Why did this commercial flight fly in circles while far from the destination?

The first "circle" is a holding pattern. We discussed those here.
In particular, it seems that you were on hold at VINIL or VEPLI, according to the approach charts (page 5 of the PDF).

The second one is most likely for separation on final approach, the aircraft was probably early and ATC has asked them to perform a 360° to increase the separation between them and the aircraft in front.


How much power is needed by aircraft IFE systems during flight?

I don't have specifics but lets extrapolate for a minute (using the Boeing 777-300 for size filled with lets say 500 seats). Assuming you are talking about IFE systems where there is a screen in every seat then you will most likely have screens similar to this. While not exactly what the airplane uses I would think they are similar. The specs for that screen claim it takes <= 8W. Lets round it out and say it takes 8w. Looking at our 500 seats thats 4000W of power. I can only assume there is a computer or two of sorts running those displays, lets say they have 500W (typical desktop supply on the more powerful side) and there are 2 of them. Thats another 1000W so you are at 5000W there. Assuming you have 120V power P=IV thats about 41 Amps of current you will draw from the system. I am running this assumption that all the screens are on at all times as I assume the system is built for that.

Cabin lighting is tough as I have no idea how many bulbs they have in there. I know that each seat has its own little lamp so you are looking at 500 little lamps running in the 1W-10W range. So maybe another 2000W for the individual lights. Overhead is tough since you cant really see the individual bulbs. It should also be noted that LED's are becoming more wide spread and draw way less power than traditional incandescent bulbs which will greatly reduce the amount of power drawn by the interior lights.


Does the pressure change inside a plane when it is opened for paratroopers?

For low deployment the cabin pressure is already equal to the outside pressure.

For High altitude jumps the pressure is reduced to the outside pressure before opening the door (and everyone puts on oxygen masks).


What does the orange colored text in a SkyVector route indicate?

The Dades 6 is an arrival procedure also known as a STAR (Standard Terminal Arrival Route).

The plate that lists the route and altitudes/speeds for the arrival can be found here.

If you are using a flight simulator, there should be an ARR/DEP page on the FMS that includes (among other things) a list of all the arrivals for the airport you have set as your destination. You can then select the arrival and the appropriate runways.


How can the effects of hot corrosion and salt deposits from sea water spray in gas turbine engines be negated/prevented?

Not aware of any anti-corrosion coatings used in engines.  The best mitigation is to shoot fresh water into the inlet with it running at the end of the day.  Seaplanes operating off salt water will generally get a fresh water hose down at the end of the flying day whenever practical.


What legal actions would be taken against a drone pilot if they flew a drone into class B airspace?

The answer is somewhat unclear, as there is limited (but emerging) case law and regulation on the subject and the outcome would depend heavily on the details of the airspace violation. However, there are some principles that we can use to shape our understanding:

The FAA has jurisdiction over anything flying, including UAS

This was most recently restated in the NTSB decision in FAA v. Pirker. Combine the definition in FAR 91.1: "Aircraft means a device that is used or intended to be used for flight in the air" with the Applicability section in FAR 91.1(a):

  ...[T]his part prescribes rules governing the operation of aircraft (other than moored balloons, kites, unmanned rockets, and unmanned free balloons, which are governed by part 101 of this chapter, and ultralight vehicles operated in accordance with part 103 of this chapter) within the United States including the waters within 3 nautical miles of the U.S. coast.

We see then, that anything flying is regulated - either under part 91, 101, or 103. Since UAS are not regulated under part 101 or 103, they fall under Part 91. Finally, the FAA has authority to impose a civil penalty for violations of the FARs under 49 U.S. Code § 46301. Note that an FAA certificate is not necessary for the FAA to assess a civil penalty: in the Pirker case, the FAA assessed its penalty on a Swiss citizen who did not hold a FAA certificate.

Finding the operator of a UAS is difficult

Finding the operator of a UAS is much harder than finding the operator of a piloted aircraft. The FAA was able to find and assess a penalty to Raphael Pirker because he posted a video he made flying the UAS online. In most situations where UAS were where they shouldn't have been, the operators either were never found or turned themselves in:

UAS crash-landed on the White House grounds
UAS interrupts wildfire-fighting activity - a reward was offered for identifying the operator
UAS reported by pilots on approach to KJFK

Basically, if you're flying a UAS far enough away from yourself that a police officer can't see the remote in your hands, you're unlikely to be found if just your UAS is detected. UAS for personal use do not currently require registration or external markings. A recent research project proposes a tracking system - but would require "affixing radio-frequency detection tags to [UAS]."

Actual enforcement would vary

After all of that, what would happen if you did violate controlled or restricted airspace and were caught? This area is pretty fuzzy, and would depend strongly on a number of criteria, including severity and intent. The FAA's toolbox for airspace violations is broad, but is generally tuned toward certificated pilots. A certificated pilot who accidentally entered class B airspace might get anything from a slap on the wrist, to a required training session with an instructor, to a short-term suspension of their certificate, based on the situation: an overwhelmed or confused pilot would get more leeway than one who just wasn't paying attention or was reckless in their navigation.

Suspension and required training are not really in the FAA's toolbox for folks without a certificate, so you likely would expect some sort of monetary fine. The FAA is limited to $10,000 in its fines, so you could not be charged more than that, and could well see something less.

Prevention is the best cure

Some UAS manufacturers are building in safety restictions on their aircraft to prevent them from flying near airports (note that, at least in the linked situation, the restricted areas are less restrictive than B airspace, so would not necessarily keep you out of that airspace.)

The FAA is also working on a mobile app which should easily allow UAS operators to determine areas to avoid. This is relevant to the enforcement situation: if you enter airspace without clearance, but the app said it was OK, that would be a mitigating factor. More to the point, the app would provide information about the status of nearby airspace, allowing you to avoid violation, and the associated penalty, altogether.


How to make a cockpit LCD display night vision compliant?

You can make an LCD screen NVG compatible by adding a filter screen on top of the display that complies with MIL-STD-3009.  You can get a copy of MIL-STD-3009 from several commercial sources or direct from the Defense Logistics Agency website.
There are a few companies that manufacture the filter screens. I would start with a search for NVIS filters.


What are the trim settings on ferried aircraft?

In case of the Short Mayo Composite, controls of the payload aircraft were locked in neutral position until separation from the carrying aircraft in the air.


Aesthetics are by far and away the last thing aircraft designers are optimising for. A better question might be, why do aerodynamically-efficient designs look pleasing, but that would likely be an art or psychology question and off-topic here.

Since aircraft could travel at appreciable speeds, designs have focused primarily on drag reduction. Smooth curves and teardrop shapes on the leading parts of shapes help with this. Before 3D fluid modelling software, this kind of design would be achieved using a combination of fluid dynamics computations done by hand, wind tunnel modelling, and likely a bit of intuition.


Is autorotation possible from a 0 rpm start at high altitude?

Go back to Estes rocket days.  There is a whole class of competition rockets known as "heliroc" or helicopter recovery.  These ascend like a conventional rocket, in a vertical(ish) path and fin stabilized; at (or near) apogee, they release a rotor by some means and the rotor spontaneously begins to autorotate, often giving a lower descent rate than a parachute.

Go even further back: look at maple seeds (aka maple keys).  They autorotate so efficiently that they'll enter stable rotation and constant (low) sink rate in as little as one blade length of fall (they do have very low wing loading, however).

So, yes, it's possible for a rotor disk to spontaneously begin autorotation from a dead stopped starting condition.  Mother Nature does it billions of times every autumn, and school children do it thousands of times every year.

Yes, this will work with a coaxial rotor, if you can keep the rotors from interfering with one another during deployment (for instance, by braking them until fully deployed).  However, since there's no reaction torque from freewheeling, autorotating rotors, there's no reason to have coaxial rotors.  It's far simpler to use an ordinary rudder for yaw control than differential collective, and you'll have half as many parts for pitch and roll.


What causes aileron and elevator flutter?

Imbalanced or loose (and, in extreme cases, structurally weak) control surfaces can cause flutter, a type of harmonic motion. Flutter is a very dangerous condition; if it is not stopped, it can cause structural failure and potentially lead to a fatal accident. V-tail Bonanzas had a series of such accidents related to flutter of the butterfly ruddervator tail.

I understand that prevention is a combination of good maintenance and keeping the aircraft below Vne (never exceed speed), or possibly other speeds in some configurations.

The appropriate reaction would be to slow down, first and foremost. Descending is probably also a wise choice.


Why are planes slower at higher altitudes?

This is because what you are looking at is the IAS indicator (Indicated Air Speed).
This represents the amount of relative air which flows over and under the wings of the plane. This is what creates lift and enables the plane to fly. This is why this instrument is so important and belongs to the primary flight instruments.

This is not to be confused with GS (Ground Speed), which can be sensed by IRS (Intertial Reference System), or by the GPS. Ground Speed is not relevant to pilot an aircraft, but it's still useful for example to determine the ETA (Estimated Time of Arrival), and for fuel estimation during flight.

The IAS indicator indicates a lower speed because the more you climb, the less air there is. So even the air flows faster, the global pressure feeling is lower.

So, actually planes are not slower at higher altitudes. They are faster (at least most planes whose flight envelope force them to fly faster when they are higher, otherwise they would stall, because they would have to increase their Angle of Attack too much to counterbalance the lack of air flowing above and under the wings). But when they reach their target Mach speed, their speed will decrease slowly as the outside air temperature is decreasing until end of climb.

Sorry for the picture being in French... But as you can see, the flight envelope of an airliner forces him to actually fly faster as it is climbing.

Different speeds

There are different speeds on an aircraft, and it can be quite confusing.

