I may be biased because I learned in gliders, but, concerning how soaring biases students to be better "stick and rudder" pilots:

The obvious one that has been covered in the linked answer: gliders don't have an engine.  The result of this is that flying a glider is an exercise in energy management and a more direct interaction with your drag polar for a given configuration--because you don't have any way to add more energy to the equation.

In other words, your duration aloft, your ability to land in a particular location (of particular importance in a glider, since you only have 1 shot at landing and it could be unexpected due to variations in ridge lift, etc.) -- everything relies on flying the aircraft so as to manage the kinetic and potential energy of the aircraft to achieve a certain end -- and you don't have any "liquid" energy (e.g., fuel) to add to the vehicle.  Generally, you're trying to fly the aircraft such that it creates as little drag as possible, so turn coordination becomes more important (also can lead to spins, depending on condition), speed to fly for prevailing conditions and flight mode becomes really important.

The quintessential example of this (at least, the one that I have a video of) is from a student at my undergrad.  He was learning to fly one of the Grob 109b motorgliders the school owned.  As part of the class, the students demonstrated their skill at managing the aircraft's energy by starting, with the prop off, 1000' above ground and maybe 600' from the end of the runway (horizontal distance).  Within 15 seconds, the aircraft would be on the ground just a little way beyond the runway numbers.  And you have to do it without exceeding the aircraft's maneuvering speed during the vertical dive, conserving enough energy to make the runway, but not too much energy (else you'd just float the length of the runway).

Another facet of the above: increased adverse yaw effect.

In a glider, keeping the yaw string straight (e.g., maintaining coordinated flight) is constantly drilled into you as one of the most important things you will do (besides flying the airplane).  I remember flying one of my last instructional rides before my checkride and my instructor walked up with a sheet, taped it over what instruments the glider did have, and said, "Let's go flying".  The only instrument I could see was the yaw string, and the point was that that was "all" I needed (I had a feel for airspeed based on pitch).

What the yaw string does is tell you whether or not you are flying straight (i.e., what direction the relative wind is going relative to the aircraft).  As noted before, this is quite important, because, if the relative wind isn't parallel to the longitudinal axis of the aircraft, your drag is going up.  Gliders are, typically, more prone to slipping or skidding (i.e., flying at angles to the relative wind, particularly in turns) due to their long wings, which, when they have an aileron deflected, can induce a greater yawing moment than your typical general-purpose aircraft with a much lower aspect ratio wing (i.e., a more shorter, stubbier span, whereas gliders are made with long, skinny wings to decrease induced drag).  This makes the aircraft's yawing moment more sensitive to aileron deflections and  more prone to fly in an uncoordinated fashion--hence instructors make it a point to train glider pilots to pay more attention to how coordinated their vehicle is at a given point in time.

This is of particular importance, not just for drag, but also for flight safety.  If you have a glider that's low, relatively slow, and making a steep turn while landing (read: flying at a high load factor, thus increasing stall speed), an uncoordinated turn can do this, or stall, spin, and crash due to insufficient altitude for a recovery.  It's a really big deal, and, again, you don't have the ability to just "add power" when you feel like you're getting slow.

Situational awareness

One trick with gliders is that you are very dependent on the atmosphere.  Say you are trying to get from point A to point B, say for a race or what have you, and you planned out your flight to run a ridge based on forecasted winds.  You're up, running the ridge at 200' (or less) above ground level, and the wind peters out and dies -- you're stuck.  When I learned to fly ridges, the mantra was to always have a place picked out such that, if the wind died right now, you'd have a place to land.  200' was relatively high among the folks I knew flying the ridge (most guys would be flying at least half that, and I heard stories about folks flying at 20 feet above the trees), and that doesn't give you a lot of time to figure out where you are going to land...and landing out (i.e., not at an airport) is not uncommon.  Glider pilots train for it, it's part of our ground school, and it's beat into us while flying.  If you're taking off via aerotow (i.e., being towed to altitude by another aircraft), the question during training is always, "If the rope breaks right NOW, where do you land?" Because you're getting energy from the towplane burning fuel on the other end of the rope, and, as soon as it's broken, you have not much time, some speed, and usually very little altitude to get safely to the ground in.

So, in the end, I'd think that glider pilots would have some edge in powered pilots in that regard.  Yes, powered pilots train for engine outs, but, in a glider, every flight is an engine out situation and you're flying at the mercy of the weather, how well you planned ahead for it, and how well you continue to plan while you're flying.  As quoted from an AOPA article:

  U.S. Air Force Capt. Danny Sorenson, who instructs in F-16s, is a glider pilot. He stated, “As a result of my glider training, I’m always thinking, ‘Where can I land this thing?’” He also noted that during his F-16 training, simulated flame-outs were never a problem for him, “It’s instinctive,” he said. “I’d just fly my pattern and glide in.”

Summing it up:

Gliders are much "simpler" flying: there's not a VOR in a glider, no ILS, no autopilot...all you have to do is fly the airplane, and do it well.  And, if you do it well, the airplane flies well.  Do it poorly and you might die (if it's that bad, since you don't have 2nd chances in important things, like landing) or you just might not be in the air for very long.  It's a much more direct connection between the pilot's stick/rudder inputs, the vehicle's performance as an aerodynamic vehicle, and how the pilot wants to use the aircraft, though, and I think that's the key...and all of these skills translate to other aircraft (even rotary wing, as I found out when flying those once).

Sources:

--My experience (PPL in gliders)

--https://www.aopa.org/news-and-media/all-news/2002/may/flight-training-magazine/gliding-your-way-to-a-pilot-certificate

-- https://www.aopa.org/news-and-media/all-news/2009/january/22/training-for-that-moment-when-every-second-counts


What happens if a plane breaks down away from a maintenance facility?

I’ve done it both in the military and the civilian world. At major airlines, it’s pretty rare that you’ll fly into a place without mechanics. That said, there are odd circumstances as pointed out in other answers. In those cases, we do our best to coordinate with the pilots to get a very good idea of what the problem is.

Usually Maintenance Operations Center techs will try to find a local mechanic or even someone from another airline to get it going. Generally speaking, if the problem was that simple, the pilots probably didn’t need to divert anyway. Other airlines don’t mind helping with parts, but manning is another story. There are labor contract issues, payroll problems, etc... It gets complicated quickly. That’s usually when they call The Mothership and decide to bring a few mechanics in to fix it.

From there, we brainstorm most likely scenarios and also the most outlandish. We try to bring everything including the kitchen sink. From experience, no matter how easy you thought it was on the phone, and no matter what you bring, there is a guaranteed monkey wrench lurking in the midst. After all, if this was just any ordinary problem, the plane would have been off the ground already.

We usually dispatch to the plane by other commercial flights, or we drive to the location ourselves. Most guys prefer to drive because we’re usually on overtime for the majority of the trip... Might as well drive 8 hours on OT too...

Once we arrive, the mess we’re in quickly becomes apparent. We usually hem and haw in gaped astonishment at what went wrong. Then we realize that nothing we are looking at is what we were told over the phone. Then we call The Mothership and explain that we need some outlandish piece of equipment. It then becomes MOC job to get us that equipment somehow or some way. Still on OT, we make our way back to the hotel and wait for the call that our stuff is on the way.

I have changed engines with skyscraper cranes, performed wire splaces with two terminals, a bolt, a nut, and a piece of tape, and made adjustments to “non-adjustable” equipment to get a plane off the ground and into a better location. Sometimes you have to be creative but judicious in the repair process.

Usually, after days of lack of sleep and suffering from overexposure to cold, heat and/or other intolerable elements, we get the airplane up and go home. After our arrival, we fill out our travel paperwork, are summarily haggled to death by bean counters who have no idea what we have  just done, and find that the 47 hours of OT we were billing the company for gets knocked down to about 12 hours plus a few denied receipts. In the end, you break even, go home, lie to the wife why there is a $2000 charge for “The Dollhouse” on the credit card and go to bed. Later that evening, you’re called to go on another trip and the cycle continues.


Why are the toggle switches in cockpits of new aircraft painted white?

The reason is threefold:

White knobs offer better contrast, and are thus easier to spot regardless of lighting conditions

The material used has improved and consistent friction and "feel" to it. Bare metal switches, especially when worn out by use may become slippery, and since some of the toggle switces have detents, operating them might be compromized.

The plastic coating (on at least most) of the switches can be renewed without replacing the whole switch assembly. For example on the larger switches white knobs are screw on -type


The definition you quote is pretty clear to me. But let me try to explain some of the background to help you understand it.

An ATC clearance always contains a clearance limit, which is the point to which the flight is cleared. Before reaching the clearance limit, the flight must obtain a clearance for the next portion of the flight. If that is not possible, the flight must not pass the clearance limit.

In most circumstances, a flight will receive its ATC clearance on ground before departure, and the clearance limit will be the destination aerodrome. The flight is then allowed to depart and continue all the way to its destination. This can be done because there is reasonable assurance that ATC will be able to coordinate the flight all the way through to the destination as the flight progresses.

In some cases, a clearance for (a portion of) a flight cannot be issued very far in advance. One example is clearance to cross larger portions of ocean (oceanic clearances), which are typically based on procedural separation and require the crew to provide very exact time estimates, which is impossible to do before the flight is airborne. Something similar is likely to be the case for certain military flights where some sort of diplomatic clearance is required to enter a countries airspace. Or maybe a flight has to cross the border between two countries that do not cooperate (a bit hypothetical in this day and age, but it might exist somewhere).

The definition of a downstream clearance is quoted in the answer. It means that, while a flight is flying in airspace A heading toward airspace B, the crew must obtain a clearance from the ATC unit in charge of airspace B before entering. This is because the flight will not be coordinated between ATC A and ATC B like most flights. How exactly this is done probably varies from place to place. The crew might contact ATC B on a secondary radio or CPDLC, or maybe ATC A can forward the request and relay the clearance from ATC B. In any case, the crew is responsible for not passing the valid clearance limit before a clearance to continue has been received.


