How does traffic handoff between ZMA and Cuba work?

After some searching, I found a paper from Wikileaks from November 19th, 2009, that reads in part:

  (SBU) SUMMARY:  Miami and Havana air traffic controllers
  signed a letter of agreement (LOA) on November 12 updating
  procedures for the coordination of flights between Cuban and
  U.S. controlled airspace.  Both sides stressed the excellent
  working relationship between the Miami Air Route Traffic
  Control Center (ARTCC) and the Havana Area Control Center
  (ACC).  The U.S. delegation agreed to review information to
  be provided by the Cuban delegation regarding flights
  operating under the rules of "due regard" that could pose a
  safety risk.  Both sides also agreed to discuss switching
  from verbal to electronic flight data sharing, on the margins
  of a regional aviation meeting in Miami in May 2010. END
  SUMMARY

Apparently handoff procedures have been a regular occurrence for a long time, and are cooperated on extensively.


Could landing gear weighing scales be used to detect lack of lift?

Technically one could develop a system that compares the decrease in weight-on-wheels during the take-off run to a theoretical lift model in order to determine whether the wings are performing as expected.

I see a number of reasons why this will not be successful a product:

Limited benefits:
The benefit of such a system is minimal. There are very few crashes due to contaminated wings or wrong flap/slat configurations. Let's assume there are one hundred thousand airline flights per day and one lift related take-off crash every 4 years. That is one in 150 million.
Available alternatives.
For both causes there are viable alternatives to detect them well before V1. Visual inspection of the wing usually detects contamination and many aircraft automatically check for the take-off configuration to be set whenever the thrust increases beyond a pre-defined trigger level.
Increase in number of rejected take-offs: No system is perfect. It will detect some contaminated wing situations and save the day, but it will also cry wolf in cases where there is nothing to abort a take-off for. If the system has a false alert rate of one in ten thousand take-offs (which would be very good and expensive to design and certify) it would cause 15000 aborted take-offs (assuming the same numbers as above) for every crash it prevents (assuming a missed alert rate of 0).

Since lift increases with the square of air speed, it is difficult to detect lack of lift early on during the take-off run. At low speed there is relatively little lift to be expected and it will be in the noise of the measurement. Also the accuracy of the airspeed indicator is relatively low at low speeds, so the theoretical lift model will not give accurate results either. As a consequence the system will only be able to detect lack of lift at high speeds. At those higher speeds, the influence of bumps in the runway start to affect the measurements as well. It is easy to see that detecting lack of lift is no so straight forward. False alerts will be raised and they will be at raised at high speeds.

High speed rejected take-offs are risky.

  Boeing studies indicate that approximately 75 percent of RTOs are
  initiated at speeds less than 80 kt and rarely result in an accident.
  About 2 percent occur at speeds in excess of 120 kt. The overruns and
  incidents that occur invariably stem from these high-speed events.

So effectively such a system will likely increase the number of accidents.


As mentioned in the comments BA flight 9 is a thorough example of why ash can be a huge issue.
Relevant points of that incident
One issue that ash creates is it cannot be seen on radar so it can be hard to track at night and must be reported by other means. This is deceiving as you would physically see what appears to be a cloud yet weather radar would not show anything.
Inside the cabin, this depends on the granularity of the ash. Some of it will be filtered by the plane's air filters as any particulate matter would. However, ash can be extremely fine and what does make its way through the filters will present itself in a smoke like manner. This may cause alarm in the cabin and a false indication of a fire.
When it comes to the exterior of the plane there are a few issues. The fine grains hitting the plane at that speed will act like sandpaper. The windshield may become scratched to the point you can't see through it (which is not actually as big of an issue as some may assume). The paint will be effectively sanded off which in the short term is not a huge issue. More importantly it could affect your instrument inputs by clogging things like the static ports and pitot tube creating erroneous readings in the cockpit.
The engines were the main issue that arose on BA 9. In short the ash entered the engine, was melted and began to adhere to the blades of the jet. In turn this blocked the engine airflow and caused an engine stall. In the process BA 9 lost all four engines; however, when they began to descend the solidified ash cooled and broke off the engine allowing a restart.
Air crash investigation covered the BA incident nicely in season 4. You can watch it here.
Other risks that BA 9 did not have
For a piston plane ash could potentially clog the air filter and starve the engine of air. Any super-fine ash that could get through the filter runs the risk of being ignited and causing detonation issue with in the engine. Likewise the sanding/grinding issue could have adverse effects on the propeller shape reducing its efficiency or even overall ability to act as an airfoil.
There is a nice wiki on it here and it appears that as of 1991 centers called "Volcanic Ash Advisory Center" have been set up to help track these very issues.


Are ham radio contacts allowed from inside an airplane?

Two-way radios are just like any other communications device. If the captain says all such devices must be in flight mode at any particular moment during the flight, you are not allowed to use it and could be arrested if you do. Also, if the captain determines that something you are doing with your communications device is interfering with aircraft communications or navigation, he may order the flight crew to confiscate your device until after landing, and you may be subject to criminal charges.


Why does the UH-1 Huey have a hump at the rear of the cabin?

A copy of the original image can be found here, which is about 5 'pagedowns' down this page, which has a number of other excellent Huey-model photos.

It's a bit of structure to guide the rotor forces into the rest of the airframe, it would not be good if this bit went missing.

Fwd/aft, left/right, up/down. The rotor provides the lifting forces and driving forces and these are quite concentrated around the rotor axis. Picture the airframe like an empty beer can - some panels are required to cope with the forces while remaining in shape.


Do airplanes with fixed gear usually turn upside down during water landing?

Depends on the airplane.  I recall reading about a guy flying across from the Aleutians to Japan, in a Piper Super Cub of all things, and he had to ditch it for whatever reason, which he was able to do next to a freighter.

To his surprise, it didn't flip over but kind of submarined, stopped, then popped to the surface nose down but upright. It's possible being a taildragger helped.  I think tricycle gear airplanes would be more prone to flipping right over because the pitching moment from water contact is a little stronger with 3 gears hanging down vs two.

I expect though, that if you surveyed ditchings you would find some do and some don't.  Pitching moment from water contact, elevator effectiveness in resisting the pitching,  amount of up elevator at water contact, speed at water contact, maybe the surface contours of the fuselage could promote it or inhibit it, all kinds of variables.

As xxavier says, it would be prudent to assume you are going to flip over, and if you don't, bonus.


How is flow separation related to the chord length of an airfoil?

The chord length is a minor influence. The main driver for separation is the local pressure gradient.

Make sure to read the first three paragraphs of this answer if you are unsure how the pressure gradient drives separation.

The chord length only comes into play via the local Reynolds number. Higher Reynolds numbers mean steeper pressure gradients can be tolerated, but the effect is rather weak. It shows in the separation point which moves back slightly on the upper side of an airfoil near stall at the same angle of attack when the Reynolds number is increased.


What does the "blue" callout mean in the cockpit of an Airbus?

At the top of the Primary Flight Display (PFD, the one with the artificial horizon in the center), there is a so-called Flight Mode Annunciator (FMA) with several columns indicating currently active and armed modes of flight guidance:

The first line shows active modes (in this case: SPEED, ALT, and HDG) in green color. The second line has additional information about armed modes in blue color, which will become active later, for example LOC (localizer) mode will become active instead of HDG upon localizer capture.

The callout from the pilots like "LOC blue" serves to remind themselves of the current flight guidance modes, and to maintain awareness of mode changes. This is also to ensure that their mental idea of "what the aircraft will do next" is up to date and fits to the current flight situation.

However, I'm not sure about the "2500" you mentioned.

On youtube you can find videos like this one explaining a bit more about the FMA. (screenshot taken from there). As the comment by @DeepSpace mentions, the screenshot and video mostly apply to Airbus aircraft. Other aircraft may have similar displays about flight guidance modes, but I am not aware of their specific color codings.


Can I count solo complex time as complex training time for a commercial certificate?

As you already noted, 61.129(a)(3)(ii) says "training" (emphasis mine):

(ii) 10 hours of training in a complex airplane, a turbine-powered
airplane, or a technically advanced airplane (TAA) that meets the
requirements of paragraph (j) of this section, or any combination
thereof. [...]

Here's the definition of training in part 61, per 14 CFR 61.1:

Training time means training received—
(i) In flight from an authorized instructor;
(ii) On the ground from an authorized instructor; or
(iii) In a flight simulator or flight training device from an
authorized instructor.

According to that definition training always requires an instructor so there's no way you could log solo time as training time. All 10 hours must be dual instruction.


What are the advantages of a forward-swept wing over a rearward-swept wing?

There have only been a few aircraft built with forward-swept wings. Most notably was the X-29, which you have pictured above. Russia/USSR built one more recently in 1997, the Sukhoi Su-47. One of the biggest claims as to the superiority or an advantage of a forward-swept wing was increased maneuverability. However, in the case of the X-29, as noted in the Flying Qualities Evaluation of the X-29A Research Aircraft,

  The high pitch instability of the airframe led to wide predictions of extreme maneuverability. This perception has held up in the years following the end of flight tests. Air Force tests did not support this expectation. For the flight control system to keep the whole system stable, the ability to initiate a maneuver easily needed to be moderated. This was programmed into the flight control system to preserve the ability to stop the pitching rotation and keep the aircraft from departing out of control. As a result, the whole system as flown (with the flight control system in the loop as well) could not be characterized as having any special increased agility. It was concluded that the X-29 could have had increased agility if it had faster control surface actuators and/or larger control surfaces.

The Su-47 was indeed a highly maneuverable aircraft, capable of pulling 9 Gs, however, its immediate predecessor, the Sukhoi Su-37, was capable of pulling 10 Gs. So it's not clear whether a forward swept wing has any real positive impact on maneuverability.

However, stall characteristics are very different. Air tends to travel towards the rearmost end of the wing. On a standard configuration (Rear-swept wing), this of course moves from the wing root to the wingtip. On a forward-swept wing, however, this moves from the wingtip to the wing root.