IAS (Indicated Airspeed) is what the instruments directly sense. It is computed by subtracting the static pressure (static ports are placed on the fuselage, vertically to relative airflow) from the total pressure (pitot tubes are placed parallel to relative airflow. This gives a measured dynamic pressure which is then displayed in knots, km/h or mp/h. This speed is showed on most general aviation aircrafts as the main speed indication (but it's actually not a speed and more a 'pressure of air feeling').
CAS (Calibrated Airspeed) is the same as IAS, but without instrument errors. It gives a speed related to the real dynamic pressure felt by the aircraft. This speed is showed on most airliners as the main speed indication (for pilot and autopilot).
TAS (True Airspeed) is the same as CAS when at 15°C, 0% humidity, 1013,25 hPa (29.92 inHg) (ISA, International Standard Atmosphere). This time it is literally the air speed (speed of the air): it is the real speed at which the relative air flows around the aircraft. It takes into account the fact that air density is not always the same. This speed is used when measuring or referring to an aircraft performance during cruise for example. It is also used during flight planning before the wind has been taken into account.
GS (Ground Speed) is the speed of the aircraft relative to the surface of the Earth (the equivalent of the speed showed in a car). In an airplane, we cannot use wheel speed to measure it because we are in the air, so we need GPS or IRS to do this. If there is no wind outside, TAS and GS are the same. If there is 30kt tailwind, GS is 30kt higher than TAS. This speed is used to know when you will arrive at your destination airport, and to know if you will have enough fuel (because the wind is taken into account). This speed is also used when the aircraft is on the ground (when taxiing, or more generally at low speeds when wheels are on the ground). Airlines or airports fix speed limitations when taxiing. The only way to know if you respect the limits is to look at the Ground Speed. Also, the airspeed indicator usually won't be active below a certain speed (45KIAS for the B737).

So, why is the primary airspeed indication (IAS or CAS) the wrong speed (not actual speed) of the air flowing around the aircraft?
This is because this wrong airspeed represents actually the real pressure feeling around the wings that is responsible for the lift. It is this parameter that we need as pilot and it is used in aircraft manuals to describe the V-speeds. It's perfect that IAS and CAS are not corrected with altitude and temperature, because if we know that our airplane stalls at 120kts for example, we won't need to care about altitude or temperature. Our airplane will stall at that same speed regardless of altitude and temperature. If we would use TAS, stall speed would be constantly changing and it would be more difficult to keep the aircraft in good and safe flying conditions.

Here is where you can find these speeds in the Boeing 737 NG cockpit:


What is the maximum angle between an airplane and runway centerline when touching down at a crab angle in a crosswind landing?

A B777 (as in your photo) would generally have a maximum crab angle of about 16 degrees when approaching and landing at the Maximum Demonstrated Crosswind Component of 38 knots.

A 38 knot crosswind is not limiting and can be exceeded provided you apply a sideslip or crab correction at touchdown. It is however limiting if you plan to touchdown maintaining the crab.

E6B Heading, Ground Speed, And Wind Correction Angle

By using a sideslip or crab correction at touchdown, Airliners will sometimes approach and land when the wind exceeds the Maximum Demonstrated Crosswind Component. If the crosswind component was 50 knots and the aircraft was had a lower approach speed (due to light weight), the crab angle during approach could be as much as 25 degrees.


Specific Acrylics for fabricating windscreen

You need cast acrylic sheet (not extruded).  If you are in North America you can get it from Aircraft Spruce https://www.aircraftspruce.com/catalog/mepages/plexiglas.php?clickkey=7342.  The cast sheet made for airplanes has UV blockers as well.

Acrylic has roughly the same tensile strength as Lexan (8-9ksi - a 1/8" sheet of acrylic or Lexan has roughly the same strength as a sheet of .032 6061 aluminum) but is more brittle and has to be formed into as close to the final shape as possible, with the minimum possible preload on the sheet and at fastener holes.

On the plus side of being brittle, although it still scratches a lot easier than glass, the surface is way harder and doesn't scratch if you look at with furrowed brow like Lexan does (although it can come with hard coatings - which tends to get removed by polishing), and is immune to fuel to boot.

Lexan is popular because it can take a lot of pre-stress and you can force it into moderate curves and clamp fasteners on it without it cracking.  But acrylic is superior for the other characteristics important to airplanes.

If your homebuilt's windshield is made up of flat sheets, it's a no brainer - cast acrylic.  If it's a curved wraparound, you'll have to form the acrylic into the curve by heating it in an oven and draping it over a form.  If fuel was an unavoidable problem because of a gas cap in front, it's probably worth going to the trouble to form an acrylic windshield if you have an oven big enough to fit the sheet.  If the fuel exposure was an unlikely to repeat fluke and you need a curved windshield, it might be easier to just do another polycarbonate one that you can cold bend.


Why is laser illumation of a cockpit an emergency?

Let me posit a hypothetical game ("Don't Try This at... well Anywhere").
It's simple - there are just 3 rules:

  Give your friend a nice laser pointer and have them stand at the end of a road
  A half-mile or so should be plenty.
  Get in your car at the other end of the road and drive toward your friend.
  Your friend's goal is to shine the laser in your eyes. Your goal is simple: try not to crash.

Clearly this is not a very safe game.
It should be clear that playing the same game with aircraft is substantially less safe. Someone attempting to "play" without your consent certainly rises to the definition of "emergency" in my book.

If you actually play this game you'll note that the laser isn't a neat pinpoint when it's shining at you.
Between scratches in the aircraft's window and the way your eye perceives light the laser pointer can completely blind the victim - check out the examples in the graphic below.

[

To date I don't believe any accidents have been attributed to laser illumination, but it is well within the realm of possibility, and the upward trend in laser illuminations of aircraft means the likelihood of such an accident is also increasing.

For more information check out the FAA's Laser Safety Initiative -- and particularly the video here.


How can a passenger tell if a flame-out / engine failure has occurred?

Mainly by the soon to happen descent and landing, probably at a place you weren't expecting to go.  :)

If you are seated behind the wing, you might be able to see smoke or flames coming out of the engine, but other times it will just quit with no visible indicaion, depending on the cause of the failure.

Sometimes (usually just after takeoff when the airplane is slow) it is obvious and you can tell by the change in the sound of the airplane (one side suddenly gets quiet or there might be a loud bang depending on why it failed), a sudden yaw in one direction (the nose pulls to one side), and an abrupt pitching down of the nose (done by the pilot to maintain flying speed).

Other times (like during a descent with plenty of speed and the engines at idle, or when the center engine of a three engine airplane fails) it can be hard for even the pilot to tell without looking at the instrumentation, so you probably won't notice it.

Another major clue would be when the seatbelt sign unexpectedly coming on, without an announcement or indication of turbulence, and the flight attendants suddenly putting things away and getting ready for landing, especially when you aren't close to your destination. Being briefed for an emergency landing is also a dead giveaway (no pun intended).


Why does a mid-wing aircraft have lower drag?

It's because interference drag (the vertical flow field forced to share space with the horizontal flow field) is minimized when the wing meets the fuselage at a 90 degree angle or more.
With a low wing airplane with dihedral, even if the sides of the fuselage are vertical, there is still less than a 90 degree angle due to the dihedral angle.  To mitigate the effect of an acute angle at the junction, traditionally a fillet fairing is installed to provide a curving transition between vertical and horizontal, reducing the intensity of the interference closest to the fuselage and minimizing flow separation.
Ideally however, it's better to have as close to a 90 degree intersection, as possible, or better yet greater than 90 degrees, and a mid wing makes this easy to do.  And if the fuselage cross section is circular, like the Grumman Wildcat, even better because the intersection is effectively a bit more than 90 degrees because the sides are curving away from the joint.  The mid wing has a number of packaging problems however (like the Wildcat's crazy landing gear, spar going right through the key cargo space on transport aircraft, etc).
The Corsair fighter killed two birds with one stone in going with the gull wing configuration; it lowered the wing at the landing gear attachment to allow a much shorter strut, and it maintained a 90 joint at the fuselage even though it was attached near the bottom.  The Corsair's gull wing achieved the benefit of a mid wing design aerodynamically, and a low wing design in its landing gear configuration.  Look at a Corsair and there is no fairing at the wing root you normally see on low wing fighters.  No fairing was necessary.
The Thorp T-18 homebuilt addressed the problem to avoid an acute angle at the wing to fuse junction, with a simple low wing, by starting the dihedral half way out on the panel, so that the mid section of the wing was flat and came out of the slab sided fuselage at 90 degrees (most T-18s use a very small fillet fairing at the back to reduce turbulence from flow separation aft of the thickest part of the wing, although some builders go with fancier ones). Thorp got the added benefit of a panel that could be built in two 4ft panels with the dihedral joint between them, allowing the wing to be skinned from a single trailing-edge-to-trailing-edge wrap of a 4 ft sheet of aluminum for each panel. Very easy to build.


Are QDM and QDR the same as 'inbound' and 'outbound' courses?

QDM is the magnetic bearing to the station.
QDR is the magnetic bearing from the station.

Not to be confused with course, which is the direction in which the aircraft is moving but has nothing to do with the heading of the aircraft. Imagine having a heading of 270 but a course of 090. That means there is so much headwind that you are moving backwards.

Radials are not the same since a radial is always a magnetic bearing from the station. Therefore flying the radial 180 both inbound and outbound will both give you a position south of the station.

This is not the case with QDM and QDR.

Flying a QDM 180 will give you a position north of the station and flying 180 (without taking the wind into account) towards the station.
Flying a QDR 180 will give you a position south of the station and flying 180 (without taking the wind into account) away from the station.

Let's imagine a VOR and an NDB located on top of each other and there is no wind factor:

Flying QDM 180 will put you on radial 000 with a heading of 180.
Flying QDR 180 will put you on radial 180 with a heading of 180.
Flying radial 180 inbound will put you on QDM 000 with a heading of 000.
Flying radial 180 outbound will put you on QDR 180 with a heading of 180.

Long story short, radials are visualised in relation to the beacon. QDM/QDR are magnetic bearings visualised in relation to the plane's nose.


How exactly should I understand the term "accidental hull loss"?

Both the MetroJet and GermanWings incidents were deliberate acts of destruction, not accidents in any common understanding of the word, or indeed in the sense defined by the Convention on International Civil Aviation.

The Chicago Convention, as it's also known, defines an accident as:

  An occurrence associated with the operation of an aircraft [...] in which  [...] a person is fatally or seriously injured [...] except when the injuries are [...] inflicted by other persons.

