Re old (1992) US VFR sectional charts-- when was the thin dashed magenta line first used?

The decision to change the airspace classification in the US to bring it into agreement with ICAO classifications was made in December 1991, as can be seen in the US Library of Congress:  Federal Register: 56 Fed. Reg. 65415 (Dec. 17, 1991).

The ICAO classification was only used from the 16th of September 1993, but as part of the familiarisation process for pilots, the legends of the charts were already updated before.

The Federal Register (FR) contains a table with the Airspace Reclassification Transition timeline.

This table shows that as of October 15, 1992, the first sectional aeronautical charts (SAC), world aeronautical charts (WAC) and terminal aeronautical charts (TAC) are published with legends that indicate both existing and future airspace classifications.

Furthermore the FR specifies that it is anticipated that a segmented magenta line will be used for class E in the future, and that starting October 15, 1992, the new colours will be used in the legends.

  An anticipated modification to the symbols on aeronautical charts is
  the addition of a segmented magenta line to represent the controlled
  airspace area for airports without operating control towers that
  extends upward from the surface (Class E airspace).

  [....]

  The legends in aeronautical charts
  will include both the existing airspace
  classifications and the airspace
  classifications to be effective September
  16, 1993. For example, the solid blue line
  that symbolizes a TCA will be followed
  by "TCA (Class B)." The first charts
  with a dual legend will be published
  October 15, 1992. Commencing
  September 18, 1993, the legends on these
  charts will be reversed (e.g., a solid blue
  line will be followed by "Class B
  (TCA)". Between March 3 and August
  17, 1994, the use of dual indication
  legends will be phased out.


What type of jack is the flight interphone on transport category aircraft?

The jack on every commercial airliner from Boeing and Airbus is a single plug U/174 type (aka helicopter).

That holds true as long as we speak of the external jacks used for the flight interphone and service interphone. In the cockpit this is a different beast. You'll find a lot of variation:

classic two-plug
U/174 (aka helicopter, impedance must be matched, no power to headset)
XLR-5 (passes power to headset, often found in Boeing aircraft)
NeutriCON (passes power to headset, often found in Airbus aircraft)
LEMO (passes power to headset, used mainly by Bose)

What you'll find in the cockpit mainly depends on what the buyer ordered. Boeing standard in their newer aircraft is the classic two-plug and a XLR-5 side by side (e.g. B747-8, B787, not sure about the B777). As an example, the company AvtechTyee supplies their 5775 series jack panel for the B787 First Officers side.


As Wikipedia explains it:

  The main purpose of an inlet cone is to slow the flow of air from supersonic flight speed to a subsonic speed before it enters the engine. Except for scramjet engines, all airbreathing jet engines need subsonic airflow to operate properly, and require a diffuser to prevent supersonic airflow inside the engine. At supersonic flight speeds a conical shock wave, sloping rearwards, forms at the apex of the cone. Air passing through the conical shock wave (and subsequent reflections) slows to a low supersonic speed. The air then passes through a strong normal shock wave, within the diffuser passage, and exits at a subsonic velocity. The resulting intake system is more efficient (in terms of pressure recovery) than the much simpler pitot intake.

If the flow was supersonic inside the engine, it would not be able to maintain fuel burn.

The pointyness of supersonic jets' inlet cone is dictated by the distance from the tip of the cone to the engine inlet and the inlet diameter. Also, the shockwave must be kept at right location in relation to the engine inlet, so the location of the cone is adjustable (by computer)

  The inlet cone is shaped so that the shock wave that forms on its apex is directed to the lip of the intake; this allows the intake to operate properly in supersonic flight. As speed increases, the shock wave becomes increasingly more oblique (the cone gets narrower). For higher flight speeds inlet cones are designed to move axially to control how the capture area varies with the duct internal throat area. For best intake operation this required area ratio gets bigger with increasing flight Mach number, hence the large inlet cone movement on the SR-71 which had to perform well from low speeds to Mach 3.2.

The engine in the first picture is not of a supersonic aircraft. It is a high bypass turbofan, and the cone in that engine has no other function but to serve as an aerodynamic form covering the end of the axel. The other picture (actually quite obviousy taken form the Wikipedia article I referenced above...) is a supersonic engine inlet cone of MiG-21MF

For the most interesting reading about supersonic engines, please see this Wikipedia article about the J58, an engineering marvel from more than sixty years ago. It still stands as one of, if not the most inspirational jet engine.

The article has a nice schliering photograph of what happens when the shocwave is not in the place it should be (NASA document ID: C-1955-37520, public domain):


What Kind of airfoil configuration is preferred for an hyper sonic plane?

At hypersonic speed the local drag grows with the inclination of the local surface against the free stream. Thus, the best shape is a thin wedge. Drag will scale with the cube of the thickness ratio of the wedge.

Depending on the maximum tolerable heat load, you should choose a pointed leading edge (highest heat load, smallest drag) or a blunt leading edge, where the separated shock will reduce local heat loads, albeit at the price of much higher drag.

Ideally, past its maximum thickness the airfoil tapers down towards a thin trailing edge, and again a wedge shape will cause the least amount of drag.

In the picture below (source) you can barely see the tip airfoil of the X-15:

It used a simple, blunt wedge at the vertical tails because the vacuum at the rear face provided additional directional stability. However, for lowest drag, a double wedge of the smallest thickness possible should be used.


Can a Pilot hold multiple foreign licenses and practice the privileges of it in each country?

Yes, a pilot can hold multiple licences from different authorities, but it's not about operating in a country. A license from an authority applies to aircraft registered with that authority, wherever that aircraft is in the world.

An FAA license lets you operate an N registered aircraft anywhere in the world, it does not let you operate a foreign registered aircraft on American soil unless that foreign authority gives permission to do so.


Why don't nonrigid airships have multiple gas cells?

With the loss of one cell you also lose the same fraction of lift. Unless you can drop an equal amount of ballast quickly, having some more gas cells isn't much of an advantage – the ship still falls out of the sky.

The Zeppelins could lift up to three times their empty weight simply because they became more efficient by growing larger. Blimps are small, so their lifting capacity is restricted. Carrying so much ballast would require a much bigger blimp.


Do Airbus aircraft fitted with ACT have additional fuel system controls?

(Source: Airbus)

Yes they do on the same overhead fuel panel. The additional pb is shown above. If it is not pushed and no fault is shown, then it is in automatic operation, and pushing it allows manual fuel transfer.


Why choose a seaplane for crew rotation at sea, supply of spares to ships, long-range search and rescue and surveillance?

The US-2 is an amphibious airplane not a pure seaplane, it can land on water and land. MTOW is a bit higher on land as well.

Purely logistics alone means that a single craft type is better.

It is better to have a jack of all trades than a bunch of specialists when building out your fleet unless you have immediate need for those specialists.

Each aircraft type that gets added to the fleet has its own maintenance handbook, maintenance schedule, set of spares, their own type rating, etc.

Helicopters have smaller tanks and can't stay in the air as long or get out as far away from base. They also cannot carry as much stuff as the US-2 can. They would be handy for search and rescue and supplying helipad-equipped vessels. However not all ships will have a helipad.

Jets cannot land out at see so they can only do the search part of search and rescue. They cannot do any supplying out at sea that doesn't involve putting the packages on a parachute.


For conventional designs, the tail is composed of two parts: the horizontal tail and the vertical tail. They play a role in the trim and the manoeuvrability of the aircraft but at different levels. The horizontal tail is mainly used for longitudinal stability (and trim) while the vertical tails used for the lateral stability (and trim).

About Stability

It is possible to talk of stability only after having defined an equilibrium point around which the stability is studied. An aircraft is in equilibrium if the forces and moments it experiences are balanced. Using a simple model for the longitudinal analysis, it can be decomposed in three relations called the trim equations. In order to keep it simple, it will be assumed here that the angle of attack and the flight path angle are zero. (Note that the same reasoning can be achieved with non-zero values but the equations then become quite messy.)

Longitudinal Equilibrium

These three equations are:

$$L=mg$$
$$T=D$$
$$M=0$$

where $L$ is the total lift, $mg$ is the weight of the aircraft, $T$ is the thrust, $D$ is the drag and $M$ is the pitching moment around the centre of gravity of the aircraft. The second equation won't be studied further since it does not help to understand the role of the horizontal tail and its influence. Looking at the following picture, one can see that usually, the centre of gravity and the point where the lift applies (called the aerodynamic centre) are not the same. This means that the lift generated by the wing creates an induced moment around the centre of gravity that one should add to the already intrinsic pitching moment due to the main wing (usually a pitch down moment for conventional airfoils).

Knowing that, it is possible to rewrite the two equations of interest including the contributions from the main wing and from the horizontal tail.

$$W+L_t=L_w$$
$$M_0+bL_t=aL_w$$

From these equations and the figure, it appears that the horizontal tail is used to generate a lift which induces a moment helping to balance the moments equilibrium and thus prevent the aircraft to spin on itself (pitchwise).

Drawback and Solution

From both the figure and the equations it turns out that the lift contribution from the tail is usually negative, meaning that more lift from the main wing is needed to keep a trimmed (or balanced) aircraft. This drawback can be overcome by the use of a canard configuration instead.

Lateral Stability

The same can be done for the lateral equilibrium and stability but there it is the vertical tail that is used. It is symmetrical so that there is no yaw induced and if there is some side force experienced, it will create a moment in order to reduce the side-slip angle.

Comparison of Lift Created by the Tail and Main Wing

For a trimmed configuration, it is easy to see that the lift created by the main wing is more or less the one created by the tail plus the total weight of the aircraft, which gives an idea of the difference between the two forces.


How to calculate your landing ground roll distance with this chart?

