Why is a 0 kt, vertical climb in a helicopter not safe near the ground? In the "Test Pilot" column in the July 2017 issue of AOPA Pilot, one of the questions was

  From reader David Franklin: If a given helicopter has a best rate-of-climb airspeed of 60 knots, its best angle-of-climb speed would be _____ knots.

The answer provided

  Assuming a no-wind condition, zero knots of airspeed would result in a 90-degree climb angle. This would be neither safe (near the ground) nor efficient but certainly would be effective.

makes intuitive sense (climbing straight up gives the best angle, of course).

But why is it not safe near the ground? Does that change if there were wind (and no correction for the wind were applied)?

A suggested duplicate indicates reasons why going straight up is not as efficient, but does not mention the safety aspect at all.

A vertical take-off, known as a "towering" or "confined area" take-off, is normally only used when it is not possible to take-off and remain in ground effect before gaining speed and climbing away.

For example, your operational need is to land in a clearing in a forest or perhaps a field surrounded by tall trees. In order to take off again, you need to  climb vertically until you've cleared the tops of the trees so that you can transition forward to gain speed.  You might need to use on at night (because you cannot see if there are any obstacles ahead) or when taking off from snow or sand when your vision will be obscured, making a vertical take-off safer.

It is technically defined as any take-off which requires you to climb vertically until out of ground effect.

In this answer, I've discussed the reasons why the power required to transition in ground effect to forward flight is much less than that required in a hover or a vertical climb out of ground effect.  Before attempting a towering take off, the pilot should conduct a power check to establish that they have enough power to hover OGE (out of ground effect).  If you do have enough power to hover OGE, then in theory, you could continue to climb vertically until the reduction in engine power output or lift (small effect) as you gain altitude reduces the power margin to the point where further climb is not possible without exceeding limits.

So, to the point of your question, why is it not safe?

The main reason is a scenario which is common to all helicopter operations, not just a towering take off.  Climbing vertically to 90 feet is exactly as dangerous as coming to a 90 foot hover in an arrival from forward flight.

This scenario is putting yourself into a shaded area of the height velocity diagram, known by pilots as the "avoid curve" or perhaps more accurately the   "dead man's" curve.  Importantly, this has nothing to do with how much power you have which of course, if the engine stops, suddenly becomes zero!

Source: Copters.com

In short, test pilots, using a fully loaded helicopter over level, prepared surfaces, try to enter auto-rotation from different combinations of height and speed.  At some point, they look at each other and say "a normal, well trained pilot, could only just auto-rotate safely from that combination of height and speed.  They plot these points on a graph, join the dots and say "see those shaded areas, don't go there".  It represents the areas where you will not have enough of the combination of potential and kinetic energy to make a safe landing.

As you can see, the towering take-off puts you deep inside the avoid curve.  This is the first safety concern.  If the engine stops, you will almost certainly crash.

I chose that curve, for an Enstrom F28, because it nicely illustrates that if you continued climbing vertically to 300 feet, you would pop out of the  top of the curve.  From this height, you could auto-rotate safely.

The second safety concern goes back to the power required. If you run out of power during the climb, the aircraft may start to descend into its own rotor vortex and can enter a vortex ring state.  In a confined area, you have no options for escaping it and certainly, all but the best pilots will not avoid a crash or, at best, a very heavy landing.  I'm a relatively low time private pilot and when I do my power checks, I want to see at least a 10% additional reserve over the measured power check.  There have been times when pilots have landed in confined areas but have then not had the power to hover OGE.  They have had to reduce the weight and/or wait for a lower temperature before trying again.

The third safety concern is the need for good skills and training.  When performing towering take-offs in typical sport and private helicopters, the pilot must be gentle on the controls. Relatively large or rapid control inputs cause large spikes in the power required. When you have plenty of speed, this doesn't really matter but when climbing vertically, you might be calling for more power than is available.  You must climb OGE slowly with gentle collective increases and, when clear of the top of the trees or other obstacle, ease the cyclic forward gently.  It is this last input which is especially risky.  If you push the cyclic forward as you would in a normal take off, you could find yourself running out of power and settling into the top of the tree with nothing left to give.  The safe way to do it is a slow climb but obviously, this leaves you in the shaded area for longer.  I was always relieved when I cleared the trees and got back into normal flight and the temptation, which must be resisted, is to increase your climb rate to reduce the time on the curve but of course, this reduces your power margins. The general principle is to use the power required and no more.  Gentle climb, gentle movements, be ready to pick up wind as you clear the obstacle, and you'd better have made sure before you get there that it's a head wind.

The fourth safety concern (and the last one to my knowledge) is not so immediately dangerous but can lead to trouble.  In a helicopter without a large power reserve, it is possible to reach a point where the power required exceeds the power available, especially if you catch a gust of wind. In this situation, the rotor RPMs will start to reduce or "droop". The only possible response is to lower the collective.  This normally means you have to give up and simply land and try again as above but any situation which leads to the rotor RPM dropping outside your control is to me, a safety concern.

All of this said, some pilots spend a lot of time operating in the shaded areas, for example in logging and power line check operations but they are appropriately trained, use machines chosen to reduce the risks, pay more insurance than the rest of us and accept the risk as "part of the job".


Is it true that there are VOR/DME and/or TACAN stations in the oceans? Are there any VORs placed in the oceans for navigation. Is it true that VORs or TACANs are placed on ships to help oceanic flights, for example flights across the Atlantic?

There are no ship-based VOR's or TACAN's specifically dedicated to transatlantic flights. Transatlantic flights navigate using the inertial navigation system and GPS.

TACAN's are used on board naval ships for military aircraft to find their way to the ships, but this is typically not for flights across the ocean.


How do messages get from the destination airport to a pilot? A captain waiting in her airliner for take-off at an airport might inform her passengers:

  We'll be waiting another ten minutes before we're able to take off, as traffic is very busy at [destination], and we have to arrive in accordance with the landing slot we've been given.

How did that information reach the pilot, and what route did it take?

The answer I am looking for might be something like: the slot controller allocates the slot in the local slot control system database. This is communicated via a dedicated digital radio satellite system to ATC at the departure airport. ATC informs the local despatch controller by telephone or short-range radio. Finally, a runner is handed a slip of paper with the details and personally puts it into the pilot's hands.

When the crew got their clearance for the trip from Clearance Delivery over the radio in the flight deck, it would've included a departure time window with the delay, and they may have been told by the CD controller why, or may have figured it out for themselves because it's a routine occurrence for the airport they were headed to (like Chicago).

Or, they were told prior to that during the planning brief with Operations. All the planning and filing is done by specialists in the airline's Operations department. The crew just shows up at Operations and picks up a package with everything prepared; the route, weather, provisional loading, fuel, etc. Going to an airport with a reservation protocol in place, they would have been briefed on that by Operations. That is all provisional however, the final routing, loading, fuel etc is determined when getting ready at the gate, and also when they get their ATC clearance by calling Clearance Delivery over the VHF radio before programming the Flight Management Computer.


What benefit does a group get from being an FAA recognized flying club? FAA defines a flying club in 5190.6b.ch10.6 and ends by saying:

  A flying club that violates the requirements for a flying club – or that permits
  one or more members to do so – may be required to terminate all operations as a flying club at all airports controlled by the airport sponsor.

So hypothetically if this were to occur, then you'd have an LLC that owns a plane that is not a flying club. Does this mean that they wouldn't be able to fly their plane or carry on like normal? Aside from being able to label themselves as a "Flying Club", what impact would this have?

If the airport you're based at has federal grant obligations (basically if they've taken money from the Airport Improvement Program) then being a "flying club" by the FAA's definition entitles you (as a group) to the same rights as any other operator at the field (like the right to fuel your aircraft with fuel you buy yourself & have trucked in, or the right to do maintenance on the aircraft), subject to the same rules and regulations the airport lays down for all operators.

The biggest material difference is that "flying clubs" aren't considered to be "commercial" ventures by the FAA (and by extension grant-obligted airports).

As an example, let's say you have a flying club & you "charge" $50/hr for the use of one of the planes, and your airport management decides that since you're charging money for the use of the planes you're a commercial venture, and need to have commercial insurance and the like.

If you meet the FAA definition of a "Flying Club" and the airport has federal grant obligations you can ask your local FSDO to step in and effectively tell the airport management to get stuffed - as a flying club you're treated more like an individual than a commercial business, and the airport is not allowed to impose those commercial requirements on you.
If you don't meet that definition the FAA won't intervene on your behalf (as far as they're concerned you are a rental outfit / commercial FBO at that point and the airport is correct in treating you as one).

Note that you can still call yourself a "flying club" even if you don't meet the FAA's definition -- I belong to a flying club that has no aircraft (we're just a bunch of folks who like to talk about flying and organize the occasional fly-out event or safety seminar - some of us own planes, and some rent from local FBOs), and it doesn't really matter to us that we don't meet the FAA definition of a flying club because we don't have any interaction with the airport where that designation would benefit us.

If you're the kind of organization that has aircraft available for the use of your members however it probably makes sense to ensure that you're organized & run in such a way as to meet the FAA definition of a flying club.


What is the relation between throttle position and engine thrust for a turbofan? I wonder how is designed the command chain from the throttle lever or the auto-throttle to the fuel injection in recent jetliners. I have 4 questions:

What is set by the throttle?

When the pilot actuates the throttle, what are they setting exactly? (I can imagine the lever position corresponds to a fuel rate, to a RPM, to a thrust value, etc).
Is this value a linear function of the throttle position (e.g. 73% of the full lever rotation is 73% of the maximum N1).

Is the throttle output standardized or customized for an engine model?

What type of output has the throttle lever: mechanical, electric, digital data?
Which subsystems in the engine receive the throttle output(s)?
Is this output customized/calibrated for an engine model, or standardized.

How are the throttle outputs processed in the engine?

Does the electronic engine control apply further adjustment to the throttle input?

How does the auto-throttle (auto-thrust) interact with the manual throttle?

