Is it legal to fly GA aircraft in temperatures above what is shown on the performance charts?

Yes, it is legal, disregarding any catch-alls such as 91.13 reckless operation or ones pertaining to pre-flight planning data like takeoff distance.

It is simply left to the pilot's good judgement for a go/no go decision depending on whether or not the flight can be completed safely.

Edit: Re-reading this answer much later, I would like to emphasize, "disregarding any catch-alls".

With regard to the catch-alls such as 91.13, this could very easily be considered illegal, but no rule with a statement clearly identifying taking off with temperatures higher than those on the charts as a prohibited action exists to my knowledge.  Do not do it.


In a slip or skid, how does one wing have a higher angle of attack and more lift?

You are mostly correct, but the fuselage distorts the airflow in sideslip such that the windward wing sees a higher angle of attack near the root, and the leeward wing a lower angle of attack. Please see the drawing below for an explanation.

The blue lines show the sideward component of air flow and the red arrows the resulting rolling moment.

This is why low wing airplanes need more dihedral, and high wing planes like your 172 almost none. Wing sweep adds more directional stability, and then you even find aircraft with pronounced anhedral, like the Harrier jump jet or the F-104 Starfighter. See this answer for more detail on this.


Why does the Embraer E-Jet Family have doors of different sizes?

It's actually more common than one might expect, and not just in the E-jet family.

The de-facto standard is that passengers board from the left and the right side doors are only used to load logistical stuff (ie catering) during the turnaround or during an emergency evacuation.

As such, the left side door(s) must fit certain FAA standards (so it fits jet bridges or the average human height, for example).

For example, on the Boeing 737 (all models), the left forward door is 0.86 x 1.83 meters while the right forward door is 0.76 x 1.65 meters, 20 percent smaller (by area).

Now you might ask "ok, so make both doors the size of the left door". It's beneficial, from engineering/structural point-of-view, to have each door as small as possible.

(http://www.boeing.com/assets/pdf/commercial/airports/acaps/737.pdf pages 73 and 77)


What is this? Multiple small cracks in passenger window

Airline pax windows are cast acrylic plastic (plexiglass) and when the panels age they can get little microcracks in the surface called crazing.  This can be formed from long term tension stress on the crazed surface as well as from degradation from chemicals (ammonia is one of the worst - NEVER use Windex or equivalent on plexiglass) or UV (acrylic cast for aircraft has a UV block in it that makes it relatively resistant to UV).

On airline windows it's mostly due to long term surface stress because the pressurization system is trying to blow the window out all the time and the outer layer is in tension.  Minor crazing is not a structural problem because it is in the outer couple thousandths of an inch of the plastic and doesn't reduce its strength significantly (1/4" thick acrylic sheet at 8ksi tensile strength, like you would typically find in a pressurized aircraft window, is roughly equivalent in tensile strength to .050" 2024 aluminum, so it's not that much different than the adjacent aluminum skin with minor abrasion surface scratches, structurally speaking).

Airlines restore windows with crazing and scratches by removing the outer crazed layer with abrasive products made for the purpose (like Micro Mesh https://micro-surface.com/).  There is an allowable minimum thickness of the acrylic and they can go down to that, and if crazing is still apparent at that point the window is scrap.


Why don't aeroplanes automatically put out engine fires?

Shutting off the computer is difficult from a technical implementation standpoint. You're handing over a lot of power to the computers and sensors letting it shut down an engine, where these usually do not have access and control. This is certainly not always a good idea.

Pulling the fire handle is a pretty aggressive move: It will typically disable hydraulics, electrical power, and bleed air coming from that engine. If you're not prepared for it, it can end badly.

The engine will often be partially functional, depending on the type of failure. If you get dual engine fire indications, you'd probably wait with shutting them down, if doing that at all. This sort of behaviour would have to be coded into the flight computers.

I don't think there are any catastrophic consequences of not switching the engine within 8 seconds rather than maybe 2 seconds. It does not make a great difference. To set off the detectors, it must already have spread a little. I don't think you could do it much faster with the pilot staying updated on what's going on.

Needless to say, computers sometimes get things wrong. There is a human level to check what's going on before proceeding.

There are times when you don't want the computer doing it's own thing. Airbus states that:

If an engine fire occurs during takeoff or go-around, the Pilot Flying shall first establish and stabilise the aircraft on a safe climb path and then proceed with the ENG FIRE procedure.

Footnote:
It could certainly be done, but with the pilot-computer relationship on current flightdecks it's not a good idea.


The roundings I know of in the context of US general aviation aren't strictly defined or enforced because they don't need to be (with the exception of racing; see below). The military might need to be more precise, but I have no idea about that.

Anyway, here are the main roundings a typical GA pilot might encounter:

Logging: to the nearest 6 minutes

Pilots usually log their flight time in tenths of an hour, i.e. they round to the nearest 6 minutes. There's no regulation on it and some people prefer to log in hours and minutes (maybe it's even required in some countries), but tenths seems to be most common.

ATC instructions and clearances: to the nearest minute

See this question for information on timing under IFR (some of it applies to VFR too); instructions, clearances and reports are given to the nearest minute. It is required to have a clock with a second hand but that's to make it possible to do timed turns, not because ATC gives instructions down to the second.

Air racing: to the second or less

In air racing, there are at least two ways of using time. In a speed race - like the Red Bull Air Race - you measure the elapsed time over the course. The timing for Red Bull is to one thousandth of a second.

In precision navigation air racing, you plan your flight over a specific course and calculate the time (and sometimes even the fuel) you'll require to fly it. When you fly the course, any deviation from the numbers you submitted beforehand - under or over - is penalized. Timing in those competitions is to the second.


What are the criteria for classifying which generation a fighter aircraft belongs to?

The Wikipedia Page for Fighter Generations has a relatively comprehensive list on how they derive at the "generation" of the fighter. For example, here is how the Air Force classifies them:

  1: Jet propulsion : F-80, Me 262
  2: Swept wings; range radar; infrared missiles : F-86, MiG-15
  3: Supersonic, pulse radar, Beyond-visual-range missiles : Century Series, F-105, F-4, MiG-17, MiG-21
  4: Pulse-doppler radar; high maneuverability; look-down/shoot-down missiles : F-15, F-16, Mirage 2000, MiG-29.
  4+: High agility; sensor fusion; reduced radar signature : Eurofighter Typhoon, Su-30, F/A-18E/F, Rafale
  4++: Active electronically scanned arrays; continued reduced signatures or “active” (waveform canceling) stealth technology, supercruise : Su-35, F-15SE
  5: All-aspect stealth with internal weapons bays, extreme agility, full-sensor fusion, integrated avionics, some or full supercruise : F-22, F-35,
  6: extreme stealth, morphing capability, smart skins, highly networked, extremely sensitive sensors, optionally manned, directed energy weapons.

Until we have a major leap in technology, it would seem we are capped off at 5th generation fighters for the moment.


What prevents BFS from becoming unstable when pitching from horizontal to vertical?

The answer here is to review the history of how Space X "does it" with the Falcon 9.  To solve aerodynamicly, they extend speed brakes from TOP of booster to get it to fall tail first.  CG buffs take note, this is how it works in gravity and atmosphere. Just like a parachute or a hang glider.

Very close observation of the video shows the lower "tail fins" folding inwards, raising the aerodynamic pressure point (in this case drag) above the CG.  The rocket now behaves as an aircraft with its CG way too far back(relative to Clift), pitching up and falling "backwards" towards the ground. Rocket thrust then slows the descent for landing.

The rocket is rotating during this maneuver to its new weight down and drag/lift up configuration, with predictable increase in velocity due to lower net drag towards the direction of "flight".

It may be helpful to draw the "lift" vertical and horizontal components here to understand the forces.
The maneuver is not unlike a 1/4 loop.  It is controlled, because CG is below the Center of drag.

In response to edit regarding yaw axis, great observation!  This is a technique considered for airliners recovering from deep stall!!!  Rock back and forth to bring V stab into play to yaw out of deep stall.

But with the rocket, the gimballed motor will stop this, and before, rudder will now not be used to break the stall, but to preserve it!  This is an aerobatic maneuver, pure and simple.

What Space X does so well is transition the "deep stall" into a controlled landing.

The concern about the V stab is justified.  The Falcon 9 speed brakes are more fool proof.  Let's hope they do not "engineer themselves into a corner" with a potentially flawed design.

POST EDIT - RESPONSE TO COMMENTS

We need to keep in mind here that the animation is what may be wrong, not the actual flight plan. @qq jkztd correctly pointed out that, if the BFR was falling vertically, with no horizontal motion, the pitch up would cause horizontal motion towards the tail (beginning to glide backwards). Although the pitch up would not induce yaw, the backwards gliding BFR WOULD be unstable in yaw. Folding in horizontal fins would make it stable in pitch. A better solution may be to initiate pitch up with some forward motion, or to simply pitch up by adding more drag to "top" with speed brakes as the Falcon 9 does, or igniting gimballed rocket motor sooner.  However, sometimes, simpler is better,


Airbus claims that:

  The A380 is compatible with over 140 small and large airports for
  regular service worldwide, and up to 400 airports when adding
  diversion airports ...

The list of airlines operating A380s and their destinations are listed here.

I didn't find details about emergency landings.


What role do the winglets on the next-generation 737 play?

The wing tips calling as "sharklet" at Airbus A/Cs and "winglet" at Boeing A/Cs. It reduces the tip vortex and helps to prevent from airflow seperation at wing tips. It have positive effects on both fuel consumption and turbulance making. Negative effect of the additional part is increase of the drag coefficent but you can keep it negligible againts the positive effects.


Why do airliners pitch up during cruise?

Mainly the options 2 and 1 from your list.

What nobody mentioned so far, but is rather important here is that the angle of attack depends on speed1 and weight. While the "speed" does not vary much for most airliners, the difference between empty and fully loaded airliner is rather large.

Now if the fuselage was tilted down, it would generate lift directed down and associated drag with the net result of simply a lot of extra drag. So the aircraft is designed so that it does not fly (in level cruise) pitched down even when light. But that means that when it is fully loaded, it flies slightly pitched up, because it needs more lift and higher angle of attack to get it.