All else being equal, increased temperature increases density altitude, and thus true airspeed for a given indicated/calibrated airspeed. Increased landing speed will increase the landing roll distance.
In your exercise above, the primary relevant condition given is a runway at 5000'. This tells you which column of the table you'll be using, i.e. the one labeled "At 5000 feet & 41 °F". Note that the temperature given there is the "standard" temperature for that altitude.
But there are footnotes. The first footnote, discussing headwind, doesn't apply because there's no headwind. But the second one, discussing temperature does. Your given temperature is 101 °F, which is 60 °F higher than standard temperature for the given altitude of 5000'. The footnote says you need to add 10% to the distance for every 60 °F higher than standard, and there is exactly 60 °F higher temperature given in the conditions, so you need to add 10%.
The standard ground roll is 495', so adding 10% to that you get 544.5' (which you might round to 545').
Note that if the temperature was, for example, only 30 °F higher, that doesn't mean you can ignore the second footnote. You should interpolate based on the information there, adding 5% in that example to the landing roll instead of 10%. Likewise a temperature 90 °F higher would require increasing the landing roll figure by 15% (assuming you think it's even safe to operate the airplane at that temperature! at 131 °F, there are lots of other problems that might argue against flying at all, including failure of paved surfaces, overheating of the engine, pilot dehydration and fatigue, etc.)
You don't say whether the runway is unpaved. The table you're using assumes a "hard surface runway". If it's a grass runway, you'd also want to apply the third footnote. Note that the footnote there is for a "dry, grass runway". A grass runway that's wet, or a gravel runway, or a snowy/icy runway could produce different results. A wet, grass runway in particular could reduce the landing roll significantly, while an icy paved runway could increase it significantly, as compared to "standard" conditions. A gravel runway might perform very similarly to a hard surface, depending on the condition.
In other words, while it's clear from the round numbers (5000' is exactly the base altitude for the column you'll use from the table, while the 101 °F temperature is exactly one unit of the 60 °F difference used for the second footnote) that this is just an academic exercise, in the real world you may have other factors to take into account, including the pilot's skill in maintaining the required approach speed of 60 mph (an even slightly faster approach can greatly increase the ground roll) and in using the brakes at their maximum effectiveness, and of course the condition of the airplane itself, especially the tires and brakes, along with the various environmental factors mentioned in the table and those I mentioned above.


Regular procedure followed by the pilots before takeoff?

Try to search "Before Takeoff Checklist". Manufacturer will provide standard checklist but airlines can modify it.


What is the aerodynamic effect of a panorama (skydeck) near the tail section of a commercial airline?

You're correct that the structure may induce separation under some conditions. However, the effects are unlikely to be significant given the (publicly) available data on the concept. From the available images, the deck is quite small, with a seating capacity of only two.

Image from gizmag.com

Also, it is located at some distance in front of the vertical fin and appears shaped to reduce drag.

Image from technology.org

The company says that it has over come many design hurdles including

  ... structural modification, structural integrity of the canopy to withstand a bird strike and flight loads, condensation, noise levels, UV protection, aerodynamic drag, potential disruption to the vertical tail's performance, safety, ingress and egress requirements per the FAA requirements.

Though this should be taken with a grain of salt (it from the company after all), there is nothing insurmountable in the engineering sense. For example, the canopies of fighter jets are of similar size in smaller aircraft and they are operated without problems.

AWACS aircraft routinely carry huge antenna on top of their fuselages; they have no problem flying, albeit with reduced performance. For example, the following image shows the E-767, the AWACS version of Boeing 767 operated by the JASDF.

"E-767 Japan AWACS 112010" by Jerry Gunner - AWACS Boeing E-767 of Hiko Keikai KanseitaUploaded by Altair78. Licensed under CC BY 2.0 via Commons.

However, it is another matter if this is going to enter into service. My take would be that this is not going to happen in current time for a number of reasons including:

The cost quoted is pretty high and downtime, too long.
cutting up pressurized fuselage is not a good idea.
The concept is going to take up seats and increase weight for questionable benefits. What are you going to see up there? the same clouds that you are going to see from normal windows anyway.


What is the horizontal and vertical fields of view for a VASI and a PAPI approach system as you come in to land?

This information is for the US, taken from FAA Order 6850 - Visual Guidance Lighting Systems.

VASI (2 bar VASI for illustration, but other configurations exist)

a. Layout

b. Aiming

  The two-bar VASI system shall have the upwind bar aimed at three
  degrees and the downwind bar aimed one-half degree lower at 2.5
  degrees; however, where necessary to provide obstacle clearance, the
  downwind bar may be aimed at 2.75 degrees.

c. Glide (vertical) path angles

d. Horizontal field of view: 10°

  Determine the minimum aiming angle by plotting all objects within an
  area  established by two lines each diverging at 10 degrees from
  runway centerline extend to 4 nautical miles, and starting at the
  runway centerline at the number one bar.  A line drawn from the runway
  centerline at the number one bar at an angle that will clear the
  highest object by not less than one degree establishes the minimum
  aiming angle.  This line and a horizontal line perpendicular to the
  runway centerline at the number one bar (downwind) establishes an
  obstruction - clear plane 10 degrees (6 degrees in special
  applications where 10 degrees is not obtainable) on both sides on the
  extended runway centerline.  The obstruction clear plane starts at the
  number one bar and extends outward from the threshold for four
  nautical miles.  In addition, the minimum aiming angle shall be within
  the glide path limitations of paragraph 4. When less than 10 degrees
  are used for determining the obstruction-clear plane, issue a NOTAM
  and request publication in the Airport/Facilities Directory.

PAPI

a. Colocation with ILS glideslope

  When siting PAPI on a runway with an established electronic glide
  slope, the PAPI visual approach path should coincide, as much as
  possible, with the one produced electronically.  To accomplish this,
  the PAPI is placed at the same distance from the threshold as the
  virtual source of the electronic glide slope within a tolerance of ±30
  feet (±10 m).  The PAPI is aimed at the same angle as the electronic
  glide slope.

b. Layout

c. Aiming

  The visual glide path angle is the center of the on-course zone, and
  shall normally be 3 degrees when measured from the horizontal.

d. Glide (vertical) path angles

e. Horizontal field of view: 10°

  The PAPI obstacle clearance surface is established to provide the
  pilot with a minimum clearance over obstacles during approach.  The
  PAPI must be positioned and aimed so that no obstacles penetrate this
  surface.  The surface begins 300 feet (90 m) in front of the PAPI
  system (closer to the threshold) and proceeds outward into the
  approach zone at an angle 1  degree less than the aiming angle of the
  third LHA from the runway.  For a 3 degrees glide path and 20 minutes
  separation between LHAs, the third LHA from the runway would be aimed
  at 2 degrees, 50 minutes elevation.  The surface extends 10 degrees on
  either side of the runway centerline extended, and extends 4 statute
  miles from its point of origin.  The surface is shown graphically in
  figure 5-4.  If a site survey determines that there is an obstacle,
  which penetrates the obstacle clearance surface and cannot be removed,
  then the glide path angle must be changed or the PAPI system moved
  further from the threshold.  By moving or re-aiming the PAPI, the PAPI
  obstacle clearance surface is repositioned so it will not be
  penetrated by an obstacle.


What's the red light in the left wing of a N.A. T-6 for?

It's the passing light. They're no longer in use.

In an era of virtually zero radar air traffic control, two planes headed for each other at high speed at night needed those [very bright] lights. They would use the right-of-way rule to stay on the 'right lane' and safely pass each other.

(jetphotos.com) Clearer view for D-FUKK.

(Code of Federal Regulations) Points (a) and (c) match the T-6.

  a strong red light to warn passing airplanes displayed usually in the leading edge on an airplane flying after dark (merriam-webster).

(Source) Early Connie's had them in the nose (b).


Why do airports have to close in bad weather?

Wind

The problem with wind is that it can be from any direction, not necessarily the direction of the runway. When the wind is coming from the side instead of straight ahead, it is called a crosswind. This means that landing aircraft have to point into the wind to remain lined up with the runway. The slower they are flying, the further to the side they must point the nose. Airliners are designed to land in these conditions, but it requires more skill to do it well. The control inputs required to compensate for a crosswind affect aircraft on takeoff as well, as then must work harder to stay lined up with the runway and stay level through lifting off. High winds tend to come along with gusts, which makes it even harder to control an aircraft. Aircraft during flight are flying faster, so changes in wind are less problematic. Once they are flying slower, the wind is much larger compared to the aircraft's speed, and control is much more critical during landing. Aircraft have crosswind limits, and even below those limits, aircraft may need to go around from a landing attempt, which introduces delays.

Another issue is wind shear, which is when the direction and/or speed of the wind quickly changes. A change of 40 knots at higher speeds is turbulence. During landing or takeoff, it can cause the aircraft to stall and crash.

Visibility

Aircraft can certainly use systems like ILS that allow them to take off or land in low visibility. However, there are many limitations with these systems. The crew must be trained to use them, the aircraft must be equipped to use them, and the airport must be equipped with them. However, when the pilots are relying on instruments, they no longer are able to see hazards like usual. Because of this, separation requirements are inreased in these conditions, which means an airport can't handle as much traffic.

Water

It's true that aircraft wheels are not directly powered. However, traction is still very important during braking, since aircraft can hydroplane just like a car can. This means aircraft need more distance to stop, and can slide off the runway if they lose traction. Frozen water in the form of ice or snow makes a plane even more difficult to steer or stop.

Combine all of the above (a typical storm that would cause delays at an airport), and you can see why airports delay flights or close when conditions get worse.


Why isn't aircraft structure inspection done by robots? Is there any known active research on the subject?

The robot, or better the software analyzing the sensor output, needs to be programmed for every eventuality. After all, wear and tear does not leave standard traces, and a human is still better in spotting when something does not look quite right. This does not concern the obvious cases, but those where experience and intuition make the difference.

Next, aircraft structures are made with human inspectors in mind. A robotic system would need to be able to access all points at least as well as a human can. This puts some heavy restrictions on the robot's physique.

Eventually, a robotic system will surpass most humans, but only after thousands of man-hours of training. Maybe someone is developing just such a system right now, but I am unaware of this.

One point remains, however: Who will be liable if the robotic system makes a mistake? The manufacturer will need to buy insurance to cover those corner cases where the robot fails, and this will come on top of the hefty expense for developing and training such a system. I expect that the military (e.g. DARPA) will be the first to make the plunge, and only when the robot has a positive track record will civilian operators start to consider using it.

The EasyJet drones are just helping to get a camera on top of the aircraft; the eventual monitoring of the feed will still be performed by humans. They are a high-tech version of a periscope, if you want.


