Is multi/quadcopter flight control similar to helicopters?

As  commented, a quadcopter is generally flown by a computer. Given command inputs, the computer controls the speed of the four rotors, as shown in the images included in the question. The four rotors give the quadcopter a wide range of maneuverability. This is why quadcopters are currently used in many research applications. They can simulate conventional fixed-wing flight, helicopter flight, or something completely different.

A quadcopter could certainly be flown with conventional helicopter controls. The four rotors allow it to be controlled by a cyclic, and the differential rotor torque allows it to be controlled by the anti-torque controls. However, unlike most helicopters, most quadcopters have fixed-pitch rotors. This is probably mainly due to size and cost constraints. The small size of quadcopters, combined with the lift being distributed among four rotors, allows each rotor to be smaller and much more resposive with RPM than a large rotor. This means that instead of collective and throttle, most quadcopters will only have throttle. Controlling the speed if the individual rotors is the end-result of their control algorithms.


What does it mean when ATC says "altitude indicates"?

"Altitude indicates" means that the aircraft has a Mode C transponder but it isn't receiving radar service, i.e. it's VFR and not on flight following. In other words, the transponder is reporting an altitude, but because the aircraft isn't in contact with ATC, they can't be sure about its altimeter's integrity or the pilot's intentions.

See the ATC orders 2-1-21:

  For aircraft displaying Mode C, not radar
  identified, issue indicated altitude


Does counter-rotating propellers on multi engine airplanes have critical engine?

The term "critical engine" can actually refer to two very different factors:

P Factor
Engine driven accessories, depending on the airplane and how it's configured.

A twin with counter-rotating propellers doesn't have a critical engine from a controlability perspective, but very often there are important engine driven accessories, like hydraulic pumps, vacuum pumps, generators, etc. that are only installed on one engine, and if you lose that engine, well it's more of a problem than the other one.

So you may lose the left engine and it has no effect on control or performance compared to the right, but that engine has the only hydraulic pump, so now you have to do the engine-failure-on-a-missed-approach song and dance, all while hand pumping the gear up.  Gets pretty busy.  In such a situation I'd consider the left engine more critical than the right one even though it's not a stick-and-rudder problem.

I think that's what the examiner was looking for.


Why does the cockpit have windows, is it a structural design burden?

Yeah, it may be better. But what happens if the camera gets dirt (as everything else does in a flight) or if the camera fails for whatever reason? If the aircraft suffered an electrical malfunction and the camera was to turn off? Also, this is way more expensive than just fitting the window. The technology would also increase the weight of the aircraft. It's a good idea that I am sure that aircraft manufacturers have contemplated. It is just too impractical.


Do modern aircraft require rudder input in order to perform a coordinated turn?

Most transport aircraft use yaw damper systems to take care of minor rudder inputs.  Most autopilot systems are actually only 2-axis - pitch and roll since the rudder's job is only to keep the tail lined up behind the nose.  The yaw damper is a separate "autopilot" system and has limited authority, sufficient to deal with minor yaw disturbances, dampen dutch roll, and counter adverse yaw from the ailerons and is active all the time whether the autopilot is on or not.

With a Y/D system the only time a pilot really needs to make a rudder input in flight is if an engine quits, because the yaw damper's authority is not sufficient to counter asymmetric thrust.  Generally in a jet, once through the departure profile, feet are on the floor even when hand flying.  They are only on the pedals to steer the nosewheel during the takeoff and be ready in case an engine quits.

On a swept wing aircraft the yaw damper is essential; if the yaw damper is off and yaw disturbances occur, dutch roll motions can start and if the pilot tries to respond with rudder inputs he almost always can't stay in phase and things get exciting.  Because of this criticality the Y/D is usually dual channel.  One of the tests done on production aircraft is to induce a large yaw movement with both YD channels off to get a dutch roll going, then engage each YD channel and make sure it stops the dutch roll.


Which airliners have carried the most passengers?

As you note the 737 and A320 have a huge leg up on most other aircraft simply by production numbers. The 737 is the unquestionably the most produced large passenger jet aircraft in history when compared to the A320 it has 20 years of extra flights under its belt which is a lot of time to move a lot of people. Its a bit dated but Boeing provides a bit of data on this and estimates:

  • The 737 family has carried more than 16.8 billion passengers; that
  is equivalent to every single man, woman and child flying at least
  twice. (2013 world population was
  7.1 billion).*

  *As of December, 31, 2013

Airbus provides a similar stat estimating:

  15,6+ billion passengers carried since Entry Into Service

  As of November 2018

So it seems that the 737 is clearly in the lead over the A320 as 5 years ago they had already carried an estimated Billion more passengers than the A320 has as of last month.

These are the only two large commercial jet aircraft that even appear on the most produced aircraft list linked above. Other sources quote the 747 as carrying 3.5 Billion passengers, the 727 comes in around 2.2 Billion in its lifetime and the 757 is somewhere in the 1.3 Billion passenger range which is similar to the A330's 1.3 Billion (as of 2013) none of which even approach double digits so the 737 is clearly the leader from the estimates I can find.


What is qualitative relationship between surge line, stage characteristic and throttle characteristic?

Since your question is divided in three parts, I do the same with my answer. First, however, we need to explain what the axes of the graph mean. The x-axis plots mass flow through the compressor, which is roughly equivalent to the tip speed of the compressor blades, and the y-axis shows the pressure ratio between entry and exit flow.

Throttle and compressor performance

The throttle regulates fuel flow, and this flow has to match the air flow. The limits are:

If fuel flow is too high: The combustion will create too much heat, so the turbine will be damaged.
If fuel flow is too low: Too little energy is added to sustain the current operating point. The engine will slow down.

If it is kept within those limits, the throttle will indirectly control the compressor speed and it's mass flow. More fuel flow will translate into higher turbine entry speeds, which will increase the torque produced by the turbine and speed it up. Since it is directly coupled with the compressor, it will see the same speed increase. This leads to higher mass flow and a lower fuel-to-air ratio in the combustor (relative to the state right after the throttle increase), such that a new equilibrium at a higher speed is established.

Throttle lines

For every pressure ratio the compressor will have a matching mass flow, and both move up and down in parallel. This is shown by the dashed lines. Depending on the blockage of flow in the turbine and the engine nozzle, different lines are shown for different grades of blockage. The solid stage characteristic line shows the limits within which the compressor will run, and a higher flow resistance narrows the range of speeds that are possible. The limits are determined by:

Lower limit: Here the compressor is run at the lowest possible speed for the given blockage, and the compressor blades run close to their maximum lift coefficient. When the blockage is increased, the flow over the compressor blades will stall and the pressure ratio will collapse.
Upper limit: Here the compressor blades run at high speed and a low lift coefficient. Running them any faster will not create enough pressure rise per stage, and again the blocking cannot be overcome.

Surge

Once the pressure rise per stage cannot be maintained (say, due to a stall of the flow over the compressor vanes), the high pressure air in the combustor will find it easier to escape at the front than to flow through the turbine and the nozzle. This leads to reverse flow and a sudden drop in combustor pressure, which in turn allows the compressor to reverse the flow and start pumping air back again. Now the pressure in the combustor rises again, until the whole process repeats.


Is there any formula that directly relate density to altitude for a wide range of altitude?

There are the right way and the easy way.

Rigorous way would be to use the ICAO Standard Atmosphere (Doc 7488-CD in 1993) a link for document
Then your code looks for temperature gradient (Table D) and uses eq.12 or 13 for pressure calculation. It depends on the temperature gradient. Then you can easily compute the density eq.14.

Easy way would be calculate density for few altitudes and fit the result with some proper function.

Cheers Robert


Do pilots reject takeoff if aircraft doors are not properly locked down?

The crew has already secured the door just before leaving the gate, cross-checked them and the pilots saw the sensors indicate closed. So if the warning goes off during take-off roll, it is not somebody's simple mistake, but something is broken. It might be the sensor, but it might be something on the door and that might be pretty bad. So as the old saying is “it's better to be on the ground wishing to be in the air than in the air wishing to be on the ground.”

Below about 80 knots the pilots will (should) reject the take-off for almost any warning or abnormal indication they get. If the problem can be fixed easily, they can just taxi around and take off a couple of minutes later. Above that speed the emergency braking is likely to overheat the brakes, so from about that up to V1 pilots will only reject for engine failures and other very serious warnings, while for other issues they'll make the circuit and return to land again.


Could placing a fan jet further in front and closer to the wing create undesired pitch motion from its exhaust?

I seriously doubt the engine exhaust hits the horizontal stabilizer except possibly when fully stalled. Otherwise, the wing downwash follows approximately the extended chordline and takes the engine with it safely below the horizontal stabilizer, which is significantly higher than the wing.

The one thing I've seen mentioned was change in the centre of gravity generally decreasing the longitudinal stability—which is most pronounced near stall, because the centre of pressure moves slightly forward with increasing angle of attack (until stall, where it moves abruptly aft all the way to midchord).

The other possible effect is that the cowling generates vortices—possibly with help of vortex generators needed to avoid stagnation in the gap between the wing and the engine—that go over the wing at high angle of attack and increase the suction peak near the leading edge and making the forward shift of centre of pressure more pronounced.

The only point regarding tail I've read is that it is not large enough to allow moving the allowable range of centre of gravity forward to improve the stability ‘naturally’.


What items could you bring on-board to maximise your chance of survival in an emergency?

Most of the items you can bring with you to maximize your chances of surviving an in-flight emergency are items you're not going to be allowed to bring with you.
About the only things I could recommend bringing along on a commercial flight are your cellphone and a personal locator beacon (PLB) of some kind, but frankly if your airliner goes down ATC is going to know where you were when they lost contact, (and the plane has an Emergency Locator Transmitter already).

You should also wear sensible clothing -- natural fibers like wool or cotton are the order of the day if in-flight fire is a concern. Polyester or other synthetic fabrics will melt to your skin and cause you to have a Bad Time.

