What kind of motion will an airplane enter into when disturbed?

The separation into short-period and phugoid motion is somewhat artificial. There is just motion. It just happens that when you fly a 'real' airplane (or solve its equations of motions), you'll have quite different timescales for angular motion (isolated pitch; low seconds) and linear motion (changes of altitude and speed; tens of seconds and even minutes).

Broadly speaking, heavier and faster airplanes with swept wings demonstrate more of this separation. At the other end of the spectrum, smaller airplane models have similar timescales for both the short- and long-period motion, and for them the separation is not meaningful (which makes it more difficult for analysis!)

So, to answer the question, both will usually occur. In some cases, depending on the airplane and your point of interest, you can ignore one or the other. On airplanes where separation is significant and motion is stable and well damped, it may also be possible to produce a disturbance that results in (practically) one kind of motion: either short-period (e.g. a small elevator impulse) or long-period (e.g. a brief application of pitch-neutral air brakes).


How high do they cut the grass on airports?

It depends on the type of bird and mammal species in native to the area and also the type of grass used in turfing; some of them may not survive if mowed very closely. FAA's Wildlife Hazard Management Manual concedes:

  Species-specific responses may be expected.  ...  Airport managers
  need to work with airport wildlife biologists to determine what species of concern in regards to aircraft safety are in their area and what the habitat needs are for those species.

For most airports, FAA recommends a height of 5-8" of grass.

  Considering bird, mammal and vegetation limitations, mowing at least monthly at a target of 5 - 8 inches may work in many airport environments as
  part of a wildlife hazard management program. ... Mowing at 5 - 8 inches should also reduce
  small mammal abundance.


Wind tunnel- test section design question?

An open jet wind tunnel has the advantage of giving a smaller effective blockage ratio than a closed jet wind tunnel. Because the jet is not constrained by walls around the jet in the test section, the airflow can distort more than a closed jet wind tunnel - giving the same flow results as a larger closed jet tunnel.
There are however disadvantages with the open jet tunnel, such as the effect of the collector on the flow (this creates a longitudinal pressure differential referred to as "buoyancy"), and the effect of the shear layer that forms at the jet nozzle (the Kelvin Helmholtz instability can create transient flow effects and can be a noise source). When standing in the test section of a running tunnel, there is a lot of secondary airflow outside of the jet because of the open section.
The test section does not need to have a pressure different to atmospheric pressure, and does not need to be sealed. There can be vents in the test or return section of the tunnel, but they may create flow disturbances as well as allowing noise into the test section.
The free shear flow around the edge of the jet can be a source of disturbance for flow in the test section, however tunnels are designed so the disturbance is still far away from the model. Of course there are pressure fluctuations that interact with flow over the model, which are difficult to control. Some wind tunnels are designed with adaptive and slotted walls, which combine the benefits of open/closed sections, however they need much more setup than just putting a model in and turning on the fans.


What is the difference between Boeing 73G, 73H and 737?

There are two main systems of aircraft type designations: IATA and ICAO codes. The ones you mention are IATA codes (all 3-character) and are often used for shortened aircraft type designation in public information.

Both code types are listed here with the corresponding full aircraft types. As you can see, the IATA information covers the type and variant, including some features such as winglets, but not necessarily extended range models or sub-variants with different engines. It also differentiates between freighters and passenger versions.

Despite the additional digit, ICAO codes are less precise and often include several variants such as freighter as well as passenger variants of the same type.

The codes given in your question translate to:

733  - Boeing 737-300
734  - Boeing 737-400
735  - Boeing 737-500
738  - Boeing 737-800
73G  - Boeing 737-700 (7th letter of the alphabet)
73H  - Boeing 737-800 with winglets (8th letter of the alphabet)
762  - Boeing 767-200
763  - Boeing 767-300
772  - Boeing 777-200
773  - Boeing 777-300
777  - ambiguous 777 type

(all passenger aircraft)

Unfortunately, as @Ralph J mentions, it's not always clear which type of code is used. Mostly, a 4-digit-code will be an ICAO code and a 3-character-code will use the IATA system, but because some ICAO codes only contain 3 digits, this isn't always reliable. For example, if you read "DC6", it could be the IATA code and refer to the passenger version, or it could be the ICAO code and you wouldn't know if it refers to the passenger or the freighter version.


Why did Boeing remove the engine chevrons on the 777-X?

The 777X is still in development and it will be powered by the General Electric GE9X (also still in development). The current talk is that GE is working on a proprietary method (has been for 20 years) that will make the chevrons obsolete. Namely the use of an oxide-oxide ceramic matrix composite, which they have unveiled already (October 2013) for the smaller Passport 20 engine.

It's a new material that can withstand very high temperatures, make the elaborate cooling methods a thing of the past, and bring back the mixer seen on old jets (since it can withstand the hotter exhaust of the new engines).

(compositesworld.com)

  The oxide-oxide CMC material replaces what would have been graphite-epoxy components in the Passport 20 – namely, the four-piece panel enclosing the engine core and a nine-piece component called a mixer, says Judd Tressler, director of Bombardier programmes for GE.

Mixing produces a more uniform less turbulent stream, turbulent stream is a lost thrust. Mixer aside, using the CMC in the turbine and combustor will save on wasted bleed air and provide better combustion respectively, both save on fuel (noise) for same thrust. With the noise level brought down, there is no need for the drag-adding chevrons.

  Likewise, GE is also looking to expand the use of oxide-oxide CMCs to other commercial turbofan engines – possibly including the GE9X, in similar regions of the engine as the Passport.


What instruments are used to indicate aircraft attitude in acrobatic airplanes?

The basics:  Acro airplanes don’t have attitude indicators because they don’t need them.  The airplanes are certified at Day/Night VFR flight only and gyroscopic instruments are not required equipment here, not to mention can be precessed and damaged by aerobatic flight.

The only attitude instruments needed here is the horizon itself and the pilot’s Mk I eyeballs to see it.

Sometimes pilots make use of aerobatic sights mounted on the wingtips; these look something like eight spoke cowboy spurs or a 45° right triangle frame and are used to fly certain reference lines during aerobatic flight.

Some acro aircraft do make use of glass cockpits and solid state Attitiude, Heading, and Reference Systems (AHARS) as a safety backup on cross country flights, but they are not used during aerobatic routines.


Why are these spec and serial numbers blank on a part's plate of a WWII US military plane?

I suspect the reason for this has nothing do with aviation and better fits at our history or statistics stackexchange counterparts.

Information about the production capacity of the enemy is of major strategic importance. Using the serial numbers of a relative few aircraft one can make a quite accurate estimate of the total number of aircraft produced. This was found out during world war II and is known as the German tank problem.

What I suspect is that after this methodology was developed, producers were asked to withheld the serial numbers from their products and/or replace them by a cryptographic equivalent.


Where can I get full audio cockpit recordings of all four flights involved in the 9/11 attacks?

The short answer: you can't. Federal law prohibits the release of CVR audio, though transcribed excerpts (if they are relevant to the investigation) are made publicly available once the accident report is released.

See 49 USC 1114(c):

  Cockpit Recordings and Transcripts.—(1) The Board may not disclose
  publicly any part of a cockpit voice or video recorder recording or
  transcript of oral communications by and between flight crew members
  and ground stations related to an accident or incident investigated by
  the Board. However, the Board shall make public any part of a
  transcript or any written depiction of visual information the Board
  decides is relevant to the accident or incident— (A) if the Board
  holds a public hearing on the accident or incident, at the time of the
  hearing; or (B) if the Board does not hold a public hearing, at the
  time a majority of the other factual reports on the accident or
  incident are placed in the public docket.


Other than fighters, which airplanes can fly straight up?

The general answer to your (general) question is: all airplanes can do that. With every air plane you can accelerate to maximum speed pull the stick until you reach 90°.
The problem is that not all planes will be able to recover safely from that maneuver.
Most planes will not maintain enough speed to continue the flight in a controlled manor.
That's why the flight management software of modern Airliners will prevent that from happening.
On the other hand there are quite a lot planes out the able to do acrobatics like this. They have specially designed  aerodynamic behavior and, if powered,  mass/thrust ratio. The powered versions also need special engines that keep running at zero or negative G.

Are you certain that every plane has enough inertia at Vne and enough elevator authority to reach 90° before stalling? – StephenS

My claim holds, when any aircraft can reach a pitch of 90° before its speed is 0 and the pitch rate does not exceed the structural limits of the plane.
When flying strait upward gravity is slowing down the aircraft with 1G (9.81m/s²).
The time to decelerate an aircraft to 0 with 1G is=
t = v/1G

While "rotating" from horizontal flight to 90° angle this deceleration gradually raises.
Therefore real time til full stop is longer. But lets keep the calculation simple.
For a Sailplane (no thrust) like an ASK21 top Speed is 250km/h = 70m/s
t =  70m/s / 9,81m/s²
t =  7,135s

The ASK21 must be able to pitch to 90° in roughly 7 second, which is a pitch rate of 12° per second (and it is, I've done it already... ;o))
Lets recalculate for an A380:
Cruising speed 900km/h = 250 m/s
250m/s / 9.81m/s² = 25s
90° / 25s = 3,5°/s

On a quick search I could not find a resource giving the maximum pitch rate of an A380, but I'm pretty sure it is higher.
Conclusion: The faster the plane the more time is available and the less pitch rate is needed to rotate to 90°.
And yes, I keep my statement that (from a physical point of view) every aircraft can reach 90° pitch. But may not safely recover from it.


Why is the JAC VOR an Initial Approach Fix for the KJAC VORDME Rwy 19 Approach?

It's not an IAF according to the FAA approach plate:

Besides not being identified as an IAF, JAC could only be an IAF if there was a charted course reversal.  As the FAA approach plate specifically says "Procedure Turn NA" that possibility is ruled out.


Is it required to have an alternate airport if you don't have a WAAS GPS?

