May a non-instrument pilot legally file IFR as long as he amends and doesn’t accept an instrument clearance?

My instrument students, when they get more advanced, file FP with their name, and in remarks say "Training xxxxxx CFII"

That way it is clear.  The FAA office investigated one student, dug up his past flight plans, and determined that the way he filed was acceptable.  The FAA told me they had reports of him going actual prior to his receiving a rating. I gather if the remark wasn't filed, there would have been more questions.

Having said all that, my recommendation is that you file a VFR flight plan for flight following, and then advise ATC upon check-in.  If you are leaving a controlled airport, normally you will advise clearance or ground prior to departure, and then when switching from the tower to departure you will check in with the phrase, "flight following."  On a workload permitting basis you will receive the same handling as IFR flights, in general, and there will be no question as to your intent.

Addendum #1
Just because there is no regulation prohibiting behavior, does not mean that an agency such as the FAA will not prosecute.  In fact, FAA issued a LOI in 2008, on just this topic, stating that if a pilot were to file an IFR flight plan, without holding an IFR pilot certificate, they would consider that intent to violate 61.3.

Now, whether that resulted in certificate action or caused a letter to be filed in your folder, I cannot say, but I would not want my certificate jeopardized by the poor judgment of filing IFR when one was not authorized to conduct IFR operations.

The 2008 LOI comes a decade or so after the incident I reported above with a student.

I don't see how any responsible person can advocate filing a flight plan which is premised upon false and misleading information. Furthermore, while there is not a specific regulation dealing with this particular lack of judgment, the FAA has made clear, with this specific matter, that would consider such a flight plan filing to be a intent to violate 91.3.  Not something that I can see advocating for anyone to do...

Addendum #2


It is all part of the camouflage.

The blue parts on the bottom make the aircraft hard to identify from below against a blue-background (sky). The dark parts on the top make it difficult to identify from above against a dark background (ground).

The white parts make the aircraft's size/shape difficult to determine. This helps to confuse the enemy by making the aircraft seem farther away than it really is.


Could flight control be achieved by rotating a wing entirely?

Yes, it has been tried before and is regularly used on many horizontal and even some vertical tails.

However, in subsonic flight an elevator will offer better efficiency. Only in supersonic designs is the full-flying tail the clearly preferred option.

To move the whole wing needs very strong hinges and actuators, but there were some which did even this:

Mignet HM 14 Pou du Ciel (picture source). It was light and flew slowly enough that moving the whole wing was not an issue.

The Vought F-8 "Crusader" and XF8U-3 "Corsair III" could jack their wings seven degrees up in order to improve fuselage attitude and pilot visibility during take-off and landing (picture source).

Even all-moving outer wings have been tried for roll control, albeit in only very few aircraft. Three I know of (and all of them were built once only) are:

Granger Archaeopteryx,
Short SB.1 glider, and
Short SB.4 Sherpa, the rotated wingtip of which is shown below (picture source).


What is the difference between a vertical stabilizer and a rudder?

The vertical stabilizer is immobile (if it starts to move, you're in deep shit), and provides stability in yaw (it keeps the aircraft pointed more or less in the direction that it's moving).

The rudder is mobile, and typically attached to the aft edge of the vertical stabilizer. It provides controllability in yaw (it allows the aircraft, if necessary, to point in a different direction than the one it's moving).

The rudder allows the aircraft to slip sideways when you want it to; the vertical stabilizer keeps it from slipping sideways when you don't want it to.

(Original via flickr.com)


What units are used by western airliners?

Airspeed, ground speed
Primary unit: km/h. Non-SI unit: knot.
In practise, knot is the main unit. At high levels, the Mach number is used, which is a measurement of speed relative to the local speed of sound.

Pressure
Pascal. Hectopascal is used for altimeter settings. In the USA they use inches of mercury.

Altitude
Primary unit: metres. Non-SI unit: feet.
In practise, feet is the main unit. Whether you say altitude or flight level depends on your reference air pressure.

Distance
Long: nautical mile. Short: metres. Vertical: foot.

Mass
Kilograms.

Volume
Litre or cubic metre.

Position
Latitude and longitude based on WGS84.

The above is according to ICAO Annex 5, which means that it is true for more or less all of the world. A few places prefer to deviate from the standard units, such as the USA, which uses a slightly different system.


Why can planes generally take more positive g's than negative g's?

It's partly pragmatic (you start from +1.0 G, so why not optimize for that???) and partly because (most) aircraft are designed to carry human beings.  Humans as well as a lot of other things are FAR more tolerant of positive G-forces than they are negative G-forces.

There's very little technical reason that you couldn't design an aircraft wing and other structures to handle high negative G loads.  But adding that strength also means adding weight, complexity, and cost.  And since the benefit of being able to pull high negative G loads is pretty small, very few designers choose to do this.


What are the effects of adding winglets to an aircraft not designed with winglets originally?

Aircraft wings are designed for specific weight and cruise speed. When later the manufacturer wants to create a new variant with higher maximum weight, it should get longer wings for optimal efficiency. However, redesigning the wing is a lot of work, because extending the wing means the root bending moment increases, which requires stronger spar, which means heavier and all the calculations have to be redone.

Here is where winglets get useful. They increase the effective wingspan, but while they are somewhat less efficient than extending the wing, they also cause lower increase of the root bending moment. Often, this smaller increase fits in the original extra margin, so winglets can be simply bolted on without having to redesign the wing, making the process much cheaper.

That's why we often see winglets on next generation of anything and rarely on the first generation. On first generation, they are designing the wing from scratch anyway, so they just make it appropriate length for minimum drag.

The main reason to use winglets from the start is if the emerging design just slightly exceeds some size category for airport gates. Then it makes sense to reduce the span to fit and add winglets so the aircraft can be used at smaller—and therefore cheaper and more common—gates.

You can read how winglets work in Is a winglet better than an equal span extension?.


Why doesn't F-15 have a protruded cone at its rear like what the Su-35 has?

As @RalphJ notes, it is not required. It is a design choice based on various considerations. The 'cone' in the Su-35 houses the RWR and the drogue chute. In case of F-15, however, the drogue chute is not used and the RWR antennae are located elsewhere (in the wing and vertical tail tips, to be exact).

The image below from a BAE systems document shows the integration of AN/ALR-56C Radar Warning Recievers in the F-15 A/E aircraft.

Integration of AN/ALR-56C Radar Warning Receivers on F-15; image from BAE systems


Would large, low aspect ratio fan/propeller blades be more efficient? Why not?

In the case of propellers, there are a number of operating and design considerations which must be taken into account here.
For example, while it is true that imparting a small impulse to a large mass wastes less energy than adding a large impulse to a small mass using a propeller, there are practical limits to how big you can make the propeller diameter before the ground handling of the airplane becomes unmanageably awkward. A huge prop might be more efficient, but you'd need a boarding ladder to get into the cockpit behind that huge prop and the landing gear struts would need to be longer and stiffer and hence heavier. Oh yes- and the prop itself would be significantly heavier.
In addition, to drive a big prop slowly and still develop full power with a piston engine requires a reduction gear of some sort between the 2400RPM of the crankshaft and whatever the turning speed of the slow prop was. The gearbox adds weight and requires an overhaul when its time is run out, and that adds cost- and a potential failure mode that is absent in direct-drive designs.
Finally, gearing down the engine to turn a slow prop magnifies the transmitted torque to the prop and therefore from the prop to the engine and airframe. That reaction torque has to be countered somehow or else opening the throttle will not just turn the prop but also roll the aircraft backwards around the crankshaft axis.
100 years of experience with geared and direct drive piston engines and all sorts of props has yielded the best solution in the form of a direct-drive engine spinning a variable pitch prop with a diameter that puts the blade tips comfortably subsonic at the max power setting of the engine.


Synoptic refers to the active system diagrams that are selectable, usually on one of the middle displays above the center console.  If you want to know what the hydraulic system  is up to, you can select the Hydraulic Synoptic and an active diagram of the hydraulic system appears, showing what's pressurized and what's not, valves open and closed, the pressure values, quantities, etc.  There will be one for most of the major systems, hyper simplified compared to a normal system schematic because only the essential information is presented.


What is the circular pavement at the end of a runway called?

It is called the turn pad. This area(pad) is usually located at the thresholds of the runway, where no taxiway exists, so in order for the pilots to make a full-length takeoff, (or taxi to the Apron) they have to backtrack amd make a U-turn on there. Gernerally speaking, these pads exist on small airports. You can see the turn pads at the 2 thresholds of the runway. Skiathos Airport, Greece
Source


Has there ever been an aircraft with three sets of flight controls?

Depends if you are asking about production or testbed stuff, NASA had at least one test bed aircraft that looks to have had at least 4 sets of controls (also covered in this question).

If you consider the space shuttle an aircraft, some of the thrusting capabilities (enough for pitch roll and yaw I belive) were operable from the arm control position.


Can hypersonic aircraft be agile without the G forces harming the pilot?

Well, 2 G's is 2 G's, regardless of what speed you're flying.  A level (coordinated) turn with 60 degrees of bank is 2 G's, regardless of your airspeed.  What changes is your turn rate and turn radius; at 20 knots, a model plane at 60 degrees bank can probably complete a 360 degree turn in a few seconds and a radius of maybe 10 yards.  At 300 knots and 60 degrees bank, a conventional jet will need a minute or two and a turn radius of probably a couple of miles.  At 2000 knots and 60 degrees bank, an SR-71 might overfly a few states making that same 360!  But it's all 2 G's for each of those aircraft.

Now if you want the SR-71 or some similar highly supersonic aircraft to have the turn rate & turn radius of your 300-knot Lear jet, then you'll get a LOT more G's -- which can induce various other issues with your supersonic beast.  And if you want either of those to keep their speed while turning in the radius of your 20-knot drone... well, let's just say that you're talking about G forces beyond the realm of all human experience to make that happen!

There are all kinds of discussions that can be had about how hypersonic aircraft can be made more maneuverable without doing things that risk losing control, flaming out the engines, creating unacceptable amounts of drag, and so on, but all of those discussions take place in the context that high speed + high turn rate = more G's, and given any 2 of those factors that you choose (i.e. how fast you want to go & how much G-loading you're willing to sustain), the third is determined.

