Can I charge for editing footage from a video that was taken during a flight as a private pilot in US?

I'm assuming you didn't do the editing while you were sitting in the cockpit, flying the plane. Charge him whatever you want for your time sitting at home on the computer. It doesn't matter where the footage was filmed, if you're charging him to cut it up, edit it together, and render. Even an aerial photography company will itemize the charges and list digital editing services separately from the filming flight.
Just to be safe, though: Make sure he pays you separately for the pro rata cost-share of the flight. You don't want to take a lump sum and have to explain what part was for the flight and what part was for something else entirely.


What's a similar looking aircraft to this illustration?

is there perhaps a similar looking one in reality?

Not really, however the fictional five-deck flying boat depicted is clearly an extrapolation of flying boats of the first half of the 20th century.

Visually, the Short Empire class is the most similar:

domed cockpit at front of hull
hull chines
four radial engines mounted in-wing with three-blade propellers
conventional empennage

Photo of a Short Empire, Public Domain

Photo of a Short Sunderland, CCASA3.0 Nick.D

The largest all-metal flying boat developed for civilian passenger service was the Saunders-Roe Princess which only had two passenger-decks.

Photo of a Saunders-Roe Princess, Public Domain

The largest flying boat was probably the Hughes H-4 Hercules, popularly known as the Spruce Goose. It was designed for military transport (hence no windows). I believe it would have accomodated both troops and military vehicles but probably no more than two decks.

Photo of Hughes H-4 Hercules, Public Domain


Why not make 94.5% read as 100%?
94.5% tells you the margin you have. It will be closer to 100% in high-thrust versions – or even higher, i.e. the limit is pushed as the thrust ratings increase. The PW1100G you're asking about, its thrust varies from 110 to 150 kN based on the installed version.
For example, the A321's 150 kN CFM56-5B3 exceeds 100% near sea level and in cool to moderate temperatures, unlike the 120 kN -5B4 (both tables below).
Note that nowadays whatever the installed takeoff N1 limit is, it's rarely limiting – meaning the engine will reach the EGT limit before it reaches the N1 (barring major failures).

Source: A321/A320 FCOM


Unmanned Drone vs Conventional Manned Fighter in Combat: How realistic?

We're nowhere near good enough with our AI for a computer simulant to best a human pilot in a dogfight unless the odds are further stacked against the human (computer flies a superior aircraft, computer has enhanced knowledge of "reality", computer has advantage in numbers, computer ignores physical limitations of plane or pilot without consequence). Most computer pilot AIs in combat sims are some combination of the very simplistic "locate your opponent, put your lift vector on him and pull up hard" and the more complex "human is doing this, so the best counter-move is this". There's also no small amount of "I am a game, the purpose of my existence is to be enjoyable for the human, so while I must present a challenge, I must not require my human to attend a year of combat flight school before he stands a chance".
These are the basics of ACM taught to every fighter pilot, however these strategies will get you shot down against a competent human pilot every time, for two reasons:

"Line up and pull up" tends to settle you into a horizontal "one-circle" turning fight to conserve energy. In that fight, the first pilot to realize it's happening and pull vertical can tighten the turning radius by trading speed for altitude, getting inside and cutting across his opponent's turning circle for a good if somewhat high-offset firing chance. If the opponent sticks with "line up and pull up" he will do just the opposite, trading altitude for speed, increasing his turning radius and putting his tailpipe in front of his opponent's nose.

Moves and countermoves in air combat are a fluid dance that computers are plain bad at. Computers can beat humans in chess because the number of valid moves is fairly low, so the computer can calculate the most advantageous chain of several dozen moves quickly. However, computers are relatively bad at Go, because both the total game tree complexity and the available moves on each player-turn are massive.
Air combat is similar; while there are a few basic strategies, there are infinite possibilities, and because air combat, though "turn-based", involves a different kind of "turn" from those in chess or Go, the computer doesn't get to sit there and think about its move for several seconds; it has to make the best move it can think of in a fraction of a second or else the human will get to make several "moves" before the computer reacts to the first one, and the way computers think, making it decide quickly usually boils down either to simplifying the decision-making or deciding in a random way.

Prioritization is still an area where computer AI is weak. Against one opponent, where your objective is to shoot that opponent down, a computer could do quite well. Facing the primary mission objective of completing a bombing run, with potentially hundreds of aircraft in the sky and thousands of military (and civilian) ground vehicles and people in a combat theater, making the decision of what object deserves your primary attention any given second is something even human pilots don't always do well. Most AIs in combat sims are fairly scripted; either the purpose of an enemy's existence is to shoot down the player, or it focuses on its mission until it cannot ignore the player. Real combat is somewhere in between, especially when your mission is something like CAS or BARCAP where your job isn't one fixed point on the ground or one plane in the air.

Now, computers have some advantages that are considered "cheating" in combat sims but would apply to an unmanned fighter against a manned one. First is the ability to sustain maneuvers in excess of a human's G-limit. As long as the airframe can handle it, the computer can pull 12g turns, or -12g, whatever. Second is that the weight of a human, plus the "man-machine interface" of the cockpit systems, is greater than the mass of a computer directly connected to the instrumentation. The computer is also much faster at working with the aircraft's systems than a human could ever be, so a computer pilot, within a couple seconds of seeing a "blip" on the radar, could have the target locked up, while a human, given the same blip at the same time, would still be slewing tracking gates in the B-scope.
A third big advantage is 720* visibility. Humans have about a 170* "cone" of visual response, and a fairly poor 5-10* window of actual focus and acuity. With an unmanned craft, we can install cameras covering virtually 360* around the aircraft in the horizontal and vertical, and have the computer monitor and track objects within the full field of vision, as well as in IR or other non-visible light spectrums, much more efficiently than a human could do the same with the same camera systems.
Therefore, the first fully unmanned combat aircraft is very unlikely to look or work like a manned one, because its designers will have done things that would be bad decisions in a manned craft, but will give the computer a maneuverability, speed or visibility advantage that could compensate for more simplistic decision-making of the AI.


Is there a niche market for A&P mechanics with an aerospace engineering degree?

There is certainly a niche for both skill sets. Part of aerospace engineering is considering maintenance. There are multiple types of positions where having an A&P license would be a bonus.

During the design of an aircraft, maintenance must be taken into account. Projected maintenance costs are important to the success of a design. Engineers must address this during the design of new parts.
Manufacturing will have a lot of aspects in common with maintenance. Engineers must support manufacturing requirements in the design phase. Supporting emerging issues in manufacturing is also an important role.
Engineering is also needed to support regular maintenance tasks. Problems come up that aren't covered in the manual, and engineers will need to advise on a solution.

Based on these subjects, the following are a few types of companies will have some positions where an A&P license could help:

Designers of aerospace parts
Manufacturers of aerospace parts
Airline maintenance departments
Maintenance, Repair, and Overhaul (MRO) companies

This focuses mostly on the commercial side of things. You can also find either civilian or military jobs supporting the military equivalent of these functions as well.


Why does the turn coordinator ball move to the right during a climb?

There are 4 left turning tendencies in aircraft with "clockwise" (as seen from the pilots seat)
turning propeller, 3 of which may apply during a full power climb out.  The four are:

Prop torque  - prop turns right, plane rolls left - more noticeable at high power/slower
  speed
Gyroscopic precession - nose goes down - plane yaws left - not a factor in a climb - some
  effect as plane levels out, also there on tail draggers as rear of plane rises during take off
  roll
Asymmetric prop blade thrust at higher AOA (p factor).  Differences in thrust of ascending
 and descending prop blades will cause yaw to the left.
Spiral slipstream striking vertical stabilizer and side of fuselage, causing yaw to left.

Number 1 has to be watched in higher performance engines during takeoff roll.  Lifting off with insufficient airspeed will cause the plane to roll over and crash.  Fortunately, in a Cessna 172, this tendency is much more modest but should not be ignored.

3 and 4 are probably the main culprits of left yawing tendency in the climb.  The answer:  pitch to safe climbing airspeed (generally Vy) at full power and "step on that ball" with
right rudder.

Post script:  the rolling tendency caused by high power lower speed torque may cause the pilot to feed in more right aileron when the better input is coordinated with rudder.  As the plane accelerates from rotation and liftoff speed to Vy, it would be easy to miss you've rolled slightly to the right due to increased aerodynamic force.  In straight line flight this would not be a major problem (unless you were dangerously near aileron reversal stall speed).  I would work on glancing down at the ball as soon as safe climb is established, perhaps while checking airspeed.  Stay coordinated.


Have Eddy current brakes ever been used/tested on an aircraft?

Eddy current brake is a misnomer: it's a damper, not a brake as in a device that works on friction forces and can completely stop motion. Eddy current dampers do provide deceleration forces, by inducing whirly electromagnetic currents in a rotating wheel - they could provide extra emergency braking power without installing extra brake pads.

However, aircraft wheel brakes are dimensioned for emergency deceleration, can provide this adequately using friction pads, and their main problem is getting rid of the heat that is created. Eddy current dampers create the same amount of heat...


Does wearing glasses mean you automatically meet the first class medical requirements?

Certainly not.  Eyeglasses can't fix everything.  Some people have very poor vision even after correction with glasses.  One example out of many, would be someone suffering from macular degeneration.


Is it possible to fully utilise excess heat from an aircraft to power other systems required for the aircraft to function?

There are heat engines that convert heat into mechanical energy, which can drive useful things around the aircraft. Examples that actually drive systems that we use are

The steam turbine used for electrical power generation in remote area's, driven by the waste heat from gas turbines.
The stirling engine, used for driving submarines due to it being whisper quiet.
The classical steam engine, also very quiet.

All these engines come at a weight penalty of course. It makes a lot of sense to add a steam turbine to a gas turbine in a power station; adding a steam turbine next to the jet engine is less clearly beneficial. It has not been done.

So yes some of the waste heat of the aircraft engines can be used. But thermodynamics says that never all heat can be transformed - the theoretical maximum efficiency is a function of the maximum and minimum temperatures. Only a heat engine with a perfect Carnot cycle, a heatsink of 0 K or an operating temperature of $\infty$ K and no heat loss other than through the engine process will transform all heat. And we cannot make that in an environment that is neither 0K nor $\infty$ K.


