At what altitude does aerodynamic forces become negligible?

Basically, you are asking the altitude at which the atmospheric forces on the aircraft (lift and drag) become negligible i.e. the point where the density of the atmosphere is so low that the impact of air molecules on the aircraft (or spacecraft as it may be) has little effect.
Generally speaking, as the altitude increases, the density decreases, but there is no fixed altitude above which it disappears- rather it gradually disappears into irrelevance. Even spacecraft hundreds of kilometers above earth's surface in low earth orbits (LEO) have to fire their boosters periodically to overcome atmospheric drag.
The image below shows the height of International Space Station (ISS) over time, which shows the loss of height due to (among other things) atmospheric drag.

This plot shows the orbital height of the ISS over the last year. Clearly visible are the re-boosts which suddenly increase the height, and the gradual decay in between. The height is averaged over one orbit, and the gradual decrease is caused by atmospheric drag; Image from heavens-above.com
Even at that altitude, the drag can be significant for the fuel available and as NASA points out,

For most of the last decade, ... the International Space Station they were circling the globe at an altitude of approximately 220 statute miles, or about 350 kilometers.
... European Space Agency’s resupply ship Johannes Kepler... will bring the fuel needed to boost the station to its normal planned altitude of 248 miles, or 400 kilometers.
“As solar activity rises, the atmospheric density in our altitude range increases causing increased drag on the vehicle. This in turn causes us to have to raise the orbit more often.”
Even though the space station orbits in what most people on Earth would consider to be the “vacuum of space,” there still are enough atmospheric molecules ... that the cumulative effect of these tiny particles contacting its surfaces reduces its speed and causes a minute but continuous lowering of its altitude, or height above the Earth.

The question now becomes different- at what altitude does effects other than drag become much more important. Though we cant set a precise value as above, it is possible to set a theoretical altitude above which the drag can be neglected (not entirely) and other things become more important. This is called the Kármán line, which Von Kármán explains as:

... flew 2000 miles per hour (3,200 km/h) at 126,000 feet (38,500 m), or 24 miles up. At this altitude and speed aerodynamic lift still carries 98 per cent of the weight of the plane, and only two per cent is carried by centrifugal force, or Kepler Force, as the space scientists call it. But at 300,000 feet (91,440 m) or 57 miles up this relationship is reversed because there is no longer any air to contribute lift. Only centrifugal force prevails. This is certainly a physical boundary ...

(Quote from Von Kármán's autobiography, from Wikipedia)
As the drag force is similar to lift (both are proportional to the square of speed and directly proportional to density), it only makes sense to consider that the drag loses its effect on the air/space craft, at least for ease of definition.
From Fédération Aéronautique Internationale:

Astronautics needed the lack of atmosphere to be viable; Aeronautics needed the presence of atmosphere. And atmosphere existed near the Earth’s ground, but did not exist far above the ground. In Astronautics, speeds impossible to maintain in atmospheric drag could be kept for very long periods without power applied to the vehicle.
In Aeronautics, level flying higher and higher meant to deal with less and less dense atmosphere, thus to the need of greater and greater speeds to have the flying machine controllable by aerodynamic forces. A speed so big in fact, that, above a certain altitude, could be close or even bigger than the circular orbital speed at that altitude ...
A lot of calculations were made, and finally it was reached the conclusion, accepted by all scientist involved, that around an altitude of 100 Km. the boundary could be set.
The 100-Km altitude, ever since named the “Karman Line”, came thus into existence as the boundary separating Aeronautics and Astronautics.

Basically, for the purposes of your question, we can take the Kármán line as the point where the atmospheric drag loses its effect on the aircraft, which becomes a spacecraft.


Who can carry out airworthiness inspections?

I can speak to the FAA requirements.  The basic requirement for the annual inspection (commercial aircraft have additional requirements) comes from 14 CFR Part 91.409

  §91.409   Inspections.

  (a) Except as provided in paragraph (c) of this section, no person may
  operate an aircraft unless, within the preceding 12 calendar months,
  it has had—

  (1) An annual inspection in accordance with part 43 of this chapter
  and has been approved for return to service by a person authorized by
  §43.7 of this chapter; or...

And the related requirement regarding who can perform this is covered in Part 43 and is in two parts; who can perform the work and who can approve the return to service.

The work must be performed by someone specified in 14 CFR Part 43.3 in which the general case is:

  §43.3   Persons authorized to perform maintenance, preventive
  maintenance, rebuilding, and alterations.

  (a) Except as provided in this section and §43.17, no person may
  maintain, rebuild, alter, or perform preventive maintenance on an
  aircraft, airframe, aircraft engine, propeller, appliance, or
  component part to which this part applies. Those items, the
  performance of which is a major alteration, a major repair, or
  preventive maintenance, are listed in appendix A.

  (b) The holder of a mechanic certificate may perform maintenance,
  preventive maintenance, and alterations as provided in Part 65 of this
  chapter.

  (c) The holder of a repairman certificate may perform maintenance,
  preventive maintenance, and alterations as provided in part 65 of this
  chapter.

And the approval for return to service must be per 14 CFR Part 43.7

  §43.7   Persons authorized to approve aircraft, airframes, aircraft
  engines, propellers, appliances, or component parts for return to
  service after maintenance, preventive maintenance, rebuilding, or
  alteration.

  (a) Except as provided in this section and §43.17, no person, other
  than the Administrator, may approve an aircraft, airframe, aircraft
  engine, propeller, appliance, or component part for return to service
  after it has undergone maintenance, preventive maintenance,
  rebuilding, or alteration.

  (b) The holder of a mechanic certificate or an inspection
  authorization may approve an aircraft, airframe, aircraft engine,
  propeller, appliance, or component part for return to service as
  provided in Part 65 of this chapter.

Requirements for mechanics and inspection authorizations are spelled out in 14 CFR Part 65, Subpart D.

The regulations also allow manufacturers and repair stations among a limited number of others to perform the work as well.  (see links)


How does an airplane move itself in the runway?

The power to move an aircraft from point A to point B on an airport is provided by the same engines that power it in flight unless you hook up a tug, in which case the tug provides the power. There have been experimental developments that provide power to the main landing gear wheels, but there have never been any real implementations of these systems. Small single-engine aircraft can be moved by hand.


Why did an iPad software failure cause a return to the gate?

iPads are used so the flight charts and manuals are electronic instead of the old phonebook that had to be printed and distributed every few months.

This means that without it the pilot has no up-to-date copy of the flight chart of the airport where he is trying to land which is a safety issue.


Why has the maximum service ceiling of Boeing and Airbus products remained about the same for 30 years?

Mainly, the optimum cruise altitude is where thrust and lift requirements for both take-off and cruise balance well. An additional benefit is the colder air which increases the efficiency of heat engines. Since this helpful drop in temperature ceases once the aircraft climbs above the tropopause, the benefits of flying higher increase most below the tropopause.

With increasing flight altitude, the airliner needs:

Bigger engines to create the needed thrust in thinner air
Bigger wings to create the needed lift

With the wings, the size of the tailplanes will also grow; this effect alone likely will weigh more than the beefing up of the fuselage structure for the increased cabin pressure. Flying higher will make almost all parts bigger and heavier.

Note that Mach 0.85 is a hard limit for efficient flight; airliners cannot compensate for lower density by flying faster. The only way to allow higher flight levels is to attach bigger wings and tails.

Another consideration is Breguet's formula: Jet aircraft have their optimum cruise lift coefficient at a value of $c_L = \sqrt{0.6\cdot c_{D0}\cdot\pi\cdot AR\cdot\epsilon}$, if we assume the thrust of high-bypass-ratio engines to vary with speed proportional to $v^{-0.5}$, which is a reasonable assumption. This means the airliner cannot fly higher by flying at a higher lift coefficient: This would decrease efficiency.

(Nomenclature: $c_{D0}$ = zero-lift drag, $AR$ = wing aspect ratio, $\epsilon$ = span efficiency)

With the wing size and the engines needed for flight at Mach 0.82 in the tropopause (Mach 0.85 is really not as efficient; follow the link to find out why this is the quoted cruise speed for long-range airliners), the take-off distance is quite reasonable and approximately matches the airports which had been defined by NATO during the cold war. Flying any higher into the stratosphere would increase the aircraft's mass due to bigger engines and wings, but would not incur the efficiency gains of increasing cruise altitude in the troposphere, where temperature drops with altitude.

Conversely, picking a lower design cruise altitude would allow to make both wings and engines smaller, but this would translate into:

Higher take-off and landing speeds, and critical speeds during take-off due to the smaller wing,
Lower take-off acceleration due to smaller engines,
For twins: Not enough thrust during take-off when one engine fails,
Lower climb speeds, so it would take longer to reach cruise altitude, and
Not fully taking advantage of the cold air up in the tropopause.

Designing for a lower cruise altitude would translate into much longer runways and less efficient flight overall.

Designing for cruise in the tropopause is simply the sweet spot for airliner designers where all conditions match well and produce a balanced outcome.


What are the advantages of towbarless pushback tugs?

Advantages of towbarless pushback.

You don't have to store different tow-bars for different a/c types. This is especially good for ground handlers who handle different airlines with different aircraft types. Also handy for ad-hoc one-off flights.
Removing need for tow-bars means one thing less to check daily, weekly, monthly, annually.
Towing with a tow-bar requires a man in the cockpit to ride the brakes (brake-rider). This also means the aircraft may require power (either from APU or from the towing vehicle) to supply hydraulic pressure. An aircraft towed with a towbar is dependent on the aircraft brakes if a sudden stop is required as the towbar will not be able to take the weight of the aircraft on its own on decelerations.
A normal tug (which uses towbar) needs to be very heavy to enable it to tow an aircraft. Without the weight, the tug will just spin its wheels. The tow--barless tug will have the weight of the aircraft on its wheels so it doesn't need to be as heavy. Just solidly built to support the engine and associated hydraulic stuff. This weight also makes the brakes more effective.
A towbarless can tow the aircraft faster as control is way better. In some busy airports they only allow you to move the aircraft across busy taxiways or during peak hours if it is either taxied under its own power or towed by a towbarless tug. Towing using tow-bar is not allowed as it is very slow.
The tow-bar has 'shear pins' which limit the force which can be applied through the nosewheel towbar points. This reduces the towing speed. They can and do break once in a while. While a spare is usually carried in somewhere on the 'bar it still stakes a few minutes to get in installed. Not fun in the middle of a pushback and may result in a blocked taxiway.
A lot of injuries are caused by towbars. Either they jacknife when something fails or a lapse in procedure caused the nosewheel steering to be activated before the bar has been disconnected. The danger here is the nosewheel is self-centering in almost all aircraft and will swing the bar if the nosewheel is not centered. Scary to see and can take your legs out.