What is a skidding turn (vs slipping turn)?

The terms "slip" and "skid" refer to two different types of uncoordinated turn - neither has much to do with the elevator, instead both depend on what the rudder is doing:

Skids

In a skid you have too much rudder input for the turn - the aircraft starts to pivot into the turn.

Because the aircraft is effectively pivoting about its center of lift while flying you can think of a skid as the outside wing advancing (seeing a faster relative wind), while the inside wing is retreating (seeing a slower relative wind). The inside wing thus generates less lift, and the plane starts to bank into the turn.
If you try to correct for that bank using aileron to raise the wing your elevator deflection effectively increases the angle of attack on that low wing, with its reduced relative wind -- do that aggressively enough and the inside (retreating) wing stalls while the outside (advancing) wing is still generating lift, and you enter a spin.

Slips

A slip is the same thing in the opposite direction: You have too little rudder input for the turn, and the aircraft is pivoting out of the turn:

In a slip the inside (low) wing is advancing, and the outside wing is retreating, so the inside wing is moving faster, generating more lift, and trying to level the plane. If you try to hold the inside wing down with aileron input you are increasing the angle of attack on the outside (high) wing to keep it up.  If the outside wing stalls because of this it will drop the aircraft into something closer to a wings-level attitude, which will also bring you out of the turn.
This is why slips are said to be spin-resistant: The stall encourages the aircraft back into a more stable configuration (coordinated flight) rather than a less-stable one (spin).

The images here are taken from BoldMethod's "Why skids are more dangerous than slips" article, which is a great read and also has a better and more comprehensive explanation of the aerodynamics involved.
My explanation above is a vast oversimplification, but the advancing/retreating wings and difference in relative wind is the one that got the idea to stick in my head so maybe it will help you out too.


What adds more weight to a twinjet? Tail-engines or wing-engines?

Tail engines add more weight. Placing the engines in pods underneath the wing relieves the bending moment in flight, allowing for lighter wing root construction. Placing them at the tail requires local beefy frame construction.

Note that the upwards bending moment in flight is the limit design factor:

In flight all of the weight of the aeroplane times the ultimate load factor of 3.5, and this is the bending moment relieved by the weight of engines mounted at the wing.
On the ground, the undercarriage supports the weight of the aeroplane at load factor 1, with a smaller moment arm. Way smaller than the ultimate bending load.
At touchdown, the spring/dampers are dimensioned such that the bending moment at maximum sink rate is below the ultimate design bending moment.

Torenbeek 1 mentions the following on this subject:

  Empty weight.
  The following factors have to be considered:

  A wing structure weight saving is possible with wing-mounted engines due to the mass relief effect on the bending moment on the inner wing.
  Engines placed too far outboard increase the landing impact loads and necessitate a large vertical tailplane.
  Engines at the rear of the fuselage require local "beef-up" and lead to loss of useful space in the tail, resulting in added structure weight and a larger fuselage for the same payload.
  Differences in weïght of the tail surfaces depend on various factors which do not permit a general conclusion.

  Summing up, we may say without too much emphasis that the empty weight of a CaraveIle-type layout will typically be 2 to 4% more than that of a comparable design with the engines on the wing.

As mentioned in this answer, at the time of B737 design Boeing had two competing designs from different teams, and the wing mount won. For an Order Of Magnitude check we can compare the wing and fuselage weights as a percentage of OEW for the DC9 and the B737-100. The weight of the wing & fuselage groups as per the table in this answer, the OEW from Wikipedia:

So indeed if we look at the weight only, the underwing configuration wins. The tail configuration compensates with aerodynamic pluses, mainly from the clean wing.

Note that these considerations were of value at the time of DC9 construction, with the narrow engines of the time. A modern 200 pax plane with high bypass turbofans has no good reasons anymore to opt for the tail mount.

1 E. Torenbeek, Synthesis of Subsonic Airplane Design


Why were turbojets the first kind of turbo-engines, instead of turboprops?

Propeller planes already existed, and turboprops were an answer to a question that was not asked in times of war. The main driving factor behind development of the turbojet was to provide great climbing power and high airspeed for intercepting enemy bombers, which the turboprop would not have been able to do. Fuel economy and engine life were of secondary importance, the Junker-Jumo 109 of the Me-262 lasted only 10 flight hours!

The piston propeller engines were very sophisticated towards the end of WWII, the super-charged Merlin piston engine powering the Spitfire developed over 2000 hp.

But the Me-262 and the He-178 were way faster than the Mustangs & Spitfires that escorted the bombers, and could only be shot down when lined up for landing. From the wiki:

  Too fast to catch for the escorting Allied fighters, the Me 262s were almost impossible to head off. [Note 7] As a result, Me 262 pilots were relatively safe from the Allied fighters, as long as they did not allow themselves to get drawn into low-speed turning contests and saved their maneuvering for higher speeds.

Turboprops would not have resulted in such an advantage, since the propeller is the limiting factor for airspeed. The lighter weight of a turbine would have been beneficial: the Merlin weighed 600 kg, and for instance the PW123 turboprop delivers 2,380 hp and weighs 450 kg - but only beneficial in the lower speed turning performance which the jet fighters learned to avoid.


Whenever Air Force 1 takes off or lands, the FAA establishes a 'Temporary Flight Restriction'.

Essentially this is a big 'upside down wedding cake' of airspace in which Air Traffic Control exercises very tight control of any aircraft operating in the TFR.  Any traffic entering the TFR without prior approval, or any aircraft deviating from ATC instructions will be intercepted by military aircraft.

When President Obama takes a bus trip the FAA establishes a TFR over the bus, that moves so as to stay over the bus as he rolls along!

Wikipedia has a good article on TFRs.


$$A = \frac{1}{\pi \cdot e \cdot AR}$$
where
$\pi = 3.14159....$, $e$ is the Oswald efficiency factor, and $AR$ is aspect ratio of the wing.


Can one become a scheduled airline pilot with just one functional eye?

Under current FAA medical regulations a pilot with one functional eye (called monocular vision) can get any class of medical, including the class 1 required for airline pilots:

  An individual with one eye, or effective visual acuity equivalent to
  monocular, may be considered for medical certification, any class,
  through the special issuance section of part 67 (14 CFR 67.401)

As the same page says:

  it has been repeatedly demonstrated that binocular vision is not a
  prerequisite for flying

Incidentally, one of aviation's most famous pioneers, Wiley Post, had only one eye. As for today, it's legal and possible to get any class of FAA medical with only one eye and therefore in principle you could fly for any US airline. Whether or not an airline would hire you is a different question, but if you're legal and qualified then why not? Blindness in one eye isn't even considered a disability by the US government if the other eye is fine.

It's also possible that if an airline declined to hire you because of your monocular vision even if you hold an ATP and class 1 medical, you might have a case for suing them for discrimination. But that's speculation, and you would need to ask another site about that. In any case, there may be more pilots out there than you think with physical limitations (for want of a better word), including ones with prosthetic limbs.


Does a METAR report variable wind direction in a clockwise direction?

According to meteocentre.com variable wind directions are encoded in clockwise order:

  This group reports variations in wind direction. It is only included if during the 10 minute period preceding the observation the direction varies by 60 degrees or more, and the mean speed exceeds 3 knots. The two extreme directions are encoded in clockwise order.

(http://meteocentre.com/doc/metar.html)


Can flaps be used to perform rotation and flare?

While this is an interesting idea, there are some key issues with it. As a GA pilot, here are my issues with that concept.

Changing flap settings causes signifigant differences in aircraft handling. If I was, say, on short final, and I changed my aircraft's configuration - it would be difficult to maintain a stable approach profile to the runway. If I were to deploy my flaps just above the runway, the aircraft would lose its "stable approach" and I would not have as much control authority over where, when, and how my aircraft touches down. There is a reason GA and Commercial pilots alike are taught to maintain a stable approach and have the aircraft fully configured well before landing.

I would never adjust flaps on take off or climb out (until at a reasonable altitude). The reason is simple. First of all, aircraft have operating limitations. You would not take off with full flaps because they generate too much drag, and hence limit aircraft performance. They are great for landing because of that same drag. However, If I were to take off with (theoretically) full flaps in a Cherokee or Cessna, it would not be safe to retract them until sufficient airspeed and altitude has been attained. Raising flaps at low airspeeds causes a noteworthy forward pitching motion and a temporary arrest of the climb rate. This is dangerous when in a low-airspeed, low-alitude situation and is warned against by CFIs.


Does turning off WAAS turn off ADS-B out as well?

This depends on the ADS-B receiver that you have, but if it is still receiving position information, but the WAAS portion is missing, you will get a lower NAC/NIC/SIL in the broadcast message. If you disable the GPS completely, the ADS-B will continue to function however the SIL for position will be the lowest level (likewise for NAC/NIC). The ADS-B will continue to function (as in send messages) but the position reports will be unavailable.

It's important to note that your transponder is still a Mode-C transponder, even if the ADS-B fails (completely or partially). You should inform ATC that you have an ADS-B or GPS failure and they will inform you if you are cleared to continue or not.

Really though as far as this is concerned, creating an actual failure is very much not recommended. If I were you, I'd just say "let's pretend that you have a RAIM message about your WAAS, what are your new minimums?" Creating an actual failure is something like pulling the bulb out of one of the gear indicators. It might be a "teachable" moment at first, but really just creates a distraction that can be done in other ways. What happens if the circuit breaker fails and the weather actually drops? Now you have a real problem...


How to calculate TAS and fuel for Diamond DA20-C1?

Your steps are all correct, as is your answer.

I'm confused by the "standard temperature" heading in the table.

Consider this table from your first link:

The column I put in a green box, if it was the only one, then the altitudes would all be density altitudes -- just like the table in the question, with the label "Standard Temperature."


What does the message content in the ARINC 615A FIND protocol look like?

Attachment 3 of ARINC 615A-3 describes the FIND function. The FIND protocol has an Information Request (IRQ) packet and an Information Answer (IAN) packet. Each packet contains a 2 byte header and a variable length data portion.

  3-4 Information Request Packet

  Source MAC address should be the MAC address of the data loader (or
  the initiator.

