Is there much turbulence in the Doldrums?

The intertropical convergence zone (ITCZ) (aka. the doldrums) is an area around the Equator which is notorious for heavy convective activity often leading to tall cumulonimbus clouds and associated heavy turbulence.

The area around the Equator receives the largest amount of energy from the sun because of the perpendicular angle to the sun. This causes relative large heating of the surface, resulting in heating of the air above the surface and ultimatively convective activity including turbulence. This also causes a large green band around the earth near the Equator with rich vegetation, because the convective activity causes large amount of percipitation.

The ITCZ is an important part of the global weather system, which is based on large cells of air generally moving in predictable patterns. The Hadley cell is a cell extending from the Equator to approximately 30 degrees north/south. Hot air rises at the Equator because of the heating caused by the perpendicular angle to the sun. This air travels at high levels as it cools down, and creates a downward flow of air around the 30 degree latitudes. As a result, the areas around 30 degrees latitude get almost no percipitation, which causes large areas of desert such as the Sahara.

The pattern repeats itself with Ferrel cells between 30 and 60 degrees latitude and a polar cell from 60 degrees latitude to the poles.


Does holding a medical certificate mean you automatically have a student pilot certificate?

This answer reflects rulemaking effective 1 April 2016
Regarding the question in the title, no, holding a medical does not mean you have a student pilot certificate.  New regulations going into effect 1 April 2016 separate the student pilot certificate from the combination medical+student pilot certificate.  Students will need to apply for a student pilot certificate with their CFI or with the FSDO (or their part 141 flight school) through IACRA.  The new student pilot certificate is plastic just like a normal pilot certificate and do not expire.
This part is true with or without the rulemaking changes
Regarding the question in the body of your post, you are already a certificated pilot with a balloon rating.  You are not a student pilot, you are a private pilot.  The regulations you are subject to are to add an airplane category rating are in 14 CFR 61.63.

§61.63   Additional aircraft ratings (other than for ratings at the airline transport pilot certification level).
(a) General. For an additional aircraft rating on a pilot certificate, other than for an airline transport pilot certificate, a person must meet the requirements of this section appropriate to the additional aircraft rating sought.
(b) Additional aircraft category rating. A person who applies to add a category rating to a pilot certificate:
(1) Must complete the training and have the applicable aeronautical experience.
(2) Must have a logbook or training record endorsement from an authorized instructor attesting that the person was found competent in the appropriate aeronautical knowledge areas and proficient in the appropriate areas of operation.
(3) Must pass the practical test.
(4) Need not take an additional knowledge test, provided the applicant holds an airplane, rotorcraft, powered-lift, weight-shift-control aircraft, powered parachute, or airship rating at that pilot certificate level.

As a balloon pilot seeking the airplane category rating with the single-engine land class you

must meet the aeronautical experience requirements in 61.109(a)
must be endorsed and found competent in aeronautical knowledge of 61.105(b), 61.107(b)(1)
must complete a private pilot airplane written exam

and then you will be able to take the practical examination and have airplane single-engine land added to your existing private pilot certificate.


What is the problem in the satellite data of MH370

This was explained back in 2014 when the data was released. It is consistent with a loss of power due to fuel exhaustion, followed by battery power restoring communication.


Why does the B-29 have eight oil needles?

Each of the four engines is represented by two needles, one in each row. The top gauges are for the nose oil; the bottom gauges are for the rear oil.
Nose and rear here refer to two sections (remember that's a twin-row radial engine). The nose case oil is also used by the propeller's governor, feathering mechanism, and reduction gear – those would explain the lower pressure range of the nose section.
During development the nose case was troublesome:

Reduction gear failures started to occur during extended climbs, forcing the addition of external oil lines from the accessory case to the nose case to shore up low nose case oil pressure (enginehistory.org; PDF).

B-29 commander training manual

More on Google Books: United States. Army Air Forces (1950). Technical Data Digest. p. 26.


Partial panel power on stall under the hood

Same as any partial panel work.  Altimeter is primary for pitch attitude.  Airspeed is secondary for pitch attitude (its indications complement the altitude data, and in a climb/descent it becomes a primary pitch indicator) and also for power setting in concert with RPM/MP.

VSI is generally considered too laggy to use for assisting in fine pitch control when partial panel and is only useful to confirm a stabilized climb/descent, because its indication might be 2-3 seconds behind what is happening at any instant.

Then it's turn and bank or turn coordinator for roll and away you go.

If you were told to do a power on stall in level flight it's pretty straightforward, just hold the altitude by altimeter watching the speed decrease, decreasing the power to get on the back side of the power curve than increasing it along with pitch to hold the altitude until the stall occurs.

If you are told to do a power on stall with a high power setting in a climb, it's a bit trickier because you have to try to judge that your pitch attitude increase is not excessive by the rate of change in altitude and airspeed.  In that case you might use the VSI to establish the stabilized rate of climb at the start of the exercise, then add just enough increasing pitch to get a gradual speed decrease from that climb state, adding pitch to maintain that decay rate of speed until the stall.


What software generated this VFR flight plan?

This flight plan was generated with Skyvector
Click here for the specific flight plan from your example
Then click "Nav Log" for the log itself.


What is this white smoke like thing, seen inside the cabin before takeoff?

Direct answer
Air conditioning causes a large drop in cabin temperature, air humidity present in the air condensates into water droplets. It is similar to mist, fog and clouds. If water droplets enter in contact with a solid they form dew and moisture. Accurately, it is an aerosol of water droplets.
Water droplets appear in air when air temperature is lowered below its dew point (see further down). This phenomenon is exactly the same than when a freezer is opened and air over the freezer is in contact with cold air from the freezer tank:

Marcellus ̶̶̶̶̶̶̶̶ freezer. Source.
Quick explanation
In your case, before air conditioning is started the cabin is filled with air from the outside, which happens to be warm and nearly saturated in water vapor. The ambient temperature is close to the dew point. The injection of colder conditioned air in the cabin decreases the temperature around the AC vents (inlet air on the picture below):

Air circulation in large pressurized aircraft, from this answer
The temperature quickly goes below the dew point causing invisible gas (water vapor) condensation into visible liquid water droplets (fog).
Due to the limited instantaneous capacity of the air conditioning system, the temperature is decreased only around the AC vents, not in the whole cabin. When the water droplets mix with the warmer air in the rest of the cabin, they immediately return to the gaseous form (vapor), and doing this they also make this air a bit colder (evaporative cooling).
As pointed out by @JanHudec the humidity level must be kept low during the flight to prevent structure oxidation. Humid air from the cabin returns through the decompression panels to the air conditioning system where it is mixed with dryer air from the packs. After some cycles the cabin air is rather dry and condensation doesn't occur anymore.
Another case of condensation:

Detailed explanation
Why does water vapor condense?
The quantity of water vapor in air is named water saturation ratio (or relative humidity) and is expressed as a percentage: 0% for dry air, 100% for air fully saturated. Saturated air cannot contain more water vapor. If vapor is added then it immediately condenses into visible water droplets.
Saturation occurs at certain combinations of temperature and pressure. For a given pressure, the higher the temperature, the larger the quantity of vapor than can be present without condensation. So condensation can occur when the temperature decreases.
Psychrometrics, the branch of physics studying how liquids and solids boil or condense, revolves around the notion of equilibrium vapor pressure, but for us mere mortals, the notion of dew point is more practical.
Dew point
The quantity of vapor air can contain before being saturated is called its water vapor capacity, it increases exponentially with temperature:

(Source)
Let's define two cases:

Full saturation: If the quantity of vapor is the maximum allowed for the current temperature (100% relative humidity), decreasing the temperature or adding vapor will cause some vapor to condensate into water.

Partial saturation: If air is not fully saturated, there is a (lower) temperature for which it becomes saturated. This temperature is referred to as dew point. So whatever the current temperature, fog can be created by decreasing the temperature until the dew point is reached.

For sake of accuracy: When water vapor is present in air, it is continuously condensed and evaporated. The dew point is the point where condensation occurs at a greater rate than evaporation and water droplets start accumulating.
Whether fog will form depends on the the dew point spread, that is the difference between current temperature and dew point. When the spread is large, the change in humidity or in temperature must be large. In your case, the spread is small, because air is wet and temperature is high.
Bhubaneshwar case
Before air conditioning system is started, cabin air is the same than at the airport: 28°C and 85% humidity. AC is going to inject air at 20°:

Quantity of vapor for 85% RH at 28°C is 23g per kg (85% * 27).
Vapor capacity at 20°: 17g per kg.

When air is injected and temperature is decreased to 20° around the vents, air becomes fully saturated, and the 6g of vapor in excess per kg of air are condensed into fog.

Cabin air relative humidity and AC fog
This air returns to the AC system, and is mixed with air from packs which condition air entering the cabin at the 20% RH targeted for the flight. The 13.6g/kg of vapor in excess (for 20% RH) are progressively extracted by outflow valves, which regulate pressure in the cabin by releasing overboard as much air as packs push in. After some cycles, air contains only 3.4g/kg of vapor (the cycle is simplified, actually we would also account for passengers perspiration and breathing, fog re-vaporization and AC air humidity)
For typical cabin of 150m3 containing about 175 kg of air, 3.5 kg of water are extracted.
Fog in the aircraft is indeed a problem, fog outside the aircraft is another one as visibility is strongly impeded. It requires flying using Instrument Flying Rules (IFR). IFR is allowed only with a specific pilot rating and aviation certification. Knowing the dew point is important to plan a flight, in particular to know whether IFR will be required. Therefore the dew point is measured and published as aeronautical information.
Measuring the dew point
The dew point may be determined with a psychrometer (a system with dry and wet thermometers):

Whirling (how to use it) and digital psychrometers
Pressure, dry and wet temperatures, dew point and relative humidity are linked by the mean of vapor pressure. By knowing three elements, the two other can be determined. So knowing pressure, dry temperature and wet temperature allows to determine the dew point. It exists precalculated charts (Mollier diagrams) to read dew point directly. There are also online calculators.
Here is a vertical profile of the temperature and moisture information (emagram) collected by a radiosonde in Ireland:

Emagram from Valentia Observatory (Ireland). Source meteociel.fr
The vertical scale is the pressure (hPa on the left, equivalent altitude on the right) and temperature is on an oblique scale, with the quantity of water at saturation for this temperature. The dry temperature is shown in read, the wet temperature in blue, and the computed dew point in cyan. When the dew point curve is close to the temperature, moisture is hight (%RH on altitude scale) and cloud/fog can occur (like under 1,600 m for this example).
Dew point and fog/mist information
KLAX ASOS report:

As previously mentioned, when the dew point is close to the ambient temperature and the humidity percentage is high, the visibility is low and fog occurs.
Common examples of condensation

Frost around the freezer pipes: Air with water vapor enter the fridge when the door is open. When air starts to be cooled below the dew point by the pipes, condensation occurs and ice forms around them.

