Why is there a compressor in an air cycle machine?

If I understand your question correctly, you don't really understand how the ACM works.

The idea of an ACM is to create 'cool' air. Especially on the ground (imagine landing on your tropical holiday destination), this means that the air must sometimes be made cooler than the outside (ambient) temperature. The second law of thermodynamics (and in this case, the law of common sense) states that you can't just cool your air against the warm ambient air, so you will need to do some special tricks.

In this case, the special trick is compression. You compress the air, which will make it quite hot (increase the temperature) (search for adiabatic compression on the internet). Then, this hot air can of course easily be cooled against ambient air, which happens in the second heat exchanger. In fact, the hotter the air after compression is, the more heat is exchanged in the second heat exchanger. This means the heat exchanger can be made smaller, which is especially useful since air-to-air heat exchangers are inefficient and thus relatively big.

Now, you expand your air again, which will cool it (decrease the temperature). However, since you already cooled it down in the second heat exchanger, it will now be cooler than when it originally encountered the compressor! This makes sense, since you removed energy from the air in the second heat exchanger. So, this way, you can cool the air down further than would have been possible by a heat exchanger (search for reverse Brayton cycle on the internet).

So, this system has two advantages:

It is possible to cool down air beyond ambient temperature, so it functions as 'airco' on the ground or at low altitude.
It is possible to cool hot compressed bleed air with a relatively small, light heat exchanger for pressurizing your cabin while not cooking your passengers medium-rare.


Where do I start learning about Avionics programming?

Ok, I was posting this as a comment but was becoming ridiculously long...

I worked for most of my professional life in fields that are somehow related.
I can see that there are three areas of study that will help you a lot here.

First: programming languages. Knowing a language used in the industry is a plus.
Now I am working in the automotive/transportation industry; I am not working on safety critical material, so we just use standard C/C++. Even at that level a good knowledge of low-level programming and software (how to write a simple driver, how to interact with a device using ioctl, etc..) are very useful.

Before that, I worked on a field related to programming languages and compilers, especially on the simulation and analysis of concurrent code. Among the others, I briefly interacted with people working for Airbus (professors that are in academia, but help to build real software).
They still see and use a lot of Ada out there, so.. knowing that is good :) I also know for a fact that Java is also used, together with special tools for verification of the code.

Which bring us to the second: everything related to the verification of software, both from a theoretical and a practical point of view, will help you hugely in this industry. Study and practice with runtime monitors and model checkers, at least. Learn about various static analysis techniques, like abstract interpretation. Take classes about that, if you can at your school.

And third: study and practice with embedded systems and with the (more rare) real-time OSes and how they work (and how you do program them).
Get yourself an arduino or a netduino (not a raspberry PI - too high level, too many resources there!) and practice with them. Lear about uboot.


This can be calculated by knowing a few formulas, or temperature relationships related to altitude. Note that all these calculations are an estimate based on standard ISA temperature and altitude relationships. See this page for other examples of this type of question.

Note the following from the question:

FL170 represents a pressure altitude of 17,000 ft
We know that the OAT is -10°C
Indicated altitude is 17,500 ft

Now, to solve for true altitude, we need to know a few additional items. We need to know that:

ISA at the surface is 15°C
Standard lapse rate is -2°C per thousand feet
To find true altitude, the difference from indicated altitude is 4 ft per 1°C deviation from ISA for every 1,000 ft

Knowing all this, we can calculate the following:

ISA at 17,000 ft (see 4 and 5 above)
Deviation from ISA (see 2 and 7 above)
True altitude (see 6 and 8 above)

This all might sound complicated, so lets run through an example problem. Let's assume a flight at FL190, with an OAT of -15°C, on a standard pressure day.

Since ISA at the surface is 15°C, using the standard lapse rate of -2°C per thousand feet, we know that ISA at 19,000 ft will be -23°C.

Given an ISA of -23°C, we see that our OAT of -15°C shows a difference of +8°C above ISA. Follow that step carefully, because the signs can be confusing.

Given that the temperature is ISA+8°C, and knowing 6 above, we can calculate our true altitude relative to pressure altitude:

$A_T$ is our estimated true altitude, in feet
$\Delta_{ISA}$ is the difference above ISA, in °C
$A_I$ is our indicated altitude, in feet
$A_{Ik}$ is our indicated altitude, in thousands of feet

$A_T=(4 \times A_{Ik}  \times \Delta_{ISA}) + A_I$
$A_T=(4 \times 19  \times 8) + 19000$
$A_T=608 + 19000$
$A_T=19608$

In some cases, a question might ask for true altitude based on a pressure altitude, instead of an indicated altitude. In such cases, substitute pressure altitude for indicated altitude in the above formula. Remember, this is all an exercise in estimation which is helpful in reinforcing the relationships between temperature, pressure, and altitude.


What would happen if the flight engineer is unavailable on a 747?

This question has been asked and answered in a slightly different form at How able were pilots of three-person cockpits at running the normal FE work?, and I refer you to that for basic info. Concerning the detail in your question:

  What difficulties would the pilots face for the remainder of the flight, including navigation and landing, with no one attending the flight engineer station in the cockpit?

It would be a nuisance for sure, but as long as there were no abnormal or emergency situations (other than the FE's personal situation), a nuisance would be all that it was. However, one could dream up scenarios that could get really sticky without the specialized knowledge that the FE would be expected to have that the pilots might not have (or had forgotten).

  For example, would one of the pilots get up and sit at the FE station, leaving the other pilot the only person at the controls? Or would the person get up, go to the FE station to read or adjust something, then sit back at the pilot's seat? Or do they not have to move at all?

The Captain can see the FE panel. Some of the gauges along the aft portion would be a little hard to read. For example, if he wanted to see what the exact pressure of the Potable water was rather than just that there was pressure, he might have to get up to get close enough. Or if a generator fault light came on, he'd probably have to get up to see what the fault was.

There wouldn't be any need to stay in the FE seat. If the flight were long, there would be some trips to the FE seat for fuel management. You can have as many as 9 fuel tanks (7 is the usual), and there are rules for the fuel burn schedule. The most important and most time consuming FE task during cruise was keeping track of what the fuel burn was, especially on the 747-100 because it didn't have the fuel capacity of the -200. For example, a -100 going from JFK to Tel Aviv would sometimes not have the fuel to make it. Abeam Athens the FE would inform the Captain either than they had the fuel to continue or that they would need to divert to Athens for fuel.

If the Captain wanted to talk to company for some reason, it was usually the FE that established contact via HF, and it was usually the FE that answered SELCALs. But the pilots sometimes did it.

Flight attendants might show up and ask for a general cabin temperature change.

Of course, it the FE had a severe medical problem, you would probably land at the nearest suitable airport just as you would for a passenger medical emergency.


Do I need a digital or analog scanner to listen to Air Traffic Control?

The voice communications for air traffic control is all analog (AM to be specific). A scanner that works in that frequency range on AM should be fine. Although a switch to digital has been considered, there is just too much coordination and investment required.

A good reference to find the right frequencies is AirNav. It will list all the frequencies for an airport.

Another good reference for many frequencies, not just airports, is RadioReference. The database there will tell you exactly how each channel is transmitted, so you know what type of radio you will need to listen to it.

Also keep in mind that ATC transmissions are line-of-sight, so you will have to be close to a ground station to hear it. The "rubber duck" antenna included with a lot of scanners is fine but a better antenna will help to improve reception. Also, military aircraft use a higher frequency range, and a lot of cheaper scanners will not receive this.


When flying to a towered airport when the tower is closed, what frequency should I use?

You use the CTAF for announcing your position and intentions, i.e. 125.85. From the AIM 4-1-9(g):

  If an airport has a tower and it is temporarily closed, or operated on
  a part-time basis and there is no FSS on the airport or the FSS is
  closed, use the CTAF to self-announce your position or intentions.

4-1-9(b) says:

  The CTAF may be a UNICOM, MULTICOM, FSS, or tower frequency and is
  identified in appropriate aeronautical publications.

125.85 is marked as the CTAF on the sectional and listed in the Chart Supplement.

Note: The letter "C" in the dark circle next to the control tower ("CT") frequency indicates that the CT frequency is the CTAF frequency at that airport.


Is it possible to use multiple primary radars to determine an object's location in three-dimensional space?

Of course. That is, after all, the whole purpose of radar: to get the position of an object and plot it on a screen. You don't even need multiple radars, one radar is enough.
If you're just talking about primary radar (i.e. bounce a signal off of the skin of the target), then you're going to have some trouble with measuring the altitude. The distances involved mean that a large change in altitude would create a very small change in the beam angle, so altitude measurements are going to come with huge error bars. In fact, civilian radars almost never bother with vertical scanning at all, because such imprecise measurements aren't considered to be worth the extra complexity. Naturally, secondary radar (i.e. transponder interrogation) doesn't have this issue, since the transponder simply tells the radar what its altitude is.


Is there a flexible "cloth-like" material that can be used as "skin" for a non-conventional wing?

Aircraft fabric would be too heavy for a person carrying homebuilt orni-contraption.  What you are looking for is 3M Mylar/Tedlar.  It has been used as a covering material for a number of ultralights like the Lazair for many years.


Do companies based in non-English-speaking countries require intra-cockpit procedural communication to be performed in English?

This is common in many international airlines.

Lufthansa Standard Operating Procedure (SOP) dictates that all flight procedural communication (checklists, standard callouts, etc.) are done in English.

The only "German" I've seen on Lufthansa's checklists is "handy .... off" in the pre-startup checklist (German English for "mobile phone .... off").


Why are push-propellers so rare, yet they are still around?

There are many disadvantages, they seem to outweigh the advantages.

Here are two:

A pusher prop is working in a disturbed airflow, causing increased vibration and noise
If the propeller is fitted behind a wing, each propeller blade is passing through the separated boundary flow twice each rotation. These cycles create additional noise and lower the efficiency of the propeller. The vibration makes the propeller blades more susceptible to metal fatigue.
Propeller clearance at takeoff
Due to the pitch up at take-off, the propeller gets close to the ground. Therefore the diameter needs to be reduced (loss of efficiency) or the landing gear struts need to be made longer (added weight). Since the propeller is behind the landing gear,  it is susceptible to debris kicked up from the gear, increasing the need for added blade protection (increased weight, loss of efficiency)

Wikipedia has a list of additional disadvantages.