1 It depends on the "indicated speed", which is not speed at all but rather dynamic pressure expressed as speed at which it would occur when moving through air of standard sea level pressure (1013.25 hPa). The pressure at high altitudes where airliners normally fly is significantly lower, so the indicated speed is usually does not exceed 250 knots when true speed is well over 400 knots.


When was trim on airplanes used for the first time?

Although Anton Flettner patented the trim tab in 1918, (as said in a comment above) it seems that 1910 was the first implementation of "trimming" (according to the following article, linked below)

https://www.flightglobal.com/pdfarchive/view/1910/1910%20-%200255.html

Although it was not adjustable in flight, it still seems like the first time any concept of trim was introduced was in early 1910. However, Anton Flettner produced the first ADJUSTABLE trim tab.


Are the advantages of a coaxial rotor on a helicopter also applicable to a ducted fan?

Part of the gain of coaxial rotors on a helicopter is not having to power the tail rotor (IIRC it takes ~10%). So for contra-rotating propellers and fans, which don't need a tail rotor, the advantage is smaller, about 6–16% [1].

Now ducted fans (assuming as used in turbofan engines) usually contain stators. These do not stop the rotation of the flow (that takes away the energy) completely, but they do reduce it significantly and with much lower complexity. The remaining possible gain would probably be at most couple of percent and that is likely not worth the increased complexity and weight of additional gears. Don't forget that turbofans run at significantly higher rotation speeds than propellers.


Why does this plane not pitch up after a dive?

My vote is that the surfaces aren't rigid enough and get twisted so much that the control surfaces can't overcome the effect. How floppy (non-rigid) are the wings and the canard surfaces? The wing looks to be sagging under its own weight! My thought too is that you're tail heavy, tail heavy will pitch both ways and you can get stuck in either positive or negative stall (or tuck). Tail heaviness causes the plane to tend towards going or falling flat like a leaf; it's usually strongest (leeast recoverable) when under the influence of negative G's. It doesn't matter whether the craft is upright or inverted; it's still "negative G's" including the caused airflows. Still, my best guess is weak surface rigidity. Good luck with your cool project!!!


Is it better to shut down the engine(s) or leave it (them) running when a gear up landing is imminent?

There's two schools of thought. First is the keep the engine on school because keeping the engine on:

Gives you more control of the airplane
Gives you the option to go around
Keeps the procedure simple and allows the pilot to concentrate on a good touchdown
Keeps the dynamics of the airplane predictable and familiar to the pilot

The shutdown the engine school's view is that shutting the engine down lowers the fire risk by cutting off the fuel and engine ignition spark.

Personally I'm with the keep the engine on school of thought. The last thing I want to be doing when I'm trying to make a smooth landing is reaching for all sorts of knobs and levers, and having to reach the fuel cutoff valve in the inconvenient places that piper likes to put them, and then learning how the airplane behaves without engine power for the first time. As soon as I touch down I am pulling the mixture, cutting off the fuel and killing the mags and the master switch, but until then I'm going to concentrate on making it the smoothest landing in the history of manned flight.


Why is Cessna 172 POH performance chart based on Pressure Altitude and Temperature instead of Density Altitude?

I have analyzed this information before, and this is what the chart looks like with one line for each weight category if you convert the temperature and pressure altitudes to density altitudes and then chart that vs. the takeoff distance:

You can see that I have drawn a sort of best-fit line for this information.  I did not add humidity as a factor because the manufacturer's charts had no relevant data.

Clearly, the trend from the manufacturer's data, when converted to density altitude, does not appear perfectly linear if you follow the data points they jump up and then start lower again in chunks of similar density altitude.

The greatest variation here is about 400 feet from the highest point in any of those clusters to the lowest point in the same cluster. That would be the yellow line around 8,000 ft of density altitude.

To answer your question, maybe they didn't use density altitude in the POH because their data appears to be irregular.

With that small margin of error here, I am comfortable using these best-fit lines to quickly calculate my data because I wouldn't make a go descision for a takeoff with a calculated distance anywhere near being within 400 feet of acceptable runway length.


No part of my Cessna Cardinal wings are airtight. Even the fuel tanks are vented to allow air in to replace the fuel this is used.
The area around the flaps, flap motor aileron control cables, etc., none are airtight.


What is the offset in a seaplane's hull?

That's called the step. Without it, you'd have to fight against the buoyancy of the rear end of the hull when you rotate for takeoff.

However, a seaplane float or hull must be designed to permit the seaplane to be rotated or pitched up to increase the wing's angle of attack and gain the most lift for takeoffs and landings. Thus, the underside of the float or hull has a sudden break in its longitudinal lines at the approximate point around which the seaplane rotates into the lift off attitude. This break, called a "step," also provides a means of interrupting the capillary or adhesive properties of the water.
The water can then flow freely behind the step, resulting in minimum surface friction so the seaplane can lift out of the water. The steps are located slightly behind the airplane's centre of gravity, approximately at the point where the main wheels of a landplane are located. If the steps were located to[o] far aft or forward of this point, it would be difficult, if not impossible, to rotate the airplane into a pitch-up attitude prior to planing (rising partly out of the water while moving at high speed) or lift off. Although steps are necessary, the sharp break along the float's or hull's underside causes structural stress concentration, and in flight produces considerable drag because of the eddying turbulence it creates in the airflow.


Is rate of turn information (both Turn Coordinator and Turn Indicator) accurate only in balanced turns?

The physics of turn coordinators, and turn rate indicators, are complex.
The since the gyro axis is not usually not perfectly horizontal, the instrument shows some response to pitch rate, as well as to turn rate.  In a coordinated turn at some particular turn rate, the calibrated markings can only be perfectly accurate at one specific pitch rate.  This means we have to specify either the bank angle or the True airspeed when we calibrate the instrument for a given turn rate.  In practice, the True airspeed is specified and assumed to be constant regardless of turn rate, while the bank angle, naturally, varies with turn rate.
Errors from flying at a different True airspeed than the instrument was calibrated for may be small enough to generally ignore in actual practice, but they do exist.
This is explored in more detail in the following ASE answers to related questions--
May turn rate indicators (and turn coordinators) be calibrated to be accurate at all airspeeds, or only for one?
Are turn rate indicators calibrated to a certain speed? If so, what speed?
In some "turn coordinators", does the gyro spin opposite to the direction it spins in a "turn rate indicator"?
If the aircraft is slipping or skidding, then the relationship between True airspeed, bank angle, pitch rate, and turn rate is altered, so the calibrated markings will no longer be accurate even if the True airspeed is the one that the instrument is calibrated for.  For example, in a wings-level skidding turn, the pitch rate is zero.  For the reasons explored in the above links, this will create some change in the turn rate indication.  The indicated turn rate will be different than if we were flying at the same True airspeed but in a fully coordinated turn.
Another way to look at it is that all turn rate indicators, and some if not at all turn coordinators, are designed so that the gimbal axis of the gyro stays approximately horizontal relative to the earth during any given coordinated turn.  If the aircraft is not banked at all, then any turn will tilt the gimbal axis of the gyro away from horizontal, which will affect the sensed turn rate.
Of course, it could happen that a change in indication due to slipping or skidding could exactly offset a change in indication due to flying at some True airspeed that is different from the True airspeed that our instrument is calibrated for.  So the full answer to the question is "Generally, yes, but it's complicated."
The details discussed in the third link above suggest that there may be fundamental differences in the way that a skid, or a slip, affects the reading of a turn rate indicator versus a turn coordinator--i.e. whether the indicated turn rate is increased or decreased-- and furthermore that there may be differences in behavior between different makes of turn coordinator, because they may not all share the same direction of spin of the gyro wheel.
This would be fertile ground for some actual in-flight experiments to make some real-world observations as to how the turn rate displayed by a given instrument is altered by slipping or skidding.  Keep the airspeed and the indicated turn rate constant, and make the aircraft slip or skid through one or more full 360-degree turns, and measure the actual time to complete 360 degrees of turn in each case.  For completeness, repeat the experiment at a different airspeed, or a different indicated turn rate, or a different amount of deflection of the slip-skid ball.  Be sure to include the extreme case of a wings-level skidding turn.  Finally-- especially if flying with a turn coordinator rather than with a turn rate indicator-- do some basic tests to see if, starting from a standard-rate turn, moving the stick or yoke aft to "pull" some extra G's tends to boost, or to reduce, the indicated turn rate.  Similarly, starting from a standard-rate turn, test whether moving the stick or yoke forward to "unload" the wing to a lower G-load tends to boost, or to reduce, the indicated turn rate.  These tests will help show which direction the gyro wheel is spinning in that particular instrument, which is relevant to understanding what is going on in the slipping or skidding situations.


In a Vmc demo, why is it important to lose 1 knot per second?

Why do we want to lose 1 knot per second in a VMC demo?

To more accurately determine where VMC is:
As Carlo Felicione's answer says, VMC changes day by day, and you want to determine it precisely.  You can't do that if you're slowing too rapidly.

To permit smooth control of the aircraft:
During a VMC demo, rudder required is determined by aircraft speed. The slower you go, the more rudder you need.  The more abruptly your speed changes, the more abruptly your rudder needs to adjust to compensate.  Since the point of a VMC demo is to determine when your rudder fails to control your heading, abrupt speed changes should be avoided.

To allow consistent control techniques:
Have you noticed that it's really hard to hold a particular vertical speed using the vertical speed indicator?  Usually, you select a pitch, hold it, and then reference the VSI to determine whether a pitch adjustment is necessary. The same is true of airspeed loss.  During a VMC demo, usually, the pilot will configure the airplane for engine-out flight and then pitch to an attitude that will create a 1 knot per second loss of airspeed. As pitch settings are fairly unchanging from flight to flight, this allows you to do the maneuver with more consistency.  You can put the rate of airspeed loss more or less in the back of your mind and concentrate on your rudder control, which is the point.

How do we know we're losing 1 knot per second?

Counting: As you say, looking at the airspeed indicator and counting seconds is a simple and reliable way to do it.

Known pitch settings: As mentioned above, pitch to a known setting and you'll get pretty close to 1 knot per second without the fuss of counting.  As you gain more experience this will become the way you'll do it.


Is this takeoff of a 767 in bad weather conditions a normal procedure?

