How can a pitot tube freeze when it's heated?

Captain Bill Palmer, in his book "Understanding Air France 447" has a section dedicated to answering that very question as it pertains to AF447. Although there is no way to know for certain he puts forward some possibilities.

He quotes a commenter on a website:

  One commenter on the Weather Graphics website’s AF447 article provided this interesting observation: “I'm an aircraft icing specialist and wanted to point out a factor that hasn't been discussed much … high ice crystal concentrations. I've seen flight test data from power rollbacks due to flight in high ice crystal environments … In our case, the crystals collected within heated, aspirated Ram Air Temperature sensors, forming a 0 ° C slush…”

He notes that just before the pilot tubes clogged, the sound of ice crystals hitting the windshield could be heard on the CVR.

  Ice crystals bounce off the exterior of an airplane and cause no visible ice accretion, but they can enter the probe inlets. When highly specific climatic conditions exist in combination with certain combinations of altitude, temperature, and Mach, the concentration of ice crystals entering a probe can exceed its capacity to melt and evacuate the moisture through its drain holes. The result is that the ice crystals form a physical barrier within the probe that disrupts the measurement of total pressure.

The particular type of ice that may have been responsible was a substance called graupel.

  Graupel forms when tiny supercooled water droplets adhere to snow crystals to the point that they engulf the snow crystal itself.

Graupel. Photo from Wikimedia commons

Capt. Palmer notes factors that make graupel a possible suspect:

  No airframe icing. The supercooled water theory is discounted by the fact that the A330's icing detectors were not triggered.
  Graupel has large enough particles to be audible on the voice recorder. It takes a particle with enough mass and inertia (a given density) to hit the fuselage with a sound, instead of flowing around it with the relative wind, like snow.
  Graupel has enough mass to temporarily overwhelm pitot anti-icing when concentrations are high enough. The pitot tubes are hot. But even if you put a snowball on a hot skillet it does not melt instantaneously. If there is enough mass in the blockage, and in combination with new particles being added to the blockage as the first ones melt, it may exceed the pitot tubes capability to melt the obstruction as fast as it is introduced. Graupel is of significantly higher density than snow.
  Graupel has sufficient blocking properties to prevent efficient transmission of dynamic pressure within the pitot tube.For example, water can flow and transmit pressure within the pitot tube, though it too can alter pitot-static readings, a physical non-fluid blockage could shield the pressure sensing port.
  The likely presence of snow or similar form, as evidenced by the St. Elmo's fire discussed by the crew. The accident report stated that the sound of ice crystals hitting the aircraft can be heard about 20 seconds before the airspeed loss and autopilot disconnect.

It must be noted that the exact cause of icing problems on the A330 was never completely identified but it was specific to the particular brand of pitot tubes originally installed. Airbus was in the process of replacing them all with pilot tubes from a different manufacturer.


You're very right. It's a static discharger or "static wick", and it is used to dissipate the static electricity accumulated during flight. The electrical buildup happens during flight through precipitation, clouds, dust, etc., and is known as "precipitation static".

Once the static reaches a certain point, it will discharge. Without wicks, this happens through antennae and can really mess with communications or navigation. Wicks make sure that process doesn't cause problems.


Are sudden turns and descents a standard emergency procedure?

There are no emergency procedures I'm aware of that requires a pilot to turn left 90 degrees and then turn right 360 degrees.

There is a procedure for situations requiring rapid descent for things like medical emergencies and fires.  They consist of a 45 degree banked, full-flap, power-idle descent flown at maximum flap extension speed.  So it is a spiraling-turn descent.

Also, the Cessna 172N checklist instructs the pilot to slip in the opposite direction from a wing fire to keep the flames blown in an outboard direction.


Is it safer to do a regular approach than a short approach?

The safest approach to a normal landing is a stabilized approach, so it's going to depend a lot on you, your aircraft, and the day's conditions. If you're operating in a confined area, then that changes things a lot, and I'm not going to address that.

It also depends on your definition of a normal pattern and approach. The FAA recommends you fly your downwind around ½ mile to 1 mile from the runway centerline, which should keep you fairly close to the airport anyway, and you should be turning base at least ¼ mile away from the runway threshold.

That said, a normal approach is going to be much safer. As you point out in your question, a short approach often requires extreme descent rates or slips (or both), and results in a much shorter final; neither of those situations improve safety. Approaching with a high descent rate just so that you can reduce it if necessary doesn't strike me as a particularly good choice for normal operations, either.


Is a lower CHT on one cylinder cause for concern?

A 60 degree difference in CHT is something worth investigating: It may not be a safety-related issue, but you want to know if it's "normal" for the engine or an indication of a problem.

In order from roughly "Most Benign" to "Worst Case", the CHT difference could be the result of:

A faulty CHT probe
Either the probe is not seated in the cylinder head well properly, or the probe/wiring is defective and causing an inaccurate reading.
Different CHT Probe Types
Spark plug gasket probes can read higher than "normal" cylinder head probes, so if gasket probes were used on cylinders 1, 3, and 4 and a standard bayonet probe used on #2 that would account for the difference.
(I can't see why this would be the case though: usually you have one gasket probe - on the cylinder where the manufacturer's CHT gauge was connected because it's using the normal bayonet probe hole - and bayonet probes in the rest, not the other way around.)
A mixture imbalance
Cylinder #2 is running richer or leaner than the other cylinders.
Since you say the engine is not running rough Cylinder #2 would probably be running rich.  (This is normally something you'd notice with Exhaust Gas Temperature rather than Cylinder Head Temperature.)
You can check for this by watching the engine monitor as you lean the engine: Cylinder #2's EGT will peak at a different time than the rest of the cylinders (early = leaner, late = richer). On fuel-injected engines this can be adjusted for by using tuned injector nozzles. On carbureted engines you just have to live with it - but at least you'll know the cause and be able to determine what "normal" is for this engine.
Fouled/Failed Spark Plug
Easy to check in-flight: Cycle each magneto; If the cylinder dies on one you've found the culprit.
(Something you should probably catch on your preflight mag check too.)
A cooling problem
If the cooling baffles for your engine are worn/damaged/incorrectly positioned you might have anomalous airflow that's directing more cooling air over the #2 cylinder head than the rest of the cylinders.
(Normally you find baffle problems because one or more cylinders are running hot, but cold is possible too.)
A cylinder problem
An exhaust valve that's not fully closing can cause low CHTs - your mechanic can confirm this with a borescope (or a compression test -- they'll hear air escaping through the exhaust if the valve isn't closing).
If this is the case it's something to attend to, because if it's ignored it can lead to an exhaust valve failure, which can ruin your day.


What were four objects seen in Flightradar24 over Germany with the callsign TWR?

Many towers in Germany are equipped with FLARM so that they are electronically visible to FLARM equipped aircraft in the area. This is especially useful for helicopter emergency medical services and law enforcement that operate in urban areas during marginal weather conditions.
The fact that the towers are not always visible on FR24 may have to do with the fact that not all their receivers are equipped with FLARM. If nobody nearby is providing FLARM data to FR24, the towers are not visible on FR24.
The speed shown has to do with the GPS receiver in the FLARM unit; they sometimes detect small speeds, even though the receiver is stationary.


How close to a Restricted Area can a pilot be cleared to fly?

ATC will separate IFR traffic from active special-use airspace according to the separation minima prescribed in the 7110.65 9–3–2:

Vertical separation: 500 feet above or below a prohibited/restricted/warning/MOA/ATCAA/ALTRV area (1000 feet above or below, if above FL290).
Radar separation: 3 miles from the periphery of special-use airspace; or for specific areas that have been designated by management as not needing 3 miles, simply "clear of" the periphery.
Non-radar separation: On airways whose protected airspace does not overlap the special-use airspace. (Remember that Federal airways extend four or more miles from each side of the centerline.)

Note that VFR traffic are explicitly mentioned as not prohibited from flying through a transitional hazard area (a term I think is used in conjunction with spacecraft launch and reentry). It is also "common knowledge" that VFR aircraft may fly through an active MOA but not active R- or P-airspace; however I can't seem to find anything that says this explicitly. R- and P- airspace is discussed at 14 CFR 91.133, which does not mention MOAs.

Without knowing the specific situation you're talking about, my guess is that when the restricted area is hot the TRACON is withholding an approach clearance using that approach for all IFR aircraft whether IMC or VMC, and only permitting VFR practice approaches to use it.


Is it possible for an SU-25 to fly high enough to shoot down a Boeing 777?

There is an excellent answer at http://scottlocklin.wordpress.com/2014/07/21/can-the-su-25-intercept-and-shoot-down-a-777/

The SU-25 is a ground attack fighter unsuited to intercepting and/or shooting down 777s. If the Ukrainian air force wanted to do so, they have better aircraft available.
The SU-25 max speed is slower than a cruising 777.
The SU-25 has an operational ceiling of 16000 ft with max weapons to 23000 ft clean, MH17 was at 33000 ft.
It is an unpressurised aircraft.
As a ground attack aircraft it probably only rarely carries air to air missiles. It can carry the R-60 infra-red air-to-air missile which has a 6 lb warhead effective against small aircraft.

An R-60 once hit and destroyed one engine of a small BAE 125 business jet at 35000 ft but failed to bring it down, apparently the missile failed to explode.
KAL902, a Boeing 707, was hit by an R-60 and made an emergency landing 40 minutes later.

The R-60 is a short-range missile (5 miles). The Russians claim the SU-25 came within two or three miles of MH17.

On the whole this makes the SU-25 a poor choice for shooting down a cruising 777.

It seems unlikely that a 777 would be shot down in this way. Not impossible, but far less likely than other proposed scenarios such as those involving BUK (SA-11) ground to air missiles.

Results of an R-60 hitting a jet engine on a small business jet.

Results of an R-60 hitting a Boeing 707 ... two R-60s were launched, one missed.

These R-60s were fired by supersonic interceptors, not by SU-25 ground-attack aircraft.


