How to improve engine-out handling on a multi-engined aircraft?

Yes providing a longer vertical tail arm is very beneficial for control in case of engine failure.

During the pre-design phase of an aeroplane the Tail Volumes are determined: area of horizontal and vertical tail, times the moment arm. This answer gives more info on some statistical data and methods.

Of course, optimal dimensioning is paramount since we're dealing with aerodynamics and we want to limit drag. The tail arm is usually limited to the useful fuselage length, leaving the tail area to be the main design parameter.


Why did it take so long for helicopters to be developed/in use?

The useful payload and the robustness of rotorcraft were not sufficient for the rough conditions on the front. Only when turbines were available with their much better power-to-weight ratio and high reliability did helicopters offer a real advantage to the military.

The de Cierva autogyro line was begun in 1920, but de Cierva focused on building unstallable GA aircraft, not weapons. The same can be said for Henrich Focke, who improved on de Cierva's designs (which he built under license) with the Fa-61, which is considered the first practical helicopter.

The only helicopters to be used by the military were the designs of Anton Flettner who used two intermeshing rotors with considerable success, the transport helicopter Fa-223 with two rotors on outriggers and the Sikorsky R-4. The Flettner 282 and the Fa-223 were ordered by the Luftwaffe, but development took a long time, with many new problems to be overcome. In the end, they came too late to be used in any quantity.

The Sikorsky design was unstable and needed considerable pilot attention. Just watch how poor Igor is working the stick to keep the VS-300 straight! It also needed years of refinement before it could be used by the military. This was the R-4 which saw limited use for rescue missions from 1944 on.

Just because something can be demonstrated once does not imply it is ready for widespread use.


How should the number of maintenance hours per flight hour for the C-17 be interpreted?

I am sure the raw data can be found somewhere in some document or budget line item but there are a few things to keep in mind.

These numbers may only be airframe maintenance preformed. According to this article it seems that P&W maintains the engines.
This article (a bit dated) states that the air force must only maintain 50% of the work in house. Again they may only be counting their hours.
The air force (and all military aircraft) are subject to their own regulations and intervals and such. Although they must play by FAA rules when flying in airspace their upkeep is to the standards set forth by the owning military body. This may make it hard to compare with general aviation or commercial aviation.

  Do the required maintenance hours scale with: size, complexity, military/commercial use?

In general yes. A piper cub is going to be simpler to maintain per hour than say an F-16 but as you know things vary. I would say that the hours scale more with complexity than size. Mainly because from a mechanical stand point a more complex engine or aircraft would have more things to disassemble and go wrong and in turn more things to put back together generally increasing maintenance time. Keep in mind this is a very general statement.

In terms of military vs commercial use, you will see a lot more maintenance on a military fighter than a commercial plane largely as a result of design. Commercial planes have lots of redundant systems and reliable parts as they are selling safety. Fighters have lots of high performance parts, some redundancy and things that may be made to wear faster in order to preform. Again a general statement but you can get the gist.

  Do those 20 hours refer to an average over extended operation of the aircraft? In other words, does this include extended maintenance where the plane might be undergoing days of intensive maintenance, skewing the numbers?

Im going to assume that this is an overall average but it may not be.


Who has final authority over Air Force One?

The pilot in command has final authority over Air Force One
Air Force Instruction 11-202, Volume 3 says the following in Chapter 1, part 1.1.1 (as in, the very first thing in the document):

1.1.1. Pilot  in  Command  Authority. The Pilot in Command (PIC), regardless  of rank, is responsible for, and is the final authority for the operation of the aircraft.

Just for fun, let's compare it to the civilian version that you referenced, 14 CFR 91.3:

The pilot in command of an aircraft is directly responsible for, and is the final authority as to, the operation of that aircraft.

Wow! Basically identical except that the military version goes out of its way to mention that rank is irrelevant.


Are modern commercial airliners flyable without operational computer systems?

For a non-fly-by-wire airliner, yes.  It's just another airplane in the end and as long as there is hydraulic power you can fly it.  If the weather is clear you don't need any electronic aids at all, if you know how to fly in the first place.

For FBW, where computers control the controls and the pilot is just telling the computers what he wants to do, they are dependent on multiple levels of electronic redundancy to account for those sorts of breakdowns.


What is this weird format (R06L/CLRD62) in METAR for runway being cleared?

The format follows a standard, although this one is different because of the  R at the front...

The format is the "Runway State Group":

First two digits are the Runway Number, 88 means all runways, 99 means a "repetition of the last message as no new information received".

The third digit is the runway deposits, it tells you what is on the runway:

  0 = Clear and dry
  1 = Damp
  2 = Wet or water patches
  3 = Rime or frost covered (depth normally less than 1mm)
  4 = Dry snow
  5 = Wet snow
  6 = Slush
  7 = Ice
  8 = compacted or rolled snow
  9 = frozen ruts or ridges
  / = type of deposit not reported (e.g. due to rwy clearance in progress)

The Fourth digit is the extent of the contamination:

  1 = 10% or less
  2 = 11% to 25%
  5 = 26% to 50%
  9 = 51% to 100%
  / = not reported (e.g. due to rwy clearance in progress)

The fifth and sixth digits are the depth of deposit:

  00 = less than 1mm
  01 = 1mm etc

to

  90 = 90mm
  91 = not used
  92 = 10cm
  93 = 15cm
  94 = 20cm
  95 = 25cm
  96 = 30cm
  97 = 35cm
  98 = 40cm or more
  99 = Rwy(s) non-operational due to snow, slush, ice, large drifts or runway clearance, but depth not reported.
  // = depth of deposit operationally not significant or measurable.

And the seventh and eighth digits are the braking action:

  28 = friction coefficient 0.28
  38 = friction coefficient 0.38

or

  91 = Braking action: Poor
  92 = Braking action: Medium/Poor
  93 = Braking action: Medium
  94 = Braking action: Medium/Good
  95 = Braking action: Good
  99 = Figures unreliable (e.g. if equipment has been used which does not measure satisfactorily in slush or snow.)
  // = Braking action not reported (e.g. runway not operational; aerodrome closed; etc.)

So we can take your example: R06L/CLRD62

Means

R06L : Runway 06 Left
/ : Deposit not reported (clearance in progress)
CLRD: Contamination ceases to exist, so two groups omitted
62: Friction coefficient 0.62

Source: Skybrary.aero But I can't find one definitive source with all the possible reporting in a METAR, sadly.

It seems that this "Runway State Group" is mostly used in European countries, I can't find an example of it used in the U.S.. Here is one good reference which I think covers 99% of the METAR data for Europe.


Is it possible to divert a plane to a distant airport?

The diversion airport is selected by the captain¹.

If the aircraft needs to divert for some urgent reason like engine failure, smoke/suspected fire/fire, medical emergency and similar, the captain will select the airport so that they can land as soon as possible. However from cruise altitude even expedient descent still takes about 15–30 minutes and the plane can cover 50–100 nmi, so they still have some choice in most places, especially densely populated areas like Europe.

But there are many less urgent reasons that warrant diversion. The most common is of course that the intended destination is closed due to weather, accident or other problem. And then there are problems like pressurization failure that require descent to lower altitude where the fuel consumption is higher, so the plane no longer has enough fuel to reach the original destination, but still has fuel to fly considerable distance.

Sometimes the plane can even reach the intended destination just fine, but some fault occurs that would be hard to fix there, so the plane returns or diverts somewhere it will be easier to fix.

In these cases, the captain calls the airline dispatching (over radio, HF radio or satellite phone) and discusses with them where they should divert to make least disruption to the overall airline operations considering things like ability to fix the diverting plane, availability of replacement plane or alternate connections for the passengers, availability of replacement crew to fly the replacement plane or this plane after it is fixed, availability of airline representatives to take care of the passengers and many other things.

So something happened and for some operational reason it was easier for the airline if they had the plane in Krakow than if they had it in Gdansk (or, if it was not possible to have it in Gdansk, better to have it in Krakow than, say, Warsaw, which was still closer). For example I remember reading about incident where wind shield cracked on a plane already on approach to their destination, Klagenfurt, and they returned to Vienna and sent the passengers by bus. Because it was apparently easier (and cheaper) for the airline than fixing the airplane in Klagenfurt without suitable hangar (with cracked winshield the plane may complete the flight, but not take off again).

¹ Except really special circumstances like violation of foreign airspace and arrest by interceptors, nobody from outside can divert the plane. The pilots do.


When/how to set the inbound or outbound course when intercepting a VOR for a DME hold?

Below is a picture possibly showing what your instructor may be telling you. (based on the information you have given in your question)


Why are piggyback launches done by dropping the carried aircraft and not by "fly-off" launches?

Its much safer, you don't kill the carrier aircraft if you drop away and have a major aircraft malfunction.  Gravity gives you the separation you need.

If you treat the two aircraft like a formation flight, which it essentially is, its dangerous for the critical aircraft to go belly up, ie blind, to the carrier.  In an emergency the first step in formation flying is to ensure separation which the critical aircraft can't do because it can't see if it's clear to descend and it may not have the ability to laterally sidestep.  Thus, a blind push on the nose could kill both aircrews.


What are these lumps on the top side of the wings of military aircraft?

They are fairings for one thing or another that projects above the wing skin.  Part of a gun or ammo feed system, fuel cap, wing fold mechanism, head of a big bolt, whatever.  Usually, components are designed in the original versions of the aircraft to fit within the wing profile, but mods and add-ons later introduce bits that project beyond it, so the easiest thing to do is fair it in with a blister.


What was the aerial chase scene plane in 'Murder in the Clouds'?

NC-406N would likely have become N-406N if reregistered or transferred. Since none of the 52 Travel Air 4000's registered nor any of the 6 Travel Air D-4000s still have the NC prefix, I'm guessing this is what has happened.

Tail N406N is listed by the FAA as a D-4000 Registered from 1991 on. If this is what you meant, then yes it is correct. Additionally, the wiki page for the movie does list a "Travel Air Speedwings" [sic] as the aircraft used in the production of the movie. I've not been able to verify if N406N is actually a speedwing vs the other models of Travel Air but a more knowledgeable expert might do so with the serial number: 1337.