Air exhaled when the weather is cold. Air in our lungs is not saturated due to the high body temperature, but becomes saturated when it starts cooling.

Air saturated by water vapor coming from a pressure cooker.

As pointed out by @RyanMortensen, saturated air on car windows (when the temperature decreases during the night, or when air is saturated without temperature change, because there is more water/rain in the air that can be evaporated naturally -- Increasing car temperature above the dew point is the solution).

Fog and clouds formation: Fog because the ground is colder than the surrounding atmosphere (early in the morning), cloud because air is cooled below the dew point while it climbs (pressure and suddenness play also a role).

Dew :-)

When water vapor changes into ice
When the dew point is below 0°C, water vapor is not condensing into water droplets, it is converted directly into ice crystals (frost).
This effect is particularly dangerous and can lead to icing in the carburetor of a piston engine. This condition can happen in areas of low pressure and low temperature, commonly created by the sudden pressure drop in the throttle venturi, due to venturi effect and the temperature drop due to fuel vaporization.
For a typical piston engine, this effect is centered on a external temperature around 10°C but extends to a large range of temperature when the engine is slowed down (descent):

Induction icing conditions
The remedy to carburetor induction icing is to heat the carburetor and raise the due point to a safe area, especially when descending.
For jet engines, induction icing (not to be confused with flying in atmosphere with ice crystals or supercooled water droplets) can cause ice to form at the engine inlet. Blocks of ice can then break, causing damage to blades, compressor stall and/or combustor flameout. It can also cause EPR probe (PT2) reading errors and subsequent FADEC fatal behavior.


How do they quickly replace the pylons after a hit during the Red Bull Air Races?

The 25m tall asymmetrical pylons used in Red bull air races are made of 9 different sections, which are connected with zippers for easy removal and installation. In this image, you can see the multiple sections that make up the pylon.

Interior of redbull air race pylons; image from redbull air race

Airgators Team Captain, Holger Leprich, who is responsible for replacing the pylons after a hit, explains the procedure in this video.

The pylons are held up using air pressure- electronically controlled equipment at the bottom of the pylon creates a positive air pressure so that the pylon stands upright.
For each competition, there are three five member pylon replacement teams (called Airgators) to ensure quick replacement- their current record being 67 sec.
The pylon is designed to tear off in case of a hit. Once the pylon is hit, the team moves to the damaged pylons location on clearance from the race director.
Once the team reaches there, a couple of guys control the electronic equipment (and deflate the pylon, if required) at the bottom of the pylon, while another two replace the damaged parts- they simply unzip the damaged part and zip in the new one, while the last one checks the pylon.
Once the replacement is completed, the team inflates the pylon. Mission accomplished.


Is separation provided in class F airspace?

RE I can't find anything about separation being mentioned:

Check appendix 4 on PDF page 103 (APP 4-1):

The third column is for the separation provided, where for Class F it is:

  IFR from IFR as far as practical

And click here for the full table (red highlight mine).


What is this fighter jet at Weymouth NAS?

It's a Panavia Tornado.

Found a site with that picture and others from the same air show. Here is a better picture of one in the same markings. It is part of the RAF No. 5 Squadron, which switched from the English Electric Lightning to the Tornado in 1988. The squadron uses a maple leaf to commemorate their link to the Canadian Corps in World War 1.

Source


Is an alternate airport always required when flying internationally?

As a simple anwer, no, it is not always required.
ICAO Annex 6 4.3.4.3 Destination alternate aerodromes

For a flight to be conducted in accordance with the instrument flight
rules, at least one destination alternate aerodrome shall be selected
and specified in the operational and ATS flight plans, unless:
a) the
duration of the flight and the meteorological conditions prevailing
are such that there is reasonable certainty that, at the estimated
time of arrival at the aerodrome of intended landing, and for a
reasonable period before and after such time, the approach and landing
may be made under visual meteorological conditions; or
b) the
aerodrome of intended landing is isolated and there is no suitable
destination alternate aerodrome.

Also, there are similar descriptions for the requirements for take-off and en-route alternates.
EASA adds aditional requirements in OPS 1.295 in the form of maximum flight time of 6 hours and at least two runways at the airport, but it is still allowed. I can only assume FAA does a similar thing


How is an airplane towed/recovered after an emergency off-field landing?

This really breaks down into a few categories:

Flyable aircraft, Flyable location

For general aviation aircraft or airliners that are in flyable condition (or only require minor repairs) and are located somewhere you can fly them out of the usual solution is to offload as much weight as possible, take off, and fly to an airport.

There are countless cases of light GA aircraft taking off from roads or fields after precautionary landings.  In the large aircraft world the Gimli Glider flew out of the racetrack, and TACA 110 took off from a nearby road.

Flyable or Salvagable aircraft, Unflyable location

If the aircraft is flyable but can't take off from its current location, or if the aircraft is salvageable but requires more extensive repair work than can be accomplished where it is, alternative transport methods need to be considered.

For light aircraft the usual solution is to disassemble the aircraft, load it on trucks, and take it to an airport where it can be reassembled and repaired to be flown away.
This is also an option for most airliners, and was in fact the original recovery plan of action for TACA 110 that I mentioned above.

Disassembly, trucking, and reassembly is generally more expensive than flying the aircraft out of wherever you landed it, but aircraft insurance policies generally include provisions for this because simply leaving the aircraft where it is will often be even less economically attractive.

Wrecked aircraft, wherever it is

If an aircraft is largely intact but unlikely to fly again in the near future (or ever) due to damage the recovery operations are effectively the same as above, but they're dictated by legal and financial requirements: Environmental regulations may preclude leaving a wrecked aircraft wherever it landed, and financially the components and materials may be salvageable or valuable as scrap. As long as the costs of recovery are less than the profit to be made (or the fines to be incurred just leaving the aircraft where it is) and the hazards involved in the recovery are manageable the aircraft will usually be recovered.

On land the aircraft (or pieces of it) will once again be loaded onto trucks to be transported somewhere where they can be examined and then stripped/sold.

Aircraft in relatively shallow water will be generally recovered by dredging or hoisting with crane if doing so is feasible. This gets most of the "big stuff" (wings, fuselage sections, etc.) though in a badly damaged aircraft smaller pieces may be left where they are. (The recovery of US Airways 1549 is particularly spectacular in this regard, as it's hoisted basically intact.)

Aircraft in deep water are often not recovered - it's simply not feasible from a financial or risk management standpoint (sending people down to an extreme depth just to recover a machine that's going to be cut up and sold for scrap is hard to justify).


Is there a limit to how many hours a person can fly per month?

With respect to air carrier operations in the US, 14 CFR 121.481 requires:

  (e) No pilot may fly as a member of a crew more than 100 hours during any one calendar month.

  (f) No pilot may fly as a member of a crew more than 1,000 hours during any 12-calendar-month period.

14 CFR 135.265 commuter:

  (1) 1,200 hours in any calendar year.

  (2) 120 hours in any calendar month.

Under Part 91, fractional ops, 14 CFR 91.1059 states:

  (a) No program manager may assign any flight crewmember, and no flight crewmember may accept an assignment, for flight time as a member of a one- or two-pilot crew if that crewmember's total flight time in all commercial flying will exceed -

  (1) 500 hours in any calendar quarter;

  (2) 800 hours in any two consecutive calendar quarters;

  (3) 1,400 hours in any calendar year.

Otherwise, there is no direct limit under Part 91. However, if you are fatigued enough to cause a problem, FAA can still charge you under general "unsafe operation" rules.


What written tests are required to become a ground instructor?

The FAA offers some nice guidance here

You may also want to check out my answer (a very close to dupe) here.


What were the Concorde's emergency procedures for an uncommanded droop-nose extension in flight?

As commented, reducing speed (and replanning flight) is all there is to it. From the Concorde abnormal procedures:

The nose has three positions:

Up
5° down
12.5° down

Holding the nose at 12.5° requires hydraulic pressure. If hydraulic pressure is lost, the crew can manually release the two uplocks, and the nose (and visor) would fall and stop at the 5° position – two additional jack uplocks stop the motion at 5°.


What are the differences between a slot and a slat?

I guess it should be movable slat.

A leading edge slot is basically a spanwise opening in the wing. Slats are aerodynamic surfaces in the leading edge, which when deployed, allows the wing to operate at higher angle of attack. When deployed, the slat opens up a slot between itself and the wing.

Image from simhq.com

In some aircraft, the slats are fixed, which opens up a slot between the wing and the slat. In this case, the terms slot and slat are used interchangeably.

"Leading edge slot" by Sanchom - Own work. Licensed under CC BY 3.0 via Commons.

A number of airliners use movable slats, in which case, the system is called slat, rather than slot.

"Voilure A319" by Nicourse - Own work. Licensed under CC BY-SA 3.0 via Commons.

In short, the system is pretty much the same, but is (usually) called slat in case of movable one and slot in case of fixed one.


Did Airbus do anything about Qantas Flight 72?

The ADIRUs presently used are totally different:

for exemple the hardware is of different generation bringing their physical dimension about twice smaller.

Todays AIRBUS used ADIRUs manage the GPS received data too. Internally the technical implementation of parameters is different, just due to technology evolution.

Most of these changes are not directly related to Qantas flight 72, but to new technology, for instance data interchange (such as sending the data of a label such as 224 as being the data of another label such as  204) due to a « bit » failure is not likely to happen nowadays as was the case in previous equipments because internally a « bit » failure is nowadays more precisely detected. Thus sending the altitude as being the AOA won’t happen today.


Do horizontal stabilisers provide any lift?

The horizontal stabilizer provides lift, but usually in the negative direction.
Could one provide positive lift?

The answer depends on cg location.

Forward CG, the answer is no.

Aft CG, the answer is yes but only if the CG was aft of the center of lift.

In other words, the more forward the CG is compared to the center of lift, the more downforce the tail must provide.  The lift from the horizontal stab in the "wrong direction" must be countered by the wing, and thus there is more induced drag.  For a given aircraft gross weight and thrust/power, there will be a higher cruise speed with a more aft CG.

There are practical limits to extreme fore and aft CG positions, and so each aircraft has an allowable "envelope" for loading for safety margin.

