How realistic is Google Earth Flight Simulator?

It is very unrealistic in most respects.

I believe there are a number of important ways you can measure realism from a pilot's perspective:

view out the windows
appearance of instrument panel
mode of operation of pilot aids like autopilot, autothrottle
flying controls

physical character
responsiveness

interaction with ATC
effects of wind, weather, turbulence, rain, ice
aeronautical characteristics of aircraft

It would be easy to focus solely on the last of these, but from my perspective this is not really the most important.

Here's a few dissimilarities that occur to me.

View

The SR22 doesn't have a HUD.

I'm pretty sure the SR22 cockpit windows would take up a much greater area of my vision than my computer screen does. Especially peripheral vision. Also in a real SR22, there is important stuff to look at below the windows.

Instruments

Do these look alike?

Controls

In Google Earth you don't have anything like the range of controls that have to be used, where are all the switches, knobs and other dohickeys you find in the real SR22?

Waving a mouse around is nothing like moving a control column around. With a control column you have a much different sense of the position of the controls. Moving a mouse involves completely different muscles and different motions.

Moving a throttle lever is completely different to pressing PgUp and PgDn buttons to move a throttle position in increments

Feel

In Google Earth you don't hear any engine, you dont feel any vibration, you don't feel any turbulence, you don't feel anything in an uncoordinated turn or when pulling out of a dive, you don't feel the unevenness of a runway.

It's hard to really feel oriented in a simulator when your sense of balance and peripheral vision tell you you are sitting upright at your desk, not inverted and spinning towards the ground.

Disclaimer

I'm not a pilot, I have sat in the pilot's seat of a small Cessna and manipulated the control-column and rudder to make a few turns and attempt to maintain speed and altitude under the direction of a pilot. I've done the same in a glider, and I have done some take-offs and landings in a fairly amazing full (though static) commercial 737 simulator with full cockpit reproduction (all seats, panels, motorised levers, switches etc that you'd find in a real 737 cockpit, wired to a large rack of computers).

 A more realistic simulator

Google Earth is nothing like any of them in almost any respect.

It's a fun game though.


Is there a way to prevent (not relieve) the hotspot caused by wearing a headset for long periods of time?

The best way to prevent the "hot spot" pressure point from the headset band is to wear a headset that doesn't have a top band (like this or this). Of course this requires that you be able to wear an in-ear headset, and some people are more bothered by that than by the headband.

Short of wearing in-ear headsets there are numerous different headset band pads you can try - I know at least one person flying with this sheepskin pad.
Some combination of the right headband position and the right pad should make your headset more comfortable for long flights.


Why don't commercial aircraft use all-movable tail surfaces like my RC plane?

What is better and easier for small-scale models is not necessarily better for larger aircraft.

First, you can't say that the fixed part "does nothing". The tail is primarily a stabiliser; without it, a normal airplane will not fly at all. Only then it is a control surface, which allows it to fly well and how you want it.

Consequently, the size of the tail is primarily driven by stability considerations. For control, you need a certain amount of it and not too much more. If you have an all-moving tail, you may find that you need to move it only very slightly, or else control will become too sensitive. This is not necessarily easier to do.

From design point of view, the all-moving tail requires that the whole stabiliser was attached to a single shaft. On a small RC plane you can afford to make it of a simple wire. On a large aircraft, this translates to something bigger than your suburb water supply pipe: stabilisers of planes like A380 or An-124 are larger than wings of some airliners. Apart from the scale problem, this makes it a single point of failure, which makes it still heavier to be reliable.

Another design problem is nice aerodynamic coupling between the moving tail and the fuselage. Often designers have to invent something like this (A330):

Source

Overall, it is usually easier and lighter to make a conventional tail and attach an elevator (and rudder) to it.

Nevertheless, quite many airplanes have an all-moving stabiliser. There are several different reasons for this.

To accommodate a large range of centre of gravity (CG) locations, i.e. load distribution, and/or different aerodynamic configurations (e.g. flaps). This requires a large amount of control. But this control is typically 'slow': the load or configuration doesn't change in fractions of a second. So the tail is split between the slow all-moving part providing the so-called trim, and the fast conventional elevator. Most airliners have such arrangement, like the A330 from the above picture. But the largest ones, the An-124 and -225, don't use it: too hard. They entirely rely on the elevator.

There is rarely such a demand for the vertical tail: airplanes are more or less symmetrical, so rarely will you find an all-moving vertical stabiliser like this.
To provide easier load balance for small airplanes with reversible control, i.e. those where the control surfaces are moved by the pilot's muscle force. If you make an elevator on normal hinges, it may be quite hard to move it at high speed. Various tricks are used to make the force comfortable (which should be 'just right', not too much, not too small). But one of the straightforward solutions is to make the whole tail move about a carefully chosen axis. For smaller GA aircraft, the scale problem is not too bad yet, so many designs use this approach, for example, Piper PA28

Source

(The thing you see at the trailing edge is not a traditional elevator, it is the anti-servo tab that provides the 'just right' force).
Normal elevator control efficiency. Sometimes, airplanes just need more control than the normally-sized tail can provide. This primarily applies to agile supersonic aircraft. There are several reasons for it:

Agile manoeuvring obviously needs more control;
At supersonic speeds, pitch stability (and thus control effort) increases significantly;
Elevator efficiency falls. The thing is, at subsonic speeds, the normal elevator redistributes the airflow over the tail such that more air is affected than just the area of the elevator assumes. The relation is $\sqrt \frac{S_{elevator}}{S_{tail}}$, so if you have elevator occupying half the tail, its efficiency will not be just $0.5$, but $\sqrt 0.5 \approx 0.7$ compared to the all-moving stabilator deflected to the same angle. But at supersonic speeds this doesn't apply, and the relation is just linear. So all-moving surfaces make more sense. Occasionally, you can even find an all-moving vertical tail, like on Tu-160 (note it has all-moving horizontal tail as well):

Source


How should a pilot respond verbally to being cleared for takeoff?

This is how FAA recommends (PDF):

  A typical takeoff clearance may state, for example, “(Callsign) 123
  RNAV to MPASS, Runway 26L, Cleared for Takeoff”.

  The expected pilot response is, “(Callsign) 123, RNAV to MPASS, Runway
  26L, Cleared for Takeoff”.


What's the benefit of this long flight (apart from marketing)?

From the this link:

  At 15:38 local time N7874, the fourth 787 built, departed Boeing Field in Seattle for an 18-hour, 22 state test flight. The crew spent the overnight hours above the United States performing ETOPS testing on the new Rolls Royce Trent 1000 TEN engine, which will power the 787-10.

Also this video from the above flightradar blog link.

The 18-hour flight was to test ETOPS, and there's no harm in some marketing as well. Also since the flight will be coming back to Seattle, it makes sense to keep the flight above the US, and near airports. Compared to venturing out in the ocean on a test.


Was there an incident when Airbus autopilot wasn't letting the airplane land?

I believe this is a hoax1. I've read through several documents describing the protections provided by Airbus flight laws (this is not autopilot; autopilot is a separate layer on top of it) and have never seen any mention of any kind of ground proximity protection. Only standard (E)GPWS which yells "terrain, pull up".

Update: Of course now there is EGPWS that gets aircraft position from GPS and can yell "terrain, pull up" when there is no airport ahead, but 25 years ago there was only GPWS based on radar altimeter which didn't know anything about position and would switch to simply read out2 the radar altimeter value whenever gear (and maybe also flaps; not sure here) was extended.

1Might have been even attempt at FUD against the then novel technology.

2That is say "one thousand", "five hundred", "two hundred", "one hundred", "fifty", "forty", "thirty", "twenty", "retard"3 (and "ten" or "five" when it stops saying "retard" and the wheels are not on the ground yet). This is useful during approach so the pilot can concentrate less on the instruments and more on outside reference and in the final phase to help judge when flare should be initiated. It will also warn "sink rate" when the sink rate is excessive (more than -1000 ft/min, the stabilized approach criteria).

3At 15 or so feet, if the thrust levers are not in idle gate, the Airbus system starts announcing "retard" and keeps announcing it until the thrust levers are placed in the idle gate (or reverse). This is specific to Airbus. I believe it can also announce "minimums" when approach minima are configured in the flight management system.


How should I build removable wings on a home build?

Planes on board of aircraft carriers have this: they need to fit all next together in a tight space, so they are made with foldable wings. This photo shows the folding mechanism:

Image source

Both sides of the split end in a full rib plate.
The two ends are connected via two large pins. The upper pin is the fold-up hinge, the lower pin is moved in-out via a hydraulic cylinder.
Aileron control is via a push-pull rod, with a connection bolt right at the wing hinge point, so that the wing part of the linkage can fold up/down.

The vertical black rod keeps the wing up. If one would like to remove the wing completely, only the upper wing pin and the aileron push-pull connection rod would need to be disconnected.


What is the theoretical maximum speed of a rocket-powered aircraft in the atmosphere?

The upper limit is given by the L/D of the rocket-powered vehicle and its thrust.
In order to follow the curvature of the Earth so it will stay within the atmosphere, the vehicle must create enough downforce by flying inverted so it can bend its flight path enough to not escape to outer space.
A practical altitude for flying this way would be dozens of kilometers up in the higher atmosphere, so drag and heat loads stay manageable. For the L/D I use the approximation given by Dietrich Küchemann (replace with a more recent one if handy):
$$\left(\frac{L}{D}\right)_{max}=\frac{4\cdot(Ma+3)}{Ma}$$
which would result in an L/D of 4 for Mach growing very large. Add to this the effect of gravity and your maximum downforce is the weight of the vehicle plus four times its rocket thrust. This force now has to balance the centrifugal force which results from flying at constant altitude:
$$m\cdot g + 4\cdot T = \frac{m\cdot v^2}{R_{Earth}+h}$$
where $R_{Earth}$ is the earth radius of approximately 6367 km and $h$ the flight altitude above ground. Now solve for flight speed v:
$$v=\sqrt{\left(g + 4\cdot\frac{T}{m}\right)\cdot\left(R_{Earth}+h\right)}$$
By flying in dense air close to the ground the lift force will be immense, but so will be the required thrust. Since flight altitude is small compared to the radius of the Earth, the equation can be simplified with a small loss in accuracy:
$$v=\sqrt{\left(g + 4\cdot\frac{T}{m}\right)\cdot6.400.000 m}$$
A more precise result would now add the effect of Earth's rotation, so flying eastwards along the equator will reduce flight speed by 464 m/s and add the same amount to the speed calculated above when flying westwards.