My emphasis added - see Annexe 13 of the Convention for the full definition - it's quite dry but interesting, if you're interested in that kind of thing. The exceptions it lists are illuminating.

Deliberate acts and "incidents"

I do think that the definitions in the Annexe are slightly odd. You'd think that the deliberate destruction of an airliner in flight should be called an incident, but an incident is apparently:

  An occurrence, other than an accident, [affecting safety].

I guess that's one way of describing a bombing or deliberate crash into terrain... but then there's also a Serious incident which is merely:

  An incident involving circumstances indicating that an accident nearly occurred. [my emphasis again]

So that would make the GermanWings and MetroJet cases incidents, but not serious incidents!

However: since "Appendix 7" of the ICAO Accident/Incident Reporting Manual lists "types of incident", and deliberate acts of destruction are not amongst them, I can only deduce that they are classified as neither incidents nor accidents. I am not sure exactly what the official terminology is for them.


How precise is an ILS (Instrument landing system)?

The ILS is precise enough to allow landings in essentially zero visibility, including those performed by autoland.

The ground based bits

The vertical range is 1.4° (0.7° above glideslope, 0.7° below) and the horizontal varies, but is a maximum of 6° wide. What this means in terms of how many feet or meters off the centerline an aircraft is varies depending on where the aircraft is on the approach, but it's generally correct to say that the closer an aircraft gets to the ILS antennae, the more precise the system is.

The specifications for a localizer antenna require that it be no less precise than ±10.5m - this is for a Cat I approach, and it gets correspondingly more precise as the category increases.

There's always the risk of interference with the transmitters; as noted in the comments, accidents have been caused by airport vehicles parked in the ILS critical area, interfering with the signals, and as the equipment ages it can require recalibration.

The airborne bits

It's possible for receivers to have issues that could affect precision; antennas can get loose connections or become covered in ice, while pilots might interpret indications incorrectly, misread reverse sensing, or intercept a 'false glideslope' from above.

Regarding accidents

You're correct - there are many accidents related to landing operations. That said, you may be including those which weren't flying an ILS approach - it's hard to say since you aren't citing anything. Still, it's possible that there's confusion between navigation precision and safety of flight.

Many (not all) of landing accidents involving instrument approaches do center around human error rather than equipment failure; pilots tuning in the wrong frequency or incorrectly setting avionics and instruments (reversing the inbound course on an HSI causes reverse sensing, that sort of thing), or people on the ground screwing up.


Are jet aircraft still at risk of hijacking by people wielding melee weapons?

United Airlines Flight 93 history shows that melee weapons are not very efficient: the passengers that are likely to outnumber hijackers at least ten to one can win if they are willing to fight.

The question remains, how likely is that passengers will go into risks to show the resistance. If it is just about changing the course to land in the different airport, they may choose to be quiet. If they have nothing to lose, I think the hijackers have no chances.


Can a passenger drone perform auto-rotation?

That drone has fixed-pitch rotors, and that pitch is optimized for thrust, not for autorotation. In the absence of power, those rotors won't autorotate. They will stop rotating 'in the right way' and then start windmilling in the opposite sense. That windmilling will cause drag and some deceleration of the fall, but not of the same magnitude as an autorotation, that is a different condition.


The wing thickness is basically the distance between the upper and lower surface of the wing (or airfoil).

`

Source: NASA.

The wing thickness is usually given as a percentage of the wing (or airfoil) chord(the distance between the leading and trailing edge). This is to make it a non-dimensional quantity for ease of comparison across different scales.


Is the Boeing 777X being certified as a derivative of the 777 Classic?

Yes, Boeing applied for an amendment to the existing 777 type certificate:

On April 19, 2017 (for the Model 777-8 airplane), and May 12, 2015 (for the 777-9 airplane), Boeing applied for an amendment to Type Certificate (TC) No. T00001SE to include the new Model 777-8 and 777-9 airplanes. These airplanes are constructed with new carbon-fiber-reinforced plastic (CFRP) wings with folding wingtips.
The Model 777-9 airplane, a derivative of the Model 777-300ER airplane currently approved under TC No. T00001SE, is a stretched-fuselage, large, twin-engine airplane with seating for 408 passengers and a maximum takeoff weight of 775,000 pounds.
The Model 777-8 airplane, a shortened-body derivative of the Model 777-9 airplane, is a large, twin-engine airplane with seating for 359 passengers and a maximum takeoff weight of 775,000 pounds.

(federalregister.gov, emphasis mine)


What are the heating tubes used during SR-71 airframe manufacturing?

It's basically an open air test oven.
The SR71's skin temperatures averaged around 5-600 deg F, up to 1000 deg F in places.  The titanium structure had to accommodate a lot of thermal expansion from all this heat, and used special skin joints and corrugation of the larger-area skin panels to accommodate the expansion.
The heating system in the clip would have been a text fixture with an array of radiant heating elements to subject a skin assembly to operating temperature to study the effects and validate the design (go to Page 29 of the linked PDF).


Does this formula hold true for a source sheet covering a closed body of arbitrary shape?

If a streamline is closed, then there's no mass flow that can go throught it. That means that inside the streamline the net mass flow produced is null. You can have for example sinks and sources inside a closed streamline, but they must compensate each other to make the streamline remain closed.

Another important aspect about source sheets is that they actually don't match with the border of the body, i.e, with the closed streamline. If they did, then some flow produced by the sources would go out of the source sheet, and some other flow would be in. The source sheet needs to be inside the border of the body. Anyway you could find a source distribution that makes the source sheet to almost match the border of the body.

What I wanted to say, is that if the streamline is closed, then the sum of sources and sinks inside the body is null. If the sinks and sources are the source sheet itself, then this proposition is equivalent to:

$$\oint_{Source\hspace{1pt}sheet} \lambda(s)ds=0\hspace{40pt}(1)$$

Note that each infinitesimal element of sheet, $ds$, produces an infinitesimal source strength of $\lambda(s)ds$ in the $s$ position. The relation $(1)$ means that the sum of all infinitesimal source strengths along the source sheet is null, or, in other words, that the net source strength is null.


Yes

AIRCRAFT CABIN SURVEILLANCE SYSTEM
Surveillance system for aircraft interior (2002)
Surveillance Cameras In Aircraft Cabins (2002)

  JetBlue Airways is the first U.S. carrier to get approval from the Federal Aviation Administration to install video cameras on all its airplanes.
  JetBlue is a successful start-up carrier based at New York's John F. International Kennedy airport. Soon after the Sept. 11 hijackings, the airline installed bullet-proof cockpit doors on all its planes. And it was the first carrier to match all luggage to passengers.

  The airline has outfitted one plane with the video surveillance system, and plans to have its 23 other jets equipped with the miniature cameras within the next few months.

  The cameras are positioned to cover the entire cabin. Some are visible, others are hidden so they cannot be tampered with

In-flight surveillance could foil terrorists in the sky (2008)

  The European Union's Security of Aircraft in the Future European Environment (SAFEE) project uses a camera in every passenger's seat, with six wide-angle cameras to survey the aisles. Software then analyses the footage to detect developing terrorist activity or "air-rage" incidents, by tracking passengers' facial expressions.

A350 cabin surveillance contract (2012/2013?)

  KID-Systeme has been selected to supply cabin surveillance equipment for the Airbus A350 XWB family of aircraft. The integrated solution will include both a cockpit door surveillance system (CDSS) and a cabin video monitoring system (CVMS).
  The CDSS provides pilots with a clear view of anyone in the area of the cockpit door, enabling them to take the appropriate action when entry to the cockpit is requested. The CVMS allows both the pilots and the cabin crew to view passengers.


Why do ground crews rotate a radial engine's propeller before a motor/cartridge start?

Radial engines - especially older large-bore designs like you find in WWII era warbirds - can suffer from a phenomenon known as hydraulic lock.

Basically while the engine is off and cooling some oil from the crankcase seeps past the piston rings in the lower cylinders, and collects there. When you try to turn the engine over with this oil in the cylinder the bottom piston contacts the oil (which is an incompressible fluid), and can't complete its travel down into the cylinder.
The stresses in the engine build until something - usually the connecting rod for that bottom piston - fails, resulting in an expensive repair bill and a grounded warbird.

To avoid this aircraft that are going to sit for a long time usually have a spark plug removed from the bottom cylinder and a hose run to an oil jug to collect the seepage.
In addition to this (or in place of it for shorter-term storage) the ground crew usually rotates the propeller through by hand enough times to ensure the bottom cylinder has gone through a compression stroke.

If there is oil in the bottom cylinder the crew will feel the hydraulic lock as extra force required to turn the propeller. They can then stop and remove a spark plug to drain the oil from the cylinder before attempting an engine start.

A similar phenomenon exists with rotary engines as Simon described in his answer, and the engine is pulled through for the same reasons.


Has a passenger or cabin crew member ever flown an airliner?

I think that in United Airlines Flight 232 Dennis E. Fitch did. While flying as a passenger on this flight, he actually was a certified flight instructor for the plane of that type so competent.

Chances to find a type-rated ATP between the passengers who would fly as if nothing may look slim but they are not zero. It is statistically more probable to find a pilot between passengers than would be just by random chance, because of deadheading.


Is turning off engines before landing "Normal"?

There's virtually no chance of the pilot deliberately switching off all 4 engines, and even less chance of all 4 engines failing at the same time. It's not entirely impossible for it to happen, but it definitely wouldn't be quietly ignored within the aviation community. I promise you that you would've heard about it afterwards.

That said, the A380's engines are modern, quiet, and actually mounted quite a long way out on the wings, this makes them fairly quiet when idling, even when compared to other aircraft. This is particularly noticeable after a long flight where they've been running at fairly high power for 8 or more hours, and is even more the case if you're not used to the A380, eg if you usually fly on common twins such as the A320, 737, 777 which are much louder within the cabin.

I suspect, but can't be sure, that the engines were simply pulled back to idle (minimum power/thrust) and it sounded much quieter than you expected.