Is a wingtip vortex strongest at the critical angle of attack?

do the vortices generally continue to increase in intensity once the plane is in a stalled condition? For the purpose of this question, assume straight and level flight in smooth air

These sentences are contradictory. Never mind.
The strength of the tip vortices post-stall depends on the wing's stalling characteristics. If the inboard section stalls first (which is desirable because it helps keep the ailerons functional) then the tip vortices will continue to increase with angle of attack until the tip section itself stalls. At that point lift near the tips drops sharply and the vortices will decrease accordingly.
If the plane is capable of post-stall flight at extreme AoA, it will not be travelling fast enough for the vortices to maintain significant energy.


Who first coined the phrase "aviate, navigate, communicate"?

I don't know the genesis of the phrase, but I heard several WWII era military pilots interleave it with stories of their sorties, and of the debriefs for those sorties.  Based upon that, I would say that the expression dates back to at least the early-1940's.


What material and shape should be used for angle of attack sensors?

A wide variety of materials would suffice as an AOA sensor merely aligns itself with the wind as a weather vane and does not carry load.  Any non-warping reasonably strong material such as aluminum plate can be used in the design.

Since we are only measuring wind direction, look no further than old style delta shaped weather vanes, also found on turbine style wind mills.

Another quick AOA sensor could be a smoke trail, a ribbon, or a string. It just needs to follow the wind stream.

A symmetrical wing shape would work fine, a flat plate is easier to construct and is adequate
to the task.


Can a helicopter operate continuously in a small, enclosed, sealed environment?

A helicopter develops lift by accelerating air downwards through its rotors.  This relies on the air above the rotors being slow enough for the rotors to accelerate that air enough to provide sufficient lift. When hovering in still air, the incoming air has zero velocity relative to the helicopter. While of course the air is conserved, in a large volume of air, the downwash is able to diffuse much more, and much of it does not immediately circulate back up above the helicopter.

If the helicopter were enclosed in a sphere, the smaller the sphere, the less the air would be able to diffuse. The downwash would circulate back to the top of the sphere, where the rotors would take that air in again. The rotors would be less effective at accelerating the air that is coming in with significant velocity, just as a propeller develops less thrust with increasing forward speed. Successful hover would depend on the helicopter being able to develop lift at a rate of circulation where the air can slow down enough for the rotors to be effective.

This seems like a experiment manageable enough that someone could try it at home...


Where can I find an image of the Thales FMS220 RMS page?

The answer is on the official website, here is a direct link:

https://fr.scribd.com/doc/204747124/Fms-User-Guide

You need to go to the website yourself because the document content is not to be disclosed without official approval.


How can I find the optimum chord wing length for this wing?

You want to fly at the polar point of the lowest energy consumption. If you describe the drag with the usual parabolic equation, you can use the optimum point derived in this answer. It is
$$3\cdot c_{D0} = \frac{c^2_L}{\pi\cdot AR\cdot\epsilon}$$

Induced drag is three times the parasitic or zero-lift drag when you fly at the polar point for minimum energy loss. But the minimum induced drag at a certain speed is also fixed once wingspan and mass are given - you can only mess up by creating a non-elliptic circulation over span, but never get better than this limit.

Now get the zero-lift drag down as much as you can (pick a thin, highly cambered airfoil which produces a high lift coefficient at the given Reynolds number, definitely no Clark Y) and size chord such that this airfoil will work at the optimum lift coefficient.

Note that this will be an iterative process. Picking a chord will influence your aspect ratio and zero-lift drag, so the optimum lift coefficient will be depend on the chosen chord.


What is the maximum slope for taxiing aircraft?

Footnote: I hope this is the correct/ current regulation. Published date is 25 January 2015.

Your question is covered (for EASA regulations) in the document Certification Specifications and Guidance Material for Aerodromes Design (link) in two sections:

Taxiway Slope (CS ADR-DSN.D.265)
Taxiway Slope changes (CS ADR-DSN.D.270)

  CS ADR-DSN.D.265 Longitudinal slopes on taxiways

  (a) The safety objective of limiting the longitudinal taxiway slope
  is to enable stabilised safe use of taxiway by an aircraft.

  (b) The longitudinal slope of a taxiway should not exceed:

  1.5% where the code letter is C, D, E, or F; and
  3% where the code letter is A or B.

  CS ADR-DSN.D.270 Longitudinal slope changes on taxiways

  (a) The safety objective of limiting the longitudinal taxiway slope
  changes is to avoid damage of aircraft and to enable safe use of
  taxiway by an aircraft.

  (b) Where slope changes on a taxiway cannot be avoided, the transition
  from one slope to another slope should be accomplished by a curved
  surface with a rate of change not exceeding:

  1% per 30m (minimum radius of curvature of 3000m) where the code letter is C, D, E,or F; and
  1% per 25m (minimum radius of curvature of 2500m) where the code letter is A or B.

  (c) Where slope changes in (b)(1) and (2)  are not  achieved and
  slopes on a taxiway cannot  be avoided, the  transition  from  one
  slope  to  another  slope  should  be  accomplished  by  a  curved
  surface  which  should allow the safe operation of all aircraft in all
  weather conditions.

The letters refer to the airport categorization.


If "flight time is compensation", how can a PPL holder legally fly at all?

Flight time is only considered compensation when the pilot is not paying all the costs associated with the flight.  If the costs are to be shared the following advice is recommended.

A private pilot can be compensated, up to a pro-rata share, of the cost of that specific flight.  This would include rental fees, fuel, oil and such.  It does not include items like insurance and annual inspection fees.

The overall regulation is found in §61.113(b & c).

  (b) A private pilot may, for compensation or hire, act as pilot in command of an aircraft in connection with any business or employment if:

    (1) The flight is only incidental to that business or employment; and

    (2) The aircraft does not carry passengers or property for compensation or hire.

  (c) A private pilot may not pay less than the pro rata share of the operating expenses of a flight with passengers, provided the expenses involve only fuel, oil, airport expenditures, or rental fees.

You should be able to see pretty quickly that you are allowed to transport yourself by private airplane to a business meeting.  There is good reason to fly to; depending on the distance, it could be quicker to fly a private airplane than it is to drive saving you time and money.  However, the moment the company decides that you should fly to all of your meetings it is no longer incidental to that business and operations must cease.

If you want to fly passengers, and also want them to pay their pro-rata share.  There are three things that must be considered.

There must be a bona-fide purpose for the PIC to make the flight.  The reason cannot be that the passenger has a business meeting at the destination and you want to get lunch.  You, as the pilot, must have a reason to make the trip, whether or not the passenger(s) come along.
The PIC must dictate where the flight is going to go.  Again, you cannot make a flight with passengers where you drop them off at one airport while you fly to a different airport.  Why would you land at the first airport, if you have no need to land there?
You cannot "hold out" or advertise that you are going somewhere and wait to see if other passengers are interested in going to the same location.  There are websites that have been shut down by the FAA for doing just that.

The Lamb Interpretation

The Mangiamele Interpretation

The Chero Interpretation

  December 26, 1985

  Thomas H. Chero
  Vice President - Legal
  AVEMCO Insurance Company
  Frederick Municipal Airport
  411 Aviation Way
  Frederick, MD 21701

  Dear Mr. Chero:

  Thank you for your letters to this office, dated September 9, 1985, and October 23, 1985, respectively, concerning the actions of the Pilots and Passengers Association (PPA).

  You are correct in stating that Section 61.118 of the Federal Aviation Regulations (FAR) prohibits private pilots from participating in PPA's operations. Section 61.118 provides that a private pilot cannot act as pilot in command of an aircraft that is carrying passengers for compensation or hire unless the flight falls within one of the four listed exceptions in 61.118(a) - (d).

  Section 61.118(b) allows a private pilot to share the operating expenses of a flight with his or her passengers. Additionally, the FAA has interpreted 61.118(b) so that the only allowable share-the-costs operations are those which are bona fide, that is, joint ventures for a common purpose with the expenses being defrayed by all passengers and the pilot. Nor does Section 61.118 permit pilots who want to build up time toward their commercial pilot certificates to carry expense sharing passengers to a destination at which they have no particular business. (emphasis added)

  PPA pilots apparently would not share in the expenses of the flights they would undertake. It also appears that PPA pilots could be flying to destinations at which they had no particular business. The PPA system is not a casual one of an individual pilot wishing to take some friends or acquaintances with him on a trip. The PPA system would violate the letter, as well as the spirit, of Section 61.118.

  Even if the pilot bears an equal share of the expenses with his or her passengers and indeed has his or her own need to fly to a particular destination, yet another problem arises. Since PPA's passengers would be solicited for flights by PPA from a broad segment of the general public, we conclude that each pilot carrying paying passengers from PPA would probably be engaged in common carriage. This means that each pilot would become an air carrier subject to the certification and operating rules of Part 135 of the FAR.

  We appreciate your calling our attention to this matter.

  Sincerely,

  John H. Cassady
  Assistant Chief Counsel
  Regulations and Enforcement Division


Where do the compressed gasses of a charged engine goes?

As long as the rpm is kept up, the charge coming out of the compressor has quite a bit of inertial mass and is more or less flowing continuously even though there is a valve downstream opening and closing.  There will be a pressure and velocity fluctuation near the valve as the charge just upstream is admitted to the cylinder, then cut off.  But because the opening and closing is happening so fast, these fluctuations taper off up stream.

This is one reason for having long intake runners on a 4 stroke; to take advantage of the inertial mass of the long cylinder of air in the intake duct.  On a non-supercharged engine, this helps with the preliminary filling the cylinder during the intake stroke because the piston doesn't actually have to "suck" initially.  As the intake valve opens, air comes rushing in pushed along by the inertial mass of all the air back up the intake duct, like a crowd of school kids jamming up in the hallway and piling out the door when it's opened at the end of school.  The ones closest to the door don't have to be pulled out; they are pushed out by their mates behind.

Anyway, the main issue is managing the intake charge and its inertial effects, and the increasing difficulty in doing this at lower speeds or idling.  I would expect you would have to do a lot of experimentation with compressor gearing/speeds and intake runner length trying to get an engine to run smoothly across the full operating range.

Your project sounds like a variation of a 2 stroke diesel, which doesn't use crankcase pressure to drive air into the cylinder like a spark ignition 2 stoke, and therefore requires a supercharger or turbocharger compressor to push the charge along in the absence of a 4 stroke's intake stroke to pull air in.  Possibly looking into 2 stroke diesels would help.