Does the auto-throttle send its command directly to the engine or to the mechanical throttle?
Is the manual throttle position adjusted, according to the A/T output?

Check out this Nasa powerpoint it provides a nice overview of some of the basics and how some of the systems are set up.

  Does the auto-throttle send its command directly to the EEC or to the
  mechanical throttle?

This may vary from design to design but the Boeing 777 uses the ARNIC standard bus to send control signals to servos that physically move the throttle levers. You can read up on the ARNIC 429 data bus here.

  Are the throttle levers customized/calibrated for an engine model, or
  are their output standardized (assuming the output is an electric
  signal). Does the electronic engine control apply further adjustment
  to the throttle input?

It seems that Rockwell Collins makes a unit that sends signals to the FADEC system instead of mechanically actuating anything.

With that in mind Im sure there are older designs out there that are closer to or a complete direct linkage from lever to engine.

  Is this correction transmitted back to the throttle lever?

I dont think so, it seems that when say full throttle is applied the throttle control will remain at full and the FADEC unit will take care of spooling it up as need be. Likewise if an engine suddenly cuts out or fuel flow becomes restricted as far as I know the throttles will remain in place. Auto throttle units will however physically actuate the throttles as need be. As per the comments here it seems this is only the case in Boeing aircraft. Airbus throttles must be set to maximum setting auto-throttle is allowed to use.


Do all airplanes have the same turning radius when operating under the same conditions regardless of size and weight? Would any airplane in coordinated, turning, level flight have the same turn radius at a given combination of no-wind ground speed, bank angle, and density altitude as another airplane of significant difference in size and/or weight?

For example, if a small airplane and a super heavy airplane could match speeds at the same density altitude, and they both held the same bank angle while holding altitude, would they generally be expected to have the same turn radius if they weren't slipping or skidding?

If yes, what are some examples of exceptions to this if any?

Take the no-wind case for simplicity.  For a given bank angle, and a given groundspeed (airspeed), there is only one turn rate that will center the slip-skid ball, so the answer to the question must be "yes", assuming that "coordination" is being defined in relation to the slip-skid ball and not some other instrument such as a yaw string.

Due to various interesting aerodynamic effects that happen when an aircraft's size is significantly large in relation to the turn radius, flying with the slip-skid ball completely centered will not always be completely optimum.  Similarly, the answer to the question would be different if the question were to specify that "coordination" were to be measured in reference to a yaw string or other similar instrument located at some given point on the aircraft, rather than a slip-skid ball. For more, read "Circling the Holighaus Way" by Richard Johnson.


Is it technically viable to reintroduce sleeping berths? The airlines are always trying to jam more passengers into each plane. I'm smaller than today's average, and I'm still often uncomfortable in a standard Economy seat.

It occurred to me that in the current design, there's a great deal of space wasted over the passengers' heads. And that many of us passengers already do our best to sleep through flights.

Hence my question: Is there any reason an airline couldn't introduce a cabin in which some or all passengers travel in a reclining, rather than sitting, position? Seems to me that  it would be more comfortable (except for claustrophobes and those who really need to work during the flight). The enclosed space would inherently reduce some of the risks of passengers being thrown around in turbulence or an emergency landing; safety belts (or cargo restraint webbing? I'm not sure I'm joking) could handle the remaining risk.

No, I don't really think it would be commercially viable ... but I'm wondering whether folks who actually Know Something about aircraft safety and loading think it's technically viable.

Some airlines already offer sleeping facilities, by taking advantage of the A380's tremendous size:

A double-bed suite on Singapore Airlines

A first-class seat on Emirates

A first-class seat on Qantas

That top bed looks very tempting, but I dread to think how much it costs!


When an airship climbs the hydrogen in the ship's cells expand. Does this mean that when the airship descends the empty cells fill with air? During WW1 a U Class Zeppelin had hydrogen cells that contained 55,795 cubic meters of hydrogen.
At sea level the cells were filled to 100% with hydrogen and this weighed roughly 4,500 Kilograms.  The cells displaced roughly 68,000 Kilograms of air and this difference gave the ship tremendous lift.
As the ship ascended to 5,000 meters air pressure would drop by 50% and the hydrogen would expand.  To keep the cells from popping the crew would release a significant amount of hydrogen.
However this is where I see a problem and I'm not sure how engineers solved it.
As the Zeppelin returned to sea level with hydrogen cells at only 50% full wouldn't it take on air in the now empty 50%?  The air is heavy and at some point the airship would come crashing down to Earth.  How did they solve this problem?

First of all, Zeppelins carried tons of water ballast in order to compensate for hydrogen seeping from the gas cells or being vented when the ship had climbed too high. Before launch, the crew calculated the ballast need based on the planned length of the flight and weather conditions. Also, the ship lost mass continuously by burning off fuel. Below you see the calculation sheet of LZ 40 from May 1915. The ship took 7.5 tons of water, distributed over several tanks along its length.

The top row of the sheet lists fuel (Benzin, 9320 kg in total), then oil (520 kg), then a side view of the ship with its 16 gas cells and below that the water ballast. The crew weighed 334 kg.
On the ground the gas bags were never full. In the later WW I Zeppelin models, only one third of the internal volume was taken up by the gas bags and their hydrogen while the rest of the hull was filled with air. As the airship climbed, the hydrogen in its cells expanded and pushed the air out. On the way down the reverse happened. The gas bags were flexible and sufficiently airtight so no air would enter them.
The photo below is from airships.net and shows the LZ-129 Hindenburg under construction. The gas cell is partially filled and is attached to the circular frames over two thirds of their circumference to distribute the lift of a partially filled cell as evenly as possible. Wire bracing distributed the load over the full frame. In the center of the hull you can see a walkway for inspection; the gas cell had a central tunnel to allow lengthwise movement over the full length of the ship. The vertical funnels for venting leaked hydrogen are not yet installed.

This is only possible with rigid ships; blimps use ballonets for the same purpose but have to pressurize them a bit in order to keep their envelope taut.


Can jet fighters be made to be 2 or 3 times bigger than they are today? I was watching videos on the Su-27 again, and this fighter appears to be a heavy version of jet fighters, which means it has longer range and can carry more weight.

This got me thinking on what is the upper limits of fighters, in terms of size and weight. Is there a fundamental limitation on how big a jet can be and still pull 9+ g's and use very high angle-of-attacks?

Why don't they make them any bigger to get more range (or endurance)? Is there a practical limit? Would it require too much strengthening of the larger wings or something like that?

For simplicity I put a number to it: 2 or 3 times bigger. Can fighter jets be made 2 or 3 times bigger and still have similar performance in maneuverability and thrust/weight ratio?

The question is not whether you can do it but why would you want to.

Fighters, like any other aircraft are designed around mission profiles;  what do you want this aircraft to do, at what speeds, ranges, altitudes, combat radii, endurance, weapon carriage and employment, stealth, etc.  Therefore you would need some sort of justification for building a fighter aircraft this size.  That justification has to be so appealing that it can overcome the negative aspects of building a big fighter.

While these profiles vary considerably between individual aircraft, they are constantly curtailed by the brutal and impartial realities of war.  Gen Stevens pointed out 4 fundamental requirements of a fighter in one of his critiques of the F-35.  These are important to remember as they have been integral in every successful fighter design over the past century of air combat.  Unfortunately, the larger the fighter, the more diametrically opposed to these realities they are and the greater the probability of failure in combat.

ATTACK YOUR ENEMY IN OVERWHELMING NUMBERS

This one is fairly simple to understand.  The greater your force is, the more difficult it is for the enemy to destroy you.  But defense ministries have limited budgets and can only spend so much on new fighters.  So the choice becomes should I buy a few advanced and highly capable fighters or lots of cheap, single purpose aircraft.  Air warfare has favored the latter.  Not only are smaller aircraft cheaper to procure, they are cheaper to operate as they burn less fuel and require less maintenance.  Consequently.  Your nation's pilot pool can get a lot of flight time in them and can become highly proficient in their operation.
SPOT YOUR ENEMY BEFORE HE SPOTS YOU

Which is going to be easier to spot from a distance: a 747 or an F-5?  Which is more likely to have a lower radar or IR signature if both employ LO features?
OUTMANEUVER AND OVERWHELM HIM

By the energy maneuvering equation, fighter design had always favored the following features:

High thrust to weight ratio
Low wing loading
Low specific fuel ratio

And this tends to favor a fighter which is basically a small, fast, nimble gas can with a compact but powerful engine and an effective armament for engaging and killing other fighters.  Not easily achievable with a larger aircraft.
KILL HIM QUICK AND MOVE ON

So now, a large, expensive, easy to spot aircraft manned by low time flight crews is now forced to engage a swarm of nimble, fast turning fighters.  They can quickly turn inside him and get to an optimal firing solution faster and more reliably.  They are also more difficult to engage and shoot using BVR weapons.  Finally OpFor has more experienced and current pilots than the larger fighter.  This now gives the larger, more expensive aircraft a very limited probability of survival.

For those reasons, history does not favor a large fighter unless it is equipped with some kind of mission system giving it a tactical advantage - and even then that is a large obstacle to overcome in terms of cost, strength, and weight.


How are winds aloft forecasts derived in the USA? This question pertains specifically to the US NWS FB Forecast Product.

Winds aloft forecasts, technically the "Wind and Temperature Aloft Forecast (FB)", are issued 4x daily, at 00, 06, 12, and 18z. At each of these 4 periods, 3 products are produced: a 6-hour, 12-hour, and 24-hour forecast. How are the forecasted values actually predicted?

I took a tour of my local NWS office and spoke to the aviation weather unit people. My 8yo daughter even got to help launch that day's weather balloon, and then we went inside and monitored the balloon's data as it ascended.

One of the data streams was the winds, which prompted me to ask: ok, so we know the winds right now for this location, but how does this knowledge allow you to forecast 24 hours into the future? And secondly, there are more FB locations that there are weather balloon sites, so how does that work?