Edit:

Your statement that

  Jet engines are by their very nature push-engines

is not entirely true.

In turbofan engines, most of the thrust is generated by the fan and compressor stages. Even in a pure jet engine, a lot of thrust is generated by the compressor. Therefore the shaft of a jet engine is tension loaded, just like a propeller shaft in puller configuration.

Source: Rolls Royce - The Jet Engine


How is shear stress distributed on an airfoil?

Shear stress is proportional to the speed gradient at the wall. This means:

A thin boundary layer produces more shear than a thick one. The boundary layer is thinnest right next to the stagnation point and grows in thickness downstream.
A turbulent boundary layer will create much more shear stress than a laminar one. Most of the shear on an airfoil happens past the transition point.
Higher speeds cause higher shear stresses. Therefore, the suction area on the upper side of the airfoil produces more shear stress than the pressure area on the lower side. In a separation bubble with speed reversal at the wall you will even get a small amount of "shear thrust".

The shear acts along the local flow direction, so it is mostly front-to-back. Only near the wingtips, where lateral flow becomes non-negligible, will a lateral shear component become noticeable.

Friction drag over chord for an E502mod airfoil at 3° AoA. Blue: Top surface, Red: Bottom surface. Source: XFOIL 6.97. The transition points are clearly visible: It is where shear shoots up again at mid-chord. Note the separation bubble ahead of the transition point on the bottom side: It is marked by negative values of shear.


Why was the boat mounted this way on the underside of the wing on the "Landseaire" flying yacht?

The reason is the "flat tail" of the boat. The drag this "flat tail" produces when mounted "reverse" is much less then the dynamic drag it would induce the other way around.

https://en.wikipedia.org/wiki/Drag_(physics)

  I don't see how the link helps explain why the flat side produces less drag than the pointed side.– Ron Beyer

The published cw coefficients (see answer of @jwzumwalt ) show the best value for the drop shape facing towards the air stream.

There is no entry for a reversed drop. But it is evident that is would have a higher cw coefficient.

A closer look at the boat reveals it also has a drop shape. But this is facing to its tail. Therefore the boat creates less drag when mounted "reverse".

  If this was the case, wouldn't the boat cause less drag moving backwards through the water also? – andy-m

It might but the usually draft of the boat is no so deep that a relevant part of the "flat tail" is actually in the water.

source: https://upload.wikimedia.org/wikipedia/commons/2/2d/Bundesarchiv_B_145_Bild-F056332-0004%2C_Bonn%2C_Bundesgartenschau%2C_Seen.jpg

On the other hand a little turbulences at the boats tail could help to keep direction in the absence of  a steering paddel...

  This explanation is wrong - an anemometer spins with the forward facing blunt half of the hemisphere causing the most drag - en.wikipedia.org/wiki/Anemometer – jwzumwalt

The most important differences between the anemometer an the drag experiment is:
The half bowls in the anemometer are hollow which "catches" the wind way better than the flat surface of the filled half bowls in the experiment.


Is the ILS CAT III system the most complex landing system available?

Yes ILS equipment for CATIII is the most sophisticated across ILS systems. As people mentioned in comments there are another types of landing systems, which could be more complex.
No it is not auto landing system.

It self CATIII is a category of a landing conditions.

Also take a look here What is different between a Cat IIIA, Cat IIIB, and Cat IIIC ILS approach?


What is the difference between an RPL and a PPL licence?

An RPL requires less training (i.e. money) but is more restricted in how far you can fly, how many passengers you can carry and how heavy the aircraft can be. You can get an endorsement to fly anywhere domestically; there is no endorsement available to fly internationally or for the other two restrictions, nor is an instrument rating available.

A PPL allows you to fly just about any small aircraft anywhere, and you can add an instrument rating as well if desired. There is still a weight limit, but it's high enough you wouldn't hit it without needing to get (at least) a commercial license anyway.

All of the training you take for an RPL will count toward a PPL, so if you start on the former and switch to the latter, you lose nothing. Or you might get an RPL first and, if you find the it too limiting, upgrade to a PPL later; the only thing you lose in that case is having to pay for twice as many tests.


How can I find traffic patterns that pass over my house?

Its not that easy for a non-pilot to do it, but there are about a dozen "Arrival Procedures" that show specific routes into ATL.

You can also see on the Atlanta Area Chart how some of the traffic might flow near your house.

The easiest thing to do, if you can pick out some of the aircraft, is to look up their flight paths on Flightaware:


Can I get official recordings of ATC audio?

In the specific situation of a pilot who is the subject of an FAA investigation, the Pilot's Bill of Rights requires that air traffic data (which includes audio recordings) be provided to the pilot. They would be expected to make the request directly to the FAA. There is a procedure for this:

To ensure that relevant air traffic data you are seeking from a government contractor are obtained, you should provide the following information:
a. Your name and your airman certificate number;
b. other relevant information (aircraft heading, altitude, call sign, transponder code, etc.) that will help the contractor locate relevant data;
c. the name/location of the contractor facility that you believe has air traffic data;
d. the date and local time of day when such data relevant to the your flight operation were generated;
e. the name of the FAA inspector, investigator or other FAA official (e.g., an air traffic controller who advises you about a possible pilot deviation) who notified you that you are under investigation;
f. the airman's phone number or email
The individual should provide that information to the FAA by email to the following address: AirmenDataRequest@faa.gov.

The instructions include a warning about timeliness:

Depending on the type of data, they will normally be stored from 5 to 45 days and then they are destroyed or discarded in the normal course of business

I don't have any information about the general case, though I imagine it depends on the facility and their workload.


What is the expiration period for a 3rd class medical certificate?

According to the table in 14 CFR 61.23 (d), the expiration date of your medical is based on your age "on the date of examination for your most recent medical certificate."
So, if you were 39 on the date of the examination, you're good for 60 months.

There is a possibility that the requirement to renew 3rd class medicals may go away completely soon. On Dec 15, 2015, the U.S. Senate passed the "Pilot's Bill of Rights 2". The bill would still need to be passed by the House and signed by the President before it would take effect. As of Dec 15, it had 152 co-sponsors of both parties in the House. According to AOPA:

Under the medical reforms of Pilot's Bill of Rights 2, most pilots who have held a valid third class medical, either regular or special issuance, within 10 years of the legislation’s enactment would never need to get another FAA medical exam. The rule would apply to pilots flying VFR or IFR in aircraft weighing up to 6,000 pounds and carrying up to five passengers at altitudes below 18,000 feet and speeds up to 250 knots.
Pilots who develop certain medical conditions, including a small list of specific cardiac, mental health, or neurological conditions, will have to get an FAA special issuance medical one time only, significantly reducing the time and money spent navigating the FAA’s medical bureaucracy.
For pilots who have not had a valid medical in the past 10 years and those who have never applied for and received a medical certificate, a one-time third class medical certification by an aviation medical examiner will be required. After a pilot has been medically certified once, either through the regular or special-issuance processes, he or she will also be able to fly indefinitely without needing to go through the FAA medical certification process again.


How to get an accurate time of arrival to the en-route alternate airport during flight planning?

This is very much like the information mandated for EDTO/ETOPS.
Computerised flight planning systems should have the ability to calculate the ETP, equal time  point (aka CP) based upon ERA/ERAs selected. If 2 ERA are required due to the length of flight, depending on the geographical disposition of the ERA you'd get an ETP for each pair, ie ETP1 for DEP Stn/ERA1, then ETP2 for ERA1/ERA2, then ETP3 for ERA2/DEST Stn.
The earliest ETA for ERA1 would be a diversion from ETP1 and the latest would be from ETP2 and you would need to subtract/add the 1 hr buffer.
And so on . . .


Is there a site that tracks all flights?

No, there will always be flights that are private, or for any other reason not traceable.


Which direction of a forward slip is safer during a turn to final?

I use slipping turns all the time.

If you want to do a slipping turn you yaw the nose OUT of the turn, being careful to keep G loads low. It's NOT a dangerous maneuver if you keep speed up and nose down while doing it although you should use a bit more aggressive nose down than in a straight side slip to account for the slight extra G from the turn.  If you keep the wings largely unloaded and let the airplane fall semi-ballistically, you aren't going to stall.

To do it safely however, you do have to know how to fly the plane.


Can foreigner fly model aircraft (quadcopter) in US without being part of an organization (like AMA)?

This answer reflects the referenced rules but does not necessarily include all laws that may apply in this situation.

The wording on the picture included in this answer is confusing. If you go to the wording of the bill, it says that the FAA:

  may not promulgate any rule or regulation regarding a model aircraft, or an aircraft being developed as a model aircraft, if--

  ...

  (2) the aircraft is operated in accordance with a community-
      based set of safety guidelines and within the programming of a
      nationwide community-based organization;

So this bill does not prohibit you from doing anything, it just says that the FAA can't make a rule specifically about model aircraft that applies to you as long as you are operating according to those rules. You still must follow any other general rules about aircraft. See the interpretation of the rule, as linked from the answer on that question, which says:

  Thus, based on the language of the statute, we conclude that aircraft that meet the statutory definition and operational requirements, as described above, would be exempt from future FAA rulemaking action specifically regarding model aircraft.

  ...

  Thus, the rulemaking prohibition would not apply in the case of general rules that the FAA may issue or modify that apply to all aircraft, such as rules addressing the use of airspace (e.g., the 2008 rule governing VFR operations in the Washington, DC area) for safety or security reasons.

  ...

  The FAA permits aircraft operations below 500 feet when flown over open water and in sparsely populated areas. 14 CFR 91.119(c). Such operations may not be conducted “closer than 500 feet to any person, vessel, vehicle, or structure.”

