Was MCAS part of 737 8 MAX MMEL list? I think the answer to this question is no, because I cannot find it in the PDF, but I'd like a more expert opinion.

The reason I'm asking is the assumption that if it was, its malfunction could have been remedied by switching to the redundant "side" (perhaps as in pilot/copilot systems redundancy), along with a correctly functioning angle-of-attack sensor (the one that didn't break).

It does not appear that MCAS was in any of the maintenance documents. This was part of the issue with the Lion Air crash. On the previous flight with the accident aircraft, MCAS acted on the faulty sensor data, but the pilots used the trim cutout and completed the flight. They had no reason to suspect that a trim issue could be related to a faulty AOA sensor, so just the warnings for IAS and ATL DISAGREE and FEEL DIFF PRESS were logged for maintenance. As you noted, if they had known the connection, they might have diagnosed the true cause and either replaced the AOA sensor or MMEL'ed it. Instead they focused on the Air Data Module and elevator feel computer. It wasn't until a couple weeks after this crash that Boeing sent a message to operators describing MCAS.

It's also unlikely that the MMEL would have allowed MCAS to be completely disabled. This would have required extra documentation and possibly training for the pilots on how the plane would handle differently without it. This additional training is what MCAS was designed to avoid, and would have defeated the purpose of having it in the first place. Also, if it were that simple, it seems like they would have taken this step rather than grounding the entire fleet.


If an aircraft decompresses at altitude will everyone start farting? From what I understand about how gases and liquids work, if the environment loses pressure, then it causes dissolved gases to come out of solution. For example, if a diver ascends too quickly, dissolved nitrogen will come out of solution causing the "bends".

I have heard that astronauts undergoing decompression training experience gastrointestinal distress from the effect.

Does this mean that if an aircraft at altitude suddenly decompresses that everybody will start farting?

No, they will not.

In the case of a rapid decompression, an aircraft will make a very rapid descent to a altitude, and while I'm not a physician or an expert on these physiological and biochemical processes, I doubt very much that would be enough time for dissolved gases to be released into the digestive tracts.

Even if it were, a person who experiences a sudden accumulation of gas in the gastrointestinal tract may experience discomfort or even pain, but it takes a while for gas to make its way to an exit - as anyone who has suffered from trapped wind will know.


What medical history questions are asked for a UK Class 1 Medical? For anyone who has been through a Class 1 medical in the UK, when they run through your medical history what sort of questions are they asking?

In the general medical examination they will go through the medical history you have written in FORM MED 160.


How much of an airplane's forward energy is lost to lift? An airplane needs to move forward to generate lift, and because energy isn't created from nothing, all the kinetic energy of lift comes in the form of drag, where air (air resistance) turns forward motion into upward motion.

Some of the drag on an airplane is therefore "productive" in that it produces lift, and some is "unproductive" in that it takes forward motion from the plane without providing lift.

What percentage of an airplane's forward kinetic energy loss due to drag is productive as opposed to unproductive?

In the most simple model for subsonic aerodynamics, drag is split into two components:

Zero-lift drag, that is all the drag created when the airplane produces no net lift. This kind of drag has again two components: Friction and pressure drag, that is the aerodynamic drag parallel and perpendicular to the local surface. This drag would dominate in a vertical dive or a zero-g parabola.
Drag created due to lift. Since that was explained mathematically first by using the Biot-Savart law for electromagnetic induction, this is called induced drag. The simplest explanation is: Lift is created by bending the oncoming air slightly downwards, and the reaction force is perpendicular to the mean angle of that airstream. Induced drag is the force component parallel to the initial direction of motion of the air relative to the airplane, and lift is the perpendicular component of that force. Thus, induced drag is lift times half the tangent of the bending angle.

While zero-lift drag increases with dynamic pressure, i.e. with the square of airspeed times density, induced drag decreases with dynamic pressure. Like this:

Drag components over speed for a typical glider (own work). The nonlinearity at the lowest speed is due to flow separation when the lift-creating limits of the aircraft are approached. The physics for large aircraft are the same, only the numbers will be larger.

Due to the dependency on the square of airspeed, the sum of both components has a minimum when they are of equal magnitude. However, given enough thrust, a motorized aircraft can sustain level flight at the far right end of that diagram when lift-dependent drag almost vanishes.


What would be the airspace class when no vignette is visible on a US VFR sectional chart? If a airport doesn't have a pink vignette nor blue vignette on a VFR sectional chart, but the airports around this particular airport has pink vignettes, would this airport's Class E start at 1200 AGL or would this airport be Class G up to 14,500 MSL?

For example, Grayson County (M20)  - circled here in red - has no pink vignette but other airports near it do:

The vast majority of US airspace where no more restrictive airspace exists has class E starting at 1200ft AGL with class G below. You can see an area of class G up to 14,500 MSL just north of the TCS VORTAC near to Truth or Consequences, NM which is south-southwest of KABQ. There are several other areas in the 48 states as well. As long as the airport you are talking about "near airports with pink vignettes" is not under the pink vignette, then G extends to 1200 AGL. If it's inside the pink vignette, G extends up to 700 AGL. Of course, if it lies within a pink dashed line indicating class E to the ground at such a nearby airport, then the airport you mentioned does not have any class G above it either.

One other helper I use - if you see any federal airways nearby and there is no blue vignette indicating the presence of class G up to 14,500 MSL then you can usually safely assume it is class E above 1200 AGL if no other more restrictive airspace overlies the area. Federal airways are 4 nm wide on each side or the course centerline and always exist within controlled airspace (class E or better). These are labeled on a VFR chart as the light blue lines with V-number labels - also called Victor airways. As such, V 49 west of the M20 airport you mentioned would be an example and is pronounced "Victor forty-nine".

At M20 - the airport you ask about - the airspace up to 1200 ft AGL is class G, then class E up to but not including 18,000 ft MSL, then class A at 18,000 MSL up to FL600, then class E to space.


How high does the ground effect last? Up to which height is the ground effect still significant enough to be taken into account? Would this height be sufficient to actually fly above the ground, overcoming at least trivial obstacles like trees?

The early transatlantic flights were done with heavy loaded planes that had difficulties taking off (only at the end of the runway, and only just). Could it be that these planes were flying within ground effect for rather extended distances, before picking enough speed to complete the take off?

There is no height at which ground effect is switched off. It just becomes less and less effective. There are two factors which determine how strong ground effect is.:

Height relative to wingspan: The downwash cannot move into the ground so the induced flow field around the wing is distorted. In a first order approximation, the wing affects mostly the air which flows through a stream tube with the diameter of the wing span. For an explanation see this answer. Once the height is above one semispan, the distortion of the flowfield comes to an end.
Trailing edge height relative to wing chord. For very small heights, the gap between trailing edge and ground becomes small enough to more or less block the proper exit of the flow below the wing. The result is an increase in ram pressure on the lower side and further distortion of the flow field such that the stagnation point moves down and the suction peak of the nose flow becomes stronger, adding nose thrust and reducing drag.

When moving up from zero height, ground effect diminishes rapidly because the gap between trailing edge and ground opens up and the ram effect vanishes. Moving up further will also weaken the first effect until at a height of one semispan the flow will be very similar to that of the airplane out of ground effect.

To illustrate how much happens on the last centimeters (or feet), look at the two pictures which I took from this YouTube video:

In the top picture the wing is clearly closer to the ground than its semispan, but the vortices from the flap edge trail straight behind the plane. Now move forward to the lower picture when the trailing edge is maybe half a chord above the ground. Now the trailing vortex is swept to the side because the flow, which is compressed below the wing, expands when it exits the gap between wing and ground. Additionally, the downwash becomes a sidewash, because it has no space below the wing left in which to drop.

This should demonstrate that most of the ground effect happens when the ram pressure below the wing builds up. Once the trailing edge is less than half the wing chord from the ground, this part of ground effect kicks in, and the aircraft sees a significant reduction in drag.


How should I request an IFR approach at the end of a VFR flight? Here's the scenario:

The flight starts night VFR, with broken ceiling at destination (class C airspace) and expected to improve according to the pre-flight abbreviated briefing. I'm IFR certified but prefer to stay VFR to dodge icy clouds along the way.

Now I'm about 15nm from my destination, talking to approach control, and the ATIS calls the ceiling overcast: it's apparent I'll have to file IFR one way or another. Approach is busy, but not overwhelmed.

What is the best way to handle this situation on the radio? I have the ATIS, picked an approach and have a squawk code (advisories):

a). Do I ask approach directly for the IFR clearance, and what is the officially sanctioned phraseology? Also: do I have to cancel IFR when I'm on the ground/see the runway, i.e., is the clearance to descend thru the layer and shoot an approach a 'real' IFR flight plan?

b). Ask approach if I can change frequency to FSS, file with them, then return to approach to pickup the clearance (and cancel when on the ground/view of runway)?

c). Other?

I did read How do you request a "pop up" IFR clearance?. In my scenario I have the time to call FSS, there is no emergency, I'm on flight following and could complete (b) if that's the best way to go.

Since you are already on flight following you are already in the system (ATC has a flight strip for you and a datablock on the radar).  Just call ATC and ask them for IFR to your destination.  Don't bother asking for a frequency change to FSS to file a flight plan, only to come right back on and ask to pick it up.

Austin Approach, Cessna 12345, request IFR to Austin

Since you have flight following ATC already knows your type, equipment suffix, location and altitude, so don't repeat it.  ATC should ask

Cessna 12345, verify you are qualified for and capable of IFR flight?1

and after you (hopefully) reply in the affirmative will issue:

Cessna 12345, cleared to the Austin Bergstrom Airport via fly heading 270, vector to ILS Runway 35-Right final approach course, maintain 2000.

