Why are aircraft designed so that the wing stalls before the tail?

You are missing the weight force. The wing should stall first because then it will produce less lift and the weight will make the aircraft pitch down.

In attached flow, the lift from wing and tail is balanced such that the combined resulting force is acting exactly at the longitudinal position of the center of gravity. If the wing stalls, the balance of lift is shifted backwards (regardless of the tail producing lift or a downforce), because now the forward part of the wing-tail-combination will produce proportionally less lift than it did in attached flow. The center of gravity will then be ahead of the resulting lift force and will pull the nose of the aircraft down.

A tail stall is bad news for the pilot and should be avoided:

A stalled tail will have much less elevator effectivity, reducing the control power available to the pilot
A stalled tail at high angle of attack is stalling at maximum lift, so it produced positive lift before. If it stalls, its lift will shrink and make the aircraft pitch up.

In a conventional configuration the tail flies in the flow field of the wing. Because the wing's downwash increases with angle of attack, the angle of attack variations at the tail are reduced. This helps to keep the flow at the tail attached over the whole useable angle of attack range of the wing. A tail stall is either caused by a wrong location of the center of gravity (CG) or by a very poor transsonic design which causes shock-induced stalling of the tail when the wing is still doing fine. Very rarely can you stall the tail by a wrong trim setting when a moveable stabilizer is used for trimming, or in a deep stall.

Some supersonic aircraft compensate for the backward shift of the center of lift in supersonic flow by pumping fuel from forward to rear. If an airplane with such a rear CG location slows down to subsonic speed, it will need to produce proportionally more lift with the tail than with the wing. If it now pitches up (say, for a tight turn) it will risk a tail stall. Note that such a configuration is aerodynamically unstable at subsonic speed.

EDIT:

Now you define the center of gravity as ahead of the wing, which makes for a very stable configuration. The tail is producing a downforce to compensate the pitch-down action of the wing's lift.

If the wing stalls first, lift will become less than weight and the aircraft will accelerate downwards. Now the angle of attack will increase at both the tail and the wing; at the tail even for two reasons:

The downward acceleration will change the local flow direction to a larger angle of attack, and
The diminished downwash from the wing will cause an angle of attack increase of its own at the tail. This effect takes a little longer to manifest itself: The delay is the distance between the quarter points of tail and wing divided by the airspeed.

Both effects will quickly create a dominant pitch-down moment for the aircraft because the tail will contribute much less downforce than before the stall, and the diminished pitch-down moment of the wing will become insignificant.


When helicopters are instructed to air-taxi direct to an airport location, are they allowed to pass above other aircraft and people?

No. A helicopter taxiing has to follow the exact same rules as any other taxiing aircraft.


What exactly are "suitcase handles" in a cockpit?

From the NTSB report

  "Suitcase handles" is a colloquial term for the longitudinal trim handles located on the center control
  pedestal. "Pickle switches" is a colloquial term for the trim switches located on the outboard side of each of
  the control wheels.

The MD-80 cockpit is shown at this page, with the trim handles on the left side of the console (item 9).

Under normal operation, the pilot will use the switches on the control column to change the trim.  If there's a problem with the thumb switches, the handles on the console are available.


Why is the Concorde, and not other aircraft, getting this fog/condensation, over the wing, at *takeoff*?

You're correct that the condensation is due to low pressure, but the wing is not stalled. The highly swept delta wing of the Concorde created lift be what is called vortex lift. From my answer in that question:

  In the case of wings having sharp, highly swept leading edges like delta wings, the leading-edge separation vortex phenomenon occurs at subsonic speeds. However, the separation does not destroy the lift as in the case of low sweep wings; instead, it forms two vortices which are (nearly) parallel to the wing edges.

The centre of the vortex is a low pressure region, where condensation forms. In this figure, you can see the vortex formation in a model of Concorde.

Flow around Concorde in a landing Configuration by Henri Werlé, ONERA, image from efluids.com

A side view of the same thing:

Flow around Concorde in a landing Configuration* by Henri Werlé, ONERA, image from efluids.com

So, basically, the aircraft is still producing lift; only the mechanism is different.

This kind of lift production is quite common in case of highly swept wings. The vortex formation is also found in a number of other cases like chines, leading edge extensions (like this F-18), etc.

Flow visualization over a 1/48-scale model of an F-18 aircraft inside a water tunnel at the Flow Visualization Facility from NASA's Dryden Flight Research Center. Image from wikimedia commons


Can any aircraft adjust the wing dihedral in flight?

There was one, and it did it to increase directional stability at supersonic speed. I am talking of the North American XB-70, of course. There were three benefits to this configuration:

Improved directional stability. Without the effect of the folded-down wingtips, the XB-70 would had lost all directional stability upwards of Mach 2. The wingtips folded down to 64.5° anhedral (or is it -64.5° dihedral?) which effectively made them into ventral fins. This answer explains how a ventral fin is especially helpful at supersonic speed, because it works in the compressed air below the aircraft.
Less shifting of the aerodynamic center. Since the transition to supersonic flight will shift the aerodynamic center back, folding the wing tips down reduces lift in the aft section of the wing, thus reducing the aftward shift.
Better capture of the compressed lower wing flow for lift creation, which is called a waverider. This increases the pressure on the lower side of the wing at high supersonic speed and allows to fly with a reduced angle of attack, thus reducing drag.

XB-70 landing with wingtips straight (picture source)

XB-70 in flight with wingtips down (picture source)

The XB-70 is also one of only a few types where every aircraft ever built had different dihedral: AV-1, the first prototype, had 0° while AV-2, the second prototype, had 5° dihedral over the whole wing to improve yaw and roll stability. Only the dihedral of the outer panels could be adjusted in flight, however. According to this source (PDF!) they were the largest moveable aerodynamic device ever used on an airplane.

Other cases of variable dihedral were less intentional, though, and there was really no advantage to it:

Like on many Navy aircraft, the wings of the F-4 could be folded for stowage. If the mechanism was not locked, the wings would fold up. The F-4 was even powerful enough to be flyable this way. When only one side folded up, the F-4 would crash, however.


What turbine temp. would result from burning pure stoichiometrically?

One may use the data I found for a previous answer for a PT-6 turboprop:

Ambient: 300K
Compressor discharge: 600K
Turbine inlet: 1200K
Exhaust: 800K

So, the combustor (between the compressor discharge and turbine inlet) adds 600K. Let's assume this happens at $\varphi=0.45%$ fuel equivalence ratio, which is equivalent to about 3% of fuel by mass. Since that's so low, we may also assume that all energy is put into heating the air (both the air used for combustion and the excess air for cooling the flow before the turbine). We start with a $\Delta T_c=1200K-600K = 600K$. Since a combustor is approximately isobaric, we can use the $c_p$ heat capacity for the reaction products, which is (for an ideal gas) not a function of temperature. We can thus simply calculate the stoichiometric temperature increase $$\Delta T_{s} = \frac{\Delta T_c}{\varphi} = \frac{600K}{0.45} = 1333K.$$ So the turbine inlet temperature is then $600K+1333K = 1933K.$ In reality, fuel heating (especially fuel evaporation) will represent a more sizeable chunk near stoichiometry, but I think it's safe to assume it's around the $1900K$ range.
Note however that the theoretical efficiency (ignoring the inevitable viscous losses from handling such a large flow of air) is determined solely by the pressure ratio of the compressor: $$\eta = 1-\left(\frac{P_1}{P_2}\right)^\frac{\gamma-1}{\gamma}.$$ So if TIT were not an issue, by enriching the mixture closer to stoichiometric, we do reduce the mass flow required through the engine (at constant power), so we proportionally reduce the viscous losses in the engine. If on the other hand viscous losses did not exist, for the most efficient design we would increase the compression ratio and lean the mixture even further to the point where the compressor discharge and turbine inlet temperature would be almost equal.


Can structural damage be detected or predicted using historical data?

Yes it can be done. However, with the advent of technologies, you can also use the real time updates of the monitored system to understand it's health. In some cases where the historical data is not available, it becomes important to assess the structure's condition based on real time updates. I feel the following links could be of interest:

https://journals.sagepub.com/doi/full/10.1177/1475921718760483
https://www.sciencedirect.com/science/article/pii/S0888327017304612


How to calculate the distance between two waypoints on an approach plate?

Point A to B = 3.2 miles, point B to C = 3.0 miles.

Total is 3.2 + 3.0 = 6.2 miles.

Click this link to see a complete legend from Jeppesen Charts showing symbols, definitions, etc. The picture below pertains specifically to your question.

(Source: Jeppesen)


Why does aircraft stability increase when it transitions from subsonic to supersonic flight?

Static longitudinal stability (also called static margin) is determined by the distance between the center of gravity and the neutral point¹. The neutral point is at a quarter of the chord at subsonic speed and moves back to half chord once the aircraft flies fully supersonically. This means that the static margin will greatly increase when moving from sub- to supersonic flight.

In order to keep the center of pressure at the center of gravity, in supersonic flight the elevator needs to create lots of downforce. The bigger the difference in lift per area between wing and elevator, the stronger pitch stability will become.

This effect makes the transition between both regimes tricky: When accelerating, aircraft experience the shift in the center of pressure as Mach tuck, and when the trim facilities are not sufficient, the aircraft might enter an uncontrollable dive.

In the reverse direction, an aircraft trimmed for supersonic flight will experience a pitch-up moment from the forward shift in the center of pressure once it slows down, which can stall it or overload the structure.

¹ I could also talk of the center of pressure here, but that would be less precise. The neutral point is the center of pressure for all angle-of-attack-dependent lift forces, and it is those which determine pitch stability.


How do typical ground marshaling signals differ for helicopters?

All of the signals used for marshaling fixed wing aircraft apply to rotary wing aircraft as well.

There are additional signals though related to hover maneuvers such as move left or right, hover left or right, forwards, etc.
and land (or rather cleared to land), take off into the hover, etc.

Marshaling large helicopters can be very difficult, especially in dust and snow conditions.

Source: ex. 7 Sqn Chinooks


Why the Antonov AN-225 has negative dihedral wings combined with a positive dihedral horizontal stabilizer?

The reason for the wing anhedral has been answered here long ago.