It looks like there are some such "sparsely populated areas" on Guam, which should meet those requirements. Staying at least 5 miles away from the airports would also be a good idea. You can see that the southern end of the island will be your best bet:

Keep in mind that there are also additional military sites there, including one in the south, that may be sensitive to such things.


Would the flyby in this video be illegal under 91.119(a)?

This depends how you look at it but there are definitely some FARs this guy is in breach of. First one that comes to mine is 91.119 on minimum altitudes, it's pretty straightforward (assuming this is an area other than congested area)

Except when necessary for takeoff or landing, no person may operate an aircraft below the following altitudes:
(a) Anywhere. An altitude allowing, if a power unit fails, an emergency landing without undue hazard to persons or property on the surface.
(c) Over other than congested areas. An altitude of 500 feet above the surface, except over open water or sparsely populated areas. In those cases, the aircraft may not be operated closer than 500 feet to any person, vessel, vehicle, or structure.

He is pretty clearly within 500 ft of that person...
You can see that there is a case for sparsely populated areas but I would argue that if there is a backyard party going on this is not a sparsely populated area.
Then as mentioned there is the catch all in.13

§91.13   Careless or reckless operation.
(a) Aircraft operations for the purpose of air navigation. No person may operate an aircraft in a careless or reckless manner so as to endanger the life or property of another.

I'd say that's reckless but of course that's up for debate. Then again it's impossible to say where this happened so we can't know what type of airspace this is in and if there were possible issues there. I would go on to say that at an altitude that low I would turn on my landing light to increase awareness and enable me to see the ground better.
If you really want to push it you could even go as far as saying that maneuver is aerobatic flight since it's an abnormal attitude (at the altitude it's being performed) and most likely not seen in normal flight. For the record that attitude looks to be about around 30 degrees which would be a standard steep turn (something I would never attempt that close to the ground).

For the purposes of this section, aerobatic flight means an intentional maneuver involving an abrupt change in an aircraft's attitude, an abnormal attitude, or abnormal acceleration, not necessary for normal flight.

If you think it fits under this definition the pilot is also in breach of 91.303

No person may operate an aircraft in aerobatic flight—
(b) Over an open air assembly of persons;
(e) Below an altitude of 1,500 feet above the surface;

I would consider a backyard party (as described in the video description) as an open air assembly of persons and he is clearly below 1500 ft.
The Counter Point: While the above points make a pretty solid case for the FAR's broken in the video, in theory if the maneuver is pre agreed upon, planned out, and executed as planned it may not be considered reckless. In the end of the day as a pilot you live at the mercy of the FAA and their decisions. In this case I would be most worried about that guy running into the propellor. I'm sure things like this happen more often than not.


Can jet fighter missiles descend or ascend?

Yes, they can. Air-to-Air or Air-to-Ground missiles are often equipped with little fins that allow certain maneuverability or also with thrust vectoring.

(Image Source: WikiPedia - Author: USAF)

(Image Source: WikiPedia - Author: Titimaster)


How does the FAA decide if a PPL applicant with ADHD can fly?

This article from AOPA outlines the issues with ADHD pretty well.
This article is from Canada but the medical policies are quite similar and you might find the basic information useful.
Bottom line seems to be that once you are formally diagnosed with the condition, that becomes a problem.  You can't be on ADHD medications at all (within the last 6 months) and if you are diagnosed (officially) and are not on medications, you have to go through a testing protocol to satisfy the FAA that are fit to fly without medication.
There seems to be a lot of misdiagnosis of ADHD and the symptoms you describe may not be severe enough to be considered a real case (you may be getting too hard on yourself; I get sidetracked on tasks by things like shiny bottle caps on the floor, get bored easily, and if you give me a Rubik's Cube, I'll tire of it and put it down after about 2 minutes, and I've been flying since the mid 70s).
When I read about the symptoms of hard core ADHD (especially over-diagnosis of kids - it's criminal in my mind) it sounds like you would be barely able to function in the world, and your description doesn't sound like it rises to that level.  I'd be wary of proceeding along the path to an official diagnosis unless you've decided it's so bad you can't function without medication, and at that point flying is out.
If you do nothing and carry on, and you have a significant case, it'll become obvious during training and you'll probably never get to the solo stage.  FAA protocols are based on a diagnosis, which should be by a psychiatrist, so I wouldn't bring it up to an AME until you get to that point.  I would explore other non-psychiatric therapies or techniques that could help with focus and discipline first, and would avoid the medical route unless it was a last resort.  Your doctor may not have been doing you any favors by suggesting you might have a serious psychiatric condition based on some comments.


Can hang glider hover straight into wind and keep same position?

The ground is not flat, and indeed slightly angled. This is enough to "hover".
Specifically, the ground slope should be equal or more than the max L/D ratio of the hang glider at the current wind speed. The wind should go 'up' as much as the glider goes 'down' per unit of distance. The ground seems to go up about 2m over a distance of maybe 10m, which is a slope of one in five. An L/D of 5 seems perfectly reasonable for a hang glider.


How to hold the heading on the Boeing 777 autopilot?

Pressing the heading hold button will assume the current heading.
Pressing heading select will follow the course as selected in the display; this can be set by pressing the rotary encoder. It is also visible on the heading bug.

The Boeing 777 primary flight display will display HDG SEL and HDG HLD for each selection respectively.


What methods exist to detect airframe icing, and how do they work?

There are a few ways to sense ice on an airframe. The DOT has a document here that outlines the various types of sensors.

First and foremost planes have ice lights that project onto the wings so they can be visually inspected.

There are completely optical sensors that use a variety of methods to detect ice.

There are also some electro mechanical devices, here are a few examples, the rest are outlined in the DOT document.

  Penny and Giles

  The Penny and Giles system uses a probe type sensor that measures ice
  buildup in terms of Liquid Water Content (LWC). This system was
  designed specifically for use on helicopters and is available for all
  turbine-powered helicopters.

  Rosemount

  The sensing probe is driven magnetostrictively to vibrate at its
  resonant frequency of 40,000 Hz. As the ice detector enters an icing
  environment, ice collects on the sensing probe. The added mass of the
  accreted ice causes the frequency of the sensing probe to decrease in
  accordance with the laws of classical mechanics.

  Sunstrand

  The Sunstrand system uses a mounted probe with a sensing surface
  facing the airstream. Beta particles are released from a Strontium 90
  Radiation Source and are collimated by a specially shaped window in
  the probe housing. These particles pass across the sensing surface to
  a Geiger-Muller tube. High voltage is applied to the Geiger-Muller
  tube to enable it to detect the radiation emitted by the Strontium 90
  source. Ice accretion on the probe decreases the beta particles
  detected by the tube. When the particle count drops below a pre-set
  level, a pulse rate discriminating amplifier energizes an icing signal
  visible to the flight crew. At this time a heater inside the probe is
  activated, the ice is removed from the probe, and the probe is ready
  to begin another icing cycle.

Some of these will work in a static situation while others may require the passage from a non icing environment to an icing situation.


Can I legally own and fly fighter jets in the UK?

I don't know of any privately owned Hawks, but there are many ex-RAF jets in private ownership, like the Jet Provost, Lightning, Gnat, Meteor, Vampire, and others I can't remember. The Ministry of Defence sells fixed-wing airplanes and helicopters occasionally at auction; when they retire the Hawk T1 you could be able to pick one up.
This CAA document goes over many of the particulars, a quick summary is that in almost all cases they would be under a permit to fly. This would require an inspection to clear it for the permit, and an (un)healthy dose of paperwork. I know of no way to get these aircraft certified, but you can get them cleared for night and IFR flight with extra paperwork and continued inspections, provided the aircraft is equipped for it. You can also get a permit to fly faster than 250kt below 10,000ft, which in a jet like the Hawk would be an advantage. Flying abroad on a UK permit aircraft is just more paperwork: you have to get permission from all the countries you'd fly over and land at, which is generally a formality, and restricted to day VFR.
One of the challenges you would find is keeping the plane airworthy. There are a few organizations that restore and maintain ex-military jets; you'd want to find out if they'd be able and willing to take it on for you before you buy it.
Of course you'd also need an awful lot of money. Jet Provosts (50s era trainers) are at the low end of jets as costs go and they still cost £600 per hour to operate!


Why don't commercial airplanes carry Earth-observing instruments?

They do! Well, at least some of them. There is for example a project called TAMDAR (Tropospheric Airborne Meteorological Data Reporting) that e.g. Icelandair is a part of. There is a document published by the Icelandic Meteorological Office about it.

Another example is MOZAIC/IAGOS: Atmospheric Research Using Commercial Airliners.


How is the climb/descent performance affected by wind gradient?

You are correct.

Suppose the headwind just 10 meters above you is 10 knots stronger then where you are now. Climbing the 10 meters will cost you some kinetic energy which is transformed to potential energy. Suppose you were flying 200 knots airspeed initially, you will end up with 198.1 knots airspeed if the transformation from kinetic to potential energy is 100%.

I derived this from simple kinematic energy equations:

$\frac{1}{2}mV_0^2 + mgH_0 = \frac{1}{2}mV_1^2 + mgH_1$

$V_1 = \sqrt{V_0^2+2g(H_0-H_1)}$

But since your headwind is increased by 10 knots, your true airspeed will be 208.1 so it has increased by 8.1 knots. Free energy from the wind!

Note that your groundspeed will reduce during such a climb, but you will be able to generate a higher than usual climb rate at constant airspeed in a positive gradient headwind field.

Note that birds make use of this technique, for example the albatross can stay airborne for days with using only minimal energy for keeping in the air.

Albatross in windshear field (youtube)


To what FAA office or personnel should one direct an inquiry about the reasons behind the airspace design at a particular airport?

By reading your linked FAA Order and finding references for responsible offices and a little follow-on search, I found this link to the Office of Mission Support within the Air Traffic Organization.

