Would an 8% reduction in drag outweigh the weight addition from this custom CFD-tested winglet?

First off, awesome question and great investigation! This kind of let's-see-what-happens inquiry will take you far should you decide to pursue aerodynamics at an advanced level (and, of course, in other pursuits). Not so long ago, I had to write a similar report: lacking the resources and knowledge of the aerospace giants, I, too, wondered why I could seemingly invent designs that on the face of things appeared vastly superior to theirs. I thought that I had winglets down cold.

Then I went to work for Boeing and started talking to the aerodynamicists. I started graduate study of aeronautics. Turns out, unsurprisingly, that there's a lot you can't get out of undergraduate textbooks and publicly available data. While I obviously can't be exhaustive here—and probably won't even answer your question to the letter—I can give you a few things to think about. To be clear, I wouldn't go much further than you have with your modeling and simulation, but if you'd like some discussion points for your paper here are some in no particular order. I've made some assumptions about your level of knowledge, so please forgive me if it's patronizing and ask me if you need clarification.

The fidelity of your baseline model

  The winglets...were those of the 737MAX....The wing is the same as that of a 737NG.

On what data did you base your model? The wing of a 737 is not a simple matter of an airfoil, some taper, and some twist. I notice that you did not include nacelles/pylons or flap-track fairings. The design of a production winglet is heavily tied to the integration of the overall wing design, including all of the extra components hanging off of it.

The reason that the 737 MAX winglets are effective

The 737 MAX uses what's branded as the Advanced Technology (AT) winglet. We know that a well designed wing extension is more aerodynamically efficient than a winglet. But the 737's wingspan must stay within certain limits in order to operate with the same ground infrastructure as previous models, so a winglet is a good solution. But what if we could have a little of both? Well, the AT winglet does exactly that:

  The lower winglet is configured such that upward deflection of the wing under an approximate 1-g flight loading causes the lower winglet to move upwardly and outwardly from the static position to an in-flight position resulting in an effective span increase of the wing.

So to really understand the efficiency of the AT winglet, you'd need to model this deflected geometry.

The other contributing item to the effectiveness of the AT winglet is its natural laminar flow:

  On previous winglets, the drag due to friction from the airflow over the winglet is one of the main detractors from efficient airflow....this is solved by Boeing using detailed design, surface materials and coatings that enable laminar – or smoother – airflow over the winglet.

The flow regime you're modeling

The AT winglets are most effective as their efficiency is aggregated over long, high-speed, high-altitude cruise legs. All you've given is a true airspeed, but for this kind of analysis of transport aircraft the Mach number is much more important. You haven't provided an air temperature, but from the density you've given it looks like this simulation is at sea level, which means your Mach number is not high enough. But this in fact might partially explain your results. Observe the drag curve:

In general, a spiroid winglet like yours reduces the induced drag at the expense of some parasitic drag. As you can see, we can afford some extra parasitic drag at lower speeds because the induced drag dominates.

If I were to make one suggestion, it would be to run your simulation at a realistic Mach number (around 0.8) and see what happens. But beware...

The limitations of your CFD software

We are getting to the point where CFD, when implemented well, is quite good for modeling aircraft performance in cruise flight. Much of the wind-tunnel testing for large aircraft these days is focused on high-lift and maneuvering conditions, where CFD falls much shorter. Of course, we always want to validate our CFD in the wind tunnel for all flight conditions, but for well-understood configurations in cruise the results often match well in terms of calculating overall performance. But the "when implemented well" caveat is key. I personally don't have experience with SOLIDWORKS Flow Simulation, but it looks like it's designed to be a general-purpose CFD software, so I would not trust its results too much for large, complex, high-speed simulations such as the ones required for this analysis.

In particular, there is the issue of turbulence. Not in the sense of unstable air that jostles an airplane around, but in the sense of chaotic flow over the aircraft's surface. So chaotic, in fact, that no computer in the world can accurately model the motion with a sufficiently short computation time. Instead, we use turbulence models that try to approximate what's happening in a way that can be solved quickly enough. SOLIDWORKS uses the k-epsilon model, which is popular for general-purpose software but might not be the best choice here. In particular, notes Wilcox,

  Even the [k-epsilon] model's demonstrable inadequacy for flows with adverse pressure gradient has done little to discourage its widespread use.

As flows over airfoils are quite influenced by adverse pressure gradients, I would exercise caution. I can tell you that Boeing makes good use of the Spalart–Allmaras turbulence model in conjunction with detached eddy simulation (Spalart is an employee). But choosing the correct CFD implementation for a particular problem is a nuanced process requiring a great deal of judgement and care.


Will increasing the wing area result in higher aircraft range?

Up to a point.
There is an optimum for wing area that shifts with operational considerations and airfoil type.
Propeller aircraft benefit little from flying higher, and due to the high efficiency of piston engines, the highest wing loading possible with the desired take-off distance will give the best result. Aspect ratio should be as high as practical; past examples used values up to 14.5 for achieving high range.
Jets benefit more from altitude but need more fuel, so my main focus will be on jets. Now it helps to look at the Breguet range equation: $$R = \frac{v\cdot L/D}{g\cdot b_f} \cdot ln\left(\frac{m_1}{m_2}\right)$$
The indices denote the state at the beginning (1) and the end (2) of the flight. For a higher range $R$ it helps to increase

Fuel fraction $\frac{m_1}{m_2}$: The higher, the better. But note that doubling fuel will not double range. Bigger wings will allow to hold more fuel, so here wing size helps.
Flight speed $v$: This allows to cover more ground while in the air. However, flying faster will produce more drag and consume more fuel once you fly faster than at minimum drag.
Lift-to-drag ratio $L/D$: Obviously, producing less drag for the same lift is equally important. In order to shift the best L/D to higher speeds, a high wing loading helps because friction drag grows less than linearly with dynamic pressure.
Engine efficiency: Less fuel for the same thrust will let you fly longer. $b_F$ is the thrust-specific fuel consumption. Since this factor is independent of wing area, it can be disregarded for this answer. Indirectly, however, it helps to have more efficient engines because then the need for a high fuel fraction is less pressing. The inefficiency of their engines is the main reason for the low wing loading of the first generation of transatlantic jets.

An increase in wing area allows for a higher fuel fraction, as long as installed engine performance is sufficient to power the larger, heavier airplane. Both the higher mass and the higher wing area will increase drag, so the optimum range speed will decrease for increasing wing area. The tipping point where increasing area further will no longer yield an increase in range is reached when the fuel fraction is already so high that increasing it further buys too little range to make up for the lower cruise speed and the higher fuel flow enroute. For most configurations, the lower power loading of the larger, heavier airplane with the same engines will most likely set the upper limit of wing size.
The actual optimum shifts with details in the airplane's layout and operation. Supercritical airfoils with their higher relative thickness at transsonic speed and more efficient engines will directly help to increase range for the same wing area. The requirement for low altitude flight and not having to take off and land can also influence the result.
Don't neglect scale: Larger airplanes have disproportionally longer ranges than otherwise identical, smaller types.


Interesting question. On the Boeing 727 there is a panel named "Cockpit Voice Recorder Microphone Monitor". A headphone can be plugged into the labelled jack to test if the cockpit voice recorder microphone is working properly. I have not checked the other model aircraft you mentioned but I assume they have the same test capability.

These microphones are usually passive devices. I doubt there is a warning system even on modern airliners to tell you the CVR mike is not working. But I would also be willing to bet good money they are no longer so easy to disable.


Why don't most military transports use modern commercial engines?

Some do; the C-17 you mention uses the Pratt & Whitney PW2000 which is also used on the Boeing 757. The USAF and USN also fly the C-40 which is the military variant of the 737 and carries the same engines.

Generally the answer is that military aircraft are built on spec for the military which is a bit different than the way the civilian market works. Civilian builders shop a design around to airlines to get some deposits then build the airframes (the notable exception being the 747 which was largely the idea of Pan-Am CEO Juan Trippe). This often causes there to be new aircraft every few years on the civilian side as Boeing needs to stay in business... On the contrary the military will put out a request for designs to meet their needs, evaluate the submissions and chose what is to be built. They can do this as often or as little as they so please (or as budget allows). If there is no active conflict or need for new tech then the military will keep flying what they have. Many military aircraft have cutting edge tech from the era they were designed in, they may however be dated by todays standards.

Much like the FAA here in the US the various military branches have their own certification programs and regulations thus upgrading and bringing in new gear may require something to be approved this can unfortunately stifle new technology being included due to high time and cost of approval. Similarly military requirements may be different, while a civilian airframe may suffice they may have takeoff length requirements or something similar that necessitate more thrust than their civilian counterpart thus variances in outfitting may occur.


At what minimum height above terrain does a vertical structure need to be indicated on a sectional map?

Refer to Aeronautical Chart Users Guide 2017. There are 351,148 obstacles in the database. Generally it is when ”a manmade obstacle is 200' above the highest terrain in the quadrant”. However, “in high density areas like city complexes, only the highest obstacle is represented on the chart”. Then they do the calculations below to show the obstacle on the chart.