What are these parts on the wing of a Boeing 737?

I try to improve on the guesswork of @aeroalias. Here we go:

Parts 1 and 3 are the two exhaust gates on either side of the aft engine fairing, which is part number 2. For a reference, see The Boeing 737 Technical Guide, page 116, by Chris Brady (Google Books link).

The flap actuation mechanism is quite a bit ahead of the flaps, and the same goes for the spoilers.

The engine on the Boeing 737 is placed very close to the wing, so the flaps would sink into the jet blast when lowered to the landing position. This would cause high vibrational and thermal loads on the flaps next to the engine exhaust, especially when the pilot increases thrust in landing configuration for a go-around. To protect the flaps, the exhaust gates were added so this part of the flap does not extend down as much as the rest of the wing flaps.

Drawing of the inboard wing flap of the Boeing 737-300/400/500. The inboard flap track sits within the wing root fairing, and the outer track sits in the aft engine fairing (picture source).


Why do pilots have the ability to turn off the transponder in-flight?

Basically everything that consumes power on an aircraft can potentially cause interference, short-circuits, or otherwise jeopardize the safety of flight and therefore must be switchable. Sometimes the switch is in the form a button, otherwise by a fuse.

There are several particular reasons that the transponder can be turned off.

If the transponder malfunctions, it may cause interruptions to all ATC surveillance in an area. There have been occurrences in the past that due to a fault the transponder it was basically acting as a radar jammer.

In one particular incident it took a while before the aircraft that caused it was identified and after requesting the pilot to switch of the transponder, secondary surveillance was restored.

Another reason is that when the aircraft is at the gate, the transponder is switched of to reduce the amount of radio transmissions. 100 aircraft on the surface of a large airport can produce a massive Radio Frequency noise, which negatively affect radar systems. When taxiing, radar replies are useful for aircraft identification, hence the transponder is switched on at push-back or engine start.

For an example to see how such requirements are worded in aircraft certification regulations, see rbp's answer.

The focus here and in the media1 on the transponder in relation to hijacks is a red herring. If an aircraft is hijacked, there are way more important things to worry about than an active radar transponder.
If hijackers turn off the transponder it means that they have access to the cockpit already.

1This answer was written shortly after flight MH370 went missing while en-route from Kuala Lumpur to Beijing. Initial speculation focussed on a possible hijack scenario.


Is a light aircraft still usable after a successful airframe parachute deployment?

For the Cirrus at least, it sounds like that the odds are that the plane will be a loss.  Thus far of 53 CAP deployments, only "9 CAPS Planes that Were Repaired and Flew Again"

Revision A7 of the Cirrus SR22 POH currently states "CAPS deployment is expected to result in damage to the airframe" that updates the earlier language that "The system is intended to saves the lives of the occupants but will most likely destroy the aircraft."

https://www.cirruspilots.org/copa/safety_programs/w/safety_pages/723.cirrus-caps-history.aspx


How can you identify an Airbus and or Boeing from the inside based on features of the interior?

You can't, unfortunately, airlines (of same type) choose different seat manufacturers, etc.

It's like asking how to identify a building's architecture from one room.

We can discuss wing shapes, or a tail camera's feed on the IFE if there's one, but what if you're stuck on the middle seat of the middle column on a wide-body without a tail camera and no wing view?


Will ATC proactively route traffic around bad weather?

Yes, ATC will reroute flights that are operating on Instrument Flight Rules (IFR).
There are lots of videos of flights getting routed around severe weather floating around on the internet! Atlanta is a great example, as is Memphis, FedEx's hub.
In addition, NASA is working on a product called Dynamic Weather Routes that will help controllers be smarter about amending planned or unplanned weather reroutes.
Sort of, for aircraft operating VFR.
VFR flights that are talking to ATC may get advisories about weather and suggested headings from the controller. I've received notifications about things like 'moderate to heavy precipitation 5-10 miles ahead' many times when operating on VFR flight following.


Can an Airbus A380 or Boeing B747 fly with only 2 engines?

First, my experience was with 747-100/200 aircraft. However, I'm reasonably certain that the subsequent variants of the 747 would perform just as well, and I would be surprised if the A380 did not as well.

  If during cruising with full load....

"Full load" is a little ambiguous. If what is meant is MTOW (max takeoff weight), note that by the time you reach cruising altitude, you're considerably lighter than MTOW.

But let's say you leveled at FL310 or thereabouts, and shortly thereafter two engines failed. Discounting catastrophic failures that leave things hanging out in the wind that generate a lot more drag than a simple inoperative windmilling engine, you should be able to fly as far as your fuel will take you, although common sense and the regulations would dictate finding the nearest suitable airport.

You won't be able to maintain your 4-engine cruising altitude. You'll drift down until you reach an altitude that you can maintain.

You'll be able to fly whether the two failures are both on one side or one on each side, but both on one side is the more problematical. We used to practice that in the sim. They always put both failures on one side to make it more interesting. The drag from the rudder necessary to counter the adverse yaw from the operating engines is significant, and as you start reducing the power for the landing, judging how much rudder to decrease and when is an interesting dance. You would have run in lots (maybe all) the rudder trim. How much of it should you take out and when. Take it all out too soon and your leg is going to get awfully tired.

While a double failure at cruise is handleable, it's easy to come up with scenarios that are not. If you had a double failure on takeoff just after V1, I doubt you'll make it. V1 and the balanced field length are predicated on one engine failing, not two.

Take a look at https://thepointsguy.com/2017/03/engines-boeing-a-747-can-fly-on/, the relevant part is:

  After almost 15 minutes in a controlled gliding descent, the crew coaxed one engine back to life, allowing them to significantly reduce their rate of descent. A few minutes later, a second engine came back on line with partial power, allowing the aircraft to enter a slow climb.

It's also worth noting, I think, that when you're doing a 3-engine ferry in a 747, you're depending on it being able to continue flying on two in case of an engine failure during that ferry flight.

A final thought about the last part of your question:

  controlling the rudder makes the airplane fly sideway.

To the best of my knowledge, the use of the proper amount of rudder to counter asymmetrical thrust does not make the airplane fly sideways. However, I am not an aerodynamicist. Perhaps one of the many here qualified in that area can comment.


Can an APU exhaust make a contrail in flight?

APU may be used in flight as second source of power or bleed air if one of the engine systems is inoperative. If it is so used, it might leave a contrail the same way engines will, though as DeltaLima notes, it's exhaust is hotter and the air behind the fuselage is more turbulent, so the range of conditions where it will leave a contrail is narrower than for the engines.

And it is an exceptional situation, so it is extremely rare. Most of the time the APU is switched off once the engines are running and only switched on again after landing, because when engines are running, they provide everything the aircraft needs.

In B737NG (the lower aircraft in the picture), the APU can be used as bleed air source up to 17,000 ft. This is too low for normal cruise, but if bleed system fails, pilots will descend to this altitude and start APU to provide air-conditioning for the remainder of flight to a suitable nearby airport. It can also be used up to 41,000 ft as power source, so the aircraft may cruise with one generator inoperative and running APU.

In A320 (the upper aircraft in the picture), the APU can be used together with one bleed air system up to 20,000 ft and for power generation up to 41,000 ft. So again, the aircraft may cruise with one generator inoperative and running APU.

However:

Normally there would never be contrail behind APU and none behind engines unless both engines failed and APU was started as backup power source (US1549 did start APU when the engines failed, though it is unlikely there was contrail at that altitude).
Contrail does not start right behind the engines. The water in the exhaust needs some time to cool down and freeze before the contrail becomes visible.


It is very common for planes to land on snow (i.e. packed snow) or even ice runways.

  How are planes kept in control with so less friction on ground?

Snow/ice friction is a function of the outside air temperature, so it depends. Another factor is whether the runway was packed, fresh snow - and the temperature the previous day. The colder it is, the more friction the snow will have (i.e. adequate braking). In warmer temperatures the snow will be slick (scarily slick at times - as in nil braking).

While flying a multi-engine airplane, one can use differential power. If you're flying a single-engine airplane - one is better off with small taps on the brake during slick conditions. If the OAT is relatively cold (well below freezing), braking can be pretty good.

  What is the procedure to perform such kind of landing?

The procedure is the same as a standard landing. However, it is awfully nice to have good contrast on the snow to see the runway. Often runways that are pure snow/ice will be more visible than the surrounding terrain. At the very least - the runway will be outlined with some sort of runway markers.

  And, on an average how much extra distance does an aircraft
  covers by landing on snow, as compared to landing on ground?

As I said before, it is really dependent upon the outside air temperature and the condition of the runway (i.e. packed snow or fresh snow).

For example, suppose there were fresh snow on a relatively warm day (30 degrees farenheight) and the snow is compacted (i.e. by humans) that day. Say, night-time temperatues drop to 0F, and the next day you land with an OAT of 30 to 35+F... that runway is going to be SLICK. However, if the temperatures were to stay at 0F - you would actually have decent braking. Even further, if the OAT dropped to -40 below...you will have excellent braking.

TLDR:

Snow conditions are always changing and braking/control of the airplane are dependent on those conditions. Snow-conditions are highly dependent on the outside air temperature and to some degree human-maintenance (for better or worse).

*source: Personal experience from flying in the Arctic.


Your best bet will be to listen to recordings of taxi clearances issued by Ground Control.
The chance that you can see replays of enough ASDE-X or other surface radar recordings to get a meaningful data set is probably about zero unless you can get agreements with whatever ATC facility you're interested in.
While it's possible that some facility may record the data that you're asking about, the general answer is that the ground controller simply issues the clearance over the radio and the aircraft complies.  If a conflict arises that requires something different, then the controller issues a revised clearance & the aircraft follows the new instruction.  But unless a particular facility is doing something special (an extra person in the tower cab recording clearances & routings in order to undertake some specific analysis, for instance, or maybe a facility doing an analysis of ASDE-X tapes for some project), there's no widespread banking of that sort of thing.
Thus the suggestion that you will need to build your database yourself by listening to something like Live ATC (dot net) and copying down the routings given.


How long can an average aerobatic plane sustain 0g?