I'm sure there are more aspects but these are the major points. Hope this clarifies a bit.


What are the "panels" on the wingtips of the Panavia Tornado?

From another cutaway drawing:

    57: Wing tip antenna

Found here, but the original source is unknown.


What causes a "BATT DISCHARGE" CAS message on the Phenom 100E?

I am not into the Phenom 100E nor the avionics.
However, me and many others think that there is not much space for interpretation on this message.
In the G1000 handbook of the Phenom 100, on page 129 in the section "CAS Messages > Caution Messages", it says:

BATT DISCHARGE Battery discharging under normal operation

Source

Source (Page 122)
This is the electrical status page as shown on the G1000 of the Phenom 100E. I marked the batteries yellow and all parts actively generating electricity and affecting load of the batteries in red.
When will BATT DISCHARGE pop up?
BATT DISCHARGE will pop up, if the load on the batteries is higher than the charge. This applies in following situations:

Master is on and systems are consuming electricity from the batteries but no engine and generator is on and no GPU is connected to the aircraft.
If the message pops up during flight, in which GEN 1 and GEN 2 usually charge the batteries, there is a problem with the generators. Additionally there can be displayed an ELEC EMERGENCY warning on the CAS.

What we see in the video

Start of engine Nr. 2 When he starts the first engine, we can see three CAS-Messages: BATT DISCHARGE, SHED BUS OFF (definition of SHED BUS below) and GPU CONNECTED. The engines on a Phenom are cranked by electricity, not by pressure air, so the BATT DISCHARGE makes sense first. However, the GPU is connected. Now, many things could happen here. Maybe an engine start is using lots of power, even more than the GPU can deliver.

After start of Nr. 2 After the start (~ 1:32), we can see on the status page, that the GPU was disconnected. The Generator of ENG 2 is already running. On the CAS there is still the BATT DISCHARGE and GPU CONNECTED to see. They disappear at the same time. This is probably because of some delay in the CAS-System. That means the battery is discharging, even though the GPU is connected (~ 0:55). It could be because of a weak GPU.

Start of engine Nr. 1 (~ 1:58) When the second engine gets cranked up, we can see, that the GPU was removed shortly after start of engine Nr. 2. However, there is no BATT DISCHARGE caution message anymore. Now engine Nr. 2 charges the battery. Maybe the generator is stronger than the GPU before. While starting Nr. 1, the SHED BUS is off again.

Unfortunately the video doesn't show, when engine Nr. 1 has started and is stabilized. It would be interesting.
Personal conclusion
As already said, I am not a pilot nor an engineer and only have the knowledge I have self-taught. On this knowledge-basis, I would say following looks most logic for me:
The GPU delivers only a small amount of electricity to the plane. It can't balance the load of the battery. I don't know if this is possible, but looks logic for me. After engine start, the generators of engine Nr. 2 provide the aircraft with lots of power, enough to charge the battery and to start the other engine.
The theory of a GPU, providing only a small amount of electricity would be supported by how the SHED BUS works, below. The EDL disconnects the SHED BUS because the batteries are loosing power. You can see this at ~1:08 in the video in the ELEC section of the MFD. It shows: BATT 1 - 23.5V and BATT 2 - 25.8V. This is well below the normal voltage of 28V. A bit later at 1:28 we see that both batteries have dropped to ~24V and are still discharging. At ~1:30 we see the generators providing electricity and the batteries are charging again fastly. Thats also when the SHED BUS is coming on again. At 1:58 the SHED BUS is off again and the batteries are down at 22V and 25V.
So, when I look at the facts, it looks like a weak GPU for me. However, there is still one question: Why is there no BATT DISCHARGE when starting Nr. 1?
My theory is: It looks like there is some sort of delay in the CAS-System. As we have seen in the video, the GPU is already indicated to be disonnected on the MFD, but the CAS still says it is connected. Maybe the message BATT DISCHARGING hasn't appeared because of the delay. We lack the last seconds of the video, so we don't know if the message maybe appears or the generators provide electricity early enough, before appearing.
(I think this question needs more attention. It's a nice puzzle question that deserves much more upvotes.)

UPDATES

I have now found GPU values I can't confirm to be true:

GPU Limits
27V to charge
26-29V for operation
800-1000 Amps

Source

The SHED BUS

The shed bus powers non-essential aircraft systems. In the case of the phenom 100 this is things like the air conditioning, passenger power sockets and entertainment systems, the toilet and some lighting.
The shed bus is the first thing to lose power (be shed) should the aircraft not be generating enough electricity through, for example, a generator dropping offline.

From my question about the shed bus by sp1.


How to find the measurement of how far Tail plane to Center of gravity of the aircraft?

First you calculate the position of the CG, then you do a simple arithmetic calculation based on the station of the tailplane.


Will reducing the electricity power in an aircraft save fuel?

Yes, in theory, but you would have to do a total energy analysis to decide if it's worth it.  On the surface of it, generators consume fuel not being made into thrust. Watts being made to power things is watts not going out the tailpipe.

A good example of the potential benefit is the switch to LED cabin lighting. A 40w incandescent light is more or less a 35w heater that makes a bit of light.  LED lights drop the power consumption by 80-90%, although if you need heat in the same space, you have to replace the heat being made by the lights, so if you did an overall energy balance analysis in that case, you might find the actual saving is negligible for the period when you need to heat the cabin in cruise at altitude (because the reduction in heat from the lights has to be replaced by more bleed air demand).

If you need cooling, it's the opposite because the heat from incandescent lights is working against you, and it's a huge benefit to get rid of the heat produced by the lights, which reduces cooling demand.

So overall, there is probably some fuel burn improvement over time switching to LEDs, very small, but something (say, 200 30w lights consuming 6kW, replaced by 200 5w LEDs consuming 1kW, a 6hp saving, maybe 4lbs/hr - not nothing, but, but as I said you'd have to take more bleed when heating, offsetting a lot of that improvement, and you'd probably have to spread it out over quite a while to get serious money out of it).

Most airlines that switch to LEDs do it mostly for reliability reasons, where labor hours savings and parts costs make a stronger financial business case than just a few pounds of fuel spread out over time, although the fuel-saving does add to the total.

Another area would be advances in avionics that reduce power consumption (you can just imagine the drop in energy demands when avionics went from vacuum tubes to solid-state in the 50s).  Even there though, it's the same issue with heat that is not really wasted when the cabin requires more heating than cooling, that steals some of the benefits you thought you were getting.

Reducing electrical demand with efficiency improvements also helps with weight savings (smaller, lighter generators).

On the other hand.... the 787 blows all that out of the water by going to the other extreme, making all sorts of services electrical, requiring really massive generators. I'm not sure that there is a net energy benefit to using electricity to replace bleed for anti-icing for example, and I think the main benefit is reliability (bleed air systems are a massive maintenance and reliability hassle).


Why does lift curve slope increase when Fowler Flaps are deployed?

Note that your plots show lift coefficient over angle of attack. This lift coefficient is referenced to a reference area which must be defined somehow. It is customary to use the projection of the clean wing area in the x-y plane for all flap settings in order to keep coefficients comparable. The lift curve slope increases because the real wing area increases while the reference area remains unchanged. The dashed line in the lower plot shows the isolated effect of camber increase while the upper solid line combines both effects (area and camber increase).


Why would the digits fade out and blink in darkness on a KX-155?

Yes, there is a trim pot on the display circuit board that adjusts the dimmer level.
The display intensity pot is R438. The red arrow points to it:

The dimmer pre-set should be marked on the outside cover, and is adjustable without removing the covers, but it only adjusts the max brightness.
It could also be the photo cell that is bad or dirty. When the display starts to loose it's brightness, that's usually a sign that it's about to go south. It can be readjusted with the pot a couple of times, then is only visible when the radio has warmed up, then finito. Try a new photocell, very easy to replace.
Be sure to observe all regulations concerning avionics maintenance!!
Source of info: http://www.337skymaster.com/messages/showthread.php?t=478


What's the difference between flight level and pressure altitude?

Flight Level specifically refers to Pressure Altitude in 100 foot increments within the Standard Pressure Region, which in North America starts at 18000 ft and above, and at various lower altitudes elsewhere.

If you are in the Altimeter Setting Region where you set local barometric pressure to get indicated altitude, you normally use indicated altitude and could state the pressure altitude if asked, but you wouldn't use the term Flight Level.


What are the effects of a rejected takeoff?

If an airplane is close to V1, the brakes - which have to absorb kinetic energy and dissipate heat - can get hot to the point where the tires automatically deflate, to prevent them from exploding. For a 747 this involves a lot of smoke and glowing brake disks.


Unfortunately if you have never held a valid medical certificate since July 14, 2006, the answer is no.  One of the eligibility requirements for BasicMed is that you must have held a medical certificate after  that date.
§61.89(d) states

The holder of a student pilot certificate may act as pilot in command
of an aircraft without holding a medical certificate issued under part
67 of this chapter provided the student pilot holds a valid U.S.
driver’s license, meets the requirements of §61.23(c)(3), and the
operation is conducted consistent with the requirements of paragraphs
(a) and (b) of this section and the conditions of §61.113(i). Where
the requirements of paragraphs (a) and (b) of this section conflict
with §61.113(i), a student pilot must comply with paragraphs (a) and
(b) of this section.

§61.113(i) required that pilot hold a valid U.S. driver’s license, meet the requirements of §61.23(c)(3), and complies with this section and the conditions listed in §61.23(c)(3).
But §61.23(c)(3)(B) states that a person operating an a/c without a medical certificate under §61.113(i) must have:

At any point after July 14, 2006, have held a medical certificate
issued under part 67 of this chapter.

As such you will have to acquire a medical in this case before you can take the checkride.


Why are aircraft windshields not unbreakable?

Windshields

In the US, aircraft windshields must conform to 14 CFR 25.775 - Windshields and windows

  (b) Windshield panes directly in front of the pilots in the normal conduct of their duties, and the supporting structures for these panes, must withstand, without penetration, the impact of a four-pound bird when the velocity of the airplane (relative to the bird along the airplane's flight path) is equal to the value of V C, at sea level, selected under § 25.335(a).

