How are pushbacks coordinated between the pilot and the tug?

Generally speaking1, when an aircraft is allowed/ready to leave (deliberately not using the word depart) the gate, things proceed in the following fashion:

The pilots are in contact with Ground Control, and when the aircraft is ready to leave, Ground approves that they can leave the gate.
The pilots asks groundcrew that the pushback can start.
Pilots are in contact with a designated personal from groundcrew (see picture below).
Pushback tractor/tug will start moving the aircraft away from gates, onto the place where aircraft will be ready to move on its own.
During the pushback, aircraft's engines are started2.
Pilots inform tug driver/designated person from groundcrew which direction the aircraft needs to be facing at the conclusion of pushback.
When aircraft is ready to roll towards its assigned taxi instructions, marshaller signals the pilots that aircraft is in the requested position and pushback tug is about to be detached.
After the tug is disconnected, the designated groundcrew personal communicating with pilots, informs the pilots and disconnects his headset. The marshaller signals (after moving away from the aircraft) the pilots that the aircraft is ready to proceed on its taxi route.
Pilots confirm and acknowledge this last signal, and aircraft starts to taxi.

I have read that different airports have different procedures for the above mentioned activities. Although, I have always seen that a person from groundcrew attaches a headset near the nose gear of the aircraft (picture below) to communicate with the pilot.

Image Source
Please see the cable connecting the headset with the aircraft, near the nose gear. You cannot follow the entire cable though.

1: This is what a typical scenario looks like. Although, there can be great variations.
2: Engines are not started near the gate as there is groundcrew servicing the airplane and to avoid damages to close-by structures.


It's an ICAO requirement, basically it's just official documentation showing that you've been trained and are  competent to act as SIC in a given airplane.

ICAO is an organization that standardizes regulations and procedures among the participating countries (close to 200 if I recall).  If you fly as SIC internationally you'll probably need an SIC type rating.

The rating is almost the same as a PIC type rating, except the rejected takeoff and taxi requirements (and maybe some others) don't have to be met.  It's basically a formality for any airline first officer as they will have met all the requirements just by going through the airline's training.


Can I get an FAA restricted ATP certificate with 1000 hours total time?

Unless you were trained through a military flight school, the answer is no.  Part 61 states that you need a minimum 1500 hors TT to apply for an ATPL unless you either attended a military flight training program or an aviation degree from an accredited institution.


If the cables break on an elevator (and the safety brakes fail), you won't be in true freefall. You'll still have friction from wind resistance, from the guide rollers on the rails, etc. The same is true in an airplane. Even if you're falling straight down, you'll still have wind resistance.

In addition, lift doesn't just drop straight to zero when the wing stalls (no matter what it might feel like to the pilot). Here's the lift-to-angle diagram for a typical wing:

(wikimedia.org)

This wing stalls at about 16° AoA. But notice that the coefficient of lift doesn't simply drop to zero, it just starts descending at that point. So even in a stall, the wings are still generating some lift, just not enough to overcome the weight of the plane.


How does a flying wing keep from going into a flat spin when maneuvering?

Sweepback helps a lot, and the rest is achieved with drag devices near the wingtips.

(Source: aerospaceweb.org)
Did you notice that the B-2 has split ailerons, and they are partially opened during flight? Their drag pulls the wingtip back, and in combination with sweep the forward wing in yaw will have a longer lever arm, so the same drag produces a bigger stabilizing yawing moment.
Differential thrust is not available on gliders, and there are lots of flying wing gliders. Horten III and IV, Fauvel AV-36 and the SB-13 are some examples. The Hortens used speed brakes near the wingtips, and the SB-13 has rudders with differential deflection (70° outwards, 20° inwards) on its winglets to increase the yawing moment.
Directional control is no problem with flying wings, even though directional stability becomes weak at high speed when induced drag is low. Flutter and a low $c_{L max}$ are the real drawbacks. Ground handling, landing characteristics and payload space are others, but can be overcome somewhat.
And flat spins are not possible with flying wings. Their spin modes are all fairly steep due to the lack of a strong inertial moment from the lengthwise distribution of masses.


What is Flexible Gunnery in the US Air Force?

flexible gunnery - the firing of swivel guns (as in an airplane)
fixed gunnery - the firing of a gun having no traverse so that the entire gun platform or aircraft must be maneuvered for aiming

(flickr.com) Swivel guns on a B-17 (underside and waist).

From Wikipedia: "Flexible Gunnery" training developed diverse skills for various aircraft and differing positions within bombers, e.g., waist gunner, rear gunner, etc.

From a 13-minute declassified US Army Air Forces training film, Flexible Aerial Gunnery: Making a Gunner, from 1943 about that gunnery course, the course included but was not limited to:

learning the machine gun types inside out
learning bullets trajectory and aiming
train on moving objects using a BB gun
train in the air by shooting at a trailing dummy attached to another aircraft
learn the different shapes (silhouettes) of enemy aircraft and learn to judge their distance through the sight to judge whether to fire
learn the different positions, including the ball turret and how it functions
train in a ball turret simulator
train at night by utilizing tracer ammo
the course took a few weeks to complete.


Flaps retract in order to reduce wing area. This has several advantages when flying fast:

The higher wing loading (weight per lift-producing area) reduces gust loads. When hit by a vertical gust, the angle of attack increases suddenly, and so does lift. If this happens at high speed (more precisely: At high dynamic pressure), the lift increase might overstress the wing. A reduced area will only produce so much extra lift before the wing stalls, which limits the extra lift from gusts.
Less exposed area also means less friction drag. Your flexible flap proposal would still leave both sides of the flap exposed, adding more surface for friction drag. Put another way, the higher wing loading shifts the lift coefficient up which generally improves L/D at high speed.
Retraction closes the gaps between wing and flap sections. While those gaps are important to maximize the lift coefficient for the lowest possible landing speed, they increase drag at all lift coefficients.

The retraction mechanism is heavy and increases maintenance cost, but it is worth it.


Why are Krueger flaps called flaps and not slats?

A flap increases airfoil camber, and can be on the leading edge or trailing edge.  The Krueger Flap is a Leading Edge Flap, the actual generic term.

The Krueger dude developed the LE flap used on some airliners so his name is attached.

A slot increases stalling AOA, without necessarily increasing camber, as in the fixed slots used on a lot of light aircraft in the 40s to improve aileron control at the stall instead of wing washout, like Stinsons and Globe Swifts, etc.

Combine the slot function of injecting slightly higher velocity air along the top to keep flow attached at higher AOA, and the flap function of increasing wing chord, together on the leading edge, and you get SLAT.

Or you could say more correctly, Slotted Leading Edge Flap.

Without the slot part though, it's just a flap, as in Krueger Flap.


Why does Vmca decrease with increasing altitude?

For airplanes with normally aspirated engines or turbocharged engine above their critical altitude, the engines produce less power as altitude increases as atmospheric air density decreases as altitude increases.  As power decreases, the operative engine requires less rudder authority to maintain directional stability due to the reduction in thrust, which allows the airplane to maintain directional authority at lower indicated airspeeds.  Therefore Vmca decreases as altitude increases.


What is the power source of the clock in glass cockpits?

There are two ways this generally works:

A low-current hot buss that is always connected to the system battery
A small rechargeable battery that powers low-power time and memory circuits

The first is common in aircraft with hard-wired systems, while the second is the case for nearly every handheld-style GPS.

While GPS does not necessarily need to be powered all the time, it dramatically speeds up the satellite position lock if it is

close to the correct time and
can produce the GPS 'almanac' (coarse orbit) from memory
can produce valid ephemeris (detailed orbit) data from memory
has a valid last known position

The time, position, and almanac information give the GPS hints on which satellites to search for first. Once the first satellite is locked on to it can acquire a time signal and the time is quite accurately synchronized to the GPS system. The almanac is successively used to search for more satellites that should be in view, but will fail over to look for others if these are not found. Once a satellite is found, if the ephemeris data has expired, it will listen for the ephemeris information which takes around 30 seconds to receive. This is the main difference in the 'hot' 'warm' and 'cold' start time for a GPS receiver.

If no power is maintained in the GPS, at the very least the time will be lost, and more typically all of the almanac information is wiped out as well, resulting in a position acquisition time of a minute or more.


How do I figure out the right pronunciation for transitions?

It would be nice if there were an authoritative, canonical, source for these sorts of waypoints, but sadly, I don't think one exists. I say that because I hear controllers sometimes using a different set of vowels or syllable emphasis "today" than they did "yesterday". If there were a single "right" way to verbalize CNERY or SCTRR, I'd expect ATC to have them all down. But in plenty of cases beyond those two, it remains unclear.

For example, the JFRYE arrival into Dallas -- is it the "Jeffrey" or the "J-Fry" arrival? You hear both from Ft Worth Center all the time.

My conclusion: no cannonical source exists.


What's the speed callout by the PNF on airliners for?

This call serves two main purposes. The first is to verify that both airspeed indicators are showing the same speed. Since airspeed = life, it's best to find out that one of them is faulty on the ground rather than in the air.

The second purpose is to distinguish a high-speed rejected takeoff from a low-speed one. Below 80kts (or 100kts or another speed set by the manufacturer and/or airline), a takeoff would be rejected for almost anything out of the ordinary.

But rejecting a takeoff at high speed carries a lot of risk - like brake fires, tyres exploding, directional control difficulty, etc. So above 80 or so knots, a takeoff will only be rejected in the case of major failures. Some modern aircraft even inhibit minor warnings from appearing after 80kts until the aircraft is airborne, because rejecting the takeoff is not worth the risk, so don't saturate the pilots with unnecessary information.

This page goes into some detail about what you would reject a takeoff for at low speed vs high speed. The criteria may vary slightly amongst airlines but the general themes are the same.


Aerospike nose cones for supersonic jets?