The max G-loading for a human is pretty well about 9 G's, so pick whatever combination of the other two factors you want.  Or go unmanned -- which with today's technology is probably cheaper.


Why are passenger seats not facing backward on an airplane?

You are absolutely correct, backward facing seats are safer.

But tradition and a subjective feeling of being treated better means that people will prefer to be seated facing forward. Some even claim that they develop motion sickness when sitting backwards. This can indeed be the case for some people in trains with their big windows, but much less so in aircraft.

Just note which seats will be occupied last in a train with lounge/mixed seating.

In order to cram the highest number of passengers into their planes, the airlines would need to convert all seats to the backward orientation, and you can be sure there will be some passengers who will complain. If passenger safety would be important to them, airlines could already use better seatbelts, like the 5-point-harnesses used in gliders and aerobatics planes, but they all use the minimum lap belt which is mandated and nothing more. Convenience and cost always win over safety.

Now I need to mention two caveats:

If passengers should be seated backwards, the industry needs to develop new seats. It will not be helpful to turn existing seats around - they would collapse at much lower loads than what a backward-sitting human can sustain. However, to fully support these higher loads, seats will be more heavy and possibly even the floor structure needs to be beefed up.
Backward-facing seating will only help in the fraction of cases where deceleration loads are too high for a forward-facing person, but low enough to make the crash survivable. If the plane flies into a mountain or ditches and sinks before people get out, the better seating will not help.

Some military transports have backward-facing seats. In some crashes, the survivability rate was seven times higher in those than in forward-facing seats. Early air travel also used mixed seating, e.g. on the Zeppelins or the Dornier Do-X. One airline to use mixed seating was Southwest Airlines with their "love seats", and business jets have mixed seating as standard. Thanks to @reirab for pointing out that United Business class also has some backward-facing seats.

Cabin of the Do-X. No seatbelts, seats not bolted to the floor. These were the days ...

Cabin of the Dassault Falcon 7X business jet.


How do you calculate the range of a VHF transmitter that is on-board an aircraft?

VHF radio transmissions are primarily limited by line of sight. The formula for this is d = 1.23 * (√h1 + √h2) where h1 and h2 are the altitude s in feet, and d is the max range in miles.


An altitude engine is a type of engine that uses a turbocharger (and less often, a supercharger) to generate sea-level pressure in its intake manifold, up to its critical altitude, at which point power will start to fall off.

Non-altitude engines will lose power as they climb because the ambient air pressure drops off at a rate of about 1" Hg per 1,000 ft of altitude (up to 10,000ft).

The altitude engine allows aircraft to fly at higher altitudes at full power, and increases the aircraft's speed and efficiency, because true airspeed increases with altitude. It also allows an aircraft under IFR to fly at higher MEAs or under VFR over higher terrain, and allows the pilot to choose a favorable altitude for weather.

The first kind of altitude engine is called a turbocharged engine, which can generate more intake manifold pressure than at sea level. For example, a Mooney Bravo M20M can generate 36" of manifold pressure, and can generate at least 30" of manifold pressure up to its critical altitude of 22,000ft.

The other kind of altitude engine is called a turbo-normalizer, which develops a maximum of sea level pressure: 30”Hg or 1 Bar. These engines will perform as well at altitude (up to their critical altitude) as they do at sea level.

A turbo-normalized engine is considered less taxing on the engine than a turbocharged engine because the former doesn't develop above sea-level pressure or high turbine-inlet temperatures. The turbo-normalized engine is also easier to fly than a turbocharged engine, since it never develops more power than would be developed at sea level.

All altitude engines also typically have a controllable-pitch prop, and develop more than 200 horsepower, so they would require both a complex aircraft endorsement and a high-performance endorsement. See 14 CFR Part 61.31.


I would suggest that you contact the Naval Aviation Museum at NAS Pensacola FL to discuss donating or loaning them.  That way his legacy can live on with a plaque stating "Items in this display donated by ___, NAVAIR Program Manager F-14 Tomcat Systems, 1972 - 1986". (or something similar)


Why would only a specific model of drone be allowed to fly over crowds?

CNN has applied for and received multiple waivers for 14 CFR § 107.39 Operation over human beings as allowed by § 107.205 List of regulations subject to waiver.

Issued August 29, 2016 — This allows "Small unmanned aircraft system (sUAS) operations over human beings in accordance with the CNN UAS Operations Manual, Fotokite Pro 1 Operator Guide, and Fotokite Pro 1 Specifications Sheet." It allows operation "over private or controlled-access property with permission from a person with legal authority to grant access" and prohibits operations over open-air assemblies of people.
Issued July 20, 2017 — This allows operations "conducted over human beings for the purpose of closed-set motion picture and television filming". Make and model of sUAS not specified, but all operations must comply with the operator's manual.
Issued October 13, 2017 — This waiver is granted for the Vantage Robotics Snap only, and allows "operations over all human beings (including Nonparticipants)". It also limits the altitude when operated over people to 150 feet AGL, as opposed to the normal limit of 400 feet AGL. I assume this is the waiver you are interested in.

The simple reason why only one particular model of UAS is allowed is that CNN only submitted that model for waiver and no others, and the FAA approved that.

This is a somewhat unsatisfying answer, but neither CNN's nor the FAA's reasoning is included in the text of the waiver itself. The rest of this answer is speculation on my part.

As can be seen on Vantage's specifications page for the Snap, the Snap is reasonably lightweight (1.37 lbs / 620 g including battery), has caged props, and has a high-quality camera. (The camera isn't a matter of safety, but it is presumably something a cable news provider is interested in.)

If a prop were to fail catastrophically, the cage would hopefully contain at least some of it, thus eliminating risk of a crowd being hit by sharp objects. The height restriction of 150 feet AGL reduces the potential for injury of a nonparticipant should the sUAS fall on them, and the prop cages prevent contact with moving parts.

I suspect that CNN applied for a waiver specifically for this model and the FAA approved it based on the following:

It's specific. The more general the application, the more likely it is to be rejected. If you know what you're working with, you can evaluate all the parameters and come up with a safe solution. If there are more variables, it's harder to reason about.
It has certain safety features as discussed above, which make it more suitable for flight over nonparticipants than some other models.
It's standard. CNN has a single platform to train their over-crowd operators on. Once again, this also has safety benefits, because the operators are extremely familiar with one model of unit, instead of broadly familiar with many different ones.
This particular model of sUAS had all the features that CNN wanted and that the FAA was interested in for this application. This may include such factors as weight, safety features, well-written operation and maintenance manual, and ease of maintenance. Additionally CNN may have liked the cost (the FAA wouldn't care about that).

The FAA maintains a list of all Part 107 waivers granted.


Can anyone explain why and how flames shot out of an F/A-18 as it crashed?

Fuel has to reach the engine to make it work, so there is a path (pipes) available for the fuel to get from the tanks into the engines.

Looking (*) at the video linked by Pierre Chevallier it looks like some fuel got pressed out of the tanks, into the engine(s) and out the engine nozzle, and in the process it got ignited.

I cannot say why the fuel got only in one engine, I can guess that the valves on the fuel lines were in different positions.

(*) I suggest using the option to visualize at x0.25 speed, starting at the 0:30 mark


Can I use radar service instead of DME or GPS for this ILS approach?

Tl;dr: This is really an edge case and I can’t come up with any specific wording that says “yes” or “no”. But from the following info I’d say you cannot unless ATC authorizes it.

Since the chart specifically indicates it as required it would be illegal to use the approach. Paragraph 5-5-4 a 2 of the AIM lists under pilot responsibilities:

  Follows the procedure as shown on the IAP, including all restrictive notations

But according to this answer ATC can approve an approach even when some equipment is inop. The answer seems to be concerning inop. NAVAID equip, rather than inop. equipment on the aircraft. Also, the section of the AIM he refers to (5-4-7d) does not include what he says. Paragraph 5-4-6d states:

  The name of an instrument approach, as published, is used to identify the approach, even though a component of the approach aid, such as the glideslope on an Instrument Landing System, is inoperative or unreliable. The controller will use the name of the approach as published, but must advise the aircraft at the time an approach clearance is issued that the inoperative or unreliable approach aid component is unusable.

This would suggest that ATC can approve an approach with inop. equipment.

If you consider telling you when you arrive at ROLTE to be “vectoring” then ATC can give you vectors as far as the FAF. FAA order JO 7110.65W, which gives instructions for ATC indicates in paragraph 5-9-1 a 2.

  If specifically requested by the pilot, aircraft may be vectored to intercept the final approach course inside the approach gate but no closer than the final approach fix.

Note that where you have highlighted “RNAV 1-GPS or RADAR or DME REQUIRED” is on the IAF at GQO, but not on ROLTE. This would indicate to me that you can count on any of those to get you to the IAF, but not beyond it. The word RADAR on the chart at ROLTE and EWADA indicate that those fixes are depicted on the ATC radar screen. This would certainly make it possible for them to tell you when you’ve reached the fix, but I don’t know if you can count on them to do it. And without that or DME you would have no accurate way of identifying the FAF. They may not have time to monitor you after you’ve reached the IAF, so that’s why I say it would require ATC approval.


Advances in rivet technology for Aircraft?

Rivets need to be harder than the material being joined by them, and the growing use of high-strength alloys has made the use of rivets of the same material as the material being joined problematic. To set a rivet, it needs to have some plasticity, which in turn is greatly reduced when an alloy is optimized for high strength.

Initially, rivets were made from aluminium alloys, but have been replaced by fasteners, especially Hi-Loks (Hi-Lock is also used) which are (mostly) titanium or steel bolts with an aluminium or titanium nut. The nut has two parts; the lower part, the collar, has the internal thread and remains on the Hi-Lok after assembly while the upper part forms a hexagonal head for tightening with a special wrench. Between both is a groove which allows the head to shear off at the right torque. This ensures consistent torque and eliminates the need for torque inspection. The wrench needs a hex bolt at its center which serves as a socket wrench and engages with the shank of the fastener to keep it from rotating with the nut.

Why titanium? Lisi Aerospace says on its website:

  By using titanium nuts rather than steel or stainless steel nuts, we
  can save up to 110kg on a single aisle aircraft and 220 kg on a wide
  body aircraft.