Tail anhedral or dihedral can have several reasons:

To avoid ground contact during rotation (when the aircraft pitches up in order to lift off the ground). This is needed with a swept tail, so tail dihedral can be found on many airliners. Clearly, the An-225 tail has ample distance to the ground, because the vertical tail surfaces extend for ⅓ of their span below the horizontal tail, so any ground contact can be ruled out even for an un-dihedraled tail.
To move the horizontal tail away from the wing wake. When you look at the tail of the An-124, you will see no dihedral and a mounting point quite similar to that of the An-225. But if the An-124 has no problem with an un-dihedraled tail, so should the An-225. This can also not be the reason.
To add some more vertical tail surface. This trick has been employed on the Handley-Page Victor or the F-4 Phantom II. On the An-225, the outer verticals would shield much of the horizontal tail and little additional side force will be created by the dihedraled horizontal tail. So this cannot be the reason, either.
For a H-tail: To move the attachment point of the vertical surfaces closer to their middle. Imagine the An-225 horizontal tail had no dihedral: Then the verticals would need to be mounted on the tips of the horizontal near their bottom (they need to be so high up in order to allow the An-225 to rotate, after all). This would mean that all side loads would act above the attachment point, producing a sizeable bending moment which has to be carried along the spar of the horizontal tail, making the outer tail structure a lot heavier. With a little dihedral, the attachment point can be moved further up, close to the middle, so the bending moments in the vertical and horizontal tails can be a lot lower.

Antonov has designed H-tails before (on the An-14, the An-22 Antei, the An-28 and the An-38), and in all cases the vertical had a sizeable part of its surface below the horizontal tail. The only design on this list which also had some tail dihedral is the An-14 from 1958, and here the attachment point is almost in the center of the vertical. So it looks like the Antonov design bureau applied a trick on the An-225 which they had known for at least 30 years before the An-225 took off for the first time.


Is there a list of aircraft types to be used with a callsign?

I couldn't find any specific guidance on this, the AIM 4-2-4(a)(3) just says (emphasis mine):

  Civil aircraft pilots should state the aircraft
  type, model or manufacturer’s name, followed by the
  digits/letters of the registration number. When the
  aircraft manufacturer’s name or model is stated, the
  prefix “N” is dropped; e.g., Aztec Two Four Six Four
  Alpha.

See also the ATC orders 2-4-21 for the controllers' side. It doesn't give any information either on where to find type and model information and the examples suggest that precision isn't very important:

  EXAMPLE−
  “Tri−Pacer.”
  “P A Twenty−Two.”
  “Cessna Four−Oh−One.”
  “Blue and white King Air.”
  “Airliner.”
  “Sikorsky S−Seventy−Six.”

If "airliner" is an acceptable identifier then anything is :-)

As you said, you can comply with the AIM simply by saying "Cessna", whether you're in a 120 or a 750. But what about experimental aircraft, or a type that the controller just doesn't know?

Personally, I think this is a practical issue rather than a formal one. If it was critical for ATC to know the performance of every aircraft then flight plans would be mandatory. As it is, both controllers and pilots rely on their working knowledge of aircraft types and the system just works. The big, fast aircraft are mostly IFR anyway so the controllers already know what to expect; the small, slow ones can all do 80-100 knots in the pattern and the controllers don't need to worry about them much.

In the unusual cases where a specific aircraft type's performance might be an issue, the pilot can always work it out with the controllers:

N12345, Louisville Approach, I need your best forward speed on the approach, can you give me 120 knots?1
Bowman Tower, N12345, we're a warbird, I need a minimum 90 knots in the pattern and request an overhead break for runway 242

1Real example, and no I couldn't
2Also a real example, but sadly not me flying


What is the type of the seaplane at the end of runway 18L on Schiphol Airport?

To clarify, it's a Fokker F-27 Friendship 500.

Manufacturered in 1971, PH-NIV has photos of it on Wiki:

Registration details here

As to how it's in Amsterdam Schipol:

  towed to entrance at Oude Meer nr Schiphol East 12.07.12 as PH-NIV in
  old Fokker proto cs owner Coöperatieve Vereniging Anthony Fokker
  Logistics UA moved to permanent display location 13.03.13 on poles in
  a lake with nose up,

So it's been there since March 13, 2013 (the same day the current pope was inaugurated, incidentally).

Before that, it was registered with several companies during its service:


During a takeoff emergency, is it safer to abort or continue the takeoff if either can be done within the available runway?

In my experience, admittedly dated (retired 1999) whether it's 'better' or not didn't enter into the consideration. A reduced-power assumed-temperature was always used (unless there was something that prohibited it) because of the cost factor, and the power reduction used was always such that there was the proper amount of runway but not 'plenty' of runway. There was a maximum amount of reduction above which you could not legally go, but that was rarely used in my experience.

All that said, it's the captain's airplane. While I was a 747 f.o., I occasionally saw captains use less than the power reduction called for. More often, but still not a lot, I saw captains simply call for a max power takeoff rather fussing with adjusting the reduced power. Max power takeoffs were always entered into the aircraft maintenance log because it was required to do one every so often. I forget the exact requirement..

When I was a captain, I almost always observed the recommended reduced power. Twice doing this it became a closer thing than I would have liked. The first time was on the reef runway at Honolulu. We were over 800,000 lbs, it was my leg, and we lifted off at the very end. I rotated a couple of knots or so early because the end seemed to be getting very close. I thought a lot about that takeoff and discussed it with a number of people. My view, and I think the consensus view was: beware of high-humidity reduced power takeoffs. Humid air is less dense than dry air, but the performance charts (at least the ones we used) didn't take that into account.

A year or so later at Dhahran, Saudi Arabia, we were bringing a full load of troops back from Desert Storm. Reduced power was called for, the humidity was very high, and it was the f.o.s leg. A little over half way down the runway I didn't like how it was looking, and called for max power. Discussing it later with the f.o. and the f.e., we had all come to the same conclusion at about the same time. I had simply been the first to verbalize.


Is a VFR flight following request implied when talking to tower and advising them of your intended airport?

It is not. You must explicitly add

  Requesting VFR Flight Following

Depending on the airport in question the tower may simply tell you to contact approach once in the air to request flight following. Other towers may set it up for you.

The notation of your destination is extraneous. When departing you generally tell the tower you direction of departure not your destination.

Flight flowing is also not an implied bravo clearance, you will need to request that once in the air. If you are taking off from a towered field you can ask for a handoff when requesting your clearance, this may help facilitate your clearance request as well as your flight following request.


Do unused parachutes need to be repacked? If so how often and why?

Yes, parachutes need to be repacked regularly. The length of the interval depends on the material of the parachute and is between 60 and 180 days. Every parachute should have a small pocket with a piece of paper which lists the most recent repack date and the name of the packer (who needs to comply with FAR part 65, subpart F).

FAA part 91.307 says:

  (a) No pilot of a civil aircraft may allow a parachute that is
  available for emergency use to be carried in that aircraft unless it
  is an approved type and has been packed by a certificated and
  appropriately rated parachute rigger—

  (1) Within the preceding 180 days, if its canopy, shrouds, and harness
  are composed exclusively of nylon, rayon, or other similar synthetic
  fiber or materials that are substantially resistant to damage from
  mold, mildew, or other fungi and other rotting agents propagated in a
  moist environment; or

  (2) Within the preceding 60 days, if any part of the parachute is
  composed of silk, pongee, or other natural fiber or materials not
  specified in paragraph (a)(1) of this section.

The reason should be clear from the regulation: If moisture is present, the growth of mold may prevent the parachute from unfolding easily.

For the T-10D parachute, which is the standard US Army parachute for airborne assault operations, the repack period is 120 days.


Does the canard config have radically different controls than classic config?

As far as in-cockpit controls, a canard has the same control setup as a conventional airplane.  Stick or yoke, throttle(s), rudder pedals.

All the differences are hidden in the linkages or hydraulics -- pulling the stick back lowers the elevator on the canard, instead of raising one on a rear stabilizer, but to the pilot it's the same.

There are some minor technique difference in actually flying a canard; stalls are very different (I've heard some canards referred to as "almost impossible to stall"), and trimming pitch is slightly different; correct CG location is very different (usually ahead of the leading edge of the wing or, at most rearward, roughly even with the leading edge of the root of a swept wing), and the engine or engines are almost always located in the rear -- but once again, the pilot manages the engines very nearly identically to a conventional airplane (with the exception that, in case of a failure, he can't just look out the window to see if an engine is on fire).


Which precautions should I take when flying in very cold / hot weather?

Pre-heat the engine
When the engine is cold, the metals may come in contact to each other, which greatly increases engine wear. The best way to pre-heat is to use a hangar.
Engine oil
Oil viscosity is closely related to temperature. If the temperature is too low, oil becomes too thick. Thick oil cannot flow around the engine compartments freely. Thin oil, on the other hand, may have reduced lubricating effect. Thus, choosing the correct oil type is important. An oil with lower viscosity may be used in cold climate, and likewise oil with high viscosity in a hot climate.
Cabin heat
Cabin heat can be useful for warming the cabin, however a leakage may lead to carbon monoxide poisoning. Carbon monoxide detectors can be useful in providing an early warning.
De-ice
Ice built up can affect aerodynamic surfaces severely. In serious cases, they may cause the wings to lose enough lift and stall. Pitot tubes and engine sensors may also give false readings if their de-ice/anti-ice system is not activated.
Density altitude
The density of cold air is greater than normal. Engine damage may be induced by pushing full throttle, which causes the engine to produce more power than it is rated.
In hot air, the density is reduced. This reduces engine performance, resulting in longer takeoff and landing rolls. Aerodynamic performance is also reduced, resulting in a higher TAS (true airspeed) for the same IAS (indicated airspeed). These effects must be taken into consideration in determining whether runway length is sufficient.
If there is high terrain near an hot airport, it may be necessary to circle the airport to climb as the plane may not have sufficient climb performance.
Surface friction
In cold conditions, the taxiways and runways are often icy and slippery. Heavy braking should be avoided.


What component of an aircraft generates its electric power?