FAR 91.167 -
(a) No person may operate a civil aircraft in IFR conditions unless it carries enough fuel (considering weather reports and forecasts and weather conditions) to -
(1) Complete the flight to the first airport of intended landing;
(2) Except as provided in paragraph (b) of this section, fly from that airport to the alternate airport; and
(3) Fly after that for 45 minutes at normal cruising speed or, for helicopters, fly after that for 30 minutes at normal cruising speed.
(b) Paragraph (a)(2) of this section does not apply if:
(1) Part 97 of this chapter prescribes a standard instrument approach procedure to, or a special instrument approach procedure has been issued by the Administrator to the operator for, the first airport of intended landing; and
(2) Appropriate weather reports or weather forecasts, or a combination of them, indicate the following:
(i) For aircraft other than helicopters. For at least 1 hour before and for 1 hour after the estimated time of arrival, the ceiling will be at least 2,000 feet above the airport elevation and the visibility will be at least 3 statute miles.

This regulation (91.167) applies to civil aircraft regardless of the equipment used for navigation (e.g. GPS/WAAS).
However, if your aircraft has a properly installed and operated GPS (see the TSO requirements in the AIM/AC references below) you can flight plan to your destination and alternate as follows:

TSO-C129() and TSO-C196() equipped (GPS aircraft) - Either the
destination or alternate, but not both,  can offer only a GPS
approach (no other type approaches need be available)

TSO -C145/-C146 (WAAS Equipped Aircraft) - Both the destination
and the alternate can be airports with only GPS approaches
available.

References: AIM 1-1-17 b 5 c/d, 1-1-18 c 9 a. AND
AC-105A, paragraph 9.5.1


What exactly rotates along the lateral axis? Is 'rotate' mathematically correct?

Yes that is the lateral axis of the aircraft.
The aeroplane rotates about the lateral axis, causing the nose to go up/down. The aeroplane then descends or climbs, causing the aeroplane axes to shift relative to earth axes. But the aeroplane axes are all defined relative to the aeroplane.


Did any VTOL aircraft implement an airfoil with engine-blown exhaust?

Near as I know every attempt to do so has never worked out.   It’s a very enticing design on paper but has always been a disappointment in real life. One of the best examples was from the 1970s. Designed as a supersonic replacements for the AV-8A Harrier, the Rockwell XFV-12A attempted to use this scheme for a vertical lift system.   Unfortunately it never met the design metrics, and the program was ultimately canceled.

Source: boxartden.com


Is the shape of the Bell X-1 wing on Virgin Galactic's VSS Unity's artwork correct?

According to this NACA (now NASA) Technical Report [Wing Loads on the Bell X-1 Research Airplane (10 Percent Thick Wing) as Determined by Pressure-distribution Measurements in Flight at Subsonic and Transonic Speeds], the wings look a bit different to the one used by Virgin.

But there might be different versions of the wing, since there were multiple versions of the X-1.

The wikipedia article shows yet another wing geometry.

Below is a composition of 3 different drawings I found via google, which show that at least there exist various different drawings of the wing


What kind of heaters are used for heated floor panels?

Electrical, connected to one of the AC buses. This is an example, absorbing 620 watts/m^2.


What are the advantages/disadvantages of placing an engine in the tail?

As you write, at the time those trijets were designed they enjoyed preferential treatment over aircraft with two engines for overwater operation. They also were more efficient than comparable designs with four engines. See here for that discussion.

However, the wing-mounted engine has some advantages:

Flutter damping when mounted ahead of the elastic line of the wing
Bending relief
Easier access for maintenance
Shorter fuel lines

The tail position was chosen because three engines were enough for the optimum size of those airliners and equipping them with four engines had lowered efficiency. If you need to put three engines on an aircraft, one has to be in the line of symmetry, and here the best compromise was on or in the rear fuselage. Had more powerful and reliable engines been available back then, you can be sure they would had used only two engines and mounted them on the wing. But we had to wait two more decades until turbofan engines were powerful enough and the certification authorities were convinced of their reliability.

The fashion of early jets to put all engines at the back was just that and had ended before the trijets were designed.


It is deterministic, meaning that if given exactly the same inputs, it will always produce the same output.

Your second question is whether it is reversible. The algorithm was deliberately designed to require an adversary to know the precise (i.e. within a few meters) latitude and longitude where the algorithm was run to be able to reverse it. This is effectively impossible unless they physically observe your exact startup location, in which case they could presumably just read your tail number off the side of your plane anyway.


What are the effects of camber location in an airfoil?

[Does] the location of the camber in the MAC's airfoil correspond with the aerodynamic center?

No.

The aerodynamic center is where the additional lift force from a change in angle of attack can be summed up. Since camber only determines the lift portion that is independent of angle of attack, changing the camber will not influence the aerodynamic center.

For a high aspect ratio wing in subsonic flow, the aerodynamic center is at the quarter chord position. With decreasing aspect ratio this point moves slowly forward until it arrives at the forward tip for a slender body.

Also, strictly speaking, there is no "location of camber" — camber is distributed over the whole chord. What you probably mean is the highest point of the camber line, but that point has little aerodynamic significance. The local curvature of that line is much more important.

  Also, does that affect the moment coefficient?

Yes.

Generally, the more an airfoil is cambered towards its rear end, the higher its pitch moment coefficient will be. This is called "rear loading" and is used in order to combine decent thickness with good lift in transsonic airfoils. You can use the lengthwise location of the highest point of the camber line as a guide how high the moment coefficient will be.

  And what about a high speed aircraft (M>1)?

That depends on wing sweep. Normally, aircraft designers try to keep the wing's leading edge subsonic over the full speed range. But I guess you wonder how the camber will influence a wing's performance once it moves at full supersonic speed. Well, the bad news is that camber will drive up wave drag without any influence on lift. Supersonic aircraft, therefore, use thin airfoils with very little camber, and the camber they have is only there because it helps in subsonic flight.


Does the A-10 Thunderbolt fly without the GAU-8?

Near as I know, the answer to the first question is no. The aircraft requires that a tail stand be fitted to it when the gun, magazine and electromechanical drive mechanism is removed for maintenance.  Operation of the A-10 without the gun would exceed the weight and balance envelope for the aircraft, making flight, as well as ground operations hazardous.

The A-10 has been proposed for use as a converted water bomber to fight forest fires but this balance problem without a counterweight installed in this region would make this very difficult.

http://fireaviation.com/2014/09/25/a-10-warthog-proposed-again-as-an-air-tanker/

If one was going to remove the gun for a ferry flight, it would have to be fitted with some kind of counterweight in its place, which would defeat the original purpose of removing the gun.


It isn't due to "lowering the demand on the engine bleed" because the air conditioning is done as part of the standard pressurization of the cabin - the air is bled from the engine, cooled to a very low temperature and then heated to the desired temperature for the cabin, so shutting the blinds wouldn't affect that because the air is still cooled and then reheated.

It is purely for jet-lag and sleeping issues - a single blind open in a darkened cabin can disrupt even those people wearing the eye masks (those things arent perfect) and can disrupt people who have woken to go to the toilet during the cabins "sleep period" (think how horrible it is if you get up in the middle of the night and turn on a bright light - its easier to get back to sleep if you keep lighting muted throughout your activity than it is otherwise).


What additional airspace will be off-limits to an a/c w/ no elect. system or xponder under 91.225 (ADS-B) compared to under 91.215?

The key difference appears to be that under the new regulations, aircraft without engine-driven electrical systems and without ADS-B-out will be barred from flying above any underlying Class B or Class C airspace, AT ANY ALTITUDE.  This is a function of FAR 91.225(e)(2).

Currently, aircraft without electric-engine-driven electrical systems and without transponders are barred from flying above underlying Class B or Class C airspace only up to 10,000' MSL.

Also, under the new rules aircraft with no engine-driven electrical systems and no ADS-B-out won't be able to fly above 10,000' MSL under a Class B or C shelf. Again this is the result of FAR 91.225(e)(2).  The only such airspace appears to lie under some outlying Class B airspace near KSLC.

This answer is based on an understanding that the restrictions imposed by FAR 91.225(e)(2) are only construed to apply within the lateral boundaries of (i.e. above, below, or within) Class B or Class C airspace.  This understanding of FAR 91.225(e)(2) is congruent with the way the FAA is currently interpreting the related regulation FAR 91.215(b)(3)(ii).  Other interpretations of FAR 91.225(e)(2) could produce much more restrictive results for aircraft without engine-driven electrical systems and without ADS-B-out, but are problematic for other reasons, and seem inconsistent with the intent of the regulation.

For more on why this seems to be the best interpretation of FAR 91.225(e)(2), and how this pertains to the rest of the regulation, see this related answer to a related question: A question about FAR 91.225(e)(2) -- pertains to ADS-B-out requirement and exemption for aircraft with no electrical system .

The truth is that the FAA has simply replaced one poorly-written piece of regulation with another.  In FAR 91.215(b)(3)(ii), the "or below 10,000' MSL" clause was completely irrrelevant.  It is likely that FAR 91.215 was intended to place greater restrictions on flight above 10,000' MSL by aircraft with no electrical systems and no transponders than ended up actually being the case-- for more see related answer FAR 91.215 (b)(3)(ii) -- transponders-- does the "or below 10,000' MSL" clause have any practical significance? .

The new regulation FAR 91.225 suffers from the opposite problem-- not only is it still not clearly stated that the "Below the altitude of the ceiling of a Class B or Class C airspace area designated for an airport" clause of FAR 91.255(e)(2) only applies within the lateral boundaries of said Class B or C airspace, but there is also a possibility of construing the "or [below] 10,000 feet MSL, whichever is lower" clause of 91.255(e)(2) as applying everywhere, not just within the lateral boundaries of Class B or C airspace.  This would have the effect of preventing aircraft without electrical systems and without ADS-B-out from flying ANYWHERE above 10,000' MSL over the 48 contiguous states, unless also below 2500' AGL.  This is clearly not the intent of the regulation, and there has to date been no suggestion that it will be interpreted this way.