What is the difference between instrument privileges and instrument rating?

The short answer is that the privileges are what the rating confers, and there are ways to get those privileges other than having the rating.

A commercial pilot licensee in most jurisdictions that follow ICAO certification guidelines may fly small planes for hire, doing service as a courier, air taxi, crop duster, etc. These do not necessarily require flying in IMC or in Class A airspace, and so a CPL holder must also have a separate "instrument rating certification" in order to fly IFR.

ATPL licensees fly in Class A as a matter of course, and that also often requires ascending and descending through the cloud ceiling which is IMC by definition. Therefore, the requirements for an ATPL in ICAO-compliant jurisdictions inherently include those required for the "instrument rating" applied separately to lower certification levels (private/commercial), and the resulting license for an airline pilot confers the same "instrument privileges" that the rating would.

Thus the difference in terminology; an ATPL holder in another country has "instrument privileges" as a consequence of his basic license and so does not need a specific "instrument rating". The same is not true for CPLs and so the law specifically requires the instrument rating as a prereq for a foreign CPL seeking an FAA ATPL.


Having trouble reading some charts (SBMG-SBLO)

Interesting academic exercise crimson_king. I don’t think you would get cleared for or use this SID/IAP combo. The airports are too close together. You are basically using your destination airport’s NavAid as the beginning/start of your departure. You will overfly the airport before you get to the VOR that starts the procedure. Then, you would have to backtrack out to the arc, using LON as your IAF.
The plate that you referenced is just an instruction on how to get to the start of your departure. There is probably a textual ODP to go with it. If you were in IMC, you would remain under radar vectors and ATC control the entire time. They would probably give you instructions like: Fly runway heading climb and maintain 5000 radar vectors direct D270L cleared the VOR Z Runway 13. This is of course abbreviated since you would have a switch of ATC from tower to approach.
Based on the information provided, For the purposes of simming, your best bet is to:

Take off from the runway of predominant wind.

Remain in the traffic pattern and climb over the airport.

Climb until you are at 5000 feet or more. The reason for this is that the only altitude information I see on the plate are the Minimum Sector Altitude and the Maximum Elevation Figures.

Fly direct to MG123 using RNAV/GPS.

Switch to VLOC/VOR mode

Fly direct to D270L.

Begin your IAP
A second option is to just fly direct to LON using your Nav radio by the shortest route possible. Use MG123 as a fly over reference point. Maintain full throttle at Vx until 5000 feet. Once you are within 12 miles DME of LON. Start your descent down to 4100 feet. Join the arc wherever you happen to enter.

Celia is not marked as an IF/IAF. So, I would avoid going directly there. It would be a perfectly good option if you were being radar vectored and cleared there by ATC.


How do I translate this propeller start procedure into English?

If the engine is already started, and if this is a turboprop with a constant speed propeller, it is most likely that the pilot is performing a pitch control check.  In this case the pilot would move the throttle into Beta, or reverse, which would momentarily cause the propeller to "push".  After this he would come back to idle, where if the propeller control lever was set to fine pitch or max RPM, the prop would spin "free".  The actual procedure and intercom voice calls will vary by aircraft and operator.

This answer presumes that he is not yelling out a window, or transmitting with aircraft callsign to a ground controller.  A video clip showing where he is on the ground, whether the prop is turning, and what his hands are doing at the time of the calls would confirm this.

If it is difficult to post a clip here, just watch what his right hand is doing:  If he appears to disengage a latch and pull the main power lever backwards, (you may hear an audible change in the engine sound as the propeller reverses pitch) and declares “propeller pushing”, then moves the lever back forward again and declares “propeller free” this would be pretty strong confirmation of my interpretation.

If that is the case, I might suggest a literal translation as you described in the question.  If you know the exact make and model of aircraft you could maybe narrow down what an English speaking pilot would say instead, but the literal translation wouldn’t necessarily be wrong either.


ICAO does actually recommend that names for significant points are unique:

3.4 The   unique   five-letter   pronounceable   name-code designator assigned to a significant point shall not be assigned to any other significant point.

However, as you already know, not all names are in fact unique. So why is that?

This is unnecessary (it would be possible to use unique names only).

No, it probably wouldn't. There are millions of named significant points around the world. Assuming points could be named completely randomly (any combination of 5 letters), just about 12 million unique names would be available (26 to the power of 5). However, points are not just named randomly, they have to follow some rules:

3.2 The  name-code  designator  shall  be  selected  so  as  to avoid   any   difficulties   in   pronunciation   by   pilots   or   ATS personnel   when   speaking   in   the   language   used   in   ATS communications.
3.3 The   name-code   designator   shall   be   easily   recognizable   in   voice   communications   and   shall   be   free   of ambiguity  with  those  used  for  other  significant  points  in  the same general area.

You can't just put together 5 letters in a unique way, you have to create a pronounceable, recognizable word, and it can't sound similar to other points in the same area. This significantly limits the number of options.

It introduces potential for confusion.

In theory, yes. In practice, this is not a problem. The risk of pilots navigating to a point with a duplicate name is next to none. Points with duplicate names are never located in close proximity, and most flight management systems will automatically select the nearest point, when inputting a route where duplicates exist. I'm not saying a mishap related to this issue has never happened in the history of aviation, but personally I have never heard of one, and I doubt I ever will.
All references from ICAO Annex 11, Appendix 2


Are there big differences between Douglas Commercial 3 and Douglas Commercial 4?

The DC-4 was a totally new design in all respects, as can be seen from the planform diagrams (wiki)

The DC-4 was larger, and structurally totally different:

Straight tapered wing (no sweepback)
Straight tubular fuselage, not the aerodynamic teardrop shape
Round fuselage cross-section. The original DC-4E was going to have a pressurised cabin. The later DC-4A did not implement this but retained the circular cross section necessary for pressurisation.
MTOW = 33,100 kg for the DC-4, 11,430 kg for the DC-3
Four engines of 1,081 kW each, while DC-3 had 2 engines of 890 kW each.
Tricycle landing gear instead of a tail dragger, as @Gerry points out.

All in all a larger aircraft, designed from scratch, implementing more modern features of a later age.


Would a vertical stabilizer that extends both above and below the centerline be benefit or hindrance?

As long as the vertical tail surface sits above the centerline (more precisely the longitudinal axis of inertia - for now we can assume both fall together), any side force will also create a rolling moment.  This is undesirable because now a yaw command will not only create the intended yawing moment, but also a rolling moment.

If you want to yaw in order to turn, the vertical tail above the centerline will even roll the aircraft in the wrong direction, so you need more coordinated aileron command than with a symmetrical vertical tail.

So the short answer to your question is: Terry is right: Extending the vertical tail below is clearly a benefit.

This can be seen by the widespread use of ventral fins in combat aircraft. Adding area below the centerline helps to reduce the roll contribution of the vertical tail in a sideslip, which improves handling characteristics (more directional stability AND lower yaw-induced roll). See the picture below for an example where the effects of additional vertical tail area are compared to the effects of a ventral fin of the same area.

At supersonic speeds, the low aspect ratio ventral fin has a nearly constant contribution to directional stability, whereas the wing-like vertical tail loses effectivity in proportion to the Prandtl-Glauert factor $\frac{1}{\sqrt{Ma^2-1}}$. The small ventral fin of the F-104 raised directional stability by 30% at Mach 2.

At high angles of attack, the vertical tail is in the wake of the fuselage which reduces local dynamic pressure and, consequently, effectivity. The ventral fin then is in ideal flow conditions, so it can help to stabilize the aircraft at high angle of attack, just when the fuselage contribution to instability is largest.


Where to find fuel type & fuel consumption info for PW 1000G engines family?

In this presentation from 2009 PW quote savings of 140 gallons on a 500 nm trip. I presume they are comparing it to current engine options such as the IAE V2500.


Why does an Avro RJ85 have four engines?

It was originally the BAe 146 and was designed for operating out of city airports such as London City Airport.

The main reason is for noise abatement. Back in the 80s, four high-bypass turbofans made a lot less noise than two contemporary engines.

Climb performance is also fantastic.  it can climb safely from most airports using much less than full power which helps keep the noise down and provides high safety margins when operating near built-up areas, for example if an engine fails on take-off.


What are the major differences in operating the Boeing P-8 Poseidon and Kawasaki P1 in the maritime patrol aircraft role?

Both the aircraft were designed as replacements for the Lockheed P3C Orion when the P7 was cancelled. While the USN decided to convert a civilian aicraft (as is the norm for most MPA), the Japanese decided to design theirs from scratch (the aircraft was supposed to share a number of items with Kawasaki C2, which given the wildly different mission requirements, didn't go very well). Almost all the differences between the two aircraft, which share a number of similarities resulted from this differing approaches to design.

The P8 was derived from 737, a commercial airliner, which means that it is optimized for high speed, high altitude flight. Previosly, the MPA were optimised for low altitude operations. The P8, on the other hand has (relatively) highly swept wings with raked wingtips, optimized for high altitude cruise. This means the development of modified operational procedures for this aircraft.

Image from ainonline.com

The P1, on te other hand, is purpose built to be a more or less a one-to-one replacement for the P3C, optimised for low altitude operation with strnthened structure. The wings are swept less and the wing area is relatively more compared to the P8.

Image from battlemachines.files

Operating the aircraft at high altitudes instead of lower ones also means that the operating principles are different. It is the main reason for the P8 not having the Magnetic Anamoly Detector (MAD), which was available in P3C (as well as P1, in the long boom in the tail). Last heard, UAVs are being developed with MADs to overcome this issue.
The P1 has larger windshields (which makes sense, as the crew would be able to scan better for ships at lower altitudes) and more hardpoints compared to the P8.
The P8 has only two engines compared to the four of P1, a significant difference. For aircraft operated in long stretches over areas without airfields, this could be a real issue. While so far no issues have been encountered in this regard, the loss of an engine in a P8 is basically a mission kill, which is not an issue with the P1.
The from-the-scratch development of the P1 alos has enabled the use of fly-by-light controls, which is a first for operational aircraft, allowing for lighter wiring and lesser interference.
One significant advantage of the P8 over P1 is that being based on one of the most successful and widely operated aircraft in history, spares and support will not be a big issue.


