Why are passengers requested to close their window blinds during a night-time takeoff? Why are passengers requested to close their window blinds during a night-time takeoff?

I understand why they are asked to open them during day-time take-offs and landings - probably because rescue teams can look inside in the case of a crash. But what´s the point in closing them at night?

The only reason I can think of is that people might mistake the cabin lights for landing lights, hence misjudging the planes orientation. Still, it is very difficult to mistake a row of cabin lights for landing lights?

This is a personal experience rather than an authoritative answer, but I thought it would be relevant.

I fly a few airlines fairly frequently and have done for many years. I've always thought that blinds should be open for safety reasons. However, a few years back I was on a flight with an airline that I'd flown many times before and had always enforced the blinds-open policy. To my surprise everyone was asked to close the window blinds. Within a year the trend had increased to point where all flights by this airline were blinds-closed. Then, a year or so after that, the policy was reverted to blinds-open and has remained since.

My theory is that someone in the senior crew, or crew training, mixed up the policy and started enforcing the wrong one (i.e. blinds-closed). I think this is plausible as the reasons for having blinds-open are not entirely obvious. It would also explain the gradual adoption of the new policy. I guess someone eventually realised the mistake, hence the sudden reversal.

Sorry for the long post and lack of sources. Will delete if deemed not helpful.


Is IAS without instrument error the same as CAS? I was reading a POH which stated something along the lines of

  NOTE

  Except as noted, all airspeeds quoted in this handbook are Indicated
  Airspeeds (IAS) in Knots and assume zero instrument error.

Why didn't they denote that as CAS (calibrated airspeed) instead, which is without instrument error? Is there a key difference between the two that I'm missing?

Even without instrument error, IAS does not equal CAS. This because there are two kinds of errors that make up the difference between Indicated Airspeed (IAS) and Calibrated Airspeed (CAS)

Installation error
Instrument error

Installation error is basically a pressure error. Airspeed measurement is a measure of dynamic pressure of the undisturbed airflow. When the pitot tube is not placed directly into undisturbed airflow the IAS will not equal the CAS. Another source of installation error are leaks in the pitot system.

Instrument error is the error introduced by ASI itself by transforming the pressure to a speed indication. For example calibration errors of the pressure sensor or excessive friction in the mechanical drive system of the dial fall into this category.

The POH in your example assumes no Instrument error, but is corrected for installation error. An implicit assumption is made that there are no leaks in the system, so the POH corrects for airflow disturbances. That is why some aircraft have different tables for different configurations; the configurations affect the airflow around the pitot tube.

In aircraft equipped with electronic Air Data Computers (ADC's) the installation error is sometimes automatically corrected by making use of angle of attack sensors, electronic configuration information and lookup tables.


Why would an airport use crossing runways for takeoff and landings? I was listening to some RealATC this evening and came to this one about an accident at LaGuardia airport. This question is not about the accident in any way, but I am using this video because it has an example of what I mean and has a labelled diagram as well.

As the clip advances, it becomes clear that at that time, planes were landing via ILS Runway 13. However, planes were being directed to takeoff from Runway 4.

Under what circumstances might a major commercial airport have planes landing and departing via crossing runways, instead of on the same, or at least parallel?

Any time the winds and traffic permit an airport may chose to use intersecting runways. You can read some interesting info on it here and here. In some cases when both runways are in use they may have the aircraft execute Land And Hold Short procedures. The pilot has the final say in a LAHSO situation and you can call no joy if you think you cant complete the maneuver as requested.

Some airports may only have 2 runways set up in an intersecting layout and may not have the luxury of parallel runways. Depending on terminal layout at commercial airports using both runways may aid in traffic flow on the ground as well as getting planes in the air.

Winds permitting generally have to do with the maximum cross wind component of a given airplane. Although generally speaking you will see this done in calm wind situations. The other cause I have seen for this is instrumentation, some airports may have intersecting runways that are not equipped the same or of the same length. As lets say the favorable runway is is 5000ft visual approach only strip and you need 6000ft to land. Luckily the airport has another intersecting runway that is a 7000ft strip (and has an ILS approach not that you need it (its nice out)). They may have you come into the other runway while they sequence small visual traffic on to the short strip (possibly having them land short if need be).


How to calculate optimal prop diameter, pitch, torque and power coefficient given required thrust? this is my first post here, so bear with me if this isn't the right place. I'm coming here from Stack Overflow, and this seemed to be the most relevant Stack Exchange for my question.

So, I'm building a multicopter (quadcopter, preferably, due to it's relatively simple design) on a scale that's more-or-less never been done before. I've decided to funnel all the money I made over the summer into this project, and I've just begun the planning stage.

I've worked out that I need about 2500 Newtons of thrust: enough to move 180 kilograms (about 80kg for the person and 100kg for the electronics, maybe more) at a rate of ~4.5 m/s^2 more than standardized gravity—13.888 m/s^2 in total, to be specific. I'd need approximately 750 Newtons of maximum force on each rotor, as my experience with building and coding (from scratch) an Arduino flight controller has taught me that the upper motors often need to work much harder during x and z movement than they would during standard y elevation.

Some other notes:

I'm pretty sure that π * diameter-in-cm * rpm / 6000 must be <340.29 (Mach I). Maybe I should be using a turbofan? Especially considering the next note...
The diameter of the rotors shouldn't exceed 30cm for convenience purposes. I.O.W. it can't be too big or else lugging it around would be a hassle.

Fuel source will (hopefully) be batteries, most likely an array of LiPo cells in series and in parallel (probably something like 10x10), each cell containing about 10,000mAh.

I struggle to continue from this point. I haven't the slightest idea as to how to pick a prop design that is most efficient for this project. My question for Aviation is this:

  Given a required maximum sustainable thrust of 750 Newtons, a mass of about 180kg, and the assumption that maximum velocity of the craft is slow enough that air resistance and other drag is pretty much irrelevant...

  How would I be able to calculate the optimal prop diameter, pitch, Kp (power coefficient), Kt (torque coefficient), as well as optimal number of blades and optimal manufacturing material? Or, would a turbofan be more optimal?

I wouldn't be surprised if your first thought was something along the lines of "this is ridiculous." Some may even suspect me of being a troll. I can assure you, I am highly committed to this project. My flight controller is insanely stable, and I believe it would be worthwhile to test its abilities on a build that is more heavy, powerful, and top-heavy than most multirotors ever built.

Could you guys point me in the right direction?

How would I be able to calculate the optimal prop diameter, pitch, Kp (power coefficient), Kt (torque coefficient), as well as optimal number of blades and optimal manufacturing material? Or, would a turbofan be more optimal?

Optimal prop diameter is simple: the largest you can accommodate = 30 cm. Disk area A = 0.07 m$^2$
Optimum number of blades: as few as possible, let's start with 2.
Use ducted rotors for a more vertical alignment of the rotor tips.
The quadcopter has horizontal rotors. Tip speed should not exceed 0.8M = 270 m/s which equates to $\Omega$ = 570 rad/s = 5,520 RPM
We have a prop diameter, RPM and thrust, now we need to determine power P and torque Q to drive the prop. We'll do so using expanded momentum theory for the hover, like in this answer.

For a rotor with solidity ratio $\sigma$ = 0.1, the thrust coefficient $C_T$  is maximum 0.01, let's use a safety margin of 20% and take 0.008. Then the maximum thrust for this rotor becomes:

$$T = C_T \cdot \rho A (\Omega R)^2 = 0.008 \cdot 1.225 \cdot 0.07 \cdot 270^2 = 50N$$

We need 15 times this thrust! In order to verify the value of $C_T$ there is another graph in Leishman that relates $C_T$ with blade-pitch angle. It turns out that $\sigma$ = 0.01 is at a blade-pitch angle of about 12 degrees, we cannot go much higher than that. Neither can we increase tip speed, our only choice is disk area.

$$A = \frac{T}{ \rho \cdot C_T \cdot (\Omega R)^2} = \frac {750}{1.225 \cdot 0.008 \cdot 270^2} = 1.05 m^2$$

You need four rotors of 1.2 m in diameter, with a solidity ratio of 0.1. With the $C_T$ of 0.008, we find a corresponding $C_P$ of 0.0007, which results in

$$P = C_P \cdot \rho A (\Omega R)^3 = 0.0007 \cdot 1.225 \cdot 1.05 \cdot 270^3 = 17.7 kW$$


When are procedure turns not required? Today, at my part 141 flight school I failed a stage check (flight test), because I did not perform a hold. I'm in com-multi training and was shooting a single engine approach in a Beechcraft Baron. I was inbound from the SSW preparing to shoot the GPS 01 approach. I knew the AUGIE route said "no pt", however, because I was a straight in approach, I believed that the hold was not required. So I started the approach at the BEJCY (IAF) rather than turning off course.

The examiner failed me right then and there. After the flight, he told me the ONLY time a hold/procedure turn is not required is where a "no pt" route is published.
Aren't there other circumstances that relieves a mandatory hold/pt?

The correct thing to do very much depends on the clearance that you were given.

If you were simply cleared direct to BEJCY and cleared for the approach, then your instructor is correct and you should have completed the procedure turn as charted.

If the clearance included the words straight in (i.e. "cleared for the straight in GPS 01 approach"), then you could not perform the procedure turn even if you wanted to, without getting permission first.

If you are receiving radar vectors to final (i.e. "Fly heading xxx, cleared for the GPS 01 approach") or if you are doing a timed approach from a holding fix then you may not perform the procedure turn either.

There are also charts which have notes saying "NOPT for arrivals between radials xxx and xxx." or similar, which would also preclude you from performing the procedure turn under the appropriate conditions.

By default, the procedure turn is required if depicted unless there is a specific reason not to.

The AIM says:

  5 − 4 − 9. Procedure Turn and Hold − in − lieu of Procedure Turn

  a. A
  procedure turn is the maneuver prescribed when it is necessary to
  reverse direction to establish the aircraft inbound on an intermediate
  or final approach course. The procedure turn or hold−in−lieu−of−PT is
  a required maneuver when it is depicted on the approach chart, unless
  cleared by ATC for a straight−in approach. Additionally, the procedure
  turn or hold−in−lieu−of−PT is not permitted when the symbol “No PT” is
  depicted on the initial segment being used, when a RADAR VECTOR to the
  final approach course is provided, or when conducting a timed approach
  from a holding fix. The altitude prescribed for the procedure turn is
  a minimum altitude until the aircraft is established on the inbound
  course. The maneuver must be completed within the distance specified
  in the profile view. For a hold−in−lieu−of−PT, the holding pattern
  direction must be flown as depicted and the specified leg
  length/timing must not be exceeded.

  NOTE −

  The pilot may elect to use
  the procedure turn or hold −in−lieu−of−PT when it is not required by
  the procedure, but must first receive an amended clearance from ATC.
  If the pilot is uncertain whether the ATC clearance intends for a
  procedure turn to be conducted or to allow for a straight −in
  approach, the pilot must immediately request clarification from ATC
  (14 CFR Section 91.123).


Does increased fineness ratio decrease skin friction drag? From the Wikipedia article on parasitic drag:

a designer can consider the fineness ratio, which is the length of the aircraft divided by its diameter at the widest point (L/D). It is mostly kept 6:1 for subsonic flows. Increase in length increases Reynolds number. With Reynolds no. in the denominator for skin friction coefficient's relation, as its value is increased (in laminar range), total friction drag is reduced.

The higher fineness ratio gives a longer flowpath, slowing the air more (=higher Reynolds). A slower boundary layer creates less friction downstream.

But increasing the fineness ratio increases the total surface area as well. And that is a recipe for increased friction. From the Wikipedia article on fineness ratio:

As the name implies, this is drag caused by the interaction of the airflow with the aircraft's skin. To minimize this drag, the aircraft should be designed to minimize the exposed skin area, or "wetted surface"

So, what am I missing?

Basically, your confusion comes from not knowing what needs to be held constant.  When you increase the fineness ratio without increasing wetted-area, i.e. you hold wetted-area constant, the overall drag goes down.  You can see this in racing shells (sculling).  The shells (boats) have an absurd fineness ratio, very narrow and very long.  This decreases the overall drag (somewhat, there are other forces at work there).

As you increase the finess ratio, at the expense of increasing the wetted area, you will need to do a trade-study to determine if you gain an advantage.  You probably will, up to a fineness ratio of 6:1.  Much beyond that the extra drag from the increase in wetted-area starts to dominate any savings in drag due to body fineness.

The inital statement is true, presuming you keep the wetted-area constant as you adjust the fineness ratio.

T


What repair can be done on this wingtip? (777) The accident happened in August 2012 and broke the wing of the Boeing 777-200 passenger jet. While taxiing at Shanghai's Pudong airport, its wingtip hit the tail of another aircraft.

What action need to be taken towards this kind of damage?

What manual is used as reference for this repair or replacement?

(Is it Structure Repair Manual or Aircraft Maintenance Manual)

What action need to be taken towards this kind of damage?

The aircraft will be grounded immediately and damage like this needs to be repaired in a timely fashion to get the plane back in the air and making money once again. Its worth noting as well (under FAA regulations) that you would also be in breach of § 23.1385 Position light system installation as the position lights are usually installed in the wing tip.