More directly addressing your question though, the items that spring immediately to my mind (and why you probably won't be taking them with you) are:

A parachute (what prompted your question)
Sure, you can bring your parachute. It's kind of a useless security blanket though.
From cruise flight you'd basically be executing a high-altitude jump (let's say a HALO jump, because you want to get down as quick as you can). You would require oxygen to remain conscious longer than about 30-45 seconds (though an automatic-opening chute may save you here), as well as protective clothing to survive the low temperatures while you're free-falling.
Those concerns aside, remember that airliner cabins are pressurized and the doors are typically "plug doors" that open inward. No human is strong enough to open that door with the cabin pressurized, and if you've lost cabin pressure for some reason you're better off putting on that little drop-down oxygen mask like the nice flight attendant told you to in the safety briefing. You're not going to save yourself if you pass out from hypoxia while putting on your chute and trying to get to the door.
An oxygen mask / smoke hood can be useful in a fire.

Most airlines are not going to let you carry an oxygen cylinder onto the plane (as others pointed out in comments, oxygen and in-flight fires can cause more problems than it solves).  That holds true for pretty much any kind of compressed gas because really, how do they know what's in that tank?
A smoke hood using a filter (or a sealed rebreather hood) with no compressed air supply may make it past security, but ask yourself honestly: "Am I proficient enough to use an emergency escape smoke hood in an in-flight emergency?" -- If you can't answer "yes" you're probably putting yourself (and others) in more danger wasting time donning the hood versus just getting out of the aircraft.

A life vest (if traveling over water)
This is overkill on an airliner (though those of us that fly little planes should seriously consider flotation devices when flying over water).
Your airline seat cushion really CAN be used as a flotation device. Those big yellow slides also detach from the plane and make marvelous floats. Frankly if you need any of these items you're in a situation where having your own Mae West isn't going to really enhance your chances of survival.
A utility knife capable of cutting your seatbelt
This is incredibly useful for a bunch of reasons, not just cutting your way out of your seatbelt. In fact I keep one in my plane. Sharp and/or pointy things make airport security nervous though - if you try to take such an item on an airline flight it will likely be taken away from you before you get anywhere near the plane.
Food and Water
Useful if you have to make an emergency landing in a remote area, but frankly airliners already have beverages (some may even still have food).
If you're carrying a light snack you're as set as you're going to be in this department.
Emergency Blankets
Nice to have, but most commercial aircraft already have shock blankets on board (and much like food/water, this is really only useful if you have an otherwise uneventful landing in a remote area).
If it makes you feel better to have your own blanket you can get pre-packed ones that can fit in basically any carry-on for about $5-10.
Signal flares
Again, mainly useful if you have an emergency landing in a remote area (and your PLB and the plane's ELT don't work for some reason). Flares are good both for signaling rescuers and for starting fires to keep warm.
I don't know if rescue flares are still routinely carried on commercial airliners, but I can say with reasonable certainty that you will not be allowed to carry on your own. They don't let you smoke on most airlines these days - they're certainly not going to let you carry on a self-igniting flare!


Why would pilots "call the company" after an aborted takeoff?

An RTO can happen for any reason, mechanical, FOD, ATC error, etc.

The boss (airline operations) will want to know what happened.

Safety

Is everyone safe?

Is anyone in immediate danger?

Prepare documents for the NTSB investigation.

Time

How much time will be lost (e.g. to cool the brakes); this can affect the schedule of this particular plane days ahead. Especially if maintenance is required.

Notify the destination airport of the delay, and also publish the delay for the next flight from said destination airport.

Maintenance

Make sure the airline's maintenance stationed at the airport can deal with the issue.

If not, get on the phone with airlines who can help.

Find a replacement plane and send it over there.

Get the all-clear from an airline engineer that the hot brakes won't affect another attempt. It depends on how hot they are.

If a delay is expected, start the clock, airlines can keep passengers on a stationary plane for so long, I guess it's two hours. Been there, it's awful.

If it will take more, find them a gate, if no gate is available, get the stairs and a bus.

Whose fault was it?

Get a grip on the PR before things get out of hand, i.e. tweet.

If anyone is suspected of not doing their job properly, start an investigation.

If the ATC is at fault, send them the bill.

If it is another airline's fault, call the insurance company.

Fuel

Not really an issue for an aborted take-off after few seconds of take-off thrust, but nonetheless run the numbers again. Both in the cockpit and in the ops center.


Have objective and verified tests been done of the effects of personal electronic devices on a commercial airliner's operation?

Yes, they have done a lot of testing, hence why they now finally realize that most electronics are of no harm, and you can use them.

The FAA announcement page has a link to a fact sheet of their report, as well as a link to the PDF of the report.

In addition to the FAA report, other agencies have weighed in (such as Boeing).  Basically, the rules were instituted in the 1960s, and remained virtually unchanged since then, so it was time to make a change.


How to know if an airport has PAPI lights?

Whether an airport has PAPI lights or not is indicated on the approach charts. For instance on this chart, there is a schematic of the airport at the bottom of page 3 that shows you where the PAPI is on the airfield.

If you are looking for airports in France, you can find all visual approach charts on the government website.
Otherwise, this wiki has various links to approach chart ressources.

Edit: If there is not indication concerning the location of the PAPI on the approach chart, you can refer to page 40 of this FAA document concerning visual aids. The schematic here describes the standard location of the PAPI relatively to the strip.


Why was the WWII RAF fighter joy stick loop design not used widely?

A control stick with a loop at the top was called a "Spade Stick".  Generally only Hurricanes and Spitfires had them.

The cockpits on these aircraft were small and it was a problem for the control column to get full travel for roll control. This was solved by making the control column rotate at about mid-stick instead of from the the floor.

Other aircraft didn't use them because the cockpits were large enough to accommodate a normal stick and still provide good leverage and side to side travel.

The loop was there so a pilot could use both hands on the stick to get more lateral force since the effective length of the stick was now much less than a conventional floor mounted control stick.

Pilots found them to be much more comfortable to hold and loop style sticks did also get used some on larger aircraft with conventional floor mounted control sticks.

Full right aileron


Is the Airbus Beluga's safety record comparable with the record of other Airbuses?

There's a history of oversize airplanes for transport. One of the earliest was the Pregnant Guppy and its successor the Super Guppy

By NASA/Tom Tschida - http://www.nasa.gov/centers/dryden/multimedia/imagegallery/Guppy/EC00-0212-2.html (image link), Public Domain, https://commons.wikimedia.org/w/index.php?curid=32895741

Boeing operates its own variant, the Dreamlifter

By scott wright (originally posted to Flickr as n780ba) [CC BY 2.0 ( http://creativecommons.org/licenses/by/2.0 )], via Wikimedia Commons

To my knowledge, none of these (including the Beluga) have had any safety incidents (although the Dreamlifter did once land at the wrong airport). I'm not sure if there's any conclusions on safety to draw from, however, as there aren't a lot of these around, as they primarily transport large materials (like aircraft parts).


Since engines are run only when the fuel pumps are on and vice versa<<

Not true. Engines can be run without fuel pumps, to allow for fuel pump failure.

The need for fuel pumps depends on the location of the fuel tanks relative to the engines, and the relative thirstiness of the engines - there are some airplanes where the fuel pumps are only used at some times (i.e. near the ground).

So it all depends.


How does the engine produce aerodynamic lift at high angle of attack?

Anything, even a metal plate creates "lift" when it is under an angle with an air flow. Lift isn't a magical attribute to "wings", it is just a physical consequence of the law of conservation of momentum: when you push a stream of air down, the reactive force is upwards.

the fuselage/engines also act as minor lifting surfaces: when they are under an angle they, inefficiently, redirect the airflow downwards.

For the engine this is also a bit due to the definition of thrust: thrust equations consider an inlet in the same direction of the thrust vector. So the inlet & compressor redirect the flow "downwards" under high angles of attack. - This effect has to show up somewhere: as a lift force generated by the engine.


The motor is converting electrical energy in mechanical energy, and unfortunately all energy conversions lose some energy to heat. This site states the cause of the heat losses as:

Friction losses due to bearings etc.
Windage losses due to air resistance.
Iron losses caused by magnetic paths of the motor (hysteresis losses and eddy current losses).
Ohmic losses from current flow.
Stray losses: other


Can commercial airliners fly over hurricanes?

In general, no- except in emergencies or 'small' hurricanes.

Commercial aircraft usually fly around bad weather (like hurricanes), not over it.
Some of the hurricanes can reach upto 50,000+ ft height, making it all but impossible for most modern commercial aircraft to fly over them (except maybe you're flying a Concorde). Even for smaller storms, the convective process over the hurricane will cause severe turbulence, affecting overflying flights.
Even for hurricanes where the  aircraft can fly over, there is the problem of safety- What will happen is something happens (for example engine failure) and the aircraft has to descend to lower altitudes? Obviously no one wants to descend into the storm.
There are some aircraft that do fly into hurricanes for scientific experiments. These are crewed by trained (and experienced) specialists and involve a lot of detailed planning. For example, the aircraft are equipped with radar that helps in avoiding the worst parts of the storm. Still, it is risky and the aircraft is exposed to significant loads and vibrations not usually exposed in commercial service.


Why are almost all STOL aircraft high-wing?

You're correct that the low wings produce more ground effect compared to their high winged counterparts. However, during takeoff and landing, it can result in undesirable handling qualities- the aircraft can 'float' the runway; on contrary, the high wing design is more stable. There are other reasons for STOL aircrafts to have high wing designs, most of which has to do with the location of their operation, as you noted:

Most of them are operated from austere airfields. The high wing location gives some protection from the debris (and obstacles).
For the same reason, engines mounted on the high wings have better protection compared to the low wing mounted ones from FOD ingestion.
Most STOL aircraft use large TE flaps. In case a low wing is adopted (and also if propeller is used, like Twin Otter, for example), the required ground clearance will require long and consequently heavy landing gear. This can be avoided in case of high wing design.
The visibility is better compared to low and mid wings.

Historically, STOL aircraft have been high wing. Also, some of the STOL aircraft are (military) cargo aircraft- the high wing means there is no wing spar across the cargo compartment; plus, the low fuselage means easier loading/unloading of cargo.


Gage or Gauge? Which is correct in the aviation industry?