For most small planes, it is the battery, which turns the electric starter motor. A generator driven by the engine or by a small propeller in the slipstream then charges up the battery while the plane is flying.
Some history:
a few older and small planes had a pull cord in the cockpit with which the pilot could pull-start the engine, like a lawn mower. For engines with no starter at all, the pilot or their assistant would grab the propeller and swing it around by muscle power to start the engine (be careful!).
Some very old planes had starters operated by a crank that you stuck into a hole in the engine cowling, and turned by arm power. This worked for small engines but was too hard to do for bigger engines. In that case, the crank turned a small flywheel up to great speed and then the engine was geared into the flywheel through a reduction gear drive, and the energy stored in the rotating flywheel turned the engine to start it. This was used in the P-26 "Peashooter" plane.
In later years, a small electric motor spun the flywheel up to speed instead of a hand crank. The Antonov An-2 still uses this type of starter, called an inertia starter, as does the Dromader crop duster with the radial engine.
Another method of starting an airplane engine was to explode a blank shotgun shell in a closed chamber and send the hot gas through a tube to a special cylinder geared onto the crankshaft, which thereby turned the crankshaft to start the engine. This is called a Coffman starter and it plays a key role in the old movie "The Flight Of The Phoenix". In some versions of this principle, the gases from the shotgun shell were sent right into one of the cylinders of the engine itself, forcing the piston down and turning the crankshaft.
This idea saw use in more modern times, where a jet engine could be started by burning a charge of solid rocket motor fuel called a cartridge inside a sealed chamber and using the hot gas to spin up the exhaust turbine. F-4 Phantom jet fighters could be started with cartridges like this in just a few minutes even in Alaskan winters- without the use of a start cart.


Can biplane or triplane designs be revived with modern materials?

Biplanes (and triplanes) became (nearly) extinct not because high strength materials (like composites) were not available, but because they became available.

One of the major reasons for use of biplanes in the early days of aviation was that the materials available were of insufficient strength for the (wing) designs used.

The major disadvantage of biplanes (or triplanes) is aerodynamic- it produces a lot of drag compared to the monoplane and the wings interfere with each other.

So, the biplane was an (aerodynamically) inefficient solution to a structural problem. As higher strength materials like Aluminum became widespread, the biplanes fell out of favor.

While they can be revived, I don't see why someone would do that, except for nostalgia (or some special uses, like aerobatics).

There are some companies who manufacture or restore biplanes, but they usually don't use (modern materials like) composites, though modern avionics are used.


What is "judgemental oversteering" in taxi procedures?

"Judgmental oversteering" means to intentionally not follow the taxiway centerline when turning. It is a technique used on large aircraft to turn on tighter or smaller taxiways.

In a sense, it is like driving a long vehicle, such as a truck or a bus. Instead of following the lines on the road, the driver would deliberately overshoot the entry of turn, i.e. delay turning the steering wheel. This technique allows the rear wheels to stay on the road instead of going over the corner which may have fences, poles, pedestrians or other obstructions.

Here is a drawing from the 747x Quiet Longer Range Family Airport Compatibility document which illustrates the tracks of each gear for the "judgmental oversteering" and "cockpit centerline" methods:

This FAA document about airport design summarizes the pros and cons for each method (p.52 of PDF, p. 34 of document):

  Cockpit Over Centerline. Taxiway intersections designed to accommodate cockpit over centerline steering require more pavement, but enable more rapid movement of traffic with minimal risk of aircraft excursions from the pavement surface. (...)

  Judgmental Oversteering. Taxiway intersections designed to accommodate the judgmental oversteering method of maneuvering require the least pavement widening. However, judgmental oversteering requires complex maneuvering, increases the risk of aircraft excursions from the pavement surface, and slows the flow of traffic.


How many commercial passenger aircraft suffer tail strikes in a given year?

A preliminary answer might be the results of searching incident reports at AVHerald

Accident    Ryanair B738 at London on Jul 29th 2014, tail strike on landing
Incident    Ryanair B738 at Alicante on Mar 27th 2013, tail scrape on takeoff
Report      Jazz DH8C at Gaspe on Sep 10th 2012, hard landing and tailstrike
Incident    Smartlynx Estonia A320 at Tallinn on Jul 31st 2014, tail strike on landing
Accident    Swiss A321 at Geneva on Mar 9th 2014, tail strike on landing
Incident    ANA B763 at Tokyo on Mar 13th 2014, suspected tailstrike on departure
Accident    TAROM B733 at Bucharest on Apr 4th 2011, tail strike
Accident    Lufthansa A333 at Chicago on Mar 5th 2013, undetected tailstrike on takeoff
Incident    Transavia B738 at Amsterdam on Apr 29th 2013, suspected tailstrike
Accident    Aeromexico B762 at Madrid on Apr 16th 2013, tail strike on takeoff
Accident    Titan B733 at Chambery on Apr 14th 2012, tail strike
Accident    Sata A313 at Ponta Delgada on Mar 2nd 2013, tail strike on landing
Report      Jetstar A320 at Sydney on Feb 6th 2012, thrust lever asymmetry during takeoff and early rotation
Accident    China Cargo B772 at Copenhagen on Apr 17th 2011, tail strike on go-around
Accident    Austrian A321 at Manchester on Dec 23rd 2011, tail strike during go-around
Incident    Air Atlanta A306 at East Midlands on Jan 10th 2011, tailstrike on landing, go-around with open thrust reverser
Incident    Air Atlanta A306 at East Midlands on Jan 10th 2011, tailstrike on landing, go-around with open thrust reverser
Accident    Emirates A345 at Melbourne on Mar 20th 2009, tail strike and overrun on takeoff
Accident    Gol B738 at Porto Alegre on Nov 16th 2011, tail strike on landing
Report      Lufthansa MD11 at Mumbai on Jun 11th 2011, tailstrike on landing
Accident    China Cargo B772 at Copenhagen on Apr 17th 2011, tail strike on go-around
Report      Kam Air DC86 at Manston on Aug 11th 2010, tail strike on takeoff
Accident    TUIFly B738 at Tenerife on Mar 27th 2011, rejected takeoff due to tailstrike
Report      Tunisair B736 at Paris on Oct 10th 2008, rejected takeoff after rotation
Accident    United Airlines B744 at Sydney on May 7th 2010, tail strike on takeoff
Accident    Northwest A320 at Denver on May 4th 2009, tail strike on landing
Incident    Austrian B763 at Beijing on Jan 29th 2010, tailscrape on takeoff
Accident    Northwest A320 at Denver on May 4th 2009, tail strike on landing
Report      Ryanair B738 at Dublin on Sep 11th 2008, tailstrike on takeoff
Crash       Avient Aviation MD11 at Shanghai on Nov 28th 2009, overran runway on takeoff
Report      Thomas Cook A332 at Montego Bay on Oct 28th 2008, mislaid manual leads to wrong takeoff speeds
Report      Thomson Airways B763 at Manchester on Dec 13th 2008, tail strike
Incident    PIA B743 at Lahore on Jun 23rd 2009, suspected tail strike leads to discovery of tail strike
Incident    Australian Air Express B463 at Brisbane on Oct 23rd 2008, tail strike on hard landing
Accident    Emirates A345 at Melbourne on Mar 20th 2009, tail strike and overrun on takeoff
Accident    Emirates A345 at Melbourne on Mar 20th 2009, tail strike and overrun on takeoff
Report      Aigle Azur A321 at Algiers on Jan 8th 2008, tailstrike during landing
Incident    Pegasus B738 at Cologne on Dec 20th 2008, tailstrike on takeoff
Report      Flybe DH8D at Paris on May 28th 2008, tailstrike
Report      My Travel A320 at Kos on Jul 5th 2007, very hard landing
Incident    Cargo B B742 at Brussels on Oct 27th 2008, tail strike on takeoff
Incident    Ryanair B738 at Dublin on Sep 11th 2008, tail strike on takeoff
Accident    Swiss RJ100 at London City on Aug 18th 2007, tailstrike on landing
Incident    Comair (SA) B732 at Cape Town on May 3rd 2008, tail strike
Incident    Ryan Int B738 at Milwaukee on Mar 14th 2008, tailstrike on takeoff
Accident    RyanAir B738 at Stansted on Feb 18th 2008, tailstrike on takeoff
Accident    RyanAir B738 at Stansted on Feb 18th 2008, tailstrike on takeoff
Incident    Delta B767 at Moscow on Jan 26th 2008, tailstrike on takeoff
Accident    Swiss RJ100 at London City on Aug 18th 2007, tailstrike on landing
Incident    LaudaAir B738 at Linz on Oct 2nd 2007, tailstrike at about taxi speed
Accident    Swiss RJ100 at London City on Aug 18th 2007, tailstrike on landing
Accident    Swiss RJ100 at London City on Aug 18th 2007, tailstrike on landing
Accident    Swiss RJ100 at London City on Aug 18th 2007, tailstrike on landing
Accident    Swiss RJ100 at London City on Aug 18th 2007, tailstrike on landing
Incident    RyanAir B738 at Dublin on Mar 20th 2007, tailstrike during takeoff

You need to check some of these, some of them mention tailstrike where none occurred (e.g. inapppropriate pilot action due to fear of tailstrike)

You may need to define tailstrike, maybe a controlled flight into terrain sometimes involves a tailstrike but wouldn't be categorised as such.


What is the usual practice in interacting with ATC at Top-of-Descent?

There are some variances in the way a pilot/crew may handle the initiation of a descent (at or near the TOD point as described in your question).  My answers below reflect my preferences based on normal circumstances. (IFR Jet operations in U.S.)

  when would ATC typically be contacted? That is, would the pilots seek to obtain ATC clearance for descent in advance of reaching TOD so that they could start down at exactly that point?

If I had not received a descent clearance when approaching (a couple of miles before) the displayed TOD I would request a descent clearance from ATC. This would help avoid being too high and perhaps struggling to meet some published altitude restrictions (e.g. if on a STAR, etc.).

  Would the pilots cross TOD and then call ATC to ask for clearance?

I would not wait until I'm past the TOD (typically) to ask for a descent clearance - see the answer above.

  Would there be a point when the pilots get early clearance to descend once the TOD point is reached but wait awhile to hit the TOD point?

(I'm not entirely certain I fully understand this question) - Prior to reaching the TOD, ATC may issue a "pilot's discretion" descent clearance (e.g., "descend at pilot's discretion, maintain flight level 210"). Then I could wait until the TOD point (displayed on my nav equipment) to start my descent.  Or I might get a "descend via" clearance on a STAR (Standard Terminal Arrival procedure) which would authorize a descent to comply with the STAR profile, and based on where I was, I could wait to start the descent at my discretion (as long as I comply with the STAR profile).


What's the function of the plate behind the wheels of the Pilatus Porter?