This ambiguity could have been avoided by simply writing FAR 91.255(e)(2) to read something to the effect of:  "If within the lateral boundaries of Class B or Class C airspace, then all operations must be conducted below the ceiling of that Class B or Class C airspace or below 10,000 feet MSL, whichever is lower."

One other point which is beyond the scope of the original question, strictly speaking, but may be of interest-- FAR 91.255 will also prohibit any aircraft without ADS-B-out from flying in any Class E airspace at and above 3,000 feet MSL over the Gulf of Mexico from the coastline of the United States out to 12 nautical miles.

Additional links to answers related to FAR 91.215 or FAR 91.225--

FAR 91.215-- may an aircraft with no electrical system and no transponder overfly Wheeler AAF at 9500' MSL?


Why doesn't frost form on a moving airplane?

Frost can be formed in two ways. On a colder object by water directly desublimating on its surface or on any object when air is saturated with water.

Frost can form on a moving airplane, but only the second way. Why would they have anti-ice on pitot tubes, propeller and leading edges otherwise?

When the air is not saturated with water, ice will sublimate. If the air is moving it carries away the sublimated vapour and thus increases the sublimation rate. When flying in visual meteorological conditions, that's generally the case, so frost won't form in VMC, thogh watch out when dew point is close to temperature; in such case light haze may form that already causes some icing while visibility is still above the VMC limit. Ram and friction heating also help sublimating the ice a bit.

However when you fly into a cloud in freezing temperature, the water droplets will freeze on the aircraft when they hit it. They will hit it on forward-facing surfaces: wing and stabilizer leading edges, propellers, engine inlets, pitot tubes and nose and windscreen. That's why these components have anti-ice, either using heating or deicing boots.

VMC-only aircraft will often only have pitot tube heating and carburettor heating, because those can sometimes gather frost in sufficiently moist air that is not yet forming cloud. This lack of anti-ice makes flying into IMC even more dangerous in winter than it already is for all the other reasons.

Icing only happens when the cloud contains supercooled water droplets, which occurs in clouds where the ambient air temperature is between freezing point (0°C/32°F) and around -40°C/-40°F when the droplets freeze to ice pellets. The exact point the droplets freeze varies somewhat because it depends on other parameters like amount of dust, but pilots can check whether they are accreting any ice by looking in the corners of the windscreen. Whether freezing conditions are to be expected will also be mentioned in the detailed weather forecast.


Do I have to notify someone or file a flight plan for a private flight in the UK?

Stapleford and Damyns Hall are both in class G airspace, so there would be no need to file a flight plan or ask permission of anyone to make the flight. The only thing you might need to do is call Damyns Hall in case they are PPR (Prior Permission Required). VFR flights generally don't need any sort of flight plan unless you are going abroad or to the channel islands. If you are going a long distance over water it's advisable as well. If flying into Damyns Hall keep in mind that the London City zone is very close by, so make sure you stay clear of it. The London TMA is at 2,500ft as well.

Both airfields are not controlled, however both have AG radios who try to coordinate flights, you technically don't have to communicate with them but you might not be allowed to use those airfields in the future if you don't use it.


What is the relationship between angle of attack and wake turbulence?

It is not the angle of attack - downwash intensity grows with lift squared and inversely to the squares of wingspan and speed. Please read this answer on how wake turbulence forms. Now let's look at the parameters you listed:

Heavy: Yes, the heavier the aircraft, the more lift needs to be created. Induced drag grows with the square of lift.
Clean: Not really. With or without flaps the amount of lift is the same. Only the lift distribution over span might be different, but this does not make much of a difference for the wake.
Slow: Absolutely! Induced drag is proportional to the inverse of speed squared.

What is missing from the list is wing span which lets induced drag grow with the inverse of its square. The angle of attack is only indirectly responsible for induced drag because lift is (within limits) proportional to the angle of attack.


Is on-board equipment for in-flight de-icing also used on the ground?

Usually, no.

There are two main methods used to deice an airplane in the air. One is letting warm air that is bleed from the jet engine to heat the wing leading edge. The other is to have have rubber air bladders (called deice boots) on the leading edge of the wing and tail surfaces that are pumped up and the ice falls off. Both of those methods are only useful to deice the leading edge of the wing and tail surfaces which is pretty much the only dangerous place where an airplane can gather ice while it is flying.

Airplanes on the ground are a different story. Ice can be built up pretty much anywhere as there is no airflow to prevent it. Excessive ice on control surfaces can make them behave "unevenly" or in extreme cases even unresponsive. Bigger chunks of ice breaking off the fuselage can get ingested by the engine and cause problems. It is therefore important that the airplane takes off ice-free. In fact, as little as frost on the surface of the wings can cause a significant loss of lift and can even cause a plane to crash.


Is it always required to calculate the fuel for an IFR alternate?

You only need an alternate if a) the weather is below the minimums you mentioned, or b) your destination has no instrument approach. That's in both 91.167 (IFR fuel requirements) and 91.169 (IFR flight plan requirements), e.g.:

  §91.167   Fuel requirements for flight in IFR conditions.

  (a) No person may operate a civil aircraft in IFR conditions unless it
  carries enough fuel (considering weather reports and forecasts and
  weather conditions) to—

  [...]

  (2) Except as provided in paragraph (b) of this section, fly from that
  airport to the alternate airport; and

  [...]

  (b) Paragraph (a)(2) of this section does not apply if:

  [...]

  (2) Appropriate weather reports or weather forecasts, or a combination
  of them, indicate the following:

  (i) For aircraft other than helicopters. For at least 1 hour before
  and for 1 hour after the estimated time of arrival, the ceiling will
  be at least 2,000 feet above the airport elevation and the visibility
  will be at least 3 statute miles.

As for how to calculate the fuel requirement to your alternate, I would just plan a direct route (or whatever you need to avoid restricted airspace etc.) and calculate your regular cruise fuel requirement. I don't see any point in trying to anticipate in detail what would happen if you actually have to divert because you just can't know that anyway.

IFR Magazine has a nice article on planning alternates that might help you with some of the practical details.


Does an aircraft like the Airbus A-320 have external sensors to detect damage to the aircraft?

This is related to an answer I gave here about why aircraft typically do not have mirrors and external cameras.

Short answer: yes aircraft do have sensors to detect damage, but not the kind of damage you're talking about.

Long answer: to design or decide what sensors to put on the aircraft and where, we have to get started with failure modes. There are at least a million way for components to fail, however, some failure are more likely to occur than others.

Do we have sensors which detect failures / abnormal situations? We do! We have sensors for control surfaces, hydraulics, gears, tire pressure, cabin pressure, engine temperature, oil pressure etc.

Here is an image of one of the cockpit screens on a Boeing:

(source)

OK, so why not more sensors?

Because sensors can fail. Now that would be a nightmare to troubleshoot: the sensor says the right outer landing light is not illuminated. Is that true? Let me exit the aircraft and take a look......

It turns out that:

Many failure modes are "internal", e.g. a valve malfunctioning. They are invisible on the exterior of an aircraft.
Aircraft rarely collide with any other objects.
Relying on visual indication is actually a good thing, because it is reliable and it's free.
Building an array of sensors covering each skin on the aircraft would be extremely complex, the construction cost would be high and the system would be heavy.
Sensors are just another component of the system. The more sensors, the more likely something will fail. At some point one has to trust the underlying component to function without relying on system indications.

Perhaps this is the kind of system you have in mind:

(Screenshot of "Stealth" (2005), 01:01:11)

Nah, that's just Hollywood artistic license.


The 3D-wing allows for air to flow over the wingtip into the low pressure zone over the wing, thus reducing the overall pressure differential and reducing overall lift.

This explains the stall at higher AoA because the additional airflow over the wing surface "energises" the air. Flow seperation happens when the kinetic energy is equal to the pressure differential that the airstream flows into, so if you can increase the kinetic energy, you can decrease the tendency of the airstream to separate.


Similar books to this: "konstruktion der luftstrahltriebwerke by Stammer and Jahrig" for Structural and machine element design of jet engine

Try this " The Jet Engine, by Rolls-Royce 5th Edition


Is there a standard time zone for flight schedules?

Customer facing documents like boarding passes and itineraries typically show local times for ease of use.  Just use airport clocks.  I would not trust the flying public to compute UTC.  It would be chaos.

Crew facing documents will usually be set to UTC, or zulu time.


The plane was designed for a US funded competition which it won, after it would get 1 million dollars in funding for further development which automatically means that the 2707 would be the cheaper plane to buy and that it had the US Government Stamp of Approval. This also meant that there were political reasons to commit to buy one of them.

The reason it won that competition is because it was slightly less loud, slightly more efficient and more technologically advanced than its competition.


Do the cabin announcements follow a common protocol?

I can only speak for carriers following FAA regulations. But, It was probably a company policy change. I have a copy of the 2017 FAR/AIM. I don’t remember there being a change since then.

One reason for an air carrier, whether large or small, to use a standard format and phrases is to make sure that every flight and cabin crew completes all of the required elements of a briefing without forgetting items. In the litigious sense, this sort of scripting is much more defendable than simply requiring the crew to mention the required information in their own way.

757toga has listed that guidelines are spelled out in AC 121-24C for US carriers. I would like to also include the locations of the regulations spelling out the requirements for passenger briefings. Other than the required information content contained in the regulations (FAR), and the guidelines in the Advisory Circular and other FAA publications, there is no further guidance on how the briefing is to be delivered. The regulations are in the following Title 14 CFR parts:

91.519
121.571
135.117

Each has a version of the verbiage included below.

