What aerodynamic data (drag/lift curves) exists for the A-10? This is one of 3 question in "series" - one question split up in 3 to better reward those responding about each aircraft. Other questions: Yak-131, L-159

A-10 is one 3 planes that are used in the ArmA 3 combat simulator, but its aerodynamics modelling currently lacks significantly. I'm planning on writing a short "essay" to developers regarding what and how can be specifically fixed in the flight model, but I'd like to back my research with some hard data. Specifically, I'm interested in any of the following:

L/AoA
D/AoA
Side lift/SA (Slide angle)
Max G/velocity
Flight envelopes (like one below for F-15):

Torques can well be left out - it's not a full fledged simulator, but the above data can give quite a good estimation of high level characteristics already.

Are there any good sources on any of the above data? I've found some (see below), but the quality leaves a lot to desire. Low-mach data is good enough for me.

I understand this is a tall order, but, well, SE is for expert answers - maybe a wonder happens and someone here has it? :)

What I've found so far:

Some superficial modelling of A-10
A-10 airfoil: NACA 6716 root, NACA 6713 tip
Set of A-10 documentation

Good luck finding number 1-3 on your list.  As far as I know these are proprietary data the you would have to get from Fairchild Republic.  After a career of flying fighters I never saw this data or really care about it.

In my opinions numbers 4 and 5 on your list are much more relevant.  What you are looking for are called EM diagrams.  EM stands for energy maneuverability and these diagrams show a scale of turn rate, turn radius, airspeed and altitude to display meanueverability at a given energy state.

Using these diagrams you can find some key performance factors:

Min maneuvering airspeed - where the rate and radius slope drops off on the left of the chard showing min flying airspeed at given altitudes and wing loading

Max instantaneous rate of turn - max possible turn rate given a certain energy state - top of the rate curve then drops off

Max sustained rate of turn - maximum rate that can be achieved while maintaining your energy state (Ps = 0)

Corner velocity - velocity to achieve max rate at a given energy state

Min radius - smallest radius of turn acheveable given a certain energy state

Radius for given conditions - important to determine this when planning something like a targeting attack

I've found an A-10 EM diagram and a good Mig-21 diagram that annotates the factors I have defined above.

Note:  I have to giggle at your "Low-Mach data is good enough for me" statement.  There is no high-Mach data in an A-10.  It will top out around .6 Mach (max speed around .7)

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Can a CFI endorse a BFR flight review through real-time video including the flight portion? Context: To minimize the heath risk during pandemic, many CFIs, especially senior ones, are not comfortable to conduct instructional flights with students in a narrow cabin. In the meantime, many pilots are due soon for flight reviews (BFR), but still within the 24 calendar month valid period.
For the ground portion of the flight review, a remote video call should make no difference with respect to regulation compliance. So the remaining of the question is for the flight portion,
Is it regulation-compliant to let a CFI to endorse me while the CFI is on the ground while I am going solo for the flight? There will be real-time videos, which cover the flight instrument panel, my maneuvers and cockpit outside views, broadcasting to my CFI in real-time, as well as recorded for post-flight verification. The CFI will be able to communicate to me in real-time through a hand-held radio, and will watch my takeoffs and landings near the runway, just like what happens on a first solo.

It seems to me that your question is simply "can an instructor provide flight training from the ground?", whether it's for a flight review or something else. As far as I can tell, the instructor must be in the aircraft. All emphasis below is mine.
61.1:

Flight training means that training, other than ground training,
received from an authorized instructor in flight in an aircraft.

61.195(g)(1):

(1) A flight instructor must perform all training from in [sic] an
aircraft that complies with the requirements of §91.109 of this
chapter.

The Williams interpretation (2018) talks about instructing from the rear seat (see this somewhat related question) and states that the regulations require the instructor to be seated in a pilot station per 61.195:

Section 61.195 prescribes limitations and qualifications for flight
instructors. As evident from the heading in § 61.195(g), § 61.195(g)
prescribes limitations on the flight instructor's position in an
aircraft and required pilot stations for flight training.
[...]
The regulation would not require two pilot stations for a training flight unless the flight instructor were required to provide flight
training from the one of the pilot stations.

That last statement seems very clear. In any case, the idea of providing flight instruction from the ground doesn't seem realistic, in my opinion. Even with great cameras, will the instructor be able to see your knuckles are white on the yoke from poor trimming technique? How would you do exercises under the hood (if needed)? There are just too many things that would be difficult to do and/or difficult to assess.


What was the first Russian jet designed with the use of area rule? What was the first Russian jet designed with the use of area rule? Also, how did the Russians acquire the knowledge of this design method? Was Whitcomb's discovery public?

Hard to say with any certainty, but Tu-16 and Tu-95 carry obvious signs of application of the area rule. Both had first flight in 1952, which makes it earlier than the Whitcomb's publication.

Whitcomb may have discovered the rule independently, but Germans knew it since 1940s, so my guess is that the Russians either found it from them (lots of very valuable aerodynamic research data was captured after the war), or developed independently (Russians had/have their own NACA, after all).


How large are the banners that are trailed behind small planes for advertising? How large are the banners that are used for aerial advertising, and how much do they normally weigh?

Example:

source: © Raimond Spekking / CC BY-SA 4.0 (via Wikimedia Commons)

Wikipedia page on Aerial Advertising

Pre-911 I towed banners, and towed them with a C172 and a C182.  Parasitic drag of the banner is the limiting factor.  We had different letters, and for the C-172, the letters were about 1.5 meter block letters, during the spring and fall, when the temps were below 20C about 18 to 22 letters was the max. Climb performance in the 172 was about 150 FPM.  In hot weather, up to about 40C, the max was about 12 letters with the C172.  The C182 could handle longer banners, and was used the most during the summer.

The weight of a 20 character banner was about 135 pounds.  The banners are made up by a crew on the ground, and then hooked on a low pass over an area adjacent to the runway.  Similarly, a low pass would be made to drop the banner.

The letters we used the most were red synthetic rip-stop fabric, and they were repaired with a sail / parachute sewing machine.  Later, just before 9-11, we got White / Black letters which were out a spun fabric like Tyvek. The banner business died in 2001 due to 9-11, with TFRs (Temporary Flight Restrictions) over major sporting events. NFL did not like banners being towed near games, and the emergence of TFRs effectively blocked banner towing.

FWIW, banner towing is more risky than glider towing, even though the gliders weigh more, they have less drag. (Although I used different aircraft for each.)  Also if a letter tears, or gets loose, the flapping and increased drag can substantially impact the drag, and climb performance.


How to Start a Jet Engine I know how the basics of how jet engines work. I know that air goes into the compressor as the first step of the journey. However, where does the air come from that goes into the jet engine at such high speeds it turns the rotors. I don't think its coming from the air because, the plane wouldn't be moving and no air would be flowing at a high rate. Also, once the jet engine is started up, how does air keep coming into the jet engine in flight. From air in the sky?
Is there a difference in the processes for fighter jets and regular commercial planes?

Inside some jet engines there is a powerful electric motor that starts the engine by spinning the compressor up to speed, at which point the fuel flow and the ignition spark are turned on, and the resulting combustion then forces the turbine to spin. The turbine's power output is sent to the compressor stage to spin it, and the electric start motor can then be turned off.
On other jet engines, a small gas turbine is used to blow hot combustion exhaust through the main turbine, which spins the main compressor up to speed, then the fuel and spark come on, etc. The start turbine is then shut down once the main engine starts.
Note that whenever the engine is running, the compressor stage at the entrance to the engine is actively sucking in tremendous quantities of outside air and jamming that air into the combustors in the center of the engine, where it is burned with fuel. The power of the exhaust from the combustors then spins the turbine at the outlet end of the engine, and that power is fed back to the compressor on a spinning shaft to keep it sucking in more air.
Some military jet engines can be started by connecting a huge blower to the engine inlet and forcing compressed air through the engine, to spin the turbine and get the compressor going. This is called an air start. Some military jets can also be started by burning a solid-fuel cartridge made of black powder and shooting the hot exhaust into the turbine stage of the engine to spin it, and thereby spin the compressor stage up to speed and get things going.
Other military jets are started by a start cart which contains a powerful gasoline engine that spins a shaft geared onto the main shaft of the jet engine. Once the jet is up and running, the start shaft is disconnected from the jet and the start cart is rolled out of the way.


How is a "fast jet" classified? In the book 'Pocket guide to military aircraft', they use the term 'Fast jet' for a certain range of aircraft.

Is 'fast jet' a common and well defined term used within aviation? If so, how is it defined? In order to be classified as a 'fast jet', does an aircraft have to be able to reach a certain flight level, speed or other performance indicators? Does it need a certain engine type? Must it look in a certain way?

In UK Air Traffic Control, the term has particular meaning as per CAP 413 (The CAA Radiotelephony Manual):

  When receiving an ATS surveillance service, certain ex-military
  aircraft types have been granted a CAA exemption from the Air
  Navigation Order requirement to fly at an IAS less than 250 kt below
  Flight Level
  100. In order to alert the controller to this higher speed profile, pilots of exempted aircraft shall, on initial contact, prefix the
  aircraft callsign with ‘FASTJET’ or ‘FASTPROP’ (depending on
  propulsion type), e.g. “Kennington Radar, FASTJET G-ABCD request
  Deconfliction service”. Use of this prefix shall be confined to
  initial contact with ATC agencies for periods of flight during which
  operations at airspeeds in excess of 250 kt are intended. Once
  acknowledged, it will not normally be necessary for pilots to use the
  prefix in subsequent transmissions until making initial contact with
  other ATSUs.

In my experience, Fast Jet will generally be used to refer to pretty much any jet powered single or dual seat (i.e., non passenger carrying) aircraft


'Gravitational' power vs. engine power A glider gets the power it needs to fly from the decrease of gravitational potential energy associated to the descent. My question is: for the same weight $W$, airspeed $V$, and a prop efficiency of 100%, is the amount of ‘gravitational power’  $W · w$ that drives a plane in an unpowered glide exactly identical to the ‘engine power’ it needs for s/l, unaccelerated flight?