What needs to be considered when changing a tire during boarding/deboarding?

I have never seen an airline (or the military) have a maintenance procedure where a tire can be changed with pax on board the aircraft. Normally, if the problem is found when pax are on the aircraft, they are asked to deplane, the maintenance is done and the pax are then boarded once more. The biggest reason is that pax moving inside the aircraft can cause the aircraft to move and the jack to tilt and cause the landing gear to hit the ground. Without a tire, that could be really bad news.


How long is maximum time to investigate an airplane crash?

According to ICAO, a preliminary report must be released after a year. There is no hard timeline for the full report:

What are a State’s reporting obligations during and after an aircraft accident investigation?
Under Annex 13 to the Chicago Convention, States in charge of an investigation must submit a Preliminary Report to ICAO within thirty days of the date of the accident, unless the Accident/Incident Data Report has been sent by that time. Preliminary Reports may be marked as confidential or remain public at the investigating State’s discretion.
The State conducting the investigation of an accident or incident shall also make the Final Report publicly available as soon as possible and, if possible, within twelve months.
If the report cannot be made publicly available within twelve months, the State conducting the investigation shall make an interim statement publicly available on each anniversary of the occurrence – detailing the progress of the investigation and any safety issues identified.

Keep in mind there is no established penalty for not complying with the above. Indeed in some cases (or countries) it can take up to a decade for a final report to be published.


Are turbine engine reconditioned after severe FOD damage caused by bird strikes?

The damage is assessed and then a determination is made whether or not its economical to repair the engine.  It will truly be taken on a case by case basis.  However, FOD damage to the engine doesn't automatically mean the engine will be scrapped, and I think you'd be surprised with the damage they can suffer and still remain in service after repair.


What is the fuel consumption of an aircraft in a holding pattern?

The fuel rate while holding depends on elements such as weight, altitude, speed and aircraft configuration.

Airbus uses the concept of green dot which is the speed with minimum fuel consumption per time unit in clean configuration.

This table shows fuel needs for a A330/A340 at 170 tons and 1,500 ft:

Fuel flow vs. speed. Source

While the green dot speed is the one offering the best fuel rate while holding, it assumes no flap and no slat. This speed may not be practical for certain airports where slats or flaps are advisable due to the rate of turn in the holding pattern.

To provide the necessary flexibility, Airbus publishes the fuel rate for three other combinations of speed/configuration (S speed is the minimum speed for flaps retraction):

Fuel flow vs. weight for 4 configurations. Source

Altitude is also a factor preventing an optimal fuel flow. Example for the green dot speed:

Percentage added when departing from the optimal altitude. Source

The total fuel required to hold can be somehow minimized by not flying at cruise speed when it is known that a hold will be required at some point. Savings can be done by flying at green dot speed to the holding point:

Source

That means determining the fuel flow depends on airline operating procedures and holding pattern design (e.g. altitude), but a maximum can be roughly predicted by looking at the manufacturer published documentation.


Can a private pilot refuel his small private airplane internationally without passing through immigration or customs?

While it depends on the country, expect to have mandatory immigration checks on first port of entry in most countries. I know this to be true for the US, Canada, Britain, Russia and the EU (Schengen area). Usually only emergency landings are exempt. But they may lead to investigations so not really an alternative to declare one in each and every country.

Usually it's best to hire a service provider to prepare all the paperwork for your trip. While their main business is to prepare commercial flights (non airliner), most also accept private pilots as clients, a few even welcome them. They will not just plan your journey regarding visas, landing and crossing permits (some countries do require preregistration for each and every flight into their territory), but also make sure to pick only airports with the right fuel available, or making it available. Selecting and booking hotels can be included as well.

Anyone I know, who ever tried to fly further than the next door country, sooner or later took such service as it makes a huge difference. Well, some had to make the experiance to get stuck for a week at some border first :))


Do all aircraft need to have horizontal and vertical stabilizers?

Depending on how you classify the control surfaces, the B-2 Spirit does not have a horizontal stab, since it is a "flying wing" design.  As you have changed the question, the other part of the answer is that the flying wings have been able to get by without vertical stabilizers as well, at least in the case of the B-2. It uses both spoilers ("split brake rudders") and thrust differential to accommodate the lack of a vertical stabilizer.

  Northrop had investigated several means of applying directional
  control that would least infringe on the aircraft's radar profile,
  eventually settling on a combination of split brake-rudders and
  differential thrust ~  Sweetman, Bill. "Lockheed Stealth" (2005) ISBN 0-7603-1940-5., p. 73

(And as with flight controls in general on the on B-2, that's helped a lot by its fly by wire flight control system).

As the Germans discovered in their flying wing aircraft (Ho229), and the USAF in the YB-35 and YB-49 programs, flying wings have inherent instability, even though some early biplane "flying wing designs" were stable enough to fly. (Dunne).

The B-2 has a fly by wire system to retain stability and handling qualities so that it does not have to make tradeoffs (loss) in performance that earlier flying wing designs did in order to make the design "stable enough."

What the elevator/horizontal stab do for conventional aircraft is allow for longitudinal control (pitch control).  If you don't choose to use that conventional method, the "effect" is that your design must find another way to establish longitudinal control and stability or the aircraft risks being unstable in that axis.

Likewise with vertical stabilizers, your design has to address stability in the yaw axis if you want to make it without a control surface acting in that axis.


How would the wave drag of an elongated Sears–Haack body change with a cylindrical mid section?

No it will not have the same wave drag.

The low wave-drag of a Sears-Haack-Body is achieved by the smoothness of the body. This means kinks are not allowed. The picture below shows the Mach-Number distribution around a Sears-Haack-Body (taken from YAMAZAKI 2014). Notice the gradual change of the Mach number along the body surface .

The following illustration shows the proposed elongation of the body by inserting a cylinder.

By adding a cylinder the curvature of the body does not change gradually (smoothly) but stops - stays constant - and starts again.

This will trigger a Prandtl-Meyer-expansion (example below, taken from here) which will distort the smooth flow around the body and thereby increase the wavedrag.


Why is the A320 pre pressurised before take-off?

In general, you want the cabin to be

pressurized in flight, and
not pressurized on the ground

If the system followed only & exactly that logic, at the moment of liftoff it would start pressurizing immediately, with the goal of overcoming the sudden change in pressure due to the aircraft's rapid climb away from the ground, but not more than that so that you don't pressurize below ground level all at once.  In practice, that ends up being a pressure "bump" right at (or slightly after) rotation, which is undesirable since it is at least noticeable and potentially uncomfortable or startling.

To prevent that pressure bump, the pressure controller is programmed to slowly pressurize the cabin slightly while the aircraft is still on the ground, so that at liftoff it is essentially maintaining the differential it has, rather than starting pressurization all at once.


What is the make and the model of this seaplane?

This is a Progressive Aerodyne SeaRey, a kit aircraft. Also on:

Wikipedia and
Youtube.

About 500 of this make had been built up to 2011 according to the Wikipedia article.

(Source: Light Sport Hangar Flyin')

This one is seemingly registered in the Philippines ("RP"), I read that at some point experimental aircraft had been grounded in the Philippines, but don't know if this was temporary only.


What is the rationale of a weight/passenger value for the ICAO TCAS requirement?

The numbers aren't random, though at first glance the rationale may not be obvious.
Weight
5700 kilograms is (roughly) 12,500 pounds - This aligns with the FAA definition of a "large aircraft" (an aircraft with a maximum certificated takeoff weight of more than 12,500 pounds).
Large aircraft tend to be "working airplanes" in passenger or cargo service, and will be operating to/from busy terminals. They will therefore benefit substantially from TCAS, and the operators can theoretically afford to equip their fleets.
Seating Capacity
Carrying more than 19 passengers further includes aircraft which may not be "large aircraft" but might be used as "working airplanes" in regular airline/commuter service carrying passengers (and would therefore benefit from TCAS, and theoretically be producing revenue to offset the cost of equipping them).
This roughly aligns with FAR 121.391 flight attendant requirements (Even relatively small aircraft - maximum payload of 7,500 pounds or less - are required to have a flight attendant on board to assist in evacuation in the event of an emergency, so it logically follows that such aircraft should be equipped with TCAS to avoid at least one possible type of emergency (mid-air collision).

As Federico pointed out, this is largely a cost/benefit trade off (nobody would argue for a flight attendant on a Cessna 150, similarly the TCAS safety features would be overkill for most Cessna 150s in the world).


There has been some reports which have noted a higher than average incidence of certain cancers in aircrew. The reports are somewhat inconclusive

  Overall, the reports suggest that pilots are at increased risk of malignant melanoma, non-melanoma skin cancer, and possibly acute myeloid leukemia, and that cabin crew are at increased risk for breast cancer and malignant melanoma. However, the question remains as to whether the observed excesses are due to occupational exposures or non-occupational factors, such as reproductive history and lifestyle

Source: British Medical Journal

Research is ongoing.


Is having a history of seeing a therapist not allowed for pilots?