For damage like this Boeings AOG team will be brought in to repair it

  The Boeing team isn’t called in for everything. Airlines have
  incidents every day, Testin says, and most airport ground crews can
  handle routine repairs—a window cracked by a bird, a component failing
  calibration. An AOG intervention is required for the big things: an
  airplane off the end of a runway, landing gear accidentally retracted,
  a flaming tail drag, two 150-ton behemoths kissing wingtips on the
  ramp.

Since it's Boeing themselves coming in, they may use a variety of reference material to fix the damage and it really will vary case by case depending on what needs to be replaced. In this case the damaged metal will be removed until they get to an area at which they can begin to joint on a new wing tip.

I cant find any great examples of wing repair being done on jumbos as its most likely done behind closed doors but here is a great video of it being done to a small aircraft generally speaking the fundamentals are the same as the designs only change in size. Remove the damaged skin, get the wing down to the ribs/spars, repair/replace ribs if necessary, re-skin wing.


Why did the AvroCar fail to fly above 3 feet? I don’t quite understand why the AvroCar didn’t reach more than 3 feet? Was it a ground effect keeping it at that height and it didn’t have the capability to fly higher?

From what can be gleaned from the Net, it was instability. The Avrocar had plenty of power but was unstable. The resulting behavior made it uncontrollable when leaving ground effect. In this publication I found an illustration which tries to explain what went on:

Any asymmetry in flow would shift the center of pressure, resulting in a wobbling motion called hubcapping (because it resembled the motion of a hubcap when dropped to the ground).

From the linked document:

  On September 29, the ﬁrst attempt of sustained ﬂight was made with the Avrocar pinned to the ground by cables. After that the vehicle took off, an uncontrollable oscillation occurred with each wheel alternately bouncing on the ground. […] These ﬁrst captive ﬂight[s] revealed then a new problem, called “hubcapping” which has never been fully resolved. The hubcapping was rapid and unpredictable swings in pitch and roll axes.


What is this sheet on a Super Étendard? What is this sheet on a Super Étendard ?

As seen on

That is the port-side ventral airbrake, as can be seen in this diagram:


What are these lumps on the top side of the wings of military aircraft? There is an online video game called War Thunder that lets you fly various planes from roughly the 30s to the late 50s. It has some pretty detailed models, and I've noticed these lumps on the wings of many planes. The planes are partly modelled on the interior and can be seen in what's called X-ray view. I've noticed that many of these lumps are placed right above where the base of the plane's gun/cannon is. This has led me to believe that they might be placed in these positions to cool the guns as air is swept over these lumps. But it turns out that in many cases these lumps aren't placed where the guns are and seem not to have this purpose. Here are some pictures of what I've talking about, I have circled them in black.

Examples of where they appear over the guns:

Focke-Wulf 190

Hawker Tempest MkII

Brewster F2A Buffalo

Sukhoi Su-6

Examples where these lump wing features don't appear above the gun/cannon:

Supermarine Spitfire

Grumman F4F Wildcat

Gloster Meteor

de Havilland Venom

Note that the last two planes are jets and have their guns mounted completely in the centre of the plane, on the nose (ie., there are no guns in the wings). Also, I've noticed that for planes that have no guns mounted in the wings only British planes (in the game) have these, namely the two jets.

I'm am wondering what the function of these things are, and what they are called, if anything? Do they serve an aerodynamic function or are they maybe to cool other parts within the wing?

They are fairings for one thing or another that projects above the wing skin.  Part of a gun or ammo feed system, fuel cap, wing fold mechanism, head of a big bolt, whatever.  Usually, components are designed in the original versions of the aircraft to fit within the wing profile, but mods and add-ons later introduce bits that project beyond it, so the easiest thing to do is fair it in with a blister.


How did ICAO SARPS come to include the 250 knots speed limit for aircraft below 10,000 feet? In certain airspace classes, a speed limit of 250 knots IAS is imposed for aircraft flying below FL100/10.000FT, according to the airspace classes defined by ICAO. How did this limit find its way into the ICAO SARPS?

The answer to this question gives a good reason why such speed limits were introduced in the USA by the FAA. I am interested in finding out why the same speed limits were de facto rolled out world wide by being included in the ICAO SARPS. Did the ICAO include the 250 KIAS below FL100 restriction for the same reason the FAA did, or are there other (additional) reasons?

For example, was this done to give pilots a better chance of spotting other traffic? To reduce the severity of bird strikes? To provide consistency with FAA rules? To allow more efficient air traffic management? To reduce noise? Or for other reasons entirely?

I am looking for actual sources on this matter, not guesses and opinions.

The tricky part is that a de facto rule is unlike a de jure rule, it's hard to pinpoint its origin as it is not based in law. The more I dig, the more it seems it is indeed a de facto rule that found its way to Annex 11.

It would take a team of aviation historians hunting through countless meeting points to get to the bottom of it.

However, I gathered some clues, mostly in reverse chronological order:

For the 250 knots during climb I found:

ICAO's REVIEW OF NOISE ABATEMENT PROCEDURE RESEARCH & DEVELOPMENT AND IMPLEMENTATION RESULTS

  Target climb speeds are given as V2 plus, no attempt was made to specify the actual target speed as it is accepted that the segment is flown to the manufacturer’s specified safety speed.

It just so happens 250 is a numerical rounding that matches most aircraft, except for heavies loaded up for long-haul flights.

Numerous parties were involved:

  ... various parties, including universities, regulatory agencies, manufacturers, air carriers and airports.

So everyone came together, and agreed to 250 knots. But that's recent and has to do with noise.

ICAO Journal TOWARDS A PERFORMANCE-BASED NAVIGATION SOLUTION

  Pilots should also avoid airspeeds of more than 250 knots below 10,000 feet above ground level (AGL), especially at times of the year when birds are migrating. Aircraft speed is more critical than bird size (body mass) in causing collision damage.

Someone should tell the geese to stop flying at FL400. (Related post.)

Activities of the European Office from 1954 to 1958 (link)

They discussed the advent of the jet age, and how the prop aircraft speeds of 250 knots are being exceeded leading to research into the consequences.

At that time, namely what affected the ATC and navigation systems because jet planes were relatively crossing sectors much faster.

It's not much but this section hints at the origin of 250 knots:

  ... significant increase in cruising speed of the jet-aircraft over the propeller-driven airline [...] around 400 knots = 750 km/h versus 250 knots = 450 km/h ...

REPORT OF THE EIGHTEENTH MEETING OF THE APANPIRG ATM/AIS/SAR SUB-GROUP

  Appendix 4 to Annex 11 speed limitations of 250 kt below 10 000 ft AMSL are required for certain airspace classes.

Annex 11 history:

  In October 1945, The Rules of the Air and Air Traffic Control (RAC) Division at its first session made recommendations for Standards, Practices and Procedures for Air Traffic Control. These were reviewed by the then Air Navigation Committee and approved by the Council on 25 February 1946. They were published as Recommendations for Standards, Practices and Procedures—Air Traffic Control in the second part of Doc 2010, published in February 1946.

Chapter 2

  2.6.3 The requirements for flights within each class of airspace shall be as shown in the table in Appendix 4.

Appendix 4 lists the now de facto limit.

It doesn't say why, so it's most likely it's what everyone agreed on at that convention and consequent meetings.

8 December 1959 is likely the date when an amendment was added to Annex 11 that detailed those figures in Appendix 4 we now know.

That's 8 years before the FAA. Check this post for the FAA's side of the story if interested.

Without access to meeting points, that's the most I could find.

Short version of the above:

At numerous conventions and meetings beginning in the 50's, many parties met again and again to discuss the jet-to-prop traffic separation, the noise impact of jet planes, and the dangers of bird strikes. They concluded V2 plus speeds should be used, but since civilian jet aircraft have the same performance more or less, the 250/10,000 rule found its way to the requirements of airspaces.

It's not hard evidence, but given what I found, it's not far fetched to assume the above is correct. Over to you.


Where to obtain a list of active NDB approaches? Does anyone know where to find a list of active NDB approaches? I can find a list of ones proposed to be eliminated, but I'm having a problem coming across a list of remaining ones.

This list comes from a database query against an ARINC 424 navigation database. The data is available on a subscription basis (for a fee) from the FAA as a raw, computer-readable data file, but it is not human readable, and querying it requires special software not accessible to the typical interested party. I have done the query for you and pasted the results.

Note the database doesn't distinguish between "NDB RWY XX" and "NDB OR GPS RWY XX" so the titles here may not precisely match what you see on the plate.

Time permitting I'll see if I can update the list (and note any changes) using the most up-to-date navigation database. This list is based on an expired (by 2 months or so) database. These approaches are dropping like flies.