Airspace analysis appears to be within their purview:

  Mission Support Services oversees the Air Traffic Organization’s
  activities in:

  Aeronautical Information Manual (PDF)
  Aeronautical Information Services
  Air Traffic Organization Environmental Reviews
  Air Traffic Procedures Advisory Committee (ATPAC)
  Instrument flight procedures production/charting
  Metroplex
  New York/New Jersey/Philadelphia Airspace Redesign
  Obstruction Evaluation/Airport Airspace Analysis (OE/AAA)
  Performance-Based Navigation (PBN) Implementation And Usage Dashboard
  Pilot Web

They provide the following contact information:

  Address
  FAA National Headquarters
  1028 - 10A
  800 Independence Ave., SW
  Washington, DC  20591

  Phone: (202) 267-8261


What factors govern the placement of a helicopter's tail rotor (left or right)?

It's hard to say the design rational used for all helicopter manufacturers. Push vs pull doesn't seem to be very important.

One example is the Bell UH-1 Huey (Left side Pull). When Bell modified the design for civilian use 205, 212, 412, 214, they put the TR on the (RH side Push). When asked about the reasoning for the original Huey/205 change, Bell engineers explained that they found better TR effectiveness with rotation of forward blade climbing, as the interaction with wake and vortices of the main rotor was more favorable in this configuration.

Now look at the AH-1 Cobra Gunship variants. Bell switched sides at least twice. Left on early models, switched to right on later 2 blade models (AH-1W). Back to Left side for the 4 blade AH-1Z. While on opposite sides, the AH-1W and AH-1Z are both forward blade climbing.

Sikorsky? S-76(Left - Climbing) H-60(Right - Climbing) H-53(Left - Climbing). One could speculate that the higher the TR is mounted, the more this rational comes into play.


Why complex landing gears are used instead of simple, reliable and light weight muscle wire or shape memory alloys?

Shape-memory alloys change their shape with temperature, with control usually achieved with electric heating in one direction, and back with convective heat transfer to the environment. There is one specific temperature where the change in shape occurs. There are two huge problems with this:

The operating temperature range for gear actuators is huge. It may easily be below -40°C on a cold arctic night, but on a hot tropical day the sun can easily heat the structure to upward of +60°C. That means the transformation temperature must be pretty high, but that means a lot of energy has to be put to heating it, especially if the ambient temperature happens to be low on the day.

Note that the actuators are not very energy efficient. A super-capacitor can give you high peak power if you need that, but will not help at all with the total energy. The work the actuator has to do is significant, so the efficiency matters.
Worse, a shape-memory alloy actuator requires constant power to remain at one end of the motion range and spontaneously returns to the other. However, gear must be stable in both end positions without requiring energy, so there would still have to be uplocks and separate actuator for extension or retraction (or maybe extension would be gravity-only, but then you have to ensure it gets reliably locked). Not really simple anymore.

I also don't think they actually scale to the required forces and displacements well. A 2 mm wire bends quite easily, 2 cm rod, not so much. The thicker will of course need more force to bend—which is OK—but it will also break much sooner, because the difference in strain is bigger.


Is there a mathematical formula to find the most efficient propeller?

Yes. The first good ones were published by A. Betz and L. Prandtl in 1919, and the latest substantial improvements were added by Larabee. Those formulas are the basis of Mark Drela's XROTOR. It will give you the chord and twist distribution over span for a prescribed speed, torque or thrust. It is best used for lightly loaded propellers - if you need anything with activity factors (power absorbed by the propeller per blade area) above that of purely subsonic airplanes, better consult prop manufacturer tables.

Generally, the most efficient propeller will be large, have two blades and will spin slowly. Depending on flight speed and desired thrust, you will need to reduce diameter, increase speed and add blades as required, at the price of lower efficiency.


What are the advantages and disadvantages of autogyro aircraft?

Image source

From the same website:

  Zooming through the sky in something that looks like a flying chair, isn't for the faint-hearted.

  These aircraft look like a cross between a small helicopter and an upside-down lawnmower.

Autogiro's are used by bush pilots for mustering in Australia, due to their versatility and relatively low cost. And are also used for police patrolling in Tomball Tx.

Image source

Advantages of the autogiro:

Versatile and small.
It can fly very slowly, safely. From this site:

  Gyros cannot stall because the rotational speed of their rotors, and hence their lift, is not dependent on forward speed. At zero forward airspeed a gyro will slowly descend, to a survivable landing.

It can land anywhere.
It can takeoff from almost anywhere if the jump start is used: the engine spools up the horizontal rotor, then after take-off drives the propeller only.
Less complicated than helicopters, resulting in lower acquisition cost - much less complicated rotor hub.
Lower running costs than helicopters.

The disadvantages:

They are classified as recreational aircraft, with implications on licensing and oversight.
Some statistics show them to be more dangerous than most recreational aircraft. From this website:

  Aviation statistics show gyrocopters to be more dangerous than most recreational aircraft. An Australian Transport Safety Bureau report on accidents between 2004 and 2013 found half of all gyrocopter accidents to be fatal, with the aircraft responsible for the worst fatality rate per hours flown.

This can also be because non-fatal accidents with autogiros are under-reported.
Licensing (in Australia) is done through the sports association, which implies no access to commercial use of gyrocopters.

The simple autogyros shown above are not built for speed with their un-aerodynamic shape. Power to overcome parasitic drag scales with (engine power)$^3$, and aircraft designed for high speed have a much more streamlined shape than the gyrocopter has. From this site:

  Gyroplanes have somewhat different flying and performance characteristics to fixed wing aircraft. They have high drag and are therefore relatively slow, with typical cruise speeds of between 50 and 60 kt. The gyro’s advantage is not top speed but its ability to fly slowly, which is why under the name autogyro they were developed in the 1930s as a precursor to the helicopter.

But the flying armchairs for sheep mustering are not the only types of autogiro's. The fastest helicopters have a vertical thrust propeller as well:

Image source

Technically not an autogiro because the main rotors are driven, but the thrust propeller helps relieving the main rotor forward thrust. The Fairey Rotodyne was a pure autogiro, aerodynamically shaped, and had a maximum speed of 166 kts. Further speed increase is only possible when applying coaxial rotors like the X-2, to remedy instability due to retreating blade stall.

Image source


Does the profit from selling duty-free items on board justify flying the carts?

Okay so there are a few points to this

Lots of different things are sold - perfumes etc, gifts, "in flight" convenience items such as headphones, plus food/drink. That means lots of sales opportunities.
"Luxury" items are high margin anyway: perfume is a big profit item even with duty. By knocking the duty off and making it "feel" cheap: they can potentially sell it for more than the RRP (minus duty), and thus make more profit than a regular shop, despite selling it for less (gross) to the passenger
You only need to carry one or two bottles of each perfume, as you won't sell a ton of them. They don't take up much space: perfumes etc are only sold to one or two people per flight, they're not the reason the cart is there... they're just an extra. Similarly headphones: you won't sell many, but you'll definitely sell some when somebody realises they left theirs at home: I bought a set of cheapo £2 headphones for £8 at a train station a few days ago because wasting £6 on a set of crappy headphones was better than the idea of a 5 hour train without any music. People will pay for convenience, and carrying one or two of these items doesn't take up much space at all.
Food/drink are the reason the cart is there. When on a flight for 1-4 hours, some people are going to be hungry/thirsty... and you have anywhere from 100 to 850 passengers. The markup on these items can be huge - £6 for a small can of beer, for example, which would cost <£0.30 from a wholesaler. You don't need to sell a huge number of pies/burgers/cans of beer/£3 cans of coke to make a decent profit. With the air-con on a plane, I find I get very thirsty and will go through a 500ml drink roughly once an hour. Similarly on a 4+ hour flight I'll tend to want a snack or meal at some stage. I'm certainly not alone in this.
Seats on these planes aren't always that expensive. On my last flight it was less than £40 for my one-way ticket on a 2 hour flight: if the trolley takes up roughly one seat's worth of space, they only need £40 in profit (or perhaps 20 cans of coke in 2 hours, at £2.50 per can) to be worth carrying a trolley. Similarly the longer the flight, the more likely people are going to be thirsty. With 190 people on board, even if only one in 10 buys a drink, that trolley has made more profit than my seat. Even considering an 8 hour transatlantic flight with 400 people on board a 767, that still only needs half the flight to buy one drink (which they probably will in 8 hours...) to make up for my £500 seat
It's expected, and is a service to some extent... people would start getting quite annoyed if they found they couldn't get a drink on the flight, even if said drink is expensive. People tend to expect to be able to get a drink, if nothing else, but usually food too. Notice that most non-local (2hr+) trains (and many local ones!) tend to have a trolley service or, more and more often, a shop on board? Even if it didn't make a profit at all, it may be worthwhile for customer happiness. This is a bit of a moot point, though, as trolley services are definitely profitable (trust me, if it wasn't, Ryanair wouldn't provide one)
Your cabin crew are there anyway for safety reasons, why not put them to use as sales people? Otherwise they're just sitting relatively idle for much of the flight. Not that I wish to discredit the work and important role that cabin crew play: they're far more important than most of us realise... but the fact remains that for much of the middle of the flight, on a routine flight and unless something goes wrong, they don't actually necessarily have that much to do considering the number carried.
The cart may be there anyway! On longer flights with meal services, the airline will already have the cart available for set times. Why not put a few bottles of perfume in the bottom for an extra profit?
Capacity limits. Aircraft aren't always limited purely by space or weight: they're also only certified to carry a set number of passengers due to things like the number of emergency exits. It may be that you can't actually carry more passengers even if you want to
The trolley can fit into space a person wouldn't. A trolley isn't person shaped, and can be stored somewhere near the back of the plane (eg where the fuselage tapers) that you couldn't fit another seat even if you wanted to. Why not use the space for something useful?


What is the longevity and replacement schedule for turbine engine blades?

There are two primary modes of turbine blade failure, that can be predicted, and hence are used to determine the lives of turbine blades at which they need to be replaced.

One is called "creep". The Wikipedia article describes the basic mechanism. The life of the blade is purely a function of "time at temperature". If the blades experiences flight time above critical material temperature limits, it accumulates a portion of creep fatigue. The total (cumulative) amount of creek fatigue is tracked, and when the blade hits that limit, it is removed and replaced with new blades. The type of algorithm used to measure creep life is called Robinson's rule, and looks like this (where c1, c2 & c3 are coefficients related to the relative damage that occurs at the associated temperatures):

Total accumulated life = c1 x time above T1 deg + c2 x time above T2 deg + c3 x time above T3 deg.