So, windshields are not indestructible partly because they are not required to be.

I guess windshields are not required to be indestructible because bodies like the FAA probably take the view that when an aircraft impacts a massive object at high speed, say a large mountain at 500 MPH, it is of no consequence whether the windshield survives intact at the bottom of a large crater of tiny aircraft fragments. It serves little purpose to make the windshield substantially stronger than the surrounding airframe.

Glass-Ceramics

Glass Ceramics are not unbreakable. For example a glass-ceramic might have a bending strength of 340 MPa (Ref p9)


Because what you are simulating is not a wing, but an aerofoil at an arbitrary $y$ station along the wing.
The linear spring simulates the wing bending and the torsional one its torsion about the elastic axis. The constants would of course be of the type $k_{e}=f(y)$.


If the the body and it's wing is mostly covered with solar panels and flies with electric motors, is it possible for that aircraft to fly?

Not a stupid question at all! This was one of the goals that solar impulse I and II set out to show. one thing to keep in mind is that its of course only possible while the sun is shining. It was able to do it but the margin of error was fairly small,

  During the day, the plane flies only by the energy from the sun. But
  in the morning and evening, when sunshine is not so strong, and
  especially at night, it must tap into its reserve of energy stored in
  its batteries. So every evening, the pilot must make sure that the
  plane’s batteries are 100% charged so that it can fly until the next
  sunrise.

Solar impulse ran on 8HP motors which is not much more than the Wrights first powered aircraft with a cruise speed of 56MPH it was not a terribly fast aircraft either but proved the concept was possible at a small edge of the spectrum.


What are "referred" speeds and "referred TET"?

Referred speed is a way of compensating for the fact that air density changes with temperature.  For example, let's say you are designing a new turbojet engine. You fire up your engine one warm sunny day in July, and note that when the shaft speed is 5,000 rpm, it's making 10,000 pounds of thrust.  But then later, on a cold winter evening in December, you run the engine to 5,000 rpm, and now it's making 11,000 pounds of thrust!  What happened?  Did your engine suddenly get more efficient?  No.  It's just that colder air is more dense.  So for that same 5,000 rpm, you are pumping a lot more mass of air. Now, where referred speed comes in.  You are going to have to tell the pilot of the plane how to set thrust.  i.e. he wants to get 10,000 pounds of thrust, no more and no less.  You can't just tell him to set 5,000 rpm, because that will be a different amount of thrust depending on the ambient temperature.  So you tell him to set a specific "referred speed".  If you go to the same referred speed, you'll always get the same amount of thrust, no matter what the temperature.

You should also look up corrected speeds.  That is a very similar concept.


Could winds of up to 150 km/h impact the structural loads on a Boeing 777?

Could winds of up to 150 km/h impact the structural loads on the B777-200LR?

Not at all.

The dynamic pressures on the plane depend on the plane's velocity with respect to the air, not the ground speed.

Flying in 150 km/h tailwind is the same as flying with no wind, the plane's indicated and true airspeeds won't be affected. True airspeed is the plane's velocity inside the fast moving wind tube.

Since the jet stream itself is moving, it just moves the plane with it. With the added bonus of extra ground speed, or if you're the pilot, a dreaded return flight—unless you can avoid the now headwind, usually they are avoided for the Pacific and Atlantic routes, not as often for elsewhere.

Here's a 1200 km/h subsonic flight: Jet Stream Blasts BA Plane Across Atlantic in Record Time


Why is the Priority Takeover button used?

It's been several years since I worked at United's flight training center, but if my memory serves me, it is there in case the system is receiving input that the pilot wants to exclude. As was explained to me, an example of this would be the other pilot becoming incapacitated, with their body leaning against the sidestick. In this case, one would want to use the Priority Takeover button to eliminate the other pilot's input.

In Captain Sullenberger's case, it is likely that he wanted to ensure that First Officer Skiles wasn't providing any control inputs that would work against his control inputs.

Now, it is also my understanding that such functionality is not useful in a "hostile takeover" event, since the other pilot can also attempt a priority takeover (or use physical force, due to the close proximity of the two pilots).


Which authority is responsible for RT licensing in the Netherlands?

The Dutch authority responsible for radio communication licenses is 'het agentschap telecom', part of the ministry of economic affairs.

More information about licensing for the aviation radio bands can be found on their website (in Dutch).


Is there an IATA airport code that is unassigned and that can be used for "any airport"?

Good question, no good answer.

In the ICAO system, the identifier ZZZZ is reserved by that agency to designate on flight plans that the airport does not have an ICAO code assigned (not all airports do; for instance Qualicum Beach Airport in British Columbia is TCCAA registered and has TC and IATA codes but no ICAO code). There is no specific combination of alphanumeric characters reserved to mean "airport not specified"; if the flight plan does not specify an airport at a particular stop, the ICAO code field will be blank (which is valid in many circumstances in general aviation; float planes can set down on any relatively calm body of water, while bush pilots routinely fly out to a dot on the map in the literal middle of nowhere to deliver supplies or people to an established but temporary campsite).

XXXX is an unassigned but unreserved ICAO code that a few websites seem to be using for testing and demo purposes; FlightStats has a page for this code but the data is sparse and nonsensical.

The IATA system labels practically all registered airports (primarily ones of interest to commercial flight, but all FAA-registered airports have a three-character code that have, with few exceptions, been adopted verbatim by IATA). The IATA has no specially reserved code for "not specified" or any other special case. The code ZZZ is currently unassigned, and is used informally by bush pilots to indicate an "unregistered" landing area similar to the ICAO system (though as IATA labels more airstrips especially in North America, this code is used more specifically for unimproved landing areas, which are common in backcountry areas of the Plains States, Northwest and Alaska). But again, that still indicates an entry was made.

If you are writing a computer system for flight planning and you want a string value to indicate that the user has not specified an IATA identifier, the safest are null, the empty string, or three spaces. "000" is probably also safe, as IATA does not and likely will never use three zeroes for any valid identifier, and OOO is also not assigned. The code "ANY" is reserved for Anthony Municipal in Kansas, but the code "NON" is not currently assigned (though with no guarantee it will remain so). XXX, YYY and ZZZ are also unassigned but other repetitive letters are.


Why do we often have more than one method of slowing down (retarding) aircraft on the ground?

I would suspect that it is due to redundance, safety and usefulness in different circumstances.

Thrust reversers are useful to slow down from high speeds, but you wouldn't want to use them when trying to stop at a gate.
Wheel brakes are powerful both at high speed and when parking, but can catch fire if the temperature resulting from the braking gets too high. Also less efficient on slippery runways.
Some (primarily) military aircraft have tailhooks despite not being designed to land on aircraft carriers. The hooks provide an alternative to ejecting and loosing an otherwise good aircraft if the systems powering the brakes fail.
Braking chutes are as far as I know mainly used on aircraft without thrust reversers; these provide an alternative to wheel brakes which is useful in certain parts of the world. Norwegian F-16 and F-35 are equipped with braking chutes as they regularly operate in areas with lots of ice and snow. Braking chutes must be jettisoned before taxiing, and has to be repacked before they can be used again, so they are less common than the other methods.

There are probably other means of slowing down I've forgotten to list. If you are on an aircraft with only one means of slowing down, what do you do when it doesn't work? Having multiple means to slow down means that any passengers or crew has a higher chance of surviving, and also that a failure can result in less damage to the aircraft.


Why don't fighter jets take off vertically?

They can climb vertically, but this works best if they are several tons below their maximum take-off mass. Fighter jet engines need a lot of fuel, and at the beginning of the flight the aircraft will be too heavy for vertical climb. Also, the landing gear would need to be rearranged if the plane is to take off from any airport.

Even a thrust/weight ratio slightly above 1 at maximum take-off mass will not be enough, because the aircraft needs some airspeed for its control surfaces to become effective. If no thrust vectoring is installed, the aircraft will be uncontrollable in its initial ascent. The Harrier VTOL jet uses bleed air which is ducted to nozzles at the extreme ends of fuselage and wing for low-speed attitude control.

It is conceivable that the fighter will hang vertically on a wall, with its wheels locked in clutches which will release it when the needed thrust is reached. With thrust vector control the aircraft could be controlled over the full trajectory until it transits to horizontal flight, and could even land vertically. But this would need specially prepared airfields and use much more fuel than a conventional take-off, leaving less fuel for the mission.


How are off-wing jet engines transported?

They have the usual transport options: shove into cargo area, on a flatbed truck, shipping container,...

They can also be attached below the wing of a large aircraft and flown with if there is no room in the cargo area.

(stolen from this question)

Notice the extra engine on the near wing.


Which photo more accurately represents Flaps 1 in a 737-800?

On the 737, flaps 1 actually means leading edge slats only and no trailing edge flaps.

Therefore the first photo is definitely wrong, while the second one is probably correct (since the slats cannot be seen).


For an aircraft, what are the differences between nonlinear and linear equations of motion?

Equations of motion (EQM) define how a rigid-body accelerate and rotate given any arbitrary external forces and moments. They are no more and no less than Newton's Second Law. When expressed in body-frame, the EQMs are:

$$\bf{F}_B = m (\dot{\bf{V}}_b+\bf{\omega }_b \times \bf{V}_b)$$
$$\bf{M}_B=\bf{I}\dot{\bf{\omega }}_b$$

where $\bf{F}$ is body forces, $\bf{M}$ is body moments, $m$ is mass, $\bf{V}$ is inertial velocity, $\bf{\omega}$ is angular velocity, $\bf{I}$ is moments of inertia, and $\times$ is the cross-product operator.

The above are vector equations, which correspond to 6 scalar equations. At this point, there is no concept of aerodynamics. Notice how the equations are inherently nonlinear, so long as there are body forces/moments that depend on the state variables (e.g. velocity, orientation, etc). This is true for most forces, with the notable exception being gravity.

Aerodynamics is nonlinear in that aerodynamic forces and moments do not change linearly with flow incidence, rate of rotation and velocity, except if the changes are small. In general, quasi-steady aerodynamic force is a nonlinear function of flow incidence, rate of rotation, Mach number, Reynolds number, etc. To capture these, N-D lookup tables constructed from estimated/measured data are generally employed in simulation models.