This can be difficult to answer, but I'll try from a US/FAA perspective.
Military Service
If you want to become a military pilot you cannot have any history of mental or psychological disorder This is from the perspective of starting out to become a military pilot. If you are already a military pilot and have some kind of mental/psychological issue that you need addressed, there is a process for doing that and returning to service. From this standpoint, self-help and "keeping it to yourself" is better than seeking treatment since you will be disqualified outright.
Personal Anecdote
How do I know this? This is exactly what happened to me. I had seen a psychologist when I was 8 or 9 years old (because he was a quack and convinced my mother (who was being treated for depression) that I needed help too). This made it into my permanent medical record. I applied for military service with the US Marines during college with the goal of becoming a pilot. I took the Air-Force Officers Qualifying Test (AFOQT) and passed with a 98% (the highest my recruiter had ever encountered). When it came time for my MEPS review they found the history (I disclosed it at the beginning, they found it via my disclosure and I provided additional documentation when asked) and disqualified me. I appealed to the review board and was denied. I appealed again, denied, and you only get two appeals (and the only recourse after that would be a Congressional/Presidental appointment). They told me I was eligible to enlist, but not eligible to be an officer.
FAA Medical Perspective
The FAA takes a different stance in that you are required to disclose to the AME any mental health visits during the previous three years. The AME will then decide if it warrants additional testing or review by the Office of Aeronautical Medicine (OAM). The FAA can also get this information via other methods (for example if your employer reported you or you are jailed for some kind of mental health disorder outburst).
Certain conditions are automatically disqualifying, such as psychosis, bipolar disorder, and severe personality disorder.
Employer Perspective
There are laws in the US protecting employees from being discriminated against for mental health issues. Many companies have reporting and monitoring programs that assist a pilot with a psychological issue to seek help and get back to flying. The FAA participates in these programs and provides a "rigorous evaluation" before allowing the pilot to return to flying.
So from a commercial service perspective it is important to be open about the issues upfront and early, especially with your AME. Pilots have been arrested for denying mental health history.


What causes the inside glass of flight instruments to get hazy?

This can depend on what the actual instrument is and what (if anything) the glass is coated in.

In some cases the instrument may not have a glass panel at all, it may be acrylic or any other type of similar material. You are mot likely seeing sun damage in this case.
It may be mold or fungus. Camera lenses suffer from a similar issue. If the aircraft resides in a humid environment, maybe even trapped in a damp hanger you can get build up. Since instruments get rebuilt sometimes (some more often than others) they are opened up and resealed quite a bit in their life times. This may not always happen in a perfect environment and even a small amount of fungus can quickly damage something.
It could be interior lubricants (oil) that are thrown around the instrument as it spins at high speed.
Some of the older units are not sealed, and for that matter some may even be vented to the atmosphere as is suggested here.
It could be dust drawn in through the vacuum system that the filter failed to draw out.

  Vacuum systems are very common for driving gyro instruments. In a
  vacuum system, a stream of air directed against the rotor vanes turns
  the rotor at high speed. The action is similar to a water wheel. Air
  at atmospheric pressure is first drawn through a filter(s).


Does a high "wing loading" require a high approach speed or does it cause a high approach speed?

It's the first of your options.

The effect of reduced drag with reduced wing area is dominant only at high speed, when friction drag is dominant. At low speed induced drag is the major source of drag, and with a given planform a smaller wing will create more drag at the same speed, not less.

Due to the possibility of wind shear or gusts you should keep some margin to your stall speed during approach, right down to the flare. Therefore, the safe approach speed dominates the landing distance, as Raymer writes.


How many aircraft can airline put in hangar?

There are no restrictions. You can put as many aircraft into a hangar as you can fit into it.

Some commercial hangars are neatly arranged.

Some are not as neatly arranged but efficiently packed.

And sailplanes can be lifted and hung from the ceiling for more space on the ground.


The F16's maneuver envelope is better under 15000 feets but usually they will go much higher altitudes. Why?

For most aircraft, the advantage of flying high is that the air is thinner, so you go faster for the same fuel burn.

For fighters, height gives you the ability to dive to gain speed, giving them the option for intercept a lower plane, or run away faster than a lower plane can follow. If they're relying on their own radar, it also allows them to see further around the curve of the earth. As Ron mentions, it also puts you out of range of some SAMs, and gives you more time to react to others.

Lastly, while the F-16's manoeuvre envelope may be better at lower altitude, what matters is the manoeuvre envelope of the aircraft they might have to fight, and the altitude they choose to fight at. The relative difference between the two types is more important than any absolute value.


How to start deriving longitudinal equations of motion for an aircraft?

Note: Answer in progress!

Part 1
(Unfortunately I'm only familiar with #1 and #3 at the moment, not #2)

(Footnote: This might be a bit simpler than your case, but hopefully it you'll be able to fill in the remaining gaps)

From this, you can some the forces up according the direction of the velocity or the lift  vector. Doing this horizontally, you get equation 1, and likewise for vertical direction your equation 3.

To make this simpler to handle, we use small angle approximation consider $\cos(0)=1$ and $\sin(0)=0$. This simplifies down to:

$$V:0=T-D$$

$$L:0=mg-L$$

(i.e. thrust equal to drag, lift equal to weight)

Part 2:

This is basically the equations of a kinetic diagram of the Free Body Diagram above, where there can be a change either in airspeed of altitude. What your second equation says is that excess thrust (T-D, Thrust-Drag) can:

be used to increase altitude: $m\times{g}\times\sin(y)$

and/ or

be used to increase airspeed: $m\times{v}$


What could these possibly incorrectly translated numbers for aircraft speed have been?

I think there is some information lost in translation.

The speeds of 13000 kmph are associated with reentry vehicles. The aircraft won't have had time to accelerate to that speeds in the first place, even if there is no atmosphere.

The (forward) speed is usually measured in mph in US (to the best of my knowledge). The vertical speed is given usually in feet per minute. Note that the aircraft speed is usually given in knots (or its Mach number) by convention.

Now, the numbers you've quoted:

7000 When the autopilot disconnected, the roll angle increased in two seconds from 0 to +8.4 degrees. In response, the Pilot Flying (PF) applied nose-up sidestick inputs, which the Investigation termed as abrupt and excessive. As a result, the aircraft started to climb at 7000 ft/min.
200 The (vertical) speed at impact was around 108 knots (10,912 ft/m), which is around 200 kmph.
13000 I'm not sure about this one. The maximum altitude reached was less than this value (~11500m actually), so doesn't make sense. The only thing that is related to this number for that flight was the depth at which the wreckage was found- 3,980 metres or 13,060 ft.

Note: Most of the data is from the Final accident report of Air France 447.


On a procedure turn, do you make the turn on the inside or outside of the procedure turn?

Section 5-4-9 of the AIM contains a lot of guidance on procedure turns, and says (in short):

If the procedure turn is charted as a teardrop or hold-in-lieu of procedure turn, then it must be flown as charted. (Does not apply in this case.)
If it is a standard procedure turn, the barbed arrow shows the maneuvering side (so the first turn should be flown as indicated), but the rest of the procedure is at the discretion of the pilot, as long as they stay within the distance specified on the chart.

I was taught (and see it as a "standard practice") to turn away from the fix defining the start of the procedure turn for the 180 degree turn, and in fact have never seen anyone fly it the other way.  That being said, there is nothing which prevents it if it can be done within the protected area and accomplishes the purpose of becoming established on the final approach course in time.

A small excerpt from the AIM (lots more information is available there):

  5−4−9. Procedure Turn and Hold−in−lieu of Procedure Turn

  ...

  On U.S. Government charts, a barbed arrow indicates the maneuvering side of the outbound course on which the procedure turn is made.
  Headings are provided for course reversal using the 45 degree type
  procedure turn. However, the point at which the turn may be commenced
  and the type and rate of turn is left to the discretion of the pilot
  (limited by the charted remain within xx NM distance). Some of the
  options are the 45 degree procedure turn, the racetrack pattern, the
  teardrop procedure turn, or the 80 degree  260 degree course
  reversal. Racetrack entries should be conducted on the maneuvering
  side where the majority of protected airspace resides. If an entry
  places the pilot on the non−maneuvering side of the PT, correction to
  intercept the outbound course ensures remaining within protected
  airspace. Some procedure turns are specified by procedural track.
  These turns must be flown exactly as depicted.

  ...


For CG calculations, where is the root chord located on a swept wing aircraft?

It's expressed in Mean Aerodynamic Cord. On a swept back wing, you can construct it as follows.


What does a typical discovery flight consist of?

A typical discovery flight is about a 30 minute on the ground introduction to the airplane and the cockpit controls, followed by a sightseeing flight of 30-minutes to one-hour.  The entire process typically lasts 1 to 2 hours.

During the flight, the instructor will have the controls for takeoff, navigation and landing, but may turn the controls over to the passenger for some gentle, easy maneuvers.

You can expect to ask numerous questions and have them answered, but you won't learn a whole lot about actual flying in a short session.

I would advise you to keep your questions to the flight training process, rather than specifics about flying that need more detailed explanations.

Some good questions may be:

How much ground school does it take to get a license?
How much flight time does it take to get a license?
What are some important milestones along the way to getting a license?
Will I have the same instructor throughout my training?
What supplies do I need for training? How much should I expect to spend?


Which manufacturer produced this fan blade?

GE Aviation

Clue 1. Parts designed at the Lynn MA plant have part numbers of the form xxxxTxxPxx, where x is a digit. 4922T12P01 fits that pattern.

The gr.in is another clue. That refers to a weight that would be used in balancing the fan. GE uses units of gr.in. I'm fairly sure that Pratt uses oz.in, snecma uses gr.cm. I'm not sure what RR uses.

But the definitive piece of information is 99207. That is a CAGE code. 99207 is registered to GE Aviation's lynn plant. I looked it up here http://www.govcagecodes.com/


Do airplanes have vapor recovery systems for refuelling?

You are correct on both your assumptions about the fuel vapour. It does have a greenhouse effect, though I would suspect that the amount of fuel required to make the air saturated in the fuel tank is not likely to be more than some tens of grams. It also presents a fire hazard.
However we again face the same issue as with many other systems that would be environment-friendly and safe: the cost.
Companies, both airlines and airport operators, carefully evaluate all cost to benefits. In this particular case the environmental effect is likely to be considered neglible, and the fire risk is tackled with other measures, such as grounding, clear-areas, ventilation etc. Those were covered nicely in the previous questions.


What is "picture flying" and does the FAA define it?

I can't prove a negative, but as CrossRoads pointed out, the phrase "picture flying" isn't used on faa.gov. At least, neither Google nor faa.gov's own search engine turn up any hits.

I searched a bit further and I did find one specific match in a Bendix advert in the Feb 2, 1953 edition of Life:

  Picture flying is the name pilots give to flying with OMNI-MAG. Merely by watching the pointer the pilot always knows where he is,
  where he is going, and how to get there

There's no real technical detail in the advert (it's actually an advert for Bendix television sets!) apart from mentioning that the OMNI-MAG uses VHF radio, but based on the picture it looks like a VOR receiver.