Typically, each stage in the turbine will have its own life. (Each blade on the same stage is not individually monitored and lifed, but rather they are replaced as a set.)

Another failure mode is low cycle fatigue. This is caused by changes in centrifugal stress, caused by rpm changes from throttle cycles. When the pilot moves the throttle a significant amount, large changes in stress occur. These cause the blade material to behave like bending a wire in your fingers back and forth to make it break (you don't break it by just bending it once, or pulling hard on both ends). LCF lives are counted in a similar fashion to creep, but rather than counting time spent above a temperature limit, throttle cycles are counted. A throttle cycle might be defined as a change in rpm from one specific value to another.

If the engine is modern, the electronic control would count the creep and LCF lives consumed. If the engine is old, and only has a hydro mechanical control, the engine manufacturer will do an analysis on the type of flying the plane is expected to do, and determine the life limits in terms of flight hours. Periodically, they will try and confirm how the plane is actually being flown, and if the flight time before replacement needs to be shortened or can be lengthened. Generally, either the creep life or the LCF life is much shorter than the other, so only one failure mode is tracked for each engine stage.

This document gives a good description of turbine blade failure modes, and how they are monitored. I doubt you get information on actual lives, that is likely proprietary to the engine manufacturer. The only info you might find is probably for very old engines that they don't care about anymore. However, if you are lucky, you might finds some numbers burried in NTSB or other countries aircraft accident reports related to blade failure.

There are also periodic bore scope inspections, that may cause blades to be replaced for unscheduled (unpredictable) failure modes (FOD damage, coating loss, thermal distress) as also mentioned in the above document.


What is the main reason why cruise flight in the transition layer is prohibited?

The main reason for the transition layer is to assure separation between the highest usable altitude (TA) and the lowest usable FL (TRL). That means it has to be at least 1000ft thick.
If the QNH is 1014 or above the transition level is always just 1000ft above the TA (5000ft and FL60) because the whole FL system is shifting upwards above the MSL. This means for each hPa above standard QNH 1013 your transition layer will be about 30ft thicker.

If QNH drops to 1013 or below the opposite happens: The base of the FL system falls below MSL, so FL000 is at -30ft MSL per 1hPa below 1013.

If QNH is 1003, the difference between 5000ft and FL60 is only 700ft because 1000ft-(10hPa*30ft)=700ft. In this case the TRL above TA 5000ft has to be FL70 to assure the separation between highest altitude and lowest FL is at least 1000ft.
So now we have a transition layer with one spare FL - FL60. If one would now fly at 6000ft we only have the above mentioned 700ft to FL70; if one would fly at FL60 only 700ft to 5000ft. This is why the transition layer may not be used for cruise flight


Can I stop crop dusters repeatedly flying over my home?

In a rural area pilots can fly pretty low, and are permitted to fly even lower while carrying out a lawful activity such as crop-dusting. Even if the pilot flew at 500 feet above your house, which is probably the maximum that he needs to stay away, it would still be loud and disturbing to your livestock.

You should try to work it out with the company and/or the pilot in an amicable way.

Unless your house is located in a congested area, the minimum altitude the pilot must maintain is 500 ft. However, if your house is located in a sparsely populated area, the pilot may be able to fly much lower than that. However, while the pilot is in the process of spraying, or turning around to spray he is allowed to fly lower than that minimum. Otherwise, the pilot may have to do dangerous steep climbs and descents.

For example, lets say the pilot is in violation of minimum altitude regulations by flying over your house at some minimal altitude below 500 ft. Lets assume you get the pilot busted and the pilot receives a warning, citation, or temporary suspension. When he comes back he can just fly over at 500 ft legally all day long, and that will probably be almost as noisy and disturbing to your livestock.

Alternatively, you can lease a small part of your land to AT&T to put a 1000ft tall cellular antenna on your property.

But seriously, as a pilot, if I heard that my flying was causing you so many problems, I would try to avoid it as best as possible, so long as it doesn't affect safety.


Why is induced drag less on a high span wing?

You start from wrong assumptions, which explains your doubts. The line

  the induced drag is due to the tip vortices

is as true as saying that wet streets cause rain. Also, the opinion that the

  tip vortices strength will be as same as the bound vortex

is wrong. Unfortunately, many authors don't understand the topic themselves and copy what others have written before without thinking the issue through. Ideally, you would forget about all what you have heard about vortices and lifting lines, but since you ask I will try to explain potential flow theory a little.

In potential flow theory, lift is caused by vortices which are caused by the movement of a wing through air. These vortices run along a closed line: Within the wing they form the bound vortex, then they leave the wing backwards as trailing vortices and are connected at the point where the movement started by the starting vortex.

Now comes the important part which most authors conveniently leave out: There is no single vortex; instead, potential flow assumes an infinite number of infinitesimally small vortices which form out of nowhere when lift is increased or speed is reduced. Consequently, no single vortex leaves the wing at the tips, instead, a sheet of vortices leaves the wing at the trailing edge. The change in strength of the bound vortices over span is equivalent to the strength of the vortices leaving the wing, so the vortices fade out towards the tips.

My advice is: If you do not want to operate or to write a potential flow code, do yourself a favor and forget all that. It is much better to interpret lift as the consequence of a pressure field around a wing which accelerates the air flowing around this wing downwards. Induced drag is simply the component of the resulting pressure forces parallel to the direction of movement, while the perpendicular component is lift. Please make sure to follow at least the last link; it gives a very good explanation what induced drag really is.

Tip vortices are the consequence of air filling the void above the downward moving air behind the wing. They are not originating from the wingtips, but the consequence of the vortex sheet rolling up (if you want to stay in that picture). Note that the distance between the cores of the vortices is much smaller than the wingspan. For an elliptic wing of span $b$, it is actually only $\frac{\pi}{4}\cdot b$

A higher wingspan allows to capture more air for lift creation, so less downward acceleration is needed. Lower downwash speed also causes a less powerful trailing vortex. Note that the mass of air affected by the wing grows with the square of the wingspan!


What would an all-flying aileron look like, and would it be a good idea?

The word aileron specifically refers to a part of the airplane, usually, but not always, connected to the back edge of the wing, that is used to control roll and to turn the aircraft when used in conjunction with the rudder.

The British Army No. 1 was based on the Wright Flyer design, and while some early airplanes did incorporate wing-warping to bend the wing itself instead of using ailerons, the No. 1 actually incorporated separate ailerons, mounted above and in front of the leading edge of the lower wing.

Perhaps, instead of aileron, you meant to say wing or airfoil. In that case, several examples exist of modern flying-wing aircraft, such as this B-2 Spirit, which designs the entire aircraft as one large airfoil.

UPDATE
Wing-tip ailerons were utilized in some designs, such as this Stout Skycar.

NASA did testing on this aileron configuration to determine whether or not this design would counteract the adverse yaw effect of traditional aileron placement. When ailerons are behind a wing with a large upper camber, it can partially shield the aileron that is deflected up, reducing its effectiveness. Moving the ailerons to the wingtips proved to significantly mitigate this issue, although not entirely - this due to the interference between the outer edge of the wing and the inner edge of the tip aileron. Nevertheless, there were also significant problems. The NASA study showed a substantially reduced rate of climb compared to traditional trailing-edge aileron. Additionally, there was a near doubling of drag from each wing, largely due to vortex generation caused by the necessary gap between tip aileron and wing. Further, while a traditional aileron may utilize multiple hinges, a tip aileron was pivoted on a shaft, where torque loading and flex became an issue. Finally, when connected via direct linkage, researchers observed that control loads felt at the yoke were often up to 3 times heavier than for conventional ailerons.
Here is an article by Bob Whittier explaining more.


How frequently are airplane windows cleaned?

I clean them whenever they are dirty to the point of affecting ability to see traffic or cause distractions.

Bugs, dust, and dirt can make it very difficult to spot traffic, birds, and obstructions, especially in hazy weather.

It is the pilot’s responsibility to “see and avoid” and clean windows play a large role in this critical safety area.

Depending on how bad contaminants are (i.e., if it’s bug season) the interval for cleaning could be as often as every flight or as little as once every few days while continuous flight operations are in effect.

Windows are cleaned with either water or special chemicals for cleaning plexiglass with microfiber or non-abrasive cloths. Also of note, human fingerprints are ideal for cleaning aircraft windows with water as they are soft and do not scratch, but the ridges pick up the dirt and easily rub off even sticky contaminants [bugs]. Aircraft windows are relatively soft and scratch very easily. All cleaning motions are done in the direction of the airflow to prevent hazing of the window from scratches... no circular scrubbing - only in the direction of air flow. Passenger windows rarely get dirty. It’s the ones for the cockpit that are directly exposed to the frontal airflow that get the worst of it.

I usually use water, my fingerprints for scrubbing, and clean microfiber cloths for drying to prevent water spots - which can obscure vision as bad as dirt.

Here is a video of the process.


At a non-towered airport in the US, what should I do if I hear a medevac flight waiting to take off while I'm turning base?

The most obvious thing to me would be to just talk to them:

  Medevac 123, this is the Diamond on base for 31, do you need to expedite your departure?

If they say no, then just continue and land as normal. If they say yes, then I'd get out of their way:

  Medevac 123, roger, we'll extend our base and fly a wide upwind to let you  out

I wouldn't worry about standard phraseology too much, the critical point is to make sure you both understand each other and if there's no well-established phrase for what you need then just say whatever seems clearest.

Extending base to upwind has the advantage that it keeps you in the pattern so you can see what's going on as the medevac flight departs and you don't waste too much time going around the pattern again. (Although unless I have an emergency of my own I'm more than happy to make whatever detour is necessary to help out a medevac flight.)

