Is A380's center of gravity really too far back?

No. Positive lift on the tail does not necessarily mean that the center of gravity needs to be aft of the aerodynamic center of the aircraft. Only when the lift per area of the tail surface is higher than that of the wing will the center of gravity move into the unstable region.

  the center of gravity is always closer to the nose of the aircraft
  than the aerodynamic forces resultant

Again, no. The center of gravity needs to be at the same lengthwise station as the center of pressure in trimmed flight, otherwise the aircraft would not be trimmed and start to pitch. With low-mounted engines there might be some thrust moment which must be canceled by a slightly forward location of the center of gravity, but this effect is small.

Next, the auto-stabilisation is not only helpful when stalling. It also provides a smoother ride in gusty conditions and makes it easier for the pilot to fly the aircraft.

Since the aspect ratio of the tail surfaces is smaller than that of the wings, lift there is bought more expensively, so it will be bad for performance if the tail produces more lift per area than the wing. Negative stability is only helpful for supersonic and highly manoeuverable airplanes. Airbus does not do that, and besides, the A380 would not be certified with negative stability.

What it does have, however, like all Airbus aircraft since the A310, is relaxed static stability. The center of gravity is still ahead of the neutral point, but less so than in conventional airliners. This does indeed help to lower drag, and the reduced (but still positive!) stability is enhanced by electronic means.


Does North Korea's aircraft registration prefix allow for only 500 aircraft?

Civil aircraft tail numbers almost always follow ITU radio prefixes. North Korea has been allocated six ITU prefixes: HM and P5-P9.
Many countries with consecutive 2-letter prefixes will move the dash so it looks like they have a 1-letter prefix, but they still only use the allowed subset. So in this case, rather than P5-00 to P9-99, they write P-500 to P-999. They could have just as easily chosen P-50000 to P-99999 if they wanted, or gone alphabetic for even more possibilities.
However, in practice North Korea only has a handful of very old civil aircraft. While there is a humanitarian exception for spare parts to keep their airlines safe, the country can’t buy any more planes, which means they don’t need more tail numbers than they’re currently using. Heck, they could probably knock off a digit and still have more than they need!


What preflight passenger briefing items are required under Part 91?

As far as I can find, the only briefing requirements in part 91 are for large or turbine powered aircraft at 91.519 (which you assume exempted from), the one you found along with the seatbelt requirement at 91.107(a)(1), and 91.1035 which deals with fractional ownership aircraft.

An AOPA article on briefings also states that:

  Operation of seat belts is the only FAA-required briefing item.

The only references to emergency exits under part 91 is 91.607 which pertains to passengers for hire. It only mentions the requirements for the number of exits and does not mention passenger briefing.


What is the relationship between temperature, dew point and the formation of clouds?

The dew point is the temperature at which condensation (a cloud) forms.

If the dew point is the same as the temperature on the ground, then there will be fog.

The temperature usually decreases as the altitude increases. This is called the lapse rate. In general, the closer the dew point is to the ground temperature, the lower the cloud ceiling will be.


The Aspect Ratio ($AR$) is defined as the ratio (hence the name) between the wingspan squared $b^2$ and the area of the wing $S$.

Since both $b^2$ and $S$ are measured with a length squared (e.g., $m^2$), $AR$ is an dimensionless quantity.

To answer the follow-on question of TomMcW in the comments, $b$ is the distance between the wingtips, no matter the shape of the wing.


For subsonic aircraft, would adopting a higher wing loading decrease drag?

Generally, you are right. Reducing wing area is reducing overall drag. Within limits.
Induced drag depends on speed and span loading. If the reduced wetted surface allows you to fly faster, reduced drag will be lower, leaving more of the power budget to overcome viscous drag. However, if wing span is reduced, induced drag will be higher at the same speed, so it is better to reduce chord than to reduce span. This can be witnessed by the recent development in airliners where the reduced fuel flow of engines has allowed to build smaller wings with higher aspect ratios. A similar but older example is the Davis wing which combined extreme root airfoil thickness and an aspect ratio of 11 to minimize overall drag and keep wing weight reasonable. Other aircraft designed for long range even sported an aspect ratio of 14.5!

If one wants to reduce induced drag, than one must fly at lower altitude.

Don't focus on induced drag reduction alone! Please remember that the lowest overall drag is at the polar point where induced and zero-lift drag are equal. Move away from this point and overall drag for lifting the same weight increases.
Turbine engines profit from colder air. Flying higher means higher true air speed for the same dynamic pressure. Therefore, wing area should be sufficient to allow operation close to the tropopause. Going higher than that does not improve things, but staying well below the tropopause means to forego an obvious advantage. Only airplanes designed for low level missions will have a wing loading well above the 600 kg/m² which is typical for airliners. That's the limit mentioned above.


What is the meaning of ACAI and ATCI in Air Cadets?

Those four letters can be abbreviations for many things related to aviation. Taking into account that this is for a staff cadet course, I think the most likely candidates are:

Air Cadet Administrative
Instructions
Air Cadet Training Instructions

Source


Why is the lower deck of the Airbus A380 curved like a single deck airplane?

The cabin interior is curved to accommodate, among other things, the brackets holding the upper deck floor beams.

These brackets are a structural feature that transfers the weight of the upper deck to the fuselage with considerably less reinforcement that a straight T-joint. The bracket acts as a small truss element, creating a triangle with the deck and the fuselage that partially turns bending loads into axial ones.

Here is an actual production cutaway, noticeably different from wiki's simplified representation of the A380's cross-section:

It would be possible to only wrap the interior lining around the brackets themselves, not along the whole length. But they're not the only thing there (although others could be rerouted; structure requires testing), and this curve saves a bit of weight, so Airbus curves the whole interior by default. An airline could request something different if they wanted to.


Why do newer 737s use two different styles of split winglets?

Since a winglet is basically a sail generating thrust (lift with a modest forward-tilted vector) from the circulating flow around the tip, extracting beneficial energy from the circulation (the thrust part) and producing an "outwash" that opposes and weakens the vortice flow in the process, it's just adding another sail beside the first one to extract more of the available energy from the flow.  From the NASA Dryden page:

  Winglets, which are airfoils operating just like a sailboat tacking upwind, produce a forward thrust inside the circulation field of the vortices and reduce their strength. Weaker vortices mean less drag at the wingtips and lift is restored. Improved wing efficiency translates to more payload, reduced fuel consumption, and a longer cruising range that can allow an air carrier to expand routes and destinations.

  To produce as much forward thrust as possible, the winglet's airfoil is designed with the same attention as the airfoil of the wings themselves. Performance improvements generated by winglets, however, depend on factors such as the basic design of the aircraft, engine efficiency, and even the weather in which an aircraft is operating.

In the case of the MAX, you can see that the lower winglet is at less than a 45 degree angle, so it's producing mostly vertical lift with a slight forward component because as you can also see its incidence is somewhat nose down relative to the main wing to optimize its AOA in the tip circulation.  It's kind of a half winglet, half tip extension.

Different engineering groups will do studies of different configurations and will say, "hey, if we do this, it'll be some little bit more efficient than if we do that, based on our particular analysis".

If you put different groups of engineers together to attack the problem, they are all going to come out with variations on what they think is the ideal configuration.  And so you see seemingly endless permutations that are, really, mostly nibbling at the margins of the major benefit that was achieved when you put one there in the first place.

Plus there is probably a bit of "styling" going on as well.  Just to be different.


Short Answer:

This will be very generic...

It depends on what type of missile it is: either IR or radar-guided.

With IR missiles, the missile is caged and locked at missile boresight.  The missile is commanded to the aircraft cueing system.  When the target enters the missile's FOV, the pilot uncages the seeker head, at this point you will hear a loud, "whiney" audible tone.   The missile then transfers to track mode.  The pilot pickles... the missile batteries become operational, fins are unlocked, autopilot takes over, midbody connector is retracted, then ignition is commanded.

With radar-guided missiles, it depends on the missile and what type of radar they have.  Usually the radar is slewed to a target and locked up.  When the pilot pickles, the missiles is either receiving data from the aircraft via datalink or is in active mode with the missile's radar tracking the target.  Eventually the missile's radar will take over and track the target.  The datalink can be terminated early by the pilot if the missile's radar can take over allowing for some pretty cool tactical stuff.

Long answer:
There is A LOT more to it, but this is very basic.  Tread very lightly with questions like this.  A lot of the stuff (especially numbers) with regards to weaponry and modern threats are classified.  And even though some of the stuff isn't classified, it's still OPSEC and shouldn't really be discussed on an internet forum.


What forward airspeed produces maximum rate-of-climb in helicopters?

There are a couple of things at play here:
First, the increase in overall lift of a helicopter as it correlates to an increase in forward airspeed actually has a lot to do with the establishment of Effective Translational Lift (ETL) or the airspeed at which the entire rotor system realizes the benefit of the horizontal air flow. This happens when the helicopter's rotor disc moves completely out of its own downwash and into undisturbed air.
Second, beyond the ETL improvement, forward airspeed in a helicopter only produces an increase in asymmetrical lift, rather than the the nice, tidy symmetrical lift dispersal of fixed wing aircraft. This is because of a principle known as (surprise, surprise) Dissymmetry of Lift. The forward airspeed is added to the rotational speed of the advancing rotor blade on one side of the aircraft and subtracted from the retreating rotor speed on the opposite side of the aircraft. While this is counteracted to some extent by mechanical adjustments (flapping, feathering, leading-lagging) to equalize the inherent rolling tendency, this means that the forward speed alone, as a catalyst for lift production, is not the be-all and end-all.
You are correct that a helicopter, under the right conditions and possessing a surplus of available power can generate lift at zero airspeed. This is why a helicopter, under these conditions, effectively has a Vx of zero, since its best angle-of-climb over distance would be a straight vertical climb.
For Vy, the best rate-of-climb over time performance, it is important to plan for torque settings at level flight. Climb performance charts show the change in torque, above or below torque, required for level flight under the same gross weight and atmospheric conditions to obtain a given rate of climb or descent.
Here is a sample calculation taken from the FAA Helicopter Flying Handbook:

Determine  torque  setting  for  cruise  or  level  flight  using  Figure 7-7.
Pressure Altitude = 8,000 feet,  Outside Air Temperature = +15 °C,  Indicated Airspeed = 80 knots,  Maximum Gross Weight = 5,000 lb.

