Can composite materials be used on super-sonic aircraft?

Sure. Almost all the modern supersonic combat aircraft incorporate a significant amount of composites in their construction. For example, in case of Dassault rafale:

  Composite materials are extensively used in the RAFALE and they account for 70% of the wetted area.

though they account for only 28% of the structural weight. This is in line with other aircraft- for example, composites contribute to around 25% of the weight of F-22 Raptor.

Dassault Rafale structural materials; image from indiandefence.com

You can see that the composites are extensively used in the wings, where the skins are made usually with composites, which enables them to be made in a single piece. The composite materials are superior to the metals used in aircraft in a number of performance parameters. The offer better strength to weight ratio and corrosion resistance, among others. According to Dassault,

  The RAFALE composite wing weighs the same as the MIRAGE 2000 metallic wing, but is 10% larger and can sustain a load that is 20% greater.

Composite materials are being used increasingly more and more in case of high performance aircraft- not only in wings (and radomes, where they have been used traditionally) but also in interior load carrying members, which have been usually made from metals. Even in case of Rafale, the wing box is made from carbon fiber composite. Another reason for using composites, atleast in combat aircraft is for stealth.

There are other areas in structural design, where the metals are better, for example, in impact resistance and in high temperature areas, where titanium is extensively used. Still in other places like landing gear, steel is used. The image below shows the use of various materials in F-22 Raptor.

Materials used in F-22 Raptor; image from allstar.fiu.edu

Again, the distribution is similar- composites make up majority of the wetted area while a minority of structural weight. In the end, the use of composites or metals are determined by their location and intended use.


Do they kill people on the ground?

Almost certainly a few do.
People struck by falling bullets are more likely to die than people shot directly. The chances of a particular bullet falling onto a person are very small but over the decades, many many bullets have been fired by aircraft.
Handgun bullets

Between the years 1985 and 1992, doctors at the King/Drew Medical Center in Los Angeles, California, treated some 118 people for random falling-bullet injuries. Thirty-eight of them died.
Bullets fired into the air during celebrations return at a speed fast enough to penetrate the skin and cause internal damage to other organs in the path of the migrating bullet. The bullet’s velocity required for skin penetration is between 148 and 197 feet per second. A velocity of less than 200 feet per second, which is easily obtained by a celebratory gunfire, is capable of fracturing bone and even causing intracranial penetration [4]. Spent bullets have the capability of reaching up to 600 feet per second during their downfall, and thus they have the ability to inflict damage to multiple body cavities [4]. The larger caliber bullets (ie, .45-caliber) reach a higher terminal velocity compared with the smaller caliber bullets (ie, .30-caliber), because of the proportion of their weight to their diameter [4].

From http://www.annalsthoracicsurgery.org/article/S0003-4975(06)00831-9/abstract

For those hit by falling bullets, the chance of the wound being fatal was far higher than a typical shooting. The hospital put deaths from regular shootings between 2% and 6%, while for those struck by falling bullets the death rate was close to one third.

From http://www.theguardian.com/world/2011/aug/24/how-dangerous-is-celebratory-gunfire

Aircraft rounds
These falling bullets were from celebratory gunfire, not fired from aircraft.
Aircraft cannon fire projectiles which are often much heavier than handgun rounds. If one falls on you, the likelihood of injury or death must be higher.

.22 Winchester magnum rimfire and .50 Browning MG rounds at same scale. source


Does runway centerline lighting provide information about distance left before end?

Runway centreline lights serve two main purposes:

Inform the pilot about where the centre of the runway is (they are installed on the runway centreline.
Inform the pilot about how far away the end of the runway is (by colour coding the final 900 m metres of runway centre line lights).

Their safety objective is to help prevent misalignments when landing and taking off, as well as to help prevent undershoots and overruns.

They are not always required, and in fact they are considered a complementary system to other visual aids such as runway edge lighting or runway markings, amongst others.


The B-17 had General Electric exhaust-gas-driven turbochargers (or more correctly, turbo-superchargers) that had pilot selectable boost levels. A selector dial in the cockpit controlled the operation of the wastegate that controls whether exhaust goes through the turbine and provide engine boost, or is bypassed directly outside.  The pilot's indication of the state of boost being provided to the engines would come from the engine manifold pressure gauges.
"Runaway superchargers" would suggest that the wastegate control systems on those engines were malfunctioning, such as the waste gate failing closed and directing all the exhaust flow through the turbo, causing the turbos to over boost the engines (the "running away" part), which would cause sky-high manifold pressures, detonation, and send the cylinder head temperatures through the roof.  This would necessitate a precautionary shutdown to keep them from blowing cylinders.
During the shutdown, even though they had oil pressure indication for the engines, the propellers, which operate hydraulically using engine oil, wouldn't feather. There is a feathering pump for each engine, normally electrically operated, that draws oil from somewhere in the system and can drive the prop into feather even without any engine oil pressure, as long as the pump itself has a source of oil to its suction inlet.
The turbosupercharger waste gate uses engine oil pressure for servo power for regulating the waste gate, that is also used to lubricate the turbo's bearings.
So... thinking it through, the turbo waste gate needs engine oil, and the feathering pump needs engine oil.  My guess is that there were oil system problems that impacted the waste gate control systems on those two engines, causing the boost runaway, and the same problem was also starving the engine's feathering pumps so that they were unable to complete the feathering of the propellers.  Maybe flak damage, or just a technical issue with the system (it would be odd for flak shrapnel to cause identical problems in two engines on opposite sides of the aircraft).
A B-17 at low altitude, well lightened, having burned off most of its fuel, dumped its bombs, and expended ammunition, would probably have been able to make it back to the UK on two engines, IF the two dead ones had feathered properly.  Having two unfeathered propellers windmilling away however, is massively draggy, and would have turned it into a two-engine glider, leaving the option of a forced landing or bailing out; and it looks like they chose the latter.


At first this reminded me of the Garmin G3X. However, it is mounted on the yoke and must be a GPSMAP 695 or 696

https://buy.garmin.com/en-US/US/p/14860


Why does the TAF provide forecasts at irregular intervals?

I assume you're referring to the FM (FROM) groups. The TAF itself is published at regular intervals but sometimes the conditions are expected to change significantly in between those times; obviously, the weather doesn't operate on a neat schedule. So the TAF will show the expected time of those changes.

According to the National Weather Service:

  FROM Group: ie. (FM1600)

  The FM group is used when a rapid change, usually occuring in less
  than one hour, in prevailing conditions is expected. Typically, a
  rapid change of prevailing conditions to more or less a completely new
  set of prevailing conditions is associated with a synoptic feature
  passing through the terminal area (cold or warm frontal passage).
  Appended to the FM indicator is the four-digit hour and minute the
  change is expected to begin and continues until the next change group
  or until the end of the current forecast.

  A FM group will mark the beginning of a new line in a TAF report. Each
  FM group contains all the required elements -- wind, visibility,
  weather, and sky condition. Weather will be omitted in FM groups when
  it is not significant to aviation. FM groups will not include the
  contraction NSW.


What is this tab above the DC-10's #2 engine?

(airliners.net via szextant.blogspot.com)

It mostly houses the same stuff that's on an underwing engine pylon: bleed air ducts, wiring, fuel and hydraulic hoses and tubes that connect to the engine core and accessories. The aft part of the structure where it tapers is just there out of aerodynamic necessity.


Can stainless steel replace titanium for Mach 3+ speeds?

Both the MiG-25 and MiG-31 designs had engines that would overheat and be damaged an anything past Mach 2.83, so both planes were limited by this. Typical speeds were closer to Mach 2.5 to extend the life of the planes. The highest aerodynamic heating occurs at the leading edges. It's possible that the MiG designs used titanium in these areas but opted for steel in most other areas, which was cheaper and easier to work with. This would have allowed the aircraft to reach speeds closer to the SR-71, even if the engines couldn't keep up.

The SR-71 was designed to cruise at up to Mach 3.3 at 80000ft, a similar altitude to the MiGs. Atmospheric heating is related to the cube of the speed. Mach 3.3 generates 10% more heat than Mach 3.2, and the SR-71 reached at least Mach 3.5. It seems the SR-71 flew faster and higher than the MiGs.

Heat is only one consideration though. Another big issue is weight. Steel is generally much heavier than a comparable structure made from titanium. The SR-71 empty weight was about 40% higher than the MiG-31, but the MTOW was 70% higher. This allows much more payload for mission equipment, but also fuel. The MiGs were designed to fly relatively short range interception or reconnaissance missions, having unrefueled ranges of 2000km or less. The MiG-31 could fly 3000km but only with drop tanks. The SR-71 was designed as a long range reconnaissance aircraft, and had a range of 5400km which enabled it to fly long missions over enemy territory.

Another consideration is size. The SR-71 was a larger plane than either the MiG-25 or MiG-31. It had a wingspan of 17m, compared to 14m of the MiGs, and a length of 33m, compared to 20m and 23m for the MiGs. This means higher forces on the aircraft structure.


Where is the fuel stored on an aircraft’s wing?

This depends on the aircraft. In many cases there is a tank inside the wing. In some cases it can be stored in a soft bladder in the wing and in other cases the wing its self is the tank.

Here is an in wing tank

Here are some in wing fuel bladders.

Mooney was known for having integrated fuel tanks in their wing designs. Here are some pictures of the tanks being resealed. They are notorious for needing a reseal every now and again but they do save in weight. Modern composite structures often don't lend to this design as jet fuel or avgas and composites don't really mix.

Here is a nice cutaway of the A330 to show where the tanks are.

It should be noted that you can generally pump fuel between the tanks however care must be taken when this is done because it can greatly effect the CG. This podcast has some really interesting information on how complex it was to manage the fuel weight on the Concorde and how it needed to be pumped around the tanks during various phases of the flight just to keep the plane stable.


Are there any examples (real life cases) of invalid FMS data affecting flight operations?