  Destination MAC address should be a unicast, multicast, or the
  broadcast MAC address.

  Source IP Address should be the IP address of the Data loader (or the
  initiator).

  Destination IP address should be a unicast, multicast, or a broadcast
  IP address (full broadcast i.e., 255.255.255.255 or class-relevant
  broadcast e.g., 220.130.48.255 for a class C).

  Opcode value should be IRQ (0x0001).

  Data list should be a null ASCII string with terminator: 0x00.

  Packet is terminated by 0x10.


How can one demonstrate/assure safety for LRU's, CBAs, SoC's and other integrated modules?

Yes, I've had some experience in dealing with complex hardware certification both with DERs and with FAA ACOs.  For the last 15 years or so, the process has been well defined as both FAA and EASA have adopted RTCA DO-254 Design Assurance Guidelines for Airborne Electronic Hardware.

I haven't run into many cases where there are any meaningful difference in interpretation of the guidelines, especially when discussing internally developed components.  There are some differences in what a DER/ACO will accept when you attempt to use commercial off the shelf (COTS) components.  DO-254 section 11.2 covers the use of COTS components but as it points out, the issue is lack of design data from the developer/manufacturer.  So coming to agreement on what is acceptable for these cases is highly variable depending on the DAL required and the available data.

For higher DAL levels it's getting harder and harder to get approval for COTS. You also have to deal with the fact that COTS parts may go through significant design changes on a regular basis.  That will impact your ability to maintain a single configuration.  Every part change has to analysed for impact and the configuration and certification updated.  That constant churn can quickly overcome any savings in procurement costs.

As to the more generic question of consistency between ACOs and DERs, it's an ongoing discussion within the FAA.  They want consistency but they don't want to to be so restrictive that all decisions get made at headquarters.  Every DER  or ACO I've met has had their individual biases and technical areas where they are comfortable.  So in that sense, there's always a bit of luck in getting one that sees things your way.  I don't think that will ever change.


What is the lowest-speed bogey a jet fighter can intercept/escort?

There is nothing stopping a faster jet from flying a zigzag pattern behind an intercept target if the goal is to remain in close contact with it, but a large difference in airspeeds would indeed hamper some tasks like observing the cabin for signs of life or unlawful interference. So the answer is yes, a jet fighter cannot perform all the tasks involved in a typical interception of an unresponsive aircraft if the speed delta is too high.

For reference, the takeoff speeds of 4.5 generation fighters like the F-16 are in the 130 kt (240 km/h) region, while the takeoff speed of something like a C172 is around 60 kt (111 km/h). The exact weapon and fuel load of the fighter will of course have an impact, but fighters scrambled for an intercept are typically light and with an almost clean configuration. I have deliberately used takeoff speeds instead of landing speeds to factor in a margin of safety in regards to control authority; both speeds are among the lowest an aircraft can sustain, but during  close approaches to a potentially hostile aircraft, some maneuverability is required.

Still, 100+ km/h is a substantial speed gap, and has led to issues in the past:

  The Po-2 is also the only biplane credited with a documented jet-kill, as one Lockheed F-94 Starfire was lost while slowing down to 161 km/h (100 mph) – below its stall speed – during an intercept in order to engage the low flying Po-2.


What special tyres (tires) are needed for high altitude takeoff and landing?

The higher takeoff speeds might exceed the speed rating of the usual tires. As a tire is rolling it deforms in two directions.

As each section comes in contact with the runway it is pressed inward by the weight of the plane. After it leaves the runway surface the deformation is in the opposite direction from centrifugal force. This constant flexing is what causes the tires to fatigue and possibly fail. The flexing also causes heat to build up in the rubber which causes the rubber to lose its flexibility.

The faster the tire spins the more centrifugal flexing occurs and the shorter the period between force reversals. This shortens the time the tire has to dissipate heat.

The two ways to increase speed rating of a tire is to reduce the flexing and to reduce heat retention. The way manufacturers reduce flexing is to add cap plies. These are usually of nylon or other synthetic material placed on top of the body plies on axial ply tires and on top of the steel belts on radial tires. These help keep the body plies from deforming outward from centrifugal force. The faster the tire must spin the more cap plies are used.

To reduce heat retention the rubber used between plies and at the shoulders must be made of compounds that have lower heat retention.

These things combined, more or stronger cap plies and better rubber compounds in key places, increase the cost of higher speed rated tires.

Image source: The Role Of Cap Plies In Steel Belted Radial Tires [pdf], David Osborne


What does the sign "Caution your blast" mean?

I'm fairly sure that sign is beside taxiway C*, and as you can see from the aerodrome chart it is right next to the main apron. Aircraft holding in this position have the main apron directly behind them.

The sign is instructing pilots to use the minimum thrust necessary to move off from that position, as there could be personnel, vehicles etc on the apron. As this is a bit of a mouthful "Caution your blast" is used.

This is further backed up by the aerodrome textual data which states:

  Pilots are requested to use minimum power when manoeuvring on and off parking stands and when entering the runway.
  The use of minimum power is particularly emphasised when holding at the the entry points to the runway and when
  entering the runway.

The other hold points around the apron seem to have a similar problem Taxiway B has the same sign. Perhaps the others do too.

(Image source: https://www.airlinequality.com/review-pages/gallery-airline-reviews/)

* This was based on personal memory of seeing this exact sign, and of being aware at which hold point we were at. I went and checked using google earth/street view. There is a good view from the terminal however the sign itself is obscured by an aircraft. However you can clearly see the building opposite from the original picture, and so the position for Taxiway C lines up.


Why would you NOT lean on takeoff with a Lycoming engine?

You are correct - you do want highest power.  But you also want an engine that doesn't overheat and destroy itself.

Your initial climb-out is at an airspeed considerably less than cruising speed so you have less air flowing through the cylinder cooling fins.  To compensate for this, flying full rich keep the combustion gasses cooler during the climb-out.

When you reach cruising altitude and level off, you may lean it out in accordance with the engine manufacturer's recommendations.

This "full rich on takeoff" procedure is not limited to Lycoming engines, either.  TCM Continental and even the older Pratt and Whitney radials also go full rich on takeoff. It is close to a universal procedure for piston powered aircraft engines.


Are there runways that are numbered only on one side?

Yes, there are runways numbered on only one side.

For example, the third runway in the Frankfurt Airport (18, Runway west) is used only for takeoffs (to the south) and not for landings. Hence only number 18 is used. The other runways are used for both takeoffs and landings and are numbered 07C/25C, 07R/25L and 07L/25R.

Thomas Römer/OpenStreetMap data [CC BY-SA 2.0], via Wikimedia Commons

This restriction is due to the fact that it will interfere with the traffic in other runways.

Number 36 is not painted.


How to know which data came from Mode S and which came from ADS-B (FIS-B)?

All the recorded transmissions you have, seem to come from the same aircraft. They come all from the onboard (Mode-S) transponder.

All transmission with Downlink Format (DF) 17 are ADS-B. Those with DF18 are TIS-B (or ADS-R), you don't have any of these (they are rare in Europe, and more common in the US)

Mode-S uses the following DF's:

DF4 - altitude reply (short)
DF5 - identiy reply (short)
DF11 - all call reply / Mode S squitter
DF20 - Comm. B / altitude reply (long)
DF21 - Comm. B / identity reply (long)


How is an Airbus A380 fuselage joined and fastened together?

With approximately 19,000 rivets.

This picture is of the wing attachments, but the fuselage joints use the same attachment method.


How significant is antenna drag on light GA aircraft?

From an aerospace engineering perspective:

The drag coefficient ($C_D$) of a round antenna is can be estimated by around $.5$ depending on shape, while for an streamlined shape it's around $0.045$.

(Source)

Drag is defined as:

$$D=\frac12C_D{\rho}V^2A$$

Thus, say you have a 0.01 m wide antenna 0.25 m long, for an aircraft moving at 50 m/s. At sea level conditions, air density $\rho=1.225 \mathrm {kg/m^3}$. Say that $C_D=0.5$. If my calculations add up, it's around $1.9 \mathrm{N}$.

Say you have the same antenna, for the same aircraft aircraft moving at 50 m/s. Air density is $1.225 \mathrm{kg/m^3}$, but this time the antenna is streamlined with $C_D=0.04$. This results in a force of only $0.15 \mathrm {N}$.

(Updates: Originally the formula included $\frac12$ twice which was wrong, and that the force was given in kg, rather than newtons; my apologies.)


Does the Airbus A350 have an Automatic Emergency Descent System?

Airbus will have it on the -1000, and will also introduce it on the -900.

A350 chief engineer Alain de Zotti says the -1000 will be able to "slightly deviate" from the flight plan, if the system is activated, and leave its cruise altitude.
As well as executing the high-speed manoeuvre the aircraft will automatically notify air traffic control of the action.

(flightglobal.com, Nov 2017)

The Falcon 7X already has it, they call it Automatic Descent Mode (ADM).

In case of a depressurization at high altitudes, the Autopilot and Auto throttle will guide the aircraft to safe altitude at maximum velocity. ADM is activated when Autopilot is engaged, the aircraft is above 30,000 ft., and the cabin altitude is 9,700 ft. or greater.

Further reading: Automatic Emergency Descent System (skybrary.aero)


How to calculate DDM in a ILS dual frequency system?

I don't think you're supposed to just average the two together somehow by themselves. The two signals are designed to be used in different zones and in practice have very different signal strengths at any point on approach.

From EVALUATION OF INSTRUMENT LANDING SYSTEM DDM CALIBRATION ACCURACIES [sic] by Dennis M. McCollum [PDF]:

  The course pattern contains sidelobes that, without the clearance pattern, could cause an aircraft to select a wrong (sidelobe) course. Within the region of the true course (i.e., + 10 degrees about the designed procedural course), the signal strength due to the course array is greater than that from the clearance array. In the regions where the sidelobes exist, the clearance signal predominates. Airborne ILS receivers are designed to respond to the greater of the two signals.

This has to do with the background in processing these signals through analog means. Both the clearance and the course signals are within the passband of the receiver.  Since this is an AM receiver and DDM is more or less a ratio of 90 Hz to 150 Hz, if the clearance or course is much stronger than the other, the stronger one prevails.

