Are there any companies that use atom interferometers in aircraft?

Probably not.

The 2012 paper Advances in Atomic Gyroscopes: A View from Inertial Navigation Applications* states in the abstract that "there are still lots of problems that need to be overcome to meet the requirements of inertial navigation systems." Even once atomic inferometer gyroscopes are able to meet the basic requirements of inertial navigation systems, it will take years of testing and certification before they will actually be used in production aircraft.

I highly suggest reading that paper if atomic physics is your thing, but for us the conclusion is gold:

  Recent progress on atomic gyroscopes has demonstrated that AIG is an
  ultra-high precision gyroscope for strategic grade inertial navigation
  in the future, and ASG is a high performance gyroscope which features
  both high precision and compact size. There are still lots of problems
  that need to be overcome when considering the atomic gyroscope for
  inertial navigation applications, however with the technologies
  available in the near future, the AIG could be used in space for
  fundamental physics research, the ASG based on comagnetometer can be
  used in strategic grade gimbaled INS, and the navigation grade ASG
  based on NMR can be demonstrated on chip-scale size. Furthermore, with
  the development of new theories and technologies for atomic
  manipulation, the future of high performance inertial navigation
  applications using AIG and ASG is indeed bright.

I would be slightly more cynical about time scales than this paper. This intro to INS notes on page 5 that it took 18 years for ring laser systems to reach maturity. No current atomic gyroscope system can meet the performance of ring laser systems, and the highest-performance AIG systems are on the order of a cubic meter. Chip-scale ASG systems have been produced, but their performance is dreadful compared to mechanical or ring laser systems.

*Note: I'm not sure how much to trust this article. It's published in a peer-reviewed journal, but there are clear copyediting errors. I don't have a better source, though, so I'll trust it for the purposes of this question. Also, note that this paper does not only have aviation users in mind; there are a lot of references to strategic INS, which I think refers to submarines, and it also talks about INS in the context of satellites.


How many of the airliners that ever existed have been lost in flight?

Okay, let's try for a first approximation. Some heavily-produced airliners; for simplicity I'm only counting jets. (ie, I don't want to try and work out how to deal with the DC-3...)

A320 family. 7481 built, 35 hull losses (0.5%)
A330. 1330 built, 11 hull losses (0.8%)
Boeing 727. 1832 built, 118 hull losses (6.4%, mostly out of service)
Boeing 737. 9401 built, 184 hull losses (2.0%)
Boeing 747. 1528 built, 60 hull losses (3.9%)
Boeing 757. 1050 built, 8 hull losses (0.8%)
Boeing 767. 1097 built, 15 hull losses (1.4%)
Boeing 777. 1467 built, 6 hull losses (0.4%)
DC-9. 976 built, 101 hull losses (10.3%, mostly out of service)
MD-80. 1191 built, 35 hull losses (2.9%)
Tu-134. 854 built, 69 hull losses (8.1%, mostly out of service)
Tu-154. 1026 built, 69 hull losses (6.7%, mostly out of service)

This is a partial list, but it includes (I think?) every type with around 1000 or more examples built. It is thus probably representative of the general population of jet airliners. Total 29,322 aircraft, of which 711 (~2.5%) were eventually hull losses.

Now, not all hull losses are flight accidents - there are ground fires, accidents, military action, hurricanes, all sorts of other things - but the majority are. It's probably reasonable to estimate that the overall hull-loss-due-to-flight-accidents-so-far rate is thus a little lower, around 2%, but probably not much below that.

Now, it's worth noting that this isn't quite the same as

  If you were born as an airliner, what is the probability that you would die at work?

...because some of these aircraft will probably be hull losses, it just hasn't happened yet. If Boeing stopped building 747s tomorrow but airlines kept flying them, the hull loss rate would steadily creep up over time until all examples were either crashed or retired. So if you want to work from that perspective, the "eventual accident rate" will be higher. I've flagged the ones which are nearly completely out of service, where these will be approaching a "lifetime" loss rate - they're noticeably higher than the others.


Why doesn't civil navigation equipment support TACAN?

Civilian aircraft can use part of TACAN, the Distance Measuring Equipment (DME) signal is the same as civilian DME. As for the directional component one big reason is that the military don't want you to.

Even if the military didn't mind there would likely be no demand as the costs of using TACANs outweigh the benefits. TACAN is essentially a more accurate version of VOR, and although the complexity and weight of the system has reduced the antenna is still apparently 100 pounds (45kg). For light aircraft that's a fair chunk of useful weight taken off. Cost-wise a VOR setup will set you back somewhere around \$6000 just for the equipment, call it closer to $8000 installed (roughly). A TACAN is a more sophisticated system which would cost a great deal more, say finger in the air of \$20,000, maybe more. TACAN antennas would need to be certified for every single airplane model, and that's going to add to the costs.

So for a light aircraft I'm going to lose usable weight to an antenna that is also going to throw off my weight and balance, and that's going to cost me at least \$20k when all the equipment, installation and recertification costs are factored in. That's big cash when I already have VOR, ILS, DME, NDB and 3+ satellite navigation systems already available. Oh, and I can also call up ATC most places and say 'help!' if it all goes wrong. There's just no benefit. My phone can tell me where I am if every system on the airplane fails as it has a built in GPS!

For commercial large airplanes it's the same situation. In addition to all the above most will have redundant inertial navigation systems, so even less need for it.


What accidents have had crew accustomization to warnings among their causes?

A notable accident was the Helios Airways Flight 522 crash, where the pressurization system was turned off and the pilots ignored the warning horn because they thought it was the takeoff config warning. From the Wikipedia page:

  As the aircraft climbed, the pressure inside the cabin gradually decreased. As it passed through an altitude of 12,040 feet (3,670 m), the cabin altitude warning horn sounded. The warning should have prompted the crew to stop climbing, but it was misidentified by the crew as a take-off configuration warning, which signals that the aircraft is not ready for take-off, and can only sound on the ground.

The official accident report explains the source of the confusion in more detail (emphasis mine):

  The Board examined the flight crew’s actions to disengage the autopilot and auto-throttle,
  and to retard the throttles upon onset of the warning horn. Given that the expected
  reaction to a cabin altitude warning horn would have been to stop the climb (there was no
  evidence to this effect), the Board considered such actions to signify that the flight crew
  reacted to the warning horn as if it had been a Takeoff Configuration Warning (the two
  failures use the same warning horn sound). [...]

  The warning horn was designed to signal two distinctly different situations. The Board
  considered the role of experience in interpreting and reacting to the warning horn. In the
  course of his career, a pilot is generally likely to only hear the warning horn when it is
  associated with a takeoff and a takeoff configuration problem. [...]

  Most pilots are not very likely to experience a cabin pressurization problem and the
  associated warning horn at any time during their line flying.

Conclusion: Never use the same warning for multiple situations, if the pilots will only get used to one of them, otherwiese they will ignore the warning for the other situtations!


Do the polar curves have large differences in takeoff than in landing?

The $C_L(\alpha)$ curve changes with flap/slat extension, so it should logically follow that the polar will also change, since the induced drag depends on the lift.

Furthermore the parasite drag will most likely change as well due to a changing airfoil surface.

So yes, the polar needs to be recalculated for all flight configurations.


For the CFIs, CFIIs, MEIs, and AGIs - How often do you find students that utilize your ratings?

First off, it depends on what kind of flying you want to do.  Remember a flight instructor certificate is not required to fly an aircraft, either personally or professionally.  The problem comes in that most professional flight jobs, either under part 121 or 135 require over 1000 hours total flight time and in some cases over 1500 hours TT.  For a budding pilot with no other sources of income, this becomes almost insurmountable without doing flight instruction, as you’re legal to do this with 250 hours TT, a CPL, INST-A, and a CFI.  If you do go the instructor route, the ratings you get for a flight instructor certificate all depend on what you’re going to do as an instructor. Instructor pay is based upon 1) the number of ratings that you have and 2) your dual given time.  Remember, the more ratings you have the more flexible your employment options are; CFIs with 152/172 time are a dime a dozen.  MEIs command the greatest salaries, though some schools only pay top dollar for multi engine dual instruction hours.  Many schools today won’t employ you without at least a CFII (welcome to the insanity of flying for a living!).  As to AGIs or IGIs, it again depends on the size of the flight school and the number of ground courses being offered.  You can also do this as an independent contractor, but you will also have to recruit clientele, this is work in and of itself.  Large Part 141 flight schools may have dedicated ground instructors for ground school, or may simply require new hire CFIs to hold ground instructor ratings.  Ground instructor ratings are relatively easy to obtain; some home study followed by a testing fee of $300 or so for both the FI and AGI will get you one.  Typical ground instructor pay is lower, on average, than flight instructor pay, but it all depends on your ratings and experience.
If you’re interested in making money as a CFI, my advice is to specialize.  As I said before a CFI with dual time in Cessnas is so common that it doesn’t command much in pay in and of itself.  Someone who can do, say, multi-engine, tailwheel, basic and advanced aerobatic training, CSIP certified, type ratings, seaplane rated, mountain flight training, warbirds, helicopters, gyroplanes, etc. can command over six figures as a CFI.  The downside is that obtaining these additional ratings will cost hundreds of thousands of dollars so entry becomes prohibitive.
Now as to the numbers of people who become pilots and then flight instructors vs come through the door with an interest in flying, I’m not sure but I’d venture a guess that around 75% won’t even solo.  Most people take a general interest in learning to fly then quit after a few flights from 1) the cost and time required to train, 2) medical or other barriers which prevent them from pursuing flight training and 3) the difficulty of flight training - many people expect something similar to the standards of US Driver’s Education or an MSF basic rider course and become disenchanted with flying when they can’t learn in a weekend by reading a 40 page booklet with a few flights.  In the United States there are only about 600,000 licensed Pilots in a country of 300 million.  Doing the math this works out to be about 1 in 500 people hold a Pilot certificate.  Pilots holding instrument ratings are around half of the total ie about 300,000.  Commercial, and Airline Transport Pilots - professional people who fly for a living - are around 100,000 and there are about 100,000 active flight instructors in the US as well.  You can check the FAA’s Airmen Statistics for more precise figures.  So if we go by the numbers of students at a typical flight school, out of 100 new people off the street, on average, only 25 will become licensed pilots.  Of those 25, 12 will get instrument ratings and 6 will go onto obtain commercial certificates and flight instructor ratings.