If you are already in the approach environment you probably won't get a climb to an IFR altitude, you'll just be given whatever altitude they need for the arrival flow.
This method is faster than filing with FSS and easier for ATC (they don't have to approve a frequency change, wait around for you to file, then have you come back and wait further while your flight plan works its way through the system).  However, bear in mind that none of the "extra" search-and-rescue information you would give to FSS (fuel and souls on board, emergency equipment, filed alternate, aircraft color and markings) will be recorded.2
If you are landing at a towered airport you will not need to cancel IFR as the local controller will do this for you.  If you are landing at a non-towered airport you will need to radio ATC or FSS or telephone FSS to cancel your IFR service.

Footnotes
1This is a relatively new requirement after a non-IFR-rated pilot accepted an IFR clearance and subsequently crashed.
2Some facilities will have you rattle all that information off on the controller's frequency or a separate unused frequency and then mark that down in the flight plan remarks, just to have it on the tapes in case it's needed. If you're only 15 miles from your destination they probably won't do this but it's a possibility.


What is the relation between roll angle and pitch angle? I was wondering about roll angle and pitch angle values.
Will I get same pitch angle at different roll angles and vice-versa?

For example. At its initial position, the aircraft is standing on the runway). I got roll and pitch values from a sensor. Lets say X and Y resp. Now, when aircraft is taking off, it is obvious that it will pitch up so  my pitch angle will change to lets say Y1. Now if I look for roll Value, will it be same 'X' or it will be different?

Roll, pitch and yaw are rotations about the principle body axis of the aircraft. Roll angle, pitch angle and yaw angle together describe the attitude of an aircraft.

The principle body axes are:

X-axis is the longitudinal axis pointing out the nose of the aircraft. Rotation about the x-axis is called roll. Roll rate is denoted $p$, roll angle is denoted $\phi$
Y-axis is the lateral axis pointing out the right wing. Rotation about the Y-axis is called pitch. Pitch rate is denoted $q$, pitch angle is denoted $\theta$
Z-axis is the vertical axis pointing down. Rotation about the Z-axis is call yaw. Yaw rate is denoted $r$, yaw angle is denoted $\psi$

Initially when all angles are 0, the aircraft is wings level, nose pointing at the horizon and heading north.

The angles $\phi, \theta, \psi$ describe the attitude with respect to this initial positions. They are called Euler angles

The rotations are applied in backwards order, first yaw ($\psi$), then pitch ($\theta$) and finally roll ($\phi$).

This describes almost every possible attitude uniquely, unless the pitch angle is +/- 90 degrees. Then roll and yaw will become ambiguous.

Now back to your question. Initially on the runway the roll angle of the aircraft is 0 degrees. If the aircraft pitches up ($q$ becomes positive for a while), the roll angle will not change.

However, if initially the roll angle was non-zero, the roll angle will be affected by a pitch-up manoeuvre. You can easily visualise this with your hands.

Open your right hand with the palm facing up, you thumb at a right angle to the fingers. The middle finger is the X-axis, the thumb is the Y axis.

Now roll your hand 45 degrees counter clockwise, keeping the fingers pointed at the horizon. Your thumb will now point 45 degrees into the air. This was a pure roll manoeuvre, the pitch angle is still 0 degrees.

Now flap your hand 90 degrees up using your wrist, this is a pitch up manoeuvre since you rotate about your thumb axis which is the Y axis.

Now you see that your fingers are all in the same vertical plane, pointing 45 degrees up to your left. If you describe this position with respect to the initial position, the pitch angle is 45 degrees, and the roll angle is 90 degrees. So pitching 90 degrees resulted only in 45 degrees of pitch, but also in 45 degrees of extra roll.

Because the roll-angle was non-zero before we started to pitch, the pitch rotation affect the roll-angle.

If your sensor is not aligned with the body axes of the aircraft, you will see a lot of cross-effects between the angles during a take-off.

The mathematical relation is well described on this page, which is also the source of the images above.


What is the optimal altitude for performance and mileage in normally aspirated GA planes? Given atmospheric condition, a typical common engine (say, Lycoming 4-cylinder), and a fixed-pitch normal prop:

What are normally the best altitudes for:

ground-speed and
fuel efficiency (range)?

Is it always highest (reasonable) altitude (say >=10,000')?  the air resistance is low but so is the engine power,  or is it usually some intermediate altitude?

Does it depend on the aircraft?  Is a Cirrus SR-20 different from a Vans RV-9 from a Cessna 182 from a Piper Cherokee?

How does the efficiency of a piston aircraft change with altitude? covers a lot of ground about the primary forces (air resistance and (normally aspirated) piston/prop efficiency) and secondary forces. But it does not answer how these forces typically combine to create "best" altitudes (for mpg and gs).  The question ultimately was about how these forces could create typical optimums at different alternatives, and whether they could be different for an SR-20 or a 182.

First off this highly varies by aircraft. Piston aircraft that fall under the GA header these days have a pretty wide range of altitude capabilities. The Piper Archer I fly wont really get over 10,000 but you can get your instrument rating and grab a Mooney Acclaim which will take you well into the flight levels and get you up to 25,000 Ft.

  best altitudes for ground-speed....

The simplest answer here is the altitude at which your tail wind component is the best. Wind speed and direction does shift with altitude and in many cases your [(increased performance/cruise time) + tail wind - (reduced climb speed/climb time)] is best where ever the tail wind component is greatest and your climb does not take impractically long.

Very Generally speaking performance increases with altitude to an extent. However climb rate usually decreases so there is a break even but it for sure varies by airframe and configuration.

  fuel efficiency...

Again this varies by aircraft as well as how you chose to operate the plane. Things like running lean of peak can effect efficiency at the cost of speed typically. Some planes have little to no change in endurance at varying altitudes (although your change in airspeed may allow you to cover more distance). At 75% power my archer has almost no change in endurance as I climb.

Variable pitch propellors also offer a great deal of power setting options that can allow you to tune your efficiency even further.


What do these numbers and symbols on the ICAO SIGMET chart represent? Anybody who can identify the numbers and alphabets in the red, green, and purple circles on the chart above?

Green are latitude and longitude.

The purple are major cities, e.g. A for Accra and B for Brazzaville (west coast of Africa traced in red above).
For the top line, here's an example breakdown:

PGCE05 represents the reference to the specific chart.
EGRR represents the WAFC issuing the data (in this case WAFC London. KKCI represents WAFC Washington). In the case of a backup situation, this will remain the same even if the data is issued by the other WAFC.
161200 represents the day of the month (16 in this case) and the hour in UTC (1200 in this case) of the analysis on which the forecast is based. Note, this time will always be 24 hours earlier than the validity time of the forecast as specified in the main legend on the PNG forecasts.

Source: Guidelines for interpreting World Area Forecast Centre Significant Weather forecasts


What qualifies as "open water" with respect to FAR 91.119? FAR 91.119 governs minimum safe altitudes.  It contains a reference to open water.  What qualifies as open water in the eyes of the FAA?

Most probably the same definition as a dictionary's:

open-water. An expanse of an ocean, sea, or large lake which is distant from shore and devoid of nearby islands or other obstructions.

I searched for a legal definition but I can't find one. It's like defining a sparsely populated area, it's hard to draw a line. So sticking to charts is best I guess.

You might want to search for maritime laws that define such boundaries, which are borrowed by aeronautical charts.

On an FAA chart it's depicted like this:

Source: FAA


Change of Roll moment with change of wing position (z-direction) If I compare two identical configurations, which only differ from each other in low wing and high wing position. We assume that the lift and drag remains constant. Will I get the same coefficients in moment for pitch, roll, and yaw? Because the force arms are the same?

For a first approximation, the coefficients will be similar enough, but not exactly identical. As you correctly point out the moment arms will be the same, but the interference effects of the wing-fuselage joint may not.

That is to say, your assumption that the lift distribution will remain unchanged will likely not hold out in reality.

The stability derivatives will not be similar, however.


Can any aircraft take off using auto-pilot? So there are some types of aircraft that can land under auto-pilot (or is that a trope?). Can those same planes go from stop (at the gate) to in-the-air flight without a pilot actually touching a control column/flight-stick?

Caveats: I'm not talking about UAV's. Also, I'm not concerned about "would you," but rather "could you."

If you are asking if a plane can be taken from the gate all the way to the sky by auto-pilot I'm quite certain the answer is no.  Not because a plane can't configure itself for take off and power up the engines (I'm quite certain it can, though I would defer to more knowledgeable people for that).  Not for that reason, but rather because there is no system in place to electronically guide an aircraft through a series of taxiways all the way to the base of the runway so that it can line up to take off in the first place.

Keep in mind, ATC gives a lot of instructions for ground operations, funnelling aircraft this way and that via taxiway A through Z.  They'd have no way of telling an auto-pilot about these directions, there's no computer to send out signals and there is no voice recognition build into the plane.  If you told the pilots, they would have no way to input the instructions into the autopilot, nor would the autopilot know what to do if it ever received such instructions.  It just isn't designed to follow taxiways.

Also, beyond just taxiway layout, there are a lot of planes in close proximity on the ground, plus bunches of other important vehicles (fire trucks, fuel trucks, de-icers, etc.)  Steering around all of those, faultlessly, would be quite the feat.  We've only just gotten to the point where a vehicle can drive across open terrain without crashing itself,  I think a plane navigating an airport (and doing it while minding ATC) is a bit of a ways off.

EDIT: Raidri's video does a much better job of showing the current state of driver less vehicles, and his comment is correct. I did underestimate how good the systems are these days.

That being said, I'm not changing my answer.  There still, currently, is no way to convey ATC instructions to the aircraft.

As a point of clarification: I saw the question as asking about technology in it's current state.  Will we eventually be able to do this.  Heck yes, absolutely.  A great deal of the technology is in place and what's left is either right on the horizon or close to it.  FAA clearance will probably take some time, but we'll get there.  I was mainly answer the question from the perspective of modern tech and what is currently ready to be installed on a plane.


Why would a helicopter hold a 'nose-up' in hover? (The Grand Tour; episode 2) SAS unit fast roping from a Blackhawk.

Why is the helicopter pitched-up? Actual scene footage have it like that for a few seconds while holding steady over a building. How come it's not flying backward?

This screen grab is from a few seconds before yours was taken. No pitch is evident here.