Quasi-steady assumption itself may not be adequate in some flight conditions, such as during rapid maneuvering or stalled flight. In these circumstances, the description of aerodynamics may need to be time-variant.


Why are there non-standard altitude callouts?

From the same channel and also an A340 at 4:26 in this video the standard '100' can be heard.

The reason is a built-in timeout, if a certain time elapses between callouts—say due to non-standard [shallower] descent rate, perhaps due to high headwind for example—the current height is called out. In other words, you get to hear a callout at regular intervals.

From an A340 manual, here is the bit about the intermediate callouts:

Just a bit of history: one of the early TAWS systems (Mk II I believe) had a rising tone instead of the 100, 50, etc., you can watch it here.

Note on terminology: those callouts are heights (radio), not altitudes (barometric).


What is the input range of common fly-by-wire controls?

A320
Max/min stick g:

+2.5 g to -1 g for clean configuration.
+2 g to 0 for other configurations.

Roll:

The roll rate requested by the pilot during flight is proportional to the sidestick deflection, with a maximum rate of 15 °/s when the sidestick is at the stop.

And as it says, is proportional to deflection. (Source: A320 FCOM)
777
I checked the 777's FCOM but did not find similar stated values/explanation.
Since there are trim switches on the 777's yoke, unlike the lack thereof on the A320's stick, the trim switches change the reference speed, and the thrust levers command pitch change. It's designed to mimic, say a Cessna: adding power pitches up; trimming down increases speed.

The trim reference speed is the speed at which the airplane would eventually stabilize if there were no control column inputs. Once the control column forces are trimmed to zero, the airplane maintains a constant speed with no column inputs. Thrust changes result in a relatively constant indicated airspeed climb or descent, with no trim inputs needed unless airspeed changes.


What is the airspeed velocity of an unladen swallow?

In general, the method of getting the airspeed of any bird is pretty much the same:

Measure the ground speed of the bird.
Measure the wind speed in the area.
Calculate the airspeed of the bird from these two values.

The following excerpt from Air speeds of migrating birds observed by ornithodolite and compared with predictions from flight theory by C. J. Pennycuick et al. published by the Royal Society details one such method:

  We measured the bird's air speed, for comparison with the predictions of theory, in two stages. First, we measured the ground speed vector, consisting of the bird's speed relative to the observer's position on the shore and its track direction, i.e. the direction in which the bird was moving over the ground, measured clockwise from true north. We also measured the wind vector consisting of the wind speed and the direction from which the wind was blowing, and then obtained the air speed vector (air speed and heading direction) by vector subtraction of the wind vector from the ground speed vector

Other researchers have used  Doppler radar for the same purpose and in case of high flying birds, one can simply fly along with the birds at the same speed and measure the airspeed.


What is the purpose of this aileron trailing edge strip?

Mr. Tom Clements—the Tom Clements—told me the following in answer to my inquiries on this matter.1 While I cannot yet offer any documentation on this in the form of a Beechcraft publication, this comes pretty close, and is—I think—definitive enough.

According to Mr. Clements, the aileron trailing edge strip serves to re-center the aileron after control surface deflection.

In the early 1970's, Mr. Clements was the first Beechcraft factory instructor in King Air 200. The Project Engineer for development of the King Air 200 was a Mr. Leroy Clay. Prior to achieving FAA type certification for the 200, Mr. Clay was discussing the prototype aircraft with Mr. Clements—Serial Number BB-1—and revealed the following, which I paraphrase from Mr. Clements.

BB-1 borrowed wingtip and aileron design from the late model King Air 90s, including the wingtip which extended beyond the outboard end of the relatively short ailerons. After its first test flight, it was decided that BB-1—with its more powerful engines, greater wingspan, different roll inertia, etc—was lacking in aileron roll authority. The design solution was to extend the ailerons outboard to the wingtips, for a greater overall aileron span.

This change proved to solve the control authority concerns, but revealed a new problem: the ailerons lacked sufficient aerodynamic centering tendency, and now tended to remain partially deflected after a roll control input. The initial solution was the bulged trailing edge strip in question. The idea was that the bulge would cause a small amount of drag, especially when deflected, which would tend to streamline and center the aileron.

I say the initial solution, because, Mr. Clements recalls that Mr. Clay, the Project Engineer, stated that the bulge was a temporary fix added to the aileron, with the intention of a complete aileron redesign to follow prior to certification. I will point out the obvious: it has been over 40 years since the King Air 200 was certified with that bulged trailing edge strip.

Mr. Clements goes on to confirm that this trailing edge strip has remained a feature of King Air models through all the 200 and 300 series.

1This exchange took place and is available on BeechTalk.com, though the content is only accessible to members. BeechTalk.com terms of service do not allow copying and reproducing member content outside the site.


What is the operational advantage of starting an RNAV SID with a VI-CF leg combination?

The PBN manual is the place to start. In Section 5 on departure procedures it includes the following reference:

  b. Leg type limitations. See Order 8260.46, paragraph 3-1-5 for
  permissible leg types.

Also, all the TERPS requirements also apply, except where modified by the PBN manual.

There's usually no one rule that applies universally. It's about finding the best solution that meets the terrain/obstacle avoidance and meets the necessary airspace and air traffic needs.  I can't say with certainty why the procedure writer made the choices they did, but I can point out a few things that would apply in the SID you reference.

The 17L/R departure is primarily constrained by the 7000 ft minimum at GISTT. It's there to keep the path within the Class B airspace.  There's a cutout with a 7000' floor around Front Range airport to the southeast. GISTT is located at the edge of the cutout.  It's far enough south to leave room to reach the minimum altitude at the published minimum climb gradient.  The VI/CF is the solution that gets you to GISTT expeditiously.  It also has an intercept angle of about 50 degrees which works well with the FMS and LNAV steering.

The 16L/R departure has two factors that push it to the VA/DF solution.  First is that it departs over runway 07/25 and there's no intercept (more later), the altitude termination defines when the turn can begin. The reason the DF to MUGBE is used instead of a CF is that there is a 140 degree course change.  You can't have a VI/CF combination with that large of a course change. Thus the VA/DF combo.  If MUGBE (or another convenient waypoint) was better located, a VA/RF leg combo could work but RF legs are relatively 'new' in the RNP FMS world and they aren't very common.


Since speed is related to dynamic pressure, then why is static pressure used instead of dynamic pressure in ASI to measure speed?

It's not. The reading on the airspeed indicator is directly determined by the dynamic pressure. The ASI uses the static pressure for the sole purpose of determining the dynamic pressure.

  Why is dynamic (or pitot) pressure not sufficient?

Dynamic pressure is sufficient, but the pitot tube doesn't give you the dynamic pressure; it gives you the total pressure, which is the sum of static pressure and dynamic pressure. In order to determine the dynamic pressure, an airspeed indicator has to find the difference between static pressure (from the static tube) and total pressure (from the pitot tube).


What is the difference between MCP and METO?

They're the same indeed. Power settings that are not time limited and can be used continuously. The answer is in the model, Cessna 150 vs. 172.

METO is an outdated term, like reading artificial horizon vs. attitude indicator. You'll also find METO in DC-3 documentation, but not MCP.


Why do they tell you to tie your lifevest on the left side during safety briefings?

After many questions to the various crew members/ground crew on the next few flights I did, I have managed to get an answer that makes sense.

You are told to tie the life vest on the left side for two reasons:

The inflate toggle hangs on the right side of the lifevest and if you were trying to tie the knot below it then you might pull it by accident, inflating the lifevest inside the plane.
If you tie the knot with a bow, instead of the double knot, then if the bow was on the right side there is a chance that you will get it tangled in the pull toggle while moving around the plane, inflating it before you exit.


Advantages of square over circular engine nozzle?

Circular nozzles have these advantages:

They can be swiveled in any direction, so both pitch and yaw moments can be produced. Square nozzles only allow to create pitch forces, because their panels can only be moved around one axis. When moved differently in two-engined aircraft, limited roll moments are also possible.
Round nozzles are lighter. As long as exhaust gas pressure is higher than outside pressure, a square nozzle will be subject to bending loads across the width of its panels. This will make a square nozzle much heavier than a round nozzle.

Actually, square thrust vectoring nozzles have just one advantage: They can be made to reflect radar waves in a few well-defined directions, while round nozzles will scatter them all around. This makes square nozzles the preferred choice for stealth aircraft, regardless of thrust vectoring.

Engine nozzles of the F-22 (picture source). Note the serrated rear edges of the thrust vectoring panels.

Engine exhausts of the B-2. Since the B-2 uses four non-afterburing engines, fixed nozzles are used. Their location helps to protect the airplane from detection by infrared (IR) sensors, but makes thrust vectoring impracticable.

Engine nozzles of the YF-23 (picture source). The lower part is longer to shield the hot exhaust against IR sensors from below.

If the goal is to mostly reduce radar reflections in the forward hemisphere of the aircraft, round nozzles can be tolerated. Only when the aircraft needs to be protected from radar-guided missiles fired from behind will the square nozzles give a clear advantage. It seems that the people behind the Sukhoi PAK FA (and other stealth fighters like the Chinese J-20) do not worry so much about this detail.

Sukhoi T-50 (prototype for the PAK FA program) from below (picture by Dmitry Pichugin)

Chengdu J-20 rear view (picture source)

However, even Lockheed-Martin and Pratt & Whitney now place maneuverability and weight over stealth in their nozzle design for the F-135 engine of the F-35 strike aircraft. Note the serrated edges on all contour steps. This helps to reduce radar returns, but is much less effective than a square nozzle. The benefit is less weight and better maneuverability.

F-35 with the F-135 nozzle visible (Picture source).


What makes someone a 'Senior First Officer'?

"Senior," is generally a subjective term.  In order to fly to the lowest authorized minimums one generally needs 100 hours in type, but other than that, one is no longer "green," after accumulating 100 hours in type.


Which MEL categories would ground a commercial airliner if they're inoperative?

If a piece of inop equipment CAN be deferred using the MEL, then the aircraft isn't grounded. When there is no MEL relief & the part has to be changed out is when you have an AOG scenario.


How much pressure do boost and jettison fuel pumps produce?

I looked up a cannister boost pump and jettison fuel pump on the Eaton website and found a cannister boost pump for the 747 that puts out 28,000 Pounds Per Hour, and a jettison pump also for the 747 that puts out 40,000 PPH.  Safe to say jettison pumps generally have a higher output than engine boost pumps, for obvious reasons.