What is the minimum speed for a scale-model of a modern commercial aircraft to fly?

If you scale down the structure of a modern airplane, it would work nicely. Since volume scales with the third power of length, but area scales with the second power, the wing loading would decrease with the scaling factor. Therefore, the dynamic pressure required to fly would also decrease with the scaling factor, as would all aerodynamic pressures. This means that all stresses within the structure will also come down, so the structural safety margin increases with the scaling factor.

What scales less nicely are the flow phenomena. The Reynolds number will come down with the 1.5th power of the scaling factor (1 power for the length and 0.5 power for the reduced speed), so the boundary layer would be relatively thicker. This would reduce the maximum lift coefficient and would make the gaps between the high lift devices of the wings (slats, flaps) too small to work properly. A simple logarithmic scaling law works well only over small changes and can not be applied here. After all, the scaling factor is close to 60. I would guess that the maximum lift coefficient is only half of what it is for the real aircraft, so the take-off speed is reduced by a factor of $\sqrt{0.5\cdot scaling\;factor}$. If the take-off speed of the original is 260 km/h, the model could take off at maybe 45 or 50 km/h.

This is quite a bit lower than the speed of the original aircraft, but still too high to fly it comfortably in a park. A wide open field would be more suitable.

At the same time, the relatively thicker boundary layer means the drag of the scaled aircraft is relatively higher, so the L/D of the aircraft comes down. Unfortunately, the flow inside the scaled gas turbines will also be negatively affected by the Reynolds number, so they will produce little thrust. In all, I am quite sure that the scaled Airbus or Boeing would not be able to accelerate to the required take-off speed since both drag increase and thrust loss due to scaling will make this impossible.

I saved the hardest part for the end. The flow in the tiny hydraulic lines would be thick as honey (but you could increase the hydraulic pressure by the scaling factor before the lines burst!), and scaling all control circuitry would result in electronic components which would cease to work completely.

In the end, my answer would be a clear no. It will require a lot of adaptions, and only then a scale model could be made to fly.


What is the belly pod on this Beech A200 Super King Air?

Short answer
It seems to be a US Army CEASAR pod, a communication intercepting and jamming system for electronic warfare, which has been flown in Iraq and Afghanistan. CEASAR is derived from AN/ALQ-227 EA used by US Navy on the EA-18G Growler.
The aircraft is equipped with missile detection and countermeasures. Two sensors are below the cockpit windscreen, two other on the aft fuselage. The chaff is released by a dispenser aft of the pod.
N40R is N46L's sister aircraft, and it also carries a CEASAR pod. The A200 variant used may be a C12-A or a C-12C (this is the model number visible on N40R fuselage). They are also known as Huron and HC-12.
High definition photo of N46R:

Photo by Keith Newsome on photobucket (source)
Detailed answer below.

About CEASAR
From Stars and Stripes:

The CEASAR, which stands for communications electronic attack with
surveillance and reconnaissance, is a rectangular metal box that holds
technology capable of both knocking out cell phones and radios and
intercepting transmissions, while an electronic warfare officer
onboard speaks directly to troops on the ground. It’s precise enough
to cover friendly soldiers while jamming insurgents, but not knocking
out communications for an entire village near a given operation.

From matthewaid.com:

Contractors Continue Flying CEASAR SIGINT Aircraft in Afghanistan
The CEASAR system mounted in these contractor-owned and
government-operated (COGO) aircraft is based on the Raytheon
AN/ALQ-227 EA system as fitted to the US Navy’s (USN’s) Boeing EA-18G
Growler electronic warfare (EW) aircraft. It is designed to provide
both a communications jamming and an intercept/monitoring capability.

CEASAR UAV replacement
Flying CEASAR on a modified A200 was already very much cheaper than using a pod on a fighter. However like for other functions, military are looking at using unmanned aircraft. The NERO pod has been designed for this purpose.
From Defense Systems:

NERO jams aboard a drone in Army test
The Army recently tested a jammer called the Networked Electronic
Warfare Remotely Operated, or NERO, attached to a Gray Eagle unmanned
combat aircraft at the Great Salt Lake Desert at Dugway Proving
Ground, Utah.

Missile Warning System AN/AAR-47
Closer view (N40R):

It detects infrared or radio sensing from a missile and commands a response, e.g. release of chaff or flare using the countermeasures dispensing system aft of the pod.
Two other sensors are located on the aft fuselage.
Sensor detail on another aircraft:

(source)

About the aircraft
From FAA, King Air A200, CN BC-1 thru BC-61 are variant C-12A used by US Army.
From JetPhotos.net this aircraft is used under call-sign Grizzly 23:

Registration: N46L
CN: BC-56
'Grizzly 23' taxies for departure to Wick.this is one of a number of
aircraft owned by Dynamic that operate on behalf of the US Army.

There are two C-12 aircraft equipped with CEASAR. The other is registered N40R, with call-sign Grizzly 12:

(source)
Huron are seconded or being replaced by Dash 8.


What is wrong with my understanding about total pressure for a rocket nozzle?

I'll just answer my own question thanks to Koyovis' comment  :)

Koyovis was right - I didn't realise the difference between how dynamic pressure is calculated for compressible vs incompressible flows.
There are some useful notes on it on pages 4-8 of this link (http://mae-nas.eng.usu.edu/MAE_5420_Web/section5/section.5.5.pdf)

In summary:
Bernoilli’s equation is

$Total Pressure = P_{static} + P_{dynamic}$

For an incompressible flow,
$P_{dynamic} = 0.5\rho v^2$

For a compressible flow, use the isentropic equation
$P_t / P_{static} = (1 + \frac{\gamma – 1}{2} M^2) ^ {\frac{\gamma}{\gamma-1}}$

To get this in a way you can compare to Bernoilli's equation, make total pressure the subject of the equation, add & subtract $P_{static}$ from the right hand side, and rearrange the equation slightly (shown in the link above) gives:

$P_t = P_{static}  +P_{static} ( (1 + \frac{\gamma – 1}{2} M^2) ^ {\frac{\gamma}{\gamma-1}}-1)$

This is the same form as Bernoilli’s equation where the dynamic pressure is:
$P_{dynamic}=P_{static} ( (1 + \frac{\gamma – 1}{2} M^2) ^ {\frac{\gamma}{\gamma-1}}-1)$

Putting in the values from the example gives the correct result.


Why do some cargo aircraft have windows?

Some cargo aircraft do have limited seating, as mentioned in the comments it could be for the relief crew, load officer, or other employees making a hop on the plane. Here is a nice blog post about  flying in a cargo plane. This article covers it pretty well also.

(source)

Some cargo planes are also old passenger planes and some of the windows may be left in place.


How are the wings of a mono- bi- or triplane referred to with regard to position?

While boats use port & starboard, aircraft (at least in the U.S.) generally don't.  "Left" and "Right" work well for most things; when talking with flight attendants (on a large aircraft), "captain's side" and "first officer's side" serve the same purpose as "port" and "starboard" (i.e. the port or captain's side is the same side of the vehicle, regardless of whether it's on an individual's left or right at the moment).  For maintenance purposes, the engines and certain other left/right-side components are referred to as the #1 and #2 (and #3 and #4 if you have them), and when talking with a pushback crew (who are in front of the airplane facing it -- so their "left/right" is opposite that of the pilots) it's common to refer to "the #1 side" (i.e. captain's) or "the #2 side" (i.e. F/O's).  When we would back up the C-130, the loadmaster on the cargo ramp looking behind us would direct "turn toward #1" or "turn toward #4", which worked out nicely.
But, I don't think I've ever heard of wings referred to as #1 & #2, or really as anything other than left & right.  (Those who've flown on aircraft carriers may report a different experience while at sea, I've not done that.) I'd say that the most general case would be to refer to a left/right wing, or on a biplane left upper, right lower, etc, and in a triplane, I'd have to assume left middle (or, perhaps less likely, left center) wing.
The Nav lights are generally referred to as left or right, at least in my carrier's operation.  You could refer to them as "the red nav light" or "the green nav light" but I don't think that's particularly common.
Various different organizations will have their specific conventions, but as a general case, plain (or, "plane") English works well & is a good place to start until the preferred local terminology is introduced.


How to sign hours on Logbook if doing aerial work in right seat on single pilot aeroplane?

I am not sure about EASA regulations but in the US you can log PIC time whenever you are the sole manipulator of the controls and properly rated to fly the aircraft.  In the US there is a distinction between the legal PIC (person legally responsible for the flight) and PIC time which is the person actually flying the airplane.  Since the plane is certified for only single pilot operations you can only log PIC time not SIC time and only when you are the sole manipulator of the controls.  The FAA regulations for logging time can be found in FAR 61.51.


What do pilots actually see through the windows?

This really depends on the type of aircraft and the seating position of the pilot. In smaller aircraft, you will have a good view of the area around you, depending on the canopy. In larger aircraft, the instrument panel and cockpit design can restrict your outside view a bit more.

Below you will find two pictures taken from the cockpit of a Super Dimona HK36, used for VFR general aviation flights. Both are approximately at eye level.

(Source: Own Work - SentryRaven)

(Source: Own Work - SentryRaven)


Who inspects commercial aircraft seats for defects (and when)?

Apart from what ymb1 and Zach Lipton mentioned, the passenger and flight crew seats are thoroughly inspected during the scheduled maintenance of the aircraft, in which the aircraft can be grounded for several days up to some weeks. Depending on how extensive is the maintenance check, the following items can also be inspected amongst others:

Condition of seat floor attachment fittings for tightness.
Reclining function, except those before and after the emergency exits (these must not recline at all).z
Removal of the seat cushions in order to inspect the seat structure.
Periodic replacement of all seat covers (washed or new).
Seat belts for condition, operation and proper attachment to the seat.
Life vests for presence, condition and expiration date.

Sometimes, when the repair is beyond the capability or the approval of the maintenance center it can be sent to a specialized seat overhauling center.

For more information and fun you can check the British Airways B747 D-check video


What does this indication of '10∼15 degree' that points toward the both edge of runway means?

That image is intended to describe REIL.  REIL are are two synchronized flashing lights. They can be either omnidirectional or unidirectional facing the approach area.  Unidirectional REIL are preferred.  More information is found in AC 150/5340-30.