Sketched above is rope angle and camera position (based on the staircase in both frames).

I think it's just the camera angle used that makes it look pitched combined with the rope's angle in the wind.


What is an Air-Filed Flight Plan? Are aircraft capable of filing flight plan when in flight? ICAO Doc 4444 mentions to input AFIL in the departure field of flight plan if it has been filed in the air. What is an Air-Filed flight plan? Can aircraft crew file a flight plan in-flight? If yes what are the equipment that support filing flight plans when in flight?

It is quite easy in the US but it depends on controller workload.  You need to be in a plane equipped for IFR flight and you need to be IFR current....[edit] to legally use a filed IFR flight plan.
If the controller is too busy they will make you file through a flight service station.  This can also be done in flight but requires you to change frequencies, reach the FSS, wait your turn, and then file.  The FSS puts you in the system.  Then you call ATC back and open your plan [edit] -or- open with the FSS.
If the controller has time, they will file you on frequency.


Why are Vertical tails generally tapered? I'm just intrigued to know why the vertical tail of a majority of aircraft is tapered? Is it due to aerodynamics, structural design or due to some instrumentation or multiple other reasons?

The vertical tail and the horizontal tail are wings, and follow the same construction rules. The span-wise lift distribution is much better if the wing is tapered: more lift at the root, less at the tip.

The wing can be built lighter, root area is larger, torsion stiffness is higher.
Vortex induced drag is lower.

As a reference, from Torenbeek: pages 232 & 233

  It is observed that nowadays there are basically three forms of straight wings: the tapered wing, the untapered (rectangular) wing and the wing with a prismatic inner portion and a tapered outboard portion.

About taper for wings (and for tail surfaces):

  Tapered wings have been adopted for the majority of aircraft since they offer an efficient solution on account of their low induced drag, high maximum lift, low structural weight...(and) acceptable stalling characteristics can be obtained, provided the wing is not too sharply tapered.

Untapered wings are inferior and cheap:

  The untapered wing is attractive from the point of view of manufacture, since only one airfoil contour is involved; this simplifies jigging as there are no compound curvatures. It is aerodynamically inferior to the tapered wing, but may nevertheless be the logical choice for inexpensive private aircraft, where the utilization factor is low and initial cost and cheapness of components are important.


What is the procedure when a required A/D inspection via an AMOC has gone overdue? I recently purchased an aircraft that was legally (and otherwise) airworthy.  There is a visual inspection due (any private pilot can perform it) every 10 hours, but the ferry pilot may have overlooked this during the 18 hour ferry trip.  The inspection due time has now gone over the 10 hour requirement.  Are there additional requirements other than just inspecting again for compliance, or must something be submitted to the FAA as to report a non-compliance issue?

Each AD is specific (and unique) to the procedures and compliance outlined in the AD. If the AD does not say otherwise, all that is needed is to comply with it (do the inspection), and then make an entry in the maintenance log book, and you will be good to go.

I have never seen an AD that addresses circumstances when not previously complied with. For example, a Cessna 172 requires an inspection of the horizontal stabilizer spar; it does not matter if no one has done it for 45yrs. All that is needed is to do the required inspection and it is good to go :)


What is minimum information required to identify if two people will be on the same flight? I asked this question on travel.stackexchange and got an amazing response but I was advised it better suits aviation.stackexchange and should ask here for a better response, so here it is.

I have a set of users and their itinerary details. I want to figure out who all will be sharing a common flight. I do not want to rely too much on the "Departure time" as people could have entered an approximate time into the system. How can I figure this out with minimal information?

Initially, I thought two people with the same flight number and same departure date would be on the same flight. But the same flight can be used again on the same day. Would the combination of "Flight no + departure date + departure city" be enough to identify a unique flight itinerary?

What would be optimal information to identify this?

I also have to keep in mind that there could be people with multiple flights in their itinerary and if at least one flight is common with another passenger, that has to be shown too.

Yes, Departure City + Flight Number + Departure Date will identify a single flight.

Where you may have a problem is if flight 123 goes from AAA to BBB to CCC to DDD on a particular day, and passenger 1 gets on flight 123 at AAA and flies all three segments, getting off at DDD, while passenger 2 gets on flight 123 at BBB and off at CCC.  To identify that those two are together on flight 123 departing BBB, you'd need to either have passenger 1 enter all the segments of his flight, even though he doesn't change planes at (nor even really much care about) BBB and CCC, or you'd need information about all the flights from some source, so that you know that "flight 123 from AAA to DDD" goes to BBB and CCC in between.


Why is the total count of people on a plane given as the number of 'souls' on board? Why don't they just say 'people' on board, why souls? What is the origin of this term? I'm thinking it comes from sailing as I think I've heard that term in reference to crews out at sea, but I'm not a sailor so I don't know.

The primary reason is probably that it ensures there is no confusion between passengers, crew, or infants. Technically, "passengers" is the number of seats occupied, "crew" is both the pilots and flight attendants on duty. So any small children brought on as "lap children" will not be included in the "passengers" count, but should be included in the total number of people on board.

I found another interesting point over on the English Stack Exchange site, which is that dead bodies are sometimes transported as well. In this case, some might consider these "people" as well. Also, in an incident, the bodies should not be confused with the regular passengers.

So, "souls" effectively communicates the number of living humans on board.

There may certainly be holdovers from the maritime influences on aviation as well.


Why don't transponders have active and stand-by value like radios? This answer explains how pilots when switching code on transponder should either carefully avoid temporarily squawking one of the emergency codes, or should temporarily put the transponder in stand-by.

Radios (both comm and nav) usually have an active frequency and a stand-by frequency and the pilot selects the stand-by frequency and then activates it with a button, which avoids temporarily selecting different frequency and limits the time when the radio is not receiving.

Why don't transponders have similar mechanism? It seems it would be much more useful for them than it is for the radio.

For navigation and communication radios the feature of having a second readout that can be pre-set to the next frequency is useful since the next frequency is usually known in advance. Your next transponder code is a somewhat random number and the moment that you will get it is not as predictable as a frequency change. Therefore there is no need for a pre-set / standby squawk code in a transponder.

Also, in a communication radio, when you pre-set the wrong frequency and cannot establish communication after the switch over, a single button press will bring you back to the original frequency. This prevents prolonged communication loss. This is similar in navigation radios.
For a transponder such a feature has no value, you won't switch back to the previous squawk code.

The problem of inadvertently selecting a special code can be addressed by other means. For example a digital interface that requires confirmation of the selected code before it is activated.


How does the power distribution change for a turbofan engine from being stationary to going at full speed? I have found out that a turbofan engine of say an F-16 is producing zero power when stationary since $Power = Thrust × Velocity$. But assuming that the engine is producing the same thrust, it appears that regardless of whether the F-16 is stationary or moving, the engine is still consuming the same amount of fuel and therefore there is power output that is constant in both cases. I also found that the power I tried to calculate from the equation above is the propulsive power, so there must be something else that is consuming the rest of the power.

To make this simple, I will use some numbers. Let's assume a turbofan engine is capable of producing 100 kN of maximum thrust with no afterburner while consuming  4 kg of fuel per second. For the sake of simplicity I'm gonna use a figure of 30% thermal to mechanical efficiency for the engine that is constant through all of the following cases and which means that  there is 30% $×$ 4 kg $×$ 42  MJ/kg = $50 MW$ of mechanical power available at all times. With 43 MJ/kg being the heat value of the jet fuel.

Case 1: The engine is stationary and producing max thrust and therefore the propulsive power is zero so I assume that the 50 MW available is completely used in heating and accelerating the exhaust.

Case 2: The aircraft is accelerating and is now at half its max speed at sea level which is say 200 $m/s$. The propulsive power is now = 100,000 kN × 200 = $20$ $MW$ and so I'm also assuming that the other 30 MW remaining of the 50 MW available are still being consumed in accelerating and heating the exhaust.

Case 3: The aircraft reached its max speed at 400 $m/s$ at sea level. The propulsive power is now = 100,000 kN × 400 = $40$ $MW$ and as before, 10 MW are consumed by the exhaust.

So, if I understand this correctly, the power distribution goes from 0% propulsive power and 100% exhaust power when the engine is stionary to 40% propulsive power and 60% exhaust power when the aircraft is at half full speed and continues to shift the power available to propulsive power at higher speed until it is 80% propulsive power and 20% exhaust power. My question now is: In simple terms and with acceptable approximations, does this shift that redistributes the power from exhaust to the propulsive power as the speed increases really happen?

Your definitions are correct and your derivations correctly use the law of conservation of energy, so yes, the power distribution change does happen.

The more important question is what does this actually mean. Energy is a rather curious quantity in that while it is conserved in each reference frame (including non-inertial as long as appropriate potential is included), the values of kinetic and potential energy will be different in each!

You can look at all the cases in the reference frame of the aircraft and then the propulsive power will always be zero, because the velocity is—by definition of the reference frame—zero. But the very same situation viewed from the reference frame of the Earth it will be as you describe, and from the reference frame of the air mass it will be similar, but the values will differ slightly as the reference frame move relative to each other at the speed of the wind.

Note that enthalpy does not vary in coordinate transformation, so the sum of the power towards moving the aircraft and towards accelerating the air stream is will be the same in all the reference frames. Most easily calculated in the reference frame of the aircraft from difference in kinetic energy between the intake and the exhaust. This is the output power of the engine itself, and comparing this with the heating value of the fuel will give you the thermodynamic efficiency. Thermodynamic efficiency of turbine engines increases with flight speed due to pressure recovery, i.e. the ram air pressure increasing the effective compression ratio.

Also note that this variance in propulsive power is there for all kinds of propulsion systems, including propellers and wheels of ground vehicles. The propulsive power is always zero at standstill, and how quickly it increases depends on the reactive mass they have available. The more reactive mass, the larger the propulsive efficiency (= propulsive power to output power) will be, and the faster it will increase with velocity. Propellers have some more reaction mass available due to larger diameter, and wheels have whole Earth available, but their thrust is still limited by the surface friction and the maximum torque of the engine (and the friction of the clutch for engines that don't produce torque at zero RPM).


