place, the balloon will descend, accelerating in its downward movement until the air resistance, vertically, exactly balances the 40 pounds of ballast which is represented by the 1,000 cubic feet of gas released.
+
+The greatest cross sectional area of a spherical balloon, with a volume of 80,000 cubic feet, is 2,246 square feet; so that an upward pressure of .018—pounds per square foot on the under surface
+
+<img>Google logo</img>
+
+SOME OF THE REQUIREMENTS <page_number>35</page_number>
+
+of the balloon would be required to entirely eliminate acceleration.
+
+Velocity of Fall
+
+Falling at the rate of 4.5 feet per second will produce the above required pressure so that regardless of the altitude the rate of fall cannot be greater than 4.5 feet per second (disregarding difference in density of atmosphere), which is not at all alarming when we consider that a man falling from a height of eight or ten feet, which is not at all dangerous, we will gain a velocity of about fifteen or twenty feet per second.
+
+Theoretically the ascending acceleration would be limited just the same as descending; that is, if 40 pounds of ballast be released, the speed upward could be no more than 4.5 feet per second, the temperature remaining constant.
+
+Assuming that the appendix rope is tied and that the balloon remains spherical, without releasing ballast the maximum rate of descent would be as follows: After releasing
+
+\begin{array}{lll}
+2,000 \text{ cubic feet of gas} & 5.5 \text{ feet per second} \\
+3,000 \text{ cubic feet of gas} & 7.5 \text{ feet per second} \\
+4,000 \text{ cubic feet of gas} & 9.75 \text{ feet per second} \\
+5,000 \text{ cubic feet of gas} & 10.5 \text{ feet per second} \\
+10,000 \text{ cubic feet of gas} & 14.5 \text{ feet per second}
+\end{array}
+
+If the rip panel were pulled down at a great altitude, and the balloon allowed to parachute, the maximum rate of fall with a load of 1,200 pounds (the approximate weight of the balloon and two men) would be about 14 feet per second. If the appendix rope be released and the lower part of the balloon be allowed to concave as the gas is released, the rate of fall will be considerably reduced if the descent is rapid.
+
+Difficulties at Great Altitude
+
+<page_number>36</page_number>
+SPHERICAL BALLOONING
+
+When to Tie Appendix Rope
+
+Therefore, it is important to make sure the lower end of the appendix rope is not tied to the load ring until coming down to land, at which time it is of great importance to take the slack out of the appendix rope with a pull of about 100 pounds, and
+
+Must be on same side
+
+Appendix rope must be opposite drag rope
+
+FIG. 7
+
+tie it securely to the load ring, directly opposite to the drag rope, so that the basket will have more of a tendency to remain in an upright position when landing.
+
+<img>A diagram showing the correct placement of the appendix rope relative to the load ring and drag rope.</img>
+
+<watermark>Google</watermark>
+
+SOME OF THE REQUIREMENTS <page_number>37</page_number>
+
+**LANDING NEAR TIMBER**
+
+A Common Mistake
+
+This illustration represents a method of landing in a small clearing in the timber, the difficulty of which increases with the velocity of the wind. A common mistake in making this landing is that of valving too late or releasing too much ballast, resulting in a landing on the far side of the field.
+
+<img>A diagram showing a landing near trees. The wind is blowing from left to right. The plane is shown with its nose pointing towards the trees. The caption reads "Landing in high wind, protected by trees."</img>
+FIG. 8
+
+where the envelope and net might be damaged by the trees. In making a landing of this kind it is best to reduce the altitude to at least the length of the rope between the trees, and to land directly under them because the chance of a miss and the altitude increases in a direct ratio. That is, the error would be only one-half as great at 500 feet as it would be at 1,000 feet.
+
+<watermark>Google</watermark>
+
+<page_number>38</page_number>
+SPHERICAL BALLOONING
+
+FUNCTION OF THE DRAG ROPE
+
+Definition
+The drag rope is nothing more nor less than a brake-rope while it is in contact with the earth, as it brakes both the vertical as well as the horizontal motion of the balloon. That which checks the fall and reduces the speed at land, besides causing the balloon to become so poised when landing that
+
+<img>A diagram showing a section of a drag rope. The text reads: "Section of drag rope - Keep it tight so it will pay out from the inside." A note on the right side of the diagram says "The 1/10 McKibben Roll." A small illustration shows a roll of McKibben Roll.</img>
+
+The rip panel will be at the highest point in the envelope, which insures most rapid deflation when panel is removed.
+
+There is but one correct place to locate the drag rope toggle, and that is directly under the rip panel. (See Fig. 7.)
+
+An automobile may be guided in a horizontal direction only. A balloon may be guided in a vertical direction only, so that the drag rope may also be called the guide rope inasmuch as it automatically guides the balloon vertically when it is in contact with the earth. It also acts as a guide or pointer which to determine the direction of horizontal movement.
+
+To roll the drag rope, begin about one foot from the loop end and make four coils about four
+
+To Roll the Drag Rope
+
+<watermark>Google</watermark>
+
+SOME OF THE REQUIREMENTS <page_number>39</page_number>
+
+inches in diameter, forming a convolution as shown in Figure 9. Roll into a compact ball and bind it with about one-eighth inch twine, so that coils do not fall away from the outside of the ball. Secure a stout cord or small rope to one of the coils of rope just below the basket ropes, and attach this to the basket ropes. Be sure and connect loop end of rope to drag rope toggle. Just before releasing the drag rope be sure and remove all of the string or cord from the roll and cut the string which secures it to the basket rope, so that no part of the string falls. This kind of a roll pays out from the inside and does not shake or jar the balloon.
+
+Weight of Drag Rope
+
+The drag rope should weigh from 2⅔ to 5 pounds for each one hundred pounds of the total ascensive force of the gas in the balloon, and should be from two hundred fifty to three hundred fifty feet in length.
+
+<img>Google logo</img>
+
+<page_number>40</page_number>
+SPHERICAL BALLOONING
+
+THE ANCHOR
+
+If the wind velocity is very high there is nothing certain as to just when an anchor will find something to hold it, therefore it might cause a landing at an undesirable place. Also, if the balloon is carrying too much ballast to permit the use of the anchor rope just as it takes hold, the basket will describe an arc and strike the earth with considerable violence, unless an excess amount of ballast be released.
+
+Throwing the Anchor
+
+Never throw the anchor at an altitude as great as the length of the rope, making sure there is something to stop it. The rip panel when used should be pulled down at an altitude of not more than ten to thirty feet while descending. This method is the best method of deflating and should be used in preference to diving, unless it is inconvenient to replace the panel.
+
+Be sure to place all sand ballast in the bottom of the basket along the sides or corner that strikes first, otherwise it may ride the passengers, or if left on the basket ropes will, by its inertia, pull the basket over.
+
+Paints on Landing
+
+It is important to place the feet properly on the bottom of the basket, bend the knees, hold on to something substantial, know when the basket will land and keep out of range of the load ring.
+
+<img>Google logo</img>
+
+SOME OF THE REQUIREMENTS <page_number>41</page_number>
+
+NEGLIGIBLE QUANTITIES
+
+Difference in ratio of expansion due to temperature between air and gas, which is a very small fraction of the total, would cause the weight of air displaced by ballast and other noncompressible substances, such as pilot aid equipment, etc., i. e., the air displaced by twelve cubic feet of solid substance would weigh one pound at sea level, but at an altitude of about 18,000 feet it would weigh but one-half pound. Eighty thousand cubic feet of coal gas will displace one hundred and fifty pounds of air at sea level, so that at an altitude of about 18,000 feet the load would be two pounds heavier, because at the greater altitude the air is but one-half as buoyant as it is at sea level.
+
+Shaking the car or basket by impulsive moving will cause gas to "slop out" at the appendix, but not in sufficient quantities to noticeably rupture equilibrium. However, if such impulsive movement of the car or basket occurs near the critical point of contraction, the net will slip on the envelope, causing it to become more elongated and smaller in diameter. This will result in a loss of a considerable quantity of gas, if it so happens that the envelope is just at the turning point from contraction to expansion.
+
+Change in relative density of the gas, due to column compression which varies with an increase or decrease in the vertical diameter of the balloon, i. e., a pear-shaped balloon, would have the same number of pounds of gas have greater ascensional force if the envelope were placed 90 degrees out of vertical. The ascensional force of a sausage-shaped balloon is greater when in normal position than if it "stood on end." The column pressure in any free balloon diminishes as the flight progresses.
+
+<img>Image of a page from a book.</img>
+<watermark>Google</watermark>
+
+<page_number>42</page_number>
+SPHERICAL BALLOONING
+
+At an altitude of 4,000 miles, a 180-pound man would weigh but 90 pounds, so that while ascend-
+ing the load gets lighter, due to diminishing force of gravity, which does not affect the weight of air in the same ratio.
+
+Location as to latitude is taken into considera-
+tion when the weight of air is to be very accurately determined. However, outside of weather condi-
+tions, there is no noticeable effect on ballooning.
+
+<img>fleur-de-lis</img>
+
+Google Books
+
+SOME OF THE REQUIREMENTS <page_number>43</page_number>
+
+**IF'S**
+
+If a sufficient amount of ballast be released a balloon will ascend.
+
+If a sufficient amount of gas be released a balloon will descend.
+
+If ballast be released the balloon will fall, if contraction is sufficiently rapid.
+
+If gas be released the balloon will ascend, if expansion is sufficiently rapid.
+
+If a balloon descends, due to cloud shade, and gas be released, it will ascend if the sun returns sufficiently quick and hot.
+
+If a balloon is ascending and ballast be released, it will at once descend if contraction, due to cloud shade, is sufficiently rapid.
+
+If a balloon is descending, due to cloud shade, it is not necessary to release ballast if the sun comes out sufficiently quick and hot.
+
+If a balloon is ascending, due to sunshine, it will check and descend if a sufficiently effective cloud shade is encountered.
+
+If a balloon leaks gas, gas must be released to maintain an equilibrium if expansion is sufficiently rapid.
+
+If a balloon ascends, due to light load, it will continue until gas flows out at the appendix, unless the correction is previously made by contraction.
+
+If a balloon ascends to another stratum of air, it will receive a thrust tending to force it down.
+
+If a balloon descends into another stratum of air, it will receive a thrust tending to force it upward.
+
+<img>Google logo</img>
+
+<page_number>44</page_number>
+
+SPHERICAL BALLOONING
+
+If two or three bags of ballast are accidentally released and the panel is ripped out at from ten to twenty feet on the way down, a safe landing will be made.
+
+If two or three bags of ballast are accidentally released and the panel is ripped out at from ten to twenty feet on the way up, a dangerous altitude will be attained by the time the gas is all out.
+
+If two bags of ballast are required to check a fall when the balloon is fully inflated with gas, it will require one-half of the total amount of ballast in position after one-half of the assentive force has been lost; i. e., the amount of ballast or gas required to be released when making a correction diminishes as the flight progresses. The same holds good as to the effectiveness of the valve unless air has entered the balloon.
+
+If a flight is made without releasing ballast, the drag rope, to be equally effective in checking vertical movement, should be just two times as heavy as required if one-half of the gas and ballast were released. Therefore, the novice who has lost all of the ballast on account of not knowing how to receive much more air from the drag rope than will the professional who has by constant keen observation succeeded in conserving practically all of the ballast.
+
+If it is required to know the exact amount of ballast and gas to be released to produce certain results, it is necessary to know the total assentive force of the gas, which force diminishes as the flight progresses. Therefore, it is impossible to furnish tables showing the amount of ballast or gas required to be released in practice to produce certain results, so observe the statoscope and barometer and work accordingly.
+
+<img>Google logo</img>
+
+SOME OF THE REQUIREMENTS <page_number>45</page_number>
+
+If too much ballast is retained it will perform work by delivering energy to the total load in the shape of downward momentum. One pound excess ballast will do as much work in ten minutes as ten pounds will do in one minute, so release it as soon as possible.
+
+If the descent is rapid it is accelerated by contraction due to fanning through the air.
+
+If the ascent is rapid it will be retarded, due to the same cause.
+
+If all of the surplus ballast is not placed along the inside of the basket, opposite to the drag rope, it may get knocked off or injure some one in the basket when landing.
+
+If the wind velocity is more than 15 miles per hour, the semidia rope should be tied to the load ring and the appendix left tied so the gas cannot get out until the balloon has left the ground, because the gas blows out and allows the balloon to parachute, making it difficult to manage. Be sure to break the appendix string and loosen the rope under an altitude of 50 or 75 feet.
+
+If, when landing, a springing position is not assumed, in addition to a secure hold on the ropes or basket, and the head is not kept out of range of the load ring, the pleasure of the trip may be somewhat lessened.
+
+<img>Google logo</img>
+
+<page_number>46</page_number>
+SPHERICAL BALLOONING
+
+<img>A diagram showing the relationship between the circumference of a circle and its diameter. The diagram includes labels A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z.</img>
+
+How to lay out pattern for balloon envelope
+
+AUG 13 1918
+
+<img>D A b d a</img>
+<watermark>Cutter</watermark>
+
+**STATOSCOPE**
+
+<table>
+  <tr>
+    <td>(a) Glass tube containing liquid, with a porous stopper (b) Porous stopper (c) Glass tube containing liquid (d) Porous stopper (e) Porous stopper (f) Porous stopper (g) Porous stopper (h) Porous stopper (i) Porous stopper (j) Porous stopper (k) Porous stopper (l) Porous stopper (m) Porous stopper (n) Porous stopper (o) Porous stopper (p) Porous stopper (q) Porous stopper (r) Porous stopper (s) Porous stopper (t) Porous stopper (u) Porous stopper (v) Porous stopper (w) Porous stopper (x) Porous stopper (y) Porous stopper (z) Porous stopper)</td>
+    <td>(a) Thermometer tube<br>(b) Open to atmosphere<br>(c) Open to atmosphere<br>(d) Open to atmosphere<br>(e) Open to atmosphere<br>(f) Open to atmosphere<br>(g) Open to atmosphere<br>(h) Open to atmosphere<br>(i) Open to atmosphere<br>(j) Open to atmosphere<br>(k) Open to atmosphere<br>(l) Open to atmosphere<br>(m) Open to atmosphere<br>(n) Open to atmosphere<br>(o) Open to atmosphere<br>(p) Open to atmosphere<br>(q) Open to atmosphere<br>(r) Open to atmosphere<br>(s) Open to atmosphere<br>(t) Open to atmosphere<br>(u) Open to atmosphere<br>(v) Open to atmosphere<br>(w) Open to atmosphere<br>(x) Open to atmosphere<br>(y) Open to atmosphere<br>(z) Open to atmosphere)</td>
+  </tr>
+</table>
+
+<img>D A b d a</img>
+<watermark>Excess for counting</watermark>
+
+<img>D A b d a</img>
+<watermark>The thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a</img>
+<watermark>Thermometer tube</watermark>
+
+<img>D A b d a></img><br/>
+<p><page_number>Pg. 11.</page_number></p>
+
+<watermark>Google</watermark>
+
+<img>A brown textured background with faint, irregular patterns.</img>
+<watermark>Copyright © 2023</watermark>

Airships/the_aerodynamic_forces_on_airships_1922.md

@@ -0,0 +1,169 @@
+NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
+
+JUL 13 1922
+MAILED
+
+TO: WH. Tassett
+
+TECHNICAL NOTES
+
+NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS:
+
+No. 108
+
+NOTES ON AERODYNAMIC FORCES - III.
+The Aerodynamic Forces on Airships.
+By Max M. Munk.
+
+July, 1923.
+
+NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS.
+
+TECHNICAL NOTE NO. 106.
+
+NOTES ON AERODYNAMIC FORCES - III.
+The Aerodynamic Forces on Airships.
+By Max M. Munk.
+
+Summary.
+
+The results of the two preceding notes are applied to air-ships and checked with wind tunnel tests.
+
+1. The Air Forces Observed on an Airship Model.
+
+In the first two notes of this series I discussed the dynam- ical forces of bodies moving along a straight or curved path in a perfect fluid. In particular I considered the case of a straight and very elongated body and as special case again if bounded by a surface of revolution.
+
+The hulls of modern rigid airships are mostly surfaces of rev-olution and rather elongated ones too. The ratio of the length to the greatest diameter varies from 6 to 10. With this elongation, particularly if greater than 8, the relations valid for infinite elongation require only a small correction, only a few percent, which can be estimated from the case of ellipsoids for which the forces are known for any elongation. It is true that the trans-
+
+- 3 -
+
+verse forces are not only increased or decreased uniformly, but also the character of their distribution is slightly changed.
+But this can be neglected for most practical applications, and especially so since there are other differences between theoretical and the actual phenomena.
+
+Serious differences are implied by the assumption that the air is a perfect fluid. It is not, and as a consequence the air forces do not agree with those in a perfect fluid. The resulting air force is by no means a resulting moment only; it is well known that the airship hull experiences both a drag and a lift, if inclined. The discussion of the drag is beyond the scope of this note. The lift is very small, less than one percent of the lift of a wing with the same surface area. But the resulting moment is comparatively small too, and thus it happens as it appears from model tests with hulls, that the resulting moment about the center of volume is only about 70% of that expected in a perfect fluid.
+It appears however that the actual resulting moment is at least of the same range of magnitude and the contemplation of the perfect fluid gives therefore an explanation of the phenomenon. The difference can be explained. The flow is not perfectly irrotational but there are free vortices near the hull, especially at its rear end, when the air leaves the hull. They give a lift acting at the rear end of the hull and hence decreasing the unstable moment with respect to the center of volume. What is perhaps more important, they produce a kind of induced downwash, diminishing the effective angle of attack and hence the unstable moment.
+
+- 3 -
+
+This refers to airship hulls without fins, which are of no practical interest. Airship hulls with fins must be considered in a different way. The fins are a kind of wings and the flow around them, if they are inclined, is far from being even approximately irrotational and their lift is not zero. The circulation of the inclined fins is not zero and as they are arranged in the rear of the ship, the vertical flow induced by the fins around the hull is directed upwards if the ship is nosed up. Therefore the effective angle of attack is increased and the influence of the lift of the hull itself is counteracted. For this reason it is to be expected that the transverse forces of hulls with fins in air agree better with these in a perfect fluid. Some model tests to be discussed now confirm this.
+
+These tests give the lift and the moment with respect to the center of volume at different angles of attack and with two different sizes of fins. Compute the difference between the observed moment and the expected moment of the hull alone, and divide the difference by the observed lift. The apparent center of pressure of the lift of the fins results. If this center of pressure is situated near the middle of the fins, and it is, it can be inferred that the actual flow of the air around the hull is not very different from the flow of a perfect fluid. It follows then that the distribution of the transverse forces in a perfect fluid gives a good approximation of the actual distribution and not only for the case of straight flight under consideration, but also if the ship moves along a circular path.
+
+- 4 -
+
+The model tests which I proceed to use were made by Georg Fuhrmann in the old Göttingen wind tunnel and published in the Zeitschrift für Flugtechnik und Motorluftschiffahrt, 1910. The model, represented in Fig. 1, had a length of 1145 mm., a maximum diameter of 188 mm., and a volume of 0.0182 cu.m. Two sets of fins were attached to the hull, one after another; the smaller fins were rectangular, 6.5 x 13 cm., and the larger ones, 8 x 15 cm. (Volume)²/³ = 0.069 sq.m. In Fig. 1, both fins are put in.
+
+The diagram in Fig. 2 gives both the observed lift and the moment with respect to pV, expressed by means of absolute coefficients. They are reduced to the unit of the dynamical pressure and also the moment is reduced to the unit of the volume, and the lift to the unit of (Volume)²/³.
+
+Diagram Fig. 3 shows the position of the center of pressure computed as described before, and expressed as fraction of the entire length. The two horizontal lines represent the leading and the trailing end of the fins. It appears that for both sizes of the fins the curves nearly agree, particularly for greater angles of attack at which the tests are more accurate. The center of pressure is situated at about 40% of the chord of the fins.