In addition to this, the FAA requires all aircraft PICs brief (or ensure briefings are done with all passengers) the operation of safety/seat belts per Part 91.107. The FAA Safety Team recommends following the S.A.F.E.T.Y. format when Part 91 General Aviation aircraft PICs brief their passengers. The acronym stands for the following:

Seatbelts
Airvents & windows
Fire Extinguishers
Exits, Emergencies, & Equipment
Traffic & Talking
Your Questions

This example guidance can be printed out at FAAST SAFETY Briefing

The example verbiage of the actual regulations is below:

  §91.519 Passenger briefing.
  (a) Before each takeoff the pilot in command of an airplane carrying passengers shall ensure that all passengers have been orally briefed on—

  (1) Smoking. Each passenger shall be briefed on when, where, and under what conditions smoking is prohibited. This briefing shall include a statement, as appropriate, that the Federal Aviation Regulations require passenger compliance with lighted passenger information signs and no smoking placards, prohibit smoking in the lavatories, and require compliance with crewmember instructions with regard to these items;

  (2) Use of safety belts and shoulder harnesses. Each passenger shall be briefed on when, where, and under what conditions it is necessary to have his or her safety belt and, if installed, his or her shoulder harness fastened about him or her. The briefing shall include a statement, as appropriate, that Federal Aviation Regulations require passenger compliance with the lighted passenger sign and/or crewmember instructions with regard to these items;

  (3) Location and means for opening the passenger entry door and emergency exits;

  (4) Location of survival equipment;

  (5) Ditching procedures and the use of flotation equipment required under §91.509 for a flight over water; and

  (6) The normal and emergency use of oxygen equipment installed on the airplane.

  (b) The oral briefing required by paragraph (a) of this section shall be given by the pilot in command or a member of the crew, but need not be given when the pilot in command determines that the passengers are familiar with the contents of the briefing. It may be supplemented by printed cards for the use of each passenger containing—

  (1) A diagram of, and methods of operating, the emergency exits; and

  (2) Other instructions necessary for use of emergency equipment.

  (c) Each card used under paragraph (b) must be carried in convenient locations on the airplane for the use of each passenger and must contain information that is pertinent only to the type and model airplane on which it is used.

  (d) For operations under subpart K of this part, the passenger briefing requirements of §91.1035 apply, instead of the requirements of paragraphs (a) through (c) of this section.

  [Docket No. 18334, 54 FR 34314, Aug. 18, 1989; as amended by Amdt. 91–231, 57 FR 42672, Sept. 15, 1992; Amdt. 91–280, 68 FR 54561, Sept. 17, 2003]


What programming languages are used for equipment onboard aircraft?

There are no language recommendations or requirements, other than what is sensible given the verification requirements in the various standards (e.g., DO-178B/C). For the highest design assurance levels, the generated code must be inspected down at the op-code level to ensure no known processor gotchas are invoked. You also end up having to test every part of every conditional, both the true and the false sides, and ensure that no jump instructions will take you someplace where you didn't expect it to go.

For these reasons, the big three languages in use in embedded avionics today are:

C++ (as a better C. The OO nature is often used only sparingly. Things like polymorphism are just too expensive to verify)
Ada (You may not like it, but a TON of current avionics are written in Ada, and are currently being maintained and updated with new features)
C - As close to the hardware as you want to get and still be highly productive (not intending to offend anyone who is productive in something else)

Assembler is frequently used for specific needs, but it would not be used to a greater degree than one of the above-mentioned languages.

What makes these languages ideal for avionics is that they are relatively close to the hardware and memory structure, not too abstract. Their tools are mature and well-known. People have years of experience certifying software written in them. And there are lots of programmers who can get up to speed in them quickly (Yes, even Ada).

Non-safety critical software, both on and off the aircraft, will be written in any of the big languages of the day: Java, C#, VB, C, C++, Python, Perl, Ruby, etc.

iPads are becoming useful inside the cockpit and are approved in limited situations. iOS apps are written in Objective-C, C, C++, and increasingly, Swift (Apple's new language).


Depends on how much fuel that they have on board.   You're not gonna be able to hold wing tanks or a centerline tank on that jet and still be able to fly supersonic, so we will have to assume that we can only use internal fuel. In a Block 50/52  F-16C, the jet holds about 7200 pounds of internal fuel with the tanks topped off. In full afterburner, the jet's F100 or F110 engine is burning approximately 800 pounds of fuel per minute.   This gives a maximum of approx. nine minutes of flight time in full afterburner.  So you  have at most nine minutes of supersonic dash available to you.

As mentioned above, while an F-16 is capable of a maximum speed of Mach 2, it can't do this unless it's in a clean configuration, that is, it does not have any external stores on the jet which create a lot of parasite drag and prevents supersonic flight with ordnance on board. Typical mission speeds are high subsonic (500-600 KTAS) for cruise and combat maneuvering.  Usually afterburning is utilized for brief periods in order to quickly accelerate the jet, such as to shorten takeoff distances, or to quickly replenish energy which has been bled off during maneuvering.  Supersonic dash can be used to egress a FLOT or airspace deep inside enemy territory once, say a bombing mission is complete and you have been informed by an E-3 that there are enemy fighters scrambling towards your position.  You jettison the external stores, save maybe a pair of AIM-9s or AIM-120s on the wingtip rails, push open the throttle and run like hell - and hope it's enough that you can make it to a friendly airbase or a tanker in time!


How does thrust relate to horsepower on turbocharged engines?

Assuming you are talking about a turbocharged propeller driven aircraft, your question
really makes it easy to explain as you have already identified the two parts of your power unit
that are affected by increasing altitude (thinner air).  The amount of air it can breath and the amount of thrust your prop can generate.

The turbo only takes care of the air breathing part, yes, it has as much power as at sea level
because to turbocharger can compress enough of the thin air to feed it. No problem there.

But the prop is still spinning thinner air, so it can not get the same "bite" as at lower altitudes
with out going to even higher RPMs.  So, when your RPMs max out due to engine limitations,
or even the tips going supersonic, that's it, no more thrust increase available.


How much hydraulic fluid is in a jet airliner?

FCOM for the A320 describes 3 independent hydraulic systems, with accumulation reservoirs for each at 6.5L,12.5L & 14.5L (1.7USG,3.3USG& 3.8USG) respectively, so +33.5 liters is a good bet, which translate to 26-33 kgs depending on fluid type.

Note that more fluid will be available in the system, but how much exactly you will need a mechanic to answer.


Is there any specific location on airframe for gaining higher drag?

If you want to arrest ascent you put the airbrake behind/below the CG.  Keep in mind the rocket will tend to remain flying "nose first", which may affect parachute deployment (from nose) on the way down.
Notice the Space X Falcon 9 has theirs near the nose allowing the rocket to descend tail first, and are only deployed once the rocket has coasted to maximum altitude, slowed down, and has begun to fall. Nearer to the ground, you use retrorockets and/or parachute.
For a high altitude sounding rocket, it may be preferable to delay parachute deployment, lest the wind carry it too far away from the launch point.


How many labels are defined in ARINC 429 for calibrated altitude?

There is no defined "calibrated altitude".
The following are all altitude related labels:

102 Selected Altitude,
107 Selected Cruise Altitude,
120 Range to Altitude,
127 Selected Landing Altitude,
131 Intruder Altitude,
144 Altitude Error,
153 Max Altitude,
162 Density Altitude,
164 Min Descent Altitude (MDA),
203 Altitude,
204 Baro Corrected Altitude #1 & Baro Altitude,
206 Altitude (Variable Resolution),
212 Altitude Rate,
220 Baro Corrected Altitude #2,
225 Compensated Altitude Rate,
251 Baro Corrected Altitude #3,
252 Baro Corrected Altitude #4,
254 Altitude Rate,
323 Geometric Altitude,
361 Altitude (Inertial)


What is an obstacle identification surface and why would a pilot intentionally penetrate it during an ILS approach?

Obstacle Identification Surfaces apply to departures and the portion of an non-precision IAP beyond the Visual Descent Point. If you are in the clouds, you should never penetrate the OIS on departure.
On arrival, the VDP assures obstacle clearance with a normal approach to landing. ILS only approaches do not have a VDP depicted so there is no OIS to penetrate. (The glide slope takes you right to the touchdown zone.) ILS/LOC (and Localizer only) approaches do have a VDP for the non-precision version of the approach. You could penetrate the OIC on a localizer approach and if that happens, visibility minimums are increased as explained in the last paragraph from the AIM below.
AC 150-5300-13-c12 Airport Design has a good visualization of the departure OIC.
(As an aside, it has lots of charts and graphs showing how departures and approaches are designed.)

AIM 5−2−8. Instrument Departure Procedures (DP) − Obstacle Departure Procedures (ODP) and Standard Instrument Departures (SID)

…if an obstacle penetrates what is called the 40:1 obstacle
identification surface, then the procedure designer chooses whether
to:

Establish a steeper than normal climb gradient; or

Establish a steeper than normal climb gradient with an alternative that increases takeoff minima to allow the pilot to visually remain
clear of the obstacle( s); or

Design and publish a specific departure route; or

A combination or all of the above.

The 40:1 obstacle identification surface (OIS) begins at the departure end of runway (DER) and slopes upward at 152 FPNM until
reaching the minimum IFR altitude or entering the en route structure.
This assessment area is limited to 25 NM from the airport in
nonmountainous areas and 46 NM in designated mountainous areas. Beyond
this distance, the pilot is responsible for obstacle clearance if not
operating on a published route, if below (having not reached) the MEA
or MOCA of a published route, or an ATC assigned altitude. See FIG
5−2−1. (Ref 14 CFR 91.177 for further information on en route
altitudes.)

5−4−5. Instrument Approach Procedure (IAP) Charts

h. The Visual Descent Point (VDP), identified by the symbol (V), is a
defined point on the final approach course of a nonprecision
straight−in approach procedure from which a stabilized visual descent
from the MDA to the runway touchdown point may be commenced. The pilot
should not descend below the MDA prior to reaching the VDP.
i. A visual segment obstruction evaluation is accomplished during
procedure design on all IAPs. Obstacles (both lighted and unlighted)
are allowed to penetrate the visual segment obstacle identification
surfaces. Identified obstacle penetrations may cause restrictions to
instrument approach operations which may include an increased approach
visibility requirement, not publishing a VDP, and/or prohibiting night
instrument operations to the runway. There is no implicit obstacle
protection from the MDA/DA to the touchdown point. Accordingly, it is
the responsibility of the pilot to visually acquire and avoid
obstacles below the MDA/DA during transition to landing.