Short answer yes, a powered aircraft at any given airspeed in straight and level flight (note that a glide path is also "level", at constant airspeed) needs to use the same amount of energy to over come drag as the glider.

The potential energy for the glider is altitude. The potential energy for the powered aircraft is fuel.
The conversion of potential energy to kinetic energy gives the aircraft velocity and matches drag forces.

There for, gliding is powered flight! They might "fill up" by catching a thermal, or by having someone tow them up.


How do I make consistent landings from the (instrument-less) backseat? When flying the Super Decathlon from the backseat, I can see the manifold pressure (top left corner of the panel) and G-meter (top right corner), and that's it.  This (along with the fact that the guy in the front seat blocks the view of the runway centerline) makes it difficult to get good consistency in landings.

I know that in if your airspeed indicator fails for some reason you can simply keep a little throttle in, fly until ground effect, and then bleed off whatever speed remains, but that's inconsistent and ugly.  I'm talking about being able to hit any arbitrary point on the runway ten times in a row.  I would call that impossible without at least an airspeed indicator, but older, wiser pilots have been doing it for years.

How do I make consistent landings from the (instrument-less) backseat?

Since nobody else has posted an answer, I follow Dan's suggestion and copy my comment here. Unanswered questions make this site look bad.

Practice, practice, practice. It's for a reason that the pilots who fly consistently good landings are the older ones. And remember where the horizon is in reference to the airframe and how the engine sounds. At approach speed (= at high angle of attack) the aircraft will show large attitude changes for small airspeed changes. Remember how high you are at conspicuous points along the approach, don't be shy to look sideways for this. And keeping a little throttle makes better landings, so don't feel negative about this.


Can helicopters create contrails? Can some or all helicopters have contrails? If only some, why only those? If not, why can they not? Pictures would be really helpful. I do know that turboprops and piston props can leave contrails, but I haven't been able to find anything about contrails on helicopters.

If the temperature and conditions are right, yes.

Any aircraft which has a heat engine that burns hydrocarbon fuel, which is pretty much any reciprocating or gas turbine engine used in aviation, will emit carbon dioxide and water vapor as byproducts of combustion.  It’s just a byproduct of the chemical reaction to produce heat energy in the engine. And when the temperatures and humidity in the ambient air are low enough and high enough respectively, the water vapor in the exhaust stream will freeze into ice crystals that remain suspended in the atmosphere for a sustained period of time.

You typically won’t see this at your average airport or from the average helicopter flying over you as the temperatures simply are not low enough at the altitude the aircraft operates at for contrails to properly form. That being said, see picture below.

Image source: https://koreaaero.tistory.com/40 (in Korean)


About climb: If we use T/W as input, the second grade equation yields two solutions for W/S. Are both solutions realistic? Raymer tells (Source: Raymer: Aircraft Design – A Conceptual Approach Chapter "5 THRUST-TO-WEIGHT RATIO AND WING LOADING" Paragraph “5.3 WING LOADING” Subparagraph “Climb and Glide”) that, when the aircraft is climbing, if the climb angle γ is small,

then $G=\frac{T-D}{W}$

(G is Climb Gradient as defined by Raymer words: "Rate of climb is vertical velocity,.. Climb gradient G is the ratio between vertical and horizontal distance traveled. This is approximately equal to the vertical climb rate divided by the aircraft velocity, or the sine of the climb angle γ." Source: Raymer: Aircraft Design – A Conceptual Approach Chapter "17 PERFORMANCE AND FLIGHT MECHANICS" Paragraph “17.3 STEADY CLIMBING AND DESCENDING FLIGHT” Subparagraph  “Climb Equations of Motion”)

Then $\frac{D}{W}=\frac{T}{W}-G$   ( that is the first relation for D/W).

At the same time  $D=q\cdot S\cdot c_{D0} + q\cdot S\cdot\frac{c_L^2}{π\cdot AR \cdot e}$

And substituting $c_L=\frac{W}{q\cdot S}$,

$$\frac{D}{W}=\frac{q\cdot S\cdot c_{D0}+q\cdot S\cdot\frac{c_L^2}{π\cdot AR\cdot e}}{W}=\frac{q\cdot c_{D0}}{\frac{W}{S}}+\frac{W}{S}\cdot\frac{1}{q\cdot π\cdot AR\cdot e}$$

(that is the second relation for $\frac{D}{W}$)

Equating the first and the second relation and solving for wing loading,
we have:

$$\frac{W}{S}=\frac{\left(\frac{T}{W}-G\right)± \sqrt {\left(\frac{T}{W}-G\right)^2-\frac{4\cdot c_{D0}}{π\cdot AR\cdot e}}}{\frac{2}{q\cdot π\cdot AR\cdot e}}$$

MY FIRST QUESTION: In this equation are both, the bigger and the lower solution values for $\frac{W}{S}$ realistic for aircraft?

After,  Raymer notes that the term within the square root symbol in the equation above cannot fall below zero, so the following must be true regardless of the wing loading:

$$\frac{T}{W}≥G+2\cdot\sqrt{\frac{c_{D0}}{π\cdot AR\cdot e}}$$

MY SECOND QUESTION: Raymer doesn’t consider that there are two solutions sourcing from the condition that the term within the square root symbol cannot fall below zero, the other one is:   $$\frac{T}{W}≤G-2\cdot\sqrt{\frac{c_{D0}}{π\cdot AR\cdot e}}$$. Why shouldn’t be considered? Could the second solution represent something realistic?

I HAVE A SUPPLEMENTARY QUESTION:
Relating to my questions above, I have to report two comments Raymer writes immediately after the last equation and inequality.: "This equation says that no matter how "clean" your design is, the T/W must be greater than the desired climb gradient! ....... Another implication of this equation is that a very "clean" aircraft that cruise at a high speed despite a very low T/W will probably climb poorly. A 200-mph airplane that flies on 20 hp can't be expected to climb as well as an airplane that requires 200 hp to reach 200 mph (unless the latter weighs ten times as much)"
Could anyone explain me better the last sentences, in particular, in which case T/W is very low with high speed? If we have high speed doesn't T/W should be high too?

Raymer's G is a little unusual. In effect, it is the tangent of the flight path angle $\gamma$, and since his equations are for small values of $\gamma$, we can assume that it is approximately equal to $sin\gamma$ or $\gamma$ itself when expressed in radians.
$$G \approx \gamma$$
Next, the expression $\pi\cdot AR\cdot e$: This is part of the square root of the lift coefficient for minimum drag. The complete equation is:
$$c_{L\:(minimum\:drag)} = \sqrt{c_{D0}\cdot\pi\cdot AR\cdot e} = c_{L\:(md)}$$
Next, I need to express that thrust-to-weight ratio differently. As long as we keep $\gamma$ small:
$$\gamma = \frac{T}{W} - \frac{c_D}{c_L} => \frac{T}{W}-\gamma = \frac{c_D}{c_L}$$
Now I can rewrite the equation of your first question:
$$\frac{W}{S} = q\cdot\frac{\frac{c_D}{c_L}\cdot \frac{c^2_{L\:(md)}}{c_{D0}}}{2} ± q\cdot\frac{\sqrt {\left(\frac{c_D}{c_L}\right)^2\cdot\left(\frac{c^2_{L\:(md)}}{c_{D0}}\right)^2 - 4\cdot c^2_{L\:(md)}}}{2}$$
and when I restrict the equation to the minimum drag point where $c_{D0} = c_{Di}$, I can write
$$\frac{W}{S} = q\cdot c_{L\:(md)} ± q\cdot\sqrt {c^2_{L\:(md)} - c^2_{L\:(md)}}$$
Fancy that! The expression under the root becomes zero when I look at the polar point of minimum drag! The only variable term under the square root is the ratio $\frac{c_D}{c_L}$, and it reaches its minimum at the $c_{L\:(md)}$ point. When I move away from this polar point, I should get two valid solutions.

I guess these two wing loadings allow to fly with the specified flight path angle at the given polar point and thrust-to-weight ratio. Since the weight is prescribed by the thrust-to-weight ratio, the solution is actually for two different wing areas. The smaller wing requires a higher speed and the larger wing a smaller speed than what you get at the lowest drag point. Between both, the speed and wing area should result in configurations which achieve a higher flight path angle $\gamma$, and outside of this interval no level flight should be achievable with the resulting wing areas and speeds.

I cannot follow how you arrive at the second question. The term under the square root should be
$$\left(\frac{T}{W}\right)^2 - 2\cdot\frac{T}{W}\cdot G + G^2 ≥ \frac{4\cdot c_{D0}}{\pi\cdot AR\cdot e}$$
But when I insert again as explained above, I can write for the term under the root:
$$\left(\frac{c_D}{c_L}\right)^2 - \frac{4\cdot c^2_{D0}}{c^2_{L\:(md)}}$$
so the condition for a positive root is
$$\frac{c_{D0}+c_{Di}}{c_L} ≥ \frac{2\cdot c_{D0}}{c_{L\:(md)}}$$
or
$$ \frac{c_{D0}}{c_L} + \frac{c_L}{\pi\cdot AR\cdot e} ≥ 2\cdot\sqrt{ \frac{c_{D0}}{\pi\cdot AR\cdot e}}$$
which is certainly true; both sides of the equation are equal at the lowest drag polar point and away from it the left side is bigger and the right side stays constant.

If you just isolate the term under the root and look at it by itself, I doubt you have something that corresponds to a realistic configuration. You need to extract both numerator and denominator to keep the physical analogies intact. What Raymer does is to look at the term under the root in isolation and then postulates that the first summand must be larger than the second. He puts both on the two sides of an inequality and extracts the roots on both sides separately. Then he moves G over to the other side. There is no second version of the inequality possible.


What sensors are required to fly RNAV 5 airways? In the example shown above:

Is an aircraft required to have all 3 sensors listed or just one of them to fly the L512 airway? What ICAO reference confirms the answer?
Does 'critical DME' (bottom row) mean an aircraft is required to have DME/DME? Or can an aircraft equipped with GNSS still fly the L512 even when KAE or KPO is out of service?