Why do BWB designs typically put the engines in the rear?

The airflow over the top of a BWB accelerates as it would do over the top of any airfoil, and by the time it reaches the wing's trailing edge, its speed has slowed back down, so any engines fitted at the back would see no advantage, from that point of view (although they might indeed have a beneficial effect on the wing's boundary layer).

There are at least two non-aerodynamic reasons for putting the engines at the rear of a BWB. The idea is for BWBs to be more environment-friendly than traditional jetliners, in terms of higher fuel efficiency and lower noise emissions.

In general, the fuel efficiency of a turbofan increases with the engine's diameter (compare the engines of the new A320 neo vs the old ceo), and you would expect a future BWB to have even larger engines than today's ones, which would be difficult to fit under an already thick wing.

Secondly, the engines at the back are also significantly quieter than under the wings, since the body of the aircraft shields people on the ground from the noise produced by the air intake (a major portion of the total noise emitted by a jet aircraft).


Why was there no thrust from the engines in the TACA Flight 110 incident?

To generate thrust, engines need fuel and air: a spark will ignite fuel (by getting heat, above the ignition point), which burn with the oxygen in the air.

On this (and other incidents), together with air, also rain (and hail or snow) in the engine, so the spark is not enough to ignite the fuel, and so the engines stop working. So, this is the important factor: air and rain enter in the combustion chamber. It is not a problem of fuel distribution, it is just a problem of not being able to ignite fuel. [On car you have air filters, and air compressors, but also a very different cycle compared to jet engines]

The continuous restart means that the engines will continuously add some sparks, so that if ignition fail one, at next turn the the ignition should start again.

The spinning means literary: the engines were spinning, but this doesn't mean they can get enough energy. The article in Wikipedia tell us that they never reached IDLE power. I think the problem is that rain has blocked many of the sparks in the engines, so the engines ignited only some time, enough to get the engine spinning, but not enough to get power.


Will VR make large professional simulators obsolete?

Based on the variety of tasks that are performed in a simulator that VR would have great trouble accurately replicating, I think the answer is likely, no.  There IS a role for "simulators" that are more accurately referred to as "procedures trainers" in that they are non-motion, but this has nothing to do with VR, as those don't use all that much visual display anyway.  Networked wargaming is a great capability that VR can add to military simulations, but that's an addition to, not a replacement of, traditional simulators.

In a full-motion simulator, there are several things about the simulator that contribute to aircrew training, and the visuals are one important part.  The replication of the entire cockpit, including every switch, lever, display, keypad, and so on is another.  When I go to the sim and practice emergency procedures, each control reacts exactly as it does in the aircraft: where I look and where I reach to put my eyes and then my hand on each control, how hard I need to pull to get the desired effect, and so on.  And where I'm reaching with my sitting height and arm's reach is ever so slightly different than another pilot does.  We both get the same control, but it's farther below a tall pilot's eye line than a short pilot's. (Slightly over-simplified, but the basic point remains.)

We also do a fair amount of manipulation of the Flight Management Computer while in the simulator, which involves typing.  Not to say that typing isn't possible in VR, but it's not exactly the same as typing on a physical keyboard.  And we're using the same physical checklists and iPad EFB's that we do in the aircraft; not sure how well VR can mimic those.

So when you consider all the parts & pieces that make up the modern simulator & its considerable cost, the physical replication of the cockpit probably isn't something you're going to be able to remove in favor of VR.

For basic flying training, some of these sorts of factors are less important, as the basic flying skills you learn on one trainer transfer quite well to another trainer, even with a different cockpit layout.  But for basic flying training, not only the visual but also the vestibular and "seat of the pants" elements are more important.  While VR goggles like Occulus Rift are probably cheaper than several large display panels for providing the out-the-window visuals, these days high quality visual displays aren't the most expensive part of most simulators, and VR can't simulate the seat-of-the-pants sensation of accelerating, stopping, turbulence, and the like without some sort of motion actuators -- hydraulic or electric.

Now, for networked purposes (i.e. wargaming where Air Force elements from multiple bases across the country or globe can participate without the time & expense of getting to, say, Nellis AFB for a Red Flag), VR has amazing potential.  But to the extent that each pilot still has his own realistic cockpit & switches, what's driving the big gains is more the network than the VR... you can network an existing visual display with about the same hardware as you'd network the Rift devices.  To the extent that the "reality" of the precise cockpit can be sacrificed, then the VR probably makes for fabulous gains -- units practicing their tactics, rather than precise switchology. Sometimes that's a perfectly acceptable tradeoff; other times, not so much.

But until the tactile feedback of VR is good enough that I can use it to practice putting my hand on a lever, pulling it out of its detent in "this" direction with "this much" force required for "this much" travel, then pushing it down "this far" with "this much" force until it hits the stop "here," I really doubt that VR will replace the high-dollar flight simulators used in military and airline training.


How do I determine the diameter of my propeller at high altitudes?

You have the process of propeller sizing backwards. This makes the question unanswerable.

I need to find the diameter of my propeller to find my thrust.

Normally, you start with a thrust demand at a given speed and work form there. After all, the propeller is needed to compensate for airframe drag at that speed plus any climb requirements. Without that, you have a glider.
Another route is to start with the torque the engine can supply. Now the propeller has to be able to absorb this torque at the given speed, producing thrust. But you still need to check this thrust against requirements in order to get engine size right.
So please do yourself a favor and find out what thrust you need. The rest should be easy. Use 85% for efficiency to arrive at a suitable $\Delta$v and assume that half of all losses are from friction.
This lets you arrive at $$\frac{\Delta v}{v_{\infty}} = 2\cdot\left(\frac{2}{1+\eta_{Prop}}-1\right)$$ which becomes 16.2% of flight speed for an overall efficiency of 85%.


What kind of valves are used to prevent flashback in turbine engines?

VERICOR POWER SYSTEMS has a patent for these valves, number US 6357216 B1 and title Flashback control for a gas turbine engine combustor having an air bypass system
The patent includes the following image:

SUMMARY OF THE INVENTION
An object of the present invention is to provide for a control and method for arresting flashback in a gas turbine engine combustion system having a venturi for delivering a mixture of air and fuel to a combustion chamber and a valve for controlling the amount of air flowing to the venturi.
The present invention achieves this object by providing a flashback control system and method having a flashback detection routine, a valve position trim routine, and a reference flame temperature adjustment routine. The flashback detection routine detects a flashback in the venturi by comparing the temperature at the venturi to the temperature of the air entering the valve. The valve position trim routine receives this flashback signal and in response causes the valve to open until the flashback is arrested. Finally, to prevent the flashback from recurring, the reference flame temperature adjustment routine adjusts a reference flame temperature in the control system so as to prevent the valve from returning to the position at which the flashback occurred.
These and other objects, features and advantages of the present invention, are specifically set forth in, or will become apparent from, the following detailed description of a preferred embodiment of the invention when read in conjunction with the accompanying drawings.

The patent can be viewed here on Google patents list, however, it has expired.


Which aircraft is shown in this TV show?

It looks like a Bristol Type 170 Freighter: (All images are from the linked Wikipedia article).

The more I look at the images you posted the more it looks like a CGI than an actual aircraft.

Regarding the registration:

To me it looks more like VH-AEN
The images you posted seem like they are from a movie. Movies often use fake registration numbers.
Next time it might be beneficial to mention the name of the movie.


Can I log flight time while I am a student?

Yes, your time you acquire during training is loggable time and counts toward your total flight time.

You will only log pilot-in-command during solo flight and during the checkride.  After passing your checkride, you will log pilot-in-command during further training in the same category and class of aircraft as well as flights during which you act as pilot-in-command.

The minimum legal requirement under part 61 for an ASEL private pilot is 40 hours.  I would shoot for efficiency and earn your certificate with the least amount of training you can, and any time you would like to pay out of pocket beyond that, fly without an instructor on board.


For altitude callouts during the landing phase (2500, 1000, 500, 400, ... 100, 50, 20, 10), the computer simply reads the data from the radar altimeter.

The radar altimeter uses radio waves to measure the vertical distance between the airplane and any ground / obstacle below. The radio altimeter is mounted on the underside of the fuselage. They are usually accurate up to feet. This is different than the standard altimeter in the cockpit, which measure air pressure.

The radio altimeter has no idea where the runway is; if there is uneven terrain leading to the airport, or if the pilots' descend profile does not match the glideslope, the readings (and thus the callouts) will not reflect the height above runway elevation.

Note that the airlines can customize the altitude callouts. Different manufacturers also uses slightly different callout patterns.

The second type of audio alerts are messages from a Terrain Awareness and Warning System (TAWS). These systems uses radio altimeter, and may combine information from other sources, such as GPS and a global terrain database, to issue alert messages to the pilots if terrain impact is imminent.

Since the radio altimeter is only capable of detecting ground directly below, it is unable to provide timely warnings in certain situations, e.g. approaching a steep hill. By integrating with GPS data and a terrain database, the computers can predict the flight path of the aircraft and issue warnings if a risk of collision exists.


Why do non-aerobatic aircraft have a negative G limit?