Edit: This AIM is consistent with what the Instrument Procedures Handbook says about non-precision approaches but not consistent with what the handbook says about the potential for obstacles on ILS approaches.
p 7-9

...if an ILS is configured with approach lights or a nonprecision
approach is configured with either MALSR, SSALR,or ALSF-1 lighting
configurations and the procedure has a published visibility of 3/4 SM
or greater, a penetration of the final approach OIS may exist. Also,
pilots will be unable to determine whether there are penetrations of
the final approach OIS if a nonprecision procedure does not have
approach lights, or is configured with ODALS,MALS, or SSALS/SALS
lighting since the minimum published visibility will be 3/4SM or
greater.
As a rule of thumb, approaches with published
visibilities of 3/4SM or more should be regarded as having final
approach OIS penetrations and care must be taken to avoid any
obstacles in the visual segment. Approaches with published
visibilities of 1/2 SM or less are free of OIS penetrations...


Is there a special procedure for mid-air refueling in the rain?

If you're VMC and simply have rain falling, the procedure doesn't change, and it isn't a big deal (talking fixed wing refueling with a boom here; other communities' procedures/capabilities may be different).  The receiver's windshield will have some amount of rain hitting it, but if it isn't particularly heavy rain then he should still be able to do the AR.

If the visibility is really bad because of the rain, or if you're getting into IMC, then that's the situation you have, irrespective of rain falling or not, and obviously you'd rather have better conditions for doing the refueling.  Going IMC momentarily while you're hooked up may not be a big deal, as you can still see the tanker, but if you lose sight then the first priority is to get positive separation between the two aircraft.


How should control surfaces be modeled in simulations?

Any control surface changes both local camber and local incidence, so it would be best if you change the coefficients accordingly. If you use a panel code, it would be enough to change the local surface inclination (= the flow direction at the local control point) by the deflection angle.

If you need formulas for the coefficients: A control surface with a cord length fraction d (of total chord length) will change the local lift coefficient $c_l$ with
$$\Delta c_l = \sqrt{d}\cdot c_{l\alpha}\cdot sin (\eta),$$
where $\eta$ is the deflection angle in radians and $c_{l\alpha}$ is the lift coefficient gradient over angle of attack of the original airfoil. The additional lift will act at a point between 50% and 25% of wing chord. The higher value is for very short flaps, the lower for all-flying surfaces (technically 100% flap chord), so a control surface deflection will add a torsional load. Drag will not be affected for small deflection angles, but when they get bigger, first drag rises and then the lift increase becomes nonlinear.

If you stay in the linear range (15° with 30% flap chord, 25° with 15% flap chord at moderate angle of attack) you can linearly add the flap effect (offset the coefficients). Going beyond that in both deflection angle and angle of attack will need a reduction in flap effectivity which can (in extreme cases) even become control reversal.

Also note that the aileron especially will twist the wing such that its effectivity is reduced at higher dynamic pressure. The details of this effect depend on the stiffness of the wing.

Your example of a NACA 0024 is already so thick that it will not tolerate big flap deflection angles and show separation on the suction side. Good wing thicknesses for subsonic flight are between 12% and 15%, and the most extreme ones (like the root of highly loaded high aspect ratio wings) will still be below 20%. Supersonic wing thicknesses are generally between 4% and 6%.

If you depend on that control surface for trimming the aircraft, don't let its effectivity decrease (as it would in reality), but give it linear effectivity (without the sine function) into infinity and punish large deflection angles with excessive drag (or whatever runs against your target parameter).


What do the tail numbers on aircraft mean?

TL:DR, SB-023 means it is airframe number 23 of the SU-30 model MKi. It is flown by the Indian Air Force.

The small rectangle is what is known as a fin flash. It generally identifies the country of origin of the aircraft and sometimes the garrison or command within that country. In this case it indicates India (not to be confused with the Irish Fin Flash. We can be sure it is India because the roundel further forward is that of the Indian Air Force.

The letters and numbers above are likely to be the "tail code" Which is a USAF term. I'm sure this term has a unique name in Indian military parlance but I can't find it. The Tail code usually describes the either the home base or  manufacturer of the aircraft as well as sequence number of the aircraft. Note that sequence number and serial number are not identical and multiple air frames may share the same sequence number as air frames are retired or refitted.

On a USAF Aircraft a two-letter code generally indicates its home base. The plane would then have a numerical code indicating year built and sequence number.

I've had a look through google images and every SU-30MKi I can find has an SB prefix to its tail code so I am going to guess that it is an indicator of manufacture and/or sub-type. Interestingly, all SU-30s and Mig-29s bear the same prefix within type (SB and KBU, respectively) but Mig-21s have a variety (I've seen UI, CI, CII, and CUI.) Which makes sense since India has fielded multiple variants of the 21 but only one variant of the 30 or 29. My observations are based on a survey of the first 4 pages of google images for each aircraft so are hardly exhaustive.

The Sequence numbers come up in discussions among enthusiasts for example.

It is worth noting that India's military designation system evolved while the country was part of the commonwealth during WWII, the time when most of the world's modern designation systems were conceived. Despite that, India employs many Warsaw pact and a few home-grown systems, resulting in a unique combination of designation system and technologies.


How does a synchro resolver converter work?

The angle of attack sensor turns the shaft on a synchro (or a resolver: they're essentially the same thing) which is a transformer whose outputs are uniquely related to that shaft angle. That's where your 3 inputs come from. There are lots of possibilities for what happens next. The shaft angle is not the same as the angle of attack. The synchro is not measuring. It's just conveying measurement information from the sensor to the flight crew and other aircraft systems.


During an LPV or GLS final approach, can the extension of the aircraft's cross-section line intersect with the Y or X OCS surfaces?

The OCS is the edge of the safe flight 'corridor.' It defines a safe volume of airspace for the approach. Since it's normal to have obstacles off to the side of the approach path the OCS typically rises as you move away from the approach centerline.
Your Case 1 is the most correct description of an aircraft flying the approach. The green 'floor' normally will extend greater than one 'dot' on either side of the localizer (or localizer look-alike) and is at least one 'dot' below the glide path. That is the reason a missed approach should be executed if you deviate more than one dot from the approach path. At the zero deviation level for glide path (your blue dashed line in Case 1 assuming the a/c is on path) the intersection with the yellow (x surface) should be beyond the full scale left/right deviation.
Essentially the OCS defines a canyon that you can safely fly through to the runway. So yes, the extension of the aircraft's cross section line can intersect the x and y surfaces, but the aircraft itself should not.


ILS provides both lateral and vertical guidance with high precision, which means aircraft using an ILS are allowed to get very close to the ground and each other without visual contact; in theory, a Category IIIC ILS is precise enough to land with zero visibility, but so far no examples actually exist.  Where ILS approaches exist, they're usually preferred.

Baro-VNAV provides only vertical guidance; it would be used for RNAV procedures in conjunction with some form of lateral guidance such as DME/DME/IRU.  Due to the pilot having to manually enter the altimeter setting and the general accuracy of altimeters, the margin of error is much higher and aircraft are not allowed to get nearly as close to the ground (or each other) as they would be with ILS.  Also, Baro-VNAV systems are known to be inaccurate at extreme temperatures (either high or low), so they aren't always available, whereas other vertical guidance systems are immune to that.

The other main difference is cost.  ILS requires both localizer and glideslope equipment on the ground for each runway served; installing and maintaining those systems is quite expensive, whereas the on-board equipment is relatively inexpensive.  In contrast, Baro-VNAV is already installed on many airliners and requires nothing on the ground, just minor modifications to RNAV procedures already being developed for GNSS-equipped aircraft.  The accompanying lateral guidance systems also already exist for other reasons, so there's little or no cost there either.  The combination allows airlines to more reliably and more safely serve the public at more airports with minimal cost to everyone, so it's a reasonable compromise for airports (or individual runways) that don't have enough traffic to justify the high costs of ILS.


As for what they are you can find that in the answer to the question here. In terms of how they work its an extension of the basic runway lighting system. There is a nice video discussing the various types here but effectively they help guide the pilot to the runway by providing them with an extended way to infer where the centerline is (beyond the runway its self) when making a low visibility approach. The system may also include a decision bar which helps a pilot by having a visual marker at a fixed distance from the threshold. Keep in mind that threshold lights lights count as runway in sight so the extended centerline can help a pilot lineup when they can not see the full length of the runway.

The colors will vary based on what the airport in question is equipped with but green is the runway threshold. Red is typically an area in front of the runway, it could be a displaced threshold or it could be an area off the runway all together. However these lights will appear on both ends of the runway and will be visible when approaching from that direction.

It should be noted that while certain lights are required for certain types of operations, lighting is not explicitly required by the FAA and there are plenty of unlit airports as well as a wide variety of lighting situations out there. The field I fly out of has REIL and 5 lights on each side of the runway which is far less than a class B airport would have but may be far more than your back country grass strip has.


Why is the nose landing gear of a Rutan Vari Eze up during parking?

For getting in, the nose has to be physically raised before the pilot can board the aircraft:

When the aircraft is parked, the NLG is retracted and the aircraft rests on the bumper at the front of the aircraft, in what is described as the 'kneeled' position.
Extension of the NLG requires the front of the aircraft to be physically raised, after which the NLG extension system is operated from the cockpit.
To begin the NLG extension, a handle in the cockpit is turned in he extend direction. This handle is connected to a shaft that turns a worm gear and crown wheel, and the rotation of the crown wheel drives the actuating rms of the NLG in the down direction.  When the NLG is extended, an extra 1.5 turns of the handle causes the crown wheel to drive the actuating arms over-centre, which locks the gear in the fully down position.

After this, the pilot boards the aircraft. On some aircraft, linear actuators seems to have been fitted for this purpose:

In recent years the application of general purpose, 12 volt, linear actuators came into use for electrical actuation of the nose gear with the airplane loaded.
With the linear actuator the airplane can be parked nose down for stability, boarded (in the nose down position) and raised by the push of a button.