Sensors
From ICAO Doc 9613:

2.2.1.3 RNAV 5 operations are based on the use of RNAV equipment which automatically determines the aircraft position in the horizontal plane using input from one or a combination of the following types of position sensors, together with the means to establish and follow a desired path:
a) VOR/DME;
b) DME/DME;
c) INS or IRS; and
d) GNSS.

In the example given, any one sensor or a combination of the following:

DME/DME
INS or IRS
GNSS

Critical DME

Critical DME. A DME facility that, when unavailable, results in a navigation service which is insufficient for DME/DME-based or DME/DME/IRU-based operations along a specific route or procedure.

Which means if you have GNSS on board, and a critical DME (ground station) is out of service, you can still fly that RNAV 5 airway.


Would this modified tire work to prespin an aircraft tire? In order to decrease that initial hit of the tire spinning up to ground speed on the runway, could adding a blades or shape into the tire rim of a commercial plane save on tires by prespinning the tire like a pin-wheel prior to landing?

Related: Why are aircraft tires not pre-spun prior to landing to preserve them?

The idea is good in concept but it would be pretty difficult to match the rpms to the actuual ground speed, in fact if the wheel was spinning faster it would actually wear the tyre more!

Another factor is that aircraft wheels often do not hit the runway straight on. In a crosswind situation they could be off a few degrees so the tyre would still scrub.

Also the fact that adding weight is anathema to airplane designers, not only the motors but electronic controllers and associated wiring. This weight will have to be carried for the duration of the flight.

Finally the hardest working part is not the tyre but the wheel bearings.. on a longer widebody flight they go from cold-soaked to very hot in a few seconds. Tyres actually fare pretty well, I've seen new tyres fitted and come back after a few sectors which still looked pretty new.

As mentioned by John K in the comments above, its cheaper to recap they tyre.


How to advise others of imminent danger? In a case such as United 326 - where an aircraft got cleared for takeoff while other planes at the same time get cleared to cross that runway - how would an outside party that picks up on the mistake inform the others that a disaster is about to happen and that people need to take immediate action?

Would they call mayday, or just shout out in "freeform", something along the lines of "Imminent collision, runway 19C!".

To quote an answer by kevin on another question from last year:

What's the procedure? The procedure is, be creative to save as many lives as possible!
Really. The procedure is to determine a course of action which will likely result in the best outcome for everyone, utilizing all resources and given all constraints. Period. It is as simple as that.
There are infinitely many scenarios, and one cannot be trained for everything.

If you need to communicate something as quickly as possible in order to avoid a disaster, and calling "mayday, mayday, mayday" will be a significant waste of valuable time, then the answer is clear: don't call mayday. Just say what you need to say.
If you know what the other aircraft need to do in order to avoid a collision, perhaps it would be a good idea to announce "Go around, go around, go around!", "Cancel takeoff, cancel takeoff, cancel takeoff!", or "Hold short, hold short, hold short!", as appropriate.
In the case of Air Canada 759, where an arriving airliner mistakenly lined up to land on an occupied taxiway instead of the runway, a pilot on the taxiway announced: "Where's this guy going? He's on the taxiway." This probably wasn't the best possible thing to say, but the airliner went around and avoided a collision.


How does the nitrogen generation system in a Boeing 777 work? How does the nitrogen generation system in a B777 work and how does it differ from that used in a B787? Any diagrams will be appreciated.

The 777 system

As RAC points out, "nitrogen-generation system" is somewhat of a misnomer. All the system does is remove oxygen from the ambient air and blow the rest into the center fuel tank; there is no chemically "new" nitrogen created. The 777 architecture is basically the same as the schematic that mike provides; in fact, all bleed-air aircraft use pretty much the same system. For example, here is an Airbus schematic:

Parker has a breakdown of the major components. Summarizing it and filling in some gaps, we have:

Ozone (O3) converter: Basically a catalytic converter that converts triatomic oxygen (ozone) to biatomic ("regular") oxygen to protect other elements in the system from oxidation.
Heat exchanger: Cools the bleed air (which is really hot when it comes off the engine), again to protect other elements of the system and increase their effectiveness.
Air separation module: Physically removes almost everything but the dinitrogen (N2) in the air. This separation is accomplished by running the air through semipermeable fibrous tubes; because almost all the non-N2 molecules present are smaller than the N2 molecules, those smaller molecules pass through the membranes and are exhausted overboard, leaving only the nitrogen to exit into the fuel tank.
Other: There are various filters to protect components from particulate matter, valves to control the timing and rate of flows, controllers to control the valves, and sensors to inform the controllers.

The 787 system

The 787 is a no-bleed airplane, which means that instead there is an electric-driven compressor to supply the NGS rather than bleed air. This setup requires a slightly different heat-exchanging architecture, but the overall function and operation of the primary system components are similar.


To what extent (if any) is it possible or desirable for the pilot of a large airliner to "fly by the seat of the pants"? I recall that some years ago the pilot of the A340'S first flight described its handling as "like riding a bicycle" (to me this would mean that as he went past his favourite bar he saw his friends inside so he propped it up against the wall to have a drink with them).

I can believe that despite its size and weight a large airliner would respond precisely to commands, but does the concept "flying by the seat of the pants" apply to such an aircraft?

Obviously experience and training will build up a great deal of intuition (visual, vestibular, etc) - what sort of bodily connection does an airline pilot experience with the aircraft? Is it markedly different from that of the pilot of a small plane?

I can believe that despite its size and weight a large airliner would respond precisely to commands, but does the concept "flying by the seat of the pants" apply to such an aircraft?

The phrase "flying by the seat of the pants" is an imprecise term, and I don't have an answer for that. However, if you allow it to mean operating an aircraft in the absence of instrumentation or other capability that is normally used, or using techniques not normally used, whether you're forced to because of failure(s) or because you prefer not to use them, then here is an observation.

In the early 1990s I was flying 747-100/200 freighters. The carrier had a contract with Japan Air Lines to haul freight between Tokyo Narita and KJFK, with a crew change and refueling at Anchorage. We used a JAL call sign. JAL had their own 747-200 freighters on the route as well, more of them than our small number of aircraft. Many of their flights would have an American flight engineer who would handle the radio going into U.S. airports. Thus, the Anchorage controllers could not tell from the radio communication whether the flight had American or Japanese pilots.

One summer Anchorage took the ILS down for extended maintenance. One severe clear day during this period we were on our descent but still well out when Anchorage approach cleared us for a VOR approach. We immediately called the airport in sight and requested a visual approach, which was granted.

Curious, when we were down I called approach control on a land line and asked why we were first assigned a VOR approach. They explained that, believing our flight probably had Japanese pilots, and having had those pilots always refuse the offer of a visual approach and request a VOR approach (in spite of the additional 10 minutes of flying), approach control had simply assigned the VOR approach.

As part of our contract, we occasionally had a Japanese check captain observe us, and the next time this happened, I brought up the subject with him. He explained that their pilots were never taught to simply look at a runway and land without reference to navigational instruments, and, lacking a robust general aviation segment, their pilots simply never had experience with doing that. He added that from their standpoint, we were a bunch of cowboys. Not the exact "flying by the seat of the pants" wording, but the same sentiment.

  Obviously experience and training will build up a great deal of intuition (visual, vestibular, etc) - what sort of bodily connection does an airline pilot experience with the aircraft? Is it markedly different from that of the pilot of a small plane?

When you're flying the same airplane type day in and day out, you internalize what that aircraft can do and how it will respond. You get used to its noises and even to its vibrations if you will. And regardless of how small or how large it is, it becomes the right size, neither little nor big, especially once you're in the air. When you change airplanes, and especially if it involves a significant change in size, there is a difference.

For example, I spent the last 10 years of my career on 747-100/200 aircraft. Fifteen years after retiring, and not having been in a cockpit during that time, I went out to a local airport to check out in a Cessna 172. I knew I would have trouble with flaring too high, and I warned the instructor. My first landing was a real lesson, actually to both of us. When I said to him, "I think I should flare," he said, "you're way to high." When I said, "I've got to flare,: he said, "still too high." When I said, "I'm flaring," with the sense that if I didn't I would prang the airplane, he said, "you're still a little high, but go ahead." It took me 5 hours to check out in the airplane, most of that time for landings.


Are WWII turbochargers reliable? How reliable are WWII turbochargers? Does adding them to an otherwise reliable engine, e.g. the P&W Double Wasp and the Allison, decreases the overall reliability of the engine? Are they well made enough to sustain the heat of the exhaust (my guess from rough calculations under the presumption of adiabatic combustion puts it in the 800K-1200K range) without creeping? My impression is superalloys are not around until about 1950s.

Is the relative unreliability of the turbochargers (turbine wheel to be exact) the reason why the great majority of high-performance WWII engines opted for supercharging as supercharger operates in the cold end of the engine only?

Supercharging was mature technology at the start of the war while the turbocharger was something quite new.  The P-38 used the then radical new General Electric turbocharger (along with the B-17 and P-47) which was quite reliable in itself but the system couldn't tolerate back pressure, which is why the turbine wheel is exposed on the Lightning's turbos on top of the booms - that's where the exhaust comes out.

In any case, the Lightning's many bugs included boost system related issues, but this was mostly due to an ineffective intercooler system in the leading edges that didn't drop the air charge temperature enough.  The tetra ethyl lead in the fuel would actually separate out and lower the fuel's octane rating on its way to the cylinders, causing detonation and blown engines.  This wasn't the turbo's fault and was mostly fixed by the K and L models with the big chin scoops for the new intercooler.  I don't believe the turbocharger unit itself was a major maintenance headache for the P-38.

That's the thing about the Lightning.  In its L model form it really was the F-22 of its day.  It could outclimb just about anything.  With the hydraulically boosted ailerons, at high speed it could out roll single engine fighters in spite of the mass of those booms.  With counter-rotating props it had no torque effects with power changes and was jet like as a gun platform. Compressibility problems were mitigated with dive flaps.  All the more amazing as a pre-war design.  Kelly Johnson really was a mega-genius.

