Why isn't testing fuel flow from both tanks a run-up checklist item?

There is a very good reason not to run this test: If it is not done perfectly your engine can become starved of fuel during takeoff.

For simplicity let's assume your fuel selector only has two positions (Left and Right) and think about what's involved in the test and a few things that can go wrong:

What are we testing?

One of the points of an engine Runup is to verify that the fuel system can deliver a fuel flow sufficient to allow the engine to develop takeoff power. There are other things we're verifying but let's stick with that item for this discussion.

How can we verify this?

We verify that the fuel system has adequate flow by running the engine up to something resembling takeoff power (most runup checklists don't have you go to full throttle, but you advance the throttle enough that the engine is demanding a significant fuel flow compared to idling and taxiing around).
To verify that your fuel system is allowing sufficient fuel flow from each tank you would have to switch tanks during the engine run-up (with the engine at runup power) and wait long enough to exhaust any fuel that might be in the system between the fuel selector and the engine.
If the fuel selector handle comes off in your hand or the engine quits you found the problem on the ground, so you can get a tow back to the ramp and get the fuel system fixed.

What can go wrong?

The test above sounds innocent enough, but it's deceptively dangerous.
Here are two possible failure modes that may make you rethink it:

The second tank doesn't have adequate fuel flow.
This could be a complete obstruction of the tank pickup or just a restriction in one of the lines, but for some reason the second tank will not supply a fuel flow sufficient for takeoff and climb out at full power.
You may miss this if you don't wait long enough at runup power after switching tanks to drain the fuel from the system forward of the fuel selector, and now your engine suddenly got quiet as you're rolling down the runway - or worse it quits 100 feet off the ground and now you're having a Really Bad Day!
You missed the fuel selector detent.
Easy enough to do, especially if fuel selector maintenance has been lacking and the positions are not really distinct (when is the last time you *really, critically, felt the clicks on your plane?). It could happen in the initial switch, or when switching back to the first tank if that's your procedure.
A fuel selector not in a specific tank position may still allow enough fuel flow to complete a runup when combined with the fuel left forward of the fuel selector, but it may be too restricted to allow a takeoff. The fuel selector may also vibrate into an OFF position during takeoff.
In this scenario maybe your engine stops at 200-300 feet, but you're still having a Really Bad Day.

In both of these scenarios the engine is still running because there is fuel in the system between the fuel selector and the engine (the two big reservoirs are the fuel strainer / gascolator & the carburetor float bowl, but there are also fuel lines that will need to drain before the engine dies).
To get an idea how long these reserves last try setting your engine to Runup power and turning off the fuel selector. You may be surprised how long the engine will run before the fuel after the selector is exhausted. Also remember the time will vary based on power setting, mixture setting, and even aircraft attitude sitting on the ground allowing more or less fuel to get to the carburetor from the lines (a nose-high attitude during takeoff may starve your engine more quickly than sitting level on the runup pad).

How can we safely conduct this test?

Making sure your fuel tanks all work is kind of important, especially if you are going to be making a flight near the endurance limit of your fuel.
There is no 100% safe way to conduct this test, but the way I was taught seems to have the fewest possible failure modes:

Start, taxi, Runup, and takeoff should be conducted on one tank.
Typically this is "the fullest tank", but if they're all equally full then either the one the fuel system return flows to if your airplane has such a thing, or just pick one.
By using the one tank for all your ground operations and your Runup you are pretty much guaranteeing that it flows sufficient fuel to allow a takeoff, and that at least this position on the fuel selector works.
After takeoff switch tanks after reaching a safe altitude.
Do this with enough fuel left in the tank you took off on to turn around and get back to where you started in case you discover the tank you switched to doesn't work, and as with any tank switch be prepared for the fuel selector handle to come off in your hand: Know where you'll put the plane if that happens!
If your engine stops a few minutes after you switch tanks…
…you now have a good reason to suspect that the tank you switched to doesn't work.
Per the first rule of troubleshooting, undo the last change you made (switch back to the working tank you took off on) and wait for the engine to get fuel again. When the engine restarts go home: You have a fuel system problem and need to get it fixed.

If after switching back to the working tank your engine doesn't restart…
…make sure you've waited long enough (it doesn't take long, but it FEELS like a long time when the engine is quiet).
If you waited long enough you may have a fuel selector failure. These don't happen often, but they do happen (and this is why you do the test at a safe altitude with a landing spot picked out).
In this unfortunate case run your engine failure checklist and expect to be making that dead-stick landing: Fixing a fuel selector in flight is probably beyond the skills and daring of most pilots.
(Of course you expected this because every time you touch that fuel selector handle you expect it to come off in your hand like I said before, right? Your CFI was like mine and a few minutes after you switched tanks they pulled the throttle on you al the time, so you got this landing made, Right?)

The test process I use and have outlined above is obviously not free of risk, but the risk level is reduced to be the same as any other fuel tank change: You can be reasonably sure that you won't have an engine failure on takeoff when you're close to the ground, trees, people, and other things we try not to hit with our airplanes, and you can pick when you take on the risk of an engine failure to be sure you can safely recover from the situation.


Where can I find a catalogue or lists of realtime, streaming (major) airport cameras?

I don't have a website link with a list, but we can create a collaborative Community Wiki with all the webcams everyone knows — feel free to edit this answer to add any you know!

Americas

Brazil

FLN/SBFL - Hercílio Luz/Florianopolis
NVT/SBNF - Navegantes

Canada

NavCanada Weather Webcams (only available at some airports, updated every 10 minutes)

Chile

All airports and aerodromes

Europe

Germany

DUS/EDDL - Düsseldorf
CGN/EDDK - Cologne Bonn/Köln-Bonn


Why were these Hawkeyes flying in a circular pattern?

They were most probably training touch-and-go passes. USN conducts carrier landing practice at NASA's Wallops Flight Facility for E-2 Hawkeyes and C-2 Greyhounds.

As Lt. Commander Mike Ferrara, an operations officer with the Navy's Carrier Airborne Early Warning Squadron 120 (VAW-120) explains in this article:

  These two aircraft are very difficult aircraft to fly — that's why, when we're up here, you'll probably see us going around for three hours at a time, take a break, and go for three more hours ...


Who is the third pilot in this Qantas Airbus 380 long haul flight?

The two stripes on his shoulders indicate he is a Second Officer. They are fully qualified pilots but only act as cruise relief pilots on long flights. New Qantas pilots are  initially employed as a Second Officer.

It is standard practice to have all pilots in the cockpit for takeoff and landing. Their role in these periods is pretty much to just keep an eye on everything in case the other two miss something. Some time after the aircraft reaches cruising altitude one of the pilots will start their break and the second officer will take over.


What is the record length of time for single-occupant flight?

What is the longest flight time for a single pilot alone in an aircraft?

13 days if a balloon counts as an aircraft.

Balloon

Steve Fossett set a record in 2002

  In 2002, he became the first person to fly around the world alone, nonstop in any kind of aircraft. He launched the 10-story high balloon Spirit of Freedom from Northam, Western Australia on June 19, 2002 and returned to Australia on July 3, 2002, subsequently landing in Queensland. Duration and distance of this solo balloon flight was 13 days, 8 hours, 33 minutes (14 days 19 hours 50 minutes to landing), 20,626.48 statute miles (33,195.10 km).

Other types of aircraft

The following information was volunteered in comments by Scary Spice and Peter Kämpf.

Glider

Charles Atger, stayed aloft for 56.25 hours, solo.

Powered airplane

Charles Lindbergh was all by himself for 33.5 hours.

Spacecraft

Ron Evans, Apollo 17 Command Module Pilot, was alone for 79 hours, 49 minutes.


What is this instrument that has "PACK" written on it and a temperature scale?

It looks like the pack temperature gauge for the air conditioning system on the 727

  To monitor the operation of the air cycle machines, each has a
  temperature transmitter at the outlet off  its compressor.  The
  temperature sensed is displayed on a pack temperature gauge for each
  pack.  As more air is directed through cycle machine to provide more
  cooling, more compression is  required from the compressor.  This
  results in a higher compressor outlet temperature.  Therefore, the
  pack temperature gauge monitors air cycle machine work load.  To
  protect the compressor from excessively high temperature an over
  temperature sensor at the outlet of the compressor will cause the pack
  to shut down if the temperature reaches the limiting value.  Another
  temperature limiting sensor located at the inlet to the turbine.

You can find a full video of how that section of the flight engineer panel works here.

Here it is on the flight engineer's panel (airliners.net).


How can the runway allocation process be optimised?

This question is extremely broad. At airports where there's multiple runways, there are numerous factors influencing which aircraft get which runway. Factors include, noise sensitive areas(so one runway should be favored over others), runway length/operational necessity, and configuration.

When an airport has multiple runways usually the tower will decide which are being advertised as arrival/departure runways. At which point the approach control will sequence to those given all the restrictions. Runway assignment usually occurs upon the aircraft entering the approach control's airspace. Once assigned to a runway, it's up to the controller to decide on the sequence, factors include airspeed, distance, and somewhat weight category. If you have multiple heavies coming in, it's often better to group them, than mix small-heavy, BUT you need to have the volume to be able to setup that kind of mix, to minimize space.


May a commercial pilot transport an owner in the latter’s experimental aircraft for compensation?

This one seems pretty straightforward to me. 91.319(a)(2) applies (because in the scenario you have described the pilot would be carrying persons - Olive - for compensation or hire).

Popeye could accept compensation to reposition the aircraft (with no passengers or cargo onboard) as a ferry pilot, but not to operate the aircraft for the purposes of transporting persons or property (besides the aircraft itself and the incidental things it might carry like extra oil) - even if the person happens to be the owner of the aircraft.


Ramjets could be miniaturized, but at some point, air viscosity and boundary layer thickness will make it impossible for them to work. Simply put, the intake hole will get so small that air will find it easier to flow around the whole thing and ignore all of its complicated inner structure.