02A  NDB RWY 26  (CLANTON, AL)
06FA NDB RWY 09  (JUPITER, FL)
06FA NDB RWY 27  (JUPITER, FL)
0F2  NDB RWY 17  (BOWIE, TX)
0F2  NDB RWY 35  (BOWIE, TX)
0M3  NDB RWY 02  (HOHENWALD, TN)
15F  NDB RWY 18  (HASKELL, TX)
16G  NDB RWY 24  (TIFFIN, OH)
1B1  NDB-A       (HUDSON, NY)
1B9  NDB RWY 32  (MANSFIELD, MA)
1G3  NDB RWY 01  (KENT, OH)
1H8  NDB RWY 04  (CASEY, IL)
1H8  NDB RWY 22  (CASEY, IL)
1J0  NDB-A       (BONIFAY, FL)
1S3  NDB RWY 26  (FORSYTH, MT)
21D  NDB RWY 04  (ST PAUL, MN)
23R  NDB RWY 35  (DEVINE, TX)
28J  NDB RWY 09  (PALATKA, FL)
2A0  NDB RWY 03  (DAYTON, TN)
2B7  NDB RWY 36  (PITTSFIELD, ME)
2F5  NDB RWY 16  (LAMESA, TX)
2F5  NDB RWY 34  (LAMESA, TX)
2G9  NDB RWY 25  (SOMERSET, PA)
2H0  NDB-A       (SHELBYVILLE, IL)
2J5  NDB RWY 17  (MILLEN, GA)
2M2  NDB RWY 17  (LAWRENCEBURG, TN)
2R6  NDB RWY 36  (BUNKIE, LA)
35A  NDB RWY 05  (UNION, SC)
3B4  NDB-B       (ELIOT, ME)
3F3  NDB RWY 18  (MANSFIELD, LA)
3F4  NDB RWY 09  (VIVIAN, LA)
3JC  NDB-B       (JUNCTION CITY, KS)
45R  NDB RWY 13  (KOUNTZE/SILSBEE, TX)
48Y  NDB RWY 33  (PINECREEK, MN)
4A9  NDB-A       (FT PAYNE, AL)
4F2  NDB RWY 35  (CARTHAGE, TX)
4K6  NDB RWY 36  (BLOOMFIELD, IA)
4R7  NDB RWY 16  (EUNICE, LA)
4V8  NDB RWY 01  (WEST DOVER, VT)
53A  NDB RWY 18  (MONTEZUMA, GA)
5R4  NDB RWY 18  (FOLEY, AL)
5R8  NDB RWY 16  (DE QUINCY, LA)
6B6  NDB-A       (STOW, MA)
70J  NDB RWY 13  (CAIRO, GA)
79J  NDB RWY 29  (ANDALUSIA/OPP, AL)
79J  NDB-A       (ANDALUSIA/OPP, AL)
7F3  NDB RWY 35  (CADDO MILLS, TX)
8A0  NDB-A       (ALBERTVILLE, AL)
8B0  NDB-A       (RANGELEY, ME)
8F3  NDB RWY 35  (CROSBYTON, TX)
8G2  NDB RWY 14  (CORRY, PA)
D73  NDB-A       (MONROE, GA)
E30  NDB RWY 35  (BALLINGER, TX)
E38  NDB RWY 19  (ALPINE, TX)
F10  NDB RWY 36  (HENRYETTA, OK)
F17  NDB RWY 17  (CENTER, TX)
F44  NDB RWY 35  (ATHENS, TX)
F46  NDB-A       (ROCKWALL, TX)
F99  NDB RWY 17  (HOLDENVILLE, OK)
I23  NDB RWY 23  (WASHINGTON COURT HOUSE, OH)
I68  NDB-A       (LEBANON, OH)
I69  NDB RWY 22  (BATAVIA, OH)
K34  NDB-D       (GARDNER, KS)
K88  NDB RWY 01  (IOLA, KS)
KAAA NDB RWY 21  (LINCOLN, IL)
KAAF NDB RWY 14  (APALACHICOLA, FL)
KAAF NDB RWY 32  (APALACHICOLA, FL)
KAAS NDB RWY 23  (CAMPBELLSVILLE, KY)
KABI NDB RWY 35R (ABILENE, TX)
KABR NDB RWY 31  (ABERDEEN, SD)
KABY NDB RWY 04  (ALBANY, GA)
KACK NDB RWY 24  (NANTUCKET, MA)
KACP NDB RWY 36  (OAKDALE, LA)
KADF NDB RWY 04  (ARKADELPHIA, AR)
KADG NDB RWY 05  (ADRIAN, MI)
KAFK NDB RWY 15  (NEBRASKA CITY, NE)
KAFK NDB RWY 33  (NEBRASKA CITY, NE)
KAHN NDB RWY 27  (ATHENS, GA)
KAHQ NDB RWY 20  (WAHOO, NE)
KAID NDB RWY 30  (ANDERSON, IN)
KAIK NDB RWY 25  (AIKEN, SC)
KAIT NDB RWY 16  (AITKIN, MN)
KAJR NDB RWY 06  (CORNELIA, GA)
KAKH NDB RWY 03  (GASTONIA, NC)
KAKQ NDB RWY 20  (WAKEFIELD, VA)
KAKR NDB RWY 25  (AKRON, OH)
KALN NDB RWY 17  (ALTON-ST LOUIS, IL)
KALW NDB RWY 20  (WALLA WALLA, WA)
KALX NDB-A       (ALEXANDER CITY, AL)
KAMA NDB RWY 04  (AMARILLO, TX)
KAMT NDB RWY 23  (WEST UNION, OH)
KANB NDB RWY 05  (ANNISTON, AL)
KANQ NDB RWY 05  (ANGOLA, IN)
KAPG NDB RWY 22  (ABERDEEN PROVING GROUNDS, MD)
KAPN NDB RWY 01  (ALPENA, MI)
KAPT NDB RWY 04  (JASPER, TN)
KAQP NDB RWY 13  (APPLETON, MN)
KARM NDB RWY 14  (WHARTON, TX)
KARM NDB RWY 32  (WHARTON, TX)
KARV NDB RWY 28  (MINOCQUA-WOODRUFF, WI)
KASH NDB RWY 14  (NASHUA, NH)
KATA NDB RWY 05  (ATLANTA, TX)
KATS NDB RWY 12  (ARTESIA, NM)
KATS NDB RWY 30  (ARTESIA, NM)
KATY NDB RWY 35  (WATERTOWN, SD)
KAVQ NDB RWY 12  (MARANA, AZ)
KAWG NDB RWY 31  (WASHINGTON, IA)
KAWO NDB RWY 34  (ARLINGTON, WA)
KAXA NDB RWY 12  (ALGONA, IA)
KAZC NDB-A       (COLORADO CITY, AZ)
KAZE NDB RWY 14  (HAZLEHURST, GA)
KAZO NDB RWY 35  (KALAMAZOO, MI)
KBBB NDB RWY 14  (BENSON, MN)
KBBD NDB RWY 17  (BRADY, TX)
KBBP NDB RWY 07  (BENNETTSVILLE, SC)
KBCB NDB-A       (BLACKSBURG, VA)
KBED NDB RWY 29  (BEDFORD, MA)
KBEH NDB RWY 28  (BENTON HARBOR, MI)
KBFK NDB-A       (BUFFALO, OK)
KBFW NDB RWY 25  (SILVER BAY, MN)
KBGF NDB RWY 18  (WINCHESTER, TN)
KBHC NDB RWY 08  (BAXLEY, GA)
KBHK NDB RWY 13  (BAKER, MT)
KBHK NDB RWY 31  (BAKER, MT)
KBIL NDB RWY 10L (BILLINGS, MT)
KBKS NDB RWY 35  (FALFURRIAS, TX)
KBKT NDB-A       (BLACKSTONE, VA)
KBMC NDB-A       (BRIGHAM CITY, UT)
KBOI NDB RWY 10R (BOISE, ID)
KBPP NDB RWY 29  (BOWMAN, ND)
KBQP NDB RWY 34  (BASTROP, LA)
KBRD NDB RWY 23  (BRAINERD, MN)
KBST NDB RWY 15  (BELFAST, ME)
KBTL NDB RWY 23R (BATTLE CREEK, MI)
KBTR NDB RWY 31  (BATON ROUGE, LA)
KBUB NDB RWY 15  (BURWELL, NE)
KBVS NDB RWY 11  (BURLINGTON/MT VERNON, WA)
KBWG NDB RWY 03  (BOWLING GREEN, KY)
KCAV NDB RWY 14  (CLARION, IA)
KCBG NDB RWY 34  (CAMBRIDGE, MN)
KCBK NDB RWY 17  (COLBY, KS)
KCCY NDB RWY 12  (CHARLES CITY, IA)
KCDA NDB RWY 02  (LYNDONVILLE, VT)
KCDR NDB RWY 20  (CHADRON, NE)
KCEU NDB RWY 25  (CLEMSON, SC)
KCFJ NDB RWY 04  (CRAWFORDSVILLE, IN)
KCFV NDB RWY 35  (COFFEYVILLE, KS)
KCGE NDB RWY 34  (CAMBRIDGE, MD)
KCHD NDB RWY 04R (CHANDLER, AZ)
KCHQ NDB RWY 36  (CHARLESTON, MO)
KCII NDB RWY 23  (CHOTEAU, MT)
KCIR NDB RWY 14  (CAIRO, IL)
KCIU NDB RWY 34  (SAULT STE MARIE, MI)
KCJR NDB RWY 04  (CULPEPER, VA)
KCKC NDB RWY 27  (GRAND MARAIS, MN)
KCKF NDB RWY 10  (CORDELE, GA)
KCKI NDB RWY 14  (KINGSTREE, SC)
KCKN NDB RWY 13  (CROOKSTON, MN)
KCMI NDB RWY 32R (CHAMPAIGN-URBANA, IL)
KCMY NDB RWY 29  (SPARTA, WI)
KCNH NDB-A       (CLAREMONT, NH)
KCNI NDB RWY 05  (CANTON, GA)
KCNK NDB-A       (CONCORDIA, KS)
KCNP NDB RWY 30  (CHAPPELL, NE)
KCNW NDB RWY 35R (WACO, TX)
KCOE NDB RWY 06  (COEUR D'ALENE, ID)
KCOQ NDB RWY 17  (CLOQUET, MN)
KCOQ NDB RWY 35  (CLOQUET, MN)
KCOS NDB RWY 35L (COLORADO SPRINGS, CO)
KCPC NDB RWY 06  (WHITEVILLE, NC)
KCQB NDB RWY 35  (CHANDLER, OK)
KCQX NDB-A       (CHATHAM, MA)
KCRS NDB RWY 14  (CORSICANA, TX)
KCRS NDB RWY 32  (CORSICANA, TX)
KCSB NDB RWY 14  (CAMBRIDGE, NE)
KCSB NDB RWY 32  (CAMBRIDGE, NE)
KCSQ NDB RWY 34  (CRESTON, IA)
KCUH NDB RWY 36  (CUSHING, OK)
KCVC NDB RWY 28  (ATLANTA, GA)
KCVO NDB RWY 17  (CORVALLIS, OR)
KCVX NDB RWY 09  (CHARLEVOIX, MI)
KCVX NDB RWY 27  (CHARLEVOIX, MI)
KCWC NDB RWY 35  (WICHITA FALLS, TX)
KCWS NDB-A       (CONWAY, AR)
KCWV NDB RWY 09  (CLAXTON, GA)
KCXO NDB RWY 14  (HOUSTON, TX)
KCXU NDB RWY 08  (CAMILLA, GA)
KCYS NDB RWY 27  (CHEYENNE, WY)
KCYW NDB RWY 35  (CLAY CENTER, KS)
KCZT NDB RWY 31  (CARRIZO SPRINGS, TX)
KDAA NDB RWY 32  (FT BELVOIR, VA)
KDAW NDB RWY 33  (ROCHESTER, NH)
KDAW NDB-B       (ROCHESTER, NH)
KDAY NDB RWY 06R (DAYTON, OH)
KDCM NDB RWY 35  (CHESTER, SC)
KDET NDB RWY 15  (DETROIT, MI)
KDEW NDB-A       (DEER PARK, WA)
KDLC NDB RWY 07  (DILLON, SC)
KDLZ NDB RWY 10  (DELAWARE, OH)
KDMO NDB RWY 18  (SEDALIA, MO)
KDMO NDB RWY 36  (SEDALIA, MO)
KDNL NDB RWY 11  (AUGUSTA, GA)
KDNL NDB RWY DMC (AUGUSTA, GA)
KDNS NDB RWY 30  (DENISON, IA)
KDRI NDB RWY 36  (DE RIDDER, LA)
KDRT NDB RWY 13  (DEL RIO, TX)
KDTO NDB RWY 18  (DENTON, TX)
KDVK NDB-A       (DANVILLE, KY)
KDXX NDB RWY 32  (MADISON, MN)
KDYB NDB RWY 06  (SUMMERVILLE, SC)
KEAR NDB RWY 36  (KEARNEY, NE)
KEAU NDB RWY 22  (EAU CLAIRE, WI)
KEBS NDB RWY 32  (WEBSTER CITY, IA)
KECG NDB RWY 10  (ELIZABETH CITY, NC)
KEFW NDB RWY 32  (JEFFERSON, IA)
KEGQ NDB RWY 13  (EMMETSBURG, IA)
KEGQ NDB RWY 31  (EMMETSBURG, IA)
KEGT NDB RWY 35  (WELLINGTON, KS)
KEHA NDB RWY 35  (ELKHART, KS)
KEHO NDB RWY 23  (SHELBY, NC)
KEMT NDB-C       (EL MONTE, CA)
KEOE NDB RWY 22  (NEWBERRY, SC)
KEOK NDB RWY 14  (KEOKUK, IA)
KEOK NDB RWY 26  (KEOKUK, IA)
KEOP NDB RWY 25  (WAVERLY, OH)
KEPM NDB RWY 15  (EASTPORT, ME)
KEPM NDB RWY 33  (EASTPORT, ME)
KERI NDB RWY 06  (ERIE, PA)
KERI NDB RWY 24  (ERIE, PA)
KERV NDB RWY 30  (KERRVILLE, TX)
KETC NDB RWY 27  (TARBORO, NC)
KETN NDB RWY 35  (EASTLAND, TX)