With this chart, first confirm that it is for a pressure altitude of 8,000 feet with an OAT of 15°. Begin on the left side at 80 knots indicated airspeed (point A) and move right to maximum gross weight of 5,000 lb (point B). From that point, proceed down to the torque reading for level flight, which is 74 percent torque (point C). This torque setting is used in the next problem to add or subtract cruise/descent torque percentage from cruise flight.
Determine climb/descent torque percentage using Figure 7-8.
Rate of Climb or Descent = 500fpm,  Maximum Gross Weight = 5,000lb.

With this chart, first locate a 500-fpm rate of climb or descent (point  A), and then move to the right to a maximum gross weight of 5,000 lb (point B). From that point, proceed down to the torque percentage, which is 15 percent torque (point C). For climb or descent, 15 percent torque should be added/subtracted from the 74 percent torque needed for level flight. For example, if the numbers were to be used for a climb torque, the pilot would adjust torque settings to 89 percent for optimal climb performance.

As you can see on chart 7.7, the green line represents the Vy speed and is relatively low, because it represents the speed at which the lowest percentage of maximum torque is required to sustain level flight in the given conditions, and thus, the speed at which there is the maximum amount of surplus torque available to climb, all while remaining in ETL flight.


How much of an improvement would a 1% weight decrease on an airplane be to the industry?

There is an easy way to get an idea of what magnitude the savings are: The Breguet equation can answer this. You first calculate a reference aircraft and then start all over with one that weighs 1% less. The difference in fuel consumption shows how much fuel is saved per flight.

Our reference design is the A320 which has an L/D of 18 and we let it fly a trip of R = 2,500,000 m. $m_1$ is take-off mass and $m_2$ landing mass. Allow for 3 t of fuel reserves and plug that into the Breguet equation, using a fuel burn of $b_f$ = 0.000018 kg/Ns and a speed of Mach 0.78, which equates to $v$ = 262 m/s in 11,000 m altitude:
$$m_1 = m_2 \cdot e^{\frac{R\cdot g\cdot b_f}{v\cdot L/D}}$$
The landing mass $m_2$ is the operational empty mass OEW + 18 t payload + 3 t of fuel reserves = 63.6 t. The take-off mass $m_1$ is 10% higher, so the difference in fuel consumption is 1% of that trip fuel of 6,239 kg or 62 kg. That is not much for a single trip.

But now consider that this one A320 will fly 50,000 trips before it retires. Over its lifetime the 1% in mass reduction will save 3,119 metric tons of fuel. This fills 29.4 DOT-111 railway tank cars!

And there are about 12,000 airliners of 150 seats and more and easily twice that number if all regional jets are included, flying 3.8 billion passengers and 53 million tons of freight per year on 35.4 million flights. If we make the heroic assumption that our A320 flight is typical, this translates into global fuel savings of about 2.2 million tons of fuel per year if only 1% of mass could be saved on every airplane.

Another way to approach this is the average fuel efficiency of modern airliners which consume between 3 and 3.5 liters of fuel per 100 passenger kilometers. Using ICAO's number of 6.6 trillion passenger kilometers in 2015, this would equate to 174 million tons of aviation fuel used per year for revenue passenger transport, assuming a mean density of kerosene of 0.81 kg/l. The same source gives an average load factor of 80%, so one fifth of seats is empty; the efficiency number above is for a full airplane, however. Therefore, our estimate needs to be increased to 217 million tons.

Saving only 1% of this would reduce fuel consumption by 2.17 million tons per year, which comes pretty close to the first estimate. This is enough to fill more than 41 Panamax oil tankers (the maximum size for the old Panama canal) or 18 Neopanamax oil tankers.

Or, to look at this from a different angle, with the current price of kerosene of 1.76 USD per gallon, the saved fuel equates to 1.25 billion USD if everyone paid US prices for Jet A-1 fuel. Compared to the average net profit of all airlines per year between 2007 and 2017, which amounts to 13 billion USD, this is almost 10% of yearly profits.

Now this doesn’t look so insignificant any more, does it?


Is there a career path to fly fast, military jets without being in the military?

There's no likely career path, if you have serious enough medical problems they will probably prevent you from getting a job in aviation flying anything commercially. However, that's a separate question, you'd want to talk to an aviation medical examiner to find out what avenues are open to you.
There is a path to flying military style jets as a civilian test pilot, which is open to anyone, however you need a lot of experience and most are retired military.
However, with enough money you can fly just about anything, former military jets do go on the market, often they aren't that expensive to buy, the big costs are maintenance and fuel. If they are to be flown non-commercially the medical requirements are usually lower too. You need to be prepared to spend between \$800-\$6000 per flying hour, depending on the type.


What is the difference between flaps and slats?

Flaps are at the back of the wing, slats are at the front.

Easy! :)

If you want it more technical: They both help to generate more lift. See these diagrams with angle of attack and lift coefficient:

As the lift coefficient is inversely proportional to the minimum airspeed, a higher CL will allow a lower Vmin.


Why close isolation valve and APU bleed air for engine fire?

Closing the isolation & APU bleed valves keeps hot bleed air away from areas near the engine that may have damaged bleed air ducting. Closing the Pack valve causes the other pack to switch to high flow, making up for some of the lost output of the affected-side's pack. The steps are together in the checklist because it's all on the same overhead panel, even though the reasons differ.


Is it technically possible to have nuclear-powered hot-air balloons?

Most likely no.

RTG does not have enough power. The burner of the hot air balloon requires 2 to 4 MW of power (here) so you need at least 4 tonnes of Pu to produce that (2000,0000 / 500 = 4000 Kg), assuming 500 W per kg (0.5 W/mg). From the source, a moderate size balloon can lift few hundred kilograms at most.

The true nuclear reactors provide much more power, but they are heavy. Hyperion, for instance, provides 25 MW and weighs 50 tons, so performance per kg is even lower. It could power a cluster of say five balloons, but they would not be able to lift 10 tonnes each.

From the other side, nuclear reactors are probably not optimised for the minimal weight, assuming that just a heat output is required. They are built to match different requirements, so some specially built device may be capable of lifting the balloon.

Lockheed Martin is developing a very promising device.


Can an automatic gearbox improve engine transmission for an ultralight?

A gearbox is not a useful addition. Some aircraft have geared propellers, but that's a single, fixed gear.
The engine has to be able to turn the propeller when it's in the highest gear you'll use, so that determines how much power is required.

In a car or motorcycle, the lower gears are used to match engine speed to wheel speed, allowing the vehicle to drive at lower speeds than 'idle rpm in top gear' without slipping the clutch or the wheels.

In an aircraft, that function is not needed: a propeller can slip freely.


The "vertical stabilizer" (or "vertical fin") provides what is known as "weathervane stability", "directional stability", or "yaw stability".  It makes the plane act like a weathervane.  A weathervane always points into the wind.

The wind a plane "feels" is not the external, meteorological wind, but rather the "wind" created by the plane's movement through the airmass (or perhaps we might prefer to say "within" the airmass).  This apparent wind is called the "relative wind".  So the vertical fin keeps the nose of the plane pointing in the direction that the plane is actually going, i.e. in the direction that the plane is moving through the air.

Imagine driving a car at high speed on an icy lake on a day with no wind.  Can you see how a big vertical fin mounted at the back of the car would provide a "weathervane effect" that would tend to keep the car lined up with the direction it is actually moving, and would tend to prevent the car from "swapping ends" or sliding sideways?

That is what the vertical fin on an airplane does.  It's a very bad thing if an aircraft "swaps ends" or slides sideways through the air at a very large sideslip angle.  In extreme cases, there's essentially nothing the pilot can do to salvage the situation, and the plane may tumble violently out of control.  It's a misconception to say that the function of the vertical fin or vertical stabilizer could be replaced by appropriate control inputs with the ailerons.  It is true in many cases that planes with relatively small vertical fins often require the pilot to make larger rudder inputs to keep turns "coordinated", i.e. to keep the nose from swinging somewhat out of line with the direction the plane is going as it turns -- we'll save saying any more about that for some other answer.

Airplanes that lack a vertical fin must derive "weathervane stability" or "yaw stability" or "directional stability" from other aspects of the aircraft's configuration, generally having to do with the fact that more surface area is behind the center of gravity than in front of it.  For example, a swept-wing configuration generates some amount of "weathervane stability" even without a vertical fin.  Imagine putting a pair of swept wings or delta wings on a pole like a weathervane.  Can you see how, as long as the pivot point were sufficiently forward, the whole assembly would tend to point into the wind like a weathervane?  That's why hang gliders don't need vertical fins.

The question appears to contain a misconception about the relationship between yaw stability and roll stability. In fact, making the vertical fin too large actually tends to make a plane LESS roll-stable or MORE spirally unstable, so that it tends to roll away from wings-level into a steeper and steeper bank and turn.  As a plane starts to roll into a turn, dihedral and sweep (if either are present) tend to generate a stabilizing roll torque that tend to roll the plane back towards wings-level, but only if the developing turn involves some amount of sideslip.  In other words the roll-stabilizing effect of sweep or dihedral are only present if the plane is sideslipping to at least some small degree.  A large vertical fin tends to prevent sideslip, and thus makes the plane behave as if it had less dihedral or sweep. That's why planes that need lots of roll stability, like "free-flight" model airplanes that must fly with no guidance of any kind from either a pilot or a computer, rarely have large vertical fins.  Even though we don't want the plane to completely "swap ends" and tumble, or to slide sideways through the air at a really extreme sideslip angle, we do need for there to be some amount of sideslip in an uncommanded bank and turn in order for sweep or dihedral to be able to bring the plane back toward wings-level.  Likewise when a free-flight model airplane is trimmed for an intentional turn, if the sideslip were somehow completely eliminated, we'd see the bank angle start to get steeper and steeper.  If a pilot were actively controlling the airplane, he could deal with this by making an appropriate control input with the ailerons, but that option doesn't exist with the free-flight model airplane.