It depends on how far in the future you are trying to predict air stability and turbulence. I am not an expert. But, I would look for some indicators.
For instance, the historic Program Charts from Friday and Saturday show a cold front moving through the area of KADS from West to East. The winds were drastically shifting as the front moved through. This would be an indicator that it might not be a good day to fly. Combine this prognostic data with the METARs from the previous 24 hours to your flight, there is cause for concern for a light aircraft. The winds and gust factors in these METARs might have given you as much as a 24 hour warning of what was to come. Then, there is the Aviation Area Forecast Discussion which will give you further guidance. Lastly (and least used), right before the fight, you could have even checked out the Skew-T/Log-P Diagram in order to judge the strength and severity of the instability.
METARs for KADS:
KADS 141352Z 19008G15KT 8SM BKN009 21/19 A2990
KADS 141447Z 19008G16KT 8SM BKN014 22/19 A2990
KADS 141547Z 19010G25KT 10SM BKN022 24/18 A2989
KADS 141647Z 20017G32KT 10SM BKN028 BKN070 25/18 A2987
KADS 141747Z 19016G31KT 10SM BKN033 27/18 A2983
KADS 141847Z 19016G31KT 10SM BKN039 27/17 A2978
KADS 141953Z 19016G30KT 10SM BKN046 BKN055 27/17 A2974
KADS 142053Z 19012G26KT 10SM BKN050 28/17 A2971
KADS 142153Z 19011G20KT 10SM SCT044 OVC055 27/17 A2972
KADS 142253Z 19016G30KT 10SM SKC 26/17 A2971
KADS 142353Z 19012G21KT 10SM SCT120 26/17 A2973
KADS 150047Z 20009G20KT 10SM SKC 25/17 A2976
KADS 150147Z 20009G20KT 13SM SKC 25/17 A2977
KADS 150215Z AUTO 20009G17KT 10SM CLR 25/18 A2980 RMK AO2 T02450175
KADS 150247Z 18008G16KT 10SM SKC 25/17 A2978
KADS 150255Z AUTO 20009KT 10SM CLR 24/18 A2981 RMK AO2 T02420175
KADS 150315Z AUTO 20008KT 10SM CLR 24/18 A2981 RMK AO2 T02410175
KADS 150335Z AUTO 20009G15KT 10SM CLR 24/18 A2982 RMK AO2 T02410175
KADS 150355Z AUTO 21007KT 190V250 10SM CLR 24/18 A2983 RMK AO2 T02400175
KADS 150415Z AUTO 22004KT 10SM CLR 24/18 A2984 RMK AO2 T02360175
KADS 150435Z AUTO 22004KT 10SM CLR 24/18 A2985 RMK AO2 T02350175
KADS 150455Z AUTO 23006KT 10SM CLR 23/17 A2986 RMK AO2 T02330173
KADS 150515Z AUTO 23006KT 10SM CLR 24/17 A2986 RMK AO2 T02380170
KADS 150535Z AUTO 25007KT 230V290 10SM CLR 24/17 A2987 RMK AO2 T02360169
KADS 150555Z AUTO 29017G23KT 10SM CLR 23/15 A2990 RMK AO2 T02330150 10254 20232 402730182
KADS 150615Z AUTO 33018G24KT 10SM CLR 22/07 A2994 RMK AO2 T02150072
KADS 150635Z AUTO 34020G30KT 10SM CLR 18/02 A2999 RMK AO2 T01820024
KADS 150655Z AUTO 35020G27KT 10SM CLR 17/02 A3002 RMK AO2 T01710015
KADS 150715Z AUTO 35015G22KT 10SM CLR 17/01 A3004 RMK AO2 T01650013
KADS 150735Z AUTO 35013G28KT 10SM CLR 16/01 A3006 RMK AO2 T01610005
KADS 150755Z AUTO 35019G25KT 10SM CLR 16/M02 A3008 RMK AO2 T01571018
KADS 150815Z AUTO 35013G18KT 10SM CLR 15/M03 A3010 RMK AO2 T01541034
KADS 150835Z AUTO 35013G22KT 10SM CLR 15/M04 A3011 RMK AO2 T01501045
KADS 150855Z AUTO 35013G20KT 10SM CLR 15/M05 A3013 RMK AO2 T01461051
KADS 150915Z AUTO 35015G24KT 10SM CLR 14/M06 A3014 RMK AO2 T01441065
KADS 150935Z AUTO 35012G19KT 10SM CLR 14/M07 A3014 RMK AO2 T01391070
KADS 151147Z 35010KT 10SM SKC 12/M07 A3020
KADS 151247Z 35012G17KT 10SM SKC 10/M07 A3022
KADS 151347Z 33005KT 10SM SKC 11/M05 A3025
KADS 151447Z 35012G16KT 10SM SKC 13/M06 A3029
KADS 151547Z 36013G20KT 10SM SKC 14/M07 A3030
KADS 151647Z 02010G20KT 10SM SKC 16/M07 A3032
KADS 151747Z 03010G20KT 10SM SKC 17/M08 A3031
KADS 151847Z 34008G15KT 10SM SKC 18/M08 A3029


Is it possible to obtain an STC for single-pilot ops in a jet certified for two pilots?

Cessna did this sort of thing for the CE-525 series (CJ) jets. Effectively the required crew varies based on cockpit arrangement/equipment. As per the type cert

  Minimum Crew for all Flights (see NOTE 5 for cockpit equipment/arrangement restrictions):

  One pilot (in the left  for all Flights pilot seat) plus additional
  equipment as specified in the Kinds of Operations Equipment List
  (KOEL) contained in the Limitations Section of the FAA Approved
  Airplane Flight Manual (AFM)

  OR

  One pilot and one copilot

Note 5 for reference:

  Approval for operation with a minimum crew of one pilot is based upon
  the cockpit equipment installation and arrangement evaluated during
  FAA certification testing. No significant changes may be made to the
  installed cockpit equipment or arrangement (EFIS, autopilot, avionics,
  etc.), except as permitted by the approved MMEL, without prior
  approval from the responsible Aircraft Certification Office.

However that is the original type cert and it was done by the manufacturer, who has the resources to test these kinds of things. Doing it on your own is bound to be cost prohibitive, even considering you may have to pay a second pilot to fly with you for the entire ownership of the aircraft.

This is also fairly similar to the case in the heavy metal world with the dropping of flight engineers and navigators when control was consolidated to the two pilots. So far as I know none of this was done via STC but appeared on the TC itself.

Technically it may be possible, practically, it seems unlikely.

If your looking for single pilot jet performance there are plenty of early era ex-military jets hitting the market that are far faster than any business jet you can buy...


Why is it necessary for pilots to have trim controls on fly-by-wire aircraft?

Airbus FBW aircraft have an Autotrim system, so the trim wheel is only there as a backup. In normal law, the trim system is invisible to the pilot. The sidestick pitch inputs control load factor, unlike in a yoke aircraft where it controls elevator deflection. This means that that the farther you move the stick forward and back the faster it pitches, but at center it is a zero load factor, so it stays at its current pitch angle.

As an example of the difference, if you want to pitch up 10° in a yoke aircraft you pull back on the yoke until it reaches 10° and hold it there. If you let the pressure off it will return to 0° unless you retrim for 10°. Whereas in Airbus normal law, to pitch to 10° you pull on the sidestick until it reaches 10° then let go. The FBW system automatically maintains the new pitch angle. If you don’t do anything else the FBW system will automatically trim the stabilizer to the new pitch angle. There is no feedback as to elevator deflection because it’s not directly controlling the elevator.

Pilot misunderstanding of the Autotrim function was a factor in the crash of XL Airways flight 888T. When the AoA vanes froze, the computer switched to Alternate 2 law, which does not have the Autotrim function. Due to the AoA fault, the autopilot had trimmed the aircraft full nose up. When the AP disconnected and control law degraded it remained there and notified the pilot that he needed to trim manually. The PF did not realize this, so never moved the trim wheel. With the stabilizer in full nose up trim he didn’t have enough elevator authority to prevent a stall and crashed into the ocean.


Identify a change in Altitude based on direction and WCA applied?

The question is confusing because the graphic doesn't match the question being asked.  Does the question actually use this graphic?  Because if it does then your WCA would be negative if you are heading East because you would be crabbing to the left to account for wind coming from the North.

In any case, if you are flying from an area of high pressure to an area of low pressure (as the graphic depicts) without changing your altimeter setting your true altitude will be lower.  Remember this simple mnemonic:  "High to low, look out below."

However, if the question is as stated WITHOUT the graphic, then heading East with a positive WCA means that the wind is from the South.  If this is the case it would be fair to assume from Buy Ballot's law that you are transiting from an area of low pressure to an area of high pressure.  In this case then the answer would be your true altitude would be higher.


How can I go from a CPL to an A320 Rating?

A U.S. pilot with a Commercial license can get a type rating by going through an appropriate course. It isn't cheap, but it can be done.

The benefit of having the type rating with only 300 hours is probably pretty slight, at least in the U.S.  Anybody hiring into the right seat of an A320 either has their own "ab initio" curriculum, or else they're probably looking for far more experience than that.  There may be a unique job out there that is looking for exactly this sort of applicant, but it seems hard to imagine.

You might be better off saving the money until you have a line on exactly what position you're after, and you're confident that they'd hire you with 300 hours (or whatever you have by then). Who knows -- you may find someplace that will be glad to hire you to fly something else, if you'll get the training on (whatever they fly) by going to get the type rating. Having the money available to spend on the needed type rating could be a lot more useful than have the 320 type at that point.


FAR 91.159 speaks for itself.  The reference point is directly below your current location.

There are other regulations that use "AGL" (sometimes stated as "Above the surface") as a reference (see FAR 91.155 or 91.119).

As a side note, FAR 91.159 is used to mitigate the risk of midair collisions but not at the expense of prohibiting necessary close to the surface operations (e.g., helicopter EMS, telephone line patrol, crop dusting).


What happens to the ejection seat after a pilot ejects?

It depends on the seat. Most modern seats, including the ACES II system common in US Fighter Jets, fall away from the pilot at a pre-determined altitude. [src]

  Once out of the plane, a drogue gun in the seat fires a metal slug that pulls a small parachute, called a drogue parachute, out of the top of the chair. This slows the person's rate of descent and stabilizes the seat's altitude and trajectory. After a specified amount of time, an altitude sensor causes the drogue parachute to pull the main parachute from the pilot's chute pack. At this point, a seat-man-separator motor fires and the seat falls away from the crewmember. The person then falls back to Earth as with any parachute landing.