Take-off within the crosswind limits is a normal procedure. From the video it's hard to tell what the crosswind was in this particular situation, so it is impossible to tell about the legitimacy of this take-off.

Rotation seems to be on the 1000ft marker, i.e. 1000 ft from the runway threshold. But in case of a displaced threshold the take-off distance available may be more than 1000ft from that point. It was airborne before the end of the runway.


Built In Test Equipment is part of a system that monitors the correct functioning of that system. It produces an alert if part of the system fails to fulfil its function.

An example would be a system with two sets of memory chips; the BITE would copy all data to set 1, then test memory set 2 by writing and reading various test patterns. If the read pattern is different than pattern written, there is a memory error. If so, an alert is raised. If not, all data is copied to set 2, and set 1 will be tested. This is procedure is repeated at specific intervals.

Another example would be a watchdog timer which triggers a signal if a timer runs out. If the system is working correctly, it will reset the timer before it runs out. The signal from the watchdog can then for example reset the hardware, take some corrective action or raise an alert.


CRM is about making use of all available resources to safely conduct a flight.  Pilots these days (even single pilot ops) have a wealth of resources available to them.  Anything you can see and anyone you can talk to is a resource, and CRM is about making efficient use of those resources.

Flying a light single you will have a subset of these resources:

Cockpit displays
Charts
Checklists
ATC
FSS
Flight Watch (EFAS)
Live Weather downlinks (e.g. XM satellite weather)

On a large transport aircraft these change a bit:

Cockpit displays
Charts
Checklists
ATC
FSS
EFAS
Onboard RADAR
The QRH (quick reference handbook)
The FOM (flight operations manual)
The other pilot(s)
The cabin crew
Passengers (Doctor in a medical emergency?  People helping in an evac?)
Dispatch
Medlink
Company Ops
For ground ops:

Fuellers
Ramp personell
Gate agents

More and more emphasis is placed on managing these resources as you move up the chain.  By the time you are taking your first 121 upgrade checkride, it is more about judgement and CRM than it is about the flying.


ARINC Specification 664 calls for quadrax cable or fiber optic cable.  Quadrax is a four conductor matched impedance (100 ohm) cable.  Connectors are MIL-DTL-38999.

image source

The primary benefit is improved EMI protection and ruggedized connectors.

The B787 uses fiber optic.  A380 uses the quadrax cable.


How to decide on which side of the runway the approach path indicator (VASI, PAPI) are placed?

Path/slope visual indicators are usually located on the left side of the runway (as seen when approaching), but may be on the right side when impractical. Good reasons for moving the aid on the right side:

Obstacle clearance, terrain, intersecting runways or taxiways.
Interference may occur on the left side, between PAPI lights and nearby lights. This is emphasized in FAA AC 150/5340-30G - Design and Installation Details for Airport Visual Aids: "Because PAPI system is dependent upon the pilot seeing a red and/or white signal from the light units, care should be taken to assure that no other lights are located close enough to the system to interfere with the signal presentation."

Installing them on both sides is beyond ICAO recommendations and FAA orders, but can be done:

For visibility improvement
In order to give better roll guidance

Some countries don't implement ICAO rules the same way, for instance in the UK, PAPI for governmental airports "may be provided on both sides of the runway" (source)

For airports providing a visual guidance for STOL operations. The PAPI associated with the steeper approach path may be located on the right side of the runway (source).

PAPI at the usual location, on the left side of the runway (source).

From Wikipedia:

  The international standard for PAPI is published by the International
  Civil Aviation Organisation (ICAO) in Aerodromes, Annex 14 to the
  Convention on International Civil Aviation, Volume 1, Chapter 5.
  National regulations generally adopt the standards and recommended
  practices published by ICAO.

From FAA JO 6850.2B - Visual Guidance Lighting Systems:

  The basic PAPI configuration is described in chapter 1, section 2,
  paragraph 16, and is shown in figure 5-1. All lamphousing assemblies
  (LHA's) should be located on the left side of the runway, as viewed
  from the approach direction. However, where terrain, cross runways,
  or taxiways make this arrangement impractical, the light units may
  be located on the right side of the runway.

  [...]

  The VISUAL APPROACH SLOPE INDICATOR (VASI) system is no longer
  installed by the FAA as a new facility. Specific details and installation
  criteria have been moved to Appendix E to provide technical support for
  existing VASI equipment and facilities.

  [...]

  The basic VASI configurations are described in appendix D, section
  1, paragraph 1 and shown in figures 1, 2, 4, and 5. All boxes (or
  light units) of the two-box; four-box, and six-box configurations are
  located on the left side of the runway (as viewed from the approach
  direction). However, where terrain or cross runways, etc., make this
  impractical, they may be located on the right side of the runway.

Washington Dulles Int'l Airport  offer several location variations, chosen for practical reasons. There is a PAPI on the left side for runway 1C and on the right side for 19C, but a reverse scheme is used for 1R/19L, and 1L/19R is just standard:


What is the correct go-around procedure in a PA-44?

Any procedure listed in the AFM for your airplane takes precedence, but a general go-around technique I use (and teach my own students) is as follows

1) Add power - on complex airplanes, verify mixture rich (or for best power at high altitude airports) and propeller controls are set for maximum RPM prior to pushing the throttles to full power.

2) Apply aft elevator pressure to arrest rate of descent and bring nose level with horizon.

3) With level flight attitude, set flaps from full to approach setting.

4) continue applying aft elevator pressure and establish climb attitude

5) Once climb attitude established and continuous positive rate of climb confirmed, retract the gear.

6) At sufficient airspeed and altitude to permit safely doing so, retract the flaps.

7) Set throttles and propeller controls for maximum continuous power and pitch for selected climb airspeed.  Trim aircraft to neutralize control pressures.


What are the differences between pre-transistor and transistor era jet engines?

The vibration levels on jets preclude the use of vacuum tubes. They may work if everything is fine and all rotating parts are well balanced, but once you have a defect and an out-of-balance condition, the electronics would fail quickly, just when you need their help the most. Especially the afterburner adds a lot of vibration when it works as designed already.

Earlier jet engines used hydraulics for adjusting things like compressor vane angles (litte stationary "wings" positioned between the rotating discs of the compressor, which help to convert rotational flow energy into compression) and the nozzle size. Like on piston engines, the amount of adjustment was much lower back then, and all adjustments were done mechanically.


Was the runway upgrade at Mataveri Airport on Easter Island really related to the Lee Correy novel "Shuttle Down"?

As much as I enjoyed reading the novel after reading the Wikipedia article about Mataveri Airport I am somewhat disappointed by my answer. The novel was published in 1980 and the official agreement between the United States and Chile was not signed until 1985 there is circumstantial evidence that the novel did not play a causal role.

In Glynn S. Lunney's Oral History from NASA's Oral History Project. Link to Full Text It appears that from very early on in the Air Force's involvement with the Shuttle Project that Easter Island was identified as a possible abort landing site. They didn't like it because of the short runway but they thought about it. Because this is an oral history it is hard to pin down exactly when these thoughts were happening but the context makes it look like it was quite early.

Naturally all of the news articles from 1984-1987 about the extension I found never mention the novel. Nor does the official text of the Agreement.

It was a fun little novel though. Which strangely enough foresaw most of the logistical problems that would arise from having a NASA retrieval crew on Easter Island. Especially the water and sanitation limits.

Having kept looking for a bit I found an interesting declassified memo from 1966! The Air Force has been considered their own manned space flight program launching from the Western Test Range heading south and using Easter Island as a possible abort landing sight. Another memo from 1967 says it got so far as actual discussions with the Chilean government. Even though these documents were classified it is clear that the idea of using Easter Island as an emergency landing site did not come from the novel.


How do you determine the proper rate of descent for landing?

Assuming you want a 3 degree glide slope, just take 5 times your ground speed in knots as a starting point.

As an example, approaching at 90kt ground speed in a light aircraft, go for 450feet per minute. at 140kt in a jet, try 700fpm. If you're flying a jet outside of 4 miles, and the controller wants you to keep the speed up at 200kt then descend 1000fpm.

It's not perfect, but it works pretty well for a first guess, and you can adjust as necessary.

Of course, your ground speed is not the same as your air speed, and even for a constant IAS it will likely vary as you descend and the wind changes. Another way to think about this is that a 3 degree glideslope is almost exactly 300ft per nautical mile. If you're 2 miles out and 700 feet up, then you need to descend a bit faster, conversely, if you're at 500 feet, you need to descend slower.

A third related rule of thumb is that your final approach speed (in CAS, although IAS is good enough in most aircraft) is 1.3 times your stall speed in the landing configuration (Vso). So if you stall at 100 knots, you want to approach at 130KIAS.

IFR approaches are all about having an initial guess at these numbers in your head, trying them out, and then adjusting as the conditions require. If you're good at the guesses then the adjustments will be very small.


Are all US airline aircraft certified into known ice?

Title 14 CFR part 121.321 regulates scheduled airline operations in icing conditions.  It requires airframe ice protection systems in order to operate in "conditions conductive to airframe icing", which they define as:

visible moisture at or below a static air temperature of 5 °C or a total air temperature of 10 °C, unless the approved Airplane Flight Manual provides another definition.