KEUL NDB RWY 30  (CALDWELL, ID)
KEVB NDB RWY 29  (NEW SMYRNA BEACH, FL)
KEVV NDB RWY 22  (EVANSVILLE, IN)
KEVY NDB-A       (MIDDLETOWN, DE)
KEWB NDB RWY 05  (NEW BEDFORD, MA)
KEWK NDB RWY 35  (NEWTON, KS)
KEYE NDB RWY 21  (INDIANAPOLIS, IN)
KEYW NDB-A       (KEY WEST, FL)
KEZF NDB RWY 24  (FREDERICKSBURG, VA)
KEZM NDB RWY 02  (EASTMAN, GA)
KEZZ NDB RWY 35  (CAMERON, MO)
KFAF NDB RWY 14  (FT EUSTIS, VA)
KFBG NDB RWY 27  (FT BRAGG, NC)
KFBY NDB-A       (FAIRBURY, NE)
KFCH NDB-B       (FRESNO, CA)
KFDW NDB RWY 04  (WINNSBORO, SC)
KFES NDB RWY 36  (FESTUS, MO)
KFFC NDB RWY 31  (ATLANTA, GA)
KFFL NDB RWY 36  (FAIRFIELD, IA)
KFFM NDB RWY 31  (FERGUS FALLS, MN)
KFHR NDB RWY 34  (FRIDAY HARBOR, WA)
KFHU NDB RWY 26  (FT HUACHUCA, AZ)
KFIT NDB RWY 20  (FITCHBURG, MA)
KFIT NDB-A       (FITCHBURG, MA)
KFKR NDB RWY 09  (FRANKFORT, IN)
KFLV NDB RWY 34  (FT LEAVENWORTH, KS)
KFMH NDB RWY 23  (FALMOUTH, MA)
KFMZ NDB RWY 17  (FAIRMONT, NE)
KFMZ NDB RWY 35  (FAIRMONT, NE)
KFNB NDB-A       (FALLS CITY, NE)
KFOE NDB RWY 13  (TOPEKA, KS)
KFOZ NDB RWY 15  (BIGFORK, MN)
KFPR NDB RWY 28L (FT PIERCE, FL)
KFPR NDB-A       (FT PIERCE, FL)
KFRG NDB RWY 01  (FARMINGDALE, NY)
KFRI NDB RWY 04  (FT RILEY, KS)
KFSE NDB RWY 34  (FOSSTON, MN)
KFSI NDB RWY 17  (FT SILL, OK)
KFSI NDB-A       (FT SILL, OK)
KFSK NDB RWY 18  (FT SCOTT, KS)
KFSM NDB RWY 25  (FT SMITH, AR)
KFTG NDB RWY 26  (DENVER, CO)
KFTK NDB RWY 18  (FT KNOX, KY)
KFTY NDB RWY 08  (ATLANTA, GA)
KFVX NDB RWY 03  (FARMVILLE, VA)
KFWC NDB RWY 09  (FAIRFIELD, IL)
KFXY NDB RWY 33  (FOREST CITY, IA)
KFYE NDB RWY 19  (SOMERVILLE, TN)
KFYM NDB RWY 20  (FAYETTEVILLE, TN)
KFZG NDB RWY 01  (FITZGERALD, GA)
KFZI NDB RWY 27  (FOSTORIA, OH)
KGAI NDB RWY 14  (GAITHERSBURG, MD)
KGBD NDB RWY 35  (GREAT BEND, KS)
KGBR NDB-A       (GREAT BARRINGTON, MA)
KGCK NDB RWY 35  (GARDEN CITY, KS)
KGCY NDB RWY 05  (GREENEVILLE, TN)
KGDV NDB RWY 12  (GLENDIVE, MT)
KGEY NDB RWY 34  (GREYBULL, WY)
KGGE NDB RWY 05  (GEORGETOWN, SC)
KGGF NDB RWY 15  (GRANT, NE)
KGGF NDB RWY 33  (GRANT, NE)
KGGG NDB RWY 13  (LONGVIEW, TX)
KGGW NDB RWY 30  (GLASGOW, MT)
KGHG NDB RWY 06  (MARSHFIELD, MA)
KGHG NDB RWY 24  (MARSHFIELD, MA)
KGLR NDB RWY 09  (GAYLORD, MI)
KGLY NDB RWY 04  (CLINTON, MO)
KGLY NDB RWY 22  (CLINTON, MO)
KGMU NDB RWY 01  (GREENVILLE, SC)
KGNC NDB RWY 35  (SEMINOLE, TX)
KGNF NDB RWY 13  (GRENADA, MS)
KGNG NDB RWY 25  (GOODING, ID)
KGOV NDB RWY 14  (GRAYLING, MI)
KGRD NDB RWY 27  (GREENWOOD, SC)
KGRF NDB RWY 15  (FT LEWIS, WA)
KGRF NDB RWY 33  (FT LEWIS, WA)
KGRK NDB RWY 15  (FT HOOD, TX)
KGRN NDB RWY 22  (GORDON, NE)
KGSO NDB RWY 14  (GREENSBORO, NC)
KGTB NDB RWY 15  (FT DRUM, NY)
KGTB NDB RWY 33  (FT DRUM, NY)
KGTF NDB RWY 34  (GREAT FALLS, MT)
KGUR NDB RWY 32  (GUERNSEY, WY)
KGUY NDB RWY 18  (GUYMON, OK)
KGVL NDB RWY 05  (GAINESVILLE, GA)
KGWR NDB RWY 34  (GWINNER, ND)
KGXY NDB RWY 34  (GREELEY, CO)
KGYH NDB RWY 05  (GREENVILLE, SC)
KGYI NDB RWY 17L (SHERMAN-DENISON, TX)
KGYL NDB RWY 31  (GLENCOE, MN)
KGYY NDB RWY 30  (GARY, IN)
KHBV NDB RWY 13  (HEBBRONVILLE, TX)
KHDO NDB RWY 35R (HONDO, TX)
KHEG NDB-A       (JACKSONVILLE, FL)
KHFF NDB RWY 11  (CAMP MACKALL, NC)
KHFY NDB RWY 01  (INDIANAPOLIS, IN)
KHHG NDB RWY 09  (HUNTINGTON, IN)
KHHW NDB RWY 35  (HUGO, OK)
KHIO NDB-B       (PORTLAND, OR)
KHJH NDB RWY 12  (HEBRON, NE)
KHLN NDB-D       (HELENA, MT)
KHMY NDB RWY 17  (LEXINGTON, OK)
KHMY NDB RWY 35  (LEXINGTON, OK)
KHNZ NDB RWY 06  (OXFORD-HENDERSON, NC)
KHOC NDB RWY 23  (HILLSBORO, OH)
KHOE NDB RWY 14  (HOMERVILLE, GA)
KHOP NDB RWY 23  (FT CAMPBELL/HOPKINSVILLE, KY)
KHQG NDB RWY 02  (HUGOTON, KS)
KHQU NDB RWY 10  (THOMSON, GA)
KHRJ NDB RWY 23  (ERWIN, NC)
KHRO NDB RWY 18  (HARRISON, AR)
KHRU NDB RWY 17  (HERINGTON, KS)
KHRU NDB RWY 35  (HERINGTON, KS)
KHRX NDB RWY 20  (HEREFORD, TX)
KHSA NDB RWY 18  (BAY ST LOUIS, MS)
KHUA NDB RWY 17  (REDSTONE ARSENAL, AL)
KHUT NDB RWY 13  (HUTCHINSON, KS)
KHVC NDB RWY 26  (HOPKINSVILLE, KY)
KHVS NDB RWY 03  (HARTSVILLE, SC)
KHVS NDB RWY 21  (HARTSVILLE, SC)
KHYI NDB RWY 13  (SAN MARCOS, TX)
KHYW NDB RWY 04  (CONWAY, SC)
KHYW NDB RWY 22  (CONWAY, SC)
KHZD NDB RWY 01  (HUNTINGDON, TN)
KHZR NDB RWY 36  (NEW ROADS, LA)
KIAG NDB RWY 28R (NIAGARA FALLS, NY)
KICL NDB-A       (CLARINDA, IA)
KICT NDB RWY 01R (WICHITA, KS)
KIDA NDB RWY 20  (IDAHO FALLS, ID)
KIDP NDB RWY 35  (INDEPENDENCE, KS)
KIER NDB RWY 35  (NATCHITOCHES, LA)
KIIB NDB RWY 18  (INDEPENDENCE, IA)
KIKG NDB RWY 13  (KINGSVILLE, TX)
KILN NDB RWY 04L (WILMINGTON, OH)
KILN NDB RWY 22R (WILMINGTON, OH)
KIMT NDB RWY 01  (IRON MT-KINGSFORD, MI)
KINL NDB RWY 31  (INTERNATIONAL FALLS, MN)
KIOB NDB RWY 03  (MT STERLING, KY)
KIOB NDB RWY 21  (MT STERLING, KY)
KIPJ NDB RWY 23  (LINCOLNTON, NC)
KIRS NDB RWY 18  (STURGIS, MI)
KIRS NDB RWY 24  (STURGIS, MI)
KISB NDB RWY 17  (SIBLEY, IA)
KISB NDB RWY 35  (SIBLEY, IA)
KISN NDB RWY 29  (WILLISTON, ND)
KISW NDB RWY 02  (WISCONSIN RAPIDS, WI)
KISW NDB RWY 30  (WISCONSIN RAPIDS, WI)
KITR NDB RWY 15  (BURLINGTON, CO)
KIZG NDB-B       (FRYEBURG, ME)
KJES NDB RWY 11  (JESUP, GA)
KJES NDB RWY 29  (JESUP, GA)
KJMR NDB RWY 35  (MORA, MN)
KJMS NDB RWY 31  (JAMESTOWN, ND)
KJNX NDB RWY 03  (SMITHFIELD, NC)
KJSV NDB-A       (SALLISAW, OK)
KJVW NDB RWY 12  (RAYMOND, MS)
KJVY NDB RWY 18  (JEFFERSONVILLE, IN)
KJXN NDB RWY 24  (JACKSON, MI)
KJYG NDB RWY 33  (ST JAMES, MN)
KJYL NDB RWY 23  (SYLVANIA, GA)
KJYR NDB RWY 17  (YORK, NE)
KJYR NDB RWY 35  (YORK, NE)
KKLS NDB-A       (KELSO, WA)
KLCG NDB RWY 18  (WAYNE, NE)
KLCG NDB RWY 23  (WAYNE, NE)
KLCG NDB RWY 36  (WAYNE, NE)
KLCI NDB RWY 08  (LACONIA, NH)
KLCK NDB RWY 05R (COLUMBUS, OH)
KLCK NDB RWY 23L (COLUMBUS, OH)
KLCQ NDB RWY 28  (LAKE CITY, FL)
KLDM NDB RWY 26  (LUDINGTON, MI)
KLEE NDB RWY 31  (LEESBURG, FL)
KLGD NDB-B       (LA GRANDE, OR)
KLHW NDB RWY 33R (FT STEWART, GA)
KLIU NDB RWY 01  (LITTLEFIELD, TX)
KLKR NDB RWY 24  (LANCASTER, SC)
KLLN NDB RWY 17  (LEVELLAND, TX)
KLLN NDB RWY 35  (LEVELLAND, TX)
KLNN NDB RWY 10  (WILLOUGHBY, OH)
KLOU NDB RWY 33  (LOUISVILLE, KY)
KLQK NDB RWY 05  (PICKENS, SC)
KLQR NDB RWY 17  (LARNED, KS)
KLRD NDB RWY 17L (LAREDO, TX)
KLRF NDB RWY 25  (JACKSONVILLE, AR)
KLSE NDB RWY 18  (LA CROSSE, WI)
KLUA NDB-A       (LURAY, VA)
KLUK NDB RWY 21L (CINCINNATI, OH)
KLUK NDB RWY 25  (CINCINNATI, OH)
KLUL NDB RWY 13  (LAUREL, MS)
KLWM NDB RWY 05  (LAWRENCE, MA)
KLXL NDB RWY 31  (LITTLE FALLS, MN)
KLXY NDB-A       (MEXIA, TX)
KLYO NDB RWY 17R (LYONS, KS)
KLZU NDB RWY 25  (LAWRENCEVILLE, GA)
KMAI NDB-C       (MARIANNA, FL)
KMAN NDB-A       (NAMPA, ID)
KMAO NDB RWY 04  (MARION, SC)
KMBT NDB RWY 18  (MURFREESBORO, TN)
KMDH NDB RWY 18L (CARBONDALE-MURPHYSBORO, IL)
KMDZ NDB RWY 34  (MEDFORD, WI)
KMEY NDB RWY 20  (MAPLETON, IA)
KMEZ NDB RWY 27  (MENA, AR)
KMFD NDB RWY 32  (MANSFIELD, OH)
KMFI NDB RWY 05  (MARSHFIELD, WI)
KMFI NDB RWY 16  (MARSHFIELD, WI)
KMGM NDB RWY 10  (MONTGOMERY, AL)
KMGR NDB-A       (MOULTRIE, GA)
KMGY NDB-A       (DAYTON, OH)
KMHL NDB RWY 36  (MARSHALL, MO)
KMIV NDB RWY 14  (MILLVILLE, NJ)
KMKC NDB RWY 19  (KANSAS CITY, MO)
KMKV NDB RWY 04  (MARKSVILLE, LA)
KMLE NDB RWY 12  (OMAHA, NE)
KMLJ NDB RWY 28  (MILLEDGEVILLE, GA)
KMMI NDB RWY 02  (ATHENS, TN)
KMMI NDB RWY 20  (ATHENS, TN)
KMNI NDB RWY 02  (MANNING, SC)
KMNM NDB RWY 03  (MENOMINEE, MI)
KMNZ NDB RWY 36  (HAMILTON, TX)
KMOB NDB RWY 14  (MOBILE, AL)
KMOR NDB RWY 05  (MORRISTOWN, TN)
KMPZ NDB RWY 33  (MT PLEASANT, IA)
KMQI NDB RWY 05  (MANTEO, NC)
KMQI NDB RWY 17  (MANTEO, NC)
KMQW NDB RWY 21  (MC RAE, GA)
KMQY NDB RWY 32  (SMYRNA, TN)
KMRH NDB RWY 14  (BEAUFORT, NC)
KMRH NDB RWY 21  (BEAUFORT, NC)