I'd also look into using an electrically driven supercharger in your design which would make it easy to experiment with different speeds and could really improve operation over the speed range by using a computer to manage it.


What is this flyer in a 1911 short film?

Given that the short film was produced in Turin (according to the Italian Wikipedia), it is likely that that the Aeroclub of Turin (1908) has more information on this aircraft.

On their website they describe the history of aviation in Turin in the 1909-1915 period(in Italian). Around that time, Turin was a center of aviation in Italy (and it still is).

There were several aircraft manufacturers, including the automobile factory FIAT (Fabbrica Italiana Automobili Torino) which at some point produced Farman aircraft under license.

One of their first employees (employee no.3) was Alessandro Cagno. He was, among other roles, the company's racing team driver. In 1909 he lost interest in car racing and turned to aviation. He became the 10th pilot in Italy, on a Farman aircraft. There are several pictures of him in his Farman III on the internet, which looks very much like the aircraft in the short film.

Below is a picture from 1911 of Cagno in his Farman III in Venice.

By Unknown - over 100 years old. Source: wikipedia

Especially this picture looks very similar to what can be seen in the film, including hills in the background.

More video material of the Farman III can be found here:

You can see that there were several variations on the model.

It may be Cagno's aircraft in the film, or another Farman. Looking at the list of early aviators in Italy, the majority of them got their license in either a Farman or a Bleriot. The latter aircraft looks very different.

Source: Contact! The Story of the Early Aviators, Henry Serrano Villard ISBN: 0-486-42327-1


Could the cargo hold of an aircraft be re-designed to carry passengers?

In principle, yes. The cargo hold is pressurised and (depending on the aircraft and the installed options) reasonably temperature-controlled. However, it's probably not feasible; there are three major issues to be worked out that I can think of off the top of my head:

Cargo hold height and windows. It's a bit hard to tell from your picture, but even on a large widebody plane the cargohold is not that high (the cabin floor is lower than halfway). The A330 (as an example) carries LD3 containers in its cargohold, which are about 160cm tall; the cargohold is not much taller than that. Most passengers cannot walk upright inside it; the cargo hold on smaller aircraft is even lower (the one on the A320 is designed to carry LD3-46 containers, which have a height of about 115cm). Also, the lack of windows would bother passengers in the lower deck.
Emergency exits. In an emergency, passengers must be able to get out of the plane within 90 seconds. At best you would need to install additional doors in the cargo hold; at worst, you will not be able to meet this requirement (because of the low ceiling, people can't move as quickly)
In a crash landing, the lower fuselage may buckle, which serves to cushion the impact for the people in the passenger cabin. You would need to show that the passengers in the lower deck can survive a crash landing.

Note that some airlines use part of their lower deck for galleys, crew rests and even lavatories.


Why are the cabin inner windows so flexible?

The inner window is just a plastic protective cover, so that you don't touch the glass, which is probably very cold at altitude. You'll notice on the inner window there is a tiny hole at the bottom to equalize pressure and prevent condensation.

See this article that explains it


What flaps position should be used for taking off from a wet runway?

The POH for a 152 lists the flap settings for takeoff as between 0° and 10°. It makes no specific mention of take off from a wet runway, however you could follow the same procedures for a soft/rough runway if you are concerned about the surface conditions.

  Soft or rough field take off are performed with 10° wing flaps by lifting the aircraft off the ground as soon as practical in a slightly tail low attitude. If no obstacles are ahead, the airplane should be leveled off immediately to accelerate to a higher climb speed

Source: Cessna 152 POH Section4 (Normal procedures)

I should note though that in roughly 180 hours on C150/152's and a short (650m) hard runway, I've never felt the need to even use flaps, let alone execute a soft/rough field takeoff as described above. It's not a particularly comfortable take off, and a wet hard-surface runway doesn't really present that much of a problem.


Why is the phrase “infinite energy” used by this (alleged) ATSB investigator?

You are correct in that this is not a quote of the report -- the final report does not use that phraseology either.  What the investigator means is that the energy is effectively infinite, as it is impossible to stop something with that much kinetic energy within the mass budget of an airplane engine cowling.


Why are tugs the least priority when talking to ground?

1) The video you are specifically referencing is JFK (as you probably know). JFK has a very complex airport layout and generally is very busy. There are a variety of reasons "tugs are last priority."

While it's not a specific rule to always allow airplanes under their own power to move first - Air Traffic Control exists to expedite the flow of traffic, which includes ground traffic, and often times tugs are just slower and because they are often relocating to different gates, pads, or hangars, they tend to get in the way of the normal flow of traffic.

Often times departing airplanes need a specific sequence (order) at the departure runway which cannot be delayed by lower-priority things such as airplanes being tugged around the airport.

Airplanes that are being tugged around are not under their own power and not burning nearly the amount of fuel that a taxiing aircraft is. Again, specifically with JFK, there are so many airplanes the ground controller must keep things moving to have an even somewhat organized and expedited flow. Often times, tugs are moving airplanes that are not filled with passengers, so the theory being "they can wait" (needs of many outweighs the needs of the few).

Even more often, and specifically with JFK, the airlines schedule causes those "tugged" airplanes to want to come into a one-way "alleyway" in the ramp when many revenue passenger filled planes are trying to exit. The tug with the airplane gets to wait, because they physically can't get into the alleyway anyways until all the airplanes taxiing move.

2) In the US, airports have what are called movement areas and non-movement areas. Movement areas are generally controlled areas, by either ATC "ground control" or by a "ramp control." Non-movement areas, contrary to its name, are areas that are not controlled by ATC or a ramp control and up to the user to maneuver without control instructions. Tugs only communicate with ground when they are on movement areas (taxiways and runways). Roads are generally non-movement areas. At some airports (JFK being one of them) when a road intersects a movement area, a vehicle on the non-movement area must always give way to traffic on the movement area. So, a tug driving around without an airplane attached would be on the road most likely, and only talk to ground control if that specific airport required a clearance to "Cross" the taxiway at the road. This is commonly referred to as a "look and go" operation. Look and go is specifically authorized only for roads that intersect taxiways at certain airports, and never allowed for runway crossings. Busses almost never operate on taxiways, except to cross them as described above. In general, unless a vehicle has a specific purpose to use the movement area, they'll use a road, because it's easier.


Has the financial situation of an airline ever negatively impacted safety?

Pan American World Airways declared bankruptcy in January 1991. In the year previously they were doing everything they could to to avoid that. To help their cash flow, Pan Am sold five of their 747s for cash to Evergreen International Airlines. The deal was that EIA would immediately lease the five back to Pan Am, which they did. Unfortunately, Pan Am soon defaulted on the lease payments and EIA began repossessing the aircraft.

EIA gave Pan Am fair warning on the repossession of the first aircraft, at which time Pan Am swapped out good components for crap components before surrendering the aircraft. Not to be taken again, when EIA repossessed the second aircraft, they did so without warning at the gate when the aircraft arrived in JFK from Europe.

I was the f.o. on the crew that was sent to get the aircraft. We were in the cockpit setting up when one of our maintenance guys came in and said that they had just received orders to boroscope the engines, which they did while we waited in the cockpit.

After an hour or so, one of our JFK managers came into the cockpit and told us that we wouldn't be going anywhere, that the airplane was not flyable as three of the four engines were significantly below required tolerances.

So, if flying a plane load of passengers across the North Atlantic with three out of four engines below required minimum maintenance standards constitutes a negative impact on safety, then, yes, a bad financial situation did indeed, at least once, cause such.


What are the considerations for coding the GPS before engine start without external power?

15 minutes is a long time to be draining the battery, it's not just the G1000 that will be running but the electronic gyros, beacon, etc. If the airplane hasn't been recently flown and it's cold outside 15 minutes may be long enough that you can't crank your engine.

There's also problems with running the G1000 while starting the engine:

It's not good for the electronics: you get all sorts of electronic noise and surges when running the starter. I don't think it's that much of a problem with modern electronics, but the G1000 is a painfully expensive piece of equipment and you want to preserve it in any way you possibly can!
You get a power sag: the starter drains a lot of power, there may not be enough to keep the G1000 going and it may restart. It it restarts you lose all that configuration you did! You could mitigate that by saving your flight plan to an SD card, shutting down the avionics for start, then re-loading it

The last issue is that 15 minutes is time you could be flying, or someone else could be flying. It's also time you might be paying for depending on the school or group you rent from (if you rent)

There's no reason to do this anyway to be honest, you can use SkyVector, Foreflight, SkyDemon, Garmin Pilot and other flight planning software to plan your flight on a tablet or other computer, load onto an SD card, then load it on to the G1000. Some of the software costs money but it's worth every penny as it gives you the opportunity to take your time planning flights rather than rushing to get waypoints in. The interfaces are also much nicer to use than the G1000.


At what angle of deflections do rudders become inefficient?

The only time you should be using full rudder is when doing a side slip - such as turning the yoke for a left turn but pressing right rudder, so you are descending and looking to your left as the plane goes forward tracking down the runway direction.  Normal coordinated turns, you would not use anywhere near that much rudder while turning.

I just found a NASA Test Report on my plane, a Cessna Cardinal, that lists control deflection amounts as a reference for a light general aviation airplane:

Angle of attack,           -4° - +20° ± 0.5°

Sideslip,                 -15° - +15° ± 0.5°

Pitch angle,              -15° - +15° ± 0.5°

Roll angle,               -75° - +75° ± 0.5°

Rudder deflection,        -24° - +24° ± 0.5°

Stabilator deflection,    -20° - + 5° ± 0.5°

Right aileron deflection, -20° - +20° ± 0.5°

Left aileron deflection,  -20° - +20° ± 0.5°


Which aerodromes are in the scope of ICAO recommendations?

Per Annex 14, international airports only, and preferably any public use airport—

  1.3.1 As of 27 November 2003, States shall certify aerodromes used for international operations in accordance with the specifications contained in this Annex as well as other relevant ICAO specifications through an appropriate regulatory framework.

  1.3.2 Recommendation.— States should certify aerodromes open to public use in accordance with these specifications as well as other relevant ICAO specifications through an appropriate regulatory framework.