So other than preventing a violent tumble when the plane "swaps ends" completely, a vertical fin generally doesn't really contribute to roll stability.


Why did the RAAF procure the F/A-18 despite being purpose-built for carriers?

Two reasons:

The airplane is extremely versatile, while having adequate performance, and is a good choice when a small airforce needs a do-everything airplane to replace multiple types.

Being designed for carriers, it's overbuilt for normal land operations in many key areas, which means a longer airframe structural life in its much easier life landing on runways.  For an air force with a limited budget and the need to run the airplane a long time, it's worth giving up some of the speed/payload/range that was sacrificed by the structural needs of carrier ops.


Could a plane take-off at 20,000 feet above sea level if the temperature is above freezing?

Like most hypothetical questions of this nature, the answer is "it depends".  Given enough runway at a light loading just about any aircraft with a service ceiling above 20K ought to theoretically be able to take off.  One of the issues you might run into would be exceeding max tire speed.


What determines the maximum ground speed of hot air balloons?

Balloons travel with the wind, so all their motion over ground comes from air movements.

do hot air balloons have the ability to control their ground speed? If so, how?

This was a burning question in the nineteenth century and many attempts were made to influence ground speed, apart from rising into higher altitudes and testing whether the wind direction there is different. Naive people added sails but had to notice that those remained limp and only added weight. Others added paddles or engines (steam, electric and gasoline engines were tried) but success was limited before Zeppelins started to make directed lighter-than-air travel routine.
An interesting variety was tried by the Swedish balloonist Salomon August Andrée who added three long ropes to his balloon, their ends dragging on the ground. This caused drag which slowed the balloon, thus giving it some speed difference versus the wind. Now, with some relative wind, sails could indeed generate a force which could move the balloon sideways. However, when tried in 1897, two of the ropes were lost during launch and the remaining one proved ineffective.

Andrèe's balloon (picture source)

Is there a maximum limit to the ground speed of a hot air balloon?

No, if the balloon rises into the jet stream, it can travel at several hundred miles per hour. There is no speed limit once the balloon is up in the air.
However, filling and launching the balloon requires calm winds; hot air balloons almost never start in winds higher than 10 miler per hour. Landing in higher winds becomes dangerous, so here also a calm wind is preferred.

What factors contribute to this speed limit?

This is not about ground speed limits, but wind speed limits: While there is no fixed limit, higher winds will prevent the envelope to stretch out completely and rise up when being prepared for launch. Instead, the windward side will remain dented. During landing, the gondola will be dragged along on the ground when wind is too high. Both these factors let balloonists prefer calmer wind for take-off and landing. Once the balloon is up in the air, no such limit exists any more.


Where does the final cooling take place in the air cycle machine of the air conditioning system?

The final cooling will be at the turbine of the ACM.

(Source)

Air passes through two heat exchangers, before finally passing through the turbine of the ACM.

Related:

How hot would pressurized air get if the air conditioning failed?
Why is air mixed with bypass air on the A/C of an aircraft?


Why does the 747 have 4 engines instead of 2?

Simply, more engines = more power, and power is needed for several things, the first of which is, taking off.  At max takeoff weight, a multi-engine aircraft has to be able to lose one engine (after reaching the go/no-go speed) and safely continue the takeoff, which means that if you could just barely fly on 3 motors, you're going to have to have 4 to meet certification (safety) requirements.  For the amazing weights that the 747 can carry, it needs some pretty powerful motors, and all 4 of them, for taking off fully loaded and meeting this requirement.  (Interestingly, if the aircraft is empty and could safely continue the takeoff on 2, it is typically allowed to take off with one engine already inoperative -- to ferry to a maintenance base, for instance.  But this requires no passengers/freight, and thus a very light airplane.)

At cruise altitude, more thrust means a higher cruise altitude is possible, which makes for better fuel efficiency.  So while a 4-engine aircraft can certainly fly on 3 engines, and in many cases (depending on weight and outside air temperature) on 2, it can't fly as high as it could with all 4.  The higher cruise altitude not only makes for more efficient flight, it also keeps you above a lot of the weather out there, and in extreme cases, a 2-engine ceiling might not clear all the terrain on your route.  (Again, this depends on weight & temperature.)

Modern engines have amazing reliability, and it's now considered routine to dispatch the twin engine 777 and 767 and A330 on long overwater routes, but 50 years ago, the reliability wasn't as great, so it was considered essential to have the redundancy so that if one engine failed over the middle of the ocean, there was still a comfortable margin, and you weren't now "one motor away" from going swimming.


Why is there always a fire truck present before refuelling?

As far as I know it is not mandated, but ICAO (for which many aviation authorities derive their regulations) states in Annex 14 Section 9.6 Ground servicing of aircraft:

  9.6.1 Fire extinguishing equipment suitable for
  at least initial intervention in the event of a fuel
  fire and personnel trained in its use shall be
  readily available during the ground servicing of
  an aircraft, and there shall be a means of
  quickly summoning the rescue and fire fighting service in the event
  of a fire or major fuel spill.

and

  9.6.2 When aircraft refuelling operations take
  place while passengers are embarking, on
  board or disembarking, ground equipment shall
  be positioned so as to allow:
   a) the use of a sufficient number of exits for
  expeditious evacuation; and
  b) a ready escape route from each of the exits
  to be used in an emergency

So you've probably been more aware of this if you were actually on the aircraft as it is being refuelled.


Was it ever possible to land big commercial jets from the missed approach point during non-precision approach?

Possible? Yes, depending. Advisable? That's a matter of opinion. I suspect most these days would probably say no unless you did a circling maneuver to another runway. And then many (most?) would say that you have no business circling at less than, say, 800 ft AGL in a 747 or the like.

Restating my first answer: Possible? Yes, for some MAPs, with some aircraft, at some weights, at some airports, to some runways, by some pilots, but not if you HAVE to fly a stabilized approach.

  Was it ever possible....

What was physically possible in the past—let's say 25 years ago so it's within the context of my experience—is still physically possible today, so I think what you might be asking is whether it was ever done.

While I don't recall ever having done it myself from the exact MAP, I think it reasonable to accept that it would have been done on occasion by some. Back in the 1990s at the two 747 carriers I flew for, we flew non-stabilized approaches when convenient, especially in freighters. Thus, in-close, down low maneuvering was not the no-no that I get the impression that it is today.

Indeed, the IGS 13 approach at Kai Tak in Hong Kong in bad weather meant you'd be popping out of the clouds a few hundred feet above buildings and then having to make a 47° right turn to line up with the runway. The decision altitude was 600 feet as I remember.


Does a constant power prop exist? What are the tradeoffs compared to a constant speed prop?

There are some aircraft that indeed have just power lever and set the RPM on schedule, e.g. the Pilatus PC-7, PC-9, PC-21 line of trainers. Since they are primarily designed for training future jet pilots, and jet aircraft only have power levers, it makes sense to skip the complexity of separate propeller and condition controls.
However normally there are some cases where you do want to set other than most efficient RPM for current power and true airspeed:

The most common is descent and approach. These are flown with high RPM because

the engine is already spinning fast, so it does not have to spool up if you need to add power to go around and
with retarded power it produces more drag, allowing to expedite the descent when needed (the Pilatus PC-7/9/21 have a ventral speed brake; most turboprops don't).

Failure modes, though for most a feather switch would probably be sufficient.


What is the purpose of classifying fighters?

People like to classify things, to divide them into categories.  Categorizing allows people to get an initial broad understanding of a complicated subject more quickly.  It is therefore very useful for purposes such as marketing and articles aimed for people who aren't necessarily subject matter experts.  However, classification is necessarily a crude tool that often isn't exact, leading to confusion and arguments about where the category boundaries lie.

People who are subject matter experts, such as designers of a new fighter plane, or military analysts trying to determine the capabilities of a new secret aircraft produced by other countries, presumably don't spend much time wondering into which category to put a given aircraft.  Instead they focus their time on the details of the subject, the same details that are too much information for the person trying to get the quick grasp of the complicated subject.

To answer your questions specifically, knowing the generation of a fighter gives someone a rough idea of its capabilities, and allows the person to quickly compare a given fighter aircraft to other fighter aircraft.  Knowing the generation of a fighter is useful for people who aren't experts on the subject who need a quick broad understanding of the capabilities of historic and modern fighter aircraft, and who need to know roughly where a given aircraft fits into the large picture.


Have there been instances where a LSA manufacturer has been audited?

Per this letter it appears that manufacturers who make LSA compliant aircraft are subject to a sort of enforced self regulation.  Basically, they are required to audit themselves every year and are told that the FAA could come and inspect their facility at any given moment, with heavy fines if an inspection is failed.

On top of this each aircraft itself is inspected by a technician before it leaves the facility to make sure that each aircraft meets the standards.

(The entire process is explained in more detail here.)

I did a bit of a search over a few of my favorite LSA news sites and I couldn't find any instances where an FAA inspection actually resulted in the proposed fines/punishments.  It seems that so far the semi-self-regulation model is working fairly well.  Well enough that, as Dan Johnson points out in that second article, it appears the FAA is considering using the same certification model for type aircraft as well.

To summarize, yes they are being audited, but by themselves.  It is also likely that outside bodies are auditing them as well, but nothing newsworthy seems to have come of any random inspections, so there is no mention of said audits.  I'm sure if somebody fails one, it will be big news.


Why are military and civil aircraft landing gear generally so different?

There is no difference between civil and military aircraft. Not the least because the civil and military transport aircraft are actually the same models. Many military planes have civil variants like Lockheed C-130/L-100, other military planes are derived from civil ones, e.g. C-135 is B707.