KMRJ NDB RWY 22  (MINERAL POINT, WI)
KMSV NDB RWY 15  (MONTICELLO, NY)
KMTH NDB-A       (MARATHON, FL)
KMTO NDB RWY 29  (MATTOON-CHARLESTON, IL)
KMUI NDB-A       (FT INDIANTOWN GAP, PA)
KMWA NDB RWY 20  (MARION, IL)
KMWH NDB RWY 32R (MOSES LAKE, WA)
KMWO NDB RWY 23  (MIDDLETOWN, OH)
KMWO NDB-A       (MIDDLETOWN, OH)
KMZH NDB RWY 04  (MOOSE LAKE, MN)
KNEL NDB RWY 24  (LAKEHURST, NJ)
KNRN NDB RWY 16  (NORTON, KS)
KNRN NDB RWY 34  (NORTON, KS)
KOAJ NDB RWY 05  (JACKSONVILLE, NC)
KOCH NDB RWY 18  (NACOGDOCHES, TX)
KODO NDB RWY 20  (ODESSA, TX)
KODX NDB RWY 13  (ORD, NE)
KOEL NDB RWY 34  (OAKLEY, KS)
KOIN NDB RWY 35  (OBERLIN, KS)
KOJC NDB-B       (OLATHE, KS)
KOKS NDB RWY 12  (OSHKOSH, NE)
KOKZ NDB RWY 13  (SANDERSVILLE, GA)
KOLD NDB RWY 22  (OLD TOWN, ME)
KOLF NDB RWY 29  (WOLF POINT, MT)
KOLS NDB-C       (NOGALES, AZ)
KOLY NDB RWY 03  (OLNEY-NOBLE, IL)
KONA NDB RWY 30  (WINONA, MN)
KONO NDB RWY 32  (ONTARIO, OR)
KONZ NDB RWY 04  (DETROIT/GROSSE ILE, MI)
KOOA NDB RWY 22  (OSKALOOSA, IA)
KOPL NDB RWY 18  (OPELOUSAS, LA)
KOPN NDB RWY 30  (THOMASTON, GA)
KORB NDB RWY 13  (ORR, MN)
KORC NDB RWY 34  (ORANGE CITY, IA)
KORE NDB RWY 01  (ORANGE, MA)
KORE NDB RWY 32  (ORANGE, MA)
KOSH NDB RWY 36  (OSHKOSH, WI)
KOSU NDB RWY 09R (COLUMBUS, OH)
KOTG NDB RWY 29  (WORTHINGTON, MN)
KOTH NDB RWY 04  (NORTH BEND, OR)
KOUN NDB RWY 03  (NORMAN, OK)
KOUN NDB RWY 35  (NORMAN, OK)
KOWP NDB RWY 35  (SAND SPRINGS, OK)
KOXD NDB RWY 05  (OXFORD, OH)
KPCW NDB RWY 27  (PORT CLINTON, OH)
KPCZ NDB RWY 31  (WAUPACA, WI)
KPEA NDB RWY 34  (PELLA, IA)
KPEO NDB RWY 28  (PENN YAN, NY)
KPHF NDB RWY 02  (NEWPORT NEWS, VA)
KPHF NDB RWY 20  (NEWPORT NEWS, VA)
KPHG NDB-A       (PHILLIPSBURG, KS)
KPHH NDB RWY 36  (ANDREWS, SC)
KPHN NDB RWY 04  (PORT HURON, MI)
KPHT NDB RWY 02  (PARIS, TN)
KPIA NDB RWY 31  (PEORIA, IL)
KPIM NDB RWY 09  (PINE MOUNTAIN, GA)
KPKF NDB RWY 36  (PARK FALLS, WI)
KPMV NDB RWY 16  (PLATTSMOUTH, NE)
KPMV NDB RWY 34  (PLATTSMOUTH, NE)
KPNA NDB-A       (PINEDALE, WY)
KPNM NDB RWY 15  (PRINCETON, MN)
KPNS NDB RWY 35  (PENSACOLA, FL)
KPOB NDB RWY 23  (FAYETTEVILLE, NC)
KPOE NDB RWY 16  (FT POLK, LA)
KPOE NDB RWY 34  (FT POLK, LA)
KPOH NDB RWY 12  (POCAHONTAS, IA)
KPOY NDB RWY 31  (POWELL, WY)
KPPA NDB RWY 17  (PAMPA, TX)
KPSN NDB RWY 36  (PALESTINE, TX)
KPTD NDB RWY 24  (POTSDAM, NY)
KPTN NDB RWY 06  (PATTERSON, LA)
KPTT NDB RWY 17  (PRATT, KS)
KPVC NDB RWY 25  (PROVINCETOWN, MA)
KPVJ NDB RWY 35  (PAULS VALLEY, OK)
KPWC NDB RWY 34  (PINE RIVER, MN)
KPWT NDB RWY 02  (BREMERTON, WA)
KPYG NDB RWY 23  (PAGELAND, SC)
KPYX NDB-A       (PERRYTON, TX)
KRBE NDB RWY 31  (BASSETT, NE)
KRCX NDB RWY 32  (LADYSMITH, WI)
KRFD NDB RWY 01  (CHICAGO/ROCKFORD, IL)
KRFI NDB-B       (HENDERSON, TX)
KRKD NDB RWY 03  (ROCKLAND, ME)
KRKD NDB RWY 31  (ROCKLAND, ME)
KRNT NDB RWY 16  (RENTON, WA)
KROG NDB RWY 20  (ROGERS, AR)
KROS NDB RWY 34  (RUSH CITY, MN)
KRRT NDB RWY 31  (WARROAD, MN)
KRSN NDB RWY 18  (RUSTON, LA)
KRSN NDB RWY 36  (RUSTON, LA)
KRSV NDB RWY 17  (ROBINSON, IL)
KRUE NDB-A       (RUSSELLVILLE, AR)
KRUQ NDB RWY 20  (SALISBURY, NC)
KRVJ NDB RWY 11  (REIDSVILLE, GA)
KRVN NDB RWY 07  (ROGERSVILLE, TN)
KRYM NDB RWY 31  (CAMP RIPLEY, MN)
KRYV NDB RWY 05  (WATERTOWN, WI)
KRYV NDB RWY 23  (WATERTOWN, WI)
KSAA NDB-A       (SARATOGA, WY)
KSAW NDB RWY 01  (MARQUETTE, MI)
KSAZ NDB RWY 14  (STAPLES, MN)
KSBD NDB RWY 06  (SAN BERNARDINO, CA)
KSBO NDB RWY 14  (SWAINSBORO, GA)
KSBU NDB RWY 34  (BLUE EARTH, MN)
KSBX NDB RWY 23  (SHELBY, MT)
KSCH NDB RWY 22  (SCHENECTADY, NY)
KSDA NDB RWY 04  (SHENANDOAH, IA)
KSDY NDB RWY 01  (SIDNEY, MT)
KSDY NDB RWY 19  (SIDNEY, MT)
KSEM NDB RWY 33  (SELMA, AL)
KSER NDB RWY 05  (SEYMOUR, IN)
KSFB NDB-B       (ORLANDO, FL)
KSFB NDB-C       (ORLANDO, FL)
KSGH NDB RWY 24  (SPRINGFIELD, OH)
KSGS NDB-B       (SOUTH ST PAUL, MN)
KSGT NDB RWY 18  (STUTTGART, AR)
KSHD NDB RWY 05  (STAUNTON/WAYNESBORO/HARR, VA)
KSHL NDB RWY 33  (SHELDON, IA)
KSHN NDB-A       (SHELTON, WA)
KSIF NDB RWY 31  (REIDSVILLE, NC)
KSIV NDB RWY 36  (SULLIVAN, IN)
KSIY NDB-A       (MONTAGUE, CA)
KSJT NDB RWY 03  (SAN ANGELO, TX)
KSJX NDB RWY 27  (BEAVER I, MI)
KSKI NDB RWY 36  (SAC CITY, IA)
KSLB NDB RWY 17  (STORM LAKE, IA)
KSLB NDB RWY 35  (STORM LAKE, IA)
KSLI NDB RWY 22L (LOS ALAMITOS, CA)
KSLN NDB RWY 35  (SALINA, KS)
KSLO NDB RWY 18  (SALEM, IL)
KSMS NDB RWY 23  (SUMTER, SC)
KSNK NDB RWY 35  (SNYDER, TX)
KSOA NDB RWY 18  (SONORA, TX)
KSOW NDB-A       (SHOW LOW, AZ)
KSOY NDB RWY 18  (SIOUX CENTER, IA)
KSPF NDB-A       (SPEARFISH, SD)
KSPS NDB RWY 33L (WICHITA FALLS, TX)
KSPW NDB RWY 30  (SPENCER, IA)
KSQI NDB RWY 07  (STERLING/ROCKFALLS, IL)
KSRB NDB RWY 04  (SPARTA, TN)
KSRE NDB RWY 16  (SEMINOLE, OK)
KSTK NDB RWY 33  (STERLING, CO)
KSTP NDB RWY 31  (ST PAUL, MN)
KSUN NDB RWY DMA (HAILEY, ID)
KSUS NDB RWY 08R (ST LOUIS, MO)
KSUS NDB RWY 26L (ST LOUIS, MO)
KSUX NDB RWY 13  (SIOUX CITY, IA)
KSUX NDB RWY 17  (SIOUX CITY, IA)
KSUX NDB RWY 31  (SIOUX CITY, IA)
KSUX NDB RWY 35  (SIOUX CITY, IA)
KSVN NDB RWY 28  (SAVANNAH, GA)
KSWO NDB RWY 17  (STILLWATER, OK)
KSWT NDB RWY 16  (SEWARD, NE)
KSWT NDB RWY 34  (SEWARD, NE)
KSWW NDB RWY 17  (SWEETWATER, TX)
KSYF NDB RWY 32  (ST FRANCIS, KS)
KTAD NDB-A       (TRINIDAD, CO)
KTAN NDB RWY 30  (TAUNTON, MA)
KTBN NDB RWY 32  (FT LEONARD WOOD, MO)
KTDW NDB-A       (AMARILLO, TX)
KTHA NDB RWY 18  (TULLAHOMA, TN)
KTIW NDB RWY 35  (TACOMA, WA)
KTNT NDB RWY 09  (MIAMI, FL)
KTOI NDB RWY 07  (TROY, AL)
KTOR NDB RWY 10  (TORRINGTON, WY)
KTOR NDB RWY 28  (TORRINGTON, WY)
KTPF NDB RWY 04  (TAMPA, FL)
KTQH NDB RWY 17  (TAHLEQUAH, OK)
KTQK NDB RWY 35  (SCOTT CITY, KS)
KTRL NDB RWY 17  (TERRELL, TX)
KTRX NDB RWY 18  (TRENTON, MO)
KTRX NDB RWY 36  (TRENTON, MO)
KTTD NDB-A       (PORTLAND, OR)
KTTN NDB RWY 06  (TRENTON, NJ)
KTUP NDB RWY 36  (TUPELO, MS)
KTVC NDB RWY 28  (TRAVERSE CITY, MI)
KTVF NDB RWY 31  (THIEF RIVER FALLS, MN)
KTVI NDB RWY 22  (THOMASVILLE, GA)
KTWF NDB RWY 26  (TWIN FALLS, ID)
KTZR NDB RWY 04  (COLUMBUS, OH)
KUCP NDB RWY 23  (NEW CASTLE, PA)
KUDG NDB RWY 23  (DARLINGTON, SC)
KUIN NDB RWY 04  (QUINCY, IL)
KUKL NDB RWY 36  (BURLINGTON, KS)
KULS NDB RWY 12  (ULYSSES, KS)
KUMP NDB RWY 15  (INDIANAPOLIS, IN)
KUNI NDB RWY 25  (ATHENS/ALBANY, OH)
KUNU NDB RWY 02  (JUNEAU, WI)
KUNU NDB RWY 20  (JUNEAU, WI)
KUTS NDB RWY 18  (HUNTSVILLE, TX)
KUUV NDB RWY 24  (SULLIVAN, MO)
KUVA NDB RWY 33  (UVALDE, TX)
KUWL NDB RWY 09  (NEW CASTLE, IN)
KUWL NDB RWY 27  (NEW CASTLE, IN)
KVHN NDB RWY 21  (VAN HORN, TX)
KVIQ NDB RWY 28  (NEILLSVILLE, WI)
KVNC NDB RWY 31  (VENICE, FL)
KVNW NDB RWY 09  (VAN WERT, OH)
KVTA NDB RWY 09  (NEWARK, OH)
KVTN NDB RWY 32  (VALENTINE, NE)
KVUJ NDB RWY 22L (ALBEMARLE, NC)
KVVV NDB RWY 34  (ORTONVILLE, MN)
KWDR NDB RWY 31  (WINDER, GA)
KWJF NDB-C       (LANCASTER, CA)
KWYS NDB RWY 01  (WEST YELLOWSTONE, MT)
KXVG NDB RWY 31  (LONGVILLE, MN)
KYKM NDB RWY 27  (YAKIMA, WA)
KYKN NDB RWY 31  (YANKTON, SD)
KYNG NDB RWY 32  (YOUNGSTOWN-WARREN, OH)
KZEF NDB RWY 25  (ELKIN, NC)
KZPH NDB RWY 18  (ZEPHYRHILLS, FL)
KZPH NDB RWY 22  (ZEPHYRHILLS, FL)
KZPH NDB RWY 36  (ZEPHYRHILLS, FL)
L39  NDB RWY 36  (LEESVILLE, LA)
L67  NDB-A       (RIALTO, CA)
M02  NDB RWY 17  (DICKSON, TN)
M18  NDB RWY 16  (HOPE, AR)
MYSM NDB RWY 10  (SAN SALVADOR, , BHS)
N94  NDB-B       (CARLISLE, PA)
NY0  NDB RWY 10  (JOHNSTOWN, NY)
NY0  NDB RWY 28  (JOHNSTOWN, NY)
S01  NDB RWY 24  (CONRAD, MT)
S39  NDB RWY 10  (PRINEVILLE, OR)
T41  NDB RWY 30  (LA PORTE, TX)
T85  NDB RWY 31  (YOAKUM, TX)
TX25 NDB RWY 17  (ATHENS, TX)
U68  NDB RWY 09  (COWLEY-LOVELL-BYRON, WY)
U76  NDB RWY 28  (MOUNTAIN HOME, ID)
X50  NDB RWY 18  (NEW SMYRNA BEACH, FL)