There are no historical aircraft with an aerospike nose, at least, none that I remember, and none that I could find after 30 mins of research. I'm not sure if there are any planned projects using it, but I doubt there are, given the purpose of aerospike noses - aerospike noses really only have one main purpose - to streamline a blunt body. This is commonly used in missiles and such (especially in SLBMs), where height/length is a constraint - a slender, sharp nose is very long, so to save height, those missiles are fitted with an aerospike that telescopes out. The flat plate at the end of the aerospace forms a detached bow shock, which makes the airflow "see" the blunt body as having a different, more streamlined shape, reducing drag. Here's a visual of that happening:

Image source - https://iopscience.iop.org/article/10.1088/1742-6596/1276/1/012031/pdf

However, the bow shock generated by a drag reducing aerospike causes more drag and a heating than the oblique shock generated by a slender nose of the same length. For SLBMs, a long, sharp nose is obviously out of question (well, you could have a telescoping sharp nose, but that would be heavy), but for aircraft, length really isn't a concern, you can make the nose as long as needed. Therefore, it doesn't really makes sense for an aircraft to have an aerospike nose.


Does a system exist that can bulk process satellite data to find a plane lost over ocean?

Update: Satellites were eventually used in the search for MA370, see this article.

This question might be better answered by the folks at space exploration but here's a shot:

Oil slicks are not uncommon at sea, so finding one from the aircraft is not too easy.
It's an incredibly large area pulling a lot of processing power. You're going to need pretty good resolution imagery over several square kilometers and then run image recognition on it. Look at this image which has a scale of 25 miles which is still a fraction of what you would need to get an idea:

The fragments you're looking for are very small in regards to waves. I suspect depending on where you are there's a large amount of noise from other rubbish which is hard to filter out, such as a white plastic sheet to a door. You might even go confusing big aircraft parts to other white boats. Yes, you can continue the search but it takes time to go through all of these and dismiss them.
A lot of volunteers searched for Steve Fossett when he went missing, and there was some attempts to locate him by satellite imagery from google maps, which was not successful.
Aircraft, while not fast, can be over the side within a few hours, while I think you have to wait until the satellites have caught all the imagery you would like.

While I think it could be done as you say, you would need to develop software and I don't think the market for it exists, but that's just my guess. Reading up it appears that satellites are used against drug cartels along the USA-Mexico border and against illegal immigrants elsewhere in the world.


Do different grades of leaded avgas differ in ways other than their lead content?

Gasoline (both avgas and mogas) grades are distinguished solely by octane rating and lead content.

In theory, the octane rating is the amount of actual octane (C8H18) it contains, with the remainder being mostly heptane (C7H16), hexane (C6H14), pentane (C5H12), etc. As you note, a higher octane rating is needed for engines with higher compression ratios.

A century ago, the only way to get high-octane gas was via distillation, and since actual octane is a tiny fraction of crude oil, this was very expensive. It was soon discovered, however, that adding TEL made gasoline behave like it had more octane than it actually did; the higher octane rating you needed, the more lead you added. Leaded gasoline was born, including the 80/87, 100/130 and 115/145 grades of avgas.

However, just a few decades later we discovered how to "crack" long-chain hydrocarbons into shorter ones. Cracking diesel produced (mostly) gasoline--and with a much higher fraction of octane than gasoline distilled directly from crude oil. This allowed creating a 100-octane grade of avgas without any lead, but some old engines actually need a little lead for other reasons, so 100LL was born.

In short, you can take any grade of unleaded gasoline and boost it to any higher grade just by adding enough lead. Start with a higher grade of unleaded, though, and you won't have to add as much.


What is the purpose of this span wise "false spar" on Affordaplane wings?

If you push up on the rib from below, it will eventually start to deform sideways, along its least stiff axis, and collapse.  The pieces in between them are just braces that prevent sideways deformation, and making the rib stronger.


What is meant by these criteria for a stabilized approach?

Although I can’t find regulations regarding stabilized approaches in the FAR/AIM, the unofficial but generally accepted definition of a stabilized approach would be

“Only small changes in heading/pitch.
How small?”
Small changes in heading and pitch would mean changes only necessary to maintain a ground track on the lateral guidance and a consistent airspeed on the glideslope. These are to compensate for drift due to things such as wind.

“The aircraft is in correct landing configuration.
What are those configurations?“
Configuration is entirely dependent on the aircraft and situation.
Typically it would include things like:
Autopilot correctly set or off;
Boost pump on;
Carb heat to hot;
Gas on the fullest tank, both, or on;
Landing gear down and locked with indicator lights lit;
Cowl flaps closed;
Flaps at the correct setting;
Mixture set at best power for density altitude;
Prop speed set at fastest setting;
Landing, position, and anti-collision lights (if not in clouds or fog) on;
All auxiliary and/or unnecessary equipment off;
Sterile cockpit;
Seats and seatback set and locked in the upright position;
Seatbelts and shoulder harnesses on and latched;
Throttle/power set at a consistent setting to provide a descent rate on the glideslope;
Landing checklists complete.

“The aircraft speed is not more than Vref+20 or less Vref.
Is this IAS or CAS or TAS?“
Vref is usually in IAS. Especially since the occasion in which you are using it would be below 3000 feet AGL, and less than 200 knots.


Do airline SOP normally recommend an in-flight engine restart in the case of an unexplained shutdown?

Your question mentions the 737 or similar. If you want answers limited to 2-engine jets, let me know and I'll remove this answer as it is for the 747-100 or -200.

Whether to restart or not depends on the nature of the failure. If there appears to be no problem to do otherwise, a restart would be in order. The checklist for an inflight start from the last airline I flew for (now out of business) is below. The code to the right of each action is who performs it: C - captain, FE - flight engineer, All - all 3 crew members.

Thurst Lever ............................... CLOSE        C

Start Lever ................................ CUTOFF       C

Fuel Pressure .............................. AVAILABLE    FE

Bleed Air Valve ............................ OPEN         FE

Engine Ignition (Sys 1 and Sys 2)

     Above 250 KTS ......................... FLT START    FE

     250 KTS and Below ..................... GND START    FE

Start Lever ................................ RICH/IDLE    C

Engine Instruments ......................... STABILIZED   ALL

Start Lever ................................ IDLE         C

Engine Ignition ............................ AS REQUIRED  FE

Electrical Power ........................... RESTORE      FE

The most likely cause for a Pratt & Whitney JT-9 engine to quit is poor technique on the part of the pilot. If you're at altitude and starting the initial descent, you should put the nose down before bringing the thrust levers back. Also, don't slam them back, take a few seconds to do it, especially if you're above FL370.

It's worth noting that on the 747, the loss of an engine (no restart) enroute is not considered a serious emergency. At the two 747 carriers I flew for, it was the captain's discretion as to whether to divert or to continue on.

Also, it's not always the case of either the engine works at the power of the other engines or it doesn't. There are situations where the engine might be available, but with partial power. As I remember there were at least two such cases, one of which was high oil temperature. Basically the work-around was to run the engine at that power setting that would keep the oil temp below the maximum.


What are the holes on the top side of the canard of Eurofighter Typhoon for?

They aren't holes they're flush screw heads.


What are the guidelines to execute a missed approach during circling?

Flying a missed approach while circling can require some judgement, as the procedures are designed to originate at the missed approach point. Going missed while circling can mean starting the procedure some distance away from the MAP. The goal of the initial procedure should be to intercept the published missed approach course, while maintaining obstacle and traffic clearance. Put another way, a pilot may deviate from the letter of the procedure, if doing so follows the spirit of it.

In this situation, I would recommend option B. The procedure will provide obstacle clearance when started from three points: 443 MSL and about 4000 feet from the RW12 threshold (LPV minima); 638 MSL and about 11,500 feet from RW12 (LNAV/VNAV); and 600 MSL over the RW12 threshold (LNAV and circling). The procedure assumes you can climb at least 200 ft/nm, so to climb 100 feet would require less than 3035 feet across the ground. This puts you within the area where the published missed approach starts. Once you reach 700 feet, you can turn directly to the VOR and continue the procedure as published. The initial turn would normally be towards the landing runway, but in this example the runway is straight ahead.

If you descended below circling minima and needed a significant climb to get back, consider circling over the airport until either reaching 700 feet before flying towards the VOR.

The FAA has recommends the thought process above in the AIM, section 5-4-21. Emphasis mine:

  5-4-21 (c): If visual reference is lost while circling−to−land
  from an instrument approach, the missed approach
  specified for that particular procedure must be
  followed (unless an alternate missed approach
  procedure is specified by ATC). To become
  established on the prescribed missed approach
  course, the pilot should make an initial climbing turn
  toward the landing runway and continue the turn until
  established on the missed approach course. Inasmuch
  as the circling maneuver may be accomplished in
  more than one direction, different patterns will be
  required to become established on the prescribed
  missed approach course, depending on the aircraft
  position at the time visual reference is lost.
  Adherence to the procedure will help assure that an
  aircraft will remain laterally within the circling and
  missed approach obstruction clearance areas. Refer
  to paragraph h concerning vertical obstruction
  clearance when starting a missed approach at other
  than the MAP.

[...]

  5-4-21 (h): ... In the event a balked (rejected) landing occurs at a position
  other than the published missed approach
  point, the pilot should contact ATC as soon as possible
  to obtain an amended clearance. If unable to
  contact ATC for any reason, the pilot should attempt
  to re−intercept a published segment of the missed approach
  and comply with route and altitude
  instructions. If unable to contact ATC, and in the pilot’s
  judgment it is no longer appropriate to fly the
  published missed approach procedure, then consider
  either maintaining visual conditions if practicable
  and reattempt a landing, or a circle−climb over the
  airport...

The AIM includes a diagram that demonstrates a pilot turning against the missed-approach instructions when that is the safer course. The missed approach requires a climbing right turn to the VOR; the pilot in the scenario on the right chooses to make a left turn as that allows the initial climb to take place over the airport.

Source: FAA AIM


What are the basics of flying non-revenue?