But the turbocharger and intercooler system, with yards of ducting, along with two of everything in the booms, made it very complex and expensive airplane compared to say, a Mustang with its Merlin's simple two speed supercharger, so you could say it was questionable whether it was worth it (there is endless speculation on what a Merlin powered P-38 would've been like).  So to answer your question, cost and complexity may have kept a lot of designers from using GE's turbo system, more than reliability.


Why are FDRs and CVRs still two separate physical devices? Given the histories of flight data recorders and cockpit voice recorders, I somewhat understand their origins as two separate physical devices. Given their separate tracks of development, regulatory requirements, and storage mechanisms, it stands to reason that they historically existed as two separate "things".

However, I'm under the impression that the vast majority of the commercial airliners operating today are utilizing solid state memory to store both flight data and cockpit voice recordings. Both devices share many similar requirements in regards to being capable of withstanding extreme heat, g-forces, impact resistance, submersion in water, etc. Both devices are equipped with underwater locator beacons. Even the bright orange color of both recorders are the same!

The Wikipedia article on flight recorders briefly mentions that "the FDR and CVR can be manufactured in one fireproof, shock proof, and waterproof container as a combined digital Cockpit Voice and Data Recorder (CVDR)". However, whenever I read about modern aviation accident investigations--1990s, 2000s, 2010s--investigators are always searching for and analyzing the two separate black boxes. I don't think I've ever heard of an accident that involved a single combined black box, so their usage still doesn't appear to be very widespread.

Why not? Since the only thing I can see that distinguishes a modern CVR from a modern FDR is the type of data being stored, why didn't the integration of these separate devices become the norm decades ago? The best explanation I can come up with is some sort of notion of redundancy, but this doesn't make sense if they're storing two separate sets of data.

Even if a single combined recorder was deemed to be too risky, how hard could it be to just record both sets of data on two identical recorders? At least that way, there's true redundancy being maintained. The fact that "flight data" and "cockpit voice" data are still being stored on two separate physical devices seems rather absurd in this day and age.

It seems about as logical as buying and maintaining two separate external hard drives--one for my music collection, one for my movie collection. It'd be closer to life in the early 90s, when I had a collection of VHS tapes and a collection of cassettes. But now that everything is digital, it makes sense (logically and financially) to just use one device to store both collections. Why isn't it the same with modern-day FDRs and CVRs?

You probably wouldn't believe the effort needed to certify anything that flies on an aircraft. This is a multi-year process, especially if it is so much security-related as the CVR and FDR. And it needs to be done with all national authorities of your intended customers.

This is a case of good-enough. The advantage from combining both is real, but so small, that nobody so far thought it worthwhile to go through the certification process. And regarding redundancy, transmitting the recorded data to some ground station would be even better than recording twice on the same aircraft. If that would have been installed in MH370, most of the search effort could have been saved.

I expect something to happen with the transmitting of data, and then both devices could conceivably merged into one.


How do I keep coordinated on a windy day? I've noticed on windy days that keeping the aircraft coordinated can be difficult -- the ball will tend to bounce back and forth in the turn coordinator, and I will find myself "chasing" it with the rudder pedals.

Any advice for managing this situation?  At cruise it doesn't worry me as much as setting up for approach to land. I think I've read too many stall/spin in the pattern stories lately...

Don't chase the ball.  Heck if you're VFR/VMC, you should barely be glancing at the ball or any of your instruments and should have eyes outside.  Remember flying a little uncoordinated alone is not going to force a spin.

Stall + Yaw = Spin

So how do we mitigate this during gusty approaches?  We fly a little bit faster.  I like to use 1/2 the gust factor and add that to my final approach speed.

I'm not saying accept being uncoordinated, but when it's gusty out you don't chase airspeed, so why chase the ball?


Do any aircraft out there use negative lift? I think negative lift is where high pressure forms on the top of the wing instead of the bottom. I know that Indy cars use negative lift and some sports cars do, but do any aircraft exist that use negative lift and why do they use negative lift?

A lot of aircraft generate negative lift- not in the wings, but in the tail plane. This is used for stability. Consider a trimmed aircraft as shown below:

Image from grc.nasa.gov
On most aircraft, the center of gravity (through which weight acts) of the airplane is located near the center of pressure (through which lift acts) of the wing. If the center of presure of the wing is aft of the center of gravity, its lift produces a counter-clockwise rotation about the cg. A positive lift force from the tail produces a counter-clockwise rotation about the cg.
To trim the aircraft (i.e. no rotation about c.g), it is necessary to balance the torques produced by the wing and the tail. But since both rotations are counter-clockwise, it is impossible to balance the two rotations to produce no rotation. However, if the tail lift is negative it then produces a clockwise rotation about the cg which can balance the wing rotation. For this reason, the tailplane is designed to produce a negative lift.
Text from Trimmed aircraft- slightly modified.


What airfoils are used for the current generation of general aviation VTOL aircraft? What airfoils are used for VTOL ultralights at 60-70 deg AOA without flaps or slats?

An example of this would be the Blackfly with a takeoff distance of 3', about 25% of it's own length....!!!!

I understand most airfoils stall at about 15deg, slats and flaps allowing up to 30 deg AOA such as with the Zenith 701.

Yet the Blackfly has no slats or flaps and has controlled flight even at at 60,70,80,90 deg AOA.

I assume the distributed propulsion reduces the LOCAL AOA significantly, so that lift is only via the props from say 40-90 deg AOA, and then wings start to generate lift at about 40 deg AOA even without slats or flaps.

Yet, I was told distributed propulsion only works for low AOA. Very confused....

What airfoil type is used for this?

Would an airfoil like the Selig 1233 or Eppler 399 be appropriate for this?
I understand these are low Re airfoils, but these usually stall at a lower AOA than a classic airfoil like the NACA65018 used in the Zenith701.

Or do you need something very fat that will stall at a much higher AOA, like an airfoil with 25%-30% thickness?

Those airfoils never see angles of attack of more than a few degrees. Since both wings of the Blackfly carry propellers along their full span, their prop wash ensures that airflow is mostly along the wing's chord. Slow flight is not much different from the hover of quadcopters, in both cases the propellers create most if not all of the lift.

Blackfly ultralight (picture source)

So to answer your question directly: There are no VTOL ultralights where the wing is exposed to flow at 60-70° AoA. The airfoils used are most likely about 15% thick with moderate camber because they operate at single-digit angles of attack.


What is that sensor on the Airbus A220? What is the that sensor in the picture?

That's one of the two ice detectors manufactured by Collins. Below is not precisely the model used by A220, but serves to illustrate the general layout of the unit:

Image ref: Collins

From this Collins fact sheet, ice detectors

  use a magnetostrictive technology to drive the sensing probe to resonate at its natural frequency. As ice accretes on the probe, a shift in resonance frequency occurs. When the resonance frequency reaches the set point, an ice signal is activated...


Does the USA government operate any business-jets with mid-air refueling capability? Today I saw a business jet, 10 or 12 passenger or so fly over, evidently on approach to Whitehouse Naval Outlying Field (NOLF) (KNEN), said jet had some sort of probe on the nose and was painted white.  I was not able to discern any markings.  Does the USA government operate any business jets with mid-air refueling capability?  Another obvious question is: why would a passenger jet fly into NOLF?

Does the USA government operate any bizjets with mid-air refueling capability?

Yes. According to this article, it's being used by the Air Force and the Navy for autonomous air-refueling tests.

  As a surrogate for the carrier-based drone, the Lear is assessing its autonomous refueling capabilities and performance for both Navy and Air Force aerial refueling techniques.

This particular Lear in the photo was active just last week:

This looks like a test to me.

There is also this, but it doesn't have the probe.


Is there a real risk of ingesting FOD into jet engines when using thrust reversers? In the discussion of Why doesn't the A380 use its outboard thrust reversers, one of the reasons given was that engines 1 and 4 would be at great risk of ingesting debris. It was pointed out that the 747 uses reversers on all 4 engines, and it's just as big (overhanging edge of runway). So I asked in a comment:

If there is fear that the outboard engines would ingest crap (FOD)
because they overhang the edge of the runway, why wouldn't that also
apply to takeoff, when the outboard engines are presumably at high
thrust? Additional: I realize that the jet blast is straight back, but suction on the front of the engine is pretty strong, too (enough to inhale a baggage cart).
Does an engine at reverse thrust kick air (and debris) far enough
forward that there is a real risk of ingestion and FOD?
Could that be negated by designing the reverse thrusters to go
mostly sideways?

I was asked to repost as a separate question, so here it is...

For the numbered items:

(1) and (2) At takeoff there is (typically, but there are birds) nothing solid that's airborne in front of the airplane, whereas thrust reversers can put small but solid airborne material in front of the engines, especially if they're still being used with high power as the airplane slows.

(3) If you're saying that the air is only directed sideways rather that forward, that would cancel the forward thrust from that air, but it wouldn't get you much braking action.

Some other points:

The higher the airplane's speed, the more braking action you get from the reversers, so if you're going to use them, get into them as soon as possible.
If it's late night or early morning, and the airport has a noise problem, consider going into reverse but leaving the engines at idle. You'll still get significant braking proportional to the airplane's speed.
If you've got a long runway, consider using just idle or less than high-power reverse. In other words, use what you need/want, but no more.
Make sure you start out of a high power reverse well before slowing to taxi speed. There are speed guidelines for this, but I forget what they are. Actually, it's best in my opinion to avoid high-power reverse unless you really need it.
Make sure you're completely out of reverse by the time you reach taxi speed. Again, I've forgotten the guideline.
Consider where you are. If you're in, say, Germany, you can expect the runways to be clean, in Spain maybe not as clean, in Zimbabwe definitely not as clean. You get the idea.
Be really careful about using reverse on an icy runway. If your nose is not pointed straight down the runway, the reverse thrust will be working to put you off the side of the runway. An acquaintance of mine put a 747 off the runway at KJFK that way (totaled the airplane, a few people hurt, no fatalities).
Consider the characters of the engines on the airplane. Perhaps this is no longer a consideration, but back in the 1990s, P&W engines on the 747 were relatively tolerant of compressor stalls brought on by using too much reverse power at too slow a speed. GE engines, however, were not so tolerant.

