After purchasing an aircraft, how do I put the transponder in my name?

I assume you have a Mode S transponder. A Mode S transponder uses a unique 24 bit address assigned by the authorities to your aircraft to communicate with Mode S radars. If you do not have a Mode S transponder there is nothing that links your transponder to your aircraft registration.

If you purchase an aircraft you need to register it with the Civil Aviation Authority in your country. With that registration you will get a 24 bit address (in some countries you will always get it, in others you need to indicate that you have a Mode S transponder). The 24 bit address is usually given as a hexadecimal string of six characters, some countries use a 8 character octal representation. This code needs to be programmed in your transponder. It may be that the 24 bit address is the same as it was before. In that case nothing has to be done on the transponder.


What bank angle creates the least energy loss in an emergency engine out 180 degree turn?

Asked and answered, since a any plane without a functioning engine is basicly a glider:
What is the optimal bank angle to accomplish a given turn in a glide?

Assuming the question refers to an engine failure after takeoff, there is a lot more to the stunt than just turning with the least amount of altitude loss. In any case, before attempting "the impossible turn" you must be above the safe altitude for the maneuver. If you have not yet reached safe altitude, you make an emergency landing in the front sector. The safe altitude varies heavily with different plane makes and models, but for example a C 172 needs about 500ft and rather aggressive (yet skilfull) handling according to tests made for AOPA Pilot 2002 july article.

To make an efficient 45 degree turn while maintaining a steady speed is not exctly a walk in the park if you have just lost an engine. Attempts to return to the runway after an engine failure during initial climb have a strong tendency to end in tragedy.


Why are the B-47’s inboard and outboard engines mounted so differently?

The forward pylon mounting of most jets with wing mounted engines is to use the engines' mass to move the overall center of mass of the wing forward, closer to or ahead of the torsional axis of the wing box.  Boeing discovered this helps with aerolasticity related issues with long, flexible, swept wings.  A bit like mass balancing a control surface, but on the root structure.

The outermost engines, being so close to the tip where the chord is short, have to be farther aft or they would move the wing's center of mass too far forward in that area.


How do terms apron, ramp, tarmac, taxiway, parking area, gate, hardstand relate to each other?

Apron and ramp (in US) mean the same, though the official term is apron. FAA Advisory Circular Number 120-57A Surface Movement and Guidance Control System defines it as:

  Apron (Ramp). A defined area on an airport intended to accommodate aircraft for purposes of loading or unloading passengers or cargo, refueling, parking, or maintenance.

Now, the apron includes parking, maintenance and service areas, including taxi lanes.

  The apron area includes the following components:

  (1) Aircraft Parking Positions.  Intended for parking aircraft to enplane/deplane passengers, load or unload cargo.

  (2)  Aircraft Service Areas.  in or adjacent to an aircraft parking position.Intended for use by personnel/equipment for servicing aircraft and staging of equipment to facilitate loading and unloading of aircraft.

  (3)  Taxilanes.  Apron areas which provide taxiing aircraft access to and from parking positions.

  (4)  Vehicle Roadways Markings.  Identified rights of way on the apron area designated for service and Aircraft Rescue and Fire Fighting (ARFF) vehicles.

So,

  Is this a binary split: Runways vs tarmac?

Kinda. Basically, the areas in airport where aircraft are involved are divided (by the FAA atleast) into runway, taxiway and apron.

  i.  Movement Area.  Refers to the runways, taxiways, and other areas of an airport which are used for taxiing or hover taxiing, air taxiing, takeoff, and landing of aircraft,exclusive of loading ramps and aircraft parking areas.

  j.  Non-movement Area.  Refers to taxiways and apron areas that are not under ATC

  Is the gate stand part of the tarmac?

Its part of ramp, so yea.

  Is a parking area different from a ramp?

It is part of the ramp/apron

  Is a taxiway considered part of the apron?

Nope. As already noted.

FAA AC No: AC 150/5300- 13A Airport Design defines runways and taxiways as:

  Runway (RW).  A defined rectangular surface on an airport prepared or suitable for the landing or takeoff of aircraft.

  Taxiway (TW).  A defined path established for the taxiing of aircraft from one part of an airport to another.

  Are aprons made of Tarmac?

Tarmac is a trademark of Tarmac limited, which supplies construction materials for a a number of airports (among others), though most of the aprons are actually made of concrete.

  Is a de-icing area part of the ramp?

As de-icing is part of servicing, it should be part of apron/ramp.

However, it should be noted that though this is the 'official' version, differing local usage means that tarmac is used interchangeably with apron/ramp.


Is there a system where plane/heli auto adjusts prop pitch/mixture?

There sure is but it is generally independent of what is traditionally considered a "glass cockpit" and is often wrapped up under the FADEC system. One of the earlier production designs for this found its way into the Mooney M20PFM which was a Porsche Powered Mooney that had an electronically inject 3.2L Porsche car motor in it. Most importantly it had "single lever operation" where the throttle, prop, and mixture were all wrapped into one lever. For a variety of reasons the plane was ultimately a failure and I do not belive any are still flying with the Porsche motor.

As Ron mentions in the comments some of the Diamond's like the DA42 are set up this way.

  So I can only spend time adjusting throttle?

This is perhaps the more important part of the question. Perhaps one of the main reasons that planes are set up with the throttle, prop and mixture adjusts is to allow for fine control. Automatic control systems generally operate in the most "efficient" range but as a pilot you may wish to operate in other ranges, run lean of peak or cruise at a very slow but efficient burn. Your POH will give you all the relevant information to operate your plane in all sorts of ways.


How does the use of Leading Edge Root Extension help in increasing stall angle?

The idea is to generate a vortex near the fuselage. In most cases we do not want any vortexes, as the unnecessary air movement always causes an increase in drag. In this case however, you need them.

As the air flow separates from this small triangle wing while at large angles of attack, it gains a rotary motion (if you look at the left wing standing in front of the aircraft it will rotate clock-wise). This vortex inducts further swirling movement across the wing.

Now, if you are familiar with fluid dynamics, you can imagine that this will decrease air pressure at the top of the wing (not much impact on the bottom side), which is what we want - higher lift is generated.

What is more important in this the case, is the boundary layer. If you provide it with energy, making it more turbulent, it will pay off with sticking to the wing surface even while flying at large angles of attack. Obviously the larger is the angle without stall, the higher lift can be generated. Therefore an airplane with wing extensions can perform sick maneuvers like cobra and other more useful in aerial combat. Of course it requires a huge amount of spare thrust, but you do not have to worry about that in military jets.


Is hybrid propulsion widely used by UAVs?

It's becoming common, particularly for endurance.  Two such commercially produced aircraft, Skyfront's Perimeter 8 and Avartek's Boxer, have several hours of hover endurance and a 5 kg payload capacity.
Academia is also taking note: here's a 2018 master's thesis that analyzes the advantages and challenges of hybrid power.
The core motivation for hybrid power is that the internal combustion engine can be optimized for nominal power, while the battery need only handle the difference between nominal and peak power.  That weighs less and costs less than a big IC engine or a big battery, while still enjoying the greater energy density of IC fuel as compared to batteries.
Compared to purely electric propulsion, two challenges are the engine vibration that corrupts sensor readings, and the louder noise that constrains where the aircraft may be flown without annoying others.


What exactly is the airspace above CYYZ (Toronto)?

Canadian Class C airspace is generally the same as US Class C airspace. Prior permission is required before entering. Canadian Class B airspace is 12,500' and above. Not a factor for you most likely.

I recommend reading the VFR legend to better understand the markings. It's all there if you purchased a map. The 125/25 marking is the ceiling and floor of the airspace. What you're looking at is the US Sectional, not the Canadian one however. The square [25] refers to the control zone around the airport. You won't be landing in Pearson, so you definitely won't be in their control zone. It extends about 8nm from the airport from surface to 2500' and most busy airports have one. All control zones are class C airspace.

What you're looking for on the VTA is VFR planning. It will have recommended routes to follow, as well warnings and information needed to be able to plan a VFR flight through the area.


Your question: What is the logic behind the delay of the signal and how is the echo signal later bound with the signal sent?

Short answer

A PESA is an array of individual antennas. Each antenna radiates the same signal, except the phase. The phase adjustment for each antenna allows for the non-moving array to behave like if it could be rotated, i.e. the direction the energy is sent to or receive from can be selected by adjusting the phase for the individual antennas.

Varying the signal phase for an individual antenna of the array can be done by delaying the signal for this antenna, which in turn is as easy as
making the electrical conductor (or waves guide) between the oscillator and the antenna longer.

PESA determines the transit time exactly like another more traditional one with a single rotating antenna. A signal sent by a PESA, after it has been sent, is indistinguishable from a signal sent by a rotating antenna radar.

Details

The principle of a primary radar is to send a radio signal in a given direction and wait for a possible echo. The direction of the radiation pattern is used in determining the direction (azimuth and elevation) of the reflecting object. The antenna must be very directional (small solid angle of the radiation pattern), else the angle determination cannot be precise.

Radiation pattern of an antenna with a parabolic reflector (source)

That means the antenna must be rotated to scan a useful portion of the sky (or ground).

To clarify the wording used, an antenna is usually composed of:

A radiator which receives the signal to be transmitted (it also collects the waves in reception). The radiator is the interface between electrons and waves and vice-versa.
A reflector used to reflect the waves from the radiator (it also focuses the waves on the radiator in reception).
Sometimes directors to narrow the radiation pattern of the system.

The radiation pattern of an antenna is mostly determined by the shape of the reflector (e.g. the parabolic reflector) which only illuminates a given fraction of the space and, due to interferences, also varies the energy based on the direction the energy is sent to or received from. Due to the reflector, a signal from the radiator will usually travels using different paths created by the multiple reflections.

Interferences are the result of combining the electromagnetic signals at a given point. For signals having the same frequency, the phase determines if signals are added (same phase) or canceled (opposite phases).

Phase determines how signals interfere (source)

We can apply this phenomenon to the multiple signals created in an antenna composed of a radiator and a cylindrical reflector.