How much does the landing gear compress on a fully loaded airliner on the ground?

The value will obviously vary for different aircraft models (and also with the loading, c.g. location etc), but the usual range can be found in the airport planning document for the particular airliner, where the values for ground clearance for the aircraft at the OEW (max. value) and MTW (min. value) would be given. The difference should give you the compression.

For example, for Boeing 737-800, the quoted value is around 15 cm (plus or minus 7cm).

Image from 737 Airplane characteristics for Airport Planning document

Note that the different parts of the aircraft 'sink' different amounts- the fuselage sinks around 15cm, while the engines (mounted on the wings) sink more- by 16cm due to the fuel in the wings.

Another 'typical' aircraft, the A320neo sinks by about 10cm.

Image from A320 Aircraft characteristics for Airport Planning document

Note that the values are given here for max. ramp weight.


How do pilots of big jets determine if they are clear of the runway after landing?

Using TLAR (That Looks About Right).  Pilot turns off a runway onto a taxiway spur and sees the runway safety area lines and just estimates a point beyond roughly equal to or greater than the length of the fuselage and places the cockpit over that point.

Other methods include geo-referenced airport diagrams on a moving map display showing the position of the aircraft.


What is the difference between turbojet and turbofan engines?

Turbojets and turbofans are very similar indeed:

both are turbine engines;
both create thrust from jet exhaust;
and both have a rotating implement in front that can be called a fan. Although in the case of the turbojet, it isn't called a fan but the compressor first stage.

$\ $ Junkers Jumo 109-004

So what is the difference? There are five types of turbine engines, named after their main means of generating thrust:

Turbojets. The very first type of jet engine as used in the Messerschmitt 262: a compressor, combustion chamber, and a turbine. The turbine extracts enough power from the combustion chases to drive the compressor. All air flows through the engine itself, and thrust is generated by the exhaust flow only. Bypass ratio zero.
Low Bypass Turbine Engines. A bit of a lengthy, non-catchy description. Part of the airflow bypasses the main engine, and is compressed by the first stage of the compressor which has a larger diameter than the main engine tube. The turbine drives the compressor and the (low bypass) fan, exhaust flow from the turbine still generates a sizeable proportion of the thrust - inversely proportional to the bypass ratio, which is 0 < BPR < about 2.
Turbofans. Same as above, named after the large visible fan-like first stage. These engines are high bypass turbine, 5 < BPR < 15 and ever increasing.
Turboprops. Main source of thrust is a propeller, which has longer, fewer blades than a fan to limit drag penalties. The turbine drives the compressor and the propeller, some exhaust flow is still used for thrust generation - according to Torenbeek section 4.3.5, about 5 - 10% of the thrust is generated by the . BPR up to about 50.
Turboshaft. Main thrust source is a rotor or other torque requiring device, like an electrical generator in an APU. All net turbine power is applied to the drive shaft, no practical thrust from the exhaust flow.

The five types incrementally use bypass airflow to generate thrust. Increasing bypass air allows for accelerating a larger mass of air at a lower speed, generating the required thrust at a higher efficiency. But bypass air volume is inversely proportional to airspeed: the faster the aircraft, the lower the amount of bypass air that can be utilised. At supersonic speeds, bypass air is very problematic for thrust generation.

The picture below shows the Olympus engine used for propelling Concorde, a pure turbojet with 2 axes and 7 compressor stages per axis.

The GE CF6 with BPR of about 5 depicted below was used for B747, A300 and DC10, and is a turbofan: the first stage of the compressor sticks out over the remaining stages, and bypasses most of the air inflow outside of the main turbojet engine. This bypass air is the main distinguishing feature between turbojet and turbofan. Visually, the large fan is very distinguishable of course.


Why is water-contaminated fuel bad, but water-injection is not?

Because of the quantity of water in the fuel, as opposed to a careful introduction of water into the combustion process.  Typical water contamination is bad in fuel tanks as water is denser than aviation fuels and settles at the bottom of the tanks.  Aviation fuels are also hydrophobic (non-polar) and so do not readily mix with water.  Therefore water will settle unmixed at the bottom of the tanks, in the fuel sumps or feeder hoppers and when ingested into the engine will fuel starve it and cause it to shut down.  Water in fuel lines can also freeze there during cold weather, causing fuel starvation as well.

Fuel samples should always be taken of the gas when it is both in storage as well as prior to flying the aircraft, especially after rainstorms or the aircraft has sat on the ground for long periods with low fuel in the tanks in a humid environment.  Fuel samples should also be taken approximately 30 minutes after refueling and the gas allowed to settle in the tanks.  A preflight sample of water contamination taken from the fuel tank sumps of a GA aircraft can be seen here.

Water injection, however carefully controls the amount of water going into the engine along with fuel at the point of combustion, allowing for continued engine operation.


What is the name of the movement which is carried out by plane beginning from the runway and ending at takeoff?

Takeoff Roll

As per the FAA handbook (page 5-2)

  Takeoff roll (ground roll) is the portion of the takeoff procedure
  during which the airplane is accelerated from a standstill to an
  airspeed that provides sufficient lift for it to become airborne.

And after that

  Lift-off is when the wings are lifting the weight of the airplane
  off the surface. In most airplanes, this is the result of the pilot
  rotating the nose up to increase the angle of attack (AOA). >
  The
  initial climb begins when the airplane leaves the surface and a climb
  pitch attitude has been established. Normally, it is considered
  complete when the airplane has reached a safe maneuvering altitude or
  an en route climb has been established.


When to switch from ground to tower frequencies at controlled airports in the US?

While I acknowledge the answer by GdD to not change frequencies until instructed, that is at odds with my experience.

When I call Ground, then request and receive taxi-instructions, I stay with Ground to the runway hold short line.   I've never had Ground give me an explicit instruction to switch to Tower.

When I start my run-up checks, I switch to Tower (unprompted) to start hearing what is happening in the airspace.  When my run-up is complete, I call Tower with a "ready for takeoff".

I've never had Ground, Tower, or any Instructor tell me differently.  I've never observed another pilot wait for an explicit frequency change instruction from Ground, and I believe that is the way I was taught.

Note: this only applies when you've taxied to the hold-short with Ground.  If Ground tells you to switch earlier, do it.  If you want to switch earlier, request it.


How are aircraft protected from lightning strikes by conductive skin?

Lightning striking a metal aircraft

  A commercial aircraft [...] is struck several times during its whole service life.
  In such a case, the airplane acts like a lightning rod. Its metal structure provides the lowest resistance for the electrical discharge on its way between the clouds and the ground. It is not uncommon that the airplane is thereby struck by a complete series of discharges, mostly between three and five, in exceptional cases up to 25.
  Since an airplane in flight has no form of grounding, the lightning first enters the structure and leaves it again a split second later. The principle behind this occurrence is known by most people from physics lessons in school. The airframe acts as a so called "Faraday Cage". Like an automobile body the aluminium structure, when struck by a lightning, passes the electric energy around the interior and keeps the passengers safe.
  The crucial technical equipment is thereby also kept safe from the high voltage and the aircraft can, in most cases, proceed normally with its flight. But to play it safe every lightning strike is documented by the cockpit crew and the aircraft is treated with a special inspection routine on its next check.

  Source: "Lightning Strikes During Flight", Lufthansa Technik

Lightning striking modern aircraft with composite structures (as noted by this comment)

  Composite parts that are in lightning-strike prone areas must have appropriate lightning protection. [...] Composite structures are less conductive than metal, causing higher voltages.
  Lightning protection on airplanes may include wire bundle shields, ground straps, composite structure expanded foils, wire mesh, aluminum flame spray coating, embedded metallic wire, metallic picture frames, diverter strips, metallic foil liners, coated glass fabric, and bonded aluminum foil.
  Lightning can also damage composite airplane structures if protection finish is not applied, properly designed, or adequate. This damage is often in the form of burnt paint, damaged fiber, and composite layer removal.

  Source: "Lightning Strikes: Protection, Inspection, and Repair", Boeing, 2012

New technology improving the lightning protection of modern aircraft

  Traditional methods to protect composite aircraft from lightning strike damage rely on a conductive layer embedded on or within the surface of the aircraft composite skin. This method is effective at preventing major direct effect damage and minimizes indirect effects to aircraft systems from lightning strike attachment, but provides no additional benefit for the added parasitic weight from the conductive layer.
  A new multi-functional lightning strike protection (LSP) method has been developed to provide aircraft lightning strike protection, damage detection and diagnosis for composite aircraft surfaces. The method incorporates a SansEC sensor array on the aircraft exterior surfaces forming a "Smart skin" surface for aircraft lightning zones certified to withstand strikes up to 100 kiloamperes peak current.

  Source: Szatkowski, G. N. at al.: "Open Circuit Resonant (SansEC) Sensor Technology for Lightning Mitigation and Damage Detection and Diagnosis for Composite Aircraft Applications", NASA, 2014

Further information can be found on the internet, see for example "Playing with Lightning in the Name of Aircraft Safety", NASA.

For the science behind the Faraday Cage and lightning striking insulators, please refer to Physics.SE.


What is this c. 1948 private plane with a sliding canopy?

It looks like a variant of the Ryan Navion, probably the North American L-17A aka the poor man's mustang.

North American L-17 Navion, Camarillo Airport Museum, Camarillo, California, USA; By Howcheng - Own work, CC BY-SA 3.0, Link


How does 'standalone' propeller efficiency change with altitude?