If access is restricted, blind fasteners are also available. Hi-Loks have been standardized and cover a wide range of sizes and shapes.

Hi-Lok fastener (picture source)

Another advance are special bolts for joining composite parts. The head of a regular fastener is too small and runs the risk of being pulled through the composite sheet. Special bolts, washers and nuts for composites spread the load out.

Composite panel fastener (picture by Alcoa Fastening systems, source)


Why the 747 testing GE-9X doesnt have a winglet?

That's because its been removed for testing. The aircraft used in for flight testing the GE-9X belongs to GE and is a modified JAL 747-400.

  The aircraft, a former Japan Airlines -400, was acquired by GE in 2010 and
  following maintenance and interior modification in Xiamen, China,
  by Taikoo Aircraft Engineering, was delivered to Evergreen Aviation
  Technologies in Taiwan for installation of data racks and instrumentation.

For carrying out the testing, GE has carried out a number of modifications for maintenance and testing:

  ... modifications are also planned to reduce the chances of aero
  elastic interaction between the extended wing of the 747-400 and the
  GE9X mounted on the inboard left strut. GE has already removed
  the standard winglets because these add unnecessary weight and a
  maintenance burden to the aircraft’s flight-test role. Later this year,
  the outer 6 feet of each wingtip also will be removed, ... Designers say the stiffer wing will reduce potential exposure to limit cycle oscillation and maintain an unrestricted test envelope.

Quotes from archive.org. Original ariticle appears to be from aviationweek.


What exactly are those openings in the bellies of many jetliners?

That's an air inlet -- technically a "Ram Air" inlet -- for the air conditioning packs.  There is a "left" and "right" pack, which supply air to the forward and aft part of the aircraft respectively (although either pack can supply enough air to keep the aircraft pressurized to its max altitude).  They use high temperature/high pressure bleed air from the engines or APU, but they also get airflow from the ambient air which is used to cool the bleed air.  The inlet noted in the question is where the ambient air enters, and there are exhaust vents for this air on the bottom of the aircraft.  THIS air isn't used for the pressurization per se (i.e. it doesn't enter the cabin), but just for cooling the air that will enter the cabin (which came from the compressor in the engines/APU, upstream of the combustion chamber).

On the ground, there are louvers that close to keep water and debris out of these ducts, and fans are used to pull in air in that configuration.  In-flight, the louvers open and airflow is generally sufficient to move the air through the system (although the fans still provide some assist).

While there is some amount of drag here, it's fairly minimal, and the ability to keep the cabin pressurized and cool is sufficiently important that the little bit of drag that's caused here is considered acceptable.

Close-up photo of the inlet door (Next-Gen 737):

Close-up photo of the inlet door (Classic 737):

Photo of exhaust louvers:

source page for all of the above (with technical discussion of the air conditioning & pressurization system): http://www.b737.org.uk/airconditioning.htm

Even more technical description of the system -- text & schematics but no photos


How do I know which airports have ILS and for which runways?

There are published instrument approach procedures for all airports served by an instrument approach.  These are commonly referred to as Approach Plates.  (In paper form). Your local pilot shop should have them, or you can order online.
Just look in the section for the airport you are going to and all the available approaches will be there.  Browse to the ones for the runway in use, and choose one that matches your equipment capabilities.  That’s the one you should request with ATC.  (After you get your instrument rating of course!)
If you have a tablet EFB application and the appropriate subscription they can be brought up on your device.
Your question about ILS glide slope not being available on the reciprocal runway has probably been answered before, but the best answer is because it requires a separate transmitter, which costs more money, and needs to be justified based on need and usage.  (I.e. Perhaps the runway without GS is favored by winds when weather is typically clear...)


Can air-superiority radar function as weather radar?

Modern airborne fire-control radars seem to have a weather mode.

GRIFO-346, VixEn 1000E, and ELM-2032 (brochure PDF links).

This page suggests a "weather observation" capability in modern combat planes:

  Digital capabilities allow a radar to change its functionality at will, resulting in the modern "multimode radars" carried by combat aircraft.


Is there a boomless sonic technology in any state at this time?

Shock wave is a physical phenomenon and as such is unavoidable. The best we can do is to reduce their intensity and reduce their effects on ground.

A method to eliminate the shock wave (theoretically) was proposed by Adolf Busemann. His airframe, called the Busemann's Biplane which consists of two triangular cross-section plates a certain distance apart (so that choking is prevented) with the flat sides parallel to the fluid flow.

Image from Supersonic biplane—A review by Kazuhiro Kusunose et al.

The idea is that the shock waves are formed internally between the two (triangular) 'airfoils' and cancel each other out at design condition, shown in the first case.

Image from Supersonic biplane—A review by Kazuhiro Kusunose et al.

At off design conditions, shock waves are produced. However, this doesn't produce any lift at zero angle of attack, as is obvious. As researchers explain,

  ... the design lacks lift: The two wings create a very narrow channel through which only a limited amount of air can flow. When transitioning to supersonic speeds, the channel ... could essentially “choke,” creating incredible drag. While the design could work beautifully at supersonic speeds, it can’t overcome the drag to reach those speeds.

Research is being carried out to overcome this issue- One method proposed is to have the wings 'morph' shapes- so that they are efficient at all speeds. Another group is working to optimize the shape of the airfoils in Busemann's Biplane so that the shock-wave is reduced at all stages of supersonic flight. However, all these studies are in conceptual stage and no experiments have been carried out so far.

NASA carried out the Shaped Sonic Boom Demonstration(SSBD), in which the fuselage of a Northrop -5E was modified (kind of like pelican's beak) so as to change the pattern of shock waves formed in supersonic flight.

"F-5E Shaped Sonic Boom Demonstration aircraft" by NASA/Carla Thomas - http://www.dfrc.nasa.gov/Gallery/Photo/SSBD/HTML/EC03-0210-1.html. Licensed under Public Domain via Commons.

NASA reported that the modifications were able to reduce the intensity of the shock wave by a considerable amount, as shown in the image below (the 'flat' pressure line is from the SSB demonstrator).

Image from Quieting the Boom- The Shaped Sonic Boom demonstrator and the Quest for Quiet Supersonic Flight by NASA

Active research is still being carried out by various organizations in this field.


What are the rules for racing on airport runways?

The adverse effect is once the layer of rubber gets too thick it starts to degrade braking performance, especially wet braking because the rubber is filling in the surface irregularities that help channel water out from under the tire.  Aircraft wheels will hydroplane at much lower speeds and with less water depth.  Airports remove excess rubber from touchdown zones once it gets beyond a specified thickness.

I would expect that the rubber from spinning car tires would be no worse than the rubber that builds up on touchdown zones on heavily used runways.  If an airport is closing a runway to use for drag racing, it can't be a very busy airport, but in theory a really heavy rubber build up could be a concern if infrequent high performance aircraft like business jets use it, you know, when no drag racing is going on.  That would be up to the airport operator what to do about it.


What determines the maximum speeds for a particular aircraft?

There are various physical things that will limit the top speed of an aircraft. Which one you will hit first depends on the airframe in question but here are some things you may encounter (aircraft dependent):

Drag will generally counter your thrust which will limit the speed you can achieve in level flight and is often the practical limiting factor on aircraft that actually fly. Level flight is important to note as you can gain a huge amount of speed if you simply enter a dive.
For propellor driven aircraft there are some practical speed limits because of the propellors.
At some point flutter will become a problem and you may literally shake the wings off the plane.
Around the speed of sound (mach 1) you are going to have all sorts of interesting things going on if you are pushing a subsonic optimized airframe to such speeds.
Ultimately, if you still have your engines and wings heat becomes the real problem. The Concorde pumped fuel through the nose to use a coolant in the mach flight regime and was in part speed limited by nose temperature. For manned flight this becomes the limiting factor at the extreme end of the envelope and aircraft like the SR-71 had a very physically demanding environment.


What physical hardware does all the avionics on the B737NG run on? Some processor from the 1980s? Or some new and improved chip?

This wouldn't fit as a comment but doesn't get to the processor level of your question. The 737NG/Max has a large number of avionics systems as shown by Airframer. Most of these have processors, some have multiple. In which of these are you interested?


Why do the transponders introduce codes instead of using aircraft registration numbers?

To expand upon voretaq7's answer, understanding the history and evolution of transponders can more deeply explain why this is the way it is (for now).

When Allied (US/UK/Others) WWII planes returned from combat missions over Germany and mainland Europe, the (brand new technology) radar controllers had no way of knowing "who" the aircraft were. To solve this problem, aircraft began carrying an electronic box that could transmit a radio signal automatically in order to identify themselves. This system was the original IFF (Identification: Friend or Foe).

This piece of electronic wizardry could be set on the ground by crew members, prior to departure, using an 8-position dial numbered from 0-7. The box would receive a transmission signal from the ground, and then transmit a reply of two bursts of energy per cycle: the first signal was the "I'm beginning my transmission" signal (a slightly louder burst of energy), and the next signal was delayed a specific amount of nano-seconds to match the frequency wavelength (and would be slightly lower in intensity).  If the transmitter was set to 0, the delay was nothing. That is, the second burst would be transmitted on the next "instance" following the begin-transmission burst. If set to 1, then there was a 1-step delay after the start-signal... all the way up to 7, which would induce a 7-step delay.

The rudimentary "computers" on the ground, co-located with the radar, would receive these transmissions. Based on the known radio frequency, the timing of these short bursts of energy onto the carrier wavelength could be interpreted back into a number. If the radio on the ground received something like:
START-nothing-nothing-SIGNAL-nothing-nothing-nothing-nothing-nothing-START-nothing-nothing-SIGNAL-nothing-nothing-nothing-nothing-nothing.... then it could be calculated that the box onboard the aircraft was transmitting the "number 2".  If the secret number for that day (briefed to pilots before they left) was "2", then the plane was identified as a "FRIEND" in the IFF system. This was the very first transponder prototype. (BTW: It is called a "transponder" because it does two things: it TRANSmits a resPONSE to a specific signal on a specific frequency.)

But the obvious first hurdle was the fact that there were only 8 numbers available, and so the transponder boxes were quickly upgraded to two settings (56 possible code combinations) and then 4 settings (4,096 possible "code" combinations).