  As a result, the dangerous tip stall condition of a backwards-swept design becomes a safer and more controllable root stall on a forward swept design. This allows full aileron control despite loss of lift, and also means that drag-inducing leading edge slots or other devices are not required. With the air flowing inwards, wingtip vortices and the accompanying drag are reduced, instead the fuselage acts as a very large wing fence and, since wings are generally larger at the root, this improves lift allowing a smaller wing. As a result maneuverability is improved, especially at high angles of attack. At transonic speeds, shockwaves build up first at the root rather than the tip, again helping to ensure effective aileron control.

Because of the capability of the X-29 to have the tips of its wings bend down when at high angles of attack, the X-29 remained controllable at an angle of attack of 67 degrees. However, thanks to modern advances in thrust vectoring, the F-22 Raptor is capable of sustaining an angle of attack over 60 degrees.

With inherent instability and problems with extra stresses on the airplane for only moderate or supposed but not observed gains in instability, it is unlikely we will see combat aircraft with forward swept wings any time in the near future. Other technologies have enabled similar or enhanced performance without the need for novel concepts.


Why doesn't temperature affect Pressure Altitude?

The picture you have displayed is correct. But, your understanding of what it is saying is incorrect. The picture is explaining the reason your Indicated Altitude will change with temperature for the same True Altitude. And, your True Altitude will change with temperature (a potentially dangerous situation) for the same given Indicated Altitude.
Your misunderstanding may stem from the fact that the Indicated Altitudes and the field level barometric pressure (or at least the Altimeter Kollsman Window) setting are the same in all three temperature scenarios. This is not the case for the pressure at 10,000 feet MSL True Altitude. The atmospheric static pressure at altitude for the three scenarios is not given. And, they can not be equal to 29.92.
The static atmospheric pressure is higher for the cold scenario and lower for the warm scenario at 100,000 feet MSL True Altitude. You would think that this would be the opposite way around. And, it is for air confined in a container. But, not for unconfined air or air confined in different sized containers.
Atmospheric air will become less dense and rise when warmed. This will create a partial void of air below it. This partial void is an area of low pressure since the surrounding air has yet to move in to fully replace the vacating air. If the air were to be cooled, it would sink onto the air below it. This would create an area of high pressure as the existing air has not moved outward in sufficient quantity yet.
How does this affect the different types of Altitude? Like this:

True Altitude is the height above MSL measured in actual feet of distance.
Pressure is just a measurement of the amount of air interacting with the measurement device and the average amount of energy each air particle has. Temperature will affect the amount of energy possessed by each air particle proportionately. This will either cause the  pressure to change proportionately. Or, it will cause the volume and density of the air parcel to change proportionately.
Barometric Pressure (Altimeter Setting, Kollsman Window Setting) is just the static atmospheric pressure at field elevation adjusted to show what the pressure should be at Mean Sea Level.
Indicated Altitude is just the reading you receive from your Altimeter. Your altimeter is just a very accurate pressure gauge (a barometer) calibrated to show the height above a specific reference line of pressure. The pressure and density of air at lower altitudes are greater than they are at higher altitudes. This is due to the sheer weight of the air from above pushing down and compressing the air below. The amounts of changes of air pressure and air density are known. This is based on observationally, scientifically and mathematically derived formulae and estimations that are based on the International Standard Atmosphere. On an ISA day, that reference line is equal to the Mean Sea Level. That is not always convenient since the atmosphere is not always at standard pressure and temperature at Mean Sea Level. So, most altimeters can be adjusted to account for non-standard barometric pressure.
Pressure Altitude is just the height above the mathematically derived line representing where the International Standard Atmosphere pressure of 29.92 inches of Mercury should be felt. Pressure Altitude is the height in feet you would feel the same pressure on a non-standard day as you would on an ISA standard day in feet MSL.  If the atmospheric pressure at MSL (or the barometric pressure at field elevation) is not standard, the two beginning levels will not be in the same place. You would have to make an adjustment to the height of MSL to derive the Pressure Altitude.   The pressure of air is derived from its volume and energy content. Temperature is a factor in this only if the air is confined or in a container.
Density Altitude is just the height above the mathematically derived line representing where the International Standard Atmosphere density. Density Altitude is the height in MSL where you would feel the same density on a non-standard day as you would on an ISA standard day.   If the atmospheric density at MSL is not standard, the three beginning levels will not be in the same place. You would have to make an adjustment to the height of MSL to derive the Density Altitude.   The density of air is derived from its weight and volume. Both pressure and temperature are factors in this only if the air is unconfined or in a container.

You derive Density Altitude by adjusting Pressure Altitude by atmospheric temperature. You derive Pressure Altitude by adjusting the True Altitude by the atmospheric pressure. You have to have each to get the next.
Case in point. If the air were confined to nice, neat, little columns with defined and rigid lateral boundaries and adjustable vertical boundaries, the average pressure in each container would remain the same. The heights of each column would be different based on temperature. For extremely tall columns, the pressures at the bottoms would all be equal. And, the pressures at the top would all be equal. But, the rate at which the pressures would change with height would be different. Since Indicated Altitude is just another way to represent the static atmospheric pressure at altitude, the Indicated Altitude of 10,000 feet MSL would be at different True Altitudes based on temperature.


Do any airplanes really have this piece Tom Cruise is hanging onto in this movie?

The plane is an Airbus A400M Atlas, a four-engine turboprop military transport aircraft.

I'm referring to this page, and there the stunt is well described.
About the door, here's an explanation:

  Visible in the released image, the A400M's new side door deflectors were added to the development aircraft fleet after initial tests with the ramp and side doors open resulted in high noise levels and turbulence inside the cargo hold, says Fernando Alonso, Airbus Military's senior vice-president flight and integration test centre.


From your description, you did nothing wrong. But, there is a possibility that one of you was on the wrong frequency. It is hard to prove that unless the radio calls were recorded. There is iPad software for recording your radio transmissions.
The more important lesson to be learned is that a nontowered  field is supposed to be pilot-controlled. But, it is perfectly legal to fly in pilot-controlled airspace without talking on the radio. Even if neither of you made a radio call, you would be within the FAA regulations.
The mistake that was made was that neither of you maintained situational awareness. You should always visually clear the traffic pattern while taxiing to and holding short of the runway. This is especially true for final approach. In the case of a high-wing aircraft, you will have to angle the nose of your aircraft downwind toward final. Otherwise, your wing will block your view of final.
P.S. It might not be a bad idea to file a NASA report.


How far would a landing Airbus A380 go until it stops with no brakes?

This is a very hypothetical question. If the aircraft has no means to slow down it has to lose all kinetic energy through rolling friction and air resistance. Both of these are very small (and get smaller as the aircraft gets slower) and will not have too much effect on a heavy aircraft like the A380 with an enormous amount of kinetic energy. Therefore the aircraft will continue to roll way beyond any runway or proper landing surface.

For high speeds, the air resistance will have the bigger impact on slowing down the aircraft (air resistance is about proportional to the square of the true air speed). Once the aircraft gets slow, the air resistance gets very little and rolling friction (highly dependant on ground surface) will be the bigger force to slow down the aircraft.


Can I compute the lift coefficient based on the NACA airfoil?

Yes it is possible.
Here is what I did, maybe it answers your question.

1) I went to airfoiltools.com into the comparison section.
2) Looked up the NACA-airfoil 2412

3) scroll down to choose the speed (Reynoldsnumber). I took the minimum and maximum to get an idea of the spread.

4) scrolled further for the polars, at sketched the $\alpha = 3^\circ$ into it

But somehow I do wonder if this is really your question.

Or are you asking for xfoil and the commands to compute it?

In case you want to compute the values without visiting airfoiltools (which most-likely use xfoil themselves) you need a tools to numerically solve the governing equations.
You can do this in many ways. Those ways differ in the way the flow is approximated. So you could go with XFoil (very simple approximation of the aerodynamics) or maybe OPENFOAM (more complex description of aerodynamics).

There is however no way to calculate these coefficients in an easy way.


Legend for SkyVector's Sectional Chart outside the US

Aeronautical agencies in Europe countries, not limited to European Union, and now Eurocontrol adhere to ICAO conventions more strictly than the US, this is historical as some European countries played a major role in ICAO creation.
Differences between FAA and ICAO approaches translate into the wording and the documentation. In accordance with Chicago Convention, these differences are listed in the country AIP, at section GEN 1.7 (examples: UK AIP, US AIP).
ICAO is an organization to facilitate international traffic, not domestic traffic, therefore it mostly deals with IFR matters, but there is some guidance for VFR too.
Sectional
The 1/500,000 VFR map is recommended and its characteristics are described in Annex 4 of the Chicago Convention, at chapter 17. The legend is described in appendix 2. The chart shown below, and its legend are compliant with Annex 4.
About annex 4, the US AIP tells us: "Charts vary in their conformance to ICAO Standards" This explains why US Sectional charts at SkyVector are different from charts covering Europe.
ICAO compliant maps are usually not public domain. In France maps are produced and published by a semi-administrative agency, the Institut Géographique National (IGN), in collaboration with the Service d'Information Aéronautique (SIA) in charge of the local AIP. They are commercial products, SkyVector cannot directly reuse them, but they can reuse public basic aeronautical information and open map bases.
In contrast, the French administration, probably by an effect of its infinite generosity, makes 1/500.000 ICAO VFR maps public via the GIS site used for various topographic/land information and aerial views.
ICAO and SkyVector versions of the same area (around Bordeaux).

ICAO 1/500.000 VFR map, France SW area
SkyVector shows a version which is significantly simplified (source: SkyVector):

SkyVector sectional map, same area
A notable difference is prohibited and dangerous areas drawn in red for the ICAO flavor. SkyVector lacks indications for activities like parachuting, and frequencies for ATC within controlled areas.
The map base is also a bit simplified, the Gironde estuary is missing though it's the continent largest (surrounded by famous vineyards, used to ferry parts by Airbus, Dassault or Ariane Espace, and also one of the places where surfers can ride a tidal bore).
The ICAO legend (a fragment showing airspace depiction, the full legend is here):

ICAO VFR map legend
VAC: VFR approach charts
If addition of 1/500.000 maps, detailed VAC are publicly accessible in the AIP for visual approach, E.g. the visual approach for Mérignac:

VAC Mérignac
Enroute
IFR enroute charts, the counterpart of Sectional and ICAO VFR charts are publicly available in the AIP, at section 2.