Aircraft are designed to have a range of allowable CG locations to make loading easier before the flight (especially for cargo aircraft), and also to allow for passengers & crew to move about the cabin in flight.

Horizontal stabilizers could be sized smaller but that would decrease loading flexibility, decrease passenger comfort, and decrease aircraft handling performance; often all airfoils and control surfaces are designed with many factors in mind, for good control harmony, good ride in rough air, for stability on instrument approaches, for flexible loadings of various belly and main deck cargo holds / passenger configurations, etc.

Flying wings and delta wing designs come to mind as aircraft without horizontal stabilizers, such as the Northrup Spirit or Convair Delta Dart.

Your other question, would manufacturers design horizontal stabilizers to provide lift?
Hopefully you can see by now this is not a design goal.  Wing design is so advanced that designers are making amazingly beautiful and high-performance wings that are most efficient at creating lift.  Look at a Gulfstream V wing or Boeing 747 wing.  It is not efficient to create a wing that doesn't work great and then needs an additional surface to help make more lift.  Exceptions to that might be bi-planes or tri-planes, as they used several shorter wings instead of 1 longer wing, but that is not practical in air transport.  How many Boeing Biplanes and Airbus Triplanes do you see traveling the globe? It's simply better to put all the lift needed into a single wing design.


Was the Shuttle Orbiter in contact with air traffic control during its descent & landing?

Well, sort of. The Kennedy Space Center, where the shuttle operations were conducted, has an ATC. but then, the show was run by NASA, not FAA.

The shuttle operations were coordinated through the Aerospace Control Officer (ACO) at the Air Force 45 th Space Wing’s Eastern Range (it used a military TACAN). FAA was informed of the shuttle landing and nothing else. NASA simply cleared the airspace for a 30 mile radius around the intended landing site to prevent collisions.

In the trajectory of the shuttle landing, FAA issued a NOTAM called 'Space Shuttle Landing Operations Advisory' to warn the users that 25 miles to either side of the nominal reentry trajectory is potentially vulnerable to debris, but the airspace is not closed, like this example:

  FDC 9/1945 (A0856/09) - ...SPACE SHUTTLE LANDING OPERATIONS ADVISORY...
  EFFECTIVE 0911271848 UTC UNTIL 0911271923 UTC SPACE SHUTTLE
  LANDING OPERATIONS 25 NM EITHER SIDE OF THE LINE BETWEEN
  2743S/17214W 0411N/16214W 2925N/13455W 3440N/11828W 3457N/11745W
  FROM SURFACE TO UNLIMITED. WIE UNTIL UFN. CREATED: 25 NOV 21:11 2009

For these actions, Special Use Airspace was activated. The ACO coordinates these actions with the FAA’s ARTCC (Air Route Traffic Control Center) in Miami, Florida


How much revenue do seat-back displays generate?

According to this article from September 2014:

  Thales estimates total revenue from IFE at \$17.6m a year for
  small/mid-sized carriers, up to \$397m a year for large carriers.

But that's for all services, not just advertising. The only specific mention I could find of advertising was this 2012 quote attributed to the CEO of Thompson Aerospace:

  Somewhere in the middle of the second question about advertising on
  the system he said: “… and we are generating somewhere between \$20,000
  and \$30,000 per month per plane with the IFE.”

The revenue is apparently generated in a similar way to internet advertising:

  [...] every 2 weeks the airline and the advertising service bureau receives
  a summary of the requests/viewings and the airline gets a check. At 1
  to 5 cents per click, the tally adds up as daily flights, sometimes
  short as an hour, record revenue and usage every passenger, every
  flight, every day, and every month

However, there's no information in the article about which airlines actually use that specific service, and I have no idea if those numbers are typical or not, or even exaggerated.

If you need more information than that and you can afford USD 4,650 to find out, this looks like a comprehensive report on the IFE industry.


How do you perform a gear-up landing in a large airliner?

Assuming that the pilots have tried everything possible and the gear just does not like to come down:

The general rule is to find a long runway, touch down as slow as possible. Here are sections extracted from Boeing 777's Flight Crew Training Manual:

Dumping fuel

  If time and conditions permit, reduce weight as much as possible by burning off or jettisoning fuel to attain the slowest possible touchdown speed.

Elevator

  After touchdown lower the nose gently before losing elevator effectiveness.

Rudder

  At touchdown speed, the rudder has sufficient authority to provide directional control in most configurations.

Speedbrakes

  (...) speedbrakes should be extended only when stopping distance is critical. Extending the speedbrakes (...) may compromise controllability of the airplane.

Reverse Thrust

  (...) an engine making ground contact could suffer sufficient damage such that the reverse mechanism may not operate. Selecting reverse thrust (...) may produce an additional asymmetric condition that makes directional control more difficult. Reverse thrust should be used only when stopping distance is critical.

Landing technique

The technique varies with the combination of failure. If one side of the main gears is missing, land the plane to the side of runway which corresponds to the extended main gear. I.e. if the left gear is down and right gear is up, land on the left side of the runway instead of centerline. Maintain wings level for as long as possible, and be prepared to brake on the left side to maintain directional control.

If all the gears decide to hide in the gears bay, land on centerline and use rudder to maintain directional control. Rudder is effective until airspeed drops too low.

After landing

Evacuate the aircraft as necessary!


How does an engine failure affect the flight of an airplane?

It does.  Asymmetric thrust will in fact force the airplane into a turn unless the pilot counteracts this by using rudder and aileron to command an equal turn force in the other direction.  Typically both opposing rudder, and banking away from the dead engine will be used to result in straight (although uncoordinated) flight.


How (and why) does engine thrust change with airspeed?

The first diagram you link to shows three lines but does not indicate what they represent. I guess the bold line is thrust over speed. Then this diagram is correct for a turbojet.

Thrust $T$ is the difference between the engine's exit impulse minus the entry impulse: $$T = (\dot{m}_{air} + \dot{m}_{fuel})\cdot v_{exit} - \dot{m}_{air}\cdot v_{entry}$$
The exit speed $v_{exit}$ of a turbojet engine is almost constant over flight speed (relative to the engine of course), so as the engine accelerates, a larger entry impulse must be subtracted from a nearly constant exit impulse. Thrust drops slightly over speed.

At higher Mach numbers, precompression from the ram effect at the intake raises the pressure level (and hence the mass flow $\dot{m}_{air}$) inside the engine, so it will develop more thrust than in static conditions. This effect causes the thrust line to bend upwards at higher speed, and since the precompression grows nonlinearly with speed, the initial drop in thrust is soon reversed. Of course, now the fuel mass flow $\dot{m}_{fuel}$ will grow in the same way, so the fuel efficiency (thrust per fuel used) will continue to drop as speed increases.

Only when flight speed approaches the exit speed of the jet will thrust go down again. The typical exit speed of a turbojet is easily supersonic, therefore this type of engine is well suited for supersonic flight.

  max engine thrust at cruise is approximately 29,360 Newtons while it's max thrust when stationary is 140,000 N

Here you have two effects combining to lower thrust. One is the reduction in the difference between entry and exit speed. This is more pronounced in a turbofan engine because the bypass flow will be accelerated much less than the core flow, and a higher flight speed will cause a proportionally bigger drop in thrust.

The second effect comes from the difference in air density between ground and cruise: Air density at a typical cruise altitude of 35,000 ft is only 0.38 kg/m³ or 31% of the air density at sea level. The original source for the cruise thrust number does not say for which altitude the figure is valid, but you can be sure that it is for about one third of ground density. Mass flow $\dot{m}_{air}$ is directly proportional with ambient density, and both effects combine. However, most sources give only a drop to a quarter of static thrust - the last table in the linked answer looks like someone mixed the values for the CFM56-5A and the CFM56-5C.


Are there any hypersonic planes in service today?

As far as supersonic commercial flight goes, Nope. The Concorde and the Tupolev Tu-144 are both long retired.
As pointed out in the comments, hypersonic commercial flight has never existed.
The SR-72 you speak of is supposed to be flying by 2025.
This article points out that

Only a few experimental planes have ever reached hypersonic speed, and the last time a hypersonic plane flew with a person on board was in 1967. That plane, the North American X-15, was powered by rocket engines, which are impractical for commercial air travel.

The same article mentions a potential 'in-development' aircraft:

The Stratofly consortium plans to begin wind tunnel tests of the engine components. But it will take many years to bring Stratofly to life. The key technologies might not be ready until 2035, Viola says, with another decade needed before flight tests are completed and the plane is ready to carry passengers.


How do you calculate the true bearing from a station (QTE)?

You are quite close to the answer, you just made a mistake with the sign of east compass deviation, hence underestimated the true heading by 6°. The actual angles are like this:

The compass deviation is given as +3° while it should be given as 3° east, like the variation. It could be misleading.

Exactly as you then developed, the unknown yellow angle is equal to:

True heading + (relative bearing - 180)
147 + (307 - 180) = 147 + 127 = 274°


What are the advantages of single vertical stabilizer over a twin set?

Why did engineers believe the twin fins to be superior?
There doesn't seem to be any single definitive reason for selecting the number of vertical fins on an aircraft design (except, obviously, for the twin-boom designs such as the Lockheed P-38 or Fairchild C-119).  I've seen all of the following cited by one authority or another as advantages of multiple vertical fins.  (Sorry, I didn't save or remember the sources.)

Reduced hangar overhead requirement.  This is the most common reason for including total aircraft height in a purchase specification, and it is a sine qua non requirement for carrier deployment.
Also I remember reading a magazine article that supplied this reason for the triple tail on the Lockheed Constellation.

Reduced cantilever stress at the root.  This may actually save weight over the single-fin design.  It may also help keep a tactical aircraft from disintegrating under the enormous stress of combat manoeuvres.

Reduced parasite drag.  The lower half of a vertical fin can be twice as thick as the upper half.  A twin tail design effectively omits the lower half and uses the upper half twice.

For multi-engine designs, operating the rudders in the engine slipstream affords improved rudder authority at low speed.  Pilots who taxi loaded bombers into takeoff position between other loaded bombers like lots and lots of rudder authority.
Also I notice that practically all the big flying boats of the 1940's Flying Clipper era had multiple vertical fins.  Those craft had some tricky low-speed steering requirements — they not only had to make their way through a busy harbor, but usually docked and undocked without a tugboat.  I'm only guessing at the connection though.

A single vertical fin can be masked by the fuselage wake at high angles of attack.  You can see how this could be a problem for modern fighter aircraft, which look like flying tennis courts.  Traditional bomber designs with their broad wings and heavy aerodynamic loading can also generate quite a troublesome fuselage wake.