Installation requirements are in section 7.7.5:

  7.7.5  REIL.

  7.7.5.1 Location.
  Locate and aim the REIL units per Figure A-79.

  7.7.5.1.1 When possible, install the two light units equidistant from the runway centerline.

  7.7.5.1.2 When location adjustments are necessary, the difference in the distance of the two lights to the runway centerline may not exceed
  10 ft (3 m).

  7.7.5.1.3 Each light unit must be a minimum of 40 ft (12 m) from the edge of taxiways and other runways.

  7.7.5.1.4 The elevation of both units must be within 3 ft (0.9 m) of a horizontal plane through the runway centerline, with the maximum
  height above ground limited to 3 ft (0.9 m) (See Figure A-93.)

  7.7.5.1.5 When the centerline elevation varies, use the centerline point in line with the two units to measure the centerline elevation.

  7.7.5.1.6 Orient the beam axis of an un-baffled unit 15 degrees outward from a line parallel to the runway and inclined at an angle 10 degrees above the horizontal.

  7.7.5.1.7 If this standard setting is operationally objectionable, provide optical baffles (per the manufacturer's instructions) and orient the beam axis of the unit 10 degrees outward from a line parallel to the runway centerline and inclined at an angle of 3 degrees above the horizontal.

As described here, the 15 degrees is the horizontal alignment, and the 10 degrees is the elevation alignment.


What is this hole above the intake of engines of Mil helicopters?

This link claims it's the central oil cooler intake for the Mi-26.


What are the WAAS requirements for RNAV (GPS) approaches?

(skyvector.com)

This is a random RNAV (GPS) approach. The answer is it depends on the minima, I highlighted above two examples.

The LP (WAAS / SBAS) approach requirements can be found in the FAA AC 90-107.

To fly the LP approach, the GPS unit on your plane (among other things) needs to be LP certified. For example, a Garmin GNS 480 unit is LNAV/VNAV approach approved, and only LP approved if you have software 2.3 or later installed.

If you want the regulatory requirements, then check the AC linked above and all the referenced technical documents (such as TSO-C146). If you want to check the capability of your GPS unit, then refer back to the manufacturer.


Has the F-35 Lightning II overheating problem been resolved?

As to the first question, it appears as fuel cooling of electronic components and other equipment is integral in the F-35 design, all branches of the armed services will not be able to remedy this problem and it will have to be solved with only fueling the aircraft with cold fuel.  The Air Force has opted to use fuel trucks painted white in order to keep fuel cool while on the ground and it may require refrigeration equipment in fuel tank farms at F-35 bases at an additional cost to the program.

The fuel problems for the F-35 are but one of several hundred faults, shortcomings and outright vulnerabilities with the troubled Joint Strike Fighter program.  While developmental issues are common in new aircraft programs, none so far have been this serious, so numerous and so overbudget without being killed.


Is it legal to listen to aviation frequencies in the UK?

Yes, you can purchase a scanner - these are freely available in the UK.

No, legally, you can't listen to air traffic control. However, in real life, this is generally not enforced. Go to any airshow or airport observation area and you'll find people using scanners openly.


What does a dollar sign mean in a METAR?

A maintenance indicator sign, $, is included when an ASOS/AWSS (Automated Surface Observing System / Automated Weather Sensor System) detects that maintenance is needed on the system.

Reference: http://www.faa.gov/documentLibrary/media/Order/JO%207900.5C.pdf

Or if you need an easy way to remember it, courtesy of the awesome Ralph J:

  It means that they need to spend some money to fix whatever is broke on the automated reporting station!


What happens at the wings when the yoke is pulled backwards?

Most aircraft have control surfaces that work in a similar manner from a little Piper up through a 747. Forward and back movement of the yoke or stick typically results in actuation of the elevator. For aircraft that have the common style empennage the wing remains unchanged. For aircraft that have elevons they move accordingly.

Pulling away from the front of the aircraft on the control column causes the aft end of elevator to move upwards relative to the airframe. This action causes the aircraft to pitch nose up.

Pushing towards the front of the aircraft on the control column causes the aft end of the elevator to move down relative to the airframe. This action causes the aircraft to pitch nose down.

Take a look at this GIF for a nice animation or this video.


Why do the outer parts of wings generate less lift?

The outer wing section generates less lift because flow around the wingtips reduces the pressure difference between both sides. This effect dies down quickly when moving inboard, but will still reduce lift somewhat at the wing root.

Screenshot of the Stanford Aero wingcalc page. This is a Java page for which you need to add http://aero.stanford.edu/wingcalc.html to the exceptions list in Java. Then you can change aspect ratio, wing sweep, taper ratio and twist. Here the lift distribution for an unswept, untwisted rectangular wing is shown which has a local lift coefficient of almost 1 at the center. Due to the low aspect ratio, wing efficiency is still at 99%

A rectangular wing can be optimal if stall characteristics and ease of construction are included:

The lower lift coefficient at the tip ensures that the stall starts at the wing root, resulting in a docile stall behavior without a sudden rolling motion.
The constant chord allows to use one single jig for building all ribs of a wooden wing.
The shorter root chord of a rectangular wing requires a heavier spar, but when wings are braced and the root bending moment is low, the weight impact is negligible.

If the goal is a simple to build aircraft with forgiving stall characteristics, the rectangular wing will be an efficient choice, especially when bracing is used. Only when performance is most important will a rectangular wing be less efficient than a trapezoidal wing.


Is it possible to obtain the lift and drag coefficients of a 3D body in ANSYS Fluent?

Yes this is possible, and it is the way lift and drag of aircraft are estimated in the pre-design phase. There is detailed methodology described in Synthesis of Subsonic Airplane Design by E. Torenbeek, Appendix E. for lift and pitching moment, Appendix F. for drag.

For lift and pitching moment, first the wing characteristics are estimated based on known research and on corrections for fuselage length, wing/body interference length etc.

For drag, first the $C_{D_0}$ of all components in the table underneath are determined, and then the lift of the wing, body, tailplane etc as function of angle of attack are added.


Why don't passenger aircraft use the trijet configuration anymore?

The fewer engines an aircraft has, the lower are its operating cost. Engines are the most maintenance-intensive part of an aircraft, and doing a hot section inspection on two large engines costs less than doing it on three somewhat smaller engines.

When the tri-jets were developed, no sufficiently large and powerful engines were available. They were already cheaper to operate than the four-engined aircraft, and too large to have sufficient power with just two. Now, with engines which can deliver a static thrust of more than 100,000 pounds, everything below a Jumbo Jet or an A380 can be powered with just two engines.

Another reason is increased engine reliability: With three or four engines, an engine failure is less of a problem than with just two engines per airplane. Previously, route planning had to keep a maximum distance of 60 flight minutes to a diversion airport. In 1964, this was waived for three-engined aircraft, but twins were still bound to this restriction. With more experience and better engines, this rule has been relaxed for twins gradually to 120 (1985), then 180 (1988), and now 370 (2014) minutes for the Airbus A350 XWB, and twins have become much more versatile for their airlines.

Some of the old tri-jet designs were quite popular with operators: The last Tupolev Tu-154 was built only in 2013. But besides the Dassault Falcon 900 and 7X business jets, I don't know of any trijet which is still in production.


How is the actual ground speed of an airliner measured?

There are generally two ways of determining the ground speed from within the aircraft.

The first is by using an inertial navigation system. This consists of a number of accelerometers and gyroscopes that measure all accelerations and rotations of the aircraft throughout a flight. By mathematically integrating all measurements this navigation system is able to compute the speed and position of the aircraft at any time. The accuracy will degrade over time but ground speed is usually not far off, otherwise position would be far off very soon.

The second method uses external radio signals. Nowadays this is mostly GPS, but ground speed is also determined by using a number of VOR (VHF Omnidirection Range) and/or DME (Distance Measuring Equipment) stations. These navigation beacons are widely available over most continents. A navigation computer would select the right set of beacons and by analysing the rate of change of the beacon bearings / distances the aircraft's speed can be determined.

Modern navigation systems combine all these methods into a one solution. GPS, inertial navigation and DME measurements are then fused mathematically together to obtain a highly accurate and robust position and ground speed.


Why is ARP (Airfield Reference Point) needed?

I don't know which country you are referring to.  These are countries that rely on TERPs for instrument procedures.
From the FAA TERPs Order 8260.3D

Definitions

Airport reference point (ARP). The official horizontal geographic location of an airport. It
is the approximate geometric center of all usable runways at an airport.

Page 2-16: The ARP is used to center the MSA on the airport.
Page 3-7:  The ARP is used to determine the distance requirements of remote altimeter settings.
Page 11-5:  The ARP is used to align the FAC with a circling only approach.
Page 14-31: The ARP is used to center the VCOA (Visual Climb over Airfield)


What are the defining characteristics of aviator glasses?

Aviators are nothing more than a marketing gimmick developed by Bausch & Lomb back in the 1930s.  The Wikipedia page on them quotes:

  They are characterised by dark, often reflective lenses having an area
  two or three times the area of the eyeball, and very thin metal frames
  with double or triple bridge (so-called ″bullet hole″) and bayonet
  earpieces or flexible cable temples that hook behind the ears. The
  original design featured G-15 tempered glass lenses, transmitting 15%
  of incoming light. The large lenses are not flat but slightly convex.
  The design attempts to cover the entire range of the human eye and
  prevent as much light as possible from entering the eye from any
  angle.

It’s possible that Bausch & Lomb referred to the style of sunglasses as aviators given the popularity of early aviation and barnstorming during the late 20s and early 30s. The brand really acquired notoriety and popularity during World War II when they were used by military personnel and began to get associated with flying. General Douglas MacArthur often wore them.  Postwar, the style became popular with a number of celebrities as well.


Why don't short runways use (downhill) ramps for takeoff?

it could always back-taxi on the runway before turning around and taking off.

So ... that would limit the steepness of the slope significantly, and thus the potential benefit.

Most other aspects are already covered by Bjelleklang's answer: Landing aircraft would either have to clear the obstacle before being able to touch down, or they'd fall over the edge if they don't brake in time (rather than, as these days, get stuck in the grass behind the runway end)


Can I get my IFR practical and oral examinations directly through the FAA if I can't find designated examiner?