Looks like a sort of gravel kit.
Real gravel kits are used by jet powered aircraft to land on rough airfields.
In this case though, the engine is in front, so it is likely that it is only there to reduce the amount of dirt raised when landing/taking-off so to reduce the chances of damaging the aircraft.
From the official PC-6 Porter brochure via pc-6.com (PDF), they call this option a mudguard:

MUDGUARD

And according to a service bulletin (pilatus-aircraft.com; PDF) there were prone to fatigue:

Operators have reported failures of the mudguard supports and stone guard mounting yokes. The failures are caused by fatigue damage.


Are three airports or four required for private pilot cross country?

The regulation means you need to land at three separate airports.  This should include landing at your original departure airport at the end of the flight.

§61.109(a)(5)(ii)
One solo cross country flight of 150 nautical miles total distance, with full-stop landings at three points, and one segment of the flight consisting of a straight-line distance of more than 50 nautical miles between the takeoff and landing locations


How do individually controlled feather like winglets work?

The "Bird of Prey" is nothing more than an artist's conception at this point so there is nothing to review from a mechanical design standpoint.

Somebody thought it would be neat to make a plane that looked like a bird, but the methods by which birds achieve flight is far different than in modern aircraft.  I don't believe there are any practical advantages to having a control surface that looks like a feather, and "function follows form" isn't a design strategy that has been proven to work.

I doubt we will ever see one fly, but it would make a fanciful sculpture, like this:


What is the current state of research on Autonomous Air Traffic Control?

Do you mean air to air? Or were you thinking of a ground system? What sort of traffic density?

If the former there are a number of concepts within the big medernisation programs like US NextGen, EU SESAR, Australian OneSky or Japan's CARATS programs.

ICAO has a global roadmap running to 2040.

VHF datalink mode 2 is up and running now, higher bandwidth satcom comming (Inmarsat SB-S/ Iris). VOIP likely to have some interesting latency effects in airspaces eith high R/T loads.

Significant global safety spectrum, ITU, regulatory, standardisation and other institutional and political challenges stand before a cool tech idea.

For spectrum look within current band allocations.

Aviation is generally incremental. Bear in mind thst your tech needs to be robust, globally portable.

If you can develop a regulstir accepted method to assure AI or ML apps then this would be a fertlle and lucrative area.


Is the National Aviation Authority the same as the Civil Aviation Authority?

The terms National Aviation Authority and Civil Aviation Authority are indeed two generic terms to describe the same thing - the government organisation responsible for managing non-military aviation within a country.

It's worth noting that the specifics of how the organisation works and what it regulates is down to each country, so the terms are broad and generic. For example, Iceland doesn't have any kind of specific CAA - rather, those roles are performed by the Icelandic Transport Authority.

In addition, it wouldn't really be right to refer to a countries authority as the National Aviation Authority or the Civil Aviation Authority (Unless that's what they've called themselves).

For example, the FAA is an example of a National Aviation Authority, it isn't known as the National Aviation Authority. The UK's Civil Aviation Authority is the Civil Aviation Authority in the UK and an example of a National Aviation Authority


Can I fly a practice LNAV approach with an iPad?

In the US, there are no regulations prohibiting you from using an iPad for navigation while flying VFR. There are also no regulations specifying what equipment you must use for a practice approach. The key to this is that it is a practice approach. Therefore, it is flown VFR. Even if you were an IFR-rated pilot in an IFR aircraft under the hood/foggles, your safety pilot would be VFR.
If you fly that same approach IFR (whether IMC or VMC), then it is an actual approach even when done as a practice approach. Just the ATC expectations are changed. Flying IFR would require the proper TSOed navigational equipment.
One word of caution would be that this might not be a safe practice flying solo. It would be best to have your iPad mounted somehow to make it hands-free. You should also practice this with your CFI (preferably) or a safety pilot first.
It would also be unwise to have to switch back and forth from the approach chart to your Foreflight  AHRS screen on the same iPad. You are in a critical phase of flight. Doing what you plan would be an unnecessary distraction and a violation of the Part 91 sterile cockpit strong recommendation (not a regulation for Part 91, yet). Either print your approach charts or carry two iPads.
Some guidance for practice approaches is provided in AIM 4-3-21.


How to know if an aircraft is climbing or descending?

Listen. Climbing aircraft need more thrust, so the noise they produce is related to their vertical speed. Since most excess performance is available at low speed, a slowly flying aircraft producing a lot of noise will most likely be climbing. Once you gain a little experience, the pitch of the engine and propeller sound of piston-engined aircraft will be a very good indicator of their thrust setting.

This doesn't work for gliders. Here you need to wait to be sure if they are climbing or descending. Only when you see that the glider flies with speed brakes extended you can be sure instantly that it is descending.


In the US, are there any operational control towers located in surface-level Class E airspace or in Class G airspace?

There are a handful of towers still in Class E/G airspace. They're rare, but they do exist and are something to watch out for during preflight planning.
As of April 2021, here's the airports I know of:

KJYO - Leesburg, VA
KPCA - Picacho ARNG, AZ
KTNX - Tonopah Test Range, NV (inside restricted airspace)

I wouldn't be surprised if there's others I missed, these aren't really cataloged anywhere.
Many of these do eventually become proper Class D airports once they have proper weather reporting capability. For example, KTRK (Truckee, CA) was an infamous one on the west coast that just got its Class D ring in 2017.
You'll also see temporary towers pop up via NOTAM for special events. These NOTAMs don't change the airspace designation, since changes to airspace need to go through the formal rulemaking process.


Here's a quick estimate for this.
The maximum altitude for level flight is when the engine can't produce the thrust required to fly fast enough to generate the lift required to balance the weight.
Ramjets work best at around Mach 3 and can operate up to Mach 6
Lift is proportional to speed squared and air density. So doubling the speed allows the plane to fly in air that is a quarter of the density.
The equations for calculating air density with altitude are moderately complex but there are a couple of tables here that show that the density at 32km is about eight times less than at 20km.
So if the SR-71 flew at Mach 3 and 25km, and if you could make a SR-71 that could fly at Mach 6, it might manage another 5 or 10 km in altitude.
Obviously that's a massive simplification because if switching engine technologies would have improved the SR-71's speed, they would have done it. Also because the SR-71 engines were ramjets when it was flying fast.
A ram jet won't get you into orbit because orbit is not just a matter of flying high enough but of reaching orbital speed - the speed where the curve of your naturally falling trajectory will miss the earth due to the earth's curvature. It's about Mach 25. And (as Ross points out) even if you could reach Mach 25, you can't circularise the orbit with an air breathing engine because that requires thrust at the highest point.


Restricted Area "popping up" around you -- can it happen, and what do you do about it?

Assuming your question is for the US airspace.

Short answer:

When the activation periods cannot be totally anticipated, the description of the area must reference the possibility of activation announced by NOTAM.

The NOTAM notice is normally not shorter than 4 hours before the activation.

While IFR flights will be prevented by ATC to enter or transit an active restricted area, non-controlled flights are under the sole responsibility of the pilot, as regard to flying within a restricted area.

A VFR pilot must take NOTAMs for restricted areas into account when preparing the flight (FSS), and should contact ATC when airborne for confirmation of the activation status.

From the pilot standpoint

You should not enter an inactive restricted area without contacting the controlling agency.

From AIM-3-4-3:

  Penetration of restricted areas without authorization from the using
  or controlling agency may be extremely hazardous to the aircraft and
  its occupants

You are not allowed to enter an active restricted area without prior permission.

From the Federal Register, 14 CFR Part 73, §73.13:

  No person may operate an aircraft within a restricted area between the
  designated altitudes and during the time of designation, unless he has
  the advance permission of (a) The using agency described in §73.15; or
  (b) The controlling agency described in §73.17.

FAA ATC, as the controlling agency, manages restricted area transit or avoidance, based on activation status, but only for IFR flights.

A pilot of a non-controlled flight (e.g. VFR) has the sole and complete responsibility for getting all information about the restrictions that may apply during its flight over a restricted area.

The briefing with FSS should include such research, contacting ATC prior to entering the restricted area seems the minimum.

From controlling / using agencies standpoint

A restricted area is part of the SUA (Special Use Airspace areas), and is jointly managed by Using and Controlling agencies.

Procedures for handling airspace matters, 21-2-4, Times of use:

  a. The times of use indicate the period during which the using agency
  is authorized to schedule and use a SUA area. These times should
  reflect when normal operations are expected to occur. In determining
  the times of use, the proponent should select the minimum period
  needed to meet the using agency's requirements. The goal is to capture
  the majority of the day-to-day activities. When the using agency has a
  requirement for intermittent, less frequent use of the airspace
  (outside the specific published timeperiod), a provision to activate
  the airspace by NOTAM may be stated in the SUA legal description.

What does that say? If some periods of activation cannot be anticipated, the phrasing "by NOTAM" must be used.

  NOTAM activation. Use "By NOTAM" or "Other Times by NOTAM" to
  indicate when a NOTAM must be issued in order to activate the area.

Regarding the notice prior to activation by NOTAM:

  (e). NOTAMs should be issued as far in advance as feasible to ensure
  widest dissemination of the information to airspace users. Normally,
  the minimum advance notice should be at least 4 hours prior to the
  activation time.

  NOTE-  Under no circumstances may SUA be activated by
  a NOTAM unless the words "By NOTAM" or "other times by NOTAM" are
  stated in the area's legal description.

A 4-hour notice is the minimum usually accepted for the publication of the NOTAM prior to activation of the restricted area. I assume the exceptions would be handled on a case by case  basis.

An area without a NOTAM mention cannot be activated outside of the published periods.

Example:

R-2305 Gila Bend, AZ
[...]
Time of designation 0700-2300 local time daily, other times by NOTAM.
Controlling agency FAA, Albuquerque ARTCC.
Using agency U.S. Air Force, 58th Fighter Wing, Luke AFB, AZ.

Related:

How to find out if Restricted Area is “hot” before taking off?
What should you do if you are forced to enter restricted or prohibited airspace?
Can gliders access restricted airspace?


Has the Beechcraft company considered building a single-engine turboprop?