So, given that the FAA seems not to use the phrase at all and the only exact hit I could find was from 1953, I suspect that "picture flying" is an obsolete phrase for following a visual course indication. Before VORs, pilots used audio signals from a four-course radio range and the advert even mentions that they won't have to listen constantly any more.

That makes me think that the phrase arose around the time that radio navigation moved from audio to visual signals, to indicate that the pilot could now look at a visual indicator rather than just listen. That transition happened in the 1950s, so it would fit with the advert's publication.


How to calculate outside air temperature at a certain altitude?

The temperature will drop around 2° Celsius (-1.98 to be more precise) for each 1000 feet you climb.

So if the OAT at 6000ft is -13°C, at 7000ft it will be -15°C, or minus 16 from the International Standard Atmosphere (ISA) which should be +1°C (15 - 2*7 = 1).


Why do some U.S. airlines require passenger headrests to be lowered during takeoff?

The answer appears to be one of clearing the view of the flight attendants. This FAA circular mentions the requirements that a FA be able to see clearly.

  (3)  Direct View.  As used in § 25.785(h)(2) [§ 25.785(h)(1)], "direct view" means direct (line of sight) visual contact with cabin area/main aisle(s), which enables the flight attendant to be made aware of passenger needs relative to safety when the flight attendant is seated with torso restraint (safety belt and shoulder harness) fastened.  Mirrors or other such devices are not acceptable equivalents to direct view, except in those cases where flight attendant proximity to the floor level emergency exit takes precedence over direct view.  Video systems may be an acceptable means of direct view, if the level of conspicuity is equivalent to that provided by line of sight visibility.

This forum thread talks about it with regards to FA regulations

  I have been told by many FA's that the reason for the headrests to be down is for FA visibility during takeoff and landing and taxi when they are in their seats. With them up they don't have a clear view of the cabin.


Why are crop dusting spray booms not integrated into the wing?

Different chemicals use different nozzles and delivery systems.  Many of the spray agents are very corrosive.  Turbulence by the sprayer can be a good thing, as it aids in mixing.

Additionally drag is not a big issue as crop dusters fly slow, and tend to have good power to weight ratios, so the drag of a spray assembly at 70 knots or 60 knots, is not a big concern.  Mixing (with air of) chemicals, reduction of airframe corrosion, and ease of removal are larger concerns.


Do Instrument Landing Systems restrict building heights and can these be overcome?

This is a fairly interesting case as it crosses international borders. Technically, as a sovereign nation they are free to build and approve construction as they see fit. Depending on where you are in the world this is handled in all kinds of different ways. Blocking the runway of another nations airport may not be great for international relations but there is nothing stopping them from doing it. There have been some fairly infamous real estate holdouts that test the limits of what you describe.

As for the latter part of your question, there have been instrument approaches that don't necessarily point you right at the runway initially. as @mfarver notes in the comments the classic example of this is the old approach into Kai Tak Airport which basically pointed you to the side of a mountain. The mountain face was painted in a checked pattern, when it came into view a right turn was executed and you were lined up with the runway. The approach is no longer in use but has been pretty notorious, you can see it in action here. With the prevalence of GPS approaches coming into use all sorts of things can be done that cant be done with a traditional straight line radio signal ILS. The issue with your described approach is that the airplane lands on the runway in the reverse direction which may not always be possible with the current winds.

The other option if things do get in the way is to have a really steep, slam dunk style final approach as they do in St. Barts. This, however can lead to other issues.


Are the student solo endorsements a “package deal” with that one specific instructor?

The FAR's don't talk about whether or not a CFI can accept another instructor's solo endorsement. If the student has the endorsement, the 90 day period has not expired, and the make and model of the aircraft in the endorsement matches, then the student is technically good to go.

That said, a good CFI would carefully review the student's log book and, if necessary, require additional instruction/review before the allows the flight school to rent the student an aircraft. The relevant FAR is 61.87.


How long does it take for an FAA licence to be delivered?

The FAA has, at least in the recent past, been backlogged with some forms and certificate issuance has been one of those items. My private pilot certificate took nearly 3 months to arrive (hence, my temporary certificate almost expired). I had to make several calls to my DPE (Designated Pilot Examiner), who then reached out to the FAA in Oklahoma City to see what was wrong. It turned out a computer glitch had erased my knowledge test report. After several times around, this was fixed and my certificate showed up within several weeks. In the USA they always send it via First Class Mail (uncertified, no tracking number). Last August (2016) my new certificate showing my instrument rating showed up just a month or so after the checkride, so much faster. If you have a question, don't hesitate to reach out to your DPE - they are very helpful and can get things moving again if they're stuck. Also, make sure you keep all test reports and other documents until you receive your certificate in case they somehow get lost in the system. And when you get your new certificate - don't forget to sign the back or it is not legally valid!

Regarding your interview - your temporary airman certificate is valid for all purposes until the expiration date. You can bring this to an interview as it is as valid as the plastic card. I don't know if a company is allowed to reject you because you only have a temporary certificate while your plastic one is being prepared - I'd look into this and maybe ask an attorney as that doesn't seem like it would be legal to me since the certificate is valid.

Cheers!


How are "Owner-Produced Parts" handled under FAA regulations?

The July/August 2002 edition of FAAviation News (now FAA Safety Briefing) has a detailed article on owner-produced parts, including advice on best practices if you want to make your own parts. It does confirm that owners have very broad authority to do so, provided that they document everything properly.
Typical reasons for producing your own parts are (I've paraphrased them from the article here):

The aircraft has been out of production for years
The aircraft is an orphan without a Type Certificate
There is no technical support because the aircraft is so old
There may be long delays in getting parts from the manufacturer
The price of official parts is extremely high

As for requirements of the part itself, the article list four characteristics that a part must have:

The part must be properly designed
The part must be produced to conform to the design
The part's production must be properly documented
The part must be properly maintained

The owner must be involved in the production but doesn't actually have to do the manufacturing himself:

The aircraft owner must participate in the manufacture of the part
in at least one of five ways for it to be considered an Owner Produced
Part.

The owner provides the manufacturer of the part with the design or performance data.
The owner provides the manufacturer of the part with the materials.
The owner provides the manufacturer with fabrication processes or assembly methods.
The owner provides the manufacturer of the part with quality control procedures.
The owner personally supervises the manufacture of the new part.

More recently, in the September 2014 edition of the Cessna Pilots Association magazine, Mike Busch has an article on replacement parts that calls the current regulations on owner produced parts "extremely liberal":

“Owner-produced parts” do not require a  PMA. These are parts produced
by an aircraft  owner for use on his own aircraft, and not  offered
for sale. There is an FAA letter of  interpretation that sets forth
precisely what  an owner's involvement must be to qualify a  part as
“owner-produced,” and it is extremely  liberal. The owner need not
actually  manufacture the part himself, so long as  he provides
specifications or materials  or supervision or some other meaningful
participation in the part's production.

Unfortunately, he didn't mention exactly which letter of interpretation covers these parts but the FAA magazine article refers to an "FAA Memorandum dated
August 5, 1993" and I guess it's probably the same one. I wasn't able to find it on the FAA site.


Is there any equation to bind velocity, thrust and power?

A propeller accelerates the air of density $\rho$ which is flowing through the propeller disc of diameter $d_P$. This can be idealized as a stream tube going through the propeller disc:

The air speed ahead is $v_0 = v_{\infty}$ and the air speed aft of the propeller is $v_1 = v_0 + \Delta v$. The propeller effects a pressure change which sucks in the air ahead of it and pushes it out. Since the mass flow must be equal ahead and behind the propeller, the stream tube diameter is bigger ahead of the propeller and smaller downstream. In reality, there is no neat boundary between the air flowing through the propeller and that surrounding it, but for computing thrust this simplification works well if the airspeed is identical across the cross section of the propeller disc.
The mass flow (mass $m$ per unit of time $t$, written as a derivation) is: $$\frac{dm}{dt} = \pi \cdot\frac{d_P^2}{4}\cdot \rho \cdot \left( v_{\infty} + \frac{\Delta v}{2} \right)$$
The mass flow is written as the volume of air with density $\rho$ per time, moving through the propeller disk with the diameter $d_P$ at a speed that is the median between entry and exit speed. The thrust is mass flow times speed change: $$T = \pi \cdot\frac{d_P^2}{4}\cdot \rho \cdot \left( v_{\infty} + \frac{\Delta v}{2} \right) \cdot \Delta v$$
If the engine has the power P, the thrust is net power divided by airspeed in the propeller disk. To arrive at the net power, you multiply the rated engine power by the propeller efficiency $\eta_{Prop}$ and the electric efficiency $\eta_{el}$: $$T = \frac{P\cdot\eta_{Prop}\cdot\eta_{el}}{\left( v_{\infty} + \frac{\Delta v}{2} \right)}$$
A good engine will have an electric efficiency above 90%, and a good propeller will give you an efficiency between 80% and 85%. Efficiency goes up with lower $\Delta v$, so a big, slowly spinning prop is better than a small, fast one.
An airship will not move fast, so the $v_{\infty}$ is low. In the static thrust case it is zero, and the thrust equation can be simplified:
$$T_0 = \frac{P\cdot\eta_{Prop}\cdot\eta_{el}}{\sqrt{\frac{2\cdot T_0}{\pi\cdot d_P^2\cdot\rho}}} = \sqrt[\LARGE{3\:}]{P^2\cdot\eta_{Prop}^2\cdot\eta_{el}^2\cdot\pi\cdot \frac{d_P^2}{2}\cdot\rho}$$
To actually know your $v_{\infty}$, you need to know the drag $D$ of your airship. The general equation is $$D = A\cdot c_D\cdot\frac{\rho}{2}\cdot v^2$$ with $A$ the frontal area of the ship and $c_D$ its drag coefficient. S. Hörner (page 14-1) gives the drag coefficient of LZ126 (later Los Angeles) as $c_D = 0.023$ for the hull alone and $c_D = 0.071$ for the complete ship, including nacelles, fins and all.
A similar result is given in NACA Report 394 which documents the tests done on models of Goodyear Zeppelins in the NACA variable density wind tunnel in 1932. There is another source, NACA Report 117 by Max Munk, written in 1921 and supposedly collecting the results of German measurements on Zeppelins which can be found here.
Your model will not achieve such low values, however, because it will fly at a lower Reynolds number, which means that friction will be higher in relation to other forces. Depending on the size and speed of your model, pick a value between 0.15 and 0.3 for first calculations.