What is the advantage of combining the rudder and brake pedals in aircraft? I've read about several aircraft having their rudder and brake pedals very close together. To me this seems confusing and prone to error. It looks easy to mistake the rudder / brake pedals and inadvertently press the wrong one when flying or taxiing the aircraft. Since these are fundamentally important controls, this could lead to disaster.

So what is the advantage of keeping the rudder / brake pedals in this configuration? Are there any historical reasons for this design choice?

All of the aircraft that I have ever seen have the rudder and braking functions combined into one set of two pedals.  To operate the rudder you press on the bottom part of the pedals, so that they slide back and forth on tracks, and to operate the brakes, you press the top part of the pedals so that they rotate towards the floor.  The left pedal operates the left wheel brake, and the right pedal operates the right brake, so you can use differential braking to turn the plane.  For rudder operation, the motion of the two pedals is locked together (i.e. press on the right pedal for right rudder, and the left pedal moves aft while the right pedal moves forward).

Because of the two different motions (rotation for brakes versus sliding for rudder) there isn't a problem with hitting the brakes when you want rudder or vice versa.  Typical early training is to operate the rudder using your toes on the lower parts of the pedals, so and to only put your whole foot on the pedal to actuate the braking mechanism.


What are the units for the bearing to center of an airport from radio aids to navigation in chart supplement? Is the bearing to the center of airport for a radio aid to navigation in the chart supplement, true course, magnetic course, is it based on the VOR's radials, or is it something else?

It's almost certainly magnetic. Page 12 of the Chart Supplement (sample airport information) has this information at the bottom (emphasis mine):

All bearings and radials are magnetic unless otherwise specified. All
mileages are nautical unless otherwise noted.
All times are
Coordinated Universal Time (UTC) except as noted. All elevations are
in feet above/below Mean Sea Level (MSL) unless otherwise noted.
The
horizontal reference datum of this publication is North American Datum
of 1983 (NAD83), which for charting purposes is considered equivalent
to World Geodetic System 1984 (WGS 84).

Because this information is in a kind of footnote at the bottom of the page, I suppose you could say that it's possible it only applies to that specific page. However, the mention of "this publication" strongly suggests that the information applies to everything in the Chart Supplement.
You can also see that it distinguishes bearings from radials, meaning that it's highly unlikely that the word "bearing" is being used to mean "radial" on p.27.


Icing conditions temperature range: SAT or TAT? Considering the general rule of thumb defining potential icing conditions: temperature between +10 and -40 degrees C and presence of visible moisture,
is the temperature range regarding TAT (total air temperature) or SAT (static air temperature)?

For the purpose of aircraft limitations, it's TAT for the upper limit of +10C.  SAT for the lower limit of -40C.

Generally once you are going faster (in the RJ, above 230kts) you only need to have cowls on for all visible moisture conditions, and wings only need to be on if actual icing is happening or indicated.  Ice can form on cowls from the temperature drop related to the inlet pressure drop, like carb ice, so the requirements are more conservative for the cowl A/I system.  Cowls are turned on and off way more frequently than wings.


Why is the Tu-95 so efficient despite having propellers that spin faster than the speed of sound? I've ready many, many times that propellers are not efficient near the speed of sound because it's so hard to get a tip-speed above Mach 1.

Then I came across this:

It's the Tu-95 "Bear", a propeller-driven bomber whose blade tips actually move faster than the speed of sound. This is the only propeller aircraft I've ever seen whose blade tips do this. There were even reports that submarines' SONARs could hear it from a long way off because those supersonic blade tips were so noisy.

And the plane has a range of 15,000 km. That's pretty good, on par with today's huge commercial airliners.

So how can propellers be very inefficient at supersonic speeds, yet something like this is buildable on propeller-power only?

Edit: Here is the main point of my question: It seems that "all my life" I've been told, "propellers are not efficient at supersonic tip-speeds, and this is what drove the industry to jet power." And yet here is this apparent counterexample, the Tu-95. So how is this possible? What am I missing?

Here is a somewhat related question asking if helicopter blades regularly go supersonic. This is another point I've heard many times: heli blades don't do that because that would make them very inefficient. I'm assuming the rotors are effectively governed by the same laws of efficiency as a propeller for a fixed wing aircraft.

Edit: the B-52 was mentioned in comparison so here are some figures:

$$\begin{array}{|l|r|r|r|} \hline
 \text{Model} & \text{Fuel capacity [L]} & \text{Loaded weight [kg]} & \text{Range [km]}\\ \hline
\text{B-52} & 181,610  & 120,000  & 16,230 \\ \hline
\text{Tu-95} & 95,000  & 171,000  & 15,000 \\ \hline
\end{array}$$

This to me says the Tu-95 is very much more efficient, because it has significantly more weight and significantly less fuel capacity, yet has about the same range.

Yes, propellers have problems at high speed, but if done right, they still have an advantage over turbofans at speeds up to Mach 0.8. Look at the inner engine gondolas of the Tu-95: They are elongated and thicker aft of the trailing edge. This was done to stow the landing gear in them, but also to area-rule the aircraft. The Tu-95 applies knowledge that was gained only in the early jet age. This, of course, also explains the swept wing.

Next, it uses contra-rotating propellers which spin very slowly (just 750 RPM). By having two coaxial propellers spinning in opposite direction, the efficiency at high speed is improved. The first propeller pre-swirls the flow so the flow conditions on the second propeller are more favorable for thrust creation.

The tips of the fan blades of a modern turbofan also move at supersonic speed, so the supersonic propellers on the Tu-95 do not create a direct disadvantage. By keeping the relative thickness of the blade near the tip low, the drag increase can be kept at tolerable levels. But make no mistake: Supersonic flow adds wave drag, and especially around Mach 1 the zero-lift drag coefficient of everything which moves through air has a maximum. It would make the Tu-95 even more efficient if it would fly at a lower cruise speed where the propeller tips are still subsonic, but Tupolev wanted to push the design to the highest useable cruise Mach number.

What you learned about propellers and jets is not wrong, but it is not a black and white world, either. Airliners use jet engines to fly at the highest cruise speed possible, but at the cost of higher fuel consumption. If they would restrict themselves to lower speeds, plenty of fuel could be saved. But too few people would book these flights, because on intercontinental routes they will take noticeably longer. Note that turboprops are still used in regional air traffic, and even the regional jets have lower flight speeds than the intercontinental jets.

Now to the efficiencies of engine types:

Piston engines are the most fuel efficient aviation engines. Their drawback is a constant power output over speed, so that thrust is inverse to speed. This helps for acceleration at take-off, but limits maximum speed. A modern piston engine uses 240 g of fuel for providing 1 kW of power over one hour: 240 g/kW-h. Diesel engines use as little as 220 g/kW-h. This number is already true for the old Jumo 205, among the first aviation diesel engines in operation 80 years ago.
Turboprop engines are next, and their power increases a little over speed due to ram pressure (which will raise the internal pressure in the engine by approx. 30% at Mach 0.8). Their power-specific consumption is about 300 g/kW-h but goes down with increasing size, so the biggest turboprops approach piston engine levels of efficiency.
Jet engines are less efficient than both, but are better for flying fast and high. Their thrust drops even less with speed, so the better basis for expressing consumption is thrust, not power. The typical fuel consumption of a modern jet engine (GE-90) is 30 grams of fuel per Newton of thrust over one hour (30 g/N-h) when run stationary, and twice that in cruise at Mach 0.85. Modern Military jet engines achieve 80 g/N-h at take-off and have roughly constant thrust and specific consumption over speed. Since most innovation happens on turbofans these days, the most modern turbofans again approach piston engine levels of efficiency, but if you compare the same technological standard, they are less efficient than their piston and turboprop contemporaries.

In all cases, thrust is created by accelerating a mass of air backwards. The general equation for propulsive efficiency $\eta$ is $$\eta = \frac{v_{\infty}}{v_{\infty}+\frac{\Delta V}{2}},$$ where $\Delta v$ is the speed increase of the mass of air due to that acceleration. This formula shows that it is better to accelerate a big mass of air only a little than a smaller mass by a lot. Propellers do this and for that reason offer the best efficiency. Turboprops use less efficient, but lighter gas turbines for creating power, but retain the efficient propeller. Civilian turbofans try to increase the mass of air by increasing their bypass ratio, and only the military is using the least efficient types with bypass ratios below 1, because they are the best choice at supersonic speed.

Below you see a plot of the thrust-specific fuel consumption in cruise condition of different engine types over their bypass ratio. The inverse relation is easily visible.

Plot of the thrust specific fuel consumption in lb of fuel per lb of thrust per hour of different engines over the logarithm of their bypass ratio (picture source).

To make a comparison between piston and turbofan engines possible, let's compare fuel consumption at take-off. The formula for static thrust of a propeller is $$T_0 = \sqrt[3]{P^2\cdot\eta_{Prop}^2\cdot\pi\cdot d_P^2\cdot\rho},$$ where $P$ is the shaft power, $d_p$ the propeller diameter and $\rho$ the air density. For our example, we use a four-bladed prop of 3.4 m diameter and an engine with 1111 kW power. Its static thrust is 10.727 kN when we assume standard atmospheric conditions and a prop efficiency of 85%. The fuel flow will be 266.6 kg per hour, and relative to thrust this is 24.8 g/N-h or just 80% of that of a modern turbofan.

I wonder if even the enthusiasts could guess what airplane I used, because I obfuscated it by using those unfamiliar metric units. I guess nobody will argue that it is not optimized for fast flight, so this comparison should also hold for the Tu-95, for which I have less data available.

Here follows the requested expansion on propeller tip speeds. Thanks to the excellent comment by @JanHudec not much is left to say: The propeller diameter is 5.6 m and their speed is 750 RPM, so the circumferential component is $5.6 \cdot \pi \cdot 750 / 60 = 220 m/s$. Add to this the cruise speed of Mach 0.67 (taken from this site — others list quite incredible numbers) at altitude, where the speed of sound is 295 m/s. Mach 0.67 equates there to 197.65 m/s, and vector addition gives 295 m/s for the propeller tips, exactly Mach 1.0. This means that the propeller is subsonic over its whole span.