So in practice measuring the course signal DDM inside the clearance region doesn't reflect what's done in practice, and I'd guess it probably isn't even a guaranteed behavior of the transmitter.  Do anything else instead in this region, like perhaps measuring just the field strength of the course signal.

But what about when slightly off the centerline?  Then you'd get a mix of course and clearance signals.  You could assume the ideal condition where a capture effect completely eliminates the weaker frequency.  Another approximation presented in the admittedly confusing paper "Current Issues in Demanding ILS Ground and Flight Measurement Environments" by Gerhard Greving and L. Nelson Sponheimer is

\[ DDM_{total} = \frac {DDM_{clearance}* CR^x + DDM_{course} } {1+CR^x} \]

Although I can't quite make out what precisely CR and X is here.

Depending on the application, it may be more realistic to model the amount of distortion expected or permissible due to clearance band interference, especially due to multipath reflections of that signal.  However, given your comments that probably won't help your specific application.


Eye requirements for private pilots license in the US?

The guidance for vision requirements are listed here.  Basically for a private pilot distant vision must be 20/40, near vision 20/40, and no requirement for intermediate vision.  The website says

  In each eye separately with or without correction

I interpret that to mean that your left eye must be 20/40 or better.  However the final authority on this would be the FAA approved medical examiner and it wouldn't hurt to go ahead and schedule a FAA Type III medical examination and see what the doctor has to say.  Unfortunately your insurance won't cover the exam and you would have to pay somewhere around $150 for it.  However you will have a better understanding of what your options are if you want to pursue flying.  Sometimes a license can be granted but with restrictions if a pilot has a medical condition.

I hope you will be able to pursue flying and wish you the best of luck!


what is the use and the locations of nacelle hinge bracket?

I'm assuming that you're talking about the part below. The part was changed from cast steel to titanium DMLS additive manufacturing technology.

Image from belement.co.il

The hinge is used to hold the engine nacelle cowling when opened. YOu can see four of them (older versions) on top of the open cowing in the image below:

Image from article.wn.com


Relation between altimeter setting (QNH) formula and the barometric formula

Formula 33a (from the US Standard Atmosphere 1976 document you quote) gives you the pressure at a specific altitude in the U.S. Standard Atmosphere, and corresponds closely to airport/station level pressure in met reports (it corresponds exactly when the real atmosphere has the same characteristics as the Standard Atmosphere). An altimeter setting/QNH is essentially a pressure at sea level (and will be 29.92"Hg/1013.2HPa when the real atmosphere matches the Standard Atmosphere, no matter what elevation the airport is).
see the weather.gov definitions here
So the two formulas (33a, and the weather.gov formula you quote) do not give the same thing.
It would be interesting to know why you need to calculate an altimeter setting, as opposed to getting it from met reports. The setting provided in met reports is a value calculated from the measured station level pressure, and this calculation is actually non-trivial.
Beware the frequently-used rule-of-thumb of 27 feet being equal to 1 HPa on an altimeter is only an approximation, and one which only "works" for low elevations/altitudes.


Should an emergency field landing be performed with landing gear down or up?

There are various factors here:

Gear acts as a speed brake, in some emergency situations if you need the added drag as you approach the field (to make the field) a gear down situation may be called for regardless of ground condition. On the flip side if the field is on the edge of gliding distance you may want to keep the gear up to improve glide. This is a judgement call during the emergency.
Gear will provide you limited steering on the ground which for what ever reason you may need. In a gear up situation you are sliding to a stop.
Gear will provide you brakes, if the field is short you are going to want this option.
If something is critically wrong with the plane and you need to do an emergency gear deploy there may be no time during the emergency.

Like anything, it depends and it will be a situational decision with merits to both aspects. You should consult the POH for your air frame as they will most likely have check lists for both scenarios.

For example in a Piper Arrow they offer a checklist of a gear up emergency specifically:

  Gear up emergency landing:

  In the event a gear up landing is required,
  proceed as follows:

  (a) On aircraft equipped with the backup gear
  extender, lock emergency gear lever in "Override Engaged" position
  before airspeed drops to 115 mph to prevent landing gear from
  inadvertently free falling.

  (b) Flaps as desired.

  (c) Close throttle
  and shut off the master and ignition switches.

  (d) Turn the fuel
  selector valve to OFF"

  (e) Contact surface at minimum possible airspeed.

Here is what happens in a small plane when the gear collapses on a grass field. A gear up landing is not an automatic hull loss, in many cases they can be repaired. Considering the age and use level of most of the countries GA fleet you may be surprised to find out just how many planes have actually been through a gear up landing.

I was always instructed during my training that ditching gear down (or with a fixed gear) in water was not really viable. There seems to be some info indicating that there is little data to support this. Of course you will find endless debate on the internet about it and some answers that fail to provide sources. Some of the misconceptions may be fueled by what happens when a float-plane digs in on landing.


Is a "GPS required" ILS (or other navaid-based) approach considered a "GPS approach" for alternate planning's sake when TSO-C129/196 gear is in use?

This is an excellent question.

However, since the approach you reference, KJAC ILS Z or LOC/DME Rwy 19, "requires" GPS, I would interpret it the same as a GPS-only approach for planning purposes and subject to the appropriate restrictions. Those are: either the destination or alternate, but not both can be a GPS-only approach airport for TSO-C129/TSO-C196 [GPS-no WAAS] equipped aircraft.  Both destination and alternate can be a GPS-only approach airport if the aircraft is equipped per TSO-C145/146 [WAAS].


How many passengers can an Airbus A380 carry?

Wikipedia lists three basic configurations for the A380-800:

407-526 (3-class)
644 (2-class)
853 (1-class)

However, different airlines have different configurations. The lowest number of seats is Korean Air, with 407. The highest number of seats is Air France, with 538. Emirates has discussed plans for a configuration with 644 seats but it does not appear on the list (or on SeatGuru).

As far as baggage, this thread states that the A380-800 might carry 19 LD-3 containers of baggage, or 3002 cubic feet, which is for about 471 passengers. The bulk hold, which is for loose baggage, can hold 1,525 kg or 14.2 cubic metres (501.5 cubic feet), and the A380-800 can carry 8,000 kg of cargo in addition to a full passenger load according to Emirates.

An average suitcase is about 0.1 cubic meters in volume. If the bulk hold is 14.2 cubic meters, then it could theoretically fit 142 suitcases. But an average suitcase weighs 50 lb, so 142 suitcases would weigh 3220 kg, which is over twice the weight capacity.

The LD-3 containers add an additional 85 cubic meters of space, or 850 bags. This is a total of 942 bags, which for around 500 passengers sounds very reasonable.

But wait, there's more! What if the rest of the cargo capacity was filled with luggage?

Emirates above claims a total of 12 PMC and 44 AKE of cargo capacity. The properties are as follows:

PMC

23 cubic meters (max)
6700 kg capacity

AKE

4.3 cubic meters
1497 kg capacity

This is a total of 465.2 cubic meters of capacity, or 4652 suitcases, or 105,505 kg. The containers could hold a maximum of 146,268 kg.

So the bulk plus container capacity is 4794 bags by volume. This is assuming every container could be packed completely full of bags with a density of 227 kg/cu m, so the actual numbers would probably be lower.


Why is the pitching moment of this symmetric aerofoil non-zero?

Under incompressible potential flow and at small angles of attack, one of the most celebrated results of Thin Airfoil Theory is that all airfoils have their aerodynamic centre at 1/4 chord; and for symmetrical airfoils, the centre of pressure coincides exactly with aerodynamic centre.

If you look at the plot in the OP, the variation of Cm between -3 and 3 deg are relatively small, indicating that the linearized theory agrees well with the nonlinearized simulation.

Beyond 3 deg, however, the viscous effects present in the simulation but absent from Thin Airfoil Theory begin to alter the results. This manifests primarily in the boundary layer, which alters the apparent shape of the airfoil, thereby making it non-symmetrical. The next graph shows the XFOIL simulation at 7deg AOA; notice that the boundary layer at upper surface thickens near the trailing edge.


Could the Cruise-Efficient STOL configuration be as efficient as a conventional airliner?

Without data, it is not possible to tell if one design will be better than another. This is because it is one thing to make a concept (which this is) and entirely another thing to manufacture and operate the aircraft (like A320/737).

Actually, the design in the video is not entirely new, It is similiar to the Boeing YC 14

developed for UASF AMST program. It is instructive to note what happened in that program.

The AMST program was initiated for developing a tactical STOL aircraft, requirements similar to the CESTOL. Even though YC 14 met the requirements, the program was scrapped for other reasons and the C17 was developed from another contender in AMST program, the YC15.

Even during development fo the YC14, the drag was more than expected and Boeing struggled to bring it under control.

However, I doubt the design as shown is ever going to be made into an actual aircraft. There are too many problems at first glance

The wing seems to pass right through the fuselage. This is not going to work in a transport aircraft.
The location of the engines suggest that the main spar will pass right through it. This will have strength implications.
In case the aircraft is used for STOL operations, the rear fuselage design should be redesigned for preventing tail strike as the landing gear in all probability will be shorter.
Putting the engine inside wing is not a great idea as it increases complexity and chances of catastrophic wing failure.

There are a number of similar programs for developing efficient STOL aircraft, none of which have come into fruition. It is going to to be the economics of the operation from small airports, rather than the aircraft itself, which will decide if these designs will ever see the light of day, let alone operate in commercial routes.


What is the source for the "rule" forbidding configuration changes below 200ft AGL?

There is no rule.  There is a convention that you should be in a stabilized condition that requires no major control inputs or power changes in the last few hundred feet.  With jets, airlines often have an operational policy that requires a stabilized approach configuration once below 1000 ft to continue with a landing.

The reason is pretty simple.  If I'm well outside a descent rate or speed parameter close to the ground, I'm forced to attempt a much more radical correction, because I don't have much time, than I would farther out.  The radical correction will, unless the pilot is very experienced and proficient on type, invariably result in an over correction, and the result is oscillation about the target parameter just as the moment of truth is approaching, and from there things get entertaining.