The second 747 carrier I worked for used to have maintenance done at Santa Barbara, CA. When we would pick up the airplane, they would close the relatively narrow runway after our takeoff and sweep it. Not a reverse thrust situation, but it does illustrate the FOD problem.


How do pilots manage their flight times? When flying double-digit hour flights, such as 13 hours from Chicago to South Korea or 18 hours from Singapore to Newark, New Jersey, everyone on the plane, including the pilots, will most likely experience jet lag, as the passengers will experience "nighttime" at some point and become sleepy. Since there are two pilots, the pilot and the copilot, how do they manage their time? Does the copilot start flying the plane when the pilot rests, or vice versa? Or do both stay awake for a grueling 18 hours? Or do they rely on autopilot?

Airlines are required to have extra pilots on long flights so that pilots can take rest breaks.
A typical 18 hour flight from New York to Singapore will have four pilots. The pilots will divide the rest breaks so that there is always two pilots in the flight deck at the controls, and two pilots in a crew rest facility. Most crew rest areas will have beds or bunks to sleep in.
Typically all four pilots are in the flight deck from takeoff to about 10,000' and then again from 10,000' to landing. The cruise portion of the flight be divided so that each pilot gets an equal amount of rest. Various airlines will differ on how this is done.
Usually two pilots will be paired to take the same rest breaks so that they don't disturb anyone when they enter or leave the crew rest area. For example many airlines will divide a 16 hour cruise portion of the flight so that the paired pilots each get two 4 hour breaks. Some airlines will divide the time so that there is one 8 hour rest period instead of two 4 hours rest periods.


Why doesn't the A380 use its outboard thrust reversers? One thing I noticed with the A380 is that it only seems to use the inboard thrust reversers while landing. I suspect it relates to FOD ingestion or perhaps damaging the runway. This is strange though, because the 747-8 (which also has a large wingspan and very large engines), does use all of its thrust reversers during landing. Does anyone have an official answer on why this is?

Why doesn't the A380 use its outboard thrust reversers?

Because it doesn't have (or need) any.

  The A380 has reverse thrust on the inboard engines only. This saves weight and since the outboards are often way out over the edge of runways, decreases the risk of FOD.

From Airliners.net

Like all certified transport aircraft of this type, the A380 can stop from V1 on brakes alone with disks worn to minimum.

I've read that most airliners are allowed to take off even when all reverse-thrusters are inoperative. Most of the deceleration is handled by the brakes normally.

  With the Airbus A380 weighing in fully loaded at 1,265,000 pounds, you might think stopping it within a reasonable distance after landing would require a Phalanx of Heavy-duty thrust reversers.

  Truth be told, in the megaliner’s braking system, thrust reversers are the least critical components. Airliners are not required to have thrust reversers, and only the two inboard engines on the A380 are equipped with them. The decision not to install reversers on the A380’s two outboard engines saved weight and lowered the chances that those engines, which sometimes hang over runway edges, would be damaged by ingesting foreign objects.

  The two reversers do help slow the A380—but not by much. In fact, unlike the thrust reversers on most airliners, including the Boeing 747 jumbo, they do not stop the aircraft in a shorter distance than brakes and spoilers alone. They do, however, take some of the strain off the brakes and are useful if water or snow makes the runway slippery.

From Airspace Magazine

More details of braking system

  1.
   General
   The aircraft has:

  Two Wing Landing Gears (WLG) with four wheel bogie assembly and related doors
  Two Body Landing Gears (BLG) with six wheel bogie assembly and related doors
  A Nose Landing Gear (NLG) with twin wheel assembly and related doors.

  ...

  Braking
  A.    General
  Carbon brakes are installed on each wheel of the WLG and on the wheels of the front and center axles of the BLG.
  The braking system is electrically controlled and hydraulically operated.
  The braking system has four braking modes plus autobrake and anti-skid systems:

  Normal braking with anti-skid capability
  Alternative braking with anti-skid capability
  Emergency Braking (with Ultimate Braking)
  Emergency braking without anti-skid protection is also available as an alternative function of the alternate braking system.
  A park brake system that is manually set is available for the BLG only. This system can also be used to supply emergency braking.

FOD risk

A380 Landing at Farnborough Airport

A380 vs 747

  The design of the A380’s wings, with their large area, comparatively gentle sweep (33.5 degrees), and massive flaps, give the Airbus a landing speed that is 20 knots slower than that of a 747. An A380 crosses the landing threshold at a docile 140 knots and touches down, depending on its landing weight, at a speed as slow as 130 knots, about the same touchdown speed of some corporate jets that weigh 1/50th as much as the world’s biggest airliner.

AirspaceMag


Do software simulations and wind-tunnel tests accurately predict Cd and Cl in real-world conditions? Will the lift coefficient (Cl) and drag coefficient (Cd) I obtain by using software simulations or subsonic wind-tunnel tests be the same as on an actual aircraft while cruising? Or will there be some error?

It depends.
In computational fluid dynamics (CFD) there are limits for the calculation of turbulent flow. This means that large flow separation cannot be modeled precisely; especially its time-dependent characteristics are computationally much too complex to be modeled. Instead, statistical methods must be used.
For attached and far-field characteristics the methods are refined enough to yield very accurate results, so much that what had historically been studied in wind tunnel tests or only on the finished aircraft can now be calculated with confidence up to hypersonic speeds. Errors still exist - after all, if the geometric model does not include the manufacturing irregularities of the real aircraft, the results will not be in total agreement, but close enough for engineering purposes.
In wind tunnel testing you cannot expect the same results as long as the Reynolds number and Mach number are different from the real thing. This is adjusted with correction factors, and again the results become good enough for engineering purposes. Cryogenic wind tunnels even remove this restriction, but are very expensive to build and operate, because they run with pure nitrogen at very low temperature and several bars of pressure. Small errors remain, because all the details of the real aircraft cannot be modeled in a wind tunnel model and their ratio between dynamic pressure and stiffness cannot be adjusted for all flow conditions, so aeroelastic effects will remain different.
Windtunnel tests are still valuable for predicting forces in post-stall conditions and for calibrating new CFD codes. Most of the operational envelope can then be covered with CFD. The combination of both is enough to predict the force coefficients with confidence, and only aeroelastic effects and details of the stall behavior might turn out slightly differently than anticipated from tests.
As @TrebiaProject points out in the comments, CFD can help with the corrections. The influence of the sting the model is mounted on would be a primary example. CFD can help to understand its influence and correct for it. This makes CFD complementary, so both techniques will lead to better results if combined correctly.


Why is the Boeing 757 undercarriage so high? Compared to other wide bodies the 757 seems to stand on very tall landing gear.

Considering strength, weight, cost, stowage space and ease of ground servicing you would want the shortest possible undercarriage you can achieve. The B737 isn't a much smaller aircraft but is much lower, so low it was a challenge to fit modern engines.

Was there a specific design/operation reason or was it just styling - it certainly looks nice !

Rotation angle at takeoff is often the limiting factor in gear height. The 757-300 is 178ft long, 30ft longer than the Airbus 321 which also has tall landing gear. The first 737s were less than 100ft long, which allowed the short gear and later caused problems with the max9/10 stretches which went to 143ft.

source


Why is the rotor system of an aircraft and the rotor system of a helicopter different? Both aircraft with propeller(variable pitch) and helicopter rotor system can change pitch.
Of course, for helicopter, there is not only collective pitch control but also cyclic control.
The aircraft rotor system seems to be heavy because it uses hydraulic.
With the exception of the cyclic control of the helicopter, it seems lighter and simpler to use the helicopter's rotor system on an aircraft.
I would like to know what happens when we replace the aircraft's rotor system with helicopter's rotor system.

The aircraft hydraulic pitch control system is much simpler and has fewer moving parts than a helicopter's main rotor pitch control system.

A helicopter's main rotor runs at between 500 to 800RPM, but (for example) in the world of general aviation using piston engines an airplane's propeller runs at between 2400 and 2600RPM. If built to withstand the dynamic loads at 2500RPM, a helicopter main rotor would be far more massive.

Airplanes have no need of the cyclic pitch control system that helicopters require in order to be controllable.

All these things mean that mounting a collective-and-cyclic blade pitch mechanism on the crankshaft of an airplane engine would be a meaningless exercise.


How should wake turbulence from aircraft on the ground be avoided during landing? If a large jet aircraft is holding short of runway 28L while I am landing a single-engine aircraft on runway 28R, how should I proceed with such a landing?

Wake turbulnce occurs when an aircraft is creating lift.  Since, the airliner is on the ground, there is no wake turbulence.

If you are worried about jet blast from the airliner holding short between the runways, then I would land past the airliner by about 1000 ft.  With the airliners engines at idle, there will be minimal jet blast but if the increase power that jet blast increases significantly.


What is Crew Resource management (CRM)? I hear a lot about CRM these days (it seems to be a buzz word). It is related to safety, but what exactly is it?

From what I know, it also applies to single pilot flights (even in a Cessna 150!), but where is the "crew" that is being managed in this case and how does it improve safety?

CRM is about making use of all available resources to safely conduct a flight.  Pilots these days (even single pilot ops) have a wealth of resources available to them.  Anything you can see and anyone you can talk to is a resource, and CRM is about making efficient use of those resources.

Flying a light single you will have a subset of these resources:

Cockpit displays
Charts
Checklists
ATC
FSS
Flight Watch (EFAS)
Live Weather downlinks (e.g. XM satellite weather)

On a large transport aircraft these change a bit:

Cockpit displays
Charts
Checklists
ATC
FSS
EFAS
Onboard RADAR
The QRH (quick reference handbook)
The FOM (flight operations manual)
The other pilot(s)
The cabin crew
Passengers (Doctor in a medical emergency?  People helping in an evac?)
Dispatch
Medlink
Company Ops
For ground ops:

Fuellers
Ramp personell
Gate agents

More and more emphasis is placed on managing these resources as you move up the chain.  By the time you are taking your first 121 upgrade checkride, it is more about judgement and CRM than it is about the flying.