There are a few classes of Non-rev travel.

Jumpseating
Online pass travel
Interline pass travel

Jumpseating
This is open to pilots and flight attendants, air-traffic controllers (not sure if this is currently true, but it used to be), certain company and government officials (e.g. the FAA and others).
In general pilots can only occupy pilot jumpseats and flight attendants can only occupy flight attendant jumpseats.  I know of cases where pilots can sit in the FA jumpseats but this is largely a topic of the Pilots and FA Union contracts.  In general pilots can jumpseat on any other 121 carrier and some 135 carriers.  Note that jumpseating does not necessarily mean you'll be in the cockpit, as current regulations stipulate you should not sit in the cockpit unless there are not seats in the cabin available.
If you list for a jumpseat you will generally be the lowest priority for a cabin seat, boarding after all other non-rev travelers and then in a specified priority order jumpseaters will fill up the cabin and then the cockpit jumpseats until space is exhausted.
Jumpseating is the most versatile of the options, but the most limited in who can use it.  It is good to keep in mind your jumpseat agreements probably allow jumpseating on cargo 121 carriers in addition to passenger 121 carriers, so keep Fedex, UPS, Atlas, etc in mind when travelling.  Your spouse/kids won't be able to join you though.
Online Pass Travel
The specifics of this travel depends on your airline, but I will speak in general terms.  Pass travel is usually available to the employee, the employeers domestic partner or spouse, the employees minor children and the employees parents.  There is usually also a program for a limited number of passes for friends (buddy passes).
Pass travel is usually limited to your airline those you have a business relationship with.  For example a regional carrier can usually pass travel on the legacy carrier they contract with.  A legacy carrier can usually pass travel on its regional contracts.  If a regional contracts with multiple legacies, you sometimes only pass travel on the legacy system of the legacy you perform flights for.  It can be complicated.
There is always a defined priority for pass travel.  In general employees ride before spouses/parents/children who ride before buddy passes (except when travelling together, you may all share the priority of the highest priority pass on the itinerary).  When multiple companies are involved, the priority levels may reflect a higher priority for the company operating the flight employees than the legacy/regional contract carriers.
Again, this will vary greatly from company to company and you will learn the specific rules that apply to you when you are hired somewhere.
Interline travel
These passes are known as ID75, ID90, etc where the number is the percent discount from a full fare ticket.  You can generally buy passes for yourself, your spouse/domestic partner and your children.  No buddy passes.
To get an ID90, you visit your travel office and request an interline ticket for a specific city pair.  For example you can buy an ID90 for Rome - NYC.  You get an old school paper ticket for that route and no specific airline.  When you want to use the ID90, you present it to the ticketing agents for the airline you want to ride that flies the route you want to fly.  They will in turn issue you a non-revue standby boarding pass.  These are generally lower priority than online pass travel when it comes time to board.  These tickets are fully refundable, so they are often purchased as backups to get home when travelling in case you cannot get back with online passes.
How it all works
If you are the employee, you have a company ID and use this to get through security.  If you are the spouse/partner/child/buddy, then you will print out a standby boarding pass and use that to get through security.  You can check bags, which will get tagged standby and should board if you do.  It can be good to remind the gate you have bags checked when you get a seat.
If you are flying on your own carrier or under your legacy brand, you generally have computer access to the passenger boarding totals.  These can often be hard numbers of people booked, checked in and standbys listed.  You can use this to gauge the likelihood of getting on a plane.  If you are travelling offline then a carrier might have a phone number available but they may only tell you "it looks good!" or "it looks bad" and will not divulge numbers.
Once you are at the gate, you play the waiting game.  You will have a boarding priority which may look something like this for a legacy carrier flight:

Legacy pilots
Legacy flight attendants
Legacy retired pilots/FA
The legacies regional contract pilots / FA
Legacy spouse/parents/domestic partner/kids
The regional contract spouse/parents/domestic partner/kids
Codeshare pass agreements
Buddy passes
Interline passes
Cabin jumpseats
Cockpit jumpseats

This will assuredly vary based on who you work for and who they contract with, and is just to illustrate the complexity of the priority structure.  Within each category listed above there is an internal priority that for many is based on date of hire, others based on time of listing.  Again, this varies.
After all the confirmed revenue passengers board, the gate will board the revenue standby passengers, and once they are on and the number of empty seats is known (misconnects, people not in the boarding area 15 minutes prior to departure, etc), they will board according to the non-rev priority.  When the cabin is completely full, no more non-revs may board except for the jumpseaters, who may then fill the available jumpseats.
Putting it together
If you wanted to non-rev from NYC to Miami tomorrow and your company flies that route, then you just wake up in the morning, list yourself, take a look at the boarding totals and head to the airport.  If you don't even want to do that and you are a pilot, you just go down to the airport, find a gate with a plane headed to Miami and list for the jumpseat on that plane.  If the many rules of priority work out, you get on and you go to Miami.
Some considerations
Pass travel often has a dress code.  Don't show up in a tshirt and shorts unless you know you are allowed, you can be denied boarding.  Make sure all of your pass riders are behaving themselves.  This is especially important to impress on anyone you give a buddy pass, as when they screw up as a pass rider, you can have your pass travel suspended as punishment.


In WW2 aircraft, where were gun cameras mounted, and did they suffer performance penalties?

It was a small 16mm film camera usually mounted, in single engine fighters, in the inboard area of the wing, within the leading edge behind a little window (the P-38's is also about the same location between the center pod and left engine) or in the nose in twins.

Look carefully at a lot of gun camera film on something like a P-51 when the sun is lighting up the prop from behind and you can see that the camera is viewing through the lower left quadrant of the propeller arc, being just a couple feet to the right of the left side wing guns.  Most fighters only had up to 30 seconds of continuous firing time in ammunition, so it didn't need to have a really large film supply.

On some systems the camera could be set to run only during firing or could be run independently and there was a little flag that appeared in the upper left corner of the film image and lifted out of the way when the guns were firing and dropped into view then they weren't.

A lot of pilots started to do away with tracer ammunition when lead computing gyro gunsights started to appear in 1944, so often the little flag is the only way you can tell the pilot is firing other than bullet strikes (and vibration from the guns sometimes) when you watch gun cam movies where no tracer is being used.

The weight penalty was negligible, only weighing a few pounds, and the drag penalty was also negligible, being buried in the leading edge behind a clear panel, like a small landing light.


Stress on wing/fuselage-joint of aerial water tanker aircraft - and possible mitigating measures

The problem isn't the relief of stress from dumping of loads.  If it was, you would have the same failures happening because of the act of landing, where the wing goes from being heavily loaded to unloaded in about the same amount of time.  And it's once per flight in any case and is something that all airplanes have to cope with.

Fatigue is all about the number of load cycles, the beefiness of the structure designed to handle it, and identifying the "weak links in the chain" stucturally.  The problem for tankers is they spend a large amount of time being subjected to very sharp  and relatively numerous gust loads during drop operations.  Working a fire, they are flying through extreme thermals and mechanical turbulence; it's a pretty rough ride.

So the airframes get "beaten up" you might say.  Effectively it's like taking a car that could handle the odd pot hole with no problem and driving it exclusively on a road full of potholes all the time.  Sooner or later something will break on the suspension, if you didn't anticipate the effects beforehand. And in the case of the C-130s that's about the long and short of it - they didn't anticipate the effects beforehand and the airplanes were already old.

So what happens is, the more extreme operating environment means the machine is living much closer to the margins of the original structural design analysis. This raises the risk that flaws in the original structural fatigue analysis will float to the surface, when they would normally stay dormant. Structural inspection programs that were working fine when the airplanes were being used in their normal role are suddenly inadequately frequent and/or comprehensive, and cracks form that were never a problem before, aren't being inspected for, and... ooops.

Unless you want to stop using them to fight fires, the answer is pretty simple.  These are the options:

Inspect more frequently, and or more invasively using NDT procedures.
Add more meat, or redundant meat (damage tolerance) to the structure.
Both (the probable result).


Ferry flights encompass much more than delivery and retirement flights.  Any time an airplane has a problem that can't be fixed on-site they can generally obtain a ferry permit to get it to an airport that the maintenance can be completed at.

At the airline I worked for, all flights, including initial delivery, were conducted by pilots on our seniority list and other airlines I'm familiar with have the same requirements in their contract language.  Our airplanes were manufactured in Brazil and a crew would be take an airline flight down to the Embraer factory, accept the airplane and fly it to a US customs station and then on to our main maintenance airport.  These flights were fairly uncommon and often went to very senior and management pilots.

Normal ferry flights for aircraft repositioning or maintenance needs were generally done by low-seniority reserve crews because those tended to be non-scheduled activity and show up with short notice.

In all cases though, at my airline, ferry flights were conducted by company pilots.  This can vary by airline and there probably isn't a universal definitive procedure common to every airline.


What types of non-permanent GoPro mounts exist for the ceiling of a Cessna 172?

I do tests on truck aerodynamics, and occasionally we put tufts on the vehicles. We then film these tufts to see how the flow behaves. We also use these RAM mounts, but sometimes one of them would come undone due to unproper mounting, dirt or flexing of the surface.

We solved this issue by adding redundancy in the form of the Rollei 3x Suction Cup Kit:

Disclaimer: Not affiliated to Rollei, this is just the first one we found.


Are the fastest moving pieces of a jet engine supersonic?

Yes, the tips of the fan blades.

Let's look at an example: The GE-90 has a fan diameter of 3124 mm and a maximum rotational speed of 2475 RPM. Their circumferential velocity is d·π·41.25 = 405 m/s or Mach 1.19 at sea level and ISO atmosphere. Now you need to add the flow speed of the air, but this calculation alone should be sufficient to prove the point.