Yes, the same propeller can be used.
Propeller thrust is proportional to air density. The same is true for aerodynamic drag, so your propeller will work at all altitudes equally well. Since the speed of sound drops with temperature, you need to pick your propeller tip speed for the coldest layer, which normally is the Tropopause. There, the speed of sound is 295 m/s and if the propeller tips don't exceed 85% of that, efficiency should be roughly constant over altitude. A small loss in efficiency with altitude must be accepted, however, since the propeller's friction drag increases with altitude.
This would not be true for airplane propellers where the drag of the airplane they are propelling is constant (actually, rises a bit) with altitude, but since your thrust demand drops in line with density, no new propeller is needed at 85,000 ft.


Puzzled by description of AoA malfunction theory on recent Lion Air accident

The Operations Manual Bulletin put out by Boeing suggests that this is a trim runaway event.  Airspeed and altitude measurements are affected by the angle of attack of the airplane.  The indicated airspeed will be lower in a high angle of attack situation.  The accident airplane was reading a higher angle of attack than reality due to a malfunction of some kind.  The new avionics in the Boeing 737-MAX correct the airspeed measurement for angle of attack so airspeed was reading higher than what it should have been.  As a result the automatic trim, which is set to keep a constant airspeed, kept trying to lower the nose since the reported airspeed was too high.

The 737-MAX Operations Manual Bulletin included procedures to disable the automatic trim.  This runaway trim event occurred during the 3 flights before the accident flight but maintenance was unable to fix the problem.

More information on the accident can be found at the Aviation Herald.


Is there a universal departure recovery procedure?

The answer depends on the aircraft. In most cases it is No, but for some it is Yes.

The MiG-29 has a green button at the right side of the stick which recovers the aircraft to a wings-level, shallow climb attitude if pressed. Note that the MiG-29, unlike its Western counterparts, is aerodynamically stable over the full angle of attack range beyond 90° and the flight control system can recover the aircraft from any attitude, altitude and thrust permitting.

Here is a quote from someone reporting his experience of flying a Malaysian MiG-29 (link)

  The stick has a red autopilot button on the left and a green auto
  recovery switch on the right for the disoriented pilot, and works by
  pressing the green panic button. The system recovers the jet to wings
  level and places the airplane in a slight climb if energy is
  available. This system is known to be reliable but is not often used.
  This is most likely due to the necessity of having to recognize that
  you are spatially disoriented prior to pushing the auto recovery
  button.

MiG-29 cockpit (picture source). The green button is clearly visible.


For airliners, a lot of money, in the tens of thousands or more. Thales Aerospace is one of the manufacturers of AOA's for transport and military aircraft -- the word "cheap" does not exist in their vocabulary and "inexpensive" is a matter of opinion. For GA aircraft they are significantly less expensive, about US\$2000 or less. For aircraft with other than standard airworthiness certificates (experimental, homebuilt, etc.) the cost falls well under US\$1000. Sometimes manufacturers don't call them AOA's, and instead refer to them as "Lift Reserve System." For a general idea of the cost of GA AOA systems, check Aircraft Spruce and search for "AOA".


The primary reason is availability -- the high pressure fuel pump is running whenever the engine is, while the airframe hydraulic systems may not be available in case of an accessory gearbox failure, hydraulic leak, or maintenance shutoff.

Also, this keeps hydraulic lines from needing to be plumbed deep within the bowels of the engine -- this has benefits in that the hydraulic system is confined to the accessory gearbox fire zone (where the engine driven pump lives), instead of having to run in several engine fire zones.


Can an IFR clearance be issued and flown through IMC in class G airspace?

The key point is in your last sentence:

  In the case of class G airspace from the ground, the airspace is uncontrolled.

Uncontrolled airspace is, well, uncontrolled. An appropriately rated, current pilot, in an appropriately equipped aircraft, may fly IFR in class G airspace without either a clearance or a flight plan. There are no clearances to waive VFR minima in class G, because the flight is conducted under IFR.

If an entire flight is flown in class G airspace, a pilot does not need to talk to a controller at all. When class G airspace is overlaid by controlled airspace, like class E, the pilot will need a clearance before entering controlled airspace. The controller will provide a clearance (FAA Order  7110.65, p. 4-3-2):

  WHEN ENTERING CONTROLLED AIRSPACE (instruction), FLY HEADING (degrees) UNTIL REACHING (altitude, point, or fix) BEFORE PROCEEDING ON COURSE.

Once the pilot is released for departure, they would depart IFR in class G, where they would be responsible for their own terrain and traffic clearance (using tools like an Obstacle Departure Procedure). As soon as they climb into class E airspace, they receive the benefits and responsibilities of flying in the ATC system.

An interesting border case is raised by wbeard52. In this case, a pilot departed a class G airport with class E starting at 700 AGL, and broke out of the clouds before entering controlled airspace. The ruling basically said that taking off in this situation without a clearance is not explicitly illegal, but falls under "careless or reckless operation" prohibited by FAR 91.13.


Why does an airliner have a shallow descent when heavier, opposite to gliders with ballast?

If you can forgive my limited Paint skills:

It's the variable/constant speed that makes the difference.

Weight changes endurance (time to ground) and not range (distance to ground) if speed is adjusted to match the new weight.
Weight changes the speed for best L/D, but does not ever change the best L/D ratio (and thus best range)

For gliders (which are adjusting speed to new weight):

ballast allows them to fly faster while maintaining best L/D. Pilot will increase speed to keep same (best) gliding ratio, albeit at an increased descent rate (fpm). You get there faster, in an increased rate, but same gliding distance (to the ground eventually).

For powered airplanes (flying at set speeds regardless of weight):

pilots usually descend from cruise at fixed airspeed, usually much above the best L/D. Higher weight means the aircraft is much closer to best L/D speed, so the flight path is much shallower. You get there in the same time, but you will be much higher when heavy.

Or if it is easier to think this way, a light aircraft is a lot further away from its best L/D speed than a heavy one, when flying an approach. Naturally this makes the light one descend more steeply.

Note that this all refers to a normal descent from cruise. Final approach speeds, just before landing, are indeed corrected for weight in a large airplane, and heavy ones will indeed have a higher Vref and land slightly faster.


Does adding a motorized fan to a hot air balloon change its class as an aircraft?

Well, a balloon already is an aircraft, specifically:

  A balloon is a lighter-than-air aircraft that is not engine driven, and that sustains flight through the use of either gas buoyancy or an airborne heater.

So if you were to attach engine-driven propellers to your balloon it would no longer be a "balloon". It would start to sound a lot more like another kind of aircraft -- an airship:

  An airship is an engine-driven, lighter than air vehicle that can be controlled in flight.

So from a licensing standpoint there would appear to be two major considerations: First the pilot of such a chimera would need to be licensed to act as pilot in command of an airship (not a balloon), and second the modification itself would have to go through appropriate regulatory channels, since it is changing the fundamental nature of the aircraft in a way that would almost certainly attract some scrutiny.

Specifically regarding the fans/propellers you're talking about, it looks like those are intended for use as inflation fans to help you out when you're setting a hot-air balloon up - once you've got the envelope inflated and the heater is doing its job you don't really need the fan anymore, and you would leave it with your ground crew.

As far as I can tell they aren't intended for use as engines for moving and steering a balloon - I suppose you could carry one aloft with you if you were feeling bold, but I'm not sure what the impact of doing so would be from a regulatory standpoint when it's not permanently attached to the balloon, and I'm not sure how effective they would be as propulsion with only a few horsepower behind them.


How do large airliners de-ice in flight?

Putting this as an answer rather than a comment because of its length.

In response to @romkyns comment, perhaps the 787 pilot knew of the heating elements within the wing but was simply telling how ice was normally handled. I really can't imagine him getting through his type rating oral without knowing that.

Had you asked me the same question back when I was flying 747-100 and -200 aircraft, I would have replied thus:

Icing isn't typically a problem because you're usually not in it long enough at a slow enough speed that the ram air temperature rise doesn't get the temperature above freezing.

If you are getting ice on climb out at your normal climb speed, it was usual to ignore it knowing that the icing would soon stop as you gained altitude, and then what icing you had would soon sublimate. If the icing was severe enough to warrant your attention, the usual remedy was to just speed up to get more ram air temperature rise, but you would, of course, be sacrificing some of your climb rate. The U.S. has a 250kt speed limit below 10,000 feet, but you don't have to (or at least didn't have to back then) observe that if there was an operational need to go faster, and generating enough heat to take care of icing was considered a good reason. You normally wouldn't have to think about that though because a 747 climbing out with flaps up has a minimum safe airspeed in excess of 250 anyway.

One indication that the icing was serious was that ice buildup on the windshield wipers would set them to vibrating and giving off a loud buzzing sound. If you let them do that too long, they could depart the aircraft. As I understood it, the time for that to happen was cumulative over the past occurrences as well as the current occurrence, as it was a matter of fatigue.

If you were icing on the approach and didn't want to or couldn't speed up, you could heat the wing leading edge with pneumatic air as described in previous answers. However, it was the leading edge slats that were heated, and when you selected the first notch of flaps, that deployed the leading edge slats, and the heated pneumatic air escaped with little or no effect.

Only once in 10 years of 747 flying did I use the leading edge heating. We were in a holding pattern at low altitude waiting for our turn for an approach into Brussels.


What risks come from passengers taking baggage during emergency evacuation?

As soon as there's a fire on board, the absolute top priority is getting everybody out as soon as possible. Aircraft are designed in such a way that, even after a crash landing (or other serious malfunction), the passengers will have a minute or two to evacuate before conditions in the cabin become toxic (fire, smoke, etc); this is done by using flame-retardant material and burn-through protection, but in an intense fire these won't protect the cabin for long, and once they fail no-one will be able to survive inside the aircraft for much longer than that. Smoke inhalation and oxygen deprivation kill just as effectively as being burned.