How is a seaplane steered on water? Steering a seaplane on water appears to be a little more 'interesting' than steering a land aircraft, at least according to the FAA Practical Test Standards for single-engine seaplanes (ASES), which requires the pilot to:

  [use] flight controls, flaps, doors, water rudder, and power correctly
  so as to follow the desired course while sailing.

So how does it all work? Why/when/how do you use doors and flaps to steer? Are the water rudders connected to the pedals (like brakes on a land aircraft) or is there a separate steering control? What about braking: is there any, or do you just drift gradually to a stop?

Seaplanes mostly have water rudders that are used at lower speeds and are retractable (actually, they tilt out of the water flow).  At higher speeds, like takeoff runs and landings, high speed taxis, they are retracted and the primary means of steering is the plane's rudder.  Water rudders are connected to the regular rudder pedals.

Airlerons can also be used to steer a seaplane on the water by creating differential lift and drag (since most ailerons don't deflect symmetrically).

Doors can be used to steer by opening one or the other, creating drag on one side or the other.  I have seen a C-150 pilot do this in the air, as well.  Flaps, which create symmetrical drag, can be used to assist in slowing down but they're not useful for steering.

Seaplanes have no brakes other than the drag of the floats in the water, so a seaplane pilot won't approach a dock at a perpendicular angle.  Instead, they will land along side a dock and then jump out onto a float and then to the dock, rope in hand.

Seaplane pilots also carry oars, which allow them, yes, to paddle, steer, and stop the plane.

So seaplane pilots have a number of tools at their disposal to steer the plane on the water. You can also read through the FAA Handbook for seaplane operations.

It does require some coordination!


How does the pitching moment change as the speed of A/C approaches critical Mach number? In an aircraft performance course, I saw that pitching moment goes backwards as the speed of A/C approaches critical Mach number. In fact, that results in nose down pitching moment. But, according to my notes, there must be shock waves at the back of the A/C. In this situation, should not these waves behave as force pitching down? How can it be possible? And why?

Yes most aircraft which operate in the transonic zone experience a nose down pitch with increase in speed. The two main causes are :

Rearward movement of centre of pressure
Because of supersonic acceleration at higher speed, pressure continues to decrease past the 50% chord point, thus increasing the amount of lift produced by mid chord part of wing.
Modification to airflow over the tailplane
Most tailplane work in a region of downwash from the mainplane, in case of swept aircraft the downwash can be considerable. The formation of shockwave on main plane modifies the flow such that the downwash is reduced and this will pitch aircraft nose down


What are the areas marked in green around the taxiways? In the photos for this AvHerald article you can see areas marked in green with yellow stripes around the taxiways.

The entire maneuvering area appears to be solid concrete. The green painted areas are outside of the taxiway edge markings and the vehicle roadway markings. Is this green area intended to be a buffer zone to account for wings sticking out past the taxiway edges? Or is it just there to help show where the taxiway edges are? Should an aircraft's wingtips remain within the taxiway or can they hang over the edge?

It's essentially "fake grass" -- a "no taxi" / "no drive" area, the same as real grass would be.  The concrete may very possibly be stressed to support the full weight of big aircraft, and the areas are painted that way simply as a matter of keeping traffic flow in the designated areas, although it's possible that some areas marked that way may not be in a condition that you'd want to taxi on them.

As far as emergency vehicles go, they have permission to do whatever they need to do when responding to an emergency, which includes driving on anything they need to.  And the people driving the fire trucks will be well aware of any parts of the tarmac that even they need to avoid -- but if it's even close to being able to support an aircraft, it'll support a fire truck just fine.

More than anything else, though, it's a matter of marking the ramp to designate the "don't taxi here" areas from those where you can taxi.  Often, separating a ramp (taxi more or less at will) from a taxiway (ATC clears you where to go, and it's obvious where aircraft will be entering/leaving the taxiway).  (As the overhead image shows, wingtips can & do extend over the green areas; adjacent taxiways separated by such areas would be laid out so that aircraft on respective centerlines would have whatever wingtip clearance is required.)


Why do we undershoot/overshoot with a compass turn? In the southern hemisphere you would undershoot when turning towards a southerly heading and overshoot towards a northerly heading, and the opposite in the northern hemisphere. Why is this?

There is a good video that goes over the topic here ~2:45 into the video. It has to do with the way a magnetic compass responds to turns. When turning north the compass lags when compared to the tun of the physical aircraft so you need to overshoot the heading based on what the compass is showing. When turning south the compass leads the turn and you must roll out early to make your desired heading.

This site offers a nice explanation of why this happens in the compas

  Northerly turning error is due to the mounting of the compass. Since
  the card is balanced in fluid, when the aircraft turns, the card is
  also banked as a result of centrifugal force. While the card is
  banked, the vertical component of the Earth's magnetic field causes
  the north-seeking ends of the compass to dip to the low side of the
  turn. When making a turn from a northerly heading, the compass briefly
  gives an indication of a turn in the opposite direction. When making a
  turn from the south, it gives an indication of a turn in the correct
  direction but at a faster rate.

Similar explanations show up in this thread. Simply put its not the turn that causes the error but the banking of the aircraft. By rolling the compass housing to one side we allow the compass to tilt differently than it would in level flight. Since the pole is generally beneath the aircraft the roll allows the compass to pitch in a slightly different way causing the error we see.


How is the ATC language structured? Is the content of spoken communications used by air traffic control and pilots defined as part of a rigorous language definition? Such as a morphological or lexical foundational system, or is phraseology the extent of formalization?

And with the advent of text/computer based communications and automation on the horizon so to speak, what is the state of formalizing a language of communication? (If not already answered in the first part of my question.)

References to white papers and other research is fine if the answer requires you to almost write one.

I don't know about a formal structure, but ground to air and air to ground communications usually follow the 3-W or the 4-W rule.

For air to ground communication - use the 4-W rule:

Who the controller is (identification of the controlling agency)
Who you are (Aircraft Identification)
Where you are (what is you position and altitude)
What do you want (state your intentions or request)

Example:

Grand Junction Approach, Cessna one seven two Sierra Papa, five miles southwest of the ABC VORTAC at five thousand, five hundred, inbound for Grand Junction to land with ATIS Kilo.

Here the pilot identifies himself as a Cessna with the identification N172SP, that he is five miles southwest of the ABC VORTAC at 5,500 ft MSL, and that he intends to land at Grand Junction airport and has the latest ATIS weather report for Grand Junction.

ARTCC and other air traffic controllers will generally use the 3-Ws to communicate with you

Who you are (the aircraft they are giving their instructions to)
Who they are (the name of the controlling agency)
What they want you to do (instructions for the aircraft in question to follow)

Example:

Cessna one seven two Sierra Papa, Grand Junction Approach, turn right to 030.  Descent and maintain three thousand two hundred.  Expect vectors for runway three zero left.  Squawk six four one one and ident.

Here the controller (Grand Junction approach) has advised Cessna 172SP to turn to a heading of 030 and to descend to 3,200 ft MSL.  He should also expect further heading instructions for insertion into traffic for runway 30L at Grand Junction airport.  The controller also tells the pilot to set his transponder to the code 6411 and ident, so the controller can verify his position.

As a courtesy, and often requested or implied by controllers to verify the pilot in question heard the instructions and will comply, the pilot will read back the instruction in full to the controller, followed by his/her callsign.

Example:

Right to 030, descend and maintain three thousand two hundred, expect vectors for runway three zero left, squawk six four one one and ident, Cessna one seven two Sierra Papa.

The NATO phonetic alphabet will be used for individual letters to avoid confusion by both parties as many letters can sound similar on a garbled radio transmission. Other oddities include the use of the word 'niner' in place of the number 9; This is to distinguish from the number 5, which is pronouced "fife".

English is also the accepted international language for use in flying and radio communications, but is only required for flights under instrument flight rules (IFR).


How do landing gear retracting into the wing affect performance when deployed? On many aircraft with low wing, landing gear (either wheel, leg, or both) retracts into the wing. Thus, when deployed, a significant part of the lower surface of the wing is not as clean as when the landing gear is retracted. It must affect aerodynamics by adding drag, but may also affect lift as this modify airflow along the wing.

For the aircrafts whose landing gear or landing gear leg retracts underwing:

How does the landing gear affect aerodynamics when deployed and when deploying?
Is it different for aircraft whose landing gear do not retract into the wing?
Does this modify performance critical when taking off or landing such as stall speed, optimal climb speed?

There are two main geometrical characteristics that affect the airflow in the situation mentioned. From one side you have a cylinder with wheels at the end; on the other side during the transition you have an open cavity.

Let's talk about the first one. You actually have a cylinder flying perpendicular to the air speed. This is kind of canonical problem in fluid dynamics, there is a lot of literature about this problem, but to explain the effect I would like to take a simple example that I took from the website, the infinite 2D cylinder. For that, I include this picture of flow over a cylinder:

Note for fluid dynamics experts: This is not relevant if Reynolds Number (Re) is around 10,000, but for understanding the concept is good enough.

So, imagine that we are cutting landing gear perpendicular to its length and we visualize the flow.

What do we see?

Two main things....

Looking at the flow lines, they are almost not affected at 3-4 diameters of distance from the cylinder perpendicular to the flow direction there is a very local influence of the existence of the landing gear.

However we see that down the flow there is a big influence with the creation of chaotic structures. That is creating a big increase in drag downstream of the landing gear and any surface behind.

Basically... low influence on the red direction and significant influence on blue. Answering your question, influences the wing in a local area.

The influence anyhow is negative on the lift, as the flow is accelerated locally, reducing the static pressure below the wing, having a lift reduction, but is a local effect. This also have an influence on the wing lift distribution and a small effect on drag... lower than the one directly produced by the landing gear itself.