Generally, according to that link, this occurs at just over 100-200 feet above ejection height. However, if you eject at high altitude, such as Captain Scott O'Grady did (26,000 ft), the seat will fall away on a sensor (either 10,000 or 18,000 feet, I don't recall which). The chute may open automatically, or if it is not set to at that height, you can then pull the chute manually, or wait until its set height to open.


How can I tell apart an Airbus from a Boeing?

I like to train being able to determine the precise model of an aircraft.
I first try to tell if it's a Boeing or Airbus, and then I look at other details to determine the model.

The idea is to learn several differences :

cockpit windows shape (Boeing has an very specific angle) ;
nose shape (pointy nose on Boeing, "fat nose" on Airbus) ;
wingtips (winglets Boeing, fence Airbus) ;
number of engines (A340, B747, A380 have 4 engines, all others have 2) ;
gear.

Since there are already nice answers describing most of these points with pictures, I will focus on the gear to add a new item to the list.

Landing Gear

Looking at the gear adds a new hint. Some landing gears are unique, which means that only looking at them will be enough to determine the precise aircraft type. These very specific gears are :

B777
B747
A340 (2 different kinds for this aircraft only)
A380

It's not worth to look at the nose wheels, because there are always 2. But the main landing gear is helpful.

I made a gear cheat sheet to help me learning them.

Once these differences have been learned, the key is to use several of them to crosscheck and ease and speed up the recognition.
For example if I see the gear

   2
2*2 2*2

I will then check the cockpit windows to determine whether Boeing or Airbus.
If it's Airbus, I will know it's very likely to be an A330! If it's Boeing, it will be harder since there are still 3 different aircrafts. If I want to be able to distinguish between them, I can learn new specific hints for this purpose.


Are planes allowed to fly through a planned professional fireworks display?

Most fireworks go no higher than 1200 ft and consumer sized stuff is more around 500ft and below. which is fairly low for most regimes of flight for all but general aviation planes and planes taking off/landing. With this in mind your main point of concern would be shooting them off near an airport, or people flying low and slow near your display.

I cant find any regulation explicitly forbidding it although its unwise and it most likely would be considered "careless or reckless operation as per §91.31" if you flew directly (and deliberately) into a display at low altitude, Fireworks are noted in the NOTAM's and it is the pilots responsibility to make themselves aware of all flight risks and en-route information as per § 91.103 Preflight action. You can see a good example here in todays NOTAMs listing various firework displays and their locations.

(source)

Its also the responsibility of the launcher to file the NOTAM in the first place.


Why is deploying speed brakes not recommended with the flaps extended?

https://www.eucass.eu/doi/EUCASS2017-318.pdf

Above shows a configuration where the flaps and spoilers are deployed. The blue line shows the vertical velocity of the wing's wake, which is indicative of the lift being generated. Since the effect of the flaps lessens outboard, that causes the downforce shown above near the end of the wing due to the spoilers.

Since spoilers are thin and are allowed to move/flex slightly under aero loads, and since this downforce is far out with a greater moment arm, any slight [asymmetric] disturbance to any outboard spoiler panel will result in a roll, when compared to:

Smaller flaps deflection: since the inboard part of the wing creates less lift (less flaps), the slope (lift to downforce) will be shallower, which lessens the impact of an outboard disturbance.
Speed-brakes are used on their own: there will be a uniform downforce distribution over the wing without the abrupt shift from lift to downforce shown above.

Note that the manual says may and slight. Do not expect a huge roll, just anticipate if it happens, the FBW is not programmed to correct it unless an input is made.

I found the same recommendation in the FCTM of the 747-400 and 737 (all variants). It's flaps 5 and 15 respectively. They don't state the reason, but buffeting was mentioned.

  The use of speedbrakes with flaps extended should be avoided, if possible. With flaps 15 or greater, the speedbrakes should be retracted (737 FCTM).

@kevin also pointed out in the comments that the 777 explicitly states there is no issue with using the S/B in landing configuration, which to me sounds like extra care was taken with the FBW or spoiler design.

Another possible reason is to lessen the load on the actuators of the spoiler panels, with the flaps deployed that's a lot of suction behind them, but that doesn't answer the rolling part.


Ultimately the cost of flying the aircraft was more than the revenue that it generated.  The Concorde began a steady decline to retirement after the firey crash of Air France Flight 4590 which killed 113 people, and again suffered setback after September 11th, 2001.  Even with the best safety record in airline history, the crash combined with the terrorist attacks led to passenger fear and low sales. Airlines that operated the Concorde eventually lost money on most flights, and long term operations were simply not sustainable.  To make matters worse, it was very limited to which airports it could fly to in the US: JFK, IAD and DFW. The FAA was opposed to the Concorde for pollution, noise and fuel inefficiency concerns.

British Airways cites mostly political reasons for the ending of its Concorde program.  They claim that the Concorde would have remained profitable had Airbus retained the airplane.  However, there was also speculation that, due to the dwindling numbers of passengers, BA realized that it could make more money carrying passengers subsonically across the Atlantic.


What is the method to calculate a finite wing's lift from its sectional airfoil shape?

There are indeed several approximations, depending on the shape of the wing. Generally, the lift curve slope is $2\pi$ only for a flat plate in inviscid 2D flow (with Kutta condition fulfilled). With thicker airfoils, the lift curve slope in 2D increases slightly. It also increases with Mach number proportional to the Prandtl-Glauert factor $\frac{1}{\sqrt{1-Ma^2}}$ and the Reynolds number.

Now to 3D flow: Once you move away from infinite aspect ratios, the lift curve slope drops. With very small aspect ratios $AR$ the lift curve slope becomes $c_{L\alpha} = \frac{\pi \cdot AR}{2}$. See the plot below for the ideal lift curve slope of an unswept wing:

Please note that the red line is only valid for AR = 0! Then the lift curve slope increases up to $c_{L\alpha} = 2\cdot\pi$  for $AR = \infty$ (and zero airfoil thickness and no friction effect), as shown by the blue line. If you know your airfoil lift curve slope, modify the result from the plot above by the ratio between the airfoil lift curve slope and $2\pi$. Now your lift coefficient will become:

$$c_L = c_{L\alpha_{3D}}\frac{c_{L\alpha_{2D}}}{2\pi}\cdot\alpha$$

with your angle of attack $\alpha$ in radians.

For an analytic approach you may use the formulas below, but stay away from the region close to Mach 1. If those (rather precise) approximations look too daunting, feel free to simplify them:

Nomenclature:
    $c_{L\alpha} \:\:$ lift coefficient gradient over angle of attack
    $c_{L\alpha\:ic} \:$ lift coefficient gradient over angle of attack in incompressible flow
    $\pi \:\:\:\:\:$  3.14159$\dots$
    $AR \:\:$  aspect ratio of the wing
    $\nu \:\:\:\:\:$  the wing's dihedral angle
    $\varphi_m \:\:$  sweep angle of wing at mid chord
    $\varphi_{LE} \:$  sweep angle of wing at leading edge
    $\lambda \:\:\:\:\:$  taper ratio (ratio of tip chord to root chord)
    $(\frac{x}{l})_{d\:max} \:$  chordwise position of maximum airfoil thickness
    $Ma \:\:$  Mach number

Note that you do not need the planform efficiency (Oswald factor) $\epsilon$ for calculating lift curve slope. That only comes into play when you compute the induced drag of the wing.


Is it possible as a pilot to get the ICAO proficiency language level for a not official language in the ICAO?

As the others pointed out, there's no ICAO language proficiency test for German.

How it works for German at least in Germany is with a special "Radio operator license" (Sprechfunkzeugnis) that's part of (German) pilot licenses. For IFR that's only in English, but for VFR you have the choice of doing it in English, German or both. It's called BZF I (English + German), BZF II (German) or BZF E (English). According to the German Wikipedia, there are similar systems in place in Austria and Switzerland.

Even for VFR in Germany it's totally possible to do it in English, as I believe there are no more German-only speaking airfields. But especially on smaller fields where radio services are provided unpaid by people in their free time, they are a bit happier when using German.

And even on the bigger VFR fields with professional ATC personnel, my experience is that it's sometimes hard for them to remember, which aircraft in the pattern is communicating in English and which in German and then they try to translate position reports they get in one language from one aircraft into traffic advisories for other aircraft in another language. That's why it's sometimes recommended for pilots flying more often VFR in Germany to maybe also do the BZF in German as most VFR traffic is still done in German.


Why is there a difference between GPS Speed and Indicator speed?

The speed indicator in the cockpit shows indicated airspeed. Indicated airspeed is usually different than GPS speed, due to wind and aerodynamic effects.
GPS speed is your speed with respect to the ground. If you are standing on terra firma it reads 0. If it reads 100 knots you will be 100NM away from where you are now in one hour, so long as you keep flying in a straight line.
Airspeed is the speed of the aircraft relative to the surrounding air. So if you are standing on terra firma with 20 knots wind blowing in your face, your airspeed will be 20 knots. If you travel at 100 knots airspeed against a 20 knots headwind wind, your ground speed is 80 knots. If you do 100 knots airspeed with 20 knots tailwind, your GPS speed reads 120 knots.
But even in calm wind conditions the airspeed indicator will read differently than the GPS speed . This has to do with the way airspeed is measured.
Airspeed is measured with a pitot tube. A pitot tube has two pressure measurement ports. One that measures the total pressure $P_t$. This port is facing the incoming airflow. The other measures the static pressure $P$ and is placed perpendicular to the airflow. The difference between the two pressures is called impact pressure (pressure rise due to the airflow impacting the pitot tube) and is denoted $q_c$.
The impact pressure is related to the speed of the airflow the pitot tube is exposed to. If the flow is considered incompressible (which is an acceptable approximation for speeds up to 200 knots) the impact pressure can be derived from Bernouilli's equation.
$q_c = \frac{1}{2}\rho V^2$

$q_c$ is the impact pressure in Pa
$\rho$ is the density in kg/m3
$V$ is the true airspeed in m/s