An aerobatic aircraft (as well as any aircraft) can sustain 0g until the pilot pulls up, the aircraft hits the ground, or reaches terminal velocity.

In order to sustain 0g  the aircraft must be accelerating towards earth at $9.8 m/s^2$ (meters per second squared). That means there isn't much time before the aircraft reaches its maximum speed. Once the aircraft can no longer accelerate at the same rate of gravity, then the occupants will no longer feel 0g. In sky diving (and physics) this is called terminal velocity, which is the velocity at which air friction prevents the object from falling any faster.

Acceleration is change in speed, so naturally you don't have to be going straight down to be accelerating towards the earth (we're talking about vertical speed). If you are going up at 200kts and begin to decelerate at exactly $9.8m/s^2$ you will "feel" like you are in 0g (free fall) even though you are continuing to go up for a few seconds. But this will only last for a few seconds before the aircraft momentarily reaches its apex and you and the aircraft begin moving towards the earth. If the aircraft can match exactly the acceleration of gravity, then you will continue to feel weightless (i.e. 0g).

But you can't continue to accelerate indefinitely towards earth without either reaching terminal velocity or exceeding the aircraft's maximum speed. So the limit of the sustained 0g flight is the pilot pulling back on the yoke and climbing to prevent the destruction of the aircraft and death of all on board.

However, even if the wings broke off of the airplane, and you were plummeting towards the ground in the fuselage of the aircraft, you would only remain weightless so long as the fuselage continued to accelerate towards the earth at $9.8m/s^2$. At some point, if you had enough altitude, the drag (wind friction) on the fuselage would prevent it from continually accelerating towards earth and you would reach an equilibrium speed where the force of gravity equals the force of drag and you would no longer feel 0gs.


What should I do if the FAA requests health records that no longer exist?

I had a very similar situation. Along with the documentation they requested that was available to me, I submitted a letter explaining my lack of the older records. This was apparently acceptable to the physician reviewing my case because I was issued a third-class medical cert. You can borrow from the verbiage I used (identifying information removed):

I am unable to provide any medical records or previous imaging related
to the injury in question. I contacted the hospital that treated me,
[hospital name] in [city, state], and was informed the records have been
destroyed. [State] law [citation of statute] requires retention of records
for “[quote document retention language from the statute].”
The injury and treatment occurred in [month] of [year].
[Hospital name] does not retain records past this requirement, and
the records you are requesting were destroyed more than 10 years ago.
Furthermore, the physician who treated me, [physician name], is no longer
practicing.

Good luck!


Can the removal of a duty-free sales trolley result in a measurable reduction in emissions?

Yes, the removal of payload will result in a measurable reduction in emissions.

First, I have to correct some math: the engines don't run at 150 kN in cruise - that would indicate a L/D ratio of only 4-5, since a typical A320 weighs around 60 tons mid-flight (give or take 10). Fuel consumption is roughly proportional to weight, so 30 kg out of roughly 60,000 kg is a 0.05% reduction, not a 0.00012% one.

As to whether one would be able to move the throttle down exactly 0.05% to benefit from the reduced weight and leave everything else equal, no, not even the autothrottle is so precise.

But that doesn't mean fuel consumption is unaffected: the balance of an aircraft's weight, lift, drag and thrust always affects its energy. At the exact same throttle setting, the aircraft will climb a fraction of a percent faster, and so finish its climb and go to lower fuel burn at cruise a few seconds sooner. In cruise, maintaining the same flight level, it can spend a minute or two at a bit lower throttle, or trimmed a bit down, which will make it arrive a few seconds sooner.

This is fundamental conservation of energy: if less of it is expended in drag, then either the engines have to work less, or the aircraft will climb or accelerate. This happens all the time - an airliner in level flight doesn't stay in perfect equilibrium throughout, but corrects for energy changes every once in a while. Even if it doesn't change how much fuel is pumped into the tanks that particular day, the effect is cumulative across all sources and persistent through random variations.

Overall the effect of weight on fuel burn is proportionate. Depending on the distance, everything aboard an aircraft can consume 10% to 50% of its weight in fuel each flight. A very rough ballpark is that, over the life of an A320, each pound of operating empty weight will cost an extra ton of fuel.

To be more specific, given the A320's fuel burn of roughly ~2,500 kg/hour, adding the trolley requires an extra 1.25 kg of fuel per hour it's in the air. For a 4-hour flight, that's an extra 5 kg of fuel. Over the 60,000 flight-hours an A320 will serve in total, that's 72,000 kg of fuel. So behind that trolley is 3 large tank trucks' worth of fuel to keep it in the air, and ~225,000 kg of CO2 emissions.

As an aside, in-flight sales of random junk really serve the airline, not the passengers. The profit margin on these items can be up to 100 times the tiny profit margin on economy tickets themselves. With airports packed full of duty-free shops, there's no shortage of shopping opportunities on an air trip. Cramped and burning fuel for every item on board, whether it sells or not, aircraft don't make for a very efficient or practical storefront.

Airlines only make up for this inefficiency by exploiting their cabin crews as free salesmen. Of course, airlines' environmental consciousness tends to correlate strongly with the price of jet fuel, so once sales profit no longer covers the extra burn, it's time to go green.


Could an aircraft be tied down, then throttle up and release for takeoff in order to use a shorter runway?

As already mentioned, aircraft cannot take off without moving through the air, because it is the airflow around the wing that generates the lift required for take-off, and the only practical way of generating sufficient airflow around the wing is to move the wing through the air. This is typically done by moving the wing, and thus also the fuselage it is attached to, forward.

There is, of course, another way to look at that: aircraft can take off without moving relative to the ground, if exposed to a strong enough wind from the front of the aircraft.

That said, keeping the aircraft stationary, "throttling the motors full power, and then letting lose" is a very common short-field take-off technique at least for propeller aircraft; there's nothing theoretical about that. The aircraft is, however, typically kept stationary by applying full brakes while applying full engine power, rather than by using an external tie-down.

The tail likely isn't designed to take the force of holding the aircraft stationary while the engine is running at full whallop, although there's no reason why such an anchor point couldn't in theory be installed (see motor aircraft towing gliders to altitude, scale up somewhat, and you're close).

Since the brakes are already there and need to be powerful enough to at the very least hold the aircraft stationary during the engine run-up prior to take-off, which happens at a significant fraction of full power and can quite well happen at a hold short point just before the runway, there's no reason to spend weight on reinforcing the tail section to that point. Instead, just use the brakes for the few seconds needed.


What is the difference between microburst and windshear?

A microburst is generally an intense down draft while wind shear can occur in any direction. It might be safe to say that a microburst is windshear but not all windshear is a microburst. From your linked pages

  A microburst is intense small-scale downdraft produced by a thunderstorm or rain shower.

and

  Windshear is any rapid change in wind direction and/or speed.


Why has the 777x been designed with folding wingtips?

The Boeing 777X website states that this is to enable a more efficient wing (read: wider span) while maintaining the airport gate and taxi footprint of the classic 777 (which ensures airlines can use the 777X on roughly the same airports and intermix operations with the classic fleet).


Why does the F-111 sometimes squirt a giant fire plume behind it? (NOT afterburners!)

The F-111 has, like many aircraft, a fuel dump port so it can get rid of a lot of heavy fuel rather quickly. Most aircraft have the dump ports on the wings, the F-111 designers put it in the tail between the engines. End result is if you dump fuel and briefly light the afterburner you will ignite the liquid fuel in your wake creating a rather spectacular trail of fire.

Aerodynamically it's completely useless, financially it's very expensive, you'd only do it in combat if you were suicidal as it greatly increases your IR signature right where you don't want it, but at an airshow it does look totally badass, especially as the afterburner is adding a lot of noise at the same time.

I would expect any pilot who does a dump-and-burn outside of an airshow (or an emergency) will have his own tail set on fire by the air wing's commanding officer.

The SR-71 had a similar issue - it leaked like a sieve on the ground. Rotating for takeoff would occasionally set fire to the JP-7 on the runway leaving a burning trail behind it much like the Road Runner.

Reply to the video:
watch the takeoff section carefully. You can clearly see the afterburners come on before the fuel dump starts.

Reply to about half the comments:
Highly unlikely they designed it to do this. The F-111 was one of the earlier swing-wing planes, that meant that you can't put much on the wings. And as the bigger tank is in the fuselage anyway, someone would have looked at the space between the engines and thought it was just right for a dump pipe. The flame effect was probably discovered later.


Can a 16 year old student pilot "pre-take" the checkride?

14 CFR Part 61.39 (a)(5) states that you can not take a checkride in the US until you are of age to hold the desired certificate.

(5) Meet the prescribed age requirement of this part for the issuance of the certificate or rating sought;

Sorry. I encourage you to take as many mock-checkrides as possible in the meantime.
Also, in addition to mock-checkrides. You can train for your instrument rating. 14 CFR Part 61.65 allows you to take a combined checkride or even back-to-back private and instrument checkrides.
§61.65 Instrument rating requirements.
(a) General. A person who applies for an instrument rating must:
(1) Hold at least a current private pilot certificate, or be concurrently applying for a private pilot certificate, with an airplane, helicopter, or powered-lift rating appropriate to the instrument rating sought;


Are there any rules requiring hands/feet on the controls at all times?

There is nothing I can find in the FARs requiring that a pilot keep their hands and feet on the controls at all times.
Such a requirement would be impractical and dangerous in many situations (such as when writing down a clearance in the air: For most people if you keep your hands on the controls while writing you will have a tendency to push, pull, or twist them, resulting in unintended attitude changes).

The most relevant sections of Part 91 would be 91.3 and 91.13:

14 CFR 91.3 (FAR 91.3) says:

  §91.3   Responsibility and authority of the pilot in command.
  (a) The pilot in command of an aircraft is directly responsible for, and is the final authority as to, the operation of that aircraft.
  . . . .

and 14 CFR 91.13 (FAR 91.13) says:

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

  (b) Aircraft operations other than for the purpose of air navigation.
  No person may operate an aircraft, other than for the purpose of air navigation, on any part of the surface of an airport used by aircraft for air commerce (including areas used by those aircraft for receiving or discharging persons or cargo), in a careless or reckless manner so as to endanger the life or property of another.