Signals summation on a cylindrical reflector antenna creates a privileged direction of radiation with some secondary (unwanted) lobes (source)

Array of radiators (electronically scanned array, ESA)

Another way of varying the privileged direction of a radiation pattern is to create interferences on a voluntary basis, so that they create a stronger signal in the desired direction, and a weaker signal elsewhere. The advantage is that this electronic direction change can be much quicker than a mechanical rotation.

One way to create interferences is to send the radar signal from an array of small radiators instead of a single big one.

Close-up of the front of the old Cobra Judy radar (source)

This type of array is quite familiar under the name interferometer in the field of astrophysics:

Siberian Solar Radio Telescope (SSRT) interferometer observing the Sun at 5.7 GHz (source)

If all radiators are fed with the same signal, then interferences will occur the same way on the whole surface and the result will be that the direction perpendicular to the array is privileged (image on the left side).

Electronic beam-deflection (left: bore sight, right: deflected (source)

The right side of the image shows what happens if the signal sent to the individual radiators is delayed in a coordinated way: Delay increases from right to left on the array. It must be remembered that delay means phase here. The direction of the signal is now oblique due to the the location of constructive and destructive interferences. The red circles indicates signal with the same phase.

See this animation too.

Delaying an electric signal is quite easy: Just increase the length of the conductor (see analog delay line). A length variation between 0 and the wave length (e.g. 10 cm for a wavelength of 10 cm -- 3 GHz) allows to sweep the whole range of possible phase values from 0 to 360°.

Indeed there are other ways to delay a signal without adjusting the length, but they are electrically equivalent. When signals are digitized, it's really easy to process them, there is less electro-mechanical constraints.

By varying the phase on individual radiators we can steer the signal as if the antenna had been rotated, but we can also focus the energy on a target.

(source)

PESA vs AESA

There are two approaches for feeding individual radiators with phase-shifted signals: active and passive:

Active means the radiator has its own oscillator to create its own signal. The active element must receive the value of the phase shift to use from a central element which coordinates the whole array.
Passive means the radiator receives the signal to be sent and just radiates it. The signal must already have the required phase. This is usually done with a single oscillator which feeds an array of phase shifters which in turn feed the array of radiators.

(source)

Transmission vs reception

The beam formed by the array concentrate the energy during transmission. The signal sent is not different than one sent with a single large radiator (rotating radar antenna). This is also a general result of adding and canceling energy by interference.

An array conforms to the general rule: An antenna is reversible, the characteristics of the radiation pattern are also valid in reception. That means:

Receive the same signal on all radiators
Add individual delays (phase shifts) to obtain a privileged direction of energy origin. The phase values are inverted compared to the ones used for sending in this direction.
Mix all signals into a single one to have them interfer and obtain a single mixed signal, equivalent to the one that would have been received with a rotating antenna.

The effect is that energy originating from directions other than the privileged one will be weakened, and the energy in the privileged direction will be emphasized.

Note that the phase is used to change the radiation pattern (process known as beam forming), but the rest of the radar is unchanged compared to a rotating single antenna one.

(Tell me if there is something that is not clear, I'll improve the post as necessary.)

Additional details

Phase shifter

As mentioned a phase shifter is used on each individual antenna of the array. It should prevent signal loss, distortion and noise addition, and the phase must be controlled accurately and quickly, by steps or continuously.

For step by step (digital), delay lines are used, with a possibility to connect a variable number of them using switching diodes (e.g. pin diodes). See more on RadarTutorial.eu with an example of 4-bit shifter (16 phase-shift values). More details on this datasheet for a 6-bit shifter on S-band.

Continuous (analog) control can rely on a resonant circuit (LC) to delay the signal. The capacity value can be mechanically changed in MEMS.

(source)

This extends past what I know in the domain, but other technologies exist, and are detailed in Array Phase Shifters: Theory and Technology (Nasa, 2007), including:

  Another style of phase shifter uses coupled microstriplines as dc
  electrodes to polarize a thin [...] ferro-electric film [...]. These
  planar phase shifters are fairly compact, low loss, easy to fabricate,
  and can provide 360° of phase shift with bias voltages under 350 V.

Phase shifters design depends on the operating wavelength of the radar.

Radiators used in a phased array antenna

Again the operating frequency impacts the radiators design.

Low frequencies may use:

A pair of crossed dipoles to allow polarization changes during the pulse travel and the reflection on the target.
A Yagi antenna.

Higher frequencies use other designs:

Notch antenna (slot). Used on Russian N011M (also note the dipole array for lower frequency scan of this hybrid radar).
Patch antenna (microstrip).
Vivaldi antenna (tapered slot) for broadband spectrum.

More on RadarTutorial.eu.


Can I do an IFR checkride in an airplane that isn't certified for IMC?

Legally, you can take your instrument rating checkride (not "IFR checkride") in an airplane that is not equipped for flight under instrument flight rules. That is because you will fly your check ride under VFR. As I did. The examiner will act as "safety pilot," a require crew member, while you are the sole manipulator of the controls under SIMULATED IMC via the view limiting device. The examiner will ask you to do the required tasks, and you will coordinate the tasks needing ATC assistance with ATC, who will remind you to "remain VFR" while you are on practice instrument approaches and so on. You cannot fly the checkride under instrument flight rules because you don't have an instrument rating. The examiner won't (or at least most won't) file an IFR flight plan as PIC using his/her rating.

But that's legal. In practical terms, at least in my opinion, any examiner is going to be reluctant, or at least suspicious, of a request for an applicant to complete the instrument rating checkride in an airplane not fully equipped for instrument flight. In particular, he or she is going to insist that the airplane be equipped for several different types of instrument approaches. My understanding is that it's up to the examiner, so check in advance if your examiner is comfortable using the airplane that you propose to use.


The induced angle primarily depends upon the following:

Coefficient of lift
Aspect Ratio (AR)
The correction factor $\tau$ (needs to be accounted for if the wing platform is not an ellipse. If the wing platform is an ellipse, then $\tau=0$)

All three are related the with the following equation:
$$\alpha_i[\text{rad}]=\frac{C_z}{\pi AR}(1+\tau)$$

The table below provides the values of $\tau$ for a rectangular wing.

You can use these values and NACA Report 824 to calculate the actual induced angle of attack for a rectangular wing for any possible airfoil.

For instance, using $\text{NACA} ~65_1-412$ airfoil at $\alpha_{\text{geometric}}=8^{\circ}$ and $AR=9$ it follows that $\alpha_i=0.05~\text{rad}\approx 2.86^{\circ}$.

It varies greatly in relation to the angle of attack, as low as $1^{\circ}$ in high-speed flight with low angle of attack and as high as $3^{\circ}-4^{\circ}$ at low-speed flight for a rectangular wing aircraft.


Why are RC rotor blades different from helicopter blades?

If the rotor was mechanically strong enough to lift the desired weight

It wouldn't be. Because of the square-cube law, lift and mechanical strength grow with second power of linear size, but weight grows with third power. The result is that at RC-scale, everything has plenty of power and strength even if made sloppily (and thus cheaply) from common materials while human-carrying-scale is really stretching capabilities of the materials and engines we have.

A highly cambered airfoil would not be strong enough for full-scale helicopter blade.

  is there any (aerodynamic) advantage to the solid aerofoil over the simpler curved surface?

I believe there is. No modern aircraft uses highly cambered airfoil.

  Surely toy manufacturers could "close the bottom" of the rotor (equating to the aerofoil shape) even if it was hollow with neglible increase in weight.

No. Efficiency is not that important at RC scale and hollow plastic is much more difficult to make (remember, plastic is made by injecting it into a mold).

  I understand the Bernoulli effect does not necessarily apply to the RC rotors

Airfoils is an airfoil whether it is flying straight or rotates. And since Bernoulli's principle is just conservation of energy for fluid flow, it always applies to it. It does not, however, mean concave lower surface would mean higher flow speed and lower lift, because the length of the path has nothing to do with lift. The air above the wing is faster—and reaches the trailing edge long before the air below—for completely different reasons. Highly cambered wings do have higher lift. They just have even higher drag.

  it may be simply a Coanda effect

Coandă effect is about a fluid jet surrounded with still fluid around it, but there are no jets of air involved here, so it can't be Coandă effect.

  but they do seem to lift well with just electric motors

That's the square-cube law again making the aerodynamic performance so much better relative to weight at RC scale.

  I have seen discussion that there is a "scale up" effect but why and if so at what size does the simple rotor start to fail

It is not just scale up (square-cube law):

Quad-copters with fixed pitch rotors (typical of the toy ones) are not controllable with failed engine. Human-carrying craft have to be.
Fixed pitch rotors deal poorly with horizontal speed, because the lift asymmetry creates big loads. Large rotors need to lead-lag and flap to compensate for this.

Both making quadcopters impractical at large scales.

Usually, quad-copters are made up to low tens of kilograms maximum weight. But where exactly is the limit might be hard to tell since larger ones may not be made simply because there is not much use for them.


Does a Boeing 737-800 Have a Ram Air Turbine (RAT)?

No it does not, it does not need one, there is a mechanical connection to the flight controls that can be used if all else fails.

The B737 flight controls are hydraulically powered.
There are three hydraulic systems: System A, System B, and Standby. Only one main system (A or B) is required for hydraulically flying the aircraft, during normal operation they are both operational.
The two main hydraulic systems have an Engine Driven Pump (EDP), which can continue delivering hydraulic pressure when the associated engine is windmilling. All three hydraulic systems are also powered by their own Electric Motor Driven Pump (EMDP).
In case of dual engine failure the APU can power the electrical systems for the EMDPs, still delivering full hydraulic power.
If the fuel has run out and the APU cannot operate, two batteries provide at least 60 minutes of backup power for the electrical systems. The EDMPs can be powered in this stage, however they provide a high load.
If all fuel is gone and the batteries are depleted, the aircraft can be flown by hand, directly overcoming the aeroforces by pulling hard! This is called manual reversion.
In manual reversion, the aileron trim tabs now function as geared tabs, assisting in overcoming the aeroforces. Elevators will have high aeroforces, high friction forces, and freeplay around centre point. Stabiliser trim wheels provide additional pitch control. The rudder has no manual reversion.