Therefore everyone has to be able to evacuate from the plane within 90 seconds, even assuming the plane is packed to the gills with passengers, and half the exits are inoperative. Given that the aircraft may be damaged after  a rough/crash landing, some of the doors may be unusable (due to fire or smoke just outside them), it may be dark in the cabin, and people may be injured and/or panicking, it's vital that nothing slows down the evacuation. To get an idea of what a 90-second evacuation of a fully-loaded aircraft looks like, see the video of the A380 evacuation test - and these passengers were calm, uninjured, and prepared. If passengers take hand luggage with them this is slowed down:

The time it takes to get it out of the overhead bins (with everyone else crushing against you to get out).
Carrying the luggage down the aisle (without tripping, hurting yourself or anyone else - again, look at the A380 video, and imagine trying to do that with a suitcase). If you lose your luggage, everyone behind you will have to climb over it to get to the exit.
Maneuvering your suitcase around the corner to the door, not getting it stuck on the door frame, with people behind you literally shoving you out the door.
Plunging down a very steep slide the height of a two-storey building (or more, in case of the A380's upper deck) at high speed, with your suitcase flailing around. At best it whacks you on the head, at worst it punctures and deflates the slide, which given the crush of passengers behind you will probably lead a few people to plummet from the aircraft doors straight to the ground.
Assuming you've made it to the ground, there is someone else plunging down the slide right behind you. If your suitcase slows you down even a little, they will plow right into you, and soon you'll have a crush of people at the foot of the slide.

In this specific case, the fire was fortunately not serious enough to defeat the cabin fire protection before the last passengers had evacuated - but as @Andy said, there are unfortunately other examples where the passengers were not so lucky. To illustrate the risk of fire after landing: Air France Flight 358 ran off the runway at landing, and despite having little fuel on board, the resulting fire completely destroyed the aircraft; luckily, everyone evacuated in time. Once there's been a major malfunction, there is no way to tell how much time you have left to get out - fire can spread very very quickly - and so you have to get out as quickly as possible. Taking luggage with you endangers your life and that of your fellow passengers.


What is the difference between a shock wave and an expansion wave?

An adiabatic expansion lowers temperature, an adiabatic compression raises temperature, analogous to the way a refrigerator and an air conditioner work. Or a bicycle pump, it gets quite hot while you're pumping air.

A shock wave compresses air - at supersonic speeds the object travels faster than the pressure information, and when the object arrives at a bit of air it compresses suddenly in a shock wave, with corresponding higher temperature.


How to make use of linear acceleration and gyroscope data?

You integrate accelerations to get speed and integrate speed to get position. So if you have angular speeds or even orientation, I don't see any use for angular accelerations. That does not mean the unit does not use them internally when calculating the angular speeds and/or orientation.

The linear accelerations can be used for dead reckoning. Airliners, and increasingly any plane with glass cockpit, have inertial navigation system that integrates the accelerometer and gyroscope data to keep track of position. It used to be primary means of navigation over ocean before GPS and now it is still used as backup if GPS signal is lost and for compensating errors by cross-referencing.

The lateral acceleration is also shown by the slip-skid indicator (used to be accompanied by turn rate in turn indicator, but glass cockpits often only have attitude indicator provided it is non-tumbling and maintains precision at unusual attitudes; see also When/How may I replace the Turn Coordinator with an Artificial Horizon?).


Can I Return Back to the Destination Airport after I Diverted to the Destination Alternate?

There are no regulations in the US that state you must land at a particular airport. It will be even more difficult to find one that says you can return to your original destination after announcing or performing a diversion. There are only regulations stating that you have to list a destination airport on an IFR flight plan. And, that there are certain situations when you must list one or more alternate destinations on an IFR flight plan.
VFR flight plans are not required in the US. Even if you file a VFR flight plan, ATC will not be made aware of your flight plan unless it is not closed prior to half an hour after your ETA. In which case, only VFR aircraft on VFR Flight Following will be tracked by ATC. The pilot can cancel a flight plan (IFR or VFR) or flight following at any time that the pilot is in VMC, entering Class G airspace or landed. Otherwise, you must fly your filed IFR flight plan all the way to your clearance limit or your alternate (once you have informed ATC of your diversion). But, you may also amend your flight plan or Flight Following at any time.
Case in point. I have diverted to an airport just to take an unplanned bathroom break. Before diverting, I informed  ATC of the diversion as well as requesting to keep my flight plan and transponder (squawk) code. When returning to controlled airspace, I was able to continue onto my original destination.
Another example of continuing on to your original airport after diverting is when the diversion airport is en route to your original airport. Having an alternate airport planned that is halfway to your original airport gives the pilot a convenient out or Plan B if the weather ahead starts turning hazardous. If the weather improves before you reach your alternate, you can continue onto your original (after informing ATC if on an IFR flight plan or Flight Following).


How do airlines manage routes when respective aircraft undergo B,C or D checks?

Essentially they plan on some fraction of the fleet undergoing some sort of maintenance check at any one time, so they build their flying schedule around the remaining fraction.  And then there is some amount of flex due to things needing unscheduled maintenance or coming out of maintenance early.

What makes the task easier is the fact that maintenance needs can be forecast fairly far in advance, and so the schedules can be built around a knowledge of how many aircraft are likely to be available.

As an illustration (not necessarily representative of any particular airline's actual numbers), let's say you have a fleet of 200 aircraft, and you know that on average each aircraft will be down for two 2-week heavy maintenance checks each year.  That works out to essentially one month out of 12, each aircraft is down, or a little under 10% of the time.  Add in a little time for shorter maintenance visits (but still longer than an overnight), plus an allowance for the fact that some aircraft just need unscheduled work, and the maintenance planners may end up telling you to plan on 175 aircraft available each day.  So that's what you build your schedule around.

Now let's say that one aircraft takes a birdstrike & an engine needs to be changed.  That is now a hole in the schedule.  It can be covered by cancelling a flight (undesirable, but always an option).  If an aircraft is finished with maintenance ahead of schedule (say it was scheduled down all day for some work, but the work is actually done by noon), that aircraft may be able to be put into service.  Perhaps it's possible to delay some sort of minor maintenance a day (not a heavy check, but something quicker) and essentially create one aircraft-day of capacity, and push the check off to a weekend day when the schedule uses fewer aircraft.  Or maybe the schedule was built with one or two aircraft available as spares that day.

Depending on a variety of factors, spares may or may not be available, or even deliberately built into the schedule at all.  Having an A-380 sitting around unused all day is an EXPENSIVE insurance policy against something unforeseen happening, but cancelling a flight on something that big is an expensive event when it happens!  If you operate all out of one giant hub and you know that your fleet of 500 aircraft (flying 450 lines every day) is likely to have 2-4 aircraft every day go to the hanger for unexpected maintenance, it's probably a good financial decision to allocate two or three of those lines as dedicated spares.  If your aircraft operate a point-to-point schedule, it's harder (or unfeasible) to keep a spare aircraft at every airport you serve, "just in case" something happens to break there.

There are complicated decisions that airlines will continuously evaluate to find what balance works best for their particular operation.  In some cases, it may be possible to substitute an aircraft from a different fleet for a broken jet... an MD80 goes to the hanger, and a 737 with a reserve crew flies the rest of the day that the MD80 would have flown.  Or maybe a 757 broke, and the decision is to use the 737 to cover the flight, and re-accommodate the extra passengers that the 757 could hold that the 737 now can't.  That's a tactical decision that the airline's operations center will make, considering the availability of both aircraft and crews, as well as the passenger loads.  (They also may pull a "healthy" 757 off of its less full schedule to fly in place of the broke 757, use a 737 that wasn't going to be very full to cover that 757's route, put an RJ on the 737's route that day, and cancel the RJ's flights "due to maintenance."  And if that inconveniences 4 flights of 40-50 people who mostly just get delayed a few hours, that's probably a better plan than stranding two flights of 200 people who'd otherwise have no way to get where they're going until tomorrow or later.)


Why don't aircraft use gimbaled engines instead of flaps?

Historically, flaps and control surfaces were moved manually: The pilot would move a stick, a control column or pedals, and pulleys or pushrods would transfer this force to the control surfaces. To do this with engines was physically impossible.

With the introduction of hydraulics, large enough forces for tilting engines were available for the first time. Some aircraft used them, but this application did not find widespread use because the possible lift increase was smaller than what could be achieved with flaps. The same goes for controlling the aircraft: Directed thrust control forces are much smaller than what was possible already with control surfaces. Also, the responsiveness of tilting a heavy engine is much worse that that of a light control surface. Consequently, moveable engines were mostly used for short take-off and landing (STOL) applications. The Do-29 was one of several experimental aircraft which could pivot the propellers to take off at lower speed. Note that in case of the Do-29 the engines stayed in place; only the propellers and their driveshafts would move. Other designs would tilt their wing and with it the wing-mounted engines. In all those cases this was only done to enable short take-off runs, not to control the aircraft.

Do-29 in the Dornier museum (picture source)

Other applications were for special cases like flying boats:

The Dornier Do-26 could tilt the rear engines up for operation on water to reduce the impact of spray on the propellers (picture source). Note that this was not for control, but for lifting the props out of the spray area.

Control surfaces are better suited for creating control moments:

Control surfaces sit at the ends of the aircraft, so they have a much better leverage. Engines were placed close to the center to minimize the control problems caused by a loss of a single engine.
Control surfaces modify the lift force, whereas engines modify thrust, which is in the order of magnitude of drag and, consequently, an order of magnitude smaller than lift.

However, this is only true as long as aerodynamics works in a linear fashion. Which is not the case with separated flow and stalled flight surfaces. To overcome this limitation, the exhaust stream of jet engines is deflected by pivoting the nozzle (or paddles, as done on the X-31). This is much easier to do than to move the whole engine. Also, since the engine stays aligned with the airframe, the intake will continue to work and the frontal area of the airplane does not increase; both important considerations which stand against pivoting the whole engine.

Vectoring nozzles on the Sukhoi 35 (picture source)

Generally, aircraft are controlled by changing moments which in turn rotate the aircraft such that the desired flightpath change is effected by the changed aerodynamic forces. There have been attempts at direct force control, however: One Dassault-Dornier Alpha Jet was fitted with moveable wing pylons which could be rotated around a vertical axis. When moved, this would create a side force which enabled the pilot to directly shift the aircraft's flight path sideways. With moment control, you first need to roll the aircraft in order to tilt the lift vector sideways and then roll back shortly before the desired sideways change is complete. This is much harder to get right with moment control than with direct force control, especially for small corrections.