So in training it's a mantra that is almost universally taught that you need to be settled in on slope and on speed when getting close to the runway.  On little airplanes, a couple hundred feet, on bigger ones, maybe 500, on transports, a thousand.  The more the mass and inertial involved, the farther out you need to be settled in.

If you are sufficiently skilled and experienced on an airplane type, all this is not quite that critical, but for a newer pilot it's pretty important.

The stuff about using the last bit of flap to stretch a glide doesn't work.  It might theoretically help you make it across a ditch before touching down if you were cutting it that close with an engine failure, but more likely it just steepens the glide angle and makes things worse.


What is the Runway Design Code (RDC) for San Francisco airport (KSFO)?

D-VI. No link. A380 requires this and operates there, so that is minimum.
E is military, VI is a high as it goes.


Can passenger distribution cause a parked airliner to tip?

It's possible.

When FedEX used 727s a lot they had regular occurrences of cargo being loaded too far back while the front was empty. The airplane would sit on it's tail. Not usually damaging but having the front door quite a bit higher than usual was an issue. If no one was on board it was awkward to get it back to normal, and FedEX really doesn't like delays. At my airport in the 90s you often saw a post attached to the tail while they ere loading.

Highly unlikely a 747 will rise up like a bucking horse, but it is possible that you can take enough weight off the nose gear of something smaller that the strut can extend. This would make the cabin door rise by about a foot, probably hit the jetway, and upset most everyone onboard. What would the passengers probably do? That's right - run downhill.


Which are the main aluminium alloys used in airliner construction?

2000s, 6000s, and 7000s series alloy are very common for aircraft construction over the past 8 decades of metal aircraft design.  Boeing aircraft are largely manufactured from 2000s series aluminum alloy.


In simple mechanical stick linkages, is there crosstalk between the aileron and the elevator movement?

In almost all cases, there is no intentional-- or discernable-- mechanical coupling between aileron deflection and elevator deflection.  However in the Schleicher Ka-6 sailplane, the mechanical linkage is designed to raise both ailerons a little bit, effectively increasing washout in the wing, when the stick is far aft.  See for example page 3 in this manual.  Some other aircraft may share this unusual feature.  You can imagine why it is desirable to have more washout in a low-airspeed thermal turn than in high-airspeed cruising flight.


Do seaplane bases ever have marked "runways" or approach lighting?

Are the landing areas marked by buoys or lights?
In at least one specific instance, Yes.

The seaplanes that operate out of Lake Union, Seattle, have "Advisory Buoys" that help make the many sailboats, kayaks, and motorboats on the lake aware that planes will be arriving or taking off.

The buoys have Pilot Controlled Lighting (PCL) that will turn on yellow flashing lights.  They are typically activated approximately 3 minutes before any departure or arrival.

The buoys do not restrict boat movement; they are advisory only.

I am not aware of any IFR procedures for a seaplane base, but I do not know for sure.


Should I use rudder to recover from power-on stalls?

Your instructor is correct.
I've never seen a C172 where the POH actually discusses stall recovery besides saying it's 'standard'. I was taught to keep the airplane in balance using rudder in the approach to the stall, and manage any wing drops with rudder in a fully developed power off stall (I'm in the UK, not sure how the US is different). However, that isn't the procedure for a power on stall. The FAA Airplane Handling Handbook section 4-8 on power on stalls states:

The pilot must promptly recognize when the stall has occurred and take
action to prevent a prolonged stalled condition. The pilot should
recover from the stall by immediately reducing the AOA and applying as
much nose-down control input as required to eliminate the stall
warning, level the wings with ailerons, coordinate with rudder, and
smoothly advance the power as needed. Since the throttle is already at
the climb power  setting,  this  step  may  simply  mean  confirming
the  proper power setting.

In a power on stall if you get a big wing drop the rudder is not going to lift the wing, and coarse rudder movements could stress the airplane, see the AA 587 crash. So balance with rudder, but most importantly reduce your angle of attack with as much forward stick as you need.


Can a helicopter stand on the ground upside down on its rotor head?

Stand on its rotor head? yes, maybe. Spin? not for long.

The rotor hub and blades are quite strong and can take the helicopter weight at-least temporarily (leaving aside the balancing issue). The blades are designed to overcome stresses in flapping and can take the load. The rotor hub however, is not designed to take loads in this attitude (it is designed to lift the helicopter, and not push it) and its capability is an open question. You could put the helicopter upside down, but its going to be a brief affair with no guarantee that the parts will ever work again properly.

However, in case you want to spin the helicopter, you run into a number of issues. You could clamp the blades down and try to spin, but the rotor hub will struggle to take the load. The load path from the rotors to the fuselage is designed to take lifting loads and not this.

Helicopters are not designed for sustained inverted flight and as a result, the systems are not designed for anything like this. For example, the gearbox lubrication system isn't going to work for long in the upside down condition. The rotating control rods aren't going to take the gear box weight, let alone the helicopters'.

But first, the dynamic loads- helicopter systems below the rotor hub are not designed to take rotating loads, let alone the horribly unbalanced one like a fuselage. Even the lightweight helicopter blades are balanced to prevent and unsafe vibrations -in a case like this, the rotating fuselage would most likely tear apart the helicopter before anything else.


Does zero-lift angle of attack depend on Reynolds number?

The aerodynamic coefficients  $c_l,c_d,c_m$ are in general functions of the angle of attack $\alpha$, Reynolds $Re$ and Mach number $Ma$. For your experiments, since you are operating in a very low $Re$ regime, assuming incompressible flow, your lift, drag, moment curves will largely depend on viscous phenomena (i.e. $Re$ number). Generally, as $Re$ number drops, the boundary layer thickens. For this reason, you will expect a lower $c_l$ number (due to viscous decambering) and a higher $c_d$.

You may also discover non-linear behaviors even on operating angles due to laminar separation bubble forming/bursting on the suction surface and this is very dependent on the turbulent intensity of your wind tunnel so the stall angles and post-stall behavior may not be the same for flight conditions where turbulent intensity is very low.

Finally, you can confirm with Xfoil that for $Re=300k \Rightarrow \alpha_{L=0}=-4.33\ deg$ while for $Re=150k \Rightarrow \alpha_{L=0}=-3.64\ deg$ for the NACA4412.


Would a ducted fan with a nozzle like a jet engine have more thrust than a normal ducted fan?

but why not use the pressure created by the fan and contract the space making the output velocity higher?

That is exactly how the pressure energy added by the fan is converted into thrust. Thrust, after all, is the product of the speed increase between free stream and exit flow, mass flow and nozzle area.

That real jet engines don't show so much contraction is due to the expansion of the core gas flow from heating. If you don't add heat, your exit area should be quite a bit smaller than the entry area.

If by "normal ducted fan" you mean one where the duct is simply a cylinder of constant diameter, then yes, a properly designed nozzle will create more thrust.


Why is there so much movement of the sidestick during this takeoff?

One of the unique aspects of Airbus fly-by-wire aircraft is that the sidesticks provide NO feedback. Because of this, the planes have an automatic trim system. Once the aircraft is pitched to a desired attitude, the pilot will then release the control stick and the aircraft will continue to fly at the selected attitude.

Correspondingly, if a pilot desires to reduce the pitch, they must push the stick forward to do so. In an Airbus (unlike most other aircraft), a pilot doesn't manipulate trim at all (except in non-normal situations).

As an aside, in the normal flight regime, Airbuses provide automatic protections from unsafe attitudes. Thus, if a pilot desires maximum rate of climb (that is possible in the current configuration), he can simply pull the sidestick all the way back. The computer will automatically keep the aircraft from exceeding maximum load factor and/or critical angle-of-attack.

To answer the other part of your question, the lateral stick movement is likely due to turbulence. Control inputs in large aircraft tend to be more pronounced than smaller aircraft (due to slower aircraft reaction times).


What is the traffic pattern altitude at KSQL?

I am based at KSQL, the TPA is 800 AGL. The A/FD er, excuse me, I mean the Chart Supplement, says "Helicopter TPA--806(800)" which seems like a typo; it's the TPA for fixed-wing also.


Delta, ta[ngo], sierra, whiskey, alpha, etc... are all letters in the ICAO phonetic alphabet, which is a system used to speak letters in a way they can be clearly understood over the radio. Just as letters like "D" and "T" have no particular meaning on their own, these letters can be used to mean many different things depending on the context.

The letters could be part of a callsign (to identify an aircraft, e.g. "november four four charlie kilo" is a particular Cessna Citation), taxiways at an airport ("turn right on taxiway hotel" means turn right onto the taxiway marked "h"), to spell out the name of a location when needed to avoid ambiguity, really anything where spelling out one or more letters is required on the radio.

You might want to read up on the basics of how aviation radio communications are conducted to help understand the format of typical communications.


Where can the airspace boundary coordinates for Fayetteville TRACON be found?

I will second @StephenS's image as the best you're likely to find with minimal effort. In fact there are a few of these images available if you do an image search for "FAA STARS TAMR" and I've included all of them at the bottom of this answer.
Real answer
If you need the specific boundaries you can submit a FOIA request. If you're a private citizen who wants the information for non-commercial use this should be free, but it may not be. Here is the FOIA form for the Air Traffic Organization FOIA Coordinator for the Eastern Service Area, which should be who you want. I would probably say you're requesting "A document showing the boundaries of Fayetteville ATCT center-delegated airspace" and that you think it would be found in the SOP and/or in the LOA with Washington ARTCC.
Alternatively, if you have a controller friend who's willing to do you a favor you could ask them to pull up the SOP/LOA for FAY from the FAA intranet next time they're at work. All facilities should have their SOPs and LOAs stored on a system that can be accessed at loa.faa.gov from behind the general firewall. This is probably against policy though, so they might not be willing to do it for you.
Unofficial but likely workable answer
The VATSIM community strives for realism, and from time-to-time submits FOIA requests to the FAA to form the basis for their SOPs and maps. The Virtual Washington ARTCC website includes a page of downloadable "facility files" that you can open in a virtual radar client in order to see the airspace boundary (by enabling the "VIDMAP" map). I have no reason to doubt this map's accuracy, as it looks quite detailed and appears to match the boundaries shown in the maps below, but there is no guarantee it is accurate or current.
To find the geographical coordinate of any given point on the map, you can type <F7>D* and click on the point. This shows the coordinate in what appears to be a hybrid Degrees Minutes.TenthsHundredths format. These coordinates must be defined somewhere in the downloaded "facility file" but I do not see a way to extract them on their own; you could get in touch with the VATSIM community to ask for the originals.
This method would probably work for any facility in the country, and although there is no guarantee of accuracy, airspace boundaries do not change often at all. It may be more time-effective to ask the various VATSIM communities for access to their FOIAed documents than to duplicate their effort by asking the FAA for each individual facility.
Interesting graphical history
An older map, still shows ARTS facilities. No date. FMH and ACK still separate. NMM is an FAA facility. JST not shown. Original

Map from September 2013. FMH and ACK still separate. NMM is an FAA facility. JST not shown. Original, 1620x1080. This is the highest-quality map of the bunch.