The A320 flight control system is pretty similar except for the manual reversion - as a last resort the RAT is deployed for powering the backup hydraulic system. The A320 has no direct mechanical link to the elevators and ailerons, only to the rudder.

Image source


What happens to the high pressure below an airfoil when the angle of attack increases?

I'm pretty sure you were right. More angle of attack means more lift. More lift is caused by higher pressure under the wing and lower pressure on top. More lift causes more induced drag.


How does an RMI respond when tuned to a VOT station?

Yes, it will point at the 180 position

VOR Test

  A VOT differs from a VOR in that it replaces the variable directional signal with another omnidirectional signal, in a sense transmitting a 360° radial in all direction

VOR Receiver Check

  With the Course Deviation Indicator (CDI) centered, the omni−bear- ing selector should read 0 degrees with the to/from indication showing “from” or the omni−bearing selector should read 180 degrees with the to/from indication showing “to.” Should the VOR receiver operate an RMI (Radio Magnetic Indicator), it will indicate 180 degrees on any omni−bearing selector (OBS) setting.


How can we design a wing for cruising at very low speeds?

The first thing you need is a large wingspan $b$. This will help to spread the lift over more air and reduce induced drag, which grows inversely with the square of flight speed $v$:
$$D_i \propto  \frac{1}{v^2} \text{ and } D_i \propto \frac{1}{b^2}$$

Large wings have a high root bending moment, which requires a strong and heavy structure. Next you should add bracing, at least on the lower side of the wing. For that to be effective, you need a high fuselage so the bracing will become efficient. Yes, those wires will add drag, but at low speed this will be a lot less than the added lift-induced drag from lifting a heavier structure.

The single bracing wire can hardly be seen on this picture of the Dedalus human powered aircraft, but it is there and saves a lot of drag at low speed (picture source)

Next, pick the right airfoils. Depending on the local Reynolds number, use thin and highly cambered ones but make sure that the pressure rise on the rear upper surface is slow enough to prevent early separation. One example is the DAE31 outer wing airfoil of the Dedalus aircraft (the inner and mid-span ones are DAE11 and DAE21). At Reynolds numbers of 500,000 to one million, turbulators positioned 2-3% ahead of the separation line will trip the flow and make the airfoil tolerate steeper pressure gradients.

Pick wing chord such that the wing area gives a lift coefficient around 1, details depending on the exact Reynolds number. Lower values go with lower Reynolds numbers.


How does the airfoil pitching moment relate to center of pressure?

The pitching moment probably has little (if any) relevance in the case of an airfoil attached to a race car.

In particular, the pitching moment is related to the fact that with a cambered airfoil, the center of pressure will forward and backward depending on the angle of attack at which the airfoil is operating.

In the case of a race car, the angle of attack won't normally vary much, so the pitching coefficient probably isn't very relevant.

I'm not sure it's really relevant, but the aerodynamic center is normally taken as being at 25% of MAC. The Cm basically then defines a torque that's exhibited at the aerodynamic center.

One other point: I'd at least assume that on a race car, the airfoil is mounted upside down compared to an aircraft--that is, it's intended to produce pressure downward, not upward. To the (I think minimal) extent that pitching moment is relevant at all, it'll be positive (whereas it's normally negative for the main wing of an aircraft). That is to say, on an aircraft the pitching moment leads to a force pushing the nose downward, but in your case it'll be a force tending to push the nose up (and the tail down).

Okay, so based on the comment, what's really desired in this case is to compute the location of the center of pressure. To do this, we really need two things: the Cm and the CL.

For the moment, I'm going to assume a Reynolds number around 500,000 or so. For an E423, your quoted Cm of -0.22 corresponds to an Alpha (angle of attack) of around 5 degrees. With Re = 500K and alpha=5, it looks like the CL is about 1.6.

The formula we need is:

hcp = hac - Cmac / CL.

Plugging in the numbers, we get: 0.25 - (-0.22)/1.6.

Running that through the calculator, we get 0.3875. So your center of pressure should be approximately 38.75% of MAC. Of course, you'll need to adjust if you're actually basing your number for Cm on a different combination of angle of attack and Reynolds number.

As noted above, in your case the airfoil is (presumably) upside-down, so that should really be a Cm of +0.22 and a lift of -1.6, but the signs cancel so we get the same result either way (exactly as you'd expect).

References:

Airfoil data
Computation


An appropriate way to practice ATC communications

Live ATC is an excellent way to listen and get familiar with your local airports procedures. I used to pick out a tail number and then pretended to be that aircraft. When ATC gave instructions, I would say back what I think the response should be.

If there are terms or phrases you dont understand, you should be able to look them up in the Pilot/Controller Glossary here:
https://www.faa.gov/air_traffic/publications/media/pcg_10-12-17.pdf

ATC and pilots should do their best to use the official phraseology in the glossary. However, the goal of communication on the radio should be clarity. If there is something you want to say but dont know how, just say it plainly without worrying about the 'official' wording.


What is the highest possible thrust generated by 15cm ducted fan?

A 15 cm diameter fan could maybe lift 4 kg of mass with a tip speed of 0.6M.
By increasing the power and the blade chord length (in other words, increasing the solidity of the rotor), this may be increased to maybe 6 kg or more, but a single fan would probably never lift more than 10 kg mass.
The thrust of a rotor is $C_T \cdot \rho \cdot \text{Area} \cdot \text{tip speed}^2$.

$\rho$ = air density ($1.225~\mathrm{kg~m^{-3}}$ at sea level).
$\text{Area}$ = area of rotor disc ($\mathrm{m^2}$)
$\text{tip speed}$ = the linear speed at the tip of the rotor = radial speed * radius.
$C_T$ = coefficient of thrust. (is usually in the order of 0.02 to 0.05 for small rotors)

Assuming $C_T$ of $0.03$, the calculation shows $40~\mathrm{N}$ ($=4~\mathrm{kg}$) thrust.
Disc area is one of the most important parameters, even a 30 cm disc would generate 4 times the thrust. 60 cm would make almost 65 kg.
Apparently, a 50 cm diameter disc can possibly generate 45 kg thrust on its own. So two of them could carry and maybe even lift-off a person equipped with this backpack (the person + the system must be less than 90 kg).


How many aircraft can an ATCo control simultaneously, on procedural and radar service?

There's probably not a specific number.   The answer will probably end up being "however many can do and maintain separation." Some sectors will include more complex maneuvering (more than one airport, several different approaches, both commercial and GA aircraft) so the airspace would have to be broken up into many smaller sectors with fewer aircraft in each to reduce workload. Whereas if you're talking about en-route, where the aircraft are not doing a lot of maneuvering the controller can probably deal with several times as many planes. If you think of arrivals at a busy airport, the airspace is broken into several different controllers, whereas often one guy in the tower is doing all of the landing clearances. That means he controls every single inbound flight whereas the approach controller is only juggling the portion that approach through his airspace. The workload per plane for the tower on landing is much lower since the approach controller will pass aircraft to him to him separated and already on ILS or with a visual on the runway. So all he is responsidle for is is making sure the runway is clear for each landing. In most situations tower only talks to the arrivals twice. Once to give clearance and then to pass them on to ground.


Why are the Antonov An-124 horizontal stabilisers directly behind the wings?

Flutter is the main reason why the horizontal tail on Antonov designs is mounted low. Many other transport airplanes do indeed sport a T-tail (C-141, Il-76, C-5, C-17, A400M).
Cargo airplanes with a rear ramp suffer from low torsional stiffness of the rear fuselage because of that large cut-out for the ramp doors. If the ramp doors are locked with many locking points around their circumference, this can be remedied but requires those locks to work well and reliably. The Antonov philosophy is to play it safe and assume that Russian maintenance crews will clear the plane even if not all locks engage.
A T-tail adds a significant mass on the lever arm of the vertical tail and lowers the eigenfrequency of the rear fuselage. This brings the torsional frequency of the tail in the range of the first antimetric flutter mode of the wing, as happened on the C-141. Putting the horizontal tail low avoids this and allows for a lighter structure.
Since the wake of the wing moves down with the downwash angle, it passes below the tail of the An-124 in cruise. Not by much, but enough to keep flow over the tail clean. At higher angles of attack the wake will hit the tail, but those should not be encountered in normal operation. If that happens, the main effect is a lower dynamic pressure on the tail, not flutter. For that to happen, you need some coupling of aerodynamic and structural oscillations. For slow flight speed, the wing flaps will bring the wake again well below the horizontal tail.


Does the extension of trailing edge flaps increase or decrease the critical angle of attack?

Both right and both wrong, both over simplifications based on unknown airfoils, and so on. Real aerodynamics is complicated and 3 dimensional.

Flaps usually increase the critical angle of attack a few degrees, but they also increase the effective angle of attack for a given pitch. So the net result is that the pitch of the aircraft will be similar at stall with or without trailing edge flaps, but the true AoA will increase.


Why does ATC ask a crew who has declared an emergency if their aircraft will be overweight when landing?

If an aircraft encounters a serious problem quite soon after departure that forces it to land immediately, the aircraft may be above its certified maximum landing weight. This is because there is still a lot of fuel in the tanks, which adds a lot of weight.

As @RonBeyer mentioned in a comment, landing overweight can have a number of serious consequences. When landing a heavy aircraft, stopping it on the runway already requires a lot of energy (or rather, a lot of energy needs to be converted into something else). If the aircraft is heavier than it is designed to be on landing, this may cause excessive stress on the brakes. In extreme cases, this can make the brakes catch fire. Now, open flames under an aircraft that is almost fully loaded with fuel is the recipe for disaster.

In some cases, even though the crew brakes hard on landing, the aircraft may be so heavy that stopping on the runway is impossible. A runway excursion will then follow (a situation where the aircraft leaves the runway onto the grass or similar). This is not neccesarily dangerous, but it certainly can be, depending on the surrounding terrain:

(image from http://avherald.com/h?article=46f3d531. This aircraft was not overweight, but I still think the situation shown in the picture is relevant to this question.)