In theory it's possible to contact the local FSDO and ask for a checkride with an FAA inspector, and it's free (see here, here, here). But personally I've never heard of anyone doing it and I can't even find anything on the FAA's website about it.

The FAA's statistics show that in 2016 there were 34,156 initial checkrides with DPEs but only 465 with FAA inspectors (two thirds of those were for ATP), so it's very unusual. That file also shows pass rates by DPE vs. inspector, by the way, and despite some online horror stories it looks like the pass rates were broadly similar.

FWIW, it's fairly common for candidates to travel/fly several hours to a DPE (see the FAA's locator tool), either because there isn't one available locally or because they want to use the 'right' one. I don't know what your friend considers "local" and how far away she's already looked, but she may want to just look further away. Of course flying somewhere adds some costs but if she's doing IR/CPL then it's probably a relatively minor cost compared to what's she already spent on training and it's another excuse to fly (if she needs one!).


Has an earthquake ever complicated or prevented a safe landing/takeoff?

Yes, there have been aircraft landing at the moment an earthquake hit. Here is an article about one in 2011: Air NZ plane landed as Christchurch earthquake hit

"It was creepy as... as the plane came down, you could see all the windows in the terminal just rolling, and all the shuttles that go out to the plane were in the tarmac just rolling.
"Somebody shouted out 'oh my god, it's an earthquake!'"
"We came down and couldn't get out, and there was a big shake while we were still in the plane. Then we sat there for an hour.

This is of course from the point of view of a passenger, not the pilots.


When do pilots engage the autopilot in airliners?

The minimum altitude for autopilot engagement is generally the acceleration height or around 400' AGL though this can vary between operators.

The question of when the autopilot is actually engaged is a more complicated question and is subject to pilot preference.  Personally, I generally hand flew until the first level off or until climbing and accelerating through 10,000 MSL.  Others may turn it on as soon as allowed and most fall somewhere in the spectrum between the two.


Are there any ILS approaches in Class E airspace?

There are plenty of ILS approaches in Class E surface area (e.g. KCLM, KHQM, KPWT). In fact the presence of an ILS will usually require that some kind of controlled airspace extends to the surface. For an untowered airport this means a Class E surface area.


How do instructors simulate instrument failure in basic training aircraft with glass cockpits?

For conventional instrument gauges, I recommend the disks above for blanking out the attitude indicator or the DG/HSI.  Post-It notes are also a common way to blank out instruments to be used.

For partial panel work in glass cockpits, manufacturers and pilot supply shops sell soft stickers custom made for this purpose.


Do paper airplanes fly like normal airplanes do?

No that’s wrong. Paper airplanes fly by the same physics that allows a 747 to fly.


Is passenger weight distribution important on a commercial flight?

On the EMB-145 the passenger cabin was split into 5 zones and we were given passenger totals in each zone from the flight attendant prior to leaving the gate.  If balance is off (this happened quite rarely for us) you would tell the flight attendant "I need 2 passengers from zone 5 moved to zone 1" or "I need a passenger from zone 3 moved to zone 2" or some other similar instruction.  The flight attendant would solicit volunteers and if no one did, they would instruct someone to move.  The move was only for takeoff and once airborne they could go back to their normal seat.

After moving passengers we would re-calculate the weight and balance to verify we were in the envelope and set takeoff trim.

Similar methods are used in larger airplanes with the cabin split into zones.

The only time we would use ballast is when we had a full cabin and not enough bags in the cargo (not common).  In those cases we would ask ops for ballast and they would put something in the cargo.  They would try to make it useful if an outstation needed something else they would just load 50 lb bags of sand.


What do the green, white and yellow bands mean on an airspeed indicator?

The FAA has a nice introduction document on flight instruments, which explains all the standard markings on a typical airspeed indicator (ASI):

  As shown in [the figure above], ASIs on single-engine small aircraft
  include the following standard color-coded markings:

  White arc—commonly referred to as the flap operating
  range since its lower limit represents the full flap stall
  speed and its upper limit provides the maximum flap
  speed. Approaches and landings are usually flown at
  speeds within the white arc.
  Lower limit of white arc (VS0)—the stalling speed
  or the minimum steady flight speed in the landing
  configuration. In small aircraft, this is the power-off
  stall speed at the maximum landing weight in the
  landing configuration (gear and flaps down).
  Upper limit of the white arc (VFE)—the maximum
  speed with the flaps extended.
  Green arc—the normal operating range of the aircraft.
  Most flying occurs within this range.
  Lower limit of green arc (VS1)—the stalling speed
  or the minimum steady flight speed obtained in a
  specified configuration. For most aircraft, this is the
  power-off stall speed at the maximum takeoff weight
  in the clean configuration (gear up, if retractable, and
  flaps up).
  Upper limit of green arc (VN0)—the maximum
  structural cruising speed. Do not exceed this speed
  except in smooth air.
  Yellow arc—caution range. Fly within this range only
  in smooth air and then only with caution.
  Red line (VNE)—never exceed speed. Operating above
  this speed is prohibited since it may result in damage
  or structural failure.

(FAA Handbook - Chapter 8 - Flight Instruments, emphasis mine)


In my experience, having permanent airplanes standing by as spares does not really happen. Based on historical data potential realtime spares, airplanes with potential availability on any given day, can be pinpointed for reschedule or delayed maintenance, should the need arise.

In reality, often the "spare" as you called it, is an airplane that can be pulled from another trip with a subsequent replacement available causing less delay than the flight generating the need for the spare in the first place.

At some airline "hub" locations, maintenance is being performed on aircraft and those aircraft can be used as spares, assuming the checks or maintenance is complete or can be delayed.

Two important points though:

It is extremely costly to have "extra" airplanes standing by to replace an aircraft that may go out of service.  Swapping aircraft is sometimes quite difficult because the type aircraft scheduled may not be available.  An alternate aircraft (different type) poses difficulty because the crew that was going to fly the B737 you were scheduled on, could not fly a substitute Airbus, for example (they either would not be qualified or not current/legal to fly the different type at a moments notice).
The airline's SOC (Systems Operations Control) or similar has a difficult challenge on most occasions dealing with maintenance delays or cancellations. It is not uncommon for the flight to just be cancelled and have the passengers put on later flights.  However, the airline's Operational management people are experienced at minimizing actual delays and maximizing aircraft utilization.


The F-22 is intended (and the competing YF-23 was intended) to be an air superiority fighter to replace the F-15.  The F-15 was a twin-engine model, as was the F-4 Phantom that it replaced.  Twin engine planes have excellent "survivability," meaning they can take a lot of hits and still stand a chance of making it home (you can lose an entire engine and still stay airborne).  They also are much higher-performance.  The F-15 can takeoff, stand on its tail and climb vertically to over 40k feet.  I've seen F-16s do something similar but they couldn't climb as high and they couldn't carry as much fuel and/or armaments while doing it.

The F-35 is intended to be a replacement for the single-engine F-16.  The F-16 is a capable workhorse but it's more of a budget, multi-role aircraft, meaning it was designed, from the get-go, to do some air superiority AND some ground attack, operating on a tighter budget.  We have considerably more F-16s in the Air Force inventory than we've ever had (or will have) F-15s and/or F-22s.

The F-15 used the same engine as the F-16 (two to choose from: either the P&W F100 or the GE F110), but two of them.  When I was in the Air Force

F-15's cost about USD 50 million
F-16's cost about USD 35 million

Two engines and a larger, heavier airframe (albeit less sophisticated) added up to a significant price premium.  In air combat, above 25k feet, my money would be on the F-15.  At altitudes below 25k feet, my money is on the F-16.  With an inherently unstable airframe and a computerized fly-by-wire system to tame it, the F-16 was wickedly maneuverable.  The increased power of two engines on the F-15 working against the greater weight really loses the advantage at lower altitudes.

The "buried" engines in the F-22/YF-23 are trying to improve the stealth characteristics.  The F-22's thrust vectoring, coupled with twin engines, make it more stealthy than the F-117 and faster and more maneuverable that the F-15 or the F-16.  The YF-23 was arguably faster, but less maneuverable.

The F-35 is intended to cost less than the F-22 (debatable as to whether that will be the final case).  And certain models of the F-35 are capable of a trick the F-22 simply can't match: STOVL.  It can do a Short TakeOff and Vertical Landing.  For the latter, the rear nozzle pivots downward 90% and a "lift fan" opens up in the forward fuselage.  The F-22 was never intended to be able to do this.  "Burying" the rear nozzle AND trying to do that would add a LOT of weight (and additional cost) to the aircraft.


How do I fly to Borrego Valley (L08) if it's inside a CA state park?

Having never flown into this airport before, I would study the sectionals and charts very carefully. The state park is one concern. There are specific notes on the sectional requesting aircraft to stay above 2000 feet. There are also restricted areas, military training areas, laser illumination areas, etc. all around the airport. Not to mention the rising terrain and obstacles as high as 7100 feet around an airport with a 522-foot field elevation and a 10,000-foot Minimum Sector Altitude. Then, the airport having to have a specific obstacle departure procedure is a big red flag for me.

If it were me flying into this airport, I would request flight following to the RNAV (GPS) RWY 26 IAP all the way in to the traffic pattern. Then, I would land straight in or circle to runway 8. The minimums are probably a full 1200 feet above the field elevation for a reason. Remember to circle South of the airfield (right traffic pattern for runway 8). And, do not overfly the area Northwest of the field nor the elementary school 1 nautical mile West of the field. This is from a quick glance of the charts and chart supplement.


Are we changing the angle of attack by changing the pitch of an aircraft?

First of all, note that the diagram linked in the question is erroneous.  The equations may be right, but the forces are drawn in the wrong proportion-- lift is erroneously shown as greater than weight, when it should be less than weight.  Also thrust appears to be about equal to drag, when it should be distinctly greater than drag.  Only when lift is less than weight and thrust is greater than drag can we build a closed vector triangle-- meaning that net force is zero-- from weight, lift, and (thrust minus drag ).  For more, see this answer to a related question Does lift equal weight in a climb? .  (If you want to see a similar diagram from an outside source, see the one included in this answer to a related question Is excess lift or excess power needed for a climb? )

Just as NASA also messes up the proportions in this diagram for gliding flight--  https://www.grc.nasa.gov/www/k-12/airplane/glidvec.html -- again, lift is shown as being greater than weight, when it should be less than weight, so we can build a closed vector triangle from weight, lift, and drag.  For more, see this answer to a related question What produces Thrust along the line of flight in a glider?