The inner part of the fan and all the compressor stages belonging to the core engine experience flow at subsonic speed, even if the whole engine is flying at supersonic speed (see picture below). To make ignition as complete as possible, the flow speed is continuously reduced the closer you move to the fuel injectors. Since the air is heated in the combustion chamber, the hotter gas has a higher speed of sound, and all the flow through the turbine is subsonic, too. This includes the low-pressure turbine. Even the 1,600 ft/s shown below at the turbine is subsonic, because at 1100°C the speed of sound in air is 720 m/s or 2,362 ft/s.

Overview of parameters in a typical jet engine.

Only in the rear part of a convergent-divergent nozzle with reheat switched on will supersonic flow again be attained. This is exactly aft of the narrowest section, called the throat, where airspeed is equal to the speed of sound, and the petals of the nozzle are the only moving parts here. And they move rather slowly.


Does the A380 have more than one auto-brake disengage switch?

The A380 has one Takeoff Autobrake setting which is RTO and five Landing Autobrake settings which are BTV, LO, 2, 3 and HI. Some may read that as four plus the BTV, which is a variable deceleration compared to fixed deceleration. As you have noted, these are selected from the Autobrake selector switch.

It is possible to disarm the Autobrake using a number of actions. One or two which have been mentioned already.

The Autobrake selector switch is set to Disarm.
The Brake pedals are depressed with a higher input than the Autobrake setting.
The Spoilers are retracted.
The Autothrust instinctive disconnect pushbutton switch is pressed. These are located at the ends of the Throttle control levers.
The RTO Arm pushbutton switch is set.

FCOM Reference for anyone interested - FCOM/DSC/32/10/30/20/00004244.0002001


Do I have any authority over airspace above my land?

In the US you have, effectively, zero rights over the airspace above your land by default: Control of airspace is entirely delegated to the FAA, and they're super serious about it.

If you designate your land as an airport you can certainly establish a control tower and request an airspace designation from the FAA - whether or not they approve your plan depends on the existing airspace around you though: If your airport would create a problem for an existing airport you'd probably not be able to get an airspace designation for it, and it may even be classified as an objectionable airport.


Is In-Seat Rest used regularly where it is legal, and is it restricted by airline SOPs?

Too complex for me to give a specific answer, and this answer is assuming only airline transport not private flights or business charters.
Duty time limits are different for every country and may involve several pages of tables and definitions, airlines hire people just to track and comply with this.

Time of day relative to the pilots home timezone. If they are working when they are accustomed to sleeping then allowable hours are reduced.
The number of pilots on duty and length of single flight. A flight with 4 pilots is allowed longer shifts than 3 pilots, and a single pilot aircraft will restrict flight time per week more than 2 pilot aircraft.
Total hours worked per week.
Time between rest breaks, length of rest breaks, and location of rest breaks (eg at duty station, break area but expecting quick response(awake), break area without quick response(sleep in bunk)
Shift length, generally the whole period between breaks of 8 or more hours on the ground.(8 hours will vary with jurisdiction, ie some are 7 hours or 10 hours) For example if starting work after holiday: work 8 hours, off for 6 hours, work 7 hours, off for 10 hours. In many jurisdictions this would legally be considered a single shift of 21 hours with a 6 hour meal break.
Days between full 24hour rest days or number of 24hour rest days per month.


Restore air traffic controllers' instructions from aircraft tracks

No - there are just simply far too many permeation's of instructions.

For example - an aircraft climbs 1000ft. This could be because:

It has just received an instruction to do so
It previously received an instruction to do so at a certain point
It is operating within a block clearance and chose to do so
It experienced an emergency or TCAS resolution instruction and did so without instruction
It made a mistake/pilot deviation and incorrectly did so

And that's just one minor change, with one aircraft. You can certainly take a guess on some of them but even ignoring unusual situations the first three possibilities are common and normal practice.

And that's just traffic presumed to be operating IFR within controlled airspace - add in VFR traffic in uncontrolled airspace (And bear in mind that they can be still be receiving instructions and clearances at that point - for example, entry into controlled airspace or landing at an airport in uncontrolled airspace) and you've got, essentially, no chance.


What are the disadvantages (if any) of using a supercritical airfoil?

A supercritical airfoil has these characteristics:

Large leading edge radius
Comparably flat upper surface
Rounded lower surface with a maximum thickness location at around 50%
Flat or even negative camber in the forward section
High positive camber in the rear section (rear loading)

The large leading edge radius allows it to create more lift than comparable airfoils at high angle of attack. After R. Whitcomb re-invented supercritical airfoils (they had first be developed by K. A. Kawalki in Germany in 1940, and British airfoil research resulted in similar shapes, first used in the VC-10), he transferred some of their characteristics to a GA airfoil, the GA(W)-1.

From the Wikipedia article on Whitcomb:

  The unusual airfoil unexpectedly aided general aviation as well; its
  rather blunt leading edge allowed it to generate high lift
  coefficients before stalling, and Whitcomb published a low-speed
  airfoil which he called GA(W)-1; it is now routinely used in light
  aircraft and gliders.

As usual, Wikipedia is mostly correct, but the use of the GA(W)-1 on gliders is everything but routine. This gives an indication of their drawbacks:

The low forward camber limits the range of the laminar bucket to lower lift coefficients. A good glider airfoil tries to maintain the laminar bucket almost up to stall.
A positive camber throughout will produce higher maximum lift coefficients than what a supercritical airfoil is capable of. That is why the GA(W)-1 uses only the blunt nose and the rear loading, but not the camber distribution of supercritical airfoils.
The high rear loading gives them a large, negative pitch coefficient which translates into a larger travel of the center of pressure over angle of attack, requiring a larger horizontal tail. In airliners this does not matter because their large flaps dictate the size of the tail.


What unique challenges/limitations will I face if I start a career as a pilot at 45 years old?

Time

All other things aside all commercial part 121 pilots have a finite end date, starting at 45 means you are going to be ~20 years behind the young guys. Since the FAA mandates retirement from part 121 operations at 65 you have 20 years left but let's look at that a bit more practically. Assuming you pay for all your own training and don't need to go the CFI route to build hours you could conceivably finish your 1500 ATP hours in a year's time if you flew full time and the weather gods were nice to you. However that's not really realistic for all kinds of reasons, weather, mechanical, practical etc. So let's say you get there in a modest 2 years. Now you're 47...

At 47 you are applying to the airlines, still need to actually pass your ATP exams, and then they need to type you into one of their aircrafts, that's simulator time and ground school time for the airline which is by no means free and takes time - this means you are getting older. They are investing in you and in their eyes they can now only get 17 years or less out of that investment unlike the young guys they may have for longer. A regional may be interested but expect long grueling days and pay on the lower side of things.

You are also starting at the bottom of the seniority tree. If you are accustomed to a nice self sufficient lifestyle now you, should not expect that working at a regional for the first few years.

There are lots of other flying jobs that are not bound by the 65 year old limit, they may be a bit more transient in nature but you can still get into a high performance airplane and be having fun. You can fly for a part 135 charter operation, be a flight instructor, tow banners, tow gliders, crop dust, fly sight seeing flights, etc. One job that I have spoken to a few professional pilots about that seems like a sweet deal is being on staff flying a corporate jet for a company, the hours tend to be decent, you end up flying some fast metal and going cool places.


What are the (new?) FAR Part 141 rules for simulator hours for private pilots?

First, the new rules you're - probably - thinking about are for an instrument rating, not a private pilot certificate. So, that means that your question is essentially this: how much sim time can be credited towards a part 141 private pilot certificate?

Assuming that your son is doing ASEL (airplane single engine land), then the requirements are in 14 CFR 141 Appendix B. You can use a sim for 15% or 20% of "the total flight training hour requirements of the approved course, or of this section [of part 141], whichever is less", depending on the capabilities of the simulator:

  (2) Training in a full flight simulator that meets the requirements of
  §141.41(a) may be credited for a maximum of 20 percent of the total
  flight training hour requirements of the approved course, or of this
  section, whichever is less.

  (3) Training in a flight training device that meets the requirements
  of §141.41(a) may be credited for a maximum of 15 percent of the total
  flight training hour requirements of the approved course, or of this
  section, whichever is less.

A part 141 airplane private pilot course must have a minimum of 35 flight hours training (a school can require more hours, but it can't require less than 35), therefore sim time can be credited for either 5.25 hours (15%) or 7 hours (20%). I don't see any way to reconcile those numbers with the ones you gave, although if your son is doing part of a much longer study course that includes instrument, commercial or ATP training then it could theoretically be a result of how his school organizes training time. That seems very unlikely to me, though.

As for your concern about lowering the package price, that's exactly why simulators are used in training (among other reasons) and there's nothing inherently wrong with using sim time instead of flight time for training. Just ask an airline pilot! But it has to be within what the FAA allows, so I can only suggest that you ask his school to put their claim in writing with references to both the FARs and their FAA-approved training program documentation. If they still make the claim, then forward all the docs to the local FSDO and ask for their confirmation.


How does the V-22 Osprey share engine power between its rotors?

It is possible to drive the two rotors of the V-22 Osprey from a single engine using a segmented driveshaft connecting both engine shafts via gearboxes:

The drive shaft is depicted in blue in the left wing. Source

Each engine drives its own rotor and the connecting shaft. If one fails the same rotation speed is maintained, but each rotor receives now half the power of the remaining engine.

A similar mechanism is also used on the CH-47 Chinook family:

Source

This is a CH-47 Chinook green drive shaft:

Source

On aircraft with two distant rotors, it is vital to have both rotating, as if one slows or stops the aircraft is unbalanced to the extend it crashes.


How much can a plane deviate from its route to Paris (CDG and ORY) before an alert is raised?

I think "it seems like (quite understandably) that planes avoid Paris intra muros" is jumping a bit to conclusions. I went to Flightradar24 and found this, without even waiting for anything interesting to happen:

It didn't go exactly over the Notre-Dame, but even on this scale you should be able to see that it did cross inside Boulevard Périphérique.