(Emphasis not mine.)

If for any reason, a country deviates from the standards, it needs to notify ICAO.

How do I know whether such aerodrome in a given country benefit from ICAO recommendations?

Deviations are published by ICAO in Supplements to each Annex. I can't speak for 3.9.6 due to paywalls. However, here are examples for Canada's deviations to Annex 14—

  Canada does not provide runway end safety areas but does provide a 60 m graded strip beyond the runway end. (More on that story.)
  Canada computes runway longitudinal slopes by dividing the difference between the maximum and minimum runway end elevation by the runway length.

Below (may not be current due to paywalls) are countries that fully adhere to Annex 14—

  Contracting States which have notified ICAO that no differences exist:

  Colombia
  Egypt
  Georgia
  Ghana
  Ireland
  Malaysia
  Monaco
  Namibia
  Peru
  Sri Lanka
  United Republic of Tanzania


How did the F28 have such a good L/D ratio?

They just got this wrong. I have flown F28-1000 and -4000, the F100 and the B767-300. The most feet per nautical mile lost of these with idle power at any given Indicated Air Speed (say 270-280 below 25000 ft) is the F28-1000 (around 475 fpnm) then the F28-4000 at about 425 fpnm, then the F100 at about 350 fpnm and the best is the B767 at about 300-330.The 425 fpnm figure for the -4000 was measured by me around 2004 to get data for MS Flight Sim. All the rest are educated guesses.


Can private pilots drop skydivers if the pilot pays a pro-rata share?

This is not so difficult. Many people like to refer to the regs without actually looking at the regs. This is all taken from §61.113.
Pro rata share is not the same as getting compensated.

(c) A private pilot may not pay less than the pro rata share of the operating expenses of a flight with passengers, provided the expenses involve only fuel, oil, airport expenditures, or rental fees.

In this scenario, the pilot isn’t holding out as a commercial operator; these are his friends.
According to any online legal dictionary, the pro rata share is defined as the total cost divided by the number of shares. In other words, the total cost of fuel, oil, airport costs, and rental fees split evenly between everyone in the plane, including the pilot. As long as it is split evenly, it’s not compensation or hire, it’s cost-sharing.
All that said, NEVER do anything because some guy on stack exchange told you that it was ok. Check the regs for yourself and contact your local FSDO for clarification.


Is there any website which is offering free real time tracking data of flights?

There are numerous web sites that provide flight tracking data, including radar and ADS-B. Most are free for personal use, but AFAIK all of them charge for commercial use. This makes sense since collecting and aggregating that data takes a lot of time, effort and equipment, and they have to recover those costs somehow. Still, using an existing service should be a lot less expensive than trying to set up your own redundant operation just for your own needs.

The sole exception is if you're trying to track ADS-B flights in the vicinity of your own facility, in which case you can easily set up a single ADS-B receiver there. But most folks want a (much) bigger picture, including non-ADS-B traffic, so please clarify the scope of your needs.


Why is the A330neo more efficient than the A350 on shorter routes?

A330-900neo    A350-900
Seating       287–440        325 / 173 (ULR)
MTOW          251 t          280 t
OEW           137 t          137 t
Unit cost     US$296.4 M     US$317.4 M
Thrust/eng    324 kN         375 kN

The A330 having fewer seats means a bigger chance of high utilization on any given flight (or having high-density small seats for shorter durations / dense routes). Shorter flights are typically more frequent on a weekly basis, so the flying customers get more spread out in a low-demand season.

With more frequent airport usage, the lighter MTOW means lower fees (typically it's a function of MTOW). Having the ability to carry some 30 tonnes more, pay for it, but not utilize it (carrying fuel), is not good.

They have similar Operating Empty Weights (OEW), which typically means a similar unit cost (~\$2K/kg), but due to the generational gap of the airframe (development cost), getting a discount on the A330neo will be easier (9% bigger discount for the -900neo as of 2014).

Turbine engines give the best fuel economy when they are running near their design power. Having extra power that an airline won't use to carry lots of fuel for an ultra long-haul flight will mean not running at the best power setting. A smaller A350 could have a derated R-R XWB, but a tailored Trent 7000 (6 inches smaller fan diameter) will provide better economy outside the ultra long-haul segment.

The A330 maintenance is also mature, with enough supply, demand, and expertise, this translates to cheaper maintenance cost, especially if the customer already has A330ceo's – flying relatively short hops rackes up airframe/engine cycles more quickly.

In short, it does indeed depend on the route. Some carriers benefited from the full potential of the 787 performance, others didn't, but each carrier is sold the right projections. See: Did any Boeing 787 operator achieve the 20% fuel efficiency improvement over the 767?

Case in point, Emirates has recently (Feb 2019) decided to purchase 40 A330-900s and 30 A350-900s. (airbus.com)


Traversing a tall suspension bridge during low overcast

Sounds pretty hazardous (and almost definitely illegal) to me
Here's the first photo of the first suspension bridge I found when I looked on Wikipedia

Guy Wires
Can you see all the really narrow guy wires below the bridge?  No?  I can't either.  If you can't see them in a photo, how are you going to see them at 100 knots?
"But Steve, maybe there aren't any!"
Yes, or maybe there are.  Are you confident enough to bet your life on it?
I thought you were the one with the plan!

Each pilot in command shall, before beginning a flight, become
familiar with all available information concerning that flight. (FAR 91.103)

Suspension bridges aren't like TFRs, they don't just appear in between the time you took off and the time you get to them.  Why didn't you know there was a bridge there before you took off?  Why didn't you have a plan for what to do when you got there already?
Boats are people too
You need to stay 500 feet from any structure.  Bridges are structures, so you need to be 500 feet away from them.  You also need to be 500 feet away from vessels and people, so if there's anyone on the river, your options just went from "bad" to "none".
But what about my emeeeergency?
All the rules go out the window if you're experiencing an emergency...as long as you're acting in the interests of the safety of the flight.  I spent some time on a foggy morning talking with an FAA inspector about this very topic (flying under bridges in emergencies) a couple years ago, and his words were to the effect of:

"It would have to be a very unique emergency for flying under a
bridge to be the safest course of action."


What should pilots state initially when telephoning a weather briefing facility for preflight weather information?

It's in the AIM 5-1-1(f):

When requesting a preflight briefing, identify yourself as a pilot and
provide the following:

Type of flight planned; e.g., VFR or IFR.
Aircraft’s number or pilot’s name.
Aircraft type.
Departure Airport.
Route of flight.
Destination.
Flight altitude(s).
ETD and ETE

Personally, I've never given or been asked for the aircraft type (although I have it on my LMFS profile so they should have it), but the other items come up. My typical request is something like this:

This is N12345, I'd like a standard briefing for a VFR flight from
KMDQ to KLOU at 5500', ETD at 1600Z, ETE 2h15


Why isn't KTEX's runway designation 10/28 instead of 9/27?

That direction (284) is the true heading, but runways are numbered according to the magnetic heading.

  Runways are usually numbered according to their direction, more precisely called runway magnetic bearing or QFU (see Q codes). (How are runways numbered?)

For KTEX:

  276 magnetic, 285 true
  096 magnetic, 105 true

While 276 should be rounded to runway 28, it could be a recent change that the magnetic heading changed to 276 from say <275. There is a process to go through, so a recent change in magnetic variation does not mean the renumbering will swiftly follow.

  Every five years, the FAA reevaluates shifts in the pole—its magnetic variation—and makes changes to runways and flight procedures as needed. (How do airports determine when they should change their runway numbers?)


What's going on with sudden acceleration/deceleration in mid-air?

Without knowing the specifics of the flight, there could be a lot of reasons for this.

One guess for the sensation of accelerating and decelerating We’re intermittent steps at fixes on the departure procedure the pilot flew out of KLGB at certain altitudes and airspeed either as part of the DP or as assigned by ATC in order to facilitate departure from SoCal airspace to enroute.  That and a little sloppy airmanship on the part of the flight crew.

As for the “circling” at KPHX,  most likely that was the pilot flying a STAR with ATC final vectoring to a visual approach or SIAP for runways 25L/25R/26 at Sky Harbor Intl.


How can the CVR from a Cessna 560XL only contain old records and none from the fatal accident?

If the fuse was pulled between the previous flight and the crash then yes, the CVR can only record when it has power

Pulling the fuse or going behind the panel and cutting the wire will prevent it from recording.


How could Airbus better tailor the A380 to the modern market?

Plain and simple, to meet current market requirements, Airbus can do pretty much nothing to make the 380 more "current".
The technical improvements suggested do nothing to change the fact that the 380 is too big, that is, it has too many seats, thus not allowing enough flexibility in this market situation.
In addition to not addressing the main problem, they would need major re-design, except for the wheeltug, which on the other hand is questionable in it's economics: save 20 minutes on ground, haul extra weight for thousands of miles...
There is no sense in technologically further developing a model that has a major "flaw" in it's economics. There are no customers, or not enough at least, for 380neo.
PS: markets are fluid. It may very well be that in furure super jumbos are coming back, but at the moment it does not look like that. If SJ make a comeback, it'll prolly be with a clean sheet design.
PPS: idling outer engines does pretty much nothing for wake turbulence. Wake is "caused" by wings, not engines.


How is ATC handed for private rural airstrips?

I can’t speak for Australia, but in the United States there are thousands of uncontrolled airports throughout the country, both privately and publicly operated.  Larger, better equipped public uncontrolled airports have good facilities such as paved runways and taxiways, instrument approaches, automated weather reporting stations, pilot controlled airport lighting, FBOs, fuel and maintenance depots, etc. but many uncontrolled airports are simply grass, gravel or dirt strips with little or no facilities, particularly in back country or mountainous areas.

Typically the decision to go into these kinds of airports is at the pilot’s discretion and the pilot alone must make the final call as to whether they can safely take off and land at these locations.  Bush pilots departing from said locations will typically carry small handheld weather stations used by mountaineers for determining local atmospheric conditions, winds, etc.  Remote airports will use a standard left hand traffic pattern flown at 1000’ AGL, but many do not due to nearby terrain and are one way in/out.  If a CTAF is not published for the airport, pilots will use the MULTICOM frequency of 122.9 MHz to announce their position and intentions.