This essentially means that any airline that can operate in IMC is going to be subject to this requirement unless they have very niche operations at low altitudes in warm lattitudes where they can stay below the 10 C level when in IMC.
Aircraft operated by airlines that operate in IMC at temperatures colder than 10 C must either have an ice detection system or a means of detecting the first formation of ice on the airframe and then activate ice protection systems or they must, in the absence of detection, always operate their ice protection when operation in conditions conductive to airframe icing.
For smaller on-demand operations operating under part 135, 14 CFR 135.227 regulates flight into icing conditions.  This regulation requires that any airplance flying into forecast icing (IFR only) or known icing conditions (VFR or IFR) has functioning de-ice or anti-ice protection.  This means a 135 operation ferrying passengers from Miami into the Bahamas probably doesn't have to worry about this, but a IFR 135 operation anywhere it gets cold probably does.
For non-121 and non-135 operations in airplanes with 20 passenger seats or more, the applicable regulation is 14 CFR 125.221 and reads exactly like the part 135 regulation.
Summary
Combined, parts 121, 125 and 135 regulate the majority of commercial operations.   The requirements of part 121 realistically mean that any airplane suitable for scheduled airline operations is equipped with ice protection.  Part 135 can utilize a broader range of aircraft and while ice protection is not required it is quite limiting for the operation if it is not present (no flight into known or forecast icing conditions under IFR).
This means that all airline aircraft (part 121) are certified for FIKI but not all passenger airplanes (operated under part 125 or 135) are certified for FIKI (and cannot operate in those conditions if not equipped).
Regs

§121.321   Operations in icing.
(a) When operating in conditions conducive to airframe icing, compliance must be shown with paragraph (a)(1), or (2), or (3) of this section.
(1) The airplane must be equipped with a certificated primary airframe ice detection system.
(i) The airframe ice protection system must be activated automatically, or manually by the flightcrew, when the primary ice detection system indicates activation is necessary.
...
(2) Visual cues of the first sign of ice formation anywhere on the airplane and a certificated advisory airframe ice detection system must be provided.
(i) The airframe ice protection system must be activated when any of the visual cues are observed or when the advisory airframe ice detection system indicates activation is necessary, whichever occurs first.
...
(3) If the airplane is not equipped to comply with the provisions of paragraph (a)(1) or (2) of this section, then the following apply:
(i) When operating in conditions conducive to airframe icing, the airframe ice protection system must be activated prior to, and operated during, the following phases of flight:
...
(ii) During any other phase of flight, the airframe ice protection system must be activated and operated at the first sign of ice formation anywhere on the airplane, unless the Airplane Flight Manual specifies that the airframe ice protection system should not be used or provides other operational instructions.

§135.227   Icing conditions: Operating limitations.
(c) No pilot may fly under IFR into known or forecast light or moderate icing conditions or under VFR into known light or moderate icing conditions, unless—
(1) The aircraft has functioning deicing or anti-icing equipment protecting each rotor blade, propeller, windshield, wing, stabilizing or control surface, and each airspeed, altimeter, rate of climb, or flight attitude instrument system;
(2) The airplane has ice protection provisions that meet section 34 of appendix A of this part; or
(3) The airplane meets transport category airplane type certification provisions, including the requirements for certification for flight in icing conditions.


Do LED lights work well for CAT III B operations?

I don't know if you can do Cat IIIB with a HUD (I'd have said that you're limited to Cat IIIA with one, but somebody may have a capability I'm not aware of) but no, LED lights generally don't wash out a HUD any worse than other lights do.  If your HUD brightness is sufficiently dim, then bright enough lights of any sort can wash it out, but that just requires you to turn the brightness up a bit.

I've never heard of or seen any "Sea of Blue" effect from LED lights, and I don't think LED lights have particularly worse glare (or any other) characteristics when used as runway lighting.  They're somewhat distinctive, but not particularly worse.

If LED lights have regulatory approval for what you want to do, I'd say that right there is the answer to your questions.  And if they don't, well, then that's also an answer.


Where can I find regulations in different countries for flight level rules based on direction of flight?

Every country's Civil Aviation Authority issues an Aeronautical Information Publication (AIP) as part of their Aeronautical Information Services (AIS) which contains the information you are looking for. Most likely the information about Flight Level rules will be contained in the GEN (General) or ENR (En-Route) section. For Europe, most information from the AIP's can be found through the European AIS Database


How does the VOR receiver pick up the signal and how are the needles controlled?

Your basic understanding of the underlying electronic principles is correct: The VOR receiver detects a phase offset between two signals, which tells the receiver what radial the aircraft is currently on. Wikipedia has a decent explanation, and this article on Digital Flight Instructor has a nice widget you can play with to see the frequency offset.

  The underlying electronic principles the receiver uses are generally not useful for pilots: if your VOR receiver dies you're not going to hook up an amplifier to an oscilloscope and try to sort out the phase offset yourself, if for no other reason than your head would be buried in the cockpit staring at the oscilloscope as opposed to looking out the window for traffic or watching your flight instruments.
  In addition, the "strobe and sweep" explanation is generally easier for students to understand: Imagine the VOR station has two lights, a white light that rotates, and a red strobe that fires ever time the white light passes the 0 degree (North) radial. By counting the time between when you see the red strobe and when the white light passes you its possible to determine what radial you're on.

The mechanism by which the needle is deflected depends on the type of indicator, but it basically boils down to "The receiver does some magic and converts it into a number of dots of deflection on the indicator". The deflection can displayed by moving needle attached to a meter (applying a specific positive or negative voltage), blinking some LEDs, or showing a graphical representation of the CDI (e.g. on a GPS display) with a mark over the appropriate dot.
How this works for each specific indicator is generally only of interest to an avionics technician, and the information would be contained in the service manual for the radio and indicator.


Mode B

SSR modes B and D are not used today, but mode B has been used in UK, Australia and some other countries for some time, and it was compliant with mode A:

  In reply to interrogation in Mode-A and Mode-B information of
  identity, which is set by the pilot, is sent to the ground
  interrogator.

Source: Radar Theory for Area/Approach Radar Controllers

Modes A and B are used with a squawk code of 12 bits, offering 4096 different identifiers. In both modes the code is selected on the SSR transponder panel, using 4 octal digits (0 to 7).

SSR transponder panel, source

For a transponder handling multiple modes, the correct mode must be selected in parallel of the squawk code.

The interrogator (SSR ground station) can request identifiers using one mode at a time, and receive answers from transponders set to that mode. Aircraft using code 1234 will only reply when interrogated using the mode their are currently set to.

All legacy modes, military and civil and mode S

SSR interrogation modes are identified by the timing between pulse P1 and P3 (P2 is used to reject interrogations from secondary SSR lobes).

SSR modes identification, adapted from source

While mode A is compliant with military mode 3 (both often referred to as 3/A), mode B is purely civil. Its purpose is assumed to be an extension of the mode A, giving 4096 additional codes to ATC.

ICAO Doc 9684 which is the reference for SSR doesn't even mention modes B and D anymore.

Mode S specificities

To be exhaustive, let's mention Mode S visible at the bottom of the previous image.

Mode S (for select) allows to interrogate transponders one at a time when necessary, to prevent FRUIT. In addition of the squawk code, mode S transponders are given by authorities a unique (and quasi-permanent) 24-bit address. This address is used by SSR interrogators to specify which transponder is the recipient of the interrogation.

The address is sent in a datablock which modulation is not a pulse like P1 and P2, but a burst of carrier which phase is reverted when bit is 1 (see a detailed explanation in section Mode S of this answer).

This burst is led by a synchronization of phase reversal (SPR) burst, at the timing of legacy pulse P6, which role is to prepare the receiver to detect possible phase reversals events, hence to decode bits at the right time. In other words this is a clock synchronization. The data themselves can be a series of 56 bit when only the address is required, or 112 bits when the "interrogation" carries an ADS-B message too (with this message, we are entering a data link mode, this is where the ATC future lives).


Does the direction of rotation of the propeller affect the direction of the thrust generated?

It depends.

For that simple kind of a fan with flat blades, yes. For anything that was ever installed on a full scale airplane, it will generate no or very, very little thrust, more likely backward.

The blades of a propeller are airfoils—like wings—mounted with suitable angle of incidence and usually slightly cambered. Any efficient airfoil is necessarily designed for one direction. If you move them backward—by turning the propeller the other way than it's designed for—they will generate very little lift. And the remaining bit may be cancelled by the camber, because the incidence will be for generating thrust backward, but the camber will still favor forward thrust.
For much more details, see
Is there an aerofoil that gives reasonably good lift for both air flow directions: forward and backward?

Only flat plates do generate lift both ways, so a simple fan with flat blades would indeed generate backward thrust. But it's not efficient in either direction in the first place, so it may be appropriate as a ceiling fan, but definitely not as aircraft propeller.


Is pressure lower than ambient on the pressure (bottom) side of an airfoil?

If the airfoil generates lift, pressure on the upper side has to be lower than on the bottom. Still, there can be suction (less pressure than ambient) on both sides.

For an extreme example, take the airfoil from US patent application 2004/0094659 A1 by Dan Somers. It tries to stabilize the boundary layer over the first 80% by creating an increasing suction over chord. The picture below is shamelessly copied from this application.

Ambient pressure is at a pressure coefficient c$_p$ of zero, and negative values denote suction, i.e. lower than ambient pressure.

All lift is generated by the highly cambered flap while the forward wing will only start to contribute lift once the angle of attack is increased from the current value of -2°. Note that airfoils for high subsonic speed show the same philosophy of a rooftop pressure distribution over their forward part with high rear loading. Such airfoils exhibit a high pitching moment and require a larger tail surface for stability, which blunts their advantage of low drag a bit. The plot below is taken from US patent 3,952,971 by Richard Whitcomb and shows just such a transsonic airfoil with a weak shock on its upper side.

This plot shows the speed difference ∆v compared to ambient, and again higher speeds which equal more suction are positive.

All those airfoils will develop a suction peak at the forward end of the upper surface and a corresponding pressure increase on the lower side once the angle of attack is increased. Now a Birnbaum-type pressure distribution will be added and at high angle of attack, this effect will dominate the pressure distribution and will ensure higher than ambient pressure on the lower side. This effect will be the more pronounced the thinner the airfoil is - a thick airfoil exhibits a stronger displacement effect which adds a little suction on both sides.

  hitting air molecules with the wings will cause them to accelerate

Not exactly hitting - it is air molecules flowing around the wing which will contribute a speed increase and hence a lower local pressure. This can best be seen by the pressure distribution around symmetrical airfoils at zero angle of attack. Note in the plot below that suction is on both sides and growing with airfoil thickness. Of course at that angle of attack those airfoils do not generate lift, but when an angle of attack is added, they will, and it will need a higher angle to push the bottom side of the thicker airfoil into the pressure region of negative c$_p$ values.

Inviscid pressure distribution of symmetrical NACA airfoils (picture source).

  Ambient pressure is higher than any wing pressure

Not quite: Note that all plots show a pressure peak at the nose and a pressure recovery to slight overpressure at the trailing edge. While most of the pressure around a thick airfoil at low angle of attack is indeed lower than ambient, the stagnation point will always ensure that this is not true for all of the airfoil.