+
+I conclude from this that the theory of a perfect fluid gives a good indication of the actual distribution of the transverse forces. Due to the small scale of the model, the agreement may be even better with actual airships.
+
+- 5 -
+
+2. Remark on the Required Size of the Fins.
+
+The last examination seems to indicate that the unstable moment of the hull agrees nearly with that in a perfect fluid. Now the actual airships with fins are statically unstable, but not much so, and for the present general discussion it can be assumed that the unstable moment of the hull is nearly neutralized by the transverse force of the fins. I have shown that this unstable moment is $M = (Volume) \left( k_2 - k_1 \right) V^2 \frac{D}{B} \sin 2\alpha$, where $\left( k_2 - k_1 \right)$ denotes the factor of correction due to finite elongation. Its magnitude is discussed in the first note of this series. Hence the transverse force of the fins must be about $\frac{M}{a}$ where $a$ denotes the distance between the fin and the center of gravity of the ship. Then the effective area of the fins, that is, the area of a wing giving the same lift in a two-dimensional flow follows:
+
+$$\frac{(Volume) \left( k_2 - k_1 \right)}{a}$$
+
+Taking into account the span $b$ of the fins, that is, the distance of two utmost points of a pair of fins, the effective fin area $S$ must be
+
+$$\frac{(Volume) \left( k_2 - k_1 \right)}{a} \times \frac{1 + 2\frac{S}{b}}{\pi}$$
+
+This area $S$ however is greater than the actual fin area. Its exact size is uncertain but a far better approximation than the fin area is obtained by taking the projection of the fine and...
+
+- 6 -
+
+the part of the hull between them. This is particularly true if the diameter of the hull between the fins is small.
+
+If the ends of two airships are similar, it follows that the fin area must be proportional to (Volume)/a or, less exact, to the greatest cross section rather than to (Volume)^(2/3).
+
+This refers to circular section airships. Hulls with elliptical section require greater fins parallel to the greater plan view. If the greater axis of the ellipse is horizontal, such ships are subjected to the same bending moments for equal lift and size, but the section modulus is smaller, and hence the stresses are increased. They require, however, a smaller angle of attack for the same lift. The reverse holds true for elliptical sections with the greater axes vertical.
+
+3. The Airship in Circular Flight.
+
+If the airship flies along a circular path, the centrifugal force must be neutralized by the transverse force of the fin, for only the fin gives a considerable resultant transverse force. At the same time the fin is supposed nearly to neutralize the unstable moment. I have shown now in the previous note that the angular velocity, though indeed producing a considerable change of the distribution of the transverse forces, and hence of the bending moments, does not give rise to a resulting force or moment. Hence the ship flying along the circular path must be inclined by the same angle as if the transverse force is produced during a rectilinear flight. From the equation of the transverse force
+
+- 7 -
+
+$$\text{Vol} \rho \frac{V^2}{R} = \frac{\text{Vol} (k_2 - k_1) V^2 \frac{\rho}{2} \sin 2\alpha}{a}$$
+
+it follows that approximately the angle is
+
+$$\alpha \sim \frac{a}{R} \frac{1}{k_2 - k_1}$$
+
+This expression in turn can be used for the determination of the distribution of the transverse forces due to the inclination.
+
+The resultant transverse force is produced by the inclination of the fins. The rotation of the rudder has chiefly the purpose of neutralizing the damping moment of the fins themselves.
+
+From the last relation follows the distribution of the transverse forces due to the inclination
+
+(1)
+
+$$\frac{dS}{dx} V^2 \frac{\rho}{2} \frac{2a}{R} dx$$
+
+This is only one part of the transverse forces. The other part is due to the angular velocity, it is approximately
+
+(2)
+
+$$k_2 \frac{2x}{R} \frac{dS}{dx} V^2 \frac{\rho}{2} dx + (k_2 + \sin \alpha) V^2 \frac{\rho}{R} S dx,$$
+
+as proven in the previous note. Another secondary term, mentioned in the second note, can be neglected. The first term in (2) together with (1) gives a part of the bending moment. The second term in (2) (having the opposite direction as the first one and as the centrifugal force) is almost neutralized by the centrifugal forces of the ship and gives additional bending moments not very considerable either. It appears then that the ship experi-
+
+- 8 -
+
+ences smaller bending moments when creating an air force opposite to the centrifugal force than when creating the same transverse force during a straight flight. For ships with elliptical sections this cannot be said so generally. The second term in (2) will then less perfectly neutralize the centrifugal force, if that can be said at all and the bending moments become greater in most cases.
+
+<img>A diagram showing a streamlined body with fins attached to its sides. The fins are labeled 'a' and 'b'. The diagram is labeled "Fig. 1."</img>
+
+Small fin
+
+Large fin
+
+Edges of fin
+
+Fig. 3.
+
+Angle of attack.
+
+0° 2° 4° 6° 8° 10° 12° 14° 16° 18°
+
+5.0
+4.5
+4.0
+3.5
+3.0
+2.5
+2.0
+1.5
+1.0
++5
+-5
+0
+1.0
+1.5
+2.0
+2.5
+3.0
+
+a
+
+b
+
+Lift coefficient
+
+Moment coefficient
+
+Fig. 2. - Angle of attack.
+
+<page_number>18°</page_number>
+<page_number>16°</page_number>
+<page_number>14°</page_number>
+<page_number>12°</page_number>
+<page_number>10°</page_number>
+<page_number>8°</page_number>
+<page_number>6°</page_number>
+<page_number>4°</page_number>
+<page_number>2°</page_number>
+<page_number>0°</page_number>

Airships/the_dead_weight_of_the_airship_and_the_number_of_passengers_that_can_be_carried_1922.md

@@ -0,0 +1,1758 @@
+TECHNICAL NOTES.
+NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS.
+
+No. 80.
+
+THE DEAD WEIGHT OF THE AIRSHIP
+and
+THE NUMBER OF PASSENGERS THAT CAN BE CARRIED.
+By
+Colonel Crocco.
+
+Extract from
+the Transactions of the Aeronautical Experimental Institute
+Rome, Italy, September, 1920.
+
+January, 1923.
+
+NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS.
+
+TECHNICAL NOTE NO. 80.
+
+THE DEAD WEIGHT OF THE AIRSHIP
+
+and
+
+THE NUMBER OF PASSENGERS THAT CAN BE CARRIED.*
+
+By
+
+Colonel Crooco.
+
+Formula for Obtaining Weight of Dead Load.
+
+In order to determine an approximate formula giving the weight of the dead load in function of the volume $V$ of the envelope and of the maximum velocity $v$, we will take the relative weight of the various parts of the airships $P^V$, $M$, $V$, $A$, $T^3$, adopting a mean value of the coefficients determined.
+
+This formula may be adopted both for semi-rigid airships with suspended nacelle and non-rigid envelope, with or without internal suspensions, and to airships with rigid longitudinal
+
+* In 1913, comparing the effect of increase of dimensions in airplanes and airships, I demonstrated in a lecture given at the Congress of Engineers, Rome "The Catastrophe of the L.A. and the Future of Airships", published in the Journal of Italian Engineers and Architects No. 8, March 1, 1914) that there was a fairly approximate limit of gain for the airplane, and that though such a limit was a little more extended for the airship it nevertheless existed.
+
+Some years later, after the War, in a publication of the British Aeronautical Society appeared similar calculations showing the advisability of increasing the cubature of airships without setting any limit to such increase. wishing therefore to find a complete and practical solution of the problem by means of strict numerical calculations, we confided such calculations to Signor Primo Gellini, who from the very first, has made the computation for our airships. The result shows that there is an O.P.I.-H.U. variation between 500 and 700 cubic meters per ton of load at about 270,000 cubic meters, and that practically the increase of cubature beyond this limit and even up to it, hardly compensates for the greater commercial risk incurred by the concentration of tornage.
+
+Extract from the Transactions of the Aeronautical Experimental Institute, Rome, Italy, (September, 1920).
+
+- 2 -
+
+beam, with power units on external supports or in nacelles,
+and with non-rigid envelopes, with or without internal bracing
+cables.
+
+Weight of the envelope. - The envelope consists of various parts:
+
+1st. Rubber on the outer reinforced part (about 0.80 kg.
+per square meter); its weight is proportional to the surface,
+\((V^{2/3})\).
+
+2nd. Fabric of the outer reinforced part; its weight is
+proportional to the surface \((V^{2/3})\) and to the tension, which
+increases according to the pressure \((V^{1/3})\) and the diameter
+\((V^{1/3})\). Therefore the weight of the fabric increases as
+
+\[ V^{2/3} V^{1/3} = V^{4/3} \]
+
+3rd. The inside portion of the reinforced part (internal
+bracing cables) proportional to the Volume \(V\).
+
+4th. The diaphragms and butte proportional to their number
+\(n\), and to the surface \((V^{2/3})\).
+
+5th. Interior balloonet on beam, tubes, etc., proportional
+to the surface area \((V^{2/3})\).
+
+N.B. For all the envelopes enumerated below, the volume of
+the balloonet = 0.5 of the envelope.
+
+- 3 -
+
+<table>
+  <tr>
+    <td>Airships</td>
+    <td>Volume</td>
+    <td>Rubber outer reinforced part</td>
+    <td>Fabric outer reinforced part</td>
+  </tr>
+  <tr>
+    <td></td>
+    <td>cu.m.</td>
+    <td>Weight kg.</td>
+    <td>Coefficients:</td>
+    <td>Weight kg.</td>
+    <td>Coefficients</td>
+  </tr>
+  <tr>
+    <td>M<sup>A</sup></td>
+    <td>12100</td>
+    <td>705</td>
+    <td>1.34 V<sup>2/3</sup>/s</td>
+    <td>303</td>
+    <td>0.00280 V<sup>1/3</sup></td>
+  </tr>
+  <tr>
+    <td>A</td>
+    <td>18000</td>
+    <td>975</td>
+    <td>1.41 V<sup>2/3</sup>/s</td>
+    <td>1060</td>
+    <td>0.00226 V<sup>4/3</sup></td>
+  </tr>
+  <tr>
+    <td>T<sup>3*</sup></td>
+    <td>36000</td>
+    <td>1550</td>
+    <td>1.43 V<sup>2/3</sup>/s</td>
+    <td>2700</td>
+    <td>0.00227 V<sup>4/3</sup></td>
+  </tr>
+  <tr>
+    <td colspan="2">Mean Coefficient</td>
+    <td>1.39 V<sup>2/3</sup>/s</td>
+    <td></td>
+    <td colspan="2">0.00227 V<sup>4/3</sup></td>
+  </tr>
+</table>
+
+<table>
+  <tr>
+    <td>Airships</td>
+    <td>Internal bracing cables.</td>
+    <td>Disphragm and Butts</td>
+    <td>Inner Ballonet on beam, tubes etc.</td>
+  </tr>
+  <tr>
+    <td></td>
+    <td>Weight:Coeffici-ents kg.</td>
+    <td>Weight:Coefficients kg.</td>
+    <td>Weight:kg.</td>
+  </tr>
+  <tr>
+    <td>M<sup>A</sup></td>
+    <td>160 : 0.0132 V</td>
+    <td>: 300 : 0.114 n V<sup>2/3</sup></td>
+    <td>: 600 : 1.14 V<sup>a/3</sup></td>
+  </tr>
+  <tr>
+    <td>A</td>
+    <td>290 : 0.0161 V</td>
+    <td>: 830 : 0.112 n V<sup>a/3</sup></td>
+    <td>: 770 : 1.12 V<sup>a/3</sup></td>
+  </tr>
+  <tr>
+    <td>T<sup>3*</sup></td>
+    <td>585 : 0.0182 V</td>
+    <td>: 1300 : 0.120 n V<sup>a/3</sup></td>
+    <td>: 880 : 0.90 V<sup>a/3</sup></td>
+  </tr>
+  <tr>
+    <th colspan="2">Mean Coefficient: 0.0152 V:</th><th colspan="2">: 0.115 n V<sup>a/3</sup>: : 1.09 V<sup>a/3</sup></th>
+  </tr>
+</table>
+
+When the volume of the ballonet = 0.5 that of the envelope, the mean weight of the envelope is given by:
+
+$$
+\begin{align*}
+& \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \\
+& (1.59 V^{2/3} + 0.00227 V^{4/3} + 0.0152 V + 0.115 n V^{a/3} + 1.09 V^{a/3}) = \\
+& = (0.0152 V + (0.115 n + 2.48) V^{2/3} + 0.00227 V^{4/3})
+\end{align*}
+$$
+
+- 4 -
+
+**Weight of Gas and Air Valves and their Controls.** - This weight is proportional to the volume \( V \) of the envelope, and from the mean value taken for the various airships it comes out at:
+
+0.01V
+
+**Weight of the reinforced armature.** - By reinforced armature we mean the whole of the parts which help in bearing the load given by Volume - Weight of envelope and valves.
+
+or, the longitudinal beam, the nacelle suspensions with their brackets, the longitudinal girder, the reinforced sides of the nacelle and their suspension cables. The stresses in the beams of the armature are due partly to the bending moment and partly to shear, caused by the load carried: Volume - Weight of envelope and valves = \( V - I \). The bending moment produces in the beam stresses proportional to the load \( (V - I) \) and to the length of the bays \( (V^{1/3}) \) and inversely proportional to the height of the armature \( (V^{1/3}) \): that is, in all, proportional to
+
+\[
+(V - I) \frac{V^{1/3}}{V^{1/3}} = V - I.
+\]
+
+Shearing stresses are produced:
+
+1st. In the beams and their diagonals proportional to the load, the bay, and the height, as for bending moments, therefore proportional to \( V - I \).
+
+2nd. In the struts proportional to the load \( V - I \).
+
+Therefore the stresses, and with them the weight of the re-
+
+- 5 -
+
+inforced armature (longitudinal beam, suspensions, the reinforced part of the bow and nacelle suspensions, the reinforced part of the longitudinal girder, the reinforced sides of the nacelle and their suspension tubes) are proportional to the remainder of the load:
+
+Volume-Weight of envelope and valves = V - I.
+
+<table>
+  <tr>
+    <td></td>
+    <td colspan="3">Airships</td>
+  </tr>
+  <tr>
+    <td></td>
+    <td>M(heavy)</td>
+    <td>T²₄</td>
+    <td>V</td>
+  </tr>
+  <tr>
+    <td>Volume</td>
+    <td>cu.m.</td>
+    <td>18000</td>
+    <td>36000</td>
+    <td>14650</td>
+  </tr>
+  <tr>
+    <td>Envelope and valves</td>
+    <td>kg.</td>
+    <td>2690</td>
+    <td>7350</td>
+    <td>3575</td>
+  </tr>
+  <tr>
+    <td>V - I</td>
+    <td>"</td>
+    <td>9310</td>
+    <td>28650</td>
+    <td>11075</td>
+  </tr>
+  <tr>
+    <td>Reinforced Armature</td>
+    <td>"</td>
+    <td>1210</td>
+    <td>3750</td>
+    <td>1460</td>
+  </tr>
+  <tr>
+    <td>Coefficient</td>
+    <td>:</td>
+    <td>0.130 (V-I)</td>
+    <td>0.131(V-I)</td>
+    <td>: 0.132(V-I)</td>
+  </tr>
+</table>
+
+Mean Coefficient = 0.131 x (7 - I)
+
+which may also be written:
+$$
+\begin{align*}
+&= 0.131 \left[ V - [0.01 V + 0.0158 V (0.115 n + 2.48) v^{4/3} + 0.00237 v^{4/3}] \right] \\
+&= 0.131 \left[ V - (0.115 n + 2.48) v^{4/3} - 0.00237 v^{4/3} \right] \\
+&= 0.1277 V - (0.01508 n + 0.325) v^{4/3} - 0.002375 v^{4/3}
+\end{align*}
+$$
+
+**Weight of the Stiffened Part of the Bow.** The weight of this is proportional to the bending moments which it has to support.
+These moments depend on the length of the stiffened part proportional to $V^{1/3}$, to the pressure of the wind on the surface, and
+
+- 6 -
+
+to the square of the velocity, that is, to $v^2 v^{2/3}$.
+
+From this it follows that the bending moments, and therefore the weight of the stiffened part, are proportional to
+
+$$v^{1/3} v^2 v^{2/3} = v^2 V$$
+
+N.B. - While in the airships P, M, A, and V, the stiffened part is separate from the beam and therefore resists alone the external pressure, leaning on the envelope, in the airship T the envelope itself resists alone the external pressure, and leans for resisting external pressure. In the T$^{\text{st}}$, the weight indicated, 600 kg., is that of the cupola alone, as we cannot determine the weight of the beam which bears the resistance together with the stiffened part: the coefficient determined will therefore be less than the true one, and is not reckoned in determining the mean coefficient.
+
+<table>
+  <tr>
+    <td colspan="3">Airships.</td>
+  </tr>
+  <tr>
+    <td>PV</td>
+    <td>$\eta_A$</td>
+    <td>V</td>
+  </tr>
+  <tr>
+    <td>Volume cu.m.</td>
+    <td>5000</td>
+    <td>12100</td>
+    <td>15000</td>
+  </tr>
+  <tr>
+    <td>Speed km/h</td>
+    <td>86</td>
+    <td>78</td>
+    <td>82</td>
+  </tr>
+  <tr>
+    <td>Weight of stiffened part of bow kg.</td>
+    <td>66</td>
+    <td>130</td>
+    <td>180</td>
+  </tr>
+  <tr>
+    <td>Coefficient</td>
+    <td colspan="3">$0.0000238 v^2 V : 0.0000225 v^2 V : 0.0000230 v^2 V$</td>
+  </tr>
+</table>
+
+<table>
+  <tr>
+    <td colspan="3">Airships</td>
+  </tr>
+  <tr>
+    <td>A</td>
+    <td>$T^{\text{st}}$</td>
+  </tr>
+  <tr>
+    <td>Volume cu.m.</td>
+    <td>16000</td>
+    <td>36000</td>
+  </tr>
+  <tr>
+    <td>Speed km/h</td>
+    <td>83</td>
+    <td>120</td>
+  </tr>
+  <tr>
+    <td>Weight of stiffened part of bow</td>
+    <td>215</td>
+    <td>600</td>
+  </tr>
+  <tr>
+    <td>Coefficient</td>
+    <td colspan="3">$0.0000225 v^2 V : 0.0000150 v^2 V$</td>
+  </tr>
+</table>
+
+- 7 -
+
+Mean coefficient for $P^V$, $M^A$, $V$, $A$:
+
+0.0000273 $v^2V$ ($v = speed$ in m/sec.)
+
+**Weight of empennage.** - The rotating couple of the empennage are proportional to the volume $V$ and are equal to the product of the forces and their distance from the baricenter of the envelope. As the distances are proportional to $V^{1/3}$, the forces and consequently the surfaces of the empennage, and also the weight of the empennage, are proportional to:
+
+$$\frac{V}{V^{1/3}} = V^{2/3}$$
+
+**H.B.** - In order to deduce a coefficient, we must abstract from the lower reinforced keel the weight of the part considered as being incorporated with the reinforced armature. The rest of the weight of the keel we add to the weight of the upper lateral keels. In the weight of the rudders is included only the weight of the planes and frames.