But no, the engines were almost certainly not simply turned off, that just doesn't happen. The only thing I can think of that would cause that would be a flame-out, and you'd definitely notice that!


Are high lift wings bad for faster speeds

Every airfoil has a range of lift coefficients where the flow around the wing is most favorable. Airfoils with high camber shift this range to higher lift coefficients. Now the question comes down to: At which lift coefficient will the aircraft operate most efficiently?
The efficiency of transport aircraft is maximized when none of the three parameters payload, range and speed can be changed without reducing the product of the three. As it turns out, wing weight has a big influence on this, especially for large aircraft: A heavier wing will reduce the possible payload. It is better to limit wing span such that the ratio of wing span to chord is between 7 and 10: This will limit the bending moment at the wing root and allow to build the wing lighter. At this aspect ratio, the optimum lift coefficient for best transport performance is around 0.4 to 0.6, a number at which the low camber airfoil will feel right at home.
At such a low lift coefficient, however, the high camber airfoil, on the other hand, will experience a strong suction peak on the lower side of its nose. At high flight Mach numbers, this will lead to locally supersonic flow and a big increase in drag as well as cyclic loads on the wing (buffeting).
Now you could correctly argue that the wing could be much smaller with a high camber airfoil for the same lift. Yes, but the wing needs to adapt to take-off and landing conditions, too, and needs to have enough volume to contain the trip fuel. And for this landing condition the wing of an airliner will even have more camber than your example airfoil:

Typical landing configuration of an airliner wing, from an article by A. M. O. Smith, McDonnell-Douglas, in Journal of Aircraft, Vol 12 No 6, 1975.


Why do localizer/glideslopes use 90/150Hz specifically?

The frequencies are chosen to allow the system to produce a localizer and glideslope 'beam' that provides proportional guidance that can adequately guide an aircraft on the approach.

Read through this Question and Answer.

As you can see in the description of the beam-forming, the width of the antenna array and the choice of the modulation signals (90 and 150 Hz) drive the ddm proportionally to the angle of approach to the antenna array.

There are also considerations tied to the broadcast signal. Higher frequencies would require more bandwidth which would impact channel spacing.

Ultimately, the choice of the two frequencies is an optimization of a design for the approach guidance. For any given runway the current system can be set to provide consistent guidance (+/- 350 feet == full scale deflection) at the runway threshold.  This is done by adjusting the distance between elements of the antenna array.


Are the vortex generators on the Cessna Caravan necessary and sufficient for safety of flight?

You need to keep several things apart:

The center of pressure is where all vertical aerodynamic forces can be summed up. It does not have a fixed location, but its location changes with angle of attack.
The aerodynamic center (or neutral point) is indeed at about 25% of the chord of a wing. Its location is fixed as long as the wing planform does not change.
The neutral point of the whole airplane is the weighted mean of the local neutral points of all horizontal surfaces. This is the most important neutral point for longitudinal stability.

In flight you will shift the center of pressure such that it is at the same longitudinal station as the center of gravity. You do this by regulating the tail lift or downforce with the help of the elevator.

  When center of pressure, $\text{c}_p$, is forward of the center of gravity, $\text{c}_g$, then [this] necessitates an up-force on the horizontal tail in order to maintain level flight.

This is true if you speak of the wing's center of pressure. In a conventional configuration like the Cessna 208 the wing's center of pressure is ahead of the airplane's center of pressure.

  How typical is it that aft-$\text{c}_g$ limits are behind the $\text{c}_p$, such as in the 208?

This is quite normal. No need for concern as long as the center of gravity is still ahead of the airplane's neutral point.

  Wouldn't this imply longitudinal static instability?

No. Stability is reduced compared to a more forward center of gravity location, but still positive.

  How do engineers typically design tails to maintain necessary up-forces in such cases?

The biggest concern of engineers in such a case are too light control forces. The force feedback loop is important for avoiding control deflections which could overstress the structure. Since the tail is in the downwash of the wing and carries less load per area than the wing, it is very, very unlikely that it stalls first. Without knowing the details, I am quite sure that the vortex generators were not added to cure a deficiency which occurs with a rear center of gravity location. Now I did some background reading and think that the vortex generators are needed to avoid early separation on the elevator in case of low-speed flight with flaps retracted and a rear center of gravity.

  Are vortex generators […] after-thought band-aids to remedy an inadequately designed tail?

Yes, they are. They normally cure one corner of the envelope where something went out of whack during flight testing or after a modification (say, an increase in gross weight or in the permissible center of gravity range).

  Does anyone have more published references about the Caravan's tail specifically?

Sorry, not me.

Now I have read the accident report and the linked transcript about the Caravan crash on October 10 in Dillingham, AK, in 2001. These are my remarks:

The witness in the transcript is very knowledgeable and I agree with all what he said.
His statement about the tail load change upon flap retraction seems spot on: Even though the accident report is inconclusive about the flap position, it seems likely that retracting the flaps coupled with insufficient lift on the tail made the aircraft pitch up and stall.
All the accident report has to say about de-icing focuses on the wing, but since lift-off speed seemed normal, I don't think ice on the wings was a problem. But what about ice on the tail? There is no mention of that.
Vortex generators on the upper side of the tail are unusual and a "red herring" about late fixes for insufficient pitch down control authority. Add some ice on the upper surface of the tail, and the fix will not be sufficient and cause an uncontrollable pitch-up with a rear center of gravity location.
That the pilot seemed to have pulled on the yoke on the way down did not help, either. Lift loss on the wing would cause a nose-down pitch change, but the aircraft remained stalled throughout its descent. Yes, it needs some effort to pitch down when the flight path is already 40° down, but this is the only way to avoid a crash. Remember AF447.

My conclusion from all this is that the Cessna 208 Caravan is stable and safe to fly as long as the tail is in pristine condition. Any contamination of ice and even de-icing fluid will compromise its ability to produce the required lift in low-speed flight with flaps retracted and a rear center of gravity.


What are the strategies for getting familiar with a GA aircraft before considering a purchase?

There are lots of ways to go about this.

Rent: as you have mentioned nearby FBO's have various planes although they are almost always Pipers (Warriors, Arrows, occasionally a Saratoga or Lance) or Cessnas since those are common trainers. You may also find a light twin here and there as well as a Grumman or something like that. In this case you can rent what you want to try and go up with an instructor.

Friends: As you fly more you will meet people at the airport. Often times these are plane owners and they have a whole variety of stuff. Eventually people may offer to take you out for a flight in their plane (which will be way better maintained than a lot of trainers). If you tell someone you are interested in purchasing the same make and model they have, they may be more inclined to take you up. You may also meet other people who are training in a different plane than you. For example, I fly the Warrior and Archer at my school and another student who I have become friendly with flies the 172. Since we are not check out in the other planes respectively and we are about at the same point (close to our check rides) Im sure we will fly with each other in the respective planes in the future.

Flight Clubs: A lot of local airports have flight clubs that sometimes own a nice variety of stuff and you may be able to meet a member and have them take you up to show you around what ever it is they have, you may even be able to join the club and get checked out in their planes.

Internet: The internet is abuzz with forums for just about every big maker out there. Some are free and others are super cheap to join if they cost anything at all. You can often times find local owners on these forums who may be willing to take you up or at least show you their plane. You would be surprised how hard it can be to find people to fly with sometimes.

Dealers: Much like cars new planes come from dealers. You can always try your local dealer (although Im not sure if they will take you up) I would think they would at least let you sit in the plane. There are dealers spread across the country but if you can rent a plane now you can always fly to them (Piper, Cessna, Mooney)

When You Buy: When (if) you buy a plane you will need to insure it. Generally insurance companies will require time in type to get the insurance. You can sometimes agree upon mandatory instructor time in the plane you just bought before you fly it solo. This allows you to be able to buy just about any plane and not have a ton (if any) time in it.

Finding Strange Planes: When (if) you go to buy a plane you will define your mission. After doing so you will begin to talk to people about what you want and you will get plenty of suggestions on what to buy that fits your mission.

Strange Planes Are Strange For A Reason: I can only assume you are training (or have your PPL) and are thinking about getting a plane. To this I will offer some advice I have been given. Planes are no small item to own, fiscally, legally, and simply physically, they require a lot of space. There is a reason the common models are common. They fit a lot of missions, are generally reliable, easy to fix and get parts for as well as easy to fly. While I lust for a Mooney M20 Acclaim Type S the truth is (money aside) I am no where near ready for a 200+ knot plane that is nothing but slippery. Remember to respect the machine.


The frontal surface is indeed used for the drag coefficient of cars.
For airplanes, however, almost* all coefficients use the wing area as their reference. This makes sense exactly because it allows to express L/D as c$_L$/c$_D$.
* For the nitpickers: Control surface hinge moment coefficients use the area of their respective control surface, not the wing surface.


How does the 3 pin ground power connector (AN2551) work?

The key to how it works is best explained with the 3rd link in OP question: the short pin provides power for a relay switch, powered = closed. When pulling the plug out the short pin disconnects first, opening the switch which removes power from the plus (middle) terminal of the plug before it is disconnected from the counter-plug.


Why are lower VHF frequencies used for towers?

There's no specific reason why the lower frequencies are used for towers, but it's not a coincidence that they are grouped together (mostly, there are tower frequencies that are not at the lower end.)
Spectrum management is a complex effort to make maximum use of the fixed amount of frequencies available for use. In the US this falls under the FAA Spectrum Engineering Group AJW-1C.
One method of ensuring reliable safe communication is the intersite analysis. Basically, frequencies have to be used by multiple ground stations based on the airspace volume that the frequency needs to cover. This airspace is referred to as a frequency protected service volume (FPSV).
The goal is that an aircraft in the FPSV will only be able to communicate with the intended ground station. Since towers have a relatively small FPSV, typically 5,000' high (AGL) & 15 nmi radius, the tower frequencies can be reused closer together than a high altitude sector frequency that may cover a 150 mi radius at 45000 feet. A frequency that was used for both high altitude and a tower would be more difficult to de-conflict.
There are also other considerations that can affect the assignment of frequencies. It's all spelled out in the 6050.32B - Spectrum Management Regulations and Procedures Manual. It's rather lengthy at 475 pages. The details of VHF/UHF Comm frequencies is in Appendix 2.