The difference depends on where the wings and engines are placed. All the aircraft actually have similar clearance from the ground. Just on some the lowest point is fuselage, on others it's the engines hanging down from the wings and on propeller driven ones it is often the propellers.

Cargo planes (like C-130, C-5, An-124 or An-224) are often built with high wings, so the fuselage is lower and therefore easier to load. This is also concern for regional airliners as they are designed to carry their own stairs. That's why BAe146, ATR-42 or Dash-8 are high-wing and other like Bombardier CRJ series have tail-mounted engines so they can also be lower. On the other hand low or mid-wing designs with wing-mounted engines have better aerodynamic properties, which is why that construction prevails for large airlines.


Why is EGT decreasing on a jet engine when the generators cut in (take over)?

EGT on some engines is proportional to the engine developed power, cutting the generators reduces the needed power, thus reduces the EGT


GPWS is mostly useful for aircraft flying in instrument conditions or at night when there is low visibility preventing a good view of the ground. Gliders aren't designed to fly in these conditions and they don't have the required instruments. They should be able to see the ground and avoid it without GPWS.


The strakes function as giant vortex generators.  They generate vortices at high AOAs to improve airflow over the rudder at low speeds.  During the Q400 test program it was found that there was some local flow separation at the lower area of the rudder (reducing rudder power and possibly creating unpleasant vibration) and this is a classic, relatively hassle-free, aerodynamic band-aid kind of add-on to address the problem without major redesign.  You don't see them on the shorter -8s.

Strakes and Vortex Generators work by creating a horizontal tornado so to speak, with the outer half of the tornado in the free stream.  This has the effect of pulling smooth free stream air into the turbulent air close to the surface, which, even though it's spiraling, is better than the random turbulent flow that is there otherwise.

You sometimes see similar strakes on the upper aft fuselage on light aircraft just ahead of the fin, like on a Chipmunk.  These are to improve spin characteristics by generating a vortice over the rudder when AOA is high as in a stall/spin.  They call them "spin strakes" in that case.


What is the difference between Hobbs Time and Tach Time?

Hobbs Time

In most planes, the Hobbs clock is started and stopped based on an oil pressure switch, so it starts when the engine starts, and stops when the engine is shut-down. While it's running, it just ticks off a tenth of an hour every 6 minutes, based on "regular wall clock time". So a tenth of idling on the ramp is the same as a tenth at cruise.

Tach Time

The tach clock isn't really a clock at all, it doesn't actually measure time, it really measures engine revolutions. But it's calibrated such that a tenth of an hour of tach time is clicked off when the engine is at cruise RPM for 6 minutes. In other words, if the plane is at cruise RPM, the tach clock will be clicking off tenths of an hour at the same rate as the Hobbs clock, and the same as the watch on your wrist. But if the engine is idling at an RPM speed that's half of what cruise RPM is, then the tach clock will be running at half the speed of the Hobbs clock.

Relation

So, for the tach clock, less "time" is clocked when the plane is idling on the ramp, or flying at low RPM. For short flights (where ramp idling time is a significant percentage of total time), and flights where you're doing a lot of pattern work (and thus operating at low RPM), tach time will be significantly less than Hobbs time.

Maintenance

When an engine is replaced or overhauled, that engine is considered to be "zero time". Whether they actually reset the tach gauge to 0 when the engine is overhauled, or if there's a way to put a time on a brand new tach or Hobbs meter when the old one dies and is replaced, I dunno, but in general, I'd assume that the aircraft's engine and airframe log books are really the official recording of the progression of airframe/engine times, so I don't know that it's particularly important whether the tach is set to the engine's time, or if it's really just used as an incremental meter.

AOPA has a nice (and long) article about this.


Does a windmilling propeller create more drag than a stopped propeller in an engine out scenario?

I would not follow the advice in the forum. While the reasoning that a windmilling prop does create more drag is sound, I have seen no empirical evidence that says how much it actually translates to in Feet Per Minute. The only studies I have seen have been inconclusive on the subject, and say there's a number of factors that you can't really control in that situation. The prop isn't that big compared to the airplane itself, so if a spinning one has 30% more drag (just a guess, as I said I've seen no actual numbers) it isn't going to make you plummet out of the sky.

What I would recommend is following the engine failure procedure in the POH of your particular aircraft. The advice to slow the airplane to try and get the prop to stop has a number of flaws:

Distraction from critical tasks: Slowing the airplane until the prop stops is taking your focus away from finding a field to land in, ensuring your passengers are briefed and strapped in, making a mayday call and attempting to restart the engine. You'll be busy enough!
Low airspeed danger: Slowing enough to stop the prop may require a very low airspeed, and you could have a stall/spin excursion, which is far more dangerous than a glide landing
Drag curve: flying very slow to get the prop to stop will put you below best glide speed, which is where you get your best glide ratio. Below best glide speed you start to develop a high rate of descent, so by the time you get the prop stopped you have lost hundreds of extra feet. You could lose more altitude than you would potentially save, and waste valuable time doing it
The chances are good that you couldn't change the prop behavior anyway: if your crankshaft has broken the prop's going to spin no matter what you do, if you've thrown a rod it's going to stop and you couldn't get it to windmill if you flew at mach 1

Doing some math puts this into perspective. Say an airplane's engine-out rate of descent with a spinning prop is 1000, and with a still prop it's 900 fpm. In a glide from 3000ft that buys you an extra 20 seconds, but it probably takes a lot more than 20 seconds to slow enough to stop the prop and then regain a stable airspeed.

Flying very slow to stop the prop is a potentially dangerous distraction, just set best glide speed and if the prop stops its a bonus.


What is the difference between EGT and TIT?

EGT is just that - the temperature of the gas leaving the gas core at the jet pipe.  TIT is the temperature of the gas in the gas generator as it exits the combustors and enters the first high pressure turbine stage.  EGT will be significantly cooler - sometimes by as much as 1500°F! - than the TIT, as the enthalpy or internal and kinetic energy of the working gas is converted into mechanical work by the turbine, reducing the pressure and temperature of the gas flow as it exits each stage of the turbine.  See the Brayton Cycle model for these kinds of heat engines.

Usually the power output for a turboprop or turboshaft is measured as the torque on the power shaft turning either the propeller or rotor transmission.  Thrust on jet engines is usually gauged by the flight crew as N1, or the ratio of the current speed of the fan/LPC/LPT spool to its maximum speed.  This is a bit misleading as the actual thrust the engine generates does not vary linearly with fan speed, but that is the benchmark.

EGT and TIT are not monitored for power output reasons so much as making sure the engine does not exceed its thermodynamic limits.  Too hot a temperature in parts of the gas core will cause serious damage to the engine, requiring major overhaul and/or replacement of the entire engine or subsections.  These temperature limits can exercise limitations on power or thrust settings for the gas turbine during operation to prevent overheating.  On a free turbine turboprop, for instance, your power settings are bounded by both the torque limits of the propeller gearbox and another kind of hot section temperature called the Inter Turbine Temperature (ITT) which is the gas temperature between the high pressure gas generator turbine and the low pressure power turbine.  These limitations cannot be exceeded in order to prevent engine damage and may restrict maximum power settings at both low and high altitudes.


Where can I find (online) manuals for refueling A320/B737 for a given destination?

Very rarely will a manual directly be used by flight crew for calculation of fuel uplift.

Flight crews generally receive an Operational Flight Plan prepared by the operator (the airline), or an agent of the operator, where calculations have been made for how much fuel will be required for the specific flight, and necessary reserves. Flight crew may elect to revise the fuel required to provide additional margin for weather, traffic or other factors.

The calculations made for the Operational Flight Plan are made with flight planning software, which in its turn uses data from performance manuals/data sets, and takes a large amount of parameters into account (routing (duh!), wind, flight altitude, speed, aircraft weight, load distribution (c.g.), alternate airport availability etc).

Flight crew can however make simplified fuel calculations using the FPPM for the aircraft type (Flight Performance and Planning Manual) (Boeing). The flight profile is however generally quite limited to a few climb/cruise/descent schedules, and the data is not what would be used on a normal line day. Distribution of FPPM (and other manuals) is generally restricted. If you however would come across a replica of a FPPM, you could probably make a usable fuel calculation using the instructions within it.


What would escorting an airliner which is the subject of a security threat by fighter jets achieve?

There are multiple reasons:

Yes, they'll shoot the aircraft down if deemed necessary. It is a grim prospect, but sometimes grim events require grim responses - there is little doubt that many lives would have been saved had the 9/11 aircraft been shot down prior to them hitting the WTC's.
It's a threat and a show of force. Not all hijackers / criminals / terrorists are keen on the idea of losing their life. For those, the threat of being shot down can contain the situation and give some control. If nothing else, being shot down would prevent their political message from getting out - you can't really negotiate the release of prisoners (Or whatever) if you're dead on a blown up plane.
The fighters can get up close and personal with the aircraft. This allows them to see it, see inside and potentially communicate with people on board. During an event where the situation is unclear they may be able to report whether the aircraft is under control and/or command of the pilots.
There are internationally recognised intercept signals that a fighter jet can perform - using lights and motion (Rocking wings etc). This will allow them to pass instructions to an aircraft with no radio capability.


Was the B727's wing supercritical (even if not so designed)?

I've got an aged book on pre-design of aircraft, which states that the B727 wing thickness was 13% at root and 9% at tip, average thickness 11% chord. $M_{M0}$ = 0.9, first flight of prototype is noted as 1963.

The 727 was a derivative of the 707: first flight 1957, average thickness 10% chord, $M_{M0}$ = 0.9. So the 707 wing was even thinner than B727, Mach number is the same. Profile of both airliners is not listed as a NACA profile.

The book references the first research paper on supercritical profiles as T.G. Ayers: Supercritical Aerodynamics Worthwhile Over A Range Of Speeds, published in 1972, nine years after the B727 prototype flew. The profiles depicted in the report seem to be thicker than those of the B727.