Very significant.
A research on blisk cost estimation with funding and data provided by Rolls-Royce states:

Integrally bladed discs, commonly known as blisks, are currently found in axial-flow compressors of gas turbine engines. Fig. 1 shows that blisks require significantly less material because the dead weight from the blade roots, disc lugs, and the disc structure required to support these features, is no longer required. This leads to a weight saving of up to 30% (Rolls-Royce, 2005), permitting higher blade speeds and consequently higher pressure ratios per stage (Steffens, 2001). A blisk compressor therefore requires one third fewer rotor stages to achieve the same total pressure ratio as a conventional design (Steffens, 2001). [emphasis added]

Fig. 1. Blisk weight saving.

Langmaak, Stephan, et al. "An activity-based-parametric hybrid cost model to estimate the unit cost of a novel gas turbine component." International Journal of Production Economics 142.1 (2013): 74-88. (PDF)


What would prevent the installation of windows on the roof of an airliner?

There are a few factors involved in this and you should check out this answer that touches on window size (same issue really). For what its worth the ceiling is prime real estate on an aircraft. Modern airliners have the over head baggage compartments there (which provide a remarkable amount of space)

The area is also used to run cabling (electronics mostly these days) fore and aft as well as power to the reading lights etc. However it should be noted that these things could most likely be routed along the floor just as well.

The real issue comes back to windows being a weak point and glass being heavy. When it comes to planes you want them to be as light as can be so excess windows will only reduce useful load and increase potential failure points. On top of all that you will have more ambient light in the plane which may bother those trying to sleep on late night flights.

If you want a better view fly an unpressurized plane!

While on the topic of small bubble canopy planes, anyone that flies GA planes (especially like the ones shown above) with out air conditioning will tell you how hot it gets on the ground (and even at lower altitudes flying) in the summer. The canopies make the inside of plane behave like a green house and really heat up. This would make the inside of a jumbo jet really bake in the summer while taxiing (which can be a long process at big airports).


Is there a height limit to national airspace?

As it stands, that 'border' between FL600 and above is undefined, and unregulated.

  There is no international agreement on the vertical limit of
  state sovereignty. Today, the need to settle this gap in the law is
  growing in importance.

  More and more states are developing their own domestic
  space launch capability. Few of these new space powers will be
  able to freely access space, or utilize the most efficient launch
  azimuths, if neighboring states can claim sovereignty up to even
  62 miles (100 kilometers). They will have even more difficulty
  returning objects to Earth if the boundary is set at that altitude.
  Even the United States and Russia are facing limitations on their
  ability to freely access space. Setting a low vertical limit on state
  sovereignty will ensure all states have equal access to space.

  Dean N. Reinhardt, The Vertical Limit of State Sovereignty, (2007)

and

  Vertical Sovereign Territory.

  Interestingly, there is no international law (or agreement) defining the vertical boundary of a nation’s sovereign territory/airspace (the boundary between outer space which is not subject to national jurisdiction and national airspace). Obviously, there is a “white” unregulated area that should be defined, not at least from national security concerns. Presently the airspace between FL 600 and up to the border between the earth’s atmosphere and outer space (generally an altitude of approximately 100 km (62 mi) (the Kármán line)) is not regulated.

  H. Bertil Nordin, U-2 and the Vertical Boundary of Sovereign Territory, (2017)


What is meant by a “cold soak" of an APU?

It means the APU has been in active or not operating in a cold environment for an extended period of time. Here, like any other piece of machinery and operating fluids are “cold soaked“, that is, has reached the ambient temperature of the environment.   During extended flight at high-altitude, and APU would encounter this as it is not normally used during cruise flight.   This does affect the ability of the unit to power up in the event of an emergency, as most machines don’t like being operated in extremely cold weather, and usually require a period of time in order to warm up.


How does the head-up display on a spitfire work?

It's not a head-up display, it's a reflector gunsight. (Follow that link to learn how they work.) It just displays a fixed reticle to aim the cannon, not any flight instrumentation.

Some (but not all) Spitfires had a gyroscopic system to compute target leading and move the position of the reticle appropriately, based on the speed of the aircraft; I suspect that your photo is of this equipment, and that's what the range adjustment visible at the bottom is. More about that can be found at How did the gyro gunsights of WW2 get the range and lead of a target?

  Seeing as it is projected, it would only be of use, if it would be dynamic, that's why I'm asking.

That's not actually true. A "static" reflector gunsight is hugely advantageous over a collimator sight (i.e. a tube that you look through) or iron sights, because the crosshairs still appear in the correct place when you move your head. Early aircraft machine guns used collimator sights, but you have to hold your eye right up to the sight to see through it. This often resulted in injuries if the aircraft jerked at the wrong time. Iron sights were subsequently popular, but you still need to line up with the sights correctly, which is time you don't want to spend in a dogfight. With a reflector gunsight, the image of the crosshairs moves as you move your head, so you only have to glance in the correct direction to line up the shot. That's why they're also popular on small arms nowadays.


How does angle of incidence affect an aircraft's stability?

The angle of incidence is the angle between the wing chord and longitudinal axis of the aircraft as depicted here. From years of building model aircraft and flying aircraft I can explain one way that it affects the aircraft, and that is by reducing drag caused by the fuselage. A given wing requires a certain angle of attack (pitch up attitude) in order to fly at a given weight and speed. If the angle of incidence is 0 degrees, then that would require a nose high attitude and expose more of the underside of the fuselage to the relative wind. However, having an appropriate angle of incidence allows the fuselage to have a more horizontal orientation (and better visibility for the pilot from the cockpit) than if the wing was mounted exactly parallel to the longitudinal axis of the fuselage.

So how does it affect an aircraft's stability? It affects an aircraft's stability by reducing its drag at certain airspeeds.


Help identifying airfield and aircraft from movie "My Spy"

The film was shot in and around Toronto, so a search of local airfields on Google Maps led me to Markham Airport. From there, Wikipedia provided this list of military aircraft on the field:

CT-128 Expeditor transport

CT-133 Silver Star

CF-5 Freedom Fighter

CF-104 Starfighter (Various Airforces)

Canadair CL-13 Sabre

Schweizer SGS 2-33A Royal Canadian Air Cadets[citation needed]

Noorduyn Norseman - shell only

The aircraft belong to the Canadian Air, Land and Sea Museum. Looking at the satellite image on Maps it would appear that a number of other aircraft have been stored there, but have now been removed.

There's a clutch of rather more complete airframes in amongst the buildings in the south west corner of the airfield.

Google Maps


What Boeing 747 rejected takeoff and runway excursion accident is detailed in this video?

The copilot rejected the takeoff above V1 in response to the engine fire warning.

The aircraft in question:

Air France plane operating as flight 187
Boeing 747-200 SCD (side cargo door) registration N4506H
Aircraft had company number 22794 and manufacturer serial number 558.

The incident occurred on the 24 of July 1988 at Delhi airport. An overview can be found here.


AIP, AIC, NOTAM, ANO (UK): How do they relate to Annex 15 of Chicago Convention?

Annex 15 of ICAO Chicago convention describes the required information for safe conduct of flights, and which aeronautical information is to be provided by ICAO members. Each country needs to provide an aeronautical information service (AIS) in a standardized form, comprising static and dynamic data.

Static: Aeronautical information publication (AIP), AIP amendments and charts. AIP is generally updated each 28 days.
Dynamic: Notam, AIP supplements.

Explanatory information doesn't fit well in the previous categories, and is grouped in aeronautical information circulars (AIC).

Details

AIP: Authoritative information issued by an ICAO member containing long lasting aeronautical information essential to air navigation.AIP list by country.
AIP amendment:  Permanent change to AIP.
AIP supplement: Temporary change to AIP.
Notam (and Snowtam): Notice distributed by a telecommunication system, concerning the establishment, condition or change in any aeronautical facility, service, procedure or hazard, the timely knowledge of which is essential to personnel concerned with flight operations. Also associated with Notam: pre-flight information bulletin (PIB), a presentation of current Notam information of operational significance, prepared prior to flight.Notams in US.
AIC: Information that doesn't qualify for inclusion in AIP or Notams but which relates to flight safety, air navigation, technical, administrative or legislative matters. This could include mid-term prevision for changes in the regulatory or technical frameworks, results of safety investigations, scientific discovery related to how weather impacts aviation...List of Canada AIC.

Full aeronautical information contains:

AIP, including amendments
Supplements to the AIP
Notams
AIC
Checklists and lists of valid Notams.

Source for the above definitions: Manual of Aeronautical Information Services, India.

Regarding The Air Navigation Order (ANO), specific to UK

  "On 7 December 1944, the majority of the world's nations became
  signatories to the "Chicago Convention", the aim of which was to
  assure the safe, orderly and economic development of air transport.
  ICAO sets out, in the terms of the convention, the rules, regulations
  and requirements to which each signatory must adhere. The Civil
  Aviation Act 1982 is the UK's means of discharging its ICAO
  responsibilities. This legislation required the creation of the CAA.
  The Air Navigation Order (ANO) is the law that empowers us to carry
  out our duties."

Source.

ANO is the legal framework valid for UK, to empower aeronautical agencies and their publications, in accordance with Annex 15.


Why must a pilot enter "Upwind" when entering the traffic pattern for RWY 9 at Linden (LDJ) airport in New Jersey?

To keep aircraft away from the multiple obstructions to the east, and also not force people to make their approach from the direction of EWR and mitigate possible conflicts with traffic from that airport.


On Airbus aircraft, can the pilot control the aircraft when the autopilot is active?

Moving the flight controls above a certain threshold will disconnect the autopilot.
From the A320 FCOM (1.22.30 Auto Flight - Flight Guidance, emphasis mine):

AP DISENGAGEMENT
AP1 or 2 disengages when:

The pilot presses the takeover pushbutton on the sidestick.
The pilot presses the corresponding AP pushbutton on the FCU.
The pilot pushes on the sidestick harder than a certain threshold or moves on the rudder pedals above a threshold.
The pilot moves the pitch trim wheel beyond a certain threshold.
The other AP is engaged, except when localizer/glideslope modes are armed or engaged, or when the rollout or go-around mode is engaged.
Both thrust levers are set above the MCT detent and the aircraft is on the ground.
The aircraft reaches the MDA-50 feet (MDH-50 feet), or 400 feet AGL if not MDA/MDH, with APPR mode engaged and a non-ILS approach selected.
One of the engagement conditions is lost.

Furthermore, in normal law with all protections available, the AP will disconnect if:

High speed protection is active;
Angle-of-attack protection is active (α prot +1° is reached);
Pitch attitude exceeds 25° up, or 13° down, or bank angle exceeds 45°;
A rudder pedal deflection is more than 10° out of trim.