As noted above, this design has been adopted for stability- As the engine is on the rear, if the pilot is not in the aircraft, it can tip backwards, damaging the propeller. This also acts as a parking brake.


Why would a VOR be decommissioned leaving the DME?

Many older Air Transport Airplanes have no GPS. I'm a pilot since 1970. I operated A330 for 5 years until 2000 without GPS. The average IRS position (Inertial Reference Systems) in the FMS was updated by DME/DME. On older airplanes we selected the DME Stations manually preferably with a 90 degree cut-angle to obtain an accurate update. A single VOR/DME station could be used for update as well but it's a lot less accurate. Example, if you are 60 NM away from a VOR, a 1° error in azimuth would cause an error of about 1 NM. All Airbus aircraft have an approval for RNAV Approaches down to an accuracy of 0,3 NM with 2 DME stations available. This is why DME's are still useful, many ILS have a DME. Conventional VORs are terribly inaccurate, Doppler VORs are much better even down to a lower altitude, but requires more space.


How to go about designing a custom airfoil?

Wing sweep, incidence, and airfoil geometry will all have to be adjusted to achieve the best performance at a certain air speed, density, and Reynolds number.

The software that egid mentioned is a good place to start. While studying aerospace in college, XFOIL was used for basic airfoil analysis in our classes.

Another program used was AVL. This analyzes the aircraft as a whole and can model other things such as dynamic stability.

I'm glad that XPlane was also mentioned, even though I wouldn't consider it the most scientific tool for testing wing geometry. It is an interesting way to test configurations since it does use the airplane geometry to simulate the performance characteristics.

In order to consider more variables such as sweep, dihedral, and different airfoils over the wingspan, computational fluid dynamics (CFD) software is used. ANSYS Fluent is one example. There are many other packages out there, and anyone doing serious commercial airfoil design will have proprietary software and methods for this.

Of course, even in the days of supercomputers and CFD, wind tunnel testing is still very important. Scale models can be tested to validate the computer models and demonstrate performance.

As far as requirements, they can get very complicated. For aircraft, of course, the primary goal is to provide the lowest drag at cruise conditions. However, many other factors include:

Preventing flutter
Provide room for sufficient supporting structure
Provide room for fuel
Methods to manufacture the shape
Good stall characteristics
No bad aerodynamics with fuselage and engines
Enough lift with flaps for low landing speed
Able to accommodate flaps, slats, spoilers, and ailerons
Tip treatment like winglets/raked tips
Wingspan must fit into available space (airport, hangar, aircraft carrier, etc.)

And probably many more. Of course, the air speed and conditions will also affect the fuselage, empennage (tail) and its control surfaces, and engines, so this will also be taken into account.


Where do aerodynamical contrails get their condensation nuclei from, when forming at high altitude?

(airliners.net)

Those are called aerodynamic contrails, and when they are colorful as the picture above, they're called rainbow contrails.

They form due to the lower pressure above the wing in cruise when temperatures are above ISA, which favor more water content in the air. The nuclei in this case are tiny water crystals that form due to the pressure (and temperature) drop above the wing. Those crystals then facilitate the persistence of the contrail behind the plane.

Source: contrailscience.com


What is the reference length in calculating the friction coefficient?

Since the site computes atmospheric conditions, only the friction coefficient $c_f$ needs a reference length. This is the length of the object causing friction, measured along the direction of airflow. In case of a wing, it is its local chord, in case of a fuselage, it's the fuselage's length.

Each part of an airplane and each section of the wing will have a slightly different $c_f$, depending on local chord length. The highest contribution to friction drag is caused at the leading edge, when the boundary layer is thin and the speed gradient at the surface is steep. The farther downstream you look, the less each additional unit of length will add to friction drag, so the average over the full length (that is what $c_f$ stands for) will become smaller for longer bodies.

To compute total drag, you need to add the contribution of each part, multiplied with its surface area relative to the airplane's total area. Yes, for a wing the upper and the lower wetted surface area will each contribute their own drag component. Since airflow is faster on the upper surface of a lift-creating wing, you would need a correction factor to account for the speed difference between upper and lower side, but if the difference is small, you can just assume the same speed everywhere. To be precise: $c_f$ is the friction coefficient of a flat plate parallel to the airstream.


Why do some airfields not have a climb gradient for LPV?

When it is not stated, it means it is the nominal value of 2.5%, i.e., for the first example, the LPV climb gradient is 2.5%. When an additional OCA/H is published, then the OCA/H and gradient values are published (second example).
From PANS-OPS:

6.2.2.2 Climb gradient in the intermediate phase. The nominal climb gradient (tan Z) of the missed approach surface is 2.5 per cent.
6.2.2.3.2 The OCA/H for the nominal 2.5 per cent must always be published on the instrument approach chart. If additional gradients are specified in the construction of the missed approach procedure, they and their associated OCA/H values must be published as alternative options.


How does aspect ratio affect the stalling angle of the wing?

Any finite span wing creates a wingtip vortex which causes an induced downwash profile that is maximum at the wingtips, and gets less as you move further inboard (towards the wing root). This is due to the vorticity causing a upwashing outboard of the wing tip, and a downwash inboard of the wing tip. If we took a theoretical wing where the aspect ratio is high enough that the span is 'near-infinite', there will be no tip-effect (vortex) induced downwash at the center (root).
Lower aspect ratio means that there is more induced downwash further inboard, and this local downwash actually helps to keep the airflow attached becuase the local flow is already flowing downwards along the later surface of the wing. You can also think of it as reducing the local incidence angle because the air is already flowing downwards.
Most wings are designed to stall first at the wing root, and for rectangular wings this is inherit due to the downwashing profile described above. For other wing shapes, designers will include "wash-out" to ensure that the root stalls first (Why does a rectangular wing stall first at the root?). Because the root is separated first, if we take away the section of the wing near the root (hence decreasing aspect ratio), the area that would have already separated is now removed, and the wing will be able to operate at a higher angle of attack.
Therefore the stall angle would increase if aspect ratio is decreased (ceteris paribus!). This is assuming that the wing is operating in the longitudinal plane only. Any asymmetrical movement (rolling and yawing), will mean that the wing could possibly stall at the tip.


That is not correct. There are three different altitude systems:

True altitude is the height above Mean Sea Level (MSL). This is what you get when you set your altimeter to QNH. Using this, your altimeter should read 200ft when you are on the runway if the airport elevation is listed as 200ft MSL.

Absolute altitude is the height Above Ground Level (AGL). This is what you get when you set your altimeter to QFE.  Using this, your altimeter should read 0ft when you are on the runway.

Pressure altitude has no relation to the ground or sea level. This is what you get when you set your altimeter to QNE (always 1013 or 29.92). You never use this near the surface of the Earth, only when up high enough that terrain or obstacles clearance isn't a concern. Pressure altitudes are expressed as Flight Levels (FL), with the last two digits omitted.


What is the difference between RTK GPS and GBAS?

There are two primary differences between RTK GPS and GBAS, function and implementing technology.

Functionally, RTK is a differential GPS (DGPS) positioning system. It allows for very precise position measurements (~1 cm). Its primary application is for survey and related measurements.

GBAS also provides a DGPS function but it adds specialized support for aircraft approach guidance. To that end it provides via data broadcast to the using receiver reference path data for a number of runway approaches. It also provides signal integrity data (e.g. fault detection and alerts) to the user.

The difference in implementing technology is that the RTK reference station and using receiver determine position by carrier-phase tracking and the GBAS reference station and using receivers use code tracking.


When is a 100-hour inspection required if alternating commercial and private use?

This FAA legal interpretation covers a lot of scenarios and it looks like it answers yours too. Although it refers to rental, not ownership, the result is the same because rental time isn't instruction or carriage for hire.

First, what the regulation says (14 CFR 91.409(b)):

  Except as provided in paragraph (c) of this section, no person may
  operate an aircraft carrying any person (other than a crewmember) for
  hire, and no person may give flight instruction for hire in an
  aircraft which that person provides, unless within the preceding 100
  hours of time in service the aircraft has received an annual or
  100-hour inspection and been approved for return to service in
  accordance with part 43 of this chapter or has received an inspection
  for the issuance of an airworthiness certificate in accordance with
  part 21 of this chapter. The 100-hour limitation may be exceeded by
  not more than 10 hours while en route to reach a place where the
  inspection can be done. The excess time used to reach a place where
  the inspection can be done must be included in computing the next 100
  hours of time in service.

The key phrase from the interpretation is this one (my emphasis), which really just restates the regulation in a simpler way:

  if [you are] going to operate the aircraft to provide
  flight instruction for hire, then the aircraft must have had an annual
  or 100-hour maintenance inspection within the preceding 100 hours of
  time in service.

Now we can compare your scenarios to the ones in the interpretation. I won't quote the document here, but scenarios 1 and 6 together cover your cases.

In the above scenario, does the 10 hour window even apply to the owner? He's flying his plane solo, not for hire, so in that capacity he should be able to fly it as long as he likes.

Correct. If the aircraft isn't going to be used to do any paid instruction or carry paying passengers then he can fly the aircraft himself, rent it out, lend it to a friend etc.

What if the owner in the above scenario teaches out of his plane for 100 hours after the annual, stops teaching and flies his plane personally for 50 hours, then decides he wants to teach in it again? Can he get a 100 hour check to get the plane legal for commercial use?

Yes, in fact he must. The aircraft requires a check within the last 100 hours of operation to be legal for flight instruction for hire, or carrying paying passengers.

Is the next 100 hour due in another 50 hours? What if instead he flies it personally for 100 hours after the 100 hour is due? Does that mean he has to get two 100 hour checks done in a row to use it commercially again? Or does he have to get a full annual to reset the 100 hour clock?