Obviously, in an emergency ATC, and in turn the fire and rescue crew at the airport, need to be prepared for such events. If ATC expects an aircraft will be landing overweight, getting the crew to confirm this will allow ATC to inform the fire crew that they can expect brake fires or a potential runway excursion. It can also enable the rescue leader to position the fire vehicles at the best possible position, which would be further down the runway than normal, since the landing roll will be longer. So basically, it's a way to get information to the rescue crew so that they can prepare for what might be coming.

Depending on the type of emergency, ATC will also ask the crew about other details, in some cases also with the purpose of passing this information on to the rescue crew, since the rescue crew will normally not be in direct contact with the cockpit as long as the plane is in the air. See also this related question: Why does ATC ask emergency aircraft about fuel on board?


What is the difference between "anywhere" and "other than congested areas" in regard to minimum safe altitude?

The difference is subtle, but here it is:

anywhere means anywhere: At all times you need to operate at an altitude where, should you lose power, you can put your aircraft on the ground without "undue" hazard to anyone on the ground.
Ignoring all airspace considerations, say you're operating over a city (a congested area), and keeping to the bare minimum requirement for altitude and distance from obstacles. Your engine now fails, and your only "landing" options all involve slamming nose-first into the side of a building. You were not operating "at an altitude allowing, if a power unit fails, an emergency landing without undue hazard to persons or property on the surface".
Since we all want to be able to make safe emergency landings this rule is largely common sense with the force of regulation.

other than congested areas is stuff like farmland or open beaches: you COULD operate much lower and closer to obstacles here and still be within the rules above (you're 300 feet AGL over an open field with a barn 300 feet to your right -- The engine dies, you set it down in the field, and everything is cool), but the FAA (and Farmer Brown in the barn milking Bessie) would prefer you not be that close to the barn in the event of say a flight control malfunction.  Most pilots also wouldn't want to be that close to the barn at that low an altitude (unless engaging in an approved aerobatic demonstration with appropriate waivers) anyway, so it's usually a non-issue.

That leaves congested areas - cities, suburbs, crowded beaches, etc - where the FAA bumps up the minimum obstacle clearances / altitudes for the comfort and safety of folks on the ground.
One could contrive a scenario where you could safely fly at 1500AGL next to a 2000-foot building (like a long, clear, mostly-empty park adjacent to it that you could fly over & use for the "anywhere" emergency landing requirement), but again if something else went wrong you might go into the side of the building. As there are more people in "congested areas" to be freaked out by an airplane flying at a safe-but-rather-close distance, and more people who could be hurt by an unexpected departure from controlled flight, the margins are increased to provide a higher minimum level of safety.
As with Bessie in the barn, most pilots probably don't want to be this close to buildings full of people (and the associate mechanical turbulence), and while circling your friends house in the suburbs is fun it doesn't have to be done low enough to pick out the individual bricks in their driveway and you really should be high enough to land on their street safely if your engine quits, which these minimums will likely allow.


From which aircraft does this vintage altimeter come from?

What you have is a Kollsman C-12 altimeter manufactured by the Square D Company in Elmhurst, New York. The 50,000 FT marking below the Military Standard number means that the altimeter is accurate up to 50,000 feet of altitude but this number might far exceed the capabilities of a particular aircraft as it was universally used on many different types. The free of radioactivity sticker means that this instrument does not have the radium dials found on earlier models (common on WW-2 instruments) or, was later retro-fitted with a non radium face. Since you purchased this instrument in Thailand I am suggesting it came from a T-28 Trojan. The Royal Thai Air Force operated 120 T-28s from 1962 to 1988. The United States Navy ceased T-28 operations in 1984 but by then many of their T-28Bs  had been modified into "Ds" as counter insurgency aircraft and shipped abroad. Since the Thai Air Force recieved all their aircraft from America, there is a excellent possibility that your instrument came to Thailand either in a ex Navy T-28 or as a spare in a support maintenance package.


What should I do if I lose situational awareness while in the pattern?

It is the advice of the FAA that you should be looking out the window quite a bit when VFR in the pattern. According to this AC related to traffic patterns:

  Collision Avoidance. The pilot in command’s (PIC) primary
  responsibility is to see and avoid other aircraft and to help them see
  and avoid his or her aircraft. Keep lights and strobes on. The use of
  any traffic pattern procedure does not alter the responsibility of
  each pilot to see and avoid other aircraft. Pilots are encouraged to
  participate in “Operation Lights On,” a voluntary pilot safety program
  described in the AIM, paragraph 4-3-23, that is designed to improve
  the “see-and-avoid” capabilities.

If you are worried you should (over) self announce, if you lose track of an aircraft you should do every thing in your power to make sure that the other aircraft know where you are in the pattern.

  Self-Announce Position and/or Intentions. “Self-announce” is a
  procedure whereby pilots broadcast their aircraft call sign, position,
  altitude, and intended flight activity or ground operation on the
  designated CTAF. This procedure is used almost exclusively at airports
  that do not have an operative control tower or an FSS on the airport.

The FAA also offers lots of advice on how to fly a pattern here.


Where can I find more information about that glass board in old aircraft carrier operations centers?

Perhaps you're referring to the status board (still in use):

(navy.mil)

  Air Traffic Controller 3rd Class Jeoffrey Keever writes the status of each aircraft on the status board in Carrier Air Traffic Controller Center (CATCC) aboard USS John F Kennedy (CV 67) during flight operations.

Windows also seem to work:

(navy.mil)

Also the low-tech but dependable Ouija board is still in use:

(navy.mil)


Is "right-of-way" based on aircraft size?

The size of an aircraft plays no role in identifying who has right of way.

The general rule is that for same-class/type (powered or non-powered) aircraft, the aircraft coming from the right has right-of-way and should be yielded to. This is irrespective of the size within the same type, but a question of manoeuvrability. For different types of aircraft, a powered aircraft will have to yield to non-powered aircraft. For more details see the related question below, ICAO Annex II, FAR 91.113 or another explanation in the Skybrary.

Technically, this means that where separation between IFR and VFR traffic is not provided and aircraft on both flight rules can operate, a Boeing 737 would have to yield to any powered or non-powered aircraft coming from the right.

In most jurisdictions you will find a passage that also details that aircraft should give way to other aircraft that are established on final approach, so a strong situational awareness in the vicinity of airports and airfields is required. Whether separation is provided between IFR and VFR within a traffic pattern, is based on the jurisdiction and the airspace class. In most cases of smaller general aviation aircraft and larger/faster general aviation or commercial aircraft operating at uncontrolled airfields, the smaller aircraft will yield to the faster traffic already on the final approach path out of courtesy or due to good airmanship. It is easier and also cheaper for a smaller general aviation aircraft to perform a 360° turn than for e.g. a Learjet on final approach.

See related question: Which way should you turn to avoid another aircraft?.

See also this YouTube video: Airplane Right-of-Way Rules - Author: Humble Aviation


In order to fly an SVFR clearance, the pilot and planned flight must meet several criteria.  The AIM 4-4-6 as well as 14 CFR 91.157 spell out the basic requirements:

You must have at least a private pilot certificate to obtain an SVFR
clearance during daylight hours as well as an instrument rating to obtain an SVFR clearance at night.  Student pilots are not permitted to request an SVFR clearance.
You must obtain an SVFR clearance to depart from Class E, D, C and B
airspace if visibility is below VFR minimums. SVFR clearance may be prohibited in some Class D, C, and B airspace due to the volume of IFR traffic.  Check the airspace NOTAMs
for these areas prior to departure.
You must have at least 1 statute mile visibility on both the ground and in the
air as well as remain clear of clouds (airplane) or simply remain clear of clouds and have at least 1 statute mile visibility for operations in Class B, C, and D airspace (rotorcraft helicopter).

All an SVFR clearance allows is for a VFR pilot to enter, depart or operate in controlled airspace using day VFR minimums for Class G airspace.  If it is done correctly by a competent private pilot and only in these conditions, it can be done safely as it provides the pilot with enough visual references to safely operate in VFR.  It is also advisable to do a realistic assessment of one's own abilities to control an airplane in marginal conditions and set conservative minimums for things like congested airspace or other weather in the area.  It is not advisable to do this if weather briefings anticipate IMC after departure.  Likewise if you have little experience operating in congested controlled airspace or if you struggle to stay ahead of the airplane under additional stressors, SVFR may not be advisable.


What is the difference between an Instrument and Equipment?

In the aircraft an instrument is related to equipment providing displayed data.


How does blade solidity ratio relate to thrust/power/torque of a propeller?

Each propeller blade is a wing in itself, and like a wing carries the weight of the plane, the propeller blade carries its fraction of the total thrust of the propeller. The more blades, the lower the fraction of each blade.

Low disc loadings are associated with two- or three-bladed propellers. Those can be found on GA aircraft and older, slow designs like pre-WW II aircraft. With turboprops and near-transsonic designs, more blades are needed to distribute the aerodynamic loads and to reduce the lift coefficient especially at the tips.

There is no strict formula, but in general a higher disk loading is associated with a higher solidity ratio.


How should you coordinate with traffic at non-towered airports?

The problem with uncontrolled airports is that sometimes the procedures and "etiquette" can be informal.  The pilots based at the airport have established their own informal procedures which are not published anywhere or are part of any rule book.  In cases like this I would consult the FBO for the local procedures (which you did do) but that doesn't mean that all the pilots at the airport abide by them.  In your situation this is what I would have done:

I would have announced on the CTAF that I cannot speak French and would request that all pilots announce their intentions in English.  By international convention pilots are required to communicate to ATC via English unless there is an emergency.  However CTAF communications tend to be more informal and the pilots at the local airport may prefer to speak in the language they are the most comfortable.  Still the intent of CTAF is to communicate with everyone at the airport to announce their intentions.  It would have been entirely proper to request the pilots to speak in English.
I would have requested the pilots performing the touch and goes to give you a window in which to back taxi and takeoff.  I find it rather rude for pilots to monopolize the pattern and runway performing touch and goes.  If they see that there is a line of planes wanting to takeoff they should leave the pattern for a while and let folks takeoff before resuming their touch and goes.  Asking politely on the radio for these pilots to do this for you is reasonable.
If they were giving you grief for not using the grass to taxi to the runway they had no right to do that.  Taxing on grass can be dangerous especially in tricycle gear aircraft where the potential for a prop hit with the ground is a real possibility.  In my case I am bound by the club rules not to taxi on any surface that is not paved.  Back taxing would be the appropriate thing to do.