Turning out right puts the pattern behind you and if you turn too early then you're potentially turning into other traffic on a long final, so it wouldn't be my first choice. But I don't think there's any standard way to break off from base and there are lots of possible variables (terrain, traffic, airspace etc.) so it's up to the pilot to decide what's safest at that particular moment.


How do the vortices affect the flow of the horizontal stabilizer upon leaving the wing?

The answer depends on the relative position of both. If the wake from the wing directly hits the elevator, its reduced dynamic pressure will reduce elevator effectiveness.

Next, when near the stall angle of attack, the wing root will already exhibit some flow separation, and the turbulence of that flow will show up in buffeting on the tail. This is sometimes desired as a stall warning, but having the tail move into the wing wake just when the aircraft stalls is generally a bad idea.

To address the lift-related vortices: Those will reduce the angle of attack change on the tail relative to those on the wing. The increased strength of the downwash speed with lower flight speed (and, consequently, higher angle of attack) means that the effective angle of attack on the tail will be reduced. This narrows the range of angles of attack in which the tail needs to work and helps to ensure that the tail will show a linear response to changes in the flow even when the wing leaves the linear range already (in other words: When the wing stalls.)


What are typical resins used in carbon fiber for aircraft? Are any resins impossible to recycle?

This will give you some detail on thermoset resins, which solidify through chemical reaction. In summary:

Epoxy is the primary resin used in aerospace, at least for structures, as it is strong and wear resistant.
Phenolic is the primary non structural resin used in aerospace, as it is fire resistant. This is important in aircraft interiors.
Polyester is cheaper than epoxy but weaker, so it shows up in less structural or weight critical applications. Boats might use this.
Vinyl ester is somewhere in between epoxy and polyester, so not as good as either. I have never used this.
Bismaleimide (BMI) is used for high heat applications where maintaining strength is important. This is a slightly less expensive member of the Polyimide family, used for similar purposes.
Cynate ester apparently has military applications, with which I am not familiar.
PEEK as suggested in comment, is the only thermoplastic in this list, which is formed by melting and solidification as by injection molding. It can be recovered for reuse with reduced mechanical properties.

Thermoset resins are generally not recyclable. When composites are intended for recycling the fibers are the object, not the resin. The resin has to be burnt or dissolved away, creating an emissions problem that needs to be dealt with.


Why did the pilot inform ATC that he is going to autoland?

From what you said, I'm assuming that the pilot had informed that he/she is going to autoland under VMC.
The main reason is that the autoland procedure requires accurate guidance and the ILS signals may be disturbed by the traffic (both surface and air). So, the pilots want to inform the ATC that they want undisturbed signal. From a Flight Operations Information leaflet from CAA, Qatar:

Most ILS installations are subject to signal interference by either surface vehicles or aircraft. To prevent this interference ILS critical areas are established near each localiser and glideslope antenna.
The ILS sensitive area is protected from all surface vehicles and aircraft when ILS Category II or III operations are conducted or anticipated.

These disturbances may happen when Low Visibility Procedures (LVPs) are not in force and may cause problems for the approaching aircraft:

When the LVPs are not in force, ILS beam bends may occur because of vehicle
or aircraft interference. Sudden and unexpected flight control movements may occur at a very low altitude or during the landing and rollout when the autopilot attempts to follow the beam bends.

Due to these reasons, it is better for the pilots to inform the ATC about their intention to autoland so that appropriate measures can be taken or if it is not possible, the same can be relayed to the approaching aircraft.

The ATC should be informed about the intention to conduct an autoland. Such
information should not be taken as a request for or expectation of the protection of the ILS but is merely given to enhance the possibility for ATC to inform the flight crew of any known or anticipated disturbance.

Also, the ATC has to adjust the aircraft spacing if autolands are being conducted, which may affect the operations.


Where are jack points typically located on an aircraft?

Yes indeed, at strong points such as landing gear structure, engine support, or wing strut. The jacks need to be out of the way of the swinging doors of course, but as close as possible to the fuselage.

This one has a special design man leg jack.


What US customs procedures must the pilot of a private aircraft follow when traveling in and out of the country?

General

Each person leaving the country must be authorized to return to the US.  (ie. they are a US citizen or their visa allows them to leave and return to the US.)
Ensure that you have all required paperwork

Pilot license
Medical
Aircraft Registration
The aircraft must have a current customs decal.

Ensure that the aircraft is properly equipped

12" Registration Numbers
Transponder

Before Leaving the US

File eAPIS

eAPIS is required to be filed at least 60 minutes prior to your departure.
Other third party services (ie. FlightPlan.com, etc.) may make this easier if you do it a lot.

File an international flight plan

May be an instrument or a defence VFR flight plan

Before Returning to the US

File eAPIS (see above)
File a flight plan (see above)
Notify customs and obtain permission at least one hour prior to landing in the US.  Record the initials of the customs officer that you spoke to just in case they misplace your notification.

Note that if you are coming from locations "south of the US" (for the specific definition, see here), you must stop at the designated airport closest to your point of border crossing to clear customs (unless you have an overflight permit).

Upon Arrival in the US

You must land at an airport of entry.
Report immediately to the designated customs location
Do not allow anybody or anything to leave/enter the aircraft until the customs official gives your permission

The only exception that I know of to this are the South Florida airports where you are expected to take all people and belongings into the customs facility for inspection.

Discard any international garbage in the approved manner.
Provide required paperwork

A Customs Declaration for each arriving family

Wait for customs to specifically tell you that you are cleared before you attempt to leave.

Notes

This is not all-encompassing, please help add to and expand this list so that others may learn from our experience!

A TON of useful information is made available by the FAA in the Guide for Private Flyers.


What are the restrictions on performing intentional spins?

There are at least three FARs that apply (maybe more?). First, "aerobatics" as defined in 91.303 seems to include spinning:

  For the purposes of this section, aerobatic flight means an
  intentional maneuver involving an abrupt change in an aircraft's
  attitude, an abnormal attitude, or abnormal acceleration, not
  necessary for normal flight.

That means the general restrictions in 91.303 would apply:

  No person may operate an aircraft in aerobatic flight—

  (a) Over any congested area of a city, town, or settlement;

  (b) Over an open air assembly of persons;

  (c) Within the lateral boundaries of the surface areas of Class B,
  Class C, Class D, or Class E airspace designated for an airport;

  (d) Within 4 nautical miles of the center line of any Federal airway;

  (e) Below an altitude of 1,500 feet above the surface; or

  (f) When flight visibility is less than 3 statute miles.

Second, spinning an aircraft not approved for spinning in the POH would be a violation of 91.9:

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

  (a) Except as provided in paragraph (d) of this section, no person may
  operate a civil aircraft without complying with the operating
  limitations specified in the approved Airplane or Rotorcraft Flight
  Manual, markings, and placards, or as otherwise prescribed by the
  certificating authority of the country of registry.

Finally, 91.13 would also prohibit spinning a non-certificated aircraft because it's a 'catch-all' regulation:

  §91.13   Careless or reckless operation.

  (a) Aircraft operations for the purpose of air navigation. No person
  may operate an aircraft in a careless or reckless manner so as to
  endanger the life or property of another.

But spinning itself is absolutely legal and is required for a flight instructor rating as described in 61.183.

EDIT: there's also a requirement in 91.307 that if non-crewmembers are on board then parachutes are required for maneuvers with 'extreme' bank or pitch, unless the flight is a test or training flight:

  (c) Unless each occupant of the aircraft is wearing an approved
  parachute, no pilot of a civil aircraft carrying any person (other
  than a crewmember) may execute any intentional maneuver that exceeds—

  A bank of 60 degrees relative to the horizon; or
  A nose-up or nose-down attitude of 30 degrees relative to the
  horizon.

  (d) Paragraph (c) of this section does not apply to—

  Flight tests for pilot certification or rating; or
  Spins and other flight maneuvers required by the regulations for
  any certificate or rating when given by—

  (i) A certificated flight instructor; or

  (ii) An airline transport pilot instructing in accordance with §61.67 of this chapter.


The lower surface lift vector points downwards in the diagram, not upwards.  The nett lift is the sum of the two lift vectors, and since the lower surface lift vector is opposite to the upper, nett lift is upper surface lift minus lower surface lift.

The nett lift points upwards in the top figure, as the upper surface lift is greater than the lower surface lift.

In the middle diagram, both upper and lower surfaces have the same lift magnitude so the nett lift is zero.  Note that the chord line of the symmetric airfoil is parallel to the airflow.  This wing section has zero angle of attack (angle between the airflow and the chord line), so both the upper and lower surfaces have the same angle of attack and generate the same lift, cancelling each other out.  On the cambered airfoil, the angle of attack is slightly negative for zero nett lift.  This is because the camber causes the upper surface to generate more lift than the lower surface for a given AoA.

In the lower diagram, the upper surface has an increased angle of attack, while the lower surface has a decreased angle of attack.  So the lift of the upper surface is increased and that of the lower surface is decreased, and the nett lift is upward.

Note that the terms "up" and "down" have to be used carefully, since we usually use those terms in the context of gravity.  A lift-producing airfoil has no concept of gravity, only of angle of attack.  The airfoils in the diagram would produce the same lift with respect to the angle of attack regardless of the orientation of the airfoil with respect to gravity.  If you turned any of these diagrams upside down, the airfoils would produce exactly the same lift with respect to the surface as they did in the original ("upright") orientation.


Why are the 747-8 engines placed differently than on the older versions?

On the 747-8 the engines are heavier and mounted farther ahead of the wing. This results in a torsion moment which reduces the incidence of the wing. As a result, even the unloaded wing will have a lower incidence than that of the older 747-200.

Boeing 747-346 of Transaero (picture source). Note that the engines are no longer tilted up (and consequently the wing tip is tilted leading edge down). The lift force twists the wing such that the incidence in flight is lower than when unloaded and on the ground, especially when the high-lift devices are extended.

Also please make sure to read @Lilibete's answer. I don't know who thought it appropriate to downvote it - it contains another reason for the change in inlet angles, namely the difference in avoidance strategies for foreign object damage.


Does Flight Following automatically include permission to fly through class C or D airspace?