The 100 hour clock is reset by a 100 hour inspection or by an annual, he doesn't need a second check. But note that if the CFI does get an annual, he still has to deduct any 'overtime' from the 100 hours:

  You may perform an annual inspection rather than a 100-hour
  maintenance inspection when the aircraft reaches the 100-hour
  limitation under§ 91.409(b). However, if you perform an annual
  inspection on an aircraft that has exceeded the 100-hour limitation,
  you are still required to subtract the excess time from the next 100
  hours of time in service.

As for going over the 10-hour excess time, the interpretation covers an equivalent scenario (scenario 6) where the aircraft is flown to 112 hours legally by renters, inspected, and then used for paid training again. The explanation is poorly written in my opinion, but it confirms that the aircraft needs an inspection before any paid training can take place - which makes sense - and the next inspection after that must be made within 88 hours - which makes less sense.

Extending that forward, it would mean that if you fly to 199 hours, you need an inspection - either 100 hour or annual - to make the aircraft legal for paid training and the next inspection would then be due in 1 hour! I don't know if that's really the intended result of the interpretation because it seems to conflict with the regulation's wording about "within the preceding 100 hours of time in service". And what happens if you rent the aircraft out for 299 hours before using it again for training?

Maybe I'm just misreading or misunderstanding things completely, but it looks like the interpretation leaves a couple of loose ends and the only definite, official way to get them answered would be to ask for another interpretation.


What is a 'deep stall' and how can pilots recover from it?

A deep stall or a super stall is a condition where the wake of the wing impinges on the tail surface and renders it almost ineffective. The wing is fully stalled, so the airflow on its upper surface separates right after the leading edge, which produces a wide wake of decelerated, turbulent air. Consequently, the dynamic pressure at the tail surface is much smaller than in unstalled flight, which is the main reason for the reduced effectiveness.

Consider this case: The aircraft flies in a nose-up attitude, but on a downward flight path. Consequently, the angle of attack of the wing $\alpha$ is much beyond its normal operating range, causing a fully separated upper surface flow. Due to the T-tail configuration, the wake is hitting the elevator such that all of it is shielded from the regular airflow.

The pitching moment of this configuration over angle of attack (blue line) looks something like this. First there is a stable region with a negative gradient at low values of $\alpha$, followed by a minimum when the wing stalls, and then a region with a positive gradient, where the separation unfolds and the tail moves into the wake from above. This region is unstable in pitch, so without control input the aircraft will not stay there, but either pitch down or up until it reaches a stable region again. At high angles of attack follows another stable region with a negative gradient:

Note that we have two trim points, one in the regular range of the angle of attack, and one way out to the right. In both cases the aircraft has a stable trim condition, so small disturbances are answered with force changes which will keep the aircraft at one of these points. Between the two, there is another equilibrium point, but here the airplane is unstable. If it pitches up slightly there, the pitch up will accelerate until it reaches the upper trim point.

Now consider the control power of the horizontal tail. When it flies in undisturbed air, it can trim a wide range of angles of attack. In the deep stall condition, however, its control power is much reduced, resulting in a much smaller range of trimmable angles of attack. If the lower end of this range is right of the point where the pitching moment crosses into positive values (here at $\alpha$ = 24°), the aircraft cannot escape with elevator deflections!

Please note that the control power is not sufficient to enter the deep stall with quasi-stationary trim changes. The pilot needs to pitch up quickly and has to overshoot the static trim range in order to cross into the stable region above 30° angle of attack. There, his range of trimmable $\alpha$s is too small to achieve the same overshoot backwards.

To get out of this trap needs other changes: Either shift the center of gravity forward, or try to drop one wing. Unfortunately, both the ailerons and the rudder will also be much less effective due to the massive separation and the wake. In a number of cases, even experienced test pilots could not escape this condition.


What is the purpose of the hole in the Cirrus SR22's parachute?

For me, it seems that air can escape the parachute by this hole

That's the point, air HAS to escape the parachute anyway, and without the hole it would do so laterally and in an uneven fashion, leading to lateral oscillations.

The hole allows the air to escape in a controlled location, avoiding undesired and possibly dangerous oscillations.

Some (most personal ones, but for example not the SR22 one) parachutes have handles that allow the user to deform the parachute: this allows some extra air to escape from the desired side, giving lateral controllability.


What could cause the Boeing "Pickle Fork" issues?

Depends on the crack characteristics, number of striations (individual propagation events) etc., whether the cracks are from a small number of near-yield overloads or many small loads from regular cycles.

This sort of thing happens quite a lot.  You are designing parts at all times to be "just strong enough" for all the various requirements and goals, since every pound over that is considered ballast.  Computer finite element analysis makes it possible to fine tune the structure during design and reduce the fudge factor needed in the slide rule days.

Endurance fatigue testing of the part is used to validate the finite element analysis. A 3:1 safety or scatter factor is applied in the fatigue endurance test.  To be certified for 90,000 cycles, the part had to last 270,000 cycles crack free in the fatigue rig.

As a back stop to all that, you have a structural inspection program to cater to the possibility that the scatter is bigger than expected or the analysis was flawed and wasn't revealed by the original endurance test.  Everything has variability, generally on a pareto distribution (bell curve).

If you only endurance test one or two articles, you can't really be sure where those two parts would fall on the bell curve.  You assume it's near the middle, and the inspection program covers your butt if you are wrong.  Which is the case here probably.   You could test a large number of forks instead of a couple to reduce the scatter factor risk, but $.

You'd need to see the lab reports for the Pickle Forks (I've read many).  There may have been microscopic flaws in manufacture (pits or nicks or voids in a forging) that created crack initiation points.  It  may be a batch issue of a defect like that on x number of parts.  Or the original analysis was off, and the fatigue testing got units that represented the right side of the bell curve (low probability) and gave an optimistic result, so the part was too skinny for the job, from a fatigue perspective, from the get go.


If the modern airliner was redesigned from scratch, would it look functionally different?

You'll only get opinions here, but from 40 years in the business, my opinion is not much.  Airplanes are a balance of compromises and after much trial and error, dead ends, and false starts, a combination hits a sweet spot in the balancing act and that becomes a near universal configuration.  When someone deviates, it MAY create a new configuration paradigm, but most of the time the reasons the universal configuration works so well are revealed, or rediscovered, by deficiencies in the attempt to strike out on a new path.

And here we are, still building airplanes along the lines of the granddaddy of them all for this particular configuration, the B-47, 73 years later.  Virtually all of the improvements that have followed are related to engines, materials and electronics.

Interestingly, you have a kind of mirror image of the same thing in the bizjet world.  There, the tail mounted twin with fuselage hugging the ground is the design config sweet spot.


Can a modified aircraft be imported and certified in the US?

Well, pretty much anything can be given a US airworthiness certificate provided it's not literally falling to pieces.  You could certificate such an aircraft as a Special Airworthiness Certificate in the Experimental category -- Specifically one of:

  Experimental -- Research and Development
  To conduct aircraft operations as a matter of research or to determine if an idea warrants further development.  Typical uses for this certificate include new equipment installations, operating techniques, or new uses for aircraft.

or

  Experimental -- Showing compliance with regulations
  To show compliance to the airworthiness regulations when an applicant has revised the type certificate design data or has applied for a supplemental type certificate or field approval.

If your goal is to ultimately get this aircraft a Standard airworthiness certificate you would probably want the latter, to allow you to conduct test/certification flights in the modified aircraft.
To then get a standard airworthiness certificate things are a bit more murky. You could get a US STC based on the European STC & using this aircraft as the example for conformity inspections and flight testing, but that would require going through the STC process.

The other option would be the 337 process, in which case you are also going to need an A&P mechanic (preferably one with Inspection Authorization) and the cooperation of your local FSDO to approve the modification as a "major alteration" (FAA Form 337 - Instructions here).

As you alluded to in your question, something like installing a Rotax engine in a Cessna 150 is a "Major Modification" that has no "FAA Approved Data" (STC procedure/drawings/etc.) to include with the 337, so you would need to submit "Acceptable Data" for your modification (the European STC is a good starting point) and work with the FAA to obtain approval for the modification.

This is something you would want to talk to the FAA about before purchasing an aircraft with such a modification (there's a good chance they may not approve the modification, which would leave you with an unairworthy aircraft, or one restricted to the Experimental category).


Why do jets with 3-D thrust vectoring never hover nose up, but instead move slowly forward?

There are limitations in the ability to articulate the thrust vectoring that would limit the ability to hover in space and requires some small amount of forward speed to keep the Sukhoi in a controllable state.  It looks like the RC jet has a vector nozzle that can operate in all directions so that it can be hovered in place like a helicopter, although I imagine the skill level on the part of the operator is pretty high.

My favourite airshow performance of all time was a guy, Wayne Handley, with a monoplane aerobatic machine, the Turbo Raven, with a PT-6 engine, which had a thrust to weight ratio of well over 1:1.  The elevator and rudder surfaces allowed him to control attitude while hanging on the prop, and the ailerons provided anti-torque control.  At Osh in 1998 or 99 I remember him hovering in front of the crowd, moving around in a square box pattern, like outlining a picture frame in the sky, then accelerating straight up until he was a speck.  He stopped doing the act after a crash, from the prop not wanting to come out of ground beta during a descent maneuver, about a year later.  Never seen anything like it since.


What is a typical ratio of aircraft in air vs. total aircraft per airline?

Well here's one way to approach it:

Excluding transatlantic and transcontinental red-eye flights, most airplanes are running between 6 am and about 10 or 11 pm and are down overnight.  Let's just say 18 operational hours per day, or 6570 operational hours per year (we could define operational hours as an aircraft "available for duty").

The average airliner flies between 2 and 3000 hours per year, so lets use 2500.

Being airborne 2500 hours out of 6570 operational hours means the airplanes are airborne about 38% of operating hours.

Allow for aircraft that are in the fleet but are non-operational because they are down for more than overnight; A checks, C checks, D checks, and also dispatch delays.  We could adjust the percentage number down somewhat, say several percent, to allow for that.

We are left with roughly (very roughly, there will be a lot of scatter no doubt) 1/3rd, or slightly better, of a fleet airborne at any one time during the operational day, if you surveyed across a national fleet.