Does a helicopter's boundary layer have different properties that are caused by the rotation? How does this affect stability of the helicopter?

You are right, the rotation does affect the boundary layer.

Normally, as a wing approaches its stall angle of attack, the boundary layer becomes thicker and the flow starts to separate near the trailing edge. On a rotating rotor or propeller blade, the slowed-down boundary layer will experience a centrifugal acceleration, so it does not come to a standstill eventually (as it does in case of separation), but merely starts to flow tipwards. Since the speed of the rotor blade increases as the flow moves towards the tip, the boundary layer experiences an additional Coriolis acceleration. Therefore, flow separation is delayed on rotors and propellers compared to the two-dimensional case (for example, when the rotor airfoil is tested in a windtunnel).

From heli-air.net:

  The helicopter rotor experiments of Dwyer & McCroskey (1971) also
  suggest favorable effects on the spanwise development of the boundary
  layer, which tend to delay the onset of flow separation to a higher
  blade section AoA and thus serve to increase the maximum thrust of the
  rotor system.

The stability is affected by other effects; here the peculiarities of a boundary layer on a rotating wing make little difference beyond the higher stall angle of attack.


How should I operate within the dashed magenta lines next to Class D airspace?

The area inside those lines is class E from the surface.


How is a composite fuselage repaired when structurally damaged?

This is pretty broad and covers a wide range of techniques.  But the airplane Structural Repair Manual (SRM) provides guidance, depending on the extent of the damage.  Typically it involves excising the damaged or delaminated structure and patching the affected area.  As with metal airframes, if the damage it too extensive the airframe may have to be written off as a total loss.


What is NH overspeed test and how it is preformed on DHC Q400 aircraft?

The same statement is made here in a document describing the PW150 turboprop engine, which powers the de Haviland Canada, now Bombardier,  Dash-8.

It gives a little more detail in section 12.23.14.4, NH overspeed protection.

It says:

  The PW150A Powerplant has an independent overspeed (O/S) protection circuitry (dual chan- nel) built into the FADEC which has the capability to cut off the fuel flow through the Fuel Shutoff Solenoid. Independent NH signals (from the FADEC) are used by the O/S circuitry. A fuel shutoff command is issued when the measured frequency of the NH input signals exceed a pre-pro- grammed threshold value of 108%. The O/S Protection circuitry is exercised on normal shut- downs by the FADEC.

So, it would appear that, when testing the overspeed protection in a normal shutdown, they do not actually allow the shaft speed to increase to 108%, but rather they electronically alter the speed sensor frequency signal, so it appears like the shaft speed is greater than 108%, which then cuts off the fuel flow.

NH is the term used to describe the high pressure shaft speed, measured in units such RPM.


What are the common private pilot practices for helicopter off-airport landing in US?

There are minimum altitudes for cruise flight but altitude may be reduced below these minimums as needed for approach to landing. I don't know of any FAA regulation that requires landing at a designated airport(or heliport)

Title 14(aerospace) of the federal code of regulations part 91.119 (part 91 is general flight rules for all aircraft) simple says that;
"Except when necessary for takeoff and landing, no person may operate an aircraft below the following altitudes:"

A: Anywhere. At an altitude as to create an "undue hazard" to people and property on the ground in the event the engine fails. (Will you hit a building or dense crowd, or will you have time to aim for an open spot?)

B: Over any congested area of a city or open air assembly of people, below an altitude of 1000feet above the highest obstacle within 2000 foot horizontal radius from the aircraft.

C: over other than congested areas, no less than 500 feet above the surface, except for over water or sparsely populated areas. In those areas the aircraft may not be operated within 500 feet in any direction from buildings or boats. So no actual minimum altitude limit if you are over a field 500feet to the side of a barn.

D:Helicopters, powered parachutes, and weight-shift controlled aircraft(hang gliders and ultralights), if conducted without hazard to person or property o the surface may be operated at less than the minimums prescribed in B and C, provided the operator of a helicopter complies with any special routes or altitudes specifically prescribed by the FAA.(Generally special provisions are only found in high air traffic areas near major airports or over high security areas.)

These are paraphrased slightly for clarification and because I type how I likes to type, but the actual wording of the law is very close.

There may also be some local laws about noise limits if operations are frequent but this is not limited to aircraft.


Why are so many tail-strike incidents not verified until later inspection?

On one hand tail strikes are mitigated long before the need for a sensor. Aircraft makers generally address it from a design standpoint before the aircraft ever flys. If that is not enough control augmentation or tighter procedures are developed to prevent it from an operational level.

Ultimately such sensors do exist and do warn the crew of a tail strike they may just not yet be certified or installed on every airframe. For example it came in handy in this incident:

  After the passengers had disembarked, the captain conducted an
  inspection of the tail skid of VZR and noticed some paint damage and
  scrape marks, however the cartridge containing the sensor for a
  tailstrike was still intact. This indicated that the tailskid had only
  just contacted the runway during the take-off.


Why does the U.S. have so many general-aviation aircraft?

Part of the reason is also historical. After World War II was over there was a large number of veterans with flying experience returning to a country that suddenly had a massive surplus of small trainer aircraft.

While the US expended huge amounts of resources on World War II, it was largely untouched by the destruction that many other countries suffered. This meant that instead of having to rebuild, the US could focus on growing the economy. Though GA declined in the Great Depression and was suspended during World War II, there had been a similar situation after World War I that had gotten the industry started.

Small aircraft were much simpler then, with a much lower cost to build and certify. This made general aviation relatively much cheaper. Also, while the US certainly had a highway system, the interstate highway system had yet to be built. Commercial aviation service was not nearly at the scale it is today and was still fairly expensive. This made general aviation a much more reasonable option for traveling around a large country.


Where are the microphones for the black box located in the cockpit?

The headsets worn by the pilots have a microphone arm. These audio channels are split and routed to the black box.

Additionally, there is at least one microphone embedded in the cockpit, usually overhead.

The black box can support recording of up to 4 audio channels, so each channel can be examined separately.

Since the headsets and overhead microphone are inside the cockpit, stereo audio is available.

Can't find any pictures for you, sorry!

Seethis sources:

Avstop

FAA (pdf)


Is training and pay different for cargo and airline pilots?

Do cargo pilots receive different training than airline pilots?

First, cargo carriers are airlines just as passenger carriers are airlines, and cargo pilots are airline pilots. In the U.S. there is no difference in the training and certification of pilots dependent on whether they fly passengers or cargo. Also, be aware that airlines you generally think of as passenger carriers can also be operating freighters as well as carrying cargo on pax flights.

Whether there are passengers or cargo in the back, the airplane is having to operate in the same airspace, and a given aircraft model, whether in pax or cargo configuration, is essentially the same insofar as flying the aircraft. Indeed, at each of the two 747 carriers I flew for, we had both pax and all-cargo aircraft, and which we were flying made no difference in our pay rate. Pay rate is typically dependent on equipment flown, union contracts, and other considerations, but not on whether there are boxes or people in the back.

There are a few differences in flying pax versus flying cargo. Some that I can think of offhand are:

With pax and within 4000 feet of the ground we limited our bank to 20 degrees unless in cloud.
With pax we tried to avoid turbulence in general. With cargo not so much. Boxes don't complain.
With pax you are less likely to be concerned about weight and balance. Pax weight and balance is relatively simple, cargo weight and balance can be more of a problem.
With pax, you of course can have passenger problems, but those are almost always handled by the cabin crew. Only once did I feel that I really had to go back to the cabin, and that was because we had an inexperienced purser. Even then I could have sent the flight engineer or first officer, but I was bored.
With cargo, you don't have to worry about passenger announcements.
With cargo, you don't have to worry about dinging the flight attendants going through 10,000 feet.

Cargo is more fun, in my opinion, insofar as flying the airplane; you feel free to do things that you might not do with pax.

Pax is more fun on layovers, and you don't have to get your own meals, drinks, etc in flight, although I flew 3-man cockpits and the flight engineer often took care of getting those things on cargo flights.

Pax can be a problem on layovers where they're depending on the full crew being available the next day, because flight attendants increase the number of required crew members, and thus the greater the chance that somebody will get sick, get beat up, get in trouble with the law, get hit by a car, or run out of money and hit up the captain for an emergency loan. I had all of those happen .

Finally, arguably the life that the pilot is most interested in preserving is her/his own. Get yourself to the destination safely. What's in the back of the airplane will follow.


Why does the stagnation point on airfoil move with the angle of attack?

At the stagnation point, the streamline is directly perpendicular to the airfoil. As angle of attack increases,  the streamline is no longer perpendicular to the leading edge (which is where the stagnation point is usually located at 0 angle of attack). This is the best explanation I can come up with for why the front stagnation point moves as it does.
The rear stagnation point is usually located at the trailing edge of the airfoil, thanks to the Kutta Condition which says that, "A body with a sharp trailing edge which is moving through a fluid will create about itself a circulation of sufficient strength to hold the rear stagnation point at the trailing edge." (according to wikipedia). The airflow around the airfoil, which is a body with a sharp trailing edge, keeps the rear stagnation point where it is.
This moving of the front stagnation point as the AoA increases is part of the reason why lift increases with increases in AoA.


Did the Mig 21 have differential stabilators to help the ailerons?

No.
MiG-21 (any modification) didn't need it and didn't have it. With its low-aspect-ratio delta wing and most mass concentrated in the centre, it was agile enough with standard ailerons.
The elevator had a single hydraulic booster driving both halves of the stabiliser.
Differential stabiliser was used on MiG-21's successor, MiG-23. That one had no ailerons at all; it had full-span flaps on its swing wing instead. Roll was controlled by the spoilers and the differential stabiliser.