In more technical terms, as the intake shrinks, intake velocity will approach an asymptotic limit regardless of flight velocity due to boundary layer friction, and for very small intakes, the air mass flow will be insufficient to sustain fuel combustion. That point seems to be somewhere in the centimeter range, but an engine becomes increasingly less useful as it approaches this point. Manufacturing parts this size isn't a problem even now.

Ramjet shells can help long-range artillery, but ramjet tank shells would not be effective in combat.

The figure of merit for tank rounds is their high-density penetrator's sectional energy at the target. Discarded sabot rounds are more effective at delivering this than any kind of engine internal to the projectile. Combat ranges are short enough to preserve the velocity.

If you had to use some sort of engine for a tank projectile, it would be a rocket. The reason is easiest to explain in numbers. At a range of 7.5 km with average 1.5 km/s velocity and a 10 kg round, to get 500 m/s of delta-V, you need 10 g = 1 kN of thrust (engine), plus 50 seconds of impulse (fuel). We'll ignore engine mass for the first approximation.

A rocket with TWR=50 and ISP=250 seconds will weigh 100 kg / 50 = 2 kg for the engine + 10 kg * 50/250 = 2 kg for the fuel, for 4 kg total.
A ramjet with TWR=5 and ISP=1000 seconds will weigh 100/5 = 20 kg for the engine + 10 kg * 50/1000 = 0.5 kg for the fuel, for 20.5 kg total.

Simply put, when flight time is this short, a heavy engine like a ramjet doesn't pay for the minute amount of fuel (or rather oxidizer) mass it saves vs a light and powerful rocket.

This applies to all combat applications within visual range: rockets are better, and guns are better still if you can afford the launcher weight. Beyond visual range, rockets or hybrid gun/rockets take over, and past 100 miles, air-breathing engines become viable.


What are typical insurance costs for airliners?

for personal airplanes(like a Cessna),

  Expect to pay anywhere from $600 per year and up depending on the airplane, your time in type and total hours.

source (http://www.planeviz.com/cost-of-aircraft-ownership-ep-9/)

while there are no estimates (that i can find) about the really big commercial airplanes like the 747, there are estimates available for smaller airplanes like the G650 (  )

the estimate for this plane in insurance is 60,000 USD per year

source (https://www.quora.com/What-are-the-yearly-maintenance-and-total-overhead-charges-for-a-65-million-Gulfstream-G650)


Why do people say aviation regulations are written in blood?

No, that's all it means. Aviation regulations tend to be put in place in response to accident reports, where a plane crashed or almost crashed for lack of the regulations. So, if you're confused why a stupid-seeming regulation exists, there's a good chance that people died because of the thing the regulation changed.

Obviously, not all regulations are like that; for instance, noise limits are based on quality of life for those near airports, not crashes. However, a good number of aviation rules came into effect as recommendations following a crash report.


Do any regional turboprop aircraft have leading edge high lift devices?

Neither the Dash 8 nor ATR families (which cover the bulk of regional TP market) do.
Your last two sentence pretty much summarizes it.  Some of the additional lift potential of a slatted wing is from the camber increase when the slat is extended, but most is from the ability of the wing to operate well beyond the normal stalling AOA of around 15-16 degrees, into the low-mid 20s.  You have to design your airframe to operate at very high pitch angles to exploit this.  I'm not sure that boots are a factor because there isn't really anything stopping a designer from installing boots on a slat (it's effectively a rubber air mattress glued on the LE with contact cement).
Jets use slats to improve safety margins at reference (approach) speeds (also lowering the reference speeds somewhat) with their more highly loaded, high speed wings (over 100 lbs/sqf, with supercritical airfoils that have poor stall characteristics - the 737 is in the 140 lb/sqf range). Turboprops operate with somewhat lower wing loadings (under 100 lbs/sqf - the Q400 is about 97 lb/sqf) and more gentle-stalling airfoils, and don't really need slats to achieve the mission objectives cost effectively.
None of the DeHavilland Canada products, even those designed for extreme STOL like the Caribou/Buffalo or Dash 7, have used slat systems.  It was preferred to use fixed leading edge cuffs (drooping LEs) and elaborate double slotted flaps (full span in some cases) to get the desired lift coefficients at "normal" approach deck angles.
The regional airliners like the Dash 8 are not designed for STOL operation in the first place (the Dash 8 is a redo of the STOL Dash 7, which was a marketing mistake, developed around a "stub runway" concept based on MLS that never materialized), so there even less of a need for them.


Why are airliner seats higher than chairs and couches at home?

The short answer,

Your couch is made for you to fall asleep on, watch football from, and generally be of any non determinant shape since no couch (as far as I know) carries a type certificate.

Aircraft seats are designed to fit as many passengers as is legally allowed and practically possible while still passing the 16G tests the FAA imposes. The 16G requirement is largely for your safety.

Most pilot seats are in some way adjustable up/down and forward/back depending on the age of your aircraft.


What are the effects of separation at hypersonic rarefied flows?

Hypersonic rarified conditions means you're almost in space.
You are asking can you stall? Maybe the first question should be can you fly?
Correct me if I'm wrong but it seems that you are trying to apply a real life exemple to a totally different area of flight. The stall you are referring to happens in transonic flight when the shock wave appearing on the extrados forces the flow to detach.
In subsonic/transonic flight lift is generated through an acceleration of the flow around the extrados resulting in a pressure loss on the succion side of your wing. If the flow detach you're losing this acceleration effect of the flow following the surface of the wing and thus you lose lift.
In supersonic flight the shock waves starts attached to the leading edge of the wing. The shock deviates instantly the flow and the more the flow needs to be deviated the stronger the shock and the more pressure increases. Lift is generated through the difference of deviation in the flow betew intrados and extrados resulting in pressure difference on both side. The boundary layers here doesn't play a huge role and I've never heard of supersonic flight stall.
In hypersonic rarefied condition the shock detach from the body and you have very high temps, and complexe chemistry hapenning inside the layer between the shock and your surface thus making the flow hard to simulate. First of all you don't really use wings in this mixture of high energetic particles so speaking of stall doesn't make sens. Then lift is mostly done the same way as in supersonic, through the differential increase of pressure being the shock but the chemistry between the few molecules of air can create weird stuff resulting for exemple in asymmetrical lift on a surface for very complexe not always well known reason.


How to model aircraft fuel consumption during the approach?

Approaches take relatively little time, and have various throttle ranges, from idle to slow level flight. I would simply model as if the aircraft were flying level for the distance of the approach, you will over estimate fuel consumption for the approach itself, but for even a 60 minute flight the error would be tiny. You simply cannot accurately predict what is going to happen.


Where can I find the planned and flown paths for certain flight routes?

Yes, depending.....
On FlightAware.com you can see the routing of a flight after it's flown, and the same flight the next day will probably file for the same route.

On FltPlan.com you can find typical routes that a plane is likely to be cleared on and have actually been cleared on over time. Pretty accurate, but you probably need flying skills to interpret it, or get training on understanding routing, airport ICAO codes, nav fixes, departures arrival and enroute routing.


Is there a relation between material choice and produced lift at rotation?

Yes.

Some materials are easier to shape (think composites versus metal) or stay in shape better over time or under stress (think metal versus wood). This difference between the intended and the actual shape will have the biggest material-related impact on lift.

If you slightly change the question and ask for useful lift (lift minus weight of the structure), the stiffness and relative strength of the specific material must be added to the comparison. Useful parameters are the ultimate strength relative to density (breaking length) or stiffness relative to density (strain length). A stiff structure deforms less under load, so its shape will change less. Ideally, the structure is shaped such that only under load it assumes the aerodynamically most advantageous shape while its elasticity helps it to avoid being overloaded (aeroelastic tailoring).

The surface finish is also material-related, but is more affected by the manufacturing method. A rough surface is better at very low flow speeds while a smooth surface is better at moderate to high flow speeds.


What is the section of the fuselage below the wings called?

The outer covers at-least, are called wing to body fairings in this Airbus document- 'Airbus Future Composite Wing'.

Wing to body fairings; image from Airbus Future Composite Wing

Elsewhere, the covers are called belly fairings by the manufacturers themselves, and also in the US patent US 20060065784 A1- Aircraft provided with a belly fairing, and corresponding belly fairing.

Anyway, the fairings enclose the center wing box and the main landing gear wheel well.


What is the largest aircraft (by max takeoff weight) in which all engines are in the tail?

I think you've got it. Surprising to see how much larger it was than the VC.10.

There was a planned development of the VC-10 that used the VC-10 wing and tailplanes with a new double-deck fuselage. This VC-10 Superb (DB.265) had a planned MTOW of 174 tons.


How is wind measured at this small U.S. airport?

Ultrasonic anemometers are replacing the traditional cup anemometers in automated weather stations.  The sensor measures the time it takes for an ultrasonic pulse to travel between the probes, which is affected by wind speed. In your second image, the object directly above the lights appears to be an anemometer.

Source

Ultrasonic sensors have the advantage of no moving parts and lower maintenance requirements. Also, with additional probes, they can measure the wind in 3D.


Why do helicopter rotors have constant section and angle of attack?

Helicopter blades do have twist. The relative air speed increases from blade root to blade tip, and therefore on an untwisted blade lift would increase quadratically from root to tip. Or going the other way, lift would reduce quadratically from tip to root. Blade twist fixes this: it recuperates the lift generated on the inboard section of the rotor.

From Ray Prouty, Helicopter Aerodynamics Vol. 1., page 248:

  By twisting the blades to reduce the lift at the tip, the flow pattern can be made more uniform and the hover figure of merit can be improved by up to about 5%. Since this may represent a 20% increase in payload and since twisted blades are about as easy to manufacture as untwisted blades, there is a good reason to use twist - and all modern helicopters do.

Due to the aerodynamic lift equation, ideal blade twist would be non-linear: again, would vary quadratically with blade span. But this ideal twist is only ideal in the hover situation, and definitely not ideal in the factory when the blade needs to be produced.