Gauge is correct. As in Oil temperature gauge, Fuel Pressure gauge, Fuel Level gauge, Cylinder Head Temperature gauge, Exhaust Gas Temperature gauge, etc.

Anyone use gage is misspelling the word.  Same with Hangar. (Not hanger)


Can a FAA "Letter of Authorization" be used when there are no pilots that are current on a type rating?

If I understand the question correctly;

Maybe

The FAA outlines a generic type rating curriculum in this AC which is worth going through as it outlines what training would potentially be required for the type cert,

FAA FAR 61.31 does allow for a waiver

  § 61.31 Type rating requirements, additional training, and authorization requirements.

  (b)Authorization in lieu of a type rating. A person may be authorized
  to operate without a type rating for up to 60 days an aircraft
  requiring a type rating, provided -

(1) The Administrator has authorized the flight or series of flights;

(2) The Administrator has determined that an equivalent level of
 safety can be achieved through the operating limitations on the
 authorization;

(3) The person shows that compliance with paragraph (a) of this
 section is impracticable for the flight or series of flights; and

(4) The flight -

      (i) Involves only a ferry flight, training flight, test flight, or
      practical test for a pilot certificate or rating;

      (ii) Is within the United States;

      (iii) Does not involve operations for compensation or hire unless the
       compensation or hire involves payment for the use of the aircraft for
       training or taking a practical test; and

      (iv) Involves only the carriage of flight crewmembers considered
         essential for the flight.

(5) If the flight or series of flights cannot be accomplished within
   the time limit of the authorization, the Administrator may authorize
   an additional period of up to 60 days to accomplish the flight or
   series of flights.

Section 3 is the important one. You would have to show that it is "impractical" for you to obtain the type rating with out the waiver to operate the aircraft and fly the required training time.

You may also have a compounded issue of then needing a second crew member who is typed in the aircraft and can provide training/co-pilot duties. Further more you cant conduct any commercial operations while doing this so you need an empty DC-4 and a lot of time (read money) to fly it. Keep in mind you may only have 60 days to accomplish all the training as well or you will need to get an extension on the waiver.

Just a general note. These kinds of situations are often best suited for an aviation lawyer who has experience dealing with the FSDO. It would be wise in this case to seek the aid of someone like that. You also may want to look for remote training if there is another operational DC-4 flying elsewhere and an arrangement could be made for you to go train with them for some time that situation may, in the long run be simpler.


What is the overhead instrument panel (pictured) near the front galley area of an A320?

(easamodul10.blogspot.com)

That panel you saw is the forward cabin circuit breaker panel. There is also an aft one.

It is used by maintenance personnel and cabin crew. For example if a toilet becomes inoperative, pulling the 'vacuum sys C/B' for 30 seconds might solve the issue.


Why doesn't GE replace all 4 engines for on their flying test bed instead of just 1?

They only change one, because that one is a new engine that is being tested.

If you are testing a new engine you change 1 at first so if it fails you have 3 others.  If you change all 4 and there is a systematic defect in the design, now you have 0 good engines instead of 3.

You will also see that the test engine isn't always one suitable for a 747.  This is because they may be testing a new design or a new alternative fuel and it is safer to test an unknown with 3 good engines (e.g. a 747) rather than with just 1 good engine (any two-engine airplane).  This increases the safety margin if the test engine fails.

Running a different engine with a different thrust rating requires some thought about asymmetric thrust.  Doing this on a 4-engine airplane simplifies this greatly over a 2-engine airplane.  Ways to accommodate different thrust from the odd engine:

De-rate the new engine so it only produces thrust equivalent to the normal engine
Run the new engine at reduced thrust
If the new engine is inboard, reduce the outboard engine thrust to balance the total yawing moment from that wing with the other side.
Don't worry about it and trim the airplane to compensate.

The other advantage to doing this on a 747 is that a 4th engine is technically not really needed as a 747 can takeoff, fly and land with only 3 operating engines.


How do pilots decide whether or not to deploy a ram air turbine?

The reason why the RAT deployed is of primary concern. The RAT should automatically deploy when (depending on the design of the aircraft) you lose all primary electrical and/or hydraulic power. In these cases, an immediate diversion is necessary because you may be one failure away from losing control of the airplane.

However there are uncommanded RAT deployments due to system malfunction, or mistake. For example, the pilot hit the RAT button by accident, or somebody accidentally switched off both generators instead of switching on both bleeds. In that case, the problem is easily rectified and then the pilot needs to decide whether to divert/return or continue the flight.

For Airbus, they state

  The uncommanded extension of the RAT is not considered to have any additional operational impact. The RAT is able to be extended in all flight envelope conditions. If there is an uncommanded RAT extension, then this is indicated to the flight crew, and hence the appropriate maintenance action, i.e. the resetting of the RAT, can be performed.

Fuel burn is minor, I think its +1% on the A320 family. The main concern operationally is that a RAT is loud. They sound like a prop plane or helicopter, so for passenger concerns, you might end up landing and having it restowed.


How to relay an emergency to ATC while on the ground?

Call the police if in doubt who to call they have contact with Air Traffic Control.

Also calling the wrong facility can mean that it can take quite a while for the information to make it to correct facility.

Finding direct line phone numbers to ATC facilities can be intentionally hard. Prank call anyone! They are usually somewhere in the local Aeronautical Publication Books but where you can get a copy of them and then finding the number inside the book is difficult. Just call the police!


Is there a graph that shows the thrust required for a given airspeed?

For horizontal flight, thrust required is the same as drag.  Go to the specific graph referenced in this answer How close is the air resistance or drag force to be proportional to the speed squared?, and you'll have your answer, or close to it.

The specific graph referenced here is for "a conceptual two-seat light sport aircraft (LSA) designed to cruise between 80 and 100 kts".  A Cessna 150 or 172 might need somewhat more power for the same cruise speed.


What is the main difference between an ETOPS certified and non-ETOPS certified plane?

The FAA ETOPS certification requires certain standards from both the airline (the operator) and the aircraft (the manufacturer).

As far as the manufacturers are concerned, the ETOPS certification is given for a particular aircraft-engine combination satisfying certain requirements. The FAA ETOPS Rules Section A deals with the Airplane-Engine Type Design Approval. According to the document, the type approval involves a two step process:

  First, the FAA determines that airplane systems meet certain design standards for safe operations during an airplane diversion.

Some of these requirements are:

The aircraft should have at least three independent electrical generators.
The auxiliary power unit (APU) (when required) can start after the airplane has been cold-soaked for several hours and can run reliably for the remainder of the flight.
System safety analyses have to show that expected system failures will not prevent safe landing at a diversion airport.
Systems with time-limited capabilities (typically cargo fire suppression) need to have the capacity to support a maximum-length diversion,
including a 15-minute allowance for a hold or go-around at the diversion
airport

  The second part of the approval process is an evaluation of engine in-
  flight shutdowns and other significant airplane system failures that have
  occurred while the airplane-engine combination has been in service.

The aircraft-engine combination should have at least 250,000 engine-hours for evaluation, though this can be reduced with compensating factors. The airplane-engine combination should maintain a target IFSD (In Flight Shut Down, defined as "When an engine ceases to function (when the airplane is airborne) and is shut down, however briefly, whether self induced, flightcrew initiated or caused by an external influence.") rate at or below 0.02 per 1,000 engine-hours for 180min ETOPS approval.

The manufacturer should also demonstrate that flying with OEI doesn't cause undue stresses to the aircrew and is safe for the airframe.

The ETOPS design approval has to be applied for with the FAA and obtained after the relevant processes. Thus, the same aircraft will not have ETOPS approval if the engine is different or even the same aircraft-engine combination won't have ETOPS approval if used by another airline or if no certification was sought.

There is another method of getting ETOPS approval called the 'early' ETOPS approval which

  ...takes a systems approach to the development of an airplane and engine. ... an applicant must demonstrate that the design flaws on previously designed airplanes are not present in the new airplane. The applicant must also consider how the maximum length flight and diversion affect the design and function of airplane systems to ensure that they have the capability and reliability for safe ETOPS flight.

After being ETOPS certified, the airplane-engine combination and the operator are under continuous monitoring with the certificate being withdrawn in case of lapses or if the IFSD rate goes above the target rate and the manufacturer's corrective action does not eliminate the unsafe condition.

As far as the LAX-Hawaii incident is concerned, according to American Airlines Spokesman, both aircraft (the 'correct' ETOPS airplane, A321H and the wrong one sent, A321S) had the same configuration, but

  There are two small differences in terms of equipment to allow ETOPS certification. Since you can’t divert for medical [on a Hawaii bound flight], you’re required to carry extra medical oxygen on board and an extra fire suppression canister

There are also reports that the (ETOPS certified) A321H has extra fuel tanks, which the (non ETOPS certified) A321S didn't have, though the AA spokesperson had said that the fuel tanks and range were the same.


If the Quadcopter is a MIMO Nonlinear System, How Can it be Controlled using PID?

Exactly as you mention later:

  Does the model need to be linearized so that PID algorithms can be used?

Yes, that's correct.

To be a little more explicit, you need two things:

linearise the system (usually around a so-called "working point", e.g. cruise conditions)
de-couple the system (because a linearised MIMO is still a MIMO, you need a set of 4 SISOs)

Achieving the first is fairly simple, as I mentioned, you "only" have to select a working point. The second is instead a little more elaborate, and requires making assumptions on the flight conditions that will be encountered, plus it is not always possible, some vehicles have their dynamics so coupled that de-coupling is not an option (and thus simple PIDs tend to be not a viable option if you have to tune them manually).


How does turbofan engine performance depend on speed and density altutude?