So basically it's perfectly legal for a pilot to fly with their arms crossed and their feet flat on the floor, even without an autopilot, as long as the pilot in command remains able to exercise operational control of the aircraft as required to ensure the flight remains safe and legal, and as long as they are not acting in a "careless or reckless manner" (like letting their altitude wander all over the place while sitting with their arms crossed).


Why do the British not produce anymore aircraft?

The root of the reason is the fact that aircraft design has become very expensive and the world economy cannot support more than a few companies anymore.

Look at other industrialized countries: They all used to have scores of aircraft companies, which all merged or went down over time. Russia might seem an exception, but the Russian design bureaus are not very productive anymore and kept alive artificially. By now, a national economy the size of Great Britain is too small to support even a single commercial jet builder.

In Augustine's Laws, Norman Augustine shows how aircraft prices have historically accelerated at a faster rate than the economy, and driving this to it's ultimate conclusion, he predicts for the US military:

  In the year 2054, the entire defense budget will purchase just one
  tactical aircraft. This aircraft will have to be shared by the Air
  Force and Navy 3½ days each per week except for leap year, when it
  will be made available to the Marines for the extra day."

There is no conspiracy about it, economics is enough for a convincing explanation. If there is a culprit for the early death of many British aircraft makers, it would be the British Government bureaucracy itself, with a helping hand given by BOAC management. Britain effectively nationalized her aircraft industry at the onset of WW II, and left it to Government bureaucrats to decide which aircraft to build next. This produced aircraft like the Saunders-Roe Princess or the Bristol Brabazon which incorporated many innovations, but were conceptually completely behind their times. When they once tried to be visionary, they steered all efforts into supersonic airliners, which also proved to become a dead end.

When British designers tried to design jet airliners, BOAC management saw no market for a jet airliner but bought the Boeing 707 less than a year later. If you desire to see a conspiracy behind the early death of many British airliner projects, maybe start looking here. The EU certainly has nothing to do with it.


Partial ownership: are there any pitfalls to owning the plane through a shell company?

The main thing to do is to realize why you're creating the corporation.  We created a 501(c)7 (in the US) corporation which is a tax-exempt organization and falls under "social club."  We did this to limit our personal liability.  However, if you are creating the corporation to limit personal liability, you have to make sure to operate like a corporation - call each other "co-owners" instead of "partners" (there are legal ramifications to this, not just semantics).  People around the airport should know it's a co-owned plane by a corporation, not that it's "your plane."  Basically if you want the liability protection of a corporation, you must act like one.

Great book to read regarding the legal side of things is "Practical Aviation Law" by J. Scott Hamilton

Depending on how you set it up (we did a 501(c)7 tax exempt, and yes, you still have to file a tax return), how you use the airplane matters too.  For example, we can't earn money using the airplane (conducting flight instruction to non-co-owners, for example), due to the 501(c)7 status.  Under other corporate structures you can.

Finally, I guess to actually answer your questions: There are some pitfalls, but I think they can be avoided.  Most group ownership things fail because of lack of communication and documentation, forming a corporation kind of forces you to spell out things explicitly and then all involved have no excuse for not knowing "the rules." (You have to write up bylaws and have at least one annual meeting, which forces the communication aspect!)


What's the name of the runway equipment referred to in this video?


Why barotitis, but only during descents and sometimes?

As a plane climbs out, the cabin pressure lowers so that it equals the same pressure as being at about 5,000 feet, the altitude of Denver. What happens inside your ear is that the pressure in the middle ear reduces to match the 5,000 foot cabin pressure, and you might sometime feel your ears "pop," just like going up in an elevator in a tall building.

When the plane descends, the pressure in your middle ear will still be at 5,000 feet, but the pressure in the cabin will go down to sea level (0 feet), and you will feel this pressure on your eardrum, which can cause a lot of discomfort until the pressure equalizes.

The pressure equalizes as air enters the eustachian tubes, which connect your middle ear to your nose and throat. The tube, however, is very narrow and can be blocked by inflammation or mucus due to a cold or other illness, and you won't be able to equalize the pressure. Flying with a cold can be very painful during descent.

The amount of discomfort each passenger experiences is going to vary widely, even from flight-to-flight. For example, if the cabin altitude is 5,000ft and the destination is Denver, then the cabin will not have to further pressurize.  Some other factors are individual physiology (some people will have bigger eustachian tubes than others), illness, ethnicity/gender/gift-of-gab (some are more prone to talking than others, and talking can relieve the pressure), etc.

As a pilot, there are two things you can do:

buy a plane with a lower cabin altitude. I recommend the Gulfstream 650, which has a cabin pressure of 2,765ft at an altitude of 41,000MSL
reduce the rates of your descents, which will give your ears a chance to equalize. ATC, however, expects you to descend at between 500 and 1,500FPM, unless you are given "AT PILOTS DISCRETION."

There are a few different ways to equalize the pressure. The most effective is the valsava maneuver, which is how some scuba divers equalize the pressure as they descend into the water. Alternatively, yawning, chewing gum, sucking on hard candy, or hyperextending your jaw may help. Little children are particularly susceptible to discomfort, and parents will give them gum or candy at the beginning of the descent.


Would a propeller extracting air from a cylinder with holes in it be an ideal lift apparatus for a VTOL aircraft?

Already invented by an Italian priest in the 17th century. His version was simpler, having no engines or propellers...

https://en.wikipedia.org/wiki/Francesco_Lana_de_Terzi


Were my airplane's wheels under-inflated?

It's absolutely normal. Above is how the manufacturer even depicts the nose tire in the airport planning manual (.pdf, page 42).

The pressures are checked by line engineers typically before leaving the hub, as well as an inspection by a flight crew member before every flight.

While not available on the CRJ900, there are many jetliners that have tire pressure sensors. See:

Do airliners or business jets have brake temperature sensors? (image of such cockpit display)
How do tyre pressure sensors in aircraft work? (how they work)


Why does an airplane require 3 pilots on board?

Actually, for all but very long haul flights, airline aircraft only require two pilots, a Captain and a First Officer. For those long haul flights that exceed the duty time in a pilot seat, a relief pilot is also carried.

Older aircraft often also had a flight engineer. Technically speaking the f.e. wasn't usually required to be a pilot, but he was a very necessary crew member. You could say that airlines became more efficient crew-wise when they moved from 3-man cockpit crews to 2-man cockpit crews. For example, the 747-100/200 series uses 3-man crews, but the 747-400 uses 2-man crews. The change was made possible by using automation and instrumentation that wasn't available when the first 747 models came out. Indirectly the increase in engine reliability also helped. If you lost an engine in an 3-man crew 747, the typical manner of handling the loss was to have the first officer fly the airplane while the captain and the f.e. worked the problem.

To illustrate the increase in automation, the 747-100/200 series had, typically, seven or nine fuel tanks, and there was a fuel burn schedule that had to be followed to keep the structural stresses and balances between different levels of the tanks within limits. The f.e. took care of that, doing it manually by throwing switches on his panel. The 747-400 and follow on models do that automatically by computer.

Basically the number in the cockpit crew is determined by safety. There's the basic consideration that if you had only one pilot, and that pilot died or otherwise was disabled, that might well be catastrophic. Beyond that, though, there's the matter of what all has to be done and for how long. Pilots make mistakes, and the longer they've on duty, the more mistakes they make. And if an emergency occurs, the work load can get very high.

You can't reasonably compare an aircraft to a car for at least two reasons. First, a car is moving in only two dimensions, an aircraft in three. Second, a car can stop moving, an aircraft can't; it has to keep moving. Let's say your car loses power. Usually that won't result in anything more than inconvenience. If your aircraft loses power, you've got a much more serious problem. Most airline aircraft have at least two engines. Losing one isn't going cause a crash in most two engine aircraft, losing all power will.


What do these white on red words indicate on a London Heathrow taxiway chart?

They are named holding points; this allows them to say things like "taxi to RABIT" rather than "taxiway Bravo, hold short of taxiway Charlie". This saves a lot of time for ground controllers at busy, complicated airports.


What are the EASA external aircraft lighting requirements for day/night/VFR/IFR operations?

For EASA (via europa.eu, Easy access version), which is very similar to ICAO Rules of the Air (Annex 2):

SERA.3215   Lights to be displayed by aircraft
(a) Except as provided by (e), at night all aircraft in flight shall
display:

anti-collision lights intended to attract attention to the
aircraft; and

navigation lights intended to indicate the relative path of the
aircraft to an observer and other lights shall not be displayed if
they are likely to be mistaken for these lights; or

in the case of balloons, position lights.

(b) Except as provided by (e), at night:

all aircraft moving on the movement area of an aerodrome shall
display navigation lights intended to indicate the relative path of
the aircraft to an observer and other lights shall not be displayed if
they are likely to be mistaken for these lights;

unless stationary and otherwise adequately illuminated, all
aircraft on the movement area of an aerodrome shall display lights
intended to indicate the extremities of their structure, as far as
practicable;

all aircraft taxiing or being towed on the movement area of an
aerodrome shall display lights intended to attract attention to the
aircraft; and

all aircraft on the movement area of an aerodrome whose engines
are running shall display lights which indicate that fact.

(c) Except as provided by (e), all aircraft in flight and fitted with
anti-collision lights to meet the requirement of (a)(1) shall display
such lights also during day.
(d) Except as provided by (e), all aircraft:

taxiing or being towed on the movement area of an aerodrome and
fitted with anti-collision lights, to meet the requirement of (b)(3);
or

on the movement area of an aerodrome and fitted with lights to
meet the requirement of (b)(4);   shall display such lights also
during day.

(e) A pilot shall be permitted to switch off or reduce the intensity
of any flashing lights fitted to meet the requirements of (a), (b),
(c) and (d) if they do or are likely to:

adversely affect the satisfactory performance of duties; or

subject an outside observer to harmful dazzle.