Why fluids are forbidden in flights, while nitrate- and peroxide compounds aren't?

First of all, your statement, that it's not allowed to bring any liquid (gels, spray cans, ...) with you on most airports is simply not true.

In the EU, any liquid must be in containers of not more volume than 100ml, and all containers must be in a transparent, close-able plastic bag of not more than 1000ml.

In the US, the rule is the same, but the limits are a bit lower for smoother numbers, like 3 fluid ounces (~90ml) and 30 fluid ounces (~900ml). (I'm not absolutely sure about this values...)

The reason behind this is... not very clear. There is a big anti-terrorism stamp on this rule, but if you question the rule, there is no reasonable answer. You can bring enough toxic substance in that bag to kill everyone on board, or even explosives to put the aircraft down.

If you ask me, the entire rule is there because the authorities wanted to make a rule to demonstrate that they are taking action. Remember that liquid baby food and personal medicine is excluded from the rule. Do you think terrorists would not abuse these exceptions? I still think this was the biggest coup ever of cosmetics and plastic bag sellers... (The latter could advertise explosion-proof bags... )

Sorry, I went a bit off-topic.

In general, it's easy to check carry-on luggage for liquids, as they (or their cans) are clearly visible on X-rays.

Explosive or oxidative material like your nitrate- or peroxide compounds are also in general banned from aircraft, from carry-on as well as from checked baggage.

However, they are hard to see on X-rays, especially if you put them into a less obvious shape. Manual inspection of your luggage would be the only way to search for these substances. In case of doubt, the staff at the safety check can do a wipe test, which means they wipe a small, special card over your carry-on (also from inside, and may be, they also check you). The card is then inserted into an analysis device, which can identify traces of forbidden substances, like explosives and drugs.

Here is a picture of a wipe test, with the analyzer in the background:

Demonstration of wipe test. Source: http://noe.orf.at

I remember flying from Zürich with a bag full of electronics. (Laptop, Laptop charger, mouse, another mouse, headphones, camera, camera charger, camera-to-laptop-cable, custom PCB, ...) and they did a very, very, really very careful wipe test.


How do the Kaman K-225 rotor "planes" work?

These are a form of servo flap, commonly found on Kaman designs, but also on at least one early helicopter (namely, a coaxial rotor aircraft built by d'Ascanio (shown below):

As opposed to controlling blade pitch from the blade root using pitch links (which are, essentially, pushrods), as in a typical rotor head, the servo flaps allow for pitch to be controlled by a control surface on the blade (similar to how controls work on a fixed-wing aircraft).  The yellow "wing" is the flap, and the black item, I'd imagine, contains a hinge and actuator rod to pitch the flap up and down, generating a force at a small moment arm behind the blade, which then alter's the blade's pitch as desired.  Instead of using an actuator to twist the blade, you're using aerodynamics to do a lot of the work for you, similar to how a fixed-wing aircraft works (except, instead of changing the rotor's effective angle of attack, you're twisting it instead).

Hence, if you look closely at the first picture you posted, you'll noticed that there is no swashplate, no pitch links, and really nothing reaching up the rotor mast from the helicopter except for a structural brace.  This system does away with pitch links and their associated actuator systems and can decrease total system weight.  In addition, as the flaps are significantly more streamlined than a typical pitch link, there is a possibility for drag savings as well.  Compare the following two rotors heads -- the first is a semi-rigid 2-bladed rotor from a Bell 230, and the latter is a typical Kaman rotor head.  The Kaman head is a picture of simplicity when you realize the only bits sticking out in the wind, beside the blade grips, are bump stops.

Bell 230

Kaman H-43

However, there's no free lunch.  The price you pay for all this is that, instead of an actuator somewhere relatively "easy" (on the body of the helicopter), you have to put an actuator (albeit a much smaller one than would be required to drive traditional pitch links) out on the rotor blade and feed both control and power out to it.  Control and power isn't too bad -- it's already done for anti-icing gear to some extent -- but the actuator can be tricky, particularly, I would think, in terms of tuning blade dynamics.  Kaman (who built the K-225 and the highly successful KMAX, which also utilizes servo flaps) found a way to do this that works great, but it hasn't really made a splash in any other manufacturer's helicopters (to my knowledge).  Rumor has it that Sikorsky and Northrop put together an entry for DARPA's Unmanned Combat Armed Rotorcraft program that had servo flaps on it, but that program got cut in 2004...so who knows?  In the interim, swashplates have been the control method of choice for upwards of 80 years and work well for those who don't have experience with flaps.

Sources: https://www.helis.com/howflies/servo.php and rotor dynamics class.


How is a transonic aircraft longitudinal stability different than a subsonic and supersonic aircraft?

At this level, there is nothing special about transonic stability.
Generally, airplanes become significantly more stable at supersonic speeds (due to aerodynamic center moving backward). At the same time, elevator efficiency drops. Transonic is simply the transition between the less stable subsonic regime and more stable supersonic regime.
Now, for an engineer as well as a pilot, transition can be a challenge, especially if it's quick. For example, most supersonic aircraft have variable stick-to-elevator ratio, and transition happens at transonic speeds. Apart from making sure that the aircraft is controllable throughout the transonic range, you need to consider what happens if the system fails at any stage.
As another example, modern fighters are often made longitudinally unstable. But this is only true at subsonic speed. They are all stable at supersonic regimes. Now you have transition between even more different states: unstable to stable (and back). Flight control systems must cope with that.
Thankfully, the transition is not too abrupt, especially for swept wings. (This, controllability, is in fact one of the main reasons to use swept wings. It's not just about drag).


What is the meaning of T/O Thrust => TRQ / N1 in a flight log?

Jet engines use N1, EPR, or lately (Airbus A350) Thrust % values for takeoff power.

Turboprop aircraft use torque. So it's either N1 or torque for your software depending on which aircraft is used for the flight.


Can the touchdown RVR be replaced by the midpoint or rollout RVR?

I'll start by pointing out from Wikipedia that—

  [The RVR] values obtained are not a reliable guide to what a pilot can actually expect to see. This can easily be demonstrated by the fact that when obscuration such as fog is variable, different values can apply simultaneously at the same physical point.

They give an example for that.

The answer to your question is yes it's possible to use the midpoint RVR if the touchdown RVR is inoperative. But, authorization is required, and it cannot be used for ILS CAT II and III.

  If the touchdown RVR VS is inoperative, some operators may be authorized, via OpSpecs, MSpecs, or an LOA, to substitute an operative mid-point RVR VS for visibility minima greater than or equal to 1,800 RVR.

Source: FAA 6560.10C


What are the flight training options for a private pilot's license in the US?

There are lots of options. Flight training is the US is usually divided into part 61 and part 141. Part 61 is general flight instruction and any FAA approved instructor can teach you under it: many part 61 instructors are independent or work for or with FBOs at GA airports. Part 141 governs flight schools that have a standard curriculum and are much more structured; they're often associated with training commercial pilots looking for airline careers. The license you get is exactly the same whichever way you learn.

There are pros and cons to both approaches, this article summarizes them well but the most important general point is probably that part 61 is 'one on one' training so it can be tailored for you and fit your schedule, whereas part 141 is 'school' training and if you can't follow their schedule then it usually isn't possible anyway. For that reason, part 61 is often the only practical option for many private pilots who have jobs and families.

Perhaps your real question here is "how do I find an instructor?", in which case you need to search the web, check out local FBOs and flight schools, ask for recommendations from pilots you know and so on. It's definitely worth investing some time to find the right instructor for you, because that can make a huge difference to your progress (and your costs).


How do helicopters avoid detection from enemies by using IR suppressors?

An IR sensor detects objects that are at a higher (or lower but that's not how missiles work) temperature than the surrounding environment, most of the helicopter won't be that much hotter or cooler than the air around it, so wouldn't distinguish it much unless you get very close. Jet engine exhaust is much hotter than the surrounding environment, so it shows up very clearly to an IR sensor from far away.

A suppressor diffuses hot exhaust into a larger air mass, lowering the temperature of the exhaust compared to the surrounding air before the sensor can see it. Lower temperature means less heat for a sensor to see.  A suppressor also makes the infra-red picture fuzzier, i.e. less of a distinct point. The lower temperature and fuzzier image decreases the effective range for a sensor, meaning it would have to be closer to detect it. Suppressors often deflect exhaust, pointing it away from where a sensor would be expected to read, or shield the exhaust.

Suppressors don't prevent an IR detection in the same way that stealth doesn't prevent radar returns, but a suppressor means you need to get closer.


Is the Soloy Dual Pac recognised as two engines or one engine?

According to the certificate is a

  Twin Power Section Turboprop

and, later, note 7: (emphasis mine)

  This engine is certificated as a unit comprising two separate power sections with the capability of single engine operation with either power section alone in multi-engine airplanes. The unit is also approved as a single engine with either or both engines operating continuously.

No explicit remark is given about pilot licensing, but given the note reported, I would say that a licence for a single engine is sufficient.


What VFR cruising altitude should be flown to the west below 4500 feet?

Yes, you would have to comply with §§91.159.  If you’re flying VFR westbound (180°-359° magnetic) at >3000 ft AGL,  you will need to fly at even thousands + 500 ft, except while in a holding pattern or turning.  For a forecast of scattered clouds, you will simply deviate from your course for cloud avoidance, then return to the route.


Time of flying from Toronto to Philippines

A direct flight from Toronto to Manila is about 16 hours. It is classified as a "Polar" flight and very little of it would be over the open ocean.

Depending on the weather and upper wind conditions, you would be initially flying either North East, or North West, from Toronto.

Most of the flight will be over land, with some of it over the frozen Arctic Ocean or Sea of Okhotsk near Russia.

FlightRadar24 PR119/PAL119


Static wicks are mostly found on aircraft that fly in Instrument Meteorological Conditions because static charges typically build up when flying in precipitation, not in clear air.

So you won't find static wicks on helicopters that are certified only for visual conditions, like the R-22, R-44, Bell 206, piston Enstroms, etc., but you will find static wicks on helis that are certified for IFR.