The dependence on density is straightforward: Thrust depends on the mass of air pushed out at the back, and this is changing linearly with density if the speeds don't change.
$$T \propto \frac{1}{\rho}$$
The dependency on speed has two factors, the intake precompression and the speed difference between flight speed and exhaust speed. First intake precompression:
$$T \propto \left(\frac{\kappa-1}{2}\cdot Ma^2\cdot\left(1-\left(\frac{Ma_{intake}}{Ma_{\infty}}\right)^2\right) + 1\right)^{\frac{\kappa}{\kappa-1}}$$
or, if we insert $\kappa = 1.405$ for diatomic gasses:
$$T \propto \left(0.2025\cdot Ma^2 \cdot\left(1-\left(\frac{Ma_{intake}}{Ma_{\infty}}\right)^2\right) + 1\right)^{3.469}$$
The term which captures the thrust proportionality to the speed difference looks like this:
$$T \propto \frac{v_{nozzle} - v_{\infty}}{v_{nozzle}}$$
Please see this answer for an explanation of the variables. The plot below shows how little the intake precompression matters at subsonic speed, but how much it does at higher Mach numbers. Note that the plot sets the pressure at the engine face to 1 when flight speed equals the assumed intake speed of Mach 0.5. This pressure recovery lets thrust climb above the static value once Concorde flies supersonic.

Explanation of the plot: This shows relative ideal intake pressure over speed, assuming that the speed at the compressor face is Mach 0.5. Note that in static conditions the air needs to be accelerated, so the intake pressure is only 84% of ambient pressure, and at Mach 0.85, the maximum speed of airliners, the intake pressure is 1.37 times higher than ambient pressure. But at supersonic speed things take really off: Pressure recovery for the Concorde was already 6 at Mach 2.0, and for the SR-71 it was 40 at Mach 3.2.

If the engine has no variable nozzle, it is fair to assume that the nozzle speed will not change over the flight speed if the throttle setting is constant. If the nozzle speed is low (= high bypass ratio), the drop over speed is steeper, which explains the difference between turbojets and turbofans.


Under FAR Part 121, is it mandatory to execute a missed approach when unable to land within the touchdown zone?

This is spelled out in 91.175(c), in particular

  Operation below DA/DH or MDA. Except as provided in paragraph (l) of this section or § 91.176 of this chapter, where a DA/DH or MDA is applicable, no pilot may operate an aircraft, except a military aircraft of the United States, below the authorized MDA or continue an approach below the authorized DA/DH unless

...

  The aircraft is continuously in a position from which a descent to a landing on the intended runway can be made at a normal rate of descent using normal maneuvers, and for operations conducted under part 121 or part 135 unless that descent rate will allow touchdown to occur within the touchdown zone of the runway of intended landing


Is skydiving in IMC (through clouds) legal and safe?

It is not legal to conduct skydiving into clouds, atleast in US. From 14 CFR §105.17   Flight visibility and clearance from cloud requirements:

No person may conduct a parachute operation, and no pilot in command of an aircraft may allow a parachute operation to be conducted from that aircraft—
(a) Into or through a cloud, or
(b) When the flight visibility or the distance from any cloud is less than that prescribed in the following table:

Is it safe? Probably. The chances of mid-air collision are pretty small, but they can happen as is does with aircraft. Midair collisions between skydivers and between aircraft and skydivers are rare, but not unheard of. There has also been reports of near misses between aircraft and skydivers through clouds. So, its better to be safe.


How to get the correct angle when doing a visual appoach before landing?

PAPI

An airport might have Precision Approach Path Indicator (PAPI) lights set up. I believe these might be what you are thinking of. They are discussed in Chapter 2 of the AIM.

Here are two pictures to show them at night.

The first, shows a plane that is on the correct glide path. Firstly, they are normally installed to the left of the runway, and according to the AIM, red should be on the right, so, I believe the picture has been flipped, however you could still use them as is.

If you are right on the correct glide scope for that runway, you would see two white and two red. .2 degrees high would show three white and one red, and .5 degrees high, or higher, four white.

Conversly, .2 degrees low will show three red and one white, and .5 degrees low or lower will show all four red.

Red and White is Just Right. All Red, You're Dead.

VASI

There might also be VASI, or Visual Approach Slope Indicator, lights. These are in many different configurations. They are also discussed in the AIM at the same link I posted above. An example of a two bar VASI light setup is shown below.

The VASI lights are the two sets of two lights next to the runway (just above the row of green lights. They are set up so that white over white is too high, red and white both showing, on glidepath, and red over red is too low.
The mnemonic for those is: red over white, alright; red over red, you're dead.

For more information, there is the AIM Page, the PAPI Wikipedia Page, the VASI Wiki Page, plus there are many other pages which are useful. If you search (using Google or BING, for example) for "runway lights papi" or "runway lights vasi" you'll get many hits.

One last comment here. The correct glide path for an airport is not always the same. If there is/are an obstacle, the glide path might be higher/steeper. If the runway is lighted, using PAPI and/or VASI lights, use them! They will keep you on the correct glidepath for whatever runway you're trying to use.

Good Luck and Safe Flying!


Sorry our experts did not weigh in on this one in more detail.

Sweeping the wing increases the "dihedral effect" of tending to create a greater roll force when struck with a side gust, as the windward wing is angled towards the gust, and the leeward away.  This is exactly the same effect as what happens in a side slip.

Swept wings also improve yaw stability.
Of course, a very sharply swept wing presents a shorter torque arm to a rolling gust than a less swept wing of equal length but greater span.

The "dihedral effect" of swept wings can be aerodynamicly countered with side area under the CG, particularly fuselage side area or landing gear spats.  Ventral fins offer another alternative.

A gust from the direction of flight will affect a swept wing similarly to a straight wing, producing a momentary increase in lift.

The venerable Tiger Moth biplane has slightly swept wings.


Dry thrust usually means the non-augumented thrust i.e. thrust without the use of afterburners or liquid injection. The maximum thrust produced by jet engines w/o afterburner is sometimes called military thrust.

The thrust of a jet eingine can be increased by using methods like water(+methonol) injection (mostly in older turbojet engines) or by using afterburners (reheat). In such cases, the (higher) thrust produced is called wet thrust.


American Airlines Astrojet - is it really 'polished aluminium'?

Yes it is polished aluminium.
On the 737 in your photo, the weight difference with a fully painted plane is about 70 kg, and this yields operating cost savings of about USD 60,000 per year in 1998 dollars, about equal to USD 88,500 in 2016 dollars.
The paint coat is repainted every couple of years, the aluminium polish must be re-buffed 3 times per year.
From the same Boeing document:

Polished surfaces are protected from corrosion by regular buffing
after washing. Painting protects against oxidation, salts, and jet
fuel spills. However, unrepaired chips and cracks in paint collect
dirt and moisture and so may become corrosion sites. Painted surfaces
are also susceptible to filiform corrosion, or worm corrosion, which
begins between metallic surfaces and paint and erodes both. It creates
hydrogen and lifts up the paint layer as it travels across the
surface.

Also, the paint protects against small scratches from sand etc which may start fatigue cracks, however since the polished skin is very closely scrutinised during the re-polishing that is not really an issue.


The final report notes:

At the time of each TAI [thermal acoustic imaging], the inspectors attributed the indication to a defect in the paint that was used during the TAI process and allowed the blade to continue the overhaul process and be returned to service. [emphasis mine]

The paint being referred to is used for the inspection. Its function is to improve the emissivity of the object.


What do "azimuth window" and "compass switch" refer to in this accident report?

They are autopilot controls are visible in this clip from the Wikipedia cockpit picture:

Source: Wikipedia

Airliner avionics have independent left and right systems for the captain and first officer. But, in many aircraft, there's only one autopilot. It's not a critical system and the crew can hand fly the plane.

The autopilot controls allow it to be set to receive data from either side. Standard procedure is for it to be set to the side of the pilot flying so it follows what the pilot flying sees. The pilot not flying can monitor the flight on their displays and detect any deviations.

Note the switch at bottom center with the option to select Port or Stbd.


Where does the oxygen come from in the deployable breathing masks?

The oxygen is provided through Chemical Oxygen Generators. Oxygen masks are triggered either automatically given certain conditions or by the flight crew.

Oxygen generators are usually installed in above each seat row. If the cabin altitude reaches a predetermined height (14,000' is standard) or if the system is activated by the flight crew, overhead panels open and oxygen masks drop out. To put the mask on, it is necessary for the intending user to pull it down and this action releases the firing pin and activates the generator.
The oxidizer core of an oxygen generator usually consists mainly of Sodium Chlorate (NaClO3) mixed with <5% Barium Peroxide (BaO2) and <1% Potassium Perchlorate (KClO4). This core is activated by the application of heat generated usually generated by a mixture of lead styphnate and tetracene which itself is activated by a small explosive charge in a percussion cap are a mixture. This explosive charge is set off by the release of a spring-loaded initiation mechanism which is restrained until released by a pull on the lanyard which is visible when oxygen masks are released from overhead panels. Once activated, the chemical reaction and production of oxygen will continue until the generator has been exhausted which is typically in the range 12 to 20 minutes.


What are the issues with building modular aircraft?

Designing "better", upgraded part is a lot of work. And then everything has to be thoroughly tested to work together, which is even more work. That's why aircraft manufacturers usually choose to upgrade as few parts as possible and only those where most significant benefit is expected.

Take for example 737. The type was upgraded with new engines several times, because evolution in engine technology brought significant fuel savings. But the wings only got winglets, which was less work than redesigning the wing. And the fuselage was not changed at all, only it is now built longer by adding some frames.

And the situation with A320 is similar. The "NEO" designation for the new series entering production stands for "new engine option", because that's what the upgrade is about. Beyond new engines and winglets there is basically no other change.

And that was just type changes as in new aircraft being built from upgraded parts. Upgrading an existing airframe is another can of worms.

Basically the joins between airframe components have to be very strong and light. The most common joining method that satisfies this is riveting, with gluing gaining popularity for composites and in some cases welding appears (aluminium is difficult to weld, but friction-stir welding seems to work satisfactorily).

Well, none of these methods allows easy disassembly. To make the components replaceable, they would have to be bolted instead. However, bolts have several major disadvantages. They can shake loose, they don't fit tightly (rivets expand to fit) and they are considerably heavier. These things make them totally unsuitable for the high-stress joining, especially for joining fuselage and wings. And drilling out the rivets and riveting in a replacement is too much work and there is a high risk of damaging the parts, which could easily make them unsafe to use.

And then there is a question of the removed parts. So you replace the wings after half of their life, because new, more efficient model is available. But the old wings could have still generated revenue. By discarding them, you've lost those money. So to pay off, the difference in efficiency must make up for that.