But the top speed is quite a bit higher. Thanks to the excellent work of Ferdinand Brandner and his team back in the Fifties the NK-12 engines developed already 12,000 horsepower back then, and their power output has since been raised to 14,795 HP. This allows a top speed of Mach 0.82, and now the tip speed comes out at 327 m/s or Mach 1.08 — mildly supersonic. This means that the outer 30% of the propeller experience supersonic flow.

I fail to find a source for the range figures you list in your question. Again I refer to this site: It is 7,800 miles or 12,552 km at a cruise speed of 400 knots or 179 m/s which equals Mach 0.606 at altitude, resulting in Mach 0.96 for the propeller tips. Therefore, it seems the best range is reached with subsonic propeller tips.


Is it practical to install seat belts in airline lavatories? Many times passengers might found themselves in the lavatory, when turbulence happens. During such times, do the handlebars inside the lavatory provide adequate support to the passenger, or does it makes more sense to install some kind of seat belt?

My question comes from the premise, that if a passenger is in the lavatory when sudden turbulence hits, he/she may not have such necessary aids to prevent injuries, which might lead to a claim of negligence against the airline.

I am mostly looking at answers concerning commercial airlines.

While it may appear at first glance that a seatbelt could simply be installed, it is not a simple answer. There would actually have to be some significant certification analyses and testing done. Seat belts tend to be fabric. While those fabric lap belts are approved for the rest of the cabin, the lavatories have different certification requirements especially regarding propagation of a fire in the enclosed space. There would have to be fire certification testing done and analyses to verify that the information gained during the certification testing was applicable to all configurations.

Also, who would want to use or even touch a lap belt that was installed in the lavatory while someone with explosive diarrhea experiences turbulence? Eww! I wouldn't want to use it as a passenger or service it as a mechanic. That is a biohazard.


Cargo aircraft temperature What is the temperature in the storage compartment on board of a cargo aircraft? I'm ordering a temperature-sensitive package by airmail and wouldn't want it to freeze.
There are many questions related to temperature of the luggage compartment on a passenger airplane but I didn't find anything about cargo-only aircrats.

Many things including bottles containing liquids break when the temperature drops below zero, so the cargo hold is always maintained above freezing; 7°C is typical (source).  This applies to both pure cargo aircraft and mixed passenger/cargo airplanes.

That said, it's harder to control for (say) cargo sitting around on tarmac while waiting to be loaded on the plane.  Your cargo shipper can likely arrange temperature-controlled shipping for you, but at a steep extra cost, and this is usually meant for perishables where the main danger is heat, not cold.  But unless you're shipping something to/from Siberia, you'll likely be fine.


How much simulator time can I use towards a part 61 instrument rating? I am doing Instrument Rating under part 61 with a CFII.

To meet the 50 hours cross country requirement (d 1), can I log some of the PIC time in a simulator?
There is a 20 hours limitation on the use of simulator (h 2). So, if I have 40 hours of simulator time and 15 of them are cross country, can I use those 15 hours towards the cross county requirement and the other 5 hours towards the 40 hours requirement (d 2)?

  (d) Aeronautical experience for the instrument-airplane rating. A
  person who applies for an instrument-airplane rating must have logged:

  (1) Except as provided in paragraph (g) of this section, 50 hours of
  cross-country flight time as pilot in command, of which 10 hours must
  have been in an airplane; and

  (2) Forty hours of actual or simulated instrument time in the areas of
  operation listed in paragraph (c) of this section, of which 15 hours
  must have been received from an authorized instructor who holds an
  instrument-airplane rating, and the instrument time includes:

  (i) Three hours of instrument flight training from an authorized
  instructor in an airplane that is appropriate to the
  instrument-airplane rating within 2 calendar months before the date of
  the practical test; and

  (ii) Instrument flight training on cross country flight procedures,
  including one cross country flight in an airplane with an authorized
  instructor, that is performed under instrument flight rules, when a
  flight plan has been filed with an air traffic control facility, and
  that involves—

  (A) A flight of 250 nautical miles along airways or by directed
  routing from an air traffic control facility;

  (B) An instrument approach at each airport; and

  (C) Three different kinds of approaches with the use of navigation
  systems.

  (h) Use of full flight simulators or flight training devices. If the
  instrument time was provided by an authorized instructor in a full
  flight simulator or flight training device—

  (1) A maximum of 30 hours may be performed in that full flight
  simulator or flight training device if the instrument time was
  completed in accordance with part 142 of this chapter; or

  (2) A maximum of 20 hours may be performed in that full flight
  simulator or flight training device if the instrument time was not
  completed in accordance with part 142 of this chapter.

The simulator doesn’t meet the definition of aircraft.

§61.1   Applicability and definitions.
Cross-country time means—
(i) Except as provided in paragraphs (ii) through (vi) of this
definition, time acquired during flight—
(A) Conducted by a person who holds a pilot certificate;
(B) Conducted in an aircraft;
(C) That includes a landing at a point other than the point of
departure; and
(D) That involves the use of dead reckoning, pilotage, electronic
navigation aids, radio aids, or other navigation systems to navigate
to the landing point.
(ii) For the purpose of meeting the aeronautical experience
requirements (except for a rotorcraft category rating), for a private
pilot certificate (except for a powered parachute category rating), a
commercial pilot certificate, or an instrument rating, or for the
purpose of exercising recreational pilot privileges (except in a
rotorcraft) under §61.101 (c), time acquired during a flight—
(A) Conducted in an appropriate aircraft;
(B) That includes a point of landing that was at least a straight-line
distance of more than 50 nautical miles from the original point of
departure; and
(C) That involves the use of dead reckoning, pilotage, electronic
navigation aids, radio aids, or other navigation systems to navigate
to the landing point.


What is this strange structure, of a type often seen by pilots in hilly regions? I spotted a strange structure near a few paragliding spots in italian Alps. It's a screen about 10 meters wide, 6 meters tall, mounted on concrete base on ridge top. Someone said it's a training target for fighter jets, is it true? If so, is it targeted with real ammo or some kind of video-based training system?

Pictured: Monte Dolada, 46°11'34.68"N, 12°20'25.41"E

It's a reflector for microwave links, a passive repeater.

More info here (article in Spanish): http://notascordobesas.blogspot.com/2015/01/el-repetidor-pasivo-de-microondas.html


Aircraft Carrier Launches: ABE Checks and Signals Somehow I got hooked on videos of aircraft carrier flight deck operations, and have been binge-watching over the last couple of days. (Glad it's a long weekend...)

I've been able to understand many of the hand signals from the Aircraft Signals NATOPS Manual (NAVAIR 00-80T-113), but I'm missing a lot of the context of what I'm seeing, because much of the video footage focuses rather narrowly on specific individuals and tasks rather than showing the "bigger picture."

I actually have many more questions than I will put down in this first post, and I will likely post more later. But here I will start off with just a few questions about the "Aviation Boatswain's Mate - Equipment" (ABE) rating, because it looks the most interesting to me.

All questions reference this video, which has some pretty clear shots of ABEs at work. (Parenthetically, I assume that the reason there are two ABEs working the catapult attachment task is that the "hands-on" one is under instruction, and his work is being checked by the other one. Have I got that right?)

At 0:27 the two ABEs appear to be waiting for some kind of go-ahead signal from someone out of frame (to whom they are pointing?), before signaling for the aircraft to be brought forward to position the launch bar in front of the catapult shuttle. Who are they pointing at, and what condition needs to be satisfied before they can proceed?
At 0:38, before signaling for catapult tension, they go through what appear to be a series of visual check-ins with three (or maybe four) separate individuals out of frame:

ahead of the aircraft;
behind the aircraft on the near side;
ahead of the aircraft again (same individual as before?);
behind the aircraft on the far side.

These checks happen quickly enough that I believe they can only be looking
for simple thumbs-up signals. What are the roles of the specific individuals they are looking to, and what, specifically, are those individuals verifying that make it okay to proceed with catapult tensioning?

When tension is finally applied at 0:44, they make a final check of the holdback bar before getting clear. What possible failure modes of the holdback bar are they looking for, specifically?
At 1:01, when the catapult officer signals “launch,” the deckedge catapult operator (center of frame, with hands raised overhead to signal “final ready”) turns his whole body first left, then right, before actuating the catapult. Is he checking something (what?), signaling something (what?), or both?

I'll take a stab at this.  It's been many years, but I was a shooter (yellow vest, green helmet).  Someone with a better memory can chime in.

You're correct that one of the hook-up operators is under instruction (U/I).  There are also 2 shooters in this video; one of them is under instruction as well.  Sometimes the instructor will give a thumbs up to indicate that the U/I operator's signals are correct and should be obeyed.

Before 0:27 they are looking toward the "island" for a green beacon that indicates the Air Boss is ready for the crew to launch planes.  At 0:27 they see the beacon turn green, then they look to the shooter for the hook-up signal.  The shooter is checking for several things: green beacon on, deck clear forward, jet blast deflector (JBD) raised, nobody on the wrong side of the foul-deck line, proper aircraft configuration (flaps down, tailhook up, etc), wind speed hasn't dropped since the catapult steam setting was entered, and thumbs up from the squadron QA folks (white shirts, behind aircraft on both sides) who are watching the jet for proper functioning, no leaks, etc.  When all those conditions are met, the shooter gives the hook-up signal, which triggers the hook-up operator to call for the jet to taxi forward.  The yellow-shirt (ABH) receives the "rolling" signal from the hook-up operator, then signals the pilot to pull forward, which causes the tow bar to drop down in front of the shuttle.
I think they are checking for a thumbs-up from the center-deck operator (sitting in the hole next to the shooter; thumbs up indicates good catapult steam pressure and good wind over the deck, which the shooter is no longer monitoring).  They also may be looking at some of the same things the shooter is looking at.
The holdback bar needs to be properly set in its slot in the deck, properly attached to the aircraft, not leaking hydraulic fluid, and IIRC there's a shiny metal ring between the orange and white sections that indicates proper functioning and tension.
The deck edge turns his whole body so everyone can see that he's looking fore and aft for clear deck forward and JBD up, and maybe also so he can see past his arms which are raised so that everyone can see he's not pushing the launch button yet.  At this point the shooter hasn't been looking forward because he has been mainly focused on the pilot and aircraft while the engine is running up and the pilot goes through flight-control checks, salute, etc.