Pouty's article is very much worth reading, and further mentions:

High twist produces vibrations by the centre of pressure traveling a lot during rotation.
Negative blade twist (tip angle lower) is good for retreating blade stall but bad for autorotation, which would be helped by positive blade twist.
Optimum twist differs for hovering In Ground Effect and Out of Ground Effect.


Is it worth it taking flying lessons even though I can't commit to regular lessons right now?

My humble advice is to take a single introductory flight in the Cessna 150 to galvanize your interest and increase your motivation. Go to ground school first and then (preferably) start your flight training (in the C150) in earnest once you have the time and money available to take lessons on a regular schedule (once a week minimum, three times a week maximum [until the later stages of your initial training -when you are practicing what you have learned and not learning new skills]).
In my experience, having too big of a gap between flight lessons can be counter-productive and make for a (sometimes) difficult learning curve.  This can lead to frustration on your part and, perhaps, result in your enthusiasm being diminished.
Frequent lessons will most quickly enhance your skills and your proficiency will improve steadily.  Additionally, recency of flight experience will provide for greater personal enjoyment and reinforce your confidence, a very important factor in learning to fly.


Why do we see a reduction in temperature in a wind tunnel by increasing the velocity, but in a real flight it's the opposite?

I believe the reason is that the air is cooled while compressed in the high pressure reservoir before the high speed wind tunnel.

When moving air is stopped (as happens around the leading edges of the aircraft), its pressure increases (per Bernoulli's principle) and since the compression is adiabatic (no heat exchanged (yet)), its temperature also increases. The final temperature is called Total Air Temperature (or stagnation temperature).

For flying aircraft, the total air temperature is its original temperature plus the increase due to compression by the leading edges of the aircraft. That's why the leading edges heat up in supersonic flight. The other sides don't, the air is not stagnant around them.

However, for wind tunnel, the air was already stagnant in the high pressure reservoir before it—high-speed wind tunnels usually pre-compress the air, because compressors can't produce supersonic speeds. It this reservoir it cools down, and then as it accelerates down the wind tunnel, it adiabatically expands, reducing its temperature well below ambient. It returns to the temperature in the reservoir at the leading edges, but around the rest of the model the air is not stagnant, so it has the lower temperature of the flow.


Voltage induced in high-tension magneto ignition system

I assume you're talking about an aircraft mag.  Mags are never really OFF off.  Instead of ON/OFF, it's more like ON, and "on but not on enough to work".

With the ignition switch OFF, grounding out the primary, the alternating current generated in the primary as the mag spins flows to ground, and it does induce a voltage in the secondary as the current alternates, but this voltage is much too low to be able to jump a plug gap.  So the mag is effectively off if not totally off.

To get a spark, the flow of alternating current in the primary needs to be fully cut off by the opening of the points within the primary to create a field collapse strong enough to generate sufficient high voltage to be induced in the secondary.


Are there any restrictions on long overwater flights by private aircraft?

I am unable to find any ETOPS restrictions for private aircraft in the FAA FAR/AIM Part 91. The FAA Advisory Circular AC 91-70B is applicable for commercial aircraft operators. Anecdotally, general Aviation single-engine aircraft (Including helicopters) make oceanic journeys on a regular basis.


What instruments were "standard" in WWI aircraft?

If you are asking about military aircraft there would often have been a compass, oil pressure gauge, a not very sensitive altimeter, a tachometer and some sort of airspeed indicator. Not sure about fuel gauges. I have also seen bank indicators. There was not the standards for instruments as in later days and some items were specific to individual aircraft types. Some of these guys could fly a sort of instrument flight but had not much in the way of navigation aids.


They're called SPAAG's -- Self Propelled Anti-Aircraft Guns. Older systems tended to fire 23 mm shells. Newer systems tend to fire 30 mm shells augmented by short range missiles.

They are equipped with radars and high-speed elevation and traverse motors for the turreted guns, so they can react quickly to fast a/c flying low ahead. They're also useful against attack helicopters, which also hug the ground (see below).

These are short range weapon systems, typically only effective under 10,000 ft, the guns at much less than that.

They're still useful even today. Medium and long-range SAM's have forced a/c to fly low, below their search and fire control radars, but within range of the guns.

This was standard NATO doctrine during the late Cold War---low level penetration---and gave rise to the F-111 (for example), which was designed to fly fast and low, hugging the bumpy terrain of Central Europe. This would have worked very well had the Soviets not fielded SPAAG's (basically modern AAA) and developed their own MANPADS (shoulder-fired SAM's). Soviet AWACS and look-down shoot-down radar also contributed to the decline of this tactic. These systems denied the use of low-level airspace so effectively that during Desert Storm, the Coalition air forces basically gave up low-level operations within the first week and switched to bombing from medium altitude exclusively (above the reach of AAA and MANPADS). Not even the A-10 with its titanium armor could long survive in that environment. Afterward, they did occasionally venture below 10,000 ft, but typically with special permission and enthusiastic support. Even after the first week, when Iraqi air defenses were ineffective, few a/c still flew below 10,000 ft because the AAA and MANPADS were too numerous to be eliminated entirely.

NATO air forces are getting around this problem by buying stealth fighters, namely the F-35A, which can hide from SAM radars, allowing it to fly at medium/high altitudes, far above MANPADS and AAA. But that's for another question/answer.

Here's an older Shilka (Vitaly V. Kuzmin - http://vitalykuzmin.net/?q=node/306):

A later Tunguska (Leonid Dzhepko / Л.П. Джепко):

And a modern Pantsir (Vitaly V. Kuzmin - vitalykuzmin.net):

(All images taken from their respective wikipedia pages.)


How are antennas integrated into stealth aircraft?

Pitot tubes
F-117 pitot tubes

Source: YouTube. Also a look at the FLIR and DLIR.
F-22 pitot tubes

Source: AIR-SCENE UK.

Incorporation of those pitot probes were a cost savings measure. They are also a dominant RCS signature source in the forward and side sectors. The original ATF proposal was for a flush air data system that would have cost many $ millions. - djcross, F-16.net

F-35 pitot tubes

Breaking Defense. More pics on F-16.net.
Canopies
The canopy keeps radar energy out of the cockpit, the inside of which is filled with messy odds and ends. The F-22 and F-35 canopies are gold-impregnated for this reason. Note: the F-22's canopy is possibly doped with indium-tin-oxide, not gold.
In the EA-6B's case, the gold keeps the a/c's own radar energy out of the cockpit---those ram-air turbines are powering two jamming pods. The coating (and a similar one applied to visors) also turn black to protect the pilot's vision from nuclear detonations.

Source: USAF

Source: Wikipedia.

Source: Lockheed Martin. Flickr set.
Notice the similarly tinted/treated window beneath the F-35's nose. That's the aperture for the EOTS (electro-optical targeting system), an IRST and ground targeting system. Also note the two small pitot tubes above the EOTS. I remember pitot plates were being developed for the F-35 (which are stealthier but more difficult to develop), but I haven't heard anything about it in a while.
Sensor apertures
The coverings are transparent to the operating bands of the radar/radio/etc underneath.
The F-22 and F-35 have fixed AESA radars. The latter is angled up to minimize returns.

Credit: Northrop Grumman. Hi res.
Some radar energy enters through the aperture. Whatever isn't reflected is absorbed by the radar itself or heaps of RAM, which hides the messy rear/sides.

via F-16.net. More AESA pics.

Fun note, the first F-35 radar pic is of an APG-81 installed on the CATBIRD:

Source: YouTube

Did the F-117 have a radar warning receiver?
It's always been a contentious point. Some say yes, some say no, some say 'I like my job.' In a lengthy 2007 interview, Lt. Col. Dale Zelko (the F-117 pilot shot down) declined to reveal whether the RWR (if any) warned him of the missile launch, citing sensitivity. He only reconfirms that he visually tracked the missiles. My guess is the F-117 may have a limited radar warning capability, but perhaps not in the relevant band. If he or the mission planners had detected and thus been aware of of the radar sites, you'd expect them to plan better routes to avoid the threats.
I leave you with a quote from Maj. Gen. Carlsons' (who flew the F-117) briefing on stealth fighters in 1999, shortly after an F-117 was shot down in Allied Force.

We started out a long time ago building airplanes that had low observable technology incorporated into their design. The SR-71 was an example of where we took the aerodynamic design and then added some radar absorbing material to the airplane to make it slightly stealthy. And I'll give you a representation of that graphically here in a minute. We went to the second generation of airplanes and you can see we designed that airplane, the F-117, essentially from the bottom up to be stealthy. It was crude technology. It was developed at a time when we didn't have the modeling and computer power we needed to make the kind of aerodynamic design that we would have liked, but we built one that we thought was very stealthy. And of course, the night that Desert Storm opened the quote from Col. Al Whitley still is famous in the Air Force: "Boy, I hope this stuff really works." And of course, you know that it did. That isn't exactly what he said.
Then we came to the third generation of stealth airplanes. We built the B-2. And of course, by that time, we had the modeling tools and the design tools and the computing power to make an aerodynamic design that was optimum. And this airplane is [a] much higher altitude, much better performing airplane than the F-117. We were able to eliminate a lot of the radar absorbing material from the structure. And by the time we got to the fourth generation, we were able to add supersonic speed, the agility of an F-15, F-16 class airplane and do that with no degradation to the stealth. In addition to that, we were able to add a number of apertures, in other words, openings in the airplane's surface for antennas, radars and other sensors. And in the F-22, as an example, there are over a hundred of those apertures on the airplane, where if we jump back a couple of generations to the F-117, there are essentially a couple of aperture openings and the rest of them we hide when we go into combat. [Emphasis mine.]

Some of the F-22's apertures...

Source
...whose functionalities were consolidated in the F-35's fewer apertures (some shown here).

The F-35's ASQ-239 EW suite, an evolution of the F-22's ALR-94, consolidates 30 senors down to 10.

[Apologies, pressed for time. This answer will be brief, unlike my previous 29,999 character response.]