You can get negative load factors (g forces) in different ways than just flying upside down:

Change in pitch: When you push on the control column, the pitch will start to decrease. Depending on how fast you do this, the load factor can even become negative from this. Some aircraft do this intentionally to reduce the g force to exactly zero:

(image source: Wikimedia)

By pushing the control column further forwards, you would get negative gs.
Wind gusts: The limiting factor for airliners1 (which rarely do the maneuver described above) is mostly due to wind gusts and up-/downdrafts. This can (for a short amount of time) result in large changes of the load factor, even into negative gs for a strong gust in the vertical direction. When experiencing strong turbulence, the airspeed should be reduced to turbulent air penetration speed (VB), which reduces the impact of the gusts.

  Turbulent Air Penetration

  Severe turbulence should be avoided if at all possible. However, if severe
  turbulence is encountered, use the Severe Turbulence procedure listed in the
  Supplementary Procedures chapter of the FCOM. Turbulent air penetration speeds
  provide high/low speed margins in severe turbulent air.

(Boeing 737 NG FCTM 1.50 General Information)

1 Limits for large aircraft from EASA CS-25:

  (1) The positive limiting load factor
  must not be less than:

  (i) 2.5 g with the EFCS
  functioning in its normal mode and with
  the high-lift devices retracted up to
  VMO/MMO. The positive limiting load
  factor may be gradually reduced down
  to 2.25 g above VMO/MMO.;

  [...]

  (2) The negative limiting load factor
  must be equal to or more negative than:

  (i) -1.0 g with the EFCS
  functioning in its normal mode and with
  the high-lift devices retracted;


Center of pressure is not a point "where the lift is most concentrated". Center of pressure has very little relation to how is lift distributed along the wing (you can have exactly same centre of pressure for infinite number of different distributions of lift).

The center of pressure is mathematical sum of all local pressure vectors along whole wing surface. But it is only, more-or-less, thought summing, this point has no special meaning in terms of stress distribution or so (at least no straightforward one).

You could as well continue to put all local pressure points into equation of movement and you would get exactly the same result. But equations with plenty small force vectors would be unnecessary complicated and if you do no need this level of complexity, it is easier to sum all forces in advance and use the summed value instead.

Note that if you would want, say, for example, calculate stresses inside the wing, you can not do like this. You would be forced to put each local pressure point into the analysis. But as long as you could assume whole wing to be solid (which is usually acceptable approximation for lot of simple problems), using single summed lift vector is easier.

If you simply sum all fractional pressure vectors, you get total vector of aerodynamic force. Which is enough to know how big force and in which direction acts on the airplane. But in order to be able to analyze rotational effects, you need to know in which point this total force acts (because same force vector shifted into different point of solid body will cause different rotation). And this is where center of pressure comes into the play, as it is the point where thought summed aerodynamic force should act in order to affect airplane (as a whole) by same translational and rotational effects as actual pressure distribution along the wing does.


For jets, how can we show that 1/2*ρ*V^2 is equivalent to 1481.3*δ*M^2?

Using the Mach number definition $M=\frac{V}{\sqrt{\gamma RT}}$, the ideal gas equation $p=\rho RT$ and the atmospheric pressure ratio $\delta=\frac{p}{p_0}$:

$$ \frac{1}{2} \rho V^2 = \frac{1}{2} \rho \cdot \gamma RT \frac{V^2}{\gamma RT} = \frac{1}{2} \gamma p \cdot M^2 = \frac{\gamma \cdot p_0}{2} \cdot \delta \cdot  M^2 $$

With $p_0=2116.2 \text{lbs}/\text{ft}^2$ and $\gamma = 1.4$ you get the desired result.


Why are airplanes sometimes led by a vehicle?

"Follow-me cars", as they are known, make it easier for pilots to get to the correct spot by the correct route.

This could be the runway before take-off, or the final stand after landing.

They're useful at airports with complex routes and relieve the pilots of some additional navigation burden; their function is one both of safety and convenience.

They might be used as a rule at a particular airport, or on request (if perhaps the pilot is unfamiliar with the taxiways, or there's an urgent need to get to a gate very quickly), or because of local conditions (signage or lighting problems, re-routing because of ground maintenance work).

However, the presence of cars around aircraft and runways is not without its own risks, and follow-me cars in fact add an extra layer of complication to airfield management.

(And sometimes, they have a rather odd marketing role... at Bologna (BLQ) one of the follow-me cars is a Lamborghini. Make of that what you will.)


What is this biplane from an old photograph?

Gloster Gladiator, also on YouTube.

(Answer taken from comment by mins.)


Why do Airbus aircraft typically have less wing flex than Boeing aircraft?

It's not a super scientific statement. There may be some half-truths referring to half-truths inferring that some design is better, just for show business sake.

"The Boeing wing is way more aerodynamic than the Airbus wing" is not something that has any value at all. All wings are by definition aerodynamic, there is no sliding scale. All wings are the result of a design process, balancing many input parameters. If an aircraft manufacturer cannot get the aerodynamics of a wing right, they have no place in the aerospace industry. Both Airbus and Boeing make very fuel efficient and safe aircraft that compete head to head in the market place.

Wing flex is one of these things that the structural engineers must cater for, after the aerodynamicists have had their go at the external shape: the planform, aerofoils etc. It can be considered a secondary design parameter that:

provides dihedral in flight, for stability when banking;
acts as a spring against turbulence;
can cause grief with flutter;
may provide difficulty for the ailerons to operate.

For a given wing shape, wing flex is the result of the ratio of strength and elasticity of the wing material. Composites are the latest in aircraft material, being lighter and stronger than aluminium. It is five times stronger than aluminium, and flexes about half when under load. But because it is stronger a lot less material can be used to make the wing lighter - even though a certain amount of carbon fibre flexes less than the same amount of aluminium, there is simply less of it. The ratio of strength over flex of carbon fibre is much higher than that of aluminium.

All aircraft with wings made of carbon fibre flex a lot more than aircraft with wings made out of aluminium. Both the A320 and the B737 have aluminium wings. For a given material and wing area, wing flex is a function of

Aspect ratio: a long, slender wing flexes more than a short, stubby wing. Or the long aluminium wing of a large airliner flexes more than the shorter wing with the same aspect ratio of a smaller airliner.
Wing thickness. The thicker the wing profile, the less sweep angle needs to be used to delay drag divergence. This is actually a sign of an aerodynamically more advanced wing, and the thicker profile makes the wing bend less

Those sort of comparisons make much more sense than "the wing of a Boeing is much more aerodynamic than that of an Airbus". That's only showbiz.


What is the maximum body weight allowed for a pilot?

In the US there's no specific weight limit in the regulations. Instead, they just say that you must be capable of performing the duties of a pilot, e.g. 14 CFR 61.113:

  The general medical standards for a first-class airman medical
  certificate are:

  [...]

  (b) No other organic, functional, or structural disease, defect, or
  limitation that the Federal Air Surgeon, based on the case history and
  appropriate, qualified medical judgment relating to the condition
  involved, finds—

  (1) Makes the person unable to safely perform the duties or exercise
  the privileges of the airman certificate applied for or held; or

  (2) May reasonably be expected, for the maximum duration of the airman
  medical certificate applied for or held, to make the person unable to
  perform those duties or exercise those privileges.

But the FAA is concerned about some conditions that are strongly linked with obesity, like heart disease, diabetes or sleep apnea. Those could be an issue for getting a medical certificate.

Apart from the regulations, there may be some practical weight limits for other reasons:

Military pilots have much stricter medical requirements (I know you're asking about commercial pilots), partly because they have some special considerations
A very large pilot may be physically unable to fit into some cockpits and/or move the controls to their limits
A very heavy pilot may be too heavy to fly in some smaller aircraft (including training aircraft) because of weight and balance limitations


Do helicopters fly a standard pattern before landing?

The FAA AIM, in 4-3-17 and the Air Traffic Controller Handbook, Section 11, explains VFR helicopter operations at controlled airports. The procedure will depend on the airport and the current traffic.

  Insofar as possible, helicopter operations will be instructed to avoid the flow of fixed-wing aircraft to minimize overall delays; however, there will be many situations where faster/larger helicopters may be integrated with fixed-wing aircraft for the benefit of all concerned.

Helicopters may operate from a designated helicopter landing area. The tower is responsible for separating them from other traffic. The helicopter can fly a much closer pattern than other aircraft, and may stay on the other side of the runway from the typical pattern. They may also operate straight in/out of the landing area, depending on wind and traffic.

They may also be cleared to take off or land in a "nonmovement" area that is not specifically designated for that activity, which could be a ramp at the airport or a location off-airport. This will be up to the tower to provide clearance and the pilot to execute safely.

Helicopters can also operate similarly to fixed-wing aircraft, taking off and landing using a runway, and following taxiways. Wheeled helicopters taxi on the ground. Otherwise, helicopters may either hover taxi, where they fly in ground effect at low speed, or air taxi, where they will fly out of ground effect up to 100 ft AGL and up to 60 kts, as directly as possible to the next point on the field, avoiding obstacles as needed.