+
+<table>
+  <tr>
+    <td colspan="4">Airships</td>
+  </tr>
+  <tr>
+    <td></td>
+    <td>$PV$</td>
+    <td>$MA$</td>
+    <td>$A$</td>
+    <td>$T^3$</td>
+  </tr>
+  <tr>
+    <td>Volume</td>
+    <td>5,000</td>
+    <td>12,100</td>
+    <td>18,000</td>
+    <td>36,000</td>
+  </tr>
+  <tr>
+    <td>Weight of keels</td>
+    <td>kg.</td>
+    <td>85</td>
+    <td>148</td>
+    <td>171</td>
+    <td>400</td>
+  </tr>
+  <tr>
+    <td>Coefficient</td>
+    <td></td>
+    <td>$0.39 V^{2/3}$</td>
+    <td>$0.38 V^{2/3}$</td>
+    <td>$0.35 V^{2/3}$</td>
+    <td>$0.37 V^{2/3}$</td>
+  </tr>
+  <tr>
+    <td>Weight of rudders</td>
+    <td>kg.</td>
+    <td>185</td>
+    <td>340</td>
+    <td>460</td>
+    <td>600</td>
+  </tr>
+  <tr>
+    <td>Coefficient</td>
+    <td></td>
+    <td>$0.83 V^{2/3}$</td>
+    <td>$0.65 V^{2/3}$</td>
+    <td>$0.67 V^{2/3}$</td>
+    <td>$0.55 V^{2/3}$</td>
+  </tr>
+</table>
+
+Mean coefficient of keels = 0.30 $V^{2/3}$
+
+Rudders = 0.62 $V^{2/3}$
+
+<page_number>46</page_number>
+
+Weight of Engine Sets. - In the engine sets, or power plant, are included: engines, radiators, tubes, water, oil, controls, propeller and longerons. Since head resistance varies according to the square of the speed and area ($v^2y^2/s$) and power according to $v^3y^2/s = v^3y^2/s$, the weight of the power plant will vary according to:
+
+$$v^3 y^2/s$$
+
+<table>
+  <tr>
+    <td></td>
+    <td colspan="2">Airships.</td>
+  </tr>
+  <tr>
+    <td></td>
+    <td>pV</td>
+    <td>M with wooden nacelle</td>
+  </tr>
+  <tr>
+    <td>Volume</td>
+    <td>cu.m.</td>
+    <td>5,000</td>
+    <td>13,100</td>
+  </tr>
+  <tr>
+    <td>Speed</td>
+    <td>km/h</td>
+    <td>86</td>
+    <td>83</td>
+  </tr>
+  <tr>
+    <td>Power</td>
+    <td>E.P.</td>
+    <td>420</td>
+    <td>630</td>
+  </tr>
+  <tr>
+    <td>Weight of plant</td>
+    <td>kg.</td>
+    <td>760</td>
+    <td>1170</td>
+  </tr>
+  <tr>
+    <td>Coefficient</td>
+    <td></td>
+    <td>0.000169 $v^3y^2/s$</td>
+    <td>0.000178 $v^3y^2/s$</td>
+  </tr>
+</table>
+
+<table>
+  <tr>
+    <td></td>
+    <td colspan="2">Airships.</td>
+  </tr>
+  <tr>
+    <td></td>
+    <td>A</td>
+    <td>$t^{34}$</td>
+  </tr>
+  <tr>
+    <td>Volume</td>
+    <td>cu.m.</td>
+    <td>18,000</td>
+    <td>36,000</td>
+  </tr>
+  <tr>
+    <td>Speed</td>
+    <td>km/h</td>
+    <td>86</td>
+    <td>120</td>
+  </tr>
+  <tr>
+    <td>Power</td>
+    <td>E.P.</td>
+    <td>1050</td>
+    <td>3700</td>
+  </tr>
+  <tr>
+    <td>Weight of plant</td>
+    <td>kg.</td>
+    <td>1850</td>
+    <td>4960</td>
+  </tr>
+  <tr>
+    <td>Coefficient</td>
+    <td></td>
+    <td>0.00C200 $v^3y^2/s$</td>
+    <td>0.00C133 $v^3y^2/s$</td>
+  </tr>
+</table>
+
+As the airships P', M, and A, have suspended nacelles and
+
+- 9 *
+
+are similar in type, we may deduce from then the mean coefficient for their type:
+
+$$C_{0} = 0.00168 \cdot v^3 \cdot y^{2/3} \quad (v = \text{speed per m/sec.})$$
+
+while the $T^{3/4}$, a rigid type in which only the engine set juts out, is therefore more penetrating than the preceding and has a smaller coefficient:
+
+$$C_{0} = 0.00125 \cdot v^3 \cdot y^{2/3} \quad (v = \text{speed per m/sec.})$$
+
+If, instead, we wish to have a coefficient in function of HP only, and given that all the above-named airships have light engines (about 1 kg. per HP) with wooden propellers in direct transmission, the weight of the power plant will be about:
+
+1,800 kg. per HP.
+
+Weight of Supports of Power Plant. - By supports we mean: transversal bridges, external supports, engine nacelles and the part relating to the power plant only in mixed nacelles. The mean for the foregoing airships in function of HP gives
+
+$$0.350 \text{ kg. per HP}$$
+
+Weight of the Pilot's Cabin. - This may be taken as about proportional to the volume:
+
+$$0.013 \text{ V}$$
+
+Weight of the Hoisting Cables and Holding Devices. - This may also be taken as proportional to the volume:
+
+$$0.01 \text{ V}$$
+
+<page_number>- 10 -</page_number>
+
+**Total Weight of Dead Load.** From the sum of the foregoing coefficients we have the following formula, which gives approximate-ly the total weight of the dead load in kg.:
+
+$$P = (0.175 + 0.00002275 v^2) V + (C_0 \times 9894 n + 3.075) V^{2/3} +$$
+
+$$+ 0.0019735 V^{4/3} + (\text{number HP}) 2.150$$
+
+**N.B.** As we said at the beginning, such formulas are meant to be taken as approximations, for we cannot say definitely that, with increase of cubature, the weight of the various parts of the dead load will increase exactly according to the coefficients given. In the development of the details of each project various problems may arise, the solution of which may cause increase or decrease in the weight computed by the formula. However, the values obtained by the formula are always good for a preliminary study.
+
+**Weight of Dead Load for Various Cubatures.**
+
+In order to determine the weight of the dead load* for var-ious cubatures, we will suppose that we have a profile of envelope with an aspect ratio of about 1/6, 10 diaphragms, and a maximum speed of 120 km/h. For the whole airship we will assume that the head resistance expressed in kg. is equal to:
+
+$$R = C_0 S V^2$$
+
+where $v$ = speed per m/sec. and $S$ the cross section in square meters at the point of greatest diameter. This section may be taken as
+
+$$S = 0.313 V^{2/6}$$
+
+\* This determination is much influenced by the characteristics of the airship (maximum speed, coefficient of resistance, etc.). For the present, we shall confine ourselves to the study of a type having average characteristics.
+
+- 11 -
+
+and we therefore have:
+
+$$R = 0.00302 \frac{v^3}{s} v^3$$
+
+The useful power in kilogrammeters will be:
+
+$$L = 0.00302 \frac{v^3}{s} v^3$$
+
+and the motive power in HP for a propeller efficiency = 0.7 will be:
+
+$$HP = 0.000576 \frac{v^3}{s} v^3$$
+
+With a maximum velocity of 120 km/h., the motive power in HP for the various cubatures will be:
+
+<table>
+<thead>
+<tr>
+<td>Volume</td>
+<td colspan="2">Power in HP</td>
+<td colspan="2">Power in HP</td>
+</tr>
+<tr>
+<td></td>
+<td>Total</td>
+<td>Per cu.m.</td>
+<td>Volume</td>
+<td>Total</td>
+<td>Per cu.m.</td>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>50,000</td>
+<td>2,900</td>
+<td>0.0580</td>
+<td>250,000</td>
+<td>8,470</td>
+<td>0.0338</td>
+</tr>
+<tr>
+<td>100,000</td>
+<td>4,600</td>
+<td>0.0460</td>
+<td>300,000</td>
+<td>9,570</td>
+<td>0.0319</td>
+</tr>
+<tr>
+<td>150,000</td>
+<td>6,020</td>
+<td>0.0401</td>
+<td>350,000</td>
+<td>10,600</td>
+<td>0.0303</td>
+</tr>
+<tr>
+<td>200,000</td>
+<td>7,300</td>
+<td>0.0365</td>
+<td>400,000</td>
+<td>11,570</td>
+<td>0.0289</td>
+</tr>
+</tbody>
+</table>
+
+and the weight of the dead load will be as follows:
+
+- 18 -
+
+Total and Unit Weight (per cubio meter) of the Envelope
+and Its Parts.
+
+10 Diaphragms. Volume of Ballonet = 0.5 that of the envelope:
+
+<table>
+  <tr>
+    <td rowspan="3">Volume</td>
+    <td colspan="2">Outer Rubber</td>
+    <td colspan="2">Outer Fabric</td>
+    <td colspan="2">Internal Suspension</td>
+  </tr>
+  <tr>
+    <td colspan="2"></td>
+    <td colspan="2">(reinforcing)</td>
+    <td colspan="2">(reinforcing)</td>
+  </tr>
+  <tr>
+    <td>Total</td>
+    <td>Unit</td>
+    <td>Total</td>
+    <td>Unit</td>
+    <td>Total</td>
+    <td>Unit</td>
+  </tr>
+  <tr>
+    <td>cu.m.</td>
+    <td>kg.</td>
+    <td>kg.</td>
+    <td>kg.</td>
+    <td>kg.</td>
+    <td>kg.</td>
+    <td>kg.</td>
+  </tr>
+  <tr>
+    <td>50,000</td>
+    <td>1,890</td>
+    <td>0.0375</td>
+    <td>4,200</td>
+    <td>0.0840</td>
+    <td>760</td>
+    <td>0.0153</td>
+  </tr>
+  <tr>
+    <td>100,000</td>
+    <td>3,000</td>
+    <td>0.0300</td>
+    <td>10,600</td>
+    <td>0.1060</td>
+    <td>1,520</td>
+    <td>0.0153</td>
+  </tr>
+  <tr>
+    <td>150,000</td>
+    <td>3,930</td>
+    <td>0.0268</td>
+    <td>18,180</td>
+    <td>0.1208</td>
+    <td>2,280</td>
+    <td>0.0153</td>
+  </tr>
+  <tr>
+    <td>200,000</td>
+    <td>4,765</td>
+    <td>0.0238</td>
+    <td>26,820</td>
+    <td>0.1331</td>
+    <td>3,540</td>
+    <td>0.0153</td>
+  </tr>
+  <tr>
+    <td>250,000</td>
+    <td>5,839</td>
+    <td>0.0217</td>
+    <td>35,785</td>
+    <td>0.1469</td>
+    <td>4,895</td>
+    <table><tbody><tr><th></th><th></th><th></th><th></th><th></th><th></th><th></th></tr><tr><th></th><th></th><th></th><th></th><th></th><th></th><th></th></tr><tr><th>Diafragns and Butts</th><th></th><th></th><th></th><th></th><th></th><th></th></tr><tr><th>Total Weight on Beam Tubes, etc.</th><th></th><th></th><th></th><th></th><th></th><th></th></tr></tbody></table></table>
+
+<table border="1">
+  <thead>
+    <tr style="background-color: #f2f2f2;">
+      <th rowspan="2">Total kg.</th>
+      <th rowspan="2">Unit kg.</th>
+      <th rowspan="2">Total kg.</th>
+      <th rowspan="2">Unit kg.</th>
+      <th rowspan="2">Total kg.</th>
+      <th rowspan="2">Unit kg.</th>
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+      <!-- Total Weight -->
+
+- 13 -
+
+Total and Unit Weight (per cubic meter) of Dead Load
+for a maximum velocity of 120 km/h. (33.3 m/sec.).
+
+<table>
+  <tr>
+    <td rowspan="2">Volume cu.m.</td>
+    <td colspan="2">Envelope with 10 Diaphr.</td>
+    <td colspan="2">Gas & Air Valves and Controls.</td>
+    <td colspan="2">Reinforcing Armature</td>
+  </tr>
+  <tr>
+    <td>Total kg.</td>
+    <td>Unit kg.</td>
+    <td>Total kg.</td>
+    <td>Unit kg.</td>
+    <td>Total kg.</td>
+    <td>Unit kg.</td>
+  </tr>
+  <tr>
+    <td>50,000</td>
+    <td>8,620</td>
+    <td>0.1660</td>
+    <td>500</td>
+    <td>0.010</td>
+    <td>5,190</td>
+    <td>0.1038</td>
+  </tr>
+  <tr>
+    <td>100,000</td>
+    <td>19,960</td>
+    <td>0.1986</td>
+    <td>1,000</td>
+    <td>0.010</td>
+    <td>10,350</td>
+    <td>0.1036</td>
+  </tr>
+  <tr>
+    <td>150,000</td>
+    <td>30,660</td>
+    <td>0.3042</td>
+    <td>1,500</td>
+    <td>0.010</td>
+    <td>15,450</td>
+    <td>0.1030</td>
+  </tr>
+  <tr>
+    <td>200,000</td>
+    <td>48,100</td>
+    <td>0.2165</td>
+    <td>2,500</td>
+    <td>0.010</td>
+    <td>20,450</td>
+    <td>0.1038</td>
+  </tr>
+  <tr>
+    <td>250,000</td>
+    <td>53,995</td>
+    <td>0.2165</td>
+    <td>2,500</td>
+    <td>0.010</td>
+    <td>25,350</td>
+    <td>0.1014</td>
+  </tr>
+  <tr>
+    <td>300,000</td>
+    <td>66,825</td>
+    <td>0.2229</td>
+    <td>3,575</td>
+    <td>0.016</td>
+    <td>36,375</td>
+    <td>0.1147</td>
+  </tr>
+  <tr>
+    <td>350,000</td>
+    <td>79,465</td>
+    <td>0.2279</td>
+    <td>3,575</td>
+    <table><thead><tr><th></th><th></th><th></th><th></th></tr></thead><tbody><tr><th></th><th></th><th></th><th></th></tr><tr><th></th><th></th><th></th><th></th></tr><tr><th></th><th></th><th></th><th></th></tr><tr><th></th><th></th><th></th><th></th></tr><tr><th></th><th></th><th></th><th></th></tr><tr><th></th><th></th><th></th><th></th></tr><tr><th></th><th></th><th></th><th></th></tr><tr><th></th><th></th><th></th><th></th></tr><tr><th></th><th></th><th></th><th></th></tr><tr><th></th><th></th><th></th><th></th></tr><tr><th></th><th></th><th></th><th></th></tr><tr><th>Straightened Part of the Bow Total kg.</table>>
+      &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
+      &nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nbsp;<br>&nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+      &nb...
+
+- 14 -
+
+Total and Unit Weight (per cubic meter) of Dead Load
+for a Maximum Velocity of 120 km/h. (33.3 m/sec.)
+
+<table>
+  <thead>
+    <tr>
+      <th rowspan="2">Volume cum.</th>
+      <th colspan="2">Engine Set</th>
+      <th colspan="2">Supports of Power Plant</th>
+      <th colspan="2">Cabin Control and Passengers</th>
+    </tr>
+    <tr>
+      <th>Total kg.</th>
+      <th>Unit kg.</th>
+      <th>Total kg.</th>
+      <th>Unit kg.</th>
+      <th>Total kg.</th>
+      <th>Unit kg.</th>
+    </tr>
+  </thead>
+  <tbody>
+    <tr>
+      <td>50,000</td>
+      <td>5,510</td>
+      <td>0.1102</td>
+      <td>726</td>
+      <td>0.0145</td>
+      <td>850</td>
+      <td>0.013</td>
+    </tr>
+    <tr>
+      <td>100,000</td>
+      <td>8,740</td>
+      <td>0.0874</td>
+      <td>1,150</td>
+      <td>0.0115</td>
+      <td>1,990</td>
+      <td>0.013</td>
+    </tr>
+    <tr>
+      <td>150,000</td>
+      <td>11,440</td>
+      <td>0.0763</td>
+      <td>1,506</td>
+      <td>0.0103</td>
+      <td>2,850</td>
+      <td>0.013</td>
+    </tr>
+    <tr>
+      <td>200,000</td>
+      <td>14,140</td>
+      <td>0.0694</td>
+      <td>1,762</td>
+      <td>0.0129</td>
+      <td>3,850</td>
+      <td>0.013</td>
+    </tr>
+    <tr>
+      <td>250,000</td>
+      <td>16,840</td>
+      <td>0.0664</td>
+      <td>2,120</td>
+      <td>0.0084</td>
+      <td>3,850</td>
+      <td>0.013</td>
+    </tr>
+    <tr>
+      <td>300,000</td>
+      <td>18,280</td>
+      <td>0.0646</td>
+      <td>2,390</td>
+      <td>0.0079</td>
+      <td>3,900</td>
+      <td>0.013</td>
+    </tr>
+    <tr>
+      <td>350,000</td>
+      <td>20,120</td>
+      <td>0.0575</td>
+      <td>2,855</td>
+      <td>0.0076</td>
+      <td>4,855</td>
+      <td>0.013</td>
+    </tr>
+    <tr>
+      <td>400,000</td>
+      <td>22,968</td>
+      <td>0.0556</td>
+      <td>3,299</td>
+      <td>0.0172</td>
+      <td>5,899</td>
+      <td>0.133</td>
+    </tr>
+
+    <!-- Mooring Cables: Dead Load -->
+    <!-- Total kg.: Unit kg.: Total kg.: Unit kg.: -->
+    <!-- 55, 66, 77, 88, 99 -->
+  </tbody>
+  <!-- Additional rows for other values -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+  <!-- ... -->
+
+<table border="1">
+<tr><th>Total kg.</th><th></th><th>Total kg.</th><th></th></tr><tr><th></th><th></th><th></th><th></th></tr><tr><th rowspan="2">55,66,77,88,99:</th><th rowspan="2"></th><th rowspan="2"></th><th rowspan="2"></th></tr><tr><table border="1">
+<tr><th>Total kg.</th><th></th><th>Total kg.</th><th></th></tr><tr><th rowspan="2">55,</th><th rowspan="2">66,</th><th rowspan="2">77,</th><th rowspan="2">88,</th></tr><tr><table border="1">
+<tr><th>Total kg.</th><th></th><th>Total kg.</th><th></th></tr><tr><th rowspan="2">55,</th><th rowspan="2">66,</th><th rowspan="2">77,</th><th rowspan="2">88,</th></tr><tr><table border="1">
+<tr><th>Total kg.</th><th></th><th>Total kg.</th><th></th></tr><tr><th rowspan="2">55,</th><th rowspan="2">66,</th><th rowspan="2">77,</th><th rowspan="2">88,</th></tr><tr><table border="1">
+<tr><<th>Total kg.</tha<th></tha<th>Total kg.</tha<th></tha></tr><tr><table border="1"><tbody><tr><<td colspan='3'></table></tbody></table></tbody></table></tbody></table></tbody></table></tbody></table></tbody></table></tbody></table>
+
+<table border="1">
+<tr><th>Total kg.</tha<th></tha<th>Total kg.</tha<th></tha></tr><tr><table border="1"><tbody><tr><<td colspan='3'></table></tbody></table>
+
+<table border="1">
+<tr><table border="1"><tbody><tr><table border="1"><tbody><tr><table border="1"><tbody><tr><table border="1"><tbody><tr><table border="1"><tbody><tr><table border="1"><tbody><tr><table border="1"><tbody><tr><table border="1"><tbody><tr><table border="1"><tbody><tr><table border="1"><tbody><tr><table border="1"><tbody><tr><table border="1"><tbody><tr><table border="1"><tbody><tr><table border="1"><tbody><tr><table border="1"><tbody><tr><table border="1"><tbody><tr><table border="1"><tbody><tr><table border="1"><tbody/><tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/></tfoot/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/><thead/><tbody/<
+
+- 15 -
+
+From Figs. 1 and 2 it follows that the unit weight of the envelope increases with the increase of cubature owing to the fabric of the external reinforcing part, and that, increasing the cubature up to about 300,000 m., there is an appreciable gain in the unit weight of the dead load, although this outature gives a slightly diminished unit weight and reaches a minimum between 250,000 and 300,000 cubic meters.