Lets back up a minute and discuss what is required to enter C and D airspace.
For C and D airspace you must establish 2 way radio communications with tower or approach controller. Let's first discuss how this works if you are not taking Flight Following. As you approach Class C airspace you hail them and wait for a response, for example,

You: "Allentown Approach Piper 1234J @ 3000 en route to Queen City Municipal"
Controller: "1234J Squawk 1-3-5-2 and Ident"

Since the controller responded with your tail number you may enter the Charlie airspace (Delta has the same requirements).
Now when you are under Flight Following, ATC will coordinate a handoff to the Approach or Tower for the airspace you are about to enter, or ATC will say "radar services terminated," and you must contact the controller/tower yourself before entering.
You SHOULD NOT change frequencies until you are told to do so, since ATC may be trying to give you a traffic advisory. You can however tune your second radio (if you have one) to the approach/tower you are approaching, and begin to monitor traffic.


What are these blades on the engine cowling of a Wittman Tailwind?

After calling the Florida Air Museum, I have discovered that this seems to be a local mystery to the employees at the facility, as well. The museum’s director assumed that they “were an attempt to counteract P-factor or torque. Something to do with balancing required power.”
Since this was little help, I did some more digging and decided that the “blades” on this Wittman seemed to function as adjustable strakes - albeit located far from any control surface and of dubious utility.
Finally, I discovered that there have been numerous experiments performed with ‘Actuated Forebody Strakes’ aimed at controlling forebody vortices as a means of complementing thrust vectoring. Additionally, a NASA study found that a large increase in yawing moment may be brought about through the manipulation of actuated forebody strakes.
In every case that I could find, the tests were concerned with fighter jet aircraft operating at high angles of attack, but it is conceivable that the owner of this Wittman W-8 was attempting to implement some of the same advantages here.
Here are the abstracts to the vortex thrust vectoring and NASA yawing moment studies:

The desirability to enhance the controllability of fighter aircraft at high angles of attack, particularly yaw control, has fostered an interest in both vectored thrust and active control of forebody vortices... The methods investigated include pneumatic or blowing techniques using surface mounted jets and slots, surface suction, variable-height deployable strakes, and rotatable-tip strakes. Flow visualization, and force and moment measurements have shown that all of the methods are effective at manipulating the forebody vortices over a wide range of angles-of-attack and sideslip, primarily through control over flow separation on the surface of the forebody. All are most effective when applied near the forebody tip.

Extensive pressure measurements and off-surface flow visualization were obtained on the forebody and strakes of the NASA F-18 High Alpha Research Vehicle (HARV) equipped with actuated forebody strakes. Forebody yawing moments were obtained by integrating the circumferential pressures on the forebody and strakes. Results show that large yawing moments can be generated with forebody strakes. At angles of attack greater than 40°, deflecting one strake at a time resulted in a forebody yawing moment control reversal for small strake deflection angles. At α = 40° and 50°, deflecting the strakes differentially about a 20° symmetric strake deployment eliminated the control reversal and produced a near linear variation of forebody yawing moment with differential strake deflection. At α = 50° and for 0° and 20° symmetric strake deployments, a larger forebody yawing moment was generated by the forward fuselage (between the radome and the apex of the leading-edge extensions), than on the radome where the actuated forebody strakes were located.

References:
Malcolm, G., & Ng, T. (1990). Forebody Vortex Control as a Complement to Thrust Vectoring. SAE Transactions, 99, 1515-1543. Retrieved August 16, 2020, from Journal of Aerospace
Fischer, D.F., Muriel, D.G., & Lanser, W.R. (1996). Effect of actuated forebody strakes on the forebody aerodynamics of the NASA F-18 HARV. NASA Technical Memorandum 4774. Retrieved from NASA.gov


Can aircraft ferry engines for other types of aircraft?

Yes.
The Antonov 124 regularly ferries even the largest engine, the GE9X, internally. Нема проблем!

GE9X being loaded into the An-124 (picture source)


Why does "no aircraft cross directly over the pole"?

This article from AA (titled "Over the Top" by Gerard J. Arpey) says,

  By the way, because of the limitations of older navigation systems, none of the polar routes we fly crosses exactly over the North Pole. At the Pole, an airplane’s compass changes from a due-north heading to due south, and that change of course could potentially lead to problems with earlier-generation autopilot systems. Fortunately, that is not an issue with the latest generation of long-haul aircraft, such as the Boeing 777s we fly, whose source of navigation is the extremely precise Global Positioning System (GPS). Nonetheless, to make polar flying equally effortless for both the new generation and the previous generations of aircraft, none of the approved civil polar routes comes closer than about 60 nautical miles from the Pole.


At what altitude might a pilot be able to see at least the brightest stars during the day?

SR-71 pilots saw the stars, but of course there is no account of the exact height, they started to see them. They were flying around at 80000 feet at some point in their mission profile. Basically you have to get above most of the atmosphere. So you should start to see stars above 43000 feet. Of course there are some other options, you see them during an eclipse or above the Arctic circles in the right season. You can always see the stars, if you know where to look and if you have a telescope, but I presume you mean to see them with the naked eye?


Viability of Magnetically started engines

Three things come to mind:

Magnets are heavy.
Not all compressor and turbine blades are ferro-magnetic.
The starter would only start the engine, and then be dead weight.

Usually, new designs are implemented when they have clear advantages over previous solutions, but I cannot see what problem this would solve. The APU is a very versatile and lightweight piece of equipment that can power up all of the systems of an airplane. Not really anyone's prime target for replacement, I reckon that captain Sully would agree.


What role did the RAT (Ram Air Turbine) play on US Airways flight 1549?

The full NTSB report can be found here and is the official source of information on the incident. According to that report Sullunberger did immediately start the APU which did deliver power and they determined they did not need to manually deploy the RAT. However the onboard systems deployed it automatically likely as a result of the initial power loss and sufficient airspeed (over 100Kts).

  Regarding step e, the pilots stated that they determined that
  electrical power was established and, therefore, that the RAT did not
  need to be manually deployed. Further, immediately after the loss of
  engine thrust, the captain started the APU.

This can be heard in the official transcript

  At 1527:14, the first officer stated, “uh oh,” followed by the captain
  stating, “we got one rol- both of ‘em rolling back.” At 1527:18, the
  cockpit area microphone (CAM) recorded the beginning of a rumbling
  sound.

  At 1527:19, the captain stated, “[engine] ignition, start,”
  and, about 2 seconds later, “I’m starting the APU [auxiliary power
  unit].”5

  At 1527:23, the captain took over control of the airplane,
  stating, “my aircraft.”

However the RAT was found to be deployed (due to the automatic systems on the aircraft) when the airframe was recovered

  When all of the airplane’s electrical power is lost and the airplane
  has an airspeed greater than 100 knots (kts), the RAT will
  automatically deploy and begin providing electrical power. The RAT was
  found in the extended position when the airplane was recovered from
  the water.


Why can’t the newest high-bypass turbofans run at their EPR, temperature, and RPM limits simultaneously at sea level?

What makes it impossible for very new turbofan designs to reach all three redlines simultaneously at sea level?

The implication in your question is that GE9X was not able to reach all three redlines simultaneously but that previous engines (e.g. GE90, GEnx, LEAP, etc) could.  That is incorrect.  Those engines could not reach triple redline either. At least not, type design unmodified.  The engines that were used to demonstrate compliance to FAR 33.87 for those engine programs were modified from their type design in order to be able to reach triple redline. Very heavily modified.

To understand why, let's talk a little about engine performance.  The three variables of N1, N2, and EGT are controlled by several conditions: the throttle setting, the ambient temperature, the ambient pressure (i.e. altitude), the forward velocity, and the deterioration of the engine (e.g. how worn out the seals are).  Now, if we are doing this test on a test stand (as opposed to flying it), then we really only have control over one variable: the throttle.  Everything else just is what it is. It shouldn't be too hard to see that you can't control 3 variables precisely with just one knob (E.g. imagine in your bathtub or shower you try to control both the water temperature and water flow rate with just one knob. You can't do it.  To control 2 variables, you need 2 knobs).

More specifically, considering sea-level static conditions, if the ambient temperature is cold, then the air is dense, so the fan pumps a whole lot of mass with every revolution and makes a lot of thrust.  You have to burn a lot of fuel to do that.  So you'll hit EGT limit first before you get anywhere close to N1 redline.  If the ambient temperature is hot, then the fan doesn't pump as much per revolution, so speed needs to be really high in order to make any kind of thrust.  You'll hit N1 redline before you hit EGT redline. You can presume that there should be one magic temperature where you could hit both of those at the same time, but if you just sit around and wait until the weather hits the exact right temperature you wanted and stays there for 150 hours (the length of the test), you'll be waiting a long time.  And even then, you still won't get to N2 redline at the same time.

Ok, so how would you run a triple redline test then, given that we can't control ambient temperature? Well first you'll need to way to vary the thrust the fan produces.  E.g. you could use a variable fan nozzle.  On a cold day, you open up the fan exit area so you can get to higher N1 speeds with less thrust, and on a hot day you throttle it down.  There are other options but this is easiest to explain.  Then you need to control N2.  The easiest way here is to open or close the variable stator vanes.  This has the effect of making the HPC do more or less work per revolution, so you can tune in the exact speed you want.

Ok, so we added a variable fan nozzle and a different VSV schedule, and we are at triple-redline.  Problem solved right?  Wrong.  Jet engines are extremely complicated devices with all kinds of interdependent requirements.  If you change one thing, you end up affecting other stuff.  Changing the VSV schedule might introduce aeromechanics issues onto the HPC blades, or change the cooling flows to different portions of the turbine.  So then you have to make other modifications to the engine, like changing the sizes of all of the different cooling pipes so you get back to the original flow rates you wanted.  But then, those changes also have other effects, which snowballs.

Historically (I mean like 1970s 1980s) the engine companies could make a few small changes and hit triple redline.  As the engines became more and more complex, more and more changes were required. At some point, the list of changes required to make the engine hit triple redline is so big that the thing you are testing is a crazy chimera of an engine that has only a faint resemblance to the actual type design.  At that point, running a triple redline test no longer makes sense.  That's what happened with 9X. Therefore, GE found an alternative way to satisfy the endurance test requirement.