"Carbon fiber filament" for Fused Deposition Modelling (FDM) printers doesn't have the properties you believe it does.  While perhaps a little stronger than a plain filament, in comparison to traditional items made of carbon fiber it is actually quite brittle and easily snapped, because the fibers are all chopped up into short pieces and mixed with the plastic resin.

To build something useful for an aircraft, you need fibers of meaningful unbroken length - either large pieces of cloth, or to run a continuous filament back and forth many times.

There have been thoughts of making FDM printers which would place a continuous carbon filament along with a thermoplastic "printer filament" as a binder, but that's not what a roll of "carbon fiber printer filament" gets you.  Also note that even a filament-stringing machine would only make structures which were strong in the plane the layers, but not against delamination between layers; to get a strong 3d shape like an aircraft panel, you would need a six axis machine which built in a way sensible for the shape of the component being built.

You could potentially use some ordinary or soluble filament to print a mold for conventional carbon fiber layup.


Is there any reason for why the cabin temperature would suddenly become very high?

Over Central Europe in the winter time, air becomes tremendously cold. Since warm bleed air from the compressor stage of a jet engine is used for cabin heating, the pilots might have set temperatures to maximum in order to warm the cabin.
But being in a climb, almost all power of the engines is required for lifting the aircraft, thus leaving only little excess bleed air to be used for heating. During normal days and outside air temperatures this should be enough, though.

By levelling out the aircraft, the engines are spooled back (less power required than in climb -> hence more excess bleed air available -> higher ability to warm the cabin in cruise than in climb). If the pilots/cabin attendants just didn't realize this circumstance rapidly enough, the cabin is being flooded with maximum heating air from the engines.


When does an airliner switch from using the tiller to the rudder?

I flew for two 747 carriers that never bought new aircraft, and thus this answer applies to 747-100/200 aircraft as originally manufactured for a number of different airlines.

The tiller is active when the aircraft is on the ground and the nose gear is compressed regardless of groundspeed as I remember.

I've never heard of a pilot accidentally hitting it at high speed on the ground, but if they did it would scrub the front tires. It wouldn't appreciably turn the airplane.

Pilots did have to be wary of having their hand within the travel range of the tiller when a tug is being hooked up. Ground handlers would sometimes work the nose gear back and forth a bit, and that action is reflected in tiller movement. If they do it quickly, the tiller will snap quickly and a hand in the way will get hurt.

The nose gear is relatively weak compared to the rudder, the brakes, or the engines insofar as its ability to turn the aircraft. To make turns off a runway onto a taxiway that is 90° to the runway, you usually aim for a 10 knots or less groundspeed. You can do a little more depending on the runway surface and what your center of gravity is, but sometimes 10 knots can be too much. I once skidded the nose gear badly at Jeddah, Saudi Arabia at midday in the summer when I failed to account for the fact that hot asphalt is slippery.

To illustrate how poor tires are in preventing sideways scrubbing, consider the 747 body gear. 747s have body gear steering for tight turns, but you can dispatch the aircraft with inoperative body gear steering. You can still make tight turns, but not quite as tight, but you do it with engine power and just scrub the body gear around, all 8 tires with a lot of weight on them. You might have difficult doing that, though, if you c.g. is greater than 26.6% mac. That's where the wing gear is, and if you're aft of that (limit is 33% to 37% typically) you're got a lot more weight on the body gear. Body gear steering is disarmed for takeoff and landing though.

Barring a strong crosswind, the usual takeoff procedure was to not use the tiller unless you were doing a rolling takeoff, starting the power up before being aligned with the runway. Once aligned and moving the rudder will do it. Even in a strong crosswind, you can forget the tiller very soon in the takeoff roll.

On landing, no use of the tiller until down to taxi speed except maybe a little use for a strong crosswind just before reaching taxi speed.

Boeing offered a rudder pedal-nose gear steering link, but almost all 747s I flew did not have that. I flew a couple of airplanes that had it. It helped in a crosswind.


What error is left uncorrected when "fast IRS align" is done?

Your question presumes that a "fast align" can be performed instead of a "full align", but is in some way deficient. But this is not the actual usage.

Starting from cold (unpowered), the IRS must always go through a full alignment to find true north, a process which takes about 7 minutes. The IRS is also manually given an initial position, usually via the FMC 'POS INIT' page. From then on, the IRS will maintain its sense of true north, but will gradually drift in position and ground speed due to the slight errors in the accelerometers. The amount of drift is small enough not to be a significant problem even for the longest flights of which the aircraft is capable, but the IRS should be re-aligned to a known state and position before each new flight. During a turn-around, the IRS could be given a full alignment, but since it is already aligned to true north, that is actually unnecessary - all that does need to be done is to reset the accelerometers to zero when the aircraft is actually stationary and give the IRS a new initial position. That is the purpose of the "fast align". The result should not be in any way 'deficient' from a full aligment, it is just saving the unnecessary and time-consuming step of determining true north when the IRS already has that alignment.


How are altitudes handled with airports near or above transition altitude?

I don't have an authoritative source for what the various regulatory agencies in the various regions use for publishing their transition altitudes, but your assumption is pretty close: airspace is planned so that no airport is "that close" to the transition level.

Some TAs are defined across large swaths, such as the US, Canadian, Australian TAs.  Some TAs are more broken up, even within political boundaries.  I believe Brazil (or at least one of the South American countries) has different TAs for different "terminal areas".

There has been on-again/off-again discussions in the European region of establishing a common TA, but (as of this date) that has not happened.  You will see fairly low TAs in low, flat areas like The Netherlands, but higher TAs in the mountainous regions.

Again, all of these TAs are "planned out" so that there is no danger of being too low while assigned to a flight level, and so that you are back on QNH well before you are on approach to an airport.


What sensors are required to fly RNAV 5 airways?

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.


While the documentation uses AGL when talking about class E airspace the chart legend uses the slightly different phraseology of

  above surface level

This avoids the ambiguity of, ground or ocean.

Interestingly the glossary uses both ground level and sea level but explicitly defines neither.


How much should it cost to get IFR-rated? What to look for?

The Part 141 flight school that I used to work at quoted around \$7,000 for their instrument package, which was 30 hours of dual flight, 20 hours of ground instruction, and 10 hours of PC-ATD simulator time. They were a Cessna Pilot Center using the old CPC King Schools course. It was a good course, and while numbers varied, I did have a couple of students who squeaked by right on the Part 141 course minimums. Other pilots added 5 to 10 hours more flight training into the mix.

In general, my gut says that it should cost an average pilot who has 100+ hours and flies semi-regularly between \$7,000 and \$9,000; probably closer to the low end than the high end, especially if the student does a bunch of self study at home on a flight simulator, possibly using VATSim as a simulated ATC.

As far as what to look for, I would recommend a Part 141 course just because the FAA is involved in the course standards, and instructor standardization is (supposed to be) part of the 141 criteria. It might be worth asking what their first-attempt pass rate is on checkrides, but that's not a meaningful long-term measure of the course's quality, just a short-term one.

You should find a course whose syllabus makes sense, includes simulator training and scenario-based flights, and make sure you work with an instructor you like. They can't be your best friend - they very well might need to give you some serious critique or cut a lesson short because things aren't going well - but you should be happy to spend a couple of hours a foot away from them in the cockpit.

I'm trying to track down the average hours to attain an instrument rating in the US; if I find it, I'll update my answer.


What regulatory load cases drive the structural design of aircraft?

The applicable US regulation is FAR 25.301-563. This obviously goes into a lot of detail about the different aspects that should be taken into account. I will try to condense the cases as much as possible, but many are conditional and relate to various other conditions. Many cases include some subjectivity as to what the FAA will require. Every certification is unique.

While the requirements are somewhat broken down into the general areas of the plane, it's impossible to say exactly which areas of the plane will be critically affected by a certain case. The impact depends on the design and configuration of the specific plane.

There are the upper level requirements:

  (a) The structure must be able to support limit loads without detrimental permanent deformation. At any load up to limit loads, the deformation may not interfere with safe operation.

  (b) The structure must be able to support ultimate loads without failure for at least 3 seconds...

  (e) The airplane must be designed to withstand any vibration and buffeting that might occur in any likely operating condition up to VD/MD, including stall and probable inadvertent excursions beyond the boundaries of the buffet onset envelope.

Definitions of various important values (which will have structural implications):

VA - Design maneuvering speed
VB - Design speed for max gust intensity
VC - Design cruising speed
VD - Design dive speed
VDD - Design drag device speeds
VF - Desgin flap speeds
VMC - Minimum control speed with critical engine inoperative
VS0 - Stall speed with landing flaps
VS1 - Stall speed, flaps retracted
CN - Normal force coefficient

All strength requirements must be met at all places within the maneuvering envelope, particularly A-I on the following V-n diagram:

Max pitch control deflection at VA (25.331)
Specified pitch control displacement (25.331)
1.5g pullup (25.335)
Discrete gust, vertical and lateral (25.341)

VC: varies linearly

+/- 56.0 ft/sec - sea level
+/- 44.0 ft/sec - 15000 feet
+/- 26.0 ft/sec - 50000 feet

VD: 0.5 times VC values

Continuous gust, vertical and lateral (25.341)
Fuel/oil loads from zero to maximum (25.343)

Addtional factors if there is a "structural reserve" of fuel considered

High lift devices (25.345)

If flaps are to be used for takeoff, approach, or landing, limit load factor of 2.0

+/- 25 ft/sec normal to flight path

Separate conditions, limit load factor of 1.0

Propeller slipstream from max continuous power at VF
Propeller slipstream from takeoff power at >= 1.4 times VF and max weight
Head-on gust of 25 ft/sec

If flaps are to be used en route:

Maneuver to positive limit load factor
Discrete vertical gusts

Maneuver load factor of 1.5 g at max takeoff weight, flaps in landing configuration

Roll maneuvering (25.349)

Airplane load factor 0 and 2/3 of positive maneuvering factor

Steady rolling velocities
Maximum angular acceleration
VA Sudden deflection of aileron to the stop
VC Aileron deflection for same roll rate as VA case
VD Aileron deflection for at least 1/3 of VA case