Here is the answer:

Data from the balloons are just 1 of many factors entered into the weather forecasting computer models, and the FB products are actually the result of two different modeling systems. The first two products (the 6hr and 12hr forecasts) are generated by the Rapid Refresh (RAP) modeling system, and the third product (the 24hr forecast) is generated by the North American Mesoscale Forecast System (NAM) model.

Both models produce numerical forecast data on a grid, with each grid point being 13km apart in the RAP model and 12km in the NAM model, and each grid point containing 50 vertical data points up to the 10mb level. From these data points, each "FB Location" is interpolated (both horizontally and vertically) to the geographical location of the depicted airport, and the various forecast altitudes.

Additional reading:

FAA AC 00-45H Aviation Weather Services. (This document explains U.S. aviation weather products and services. It provides details when necessary for interpretation and to aid usage. Chapter 5.13 discusses the FB product)
NWS Instruction 10-812 Aviation Wind and Temperature Aloft Forecast. (This instruction provides guidance to NWS offices, outlining preparation and format of wind and temperature aloft forecasts in support of commercial and general aviation. It also lists each location where a forecast is provided)

Interesting Trivia:

All forecast locations correspond to an airport, except for 7 locations in the Gulf of Mexico, 1 location off the east coast of northern Florida, 5 locations in the Gulf of Alaska, and 1 location near the end of the Aleutian chain. These 14 additional forecast locations correspond to heavily traveled air routes.
The RAP model runs hourly, and provides forecast data 21 hours into the future.
The NAM model runs every 6 hours, and provides forecast data 84 hours into the future


What role did the RAT (Ram Air Turbine) play on US Airways flight 1549? An article in June 2018 Flying Magazine regarding the RAT by a Rob Mark explains that Capt. Sullunberger deployed the RAT for additional power to guide the plane down to the safe ditching on the Hudson River.

My understanding is, according to all the narratives, the book, and the movie, what saved the day (with the exception of the amazing skills of the flight crew) was the immediate starting of the APU by Capt. Sullenberger that was not even on the QRM check list,...and not the RAT.

I am wondering if both (APU and RAT) were used on that flight or the APU only? And if so, has Flying Magazine author made a mistake?

The full NTSB report can be found here and is the official source of information on the incident. According to that report Sullunberger did immediately start the APU which did deliver power and they determined they did not need to manually deploy the RAT. However the onboard systems deployed it automatically likely as a result of the initial power loss and sufficient airspeed (over 100Kts).

  Regarding step e, the pilots stated that they determined that
  electrical power was established and, therefore, that the RAT did not
  need to be manually deployed. Further, immediately after the loss of
  engine thrust, the captain started the APU.

This can be heard in the official transcript

  At 1527:14, the first officer stated, “uh oh,” followed by the captain
  stating, “we got one rol- both of ‘em rolling back.” At 1527:18, the
  cockpit area microphone (CAM) recorded the beginning of a rumbling
  sound.

  At 1527:19, the captain stated, “[engine] ignition, start,”
  and, about 2 seconds later, “I’m starting the APU [auxiliary power
  unit].”5

  At 1527:23, the captain took over control of the airplane,
  stating, “my aircraft.”

However the RAT was found to be deployed (due to the automatic systems on the aircraft) when the airframe was recovered

  When all of the airplane’s electrical power is lost and the airplane
  has an airspeed greater than 100 knots (kts), the RAT will
  automatically deploy and begin providing electrical power. The RAT was
  found in the extended position when the airplane was recovered from
  the water.


What made 800 feet and later 1,000 feet attractive as the standard traffic pattern altitude? The value of a commonly understood traffic pattern altitude is obvious, but what is the history behind TPA of eight hundred feet in particular? Why not 700 or 900?

Was the later move to 1,000 AGL because of easy math only, or were there other reasons?

The traffic pattern altitude (and the pattern turn direction) is set by the airport owner in coordination with the FAA. Refer to section 8.

Airport traffic patterns are often 1000 ft. AGL today. In recent past, the typical altitude above ground level was 800 ft. Flying Magazine, in a September 1958 article states:

  Under VFR conditions proper entry into the zone is sadly neglected. Before you enter the control zone you should be at the Pattern Altitude which is more or less standard rule at every airport in the country--800 to 1,000 feet for light aircraft, 1,200 to 1,500 for heavy or fast aircraft. This provides you with altitude, yet gives plenty of room to make your turns. Letting down in traffic makes you vulnerable and blind, at the same time increasing the odds of hitting someone you will never see"

Experts and non-experts seem to agree an altitude increase would be beneficial:

Better noise abatement near the airport environment
Increasing tower heights
1000 is easier to remember than 800

Fun facts:

Tangier island/KTGI airport elevation is 6 ft mean sea level. The traffic pattern altitude is 605 ft.
Truckee/KTRK is 5901 ft. MSL with an 1100 ft. TPA.
Sedona/KSEZ is 4830 ft. MSL. The TPA is 1173 ft.

Pilots flying into Sedona must be precise, haha!


What is the reason for this discrepancy regarding the CRJ100/200's stickpusher-activation angle? The AC646 accident report contains a discrepancy regarding the angle of attack at which the stickpusher of the accident aircraft (a CRJ100, formally a CL-600-2B19, referred to in the aforelinked AAR as a CL-65) would have activated:

The stick pusher mechanism is designed to prevent the aircraft from entering an aerodynamic stall by applying a control column force to pitch the aircraft nose down as the aircraft reaches its computer-calculated pusher (stall) AOA. The Canadair Regional Jet Airplane Flight Manual (AFM) contains a chart (page 06-01-23) which allows calculation of the aircraft stick pusher (stall) speed for various aircraft weights. For 44 180 pounds, the aircraft’s estimated weight at the time of the accident, with the flaps set at 45 degrees and the landing gear down, the pusher activation speed would have been about 109 knots calibrated (109 knots indicated) at one g. At the moment of the aerodynamic stall, the aircraft was at a g loading of about 1.227, and the pusher activation speed would have been about 120 knots, the natural stall speed would have been about 116 knots, and the pusher activation AOA would have been about 13.5 degrees. [...] At the moment of stall, the flaps had retracted a few degrees from 45 and the g was increasing, both of which would cause a slightly higher pusher activation speed; however, there would be no effect on the pusher activation AOA.
Information from the flight recorders indicates the following events occurred during the attempted go-around: the stick shaker activated when the aircraft was at 129 knots as the pitch was being increased through 4 degrees; and the right roll and stall onset occurred and the warbler tone activated when the aircraft was at 124 knots and with the pitch at 9.7 degrees. At the time the warbler sounded, the left and right AOA vane readings were approximately 8.7 degrees and 9.4 degrees, respectively. The pusher did not activate because, while the right AOA reached its trip point, the left AOA did not.  [TSB Aviation Occurrence Report A97H0011, page 8 (page 18 of the PDF), my emphasis.]

In the first of the paragraphs quoted, the stickpusher-activation angle of attack is stated as approximately 13.5 degrees (a value which, according to the report, would not have been altered by the aircraft's rapidly-increasing AoA); however, the very next paragraph implies that the stickpusher would have activated at an AoA of between 8.7 and 9.4 degrees (the right AoA sensor, reading 9.4 degrees, is stated as having reached the stickpusher point, while the left sensor, reading 8.7 degrees, had not reached the activation threshold by the time the aircraft stalled, thus implying that the threshold AoA for activating the stickpusher was above 8.7 degrees but below 9.4 degrees1), rather than at about 13.5 degrees.
How to reconcile this discrepancy?

1: Due, presumably, to the potentially-catastrophic results of a spurious stickpusher activation at low altitude, the CRJ100/200's2 stickpusher does not activate unless both of the aircraft's angle-of-attack vanes measure an AoA at least as high as the stickpusher-activation threshold; in contrast, all the automatic high-AoA protections that do not alter the aircraft's flightpath (continuous ignition, stickshaker activation, autopilot disengagement [same threshold as for the stickshaker], stall-warbler activation [same threshold as the stickpusher], and stall-warning-flashing-light activation [also same threshold as stickpusher]) activate even if just one of the two vanes measures an angle of attack equal to or greater than the requisite threshold.
2: Although the accident aircraft was a CRJ100, the CRJ200 is identical to the CRJ100 except for using a slightly-different variant of the CF34 engine; the two even share the same CL-600-2B19 classification (making it somewhat difficult, when reading AARs discussing first-generation CRJs, to figure out whether the aircraft being referred to is a CRJ100 or a CRJ200).

Your wrote:

a value which, according to the report, would not have been altered by the aircraft's rapidly-increasing AOA

The report did not say that (but I can see how that confusion can arise). It said the 1) flap retraction and 2) increasing g load -- would not alter the AOA trip point of 13.5 -- no mention of rapidly-increasing AOA:

the flaps had retracted a few degrees from 45 and the g was increasing, both of which would cause a slightly higher pusher activation speed; however, there would be no effect on the pusher activation AOA. [emphasis mine]

"Both of which" references the two conditions 1) and 2).

What would alter the trip point however is explained on the page before:

When the AOA is changing, the computer notes the rate of change and, if necessary, applies a correction to activate the protection system ahead of its normal trip points. [emphasis mine]

Which is what the computer did, as explained on page 49 (PDF page 59):

The left-hand and right-hand AOA vane angles as recorded on the FDR were compared with the shaker and pusher boundaries adjusted for the phase advance resulting from the rate of increase of aircraft AOA. This comparison revealed that both AOA vanes reached the shaker trip point, but only the right-hand vane reached the pusher trip point (...) [emphasis mine]

In other words, the trip point would be the AOA phase advanced to account for the AOA rate in the Stall Protection System computer. Which as you noted, was somewhere between 8.7° and 9.4° for the stick-pusher.


Why does Martin-Baker use a Gloster Meteor as a testbed for ejection seats? Martin-Baker uses a Gloster Meteor for testing ejection seats, according to their website.

While it's a stylish plane, and a true delight that there are still airworthy fuselages of this plane left, it seems strange to use such an old aircraft as a testbed.