Well, it is extremely unlikely to do so. The new engines of 737MAX or A320NEO save about 15% of fuel, but engines are the component where by far largest benefit could be gained. Redesigning any other component can save at most few percent.

Yes, some airframes did get structural upgrades (upgrading avionics or other small components is of course easier and thus done more often), but usually these were military aircraft where the changes provided some other benefit that was worth the effort.

And some more airframes got refitted to different engines, but engines have shorter life, so they have to be designed to be replaceable. And even there it is usually military aircraft and usually only because the airframes are used much longer. For example KC-135 was reengined, but that was about the time its civilian counterpart, B707, was scrapped altogether.

But most of the time, replacing parts of an aircraft would not prevent any wastage but rather create a lot of it.


What must ATC do, following a reported laser sighting by a plane?

Here's what the regulations say ATC should do:

Broadcast on all appropriate frequencies a general caution warning every 5 minutes for 20 minutes following the last report;

Include information on the ATIS broadcast for one hour following the last report;

Report the incident through the Domestic Events Network (DEN), or to their overlying TRACON or ARTCC facility.

As for the pilots, lasers are regarded as an emergency, so you are permitted to take evasive action.
Other aircraft are also permitted to request clearance to avoid the area.

Here are the relevant FAA orders:
FAAO JO 7110.65:

10-2-14. UNAUTHORIZED LASER ILLUMINATION OF AIRCRAFT
a. When a laser event is reported to an air traffic facility, broadcast on all appropriate frequencies a general caution warning every five minutes for 20 minutes following the last report.
PHRASEOLOGY- UNAUTHORIZED LASER ILLUMINATION EVENT, (location), (altitude).
b. Terminal facilities must include reported unauthorized laser illumination events on the ATIS broadcast for one hour following the last report. Include the time, location, altitude, color, and direction of the laser as reported by the pilot.
NOTE- All personnel can expect aircrews to regard lasers as an inflight emergency and may take evasive action to avoid laser illumination. Additionally, other aircraft may request clearance to avoid the area.

FAAO JO 7210.3:

2-1-27. REPORTING UNAUTHORIZED LASER ILLUMINATION OF AIRCRAFT
All FAA Air Traffic Control facilities, Federal Contract Towers and Flight Service Stations shall report unauthorized laser illumination incidents through the Domestic Events Network (DEN), providing the following information:
a. UTC date and time of event.
b. Call Sign, or aircraft registration number.
c. Type of aircraft.
d. Nearest major city.
e. Altitude.
f. Location of event (e.g., latitude/longitude and/or Fixed Radial Distance (FRD)).
g. Brief description of the event.
h. Any other pertinent information.
NOTE- Facilities without direct access to the DEN shall forward the information through the overlying TRACON or ARTCC facility


Runways are usually numbered according to their direction, more precisely called runway magnetic bearing or QFU (see Q codes).

Consider a plane flying toward the runway on final approach in a day without any wind. Divide its magnetic heading by 10, round it to the nearest whole number and you'll usually get the runway number. For example, if the magnetic heading is 345° then 345/10=34,5, so the runway number will be 35 which will be a runway used for landings (and takeoffs) to the north.

Opposite ends of the same runway have different numbers, 18 (which represents 180 degrees) apart. A runway with 35  for landings to the north will have runway 17 for landings to the south. Even though these are the same strip of concrete, they are treated as separate runways by pilots and controllers.

If there are two airports near one another with runways at the same angle, sometimes one of the airports will add or subtract one from the runway number to help planes differentiate between the airports.

Occasionally a runway number will change when the magnetic declination angle changes in such amount, making the runway magnetic bearing divided by 10 and rounded to the nearest whole number increase or decrease.

Some runways in areas of large magnetic declination use true instead of magnetic headings for the runway numbers. This is not unusual in northern Canada and Greenland.

When there is more than one parallel runway at an airport, L, R, or C may be appended to the runway number for Left, Right, or Center. These are based on the approach direction, so, for example, the runway 35L would be called 17R from the opposite direction.


Why is there a grid below the antennas of an VOR?

I think this is an example of a counterpoise:

  [It] is a network of suspended horizontal wires or cables (or a metal screen), used as a substitute for an earth (ground) connection in a radio antenna system (...) when a normal earth ground cannot be used because of high soil resistance or when an antenna is mounted above ground level.

Generally used for LF and VLF antennas as that is where they are most efficient.

An example from that Wikipedia page of an AM radio antenna counterpoise:


How does a diffuser (in ground effect) accelerate the air in front of it?

Even though this isn’t strictly an aviation question, it does involve aerodynamic principles.
To put it simply, the diffuser’s main purpose is to gradualize the transition from rapidly flowing air under the car’s body as it transitions back to the speed of the ambient air behind the car.
There is a high pressure zone in front of the car from air particles colliding with the vehicle, and a low pressure zone in the wake behind the car as airflow is attempting to rejoin on the other side. This high to low flow draws air under the car where space is limited. This limited space results in an increase in speed and a decrease pressure, thus increasing downforce as the pressure below the car is less than the pressure on the top and sides of the car. This is Bernoulli’s equation at work.
However, the rapidly moving air experiences adverse pressure gradient at the rear of the car and airflow separation results in significant turbulence. This turbulence not only increases drag, but limits how quickly air can be evacuated from underneath the car. By carefully shaping a diffuser, the airflow can be slowed more gradually, easing its transition back into the ambient flow, minimizing turbulence which increases the flow speed under the car, decreasing the pressure and increasing downforce on the wheels even further.
The diffuser is shaped to increase the airflow speed in front of this funnel to ‘push’ a low pressure zone in front of the funnel, more effectively drawing air into the diffuser.


Why are you required to commit to a full stop landing if reverse thrust is selected?

The biggest problem is that thrust reversers take time to move. During that time they are still producing reverse thrust (even if only at idle) and slowing you down. They must all completely close before you get forward thrust and can add power to start accelerating again.  Then, what happens if they don't stow, or only part of them stow?  Now you've used up valuable runway that could have been used to stop (or at least slow down more) and are no longer in a position to takeoff from. The consequences can be pretty severe.


What is the function of variable inlet guide vanes in terms of pressure change?

You need to be careful in understanding the significance of the variable guide vanes (VGVs) being variable.  You could think of them as a bit like venetian blinds -  when they they are most open they present the least obstruction to the air flow, much as you get the most light through a set of blinds when they are at the right angle to the incoming light. As you close them, you get less flow (light) through them, as they present a greater obstruction to the flow.

The VGVs are only variable to maintain stable flow in the compressor at conditions away from the design condition.  The design condition for jet engines is always high power during cruise (or at the top of the initial climb to be pedantic), so the VGVs only start to close at reduced powers.

At high power the vanes are at their most open to maximise flow through the engine, minimising pressure losses across them and maximising thrust.   As they are gradually closed when power is reduced, they present more of an obstruction to the flow (acting as effectively a variable area throttle valve in the path of the flow being closed down), so presenting an increased pressure ratio loss (or if you prefer reduced pressure recovery).

The increased use of VGVs really shows designers pushing at the limits of airflow stability in pursuit of better efficiency by maximising pressure ratio per stage at the design condition, at the cost of the increased weight of the mechanisms to drive the VGVs.

Not sure I expressed that very well, but first post on stack exchange.


How much force are large aircraft brakes able to exert?

This has been answered before, but in a different context. Therefore, I copied the essential part here:

Emergency procedures at take-off weight will produce the biggest braking loads. I will calculate the highest possible braking loads for a Boeing 747-400 that weighs up to 400 tons on take-off. For this I need this plot of a polynominal for the braking coefficient, which is the ratio between vertical and horizontal forces before the tire skids. I do not know the source; I collected it somewhere in the past and never found a reason to doubt its validity.

Shortly before the aircraft comes to a stop, the highest friction coefficient is reached, and then little lift is produced by the wings, so the vertical tire loads are those of the static case. The braked wheels are the 16 main wheels; I assume that the unbraked noswheels carry 4% of the total weight. At 96% of 400 tons acting on those 16 wheels, this is 24 tons = 235,344 N = 52,907 lbs of downward force per wheel. Since the friction coefficient is 1 at low speed, the same load is transferred horizontally from each wheel to the ground and into the gear struts.

And, yes, brakes will lock on a dry runway if the disk brakes are fully engaged.


What are the major hazards in operating a PT6 Turbine Engine?

You MUST NOT allow the EGT or ITT (whichever is applicable) temperature limit to be exceeded in any turbine engine. If it gets close to occurring during start on a PT-6, you need to abort the start by stopping fuel flow into the engine, then conduct the appropriate checklist for an aborted start. Unlike the Honeywell / Garrett TPE single-shaft engines, the PT-6 normally won't get close to the temperature limit on start. The Garretts I used to fly in Metroliners had to get right next to redline and stay there on every start. One reason that PT-6 engines are so much more relaxing to fly.
On takeoff / climb, just don't exceed the maximum temp limit; regulate the power lever(s) to keep below it. I've never had a failure of a Pratt except for bleed air leaks.
Airlines count cycles as a start, flight, and shutdown. If one of these did not occur, you did not have a cycle.


Can carrier-based aircraft takeoff while the carrier is stationary?

Aircraft carriers using STOBAR (the skyramp) always need to maintain a speed of about 55kmph in order for the aircraft on them to take off. This is done to generate enough windspeed on the deck to assist the aircraft to take off. And STOBAR system already hampers the carrying capacity of aircraft, so for takeoff from a STOBAR carrier at rest, a further reduction in takeoff weight of the aircraft would be required to generate enough lift for the aircraft to take off at such low speeds. This reduction in weight would depend on the aircraft carrier and the aircraft as such and might create scenarios where this is entirely not possible.
For Aircraft Carriers equipped with CATOBAR, the conventional steam piston drive which is used to catapult the aircraft provides approximately 95 MegaJoules of energy to accelerate the aircraft to speeds where it can takeoff safely. Hence the arguments stated about the STOBAR carriers can be sequentially applied to this class as well. But recent Electromagnetic Aircraft Launch System provides around 122 MegaJoules of energy to accelerate the aircraft. Given the extra amount of energy available to accelerate the aircraft at higher speeds, it is quite possible that it is going to be easier for the aircraft to take off from a static aircraft carrier equipped with electromagnetic catapults when compared to the aircraft carriers equipped with convention steam piston catapults. But the exact details for the feasibility of this idea would be a matter of national interest and might not be available online.
Also, one should not ignore the extra amount of stresses that an aircraft would have to face while taking off from a stationary aircraft carrier as it would have to accelerate to a higher speed at the same available length of the runway and hence this might prove detrimental to the lifetime of the aircraft.
Edit:
Under research technologies such as Ground Carriers, if implemented would also assist further in reducing the weight of the aircraft and hence make it easier for the aircraft to take off from carriers at much lower speeds.