Additional comments: most of the time the shooter and center-deck operator are below decks inside the glass "bubble" but they do practice deck launches to stay proficient.  I did my shooting on an older ship that didn't have the bubble at all.  Needless to say, communication is purely visual because you can't hear anything.  Even the operators with radio or phone headsets can't hear anything when jet engines are blasting nearby.

Finally, if you think this looks complicated and dangerous, remember this video was taken in daytime in good weather.


Why do most A320s make that distinct scream on takeoff? I've noticed that the engines on the A320 make a very a distinct sound on takeoff. Is there something about the CFM-56 series that causes this?

This noise can be heard in this video.

The whining noise is generated by the rotating components in the engine. At takeoff power for an engine of that size, the fan is rotating at about 5200 rpm. This is about 86 times per second. There are also 22 blades on the fan at the front of the engine. This means a given point sees a fan blade pass about 1900 times per second. Each fan blade changes the pressure as it passes, resulting in a tone of about 2kHz. This is the whine that you hear. At takeoff the tips of the fan blades are going supersonic, each one creating a shockwave.


Can flaps be used to perform rotation and flare? TL; DR using flaps to directly control sink/climb rate near ground = simpler and faster response = easy to fly airplane?
Rotating is the pitch up during takeoff that causes the aircraft to leave the runway.
Flare is the pitch up just before touchdown that causes the sink rate to drop.
In both maneuvers, a downforce is applied to the tail, to re orient the aircraft to increase the angle of attack, so as to increase lift. The objective is this lift, rather than a change in orientation.
Hence, would it not make sense to use a method to directly alter lift, if available? Specifically, would it not make sense to increase the flap settings just for the moment these maneuvers are done? Takeoff is done at a non-maximum flap setting. When the airspeed nears the required value for liftoff, flaps could be lowered to full. Final approach can be done with takeoff flaps, and just above the runway, instead of pulling back, the flaps could be lowered.
I know the flaps are slow to deploy, but the moment of the fuselage makes pitching slow as well, doesn't it? Even if the slow movement of the flaps erodes any advantage in terms of response time, the decreased angle of attack at the leading edge would be favorable in terms of stall characteristics, wouldn't it? And the requirements to touch the main gear first on landing could be satisfied with even a relatively small pitch angle. And tail strikes could be avoided.

While this is an interesting idea, there are some key issues with it. As a GA pilot, here are my issues with that concept.

Changing flap settings causes signifigant differences in aircraft handling. If I was, say, on short final, and I changed my aircraft's configuration - it would be difficult to maintain a stable approach profile to the runway. If I were to deploy my flaps just above the runway, the aircraft would lose its "stable approach" and I would not have as much control authority over where, when, and how my aircraft touches down. There is a reason GA and Commercial pilots alike are taught to maintain a stable approach and have the aircraft fully configured well before landing.

I would never adjust flaps on take off or climb out (until at a reasonable altitude). The reason is simple. First of all, aircraft have operating limitations. You would not take off with full flaps because they generate too much drag, and hence limit aircraft performance. They are great for landing because of that same drag. However, If I were to take off with (theoretically) full flaps in a Cherokee or Cessna, it would not be safe to retract them until sufficient airspeed and altitude has been attained. Raising flaps at low airspeeds causes a noteworthy forward pitching motion and a temporary arrest of the climb rate. This is dangerous when in a low-airspeed, low-alitude situation and is warned against by CFIs.


Under EASA rules, what do I need to do to be able to perform aerobatics? In addition to the aerobatics mentioned in the title, I would also be interested into formation flying.

Is there a specific licence to be acquired? Does a licence covers both?
What are the requirements?

The appropriate rules are in FCL.800 Aerobatic Rating

A licensed pilot may not undertake aerobatic flights unless they hold an Aerobatic Rating
40 Hours of Flight Time (or 120 launches for sailplanes as PIC) completed after issue of respective license
Aerobatic Training course including theoretical knowledge and 5 hours or 20 flights
Aerobatics must subsequently be flown in same category aircraft as used for rating
No revalidation/renewal requirements
Be issued a certificate of satisfactory completion of the instruction for the license endorsement

So there is no specific license to be obtained, however there is a specific rating, which is just an endorsement in your logbook.

Its not clear from the documents that I've read that formation flying qualifies as aerobatics. Some other countries don't consider formation flying an aerobatic operation.


What does the letter "D" next to the VOR frequency and name mean? In most charts there is the letter D next to the VOR freq. What does this mean? I assume the H and L in brackets in other charts mean high and low VORs (correct me if im wrong). But what does the D itself stand for?

Since you're specifically referencing a Jeppesen chart, we'll go right to the source.

Jeppesen's "Introduction to Jeppesen Navigation Charts" has a glossary and explanation of all terms and symbols.

The answer to your question reads as follows:

  1 — VORDME. Low and High/Low charts include a Compass Rose with VHF
  Navaids. Shadow box indicates navaid is airway component, with
  frequency, identifier, Morse code and INS coordinates. Small "D"
  indicates DME/TACAN. Class indicated by: (T) Terminal, (L) Low, (H)
  High.

So, the D indicates that the VOR has a co-located DME radio.

(and, no need for correction to your assumption: the H and L in brackets do, indeed, refer to a High or Low class of VFR)


what is the statistical risk of head rotor failure? What are the chances of rotor failure? What percentage of crashes are related to a malfunction of the rotor head?

I worked medium and heavy transport helos in the Marines, and I never heard of an incident caused by a rotor head failure. Blades, transmissions, all kinds of other things, sure, but not main rotor heads.


How far should commercial jets be from each other when on the runway or while departing? Does anyone know how far should a commercial jet (787,777,etc...) be away from each other in runway or in process of taking off?

Are there public resources that I can look up?

The FAA's Federal Aviation Regulations (FAR's) are all publicly listed here.

There are a wide variety of cases to consider on the ground and during departure but you can find a lot of the regulations/guidelines in this document.

For example here is the case for wake turbulance seperation,

  Separate a small aircraft weighing 12,500 lbs. or less taking off from an intersection on the same runway (same or opposite direction
  takeoff) behind a departing small aircraft weighing more than 12,500
  lbs. by ensuring that the aircraft does not start takeoff roll until
  at least 3 minutes after the preceding aircraft has taken off.
  Separate a small aircraft taking off from an intersection on the same runway (same or opposite direction takeoff) behind a departing
  large aircraft (except B757) by ensuring that the aircraft does not
  start takeoff roll until at least 3 minutes after the preceding
  aircraft has taken off.

That is just one example, the document is very lengthy and covers a lot of cases, you should be able to find what you are looking for. You should also keep in mind that things like weather and local airport policies will cause the regulations to vary a bit. For example a local noise abatement may cause the seperation/interval timing to be larger than required to adhear to the noise abatement.

That covers mostly what ATC will see and do, you can take a look at this document for how pilots look at departure procedures.


Can I model propellers used in electric aircraft the same way as I model RC quadcopter drones? I am writing an article about mathematically modelling a flying car, using D'Alembert's principle. I need some information about the propellers ... When I worked with the mathematical model of a small RC quadcopter I found that many researchers consider the thrust of the propeller proportional with the square of its angular velocity and the same for the torque of the propeller. I am interested in something similar for the bigger propellers ... Is the assumption still holding? Can someone give some numerical values for the constants? The flying car (VTOL vehicle) I am modelling has six propellers, therefore I need less then 1000 N of thrust for each propeller. Therefore my first question is: Is it ok to say

$F = a \cdot \omega^2$
$T = b \cdot \omega^2$ for big propellers? $F$ is the thrust of the propeller along its axis, and $T$ is the torques developed by the motor to rotate the propeller. Please give some examples of commercial products ... if possible. Thank you!

The thrust T of a rotor can be given as:
 $$ T = C_T \cdot \rho \cdot A \cdot (\omega \cdot R)^2$$

With:

$\rho$ = air density [1.225kg/m$^3$] at sea level
$A$ = area of the rotor disc [m$^2$]
$\omega$ = angular speed of the rotor [rad/s]
$C_T$ = thrust coefficient.

$C_T$ depends on the configuration of the rotor: blade pitch, number of blades, blade chord etc. It can range from 0 to 0.01, without knowing more about the config of your rotor we can take the average at 0.005 the value 0.001, see update below.

The torque Q follows a similar format:

$$ Q = C_Q \cdot \rho \cdot A \cdot (\omega \cdot R)^2 \cdot R $$

For a given $C_T$, we can look up $C_q$ in the following figure, valid for a propeller solidity of 0.1. For a $C_T$ of 0.005 we find a $C_Q$ (= $C_P$!) of 0.0004, for the updated $C_T$ of 0.001 the $C_Q$ = 0.00015  Source:

Update

The above $C_T$ is valid for helicopter rotors. For quadcopters with their much smaller rotors, induced power losses, tip losses etc are much higher. This document gives a detailed discussion on $C_T$ of small rotors, although a direct comparison cannot be made since they use a different definition of $C_T$. With this in mind, and using the definition of $C_T$ as above, a better choice for $C_T$ would be 0.001, and the corresponding $C_Q$ is 0.00015.


What are the major non-pilot causes of GA accidents? I'm considering getting a private pilot license. From what I've read, pilot error is the leading cause of major airline crashes -- such as on this page, but that's for major commercial carriers. As the pilot, pilot error is something that I can address myself. One of the things that concerns me is the chance for an accident due to circumstances beyond my control.