Condition of the airport and runway are often not monitored and it is up to the pilot to determine if they can be used.  Arriving traffic will often make a low, slow pass over the airfield to determine runway condition and look for obstacles which could impede landing.

All types of aircraft can and do use such airports but most often the aircraft operating from them are specially build bush aircraft with good STOL flight characteristics plus beefy landing gear and tires for operating from unpaved strips or off field operations.


For UAS, the aircraft may be below the service volume of a VORTAC most of the time.  Furthermore in the US sUAS are normally line of sight to the pilot so in theory if GNSS is unavailable, the pilot will control visually.  Finally the variability and uncertainty of VORTAC is high enough so as to make it impractical for UAS stability, drift and position control


What are the FAA requirements for when to use an airline call sign & flight number versus the aircraft registration number?

I found something relevant buried in the depths of JO 7340.2 on contractions (i.e. abbreviations) for airlines, aircraft types etc. Section 1-4-2 says:

  The company designator, together with a flight number, serves as the
  aircraft identification in the ATC system. Company designators are
  valid only for company business in accordance with the provisions of
  its operating certificate or servicing organization. Pilots will use
  standard identification procedures for personal flying

Compare that to the quote from your safety organization:

  commercial flights are always conducted under a flight number, and
  private operations (e.g. repositioning flights) are always conducted
  under the aircraft registration number.

If you remove the words "e.g. repositioning flights" then it's saying almost exactly the same thing. What's really odd is that the checklist uses repositioning as an example of a "private operation" (the JO uses the words "personal flying", which has different connotations). I think most people would say repositioning is definitely company business. Perhaps it's just sloppy wording or a poorly chosen example.

As for the safety organization's claim that there are specific requirements in 8900.1, I couldn't find anything. The only vaguely similar thing I found is the 'use it or lose it' clause in 2-275:

  B.    Failure to Use Three-Letter Company Designator and Telephony
  Designator. ATO AJV-2 will place on a watch list any company that does
  not use an assigned three-letter company designator and telephony
  designator for 2 years on an instrument flight rules (IFR) flight plan
  in U.S.-controlled airspace. ATO AJV-2 will revoke and release any
  three-letter company designator and telephony designator that are not
  used for 3 years on an IFR flight plan in U.S.-controlled airspace.

Whoever wrote your checklist might be saying that you need to make sure that you're using your company call sign regularly to make sure you don't have it revoked, but that seems like a real stretch to me. And even if that is the case, it wouldn't explain why repositioning flights should be different. Since 8900.1 is a very large reference library, I'd ask the safety guys to point you to the exact document and wording.

Looking in the other usual sources (FARs, AIM, P/CG, ATC orders etc.) that you and Ron mentioned, I couldn't find any specific legal or regulatory requirements either. Almost every reference in FAA sources says "registration or call sign" or something similar (e.g. the AIM's instructions on filing flight plans), and the FCC regulations allow either in radio use (47 CFR 87.107).


Is there a resource that lists what's outdated in "Stick and Rudder"?

I'm not aware of such a list although I would say 99.99% of this book is not outdated.

Maybe some of the terminology is outdated when it talks about the "gaits" of the aeroplane for example which is an horse term apparently.

I wouldn't say anything else is though certainly not the concepts, because the air is the same, the laws of physics are the same and human nature the same as it was 70 years ago. Its a very insightful book that should be every pilots reading.

Maybe it goes on more about tail-wheel aircraft and there are fewer of these aeroplanes around today but this only applies on the ground and is still very interesting even for nose dragger pilots like me.


Do fighter jets have deicing in their wings?

No they do not nor are there any modern fighters that I am aware of that are intended to operate in icing conditions nor would they pass the FAA’s certification processes for flight into known icing.

As an example from the Grumman F-14D NATOPS Flight Manual, Section 18 - Extreme Weather Operations.  The basics are that Tomcat aircrews are advised to avoid areas where icing is probable and that extended flight in an icing environment is considered an emergency.

  Icing conditions should be avoided whenever possible. Before flight, check freezing levels and areas of probable icing from weather service.

  The primary concern with flying in icing conditions is ice accumulation sufficient to cause engine damage. Ice accumulation on engine probes located between the engine guide vanes and above the number three inlet ramp is not detectable from the cockpit. Aircraft maneuvers or landing impact can dislodge accumulated ice and can cause severe FOD to the engine. Visual detection of icing on exterior surfaces and/or illumination of the pilot’s INLET ICE caution light should be treated as indications of the potentially more serious problems described above. The following precautionary action should be taken immediately in known or suspected icing environments:

  ANTI−ICE switch  ORIDE/ON.
  CABIN AIR DEFOG lever  FWD DEFOG.
  Engine instruments  Monitor Frequently.

  Carefully monitor rpm and EGT indications. A reduction of rpm or an increase in EGT accompanied by a loss of thrust is an indication of engine icing.

  Avoid clouds and other areas of visible precipitation.
  If unable to avoid precipitation, adjust aircraft Mach or altitude as necessary to remain outside of the icing zone shown in Figure 18−1.

  Extended operations in icing conditions should be considered an emergency situation. If time and fuel permit, a descent below the freezing level is recommended. If unable, altitudes above approximately 25,000 feet or ambient temperatures below −30°C are generally free of icing conditions. If inadvertent or unavoidable operation in known or suspected icing conditions has occurred, an effort should 18.1.

  Before flight, check freezing levels and areas of probable icing from weather service.
  The primary concern with flying in icing conditions is ice accumulation sufficient to cause engine damage. Ice accumulation on engine probes located between the engine guide vanes and above the number three inlet ramp is not detectable from the cockpit. Aircraft maneuvers or landing impact can dislodge accumulated ice and can cause severe FOD to the engine. Visual detection of icing on exterior surfaces and/or illumination of the pilot’s INLET ICE caution light should be treated as indications of the potentially more serious problems described above. The following precautionary action should be taken immediately in known or suspected icing environments:

  ANTI−ICE switch  ORIDE/ON.
  CABIN AIR DEFOG lever  FWD DEFOG.
  Engine instruments  Monitor Frequently.
  Carefully monitor rpm and EGT indications. A reduction of rpm or an increase in EGT accompanied by a loss of thrust is an indication of engine icing.
  4.Avoid clouds and other areas of visible precipitation.
  If unable to avoid precipitation, adjust aircraft Mach or altitude as necessary to remain outside of the icing zone shown in Figure 18−1.

  Extended operations in icing conditions should be considered an emergency situation. If time and fuel permit, a descent below the freezing level is recommended. If unable, altitudes above approximately 25,000 feet or ambient temperatures below −30°C are generally free of icing conditions. If inadvertent or unavoidable operation in known or suspected icing conditions has occurred, an effort should
  be made to eliminate the ice before landing by remaining well below the freezing level for an extended period of time.

  WARNING: Icing conditions can cause heavy ice accumulation in the inlet ramp areas or on engine probes and the compressor face. Aircraft maneuvers and arrested landings may dislodge this accumulation and cause extensive engine FOD or failure. A straight−in field landing is preferred. Minimum power setting after landing is recommended.

Similarly the F-16 A/B flight manual offers similar advice:

  Flight in areas of icing should be avoided whenever possible. If icing conditions are anticipated or cannot be avoided, tum ANTI ICE switch to ON ~ and PROBE HEAT switch to PROBE HEAT. Frequently check the aircraft leading edges for indication of ice buildup. Make all throttle movements slower than normal when in potential icing conditions to reduce possibility of engine stalls and/or stagnation. Consider diverting to an alternate field if required to avoid icing conditions.

Fighter aircraft, with their thin, low aspect wings and sharp leading edges are actually more susceptible to ice accumulation than other kinds of aircraft wings.  They do have one advantage in the sheer climbing power and maneuvering capability to get out of an icing area with a slow to moderate accumulation rate.  Fast ice accumulation could be very dangerous to an fighter, especially during low speed operations ie descent into a terminal environment and landing in marginal weather.


What are some of the more common procedures when faced with a hung landing gear?

As referenced in a comment, the generally accepted thing to do is to refer to the aircraft emergency checklist/AFM to see what it says to do.

This will vary by aircraft design, but usually involves testing the indicator lights, and then activating alternate means of extending the gear as needed.


Is it true that high-bypass engines are inherently inefficient at higher speeds?

Power consumption=Kinetic energy=$1/2mv^2$.
  Thrust=momentum change=$mv$.

This is only true if the engine is perfectly efficient internally and the air is still relative to the aircraft.

If the air is moving relative to the aircraft (and the engine is still perfectly efficient internally) then.

Power consumption=Kinetic energy=$\frac{1}{2}mv_e^2 - \frac{1}{2}mv_a^2$ = $\frac{1} {2}m((v_a + v_\Delta)^2 - v_a^2) = \frac{1} {2}m(2v_av_\Delta + v_\Delta^2) $
Thrust=momentum change=$m(v_e-v_a) = mv_\Delta$

Where $v_a$ is the ambient velocity (relative to the aircraft), $v_e$ is the exhaust velocity (relative to the aircraft) and $v_\Delta$ is the difference between the ambient velocity and the exhaust velocity ($v_e - v_a$).

If the exhaust velocity (relative to the aircraft) is smaller than the ambient velocity (relative to the aircraft) then you have negative thrust (aka drag).

If the exhaust velocity (relative to the aircraft) is much larger than the ambient velocity (relative to the aircraft) then most of the power is wasted (the $v_\Delta^2$ term is larger than the $2v_av_\Delta$ term)

If the exhaust velocity is only slightly higher than the ambient velocity then most of the power goes into useful thrust (the $2v_av_\Delta$ term is larger than the $v_\Delta^2$ term)

What this means if that if the engine were perfectly efficient internally then the advantages of a higher bypass ratio would drop off with speed, but there would still be a slight advantage to the engine with higher bypass ratio.

But that is a big if, in particular we assume that all the energy in the intake stream is captured and returned to the exhaust stream.

Lets consider what happens if we instead assume that the energy in the intake stream is lost.

Our power consumption equation becomes.