Has anyone compiled all the NTSB accident reports and broke down the percentages for cause of accident and fatalities?

There's a book called "The Killing Zone - How and Why Pilots Die" by Paul A. Craig which has a great deal of statistical work in it around aircraft accidents which may be useful to you. It's an alarming title which might make you think it's some sort of sky is falling mentality, but it's actually very sensible, statistics-based information about aviation accidents.


Why is an air intake located on the root of the tail on some aircraft?

That is the Ram Air Inlet for the air conditioning system:

Ram air, taken from the air scoop in the base of the vertical fin, is used as the cooling medium for  the  heat  exchangers.  Ram  air  passes  across  the  precooler  and  the  dual  heat  exchangers, extracting heat from the bleed air used by the air-conditioning packs. The ram air is discharged through exhaust louvers on the upper left and right sides of the aft fuselage.

During unpressurized flight, ram air may be used to ventilate the cockpit and cabin.

(Bombardier Challenger 605 - Air Conditioning & Pressurization)
The reason why it is located there is obvious from the picture above: the two air conditioning units (ACUs) are located just below so this provides the shortest duct. For tail mounted engines, this is the optimal location for the ACUs (also called PACKs) because the bleed air ducts from the engines (or APU) can be short this way. The ram air can also be used for ventilation when the pressurization has failed.
For wing mounted engines, the PACKs are usually located in the belly. The inlets are then found on the underside of the aircraft:
What exactly are those openings in the bellies of many jetliners?
On some turboprops you can also find them on the side:
What's this hole on the ATR-72?


Why are passengers not given the option of shoulder harnesses?

I'll address these one by one.

Should shoulder harnesses be installed, at least to enable passengers to decide to use them or not?

No. They would not serve a significant purpose to improve safety in those seats, and they would add weight and increase maintenance costs for airlines.  Keep reading, and this will come to light collectively with my full answer.

Why would shoulder harnesses be obligated for flight attendants in their jump seats, but not for passengers?

Those seats aren't lined up in rows, therefore there is no seat in front of them that they would hit and be stopped by.  Think of it like a school bus with no seat belts; the passengers will be stopped by the seat in front of them in a low-force crash, but the bus driver wears a seat belt because there is a steering wheel and windshield in front of them, not a padded seat.

How is 4 true? (It is superfluous in a crash when compared to the same safety from a lap belt)

Essentially, if there is a crash that will kill people, the shoulder harness will not be the thing that makes a difference.  The lap belt isn't really even there for crashes.  Extreme turbulence could throw someone up out of a seat; a lap belt is sufficient to prevent this.

A shoulder strap is designed to reduce impact with an object on board a vehicle. A car, we can safely assume, will remain in one piece if it hits a concrete wall.  Airplanes do not have structures designed to withstand impacts like that. If a plane disintegrates in a crash, the passenger, packaged along with the lap belt, shoulder strap, and all, will come to impact the external object directly due to structural failure.  No seat belt can save you from a total structural failure.

Do the safety benefits not outweigh the costs?

Since there really is no safety benefit whatsoever in adding them in the seats that don't already have them, no.  It would be security theater that costs airlines a lot of money.

Regarding Pilots

Notice I highlighted the low-force impact statement up above in regards to buses.  Let's say there is a low-force impact in a plane such as a taxiing crash that jars everyone on board. The passengers will hit the seats in front of them, not that the seats are even necessary to prevent injury.  However the pilots, on the other hand, have a lot of hard instrumentation in front of them such as throttle quadrants, and other things you don't want accidentally shoved forward during a ground crash.

It appears that very little actual research has been done on this subject. For example, this European Transportation Safety Council report states,

  Many proposed safety measures require further research before their benefit to cabin
  safety and the optimal design can be firmly established. In most cases, the availability
  of accurate, validated analytical models is indispensable.

It also states,

  It must be emphasised that these [death count] figures are at best estimates, since insufficient detailed
  accident information is available.

and,

  A fundamental limitation to this process, however, is the lack of adequate accident
  information for a sufficient number of accidents to allow full cost benefit analyses to be
  performed. The absence in many accident investigations of detailed information on
  injury mechanisms and cause of death makes the precise estimation of the potential
  benefits of any one measure very difficult.
  The Cherry study (1995)*
  , one of few studies which have performed a detailed trade-off
  concerning the full range of possible survivability measures, provides insight into
  available options. However, the small number of accidents available for investigation
  in such studies means that the basis for determining priorities still relies heavily upon
  best expert judgement rather than a truly numerically-specific approach.

...and lastly,

  Three-point lap and shoulder harnesses:
  As mentioned above, passengers who are restrained by a lap belt only and who do not
  take up a brace position prior to impact, are likely to suffer serious injuries due to the
  flailing motion of the upper body. As with rearward facing seats, the provision of
  three-point shoulder harness restraint systems would prevent this situation. If all
  passenger assumed the brace position prior to impact, the additional benefits of a threepoint
  shoulder harness would be small. In reality, however, for a variety of reasons,
  occupants generally do not assume a proper brace position, so a three-point lap and
  shoulder harness would be likely [to] improve occupant protection substantially.

So, after reading this document, I did not find any numerical evidence contained within to support its claims, and it even states that it has very little research to go on and appears to be written in an almost purely speculative and subjective manner, which leads me back to the original point above...

A shoulder strap will not save you from a structural failure, and if the plane bumps into something while rolling wheels-down on the ground, the seat in front of the passenger will absorb their impact.


What is the methodology for assigning airport codes?

There are different kinds of codes assigned to airports. IATA codes, which are the three letter codes you mention; are for travel industry identification purposes (by the way, these aren't restricted to airports - train stations also have these codes). These are used by airlines and travel agents.

The other four letter codes are ICAO codes. These are used for navigation, air traffic and flight planning.

ICAO codes have a defined standard, each region is assigned a letter and all codes begin with that letter. Canada is assigned a practical C, US is K:

IATA codes however, are arbitrary. For some reason, Canada was given 'Y' and so all IATA codes in Canada begin with Y.

There is YYC (Calgary), YVR (Vancouver), but then you have YQX (Gander) and YXS (Prince George) and YUL (Montreal-Trudeu).


How do I paint an airplane with an electrostatic paint gun?

I am a retired aircraft painter.

For electrostatic painting: ensure that the aircraft is grounded; ensure that you are grounded to the gun; use compatible electrostatic paint, this is a must.

My suggestion is, unless you are greatly concern about overspraying, to use a normal system on small aircraft, such as suction fed or gravity fed, as it will do the same job. Application is the same for all systems.

Hope this helps


My recollection of the Modulus of Rupture is about 6000 psi for aircraft graded sitka, based on the maximum allowed grain runout, and a maximum of around 10000 for straight grain.  But you should be able to find everything you need in the old Forest Products Laboratory study at this google search link.

The key weakness in spruce (and wood in general) used for wing spars I've learned over the years is the propensity for dormant failures in compression, typically following a wing tip strike on a strut braced airplane, that places massive compression stress in the wood above the strut attach bolt.

It collapses the cell walls in that area, evidenced by only a tiny line across the grain, that may or may not even be inspectable, and which drops the wood's tensile strength in the affected area to a fraction of normal.

Dormant, because you don't find out about the problem until some day when the wing is loaded inverted for some reason, so that the failed section is loaded in tension, and oops there it goes.  For this reason I advise people to stay far away from an airplane with wood spars that's ever had a wingtip repair.


Why do holds at or below 14,000 feet have different procedures?

The reason for a different turn rate at higher altitude is because of the physics of Indicated (IAS) and True (TAS) airspeed. Many aircraft would find it impossible to do a standard rate turn at high altitudes.

A standard rate turn is 3° per second. This is also known as a two-minute turn because it would take 2 minutes to make a full 360, or 1 minute for a  180°, like each end of a holding pattern.

The bank angle required to make a 3°/sec turn is a function of TAS and bank angle. The formula is:

$bank\,angle =\frac{turn\,rate\cdot TAS}{1091}$

So a standard rate turn at 170kn TAS requires a bank angle of 25°. As bank angle increases so do load factor and stall speed. A 25° bank yields a 10% increase in load factor and a 5% increase in stall speed. For this reason FAA and ICAO regulations require holding patterns to be standard rate, but not to exceed a 25° bank angle.

Here's where the altitude enters the equation. The relationship between TAS and IAS is dependent on air pressure and density. At 5000 feet in standard atmosphere an IAS of 160kn yields a TAS of 170kn. A standard turn at 170 KTAS would require the maximum bank angle of 25°. But in the thinner air at 14,000 that same 25° bank at 170 KTAS is only 142 KIAS.

So as altitude increases, a standard rate turn requires a slower IAS and a higher bank angle. At higher altitudes it would become impossible for many aircraft to make a standard rate turn without stalling. So at 14,000 feet the required turn rate is decreased to 2°/sec, which is a three minute turn (thus 90 seconds for a 180°). Where a standard turn at 14,000 IAS is limited to 142 KIAS, a 3 min turn can be performed up to 212 KIAS.

This is the reason turn rate must be lowered at higher altitudes.


Without the M, people would simply confuse the military cargo plane with the civil airliners that Airbus builds (e.g. A320, A380, etc).


Are modern aircraft provided with analog consoles in case of a software failure?

All commercial aircraft have some form of redundancy in their instrumentation, but it's not always in the form of "analog" instruments. The backup is often electronic itself. But the overall system is designed with a very high level of redundancy.

A typical modern jet aircraft has an Electronic Flight Instrument System (EFIS), which is the large screen Primary Flight Display (PFD) you see in front of both pilots. There are usually also one or more Multifunction Displays (MFDs) in the middle between the pilots. These displays form the primary instrumentation.