What's the cause breakdown for general aviation accidents? What are the most common mechanical failures?

For a statistical overview of General Aviation accidents I suggest checking out the Joseph T. Nall Report prepared by the AOPA Air Safety Institute. Everything I'm citing below comes from the most recent report (the 23rd report, covering 2011).

The leading causes of accidents in 2011 were:

Pilot Error - About 77%
This includes poor flight planning, weather encounters, and a host of other things that we could at least theoretically avoid if we actually did the things we were taught to do in training.
Mechanical or Maintenance related - About 13%
This includes engine failures, control system problems, landing gear failures, etc.

The largest chunk of mechanical failures are "powerplant failures", which account for 38% of the mechanical failures, or a bit under 5% of total accidents.

Everything Else - About 10%
This includes freak occurrences like a flight instructor "walking into a moving propeller" (I kid you not, it's in the report!). A large chunk of these are also engine failure for causes that could not be determined.

If we add all the engine/powerplant failures together (the explainable ones from "Mechanical" plus the unexplained ones from "Everything Else") they come out to be  11.5% of total accidents, and are statistically the number two cause of Non-Commercial General Aviation accidents after "Pilot Error".


What is the difference between RVR and visibility? What is the difference between Runway Visual Range (RVR) and visibility? Looking at the definitions, both RVR and visibility tells the pilot whether they have enough visibility to land on the runway or not? Are they measured using different instruments or is there something else that I missed out?

The definitions are somewhat different:

Visibility for aeronautical purposes is the greater of:

the greatest safe distance at which a black object of suitable dimensions, situated near the ground, can be seen and recognised when observed against a bright background;

the greatest distance at which lights in the vicinity of 1000 candelas can be seen and identified against an unlit black background.

Runway Visual Range (RVR) is the range over which the pilot of an aircraft on the centre line of a runway can see the runway surface markings or the light delineating the runway or identifying its centre line. (ICAO Annex 3)

(Visibility on SKYbrary)
The RVR is specific to the runway and its actual lighting system (i.e. can be different for different runways of the same airport at the same time), where visibility only refers to the general range an object or light can be seen in the current conditions.

RVR can be measured along the runway, e.g. using a transmissometer:

RVR equipment is typically found at larger airports, and RVR visibilities can be reported for up to four designated runways at an airport. It's calculated using sensors like this:

The sensors are located along the runway, and they're approximately 14 feet higher than the centerline of the runway.
On most runways equipped with RVR, there are three sensors: a touchdown sensor, a mid-point sensor, and a rollout sensor.

(boldmethod.com)
On the other hand, visibility is typically measured by detecting scattered light from a strobe (scatterometer):

The most common method of measuring the extinction coefficient is the forward scatter system. A high intensity xenon strobe transmitter directs a beam of light in the visible spectrum at the air close to the sensor and a photo diode at the adjacent receiver is used to detect the amount of light received. The extent of scattering is increased by the presence of particles of water, dust, sand or smoke. The use of transmitted light within the visible spectrum allows this type of instrument to most accurately simulate human perception of visibility. The range of visibility for which a measurement can be derived is typically between 15/20 m and 20/30 km with an accuracy up to 10 km of +/- 10%. A typical instrument is illustrated below:

(Automated Cloud Base and Visibility Measurement on SKYbrary)
For more details on measurements, see:

How is the visibility at airports measured?

How do visibility and RVR compare?
The ICAO Aerodrome Meteorological Observation and Forecast Study Group published A Comparison of RVR and Visibility Reports:

Previous studies have shown that the reported value of RVR is typically higher than the associated visibility value. [...] These findings are consistent with the fact that the assessment of RVR takes advantage of high intensity runway lights while the visibility assessment is based upon lights of moderate intensity.
[...]
A comparative review of the 5,662 METAR / SPECI from three aerodromes over a five year period that contained both prevailing visibility and RVR information revealed that, in equivalent terms for 2825, or 50 per cent, the RVR report was less than the visibility.
[...]
meaningful predictions of RVR from prevailing visibility reports can only be  accomplished if the assessment of both RVR and visibility is by reference to common sensor(s).

It seems, RVR is typically higher than visibility, but only if the runway lighting system is using high intensity lights.


What do aircraft designers like Burt Rutan do to cheaply practice geting good at designing aircraft? I am a new aircraft designer, and work for a small company (which doesn't have the enormous resources of a Boeing or Lockheed) so we have to work with limited resources to get good at our trade. I've been looking over different approaches for becoming a master designer, and for learning the shortcuts and tips all great designers pickup over the years of practicing their art.

From reading, it seems most good designers got their experience by essentially apprenticing with great engineers, or having the freedom to try stuff and see if it worked or not. I was thinking how a designer could get good in a small company like mine and came up with the following options:

1) Leave the company for a larger, better funded company like Boeing and come back

Pros: Have freedom to try stuff since company has the budget to absorb mistakes, and get to interact and learn from experienced engineers at company.

Cons: From all the people I talk to, nobody can take an aircraft (even a model) to full completion since the big companies compartmentalize the skills they pick up, meaning they good at making their widget or subsystem, but never work on integrating everything together to make the whole system.

2) Build a lot of R/C models to learn the fundamentals by flying, crashing, and repairing the aircraft

Pros: Get a ton of flight experience and building experience so will quickly learn what works, what doesn't work, and learn how to take aircraft from design to flight fully.

Cons: Aerodynamics do not fully scale unless the R/C models are somewhat large (around the 10-15 kg mass), which means crashes, even minor ones, cause a LOT of damage, which gets costly quickly. Replacing busted motors, shafts, wings, and the time that is needed to do this can quickly eat into any real experience.

3) Use a digital flight simulator like X-Plane or Kerbal Space Program to learn what flies and doesn't

Pros: This is the ultimate for cheapness. I can design and crash an infinite amount of times at no additional cost, as well as fly the aircraft at full scale and see all of the response characteristics in a variety of conditions.

Cons: Building the aircraft in the physical world does not mirror how its built in the software, meaning a lot of new factors (like weight gain, manufacturing inaccuracies) come into change how the actual aircraft flies compared to the simulator aircraft. Also, the simulator has limitations in its physics model, so things like stall behavior or transsonic drag will differ significantly between simulator and real life.

4) Use a hybrid system, using 3D printing, modular parts, R/C aircraft, and flight simulators

Pros: This will teach me how to take a design to completion by first designing/flying aircraft in simulator using modular parts (like in Kerbal Space Program), then print those modular parts (wing sections, fuselage sections, wing/fuselage joints, etc.) in real life using 3D printers, and assemble the aircraft at small R/C scale to fly, before finally going to full scale using the same modular parts, only scaled up. It lets me make mistakes and learn without bankrupting the project since I learn how to avoid the big mistakes while the consequences are still small.

Cons: I will need to design and build modular blocks light enough with the same performance as that in the simulator at both R/C and full scale. Also, while somewhat easy for airframe components, building engines this way would still be costly, as some combustion engines have different performance at small scales than large scales (heat leakage and manufacturing tolerances become more important at the small scale than at large scale) meaning it might cost too much to build the system of modular parts.

What option did designers like Burt Rutan use for getting good at aircraft design?

Let's look at every of your concepts:

Joining a large company: As you noticed yourself, you won't get a broad range of skills, but a deep understanding of a narrow field, unless you rotate between departments every few years. This will be hard to pull off, and will take time. If you are good at what you do, your boss will try to keep you (they always try to promote the duds away in big companies, and the good people get stuck. Really!)
Building RC models is great if you want to become a configuration expert at low speed aerodynamics. You will gain no experience in transsonic aerodynamics, structure, systems - 90% of the needed knowledge cannot be gained from model aircraft. But after 20 models you will be great at understanding flight mechanics and the pros and cons of different configurations.
Forget flight simulators. Things only get interesting once you leave the realm of attached flow. Stalls, spins, flutter, oscillating shocks - that is what you need to understand when you want to do good work, and flight simulators will not teach you this. At all. Also important is to understand the effect of single failures on the whole aircraft, and designing for robust response. Again, no simulator will give you anything even resembling a realistic response.
Hybrid: Now we are talking: Keep your eyes and ears open! Visit conferences, museums, exhibitions and talk to the people. Get a pilot's license and fly yourself! Read books and technical reports. Be open to all things, be it metallurgy, fuel chemistry or whatever. Try to do stints in workshops and flying clubs. Volunteer for workshop duty and do maintenance and repairs. Don't be shy to ask, and if you see something strange, don't stop until you have arrived at a convincing explanation. Do this 10 hours a day for 10 years, and you will collect the necessary all-around knowledge.

The best way will be to participate in as many aircraft design projects as possible, from start to finish. This has become extremely hard, and some engineers will spend their whole professional life working on just one design. Let's face it, the golden days where you would work on a new design every year were maybe 80 years ago. On the other hand, the Internet can bring you an incredible wealth of information and past experiences from which to learn. Like this site. Use it!


Could an AN/APG-79 AESA radar "lock-on" a single bird? Could a fighter pilot in 2015 using an AN/APG-79 AESA radar "lock-on" a single bird?

I know that modern radars like the AN/APG-79 in modern combat aircraft like the F/A-18F filter out false alarms with Doppler processing and use what could be called "filters". Could an F/A-18F pilot "lock-on" a single bird using STT (Single-Target Tracking) mode or by using any other radar modes?

Depending on the radar, the accuracy fallow might be too big for a smaller object as radar resolution and accuracy matter a great deal in detecting and hitting a small target, that is why usually birds do not show up on radar or are actually filtered out as they could not hit targets that small anyway…
Resolution refers to the size, meaning electromagnetic size or radar cross section (RCS), of the objects a radar can detect. The smaller the minimum detectable RCS of a radar system, the better its resolution. A radar with poor resolution might see a supertanker sailing past but not a tugboat, for example.
Accuracy is referring to the degree of uncertainty in the radar’s calculation of the target’s location. A very accurate radar, for example, might tell you that it’s detected a target at a distance (range) of 87.118km ±10cm from the radar antenna. A much less accurate radar seeing the same target might report its range as 90km ±100m.