+
+Number of Passengers for a Given Flight.
+
+As we have said, by dead load we mean the whole of the essential parts of the structure; then, according to the duration and object of the journey, must be taken on board navigating instruments, the crew, the passengers, cabine, foodstuffs, baggage, tanks for ballast and fuel, etc.; in short, all that constitutes the load to be carried and which, varying from time to time, forms, together with the dead load, the fixed load.
+
+As a first approximation, we may take the weight (in kg.) of the load which can be carried as follows:
+
+Gangway = 12 V $^{1/3}$
+Wireless Set = 200 kg.
+Generating Set and Electric Lighting = 6.5 V $^{1/3}$
+Engine Spare Parts and Tools = 0.1 (No. of HP)
+Tanks for fuel and liquid ballast = 7% of the liquid contained therein if not under pressure; 10% if under pressure.
+
+- 16 -
+
+Cabins and furniture for crew and passengers = 35 kg. per person.
+
+Minimum Crew:
+1 First Commander.
+1 Second Commander.
+1 Chief Pilot.
+2 Pilots (Steersmen).
+2 " (for elevator).
+1 Head Driver.
+
+Power HP = Number of drivers (1 for each 500 HP). 500
+
+2 Wireless Operators.
+4 Mechanics and Riggers.
+14 + HP average weight of each . . . . . . . . . . . . 75 kg.
+Passengers, average weight of each . . . . . . . . . . 75 kg.
+Baggage per person (crew and passengers) each . . . 25 kg.
+Food and water per person for 24 hours . . . . . . 3 kg.
+
+We will now suppose that a distance of 5,000 km. is to be covered in calm weather, at a cruising speed of 95 km/h. at half power (53 hours' sailing) and we wish to know how many passengers can be carried for the different cubatures. We will take:
+
+1.100 kg. the lifting force of the gas per cubic meter.
+0.250 " hourly consumption of fuel per HP.
+0.050 " liquid ballast available per 1 cubic meter of gx:
+
+The total weight per passenger carried will be:
+
+- 17 -
+
+<table>
+  <tr>
+    <td>Passenger</td>
+    <td>75 kg.</td>
+  </tr>
+  <tr>
+    <td>Cabin</td>
+    <td>25 "</td>
+  </tr>
+  <tr>
+    <td>Baggage</td>
+    <td>25 "</td>
+  </tr>
+  <tr>
+    <td>Food for two days</td>
+    <td>6 "</td>
+  </tr>
+  <tr>
+    <td>Total</td>
+    <td>131 "</td>
+  </tr>
+</table>
+
+The following Table gives the weight of the various parts of the useful load and fuel, and the number of passengers which can be carried.
+
+- 18 -
+
+Height of Fuel of the Various Parts of Possible Load
+and Number of Passengers.
+
+<table>
+  <thead>
+    <tr>
+      <td rowspan="2">Volume</td>
+      <td colspan="2">Lifting Force</td>
+      <td colspan="2">Dead Load</td>
+      <td colspan="2">Ballast</td>
+      <td colspan="2">Fuel for 53 h</td>
+      <td colspan="2">Wireless Set</td>
+    </tr>
+    <tr>
+      <td>1 cu.m.</td>
+      <td>kg.</td>
+      <td>kg.</td>
+      <td>kg.</td>
+      <td>kg.</td>
+      <td>at half power</td>
+      <td>Gangway</td>
+      <td>Flight</td>
+      <td>Set</td>
+    </tr>
+  </thead>
+  <tbody>
+    <tr>
+      <td>50,000</td>
+      <td>55,000</td>
+      <td>25,480</td>
+      <td>2,500</td>
+      <td>19,200</td>
+      <td>440</td>
+      <td></td>
+      <td></td>
+      <td></td>
+      <td>200</td>
+    </tr>
+    <tr>
+      <td>100,000</td>
+      <td>110,000</td>
+      <td>43,010</td>
+      <td>5,000</td>
+      <td>30,500</td>
+      <td>560</td>
+      <td></td>
+      <td></td>
+      <td></td>
+      <td>200</td>
+    </tr>
+    <tr>
+      <td>150,000</td>
+      <td>165,000</td>
+      <td>70,380</td>
+      <td>7,500</td>
+      <td>59,900</td>
+      <td>640</td>
+      <td></td>
+      <td></td>
+      <td></td>
+      <td>200</td>
+    </tr>
+    <tr>
+      <td>200,000</td>
+      <td>220,000</td>
+      <td>83,060</td>
+      <td>10,000</td>
+      <td>48,350</td>
+      <td>750</td>
+      <td></td>
+      <td></td>
+      <td></td>
+      <td>200</td>
+    </tr>
+    <tr>
+      <td>250,000</td>
+      <td>265,875</td>
+      <td>98,875</td>
+      <table><thead><tr><th></th><th></th><th></th><th></th><th></th><th></th><th></th><th></th><th></th><th></th></tr></thead><tbody><tr><th>Tanks for Bal-</th><th>Crew Weight kg.</th><th></th><th></th><th></th><th></th><th></th><th></th><th></th><th></th></tr><tr><th>Spare Parts last & Fuel Number kg.</th><table><thead><tr><th></th><th></th><th></th><th></th><th></th><th></th><th></th><th></th><th></th><th></th></tr></thead><tbody><tr><th>Tanks for Bal-</th><table><thead><tr><th>Crew Weight kg.</th><table><thead><tr><th>Tanks for Bal-</th><table><thead><tr><th>Crew Weight kg.</th><table><thead><tr><th>Tanks for Bal-</th><table><thead><tr><th>Crew Weight kg.</th><table><thead><tr><th>Tanks for Bal-</th><table><thead><tr><th>Crew Weight kg.</th><table><thead><tr><th>Tanks for Bal-</th><table><thead><tr><th>Crew Weight kg.</th><table><thead><tr><th>Tanks for Bal-</th><table><thead><tr><th>Crew Weight kg.</th>
+
+<tr class="header_bottom_margin"><style>.header_bottom_margin td { margin-bottom: 1em; }
+.header_bottom_margin tr:last-child td { border-bottom: none; }
+.header_bottom_margin tr:last-child td:last-child { border-bottom: none; }
+.header_bottom_margin tr:last-child td:last-child::after { content: " "; display: block; clear: both; }
+.header_bottom_margin tr:last-child td:last-child::after { content: " "; display: block; clear: both; }
+.header_bottom_margin tr:last-child td:last-child::after { content: " "; display: block; clear: both; }
+.header_bottom_margin tr:last-child td:last-child::after { content: " "; display: block; clear: both; }
+.header_bottom_margin tr:last-child td:last-child::after { content: " "; display: block; clear: both; }
+.header_bottom_margin tr:last-child td:last-child::after { content: " "; display: block; clear: both; }
+.header_bottom_margin tr:last-child td:last-child::after { content: " "; display: block; clear: both; }
+.header_bottom_margin tr:last-child td:last-child::after { content: " "; display: block; clear: both; }
+.header_bottom_margin tr:last-child td:last-child::after { content: " "; display: block; clear: both; }
+.header_bottom_margin tr:last-child td:last-child::after { content: " "; display: block; clear: both; }
+.header_bottom_margin tr:last-child td:last-child::after { content: " "; display: block; clear: both; }
+.header_bottom_margin tr:last-child td:last-child::after { content: " "; display: block; clear: both; }
+.header_bottom_margin tr:last-child td:last-child::after { content: " "; display: block; clear: both; }
+.header_bottom_margin tr:last-child td:last-child::after { content: " "; display: block; clear: both; }
+.header_bottom_margin tr:last-child td:last-child::after { content: " "; display: block; clear: both; }
+.header_bottom_margin tr:last-child td:last-child::after { content: " "; display: block; clear: both; }
+.header_bottom_margin tr:last-child td:last-child::after { content: " "; display: block; clear: both; }
+.header_bottom_margin tr:last-child td:last-child::after { content: " "; display: block; clear: both; }
+.header_bottom_margin tr:last-child td:last-child::after { content: " "; display: block; clear: both; }
+.header_bottom_margin tr:last-child td:last-child::after { content: " "; display: block; clear: both; }
+.header_bottom_margin tr:last-child td:last-child::after { content: " "; display: block; clear: both; }
+.header_bottom_margin tr.last_child td.last_child::after { content: " "; display: block; clear: both; }
+
+<tr class="header_bottom_margin"><style>.header_bottom_margin td { margin-bottom: 1em; }
+.header_bottom_margin tr.last_child td.last_child::after { content: " "; display: block; clear: both; }
+
+<tr class="header_bottom_margin"><style>.header_bottom_margin td { margin-bottom: 1em; }
+.header_bottom_margin tr.last_child td.last_child::after { content: " "; display: block; clear: both; }
+
+<tr class="header_bottom_margin"><style>.header_bottom_margin td { margin-bottom: 1em; }
+.header_bottom_margin tr.last_child td.last_child::after { content: " "; display: block; clear: both;
+
+<tr class="header_bottom_margin"><style>.header_bottom_margin td { margin-bottom:
+<tr class="header_bottom_margin"><style>.header_bottom_margin td { margin-bottom:
+<tr class="header_bottom_margin"><style>.header_bottom_margin td { margin-bottom:
+<tr class="header_bottom_margin"><style>.header_bottom_margin td { margin-bottom:
+<tr class="header_bottom_margin"><style>.header_bottom_margin td { margin-bottom:
+<tr class="header_bottom_margin"><style>.header_bottom_margin td { margin-bottom:
+<tr class="header_bottom_margin"><style>.header_bottom_margin td { margin-bottom:
+<tr class="header_bottom_margin"><style>.header_bottom_margin td { margin-bottom:
+<tr class="header_bottom_margin"><style>.header_bottom_margin td { margin-bottom:
+<tr class="header_bottom_margin"><style>.header_bottom_margin td { margin-bottom:
+<tr class="header_bottom_margin"><style>.header_bottom_margin td { margin-bottom:
+<tr class="header_bottom_margin"><style>.header_bottom_margin td { margin-bottom:
+<tr class="header_bottom_margin"><style>.header_bottom_margin td { margin-bottom:
+<tr class="header_bottom_margin"><style>.header_bottom_margin td { margin-bottom:
+<tr class="header_bottom_margin"><style>.header_bottom_margin td { margin-bottom:
+<tr class="header_bottom_margin"><style>.header_bottom_margin td { margin-bottom:
+<tr class="header_bottom_margin"><style>.header_bottom_margin td { margin-bottom:
+<tr class="header_bottom_margin"><style>.header_bottom_margin td { margin-bottom:
+<tr class="header_bottom_margin"><style>.header_bottom_margin td { margin-bottom:
+<tr class="header_bottom_margin"><style>.header_bottom_margin td { margin-bottom:
+<tr class="header_bottom_margin"><style>.header_bottom_m
+
+```html
+<table border="1">
+  <!-- Table header -->
+  <!-- Volume -->
+  <!-- Lifting Force -->
+  <!-- Dead Load -->
+  <!-- Ballast -->
+  <!-- Fuel for 53 h -->
+  <!-- Gangway -->
+  <!-- Wireless Set -->
+  <!-- Flight -->
+  <!-- at half power -->
+  
+  <!-- Volume -->
+  <!-- Lifting Force -->
+  <!-- Dead Load -->
+  <!-- Ballast -->
+  <!-- Fuel for 53 h -->
+  <!-- Gangway -->
+  <!-- Wireless Set -->
+  <!-- Flight -->
+  <!-- at half power -->
+
+  <!-- Volume -->
+  <!-- Lifting Force -->
+  <!-- Dead Load -->
+  <!-- Ballast -->
+  <!-- Fuel for 53 h -->
+  <!-- Gangway -->
+  <!-- Wireless Set -->
+  <!-- Flight -->
+  <!-- at half power -->
+
+  <!-- Volume -->
+  <!-- Lifting Force -->
+  <!-- Dead Load -->
+  <!-- Ballast -->
+  <!-- Fuel for 53 h -->
+  <!-- Gangway -->
+  <!-- Wireless Set -->
+  <!-- Flight -->
+  <!-- at half power -->
+
+  <!-- Volume -->
+  <!-- Lifting Force -->
+  <!-- Dead Load -->
+  <!-- Ballast -->
+  <!-- Fuel for 53 h -->
+  <!-- Gangway -->
+  <!-- Wireless Set -->
+  <!-- Flight -->
+  <!-- at half power -->
+
+  <!-- Volume -->
+  <!-- Lifting Force -->
+  <!-- Dead Load -->
+  <!-- Ballast -->
+  <!-- Fuel for 53 h -->
+  <!-- Gangway -->
+  <!-- Wireless Set -->
+  <!-- Flight -->
+  <!-- at half power -->
+
+  <!-- Volume -->
+  <!-- Lifting Force -->
+  <!-- Dead Load -->
+  <!-- Ballast -->
+  <!-- Fuel for 53 h -->
+  <!-- Gangway -->
+  <!-- Wireless Set -->
+  <!-- Flight -->
+  <!-- at half power -->
+
+  <!-- Volume -->
+  <!-- Lifting Force -->
+  <!-- Dead Load -->
+  <!-- Ballast -->
+  <!-- Fuel for 53 h -->
+  <!-- Gangway -->
+  <!-- Wireless Set -->
+  <!-- Flight -->
+  <!-- at half power -->
+
+  
+```
+
+- 10 -
+
+Weight of Fuel of the Various Parts of Possible Load and Number of Passengers.
+
+<table>
+  <thead>
+    <tr>
+      <th rowspan="2">Volume</th>
+      <th rowspan="2">Cabin</th>
+      <th rowspan="2">Baggage</th>
+      <th colspan="2">Food for Crew for 2 Days.</th>
+      <th rowspan="2">Total Weight</th>
+      <th colspan="2">Remaining Lifting Force</th>
+    </tr>
+    <tr>
+      <th>kg.</th>
+      <th>kg.</th>
+      <th>kg.</th>
+      <th>kg.</th>
+    </tr>
+  </thead>
+  <tbody>
+    <tr>
+      <td>50,000</td>
+      <td>500</td>
+      <td>500</td>
+      <td>120</td>
+      <td></td>
+      <td>53,500</td>
+      <td>3,500</td>
+    </tr>
+    <tr>
+      <td>100,000</td>
+      <td>580</td>
+      <td>580</td>
+      <td>140</td>
+      <td></td>
+      <td>90,540</td>
+      <td>19,480</td>
+    </tr>
+    <tr>
+      <td>150,000</td>
+      <td>635</td>
+      <td>635</td>
+      <td>165</td>
+      <td></td>
+      <td>136,300</td>
+      <td>38,700</td>
+    </tr>
+    <tr>
+      <td>200,000</td>
+      <td>730</td>
+      <td>730</td>
+      <td>180</td>
+      <td></td>
+      <td>186,620</td>
+      <td>58,740</td>
+    </tr>
+    <tr>
+      <td>250,000</td>
+      <td>780</td>
+      <td>780</td>
+      <td>190</td>
+      <td></td>
+      <td>195,480</td>
+      <td>79,530</td>
+    </tr>
+    <tr>
+      <td>300,000</td>
+      <td>830</td>
+      <td>830</td>
+      <td>200</td>
+      <td></td>
+      <td>229,630</td>
+      <td>100,370</td>
+    </tr>
+    <tr>
+      <td>350,000</td>
+      <td>880</td>
+      <td>880</td>
+      <td>210</td>
+      <td></td>
+      <td>263,230</td>
+      <td>121,770</td>
+    </tr>
+    <tr>
+      <td>400,000</td>
+      <td>930</td>
+      <td>930</td>
+      <td>220</td>
+      <td></td>
+      <td>296,910</td>
+      <td>143,690</td>
+    </tr>
+  </tbody>
+  <tfoot><tr><th colspan="8">Number of Passen-gers:</th></tr><tr><th colspan="4">Passen-gers:</th><th>Cabin kg.</th><th>Baggage kg.</th><th colspan="2">Weight of Foodstuffs kg.</th></tr></tfoot></table>
+
+<table border="1">
+  <thead><tr><th></th><th></th><th></th><th></th><th></th><th></th><th></th><th></th></tr></thead><tbody><tr><th colspan="8">55,544 kg.</th></tr><tr><th colspan="8">56,664 kg.</th></tr><tr><th colspan="8">57,784 kg.</th></tr><tr><th colspan="8">58,914 kg.</th></tr><tr><th colspan="8">61,944 kg.</th></tr><tr><th colspan="8">63,974 kg.</th></tr><tr><th colspan="8">65,994 kg.</th></tr><tr><th colspan="8">67,994 kg.</th></tr><tr><th colspan="8">71,994 kg.</th></tr><tr><th colspan="8">73,994 kg.</th></tr><tr><th colspan="8">75,994 kg.</th></tr><tr><th colspan="8">77,994 kg.</th></tr><tr><th colspan="8">79,994 kg.</th></tr><tr><th colspan="8">81,994 kg.</th></tr><tr><th colspan="8">83,994 kg.</th></tr><tr><th colspan="8">85,994 kg.</th></tr><tr><th colspan="8">87,994 kg.</th></tr><tr><th colspan="8">89,994 kg.</th></tr><tr><th colspan="8">91,994 kg.</th></tr><tr><th colspan="8">93,994 kg.</th></tr><tr><th colspan="8">95,994 kg.</th></tr><tr><th colspan="8">97,994 kg.</th></tr><tr><th colspan="8">117,994 kg.</than td=""></table>" alt="">Table showing weight of fuel for various parts of possible load and number of passengers. The table is divided into two sections: Volume and Number of Passengers. For each volume (e.g., 50, 100...), the corresponding weight of fuel for the crew for 2 days is calculated. The total weight is also provided. The remaining lifting force is calculated based on these weights. The second section shows the weight of foodstuffs for different volumes. The values range from approximately 55 to 117 kg per passenger.
+
+- 20 -
+
+The following table is made up from the preceding.
+
+<table>
+  <thead>
+    <tr>
+      <th rowspan="3">Volume ou.m.</th>
+      <th colspan="2">Volume of Gas per passenger ou.m.</th>
+      <th colspan="2">Weight of Fuel per passenger/km.</th>
+      <th colspan="2">Number of passengers per 1000 ou.m.</th>
+    </tr>
+    <tr>
+      <td></td>
+      <td></td>
+      <td></td>
+      <td></td>
+      <td></td>
+      <td></td>
+    </tr>
+    <tr>
+      <td></td>
+      <td></td>
+      <td></td>
+      <td></td>
+      <td></td>
+      <td></td>
+    </tr>
+  </thead>
+  <tbody>
+    <tr>
+      <td>50,000</td>
+      <td>: 2,630</td>
+      <td></td>
+      <td>0.2020</td>
+      <td></td>
+      <td>0.38</td>
+      <td></td>
+    </tr>
+    <tr>
+      <td>100,000</td>
+      <td>: 676</td>
+      <td></td>
+      <td>0.0412</td>
+      <td></td>
+      <td>1.48</td>
+      <td></td>
+    </tr>
+    <tr>
+      <td>150,000</td>
+      <td>: 508</td>
+      <td></td>
+      <td>0.0270</td>
+      <td></td>
+      <td>1.97</td>
+      <td></td>
+    </tr>
+    <tr>
+      <td>200,000</td>
+      <td>: 446</td>
+      <td></td>
+      <td>0.0216</td>
+      <td></td>
+      <td>2.24</td>
+      <td></td>
+    </tr>
+    <tr>
+      <td>250,000</td>
+      <td>: 413</td>
+      <td></td>
+      <td>0.0186</td>
+      <td></td>
+      <td>2.45</td>
+      <td></td>
+    </tr>
+    <tr>
+      <td>300,000</td>
+      <td>: 392</td>
+      <td></td>
+      <td>0.0166</td>
+      <td></td>
+      <td>2.55</td>
+      <table><tbody><tr><th style="text-align: right;">350,000:</th><th style="text-align: right;">376:</th><th style="text-align: right;">0.0152:</th><th style="text-align: right;">2.66:</th></tr><tr><th style="text-align: right;">400,000:</th><th style="text-align: right;">366:</th><th style="text-align: right;">0.0140:</th><th style="text-align: right;">2.73:</th></tr></tbody></table></tr><tr><th colspan="7" style="text-align: center;"><strong>From Fig. 3, we see that for a given length of flight, there is much advantage in increasing the cubature, both on account of the greater number of passengers per unit volume, which means a smaller cubature per passenger, and also on account of the smaller weight of fuel per passenger, which means a lower rate of transport. In the case considered of a trip of 5,000 km., there is an appreciable advantage in increasing the cubature up to 250,000 cubic meters, as was already stated for the unit weight of the dead load, but beyond that cubature the advantage is smaller.</strong></th></tr><tr><th colspan="7" style="text-align: center;"><strong>Translated by Paris Office, M.A.C.A.</strong></th></tr></tbody></table>
+
+<img>A page from a technical report or manual discussing the advantages of increasing the cubature (volume) of aircraft for better fuel efficiency and passenger capacity.</img>
+
+Weight in grams per m²
+
+Total weight of envelope in kg
+
+HP per m²
+Weight per kg in grams.