Yes.
https://www.google.com/search?q=single+engine+king+air
Top result:
http://www.flyingmag.com/aircraft/beechcraft-reborn

Perhaps the most intriguing product floated by HBC at its NBAA press conference was a single-engine turboprop. The company says the airplane has no public name or designation but will “absolutely,” said Holcombe, be “called a King Air.” That name, of course, has never been bestowed upon a single-engine airplane before.
This King Air, however, will be no scaled-back PT-6 single. Like the remarkably roomy and powerful Pilatus PC-12, the Beechcraft single will be big. Its fuselage will be — get this — based on that of the Premier 1A, which, HBC claims, has the best cabin of any bizjet in its class. It will certainly be huge for a single. In addition to the voluminous cabin, the single would feature a large side loading door, room for eight to 11 occupants and industry-leading pressurization. The composite fuselage allows for efficient pressurization. HBC says it will build the fuselage in the same way it builds the Premier 1A today, using state-of-the-art winding technology for extremely light and strong composite structures.


What is the shortest regularly scheduled commercial flight?

Westray to Papa Westray

Flights on this route are scheduled for one and a half minutes, and actual flying time is closer to one minute. The record for the fastest flight is 53 seconds.

By road/ferry it's 59 minutes according to Google Earth:

It's flown with a Britten-Norman BN-2 Islander.


Does the "bat wing" aircraft paint design have a proper name?

Although aeroalias is correct that this is often associated with Gee Bees, I think a more 'generic' term is a scalloped paint scheme, e.g.:

American Champion paint options
C130 paint schemes
Model biplanes


What is the purpose of the fin sweep on small piston airplanes?

Two benefits to fin sweep on a type like a 152 or 172:
Marketing, and aerodyanamics.
The airplane looks "cooler", "going fast when it's tied down" with the sharply swept fin; this makes it easier to sell to casual pilots and those who'll rent the plane to casual pilots.
However, there's also another advantage.  The sweep moves the tail area to the rear without adding dead weight of structure far out in the tail.  Thus rudder authority and yaw stability are gained with little increase in overall weight, compared to the previous generations of the same models in the Cessna line, for instance (look at a 180 from 1960 for comparison to a modern 182).


What's the plug used on airliners for ground power?

What's the plug pair called?

I don't think there's an "official" name for it, but it's usually referred to as the "ground power connection" or something similar. Also, there's usually only one connection; only the biggest commercial aircraft need two connections simply because one connection can't supply enough power.

  What's the ISO/whatever standard involved?

ISO 6858

  What do they look like close-up?

I wasn't able to find a copyright-free picture, but here's a PDF catalog from an aircraft parts supplier that has some pictures. (Note that this catalog also has a bunch of rarer plugs in addition to the common ones.)

  Is it pretty standard today worldwide?

The international nature of aviation kind of militates towards better standardization than most other fields. It's not perfect, but you're a lot more likely to find a compatible plug for your plane in a foreign country than you are for, say, your electric razor.

  Is the plug identical for the hugest airliners as for say commuters?
  Is the power specs identical for the hugest airliners as for say commuters?

The plug is based on what kind of power the airplane needs, rather than the size. So, all airplanes that take 120V 400Hz power will (usually, see above about standardization) have the same plug.

  Is the plugpair used on any non-aviation (say, industrial) cases?

No, not that I know of.

  Do some craft have more than one type of plughole (ie, to allow for different airport standards?)

It's a pretty big world, so I'm sure that some airplane, somewhere, has multiple plugs.

  And military aircraft?

That I don't know. Someone else will have to answer that one.

  Do any small personal craft (I mean 2-4 seater craft) use the same plugpair, or in some cases do they just use a domestic-like plug (rather as a motorhome may have), or generally do small craft never have this?

Generally, most small aircraft use 28V DC power, the connector for which can be found in the catalog I linked to.

  Is there a switch (for example, perhaps near the pylon in the first photo?), or a switch near the plug, or does it just hot connect?

Generally, the switch is in the cockpit rather than next to the plug, and it's the pilot's job to make sure there's no hot connect/disconnect.


More information on PanAm's first trans-Pacific flight

There are many sources of information about these flights that you can find by doing an Internet search. For example, I just used "panam clipper flight sfo to mnl".

The following links should get you started:

In addition to some aircraft information, this link has a schedule image about halfway down the page:
https://www.pacificaviationmuseum.org/pearl-harbor-blog/pan-ams-pacific-clippers/

This link has more Manila-specific info, with a video.
http://www.lougopal.com/manila/?p=1463

The following link, in the paragraph "Building Bases Across the Pacific" will answer your last question regarding MDY/AWK:
http://www.clipperflyingboats.com/transpacific-airline-service


North Atlantic Tracks entry and exit points

You can find the routes them selves here, the start and end points are noted like other airway intersections by phonetic names. You can look up the names here (use world hi maps to see them) for exact locations. For example you can see a route start at TUDEP and if you take a look on SkyVector you will find (lat/long in the top corner):


If a shoulder harness becomes INOP in an aircraft certified before 1978, is it still required equipment?

Shoulder harnesses have been required for all aircraft manufactured since December 12, 1986 for all seats, July 19, 1978 for front seats.
14 CFR 91.107 (2) and (3) is pretty clear:

(2) No pilot may cause to be moved on the surface, take off, or land a U.S.-registered civil aircraft (except a free balloon that incorporates a basket or gondola, or an airship type certificated before November 2, 1987) unless the pilot in command of that aircraft ensures that each person on board has been notified to fasten his or her safety belt and, if installed, his or her shoulder harness.
(3) Except as provided in this paragraph, each person on board a U.S.-registered civil aircraft (except a free balloon that incorporates a basket or gondola or an airship type certificated before November 2, 1987) must occupy an approved seat or berth with a safety belt and, if installed, shoulder harness, properly secured about him or her during movement on the surface, takeoff, and landing.

So what I read above can be interpreted as "if it's installed, it's required".
Some aircraft required an STC to retrofit the belts, you'll need to find out if that is the case (if it is, you can't remove it, but if there is no STC it could possibly be removed, a call to your local FSDO can clear that up). However I've been told that if the aircraft is equipped with shoulder harnesses, then they are required to be used.


Should time in turbojet aircraft be logged as complex?

Complex ratings apply only to aircraft with propellers, so any kind of jet aircraft is by definition not complex.


What kind of microphones does aviation use?

Microphones used in aviation are usually electret condenser microphones that do not require any phantom power (obviously there are different types as well).

While General Aviation Aircraft and many airliners use the dual PJ connectors (PJ-055 for headphones + PJ-068 for microphone), the Airbus and ATR aircraft (and probably some others) use XLR connectors. Most helicopters use the combined U-174 connector for both headphones and microphone.


Can I use a LAPL/PPL issued by the UK CAA to fly outside Europe?

The EASA issued LAPL(A) is limited to 2to MTOM, 3 passengers max and only valid in European countries. A PPL(A) issued by an EASA country does not have these restrictions, but can be subject to local restrictions in the non-European country you want to flyin, e.g. you cannot use the EASA PPL(A) to fly in the US without further paperwork.
For more information, see the UK CAA's page on the LAPL.

Your LAPL(A) is a lifetime licence that contains SEP(land) and/or TMG privileges restricted to non-complex EASA aeroplanes with a maximum take off mass of 2 metric tonnes and a maximum of four people on board.
You can fly more complex aeroplanes within the privileges if you have 'differences training' signed off in your log book by a suitable instructor. The LAPL is also valid on non-EASA UK registered aircraft in the UK.
The LAPL requires an in-date EASA Part-Med Medical Certificate, at LAPL level, but Class One or Class Two certificates can also be used. A valid JAA Class One or Two medical certificate is also acceptable. But you cannot use your LAPL with an NPPL medical declaration.
The SEP(land) or TMG endorsement on this type of licence is not issued as a rating. So there is no rating expiry date. Instead you must follow self-validity checks on your own flying history for the past 2 years to ensure currency on the day of your planned flight.

Further Reading from the UK CAA:
EASA Light Aircraft Pilot License Aeroplane - LAPL(A)
EASA Private Pilots Licence Aeroplane - PPL(A)


Should the aircraft logbook be with the aircraft, or should it be on the ground?

This is depending on which country the airplane is registered in, as the requirement to carry the logbook can be implemented per country, e.g. Germany requires the logbook to be carried onboard the airplane.[LuftBO §30 Abs. 5]


Is gravity less on an airliner at cruise altitude?

There is less gravitational force, but by how much? An insignificant amount.
The gravitational force of attraction between two objects is given by,

$\displaystyle F_{\mathrm g} = \frac{G m_{1} m_{2}}{R^2}$,

where,

$G$ is the graviational constant,

$R$ is the distance between the object's centers, and

$m_{1}$ and $m_{2}$ are the masses of the objects.

Instead of finding the variation in force between the aircraft and earth, it would be be better to find the variation in the acceleration due to gravity, $g$ (as $F_{\mathrm g} = m_{\mathrm a} g$, with $m_{\mathrm a}$ being the mass of the airliner)

We have, on earth's surface,

$\displaystyle g = \frac{G m_{\mathrm e}}{R_{\mathrm e}^2}$

where,

$m_{\mathrm e}$ is the mass of the earth, and

$R_{\mathrm e}$ is the radius of the earth.

For the aircraft at an altitude $h$ above the surface of the earth, this becomes,

$\displaystyle g_{h} = \frac{G m_{\mathrm e}}{\left(R_{\mathrm e} + h\right)^2}$

Taking ratio, we get,

$\displaystyle \frac{g_{h}}{g} = \left(1 + \frac{h}{R_{e}}\right)^{-2}$

Plugging in numbers, we get, for an airliner cruising at 12 km,

$g_{h} = 9.773\ \mathrm{m\ s^{-2}}$,

or about 0.37 % less compared to the sea level value. This is quite small and would not be noticable to all but the sensitive instruments.


What would have happened if the jet engine on my aircraft had ingested caulk from the pavement?

Well, not an expert on caulking, but birds go through plane engines sometimes, and they seem to be roughly the same consistency overall (if you account for the dirt and pebbles that are sometimes stuck to caulking.) So it possible they would have the same effect.

If you're curious about what would happen if it's like a birdstrike you can take a look at the Miracle on the Hudson, or this 757 that had a birdstrike on takeoff.  With the 757, they simply went around and landed the plane since they only lost one engine...

Anyway, you folks were still on the ground, so all that would have happened is that the engine would have flamed out while you were sitting there and the plane would need to be taken to service to check for damage.  It would have been annoying to have to switch planes, but it wouldn't have been dangerous to any of the passengers or crew.