On the A320, why is it not recommended to use the HP ground unit when the APU Bleed is on? Can someone explain what the HP ground unit is used for? And what damage happens to the bleed system if it is used?

The uses of the HP air of the pneumatic system are in the FCOM:

  air conditioning
  engine starting
  wing anti-icing (see here)
  water pressurization
  hydraulic reservoir pressurization

The HP air sources are engine bleed, APU, and HP ground connection. The Bleed Monitoring Computers (BMC) do not recognize if the ground cart is connected or not.

The BMC of the engines can detect overpressure and overheat and act accordingly (check FCOM for logic schematic). However, the APU logic does not check for overpressure and overheat (see below).

Having APU and ground as dual HP sources can lead to overheat and/or overpressure of the pneumatic system.

Even when starting an engine with external pneumatic power, engine bleeds should be selected off (no need letting the BCM catch an error for you).


Do military tactical transport flights provide seatbelts for all occupants? In several movies I have watched recently, the temporary bench style seats of tactical transport aircraft such as the C-130 do not show seat-belts. I would not be surprised that some instances of seat belts would be ignored during times of war but let's limit this question to standard operations.

So, is it standard practice for transport aircraft such as the C-130 or Chinook helicopter during large personnel missions to provide all occupants with seat belts?

Every one I've been on has had them going back to the 70's. Here's a picture that clearly shows them:

Source: Wikimedia


Would cone shapes grills in front of jet engines prevent damage in case of a bird strike? If cone shaped grills pointing forward were in front of jet engines would they make bird parts slide outside towards the back of the engine and away?

No, that wouldn't work.

Kinetic energy is measured using the formula $\tfrac12mv^2$ . This means that the kinetic energy of a 4.5kg goose at 170 knots is about the same as a motorcycle at 30mph. At 400 knots that goose's kinetic energy is the same as a small car at 30mph. Remember that velocity in this case is not the speed of the goose but the speed of the airplane hitting it, any grill would have to be immensely strong to survive that kind of impact, meaning it would have to be thick and heavy. This will block airflow to the engine, which is a big problem. If the heavy, hard metal screen fails it will get sucked into the engine and cause far more damage than a soft, squishy bird.

One method for the mass production of french fries is to shoot potatoes at a mesh screen at high speed using a water cannon, when the potato hits the screen its speed forces it through, slicing the potato perfectly in a fraction of a second. A similar thing is going to happen to a bird which hits a screen in front of the engine, rather than being deflected it will simply be sliced and ingested into the engine anyway, or it could potentially be caught on the mesh of the grill and impede airflow further.


What aspect ratio is best for Wind Tunnel Testing an aerofoil with Small Additives? Vortex generators will be 3D printed on a panel, which is then to be slotted onto a foam aerofoil to be tested in the wind tunnel for performance and flow physics.

What I want to know is which aspect ratio to use?

Rectangular wing, need a chord length and span.

Max wing span is 700mm.

What is it you want to test?

Do you want to test the 2D characteristics of an airfoil? Then make it the width of the windtunnel. The wind tunnel walls act like mirrors, so you will have the behaviour of an infinite wing.

If you want to test a 3D wing on a model, you need to use coherent scale. Use the same scale for the fuselage/wing/empennage.


Has a life raft ever been successfully deployed in case of an accident? Has a life rift ever been successfully deployed in the event of an air accident?

By successfully I mean removed from the aircraft, placed on the water, inflated and used by passengers/crew as a life raft.

Sure.  For example, Eddie Rickenbacker and 6 other people spent 3 weeks adrift aboard life rafts after their B-17 ditched in WW2.

Read more -- https://www.historynet.com/eddie-rickenbacker-and-six-other-people-survive-a-b-17-crash-and-three-weeks-lost-in-the-pacific-ocean.htm


How can I overlay a VFR sectional on another map to identify features and landmarks? How do I know which highways and landmarks on a VFR sectional align with which real-world features? Is there a way to overlay the VFR sectional map from the FAA on top of Google Maps or Bing?

Edit: I'm asking in relation to VFR flight in general where you are responsible for your own navigation, and not about a specific route of flight.

Seems to me you're going to be directed by SoCal approach that whole route per the routing shown in Skyvector.com, especially with the LAX Class B right there, and the TFR will be the last of your worries. Put your enroute and the final destination into your GPS (Foreflight or whatever), and be ready for deviations.


If an airplane touches down short of the runway, and doesn't reach it, is it still a runway excursion? In light of the two recent incidents where aircraft landed roughly 1000 ft short of their intended runways, Air Canada AC-624 at Halifax and Asiana OZ-162 at Hiroshima, I started thinking the definitions used when labeling them.

At least in the first case, the airline labeled it a runway excursion. Given that the airplane never actually exited the runway (it touched down short and slid onto the runway), I'm a little confused, what is the definition of a runway excursion? If an aircraft never actually comes in contact with the runway, is it still a runway excursion? At what point does it simply become an off airport landing?

It depends.

Skybrary says

  The Runway Excursion category includes also two types of occurrences which do not fit the ICAO ADREP definition for a runway excursion, however considered appropriate for inclusion due to the commonality of a number of causal and contributory factors and/or mitigation approaches:

  An aircraft attempting a landing touches down in the undershoot area of the designated landing runway within the aerodrome perimeter.
  A runway or taxiway other than the designated one is used for a take off or a landing.

My emphasis.

The European Commercial Aviation Safety Team (ECAST) in the European Strategic Safety Initiative (ESSI) use the Skybrary definition when writing about Runway Excursion Prevention

  Articles within the Runway Excursion Category in SKYbrary:

  Overrun on Take Off
  Overrun on Landing
  Directional Control
  Undershoot on Landing
  Wrong Runway

My emphasis.

In an article "Language and safety issues" in Eurocontrol's magazine in 2011, Bert Ruitenberg wrote:

  The whole idea of putting a label such as “runway incursion” or
  “runway excursion” on a safety occurrence is to make it easier to
  file the data from the event somewhere and to compare it with
  similar occurrences. With the definitions above, a take off from a
  taxiway would be considered as a Runway Excursion when the
  Skybrary definition is used, but not with the other RE definitions
  (and rightly so, I say, better label it a “taxiway take off”). Moreover,
  in the ICAO definition, the B777 undershoot at Heathrow
  would not be a RE, but with the Skybrary definition it would be.
  Dear Safety Managers of the world, there still is a lot of work to
  be done...


What is this tube connected to a 757 for? In this photo, there is a 757 at Narita Airport with a tube connected to the belly.

Source: Airliners.net
The tube is in the middle of the plane.
There is a similar question about this tube, but here it seems to be connected to the ground and not to the jet bridge.
Does anybody know something about this tube?

What Mike said is correct, but I thought I'd add a little more.

The hose is technically called the "PCA Hose" which stands for Pre-Conditioned Air Hose. The hose supplies pre-conditioned air to the aircraft from a ground based unit, that is typically electrically powered and is usually mounted on to each jetbridge. The air can be cold or hot, depending on the needs of the day. The aircraft has a connection that feeds directly into the aircraft's air distribution mix manifold, which is where recirculating air is mixed with fresh pack air before being sent back to the cabin. The ground port connector port has an exterior door and an internal check valve to prevent pressured air from escaping in flight (the 757 actually has two internal check valves that are in series).

When the pre-conditioned air is connected to the aircraft, a small amount of it is sent directly to the cockpit and is 100% fresh (at least on Boeing aircraft), while the remaining PCA air is sent to the mix manifold where it mixed with recirculated cabin air before being released into the cabin.

The main reason to use pre-conditioned air is that it allows the crew to shut off the APU (and air conditioning packs) at the gate, which reduces fuel burn, emissions, noise and maintenance cost. When fuel costs went up dramatically in the mid '00s, there was a major push at airlines to eliminate APU run times, because it is much cheaper to run a ground based, electric air conditioner than running the mini-jet engine to produce bleed air. At the same time, there was also a push to ensure that aircraft were connected to ground electrical power as well, for the same reason.

There are some downsides of using PCA air. First, the hoses get a ton of debris in them and the hoses themselves breakdown internally. All of this debris gets blown back into the aircraft and clogs up the ducts and gaspers. This drives a lot of extra maintenance cost on the air distribution system, which didn't used to require much maintenance. Screens help some, but don't fully fix the problem. Second, ground crew tend to always use the max flow setting on the ground unit, and this can over pressurize ducts on narrowbody aircraft, leading to their failure (especially when the ducts are clogged).

Third, many crews/airports think that on a "hot day" you still have to run the APU, this is false and actually counter productive the cold ground air blows directly on the mix manifold's temperature sensor, so the airplane thinks the air is too cold and starts adding "trim air" from the APU to heat up the mixed air. So running the APU actually makes the cabin hotter, but then the ground crew thinks "since the aircraft is hot with the ground air and APU, imagine how hot it'd be with just the ground air!" I've seen this a lot more at airports where 85F is considered a hot day, as opposed to airports where 105F is considered hot.

Finally, there is a lot of infrastructure and maintenance that goes into all the ground equipment and at some airports, the ground units are actually diesel powered. So at the end of the day, using PCA air and ground power probably save some money, but it definitely isn't "free."

Edit: As to the reason the PCA hose pictured is coming from the ramp instead of the jetbridge, this has to with the infrastructure setup at each airport. There are many systems that can route the PCA air underground. I assume that most of these systems use a centralized plant loop with chilled water/steam pumped throughout the terminal, then use a heat exchanger at each gate. Take a look at the recent setup at SEA for more information: SEA PCA Centralization Project. This Cavotec brochure has some interesting information and graphics as well: Cavotec Brochure (PDF)


Is emergency floor lighting fluorescent? I just read this question (about emergency lighting) for which nobody highlight the title mention fluorecence. As this lighting's requirements include operability with failure of normal electrical power, having fluorescent strip doubling a ramp of lights make sense. However, the pictures illustrating the answers shows seat-mounted lights.

My question focus on the emergency floor lighting installed on the floor. Do this kind of emergency lighting use fluorecent elements?

Fluorescent (more specifically phosphorescent as the re-emission of absorbed light happens on a longer time scale) plastics are sometimes used for exit indicators as they're better than nothing when every other system fails, however they have some drawbacks that limit their usefulness, and so they're not relied on as a primary source of emergency illumination in aviation:

They're not very bright. Even a battery-backup 5-watt incandescent provides more light, and when passengers are trying to find the exit through a cloud of smoke from an engine fire, bright saves lives.
They lose brightness quickly. Here are samples of zinc sulfide on the left and strontium aluminate on the right of each picture. The first picture is immediately after the light source goes out. The second is after just four minutes of darkness:

They rely on external light sources illuminating them for a minimum time. On night flights (when luminescent exit indicators would be most needed), the cabin lights are often dimmed, reducing the effectiveness of photoluminescent strips. Passenger garments overlapping the strips, such as skirts or waist-tied jackets, will have a similar effect on individual strips.
Most pigments react most strongly to UV light which is undesirable for most other purposes. UV light is invisible to us so it's wasted energy, and it yellows plastics (such as cabin trim) which ages airliner cabins more quickly. Light sources that minimize UV are preferable for any purpose except for "charging" photoluminescent strips.
They can't be turned off. When cabin lights are dimmed for passenger comfort on a night flight (letting people sleep etc), the photoluminescent strips will make the cabin look like a cheap Halloween party for up to ten minutes after.

In short, there are better options, especially now with white LEDs that are more efficient and less of a fire hazard than incandescent lights. A simple lithium button battery in the same assembly as the light could keep a 50-lumen LED array going more than long enough even in a complete electrical failure, and LEDs bright enough for this purpose are becoming ridiculously cheap thanks to advances in LED lighting for homes and businesses.


How accurate is XFoil / XFLR5 at 'kinda high' Reynolds numbers? How accurate is XFoil/XFLR5 at Reynolds numbers between 2 million and 10 million?

From my understanding it's only accurate at lower Re values.

Before version 6.9 (30 Nov 2001), XFOIL had some problems at Re > 3 million, but that's now been fixed.  Its documentation says:

  The BL equations are normally discretized with two-point central
  differencing (i.e. the Trapezoidal Scheme), which is second-order
  accurate, but only marginally stable.  In particular, it has problems
  with the relatively stiff shape parameter and lag equations at
  transition, where at high Reynolds number the shape parameter must
  change very rapidly.  Oscillations and overshoots in the shape parameter
  will occur with the Trapezoidal Scheme if the grid cannot resolve this
  rapid change.  To avoid this nasty behavior, upwinding must be introduced,
  resulting in the Backward Euler Scheme, which is very stable, but has
  only first-order accuracy.  Previous versions of XFOIL allowed a specific
  constant amount of upwinding to be user-specified.  Currently,
  XFOIL automatically introduces upwinding into the equations only
  in regions of rapid change (typically transition).  This ensures
  that the overall scheme is stable and as accurate as possible.


Why did the altimeter in an F-16 jump suddenly as it passed through Mach 1? In this video, Destin — the creator of YouTube channel Smarter Every Day — rides in an F-16 with a USAF Thunderbirds pilot. If you start watching the video at the 11:06 mark, you will see what happens when the aircraft passes through Mach 1, namely, that the altimeter reading suddenly jumps.
Destin explains that this jump in the altimeter reading is because the air pressure downstream of the normal shock wave that is impinging on the pitot-static tube of the aircraft is lower than the air pressure upstream, but by the laws of compressible airflow, this would be total air pressure, not static air pressure.
As static air pressure, which is sensed by the altimeter, is always higher downstream of a normal shock wave, why is it that the altimeter reading registers a sudden jump and not drop instead?

The altimeter doesn't measure static air pressure, it measures actual air pressure. So, to get an accurate reading of the static air pressure, the static port has to be carefully placed so that the ram air pressure (caused by the forward motion of the plane ramming into the air) and the slipstream pressure (caused by air rushing past the static port opening) cancel each other out (or nearly so).
So, Destin is correct: The actual air pressure after the shockwave is lower, causing a jump in the displayed altitude.


When filing an ICAO flight plan with LPV, is marking GNSS equipment necessary or redundant? Should equipment 'B' (LPV) and Equipment 'G'(GNSS) both be filed simultaneously in an ICAO flight plan, or does equipment 'B' simply imply GNSS?