  [Static wicks] are used on aircraft to allow the continuous
  satisfactory operation of onboard navigation and radio communication
  systems during precipitation (p-static) conditions. Precipitation
  static is an electrical charge on an airplane caused by flying through
  rain, snow, ice, or dust particles. When the aircraft charge is great
  enough, it discharges into the surrounding air. http://en.wikipedia.org/wiki/Static_discharger


How do I say these situations, according to the runway's status?

In the US, you would use "closed". From the FAA's Pilot/Controller Glossary:

  CLOSED RUNWAY− A runway that is unusable for aircraft operations. Only
  the airport management/ military operations office can close a runway

And this is part of the example ATIS broadcast from the same document:

  Left approach in use, Runway Two Five Right closed, advise you have
  Alfa.

I don't know if ICAO uses a different term, but "closed" is probably going to be clear to most pilots (and non-pilots, for that matter).


How do linear actuators for flight controls work in fighter jets?

The working principle is surprisingly similar between the RC as you've described and most actuator powered aircraft. The linear actuator extends/retracts a pushrod, which is connected to a horn attached to the pivot point on the control surface.
Below is the zoomed-in picture from the OP. I've taken the liberty of highlighting the two rudder actuators and the left stabilator actuator. The one attached to the stabilator is the most revealing: the pushrod essentially connects to a horn, which translates the linear motion to a rotational one.

Ref: https://conceptbunny.com/lockheed-martin-f-22-raptor/
Due to aerodynamic and stealth reasons, this mechanism is hidden under a smooth fairing for the F-22. But for other airplanes, you can see small blisters under their control surfaces that fair the actuator. Below is a picture of the Boeing 787 aileron. The blisters have been highlighted.

Ref: https://commons.wikimedia.org/wiki/File:Low-speed_aileron_of_Boeing_787.jpg
The linear actuator itself is almost always energized via hydraulic fluid, whether it comes from a central hydraulic system or an self-contained hydraulic systems (EHA). The following diagram illustrates the working principle:

Ref: https://www.machinedesign.com/mechanical-motion-systems/linear-motion/article/21832047/whats-the-difference-between-pneumatic-hydraulic-and-electrical-actuators


How long will one remain conscious in the event of a sudden cabin depressurization?

The question you're asking roughly translates to What is the time of useful consciousness at 39,000 feet?. The answer is "About 15-20 seconds, once the pressure bleeds off." The FAA has a handy table for this:

From Chapter 16 of the Pilot Handbook of Aeronautical Knowledge.
You can get a PDF of Chapter 16 here, or you can grab the whole thing from the FAA

The Time of Useful Consciousness will vary depending on personal physiological factors (e.g. if you're a smoker your blood doesn't oxygenate as well - you will probably have less time. If you're a mountain climber in excellent shape and used to breathing rarified air on your climbs you'll probably have a little more time).

In the case of a non-explosive decompression (say a pressurization system failure) you'll probably have more time than this from the start of the event to the point where everyone is unconscious: the cabin pressure will take time to bleed off. Whether that time is seconds or minutes depends on the nature of the leak.

Presumably while the pressure is bleeding off the aircraft's systems will complain about the loss of cabin pressure and give the pilots a chance to address the problem (fix the pressurization system or descend to a safe altitude). Unfortunately the effects of hypoxia can start setting in before the crew realizes what's going on (which is one of the contributing factors in the loss of Helios Flight 522, which suffered just this kind of gradual depressurization).


What is the maximum altitude allowed to fly a model plane/copter in Germany?

The maximum altitude you can operate your RC plane or copter vertically without any clearance from ATC or another government body is the upper limit of class G airspace in Germany, which is the first available airspace from GND to the lower vertical limit of controlled airspace C/D/E, which can be 2.500ft AGL1, 1.700ft AGL or 1.000ft AGL, depending on surrounding airspace and airports in the vicinity. You can register at the website of the DFS AIS to obtain the ICAO charts for your area and take a look at the airspace structure near you.

The actual ceiling of airspace G can be significantly lower in the vicinity of larger airports, where the controlled airspace C/D/E has been lowered. The below picture shows how the dark green section around Frankfurt Airport has an airspace C with the vertical limits 1.500ft (MSL)/FL100. The airspace E in that area (not visible in this picture) has a vertical limit of 1.000ft AGL/C. Some areas within that section already have an elevation of 700-1100ft MSL, which leaves less than 100-400ft of airspace G before the overlying airspace C begins.

If you want to get your RC plane or copter into class C/D/E airspace, which is controlled airspace, you will need to obtain a clearance through the ATC unit in control of the sector or the FIS sector responsible, as postulated in LuftVO §16a

  § 16a LuftVO
  Besondere Benutzung des kontrollierten Luftraums
  (1) Bei Inanspruchnahme des kontrollierten Luftraums ist von der zuständigen Flugverkehrskontrollstelle eine Flugverkehrskontrollfreigabe einzuholen für
  1. Fallschirmsprünge und den Abwurf von Gegenständen an Fallschirmen;
  2. Aufstiege von Flugmodellen und anderen fern- oder ungesteuerten Flugkörpern mit Eigenantrieb;
  3. Aufstiege von unbemannten Freiballonen mit einer Gesamtmasse von Ballonhülle und Ballast von mehr als 0,5 kg sowie Aufstiege von gebündelten unbemannten Freiballonen und Massenaufstiege von unbemannten Freiballonen.

Please also mind LuftVO §15a, which dictactes that any RC plane or UAV needs to remain within the visbility range of the controller, so the maximum altitude can vary depending on the size of your RC plane or copter, the weather minima at your location and your own eyesight:

  (3) Der Betrieb von unbemannten Luftfahrtsystemen ist verboten, wenn

  1. er außerhalb der Sichtweite des Steuerers erfolgt oder
  2. die Gesamtmasse des Geräts mehr als 25 Kilogramm beträgt.

1: AGL = Above Ground Level
2: MSL = Mean Sea Level


What does BUS mean in the startup procedure?

A bus is a strong connection that distributes current. It's not limited to the conductive part, it is usually understood as including the switches and relays that manage its connection to the rest of the wiring.

(Keep in mind that with AC, when two different sources are used to feed the same component, frequency and phase need to be adjusted and must coincide, else energy would be lost, and voltage increased / decreased, possibly to a dangerous level.)

The transfer buses in that case have a logic detecting multiple current sources, e.g. battery and ground supply, and selecting which one to use to feed the bus. The crew has some authority on this process, using switches:

(Source)

There is one transfer bus on each side of the aircraft. They feed other buses, like galley and main buses, with energy, typically from the engine generators.

They are connected by the tie bus (between BTB1 and 2 on the image, it's name doesn't appear), for redundancy purposes.

Boeing 737 NG, modified (source)

Before the two engines are running (and their generator supplies current), the tie bus allows the ground power, or the APU, or a single engine to feed the whole aircraft.

Transfer buses can be disconnected from the tie bus for normal use, each engine generator providing energy to different smaller buses, creating a redundancy.

If one source fails, the other can feed the whole aircraft by connecting the tie bus. Another connection can be used on the DC part (cross-bus tie relay). This mode is useful and required when performing an approach with the autopilot (e.g. ILS cat III).

Conversely if one transfer bus creates a security problem, it can be switched off.


Engine options for the 777-300ER: GE90-110B1 or -115B?

According to the EASA Type Certificate Data Sheet (TCDS) of the Boeing 777, only the GE90-115B engines are approved for the 777-300ER:

5. Engines:
Two (2) General Electrical GE90 Turbofan Engines
Models installed: GE90-115B,
EASA Type-Certificate No.: EASA.IM.E.002
Limitations: See Engine Data Sheet No. EASA.IM.E.002

The GE90-110B1 model is listed for the Boeing 777-200LR and 777-200F models. In the Wikipedia table, the engine entry is for all of these models together.


Why are military planes painted differently than civil planes?

This wiki article speaks to this somewhat. In modern-day air forces, the paint job will depend on the mission the aircraft is used for. However, with the improvement of radar, visual camouflage is less important than it used to be.

Blacked-out aircraft

Some aircraft are paint black or nearly black for use in night missions. The F-117 (shown above) was painted with a radar-absorbent paint and also primarily flew at night, lessening its probability of detection. Other aircraft, like the special operations MC-130 and AC-130 are painted very dark grays or blacks to lessen their probability of detection since they are primarily used at night in support of covert missions, often at low level where visual detection is the main threat. Modern Examples: B-2, MC-130

Ground camoflauge

Some aircraft are painted to blend in to the ground. Some of these are those designed for low-level attack roles (like the Tornado pictured above), to limit the chance of visual detection by enemy fighters from above since their radar signature is unlikely to be detected so low to the ground. Others, like the now-retired Saab 37 Viggen, may be camouflaged to prevent detection when parked on the ground, as many were dispersed around Sweden, sometimes hidden in forests, to prevent single attacks from taking out many defenses. Many military helicopters are also painted either a patterned or dark green color to blend into forests. Some aircraft have been painted tan to blend into desert environments. Modern Examples: Su-25, Super Tucano

Air camouflage

Many air superiority fighters, and a large group of combat aircraft in general are painted in some way to blend into the sky. I have read that the human eye has difficulty picking a gray plane out against the blue sky (or grayish clouds), and most USAF and NATO planes are painted in some form of "Air Superiority Gray". Additionally, many will have different-colored tops and bottoms to help blend in from above and below. This excellent aviation.se Q&A talks about false cockpits on military jets that contribute to better dogfighting performance. Some aircraft, like the Su-27, may have several different grays and whites painted on it to break the aircraft's shape up. Modern examples: F-22, MIG-29

There may be other aircraft that have unique paint jobs to assist in a specialized mission - a darker color on one area to help with sensors, special coatings to minimize damage from a nuclear flash. Overall, it is not as common as it used to be for aircraft to be green - most US Military aircraft were green in color during the Vietnam War, but as the distance of aerial combat has increased, so have the camouflage schemes. Grays are probably the most common paint jobs now among military aircraft of many countries, with other aircraft having specialized paint jobs for specialized roles.