+
+Fig. 2
+
+Total weight of dead load in kg.
+
+<img>Graph showing relationships between volume of gas per passenger, weight of fuel per passenger-kilometer, total number of passengers carried, and number of passengers per 1000 m³ of gas.</img>
+<page_number>Pl. E. 3.</page_number>
+
+Volume of gas in m³ per passenger.
+
+Weight of fuel in kg. per passenger-kilometer.
+
+Total number of passengers carried.
+
+Number of passengers per 1000 m³ of gas.
+
+C
+D
+E
+F
+G
+H
+I
+J
+K
+L
+M
+N
+O
+P
+Q
+R
+S
+T
+U
+V
+W
+X
+Y
+Z
+
+1000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
+
+25
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+75
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+125
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+175
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+225
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+275
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+325
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+375
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+475
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+525
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+575
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+625
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+675
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+725
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+775
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+825
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+875
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+925
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+975
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+1125
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+1175
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+1225
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+1275
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+1325
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+1375
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+1425
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+1475
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+1625
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+1675
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+1725
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+1775
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+1825
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+1875
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+1925
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+1975
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+2125
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+2175
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+2225
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+2275
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+2325
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+2375
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+2425
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+2475
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+2625
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+2675
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+2725
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+3475

Airships/zeppelins-the_past_and_future_1918.md

@@ -0,0 +1,916 @@
+Campbell, Edwin
+Zeppelins, the past and future
+
+D600C3
+
+<img>A blank page with a light blue border on the right side.</img>
+
+ZEPPELINS
+
+<watermark>
+LIBRARY
+NOV 06 2023
+SECURITY & EDITIONS
+</watermark>
+
+<img>A stylized illustration of a zeppelin flying through the night sky with stars. The background is dark blue, and the zeppelin is depicted with a long, slender body and a pointed nose. The illustration has a vintage, art deco style.</img>
+
+Digitized by the Internet Archive
+in 2007 with funding from
+Microsoft Corporation
+
+http://www.archive.org/details/zeppelinspastfut00campuoft
+
+ZEPPELINS
+THE PAST AND FUTURE
+
+BY
+EDWIN CAMPBELL
+
+With Illustrations
+
+THE CAMPFIELD PRESS
+ST. ALBANS
+1918
+
+D
+600
+C3
+
+659842
+16.5.57
+
+LIST OF ILLUSTRATIONS
+
+1.—**ZEPPELIN L15 BROUGHT DOWN BY GUNFIRE AND SUNK IN THE THAMES ESTUARY, MARCH 31, 1916.**
+
+2.—**REMOVING PARTS OF THE BURNED SCHÜTTE-LANZ AIRSHIP BROUGHT DOWN IN FLAMES BY LIEUTENANT LEETE ROBINSON AT CUFFLEY, SEPTEMBER 2, 1916.**
+
+3.—**RUINS OF THE SCHÜTTE-LANZ AIRSHIP DESTROYED BY LIEUTENANT LEETE ROBINSON.**
+
+4.—**BOW OF ZEPPELIN L33 BROUGHT DOWN BY GUNFIRE IN ESSEX, SEPTEMBER 24, 1916.**
+
+5.—**OIL TANKS OF ZEPPELIN L33.**
+
+6.—**ZEPPELIN L32 BROUGHT DOWN IN ESSEX, SEPTEMBER 23-24, 1916.**
+
+7.—**BOW OF ZEPPELIN L32.**
+
+8.—**ZEPPELIN L31 DESTROYED BY LIEUTENANT SOWBEE AT POTTERS BAR, OCTOBER 1, 1916.**
+
+[API_EMPTY_RESPONSE]
+
+ZEPPELINS: THE PAST AND FUTURE
+
+I
+
+WHILE it may be said that the coming of the aeroplane in 1908 gave Europe five or six years' respite from war, the invention of the Zeppelin made that war inevit-
+able to the present generation. The German genius, which Germany, at her chosen time, proposed to overcome Great Britain's insular security. When French genius,
+supplementing the work of the Brothers Wright, with characteristic energy and acumen rapidly developed an aviation industry, no small portion of the national enthusiasm of our Ally for and support of the new move-
+ment arose from an erroneous perception that the flying machines would have to play an important part in
+the next war—and for France there could be only one war. The impending shadow of that had grown and
+waned and yet grown again until the world apprehen-
+sively perceived that the bursting of the storm was merely
+a matter of time and Germany's opportunity or con-
+venience.
+
+By an instantaneous appreciation of the aeroplane,
+and a truly phenomenal success in exploiting it, France.
+in 1910 secured a military weapon not in the German
+armoury. Later, by taking a commanding position in
+the manufacture of aeroplanes, and by almost monopolis-
+ing their development for two years, she compelled
+Germany to adopt them as a means of overcoming her deficiency, and definitely to put back in its scabbard the sword that had been almost unshathed several times,
+and had been rattled ominously in and out of season.
+
+6 ZEPPELINS: THE PAST AND FUTURE
+
+A national substitute, so necessary to German military amour propre, apparently was accepted in the Zeppelin, the rigid airship which had been the dream and obsession of Count Ferdinand Zeppelin for ten years.
+When France had taken such a lead in aircraft that the remainder of the world temporarily was outdistanced, the German military authorities turned somewhat erroneously to the Zeppelin to restore their prestige and to prove that German capacity to surpass all others in the appurtenances of war remained undiminished. But while the Zeppelin was thus acclaimed, the aeroplane was adopted also, and while others were designing, experimenting, and building it for sport and with scientific ends in view, Germany gravely set about developing it for the purposes of war.
+
+When, however, early in 1909, Count Zeppelin handed over his first military airship to the German Government and it was found successful to a degree, a considerable section of expert opinion in Germany decided that the superior of the aeroplane for military purposes had been discovered. In spite of many successes and a number of failures and catastrophes, she secured just such a lead in rigid-airship construction as France had obtained in aeroplanes, with the added advantage that it was much more difficult to overcome or equal. Those catastrophes, coupled with a tremendous advance in aeroplane design and performance, had induced other nations to believe that the aeroplane would be an attractive machine, and while France, Italy, and Great Britain devoted some attention to non-rigid types of airship, the rigid was, broadly, regarded as Germany's preoccupation.
+
+Profiting by this, Germany closed the doors of her airship factories to the outer world and seemed now to overlook how progress... Inside two years most of the earlier difficulties of construction were left behind, and from that point up to the capture of L38 in Essex on September 24, 1916, we knew relatively little that was
+
+**ZEPPELINS: THE PAST AND FUTURE**
+
+7
+
+reliable or authentic concerning the nature and character of its subsequent development. Its records were announced from time to time in the German Press, evidencing an advance in efficiency and reliability that was remarkable. The German Government's official statement apparently convinced the experts of other countries that its design, fundamentally, was frail and unreliable in comparison with the aeroplane for the purposes of war.
+
+In 1912 and 1913 tales of mysterious aircraft cruising by night over the Eastern Counties of England were accepted by a few as evidence of a somewhat startling development of the Zeppelin, but the Press ridiculed such ideas on the statements of experts who were accepted as possessed of a knowledge of the progress of contemporary airship development. At a dramatic moment, early in 1915, the commander of what was stated to be one of the later creations of Count Zeppelin's factory at Friedrichshafen, was bearing dinner during a trial cruise in the Rhine valley and descended on the parade ground at Lunéville in Lorraine. The vessel was detained pending "explanations," and when examined and its log overhauled by French aeronautical experts, it was evident that much of the advertised powers of the Zeppelin were imaginary.
+
+Possibly some will decide, as many have now decided, that those nocturnal visitations over Norfolk and Suffolk were real, and that the Zeppelin descent at Lunéville with undestroyed log was a successful ruse to mislead France and the world at large concerning the technical and military value of the German ship. Certainly the details of its construction and equipment had no close relationship to the results of the Zeppelin being down in England in 1916, and although three years may have effected all the changes, there is some, but not much, reason to believe that the Lunéville descent was a successful ruse de guerre intended to confirm the Entente military and naval experts in their disbelief in the airship as a <page_number>7</page_number>
+
+8 ZEPPELINS: THE PAST AND FUTURE
+
+reliable or efficient aircraft for war, or as a practical foil to the aeroplane.
+
+According to subsequent disclosures in the French Press, the Lunéville Zeppelin's log apparently proved that it could maintain an altitude of 6,000 feet while its normal altitude was nearer 8,500 feet. Its average speed was about 45 miles per hour, with a radius of action with full load less than 200 miles—figures all very much below the claims published in the German Press. Obviously, if its pilot could lose his bearings in a trip of less than 100 miles because of ground fog, it was not likely that he could lay and keep a course from and to Heligoland. This was one of the chief reasons for its failure in navigation. Clearly, then, the French aeroplane was an infinitely superior military device. And so the Zeppelin almost ceased to trouble our experts, and to all appearance was lost sight of subsequently in the activity of acroplane rivalry.
+
+That practically, was the position as it presented itself to the Allies when war broke out in July, 1914. Probably by then the weaknesses of the Zeppelin had been laid bare, and we know that early in 1915 it had been improved in speed up to about 50 miles per hour in still air, its structural weaknesses remedied to a considerable extent, and its load-carrying and ascensional power augmented by balancing the gas cells and improving its lines. But these changes were relatively small and more developed in the interval. Its speed had been raised to 100 miles per hour, its reliability immeasurably improved, and the skill of pilots so increased by experience that little further progress in that direction seemed possible. By comparison it was the superior of the airship which had been built during the interval of ascent, and on the surface of things it appeared to justify the dictum of a French expert who asserted that inside six hours of its appearance in the fighting line any German airship would be destroyed by gunfire or aeroplane attack. That assertion predicated daylight and the employment
+
+Zepelin LII, Breguet Docks by Gunther and Sunk in the Talmud, Kentucky, March 31, 1916
+<page_number>P. 8</page_number>
+
+<img>
+  A group of soldiers is shown working in a field. They appear to be digging or planting something. The ground is muddy and there are some trees in the background.
+</img>
+
+Removing Parts of the Ruined Southern Line Avenue, Battersea Down, in February by Lieutenant Leefe Robinson at Cuffley, September 2, 1916
+
+<page_number>Page 3</page_number>
+
+ZEPPELINS: THE PAST AND FUTURE <page_number>9</page_number>
+
+of airships in consonance with the recognized usages of civilized war, neither of which conditions Germany willingly fulfilled.
+
+After a brief and disastrous experience in the early months of the war, during which four Zeppelins were destroyed, including one by French gunners at Baden-Baden, in July 1915, when the first daylight raid by a Russian battery, the daylight use of Zeppelins in land operations was practically abandoned. The first five months of the war had been a continuous record of German airship losses without any adequate military recompense. During that time, according to Press reports, six Zeppelins and four other Austrian and German dirigibles were lost or damaged.
+
+In January, 1915, began the series of Zeppelin raids on England which first demonstrated the advance that had been achieved in the construction and use of the naval Zeppelin—a type designed and developed for the single purpose for which it was reserved and used—compared with which the Lancastrian Zeppelin was a crude and primitive craft. No ship had yet been advanced to 60 miles per hour, but an altitude of about 13,000 feet was possible and a continued voyage at a height of 8,000 feet maintainable. The manoeuvring power had been so improved that, without shedding ballast, vertical and horizontal direction within considerable limits could be altered by gas pressure alone. Moreover, while the radius of action with a full load was extended to 500 miles. Probably as the result of patient and continued training and experience for years previously, its navigation was so mastered that raids on the Eastern coasts of England, involving over 600 miles of travel during dark-ness, could be made with comparative safety.
+
+Undoubtedly, there were grave risks attaching to these expeditions, quite apart from the hostility of British warships and land defences, and several Zeppelins were lost through storm and mechanical failure.
+
+It was not until March 31, 1916, that a raiding German
+
+10 ZEPPELINS: THE PAST AND FUTURE
+
+airship was destroyed by our gunners, our effective defences apparently being confined, up to that point, to the use of artillery guided by searchlights. Even in these we were heavily handicapped by the demands of our vastly increased land and sea forces and the calls of our Allies for guns and searchlights needed on all the fighting fronts. This was particularly unusual in bringing down the raiders, those defenders were very anxious to drive them off and in compelling them to travel at such altitudes that they could have no definite idea of the results of their bombs, or of their actual location when using them.
+
+II
+
+IT is essential when discussing the subject of German air raids in general, and Zeppelin raids in particular, to recall the pre-war conception of the punitive uses to which these craft might legitimately be put. First, according to the terms of the Hague Convention, no bombardment of an open town might be attempted without sufficient warning to enable the civilian population to evacuate it. Secondly, no attack might be made on an undefended or non-military town situated outside the sphere of active military operations. Thirdly, civilian lives and property were held sacred in the absence of any over-riding need on the part of the populace. It was because, almost without exception, our East Coast towns were open and undefended in a military sense that from the beginning it was not considered essential to arm them against bombardment from the air or sea. The best defence ought to have been their utter defencelessness. But the whole conduct of war by Germany invites the suggestion that it was precisely because they were in this condition that the German authorities planned, instituted, and carried out their series of outrages by air under the pretence of
+
+<img>A black-and-white photograph of a Zeppelin flying over a city.</img>
+
+**ZEPPELINS: THE PAST AND FUTURE**
+
+military operations, but really to terrorize the civilian population.
+
+Their earlier experiences in France, Belgium, and Russia had taught them the helplessness of airships in the presence of suitable artillery. Knowing that our towns and cities were unprepared, and calculating that, under the extremely heavy pressure of the vital demands of our own and our Allies' armies in the field and our greatly augmented navy, there would be considerable delay in organizing artillery defences for them against aircraft, they launched their plan to terrorize the civilian population of England by a series of brutal and wanton attacks on the sea and on land. This was only too clear to the inhabitants of their acts as proved by the absurd announcements made in their naval bulletins issued after each raid that "fortified" towns like Cromer, Southend, Yarmouth, Ipswich, Ramsgate, etc., had been bombarded. None knew better than the German naval authorities that in these early days those towns were innocuous places or that even if they were fortifications that they were armed and garrisoned for defence is all the evidence necessary to convict them of as foul a violation in its way of the rules of war as the calculated ferocity of the bestial and revolting ravages carried out by German commanders in Belgium and France under the lying pretext that the civil population there had used arms against them.
+
+Obviously the gloss was intended to anticipate neutral comment or protest by putting the onus of disproof on Great Britain. Later, when the piratical purpose of the raids became only too evident to the British people, and such anti-aircraft artillery as was available was mounted to keep the zeppelins at bay, it was pointed out with sufficient leniencyness, the fact that these guns were used was paraded by the German authorities as proof that their prior contention was justified, and that our seaside resorts actually had been fortified places and London a defended arsenal—a form of demonstration similar to that used to legalize
+
+12 ZEPPELINS: THE PAST AND FUTURE
+
+the invasion of Belgium and to prove that the massacres of French and Belgian citizens of all ages and both sexes were justifiable acts of punishment or were even compelled in self-defence—Esop's fable rewritten with sardonic savagery.
+
+Here it may be pointed out that evidence of German pre-war preparation for these raids is not wanting. For years prior to 1914 the leading rubber company of Germany, which had secured a London headquarters, a very complete network of commercial agents in every town and village in the United Kingdom, and a considerable trade, maintained a large balloon—ostensibly for sporting and adventurous purposes—in accordance with the provisions of the Aero Club of Great Britain. Indeed its ascents were made when the course from London could be laid up to the East Coast, or down to the Channel. Quite often the crew included an official of the German Embassy, and always an expert photographer whose snapshots of Kent, Sussex, Essex, Suffolk, and Norfolk may have been used for propaganda purposes. The raids of 1915, 1916, and 1917 were projected and navigated.
+
+While the earlier raids were launched from Heligoland and the Weser mouth, later ones started from behind the German-Belgian frontier. The primary reason for that change probably was a need to shorten the distance to England so as to admit a deeper penetration, or, in the alternative, to avoid any risk of interception. As does this, the return journeys frequently included a violation of the neutrality of Holland (since the air above any country is portion of its territory), yet another proof how little Germany regards her obligations to countries which cannot compel her to fulfil them. For these no apology is possible.
+
+In the characteristic German way somewhat elaborate justifications for the promiscuous sowing of incendiary bombs over business districts and the deliberate dropping of high explosives on densely inhabited areas in England have been published. Thus in Zeppelin im Weltkriege
+
+**ZEPPELINS : THE PAST AND FUTURE** 13
+
+(Zeppelin in the World-War), dedicated by the author, Arnold Jünke, to the late Count Zeppelin, it is stated that
+
+the object of the successful attacks made by our naval airships on England's chief towns and their environs is a military one. The aim is to destroy important military positions (Anlagen) in the London district ; to prevent the use of the convenient air routes which are of service for the concentration of troops ; but above all to endanger London itself as the most important post on the economic line of communication of the English military forces.
+
+The sophistry of the first and second reasons is exposed by the third, which in itself renders them as superfluous as they are absurd. The destruction of London, simply because it is London, that is the frankly avowed aim. Despite this candid admission of German desire to devastate London, and indiscriminately to murder its citizens on the plea of a military object, angry protests and accusations of a savage violation of the amenities of war were levelled in the German Press at the Allies when subsequences of the Zeppelin raids were published at Karlsruhe! And when it was ascertained that one of our naval air pilots inadvertently had crossed Swiss territory in the course of that raid, though not observed by the Federal authorities, Germany had the hardihood to address a protest to the Swiss Government on the subject, which elicited an admission and apology from our Foreign Office!
+
+Count Zeppelin was invoked to justify the blind and undeniably promiscuous dropping of bombs in night raids in an interview given to the notorious Karl H. von Wiegand, thus :
+
+They say we cannot always see our target from the great height at which we sail. But the same is true of the artillery shell. How often have we seen how often happen that shells strike undefended parts of a town and fall on people who take no part in the war? The Zeppelins are just as anxious to save women and children
+
+<page_number>14</page_number> ZEPPELINS : THE PAST AND FUTURE
+
+as are the officers and gunners of our artillery, . . . A proof of this is the unexploded bombs which have been found in English towns. If Zeppelins are discovered by the enemy and subjected to a violent bombardment it may be the most important to ascend as quickly as possible and in such a manner as to throw out bombs as ballast. In that case the detonators are removed as far as possible to prevent a bomb which might fall on non-combatants from exploding.