Improved position and field of fire for a tail gunner.  I don't see it myself but I've heard the claim so I'm including it here.
I concede that the tail gunner slot in the Avro appears to benefit from the absence of bracing structure.

Reduced rudder-induced roll due to a shorter rudder offset moment.  Fast tactical military aircraft have short wings, and you don't want the rudder to extend further from the roll axis than the ailerons do.  On the other hand, the rudder doesn't need to go all the way to the top of the fin, does it.

Twin fins can be canted to reduce radar return.  They usually are, although I don't understand how the designers know where the hostile radar will be.

On the A10, the vertical fins actually mask the hot engine exhaust over a large angular area.  Thus in order to aim a ground-to-air heat-seeker up the tailpipes of an A10 you have to be directly behind it.  Which means that a few seconds ago you were directly in front of it, so good luck with that.


What solutions are there against deep stalls?

The Airbus A400M military transport was equipped with a rocket engine pointing downward which could produce a 5-second burn during testing of deep stall characteristics. It isn’t standard equipment though.


What will create a "traffic puck" on the UAT band?

The answer is "yes" if

a) you configure your 1090 out system to request ADS-B uplink at 978 MHZ (this feature was added to the message structure in DO-260B)
b) your 1090 ADS-B out message is confirming certain minimum "quality" standards related to both the quality of the position information (GPS Integrity or "NIC") and the quality of the avionics (SDA or system design assurance)and the quality of the install or SIL  The specifics of what quality message triggers the system is under review by the FAA, but if you equipment is certified (TSO'd) and the install is in accordance with AC-20/165B you will be fine.

Note, if you have a UAT ADS-B you can specify which uplink frequency you want in the same way.

Further note - almost all ADS-B system are single band transmitters (ADS-B Out) and dual band receivers (ADS-B In).

Nuance - the uplink is broadcast to the quadrant (relative to the ground station) where you are flying.  This can lead to aircraft with no or "below quality" ADS-B out receiving traffic intended for another aircraft.  Depending on geometry this can create a partial traffic picture which can be quite misleading and potentially dangerous


Why don't we get more user-friendly weather reports than METARs?

One use case where the compact METAR format is tough to beat is rapidly scanning meteorological trends. For that purpose, METARs are user friendly in the sense that they are expert friendly.

For example, a friend invited me to fly with him today on an Angel Flight mission that would have required a landing at Nashville. We had to scrub because the weather is unfavorable and not getting any better according to the TAF and ADDS METAR Data:

Data at: 1616 UTC 11 Mar 2016
KBNA 111553Z 36006KT 1SM R02L/4000V6000FT -DZ BR OVC005 14/12 A3024 RMK AO2 DZB51 SLP239 P0000 T01390122 $
KBNA 111541Z 35005KT 1SM BR OVC005 14/12 A3024 RMK AO2 SFC VIS 1 1/2 $
KBNA 111527Z 01006KT 2SM BR OVC005 14/12 A3022 RMK AO2 SFC VIS 2 1/2 $
KBNA 111453Z 02008KT 3SM BR OVC005 14/12 A3021 RMK AO2 SLP227 T01390122 53015 $
KBNA 111451Z 02007KT 3SM BR OVC005 14/12 A3021 RMK AO2 $
KBNA 111434Z 01007KT 2SM BR OVC004 14/12 A3020 RMK AO2 $
KBNA 111353Z 02007KT 5SM BR OVC004 14/12 A3019 RMK AO2 SLP219 T01390122 $

A subsecond scan confirms that the low overcast ceiling is stuck at four to five hundred feet AGL for the past several hours. Try outdoing that using the same information in decoded METAR format.


What is the best way to remove stuck screws from Cessna wing tank cover?

First the standard disclaimer: If you're in the US and you're not a licensed A&P mechanic, take the plane to your mechanic. (If you're working with your mechanic on this job and helping out by removing the cover plates you've reached the point where it's time to go tap them on the shoulder and ask for help, because the steps to remove frozen screws can do serious damage if you mess up).

Disclaimer over, on with the answer:

Frozen screws on infrequently-opened access panels are pretty common, and there are a few ways to get them free. You'll note I've drawn a line in this answer: Anything above the line you can probably do on your own, if you have to move to the techniques below below the line let your mechanic do the work (at least until you're confident you can do it without messing up).

Step one for removing a frozen screw is to make sure they're not painted in place - you'll need a paint cutter (your mechanic probably has one) and/or an x-acto knife. Cut the paint around the head of the screw using the paint cutter (or the x-acto knife and a very steady hand), and use the x-acto knife to clean out the screw head so your screwdriver can get a good grip.
Sometimes this is all it takes and the screw comes out on the next try. If not, keep going.

Step two for removing a frozen screw is to use a "penetrating lubricant" - Kroil is commonly used, and Corrosion-X can also do a good job (more about that later). Put a little on each screw and let it work its way into the threads for a while (15 minutes is a good starting point), then try to break the screw loose again. It may take more than one application of penetrating oil to do the job.
Two notes about penetrating oils: One, they need to be able to get to the threads in order to work (that's why step 1 involves cutting the paint). Two, don't use one that contains silicones (they will embed in the metal grains and make future paint jobs a major pain).

Hopefully the penetrating oils will work, otherwise you're going to move on to more destructive processes.

Step Three involves getting a little more aggressive with the screw in question. Typically by the time you get here you've at least slightly damaged the head trying everything else, so grab a grinder or dremel and cut a flat line into the screw head. This will give you purchase for using a regular (flat-blade) screwdriver, which will hopefully let you apply more torque to the screw. You also want to keep applying penetrating oil while you do this.
The trick to Step Three is cutting the head deep enough that the blade won't cam out, but not so deep that you compromise the head-to-shank connection in the screw and snap the head off when you try to turn it. This is a bit of an art, so it's best to have your mechanic step in at this point. If you screw up here you're on to step four, and you don't want to get to step four. . .

Step Four is drilling the f#!@ing screw out. When all else fails you take a drill right through the screw, demolishing it. Your mechanic almost certainly has appropriate drill bits for this, and the skill to do it without seriously messing up the screw hole / nut plate / cover panel / surrounding skin.
Even a skilled mechanic may damage rivnuts or nutplates drilling out a screw, and will then have to replace the damaged piece before a new screw can be inserted.

Avoiding the problem in the future

Once you get the screws out (and your mechanic will - eventually - mechanics always win when screws pick a fight) there are some steps you can take so the next person who has to get this panel off doesn't suffer as much as you did.

Don't paint the screws/panel in place.
If you damage the paint getting the screws out touch it up and let the touch-up cure before you put the panel/screws back on so the paint isn't acting as a glue holding it all together.
Also for the love of sanity don't paint the screws - See #2, and if you repaint the plane do it with this panel off.
Replace the standard screws (probably cad-plated steel) with stainless steel screws.
Stainless screws will corrode, but they're much slower at it than the cadmium-plated steel screws (the cadmium plating that keeps them from rusting in place gets rubbed off as you screw them in). Stainless screws also don't need to be painted like the cadmium-plated ones do, so you won't have to pick paint out of the screw head.
Apply a corrosion treatment before reassembly.
Blast the nutplates/rivnuts/etc. with Corrosion-X or similar - also try to hit any other areas you can reach while the panel is open and things are apart.
Apply a corrosion treatment to the airframe regularly.
Less important if the aircraft is kept in a hangar, but for aircraft tied down on a ramp having a corrosion treatment done every few years will help keep screws from freezing in place.


For flight planning must the forecast weather be above minima one hour before, after or at ETA? (EU-OPS)

Weather above planning minima one hour before and after ETA for flight planning and for determining alternate requirements (2 alternates vs 1).
Weather above planning minima at ETA for commencing flight.
Weather above operating minima at ETA for continuing flight.

One way you can think of it: in the cockpit weather at ETA. In the briefing room weather one hour before and after.


If I were to scratch build a helicopter, as the manufacturer, would I need a pilot's license to fly it?

Depends on what you build. It is possible to build a helicopter that qualifies as an ultralight, and thus no license needed.

If it exceeds the weight and power restrictions for an ultralight, then it is an experimental aircraft, that requires at least a solo ticket.

I would strongly suggest that rather than scratch build your own, an experience you might not survive, you take a look at what I'm currently lusting after:

Mosquito Helicopter

In kit form (which technically makes you the builder), it can be had in ultralight form, with limited range.

Or in experimental form with a more powerful 2 stroke engine and larger fuel capacity.

And finally, the (sigh) gas turbine powered version.

One advantage of building the experimental kit is: as the builder, you can perform all maintenance and the annual inspection yourself.

Another advantage of going the more capable experimental route is: you can log the hours.


Did the Swiss Air Force assist Austria in self-defence during the Yugoslav War?

I'm likely reading the same sources than you read. The chance of the event you are searching for ever occurred seems slim. As you wrote, Austria worked hard to maintain its neutrality policy.

From Wikipedia, it seems clear Austria was not using guided missiles before 1993, but indeed other weapons can be used to shoot down an enemy.

The article seems to be exhaustive for significant elements related to flights over the country by foreign aircraft, and still doesn't mention any destruction between 1970 and 1993.

There was a major incident in 1991 with Yugoslav MiG-21, but no mention of a shot down. This incident and the similar ones the same year led to the adoption of guided Sidewinder missiles by the air force two years later.

  From 1970, Austria purchased a total of 40 Saab 105 lightweight
  multi-role aircraft with the intention to deploy them in trainer,
  reconnaissance, interception and ground attack roles. As it became
  clear in the 1980s that the sub-sonic aircraft were inadequate for air
  combat and airspace interdiction, Austria purchased 24 reconditioned J
  35 Draken fighter aircraft to supersede the Saab 105 as the Austrian
  Air Force's main interceptor in 1988. The Saab 105 remained in service
  as a trainer/surveillance aircraft.

  Shortly after, the Draken saw their first major use in airspace interdiction starting 1991 during the Yugoslav Wars, when Yugoslav
  MiG-21 fighters crossed the Austrian border without permission. In one
  incident on 28 June a MiG-21 penetrated as far as Graz, causing
  widespread demands for action. Following repeated border crossings
  by armed aircraft of the Yugoslav People's Army, changes were
  suggested to the standing orders for aircraft armament.

  Since 1955, Austria's armed forces had been forbidden to operate any
  guided missile system, including Air-to-air missiles and
  surface-to-air missiles. In the post-Cold War environment, and with
  gun-armed aircraft a relic of a past age, the Austrian Parliament
  voted to amend this section of its state treaty and in January 1993
  modern AIM-9 Sidewinder missiles were ordered from Sweden to arm its
  fighter aircraft.