The photos in the question focus on the wing root, however the shape of the wing root is not indicative of that of the rest of the wing, but determined by a lot of structural and aerodynamic factors: placing of landing gear, fairings for aerodynamic interference etc. Furthermore, the overwing exit is there and evacuation of passengers should not be too difficult, caused for instance by a bulgy shaped cross section. It would make sense if this bit of the wing was designed mainly with evacuation in mind.

So it appears from the published date of the research work on Supercritical wing design, and from the similarity with the much older B707: no, the B727 did not have supercritical wing profiles.

Update

The main advantage of a supercritical wing is that it enables reducing the wing sweep. There was some progress between 707 and 727, because wing sweep was reduced from 35º to 32º on the 727. However, the A320 has a comparable $M_{M0}$ and has wing sweep of 25º. So again without knowing what exact wing profile was used and based on order-of-magnitude checks, it does not look like the 727 had supercritical wing profiles.

The profiles of supercritical wings I've seen are flat on top indeed, and horizontal and thickish and have a characteristic curve at the end. Flatness per se does not indicate that the profile is supercritical, for example NACA 23015 isn't.

 The horizontal flat bit on top allows the supersonic area to expand calmly again, but it needs to be horizontal, like indicated in this figure from E. Torenbeek, Synthesis Of Subsonic Airplane Design:

Update 2

A fascinating film explaining how high subsonic speed was achieved before supercritical rear loading profiles were implemented on aircraft. Discoveries like these are what I love about the Aviation SE site. From this question & answer


Should reliance on Auto-Flight Systems continue to increase in favor of manual flying skills?

The FAA certainly believes that manual flying skills are eroded in an airline environment, although to what degree is unclear. SAFO 13002, Manual Flight Operations, says:

  Autoflight systems are useful tools for pilots and have improved
  safety and workload management, and thus enabled more precise
  operations. However, continuous use of autoflight systems could lead
  to degradation of the pilot’s ability to quickly recover the aircraft
  from an undesired state.

The SAFO is very brief, but there's a little more information in this document from the Air Carrier Training Aviation Rulemaking Committee (ACT ARC):

  The Flight Deck Automation Working Group (FltDAWG) identified that the
  lack of practice with automation has contributed to the degradation of
  manual flying skills. European Aviation Safety Agency (EASA) safety
  information bulletin 2013-05 comments that continuous use of automated
  systems does not contribute to maintaining pilot manual flying skills.

That document references a 2014 NASA study called The Retention of Manual Flying Skills in the Automated Cockpit. Its conclusion was:

  We found that while pilots' instrument scanning and aircraft control
  skills are reasonably well retained when automation is used, the
  retention of cognitive skills needed for manual flying may depend on
  the degree to which pilots remain actively engaged in supervising the
  automation.

The detailed analysis showed that motor skills are generally not degraded much (e.g. hand flying approaches) but cognitive (mental) skills like navigation and visualization are much more significantly affected:

  Pilots sometimes struggled to maintain an awareness of where the
  airplane was with respect to the planned route, to reference their
  charts to keep track of what came next, to configure the airplane anew
  as they passed each important waypoint along the planned route, and to
  recognize and deal with instrument systems failures when they arose.

At least based on that information, it appears that the physical activity of manual flying isn't badly affected by automation, even flying on instruments. The risks that NASA found seem to be broader and related to mental awareness and alertness, including the ability to troubleshoot.


Can you get sucked out of a hole in an aircraft?

Yes, it's real. Here's the official accident report on BA5390, which says:

  The commander had been partially sucked out of his windscreen aperture

And:

  The two men tried to pull the commander back within the aircraft [but]
  the effect of the slipstream frustrated their efforts

There's also Aloha 243 where one cabin crew member was ejected, although that was a really extreme case.


What criteria are used to classify an airport as a satellite airport?

The answer is found in §91.130 and AIM 3-2-4.

A satellite airport is any airport under the class C shelf outer are of 20NM.

  §91.130   Operations in Class C airspace.

  (a) General. Unless otherwise authorized by ATC, each aircraft operation in Class C airspace must be conducted in compliance with this section and §91.129. For the purpose of this section, the primary airport is the airport for which the Class C airspace area is designated. A satellite airport is any other airport within the Class C airspace area.

  (b) Traffic patterns. No person may take off or land an aircraft at a satellite airport within a Class C airspace area except in compliance with FAA arrival and departure traffic patterns.

What does Class C airspace area mean?

  AIM 3-2-4 Class C Airspace Sub Paragraph 3 Note 4

  Though not requiring regulatory action, Class C airspace areas have a procedural Outer Area. Normally this area is 20 NM from the primary Class C airspace airport. Its vertical limit extends from the lower limits of radio/radar coverage up to the ceiling of the approach control's delegated airspace, excluding the Class C airspace itself, and other airspace as appropriate. (This outer area is not charted.)

I believe the answer above is correct.  There is also another way of looking at it.

  §71.51   Class C airspace.
  The Class C airspace areas listed in subpart C of FAA Order 7400.11D (incorporated by reference, see §71.1) consist of specified airspace within which all aircraft operators are subject to operating rules and equipment requirements specified in part 91 of this chapter. Each Class C airspace area designated for an airport in subpart C of FAA Order 7400.11D (incorporated by reference, see §71.1) contains at least one primary airport around which the airspace is designated.

That document shows the boundaries of Class C Airspace Area and does not include the outer area.

  ASO SC C  Myrtle Beach, SC Myrtle Beach International Airport   (lat. 33°40'47"N., long. 78°55'42"W.)

  That airspace extending upward from the surface to and including 4,000 feet MSL within a  5-mile radius of the Myrtle Beach International Airport, and that airspace extending upward from 1,200 feet MSL to and including 4,000 feet MSL within a 10-mile radius of the Myrtle Beach International Airport.  This Class C airspace area is effective during the specific dates and times of operation of the Myrtle Beach Approach Control facility, as established in advance by a Notice to Airmen.  The effective date and times will thereafter be continuously published in Airport/Facility Directory.

  AMENDMENTS  03/27/97  62  FR  6698  (Added)

Since the information from the FAA conflicts with one another, I would ask for a legal interpretation.


Why are smaller wings in the front with these VTOL aircraft?

It's because with the canard configuration, the smaller stabilizing surface is a lifting surface instead of the down force surface of a conventional tail.

(A regular tail airplane is a seesaw with someone sitting on one end and another pushing down at the other; a canard airplane is more like a table with most of the weight at one end where the fat legs are and skinnier more lightly loaded legs holding the other end up.  Canards get their pitch stability from having a steeper lift slope at the canard surface, whose airfoil is chosen to achieve that purpose, so the nose will rise with increasing speed and drop with decreasing speed).

So if you want to as much vertical thrust as possible from the available flying surfaces, it makes sense to use the Canard configuration where all the surfaces are lifting.  Canards are nothing new; the Wright Flyer was the first.  You don't see them everywhere because there are significant limitations, but in a VTOL configuration like this, the Canard layout is mostly a plus.


Indicated vs. True is a hard one, as every aircraft has an instrument error and a position error. Once calibrated into Calibrated Air Speed however, this document gives CAS as a function of TAS:

All of them more or less straight lines, gradients a function of the altitude.

For temperature: the rule of thumb of density altitude can be used. From this website:

  Keep in mind the standard temperature is 15 degrees C but only at sea level. It decreases about 2 degrees C (or 3.5 degrees F) per 1,000 feet of altitude above sea level. The standard temperature at 7,000 feet msl, therefore, is only 1 degree C (or 34 degrees F).

So the procedure is:

Convert pressure altitude with temperature deviation. Ground temperature = 10 °C so density altitude = (10 - 15) * (1000/2) = -2,500 ft
Find TAS at 30,000 ft by subtracting 2,500 ft, then applying the TAS thumb rule of 2% / 1,000 ft: TAS @ 27,500 ft = 27,500 * (1.02/1,000) = 1.55 CAS.

At 30,000 ft and ground temperature of 10°C , TAS = 1.55 * CAS


Is alpha induced angle real on 3D wing or just math concept?

1. Summary

Induced angle of attack is technically a mathematical concept. You can't measure it directly via flow sensors [from an isolated wing]. However, it is extremely useful in understanding and predicting the production of induced drag.

Just like Newton's theory of gravity is a mathematical abstraction; but, if it helps you in understanding and predicting outcomes, you might as well accept it as real. Read the following subsections if you want to understand the potential flow aerodynamic modeling a bit better.

EDIT: provided that you have an extremely long wing (and tunnel width) to call 2D section, and provided you have a corresponding high aspect ratio wing to call 3D section, the difference in AOA measured at the same chordwise location should converge to the induced AOA.

2. Lifting-Line

Induced angle of attack comes from an aerodynamic modeling method, called Lifting Line Theory, which approximates the whole wing as one single bound vortex line that changes in vorticity strength across the span. The change in vorticity is shed via trailing vortices across the span.

Since vorticity induces cross-flow, this model predicts net downwash (downward airflow) at every point along this vortex line. And since the wing is just a line, we can neatly separate out the free-stream velocity, which may have a free-stream angle of attack, or geometric angle of attack, against the line, and a downwash velocity that modifies the flow incidence, which we can call induced angle of attack.

Image ref: https://www.researchgate.net/figure/Lifting-Line-Theory-Scheme-Epps-2010_fig1_273450664

This simplified model predicts surprisingly accurate lift for straight, mid to high aspect ratio wing, in low subsonic flight. It also predicts a new kind of drag, called induced drag, which is totally absent in 2D subsonic [potential] flow.

Now, my question is, is any wing a single vortex line? Of course not. It's a model that gives very useful engineering results. The immediate shortcoming of the model is that it doesn't predict the flow field around the wing well, at all. How can it? It's a line!

3. Lifting-Surface

We can do better by approximating the whole wing as a lifting surface (or its cousin vortex-lattice), with the whole surface producing and shedding vorticity. This model is able to predict the flow field near the wing much better, by producing a different value of downwash at every spanwise and chordwise point. In front of the wing, there will be upwash. So if you measure flow incidence in front of the wing, you will measure higher incidence than the free-stream one.