Where are "standard taxi" instructions published?

You can find a nice article on standard taxi routes here. They are included in the NOTAMS, or on Jepp charts if you have access to them. The full standard for publishing them can be found here.

This is what they look like:

(source: own image)

As ymb1 points out in the comments you can access them here as well.


Can two airports have a different ICAO code but share the same IATA code?

You're right that two airports can share the same 3-letter code, but they're not necessarily IATA codes (they could actually be FAA identifiers, or just locally assigned codes).

In implementing Otto the Autopilot in our chat room, for commands like !!weather JFK, I needed to find a way to reliably convert IATA codes to ICAO codes. I ended up using the same source as you linked to, and imported the columns we needed into MySQL. A quick query shows 65 (i.e. >=130) duplicates:

AHT AJL API APS ARS AUS BJW CGY CLG CPO CSZ DDU DZN GIG HKG HYD IOR ISG IZA JFR JRS KFE KMM
KWB KYF LIM LUZ MCJ MCU MJF MNI MPD MPT MRE MUC NST NWT OBI OHE PCO PDG PHG PIV PPJ PRI PRM
PSV RCH REQ RZS SEA SFK STI SYC SZR TFY THO TNO TPJ UCN ULG VME VQS WRW YDT

The problem is, that IATA wants you to pay several thousand dollars for access to their list. So OurAirports attempts to collect all the known IATA codes, but it is user-editable, like Wikipedia. So there are inaccuracies in their database; and as I mentioned, there is some overlap between IATA/FAA/local.

The actual IATA codes are unique (although sometimes reused).


What do EU pilots use for IFR enroute charting (besides Jeppesen)?

In Europe, like in most of the world, IFR enroute charts are published in ENR 6 of the national AIP, which can be found notably from Eurocontrol @IS online. Some countries publish these charts in sections ENR 3.x.
Some countries like Spain even publish electronic charts.
More details (route data tables) about IFR routes are published in the following sections:

ENR 3.1 Lower ATS routes
ENR 3.2 Upper ATS routes
ENR 3.3 Area navigation (RNAV) routes
ENR 3.4 Helicopter routes

Note: this organisation of routes will change soon.
There are numerous companies offering flight manuals beside Jeppesen and Lido: Navblue is one example.


What is the difference between GPS, GNSS and RNAV?

As stated in the othe answers,

GPS is the US Global Positioning System
GNSS is an umbrella term that encompasses GPS as well as other nations' satellite systems that achieve essentially the same capability

RNAV is the aircraft capability that allows you to navigate from point to point, defined by Latitude/Longitude and independent of any ground-based system.  There are various ways that the hardware in the aircraft maintains its position.  It may use GPS sensors, it may use GLONASS, it may uses a combination of satellite systems, it may use DME/DME updates from ground-based navaids.  But the point of RNAV is that for the most part the procedures are agnostic with regard to how the position info is obtained.

Thus, you can have RNAV routes and approaches, meaning that the airway or approach segments are defined by Lat/Lon waypoints, and as long as your system meets defined accuracy tolerances (usually 1.0 NM enroute and 0.3 NM for an approach in the US), you can fly that airway or approach.  There are more stringent tolerances incorporated into RNAV(RNP) approaches, and these require that the system can monitor its accuracy and alert the pilot if the system isn't confident that its position is accurate to within a specified performance.  This can be set to match whatever is required on the approach; 0.1 NM is common, although there are other values that can be specified.

In the US, the FAA typically distinguishes basic RNAV approaches by designating them RNAV(GPS) in the title, as opposed to RNAV(RNP).  (The RNAV(RNP) approaches require a couple of additional things beyond basic RNAV, but those are beyond the scope of this question.)  Internationally, "RNAV(GNSS)" is often used instead of "RNAV(GPS)" in the approach title, but functionally they're pretty well the same thing -- it's simply a nod internationally to the fact that if your FMC knows where it is, the approach designer doesn't care which satellite system it's getting its position data from.

In the "old days", it was possible to have RNAV operations that worked by taking radial/DME data from a single VOR and creating a pseudo-VOR essentially whereever you wanted, and the HSI or other display would act as if the VOR were in the new location.  This was very early RNAV capability, in that it allowed you to fly a straight line course by keeping the HSI centered rather than flying VOR to VOR.  These days, that capability is pretty much gone, in favor of the much greater capability of GPS.


Is it dangerous to do a skidding turn to lose altitude without increasing airspeed?

As Ron Beyer pointed out in a comment, your instructor was showing you a forward slip - a pretty standard maneuver for light aircraft.

A spin would involve full rudder and a stalled wing, which usually means pulling the yoke or stick back a lot.  That's why overshooting the base-to-final turn can be dangerous - you likely already have a lot of rudder in and it's tempting to pull back on the yoke to try to tighten up the turn.  An unexpected spin at low altitude is not recommended as recovery tends to be both abrupt and fatal.

As long as you're keeping the yoke more or less centered forward and back and your airspeed up, there should be nothing to worry about.


Should ADS-B airborne and surface squitter transponder registers both be updated regards air/ground status?

I don't have the 1090ES MOPS at hand here, but it makes sense to me that both should be updated.

At the moment that the registers are updated, it is not necessarily clear whether an airborne or a surface squitter will be transmitted next. In the period between update of the register and transmission of its contents, the vertical status of the aircraft can change.


Yes, it is called in-seat-rest.

  This is the process whereby pilots may take short periods of sleep (naps), while temporarily relieved of operational duties in accordance with carefully prescribed ‘controlled rest’ procedures, when part of a two-man operating crew of an in-flight aeroplane.

Source: skybrary


What is the make and model of this biplane?

It's a De Havilland DH.83 Fox Moth

 Source Wikipedia. Photographer:  Chris Finney
With a bit of image contrast and brightness modification, the registration can be read on the underside of the wing: VT-AEA.
VT is the registration prefix for India since the 1930's
The historic registration can be found on www.airhistory.org.uk and here.

Registr.
Type
Serial #
Reg. History
Owners
Date
Cert. #
Fate

VT-AEA
DH.83 Fox Moth
4043

The Bombay Flying Club Ltd
01.05.33
173
Reregistered 6.12.37

VT-AEA
DH.83 Fox Moth
4043
VT-AEA
GB Keshein, Bombay
6.12.37
173/2
Reregistered 1.2.38

VT-AEA
DH.83 Fox Moth
4043
VT-AEA
Air Services of India Ltd, Bombay
1.2.38
173/3
Cancelled 10.7.41

The aircraft was first owned by the Flying club of Bombay since 1933, then briefly by G.B. Keshein in Bombay and then by Air Services of India until 1941.


What are the meanings of these terms related to instrument flight?

Homing & 0° relative bearing

Homing is a technique used with ADF/NDB navigation, where you point the ADF needle at 0° relative bearing, which means that your nose is directly pointed at the navigational aid you are trying to reach. The same technique can crudely be used with VORs and GPS, where homing onto a VOR would be changing the inbound radial every few minutes to establish a new heading to the VOR or using GPS GOTO every few minutes.

This is considered a poor navigational technique, as it purposely neglects wind correction and this the aircraft can get blown off track significantly. You also increase the leg time with this, as you take longer to reach the navaid than with wind correction applied.

(Image Source: navfltsim)

0° relative bearing refers to your longitudinal axis being in line with a navaid, mostly NDB. If something was straigh at your 3 o'clock, it would have a relative bearing of 90°, irrespective of your current magnetic heading.

Tracking

Tracking is technically the same as Homing, however wind correction is applied. Simplified, you account for wind direction and speed and correct your magnetic heading by the wind correction factor, giving you a new corrected heading, which allows you to track to the navaid you are trying to reach.

(Image Source: www.avstop.com)

Hold, Hold pattern and Hold entry

A hold or hold pattern is a racetrack defined by inbound course to a fix, a turn direction and turn time, usually given in minutes. A standard hold will usually be right turns with a timing of 4min for the racetrack, which is 1min for each 180° turn and 1min for each straight legs. Depending on from where you are trying to enter a hold, there will be different hold entry techniques.

(Image Source: www.americanflyers.net)


What is the bulge under the engine of the Mirage III and some of its variants?

For the Mirage III, it's a fuel tank (that also allows a camera attachment). See cutaway below (item 157).

Also from Wikipedia:

  The Mirage IIIRS could also carry a centerline pod for conducting photo reconnaissance missions, as well as an integral fuel tank underneath the aft belly; this tank could carry a smaller fuel load, but also allowed for a rear-facing film camera to also be added. When fitted with the reconnaissance pod, supersonic performance was severely diminished.

Source: aviadejavu.ru (composite of two pages: 16-1.jpg and 16-2.jpg; use links for full-res)


How can I modify a fuselage to increase the payload?