How high can an airplane be spotted with eyesight?

Note: There is some confusion in the comments about this answer. What I am answering here is the question:

  Suppose a plane has a wingspan of 15 m then at what distance it will appear as a faint dot? What is the correct way to calculate this?

This does not imply that you cannot see the airplane at a greater distance any more. It just means you cannot resolve it any more, i.e. it will appear as a faint dot.

This can be estimated with the Rayleigh criterion. The angular resolution of the human eye is given by

$$ \theta = 1.22 \frac{\lambda}{D} $$

where $ \lambda $ is the wavelength of the light and $ D $ is the pupil diameter. Using typical values of $ \lambda = 550 \, \mathrm{nm} $ (highest sensitivity of the human eye) and $ D = 3 \, \mathrm{mm} $ during the day, we get a resolution of

$$ \theta \approx 2.24 \times 10^{-4} \, \mathrm{rad} \approx 0.013^\circ $$

If the aircraft is $ w = 15 \, \mathrm{m} $ wide, the distance at which this corresponds to this angle is given by

$$ d = \frac{w}{\tan \theta} \approx \frac{w}{\theta} \approx 67.1 \, \mathrm{km} $$

Most planes only fly up to FL410, which is about 12.5 km, so you could always distinguish them from a faint point with the naked eye. As Zeiss Ikon pointed out in the comments, the actual resolution of your eyes may be worse because your eyesight is probably not perfect. This is however an upper limit on the resolution.


When does the ATC assign runways to aircraft arriving at an airport?

While exact distances & times vary depending on which airport and what runway configuration you're working with, the most reliable answer to the question is, usually on initial contact with the Approach controller.
As an example, here is the SITTH2 RNAV arrival into Atlanta (pdf link):

Inbound to ATL, you'll be cleared for that arrival, and you'll know that regardless of the runway assignment, you can plan to cross SITTH at or above 14,000' and TIZZY at 12,000'.  But as far as runway assignment, you're making a best guess.  Coming in from the southeast like this, the farthest south runway in ATL, runway 10, would be a fair guess, or the outboard of the 9/27 runways (so, 9R -- since they tend to arrive on the outboards, 9R/27L and 8L/26R, and depart on the inboards) if traffic is light. (Airport Diagram for ATL)  But that's not certain until you're talked to Atlanta Approach.
The approach control is the facility that builds the plan to distribute the inbound aircraft (which they can see hundreds of miles out, along with projections when each one will arrive at the "cornerpost" like TIZZY), and they'll have the plan that Delta 123 will get runway 10, Delta 456 will get 9R, American 789 will get 10, and Spirit 987 will get 8L.  And so on initial contact with Approach, the crew will be told, typically, to "Descend via the SITTH2, runway 9R".  At this point, the crew can update (if necessary) the runway in the FMC, review the approach for that runway, and check that the points in the FMC match what the chart shows  (i.e. after TIZZY, going to FRYES and following points for 9R or 10, or to GAASS etc for 8L).
It's not impossible, but it's uncommon for Approach to subsequently change the runway after this, although a crew can always ask.  (The exception to this is Denver; they seem to rebuild their plans every few minutes.)  If there isn't a lot of traffic, ATC may be able to accommodate a crew's request.  In ATL, there isn't a big difference getting to the gate from the north or the south complex; at DFW, it can be a significantly longer taxi, so there are more requests there for "request east side if we can" to try to get a runway corresponding to the terminal where they're parking.
Once the aircraft is on with Tower, it can be possible to switch runways; this is very dependent on traffic and happens only in visual conditions.  This would mostly be swapping to an inboard from an outboard runway, rather than from a north-complex to the south-complex (or vice-versa).  Atlanta doesn't do this much; in Phoenix, it's pretty common, since the inboard runway on the south side of the airport (25R / 7L) is closer to the south-side gates & doesn't involve crossing a runway to get there, as compared to the outboard runway (25L / 7R, which is typically assigned for inbounds to PHX from the south).  If Tower doesn't have anybody getting close to the inboard runway for takeoff, they may offer it to somebody on final.  And the crew can ask -- although if there's somebody who's approaching the runway for takeoff, the answer is likely to be "no."


What is the physical-based/theoretical reason why supersonic area ruling works?

That's because Bernoulli's principle breaks down at and above supersonic velocities.

In the subsonic realm, when an atom is sped up, it doesn't have much time to spend pushing around a fixed place (it passes by that place quickly). In doing so, the static pressure drops as the speed increases. And in doing so, the neighboring atoms, who are also not doing as much repelling, can group together.

In Busemann's and Whitcomb's metaphor, the tube of air gets thinner.

In supersonic flow, much like the reason behind shockwaves, the communication between atoms breaks down. They are moving too fast for the air to carry out the effect of moving fast (pressure disturbances cannot propagate), and thus, the tube of air doesn't get smaller. This results in an increase in the drag versus the calculated one; instead of the tubes getting smaller, they remain both big and fast.

Drag increase is highest when there is a sudden cross sectional change. Consider the face of a box compared to a cone pointy-end first.

Applying that, the supersonic area rule aims at keeping the cross sectional size of the whole vehicle constant without abrupt changes. If thinning the fuselage where the wing meets it is not possible, then gradually thickening it before the wing starts is also an option.

The tubes not getting smaller, and considering the cross section of the vehicle as a whole, were the reasoning behind the area rule.

Reference and further reading: Chapter 5 - The Whitcomb Area Rule - From Engineering Science to Big Science, via NASA.


How does the Aerobridge dock with an aircraft?

Well jetways don't exactly 'dock' with an aircraft; there is no hard coupling between the tunnel and the airplane like say that found with a spacecraft docking.  Rather they are just maneuvered up against them with a soft canvas hood which can be actuated around the fuselage allowing protection from the weather for passengers and crew.

The jetway is maneuvered to and away from an aircraft via a small control panel near the hood of the jetway which controls an electrically driven wheeled drive supporting the terminus end of the jetway as well as screw jacks in the support pillars for elevation control.  This allows a user to translate the length of the tunnel or rotate it about its connecting point to the terminal.  The tunnel can do this by means of telescoping sections.  The terminus of the jetway can be swiveled to match the curvature of the fuselage and the tunnel makes contact with the jet at the base of the terminus, usually with a neoprene bumper to prevent damaging the fuselage.  The hood can then be lowered for weather protection.

The jetway will reverse this process after the main cabin door has been closed and secured and before pushback to prevent contact and damage with the aircraft during pushback.


First you need a wing that is representative of a flightworthy article.

Next, you need to collect the significant load cases. The most obvious one is that of maximum lift, but sometimes wings have failed even when they were strong enough to support the maximum bending moment. Torsion from aileron deflections and flutter are important, as is the in-plane bending moment from lift at high angle of attack.

Normally, the wing is placed in a rig and computer-controlled hydraulic jacks are used to pull on it, but this can be made much simpler. Below you see the ultimate strength test on the MIT Dedalus wing: Discarded soda bottles were collected, filled with a pre-calculated amount of water and hung from the main spar while the center of the inverted wing was lifted up by a forklift.

Load test on Dedalus wing. Yes, the guy with the Daedalus shirt is Mark Drela. Own work.

Besides the maximum strength tests, fatigue tests are of equal importance. Here a statistical load distribution (frequent low loads, infrequent high loads) is applied to the wing over thousands of hours. These tests stretch into the early operational phase of a design, such that the structure is cleared for more hours as the test progresses.


Is this planned building in a runway approach legal?

If it falls within the limits set out by FAA FAR Part 77 then its legal. You can find a nice breakdown of Part 77 here but you would need measurements more precise than what google maps is going to give you to be sure. Depending on the height the FAA may also require them to light the top of it. This is actually an interesting break down as the FAA is a federal organization and building approval generally comes down at the city/town/municipality level. If a building is approved for construction by a city one can assume it is legal to be built and that the city accounted for the FAA regulations. According to AC 150/5190-4A which quotes the Airport an Airway Improvement Act of 1982 it looks like its on the city to ensure that nothing gets in the approach path:

  ...Sec. 511 (a) SPONSORSHIP. As a condition precedent to approval of an
  airport development project contained in a project grant application
  submittted under this title, the Secretary shall receive assurances in
  writing, satisfactory to the Secretary that ... (4) the aerial
  approaches to the airport will be adequately cleared and protected by
  removing, lowering, relocating, marking, or lighting or mitigating
  existing airport hazards and by preventing the establishment or
  creation of future airport hazards; (5) appropriate action, including
  the adoption of zoning laws has been or will be taken, to the extent
  reasonable, to restrict the use of land adjacent to or in the
  immediate vicinity of the airport to activities and purposes
  compatible with normal airport operations, including landing and
  takeoff aircraft; ...."

In other words, the city needs to have zoning laws that keep the approach path clear. This is largely covered under the above linked Part 77 but generally speaking if the building has been approved its more than likely legal as per approved zoning laws.

A bit of a related story: you should not put it past people to build out of spite. A farmer once built a silo right off the end of Chatham Airport's runway to try and stifle traffic that he claimed was buzzing him while he was working. The silo is now gone and I cant find any info on what happened to it but this was also some time ago and I dont know what the regulations were when it happened.

And in some rare cases, if there is something in your way, an approach can be devised around it.


(Source) Drain system.

ICAO SARPs Annex 14 does not mention a direction of slope, it only says:

  Recommendation.— On an aircraft stand the maximum slope should not exceed 1 per cent.

So that's fairly level. But tiny slopes are needed, but not necessarily facing away from the terminal. They are needed to guide the rain (and any fuel) toward the trench drain system.

Not always are the drains parallel to the terminal and behind the parked aircraft. They can be parallel to the plane's longitudinal axis or even at the terminal.

I have never seen a parking that intentionally overshoots the mark. What you may have seen is a small backward jerk, like when trains stop. That's due to the offloading of the nose landing gear.

Pilots are guided in via stand guidance systems or ground marshallers. And they stop when the stop sign is shown. Guidance systems are never calibrated to overshoot the spot (the pilot might end up having to blame the birds).