Image ref: Drela, Flight Vehicle Aerodynamics

At this point, you should realize that the induced angle of attack is no more (because there is different downwash at every chordwise point). But for the same high aspect ratio, straight tapered wing, both lifting-line and lifting surface will agree on prediction of lift and induced drag.

So once again, is a wing a flat surface of vorticity? Of course not. Wing has thickness that lifting surface doesn't handle, and nor does it predict boundary layer.


Can non-instrument rated pilots request practice approaches?

Sure you can! There's nothing wrong with shooting practice approaches if you're not instrument rated (in the US, at least) as long as you don't actually accept an IFR clearance.

You would probably be better off asking approach control for practice approaches rather than tower, if you have approach available to you.


Could the crew of XL Airways Germany Flight 888T not hear important chimes, due to the stall warning?

When the stall has developed the aircraft is no longer in normal control law for any axis (see more in FCTM at OP-020. P 14):

As soon as the aircraft is outside the flight envelope, the control laws transition to abnormal attitude which is the combination of:

Roll direct
Pitch alternate
Yaw alternate.

This is something between alternate and direct, and is intended to allow the crew to recover from the abnormal attitude and reenter the flight envelope without being prevented by some protections.

A stall (an excessive angle of attack) is one of the conditions to switch to the abnormal attitude laws. You may read this article too, while on a simulation site, it is very well written. There is also a presentation on SKYbrary at Eurocontrol.

When the stall warning aural warning is active (voiced "Stall" and cricket), the crew is expected to know they are in abnormal law.

Reconfiguration in abnormal attitude law is indicated by different clues on the PFD (e.g. $\alpha$ prot and $\alpha$ max indication removed from the speed strip, and green = replaced by amber crosses).

Source

Source

and the master warnings are activated. The aural alert is a single chime, (level 2 failure confirmed in this report, page 25). The reconfiguration is also indicated on the ECAM, but the indication can be moved towards the bottom of the list if messages with higher priority arrive.

The law is reconfigured as direct when the landing gears are lowered.

Regarding the aural warnings associated with stall and law reconfiguration, they are audible at the same time, or are intercalated, but none cancels the other, as it was heard for AF447 and reported in this article (C-chord is the single chime):

  In sequence the alarms were sounding PULL UP, C-chord, STALL, C-chord,
  PULL UP, PRIORITY RIGHT.


What will the impact to GA be if DTC DUAT goes away?

I think that there would be little practical impact, except for those people who are heavily invested in DTC DUATS specifically and have to switch to another system.

First, there are two DUATS providers: DTC and CSC. Even if DTC goes away, CSC is still available, at least for now, and it provides exactly the same service as DTC (see this question).

Second, Lockheed Martin Flight Service (LMFS) provides all of the information and flight plan filings that DUATS does, and also provides briefings with a human briefer. So there is a completely separate alternative to DUATS available, although admittedly switching tools always has some cost in terms of time and learning at least.

I assume the main impact would be on people who use DTC DUATS as their primary flight planning and filing tool and use it directly, rather than via another tool. For example, I use Garmin Pilot with CSC DUATS but I could switch to DTC simply by changing the data provider option. Some flight planning tools also support LMFS flight plan filing and I guess that more and more will in future, if only for competitive reasons. But if you use the DTC DUATS website directly and are very experienced and comfortable with it then switching to LMFS or anything else would have a learning curve.

But in the end, people won't quit flying or even cancel flights just because DTC goes away. They'll just complain a bit, choose a new platform (probably LMFS) and get on with it.


Why are so few heliports depicted on sectionals?

I would disagree with the statement that pretty much every grass strip is charted.  This is common in CONUS, Alaska and Canada. There are at least 30 within a 10nm radius of mine which are not. The reasons for charting grass strips are usually:
1. You are inviting people.
2. You want to notice people that the strip is restricted.
3. You are in an area, where charting your strip for emergency use is a public service you choose to offer.
4. You have tenants on your strip, and you want to ease their navigation and those who may visit.

As for heliports being charted: If they are intended for public use, they frequently are.  They are also charted if they have allot of traffic (eg Hospital / EMS / police barracks). Many private helipads do not wish to invite the public, and there is no purpose in charting them.


Assume cruising at 4,000 ft, throttled to about 20 inches MP and 2,000 rpm. Now reducing the rpm to 1,200 without changing anything else will cause the MP to rise sharply. The ambient pressure hasn’t changed, the throttle plate hasn’t changed. The only thing that has changed is the speed at which the pistons are pumping the air. Since they are moving much more slowly at the lower rpm, they are not sucking nearly as hard – not creating as much of a vacuum – so the MP goes up, towards ambient pressure. The pistons are sucking far less air, the speed of the air going through the intake is less and fuel flow is less. This means there is less power being developed, in spite of a much higher MP.


What methods are used to perform head tracking in the cockpit?

Accelerometers are used, however for lower latency and higher definition, tracking infrared emitters is the better choice1.

The A-10 as you wrote uses inertial or magnetic trackers. The Eurofighter helmet uses infrared tracking.

  ... the Typhoon’s HMSS features lower latency, higher definition, improved symbology and night vision.

It's the one on the left (1source).

You can already see it has an organic brain of its own; those bumps are the IR LEDs for tracking.


What does the term "trimming" most commonly mean in aviation?

In short: trimming neutralizes the force required to keep control surfaces in a specific position.

Most (if not all) aircraft have some sort of elevator trim control. For example, when the pilot has to keep pulling back on the yoke/stick during a climb, trimming "nose-up" will neutralize that force. The elevator will then remain in the same position without any force required on the part of the pilot. Trimming is usually done by means of a Trim tab on the control surface and is controlled by a trim wheel.

Elevator trimming is used:

During climbs: to maintain a constant air speed and rate of climb
During descents: to maintain a constant air speed and glide path
During level flight: to maintain altitude and speed

Although elevator trim is the most common, trimming can also be done on rudder (quite common) and ailerons (only on larger aircraft).

Rudder trim is used to maintain coordinated flight without rudder input by the pilot. Many single engine planes with powerful engines require rudder trim to offset the "left-turning tendency" caused by P-factor and propellor wash hitting the rudder. Aircraft without adjustable rudder trim will usually have a fixed trim tab on the rudder.

Most autopilots will control the elevator trim wheel because the servos controlling the elevator could easily be overpowered by the required force.

It's important to note that in most cases (especially on small airplanes) trimming doesn't actually move the control surfaces. It changes the force required to deflect the control surfaces. Although there are many types of trimming devices, the common trim tab makes the airflow do all the work. The trim tab causes the airflow to push the control surface in a specific position. On larger aircraft with hydraulically operated control surfaces, trim tabs are less common (see also this answer to another question)


You can find the 4 segment climb profile described for transport category airplanes in the (old) Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25A) Ch 10 and codified in 14 CFR 25.111.  The full 4 segment profile described below assumes an engine failure at $V_1$ and stipulates a climb and speed profile to clear obstacles.  During normal all-engine ops this profile is still technically in place but you'll hit your speed and altitude targets in such a way that you'll takeoff into a climb with increasing airspeed and no intermediate level off (you will still likely use parts of the profile for your flap retraction schedule).
The segments of the climb are:

Liftoff to 35' and $V_2$
At liftoff you are assumed to be in takeoff configuration with at least one engine not operating.  After liftoff you will retract the gear and accelerate to $V_2$ while climbing.  The goal here is the reach 35' height before the end of your takeoff distance.  Note that for propeller aircraft, this height is 50' instead of 35'.

35' to acceleration height flown at $V_2$
During this segment you climb at $V_2$ until you reach a height at which it is safe to level off and accelerate.  This height is called the acceleration height and is normally 400' AGL.  However, this value can vary per runway and will be available to you in your performance data for a particular runway.

Level flight at acceleration height to $V_{FS}$
You are clear of all obstacles, and now your goal shifts from altitude to airspeed.  Level the airplane and accelerate.

Continue climbing at $V_{FS}$ to 1500' (typical)
Once $V_{FS}$ is reached you will continue to climb at that airspeed.  This will also mark your transition from takeoff flaps to a clean configuration.  The height of 1500' is a typical value but may be different based on obstacles for a specific runway.

Enroute climb
Upon reaching 1500' (or whatever altitude is used in the previous segment) at $V_{FS}$ you transition into your enroute climb.  At this altitude you will begin to perform checklists for the engine failure you experienced between $V_1$ and liftoff and your after takeoff flows and checklists.

Fig 10-36 FAA-H-8083-25A pp 10-30
A transport category airplane with an engine inoperative must be able to meet the climb gradients stipulated in the image above.  The climb gradients vary by number of engines,


Did the FAA order the installation of "Cooper vanes?"

The answer to both of your questions is "yes". The FAA ordered, in effect, the installation of "Cooper Vanes" and did do so in 1972.

The reason you could not find the answer may have been that the modifications were not called "Cooper Vanes" by the FAA and nor was the FAA targeting the 727 specifically. Instead they addressed ventral and tailcone exits on any aircraft.

CFR 14, Part 25 (Airworthiness Standards: Transport Category Airplanes), Subpart D (Design and Construction, Emergency Provisions) contains, since 31st of December 1972, the following text (emphasis mine):

  Sec. 25.809

  Emergency exit arrangement.

  ...

  (j) When required by the operating rules for any large passenger-carrying turbojet powered airplane, each ventral exit and tailcone exit must be--

  (1) Designed and constructed so that it cannot be opened during flight; and

  (2) Marked with a placard readable from a distance of 30 inches and installed at a conspicuous location near the means of opening the exit, stating that the exit has been designed and constructed so that it cannot be opened during flight

This rule was announced in the Notice of Proposed Rulemaking. Notice No. 72-15, Issued on June 6th, 1972.

It clearly references the hijackings as the reason for this change.

  ....