How to make ourselves more visible to other aircraft?

Transponders, ADS-B (which, honestly, is pretty much just an outgrowth of transponders) and exterior lights have already been mentioned. I'd like to add one more thing: speak up!

You've probably got a microphone right in front of your mouth, which is ultimately connected to a radio transmitter which is hopefully tuned to a frequency monitored by nearby aircraft.

To help make yourself more visible to other aircraft, press the transmit button and give your location and intentions, to let them know at least one place where they should look.

As a real-world example, another pilot did this the other day as I was in the air, saying something like "XX Radio, SE-XXX on downwind 21, for touch and go". My instructor took the opportunity to quiz me about where they should be given that, and they were pretty much exactly where I expected them to be. Not only did we now know where they were (position and, by inferrence, approximate altitude), which we could have known by looking for other traffic, but we also knew what they were planning to do. In this case, there was no risk of a traffic conflict between us, but you never know who else is out there.

Unless the traffic situation is congested, or there's something like emergency traffic going on, the occasional radio call with your position and intentions can do little but help others.


What's the difference between setting auto brakes to MAX vs. RTO in Boeing Aircraft?

For the 737:

RTO is used for takeoff, and puts full hydraulic system pressure to the brakes. The other autobrake settings, 1, 2, 3, and Max, are used for landing, and brake to achieve a specified deceleration rates. In autobrakes Max, you get very firm brake application, but it's still something less than unmetered system pressure to the brakes.

In all cases, the anti-skid system will prevent a wheel from locking up by reducing (modulating, actually) hydraulic pressure to a particular brake.


Why can a Pilatus PC-24 land on unpaved and short runways like no other business jet?

The Wikipedia page on the Pilatus PC-24 gives you some hints:

  The PC-24 is a twin-engine business jet, a larger jet-powered follow-on to the earlier Pilatus PC-12. It is considered to be a short takeoff and landing (STOL) aircraft, being designed to operate from short and rough airstrips. It incorporates an advanced wing design, with a large double-slotted flap system to achieve the necessary performance, having a stall speed of only 81 knots at the maximum landing weight. Pilatus has claimed that the PC-24 possesses performance attributes which are unmatched by any jet aircraft on the market. It possesses a takeoff distance of 820 m (2,690 ft) and a landing distance of 770 m (2,526 ft).

...

  The PC-24 is powered by a pair of Williams FJ44-4A turbofan engines. [...] The engines are mounted on the upper portion of the rear fuselage to prevent foreign object damage (FOD) during operations at rough airstrips. Other FOD-reduction measures include the enlarged flaps and chines on the nose wheel of the landing gear. The exhaust ducts of the engines feature an aerodynamic modification, having been shaped so the outflow contributes to the thrust vector during takeoff, reducing the takeoff roll distance.

So, in summary:

Advanced wing design with double-slotted flaps
Low stall speed
High mounted engines
Large flap and main nose wheel chines
Reduced take-off roll through vectored thrust
(Thanks to Peter Kämpf) Lower Wing Sweep to add effectiveness at low speeds at the expense of cruise speed.

There really isn't a lot that is going different from other business jets other than a shorter take-off/landing roll. The design isn't dramatically different, and it doesn't mention it but it probably has reinforced landing gear.

No production PC-24's have been delivered as of yet, so its hard to tell what they look like. The test PC-24's only have 150 hours behind them so they may not have had any rough-strip experience. It's difficult to say exactly what the modifications are because they may include other things like FOD deflectors on the wheels.


What can passengers do if they realise their plane is not on the right path?

Okay, so, going with the idea that you have a compass (and also with the idea that this can be a general question, not necessarily about flight MH370).  If you're heading from Tokyo, Japan to Seattle, Washington, USA (direct), then you could be reasonably certain the craft should be somewhere between headings 45 and 135.  So if you notice the craft is on a heading of 270 (ie., clearly you're going in the opposite direction) and this direction has been sustained for say, an hour, I'd think it would be okay to at least ask the cabin crew what's going on.

As with any time you are raising a concern with the cabin crew, you should be polite.  As has been stated, they are used to passengers being a bit nervous and, as a result, they can easily interpret belligerence as a sign of irrational fear.  And, as you might guess, it's easy to ignore someone if you feel they are being irrational.  So, if you want be taken seriously, be polite.  You're far more likely to get an actual answer, or raise a valid concern even.

So, if you just ask, "why are we headed west instead of east" they may have a very simple answer like, "well, the pilot mentioned we might have to take an odd route to avoid some weather" or "this is the flight to Bombay India, how did you get on it?"  Or, they may have no idea and be concerned themselves, so they go and ask their superior.  Thus, goal achieved, you've alerted the flight crew :).

Either way, so long as you're polite and don't become insistent (or belligerent) that you are correct, I can't see any harm in just asking.  And sometimes asking is what leads to a problem being solved so...  I'd say go for it.


Was the safe landing of Southwest flight 1380 extraordinary or expected?

Based upon the damage done to the aircraft, the fact that it retained a functioning engine, and the location of the engine failure and divert, no there was not a real immediate danger of crashing.

To be fair this incident was an emergency which caused structural damage to the aircraft and breach of the cabin structure, resulting in the loss of life of a single passenger.  It was also a freak accident and I don’t see any evidence that the aircraft or engines used have some kind of inherentt design or engineering fault the prophesizes more failures or future risk.

It’s possible that we did dodge a bullet and that, by pure chance, the failure of the fan blade and where it was ejected from the fan casing could have resulted in far more damage to the aircraft and critical systems like flight controls, fuel, hydraulics, landing gear, major structural members, etc that COULD have resulted in the very realistic probability of a much more devastating accident when the aircraft either attempted to land or could not maintain level flight further.


Does the size of control surfaces affect maneuverability, and if they are smaller, is it easier to stall?

There are at least 3 possible cases and unfortunately your question doesn't tell which one you would consider valid.

The maneuverability (the maximum rate of rotation?) can be measured by the moment of the force exerted by the surface at the CG.

Let's consider the area of the control surface is smaller, and...

All other parameters are unchanged, in particular surface airfoil, center of pressure, and angle of attack:

As the currently selected answer tells, the maximum lift available from the control surface is lower, hence the maximum moment is lower, and the maneuverability is reduced.

As the airfoil and the angle of attack are unchanged, the stall characteristics are unaffected.

This theoretical case is unlikely to be seen as the designer would certainly compensate the reduction of the area by some other change.

The surface is moved to a location further from the CG to maintain the moment with the smaller lift force:

Neither maneuverability nor stall characteristics are affected.

The angle of attack is increased to generate more lift and compensate for the smaller area:

Maneuverability is decreased as the maximum lift obtained with the maximum angle of attack is decreased.
Stall is easier to trigger as the angle of attack (for an equal moment) is closer to the stall angle.


Why does each fan blade have a different mass and frequency?

Because manufacturing processes are not perfect, and the minute differences between parts as-designed and as-produced are amplified by the high rotational speeds and large diameters of modern jet engines.

Take a following back-of-the-envelope calculation: disregard incoming airflow velocity and assume a hypothetical fan with a 1 meter diameter rotates at such rpm that the blade tip has a tangential velocity of 80% of the speed of sound at 35kft in ISA. The equivalent rpm would be 2817.
$$
a_c=\frac{v^2}{r}=\frac{(295\cdot0.8)^2}{1}=55.7\cdot10^3 \; \mathrm{[m/s^2]}
$$

That's the acceleration on the blade tip. If this blade were to be just 1 gram overweight, the force exerted on it would be:
$$
F_c=m\cdot a_c=0.001 \cdot 55.7\cdot10^3=55.7 \; \mathrm{[N]}
$$

that force is more than the weight of a 5kg dumbbell and it alternates its direction almost 3000 times per minute.

Its not that fan blades are hard to manufacture precisely, but that the application in which they are used is unusually demanding and any small imperfection in the blade will make itself known very loudly.

As for why the frequency is different, it is because the vibration modes of any system depend on the spatial mass distribution, like a pendulum which changes its natural frequency if you shorten the distance between the mass and the fulcrum. So the two issues you mention are directly related: a few milligrams of metal missing at the tip will shift the center of mass, and with it the natural frequencies of the blade.

In reality the whole vibration issue is a bit more complicated for continuous bodies, which effectively have infinite natural frequencies, because unlike ideal pendulums, their mass is distributed over infinite points in space, but that is a bit beyond the current point.

The important part is not to have any natural frequency coincide with the rotational frequency of the fan, because that would quickly lead to rapid unplanned disassembly: the vibration amplitude would be amplified with each revolution until the blade failed.


How does the lift coefficient of an A380 change when flaps are extended?

As mostly when questions are vague, the answer is: It depends.

If nothing else changes, the nominal lift coefficient stays the same. A coefficient is referenced to an area, and for aircraft this is the reference area which is derived from the wing area. Regardless of flap settings, the reference area stays fixed, and so does the lift coefficient because neither the mass nor the speed of the aircraft have changed when flaps have been set.

In reality, the aircraft will slow down when flaps are extended, and it can afford to do so because drag is increased and stall speed lowered. Now, with the lower flight speed, the lift coefficient will go up in proportion to the ratio of the speeds before and after squared:
$$c_{L_{flaps}} = c_{L_{clean}}\cdot\frac{v_{clean}^2}{v_{flaps}^2}$$
Again, this assumes the same reference area.

In a wind tunnel where the aircraft model is fixed to a sting and the angle of attack is controlled, setting flaps will increase the lift coefficient by the difference in zero-lift angles of the aircraft with and without flaps, multiplied by the lift curve slope of the aircraft.

$$c_{L_{flaps}} = c_{L_{clean}}+ (\alpha_{0_{clean}} - \alpha_{0_{flaps}})\cdot c_{L_{\alpha}}$$

Note that the lift curve slope increases when setting flaps increases the effective wing area. Again, all is referenced to the unchanged reference area.