You might want to refer to a country's specific AIP just to be sure that there aren't local differences.
Not to be used in lieu of the above, AIP, or airport textual data, what follows is my summary by light type:

navigation lights:

in-flight at night
moving on movement area at night
stationary and inadequate area illumination

anti-collision:

in-flight by day and night
taxiing; being towed -- unless too dazzling; generally in busy controlled airports the ATC will ask for them to be switched off; see (e)

red beacon (or similar):

engine running day or night on movement area


Do Air Traffic Controllers have to remember stall speeds for different aircraft?

No because aircraft are categorized by their speed at the runway threshold (1.3 times stall speed).

VAT —Speed at threshold used by ICAO (1.3 times stall speed in the landing configuration at maximum certificated landing mass)

By knowing the category, ATC is able to use appropriate speeds. The category is not actually listed anywhere, so the controller will have to know the approach category by heart for each aircraft type. E.g. if the controller sees "B738" as the aircraft type in the flightplan, they have to know that the corresponding approach category is C.

More:

ICAO Doc 8168 PANS-OPS Vol 1
14 CFR Part 97.3 (for the US)


Where is the control loop of the actuator closed?

Different aircraft and manufacturers take very different approaches.

1. Boeing 777

The B777 has three Primary Flight Computers (PFC) that are responsible for flight control laws computation and four Actuator Control Units (ACE) that are responsible for the closed-loop control of their responsible flight control surfaces.

The ACE is primarily an analog device, including the actuator control portion. Note that analog here refers to any control system that is not a general-purpose computer. Analog devices have a finite number of possible failure modes. For this reason, it is enticing from a common-mode/generic failure perspective that bedevils digital computers. The main disadvantage is that it is less flexible and powerful than a digital computer.

Ref: http://www.davi.ws/avionics/TheAvionicsHandbook_Cap_11.pdf

2. Airbus A320

The A320 closes the actuator loop directly on the five flight control computers: 2 Elevator and Aileron Computers (ELAC) and 3 Spoiler Elevator Computers (SEC), plus 2 Flight Augmentation Computers (FAC) for rudder controls.

In order to combat against common-mode failures, SEC, ELAC and FAC are designed to have completely different architectures by different design teams. Software is also designed to ensure dissimilarity across the command and monitoring channel of each computer.

An in-depth discussion on common-mode failures can be found in this paper, which cites software, and in extension, general-purpose computing, as a major source of common mode failures.

Ref: http://www.davi.ws/avionics/TheAvionicsHandbook_Cap_12.pdf

3. Airbus/Bombardier A220

The A220 accomplishes the closed-loop servo control in Remote Electronic Units (REU) located fairly close to the control surfaces and their actuators. For this reason, a total of 10 REUs are located across the aircraft.

The Primary Flight Control Computers (PFCC) normally compute the flight control laws. Since REU is a digital computer, in the scenario where all PFCCs fail (for example, a generic failure) and if sufficient number of REUs remain operational, the REUs can take up the slack to run Direct Mode control laws.

The primary advantage of this setup is the reduced wiring weight compared to centrally located servo-loop controllers, as well as higher failure tolerance in the case of single servo-loop failures.

The primary disadvantage, once again, is the common-mode failure across the REUs. Due to the high number of REUs, it becomes prohibitively expensive to design sufficient dissimilarities into them. For this reason, a third backup control loop, in the form of an analog Alternate Flight Control Unit (AFCU) is needed to cater for this remote failure mode.

Ref: https://quizlet.com/421493192/a220-lod-ch9-flight-controls-flash-cards/


Do aircraft really have text communication over FMC?

Yes. Text messaging over ACARS has been commonplace since the 1980s. It is air-to-ground and ground-to-air, not air-to-air. It is commonly used to exchange flight plans, weight and balance data, ATC clearances, schedule updates for passengers' connecting flights, and other operational purposes, but also sometimes for fun (e.g
birthday wishes, sports game results). It's primarily used between an aircraft and the airline's dispatching department, but can also be used directly between the pilots and ATC under some circumstances.


Are there any missile systems as of 2019 capable of shooting down aircraft in excess of mach 6?

The Russian S-400 SAM System is claimed to be capable of speeds in excess of Mach 12 and ranges of 400 km (250 miles).  It can, in theory successfully engage and defeat hypersonic targets, albeit with a much smaller lethal envelope than against conventional aircraft or missiles


How are bags transported from the terminal to the airplane?

From your photo this answer assumes a hub airport.
Some background first: after check-in, the belt conveyor system moves each bag onto its own tray – that's the modern individual carrier system (ICS) which mitigates jams, misreads, and lost baggage. Depending on how early the check-in took place, the tray will either go to a holding area, or directly to the baggage makeup area/space (BMA) where the bags are unloaded onto another belt conveyor system for cart/ULD loading.
BMA is the place you referred to as sort area. There is typically one BMA per airline per pier, and since big airlines usually have their own piers, it's one BMA per pier. Example for San Francisco Intl (see tan colored areas):

— https://www.flysfo.com/about-sfo/sfo-tomorrow/passenger-terminal

Two hours or so before the flight's STD (scheduled time of departure), comes the cart/ULD staging. The cart train length varies; IATA recommends 3 carts per narrow-body and 5–6 per wide-body. Airlines however implement this as best fits them. Easyjet for example stages one cart per narrow-body at Liverpool (internationalairportreview.com).
Regarding how many gates are served per BMA, one of the methods used to estimate the floor area required for a BMA when designing an airport is the EQA, or Equivalent Aircraft factor (see FAA AC No: 150/5360-13 for more).
In short, it's option 2.


How do I calculate aircraft range with these parameters?

If the fuel flow rate and the true airspeed are for the same polar point, the answer is easy. You cannot, however, determine if this is your maximum range because you do not know any other points of the polar.

Your fuel consumption is MTOW - MLW. The flow rate will give you the flight time when you divide the fuel by the flow rate. With the flight time you can calculate the range by multiplying it with the airspeed. Hint: Convert all data into metric first so you don't screw up the calculation.

The maximum range can be done the same way using MTOW - MZFW for the fuel mass. MZFW - OEW will tell you how much payload remains at this point. The only impossible part is the transfer range point - use the maximum range and assume that the aircraft will fly as far with a lower take-off mass as with MTOW.

The Breguet equation will not work in this case.


Why can't ramjet diffusers be stacked to achieve a good overall pressure ratio?

A diffuser is simply an expanding piece of pipe that converts kinetic energy (i.e. velocity) to pressure energy (i.e. pressure) according to Bernoulli's principle (which is just a formulation of the law of conservation of energy for fluid flow).

The air enters the diffuser with the velocity corresponding to the speed of the aircraft, and must still retain some speed through the combustion chamber. So only the speed above that can be converted to pressure. Few hundred km/s is already more than the speed in the combustion chamber, so there is some pressure gain, and the engine starts to work at all, but only above M2 the pressure gain becomes comparable to what a trubo-compressor can provide.

Also diffuser is simply an expanding piece of pipe and stacking two expanding pieces of pipe behind each other is still just an expanding piece of pipe. And two expanding pieces of pipe with a narrowing piece in between is no better than one of them, because the pressure only depends on the initial and final cross-section and not on the shape in between.


Off-center fan in geared turbofan - does this exist?

There are no off-centered turbofan engines in service today. However, United Technologies Corporation (UTC), has patented an engine with an angled core (Pratt & Whitney is a part of UTC).

Image from US patent Gas turbine engine with separate core and propulsion unit
US 8789354 B2

Air from the fan is ducted around the side and back of the core to enter from the opposite direction. The hot gas will be discharged forward through a power (low-pressure) turbine connected to the fan via a gear system. The turbine, gearbox and fan will be connected through a short shaft.

Source: aviationweek.com

The design is expected to have some advantages due the unconventional layout adopted, like:

As the core and fan are separate, core can be easily removed for maintenance.
As the compressors (in cores) are at an angle to each other, the possibility that uncontained failure in one engine will damage another engine is reduced (when the engines are installed in the double bubble D8 configuration)


How accurate is XFoil / XFLR5 at 'kinda high' Reynolds numbers?

Before version 6.9 (30 Nov 2001), XFOIL had some problems at Re > 3 million, but that's now been fixed.  Its documentation says:

  The BL equations are normally discretized with two-point central
  differencing (i.e. the Trapezoidal Scheme), which is second-order
  accurate, but only marginally stable.  In particular, it has problems
  with the relatively stiff shape parameter and lag equations at
  transition, where at high Reynolds number the shape parameter must
  change very rapidly.  Oscillations and overshoots in the shape parameter
  will occur with the Trapezoidal Scheme if the grid cannot resolve this
  rapid change.  To avoid this nasty behavior, upwinding must be introduced,
  resulting in the Backward Euler Scheme, which is very stable, but has
  only first-order accuracy.  Previous versions of XFOIL allowed a specific
  constant amount of upwinding to be user-specified.  Currently,
  XFOIL automatically introduces upwinding into the equations only
  in regions of rapid change (typically transition).  This ensures
  that the overall scheme is stable and as accurate as possible.


Have I made a calculation mistake in this ATPL question that uses the CAP 698 Chart?

The relevant section (3.2.3) of CAP 698 explains how to calculate this as follows:

Distance to Reach given height.
To calculate the ground distance travelled in order to attain a given height above
reference zero:
a) Convert the IAS 100 kt to a TAS, assume no position error.
b) Apply the wind component to the TAS to obtain the ground speed.
c) Determine the climb gradient from the graph.
d) Calculate the still air distance using the formula:
$$\text{Still Air Distance} (ft) = \frac{\text{Height Difference} (ft)}{\text{Gradient}} \times 100$$
e) Calculate ground distance using the formula:
$$\text{Ground Distance} = \text{Still Air Distance} \times \frac{\text{Groundspeed}}{\text{TAS}}$$

Assuming your calculation of TAS is right, and your interpretation of the graph is right (which I agree with) you can plug this into the above calculations and confirm the answer is indeed:
Ground Distance = 15,995ft
However, if we play devil's advocate and reverse engineer the climb gradient from the expected answer, you'll see there might be some human/interpretation error at work.
Taking the published answer of 16,850ft and dividing by $\frac{\text{Groundspeed}}{\text{TAS}}$ gives us a ground distance of 19,690ft. Take this and Divide by 100 gives 196.9. Then doing $\frac{1}{196.9} \times \text{Height Difference} (ft)$ gives a resulting climb gradient of 10.2 - this is all just mathematics, no aviation knowledge required.
Now, can you say for sure that you've not misread/misused the chart? Once again I got the same result as you by looking at it in low def on a screen. But it's possible we both miscalculated the climb gradient.