Did Concorde's sonic booms affect other air traffic?

According to this airliners.net post (written when the Concorde was still flying, BTW), the Concorde's sonic booms could often be heard from other aircraft, but never posed problems for said other aircraft:

Sometimes, to the South of Ireland, during the early part of the acceleration on a Westbound flight, Concorde flies over subsonic traffic that is arriving from the USA and cruising around FL370-FL410. If close to this traffic, by which I mean 10-15 miles, then ATC will often warn them that they may be "boomed" as the shock waves pass over them.
From the reports I've heard from some of these crew, this can vary from nothing to a clearly audible double boom, but nothing to cause any concern or alarm.


Where do military aircraft carry flares?

The location of the flare/chaff dispenser (FCD) depends on the aircraft type and even in case of the same aircraft, they can be located in different place, depending on the version and customer.

For example, the F-16 carries the FCD in its body fairing, as can be seen in the following image of Hellenic Air Force F-16 Demo Team “Zeus”.

Image from theaviationist.com

The following image shows a close view of FCD.

Image from f-16.net, credited to Capt. Lance

The following image shows an Israeli F-16B 'Nezt' having FCD between its ventral fins.

Image from theaviationist.com

Initially, most of the FCDs were retrofitted to the existing aircraft and were simply attached to them. However, most of the modern aircraft have FCD bays integrated into their fuselage. Still, some aircraft can carry extra flares/chaffs in their pylons (called PIDS (Pylon Integrated Dispenser System)), as shown below in an RDAF aircraft.

Image from f-16.net, credited to Erik Frikke

Also, most of the combat aircraft have the FCD in the bottom, while transport aircraft (and helicopters) have them on their sides.


How do changes in certification requirements affect previous type certificates?

New rules don't affect t existing designs....

Certification basis is declared by the maker and agreed with the certifying authority...Or authorities... ( ideally it's a common certification basis to avoid extra testing, or building aircraft to  different standards) That basis must reflective rules in existence at the time of application. New or pending  rules may be imposed by Special Conditions or equivaent. Any modifications to that approved design are normally to the same certification basis.

But if a new design comes along, it's the applicable rules at the time of application..

If a change is needed to all aircraft of a certain "class" e.g. Introduction of TCAS, ACAS , then that is imposed by operational requirements, such as Parts 91, 121, 135 etc or their equivalents.


Are "Tally-ho" and "no joy" acceptable ATC terms for civil operations?

As a private pilot, I have heard "Tally-ho" and other pseudo (British?) military phrases used when talking to ATC.  I understand "Tally-ho" to be equivalent to "target(s) in sight" or "inbound" or even in some cases "affirmative", and that's the problem.  It is important to be clear and precise when communicating on the radio, however, the folks working at ATC seem to understand these phrases.

FAA:

I've read the AIM - Aeronautical Information Manual and Pilot's handbook of aeronautical knowlage (Both available for free download from the FAA's website) and I don't remember seeing these phrases anywhere.

Other texts caution against using these colorful phrases instead of standard phraseology because problems stemming from varied interpretations.  It is important to be clear and precise when communicating on the radio.

I think the correct terminology is: "Traffic In Sight" and "Negative contact"


Are there certification requirements for an emergency descent?

There is a descent requirement, but it's perhaps not in the way you imagine as it has to do with oxygen supply. FAR 122.333 subpart K states:

  (b) Crewmembers. When operating at flight altitudes above 10,000 feet,
  the certificate holder shall supply enough oxygen to comply with
  §121.329, but not less than a two-hour supply for each flight
  crewmember on flight deck duty. The required two hours supply is that
  quantity of oxygen necessary for a constant rate of descent from the
  airplane's maximum certificated operating altitude to 10,000 feet in
  ten minutes and followed by 110 minutes at 10,000 feet. The oxygen
  required in the event of cabin pressurization failure by §121.337 may
  be included in determining the supply required for flight crewmembers
  on flight deck duty.

This specifies that a turbine aircraft must be able to descend from it's maximum certificated altitude to 10,000ft in 10 minutes or less. This means the maximum descent speed is variable to maximum certificated altitude, so if an aircraft's ceiling is 42000ft it must be able to descend at least 3200fpm, it it's 25000ft then 1500fpm.

As for how that's done I don't think the regulations say, it's up to the manufacturers to develop aircraft that can meet the requirement.


Is there a detection method available to detect a plane without using RADAR?

Radar is, by far the most widely known and used of the active detection methods.

Passive methods include the use of visual and infrared search and track systems such as the F-14's Television Camera System or the Eurofighter Typhoon's PIRATE infra red search and track systems.


How do planes receive their flight plan?

The airline files the flight plan to the air traffic control (ATC) on behalf of the crew. The crew receive the print out before the flight.

The airplane "receiving" the flight plan can then mean one of two things:

Flight plan programming

The crew will use this printed flight plan to setup/program the FMS in the cockpit.

Alternatively, the airline can send the flight plan to the crew wirelessly via ACARS, the crew then prints it out in the cockpit.

If the route flown is frequent and rarely changes, the airline can have it saved on the plane, the crew will then load the saved plan, and revise it—making sure it matches the print out.

It's time to get on with the flight

The crew will call ATC on radio requesting clearance to their destination as filed.

If everything matches, they get the go-ahead. If not, amendments will be relayed, and changed accordingly in the FMS.

Alternatively, the clearance can be requested digitally using the ACARS, CPDLC-DCL, or in the near future, SWIM.

Any digital communication is subject to airport, airline, and airplane equipment.


How many layers do the Boeing 787 cabin windows have and what might make them fail?

This article about the Boeing 787 Dreamliner states that

  [...] The Dreamliner’s new windows are made of two thin layers of glass with gel wedged between them. [...]

The windows have also a failsafe mechanism in order for the outer pane to crack or fail first, it's this tiny hole that you may have noticed, which serves to regulate the pressure exerted from the cabin to the window.

I couldn't find a more technical article about aircraft windows, but I found an AIAA article about Space Shuttle's cockpit window system, if you are interested about something a little bit more extreme!


Locked out of private jet - how do you get in?

It depends on the exact model. Bobby pins or any key that physically fits will get you into some, you'll need real picks for others, and some custom jobs may require a police snap gun or a locksmith's services. This doesn't correlate with aircraft price: the larger and more advanced, the less likely it is to have any locks at all. At the high end, jumbo jets have no locks and have a (not so) convenient hatch in the gear well, so you can climb inside even without a ladder.

Mechanical locks, with the exception of the more robust types used on burglary-resistant safes and vaults, offer only very superficial security. Airplanes are protected against professional threats by external access restrictions (fences, hangars, guards). When parked at a small local airport, opportunistic theft is deterred by "security through obscurity": very few people are able to operate one, with model-specific skills are involved, and even fewer could make use of a stolen jet. Unlike car parts, aircraft parts come with paperwork.

The locks used on most aircraft doors are small pin and tumbler cylinder types that can only protect against passers-by. The stock locks on the most popular light planes even use wafer tumblers, which offer no resistance to picking - some light bumping with a key from another lock of the same type will get it open. Quite a few owners have opened plane doors with a wrong key by accident.

If you're not concerned about property damage, as in an emergency situation, no picking skill is required to open the kind of locks you'd find on a private aircraft. A non-matching key or a flat-head screwdriver, jammed into the keyhole and forcefully rotated with a pair of pliers, can break small cylinder locks' pins and allow the lock to open. Larger locks require a bit more effort, but it's all fairly intuitive work of destroying what's in the way of opening the latch.

In non-pressurized aircraft, you can also bypass many locking mechanisms by applying well-directed force, which slightly deforms the door to allow the latch can exit the door frame. In some cases this can be done non-destructively, just by elastic deformation. Pressurized doors fit too tightly for this, but the lock is still a standalone device, not tied into the door's operating and sealing mechanism, so damaging it won't leave the plane inoperable.

24 hours is far more time than would ever be needed. 1 hour is enough time to get a professional locksmith, which, with proof of ownership, can get you into any stock aircraft/boat/car/other vehicle with usually no damage to the lock. Another hour will get you a new set of keys, or a change of locks with new working keys.

The time it takes to get into a locked aircraft, in an emergency situation, should be between 20 seconds and 20 minutes, depending on the plane, the characters' skills and equipment, and their willingness to damage the lock. For a larger jet you'll definitely be going after the lock, not the door.

The only entry-resistant doors in aviation are those separating airliner cockpits from the passenger cabin, with electronic locks and solid locking mechanisms. They're rated against different threat models than UL vault doors, but my best estimate based on their construction and weight would place these doors at around TL-15 level, with about 15 minutes of power tools resistance.

For reference, the highest ratings for safes and vaults are TRTL-120 and TXTL-60, indicating 120 minutes contact time resistance against power tools and torches, or 60 minutes against explosives and small thermal lances. In absence of a security response, 24 hours and a good hardware store can get you into Fort Knox.


Why do electronics have to be off before engine startup/shut down on a Cessna 172?

You shut the components off to protect the sensitive electronics from electrical surges that may occur during start up of the engine.
Circuit breakers are designed to trip open if too much current in amps is drawn from the power source by the electrical components or a short circuit downstream of the circuit breaker. They do not necessarily protect the components from too much amperage and/or voltage generated and pushed through the circuit breaker from upstream of the circuit breaker.
To be safe, disconnecting the components from the power source via a physical switch that can be opened Is prudent to mitigate the risk.


Could airline tires be deflated in mid-flight to reduce weight?