On the other assumption that Switzerland provided military assistance, again no mention of such cooperation until recent year, with the EU treaties.

It seems the overflights of Austria by non authorized aircrafts was quite intense --daily-- at the time of the Yugoslavia war.

You may be right when saying that Austria could be reluctant to disclose a shooting. The fact that it would have happened before the widespread use of Internet is not something that could prevent the event to be recounted online today.

Not relevant downing:

Jan. 1992: Two EU helicopters downed by Yugoslav MiG-21, Austria radars detected the downing.

Additional documentation:

The Austrian Air Force - In the Past and Today
Austrian Air Force
Austrian Air Force
A well documented list of interceptions over Austria
Austrian Draken's on high alert


Adjustment for non-balanced passenger loads?

Asymmetrical lateral loads within the fuselage are not far enough away from the longitudinal axis to generate any significant moment arm.  It is an issue, but not one that is planned around or proactively compensated for.  Any imbalance in flight can easily be overcome with a little bit of aileron trim.


How to calculate the stability derivative of Pitch Moment with respect to AOA rate?

$q = 0$ means no change of pitch angle. You also have a constant rate change in AoA ($\dot{\alpha} = const$).

The difference between the pitch angle ($\theta$) and AoA ($\alpha$) is the flight path angle ($\gamma$).

$\theta = \alpha + \gamma$

From this it follows that the flight path angle changes opposite to the change of change of AoA.

$\dot{\gamma}=-\dot{\alpha}$

This is not a manoeuvre that will happen in real life. An approximation of such a situation can happen when after a brief but strong pull-up the pitch angle is kept constant while the path angle of the aircraft is still increasing. The rate of change of the AoA will not be constant in such a manoeuvre.


How are Virgin Galactic's SpaceShipTwo's windows so large?

Here are a few ideas:

First and foremost, we're not handling metals here. Composites have the advantage of being able to be made stronger by adding on a few layers around high-stress area like windows. This was difficult with metals since this needed some sort of fasteners or adhesives to do. This reinforcement is seen in the photo below.
The windows are designed to keep an even pressure all around in the context of the fuselage shape at that point. You'll notice the flange design which keeps the fuselage shape and stop it from popping open. This is a little like the thicker part of a bottle neck. This is very difficult (if possible) to do well in a metal fuselage to this extent.

(source: msn.com)

The usage is completely different. Concorde was a commercial aircraft, intended for many years of operation. This is a very low-cycle aircraft which will see a fraction of that flying. The number of pressurisation cycles is a lot lower, putting much less force on the windows.
As for safety, the style of flying is completely different. Probably flown by test pilots, the aircraft might never even experience rain and will fly under very predictable conditions, with very few flight cycles.
Periods of elevated temperatures gradually degrades many materials, this is much less a concern with short flights. If I gather correctly this is the main issue with sustained high-speed flight, as seen on Concorde and SR-71 and other aircraft.

(source: guardian.co.uk)

Composites have a lot lower thermal expansion (CFRP vs. Aluminium is an order of magnitude lower) which reduces issues with expansion in the fuselage.
Concorde was a commercial aircraft with weight and operating price in mind. This aircraft is built for this purpose, with the windows considered as a main feature from the start. You could probably have been able to make the windows a lot larger on Concorde, at the unacceptable price of weight, production and operating cost.
Needless to say that knowledge of materials and structures has advanced substantially, all our these features can be modelled in detail on computers, not necessitating the traditional conservative approach.
As for redundancy, predecessor SpaceShipOne had double pane windows and double seals everywhere. For the passengers without suits, if a window were to blow entirely, you're most probably out of luck.


Have there been accidents involving flight simulators?

I have been attempting to find information on this question for quite a while, and judging by the lack of answers, I am assuming that Zeus, in the comments to the question, is right: that accidents involving a flight simulator, to the extent that they are severe or sensational, are very rare. More often, accidents would be considered “workplace incidents” and would go unreported outside the company.
In Larry Milberry’s text The Story of CAE (2015), while discussing safety procedures and accidents in the development of flight simulation motion systems, several accidents did indeed happen, but none which involved injury:

There was a failure of a British Airways simulator where “a
malfunction drove the cockpit at maximum pitch-up velocity into the
end of travel, breaking the upper bearings and sending the simulator
to the floor.”
During the testing of the (never installed) Iranian CH-47 simulator
“there was a motion system failure. The simulators unusual vertical
configuration meant that any uncontrolled loss of hydraulic system
pressure would cause the flight compartment to lurch nose-down…
The potential for Murphy’s law to take over was there in spades, and
one day the interlocks did fail…”

In my pursuit of this question, working through historic newspapers, I have come across several tangentially related, though ultimately unsatisfactory, examples to my question: the 1967 oxygen fire in the Apollo 1 capsule simulator that killed 2 airmen (and 16 rabbits), an eerie repeat of the explosion which killed the 3 astronauts the Friday before; the 1991 B52 crash during the Gulf War which again was an "eerie repeat" of a “crash-in-the-box” during previous training; the 1991 deaths of two pilots “simulating” the attack on Pearl Harbor in Florida; the 2001 attempt by a man to open the emergency door mid-flight saying “it’s OK, we are just on a simulator”; and finally, many instances where flight simulators have been used to familiarize those with intent to hijack a plane.
Again, these are not what I am looking for, but they are the types of things you find when you start searching for this particular information. My sense is that there must be examples of accidents in flight simulators which have been significant but which, likely due to them being workplace accidents, did not receive media attention. Nonetheless, maybe this answer will help provoke the memory of others to contribute a more precise answer.


Why did this pilot have his single-engine license revoked?

Lets break this down as best we can.

For starters you've made an error in your assertion. The pilot hasn't had their license revoked, just simply their SEP rating. There's a difference. The person in question can still do their day job as a pilot, on a type-rated aircraft. They have accepted a suspension of their Single Engine rating.

On some finer points mentioned in the linked news article:

  [...] both pilots and passengers do not use shoulder harnesses

The Indonesian Aviation Regulations specify

  For small civil airplanes manufactured after [27 December 1993], an
  approved shoulder harness for each front seat.

If we make an assumption that this flight was carried out in an aircraft manufactured after 27th December 1993, then both front seats should have been equipped with shoulder harnesses which should have been worn. Hardly the crime of the century, but there you go.

  Second, Vincent gives flying control to unauthorized people

This one is a bit tenuous, unless the PiC has an instructor rating he is "officially" not supposed to allow someone else to manipulate the controls. Finding exact wording to back this up is not easy. I think most pilots (of light aircraft) have let their passengers have a go at the controls.

  Third, he was deliberately maneuvering zero gravity

This in and of itself isn't the problem, I suspect the problem was whether he was doing so in an entirely safe manner. He gave no warning to his passengers that I could see, and I'm not convinced he performed the checks suggested before such a manoeuvre that would make it safe.

They could easily just cite the following:

  No person shall operate an aircraft for the purpose of air navigation or for operations on
  any part of an airport (including areas used by those aircraft for receiving or discharging
  persons or cargo), in a reckless or reckless manner so as to endanger or be likely to
  endanger the life or property of any person.

The wording of this regulation is fairly similar across many aviation regulators, and is often cited for "You did something against regulations".

Sources:

CIVIL AVIATION SAFETY REGULATION - Republic of Indonesia


What do Turnaround Supervisors do before departure?

It depends on the airline and their specific procedures. Turnaround supervisors are in charge of ensuring all ground services are performed correctly and safety. The turnaround supervisor is also responsible to verify the load placed onboard the aircraft matches what was specified on the loading instruction report. Calculations can vary between cargo and passenger flights, but usually cargo involves more calculation and observation to ensure the load is adequately secured. The turnaround supervisor may need to crosscheck the information on the loading instruction report and the loadsheet received in the cockpit to ensure the flight crew received accurate information necessary to calculate takeoff speeds.

The National Airlines crash in Afghanistan highlights a serious case where the training of the individuals responsible for securing and calculating the necessary amount of load restraint was grossly inadequate.


Has there ever been a report of a helicopter flying into a downburst?

Yes, it would be really amazing if it had never happened. Since "reports" are only required in the case of accidents, here are extracts from three NTSB summaries:

WPR13CA155

  During descent for an off-airport pinnacle landing, the helicopter
  encountered a downdraft about 75 to 100 feet above ground level (agl),
  and the pilot receiving instruction increased collective input. The
  flight instructor advised the pilot receiving instruction to be less
  aggressive using the collective as the flight continued to the landing
  area. As the helicopter descended through about 10 to 25 feet agl, it
  encountered a second downdraft, and the pilot receiving instruction
  increased collective again, which was followed by a decrease in rotor
  rpm.

ANC09LA098

  During the approach to the 5,657 foot level site, the pilot said he
  encountered a downdraft as the helicopter approached the site, and the
  helicopter descended below his anticipated approach path. He initiated
  a go-around, but the helicopter continued to descend, and landed hard,
  about 150 feet short and down slope of his intended touchdown point.

WPR09CA470

  As he flew the helicopter out of the leeward side of the peak, he
  encountered a downdraft. He maneuvered the helicopter toward a wide
  open valley that descended about 5,000 feet below. The downdraft
  pushed the helicopter into the face of the mountain, despite the
  pilot's application of full collective and descending flight into the
  valley.


Is trimming for constant speed equal to trimming for constant angle of attack?

Short answer: Yes

Generally you are right. You are trimming the aircraft for a point on its polar, and that point is reached at a specific angle of attack.

You say yourself we should neglect secondary effects like the propeller blast, and under this condition you are right. Trimming means to set the distribution of lift between wing and tail surface, and this directly sets the angle of attack.

Now the more elaborate part of the answer

You trim the aircraft for a specific dynamic pressure, that is the product of air density and flight speed. If you slightly change your question from "trimming for constant speed" to "trimming for constant indicated speed", you gain precision and the answer is still yes. With a change in altitude you will also affect the Reynolds number the aircraft flies at, and the same polar point is reached at a slightly higher angle of attack the lower the Reynolds number gets when the aircraft climbs into colder air.

In turns the lift demand is increased. Not changing trim during a turn will let the aircraft speed up to increase lift at an unchanged angle of attack. That is why you pull more when turning - you want to increase the angle of attack, so speed can stay constant. When speeding up, you again change the Reynolds number and indirectly also the angle of attack, but this effect is very small.