Unsymmetrical gusts

Yaw maneuvering (25.351), speeds from VMC to VD

Sudden max rudder deflection (conditional definition)
At that max deflection:

Yaw to overswing sideslip angle
Yaw to static equilibrium sideslip angle

Rudder suddenly returned to neutral

Engine torque (25.361)

Limit engine torque at takeoff power and prop speed, 75% limit loads of V-n condition A
Limit engine torque at max continuous power and prop speed, 100% limit loads at V-n condition A
For turboprops, previous conditions with prop control system malfunction
For turbine engines:

Torque from sudden engine stoppage
Torque from max engine acceleration

Engine/APU side loads (25.363)

Limit side load factor

Pressurized compartments (25.365)

All flight loads in addition to pressure differential 0 to max relief valve setting
External pressure distribution in flight
Landing loads combine with max pressure allowed at landing
Pressure including safety factor for high altitude aircraft (>= 45,000 feet)
Sudden release of pressure for critical components

Also affects bulkheads, floors, and partitions

Other emergency depressurizations

Engine failure unsymmetrical loads (25.367)

Failure of critical engine (for turboprops, also failure of drag limiting system)

Speeds from VMC to VD, due to fuel flow interruption
Speeds from VMC to VC, due to mechanical failure

Includes pilot corrective action

Gyroscopic loads (25.371)

Must be considered at max appropriate RPM for certain other cases

Speed control devices (25.373)

Symmetrical and yaw maneuvers and gust conditions, each setting with max speed

If automatic/load limiting features, include corresponding speeds/positions

Control sufrace/system loads (25.391)

Considering other limit load cases

Loads parallel to hinge line
Pilot effort effects
Trim tab effects
Ground gust conditions
Unsymmetrical loads
Auxiliary aero surfaces

Landing load condtions (25.473)

Descent at 10 fps, design landing weight
Descent at 6 fps, design takeoff weight
Both cases should be considered in the following cases:

Level landing
Tail-down landing
One-gear landing
Side loads

Rebound landing
Ground handling
Taxi, takeoff, landing roll
Braked roll
Turning
Tail wheel yaw
Nose wheel yaw/steering
Pivoting
Reversed braking
Towing loads
Unsymmetrical ground loads

Seaplanes (25.521)

Step, bow, stern landings
Unsymmetrical landing
Hull/main float bottom pressures
Auxiliary float loads
Seawing loads

Emergency landing (25.561)

Occupants must have reasonable chance of escaping serious injury in minor crash landing if occupant experiences the following forces:

Upward 3.0g
Forward 9.0g
Sideward 3.0g on airframe, 4.0g on seats
Downward 6.0g
Rearward 1.5g

Large masses should not:

Cause injury to occupants
Penetrate fuel tanks
Block escape

Protection of occupants in dynamic conditions
Ditching strength

Fatigue and damage tolerance (25.571)

Residual strength with certain failed structure:

Limit symmetrical maneuvers
Limit gust conditions
Limit rolling conditions
Limit yaw conditions
Pressure differentials
Limit ground loads

Safe-life evaluation, if failure conditions are not practical
Sonic fatigue
Safe flight with damage from:

4 pound bird at VC at sea level and 0.85VC at 8,000 feet
Uncontained fan blade impact
Uncontained engine failure
Uncontained high-energy rotating machinery failure


Is this a reasonable way of thinking about an auto-rotation?

First off, auto-rotation is a general term for all helicopters and the process varies between different air-crafts and the cause of the auto-rotation. For example, in auto-rotation due to loss of tail rotor thrust you can (and should) descend with some collective power and reduce descent rate. Also, in such auto-rotation there is also a mandatory step 2.5 - cut the power. Otherwise, the craft will rotate out of control in the quick stop.

Also various helicopter types behave differently while auto-rotating such as bigger helicopters start flaring at least 125 feet above ground.

As for the steps described - I'll agree that they break down nicely the process into other familiar processes, even though obviously not entirely accurate. I think the main difference is that flaring from altitude in a 1500-3000 ft/second descend and approaching a quick stop usually with speed forward rather than downward - require significantly different flight technique and practice.


Can coaxial rotors be mounted on a piston engine like the Lycoming O-320?

Stan Hiller's earliest helo designs were coaxial and used relatively small 4-cylinder aircraft engines to drive the coax transmission, so it is indeed possible to power a small coaxial helicopter with a relatively small piston engine.
Hiller also found that autorotating a coax main rotor blade setup was difficult and so his later designs used a more conventional single main rotor blade and a tail rotor.


What is the average total flight time to get a private pilot license in SF bayarea, CA?

The SF Bay Area is more complex than some other airspaces. This does not mean that it will require more time, you just need to prepare for it.

I live on the SF peninsula and while I do not have a broad survey, I trained at the same time as two friends so I have three datapoints. I got my license with 41hrs training, one friend was under 50hrs and the other somewhere in the 60s. I doubt this is above the national average. This was some years ago, but the sky was already full. I guess now it is more full.

I picked my own instructor and did not let him teach me anything that I could learn from a book or on my own. We had every session topic planned ahead of time and I made sure I was well prepared. Far more important than where you train is your own attitude and diligence in preparation.


What is the difference between Mechanical Engineer and Aerospace Engineer?

If you want to work on the landing gear or passenger seats, a mechanical engineering education is the best qualification.
If, however, you want to work on control surfaces or fairings, an aerospace engineering education is better suited.
While both teach similar basics, the aerospace education is much heavier on fluid mechanics and lightweight design. Having studied aerospace engineering in Germany, I was shocked to learn that master students in Aero/Astro at MIT had no idea how to design a screw connection. Therefore, much depends on the country and its ways of teaching. In the US you will get an excellent education in one narrow field at the cost of breadth. In other countries your education might take longer and give you less expertise in one field but will cover the fundamentals much better.
In general, at university you will be taught how to learn. You will learn the basic stuff which will enable you to read special literature and you will learn where and how to locate resources that help you along. This will be the same in both branches and it depends on you to round out your knowledge yourself.
To quote from an earlier answer:
Take the example of Ed Swearingen: He never went to engineering school, but spent years working with airplanes, gradually moving from handling to repair to improving them. In the end, he was a successful self-employed consultant who helped with a number of airplane designs and created some of his own designs, too.
So here is what I propose to do:

Hang out at a local airport (ideally one with lots of hardware passing through the local repair shops).
Don't shy from getting your hands dirty and from asking questions until you are satisfied with the answer.
Try to find experienced engineers and work closely with them.

Do that for 10 years and you will be hard to beat as an aircraft designer. If you happen to attend University in Germany, be sure to become a member of one of their Akafliegs - that is the best start into an aviation engineering education.
It also helps to build and fly model airplanes. Models can give you valuable lessons in aerodynamics and flight mechanics.


How does a gyro compass indicate true heading?

The directional gyro (DG) does not know about heading. Its gyroscope will hold its position (e.g. the heading you set from the magnetic compass) in space. The plane is turning "around it", but DG is holding its position, so you can read the heading from the scale fixed to the airplane while the gyroscope holds its position in space. Only friction and other forces (acceleration forced upon the aircraft) force the gyroscope to wander from its position.
E.g. the gyro shows a magnetic heading if set using a magnetic compass and it shows a true heading if set using a GPS (or some map feature like a road with a heading visible on a map).


Are the A400M propellers rotating in the wrong way in "Mission Impossible: Rogue Nation"?

I have seen the movie, but it failed to occupy my memory... anyway:
Yes, the A400M propellers are contra rotating, and more specifically DBE as you described. I am not 100% sure, but I'm willing to bet all A400M's ever produced have this configuration.
So if the propellers seem to rotate in the "wrong direction" there are two possible causes:

it is an effect caused by camera shutter speed in relation to propeller rpm. This may make the propellers seem to rotate in ever which way, or even stay still, as you can see in this youtube video.
the whole scene is cgi, so there actually is no real plane involved. My money is on this...

The propeller blade angle in A400M, as in any larger modern propeller aircraft is adjustable.
This type of propellers, or  the governor adjusting the blade angle (pitch) of the propeller to be precise, are typically constructed in such a way, that when the engines are off, there is no oil pressure, and the blades are set in feathered position. So when the engine starts up they will be feathered, and when the engines are shut down, the propellers will adjust to feather. This is basically a safety feature to minimize drag in engine failure situation. To prevent thrust from forming during and immediately after start, the propeller adjustment is set to feather by pilot, this prevents the propeller angle change as oil pressure in the system rises and governor would otherwise start to adjust the blade. As you commented below, it is totally possible the scene is played in reverse, as the blade position would be the same in both shut down and start.
The picture you posted in the question shows propellers in feathered position, so they are not producing thrust. If this is a screen capture from a scene where the plane is taking off, it most definitely is cgi. With propellers feathered, the plane will not be gaining speed, and definitely not taking off.


Could gliders be a clean, practical alternative to other forms of transport?

There's one thing that will forever prevent an unpowered aircraft from entering commercial passenger service: the inability to make a second attempt at a landing.
Airliners, with all their instrumentation, very experienced pilots, and such don't make go-arounds frequently -- but especially during weather, they do make go-arounds.  A passenger sailplane absolutely can't make a go-around, so if it gets crossed up due to a crosswind gust low and slow, instead of advancing throttle and climbing out, all the pilot(s) can do is pick where and how hard to crash.
This complete lack of second chances, as much as any of the other objections raised in other answers, will ensure that unpowered aircraft will never see commercial service.  It can also lead to "landing out" where you wind up having to retrieve your passenger glider from a farmer's field, freeway, or worse, along with its payload and crew.
The other big issue is how to launch these immense sailplanes -- with a common sport glider or competition sailplane, you're towed into the air by either another airplane, a winch, or occasionally a car or truck.  The winch that could launch something the size of a 737 high enough to fly off in search of its first lift would be so big and expensive it would severely limit the number of airports that could service such craft.  The airplane that could do it would be at least as big as that 737.


Transport Category airplanes (e.g., commercial jets) have performance limitations that are different when operating on one engine versus two engines.