Like ratchet freak says, they will generally come in horizontally while descending, flying into the wind, and then come into hover, where they will then be instructed by the tower to taxi to wherever they are going on the field.

Some airports, like in this photo of "spot Charlie" on Taxiway Zulu at Hayward Aiport, may have marked spots on the taxiways or non-movement areas for helicopter operations. In this case, students practicing landings and autorotations will be instructed: "Clear to land, Spot Charlie" to keep them off of the main runway 28L, while in left traffic on the opposite side of the runway of the smaller 28R.

As with any aircraft, the final authority for safety is the pilot, and they must be aware of their limitations and the conditions around them.

At non-towered airports, the procedures can be similar. The pilot should take the wind direction and traffic into account, and announce their intentions on the appropriate frequency.


Is it possible to fly an ultralight aircraft with a 13.4kW engine?

The earliest ultralights (hang gliders with add-on engines) used engines with as little as six horsepower (about 4 kW), possibly smaller.  That said, these aircraft were originally built as foot-launched gliders, and even so had safety issues and many incidents due to poor climb rates.

The main requirements for the engine in an ultralight are climb performance (which translates directly into takeoff acceleration) and reliability.  With the correct propeller and acceptable dry weight, an 18 hp (13.5 kW) engine might be acceptable, but every additional kilo of engine mass (compared to engines built for lightness) is one less kilo of structure, and the RPM figure given seems to point to a four-stroke engine, which will generally be heavy for its power output as compared to the two-stroke type.

Four-stroke engines have been used in larger aircraft for more than a century, but those are mostly engines designed and purpose-built for aircraft use.  An engine designed for garden or yard equipment, generator, or compressor service will usually be heavier.  You'll have more trouble finding an optimized propeller for 3600 rpm than for 5500, in that power range.

In the end, if that's a cast iron four-stroke engine, it's unlikely you'll make your overall dry mass budget to stay within US Part 103 requirements without compromising structure, and you're likely to see performance issues with minimal power and maximum takeoff weight.


What type is this Syrian light attack aircraft?

Its a Syrian Aero L-39 Albatros.

You can see the same image (just a bit sooner on the second missle lauch) when searching Google for Syrian L-39 (second result).


A320/321 FMA indications with Both Flight Director Channel Failed

On the A320, the FAC takes commands from the FMGC to compute the FD bars. The FD bars and  certain FMA annunciations and speeds are provided to the DMC for display on the PFD.

Your FD loss scenario is a partial FAC failure which is why AP continued to work, since the FG function of the FMGC was operational, but the FMA annunciations are faulty. Yaw control is also a function of the FAC which affects ROLLOUT.

See Airbus Safety First Magazine 23 for a similar scenario: the aircraft was operating with an ADR channel disabled under MEL, encountered windshear causing discrepant AOA measurements, the FACs only had two measurements so they tripped off causing the crew to lose FD, characteristic speeds, and FMA.


How do acrobatic pilots avoid pulling too many G’s and passing out?

There are certain things you can do to increase your G tolerance without a G suit, mostly static tension exercises like squeezing your diaphragm, lower torso and thigh muscles, isometric exercise style, to slightly slow down the blood flow to your legs during the pull.  Plus just really good physical fitness so your body can handle weighing 4 or 5 times normal for short periods (neck muscles are critical for this, more so if you're wearing a helmet).

Beyond that, and without a G suit, it's just awareness of how hard you can pull and knowing where to ease off.  You have a G meter in the plane to indicate where you are, but if experienced you should be able to tell within reason by the sensation.

You start to lose your vision (grey out) before you pass out completely, so that is a key warning sign that you'd better back off right now.  However someone who pulls too hard too fast may pass through the grey out period to pass out phase too quickly and it's lights out for a bit.   In the end, the pilot just misjudged and screwed up, probably by getting himself into a situation where the choice was to pull too hard or hit the ground.

Great link provided by a commenter for more info.


What rules allow a student pilot to add oil to an airplane?

The FAA doesn't consider adding oil to be maintenance. The Hochberg (2016) interpretation says:

The subject of adding oil is often debated; however, we note that it
is not an item included in part 43, appendix A, paragraph (c), which
lists items the FAA considers to be preventive maintenance.

Also see the FAA's Flight Standards Information Management System, under Elements of Maintenance (emphasis mine):

In broad terms, it has been generally upheld that basic servicing
tasks, such as fueling and adding oil, are neither maintenance nor
preventive maintenance. But even that has some caveats. When adding
oil requires a precise sequence of steps or partial disassembly to
gain access, then that would be considered a maintenance activity.
Adding oil to an oleo strut for example, would be a maintenance
activity, whereas adding a quart of oil to a GA aircraft would not.

Since adding oil isn't maintenance - at least not in a simple GA aircraft - part 43 is irrelevant and there's no requirement to have any type of certificate to be allowed to add it.


Why aren't the passenger seats designed as jump seats (foldable) in commercial airlines?

You're in luck. Airbus has filed a patent for that. (Not a joke.)

  Airbus said the design was a response to recent demands from low-cost airlines to cram more seating into existing plane interiors – often to the detriment of passenger comfort.

Just when I thought the below can't get any worse.

(Original, sardine edit by @TomMcW)

There is also this concept:

  Although the patent has been filed, whether or not the seats will become popular depends on whether or not airlines want to pick up the design.


Air battle manager has the following duties:

Plan and execute theater air operations
Analyze national defense strategy
Develop and conduct flying and simulation exercises
Conduct, manage, evaluate and improve unit training and readiness
Create operational policies

Further information can be found at AirForce's website.

In USAirForce, there are seven categories of aeronautical ratings. They are:

Pilot
Navigator
Combat Systems Officer (CSO)
Air Battle Manager (ABM)
RPA Pilot
Observer
Flight Surgeon

For further reading about these ratings, read here.


Altimeter disagreement. What's the crew procedure to deal with that?

Since you describe a captain and FO, I'm going to assume that you are asking about a larger aircraft, like say an airliner or business jet.

Part of the certification of these types of aircraft require them to have a third (standby) altimeter in addition to the two primary altimeters.

When there is a discrepancy, the typical procedure (keep in mind that a pilot should always follow the manufacturers checklist in these situations) is to cross-check the three altimeters and find the two that agree so that the bad one is then excluded.


Is there a special ULD to be loaded at the main cargo door?

No, the container near the door is the same as the others. The containers do not fill the entire cabin all the way around, which leaves enough space above for things like the door hydraulics. The containers on the upper cargo area below are all 88" x 125", which corresponds to a standard LD7 container.

Source


Do cabin evacuation tests include passengers with limited mobility?

As @mins said in the comments, the 90 seconds is a limit for a evacuation test. Having equal test requirements means that all planes have a minimum, similar evacuation capability.

That said, the conditions of an evacuation test are rather benign: people participating in them know nothing is really wrong, there are no hazards like smoke or fire, and the plane is in a normal attitude (no broken gear or hull, engines stopped). See

            .

In real emergencies, the time to evacuate may be greater than 90 seconds, and the crew and ultimately the captain has the responsibility to ensure that everyone has been evacuated safely and leave the ship the last. So, crew incapacitation left apart, you wouldn't be left behind.


Is it legal for an SEP airplane to fly above its service ceiling?

You didn't say which country you're asking about, but in the US it's legal. Your definition of service ceiling is correct, and there's no regulation that I know of that requires you remain below it.

The only clear case I can think of would be if the POH says that the service ceiling is an actual limitation and you shouldn't operate above it. Exceeding limitations in the POH is a violation of 14 CFR 91.9(a):

  Except as provided in paragraph (d) of this section, no person may
  operate a civil aircraft without complying with the operating
  limitations specified in the approved Airplane or Rotorcraft Flight
  Manual, markings, and placards

The AIM 5-3-3 requires you to report to ATC if you can't maintain a 500ft/min climb rate, so I suppose that not doing that could get you in trouble somehow. But there's no actual regulation, as far as I can see.

There are other, contrived scenarios that you could invent. If exceeding the service ceiling would require specific equipment or training that you don't have, then you could be in violation of various regulations, but that isn't because of the service ceiling itself.

And finally, there's the catch-all 91.13:

  No person may operate an aircraft in a careless or reckless manner so
  as to endanger the life or property of another.

If you do operate above the service ceiling and something goes wrong, then the FAA could bust you on that. Trying to get over mountains at or close to your service ceiling could be an example.


Was ATC overstepping its boundaries when advising a pilot to ignore a cell warning?

The controller didn't overstep his boundaries, and he didn't tell the pilot to ignore a weather warning.

Shamrock demanded something that's extreme for the NYC airspace: runway heading for 15 miles. Usually asking for right or left deviation is sufficient, and that appears to be what the previous Delta departure did.

Once Shamrock declined an easterly heading, the controller had no choice but to vector them in a temporary hold. The controller was frustrated because the previous departures had been accepting turns to the east and his radar didn't show signs of significant precipitation. He also astutely pointed out that this weather was 5 miles from the runway departure end. Aer Lingus should have been able to paint that on their radar or see it with their eyes before they departed. Their clearance was to the GREKI fix so they knew they'd be heading that way after departure. That doesn't mean Shamrock was wrong. After all, they are flying in actual, and the controller is sitting in a room at zero knots, but in the incredibly dense NYC airspace, it can create an emergency if you have to deviate that much.