When you change the power setting, you add energy to the aircraft at a different rate. Thrust becomes bigger and is counteracted by the sum of drag and the component of weight which acts in parallel to the thrust vector. Now the vertical component of weight is reduced, and so is your need for lift - but ever so slightly. This effect by itself means you will fly at a slightly smaller speed which will also very slightly affect the angle of attack. But since you did not change trim, the distribution of lift between wing and tail is unchanged, so the angle of attack is the same, save for a minuscule Reynolds number effect.

Increasing thrust will also increase the prop blast over the tail surfaces, making them more effective and slightly changing the balance of the aircraft. Depending on the direction of tail lift, the result is an increase or a decrease in angle of attack, but this is precisely the effect you wanted us to disregard.

Another secondary effect is a constant loss of weight as the engine burns fuel. This makes the aircraft lighter, so it requires less lift and a smaller angle of attack over time to remain at the same speed. Since you trimmed a specific polar point, the aircraft would need to slow down in order to stay at this polar point at its lower weight. But the lower weight also creates less drag, so instead of slowing down the aircraft will climb. Now the reduced density will require more angle of attack and will reduce engine output so in the end the same angle of attack is maintained at a higher altitude but a slightly lower indicated airspeed.


Did DB Cooper's aircraft land safely with the aft stairs open?

The aft airstair was partially deployed for the duration of the approach and landing.
The transcripts of ATC communications between NW305 and various ground stations are freely available (and a fascinating read). The relevant communications (with Reno) begin on PDF page 87 (numbered 213). Below are the mentions of the airstairs from that point on, with times given in PST, 1971-11-24. I added the text in brackets for clarity.

22:35, NW305: OKAY AH WE'RE TRYING TO MAKE CONTACT WITH [Cooper in] THE BACK [of the airplane] NOW AND AH WE'RE GOING TO GET THESE
STEPS UP BEFORE WE CAN MAKE OUR LANDING...
22:43, RENO: NORTHWEST THREE ZERO FIVE WHAT'S THE STATUS ON THE STAIRS NOW SIR
22:43, NW305: AH WE HAVEN'T BEEN ABLE TO GET AHOLD OF ANYBODY [in the back of the plane] YET UH TRYING TO CONTACT HIM AND THEY'RE STILL
DOWN SO I WE HAVEN'T DECIDED YET AH WE MIGHT COME IN AND LAND WITH
THEM DOWN THERE'D BE SOME SPARKS SO
22:48, NW305: APPROACH AH THREE ZERO FIVE WE CAN'T SEEM TO RAISE HIM BACK THERE WE KIND OF HATE TO WE'D JUST AS SOON LAND WITH THE
THING HANGING DOWN IT ISN'T ALL THE WAY DOWN AND THEN PROBABLY WON'T
HAVE ANY PRESSURE ON IT SO WE HOPE IT'LL (unintelligible) FREE...
22:57, NW305: ...WE'RE NOW MARKER INBOUND AND UH AH WE'RE GOING TO BE LANDING WITH THE AIR STAIR IN THE DOWN POSITION AH WE DON'T SEEM TO
GET ANY RESPONSE FROM OUR FRIEND IN THE BACK
[The aircraft touches down and is taxiing.]
23:03, NW305: SEE ANY SPARKS COMING OFF THE TAIL AT ANY TIME ON AH TOUCHDOWN
23:03, RENO: NEGATIVE NONE AT ALL THE ONLY THING THAT'S VISIBLE ON THE TAIL IS LIGHT AH APPARENTLY ON YOUR RAMP
23:03, NW305: ROGER UNDERSTAND STAIR LAMPS AH STAIR LIGHTS
23:03, RENO: I DO SEE SOME AH SPARKS NOW JUST A FEW AH TRAILING YOU AH AS YOU'RE TAXIING IN
23:03, NW305: OUR AH PASSENGER TRIED TO DISEMBARK
23:03, RENO: I STILL DON'T AH GETTING A FEW SPARKS NOT VERY MANY AT ALL
23:03, NW305: OKAY WE'LL TRY TO SLOW OUR TAXIING HERE AS MUCH AH IT PROBABLY IS DRAGGIN AH

Why did the crew not retract the airstair before landing?
The airstair can only be operated from two positions: one in the main cabin and one on the exterior of the aircraft. It cannot be operated from the flight deck. The testimony of Tina Mucklow, the flight attendant whom Cooper interacted with almost exclusively, reveals that

Approximately four minutes after takeoff, [Cooper] stood up, told [Mucklow] to go to the cockpit and close the first-class curtains, and for no one to come out from behind the curtains.

It should be noted that the airstair was still closed and locked at this point. In fact, it was Cooper himself who performed the deployment:

...he asked her to demonstrate to him the procedure for opening the rear door and extending the stairway. She did this and was under the impression that he understood how to do it. She commented that it occured to her at this time that this was the only function of the aircraft which she had discussed with the hijacker during the time she had been with him which he did not seem to be fully aware of.

Even though before Mucklow left Cooper in the cabin "...she pleaded with him to take the bomb with him and he said he would take it with him or disarm it...", nobody could be sure, so complying with his demand for no one to enter the cabin was the obvious choice. Even after the crew suspected he had jumped, there was still some chance that he was present. That—on top of the clearly dangerous situation of being unrestrained in an airborne jet transport with a door open—compelled the crew to sit tight in the cockpit and land with whatever configuration they could control from there. Indeed, third officer and right-seater on the flight Bill Rataczak stated that

...no member of the crew departed from the cockpit to check on the presence of the hijacker following the arrival in the compartment of hostess Mucklow, who had locked the door behind her.

How did the airstair remain partially deployed on its own?
The airstair is in contact with the tarmac when deployed on the ground. In fact, it's designed to essentially wedge itself against the ground and act as a tail stanchion to keep the airplane from tipping backward during loading and unloading. Early 727s such as N467US had mechanical locks for the airstair in both the extended and retracted positions to accomplish this function.
However, the crew had evidence that the airstair was not locked, as Mucklow "observed the red indicator light go on the [flight engineer's] panel indicating that the stairs had been lowered." On the 727-100, that light would be de-energized only if the airstair was locked either up or down. (On the -200, a green light was added to indicate a fully extended and locked position.) The ATC transcript indicates the captain's later belief that the airstair wasn't "all the way down", so it's reasonable to assume the warning light remained illuminated.
That the airstair didn't lock down when deployed indicates that it never fully extended. It is likely that the air loads simply prevented full extension. The airstair hydraulic actuators were not designed with the strength necessary to overcome a 170-knot airstream, especially on early 727s. The extension was limited by the airspeed and subject to fluctuations with changes in the airstream and the weight of Cooper upon the stair.
The inability to fully extend the airstair in flight was even known on the ground beforehand, as the transcript of communications between NW305 and the airline's base at MSP reveal (I cleaned these up):

18:38, MSP: DON'T KNOW OF ANY WAY TO LOCK STAIRS IN AN INTERMEDIATE POSITION.
18:40, NW305: ...STAIRS WILL OPEN ABOUT 20 DEGREES AT 120 KNOTS. IS THAT ENOUGH FOR AN INDIVIDUAL TO ESCAPE THE AIRCRAFT?
18:40, MSP: WITH HIM ON STAIRS WILL OPEN POSSIBLY ENOUGH FOR HIM TO GET OUT. REMAIN UNPRESSURIZED. BE IN LANDING CONFIGURATION WITH
FLAPS. SLOW TO [APPROACH] SPEED BEFORE TRYING TO EXTEND STAIRS.

As it turns out, the stair could not be opened much if at all at 170 knots during a climb, and the captain had to "have 'er about down to a hundred and sixty knots" and level off at 7,000 feet to get the resistance low enough. It makes sense that a higher angle of attack would cause a greater air load on the door due to the increased frontal area. It also makes sense that the airflow alone would be insufficient at any speed to completely re-close the door due to the geometry of the empennage, the weight of the stair, and some hydraulic damping. Once the door was open, the crew were able to climb again to 10,000 feet and keep the airspeed "in the vicinity of one seventy, one eighty [knots]".
Although the hydraulic actuators would have provided damping, the swirling wakes from the landing gear and flaps—not to mention the aircraft turbulence inherent when flying low and slow over mountains in a storm—undoubtedly wrenched the stairs up and down considerably. Cooper's exit has been romanticized as a high-dive into the unknown, but it was more like trying to exit a springboard during an earthquake, with his own weight just exacerbating the problem. We know as much from Richard McCoy, Jr., a copycat hijacker who survived his jump (at the same airspeed) and was later captured and interviewed:

...[McCoy] stood geared up in the open doorway for a very long time before
descending the aft stairs. It was almost midnight, the sky was black,
and the wind was freezing, yet his hands were sweating. Finally, he
was able to collect his wits, take a deep breath and step outside onto
the stairs.
As he stepped out, the entire stairway dropped two feet under his
weight. Knocked off balance with his 70-pound duffle bag between his
legs, he grabbed the right handrail and wrapped both arms around it,
desperately holding on. The stairs shook and vibrated. The noise from
the jet engines on either side of him was horrendous.

In fact, it was cabin-pressure fluctuations caused by Cooper descending and exiting the airstair that allowed for the determination of exactly when he jumped (8:11pm PST):

Crew reported oscillation of cabin rate-of-climb indicator. This probably due to [Cooper's] weight now on stairs, stairs extended further, resultant effect on cabin pressure.

The FBI's analysis was that "When [Cooper] jumped, the air stairs were forced closed (by outside air pressure) causing an increase in air pressure similar to shutting a car door with the windows up". Although we've established that the door was not forced completely closed and locked, it's clear that the airstair was able to hang somewhat freely in the airstream, its deflection affected by air loads, the weight of Cooper, its own weight, and any dampening provided by the actuators.
What was the risk of landing with the airstair deployed?
The crew knew from the cockpit indication that the airstair was neither down and locked nor up and locked. But they had prepared somewhat for the idea of landing with a deployed airstair before they even departed Seattle:

19:27, MSP: IT WOULD PREVENT ANY SUBSEQUENT TAKEOFF IF YOU LAND WITH [THE AIRSTAIR] DOWN.