Regulatory requirements for commercial operations require that a flight in a two engine transport category airplane be planned to be successfully flown if one of the two engines fail.

The issues are fairly complicated, but the airplane must be configured and operated considering all existing circumstances (airport/runway/weight, etc.) so that if one of the two engines fails at the most critical time the flight can be continued to a safe landing at the original departure airport, the planned destination, or a suitable alternate airport.

For example, if you are departing Chicago in a B757 and the weather is so bad that although takeoff is allowed, landings are not, and an engine failure occurs (just as the aircraft is lifting off the runway) the capability of the airplane must allow an obstacle free climb, enroute and approach to a pre-planned alternate airport on a single engine.

Another example, if you are halfway between San Francisco and Hawaii in a B767 and an engine failure occurs, the airplane must be able to return to SFO or go on to some place in Hawaii on the remaining engine. (the technical components are a bit more detailed than my simple explanation, but the outcome is the same)

Most trans-ocean flights today are done in two engine transport category airplanes (e.g. B767/777 or similar) and the design criteria (see FAR Part 25) are such that continued operation after a single engine failure, if properly considered in the performance planning for the flight (which needs to happen), ensures a safe continuation to a suitable airport.

Of course, the single engine operational profile will be different (altitude, speed, etc.)


How was the 'bump' removed from the Airbus P2F?

The A330 P2F features a fully-powered Cargo Loading System (CLS) that is perfectly capable of loading/unloading even the heaviest pallets even with the aircraft "on the tilt". Therefore, no 'tilt remedy' is required.

Flight Global, 15 February, 2012:

  The P2F version will retain the passenger aircraft's geometry and incorporate a powered cargo loading system to enable pallets to be moved "uphill" on the main cargo deck.


How to calculate power required to drive an isolated fan of a TurboFan engine?

https://en.wikipedia.org/wiki/General_Electric_GE90:

  The LM9000 is an aeroderivative gas turbine available in two options; the LM9000 without water augmentation outputting 66 MW (89,000 hp) at a 42.4% efficiency before cogeneration, and the LM9000 with water augmentation outputting 75 MW (101,000 hp) at a 42.7% efficiency before cogeneration.

An aeroderivative gas turbine is basically the same turbine with a driveshaft connected to the low pressure stage instead of the fan. So its shaft output power would be roughly equivalent to the power that goes to the fan in the turbofan version.

The 66MW (the aero version does not use water augmentation) figure corresponds to max continuous power or a bit less. The take-off power is even more.


Why do older airplanes have the wing curved upward like a 787?

You are confusing 2 concepts here, dihedral and winglets. What you are showing in the picture is dihedral, which is not a curvature but an angle positive from the horizontal. This angle helps improve lateral (roll) stability in flight. This is nothing new, almost all commercial jets have dihedral. Winglets improve efficiency. A Boeing 787 has both.


Can thrust be selected manually in a plane with autothrust? If yes, how?

You are correct that different planes operate slightly differently, but they are mostly pretty similar. Just as with the autopilot, the autothrust can be disconnected and the airplane can be controlled manually.

Below is an image of the Mode Control Panel on the 737 NG, which is located just below the windshield. The section that controls autothrust is located towards the left side. To disconnect the autothrust, you can just flip the "arm" switch to off.

Source

Below is an image of a 737 NG cockpit, with the thrust levers located in the middle. With autothrust on, the levers are moved by the autoflight system to correspond to the autothrust setting. The levers can be moved by the pilots but the system will try to drive them back to the commanded position. Once autothrust is turned off, the system no longer moves the levers and they can be controlled by the pilot manually.

Source

Airbus planes such as the A320 are a bit different. The levers do not move to match the autothrust setting, but autothrust can still be turned off to use the levers manually. The levers can also be pushed forward past the "climb" detent, which overrides autothrust to choose higher thrust settings.


Is there any disadvantage to slipping as a way to lose altitude?

To address your questions: First, slips are perfectly reasonable for controlling descents. In some aircraft, for example, many Cessna 172s, are placarded warning against extended slips with full flaps.  In the 172 case, there may be some buffeting.

Years ago, slips were emphasized more than they are today. Of course there were more primary aircraft without flaps then.  So today the vast majority of primary trainers have flaps, and with time instructors have simply avoided emphasizing slips as much.  Consequently, the forward slip becomes more of a saving maneuver than a routine maneuver.

Your mileage will vary. There are some instructors who put more emphasis on slips for energy management. Most instructors will emphasize them for more "urgent" maneuvers like making a field with a simulated engine out.

Addendum #1
Being the best pilot you can means constantly developing skill and adding new tools to your bag.  Slips are normally covered when doing simulated engine outs.  I also cover them first with pre-solo students when we cover other emergencies such as flap failure (asymmetric flap extension) or electrical failures with electric flaps. Slips are also helpful when there is a cabin fire, and help clear smoke faster (it's never really fast enough) in planes with bilateral windows.

Addendum #2
Slips have an advantage over flaps, in a temporal sense. You can slip, and then take it out, then put it back in.  As much or as little as you want.  Since flap changes normally mean trim changes, and in the case of the 172 there is a flap motor limiting application and removal rates, the same cannot be said for using flaps. As an example, landing during very turbulent and gusty conditions, I might only use partial flaps, and use slips for glide path management, particularly if going to some mountain top strip with all kinds of up and down drafts influencing the path. Just another thought, for someone as they consider enhancing their proficiency with slips.


For length in aircraft design, and in weight and balance manuals, what measurement unit does Airbus use?

Structures are soft metric. Airbus uses inch hardware so some measurements make sense in inches but are drawn with an ugly mm number. The coordinate system is in metric.

The rest of the aircraft is hard metric. For example, MTOW and fuel capacity is in a nice number of kg.

Documentation and instrumentation is localized according to the operator. Mass, as in fuel, can be switched between kg and lbs on ECAM, and all the manuals and W&B will follow.

There's a few units that aren't localized, most notably pressure is always in PSI and engine oil is always given in quarts (probably since it comes in quart cans).


If an A/C have Radio failure ( sqk 7600 ) How the ATC will give him instruction or how will he land?

This is a question with many answers, depending on the conditions of the flight. Let me limit myself to private recreational aviation (what the FAA calls Part 91) in a single-engined propeller aircraft.

If you are flying Visual Flight Rules (VFR), there are some airspaces you need to stay out of. For instance, US and Canadian Class B and C airspaces require radio communication. You won't be able to land at airports in such airspaces without some other arrangements.

You can give a signal that you are lacking radio communication. Squawking 7600 on your transponder is one way. Flying a triangular pattern, which might be visible to ATC on radar, is another way. I have sometimes used my cell phone to call ATC's phone number.

Control towers in the US and Canada might well have "light guns": bright spotlights which the controller can point at an aircraft, and colour red or green, and shine continuous or blinking light. A continuous green light from tower to an aircraft preparing to land means that aircraft is cleared to land.

If you are flying Instrument Flight Rules (IFR), there are specific procedures to follow if you are unable to communicate with ATC.  Frequently they boil down to holding for a few minutes, then continuing on your flight planned route.

Remember that some aircraft have no electrical system, let alone radios. They fly, take off, and land just fine. There are many airfields with no control towers. There is uncontrolled airspace in which to fly. In these cases, pilots maintain safety by seeing and avoiding other aircraft. Pilots fly traffic patterns before landing, and sequence themselves cooperatively.  Lots of aviation works just fine without radio communication between pilots and ATC.


Is there any airline company owner who also works as a pilot?

Yes, Niki Lauda, former Formula 1 pilot and ATPL holder, founded Lauda Air, for which he also worked as PIC.

  Lauda returned to running his airline, Lauda Air, on his second Formula One retirement in 1985. During his time as airline manager, he was appointed consultant at Ferrari as part of an effort by Montezemolo to rejuvenate the team. After selling his Lauda Air shares to majority partner Austrian Airlines in 1999, he managed the Jaguar Formula One racing team from 2001 to 2002. In late 2003, he started a new airline, Niki. Lauda holds a commercial pilot's licence and from time to time acted as a captain on the flights of his airline. Lauda Air ceased operations in July 2013.


How do I find the three factors of the hinge moment coefficient?

First download and install xfoil from this site
http://web.mit.edu/drela/Public/web/xfoil/
if you use ubuntu - sudo apt-get install xfoil

user manual and typical session inputs are also there. please refer to them as you haven't used it before.

And there are many video tutorials in youtube.
[Link removed I cant put more than 2 links here- Just search xfoil tutorial in youtube]

For this specific case;

open your airfoil in xfoil
xfoil name.dat
Set the flap as you want
enter GDES and FLAP and follow the prompts.
Type these commands in sequence
exec
[enter]
pane
Enter OPER menu and set the RE number
oper
visc 1e6 (1 million Re for this case)
type  these commands in sequence
hinc     (hinge moment togle enabled)
    pacc     (accumilate polar - give a file name)
aseq 0 10 0.5 ( sequence of alfa to run - here from 0 to 10 in 0.5 increase)
Open the resulting file. which has two coloums along with other parameters to show alfa and hinge moment. (first and sixth)

plot it or linearize it or whatever you like to do to find the above parameters.

PS: Another suggestion is XFLR5. It is same as XFOIL but with GUI. you may find it easier.


What's the meaning of "straight and level"?

Is this use of "straight and level" correct? What is the definition of
  straight and level, if any, regarding heading, attitude, speed,
  altitude?

In the airplane flying handbook the FAA defines straight and level flight as

  Straight-and-level flight is flight in which heading and altitude are
  constantly maintained.

My understanding and the instruction I have received has always lead me to understand that Straight-and-Level is independent of Attitude and Speed. However to maintain straight and level flight at a given speed you will have to put the aircraft in a given attitude. Generally speaking at lower speeds aircrafts have a higher nose up attitude to maintain level flight and a more nose down attitude at high speeds to maintain level flight but this can vary by design and wing mounting.