How many flights can be made under EASA permit to fly?

Assuming you mean a temporary Permit to Fly (rather than a 'permanent' one) for an aircraft normally flying under a C of A, then this site states that:

  You will be required

  to supply a validity period while completing the application.
  Temporary permits are usually issued for less than a month, but you should allow enough time for the flight to be conducted, taking into account weather conditions etc.

I'd guess it is intended for an aircraft to be ferried in order to renew its C of A or at the end of its operational life?


What is the equivalent height of a parachute landing?

As you have intimated in the question, how hard you hit the ground is very dependent on a number of factors.

When I did my training to jump using a classical tethered round chute we practiced landing from a platform of about 5 feet, so six is perhaps a hard landing. That's, roughly, hitting the ground at 12mph.

Folks like the Red Devils typically use an parafoil chute. Basically a self inflating wing. These can be steered and pitched upward to bring the trooper to a stall or even go up if they have enough forward velocity. So yes, you will often see them stop in mid-air and step down. This means this type of parachute has NO equivalent jump height. In fact if flown incorrectly you can crash into the ground at serious speeds.

Regular "military style" parachutes provide no control over lift and only minor control over direction. With these your descent rate is totally dependent on size, weight and air quality.

Interestingly, with a regular chute, what makes landings "harder" is not so much the effective height but the amount of horizontal velocity.

You are trained to drop and roll when you hit the ground to absorb the impact.

This works great if you have any horizontal velocity to help you initiate the roll. If however you are coming straight down it's not so easy.. and your knees end up in your chest...  as I found out the one and only time I jumped out of an aging Cessna.  Too much horizontal velocity and that roll gets rather violent.


Are Belarusian ATC recordings available for Ryanair Flight 4978?

Not every country allows recording and publishing of ATC communication. The UK for example does not: Is it illegal for Joe Public to listen to ATC in the UK?
While I don't know for sure, I'm guessing Belarus does not allow it. LiveATC has a coverage map, which shows the destination airport EYVI (Vilnius) is covered, but nothing in Belarus is:

I therefore doubt you will be able to get the recording. Since the incident is currently being investigated by multiple countries and organizations, a recording or a transcript might be available in the future as part of the investigation report.


How much drag does a RAT deployment add?

Since he doesn't manage to make it back to the runway from his 2000 ft engine flameout run I was wondering if not deploying the RAT would make any difference due to reduced drag?

No, because it deploys automatically. Note that in the video in the first attempt the step is not done because there is less time. It is probably included in the checklist just in case the automation didn't do it's job.

Nevertheless, let's try to estimate the drag. All I could quickly find about the RAT is that the attached electric generator provides 5 kW, but that should be enough. We need to take into account the hydraulic pump and power losses, but the generator wouldn't be insignificant part of the load, so we could guess that the turbine does not have more than 50 kW of drag.

Now potential energy is $E_p = mhg$, differentiating by time we get $P = v_{vert}mg$ and solving for vertical speed $v_{vert} = \frac{P}{mg}$. Taking some “median” weight of 60 t (A320 has MZFW 62.5 t and MLW 66 t) and substituting we get:

$$v_{vert} = \frac{50\ \mathrm{kW}}{6\cdot10^4\ \mathrm{kg}\cdot 9.8\ \mathrm{ms}^{-2}} \approx 0.085\ \mathrm{ms}^{-1} \approx 17\ \mathrm{ft/min}$$

So the deployed RAT increases the rate of descent by less than 20 ft/min.

Now the video mentions the best glide speed would be 205 knots (I suppose it is for the 1+F configuration; for clean it sounds too low, though I don't have a reference for this). Since the L/D ratio is around 18, that would give the total descent rate about:

$$v_{vert} = \frac{205 \mathrm{knot}}{18} \approx 11 \mathrm{knot} \approx  1150 \mathrm{ft/min}$$

Except, well, 18 is clean L/D. The L/D at 1+F is a bit lower. I don't have reference for that either, but something like 10–12 sounds right, so:

$$v_{vert} = \frac{205 \mathrm{knot}}{12} \approx 17 \mathrm{knot} \approx  1730 \mathrm{ft/min}$$.

That is about 100 times more. So the RAT might increase drag by 1%. It was very rough estimate, so it may be 2% or 0.5%, but it definitely isn't that significant.

  Would the on-board batteries and windmilling engines be able to provide sufficient power for control surfaces?

The training manual mentions that

  If engine wind milling is sufficient, additional hydraulic power may be recovered.

without saying at what speeds that would be, but generally the speed for wind milling engine restart are significantly higher that the best glide speed. I'd say the necessary speed would be more than 250 knots.

  Also, are there real life incidents of a 2000 ft (or lower) dual engine failure that made a safe return to the runway? Sully Sullenberger's A320 had reached approx. 3,000 ft, yet he was forced to ditch rather than return.

I can't find any other incidents involving dual engine failure on A320-family aircraft besides US Airways 1549. And I am not aware of any incidents on any other aircraft that would fit that criteria either.

It should however be noted, that flight 1549 likely had enough altitude to return to the runway—if the manoeuvre was executed perfectly. A small mistake and they'd crash into populated area since the airport is in the middle of a city. The Sullenberger's great airmanship was in that he chose the worse option that he was certain he can make over the better option where he was not.

  Does the energy management differ drastically from type to type? i.e. Among dual engined aircraft would some be easier to land from a 2000 ft dual engine failure than others?

Principally it's the same for any type. But since turn radius increases drastically with speed, slower aircraft can turn faster and thus could return from lower altitude.

Here's a related question that discusses the manoeuvre; and it's dangers: Is it even remotely feasible to turnback a single engine aircraft with an engine failure?


Which fixed-wing aircraft has the highest number of required flight crew members?

The Antonov An-225 Mriya requires a crew of six- you have the pilot, copilot, 2 flight engineers, navigator and a communications specialist/radio operator.

An-225 cockpit; image from sas1946.com


Do some flying techniques wear aircraft out quicker than others?

Let’s start out by agreeing that “Flight” got lots and LOTS of details very very wrong in more ways than 1 thread can list.  Any pilot who did a tiny fraction of what the “hero” does in that movie would be reported, and drug/alcohol tested, and fired, in very very short order.  Whoever decided to write a script with that sort of thing going on as its premise, has his head planted very firmly in an alternate reality to the one that the rest of us live, and fly, in.

That out of the way, let’s talk about the specific questions asked, starting with the “dramatic takeoff.”  In the military, there can be missions where “you do have to go out, you don’t have to come back” — i.e. your chances of survival may not be very good, but this is war & you’re going to launch. In the airline world, the reverse is the case: takeoffs are optional, landings are mandatory.  If you don’t see the path for the whole flight being completed safely, you don’t take off. Period, dot, end of story.  There is no airline flight out there these days that is “the last flight out of Saigon” (where you’re going to attempt the takeoff because the alternative is just too awful).  If the weather around your departure airport is dangerous, then you wait until it isn’t.  If you think you’re going to need “macho maneuvers” to get out of town, you have no business taking off.

There will be times when what looked like a decent ride turns out not to be, or you knew that the ride would be somewhat bumpy & things turn out to be worse.  That’s the limitation of how much information you have about the atmosphere.  And yes, you will be working to find a better ride.  However…

There is nothing particularly exciting about finding a better ride — it’s simply the same sort of climb or descent that’s used getting to and from cruise altitude. And changing course to find a better ride will be the same 20-30 degree bank turn that everything else is maneuvering the airplane. Nothing dramatic, nothing macho, nothing wild.
Also, if the unexpectedly bad ride scares the passengers, well, that’s the way things can go, but if what the PILOT is doing is scaring the passengers, then HE IS SCREWING UP!  There is essentially no scenario you can come up with where doing something that scares the passengers is the right answer.  If you got to the point where something “scary” is required to avert disaster, then either you’ve had the one-in-a-million combination of bad things happening to you, or else you screwed up by letting yourself get to that point.  (Okay, rolling inverted in the movie to control the uncontrollable pitch is in that sort of category. Could that have actually worked for the Alaska flight? No idea. But that’s how creative you have to get to come up with any sort of scenario which such crazy behavior makes sense.)

If the copilot is telling the captain that he’s flying too fast, then one of two things is going on: either the copilot doesn’t understand what is & isn’t “too fast” (which can happen), or else the captain is, in fact, flying too fast.  And any captain that makes very many copilots uncomfortable like that is going to be having a talk with his Chief Pilot before very long.

  “Do pilots flying commercial airliners feel or have a responsibility
  not to subject a machine to extreme mechanical stresses…?”

Yes, absolutely. And the Flight Data Recorder will record what happens. If you do something that grounds an airplane for an inspection and/or repairs, you’ll probably be explaining yourself to somebody before too long.  More than that, you have a responsibility to your passengers to give them a safe flight, as comfortable as possible, with as little drama as possible.  And sometimes that means that things won’t happen on schedule, because we’re going to wait out whatever adverse weather condition is out there.

  “ … or is the assumption that nothing they can really do has not been
  foreseen by the designers?”

Airliners today are pretty tough, but a sufficiently negligent pilot can mishandle them to the point of catastrophic failure. (Fly-by-wire gives some protections in this regard, but also allows for failure modes that are easier to catch in non-FWB aircraft — Air France 447 as an example of the latter.)  The designers known that somewhere in the aircraft’s lifespan, the flaps will be oversped, and there is ample safety margin there.  But if you go pulling 9 G’s on a full airliner, the designers can’t help you, and you are absolutely beyond any margins they gave you.

In general, the range of techniques that 99.9% of airline pilots will use won’t greatly affect the service life of an aircraft. It will be limited (typically) by pressurization cycles more than by anything else.  And that’s because the culture IS to keep things safe, and calm, and as smooth and as low-drama as possible.

Did I mention that “Flight” really is about an alternate universe mostly unrelated to our own?