What is a good spin aircraft for someone that is heavy?

A Cherokee 140 should do it. Fill to just below the tabs and get an instructor that weigs 180 lbs.


Where is the landing distance for seaplanes specified?

is there a specified distance for the landing areas of seaplanes?

A cautionary note: As @MikeSowsun said, the required distance to land a seaplane is MUCH shorter than that required to takeoff. For operational planning purposes, what you should be interested in is takeoff distances. My offhand guess is that landing distances are less than half that of takeoff runs. At least that was I think true of the old J3 floatplane I used to fly.

Now I assume you're including floatplanes as seaplanes. There are relatively few hulled seaplanes these days as compared to floatplanes, and compared to the numbers of the wheeled configuration of a given aircraft for which floats are available, the number of floatplanes is relatively small, which may account in part for the POH (pilots' operating handbook) for aircraft usually not providing performance data for float configurations. There are also differences in performance depending on the make and model of the floats being used.

All that said, you can often find performance details for current production floats on a given aircraft on the float manufacturer's website. For example, http://www.wipaire.com/aircraft_page/cessna-caravan-series/ gives that information for the Cessna 208 on Wipaire amphibious floats. In this instance, the takeoff run on water with the Caravan's small engine is 2341 feet, takeoff over a 50 foot obstacle 3660 feet. The same manufacturer's figures for a Cessna 206 on their amphibious floats is 1770 feet takeoff run, 2850 feet over a 50 foot obstacle.

  just making the landing area by guessing?

Not by guessing, but looking at the intended area of operation in the light of past experience and judging whether they can takeoff from that area.


Is it safe to use a propeller plane to fly commercially over the Tibetan Plateau?

The video starts with Mt Everest straight ahead while in a left turn. And based on the video description, the flight took off from Kathmandu. The Nepalese AIP depicts this Mountain Flight Route, shown in red below, and the turn we see is the video would be the turn going back to Kathmandu.

— https://e-aip.caanepal.gov.np

Note that the Tibetan Plateau is north of the Himalayan range. If something goes wrong, a safe altitude less than the Jetstream's 15,000 feet limitation is within reach to the south or on the way back to Kathmandu:

— skyvector.com


The FARs "require" the wearing of parachutes for certain types of maneuvers. Is parachute training required?

No, no training required. But I tried to train my aerobatic students.

I was trained. Working as a CFI I told my students how to adjust the straps, where the D ring was and how to pull it after exiting the aircraft.  I suggested how to end the ride down with minimal damage to themselves.

As far as when to pull the pins on the door and depart is concerned.  If they hadn't heard me say "Jump" the noise of the air rushing in through the hole caused by my missing door and the lack of my butt in the seat - was a reminder that is was time to leave.


What does "wraparound" mean in the context of flight controls?

Wraparound is a method used to ensure flight control computer (FLCC) commands are reaching the actuators as they were inteded.

To maintain a desired flight condition FLCC calculates necessary control surface movements. These calculations are translated into control signals that are sent to actuators. These signals are periodically monitored by wraparound loop to verify they match the command originally calculated by FLCC.

This is the quickest (and the only viable) way to verify system integrity, since there is no need to wait for aircraft sensors to verify the plane did what FLCC wanted. Should the wraparound signal not match what FLCC commanded, the control reverts to a backup system.

Without wraparound, faulty signals would lead to incorrect control surface movements, that would in turn lead to corrective action by FLCC, and should the fault in the signal delivery persist, the corrective action would of course be also wrong.
Pilot action to supress these incorrect control outputs would be difficult at best, impossible at worst, since commands given by pilot are delivered through the faulty system. In the case of modern, unstable fighter jets, the worst possible outcome is the most likely one.

A diagram of wraparound arrangement can be seen here: NASA technical paper 2857, page 91

Wraparound is pretty well described in this patent application: Failsafe digital bus to analog protocol converter system

  A failsafe avionics interface unit (10) serves as a protocol converter system for translating data for control purposes from a digital communication bus (65) to an analog control channel as an upgrade or interface to an existing analog control system. The avionics interface unit (10) includes digital interface bus logic (101), a digital data processor module (102), an analog interface, and a mode selection circuit (104). Data communicated over the digital interface bus (65) is periodically translated into equivalent analog control signals. For safety purposes, the avionics interface unit (10) ensures the integrity of the system by repetitively looping back or wrapping the digital equivalents of the analog output signals and comparing them to commanded digital control values. The protocol converter system additionally monitors communications over the digital data bus for data continuity. If the difference between a wrapped digital equivalent of an analog output signal and an expected value exceeds tolerable limits or if communication fails, the system disconnects its interface from control using redundant software and hardware and returns control to the analog control system (51).


What is the aerodynamic advantage to a cuffed wing like the Cirrus SR-22?

Here we go:
http://whycirrus.com/engineering/stall-spin.aspx

  Spin Prevention
  Cirrus chose, in the very earliest stages of designing
  the SR20 to take on the challenge: to minimize the risks associated
  with inadvertently stalling an airplane. The approach chosen was to
  employ wing technology developed by NASA reducing the potential for
  spin entry after an inadvertent stall. The most visible aspect is the
  discontinuous leading edge dividing the wing into distinct parts.
  ...
  How does this wing design work?
  The outboard section of the Cirrus wing flies with a lower angle of
  attack than the inboard section. When the inboard section, which
  produces much of the lift, stalls the outboard section, where the
  ailerons are, is still flying. The result is that a stalled Cirrus
  airplane can be controlled intuitively using aileron.


Inviscid aerodynamics: why is circulation zero at the wingtip?

Prandtl's lifting line assumes that the form of the solution for its equation is similar to an elliptical solution with small variations.

$$
\Gamma(\Theta)=4sV_{\infty}
\sum_{n=1}^{\infty}A_nsin(n\Theta)
$$

Which, essentially, assumes that the circulation at the tips is 0, so the tip is not producing lift at all in any assumemd solution. The theory assumes that the tip pressure difference is 0 and actually no speed normal to the surface.

This theory explains that the drag due to lift is NOT a drag produced at the tip, is drag of the complete wing as a single element and the tip vortex is not produced at the vortex, is produce down the wing due to the circulation variation along the wing.

Which drives the typical picture (via helicel)


Does it make sense to say an aircraft has an attitude of 3° or that it has a flight position of 3°?

Actually most of the time when referring to "attitude" we are talking only about pitch attitude.  You can call bank angle "roll attitude" but it's more typically called "bank angle" in common usage.   If I have an airplane in a turn and I'm descending, you can just say my attitude is too low and I need to raise it, and I won't be confused as to whether you're referring to pitch or roll and will know I need to increase pitch attitude.

So 3 degrees of flight attitude would clearly, to me at least, refer to flight with the airplane's pitch attitude 3 degrees above the horizon while in level flight (or turning for that matter), not climbing or descending, which sounds like a pretty typical number.


What is the name and purpose of this part on the flap at the DA40?

It is an actuator fairing. It covers the flap actuator so to minimize the drag created by it.

An actuator directly exposed to the airflow would create more drag, increasing fuel consumption and reducing the flight range.


What did Fiji have to do when it incorporated GPS into its aviation system?

This early ICAO document covering the introduction of GNSS (GPS) should cover the whole topic quite well. I would skip to section 3 (page 75) Information on Fiji’s Early Application of GPS Technology. But the highlights are effectively:

  Fiji consists of 300 islands (mostly volcanic) scattered over 200 000
  square miles of ocean. Of these, only 100 are inhabited. There are
  nineteen airfields, plus seven that are privately owned, but only five
  of the nineteen have NDBs and one has VOR-DME. This means that 80 per
  cent of the area is without any form of navigation aid. There are also
  helicopter and seaplane operations. Navigation has been accomplished
  primarily through visual flight rules or dead reckoning.

  ...

  Fiji became involved in FANS and GPS in 1990/91 through briefings given by CAA Australia, and became
  convinced of the safety and cost benefits to be gained. Ad hoc trials, including long distance oceanic flights with a
  hand-held GPS receiver convinced Fiji of the potential of the GPS.

  ...

  Under a Memorandum of Co-operation (MOC) the United States FAA provided equipment and operational and
  technical support to carry out trials and demonstrations. GPS receivers were provided for installation in all domestic
  IFR aircraft. These early receivers were not certified, and special procedures were developed to ensure that all the
  information provided by the GPS was confirmed by other navigation sources.

  ...

  Some of the main features are listed here.

  • GPS routes had been designed to all nineteen aerodromes. The GPS route charts show GPS airways and GPS
  way-points at the intersections.

  • GPS checkpoints were established and surveyed on all the aerodromes, initially using a GPS receiver but
  now these have been resurveyed by an outside contractor to WGS-84.

  • Outside areas of VOR/DME coverage, the pilot DR is now replaced by GPS procedures.

  • Cloud break procedures were also designed to enable pilots to descend below cloud and make visual contact
  with the island, so that in most cases they leave a pilot at 1 000 ft above obstructions, five miles out, on the
  extended centre line. This information together with way-points were entered into the GPS receivers via data
  cards, by the CAA Fiji.

  • Pilots and controllers were trained and examined on the rules and procedures. Pilots also had to undergo a
  practical test before being approved and pilots may not use the GPS unless they are approved.

  • Based on this initial experience, the charts have been further simplified so that pilots can now select, on the
  GPS receiver, straight-in approach or cloud break, when this was needed.

This early 90's advertisement for Trimble GPS units also makes claims to being the ones that were used on these first approaches.

According to the document Fiji basically moved everything over to GPS; en-route navigation, approaches, the whole shebang. This helped them fly safer in IFR and have way more coverage than their limited ground based beacons gave them. The US helped not only create procedures, plates and information but also equipped all Fiji based operators and airfields.


Why is the reheat exhaust flame of some fighter aircraft blue while for some it is orange?

I agree with Simon's comments. Lighting and ambient lights make all the difference.

The flame is always equally bright, so if the ambient light is lower, the difference between the flame and the rest of the image is larger. When the difference exceeds the dynamic range of the film or sensor, the image of the flame becomes saturated in all channels and ends up as white. Note, that all the images with white flame are night ones.