In this case I would say it was used a bit improperly. The statement should have been more along the lines of "the pilot should have maintained his heading and conducted a straight ahead emergency landing. You can read more on why that is here.

You can refer to the full NTSB report of the accident here for all the details.


How far away from a wing's surface does the air stream remain unaffected?

A precise answer would be: Only outside of the supersonic shock cone. In subsonic flow the change has unlimited range, but dies down with the inverse of the distance.

A mathematical description is possible with the Biot-Savart law. It was first formulated for calculating the magnetic field induced by a current, but can equally well be applied to aerodynamics.

Now it depends on how much error you still accept. If you need the interference-free distance between two biplane wings, express that distance in multiples of the wingspan - that is how it scales. A few wingspans of vertical separation should be enough to make the interference between wings negligible. In flow direction the distance must be much larger: Munk's displacement law postulates that in inviscid aerodynamics the distance in flow direction between two wings makes no difference. In reality, air traffic control requires a separation of up to 8 nautical miles between heavy airplanes for the turbulence to die down or be washed away by wind.


Why do aviation careers have age limits?

I'm no expert, but I can think of two general reasons: risk of incapacitation, and general physical limitations (reaction speed, stamina, the ability to maintain concentration for extended periods etc.). The age 65 limit only applies to part 121 ATP pilots, by the way; you can still be a commercial or private pilot for as long as you can keep getting a valid medical.

Older people are simply at greater risk of heart attacks and many other medical conditions, and they're also much more likely to require medication that may not be approved by the FAA or other national authorities. Of course that doesn't mean that every older pilot is the same but I guess that the FAA has decided that since the risks increase with age, at some point they become unacceptable. To understand the specific reasons for that decision you would probably need to dig up the original NPRM or transcripts of the public debate/hearings, but I have no idea if that's possible or not.

Then the other aspect is general physical and mental condition. They both deteriorate with age, and the NTSB sometimes mentions that as a potential factor in accidents:

  On the day of the accident, the pilot had flown several formation
  sorties. The day was hot, and the formation activities were demanding.
  The accident flight was relatively long, and the co-owner of the
  airplane guessed it was about 45 minutes long. Most formation sorties
  were 30 minutes or less. The accident pilot was in his early 70s and
  was by far the oldest member of the flight. Due to the pilot’s age,
  the demanding schedule, and the length of the formation sorties,
  fatigue could have been a factor, although it could not be
  conclusively determined.

Of course, any discussion like this is a generalization and I'm sure it's easy to find individual 70-year old pilots or controllers who are 'sharper' than younger ones (after all, experience counts for a lot too). But there's no escaping the overall pattern that older people in general are more prone to medical issues and less physically/mentally capable than younger ones, and at least one US court has ruled that there's no effective way to determine individual risk so a general rule is not discriminatory:

  The court also concluded that ExxonMobil had established, through the
  testimony of several medical experts, that the risk of sudden
  incapacitation in flight significantly increased with age, and that
  there are no adequate means of individually testing each pilot to
  determine whether a pilot was at risk to suffer such an
  incapacitation.


What aircraft equipment produced the three recordings of unidentified aerial phenomenon released by the US Pentagon in 2020? What does black signify?

The video was taken from an F/A-18 Super Hornet. This narrows down the recording equipment to either the ATFLIR or LITENING targeting pods. These pods perform essentially the same function. These pods can provide infrared imagery like that seen in the clip. Both pods are used on American military aircraft. I can't speak to the gray levels because I'm not familiar with the systems themselves, unfortunately. Hope this helps.


Are same-era military aircraft cockpits designed to be familiar to transitioning pilots?

Unless there is regulation enforcing certain aspects (e.g. as in the automotive sector), it is practicability would be the most probable cause leading to similar-ish cockpit designs.

Another reason would be convention, e.g. prior to the introduction of the side-stick, the center-stick was the way to do it.

Also, ergonomics is a very strong driver. During the landing approach, you wouldn't want to take your eyes far away from the windscreen to check altitude, speed and rate of sinking. Thus, these instruments are found in similar locations in most airplanes.


Did Airbus bring back LAF (Load Alleviation Function) on A320s with Sharklets?

LAF is a function that alleviates load on wings roots, but was causing early wear to the actuators and to ailerons and spoilers hinges.

No LAF is not available on latest A320’s


How does a taildragger take off? Does it rotate?

There are three different schools of thought there, and one can be selected based on the capabilities and characteristics of the tailwheel aircraft you are flying.

Fly the tail off the ground:  After achieving full power during the start of the takeoff roll, apply forward stick pressure until the tail lifts off and the aircraft assumes a level attitude on the main gear, then hold that pitch attitude for the rest of the takeoff roll.  This technique can be done in most underpowered taildraggers and is useful for short field takeoffs and landings as it minimizes parasite drag and flat plate area during the takeoff roll.  It will require a healthy bootful of right rudder to counter the change in P-Factor as well as gyroscopic precession from the propeller.

Let the tail fly off the ground:  After applying full power with full aft stick deflection, neutralize pitch input to the stick and continue the takeoff roll.  As speed builds, the tail will lift off the ground naturally.  This is the recommended technique when flying high performance tailwheel planes like WWII fighters, etc.  where good rudder authority is needed to counter P-Factor changes and precession.

3-point takeoff:  Apply full power and hold full aft stick as well as additional right rudder to counter for P-Factor.  As speed builds in the takeoff roll, gradually ease up on stick pressure but hold just enough to keep the tailwheel on the runway.  As the airplane lifts off the runway care must be taken to quickly adjust elevator pressure to hold a gradual climb and prevent rapid pitch up and stall.
I once flew an MX2 with an oversized prop offering only about two inches of ground clearance resting on the mains in level attitude.  We were taught to only do 3-point takeoffs and landings and specifically warned not to attempt anything else to prevent a propstrike.


Partial Serial numbers on Military Aircraft - what combination is unique?

I can only address the AF system, but I assume the other services systems are similar.  The AF serial numbers for vehicles (the system applies to all vehicles including ground vehicles) are made up of the letters "AF" followed by the contracted delivery year (2 digits) followed by a sequential number that restarts at 1 every year.  The pic below is of an F-22 assigned to the 1st Fighter Wing (the FF code).

So this aircraft was purchased in 2008. The sequence number is 161, and would have been assigned from a block of numbers provided in the contract.  The contracting officer was given the block by the office that keeps the master list.

It's worth noting that the paperwork and the data plate is where it has to be complete. What's painted on the a/c is just used for the convenience of the crews. For some a/c such as KC-135's and B-52's whose production run was less than 10 years, they often just us the last digit of the year and the sequence number.  Most of the tankers I see have a 5 digit number that starts with 2, for 1962.

In a fighter squadron, most 'local' documentation just refers to the last 3 digits.  example: 061 and 813 were how we referenced two of the F-16s in the test squadron.


How does one develop artificial stabilization for aircraft uncontrollable without it?

Most modern high agility ariplanes (such as fighter jets) are unstable in the sense that (among other things) their center of gravity (nearly) coinsides with their center of lift (i.e. they are wildly out of balance). The benefits include the ability of the airplane to react to control inputs nearly instantaneously. That the design will be unstable can be determined at a very early stage in the process (during the 'sketch' phase, really). Given a fast enough control system, nearly anything can be controlled (and modeled) so to answer your second question, to design a control system, all one needs to know is how complicated the system is (the order of the system) and how fast it should be. The first question can be answered based on very general principles (most aircraft can be modeled by a fourth order system). The second question is also easy to estimate (100 Hz is usually enough, don't ask me how I know this).

Of course, tricky regimes (supersonic, transonic, supercritical angle of attack, etc.) might require some time in the tunnel but these are to determine some parameters of the general model that has been decided on at the design stage.

That the system works is usually not in question before the plane is tested. Whether a human pilot will find it controllable is another matter. This is why the design of a modern high agility aircraft is done in parallel with a simulator design to see how the pilot would react. The simulator of course, is based on the same model that the actual design is (and is constantly modified as more experimental data becomes known).

Finally, even if the airplane is well designed, and everything works, the certification stage is where most accidents happen. For example, to test the single engine performance of a twin engine airplane the tests must be carried out at near sea level pressure, quite low to the ground. Not much time to react when the plane gets too slow.

A good book to read about these issues is Aircraft design: a conceptual approach by D. Raymer. You will quickly discover that one can practically calculate the look of the plane (controls location, high-wing, low-wing, where the engines go, etc.) based on its mission.


Should I monitor the emergency frequency (121.5 Mhz) at all times?

Airlines routinely set comm 2 to 121.5 when they don't need it for talking to company or getting ATIS.  But for a light aircraft pilot in busy airspace, the second comm is a really useful tool for reducing workload by being able to preset frequencies, and dedicating the second comm to 121.5 all the time takes that feature away, for the very small chance that you're hear someone's ELT go off or broadcast an emergency that will be heard by ATC anyway.  Very few GA pilots monitor guard frequency regularly.

On the other hand, if you are flying over a remote area, it's not a bad idea at all and you could save someone that crashed with a non-406 ELT.


What are the reasons to evolve from trim tabs to moving the entire surface (e.g. stabilizer)?

Trim is used to zero the stick forces at the desired flight condition, and with the small, slow early airplanes, an adjustable spring somewhere along the control cables would do. When speed increased, trim tabs were introduced, because their trim force goes up and down with dynamic pressure, whereas the spring would always create the same force. This would require re-adjustment with every speed change.

With the increasing size and speed of airplanes, manual control required ever more complicated means of force reduction (Flettner tabs, spring tabs), and the relative chord length of all moving surfaces shrank to allow for more control with less force. The moment around the hinge of a control surface increases with the square of the chord, but the lift change for a given deflection angle increases only with the square root of the chord.

In parallel, wing loadings increased, which required high-lift devices to keep take-off and landing speeds down. These add a lot of lift in the rear part of the wing, creating a strong nose-down moment, and now a simple control deflection would not suffice to trim the airplane. The reduced chord length meant that high deflection angles would have been required for trim, reaching far into the region of deflection angles with declining effectiveness. That is when adjustable stabilizers came up: The trim change with all configurations was simply too big to be covered by the elevator alone.