What's the difference between positive and negative pressure relief valves?

The positive pressure relief valve opens in case the cabin pressure is too high in comparison to outside air Pressure. This happens if the pressure differential is higher than 8.85 psi / 0.61 bar (Airbus). It is most likely to happen in malfunction of the outflow valve (stays closed).

The negative pressure relief valve opens most likely during descent, when the cabin altitude is still at 8,000 feet (normal condition) but the aircraft itself is lower than that. That means that the pressure outside of the aircraft is higher than inside. The valve opens at a differential pressure of -1 psi / 0.07 bar.


Crosswind landings are always uncoordinated. I'm not familiar with big jets, but I believe they simply kick the rudder to align the nose with the runway and let the momentum carry it in the right direction until it touches down, but I might be mistaken here.

In a smaller aircraft (like a piston single) you're taught to drop a wing into the wind and effectively land in a side slip.

This is all perfectly safe, the dangerous situation you're talking about is a skidding turn, where you apply too much bottom rudder, letting the 'inner' wing slow down to the point of stalling. This only applies to an actual turn however, if you're flying straight, coordinated or not, there's still more or less the same airflow over the wings. You could however experience other aerodynamic effects where fuselage and airfoils effectively perturb the air for other airfoils and might cause a wing drop or pitch change, but it depends on the properties of the aircraft.


What were the effects of the oil crises on the Concorde ticket prices?

The Concorde started service only in 1976, so there never were actual pre-crisis prices. This makes your first question impossible to answer. Of course the airlines which ordered the Concorde had their plans how much to charge, but kept that a commercial secret.

When service started, the plane lost money. What happened next is an interesting lesson in economics. From A Pricing Lesson from the Concorde:

  The Concorde team decided to do some market research. They asked
  businessmen how much they thought a Concorde ticket cost. The answer,
  “Most of them didn’t know. It was their secretaries or travel
  companies doing the bookings. When they were asked to guess, because
  they were senior, very important people, they all guessed that the
  fare was higher. ” – explained Captain Jock Lowe, Concorde resource &
  Planning Manager.

  This insight led to a new pricing strategy. Captain Lowe described “So
  very simply, we said, we’ll charge them what they think they are
  paying. And so we put the fares up”.  There was a discrepancy between
  what the company was charging and the value customers saw in the
  product.

  Concorde ticket prices were doubled to over $7,000,  one way, in
  today’s prices. As a result, Concorde was repositioned to provide a
  super-elite class for bankers, the rich, and the famous. Concorde
  became the place to be seen.

Generally, ticket prices were 1st class + 20%. So what affected ticket prices most was the all too human tendency to show off; the mechanism that makes luxury brands possible. Fuel became less significant.

Now let's look at the fuel cost. This table only starts in 1975 (but covers the full operational history of Concorde), and when I apply your factor of four, the pre-1973 price of jet fuel would had been 8 cent per Gallon. This means the nominal price has gone up by a factor of 50 when compared to the peak in 2008.

The Concorde typically needed 214 Gallons of fuel per passenger on the Paris - New York route (see my comment for evidence; using @mins much better source gives 236 Gallons), so that means fuel cost per ticket would look like the plot above, multiplied by 214 or 236. At the start of operations in 1976 that would had been about 70 USD per ticket, would had jumped to 200 USD per ticket at the start of 1981, would had dipped below 100 USD briefly in mid-1986 and again in 1998. The peak would had been above 800 USD in mid-2008 had the Concorde still been in operation at that time and would today be nearly 300 USD.


The airport is buying fuel and selling to airlines. And more over, they provide different types of fuel on prior request by the airliner. Reference : VCBI


Lighter materials such as plastic will naturally float.

Composites can have large sections of honeycomb core with trapped air. Even if these parts are broken, the honeycomb is sealed against both sides of the panel, still trapping air.

Large sections, whether made from composite or metal, will generally be hollow to save weight, and sealed to prevent collecting moisture which could cause corrosion. There may be small drain holes, but they wouldn't be enough to cause significant leaks.

Fuel tanks are sealed but they are also fairly large and contain baffles to allow fuel to flow within the tank. As you would guess, a catastrophic crash would be unlikely to leave a significant portion that doesn't contain holes.

The parts found suspected to be from MH370 all have these qualities.


What are these boxes built into the tails of some fighters?

You're right. It's the ECM/EW antenna/equipment (fairing) in all the aircrafts except Typhoon.

This photo shows the details of EW/ECM suite in Gripen.

Source: www.w54.biz

In Typhoon, it is the engine bleed air heat exchanger. The part is in detail here.

Source: b-domke.de


Do airlines employ FAs from their destination countries?

The 747 carrier I retired out of had FAs based in New York and Tel Aviv, and were residents of their respective countries. The citizenship of the JFK FAs was not a factor insofar as I know as there were numerous green card holders.

Non-stop flights between JFK and Tel Aviv (and return, of course) were staffed by Israeli FAs. All other flights were staffed by JFK FAs. The primary reason for this arrangement was cultural. For JFK/TLV the back quarter or so of the aircraft was allocated to Hasidics to attempt to satisfy their preferences. For example, no movies were shown in the back because they were objectionable to the Hasidics.

The advantage of having Israeli FAs on the direct flights was that they knew how to handle the Hasidics. Scheduling problems would occasionally result in JFK FAs operating a JFK/TLV flight. It was not uncommon on such flights for the cabin crew to request a cockpit crew member to come back to help mediate a dispute. I never received such a request from an Israeli cabin crew.


Yes, every aircraft has a registration number--or "tail number" since it is commonly painted on/near the tail. This links each make/model/serial combination to a specific owner, similar to a car's license plate.

Each country assigns tail numbers with that country's unique one-, two- or three-letter prefix(es), e.g. "N" for the USA and "XA" for Mexico, followed by some number of letters and/or digits according to their chosen scheme. Some countries allow requesting a specific number not already in use (or reserved), similar to vanity license plates.

For non-commercial flights, a plane's tail number is used as its radio callsign since it's guaranteed to be unique. Commercial flights typically use the carrier's callsign plus flight number.


How do the cabin noise levels of the A380 and the 777 300 ER compare?

From a luxury round the world flight on several different models of aircraft on several different airlines, a traveler used the exact same sound meter at his seat in either business or first class to measure ambient noise level during cruise.

Here is a chart I made of his measurements, including carrier and age of aircraft. As you can see, long haul aircraft are quieter than short. Carrier and age of aircraft also seem to make a difference.

For this set of measurements, the b773 is 3db (or 25%) louder than the a380.


Why isn't transition altitude standardized in Europe?

You're right that having a common transition altitude is better- efforts are underway in Europe to set a common transition altitude. Multiple studies have been carried out by Eurocontrol and it has been noted that it is better to have a single transition altitude. For example, from an aircrew prespective:

  The multiplicity of transition altitudes and the national rules and procedures make the European environment  very  complex.  This  can  lead  to  a  lack  of  altitude  awareness  and  altimeter  mis-settings  and  is  operationally  unsatisfactory.

and

  Establishment of a common transition altitude has a clear safety benefit.

Similarly, from the ATC perspective:

  The establishment of a common TA for ECAC States and the EUR Region is a  fundamental element in achieving the goal of a unified sky and the safety policy of reducing risks to the greatest degree practicable.

The reason such an unsatisfactory state of affairs have persisted is that people have become used to that- the second document makes that point:

  ATC providers, as is human nature, grow comfortable with what they are most familiar.

The main reason is that there is no requirement for any common transition altitude. The relevant ICAO document simply states:

  2.1.2.1    A transition altitude shall normally be specified for each aerodrome by the State in which the aerodrome is located

and

  2.1.2.3    As far as possible, a common transition altitude should be established: ...

As a common transition altitude is not exactly a requirement (in-spite of its advantages) different European states have historically established their own TAs, to be decided by the aerodromes or the regulatory authorities.

As they have become comfortable using it (and no major accidents have happened because of this), there is no serious move towards the establishment of a common transition altitude (through arguably, this is the case with much of the world- common transition altitude is not that common). In the UK, CAA has launched a consultation process to raise the transition altitude to 18,000 ft, which notes that,

  ... it has been agreed that the TA in the UK will be raised to 18,000ft.


How often do commercial flights go-around?

As mentioned here:

  Go-arounds occur with an average rate of 1–3 per 1000 approaches.

Most of the videos on YouTube are of go-arounds because of weather. This is not a common scenario as many flights divert to other airports where weather is less severe.


What determines the noise an aircraft's undercarriage makes at the moment it leaves the ground?

Without hearing it I would imagine that what you are hearing is the landing gear reaching full extension and hitting it's mechanical limit. Think of it like one of those bicycle air pumps, and the sound it would make if you pull that handle all he way up. It's the same basic mechanism, except upside down, and the landing gear should be full of hydrolic fluid to support the force of the aircraft landing on it.

One aircraft has a mechanism that has a hard stop at the end of the stroke, and so you hear the extra forces being translated as that sound. The other aircraft has a softer end, so maybe there is a spring or rubber bumper pice or something that softens the end of the extension.


Can ATC handle a flight as emergency although the pilots have not declared an emergency?