Also the blue sensor is slightly sensitive to near infrared (being about half wavelength of the blue light), so when high sensitivity/long time are used, this causes the blue glow around the white flames on night images, while on day images with lower sensitivity it is not noticeable.


Which gas is used to fill the evacuation slides of modern aircraft?

They are filled with carbon dioxide, oxygen and nitrogen. See here for reference.

From the linked article:

  Slides inflate with an initial boost from a canister of compressed
  carbon dioxide and nitrogen. The canister provides only about
  one-third the volume needed to inflate the slides. The remaining
  volume is supplied by ambient air, channeled into the slides through
  aspirators.

  When the inflation mechanism is triggered—by a lanyard pulled by the
  slide as it tumbles from its storage case—gas from the canister
  accelerates through the aspirators at high speed, creating a vacuum
  that sucks ambient air into the aspirators through louvers. When the
  slide is fully inflated, the louvers close.


How is the flight of a tricopter controlled?

There are few examples of three-rotor helicopters. On of them is the Cierva W.1 Air Horse. According to Wikipedia, torque balance, and hence, yaw control
'was provided by slightly inclining each rotor axis to generate horizontal thrust components to provide anti-torque moments. The three rotor configuration was foreseen by Belgian helicopter experimenter Nicolas Florine in his patent of 1926 which presented the aforementioned means for balancing the reaction on the fuselage of two or more torque driven lifting rotors turning in the same direction.'

https://en.wikipedia.org/wiki/Cierva_Air_Horse

Pitch and roll control was obtained by regulating the lift of the rotors.

https://www.flightglobal.com/pdfarchive/view/1948/1948%20-%202048.html


How are coefficients of equation of sideslip angle in the paper "A general Solution to the Aircraft Trim Problem" calculated?

First, some note on this paper: from my cursory reading, it always assumes zero atmsohperic wind relative to the ground. That's why the wind axis represents the true motion of the aircraft. In general, this is not true, therefore $\psi_W$ and $\theta_W$ are not the track and flight path angles.

Now onto your question. When you consider zero wind, then the angular difference between the y wind axis ($\hat{j}_{W}$) and the y body axis ($\hat{j}_{B}$) is the sideslip angle, $\beta$. This is consistent when you consider flow incidences as 3-2-1 Euler rotation from the body axis, where yaw (sideslip) is the last rotation:

$$C_{BW} = \begin{bmatrix}\cos\alpha\cos\beta & -\cos\alpha\sin\beta & -\sin\alpha \\
\sin\beta & \cos\beta & 0 \\
\sin\alpha\cos\beta & -\sin\alpha\sin\beta & \cos\alpha
\end{bmatrix}$$

Mathematically, this can be immediately seen when you rewrite the rotation matrix in its equivalent direction cosine form:

$$C_{BW} = \begin{bmatrix}\hat{i}_W \cdot \hat{i}_B & \hat{j}_W \cdot \hat{i}_B & \hat{k}_W \cdot \hat{i}_B \\
\hat{i}_W \cdot \hat{j}_B & \hat{j}_W \cdot \hat{j}_B & \hat{k}_W \cdot \hat{j}_B \\
\hat{i}_W \cdot \hat{k}_B & \hat{j}_W \cdot \hat{k}_B & \hat{k}_W \cdot \hat{k}_B\end{bmatrix}$$

So: $\cos{\beta}=\hat{j}_W \cdot \hat{j}_B$.

The gradient of the Cartesian equation of a plane is its unit normal, when normalized. For the $x_W z_W$ and $x_B z_B$ planes, the normal is simply their y axis (i.e. $\hat{j}_W$ and $\hat{j}_B$, respectively.

Lastly, eqn (72) can be worked out when $\begin{bmatrix}x & y & z\end{bmatrix}^T$ in the planar equations are in the inertial frame ($_V$), and transformed to the respective frames. The coefficients can then be derived and massaged to obtain (72).


Is any endorsement required to take the Advanced Ground Instructor test?

No endorsement is needed. The AGI and IGI written tests can be done without anyone's endorsement.

Additions:

You also don't need an endorsement to take the CFI, CFII, or FOI written tests, btw.
Your reference to 61.193 has nothing to do with this. For one, it's 61.193, not 61.139 (but your link itself is correct), and second, these are not endorsements for written tests. In 61.193 it says "to train and issue endorsements that are required for: ..." and that does not include any endorsements for the AGI, IGI, FIA, FII, and FOI written tests. Such endorsements, as they pertain to a ground instructor, would, for example, be a 61.217(d) endorsement (not written test).
"... flight instructor privileges include providing an endorsement to take the test." No, they do not. They include providing an endorsement for a ground instructor certificate/licence (not written test), and endorsements for written tests (in general -- not for the ground instructor).

When an endorsement for the written test is needed, then that prerequisites say that explicitly, such as for the PPL, IR, CPL, ATPL, etc., such as in 61.65.(a)(4), for example.


How to fly LOC approach when IAF is a specific DME from LOC, but LOC has no DME?

You have a few different points here but the short version is: IWA is a VORTAC and I-IWA is a localizer, i.e. they're different navaids. DME is available from IWA and it's optional but not required for the I-IWA localizer approach. If you do have it, you can use it to identify the ORIYE fix and use the lower minimums at the bottom of the plate, e.g. 1800-1 for category A. If you can't identify ORIYE, you can only go to the regular minimums of 1940-1.

First, I suspect you're confusing I-IWA (a localizer) with IWA (a VORTAC) but they're different navaids that use different frequencies, as shown on the chart. The I-IWA localizer provides lateral and vertical (glideslope) guidance but not DME, which you get from the IWA VORTAC. If you don't have a DME receiver, you could use an IFR-certified GPS instead.

Second, if I understood your question correctly about approaching from the northwest, you're asking how to identify SNOWL without using DME. SNOWL is an intersection ("SNOWL INT") and you can identify it using VOR only, by finding the intersection of any two of these radials:

IWA radial 122
PXR radial 109
TFD radial 028

Third, as far as I can see from the plate, DME is the only way to identify ORIYE (remember that you could use GPS instead of an actual DME unit). When you look at the minimums at the bottom of the plate you can see that the regular category A localizer minimums are 1940-1 but there's an extra set of minimums that you can use if you can identify ORIYE and they let you get lower, to 1800-1. In other words, if you have DME then you can use it to identify ORIYE; if you don't, you ignore ORIYE. Either way, you still have to use the correct set of minimums.

Finally, SNOWL is 6.4 DME from the IWA VORTAC, but only 5.8 DME from the "airport profile" (see the chart legend), i.e. the runway. That means, the runway end is 0.6 DME from IWA (that distance is also shown on the profile).


How did pilots avoid thunderstorms and related weather before “reliable” airborne weather radar was introduced on airliners?

They looked out the window!

If you are talking about a developing thunderstorm, especially during the day, they can be quite easy to see in front of you provided decent visibility. Here is some good footage of what it looks like to fly around a towering cell, you will note its fairly easy to see. At night, lightning, even in the clouds tends to be a prominent effect and is a good indicator of "dont fly there". Here is a good picture of that effect (as well as a little story about flying around it).

Of course, summer haze, the dark of a moonless night, shifty weather, or just plain old mistakes sometimes lands planes right where they should not be sometimes with disastrous results.

Here is an interesting report on thunderstorms and aircrafts from 1948 that may have some interesting info for you.


Why are manufacturers assumed to be responsible in case of a crash?

I'll assume you're talking about an English common law jurisdiction (UK, US, Can, Aus, NZ etc.).  In those places it's always "innocent until proven guilty", the key thing being what "proven" means.
You have to separate criminal liability, breaking of a law in the criminal code, from civil liability (a civil wrong, or "tort" in English common law).  The criminal liability standard of evidence is "guilty beyond a reasonable doubt" at trial, and tort liability standard is "guilty based on preponderance of evidence" at trial (that is, more likely than not in the assessment of a trial jury (in the US) or a judge).
So a manufacturer or an airline is only exposed to criminal liability where an incident involved the violation of a criminal statute. You can't throw the "company" in jail, so an individual has to be on the hook and so the authorities would have to identify a criminal code violation committed by an officer or employee of the company, and it would be that employee or officer that would be going to jail (for something like violation of a criminal negligence statute).  And in that case the standard is guilty beyond a reasonable doubt.
In the case of civil liability, the corporation itself, or potentially its officers personally, are on the hook, the penalties being solely financial (employees are normally shielded from civil liability in a limited liability corporation) and the "preponderance of evidence" standard of guilt applies.
The thing is, both of these conditions require a court trial.  Either government prosecutors go after individuals (officers of the company or employees) for criminal violations that include fines and/or jail time for those convicted of criminal acts, or non-government individuals that have been harmed (families of passengers killed for example) go after the corporation in civil court, and the corporation is only guilty of a tort (civil wrong) if a judge or jury finds them guilty.
So in both situations it's "innocent until proven guilty"; the difference is in who the accuser is and what the standard of evidence is.
Now, outside of the Anglosphere, all bets are off, and you may very well find places where guilt is assumed and company has to prove its innocence to get off the hook for either criminal or civil liability.


What's the difference between racetrack and holding pattern?
  Are they only synonymous?

When used in the context of holding, racetrack pattern and holding pattern refer most of the time to the same pattern, because a holding pattern is a usually designed as a racetrack. Holding terminology:

Holding (or flying a hold) is a maneuver designed to delay an aircraft already in flight.
A holding pattern is the pattern used to hold, regardless of the design of the pattern.
A racetrack holding pattern is a specific design of holding pattern. From Wikipedia:

  A holding pattern for instrument flight rules (IFR) aircraft is
  usually a racetrack pattern based on a holding fix.

Holding patterns are defined relative to a holding fix and are usually timed because aircraft have to remain within a given protected space around the fix.

However a holding procedure which uses a racetrack pattern and a racetrack procedure which uses a racetrack pattern are two different things aimed at two different purposes.