Now as to your questions-- to a first approximation we can think of our pitch control inputs-- the position we are placing the control stick or yoke in, in the fore-and-aft direction-- as most directly governing angle-of-attack, not pitch attitude in space.  Pitch attitude in space is influenced by the climb angle which is influenced by power setting.  Now, there are all kinds of inter-relationships that complicate things-- for example on a high-wing plane with flaps down, adding power may produce a strong downwash over the tail that tends to lead to an increase in angle-of-attack.  But to a first approximation we can think of our pitch control inputs as governing angle-of-attack.  There is a slight delay between a change in pitch control input and a change in angle-of-attack, due to the aircraft's rotational inertia in the pitch axis.

If I tell you that I've increased my aircraft's pitch attitude by 10 degrees but I don't tell you what I did with the elevator control to make that happen, nor do I tell you whether I've added power or not, then you have no way to guess whether I've kept the angle-of-attack constant and started climbing due to added power, or I've managed power as needed to keep altitude constant while transitioning to a higher angle-of-attack and lower airspeed, or any number of other possibilities-- I might even have put the stick or yoke forward to decrease the angle-of-attack and still added enough power that the aircraft transitioned into a climbing flight path resulting an in increase in pitch attitude.  For example when a jet fighter aircraft is climbing vertically on raw thrust alone, the control stick is probably forward of the position where it would be during horizontal flight at the same airspeed.  Certainly the angle-of-attack is lower in the vertical climb, than in horizontal flight at the same airspeed!

From the standpoint of what is really going on physically with the aircraft, most flight training curricula vastly over-emphasize the idea that the pilot is directly controlling the aircraft's pitch attitude.  What he's really doing is controlling angle-of-attack and power setting.  Yet the former way of looking at things works well enough in actual practice (e.g. flying an ILS glide slope by referring to an attitude indicator rather than an angle-of-attack meter as the primary guide to pitch control) and is simpler to think about.

A key point is that our flight operations are usually conducted on the "front side of the power curve", where for a given power setting, an increase in angle-of-attack usually results in an increased climb rate and an increased climb angle.  Therefore moving yoke or stick aft results in an increased angle-of-attack AND an increased climb angle (or a decreased glide angle) AND an increased pitch attitude. On the "back side of the power curve", like just above stall speed, an increase in angle-of-attack will generally lead to a decreased climb angle or increased sink angle, and the aircraft will end up in a more nose-down pitch attitude, so the idea that we're somehow directly controlling pitch attitude with the control yoke or stick no longer works very well.

Your question indicates a desire to better understand some of the physical relationships at play.  Lift is proportional to (lift coefficient * airspeed squared).  Lift coefficient is determined by angle-of-attack, with higher angles-of-attack creating higher lift coefficients.  As shown in the vector diagrams attached to the two links given at the start of this answer, for shallow to moderate climb or dive angles, lift is NEARLY equal to weight.  Actually, lift is a little less than weight unless the flight path is exactly horizontal, but for shallow to moderate climb or dive angles, the difference is small.  Since weight is staying constant, we can conclude that for shallow to moderate climb or dive angles-- with no other accelerations going on (airspeed is staying constant or changing only slowly, and the flight path isn't curving up or down, and the wings aren't banked so the flight path isn't curving to describe a turn), lift is also staying nearly constant.  This means that for shallow to moderate climb or dive angles, airspeed ends up being a pretty good guide to angle-of-attack-- to keep lift nearly constant, if the airspeed is low, the lift coefficient and angle-of-attack must be high.  So the airspeed indicator is in essence an angle-of-attack gauge.  At very steep climb angles where lift is quite a bit less than weight, things get more complicated-- if the aircraft is climbing straight up, lift must be zero, so lift coefficient must be zero, and angle-of-attack must be nearly zero (actually it must be slightly negative, unless the airfoil is completely symmetrical), no matter what the airspeed indicator reads.

In actual practice in general aviation, commercial aviation, etc, a shallow to moderately steep climb is NORMALLY carried out a higher angle-of-attack and lift coefficient--and therefore a lower airspeed-- than we'd use for high-speed cruising flight.  It's more efficient this way, and it also gives us the most climb performance out of a given, limited amount of thrust available.  Why?  Because a high lift coefficient also correlates with a high ratio of (lift coefficient to drag coefficient), which means a high ratio of lift to drag.  For shallow to moderate climb angles, the higher the L/D ratio we can achieve, the steeper we can climb for a given amount of thrust.  This is explored in more detail in the first link given in this answer. To look at climb rate rather than climb angle, we'd have to look at a chart of (power-available minus power-required) at various airspeeds or various angles-of-attack, but we'd come to a similar conclusion-- our best climb performance will be achieved at an angle-of=attack well above what we'll be using in high-speed cruising flight.

The diagram in the original question doesn't touch in any way on the relationship between airspeed, angle-of-attack, lift coefficient, magnitude of lift vector, and L/D ratio, so it doesn't help us to understand why a shallow to moderately steep climb is normally carried out at a higher angle-of-attack than we'd use for high-speed cruising flight.

Your question included the statement "if I pitch the airplane up, but also increase power and am able to maintain the same speed, then no, the AoA hasn’t changed, although it may have varied in the transition between one situation and the other."  For shallow to moderate climb angles, your statement is true for all practical purposes, but it is not EXACTLY true.  If we want to be very precise about it, we could note that since lift is slightly reduced in the climb, if airspeed stayed constant than angle-of-attack must have been slightly reduced, and if angle-of-attack stayed exactly then airspeed must have been slightly reduced.  This same idea came up in these two related answers to related questions, though in these cases the lift vector was reduced because the aircraft was in a descent rather than a climb -- 'Gravitational' power vs. engine power and  Descending on a given glide slope (e.g. ILS) at a given airspeed-- is the size of the lift vector different in headwind versus tailwind?


What's the point in escorting a threatened flight with two fighter jets?

Fighter jets escorting planes after various sorts of emergencies seems to be standard procedure in many countries, you hear about it quite frequently. It's sometimes implied in the media that if the situation would turn into a 9/11-type hijacking it might be necessary to shoot the plane down but nobody seems willing to fully clarify who could take such a decision and under what conditions on the record.

Now, in most cases, there isn't even a suggestion that a hijacking is happening but it's difficult to determine that in a timely manner and there are still two things fighters can do in other cases:

Get a visual confirmation of the situation aboard the plane (Is the plane damaged? The cockpit windows obscured? Who is in the cockpit?)
“Guide” a pilot who has lost communication to an airport.

Also, one factor is that being able to scramble jets is often seen as a basic requirement to assert sovereignty (witness the mini-controversy in Switzerland when it was revealed that the air force could not do it at certain times of the day) so politically it seems difficult to entirely give up on it, even if it could be argued that it's a waste of money for smaller countries to maintain an air force that does very little beside this type of missions.


Are the A380 engines interchangeable (given they are not all equipped with reverse)?

The Airbus A380 comes with two engine choices:

Rolls-Royce Trent 900
Engine Alliance GP7000

The thrust reversers are not part of the core engines. The reversers are developed by the company which produces the engine nacelle, in this case Safran Nacelles. They developed nacelles for both engine variants for the A380, including the first electrically actuated reversers:

  Safran Nacelles nacelle systems equip the Airbus A380 powered by four Rolls-Royce Trent 900 engines or four Engine Alliance GP7200 engines. [...] they are the first in the world to have a thrust reverser with an Electric Thrust Reverser Actuation System (ETRAS®).

(source: safran-nacelles.com)

(image source: safran-group.com)

Are the nacelles interchangeable?

No, the nacelles for the outer engines are different from the inner ones to save weight. This article says:

  Four nacelles were developed for the A380: one inboard nacelle (with a thrust reverser) and one outboard nacelle (without), for each of the type's two engines, the Rolls-Royce Trent 900 and Engine Alliance GP7200.

As ymb1 pointed out in the comments, this is confirmed by the type certificate for the Trent 900:

  At engine certification, the engine has been approved for use with Aircelle Thrust Reverser Unit
  (TRU) at the inboard engine positions (part numbers ASE 0010-XX-0 for the left hand installation
  and ASE 0050-XX-0 for the right hand installation) and for a Fixed Fan Duct (FFD) in the outboard
  engine positions (part numbers ASE 5010-XX-0 for the left hand installation and ASE 5050-XX-0
  for the right hand installation).
  The TRU and FFD do not form part of the engine type design and must be certified as part of the
  aircraft type design.

and also for the GP7000:

  This engine is approved for use with Airbus thrust reverser system P/Ns (left and right)
  L78DR130000xxx / L78DR230000xxx and with Airbus fixed fan duct P/Ns (left and right)
  L78DR140000xxx / L78DR240000xxx.


Is there a way to find out which runway is used by which flight on a particular day/date?

(Guessing the) Runway Selection

For spotting airplanes, you want to know which are the current active runways. The runway history of planes or flights shouldn't matter much, unless your plane of interest is limited in what runways it can use.

Large airports have many parallel runways. In general, outsiders will not have enough information at hand to predict the active runways. The factors that are considered for the selection of active runways are the following:

  Aircraft take-off and land into the wind, or with minimal tail wind.
  Based on the wind direction, air traffic control will decide which
  runway is to be used at any given time.

  Larger airports tend to have more than one runway, so that a runway is
  always available depending on the wind direction. Airports with just
  one runway are generally constructed so that the runway is aligned
  with the prevailing wind.

  Runway selection is monitored at all times, as weather conditions can
  quickly change. Every runway has a wind indicator known as an
  ‘anemometer’, and wind observations contribute to the runway selection
  decision. Pilot reports of upper level winds can also impact on runway
  selection.

  When a runway is selected, it needs to be available for an extended
  period of time to allow pilots to plan their descent, approach and
  landing. As this involves anticipation of developing trends, aircraft
  may continue to land on a runway for a period when weather conditions
  at a local level no longer appear to warrant it.