You should fill both G and B.
If I understand the last row of the official ICAO guidance correctly, field 10 (equipment code) of the flight plan must contain at least B and G if you want to fly LPV approaches:

(cropped from ICAO Guidance for the provision of NAV/COMSUR information in the New ICAO 2012 Flight Plan)
You will also have to enter "NAV/ SBAS" in field 18.
This is also confirmed by the following information on the ForeFlight support page:

When specifying a PBN code, be sure to also specify R (Code for Performance-Based Navigation (PBN) Approved) and the associated sensors that the PBN code requires. For example, PBN Code D2 is RNAV 1 using GPS, therefore Equipment Code G (GNSS) must also be specified.
[...]
These tables are a general aid for entering filing codes in ForeFlight and are not an authoritative or comprehensive equipment specification. Consult the AFM or AFM supplements for your aircraft to determine which codes are actually appropriate before attempting to file using ForeFlight. The codes listed below are in addition to the other ICAO Equipment code that may be appropriate for your aircraft.
WAAS

GNS 430W - R, B, and PBN B2, C2, D2
GNS 530W - R, B, and PBN B2, C2, D2
GNS 480 - R, B, and PBN B2, C2, D2
GTN 6XX/7XX - R, B, and PBN B2, C2, D2
GPS 175 - R, B, and PBN B2, C2, D2
GNX 375 - R, B, and PBN B2, C2, D2
G1000, 2000, 3000, 5000 WAAS - R, B, and PBN B2, C2, D2

(foreflight.com, emphasis mine)


Which airplanes are exempt from Europe's 2015 CPDLC (Link 2000+) requirement? In February 2015, all flights above FL285 in EU airspace are required to have CPDLC/Link 2000+.

However,  I have been told by an avionics provider that some aircraft types are exempt from the requirement.  Where can I find the complete list of exemptions?

The European Commission has published the Commission Implementing Decision of 9.12.2011
on exemptions under Article 14 of Commission Regulation (EC) N° 29/2009 (the CPDLC rule)

It contains the following table of aircraft that are permanently exempted from the CPDLC implementing rule.

╔════════════════════════════╦════════════╦════════════════╗
║           Model            ║  ICAO Id   ║ Marketing Name ║
╠════════════════════════════╬════════════╬════════════════╣
║ Airbus A318 - 112          ║ A318       ║ A318           ║
║ Airbus ACJ - 319           ║ A319       ║ ACJ 319        ║
║ Airbus ACJ - 320           ║ A320       ║ ACJ 320        ║
║ Airbus A330 – 200/300      ║ A332/A333  ║ A330           ║
║ Airbus A340 – 200/300      ║ A342/A343/ ║ A340           ║
║              /500/600      ║ A345/A346  ║                ║
║ British Aeropace AVRO      ║ RJ1H       ║ AVRO RJ        ║
║     RJ100                  ║            ║                ║
║ Dassault Falcon 10 and     ║ FA10       ║ Falcon 10      ║
║     Falcon 100             ║            ║                ║
║ Dassault Fan Jet Falcon    ║ FA20       ║ Falcon 20      ║
║     Basic and              ║            ║                ║
║     Serie C/D/E/F/G        ║            ║                ║
║ Dassault Mystère-Falcon    ║ FA20       ║ Falcon 20      ║
║     200, 20GF and 20-      ║            ║                ║
║     C5/D5/E5/F5            ║            ║                ║
║ Dassault Falcon 50EX and   ║ FA50       ║ Falcon 50      ║
║     Mystère Falcon 50      ║            ║                ║
║ Dassault Falcon 900, 900B, ║ F900       ║ Falcon 900     ║
║     900C and 900 EX        ║            ║                ║
║ Dassault Falcon 2000       ║ F2TH       ║ Falcon 2000    ║
║     and 2000EX             ║            ║                ║
║ Gulfstream GIV             ║ GLF4       ║ Gulfstream IV  ║
║     and GIV-SP             ║            ║                ║
║ Gulfstream G300            ║ GLF4       ║ Gulfstream 300 ║
║ Gulfstream G400            ║ GLF4       ║ Gulfstream 400 ║
║ Gulfstream GV              ║ GLF5       ║ Gulfstream V   ║
║ McDonnell Douglas MD11-F   ║ MD11       ║ MD-11          ║
║      and MD11-CF           ║            ║                ║
╚════════════════════════════╩════════════╩════════════════╝


Why don't multiengine aircraft have to demonstrate spin recoverability? (Building off this earlier question about spin-testing airliners.)

For normal-category aircraft1 in the U.S. (at least), only single-engine (or, in the case of some gliders, no-engine) airplanes need to demonstrate the ability to recover from a one-turn (or, if the aircraft is intended to be certified for intentional spinning, six-turn) spin.  This means that, for instance, the single-engine Cessna 208 (MTOW 3630 kg) has to be successfully recovered from a one-turn spin, whereas the much-smaller Piper PA-34 (MTOW 2155 kg) is exempt from this requirement solely by virtue of having a second engine.

There is nothing about multiengine aircraft that makes them inherently resistant to spinning compared to single-engine aircraft; indeed, if anything, it would be expected to make spins somewhat more likely (think "aftermath of botched or absent pilot response to an asymmetrical engine failure"2).  If, instead, the number of engines is being used as a proxy for the size and intended audience of the aircraft (as suggested in this comment on the aforelinked question), then I don't see any reason not to simply use a dividing line based directly on weight (especially since, as noted above, there are many large single-engine airplanes and small multiengine airplanes).3

Given all this, why aren't multiengine airplanes (especially small multiengine airplanes, such as the aforementioned PA-34) required to demonstrate spin recovery like their single-engined compatriots are?

1: Utility and aerobatic airplanes do have to demonstrate spin recoverability even if they have more than one engine.

2: Especially for multiengine tractor-propeller aircraft with wing-mounted engines, where, when flying at very low airspeeds, simply shutting down one engine or losing it to a mechanical failure can be enough to immediately stall its respective wing (due to said wing losing the air previously being blown over it at high speed by said engine's propeller).

3: Granted, even large multiengine airliners can find themselves spinning on occasion, something that (inadvertently) happened to (for instance) the first 307 and the first 737;4 however, I accept that an airplane requiring an ATPL and a specific type rating, not to mention a second pilot, is (by virtue of hopefully-good piloting) rather less likely (barring a major structural failure) to be placed in a spin than one requiring merely a PPL, and also that very large aircraft such as these are likely to become debris clouds if spun.

4: For the record, both the Stratoliner and the 737 were successfully recovered from their spins, although the former then almost immediately disintegrated in flight due to an overly-aggressive pullout from the subsequent dive.5

5: Hey, I can nest footnotes!

Because it would impose severe constraints on their design.

Factors such as mass distribution make many twin-engine and multi-engine aircraft inherently resistant to spin recovery, despite the large rudder or large rudder moment-arm that is often present on these aircraft.  In many cases these aircraft are prone to flat spins.  Also, during the recovery from a nose-down spin, a large aircraft may exceed Vne before pulling out of the resulting dive, or may be overstressed during the pull-out.  In the real world, a pilot should avoid spinning a typical twin-engine or multi-engine aircraft, because recovery might not be possible.

"No multiengine airplane is approved for spins, and their spin recovery characteristics are generally very poor."
-- from https://www.flightliteracy.com/stalls-in-multiengine-aircraft/

Related questions on ASE:

Is spin recovery possible in an airliner?

Why aren't airliners spin-tested?

Other related links:

https://www.flightliteracy.com/stalls-in-multiengine-aircraft/

https://www.pprune.org/flight-testing/226351-spinning-airliner.html

https://www.airlinepilotforums.com/hangar-talk/6370-spinning-airliner.html

google "spin recovery twin" or ("multi") for much more


Do steam-gauge VSIs compensate for altitude? A Vertical Speed Indicator indicates rate of altitude change. Traditional VSIs use a calibrated leak to measure the rate of pressure change, and therefore the rate of altitude change.

However, pressure does not change uniformly per altitude: in a standard atmosphere, air pressure at 0 MSL is 29.921 inHg, and at 1000 MSL is 28.856 inHg: a 1.065 inHg difference. But 10,000 MSL is 20.577 inHg and 11,000 is 19.791 inHg: a .789 inHg difference. A calculation suggests that a VSI calibrated for sea level and climbing at 1,000 ft/min would indicate 739 ft/min at 10,000 feet.

The airspeed indicator has a knob to calculate true airspeed based on altitude and temperature, but the VSI has no pilot-accessible controls. Glass panel instruments would presumably handle this automatically, but is there any correction for altitude in a steam-gauge VSI?

Yes.  It appears to be the case for "steam gauges".  At least for a traditional vertical speed indicator.  It's a great question and not one I had considered before.  At first glance, I suspected you may be right, though I don't ever remember actually learning that.
To prove the theory, one pilot apparently took his airplane with a traditional steam gauge altimeter/VSI up to FL220 and found the following:

=>Your altimeter is perfectly accurate at the airport if you enter your barometric pressure correctly.
=>At the cruise altitude of about 8,500 feet or so, your altimeter is off by about FIVE-HUNDRED FEET.
=>At that altitude, it does not matter much that your altimeter is off, because everyone else’s is off by the same amount, and you are far from the airport, and thus landing.
=>The error always seems to be off in the safe direction: You are always HIGHER than you think. Clearly, when they designed the system in 50’s, they designed the altimeters to follow the most conservative lapse-rate we could encounter, so in real-world flying, we are almost-always much HIGHER than we thought, which must be the safest error we can make.
=>The vertical speed indicator perfectly tracks the PRESSURE-based altimeter, not the true altitude, so the vertical speed indicator can be perfectly used to see how much the altimeter will change over time, the ACTUAL climb or descent rate of the plane is actually considerably DIFFERENT… at high altitudes, by 1,290 parts in 24,000, or just OVER FIVE PERCENT.


Aircraft lightning: What are the requirements for airworthiness? Can you enlighten me about the airworthiness requirements in the field of lightning, for commercial aviation:

Which voltage or intensity is the aircraft required to sustain?
How is it demonstrated in practical?

Any major certification agency will be good.

When dealing with lightning protection, there are two significant areas that must be addressed: direct effects of lightning and indirect effects.

The FAA provides guidance on these two areas in the following advisory circulars:

20-155A - Industry Documents To Support Aircraft Lightning Protection Certification

20-136B - Aircraft Electrical and Electronic System Lightning Protection

The lightning zone analysis from the AC 20-155A will define the test requirements for the airframe and help determine the level of testing for installed equipment based on its location in the aircraft.

At the aircraft level it can be a very complex and drawn out process negotiating the specific testing required with the FAA. Once that is done, requirements and verification for the equipment can be developed.  A short summary of that process from AC 20-136B is:

  6. Steps for Showing Compliance.
    a. The following seven steps describe how you may comply with 14 CFR
  23.1306, 25.1316, 27.1316, and 29.1316 requirements for your aircraft’s
  electrical and electronic systems:
  (1) Identify the systems to be assessed.
  (2) Determine the lightning strike zones for the aircraft.
  (3) Establish the aircraft lightning environment for each zone.
  (4) Determine the lightning transient environment associated with the systems.
  (5) Establish equipment transient design levels (ETDLs) and aircraft actual transient
  levels (ATLs).
  (6) Verify compliance to the requirements.
  (7) Take corrective measures, if needed.
   b. The steps above should be performed to
  address lightning transients induced in electrical and electronic
  system wiring and equipment, and lightning damage to aircraft external
  equipment and sensors that are connected to electrical and electronic
  systems, such as radio antennas and air data probes. Additional
  guidance on lightning protection against lightning damage for external
  equipment and sensor installations can be found in SAE ARP 5577.

Testing of individual LRUs is typically under RTCA document DO-160G - Environmental Conditions and Test Procedures for Airborne Equipment.  Section 22 covers Lightning Induced Transient Susceptibility and Section 23 covers Lightning Direct Effects.


Why only the outboard ("low speed") aileron drops when there is no hydraulic pressure on the 747-8? As the title says, why only the outboard ("low speed") aileron drops when there is no hydraulic pressure on the 748?

(Full resolution)

The Boeing 747-8 (unlike the 777) is not a full fly-by-wire aircraft, but some fly-by-wire controls have been added to the original 747 design. The inboard ailerons are mechanically connected to the flight controls, while the outboard ailerons are not. This allows them to droop without hydraulic power.

From the Boeing 747-8 FCOM (9.20.6 Flight Controls - System Description):

  Roll Control

  Inboard ailerons are mechanically controlled and hydraulically powered. Outboard ailerons and all spoilers are electronically controlled and hydraulically powered.

  Aileron and Spoiler Roll Control

  Rotating either control wheel positions ailerons and spoilers. Above approximately 258 knots/.53 Mach, the outboard ailerons are commanded to the neutral position to prevent overcontrolling. The outboard ailerons become operational at lower airspeeds. Inboard aileron deflection is limited when flaps are extended beyond 10.

  To improve takeoff performance and reduce noise, the outboard aileron is deflected down for flap detent positions 10 and 20. The downward deflection is removed if the angle of attack is above stick shaker. The inboard aileron is deflected down when the flaps are selected to 10 or greater.

  All spoiler panels operate with the ailerons. Spoiler panels are deflected up or down based on Speedbrake lever and control wheel inputs.

The following image from modernairliners.com shows all new features of the 747-8 wing including the Aileron droop.