In the US, a controller has the authority to treat any situation as an emergency, and they do.  I have had controllers "declare" an emergency multiple times, even when I thought I did not have an emergency.
There are some advantages to the controller.  His work gets shed to others, and his supervisor is at his side to assist.
At one point, after ice, delays and trying to get into a DC airport close to the Christmas holiday, I declared "minimum fuel" which I didn't consider an emergency.  I just wanted to let the controller know that if they vectored me towards West Virginia again, I would be landing close to or at reserves.  The weather at the destination was far better than the ice I have been flying through at 13,000, but I wanted to avoid plunking down at Martinsburg, away from my destination to buy another load of fuel.
Immediately I got handed off to a Dulles controller, whose radar had better coverage than Baltimore Approach who handled approaches normally for my destination.  I got kid glove treatment, and did not get further delays, and landed at my destination without any incident.  After the paperwork, I dipped the tanks, and figured I still had about 27 minutes more fuel than my minimums for IFR night flight with a diversion to better weather.
Similarly, having gear problems almost always gets an "emergency" status.
I will say one thing, when I was dealing with a cockpit fire, and the controller kept asking again and again the same questions it was distracting, but they are trying to get their job done the best as they can, just as the pilot is.  In my case, I just stopped answering lower priority questions.  In the case of the cockpit fire, I killed the master switch (at night), and another pilot in the back brought ATC up on his handheld radio.  Up front we dealt with the fire, and delegated the communications to a guy in back.
So in application to the LNI610 and other situations, it makes sense that the pilots exercise their ability to tell a controller to "standby."  It works some of the time.
I am not as familiar with the US Controllers Handbook as I have been in the past, but I am confident that the controllers have authority to declare an emergency.  But keep in mind that they are products of their environment, just as pilots are, and they have training, objectives, experiences and organizational expectations which change and vary.


What is the minimum takeoff fuel requirement policy for commercial aircraft?

14 CFR 121.639 Requires an airliner to have enough fuel to reach the destination, then fly to the (most distant) alternate, then fly after that for 45 minutes. If you want to know exactly how much fuel that is for a particular airplane on a particular route, you have to refer to that airplane's POH and plan the flight. It will also depend on the winds aloft and what airport is chosen as the alternate.


What is the legal interpretation of rest for FAA Part 135 operations?

The 10 hours of rest need to be uninterrupted, planned, and not spent on call. Essentially, the pilots need to have 10 hours in which they are not obligated to do any work for the company at all.  Note that it does not mean "10 hours of sleep", and it is up to the pilot what they do with their time off.  (They can even technically fly for another 135 operator during that time, but they run the risk of being "careless and reckless" if they aren't well rested.)

NATA has an article about some of the FAA's legal interpretations (pdf) that's pretty interesting and relatively recent (2011). Their paraphrase of the FAA's varying interpretations is this:

  the FAA has said that for a “rest period” to be legal it must be: 1) continuous, 2) determined prospectively (i.e. known in advance) and 3) free from all restraint from the certificate holder, including freedom from work or freedom from the present responsibility for work should the occasion arise.  Being on call is specifically mentioned as not rest.

This is an interpretation that is repeated throughout a lot of articles and forum discussions. It's also often pointed out that many (most?) 135 carriers blatantly ignore these rules, as most charter operations require pilots to be on call.

For example

You arrive at 19:00, and are done with paperwork / postflight / etc by 19:30 and leave the airport. The moment that you leave the airport is the beginning of your rest period; it will need to last 10 uninterrupted hours, which means until at least 0530 the next morning (1930 to 0530) to mean anything.

If you get a call from dispatch at 21:00 telling you about a flight that might take place in the morning and that you must be available for a call at 05:00 just in case - your rest ends at 05:00. Because your rest period ended 30 minutes early (when you were required to be available), you did not get the 10 hours of rest and can't take a flight without violating 135.267(d).

Another caveat:

There are no explicit limits on duty time (the exception being 135.267(c) involving a "regularly assigned duty period of no more than 14 hours" which doesn't apply to most 135 operators).  The limit is on planned flying conducted under 135.

As long as you plan on parking the airplane when you can show 10 hours of rest in the previous 24 hours (which is why some people incorrectly assume that you are limited to 14 hours of duty: 24 - 10 = 14!), you can be kept on duty afterwards.  You can even fly under Part 91 for the company.  You can clean the airplane, or do office work.  While none of that is rest and it is still duty, it is legal unless you get in the airplane to fly under Part 135 without getting the required rest.


Why does JetBlue have aircraft registered in Germany?

I am the pilot who delivered this aircraft on Friday.
The German registration remains on the aircraft up until the time we (JetBlue) purchase the aircraft. Prior to transfer of title, we perform a series of ground tests and flight checks.  This is all accomplished while Airbus still owns the aircraft.  Once any discrepancies are corrected, and we accept the aircraft, we buy it, the ownership changes and the temporary (German) registration is removed. This is typically the day prior to ferrying it over to the US.
As for the Hamburg/Toulouse question- TLS does not produce A321 aircraft, so all of our JetBlue deliveries come from either Hamburg or Mobile, AL.


Do airliner cabin filters trap viruses or other pathogens?

Modern airliners use HEPA filters to filter the air before re-circulation. This will remove almost all airborne pathogens like viruses:

  The overall risk of contracting a disease from an ill person onboard an airplane is similar to that in other confined
  areas with high occupant density, such as a bus, a subway, or movie theatre for a similar time of exposure.
  anywhere where a person is in close contact with others.

  That said, the risk on airplanes is probably lower than in many confined spaces because modern airplanes have
  cabin air filtration systems equipped with HEPA filters.

  HEPA or high efficiency particulate air filters have similar performance to those used to keep the air clean in
  hospital operating rooms and industrial clean rooms. These filters are very effective at trapping microscopic
  particles as small as bacteria and viruses.

  [...]

  Air filters can remove very small particles such as bacteria and viruses. Virtually all viruses and bacteria are
  removed; even the most difficult particles in the range of 0.1 to 0.3 micron are filtered out with an efficiency level
  of of 99.995%. Contrary to popular belief, very small particles below 0.1 micron are easily filtered out by the
  mechanism of diffusional interception.

(IATA Briefing Paper - Cabin air quality - Risk of
communicable diseases transmission, emphasis mine)

The following image shows the location of this filter in front of the re-circulation fan for a Boeing 737:

(Boeing 737 NG FCOMv2 2.30.5 Air Systems - Air Conditioning System Description)


What is the true formula for parasite drag?

The philosophy employed on the Stanford site is to convert the product of drag coefficient and corresponding surface area to a "drag area", which is technically the area of a body with a drag coefficient of 1. See page 1-8 in Sighard Hoerner's book "Fluid Dynamic Drag" for the definition and tons of helpful real-world data on drag.

To convert this into a drag force, it still needs to be multiplied with the dynamic pressure, which is the product of the square of the velocity, the air density and the factor 0.5. No further inclusion of the surface area is needed, as this is already factored into the drag area values of each drag component.

Using the drag coefficient lets you compare the relative dragginess of drag components (friction drag, pressure drag, ...). If you want to compare the dragginess of aircraft components (wing, fuselage, tail surfaces, ...), using their drag area adds a factor for their size, making it easier to compare the relative influence of the drag of different aircraft components on total drag.

To answer your second question: Planform area is the wing area you see in the top view of an aircraft, and the wetted area is the actual area which is exposed to airflow. If you start with the planform area, you need first to subtract the part of the wing which is inside the fuselage. Next, you double the result to account for both sides, top and bottom, and then you divide this sum by the cosine of the dihedral angle and the cosine of the incidence angle to arrive at your wetted area.


Regarding the confusion, if this is for your thesis like your previous question, ICAO Doc 10037, which supercedes Doc 9694, should clarify many things. But there could be more applicable references based on your research topic (you can ask your advisor to make recommendations).

Regarding your questions:

Does FANS 1/A have ADS-C?

Only "FANS 1/A ADS-C" does, if "ADS-C" is not in the name, then no. Applicable standard is DO-258A/ED-100A.

If it does not, what is used for position reporting to the ATC?

ACARS is used. ADS-C is mainly about automatic reporting based on fixed intervals, for example. Otherwise the reports are submitted manually – like making a position report via voice, but instead via ACARS (which is supported by FANS 1/A).

Is satcom used in the FANS 1/A as a message-transporting service?

Yes.

FANS 2/B has LINK2000+ CPDLC and ADS-C (...)

Actually, that's FANS C. It includes both CPDLC (LINK2000+ / ATN-B1) and ADS-C. It made its debut recently.

I think you are confusing position reports, with ADS-C. While ADS-C provides position reporting, it is not the only way, as explained earlier.

What is the role of FMS?

There isn't one blanket answer.

An FMS is where all the position sources feed, whether the FMS can distinguish between mandatory reporting points, and whether it allows the position to be overwritten by the crew, it depends on the aircraft and the installed FMS.

For example for the Boeing B737, B777, B757, B767, B717, MD90, MD10, MD11:

  The FMCs on these Boeing aircraft do not distinguish between ATC mandatory waypoints and FMC sequenced waypoints for position reports. However, the FANS 1 of these aircraft will allow the flight crew to overwrite the FMC- determined default "reported waypoint" position and time.

Source: Doc 10037 § C.5 FMS processing of waypoints in position reports


The RAT is automatically deployed on many aircraft, including the CRJ and A320 series, but it can be manually released as well. In between the loss of power and the RAT spins up you have the batteries to fall back to which are normally fully charged.
The Airbus Manual has the following comment on the APU:

In case of total loss of all main generators, the RAT is automatically
extended and drives the emergency generator via a hydraulic motor. The
EMER GEN supplies the AC ESS BUS and the DC ESS BUS via the ESS TR.
The ECAM WD remains powered, with associated procedures presented.
Alternate law is operative through ELAC 1 and SEC 1
(Source)

While this is for the CRJ, who call it an Air Driven Generator (ADG):

In the event of a complete AC power failure in flight, the ADG will
automatically deploy and supply emergency AC power to the ADG bus and
to the AC essential bus. If the automatic deploy function fails, the
ADG can be deployed manually by pulling the ADG manual release handle
on the ADG CONTROL control panel at the rear of the center console.
(Source)

A RAT, with the spring loaded actuator visible:

I think most if not all are spring loaded, and have a little help from gravity on the way. You'll also notice that many are stored to be pushed into place by the jetstream.
Have a look at this video below around 0:20. The slow upwards motion suggests that it's having to reload the spring energy at 1:20. The doors are attached mechanically.
Taking a look at the Airbus Electrical System:

As can be seen, there's a hierarchy to electrical power use, and the battery feeds the essential busses, where the RAT deployment would be included. If I'm not mistaken, power is very limited: You loose some of the more fancy control computers along with the non-necessary stuff, like the copilot's displays, as can be seen in the following video.
Bear in mind that some aircraft, such as the 747 (up to -400), do not have a RAT on the aircraft, and rely on the windmilling engines to provide sufficient hydraulics to control the aircraft, and as such there's no deployment of sorts necessary.