Nice of them to give you a free coffee though, considering you may have saved them a few hundred thousand in engine repairs if the next jet in that slot had managed to actually ingest the caulking ;).


Background
The Sequenced Flashing Lights are part of some approach lighting systems and are a row of strobe lights that flash in sequence to direct the pilots eyes to the runway.  They are useful in conditions of bad weather, as they quickly catch the eye and help the pilot locate the runway threshold which might otherwise be hidden; however, during normal operations they can actually be distracting.  These lights appear to run towards the runway and are often called chasers, the rabbit, or the running rabbit.
Kill the Wabbit
Because these lights are very bright, and often distracting during normal operations in clear weather, it is not uncommon to hear pilots ask the controllers to kill the w/rabbit on their approach.  I personally find them overkill, and have heard many other pilots asked them to be turned off as well.

Photo credit ATG Airports


Is autorotation possible in a tandem rotored helicopter?

On the Chinook, the sprag clutches that allow the drive system to freewheel when an engine fails are between each engine's step-down transmission and the "combining transmission" that receives torque from each engine and sends it to the front and rear rotor transmissions.

This means that the entire drive line between the rotors always remains engaged and in sync regardless of whether any power is being supplied. If one engine fails, it's simply disconnected from the drive system by its sprag clutch with the remaining engine doing the work, like any helicopter.  And if both engines are shut down, same deal; both engines are disconnected by their sprag clutches and the still interconnected rotor system will autorotate with the correct blade intermesh maintained.

So the Chinook can loose one engine and continue flying (more or less), or lose both both engines and glide to land like any multi-engine helicopter.  If you loose one of the gearboxes or drive shafts in the interconnected system however, now you have an unpleasant situation.


What makes the perfect landing in a tail-dragger?

They both have their uses.

A wheel landing (landing on the mains, keeping the tail in the air) gives you better rudder authority on the ground, which is useful in a crosswind or during touch-and-gos. However, there is a point where as your airspeed slows, your rudder authority falls off quickly. This can be dangerous in a crosswind for obvious reasons. Most pilots avoid this condition by keeping the tail up for as long as they can, then quickly planting it on the ground when it begins to fall. The rudder is kept up in the airstream for as long as possible, and then you quickly transfer your turning control from the rudder to the tailwheel.

A three-point landing is useful for getting on the ground and stopping quickly, because the additional wheel provides more friction. It also avoids the situation in the previous paragraph, because you land with the tailwheel down and have full turning authority the entire time.

So in general, there is no preferred landing style in a tailwheel airplane. This may not be true for specific models of aircraft, however.


What does a white over red VASI indicate?

"White over red" isn't actually possible unless the VASI installation is badly off, or else if you're upside down on final.  If the top lights are white, you're above their glidepath angle, and if the bottom lights are red, you're below theirs.  With a standard VASI installation done correctly, you can't be in both places at once -- if you're above the path for the upper lights, you're above the path for the lower lights as well, and vice versa.

The "white over red" is simply a nonsense answer thrown in to some test questions in order to see who understands what's going on with a VASI system.  Most folks will remember that when you're on the proper glidepath you'll have one set of red lights & one set of white lights, but which one should be where?  As long as you understand how the lights work, you can correctly answer that red above white = on glidepath.

My best guess at the mnemonic is that they're suggesting you're "standing on your head," or in other words upside down, in order to see the lights in that position.  I wouldn't get too wound up about the lame rhyme in the memory aid.  Just know that with all white, you're high; with all red, you're low, and with red over white, you're on path.


Would a Chinook helicopter fly better with contra-rotating along with counter-rotating propellers?

No.  The RC model there is using counter-rotating rotors because the upper rotor with the stabilizer bar has a specific function that makes the model controllable in the first place.

The Chinook already benefits from built-in anti-torque control so that would be a waste of time and oodles of money on the real one.

Fun fact about the Chinook: it can climb better, and fly on less power overall, going sideways. Both rotors are able to bite clean air, achieving translational lift, when going sideways.  When going forward, the rear rotor has to cope with the wake of the front one.


Do older aircraft require increased general maintenance?

The very simple answer to your first question is just yes.

As something (or someone) age, more maintenance is required. It varies from case to case and you cannot have one size fits all rule or guideline.

FAA has published a thorough guide for maintaining older airplanes (PDF). For the relation of age on maintenance costs, this article (PDF) discusses it in detail.

Getting to your last question, it also depends on an individual case. Please also note that when an airplane is grounded, it is not required to be scrapped in all cases. Sometimes museums are interested in it, or it can be installed as a roadside monument or placed in an aircraft boneyard.

Regarding when an aircraft needs to be retired or scraped, these two articles are a good read:

When to replace an aircraft
How old is too old?


What was this mystery flash on an airport runway?

It's likely to be a flare / flash bang for bird control. Schiphol uses these (amongst a wide variety of methods).

  Bird dispersal equipment

  There are various resources a bird controller
  can use to keep birds away from the runways. Standard equipment
  includes a flare gun with noise blanks, a bird alarm call system and a
  green laser.

  The flares and noise blanks come in various types,
  including a number of ‘whizzers’. The flare used depends on the bird
  species and the number of birds the controller wants to scare away.
  Some species respond better to a loud bang and others to a screeching
  noise. Bird controllers also have all the most common bird alarm calls
  at their disposal, which act as a warning for the other members of the
  species to leave the area as soon as possible. All bird controller
  vehicles are equipped with a mobile green laser. This is a type of
  torch that emits a green laser beam to chase water birds away from the
  surrounding ditches.

Source: Schiphol Bird Control information brochure

At Schiphol the Bird Control vehicles are equipped with ADS-B. This makes them visible on flightradar24. If you remember the day of your flight, you maybe able to see if they were operating in the area near your taxiing aircraft. The cars have callsign Kievit (peewit / lapwing) and use abbreviation "KV#" as flight ID on ADS-B.


Why does the spiraling slipstream from a propeller hit the left side of the fin?

The air flow is not a spiraling tube like shown on the picture for simplification, or as suggested by the condensation on the second image. Actually all air behind the propeller is:

In rotation, the direction being impulsed by the propeller rotation. This rotation is maximal for air close to the propeller, and by effect of viscosity, a gradient exists in air until a certain distance where it is negligible.
In translation, due to the aircraft moving forward (or air moving backward when the aircraft is holding on the ground).

The resulting motion relative to the aircraft is a cylinder of air moving in an oblique direction, as represented in your image. Note this is not a spiral with non-rotating air in between, but really a continuous cylinder.

Actually the speed/pressure is not uniform within the cylinder, there is indeed a sinusoidal undulation, but the intensity never decreases to zero.

  If the fuselage was shorter/longer, would the spiraling slipstream
  from a propeller hit the fin on the right side as opposed to the left?

No, the result is that whatever the propeller pitch or the fin distance to the propeller, air is continuously hitting the vertical surfaces in a circular motion from the left (when seen from a location behind the aircraft).

  It may seem hard to hit the right side, but imagine hitting the top of
  the elevator on the right side.

The right side of the fin (as well as all surfaces in the shadow of the rotating air) sees a pressure decrease.

The more the distance from the the aerodynamic center of the aircraft, the higher the torque created on the aircraft, and the higher the tendency to rotate.

  Does this slipstream affect the pitch as well as the yaw?

The tendency is:

To yaw for the vertical tail components and the fuselage.
To bank for the horizontal tail components. This is not a pitch moment, because each side of the tail receives an opposite force. This force is balanced by the torque created by the propeller rotation on the aircraft.
To bank for the wing. This force is also balanced by the propeller torque.

Note that because there is a pressure undulation, the surfaces are hit by a slipstream varying slightly at the frequency of the blades.

For more details and theory: Propeller-Rudder interaction (in water, also applicable to air).

  Is the following image related?

The condensation happens at the tip and trailing edge of the propeller blades, and is then carried aft by the movement of the air cylinder. So it is completely related. Note that:

Air between condensation trails moves at the same speed (except the undulation).
There are two interleaved helices for a two-blade propeller.

Related effects:

The P-factor produces an additional yaw moment.
An increase in the propeller power changes the downwash, hence the efficiency of the horizontal stabilizer, and a pitch tendency.


It's a SATCOM (Satellite COMmunication) antenna. It has several purposes, one of them is internet connection for the passengers.

There are different types and configurations. On some aircraft the antenna is in the front, on some it's in the back, some have two.

(image from http://www.b737.org.uk/latest-2016-04-06.htm)


Can an unserviceable component be fitted on a serviceable aircraft for a maintenance check?

EASA Regulations do not specifically preclude you from doing what you are planning to. They leave an awful lot of room for interpretation. How you do your maintenance is up to you, as long as you meet the core requirements and that your processes can be audited.
Additional rules for this type of activity would normally covered by a local procedure (such as Robbery). If you do not have a covering procedure internally then you should absolutely be checking with your Quality Assurance department to validate your actions before undertaking the procedure.


As jwenting pointed out, there isn't one "airport tax" - there's a whole bunch of them, and they're not all taxes (some are "fees").

airlines.org has a list of the common ones you'll pay in the USA, and approximately what they cost you.

Broadly the taxes you're paying on airline tickets break down into two categories:

Taxes that fund the Airport and Airway Trust Fund
These taxes pay for Air Traffic services (a little under half the operating butdget for ATC), maintenance of the airway infrastructure (radio navigational aids, RADAR sites, etc.), research and development to improve the airway infrastructure (e.g. NextGen), and to fund the Airport Improvement Program (which provides grants to airports, mainly to implement safety improvements).

The actual tax categories themselves break down further (again, airlines.org's breakdown is excellent).

Fees that fund DHS programs
These are often called "security taxes", and include things like the "September 11th fee", APHIS fees (for inspecting plants and livestock), and customs/immigration charges.
Note that all of these are technically fees, not taxes -- these are only levied when a flight is using the services the fee is funding (or at least that's what's supposed to happen. In practice the airline is responsible for paying the appropriate fee as a cost of doing business. They can recoup that cost any way they'd like (typically they lump it in with "taxes" or itemize it out on the ticket rather than including it in the base fare, so they can advertise lower base fares).