To which reference point on the aircraft is the altimeter reading relative to?

The placement of a probe for a pressure  altimeter has exactly the problem you mention, but they only need to be accurate within 75 feet, so placement is not a problem.

For large aircraft, they use a "radar altimeter" which uses an electromagnetic beam to measure the distance to the ground, the same way police radars measure car speed. Radar altimeters are accurate to within a couple of feet.


When approaching stall, why does the center of pressure move back?

The center of pressure is generally not the best way to characterize the aerodynamic forces on an aircraft since it varies with AoA.  That is why the neutral point or aerodynamic center is used instead.

Having said that the center of pressure is the location of average pressure force acting on the wing or aircraft.  Mathematically it is found by taking the sum of integral of the magnitudes of pressure and shear stress acting on the surface and multiplying it by a distance (for an airfoil from the LE) on the upper and lower surfaces resulting in a moment at the LE, or reference point.  This is then divided by the sum of the integrals of the pressure and shear stresses acting on the upper and lower surfaces.  My explanation does not do it justice see http://web.mit.edu/16.unified/www/FALL/fluids/Lectures/f03.pdf

It can be somewhat complicated to calculate for an entire aircraft but in general for an airfoil it does move forward up until the point of stall or critical point after which it then moves aft.  See https://www.reddit.com/r/aviation/comments/2kibfo/why_does_the_centre_of_pressure_move_rearward/ for a good simple explanation of this.

The movement of center of pressure is highly dependent on the configuration of the aircraft (airfoils are much simpler) and unless you are certain of the specifics of the configuration generalizing the center of pressure movement is inaccurate...


What is the maximum decibel noise level of a stage 4 rated engine?

I have found an answer. This datasheet (easa.europa.eu) lists the noise levels for an aircraft with the engines and the stage 4 limits:


Below what altitudes do shock waves form?

Shock waves form any time the speed of the airflow over or around a vehicle exceeds the speed of sound.
The local speed of sound varies with ambient temperature in a well-defined way; in general it goes down slightly as you climb higher.


What is the hole located below the 2nd or 3rd window of Boeing 737?

Static ports. (capt & FO).

For sensing static (atmospheric) pressure ultimately used by various flight instruments (such as airspeed indicator, altimeter, etc.)

(Source: b737.org.uk)


How does the Mi-26 tilt its rotor like this?

It's real and it's simply the blades running at the flapping hinge limits with the cyclic stick full forward.  The blade on the back is at its up limit and the one at the front at its down limit, resulting in an overall disc angle of about 30 degrees off horizontal.  It's being done to accelerate along the ground as fast as possible.  In the air, the machine's body will follow the tilt of the rotor quickly enough that this sort of angle is almost never experienced unless the pilot made a sudden extreme input in flight.

This (blades hitting flapping limits) is something that only multi-blade articulating rotors can tolerate.  You can't do that with a two blade teetering rotor because contacting the blade flapping travel stops, known as mast bumping, will break the mast.


Airport apron refers to the area of an airport where aircraft are parked, unloaded or loaded, refueled, or boarded and looks like this:

Image from airplane-pictures.net
This probably originated from the word defining theatrical apron:

1903 A. B. WALKLEY Dramatic Criticism 108 The ‘apron’ is the technical name for the stage-area in front of the curtain. In the Elizabethan theatre it jutted right out among the public, who surrounded it on three sides. This ‘apron’ slowly shrank..till at last in our day it has altogether disappeared.

As the airport apron looks similar to this, it probably go its name. The following image shows an apron stage (The Visy Theatre in Brisbane Powerhouse)

Image from gtaust.com
As for why its like this, the following explanation seems the most plausible:

Waay back in the day, airports were simply 1/2 mile or 3/4 mile squares of flat grass-covered former farm field with a small terminal building in one corner. Planes landed & took off on the grass, and parked in front of the building to load & unload.
Given the reality of rain & snow, the area in front of the building would get muddier faster thatn the rest of the field. Between plane traffic, fuel truck traffic, cargo wagon traffic & passengers (& horses), churning the surface to mud would be pretty much a sure thing.
A pretty obvious innovation would be to pave a more-or-less fan-shaped area in front of the building where the airplanes could park.
Which when viewed from above, would look like an apron

As for tarmac, it is simply a synonym for Asphalt, which was used in apron's construction.
Note: The historical term apron bears similarities to modern ramp, as in 'walk the ramp'


How can I check pitot static leak without a test box?

There are lots of challenges to testing a static system the way you describe.

First, you need something to fit over the static port (not too hard if it's a single fuselage port, slightly more difficult if it's two of them, and if it's on a mast like on some Piper aircraft you just lost a lot of "seal area" and made the task very difficult).
You can get around that with test kits by taking the static line(s) off & screwing the test kit directly to the plumbing, or by using a variety of adapters that come with the kits.

Second, you need to produce a known absolute pressure in the line and hold it for a given duration to check for leaks.
That's most of what those fancy boxes do - they bring the line to a given pressure altitude, and then you watch the altimeter and/or line pressure to see if it leaks air back into the system.

All that said, if you're willing to deal with a really rough test, you can still do this with a syringe and some medical tubing. This RV-12 builder shows you how:

Attach a syringe to some surgical tubing.
Put some air-tight tape over your other static port (if applicable)
Put some modeling clay around the static port.
DON'T get it in the hole - make kind of a cup around the hole.
Put the surgical tubing into the modeling clay and press the clay tight around the tube to seal the chamber over the static port.
Pull on the syringe until you "climb" to a convenient altitude.
Hold or lock the syringe in place and watch the altimeter to see how long it takes for air to leak into the system and lower your altitude.

This is nowhere near as precise as proper calibrated test equipment, but it should help you detect a gross leak in the static system.


How many pilots does an airline hire for each new plane they purchase?

The answer depends greatly on the airline's operations, as the constraints are very different between long-haul and short-haul trips, whether relief crews are required, layover times, need and distribution of reserve pilots, and other factors: some pilots employed by an airline will be performing management duties, on leave, training, etc.

Assuming the numbers on airlinepilotcentral.com are accurate, we can look at some averages:

Emirates: 4,300 pilots, 258 aircraft: 16.7 pilots/aircraft
Delta: 14,600 pilots, 881 aircraft: 16.6 pilots/aircraft
United: 12,491 pilots, 763 aircraft: 16.4 pilots/aircraft
Southwest: 96,14 pilots, 748 aircraft: 12.9 pilots/aircraft
SkyWest (US regional airline): 4,621 pilots, 453 aircraft: 10.2 pilots/aircraft


If I were to build a J3 cub twice the size of the original using the same CG would it fly?

Unfortunately a simple scale-up would fall victim to the square-cube law: all dimensions times two means the volume and weight are 2x2x2 = 8 times the original, while the wing area is 2x2 = 4 times the original. It is the wing area that keeps the aeroplane up. It is the reason why birds cannot get any larger than they already are.

Someone in the 1920s analysed this and predicted that the maximum size for aeroplanes would be about that of the DC-3, but improved technology has proved that prediction wrong. A B777 has a way higher wing loading than a DC-3 of course. The square-cube law is not a law, it can be defeated by engineering. Point is that linearly amplifying all dimensions does not work.

  How big of an engine would I need, if the original is 65hp?

Minimal: 8 x 65hp = 520 hp. We need a serious amount of extra thrust.

From this answer:

$$D =  C_{D0} \cdot \frac{1}{2}  \rho  V^2 \cdot S + \frac{2  W^2}{\pi  A e \cdot  \rho  V^2 \cdot S} \cdot $$

$C_{D0}$ would stay the same if everything is scaled up
S = wing area = 4 times as high
W is 8 times as high.

$D_2 = D_1 \cdot (4 + 8^2/4) = D_1 \cdot 20$

So you need 20 times as much thrust at the same speed.

Increase V and the first factor increases, second factor decreases. There are of course many optimisations possible (weight saving, wing loading increase etc), but that goes beyond the scope of the question.

  What would be the weight of the up-scaled plane? Simply twice the weight?

Eight times that of the original.

  What would be the stall speed?

Higher than that of the original because the wing loading is higher. Depends on the flaps & slats installed.

  How fast would it go? 75mph?

Yeah it might..but it would probably need to go faster as @xxavier mentions.

  Is there a software program to test aircraft design?

FlightGear is an open source flight simulator that allows you to link your own flight dynamics model into it.


Why can't most jets safely use reverse thrust while airborne?

The problems are two-fold:

The airspeed is much higher in flight than when landing, so the thrust reverser doors would have to be much stronger, and therefore heavier to withstand the additional forces, along with the relative wind making them harder to close.
What happens when it gets stuck in the deployed position?  Now you have to shut down a perfectly good engine and have additional drag on the airplane while in flight.
(Bonus) It isn't really needed on most airplanes with spoilers, flaps, etc. that accomplish the same thing.


The vortex lift is the method by which highly swept wings (like delta wings) produce lift at high angles of attack.

In the case of wings having sharp, highly swept leading edges like delta wings, the leading-edge separation vortex phenomenon occurs at subsonic speeds. However, the separation does not destroy the lift as in the case of low sweep wings; instead, it forms two vortices which are (nearly) parallel to the wing edges.

Vortices over a delta wing with a sweep angle of 70°, Separation in three-dimensional steady flow, ONERA

In case of Concorde, the vortices look like this:

Vortices over the Concorde wing, Separation in three-dimensional steady flow, ONERA

A cross-section of the vortices looks like this:

Flow above the Concorde Wing, Separation in three-dimensional steady flow, ONERA

Unlike the (bound) vortex of the conventional wing, these are real in the sense that they represent an actual mass of air rotating at high speed compared to the air in front of the wing.

The vortices form 'vortex sheets' along the wing. Air is sucked into the vortex sheets and accelerated downward. As the airspeed in the vortex is high, the pressure is low. This low presssure on the upper surface produces lift.

From Low Aspect Ratio Wings at High Angles of Attack at adg.stanford.edu:

  ...the leading edge vortices, increase the wing lift in a nonlinear manner. The vortex can be viewed as reducing the upper surface pressures by inducing higher velocities on the upper surface.