The Gloster Meteor was one of the very first turbine engine planes, made during the Second World War. In terms of electronics and structure it's a far cry from a modern fighter.

How does this make sense? Wouldn't it be better to test ejection seats in the aircraft they will be used in, with the correct structure and canopy?

Aviation week did a bit on the plane last year

  "In spite of its considerable vintage, the sturdy British attack
  aircraft has all the attributes required for a stable, high-speed test
  platform" says Andy Gent, Martin-Baker’s head of flying and chief
  pilot. “From a test perspective the Meteor is ideal. The tail boom is
  fairly long and the fin is not very high. The engines are also spaced
  out a fair way out along the wing, so the efflux from the ejection
  test and exhaust from the gun and rocket motor isn’t potentially going
  down the engine intakes,” he says.

  Based at Martin-Baker’s Chalgrove, England, test facility, the fleet
  is made up of two Meteors, WA638 and WL419, both of which have been
  with the company since the 1960s. “They are doing the job so why would
  you ever go through the heartache of getting another aircraft?” says
  Gent.

In short, it does not fly all too much, it gets the job done and its well built. Similar reason most older aircraft are still flying these days.

The article goes on to say that they have little intention of changing this any time soon:

  Marketing Director Andrew Martin notes the company is one of only a
  handful that performs airborne ejection tests, and that the Meteor
  will continue to be used for the foreseeable future. “It is a tough
  thing to evaluate, and right now while we have these phenomenal assets
  we are not going to really think about a replacement in great detail,”
  he says. With the final retirement of the last Royal Air Force
  (RAF)-operated aircraft in the target towing role in the early 1980s,
  Martin-Baker acquired a large stock of spares and Rolls-Royce Derwent
  8 turbojets. Because of that and the ample remaining airframe life,
  the company is no rush to find a successor.

Also a bit of a side note, this is not their only testbed. MB also uses a high speed sled for testing at their Langford Lodge, Ireland facility. This allows ground testing of the seats at flight speeds. They also test static scenarios in what appears to be cockpit mock ups as generally speaking seats are certified for Zero-Zero use. Varying governing bodies may require different testing and live demonstrations as per their certification process leading to different testing procedures.


What is the history of the CFI spin endorsement requirement? FAR 61.183(i)(1) requires that a Flight Instructor candidate receive a logbook endorsement certifying proficiency in slow flight, stalls and spins.
How long has the requirement for spins been in the regulations?
Is it possible that there are CFIs in the field that do not have this endorsement?

I can't find a definitive answer but it looks likely - but not certain - that endorsements were introduced sometime between 1980 and 1991.
An AOPA article says that spins became an instructor-only thing in 1949, per CAR Amendment 20-3 (which I can't find online). That doesn't say anything about when an endorsement was introduced, though.
AC 61-67C - Stall and Spin Awareness Training has some historical information on page ii, including this (emphasis mine):

In January 1980, the Federal Aviation Administration (FAA) announced
its policy of incorporating the use of certain distractions during the
performance of flight test maneuvers. This policy came about as a
result of Report No. FAA-RD-77-26, General Aviation Pilot Stall
Awareness Study, which revealed that stall/spin related accidents
accounted for approximately one-quarter of all fatal general aviation
accidents. National Transportation Safety Board (NTSB) statistics
indicate that most stall/spin accidents result when a pilot is
distracted momentarily from the primary task of flying the aircraft.
Changes to part 61, completed in 1991, included increased stall and
spin awareness training for recreational, private, and commercial
Pilot Certificate applicants. The training is intended to emphasize
recognition of situations that could lead to an inadvertent stall
and/or spin by using realistic distractions such as those suggested in
Report No. FAA-RD-77-26 and incorporated into the performance of
flight test maneuvers. Although the training is intended to emphasize
stall and spin awareness and recovery techniques for all pilots, only
flight instructor-airplane and flight instructor-glider candidates are
required to demonstrate instructional proficiency in spin entry,
spins, and spin recovery techniques as a requirement for
certification. Part 61 was extensively updated in 1997.

In version A of the Flight Instructor PTS (May 1991), candidates are required to demonstrate a spin but the examiner can accept an endorsement instead, at their discretion (pp. 2-xliii - 2-xliv):

At the discretion of the examiner, a logbook record attesting
applicant instructional competency in spin entries, spins, and spin
recoveries may be accepted in lieu of this TASK.

The task itself is described as:

Demonstrates and simultaneously explains a spin (one turn) from an
instructional standpoint.

So we can say for sure that since 1991 at least, instructor candidates have been required to either spin the aircraft during their checkride or have an endorsement saying they were capable of doing it. (I say "since 1991" because the same wording is still in the CFI PTS today.)
Of course, getting the endorsement requires spinning anyway (see AC 61-67 again), meaning that the candidate always had to spin an aircraft in order to qualify. The endorsement wasn't a way to avoid doing that.
I can't find any earlier sources or PTS versions that show the pre-1991 requirements, maybe someone else will have more luck.
And to answer your second question, 1991 was 'only' 29 years ago. It seems very possible that there are instructors who have been active for longer than that. If you're wondering if some instructors out there may never have spun an aircraft, the AOPA article implies that they've 'always' been required to spin aircraft anyway, regardless of exactly when the endorsement became an alternative to doing it in the flight test.


What airplanes can I fly with an EASA PPL license? Weird as it might seem, I'm not 100% sure what airplanes I can fly
with an EASA PPL(A) license. During the training the instructors would
tell me that I can fly airplanes up to 2000 kg MTOW and 5 passengers
or so, but I think they are wrong and this applies only to the (old)
national rules (Germany in this case).

The license states that I have a SEP (land) class rating. I have
searched through the EASA rules (a cumbersome task on its own) and
nowhere could I find a weight or passenger limit, nor a specific
definition of what exactly qualifies as a SEP.

So the question is, what aircraft am I entitled to fly with my PPL(A)
license? Do aircraft with specificities such as a retractable
gear fall into the same category? Please also point to the source
of the applicable legislation.

By the same token, may I/may I not fly light aircraft such as e.g. a
K-10 Swift?

I was wondering about the same and here is what I found.
Yes, for LAPL license holders, when switching to another airplane within the same class rating (don't mix it up with type rating) the familiarization training shall be performed and signed off by instructor. It's stated in the "FCL.135.A LAPL(A) — Extension of privileges to another class or variant of aeroplane" section of the "Part FCL".

Before the holder of an LAPL can exercise the privileges of the licence on another variant of
aeroplane than the one used for the skill test, the pilot shall undertake differences or familiarisation
training. The differences training shall be entered in the pilot’s logbook or equivalent document and
signed by the instructor.

There is no such requirements for PPL(A) holders.
Further away there is the section "FCL.700 Circumstances in which class or type ratings are required" which has class rating SEP (land) with many aeroplanes: SEP (land), SEP (land) with variable pitch propellers, SEP (land) with retractable undercarriage etc.

All those are aeroplanes. The D to the right means that

Whenever (D) is indicated in one of the lists mentioned in paragraphs (a) to (c), it indicates that differences training in accordance with FCL.710 is required.

Ok, going down to the "FCL.710 Class and type ratings — variants" where we have

In order to extend his/her privileges to another variant of aircraft within one class or type rating, the pilot shall undertake differences or familiarisation training.

I don't know why aircraft is used in this section instead of aeroplane, but later again it's explained as

(a) Differences training requires the acquisition of additional knowledge and training on an appropriate training device or the aircraft.
(b) Familiarisation training requires the acquisition of additional knowledge.

Conclusion: the minimum required is "Familiarisation" which is just "acquisition of additional knowledge" which has no any requirements for legal sign off or so.


What follow-up actions, if any, does the FAA take when a pilot declares an emergency in flight? This question focuses on what the FAA is required to do when pilot declares an emergency, as opposed to what a pilot is required to do. (The answer to this question is not covered in typical pilot training).

Example: Pilot loses situational awareness and becomes lost. Pilot is low on fuel and declares emergency and ATC provides vectors; pilot turns towards nearest airport. Pilot arrives at airport and makes an uneventful landing at small airport. No other traffic was diverted, aircraft and passengers fine, pilot did not deviate from any Part 91 FARs.

After the emergency is over, what legal, administrative, or investigative actions will the FAA or other official bodies take?

I understand that when a pilot declares an emergency the pilot gets priority from air traffic control, and may take reasonable actions for the safety of the flight even if it means deviating from part 91 regulations.

It would appear that, so long as there was no incident or accident, no one is injured, and no regulation is broken that FAA will take a "no harm, no foul" approach.

I'm curious if any one has source information as to what should the pilot expect: a call from ATC, an investigation, nothing, etc.? (Assume no FAA deviations, no injuries or accidents, etc.)

I don't know the FAA policy, but normally, you don't report deviations from the regs, unless asked to.  I have declared emergencies, gotten priority handing in the DCA area, and a variety of eyebrow raising events over the years.  However, the FAA has never asked me to submit a written report. Once or twice, I have gotten a call from an operations inspector, and answered their questions, and that was all that became of it.

In general, if you had a bad day, don't tell about it. Just get on the ground safely, and be polite to people, and hope that you don't have any further review.  Of course, you must comply with NTSB 830, but if you are required to do that, you have had a really bad day, and might want to get some help (aviation attorney).


Where does fuel from the boost pumps go before engine start? For example let’s take the PT6A-27.

In every video related to engine start I see, the fuel boost pump is turned on, and then the fuel pressure goes up.

Example:

My question is: where is that fuel going if the condition lever is still at the idle cutoff position? Don’t you flood the engine?

I can’t say for sure about the jet engine mentioned. If I think of it like a piston engine, the fuel pump pressurizes the fuel lines. That in no way means that the fuel is entering the combustion part of the engine (cylinders in my case). It just means that the fuel lines leading to the fuel distribution point (carburetor or EFI) are being fed fuel at a certain pressure. A primer is a different story. It is feeding fuel directly into the combustion chamber by using pressure.