But there was still a "problem": the codes were set on the ground and could not be changed. Any mid-mission compromise of the number being used that day prevented aircraft already airborne from changing their codes. The next technological leap was to develop a panel-mounted system where the pilot could change each of the four dials manually.

This technology eventually entered the civilian arena. To distinguish between different types of transponders and who was using them (mostly a frequency issues - military freq vs. civilian freq), different categories came about, called "modes".  A "Mode 2" transponder was the above described 4-digit, octal, set-on-the-ground-and-leave-it system. A "Mode 3" transponder was the newer, pilot-sets-it-in-the-air version, but still using military frequencies.

When the civilians began using the same technology on approved civilian frequencies, the designation was "Mode 3-A", often just called a "Mode A" transponder. Combined with the advent of civilian air traffic surveillance radar, controllers could now distinguish "who was who" on their screens, by assigning each aircraft its own unique number.  This was great for a while, but the only thing controllers could see was the "blip" and its assigned number. The radar computer could also calculate ground speed, but not altitude. So, the controllers relied on the pilot to report their altitude verbally.

This led to the next technological leap forward in transponders. If that same radio could somehow be connected to the aircraft's pressure system (the same one that drives altimeters and vertical speed indicators), then it could probably somehow be configured to transmit that altitude data as well. That technology was thus invented, and the designation "Mode 3-A/C" was applied to the civilian versions... commonly (and still popular today) called a "Mode C Transponder".

This (finally) gets us to the original question: Why don't aircraft program their own registration numbers into the transponder?  Since there are only four octal digits available, there are three immediate problems: first, the numbers 8 and 9 are not usable; second, no letters are available; and third, with only 4096 possible combinations, and way more aircraft than that in the world, it is very highly possible that two aircraft in the same vicinity could possibly have the same number.

The advent of "Mode S" transponders, with "current-day" technology, can now transmit (as well as receive) all kinds of information, including the aircraft's specific identity like the question-asker thought should be the way it is. But, backwards compatibility for all of those aircraft still flying around out there with "Mode C" transponders still requires ATC to assign a unique code to an aircraft and the pilot to plug that number in.

Additional trivia, not directly related to the question: Since Mode C transponders are limited to the numbers 0-7, how can they transmit altitude data that might contain the numbers 8 and 9?

The answer is in an aspect of binary coding called a "Gray Code" (or sometimes a "Gillham Code"). The world's avionics people standardized on a set of codes to represent a set of altitudes in 100-foot increments. As a couple of examples, an aircraft at a pressure altitude of 8,500 feet would send the 4-digit code of 6220.   Sitting at a pressure altitude of 0 would result in the code 0620. The receiving ground station would evaluate both the pressure altitude received by the aircraft, as well as the current station pressure setting (commonly called the "altimeter setting"), and convert these into the aircraft's actual MSL altitude for display on the radar screen.

I was able to find this list of altitude-code conversions:

https://web.archive.org/web/20120726003224/http://www.airsport-corp.com/modecascii.txt


Under VFR, can a pilot fly above a layer of clouds?

Yes, it's legal to operate under VFR without any visual reference to the surface. It's called operating VFR over-the-top, not to be confused with VFR-on-top which is an IFR clearance. Over-the-top is defined in 14 CFR 1.1:

  Over-the-top means above the layer of clouds or other obscuring phenomena forming the ceiling.

There are some exceptions and restrictions, though (this list may not be complete):

Recreational pilots must have visual reference to the surface (14 CFR 61.101)
So must sport pilots (14 CFR 61.315)
So must student pilots (14 CFR 61.89)
If the pilot has a foreign-based private license then all restrictions on the foreign license apply, which could prevent VFR over-the-top (14 CFR 61.75)
Large, turbine or fractionally owned aircraft must be equipped as for IFR (14 CFR 91.507)
If flying for an airline or other operator, their OpSpecs must allow it


Why does Thai Lion Air use loads of 737 ERs for 1-2hr routes?

Operationally speaking, this may come as a surprise, but it's not the range of the ER, rather the additional exits and flat bulkhead, which allow more seats (note: Lion Air was the launch customer of the -900ER).

Exits: even if there is room for more passengers, a limiting feature is typically the exits. More exits, more passengers can evacuate in the same duration in an emergency.
Bulkhead: the typical bulkhead is spherical; a flat one would allow more floor area.

The 737-900ER is the same size as the 737-900, but can carry an 26 additional passengers in a one-class configuration. It incorporates an additional pair of exit doors and a flat rear-pressure bulkhead that boosts maximum capacity to 215 passengers in a single-class layout.
— Boeing 737-900ER roll-out in Renton; flightglobal.com; 10 August, 2006

(planespotters.net) One additional exit per side.

(airliners.net) An example of a flat bulkhead on the Boeing 727.


What aircraft had the first pilot-assisted controls?

It was the Lockheed Constellation and the P-80, both introduced in 1943. The DC-3 had hydraulic flaps, but the Connie was the first to have hydraulic flight controls.

  The DC‐3 had wings flaps powered by hydraulics (1934). But it wasn’t until the early 1940s that hydraulics were used to power the primary flight control surfaces on the Lockheed Constellation and P‐80 (first US Jet Aircraft).

Source: A History of Aviation Actuation, Control and Fluid Power (PDF)

Also in 1943, the Lockheed P-38J-25-LO version of the WWII fighter aircraft was fitted with hydraulic boosted ailerons.

Source: Lockheed P-38J Lightning, Joe Baugher


Did Flight Engineers progress to be pilots?

Before the turn of the century (I can't believe I'm using that phrase, as I retired in 1999) and especially back when all 3 engine and 4 engine airliners had a flight engineer, the usual career path at many airlines was to hire in as an Flight Engineer, or FE (two stripes), progress to an First Officer, or FO (three stripes), and then become a captain (four stripes).

This all began to change, of course, with the advent of large 2-man cockpit aircraft. The change was not without controversy and some pain. For example, at least one initial operator of the 737 ran a 3-man cockpit for a time. The 3rd guy was, as I remember, referred to as the GIB (guy in back). He sat in the jumpseat and read the checklists, which was one of the tasks an FE typically had in 3-man cockpits.

As it happened, the two jet carriers I worked for hired pilots into the FO seat and used professional FEs. I spent a couple of years on the 727 and then 10 years on the 747.  During that time, every FE save one that I flew with was ex-military, and with few exceptions all were A&Ps. That was desirable in case a maintenance sign off was needed when you were someplace where maintenance was not otherwise available.

Occasionally you would encounter an FE who had been a captain.  The pilots were required to retire at 60 back then, but FEs weren't.  I only knew one such individual, and I always liked flying with him.  The more expertise you have in the cockpit, the better.

In the two 747 carriers I worked for, an FE would sometimes transition to the FO seat, but that was relatively rare, and the costs were typically the individual's to bear.  Interestingly, when I retired in 1999, I had flown with an ex-military FE who years later became the chief pilot of the airline involved.


Is a reversal of heading allowed in the NYC Hudson VFR corridor?

I've never flown the corridor myself but from what I can find online it looks like a U-turn would be a case of "legal but not safe". 14 CFR 93.350 defines two different types of traffic in the SFRA and the FAA's kneeboard guide has a 'plain English' summary:

  Fly in proper altitude range

  Transient operation* [1,000 ft up to, not including, 1,300 ft MSL]
  Local operation** [Surface up to, not including, 1,000 ft MSL]

It also explains what those operations are (emphasis mine):

  Transient operation: Aircraft transiting the Hudson River Exclusion from end to end without intending to signicantly [sic] change heading, altitude, or airspeed.
  Local operation: Any aircraft within the Hudson River Exclusion that is conducting an operation other than overflying.

Those definitions certainly seem to allow for turns and maneuvering as part of "local operations". However, as Dave pointed out, the corridor is very narrow and maneuvers in a fixed-wing aircraft might be risky. In fact, there's already been one high-profile accident in the East River corridor where the aircraft hit a building after trying to a make a tight U-turn in a strong wind. I suspect that most aircraft maneuvering actively in the SFRA are probably helicopters rather than fixed-wing airplanes.

If you search newsgroups and forums about this you'll find a lot of comments about helicopter traffic at very low altitudes, and many pilots say that turning in the Hudson River corridor isn't a great idea. This thread is a good example.

The FAA has a safety course for the SFRA, by the way. I haven't done it but it might have more information.


Is it safe to fly a glider when I can't move the stick fully left and right?

Yes, it is safe.

Well, there is a reason why the stick travels as far as it does. One is the restriction in long-term maximum stick forces of 15 N (see §22.143(b) in the linked PDF), which is easier to fulfil if the stick has more travel. The other is the required roll speed to switch from +45° roll angle to -45° roll angle within 5 seconds for a glider with 15m wing span (see §22.147), which is easier to fulfil if the ailerons have a wider deflection range.

I found myself in the same position on several occasions (after all, I am 6' 6" tall when standing upright - most gliders became only flyable for me after I had fitted a new instrument panel, the 2-33 being a notable exception) and for me it was enough to be able to yank the stick fully to one side when I had lifted my leg off the pedal on that side, so the stick would fit below my knee.

If you want to fly a coordinated turn, the knee on the side where the stick should go will be stretched, in order to push the rudder to full deflection, so then the stick should be able to travel where the knee had been with a centred rudder. This will be the normal case - isolated full aileron without rudder should be the exception.

If you are concerned about unusual attitudes: You will not fly aerobatics, will you? And in order to end a spin, rudder is far more important than aileron, which should be kept centred in a spin.


What do the white dumb-bell signals indicate?

I keep thinking of some of the big fly ins (like Air Venture in Oshkosh) where pilots are allowed to park on the grass.

During the fly in they might use that second symbol (dumbbell with stripes) to let people know it's okay to park on the grass, but you still need to take off, land, and taxi on official taxiways and runways (as defined by the event rules).  Thus significantly increasing capacity during the event.

But during other weeks that same airport probably doesn't want anyone taxing onto, or parking on, the grass.  So they would display the first symbol (dumbbell with no stripes) to remind everyone that the exception is gone, and the rules have changed back to what you would normally expect at most airports.  Thus people would be aware they need to stay off the grass and use official tie down areas for parking.