The controller was harsh and made his frustration evident in the way he chose his words. The pilot stroked his ego by saying his boss would call the controller's boss.

Once you strip away the emotions, the pilot and controller did their jobs. The pilot kept his airplane clear of weather that he determined to be dangerous. The controller did the only thing he could to keep the Aer Lingus flight out of that weather and away from conflicting traffic.


What's this stick-like thing on the glass of C-130J?

It's part of the windshield anti-icing system, and is the same as on the Navy's C-130T. From the NATOPS flight manual for the T model, page 2-150:

The three windshields, the two windows on each side of the windshields, and the two lower windows in front of the pilot are NESA-type. These panels are heated by applying unregulated ac power from the left-hand ac bus to a resistance material between the layers of glass. The ac power is applied by automatic dc control systems that cycle to maintain window temperature within specific limits. A center windshield system controls heating of the three center windshields, and a side and lower system controls heating of the side and lower windows. The two systems are identical except for the amount of total ac power provided.


How much water does the Emirates A380 carry in order to provide onboard showers?

570 litres, apparently:

  To cater for the showers, the airline's 489-seat A380s are fitted with
  two optional auxiliary potable water tanks installed in the centre
  wingbox, which increases capacity from the standard 1,700 litres
  (450USgal) capacity in six tanks to 2,270 litres - ie around 2.3t.

That's assuming that the 570 litre increase is entirely allocated to the showers, which may not be literally true.


Why does not the lift produced by main wings create pitch moment?

Of course it creates a pitching moment! Now we need to define around which reference point this moment should be measured.

If the reference point is the center of gravity, it is even equally strong as the pitching moment of the elevator, it only has the opposite direction.

If you use the aerodynamic center as the reference point, the moment will be less strong. If the wing airfoil is symmetric, the moment will actually be zero (ideally), but with a cambered airfoil there is still a measurable moment left.

A moment is always a combination of a force and a lever arm, measured perpendicular to the direction of the force. Only when the lever arm is zero will the moment disappear. If we use the center of gravity as the reference point, the weight will have no lever arm and will contribute no moment, but the distance between the wing's lift and the center of gravity is large, so this moment is large, too.


Are there other examples of human-electric hybrid aircraft?

Yes. I assume by hybrid you mean that propulsion is provided by a solar-powered electric motor while the control system is powered by a human pilot.

From Paul McCready came Solar Challenger in 1981, certainly less flimsy than the Gossamer Penguin.

Solar Challenger (picture source)

In the same year, Solair I flew for the first time, followed by Solair II in 1998. Both were built by Günther Rochelt, who also built human powered aircraft.

Solair II (picture source)

Rochelt's Musculair 2, the fastest human powered aircraft until today, inspired Eric Raymond to build Sunseeker in 1990. Sunseeker II improved on those designs again, still using the layout pioneered by Musculair 2. It flew first in 2002.

Sunseeker (picture source)

Icaré 2 was based on glider technology and flew first in 1996.

Icaré 2 (picture by Uli Reinhardt, Zeitenspiegel (Zeitenspiegel) [CC BY-SA 2.0 de, GFDL or CC-BY-SA-3.0], via Wikimedia Commons

With Sunseeker Duo the first solar-powered two seater flew in 2014.

For a comprehensive history of solar flight see here (PDF), and for some more background see here.


What are the effects of an increase in altitude upon ESHP of a turboprop engine?

You have confused a turboprop engine with a turbocharged engine. They are very different and have very little in common.

A turboprop engine is powered by a turbine engine geared to a propeller. Turbine engines have less power available at higher altitudes so answer "A" is correct.

A turbocharged engine is a piston engine which is fitted with a small compressor driven by exhaust gas pressure. The compressor (turbocharger) can increase manifold pressure to restore sea level power at altitude. (Turbo-normalized) A turbo charger can also supply greater than sea level manifold pressure for more power. (turbo-supercharged)

Both types of turbocharged piston engines can maintain full rated power as they climb, but they will eventually reach a limit where full power can no longer be maintained.


Which military aircraft does this seem to be? [F-16 vs MiG-21]

It's a MiG21. There was another photo showing the front section area and the unmistakable nose cone of the MIG21.


What is the exact meaning of "attitude", does it include translational movement?

Your assumption is correct, attitude is orientation in space and it excludes translation.

Object orientation in space can be defined using multiple systems. The one used in aviation uses three angles:

heading or yaw (around the yaw axis)
pitch (around the lateral axis)
roll or bank (around the longitudinal axis).

Source.

Attitude is usually understood as orientation relative to the horizontal plane, that is only two angles:

pitch
roll/bank.

In the common definition heading is not taken into account. For example, in no wind condition, "level flight" is usually obtained by maintaining a constant attitude, that is constant pitch and roll angles. We'll find this sense in the expression flying by attitude, nose-up attitude or unusual attitude.

Attitude is visualized using an attitude indicator (aka artificial horizon):

Attitude indicator, indicating 5° right roll and 10° down pitch

In some applications attitude may include heading as well, and thus becomes a synonym for orientation in space using the three angles:

heading/yaw
pitch
roll/bank.

This use is more often found in flight dynamics and astronautics than in aviation. In this sense attitude and speed help determine the velocity vector. More on that in attitude reference frames.

Heading reference must be specified. In aviation heading reference can be geographic or magnetic North and has its own instrument, the horizontal situation indicator or directional gyro (or the compass as a backup instrument):

Directional gyro, indicating a heading of 113°. Source

The three angles can be combined into a single instrument, this is often the case for head up displays:

Source.

3-angles attitude can be quantified as a quaternion or a matrix of angles, usually Euler's angles (actually Tait–Bryan's angles).

It can be visualized using a spherical attitude indicator (more at Space Exploration):

Orbiter attitude indicator, source


This is the difference between flying and in orbit. In orbit, you are indeed falling toward the earth, but the spacecraft is too, and you're going fast enough that you keep missing the earth.

In an aircraft, because it's staying aloft due to lift, it is not falling. This is why you experience the pull of gravity on a plane.

Some aircraft are designed to feel weightlessness, see Vomit comet.


What are the disadvantages of using just rudder to roll an airplane?

It works in a half-assed way but the key word is half-assed. You'll always be skidding around the sky since sideslip is required to obtain and maintain any rolling moment.  Control response can be somewhat laggy, since you have to induce a skid and wait for the roll, depending on how much dihedral you have.  So to have something approaching snappy control response, you need way more dihedral than is necessary for normal lateral stability.  The inability to cross control limits the ability to handle crosswinds and prevents you from using sideslip to increase descent rate.

So it works after a fashion, but will never be as good as full 3 axis.  The thing with ultralights is that because of the really low mass/large surface area, they are really strongly affected by turbulence, and when close to the ground, half-assed control authority is the LAST thing you want.

Control authority is not a place I would cut corners in the interest of simplicity.  I think that the attraction of 2 axis control for ultralight designers was in the idea that non-pilots getting into ULs would think "Hey that must be only 2/3rds as difficult to learn as 3 axis.  Must be better."


How do you indicate whether the supply of power to the gyroscopic instruments is adequate?

For suction powered gyroscopic instruments there is usually some suction gauge to indicate the quality of the vacuum. See this question for more details in what the instrument shows.


What justifies a biplane over a braced monoplane?

Back in the pioneer days both types competed fiercely. The braced monoplane has similar structural depth to the braced biplane but less than twice the total wing area, so many argued in its favour. On the other hand, the shallower angle of its bracing wires introduced greater compressive forces in the wing spars, so they had to be strengthened and that added weight.
The monoplane suffered its first drawback around 1911 when, first in France and soon after in Britain, examples started falling out of the sky and for a time they were banned from military service. The French problem turned out to be a mistaken design assumption leading to over-thin bracing wires, the British to be the Ministry-specified cowling fasteners coming adrift. They were soon flying again, but the damage to their reputation was done.
Nevertheless, a few types were still in service when war broke out, especially with Germany. The Etrich Taube and Fokker Eindecker helped to restore their reputation, especially when Fokker developed interrupter gear for the machine guns, unleashing the Fokker scourge. But this would prove the high point of the braced monoplane's career.
The advantages of the biplane you mention - high strength and short span - proved to give greater manoeuvrability, stiffness and damage tolerance when it mattered, and the monoplane quickly became obsolete.
The biplane remained dominant until engine powers rose sufficiently to take planes beyond 200 mph or so, where the greater weight of the unbraced or cantilever monoplane was a price worth paying for cleaner aerodynamics.


Could the Shuttle Carrier Aircraft do a transatlantic flight with a Space Shuttle orbiter on its back?