Side note: I see question like this come up fairly regularly on other aviation forums, and a reasonable amount of time it is student error and a reasonable amount of time it is publication error. Make of that what you will.


Why do high altitude air-launch plane designers choose to use two fuselages?

It is simple to maintain symmetry if the launch vehicle is in the middle, with two fuselages on either side.

With only one fuselage, the departure of the launch vehicle would change the symmetry, and therefore the lateral stability.

One possible exception is if the launch vehicle is directly above or below a single fuselage.  This was done with the M-21 carrying a D-21 launch vehicle, where the D-21 was directly above the centerline of the M-21.


Which way should you turn to avoid another aircraft?

In shipping there are standard international rules about which way boats should dodge each other.
  Are there similar rules in aviation?

Why yes, there are - in fact they're basically similar to the maritime rules!
They're described in ICAO Annex 2 (or for US pilots, FAR 91.113).

Basically, for aircraft of the same type (e.g. two airplanes) in the air the rules are:

Approaching head-on: Both aircraft alter their heading to the right.
Converging: Give way to the aircraft on your right.
Overtaking: Pass "well clear" to the right of the aircraft being overtaken.
(The aircraft being overtaken has the right of way. The overtaking plane maneuvers to remain clear.)

The rules for converging aircraft are more complex when the aircraft are not the same type - basically the more maneuverable aircraft gives way to the less maneuverable aircraft (because something like a balloon can't really maneuver to avoid a collision) - you can read the details in either of the links above.

Also while it's not explicitly spelled out in ICAO Annex 2 (or at least I didn't see it) aircraft in distress generally trump the "right of way" rules. (This is really common sense: if an aircraft is recognizably in distress you do everything in your power to stay out of their way and help ensure a safe outcome to whatever their situation is.)


Yes, they do. The elevator vortices I have observed are pinned to the trailing edge corners of the elevator and are made visible when the aircraft is traveling through moist air that is very close to the dew point temperature, and at a significant angle of attack. There's a hotel at LAX where you can look out the windows and watch planes fly by on final, just before touchdown; on a foggy afternoon they are all trailing vortices behind them.


Why do some fighter jets have movable horizontal stabilizer instead of elevators installed on the stabilizers?

All parts of an airliner's horizontal surface move, not just the rear part. The rear part, called an elevator, can move much faster and is for maneuvering. The forward part, called a (trimmable) stabilizer, is for trimming and moves slowly. It is moved in response to changes in loading, speed or flap settings and positions the tail surface such that only small continuous elevator deflections are needed. It doesn't need to move fast - high load factors would upset the passengers and overload the structure.

A330 port tailplane root (picture source). Note the markings which show the range of incidence angles covered by the trimmable stabilizer.

Benefits of a stabilizer-elevator configuration:

Camber: The elevator deflection changes the camber of the airfoil of the tail surface and makes the production of the intended lift change more efficient. If the elevator deflection is supposed to create a downforce, negative camber is produced and vice versa. This reduces the drag which is created in order to maneuver the aircraft.
Lower control forces: By moving a smaller surface, less hydraulics power, and on small aircraft, less muscle power is needed for the same moment change than with a full-flying tail or all-moving surface. Makes sense, right?
Better tailoring of the hinge moment derivatives: Two effects are important for getting the control forces right: The change in hinge moment over deflection angle ($c_{r\eta}$), and the change in hinge moment over angle of attack ($c_{r\alpha}$). With tabs, the right elevator hinge position, nose shape and control horns, both can be tailored individually, while a full-flying tail or all-moving surface will give the designer less freedom to manipulate both independently. Note that full-flying tails only emerged with hydraulic controls, because only those systems can manage the control forces of all-moving control surfaces at high speed.

Horn balance and overhang balance on control surfaces (picture source)

Benefits of a full-flying tail surface

By avoiding a contour break due to a flap deflection, all-moving control surfaces can avoid the shocks which would otherwise occur at high subsonic speed. This is their main benefit for combat aircraft.
At supersonic speed, the uncambered surface will produce less drag, so for supersonic speed the all-moving control surface is more efficient.
By moving all of the tail surface at high speed, an all-moving control surface will produce the highest rate of moment change over time possible. To produce also the highest sustained moment change, however, it needs to be larger than a comparable stabilizer-elevator combination because it forfeits the benefits of variable camber.
The all-moving control surface has no gaps which could add radar reflections, allowing for a more stealthy design.
Lower mechanical complexity. This is somewhat offset by the need for much beefier hydraulics.


How does bank angle differ from roll angle with respect to stability in fixed-wing aircraft?

In my experience, "bank angle" and "roll angle" mean exactly the same thing. I've only ever heard of one meaning of either term.

For completeness, here are some "plain English" definitions of all three Euler angles:

Pitch is the angle that the nose (the longitudinal axis) forms with the horizon. If the nose is pointed at the horizon, the pitch is 0°; if it's pointed straight up, the pitch is 90°; and if it's pointed straight down, the pitch is -90°.

Heading (sometimes called "yaw angle") is the horizontal direction that the nose is pointing, measured clockwise from true north.

Bank angle (sometimes called "roll angle") is the amount that the aircraft would have to roll (rotate around its longitudinal axis) in order to bring the wings level (which is to say, bring the lateral axis parallel with the horizon), with the top side of the aircraft facing above rather than below the horizon.

Pitch ranges from -90 to 90. The other two angles have a range consisting of a full circle; I think bank is usually expressed as a number from -180 to 180, and heading as a number from 0 to 360.


Where to get Initial EASA Class 1 Medical?

It depends on the country you are going to take the medical examination.

Normally, the national civil aviation authorities of each European country will have this listing. For instance, in Spain, AESA publishes here the approved medical centers where applicants can take their initial and successive examinations.

So I suggest to first find out the authority from your country and always make sure with the medical center that you are going to take a certified EASA Class 1 medical examination.


How can I tell a GPS installation is acceptable for IFR use?

The easiest way is to read the Aircraft Flight Manual (AFM) or Aircraft Flight Manual Supplement (AFMS). If the the GPS was installed at the factory, it will be addressed in the AFM. If it was installed later via an Supplemental Type Certificate (STC), there must be an AFMS to cover the operation of the GPS.

If the GPS installation was not at the factory, there should be an a/c logbook entry showing the installation and STC approval.

As specified in AC 20-138D:

  19-9. Operations manual or AFMS/RFMS.

  An AFMS/RFMS must be provided that contains the limitations and
  operating procedures applicable to the installed equipment
  configuration. The AFMS/RFMS must address the operation of the
  equipment and the related components as they are installed (e.g.,
  remote source selector). An AFM/RFM supplement is required if the
  installation is based on a prior approval that had an AFM/RFM, or if
  there are any limitations associated with the operation of the
  equipment.

The key information is covered by the first sentence -- limitations and operating procedures. If the GPS is not approved for IFR, there must be an operation limitation in the AFM/AFMS that states that (and in all of these cases I've seen, the FAA also required a placard stating "GPS not approved for IFR flight.")

If the information is not included in the AFM or AFMS, I would question the approval of the installation as all installations require the AFM/AFMS.

As for the database, it expires every 28 days. Turn the GPS on. If the database is not present or expired, you will get a message to that effect.


Being told to monitor a frequency, when are you allowed to transmit on that frequency?

First a note on phraseology. In the context of your question, I believe the FAA uses monitor like most of the world uses stand by. I'll be covering the general procedure - if you are in FAA land, replace stand by in my answer with monitor.

If told to monitor a frequency, you are not expected to transmit on that frequency. Monitor is used when a pilot is requested to listen on a frequency to retrieve information from a broadacst. For example, I might tell you to Monitor ATIS 122.750. I then expect you to tune 122.750, listen to the ATIS transmission, and then return back to my frequency afterwards.

If told to stand by on a frequency, you are expected to tune that frequency and wait for air traffic control to contact you there. For example, Standby for Tower on 118.1. When standing by on a frequency, air traffic control is supposed to contact you, not the other way around. However, if you do not get contacted within a reasonable amount of time, you should go ahead and transmit. There is no fixed rule for how long you have to wait - use common sense - just like you would if told to stand by on your current frequency. For example, if you are waiting in line for departure and there are 3 aircraft ahead of you, don't expect the tower to call you before you are next in line for departure. On the other hand, if you are holding short of the runway and there appears to be no other traffic around preventing you from taking off, if the tower hasn't called you within a minute or so, please do try to call them instead. Maybe the controller is busy dealing with other stuff, or maybe they have simply forgotten about you. It does happen, although not often. You could also accidentally have tuned the wrong frequency, and might only realise this when no one replies to a call made by you. It goes without saying that, if you have a safety related message, you transmit it without delay.


Which map projection is typically used on ATC radar screens?

I can only speak by experience, and this is relevant to PALLAS installed in Greek ACC and LGAV approach. What I concluded while discussing with ATCOs is that the projection used is gnomonic. Unfortunately I haven't read any document to prove it (this is pure observation) and even if I had I couldn't cite it (for obvious confidentiality-related reasons).

Anyway, gnomonic is the projection I've used while developing the PALLAS simulator for HCAA and the results were identical. So what characteristics has the gnomonic projection:

Every straight line you draw on it, is part of great circle. This is of great importance since great circle arc between 2 points is the smallest distance between those 2 points. And when flying you want to avoid extra miles
It heavily distorts areas of the map away of the projection center, but gives a very good approximation close to the center. That makes it suitable for relatively small geographical ares.
You can never see a whole hemisphere. If you have a look at the article in Wikipedia, you will see why.