In essence, I think the first symbol exists mostly because of the second one.  At airports where there are occasionally exceptions along the lines of those described above, they may also want a symbol to help pilots know when the exceptions are not in effect.


Has the typical cabin pressure in airliners changed in recent decades?

Let's take the Boeing 737 as an example: an airliner that first flew in 1967 and is still being produced, its variants—old to new—indeed show a trend of increasing pressurization capability.

Note that even the 1967 variant had an automatic controller for the cabin pressurization, and the 200Adv and the Classic shared the same max ceiling of FL370.

The better the engines and the aerodynamics are, the higher they'll fly, and the stronger the aircraft will be made to offer better cabin altitude. However stronger is now easier than in the past thanks to the materials engineering advancements.

  1/200 (7.5 psi) → 200Adv (7.8 psi) → Classic (8.65 psi) → NG (9.1 psi)

The higher those values, the lower (denser) the cabin altitude is, for a plane flying at the same altitude.

Those values are the limits, each variant will use lower values in the day-to-day operations to reduce the stresses.

Source of the figures: b737.org.uk


Yes, the cockpit of the F-16 is pressurized. However, there are two types of cabin pressurization:

Isobaric Pressurisation: The system maintains a constant cabin pressure (usually between 2000 and 8000 ft) as the atmospheric pressure decreases. This is used in commercial aircraft.
Hypobaric Pressurisation: In such a system the pressurisation commences at a
given altitude and cabin altitude is maintained at this value until a preset pressure differential is reached. With continued ascent the pressure
differential is maintained. This is used in military aircraft including the F-16, as the weight penalty of the Isobaric system would seriously affect the range.

Provision of supplemental oxygen in the aircraft ensures that the occupant receives increasing quantity of oxygen in the inspired air. The aircraft oxygen system (regulator assembly) ensures that the correct percentage of oxygen is added from the on-board Oxygen reserve to the inspired air in order to maintain lung pO₂ at 103 mm Hg.


What is the usual range of Approach and En Route ATC VHF radios?

VHF radios are line-of-sight, and typically the range is limited not by the transmit power but by terrain and the aircraft's horizon. PPL students are taught a rule of thumb: the range in nautical miles is the square root of 1.5 times the aircraft's altitude in feet. This makes your range roughly 40 nm at 1000 ft, 90 nm at 5000 ft, and 120 nm at 10000 ft.

En-route stations intended to be used over a wide area will typically use several transmitters on high ground many miles apart, to ensure reception over their whole operating area. Even so, low-level flying can put you into a blind spot between transmitters.


Some of the early radial engines that operated by rotating the entire engine along with the prop, specifically, the very popular Le Rhone didn't have proper throttles. The pilot controlled engine speed by switching the ignition on and off.

This wasn't so much a limitation of that particular design, as a limitation of engine tech in general at that time. Wilhelm Maybach first devised the jet spray carburetor (patterned after a scent spray) in 1893, but the throttle body didn't appear for another ten years. Those early engines had only two speeds: wide open, or off.

Thus, the reason that many of the early WW1 fighters are constantly revving their engines on the ground... the pilot was switching the ignition on and off. Must have made for interesting ground handling.


How do turbofan nacelle lengths compare?

Meeting noise regulations is the primary reason for using a long nacelle. Some engines may not need it. Since it adds weight and drag it is not used unless required. Use may be partially offset by improvement in efficiency, but this does not normally justify usage on its own.

If a particular engine design does not meet the specification, the long nacelle can block certain emissions 90deg to the engine axis which might make the installation compliant. Noise is generated where flows of dissimilar speed mix.

flow from a core mixing

An extended nacelle encloses noise from the instabilities, shielding an observer abreast the noise source where certification measurements are made. A short nacelle provides no shielding.

The engine installation has to meet noise requirements when it is certified for use on an aircraft. Some manufacturers surpass the requirements, attempting to appeal to customers that might be more noise sensitive. Rolls claims to have the quietest installation on the 330 and they are the only one with the extended nacelle. The underlying engines differ in design; they also differ in noise output. It wouldn't surprise me if the 700 core failed to meet the reg with a mid nacelle, exceeded it with the long, and the marketers turned necessity into a feature. The Trent 7000 is developed from the 787's Trent 1000 and has a different core and its installation on the A330neo
uses a mid length nacelle.

A similar but less critical situation exists for the flow from the front fan. The short nacelle on your 747 example would not provide as much noise shielding from the front fan as the mid length nacelle. The PW4000 is a derivation of the JT9D, so it is not the same engine as you state. More importantly, its certification on the 747 took place some twenty years after the JT9D under more strict noise regulations, hence the longer nacelle.


Are mode C altitude returns valid for aircraft separation?

Yes, they are separated. Both according to mode C (in your example, there is 1,100 ft between them - not 900) and in general. It is normal for there to be small deviations in mode C in the range of 100 to 200 ft. If I have two aircraft crossing each other, supposedly with 1,000 ft in between, but the indicated (mode C) separation is slightly less, I will certainly ask the pilots if they are indeed at their assigned altitudes. If they confirm, then all is well. A pilot report generally overrules mode C (to the extend where there is even a procedure for asking the pilot to turn off mode C reporting if there is a discrepancy between pilot report and mode C).


Which "pilotless aircraft" did the authors of the 1944 Chicago convention have in mind?

Note that the article says that

  No aircraft capable of being flown without a pilot

At that point of time there were a number of radio controlled aircraft which could be flown without a pilot on board (for example, the RP series aircraft and OQ-2 Target drone, of which thousands were made). The authors of convention most probably had these in mind when they frame the article 8.

This ICAO document on Unmanned Aircraft Systems also points in the same direction:

  4.3  Article  8  details  conditions  for  operating  a  “pilotless”  aircraft  over  the  territory  of  a  contracting  State.  To  understand  he  implications  of  this  Article  and  its  inclusion  from  the  Paris  convention  of  1919  (Article  15)  into  the  Chicago  Convention  of  1944,  the  intent  of  the  drafters  must  be  considered.  Remote-control  and  uncontrolled  aircraft  were in existence at the time, operated by both civil and military entities. “[A]ircraft flown without a pilot” therefore refers to  the  situation  where  there  is  no  pilot  on  board  the  aircraft.  As  a  consequence,  any  RPA  is  a  “pilotless”  aircraft,  consistent with the intent of the drafters of Article 8.

(emphasis mine). So, the authors of the 1944 Chicago convention most probably had radio controlled aircraft in mind.


How do fuel trim and air bubbles prevention work in inverted flight?

A typical GA airplane will draw fuel from at or near the bottom of the tank.

An aerobatic airplane will have a hose from the engine to the middle of the tank, then on the inside of the tank there will be another flexible hose with a weight on the end.  This inside hose is called a "flop tube".

When the plane is in upright flight, the "clunk weight" on the bottom of the "flop tube" (these are the real terms for them, I'm not making this up!) will rest on the bottom of the tank and draw fuel from there.

When the plane is inverted, the weight will move (along with the fuel) to what was formerly the top of the tank.

This ensures that as long as the tank has a reasonable amount of fuel in it, the clunk weight will be submerged most of the time.  There are occasions (usually rolls while going straight up or down) where the weight (and end of the flop tube) is momentarily exposed to air in the tank.  The engine will "hiccup", but there's usually enough inertia in the propeller and engine parts to restart the engine by itself when fuel flow is restored a fraction of a second later.

There's an additional component - a special header tank - that helps by confining the flop tube to a very small tank that's 100% full of fuel 99% of the time.


How could MH370 fly west when satellite pings went east?

You have an error in one of your major premises.

You say "satellite pings went east".

That can't be derived from the data you have shown. The chart is showing Doppler shift. A westbound aircraft that is decelerating, or simply decreasing its component of velocity toward the satellite (by, for example, turning slightly southbound) will result in a change in the Doppler shift.

Deviations up and down on that chart don't correspond to the velocity being east or westbound, but accelerations towards or away from the satellite.


How common is it for flight attendants to have pilot certificates?

In my experience, it is uncommon but certainly not unheard of. Maybe between 1% and 5%, as a ballpark.  A flight attendant married to a pilot who owns his own aircraft has access to the plane and instruction, so that's one scenario. In another case, an F/A I flew with a few times was building time as a CFI and doing right-seat work at SimuFlight, before she left our airline to start with a regional. (Wouldn't be at all surprised if she's flying at a major right now.)

Among flight attendants, there are a lot of really interesting stories of how they got to be where they are. Sometimes the generalizations fit, but when they don't, you find an amazing breadth of experiences in that group.


from
http://code7700.com/high_latitude.htm

Apparently defined by Transport Canada:

https://www.tc.gc.ca/media/documents/ca-publications/AIM-2018-1-E-ACCESS.pdf

page 192


Would a flying-wing drone fly farther if filled with helium?

If the end result of the sealed wing filled with helium is lighter than the same wing filled with a normal atmosphere (nitrogen, oxygen, and assorted other gases), then yes - a lighter aircraft will, all else being equal, have better performance and thus longer range than a heavier one.
If you'd actually be able to achieve economic benefit is doubtful - the delta in weight will be offset by everything required to seal the wing up, and the gain in efficiency may be pretty tiny. Beyond that, if mechanics need to access stuff inside the wing, you'll be paying to replenish the helium whenever that happens. Plus, the volume inside the flying wing is normally where things like fuel, passengers, crew, cargo, engines, and etc would go; you may find that you don't have all that much available space left to fill with helium.


According to the Washington Post, Air Force One never refueled in mid-air with the president on board.
If it needs to refuel, it usually does so at one of the U.S. military bases across the world.

The retrofitted Boeing 747 that usually serves as the presidential jet can indeed refuel in flight — but it has never done so with the president on board, military officials say.
It has enough range to fly from Washington to Iraq without needing more fuel. On longer trips to Asia, it typically stops at U.S. military bases in Alaska or Germany.
— Five myths about presidential travel


For calculating $V_{stall}$, why should be used $C_{L,max}$ and not $C_{L,min}$ (that would be more prudent)?