The airspeed indicator is calibrated for standard sea level conditions, where $\rho$ is 1.225 kg/m3. In reality the aircraft will fly at altitude and therefor the actual density of the air is lower. Therefor the indicated airspeed will be lower as well. For example if an aircraft flies 75 m/s (about 146 knots) at 6000 ft the density will be 1.02393 kg/m3.
$q_c = \frac{1}{2} 1.02393 \cdot 75 ^2 = 2879.8 \textrm{ Pa}$
The equivalent airspeed at sea level for the same $q_c$ is:
$V_{EAS} = \sqrt{\frac{2 q_c}{\rho_0}} = \sqrt{\frac{2 \cdot 2879.8}{1.225}} = 68.6 \textrm{ m/s}$
Your airspeed indicator will read only 68.6 m/s (133 knots) despite the fact that you are moving with 75 m/s (146 knots) with respect to the air.
Conversion of true airspeed to the equivalent airspeed can be done directly by:
$V_{EAS} =V\cdot \sqrt{\frac{\rho}{\rho_0}}$

$V_{EAS}$ equivalent airspeed (m/s)
$V$ true airspeed (m/s)
$\rho$ actual air density (kg/m3).
$\rho_0$ density at standard sea level conditions (1.225 kg/m3)

The effects of the lower density on your aispeed indicator become more pronounced the higher you go. Once you go faster than about 100 m/s true airspeed the effects of compressibility can no longer be ignored and the above no longer applies. Airspeed indicators are corrected for effects of compressibility and therefore don't use the equivalent airspeed but instead use calibrated airspeed for calibration.
$V_{CAS}=a_{0}\sqrt{5\left[\left(\frac{q_c}{P_{0}}+1\right)^\frac{2}{7}-1\right]}$

$V_{CAS}$ is calibrated airspeed
$a_{0}$ is the speed of sound under standard sea level conditions (340.3 m/s)
$P_0$ is the static air pressure under standard sea level conditions (101325 Pa)
${q_c}$ is the impact pressure

The impact pressure is also a bit more complex for compressible flow:
$\;q_c = P\left[\left(1+0.2 M^2 \right)^\tfrac{7}{2}-1\right]$

$P$ the static pressure
$M$ the Mach number

Effectively, the higher and faster you get, the greater the difference between the indicated airspeed and the true airspeed.
For example, Mach 0.8 at 40000 ft in no wind will result in a GPS speed of 489 knots, but a calibrated airspeed of only 242 knots, which is less than half.
Therefore at high altitudes and speeds, the indicated airspeed will be lower than the ground speed / GPS speed, unless you have extreme headwind.


Does the Piper PA-28 Cherokee have a limitation on its maximum lifetime flight hours?

Short answer, not in the United States; as long as the airframe is regularly maintained and passes its mechanical inspections, it can continue to fly. Some reasons this is so (when it might not be true for other models) include:

The Cherokee is non-pressurized. Pressurized aircraft are often rated for a lifetime limit of pressurization cycles (determined by the number of times the aircraft rises above and then descends below the altitude at which the pressurization system kicks in, typically 8000ft MSL for many small craft). This pressurization stresses the airframe in ways that eventually more or less requires the entire fuselage to be replaced in order for the airframe to pass its next mechanical as originally rated. The Cherokee, however, has no system for full-cabin pressurization and so its fuselage is not subjected to these stresses.
The Cherokee (180 or 235) is not rated for aerobatic maneuvers, and so does not typically perform them. Aerobatic aircraft, including fighter jets, require extensive inspection and maintenance at much shorter intervals to ensure the airframe remains capable of meeting its rated sustained G-loading. Coupled with regular testing of those ratings by the pilot, aerobatic aircraft are more quickly retired from service when it becomes impractical to repair or replace overstressed structural members.
The Cherokee is not commonly used in Part 121 or 135 operations involving passengers or air freight. As a four-seat single-engine, its capacity for passengers and cargo is limited, and so its usefulness to major airlines which are subject to Class D(econstruction) inspections every 6 years is sharply limited. Bush airlines like Era Alaska might see some use as more or less an air taxi, but even these outfits prefer somewhat larger planes for more flexibility and longer range.


What is the definition of "Sideline" in reference to aircraft noise?

The definitions are specific.
(They are defined in FAR Part 36).
I'm writing also the Take-off and approach noise definitions just for your information.

  Sideline noise: is defined and measured 1476 ft (450 m) from the runway centerline at a point where the noise level after liftoff is greatest.

  Take-off noise: is defined as the noise measured at a distance of 21,325 ft (6500 m) from the start of the take-off roll,
  directly under the airplane.

  Approach noise: is also defined and measured under the airplane when it is at a distance of 6562 ft (2000 m) from the runway threshold.

For each of these conditions the maximum noise level is a function of maximum takeoff gross weight, and for the take-off case the limits depend also on the number of engines.


Why are callouts of changes in the Flight Mode Annunciator not automated?

The responsibility of checking the FMA after a mode-change is not the PM's alone. If the PF calls for VNAV, the PM will select VNAV, now both of them need to check VNAV is active.

Regarding aural alerts, there are already alerts to when the flight deviates from the norm, for example an altitude warning (which doubles as approaching target altitude), stick shaker, low-speed / over-speed, etc.

But, your question is about changing the flight-mode, say from VNAV PTH to VNAV SPD, or VNAV to FLCH. As mode changes are a direct consequence of crew commands, I don't see a benefit.

One downside I can think of is that the ATC will hear a lot more aural warnings as the crew changes the modes while reading back an instruction.

As for the effectiveness of such system, say in case the crew pressed the wrong button and they were too tired to double-check the FMA, they shouldn't be flying in the first place.

  The analysis of accidents and numerous scientific publications have demonstrated that operational stress and fatigue can result in pilots neglecting crucial information, such as visual and aural warnings. This phenomenon, called channelized attention is defined as being “the allocation of attention to a particular channel of information, diagnostic hypothesis or task goal, for a duration that is longer than optimal, given the expected cost of neglecting events on other channels, failing to consider other hypotheses, or failing to perform other tasks” (Wickens, 2005). It seems possible that this phenomenon might occur during the go-around phase which is often unexpected, uncertain and of sudden onset, and may take place after many hours of flight.

(Emphasis mine.)

That's from a BEA study on Aeroplane State Awareness During Go-Around.

Too many alerts and any human will become used to the regular sound with mode changes regardless of what the aural warning says. Eventually it'll become background noise.

The ideal level of warnings is not to overload all the senses, and let the aural warning be when something is crucial, so the training can kick in with speedy recovery actions versus a relatively slow diagnosis of the situation.


Why pets are allowed only on select flights?

The USDOT has a list off things related to this matter here but there are many factors.

International Travel: Since flights often go between countries that also means they cross jurisdictions. Many countries have varying laws on importing and exporting different animals. As such airlines may not always allow you to carry animals since it may not be legal.
Contamination: Animals can carry a wide variety of disease and other things. An airline my chose to not carry animals to avoid any potential issues. Even if in the cargo hold it can not be guaranteed that the animals fur wont come in contact with another passengers baggage. If that passenger had an allergy to that type of fur they may later have an issue.
Food: Placing an animal in the baggage hold prevents anyone from effectively feeding the animal which the DOT does seem to have some regulations on for longer flights.
Temperature: Although it is pressurized the baggage compartment is by no means warm. This prevents a potentially dangerous situation for animals as well.

As for bringing an animal on the plane (aside from service animals which are not considered animals). It would seem that the FAA leaves this specific matter up to the airlines. According to this document when it comes to

What are the FAA rules regarding traveling with pets in the passenger cabin?
The Federal Aviation Administration (FAA) allows each airline to decide if they will allow you to travel with your pet in the passenger cabin. If an airline does allow you to bring your pet into the cabin, we consider your pet container to be carry-on baggage and you must follow all carry on baggage rules (14 CFR part 121, section 121.589):


What does rudder input control in normal law in an A320?

You are correct. On all Airbus FBW aircraft, the rudder pedals normally control the sideslip angle, beta. See this presentation for a source, slides 3, 5-6.

As a note, on pre-A345/A346 models, the rudder pedals are mechanically connected to the rudder. However, the FBW system adds in an additional input, via the yaw damper servos, to drive the rudder to the position the FBW control loops want.

Additional details can be found in Advances In Aircraft Flight Control, M. B. Tischer, page 90:

  Finally, it was decided that the rudder pedals would command a combination of sideslip and roll angle to restore some of the conventional aircraft behavior.

Figure 5 shows that the rudder command is a gain-scheduled proportional control based on sideslip, yaw rate, roll rate, and roll angle. The gain scheduling is based on airspeed and high-lift configuration.


What is the Effect of Unsynchronized Propellers?

I would agree with the other comments, in that I don't think the extreme buffeting could be caused by out-of-sync props. Maybe if you lost a chunk of a blade and you had out-of-balance props, but that's a bit different. Or if one of the props came WAY out-of-sync. But I know nothing of the Orion aerodynamics or engineering.

My twin experience has been more of the light piston and turboprop variety, but I can tell you that out-of-sync props produce a "whah whah whah" sound that will drive you absolutely bonkers. As soon as I was straight and level, I'd match rpms/prop pitch on my engines (or turn on the prop sync) to get rid of the noise. I never wanted to try it long enough, but apparently acoustic oscillation like that can cause serious fatigue. And I would imagine that long-term exposure can't be good for the airframe.


Why do we never see high-bypass turbofan engines sharing the same nacelle on large airliners and similar aircraft?

Short answer

It's the vastly different flow conditions from static to cruise which demand a separate placing of high-bypass-ratio jet engines. They would produce less thrust and more drag when paired.

Why were there paired engines at all?

The early jets had their engines mounted directly beneath or in the wing, and comparisons between separately mounted and twinned engines showed a slight advantage for the latter due to lower wetted surface area and less impact on the wing.

Arado built two four-engined prototypes of their Ar-234 jet, one with separate engines (V6, see directly below) and one with paired engines (V8, further down). The V8 became the prototype of the C version of the Ar-234.

However, with the increasing airflow of high-bypass-ratio engines the interference between both will turn pairing into a disadvantage. In cruise, only the central stream tube flowing towards the engine will be ingested, and the rest will spill over the intake lip. Placing a second engine directly next to the first will block the flow of spilled air on that side and will increase spill flow on the opposite side. This will most likely cause massive separation there if the intake is not heavily modified, leading to a noticeable drag increase. Also, the now asymmetric flow in the intake would reduce the efficiency of the fan - it needs very homogenous flow over the full cross section in today's engines.