What are these windows/portholes on the English Electric Canberra bomber?

It's called a "Direct Vision" (DV) window. The canopies are sealed shut, so the small DV window is provided as a way to open a small hole if required. For example, to communicate on the ground or in the event of icing or other canopy issues.

Edit: I wasn't able to find a formal source, but this page is fairly authoritative:

http://alverstokeaviation.blogspot.com/2016/08/english-electric-canberra-technical-tour.html


Would there be a purpose for a set of compressors in an electric turbo fan?

No.  The only purpose of the compressor is to provide high pressure air for the combustion chamber and turbine.  If there is no combustion chamber and no turbine, then you do not need a compressor.  Just drive a big ducted fan (or propellor, your choice) with your electric motor.


Can static electricity affect navigational instruments?

This will depend on the system, but the over all answer would be Yes at least to some extent. When talking about VOR/VORTAC/DME/NDB/GPS or any other nav system that relies on both a device in the plane as well as a device elsewhere we must consider how these devices talk. In this case we are talking about radio waves (em propagation), and lighting does produce an EM field so it has the capability to interfere.

That being said "interference" has both a technical term and a reality IMO. On paper, yes this may interfere with the signal but in reality lightning is fast and isolated so its momentary interference may not interfere with the operation of the device over a usable amount of time or may cause a momentary drop out.

Local INS (Inertial Navigation Systems) if you have it would remain generally unaffected.

There is another issue that presents itself if the lighting is very very close to the aircraft and will be more of an issue with composite aircraft. For what it's worth, if the whole skin of an airplane is conductive (as with metal skinned aircraft) it will act as a pretty solid Faraday cage. This will vary from plane to plane but is generally true. Thus if the lightning generates a strong enough EM pulse the interior of the plane will be protected from it. On a composite based plane you potentially expose yourself to flux related power surging. It should be noted that the critical electronics are protected from this kind of damage.


Why is the APU located in the tail for almost all commercial aircraft?

Dead space... Not much room in the tail to put other stuff, and it fits. Plus it has a nice empty space just outside for the exhaust pipe to exit without the hot gasses hitting anything.

Put the APU in the nose and you need a long pipe somewhere to get rid of the exhaust. More weight, more space, etc.
Put it in the wing and you're looking at uneven weight distribution (you want it at or near the centerline).
Leaves the tail area as a logical place, and there just happens to be space there as well in most aircraft.


Does Molecular Weight of a Gas affect its lifting properties at the same velocity over the same wing?

The wing will produce much less lift in helium than in air; all else being equal, lift is proportional to the molar mass of the gas in question.

The lift equation states that lift $L$ is proportional to the air density $\rho$ (rho):

$$L = \frac12 \rho \ v^2 \ S \ C_L,$$

where $v$ is the true airspeed, $S$ is the wing area, and $C_L$ is the coefficient of lift.

Meanwhile, one form of the ideal gas law tells us how the air density $\rho$ is related to the molar mass $M$:

$$\rho = \frac{MP}{RT},$$

where $P$ is the (static) pressure, $R$ is the gas constant, and $T$ is the absolute temperature.

Combining both of these equations, we find that

$$L = \frac{M P \ v^2 \ S \ C_L}{2 R T}.$$

In words, lift is

the molar mass of the gas,
times the static pressure,
times the square of the airspeed,
times the wing area,
times the coefficient of lift,
divided by the absolute temperature,
divided by a constant (the gas constant $R$),
divided by $2$.


Why do some approaches have suffix letters such as Y and Z?

The naming convention is explained in Chapter 4 of the FAA's Instrument Procedures Handbook:

  When two or more straight-in approaches with the same  type of
  guidance exist for a runway, a letter suffix is added  to the title of
  the approach so that it can be more easily  identified. These approach
  charts start with the letter Z  and continue in reverse alphabetical
  order.

The TERPS explanation (section 161) is a little more specific:

  d. Duplicate identification suffix. When more than one procedure to the same runway uses the same type of navigation system for lateral
  guidance within the final approach segment, differentiate each
  procedure by adding a non-repeating alphabetical suffix using the
  letters “S” through “Z.”

The Handbook gives the example of two approaches at Chicago Midway (KMDW), which has the RNAV (GPS) Z RWY 13C and RNAV (RNP) Y RWY 13C approaches. They're both straight-in GPS approaches to the same runway, but one requires RNP and the other doesn't.

As the question itself and this comment note, there are plenty of other possible differences between approaches to the same runway; RNP is just one example. Having multiple approaches allows an airport to accommodate aircraft with different equipment and capabilities or, as section 140 of the TERPS puts it, to "gain an operational advantage":

  To permit use by aircraft with limited navigational equipment, an IFP [Instrument Flight Procedure]
  should be formulated using a single navigation source whenever
  possible. The use of multiple navigation sources of the same or
  different types may be permitted to gain an operational advantage

I have no idea how to find out why a specific runway has multiple approaches or how the approaches were designed; presumably it's something that the FAA and the airport operator (and maybe even the airlines) work out based on local runway use and traffic requirements.

In the example in the question, one plate requires GPS, the other DME or radar. So a non-GPS equipped aircraft can still use the ILS, but with different ways of getting to it, different minima, etc.

Note that there's a similar naming convention for circling approaches:

  Approaches that do not have straight-in landing minimums  are
  identified by the type of approach followed by a letter.  [...] As can
  be seen from the example, the first approach of  this type created at
  the airport is labeled with the letter A,  and the lettering continues
  in alphabetical order.

Their example is Rogue Valley International - Medford (KMFR), which has the following circling approaches:

VOR-A
LOC/DME BC-B
VOR/DME-C
RNAV (GPS)-D

There's no explanation that I could find in the Handbook or TERPS to explain why circling approaches must have a letter even if the navigation systems are different. But as @RalphJ mentioned in a comment, this provides a clear way to identify multiple circling approaches using the same guidance, e.g. a VOR-A approach from the north and a VOR-B one from the south.


Where can I find detailed steps on how to perform all ACS maneuvers?

Interesting question.  In the past, the preamble to the PTS showed reference material that can be used to throughout the PTS.

With the new Airman Certification Standard (ACS), those references are incorporated into each task.  For slow flight below it lists the references as FAA-H-8083-2, FAA-H-8083-3 and POH/AFM.

 Private Pilot Airplane ACS

Undoubtedly, it will list the Airplane Flying Handbook as a reference.  All the maneuvers and techniques are in that book.  It is generic and the POH takes preference if there are disagreements.

Airplane Flying Handbook (FAA-H-8083-3)

Risk Management Handbook (FAA-H-8082-2)


For purposes of the FAA instrument written, which system becomes primary for pitch following an AHRS failure?

The AHRS is the Attitude and Heading Reference System. It is synonymous to the Gyroscopic systems of a steam gauge aircraft.
The ADC or Air Data Computer is synonymous to the pitot-static system in a steam gauge aircraft. Just like a steam gauge aircraft, the AHRS and the ADC are two separate systems. And, for good reason. They compliment each other while at the same time providing a redundant backup when needing to fly partial panel.
The PFD is the Primary Flight Display. It is synonymous to your PC computer monitor. If your PC is not working, it does not mean that your monitor won’t work. And if your PFD does not work, a TAA will have an MFD (Multi-Function Display) that can display the same info.
That being said, the AHRS is not as important in VFR flight as the ADC. Ask yourself the question of which parts of the AHRS are required by subsections b & c of Title 14 Code of Federal Regulations Part 91.205. No gyroscopic instrument is required by 91.205 for VFR flight. As long as the magnetometers are working and displaying properly, you are still capable of flying relatively safely. Even if the magnetometers are inoperative, you should still have your magnetic compass to meet the requirements of sub-section b.


How long is the training to get a Boeing 777 rating if one has a 737-200 rating?

A flight school can offer an "abbreviated type rating course" which takes into account skills from previous type ratings, assuming you have flown an adequate number of flight hours on those ratings.

Boeing also offers a shortened type rating course, details are halfway down their page. To answer your question, Boeing claims 13-15 days for their training and requires 1,000 hours of experience, but it does not depend on a specific rating. There is an even shorter 777-787 conversion as well, that requires a 777 rating.

I think their assumption is that they can skip a lot of basic handling, CRM, checklist type training and focus on the technical aspects. A training provider with the proper approvals could offer a similar class.

Also, for reference, there is the Airbus A320-A330-A340-A380 conversion training which uses the proprietary term "cross crew qualification", and takes less than 2 weeks versus 6 for a full rating. This is done under a EASA approved syllabus, which allows you to do it at any qualified school. Here the requirements are 150 FH on the appropriate Airbus type, and 3 months of experience.


How does aircraft design affect carburetor ice?

I've downvoted the answer from Habu because it ignores a major difference in engine design.

For small GA planes, the Lycoming engines have the carburetor bolted to the bottom of the crankcase where it gets some heat from the hot oil.  Fuel/air exits the top of the carb where it is routed through pipes inside the crankcase where the hot oil further increases its temperature. This makes the Lyc generally resistant to induction icing.

In Continentals, the updraft carburetor is not mounted on the hot crankcase but on part of the manifold assembly, insulating the carb itself from the heat of the crankcase, and the fuel/air mixture is routed directly to the intake manifold and not through the engine crankcase which holds the hot oil.  The result is that the TCM O-300 engine has earned the reputation of being an icemaker. The difference in the POH instructions as to how to fly each engine is directly attributable to engine design and it has absolutely nothing to do with the weather in Vero Beach versus Wichita.

I'm going to post line drawing images of the two engines to illustrate the point. First: Lycoming.  Second: Continental

What the original poster is missing is that for most of its history, the Cessna design used Continental engines.  Now that it has switched to Lycoming engines, the difference in the engines is probably zero, but they have not abandoned the former POH instructions as that might be confusing to the pilots that fly these planes.  After all, using carb heat more often as a default procedure for the Lyc powered Cessnas is a safe procedure.