You might want to take a look at this picture which is not from the real system but the simulation. Unfortunately I don't have photo of the system that shows the concept, but I hope this does. Note the 19th and the 30th meridians that are straight lines (every meridian is a great circle arc) and how they converge to the north. Also note the blue-ish line measuring a random distance. This is guaranteed to be a great circle distance. So every straight line on the map, either from a tool like the one pictured or an airway, is a potential trajectory for an aircraft to follow. That way you see the "truth" each time you see a straight line.

Copyright: own work, tool DARSSY

PS: Now regarding your actual question of what projections are commonly used: others have mentioned stereographic while I mention gnomonic (and I'm pretty sure it is this one) for PALLAS. So there is no such thing as commonly. Projection is a tool. And as such you have to pick the right one for each situation. Now I don't know what your professional interest is, either a pilot, ATCO or a fellow developer wanting to write his/her own simulator (or even CWP???) in any case I would suggest you contact someone that knows the internals of the specific system you are interested in.

Regarding accuracy, you first need to address radar accuracy which is affected by coverage, track distance from the radar, atmospheric conditions and other factors that fall beyond the scope of the answer. Then you can wonder if it's worth the pain to analyze if the projection might trick the controller into errors.


What Paper Format do Boarding Passes use?

Standard boarding passes are the size of an IBM punchcard, 7⅜ by 3¼ inches (187.325 mm × 82.55 mm) because paper and printers in that size were readily available at the time, and then inertia kept the size the same even when punchcards fell out of use and it became a specialty item.

Many airlines have switched to rolls of 3⅛ inch (79.375 mm) thermal paper, as is now commonly used in cash registers. For a new system, this is probably less expensive and easier to prototype.


What first aid equipment is on a commercial aircraft?

Obviously, first aid kits have items that save your life. The contents of the First aid kits or Emergency medical kits (EMKs) vary based on the jurisdiction. For example, FAA requires the following items

  ... on all airplanes of air carriers operating under part 121 for which at least one flight attendant is required. EMKs and AEDs are “no-go” items and must be carried as indicated on the Minimum Equipment list.

Contents of EMK; table from FAA Advisory Circular 121-33B Emergency Medical Equipment.

On the other hand, Indian DGCA requires the following items in first aid kits:

First Aid contents; table from DGCA Document No: F No. 11-690/CAR X-II/2010/AI(2) Provision of Medical Supplies in Aircraft

Most of the requirements are broadly similar, while there are some region (or country) specific differences; for example, DGCA requires rehydration solution to be carried, presumably due to heat. FAA, on the other hand requires Automated External Defibrillators (AED) to be carried for aircraft with payload more than 7500 lbs (DGCA requires it only in international flights of over 2 hours).


Can a plane land on an aircraft carrier without support from its crew?

The Nimitz Class aircraft carriers are the largest warships ever built. With over 6,000 personnel (crew and aircrew), the carrier has a displacement of 102,000t, and a flight deck length of 332.9m.

From: Nimitz Class Aircraft Carrier - Naval Technology
https://www.naval-technology.com/projects/nimitz/

332.9m * 39 in/m * 1 ft/12in = 1081.9 ft.  I think many small (2-4 seat) aircraft could land & stop in that distance. I'm pretty sure I could in my Cessna 177B, fixed gear, with micro-vortex generators for slower landings. Even without any headwind to help slow down.

From the 177B Pilot Operating Handbook:

  LANDING PERFORMANCE:
  Ground Roll    ---------------------------------------------------- 600 FT

And that was before the micro VGs, so it should be even shorter now.


Is there ATC audio from the Sled Driver Speed Check story?

Sadly, there likely are no official recordings of this story.

Unfortunately, there was no LiveATC.net archive at the time, and unless there is an accident or incident, audio is not routinely archived by the FAA or NTSB.

Even when you want to request recent data, the FAA warns, "Because air traffic data is routinely destroyed or disposed of in the normal course of business, time is of the essence." (I've seen elsewhere but couldn't find an official source that it can be anywhere from 5-45 days), so even if you could find a date of this event, you wouldn't be able to file a FOI request.


Transonic Airfoil with high critical mach number

First I have to say that XFOIL is not the right tool for such a high Mach number. Professor Drela has written ISES to address the shortcomings of XFOIL at transsonic speed.

Next, the critical Mach number is well defined as $$c_{p_{crit}} = \frac{2}{\gamma\cdot Ma_{\infty}^2}\cdot\left(\left(\frac{2}{\gamma+1} + \frac{\gamma-1}{\gamma+1}\cdot Ma_{\infty}^2\right)^{\frac{\gamma}{\gamma-1}}-1\right)$$
which can be simplified for air as $$c_{p_{crit}} \approx \frac{1}{0.7\cdot Ma_{\infty}^2}\cdot\left(\left(\frac{5+Ma_{\infty}^2}{6}\right)^{3.5}-1\right)$$

$\gamma$ is the ratio of specific heats and is 1.405 for air.

For $Ma_{\infty}$ = 0.88 this is -0.23 which is too little to even accommodate a moderately thick airfoil without supersonic flow. Therefore, your wing needs sweep to function well. Even then, I recommend a supercritical airfoil which will have supersonic areas at this speed but without a big drag penalty. Take your pick.


Is it possible to know why an airline operates specific equipment on certain routes?

There are many factors, but you can often predict what class of plane will be used for a particular route by the distance and demand.

For smaller cities, they want to fill the planes, but they also need several flights per day to cover the fixed costs of serving that airport (and make things convenient for customers), so it's often better to have a commuter jet bouncing to the nearest hub and back several times per day day than one large plane that carries an entire day's worth of passengers in one shot.  For larger non-hub cities, they'll do roughly the same thing but with mid-size planes.

Between hubs, they'll run the largest narrow-bodies to connect all the various small cities not served by a common hubs, plus hubs themselves tend to be large cities with plenty of native demand too.

For international, they'll run wide-bodies because they need higher fuel capacity, and there's rarely a convenient time for customers due to the long flight times combined with crossing several time zones, so you might as well pack them into as few planes as possible.

Notably, some carriers fly several different types, each optimized for specific route types, while others fly just a few types (or even just one) because that makes maintenance, pilot training and fleet scheduling easier--but may limit what kinds of routes they can fly profitably.  When airlines merge, they'll usually have similar fleets--and in cases where they don't, they'll quickly start dumping types they don't like and replacing them with types they do.


Why is ditching speed higher than stalling speed?

As far as I'm aware - and maybe a seaplane pilot could give a better answer - one of the big issues with ditching is judging your height above the water. If you stall it in, you might get it wrong and lose control completely.

I checked the POH for a 182RG, which has a Vso of 39 KIAS and ditching speed of 60 KIAS. The ditching checklist gives descent rate as the primary consideration, not airspeed:

  Power -- ESTABLISH 300FT/MIN DESCENT at 60 KIAS

In the amplified procedures section, it says:

  Avoid a landing flare because of difficulty in judging height over a
  water surface

In other words, better to descend slowly under control until impact than stall it at an unknown height above the water. As Bob Hoover famously said, "If you're faced with a forced landing, fly the thing as far into the crash as possible".

I did a bit of Googling and found similar checklists for other aircraft, e.g. a Piper Arrow:

  Power--ESTABLISH 300 FPM DESCENT AT 90 MPH


What is the criteria for selecting BNR or BCD as data encoding in ARINC429

The general ARINC guideline for publishing data is to publish both BCD and BNR values when both types are defined. That allows the receiver of the data decide which to use. If only one form exists, then that's the way it's coded. It ultimately comes down to what the ARINC committee decided made the most sense.

Typically, BNR coded data is used by computational functions -- things that process the data value and expect the greatest precision in the number. They don't really care whether the number is easily readable.

BCD coded data is typically used by display systems as pilots like to read decimal numbers the numbers can easily be scaled to a readable display, e.g. DME range in NM rounded to the nearest 0.1 NM or bearing to the nearest 1 degree.

BCD is also used in control panels where the data is discrete decimal data (radio frequencies) and the crew enters a decimal value.


How is fuel removed from a light aircraft if required for weight and balance?

Several ways.

First, determine if there really is a weight and balance discrepancy with a proper weight and balance calculation.  If the aircraft is overweight and out of CG, can you simply remove some baggage or other non essential cargo in order to return to the weight and balance envelope?  If so, then do this, perform another weight and balance calculation and if it is within the envelope for safe flight, problem solved.

If the airplane is within gross weight but outside of CG, can you move some payload around to another fuselage station e.g. A fwd baggage compartment, etc so the CG can be moved within limits?  If so, do that, then do another weight and balance calculation.  If you're within the envelope, you're good to go.

If you cannot lose or rearrange any other non essential baggage in the cabin and you're still overweight, first verify that removing said amount of fuel will 1) keep the aircraft within weight and balance limits and 2) will be enough to safely complete the flight with the required onboard reserve, you have two basic option, drain it out, siphon it out or burn it off.

Before beginning this exercise, make sure you have an accurate means to gauge just how much fuel is in the tanks currently.  The tanks are generally placarded with their useable capacities or this will be listed in the Pilot's Operating Handbook for the aircraft in question.  Sometimes takes also have pre-marked indicators inside the tanks where a known quantity of fuel will level with these markings or metal tabs.  Some firms also sell gauges for determining fuel quantity in the tanks; just make sure you have one that's approved by the manufacturer for your make and model airplane.  DO NOT use the cockpit fuel gauges in a light GA aircraft to determine onboard fuel quantity; by regulations these are only required to be accurate when they read as empty (how convienent).

You could drain fuel from the tanks through the sumps, generally located under the wings.  A tool with a rod would be required to open the valve on the sumps and you could use a tube with a funnel on it to collect the fuel into a container.

Siphoning the gas may be easier using a tube through the gravity filler ports on the top of the wings.  One downside is that these filler ports are often on the highest part of the tanks and may require a long hose to siphon the gas.

The third option is simply to burn off the gas by making a flight prior to the arrival of the passengers for the planned trip.  Using the takeoff, climb, cruise and power settings charts in the Pilot's Operating Handbook, you can make an accurate estimation as to how long it will take and what power settings to use to consume the excess fuel prior to loading for the trip.


Can a vacuum cleaner create sufficient vacuum to operate the artificial horizon?