Power consumption=Kinetic energy=$\frac{1}{2}mv_e^2$ = $\frac{1} {2}m(v_a + v_\Delta)^2) = \frac{1} {2}m(v_a^2 + 2v_av_\Delta + v_\Delta^2) $

For a given thrust $m$ is proportional to $\frac{1}{v_\Delta}$ so our goal is to minimise. $\frac{1}{v_\Delta}(v_a^2 + 2v_av_\Delta + v_\Delta^2)$ = $\frac{v_a^2}{v_\Delta} + 2v_a + v_\Delta$ differentiating with respect to v_\Delta and setting to 0 gives $-\frac{v_a^2}{v_\Delta^2} + 1$ which (given that v_\Delta must be positive) gives $v_a = v_\Delta$

Having considered an optimistic and a pessimitic case we can conclude that the optimal exhaust velocity for efficency is greater than the ambient velocity (otherwise you would not produce thurst) but probably less than twice the ambient velocity.


What are these bomb-shaped things attached to some propeller aircraft?

That is a weather radar pod.  On multi-engine aircraft, it is typical to install radar in the nose.  But that is not possible in a single engine propeller plane.  So, when radar is installed in one, it is most common to hang it under a wing as shown in the photo.  Here's a link to such a pod


How do I calculate the tail size of my rc plane?

There's a formula for calculating minimum tail volume coefficient (tail area X distance from the wing) for light aircraft.  Not sure if the same value applies to RC but it's a good starting point. This is from David B Thurston's book Design for Flying (Thurston was an engineer on numerous Grumman programs going back to the Hellcat).

(Tail Arm ÷ main wing MAC) X (Tail surface area ÷ wing area) = .55 or greater

Tail Arm is the distance from the C of G to the 30% chord point of the horizontal tail.

.55 minimum is for a symmetrical airfoil section tail typical of light planes like Cessna 150s.  I would use a higher number for a flat sheet tail surface, and being RC, so maybe .6 to .8.

While you're at it, Google "tail volume RC aircraft" and you'll find some more information specific to RC that'll be helpful.


Is there a benefit to a pilot/aviator having an FCC GROL license?

There's no tangible benefit to having a GROL in getting a pilots license of any kind as getting the license generally confers the right to use aircraft radios. In some places you need to get an RT license for aviation as a separate test, however that's pretty minimal. A GROL is only good for repairing, maintaining, and running certain types of radio stations.

An A&P will let you work on airplanes, but it also does not help get a license. An A&P will give you insights into how an airplane works, but you can get those insights without an A&P. Having an A&P and a pilots license might be a different story if you plan to work in remote locations where being able to fix your aircraft when it breaks is useful. It won't help you get a flying job in most places.


Straight Wings VS Delta Wings, Variable wing with Forward swept capability

At low speed, the key to reducing "induced drag" is to have a high aspect ratio, that is, you want wings that are long and skinny. Think gliders. Now of course, these are not easy to build, and for entirely practical reasons you might want something that's more square-ish than a glider. That's one of the many engineering trade-offs every aircraft design requires. Check out the svelt wings on this Q400:

Things become more interesting as speed increases.

First, as you enter the transonic area above around 450 mph, a new form of drag begins to form, the so-called "wave drag". The way to reduce this is to make the wing as thin as possible, or to be more specific, have as little curvature on the top and bottom edge. Ultimately you want an almost flat plate.

Now of course, lift is generated by that curvature, so that's a problem. And when you try to reduce that curvature to lower wave drag but still want the same lift, well then you have to make the wing larger front-to-back (think about it) and now your induced drag goes up, and skin friction too in most cases.

So then there's a trick. If you sweep the wing to the rear then the air flowing over it travels across a longer distance. So it thinks the wing is longer front-to-back and has less curvature, and that lowers wave drag. Yet at low speeds, the air smoothly flows over the curves and sees the original wing profile. So you get a thick wing that looks thin. Check out this F-86, notice that the wings are actually pretty thick:

Now as you go supersonic, things change yet again. In this case the drag is minimized by having the least width you can get away with. So for these sorts of designs you want short stubby wings with lots of chord (front-back) and you end up with the F-104.:

Now you have a wing that is absolutely terrible at low speeds, and for that reason, lots of F-104s crashed while the pilots tried to keep up with the plane while landing at redonkulous speeds needed to keep the thing in the air.

Deltas are mostly just swept wings with the inside filled in. If you want to see an example that really illustrates this, look at the English Electric Lightning:

If they filled in that little part, it would be a delta. But there is one trick that you get in a delta you don't get in a swept wing...

At very high angles of attack, with the nose high, the air along the leading edge of the wing can generate a vortex right along the fuselage. If there is a wing under it, this generates lift. Poorly, with lots of drag, but lift. So then you get this little one-trick-pony effect; this will works really well at high speed, but also works OK at really low speeds too. But it only works if the vortex is above actual wing, so the Lightning didn't get all the advantage here.

The problem with deltas are that they are big and heavy, but they also get more room inside for fuel. More trade offs. But then someone came up with a new idea: make a normal swept wing and then add a little bit of delta:

You can even see the vortexes in this image. In this case the little-bit-of-delta is called a "leading edge extension".

Variable wings are simply an attempt to put all of these on a single aircraft. Rotate them forward and you have a nice long skinny wing like the Q400. Rotate them back and you have a really swept wing or even a delta, and at the same time the width is being reduced. So now you can go fast or slow. Just weighs a lot.

Swept forward is basically identical to swept back. This isn't about lift in this case but an attempt to control something called spanwise flow. Check out this MiG-17's wing:

Do you see those metal plates? What happens on a swept wing is that the shape causes some of the air to move sideways. This is a Bad Thing. So these plates grab sideways moving air and redirect it over the wing again. The same thing happens on deltas, check out the notch on the CF-105, same idea:

Now the idea here is that the wind is following the wing's leading edge. So what happens if you sweep it the other way? Well then it follows the wing into the fuselage, and stops. Presto, problem solved and no plates or notches! The problem is that it's really hard to actually make one that doesn't snap apart, which is why it's not common.


Why is wireless avionics intra-communications (WAIC) not used for air-air or air-ground communication?

WAIC is designed to be extremely low power.

Its low power is not be enough to reliably reach a receiver on the ground, satellite, or other aircraft.  Increasing the power would create all sorts of other problems, including problems with spectrum allocation, and data collisions.

There is simply no demand for a more complex system to do these other tasks.

The basic engineering principle is KISS


Are military and passenger jets insured?

A partial answer for the case of military peacetime accidents: the government concerned seems to take responsibility for compensation - a few examples:

Cavalese cable car disaster (1998)
2012 Virginia Beach F/A-18 crash


Here is an interesting presentation that discusses most of the communications systems on the A320 family (looks like the pictures you have and should apply in general). The CIDS (cabin intercommunication data system) starts about halfway through on page 21. The FAP is part of this system and can control:

Passenger reading lights
Passenger call buttons
Cabin lighting controls
Cabin system monitoring/testing
Passenger entertainment system
Passenger address (PA)
Automatic announcement and boarding music
Cabin/Service interphone and calls
EVAC signal
Emergency light
Door bottle pressure monitoring (either oxygen or escape slide?)
Door proximity sensors (doors closed properly)
Smoke detection
Water and waste tank quantities

The acronyms you listed are:

Cabin Assignment Module (CAM)

All the software for specific customer layouts and defined parameters in the FAP (same as OBRP).

On Board Replaceable Module (OBRM)

This is a generic term for any module that is easily replaceable. In this case it refers to the module that contains all the information used by the FAP (same as CAM).

Prerecorded Announcement and Music (PRAM)

A good list of Airbus acronyms including these can be found here.


Can I log any PIC time if my medical certificate is out of date and I haven't flown in 20 years?

To answer your question, specific to the US, you may log your fam flight with a CFI as dual received, and also as PIC for the time you are the sole manipulator of the controls (which will likely be the entire flight).

You don't need a medical to log PIC, but you will likely need one to act as PIC, depending upon what you are flying.

But for training, you clearly can log time as PIC when you are the sole manipulator of the controls, in a class and category for which you are rated.

Have fun!


On which part of the descent does a pilot begin to flare?

This answer is a bit dated since it applies to 747-100 and -200 aircraft in the 1990s. However, the same principles still apply, and I'm sure the same technique would work now on current 747s. Whether or not anybody uses this protocol now I do not know.

We flared the aircraft by the numbers without reference to peripheral vision. The use of outside vision was, of course, critical for runway alignment and any necessary crosswind corrections.

We flared with reference to the radar altimeter. If it was a 'talking' altimeter, it would announce the altitude of the main landing gear above the ground in the following increments: 100, 50, 40, 30, 20, 10, with the increments being in feet. If the the radar altimeter was an old non-talker, the flight engineer would read those increments.

Coming down the typical 3 degree glideslope on a stabilized approach, the nose would be 5 degrees up, and the fuel flow would be about 5,000 lbs per engine. When you heard the 100 foot call, that served simply as an alert. When you heard the 50 foot, you pulled most of the power and raised the nose 2 more degrees. When you heard the 10 foot call, you pulled the rest of the power while raising the nose an additional one degree, maybe a little more if you had the runway length to try for a real greaser at the risk of floating. Then you just waited. Touch down of the main gear would occur within 1 to 3 seconds. If it didn't occur within that time frame, you were floating and would want to reduce your pitch a degree or so.

These 'numbers' would be adjusted if you were making a non-stabilized approach, which we often did back then when conditions permitted because stabilized approaches used more time and fuel. Plus, a non-stabilized approach is more challenging and thus much more fun. As I understand it, they're frowned upon these days even to the point of ops specs requiring a stabilized approach.


How to measure thrust produced from combustion chamber of Gas Turbine Engine?

Option 1: Thrust is a force, and Force = mass * acceleration, and acceleration is change in velocity.  So you need to measure the mass flow, the velocity upstream and the velocity downstream.  It is probably sufficient to just measure the air mass flow upstream, and measure the fuel flow, and not measure the air mass flow downstream.

Option 2: instead of measuring the air, measure the reaction force.  i.e. at some point, you have to support your combustion chamber.  It will be bolted down to the floor somewhere.  Where ever that is, get a load cell. That is a thing that directly measures force.