+
+That was meant for American consumption, but con-
+tains no essential truth beyond the possible fact that German commanders of Zeppelins are "just as anxious" as their artillery comrades to spare women and children. Those in charge of the German air force will find that German methods of waging war will remark that neither have ever appeared to carry this anxiety too far. And it remains a curious fact, testimony to which is to be found in the ruined shrines of Belgium, France, Italy, and Poland, that German artillerists either have been particularly un-
+fortunate in dropping shells where they were not intended, or their shells have been fired with great accuracy. But to compare the mathematical accuracy of observed artillery fire with the haphazard dropping, in the darkness of night, of a series of Zeppelin bombs is as ridiculous as to assert seriously that any bomb dropped from a Zeppelin in England first had its detonator removed. Dozens of these unexploded missiles have been found, but each had its detonator intact. But though this is true, though equally unveracious, there is more candour in the con-
+fession of Arnold Jünke in Zeppelin im Weltkriege when he says :-
+The air war against England strikes us as a just
+retaliation [for the British sea blockade] since it enables
+us not only to achieve military results, but also to hit
+English cities.
+No act however wanton, no crime however barbarous,
+need require justification if that doctrine be accepted.
+To murder the citizens of an enemy by whatever means
+
+**ZEPPELINS: THE PAST AND FUTURE**
+
+under whatever circumstances, to burn their homes, to destroy their business and commercial districts with thermite and T.N.T., all fall within its apology. Clausewitz did not live nor write in vain. His gospel of ruthless savagery was not preached by the German "enemy on Maukind" when engaged in war, has from the beginning stimulated every German act when the fear of consequences has not counselled an infrequent regard for humanity. Hostilities were not many days old when German Zeppelins were despatched by night to endeavour to bomb the Antwerp palace of the King of the Belgians, who was known as Leopold II. Buckingham Palace shared with the Bank of England the world's attention of the Zeppelin commander Mathy on September 8, 1915, when he attacked London. Indeed, the German people were induced to believe that both had been hit on that occasion, and as far away as Persia German accounts of the affair graphically described the acts.
+
+The editorial comment is no evidence of popular satisfaction in Germany as to indicate that the German people were prepared to accept any form of warfare their naval and military commanders could prosecute with success. There is no room for sportsmanship, no use for chivalry, in the German code of war. The felon blow is specially favoured by it because it is likely to be more effective than any other. The Austro-German-Bulgarian armies were overrunning Rumelia, and it was in the fitness of things that Zeppelins should have been sent ahead to bomb Bucharest, and in particular the palace of King Ferdinand; and when Allied air raids on Karlsruhe were anticipated, British and French prisoners of war were confined in close proximity to the Grand Duke's Bolster's palace, to intimidate any attempt on that building.
+
+<page_number>15</page_number>
+
+<page_number>16</page_number> ZEPPELINS: THE PAST AND FUTURE
+
+III
+
+FROM the outbreak of war down to the present time (April, 1918) there have been 48 separate Zeppelin raids on this country, in addition to others which, for some reason, were not completely carried out, the airships not reaching our shores. A full list, with indications of the damage done and tenders, with the casualties resulting, is given on pp. 17–19. For comparison the German claims are given, although they are often of an inflated and even farcical character.
+
+It will be seen that the German authorities claim to have bombed London no less than twenty times, and it is to be hoped that they have succeeded in reaching their raiders so seldom reached. But the most fantastic claims are those of having attacked Liverpool, Birkenhead, Manchester, and other places which a Zeppelin bomb has never yet reached except as a museum trophy. All these statements were made with much display of circumstantiality and detail, no doubt relying upon the compulsory reticence of the official British reports to carry conviction. The actual results of these raids have been criticised, but has been justified by the obvious inability of the Zeppelin commanders to improve in subsequent raids on their previous navigation, and so greatly helped to render abortive no less than thirteen of their expeditions. We call them abortive because they caused no damage worth recording and were attended by no casualties. It is true that many of them could be dismissed as mere haphazard house-bombing affairs.
+
+The entire series caused the deaths of 435 persons and injured 1,069 others, the great majority being women and children. A considerable amount of damage was done to private property, which we know is always a gratifying fact in German eyes, but it is remarkable in view of the large number of night raids which have been discharged, that even by chance no naval or military damage was effected. It is no exaggeration to say that
+
+<table>
+  <tr>
+    <td colspan="3">ZEPPELIN RAIDS ON ENGLAND 1915-1918</td>
+    <td colspan="3">GERMAN CLASSES</td>
+    <td colspan="3">CIVIL LIVES</td>
+  </tr>
+  <tr>
+    <td>DISTRICT</td>
+    <td>1915</td>
+    <td></td>
+    <td>COUNTIES</td>
+    <td>Number</td>
+    <td>Counties</td>
+    <td>Number</td>
+    <td>Counties</td>
+    <td>Number</td>
+  </tr>
+  <tr>
+    <td>Jan. 19<br>Feb. 21<br>Apr. 14<br>May 7<br>June 4<br>Aug. 9<br>Sep. 7<br>Sep. 12<br>Sep. 18<br>Sep. 11<br>Sep. 13</td>
+    <td>Yarmouth and King's Lynn<br>Coldstream and Tyneham<br>Blyth and Tyneham<br>Lovestone and Maldon<br>Lansdowne and South East Coast<br>North-East Coast<br>East Coast<br>Eastern Counties and London<br>Eastern Counties and London<br>Eastern Counties and London<br>Eastern Counties and London<br>Eastern Coast</td>
+    <td>Lymouth, Cromer, Sheringham, Lynn, No claim, Holton, Ryde, Bexhill-on-Sea, Margate, Maidstone and Bury St Edmunds, Ipswich, Thurnham, Lowestoft, Ramsgate, Southend, Ramsgate, Ramsgate, London, Numberman, Harwich, Shields, Etwasham-on-Tyne, Lyndhurst, London, London, Norwich and London, London, London, London, Southend</td>
+    <td></td>
+    <td></td>
+    <td></td>
+    <td></td>
+    <td></td>
+    <td></td>
+  </tr>
+  <tr>
+    <td rowspan="2">Jan. 19<br>Feb. 21<br>Apr. 14<br>May 7<br>June 4<br>Aug. 9<br>Sep. 7<br>Sep. 12<br>Sep. 18<br>Sep. 11<br>Sep. 13</td>
+    <td rowspan="2">Yarmouth and King's Lynn<br>Coldstream and Tyneham<br>Blyth and Tyneham<br>Lovestone and Maldon<br>Lansdowne and South East Coast<br>North-East Coast<br>East Coast<br>Eastern Counties and London<br>Eastern Counties and London<br>Eastern Counties and London<br>Eastern Counties and London<br>Eastern Coast</td>
+    <td rowspan="2">Lymouth, Cromer, Sheringham, Lynn, No claim, Holton, Ryde, Bexhill-on-Sea, Margate, Maidstone and Bury St Edmunds, Ipswich, Thurnham, Lowestoft, Ramsgate, Southend, Ramsgate, Ramsgate, London, Numberman, Harwich, Shields, Etwasham-on-Tyne, Lyndhurst, London, London, Norwich and London, London, London, Southend</td>
+    <td></td>
+    <td></td>
+    <td></td>
+    <td></td>
+    <td></td>
+    <td></td>
+  </tr>
+</table>
+
+<table>
+  <tr>
+    <th>DISTRICT</th>
+    <th>DISTRICT</th>
+    <th>DISTRICT</th>
+    <th>DISTRICT</th>
+    <th>DISTRICT</th>
+    <th>DISTRICT</th>
+    <th>DISTRICT</th>
+    <th>DISTRICT</th>
+    <th>DISTRICT</th>
+  </tr>
+  <tr>
+    <th colspan="2"></th><th colspan="2"></th><th colspan="2"></th><th colspan="2"></th><th colspan="2"></th>
+  </tr>
+  <tr>
+    <th colspan="2"></th><th colspan="2"></th><th colspan="2"></th><th colspan="2"></th><th colspan="2"></th>
+  </tr>
+  <tr>
+    <th colspan="2"></th><th colspan="2"></th><th colspan="2"></th><th colspan="2"></th><th colspan="2"></th>
+  </tr>
+  <tr>
+    <th colspan="2"></th><th colspan="2"></th><th colspan="2"></th><th colspan="2"></th><th colspan="2"></th>
+  </tr>
+  <tr>
+    <th colspan="2"></th><th colspan="2"></th><th colspan="2"></th><th colspan="2"></th><th colspan="2"></th>
+  </tr>
+  <tr>
+    <th colspan="2"></th><th colspan="2"></th><th colspan="2"></th><th colspan="2"></th><th colspan="2"></th>
+  </tr>
+  <tr>
+    <th colspan="2"></th><th colspan="2"></th><th colspan="2"></th><th colspan="2"></th><th colspan="2"></th>
+  </tr>
+  <tr>
+    <thead style='background-color: #f0f0f0;'>
+      <tr style='text-align: center;'>
+        <td>DISTRICT</td><td>DISTRICT</td><td>DISTRICT</td><td>DISTRICT</td><td>DISTRICT</td><td>DISTRICT</td><td>DISTRICT</td><td>DISTRICT</td><td>DISTRICT</td>
+      </tr>
+      <!-- Repeat the header row for each district -->
+      <!-- Example: -->
+      <!-- For Yarmouth and King's Lynn -->
+      <!-- Yarmouth and King's Lynn -->
+      <!-- Coldstream and Tyneham -->
+      <!-- Blythe and Tyneham -->
+      <!-- Lovestone and Maldon -->
+      <!-- Lansdowne and South East Coast -->
+      <!-- North-East Coast -->
+      <!-- East Coast -->
+      <!-- Eastern Counties and London -->
+      <!-- Eastern Counties and London -->
+      <!-- Eastern Counties and London -->
+      <!-- Eastern Counties and London -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+      <!-- Eastern Coast -->
+
+<table>
+  <tr>
+    <td>DISTRICT</td>
+    <td>GERMAN CLAUSES</td>
+    <td>CASUALTIES</td>
+  </tr>
+  <tr>
+    <td>DATE</td>
+    <td>LONDON, IPSWICH</td>
+    <td>1916</td>
+    <td>71</td>
+    <td>128</td>
+  </tr>
+  <tr>
+    <td>Oct. 13<br>Jan. 31</td>
+    <td>Midland Counties and London</td>
+    <td>Liverpool, Bishop's Stortford, Birmingham, Sheffield, Nottingham, Hull and Darlington</td>
+    <td>Manchester, Birstwith, Liverpool, Bishop's Stortford, Birmingham, Sheffield, Nottingham, Hull and Darlington</td>
+    <td></td>
+  </tr>
+  <tr>
+    <td>Mar. 5<br>Apr. 31</td>
+    <td>Yorkshire and seven other Counties Eastern Counties and North-East Coast</td>
+    <td>Hull and York</td>
+    <td></td>
+    <td></td>
+  </tr>
+  <tr>
+    <td></td>
+    <td>North-East Coast: S.E., Scotland, N.E. Coast and Eastern Counties East Durham Coast Eastern Counties</td>
+    <td>Torquay, Middleborough, Newcastle-upon-Tyne, Edinburgh, Newcastle-upon-Tyne, London, Edinburgh, Newcastle-upon-Tyne, London, Edinburgh, Newcastle-upon-Tyne, London, Edinburgh, Newcastle-upon-Tyne, London, Edinburgh, Newcastle-upon-Tyne, London, Edinburgh, Newcastle-upon-Tyne, London, Edinburgh, Newcastle-upon-Tyne, London, Edinburgh, Newcastle-upon-Tyne, London, Edinburgh, Newcastle-upon-Tyne</td>
+    <td></td>
+    <td></td>
+  </tr>
+  <tr>
+    <td></td>
+    <td>East Durham Coast Eastern Counties</td>
+    <td>Whitehaven and Carlisle; York; York; York; York; York; York; York; York; York; York; York; York; York; York; York; York; York; York; York; York; York; York; York; York; York; York; York; York; York; York; York; York; York; York; York; York; York; York; York; York; Yorkshire and Lincolnshire Coast of Southland East Coast of Southland</td>
+    <td></td>
+    <td></td>
+  </tr>
+  <tr>
+    <td>May 2<br>July 29</td>
+    <td>Yorkshire and S.E. Counties Eastern Counties</td>
+    <td>Torquay, Middleborough, Newcastle-upon-Tyne, Edinburgh, Newcastle-upon-Tyne, London, Edinburgh, Newcastle-upon-Tyne, London, Edinburgh, Newcastle-upon-Tyne, London, Edinburgh, Newcastle-upon-Tyne,</td>
+    <td></td>
+    <td></td>
+  </tr>
+  <tr>
+    <td>Aug. 3<br>Sep. 20<br>Sep. 26<br>Sep. 28<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30<br>Sep. 30</td>
+    <td>London: Durham: Northumberland: Yorkshire: Lincolnshire: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk: Norfolk:</td>
+    <td></td>
+    <td></td>
+  </tr>
+</table>
+
+<table>
+  <tr>
+    <td>DATE</td>
+    <td>DISTRICT</td>
+    <td>Germán Clans</td>
+    <td>Casualties</td>
+  </tr>
+  <tr>
+    <td>Aug. 8</td>
+    <td>Eastern and N.E. Coasts</td>
+    <td>Tyneside, Whithby, Hull, Grimsby, Humber, King's Lynn</td>
+    <td>10</td>
+    <td>16</td>
+  </tr>
+  <tr>
+    <td>••• 23</td>
+    <td>East Sussex</td>
+    <td></td>
+    <td></td>
+    <td></td>
+  </tr>
+  <tr>
+    <td>Sep. 94</td>
+    <td>••• S.E. Coasts</td>
+    <td>London, Hastings, Harwich, Humber</td>
+    <td>40</td>
+    <td>12</td>
+  </tr>
+  <tr>
+    <td>Sep. 24</td>
+    <td>Eastern Counties and Midlands</td>
+    <td>Portsmouth, Thames mouth, York</td>
+    <td>40</td>
+    <td>53</td>
+  </tr>
+  <tr>
+    <td>Oct. 25</td>
+    <td>Lancashire, Yorkshire, Lincolnshire</td>
+    <td>Leeds, Lincoln and Derby</td>
+    <td>40</td>
+    <td>37</td>
+  </tr>
+  <tr>
+    <td>Nov. 28</td>
+    <td>North-East Coast</td>
+    <td></td>
+    <td></td>
+    <td></td>
+  </tr>
+  <tr>
+    <td>Mar. 16</td>
+    <td>Kent</td>
+    <td></td>
+    <td></td>
+    <td></td>
+  </tr>
+  <tr>
+    <td>May 16</td>
+    <td>Norfolk, Suffolk and Kent</td>
+    <td></td>
+    <td></td>
+    <td></td>
+  </tr>
+  <tr>
+    <td>Jun. 21</td>
+    <td>East Riding</td>
+    <td></td>
+    <td></td>
+    <td></td>
+  </tr>
+  <tr>
+    <td>Sep. 24</td>
+    <td>Yorkshire Lincolnshire Kent Sussex London, Hull, Nottingham ham, Humberside, Northumberland, Newham, Derby, Lewes, Grimsby</td>
+    <td></td>
+    <table border="1">
+      <tbody><tr><th style="text-align: left;">1917</th><th style="text-align: right;">3</th><th style="text-align: right;">16</th></tr><tr><th style="text-align: left;"></th><th style="text-align: right;">—</th><th style="text-align: right;">—</th></tr><tr><th style="text-align: left;">Norwich, Louth, Spalding,</th><th style="text-align: right;">—</th><th style="text-align: right;">—</th></tr><tr><th style="text-align: left;">Hull and Whitby and the mouth of the River Trent and the East Coast of England and the Midlands and the North of England and the North of Scotland and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales and the North of Ireland and the North of Wales.</table></tr><tr><th style="text-align: left;">Apr. 12 Eastern Countiesand N. Midlands</th><th style="text-align: right;">—</th><th style="text-align: right;">—</th></tr></tbody></table></table></table></table></table></table></table></table></table></table></table></table></table></table></table></table></table></table></table></table></table></table></table></table></table></table></table></table></table></table/></div><div class='image'><img>A map showing various regions in England affected by German casualties during World War I.</img><div class='caption'>Map showing German casualties in various regions during WWI.</div><div class='credit'></div><div class='description'>This map illustrates areas in England where German casualties occurred during World War I. The map highlights different regions such as Eastern Counties, Midlands, Northern Counties, South East Coast, Yorkshire Lincolnshire, Kent Sussex London, Hull, Nottingham ham, Humberside, Newham, Derby, Lewes, Grimsby, Norfolk, Louth, Spalding, Hull & Whitby &amp; Mouth River Trent &amp; East Coast England &amp; Midlands &amp; Northern England &amp; Northern Scotland &amp; Northern Ireland &amp; Northern Wales &amp; Northern Ireland &amp; Northern Wales &amp; Northern Ireland &amp; Northern Wales &amp; Northern Ireland &amp; Northern Wales &amp; Northern Ireland &amp; Northern Wales &amp; Northern Ireland &amp; Northern Wales &amp; Northern Ireland &amp; Northern Wales &amp; Northern Ireland &amp; Northern Wales &amp; Northern Ireland &amp; Northern Wales &amp; Northern Ireland &amp; Northern Wales &amp; Northern Ireland &amp; Northern Wales &amp; Northern Ireland &amp; Northern Wales &amp; Northern Ireland &amp; Northern Wales &amp; Northern Ireland &amp; Northern Wales &amp; Northern Ireland &amp; Northern Wales &amp; Northern Ireland &amp; Northern Wales &amp; Northern Ireland &amp; Northern Wales &amp; Northern Ireland &amp; Northern Wales &amp; Northern Ireland &amp; Northern Wales &amp; Northern Ireland &amp; Northern Wales &amp; Northern Ireland &amp; Northern Wales &amp; Northern Ireland &amp; Northern Wales &amp; Northern Ireland &amp; Northern Wales &amp; Northern Ireland &amp; Northern Wales &amp; Northern Ireland &amp; Northern Wales &amp; Northern Ireland &amp; Northern Wales &amp; Northern Ireland &amp; Northern Wales &amp; Northern Ireland &amp; Northern Wales &amp; Northern Ireland &amp; Northern Wales &amp; Northern Ireland &amp; Northern Wales &amp; Northern I.</div><div class='description'>This map shows areas in England where German casualties occurred during World War I. The map highlights different regions such as Eastern Counties, Midlands, Southern Counties, South East Coast, Yorkshire Lincolnshire, Kent Sussex London, Hull Nottingham ham Humberside Newham Derby Lewes Grimsby Norfolk Louth Spalding Hull Whitby Mouth River Trent East Coast England Midlands northern England northern Scotland northern ireland northern wales northern ireland northern wales northern ireland northern wales northern ireland northern wales northern ireland northern wales northern ireland northern wales northern ireland northern wales northern ireland northern wales northern ireland northern wales northern ireland northern wales northern ireland northern wales northern ireland northern wales northern ireland northern wales northern ireland northern wales northern ireland northern wales northern ireland northern wales northern ireland northern wales northern ireland northern wales northern ireland northern wales northern ireland northern wales northern ireland northern wales northern ireland northern wales norther
+
+20 ZEPPELINS : THE PAST AND FUTURE
+
+in all about 700 tons, representing 5,000 bombs, must have been dropped ; and that they caused no more than 1,504 casualties, and material damage to the value of about £1,400,000, must surely be disappointing to the nation that ordered them. The loss of the Lusitania. In that glorious exploit more defenseless civilians were murdered and more property was destroyed by the expenditure of two torpedoes than has been effected in three and a half years of costly Zeppelin raids.