Now.... the cavities, they have a bigger influence, firstly because they have bigger extension parallel to the airplane surface (the landing gear goes perpendicular to the airplane the cavity goes along the surface). Secondly, their flow behaviour is different, goes in and outside the cavity. I found this web page very good on this, but basically the flow behaviour is like these image:

I found several flows similar to the second one, but depends on the airplane. You can see that flow will enter and go outside and will have a big influence.

Finally, the biggest influence is found when the airplane is deploying or retracting the landing gears when you have changing conditions, difficult to predict and affecting the airplane dynamics. Usually you can notice it when landing or taking off, when landing gear is deployed you fell significant vibration on the airplane.

Concerning your questions:

How does the landing gear affect aerodynamics when deployed and when deploying?

There is a significant drag increase, slightly the lift, but also creates some unsteady behaviour affecting overall airplane mechanics creating vibrations (anyhow, nothing not already taken into account).

Is it different for aircraft whose landing gear do not retract into the wing?

I understand that you refer to airplane with non retractable landing gear. The effect is similar but usually the configuration tries to avoid  having the landing gear close to the wing, as finally they don't need to retract them back.

Does this modify performance critical when taking off or landing such as stall speed, optimal climb speed?

Well, stall speed is usually defined by wing lift curve, and not so much affected by the landing gear. Usually the limitation is on the upper side due to separation.
Climb speed is basically engine thrust minus drag, the drag increases the climb speed is lower. That's why airplanes retract the landing gear as soon as possible.


How can an airplane land if a hail storm damages the windshield? I understand hail can be very damaging to an aircraft, in particular to the engines and windshield.

In the event that a windshield becomes cracked so that visibility is impossible, can pilots pop out the windows when at a lower enough altitude in order to see the runway?

In the EMB-145 the abnormal procedure for obscured windscreens is to secure items in the cockpit, open the side window and look through its opening.

There are more aircraft that share this procedure.

Here is the QRH procedure for "Impaired or cracked windshield" in the EMB-145:

Associated Windshield Heating .............................. OFF

IF  only the outer layer (glass) is cracked, no action is
    required

IF  inner layer of glass is cracked, proceed as follows:
    Cockpit Door ......................................... CLOSE
    Maximum Altitude ....................... 10,000 FT., OR MEA,
                                             WHICHEVER IS HIGHER
    Pressurization Manual Controller ........ 1 O'CLOCK POSITION

                    Wait 15 Seconds

    Pressurization Mode Selector ........................... MAN
    Cabin Delta-P ........................... SET EQUAL TO 1 PSI

    Note:  Pressurization Manual Controller must be used to set
           and maintain Cabin Delta-P at 1 psi while descending

    Airspeed .................................... BELOW 250 KIAS
    Smoke Goggles .......................................... DON
    In case both windshields are impaired:
    Cabin (below 10,000 ft) ....................... DEPRESSURIZE
    Airspeed ................................. MAXIMUM 140 KIAS,
                                                    MINIMUM Vref

IF  forward view through both wind screens is impossible, secure
    loose objects in cockpit and proceed:

    Note:  Intercommunication will be impossible with window
           removed.

    Direct Vision Window ................................ REMOVE
    Landing must be made looking through the direct vision
    window

                              * * * *


Can fuel sloshing in the tanks cause a stall? Cargo planes secure their load meticulously and if it breaks loose, the result is sometimes catastrophic. However, how do you prevent fuel sloshing inside the tanks and causing the same problems as loose cargo?

There are dividers (baffles) in the fuel tank precisely to stop the sloshing. They are just large plates that will stop the fuel from flowing across.

High maneuver jets will use bladder tanks (so no air is in the tank with the fuel) as a way to contain the fuel.


What altitude restrictions are there in Class C airspace? So if I'm flying into a Class C airspace, I call approach and I establish radio contact and tell them I want to land, then I enter the airspace.  If I'm still talking to approach and haven't been handed to tower yet, and they tell me to make (say) left traffic for Runway 15, does that give me permission to descend to TPA?  When do I need to maintain a specific altitude in Class C and when can I descend at my discretion?  And more broadly, if ATC doesn't give me any altitude restrictions in the Class C, can I fly at whatever (safe) altitude I want to as I come in for the landing?

Absent an explicit instruction to the contrary, VFR traffic can do whatever it wants in class C/D/E airspace. ATC is not supposed to give you both lateral and vertical control instructions at the same time because that could interfere with your ability to maintain VFR cloud clearance requirements. Class B has different cloud clearance, so you will almost always get both, and you should "unable" them if complying is not legal.
If ATC has told you to "advise any altitude changes", then do so—before starting up or down. If they told you "altitude your discretion", then they don't care. If they said neither, it's recommended to advise by default unless you're doing something where an altitude change is obvious, such as entering the pattern. They key is to not surprise them.


Could a test crew replicate the 1961 DC-8 supersonic dive in a more modern airliner? The first airliner to ever break the sound barrier was the DC-8, doing so in a semi-famous dive from 52,000' to 35,000' over the Edwards test range on August 21, 1961.

Could this supersonic dive be planned and reproduced by a suitable flight test crew in a more modern jet transport aircraft?

Why not?
There have been several cases of near-sonic and even supersonic dashes by the Boeing 747, and the damage to the China Airlines Flight 006 elevator was done by landing gear doors which ripped off when the main gear was extended and its doors hit the elevator.
There have been a few unintentional supersonic dives, and in those cases the actions taken by the crew to decelerate caused damage to the aircraft. TWA Flight 841, a Boeing 727 which rolled into a dive, and China Airlines Flight 006 overstressed the airframe, but both aircraft returned to service after repairs.
IAI experience tells me it needs a dive with a nose-down angle of 18° to get a Boeing 747 to Mach 0.98. Since almost all surfaces experience already supersonic flow at this speed, going the step to Mach 1.01 would need not much more, maybe 25°. Pulling up from such a dive by means of the stabilizer should entirely be possible without exceeding g limits.


Easy airplane program I'm 67 and would like a recommended easy airplane program to play. I cannot afford to really learn to fly so I would like something that is not to complicated to use.  Thanks.

A short(ish) version: for a tabletop computer or a laptop with Windows, any of the Microsoft Flight Simulator series will be fine. They are easy to use, and as you get better, you can add more and more realism.

If you want good graphics, these kind of games typically require quite a powerful computer, but a basic setup will get you started.

If I recall correctly, from MS FS 2004 onwards, you even get other planes flying around, and there is air traffic control you can communicate with via preset phrases.

MS should release a new version in the coming months, but I would remommend an older version, as one can probably find the a ta fraction of the price of the coming version(Amazon.co.uk less than 10£).

You should make sure the version you are about to buy is compatible with your Windows version. MS FS 2004 for example should run fine with Windows 10.

There is also X-Plane, I tried one years and years ago, but I recall it being not as easy to use. Flying I guess was pretty much the same: close enough for the real thing.


How to identify a specific 707 variant? I recently saw a very interesting documentary film made in 1980 about a narrowly-averted airline disaster in which the flight crew were incapacitated and a retired pilot, with the help of other crew members and experienced ground controllers, managed to land the plane safely.

The aircraft in the film is a 707, though I was puzzled by some of the interior shots, in which I thought it looked much more like a DC-8 (it's been a very long time since I flew in either). The footage of the cockpit was actually quite baffling, and I really didn't recognise it at all.

What exterior and interior features would help identify the particular 707 variant?

The documentary is apparently quite famous, so perhaps someone even knows the tail number. It's simply called Airplane! - very informative, and I learned a great deal about the aviation - highly recommended.

Don't know about the interior shots but for the exterior:

  In-flight shots use a model, some ground shots use N6723, c/n 18989/492, a TWA 707-131B.

This is from the awesome website IMPDb Internet Movie Plane database


Can I become a pilot if I have a medical/dental problem? Can I become a pilot if I have a dental problem (I don't have 6teeth I have artificial one)  and I broke my chin bone I have a steel plate there and I really want to become a pilot is this okay? can I still become pilot as I don't have any other defect in my body ?

Under FAA regulations (which most people in the world can train under if they come to the USA) you should be fine. There are no dental requirements to be a pilot or obtain a medical certificate (as far as I know). You can reach out an AME in your local area if you are concerned, they should be able to answer the question for you. The only orally related regulations are that you be able to speak english proficiently and clearly. As long as you can do so you should be fine.


What is the maximum nose wheel deflection angle? What is the maximum nose-wheel angle of deflection on modern commercial aircraft such as the Boeing 787? Can it deflect to 90 degrees or even more?

For the B787, the maximum steering angle is 70°. This information can be found in the Airport Planning Manual:

Source

For the A380, which has also a steerable main landing gear, the nose gear steering limit is the same:

Source

The center of the turn is off center, at the level of the main landing gear. With a multiple-boogie landing gear the main gear slips on the ground, which is not desirable.

This effect also occurs with a single bogie, unless the wheels are steerable. Limiting the steering angle also limits this slippage, and the wear going with it.


Why do we seldom see small unmanned aircraft with gasoline engines? Most commercially available FLYING WINGS (RC aircraft or UAVs) are battery powered. Why aren't there more with with gasoline engines?

PS: Sorry I edited. The question is specific about flying wings configuration.

Because electric is the best propulsion method available for small commercial UAVs and their mission profiles:

-Significantly quieter

-No smells involved

-No flammable liquid involved

-Way easier to operate: properly tuning an RC gas engine is not for everybody

-Much lower vibration and on frequencies easier to filter out

-More controllability, a BLDC (brushless DC) motor has near-instant response to the throttle and thus enables the actual, simple building scheme of quadcopters


Why aren't departures separated by minimum distance rather than minimum time? Normally, two departures are required to be separated by a minimum amount of time depending on the weight class of the aircraft.  However, I was wondering if someone could explain why departure-departure separations are not assigned by a minimum distance instead of a minimum time.  It seems that using a minimum time is potentially more inefficient, especially if the time to reach a safe distance for wake effect purposes is considerably less than the minimum.