The answer is a qualified yes: It's theoretically possible, but wholly impractical to provide a pressure source to your gyros from within the cockpit, at least the way you're describing.

Air-Driven gyros require a relatively constant pressure differential somewhere between 4 and 6 inches of mercury to operate correctly (this can be "suction" or "pressure", but as vacuum/suction systems are more common let's stick with that term). We can split the difference and say we want to supply 5 inches of vacuum (which is usually right in the middle of the "green arc" for most vacuum gauges) - this is sufficient suction to keep the rotor spinning at an appropriate RPM so the instruments function as expected.

Because a constant vacuum is required we can kill off one of the options: You won't be able to suck air through a straw to do this -- you would be constantly over-speeding or under-speeding the gyro rotor as you produce either too much vacuum (inhaling) or not enough (when you have to let go of the straw to exhale).
The variable pressure would vary the rotor speed, and your instruments would be totally unreliable within a few breaths, defeating the purpose of the exercise.

A household vacuum can provide the necessary pressure differential (these fine vacuum-rating folks tell me that "An average vacuum will have a [suction] rating of around 80 inches of water", which Google tells me is around 5.9 inches of mercury. If you could hook the vacuum up to the aircraft's system downstream of the vacuum regulator (where the main vacuum pump hooks up) you could theoretically power your gyros normally.
There are some caveats to using a vacuum cleaner idea besides the obvious "How are you going to hook the vacuum up to the system?" question:

The vacuum cleaner specifications are presumably at or near sea level - they might not be able to provide adequate suction at higher altitudes.
Powering the vacuum cleaner in this scenario is left as an exercise for the reader (most aircraft with air-driven gyros don't have household AC power in the cockpit - you could install an inverter, but vacuums pull quite a lot of power, so you'd need a high-amperage circuit to supply it. The draw from the vacuum may exceed the capacity of the plane's electrical system, and to remedy that we're getting into complicated major alterations...)

There are other more practical alternatives to an engine-driven vacuum pump to consider if you're worried about the reliability of your vacuum source:

Precise Flight makes a standby vacuum system that ties into the engine intake.
For normally-aspirated engines this works well as long as the engine is operating at part throttle: The manifold pressure differential is sufficient that it can supply suction for your gyros.  The downside is that you can't guarantee a stable vacuum source: at full throttle there will probably not be sufficient suction to operate the gyros (particularly at altitude).
Pneumatic venturi tubes can be used to supply vacuum for aircraft in flight.
These are bolted on to the airframe and use the slipstream air moving through a venturi to create the necessary vacuum. In extremely slow flight these may also fail to provide adequate vacuum.
Electric standby vacuum pumps are a popular option as they offer you the ability to keep using your main vacuum instruments regardless of throttle position or airspeed. The primary drawbacks are weight, space (for the installation), and power to run the motor.
Electric gyro instruments are a popular option (though somewhat expensive): They provide a backup for the air-driven system using an independent power source.


What’s service does ATC service include?

Air traffic control service is a service provided for the purpose of:

  preventing collisions:

  between aircraft, and
  on the manoeuvring area between aircraft and obstructions; and

  expediting and maintaining an orderly flow of air traffic.

  (ICAO Annex 11)

When saying a flight is provided with ATC service, it is just another way of saying that it is a controlled flight. That is, a flight where the pilot can't just do what they want, because the flight is subject to an ATC clearance; the ATCO will clear the flight to follow a certain route and fly at a certain level.

Importantly, all controlled flights are coordinated as long as they remain in controlled airspace. This ensures alerting service throughout the controlled portion of the flight. This coordination also extends to military units (so we don't have a repeat of Korean Air 007). Controlled flights are also provided with flight information service (traffic info, weather info, info on nav-aids etc.)

As stated in the quote above, ATC service is provided for the purpose of preventing collisions. However, actual separation is not necessarily guaranteed to be provided by the ATCO. The class D airspace you mention is a great example. Separation is only guaranteed to be provided by ATC for IFR-IFR conflicts. In other cases, it is ultimately the responsibility of the pilot* to prevent collisions, which they are able to do based on the flight information service provided.

*: the controller can still decide to provide separation, but is not required to do so.

Note that separation on the manoeuvring area (which includes the runway) is provided regardless of airspace class.


What is the general process for flying a private aircraft to another country?

It really depends on the laws of the country you are planning to flight to.

If you want to fly between states in the US, there is no requirement to do any paperwork. Federal Aviation Regulations allow you to fly any distance domestically without filing a flight plan, assuming you are flying under visual flight rule (don't need ATC service), and don't need to fly through any restricted airspaces (most of the US airspace isn't restricted).

Canadian laws require flight plans for all flights longer than 25 nautical miles. However, filing a flight plan doesn't necessarily involve paperwork. Most people do it over the phone.

Flying in Western Europe is similar, but since most airports in Europe require advanced notice (and payment of a landing fee), you'll also have to call the destination airport. Technically you can still fly anywhere you want without doing that... you just won't be able to land.

I don't know much about flying in Eastern Europe, Middle East, or Asia, though if you are in a place like China, where the entire national airspace is restricted and you need a clearance from the military for every take-off... I am guessing there will be paperwork involved.

If you are flying between US/Canada/Mexico, in addition to filing a flight plan (5-10 minutes), you'll also need to notify customs of the destination country so they can expect your arrival to clear you. That also just takes a short phone call.

If you are flying in/out of the US, you'll also need to file eAPIS (electronic advance passenger information system) online. Basically just have to give them names, day of birth, and passport numbers of everyone on the flight, and they will email you a preliminary clearance. You still have to clear customs normally once you land.


Are airlines responsible for Airport security or Airports concerned or third-parties on terminal-side?

In the United States of America passenger and baggage screening is handled by the Transportation Security Administration (TSA). It is a government run agency and deals with the pat downs, X-Ray machines and frisks. This will get you through "security" and to the terminal area and ultimately on to the plane.

If you are coming in from another country you will need to pass through customs which is managed by its own agents and falls under the jurisdiction of U.S. Customs and Border Patrol who are also a federal agency.

At some of the really busy airports here in the US its not uncommon to see local police officers helping out with things like traffic flow and passenger management of those entering and exiting the facility and security in general.


When calculating lift, using the the NASA lift equation, can any value be increased, ie. velocity or surface area, for increased lift?

Can any one of those values be increased for greater lift?

Certainly.  But increased lift will not be the only effect.

  If I doubled my velocity would I double the lift that the velocity provides? But if I added 25% to the surface area of the wing, my drag also increases. How does that factor into lift? By decreasing velocity?

It doesn't directly factor.  The formula gives you the approximate lift given certain conditions.  It doesn't tell you if those conditions are reasonable or achievable.

You're correct that increasing the wing area or speed will increase drag.  But this equation doesn't tell you how much.  You'd need to look elsewhere to find out the specifics.  The drag increase will not be linear with either one.


What is this extension at the tip of the Supermarine Southampton's wing?

Source: Supermarine Southampton Flying Boat - Nightime 'Landing' (YouTube)

It's a standard flare bracket – controlled from the cockpit,[1]:76 it holds a burning flare to illuminate the water surface at night when landing.[2]
This particular streamlined design is most likely based on the 1922 patent by Holt Harold Edward Sherwin.[3] It's a clamshell device; when open, the two halves help reduce the heat going up. Those flares are also re-ignitable. The earliest design, also by Holt, was filed in 1917.[4] They are also known as Holt flares.

See item 18 in the front and lower-wing views above.[1]

Provision is made on the rear spars of the bottom outer main planes for the attachment of the standard flare brackets. The flares are controlled by push buttons on the port side of the pilot's instrument board.[1]:76 [emphasis mine]

The Air Navigation Directions (...) require aircraft to be equipped with landing lights (lamps or wing-tip flares) for flights by night (...) The construction of the flare brackets and their position on the wing of the aircraft must be such as to prevent the flame from the flare overheating the wing or aileron fabric when the aircraft is in flight or standing on the ground.[2] [emphasis mine]

Source: twitter.com; cropped

In the crop above, the object at the leading edge is a navigation light, the one below at the trailing edge is the flare bracket.
(My guess, with the engines near idle for landing, there wasn't enough electrical power for bright lamps, or they were heavy and/or unreliable back then.)

1: Great Britain. Air Ministry. (1929). The Supermarine Southampton Boat Seaplane, Mark II. (Metal Hull) Two Lion Engines ... Air Ministry. Issued November, 1929. London: H. M. Stationery Off.. (hathitrust.org)
2: (1939), "A German Long‐Range Flying‐Boat: Some Particulars of the Latest Dornier Seaplane to be put into Service on the South Atlantic Route", Aircraft Engineering and Aerospace Technology, Vol. 11 No. 9, pp. 357-369. https://doi.org/10.1108/eb030544
3: Sherwin, Holt Harold Edward. "Landing light or flare for attaching to aircraft." U.S. Patent No. 1,423,326. 18 Jul. 1922.
4: Sherwin, Holt Harold Edward. "Flare for use on aircraft." U.S. Patent No. 1,360,527. 30 Nov. 1920.


How are range and frequency related in HF communications?

Neither or both, depending.
Unlike VHF and higher bands, which travel mostly via line of sight and therefore have limited range depending on altitude, HF radio relies on skywave propagation. This means the radio waves travel up, bounce off a layer in the upper atmosphere and then travel back down to the receiver. They may even bounce up and down between layers several times, allowing one to receive signals from the other side of the planet. You may be able to talk to stations far away but not nearby, or the bounces may not work the same in both directions. It’s unpredictable.
All of this odd bouncing depends on atmospheric conditions, which vary from place to place and even from hour to hour. Worse, different parts of the HF band will behave differently at the same time and place, so it has been broken up into several sub-bands of frequencies that tend to behave similarly.
That is why oceanic flights are given two HF frequencies in different sub-bands: at least one of them will probably work. Probably. And which one (if any) may change over the course of a long flight!
Worst of all, because of this long-range behavior, every station on the planet needs a unique frequency, and there isn’t a lot of bandwidth to go around, which is why it is chopped up into very narrow channels that give horrible sound quality. So, HF is only used when absolutely nothing else will work (or is available).