Racetrack procedure

ICAO makes a specific use of the phrase "racetrack procedure" in Doc 8168 (PANS-OPS):

  Racetrack procedure: A procedure designed to enable the aircraft to
  reduce altitude during the initial approach segment and/or establish
  the aircraft inbound when the entry into a reversal procedure is not
  practical.

and

  A racetrack procedure consists of: a) a turn from the inbound track
  through 180° from overhead the facility or fix on to the outbound
  track, for 1, 2 or 3 minutes; followed by b) a 180° turn in the same
  direction to return to the inbound track.

For ICAO, a racetrack procedure is a turn procedure, or course reversal procedure, in the instrument approach procedure, comparable to other procedural turns, and has nothing to do with delaying the aircraft. The procedure turns come in different flavors:

Source.

Holding procedure

Holding procedure definition from ICAO Doc 8168 (PANS-OPS):

  A predetermined maneuver which keeps an aircraft within a specified
  airspace while awaiting further clearance.

It can be used to delay the aircraft, but also to change its altitude using a holding pattern and stack. Note there is no reference to a specific pattern.

Source.

However, when holding, the pattern followed is often a racetrack pattern (more details about this in: How is a standard holding pattern flown?)

Depiction on instrument plates

Holding patterns are depicted using regular lines, they are optional
Procedure turns patterns are depicted using bold lines, meaning they are mandatory. Exceptions are noted "NoPT" with indication of the arriving course.

Adapted from AirNav.com.


What are the numbers in boxes on an A320 ND when terrain is shown?

14600 ft and 7300 ft.

A320 FCOM DSC-31-45 :

  Minimum and maximum elevations encountered ahead of the aircraft, within the selected ND range.


Calculating distance from VOR station with radial and heading

Bad news: the question is unanswerable.
Good news: you're right to be confused!

With a groundspeed of 120 knots and a constant ground track, after 10 minutes the airplane will have moved 20 miles in a straight line. There's no getting around this fact.

If the airplane doesn't parallel a radial, and yet it moves, the radial it's on must change.

If it's still indicating the same radial after non-parallel movement, the only option is that the indicator is in error.  But the question removes that possibility.

The only way I can think to make this situation possible is that maybe you've tuned the world's most bizarre VOT. But even still there's no possibility for a valid answer for the question.

The original question:

At time t(1) an airborne VOR receiver shows that the aircraft is on the 30deg radial from a VOR station. The pilot maintains a ground track heading of 120deg with respect to magnetic North and 120 knots ground speed. At time t(2) , 10 minutes later than t(1) , the VOR receiver indicates that the aircraft is on the 30deg radial from the same station. Assuming no errors, what is the pilot’s distance from the VOR station at time t(2) ? If the pilot had access to airspeed, can the range be determined from the VOR measurements? Can it be determined if the pilot had access to ground speed and ground track heading?


Helicopter mast bumping in low g condition

The answer is yes it could be used in that flight profile as the pilot of that AS300 was never in a low G condition with the rotor unloaded during those maneuvers.  Once he dropped the concrete, though he’s descending, he’s also accelerating at a high power setting, which is keeping the rotor loaded.  However, zero G mast bumping is still a risk that must be considered and thoroughly mitigated for during preflight for all helos with a semi rigid rotor system.
Mass bumping only occurs on helicopters with a semi rigid or teetering rotor system. It has to do with how a semi rigid rotor is supported by the mast in an under slung condition, where excess flapping can result in mast bumping.  It will generally occur in conditions like zero-G pushovers at low power settings or when attempting a steep slope landing.  Mast bumping is not possible on rigid, fully articulated, or elastomeric rotor systems where the rotor mounts cannot strike the mast, even with excess flapping.
Here is a pretty good recap on the subject of mast bumping.

Even helos with two bladed semi-rigid rotor systems can be flown through some pretty extreme maneuvers, provided the pilot flies within the design limits and does not unload the rotor.  I remember West Coast JetCopters, who provided the Bell 222 for the television series Airwolf, did some pretty extreme flying on those choppers and a 222 does use a teetering rotor system.  They just had really, really good pilots at the controls.  See 0:57 in the video below where the stunt pilots put a 222 through the helo equivalent of a hammerhead stall.


Is the seat-belt sign activation when a pilot goes to the lavatory standard procedure?

In the US they do very similar theater when a pilot needs to relieve himself. There is an announcement that nobody is allowed to come forward, and grim looking flight attendants are blocking the aisles with coffee trolleys. The details surely depend on the airline.

Each of these procedures goes back to some bad incident. The cockpit doors are locked since 9/11. Since Germanwings 9525 (PIC on toilet, co-pilot had a death wish, cockpit door locked), a flight attendant has to replace the pilot in the cockpit. I'm not sure if there was an incident calling for body-guarding a pilot outside of the cockpit, but maybe someone can comment.

Even though it is much more likely to get killed by your angry spouse or just falling down the stairs at home, security procedure theater is in fashion, and it is just getting worse and worse. Yes, it is very plausible that the seat-belt sign activation in your flight was standard procedure to ensure that the PIC could pee in peace.

This photo of Thomas Cook Airlines (UK) is courtesy of TripAdvisor

Some similar reports found in the depth of the internet:

boards.ie in August 2013:

  Noticed this last night on a Ryanair flight.

  Internal phone call to stewardess was then followed by the fasten seat
  belt sign going on. We were forced to sit down with a by then crying
  baby (who had been just about dozing off being rocked whilst standing
  up) Once we were all sat down cockpit door opens, one of the pilots
  exits and was replaced by an air hostess in the cockpit. He visits the
  loo, comes back out, rings in, door opens, swaps with the air hostess
  and then the lights go back off. Not a hint of turbulence during the
  time period involved. [...]

flyertalk.com in August 2008:

  In the middle of a flight today from LAX-ORD, the seat belt sign was
  turned on and the pilot or co-pilot came out of the cockpit to use the
  bathroom. As soon as the pilot went back into the cockpit, the seat
  belt sign was turned off. It was perfectly smooth throughout this
  portion of the flight, so it was obvious that the seat belt sign was
  turned on just for the pilot to use the facilities. [...]


What is the format specification for Avidyne R9 flight data?

According to section 12-4 of the Release 9 Pilot's Guide, data logs are saved as a simple .csv file that can imported into any spreadsheet software (like Microsoft Excel) for analysis.

There are many free tools that can covert Excel files to KML for Google Earth, ie: http://www.earthpoint.us/exceltokml.aspx


Can a Kline-Fogleman airfoil be used for engine turbines?

KF airfoils result from folding paper airplanes. In a way, most paper airplanes employ an airfoil with a stepped contour. At the scale of paper airplanes, this step possibly forces a laminar-turbulent boundary transition which might allow the airfoil to stall at a higher angle of attack.

A regular NACA 23015 has an optimum L/D of close to 50 at a Reynolds number of 200,000 and 9° angle of attack. Airfoiltools gives it as 48.5.

If you doubt the XFOIL data from Airfoiltools, NACA TR 824 gives essentially the same values using wind tunnel data, however, you need to pick Airfoiltool data at a higher Reynolds number to compare the two.

Since the L/D of the conventional airfoil is two an a half times better than what you calculated with ANSYS, I recommend that you review your results. And no, I would not recommend their use in turbines. The exposed corner at the step will face extreme heat loads and film cooling will probably fail there.


How does air traffic control communicate with an aircraft?

1) Why doesn't the tower use satellite throughout the flight?

The narrow answer is that the control tower is responsible for a small geographic area.  The "tower" doesn't want to talk to the craft at other points in the flight, so the need is not there.  It only wants to talk to the plane when it is close to the tower's airspace.

Other components of air traffic control that do need to talk with airplanes in flight also divide up regions of the airspace and have radio equipment situated to talk to the necessary craft.

A larger answer is that ground control and aircraft communications were under major development for decades before satellite communications were available.  The system we use today is heavily based on line-of-sight VHF communication radio over most populated areas.  Since these systems are already installed in many thousands of aircraft, changing to something different like satellite communication requires a significant benefit, someone to pay for it, and a lot of time to allow for the change.

  2) Does a control tower only send voice services through the direct
  link? or does it send data as well?

Data is beginning to be sent via CPDLC.  You can search for CPDLC on this site and find several questions and answers about it, but it is considered only a supplement to the voice communication of ATC today.

  Aren't there security issues or power safety issues involved in ground
  to air transmissions?

Unauthorized transmissions are possible, but they are managed and haven't traditionally been a big problem.  There's another question about What prevents someone from hijacking a radio frequency mid-air?.  But much of the answer is that since ATC is monitoring the frequency, unauthorized transmissions would be heard and responded to.  I'm sure that future digital delivery will change some of these issues, but that's likely to be true whether the message is transmitted via local radio transmitters or satellite.

Not sure if that's what you meant by security issues.  I'm not familiar with power safety issues.


How much does an airliner cabin elongate at altitude?

We can identify three effects that have an effect on cabin length:

Stretching due to the bulkhead pulling on the end of the fuselage;
Shortening due to the fuselage expanding in diameter (Poisson effect)
Shrinkage due to temperature

These are simple solid mechanics problems. Given an airplane with length $l$, diameter $d$, wall thickness $t$ made with a material with Young's modulus $E$ and Poisson ratio $\nu$ and linear expansion coefficient $\alpha$ pressurised to a pressure differential $p$, cooled to a temperature differential $\Delta T$....
$$\Delta L = \dfrac{d p L}{ 4 t E} - \dfrac{\nu d p L}{2 t E} - \alpha \Delta T l$$
$$\Delta L = \dfrac{d p L(1-2\nu)}{ 4 t E} - \alpha \Delta T l$$
Let's have a wall thickness of 3mm, diameter of 4m, length of 40m subjected to 0.5bar and 70°C temperature difference. Aluminium $E=$70GPa, $\nu=0.33$, $\alpha=25\mu m/m°C$. Filling in the numbers, we obtain $$\Delta L=3.2mm-70mm\approx-67mm$$
So thermal expansion definitely has the upper hand here, shrinking the fuselage by a few centimetres in total, whereas pressurising the fuselage can only expand it by a few millimetres. The numbers here are very much approximate but the order of magnitude will not change much with "real" numbers.


Are turns, while under the control of a two-axis autopilot, uncoordinated?