The different control laws act in the F/CTL COMPUTER in the following diagram:

(source: FCOM 1.27.10 Flight Controls - Description)
They are independent of the autopilot and the protections are available regardless of whether or not the autopilot is engaged.


What does the NCrit parameter indicate in a CFD analysis?

The whole setting group is called transition settings, and refers to the boundary layer transition point (from laminar to turbulent).
The forced transition trip locations are exactly that, expressed as a fraction of the chord, for the top and bottom surfaces. They are akin to placing a trip strip at those locations.
The Ncrit value is a measure of free flow turbulence and is used to simulate the transition location when no forced trip location is given. XFLR5 uses the same method as XFOIL, which is an adaptation of the $e^N$ transition theory. Note this linear theory loses its validity at a fluctuation level of 1 to 1.5 percent, which corresponds to an N-factor of 6.9 to 7.3, meaning it is not suitable for highly turbulent flows.

As to what this is important for, the turbulent or laminar nature of the boundary layer affects flow separation and viscous drag. A turbulent layer will generate more drag, but separate at higher airfoil angles of attack.
Where this gets really interesting is at low Reynolds numbers, where a laminar layer will detach, but become reattached if turbulence is introduced into the airflow ahead of the airfoil, such as by a turbulator. It will then remain attached if the turbulator is removed, displaying a hysteresis loop. The same effect will of course occur in the opposite direction, with a barely attached turbulent layer detaching and staying that way if the free flow turbulence decreases enough to cause it to turn laminar.
I must note that this effect is confined to low Reynolds numbers, on the order of $10^4$.


What is this on the aft end of this GEnx engine?

The pipe is the center vent tube which vents air from the oil sump.

From airliners.net (User MD11Engineer):

  All gas turbine engines use pressurized seals for their shaft bearing compartments to keep the oil in. The result is that the scavenge oil returning to the oil tank via the scavenge pump, chip detectors and scavenge filter contains a lot of air, it is more a foam than a liquid.

  Engines use a centrifugal oil / air separator in the circuit to remove the air from the oil and to vent the system to the ambient to avoid overpressure.

  PW and RR use centrifuges attached to their main gear box, which vent overboard through a hole in the cowling.

  GE and CFM use the hollow N1 shaft as a centrifuge. The heavier oil sticks to the inside of the shaft and gets returned into the circuit via holes, while the lighter air stays in the center and gets blown out through the pipe in the back.

  The air blown out is not completely free of oil, so when the engine has just been shut down, you´ll see some oil vapor coming out from this pipe.

Source: www.airliners.net

Similar vent is found in other GE engines, like the GE90.

Source: airwaysnews.com

The system looks like this:

Source: CFM56-3 Training Manual, thanks to mins.

This is the actual part in GE90-100:

Source:standardaerocomponents.com


Why is an approach that relies on both LOC and PAPI not considered a precision approach?

I think you're overlooking the primary reason pilots fly instrument approaches: the conditions do not permit flight by visual reference.

The fact that a PAPI provides vertical guidance is more or less useless if you can't see it. Most ILS approaches involve a descent of at least 1500' from glideslope intercept.

If you break out from the clouds at ILS minimums, you can be as low as 200' above the runway surface; at 3°, that's around 3/4 miles from the touchdown zone and the PAPI. It's highly unlikely that the PAPI would be visible prior to that point, meaning the approach would be made with purely lateral guidance.


What safety mechanisms prevent thrust reverser deployment in mid-flight?

On a Boeing 777, the thrust levers need to be at their idle stops otherwise the thrust reverse levers physically cannot be moved aft. Once the thrust levers are at their idle stops and the  reverse levers are moved to the reverse thrust position there will be three signals provided to the thrust revereser actuation system (TRAS).

These three signals to the TRAS energize the thrust reverser sync lock valve
(SLV), the directional control valve (DCV), and the isolation valve (IV). At a reverse thrust lever angle of 11 degrees, the SLV is energized by closing a microswitch in the thrust lever assembly. The SLV then sends hydraulic pressure to the sync lock on each thrust reverser sleeve to accomplish release.

At 24 degrees reverse thrust lever angle, the DCV is energized by a microswitch in the control column assembly where the thrust levers and reverse thrust levers reside. The valve is shuttled by system pressure to the deploy position.

At thrust resolver angle of <31 degrees the IV is opened by a signal from the electronic engine control (EEC), and system pressure, by way of the DCV, is ported to the actuators. The IV command, from the EEC, also requires the engine to be running and the airplane to be on the ground.

Air/ground logic uses radio altimeter signals, with ground mode for the thrust reversers being < 5 feet. The locks within the locking actuators release and the thrust reverser sleeves move aft. After the thrust reverser sleeves move aft by a measure of 60%, interlock releases and the levers can then be moved to their maximum reverse thrust position.


What is the purpose of a movable inlet on a jet engine?

Jet engines require the air that flows into them to be subsonic. Supersonic air hitting the front fan would cause shockwaves inside the engine, with undesirable results.
So the job of the intake on a supersonic aircraft is to slow down the air to subsonic speeds. The intake is designed to set up a series of shock waves. The air will slow down to subsonic speed as it crosses these shockwaves.
The location of these shockwaves changes with speed: the higher the speed, the shallower the angle of the shockwave and the further the shockwave will reach down the intake duct. So if you have a fixed-geometry inlet, your maximum speed is limited: there is a speed at which the shockwaves will intersect the front fan.
Variable intakes avoid this problem: the movable vanes in the inlet aim the shockwave so it stays in front of the front fan at all speeds. This enable a higher top speed to be reached.
If you accept a lower top speed, you can avoid the extra complexity of a variable inlet. For the F-22, for example, a variable inlet would make it more difficult to maintain a low radar cross section, so the tradeoff was made to maintain stealth and lower the top speed.


How does rudder size influence its ability to produce lateral lift?

The figure of 35% might be ideal for a rudder on GA aircraft with decent effectiveness and high enough control forces so a good control feel is achieved.

Generally, a rudder on a vertical tail is like a flap on a wing. It changes both camber and incidence of the vertical when deflected, thus helping the pilot to adjust the lateral lift force acting on the whole vertical. Therefore, the same formulas as those for flaps can be used for rudders.

A simple approximation for the amount of lift coefficient change per flap deflection angle $\eta$ is
$$c_{l\eta} = \sqrt{\lambda}\cdot\eta$$
where $\lambda$ is the relative chord of the flap and $\eta$ needs to be in radians.

Hermann Glauert derived a formula using potential flow theory that is sligthly more complex:
$$c_{l\eta} = c_{l\alpha}\cdot\frac{2}{\pi}\cdot\left(\sqrt{\lambda\cdot(1-\lambda)}+arcsin\sqrt{\lambda}\right)$$

I plotted both together with a correction of the Glauert formula using wind tunnel data above. It is remarkable how close the simple formula matches the experimental data already.

To be effective, the control forces on a rudder must not be too high, but also not too low in order to give good feedback to the pilot. For GA aircraft and gliders, a relative chord of 25 - 35% has been found to give the best combination. Control forces grow with the square of the relative chord of their control surface since both their area and the lever arm of the additional forces acting on them grow linearly with their relative chord.

In order to calculate the lateral lift change of the whole vertical, you need to know its lift curve slope $c_{l\alpha}$ which is affected by its aspect ratio and sweep angle, just like a wing is.


Which way (if at all) do the ailerons need to be deflected in a full-rudder sideslip in a Cessna 152 or 172?

Yes. If you apply full rudder with no aileron, you initially just get a flat skid, but then differential lift starts to have an effect and the inside wing drops because that wing has slowed down, the fuselage is obstructing some of the flow on that side, and if there is wing dihedral, it creates a geometric angle of attack differential. One or more of these factors generate the rolling torque.  It's called "roll/yaw couple".

Some airplanes roll with rudder-only input stronger than others.  On swept wing airplanes the effect is intensely magnified due to the wing sweep and they roll really hard once the yaw angle exceeds 10 or 20 degrees.  Pilots doing jet type ratings discover this right away on their first V1 cut (engine failure) on take off when they don't correct the yaw from asymmetric thrust fast enough and it's taking full aileron just to keep from flipping over.  Side slips are generally not done in swept wing airplanes except in some extreme circumstance.

So the amount of opposite aileron to maintain a constant heading side slip is a function of how strong the airplane's roll/yaw couple is.  A 172 or 152's roll/yaw couple is moderate and you will need some opposite aileron just to keep the wings level.  Plus, to prevent a skidding turn, the amount of aileron has to be more than the minimum required to keep the wings level because some opposite bank is also required to keep the heading constant or else the skid itself starts to pull the nose around. So you end up with quite a lot of aileron in, maybe one third to one half of the available travel, with the wing banked perhaps 10 to 20 degrees, to keep from turning.

There is a lot of variation from airplane type to airplane type and on some the roll/yaw couple is quite weak and it takes only light aileron inputs to hold heading in a skid.  On any airplane you are flying for the first time, this is something you experiment with to find out how strong the roll/yaw couple is and how much counter aileron is required in a side slip.


How often does evacuation happen as shown during the pre-flight safety videos/stewardess instructions?

I didn't do statistics, but The Aviation Herald lists units to low tens a year worldwide.

Most of them happen at airport due to fire indication (sometimes even false) or smoke on board.

On the ground, fire spreads a lot faster than while flying, because when flying, the wind is too strong and blowing the flames off. The most notable example would be China Airlines B738 at Okinawa on Aug. 20th 2007, airplane in flames arriving at stand. The aircraft was already at the gate when the flames were first noticed, evacuation was immediately initiated and by the time everybody left, it was already engulfed in flames, about 3 minutes after the fire started. While China Air might not be "western" in strict sense of the world, it is largest airline on Taiwan and follows the same standards.

Another notable accident is Egyptair B772 at Cairo on Jul 29th 2011, cockpit fire.