The EFIS itself is designed with a very high level of redundancy between the pilot's and copilot's side displays. Both are on independent electrical circuits and receive information from independent input computers (air-data [ADC], attitude/heading [AHRS], etc.). Both can usually also be switched over to the other set of input computers. Usually, the MFD can also be configured in a "reversionary" mode where it looks and acts like a PFD.

If the entire EFIS system should fail, there is also a backup set of instruments. In modern times this backup is usually one or two Electronic Standby Instrument Systems (ESIS). These are essentially smaller, condensed "PFDs" that display critical information. They usually either contain their own miniature AHRS/ADCs or are connected to isolated computers. They are also powered on a totally independent electrical circuit and often have their own dedicated battery as well, separate from the main aircraft battery.

Modern engines are controlled by completely different computers called Full-Authority Digital Engine Controllers or FADECs. Two or more FADEC channels are provided for each engine, so that if either channel fails, the other can take over. FADECs are also considered flight-critical items, and are designed with fail-passive capability: even if both FADEC channels fail, the engines can still run and be controlled more primitively and less efficiently.

Electronic pressurization controllers don't always have redundant computer modules, but a manual pressurization control mode is always provided. In the worst case, the pilot has the ability to manually open or close the cabin outflow valve to control cabin pressure. And redundant pressurized air sources are available from each engine.


Are the Boeing 747-8 engines more efficient than the 747-400 engines?

Yes. According to GE, the GEnx-2B consumes 15% less fuel than the CF6, which was contemporary to the PW4084 on the 747-400.

The bypass ratio of a jet engine makes it more efficient, not less. A higher bypass ratio provides more thrust from the fan air, which means the core section can use less air and therefore less fuel to provide less thrust. This increase in efficiency is the reason turbojets evolved into turbofans and have been increasing in bypass ratio as technology improves.

One consequence of a higher bypass ratio means the engine does get larger and heavier. However, the increase in efficiency is more than enough to offset these costs.

Besides increasing the bypass ratio, there have been many internal improvements in the GEnx line of engines, discussed in the GE link above. These changes include composite fan blades and fan case, which can be lighter than the metal alternatives. Throughout the engine there are also aerodynamic improvements to increase the efficiency of air flow through the engine, as well as more new materials and manufacturing technology.


Can I fly IFR in VMC if my instrument rating is not current?

No, you cannot. 14 CFR 61.57 (c):

  (c) Instrument experience. Except as provided in paragraph (e) of this section, a person may act as pilot in command under IFR or weather conditions less than the minimums prescribed for VFR only if: [instrument currency requirements]

To accept an IFR clearance as PIC, even in VMC, you must be instrument current.


Why does the LP compressor rotate in the opposite direction of the HP compressor?

Contra-rotating spools are a very recent development, apart from the Bristol-Siddeley (later: Rolls-Royce) Pegasus engine for the Harrier. The Rolls-Royce Trent 900 started the trend when its high pressure spool was made to rotate in the opposite direction to the other two spools. From Wikipedia:

  It is also the first member of the Trent family to feature a
  contra-rotating HP spool

Next was General Electric with the GEnx, a two-spool design with a high pressure compressor rotating clockwise while the low pressure compressor rotates counterclockwise.

Contra-rotation means that the relative speeds between the spools are increased, increasing the bearing losses between them. However, contra-rotation helps to increase efficiency - now the stator between the last low pressure stage and the first high pressure stage of the compressor and the stator between the last high pressure turbine stage and the first low pressure turbine stage can be left away which reduces parts count, engine length, engine mass and friction.

Again Wikipedia:

  Counter-rotating spools for the reaction turbines to reduce load on
  guide vanes.


Why is tethered hover testing performed on helicopters?

The cable is attached to the helicopter with a tensionometer.  This can be used to vary the effective weight of the helicopter by varying the tension applied to the cable.

The cable length can also be varied from 0 height, to hovering in ground effect and  hovering out of ground effect.

This test enables data to be gathered quickly for the helicopter performance from minimum to maximum weight on the ground, IGE hover and OGE hover without the pilot having to control height (since the cable does this) and with quick and easy changes to the effective weight without having to add ballast to the helicopter for each weight.

This test is a simple and quick, albeit risky, way to gather data on hover and climb performance throughout the weight range.


What is this aircraft that appeared at Oshkosh 2017?

That would be the Boeing YL-15 a scout plane of which only 12 were built.

Here is the EAA's article about the airplane from the airshow.


Are high bypass turbo jet engines suitable for tail and body mounted engines

it depends on what you call 'high-bypass'. The RB.211 engine was tested in a tail mount on a VC-10:

For tail-mounted high-bypass engines, the engine mount gets long, which means it gets heavy.

Tail- and bodymounted engines in general have drawbacks that also apply to high-bypass engines:

the high position means maintenance access requires special equipment and takes longer
for bodymounted engines, engine choices are limited by the amount of space available (unless you redesign this part of the fuselage, which can get expensive)


Why are the B-52's vortex shedding panels angled?

The angle of the edge shapes is such, that as the spoilers are stowed, the edge shapes are aligned with the airflow over the upper surface of the wing.

If the shapes were perpendicular to the spoiler trailing edge, they would form an angle of about 35 degrees to the airflow. This would cause turbulence, as the spoilers are not retracted 100% flush with the upper surface of the wing. The turbulence would lessen the lift of the wing and the effectiveness of the flaps (shown extended in the picture), and add drag.


Do runway markings vary from country to country?

Yes, examples are touchdown zone markings and runway number sizes.

How much do the runway markings vary from USA to Europe?

Europe is too big to manually check each country, but it doesn't vary by much. Numbers are still numbers and TDZ markings still follow the same pattern.

Even smaller airports, say in the US, don't necessarily match bigger airports.

Difference are submitted to ICAO to be included in supplements to Annex 14 when it comes to international airports (typically). And each country's AIP will list the differences from ICAO Annex 14. So if you are interested in a certain country, check its AIP. If interested in the recommended standards, check Annex 14.


Why can we not use full throttle in a C172 when cruising at lower altitudes?

These engines are not designed to run at maximum horsepower output all the time with a lean mixture.  They are designed to cruise at 50-75% of their rated max power, and deal with that level of internal heat and friction over the long term.  Even this is fairly hard compared to a car that runs at perhaps 20% of rated power when cruising at 60 mph.
Running them wide open means maximum heat, maximum wear, for not much benefit considering the power required to go faster is nearly the cube of the speed increase. You must run with the mixture full rich to keep the engine cool at all, and fuel burn is a lot higher because you are dumping unburned fuel used for cooling at full power out the exhaust.  It's not worth it in other words, unless you are racing, so the concept of cruising at not more than 3/4 of rated max power is a very old convention in piston engines, and mixture leaning shouldn't really be done above that.
You can run one of these engines at full throttle with a rich mixture with the RPM near red line all the time if you want, but only if you don't mind paying for the 20 thousand dollar premature overhaul from flogging the poor engine like a mule (the exhaust valves will hate you for all eternity).
It's pretty much the same thing as hooking up a big heavy trailer to your car, that required foot on the floor all the time just to stay at highway speed.  How many miles do you think that car's engine would last?(Although the Lycoming being run that hard will still probably outlast the car engine in the same shoes.)
However, when you go up, by the time you get to 8000ft, 75% of maximum output is all that is available with wide open throttle (WOT) in the thin air, so 75% cruise, normal operation, requires WOT and no harm is done. And as you go up further, you find you can't even get 50% with WOT and pretty soon you're at your service ceiling.


How many active Cessna 172 aircraft (or any other make/model) are there in the United States?

The FAA database
In the zip-file you find a number of text files, and a PDF file called 'ardata.pdf'. This file is the key to the other documents.
The 'master.txt' file contains all aircraft records and 'ACFTREF.txt' contains all aircraft types and their id's in the register.
The third column in 'master.txt' is 'MFR MDL CODE', which corresponds to the first column in 'ACFTREF.txt' called 'CODE'.
By finding the right aircraft codes you can find the number of corresponding aircraft in the 'master.txt' file.
My procedure
I imported both text files in Excel and filtered the aircraft file to contain only the Reims and Cessna 172 variants. This resulted in a list of 54 variants.
Then I filtered the master file using the codes I found, resulting in 20,789 aircraft. This number is the total number of Cessna 172s that have a registration assigned to them in the United States.
However, not all aircraft with an assigned registration are actually active. For example, N-numbers can be assigned to reserve a registration while the aircraft is being transferred/imported or may be cancelled while the N-number still is assigned. This is also included in the 'master.txt' file as the 'STATUS' column.
I decided to only look for valid registrations (indicated by the letter 'V'), which returned 18,914 results. So there are 18,914 civil Cessna 172s with a valid registration in the United States. The actual number of Cessna 172s in the US will be lower, since US-registered aircraft may also be operated in other countries. And some of the aircraft with a valid registration may not be active, but I assume that number is low, so a guess of 18,000-19,000 active C172s will be accurate.


Why is air accelerating over the wing surface?

The Abdullah's answer is correct to it's level of approximation, but I'd like to expand on why the pressure is reduced on the leeward side.
As the air encounters the leading edge, it is pushed out of the way. Due to first law of motion, it would like to continue moving outward from the wing and avoid the area just above the wing. But besides inertia, air also has viscosity, which prevents sharp changes in air velocity, so the incoming air trying to pass high above the wing drags the air near the wing along. But when the air just above the wing is pulled out aft, there is shortage of air just over the wing, which means low pressure.
This low pressure causes the air bend around the wing, and since it pulls air from all sides, accelerate as it enters the low pressure region over the leading edge and decelerate again as it leaves it over the trailing edge.
Without viscosity (e.g. in liquid helium) the pressure would not be reduced, because the oncoming fluid would just continue straight over the highest point and the area over the receding part of the upper surface would be filled with stagnant fluid moving with the wing. In fact that's exactly what happens in stall – as the curvature increases (due to higher angle of attack), at some point the viscosity is no longer enough to keep the air moving, the area over the wing gets filled with air just whirling around and not moving away, so there is no longer shortage of air, the sucking of oncoming air stops and the generated lift rapidly decreases – just the lower surface still generates some.