Source: adg.stanford.edu

Basically, the vortices increase the lift from the baseline (potential flow) values, with the extra force being equal to the loss of leading edge suction associated with the separated flow in high angle of attack highly swept wings. This analogy gives the same result as before.

A Concept of the Vortex Lift of Sharp-Edge Delta Wings based on a Leading-Edge suction Analogy, Edward C. Polhamus, NASA Technical note D-3767

A major advantage of vortex lift generation is that it is effective at high angles of attack, over which the wings would normally stall. Actually, that Concorde used this method of lift generation is the reason for the high AoA during landing and its droop down nose.

Source: http://soliton.ae.gatech.edu

One thing to be noted is that vortex lift generation happens at high angles of attack or in case the wings are designed to generate separated flow (with sharp edges as in Concorde) in normal conditions. Otherwise the lift generation is by conventional means.

The same mechanism is responsible for lift generation in:

Strakes

By U.S. Navy photo by Mass Communication Specialist 2nd Class James R. Evans [Public domain], via Wikimedia Commons

Chines

Image from Effects of Vertical Tail and Inlet/Strake Geometry on Stability of a Diamond-Wing Fighter Configuration by Mitchell E. Fossum et al., accessed through http://enu.kz/

Canards

Source: forum.keypublishing.com


Because there is a maximum deployment speed for things like flaps, gear extension (and sometimes retraction). Exceeding these speeds and using those devices can cause damage to control surfaces or other equipment. The speed check is there so that when the PF calls for flaps, the PM remembers to check the speed before performing the action.


Why are different distances listed for the ILS and the LOC on this approach chart?

A very weird case, but each country can do things their own way.
The ILS FAF - GS intercept at 2700' - is 0.2 NM inside the LOC FAF. In the FMC database, the former is coded as FI01, and the latter is VI311. The LOC FAF is also 6.5 DME off of the LOC DME, identifier IAV, which corresponds to 7.4 DME off of VNO (the Vilnius VOR).
The key to seeing this is to consider how you get different distances from the VI312 IF point to the depicted FAF(s). Since VI312 is a single point in space, you can see where the two FAF's are relative to it... the ILS FAF is 0.2 NM farther away (which corresponds to it being 0.2 NM closer to the runway in the other set of blue-circled numbers.
Why the approach designer made the LOC FAF not quite coincident with the ILS glideslope intercept point, is its own question, and I have no insight there. (Totally mystified, in fact.)


What is the advantage of increasing an aircraft's horizontal tail surface area?

Increasing horizontal stabilizer area increases pitch stability and the permissible range for centre of gravity at the cost of some aerodynamic efficiency.

Stability in pitch means that the aircraft tends to maintain constant angle of attack (which roughly corresponds to maintaining constant speed with pitch). An aircraft is stable in pitch if the aft surface flies at lower angle of attack than the front surface (this applies to both conventional tails and canards).

Making the horizontal stabilizer larger does the following:

The absolute change in lift force on the horizontal stabilizer when angle of attack changes is larger, so the aircraft returns to the trimmed angle of attack faster (increased stability).
As centre of gravity moves aft, the difference in angle of attack between the surfaces decreases to keep the plane balanced, reducing pitch stability. If the horizontal stabilizer is larger, the angle of attack changes more slowly for the same change in lift, so the centre of gravity may be permitted further aft before the aircraft becomes not stable enough.
As centre of gravity moves forward, the difference of angle of attack between the surfaces increases until angle of attack of the horizontal stabilizer exceeds its stall angle of attack and control is lost. If the horizontal stabilizer is larger, it can provide more (downward!) lift before it stalls, so the centre of gravity can be permitted further forward before loosing control authority.


If the profile of a wing pulls a plane up, why can planes fly inverted?

Normally, an airfoil is optimized for best lift/drag (L/D) efficiency for a certain flight profile (usually a compromise). Since most of the time for most aircraft inverted flight is not an issue, you get an airfoil that is optimized for upright flight, and this is best achieved with asymmetric geometries.

However, depending on the angle of attack any airfoil can (and will) generate "negative" lift, only much less efficiently so, than for the optimized regime,  resulting in increased drag.

The desired angle of attack for conventional aerodynamically controlled aircraft is maintained by the elevator. For symmetric airfoils commonly used for aerobatic planes, the performance for upright and inverted flight is quite similar. For 99% of all other airfoils inverted flight will work up to a certain point, depending on the available power, CG, the maximum lift and rudder forces availabe before stall. As a result, for some aircraft, a stable inverted flight cannot be maintained, while for others it could be (but with varying penalty to performance, stall speed etc). The aerodynamical possiblity of inverted flight is of course limited by structural and other considerations.


How can a headset cause continuous transmission (PTT blocked)?

Apparently the tip connection is being grounded activating the PTT. From the photo the only thing that could possibly be a problem is the Compilot plug being a tiny bit longer than the DC. But the detent in the tip is what should decide where the plug sits in the jack and that looks fine. It almost has to be a wiring problem in the Compilot. If you have a multimeter check for continuity between the barrel and the tip. There should be no continuity unless a PTT button is being pressed.


What is the difference between en route and airway?

Enroute: An aircraft that is on its way to its destination.

Air Route: A specific route that an aircraft takes, just like a car route, taking specific highways and roads to get to your destination. Planes do not go a straight line from their origin to destination.

Airway: A highway in the sky. That is what planes fly in their route. So for example 2 planes flying the V23 Airway would have them flying the same path on the airway specifically.


How do the Beech Bonanza's ruddervators work?

In the Bonanza, a mechanical mixer controls ruddervator movement based on pitch and yaw commands. Here's a typical V-tail mixer (this is not of a Bonanza though):

(source: eaa1000.av.org)
There are two rods extending off to the left of this photo that connect to the actual ruddervators. Rightward motion of the top rod (due to either rightward motion of the entire mixer assembly due to a pitch command, or clockwise rotation of the assembly due to a yaw command) will deflect the ruddervator one direction; leftward motion deflects it the other direction. Similar for the other ruddervator connected at the bottom.
I can't completely answer the second part of your question, whether yaw authority is reduced when pitching or vice versa. It depends on where the limit stops are installed in a Bonanza. If the stops are set on the ruddervator side (left side in photo above, so that the mixer's range of motion is limited by its leftward connections), the amount of available rudder will be reduced when pitching. (Sorry I can't answer that part of the question, but I thought the information about the mixer would still make a useful answer.)
The airplane is obviously designed so that sufficient authority is available in all situations. (This means making the two fins of the V longer than those of a traditional horizontal/vertical stabilizer design so that similar control surface area is available.)


Who opens an airliner's door first after it lands?

It depends on the type of aircraft. But USA today/Ask the Captain gives a nice explanation:

  Question: I was wondering what takes so long to get the exit door open after we land. Could you please go through the steps?

  Answer: Once the airplane arrives at the gate and is properly chocked, the captain shuts down the engines and switches off the “Fasten Seat Belt” light. The anti-collision light (this is the red blinking light on the top and bottom of the airplane) is switched off, informing ground crew that it is safe to approach the airplane.

  Ground crew members then begin to position the jet bridge, aligning it with the door.  Once the jet bridge is mated to the aircraft and the cover is in place, the ground agent either opens the door or taps on it for the flight attendant to open it. This varies depending on the type of airplane to minimize the chance for an inadvertent slide deployment.

  Once the door is initially opened, the ground agent assists in fully opening it and ensuring that it is locked in the open position.

  This is the generic procedure for most jet airliners. Regional or smaller airplanes have a slightly different procedure as their stairs are built into the door.


Is this new intake of Airbus and Boeing aircraft's NACA inlet?

Those inlets don't require the NACA duct profile because the openings are presented toward the airflow, being on a sloping surface relative to the freestream.  The NACA profile in those locations serves no useful purpose and is a probably less effective, if anything.
The NACA duct profile was developed for inlets on surfaces that are completely parallel to the airflow, like along the straight sides of a fuselage or nacelle, where the freestream flow just passes on by (like a static port you might say).  They were developed as a low drag alternative to the traditional scoop projecting into the airstream that you would normally have to use in such a location.
The sides of the NACA Profile, induce a change in direction of the ram air free stream without any projections (it's thought that the sides of the ramp act like vortex generators and it's the vortices that "pull" the free stream down the ramp) so that ram air is drawn down the ramp to the inlet opening.  On a sloping surface like a wing root fairing as in those pictures, the ram air is directly impinging on the opening (as if it was a scoop sticking out) and doesn't need any "airflow redirection tricks" like the curved sides on the NACA inlet ramp.


What do these symbols indicate on the ATC display?

The white squares are aircraft - it's course is indicated by a line. Then there is a datablock showing Callsign "FWA170C", its altitude F053 = Flighlevel 53 = 5300ft, climbing to an assigned flightlevel 190 = 19000ft.
A = altitude - below a defined transition level
F = flightlevel (steps of 100ft) - above a defined transition altitude

Transition altitude and level depend on the location and weather.

Then you have the airports, navaids, nav-fixes and the control zones showing.


Why do heavy departures wait 5-10 minutes on the runway at ZRH?

The usual reason is, that departures from runway 16 are not allowed to climb straight ahead due to noise restrictions over downtown Zurich. Instead they need to turn left, where they cross the departure path of runway 14. So if there are arrivals on 14, no departures on 16 are cleared, as in the case of a go around on runway 14, its departure sector must remain free. I've been watching planes stuck for half an hour at the line up 16 for that reason. Imagine that waste of fuel... ZRH's runway capacity, despite having 3 runways, is thus actually lower than for a parallel 2-runway setup (think about London Heathrow e.g.).


What is the runway holding short line on Taxiway B between B2 and B3 at KFAT for RWY29L?

That’s a hold line for aircraft taxiing on Bravo while large aircraft are departing Rwy 29L to prevent aircraft from taxiing behind the blast pad for 29L and potentially being tossed around by the jet blast from the departing aircraft.


Are there cases of a thrust reverser used on a turbojet engine?

Yes.