The stall speed is the speed at which you can still fly the plane in level flight. This is important, because strictly speaking, stall happens at a certain angle of attack, not at a certain speed. In other words, you can safely fly a plane way below stall speed - the problem is that you'll be doing it nose-down in order to keep the angle of attack to a minimum (and that as such you will quickly exceed the stall speed again - hey, we just did a stall recovery maneuver!)

So, let's see what happens when we approach stall speed from a higher speed, while flying level. As we slow down, we must increase our angle of attack to maintain level flight - this way, we are increasing the $C_L$ of the wing, as to keep the lift $L(=W)=\frac{1}{2}\rho VSC_L$ constant when reducing our $V$. Ideally, we'd like to keep increasing our $C_L$ as we reduce our $V$ - however, this means we keep increasing our AoA (angle of attack) until it gets past a critical point, where the airfoil stalls due to flow separation at the suction side of the airfoil.

So really, using $C_{L,min}$ would be nonsensical - if your wings would have a lift coefficient so low at such a low speed, I can guarantee you that $W>L$, i.e., you plummet from the skies. We need to increase our $C_L$ to maintain level flight, and the stall speed is exactly the point where we can no longer increase our $C_L$, or in other words, we arrived exactly at $C_{L,max}$.


How do radio altimeter systems compensate for objects on the ground?

Objects on the ground are negligible because the radio altimeter is not designed nor used to such high precision.

There are several uses of the radio altimeter. The first one is for timing the flare during the last portion of the landing. Since the flare maneuver starts after the aircraft has crossed the runway threshold, at this time the aircraft is over flat ground.

The second usage is terrain awareness. The radio altimeter will trigger the GPWS "terrain! terrain! PULL UP" warning if the reading is too low. If you are in a range where the height of cars or trees matters, you are too low anyway.

You may imagine that pilots use the radio altimeter as their main data source for height above ground during the landing phase. That is not true - the barometric altimeter is always the primary instrument to use, until the flare portion at least. That is why pilots need to adjust the altimeter to the local air pressure setting. However, the radio altimeter can provide useful situation awareness. For example, you are landing at an airport with elevation 2,200 feet, you are 10 miles from the runway, and your altimeter reading is 3,800 feet. Suddenly you hear the automated voice "five hundred" in your cockpit. Needless to say something is wrong.

Pilots cross check the barometric altimeter with the radio altimeter during landing. The airport elevation is usually dialed-in somewhere on the cockpit display for quick lookup. When the automated "five hundred" announcement is made (or announced by the pilot not flying / flight engineer on an aircraft without automated announcement system), you quickly glance at the barometric altimeter to see it is 500 feet above airport elevation. It does not have to be exactly 500 - 492 or 518 will do as well. Then you cross check the distance to runway threshold with the DME (if available). Again, you don't have to be exactly 0.8 nautical miles or whatever distance the calculator come up with. As long as you're reasonably close, it is good enough.

If the pilots are using the ILS, then vertical guidance will be provided by the glideslope signal until decision height, at which point they will switch to the barometric altimeter again.


Why is there still a preference for turboprop airliners over the new regional jets?

The simple answer is turboprops are more profitable on short stage lengths, say up to 400 miles or so, where the limited ceiling and slower speed are less of a detriment and the turboprop's better seat mile fuel burn is a bigger factor.  This allows lower ticket prices. Once you are getting out toward 1000 miles or more, it becomes worthwhile to go higher for both efficiency and weather avoidance ability, and jets start to become more profitable.

The -8 400 extends this somewhat and can almost match jets on moderate stage lengths on total trip time, so it bridges the gap between TPs and jets to a degree.  It's noise and vibration cancellation system helps this a bit by making the trip a bit less unpleasant.

There are other complications.  Depending on the market, pax may be willing to pay more for jet service on short trips, especially in affluent markets.  There are RJ operators in the US that run CRJ200s or 900s on very short runs that would be way cheaper served by TPs because their customer base demands jets and it's worth running those routes at razor thin margins to keep the customer base.

Other factors include things like maintenance sophistication.  Older TPs require less electronics-savvy technical expertise and a small operator having great difficulty retaining mechanics trained to figure out software based control systems will be attracted to simplicity.

One of the biggest drawbacks to the -8 400, and which in truth is killing it vs its ATR counterpart in sales, is the level of electronics sophistication is high compared to other turboprops, nearly jet-like.  When Canadian regional Air Canada Jazz acquired the -8 400, their -8 technical team was warned by their RJ technical team to get ready because the airplane was closer to a CRJ900 maintenance wise (systems run by black boxes vs hydromechanical components that any wrench turner can figure out) than an older -8.  The training level of the technicians becomes critical in achieving decent dispatch reliability.

TP vs C Series (soon to be renamed the Airbus somethingorother)?  Same thing. Depends on the mission requirement.  The C Series' competition is other jets, not turboprops.


Why do some turboprop engines require motoring after shut down?

Rotating the propeller of the Cessna 441 Conquest II is to cool the Garrett TPE331 engine in the aircraft. From airliners.net

  On the Garrett TPE331's we were trained to spin the props after shutdown to get cooling air flowing through the engine, this was done right after shutdown. Half an hour after we did the prop spins we had go back out to the aircraft and rotate the propellers one blade width. Moving the prop one blade width rotated the engine one half turn, this was to prevent the shaft from sagging as the engine cooled causing turbine blades to rub.

The reason is given as:

  Direct drive turbo prop engines sometimes require this to remove residual heat from the engine because once the prop stops turning, so does the engine. When the pilot turns the prop, depending on the gear ratio, he is actually spinning the engine very fast. This helps move some of the heat out of the engine.


It is possible for an airplane to get infested by animals?

Yes, I have personally worked on multiple aircraft that were infested by animals.

All of these aircraft were small planes, single engine Cessnas for example. A typical example would be one or two small mouse nests in the wings. I also found at least one wasp nest in an aircraft wing.

The worst I ever saw was a Mooney that had extensive mouse nests throughout the airframe. That aircraft had been unairworthy for at least a year by the time I saw it.

That Mooney ended up being parted out and scrapped, largely because of extensive corrosion in the wings which was either caused by, or aggravated by, the mouse nests. Urea can induce corrosion in aluminum, and finding a mouse nest or other evidence of rodent activity should prompt closer inspection. All the other instances of mouse nests that I have found in airframes were in aircraft that flew several hundred hours a year and these did not suffer any major damage.

I have also heard stories from many pilots and mechanics of finding birds nests—for example in engine intakes or the empennage—and of rodents chewing into or through electrical wiring. There is also the classic warning to check the pitot tube in case a mud wasp has clogged the intake with a nest. I have never witnessed any of these occurrences myself.

The mud dauber wasp is notorious and is suspected of being a contributing factor in at least one fatal airline accident that I am familiar with: Birgenair Flight 301.

Photo source, courtesy of the FAA

Many means of prevention are available, including typical pest prevention methods such as traps and poisons—in my experience all reserved for use in the storage hanger. The most aviation specific forms are the various covers used to protect pitot tubes, engine inlets, etc.

Photo source, courtesy of the FAA

As far as the possibility of animals surviving, I suppose the odds are low. I have never encountered a live animal in an airplane (pets excepted). For any animal stowing away on a pressurized aircraft operating at high altitude I should think the low oxygen partial pressure and temperature would both discourage survival outside the pressure vessel.

Some flights, particularly international ones, apparently make a practice of spraying some form of pesticide in the cabin to kill mosquitoes and other unwanted creatures.


How does an aircraft move on the ground?

For movement on the ground the aircraft uses it own engines, however since the aircraft cannot move backwards on its own, there are pushback trucks on the airport

A pushback truck lifts the front weel of the aircraft, their role in most airports is to move the aircraft away from the parking spot on to the taxiways. Here the truck is removed and when all platform staff is out of the way the engines are started one by one. From here on the aircraft moves on its own power to the runway. In the aircraft you will hear the engine spinning up when power is demanded for acceleration.


What are the role and responsibilities of "fleet captains"?

A fleet captain basically deals with fleet specific issues. For instance if a new procedure is introduced in the company how is this going to be implemented on the fleet. The most recent example in my company has been the implementation of "RNP" approaches (GPS only approaches) that was introduced across the company but what does it mean for our fleet; where is this displayed on our specific aircrafts what calls should be made depending on the various cues we getting our aircraft etc...this is the kind of answers the fleet captain would have to give to the Chief Pilot in the this example the training department would be heavily involved as well with the respective CFI's(Chief Flight Instructors) again fleet specific. Depending on the company structure the fleet captain might be associated with daily issues or even disciplinary procedures in association with CP, HR etc...
Hope that helps :-)


Why does the FAA require special authorization to act as PIC in the North American T-28 Trojan?

As the T-28 is a vintage military surplus aircraft it is normally certificated in the Experimental-Exhibition category. For most aircraft in this category, there is no type rating in the traditional sense. For years, the FAA managed these aircraft and pilot qualifications for them on a case-by-case basis. Approval to fly them was (and for some vintage aircraft still is) granted by a Letter of Authorization (LOA).
About 15-20 years ago, in an effort to reduce the regulatory burden on both the FAA and pilots they moved to a process that more closely aligns with type ratings. It is managed under the Vintage & Experimental Aircraft Program.
The stated coverage of the program is:

This program standardizes pilot certification in the following U.S.
aircraft:

Vintage Type Certificated aircraft which require a type rating
Experimental turbine-powered aircraft
Experimental aircraft with a maximum gross weight in excess of 12,500 pounds, or
Experimental piston powered aircraft with an engine over 800 HP and a Vne (never exceed speed) greater than 250 knots

The T-28 falls under the last bullet as it has more than 800 hp.


What would be the Sref i.e. Reference Wing Area for Drag Build Up Calculation in case of a box wing design?

You could argue for one or for both, but ultimately, it doesn't matter - as long as you are consistent and use the same reference area throughout your calculation/analysis.
If I personally were to choose, I would go for both, on the basis of total lifting area.
EDIT for details ------
Well yet again, it doesn't matter. You will get some value for your $C_{Dmin}$. Then later for other calculations you will use the same $S_{ref}$ and you will get comparable drag coefficients. Finally, when you use $D_{total} \text{ [N]} = C_{D} \cdot 0.5 \cdot \rho \cdot v^2 \cdot S_{ref}$ you will input same $S_{ref}$ and you will get the same Newtons regardless of chosen $S_{ref}$.
What matters is that you're consistent, i.e. if you use $S_{ref} = 10 \text{ m}^2$, use that for everything. If you use $S_{ref} = 20 \text{ m}^2$, use that for everything.
Additionally, do recheck the wetted area argument. $S_{wet} \neq S_{ref}$, because $S_{wet}$ includes both upper and lower surface of each wing, whereas $S_{ref}$ includes only the planform surface.