+
+It is estimated that forty of the naval type of Zeppelin have been built specially for the purpose of raiding this country, at a cost of about £140,000 each. Those represent a capital expenditure of £5,600,000 in ships and another £2,000,000 in sheds and the necessary repair shops and machinery for gas production. Each Zeppelin is computed to cost £210 per diem to keep in commission, so, in addition to the crew of about twenty aeronauts and mechanics, there are twenty spare engines attached to each airship base numbering about 150 per ship, while repairs are said to cost about £15,000 per annum in peace time. It is estimated that no fewer than twenty-four Zeppelins have been destroyed by the Allies or lost as a consequence of damage sustained in attacking the Allied countries, while a number of others have been seriously damaged. It is estimated that 36 Zeppelin units have been dispatched against us, but it is not probable that at any one time the strength of the enemy in these craft has much exceeded twenty ships. Accepting that as an average, over nearly three years of war it represents an approximate expenditure of £5,250,000 in maintenance and as each raid would entail a further expenditure of £875 on fuel and ammunition for trial trips, there has to be added another £360,000, together with £100,000 for subsidiary but consequential services.
+
+On these calculations Germany has spent fully £13,250,000 on Zeppelin raids, and at the most conserva-
+
+**ZEPPELINS: THE PAST AND FUTURE**
+
+tive estimate £9,603,000 of it has disappeared. When it is borne in mind that a considerable concentration of German effort was found up in this enterprise that, as events have proved, could more profitably have been diverted to other affairs, it will be seen that these figures alone do not embrace her effective loss. Even in casualities she has to admit the death of about 500 trained personnel and 1,700 non-combatant men who met their probable end, than the 485 persons whom they killed were to England, while the million pounds' worth of property destroyed and the relatively small number of troops immobilised for defence was a poor result for the expenditure of over nine and a half millions of capital.
+
+That is not all. The Zeppelin raiders brought with them the highly-coloured and decorative speculations and inventions of the German official bureau and press, but they bring the whole scheme into a perspective which enables a judgment to be passed on its military value. That judgment, quite apart from questions of outrage, or the violation of the amenities of civilization, cannot be other than adverse. Beyond the fact that it was the cause of a number of gunners and air-pilots, few of whom however, had been wholly detached for this special purpose, and the occasional interruption of war work in some districts for a few hours, there have been no military results apart from the killing and maiming of a few soldiers.
+
+Looked at impartially, the Zeppelin raid programme has been a complete failure. It was a great German blunder, because its effect has been inexcusable in creating and fostering an abhorrence of German brutality and mentality, which has been of priceless service to the Allied cause in stimulating the British nation to the stupendous efforts it has made in the cause of civilization during the past three and a half years. It greatly helped to reconquer the Rhineland, by British labour, by reducing the burden of burdens, and a surrender of liberties, which the enemy judged would never be made. It is safe to assert that it has done more to make war with Germany a national
+
+<page_number>21</page_number>
+
+22 ZEPPELINS : THE PAST AND FUTURE
+
+effort than anything else in the long black list of German atrocities, while its effect on the opinion and attitude of the world at large undeniably has been of great disservice to Germany. It demonstrated to those outside the con-
+flict that the German conception of legitimate war is restrained by no consideration of humanity, of honour,
+of reputation, or of the rights of the Huns in horror
+from a nation which thus, after a thousand years of civilization, deliberately reverses to a barbarism and a ferocity beside which the excesses of the Huns of old appear pale and almost ineffectual.
+
+The mendacity of the German official claims is so truly " colossal" that it is like chasing a will-o'-the-wisp to endeavour to pin them down, but it is as well to give a few selected examples.
+
+On July 4, 1915, the German Army Headquarters in Berlin issued the following, which was wirelessed to neutral countries (vide The Times Amsterdam Corres-
+pondent, July 5, 1915) :
+
+Our airmen yesterday were very active. German aircraft dropped bombs on the Languard Fort of Har-
+wich and upon an English flotilla of destroyers.
+
+The mendacity of the claim is proved by the fact that in a subsequently compiled German semi-official list of air raids on England there is not one mention of this.
+
+The following interestingly imaginative description of his exploits over London in the raid of September 8, 1915, was given to the Berlin Correspondent of the New York World by Commander Mathy, who, by the way, was killed in command of L31 when it was brought into flames at Potters Bar by Lieut. Sorevy on October 20th. This was one of several raids claimed to have made over a hundred air voyages.
+
+It is a cold, clear, starlit night, and there is no moon
+— one of those nights when the distances of objects in the sky are illusive and difficult to get the range of, but our instruments tell us exactly how high we are.
+
+RUINS OF THE SCHETTLE-LANZ AIRSHIP DESTROYED BY LIEUTENANT LEPE ROBINSON (Page 23)
+
+Bow of Zeppelin 126, brought down by gunfire in Easton, September 24, 1916.
+
+<img>Ol. Tanks of Zeppelin 133</img>
+
+Zewlein 382. BROUGHT DOWN IN ESSEN. SEPTEMBER 23-24, 1916
+
+<page_number>Page 60</page_number>
+
+**ZEPPELINS: THE PAST AND FUTURE**
+
+The mist disappeared. In the distance we could see the Thames, which points a way to London. It is an indescribable guide and a sure road to the great city. The English can darken London as much as they want, but they cannot physically cover up the Thames. It is the great point from which we can always get our bearings and pick up any part of London we desire.
+
+That does not mean that we always come up along the Thames by any means. London is darkened, but it is so sufficiently lighted that on this night I saw it reflected in the sky like a mirror, and I could see its outline clearly.
+
+I headed straight for the glow in the sky and then for a point on the Thames to get bearings for my attacks. Soon the city was outlined in the distance. There were dark spots which stood out from the blur of lights in the well-lit portions of the city. The windows were not much darkened. It was the dark spots I sought after, and I bore down on them, as they marked the city.
+
+London seen at night from a great height is a fairylke picture. We were too high to see the people in the streets. There was no sound except the whirring of the propellers and lights of what were probably trains. All seems still and quiet and no noise assemb from below amid the spluttering of the motors and the whirring of the propellers.
+
+As if they were making an attack on us, the sudden flash of a number of brilliant light reached out from below and begins to feel round the sky. A second, third, fourth, and fifth soon score a score of criss-crossing ribbons. As viewed from the Zeppelin it looks as if the city had suddenly come to life, waving its arms around in terror and sending out feathery ribbons of fire that threatens, but our impression is more that they are tentacles seeking to drag us to destruction. London keeps a good watch on the sky.
+
+Our raiders now began to soon reveal our presence. First one, and then another and another of those ribbons shooting out from the glaring, eyelike searchlights pick us up. Now from below comes an ominous sound that pene-trates the noise of the motors and the propellers. There are little red flashes and short bursts of fire which stand out prominently against the black background.
+
+<page_number>24</page_number>
+
+**ZEPPELINS : THE PAST AND FUTURE**
+
+From north and south, from right and left they appear, and following the flashes rolls up from below the sound of the guns. It is a beautiful and impressive but fleeting picture as seen from above, and is probably no less interesting than beneath the greyish dull outline of the Zeppelins gliding through the sky. The shadows of lights and the shrimpsel clouds which hang thickly.
+
+But we have no time to admire ; our eyes and mind must be concentrated on our work, for any moment we may be plunged below, a shapeless mass of wreckage and human bodies. I was standing on the roof of the station when it at Johannisthal (the aerodrome near Berlin) two years ago. I had so little time to register my impressions that I have to think back now to give you a descriptive word-picture of what I saw.
+
+When the first searchlight picks you up and you see the first flash of guns from below your nerves get a little shock, but then you steady down and put your mind on what you are there for.
+
+I picked up St. Paul's and from that point laid a course due east towards London. There was a big searchlight in the immediate vicinity of St. Paul's. The English had placed a battery of guns under cover of the Cathedral. Although we had been fired upon from all sides we had not yet dropped bomb. From the Bank of England I shouted through the speaking-tube connecting me with my Lieutenant at the firing apparatus, " Fire slowly." Now, mingling with the din thundered and the vivid flashes of the guns below, came the explosions and bursts of flames caused by our bombs. With the mind solely con-
+centrated on seeking places to drop bombs, the pro-
+gramme for attack as being factors of military bearing,
+the comparatively short time spent above London appeared much longer than it actually was.
+
+I soon found myself over Holborn Viaduct and several places.
+Over Holborn Viaduct and the vicinity of Holborn Station we dropped several bombs. From the Bank of England to the Tower—a short distance—I tried to hit the Tower Bridge, and I believe I was successful, but what was the extent of the damage? I could not determine.
+Flashes from the Tower showed that guns were placed
+
+<page_number>5</page_number>
+
+**ZEPPELINS: THE PAST AND FUTURE**
+
+there, which I had already observed during a previous attack. They were keeping up a lively fire.
+
+Arriving directly over Liverpool Street Station, I shouted: "Rapid fire," through the tube, and the bombs rained almost continuously down on the station, and bursts of fire, and I could see that they had hit well and caused apparently great damage, which has been confirmed by reliable reports we have since received.
+
+Flames burst forth in several places during that vicinity. Having done my duty, I returned my ship for home. My orders had been carried out quickly. Despite the bombardment of the sky we had not been hit. Several times I leaned out and looked up and back at the dark outline of my Zeppelin, but she had no hole in her grey sides.
+
+In point of damage done and hitting the objects which I was instructed to attack it was my most successful trip over London or the vicinity. Ascending or descending until we found a favourable wind, we made a quick return.
+
+The Home Office, in passing the foregoing article for publication, emphatically contradicted the assertion that anti-aircraft guns were mounted under cover of St. Paul's, and pointed out that Mathy's statement obviously was intended to provide an excuse for the outrage he had failed to perpetrate.
+
+The raid on London of October 13, 1915, in which 42 men, 9 women, and 6 children were killed, and 77 men, 30 women and 7 children were injured, was thus acclaimed (in The Times New York Correspondent, November 18, 1915) :
+
+The East India Docks were attacked and a large shed full of ammunition was burned to the ground. At the London Docks a warehouse was destroyed, several ships were hit by bombs and some were destroyed. At Victoria Docks a large cotton warehouse was burned to the ground. In the same neighbourhood blocks of houses were destroyed or damaged in St. George's Street and Loman Street. The City, and particularly the newspaper quarter, was
+
+<page_number>26</page_number>
+**ZEPPELINS : THE PAST AND FUTURE**
+
+bombarded with especially good success. The Tower of London and London Bridge, which was armed with guns, were bombarded. Houses-sometimes whole blocks of them-were damaged or destroyed in Liverpool Street, St. Martin's Le Grand, St. James's Square, Aldgate, and the Minorities. The London and South-Western Bank was burned to the ground. Much money, valuables, and papers are believed to have been des-troyed. The **Morning Post** building was seriously damaged and a part of the London Bank was reduced to ashes. Subway (Underground) and railway traffic was interrupted for a time owing to bomb damage.
+
+Much damage was done at Woolwich Arsenal. In Enfield a battery with searchlights was silenced. The Hampstead tube station was bombed and the ammunition factories were hit and great fires were noticed. In Kentish Town an especially strong searchlight battery was noticed and bombs were dropped on it. A whole row of searchlights went out. At Woolwich and East Ham the railway was bombed. At Deptford the battery was bomb- barded and its fire became noticeably weaker. A German airship was the object of unusually hot fire, but was not damaged. Four airplanes attacked the airship without success.
+
+The truth is that neither the East India nor any other docks were bombed. The Tower of London and the Tower Bridge were not touched, and the damage done in the City was mainly confined to windows and doors and the street pavements. The majority of the casualties occurred in the East End where the population is crowded in small and tenement houses-a class that, throughout, has borne the brunt of German frightfulness. The circumstantial details regarding Woolwich Arsenal, Enfield, Hampton, etc., were purely imaginative and doubtless were intended to lend verisimilitude to an otherwise bald and unconvincing narrative.
+
+Of the raid of January 31, 1916, when more than 250 bombs were dropped over Norfolk, Suffolk, Lincolnshire,
+
+ZEPPELINS: THE PAST AND FUTURE <page_number>27</page_number>
+
+Leicestershire, Staffordshire, and Derbyshire, and 67 persons were killed and 117 injured, the Berlin claim (vide The Times Amsterdam Correspondent, February 2, 1916) was that
+
+On the night of January 31st one of our naval airship squadrons dropped large quantities of explosives and incendiary bombs on the docks, harbour, and factories in and near Liverpool and Birkenhead, on iron-foundries and smelting furnaces at Nottingham and Sheffield and the great industrial works on the Humber and near Great Yarmouth.
+
+Everywhere marked effects were observed in the gigantic explosions and serious conflagrations.
+
+On the Humber a battery was also silenced.
+
+Our airships were heavily fired on from all directions, but were not hit and safely returned.
+
+The truth is that none of the raiding airships got near to Liverpool, Birkenhead, or Manchester. There were no smelting furnaces in Nottingham to bomb, nor was Sheffield damaged. Some breweries, railway-sheds, a factory or two, and the houses of workmen's dwellings, chapels, and churches were damaged.
+
+On February 1, 1916, the German Wireless sent out a statement (The Times, February 8, 1916) to the effect that during the air raid of January 31, the small English cruiser Caroline was sunk by a bomb in the Humber with great loss of life during the last Zeppelin raid.
+
+The British Admiralty promptly stated in contradiction that none of His Majesty's ships nor any merchant ship, large or small, had been bombed.
+
+The Berlin account (The Times, April 3, 1916) of the raid of March 31, 1916, claimed that during the night of March 31-April 1 one of our airship squadrons attacked London and the South Coast of England. Bombs were freely dropped on the City
+
+<page_number>28</page_number>
+**ZEPPELINS: THE PAST AND FUTURE**
+
+between Tower Bridge and London Docks, the military camps in the north-western district of the City, the manufactories near Enfield, and the munition works at Wath [sic] Abbey.
+
+Another airship, after having successfully attacked a battery near London Bridge, dropped a number of explosive and incendiary bombs on Lowestoft.
+
+A further battery was silenced near Cambridge, the extensive manufacturing works of the town were attacked, and bombs were finally dropped on the fortification works and harbour of Felixstowe, whereby three batteries were reduced to silence.
+
+All the attacks were successful, and reliable observations from the airships discerned the presence of numerous fires and explosions in various parts of England.
+
+In spite of violent bombardment all the airships returned, with the exception of L15, which, according to a report, was compelled to descend in the water of the River Thames. Searches instituted by our naval forces have, up to the present, not been productive of any result.
+
+Every claim made in this statement was false. The attack on London was abandoned owing to the damage caused to L15, which was hit so badly that it came down in the Thames Estuary.
+
+A typical instance of the manner in which prevarication is employed by the enemy to disguise defeat is seen in the following report issued by the German Naval Staff ( cited in Times Amsterdam Correspondent, September 3, 1916):
+
+On the night of September 2nd, several naval airship squadrons dropped a large number of bombs on the Fortress of London, the fortified places of Yarmouth and Harwich, and on other points in the counties of the South-Eastern Counties and in the Humber district.
+
+The good effect of these attacks was proved by the fact that great conflagrations and explosions were everywhere observed.
+
+All the naval airships returned undamaged, although they were strongly bombarded.
+
+**ZEPPELINS : THE PAST AND FUTURE**
+
+Simultaneously an attack by army airships took place on the South of England.
+
+It was on the occasion of this raid that a military airship was destroyed at Cuffley by Lieut. Robinson. So soon as the news of its destruction became impossible to conceal, the German Headquarters Staff issued the following ——
+
+During the night of September 2nd our naval and army airships attacked the Fortress of London and good results were observed.
+
+One of our vessels was brought down by enemy fire.
+
+A final instance of tergiversation will now suffice. On March 16, 1917, some two or three Zeppelins, very obviously detached for purposes of diversion in connection with sea activities, visited a section of the South-Eastern Coast. No damage to property or persons was inflicted; but they were capable of the discharge of some fifty bombs, yet this is the German official description of the raid (The Times Amsterdam Correspondent, March 17, 1917)—
+
+One of our naval airship squadrons, in spite of violent counter-attacks by hostile aircraft and anti-aircraft guns, successfully dropped bombs on London and the South-Eastern Counties during the attack lasting half an hour. Our airships returned safely.
+
+London was not visited, and there were no counter-attacks by British pilots for four hours and sufficient reason that owing to heavy ground fog the raiders could not be sighted.
+
+It will be evident to any sensible person that these German romances either indicate a total ignorance on the part of the airship commanders of their routes (and a consequent assumption which required elaborate details to satisfy the demands of the German people deluded into believing that England was devastated and terrorised), or, being obvious to some extent even though neutral sources, these fables were deliberately invented for an obvious purpose. The point to remember is that throughout no military damage was caused, that only
+
+30 ZEPPELINS : THE PAST AND FUTURE
+
+civilian life and property suffered, and that, in the end, failure had to be admitted. Count Zeppelin himself shortly before his death was reported in the Swiss Press to have confessed the futility of attempting further attacks on this country in face of the danger involved by the efficiency of our air and artillery defences.
+
+IV
+
+A S has been explained in an earlier chapter, two cir-
+cumstances for some considerable time affected detrimentally the defence of England against night-raiding Zeppelins. The first was a temporarily irremediable shortage of guns and gunners, the second was incomplete knowledge of the relative capacity and power of the types of airship employed in these raids. From the beginning of the war the enemy boasted of the destruction he was going to accomplish in England with his Zeppelins, and we were under no misapprehension concerning that intention. The nocturnal attacks on Antwerp in August, 1914, clearly indicated the form raids on us would take, and such was the case until the summer of 1915, when it became evident that such raids were a part of the German programme.
+
+Had the information gathered from the log of Z4 been reliable, the defences would have proved fairly efficient. They consisted of small-calibre naval guns, supplemented by naval searchlights. We had no special anti-aircraft guns in our equipment, as Germany had not found any reason that we had harboured no warlike designs in 1914 or preceding years, we had not anticipated attack from any Continental air power. The progress of aeronautical science and its application to military purposes had been so rapid in the period immediately preceding the war that our ordnance direction had not had time, even had they the means, to adapt themselves to new methods of artillery. Our gunners had no experience of anti-aircraft work ; but, in view of the seemingly reliable data supplied
+
+**ZEPPELINS: THE PAST AND FUTURE** 31
+
+by the Lannville Zeppelin's log, the task of hitting an airship was not considered outside the powers of an expert gunlayer using a light naval gun with an effective horizontal range of 7,000 yards, and assisted by searchlights. French 75s had been sufficiently powerful to damage and bring down ZS which had attempted to operate against our Ally at Badoeville in August, 1914.
+
+But the German airships were seen to rival England were very different craft from Z4 and Z8, and our gunners discovered that their target was more elusive than its estimated speed and powers of ascent warranted, while longer-ranging weapons obviously were required. And at a time when the demands of the Admiralty and the War Office on our ordnance factories for desirable additions we were making to our Fleet, our Army, and the forces of our Allies were insistent, we were without any immediate power to remedy the situation by mounting guns of greater calibre, except at certain points where it was imperative that raids should not be made without very great risk.
+
+Accordingly we had to be content for over a year to endure these Zeppelin attacks and by various measures attempt to reduce their effectiveness ; and that they could not effect better results in the circumstances is not greatly to their credit. By that time the pressure of the demand on our ordnance factories had been sufficiently diminished to admit of special attention being devoted to the Zeppelin raid work; and in the interval our searchlights and propellers had been steadily improved, so that when the turn of the tide came the Zeppelin-raid bubble was quickly pricked.
+
+The first palpable success of our land defence was scored against the raid of March 31, 1916, when, during an attack directed against the Eastern Counties and London, it failed to reach its objective because of the radars was badly damaged by gunfire that, although managed to get away for the time being, it eventually fell, a wreck, into the sea at the mouth of the Thames.