The Rolls-Royce/Snecma Olympus 593 [Wikipedia] were pure turbojets and they had thrust reversers.

Source: Wikimedia

Also, T/R on Concorde were also used in flight (If I remember correctly, only the inboard ones were used in flight) because Concorde didn't have spoilers.

Being a civilian aircraft, with the engines mounted under the wing, Concorde didn't have any real problem with thrust reversers


Has the FAA moved to change its use of gender-specific words like airman?

This AC from 2009 lays out some regulations on it for part 21 regulations

  j. Replace the masculine pronouns “he” and “his” with gender-neutral
  terms. The new rule uses plain language.

It looks like they also made a lot of changes to the medical code in 1996 that covers it as well.

  Where appropriate, changes are made to eliminate gender-specific pronouns, to replace ‘‘applicant’’ with ‘‘person,’’ to use current
  position titles and addresses, to correct spelling and improve syntax,
  and to adjust section and paragraph references.


IAP / "Instrument Approach Procedure (IAP) Charts" What does "Procedure NA" Mean?

Although the wording on the chart is very confusing, it appears to indicate that you can not make a course reversal at the VORs themselves. Probably due to the congestion of the airspace and associated airways. This is only the case when using the VORs for navigation to the IAFs since neither of the VORs is an IAF. However, the IAP is an RNAV IAP. So, you can disregard the VORs and use GPS only to navigate to the IAFs as long as you stay above he 4200 foot Minimum Sector Altitude and cross the IAFs at or above 4400 feet. Beware of the higher terrain with MAximum Elevation Figures of 5600 and 6600 feet NNE of the IAP.

In other words, it means that the entire procedure is invalid if you are using VORs to navigate to the area in some circumstances. If you are coming from the North and West, you are required to use LEB. If you are coming from the South and East, you are required to use CON. If you are using GPS only, you are required to navigate to the IAFs directly (not necessarily Direct-to) using GPS and not VORs.


Can we eliminate the center tank of large passenger planes?

I'm assuming you're talking passenger safety in the event of a ground impact - if anything happened midair, it wouldn't really matter if it were in the fuselage or one of the wings.

Moving the fuel somewhere else is going to have center of gravity implications. Moving it to wing pods or lager nacelles in particular would increase drag, which would require the plane to have even more fuel on board, which seems counterproductive to decreasing the fuel risk to passengers (and, of course, would substantially increase the cost of operating the flight).

Some military aircraft do carry fuel in removable underwing fuel pods (particularly fighters being ferried somewhere, where increased endurance/time between refuelings is more important than performance for that particular mission). However, that's less a safety design and more the lack of anywhere else to put the extra fuel on a small aircraft.

If an engine fails, the rate of fuel consumption is going to be different on each side of the plane. Although both are rare, you likely have far more situations where different wings use fuel at different rates than situations where having fuel feed under the body would be dangerous. If that's true, then removing the cross-feed line would be more dangerous than leaving it in.


Why do flight control cables not slacken during the cold temperatures at cruise?

If you look closely at your drawing you will see the cables are not really simple pull cables but really act like steel belts. That is, there is a pulley at each end and when you actuate the control the cable is rotated around the system in a loop.

The end pulleys and or idler pulleys are spring loaded to maintain a predefined tension on the cables and should take up any slack in the system caused by operation, temperature, or aging of the cable.

If the top left pulley above is the yoke in the cockpit, and you turn it, the top cable rotates around the loop, like a belt, and turns the actuator bottom right. Note that also means when you turn the yoke, it does not pull significantly on the springs, the cable just rotates.

Interestingly, the Concorde had to handle both contraction and expansion. When cruising at supersonic speeds the aircraft stretched up to about ten inches.

ADDITION:

For non looped cables, and occasionally for looped cables where the cable needs to traverse between objects that move relative to one another, cable housings are also used.

You are probably familiar with these on bicycles. The trick to them is the ends of the housing are attached, or anchored, to the frame somewhere. The housing is flexible so can be arranged in a loop or s-shape that can be extended or compressed as the fixed end points move relative to one another.

The control cable on the other hand always has a fixed length within the housing despite the change in the end positions.

The issue with these though is friction is high compared to pulleys, the inside of the housing can become contaminated with dirt and debris, and it is impossible to inspect the cable within the housing.

As with the looped system, a spring is still required, usually at the business end, to pull back on the cable. In the single cable case, actuating the cable from the control end also involves pulling on the spring.


Where can I find electrical pinout of C152 microphone jack and DC bias?

There are some great resources on webpages mostly aimed at home builders and experimental aviation enthusiasts as well as some electrical engineering forums.

Most of these aviation radios are set-up for use with a carbon microphone. They are fairly simple pieces of kit. If my memory serves me correctly the acceptable forward bias voltage range is set by the RTCA (https://www.rtca.org/) however I can't find a solid reference for this.

As far as I know, so called "GA plugs" (The 5.25mm/6.35mm style plugs) are wired as follows:

Sleeve             GND                           GND
Ring         MIC OUT/BIAS IN                    8-16v (Short circuit current ~150ma)
Tip       PTT  (Switch shorts to GND)            PTT

The reasoning behind the PTT switch still being assigned is for handheld backup microphones.
Many newer headsets don't use carbon microphones and use the electret capsule style microphones instead and therefore require some complex electrical engineering wizardry to drive.


The main wing comes in two pieces, left and right wings, and they are bolted to the lower center fuselage section, which also houses the center fuel tank.

Fuselage/wing fillets (fairings) are added after.

The frame you captured shows the rear wing—the horizontal stabilizer. It is slid in and then bolted, more precisely attached to the mechanism that moves it.

(Same video)


What does 3Q8 mean in the aircraft model Boeing 767-3Q8?

Those are Boeing's customer codes. They denote which airline the aircraft was originally built for, not necessarily the airline that owns/operates the aircraft currently. For example, Southwest's customer code is H4 but they operate some 737-7BD's, which are from the AirTran acquisition. In your case, the Q8 means it was originally built for ILFC, a leasing corporation.  A full list is available here:
http://en.wikipedia.org/wiki/List_of_Boeing_customer_codes

Your assumption about replacing the customer code with 0s to get the plain old model is correct.


Certified FDR's for commercial aircraft don't have USB ports. They have interface ports because you obviously need to be able to extract data, but they are usually proprietary and each one uses a specific cable for the FDR you want to talk to. To do what you want to do you'd have to design a device that talks to FDR units to download and decompress the data. There are commercial test set units out there that can do this. They are not cheap. As was mentioned in a comment, to do this while in flight will require an STC from the FAA. Also, converting between ARINC and USB doesn't make sense. ARINC is a company, USB is a computer interface specification.

That said, I don't think connecting to the FDR is the best way to do this. As was mentioned, ACARS may already do part or all of what you are interested in doing.


Is it safe to mix different types of fuels in a jet engine?

While turbine engine can be made to burn almost any fuel, a specific engine might not run with fuel it is not tuned for for several reasons:

The high pressure fuel pumps only work with stuff that is sufficiently lubricating. They don't use grease, because it would be too easily washed out at the operating pressure, and the pressure is needed because the fuel is injected directly into the combustors at the highest pressure present in the engine. This rules out too much gasoline—note that spark-ignition engines, even when they have direct injection, inject during suction, so at low pressure.

With little enough gasoline, the pumps wouldn't mind, and I heard some militaries had backup plan for diesel engines—which have the same issue—to mix gasoline with some oil as an emergency fuel. However to know how much gasoline is safe somebody would have to test it and nobody is going to sacrifice a very expensive piece of equipment that is a turbine engine for a test with so little value as this since there is no shortage of proper jet fuel.
Each fuel has different heat of combustion, so it needs to be metered differently to keep the engine within the rather narrow range of operating pressures and temperatures. If the heat of combustion is too low, the pressure won't be enough to keep the turbine spinning and the engine will flame out, and if it is too high, the pressure will exceed the capability of the compressor which will stall and the engine will either flame out or go through a cycle of stalls that will thoroughly destroy it.

The adjustment might be as “simple” as updating the firmware in the FADEC, but it is still a lot of work to do all the necessary measurements and then do all the tests for the modification and since there is no practical use, nobody did.
The length of the combustor also has to match the speed of combustion, so if that is different enough, you need a differently built engine altogether.

So the engine will probably tolerate some different fuel mixed in the tanks, but nobody can tell you how much exactly, because it wasn't tested.


Could a variable sweep aircraft also use negative angle?

Yes it could, but don't hold your breath.

Forward sweep means that the aeroelastic forces will twist the wing at high lift into an increased angle of attack, so such a wing needs to be stiff in order to avoid divergence (PDF!). Also, aileron effectiveness is excellent, so a forward-swept configuration is a good choice for dogfighting.

Since backward sweep is mostly helpful at trans- and supersonic speed, swing wings were the right answer when very high top speeds (Mach 2+) needed to be combined with high loads at take-off and short field length requirements. When flying ever faster went out of fashion in the 1970s, the attractiveness of variable sweep disappeared.

Forward sweep helps both in air combat and in transsonic flight, so there is little advantage in a variable-sweep configuration with forward sweep. An aircraft optimised for air combat has little need to fly Mach 2+, so the moderate sweep angle is a good choice for most of its flight time. Also, the aeroelastic instability increases with sweep angle, so more than moderate forward sweep needs a very stiff and heavy wing.


The YF-23 lost the Advanced Tactical Fighter program to the YF-22, however it has not been made public why. The ATF evaluation is still classified and details about the YF-23's performance are not easy to come by. They are both excellent aircraft, performed similarly, and there is much speculation why the YF-22 won.

Global Security states that...

  According to the Air Force, factors in the selection for production of the F-22 were a better designed for maintainability, greater potential for future development, and slightly lower cost. Secretary of the Air Force Donald B. Rice stated that the choice was based on confidence in the ability of the Lockheed team and Pratt & Whitney to produce the aircraft and its engine at projected costs. Emphasizing the importance of the Lockheed team's management and production plans, he denied that either prototype was significantly more maneuverable or stealthy. A popular view is that the decision reflected a preference for maneuverability over stealth

A derivative of the YF-23 was proposed for the 2018 Bomber, but that idea died when the program was cancelled in 2006.