Can an empty 747-400 with minimal fuel take off on two engines? This is a fanciful question. 747s are allowed to take off on 3 engines for maintenance ferries (I did a couple), but a 2 engine takeoff is not a practical or legal consideration. However, my gut level feeling is that it could be done in optimal conditions, but I'm interested in what the more technically oriented people here have to say.

The aircraft for this thought experiment is a 747-400ERF, a freighter with a basic operating weight of 351,088 lbs and a max takeoff weight of 910,000 lbs. Let's say we want to take off and make a 15 minute swing about the countryside around Moses Lake, WA with its 13,500 runway, elevation 1189 feet, on a STP day with no wind. It's flat land, there are no departure or arrival path obstacles.

We want to land with no less than 15,000 lbs of fuel, and the takeoff and flying is going to take around 20,000 lbs. Thus our takeoff weight is going to be around 386,000 lbs, which is roughly 42% of the max takeoff weight.

We have half our engines inoperative, but we are significantly less than half as heavy as the max takeoff weight. To make it easy, let's say that engines 2 and 3 are operating (the inner most engines on each side).

So, what say you?

Hmm... I guess this will come down to how much of the drag is induced drag vs. how much is form drag. The induced drag will obviously be much less, but the form drag will not be much less than flying at the same airspeed at MTOW.

Given the requirement that it must be capable of continuing a takeoff and climbing out at MTOW on 3 engines, though, I'd be very surprised if it weren't capable of doing so at 42% MTOW on 2 engines.

For the most convincing argument in favor of 'yes' I can think of off hand, there's this. GE flew a 747 on one engine. Granted, that engine happened to be a GE90-115b, the world's most powerful commercial jet engine, which is used on the 777-300ER. However, the GE90-115b is rated at 'only' 115,300 lb. of thrust, while a pair of PW 4062s on a 747-400ERF would produce a total of 126,600 lb. GE's aircraft is a modified 747-100. Since Wikipedia lists its operating empty weight at 358,000 lb. and it was hopefully carrying some fuel in addition to that, its weight was likely not much different from the 386,000 lb. in your scenario. Additionally, in GE's case, some of the lift would have to be used to pull against the yawing moment created by flying with only the #2 engine producing thrust.

In light of this, I'd say that the answer is almost certainly, yes, it's possible. Advisable, of course, is a different matter entirely.

GE's Test Bed 747-100 with the GE90-115b mounted in place of its #2 engine. Source: Wikipedia


To flap or not to flap? I am learning to fly an Ikarus-C42. The instructor I have recommends to all students that they land without flaps, because it is less to think about and because it gives you more airspeed, thus less chance of stalling or losing control on approach.

Now, I'm not one to second guess someone much more experienced than me, but I do have to ask - is this truly best practice?

I have conducted some reading on the subject and it seems that not using flaps and the consequent high speed landings performed by many students is one of the main reasons for the high incident rate that involve overshooting runways (not to mention the excessive wear on the brakes). Additionally, it doesn't seem to prep you well for the 'real world'. I can't imagine telling your F.O on a 737 'Don't worry about flaps today, it's too much to think about' :D

You don't say which variant you're flying, but the C42B is perfectly capable of both taking off and landing with zero flaps on a reasonable-length runway. I've done it on several occasions with huge margin even for touch-and-gos on my home field's 1300 m asphalt runway. You do need to adjust the angle of attack (via pitch), but if you're flying the airspeed you'll basically be doing that anyway, so no big deal.

Extending flaps give you better flying characteristics at low airspeed, but increases drag. If you're flying the approach at reasonably high speed, then you likely don't particularly need the extra lift, and in fact it might even be detrimental especially once you're wheels on runway and trying to slow down. With flaps extended, you also need to monitor your airspeed more closely to make sure you aren't exceeding VFE.

On the flip (flap?) side, the C42 flaps lever manipulates the flaps directly -- it's just a cable going through the fuselage. Any time you're handling the lever, you are fighting directly against the airflow around the wing, with no help from e.g. elevator trim, let alone hydraulics or even electrics. I know that the effects of this came as a bit of a surprise for me the first few times I retracted flaps in flight; it's very easy to end up with a rough flaps retraction if you aren't prepared for the force involved.

You're supposed to be flying the airplane all the way to the ground, and only bleed off the flying airspeed very late during the landing, in the flare when you should end up at stall speed with the wheels just barely above the runway.

It's possible that your instructor feels that the added complexity of also handling the flaps lever (and the resultant drag changes) simply may risk being overwhelming at first. It's not like there isn't already a lot going on during a standard traffic pattern coming in to land; there's airspeed, altitude, auxiliary pump, carb heat, scanning for traffic, radio communications, keeping good tabs on your position relative to the runway, lining up for final approach mind the wind, making sure your turns are coordinated, during crosswind landings the final turn to align the airplane (as opposed to the direction of travel) with the runway, ...

Your instructor likely has a plan for how to introduce the use of flaps during landing; you are most likely going to need them by the time you're doing short-field work, if not before. You also can, and should, discuss with your instructor anything where you don't feel that you understand the instructor's rationale. Asking strangers on the Internet for advice is fine, and can provide additional insight (which can be quite valuable!), but should never be a replacement for asking your instructor.

  high incident rate that involve overshooting runways

If you're too far along the runway to land safely, just go around and make another attempt. (Landing long is fine, just annoying if you need to taxi all the way back; overshooting the runway is not.) It's good practice for everything except the flare, braking and taxiing, and it's good practice for go-around procedures. I've made the decision to go around in situations that very likely were perfectly fixable (things like being too high on final, or drifting to the side while still a moderate distance out on final) but I am of the opinion that it's better to go around and do it right, than try to press on when things are stacking up against you, especially if you're new. With experience, you'll learn what can be fixed in-place and what truly warrants a go-around.

Just make sure you tell the instructor what you're doing. Crew resource management isn't a big focus in single-pilot light aircraft, since you'll mostly be flying by yourself and certainly a lot of the time without another pilot in the other seat, but I find it's a good idea to follow the general principles anyway.

  Additionally, it doesn't seem to prep you well for the 'real world'. I can't imagine telling your F.O on a 737 'Don't worry about flaps today, it's too much to think about' :D

I know you added a smiley, but it's no joking matter. Don't treat, or think of, the C42 like a commercial jetliner. Don't think learning to fly a C42 will allow you to just drop into the cockpit of a jetliner (even a realistically simulated one) and fly the latter. It isn't, it will never be, it won't, and the C42 handles quite differently from the big iron. That doesn't make the C42 any less "real world".


What is this biplane? What is this biplane shown above?

Blackburn T.5 Ripon

The Blackburn T.5 Ripon was a British carrier-based torpedo bomber and reconnaissance biplane which first flew in 1926. It was used by the Fleet Air Arm as a torpedo bomber from 1930 until 1935. Ripons were also sold to Finland, where they continued to be used in action in the Winter War and the Continuation War until 1944.

(Source: iwm.org.uk) The exact one, number 4 on the side.

A Blackburn Ripon Mk.IIA torpedo bomber of No 811 Squadron touches down on the flight deck of the fleet aircraft carrier HMS FURIOUS.


How to accurately determine Navigation Accuracy from FAA's PBN Criteria (Order 8260.58A)? I am trying to understand how to determine the Navigation Accuracy for a given flight phase of an Instrument Flight Procedure, from the US Standard for PBN Instrument Procedure Design (Order 8260.58A). However, I am unable to understand how to determine the aforementioned accuracy under certain circumstances, given that, for example in case of A-RNP navigational specification and STAR flight phase, it states that:

  1-2-4.c, Table 1-2-1 A-RNP permits a range of scalable RNP lateral navigation accuracies. Apply the largest RNP for the flight phase unless a smaller value is required to achieve a desired ground track or is operationally required. RNP APCH applies to final flight phase.

My question is, in other words, why a desired ground track would require a smaller navigation accuracy value? Under what circumstances such a ground track would be desirable and, since the goal is to provide an adequate Obstacle Clearance Area, doesn't this mean that smaller accuracy value would lead to a smaller obstacle clearance area?

It is a really technical question and I do not expect to be a popular one, but I would really appreciate if someone could point me in the right direction.

Im more familiar with EASA then FAA but im sure there are similarities:

why a desired ground track would require a smaller navigation accuracy value?

RNP 2: the aircraft must be within ± 2 nm of the indicated position 95% of the flying time (Required for Basic RNAV).

RNP 1: the aircraft must be within ± 1 nm of the indicated position 95% of the flying time (Required for Precision RNAV).

So flying in a congested airspace (for example the NAT-OTS routes) ATC can accommodate more aircraft with smaller separations.

the goal is to provide an adequate Obstacle Clearance Area

Yes, as well as separation and spacing of aircraft.

doesn't this mean that smaller accuracy value would lead to a smaller obstacle clearance area?

In theory yes. But Obstacle clearance requirements around Airports and high terrain take into account all aircrafts including general aviation and older aircraft without PBN, RNP equipment so while you are right with more accuracy the approach and departure corridors lead to smaller clearance areas due to the regulations the actual clearance areas could stay the same.

More likely there will be changes at the approach and departure procedures (points, fixes and routes).

Hopefully you found something helpful.


Does tailless means no tail at all? When I was reading about the HAL Tejas I observed that it was described as a "tailless" plane. However I could see a tail in the picture.

After careful reading I am assuming that being tailless means not having any tail planes a.k.a horizontal stabilizers.

Does tailless means no tail at all?

Tailless means no horizontal tail, but a vertical tail is still allowed. Examples are the Convair F-102 or Convair B-58.

Convair B-58 Hustler (picture source)

Compare this to a flying wing: Here even the vertical tail is left off. Since a classic delta would have too little lever arm for yaw control, this requires a higher aspect ratio wing. An example is the Horten IX:

Horten IX V1 prototype aircraft (picture source)


How is the fuel quality monitored/assured for jetliners? With tens of thousands of flights daily, many out of smaller and perhaps 'sketchy' airports, it would seem that serious incidents caused by contaminated fuel should happen a lot more often (in a quick Google I only found two). Do commercial jets have some system whereby the airplane itself can verify fuel quality as it is loaded? Or do pilots & airlines rely entirely on the fuel supplier?

As you can see, the supply chain is big (with filters and water separators at various points). The short answer is that standards and quality checks are followed.

As for the jetliners, as far as I know they can't detect the fuel quality, but some can alert if issues arise in the fuel filters. The certification standards focus on engine restart capability and that it...

  ... should be demonstrated for the momentary shutdown from a high power or thrust setting, associated with the takeoff and climb flight regimes, and the extended shutdown at medium to high altitude where the engines may be "windmilling" and/or "cold soaked."

Fuel contamination is of the reasons mentioned in the engine restart section.

ICAO's Manual on Civil Aviation Jet Fuel Supply (on SKYbrary; PDF) is comprehensive as to the practices involved (the image above is from the manual).

  1.2.1 Any business entity involved in the aviation fuel supply chain has an obligation to implement and comply with industry and/or company proprietary PSPs, as described in this manual, that cover the activities in which they are involved.

Supply and distribution, aircraft operators, and airport operators, each follow their respective policies, standards and procedures (PSP).

  3.10.1 Any organization that manufactures, supplies or handles aviation fuel should have a documented training programme for its personnel. The programme should cover product quality, safe operation of equipment, emergency procedures and occupational health, as well as management systems for operational safety, environment and security. In particular, the programme should include in its scope a systematic way to identify hazards and effectively control risks to fuel quality, personnel, and facility and equipment or aircraft safety.

At each step the manual lists the various industry standards and manuals to follow.


Any biplane flying wings after 1914? Were any biplane flying wings built and flown after the 1912-1914 variants of the Dunne D.8? If not, why?

Wikipedia mentions merely that this type was too stable and insufficiently controllable, but that's not inherent to this layout.  And the biplane's stiff truss structure remained useful for the next half decade.

OK, I found one, from a friend's suggestion about hang gliders.  The late 1970's UFM Easy Riser, initially a go-kart engine strapped to a foot-launched hang glider, the "first ultralight."
But this is even more Octave Chanutesque than the 1912 Dunne!  Are there any, shall we say, nonprimitive models?  If not, why?


What can cause my radio to transmit nothing but a terrible noise? I have replaced the noise filter and checked the jacks. It does not matter what headset or jacks are used. I replaced the audio panel and had the radio serviced. When I transmit all I hear is a low screech. Others simply reply to transmissions with a simple I cannot understand anything.
Two people can talk inside the airplane with no noise and reception is clear. I have also checked voltage and connections going to the radio as well as installed a new high quality line filter. Both push to talk switches cause the same noise, I have tried flipping things on or off running the trim etc. no change.

Being able to talk inside the airplane is not related to the radios function, the intercom (generally part of the audio panel these days) is what allows cross talk between headsets.
It sounds like you have checked all your connections which is always a good first step but after that:

Check your ammeter when the radio is in operation and make sure you have sufficient current to run the radio, if you are showing a heavy discharge on the system you may not have sufficient power to run the radio (the presence of 12V or 24V does not indicate you have enough power to run the radio)
Check your radio grounds (also lots of good info here) as they can be the source of a lot of static.
If both talk switches cause the issue (and they are wired properly) I would take a look at the radio unit its self. Perhaps have it pulled and bench tested with known good components to isolate any other factors from the aircraft. This may also assure you the radio was serviced properly when it was serviced.