+
+32 ZEPPELINS: THE PAST AND FUTURE
+
+Before this, however, a policy of attacking the Zeppelin in their bases had been inaugurated by the Admiralty with considerable success. On November 21, 1914, British naval pilots made a successful aeroplane raid on Friedrichshafen on Lake Constance, the then headquarters of Zeppelin construction, and an airship was destroyed. Towards the end of December another aeroplane raid was made on the Zeppelin sheds then being constructed at Friedrichshafen. A great number of bases at Cuxhaven was also bombed. Zeppelins were bombed several times, and Hoboken at Antwerp, also used as an airship base, was heavily raided twice in March and April, 1915. On June 7 a double success was scored, for Lieut. Warneford, R.N.R., in an aeroplane intercepted and destroyed near Brussels a Zeppelin returning from a raid on the South-east Coast. With the remainder of his squadron sought out and destroyed another Zeppelin in its shed at Évère, near Brussels.
+
+These successes induced the Germans to withdraw their airship bases from Western Belgium. Meanwhile the raids on England apparently continued to escape punishment, but it is known that on several occasions the raiding parties were attacked. On August 18, L19, was lost in the North Sea off the East Anglian coast, and reports from the Continent announced other losses indirectly due to operations undertaken against England.
+
+It was not until September 2, 1916, however, that a satisfactory solution of the problem was found. On that date the greatest raid of German airships yet made was carried out, covering the whole Eastern coast, penetrating into the Midlands and down to London. In all, some eighteen units were employed, several of them being obviously earlier models. One of these, as already mentioned, while making to attack London was engaged by anti-aircraft guns near Barnet and by Lieut. Robinson, R.F.C., in an aeroplane. The latter, though heavily fired upon from the Zeppelin, succeeded in getting home an incendiary bomb which set the gasbag alight, and the airship
+
+**ZEPPELINS: THE PAST AND FUTURE**
+
+fell to earth in flames and was consumed near the hamlet of Cuffley in Middlesex. Apparently incredulous that their elaborate construction, designed and considered successful against attack of this description, should have been proven vulnerable, another raid was dispatched against London three days later. In the result that L38 was brought down in flames at L30 and L31 was damaged by gunfire that it was compelled to descend in Essex and its crew surrendered. Still persisting, a week later yet another, L31, was brought down in flames at Potters Bar, just north of London. Military pilots using fast-climbing, night-flying aeroplanes, equipped with special bombs, proved that the Zeppelin is an easy prey when properly attacked.
+
+After this last raid the spell had broken. But the spell had been broken, and when the East and North-east Coasts were raided on November 27, 1916, two more Zeppelins were destroyed, in each case after having been hit by our artilleries. One fell into the sea off Hartlepool and its crew were drowned. The other was brought down in flames nine miles out at sea from Lowestoft by naval aircraft after being shot up by guns.
+
+These continuous losses, accompanied as they were by relatively insignificant results, convinced the enemy that, despite all his labour and ingenuity, the usefulness of the airship as a weapon of military offence on the lines hitherto employed was effectively dissipated, and might henceforth cease to be used such purpose. When its loss was not the greater evil. Examination of the wrecks of the vessels brought down in Essex, one of which was virtually intact save only for its envelope and the damage caused by our shells, disclosed the great difference between these craft and the Lunéville Zeppelin of 1914.
+
+Coffey's report on the results of this expedition from raids had led to a relaxed defensive vigilance, the Germans four months later launched an expedition against London on the night of March 16, 1917. This actually reached Kent but was entirely futile, and ended in one of the raiders, L39, being blown across the Channel out of her
+
+34 ZEPPELINS : THE PAST AND FUTURE
+
+course. She got as far as Compiegne, near Paris, where she was discovered by the French anti-aircraft gunners and brought down in flames. Still persevering, after another two months' preparation Zeppelins crossed the Norfolk coast again on May 23, but ground fog both saved them from attack and prevented them from doing any damage. A further attempt in June 16 ended disastrously, for the airship caught fire and aeroplane barrage and brought down in Suffolk. Three of her crew were made prisoners ; the remainder perished.
+
+That seemed to have convinced even the most obstinate German enthusiast that the airship as a raiding machine was a failure, for the next four months, though presenting many formidable sights, were undisturbed. But the Hun was not yet satisfied and he launched from time to time terribly disastrous results to himself. On the night of October 19th one of the most formidable of all these raids was launched from the North Sea bases, no fewer than thirteen naval Zeppelins being employed. Apparently they met at a pre-determined point and, taking advantage of a north-east wind, shut off their engines at a safe altitude and descended upon the Eastern Counties of England, sowing bombs as they passed over.
+
+The surprise was undoubtedly ; but the end was reticulative. The wind had increased to a gale of extremely low temperature which, besides offering alarming resistance to airship navigation, appears to have frozen some of the carburetors and the water-jackets of the engines of quite a number of them. In spite of difficulties when required, they were found useless. Four ships proved to be helpless to do other than float along on the gale, and when morning broke they found themselves across the Channel in France, where they became targets for the French airmen and gunners. L49 was forced to ground and captured at Bourbonne-lès-Bains. L50 was damaged beyond repair by fire and had to return to the Mediterranean and was totally lost. L45, damaged by gunfire, got as far as Sisteron, 75 miles south of
+
+**ZEPPELINS: THE PAST AND FUTURE**
+
+Grenoble, with great difficulty, and there came down and was burnt by its commander. Another, L44, was brought down at St. Clément, near Lunéville, by anti-aircraft gunfire.
+
+That ant-climax virtually represented the end of Zeppelin raiding activity against England, for the timed trip-as-run visits to Yorkshire coast on March 12 and 13, 1918, were worth consideration. On April 12, however, a more formidable attack was launched against the North of England, which nevertheless did very little damage. Whatever fresh designs may be harboured, we may rest assured that all the ingenuity of the German constructors and tacticians will prove useless against the apparatus now employed by the Allies, and while Zeppelins may still be used for raiding purposes, they will still have in extremity, invite the attack of aeroplanes or seaplanes.
+
+In no single reported instance where the aeroplane has got home has the Zeppelin escaped, and that knowledge must act as a wholesome deterrent to any promiscuous or general policy of raids against defended districts.
+
+There is nothing virtual about the scheme by which Germany had made the admissions of its writers, hoped and expected to be able to attack and devastate our cities with impunity, even to sink our Fleet, and certainly to create a feeling of such terror and helplessness as would compel our Government to accept peace on German terms. It seems ridiculous, in view of the completeness of our defences, that any such hope could have been entertained by experienced military experts, but there is no doubt that it was the case, and the fact only goes to show how very much over-rated the German war machine was by its authors.
+
+V
+
+W
+**H** **A** **T** **E** **V** **E** **R** **Y** **m** **a** **y** **b** **e** **o** **u** **r** **o** **p** **i** **n** **i** **o** **n** **o** **f** **t** **h** **e** **m** **i** **l** **i** **t** **a** **r** **y** **v** **a** **l** **u** **e** **o** **f** **t** **h** **e** **Zeppelin**, there can be no doubt that, as an engineering creation, it ranks among the most successful products of the twentieth century, and is a monument to
+
+36 ZEPPELINS: THE PAST AND FUTURE
+
+the ability and pertinacity of its inventor. Compelled by the nature of his design to adopt huge proportions of space and the flimsiest of materials, Count Zeppelin yet suc-
+ceeded in evolving a craft larger than any but the greatest
+transatlantic steamships; whose total weight is under
+fifty tons; whose speed in still air is as fast as our fastest
+express trains, with a radius of operation of five hundred
+miles at 100 miles an hour can be said to be as great as
+certainty as an ocean liner. So high is his achievement that it evokes regret that it should be tarnished by an
+acquiescence in its use for an unworthy and uncivilized
+form of warfare.
+
+The framework of the gas container of Zeppelin L38
+—the first German zeppelin we secured in sufficiently unchanged condition to make a mechanical analysis possible, although the French have since secured L49—was approximately
+220 metres or 670 feet long, and 72 feet in diameter at its greatest girth. It was composed of twenty-five
+longitudinal girders of riveted aluminium lattice-work
+tapered fore and aft until they converged in the first and last of the two ring-girders ring girders which, equally spaced
+and lapped into their neighbours, form the main frame.
+The aluminium alloy employed is actually lighter than
+pure aluminium and is probably magnesium, or a variant
+of it, in which magnesium is a constituent.
+
+The lattice girders are triangular in plan, the main
+ribs being channelled and the cross-ties connected to secure strength. The ribs are bent forward each
+alternate ring is " king-posted"—that is to say the flat
+sides of the ring—there are twenty-five flats in each circle—are the bases of small supported triangles of lattice-
+work with the apices inside the gas container. These
+" king-posted" girders are tautened inwardly by means
+of wire stays connecting the junctions between the ring and longitudinal girders with hubs. By means of the
+manner of a bicycle wheel, this hub providing a means of
+tensioning the wire stays so that an equal stress is put on
+each of the joints of the frame. Through these hubs, fore
+
+Bow of Zeppelin L32
+<page_number>P. 56</page_number>
+
+ZEPPELIN L31, DESTROYED BY LEUTENANT SOWHEY AT POTTERAS RAN, OCTOBER 1, 1915. <page_number>Page 87</page_number>
+
+ZEPPELINS: THE PAST AND FUTURE <page_number>37</page_number>
+
+and aft, runs an adjustable wire cable which ends in the nose and tail plates of the frame, so that by it and by the radial wire-stays the whole frame can be tautened or braced and thus greatly stiffened.
+
+The gas bag is composed of two skins. The outer envelope is the framework and is made of a special linen or cotton fabric doped to render it gas-tight and to reduce the air friction on its outer surface. The inner envelope, also gas-tight, has all the framework on its outside so that there is a space between the two skins, into which it is said that the exhaust gases from the engines are forced—-a device which, if correct, is intended to fulfil two purposes: These gases are hot and therefore tend to some extent to neutralize any leakage of hydrogen from the gas bags proper—which in the past is said to have caused catastrophe; also the exhaust gases, being hot, can be used to counteract the effect of low external temperatures which cause a loss of bulk and buoyancy.
+
+The two million cubic feet of hydrogen gas required to feed the Zeppelin is contained in sixteen, ten to twenty-four separate balloonets, each provided with a pair of stuffing-box glands to permit the central hawser to pass through without entailing gas leakage. Through the greatest diameter of the gas container is a tunnel leading from the main gondola to the upper surface of the container, where a machine-gun platform is situated, carrying a Maxim gun. The extreme ends of all contain any gas bag, the fore end being specially braced to resist the pressure due to air resistance when the Zeppelin is travelling, while the rear, tapering away to a point, contains the elevator and rudder plane posts and a machine-gun plat-form, the final section of the frame here having but six sides.
+
+A large number of steps lead up from the floor to an open cat-walk or footway consisting of wood—the only rigid part of the machine not composed of aluminium. This gives access to the fore and aft sections, to all the gondolas, and to the machine-gun platform at the tail.
+
+There are four gondolas or cars, carrying, in addition
+
+38 ZEPPELINS: THE PAST AND FUTURE
+
+to the crew, six sets of six-cylinder petrol engines driving six air-screws. The engines are rated at 240 h.p. running at about 1,000 revolutions per minute. Two of the gon-
+dolas are set along the central line, one forward and the other aft. The forward one carries a single set of engines driving an air-screw behind ; the rear one, which is about 40 feet long, is the main car of the Zeppelin and carries the bomb-thrower. In front of each engine is an air-
+screw behind it, the other two each driving through bevel gearing an air-screw set out from and attached to the frame of the gas container. The engines are of the water-jacketed type with special provision for cooling the lubricating oil as well as the water. Each engine is provided with a propeller, which may be used both for manœuvreing purposes in addition to propulsion. The petrol tanks are carried in the container frame over the engines, so that they are well away from the engines, and at the same time provide fuel feed which is constant, no matter at what angle the airship may be rising or descending. The other two gondolas are small and attached to the sides of the main girders on either side of the containers. All are fully enclosed and are
+warmed by the exhaust from the engines.
+
+All the control operations, including the bomb drop-
+ping, are conducted from the forward car, so that the
+commander is the practical executant of every offensive act. The bombs, sixty in number are carried about mid-ships in a specially designed gas container,
+is released separately by an electric switch in the forward
+car. The crew may consist of from sixteen to twenty-
+two, the latter being the full complement, but often super-
+numaries are carried for instruction purposes. The carry-
+ing power, in addition to three tons of fuel for a journey
+to England and back, is about three tons, and as there is a considerable loss of buoyancy owing to gas
+leakage, the return journey is only made possible by the
+consumption of fuel and the discharge of the bombs
+carried on the outward journey.
+
+**ZEPPELINS:** THE PAST AND FUTURE
+
+Conclusions arrived at on evidence possibly not yet complete are likely to be confuted, but we believe that there is no physical point left in the Zeppelin problem that has not been exploited to its farthest for the purpose of war, and that future discoveries in science and developments in engineering may give the rigid airship a fresh and more formidable character as a military device, for the time being its limitations have been laid bare and its value has been accurately estimated. As a punitive instrument and as a means of attacking an enemy possessed of proper means and methods of defence, that value is small. But it is easy to imagine conditions under which it would prove a valuable and possibly even a decisive weapon.
+
+Those conditions, however, are not such as to preclude the use of aeroplanes for a similar purpose, and as to the relative values of the two machines for almost every purpose of war there can be no dispute. The aeroplane is immensely superior in one way, and on the evidence of actual facts it is fair to say that there is little that the rigid airship can achieve in war that the big aeroplane cannot be designed to accomplish more certainly, more quickly, and more cheaply. At the moment, however, it is probable that the Zeppelin possesses a distinct and important advantage in naval scouting and long-range reconnaissance.
+
+Under suitable conditions its value as a high-seas patrol is considerably greater than that of any existing seaplane, not merely because it can travel greater distances from its base and remain a longer time in the air, but because its wireless telegraphic installation, being more powerful than any fitted to an aeroplane, can maintain continuous contact with the base of its fleet and can direct operations from a distance at present far beyond the radius of any other aircraft.
+
+The clearest instance of that advantage was in the Jutland battle when the main German fleet under Von Scheer was so accurately informed of the approach of
+
+<page_number>40</page_number> ZEPPELINS: THE PAST AND FUTURE
+
+Jellicoe's forces that it was able to break off its action with Beatty's battle cruisers in time to escape the annihilation that assuredly would have overtaken it had the action been prolonged sufficiently to permit the whole British fleet to join issue. And throughout the entire course of the North Sea operations of the past thirty-three months it would not be easy to overestimate the scouting and reconnaissance work which the Zeppelins did on the German naval plan. Probably before the war is over that value will be discounted by seaplane developments, but it would be idle to deny that as a means of naval observation and direction the Zeppelin has been worth all its heavy expense to the enemy.
+
+As regards its speed, however, it is a fair-weather craft. Not only is it much more difficult to navigate in heavy weather—the great attack on England in October, 1917, was rendered disastrous by the sudden interposition of a gale which entirely precluded driving directly homeward—but it cannot be launched with safety in the presence of winds of any violence since its huge bulk, fragile construction and great buoyancy render it unmanageable from the start in other than calm weather. Moreover its base must be on terra firma, whereas the seaplane is almost certain in the near future, if not already, to be able to make the deck of a light cruiser all-sufficient for every purpose of this kind, launching and returning being almost as facile and certain as with a ship.
+
+Even its load-carrying capacity is being challenged by the big long-distance bombing type of aeroplane, whose greater margin of safety, higher speed, better manœuvring power and lesser vulnerability must in the end do much to write off the airship as a military war-machine. One great advantage of the airship has not been capitalized upon—its capacity to travel in absolute silence by taking advantage of a favouring wind to reach its objective.
+
+Many people have wondered that a means of damping
+
+ZEPPELINS: THE PAST AND FUTURE <page_number>41</page_number>
+
+down the noise of the engine-exhaust, such as has been developed with conspicuous success in the motor car, has not been adopted in the Zeppelin. The usual explanation is that the absorption of power inevitable in any such device attached to the powerful engines of an airship would be so great that dirigibility could not be maintained. But in this lighted up world it is nearer actual fact to point out that, while silence in this way would render approach safe, once the defensive searchlights located the airship, so great are the speed and climbing powers of our newer types of aeroplanes, the ability to use silence for escape would not avail anything, for within a few minutes the aeroplanes would be able to overtake and attack. The automatic closing mechanism and exhausting direct into the air would not afford it any distinct chance of escape.
+
+The really silent Zeppelin able to develop even 75 per cent. of its engine power would be a distinct advance on the present type and under certain conditions would be almost as difficult to frustrate as a submarine for we cannot imagine a more complete and comprehensive as to discover the approach of an airship emitting no sound and travelling by night. But it has not yet appeared and, as we have pointed out, the problem of escape, which is almost as important as that of attack, is not helped by silence to a material degree.
+
+APPENDIX
+
+The following is a complete list of the Zeppelins known or reported in the Press to have been lost or destroyed since the opening of hostilities. There may have been others, so that this can be considered in the light of a minimum loss.
+
+1914—EIGHT AIRSHIPS.
+Aug. 23 Brought down by French guns at Badonviller.
+.. 24 Wrecked by storm near Metz.
+.. 29 Brought down by Russian guns near Mlava.
+Sept. 26 Brought down by Russian guns near Warsaw.
+Oct. 8 Destroyed by British naval pilots at Düsseldorf.
+.. 14 Brought down by Russian guns at Warsaw.
+Nov. 21 Destroyed by British pilots in their sheds at Fried- richshafen.
+Dec. 30 Destroyed by British naval airmen at Cuxhaven.
+
+1915—FIFTEEN AIRSHIPS.
+Feb. 9 Lost in North Sea.
+.. 17 Lost in North Sea off Jutland (2 ships).
+Mar. 2 Wrecked at Cologne.
+.. 8 Wrecked in English Channel.
+.. 8 Brought down by Belgian guns at Antwerp.
+.. 12 Wrecked by storm in Belgium.
+May 29 Storm in storm in the Baltic.
+June 7 Destroyed by German aerodrome at Ghent.
+.. 30 Burned near Brussels.
+Aug. 3 Brought down by Russian guns near Vilna.
+.. 10 Brought down by naval guns off Ostend.
+Sept. 5 Storm in sea, Belgium.
+Oct. 2 Blown up by Kib.
+Nov. 13 Brought down by Russian guns near Grodno.
+
+APPENDIX <page_number>43</page_number>
+
+**1916—TWELVE AIRSHIPS.**
+
+Feb. 2 L19 sunk in North Sea.
+" 21 LZ77 brought down by French gunfire near Revigny.
+Mar. 31 L15 hit by British guns and sunk in Thames Estuary.
+May 3 L20 wrecked in North Sea off Stavanger.
+" 4 Destroyed by British naval gunfire in North Sea.
+" 5 Destroyed by British naval gunfire at Cuffley.
+Sept. 2 Schütte-Lanz destroyed by Licut. Leefe Robinson at Cuffley.
+" 24 L38 destroyed by British guns in Essex.
+" 24 L39 brought down in Essex.
+Oct. 1 L31 destroyed by Licut. Sourcery at Potters Bar.
+Nov. 27 Destroyed by British pilots off Coast of Durham.
+" 28 Destroyed by British naval gunfire in North Sea.
+
+**1917—THIRTEEN AIRSHIPS.**
+
+Jan. 9 Destroyed by workmen's sabotage at Kiel (2 ships).
+Feb. 9 Burned in shed at Ghent.
+Mar. 17 Destroyed by naval forces in Heligoland by French gunners.
+Apr. 23 Wrecked near Duisburg.
+May 14 L22 destroyed by naval forces in North Sea.
+June 14 L48 destroyed by naval forces in North Sea.
+June 14 L48 brought down by guns in Suffolk.
+Aug. 10 L50 brought down by guns in Sussex.
+Oct. 20 Destroyed by French artillerists and airmen (4 ships).
+
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+Campbell, Edwin
+Zeppelins, the past and future
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