Here is some old material used in Europe to prepare for the transition from AIS to AIM: AIS to AIM: Enabling the Net-Centric Information Environment by Roderick van Dam, Head of Eurocontrol Legal Service. The document references two legal cases where navigational data and hardware were involved.

Pakistan International Airlines

  Bejon v. Pakistan International  Airlines (Toulouse Court of
  Appeal, 1998) Liability of Jeppesen raised.  Jeppesen argued that
  approach map  was based on map provided by States.  Court concluded
  that map was  technically acceptable This case confirmed  the risk
  related to  the publication of Aeronautical data.

More: PIA Flight 268.

American Airlines

  American Airlines v. Jeppesen- Anderson and Honeywell (US Federal
  Court, 2000) The Accident Report had concluded: the probable causes
  of the accident were  related to failures of  the flight crew;
  contributing factor was related to FMS-generated navigational
  information; AA blamed the Jeppesen software in the  Honeywell
  computer; alleged that products  helped caused the crash; A Federal
  Jury found  that Jeppesen was  17% at fault and Honeywell 8 % at
  fault.

More: American Airlines Flight 965.


Are the ICAO phonetic numbers used anywhere?

Is there any country, military, or agency that regularly uses the full ICAO (NATO) approved phonetic number pronunciations? Is it taught to any pilots?

Yes, pretty much every country in the world. As you mostly have experience flying in the USA, where the native language is English, you may not be used to hearing these pronunciations so much. People whose native language is English tend to pronounce words [and numbers] as they would in normal speech. In most of the world, however, English is by no means the native language, so controllers and pilots alike will use the pronunciation guidelines created by ICAO to ease understanding across multiple dialects and accents.

As an example, the Danish aviation regulations has an exact copy of the table you present in your question, and it is used by everyone.


Do helicopters use more fuel when hovering?

Yes it is correct that helicopters use more fuel when hovering: the engine needs to apply more power to overcome drag. Here is a graph of the engine power required for different airspeeds, from J. Gordon Leishman, Principles Of Helicopter Aerodynamics:

The line for total power goes down between 0 - 70 kts with increasing airspeed, this is caused by the line for induced power: power required to overcome the induced drag of the helicopter blade. The total required engine power is the summation of:

Induced power. The power required to overcome the induced drag of lift creation, further detailed below. Propulsive power relates to the engine exhaust velocity now being helpful, and to the rise in induced power at higher speeds due to compressibility drag.
Profile power, required for the blade profile drag.
Parasitic power, for the drag caused by the air frame, rotor hub etc. Zero in the hover, very dominant at top speed. Helicopters have shapes that are way less aerodynamic than fixed wing planes, and this source of drag becomes very significant at higher speeds.
Tail rotor power. Up to 20% of the main rotor power both in the hover and at top speed, very low in the middle due to the helpful vertical tail. At top speed the torque of the main rotor is high and the tail rotor must do more work, unless the vertical tail can be adjusted.

Induced power is dominant in the hover. Induced drag is caused by the backwards tilt of the lift vector: the higher the angle between blade and free stream, the more the vector is tilted backwards, which causes both loss of lift and increase of drag. The equation for lift L is:

$$ L = C_L \cdot \frac{1}{2} \cdot \rho \cdot V^2 \cdot S$$

and at a given altitude, the two variables here are $C_L$ (lift coefficient) and $V$ (airspeed at the blade). $C_L$ is an approximately linear function of angle of attack at the blade, so lift increases linearly with blade tilt-back and quadratically with increasing airspeed over the blade.

Above graph from Leishman shows the velocity distribution over the blades when hovering, and at airspeed. Quite a complicated situation - when hovering, the airspeed reaching the blade is only the rotational speed of the rotor, at forward speed the blade going forward has rotational speed plus airspeed.

The helicopter does not roll over and both forward blade and retreating blade deliver the same amount of lift, with the rearward going blade tilted back more than it was in the hover. But the forward going blade is tilted back a lot less: airspeed has a quadratic influence.

Note that the circle in the plot at fwd airspeed is not stalled flow, but reverse flow: the air streams in at the back of the blade. So drag is now negative, the airstream helps to propel the blade! However there is loss of lift in the reverse flow area.

Induced power reduces with airspeed at first according to the simple 1-D impulse consideration (more air mass through the disk), and later increases as the disk is increasingly tilted forward and must do more work to overcome losses from rotor profile drag, airframe parasitic drag, and compressibility drag.

There is also an interference effect of the downwash over the fuselage: in the hover the air streams straight down, while in forward flight the rotor wash is more aligned with the fuselage, catching more of a streamline shape. Parasitic drag is of course dominant at top speed, while offloading the rotor by using fixed wing surfaces reduces the induced power at high speeds - but from hover to moderate forward speeds it is purely the reduction in lift induced power that creates translational lift.


How do rate gyros and other sensors send information to the flight control computer in an F-16?

The F-16 uses a MIL-STD-1553 data bus and was the first aircraft to do so.

References:

https://www.testandmeasurementtips.com/making-measurements-mil-std-1553-connections/
https://www.aim-online.com/wp-content/uploads/2019/01/aim-ovw1553-u.pdf


If a beginner paraglider / paramotor wing fully stalls, how much vertical distance is needed for recovery?

Any extra second in recovery adds up to 60 meters of height. For this reason there is no way to tell how much height the next stall will require.

From the manual of Gin Bolero 6:

Page28, Dynamic Stall: the sink rate in a controlled stall induced by pilot is approx 8m/s.

Page20, Spiral Dive: you need 120-150m clearance to attempt a spiral Dive.

If you took an SIV course and trained in Dynamic Stall, you will find the answer. This is as far as I can go at answering your question. Any further appreciation or direct answering would be a mistake and huge liability.


Is it possible to design a helicopter with fixed rotor blades only (no blade angle/flap/pitch)?

Scaling laws are your enemy here.

Model helicopters can be controlled with changes in rotational speed, but for full-sized helicopters the energy needed to quickly change the speed of their rotors relative to the energy needed for lift creation is far too high. In detail:

The moment of inertia of a scaled-up rotor changes with the fifth power of length. The mass of the rotor changes with the cube of the linear scale, and the moment of inertia adds another factor proportional to the square of the linear scale.

A bigger object also needs slower changes, but time scales only with the square root of the linear scale. Next, the engine power available for speed changes will scale with the 3.5th power of scale*.

This still leaves a deficit of one power in the engine power available for speed changes when the helicopter is scaled up.

Lift asymmetries in forward flight can be dealt with by adding a second, counter-rotating rotor, but scaling laws can not be designed out. As Jan Hudec points out, you need to repeat the same trick for forward-backward lift shifting, so four rotors would be the minimum to control this type of helicopter in all directions.

* Proof: Thrust must exceed weight, so thrust goes up with the third power of scale. Rotor disk area scales only with the second power of scale, so a higher acceleration through the rotor disk is required to create more lift per rotor area. If we look at the power required in the static case
$$P_{min} = \frac{\eta_{Prop}}{T_0}\cdot\sqrt{\frac{\frac{4\cdot T_0}{\pi\cdot d^2}\cdot g}{2\cdot\rho}}$$
and insert the scaling factor in all scaleable variables, a power of 3.5 remains for the minimum power $P_{min}$. This is more than the increase in static thrust because the efficiency of the rotors declines with higher disk loading.


Certification of Aircraft Phone/Tablet Mounts/Holders

For general aviation no certification is required, neither is certification required for at least some commercial operations like flight training, at least for the regulatory bodies I'm familiar with (FAA and EASA). I've seen Ram and Garmin mounts being used on some smaller passenger and cargo operations as well, usually GPS and tablets in older prop airplanes like the DC3, Beechcraft twins and the like.

As for carrier airline operations I am not sure.


What is the purpose of sum voltage monitor?

It compares the commanded position with the actual position, it is the standard feedback loop.


Are a gyrodyne and a compound helicopter the same thing?

I have now found a couple of pretty authoritative definitions for a gyroplane:

FAA Rotorcraft Flying handbook: For Gyroplane Use Only:

  "The 'gyrodyne' is a hybrid rotorcraft that is capable of hovering and yet cruises in autorotation. The first successful example of this type of aircraft was the British Fairy Rotodyne, certificated
  to the Transport Category in 1958. During the 1960s
  and 1970s, the popularity of gyroplanes increased with
  the certification of the McCulloch J-2 and Umbaugh.
  The latter becoming the Air & Space 18A."

Electronic Code of Federal Regulations (e-CFR) Title 14. Aeronautics and Space Chapter I. FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION Subchapter A. DEFINITIONS AND GENERAL REQUIREMENTS Part 1. DEFINITIONS AND ABBREVIATIONS, Section 1.1. General Legal Information Institute, Cornell Law School.

  "Gyrodyne means a rotorcraft whose rotors are normally engine-driven for takeoff, hovering, and landing, and for forward flight through part of its speed range, and whose means of propulsion, consisting usually of conventional propellers, is independent of the rotor system."

So it may be that the gyrodyne fully offloads the rotor and relies on autorotation during cruise, while the compound helicopter drives its rotor throughout. But I can find no authoritative definition of a compound helicopter.

Technically, under autorotation the rotor disc tilts backwards and air flows up and over the blades from below, while under powered drive the rotor disc tilts forwards and the blades drive air downwards from above. It would be nice to think that this was reflected in the two definitions, but there are obviously borderline cases where the disc angle and loading are not quite textbook.


What does the behaviour of water on the skin of an aircraft in flight tell us?

This effect is likely caused by something called the "boundary layer," first defined by German engineer Ludwig Prandtl in a paper he presented in 1904 at the third International Congress of Mathematicians in Heidelberg, Germany. From Wikipedia:

The effect of the paper was so great that Prandtl became director of the Institute for Technical Physics at the University of Göttingen later in the year.
Over the next decades he developed it into a powerhouse of aerodynamics, leading the world until the end of World War II. In 1925 the university spun off his  research arm to create the Kaiser Wilhelm Institute for Flow Research (now the Max Planck Institute for Dynamics and Self-Organization).