Map from September 2014. Very poor quality, hard to tell the differences from 2013. FMH and ACK still separate. NMM is an FAA facility. JST not shown. Original

StephenS's undated map. FMH and ACK have merged to create K90. NMM is an FAA facility. JST not shown.

Map from July 2018. This version shows ARTCC boundaries as well! K90 has been absorbed by A90. NMM is now run by the DOD. JST is a wholly new approach facility running airspace delegated by ZOB, located between PIT and MDT. The facility covering Edwards AFB and the R-2508 complex is now designated E10, "High Desert TRACON," instead of EDW. Also shown are the then-in-progress airspace consolidations (Section 804 or otherwise): MFR to EUG, YKM to PSC, MSO to GEG, RNO to SCT, BZM to BOI, GJT and PUB to D01, SJT to MAF, FYV to FSM, COU to SGF, LYH to ROA. Original

Map from June 2019. STARS is almost ubiquitous, with only two ARTS 2E and four ARTS 1E facilities left that I can see. Transfers of YKM to PSC, COU to SGF, and LYH to ROA are complete (as are the others from 2018, I think, but the arrows are still drawn because the airspace is not contiguous). MKG, MBS, LAN, and FNT have been combined into a super-TRACON at AZO now known as "Great Lakes Approach." Original

As of 2021, I believe there are no remaining ARTS facilities; all facilities are using some flavor of STARS. E10 is now JCF, "Joshua CCF." MFD and CAK have both been consolidated to CLE. PSC is being consolidated to GEG, taking YKM airspace with it. PIA and SPI are being consolidated to T75. HUF is being consolidated to IND. There are probably some more I'm not remembering.


Why don't bypass ducts in jet engines narrow down the flow to accelerate it?

if you decrease the duct cross-section, you must apply work to accelerate the flow through the smaller duct. this means the fan driving the duct has to work harder (it must absorb more shaft horsepower) against that constriction in the flow and you derive no benefit- unless you mount the fan on a more powerful engine, in which case you are burning more fuel to drive the fan-and-duct system. So, there is no free lunch available here.


Why Clyde P. / Boeing B-52H Stratofortress flight from 1962 took the longer route?

The B-52 Stratofortress is a military jet, and specifically a US military jet, which if flown over USSR was very much in risk of being harmed. Thus, it was an intelligent decision to follow a longer route, rather than being a victim of ongoing cold war, following the longer route could have also helped the crew in achieving the longest flight record. Secondly, the B-52 did not have a very good history even before 1962, thus taking precautions was a necessity for the crew, and they did this by choosing to fly over more helpful nations.  Also, aviation was not developed very much in Asia back in 1962 with very few strips of a large distance, to be used in case of emergency.

For more information, you may refer this and this!


How to find out if Restricted Area is "hot" before taking off?

Restricted areas that have scheduled times will be noted in the (sectional) chart margins. In this example you'll find this at the bottom of the Washington sectional chart:

Ones without regularly scheduled hot times will say something like 48 hrs in advance or other times by NOTAM.

As you've noted though restricted areas with posted hours may not always be "hot" during those hours - sometimes you get lucky. The best way to check if you're going to be lucky prior to departure is to ask Flight Service (1-800-WX-BRIEF): The briefers have access to the same data as ATC, and will know definitively if a restricted area is hot (at least as of the time you call them).

Obviously you should still call the controlling agency when airborne to verify the status of any special use airspace prior to entering it (briefers can make mistakes, and some restricted areas may be activated on short notice which means they may go hot while you're enroute).


What is the difference between RTOP, MTOP, and MCP?

MCP is maximum power that can be used indefinitely without shortening the life of the engine.  You might use MCP when you need all the available power during single engine cruise, to maintain an altitude for obstacle clearance, or when climbing single engine.
MTOP is normal maximum for takeoff and initial climb, with a time limit. If you exceed the time limit, you will shorten the life of the engine.
RTOP is a power reserve for special situations, like when an engine quits, where the engine goes above MTOP to save your butt.  When that happens on modern turboprops the dead engine will autofeather and the live one will automatically go into RTOP (sometimes called "power uptrim" or something similar).  If it does so it may have an impact on engine life or may require a special inspection later.


Does simulator time count as time in type?

Unfortunately, no.

135.225 - IFR: Takeoff, approach and landing minimums (e) requires:

  The MDA or DA/DH and visibility landing minimums prescribed in part 97
  of this chapter or in the operator's operations specifications are
  increased by 100 feet and 1⁄2 mile respectively, but not to exceed the
  ceiling and visibility minimums for that airport when used as an
  alternate airport, for each pilot in command of a turbine-powered
  airplane who has not served at least 100 hours as pilot in command in
  that type of airplane.

So this means that our question becomes:  Can a pilot log PIC time when "flying" a simulator?

The answer to this question comes from 61.51 - Pilot logbooks, where you will notice that none of the bold parts (marked by me) have been met in the situation that you describe.  Generally, PIC time requires you to be PIC of an aircraft, and does not provide for PIC time when in a simulator unless you are providing instruction:

  (e) Logging pilot-in-command flight time.

  (1) A sport, recreational, private, commercial, or airline transport
  pilot may log pilot in command flight time for flights-

  (i) When the pilot is the sole manipulator of the controls of an
  aircraft for which the pilot is rated, or has sport pilot privileges
  for that category and class of aircraft, if the aircraft class rating
  is appropriate;

  (ii) When the pilot is the sole occupant in the aircraft;

  (iii) When the pilot, except for a holder of a sport or recreational
  pilot certificate, acts as pilot in command of an aircraft for
  which more than one pilot is required under the type certification of
  the aircraft or the regulations under which the flight is conducted;
  or

  (iv) When the pilot performs the duties of pilot in command while
  under the supervision of a qualified pilot in command provided—

  ...

  (2) If rated to act as pilot in command of the aircraft, an airline
  transport pilot may log all flight time while acting as pilot in
  command of an operation requiring an airline transport pilot
  certificate.

  (3) A certificated flight instructor may log pilot in command
  flight time for all flight time while serving as the authorized
  instructor in an operation if the instructor is rated to act as
  pilot in command of that aircraft.

  (4) A student pilot may log pilot-in-command time only when the
  student pilot—

  (i) Is the sole occupant of the aircraft or is performing the
  duties of pilot of command of an airship requiring more than one pilot
  flight crewmember;

  (ii) Has a solo flight endorsement as required under §61.87 of this
  part; and

  (iii) Is undergoing training for a pilot certificate or rating.


Out of sight planes during final approach

The 2nd plane's pilot should notice that he is not receiving the localizer on his instruments and break off the approach.


Why does the main battery discharge with the alternator running?

Our mechanic had a similar issue with a Piper Cherokee where the battery would only charge intermittently.  It turned out there was a bad connection at the Master Switch which ran from the Alternator/voltage regulator to the Master Switch. Most of these types of electrical issues tend to be bad wiring. I would check your wiring thoroughly.


Is it possible for an airplane to produce thrust from compress air without using fuel?

First of all, where does the compressed air come from? Is it stored in big tanks, or do you compress it as you fly?

Assuming you use the second way (the first would be quite inefficient), you need to power the Air Compressor, which means you need to generate energy.

If you do not want to use fuel, then it has to be powered by electricity, i.e. an electric plane. This is basically how the Airbus E-Fan works, using two ducted fans powered by electricity (as @Zach Lipton said in the comments)

So to answer your question, yes, your theory works. There are already a few prototypes using it.


When do the Boeing 737 Next Generation aircraft reach End-of-life?

Airliners aren't given "end-of-life" dates, unlike, say, Windows 95. They also don't eventually become "unsupported", like an iPhone.

A plane will be kept flying while it's safe and economical to do so.

In the case of a particular aircraft, that will depend on many things that have nothing to do with the aircraft itself (oil prices, perhaps) that make it uneconomical to operate.

Older planes are less fuel-efficient, and at a certain point a passenger airliner may be transferred to cargo duties (where fuel is a smaller proportion of the total cost of owning and operating it) and eventually, if no-one wants to keep flying it, it will be retired.

The point at which a plane becomes uneconomical to operate also has to do with how the aircraft is used - an aeroplane that has been through more pressurisation cycles will enter a more expensive regime of checks or maintenance sooner than one that has not (if an aeroplane will need to undergo more extensive checks for fatigue after say 50 thousand cycles, that might be the point at which an operator decides to replace it).

Almost any aircraft can in fact be kept safe to fly (if it were safe to fly in the first place) if you're willing to spend enough money doing so. This is why the comparison with iPhones and operating systems is instructive; probably nobody on earth has enough money to persuade Apple to keep providing iOS updates and manufacturing spare parts for the iPhone 4, but the economics of operating and obtaining spares and doing maintenance on 737s is quite a different matter.

The 737 −600/-700/-800/-900 models are still being produced, and past experience suggests that such aircraft have something like a 30-year working life span.

You never know however if unexpected events (like an oil crisis, or the discovery that airliners cause serious health issues in law-makers' children) will dramatically change the economic environment in which they operate - that's in the hands of fate.


Why are some modern military trainer aircraft so bulky?