  Other factors that air traffic control will take into consideration
  when deciding which runway to use include:

  the number and type of aircraft programmed for the airport
  length of runway(s)
  weather conditions (both present and forecast); including wind velocity and gradient, wind shear, wake turbulence effects and
  position of the sun
  availability of approach aids in poor visibility conditions
  location of other aircraft
  taxiing distances, including availability of taxiways
  braking conditions.

  Some airports also have ‘preferred runway’ systems. This means that if
  wind conditions, workload and traffic conditions permit, a particular
  runway will be used to move traffic as efficiently as possible to
  reduce the noise impact over residential areas.

This text is quoted from a short informational document on runway selection published by Airservices Australia.

ATC radio communication

It is possible to listen to ATC radio communications with a handheld scanner (always check if this is legal in your country!), or via the internet (LiveATC). There are different channels including Departure, Approach, Ground, and ATIS.

ATIS

Busy airports are usually equipped with Automatic Terminal Information Service. ATIS continuously broadcasts relevant information about the airport and immediate surroundings for pilots. This includes the actual runway in use. One can receive ATIS via VHF, or via phone. Frequencies and phone numbers are published in different ways. Airnav.com might be useful for the USA. LiveATC provides streaming of ATIS.

Ground

Aircraft are cleared for taxi to a runway on the Ground channel.

Approach

Aircraft receive their instructions and clearance for a runway on the Approach channel.

Websites

Airports

Some airports are publishing their actual active runways on a website. For instance:

Amsterdam (Schiphol): "Baangebruik Schiphol".

This airport always assigns 1 active runway for landing and 1 active runway for starting. In the rush times, it opens an additional runway for landing or starting. In the snapshot above, the 2 runways for landing are red, the single runway for starting is blue.

Brussels: Runways in use

There are probably not that many airports publishing this information to non-pilots, but surely there are more. Please comment if you know any other!

Flight Tracking

If there is no information available from the airport directly, you can always use flight tracking web sites like the ones you have listed in your question to observe which are the current active runways, for starting and for landing respectively. Keeping in mind that the assignment of active runways is not random, it is always reasonable to guess that the next aircraft will use the same runway as the previous ones. For approaching aircraft it is often possible to see if it is directly pointing to a runway, or if it follows a pattern to a runway that other aircraft have taken before.

Standard patterns and Operational procedures

If interested and willing to dig a bit deeper, you can always find and study standard approach patterns and operational procedures of your airport, e.g.

Operational Procedures at Tokyo International Airport (Haneda)
search the internet for "RJTT SID STAR"

In combination with flight tracking web sites, this will allow you to recognize the usual patterns, and predict earlier where a tracked plane is going to land.


What are the opimum values of Cl during descent?

I am going to work in SI units for all engineering work, anything else would cause instant insanity on my side. I'll leave the altitude in feet (isn't used) and convert speed from knots to m/s so you can follow the flow easily. Since $C_L$ is unitless it should not matter what units you use in the calculation as long as you are consistent.

Altitude: 34000 [ft] (not used)
$V$ (true air speed): 442 [knots] = 227 [m/s]
S = 112.6 [m2]
$\rho_0$ = 1.225 [kg/m3]
$\frac{\rho}{\rho_0}$=0.322 [-] (from your table)
$\rho$ = $1.225 \cdot 0.322 = 0.394$ [kg/m3]
$\frac{1}{2}\rho V^2 S$ = $\frac{1}{2} 0.394\cdot 227^2 \cdot112.6 = 125\cdot10^4 $[N]
$m$ = MLM = 64500 [kg]
W = $m\cdot g$ = $64500\cdot 9.81$ = $63\cdot10^4$ [N]
$C_L$ = $\frac{W}{\frac{1}{2}\rho V^2 S}$=$\frac{63\cdot 10^4}{125\cdot 10^4}$ = 0.5

I did take full maximum landing mass for this calculation. If you want to apply corrections then note that the $C_L$ value scales linearly with the mass.

One further note:

I assume your data is derived from ADS-B. ADS-B transmits groundspeed, whilst you should work with true airspeed in these formula's. The difference between them is the tailwind (or headwind) component.


Can ATC provide VFR flight following to a VFR aircraft in class E airspace?

They can. I often pick it up here in the Northeast since the airspace is fairly busy. Generally speaking I was taught that flight following is always a good idea. It is a useful tool to you in the cockpit and can provide advisories of fast moving hard to see aircraft as well as those that may be approaching to overtake you. Generally it helps to improve your radio skills and may reduce your work load ultimately.

As for who to contact, that can change. I had this very question during my training (asked here) and you can find the answer here. If you are departing from a controlled field you can sometimes ask the tower to set it up which they may or may not do. The Airport Facility Directory will have an "approach" and/or "departure" frequency listed for most fields which is generally who you call. If you are in the wrong area they generally send you over to the right controller.


You would copy the cross-setional shape of the frisbee plastic disc toy, which generates lift as it spins and travels through the air by using a shape which looks like the leading edge of a wing no matter which way it is pointing. a wing with two "leading edges" like this is not as efficient as a wing with a tapered trailing edge, but it works well enough to fly significant distances and provide fun for its users.


If the FAA considered making videos itself (i.e. separate from any unrelated rule violations within those videos) to be a problem, they would have put a stop to it long ago, either by explicit rulemaking or the catch-all "careless or reckless" when no other rule applies. They haven't, at least with respect to GA pilots--who are allowed to do all sorts or things that charter and airline pilots are not.

Several YouTubers I follow have said they mount the cameras and start recording before preflight, don't touch them again until after the plane is down and secured, and edit out the boring parts later that show this.  That seems to mitigate the physical safety issues.

The other issue is pilot distraction if they're talking to the camera, but I don't see that as any worse than talking to passengers, which is commonly accepted within reason, and is perhaps less of a risk since the camera doesn't talk back.


It is possible to feel a difference between helicopters with clockwise direction rotor and counterclockwise rotor?

Yes, the pilot would certainly notice the difference.

When the engine applies clockwise torque to the main rotor, the body of the helicopter experiences counterclockwise torque. When the pilot increases collective to increase the amount of lift the main rotor produces, the engine will need to apply more torque to overcome the rotor's increase in drag. Therefore the pilot would have to apply right pedal to prevent the torque from turning the nose of the helicopter left.

If the rotor turned counterclockwise instead, these directions would be inverted. So if the pilot was flying the helicopter with the assumption that the main rotor turns in the opposite direction that it really does, he would tend to apply the wrong pedal and the helicopter would start yawing.


How to replace two propellers on the same aircraft reaching the time limit?

Since replacing a propeller with the same propeller that is in the Type Certificate is not a major repair, the FAR(s) (CFR Title 14) that most apply are 43.7 and (assuming the airplane is under Part 91) 91.407.

43.7 states:

  (a) Each person performing maintenance, alteration, or preventive maintenance on an aircraft, engine, propeller, or appliance shall use the methods, techniques, and practices prescribed in the current manufacturer's maintenance manual or Instructions for Continued Airworthiness prepared by its manufacturer, or other methods, techniques, and practices acceptable to the Administrator, except as noted in §43.16. He shall use the tools, equipment, and test apparatus necessary to assure completion of the work in accordance with accepted industry practices. If special equipment or test apparatus is recommended by the manufacturer involved, he must use that equipment or apparatus or its equivalent acceptable to the Administrator.

  (b) Each person maintaining or altering, or performing preventive maintenance, shall do that work in such a manner and use materials of such a quality, that the condition of the aircraft, airframe, aircraft engine, propeller, or appliance worked on will be at least equal to its original or properly altered condition (with regard to aerodynamic function, structural strength, resistance to vibration and deterioration, and other qualities affecting airworthiness).

So you must follow the maintenance manual and put the airplane back in a state at least as good as original. If you think that putting them both on does not qualify to satisfy this requirement, then you should do them one at a time. If it does satisfy this, then in that case, 91.407 comes into play, which states:

  (a) No person may operate any aircraft that has undergone maintenance, preventive maintenance, rebuilding, or alteration unless—

    (1) It has been approved for return to service by a person authorized under §43.7 of this chapter; and

    (2) The maintenance record entry required by §43.9 or §43.11, as applicable, of this chapter has been made.

  (b) No person may carry any person (other than crewmembers) in an aircraft that has been maintained, rebuilt, or altered in a manner that may have appreciably changed its flight characteristics or substantially affected its operation in flight until an appropriately rated pilot with at least a private pilot certificate flies the aircraft, makes an operational check of the maintenance performed or alteration made, and logs the flight in the aircraft records.

  (c) The aircraft does not have to be flown as required by paragraph (b) of this section if, prior to flight, ground tests, inspection, or both show conclusively that the maintenance, preventive maintenance, rebuilding, or alteration has not appreciably changed the flight characteristics or substantially affected the flight operation of the aircraft.

I would argue that a propeller change cannot be satisfied by (c) above and does require a flight test. However, there is nothing that requires separate flight tests UNLESS the maintenance manual requires it, in which case part 43.7(a) from above comes into play. But as a "fail safe" a good run-up on the ground at high throttle with the brakes applied, followed by an inspection of the work can give good confidence in the work prior to the flight test.


Why do we commonly use a "/" in acronyms in aviation world?

It's not just aviation, it's standard in English.

  The slash has become standard in several abbreviations. Generally, it is used to mark two-letter initialisms such as A/C (short for "air conditioner"), w/o ("without"), b/w ("black and white" or, less often, "between"), w/e ("whatever" or, less often, "weekend" or "week ending"), i/o ("input/output"), r/w ("read/write"), and n/a ("not applicable"). Other initialisms employing the slash include w/ ("with") and w/r/t ("with regard to"). Such slashed abbreviations are somewhat more common in British English and were more common around the Second World War (as with "S/E" to mean "single-engined"). The abbreviation 24/7 (denoting 24 hours a day, 7 days a week) describes a business that is always open or unceasing activity.

(Slash (punctuation) § Abbreviation, Wikipedia)

Note that there is a difference between abbreviation and acronym, though that line in recent usage is blurred.

Boeing uses VS for the 777, and V/S for the 737. Language is more about what's more common, preferred style, and/or trends (e-mail becoming email). For example, knowing when to use a hyphen, space, or no-space, for compound words requires checking a dictionary. There aren't fixed unchanging rules to follow really in language.