The math in the paper is complicated and frankly well beyond my paygrade, but the way I understand it, what I think you are seeing is caused by a laminar boundary layer that forms very close to almost all surfaces of the aircraft. It is a layer of air with high viscosity, low turbulence, low speed relative to the air farther out from the surface, and causing an increase in drag. That's why the water doesn't blow away or evaporate.
The image below is one I found which does a good job of presenting the two types of boundary layer -- laminar and turbulent. Look at how smooth the laminar boundary layer looks compared to the turbulent boundary layer. This might help to understand the concept better.

The boundary layer is also something I experienced with an experimental aircraft I restored that had an opening on the top right of the fuselage to feed air into the fuel injection system intake. As it was, air would essentially stop flowing into the system when the aircraft accelerated, and the engine would stop. Not good. In order to stop that from happening, a raised scoop had to be installed that extended above the laminar boundary layer and into the turbulent boundary layer. That solved the problem.


When a manufacturer is making an aircraft to compete with another manufacturer's products, they have the public marketing material to go off of, as well as what their customers tell them the other aircraft can do, and what they are looking to buy. The general performance capabilities and costs are what is most important at the high level of making a competing product.
More in-depth study does help for detailed information, and there are multiple ways that this can happen.
Manufacturers will end up with airplanes from other manufacturers through trade-ins. Just like with car dealers, they may offer to buy older aircraft from a customer as part of the sales deal for new aircraft. Unless they are headed for scrap, these aircraft are generally worth more intact on the used market than dismantling them but it certainly allows closer study.
Manufacturers can also look for parts on the spares market like any other buyer, and get specific parts of interest that way.
Information can also be found in safety bulletins or accident reports if a certain system or component is involved.


What deviation from the official flight path is allowed during takeoff and landing?

Instrument flight and visual flights have very different standards and expectations regarding flight paths, and aircraft being guided in real time by ATC in a radar environment are different again.
For instrument path design, I believe what you are looking for is called a TERPS design standard(terminal procedures specifications). In the USA most of this is contained in FAA orders 8360.3 and 8360.19 the CAA, EASA or ICAO probably have some equivalent. However IFR path design mainly considers only ATC controlled vs uncontrolled airspace and restricted areas, not much weight is given to the various classes of controlled airspace. The different classes of controlled airspace exist primarily around ATC workloads.(traffic density) TERPS are mainly concerned with obstacle clearance, availible navigation and equipment failure contingencies.
This is not specific to the UK, but planes have the same physical limits everywhere so standards are similar. The industry standard final approach for instrument flights is 3 degrees or 318 feet per NM, steeper only when required for physical obstacle clearances. The obstacle clearance on approach generally changes from 1000ft in the initial segment to about 250feet at the missed approach point.(dependent on the exact form of navigation)
The standard minimum expected climb performance is 200ft/NM but the obstacle evaluation surfaces are only 152ft/NM (40:1) up to the en-route obstacle clearance. These climb slopes are reduced at high altitudes but that is not relevant to an airport in the UK.  Also EASA and the FAA have slightly different methods for setting the details, like where the slope starts, but the end result is similar. Normal climb performance in modern aircraft is usually above 400ft/NM not withstanding engine failure, or mechanical trouble like stuck flaps, lightly loaded jets can climb much steeper slopes.
As for lateral clearances, this is a bit complex and based on the type of navigation, a localizer/ILS final will have a wedge of plus or minus 3 degrees to either side of the center path and the wedge will be 700 feet wide at the runway threshold. This is usually up to about 1000ft above the airport. there are wide safety buffers either side of this 6degree wedge. With other forms of final guidance the path may be over a mile wide at its most narrow.
The initial segment and low routes are most often plus and minus 4NM from the center path, plus a 2NM obstacle safety buffer [12 miles total width].
WAAS(SBAS) enabled GPS nav can allow terminal area paths of plus or minus 1 mile from center-line(they still require a large safety buffer beyond this), reducing to 0.3miles on final and with some equipment a narrowing wedge similar to the affore mentioned LOC/ILS.


Why can't wing-mounted spoilers be used to steepen approaches?

They can. The Airbus A318 and Embraer E190 both do this in steep approach mode. You can see spoilers extended in this video of a A318 landing and a similar approach in an E190 at London City Airport.

Going back further, the Lockheed L-1011 did this with a system called Direct Lift Control. When landing flaps were selected, spoilers raised a set amount. Small movements on the yoke raised or lowered the spoilers instead of adjusting the elevators. This made for a very smooth approach and landing.

The common point is that these aircraft use electronics for spoiler control. It's too complicated to do this in a cable flight control system. You need to have the system retract the spoilers quickly in cases like go-around and stalls. As I recall, steep approach mode on the A318 activates a different set of gains on the flight control loops for better handling qualities in that configuration.

Finally, a number of fighters have the same system, and some glider pilots do this manually.


Who owns wrecked airplanes in international waters?

Insofar as it relates to MH370 the treaty sections Pondlife quoted would probably work quite smoothly if it were found by a government or someone working on behalf of the govt. The question arises as to what happens when James Cameron goes and finds it. (Inevitable, am I right?)

If it is located by a private party then the law would not be quite so clear. It would fall to courts and there would be legal claims falling under admiralty law, salvage law and those might even be superceded by laws governing criminal investigation at sea.

Generally under ocean salvage law the original owner continues to own it, but the salvaging party is entitled to a substantial award or prize. To complicate matters, there are two international conventions on salvage law, one from 1910 and a second one from 1989. Some countries recognize one of them and object to the other.

If Malaysian Airlines is no longer in business when it's found that will make things even more unclear. Probably the best analog would be the Titanic case. The company that recovered most of the artifacts sued to be declared owner. A US court declared jurisdiction and ruled that as compensation for the cost of recovery they had the right to display the items, but they do not own them.

  After a series of court battles, an American company, RMS Titanic Inc (RMST), emerged as the owner of the salvage rights, allowing it to keep possession and put on touring display the 5,900 artefacts it has lifted from the ship during six dives.

From an article in The Guardian

So far no one owns them since White Star Line is long gone. The US and UK quickly hashed together a treaty to declare them a public memorial so the artifacts can't be sold off to private collectors.

  An international agreement signed by Britain and the US designates the Titanic as an international memorial and seeks to protect it from being plundered or damaged by unauthorised dives.

from the same article*

With all these things at play there is simply no telling what would happen with it.


I've never heard of the term, but from the context of the explanation it appears that they refer to a situation where the elevator neutral position is relative to the stabiliser, not to the aircraft. So stick moves elevator relative to aircraft and stabiliser, trim moves elevator relative to aircraft only because the elevator neutral position follows the stab position. Like the stabiliser/elevator arrangement on the B737.

Image source


Constant TAS versus constant GS: What is the influence on turning circle?

If you maintain a constant bank angle (30 degrees for a 1.15 g turn) and maintain constant true airspeed of 200 Knots, your path will be as shown in the chart by the yellow line.

If you maintain a constant ground speed (150 knots) and a constant acceleration 1.15, then your path will be as described by the grey line. It will be as if there is no wind, however it requires thrust variations and bank angle variations.


Helicopters with landing skids, no wheels; How are they taken in and out of a hangar?

Basically, you put wheels on the skid and tow them.

In some cases, towing wheels are attached to the skids (which usually have sleeves in them for mounting), and a tow bar is attached to the front (one or two sets of wheels may be attached to the skids), which is then towed by a vehicle.

Image from incrediblediary.com

There are also specialised tow carts available for helicopters, which basically grip the skids (usually in a couple of places on either side) and lift them up, after which the helicopter can be moved by the operator by controlling the cart.

Image from hasmak.com


What is the purpose of having contra-rotating props on an aircraft?

According to my experience, you have two problems with props:

Torque
Exhaust Speed

If you use contra-rotating propellers, you eliminate the torque reaction problem because you now have two contra-rotating propellers each cancelling out the opposite's torque.

Also you increase the speed of air accelerated by the propellers, thus the aircraft’s efficiency at relatively high travelling speeds is increased.

Normally, the propeller can only be operated effectively at low Mach numbers and increasing the RPM above a certain point will only cause the air behind the propeller to compress but not accelerate. Using a second propeller with higher pitch angles can generate high enough airspeed without the problem of compression because the second propeller is rotating inside the airstream generated by the first propeller.

Correction
However, having a different speed and pitch WILL induce a torque effect.


When passing a waypoint, when exactly are we on the next leg?

The transition point as defined in RTCA DO-283 RNP MOPS is the point where the aircraft's path passes through a vertical plane that bisects the inbound and outbound legs going through the waypoint.

That generic description covers all the possibilities of the aircraft passing the waypoint regardless of how good or bad it is following the defined path.

Realistically, in the case of the fly-by waypoint, it's the point half way through the transition turn where the waypoint is directly abeam the flight path.

The same rule (crossing the bisecting plane) applied to the fly-over waypoint results in the transition occurring at the waypoint.


What is the purpose of this item next to the cockpit window on the B737?

That protrusion makes it so that the pilot can only grasp, and activate, the handle by sliding his hand in to it from behind - which requires a deliberate action, rather than by accidentally resting one's hand on it from above. Since the window opening inadvertently is undesirable, it makes sense to block off the most likely means on unintentionally grabbing the handle.

It also provides a visual reference for the handle being in the locked closed position... if the handle is aligned with the fairing, it's locked; if not then it isn't.


Did Boeing subcontract the manufacturing of the wings on the B757 series?

The 757 Wing and Center Body Section was manufactured at the Renton plant at KBFI.


What's the difference between "Nonstop Commercial Air Tour" and "Aerial Photography"?

Short answer: as far as I can tell, an air tour implies photography, but photography doesn't imply an air tour. The regulations define various criteria for determining if a flight is an air tour, but there's no 100% clear definition.