What is the main materials of the windshield? And how do they function in bird strike? I would like to know what the latest materials used for civil and military aircraft windshields are.
And I wonder if the materials are advantageous in the event of a birdstrike.

Here is an example of the latest and greatest.

http://www.ppgaerospace.com/getmedia/926cb26f-e047-477d-b604-62d079f494bc/B787_TD_FINAL.pdf.aspx?ext=.pdf

You will notice that instead of multiple glass laminations separated by plastic interlayers of traditional aircraft windshields, the 787's windshields are basically two thick layers of acrylic plastic (plexiglas) as the main structural element, with interlayers to separate them and just a single outer layer is high strength glass.   This would provide superior birdstrike resistance while the glass outer layer maintains a hard outer surface that won't scratch easily.


What are the conditions for an airfoil to be a "thin airfoil?" I know about the theory differences between regular airfoils and thin airfoils, but is there any condition for saying a given airfoil can be analyzed as if it is thin? The extreme case of infinitely thin makes sense, but I am curious if there is some cutoff dimension that determines thin or not thin.

There is no hard boundary. Normally it is around 8% relative thickness, details depending on camber and nose shape.

Typical for a thin airfoil is a stall originating from the nose, with a sudden separation of upper side flow, while thicker airfoils start to stall with a separation starting from the trailing edge and moving gradually forward. This gives thin airfoils a nasty stall behavior while thick airfoils stall in more benign ways. The stall behavior depends not only on thickness but also on camber and the geometry details of the airfoil nose, but can be used to separate thin from thick airfoils.

Thin airfoils make sense in two applications:

when the local angle of attack is well controlled, such as in flaps and turbo machinery, and
for trans- and supersonic flight where thickness causes wave drag.

In all other applications thicker airfoils with a blunter nose should be preferred because they allow to store more fuel and to make the load-carrying structure more efficient. The upper limit of practical airfoils is at 20% to 22%, the root thickness of the Davis wing as used in the B-24 and B-29.


When/where must a flight go missed on the JFK VOR/GPS 13 L/R approach? I'm looking at "exciting" approach plates, and I always come back to JFK VOR/GPS 13L/R.

I think I have come to understand most of the elements of this unusual approach, and enjoy seeing flights make that "dramatic" right turn just before landing, but here is what I can't figure out, even after reading over the plate multiple times:

With such a long distance (relatively) from the MAP to the runway, and additional features such as lead-in lights involved, when and where should the pilot consider, or decide, to break off the approach and go missed (climb and head for DPK)?  Upon crossing the MAP, is it sufficient to have the ground and/or first set of lead-in lights in sight?  Should the pilot see more than that, such as the actual runway?  If weather temporarily (about 3 to 5 seconds) blocks off the view of the ground or lead-in lights can he continue?  Basically, what is the minimum criteria for being able to continue the approach, after the MAP?  Must the runway be in sight at all times, or is knowledge of position (based on lead-in lights, etc.) enough?

This approach is different than most others, in that it has a fly visual section of the approach, as noted in the lower portion of the plan view:

  When visual reference established, fly visual to airport via lead-in lights to Rwy 13L or 13R.

When flying the approach, the pilot must have visual contact with the ground, and be able to maintain visual flight by reference to the ground. Arriving at DMYHL, the flight visibility must be at least two miles, and there must be at least an 800-foot ceiling. Considering that DMYHL is either 2.6 or 3.6 NM from the landing runway, it's entirely legal to continue flight without the runway in sight. Without ground contact and the required visibility and ceiling, a missed approach must be executed at DMYHL.

After passing DMYHL, any time the pilot loses visual contact with the ground, or is unable to fly the Fly Visual path as charted (if, for instance, they could see the ground near them but not the lead-in lights) they must execute the missed approach at that time. Note that continuous ground contact must exist - the lead-in lights could disappear behind a small cloud for 3-5 seconds if the pilots still had the approach path in sight, but the aircraft would not be permitted to enter a cloud after the MAP.

For reference, the AIM contains the following information about Fly Visual segments (AIM 5-4-5(l), page 5-4-19 or 345):

  l. In  isolated  cases,  an  IAP  may  contain  a  published  visual  flight  path.  These  procedures  are
  annotated “Fly Visual to Airport” or “Fly Visual.” A
  dashed arrow
  indicating the visual flight path will be
  included in
  the profile and plan views with an approximate heading and distance to the end of the runway.

  1.
  The depicted ground track associated with the
  “Fly Visual to Airport” segment should be flown as
  a  “Dead  Reckoning”  course.  When  executing  the
  “Fly Visual to Airport” segment, the flight visibility
  must not be less than that prescribed in the IAP; the
  pilot must remain clear of clouds and proceed to the
  airport  maintaining  visual  contact  with  the  ground.
  Altitude on the visual flight path is at the discretion
  of the pilot, and it is the responsibility of the pilot to
  visually  acquire  and  avoid  obstacles  in  the  “Fly
  Visual to Airport” segment.

  2.
  Missed  approach  obstacle  clearance  is
  assured only if the missed approach is commenced at
  the  published  MAP.  Before  initiating  an  IAP  that
  contains a “Fly Visual to Airport” segment, the pilot
  should have preplanned climb out options based on
  aircraft  performance  and  terrain  features.  Obstacle
  clearance is the responsibility of the pilot when the
  approach is continued beyond the MAP.

  NOTE−
  The  FAA  Administrator  retains  the  authority  to  approve
  instrument approach procedures where the pilot may not
  necessarily have one of the visual references specified in
  14 CFR
  §91.175 and related rules. It is not a function of
  procedure
  design to ensure compliance with
  §91.175. The
  annotation  “Fly  Visual  to  Airport”  provides  relief  from
  §91.175 requirements that the pilot have distinctly visible
  and identifiable visual references prior to descent below
  MDA/DA.


Does FAA have any info on army air corps pilots during wwII (know the FAA was formed later)? Did the FAA (or its precursors) have any relationship to Army Air Corps pilots during WW2?  If so, how would I request information on my deceased father.  Most of his military records did not survive the fire in St. Louis.

Unfortunately no, the FAA does not certify or track military pilots. The only records the FAA has or carried over from CAA would have is if he converted his hours for a certificate, but I would be surprised it would be anything more than a number.


What is the flight time limitation for commercial air transport operation in Europe? What is the maximum hours of flight time that a pilot can work legally in Europe? (daily, monthly and yearly)

For EASA, flight times and duty periods are limited (PDF p.25) to:

(a) The total duty periods to which a crew member is assigned shall not exceed:
  (1) 60 duty hours in any 7 consecutive days;
  (2) 190 duty hours in any 28 consecutive days.
(b) The total flight time of the flights on which an individual crew member
    is assigned as an operating crew member shall not exceed:
  (1) 100 flight hours in any 28 consecutive days;
  (2) 900 flight hours in any calendar year;
  (3) 1000 flight hours in any 12 consecutive calendar months.


What is TOGA LK in Airbus 320? How to come out of TOGA LK? What is TOGA LK in Airbus 320? How to come out of TOGA LK? I see it comes in Windshear Escape Manoeuvre. How is it related to Alpha Floor.

TOGA LK (TOGA thrust locked) is displayed on the FMA after an activation of the ALPHA FLOOR protection when the activation conditions are no longer fulfilled (A FLOOR is displayed during the ALPHA FLOOR condition). The idea is that the thrust does not automatically reduce again after ALPHA FLOOR because this could result in a situation where the speed decreases again. The procedure to get out of TOGA LK is described in the FCTM (Flight Crew Training Manual):

ALPHA FLOOR
When the aircraft’s angle-of-attack goes beyond the ALPHA FLOOR threshold, this
means that the aircraft has decelerated significantly (below ALPHA PROT speed):
A/THR activates automatically and orders TOGA thrust, regardless of the thrust lever
position.
The example below illustrates that:

The aircraft is in descent with the thrust levers manually set to IDLE.
The aircraft decelerates, during manual flight with the FD off, as indicated on the FMA.

When the speed decreases, so that the angle-of-attack reaches the ALPHA FLOOR
threshold, A/THR activates and orders TOGA thrust, despite the fact that the thrust
levers are at IDLE.
When the aircraft accelerates again, the angle-of-attack drops below the ALPHA
FLOOR threshold. TOGA thrust is maintained or locked. This enables the flight crew
to reduce thrust, as necessary. TOGA LK appears on the FMA to indicate that TOGA
thrust is locked. The desired thrust can only be recovered by setting A/THR to off,
with the instinctive disconnect pushbutton.
ALPHA floor is available, when the flight controls are in NORMAL LAW, from liftoff
to 100 ft RA at landing. It is inhibited in some cases of engine failure.

(Airbus A320 FCTM - Operational Philosophy - AP / FD / ATHR, emphasis mine)
The TOGA LK state is not necessarily linked to a Windshear, but since ALPHA FLOOR is part of the Windshear escape strategy, it can certainly appear in this context. The FCTM describes the following strategy to escape a Windshear:

There are three efficient tools to assist the flight crew to escape:

The alpha floor protection
the SRS AP/FD pitch law
The high angle of attack protection

When the alpha floor protection is triggered, the A/THR triggers TOGA on all
engines. The FMA displays A FLOOR, that changes to TOGA LK, when the
aircraft angle-of-attack has decreased. TOGA/LK can only be deselected by
turning the A/THR off.
The SRS pitch mode ensures the best aircraft climb performance. Therefore, the
procedure requests following the SRS pitch bar and possibly full aft stick, in order
to follow the SRS orders and minimize the loss of height.
The high angle-of-attack protection enables the PF to safely pull full aft stick, if
needed, in order to follow the SRS pitch order, or to rapidly counteract a down
movement. This provides maximum lift and minimum drag, by automatically
retracting the speed brakes, if they are extended.

(A320 FCTM - Supplementary Information - Adverse Weather, emphasis mine)