Did the cusp in the Boeing 377/C-97/KC-97’s fuselage structure cause fatigue problems?

You can actually see the same effect happening with soap bubbles when they touch and form a flat film connecting them. You can actually still see this type of fuselage in use in the Boeing 717 (Douglas/McDonnell Douglas DC-9). A lot of other narrowbody airliners also have it, but the outer panels fair over the intersection between the two fuselages.


What regulations exist for ATC real time RADAR simulator software?

So according to EASA, it is the AMCs/GM for Regulation 2015/340, Part ATCO.OR (Annex III to Decision 2015/10/R) and specifically in AMC1.ATCO.OR.C015(b)(b) where is specifies 11 criteria regarding STD standards, among them being accuracy of aircraft performance, voice recognition realism, equipment, data displays, etc:

  STD criteria

  If  a  synthetic  training  device  (STD)  is  used  for  training, it should
  be approved by the competent authority as part of the course approval process
  for  any  training  plan.  Training  organisations  should  demonstrate  how  the STD  will  provide  adequate  support  for the  intended training,  in  particular, how  the  STD  will  meet  the  stated  objectives  of  the  practical  training exercises and enable the performance objectives to be assessed to the level determined in the training programme.

  This  demonstration  and  the  related  documentation  should  include  the
  following relevant criteria:

  (1) the  general  environment,  which  should  provide  an  environment  in
  which  STD  exercises  may  be  run  without  undue  interference  from unrelated activities;

  (2) the STD layout;

  (3) the equipment provided;

  (4) the  display  presentation,  functionality,  and  updating  of operational information;

  (5) data displays, including strip displays, where appropriate;

  (6) coordination facilities;

  (7) aircraft   performance   characteristics,   including   the   availability   of manoeuvres,   e.g.   holding   or instrumental landing system   (ILS) operation, required for a particular simulation;

  (8) the availability of real-time changes during an exercise;

  (9) the  processes  by  which  the  training  organisation can be assured that staff associated with the training conducted with the use of an STD are
  competent;

  (10) the degree of realism of any voice recognition system associated with
  the STD;

  (11) where  a  simulator  is  an  integral  part  of  an  operational  ATC
  system, the  processes  by  which  the  training  organisation  is  assured  that interference  between  the  simulated  and  operational  environments  is prevented.

  The  extent  to  which  the  STD  achieves  the above criteria  will  be  used  to determine  the  adequacy  of  the  STD  for  the  proposed  use.  As  a  general principle,  the  greater  the  degree  of  replication  of  the  operational  position being  represented  the  greater  the  use  will  be  possible  for  any  particular training.


What was the lift equation used by the Wright brothers?

The Wright brothers' equation is
$$L=kV^2AC_L.$$
where $C_L$ is the ratio of the $L/D$ of a specific wing (AoA, span, chord, camber, thickness all set and fixed) to a perpendicular board into the wind of the same $A$, $k$ is experimentally obtained, and is specific only to the medium (air or water).

In a sense, the Wright's lift equation is seeing lift from a momentum transfer perspective, i.e. the $kV^2$ term corresponds to the momentum flux of the incoming air, and the term $AC_L$ describes how much downward discharge is produced at the price of how much drag.

While the modern lift equation is
$$L=\frac{1}{2}\rho V^2AC_L.$$
This is derived from the Kutta-Joukowski theorem:
$$L=\rho V\Gamma,$$
where $\Gamma=\int_C{\bf v}\,\mathrm{d}{\bf s}$ is a line integral of the second type around a close and simple route around the wing. $\Gamma$ is proportional to $V$. And $C_L$ is defined as
$$C_L=\frac{L}{\frac{1}{2}\rho V^2A}.$$ $C_L$ is not calculated through analytics, but derived through $A,\rho,V$ as obtained in experiments.


What call sign does Marine One use when the President is not on board?

Marine one is the call sign of any of the (300+) United States Marine Corps aircraft carrying the President of the United States. So, if he's not on board, the aircraft reverts back to its original radio call sign.

In case you are asking about the Marine Helicopter Squadron One, you can find the ID from helis.com. HMX-1 uses the call sign 'NIGHTHAWK' usually, but this is prone to change depending on the circumstances. From the site:

  In Korea, call signs changed on a regular basis; during the Vietnam War, squadrons might use the same call sign for more than a year. Today, squadrons deploying to a combat zone,i.e. Iraq and Afghanistan, are assigned a "theater" call sign for use during that deployment only.


How A330-200 or 243 would be much safer under the ETOPS terms?

ETOPS (Extended Twin Operations - at least that’s what it used to be called) is a set of rules comprising of flight planning, flight operations, aircraft maintenance, flight training and administrative procedures which are geared towards making aircraft operations safe in those regions where diversion airfields are not easily found, e.g. when crossing large oceans.

When these rules are obeyed (i.e. when operating under ETOPS), that should make flying very safe.


what is the earth resistance to be maintained while aircraft is on ground and during ground checks for military aircrafts

For the US Navy, according to this instruction:

  The maximum resistance allowable for the cable (MS27574) itself shall
  not exceed 0.5 ohms.

  The cable’s operational (in use) maximum resistance shall not exceed
  10 ohms.

The difference in values corresponds to the loss of quality in the electrical contact at both ends of the wire (clips). Contacts are allowed to be as resistive as about 5 ohms. For comparison hand to foot impedance is about 500 ohms at 100 Hz, meaning the current will be 50x lower in the body than in the wire in case the aircraft is not at the potential of the ground.

You'll find a similar requirement of maximum 10 ohms in: TO 00-25-172, Ground Servicing of Aircraft and Static Grounding/Bonding from USAF.


It looks like a Cessna 208 Caravan to me:

These are single-engine high-wing turboprops, useful for a variety of cargo and passenger-hauling tasks. Here's what a 208 in seaplane configuration looks like on the outside:

Your photo looks like an older plane with the original radio stack and no glass, unlike these newer cockpits. In addition, somewhat startlingly, the right-hand control column and yoke have been removed, but they bothered to keep the copilot's 6-pack. That's odd, from my sensibilities, and it tells me the plane was altered in the cheapest possible way for use as a pure short-range passenger ferry. The right-hand seat can now accomodate an extra passenger (and becomes the best in the house for enjoying the view), without the possibility of that non-flier binding up the pilot's controls.


Why do you think Pakistani LACM and SLCM have different ranges?

Probably, the changes needed to make the missile sea-launchable affected the range by either decreasing the size (fuel capacity) or increasing the weight of the missile, or both. Launching an air-breathing missile by first shooting it through the water is significantly different than launching it straight into the atmosphere from the land-mobile launcher, so it isn't surprising that other changes had to be made to the missile itself -- changes that reduce its range.


Why could these aircraft not prevent total hydraulic failure?

There is no general answer, but the closest one would be bad luck.

In the DC-10-10, the aircraft of UAL232, all three hydraulic lines went through one hole in the tail bulkhead which was damaged when the engine failed. This is no real redundancy, and it was bad luck that this particular spot had been hit.

In the Lockheed Tristar, the same accident would had damaged probably just one line. There, the three hydraulic lines are separated as much as possible in the tail section (one on top, one on the left side and one of the right side of the fuselage). Lockheed has more experience with military design than Douglas, so the Lockheed engineers were more aware of redundancy issues.

In the A300 involved in the Baghdad attempted shoot-down incident, the same bad luck happened. Normally, each aileron is powered by two out of three hydraulic circuits, so one would remain if the other two are hit. Note that the green and yellow circuits were lost immediately, while the blue circuit failed only 20 seconds later. But in this case the damage extended to the spoilers, so all three circuits were affected in the end. There is only so much damage you can protect against.

Also for JAL123 the damage was just too extensive to not involve all four hydraulic circuits. The rear pressure bulkhead burst and blew most of the vertical tail surface away. It can be argued that the real culprit, however, was the chief pilot's refusal to don his oxygen mask. But the aircraft was only marginally stable and very hard to control.

Hydraulic fluid needs to be pumped continuously to heat it so its viscosity stays low. If you add shutoff valves, this pumping could be impeded. Note that the spoilers of the Baghdad A300 were not sucked open because non-return valves blocked the lines to the spoilers, helping in keeping the aircraft flyable.

If you put shutoff valves along the hydraulic lines, you open up a new avenue for failures. The idea of hydraulics is that you use just one pump and can create the maximum force at any point, since rarely would you need to move several actuators at maximum load in parallel. Splitting up the circuitry to enable the pilot to isolate parts of the airplane will take away this advantage, resulting in a more complex, heavier hydraulic system. And who knows if those added parts would not malfunction or be mishandled, resulting in a new class of entirely avoidable accidents.


Studying bird flight and insect flight: Would studying aerodynamics of airplanes be useful?

The biggest factor, besides the basic insect ornithopter wing mechanics, is air viscosity effects, or Reynolds Number.  To insects, the air is extremely "thick" with extremely low Reynolds Numbers, and the optimal airfoils are single surface membranes - insect wings. As Rn gets higher, the desired airfoils get thicker (bird wings) and thicker until you are in very high speed flight and the wings have to start getting thinner again.

Anyway, for a basic overview of all of this, I can't recommend the book Miracle of Flight by Stephen Dalton highly enough.  It's a book for the layperson that illustrates flight pretty much up the Reynolds Number range, starting with insects, then birds, then the man-made stuff.


Can cameras and LCD screens replace cabin windows?

Note that the windows are a safety feature: You need to see outside in case of emergency, e.g. to know which side of the plane is surrounded by flames, or how deep in the water you are. This is actually the reason why the inner lighting matches the outside conditions for take-off and landing and the window shades have to be open. Even worse, the potential rescuers need to see inside to know the conditions in the plane (flames, smoke, attackers, debris etc.), so you would need to have some system that reliably works both ways.

I don't see how your hypothetical plane would get certified with even more emergency features relying on electricity and on something that's basically an entertainment system.