On the other side of the Channel, such overflights are extremely routine when Heathrow operates east-to-west (as it usually does). Here's one (again found live, without waiting for it) that could have dropped bombs on the Crown Jewels if it had any to drop:

Perhaps more relevant than the Crown Jewels, this flight path is just a few hundred meters from the City of London skyscrapers. If the pilots had wanted to reenact 9/11, they could have crashed into something tall and famous about 10 to 20 seconds after deviating from their expected horizontal flight path. (But they'd need a bit more time than that to descend -- call it a minute or so from the first non-routine control input).


How the Log Periodic Dipole Antenna of Localiser help in varying modulation depth?

Mod Depth (more commonly called modulation index in electrical engineering) is the amount a carrier signal is modulated.  Mod depth has nothing to do with antenna configuration and is set by the transmitter (or more precisely the modulator).  The log periodic antenna controls the width of the various beams.  A larger antenna means a smaller beam and smaller beams mean you will have more precision on an ILS approach.  As far as the discrepancy between the 40% and 20% mod depth for ILS systems I will always believe the manufacture.  It seems like the documentation you posted is describing a simple hypothetical setup to help you understand the concept.  I believe most ILS systems use more than two beams. The degree of mod depth shouldn't matter too much as long as your Signal to Noise Ratio is high so I wouldn't get caught with the amount of mod depth in ILS systems.


On an IFR flight, should I avoid class B and include approach fixes/procedures in the route?

You don't need to.  If enter a start & end point at https://skyvector.com/, it can suggest standard routings for you.  You can follow those, or tweak it up some.
For example, 6B6 to WWD, standard routing will put you on V1 and will take you out over the water quite a ways, farther than I prefer to be in my single engine 4 seater. I'd tweak that to route over JFK, Colts Neck VOR, Atlantic City instead, having been cleared for that route several times by NYC approach. IFR at 6000, and VFR even, at 6500 feet.

I've also talked to pilots going north & eastbound who were IFR and routed north around the NYC Class B, sometimes quite a few miles out of the way. So it really depends on what the weather is doing and how busy the Class B is at the time of your transition.

For the approach part, I'd leave that out as conditions can change and your approach will be determined by the weather at the landing end and ATC will assign what to use as you get closer, or you can request a Visual Approach if the weather is nice and you don't need the approach. One thing you can do is put "No SID, No STAR" in your flight plan if you don't have them on hand.


Why does Google's Wing drone have dimples?

These are not actually dimples but shallow bulges. I found a higher-res image online and checked it out. You have to expand the image to full-size and look closely; the angle of sunlight and shadow gives them away:

Similarly, this side view shows that the bumps continue down the side:

The drone is not very large, less than 2 m (6 ft) long. They are not large enough to have significant aerodynamic effect at the speeds the drone flies. Lots of much faster planes have rows of rivet heads which stand out more than these do. They are about the size, shape and spacing one might expect from internal fixings holding a light supporting framework together, maybe there are pop-rivets under there. Another possibility is anchor points for internal equipment or wiring.
To be honest I am disappointed. Dimples are used on golf balls to stabilise flight and have in the past been studied as a way to reduce drag on aircraft. I had hoped at first that work might have been brought back to life. Then again, some cetaceans (whales etc) do have knobbles on their fins, we think to control the boundary layer and reduce drag, but these are just too small and shallow and not organised in the expected way for that.


What is the reasoning behind Kamov twin-rudder design?

It's kind of a hard one. It looks like in this helicopter directional stability is a challenge because:

the tail arm is quite short;
there is no tail rotor, which provides directional stability just like a vertical tail does.

An aerodynamic surface is most effective around zero angle of attack of the air stream - slipstream angle $ \beta $ in this case. Most profiles stall at angles around 15 degrees, and are therefore most effective at -15º < $ \beta $ < 15º.

If we have a look at lift L and drag D of the vertical surfaces, with dynamic pressure q in N/$m^2$, A = total vertical tail area in $m^2$, and $C_L$ and $C_D$ dimensionless coefficients:
$$ L = C_L * q * A$$
$$ D = C_D * q * A$$

The two images above are from Principles of Helicopter Aerodynamics by J. Gordon Leishman Figure 7.51. They show the coefficients over a full range of 360 degree, and we can see that:

In the $C_L$ plot, after the stall point at about 15º there is still quite some lift left, that increases again but to a lower peak at about 45º according to flat plate lift theory. That means that between 15º and 45º, there is not much increase/decrease in lift: $dC_L/d\alpha$ is almost zero and the surface is very ineffective in stabilising in this range. There is even a little dip in the curve just after the stall where the angle might get stuck.
In the $C_D$ plot, there is a deadband between -15º and 15º, after which the drag jumps up dramatically and has a relatively high $dC_D/d\alpha$. Since drag is defined as the force in line of the air stream, at higher angles of attack drag actually helps in getting the surface back to neutral (At 90º lift is zero and all force is drag)

So with the above in mind, what it looks like to me is that due to the short tail arm the vertical surfaces must deal with helicopter slipstream angles > 15º. By canting them inwards, one surface operates in the effective $C_L$ range, and the other surface operates outside the $C_D$ deadband, in doing so channeling the drag forces into a stabilising moment.


Does every state in the US require aircraft and pilot registration?

No.

It varies from state to state. New York, for example, requires tax payment but no aircraft or pilot registration. New Jersey doesn't require any registration and didn't mention any taxes. In Delaware, registration is required but taxes can be waived if you register your aircraft under your corporate, instead of your own name. Iowa requires registration and so does Ohio.

I could not find a single resource which lists all states and their aircraft and pilot registration requirements. FAA does not have this information, probably because FAA does not care about state regulations.

We can create a Wiki on this topic here.


G1000: Is it possible to balance the radio volume for pilots and passengers?

You can't control the radio volume separately for the passengers but you can control the intercom volume separately. If the passengers' headsets have individual volume controls you can ask them to turn down the volume and you can then compensate by turning up the passenger volume for the intercom. That way the overall intercom volume will be about the same but the radio/ATC volume will be lowered.

If all else fails, you could turn off the radio completely for your passengers :-)


How to determine aircraft altitude and speed, as a passenger?

I always track my flights, so here is my experience:

App using offline maps

As it has been said, you will need an app which can download maps prior to the flight. I never had a flight with onboard wifi, but I guess, there's usually a data volume constraint, which could make it expensive.

I use Mapfactor Navigator (Android), which is an offline navigation system for cars etc.
The maps can be obtained from within the app, the user has the choice between free maps from the OpenStreetMaps project and TomTom maps, which you have to pay.
The maps can be downloaded per country, and big maps are subdivided into smaller pieces. For example, the very detailed map for Germany is divided into four parts, together about 0.8GB of data. The entire USA can be downloaded per state, all together 1.7GB.

It's possible to configure several fields at the bottom of the screen to display speed, altitude, GPS coordinates, distance to destination and so on.

I mainly use this app to explore a country (e.g. by car) on vacation, but it's also fun to use it on board to see what's that location below us.

You may switch off speed camera warning. I once got a warning over Switzerland. The 840km/h were well above the max speed limit of 120km/h, and the fine should have been in the order of seizing all property of the airline. For some reason, the pilot didn't care...

OK, lots of advantages, but there's also a drawback: The app can not just record your flight, though a menu for tracking exists. Nor can it display your currently covered track. It can only record a track when it's navigating you, but you don't want to hear "turn around! turn around!" all the time...

Tracking app

Again, there should be thousands of apps out there. I'm using Open GPS Tracker, which can also display your position / track on an online map. So, you just see a point moving on a gray screen while flying.

However, this app allows to record your track, with up to one point per second, and at the end, you can export it as GPX file, which is the standard. It can be opened by many map tools, also by googles MyMaps or what it's called. The file contains coordinates, precision, time, altitude, speed, number of satellites and course.

One hint: This app makes a sanity check between speed reported by the GPS module and speed calculated from recorded points. If this fails, it doesn't display/record any speed. This often happens onboard, so switch this check off.

Here is a flight from Düsseldorf (DUS) to Las Palmas, Gran Canaria (LPA), including altitude profile, drawn with Marble (Linux KDE program):

Precision

An airliner is usually made of aluminum, which makes it a huge faraday's cage. The reception of any radio waves is very limited (through the windows), and so is GPS.
And as GPS needs a line of sight to several satellites spread as much as possible over the entire sky, the only chance is to have a window seat. There, I usually get a very good GPS signal, while it's already very bad to unusable on the next seat, and don't even think about it on the aisle seat.

Having a window seat, I usually get a good signal. While taxiing, the precision is quite good, as on this flight from Frankfurt (FRA):

Of course, the strength and accuracy of the GPS signal relies on the quality of the GPS module of your phone. My last phone wasn't so good, I often had jumps of several 100m sidewards, or from 7000m to 10000m altitude. This is just because accuracy comes with the number of satellites, which usually increases with altitude. And: The first aim of GPS is to locate your position, the altitude usually is less important. With my current phone, I don't see such problems. No sudden steps aside, and altitude and speed were quite the same as displayed on the entertainment system.

Well, not entirely. I noticed my phone showing an altitude about 50m too high when landing on my last flight. The 20m shown by the entertainment system were plausible, as the airport was nearly on sea level / in the sea. But the too high altitude was still there, even at the beach. Keep in mind the earth isn't a sphere, it's an ellipsoid, though even that's not correct, it's more like a potato. So, sea level isn't the same everywhere. High quality/price GPS receivers know this and contain data to compensate it, but cheap ones just use the ellipsoid model. (However, 50m is nothing during flight, and what do you expect from a phone inside the cabin...)

More hints

For a working GPS, the receiver needs a list of all GPS satellites and their precise orbits ("almanach"), current time and its rough position. If it does not have its rough position, it takes much more time to get a fix (first GPS position). And if it doesn't have a recent almanach, it has to listen to the satellites for a while, as they slowly broadcast it.
As reception of radio signals is quite difficult inside the cabin, it may be very hard to get a fix, and even impossible to get the almanach.
So, it's good practice to prepare your phone before the flight, as reception will be better, and assisted-GPS allows to retrieve the almanach and current position via the mobile network.