As mentioned in another post, more pressure and fuel is supplied by the fuel pump than is needed by the engine. In the case of a Cessna 172SP, the excess is routed to a reserve fuel reservoir. Here is a schematic of the fuel system from the POH.


What is needed to certify an aerodrome as an airport in Canada? So here.
All airports are aerodromes. All aerodromes are not airports.
Difference between Airport and Aerodrome:

An aerodrome or airdrome is any place from where flight operations can take place. This can include an airstrip in the middle of nowhere to a commercial airport in the biggest city in the world. An airport is a special type of aerodrome that has satisfied certain certification criteria or regulatory requirements of the ICAO that a regular aerodrome may not have achieved.
The term airport implies a certain stature of having satisfied certain certification criteria or regulatory requirements of the ICAO that a regular aerodrome may not have achieved. Hence it can be said that all airports are aerodromes, but not all aerodromes are airports.

So then what facilities and services does an aerodrome need to have, in order to be certified as an airport in Canada?

Original Answer
Aerodrome
It is an area where:

aircraft land
aircraft take off

Runway may not be present (in case of a water aerodrome).
Airport1
By definition2, an airport is an aerodrome with facilities for commercial aviation flights to take off and land
It is an aerodrome which has:

facilities to store and maintain aircraft
at least one designated operational landing/takeoff area (runway or helipad)
hangars
terminals
fixed base operators
airport aprons
air traffic control centers
passenger facilities (restaurants and lounges etc.)
emergency services
customs3
immigration3

Edit
I noticed that the question is updated to be only for Canada. In that case, airport requires the following:

have a safety management system in place
comply with airport safety standards and security requirements

Further reading
Aerodrome
Airport
Airport Design and Engineering Standards (by FAA)
Aerodrome Standards (PDF by ICAO)

1: Not all airports must have all of these to qualify as an airport.
2: I could not find specific regulations which define an airport.
3: In case of an international airport


Are there any helicopters equipped with pressurized cabins? I would think that a pressurized helicopter is impractical since helicopters are usually flying at low altitude, but has a pressurized helicopter ever been conceived or built?

Helicopter cabins are not usually pressurized as they are not expected to be operated at high altitudes.

The largest operational helicopter, the Mil Mi 26 Halo has a pressurized crew cabin.

The Russian Mil Mi-24 Hind and Mil Mi 28 Havoc feature pressurized cockpits. However, these are for operating in an NBC environment, not for high altitude operation.


How do groundspeed and IAS change during eights on pylons, and how should I manage them? When performing eights on pylons I know that groundspeed (GS) reduces as we fly into the wind and increases as we fly with (or away from) the wind. This is the direct cause for the need to constantly change altitude (PA).

My question is in two parts:

As I descend into the headwind, why does my indicated airspeed (IAS) increase while my GS is reducing (and vice versa when flying with tailwind)? I have made a chart that shows XX GS = XX PA. When I look at my actual GS, I then look at my chart and find that I am at the correct PA for that GS but my IAS seems to spike in the descent and plummet in the climb.
Should I use the throttle to hold my IAS as it was in the entry?

Answering the easy question first:

No, you should leave the throttle alone once you've begun the maneuver.

As for the other question:

Without seeing your technique, I suspect your IAS is changing because of your climb/descent rate

I don't know how quickly you're climbing and descending, but if you're trying to hit specific speeds at various points during the maneuver, it's likely that you're going to end up flying mechanically and abruptly. An eight-on-pylon should ideally be flown with your eyes mostly scanning outside, and only occasionally coming inside to reference your altitude and speed.

If you're trying to hit pre-computed numbers rather than looking outside and keeping the pylon on the lateral axis through smooth application of the controls, then my guess is that you'll be climbing and descending more than you need to, and you'll be doing it more abruptly than you need to, which may lead to large changes in IAS.

Have a look at the Airplane Flying Handbook, page 6-17:

  With prompt correction, and a very fine control pressures,
  it is possible to hold the visual reference line directly on the
  pylon even in strong winds. .....  It is important to understand that variations in pylon position are according to the apparent movement of the
  visual reference line. Attempting to correct pivotal altitude
  by the use of the altimeter is ineffective.

(emphasis mine)

This part of the answer may be entirely incorrect, because I don't know what your flying technique is. If you can give us more information, we can give better answers.


What are the advantages of Chemical Oxygen Generation over Gaseous Canisters on board of aircrafts? I'm looking to get a bit of info on Chemical Oxygen generation, especially as done on aircraft. I understand the process of Chemical Oxygen Generation. I'm also aware that weight for weight it produces far more oxygen than Oxygen gas canisters.

What I want to know is are there any other advantages? Does it have added safety benefits when compared to high pressure gaseous oxygen storage? The Oxygen candle burns extremely hot when it goes off but I'd imagine high pressure gas canisters could be far more dangerous and prone to exploding if damaged?

Pressurized oxygen tanks have two big minus points: they are heavy, and they are essentially a small bomb. But they have two big plus points: they can be refilled easily and they don't generate any heat when you use them.

Chemical oxygen generator plus points are they are lightweight, self-contained and more-or-less maintenance-free (they don't leak). Minus points are they are single-use, time-limited and cannot be shut off.

As nearly everything in aviation is a balance of good and bad, we often see both systems being used at the same time. The flight crew will use oxygen on a regular basis - sometimes procedurally, sometimes just to clear up a headache. They need to be able to turn it on and off, and the airline doesn't want to replace the system each time.

Passengers rarely need oxygen, and when they do it's only until the plane descends to breathable altitudes (which will happen really quickly).


Viability of Magnetically started engines I am working on a school project of mine which involved testing the viability of a magnetically started jet engine. By magnetically started, I mean that there are magnets which accelerate the main shaft to speed to start the engine. The point of this is to remove the need for an APU, saving space and cost on airliners and military jets.

To provide intake air to the engine to allow it to start up without an APU, there would be a system on the bottom of the engine with small electric fans to push air to the wet section of the engine to start combustion. During the flight the electric fans would be turned off and the intake section would be used like a RAM air intake for the wet section of the engine. The magnets would be powered by the battery in the aircraft, and the small electric fans would be powered by a separate battery in the engine itself.

With all that in mind, would this be viable in a commercial or private environment? Or does the APU do its job too well to replace it?

Three things come to mind:

Magnets are heavy.
Not all compressor and turbine blades are ferro-magnetic.
The starter would only start the engine, and then be dead weight.

Usually, new designs are implemented when they have clear advantages over previous solutions, but I cannot see what problem this would solve. The APU is a very versatile and lightweight piece of equipment that can power up all of the systems of an airplane. Not really anyone's prime target for replacement, I reckon that captain Sully would agree.


Are all flights planned? Do (GA) pilots necessarily have to plan every flight, or can someone just go up and fly? Please note I don't mean actually 'filing a flight plan', but does every flight need to be carefully plotted out in advance?

I can get in my car and just drive. If I really wanted to, I could point its nose West and drive until I wanted to stop. In the first years of flight, like during the barn-storming era, a pilot with a plane could hop in and fly as long as he had gas, it seems like there is less enjoyment of "flying for flying's sake" and more 400 hours of planning for a 4 hour trip.

You didn't specify the jurisdiction that you were asking about, but in the US there is a regulation that covers the minimum that you must do before flying.

Much of it is common sense:

You want to check the weather, because it can impact you much more than it usually does in your car and you don't want to get stuck in a really bad situation.
You want to check the Notices to Airmen (NOTAMs) to make sure that you can use the airport (i.e. it isn't closed, or the runway isn't closed, etc.)
You want to make sure that you have enough fuel, because you can't just pull over at the nearest gas station when you get low.
You want to make sure that the runways are long enough and that the airplane can climb well enough so that you don't crash into something.

That being said, if you are familiar with the area and the airports in the area, you have used them before and are already familiar with the performance numbers for your airplane, then you don't really need to do much more than check the weather/NOTAMs and make sure that your airplane is legal and safe to fly.

Things are a little different than back in the barnstorming days, but then there are fewer accidents too.  :-)

  §91.103   Preflight action.
  Each pilot in command shall, before
  beginning a flight, become familiar with all available information
  concerning that flight. This information must include—

  (a) For a flight under IFR or a flight not in the vicinity of an
  airport, weather reports and forecasts, fuel requirements,
  alternatives available if the planned flight cannot be completed, and
  any known traffic delays of which the pilot in command has been
  advised by ATC;

  (b) For any flight, runway lengths at airports of intended use, and
  the following takeoff and landing distance information:

  (1) For civil aircraft for which an approved Airplane or Rotorcraft
  Flight Manual containing takeoff and landing distance data is
  required, the takeoff and landing distance data contained therein; and

  (2) For civil aircraft other than those specified in paragraph (b)(1)
  of this section, other reliable information appropriate to the
  aircraft, relating to aircraft performance under expected values of
  airport elevation and runway slope, aircraft gross weight, and wind
  and temperature.


How does a pilot replace their logbook if it has been lost? I got my private pilot license when I was 17 but was unable to continue flying. I am moving into a position to get back in the air, but I no longer have my log book as it was lost between moves. What is the best way to move forward?

The best approach is to start a new logbook with totals that carry over from your latest FAA 8710 - in this case, it sounds like you will roll back to the hours from when you earned your private pilot certificate. There are some other options listed in FAA Order 8900.1, 5-172, but it's unlikely any of them will work for your situation (except, perhaps for "Receipts for aircraft rentals", if your FBO is still open and still has the records).

You can request a copy of your 8710 from the FAA, which I'm gonna quote here because that's the best way to not screw anything up:

  Airmen who have lost their logbooks or flight records may request copies of their files from the FAA [by sending this form] to the following:

    FAA Airmen Certification Branch, AFS-760
    P.O. Box 25082
    Oklahoma City, OK 73125

  or

    FAA Aeromedical Certification
    P.O. Box 25082
    Oklahoma City, OK 73125

Once you receive the copy, the first line in your new logbook should probably summarize all the totals from the 8710 (just like if it was a flight). The remarks would specify "time forward from 8710 dated DD/MM/YYY" or something to that effect.