Absent other control factors, potentially. It is up to the pilot to maintain coordination with the rudder. However, autopilot turns typically happen at cruise speeds and at gentle bank angles, so the ball won’t get terribly far outside its cage. Even for airplanes with aileron-rudder linkage designed to automatically compensate for adverse yaw, Jan Hudec enumerates other contributors such as P-factor that add slip or skid in a turn.

That’s just for a single-axis autopilot. Your question asks about dual-axis autopilots that have another dimension in which to go “uncoordinated,” viz. pitching up too steeply for the current power setting and causing an aerodynamic stall or pitching down so as to exceed $V_{NO}$, $V_{NE}$, $V_{FE}$, etc.

Being outside sweet spot of the flight envelope is a significant factor behind why many POHs and checklists call for the autopilot to be disengaged below certain altitudes and in critical phases of flight. Cockpit automation when properly understood, used, and monitored is great for reducing pilot workload, but no mechanism should be treated as fool-proof.


Fuel jettison in Top Gun, is there any reason to do this other than show-boating?

Doesn't look like it was any 'tactical' reason- rather it was used to get a cool shot, which is totally OK with me. From rulit.me:

  While setting up for a filming pass, the camera crew had difficulty spotting the gray F-14 against the mountainous background. Over the radio, Rat asked the pilot to blip the fuel dump switch and make a mini-cloud. The resulting effect of the atomized fuel swirling in the Tomcat’s vortices looked so good that this technique was used several times in the finished film.

I think they're talking about this scene:

Image from youtube screenshot

Looks like they used this technique to frame the aircraft against featureless mountains, sky etc.

Note: The site seems to have taken the quote from Topgun Days: Dogfighting, Cheating Death, and Hollywood Glory as One of America's Best Fighter Jocks by Dave Baranek.


What separation and information does ATC provide in different airspace classes?

Different countries have different meanings to the classification of Airspace. I am only looking at the controlled airspace for ICAO.
Controlled airspace is an airspace that an aircraft would need a clearance to enter, this doesn't mean all aircraft need a clearance to enter just some aircraft.
Classes of Airspace
Class A is for IFR flights only, all aircraft are separated from all aircraft and are known to Air Traffic Control (ATC).
Class B is like Class A but with VFR. IFR and VFR are cleared to enter, all aircraft are separated from all aircraft and are known to ATC.
Class C is where the major confusion on separation usually begins. IFR and VFR are cleared to enter, all flights are provided an ATC service. IFR flights are separated from IFR and VFR flights, but VFR flights are only separated from IFR flights. VFR aircraft are only passed traffic on other VFR aircraft. All aircraft are known to ATC. I will go into what they do when they get in conflict at the end.
Class D both IFR and VFR are cleared to enter, all aircraft are provided an ATC service. IFR aircraft are separated from IFR and passed Traffic on VFR flight. VFR flights are only passed traffic on other aircraft. All aircraft are known to ATC.
Class E IFR are cleared to enter and VFR are permitted to enter, only IFR aircraft are provided with an ATC service. IFR aircraft are separated from IFR aircraft and passed traffic on known VFR aircraft. VFR aircraft do not need a clearance and are not usually known to the Air Traffic Controller.
Class F No one is given a clearance. IFR aircraft are given traffic on IFR Aircraft and known VFR. But all pilots are responsible for their own separation.
Class G No one is given a clearance. Traffic is only passed where it is requested, and only on known traffic. Only those requesting traffic or are seen on a radar are known to ATC.
Answers to Specific Questions

I fly a rotor-wing at a class D airport. Under VFR, we should only receive "traffic information", correct?

Yes, that is correct.

But in reality, we still have to request ATC's permission to take off etc. and they can instruct us to hold, give way and so on. Doesn't that mean that we are in fact being "separated" from other traffic?

When talking about Class D airspace: you are only separated from other aircraft when on the runway; when you are in the air you are not being separated. You instead will be passed Traffic Information on other flights. You however are still subject to the conditions of your clearance (Route, Level, Holding Instructions, etc.).

And theoretically, if IFR traffic is controlled by ATC in class D but VFR is not, and IFR is not separated from VFR, how should conflicting traffic avoid each other? If an IFR flight sees a VFR one in its way, who should do what? (Practically, the pilots will obviously maneuver to avoid each other, but what does the theory say?)
Finally, since IFR flights only get "traffic information" about VFR flights but not "separation", what happens if a VFR flight gets in front of an IFR one on final approach to land? Won't ATC tell the IFR flight to go around, or will they do nothing because they don't provide "separation"?

If one or both aircraft are under a clearance the cleared aircraft will request an amended clearance to avoid the traffic:
ABC request 10NM right of track due traffic

or
ABC request descent 4500 due traffic

If there is not enough time for the amended clearance the Pilot in Command (PIC) can just break their clearance to avoid the traffic; either passing the aircraft on the right or changing levels. The PIC in some countries will be considered to have broken their clearance but it is usually only a slap on the wrist for letting it get that bad that you couldn't request the clearance change.
Reality can sometimes be a very different scenario. Some controller unofficially will separate VFR from IFR, but no one knows. Don't trust that this will happen.
Also controllers may give suggested amended clearances like:
ABC traffic XFV PC12 crossing track left to right at time 23,
6500 is available advise.

or
ABC traffic unknown VFR 25NM oposite direction 500 ft below unverified,
higher available advise

If the aircraft is not subject to a clearance then they can just move to avoid the traffic under the Rules of the Air.
In uncontrolled airspace it really is see and avoid. Because the Air traffic Controller may not have all the aircraft that are traffic for you. This also includes Class E airspace where the controller doesn't know about all the VFR aircraft.
Duty of care means that the controller may intervene if they think the pilots aren't separating themselves.
I work with Class D and C Towers with lots of VFR traffic. Because the traffic are aware of each other they usually request amended clearances well before the traffic is a problem.


How can I avoid floating during short-field landings?

I did all my training in PA-28's (Warrior and Archer II mainly) and here is my advice)

First off, practice makes perfect in all cases here.

Second, I am not a CFI and you should ALWAYS seek the experience of a CFI to help you learn how to fly properly. Discuss everything with your CFI before trying anything.

The PA-28 is one of the most benign airframes and even in the bumpiest the bumpiest of conditions you can fly it by the numbers every time. Floating on landing is generally caused by (in my experience) 2 things.

Excessive speed on final - Remember you will only land nicely once you have gotten rid of all excess speed. This happens during your round-out and flare to landing. On a short field even a perfect landing will take up more runway if you are overspeed since you need to bleed that speed off.
Ballooning - This is generally a result of over speed and over flaring. Since the PA-28 is a low wing (compared to the high wing of the C172) an over-flare to early will cause significant ballooning as you effectively bounce off the ground effect. A proper timed round out and flare will come in time.

One thing you can do to mitigate this (and I found this helped as a student pilot for me) is to fly a longer final leg (and thus a longer downwind). When I was learning to fly a stable approach it took time for me to get the settings in and really nail the approach. A longer final will help you settle the plane into place as a student and really nail a maneuver like this. Generally tight patterns are taught but if its safer and better for you to fly a longer final and nail the maneuver, do it.

In the PA-28's you can (and should) be right on 65 kts when doing a soft field. Practice descending at a constant airspeed at altitude with your instructor. 500ft/min right on 65Kts with full flaps, then come back into the pattern and use what you learned to come in right as you should.

Cut the power a bit earlier. Generally you are most likely taught to cut the power over the numbers and touch down at the markers. In a short field situation you can cut the power a bit earlier, pitch down to keep you speed up, and touch down right on the numbers. You should have no issue getting the plane down in under 1000Ft.

Train at an actual short field (or as short as you are allowed to fly). My flight school generally had us going between 5000ft airports with 2 runways (we were based at KPNE). Crosswinds were never really an issue and runway length left plenty of margin for error. My instructor made it a point to take me to 3000 X 60 fields to really get practice in (the shortest the fligh schools insurance would cover). Depending on where you are training out of this may not be an issue.

One more general habit of new pilots is over correcting and getting your self into an increasingly corrective state. This happens both laterally and vertically but in your case the vertical over correction is going to be the killer. If you are comming in and notice that you are low you add power, pitch up a bit and now you are too high. You pull power and pitch back down but this builds up some speed. Now you find your self over correcting all over the place to get back to a stabilized aproach. This is where the long final will help. You need to really get the plane on that 65Kt mark, trim it off, leave the power alone and fly it in. If you get bumped by a gust or a thermal wait a second and see if the termal settles then and only then should you come in with a small correction.


Do any airlines have Braille emergency checklists?

It would be counter productive

It takes time to learn (especially touch reading)
It takes time to keep proficient

This is time spent on a skill useless for >99,999999% of flights

This is time NOT spent on more useful safety trainings

This wouldn't work anyway

It would be very slow to find the correct checklist then read it
If the aircraft is shaking, it would hinder your speed/prevent your from reading
You have to take your hands of from other controls to read

There is better alternatives

Simply having a recording/speech synthesis/speech command would solve it.

  This is time NOT spent on more useful safety trainings

This one is a killer


What's the difference between a balked landing and a go-around?

The only term in the Pilot Controller Glossary is Go Around, so should technically be the only term used, at least when communicating with ATC:

  GO AROUND- Instructions for a pilot to abandon his/her approach to landing. Additional instructions may follow. Unless otherwise advised
  by ATC, a VFR aircraft or an aircraft conducting visual approach
  should overfly the runway while climbing to traffic pattern altitude
  and enter the traffic pattern via the crosswind leg. A pilot on an IFR
  flight plan making an instrument approach should execute the published
  missed approach procedure or proceed as instructed by ATC; e.g., "Go
  around" (additional instructions if required).

  (See LOW APPROACH.)

  (See MISSED APPROACH.)

The ATP PTS also includes a Rejected Landing, which is what our simulator instructors refer to as a Balked Landing, and must be at or below 50 feet AGL.  It has the following note describing it in the PTS:

  NOTE: The maneuver may be combined with instrument, circling,  or missed approach procedures, but instrument conditions  need not be
  simulated below 100 feet above the runway.  This maneuver should be
  initiated approximately 50 feet  above the runway or landing area and
  approximately over  the runway threshold or as recommended by the FSB
  Report.

The pilot follows the same procedures for both of them by aborting the landing, cleaning up the airplane, and flying the appropriate procedure afterwards.