But again, with either of these two options, I would expect that your measurement thrust measurement will be pretty close to zero.  A combustion chamber will not generate a large thrust on its own.  You need a nozzle in order to generate a significant amount of thrust.


Why don't commercial airliners use variable sweep wings?

Variable geometry is not used in commercial aircraft design for the same reason that they initially became popular in the 1960s but have fallen out of favor in more recent times: any kind of aerodynamic performance gains associated with the design is not worth the additional weight increase, and subsequent decrease in payload, associated with variable sweep wings.

There have been attempts to do so in the past. The ill-fated Boeing 2707 SST was supposed to make use of swing wings but designers could not achieve their payload goals with the design.   Usually more judicious application of aerodynamic principles during initial design is far more advantageous then beginning to design out right with a swing wing.


Can instrument training be done in IMC with an instrument-rated safety pilot?

If you are the sole manipulator of the controls then yes you can log PIC time in this scenario, however you cannot act as PIC. The FAA discusses this in at least two letters of interpretation Speranza 2009 and Walker 2011. Both which lay out effectively the same situation (I would advise reading them) but in short they go into the fact that acting as PIC is not the same as being the sole manipulator of the controls and thus logging time as PIC.
Interestingly the IFR Rated pilot cannot log the PIC time while you are the sole manipulator of the controls as there is no prevision for that in the safety pilot regulations. The FAA words it as follows:

However, Pilot A may not log PIC time for the portion of the flight during which Pilot B is the sole manipulator of the controls, and is logging PIC time, because there is no provision for this logging in 61.51(e)
...
Although Pilot B [non IFR Rate Pilot] properly may log PIC time for a
portion of the flight as discussed previously, Pilot B could not act
as PIC and was not a required flight crew member for any portion of
the flight under the aircraft's type certificate or the regulations
under which the flight was conducted.
Speranza 2009

If you are in IMC then you do not need a hood as you would log that as actual IMC
The Herman Interpretation (2009) may also be relevant reading r.e. logging PIC vs Being PIC


Does the NTSB ever not follow up a preliminary report?

As a retired NTSB employee, I can say that reports with an FA number like that one should definitely close out with a probable cause determination, typically within a year.  Two years is an outlier, and the delay is likely attracting some internal attention.  If you really want to find out about the status, you can call 202-314-6290 and ask for the Ashburn field office.  It's probably their case, and the manager should be able to figure out what's holding it up.


What is being depicted w.r.t. AoA in this video?

There are several colored lines.  Which one are you asking about?  I'm assuming you are referring to the (cyan?) and red lines in the upper right inset.

The cyan line shows the current direction of the airflow.  When compared with the orientation of the airplane can show the angle of attack.  At this time, the relative wind is coming at a very steep angle to the airplane and the wing is stalled.

Another way to see it is that reversing this arrow shows the direction the airplane is moving through the air.  In a no-wind situation, this would also be the direction the plane is moving with respect to the ground.

The red line is at a constant angle with respect to the airplane and shows how low the airflow can go without causing a warning.  As it is below this line, the stall warning has sounded.


Where can I get a high-res photo of the RAT from an A320 Airbus?

Airliners.net is the photo directory of aircraft on the internet, a quick search turns up this beauty :) You can also diversify your search to A318, A319 and A321 since it's in principle the same equipment.

Aidyn Iskakov - Almaty Spotting Club

http://www.airliners.net/photo/Air-Astana/Airbus-A320-232/2419974/

(source: airliners.net)


How to interpret the electrical information on a G1000 T206H?

You've actually answered your own question back there:

  A negative current value (shown in amber) indicates that the battery is discharging. In the event the alternator is not functioning or the electrical load exceeds the output of the alternator, the main battery ammeter indicates the main battery discharge rate

The 28.3 Volts reading is the electric energy charge supplied by the aircraft alternator (60-Amp alternator is standard and a 95-amp one is optional) through the main bus, whereas the M amp reading is what's happening to the main battery. In the situation you've described, you've got so many electrically-powered systems running, that the alternator, though operating normally, is unable to supply them all, so additional power is drawn from the battery.

The 206 PIM states that the Main battery Ammeter is color-coded white for values greater than -1.5 Amps, meaning that Cessna is not concerned with battery drains of 1.5 Amps or less (i.e. readings between -1.5 and 0). If the discharge rate is greater than 1.5 Amps (reading lower than -1.5), then the reading will be color-coded yellow. See below for an example of this.


Are helicopters expected to follow the lateral guidance of taxiways in a hover taxi or air taxi?

Yes, unless given an explicit clearance to hover taxi direct to a location on an airfield.


Why are clearing turns supposed to be shallow bank?

Clearing turns solve two problems: seeing other aircraft and helping them to see you.
Banking will make you more visible to other aircraft, who may not have noticed you before. A lower bank angle (and thus turn rate) gives them more time to see and avoid you. But a very low bank angle also doesn’t make you as visible in the first place, so it’s a balance.
I was taught 20-30°, and I’ve never had anyone say later that was too much or too little. I also don’t have to worry much about losing altitude at moderate bank, so I can keep my eyes outside scanning for traffic—not checking the altimeter every few seconds like during “real” maneuvers.


Is there any form of checklist that a pilot needs to go through before they use their ejection seat?

Yes there are checklists but a lot of the training is done by practice exercises so the procedure becomes instinctive during an emergency.

The exact procedures to be used vary based upon airframe, cockpit configuration, and ejection seat make and model.  Here are two examples, one from the F-16A/B aircraft and the other from the F/A-18E/F aircraft.

From the F-16 USAF Flight Manual.

And from the F-18 NATOPS Manual.

Again there are a lot of mitigating factors here, specifically, airspeed, altitude, attitude, aircraft controllability and imminent danger to the flight crew which must be taken into consideration to order to make the decision to eject.  Since an ejection seat is nothing more than a device to provide an additional velocity vector to the aircrew in order to provide time for the main parachute to open and safely lower the occupant to the ground, they have specific altitude, airspeed and attitude envelopes in which they may be operated to ensure maximum chance of aircrew survival.  This should be reviewed and thoroughly understood by the aircrew prior to use.

There have been a few instances where the seat was used outside of the envelope.  One notable instance being Soviet test pilot Anatoli Kobachev when he punched out of a MiG-29 during a low altitude, high AOA pass at the 1989 Paris Air Show.  His delay was to direct the stricken aircraft away from the crowds and very fortunate that he didn’t die.  He walked away from the accident.

The checklists above should be used only IF TIME AND WORKLOAD PERMIT.  Again flight crews practice ejection procedures separate from aircraft operation in order to become uncounsciously competent in the operation of the seat.  They typically order the cockpit and workstations for aircraft egress prior to situation where there is an increased probability of needing to abandon a disabled aircraft.  These include takeoff, landing, and entering a theater of combat, etc.  Checklists will be use here prior to these events and crews will probably brief ejection procedures here as well.  Carrier operations, in partcular will have crews ready to eject at a moments notice and anticipating emergencies such as a cold cat shot or arresting gear failure during launch and recovery operations, both of which will probably require an immediate ejection to save the lives of the aircrew.

Correct cockpit preflight procedures must be done by the aircrews prior to operations to ensure safe ejection as well.  Crew must attach the leg restraints as well as correct attachment of life support umbilicals such as oxygen, anti-G, radio and HMCS data lines to ensure they separate properly during ejection without causing serious injury or death.  Shoulder straps must be attached into the occupant’s parachute harness to connect them with the seat’s recovery parachute (some seats do not have this; the pilot will wear a separate parachute system as part of their life support garb in this case).  Charts, kneeboards and other foreign objects must be placed such that they do not interfere with the operation of the ejection handles or the seat safing handles.

The ejection process again is going to be based upon the cockpit configuration and seat type, but typically if the aircraft commander says EJECT! EJECT! EJECT!, you will pull your legs and extremities clear of the legwells and flight controls, head back against the seat headrest, grasp the ejection handles, disengaging the grip safeties and PULL HARD.  The ejection itself will happen fast and very violent with a BANG! BANG!  The canopies will either break away with a pyrotechnic charge or be fractured with a similar charge sounding like a shotgun blast at close range.  This is followed a split second later with a jolt and explosion as the pneumatic catapult throws you clear of the cockpit and the seat rocket motor ignites, giving you an approx. 20g acceleration clear of the cockpit.  After this, the recovery process becomes pretty automatic.  Air data sensors feeding a small computer in the seat right the occupant using a drogue chute, followed by seat frame separation and deployment of the main recovery parachute.  The pilot may be required th pull an additional handle for deployment of the seat pan and life raft for a water egress as well.

Wind blast will be a major factor and all material suggests that an ejection be intitiated at the lowest airspeed, if possible.  High speed ejections will invariably result in serious injuries as due to wind blast, as this chart from an F-16 flight ops manual suggests.

Ejection at supersonic speeds is usually fatal, with very few exceptions.  This pilot was very fortunate to survive a supersonic ejection, but was seriously injured in the process.


"right traffic pattern" vs. "right-hand traffic pattern"

"Right traffic pattern" and "right hand traffic pattern" are one in the same.  Usually on the radio either a controller or a pilot will abbreviate it to simply "right traffic" to expedite radio communications.

For example, A C-152 student pilot is inbound for a controlled airport and says something like "Plainview Tower, Cessna one two five X-ray ten miles to the south at two thousand, inbound with ATIS Golf."  If a controller wants a student pilot to fly a right traffic pattern to land on runway 16 which is active, they might say something like "Cessna one two five X-ray enter right downwind runway 16.  Report abeam the tower."  The pilot then responds reading back the instructions to the controller and might say "right downwind one six.  Report abeam.  Two five X-ray."


In the US, yes. There are no restrictions from the FAA on the size of aircraft you fly with a private pilot certificate. If the aircraft requires a type rating, you would have to get that added to your certificate along with the category and class. The insurance carrier covering that aircraft would probably have much more stringent requires over and above the FAA requirements.
John Travolta has/had a Boeing 707 (similar to a B737) that he flies out of his private home/airport.