Best of luck getting your records back!


What airport proposal(s) has London seen after WWII? Instead of Thames Estuary Airport from Maplin in 70s to the latest inner Thames Estuary Airport, is there any proposal airport(s) raised after WWII but cancel/rejected eventually?

I know there is a airport proposal in the north-west London but it is cancelled eventually. Does anyone know about this?

In stead of these two, is there any other airport proposals?

There was one more proposal before Thames Estuary Airport. That was the Cublington airport, which was rejected by planner Colin Buchanan,as "an environmental disaster." Later the government rejected the proposal of this airport, and rather went for Thames Estuary.

Other than that, there are no more proposals for new airports, but there are certain plans for expanding existing Heathrow and Gatwick.

The Airports Commission says there is a need for one additional runway in the South East of England by 2030.
It has shortlisted three options:

A third runway at Heathrow
Lengthening an existing runway at Heathrow
A second runway at Gatwick

Read in detail about all of them HERE


Is it worth reporting that I saw a green laser being pointed at the aircraft as a passenger? I was on approach to Vienna yesterday evening when I observed two 2-second green laser flashes 5 seconds apart from one of the rear passenger windows of the B737 where I was seated being pointed at the aircraft.

I'm wondering if and what I should do since green lasers are dangerous, and I'm convinced the aircraft was being targeted. Should I report this to the relevant authorities? Is it very common or a rare occurrence? The co-pilot didn't seem very bothered about it in any case and he hadn't seen it.

Updates:
20th December 2014: Sent an email to the relevant Austrian authorities. Will see if I get a reply.
22nd December 2014: Sent a report to AustroControl as well.
8th June 2015: No reply to date.

In that case I would definitely report the incidence!  It doesn't have to be done by police, but you can give the airport authority a call, that way you don't have to make too much of a big deal about it, and still informed the ones that need to know. They can then advise pilots and keep their eyes open for it. If there is a attack on the airplanes, it is important that it is being reported before it is too late. If not, then you didn't make a big deal out of it and are not in trouble for wasting time and money.

So, a call where you could explain what you have seen and give a opinion is your best bet, if they tell you off then hey, you've tried it!


Is it safe to mix different types of fuels in a jet engine? Hypothetically, if:

one got stuck somewhere at a remote airport
the jet aircraft or airliner they are flying had a 1/3 tank full of the proper jet A1 fuel
there was a tanker at the airport with 1/3 gasoline or petrol and another with diesel (the one used in trucks and passenger cars)

Would filling up the tanks and mixing all three fuels be safe for the operation of the jet engine, given that jet engines can burn any fuel?

Would the pilots expect to cover as much distance if they needed all the fuel to reach their closest destination safely to refuel?

While turbine engine can be made to burn almost any fuel, a specific engine might not run with fuel it is not tuned for for several reasons:

The high pressure fuel pumps only work with stuff that is sufficiently lubricating. They don't use grease, because it would be too easily washed out at the operating pressure, and the pressure is needed because the fuel is injected directly into the combustors at the highest pressure present in the engine. This rules out too much gasoline—note that spark-ignition engines, even when they have direct injection, inject during suction, so at low pressure.

With little enough gasoline, the pumps wouldn't mind, and I heard some militaries had backup plan for diesel engines—which have the same issue—to mix gasoline with some oil as an emergency fuel. However to know how much gasoline is safe somebody would have to test it and nobody is going to sacrifice a very expensive piece of equipment that is a turbine engine for a test with so little value as this since there is no shortage of proper jet fuel.
Each fuel has different heat of combustion, so it needs to be metered differently to keep the engine within the rather narrow range of operating pressures and temperatures. If the heat of combustion is too low, the pressure won't be enough to keep the turbine spinning and the engine will flame out, and if it is too high, the pressure will exceed the capability of the compressor which will stall and the engine will either flame out or go through a cycle of stalls that will thoroughly destroy it.

The adjustment might be as “simple” as updating the firmware in the FADEC, but it is still a lot of work to do all the necessary measurements and then do all the tests for the modification and since there is no practical use, nobody did.
The length of the combustor also has to match the speed of combustion, so if that is different enough, you need a differently built engine altogether.

So the engine will probably tolerate some different fuel mixed in the tanks, but nobody can tell you how much exactly, because it wasn't tested.


What does the 'hp' rating actually signify, with respect to an aircraft engine? Let's say I've got a Cessna C172S with a Lycoming IO-360-L2A engine that produces 180 hp (that's the power output for sure). Let's say I've also got a water pump, that is rated at 1 hp (power input or output?).

  Is the Lycoming engine 180 times more powerful than my water pump?

Can they be compared with each other - one's based on electricity, and the other is based on fuel combustion)? Or have I got it all wrong? The Airbus E-Fan has 2x30 kW (2x40hp) electric motors, and it's slow (with respect to the 172S), cruising at only around 86 kn.

  1 Horsepower = 745.7 Watts

that means 180 HP = 134244 W (or) 134.244 kW! Did I get that right? Again, is that the power draw or the power it can produce (they are kinda different right)? In order to get the same power, should an equivalent electric motor be rated at around 135 kW ?

Let's say I have another (read experimental) aircraft of just a quarter the weight of the 172S and very similar drag-profile. Does that mean I only need a 45 hp engine to achieve similar performance?

What is horsepower? It is a measure of the work a horse can do in an hour, invented in the time of the steam engines in order to make sense of what they could do, in a time when all work was done by humans and horses. As usual before the SI, there were many definitions of horsepower. Here is the one from wiki, on what a metric horse could do:

Notice that there is a time element in the picture: if the horse takes all day to raise the weight one metre in height, he is not very powerful.

Nowadays, the unit of power is the Watt, after James Watt who coined the horsepower unit to sell his steam engines. It is defined as the force in Newton, required to move 1 kilogram over one meter in one second:

$$1 W = 1 \frac{N \cdot m}{s} $$

In these units, you can see a force times a velocity, and that is one way of looking at what power is: you need more power to drive faster up a hill. But these are linear entities, and most power is made by rotary engines. Rotary units are torque (N*m) and how fast the engine is spinning (rad/s).

With engines, it makes a difference where power is measured. There are always losses caused by friction and by energy conversion, and the closer you measure at the output shaft of the engine, the higher the reading. This is what vehicle manufacturers rather do: car engine power is measured at the crankshaft, not at the wheels that actually propel you over the roads, because between engine and wheels there are transmission losses.

The question why power is used for engine rating, and not force or torque, is an interesting one. It is force that accelerates us: $ F = m \cdot a$. We can gear the motor force or torque output as required - if the gearing had no losses, power before and after gearing would be the same. So horsepower is useful to compare capabilities of engines, regardless of gearings. However they wil always be maximum capabilities.

With an aircraft, the engine power needs to propel the aircraft via the propeller. The propeller delivers thrust T, and can drive the plane at speed V, maximum speed being where drag equals thrust. Engine power is thrust times airspeed, plus the power required to overcome losses: mechanical losses due to friction, and aerodynamic losses due to propeller efficiency.

Your question on having an aircraft a quarter of the weight and similar size. The thrust is required to overcome aerodynamic drag, both friction drag and induced drag from lift. Friction drag will remain equal, lift induced drag will be 1/4th of the full weight version. You will need more than 45 hp to get the quarter weight aircraft to travel at the same cruise speed.

The picture is from this most informative source: parasitic power stays the same, induced power reduces by a factor 4. Notice that at low speeds induced power is dominant, at high speeds parasitic power is dominant. So with a 45 hp engine you will get off the ground if the weight is reduced by factor 4, but the maximum speed will be way less.


When wiil this person be able to replace his engines on a bunch of smaller ones to attach them on clothes? That is the real question that bothered me.
 UK 'Iron Man' suit

From the outlet cowling and nozzle, it they look to me like 6 standard RC jet engines (JetCat or so; JETCAT P200RX, for instance, has about 50 lbs of thrust, so in the right order of magnitude).

I don't think there would be any benefit whatsoever to using many miniature engines.


Are modern Airbus aircraft protected from excessive rudder input? When in normal Law are Airbus aircraft now protected from the types of excessive rudder input that caused the crash of American Airlines 587 (as dramatized in Mayday, S13E05)?

Yes, A320 and all newer models have rudder travel limiter that limits the maximum rudder deflection depending on speed.

It should be noted, that this has nothing to do with normal law. Normal law governs pitch and roll. Rudder is controlled by (hydro)mechanically connected¹ pedals and yaw damper, which is independent from the system controlling pitch and roll and simply reacts to side-slip (lateral acceleration actually, only A350 will have side-slip vanes) induced by the roll.

¹ Different Airbus models have different subset of controls with direct hydromechanical link as a backup in case of electric failure, so I am not sure rudder pedals have it on all models. They do on A320.


How exactly does a pilot engage the autopilot? I have a number of questions about auto-pilots but rather than deluge you with a long prose here let me break them down into separate questions over the next little while.

From playing around with simulators I know that the pilot has the ability to enter desired altitudes, climb rates, heading etc into the auto-pilot. However, and forgive me, whenever I see a pilot engage the auto-pilot in movies etc, it is simply a flip of the switch.

So that got me wondering how the transition is made in actuality.

Does the pilot need to enter the current altitude, heading etc before flicking the switch or does the AP take the current numbers and hold those automatically.

If it is the latter and the aircraft is in say a climbing turn when the switch is clicked.. then what? Does the aircraft continue in that pattern or what?

“One Switch” to operate the Autopilot is not true. That’s just the movies.

Autopilot systems vary in each aircraft. Larger jets have it divided into two: Auto-Throttle and Auto-Pilot. Smaller aircraft/piston aircraft don’t really have auto-throttle capabilities.

The Autopilot is not just to “maintain” current flight path. It really can fly the entire flight from take-off to touchdown. This includes flying a departure procedure, en-route navigation, arrival procedure, an approach and touchdown.