You want to reduce weight by removing a few kilos of air, and adding an equal, if not greater, amount of kilos of pumps needed to reflate the tires (see David Richerby's answer for details), not to speak the additional costs incurred for periodically checking the correct functionality of said pumps, that would be marked a "safety critical" (because a landing with deflated tires would have really bad consequences) and require being checked quite often.
So, feasible maybe. Safe not really. Meaningful I don't see how, particularly when there is the risk of tire burst, as shown in this video linked by March Ho.
A lighter alternative would be to use bleed air from the high pressure section of the engine, but it would still probably(*) be heavier than the air you are pushing out (you need heavy duty pipes to transport high pressure air from the engines to the wheels), and not a good solution safety-wise: what would happen if you have to land without engine power?
(*): as user3528438 mentions in their comment, it would depend on the wheel size.
Additionally, this Goodyear manual provides insight in some other problems: (emphasis mine)

ALLOW 12-HOUR STRETCH AFTER MOUNTING

All tires, particularly bias tires, will stretch (or grow) after initial mounting.
This increased volume of the tire results in a pressure drop.
Consequently , tires should not be placed in service until they have been inflated a minimum of 12 hours, pressure rechecked, and tires re-inflated if necessary.

It means that the tire needs adjusting after being inflated, possibly removing the possibility of inflating and deflating it continuously (or, alternatively, you have to reinflate it at least 12 hours before landing). Note that this manual is written for current operations, that call for a replacement/inspection of the tire if pressure drops below 80% of nominal value. Procedures should be rewritten for inflation/deflation cycles, and this could be a factor.


Can I become a pilot if I have a medical/dental problem?

Under FAA regulations (which most people in the world can train under if they come to the USA) you should be fine. There are no dental requirements to be a pilot or obtain a medical certificate (as far as I know). You can reach out an AME in your local area if you are concerned, they should be able to answer the question for you. The only orally related regulations are that you be able to speak english proficiently and clearly. As long as you can do so you should be fine.


As of June 2019, can a DPE in the United States renew a CFI's certificate based on completion of a FIRC?

Yes they can
I asked a DPE to renew mine a couple days ago and they did.  Sometimes asking nicely is the best way to learn.


Why does elevator still raise and lower the nose when the aircraft is steeply banked?

At 45 degrees Angle of Bank pulling back will both tighten the turn, and cause the nose to rise equally because you are halfway to 90 degrees.  You are correct though, at much steeper angles of bank the control inputs function the other way:  In a very steep high G turn the angle of bank is used to control altitude, and back pressure is used to control the rate of turn.  You definitely don't want to use rudder in this case though, bad things can happen in an accelerated stall with yaw.


Assuming there is no wind, a circular pattern is most easily achieved by flying a constant speed and a constant bank angle. Maintain coordinated flight (no  skidding, no slipping). There is no difference in turn dynamics between a conventional glider vs a delta wing glider.


What are these circles around the propeller?

They are tip vortices formed by the propeller, just like the wing tip vortices.

The propeller produces thrust, just like the normal wing produces lift. As any wing of finite length produces vortices, the propeller also produces them and that is what you see in the picture.

This is not only limited to propellers. The helicopter rotors also do the same thing.


What are the limitations on a steep approach?

This presentation gives the following limitations for A318 steep approaches:

Maximum authorised Flight Path Angle: -5.5°

MLW unchanged (57.5t)

FWD and AFT CG limits unchanged

Maximum altitude for landing: 2000ft

Tailwind limit for landing: 5Kt

Crosswind limit for landing: 26Kt gust included

AUTOLAND is not allowed

CATII and CATIII are not allowed

All engines operative only


How do I properly report sighting a drone or hobby UAV to ATC?

Great question, and I'm not sure there is an entirely established procedure for this yet, as drones are still a relatively new development.

First, your responsibility as a VFR pilot is "See and Avoid".
So if you think its headed towards you, maneuver to avoid it (provided you're not making dangerous, drastic moves!)

Secondly, I'd report it to the tower as:
"Bay View Tower: N227TW:  I see a drone in the airspace, my 2 o'clock, slightly below, less than one mile, headed towards the airport"

At best, the tower may be able to say they're already talking to the drone operator.  Otherwise, tower may simply say, "Roger: keep me updated, deviate from the pattern at your discretion"


Why don't bombers have close-in weapon systems (CIWS)?

The main reason is the same reason why CIWS are not used on ground vehicles - anything smaller than a ship just doesn't have enough space/weight allowance to fit one, let alone two. The lightest CIWS I found, an outdated version of Soviet AK-630 system, weighs in at 1 ton (later versions are much heavier), has a turret ring 1m across, is 1 meter high above deck and needs 2m of space below (which means that installing one would also going to be aerodynamically awkward) - and all of this does not include the ammo supply (2000 shells for this version translate to additional 0.2 tons, later versions, again, had more ammo). All modern CIWS weigh at least 6 tons, are considerably bigger, and some of them also need an external targeting radar - and I assume not all bombers have the equipment needed by default. Aircraft also has more approach vectors to cover - a ship only needs CIWS installed on top, but a bomber would also need defence in the lower hemisphere; so for complete coverage we would need even more guns, which would mean even less speed and payload.

Even if we would manage to fit some in - gun-type CIWS effectiveness is disputed. Their limited range means that even a succesfull kill on an incoming missile might not protect the ship from an impact - and what would be a minor inconvenience for a warship, will be a deathblow to an aircraft. Missile-based defences are usually considered a better choice, as they can engage and destroy incoming missiles at significant range from the protected object - but they are even heavier and bulkier than guns.

And last, but not least - modern strategic bombers tend to eschew defensive armaments at all, because their main weapons are missile-based, and imply a launch at safe distance from the enemy.

Thus - modern CIWS on a bomber are impractical. They are heavy, bulky and do not provide immunity to missiles, so might as well stay on the ground.

P.S. On a closer inspection, several other bombers had or have radar-controlled tail guns - Tu-95 or early B-52, for example. B-52's tail turrets were removed after a friendly-fire incident where radar-homing HARM missile locked onto the gun's targeting radar - another downside that I haven't noticed before.


Could an airplane dock with a set of wing extensions while airborne?

Actually, a similar concept was tested by the USAF in the 50s (like most things in aviation, it seems).  Under the name of Project Tom Tom, the military was looking into the possibility of coupling a parasite fighter (an F-84 in this instance) to a B-36 as a long-distance escort as it flew into the Soviet Union by joining the two aircraft together at the wingtips.  Flying as such, the F-84 would actually power down its engines during coupled flight and could receive fuel from the B-36.  However, the aspect with greater relevance to the question is that the B-36 would actually derive an aerodynamic benefit from this arrangment as well.  In theory, the combined aircraft would also benefit from having an artificially elongated wing as well, and, while I remember reading last year that this actually did result in superior fuel efficiency for the combined aircraft during cruise, I am at a loss to find that source right now.  At any rate, with respect to this question, the B-36 effectively docked with a pair of "wing extensions" (in this case, a pair of F-84s) while in flight and derived a benefit in cruise.  A video of the concept can be found here:

            .  Also, more reading can be found in this text Flying Aircraft Carriers of the USAF: Wing Tip Coupling by Brian Lockett.

Naturally, there were significant downsides to this idea.  While the F-84 actually did manage to engage the coupling mechanism on the B-36 on test flights, logging at least a couple hours of continuous, coupled flight, significant stability and safety issues were uncovered during testing that led to the scrapping of the project.  As noted in a quote from the project summary report:

  The wing-tip coupling mechanism as developed and flight tested in the Tom-Tom program is not considered satisfactory for tactical use and was barely acceptable for test flying. It appeared that a new difficulty and a now shortcoming were uncovered on virtually every test flight. The extent of rework necessary before the coupling mechanisms as designed were acceptable as flight test articles is covered under the DESIGN section of this report.

Similarly, issues with aeroelasticity turned out to be a much larger issue than originally expected (in part because of the change pitching/heaving forces as well as wing mass distribution and stiffness at the joint).  I think that Aurora Flight Sciences ran into similar issues when they were designing an entry for DARPA's Vulture project...the idea was to join multiple vehicles (that were essentially flying wings) to create a super-efficient, high-altitude, solar-powered, surveillance aircraft.  Due to conflicting requirements on wing structure and aircraft weight, I think that ultimately didn't fly...but I don't have any of the details for that.  Just what I remember from a presentation I saw many years ago.

At any rate, I guess that my answer is: yes, it could.  But it is VERY difficult and dangerous to do (at present).


What criteria make an airport suitable for a technical stop for a large airliner?

Some factors might be:

Price of fuel at the various airports?
Landing fees?
Are any of the airports so busy that you might have to hold waiting for landing clearance? (You don't want to plan a fuel stop at LHR).
Can you expect long taxis in some places? (All other things being equal, a single runway with a ramp next to it is better news than something like Schiphol or O'Hare).
If you're carrying passengers, are some of the airports in countries with significantly more cumbersome immigration rules applying to technical stops than others? Some may want airport transit visas from passengers of certain nationalities even if they don't disembark.
Political considerations such as the ones mentioned by Terry in the comment.
And, of course, the total expected fuel burn for the two legs, which will depend on your refueling points. Your operations department will make concrete calculations for a number of likely stops, and weather has an influence on top of geography. If you have several possible airports that all happen to be right on the shortest path between your origin and destination, the math will tend to favor a refueling stop roughly in the middle -- this will minimize the total cost-of-lifting-enough-fuel-for-the-rest-of-the-leg.

Finally, if you're planning a recurring scheduled flight, will any of the options provide a business opportunity to take on some extra passengers on days where the demand from the actual origin is low?


Are there differences in tool standards between aircraft manufacturers?

According to a friend of mine that has worked as an aircraft mechanic for the last 30 years or so, it depends on the manufacturer.  For example:

American made aircraft, including Boeing, use SAE sized tools (US standard sizes)
Airbus uses metric tools
Hawker uses British Standard Whitworth tools
Dassault Falcon uses (believe it or not) a combination of SAE and metric.
Bombardier uses SAE


What could cause uneven fuel levels in a Cessna 172?

Consulting your handy POH (or one for a 172N that I Googled up) you'll find the fuel system diagram looks like the one below (click to enlarge - most high-wing gravity-fed fuel systems are similar).