First, the regulatory definition of "commercial air tour" is in 14 CFR 110.2:

  Commercial air tour means a flight conducted for compensation or hire in an airplane or helicopter where a purpose of the flight is
  sightseeing. The FAA may consider the following factors in determining
  whether a flight is a commercial air tour: [...]

It's worth reading the "following factors", by the way.

Second, there's no formal definition of "aerial photography". See the Sapp (2007) interpretation (emphasis in the original):

  In a 1989 interpretation, the FAA discussed the meaning of "aerial
  photography" [...]
  the phrase was not defined in the regulations [...]
  "aerial photography" connotes a condition where taking pictures or
  filming is done from the air

Third, the Ragland (2015) interpretation specifically mentions photography as one purpose of an air tour (emphasis mine):

  Specifically, you asked whether §119.l(e)(4) allows persons to conduct
  commercial air tour operations, for purposes of sightseeing and
  photography, without obtaining either a letter of authorization
  (LOA) in accordance with §91.14 7 or a commercial operating
  certificate in accordance with part 119 of the federal aviation
  regulations.

  You assert that the conclusion in a January 5, 2011
  interpretation issued by our office "appears to reinforce the need for
  Operators to apply for a LOA from their local FSDO to conduct
  'sight-seeing tours' within a 25 statute mile limitation under 14 CPR
  91.147." We agree.

Finally, the same interpretation says you can't operate a commercial air tour under the aerial photography exemption:

  We further note that the exception in §119.1(e)(4) for certain "aerial
  work operations," such as banner towing, aerial photography or survey,
  and powerline or pipeline patrol, does not extend to air tour
  operations in which the primary purpose is sightseeing.

So, putting all that together - and remembering that I'm just SGOTI - it appears that:

Air tours within 25SM require an LOA and are assumed to include photography
"Aerial photography" is a separate activity from "sightseeing"
The FAA seems interested in the "primary purpose" of the flight

In your scenario, it sounds like the photographer is asking for a straightforward aerial photography flight: the primary purpose is to take photographs, not to get a tour of an area. And if the photographer actually makes money from their work, that's a strong indicator that they aren't just "sightseeing". But that's just my opinion.


Why do the ailerons of this flying wing work oppositely compared to those of an airplane?

Most likely the adverse yaw effect (due to the induced drag of the increased lift on the down-aileron side) is causing the wing to yaw the opposite direction from the intended roll, and the yaw causes the dihedral induced roll (proverse to the yaw) to override the aileron input.
This situation is very commonly seen with very slow flying model aircraft -- indoor Peanut scale, for instance, or Penny Plane models, will often be set to turn left by putting a relatively tiny tab under the left wing, where you'd expect the lift to cause a roll to the right.


Section V of the Block 50 F-16 Flight Manual, is the "operating limitations". It says:

  MAXIMUM AIRSPEED OPERATING LIMITATIONS
  Refer to figure 5 3. Maximum operating airspeed is 800 knots from sea level to 30,000 feet MSL. Above 30,000 feet MSL, the aircraft is limited to 2.05 mach.

The introduction to section V states (my emphasis):

  The aircraft and system limitations that must be observed during normal operations are presented in this section..

What does "observe" mean? One might assume that means the pilot can just sit back and watch them automatically occur, or the pilot must "observe" them by knowing and acting apon them. As evidence it is most likely this second interpretation, the list of contents in this section appears to be many things that the pilot needs to do.

It does not seem like a list of things the aircraft does automatically.

But more signifficantly, the contents of the flight manual also includes a section describing the flight law control system (FLCS) limiters:

and:

There is no mention of maximum speed.

So, it looks strongly like the FLCS limits 4 things (AOA/G, roll, yaw, rudder authority), and warns you about some other things (low speed), but does NOT limit maximum speed.


What type of license do you need to solo a glider in the UK?

This is on the BGA website under (unsurprisingly) Laws & Rules

  There is no requirement for glider pilots to comply with EASA regulations for pilot licencing until 8 April 2020. The relevant BGA requirements and guidance continue to apply.

You can further follow links to the BGA Certificates, including a Cross Country endorsement:

https://members.gliding.co.uk/library/bga-requirements-guidance/gliding-certificate-endorsements/

In part:

  The Cross-Country Endorsement can only be issued if the applicant has already qualified for a Bronze Endorsement or SPL/LAPL(S) and has the approval of theCFI.


What are the abandoned technologies in aviation industry

The biggest one that comes to mind for me is Cathode Ray Tube technology for cockpit displays.  Rockwell Collins (called something else now) has ceased production of CRT displays and users of Proline CRT Primary Flight Displays, Secondary Flight Displays and EICAS systems are in a scramble to replace the CRTs when they wear out.  There are a number of companies offering LCD units to upgrade CRT units under STC and this is happening across the airline industry.

Another one could be navaids like Non Directional Beacons that are starting to go the way of the A/N Range and the related receivers, and eventually other analog navigation equipment.

Mechanically, not that much.  Light aircraft are still built today with magnetos that use points and condensers like tractors from the 40s.  They are simple and work.  The business is very conservative, a vital self-preservation characteristic in such a life-or-death environment, and things that are simple, work, and are easy to fix and easy to diagnose, and let you know when they are degrading, are hard to replace.


Why do aircraft on Flight Radar 24 jump around randomly sometimes?

FR24 relies for most of the tracks on ADS-B data. Part of the ADS-B transmissions is the position. There are three causes of the behaviour that you observe:

1). Aircraft landing next to the runway

The position source onboard the aircraft is not always GPS. Mainly older aircraft (e.g. Fokker 100) have their Inertial Navigation System (INS) coupled to the ADS-B transmitter. The INS relies not on external radio measurements but only on measured acceleration and rotation to track its position. It is usually correct at take-off, but it develops biases over time and therefore the landing appears quite often next to the runway. I can assure you that this is mostly misleading.

2). Short time track offset

In most aircraft the ADS-B position is from GPS. When the GPS loses its  position fix, the system falls back to INS. As described above, the INS position is slowing drifting from the truth during the flight, so the ADS-B track will shortly jump aside to the INS position until the GPS comes back. When short (e.g. 1 position update) the offsets appear as spikes.

3). Long distance jumps (180 NM, 360 NM)

Due to the limited number of bits available in the ADS-B messages, position is encoded in a complex format called Compact Position Reporting. It requires at least two position messages to decode the first position of a track, from that point onward, every message will constitute a position update. When no proper verification algorithms are used in the software, it may occur that a receiver station initializes the track wrongly, usually causing a jump of 180 or 360 NM.

Also note: When INS is used a the position source, the ADS-B data contains an indication that the data is not to be trusted, but that is silently ignored by FR24.


How are wind tunnels used with scale models?

During development, a lot of different wind tunnels are used. Scales range from full scale to less than 1/100, and sometimes not only the geometric, but also the dynamic and elastic properties of the aircraft to be tested must be modelled correctly.

Today, preliminary work is mostly done in numerical simulations, but before the availability of computers, early wind tunnel models would be between 1/50 to 1/16 scale (depending on the size of the real article and the available wind tunnel), often using modular models on which different engine placements or tail geometries could be tried out. Since wind tunnel testing costs real money, early tests are restricted to small, low-cost tunnels which run at ambient temperature and density. Differences in the Reynolds number between test article and the real aircraft are covered with correction factors and experience.

Only when a design is moving ahead during development, bigger and more expensive tunnels are used. Again, matching the Reynolds number is not possible and not even necessary for some tests: For a spin tunnel the test article must be scaled dynamically (so it has correct moments of inertia), but separated flow is less affected by the Reynolds number, so the precision of a 1/20 scale model is sufficient. Also, a free-falling model in a spin tunnel needs quite a bit of space to move around, so even small models already need test sections with a diameter of several meters.

To reduce cost and avoid the tight schedules of wind tunnels, free-flying or radio controlled models are also used. Watch how Dornier engineers tested the dynamic behavior of the then-new tricycle gear of the Do-335 in this video (starting at 2:00') or ditching characteristics (starting at 2:13').

Only when both Mach and Reynolds number need to be matched, cryogenic and pressurised wind tunnels are used. Due to their energy demand and availability, such tests need to be scheduled years in advance and meticulously planned. Models can run into millions of dollars or Euros, so such tests will mostly narrow down parameters which had been measured previously in simpler tests. Large tunnels like the 9.5x9.5m LLF in Marknesse (the Netherlands) are mostly used for low-speed and high-lift characteristics testing since its 12.6 MW engine can only support a speed of 62 m/s at full power. On the other end of the scale are hypersonic blow-down tubes which support a testing section of 0.5m diameter in which Mach 6 can be achieved for a fraction of a second.

Full-scale testing in a wind tunnel is only possible with small aircraft - see the answers to this question for examples. Even then, the speeds do not match the top speed of the aircraft, so the loads are a fraction of the real loads.

Jan Roskam observes in his book "Roskam's airplane war stories":

  It certainly is an unusual luxury for an engineer to have full
  Reynolds Number tunnel data available.


Why is the air inside airliners so dry (low humidity)?

What happens during a flight cycle is the humidity is high during departure, from ambient air and the moisture from the pax, but over time the air dries out because the bleed being supplied to keep the pressure hull "inflated" is coming from the engine compressors, which at 35000 ft has almost no humidity, and what humidity there is is being extracted by the Air Cycle Machines that condition the bleed (by heat exchanger condensate).

It's important to note the air cycle air conditioning process (787 excluded): Take hot high pressure bleed air, take away some of the heat with heat exchangers while keeping the pressure up, boost the pressure and temperature some more with an air cycle machine - more or less a turbocharger that feeds itself - , cool that off some more with more heat exchangers, then  finally allow the significantly cooled but still very high pressure air to expand and drop down to just above cabin pressure.  This process can take 500F air bleed from the engine compressor and chill it to -40 if you pass all of it through the air cycle machine (only some goes through, and gets mixed with bypassed bleed after, and the air cycle discharge itself is normally kept to not less than > freezing).  Anyway, this process takes whatever humidity there is and removes it, leaving bone dry air.  Moisture control is a big deal with Air Cycle Machines because condensate water that forms during the cooling process will rapidly erode the ACM turbine and ruin the ACM, so you have water separators that extract moisture that condenses from being chilled.