Finally: The battery.
Running my two apps on a 4.5h flight takes about 80% battery, and I have a laaarge battery. Of course, this also depends on display-on time. But the endurance could by tested before the flight, and if it's too short, a power bank my help.


Why are predator drones being used over civilian California?

An article from 2001, TESTING SPY PLANES GRAY BUTTE AIRFIELD TO BE REOPENED says,

  General Atomics, which makes the Predator in San Diego, has been conducting final production tests and checkout flights at El Mirage, three miles inside the San Bernardino County line.

See also EL MIRAGE FLIGHT TEST FACILITY


What is required to be an "FAA-qualified helicopter aerobatics pilot"?

I think this depends on what "FAA-qualified" means: the FAA defines aerobatic flight in 14 CFR 91.303 but it doesn't issue any pilot certificates or ratings for aerobatics. I did find several references to FAA Form 8710‑7, Statement of Acrobatic Competency (e.g. here), but the form itself isn't even listed on the FAA's form page.

There is an FAA document called Guidelines for Pilots Seeking All-Attitude Training which states that there is no special certification required:

  [...] no separate certificate, rating or endorsement is required to
  specifically qualify an individual as an all-attitude instructor

And:

  Anyone claiming to be an all-attitude instructor must at least hold a
  valid Commercial certificate if working for compensation or hire. The
  instructor must also be a certificated flight instructor (CFI) to
  provide FAA endorsements. Other than that, CFI credentials are not
  necessary for anyone to claim to be an all-attitude instructor.
  Therefore, caveat emptor - buyer beware - applies when seeking
  instruction.

Although their definition of "all-attitude" isn't exactly the same as "aerobatic", the document seems to make it clear that aerobatic training is not directly regulated. And looking through a variety of aerobatic websites including the IAC one, there is no mention of any required FAA certification. Endorsements for tailwheel, high-performance or complex aircraft are often required, but that's because of the aircraft itself, not the aerobatic activity.

But this profile gives some clearer information:

  Once the helicopter was ready, the FAA needed to certify it in order
  for Chuck to perform stunts with it. Once the aircraft was certified,
  the next step was to also get him certified, which ended up being a
  complicated process. The FAA was not sure how they could certify him,
  so they turned to Rich Lee, chief pilot for Boeing, who evaluated him.
  “He wanted to make sure that I did have all my screws in my head and
  that they were not loose”, said Chuck, laughing.

My guess is that the FAA first issued a new airworthiness certificate and/or waiver for the modified helicopter. That's very common and it would be same for a home-built aircraft, for example. Second - and this is a guess - they had the Boeing guy evaluate him for the Statement of Acrobatic Competency that I mentioned above. Although I can't find it on the FAA site, it obviously existed in the past and if you look at this example from the EAA Warbirds site, you can see that the evaluation process was (is?) 'outsourced' by the FAA anyway, presumably because they have no experts available internally:

  I desire to take advantage of an FAA procedure for the evaluation of
  my competency by a Warbird Aerobatic Evaluator (Warbird Evaluator) on
  the list maintained by the EAA Warbirds of America, Incorporated.

I suspect that putting a unique airworthiness certificate together with a unique Statement of Acrobatic Competency resulted in a uniquely "FAA-qualified" acrobatic helicopter pilot.

Finally, according to Aaron's LinkedIn page he is the:

  First FAA Certified Helicopter Pilot to recieve a Helicopter Aerobatic
  Certificate from the FAA.

That again seems to emphasize the helicopter, not the pilot.


What is required for transatlantic flight in a private plane?

While probably legal to fly over the Atlantic VFR, it appears getting out of Canadas airspace is a different matter. After a bit of googling I found this article on COPA's website, saying:

  Both for flying in the northern parts of Canada as well as in
  Greenland airspace, an ADF is legally required (refer to TC AIM
  3.16.10 and CAR 605.18). I didn’t have one, so one had to be installed. Other than that, FDOW didn’t need any modifications. IFR
  approved GPS is an absolute must; we had three GPS receivers on board.

  Speaking of IFR: As per CAR 602.19, pilots attempting trans-oceanic
  flight must hold an instrument rating. Even though an IFR flight plan
  is only required above 5,500 feet across the Atlantic, NavCanada will
  not issue an oceanic VFR clearance when leaving Canada. In addition,
  it is extremely unlikely for any airplane to stay in VMC during the
  whole trans-Atlantic flight. Therefore, it’s mandatory that both,
  pilot and airplane are certified and current IFR.

That being said, weather over the Atlantic can be very treacherous, especially if you're unable to climb on top.

There are quite a few stories around about crossing the Atlantic in smaller airplanes, there's also an Ice Pilots NWT episode (season 1 episode 9) where they ferry two water-bombers to Turkey, although not very technical, it's a nice watch.


Taking the Sukhoi Su-35 for example, it has two engines, each capable of producing 86.3 kN of dry thrust, combined they produce 172.6 kN. With afterburner they produce 284 kN (142 kN each).

The jet engine on the American F-22 produces 156 kN with afterburner, close to the 142 kN of the Su-35.

Soviet Union / Russia made the Kuznetsov NK-32 military jet engine, capable of 137 kN (dry) and 245 kN (wet).

So, the ability or technology to make a powerful jet engine is not the reason. It's just powerful engines are much bigger.

The main reasons for selecting a twin engine design are:

Slimmer design, two smaller engines make for a slimmer profile than one big engine.
Redundancy, in case one fails, especially important for big fighters.
Afterburners are easier to make for smaller diameter engines.


Pressure Distribution Pattern around Wing

Last question first.  Yes, air does try to "rush" from high to low pressure, but the movement of the wing creates a condition where the net movement of the air relative to the wing will be downwards and backwards, and lower pressure remains above the wing. This is why airspeed is so important.

Understanding the arrows in the diagrams is a bit like reading music or another language.  They are simply pointing from lower to higher pressures.  Isobars on the weather map show the same thing as pressure gradients.

Also important is to know that you are looking at a fully symmetrical airfoil.  There will be equally opposing lower pressure areas top and bottom at 0 angle of attack.  This is why many airfoils have a flat or even concave bottom to help create higher pressure underneath the wing.  But even a fully symmetrical airfoil will have a pressure differential as AoA increases.


How does pressure increase in a multistage compressor?

Firstly, your intuition doesn't really apply in terms of basic thermodynamics (but, as I'll explain, you're kind of right):

  Boyle's Law: "For a fixed mass of gas, at a constant temperature, the product (pressure x volume) is a constant."

Pressure does increase linearly [assuming the temperature stays the same]: if you squash an amount of a gas into half the volume, the pressure will double (assuming you keep the temperature the same). If you squash it into half the volume again, the pressure will double again (4x the original)

However you're also right in that we don't simply increase pressure by the same amount as we go along: Each stage compresses the air by a different amount (otherwise an engine would look like a weird triangle). and perhaps more importantly we can't maintain a constant temperature in an engine... as we compress the air into a smaller volume the temperature increases unless the air is being cooled in some way.

Essentially, though, you can calculate the pressure change at each stage if you know how much the volume reduces by (ie how much smaller each chamber is than the last) and the temperature of the air in each.


Compressor-Turbine: Why a shaft and not kind of a "rotating drum"?

There are a few very practical reasons why turbine engines use inner shafts/spools.

First, jet engine spools are very high speed rotating parts, this means they are subjected to high amounts of centripetal force. Centripetal force is calculated by $F=mr\omega ^2$ were F is Force, m is mass, r is radius of gyration and $\omega$ is angular velocity. So obviously the larger the radius of gyration the higher the forces that the rotors must carry. To reduce the radius of gyration manufacturers try to push the mass of the rotors as close to the centerline of the engine as possible. In the picture below (source) I have circled the HPC, HPT and LPT rotors. You can see how they are very thin under the blades and then have a large bulb very close to the engine centerline. Moving all of this mass towards the centerline, lowers the radius of gyration, and thus reduces the centripetal force. By reducing the centripetal force, you can reduce the strength of the rotors as well, since they don't have to carry as much load. This allows you to remove mass from the rotors, further reducing the centripetal force and overall weight of the engine.

Next, you want the bearings to be as small as possible. This is because as the radius of a bearing increases the linear velocity of it also increases, via this equation: $v=\omega r$. The faster the linear velocity the higher the wear, the greater the friction and greater the heat generation. So there is a push to make the bearings as small as possible given other constraints. In the image below I have circled the bearings, the red circles are on the low pressure spool bearings, while the blue circles are the high pressure spool bearings. This isn't always done, but it is becoming very common for the aft high pressure bearing to actual ride on the low pressure shaft. Typically these shafts spin in the same direction, so the bearing speed is reduced by this equation $\omega_{AftHPbearing}=\omega_{HP}-\omega_{LP}$. Bearing friction reduces the efficiency of the engine, and bearing wear is a significant maintenance driver.

(This is getting long so I am going to truncate the rest) There would be many other issues as well, such of blade mounting (dovetails in compression instead of tension), blade design (compression instead of tension), possible increase in leakage paths, containment, stator structure design (now all of your stators are attached to a stationary shaft that can only be supported at the ends), control of variable stator vanes, getting the fuel into the combustor, how do mount the engine, etc.

Edit: Just reread the question and realized you were also talking about making the combustor bigger. Modern combustors are getting smaller and are much smaller than they were in the original jet engines. You can also see in the pictures above, they already don't use all of the space available to them and if they needed more space the arm (shaft) connecting the HPT and HPC could be lowered some more.


How many types of tape do airplane mechanics use?

I can't speak for General Aviation, but based on the number of tapes I've seen, it wouldn't be outside the scope of reality to think the aircraft manufacturers have a partnership with 3M to come up with as many different types of tape as possible.