Here are some recent evacuations mentioned on AvHerald:

Air France B773 at Paris on Jul 28th 2013, evacuation while boarding due to fumes
US Airways B752 at Kona on Jun 8th 2013, evacuation during push back causes 4 injuries
PSA CRJ2 near Philadelphia on Apr 17th 2013, smoke on board, evacuation
Easyjet A319 at Belfast on Jan 6th 2011, taxiway de-icing prompts evacuation

Notice, that they are all smoke or fire events. For some other reasons, see e.g.:

Wizz A320 at Rome on Jun 8th 2013, left main gear did not extend
Alitalia A320 at Rome on Sep 29th 2013, right main gear did not extend

two similar accidents where both aircraft were evacuated via slides. The reason in these, and many other gear collapse incidents, is that they don't want to wait in a damaged plane where there is a risk of fire, plus the difficulty of getting stairs to the aircraft resting in strange attitude.


Is a Mode C or S Transponder a type of Mode 3 Transponder?

Modes 3/A and C are very similar, but the interrogation pulses are timed differently and the responses mean different things.

If you send a mode 3/A pulse, you get a mode 3/A reply (or nothing). The response is a 12-bit number called the squawk code, which is conventionally written as four octal digits, plus an optional ident bit.

If you send a mode C pulse, you get a mode C reply (or nothing). The response is a 12-bit redundant encoding of the pressure altitude between -1200 and +126700 feet, in 100 foot increments.

Note that mode C does not include a squawk code; it is only the altitude. In practice, though, every mode C radar and transponder is also capable of mode 3/A. Likewise, every "mode C" radar always sends both types of pulses and internally combines the two responses, so it looks like a single system. (TCAS only sends mode C pulses since it doesn't care about squawk codes.)

Mode S is almost a completely different system. It includes selective addressing, data frames, message types, and much longer messages (56 bits). It also uses a different, more efficient encoding to allow moving all that extra data without losing efficiency. Of course, for backward compatibility, all mode S transponders can also do mode 3/A and C using the old 12-bit system if needed. Likewise, Mode S radars also send mode 3/A and C pulses, but they're modified very slightly so that mode S transponders will know to ignore them.

1090 Extended Squitter is a relatively minor extension of mode S. A "squitter" means a transponder that sends replies without being interrogated, and "extended" means it added some new message types with 112 bits per message (to hold ADSB data) instead of the previous 56. That's it.


I think - and I may be wrong - that your question assumes that ATC services are the same in a TRSA and in class E in general. Or perhaps that TRSA Service and flight following give you exactly the same thing.
In fact, TRSA service is slightly different: it provides everything that Basic Radar Service does (e.g. safety alerts, sequencing), plus separation services for all participating aircraft. Usually, ATC doesn't provide any separation service to VFR traffic in class E.
The ATC Orders (JO 7110.65) sections 7-6 and 7-7 cover Basic Radar Service and Terminal Radar Service; you can read more details there. Since the ATC services available in a TRSA aren't the same as those available in general class E airspace, that seems to me like a valid reason to chart it.


What fuel would a Bell Huey helicopter use in 1964?

In 1964, the Huey would use JP-4 or JP-5 .

When fitted with models T53-L-5 or T53-L9, the Huey would burn JP-4.
With engine variety engine T53-L11 it would burn either JP-4 or JP-5. The JP-5 type fuel was mainly used for Navy operations.


Is a 40-year-old person too old to start an ATC career?

Some years ago (in the 80s) I tried out for ATC in Canada and took the preliminary screening test, which was a series of 25 diagrams representing radar displays with targets moving around different airways, crisscrossing each other in various directions, and you had to answer 2 questions for each diagram, whether or not targets at different speeds and altitudes would conflict with each other (there was a table with all the targets' speeds, tracks and altitudes).  It was a timed test and I wasn't paying attention so I was at question 45 when time was called and you had to drop your pencil right away.  So I didn't answer the last 5.

I got one or two wrong, giving me a score of 43, a "pass" for the test, but there so many applicants they were only taking candidates with scores over 45 for the next stage.  Probably would have made it if I'd just answered the remaining 5 at random.

Anyway, actual background is not that important. They are looking for a very special set of mental skills, and someone has them or they don't.  Mainly, a very high cognitive and spatial IQ, and a very powerful memory.  To the extent that educational background matters, it would mostly be as a sign of intelligence.

I used to know a centre controller who told me that once trained and experienced, and having the required mental abilities in the first place, and the fact that the high stress periods don't last an entire shift (there are "rush hours" where things are intense, then relatively quiet) the job wasn't nearly as tough as the public perception.

She should just go ahead and apply and start the screening process, as I don't believe there are any specific professional or educational prerequisites, and there is no harm in trying.  She will probably find out pretty quickly whether there is a chance.  One thing going for her is the overall personnel supply situation which is affecting ATC to some degree as much as other parts of aviation (shortages of applicants with what it takes).


What happened to the Fokker 100 revival project?

NG Aircraft still exists, or at least, they still have a website. The big roadblock is financing the development of the aircraft. I did a search in Dutch government records: the most recent mention is in 2016, indicating that at that time sufficient funding has not been found yet to start development in earnest.

LinkedIn shows 11 employees.


According to this document about the landing gear system, the wheel dimension  of the main lading gears is 1400x530 R23. This is not the standard notation known from car tires, but it says that the diameter is 1400mm and the width is 530mm, so the tread has a surface of about 2,3m².

The same document further states:

  Depending on the flight phase, a warning will be triggered if a
  tyre pressure is detected below a given percentage of the nominal tyre pressure (for 5 seconds continuously).
  Likewise, a warning will be triggered if a differential pressure above a given percentage is detected across tyres on the same axle (measured from the tyre with the higher pressure).

though no concrete threshold is given.

The nominal pressure of the tires is 15Bar (atm) and will quickly fall, even when there's just a tiny leak. So no wonder there was a warning during climb.

During the 13h flight at up to 40.000ft, the pressure could easily fall to the environmental pressure of about 0.2Bar at that altitude. And from that altitude, it takes only 30min to landing (taken from flightaware for a BA32 flight), which may not be enough to equalize tire pressure to ambient pressure through a tiny leak. Also, ambient pressure will rise slowly in the beginning and reach 1Bar at ground quite late.

Considering the pressure in the tire was still 0.2Bar when landing, the pressure difference to the ambient caused a force of 176kN on the tread, which equals a weight of 18t or 39700lbs! (one could also say: 4.5t or 5000lbs on each of the sides of this square shaped tire.)

So it's no wonder that the tire was compressed, though this doesn't explain why the tire choose the square shape.

In general, the tire tries to minimize its volume while the surface is constant, but it can't change to any shape. Its stiffness and the rim only allow the tread to bulge inwards. From math, we know that the more sides a symmetric polygon has, the more surface it has w.r.t its circumference. So the less sides, the better.  A triangular shape seems not to be possible due to the rim and the needed large force to bend side walls. A pentagon doesn't provide enough reduction of volume, so a square is the best choice.

So though the picture looks really crazy, the square shape is not that surprising.

However, a tire does not think about how to collapse best to minimize volume. It starts an one or more points and evolves. If it starts with three bulges, it could have stayed with it, and the A380 had landed with a triangular tire. May be, a fourth bulge has developed at some point. Maybe, the shape in air was different, and some punched during landing pushed the tire into that shape.

Finally, one can only say that it's clear that the tire collapses to something like this due to the ambient pressure working against the low pressure inside, but one can not really predict the resulting shape. But the rectangular shape seems to be the best to minimize volume.


Is the airspeed for the minimum the same for the theoretical power required curve as for the shaft power required curve?

The OP is asking about power required, not power available, which, in my mind, would change the answer.

From an aircraft performance perspective, power required is the product of total aircraft drag and inertial speed ($P_R=TV$), applicable only for steady unaccelerated flight. Thus, the minimum of that curve is dependent on profile and vortex drag. In potential flow, it would be where $3C_{D_0}=C_{D_i}$ (see this answer for derivation).

Shaft power required is the power needed to be transferred to the propeller in order to achieve the aforementioned $P_R$. From the actuator disk theory, we know that it must be larger than $P_R$. The shape of this curve would depend also on the propeller itself (e.g. pitch, diameter, airfoil) and its control system (e.g. constant vs variable pitch). Therefore, the minima of the two curves do not have to coincide.

To illustrate this, I've gathered some RC propeller data from APC, which according to its website are generated based on vortex (potential) theory. The drag polar is based on a joke planform designed to accentuate the curvature of the polars:

$C_{D_0}=0.02$ (this is way too low for an RC planform)
$e=0.85$
$W=25lb$
$A=8$
$S_{ref}=15ft^2$

The figure below shows the power required (P_R) for level flight and the shaft power (torque * rotation speed) needed to sustain the level flight for a few prop configurations.


I had never heard of this or seen an approach with a holding fix at the FAF or outer marker when I ran across a question on timed approaches from a holding fix in Gardner’s Complete Advanced Pilot. As you can see from the quotes at the bottom of the post, it is unlikely to ever be used. But they are still available to the controller, FAA Order JO 7110.65W Air Traffic Control.

FAA_H_8083-15B Instrument Flying Handbook 2012

Timed approaches from a holding fix are conducted when many aircraft are waiting for an approach clearance. Although the controller does not specifically state “timed approaches are in progress,” the assigning of a time to depart the FAF inbound (nonprecision approach), or the outer marker or fix used in lieu of the outer marker inbound (precision approach), indicates that timed approach procedures are being utilized.

In lieu of holding, the controller may use radar vectors to the final approach course to establish a distance between aircraft that ensures the appropriate time sequence between the FAF and outer marker or fix used in lieu of the outer marker and the airport. Each pilot in the approach sequence is given advance notice of the time they should leave the holding point on approach to the airport. When a time to leave the holding point is received, the pilot should adjust the flightpath in order to leave the fix as closely as possible to the designated time.

Timed approaches may be conducted when the following conditions are met:

A control tower is in operation at the airport where the approaches are conducted.
Direct communications are maintained between the pilot and the Center or approach controller until the pilot is instructed to contact the tower.
If more than one MAP is available, none require a course reversal.
If only one MAP is available, the following conditions are met:

a) Course reversal is not required; and

b) Reported ceiling and visibility are equal to or greater than the highest prescribed circling minimums for the IAP.
When cleared for the approach, pilots should not execute a procedure turn.

The actual order specifies that Timed approaches using either nonradar procedures or radar vectors to the final approach course may be used at airports served by a tower if the following conditions are met and goes on to give similar conditions.