Short Answer
A procedure had been established to return from a Transoceanic Abort Landing (TAL) site to the Kennedy Space Center (KSC) using the Shuttle Carrier Aircraft (SCA). The maximum weight that could be ferried from Europe was approx. 87,000 kg, so so weight had to be removed from the orbiter prior to being mated.
The SCA had a maximum range, unmated, of 5,500 nautical miles, however when matted the range decreased to 1,000 nautical miles, using reserves. 4,500 NM were lost by carrying the orbiter. The SCA would have had to stop in UK, Iceland, Greenland, and Canada.
A test for in-flight refueling had been conducted but no solution was developed. From our friends at Space Exploration:

Studies were conducted to equip the SCA with aerial refueling
equipment, a modification already made to the U.S. Air Force E-4
(modified 747-200s) and 747 tanker transports for the IIAF. However,
during formation flying with a tanker aircraft to test refueling
approaches, minor cracks were spotted on the tailfin of N905NA. While
these were not likely to have been caused by the test flights, it was
felt that there was no sense taking unnecessary risks. Since there was
no urgent need to provide an aerial refueling capacity, the tests were
suspended.

A tailcone covering the 3 aft engines and the thrusters was used to reduce the drag and the buffeting on the SCA vertical stabilizers. It also protected the engine nozzles from being damaged in flight.
See below if you are interested by more details of the recovery plan.

Plan Used After Landing at the TAL Site
Operations to be conducted to return the orbiter to KSC were documented in a plan that couldn't be identified with certainty, however the US Department of Defense (DOD) plan to support the turnaround is quite descriptive of the operations. From DDMS TURNAROUND FUNCPLAN 3611-03 (C=TAL day):

The turnaround operation, to include redeployment of
personnel and equipment, may require up to 120 days to complete. [...]
C+18: JTF-DDMS staff coordinates with NASA for ferry flight route
support.
C+22: JTF-DDMS staff presents initial ferry flight support plan to NASA management.
C+26: NASA begins 24 hour turnaround operations to prepare and
mate the orbiter to the SCA for return ferry flight. [...]
C+53: Pathfinder and SCA arrive at landing site.

Slides explaining the DOD plan are also available.

TAL Site Operations
Each of the TAL site was equipped for the Orbiter landing and turnaround operations:

Navigation and landing aids
Weather equipment
Dedicated ground-support equipment
Emergency equipment
C-130 aircraft support

From Nasa Fact - Space Shuttle Transoceanic Abort Landing Sites:

Each TAL site is covered by a separate international agreement. The
TAL sites are referred to as augmented sites because they are equipped
with space shuttle-unique landing aids and are staffed with NASA,
contractor and Department of Defense personnel during a launch and
contingency landing.

Shuttle's Microwave Landing System (source)
In addition:

Safing and deservicing of the orbiter would be initiated by the
deployed TAL team and augmented by a team known as the Rapid Response
Team. [...]
The TAL site ground operations manager would initially be in charge
until relieved by a higher-ranking management official who would
arrive on the response/investigation team aircraft.
Within 24 hours, the response/investigation teams would arrive at the
TAL site aboard C-17 aircraft carrying personnel and equipment.  Most
of the equipment would come from Kennedy Space Center and Dryden
Flight Research Center in California.
Following the advance response/investigation teams contingent, the
Deployed Operations Team, consisting of additional personnel and
equipment, would begin arriving at the TAL site for the orbiter
turnaround operation. NASA estimates it would take about 19 C-17/C-5
aircraft sorties, a significant Navy sealift operation, and 450 NASA
and contractor personnel to complete the turnaround. [...]
Payloads and/or airborne support equipment will remain onboard the
orbiter for the flight back to Kennedy Space Center unless the
capability of the shuttle carrier aircraft, landing site location or
other requirements dictate other wise.

Lightening the Orbiter at the TAL Site Before Ferrying to KSC
Weight limits of the SCA:

Basic weight, NASA 905, 318,053 lbs (144,269 kg), NASA 911, 323,034 lbs (146,528 kg)
Maximum gross brake release weight, 710,000 lbs (322,056 kg)
Maximum gross landing weight, 600,000 lbs (272,160 kg).

From Space Transportation System Cargo Abort and Recovery Operations:

The ferry weight from contingency landing sites in Europe and Africa
is constrained to approx. 192,000 Ibs. (approx. 87,000 kg). The ferry
weight from the Pacific contingency landing sites is further
constrained to 154,000 Ibs. (approx. 70,000 kg).
This requires not
only removal of the payload but removal of Orbiter main engines,
tires, landing gear and other components as well. In addition, the
Orbiter Z axis (vertical) and X axis (longitudinal) center of gravity
location must be within a limited envelope, as shown in Figure 1.

From The Conquest of Space, Ferrying the Shuttle - Part Four: The Shuttle Carrier Aircraft:

A typical route might take the pair from
continental Europe to England, then on to Iceland, then Canada, and
finally to the United States.

(Additional information might be found in JSC-NSTS-08934-VOLUME-4, Space Shuttle Orbiter Ferry Plan.)

Mating and Demating the Orbiter
Photo gallery of Discovery mating at Edwards and demating at KSC (STS-114).

(Source: Nasa -- STS-114: Mission Complete)
The mating structure above couldn't be used at a TAL site, so a crane would be available for the operation:

Columbia being prepared at White Sands. Photo by Steve Schmidt.(Source: Abandoned and Little-Known Airfields)

Ferrying the Orbiter
From Nasa Fact, Shuttle Carrier Aircraft.
There were two SCA:

NASA 905: Obtained from American Airlines in 1974.
NASA 911: obtained from Japan Airlines in 1989.

They were B747-100 and B747-100SR, modified by Boeing into their SCA configuration.

(Source: Nasa Fact, Shuttle Carrier Aircraft)
They were engined by four Pratt and Whitney JT9D-7J, and had a fuel capacity of 316,307 lbs (143,477 kg).
The SCA didn't flight very fast: 250 kt or M .6, due to the drag from the orbiter and the additional vertical stabilizers. Its typical cruise altitude was also rather low to prevent freezing of the orbiter fluids:

with orbiter, 13,000-15,000 ft
unmated, 24,000-26,000 ft.

The range was hence a bit shorter than if it flew higher. Typical range:

Mated, typically 1000 NM (with reserves)
Unmated, maximum 5500 NM.


What is the significance of the speed of sound to aerodynamics and aircraft design?

Your question shows that you know that the speed of sound is the speed of small pressure changes in a fluid, and moving faster than that will give the fluid ahead no warning of an approaching disturbance. I will, therefore, dig a little deeper in my answer, fully knowing that I can only scratch the surface. I encourage you to ask more specifically if one topic piques your interest but is not sufficiently explained.

Short answer

The speed of sound is significant in aircraft design mainly in:

Splitting the flight regimes into two areas with markedly different flow behavior,
helping to convert a geometry for compressible flow to one which can be calculated by simpler, incompressible methods,
limiting the maximum practical flight speed for efficient air travel and
giving the designer hints how to push this boundary up.

In the combustion of gasses the speed of sound is of less significance than the speed at which a flame advances. This is more complex (PDF!) and depends on the turbulence level, mixing ratio, temperature and the activation energy for the combustion reaction to start.

Explanation

To explain the influence of the speed of sound let me look at the molecular level: Air is a collection of molecules which zip around constantly, bumping into each other frequently. We express this with macroscopic parameters:

The intensity of the collisions is measured as pressure,
the number of molecules per volume is measured as density, and
the speed of the molecular movement is measured as temperature.

At rest, the frequency and intensity of these collisions is the same in all directions. If something moves through the gas at a speed far below the speed of sound, the collisions are still roughly of the same intensity all around. The local intensity may vary, but the molecules will stay equally distributed over the volume. This means that the disturbance will cause a change in pressure, but density will be unaffected.

Similarity methods

Moving faster, the disturbance will cause more intense collisions in the direction of movement and will start to push the molecules together: Now it will also cause weak density changes, and those grow with the square of of its speed. To regain an equal distribution over space, the molecules will now move sideways (and up and down), and the pressure changes will reach farther out to the sides. When you compare the pressure fields at different speeds, the "faster" field will look like one made by a more narrow disturbance at lower speed. This effect is captured by the Prandtl-Glauert factor $(1-Mach)^2$. Scaling the Y- and Z-coordinates of an aircraft geometry (where X is in flight direction) with this factor will result in a geometry which can be calculated with incompressible methods.

At the speed of sound this factor has a singularity, so its application should be restricted to speeds below Mach 0.7. Above Mach 1 a similar transformation can be applied, now using the Ackeret factor $(Mach-1)^2$.

Convergent and divergent flow

The ratio of density changes to pressure changes continues to increase such that in supersonic flow the density changes become dominant. This shows when looking at the flow in an expanding or contracting duct:

Subsonic flow in an expanding duct will slow down to preserve density and will accelerate in a contracting duct.
Supersonic flow in an expanding duct will accelerate further, reducing density and pressure, and decelerate in a contracting duct.

This different behavior is used when accelerating the compressed gasses flowing from an aircraft turbine: First the nozzle diameter is reduced until the gas accelerates to the speed of sound. To accelerate the gas further, now the diameter has to increase again in flow direction. The result is a convergent-divergent nozzle, a typical part of supersonic jet engines.