For wiring repairs alone, I know our shop keeps at least 20 various types of tape on hand in our bench stock area to grab in a hurry. There are probably another 20-30 other types of tape we may use in rarer situations, but don't keep on hand. We'll usually order that on an as needed basis.

There are a number of different types of "Speed Tape" as well. These are commonly used as very temporary structural fixes for small holes, dents, etc... on certain parts of the aircraft. It looks a lot like a sheet of aluminum foil, but it's some of the stickiest stuff I've ever dealt with.

I know we also have different Mylar tapes that are used for a number of different applications. One of the applications, in particular, is when floor panels are sealed. The sealant can take 24-30 hours, in some cases, for a tack free cure. Since we want to use the airplane sooner, we can cover it with Mylar tape. It'll allow it to cure while under the tape. After the cure, we'll simply pull the tape up and continue business as usual.

There are a number of other specialized tapes I've seen for various other applications. I do know that I have seen duct tape on bleed duct insulation. This is rare, but sometimes the insulation gets torn and people use duct tape to repair it. Quite frankly, I've never stopped to look and see what the approved tape is for that, but if there was one and only one application for duct tape, that might be it.

I can't offer you an exact number, but they most certainly number in the hundreds if not thousands! Oh, and one other thing I've noticed is that Boeing tapes are usually different than the tapes specified by Airbus! So, each manufacturer has chosen certain tapes for certain applications and purposes, although some are interchangeable.

If you really wanted to get crazy and technical, each tape comes in different widths too. All of these come in standard widths of 1/4", 1/2", 1", 2", and 3". I'm sure there are other width's too, but I know I've seen all of those sizes.

Quite frankly, it's dizzying and unbelievable how much tape is on an airplane!


What was the reason why 9M-MRO burned more fuel on one engine?

Those engines all look the same to me.

1.5T per/hour difference does seem excessive, but probably not unheard of.  It could be just because one engine is newer than the other and has less wear on it.

If you look at APPENDIX 1.6B of that same report it shows that the right engine consumed about 1.5% more fuel during Takeoff and Climb, not 1.5T more, so it may just be a typo.

(APPENDIX 1.6B WF is fuel flow in lbs/hr)

Here are some crops of the photos you linked to:

Jan. 15, 2012

Feb. 16, 2013

Oct. 28,2013

Jan. 22, 2014

Feb. 8, 2014

Feb. 10, 2014


Why can airliners not fly as fast as fighter jets?

There are 2 big reasons:

Speed costs lots of money. Fighter jets can go much faster than passenger jets but they spend most of their time cruising as the same speeds because it is more fuel efficient. Faster airplanes need more exotic materials and would be more expensive to build. The engines would need to be bigger and more powerful and would cost more, and to go very fast uses a lot more fuel as air resistance increases exponentially with speed. Concorde tickets were very expensive not because of any sort of exclusivity, but because that's what it cost to operate it. Newer technology could probably decrease that somewhat, but it would still be very expensive. Air forces can operate fast jets because they have the funding, airlines have to make a profit
Passenger jets fly pretty close to the speed of sound already, to go much faster they would need to break the sound barrier, which creates a very loud sonic boom that disturbs people on the ground and can break windows in some cases. Supersonic travel over land has largely been banned because of that, so unless you are over water you can't go any faster anyway


How does a pilot receive weather information when overflying the oceans?

It depends on what info you're after: During cruise I'm mainly interested in threats to the aircraft which normally manifest as echo on the weather radar (clear air turbulence being one famous exception) or by looking out of the window.

Do you want info on your destination and alternate airport you listen to a HF VOLMET station or ask ATC via HF (cumbersome and annoying due to often poor reception).
In our shiny new world we could also ask ATC via an CPDLC free text message. The controller simply uplinks you a message with the requested information.
Depending on your operator there might be a plethora of other information available via ACARS which - when equipped - can communicate via satellite. At my company we can get:

Updates on the winds aloft (important for fuel calculation)
Airport weather information (ATIS, METAR, TAF)
Sigmets

In general, the weather you really need is readily available. An ocean crossing is only a couple of hours. This timeframe is covered by the TAFs. So you shouldn't be too surprised when you don't have all that fancy stuff mentioned above and ask ATC once VHF COM is reestablished or you can receive a VHF VOLMET station.


It just was not a great fit for the use case it was built for at the time it was released:

The Boeing 747SP was hit by the same problem that many airlines have
suffered from throughout history… rising fuel costs. The aircraft was
heavy, didn’t carry as many passengers as a normal 747 and was
expensive to run (four engines after all). Boeing had expected to
build up to 200 of these aircraft, but their dreams were never
realized.
Additionally, by the early 1980’s, other aircraft started to arrive
that could easily perform the same route and provide a better
passenger experience. The last commercial flight of the Boeing 747SP
flew in 2006 for Iran Air. As the country is currently under embargo
and spare parts cannot be flown in from Boeing, it is likely that they
retired them out of necessity, rather than just replacing them with
something better.

It was a clunky 4 engine fuel hog, which was not great with rising oil prices

The aircraft, despite its long range, was not popular with airlines,
and only 45 were built. This was mainly due to its four-engine
configuration, which meant high fuel usage and higher costs for
airlines, making it difficult to break even on ultra-long-haul
flights. Shorter flights weren’t profitable either, as the 747SP’s
high fuel capacity added weight and increased fuel burn on short hops.
The aircraft’s failure was not due to a lack of effort on the part of
airlines.


Which organisation deals with Aviation Law - IATA or ICAO?

ICAO does deals with law, although not directly.
The Convention on International Civil Aviation and its 19 Annexes form the basis of International Air Law. Although the Convention text itself is not directly a law, the 193 ICAO Member States ratify the ICAO Standard and Recommended Practices, albeit sometimes with minor modifications.
From this answer:

ICAO is the International Civil Aviation Organization, a specialized
agency of United Nations. It was created after the Convention on
International Civil Aviation (the Chicago Convention) of 1944 was
ratified in 1947. The purpose of ICAO is according to the convention:

"WHEREAS the future development of international civil aviation can
greatly help to create and preserve friendship and understanding among
the nations and peoples of the world, yet its abuse can become a
threat to the general security; and
WHEREAS it is desirable to avoid friction and to promote that
co-operation between nations and peoples upon which the peace of the
world depends;
THEREFORE, the undersigned governments having agreed on certain
principles and arrangements in order that international civil aviation
may be developed in a safe and orderly manner and that international
air transport services may be established on the basis of equality of
opportunity and operated soundly and economically;
Have accordingly concluded this Convention to that end."

Within ICAO, the 191 Member States and a number of global aviation
organizations work together to develop international Standards and
Recommended Practices (SARPs). These SARPs are the reference for
states developing their national civil aviation regulations which are
legally enforcible. This is an important aspect: ICAO SARPs are not
legally binding by themselves, they form the basis of national
regulations which have legal status.
In this way civil aviation regulations are harmonized all over the
world, with slight differences based on the actual implementation in
national regulations. These local differences are then reported back
to ICAO and published.

IATA is a trade organisation representing the interests of their member airlines. They don't deal with law in the sense that their directives are not embedded in law.


Can an aircraft be stalled at low altitude and safely land on water?

That is the normal procedure for water landings with land airplanes. You fly parallel to the water as low as possible until the flight speed is too low to carry the full weight of the airplane. If it can be done safely, however, depends on a lot more than only the landing technique. Some aircraft will not swim and the drag of the landing gear might cause the aircraft to topple over.


What are the requirements to obtain an FAA private pilot's license in Bosnia?

You would have to find a US-licensed CFI in Bosnia to give you the training, and then a Designated Examiner in Bosnia to give you the oral and practical exams. The first may be doable, the second pretty much impossible unless you want to pay someone to come to Bosnia. Certainly it would be much easier (and probably cheaper) to come back to the US for a few weeks and do nothing but finish your ticket.


What should I expect during a first class medical examination?

You can see the requirements for all FAA medicals in 14 CFR 67.

Specifically, Subpart C (67.2xx) deals with second class medicals and Subpart B (67.1xx) deals with first class medicals.

The only difference my cursory read of these regulations revealed is:

x.111 - Cardiovascular. A first class medical requires EKG after your 35th birthday and every year after age 40.

This leads me to believe any real differences are likely in the ME's guidelines for issuing the medical, and I am not familiar with those.

The only other differences relate to duration and requirement for the exercise of privileges.

On your second question, if you apply for a first class medical and for some reason could not qualify for one, you will be denied or deferred even if you could hold a lower class medical (this is also true of a second class application).  The only possibilities at the end of a medical exam are walking out with a medical of the class you applied for or walking out without a medical.  There is no fallthrough to a lower class.

If you have an issue that you believe would inhibit your ability to get a first class medical, an avenue to explore this is through AOPA where you can talk with a doctor and get advice on your ability to pass a medical and support in handling a deferred medical application.


Reduction in Service Ceiling / Change in RVSM

1(a). Yes, in the US, below 18,000 feet and above 3,000 feet, airspace seperation is 500'.

3,000' and above to 18,000 feet:
IFR traffic, eastbound fly at odd thousands
VFR Traffic, eastbound fly at odd thousands + 500'
IFR traffic, westbound fly at even thousands
VFR traffic, westbound fly at even thousands + 500'

(I always figured that was because "east is even" would be too easy to remember.  JUst like Nav lights, red is in the left because "red on the right" would be too easy to remember. Red/Green is likely a carryover from boating tho.)

1(b), I don't know about Europe.

2 I believe service ceiling is more a factor of jet engine efficiency and aircraft drag.  Piston engine's need to be turbocharged or turbonormalized (make sea level power at altitude) to make the high teens need to make air denser for the engine to make power - if you can get up there, the drag drops a lot and you can go a lot faster.  Jets are big compressors in essence and can make all the dense air they need to burn jet fuel with.

Why don't more jet arcraft fly higher? Maybe it's not worth it drag reduction-wise, or time savings enroute-wise, to climb higher and then to descend back down.