The AIM has an example of how they might be used.

The sons of the guys who wrote that procedure are now in the “Old Controllers’ Home”, I can only guess at their intent. The last time I had to run timed approaches was when I was taking non-radar problems to certify on Denver Sector 26 (COS/PUB low) in 1968! R Butler – ATC Controller

We did some timed approaches when I worked a U.S. non-radar approach control in the ’80s. Don’t believe there are any non-radar approach controls left, and I don’t know a single radar controller who would try it if there were a radar outage of some sort. We also had to run them at the FAA Academy in training back in the ’70s. You would need to assign different missed approaches to succeeding aircraft, so #2 doesn’t catch #1 on the miss.

It’s a lot of radio and brain work to do successfully. Non-radar at a radar facility, (because of an outage) is usually very limited now. (One in, one out) Backup radar systems preferred, even if not as accurate. vector4fun


To what extent does pressurisation increase the rigidity of an airframe?

Disclaimer: I am not a pilot, nor do I have anything with planes. I am a mechanical engineering student, so I do know quite a bit about the strength of materials.

What you should know is that whenever something is filled with air, that air is trying to achieve a state in which it has the lowest pressure, meaning it is trying to increase in volume. This is the reason balloons are roughly round, because a sphere has the largest volume for the lowest surface area. The same pretty much applies to planes. What generally happens when you bend a tube (and a fuselage is in essence a big tube) is that two sides are getting closer, making it easier to bend because the second moment of area decreases. This does however mean that the hull becomes less round, thereby decreasing the volume. The air inside will try to prevent this volume change,  which makes it harder to bend the tube, which means the stiffness increases. Note however that more stiffness does not necessarilly mean it is also stronger.


How to deal with turbulence while flying glider? (Cautions in applying rudder)

Everyone chooses what to worry about. I would not choose to worry about this.

Is such risk realistic in glider flying?

What does "realistic" mean to you?  If it means "could it happen" then sure, it could.  Plenty of things could happen.  If a possibility greater than zero is all it takes for you to worry then by all means, stop reading.  Don't forget your shark armor and anti-meteor hard hat when you go out next.
However, most people consider "realistic" to include likelihood. Is it likely? Well, I searched through the last 8 years(1) of the NTSB accident database for glider accidents involving the term "breakup". Of the three relevant results, two involved aerobatics.  How many glider flights have there been in the last 8 years? Probably plenty of them.  Do you plan to do aerobatics?  If not, then your accident statistics are one in plenty.  Only you can decide if that's too scary for you.
It is not on the NTSB 10 most wanted list.  I have not read about it in FAA Safety Briefings.
In my experience, new students don't know what is important, so as a proxy, they worry about things that are vivid.  In-flight structural failures that have videos made about them are highly vivid.  That's why my original answer started out by saying "this is not a valuable use of your attention".  If I were your instructor, I would advise you to focus your concerns on flying proficiently and learning good decision making.  If you do that, the concerns here will take care of themselves.

If one encounters air turbulence in while flying glider, how to deal with it, and what to avoid?

There is no "if" here.  You are definitely going to encounter air turbulence. That's how you know you're doing it right.
How to deal with it? Pay attention to your instructor, monitor your attitude, remain calm, and fly the aircraft.

(1) - Why 8 years?  Because I got bored.


Is it possible to see the same sunset twice from an aircraft?

Concorde did something similar: it would take off from London at sunset and then fly West faster than the Earth's rotation, so you would get a sunrise in the West on board.

This capability was also used for solar eclipse flights. While a solar eclipse lasts no more than 8 minutes on the ground, Concorde was able to stay in the Moon's shadow for 74 minutes.


What is the status of a bravo airspace when the associated TRACON is evacuated?

In cases where a given unit of airspace (for example, a Class D circle around an airport with a tower) is only in effect part time, there is always a note to this effect in the FAA's "Airspace Designations and Reporting Points" document.  The current (August 2019) edition of this document is FAA Order JO 7400.11D.  The Class B airspace for KSLC is listed on pages B-25-26 and there is no notation that it is only in effect part-time.  In fact this is true of all Class B airspace.  Some Class C airspace is only in effect part time-- an example is Lincoln Airport (KLNK) in Nebraska.  However in such a case the airspace opens and closes according to a set schedule that is published in the Airport Facility Directory or in NOTAMs.

The Class B airspace at KSLC definitely does not stop existing when an unexpected circumstance closes the associated air traffic control facility.  In the absence of authoritative information to the contrary, you need to assume that you should not enter the airspace without a clearance.  Checking for NOTAMS would be one way to check whether the FAA has temporarily authorized some unusual procedure for the special circumstance you describe.

In a NOTAM search via this link selecting an "archive" search (click on "location" tab for this option) and using "KSLC" as the search term, we see various NOTAMs for March 18 (ILS approaches unavailable, etc) but nothing indicating that any part of the Class B airspace was temporarily revoked.  Some of the NOTAMS key to messages that may be seen on this
Air Traffic Control System Command Center website.  It appears that none of the NOTAMs or messages pertain to alternative ways to get clearance to enter the Class B airspace.


What is the relationship between the UH60 Blackhawk stabilator function lateral sideslip and pitch coupling?

The sideslip to pitch coupling is a result of the canted tail rotor and the asymmetry of the main rotor downwash. The tail rotor thrust pushes the tail to the right and upward (pitch down). The main rotor downwash across the tail boom also generates a pitch up motion.  The 'static' position of the stabilator is set (stab range is 10 deg up to 45 deg down based on airspeed) to counter this pitch tendency.

A right sideslip condition will result in a reduction of tail rotor vertical thrust resulting in a pitch up motion. The stabilator is programmed downward to counter the pitch up. Conversely a left sideslip will result in increased tail rotor vertical thrust and a pitch down motion.  In this case the stabilator will be programmed up to counter the downward pitch.


Is DAL-A required for twin-engine helicopters with FADEC?

With no reversion to a direct mode, ie retaining control of the engine possibly with limitation after fadec failure would imply DAL A since that fault results in loss of ability to maintain flight.

With some form of control reversion, the authorities would accept a much lower dal.

You cannot claim credit for the second engine since both engines use common. Software and hardware. So any common cause, common mode fault could take out both engines.

For part 29 helicopters  I would expect Dal A, part 27 probably B..


Why does only class C airspace have an "outer area"?

The Class C outer area is the airspace surrounding Class C airspace out to 20nm, and from the lower limit of radar coverage to the top of the controller's airspace.  The outer area is not charted, although you can see in the white boxes (in the chart below) adjacent to Class C airports that you can initiate communication within 20nm.

ATC offers Class C services (e.g., flight following) on a workload-permitting basis to participating aircraft operating in the outer area, and aircraft in 2-way radio communication will receive IFR/VFR aircraft separation services.
So you can think of Class C airspace as 3 concentric rings: the 20nm outer area, the 10nm shelf area, and the 5nm surface area.
Source AIM 3-2-4


Why does stall speed decrease when flaps are deployed?

Your stall speed decreases because the $C_{L_{MAX}}$ of the wing increases with flaps deflected.

Deploying flaps increases wing camber and increases both $C_L$ and $C_D$ at the same AoA and airspeed. Depending on the type of flap, the critical AoA actually reduces: the airfoil with simple flaps deflected stalls at a lower AoA than without flaps.

Slats or leading edge flaps do not change the $C_L$ at the same AoA, but allow for a higher AoA and therefore higher $C_L$ before the airfoil stalls.


How to compute quaternions from raw IMU and magnetometer data?

If all equations are digitally computed multiple times per second, all variables are updated at every frame and the integration error is only one time-step old. Full Flight Simulators use four sets of quaternions to compute the state of the aircraft in earth reference frame. To illustrate how it is done in FFS flight dynamics, here is a partial set of the steps that take place:

$$ \dot{E_1} = 0.5 \cdot (-E_4 \cdot p - E_3 \cdot q - E_2 \cdot r) + E_1 \cdot C_Q * C_{Q\Delta t}\tag{1}$$
$$ E_1 = \dot{E_1} * \Delta t \tag{2}$$
$$ \Sigma E^2 = {E_1}^2 + {E_2}^2 + {E_3}^2 + {E_4}^2 \tag{3}$$
$$ C_Q = 1 - \Sigma E^2 \tag{4}$$
$$ E_{1P} = E_1 * \frac {1}{\sqrt{\Sigma E^2} } \tag{5}$$

Equation (1) is one of four equations for $\dot{E_1}, \dot{E_2}, \dot{E_3}, \dot{E_4}$, while $p,q,r$ are aircraft roll, pitch, yaw rates.
$C_Q$ is a quaternion correction factor which uses the sum of all quaternions squared.
$C_{Q\Delta t}$ is a timing correction factor and should be less than the iteration rate in Hz. A constant value is empirically chosen that gives good stability.
Equation (2) is a simple Euler integrator using the actual time step of the computation frame. So if we're computing at 1000 Hz, $\Delta t$ = 0.001.
$ E_{1P}$ is the prime quaternion substituted in the transformation matrix from body to earth axes.


Airbus control architecture - where does the actual autopilot live?

Short answer: Autopilot is a feature of the Flight Management And Guidance System (FMGS), and in particular each of the two Flight Management And Guidance computers (FMGC) manage its autopilot.

  Are the ELACs and SECs merely actuator controllers for the control
  surfaces?

Correct, but they are reconfigurable in case of failure of one of the SEC, ELAC or FAC. In addition the ELACs are used to detect the excursion off the flight enveloppe (e.g. alpha prot). They inform the FMGC of such situations.

  It seem that ELACs and SECs are autopilots themselves

No, AP is a separate function of the FMGC (and of the FAC).

FAC, ELAC, SEC are flight control computers, but are not equal.

FAC (Flight Augmentation Computer) in particular is devoted primarily to rudder control, and all the associated functions (e.g. yaw damper). It is a main component of the autoflight system.
Ailerons and elevators are directly controlled by the Flight Management and Guidance System (FMGS), which includes the autopilot.

Autoflight system presentation by Airbus:

  The auto flight system (AFS) installed on the aircraft is made up of
  two types of computers :

  the flight management and guidance computer (FMGC)
  the flight augmentation computer (FAC)

  and two types of control units :

  the flight control unit (FCU)
  the multipurpose control and display units (MCDU).