So there are a number of ways you could wind up with uneven fuel burn with this plumbing.
The most common ones are:

(Uncoordinated) Turns
If you're flying lots of left-hand traffic patterns (or you're making lots of left turns for some other reason) that means your left wing is frequently lower, and gravity favors pulling fuel from the right tank. (Note that it doesn't have to be a turn - prolonged slips can also cause uneven fuel flow.)
If I had to take a guess, I'd say this is probably your culprit. Were you making a lot of left turns?
Pressure
The fuel vent tube on the left tank faces into the wind - this pressurizes the left tank first (and the right tank through the breather tube connecting the two) - it's a little extra encouragement for fuel to leave the tanks and flow into the engine. In some aircraft this leads to the left tank draining faster (because it's at a slightly higher air pressure than the right tank) - this can become particularly pronounced if the breather tube between the two tanks is blocked.

Various blockages
A partial blockage in either of the tank fuel lines, the fuel selector valve, the vent, or the breather line between the two tanks could theoretically cause uneven fuel burn (the vent/breather blockages being a special case of "pressure" from (2) above).
Pilot Error
It's possible to mis-position the fuel selector in such a way that you're getting adequate fuel flow to run the engine, but one tank is more restricted than the other.
This is unlikely if the aircraft is properly maintained (the fuel selector should have nice, identifiable detents that it clicks into, letting you know it's in position).

For more detail on causes for uneven fuel burn (and tips for troubleshooting it with your mechanic) check out Cessna Pilot's Association Technote 003.

Is uneven fuel burn dangerous? Maybe.
It's certainly something you should be aware of (part of why you want your fuel gauges to be at least somewhat accurate is so you can tell if your fuel burn is uneven in flight and correct it by switching to the fuller tank briefly).

Uneven fuel burn can be an annoyance (a 5 gallon difference is about 30lbs - potentially enough to notice on the controls), but it can also be a safety hazard: If allowed to go uncorrected you could theoretically get yourself into a situation where the right fuel tank is empty, and in a steep enough left turn you may not have enough pressure from gravity to get fuel from the left tank into the engine.

In an extreme case your right tank may be empty and your left tank may be so low as to unport the fuel pickup tube in a turn, potentially leading to attitude-induced fuel starvation ("The noisy part of the plane gets quiet until you level the wings").


Is there a typical time on site during an investigation of a major accident?

There are simply too many variables to answer this question, even in general terms.  And wreckage accessibility is just a small part of it.

If an aircraft runs off the end of the runway and the pilot survives to make a statement that can be corroborated by another crewmember, tower and other eyewitnesses, as well as weather reports, it doesn't take much time to wrap things up.  Probably a few days is all that is actually needed on-site.  Most of the work at that point is administrative in writing the report.  The aircraft may even be mostly intact and towable.

However, when all you have is a smoking hole in the middle of a pasture, as accessible as the wreckage may, be the investigator's workload is massive.  Sifting through all the broken pieces, numbering and cataloging them, plotting locations in the debris field, etc. can take months in itself, and then the real investigation begins.  Not to mention the cleanup.


How can the F-16 remain stable when there is a loss of hydraulic power?

As I understand it (I'm neither an F-16 pilot nor an F-16 mechanic), Relaxed Static Stability doesn't mean the aircraft is unstable, just that it's less stable than the long-established standard.

To put it another way, if you build a free flight model airplane scaled from an F-16, you'll have to put the center of mass significantly further forward than its location in the full size, piloted F-16, in order for the model to have static stability.  The same is true of many radio control models intended to be flown by an experience model pilot -- they're what's call "neutrally stable".  The primary characteristic here is that these models will "go where you point them" and require that you "fly them all the time" -- unlike a trainer, or many/most scale models of piloted aircraft, you can't just set the throttle to cruise and take your eyes off the airplane, and expect to find it in a predictable location a minute later.

The same is (mostly) true of the F-16, in that, in most flight regimes, it's stable enough that as long as a violent maneuver wasn't in process when the flight computer restarts, the aircraft won't be badly out of shape by the time the computer returns to full function.  Back in the 1980s, however, it wasn't unheard of for a pilot to have to eject due to a fly-by-wire system failure; my parents lived near Hill AFB and would hear by local rumor mill and newspaper of "another F-16 crash" every so often.

Bottom line (again, based on my understanding as an "interested bystander") is that the F-16 is just about stable enough that it can remain recoverable through a control system restart, if it was in a steady state flight condition beforehand.


Would it be possible to use 3D printed node based structures to make cheaper GA planes?

3D printing is unlikely to make anything cheaper in the near future. With current printing technologies it's an order or magnitude or two more expensive per unit than volume manufacturing techniques such as extrusion or injection moulding.

It's notable that the company you link to chose to make a supercar rather than a low-cost small car. There's little price competition in that market, as brand loyalty dominates. Most supercars are bought as status symbols or for fun rather than for their actual road performance. Most of the incumbents manufacture very small runs with a lot of hand assembly: exactly the kind of manufacturing that 3D printing is competitive for. On top of that, because of the status symbol marketing, there's huge room for new players to differentiate based on a green image. Tesla has done this in the last few years, which is why some of DMF's marketing material focuses on dissing electric cars.

Runs are small in GA too, so there's potentially a wider niche for these techniques to fit into. The market that would most closely fit IMO is kit aircraft. A kit that's primarily 3D printed parts joined by standard spars, with a flexible outer shell, could have shorter lead times and less tooling cost.

After discussing this with some mechanical engineer colleagues today, they pointed out how 3D printing of metals is now being used as a complement to CNC machining in the rocket industry. For a part that has to be machined from a single piece of metal, they 3D print a shell that's slightly larger than the required shape, and then machine it to the correct shape. It allows you to achieve the tolerances you get from machining (which 3D printing can't yet deliver), but without the waste you get from cutting down a solid block.

It's an aside to the main question, but it's a way that 3D printing could be used to reduce the cost of some components and allow designs that would have been economically infeasible.


What accuracy is required in todays ADS-B position reporting?

You can report any accuracy you want over ADS-B, as long as the position source is compliant with TSO-C129 (or later revision), TSO-C145a/C146a (or later revision), or TSO-C196 (or later revision).

ADS-B gives amongst others:

a position,
an associated Navigation Integrity Category (NIC) based on the GPS Horizontal Protection Limit; and
an associated Navigation Accuracy Category for position (NACp) based on the Estimated Position Uncertainty / Horizontal Figure of Merit.

If the positioning system cannot provide integrity or accuracy, the ADS-B transmitter will encode the NIC/NAC as 0 (unknown). This warns users of the ADS-B data that the position source is not to be trusted.

In day-to-day operation, ADS-B is required to provide:

an integrity limit less than 0.2 nautical miles;
a reported accuracy of less than 0.05 nautical miles;

Practically, GPS will occasionally give lower accuracies / integrity, but it will be reflected in the NACp / NIC so that users of the data can decide how to handle this lower quality data for their purposes.

Mobile phone A-GPS chips are typically not certified under the TSO's mentioned above and they don't provide integrity information. These chips are thus not suitable for ADS-B.


Hong Kong International Airport represents the largest single airfield installation of interlocking concrete pavements. Since most of the airport is on reclaimed land, anticipated settlement required that flexible asphalt pavement be used instead of rigid concrete for runways. Concrete pavers also provide a more fuel-resistant surface than asphalt.

Source

See also

Concrete Block Paving
for Airfields
Airfield pavement design with concrete pavers
Evolution of Interlocking Concrete Pavements for Airfields
THE USE OF INTERLOCKING CONCRETE BLOCKS ON AN AIRCRAFT PAVEMENT IN AUSTRALIA


How to land a sports plane with tailwind?

Land normally.  Check your POH (Pilot Operating Handbook) first to ensure you have enough runway including the extra needed for a tailwind.  The only thing to watch out for is that winds tend to moderate as you get closer to the ground.  In a headwind landing, the relative wind will decrease, In a tailwind landing the relative wind will increase, so there will be an increased tendency to float way down the runway.  Be on speed for a short field landing technique.


Does the RA (resolution Advisory) from TCAS II take into account the stall margin required?

Yes, but not directly. The TCAS is a generic box that doesn't really know anything about the aircraft performance. What it does have is a number of input discretes that allow other aircraft systems to indicate that the aircraft climb performance is limited. Other discretes code the altitude above which the aircraft cannot perform an RA climb. What drives these discretes will be unique to a specific aircraft type and defined during the STC process.

ARINC 735A TCAS Characteristic defines the following:

  Climb Inhibit Discrete Input #1 through #4
  Increased Climb Inhibit Discrete Input #1 through #4
  Performance Limit Discrete Input
  Aircraft Altitude Limit Program Pins

Based on these inputs the TCAS logic will compute an RA that does not require the aircraft to climb when it is not able to safely do so.


How useful is skyscrapers and high buildings lighting to get a visual reference for pilots by night? (not obstruction lights, just general lights)

Buildings and their lights can be very useful to aircraft in VFR conditions at night to orient themselves regardless of the type of aircraft.

Three building lighting examples that I often used were:

When flying Metroliners for a commuter airline that operated to Walla Walla, WA, I would call for a visual approach to the airport when I saw the Washington State Penitentiary. It's distinctive pattern of bright lights, especially those around its perimeter, made it stick out like a sore thumb.
When flying night freight in 727s, from many miles out, we could see the blue neon lighting outlining the Sofitel Hotel just across the road from the southwest corner of Miami International Airport.
Back in the late 1990s, the high rise hotels along the beach at Tel Aviv had a distinctive pattern. Head just to the south of them and you were lined up for Ben Gurion airport when approaching from the west.

Really, if you go into most urban airports regularly at night, you learn to recognize the pattern of the lights and can use them to orient yourself.

Freeways with heavy traffic are also helpful. Interstate 5 running south from Albany, OR to Eugene, OR has a 33 mile straight stretch that produces a line of headlights. Aircraft approaching from the north can aim about 15° right of that line and be headed to the Eugene Airport.


What is the red barb for in the NOAA weather briefing?

They do represent gusts:
From AviationWeather.gov:

Figure 1: Station Model Plot
In many cases, the data are plotted using standard symbols and
plotting models. Fig. 1 shows the station model used in the METAR and
TAF plots.