Wave drag

Now picture the aircraft in slow motion from the side as it slices through the air at supersonic speed: Since pressure increases while the aircraft body expands and decreases once it contracts, you will have two drag components in supersonic flow which do not exist in subsonic flow: Forward facing parts experience higher pressure and rearward-facing parts experience suction. This effect is called wave drag and makes supersonic flight inherently less efficient that subsonic flight.

Transsonic design

The same effect also affects the pressure field around an aircraft which is moving close to the speed of sound. Its movement displaces air and has an effect similar to a contracting duct, accelerating the flow in its vicinity as long as the aircraft grows thicker in flow direction, and decelerating it again over its rear half where it contracts. Once this local flow reaches the speed of sound, it will accelerate further while the aircraft contour contracts, leading to a supersonic pocket of air which will not slow down. It does so eventually, collapsing in a local shock which can cause flow separation and high local drag. Even worse, this separation will affect the whole pressure field and reduce the speed increase, which opens a feedback loop which will make the shock fluctuate. This oscillating shock can excite vibrations, render control surfaces ineffective and can incite flutter.

To reduce the local speed increase the surfaces of airplanes can be swept so the flight speed can be increased without running into the aforementioned transsonic effects. Also, sweep will smear out the sonic effects when accelerating through Mach 1, so the drag peak around Mach 1 can be greatly reduced.

Around Mach 1 it is important to limit the rate at which the aircraft's body expands or contracts over the direction of flight, and the wider-ranging nature of pressure changes allows the designer to expand one part of the aircraft to compensate for the local contraction at a different part when both are at the same position relative to the direction of flight. The consequence of this is the area rule which shows in coke-bottle fuselages or big flap track fairings.


Why does the elliptical wing have the lowest drag?

Induced drag is caused by the backward inclination of the lift vector. Lift is defined as the aerodynamic force perpendicular to the flow direction, and since lift is created by deflecting this flow downwards, the resulting force is slightly inclined backwards.

The formula for the deflection angle (called downwash angle) $\alpha_w$: $$\alpha_w = arctan \left(\frac{2\cdot c_L}{\pi\cdot AR}\right)$$

To arrive at the drag, you now need to multiply the local lift with this angle. For small $\alpha_w$s the arcus tangens can be neglected, and we get this familiar looking equation for the backwards-pointing component of the aerodynamic force: $$c_{Di} = \frac{c_L^2}{\pi\cdot AR} = \frac{\alpha_w^2\cdot\pi\cdot AR}{4}$$

Now consider a wing which will do this unevenly over the wingspan. Some parts create a lot of lift and, therefore, a lot of downward deflection. Others produce less lift and less deflection. Due to the quadratic dependency of induced drag with downwash angle, the sum of all parts will always be higher when there are variations in the local downwash angle over span. Only the wing with a constant downwash angle will have the minimum induced drag for a given lift.

This is not necessarily an elliptic wing. By selecting the right twist (incidence variation over wingspan), any planform can be made to produce a constant downwash angle, albeit at only one angle of attack. Only the elliptic wing will combine the constant downwash angle over span with a constant lift coefficient over span such that variations in angle of attack still result in a constant downwash angle.

This is strictly true only in inviscid flow and when elastic deformation and the weight of the wing (which contributes to the need for lift and hence induced drag) are not considered. Also, an elliptic wing will produce nasty stall characteristics. Adding handling, friction and structural weight will shift the optimum to wings which produce more lift near the center. The exact optimum also will depend on the absolute size of the wing because the structural mass fraction goes up with size due to scaling laws.

Nomenclature:
    $AR \:\:$  aspect ratio of the wing
    $c_{Di} \:\:$  Induced drag coefficient
    $c_L \:\:\:$ lift coefficient
    $\pi \:\:\:\;$  3.14159$\dots$


Do box-wings suffer from induced drag the same way as normal wings?

The box wing is only better when you compare wings with identical span. The two wings of a box wing work in different Treffz planes, so the downwash is spread out vertically. The difference in induced drag to a single wing is not big, just a few percent. The friction drag is higher (see below), as is the structural mass, so the box wing needs to create more lift. This makes the induced drag of a box wing effectively higher than that of a single wing.

What is induced drag, anyway? It is the consequence of creating lift over a limited span. The wing creates lift by deflecting air downwards. This happens gradually over the wing's chord, and creates a reaction force orthogonally to the local speed of air. This means the reaction force is pointing up- and slightly backwards. This backwards component is induced drag! Wingtips are not involved and are not causing induced drag. Lift creation is.

If you fly fast, there is a lot of air mass streaming past the wing per unit of time, so you need to deflect the air only slightly. Your induced drag is small. Sames goes for a large span: There is more air which can be deflected, so the induced drag is small.

A box wing needs two slim wings per side, which will have a smaller chord than a single wing of the same surface area. So their Reynolds number is smaller, and their friction drag is higher. Also, the wing spar is less thick and will need to be heavier to carry the same lift!

If you drop the restriction of keeping span identical, the optimum single wing can afford to have more span (due to its better structural efficiency), and away goes the advantage of the box wing. And once you look at the full picture and add structural mass, the box wing never had this advantage in the first place.

Yes, but what about the Synergy?

The Synergy is a clever design with some advantages, but it cannot cheat physics. These are the advantanges:

The pusher prop keeps the airframe free of wake turbulence, so more area can be kept in laminar flow.
The pusher prop sucks the air from the rear fuselage, effectively avoiding separation.
The two stubby tailbooms and fins give great protection for the propeller area on the ground.
The compact layout keeps the stabilizing effect of the propeller small, so maneuverability does not suffer much.
The use of composites and glider airframe technologies reduce friction drag.
The diesel engine consumes cheaper jet fuel and is more fuel-efficient than a gasoline engine.

Note that I did not mention the box wing design?

Here are the disadvantages:

Wing sweep in a propeller aircraft looks cool, but increases drag, because the wing must be bigger to create the same lift.
In total, this configuration has four vertical tails, each of them with its own interference drag and a short chord which, again, increases drag over a comparable single vertical tail.
The stretched-out horizontal tail is also less effective than a smaller single surface with more chord and more distance from the center of gravity.
The compact layout provides little pitch or yaw damping. I wonder what the ride qualities in gusty weather are.

I would expect that a more conventional layout along the lines of the fs-28 would be even more efficient.

Akaflieg Stuttgart fs-28 in flight (picture source)


What's the best way to see accident rates for a particular make/model of aircraft?

You can search the NTSB's accident database here:

https://www.ntsb.gov/_layouts/ntsb.aviation/index.aspx

Results can be filtered by date, aircraft type, location, etc.

Another good reference source would be the General Aviation Manufacturer's Association.

https://gama.aero/

Their annual report publishes accident data on general aviation aircraft.  The organization may be contacted for further information on this subject.

https://gama.aero/wp-content/uploads/2016-GAMA-Databook_forWeb.pdf


ACARS encoding is usually different from customer to customer.  Decoding it can be very difficult, even if you have access to the aircraft to have some idea of what is being sent.  Usually, the manufacturer won't share the details with anyone other than the original customer, expecting subsequent operators to pay for custom coding on the ACARS.  A general introduction to the basic standard codes can be found here; www.universal-radio.com/catalog/decoders/acarsweb.pdf .   The 'out return in' messages are pretty much standard.  No doubt there are enthusiasts out there who have decoded at least parts of the carrier specific/aircraft specific coding.  I worked with an ACARS equipped fleet where most of the messages sent were carrier specific and I never did manage to get the decode of the top of climb (TOC), cruise (CRZ) and top of descent (TOD) reports that were being sent automatically, despite the co-operation of the vender and the original customer, as the original customer had thrown that information away.

LIkely decode from the data you have supplied;

POSN70071W097007 = Postion North 70 degrees 07.1 minutes, West 9 degrees 00.7 minutes.

Sorry, it isn't much.  G-INFO isn't the registration either, it would seem.  Registration information is usually hard encoded in a custom plug for each aircraft's ACARS system.


What is an afterburner and how long can a jet fly on afterburner?

An afterburner is a secondary combustion system which burns additional fuel downstream of the combustion chamber, to further increase thrust at the expense of much higher fuel consumption.

This is the Pratt & Whitney F100 afterburning turbofan, variants of which power the USAF's 4th-generation fleet of F-15s and F-16s:

The final spoke-looking thing just beyond the turbine fins, plus all the space between the turbine core and the exhaust nozzle, is the afterburner. In this area, fuel is sprayed directly into the exhaust stream from the turbine core, where the heat from the air leaving the core is enough to ignite it. This additional pressure adds to the thrust produced by the turbine.

As I said, though, the tradeoff is increased fuel consumption, sometimes usually dramatically so. The F-16 at full military power and low altitudes burns about 8000 pounds of fuel an hour, which with a full droptank configuration gives it about 2 hours' flight time. Cruising at higher altitudes, that flight time can be further extended as both the higher altitude and the lower throttle setting (about 80%) reduce fuel flow rate by up to 40% versus low-altitude flight.