  The functions of the FMGC are :

  autopilot (AP)
  flight director (FD)
  automatic thrust control (A/THR)
  flight management.

  The functions of the FAC are:

  yaw damper
  rudder trim
  rudder travel limiting
  calculation of the characteristic speeds and flight envelope monitoring
  acquisition of the yaw AP order.

Redundant FMGS are divided in two functions: Command (issue commands to flight controllers) and Monitor (monitor the result of the commands, e.g. by analyzing air data and inertial data to detect anomalies).

The FMGS has different functions:

It uses the navigation database containing aerodromes, waypoints, navaids, procedures, etc, for the routing of the aircraft.
It takes into account aircraft performance data to manage the vertical aspects of the route.
It controls navaid receivers (VOR, DME, ILS, etc) and use navigational data.
It receives air data (from pitot, static pressure sensor, pitch angle probe) and inertial data.
It monitors the progress of the aircraft on the route programmed into the flight plan.
It issues flight guidance cues using the flight director indicators on the PFD.
It takes into account short term instructions entered by the crew using the FCU, and long term instructions entered using the MCDU.
It manages flight control laws and laws reconfiguration after controls failures.
It is coordinated with the Autothrust system which, with the FADEC, control fuel flow and engine thrust (FMGC is interfaced with ECUs/EECs).

The manual way of controlling the aircraft is:

FMGC gives instructions to the crew using the flight director cues and the yaw cue.
The pilot follows the cues with the controls (rudder pedals, side stick)
Pilot commands are taken into account by the flight control computers (FAC, SEC, ELAC) which determine the way control surfaces will be moved, possibly limiting the deflection ordered by the pilot to maintain the aircraft within its flight envelope.
FAC, SEC and ELAC orders are sent to respective actuator controllers.
Two notes on this transmission:

There is a final control function on the actuator, to allow actuator redundancy for control surfaces, e.g. for elevators:

  Each servojack has three control modes: Active: The jack position is
  electrically-controlled, Damping: The jack follows surface movement,
  Centering: The jack is hydraulically retained in the neutral position. (Source)

ELAC, SEC and FAC can be reconfigured according to law degradation status, the outputs of these FCC can be sent to different actuators, so the electrical circuit between an FCC output and an actuator input includes some switching circuitry.

Because of the two notes above, sending an electric order to the actuator doesn't mean the actuator will move the control surface, it depends on the current mode.

When the autopilot (AP) is engaged:

The cues displayed by the FD and yaw indicators are converted directly into orders to the flight control computers. So AP is just automating what the pilot would have done when following the cues.

While in cruise only one AP can be engaged, landing may requires the two AP for automated approach and landing.

FMGS computer location

Source of all images: A320 family ATA-22 Autoflight Maintenance.


If an aircraft flies straight ahead, does it follow an orthodrome/great circle?

There isn't a perfect answer to this, but effectively yes.

Anything that moved in a completely straight line would of course leave the curved  surface of the Earth and go off in to space. And realistically no vehicle of any kind could perform the (lack of) manouvers described above with no control changes.

To perform the best approximation of 'straight flight' while staying on the surface of the Earth would mean deviating from the true straight line only in a direction perpendicular to the Earth's surface. This in turn means staying in the plane defined by containing the vector of direction of initial motion and also the centre of the Earth. The intersection of the Earth's surface with this plane - i.e. the path the craft would actually follow- would be the great circle. And in answer to the last part, yes, when flying a great circle the heading constantly changes.

EDIT: This does, of course, assume a reference frame relative to the Earth, as pointed out in comments..


When was the Speed Trim System implemented on the Boeing 737?

Boeing's patent (US4676460A) for the STS was filed on 1984-11-28, the same day of the 737 Classic (3/4/500 series) entering service.

So since the addition of the bigger engines on the Classic, it's been there.

Below is from a 737 flight manual of a company that had both the Classic and NG at one time, which highlights the differences between the two series.

The 3 (for -300) in a circle is non-EFIS, in case you're wondering how the two 3's differ.


Can you safely operate a 777 with diesel?

No. The fuel system would risk to clog up with gelled diesel fuel in the low temperatures at cruise altitude. If you had omitted "safely" in your question, the answer might be different.

Before I repeat what others have written before, I refer you to this excellent answer by @voretaq7. The essential part is:

  Why don't we burn highway diesel or heating kerosene in a 747? In a
  word, purity. The additional controls imposed on Jet-A fuel by the
  associated standard produce a product with well-known properties. When
  you fuel a plane with Jet-A you can be confident that fuel won't
  freeze in the tanks at altitude (at least not unless you cold-soak it
  below -40 degrees). You also know the fuel will be "clean" and won't
  gunk up fuel filters or leave deposits inside the combustion core of
  the engine that can cause problems later.


Why are almost half of the world's helicopters in North America?

What are most of these civilian helicopters in North America being
  used for?

As listed below, Medical and Police use are quite common in the US. The Coast guard runs a fleet of rescue choppers and divers along with their boats. Many news stations also run helicopters for traffic and other areal coverage. There is a fairly sizable market for Powerline, Pipe-Line and Survey related work from rotocraft. There is even a case for moving precarious items.

There is of course a large market here in the US for private, owner flown/operated helicopters in the US. This is at least in part due to the lower costs of private flying in the states. The US airspace system is largely funded by taxes on avgas as well as other federal funding and does not have the same user fee structure that Europe has implemented. In other words here in the states you need to pay to rent or own the plane and gas it up but the use of the air is free. In Europe you will have the same costs with an added cost to use the airspace. In Europe you can also expect AvGas prices to be a bit higher across the board. Although many helicopters are turbine based and run on Jet-A.

  More specifically, in North America what are the uses for helicopters
  that aren't common in other parts of the world?

Moving people relatively trivial distances... In many places, general sightseeing. If your bold enough, aerobatics. Although many of these uses are also common elsewhere in the world. However due to the nature of aviation laws here in the US, its a bit easier (and somewhat cheaper) to fly small aircraft.

  Does this unique demand come mostly from offshore drilling, police, or
  medical usage?

Police and Medical is fairly common around the world. Oil rig transport occurs only in places where off-shore rigs are used/drill (many reside close to the US or Asian shores).

  Why don't they use helicopters for those purposes in other countries?

They do, for example the UK has a pretty large helicopter medical effort and there is the WestPac life saver helicopter service in Australia. There are efforts in Greece and many other places in the world for that matter.


Turboprop engines typically have a core which includes a compressor and turbine that rotate as a unit (although an engine might have more than one such "spool"). The gas generated by the core drives a "power" turbine which, via a gearbox, drives the propeller, which by the way has a non-trivial rotating mass. The core and power sections rotate independently of each other. So, upon a commanded power increase, the core will first spin up, throwing more gas at the power turbine which will then speed up. The delay is therefore due to the rotating mass of the propeller and the fact that it rotates independently of the engine core.

For what it's worth: turboprop engines are just a specific application of a turboshaft engine - where the energy of the gas produced by the core is captured through a power turbine to drive a shaft, which could be used to power anything - propeller, helicopter rotor, electric generator, etc.

I should add that there are exceptions to the above, like the Garrett TPE331 which have only a single shaft.


Can a human get sucked into a jet engine?

Yes. Human beings can get sucked into jet engines if they are close enough- this has happened multiple times in a number of aircraft ranging from A319 to A6E intruder.

However, it happens only in rare cases- usually in case of miscommunication or a mistake, when safety procedures are not followed. The following image shows the safety hazard area for aircraft engines.

A warning poster, available from Boeing, reminds ramp and maintenance workers
about the dangers of engine ingestion; image from Boeing Aero

In addition, the engines also have hazard-area warning decals on the nacelles to warn the ground personnel of the dangers.

Warning signs on engines; image from Boeing Aero.

As for the maximum weight that can be ingested, it will vary with the engines, though they have been known to ingest items from safety pylons to baggage containers, and of course people.


Could a helicopter fly like a plane this way?

You've described a tail-sitter aircraft. Instead of a helicopter that tilts sideways to cruise, it's a airplane that can sit on its tail and uses thrust to take off vertically, before transitioning to fixed-wing horizontal flight. This makes more sense since a plane spends more time in cruise than takeoff.

They were first demonstrated by Nazi Germany during WWII. A major benefit over the tiltrotor or tiltwing is that you don't need the bearings that can support the thrust of the engines or lift of the wings. You can also use a single centerline engine. Existing designs use contra-rotating propellers or jet thrust vectoring for anti-torque instead of the helicopter tail rotor.

The idea has been revived recently for UAVs, which don't have the occupant comfort problem:

Aerovironment SkyTote (US Government photo)


Can this design provide more lift force than thrust from engine?

Because there is no free lunch.  A single wing behind a propeller or a fan can see some amount of performance gain from being in the propeller's slipstream, but, when you start stacking multiple wings together...it gets a little trickier.

A single wing can get an advantage from the swirl induced by the propeller, in addition to the increased speed you've remarked upon.  In a thesis written by LLM Veldhuis on wing propeller interactions, he notes that, when you have a propeller operating in front of a wing and rotating such that the inboard blade is always moving up, it changes the local angle of attack on the wing behind the propeller.  This modifies the lift distribution (notionally shown in the figure below) and ultimately decreases the induced drag of the wing for a given operating lift coefficient.  A set of experiments by Witkowski et. al. (Propeller/wing interaction) in the 1980s recorded a wing seeing up to 40% savings in induced drag based on the adjustment of a tractor propeller's rotation rate!

This is what I've, at least, seen cited at the most prominent effect of having a tractor propeller in front to of a wing.  If you have a small enough wing, though, say on the scale of UAV, there's a good chance you could have a significant portion of your wing in the propwash, which can keep the flow attached to the wing at higher angles of attack, letting you, potentially, keep a control surface or two unstalled and able to maneuver the aircraft when they normally wouldn't.