Saw this plane in Falkland war documentary. What type is that?

Looks a lot like the FMA Pucará :

https://en.wikipedia.org/wiki/FMA_IA_58_Pucar%C3%A1


How can I tell if an aircraft (N-number) is already equipped with an ADS-B transponder?

If it's onesy twosy, you can try searching flight logs of specific aircraft to see if ADS-B output is recorded.  Here is an example: track log showing ADS-B returns

There is not a free database.  You could purchase a database query of flights that have been tracked by ADS-B.  Depending on the number of aircraft you need, this will affect the cost.  Flight Aware will quote this kind of job.

The FAA database does not provide this information.  It does provide mode-S code information, but that is whether or not the aircraft is so equipped - nothing for ADS-B (yet).


Do I get two different certificate cards if I earn both a pilot and an instructor certificate in the US?

Yes.. The certificate number will not change.  The flight instructor certificate includes CFI at the end of your number.

  §61.5   Certificates and ratings issued under this part.
  (a) The following certificates are issued under this part to an applicant who satisfactorily accomplishes the training and certification requirements for the certificate sought:

  (1) Pilot certificates

  (2) Flight instructor certificates.

  (3) Ground instructor certificates.

Part 63 provides guidances on flight engineer and flight navigator certificates.

Part 65 provides guidance for ATC tower personnel, mechanics, repairman, parachute riggers, and dispatcher certificates.


How to say the name of this approach clearance: COPTER RNAV (GPS) 027°

Based on the 7110.65 2–1–17h, "degrees" is never used. Based on Note 9 under 4–8–1a, the text in paranthesis is omitted. So, ATC would say:

Cleared Copter RNAV zero two seven Approach

or

Cleared Copter RNAV heading zero two seven Approach

If you were requesting it, you'd say "Requesting Copter RNAV zero two seven approach."
However, since it is the only Copter approach at JFK, you could probably just request "the copter approach" and they'd know exactly what you're talking about. But ATC is required to use the phraseology as indicated in the Order linked above.


What are the considerations for landing on ice runways?

In Greenland there are a number of ice runways and I have heard that it is no difficulty landing on them. One would think they would be slippery and the aircraft might slide off the runway or ground loop. However apparently that does not happen.

Yes it does.  Go to Youtube and search for "Alton Bay Ice Runway" for examples.

  Are there any special considerations for landing on an ice runway?

First, understand that you are making a short field landing, NOT a soft field landing.  A soft field landing (well, mine anyway!) will eat up much more runway length.  Ice is hard, and you can hammer it down if necessary.

Second, do not use your brakes until under about 5 knots. Use aerodynamic braking instead.  Yoke full back on the ground.

  Is there an increase in minimum landing distance?

Yes!  Aerodynamic braking is pretty ineffective below 20-30 knots.


How do airlines dispose of a passenger jet when it's no longer airworthy?

Generally the planes are scrapped by a recycling company. The parts will either be removed and sold as spares, or chopped up and recycled or disposed of. So a lot will depend on how easy it is to remove the part, and how much of a market there is for it. Airplanes are disassembled to a large extent during heavy checks, which can provide an opportunity for substituting in spares.

Engines: Probably the most valuable part of the airplane. These will be removed and either used as whole spares or for spare parts, depending on the condition and how many of the type are still in service.

Cockpit instruments: These will be removed and used as spares as well, if there is enough of a market (everyone wants those fancy glass cockpits these days).

Interiors: These may be removed as well, they can be used as spares.

Control surfaces: These can be removed and used as spares as well.

Windows: These can be removed and reused.

Systems: Pumps, electronics, lights, actuators, etc.: Most of these can be removed and sold as spares.

Landing gear: This can also be removed and reused, depending on the number of cycles it already has.

Tires: The tires may be reused if not worn out. The tubes may not be reused.

Airframe: Although some parts may be able to be used, generally the effort and the fact that there are probably many cycles on the part will prevent much from being used as-is. The metal will be chopped up as scrap. They are already working on recycling major composite structure as well, since manufacturing scrap is already being created. According to Boeing, with modern recycling processes, the metal, plastic, wires/electronics, and carbon fiber composites are used for:

15% High-grade industrial
50% Low-grade industrial
35% Landfill

As it often is with business charts, it's not clear if these are by weight, volume, or what. This company claims to recycle 90% of the weight of an aircraft.

There are of course cases like Steve V. mentions where the plane is donated to some institution, but this doesn't happen to most planes. There are also ways that airplane parts find other uses.


Is it possible to fly horizontally with zero angle of attack?

Unless you tell us which book you read this in (and what exactly it said), it is not possible to answer your question (the answer depends on whether the zero angle of attack is that of the airframe or the airfoil (wing)). We can try for a general answer though.

As far as angle of attack is concerned, there are two kinds- geometric and absolute. First, angle of attack is the angle between some reference line and the freestream (i.e. the velocity vector). The selection of reference line determines the 'kind' of angle of attack.

Geometric angle of attack, $\alpha$ is the angle between the chord and freestream; this is the one usually used. Absolute angle of attack, $\alpha_a$ is the angle between the freestream and the zero lift line (the line, which when parallel to the freestream, produces no lift in the wing).

The geometric and absolute angles of attack can be related through $\alpha_a = \alpha - \alpha_{L=0}$, where $\alpha_{L=0}$ is the angle between the chord and zero lift line.

Relation between geometric and absolute angles of attack, image from gtae6343.wikia.com

For a cambered airfoil, the zero lift line is negative i.e. the airfoil will produce lift even when the geometric angle of attack is zero (in this condition, the absolute angle of attack is positive). For a symmetric airfoil, of course, the zero lift line coincides with the chord and as such, the airfoil produces no lift when the geometric (or absolute) angle of attack is zero.

As far as the lift is concerned, what matters is the absolute angle of attack, while we usually use the geometric one. Simply put, what matters is the absolute angle of attack of the wing. If this value is positive, lift will be produced and level flight is possible, whatever the aircraft attitude.


If the engine of a helicopter fails, is it possible to land safely?

You're asking two different questions, actually.

If the engines fails in a helicopter, the rotor will usually rotate and the pilot can land the helicopter by autorotation. The record is from an altitude of more than 12km by Jean Boulet when he descended via autorotation as the engine flamed out and couldn't be restarted.
If the rotor seizes for some reason in a helicopter, there is no lift produced and it will fall down. For tilt rotors like V-22, if the conditions permit (if it is in aircraft mode), the aircraft can be glided like normal fixed wing aircraft.


Could an airliner abort a landing after using the brakes system while landing?

Immediately after touchdown, the autobrakes will start to function, and may start applying the brakes depending on the aircraft's deceleration and the commanded deceleration.  If the pilot hasn't yet started to deploy the thrust reversers, a go-around is still possible at this point.  Advancing the throttles will disengage the autobrakes, and it's a normal balked landing from that point.

Also, advancing the throttles will stow the speedbrakes as well -- this is the way the system is designed, for exactly this sort of a condition.

As discussed elsewhere, once the thrust reversers are deployed, you are committed to stopping; a go-around is no longer safe to attempt after that.

If the brakes malfunctioned in a manner that the crew only became aware of after landing, chances are that they'd only become aware of it well after the thrust reversers were deployed, so the go-around isn't going to happen in response to that.  Thankfully, the wheel brakes on modern airliners are extremely reliable, and I can't think of any example of this sort of a failure.  If it did happen, you'd stay in max reverse as long as possible, use the EMAS if the runway has it, and use any available braking that you have (i.e. if the brakes on one wheel had failed but the others hadn't).  But it's not something that tends to happen on modern jets.


When I use a plotter to identify a direction from a VOR, what heading or course is it exactly?

If you are using a sectional chart and a plotter only, with no other information, remember the following:

If you are using the plotter relative to the sectional grid lines, you are measuring True Course.
If you are using the plotter relative to the compass rose around the VOR, you are measuring Magnetic Course.
True and Magnetic Heading can not be measured directly using the sectional and plotter. It must be calculated. You need to have the wind speed and direction to calculate any heading direction. You can calculate True Heading from Magnetic Heading. You can calculate Magnetic Heading from True Heading.
If you are in the aircraft, you can measure your Magnetic Heading by looking at your Magnetic Compass. You can calculate your True Heading from the Magnetic Heading, using the Magnetic Deviation, and the Magnetic Variation. Conversely, you can calculate your Magnetic Heading from your True Heading using the Magnetic Deviation, and the Magnetic Variation.


How are electronic instruments and other equipment powered in a glider?

Gliders generally use "Gel Cell" or Sealed Lead Acid rechargeable batteries, a little bigger than a block of butter, that will run designed-for-glider low wattage radios, and sometimes transponders, and FLARM systems (a kind of TCAS) and various other gadgets, and are good for several hours of operation (the total current draw of all the services might be under 1A when not transmitting on the radio, so a 5 AmpH Gel Cell 12v battery might be plenty unless you are talking all the time). Enough for normal glider flights and tasks, and if necessary you can hook up a second one if expect to be out for more than 4-5 hours.

Some newer batteries of the more exotic Lithium chemistry are starting to come on the scene, but the thing is the gel cells are light enough and are effective and trouble free, and don't require an STC (Supplemental Type Certificate; basically a 3rd party field modification), so the switch away from gel cells will be slow.

Recharging in flight with a turbine would be a real L/D killer so it's out of the question.  Much better just to install provision for a second battery for long flights.


How do you calculate the wing moment coefficient knowing the moment at each spanwise station?