Ceil - Ceiling height in hundreds of feet. This represents the height of the lowest broken or overcast cloud layer.
Id - The 4 letter ICAO identifier for the site. KRFD is Rockford IL.
Windbarb - The wind barb. The stick points in the direction the winds are coming from. Each full barb represents 10 knots of wind.
Each half barb represents 5 knots. Red represents wind gusts. In this
case, you have winds from the SSW at 25 knots with gusts to 30 knots.

So for example, these:

The one on the left represents wind of 15 knots gusting 20, and the one on the right is 15 knots gusting 25.
Odd ones like this:

Mean 5 knots gusting 10. Why they don't overlay I'm not sure.


Are the instrument panels in the cockpit spill / waterproof?

No they are not, at least not fully. There have been instances of equipment failure caused by coffee spills, resulting in the need to abort the flight.
This example shows a flight that needed to divert because a coffee spill disabled the communication equipment.
This Boeing 707 had to make an emergency landing after the crew inadvertently spilled water on the autopilot panel causing the stabilizer trim wheel started to rotate. Control was lost as the plane pitched up and down. Three people died in the accident.
This Boeing 737 report had smoke in the cockpit because the previous flight crew spilled coffee and sugar over the avionics.
This Boeing 720 suffered control problems (resulting in Dutch roll) after a coffee spill cause a short circuit in the yaw damper.
This Airbus A330 diverted for an emergency landing after liquid was spilled onto electronic devices in the cockpit causing the smoke.

Source: Transport Accident Investigation Commission of New Zealand


Is it possible to stall a stationary helicopter through excessive collective input?

Helicopters use speed of the wing as a proxy for angle of attack in a similar manner to airplanes; in the airplane's case it's forward airspeed and in the helicopter's case it's "rotary airspeed", expressed as rotor rpm.  In the airplane you have the bottom of the green arc on the airspeed indicator; in the helicopter it's the bottom of the green arc on the rotor tach.  In the airplane there's a stall warning horn; in the helicopter there's a low rpm warning horn (that's the only "safety system" to prevent blade stall).
If you're in a hover, there's nothing stopping you from yanking the collective pitch all the way to the up stop.  This shouldn't be sufficient to induce blade stall because the machine will respond by both climbing and increasing the vertical downwash of air, both of which will make the actual blade AOA increase less than the physical pitch change made by pulling collective, as long as rotor rpm stays in the green arc.  Whether this action keeps the rpm in the green is another matter, and on turbine machines it's likely to overtorque/overtemp the engine(s) even if rpm is kept in the green.
If you pull pitch like that and the engine can't deal with the load even at maximum power, the rpm will quickly decay and once it goes below the green arc, blade stall could (will) occur at some margin below the green arc.  When blade stall occurs from low rotor rpm while in a hover or at very low speed, the rpm decays even faster, the blade drag is too high for the engine to fight against, and the machine starts to settle vertically, causing blade AOA to increase further.
Before you know it the blades are WAY above stalling AOA, and you become While-E-Coyote strapped to an anvil and down you go; there's no recovery once a vertical descent with a stalled rotor starts, engine or not (if this happens in an engine out autorotation at altitude, the rotor will be close to stationary by the time you hit the ground - I recall a Robinson R22 incident from the 90s where the pilot lost engine power due to suspected carb ice, while flying along at 1000 ft, and didn't lower collective in time to get a proper autorotation started, the rotor rpm quickly decayed, the rotor stalled, and the machine just fell out of the sky like a wounded goose).
So the limitations are not so much about collective movement, it's the effect of collective movement on rotor rpm (and engine limits) that is critical, and the pilot has to monitor rotor rpm and respect the bottom of the green arc and the rotor rpm warning horn to stay safe, knowing that if the limits are exceeded and a stall happens, there is probably no recovery.
So, if you are hovering 10 feet in the air and you let it happen, it's a hard landing with maybe the tail boom getting chopped off.  If it happens while hovering at, say, 100 ft, the result is fatal.
To answer each question specifically:

Yes you can pull full collective any time. But the key safety parameter isn't collective position, but rotor rpm.
The only safety system is the rotor tachometer and the low rpm warning horn.
Yes, IF the engine has sufficient power to maintain rotor rpm in the green while pulling full collective. Some helicopters may be able to do this some may not.  If it can't, the rotor stall won't occur until the rpm decays to some point below the green arc, and once that happens, you are done, even if the engine is still making power.
Excessive collective input is revealed not by the actual lever movement, but by its effect on rotor rpm, which is the most critical parameter for the pilot to monitor. See here for a Robinson safety letter that talks about low rotor rpm rotor stall to see just how critical this parameter is.


What happened to the power plants after an aircraft is retired?

They'll go on another airplane, or go into inventory as spares, or maybe go for overhaul if they are becoming or close to becoming worn out (the can be run until the Inter Turbine Temperature at takeoff or oil consumption becomes excessive, or they fail an internal inspection, or suffer excessive vibration etc).  Engines are changed all the time, every few years, and can be thought of as a separate asset from the individual aircraft.


Is flow turning different from the Magnus Effect? If so, how?

When air comes into contact with a barn door or whatever at an angle, it will want to follow the top surface down (due to viscosity). Air will try to stick to the surface as much as it could, it usually fails above angle-of-attack of 15° or so.

When the flow sticks, the part exactly at the surface will have zero velocity. Above that part (layer) it will be a bit faster, and so on. Think of the layers within 2-3 cm of the top surface (that's the boundary layer).

Since the top most layer is the fastest, and the bottom is the slowest, the air will turn down (like a tank with different speeds for the different tracks).

The phenomena can be thought of as a force pointing down and causing the air stream to bend. With the airfoil's reaction being an opposite upwards force.

This downward motion pulls air from above and directs it down, causing the downwash. Bringing air from ahead and below is the upwash.

This rushing of air above the surface decreases the pressure, below the opposite happens but at a smaller magnitude. The end result is pressure differential and the air below pushes up toward the lowest pressure.

Flow turning:

Above is considered flow turning, the turning may become more apparent when you look at what happens to the air by a passing airfoil. It is usually depicted like this:

(Sources and more: allstar.fiu.edu, this video, and this video.)

Above is a different frame of reference of looking at how the lift is created. It has nothing to do with the Magnus effect. See PK's answer, both are lift, both can be described in many ways.

The Magnus effect:

The Magnus effect is of usually a spinning cylinder or ball, where the top/bottom surfaces change the speed of the flow in opposite ways. For example, in a back spin, the top surface moves in the same direction as the air stream, further accelerating the air near the top surface and further pulling more upwash, etc.

(Source)


Why do the RNAV (GPS) approaches to KAPC not use the same missed approach procedure as the ILS/LOC approach?

As best I can understand from the TERPS, it's because there are certain criteria for RNAV missed approaches that wouldn't be met by copying the ILS missed approach.

Specifically, I found the following (see chapters 7 and 15):

In RNAV missed approaches "turns shall not exceed 120°", but the ILS missed approach requires about a 180° turn. There's some related information here about the FAA testing turns greater than 120° in RNAV instrument procedures, it looks like some avionics can't handle them properly.
RNAV missed approaches are made up of legs between waypoints, and the first leg after the MAP has a required minimum length "to allow the aircraft's stabilization on course immediately after the MAP". Unfortunately I couldn't identify what that length is, because the FAA's PDF quality is abysmal and some information is unreadable, but the ILS missed approach requires a turn after a climb of less than 300' (from 214' to 500'), so the distance traveled in that time would presumably be quite small. If the RNAV minimum leg length is significantly greater than that distance, then it might be necessary to continue straight ahead, as both RNAV approaches do.

I'm certainly not a TERPS expert and there may well be other reasons for not using the ILS missed approach, but those two points seem to show that the criteria for designing missed approaches is different enough between procedure types that you can't just 're-use' them freely.


The key in flying a good roll is to keep the aircraft's nose up in anticipation of the lift requirement when flying in knife-edge or inverted flight. Since in knife-edge the elevator and rudder will assume each others function, you will need rudder as well as elevator for directional and pitch control. Also, depending on adverse yaw, some rudder is required to hold yaw to zero when applying ailerons. The procedure is as follows:

Speed up, so you are fast enough for roll maneuvering and inverted flight.
Pitch up a few degrees. How much depends on wing incidence and zero-lift angle of attack. Look out for some feature on the horizon: This will help you to keep your direction constant.
Stop the pitching motion, then apply full ailerons. Correct the aileron-induced yawing motion by applying gentle rudder (trailing edge in the direction of the up-going aileron). Your goal is to keep the fuselage pointing at the chosen feature throughout the maneuver.
With increasing roll angle, apply rudder to keep the nose up. At the same time, push the stick gently to avoid course deviation. At 90° roll angle, both elevator and rudder have changed their function: The elevator will now control direction, and the rudder will control pitch.
Keep the rotation rate and push the stick more when changing from 90° to 180° roll angle. In inverted flight you need to keep the aircraft trimmed, and depending on the static stability and speed this can require considerable negative elevator deflections. At the same time reduce rudder deflection such that the fuselage will still point into the initial direction. At 180° roll angle both elevator and rudder have returned to their old function, but pulling will now start a dive.
On the way to 270° you will again need to add some rudder, now in the opposite direction, to keep the nose up. Again, elevator and rudder will exchange their functions.
Once you return back to normal flight attitude, stop the rolling motion and reduce rudder deflection back to zero.


What does "S-ILS" signify in an FAA NOTAM?

The S is for the straight-in portion of that approach (this is explained in the Abbreviations section of the Terminal Procedures Publication (See here - it's in the Abbreviations section of "Legends and General Information" at the bottom).  In this case the decision altitudes, height above thresholds, and weather minimums have changed.

Check out the approach plate and at the bottom you'll see S-ILS 15, S-LOC/DME 15, CIRCLING, etc.


Did the space shuttle have a stall warning system (such as a stick shaker)?

The shuttle was not built with this capability. NASA AMES had a project MIDAS intended to improve the shuttle's cockpit information display and management. In its list of problems to address:

  Finally, there is no warning or guidance/autopilot limiting when approaching a stall on entry.