Mucklow advised Cooper more than once of this fact, given that Cooper had stated intentions to get to Mexico and that Reno was just a necessary refueling stop along the way due to Cooper's wanting to be flown low and slow.
Landing with a deployed airstair could have a range of consequences that had never been investigated or analyzed, so most likely the airline was playing it safe. At the very least, a detailed inspection would need to be carried out before the airplane flew again. If the stair were downlocked, the results of a landing would depend on what failed first. If only the latch failed, you might get away with just dragging the stair, which would cause some exterior damage but overall that'd be a relatively minor fix. If nothing on the airstair failed, I suppose you could bend the entire fuselage. I'd also worry about bits and pieces of failed components being rocketed around the empennage or into the cabin.
Fortunately, at this point the crew was safe from the worst outcomes because the stair was not downlocked. In fact, as we've seen, the crew knew that even at 120 knots the airstair would not be deployed far enough to strike the ground upon touchdown. That speed is in the ballpark for an empty 727 on landing, but even at a lower speed it's entirely plausible that the airstair did not strike the ground on touchdown, and was only able to fully extend once the aircraft was at taxi speed.
What damage did the aircraft sustain?
Given everything we've covered so far, the damage was probably not extensive. Dragging the stairs along at taxi speed would mean not much more than some sheet-metal repair. Looks like some of the railing paneling sheared away, probably in the air:

There's also the placard found in the forest a few years later that got ripped away at some point during the flight.
In any case, the crew was able to easily deplane via the deployed aft stairs:

23:14, NW305: ...WE'LL GO DOWN THE BACK STEPS AND AH AH WE'LL BE TAKING LEAVE OF THE AICRAFT AND SHUTTING IT DOWN AT THIS TIME...


How can we physically define reynold number variation in terms of characteristic length?

The freestream Reynolds number ($Re_c$) of the wing and hstab would be different due to different chord lengths:

$$Re_c=\frac{\rho_\infty V_\infty c}{\mu}$$

where $\rho_\infty$ is the freestream air density, $V_\infty$ is the freestream airspeed and $c$ is the reference chord (of the wing or hstab). I'll discuss the physical significance of reference chord below.

1. Viscous drag

The physical significance on drag is best understood from the flat plate Blasius solution in laminar flow. The overall friction drag coefficient ($C_f$) decreases as a square root of freestream Reynolds number:

$$C_f=\frac{1.328}{\sqrt{Re_c}}$$

So the longer the chord (i.e. higher Re), the less significant the boundary layer viscous effects are to the overall drag. This is further illustrated in the graph below.

Image ref: https://www.sciencedirect.com/topics/engineering/friction-drag-coefficient

Take note, however, that the dimensionalized (total) friction drag still grows since $C_f$ here is non-dimensionalized with respect to the reference chord, $c$.

2. Turbulence transition

Increasing the chord doesn't increase the momentum thickness in absolute terms. However, the relative thickness with respect to the chord is different for different chord lengths:

$$\theta(s) = \frac{0.664\sqrt{\mu}}{\sqrt{\rho_\infty V_\infty}}s^{1/2}$$

where $s$ is the chordwise position from the leading edge.

Since natural transition is a function of the momentum thickness Reynolds number (Ref. Drela, Flight Vehicle Aerodynamics), which increases with respect to the momentum thickness, transition to turbulence will occur at similar chordwise location, $s$, in absolute terms, but earlier in relative terms ($s/c$) for the longer chord.

This has the effect of increasing the stall angle of attack for the larger chord, manifested in the effective increase in the freestream Reynolds number.


What astronauts and/or pilots had their "own" T-38 for transportation and practice?

No pilot or astronaut has "their own aircraft". Not in any unit I've ever seen.
Their name might be painted on the side of one, but they fly whatever the maintenance shop gives them for that day and mission.
Transportation? Sure. "Major Snuffy has to go to Houston for some training on the FooBar hardware. Ralph, take him, and go back on Thursday to pick him up."
Of course, this counts towards flight hours, mission and route planning, etc, etc.
"Borrow" a jet"? When I was stationed at Griffiss AFB NY in the late 70's, we sometimes had a pilot go for a weekend cross country. Leave Thursday or Friday afternoon, come back Sunday afternoon. Off to Frostbite Falls, MN Regional airport, to visit Mummy and Daddy for a couple of days. And we were loading golf clubs, skis, whatever, in the underwing travel pod.


Why do almost all overwing exit slides open over the trailing edge of the wings, and almost none over the leading edge?

The special cases you listed (minus the very special case Concorde) hold the clue.
The Il-62, DC-10, and MD-11 are all tail-heavy due to the tail-mounted engine(s).
The emergency exits are designed inside-out, not outside-in, meaning, the locations are not only dictated by each exit's size, but by the cabin's seating arrangement first.

(e) Uniformity. Exits must be distributed as uniformly as practical, taking into account passenger seat distribution.
(...)
(4) For an airplane that is required to have more than one passenger emergency exit for each side of the fuselage, no passenger emergency exit shall be more than 60 feet from any adjacent passenger emergency exit on the same side of the same deck of the fuselage, as measured parallel to the airplane's longitudinal axis between the nearest exit edges. (14 CFR § 25.807)

The tail-heavy examples by design have the main wing more aft, leading to that scenario. The rest, the opposite.
The DC-9 extended family[a] is more special, as there's an exit in the tail (also usable for entry):

Source: aircollection.org

And with the floor-level exits right ahead of the engines being not full-size (compared to the forward doors), it's been balanced that way. Otherwise it would have used an exit arrangement similar to the Il-62's, or the Vickers VC10 with a large exit forward of the wing in some configs, and/or over-the-leading-edge overwing exits in others:

Different VC10 configs; sources: wikimedia.org and wikimedia.org

The A310's reason is the original A300 fuselage that was shortened. If there are other configs, it would be related to passenger capacity.

a: optional on DC-9, standard on MD-80/90, removed from B717[1]
1: Becher, Thomas. Douglas Twinjets: DC-9, MD-80, MD-90 and Boeing 717. Crowood, 2002.


How does a pilot make sure they have received all applicable NOTAM's?

A quick lookup tool is PilotWeb.

The pilots may receive NOTAMS during flight briefing.  The best way to ensure that you are getting proper NOTAMS is to request all NOTAMS for the route of flight you have filed when you speak with the flight briefer.  The briefers are trained professionals, and they know what NOTAM information to provide to pilots, but it must be requested!

The FAA says this in regards to a standard briefing:

  Notices to Airmen (NOTAMs)

  (a) Available NOTAM (D) information pertinent to the proposed flight,
  including special use airspace (SUA) NOTAMs for restricted areas,
  aerial refueling, and night vision goggles (NVG).

  NOTE- Other SUA NOTAMs (D), such as military operations area (MOA),
  military training route (MTR), and warning area NOTAMs, are considered
  “upon request” briefing items as indicated in paragraph 7-1-4b10(a).

  (b) Prohibited Areas P-40, P-49, P-56, and the special flight rules
  area (SFRA) for Washington, DC.

  (c) FSS briefers do not provide FDC NOTAM information for special
  instrument approach procedures unless specifically asked. Pilots
  authorized by the FAA to use special instrument approach procedures
  must specifically request FDC NOTAM information for these procedures.

  NOTE- NOTAM information may be combined with current conditions when
  the briefer believes it is logical to do so.

  NOTE- NOTAM (D) information and FDC NOTAMs which have been published
  in the Notices to Airmen Publication are not included in pilot
  briefings unless a review of this publication is specifically
  requested by the pilot. For complete flight information you are urged
  to review the printed NOTAMs in the Notices to Airmen Publication and
  the A/FD in addition to obtaining a briefing.

If someone is performing a self-brief via 1800wxbrief.com, which is the best internet briefing site in my personal opinion (because it will tell you if you make a mistake rather than purge your flight plan without telling you), they can see NOTAMS invoked by relevance to their proposed flight path.

So to be sure you're getting everything, call 1-800-WXBRIEF via phone and file that way and request NOTAMS from the briefer.

One last thing that needs to be reiterated here:

  "This
  question
  talks about the many types [of NOTAMS]."

There are various classifications of NOTAMS, but for all intents and purposes in the civilian world, we have two types of NOTAMS; Distant-(D) and FDC.  That's it.

Civilians haven't had local NOTAMS in the US since 2008 when an advisory circular announced that they were being packaged into NOTAM-(D)s


What's the difference between the Multi Engine Instrument Rating and Instrument Rating in Canada?

Your IFR is either Group 1, 2 or 3.

All aircraft, including single, multi, multi centerline thrust (like a Skymaster).
Multi centerline thrust and singles.
Singles only.

For group 1 you have to do the ride in a conventional twin, which means you need a multi-engine rating first.  There is no written exam for the multi. It's just the training course and recommendation from the instructor for the check ride.

You can do a Group 3 IFR in a 172, but for the Group 1 you will still have to do a new check ride in a twin, so there is not much point in doing a Group 3 unless it's just to fly your own airplane IFR.

Just about everybody incorporates their multi engine training into the IFR training, does the Multi checkride at some interim point, then the IFR checkride in the same twin later on.

The main difference between the IFR checkride done in a single, vs one done in a twin, is the examiner gives you an engine failure drill to do on a missed approach when you do it in a twin. Otherwise they are about the same.


How can a helicopter be designed without a tail rotor?

The torque in a helicopter is generated by the engine driving the main rotor in one direction, which causes the fuselage to spin in the other direction. The tail rotor shaft is horizontally mounted and hence creates it own 'lift' to provide anti-torque. The pitch of the tail rotor gives directional control.

Common ways to design a helicopter without a tail rotor:

Tandem rotors : Two main rotors mounted one in front of the other. The rotor discs spin in opposite directions. All power from the engines is used for lift. Example: CH-47

Transverse rotors : Two main rotors mounted side-by-side. Example: Kamov Ka-22

Co-axial rotors : Two rotor discs are mounted one on top of the other. The engine units power both rotors. This structure requires a very complex swashplate mechanism. Example: Kamov Ka-25

Intermeshing rotors :  In this main rotor assembly, the two set rotor masts are installed at a slight angle to each other, in a transversely symmetric manner, so that the rotor blades intermesh without colliding with each other. Example: Kaman K-MAX

Tip jet : This is an interesting solution to the no-tail-rotor problem. Instead of driving the rotors with a turboshaft engine, compressed air is sent through nozzles installed at the tips of rotor blades. The engines effectively push against the air rather than the helicopter fuselage. The rotor spins just like a Catherine wheel. Example: Hiller Hornet

NOTAR : NOTAR - NO TAil Rotor uses a fan inside the boom to build a high volume of low-pressure air, which exits through two slots and creates a boundary layer flow of air along the tailboom utilizing the Coandă effect. The boundary layer changes the direction of airflow around the tailboom, creating thrust opposite the motion imparted to the fuselage by the torque effect of the main rotor. Example: MD-900

Refer to Wikipedia for more!


What is the unit for ground speed reported by ADS-B?