You mentioned the oversized canopy for two, staggered for better visibility, and really that is the main feature that stands out.  Consider that trainers are typically quite a bit smaller than their full combat brethren and this feature is even more out of proportion.  Also, full sized combat 2 seaters generally have a Weapon System Officer in the back seat, so good forward visibility isn't as crucial as it is in a pilot trainer so less upward stagger of the back seat is needed.
The human body doesn't scale up and down like an airplane design, it is the constant that must be designed around. Think about it, you are fitting two 6 foot tall people in a fairly small plane vs often one in a larger plane; naturally the space for the bodies will be a much larger overall percentage of the size of the  trainer.
If you were to compare a 2 seat trainer next to a larger 2 seat combat aircraft like the F14 Tomcat, (with its huge engines...) I think you would find that the cockpit areas are actually pretty similar in size.  They are just more pronounced in the smaller plane.
Other than the cockpit area they really aren't "bulky" at all.  In fact the two pictured are VERY compact and streamlined, by just about any standard.


What are the meanings of various reference lines and sections in a take-off distance graph?

You need to read such graphs strictly from left to right. Each new panel adds the influence of another parameter, and when you are done, the result is corrected for altitude, take-off weight, wind and obstacle height. Except for the leftmost panel, the groups of lines only help you to find the correct slope and do not represent a certain altitude.

You start with the outside air temperature. Pick what the instrument in your cockpit indicates, and go from the temperature axis straight up until you intercept the line which is closest to your given pressure altitude. This can be read directly from the altimeter if it is set correctly. You can try to interpolate between lines, but to be safe pick the next higher value.

Next, move horizontally to the first reference line. From there, follow the slope of the lines until you intercept the x-position which corresponds to your aircraft's mass. If you start between two lines, you should move such that the relative vertical distance to the neighboring lines does not change. Note that the take-off mass is also a value you should know already if your preflight was done properly.

From that point, jump off horizontally until you intercept the next reference line. Depending on wind direction, follow either the dashed or the solid lines until you arrive at the x-position which corresponds to the wind component in runway direction. You will note that for headwind you will move slightly down, so headwind shortens the take-off distance. Makes sense, right?

The last panel helps you to find both the take-off roll (obstacle height zero) and the take-off distance over a 50 ft obstacle. Here you can only extract the values at the x-positions 0 and 50 and interpolation will not work. The y-axis all the way on the right now will tell you the distances in feet.

The reference lines show the values for the standard take-off at MTOW and calm wind. The examples given by the red lines are for two different situations:

Solid red line: OAT is 90°F, pressure altitude is 2000ft MSL, take-off mass is 2500lbs and with a headwind of 20kts the take-off roll is 500ft. At this point your speed should be 62kts (see table).  This is the result for your first question.
Dashed red line: OAT is 15°C, pressure altitude is 6000ft MSL (rounded up from 5650ft), take-off mass is 2950lbs and with a headwind of 9kts your take-off roll is 1400ft and the distance needed to clear the 50ft obstacle at 1.3*stall speed is 2300ft.


Could an airliner with only one functioning engine recover from a stall?

Yes, but the challenge is managing the asymmetric thrust effects when applying power during the stall recovery.
Pilots are trained in the sim for two stall (actually, just stick shaker onset) situations: high altitude and low altitude.  Low altitude stall recovery training is normally done by slowing until the stick shaker starts, then adding max thrust while lowering the pitch attitude moderately, only enough to keep the speed just above stick shaker onset.
The objective is to minimize altitude loss while accelerating.  The training doesn't actually get the airplane to a full aerodynamic stall; pilots are trained to start the recovery as soon as the shaker goes, which is still a few degrees below the actual stall AOA (as a rule, only production or experimental test pilots will take airplanes past stick shaker right into the natural stall, or stick pusher activation if equipped with one).
I don't believe anybody actually trains for stall recovery while single engine (I never did when training on the CRJs).  In any case, if you had to deal with that, you just have the added complication of managing the yawing motions caused by the asymmetric thrust, and the much more sluggish acceleration, so in addition to managing pitch, you are pretty busy with your feet to keep the airplane straight, and you would have more altitude loss.
At high altitude, it's similar, except that the recovery maneuver is much more aggressive in the thin air. With little to no reserve power, you pretty much have to dive to gain speed, and you cover a lot more distance through space to get the same indicated airspeed rise than at low altitude, so the indicated speed increase is slower.
So you pitch over a lot more, with no effort to minimize altitude loss and you let the airplane dive and wait for the speed to come up. If you were single engine (you would be descending anyway to single engine ceiling if you were) you would be doing the same sort of fancy footwork to allow for the asymmetric thrust and keep the plane straight, to the extent that you have thrust to work with to help accelerate.
So you could say a single engine stall is perfectly recoverable, but the extra workload increases the chance of secondary problems from mishandling (like secondary stall).


Do bluetooth aviation headsets and/or music negatively affect safety?

To my knowledge there are no studies correlating ANR (or good quality passive) headsets with an increase in pilot error, but a several have been done on noise fatigue. There's even an old FAA advisory circular on the subject which basically boils down to "Multi-hour flights listening to the engines drone on and on will make the pilot cranky and error-prone"  - so from that perspective any good-quality headset is a safety enhancement.

As far as missing auditory cues because of ANR (things like the stall warning, funny engine noises, etc.) it's generally not a concern: ANR headsets are good, but they're not THAT good. Because of the way ANR works sudden sounds will cut through. You'll miss "long-term noise" (like the beat frequencies Falk mentioned from unsynchronized propellers), but you're not likely to miss anything safety-critical.
(One notable exception: ANR headsets are good at cutting out wind noise, so if you have a partially unlatched door you won't hear that.)

What you will notice with ANR headsets is that when the battery dies things get loud - sometimes louder than cheap passive headsets. Carrying extra batteries is a must with ANR headsets since having your noise reduction go away in the middle of a flight would be somewhat unpleasant.

As far as music, that's a mixed bag.  Much like having a CD playing in your car, I don't believe it's a significant safety impact unless you're being irresponsible with it (blasting it at a volume that drowns out everything around you, or rocking out when you should be watching for traffic).

Additionally, all the intercoms and headsets I've seen give the com radio priority, and will either cut out or substantially mute the music input when there's radio traffic.  This makes you less likely to miss radio calls, but it also makes listening to music in the plane an absolutely DREADFUL experience (in the northeast where I am there's always somebody talking on the frequency - if you hear half of the song between the radio cutting in it's a good day).

I personally find the distraction from the music muting/unmuting to be more of an issue than boredom from not having music in the first place (if you're that bored you can always look out the window, or tune a local CTAF frequency and listen to the antics), but your experience may vary substantially if you're in an area where the radio is quieter.

Policies for commercial pilots would vary depending on the operation, but for airline pilots using your personal cell phone is forbidden, and before it was forbidden by the FAA it was usually prohibited by the airline.

Part 91 operations (a ferry flight, or a crop duster spraying the local fields) wouldn't be subject to that restriction though, and making a phone call or listening to music would be permissible under the FARs. With all the studies on the negative safety effects of using a cell phone while driving I wouldn't recommend the phone call, but I imagine crop dusting is more fun if you have some music to listen to…


Are they really?

In a high wing aircraft the center of lift is above the center of gravity. This will not increase stability when the aircraft banks, however, as you rightly say, will help once the aircraft is in a sideslip. In order to keep the fuselage at an angle to the airflow, the wing has now to create a sideways lift component, which it does by flying at an angle to the horizontal. This roll angle of the aircraft will shift the center of gravity sideways, so it is not exactly below the center of lift, but offset laterally. This lateral offset seems to produce a rolling moment which works against the roll angle.

Below I sketched the major forces in a sideslip. Note that the aircraft has a sideways speed component which creates a side force on fuselage and tail (green) which needs to be counteracted by the sideways component of lift (blue).

Short Sandringham in sideslip (based on this source)

But still the weight (black) is attacking at the center of gravity, so it will not roll the aircraft, and the lift is in the vertical plane of symmetry, so it, too, will not create a rolling moment. Ergo, we have no stabilizing effect due to the high wing location!

In a sideslip of a high-wing aircraft the windward wing root will see a slightly increased angle of attack while the leeward wing root will experience a reduced angle of attack due to the crossflow around the fuselage. This would indeed create a rolling moment because it will shift the center of lift sideways, out of the plane of symmetry. In a static sideslip the pilot will deflect the ailerons to maintain the roll angle as well as the rudder to maintain the sideslip, shifting the lift vector back into the vertical plane of symmetry. Now any stabilizing effect of the lift asymmetry is on purpose cancelled by the pilot!

However, this is achieved in a low wing airplane by adding dihedral. Therefore, a low wing aircraft can easily be made as stable as a high wing aircraft in a sideslip.

You will notice that the lateral aerodynamic force (green) acts above the center of gravity and also produces a correcting rolling moment. This is dictated by the location of the vertical tail, which contributes little to the location of the center of gravity, but produces a considerable share of the lateral force (reduced in the sideslip case by rudder deflection, however). This rolling moment, though, is almost independent of wing location. In a low wing, the center of gravity will be lower in total, especially when the engines are mounted on the wing, so the rolling moment contribution of the vertical tail is somewhat higher. The effect is small in a sideslip since the rudder deflection means that the fuselage contributes the majority of the side force. And this is not the pendulum effect which you asked about and which does not exist.

In airships, the pendulum effect is real, however: Since buoyancy always acts against gravity, a lateral offset of the heavy gondola will create an uprighting moment, just as it does in a pendulum. When turning, the heavy gondola will be pulled sideways by centrifugal forces, and the airship will roll. Since the turn is commanded with rudder, the rotation will give the rudder a small nose-down moment, which must be compensated by a nose-up elevator command. The pendulum effect will ensure that the gondola is at the lowest point in straight flight.

P.S.: Thanks to the hint of @kepler22b I have now discovered the keel effect page on Wikipedia. It also mentions the pendulum effect and calls both the fuselage contribution to the dihedral effect. Man, if there is ever a competition for the most misleading name of an effect, this would be the winning entry.

A pendulum is a mass mounted below the hinge point, so it will stabilize in the down position. A flying airplane is not hinged, so all motion is around the center of gravity. There simply is no pendulum effect in airplanes.