You can use the Lifting Line Theory to first calculate the downwash at each spanwise station, which are then converted to the induced AOA ($\alpha_i$).
The sectional moment coefficient and lift coefficient are:
$$c_m = c_{m_0}+c_{m_\alpha}(\alpha-\alpha_i)$$
$$c_l=c_{l_0}+a(\alpha-\alpha_i)$$
To get the total moment of a straight tapered wing (about the root chord leading edge for simplicity), it's a simple integration away, noting that the sectional moment is usually about the 1/4c of the local chord:
$$M_{LE} = q_\infty \int_{-b/2}^{b/2}{\left[ c(y)c_m(y)-\left(x_{LE}(y)+\frac{1}{4}c(y)\right)c_l(y) \right]c(y)dy}$$
where $c$ is the local chord length, $x_{LE}$ is the distance from the root LE to the local leading edge, and $q_\infty$ is the free-stream dynamic pressure. You'll have to normalize against a reference chord (e.g. MAC) to get the moment coefficient.
Finite large sweep wings have crossflow gradient that would render Lifting-Line Theory unreliable. You'd have to use a vortex surface method, such as Vortex Lattice, to derive accurate predictions.


What is the purpose exactly of a ‘Control Check’?

Technically speaking, a control check is part of any pre-flight.

In the case of Qantas 32, one engine had exploded, punching holes in the wing and setting off a host of warnings, so there was a reasonable expectation that some of the controls might also have been damaged.

What the pilot did was put the plane through some basic maneuvers to see how the controls responded in their now potentially damaged form. And found that roll rate had been affected, something he factored in on the subsequent landing. He also found that pitch control had not been affected, which meant he could make a reasonably conventional approach to the runway.

Better to find out how much the controls had been affected when there is time and altitude to recover from an unexpected response, than to find out on final approach, where the margin for recovery is very slim to none at all.

During flight, this is not normal. It is prudent if an inflight incident may have damaged some of the controls, so that the pilot knows the level of controllability they have to work with.


What type of commercial aircrafts generate strong Wake Turbulence?

Big ones.

Wake turbulence is primarily proportional to the aircraft's weight, since this is generally directly related to the size of the aircraft and the amount of air the wings need to move to provide enough lift. Aircraft are categorized with respect to wake turbulence based on their maximum certificated takeoff weights. FAA AC 90-23G describes classes for ATC purposes as follows:

Super - Interim class for the A380 and AN225
Heavy - 300,000 lb or greater
Large - 41,000 - 300,000 lb
Small - 41,000 lb or less

Heavy and Super category aircraft are required to add their category to their callsign when contacting ATC, e.g., "Speedbird 12 Super".

Aircraft in higher categories have larger separation requirements when in front on aircraft in smaller categories, such as between takeoffs or landings, and ATC will issue caution messages cautionary advisories when required (Section 2-1-20).

The AC linked above discusses further on wake turbulence, such as how it propagates and how it should be avoided or escaped.

The FAA is also working on a 6 category system (A to F), which is in effect at MEM, SDF, CVG, and ATL. There are plans to expand this to the Metroplexes of Houston, New York, Charlotte, Chicago, and Northern California in 2015.

  This approval was based on years of joint research and development by
  the FAA, Eurocontrol, scientific experts in wake, and experts in
  safety and risk analysis. Categories are now based on weight,
  certificated approach speeds, wing characteristics, along with special
  consideration given to aircraft with limited ability to counteract
  adverse rolls.


The comments explain the logic behind a winglet well, so I will focus on the remaining questions:

  what would be the optimal airfoil selection for the winglet?

As a first rule of thumb, continue with the wing airfoil. A cambered winglet will be most efficient, because winglets are only beneficial if they produce lift. How much? This depends on the ratio of wing tip chord to winglet root chord. Ideally, there should be no break in the spanwise distribution of circulation, so the product of local wing chord and local lift coefficient should be the same at the transition and taper out towards the winglet tip.

  would the geometric twist affect the performance of the winglet?

Yes: The incidence must be chosen such that the desired lift coefficient is trimmed at the operating point (which is the cruise condition in case of airliners). Twist will only be needed when the planform differs a lot from the elliptical distribution. When flying with a high wing loading (again, just as airliners do), be sure to include the effects of aeroelastic deformation: They can be quite severe around the wing tips in cruise.


Why are student pilots' shirt tails cut after they complete their first solo?

Supposedly, this is because in the early days of flight before intercoms were common instructors used to sit behind their students in a tandem aircraft and pull on their shirt tails to give directions. After successfully soloing, the student has shown that he doesn't need that direction any more and therefore doesn't need his shirt in one piece either.

This isn't a universal tradition: I had the end of my tie cut off to mark my first solo (in South Africa). I had to go out and buy a tie first!


How is the the turning error of an aircraft magnetic compass calculated?

First of all, in real life the overshoot will depend on the bank angle, so it is not really practical to do calculations unless you are doing some kind of special, precision flying or acrobatics. Normally you just get a feel for the overshoot and compensate intuitively. Exact calculations can be useful if you are doing precise figure-8's or something like that.

To actually do the calculation (which is based on a shallow turn 15-degrees to 20-degrees):

Target heading:

270 or 090 no correction necessary
northerly -- need to overshoot
southerly -- need to undershoot

Amount of correction (as variation from East/West parallel):

90-degree difference (eg heading 000) -- use 30-degree correction
60-degree difference (eg heading 330 or 030) -- use 20-degree correction
30-degree difference (eg heading 300 or 060) -- use 10-degree correction

Example 1:

You are on a 110 heading and want to turn to 030. You need a 20-degree overshoot. Turn left and roll out when you reach heading 010.

Example 2:

You are on a 335 heading and want to turn to 240. You need a 10-degree undershoot. Turn left and roll out when you reach heading 250.


Do high-wing aircraft represent more difficult engineering challenges than low-wing aircraft?

Actually, in aircraft construction tension is preferable to compression: aeroplanes are thin walled structures, and compression forces introduce buckling.

In a low wing aircraft, the fuselage is pressing downwards on the top half of the wing, the bit that is under compression. In fact, quite complicated frame structure members are required for the fuselage/wing intersection for low wing aircraft: they need wing dihedral, so the wing looks pre-buckled at the spot of largest bending moment.

So although high vs low wing does have some differences in structural implementation, those are not the deciding factors in the layout. The design considerations for operational use are what drives the choice high-low-mid wing. Picture below from Torenbeek, depicting the Galaxy C-5.

High wing designs are usually applied for aircraft that need quick loading/unloading, and/or operate from airports with limited ground equipment.

Wing out of the way: good for loading/unloading, and for long extended flaps on STOL aircraft.
Floor close to the ground: easy cargo handling, good access for passengers, no need for airstrips.
More room for propellers.
Lowest induced drag at high lift.
Self stabilising roll behaviour.

Mid wing has the lowest drag of the three layouts at high speed, but poses a particular problem in running the wing through the fuselage. The wing must be a complete structure, because it has the highest bending loads in the wing centre and we don't want any holes there, best to make the hole in the fuselage to lead the wing through. But this bit of the fuselage cannot be used for passengers or cargo.
Low wing is usually applied in passenger aircraft because:

The undercarriage can be easily retracted.
The wing forms an impact structure that absorbs energy in case of a crash. Although the fuel tanks are in the wing...
The wing is fully underneath the floor and does not impede on the thoroughfare in the fuselage.
Optimal use of ground effect during take-off and landing.

In the 1950s, for the F27 the decision was taken to implement a high-wing design for its intended successor to the DC3: market analysis showed a significant market share outside Europe and the USA, at airports without the latest facilities. From wikipedia:

  while a high-mounted wing had been selected as it produced a higher lift coefficient than a lower counterpart, it also enabled easier ground loading due to a lower floor level and provided unfettered external views to passengers without any weight increase.

And who wouldn't want unfettered external views?


Yes, they are NOTAM'ed. In the FAA case, the FAA wants to know first when you intend to launch, where from (distance and direction from a town on a map), how high you expect to go and what direction you expect it to travel in. 24 hours before launch, you have to call your local Flight Service Station (FSS) and file a Notice to Airmen (NOTAM) giving the launch site, date and time, expected max altitude, expected rate of climb, expected direction of travel and landing spot. Your local FSS will have an 800 number. These people can also give you the winds aloft if you ask. Most pilots have no use for winds aloft over 30,000 feet, so tell the FSS that you're launching a balloon and ask for wind speed and direction for as high as they have data for. This will typically be about 50-60 thousand feet. Try to get the winds aloft for a reporting station to the west of you because 24 hours later, those winds will have likely moved to your location.

The NOTAM will look something like this:

"High altitude balloon release 5.49 WNW of KAGC, E/SE bound reaching Flight Level 600 (60,000 feet) on June 6.  Launching time between 1200 and 1300Z.  E/SE direction of drift.  Landing time no later than 1700Z"


What is this orange container labeled "Flight kit wheel"?

Short answer
Corsair is a small airline, with a limited number of aircraft, serving airports in remote islands from Paris. For their economical survival their aircraft must keep a high operational ratio. However:

The airline may not have a maintenance facility at destination, either a owned facility or an agreement for maintenance services from another company locally based.

The facility may not have a satisfactory stock of spare parts for their aircraft or the required tools, and no possibility to obtain them in a very short time, even from their main base.