You really only have two options; stretch or swell.
The Q400 already has a "combi" configuration option with 50 seats forward and a cargo hold taking up the aft third of the cabin, so if you want to just add another couple of plugs, one (smaller plug) forward of the wings and one aft, to get 74 seats plus a large cargo area, you can do that and just adjust the structural requirements to deal with the even longer flying pencil that results.  You can have a cargo hold aft and pax cabin forward with the appropriate weight and balance requirements and limitations for loading pax vs cargo same as any other split combi layout.
In the case of the Q400 itself, its configuration is already at the extreme limit of what you can do with fuselage stretches on that sort of 4-across tube diameter, having started with 36 seats in the original.  The plane suffers from tail clearance problems because of this, due to limits on how much the gear legs could be extended to account for the long tail (landing with less than full flaps - there are a couple of intermediate landing flap settings - has a high risk of tail strikes and pitch attitude must be very carefully managed in the landing flare).
I think you'd get a better aircraft by going with "swell" and increasing the tube diameter enough to get a 5 across cabin (around 2 feet), with 2 on the left side and 3 on the right. A 74 pax 5-across cabin would only need 15 rows, leaving the rest free for cargo, and this extra width plus shortened passenger area might even allow you to shorten the fuselage a bit, leaving some stretch-ability potential in your initial design (you might even get bonus points for taking this into account).


Where is Ronda's airstrip, or why does Ronda have an airport code (RRA) if it has none?

Apparently, there is an airstrip a roughly 4 km east of the town, as confirmed by an IGN map, IGN aerial photography, and Openstreetmap (Thanks Muzer).  It does not give the impression of active use; a Panoramio photo shows a field of sunflowers.  Its full name on the topographic may is Pista de aterrizaje de CMA, which means Runway of the CMA, where CMA may be Consejería de Medio Ambiente, ar the Andalucian government's Ministry of the Environment (thanks Henning Mankolm).


Is there a standard international Minimum Obstacle Clearance Altitude (MOCA)?

The MOC value you are referring to is related to the en-route phase of an IFR flight, so your statement that it is the lowest altitude a plane can descend to when approaching the runway is wrong. That value depends on the type of approach, aircraft equipment and various other factors. It is not a fixed value shared among different airports. You probably have MOC confused with Minimum Descend Altitude (non-precision approaches) or Decision Altitude (precision approaches).

However, to answer your actual question, 300 metres is an ICAO standard for MOCA (Minimum Obstacle Clearance Altitude) in the primary area for the en-route phase of an IFR flight. So other countries use the same value, unless they have special local rules specifying a different value.

Note than, in mountainous areas, the minimum obstacle clearance applied, depending on terrain elevation, is 450 metres for terrain between 3000 ft and 5000 ft, and 600 metres for terrain higher than 5000 ft.

Minimum Obstacle Clearance Altitude (MOCA) on Skybrary


Do some radial engine planes have a two-speed starter motor?

There seems to be only one starter speed:

  Proper sequence for starting radial engines...DC-6B style, with P&W
  R-2800's.

  Engage start and start safety switches.
  Rotate thru 9 blades.
  While continuing to rotate the engine with the starter, engage primer and
  ignition boost switches, and at the same time, select magnetos to
  'both'.
  When engine fires, continue starting with the fuel primer
  engaged, releasing the start and start safety switches.
  Slowly move
  mixture control to the autolean position, then release fuel prime
  switch.
  Engine continues to run (hopefully).
  Taxi in autolean, until
  engine run-up desired.
  Complete run-up and propellor checks in
  autorich.
  Return mixture to autolean.
  Prior to takeoff, ensure engine
  mixture controls are in autorich (very important).

  Have a pleasant day, thereafter (hopefully). ;-)

  DC-3 about the same, except...

  use autorich for all ground ops.
  Engine
  type, P&W R-1830-92.
  Curtis Wright engines...can't remember.

  Stratocruiser, same as the DC-6B. DC-7 and Lockheed 1649, same also,
  as the DC-6B.

  NB. Operating in autolean helps to prevent plug fouling while on the
  ground.

[Posted by 411A on May 18th, 2008 at pprune.org]


Are there any civilian planes with seating arranged in a round area?

The simple answer is no.

Why a round seating design is not feasible? We need to look at a few aspects.

Real Estate
An airplane fuselage is rectangular (roughly speaking) in shape (when viewed from top). Airplane seats are rectangles. If you place rectangular boxes in a circle, you can fit lesser number of boxes than if you place them in a rectangle of the same area.

Airlines have just one goal to achieve, i.e. make money. Yes they take people from point A to point B too but if demand arises for joyrides, airlines will not be hesitant to start that.

By fitting more people in lesser space (not in inhumane positions mind you, governments don't allow it), they make sure that their profits soar.
Loading/Unloading Passengers
In a circular configuration, people will be a lot more confused to find their seats. People are already so confused and disillusioned when boarding a regular airplane that flight attendants have to guide every single person about where the seat is. Don't believe me? Notice how the flight attendant will snatch the boarding pass from your hand if you try not to show it.
Servicing Meals
Trolley carts used in airplanes are designed for straight aisles. In case of circular aisles, it would be very hard to maneuver them because flying airplanes do get bumps every now and then.
Evacuation
In case passengers need to be evacuated, a circular design would not be very practical. Since all people will not facing forward, simple emergency instructions, e.g. move to the front/back/left/right of the airplane can be confusing and will waste time. Locating an emergency exit will be harder too than in a normal airplane.
History
People are used to the conventional design. The present design is in use for over half a century. In addition to airplanes, trains, buses, cars and buggies have the same configuration.

I am not sure how that (and some other) news channel found about Airbus's new design. Airbus does disclose the future innovations it is working on, and flying doughnut is not mentioned there. It could be that is it on paper only at the moment. The patent information mentioned in your referenced article cannot be found with United States Patent and Trademark Office, or at Google Patent Search.


Why are primary and supportive instruments in instrument flying different depending on the phase of flight?

Because during certain maneuvers, certain instruments provide more relevant information to a pilot than do others.

In straight and level flight, the heading indicator provides more relevant bank information as it tells you whether your current bank attitude is maintaining the desired heading.  The altimeter is providing the most relevant pitch information as it’s telling you whether your current pitch will maintain the correct altitude.  The airspeed indicator is the best indication for your required power as it’s telling you if the current power settings will maintain the desired airspeed.  Other instruments provide supporting information.  Here in straight and level flight the attitude indicator provides good supporting bank and pitch indications, the VSI provides supporting pitch information, etc.  Supporting instruments change to primary instruments in certain maneuvers and vice versa.

And, incidentally, in a established constant airspeed climb, your primary for bank is the heading indicator and your primary for pitch is the airspeed indicator.  Primary for power is either the tachometer, manifold pressure, torque, or fan speed gauges, depending on the aircraft you are flying.  Typically you would set to maximum continuous power in a light airplane for this situation.


Why are some legs of a SID considered transitions, even when there's only one?

After some digging and exploratory route planning in ForeFlight, it seems I've arrived at an answer that satisfies me: the last waypoint is listed as a transition only if the departure officially ends prior to it, and flying to the transition is optional. If there are other (more correct or plausible) answers, I'd still love to hear them.

The text description of each plate describes where the SID ends. In the case of BAYPO8, the last instruction is on-track to BAYPO. In the case of ENDED8, the text describes on-track to LACEN. So, it would seem that flying to LACEN is required when assigned the ENDED8 departure, however flying to CAMJO is optional for the BAYPO8, because you can drop off the procedure after BAYPO.

This is supported by the route planning features of ForeFlight. When I selected BAYPO8, and then "No Transition," my route of flight for the departure ended at BAYPO. I also had the option to choose the CAMJO transition. This is also supported by analysis of other similar departures that include only one final waypoint option.


What is the process to contest a local FAA (FSDO) policy which appears to contradict their guidance?

If you want to force a policy change, write directly to FAA Chief Councel.  If CC writes an opinion that aligns to your position then the FSDO really can't have their own opinion.  If, however, CC disagrees with you then you're sunk unless you want to take it to court.


How long can I use an FAA license in Colombia without having to validate it?

You could fly US-registered aircraft in Colombia with your FAA license, but if you want to fly Colombian aircraft then you need to either validate your FAA license or get a Colombian one.

You validate your FAA license (or any ICAO license) by getting a Colombian "provisional" license. It remains valid as long as your FAA certificate and medical are valid. See section 2.1.7 of the Colombian regulations:

  2.1.7. CONVALIDACIÓN

  Cuando la UAEAC convalide una licencia extranjera otorgada por un
  Estado contratante de la OACI, en vez de otorgar su propia licencia,
  hará constar la convalidación mediante autorización apropiada que
  constará en una licencia provisional la cual deberá acompañar a la
  licencia extranjera y reconocerá ésta como equivalente a las otorgadas
  por dicha autoridad aeronáutica colombiana. La validez de la
  autorización no podrá exceder el plazo de validez  de la licencia
  extranjera.

Note that the process of validation depends on your personal situation, especially whether or not you plan to become a Colombian resident (see 2.1.7.1).


Difference between general visual inspection and pre-flight check inspection

A GVI is a maintenance procedure that has to be performed by a mechanic qualified to do so, to satisfy a Maintenance Program requirement, and which will require a maintenance release to be signed off.

A pre-flight inspection is an inspection performed by a pilot in command (or someone delegated by the PIC - like a First Officer, or a mechanic) to satisfy the PIC that the aircraft is safe for flight.

The pre-flight, being a look-over to make sure nothing has fallen off, is dribbling fluid, or is flat, is going to be more superficial than a GVI and usually doesn't involve getting your hands dirty (at airlines it's usually done by the First Officer while in uniform) and normally doesn't involve opening access panels or doors (but could).  Also the pre-flight is a whole-aircraft once-over while a GVI is usually system or zone specific in keeping with its Maintenance Program objectives.


What is the best altitude to penetrate a thunderstorm?

The obvious answer you mentioned should be reiterated: Avoid thunderstorms whenever possible! Just because there are "best penetrating altitudes" doesn't change the fact that thunderstorms are extremely hazardous to aircraft and should be avoided in the first place.

With that said, the FAA's Advisory Circular 00-24C mentions that, if unable to avoid penetrating a thunderstorm:

  To avoid the most critical icing, establish a penetration altitude below the freezing level or above the level of -15ºC.

This is to help minimize rapid accumulation of clear ice:

  Supercooled water freezes on impact with an aircraft. Clear icing can occur at any
  altitude above the freezing level but at high levels, icing from smaller droplets may be rime or
  mixed rime and clear. The abundance of large, supercooled water droplets makes clear icing very
  rapid between 0ºC and -15ºC, and encounters can be frequent in a cluster of cells. Thunderstorm
  icing can be extremely hazardous.