Theoretically, it is possible for a pilot to not touch the aircraft controls (yoke/stick/throttle) after liftoff all the way until touchdown even if the mission is a complex IFR flight. Realistically, pilots love to fly and they will fly.

Many settings exist for each autopilot system, and these include (but are not limited to):

Lateral Navigation

Heading Mode (fly the “selected” heading”)
Nav Mode (fly the “selected” nav course)
Roll Mode

Vertical Navigation

Altitude Select Mode (Maintain the selected altitude)
Vertical Descent with a fixed speed
Vertical Descent with a fixed rate
Approch Mode (Vertical Descent with Glideslope)

Auto-Throttle

Maintain Selected Airspeed
Accelerate/Decelerate to Selected Airspeed

However, there is that master AP Switch that’ll disable all things related to the AP.


Is there a Take-off speed category? ICAO Annex 14 recommends that "Runway centre line lights shall be provided on a runway intended to be used for take-off with an operating minimum of an RVR of the order of 400 m or higher when used by aeroplanes with a very high take-off speed, particularly where the width between the runway edge lights is greater than 50 m." (section 5.3.12.4).

I wish to know whether aircraft are categorized by take-off speed (like they are by approach speed), or which aircraft fall in the category of having very high take-off speed.

Never heard of any sort of takeoff speed "category" applied to operators in US rules, but we do have rules (in an airline's OpSpecs) for our aircraft that tell us at what min visibility centerline lights are required for takeoff (and landing as well).

If an airport were considering investing in Centerline Lights, that recommendation, combined with a little research into the requirements of the airlines who'd potentially operate into & out of that runway, would provide a basis to determine what incremental gain in utilization the runway could have. (Along with some meterology hisoric data -- numbers of hours/days at or below a given RVR value.)

The term very high take-off speed does seem a little nebulous; airliners' takeoff speeds are pretty high compared with most General Aviation aircraft, and unless you're building a runway for fighter or experimental jets, there aren't that many aircraft with higher takeoff speeds than we have that it would seem worthwhile to install CL just for them.

But, who knows... Maybe another ICAO document does define that term somewhere.


Can ATC tell if aircraft is being flown manually? Was wondering if ATC can detect if aircraft is being flown manually vs. autopilot and if that affects their clearances given out for surrounding aircraft?

More specifically, can they tell through ADSB signal or just by observation (holding flight level, turn rate, correction for wind, etc)?

I would imagine that in high winds/bad weather non-AP operation would need to be better isolated from other aircraft?

No, the air traffic controller cannot see the whether the autopilot is used or not.

However, in the Mode S radar and ADS-B protocols there are messages defined that contain state of the autopilot. Currently there is no requirement that this data is provided by the aircraft, but some aircraft/transponders do provide the information nevertheless. The data is not displayed to the controller though.

In some control centres the aircraft's Mode Control Panel / Flight Control Unit Selected Altitude can be displayed to the air traffic controller. The information can be used to reduce Level Busts.

From observations of the radar track it is difficult to tell. A competent pilot will be able to maintain altitude and heading in such a way that it is difficult to see the difference from an autopilot at the resolution of the ATC display.

There are circumstances where the pilot is required to use the autopilot, especially to keep separation from other aircraft. In Reduced Vertical Separation Minima (RVSM) airspace the vertical separation is 1000 ft between Flight Level 290 and FL410. The aircraft must be flown using the autopilot in this airspace to ensure the flight levels are adhered to strictly.


Can a 747 land at Ovda? Since Ben Gurion International Airport is closed, flights are being directed to Ovda, with a 3000 meter / 9,843 foot runway. Can large passenger jets, such as the Boeing 747, land at such an airport?

I understand that a 747 at MTW needs about 10000 feet to land safely, but it can be done in a pinch at 6000-7000 feet. Would a commercial airliner fly flights to a temporary airport such as Ovda considering the shorter runway (i.e. not emergency conditions)?

Also, if I may ask, in the linked thread a 747 pilot refers to the 747 as "a gigantic replica of the North American F-86". To what might he have been referring?

So, given Terry's remarks, GdD pointing out that the density altitude for Ovda is around 4300', and the current B744 Airport Planning Document, we can use the unadjusted (there's also a temperature adjusted version, but you don't need that when you have a density altitude in hand) T/O distance chart for the appropriate engine type (I'm going to use the CF6 version for example's sake) to compute how heavy a 747 out of Ovda can be.  (The chart you need is on page 72 on the PDF, by the way.)

Looking across the chart at the 10,000' line gets you an intersection with the 4000' altitude curve about halfway between 750,000 and 800,000 lbs; let us call this 775,000 lbs for argument's sake.  Since we have a slightly shorter runway and a somewhat higher DA, 760,000 lbs is a reasonable MTOW for a 744 out of Ovda; if you wished to be extra conservative, you could cap your MTOW at 750,000 lbs.

As per PDF page 15 of that same document, the typical operating empty weight of a B744 is about 394,000 pounds.  Adding the 120,000 pounds of passengers Terry quoted onto this leaves you with 236,000 lbs of fuel minimum, which is more than enough to get to anywhere in Europe with fuel to spare.  If you want figures, you can use the payload/range charts on PDF page 55 to get a max range of 4200 miles, which as per the great-circle mapper is enough to get you to anywhere in Europe or Africa, as well as the Indian subcontinent and much of SE Asia and China.

As to the landing half of it, the landing distance charts on PDF pages 94 and 95 can be used, assuming a wet runway, a 4300' density altitude for Ovda, the passenger configuration MLW of 630,000lbs, and the ability to use Flaps 30 (Flaps 25 yields a longer landing distance) we get a runway length of around 8700'; this'd be somewhat tight (you'd want to use max autobrakes and your reversers, and make sure you came over the fence at Vref with a firm touchdown to avoid floating in ground effect), but passenger flights don't land at MLW very often, so it'd be a workable operation.


Where's the A318 on the runway that caused a 747 to go around? I screenshot 1:00 of a 480p YouTube video. The autopilot proclaims Minimums at 1:01, and the pilot flying decides to go around at 1:02 because an A318 was still on the runway, but I can't spot it, or any airplane, on the runway in the video! Can anyone? Or does anyone possess this video at a higher resolution?

Look for the blinking light in the center of the runway
That's the strobe lights of the A319. It's all you can see of it in the video.  I had to step frame by frame through the video to capture a frame where it was visible and another frame where it wasn't.

Sorry for the turbulence.  :)


Placement of positioning lights on A320 winglets I was flying with an A320-214 that had big winglets (I think they were called Sharklets). I noticed that the positioning lights were facing forward on the leading edge of the winglet (the "notch" in the picture).

I was wondering why the light is placed there, because it seems to be very unoptimal.

Isn't the light mostly blocked when viewed from behind? Why is not not placed at the top of the winglet? Is that even a big concern?

Position lights are only visible in certain sectors (see image). The red and green lights on the wings are not supposed to be visible from behind.

Image source: Learn to fly


How did shortening the 707 increase its range? According to the Wikipedia entry for the 707-120:

  The 707-138 was a −120 with a fuselage 10 ft (3.0 m) shorter than the others, with 5 ft (1.5 m) (three frames) removed ahead and behind the wing, giving increased range. Maximum takeoff weight was the same 247,000 lb (112,000 kg) as the standard version

With the same MTOM between the -120 and the -138, what made the difference in the range? Was it simply less parasitic drag from the shorter fuselage?

I would presume that the fuel capacity (stored in the wings - center section tanks didn't come about until the -320) would have been the same.

I see notes on the -120B which switched to the P&W JT3D-1 engines which were more fuel efficient. That would account for greater range, but that doesn't apply to the -138 (at least not at launch).

If the fuse was shortened that much (reducing both the weight of the airframe and its cargo-carrying capacity) and the maximum takeoff weight stayed the same, the most natural explanation is that the plane's allowable fuel load at takeoff or the tank's capacity was increased.


What tests are done on aircraft wings for testing the effects of lightning? During the testing phase of aircraft wings, there are lot of testing like temperature, pressure, humidity, vibration and load/stress. Apart from these, does any one have idea which other tests are done on them for complete qualifications like like lightning?

Almost all the tests done on aircraft wings can easily be categorized in one of the areas you mentioned.

The only remaining thing I can think is bending an aircraft's wing. It is stated on BBC as:

  Many modern passenger jets can flex their wings nearly 90 degrees in a test rig.

For B787, it is reported:

  During the test, the wings on the 787 were flexed upward
  “approximately 25 feet” which equates to 150 percent of the most
  extreme forces the airplane is ever expected to encounter during
  normal operation. The test is used to demonstrate a safety margin for
  the design and is part of the certification process to show the
  airplane can withstand extreme forces.

This video shows (also this one) how much force a wing can take before breaking.

OP asked about tests for lightning effects. Lightning commonly strikes the nose, wingtips, engine cowlings, and tip of the vertical tail. Hence, wings are not the only parts of an airplane which needs to be protected against lightning.

To avoid reinventing the wheel, please see the following questions:

How is an on ground lightning strike test conducted?
What happens when an airplane gets struck by lightning?


What is the typical space allocated to first class vs. economy class passengers? I'd like to know the space allocated to a typical first class passenger compared to that allocated to a typical economy class passenger.

For example, from SeatGuru, I can get the pitch and width of the seats on a British Airways Boeing 747 (economy is "World Traveller"). But can that give me the actual space allocated? Also, the first class seat is an "open suite" - does that mean there's space beyond pitch and width? Anyone ever done this calculation (in square feet or square meters)?

Width and pitch give you the space that is allocated to you and your seat. First Class seats are more bulky than Economy seats, so the actually usable space is a smaller fraction than in Economy. I wonder how the square meters would convey more information; generally, in Economy you are boxed in by your neighbors, while in First you can outstretch without reaching the limits of the cabin space allocated to you.