Then at altitude, there's almost no ambient moisture in the first place and you end up with really dry air from ambient being pumped in, how much depending on how leaky the pressure hull is (they can leak quite a lot) offset by humidity coming from all the pax.  At high altitudes after a period of time the dry incoming air wins out and the pax humidity isn't enough and everybody starts to dessicate, again, depending on how leaky the pressure hull is.  An older leaky airplane will get a lot drier inside than a newer relatively tight one.

As Mackk says, one of the big issues is that what moisture does get around the cabin ends up condensing on the inside of the pressure hull.  It slowly gets absorbed into the insulation.  Airliners that operate in humid environments down low will carry hundreds of pounds of water in the cabin insulation because of the condensation cycles from flights, and you will often see insulation set out to dry when airliners are in for heavy check inspections.  What water doesn't soak into the insulation collects at the bottom of the fuselage and promotes corrosion (one solution is to pump dry conditioned air directly into the space between the insulation and skin - so called "zonal dryer" systems).

Anyway, you can see there is a this-or-that problem.  Air moist enough to keep pax happy plays havoc with the interior. Air dry enough for a happy interior generates dry air complaints.  In general, the industry tends to go with the latter.


How long does it take Boeing to develop an aircraft?

For the general question, the answer will be "it depends on the aircraft." Specifically for the 787, though, the '7E7' program was officially announced on January 29, 2003. The program was later renamed to 787. It received its type certificate on August 26, 2011 and flew its first passenger revenue flight on October 26, 2011.

So, from the time the program began to the time of the first revenue flight was about 8 years and 9 months.

Of course, this is not including the R&D time invested on different projects whose R&D ended up being used either partially or completely in the 787 design before the 787 program itself began.

It should also be noted that not every airframe they start developing ever actually flies. Notably, Boeing worked on designs including larger 747 variants and the Sonic Cruiser (which would have cruised at Mach 0.98) before beginning the 7E7 program.

In addition to completely new airframes, aircraft manufacturers also commonly make derivative airframes based on existing product families. Current examples of derivatives in development include the 737MAX, A320neo, 777X, and A330neo ("neo" stands for "new engine option.") However, development time on derivatives can vary widely depending on how much modification is being made to the existing airframes and the level of resources being devoted to the project (which depends on market pressure.)

For a past example, the 2nd-generation Boeing 777 aircraft were announced on February 29, 2000 with the first aircraft, the 777-300ER, being certificated on March 16, 2004, and first service entry on May 10, 2004. This gives a time of about 4 years and 2 months from announcement to first service entry. This was likely slowed by the sharp downturn in aircraft orders following the 1999-2000 ".com bust" and, especially, the September 11, 2001 terrorist attacks in the U.S.

Also important is the FAA rule for applying for a type certificate. This will apply for new programs like the 787, but not for derivative programs like the 777X, which amend the original type certificate and do not need a new one. In 14 CFR §21.17:

  An application for type certification of a transport category aircraft is effective for 5 years and an application for any other type certificate is effective for 3 years...

So once Boeing applies for a new type certificate, they have 5 years to get the type cetificate approved, unless they convince the FAA upfront that more time is needed. If the time runs out they must reapply, and the new type certificate would require the aircraft to comply with all new regulations passed since their original application.


Are there any civilian powered-lift aircraft besides the AW609?

I suppose some kinds of roadable aircraft aka 'flying car' designs would qualify under the powered lift category.  One example which nearly escaped the prototype stage was the Moeller SkyCar.

But beyond the Agusta AW609, I cannot think of any other powered lift category aircraft which are, or may be soon, available for sale to the general public.


Why is Hydrazine used to power the F-16's EPU?

To fill the voids in aeroalias' answer:

Hydrazine is a monopropellant, something which does not need to be mixed and burned to free up the energy contained in its chemical bonds. This energy is freed by letting the hydrazine stream over a catalyst, in case of the F-16 EPU that is iridium. This breaks the chemical bond, producing ammonia, nitrogen gas, hydrogen gas and heat which converts the water into steam. Heating increases the volume of the gasses and the steam so they pick up speed, just like the gasses in the combustion chamber of a jet engine. In the catalyst chamber of the F-16's EPU the temperature reaches more than 800°C in just a couple of milliseconds, and no combustion is involved! This high-pressure, high-speed gas flows through a small turbine which in turn drives a generator and supplies hydraulic pressure.

Compression is not needed because pressure is supplied from the bottle containing the hydrazine-water mixture. Using a monopropellant also avoids any ignition problems and makes the setup very simple. Since hydrazine is quite stable at high pressure and ambient temperature, the shelf life of a hydrazine engine is high, and the liquid state of the hydrazine-water mixture makes its storage very compact. Just what you need in a fighter aircraft.


If ATC doesn't assign an obstacle departure procedure in an IFR clearance, what should you do?

To answer your question directly, yes you can use the ODP to depart an airfield regardless of if ATC has specifically given it to you. You may use it until you reach the prescribed altitude in your IFR clearance or the beginning of the cleared routing. However, if ATC has given you specific instructions for your departure, you have to either accept those instructions and follow them. Or, decline the clearance and ask for what you need. After all, you are the Pilot in Command solely responsible for the safety of your own flight.
That being said, I have never heard an IFR clearance where the departure procedure is not explicitly spelled out. It does not have to be in the form of an official charted Obstacle Departure Procedure or complex instructions. As a matter of fact, it is usually a fairly simple instruction in order to put you in a position for ATC Departure to pick you up on Radar. It should sound like this:

C - Cleared to [your destination]
R - Fly runway heading. Radar vectors to the [blank] departure. Then as filed.
A - Altitude 3000 [or so]. Expect 10,000 in 10 minutes.
F - [Frequency you will use for departure].
T - Squawk [transponder code].

The “fly runway heading” statement means that you will fly the course of the extended center line of the runway of departure. And, continue to do so until told otherwise by ATC.
They may replace that statement with “Upon departure, turn right [blank] heading. This generally means you have the leeway to begin your turn once you are beyond the traffic pattern and/or above 1000 feet AGL.
If they stipulate for you to make an immediate turn to a specific heading as practical, do so as soon as you are above a safe altitude to bank the aircraft. I would generally make the turn when I have reached the Departure End of the Runway and above 400 feet AGL. ATC may give you an altitude at which to make that turn. In which case, make the turn at that altitude regardless of if you have reached the DER or not. Typically, ATC will not have you make the turn lower than 400 feet AGL. They would deem this as the practicable altitude for a turn. In an emergency or urgent situation, ATC may request a turn as low as 200 feet AGL. They would not want you banking low and slow in IMC.
If ATC does not give you a specific set of departure procedure instructions, the FAA recommends in the AIM that Part 91 flights should follow the charted ODP if one is available. This is only a recommendation and not a requirement. I would highly recommend informing ATC if you plan to amend their clearance instructions by departing on the ODP.
Something you may want to consider is that the numbers you alluded to in your questions are bare minimum performance values for certification of a Departure Procedure. You, as the PIC, should not be following these numbers. If your aircraft can not achieve 35 feet AGL way before the DER, and a climb rate of 200 feet per Nautical Mile, you probably should not be flying that aircraft, at that airfield, on that day, in those conditions (weight, weather, etc).
Below are the FAA recommendations for this found in the Aeronautical Information Manual Chapter 5-2-9:

a. Instrument departure procedures are preplanned instrument flight rule (IFR) procedures which provide obstruction clearance from the terminal area to the appropriate en route structure. There are two types of DPs, Obstacle Departure Procedures (ODP), printed either textually or graphically, and Standard Instrument Departures (SID), always printed graphically. All DPs, either textual or graphic may be designed using either conventional or RNAV criteria. RNAV procedures will have RNAV printed in the title; for example, SHEAD TWO DEPARTURE (RNAV). ODPs provide obstruction clearance via the least onerous route from the terminal area to the appropriate en route structure. ODPs are recommended for obstruction clearance and may be flown without ATC clearance unless an alternate departure procedure (SID or radar vector) has been specifically assigned by ATC. Graphic ODPs will have (OBSTACLE) printed in the procedure title; for example, GEYSR THREE DEPARTURE (OBSTACLE), or, CROWN ONE DEPARTURE (RNAV) (OBSTACLE). Standard Instrument Departures are air traffic control (ATC) procedures printed for pilot/controller use in graphic form to provide obstruction clearance and a transition from the terminal area to the appropriate en route structure. SIDs are primarily designed for system enhancement and to reduce pilot/controller workload. ATC clearance must be received prior to flying a SID. All DPs provide the pilot with a way to depart the airport and transition to the en route structure safely.
e. What criteria is used to provide obstruction clearance during departure?

Unless specified otherwise, required obstacle clearance for all departures, including diverse, is based on the pilot crossing the departure end of the runway at least 35 feet above the departure end of runway elevation, climbing to 400 feet above the departure end of runway elevation before making the initial turn, and maintaining a minimum climb gradient of 200 feet per nautical mile (FPNM), unless required to level off by a crossing restriction, until the minimum IFR altitude. A greater climb gradient may be specified in the DP to clear obstacles or to achieve an ATC crossing restriction. If an initial turn higher than 400 feet above the departure end of runway elevation is specified in the DP, the turn should be commenced at the higher altitude. If a turn is specified at a fix, the turn must be made at that fix. Fixes may have minimum and/or maximum crossing altitudes that must be adhered to prior to passing the fix. In rare instances, obstacles that exist on the extended runway centerline may make an “early turn” more desirable than proceeding straight ahead. In these cases, the published departure instructions will include the language “turn left(right) as soon as practicable.” These departures will also include a ceiling and visibility minimum of at least 300 and 1. Pilots encountering one of these DPs should preplan the climb out to gain altitude and begin the turn as quickly as possible within the bounds of safe operating practices and operating limitations. This type of departure procedure is being phased out.