What about the little planes?
General aviation doesn't pay "ticket taxes", but that doesn't mean they get to escape paying for the infrastructure the flights are using. The government recognizes that the air traffic system costs money, and they like to ensure that the money is available.
Accordingly there is a tax levied on all aviation fuel purchased in the US:

Airlines currently pay about $0.04/gallon in taxes for the jet fuel they burn
Non-Airline flights burning jet fuel pay about $0.22/gallon in taxes
(the higher rate making up for the other taxes they're not paying)
Piston-powered planes burning aviation gasoline pay $0.19/gallon in taxes
(higher than what the airlines pay for jet fuel, but lower than the standard jet fuel tax because piston planes don't travel as far, and are thus less of a burden on the air transport system)


Is it possible for ATC to see who’s transmitting on the radio on their radar?

A version of this has been implemented in some areas, such as the Maastricht Upper Area Control Centre, using radio direction finding equipment.
The EUROCONTROL website provides an explanation of the system, including an image of how it appears on radar displays:

Using triangulation software, the Radio Direction Finder, recently deployed throughout MUAC’s international airspace (the upper airspace of Belgium, the Netherlands, Luxembourg and north-west Germany) calculates accurately an aircraft’s position on the basis of its radio transmissions.
In densely occupied airspace, the Radio Direction Finder assists the controllers in rapidly identifying which aircraft is transmitting on the frequency.  This is particularly useful in MUAC’s sectors where controllers handle up to 25 aircraft at any one time, and is a prerequisite for the implementation of the free route airspace, planned at the end of the year. The origin of a voice transmission appears clearly on the controller’s integrated Human Machine Interface and is totally independent of conventional radar- and GPS-based aircraft localising techniques; this feature contributes to reducing call sign confusion, read-backs from wrong aircraft or crossed transmissions.


My driver's license was suspended for not having insurance. Should I even bother to apply for a medical?

A sport pilot license does indeed require a valid driver's license OR a minimum third-class medical certificate. If you don't have a medical certificate, you cannot exercise sport pilot privileges until your driver's license is reinstated.


What does "POS ITERV WAS CHGD" mean on the ACARS page of a Boeing 737?

Your aircraft is reporting its position periodically over the Aircraft Communications Addressing and Reporting System (ACARS) to the airline operations centre (AOC).

Since there are costs related to sending these position messages, the interval in which these message are sent drives operating costs for the airline.

This patent from China Southern Airlines (original Chinese version here) describes the behaviour you have observed on the MCDU. Apparently it allows the AOC to change the position reporting interval over ACARS remotely. If the interval is changed, a "POS ITERV WAS CHGD" text is displayed on the MCDU scratch pad.

The relevant text from the patent (including translation & typesetting errors):

  ...

  [0087] PTIC message display unit, see FIG. 6, the module receives PTIC
  PTIC uplink triggering instruction, parsing PTIC variable, position
  determined by the adjusted multicast time interval T3, if the variable
  is valid PTIC, is given in M⑶U unit tip text message to inform the
  crew of the current position of the broadcast time interval has been
  changed, the present invention uses "P〇S ITERV wAS CHGD" text gives
  the unit prompts; the message is always displayed in MCUD the scratch
  area (Scratchpad) until a new the message will disappear after replace
  the unit or manually pressing CLR keyboard. ...


The letters on top of the tail fin is called a registration or tail number, like a license plate if you will.

In this case searching the Canadian Civil Aircraft Register (historical search) for C-FCGV reveals that it is a Beech model 65-B80 with serial number LD 408 and the owner was "Govt Canada Dept Of Transport".

  Introduced in 1966 the B80 was to be the final production model. The B80 was by far the longest produced Queen Air with production lasting some 12 years. Its major improvement was the increased gross weight to a 8,800 lb (4,000 kg). This gave the B80 a useful load of well over 3,000 lb (1,400 kg). Production ended in 1978.

It was removed from the register on 1988-02-03.


Is there a way to fly an UAV over a roadway?

For certain operations the FAA does grant waivers to 14 CFR § 91.119(b) and/or (c). These waivers are generally granted for the purpose of allowing pipeline or powerline patrol, aerial survey, or for other operations that are in the public interest. The waivers are also generally granted to the operators of certified or restricted category aircraft, not UAS.

If you represent an operation for which a waiver would be in the public's interest and can demonstrate that the operation would be conducted safely, you might qualify for a waiver.

However, even for that waiver, you have to demonstrate strong evidence to gain a minimum distance of less than 500 feet:

  3-185 A. Unless it is necessary to
  safeguard human life or it can be determined to be in the public interest and contributing to the public health, welfare, and safety, the 500-foot minimum separation distance from persons on the surface shall not be waived.

Note that 14 CFR § 91.119(a) and (d) are never to be waived.

See this document for more information on the above discussed waiver.

Now, all that being said, I don't know if the above example of a waiver apples directly to your question or not; perhaps 91.119 is not the regulation that you were concerned about. Regardless, that waiver is an example of what can be worked out.

The current UAS issue is uncharted water for the FAA; there may or may not be precedent for an operation or exemption. Bottom line, if you have a really good reason to do the operation you want to do, you might be able to work it out with the FAA. Otherwise, you will have to stick to the rules as they are.


On the ICAO Flight Plan Form, does /S replace O, V, and L?

I wanted to address your formatting first since equipment type identifiers come before the transponder identifier (i.e. before the slant). The format for the new ICAO Domestic flight plan form for item 10 (equipment) is as follows:

(equipment type letters) / (transponder type)

So as an example, if your aircraft has standard equipment, VOR, GPS (GNSS), DME and you were Mode C Transponder equipped, your entry for item 10 would look like this:

SGD / C

*notice that your equipment type doesn't include "O" for VOR since S also includes VOR.

To answer your concrete question, S does indicate the presence of O, V, and L.

I've attached the following tables from 5-1-21 and 5-1-22 in the AIM for your reference. Table 5-1-4 covers equipment letter identifiers and table 5-1-5 covers transponder letter identifiers.


How does an airliner deal with cabin altitude at an airport above 8000 ft?

Here is the text extracted from Boeing's 777 Flight Crew Operations Manual:

In cabin altitude controller cruise mode, maximum cabin altitude is 8,000 feet. When the takeoff field elevation is higher than 8,000 feet, the cabin descends to the cabin cruise altitude while the airplane is climbing.
When the destination airport elevation is greater than 8,000 feet, cabin altitude controller cruise mode maintains a cabin altitude of 8,000 feet.
(...)
At touchdown, the outflow valves open to depressurize the cabin.

Therefore, when the airplane is on the ground, its cabin altitude is always equal to the ambient altitude. When it is in the air, the maximum is 8000 feet. Whether the cabin altitude will climb to 8000 feet or descend to 8000 feet depends on field elevation.
The reverse happens upon landing. If landing at an airport at 10,400 feet, the cabin altitude is <= 8000 feet until touchdown, then raises to 10,400 feet.
This make sense - if the outside pressure is greater, how do you open the door? (well with enough force you can, but I will leave it to your imagination as to what happens the moment the door is opened).


Reason for the multiple sidelobes in an ILS glideslope signal

All directional antennas have sidelobes (and all real antennas are at least somewhat directional). I won't get into detail of the fundamental physics reasons behind that, as that's beyond the scope of the aviation stack exchange, but briefly it's related to diffraction and the Fourier relationship between the aperture distribution and the far-field radiation pattern.

Various design techniques can reduce the amplitude of the sidelobes, sometimes to the point where they're undetectable or at least insignificant. However, these all involve tradeoffs that compromise other performance parameters, size or cost, so if the sidelobes aren't problematic or can be easily avoided operationally, it's not worth trying to suppress them. Also, most glideslope antennas use passive phased-array techniques, and phased arrays are especially prone to sidelobe generation (called grating lobes in that case).


What are the limitations of the aerodynamics modelling used in flight simulators?

Size matters here. Big aircraft have more inertia and take much longer to respond, but can equal out small-scale turbulence better. Your drone idea for training will not be representative of the big airplane at all.

Turbulence can be modeled quite faithfully - you just need to fly once through rough air, collect all the data and replay it in the simulator. The changes due to different pilot responses can be added on top without much loss in accuracy against a real flight.

Where models for airliner crew training break down is when the linear range of aerodynamics is left. Their post-stall and spin behavior is most likely not suitable for training, but that is not what they are designed for. Military aircraft simulators can even model the post-stall regime well, but need a lot of aerodynamic data, and most of that data is from wind tunnel models and not from real flight test.

What the simulation does is to plug the actual values of angle of attack, angle of sideslip, airspeed, power level angle and control deflections into matrices of coefficients and calculate the result from linear addition. That works well as long as the forces vary linearly of the flow angles, and correction factors will give you still good agreement with reality well into a stall. The coefficients are a mixture of CFD, wind tunnel data and flight test data. Gust loads can be modeled with Markov matrices which produce a realistic distribution of gust intensities, so even external, stochastic factors can be modeled faithfully.

I have less knowledge of helicopter simulators, and I would assume that flying near tall buildings can only be modeled in general terms, but not well enough to train a pilot for a specific location and weather condition.


Can anyone help identify this old 1930s plane?

That is the Boulton & Paul Overstrand. A twin-engine biplane medium bomber, built for the Royal Air Force of the United Kindom starting from 1933. The last one was already retired in 1941. Apparently this was the first bomber with a closed power-assisted gun turret.


What is a Cessna 172's maximum altitude?

The absolute ceiling, or the maximum height an aircraft can fly to, is usually not published; manufacturers usually use service ceiling as the benchmark.  Service ceiling is the maximum altitude which the aircraft can attain flying in air at Standard Temperature and Pressure (29.92" Hg and 15° C at MSL) and still be able to climb at a rate of at least 100 feet/min.

Depending on the model 172, this is between 13,000-15,000 feet ASL.  A Cessna 172SP has a published service ceiling of 14,000 feet ASL.

Again whether an airplane can attain these altitudes on any given day is dependent on the condition of the air.  The aircraft may be able to ascend higher than this on days when the air is very cold and there is a high local barometric pressure or lower on days when the air is warm and/or at a low barometric pressure in the region.


What does the last digit mean in a Piper Arrow model number?

The number notes the model

PA-28R-180 180bhp Cherokee Arrow with the ‘Hershey Bar’ wing.

PA-28R-200 200bhp Arrow II with the lengthened fuselage.

PA-28R-201 200bhp Arrow III with the tapered wing.

PA-28RT-201 200bhp Arrow IV with the tapered wing and T tail.

PA-28RT-201T Turbocharged Arrow IV.