Transsonic flight was next, and here the adjustable tail incidence is crucial to trim the aircraft trough the transition from subsonic to supersonic flight. A contour break from a deflected elevator could cause shocks which could produce elevator reversal. The dynamic pressures of jet flight put an end to manual control - the last, famous examples were the Canberra or the Dash-8 (Boeing 707 prototype). Now hydraulic actuators were used, but still it makes sense to use aerodynamic means to reduce control forces, because the size and power requirements of the actuators can be reduced with clever hinge moment reduction. The trim tabs were initially moved by cables, but soon they used electric actuators.

Since rudder and ailerons are not affected when the high-lift devices (Fowler flaps, slotted flaps) are deployed, they still use simple trim tabs. Newest developments are electric control surface actuators which can help to save mass and avoid the messy hydraulics. The RQ-4 uses electric actuators because the hydraulic fluid would have to be pumped continuously through the lines in order to keep it warm enough at the high operating altitude. Only the landing gear still uses hydraulics for retraction.


How can I find which engines are used on the different A320 weight variants?

Each section will list the specific models that it applies to. For example, in the Maximum Certified Masses section for the A320 (1.III.13), you'll see the first section applies to the A320-211/A320-212/A320-231, and it lists the 19 variants of these models.

Next you consult the engines section (1.III.5), which will tell you, for example:
A320-211 - Two CFMI CFM 56-5A1 jet engines (MOD 20141), or CFM 56-5A1/F jet engines (MOD 23755).


Why aren't leading edge root extensions used on airliners?

Leading edge extensions like slats are used in airliners. Most of these are controlled ones, so as to improve low speed characteristics.

By Adrian Pingstone (Arpingstone) - Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=4761104

The dog tooth extensions were used in some older airliners like the Ilyushin Il-62 and the Vickers Super VC-10, he reason being the requirement to reduce drag.

By Sergey Lysenko - File:Air-to-air with a Russian Air Force Ilyushin Il-62M.jpg on Wikimedia Commons, originally published on http://russianplanes.net/id164205, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=40618026

The other leading edge extensions like LERX (and even dog tooth) are mostly found in high performance combat aircraft as these increase the stall angle and improve maneuverability; these are not the typical concerns in the commercial airliners. In airliners, vortex generators are used for preventing separation at low speed (high aoa).


What does the statement painted on this P-51 mean?

They are instructions for a compatible fuel substitute for 100/150 octane fuel per Technical Order 06-5-1 if AvGas is unavailable to the service crews in an emergency.


There’s no “throttle down” per se in jet engines.  However engine thrust does not vary linearly with spool speed and most engines operate within the 70-100% of maximum speed, with most of the thrust range between 85-100%.

In addition, there is a lag time for the engine to “spool up” from an idle power setting to effective thrust output which has to be taken into account during operation.  This is one reason that most jet aircraft have speed brakes.  They allow the pilot to maintain a higher thrust setting which allows for quicker response time to thrust lever inputs for a given airspeed at the expense of more parasite drag and fuel consumption.  Critical areas of flight such as VFR patterns, instrument approaches, short final, and go arounds, where near immediate thrust response is required makes this a useful flying technique in jets.


What is the significance of 104% for throttle power and rotor speed?

This happens when the maximum output was changed after design.

100% is simply a reference to a certain value. In the space shuttle's case, the engine output was increased after the initial design. Instead of updating the engine value everywhere, they decided to simply keep the initial value constant.

The same goes for N1 in turbo engines. 100% N1 is simply referencing a certain datum defined by the manufacturer. Going over 100% is not necessarily unsafe.


Does lift generation create a vacuum over an airfoil?

I think this is simply a terminology issue.

There is no vacuum in the physical sense on the upper surface of an airfoil. There is an area of low pressure, though, which in certain context is also called a vacuum.

A great example for this linguistic imprecision is my vacuum cleaner, inside of which there is no vacuum in its physical sense by far, but clearly it sports considerably lower pressure than the atmosphere in the rest of my living room.


“, remain VFR” — may I enter Class C airspace?

Yes, you were allowed to enter the class C in that case, but you weren't cleared to do it because no clearance is needed to operate in class C, just communication with ATC. The AIM 3-2-4 has the best explanation of this (see also the basic regulation in 14 CFR 91.130):

  If the controller responds to a radio call with, “(air craft callsign) standby,” radio communications have been established and the
  pilot can enter the Class C airspace.
  If workload or traffic  conditions prevent immediate provision of  Class C services, the controller will inform the pilot to remain
  outside the Class C airspace until conditions permit the services to
  be provided.
  It is important to understand that if the controller responds to  the initial radio call without  using the  aircraft identification,
  radio communications have not been established and the pilot may not
  enter the Class C airspace.

So if the controller used your callsign then you've established radio communications and you can enter. This also applies to class D but not to class B, where you need an actual clearance to enter. (This is a classic exam question/scenario, by the way.) As @rbp suggested, the instruction to "maintain VFR" was probably the controller's way of letting you know up front that he was too busy to give you a pop-up IFR clearance or whatever else you might have wanted. (Maintain is an official ATC term, remain is not, although the controller may still have used it accidentally.)

As for flying into busy airspace, it's up to you as PIC to determine what's safe and what isn't. If you had the HSV ATIS (so you can anticipate traffic patterns), were squawking 1200, were in communication with ATC and were keeping your eyes outside the cockpit then there's not too much more you can do (you could turn on all your lights if you think you need to make yourself more visible). But, if you ever feel unsafe or uncomfortable in any flight situation then you shouldn't hesitate to take action - like staying clear of the class C for a few minutes - if you do feel it's necessary, that's simply part of gaining ADM experience.


What are the reasons why we do not have VTOL commercial airliners?

Commercial airliners are significantly larger, and therefore heavier, than aircraft with use V/STOL. Because of that, it would take more fuel and engine power to run that airplane, driving up the cost of running it. There are also many other airframe stress and balance factors that come into play when doing VTOL.
If you are including turbo-prop airliners in your definition of airliners, they could do V/STOL with a configuration like the V-22 Osprey because they are small enough.


At what point does the throttle control RPM on a constant speed prop?

What happens is when you're on final and you move the prop to MAX RPM, the prop governor moves the blades finer until the RPM is at red line, then governs RPM there by adjusting blade angle as required.  As you reduce throttle, the governor moves the blades finer and finer trying to keep the RPM that has been set (maximum or redline RPM in this case).

As throttle is further reduced the blades hit the fine pitch limits of the propeller hub and can't go any finer, so the governor can't unload the engine any more to keep the RPM up.  As you continue to reduce throttle you basically now have a fixed pitch prop with very finely pitched blades and down comes the RPM.  As long as throttle is below the level that will speed the prop up above redline (or whatever the governor setting is), RPM will vary directly with throttle, like a fixed pitch prop engine.

Add power and RPM rises until it hits the governor setting, then the governor starts to coarsen pitch to load up the engine, to keep the RPM at the setting.

The point at which the prop "comes off the governor" is determined by the pitch limits of the blades within the hub.  The part the mechanic can adjust is the RPM set by the governor when the prop lever is at MAX, which is normally redline RPM +/-.


Are the captain's and first officer's brake pedals always mechanically linked?

It is cost effective for one. With an unlinked system, you now need to resolve disagreement between inputs some other way. Software has its own challenges. It's also instant, non-verbal communication between captain and first officer. A pedal moves and the other's pedal has already moved. No confusion or pilot effort to communicate it.


How do the flight decks work in unison on the Stratolaunch?

On Stratolaunch Systems, there will only be one cockpit as mentioned here:

  The pilot, co-pilot and flight engineer will be in the right fuselage
  cockpit, while the left fuselage one is empty and unpressurized.

News can be misleading. This article's title says that each fuselage has its own cockpit but later, it clarifies:

  The left-hand fuselage has what looks like a cockpit with windows to
  onlookers, but the section is in fact empty and unpressurised.

It does look like there both fuselages have cockpits.

Image Source


What was used instead of the failed engine when ferrying the Air France Flight 66 aircraft back?

Here's another article from Oct 15th. They flew out a spare A380 engine. As of the 15th, it wasn't clear yet if this engine will be connected and running during the flight, or if it'll just be there to complete the airframe and act as a counterweight.

Leaving the broken engine in place would do more damage to the engine, complicating the investigation.

Pieces breaking off from the engine may have damaged the wing, the pylon or the connectors on the pylon (power, fuel, electronics etc.), they need to inspect for damage before deciding if the spare engine can be connected and running.

The plane will be empty for the recovery flight, so there's some margin to fly on 3 engines. They have to account for the possibility of an engine failure, leaving 2 operational engines, so the flight is planned to ETOPS rules.
There's a procedure to reduce the effects of asymmetric thrust.

If the engine is left off and windmilling, it needs lubrication, this may limit the length of the flight.


What is pressurization influence (if any) on maximum G load an airliner can withstand?

For skins in the upper half of the fuselage in bending tension, the pressure acting on the skin is just adding to the tension stress on the skin from fuselage bending, so it doesn't help there.  For skins and stringers in areas of the fuselage where loads are in compression, the pressure if anything will displace the structure (bulge it out) in effect "bending the column" and making it less able to take compression loads (maybe only a few thousandths of an inch, but still something).  On the other hand, the pressure will tend to help keep the tube circular, so it will probably tend to reduce stress on circular frames that are resisting the tube from collapsing in bending.

The most stressed area in the fuselage is compression stress at the bottom just behind the wing, (next to the pivot of the seesaw you might say) and there is usually a heavy compression beam structure down that that is not helped or hindered much by how much pressure is acting on the pressure hull.

Overall, none of this is taken into account in the structural design and there normally aren't any specific structural restrictions between pressurized and unpressurized flight as far as G loads go.  For example, you won't see different published G limits, or Turbulent Air Penetration Speeds, or Maneuvering Speeds, for pressurized and unpressurized conditions.