Note: “Practical” or “feasible” may exist in some existing departure text instead of “practicable.”


Can a CFI give training outside the US in a non-N registered aircraft?

I can not find any prohibition against a US FAA certificated flight instructor giving instruction in a foreign country for a US FAA issued pilot certificate or endorsements. Title 14 of the Code of Federal Regulations Part 61.51 specifically allows a CFI to give instruction in a foreign aircraft registered in a country that is a member state of ICAO. Part 61.41 specifically allows a foreign CFI from a country that is a member state of ICAO to give instruction.
So, this implies that a US CFI can give instruction in a foreign country for a US FAA issued pilot certificate or endorsements. Just as long as the CFI has authorization to fly the foreign registered aircraft in the country of question. Depending on the country, they may need authorization to fly for hire. Depending on the country, they may need authorization to instruct as well. This may only apply to instructing for the issuance of a certificate or endorsement for that country.
So, at the very least, instructing in an aircraft of foreign registry in a foreign country for a US certificate may only require foreign validation of the CFI’s pilot certificate. But, maybe not their instructor certificate.

§61.41 Flight training received from flight instructors not certificated by the FAA.   (a) A person may credit flight training
toward the requirements of a pilot certificate or rating issued under
this part, if that person received the training from:
(1) A flight instructor of an Armed Force in a program for training
military pilots of either—
(i) The United States; or
(ii) A foreign contracting State to the Convention on International
Civil Aviation.
(2) A flight instructor who is authorized to give such training by the
licensing authority of a foreign contracting State to the Convention
on International Civil Aviation, and the flight training is given
outside the United States.
(b) A flight instructor described in paragraph (a) of this section is
only authorized to give endorsements to show training given.
§61.51 Pilot logbooks.   (j) Aircraft requirements for logging flight time. For a person to log flight time, the time must be
acquired in an aircraft that is identified as an aircraft under
§61.5(b), and is—
(1) An aircraft of U.S. registry with either a standard or special
airworthiness certificate;
(2) An aircraft of foreign registry with an airworthiness certificate
that is approved by the aviation authority of a foreign country that
is a Member State to the Convention on International Civil Aviation
Organization;
(3) A military aircraft under the direct operational control of the
U.S. Armed Forces; or
(4) A public aircraft under the direct operational control of a
Federal, State, county, or municipal law enforcement agency, if the
flight time was acquired by the pilot while engaged on an official law
enforcement flight for a Federal, State, County, or Municipal law
enforcement agency.
§61.195 Flight instructor limitations and qualifications.   A person who holds a flight instructor certificate is subject to the
following limitations:
(a) Hours of training. In any 24-consecutive-hour period, a flight
instructor may not conduct more than 8 hours of flight training.
(b) Aircraft Ratings. Except as provided in paragraph (c) of this
section, a flight instructor may not conduct flight training in any
aircraft unless the flight instructor:
(1) Holds a flight instructor certificate with the applicable category
and class rating;
(2) Holds a pilot certificate with the applicable category and class
rating; and


Was the airframe involved in the LOT Flight 16 accident repaired?

From Wikipedia:

  The damage to the plane was so extensive that the airline chose not to make repairs. The aircraft was scrapped in November 2013.

I can't find information on the figures, but for Qantas Flight 32 the figure to repair it was ~$145 million.

Nowadays you can buy a used 777 for 2% of its list price. A fraction of the $145m figure above to fix an A380.

New 777 is 277.3 million, used is 7.7 million.

I hope that helps.

So cost of repair, age of aircraft, cost of adding a used plane to the fleet instead, etc.


Can you become a commercial airline pilot in Europe while being monocular

Pilot certificates don't give you permission to fly in a location, they give you permission to fly an airplane registered by that authority anywhere in the world. In other words, if you have an FAA pilot certificate you can fly a US registered airplane no matter where it is. If you have an FAA ATPL and appropriate class of medical you can work for any airline that flies US registered airplanes. The same is true for any licensing authority.

The reverse is not true, you could not get a FAA certificate and fly a UK registered airplane, for example, even if it was in the US. There are some cases where you can get a local certificate on the basis of another equivalent certificate, but I believe you always need to be able to pass the local medical.


I think that 14 CFR Section 91.205(b)(12) defines "overwater".

  (12) If the aircraft is operated for hire over water and beyond
  power-off gliding distance from shore, approved flotation gear readily
  available to each occupant and, unless the aircraft is operating under
  part 121 of this subchapter, at least one pyrotechnic signaling
  device. As used in this section, “shore” means that area of the land
  adjacent to the water which is above the high water mark and excludes
  land areas which are intermittently under water.

Then 14 CFR Section 121.573 outlines the passenger briefing requirements for flights with overwater operations:

  §121.573   Briefing passengers: Extended overwater operations.

  (a) In
  addition to the oral briefing required by §121.571

  (a), each
  certificate holder operating an airplane in extended overwater
  operations shall ensure that all passengers are orally briefed by the
  appropriate crewmember on the location and operation of life
  preservers, liferafts, and other flotation means, including a
  demonstration of the method of donning and inflating a life preserver.

  (b) The certificate holder shall describe in its manual the procedure
  to be followed in the briefing required by paragraph (a) of this
  section.

  (c) If the airplane proceeds directly over water after takeoff, the
  briefing required by paragraph (a) of this section must be done before
  takeoff.

  (d) If the airplane does not proceed directly over water after
  takeoff, no part of the briefing required by paragraph (a) of this
  section has to be given before takeoff, but the entire briefing must
  be given before reaching the overwater part of the flight.

Lastly, the requirement for printed safety booklets is from 14 CFR 121.571(b)  And to answer your last question, it needs to have only information pertinent to the flight, so if the airplane is not going to fly overwater at all, it doesn't need to have it.

  (b) Each certificate holder must carry on each passenger-carrying
  airplane, in convenient locations for use of each passenger, printed
  cards supplementing the oral briefing. Each card must contain
  information pertinent only to the type and model of airplane used for
  that flight, including—

  (1) Diagrams of, and methods of operating, the
  emergency exits;

  (2) Other instructions necessary for use of emergency
  equipment; and

  (3) No later than June 12, 2005, for Domestic and Flag
  scheduled passenger-carrying flights, the sentence, “Final assembly of
  this airplane was completed in [INSERT NAME OF COUNTRY].”


How long can ATC operate for without main power?

Nearly all generators designed to serve as a backup power source in a safety critical environment (Hospitals, Air Traffic etc) will be designed to run 24/7 "indefinitely" with hot refuelling.

Obviously there will be a real world practical limit to that, but it will be many days if not even weeks potentially depending on the generator.

I suspect there will be huge variation in the type of standby equipment available, pre-loaded fuel and so on depending on the mission. For example, it would be entirely possible to have two generators which can switch over - allowing the other to be serviced and maintained.*

*NB: I don't know if this is an actual "thing", but I'd expect it in certain circumstances, for example, military.


Where can I find details about a Cambridge Scientific Instruments Fuel/Air ratio Indicator?

The 11622-1 is a type A-7 single-engine exhaust gas analyzer. You can see it here on page 8. The instrument just tells you if the fuel/air mixture is too rich or too lean. Electrical inputs are simple; 12vdc and ground. Any competent instrument technician can open it up and see which pin is what. But that's only the beginning... the system includes tubes and an analysis cell, and the cell is probably pretty much useless by now, if it is still installed, but you can always try your luck.


What are the applications, advantages and limitations of Gyrodyne rotorcraft?

The compound helicopter similarly has a separate propulsor for thrust. The gyrodyne differs from it in allowing the lift rotor to autorotate without power during forward flight.

Both are capable of flying faster than a conventional helicopter, while retaining its VTOL abilities. It is thus an attractive idea wherever both high speed and VTOL/hover are required such as military, rescue and executive in-city applications.

However the extra weight and complexity of the thrust system make the already limited, complex and expensive helicopter even more so. Moreover the speed increase over a conventional helicopter is not great enough to be game-changing. Various programmes have led to several prototypes flying, of both gyrodynes and compound helicopters, but there are few if any applications where the high costs and reduced payload justify the modest extra speed over a helicopter.

The Fairey Rotodyne city commute gyrodyne flew but was then cancelled by the UK government.

Several compound helicopters such as the Lockheed Cheyenne have been developed for the US military but then cancelled.

When the USA wanted a fast VTOL military transport, they opted instead for a convertiplane, the Boeing V-22 Osprey. Its speed increase over a conventional helicopter has also turned out to be disappointing.

Maybe one day.


Stick in center console, how to easily write down clearances and other similar information?

One technique many airline pilots use is to enter letters and numbers on the FMC keypad to use as a reminder for complicated taxi instructions.

“taxi via Hotel, cross 15L, right turn Bravo, hold short Alpha One” could be entered on the keypad as: HX15LB/A1 or possibly H X15L B/A1

There really is no requirement to write down this type of instruction, or any VFR clearance. It is just a reminder and makes for good airmanship.

Many FOs in the right seat seem to use their left hand when entering data in the FMC as it can feel awkward to reach over and punch buttons with your right hand.

In your case you might be able to use an iPad or some other type of electronic device on a knee pad to punch in some “shorthand” with your left hand to help you remember what ATC says.


Can you identify this aircraft at Chilliwack(YCW)?

It's a De Havilland DH104 Dove. It did have a registration of N4913V but it was cancelled in 2012.

The Dove is an airliner that can seat 8 passengers, and 542 were produced from 1946 to 1967.


What happens if a student busts Dallas Fort Worth bravo airspace?

Just to make it perfectly clear:

If you accidentally enter a controlled airspace without clearance, as soon as you realise what has happened, the first thing you do is contact the responsible ATC unit! Period.

Panicking, initiating a rapid descend to leave the airspace or simply pretending it didn't happen is extremely bad airmanship, and will surely get you in trouble if you get caught. On the other hand, admitting you made an honest mistake and asking ATC what the best solution is might still get you in trouble in some countries, but it is definitely the safest solution for everyone.