There are some questions on the topic on English Language & Usage Stack Exchange.


How may I verify WAAS channel number on G1000?

I don't know if you can check or set the WAAS channel number directly (and I couldn't find anything about it in the C172 G1000 manual) but even if you can there's really no point. When you load the approach, the G1000 gets the WAAS channel number from the database as part of the general approach definition and configures everything automatically.

I heard or read somewhere that the original concept was that pilots would 'tune' the WAAS channel in the same way that they tune an ILS frequency, but that idea was dropped because an RNAV approach is totally dependent on the database anyway: if you trust the G1000 to load all the waypoints, altitudes and other information correctly from the database then there's no reason to think it will load the wrong WAAS channel.

As for your specific questions:

(1) How may I know which approach I am able to shoot?

You read your G1000 manual, check the approach database, and review the approach plates to make sure that the approach is available and you meet all the requirements. If the approach is in the database that doesn't automatically mean that you can fly it, there can also be climb performance or altimeter setting requirements (for example) that are unrelated to the G1000.

(2) Is the WAAS channel number automatically selected when I load the corresponding flight plan in G1000?

Yes. The G1000 sets up the approach completely for you, the only input required (usually!) is to load the approach and select how you initiate it, i.e. via an IAF or radar vectors.

(3) [Can I] get the LPV glide path guidance without loading any particular approach (set the WAAS CH number for instance?)?

No, this wouldn't make any sense. The LPV glideslope is constructed virtually by the G1000 for each approach and the WAAS input just provides correction to an existing GPS position, it doesn't give you a position directly. So even if you could receive the WAAS corrections directly (and maybe you can, for all I know), the G1000 wouldn't be able to generate a glideslope without all the other approach information about the runway, elevation etc. It would be like asking, "the magnetic declination here is 4°W, what's the correct magnetic heading to fly from A to B?" Unless you know the uncorrected heading, the correction by itself isn't useful.


How I determine numerically the roll rate of an aircraft?

In order to determine the roll rate of an aircraft, all you need to do is to set the rolling moment from aileron deflection equal to the roll damping of the wing (actually, of the whole aircraft, but the wing dominates roll damping anyways). So you set
$$c_{l\xi}\cdot\frac{\xi_{left}-\xi_{right}}{2} = -c_{lp}\cdot p = -c_{lp}\cdot\frac{\omega_x\cdot b}{2\cdot v_{\infty}}$$
$$\Rightarrow\omega_x = -\frac{2\cdot v_{\infty}}{b}\cdot\frac{c_{l\xi}}{c_{lp}}\cdot\frac{\xi_{left}-\xi_{right}}{2}$$

The symbols are:
$\kern{5mm} \xi\:\:\:\:\:$ aileron deflection angle
$\kern{5mm} v_{\infty}\:\:$ velocity
$\kern{5mm} b\:\:\:\;$ wing span
$\kern{5mm} c_{lp} \:\:$  coefficient of roll damping, using $\frac{b}{2}$ for its reference length
$\kern{5mm} c_{l\xi} \:\;$ coefficient of rolling moment due to aileron deflection
$\kern{5mm} p \:\:\:\;$ dimensionless roll rate
$\kern{5mm} \omega_x \:\:$  rolling speed in rad/sec

Damping decreases with altitude, and in this equation the increase of flight speed with altitude will make sure that roll damping decreases accordingly.


How hazardous is it if an engine cowl falls off?

I work in aero engine safety but not for the company that manufactured the engine in the event you mention.

Parts falling off engines is Not Good. We worry about them hitting people below the aircraft. And as Koyovis mentions, losing the nacelle or portions thereof (looks like in this case it was the intake and fan cowling) can change the aeroelastic properties, thus inducing vibration, which is not comfortable for the passengers or crew (reducing their ability to do their jobs) and adds additional loads to other engine parts.

It is not true as mins states that the cause or consequences are unknown. The regulatory authorities require manufacturers to submit a detailed (thousands of pages long) Failure mode, effects, and criticality analysis (FMECA) that covers every part of the engine, what could go wrong, what the consequences could be, and what we are doing to make sure it won't go wrong or that the effects are minimized if they do. While I don't work on that engine, I am confident that structural failure and release of the intake is in the FMECA.

In my professional judgement, in the scale of failures affecting engines defined by the FAA (catastrophic, hazardous, major, minor), this failure would be major, due to a large part falling off the aircraft able to hit a person below, the reduction in safety margins caused by increased vibration, and the damage to critical parts (fan blade) from debris ingestion as mentioned in one of the other answers.

Since the fan blade was seriously damaged, the pilots likely shut down the engine (otherwise the vibration would have been insanely high). But as you mention a single engine shut down is not considered hazardous - we design for that situation. Nevertheless many pilots choose to land after a single engine shutdown.


What is the aerodynamic reason that the An-225's vertical stabilizers are not simply vertical?

I'm fairly sure (but have no sources to confirm) that the reasons are purely structural. The vertical stabilisers are simply set at a right angle to the horizontal one. This is just the easiest thing to do, and it also provides better clearance with deflected lower rudders. The aerodynamic consequences of this (for such small angles) are pretty minor.

Now there are good aerodynamic reasons to have dihedral on the horizontal stabiliser (which causes the whole tilt), but this is a different question, and it applies to many airplanes.


Why commercial planes fly at high altitudes?

Because while the dynamic pressures of air reacting on the wings at those altitudes remains the same, the speed of the relative winds, and, as a consequence the aircraft’s ground speed is much higher at higher altitudes than near sea level.  This is as a consequence of the air density being much lower at high altitudes than down low.  Cold thin air facilitates true airspeeds 100-300 knots higher than indicated airspeed does.  Therefore per unit of fuel consumed to overcome drag, the airplane travels much farther and consumes less fuel over the course of the flight.

Example:  jet airplane flying at a pressure altitude of 37,000 ft, Outside ambient temperature is -47°C.  If the calibrated airspeed the pilot reads in the cockpit is 300 KCAS, the true airspeed is 575 KTAS.

Add to this that these altitudes do allow the aircraft to access the upper level winds of the jet stream, which range between 30 to over 160 knots on certain days, which can facilitate a healthy tailwind for eastbound flights around the globe.  It is not uncommon for commercial aircraft to log over 650 knots groundspeed in these conditions, further reducing fuel consumption.

As the speed of sound varies proportionally with temperature, compressibility limitations prevent this form being used beyond Mach .8 - Mach .9 due to Cp movement and control buffeting, depending on the aircraft.    There also is a point in the flight envelop where the Stall speed Vs corresponds with the maximum Mach number - see “Coffin Corner” for further details - so this limits the maximum operating altitude based upon outside air temperature as well.  Nonetheless, high subsonic air travel remains one of the most efficient means of moving large numbers of people and cargo quickly around the globe.


Can an Autogyro with wings survive a rotor mechanical failure? Will it be safer?

That is a very broad question and covers many topics, but I will try to answer as best I can and not miss anything.

A quick note on the wings.  Adding wings as a safety aspect to the aircraft kinda defeats the purpose of an autogyro.

Would it survive to a rotor destruction? The likelihood of an autogyro surviving rotor destruction is extremely remote. Best case scenario would be the entire rotor assembly detaches from the mast and flies away from the aircraft.  Worst case scenario only 1 or 2 blades fly off. (Honestly would be more likely to happen IF rotor destruction were to take place.)  In this situation the imbalance in the rotor would be so violent that surviving, let alone actually flying, an autogyro in such a configuration would be truly "Hand of God" type miracle.  If you want to see something similar try removing a blade or two from a fan and you will see this imbalance in action.

Taking the best case scenario could the pilot make an emergency landing? Yes, but their options would be limited, assuming you can recover AND get into the best glide configuration by 5,000' AGL you would likely have less than 8.3 minutes to find a field and get ready before landing. Lower altitudes will provide even less time before contacting the ground.  (This number is only approximate for a 9.3:1 glide ratio and it would be unlikely for wings on an autogyro to even do that well.)

Is it safe to build an autogyro with wings? Yes, as your picture shows it does work.  A few companies today, such as Carter Aviation Technologies, use that design albeit with much shorter wings designed to work in conjunction with the rotor.

Does it have an increased operational cost? Possibly.  Those smaller wings mentioned in the paragraph above actually increase the efficiency and reduce the operational cost.  The problem is that those types of wings are almost entirely useless without the rotor.  Wings big enough to provide a decent glide ratio and time for the pilot to react to rotor destruction would end up providing more drag and require a larger engine to overcome it thereby increasing the operational cost.

As far as turbulence goes, you could see more turbulence with larger wings but with small wings like on the CarterCopter, the additional turbulence added to the aircraft because of the stiff wings would be minimal.


In the US, is it customary to tip the line personnel?

I've never tipped for aircraft refuelling or other line services, and have never been criticized or looked at the wrong way for not doing so. That said, tipping in the US has nothing to do with the industry in which the person works; it's a personal reward for good service, and it is both appreciated as well as remembered the next time you are there.


What triggers the PTU (Power Transfer Unit)?

(A320 PTU (Vickers), source)

The Power Transfer Unit is well known on Airbus due to its barking-like sound (refresher: Video of a PTU in action). The sound comes from a pump which creates a 3,000 psi pressure being quickly switched ON and OFF.

(Source: Youtube)

The PTU is a safety system to ensure hydraulic pressure is available, specially at takeoff, even if one or two hydraulic circuits have failed.

The PTU can restore pressure in a deficient circuit without actually transferring fluid from the working circuit to the deficient one. This prevents throwing hydraulic fluid from the working circuit overboard if the deficient circuit is leaking.

The PTU is always activated, but is actually triggered based on a pressure differential.

When is it activated?

On Airbus A320 series, the PTU is actually the second source of pressure for the yellow and green hydraulic systems, after the EDP. It's always ON, ready for the pump activation if there is a pressure drop on the yellow or green hydraulic system and the differential pressure is more than 500 psi.

  Airbus A318, A319, A320 and A321 aeroplanes are equipped with three
  hydraulic systems and they can be safely controlled with only one
  system operative. A bi-directional PTU enables the yellow system to
  pressurize the green system, and vice versa, without the transfer of
  fluid from one system to the other.