§61.31 Type rating requirements, additional training, and authorization requirements.
(a) Type ratings required. A person who acts as a pilot in command of any of the following aircraft must hold a type rating for that aircraft:
(1) Large aircraft (except lighter-than-air).
(2) Turbojet-powered airplanes.
(3) Other aircraft specified by the Administrator through aircraft type certificate procedures.
(b) Authorization in lieu of a type rating. A person may be authorized to operate without a type rating for up to 60 days an aircraft requiring a type rating, provided—
(1) The Administrator has authorized the flight or series of flights;
(2) The Administrator has determined that an equivalent level of safety can be achieved through the operating limitations on the authorization;
(3) The person shows that compliance with paragraph (a) of this section is impracticable for the flight or series of flights; and
(4) The flight—
(i) Involves only a ferry flight, training flight, test flight, or practical test for a pilot certificate or rating;
(ii) Is within the United States;
(iii) Does not involve operations for compensation or hire unless the compensation or hire involves payment for the use of the aircraft for training or taking a practical test; and
(iv) Involves only the carriage of flight crewmembers considered essential for the flight.
(5) If the flight or series of flights cannot be accomplished within the time limit of the authorization, the Administrator may authorize an additional period of up to 60 days to accomplish the flight or series of flights.
(c) Aircraft category, class, and type ratings: Limitations on the carriage of persons, or operating for compensation or hire. Unless a person holds a category, class, and type rating (if a class and type rating is required) that applies to the aircraft, that person may not act as pilot in command of an aircraft that is carrying another person, or is operated for compensation or hire. That person also may not act as pilot in command of that aircraft for compensation or hire.
(d) Aircraft category, class, and type ratings: Limitations on operating an aircraft as the pilot in command. To serve as the pilot in command of an aircraft, a person must—
(1) Hold the appropriate category, class, and type rating (if a class or type rating is required) for the aircraft to be flown; or
(2) Have received training required by this part that is appropriate to the pilot certification level, aircraft category, class, and type rating (if a class or type rating is required) for the aircraft to be flown, and have received an endorsement for solo flight in that aircraft from an authorized instructor.


Why don't we place the engine in the front of the wings?

They can be, as on the An-72/74, which has the engines mounted above and forward of the wings in part to increase lift, utilizing the Coanda effect.
One downside is that this makes access for maintenance more difficult, which is a large factor in operation costs.
https://en.wikipedia.org/wiki/Antonov_An-72
https://en.wikipedia.org/wiki/Coand%C4%83_effect


How feasible is it to sell a plane with an expiring annual?

I also know that a lot of people prefer to sell planes with fresh annuals.

I think the reality (from what i have seen) is that a a lot of people end up selling planes with a fresh annual. Essentially any smart buyer is going to want a pre-buy inspection and they are often willing to pay for them. In many cases pre-buy inspections are close to if not the same as an annual so the mechanic will often do the remaining work and sign it off as an annual resetting the clock. Any potential buyers are going to want to test fly the plane so its going to need to be air worthy. I would suspect the soon expiring annual has a small impact on price (in and around the cost of the annual which is comparatively low for a 150).

You may find a buyer fast and unload the plane while its still airworthy, taking a bit of a  hit for the soon to expire annual or you may get it done and raise the price close to the cost of the annual.


What does it mean when an aircraft is statically stable but dynamically unstable?

Static stability means that a deviation from a trimmed state produces forces which return the system to this trimmed state.
If these forces produce an overshoot which increases over time, such that the system oscillates around this trim point with increasing amplitude, the system is dynamically unstable. The long period oscillation (phygoid) of gliders is often unstable because their L/D is high enough to push them into unstable territory.
Dynamic stability means that the oscillations die down over time. Without static stability the system would simply leave the trimmed state without any tendency to return. This tendency to return is the prerequisite for the oscillation, whether stable or unstable.


How low can a helicopter legally fly over the water with boats below?

There's no minimum altitude over open water but the pilot must stay at least 500ft away from the boats, per 14 CFR 91.119:

  (c) Over other than congested areas. An altitude of 500 feet above
  the surface, except over open water or sparsely populated areas. In
  those cases, the aircraft may not be operated closer than 500 feet to
  any person, vessel, vehicle, or structure.

There's also a catch-all regulation that prohibits endangering other people, 91.13:

  (a) Aircraft operations for the purpose of air navigation. No person
  may operate an aircraft in a careless or reckless manner so as to
  endanger the life or property of another.

It's very hard to tell from the photo how far the helicopter is from the boats but if your friend believes it was closer than 500ft, she can report it to the FAA.


Does the captain always control thrust on takeoff?

I believe your referenced material is mixing up "Captain" with "Pilot Flying". The person in control of the aircraft should have their hands on the throttle, Captain or not.

  If the take-off needs to be aborted, can't the captain just command the FO to "abort" or take control by saying "I have control" or similar?

Having your hands on the throttles has a number of advantages:

You don't have to waste seconds (which at 200mph means about 300 feet per second)
You don't have any confusion (i.e. "What did you say?")
You don't need to discuss it with the other person (you say abort, FO says OK)

A lot of companies require both the PF and PNF's hands to be on the throttle at the same time, which has the advantages of 1) assuring that the throttle is set to its maximum power, and 2) either one can abort without having to command the other to do it. Either pilot (or the FE if they exist) have the ability to call an abort before V1, and the entire cockpit crew should follow that course without discussion until clear.

  I also recall seeing videos of the flight engineer pushing the throttles.

There are also cases where if a FE is required (which usually is not the case anymore), that the FE also has their hands on the throttles along with the pilot/copilot.

  Finally, will pulling back the throttles be enough to abort takeoff safely without braking? Surely it would just cause more problems?

Depending on how fast you are going, it is almost always the case that you will have to brake as well. Airplanes are pretty slick at rolling down the runway and relying on drag alone to stop you will probably result in an overrun. Usually the PF will be the one on the brakes, but the PNF may also be applying pressure just in case.


Can an airfoil have multiple aerodynamic centers?

No, it's not possible to have them simultaneously. Here's a proof by contradiction:
Assume that there are two points on the airfoil that have constant pitching moment, located at $x_0$ and $x_1$, each having constant moments $M_0$ and $M_1$, respectively, and that $\frac{\partial{M_0}}{{\partial\alpha}}=\frac{\partial{M_1}}{{\partial\alpha}}=0$ (which make them aerodynamic centres).
Therefore, using the $M_0$, we can write the moment about any other point as:
$$M(x)=M_0 + L(x-x_0) \tag{1}$$
where $L$ is lift and is a function of the AOA, $\alpha$.
Using (1), we can try to calculate the moment at $x_1$, which gives:
$$M_1 = M(x_1)=M_0+L(x_1-x_0) \tag{2}$$
Differentiate (2) with respect to $\alpha$, and we get:
$$\frac{\partial M_1}{\partial \alpha} = \frac{\partial L}{\partial \alpha}(x_1 - x_0) \tag{3}$$
But (3) can't be zero since $\frac{\partial L}{\partial \alpha}$ is always non-zero, which contradicts with the assumption that $\frac{\partial M_1}{\partial \alpha}=0$.
However, if the lift is non-linear, then the AC will move around at different AOAs, each satisfying local linearity of the aerodynamic center definition.


How does the FADEC prevent compressor stall during rapidly increasing thrust demand?

Of course it depends on the engine, and the exact how is proprietary information. That being said, nowadays jet engines are designed to allow faster acceleration than before. So it's not just the fuel rate the FADEC controls.

COMPRESSOR AIRFLOW CONTROL
To limit compressor surge and to provide good acceleration, the engine
is equipped with a Variable Bleed Valve (VBV) system and a Variable
Stator Vane (VSV) system.
Both systems are fuel operated by the HydroMechanical Unit (HMU)
and controlled by the Electronic Control Unit (ECU).
— CFM56-5B training manual

As for the parameters being monitored, first let's look at the common stations:

(Source)

With the basic station numbers now known, let's look at what the ECU (part of the FADEC) monitors and controls:

During testing, data for the optimal accelerations for all conditions (forward speed, air density, engine angle of attack, etc.) is collected. From there the FADEC is programmed to stay within those limits.
If a pilot demands full thrust from idle on ground on a hot day, the FADEC will have an idea of the initial fuel flow and rate to supply, and how to control the variable stators and bleed. From there it will monitor the many parameters, and adjust accordingly.
The same can be achieved on older engines using purely hydro-mechanical systems, but of course not as efficiently. There are of course different ways to override the FADEC and demand more power than the FADEC was designed to allow.
For the CFM above, the fuel flow commands depend on:

engine oil temperature,
Fuel Level Sensing Control Units (FLSCUs) shut off signal,
A/C on ground and low fuel flow return level,
A/C in flight and low or high return fuel flow level,
N2 speed,
engine fuel flow demand.

This flightglobal.com article about the GE flying testbed discusses the benefits of fine tuning the FADEC from real data including extreme angles of attack.

We think of the FADEC monitoring system as being like a screwdriver. We're using it to adjust and fine-tune the turbine clearances in real time by using the data to modify the control software and make it more efficient.
(...)
[Testing at] angles of attack of between 30° and 32°. The high-inlet-angle test is required for fan-stress and inlet-stability evaluation.

Trivia: In the making of the 777, the management wanted to skip the in-flight testing of the P&W engine (the first 777 engine). As those tests cost millions. They eventually played it safe and tested it on a 747 testbed, guess what happened:

The engine surged on its third takeoff, despite the numerous static tests they made.


What is the effect of aft centre of pressure movement on static longitudonal stability?

Moving the CP aft will have the same effect as moving the CG forward: increased longitudinal stability.

The arm of the Lift force is now increased and the ratio of momentum generated by the wing vs horizontal stabilizer is decreased, leading to positive longitudinal stability.


What are the Requirements for the implimentation of Low Visibility Procedures at an airport?

It is the RVR values that are used to determine the applicable minima.
The switch from normal to LVP Ops varies from airport to airport but the changeover process typically commences when the dropping vis approaches 1000mtr (say roughly 1200m) and is dropping so that the ILS Cat2/Cat3 LVP can be offered as the vis/rvr falls to below Cat1 requirements. More detailed info can be found in the country AIP and the same info would be spelt out in the Jepp or equivalent.
The Low Visibility info is specified in Sec 1.3 in the 10-1P series pages of the Jeppessen Terminal charts, ie "Airport Briefing" pages.