  In spite of concerted efforts made by the FAA and the air carriers,
  incidents continue to occur wherein the safety of the flight of
  aircraft engaged in passenger-carrying operations under Part 121 of
  the Federal Aviation Regulations has been jeopardized by persons
  intending to harm the crew or take command of the airplane. On a
  number of occasions in recent hijackings, the ventral exit of an
  airplane has been opened and a hijacker aboard has parachuted from the
  airplane through that exit. The agency recognizes that every possible
  step must be taken to deter persons from boarding aircraft for such a
  hijacking purpose. Accordingly, the FAA deems it appropriate to
  propose certain amendments to Parts 25 and 121.

  Specifically, it is proposed to amend Sec 25.809 to provide that, when
  required by the operating rules, for any large passenger carrying
  turbojet powered air-plane an approved means must be provided so that:

  (1) takeoff cannot be started if either the ventral exit or tail cone
  exit is not locked; and

  (2) neither the ventral exit nor the tail cone
  exit can be opened in flight.

  A similar amendment is proposed to be made to Sec 121.310, to become
  effective with respect to persons conducting operations under Part 121
  six months following its adoption.

  However, it is to be noted that to achieve compliance with the
  proposed regulation both the ventral exit and tail cone exit would
  have to continue to meet all of the requirements applicable to their
  approval as emergency exits. Specifically, to achieve compliance, the
  conditions that would have to be met to obtain approval of
  modification to the locking mechanisms of these two exits are as
  follows:

  (1) The mechanism must be locked while the airplane is
  aloft;

  (2) Takeoff of the airplane cannot be started if either ventral
  or tail cone is not locked; and

  (3) The exit must be available for use
  in the event of an emergency.

Since Part 25 is for airworthiness certification of new aircraft, an additional change was proposed to Part 121 so that operator of existing aircraft were given 6 months to apply the new rules to already certified aircraft.

Somehow the change to Sec 121.310 cannot be found in the FAA Regulatory and Guidance Library (at least not dated 1972), even though the final rule of 30th November 1972  includes it.

A revision of 121.310 from 1997 includes the text.

Special thanks to the FAA for making the pre-internet era rulemaking archives easily accessible through the internet.


Do helicopters have automatic tail rotor compensation for anti-spin?

Autopilots control the flight path, they usually concern themselves with the travel of the centre of gravity of the aircraft. Stabilising the aircraft is more the job of the human pilot. In a helicopter that is indeed not an easy job - larger helicopters have a mechanical mixer that helps the human do that, a set of lever arms that input extra tail rotor as collective is applied, for some automatic compensation of the increased torque of the main rotor.

Having to indefinitely put pressure on a flight control is an annoying issue for fixed wing pilots as well, that is why they can be trimmed. Stick and pedal forces can be trimmed away, so that the neutral point of the control becomes the point of zero force: once the control is trimmed, you can take your hands or feet off of it and it stays there.

In fixed wing aircraft, trim is usually adjusted with a flick switch on the handle. Flick it sideways and the roll control spring neutral point moves, flick it forwards and the pitch spring neutral point adjusts. Helicopters have such a switch as well, and that works well for fine control in cruise. But in the hover there is a lot of swishing action of all flying controls, and the beep trim switch is just too slow to follow this. Spring forces that are normally helpful, are now a hindrance.

That is why helicopters in addition have a trim on/off button: when selected, all feel forces cancel and the stick or pedal is very light, only a bit of friction and damping. What happens is that the feel forces neutral point automatically follows the stick position. Once the helicopter is stable, the trim forces can be selected ON again, and hands and feel can be removed - although I believe this is never a good idea in a helicopter.


It is possible, but not using typical modern construction techniques.
You have to build a structural frame and then clad it with a non-structural skinning. This technique was widely used in the early days, although the skinning was doped fabric and not transparent.
The frame technique is still used for many ultralights and hang gliders, and some transparent films are strong enough to be used for the skinning. But these types seldom have a significant fuselage. One exception I can think of is Paul MacCready's man-powered Gossamer Condor and Gossamer Albatross prize-winning man-powered aircraft, which had a fuselage nacelle slung under the wing, containing pilot Bryan Allen and the drive train.
Some helicopters such as the Bell Sioux have such large "fishbowl" cockpit glazing that it exposes all the cockpit innards. The Edgley Optica was a prototype observation aircraft along similar lines.
Talking of cockpit glazing, some flying wings had a prone pilot with the glazing forming part of the wing leading edge. These included some of the Northrop and Horten designs.
The Junkers G.38 airliner accommodated some passengers in wing cabins and the glazing to these formed the wing leading edge.
So yes it can be done in principle. But materials such as plexiglass or mylar film are not really suited to such things as enclosing engines or resisting birdstrike, while strengthened glass or polycarbonate get heavy and expensive so that on most planes, only small windows are practicable.
Advanced materials such as structural glass are being increasingly used in architecture, and I have no doubt that the manufacturers and researchers will keep pushing the envelope to develop new materials and new applications. But I don't know of any research focused on airframes.


Where does one request a VFR transition route through class B?

There's an AOPA Air Safety Institute video, "Ask ATC: Am I Cleared for Class B?":

In this and other "Ask ATC" videos, they point out that if you're in VFR flight-following, ATC will not clear you for Class B without your requesting it, even if your current flight path will obviously enter that airspace.
If you are getting ATC VFR flight-following, you should make the request in the course of normal communications, but no later than the point where you can easily divert if clearance is denied.
If you are not talking to ATC, you must first get their attention ("November 12345, request"), then on acknowledgement (when they'll probably abbreviate your call sign, which means you can, too), give your aircraft make/model (which tells ATC your capabilities), relative position (which tells them where to look for your radar return), altitude(s) (level/climbing/descending, which they won't get directly from your transponder), and intentions (your request). This, too, you should do well before the point when diverting around the airspace becomes inconvenient.
(If you're squawking 1200, they'll give you a squawk at the same time, probably an altimeter setting, and possibly altitudes and vectors through the Bravo, so be ready with your lapboard or tablet. Don't hesitate to ask for a re-read, or even to ask them to speak more slowly—in another "Ask ATC" video, they say that controllers often accelerate their speaking pace over the course of a shift without realizing it, they know that VFR pilots aren't as practiced in ATC comms, and they'd much rather you ask for them to repeat more slowly than for you to make a guess.)
So long as you're already handed-off to (if flight-following) or have made contact with the ATC with jurisdiction over the Class B, you can theoretically do it as early as you like.
So there's a bit of a trade-off: later makes it harder to divert, but easier for ATC to have awareness of you. Earlier makes it easier to divert, but ATC may not be ready to clear you if you're far enough out that the traffic situation may change significantly before you enter the airspace.
(Since you're probably significantly slower than most of the aircraft in the Class B, that makes it even more likely that the situation will change.)


Do aircraft have siren to warn public in case of a crash over land?

I understand where you are at with this, I'm going to start off with a bit of math to show how it's not workable. Commercial airliners move quickly, even in a controlled glide one is going close to 3 miles (4-5 km) per minute. To give people on the ground enough useful warning to perhaps find some sort of cover you would need to give at least 20 seconds. This siren would have to be able to penetrate the walls of buildings and houses and cut through the background noise of a built up area at least a mile ahead. This is a very powerful siren and you'll have the following challenges:

At close range you would deafen anyone nearby, injuring the people you are trying to warn
The mechanism to generate this siren would likely be large, heavy, and challenging to design into an aircraft frame
You would need a great deal of mechanical or electrical power to generate that amount of noise. If you have no engine power you won't be able to sound the siren, and if your engines are working you won't need to as the engines make very good sirens already

There are very, very few cases where a siren such as this would save very few lives compared to justify the costs.


How is pitch controlled in a flying wing?

You basically have the answer right inside of the question (as was mentioned in the comments).  In order to make the plane pitch up and down you have the ailerons move up or down in unison (usually called an elevon at that point, again, as noted in comments.)

Here's a handy diagram to give you some idea of what we're on about:

In the second image the movement of both elevons upwards will pitch the aircraft up as well.  And the elevons going in opposite directions, like the last image, will cause the plane to roll (in this case to the left.)

There are more complex maneuvers as well, like pitching and rolling at the same time. These maneuvers are simply managed by differential deflections of the elevons.  Meaning, if you want to come up and to the left you could leave the right elevon neutral(ish) and pitch the left elevon upwards.  This would push down the left wing, rolling you to the left, and pitch the nose up as well.


What is the stability of a 777-like plane if the engines flameout and the autopilot disconnects and the pilots don't make any inputs?

Assuming CG is within limits, the plane is straight, level, and both engines flame out simultaneously, lacking any control inputs, the plane will dive until it reaches its elevator trim speed, then glide at that speed until it impacts.  As the directional and roll stability would be fairly good with the 777, without variable cross wind effects or any other yawing tendencies, it would probably be a straight in crash.

This scenario could be tested under controlled conditions.


How to decode this METAR published during huricane Harvey?

I suggest changing the title, else this question is of relatively limited interest: the METAR message for KNGP has been already updated with new values.

How to set the altimeter when the "sea level pressure" information is not available?

ATC will be able to provide the information. When aerodrome QNH is not available, the Regional Pressure Setting is used ("safe" setting for the highest location of the region).

6////: Group 6RRRR, 3- and 6-hour precipitation amounts

3- and 6-hour precipitation amounts are missing, sensor not operative or not reachable.

402610239: Group 4snTTTsnTTT, 24-hour max/min temperature in tenths degrees

Maximum temperature in the past 24 hours + 26.1 °C.
Minimum temperature in the past 24 hours + 23.9 °C.

53014: Group 5appp, hourly pressure tendency and and actual change in tenths hPa

Atmospheric pressure now higher than 3 hours ago. Decreasing or steady, then increasing; or increasing then increasing more rapidly.
Variation is 1.4 hPa

PWINO: Sensor status indicators (RVRNO, PWINO, PNO, FZRANO, TSNO, VISNO_LOC, CHINO_LOC)

Precipitation identifier information (rain or snow) not available.