Another point to mention is that, regardless of there being a recommended "penetration altitude," it is important to maintain a constant attitude, not altitude:

  It is almost impossible to hold a constant altitude in a thunderstorm, and maneuvering
  in an attempt to do so greatly increases stress on the aircraft. Stresses are least if the aircraft is
  held in a constant attitude.

But again, emphasizing the dangers of thunderstorms, the circular states:

  Never regard any thunderstorm lightly, even when radar
  observers report the echoes are of light intensity. Avoiding thunderstorms is the best policy.

and

  Weather recognizable as a thunderstorm should be considered hazardous,
  as penetration of any thunderstorm can lead to an aircraft accident and fatalities to those on
  board.


Could you help me identify this plane (miniature model)?

Both the Sopwith Camel and the Nieuport 11 mentioned elsewhere had rotary engines with a rounded cowling, but the model in the photograph appears to have a square cowling. This suggests it might be a Royal Aircraft Factory S.E.5 or S.E.5a which had a V8 engine.

Wikimedia Commons


How to control torque effects on the ground?

The Lockheed U2 had the same problem (bicycle wheel base and they had to prevent one end being dragged on takeoff).

They solved it by adding "pogo wheels" that self detach on take off. (the ones on the orange sticks.)

(source wikipedia)


Firstly, there are:
For example this company currently makes a biplane
But the main reason is that they're inefficient, and don't really do much that a monoplane can't.
They produce a lot of drag compared to the amount of lift they produce, meaning they use a lot of fuel to travel the same distance. They have fairly poor visibility, which is usually considered a bad thing!
They do have a few advantages - they have a good roll rate, making them quite maneuverable, and they have a very low stall speed and can fly on little power, meaning they can fly slowly very well (where their increased drag doesn't make much difference: drag increases with the square of airspeed)
Overall, though, the above makes them suited only to aerobatics, which can also be performed by monoplanes. Advances in wing design and composite materials take away most of the advantages of a biplane for any other use: ie actually travelling (the main purpose of an aeroplane) and carrying a load.
Overall, then, they're more complex than a monoplane, less efficient, and aren't much more manoeuverable. They have more disadvantages than advantages.
Biplanes were popular in WWI not because of any inherent advantage, but simply because technology hadn't advanced far enough to allow any other options. Once the monoplane was properly developed, it allowed much higher speeds (450mph for a late WWII fighter, 300mph for an Early WWII fighter, compared to around 120 mph for a late WWI fighter). High speed fighters beat low speed fighters (at least before stealth technology and guided missiles)
There were a few leftover biplanes in WWII - The Fairey Swordfish torpedo bomber was one of the most widely used, as the low speed and good lift from the biplane design allowed it to carry a heavy torpedo, while the drag issues didn't matter at the slow speeds they needed to fly to be able to release the torpedo properly and on target. Others were the Gloster Gladiator (UK), Fiat CR.42 (Italy) and Polikarpov I-15 (Soviet Union) which achieved varying levels of success in the early stages, but were well and truly outclassed when facing even early-war monoplanes.
This answer on a similar question gives some useful context about the direct advantages and disadvantages. It doesn't directly explain why biplanes fell out of favour, but it may help understand my own answer here.


How do I determine which radial intercept angle to use?

There is no definite answer to this question.

If you are far away from the beacon radials are far away from each other and thus small intercept angle would be insufficient to reach desired track in feasible time. Also, if you are, say, five miles away from the beacon intercept angle of thirty degrees would be acceptable for C172 but an overkill for transport category jet traveling at 450kts of ground speed. Then again, the mentioned jet would assume the same 30 degree intercept angle to join final track for an approach.

The question has also to do with current aircraft track in relation to the desired track. If you are for example tracking radial 150 inbound towards a beacon and you want to change to radial 180 an intercept angle of 30 degrees would keep you on radial 150 and you will not intercept the desired track until you are overhead the beacon.

The only rule seems to be that when vectoring for approach ATC gives a maximum intercept angle of 30 degrees.


Has there ever been a US airport with identifier PM2?

No. PM2 would not be a valid ID in the FAA system. According to the FAA order defining the system:

  1−2−7. ASSIGNMENT SYSTEM §c. Most one−number, two−letter identifiers have been assigned to aviation weather reporting and observation stations and special−use locations. Some of these identifiers may be assigned to public−use landing facilities within the United States and its jurisdictions, which do not meet the requirements for identifiers in the three−letter series. In this identifier series, the number is always in the first position of the three−character combination.
  (emphasis mine)

So two letters followed by a number is not a valid ID.


How is the total drag variation with velocity related to altitude?

At higher altitude, density is lower. For the same true airspeed and the same drag coefficient, higher altitude will have less total drag.

However, there are factors affecting drag coefficient itself:

Due to the lower density, the lift coefficient must increase for the same TAS. This results in increased induced drag.
Decreasing density also decreases the Reynolds number, which increases the skin friction drag, especially for speeds as low as the ones shown in your graph.

Therefore, it can be expected that the trend will invert below a critical speed.

The answer is h2 > h1 from the above rationale.


Why flaps can deflect up to 25°+ without stalling the wings?

The X-axis this is the angle of attack of the wing and not the angle of deflection of the flap. When the angle of deflection of the flap is 25%, the angle of attack of the wing will be much less.


Can jet fighters be made to be 2 or 3 times bigger than they are today?

The question is not whether you can do it but why would you want to.

Fighters, like any other aircraft are designed around mission profiles;  what do you want this aircraft to do, at what speeds, ranges, altitudes, combat radii, endurance, weapon carriage and employment, stealth, etc.  Therefore you would need some sort of justification for building a fighter aircraft this size.  That justification has to be so appealing that it can overcome the negative aspects of building a big fighter.

While these profiles vary considerably between individual aircraft, they are constantly curtailed by the brutal and impartial realities of war.  Gen Stevens pointed out 4 fundamental requirements of a fighter in one of his critiques of the F-35.  These are important to remember as they have been integral in every successful fighter design over the past century of air combat.  Unfortunately, the larger the fighter, the more diametrically opposed to these realities they are and the greater the probability of failure in combat.

ATTACK YOUR ENEMY IN OVERWHELMING NUMBERS

This one is fairly simple to understand.  The greater your force is, the more difficult it is for the enemy to destroy you.  But defense ministries have limited budgets and can only spend so much on new fighters.  So the choice becomes should I buy a few advanced and highly capable fighters or lots of cheap, single purpose aircraft.  Air warfare has favored the latter.  Not only are smaller aircraft cheaper to procure, they are cheaper to operate as they burn less fuel and require less maintenance.  Consequently.  Your nation's pilot pool can get a lot of flight time in them and can become highly proficient in their operation.
SPOT YOUR ENEMY BEFORE HE SPOTS YOU

Which is going to be easier to spot from a distance: a 747 or an F-5?  Which is more likely to have a lower radar or IR signature if both employ LO features?
OUTMANEUVER AND OVERWHELM HIM

By the energy maneuvering equation, fighter design had always favored the following features:

High thrust to weight ratio
Low wing loading
Low specific fuel ratio

And this tends to favor a fighter which is basically a small, fast, nimble gas can with a compact but powerful engine and an effective armament for engaging and killing other fighters.  Not easily achievable with a larger aircraft.
KILL HIM QUICK AND MOVE ON

So now, a large, expensive, easy to spot aircraft manned by low time flight crews is now forced to engage a swarm of nimble, fast turning fighters.  They can quickly turn inside him and get to an optimal firing solution faster and more reliably.  They are also more difficult to engage and shoot using BVR weapons.  Finally OpFor has more experienced and current pilots than the larger fighter.  This now gives the larger, more expensive aircraft a very limited probability of survival.

For those reasons, history does not favor a large fighter unless it is equipped with some kind of mission system giving it a tactical advantage - and even then that is a large obstacle to overcome in terms of cost, strength, and weight.


Is it really cost effective to put a motion system underneath a Full Flight Simulator?

While a simulator with motion simulation is more expensive to own/operate than a simulator without motion simulation it is still cheap compared to a real airliner

So if the regs say a particular type of training can be done on either a real airliner or a full motion simulator then it is likely to be cost-effective to use the full-motion simulator.

And as a bonus you can run scenarios with a high level of realism that would be too dangerous to run on a real airliner. Emergency training in real aircraft has to strike a balance between training pilots to deal with adverse conditions and avoiding accidents during training.

  Why do we have to have motion systems on simulators? We get motion information from our central and peripheral vision, right?

A pilot gets motion information from 3 different sources.

His body
His vision
His instruments.

Unfortunately item 2 on that list is sometimes unavailable and item 1 has terrible medium to long term accuracy.

In normal life our brain uses a combination of our bodies motion sensitivity and our perhiperal vision to build up a picture of where we are. In the absense of visual information it will continue to try buliding up a picture of where we are but the accuracy of that picture will quickly degrade.

It's one thing for a pilot to be able to make correct decisions when his only source of motion information is his instruments. It's quite another to make correct decisions when his body and his instruments are apparently in conflict and he has no visual references.


According to Wikipedia:

  "The origin of the name Dutch roll is uncertain. However, it is likely that this term, describing a lateral asymmetric motion of an airplane, was borrowed from a reference to similar-appearing motion in ice skating. In 1916, aeronautical engineer Jerome C. Hunsaker published the following quote: "Dutch roll – the third element in the [lateral] motion [of an airplane] is a yawing to the right and left, combined with rolling. The motion is oscillatory of period for 7 to 12 seconds, which may or may not be damped. The analogy to 'Dutch Roll' or 'Outer Edge' in ice skating is obvious." In 1916, Dutch Roll was the term used for skating repetitively to right and left (by analogy to the motion described for the aircraft) on the outer edge of one's skates. By 1916, the term had been imported from skating to aeronautical engineering, perhaps by Hunsaker himself. 1916 was only five years after G. H. Bryan did the first mathematics of lateral motion of aircraft in 1911."

Sadly, this question is probably not answerable beyond what wikipedia has on this site (unless there is an English Major looking for a Ph.D. thesis. ;)