A common solution is to bring parts aboard, in particular MEL components. It's a balance between the cost to carry the container and the cost of extra wait time (better said by FreeMan in a comment below: The weight penalty is much lower than the wait penalty.)
These containers marked Flight kit, Fly away kit (FAK), Do not unload, Do not offload, etc, contain components or tools intended to remain on board and be used at the next stopover in case of necessity.
It's relatively common to see FAK for spare wheels. One of the reasons is when the crew executes a rejected take-off just prior to V1 speed on a large aircraft, brakes are subject to intense heating propagated to the wheels. Tires inflated with nitrogen at about 1,300 kPa (that's about 13 bars or 200 psi) could blow out beyond a certain temperature, causing damages/injuries. To prevent such explosion, wheels are fitted with fusible plugs melting to allow tires to deflate safely.
After such event, the plugs (and possibly the tire) have to be replaced. A common option is to change the whole wheel and perform inspection and repairs later. The kit contains the necessary tooling and parts for this replacement. This might take 30 minutes or so.
As FreeMan also mentions, sometimes the mechanic who is going to replace the wheel is onboard. That was the case (at the time the photo was shot) for Corsair for certain destinations where there is no permanent maintenance team at the stopover.
Corsair, a small airline serving remote locations
And actually Corsair is a small French airline based at Paris-Orly (LFPO), which has a taste of holidays. Their 5 aircraft take people from Paris to beautiful beaches on islands where airports don't have large maintenance facilities (Fort-de-France, Pointe-à-Pitre, La Réunion, Saint Martin, Palma ...)
For a long time Corsair used Boeing 747 Classic, meaning also less common spare parts.
In such a small airline, when an aircraft is grounded the schedule of the others is indeed disrupted, the shorter, the better.
Flight kit

Loading a flight kit, source Linde

Flight kit, Air France (translates to "Fly away kit, do not unload"). Photo by A380spotter at Flickr

Flight kit wheels in cargo hold (Malawi elections inspection). Source
Secured content
Parts in the container are secured to prevent them from moving.

AKN FSK container for Air France (Source)

(source)
See also: Do any aircraft carry spare parts for making repairs?

Corsair, formerly Corse Air, comes from Corse island (the birth place of Napoleon Bonaparte). Their business has known ups and downs several times, they are now part of Dubreuil Group. Corsair 747 had over time famous tail numbers: F-GSEA, F-GSEX, F-GSUN, F-GSKY, F-HLOV, etc.

F-GSEA landing at Princess Juliana. Source: JetPhotos, photo by Rogier van der Velde


Is there any evidence that the downwash vortices impact the performance of a wing?

You've correctly called them downwash vortices. They are caused by the air behind the wing—over all of its span—moving downward, while the air outside the span does not, which creates a pair of vortices that move downward at half the speed of the downwash (and somewhat slower later as there is more air below them in their way).

The air moves down behind the wing because the lift is an upward force acting on the wing, so the corresponding reaction force is downward and acts on the air, which, being free to move, accelerates downward.

This acceleration of air, however, requires energy (because its kinetic energy increases), and because energy is conserved, work has to be done to provide it. This work is done by induced drag.

There are several other ways to show, from basic laws of physics, that induced drag is a necessary consequence of producing aerodynamic lift that is proportional to the amount of lift and inversely proportional to wing span and dynamic pressure  (that is density and square of speed). If the span-wise distribution of lift is suboptimal, it will increase the induced drag, but there is a known minimum for optimal, elliptic, distribution, and it is well known it can't be reduced below that.


For the U.S., can a non-cabin crew act as a cabin crew? Yes, except for safety duties.

  U.S. air carriers periodically use company employees in the cabins of its aircraft for the purpose of conducting certain passenger service activities, such as serving beverages, conducting customer relations, or acting as translators. These persons are not assigned to flights to perform safety duties. These company employees are not acting in the capacity of an F/A nor are they, in general, trained or qualified to act as a F/A. The regulations do not prohibit the use of non-F/A personnel by an air carrier. However, their presence could conceivably interfere with the F/As if they were not properly instructed.

Source: FAA

My interpretation is technically yes, especially that pilots are trained in safety duties.

But that's not to say there wouldn't be a union rule against it.


Is it possible to land a commercial aircraft with an elevator trim stuck at a high degree?

From the Boeing 737 emergency procedures:

After all attempts fail to free the stabilizer...

  Anticipate higher than normal elevator forces during approach and landing.
  The thrust reduction at flare will cause a nose down pitch.
  Note: Elevator control is sufficient to safely land the airplane regardless of stabilizer position.

Note on terminology: Most jet-liners (including the 777 and 737 as the question requests) use a trimmable horizontal stabilizer (THS), in which the pitch trim is achieved by positioning the whole rear wing up/down -- as opposed to using trim tabs.

(airteamimages.com) THS of an Embraer ERJ-190.


Did I witness an engine test for a 757 at MAN?

See this avherald report: https://avherald.com/h?article=4db1ccdb&opt=1

A Jet2.com Boeing 757-200, registration G-LSAN performing a test flight from Manchester,EN to Manchester,EN (UK), was in the initial climb out of Manchester's runway 05L when the right hand engine (RB211) emitted a loud bang and streaks of flame. The aircraft levelled off at 5000 feet and returned to Manchester for a safe landing on runway 05R about 25 minutes after departure.

So yes, it was a test flight, but it obviously did not go according to plan, resulting in an engine failure.


How to call a cartesian (END) coordinate system, that is referenced in surrounding air?

Some people call it Amosphere-Fixed reference frame.
(see at: heli-air.net)

Just to add a thought, this name seems to imply a global reference system, whereas the velocity of air molecules may be very local.


Where can I find more about a cargo pickup technique that doesn't require landing the plane?

See the notes on this page under the "Delivery" section. Looks like its formally called " long-line loiter". There is a brief note on it here and a US Patent here and this manual from the 70's that seems to show how to do it and some related research on it.

Here is a nice image of the maneuver


Should landing light be off during line up and wait position?

Counter-intuitively, the FAA answer (see chart on page 1-9 and text on page 1-10) is actually, they should be off during the line-up-and-wait phase.

When cleared to ...

  “Line up and wait”—when entering the departure
  runway without takeoff clearance, turn on all exterior
  lights (except landing lights) to make your aircraft
  more conspicuous.

Then when takeoff clearance is received, the expectation is that landing lights will be turned on.

The best rationale I've seen for this is so that Tower controllers (and other aircraft) have an immediate visual cue that an aircraft "on the numbers" understands that it has been cleared for takeoff, or not.

Another FAA document, SAFO 11004 (these are "best practice" recommendations, not requirements):

  Exterior Lighting:

  o Taxi with taxi light on when moving, off when stopped.

  o Turn on all exterior lights when crossing any runway.

  o If cleared to “Line Up and Wait”, turn on all exterior lights except landing lights.

  o When “Cleared for take-off”, turn on all exterior lights, including landing lights

  o If you see an aircraft in take-off position on a runway with landing lights ON, that aircraft has
  most likely received its take-off clearance and will be departing immediately.


Why does a flight booking mention that the plane has wingtips?

This is nothing but a silly marketing exercise. Wingtips (or rather winglets: all airplanes have wingtips:) are seen by the public as a cool and very visible feature, characteristic of newer models. So perhaps they want to say that our airplane is new, and not the 1968 model with the same designation.


Is "laze" (lava + haze) as hazardous as volcanic ash to turbo engines?

Laze is produced by lava running into the ocean, which limits both volume and dispersion of harmful products. Volcanic ash can be blown high into the air in astonishing amounts by explosions at a volcano summit, making it possible for wind to spread the particles over a wide area.

The 2010 eruptions in Iceland blew ash several kilometers into the atmosphere and across much of Northern Europe, shutting down air traffic for days. Both types of emissions have abrasive particulates and corrosive chemicals, so the biggest determinants of harm are dispersion and volume. Ash is by far the more dangerous.

see Kileua sends ash 30,000 feet high and this isn't even considered a very explosive volcano.


What are the drawbacks for manufacturing a large airliner capable of water landing?

Maintenance. Ditching survivability calls for overwing engines, as underwing ones act as scoops and torque the aircraft. But underwing engines are quieter for the pax and much easier to access. Plus, you'll need to make most of the openings airtight, and regularly inspect and replace the seals.

But of course weight, drag and extra fuel are a big deal - with better materials you'll still be picking between better reducing fuel usage or improving ditching survivability. The latter is also only helpful in controlled ditchings, which are mostly being prevented through engine reliability.

That said, airliner design has shifted from "don't crash" to considering crashworthiness at every stage. So it's possible that ditch-worthiness might become a larger factor in design. But it's going to take a couple high-profile high-fatality controlled ditchings for the authorities to make the call to sacrifice fuel efficiency for it, which is currently a big deal due to rising oil costs and AGW concerns.


If indicated air speed does not change can the amount of lift change?

Your friend is right.  Wind shear will greatly degrade or increase the lift depending on the change in direction and velocity of the shear.

If you are flying at 50 KIAS into a 50kt headwind, your ground speed will be zero knots.  If the wind shears to perpendicular to your flight path, your airspeed drops to zero knots and you fall out of the sky.  If it shears to 180deg in, says a microburst your airspeed is now -50kts or 50kts from the tail end almost certainly causing a departure from controlled flight.  In both cases at low altitudes the result is almost certainly fatal.

Conversely, if you were flying at 50KIAS and had a 50kt tailwind and the wind then sheared 180deg to a 50 kt headwind, you would abruptly jump to an airspeed of 100KIAS.  The airplane would rise very rapidly; you would feel the vertical acceleration in your seat.  This situation isn't as dangerous as shearing to a tailwind at low altitudes/speeds but it could be dangerous if one was cruising past Vno (yellow arc) where there is a risk of structural damage to the aircraft.

Your friend is right; microbursts are very dangerous.  The combination of wind shears as much as 90kts and severe downdrafts in the apex of the storm make it one of the most hazardous weather phenomena an aircraft can encounter.  They can even be catastrophic to large airliners at low speeds.  On August 2, 1985, a Lockheed L-1011 TriStar encountered a microburst while on final for KDFW and consequently crashed, killing 137 people.


Why is the Boeing 757 undercarriage so high?

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

source


Why are airplane passengers boarded from front to back?

A number of airlines (including Delta) use a 'zone boarding' procedure. In short, the first/business class board first, followed by 'blocks' of passengers, usually from rear to front (In your aircraft, this was apparently done the opposite way).
However, it is important to point out that the back-to-front is not very efficient, atleast if you take into account the time taken to seat everyone. Experimental evidence indicates that the back to front method is one of the least efficient of all the boarding methods. The table below shows the time taken for 72 people to board a (mock) airplane using various methods.