See this decoder and this list of METAR abbreviations.


How does a pilots license of cluster ballooning differ from other ballooning or unpowered flight?

The license required for operating a manned free balloon would be a "Lighter-than-air, Balloon" license (as opposed to a "regular" license, which is usually thought of as being for "regular" Airplanes - the kind that take off and land using runways, as opposed to lakes).
Cluster balloons are, for all regulatory purposes, just "balloons" - the only difference is rather than having one monolithic envelope filed with hot air like the balloons most of us are used to seeing they have a bunch of smaller envelopes, usually filled with helium.

An Airman Registry Search shows that there is one "John Ninomiya", with a commercial pilot's license for lighter-than-air balloons, which is consistent with what I'd expect.

A lot of the requirements for a private pilot license in balloons are similar to what you need to do to get a private pilot license in an airplane - for example you still need to learn the same regulatory environment, you'll learn to read the same charts, you'll cover flight planning and weather, etc.

The differences are that you'll be learning balloon systems rather than aircraft systems, and the experience requirements under FAR 61.109 are pretty radically different because of the fact that balloon flying is pretty radically different from flying around in an airplane.

You can peruse Part 61 of the FARs for all the specific details on training requirements for lighter-than-air balloon pilot certificates - Subpart E  (Private Pilots) is probably where you want to look.


Has anyone researched or built an aircraft that controls pitch and roll by pumping liquid within the airframe?

The aerodynamic forces resulting from surface deflections are orders of magnitude larger and faster (in their rate of change) than the gravitational forces obtainable by shifting the centre of mass.

Additionally, as OP seems to realize, yaw control would not be feasible with this method.

So overall it would not be impossible, but it has no clear advantages to outweight the heavy disadvantages. I am also unaware of any prototypes or tech demonstrators using this method.


These are colloquially called "flight numbers," though technically that term refers to just the numerical portion. Pretty much all travelers will use this name for them.

According to Wikipedia, the International Air Transport Association (IATA) officially uses the name "flight code" to refer to the whole portion. Unfortunately, the cited IATA document is behind a paywall, so I can't independently verify that.

In particular, the type of flight code in your example is of the ICAO variety and is also being used as the callsign for that particular flight for radio communication purposes. In the U.S., it is customary to use the airline's callsign plus the flight number as the callsign for a particular flight. Some other countries use the Aircraft Registration Code (commonly called the "tail number") of the aircraft instead of the airline flight number as the radio callsign. General aviation aircraft (which don't have airline flight numbers) will also normally use their tail number as their callsign.

When used as a call sign, a flight code will use the ICAO code for the airline. However, for purposes of airline reservation systems, it's common to see the flight number listed with the airline's (2-letter) IATA code rather than its (3-letter) ICAO code.

When a flight number is used as a callsign and is spoken on the radio, the airline's callsign will be spoken instead of the letters in the flight number. For example, your example of AWE685 will be pronounced "Cactus Six Eight Five" on the radio, since "Cactus" is the callsign for U.S. Airways.

For reference, the use of "AWE" and "Cactus" for U.S. Airways is a relic of when U.S. Airways merged with America West Airlines. They kept the name of U.S. Airways, but the ICAO code and callsign of America West (whose main hub was in Phoenix, AZ, hence the "cactus" callsign.)


What direction should a traffic pattern be at an uncontrolled or non-towered airport?

When aviation literature mentions "the standard traffic pattern", it's usually a left-hand counterclockwise pattern; regardless of wind direction, the runway will always be to your left side and you make left turns to follow the pattern through crosswind, downwind and base legs. This is the default pattern direction when there are no overriding signals.

However, this is only the default, and airports are free to change the procedure as needed to comply with local terrain or development. An airfield near a neighborhood to its east, for instance, may require that traffic circle around the west side of the airport; therefore this airfield's 17/35 runway will require a left-hand pattern when using runway 35, but a right-hand pattern when using runway 17.

When an airfield establishes a non-default traffic pattern, they must provide this information to pilots in a readily-visible manner. The standard recommended (though not required) set of runway and pattern indicators is known as the segmented circle, so called because its most visible identifying feature from a distance is a 75-foot circle of dashed lines:

In the center of the circle as pictured is the runway direction indicator aka the tetrahedron; this will indicate which strip of asphalt to use and which direction to take off and land on it (the narrow end points in the direction that planes should take off and land).
Off to one side is the windsock, which is the only piece of equipment that is required at any airfield; it indicates approximate wind speed and direction. FAA guidelines for the sock say it should reliably turn to the wind direction at 3 knots, begin to inflate at 5 knots and be fully extended at 15. The windsock can replace the tetrahedron in the center of the circle; in that configuration you would simply approach the airfield using the runway closest to the direction in which the tip of the windsock is pointing (if winds are calm and/or the airfield has multiple runways, the tetrahedron is preferable).
On the ground just outside the segmented circle are L shapes; these are the pattern indicators, and point in the direction of the base leg when approaching the runway from that end (so if you're following the pattern, the end of the L should be pointing at you before your turn to final).

So, the circle in the above picture tells aviators several critical things without any human (or computer) having to relay the information vocally:

The approach direction is from the upper right to the lower left of this picture.
The wind is roughly in line with the runway, so no crosswind landing procedure is required.
Winds are very strong (the windsock is fully extended which indicates wind speeds in excess of 15 knots) so ground speed will be much lower than IAS at takeoff and landing.
Most relevant to your question, airfield traffic should be on a right-hand pattern at this time; if the winds and thus the runway in use were opposite, traffic would use a left-hand approach.


The best glide flap setting is a matter of definition. If the base airfoil was optimized for high lift (like, say, the Wortmann FX63-137), the cruise flap setting would be some trailing-edge up position. If that is defined as 0°, and the take-off setting is the one for which the airfoil has originally been optimized, then it should not be too surprising that it allows the best L/D.

A high zero-lift drag coefficient, like from a fixed landing gear, will drive the optimum L/D to low speeds and a high lift coefficient. That is where the Wortmann FX63-137 excels and the reason why the optimum L/D of the Katana is at such a low speed. The Katana has inherited this airfoil from the H36 Dimona motorglider, and here it had been selected to meet the minimum sink speed requirement at that time for certification as a motorglider.

Airfoil trivia: The Wortmann FX63-137 has originally been designed for a human powered aircraft project. This explains its very high maximum lift at low Reynolds numbers.


What are the following documents about aircraft maintenance?

A service bulletin is a document that the manufacturer of an aircraft issues directly to operators of related aircraft. It mandates some maintenance / replacement / check activities.

A rapid revision is a change to the maintenance documents, that is not released officially according to normal procedures, yet.

A non conformation report is any discrepancy found in the aircraft / system such that the related system does not look / operate / behave / function as expected. This document is mostly a form that the ground crew / technicians / pilots generate.

Disclaimer: these are general information and details would change depending on whether the aircraft is a civil or military one, and the certification type. This answer is written in the perspective of military aircraft, for general knowledge.


Does a 709 ride mean the end of my career?

Depends on the reasons the FAA had to justify the need for a 709 ride.  If it was some kind of bureaucratic maneuver without justification for doing so and you pass the ride with flying colors, probably nothing.  If there was a serious discrepancy in your airmanship which required a 709 ride to verify improvement on your part, it's going to depend on whether it was a one time event or a trend in airmanship deficiency resulting in the check ride.  In addition have there been further reports of deficiency in your airmanship after the 709 ride?  That will also have an effect on an employer's judgment of you as a potential employee.

Whatever the reasons for the 709 ride, an employer is going to see it, so be prepared to explain anything associated with it.

Look at this from the employer's perspective:  I'm going to put you in charge of a big, heavy multimillion dollar machine that you are going to pilot several miles off the ground at speeds close to that of sound.  If anything goes wrong, you're going to get killed, someone else on board is going to get killed, people on the ground are going to get killed and I'm going to get sued, go bankrupt, end up in jail, or all three if your negligence can be traced back to me.  Is there anything in your background which make me suspicious this is likely to happen if you are in my employ as a pilot?

The fact that you do make mistakes, possibly even serious ones, is not necessarily the issue here; everybody makes mistakes.  The last time you flew on an airliner the flight crew probably screwed something up.  People with thousands of PIC hours learn something new on their next flight and it's a mark of a good pilot that you can identify your own faults and fix them.  The Blue Angels have a private saying amongst themselves that "We've never flown a perfect airshow and we probably never will.  But we strive for the perfect airshow each and every flight".  Striving for perfection as a personal motivator is the mark of a good airman and looks good on a resume, no matter how balls up some flight in your logbook was.

The real issue here is do you have a recent or chronic history of uncorrected gross negligence or inability to handle the kinds of aircraft a potential employer flies which raises red flags as to your airmanship or trustworthiness.  If you have a spotty record or recent 709 ride in your recent past, take a couple of years staying on with your current employer and do an outstanding job.  Work on your airmanship and develop a stellar reputation with them as a pilot.  That will go a long way to erasing the past, or at least mute its bite.

Speaking of trustworthiness, DO NOT LIE TO A PROSPECTIVE EMPLOYER ABOUT A 709 RIDE OR ANY OTHER FAILED CHECKRIDE.  Aviation is built upon an honor system and any kind of detected lying or deceitfulness on your part is an automatic fail with no second chances, no matter how squeaky clean your career is up to that point.  If they ask about it, tell it like it was, no more, no less, and let the chips fall where they may.  It will yield the best possible outcomes, even if you don't get the job.


Do modern aircraft have sensors to determine weight of the aircraft?

No, the 737 does not have such sensors installed because it is less expense to compute the zero-fuel weight (and thus takeoff and enroute and landing weights, by adding fuel on board) by taking the known aircraft empty weight and adding to that the weights of the people and things that are on board.

I've never heard of any attempt to install any such sensors on a 737. Some FMC software can use in-flight performance data to estimate gross weight and alert the pilots if that estimate varies too much from the computed weight, but that is an entirely different approach.