The Arrow III was introduced in 1977 with the tapered wing and larger stabilator.  This improved low speed handling characteristics and increased the total fuel capacity from 50 to 77 gallons.


Why don't we have video recording of runways takeoffs/landings?

Because video is mostly useless for investigation.

The investigators need to know the exact flightpath, which is already recorded by the ATC radar and by the flight data recorder, they need to know whether and which systems failed, which is recorded by the flight data recorder, and they need to know what the pilots were doing, for which they have cockpit voice recorder and the radio communication is also recorded in the ATC facility (tower).

Video would be worse for determining the flight path than both ATC radar and FDR and while ATC radar does not have attitude, FDR does and again more precisely than video. Plus video might, depending on angle, have external damage, but that can generally be determined by examining the wreckage quite fine.

So video would add very little information over the existing recordings and thus it is not cost-effective to add it for just this purpose at all airports (it may be used if it is installed for security purposes).


They said "TBM" "Three-Bravo-Victor" (3BV). TBM is the aircraft make, a TBM and 3BV is the last 3 letters of the callsign.

The maneuver really isn't traffic avoidance so much as exactly what the controller said, spacing. They need to keep a minimum distance between traffic so having the TBM (a fast aircraft) perform an S-turn allows the aircraft in front of it more time to get further away.

Usually if you are in the pattern they will ask for a 360 turn, but if you are in a long straight-in and they just need a little bit of spacing, they will ask for the S-turn. For the S-turn approach you would simply turn 90 degrees to the course, then roll 180 degrees to face the opposite direction, then 180 degrees back around and 90 degrees back on course.


Is aviation software translated into the users' native language desirable over English?

English is the native language of aviation...
I myself always get mightily annoyed at poorly translated software, which is 90% of all software provided in multiple languages. IF you provide multiple languages, allow the user to switch between them AND get professional translators to do the work.

Would it sell? Probably, if it's good enough. But I don't see the language options as being a major selling point. Certainly not so big that having them will make a large number of potential customers choose it over another product that has more options elsewhere but lacks language selection.
In some places maybe, where English is less than common and not generally used by ATC.
Whether that's where your intended market is I don't know.


How does air conditioning work on a commercial airliner?

Came across this diagram that sums it up pretty nicely:

You get 'bleed' air from the engine compressor stage. On 'bleedless' aircraft, such as the B787, this is done by electric compressors instead.
Air temperature and pressure is adjusted as necessary in the conditioning packs since it heated up a lot when it was compressed.
Air is then distributed to the different 'zones'. A bit of the cabin air is recirculated.
Some areas, such as the cockpit, generally receive air directly from the packs without recirculating at a slightly higher pressure, to blow possible smoke away from the interior and to prevent smoke being recirculated into the cockpit. For the same reason, you try create a flow out through the baggage hold.

Here is a more complicated diagram from avsoft's website for a CRJ200:


Why would a pilot request an unusual approach/runway to ATC?

For currency, airline pilots have to do various approaches every so often to remain current or for the plane to be current (RNAV/ILS Cat II/III approaches). So, every now and then when coming to another airport they could request to shoot that approach instead of the one being used. Sometimes it's a non event (no traffic, or the few other aircraft either fit well before or behind them); other times, it could hinder the flow of operations if they're allowed to do full or certain procedures (various circling to land procedures).

Another very common request that falls in this category is to land or depart in the opposite direction of what's being advertised. This in recent years has become more cumbersome for controllers (due to more and new rules implemented), so it's being used less often.

Sometimes when there's little traffic it's fairly easy to accomplish this kind of arrival or departure. Other times, it becomes a nightmare, and unless it's operationally mandated the pilot will be told, unable opposite direction, due to traffic. When it's operationally needed, then it will be told to hold somewhere to wait until there's space to get them out for departure; or vectored around or put in holding if needing to land opposite direction, and they can be accommodated.


What are these hooks on the A320's wing used for?

In the event of a water evacuation, there is a line associated with each overwing exit that is extended, and clips to that yellow bracket, as a guide to get everyone out on the wing.

From Wikipedia, these are for overwing exits.

  The use of overwing exits in a ditching varies from airline to
  airline. On aircraft fitted with overwing exits, there is typically a
  raised escape rope bracket (about a third of the way from the door)
  attached to the wing's upper surface and typically painted yellow.
  This is accompanied by an escape rope found in the frame of the exit
  after opening the hatch. Once this rope is attached to the escape rope
  bracket, it will aid passenger evacuation onto the wing to await
  rescue or to enter the water (depending on the airline's procedures).
  On aircraft with life rafts to be launched via the overwing exit, the
  wing will be used to provide a boarding platform onto the life raft.
  On certain regional aircraft, the overwing exits are the only escape
  route in the event of a ditching.


Which antenna on an commercial airline airplane is used for the transponder (SSR)?

Short answer

The SSR antennas are labeled ATC L and ATC R (two at the top, two at the bottom).

Source

Both SSR and TCAS systems use the same communication protocol and use the same frequencies (1030 and 1090 MHz). They could well use the same antennas. However for best performance, SSR antennas are omnidirectional and TCAS antennas favor some sector, usually by beam forming.

On this B767-200 picture, TCAS antenna is the flat one at the front, and the yellow SSR antenna is a bit behind (only one):

See the full and higher quality photo by Ramon Jordi

Another airframe with two SSR antennas:

See the full and higher quality photo by Temo Madrigal

I was not able to find a good view of the SSR antenna on a B767-200, but on this A320, the two side yellow SSR antennas are more visible (as well as the single DME antenna behind):

A320 SSR antennas, source

Use and needs are different

  I guess that are sharing the same antenna. Am I right?

As said, you could be right as SSR and TCAS operate on the same L-band frequencies, and can't time overlap. But they have actually dedicated antennas, because they need different radiation patterns:

Transponder initial function consists in responding to SSR interrogators on the ground, and now in broadcasting ADS-B squitters in addition. The bottom SSR antenna is of some omnidirectional type, commonly a quarter wavelength monopole), Because the fuselage is not a perfect ground plane, the radiation pattern doesn't peak at the horizontal as one would expect, but has a privileged direction at 30° (source) below the aircraft plane, a low gain in the horizontal plane, and is nearly blind on its nadir.
TCAS on the contrary need to have a good reception in or close to the horizontal plane and around the nadir. They are the directions where the most immediate threats are coming from.

This is why the TCAS antenna is designed differently. Let's see the backside of the TCAS antenna shown earlier:

Source

Hum... not one antenna connectors, but four!

The flat shape of the TCAS radome (sometimes round) contains a 4-element phased array antenna which can be set to cover an hemisphere, but which can also focus on a quarter of this hemisphere. Example of design using a switched beam-forming network (SBFN):

Source: Microwaves & RF

The four outputs labeled A1..A4 are connected to the four individual connectors under the radome.

TCAS uses the steering obtained with the array to select which direction to send interrogations and to listen to responses, in order to reduce synchronous garble from close mode C transponders responding simultaneously to the aircraft (1.7 NM radius), and FRUIT from all aircraft responding to a ground ATCRBS interrogation.

TCAS reverts the bottom antenna to the omnidirectional mode (same phase on the four antennas) and decreases RF power in landing and takeoff phases, to prevent radio spectrum overload.

For a Mode S transponder aircraft, we would have this kind of configuration:

ACAS II Guide

Note there is a connection between TCAS and SSR to inhibit each other when they are using the frequencies and protect their RF input. If I remember well, SSR mode has the priority (at least when the TCAS is not in a TA/RA phase).


What is this c. 1930 beautiful monoplane seen in Oakland?

(wikimedia.org)

It looks like the Lockheed Model 8 Sirius, or a variant of it.

First flight was 1929, and 15 were built.

  Two versions of the same basic design were built for the United States Air Force, one made largely of wood with a fixed landing gear, and one with a metal skin and retractable landing gear, designated Y1C-25 and Y1C-23, respectively. Its basic role was intended to be as a utility transport.


Why would an ILS have a glide path angle less than the preferred 3°?

I won't pretend that I understand the physics of this, but one possible explanation is in FAA Order 6750.16E - Siting Criteria for Instrument Landing Systems. Section 3 discusses terrain effects on the ILS signal, and it notes that approaches that are partially over water may have signal quality issues. One way to address that is using a lower glide angle, per this section on page 3-4 (emphasis mine):

Where the Fresnel zone is smooth but not consistent, as where the
approach path is partially over water, a change may be encountered in
the received signal as the coefficient of reflection changes abruptly.
This effect is unavoidable; however, it can be minimized by
establishing the lowest possible glide angle (and, therefore, the
lowest possible grazing angle) and/or locating the glide slope
antennas within the specified criteria, so that the change in the
received signal does not occur within a critical part of the approach.

I don't know exactly which procedure you're looking at, but Larnaca is a coastal airport and it looks like approaches to 04/22 are at least partially over water.
I have no idea if the same issue occurs with other types of terrain. Someone mentioned in comments that the ILS at KTUL (Tulsa, Oklahoma) has a 2.75° glideslope landing south, but 3° landing north. KTUL isn't on the coast and there are no large bodies of water directly north of it. Maybe the same signal issue occurs there for different reasons, or maybe there's a completely different reason.


What information does a pilot have about aircraft operating on an intersecting runway?

As the question mentions, good situational awareness is an excellent safety tool. ATC is responsible for runway separation at towered airports, but pilots can play an important part of backup in the case of a human mistake.

The United pilots may or may not have been able to see the Atlas 747 on TCAS, as the terminal building that obstructed their view could also have blocked the transponder signal. TIS-B (Traffic Information Systems - Broadcast), a part of ADS-B, provides traffic both in the air and on the ground. ADS-B was not available in 1996, but if the same situation happened today and the United aircraft had an ADS-B signal on the surface and displayed TIS-B information, they would see the Atlas 747 on their displays. Whether or not that information would be useful to avoid an incursion in a cluttered runway environment is unclear.

The FAA is implementing a system to provide exactly the type of warning you're describing. Runway Status Lights (RWSL) use surface RADAR and lights embedded in the pavement to detect conflicts and alert pilots that a runway is unsafe to enter or take off from. In this situation, the United pilots would have seen red takeoff hold lights to inform them that the runway is unsafe for departure. The FAA plans to have RWSL operational in 17 airports, including Chicago O'Hare, by 2017.