However, that's not lift, and it doesn't quite answer the question about the multiplane setup.  The problem with stacking wings so closely to each other goes back to investigations in the 1920s and can be most easily explained, I think, with the venturi effect.  When air is accelerated by the curvature of a wing, the static pressure decreases and you can a suction force, which, on the upper surface of a wing, translates into lift.  However, stack two wings (or other objects) closer together (as in the picture below), and you get something...not so good.  The image below is from a conceptual rotorcraft design submitted by the University of Maryland for the 2016 American Helicopter Society Graduate Design Contest and is a kinda strange thing called a quadrotor-biplane-tailsitter (we named it Halcyon).  However, the upshot of the image (which is colored by local pressure -- the more negative the Cp, the lower the pressure) is that, due to the wings and fuselage (the bit in the middle), you are playing a game of diminishing returns.

While the bottom wing sees very high velocity air going over it, leading to very high lift, that same low pressure zone also generates a strong downforce on the fuselage, effectively mitigating a lot of your lift (the design team estimated that it killed almost all of it, actually) from the lower wing.  The upper wing, since there's a little extra space, isn't as effected by that same phenomenon, so, in the end, the aircraft had enough lift, in theory, to fly...but it's not an efficient configuration at all.  The same would be true for a stack of wings.  In a 1923 paper by Max Munk entitled General Biplane Theory, he estimates that, in order to minimize interference effects between wings, they should be spaced apart by at least 3 chord lengths.  That would easily move your wings so far apart that not even two wings could easily stay in the propeller wake...at least for full size aircraft.


What did they do before on-board toilets?

Go to the toilet before departure, and hope you can find somewhere to land if nature calls suddenly :)

Same really as before a long car journey today...

Of course aircraft of that time didn't have very long endurance, so the situation wasn't likely to arise that you'd need to make a pit stop to let nature take its course. You'd have a scheduled stop anyway well before that.


Do I need to get a new AFSP approval if I change to a new part 61 instructor?

Yes, you will need to apply for AFSP approval for your new training provider. The Application Guide for the AFSP says in step 7:

  It is possible for a Candidate to have several active training requests at a given time. These requests may be for the same or different flight training providers. Each training request form will be processed separately; AFSP approval is valid only for the Provider listed in the application.

So if you needed AFSP approval for your original training provider, you will need a new approval to switch to a different provider.


Why are the engines not tucked underneath the wings of airliners?

To bring the Center of Mass forward, and to be able to raise the jet engines, which then permits shorter and lighter landing gears.

This is what the 737 did when it moved to the bigger CFM56 engines:

Old vs new:

(Top, bottom)

Related: Why do we use pylons to mount the engines on jetliners?


At what minimum occupancy ratio can airlines operate profitably?

They can operate with 0 passengers, but will most likely not generate any revenue (unless cargo is carried to generate additional revenue). Revenue and profit on a passenger flight (assuming no paid cargo) will be based upon how many tickets were sold at which price, so the number of passengers required for any given flight to break even will be variable and cannot be answered in a general way.


Is there any requirement that airports have distinct names?

There's no requirement for names. Location codes can't be the same though.


Why is the B787 one of the few aircraft with electro-thermal wing anti-/de-icing?

Partially because 787 has no bleed air available for any purpose. Its engines do not draw bleed air traditionally. Any pneumatic system draws air from other pumps. Hence electro-thermal wing anti-ice system is needed since no bleed air is available.


Do the captain and first officer log the same hours for a flight?

Both log time, they just log it as different things. This is similar as a student and instructor logging time, but for different roles. The captain is the pilot-in-command and thus logs 'PIC', the F/O is second-in-command and logs 'SIC'.

The pilot who is tasked with controlling the plane is called 'PF' or "pilot flying", and the other is called 'PNF' or "pilot not flying", or "pilot monitoring". This doesn't affect who's PIC and who's SIC though, and if I understand correctly, it's not generally logged who's actually flying.


How to select a Lead In Fighter Trainer in the presence of both single engine and twin engine fighter jets?

Fighter lead-in isn't about becoming an expert in the training jet, it's about learning the fundamentals of flying tactical aircraft -- air combat maneuvering, strafing, bombing, etc.  So the difference between the aircraft flown in LIFT and the aircraft that the pilot will go to next isn't all that important.

I've never heard of any issues the US Air Force had with students flying AT-38's (2 engines) in fighter lead-in training then going to F-16 training.  The unique aspects of operating the single-engine F-16 are all covered during the F-16 course, and there are LOTS of differences between that and the AT-38.  Removing one of those differences, the # of engines, wouldn't be worth adding a whole new aircraft to the LIFT course -- a very expensive proposition for negligible gains.

So no, the number of engines in the eventual aircraft vs in the LIFT trainer is immaterial.


Why has the range of movement of the control surfaces changed over the past year?

We found the problem. The control stops are under the seat and are made of plywood. It looks like at some point in the past someone had added a small layer of plywood to reduce the control deflections but that over time the glue had deteriorated or the wood had swollen, so that there was now too much stop. Removing the extra ply and sanding the glue back to the wood fixed the problem.


Can a Boeing 767-200 fly at 510 knots at a height of 400 metres?

The speed is secondary - what determines the physical limits of the Boeing 767 is Mach number and dynamic pressure.

510 kts at 400 m in standard atmospheric conditions equals Mach 0.775. This is well within the limits of the Boeing 767. But at 400 m it produces a dynamic pressure of 40,567 N/m², and that is too much. The maximum dive speed $v_D$ of the 767 is 420 kts.

This only means that flying at 510 kts is illegal, but it is still possible. If the airplane dove down to those 400m from enough altitude, it would entirely be capable to reach this speed, but would slow down once it stops diving.

There are several effects which can cause a catastrophic failure when flying too fast:

When the aircraft flies into a gust, the resulting load factor can overstress the structure.
When the pilot commands large control inputs, he will also overstress the structure.
Flutter might also cause structural damage.

The maximum Mach number of the 767 is 0.91 (0.05 above the maximum cruise Mach number, which is 0.86), and this corresponds to 523 kts in 11,000 m.  Thankfully, certification requirements demand a margin of 20% between the maximum speeds and flutter onset speeds, so flutter might be close, but is still tens of miles per hour away when diving to 510 kts. Remember, to experience flutter you need also to excite the motion first. Here is a good discussion of this topic.

In short, flying a Boeing 767 in 400 m at 510 kts is not recommended, but is entirely possible and most likely even safe when done in calm air and by a calm pilot. It only won't last long, because the engines will not produce enough thrust to maintain that speed. Flying this dive requires guts, but no special skills.


Why do glider licences have fewer restrictions than powered aircraft?

First of all, gliders fly slowly. Everything happens more slowly than in other aircraft, and this helps to make flying them less challenging than you might think. Flying them well is a different matter - this requires a lot of skill and good physical health.
Historically, the early age limits were introduced in Nazi Germany when the Deutscher Luftstportverband (DLSV) and later the NSFK organized groups of adolescents to let them build and fly gliders. Flight training started at the age of 14, mostly in very simple, bungee-launched gliders like the Zögling or SG-38 which were flown in summer and built or repaired in Winter. Since bungee launching is a very labor-intensive process and flights last only a few seconds, this was less about pilot training than keeping the young occupied and under the influence of the Nazi party.

Bungee launch of a Zögling glider (picture source)
And it worked. Accidents did happen, but were almost never fatal since all operations happened at low speed and altitude. Therefore, these age limits were exported together with the idea of flying unpowered aircraft.
Note that in Europe the same health certificate is required for glider flying as for flying GA aircraft.
Now to your concerns about the demanding nature of gliding:

Glider flying is done from airfields which are suitable for GA aircraft (or the gliders could not be aerotowed) or winch launching. 800 meters is about the minimum, and this leaves plenty of space to land a glider.
Flight training is done initially only in the direct vicinity of the airfield, and students are supposed to stay within a cone which allows them to reach the airfield at any moment. Flying cross-country comes much later, when the students have made more than a hundred landings and know how to get the plane down in a certain spot. Again, the slow speed helps to make such landings simple if the pilot is prepared.
Today, training is initially in two-seaters, so there is an experienced pilot around for the first landings and the first cross-country flights.
Aerotowing is also quite simple, and altitude management while in tow is more challenging than keeping the right distance from the towplane. Again, this is done initially in two-seaters, and all the glider pilot has to do is to fly with the same bank angle as and slightly above the towplane. The rope takes care of the rest.


What are the rules for right-of-way on final approach: by aircraft category or only by height?

The C172 has right of way, it's lower. The rules are in 14 CFR 91.113 and the only place where categories are mentioned is in 91.113(d), which is specifically about converging traffic at "approximately the same altitude". For landing traffic, the lower aircraft has the right of way.

People spend lots of time and energy discussing who has right of way on final, what "on final approach" really means, if it's OK to cut off a faster (or slower) aircraft, if an aircraft on a 5-mile final prevents other aircraft in the pattern from landing etc. But the discussion often becomes a bit academic: practically speaking the point is to be safe, not create any problems, and not cause other aircraft to go around or maneuver to avoid you. Think of it like pulling out of a side street in your car: if another car is coming then you shouldn't cause him to brake hard or swerve to avoid you.


While flying having trouble estimating how far I am from Airport

My GPS tells me the distance.

Otherwise, my experience says:

15 miles (and about 3,000 AGL) is where I'm not entirely sure I have the airport picked out.
10 miles is where I can see the airport, but not pick out specific details and airplanes.
5 miles is where I can see the airport clearly, and setup for the centerline.


Why shouldn't the pilot change the aircraft's configuration while avoiding windshear during landing?

As far as landing is concerned, it is better to leave the landing gear down because if something goes down and the aircraft touches the ground, it is better to do so with the landing gear rather than the aircraft fuselage. Also, the retraction process may increase drag, not what is desired.

During landing, the retraction of flaps (which may be already at their max) can cause loss of lift (as you noted). Reduced airspeed due to windshear causes loss of lift; retracting the flaps in this condition is not desirable.

There is also the point that during the critical moments when the pilots are trying to pilot the aircraft during wind shear, their attention should be in flying the aircraft and not in fiddling with controls.

From FAA Advisory Circular 00-54 Pilot Windshear Guide:

  CONFIGURATION

  Maintain flap and gear position until terrain clearance is assured. Although a small performance increase is available after landing gear retraction, initial performance degradation may occur when landing gear doors open for retraction. While extending flaps during a recovery after liftoff may result
  in a performance benefit, it is not a recommended technique because:

  1) Accidentally retracting flaps (the usual  direction of movement) has a large adverse impact on performance.