Why is the MD-80 magnetic compass behind the first officer's seat?

In most aircraft, the standby magnetic compass is mounted well above the main instrument panel, usually above the central window post, in order to reduce interference. In the three piece window of the MD-80 (without a central window post), this is not possible, resulting in the different location for compass.

All the Douglas jet aircraft has this type of mounting. According to this thread, the compass was first mounted on the instrument panel, which resulted in severe interference, resulting in its relocation. From the thread:

  I understood that, early in the 60's, the compass was relocated in all DC-8 production due the three section type of the windshield (the compass has a lot of error/deviation at the center of the glareshield panel).

Note: I'm not able to find original documents supporting this. All the documents I can get simply instruct to check the compass using mirrors in the glare shield.

This design decision was used in all the later Douglas models, DC-9, MD-80/90 right upto Boeing 717 (which was developed as Dc-95); incidentally, all these models used a three piece front windshield devoid of center post.


What are approach control's expectations regarding weather information for flights to satellite airports?

I fly out of a controlled satellite class D (KLOU, Bowman Field) below a class C (KSDF, Louisville International) so I'm fairly familiar with this scenario, at least in the way that it's handled there. The short story - in my experience - is that Approach only cares about you having the numbers or ATIS for the airport where you'll actually land.

First the theory. The ATC orders say:

  7−1−3. APPROACH CONTROL SERVICE FOR VFR ARRIVING AIRCRAFT

  Issue the following where procedures have been  established for
  arriving VFR aircraft to contact approach control for landing
  information:

  a. Wind, runway, and altimeter setting at the airport of intended
  landing. This information may be omitted if contained in the ATIS
  broadcast and the pilot states the appropriate ATIS code or if the
  pilot uses the phrase, “have numbers.”

Note the "airport of intended landing", they aren't going to pester you to get the ATIS for somewhere that you aren't going to.

Second, the practice. If I'm inbound to KLOU on flight following (don't leave home without it!) then my first contact with Louisville Approach usually goes like this:

  Me: Louisville Approach, N12345 level at 6500
  Appch: N12345, roger, Louisville Altimeter is 2992, report when you have the weather at Bowman, information Kilo is current
  Me: N12345 has Kilo at Bowman
  Appch: N12345, roger [and further instructions as needed]

As a controlled field, Bowman has ATIS, not "the numbers" but I've had more or less the same exchange at other places.

I think that Ron's comment about information is useful here: when I'm inbound I usually have both the KSDF and KLOU ATIS anyway, just in case. Also notice how the KSDF controller helps me: the KLOU ATIS could have changed from Kilo to Lima between the time I got it and the time I called Approach. By telling me that Kilo is current, the controller is effectively telling me if I have to go and get the ATIS again or not.

As for just passing through class C, the very few times I've done that ATC has simply given me the local altimeter setting and that's it. I'm not landing, so they don't seem to care if I have the ATIS or not.


When I have had to file NOTAMs for skydiving demonstration jumps, I just called AFSS (1-877-4-US-NTMS) and asked to file.  The folks at Lockheed are way more helpful than the Feds used to be and will walk you through the process, but it is still good to have your information together before you call.  At a minimum you need a description of your activity, altitudes in MSL, times in zulu, and a location.  Location should be in reference to an aiport or nav aid ("Within one nautical mile of the BFE airport", or "27nm from the BADGER VOR on the 340 radial, for a radius of 2 nm").  If the activity requires authorization, you will also need to have that squared away before calling.


What's the difference between overrun and overshoot landings?

They are more or less the same and are often used interchangeably. FAA AC 91-79 Runway Overrun Prevention defines runway overrun as:

  A runway overrun event is a departure of the aircraft from the end of the intended landing runway surface.

It means that the aircraft has touched down on the runway before going off it. Overshoot is used in the same sense (note that overrun/overshoot occurs both in TO/landing).

However, there is one case where they are used differently. Overshooting the runway also can mean that the aircraft has touched beyond the end of the runway i.e. missed the runway entirely.


Why has the Bombardier CSeries been delayed in starting service with Delta Air Lines?

This delta news brief from February of this year alludes to the fact they are waiting for the Alabama production facility to be completed, presumably where they will build the aircraft.

  Delta still intends to take as many deliveries as possible from the
  new Airbus/Bombardier facility in Mobile, Alabama, as soon as that
  facility is up and running. However, as the ITC notes, the airline has
  contractual commitments to begin taking deliveries later this year and
  the ITC decision clears the way for Delta to accept deliveries in
  Canada as well....

  ....and while pleased that imports from Canada can now be part of the
  near-term solution, Delta looks forward to taking U.S. manufactured
  aircraft from Mobile when that facility opens.

This article notes that during an earnings call they mention early 2019 as the projected start of operations for the aircraft. The article also notes they were slated to take 15 aircraft in 2018 but "program delays" prevented this. The article does not detail what those delays were (presumably the lack of the Mobile facility contributed along with the tariff issues).


Is mode C required for CVFR in Canadian Class B airspace?

The vast majority of GA airplanes have Mode C transponders and when you ask for the clearance, you will be given a transponder code to squawk.  If you don't have one, you have a problem and you probably won't get a clearance except in special circumstances.  Not only do you need a  Mode C transponder, it has to be calibrated and certified every 2 years by an AMO.

You could call Terminal while still clear of the Class B, tell the controller you are no-transponder would like to go from A to B, and see what happens: the controller may let you transit by reporting position at specific points if the path is out of the way.  Or maybe not.

Better yet, call the applicable ATC unit on the phone and find out if you can get permission to transit Class B non-transponder for a particular reason.

As a general practice however, the answer will almost certainly be no.  Just go around or under.


Can I get a restricted ATP based on part 61 training?

Part 61.160 says no:

  (b) A person may apply for an airline transport pilot certificate with
  an airplane category multiengine class rating or an airline transport
  pilot certificate concurrently with an airplane type rating with a
  minimum of 1,000 hours of total time as a pilot if the person:

  (1) Holds a Bachelor’s degree with an aviation major from an
  institution of higher education, as defined in §61.1, that has been
  issued a letter of authorization by the Administrator under §61.169;

  (2) Completes 60 semester credit hours of aviation and
  aviation-related coursework that has been recognized by the
  Administrator as coursework designed to improve and enhance the
  knowledge and skills of a person seeking a career as a professional
  pilot;

  (3) Holds a commercial pilot certificate with an airplane category and
  instrument rating if:

  (i) The required ground training was completed as part of an approved
  part 141 curriculum at the institution of higher education; and

  (ii) The required flight training was completed as part of an approved
  part 141 curriculum at the institution of higher education or at a
  part 141 pilot school that has a training agreement under §141.26 of
  this chapter with the institution of higher education; and

  (4) Presents official transcripts or other documentation acceptable to
  the Administrator from the institution of higher education certifying
  that the graduate has satisfied the requirements in paragraphs (b)(1)
  through (3) of this section.


What is the purpose for two nitrogen charged chambers in an oleo strut?

Two chambers at different pressures creates a variable rate spring. Initial landing shock is absorbed by the low pressure chamber until its nitrogen is compressed to that of the higher pressure chamber, which then has sufficient volume to allow the desired amount of further compression at the higher pressure. The lower pressure chamber would have already consumed virtually all its volume.

The illustration is somewhat misleading in that the floating piston in the high pressure chamber should appear bottomed out when the strut is extended. There is no way for a fluid to be in equilibrium at two different pressures.


Do commercial pilots have their own lavatory?

In an Airbus A320; pilots share the toilet with the passengers. On AirAsia, a flight attendant blocks access to a toilet when the pilot enters the lavatory.


How much lag does an Attitude Indicator experience?

There is no virtually no lag on attitude indicators. The traditional ones are based on a mechanical gyroscope. Due to the gyroscope being gimbaled, it remains in a fixed attitude.

When the aircraft changes attitude, the gyroscope in the attitude indicator remains at its original orientation. When you look at the attitude indicator you are looking basically directly at the gyroscope, packed in a nice horizon displaying wrapping.

The modern attitude indicator in a glass cockpit gets the attitude information from the Attitude and heading reference system (AHRS). There is of course some lag associated with digital data transfer and display refresh rate, but these effects are too tiny to be noticeable by humans.

The first generation of these systems used mechanical gyroscopes as well. Nowadays most AHRSs uses Ring Laser Gyros or Fibre Optic Gyros. These gyroscopes use relativistic effects of light travelling clockwise and counter-clockwise through a circular path. The accuracy of these systems is very high and there is no delay.

Another technology that is used is are Micro-electromechanical Systems (MEMS) gyroscopes. The are based on a vibrating structure. The direction of a vibration tends to remain in the original direction, even though the supporting structure rotates. MEMS are relatively cheap compared to RLG and FOG but they are less accurate. Due to developments in the automotive and mobile telephony industry where attitude sensors are used for various applications the accuracy of MEMS gyroscopes has improved while their costs have decreased. This makes them now interesting for application in avionics.


What is the reason for the T- shaped rudder trim tab on the DA42?

The feature was added to reduce undesirable flutter discovered during flight test.  It appears on the rudder trim tab of the DA-62 as well.


Does a skinless fuselage add to the likeliness of an unrecoverable spin?

Well, I would solve with transparent Monokote if it was a model.  No accounting for people's taste.

Although some very early aircraft featured that look, designers soon realized that covered "slab" sides not only reduced drag, but also improved directional stability.  Note that covered area aft of CG acts as an extension of the empennage, allowing for a smaller Vertical stabilizer.  Many 100 years ago were comparitively tiny.

As far as behavior in a spin, what he has on the tail may be sufficient for safety, as well as good CG management.   But I would certainly not recommend denuding your fuselage for a certain "look" without some expert advice and testing.

Designers do compare side area ahead of CG to aft of CG to estimate yawing tendency in a slip.  So he may be OK.