Table from Experimental test of airplane boarding methods by Jason H. Steffen and Jon Hotchkiss
The basic problem in following back-to-front method, according to the author is that it is a serial process:

The passengers would rush into the cabin, proceed toward the back—and come to a screeching halt as the first one or two passengers stowed their luggage. The first 30 passengers (the back five rows) would take up nearly the entire length of the cabin. The rest of the line has simply moved from the airport gate into the jetway or cabin—and it moves no faster.
... In this case, only one passenger at a time is seated. The aisle in the airplane isn’t used effectively.

There has also been studies on optimal boarding procedures, which indicate that optimal procedure is different from what any airline follows.

There was a mythbusters episode that simulated boarding an airplane using various methods in vogue. Making allowances for the lack of scientific rigor, the results of boarding 173 passengers were pretty much the same- back-to-front is the slowest method.

Image from mythbustersresults.com


How are electronic systems locked and connected in the electronic bay?

The LRUs are attached to trays which house the electrical connectors and the cabling behind them:

source

The hold down mechanisms vary in design, but it appears they generally attach the LRU to the tray at the front, the back likely being held in by the electrical connectors at the back.


Do solo night time and “towered” landings total separately toward the solo night requirements in FAR 61.129?

Night time does not need to include a landing at a controlled airport to count.  You just must have at least 10 solo night landings at a controlled tower, as well as 10 hours of solo night time, they don't have to happen together (though whatever time it takes you to get those landings counts toward the 10 hours too).

The pilot in your question would have 501 solo night hours and 10 towered landings.


In the US, in actual practice, workload permitting, will ARTC facilities grant SVFR clearance for surface-level Class E "extensions" (E4 airspace)?

In the US, in actual practice, will ARTC Centers and Approach Control
facilities grant clearance for Special VFR operations in E4
surface-level Class E "extensions"?

Some will, and some won't.

Does the answer vary between different ARTC facilities?

Yes.
Note the range of comments below obtained from questions posed by telephone in May 2019 to various ARTC Center and Approach Control staffers-- in most cases, the "Watch Officer" on duty, or else an "Airspace Specialist"--
(The summaries below are based on written notes and are not verbatim transcriptions.  The actual airspace descriptions are not from the staffers but rather are from the FAA's "Airspace Descriptions And Reporting Points" document, JO 7400.11E.)
Note also that in no case did the staffer indicate that the specific reason that SVFR would not be approved for an surface-level Class E "extension" was because it was designated as E4 airspace rather than E2 airspace.  Airspace definitions for some airports are actually written so that the surface-level Class E (E4) "extensions" convert to E2 surface-level Class E airspace when the control tower is closed, but no staffer ever indicated that that change in status would have any effect on whether a Special VFR clearance might be granted for that airspace.  Several staffers were not even aware that surface-level Class E airspace was broken down into several different subcategories (e.g. E2 versus E3/E4) in the FAA's "Airspace Designations and Reporting Points" document.
Facility-- Harrisburg Approach (PA)
Airport: KLNS-- Lancaster-- PA
Airspace description-- Part-time Class D, turns to surface-level Class E (E2) when tower closes.  Surface-level Class E (E4) "extension" to SE, converts to surface-level Class E (E2) when tower closes.
Staffer stated that when tower is closed, Harrisburg Approach may issue SVFR clearance for the entire "surface area", which does include the airspace in the "extension", because it  goes down to the surface, whether the tower is open or closed.  In response to my questioning, said it has nothing to do with whether the airspace is E2 or E4-- it's all "Echo" to them.  Said tower is only authorized to issue SVFR clearance for the Class D airspace, but if tower contacted Harrisburg Approach with a request, odds are good a SVFR clearance could be granted for the E4 extension as well.  Stated tower has to call Harrisburg Approach anyway when granting a SVFR clearance so it would not be a burden to ask.  Noted that S37 is within the E4 extension so a pilot flying from KLNS to S37 might have good reason to want a SVFR clearance including the extension.

Facility-- Seattle Center ARTCC
Airport-- KACV-- Arcata CA
Airspace Description-- surface-level Class E (E2) circle around airport effective 24/7, surface-level Class E (E4) "extension" to SE effective 24/7, depicted as separate areas on the sectional chart--
Staffer said a SVFR clearance could indeed include the entire Class-E-to-surface area.  In response to my questioning, stated made no difference whether the airspace was E2 or E4.

Facility-- Salt Lake City ARTCC
Airport-- KSHR --Sheridan County-- WY
Airspace description-- surface-level Class E (E2) airspace, effective 24/7, extends far to NW and SE of airport
Staffer's initial response was that a SVFR clearance would be limited to a certain radius from the airport such as 5 miles, but after taking a closer look at the sectional chart said a SVFR clearance could indeed include the entire Class-E-to-surface area.  Stated that since the area is quite large, let ARTCC know if you only need the northern part or the southern part.
The staffer also offered opinions on the airports below, while noting that they are not actually in the Salt Lake City ARTCC area of responsibility--
Airport-- KBIH -- Bishop-- CA
Airspace Description-- surface-level Class E (E2) circle around airport effective 24/7, surface-level Class E (E4) "extensions" to N effective 24/7, all depicted by a single dashed magenta line on the sectional chart--
Staffer said a SVFR clearance could indeed include the entire Class-E-to-surface area. In response to my questioning, stated made no difference that extensions were E4 not E2.
Airport-- KTVL-- South Lake Tahoe-- CA
Airspace Description-- surface-level Class E (E2) circle around airport effective 24/7, surface-level Class E (E4) "extension" to N effective 24/7, depicted as separate areas on the sectional chart--
Staffer said a SVFR clearance could indeed include the entire Class-E-to-surface area.  In response to my questioning, stated made no difference that extensions were E4 not E2.

Facility-- Minneapolis ARTCC
Airport-- KSTC-- St. Cloud MN
Airspace description-- Part-time Class D, turns to surface-level Class E (E2) when tower closes.  Surface-level Class E (E4) "extension" to SE, converts to surface-level Class E (E2) when tower closes.
Staffer stated that tower could only issue a SVFR clearance for the Class D airspace, but if tower were closed and pilot contacted Center, a SVFR clearance might be able to include the extension to SE.  Wasn't sure about this, said no one had ever asked.  Noted that there is small airport just inside the far end of the extension so there might be reason to desire such a clearance.  Was unfamiliar with designations E2 and E4 and planned to do more research on the topic.

Facility-- Oakland Center
Airport-- KBIH-- Bishop CA
Airspace Description-- surface-level Class E (E2) circle 5 miles in diameter around airport effective 24/7, surface-level Class E (E4) "extensions" to north effective 24/7, all depicted by a single dashed magenta line on the sectional chart--
(Staffer indicated that the above description was only valid for the winter season.  Stated that the summer configuration was class G up to 1200 feet.  That has apparently now changed, as the 2-25-21 Chart Supplement simply says "AIRSPACE: CLASS E")
Regarding the winter configuration, staffer said a SVFR clearance would not be granted beyond 5 miles of the airport because the purpose of a SVFR clearance is just to get pilots up away from the airport or down into the airport, and the terrain to the north is mountainous so they don't want pilots flying SVFR there.  Also stated that the purpose of the extensions is to facilitate instrument arrivals and departures so they wouldn't want pilots flying SVFR there.  Said even in a case where terrain were flat they likely would not grant SVFR beyond a certain radius from the airport conforming to the basic inner Class D or Class-E-to-surface circle, because the extensions are to facilitate instrument arrivals and departures.  In response to my questioning, said it had nothing to with whether the airspace in the extensions was E2 or E4.

Facility-- Kansas City ARTCC
Airport-- KTOP-- Phillip Billard near Topeka KS
Airspace description-- Part-time Class D, turns to surface-level Class E (E2) when tower closes.  Surface-level (E4) "extension" to SE effective 24/7.
Staffer stated that a SVFR clearance could not include the extension because the purpose of a SVFR clearance is just get to pilots up away from the airport or down into the airport and if you can't do it within the D circle you should file IFR or not fly.  Stated that the purpose of the extension is to protect IFR traffic, so they wouldn't want to issue a SVFR clearance there.  In response to my questioning, stated made no difference that the airspace in the extension was E4 rather than E2 -- they just call it "Echo" and don't make that distinction.  Comments were not specific only to KTOP but also stating the general principle involved.

In essence, whether or not SVFR clearance will ever be granted by ARTC for a specific chunk of surface-level Class-E airspace that projects some distance from the basic circle of surface-level controlled airspace around an airport, seems very much to depend on the "culture" of the particular ARTC Center involved, as well as factors such as terrain hazards specific to the particular geographic location involved.

Note that the related answer Does an SVFR clearance extend to Echo surface extensions? quotes a 2010 letter from the FAA ATO Western Service Center stating that their opinion is that the FARs do not permit SVFR to be authorized in E4 surface-level Class E "extensions".  The original query that provoked the answer was apparently specific to KSTC, an airport where all the surface-level controlled airspace reverts to Class G airspace when the tower is closed, so all requests for SVFR would always be directed to the tower, and ARTC would not be used to receiving any requests for SVFR for any of the airspace associated with that airport during the hours that the tower was closed.  Yet the letter is phrased more broadly and indicates as a general principle that SVFR should not be permitted in any E4 surface-level Class E "extensions".
Clearly, not all ARTC facilities follow this guidance.

See these other related ASE questions and answers--
Does FAR 91.155c apply to class E surface extensions?
What indication has the FAA given that phrases like "surface area of Class E airspace designated for an airport" do or don't include E4 "extensions"?
What are the historical precedents of today's E2 and E4 airspace? (US)
Which parts of class E airspace can an ultralight (part 103) fly in without prior ATC authorization?


What kind of Gyros are being used in smaller regional jets?

Yes small planes have electric gyros as well. It can be as sophisticated as Garmin 1000 in Cessna 172 or Russian made electric artificial horizon gyro powered by accumulator in a glider Blanik L13. I heard battery didn't last very long though:) Also all turn rate indicators have gyros and the ones I saw were electric powered. This ensures that you can still survive if a vacuum pump fails. Turn indicators used in the eastern block made gliders are powered by simple 4.5V battery.