  2) If landing gear retraction had been initiated prior to recognition of the encounter, extending flaps beyond a takeoff flap setting might result in a continuous warning horn which distracts the crew.


Are there any known maintenance issues with older Mooney wooden wings?

You may want to look around here or here or even here but the short answer is they are a wooden wing airplane that comes with all the issues a wooden wing airplane does. One of the major things to look out for is the M20A's that had a wooden tail, those should generally be passed up on. The later planes should require some inspection of the joints where the tail meets the rest of the airframe as it is a stress point (if memory serves). For what its worth you are better off with a metal mooney. With a wood plane you need to inspect for rot the way you would for corosion on a metal plane.

Like any wood aircarft the M20A's can suffer from delamination which would need to be checked for. unfortunatly the list of people that still work on wooden planes is dwindling with time so it may be hard to repair this. It would be well worth the effort to seek out a mechanic that has experience with the A model and can work on a PPI for you.

You can find all the AD's for the M20A here.


What was the earliest plane in push-pull configuration that flew or at least took off?

I have found a plane, that had both a pusher and a tractor propeller, which flew for the first time over Cotroceni airfield, Bucharest, Romania, on June 17, 1910. Likely there are other planes like this that flew before.

Vlaicu I plane during construction

Newspaper article about Aurel Vlaicu's first flight June 17, 1910

Source: A Vlaicu I - Wikipedia


Is there a formula to compute the elevator angle to stabilize takeoff?

You need more than the correct elevator incidence. Natural longitudinal stability works by distributing lift over the flow direction such that forward surfaces create proportionally more lift than rear surfaces.

Now it is important to know that only pure supersonic lift will be evenly distributed over the chord length of a wing. In subsonic flow the center of lift is at 25% (and even less for wings of small aspect ratio), so you now need to place the center of gravity such that it will be ahead of the 25% chord line of the sum of all lifting surfaces. To distribute lift for this forward center of gravity location, the incidence of the elevator needs to be several degrees smaller that that of the wing. Adjust incidences (say 5° for the wing and 0° for the tail), and then trim the center of gravity by adding ballast or shifting masses to make the aircraft fly straight.

Since airfoil camber shifts the incidence of zero lift to more negative values, you can alternatively use a cambered airfoil for the wing (say, at now 2°) and use a symmetric airfoil for the elevator at again 0° incidence.


What is the relation between airspeed and generated heat at constant drag?

You express a desire to simplify things by assuming a weightless rocket engine, so I follow with a weightless vehicle which only creates drag to overcome aerodynamic resistance.

This resistance has two parts: One is adiabatic compression when the air ahead of the approaching vehicle is compressed, and the second is friction. Friction shows up in strong shocks and in a layer of high shear stress around the vehicle which is called the boundary layer. Let's also neglect other heat sources like solar radiation which becomes more intense with altitude.

If we look at small changes, the adiabatic temperature rise ∆T due to a deceleration from a speed v to zero is:
$$∆T = \frac{v^2}{2\cdot c_p}$$
where $c_p$ is the specific heat at constant pressure (unit $\frac{J}{kg\cdot K} = \frac{m^2}{s^2\cdot K}$). The amount of heat Q which gets transferred to our vehicle depends on this temperature increase, but also on the air density $\rho$ and the flow speed:
$$Q = v\cdot\rho\cdot c_p\cdot∆T$$
Denser air contains more heat energy, so the proportionality with density should make sense. But why speed? If the hot air is replenished at a faster rate, more heat can be transported to the vehicle's surface per unit of time. Now we have a heat flow which grows with the cube of flow speed, but that is not all. We still need to understand how density will be affected. When air is heated, density drops, but the flow at the forward facing parts of the vehicle is compressed as well, so density goes up in the end:
$$\frac{\rho}{\rho_{\infty}} = \left(1 + \frac{\kappa}{2}\cdot Ma^2\cdot c_p\right)^{\frac{1}{\kappa}}$$
with $\kappa$ as the ratio of the specific heats and $Ma$ the Mach number of the flow. Now things get messy because all parameters will change with temperature, so let me short-cut to NACA report 1381 which covers the re-entry heating of spheres. Here the rate of heat transfer is proportional to the cube of speed, so flying faster at constant dynamic pressure will cause a quadratic rise in the temperature of the surrounding air and a rate of heat transfer rising with the cube of speed due to convection.


What would prohibit a T-38 Talon from being certified in the Acrobatic category?

That an aircraft is eligible for a category is not a basis to say that the aircraft should be certified in that category. In other words, though there is nothing prohibiting T-38 being certified in acrobatics category, FAA will not certify it unless someone approaches it for that reason.

The T-38 would come under military surplus aircraft, which is covered by FAA Advisory Circular 20-169 for Military and Special Mission Modifications and Equipment for Commercial Derivative Aircraft.

However, there are some T-38s being operated by civilians in US, which are type certified under FAA Experimental Category (most are used by NASA, Boeing etc for research). One of the aircraft owned by Thornton Corp. is certified under the 'Exhibition' category, which permits the user,

  to exhibit an aircraft’s flight capabilities, performance, or unusual characteristics for air shows, motion pictures, television, and similar productions, and for the maintenance of exhibition flight proficiency.

I'm not sure if this aircraft has been used in that manner though.


How does one determine runway orientation without a local wind rose?

Assuming that you are not bound by local topography and thus can build the runway in, theoretically any direction you like, there are a few things you can do. First, you could set up a small weather station and record some data. You could then use this data to determine your direction. You can also use a site like this one to see the historical wind/weather data in the area. This will help you get an idea of the prevailing winds at near by.


Are well-known IR AAMs 'compatible' with aircraft from other countries?

The integration of weapons in an aircraft is based on four major issues.

The first issue is the mechanical compatibility: will the airplane break when you transport or fire the missile, because the missile is too heavy and/or is too powerful?
Typically, I don't think you can fire an AMRAAM from a P-51 Mustang....
This is a huge problem, but for the examples you give, the missiles are similar to each other so there is a great chance that both Sukhoi, Mig and McDonnell Douglas fighters have enough mechanical strength to transport and fire the missile. If there is not, you cannot do a lot of things to correct it, unless you change your airplane or your missile.

The second issue is about aerodynamics: will the missile, when fired, hit the airframe? It is likely the air flow around the airframe will create whirls which that might cause the missile to be pushed into the airframe.
This issue is often solved by studying how the missile will behave in the whirls of the aircraft, and by designing it to go away from the aircraft.
Note: you also don't want your air to air missile to go straight down, because it will lose the target. So this question of aerodynamics is always important

The third issue is about sensors: if you fire a missile, you first need to "tell" it what its target is. So you need to have sensors (or external sensors from which the aircraft has info by radio) in your aircraft.
By extension, you need to have the good sensors in your aircraft (the appropriate distance to use the full distance of the missile....). Again, for the modern fighters you mentioned, it will in general be OK. Even more if you're speaking of infrared missiles that don't have that much information before launching.

The fourth issue is electrical and electronic interfaces. In most of the cases, you can plug them in.
But you might have to adapt the current and tension on the electrical interfaces. On that point, you are lucky because the aircraft industry uses conventions of frequency for electrical current in order to have components with the smallest weight. So there is a good chance that Russian as well as Western jets have the same frequency of currents, and can adapt the tension and current.
On the electronic interface, you might have to change the missile launcher on the aircraft to have the correct plugs. I don't know how huge is it to change a missile launcher, but I guess that if it is possible for military people to do it, it takes at least a few hours.

To conclude, there is a high probability that all the missiles you mentioned are compatible with some industrial adaptations provided to the missile and/or the missile launcher, and some programming to do in the aircraft combat system. However, combining these missiles requires that the crew doing it knows in depth both the Western jet technology and the Russian missile technology.... which might be difficult in our political reality!


What do the components of a shockwave's visual artefacts represent?

What you see are changes in the refractive index of the air, caused by the different pressure and temperature at different places. Sometimes, with the right conditions, there may be zones of transient condensation of water vapor, that add to the effect...


Single-engine plane with long range flyable in Europe

There are definitely aircraft which meet some of your criteria, namely range above 800nm and can be flown IFR. I'm not going to list them all, notable examples would be the Mooney M20 series, the Cirrus SR22, Cessna 182 and Cessna 210. No doubt there are more. The issue will be cost, you can find older M20s and Cessnas for your budget, the cheaper they are the shorter time the engines have until they need a costly overhaul and the more work they'll need.


What are RW values in Venule increments?

The best way to get a definitive answer is likely to email the FAA (there's a link at the bottom of the AIP page) but my strong suspicion is that both RW and Venule are errors caused by scanning in an old document, or maybe manually entering it.
First, if you go back to a 2002 version of the FAA's ATC orders 7110.65, there are references to "RVR/RVV" values. I suspect that "RVV" was scanned or manually entered at some point as "RW" and no ever noticed. In fact, if you search the FAA site for "RVR/RW", the only hits appear to be old, scanned copies of paper documents.
I also found an explanation that shows that RVR and RVV were often used together, which to me supports the idea that "RVV" is the correct abbreviation:

g. RVR/RVV.

Provide RVR/RVV information by stating the runway, “visual range” or “visibility value,” as appropriate, and the indicated value. The
abbreviations “R-V-R” or “R-V-V” may be spoken in lieu of “visual
range” or “visibility value.”

The latest 7110.65 doesn't refer to RVV any more, by the way:

This changes [sic] removes all references to Runway Visual Value (RVV)
from this order.

Second, "Venule". Based on the dictionary definition and Googling, it's clearly a medical term, not an aviation or meteorological one. So what might it have been? The PC/G definition from the old 7110.65 linked above says:

Runway Visibility Value (RVV)- The visibility determined for a
particular runway by a transmissometer. A meter provides a continuous
indication of the visibility (reported in miles or fractions of miles)
for the runway. RVV is used in lieu of prevailing visibility in
determining minimums for a particular runway.

I can't think of a word close to "Venule" that means "in miles or fractions of miles" but possibly the original text was "1/4 mile increments" or "¼ mile increments" (or another fraction). Depending on the original text size, font etc. it's possible that "1/4 mile" become "Venule".
Anyway, this is all speculative even though I think it's very plausible. I'd definitely email them if you want an authoritative answer.