Depending on the exact details of the airspace infringement, it may be extremely dangerous if you try to solve the problem on your own. By suddenly descending to leave the airspace, you risk colliding with traffic below you. If the airspace in question is of a military kind, turning a blind eye to your mistake and maintaining radio silence will potentially result in a visit from some aircraft with a lot more weapons than yours.

Anyone can get lost and make mistakes. If you do, ATC is there to help you - not to punish you for an honest mistake. Make use of that help!

As for procedures about which forms need to be filed after an incident like this, I will leave it to someone with knowledge about FAA specific procedures to answer.

You can read more about Airspace Infringements at SKYbrary.


Why are safety demonstrations done while taxiing?

Many passengers don't reach the gate until seconds before the gate closes for a variety of reasons. They won't get the pre-boarding briefing.

Taxiing is the only time before takeoff where the crew knows for sure that all passengers that will be on the plane are there.


Why were the fronts of the Messerschmitt Me-109 painted yellow?

You're right that the yellow tactical markings were used in order to reduce the friendly fire incidents (similar to the Allied D-Day stripes). As noted by Alan W. Hall in Messerschmidt Bf 109 warpaint:

  Quick identification has always been a necessity in aerial conflict ... Channel front fighters of the Luftwaffe started carrying yellow cowl and rudder markings. Some painted the entire cowling forward of the windscreen yellow, while others just painted the undersides of the cowling.

The image below shows some of the various tactical markings used at the time.

Bf 109 tactical markings; image from asisbiz.com

While the yellow paint seems to have been used before, it saw widespread use from August 1940 during Battle of Britain, and was used in some cases in other theaters too. Also, other aircraft like FW 190 also used some variations, like the yellow painted rudder.


Is trigonometry used by commercial pilots?

Note that this answer was given to the original question, Do pilots need to use trigonometry as part of their routine job? If so, when is it most used and for what? The question was subsequently edited, after this answer was accepted. Much of the information provided in this answer does not now apply directly to the current question, but it does serve to provide context and for this reason it has been retained.

Pilots use trigonometry primarily for calculations involving wind angles, either for navigation or for cross-wind components for takeoff or landing. Note that pilots often accomplish these calculations with a flight computer such as the E6B, a circular slide rule:

Image by Dave Faige — Source — used under CC BY-SA 3.0

Many such flight computers are available, including electronic versions, such as the Sporty's electronic E6B. Personally, I now prefer to use web-based software, but in flight school my preferred calculation method was a TI-83 programmed to do vector addition and other pre-flight calculations. In the cockpit, the CR-3—a pocket version of the larger E6B mechanical flight computer and which can be operated with one hand—is usually the most functional method.

Regardless of how they are performed, such calculations are typically for the purpose of either:

Calculating wind correction angles for cross-country navigation based on forecast wind conditions, or
Calculating crosswind component for takeoff or landing based on reported wind conditions.

The later are fairly straight-forward; the former are more complex. Crosswind component is a simple tangent calculation. Wind correction angles are more complex involving vector addition taking into account magnetic course, true airspeed, forecast wind angle, and forecast wind speed.

Now, the original question was merely, do pilots need to use trigonometry. The answer to that question is, "Yes". The question has since been edited to specify the use of trigonometry "directly, with trigonometry knowledge". The answer to that question is, "No", pilots do not need to have a working understanding of trigonometry, though they do need to be capable of computing the above described wind problems. A pilot need not understand the trigonometry used by the calculator, slide rule, or FMS that he or she uses to perform these calculations. I know good pilots who have no real working knowledge of trigonometry and do quite well without it.

For a pilot flying in the IFR environment, wind correction calculation is less frequently a needed calculation since most navigational means provide for wind correction in some way. This is especially true of GPS or RNAV navigation, because the ground track can be compared to the aircraft's heading to show wind correction angle.


Can I file IFR DIRECT with a non-WAAS GPS?

This question was answered here on this Website.  Read the second answer.

Yes you can file direct even without a GPS.  However it would be advisable to perform a RAIM check during your pre-flight along your intended route and determine that you would be in RAIM during the route.  If for some reason your GPS loses RAIM capability then you should proceed using VOR/DME/ADF.  You can still fly direct with using only VORs although that will be more difficult.


Is there any publicly available research that projects pilots' loss of proficiency due to lack of flying (or guidelines to prevent it)?

Any decent accident investigation report will show the flight hours flown by the pilot/crew, broken into a matrix of all / acft type in question, and during certain periods of time. These reports are publicly available on different national investigation authorities sites (for example NTSB). The reports also evaluate the currency of the pilot/crew, and mention if it is considered to be a factor in the accident.
If you are looking for an easy way out, in form of a scientific study on these reports, sorry, can't help with that one.
As mentioned in comments, currency in flying does not equal proficiency, and you seem to understand this. Being current does not guarantee one is proficient, not by a long shot, so you are digging a real can of worms here, beware :)
I do think you would benefit reading up on pilot training literature, namely the "human performance & limitation" module. IIRC it contains some very relevant information on the subject of your interest. Such as how experience needs support of other positive personality traits to manifest itself as safety, and perhaps proficiency if you will.


Can airplanes transmit/relay flight data to ATC's periodically while in flight?

No, there's no data relayed like this to ATC. All ATC really gets is the filed flight plan, and then the transponder data. ATC just cares about organizing all the traffic in the skies, and making sure it is safe, orderly, and expeditious.

Some airlines use a system similar to this to relay maintenance data to the airline from the aircraft, that's how AF447 was found to have something wrong, and how they generally found it's location quickly(I think within 48 hours debris was found from the a/c due to the location info through ACARS(Aircraft Communication and Reporting System)). This system, and it's capabilities are optional and variable depending on what the airline wants to spend. This is why there's so much controversy over the loss of MH370, since they didn't have the full reporting schedule, and a very basic version.


Does turbulent flow encourage/avert flow separation?

Turbulence delays flow separation. This is why we attempt vortex generators and turbulators in aerodynamic design when local flow separation is an issue.

A. Adverse Pressure Gradient

Fundamental to the generation of subsonic lift, as airflow accelerates over the leading edge, its pressure drops, resulting in net suction. At some point, usually corresponding to the point of re-converging airfoil geometry, the flow begins to decelerate as its pressure rises, eventually equating to the flow pressure on the lower surface at the trailing edge. This process is called pressure recovery, and the increasing pressure profile along the upper surface is called adverse pressure gradient.

Image modified from: https://conself.com/blog/calculate-lift-drag-with-paraview/

B. Laminar Boundary Layer

Within the boundary layer, which is a thin envelope flow close to the airfoil surface, an adverse pressure gradient in the external flow can slow the flow close to the surface (which is already much slower than the external flow due to no-slip condition) to a standstill. At that point, the separation occurs. This is more or less the story with laminar boundary layer where the flow is smooth.

Image ref: https://en.wikipedia.org/wiki/Flow_separation#/media/File:Boundary_layer_separation.svg

C. Turbulent Boundary Layer

Now in the case of a turbulent boundary layer, there is a lot more mixing going on within the boundary layer due to eddies. As a result, there is continued energy injection into the bottom layer flows, which delays the flow separation that would normally occur in a laminar boundary layer.

Image ref: http://www.bakker.org/dartmouth06/engs150/11-bl.pdf


Evolution has created this wonderful thing called stress. We tend to think of stress as something negative that is to be avoided, and that is certainly true: prolonged periods of stress will do all sorts of damage to your body and mind.

However, for short periods of time, stress is a wonderful invention that lets us survive situations we otherwise wouldn't: when we come under stress, when that sabre-tooth tiger pops out from behind the bushes, our autonomous systems produce anti-inflammatory agents, dampen our pain reception, flood our system with performance enhancing drugs, improve our perception, shorten our reflexes, increase our energy levels … and, yes, also repress our sneeze and cough reflexes.

Have you ever had the experience that, after a long period of stress, just when you were finally looking forward to some well-deserved vacation, you get sick at the most inopportune time, right at the beginning of your vacation? Well, actually, you didn't get sick, you were sick all along, but during the stress period, your body suppressed the symptoms, and as soon as the stress goes away, the illness, wich may have been brewing for days or even weeks, breaks out in full.

So, to answer your question:

  What if a aerobatic fighter pilot sneezes in middle of a maneuver?

He doesn't. Stress will prevent him from doing so.


Are there any airports that do not have an IATA code but have a huge number of traffic?

According to this thread, pretty much anything with scheduled air service will have an IATA code to facilitate booking.
From looking at the FAA data, it looks like everything with more than 10,000 enplanements (enplanement=1 passenger boards an aircraft) is considered a "primary" airport, and they all have an IATA code unless the airport is strictly general aviation and unscheduled service.
For these reasons, you probably won't find anything with "huge" passenger traffic but no IATA code. There may be airports with unscheduled service to major hubs, though.


Why do we see many more 5th and 8th freedom cargo flights than passenger flights?

I think the answer is simply that Cargo is far less picky about how it gets to its destination, as compared to People. A pallet can easily take three different flights to arrive at it's recipient, whereas most passengers wouldn't tolerate so many transfers.
Fifth freedom cargo flights are also often irregularly scheduled. For example, Atlanta Hartsfield-Jackson Airport receives the occasional cargo flight from Turkish Airlines and Singapore Airlines. It frequently receives flights from Korean Air Cargo and Cargolux, but these often originate at a variety of cities, such as Chicago, Dallas, or Anchorage.
In short, cargo is more flexible, which allows cargo airlines to be more flexible.


Have there been fully pneumatic aircraft?

Yes there have been, and some of them are still flying.

This article is about the fully pneumatic actuation systems on board the F27s built by Fokker and by Fairchild. If there was a leak, it was leaking clean air. System pressure was 3,300 PSI = 228 bar.
Some of the advantages cited:

Many factors favored the use of pneumatic systems on the F-27, most significant of which was an approximate 100-lb weight saving over electrical and hydraulic systems.