  In flight, the PTU operates
  automatically if a pressure drop in one of the systems is detected.
  The PTU ensures optimal hydraulic system availability for take-off.
  (Source: EASA safety bulletin)

Automatic inhibition below 1,500 ft in case of leakage

The PTU cannot restore the correct pressure in a circuit with a permanent leak. In this case, the PTU, and possibly the working hydraulic system, eventually overheat. The crew receives a failure amber caution on the ECAM display and, up to recently, had to switch OFF (inhibit) the PTU manually to prevent damage.

  In case of loss of hydraulic fluid of the yellow or green system, the PTU
  cannot pressurize the failed system and must be switched OFF as
  required by ECAM procedure to avoid a PTU overheat which may occur two
  minutes later.
  (Source: EASA safety bulletin)

A320 PTU switch (source: Baltic Aviation Academy which, by the way, has plenty of quality training videos)

To avoid distraction from non-essential warnings during takeoff and landing, the ECAM message is not displayed when airborne below 1,500 ft height. There were several incidents (e.g. G-EZDM) where overheating became harmful before the amber ECAM message appeared at 1,500 ft, causing the temporary loss of a second system. Airbus added logic for automatic PTU inhibition when the aircraft is airborne, but still below 1,500 ft.

The previous quotes are from an EASA bulletin related to this modification (also detailed in Safety First, the Airbus safety magazine), with a failure scenario that had to be prevented:

Principle

A PTU is connected to two independent hydraulic systems: The first to drive an hydraulic motor (or turbine) mechanically connected to a pump. The second hydraulic system is pressurized by the pump.

PTU principle, source

PTU can be reversible (each hydraulic system can drive the motor or be pressurized by the pump) or not (the same system always drive the motor).

(Actual PTU schematics, source)


Is there any difference in landing minima between ICAO and FAA?

In most cases, FAA approach charts do not provide a requirement for a ceiling as you say, but rather provide the minimum altitude that a pilot may descend to without having the runway environment in sight (the DH/MDA) and the minimum required visibility.1
In fact, as described in the FAA Instrument Procedures Handbook, Page 4-7 and in the AIM, section 5-4-20(e), air carrier pilots, who are restricted from even beginning an approach if the reported weather is below minimums, are only restricted by the visibility and may fly the approach  when the reported ceiling is lower than the minimum altitude on the approach plate (note that this does not apply to Part 91 operations).
The main reason for this is that a ceiling does not necessarily cover 100% of the sky over the airport environment, and it is quite possible to see the runway even when there is a reported ceiling.

References
FAA Instrument Procedures Handbook, Page 4-7 says:

14 CFR Part 135, section 135.225 states that pilots may not begin an
instrument approach unless the latest weather report indicates that
the weather conditions are at or above the authorized IFR landing
minimums for that procedure. 14 CFR Part 135, section 135.225 provides
relief from this rule if the aircraft has already passed the final
approach fix (FAF) when the weather report is received. It should be
noted that the controlling factor for determining whether or not the
aircraft can proceed is reported visibility. RVR, if available, is the
controlling visibility report for determining that the requirements of
this section are met. The runway visibility value (RVV), reported in
statute miles (SM), takes precedent over prevailing visibility. There
is no required timeframe for receiving current weather prior to
initiating the approach.

AIM, section 5-4-20(e) says:

e. Published Approach Minimums. Approach minimums are published for
different aircraft categories and consist of a minimum altitude (DA,
DH, MDA) and required visibility. These minimums are determined by
applying the appropriate TERPS criteria. When a fix is incorporated in
a nonprecision final segment, two sets of minimums may be published:
one for the pilot that is able to identify the fix, and a second for
the pilot that cannot. Two sets of minimums may also be published when
a second altimeter source is used in the procedure. When a
nonprecision procedure incorporates both a stepdown fix in the final
segment and a second altimeter source, two sets of minimums are
published to account for the stepdown fix and a note addresses
minimums for the second altimeter source.

Notes
1 Under relatively rare conditions, TERPS specifies that a ceiling is required for a specific approach, but this will be notated on the approach chart with the words CEILING REQUIRED.


Can I use an expired IFR-certified GPS with an out of date database in lieu of DME?

The answer would appear to be "Maybe", per the AIM (table 1-1-6): You are permitted to use an IFR-approved GPS "In Lieu of ADF and/or DME", however the footnote (3) to that table tells us that this use

  Requires current database or verification that the procedure has not been amended since the expiration of the database.

So if you're using the GPS to calculate something like "5 Miles DME from JFK VOR" that would seem to be acceptable (the FAA is unlikely to pick up JFK VOR and move it without making a lot of noise about it), but if you're using by punching in a fix that's defined by DME and a radial you would need to somehow verify that the fix hadn't been redefined.

You can accomplish that verification in a number of ways (a current IFR chart on your iPad or a current paper chart seem like obvious ways). As long as you can satisfy yourself (and the FAA) that the data in the GPS is accurate the operation would appear to be permissible.

It would also appear that if you verify that the fix has been redefined (say FUBAR was 5 DME, now it's 6 DME) you could still use the GPS distance data in lieu of DME, just not the incorrectly-programmed fix. That is, you could determine when you're 6 miles DME from JFK VOR, and since you know the FAA didn't move the VOR and that the fix is now at 6 miles you now you're where you want to be.


What safety features prevent jets sucking in ground staff or equipment?

No, there are no safety features. Only safety procedures on the flight deck and on the ground.

Basically it all boils down to that nobody may go near any aircraft (jet or prop; they are both similarly dangerous) that may have engines running. When starting the engines, the pilots first turn on the beacon (the red flashing lights on the belly and tail), then check the ground crew has left and only then start the engine(s). And similarly upon landing, the pilots shut the engines down, wait a bit to let them spool down and turn off the beacons; then the ground crew should ask (via radio or the wired intercom connected to a socket at the nose) whether the engines are indeed off and only then they may start working.

Since start-up normally only happens after push-back, so away from the terminal, there is usually no risk then. Upon arrival however the ground crew needs to come to the aircraft relatively quickly and insert chocks to the wheels, so the correct procedures are important.

Here see a recent accident where ground worker was injured because the procedures were not followed (he was coming from the rear, so he was only blown away, not sucked in).

In that incident, the engines were at idle. They are still very dangerous in that case. I found an Airbus document which shows danger areas, for A320 with CFM56 engines, at idle as:

suction danger 2.2m (7.2ft) from engines (semicircle forward and to the sides of the engine and back to 1.5m behind the inlet) and
exhaust danger to 55m (180ft) behind the nozzles with 30° spread with exhaust velocity exceeding 105km/h (65mi/h) for 17m (55ft) aft of the nozzles.

At full power the suction area grows to 5.9m (19.5ft) radius and the exhaust danger to 275m (900ft) with velocity over 105km/h down to 150m (500ft) aft.


How good is the ground visibility by a moonless night In the Grand Canyon?

No, in a remote area on a moonless night, it’s a black hole.  It’s the blackest darkness you can imagine with a few pinpricks of light from remote settlements on the ground or vehicles.  I have heard a few stories from pilots flying at higher altitudes on moonless nights, such as Maj Brian Shul who did this over the Arctic Ocean in an SR-71, where they shut down cockpit lighting and found that starlight was intense enough to illuminate their instruments.  I also know of tales from Navy pilots who have flown fighters in dark night over water who can’t see anything out in front of them.

These conditions require total reliance on instruments to know which way is up and plenty of people have become spatially disoriented flying like this and crashed.  I have heard some hairraising tales from drug runners like Barry Seal, Carlos Lehder, etc., who used to fly airplanes low level over the ocean at night in order to avoid detection, remaining about 50ft or so off the deck.  One guy they interviewed for the MSNBC documentary Cocaine Cowboys used to do this approaching the Keyes south of Miami for a drop off.  He used to say if he could see the light glow of Miami off his nose he was fine but if he could see the glow from both Miami and Tampa, he was too high and risked detection.  God help you if you had a bad altimeter setting in these conditions.

I will make my own comment, as a professional pilot, that dark night conditions over remote areas or open water are downright eerie and there’s is always an uncomfortable feeling in myself when doing PIC operations in these condition.


Are Sophisticated Planes with Multiple Computer Interfacing Safer to Fly than Traditional Aircraft?

how in the world is it possible to have a comprehensive knowledge of
  all of the sophisticated computers and electronics that are required
  to interface to fly a plane safely?

The same way you learn about any aircraft, you study the operational manuals and related documentation. In theory aircraft that use the airbus fly by wire system are safer as they offer protection against the pilot inadvertently putting the aircraft into a dangerous situation (high G, stall, etc.).

I think that there are some misconceptions in your question about the required training for flying something like an A320. Pilots are required to know how the aircraft will respond in all situations and the errors and messages the computer may throw at them. This is no different than understanding what a tumbling mechanical attitude indicator is doing or how to identify a bad analog instrument. Broadly speaking failures are failures and identifying them has more to do with situational awareness, understanding of your systems, and to some extent experience. Digital cockpits merely change the text and pictures in the books but still require the same basic fundamentals to identify a failure.

Some might also say that analog cockpits are more complicated than their digital counterparts. So much so that jets that once required a crew of 3 in the analog days can now be flown by two.

  It seems to me that in truth, pilots have just enough knowledge to
  operate these new planes and systems under normal conditions and the
  moment a malfunction occurs it becomes a race to a safe landing with
  only troubleshooting guides to help understand what is happening and
  try to offset it long enough to get the plane safely of the ground.

Pilots do not have just enough knowledge and frankly that is short changing the vast amount of hours required to be in command of even an A320. Pilots train in full motion simulators for all kinds of emergencies so that when the time comes they only need a quick reference card to get the plane safely on the ground.

Digital aircraft are not necessarily kaput if one thing fails and systems are designed such that a failure does not cause down stream effects. Systems often can independently be shut off and pulled out of sequence in the event of a failure. On top of that there are lots of failure modes (even in the side stick planes) that allow for all kinds of direct control.

But how does this all tie into a plane being safer...

The FAA main advice in any emergency is to "fly the plane" most training stresses (and most accidents cite a lack of) "Situational Awareness" so if we can provide a cockpit that offers a pilot more information on how the plane is flying, where they are, and whats going on we can make it easier to fly the plane and maintain your situational awareness in any event (even if some systems are failing). That all trickles out, ultimately, to a safer plane.