Why is taxiing super slow after an ILS CATIIIB landing in almost zero visibility?

The reason for using taxiway C is described in the Low Visibility Procedures from the AIP:

4.4.4 At present, TWY ‘C’ and Stand no 11 to 14 are equipped with CAT IIIB lighting system as per short term interim plansubmitted to DGCA by AAI and agreed to by DGCA vide letter no. AV.20015/09/08-AL dated 15-07-2014. Therefore, duringCAT IIIA and CAT IIIB operations, arrivals and departures shall use TWY ‘C’ only.

So the reason you had to taxi via C is because C is the only taxiway with sufficient lighting to support CAT III operations. For CAT III operations, taxiway centreline lights are required. The other taxiways at Lucknow only have taxiway edge lights.
Source: https://aim-india.aai.aero/eaip-v2/eAIP/EC-AD-2.1VILK-en-GB.pdf
The reason you had to backtrack (turn around on the runway and taxi back in the opposite direction) must be that the plane was not slow enough to vacate via C when you passed it the first time. I know you said you had already slowed down, but in thick fog it can be pretty hard to estimate speed, especially when looking out a side window. The pilots obviously have access to precise instruments, and must have determined that the aircraft had not slowed down enough.


Under which conditions is full rated power instead of METO power required for takeoff (DC-3/C-47 with Pratt&Whitney 1830 twin wasp engines)?

Let's consider your case of a 2300 ft (700 m) takeoff roll. Your link lists the procedure as reducing power upon reaching 90 kt (46 m/s). To make things easier we can assume constant acceleration. That won't be true in real life but it will give us an approximation.

Two basic equations for acceleration, relating distance $s$, acceleration $a$, time $t$, and velocity $v$:

$s=\frac{1}{2}at^2$

$a=\frac{\Delta v}{t}$

Substituting our known values in, we get:

$700\ \mathrm m=\frac{1}{2}at^2$

$a=\frac{46\ \mathrm{m/s}}{t}$

Soving for $t$, we get about 30 seconds (and $a=1.5\ \mathrm{m/s^2}$). Even accounting for acceleration reducing as speed increases, that suggests there's plenty of room to reach 90 knots in less than one minute.

If we look at what takeoff roll would result if we need 60 seconds to reach 90 knots, we get 1380 m, or 4500 ft.

To verify this you can also look up videos of DC-3 takeoffs. Like this one, which seems to take about 30 seconds:

I agree with the comments, piston travel changing significantly with power setting does not make sense.


What are the drawbacks of a liquid hydrogen jet engine?

Here are a few drawbacks:

Lesser energy density per volume

For the same amount of energy, you need more space, not yet available in current designs

Boil off

The hydrogen will slowly boil off, and vented to the atmosphere. Hydrogen IS dangerous, and this will negatively impact long flights.

Logistics

Fuel is common everywhere in the world and easy to store. We have yet to build a world delivery network for hydrogen.


How many aircraft types can a 135 pilot be assigned to?

There is no FAA regulation limit for the number of types a Part 135 pilot can be assigned to, providing all training programs are followed.  Insurance and safety auditing companies usually have guidelines requiring no more than 2 types to be assigned at a time so the 2 aircraft limit has become something of an industry standard.

There may be non-US regulations that address this issue.


How are modern jets modified to takeoff/land on a dirt runway?

Just to roll around on "unimproved" airfields (grass/dirt/gravel strips), the biggest thing planes need is simply a decent set of tires:

This MiG-29UN trainer shows off the fairly beefy main tires put on these planes specifically to allow them to more easily roll over minor imperfections in the runway/taxiway surface, including dirt/gravel/grass strips (though here it's landing on a traditional asphalt/concrete surface). Compare these to the relatively small gear wheels and low-aspect rubber on the similarly-sized F-16:

(source: f-16.net)

Now, your question oversimplifies things, because "foreign object debris" or FOD is in fact a primary danger of unpaved airstrips for jets, and this danger has to be accounted for in the design. Here's the main reason the MiG-29 can take off from dirt:

MiG-29s and similarly-minded Su-27s, and their variants, have special doors to close off the lower intakes normally used in flight, instead drawing in air through the gill-like ports over the top of the wing strakes. This prevents the engine from ingesting dust, rocks, birds, rodents, etc on takeoff and landing.

This engine protection system, while effective, adds mechanical complexity and weight which U.S. designers and military brass have generally thought unnecessary given that requirements rarely include the ability to operate from unimproved strips. Most U.S. fighters in the jet age, therefore, have had to operate from airbases with some form of paved runway surface (and the U.S. military actually has higher standards for runway surface quality than most international airports). The U.S. arsenal does, however, have several aircraft that are specifically designed to operate from rudimentary airstrips at forward bases. These designs avoid FOD damage primarily by keeping the engines up as high as the design will allow. For instance, the A-10's two engines are on pods angled up on the fuselage between the wings and tail for a variety of reasons including FOD avoidance:

Most of the other designs in the Western arsenal that can do this are high-wing designs with wing-mounted engines, which keep them out of the dust produced by takeoff and landing in a similar fashion. Here are a C-130 and C-17 landing at an Afghanistan forward base:

The Harrier is a notable exception to this general strategy by Western designers of just keeping the engines out of any debris cloud. While it's probably not done routinely, a Harrier can set down just about anywhere, and as this picture shows, it ingests no small amount of dust in the process:


Why do some flights make turns shortly after takeoff?

It is mostly standardized procedures.

I take as example Amsterdam airport (AMS), but the following is applicable to most, if not all, major commercial airports.

Let's look at the departure charts, in particular this one:

as you can see, if an airplane is departing via that runway, it MUST follow one of the two specified paths to exit the airspace of the airport through the "ANDIK" waypoint. It has different paths for the other exit waypoints, but they are similarly defined and limited in number.

In the link you will find similar charts for each of the runways.

Within restrictions due to factors like terrain, noise abatement over populated areas (as Dan's mentions in his answer), areas restricted due to security and safety (over city centres, government and military installations, nuclear power plants and such) or used for other purposes (military operations, space launch and such), these routes are defined so they don't intersect (much).

This ensures arriving and departing aircraft don't come close to each other, which greatly reduces the risk of collision and allows responsibility for different routes to be split among several controllers who can each handle their assigned routes mostly independently of the others.

Weather conditions and other factors will dictate which runways are used, but the runway will dictate how the airplane will exit the airport's airspace, after the appropriate exit waypoint has been selected (you generally would not use a waypoint on the north side if you have to go south).

So, to summarize:

you have a limited amount of exit waypoints
you have a limited amount of runways
weather will restrict your choice (well, the airport's tower will do this for you) of runway
your destination will restrict your choice of exit waypoint
for each runway-waypoint pair you will have one or two possible routes

This results in the kind of behaviour you have observed.


Under what conditions do airliners retire aircraft and sell them to other airlines?

Some reasons for an airline to sell some of its fleet:

they need quick cash (as ratchet freak points out). This usually means the company is in serious trouble
they're changing their route network and there's no more need for it (e.g. KLM dropped a lot of very short flights in the 1990s and early 2000s, and got rid of the aircraft that were operating them as they were inappropriate for the longer routes that replaced them)
they bought out another airline and have no need for (all) its aircraft, or want to replace them with other types to keep their fleet homogenous (operating many similar types is less economical than operating a smaller number of types)
they're splitting part of their operations to a new company set up for the purpose (the new company becoming the new owner of the aircraft, usually for a symbolic fee), for example a regional affiliate or a charter operation
it may be more economical to replace the aircraft then to keep them. When NWA decided to replace their DC9 fleet with A320s this was for economic reasons (lower maintenance and fuel cost for example), not because the aircraft had run out of fatigue life. The aircraft were old so most probably were scrapped, but some may well have ended up with airlines in other countries, replacing even older aircraft or expanding existing DC9 fleets there.
and some airlines just want to portray a public image of always flying shiny new aircraft. I believe Singapore Airlines used to have a policy like that and replace everything it bought relatively quickly (more so than most other airlines at least). PanAm was like that as well. If you have a reputation of exclusivity, this may add to customers' willingness to pay premium to fly with you


What airfoil type is used on the B727-200F?

My favourite book for questions like this is Obert’s Aerodynamic Design of Transport Aircraft. It shows pressure distribution on the 727 wing and gives some AIAA papers as sources. If you track these down, that might reveal more. Unfortunately no airfoil reference is given; however it is very likely that the 727 uses a proprietary Boeing airfoil.

Posting as answer despite not really answering, as it is still more than a comment...


Logging time towards commercial pilots license

I am assuming that you are already a private pilot working on your commercial ticket. There is no requirement to do your solo hours at one flight school. Just make sure your primary instructor knows what you are doing and is OK with it.


Can an airport without an FAA controlled tower have their own tower and controllers?

Yes, in fact there are a number of Non-Federal Control Towers (NFCT) in the United States.  These are NOT the same as Federal Contract Towers (FCT), which are funded by the FAA and operated by contract personnel.

NFCTs, on the other hand, are usually funded by the local airport authority.  Some examples (not authoritative or all inclusive): Mojave (MHV), Laughlin/Bullhead City (IFP), and Merritt-Titusville (COI).

Unfortunately, there isn't a consolidated list of all NFCTs.  Rather, they are tracked by their respective FAA region.  Here are the Southern and Western-Pacific Hub Organization Orders that list their respective NFCTs (not sure if they're current).

Operation of NFCTs is covered by AC 90-93b.


How do flight crew train/demonstrate ditching evacuation?

Flight crew training facilities have a big pool with a mock aircraft hull with slides and rafts.

Real aircraft are rarely used for training. It's much cheaper to build a fake aircraft interior into the building and use that than to tie up an aircraft that should be making money. It also lets the instructors simulate more dangerous scenarios, like smoke in the cabin, safely.