The aisles are wider in First, but it will be hard to make a concrete claim on "your" part of the aisle. Cabin crew in First will be more tolerant of eccentric behavior, so your mileage varies. Also note that in First on wide-bodied Aircraft every seat will have direct access to the aisle, so you will not need to step over the feet of your neighbor.

You also get more space for your baggage (luggage). On narrow-bodied aircraft two people sit in First Class where six would sit in Economy, so you get three times more space in the overhead bins. On wide-bodied aircraft this difference is even more pronounced, count on having in First the space of 5 ore more Economy seats. The bins are smaller, though.

Also, the steward will take care of your coat in First, so your space requirement is reduced as compared to Economy.


How do pilots know that the switch/knob they just switched on/off actually did what it's supposed to do? With the plethora of switches/knobs/buttons etc present in airplane cockpits, how can pilots be really sure that a button they just pushed (either to enable/disable some electronic system or move some non-visible part of the plane for example) has actually done its job correctly?

Is there some sort of visual or auditory feedback?

Or do they have to always assume that these have worked, until they realize otherwise by observing the airplane or other related systems behavior?

Depends on the system in question, but typically the following indications will serve as a means to verify that a system is functioning correctly.

Activation lights - some cockpit switches will illuminate when commanded by crew.  Granted this only can serve as an indication that the switch was engaged.

Indicator lights eg landing gear position lights, etc - remote switches on mechanical systems which are activated when said system are in a required positions or functioning.  The switch then can illuminate lights on an instrument panel.

Mechanical indicators eg flap position indicators - system provides either a mechanical or otherwise signal back to an indicator which mechanically moves in unison with with the system.

Information Displays - integrated flight decks and multifunction displays take inputs from similar remote mechanical, thermal, pressure and electrical inputs from aircraft systems and display either textual or graphic indications on displays.

Kinsethetic reactions - eg lowering flaps will cause the airplane  to decelerate and pitch up, landing gear actuation will cause sounds, vibrations, wind noises, etc.

Correct system function - eg autopilot mode engaged and the airplane is doing what the crew expected of the command.


What are the correct procedures for military aircraft interception over international waters? I recently read this list of errors in the film Top Gun.  The list is long and fairly well done, but there is one I realized when thinking about that movie and that is Maverick may have actually caused an international incident at the start of the film that precipitated into the climactic dogfight at the end.  That is, they intercepted the MiGs at the beginning of the film in an unprofessional and hostile manner which is not used when intercepting another aircraft over international waters.

Aircraft interceptions are a common occurrence in international airspace but there are specific procedures involved and protocol used to avoid an international incident.  Typically a two ship flight will maneuver alongside an unknown aircraft to visually identify it.  Any additional actions ie creating a collision hazard from a head on cross or hard maneuvering onto an aircraft’s six then tracking it with a fire control radar, as Maverick does at the start of the movie can be interpreted as a hostile act and could actually warrant use of force.  Therefore Maverick may be the aggressor here and the second MiG maneuvering for a shot at Cougar and lighting up his F-14 with its fire control radar would be a reasonable response to the F-14 two ship’s aggressive act over international waters.

  Goddamnit, Maverick!

Soviet aircraft routinely approached US carrier battle groups during the Cold War, in some cases coming within 1/2 mile from the battle group.  They were intercepted on a regular basis but never in such an aggressive manner as is shown in Top Gun.  Unless said Soviet aircraft were acting in a provocative manner with posed a direct threat to the ship or the air wing aircraft, there really wasn’t much you could do as you were in international waters and subject to international law.  Doing otherwise would have been an act of war.

So am I wrong in this assessment?  Is the intercept of an unknown aircraft as shown in the movie uncalled for and hostile to the MiG pilots who were only engaged in their own maneuvers over international waters?  Can anybody shed further light as to how the USN would professionally intercept a bogey over international waters?

The F-14 and its AIM-54 Phoenix missile was originally built for a particularly unfriendly intercept of Russian bombers from 100nm away in war time.

In peacetime, the TU-95 Bear bombers still needed to be intercepted.  That practice, at least in the north Atlantic, was usually for one of a pair of F-14s to fly directly toward the intercept point and well above it, while the other was several miles in trail and on the side that would be to the rear of the bomber(s) after intercept.  The first would overfly and make a descending turn to end up about a mile in trail, holding position there while the second did the same thing.  This ensured that (depending on ROE) weapons could always be directed at the bomber by one or the other F-14's throughout the approach.

Sometimes the F-14s were tasked with (really, permitted to) close with the Bear to "gather intelligence".  This resulted in lots of great pictures. You'll note that usually the F-14s in those didn't carry Sparrow or Phoenix missiles so they'd constitute less of a threat while closing (there were exceptions, though).  The Bear is about the size of a B-52, and depending on the day's plan you could come within a couple (Bear) wingspans of one. This in theory was risky (they had a rear gunner who's arc of fire you were to avoid) and took it out of your missile envelope, but you did have a gun...

As the Bear got closer to the carrier, more F-14s would arrive and things would get a little spread out for deconfliction.

But everything was smooth, slow, and initially done from a significant distance. Nothing at all like the Top Gun intercept, which would have permanently grounded all four crew members.


Who is responsible for providing ATC in a TMA? I know that TWR, APP, and ACC control ATZ, CTR, and en-route; but I'm not sure about the control service which is responsible for monitoring TMA (APP or ACC?!).

Could you please clear the case (preferably by a European reference)?

It depends.

Air traffic control service in a TMA can be provided by either an air traffic control tower (TWR), an approach control unit (APP), or an area control unit (ACC) - or any combination of those.

A TMA is typically considered to be APP airspace, but there is no rule preventing a TWR or ACC from covering a TMA, and there are many examples of this happening throughout the world.

The typical division, if you need a simple answer, is:

TWR provides service in a control zone (CTR)
APP provides service in a TMA
ACC provides service in a control area (CTA)


In the attached image of the Hoffman development of Arup design, the wing is shaped in a somehow anhedral way. Why? Most airplanes of its days had a Dihedral, or a wing thickness tapering with a 'V' shape, this one is the opposite, hints exist as done to avoid: 'Dutch Roll', or that the ordinary way will impair performance. What is it??

This plane is very interesting as it highlights a few design options.  Firstly, in seems to have neither significant dihedral nor anhedral, but it does have landing gear underneath it, lowering its CG for stability.  Being low aspect ratio, the builder probably decided to forego dihedral as cross wind gusts could make for a rolly, uncomfortable ride.  A slight sweep in the leading edges of the wing would provide some "dihedral effect" when rudder was applied.

Now for the wing itself, not albatross or eagle, we'll go flying squirrel here.  But notice how low the landing speed is.  This is a virtue of lower AR wings, though not as efficient as high AR (albatross) wings, they do stall at significantly lower speeds.  This design was also applied to the Navy "flying flapjack" and it performed well.

And thanks for the article, the ads made good reading too!


Is it possible for crew oxygen to exacerbate a flight deck fire? Crew oxygen is, as I understand it, a very high percentage of purity.

Oxygen-enriched air acts as an accelerant to a fire, causing things to ignite which wouldn't in ordinary air, and making fire more difficult to put out. Nice illustration of what oxygen-enriched atmospheres can do to shirts: here, p. 5. This also says that hair and clothes can trap oxygen, and this can be very dangerous. A spill from a mask might well accumulate in hair and clothes.

Also, although I'm not a chemist, it does appear that the margin between normal air and dangerous oxygen-enriched air is quite a slim one: this document says that at over 23% concentration "mixtures must be handled with all the precautions and care of pure oxygen as they start to change fire chemistry and enhance combustion."

In the event of flight deck depressurisation occurring simultaneously with a fire, and the crew using their bottled oxygen, could the following events pose a serious danger:

leak in one of the tubes involved in supplying the oxygen
crew member taking off their mask (and using a portable oxygen supply
instead)
crew member inadvertently pulling an oxygen tube out of its attachment in the course of some bodily manoeuvre
crew member switching their mask to "emergency mode" i.e. where constant pressure is maintained to prevent inhalation of noxious substances, but also perhaps resulting in leaks of oxygen from the mask? (here)

Not an aviation person so don't know how often emergency mode actually gets used, but if the FD were filling with smoke wouldn't you switch to emergency mode to try not to be breathing it in? But could this exacerbate the fire?

Unless my thinking is flawed in some way, wouldn't that mean that descent to an altitude where you no longer have to use oxygen might be quite an important priority in the event of a FD fire? Or maybe blowing an inert gas like argon into the FD*?

Just a final thought: oxygen-enriched fires also burn at particularly high temperatures (Apollo 1, EgyptAir 667). So the danger of such a fire actually destroying navigational or communication equipment and effectively killing the plane might be greater.

* High-concentration argon poses its own danger but for this specific situation, where the crew are on bottled oxygen, it might be OK until the fire was out.

Wouldn't [a] descent to an altitude where you no longer have to use oxygen might be quite an important priority in the event of a [flight deck] fire?

It is an important priority. Below is the first page of the procedure for the Airbus A320:

Going through the procedure, if things got out of hand, there is:

  At ANY TIME of the procedure, if situation becomes UNMANAGEABLE :
  IMMEDIATE LANDING............................CONSIDER

And even opening the cockpit window is an extreme option for smoke that is too much to be ventilated.

A note on the depressurized cabin/cockpit scenario: Since there is depressurization, any scenario where a hose leaks, the supply will quickly dissipate towards the pressurization leak source (and not saturate the cabin/cockpit). (It will also help dissipate any smoke.)

So it's the opposite, one would link pressurization with oxygen saturation.

One of the items on the smoke checklist is turning off the air supply systems (called PACKs) and using the manual system to deliberately depressurize the plane:

  PACK 1+2............................................................OFF
  MODE SEL..........................................................MAN
  MAN V/S CTL.............................................. FULL UP

"MAN V/S CTL" means "Manual Vertical Speed Control", basically how the cabin altitude (a pressurization term) is set. Full up means max positive rate, which will equalize the pressure with the outside – dumping pressurized air so to speak.