Conversely, at low speed the engine sucks in air from all around and will face competition from a second engine, such that both will not be able to ingest as much air as when mounted separately. The consequence of pairing would be reduced thrust during take-off.

The initial disadvantage of separate engines, their collective impact on wing aerodynamics, is now greatly reduced by mounting them on pylons, so they are ahead and below the wing.


What is the scratching sound produced by aircraft on the ground (taxi-in/taxi-out)?

There is a variety of sounds an aircraft can produce, some even depending on the type of aircraft you are sitting in. Without any further data or reference, the most likely events that you can hear during pushback, taxi or vacating the runway are:

Cargo Doors being shut and locked
Flaps being extended to take-off position
Flaps being raised after landing

There are many more things that you can hear from the cabin, so without further information, it will be difficult to pin-point.

Another option, if it was predominantly on Airbus aircraft, is the Power Tranfer Unit, which is described to sound like a barking dog or like a drill.

See also this question and the answers:
What is this sound from Airbus aircraft before take off?


Do commercial aircraft have electrical outlets?

Several of the answers here seem to suggest that this only happens in first or business class. While that was historically true, it's not so true anymore. Airlines such as Cathay Pacific and Korean Air, for instance, have them at every seat in most (or all?) of their long-haul aircraft. Delta also has it in parts of economy on several of their long-haul configurations as well as in all of economy on their recently-acquired 717s and 737-900ERs. You can check with your specific airline or with sites like Seat Guru before booking to determine what is available on any given aircraft and at which seats.

As Lnafziger said, some airlines' systems require adapters, while others don't. At least from personal experience, it seems that most of the recent ones do not. On Korean Air, Cathay, and Delta, the plugs are designed to be able to fit any of the standard power plug types (e.g. North American, European, Asian, etc.) Since most new electronic devices use auto-switching power supplies, they should accept the 110V/60Hz supplied by most of these systems, even if they're designed for 220V/50Hz markets.

Here's a picture of one of the outlets in economy on the Delta 717s. Notice that the holes are cut such that any of the standard plug types will fit in it. The slot on the bottom is a USB power port.


Airliner parts have a tiny market outside of the airline and maintenance businesses (in the sense thst the general public generates no demand) which means that there probably aren't many places to shop for unairworthy (read: cheap) spares.  I would place "want to buy" ads on Barnstormers and maybe cruise the site from time to time clicking through relevent categories.  I did see one ad offering 737-200 parts but you'll have to contact the seller to see exactly what they have and how much they want.

You could certainly buy a new part but you will not like the price tag.  I imagine that an unairworthy spare for an -800 series will be hard to find compared to a -200, for example, because of the quantity of inoperative junk parts generated thus far by the respective fleets.

Good luck!


What are these criss-cross patterns close to Cambridge Airport (UK)?

In 2017 there was a major archeological dig in the area of Hatherdene Close and Coldhams Lane at the south end of the Cambridge airport.  The "criss-cross patterns" are additional exploratory trenches as part of a "Preliminary Archaeological Investigation".

Welcome
to the public consultation on the emerging development proposals for the creation of a new
neighbourhood at Land North of Cherry Hinton

Anglo-Saxon artefacts unearthed on Cambridge building site

The area is also the subject of a Planning Document. I had a quick read through the document and I found a reference to "Preliminary Archaeological Investigations", which are the trenches seen in the aerial photo.

LAND NORTH OF CHERRY HINTON Planning Document


Why do flight attendants continue to stand, when the seatbelt sign is on?

I worked as a flight attendant for several years and I am still employed within the industry but in a different capacity, so I know a thing or two about this topic.

Flight Attendants (FAs) are strictly required to be seated during take-off and landings only and usually not during descent or climb, unlike passengers who are usually required to be seated and buckled. Then it depends on the local rules for how long they are supposed to stay there. In some airlines, the FAs must sit as long as the seatbelt sign is lit, while in others they can move about once the gears are up (you can hear this easily, as they make a loud sound when they are retracted). Other airlines might state FAs can move once the plane reaches a certain altitude and/or are given some sort of sign from the cockpit.

There is not one type of turbulence, but various classifications. Some of them are just light (small bounciness) and some are dangerous and can injure (or kill) people who are not seated and buckled. It is usually cabin crew who are the victims (I have personally been through this kind of turbulence).

Usually, pilots will, during the pre-flight briefing, brief the cabin crew of any expected turbulence and will usually say something like: "seatbelts are for everybody" or "seatbelts are for passengers". If things during the flight end up different from the forecast that was given to the pilots prior to the flight, the pilots will call the cabin crew and inform them. They will tell the cabin crew whether to continue the service because it is a light turbulence, they may suggest only to serve cold beverages, or tell the FAs to sit tight and secure everything if approaching severe turbulence.

This is basically the "secret" behind it. There is no magical training given to cabin crew on how to defeat the laws of physics and stand balanced while in turbulence; it is just the word from the pilots as they are the most knowledgeable about the weather conditions. The crew are only trained on types of turbulence and on how to secure the cabin and service carts quickly in case of sudden severe turbulence that was not detected in advance. In that case, they are told to hang on to anything and secure themselves.

Passengers, on the other hand, are required to be seated and buckled during all phases of the flight except cruise and when there is no turbulence. This is simply due to liability and not to add more complication in these critical times.


How do pilots do a preflight inspection of tail-mounted engines?

In personal experience, I often look for a step ladder to inspect ground inaccessible engines and control surfaces and I have seen others look at their aircraft from a second story window.

My personal practice is to walk around the aircraft prior to every flight, not just at the first flight of the day, but I often had to make time for that. It may not be common practice. But that is an aside.

Here's the reality. If you are talking about the walk-around that the pilot or flight engineer might do, there are not up close inspections of the elevated engines and control surfaces. The walk-around will look for leaking oil, missing $1500 fasteners or whatever, but one is not checking the dipstick prior to engine start.

How are things inspected?  The manufacturer factors that into the design.

From an operational standpoint, the pilot(s), FE will look at performance during engine start, and make sure that the profile does not deviate from the expected temps, flow, etc.

In summary, if you can't get to it, it is not likely on the walk-around checklist.

Addendum.  At least one company is seeking FAA approval to utilize drones in aircraft maintenance inspection (not pre-flight) processes, which would reduce the cost and risks associated with scaffolding and lifts. As part of their application to FAA, there will be demonstration periods where aircraft are inspected with both methods, and results are shared with the FAA.


What are the limiting factors when flying a model UAV plane to high altitude?

The same rules apply as for "real" airplanes, and the topic has been covered well in previous questions. With model airplanes, scaling laws make the task easier, rsp. the possible maximum altitude higher. I would suggest to hang the plane below a balloon to get it up without draining batteries. NASA has done it before with a remotely controlled glider.

For the limiting factors please see this question.

Here is a question for the maximum altitude of propeller aircraft.

Here is another on the feasibility of geostationary drones.

Depending on the acceptable fragility of the design, a model aircraft should easily go down to a wing loading of 10 $kg/m^2$ and then be flyable at 36 km of altitude. At a true airspeed of 155 m/s it will fly at half the speed of sound and the Reynolds number on the wing with an assumed chord of 0.25 m will be below 20,000. You need to fly it with a lift coefficient of 1.1, which will be a challenge at the low Reynolds number, and the L/D will probably be less than 10, so your propulsion needs to be quite powerful to hold the altitude up there. I haven't done the numbers, but the propeller will be huge. With back-of-the-envelope calculations, my answer for the maximum altitude is 36 km.

Turbulence should be of no concern - all flow patterns up there are of extremely large scale.

The low temperature should also be tolerable if all systems are electric. It is not so cold up there: The standard atmosphere gives -34°C.


Which FAA regulations require compliance with TCAS II Resolution Advisories?

The requirement to respond to the TCAS II resolution advisory is somewhat indirect.  one key fact is that any TCAS installation has to be approved:

  14 CFR §91.221   Traffic alert and collision avoidance system equipment and use.

  (a) All airspace: U.S.-registered civil aircraft. Any traffic alert and collision avoidance system installed in a U.S.-registered civil aircraft must be approved by the Administrator.

  (b) Traffic alert and collision avoidance system, operation required. Each person operating an aircraft equipped with an operable traffic alert and collision avoidance system shall have that system on and operating.

Key points here:  1. The installation must be approved.  2. If it's installed, it has to be used.

From Part 121:

  14 CFR §121.356 Collision avoidance system.
  Effective January 1, 2005, any airplane you operate under this part must be equipped and operated according to the following table: {Detail omitted}

This says anyone under Part 121 must have A TCAS installed and operating.
If you go back to Part 21, you can find that the installation approval requires a Type Certificate, Supplemental Type Certificate, or an Amended Type Certificate.

Part of getting that installation approval is a requirement for Airplane Flight Manual (AFM) or an AFM Supplement.  With regards to TCAS, the airworthiness approval is addressed by

  AC 20-151B Airworthiness Approval of Traffic Alert and Collision Avoidance Systems (TCAS II), Versions 7.0 & 7.1 and Associated Mode S Transponders

Chapter 5 and Appendix A cover the requirements for the AFMS for TCAS.

While the AC is advisory, it is spelling out a means of complying with the rules, which in Part 23 (small A/C) and Part 25 (air transport) require a flight manual.

Elsewhere:

  14 CFR §91.9 Civil aircraft flight manual, marking, and placard requirements.

requires operation in accordance with the limitations of the AFM.

In Part 121, airlines operate in accordance with their Op Spec, which will include similar rules.

And there is specific wording to address clearances and response to TCAS:

  14 CFR §91.123  Compliance with ATC clearances and instructions.
  (a) When an ATC clearance has been obtained, no pilot in command may deviate from that clearance unless an amended clearance is obtained, an emergency exists, or the deviation is in response to a traffic alert and collision avoidance system resolution advisory. However, except in Class A airspace, a pilot may cancel an IFR flight plan if the operation is being conducted in VFR weather conditions. When a pilot is uncertain of an ATC clearance, that pilot shall immediately request clarification from ATC.
  (b) Except in an emergency, no person may operate an aircraft contrary to an ATC instruction in an area in which air traffic control is exercised.
  (c) Each pilot in command who, in an emergency, or in response to a traffic alert and collision avoidance system resolution advisory, deviates from an ATC clearance or instruction shall notify ATC of that deviation as soon as possible.

This basically acknowledges that pilots will respond to an RA and that they should report it as soon as they can after the fact.