Lighter weight
Faster operation
No flammable liquids
Cleaner and easier to maintain

The systems were designed 50 years ago, fully aeronautical lightweight design. Could most definitely be used to pump up the tyres in this question to 16 bar.


Do flight regulations prohibit sleeping on the floor of an airliner?

That depends on the air carrier and the regulatory body they're certified by. Finland is part of the EU so I'm assuming that Finnair's certificate is under EASA aviation safety regs. Specifically, a quick Google search finds:

CAT.OP.MPA.165 Passenger seating:
The operator shall establish procedures to ensure that passengers are seated where, in the event that an emergency evacuation is required, they are able to assist and not hinder evacuation of the aircraft.

Finnair would also write their own SOPs to ensure they meet all the EASA regs.


What if the tower Is obstructed by clouds?

If cloud ceiling or visibility falls below certain minima, the ATC tower will initiate "Low Visibility Procedures (LVP)". These are different from airport to airport and depend largely on the available equipment.

Some airports have surface movement radar (SMR), also known as ground radar, which will let air traffic controllers monitor aircraft on the ground on a dedicated radar screen. At airports with SMR, ground movements are virtually unaffected by LVP.

At airports without SMR, controllers will rely on their mental image of the traffic situation to control aircraft on their ground. (Note: controllers do this even if visibility if OK. You could ask a controller to close their eyes at any point during their work, and they would still know what was going on outside the windows). Obviously, the controller will need to update their mental picture as planes move around. With limited visibility and no SMR, this will mainly be done by pilot reports. Basically, the controller will ask the pilot to inform them when they pass or reach certain parts of the aerodrome, such as a certain taxiway or runway.

One additional piece of equipment that is very common to use during LVP is stopbars. Stopbars are a row of red lights that span across a taxiway and can be switched on and off by the controller. During good visibility conditions, controllers will visually scan the runway area to make sure no aircraft inadvertently enters the runway without permission. Since such visual scanning is not available during low visibility, turning on stopbars near runway holding points serve as an extra reminder to pilots that they have not received permission to proceed.

Low visibility procedures can also include special rules or procedures that come into effect if the visibility becomes really, really bad. For example, where I work, if visibility falls below 200 metres, only one aircrat is allowed to move at the entire airport at a time. So if one aircraft is moving around, all other aircraft have to wait at the gate until that one aircraft is in the air. Obviously, this requires quite a bit of planning work from ATC, but safety always comes first.


Why does Airbus suppress stall warnings in certain situations?

Stall warning was inhibited below 60 knots airspeed, in order to eliminate nuisance warnings during taxi and other situations. It is well below the stall speed of an A330 in cruise configuration:

landing speed with flaps extended is in order of 135 knots;
stall speed in landing configuration would be in order of magnitude of 120 knots;
stall speed in cruise configuration way above that.

It was indeed a very tragic circumstance, one of the factors preventing the flight crew from recovering from their situation. The solution however, perhaps in addition to enabling stall warnings for very low speeds in cruise configuration, is to train flight crews in recovering from a fully developed stall. During recovery, the load factor must remain under 2.5 g, the structural limit for an airliner.

This is now mandated by regulation authorities, and the first systems have been certified for training use at airlines. FAA has published 14 CFR part 60 Change 2 for upset recovery training. Alaska Airlines had the first Part 121 simulator certified for Full Stall Training under Part 60 Change 2, in April 2016. The simulator is a B737-800.


Why does the lack of a magneto affect engine RPM?

Firstly, to understand the answer, we need to understand that the Cessna 152's and 172's run a 4 Cylinder, Horizontally-opposed Engine. Each Cylinder has 2 spark plugs, one on the top side of the cylinder head, and one on the bottom side. The spark plug ignites the fuel/air mixture that has been sucked into the engine, and causes a controlled burn to push the piston down the cylinder and turn the crankshaft in turn (hence turning the propeller as it is connected to the end of the crankshaft).

Now, as I've stated, each cylinder has two spark plugs, one connected to the "left" magneto, and one connected to the "right". If we turn one magneto "off" (or ground it to be politically correct), only one spark plug in each cylinder will "fire" to ignite the fuel/air mixture. This causes the mixture to have a delayed and less effective burn, meaning that the piston does not get pushed down the cylinder as effectively, meaning the crankshaft will not rotate as fast, and hence, leads to a drop in the Propeller RPM (Revolutions per Minute).

We check the magnetos on the ground to check that:

A. They both work, and the engine won't die if we lose a magneto (we should be able to return to land on the remaining serviceable magneto)

B. We are checking that there is no "Spark Plug Fouling". The fuel we use in aviation contains lead, and hence after a time of running the engine at low power settings on the ground, the lead in the fuel will accumulate on the spark plug head (instead of being burnt off when the engine is working under power), and cause the spark plug to let off a limited spark, or completely block the spark, hence again, making our engine less efficient.


Why doesn't a single engine airplane rotate along the longitudinal axis?

First, it's about torque, not power.  A helicopter rotor has a large amount of torque at a relatively low RPM.  A single engine airplane has much less torque at a higher RPM (Power = Torque X RPM).  On top of that, for a craft of similar size, the helicopter will have much more power (it has to lift the copter directly.)  So the helicopter has to deal with torque levels several multiples higher than that of a single engine aircraft.

As to the solution, most single engine aircraft have the vertical stab offset by a small amount to generate a counter force to the torque.  If you look at some high power aircraft such as the P-51, it's a noticeable offset. And that's set for cruise power.  Takeoff power requires additional rudder input.

It should also be noted that for smaller aircraft, P-factor is a bigger turning force during climb than engine torque.


Do aircraft carriers always face into the wind?

During flight operations, the aircraft carrier strives to maintain 30 knots of wind down the angle of the flight deck.  Generally speaking, the carrier will adjust its speed and course through the ocean to maintain the desired winds.  However, shifting winds and the sheer magnitude of the carrier may mean that the winds are generally down the angle, but may involve a crosswind component.  Also, the structure of the carrier, because of its enormous size, actually influences the flow of the wind, and can create pockets of low pressure in the approach where high sink rates can develop.


Why do we need to fly at lower altitudes at night to prevent hypoxia?

The main reason stated by aviation authorities is due to the impairment of vision, your rods provide the majority of your sight in low light conditions and are affected by the lower oxygen levels. However, your colour perception (provided by your eye's cones) is also affected and this is already degraded at night due to the lower light levels.

The below quote is from an EASA General Aviation Safety Briefing on Preventing Hypoxia

  Hypoxia also impairs night vision. Because the rod cells in the eye, which give us night vision, require a lot of oxygen, a lack of oxygen causes visual impairment.

Regarding your friend's point on the diurnal atmospheric changes, this should not be a factor as the suggested altitudes by the aviation authorities on hypoxia prevention should be given as a pressure altitude (i.e. the altitude with the standard altimeter setting of 29.92 inHg or 1013Hpa)

Hope this helps


Where can I find records of old FAA registrations?

NC, NR, NL or NX are not necessarily older aircraft. Any aircraft more than 30 years old can use NC instead of just N.

So, to find the a/c registration you just take out the C.

I own a glider that was built in 1965 so my numbers are NC and 5 digits.

It should be the same for R, L, and X, which are any aircraft that has a restricted, limited or experimental airworthiness certificate can use those letters after the N. See FAR Part 45.22.


How many aluminum panels on the top of a 172M wing from 1972?

You way want to take a look at this video of a 172 wing rebuild. The wing is not lots of tiny panels but what you are seeing is the areas that the rivets are placed to hold the larger panel on.


What is the difference between Assumed Temperature and Derate takeoff thrust?

The difference is in the minimum control speeds ($V_{mcg}$ and $V_{mca}$).

In Assumed Temperature takeoff thrust, the pilots are allowed to advance the thrust levers to full rated takeoff thrust. However, in Derated takeoff thrust, the levers should not be increased beyond the fixed decate limit, otherwise a engine failure may result in loss of directional control.

From Boeing 737 FCTM (my emphasis):

  The fixed derate is considered a limitation for takeoff. Takeoff speeds consider ground and in-air minimum control speeds (VMCG and VMCA) at the fixed derate level of thrust. Thrust levers should not be advanced beyond the fixed derate limit unless conditions are encountered during the takeoff where additional thrust is needed on both engines, such as windshear. A thrust increase, following an engine failure could result in loss of directional control.

The minimum control speeds are calculated based on the full rated takeoff thrust. The rated thrust is lowered in Derated takeoff but not in Assumed Temperature takeoff. Therefore, by calculating the minimum speeds based on a lower engine rating, the pilots can be ensured that sufficient directional control can be maintained on a slippery runway, whereas there is no such guarantee for Assumed Temperature takeoff.

On a dry and long runway, there is no operational difference between Assumed Temperature and Derated takeoff.

From the Boeing 777 FCTM (my emphasis):

  Reduced takeoff thrust (ATM) may be used for takeoff on a wet runway if
  approved takeoff performance data for a wet runway is used. However,
  reduced takeoff thrust (ATM) is not permitted for takeoff on a runway
  contaminated with standing water, slush, snow, or ice.

And:

  Derated takeoff thrust (fixed derate) may be used for takeoff on a wet
  runway and on a runway contaminated with standing water, slush, snow, or
  ice.

The Boeing 737 FCTM has a nearly identical description.

The A330/A340 FCTM explains that the slower $V_{mcg}$ / $V_1$ can also allow increased MTOW on short runways:

  When taking off from short or contaminated runways where ASDA [Accelerate-Stop Distance Available] is the limiting factor, a reduction in the minimum control speeds may generate a take-off performance benefit and a higher MTOW.


What is the difference between stopbars and Intermediate Holding Position Lights?

Intermediate position holding lights may be used at larger airports as an additional means of controlling traffic while moving on taxiways to give way for other surface traffic an a taxiway intersection.  Stop bars are used to provide additional identification of the boundaries of runway safety areas and ILS critical areas to prevent runway incursions.