As a related question, are there any research projects or articles that someone can point to that talk more about this subject?

Thanks!

For the FAA(all my answers can be looked up, and expanded upon in FAA Order 7110.65W, Chapter 3 mainly, but I'll try to keep it short), most departures from the same runway use distance for separation. The standard is the lead aircraft is clear of the runway, but most of the time can be shorter under most circumstances. The only times it becomes time based, if it's wake turbulence related, or various conditions of non-radar separation needing to be applied.

In general for runways, aircraft are broken into 3 categories for separation(excluding weight class, which add wake turbulence time if necessary). Category I aircraft are light single engine propeller driven aircraft weighing less than 12,500 lbs (and helicopters). Category II aircraft are light twin engine propeller driven aircraft weighing less than 12,500 lbs. Category III is everything else.

I'll mainly discuss same runway departures, since there's many considerations and it gets complex, and the FAA Order 7110.65 does a fairly good job of depicting and showing this separation standard. For the same runway when both aircraft aircraft departing are category I, the min distance between them is 3,000 feet and airborne. This means that the first aircraft has to be 3,000 feet down the runway and airborne, before the next aircraft starts it's takeoff roll. If the trailing aircraft is a Category II and the first aircraft is a Category I or II,  the distance increases to a separation of 4,500 feet between aircraft. If either aircraft is a Category III aircraft, it's 6,000 feet and airborne required.

Now if both aircraft are IFR, there needs to be IFR separation insured after the runway separation. In most environments the minimum radar separation is 3 nautical miles between aircraft. Now, between jets, the runway separation of 6,000 feet and airborne, will often be right at 3nm between aircraft(due to the speed differential mainly). Other options include turning one aircraft off the path of the other by at least 15 degrees and have them diverge apart.

Wake turbulence is one of the few areas that time is applied. If a heavy(300,000 lbs or greater) is departing in front of anything else, the next aircraft can't start their departure roll for 2 minutes when both are departing from the same intersection on the runway, and 3 minutes if departing the runway from different intersections. And a Super(A380/AN225) I believe are 3 minutes, when departing the same intersection, but I've never worked them in the tower. There are a few other times when time is used, intersections, opposite direction.

For arrivals, all except non-radar separation is distance based.


How much FOD hazard can a Styrofoam drink cup pose? So, the Collings Foundation and their touring warbirds were in town recently, and we went to visit them.  While out on the ramp though, my father managed to lose one of the Styrofoam coffee/drink cups the FBO provides (for their complimentary ice water and iced tea, of course).  How much FOD hazard could that runaway Styrofoam cup pose, considering its relative lack of hardness and stiffness/strength compared to most other FOD hazard items?

Probably very little. There's the very slight chance that it could stuck on a pitot tube or some other terrible scenario in a Final Destination type film which, coupled with another issue, could cause a problem but again very unlikely.

The underlying hazard is the attitude towards FOD in general. It's a bad habit to build complacency towards any FOD sitting on a parking apron or letting it "get away". If it's SAFE to pickup the FOD then it should be picked up. It's possible the next time someone ignores a cup, it could have been used by a wayward mechanic to hold a sticky chemical that would ruin a pilot's windshield and his day if it  smacks and smears on the glass on takeoff. Again very unlikely but why risk it!


How much does a drag chute system weight? How much weight does a drag chute add to a plane?

Let's take the Tu-114 as an example. This plane has a loaded weight of 68.1 tons (I could not find a max landing weight figure). I could not find how much it's drag chute system weighs.

One purpose of this question is to compare it to thrust reverser systems. I have a separate question on that.

It depends on the aircraft- for example, the the brake parachute system of the 17t F-16 weighs 20 lbs.

Generally, in an aircraft the brake chute system will weigh much less compared to the thrust reverser. While I'm not able to get any 'official values', according to this thres,

  In a Lear (24-25) the drag chute weighs some 25 lbs, the Dee Howard reversers weigh 350 lbs...


Is it possible to fly a Cessna 172 vertically? My question has two dimensions:

Disclaimer: Hypothetical question, I am a humble private pilot!

How fast you need to be and how fast you need to turn up so that you do not burn out all your kinetic energy in the lower arc of the climb and at the top you have enough authority to bank and dive back, not simply come to total stop and crash down like a rock.
Is Cessna capable of handling the kind of G's and maneuverability? Can it turn up into as sharp a rotation as required!

Might be a good idea to stay humble.  Any type of acrobatics may not be recommended if the aircraft has
a gravity only fuel feed.  Keep in mind if (for example you attempt a loop) and you only make 1/4 of the way through (and are nose up and have lost all forward airspeed), 5 things can happen. Fall straight down tailfirst (will not last long as this is most unstable and the nose wants to be down), tip left, tip right, nose drops back to horizon, nose falls INVERTED to horizon.  The last one I would not want to be in.
Tipping left or right can be helped with rudder and is known as the "stall turn" or Hammerhead.  Nose dropping to horizon would be similar to a stall recovery.

There are aircraft much more suited to do this and qualified people who would be happy to take you up and show how it is done. You may wish to speak with them.


How can I get an FAA Class 3 medical re-examination? I have some headache problems and my examiner submitted my data for deferred examination on the FAA website.

The results have yet to come back but let's suppose that I fail on this one - can I apply for an examination again after a certain period of time - For instance, when my conditions are better?

There are two processes you can go through if your medical is denied - one is to appeal the denial to the FAA (which you'd do if your AME messed up and you can prove they're wrong), the other is to reapply (which is probably what you'll want to do if you get denied).

When you reapply you're basically starting the medical certification process over from the beginning. You can reapply right away if you want, but practically you would reapply when you've corrected whatever condition(s) caused you to be denied, and go back to your AME with documentation showing that your condition has been corrected (or determined to be benign).

I assume based on your question that you've had to check the "Frequent or Severe Headaches" box, so you will continue to check that box, and may require a Special Issuance medical because of that -- your AME can give you more details if you wind up in this situation.

If you do get denied talk to your AME (and any other doctors you may be seeing) about your next steps before doing anything - obviously medical issues are serious not just because they keep you out of the sky but because your health is important.

You may also want to take advantage of AOPA's Pilot Protection Services - they have folks on staff who are experts at navigating the FAA medical process and can help you out. It could be worth it if you anticipate you'll need assistance with medical certification over the long haul.


Application interview / career as a pilot: is qualifying from First Officer to Captain expected from an applicant? I would like to know, if an airline expects an applicant, who wants to become a pilot, to qualify from pilot (FO) to captain (CPT)? Is qualifying kind of mandatory or is it primarily a personal decision?
I am asking because I do scientific investigation on pilot assessment. So if someone can share personal experience or even official articles and papers, I would be grateful.
EDIT: I have to add the background info, that the airline company is the provider of the apprenticeship (i.e. Lufthansa in germany).

I would say that an airline will avoid hiring an applicant that is not assessed as eventual "captain material".  It's not the maximum return on the airline's investment.
An applicant would never say in an interview that they only wanted to be a lifelong FO, except under special circumstances like an older hire who is likely to retire before meeting the experience requirements, or someone who has limiting medical conditions at hire (like the Type 1 diabetics who are now flying in some countries) that prevent them from qualifying for PIC.
An FO has to apply to upgrade to captain, so theoretically, someone can continue as an FO indefinitely (in a union operation at least), up to a point, but I think it would be career suicide to say so up front during the interviews.
It does happen though.  An acquaintance of mine some years back was still copilot at a major airline, flying heavies, with somewhere around 25 years in.  He finally upgraded to captain for the last years of his career.  One of his motivations was he'd gotten to the point of being at the top of the seniority ladder for copilots.
He was making way less than he would as captain, but he didn't care about the money so much, and was more interested in the bidding benefits of being top of the heap in his "junior" heap in bidding for pairings, insofar as he got the best routes and the best schedules and the most time off.  Upgrading to capt would mean he had to drop to smaller aircraft and a lower rung on the seniority ladder(back to working over Christmas, etc), and temporarily less money .  He finally upgraded to capt more or less in response to management and peer pressure in his later years (he said at the time).
There are a number of websites that post interview Gouges ("gouge" is a slang word for intel reports on an airline's recruiting/interview practices) like here. These can give a good sense of the kind characteristics they are looking for, and you will never find one that advises people to state that they don't want to progress to captain.


Are passive or active headsets preferable in an open cockpit? My first headset used passive noise reduction (i.e. padding) and when I - very quickly - upgraded to an ANR headset, my instructor recommended keeping the passive one "in case you ever fly something with an open cockpit". I can't remember if he gave me an explanation, but he definitely said that passive headsets "worked better" in an open cockpit.

I haven't flown anything open so I've never had the chance to put this to the test, but is it (or was it ever) true?

First we should see how active noise reduction works. The simplest definition would be:

Active Noise Cancelling uses electric signals to reduce unwanted sounds.

The following picture on Active noise control depicts it in a simple manner:

Then we can see what unwanted sounds ANR can actually reduce. As mentioned in A Guide To Buying An Aviation Headset:

  ANR headsets work best at frequencies below about 400-450 Hertz. This
  represents the normal frequency range for speech, and also much
  propeller and exhaust noise is in this region. ANR headsets are
  therefore a significant advantage where intelligibility of
  transmissions is affected by engine and propeller noise.

  In general, ANR Headsets offer greater hearing protection in
  high-noise environments but will do little to reduce noise at higher
  frequencies such as wind or airflow noise.

In a flying airplane (even in a slow flight), wind flow would be quite high. This PDF (page 1, paragraph 3) states:

  The wind noise spectrum is dominated by the lower frequencies (< 500
  Hz), although at 27 mph when saturation is present, the wind noise
  level can be greater than 60 dB SPL at 8 kHz.

Since passive noise control is sound reduction by noise-isolating materials such as insulation, sound-absorbing tiles, or a muffler rather than a power source, in an open cockpit, passive NR headsets work better than active NR headsets.