What is the influence of yaw on P-factor?

As a starting point, you need to thoroughly understand why P-factor tends to make a left yaw torque (in the case of a clockwise-rotating prop, as viewed from behind) when an aircraft flies in a nose-high "angle-of-attack".  Note that by the aircraft's "angle-of-attack", we mean the aircraft's pitch "attitude" in relation to the flight path, not in relation to the ground.  Do you see how this increases the lift or thrust generated by the down-going half of the prop disk, and decreases the lift or thrust generated by the up-going half of the prop disk?  Thus creating extra thrust from the right side of the prop disk and making the aircraft tend to yaw to the left, in the case of a clockwise-rotating prop (as viewed from behind)?  If not, you might benefit from reading the section entitled "P-factor" from John Denker's "See How It Flies" on-line tutorial website.
Once you've digested that, you'll observe that for a mental "shortcut", we can model the effect of P-factor as follows:  think of the spinning prop as a solid disk.  Pick the point on the disk that is "tilted backwards" in relation to the actual flight path.  This would be the top of the disk in the case of an aircraft flying at a high angle-of-attack.  Now rotate your chosen point 90 degrees in the direction that the prop is rotating-- which for this explanation we'll assume to be clockwise, as viewed from behind.  So now you are looking at a point on the right edge of the prop disk, as viewed from behind.  P-factor can be modeled as an extra forward "thrust" or "push" applied to the prop disk at this point.  This will tend to make the aircraft yaw to the left.  Note that this has nothing to do with gyroscopic precession-- it's a purely aerodynamic effect.  This mental shortcut isn't meant to explain why P-factor occurs, just to quickly determine in which direction it acts.
Once you are comfortable with this "shortcut" for figuring out which part of the prop disk will be "loaded up" by the P-factor effect, consider that sideslip tilts the prop disk in relation to the direction of the flight path, just as flying at a high angle-of-attack does.  In a sideslip with the nose pointing to the left of the flight path (ball to the right, yaw string to the left), which part of the prop disk is "tilted backwards" in relation to the direction of the flight path?  The left-hand side.  So if the prop is rotating clockwise as viewed from behind, the P-factor effect can be modeled as an extra forward "push" on the top of the prop disk, and a decreased forward "push" on the bottom of the prop disk.  This will create a nose-down pitch torque.
Kershner could have been more clear in his language here, particularly in relation to his use of the word "yaw".  It's critical to note that we are actually talking about the sideslip angle here, not an actual yaw rotation rate.1  An actual non-zero yaw rotation rate creates a pitch torque in the opposite direction, through gyroscopic precession -- yawing to the left will pitch the nose up.  Just as flying at a high angle-of-attack creates a left yaw torque through P-factor, while pitching the nose down (as when a tail-wheel aircraft lifts the tail during the take-off roll2) creates a left yaw torque through gyroscopic precession. One effect is related to the aircraft's attitude in the relation to the direction of the flight path, and the other effect is related to the direction and rate of change of the aircraft's attitude in space.
Footnotes--

Clearly, the word "yaw" is often used in several different ways in aviation.  Most correctly, it refers to an actual rotation about the aircraft's vertical axis, but it's not uncommon to use it to mean essentially the aircraft's "yaw attitude" in relation to the "relative wind" or actual direction of the flight path though the surrounding airmass-- which is exactly the same thing as the "sideslip angle".  (The term "yaw string" is a classic example of this usage-- and the "yaw string" is sometimes also called the "slip string".)  When Kershner says "if the aircraft is yawed", you should read "if the aircraft is yawed into a sideslip or skid and then held there", or "if the aircraft is allowed to fly in slipping or skidding attitude".

Harvey S Plourde's book "The Compleat Taildragger Pilot" contains a great graph showing the individual and combined effects of all the different factors that contribute a left-yawing tendency during the takeoff roll in a tailwheel aircraft, from the start of the takeoff roll all the way to the moment of liftoff.  Different factors are dominating at different points in the takeoff roll.


What is that A340 cockpit panel on the glareshield?

That display is part of the AFS (Auto Flight System) Control Panel on the FCU (Flight Control Unit):

(Airbus A340 FCOM - Auto Flight - General)

The general idea of the FCU is that you can push in the knobs, which will put the respective autoflight mode in an automatic setting (called managed mode) and show dashes in the display, and you can pull the knobs out and then rotate them to manually overwrite values (called selected mode).

In your example, the display currently shows:

SPD 250: The autothrust system is maintaining a manually selected speed of 250 knots.
HDG ---⚫: The lateral autopilot mode is in managed mode, meaning the aircraft will follow the flight plan programmed into the FMGS. See also this answer.
ALT 08000: The current target altitude for the autopilot is 8000 feet.
V/S -1000: The vertical autopilot mode is to maintain a manually selected descent of 1000 feet per minute.

The FCU allows you to switch between selecting a heading (HDG) vs. a track (TRK) and a vertical speed (V/S) vs. a flight path angle (FPA) with the button at the center. The HDG and V/S in the center of the display mean that the current mode is in heading and vertical speed.


What procedures are followed for a planned landing in a field?

Not just helicopters. It happens all the time in my neck of the woods (Alaska) in small planes with big bouncy tires. We probably have more "field landings" (called bush landings, or "off airport operations") than landings at actual airports. OK, well maybe not quite that many - but enough that my local aviation college has an entire semester course dedicated to it for it's professional piloting program.

The first act is usually a low pass to inspect the conditions and determine the best landing direction (if there is more than one option), assuming that the winds will allow it. If there are other aircraft in the area, which sometimes happens at popular hunting/fishing/floating drop-off locations or glacier tours, then self-announcing on frequency is done like at a non-towered airport.  But, it's usually remote enough that it's not done.

Quite frequently, it's two planes for one party's charter - one to carry the people, and one to carry their gear. In that case, they're usually talking to each other the whole way, and know each other's intentions anyway.


How big is the TP400-D6 turboprop installed on the A400M?

According to the MTU Aero Engines technical data of the TP400-D6:

  Propeller diameter: 209.8 in

(mtu.de)

That is a propeller diameter of 5.33m. I also could not find more details about the nacelles, but one can estimate the size from a photograph. I used this image from aviationtoday.com, which shows the aircraft from the front. With the known propeller diameter, I estimate the nacelle to be about 1.2m wide and about 1.85m high:

I don't think it is possible to derive more precise numbers due to the inaccuracies resulting from the perspective.


Does it make sense towing airplanes to the head of airstrip by external (eg electric) means?

Was [towing unit or motors in landing gear] ever tested or assessed?

Yes.
2014 Main Gear

Using the Auxiliary Power Unit (APU) generator to power motors on the main wheels, the EGTS taxiing system allows aircraft to push back without a tug and then taxi without requiring the use of the main aircraft engines. One wheel on each main gear is equipped with an electric motor to drive the aircraft

From EGTS

Airbus signs MoU with Honeywell and Safran to develop electric taxiing solution for the A320 Family

From Airbus press release

Lufthansa Technik has proven with a technology demonstrator that aircraft can be driven on ground by electric motors.

From Lufthansa Technik (with video)

2015 Towing Unit

As of 2015 Taxibot, a semi-robotic towbarless tractor which meets and connects to aircraft, is the only alternative taxiing system certified and currently in use by airlines in the market.

From Wikipedia

2016 Nose Gear

Honeywell and Safran have pulled the plug on their jointly conceived electric taxiing system, while rival developer WheelTug aims to enter service with its system in 2018.
"After thorough market analysis", the US supplier says, the two partners "agreed to stop work on the Electric Green Taxiing System due to dramatically lower oil prices and the current aviation industry's economic environment".
EGTS had been scheduled to enter service this year, with Honeywell and Safran having planned to produce a system for line- and retrofit on A320-family and Boeing 737 jets.
Meanwhile, Gibraltar-headquartered WheelTug plans to enter service with its nose gear-mounted electric drive system in 2018.
... initially on 737s and, at a later stage, on A320-family ...
Neither Airbus nor Boeing are supporting the programme

From FlightGlobal


Can I fly through these military airfields' class C airspace?

When entering Class C Airspace:

Since all the airfields are Class C you would need to contact the approach control prior to entering.  Approach control should be able to direct you appropriately from there.  Approach control would handle traffic at all three airports. If the military airfield does not want civilian aircraft to cross the field for any reason approach control will direct you around it.  If there is nothing going on at the military field then approach control could let you cross over the field.

When Departing Pensacola Field:

When departing Pensacola field you can request a Northeast departure through Clearance Delivery.  You could be granted the request to fly Northeast directly from the airport or they could make you fly East for a while then make a turn North to avoid the military airport.  Nevertheless you have to follow ATCs instructions whenever you are in Class C airspace.

Side Note:

It is fairly common that when you have military airfield close to a Class C airport, the class C airspace will be extended over the military fields as well so that one approach control would handle all the traffic and deconflict traffic for all of the fields.  A similar situation exists for the Tucson area where the Class C includes Tucson International and Davis Monthan AFB.


What is an autogyro, and why would I ever want to fly one?

What is an autogyro?

Autogyros have been around for decades. They are also known as gyrocopters, gyroplanes, and autogiros. Gyroplane is the official FAA designation. It is basically a rotary wing aircraft just like a helicopter because the rotor  provides lift instead of wings like conventional airplanes.Since the rotor is not powered, an Autogyro uses a separate source for propulsion, just like an airplane. In other words, an Autogyro uses a propeller for forward motion and a freely rotating, un motorized rotor for lift.

http://www.jefflewis.net/autogyros.html

  How do you fly one?

There are only three flight controls: a control stick, rudder pedals and a throttle.

Autogyros do not stall, so it is a lot safer to fly an Autogyro than say a helicopter.You can expect control responses to be faster in a Autogyro than an airplane because you are moving the whole wing  instead of just a  tiny control element attached to a wing. Generally speaking, the control response will not be as quick as a helicopter because of the lower operating rpm of the Autogyro’s rotor system.The critical task in flying a Autogyro is managing the energy of the rotor. If you fail to maintain air flowing through it, the speed drops drastically, and so does the rotor's ability to provide lift.