ADS-B* encodes the ground speed in NM/s (nautical miles per second) in $2^{15}$ increments of ≅ 0.22 knots each such that:

  0 ≤ Ground Speed < 2 NM/s

As of June 2015*, it is optional to report the ground speed (users can use two position reports to get the speed). Decoding to Knots (NM/h) is more common though for aviation for most of the world.**

* Eurocontrol Standard Document For Surveillance Data Exchange
** ICAO (Annex 5) recommends km/h but permits the 'temporary use' (as they put it) of non-SI alternative units for vertical/horizontal distances and speed.


What hardware standards should the flight control computer pass?

In the US for commercial aircraft, SAE-ITC provides recommended design standards in ARINC Characteristic 701-1 Flight Control Computer System (FCCS).

The recommended environmental standards are in Attachment 6 of ARINC 701. This references environmental categories defined in RTCA DO-160. The issue is that ARINC 701 references an earlier version of DO-160 than the current DO-160G.

The main reason ARINC 701 has not been kept current (701-1 was the last update in 1983) is that the aircraft manufacturers consider the FCC an integral part of the aircraft and they provide the detail design specifications to their FCC supplier. The specifications typically reference DO-160 (whatever version is current when designing the aircraft). The actual categories and test levels are specified based on their analysis of the environment where the equipment is installed in the aircraft.

To summarize; the FCC hardware will have to meet the customer's specification which is usually in terms of RTCA DO-160 tests and categories. The actual levels are unique to each aircraft.


Does the "Maintenance Indicator" sign on a METAR imply we can't trust it?

Not necessarily.

Automated stations have a number of sensors for detecting,

Wind speed and direction
Visibility
Obscurations to vision
Cloud coverage and ceiling
Temperature and dew point
Barometric pressure and altimeter setting
Precipitation
Freezing rain (Icing)
Lightning (thunderstorms)

It is likely that some of these are not functioning properly, while the others are working correctly. In such cases, the METAR reports contain sensor status indicators which give information about the sensor which has failed. For example, consider the following METAR:

  KMEM 230853Z AUTO 18014G18KT 10SM CLR 16/M02 A3008 RMK AO2 SLP117
       T01561022 TSNO $

Here, TSNO indicates that the automated station is equipped with a lightning detection system and that sensor is not operating. Following is a list of sensor status indicators:

RVRNO- Runway Visual Range is missing.
PWINO- Present weather identifier sensor (is fitted and) is not operating
PNO- Tipping bucket rain gauge sensor is not operating.
FZRANO- Freezing rain sensor is not operating
TSNO- Lightning detection system sensor is not operating
VISNO_LOC- Secondary visibility sensor is not operating.
CHINO_LOC- Secondary ceiling height indicator and that sensor is not operating.


How does the FAA BasicMed affect the safety pilot for somebody flying under the hood?

Short answer: the safety pilot with BasicMed must be acting as PIC, but all other regulations and considerations are the same (i.e. as if the safety pilot had a regular medical).

You have quite a lot of points in your question, but I'll try to break it down.

"[...] aren't safety pilots acting as PIC because they are required crewmembers?"

Not always. Being a required crewmember is not necessarily the same as being PIC, e.g. a typical airliner requires two pilots but only one of them is PIC. When you fly with a safety pilot there are two ways to do it:

The safety pilot acts as PIC; the pilot under the hood is a required crewmember
The pilot under the hood acts as PIC; the safety pilot is a required crewmember

As you (and the FAA FAQ) said, BasicMed only allows pilots to act as PIC, not as non-PIC required crewmembers. Therefore only scenario 1 is possible for a safety pilot with BasicMed.

Practically speaking, scenario 1 is what most people do anyway, because it allows both pilots to log PIC time; remember that acting as PIC and logging PIC time are two different things. (In scenario 2 the pilot under the hood would log PIC time but the safety pilot would log SIC time.)

"a BasicMed pilot can only be a safety pilot in VMC"

The concept of a safety pilot only applies to VMC; in IMC you're in real instrument conditions, not simulated ones. Perhaps you meant VFR, not VMC? This question (which you already found) is about acting as a safety pilot under IFR.

"Can I be a safety pilot for a non-instrument rated pilot when I have my BasicMed physical, as long as the flight is in VMC?"

Yes, if you act as PIC, as described above. And again, a safety pilot is only needed in VMC.

"Can I log PIC time while the pilot under the hood is flying?"

Yes, and this has nothing to do with BasicMed. Because simulated instrument flight requires a safety pilot (91.109), that means that if you're the safety pilot and acting as PIC, then you can log PIC time as described in 61.51(e)(iii) (emphasis mine):

  When the pilot acts [...] as pilot in command of an aircraft for which more than one pilot is
  required under the type certification of the aircraft or the
  regulations under which the flight is conducted


Is a night VFR rating a prerequisite for an EASA CPL?

According to FCL.610 (IR - Pre-requisites) you need to have a PPL or CPL and a night rating to apply for the IR.
If you do not have the IR, the night flying qualification (NFQ) is no requirement to start training for the CPL. According to the AMC appendix 3 of the Notice of proposed Amendment (NPA) No. 2008-17B night flying is part of a training course for the CPL.And FCL.315 states, that the applicant for a CPL shall complete a trining according to the appendix 3, cited above.

SO: If you have the IR, you should also have the NFQ but you do not need the NFQ to start training for the CPL.
However, you only need 5 hrs night flying to get the NFQ and there is no examination, i.e. the FI rates your skill.


Why does the DC-9's antiskid system have to be manually disarmed during landing rollout following a ground-shift-mechanism malfunction on takeoff?

Historical yet pertinent note: Concorde was the first plane to have electronic anti-skid, which means the DC-9 (also electronic) had the system installed after entry into service.

The relevant patent for this answer is: Anti-skid control system for aircraft.

The nose gear ground shift is part of the anti-skid system (see below; click to view).

  Source: DC-9 FCOM

Here's how the circuitry works:

In flight (mode), the ground shift fakes a fast wheel spin, but with no actual wheel spin, the circuitry then thinks there is a lock, and sends a brake release signal. This ensures the plane doesn't touch down with the brakes on.
After touch down and wheel spin, speed transducers send AC signals, which are converted to DC for the circuits.
Once the wheels are above 10 MPH, the brake release signal is removed, i.e. braking is now allowed.
Once firmly down with the gear compressed (nose gear in the DC-9), the squat switch switches off the fake signal. However, that takes full effect only when the circuit is de-energized, which happens when the wheels slow down below 23 MPH (20 knots).

In the case here – with the plane still in flight mode due to the pulling of circuit breakers after the malfunction – any time the plane is stopped (or circuitry is de-energized), the circuitry would release the brakes (thinking there's a lock).

Note: The newer MD-80 has the same procedure minus the manual disarming of the anti-skid, which hints at newer circuitry.


What does the crosshatching mean on this VOR-DME?

You're right. From FAA Aeronautical Chart User’s Guide,

  NAVAIDS in a shutdown status have the frequency and channel number  crosshatched. Use of the NAVAID status “shutdown” is only used when a facility has been decommissioned but cannot be published as such because of pending airspace actions.

Image from FAA Aeronautical Chart User’s Guide, 12th Ed.

FAA is in the process of reducing the VOR based navigation network to minimum levels so as to provide only an alternate means of navigation in case of Global Navigation Satellite System (GNSS) outage. This VOR Minimum Operational Network (MON) is expected to be in place by the year 2020, which will permit non-GNSS guidance to an airport within 100 nautical miles (nm) that has an ILS or VOR approach procedure.


Why does the CF-100 autopilot have a toggle switch labeled 'ATTACK'?

The [Avro Canada CF-100] Mk 4 had collision-course fire control, the new interception method in which the radar and autopilot interlinked to steer the aircraft automatically to launch the rockets in a salvo to pass through a "box" of sky at the same time as the hostile aircraft. It freed interceptors from the need to attack from behind, and in a side on interception gave a much better reflective target for the radar.
— all-aero.com

By coupling the radar to the autopilot, the autopilot would steer the aircraft for a firing solution toward where the [unguided] rockets would meet the target (the CF-100 was armed with Mighty Mouse).

Come to think of it, it's the airborne version of a Torpedo Data Computer.

The [F4D Skyray]'s search radar would be used to locate an incoming bomber after initial vectors. The fire-control system would then direct the pilot on a collision course until it determined that the moment had come to fire a salvo of unguided 2.75-inch folding fin rockets. The pilot would then be free to break away. The collision course and rockets were necessary because there was not enough time to position the fighter for a classic attack with guns.
— U.S. Naval Air Superiority: Development of Shipborne Jet Fighters - 1943-1962 p.143

A similar system was also used on the Douglas F4D Skyray, but it seems it was guidance only, i.e., no steering.
The Skyray text above hints as to why the CF-100 would also have a BREAKAWAY toggle switch.


If the VVI, FPM, airspeed indicator somehow failed you can use fuel flow to help you with your attitude (climbing or descending)?

Without an Attitude Indicator, changes in altitude at a constant power setting gives you a fairly good indicator of pitch. If your Airspeed Indicator, Vertical Speed Indicator, and Attitude Indicator all failed at the same time, you would use your Directional Gyro and your Altimeter to stay straight and level. You would cross check that with your Magnetic Compass and your Turn Coordinator.
If your Altimeter fails you, you would keep wings level with your DG, TC, and Mag Comp while monitoring your Tachometer RPMs on a fixed prop or your Manifold Pressure on a constant-speed prop. This would give you a more immediate indication of pitch than your fuel flow counter. The DG, TC, and Mag Comp in most aircraft work off of separate systems from each other to avoid all three going inoperative at the same time. They are your instruments to indicate bank and turn.
The ASI, AI, VSI, and Altimeter are all pitot static instruments. And iced over pitot tube and static port can cause them to be inoperable. Using you alternate static port or breaking the glass face of your VSI will make your Altimeter work, making this scenario a non-issue.
Using a built-in GPS or an external AHRS like the Stratus will give you an unofficial altitude in a pinch.


No, you were not nearly involved in an accident.

If the flight crew is ready to go, an Airbus A320 takes about 40-50 seconds from the moment take-off clearance is given until lift-off. As soon as the aircraft is off the runway, the next one can land. On some busy airports, 60 seconds between take-off clearance and the next landing is a daily occurrence.

In 60 seconds, there is a lot that can prevent an accident. For example, ATC could instruct the incoming aircraft to go around should the departing traffic not be ready to take-off. This is quite a normal event which happens every day at busy airports around the world. In such a case, the aircraft ready for take-off would have to wait for the incoming traffic to pass overhead. It sounds like you may have experienced such an event.

Here is a video of something similar happening in Birmingham.

Since it is a 'normal' event, there is no central database that tracks these issues.