In full afterburner at low altitudes, the F-16 can burn in excess of 64,000 pounds an hour. At full throttle, a U.S.-variant F-16 with maximum external fuel stores has about 20 minutes until it's on emergency reserves (which would only last an extra minute or so at full afterburner). The speed gain is minimal; the F-16 cruises at between 450-550 knots, while full afterburner only increases that to about 700-800 knots with a typical underwing loadout. So, burning 8 times the fuel, you get around a 50% speed boost.


What is the relation between N1 and Wing anti-ice

When engine or wing anti-ice are needed, the required amount of bleed air increases. In order to provide enough bleed air at the required pressure, the engine idle speed must be increased. That way, the compressor runs faster, which provides more high pressure air to the bleed valves. Note that this will result in more idle thrust as well, which can have an impact on descent performance as discussed for the Boeing 737 here: What is the impact of thermal Anti-Ice on descent performance?
For the A320, this is already taken into account for the descent calculation:

The idle segment assumes a given managed speed flown with idle thrust plus a small
amount of thrust. This gives some flexibility to keep the aircraft on the descent path if
engine anti-ice is used or if winds vary.

(Airbus A320 FCTM - Normal Operations - Descent)
When more bleed air is taken out of the compressor stage of the engine, the EGT (exhaust gas temperature) will increase because more fuel flow is required to maintain the same N1 speed. This implies that the N1 or EPR limits must be decreased in order to protect the engine, meaning the lower limit will result in the same EGT as before.


No.  The aircraft in question do not have ballistic protection, though they do offer system redundancy for battle damage and have to meet certain survivability criteria in live fire tests during development.

Just a note:  the only armor an A10 carries is a titanium pressure vessel for a cockpit which can take the kind of ballistic punishment you described.  It’s main defense is system redundancy, self sealing fuel tanks and engines mounted well away from the airframe and fuel.

Again the chief reasons combat aircraft do not carry external ballistic armor is any kind of armor over the exterior which can deflect the kind of AP/HE/Frag type warheads used in AAA/AAM/SAM warheads would make the aircraft prohibitively heavy and drastically reduce the warload and performance metrics the airplane needs to survive in combat.  And fighters like the F-16 and F-22 are considerably more vulnerable to enemy fire with engine surrounded by fuel tanks, causing even properly placed small arms fire to be catastrophic.


What is required for a pilot to fly in another country?

For your specific example, Philippines Civil Aviation Regulations Part 2 (Personnel Licensing), section 2.2.4 covers "Validation and Conversion of Foreign Licenses and Ratings." It states that a holder of a license from a "Contracting State in accordance with ICAO Annex 1" (this includes the United States) is eligible for "validation" of their foreign license. The validation process involves presenting the appropriate documentation of your license, ratings and logbook. For more than just PPL privileges, you must also pass a "skill test" and demonstrate the required knowledge and ability. The conversion ("validation certificate") gives you the same ratings you had on your US license and is valid for 1 year.

The FAA has a very similar policy for foreign-to-US license conversion, covered in 14 CFR §61.75. As in the Philippines, the FAA does not require a skills test for private pilot privileges, but a written knowledge test is required for conversion of an instrument rating.

Another question here on ASE discusses conversion from EASA (Europe) to FAA (US).

Most other ICAO states recognize each other's licenses in a similar manner. In all cases you have to present your license and proof of experience, and in some cases pass a written test and/or checkride. I haven't look up the exact regulations for, say, EASA (Europe) or CAAC (China) but I'm sure they aren't far off from the examples above. In reality diplomatic considerations probably also come into play: a holder of an Iranian license would probably run into problems attempting to convert/validate their license in Israel, even though both are ICAO-contracting states, since they aren't on very good political terms to say the least. But this will likely be the exception rather than the rule.

(There are only 3 non-ICAO states: Dominica, Liechtenstein and Tuvalu.)


How to find runway Centerline spacing on airport diagrams?

The scale is usually depicted on the chart. Just take a ruler and measure.


How do you navigate in your car?

Before you depart, you have a general understanding of which direction you're going.
(the supermarket is to the east of my house, about 3 miles.  I believe it will take me about 5 minutes to get there).

When you start driving, you keep your eyes open looking for information and clues.
(The yellow lines on the road denote a two-way street.  Certain landmarks are familiar and expected.)

As you proceed, you may refer to your car dashboard to make sure things are as expected
(My speed is 43MPH.   I had planned for 45MPH... pretty close.  My engine is running at 2,500 RPM, which is appropriate)

You may have advanced instruments as well
(The GPS in my car is telling me to take the next right turn, and go 1/2 mile)

Its very much the same with flying.

Pilots have pre-flight preparation where they go over a general plan.(we're going to fly north, on a heading of about 025 for 3 hours.  We'll be passing over a large lake, and landing at our destination with a city off to our left)

As they move towards the runway, they look for other airplanes, read the signs around the  runway, and refer to their maps.
(I see a sign indicating I'm on taxi-way Bravo, approaching Runway 31.  I see yellow markings on the pavement indicating I should get permission before I cross)

Once they take off, they look at their instruments to verify they're going at the expected speed, altitude and direction.
(Altitude is 35,000 feet, as planned.  Engines are at the right pressure, and speed is 440 knots, as expected)

They can look out the window for large landmarks, lakes, mountains, cities, etc.
(I'm passing by the mountain I saw on the map.  I see the river valley below me, and a large city ahead of me, just like I planned)

They may use advanced services like GPS Navigation, Radar and radio signals to help navigate.
(My GPS is showing my position and direction.  It says to turn a little to the right to stay on course.   The navigation radio says I'm 25 Nautical Miles away from the radio transmitter)

And they can talk to Air Traffic Control who can observe them on radar, and advise them to make adjustments to their course for navigation, and to stay separated from other airplanes.

If they cannot see out the window, navigation does become a bit more complicated, and reliant on Instruments, GPS, Radar and Radio.But given a very careful plan of "Fly for exactly 31 minutes, at exactly a heading of 027, at exactly a speed of 130Kts", it is pretty remarkable how close the airplane will end up to the intended destination.
That process is called Dead Reckoning.  It requires some detailed advanced planning, but isn't that difficult.   Combining Dead Reckoning with Instrument flying, and pilots can go through zero-visibility and still come out at the intended location.


How fast can fuel be siphoned out if you leave the cap off?

It can happen very quickly.

I don't have exact numbers, but an acquaintance had this happen in a Cessna 172 and the entire tank was emptied in just a few minutes - the amount of time it took to do one circuit of the pattern and land. The fuel cap was not in the filler neck on departure, and was hanging from the chain, banging against the wing. The moral of that story is: never assume the fuelers put the cap back in.

I've personally flown an older Cherokee 160 that had a loose fuel tank gasket. When doing slow flight, the pressure above the wing was so strong that it would start to ooze fuel from the cap. Fuel would flow in a rather frightening amount back along the wing, and that's with the cap still on.


Why haven't helicopter CAT III procedures ever been developed?

Because many copter autopilots are capable of flying a Cat I ILS to 200AGL, and then descending on autopilot into a hover at a pre-determined altitude above the runway. The pilot can then descend down to the runway surface without any forward visibility. The radar altimeter is used to judge distance to the ground. Because of the unique capabilities of helicopters and their autopilots, Cat II and Cat III are superfluous.


When an alternate minimum applies, does it change MDA or DA?

From the FAA Instrument Procedures Handbook, section 6-4: "The 600-2 and 800-2 rules, or any exceptions, only apply to flight planning purposes, while published landing minimums apply to the actual approach at the alternate."


Which manuals should I study before flying to France, Portugal and Switzerland?

For common procedures and or VFR rules you want to check the respective countries' AIP:

Switzerland   http://www.skyguide.ch/en/services/aim-services/
the other countries you mentioned can be found from this link collection http://www.eddh.de/equipment/ais.html

you may want to check the website of Eurocontrol here you can find IFR standard arrivals and departures

No warranty! Please prepare your flight carefully.


Cruise Mach Number less or more than Critical Mach Number

The critical Mach number $M_{crit}$ is defined as the lowest Mach number at which the airflow over some point over the airfoil reaches supersonic speed, that is, Mach 1. Usually, flying greater than $M_{crit}$ will produce a normal shockwave perpendicular to the flow, at the point of minimum pressure on the airfoil. I must note that if flying slightly above $M_{crit}$, there is a possibility of the isentropic recompression of the fluid, which means that no shockwave will be formed and thus no losses in form of the entropy will occur. This is especially the case with supercritical airfoils flying slightly above $M_{crit}$.

Critical Mach number for a typical transonic airliner is not equal to divergence Mach number $M_{dd}$. In fact, many aircraft will exceed $M_{crit}$ during the cruise, which you can see on the following video:

            . I believe that the average value of $M_{crit}$ is around $0.78$ for today's airliners like A320 or B737.

Exceeding $M_{crit}$ does not mean the aircraft reached $M_{dd}$ or is about to lose control. Control difficulties may be possible if $M_{mo}$ is exceeded.

For A320 and B737, the maximum operating Mach number $M_{mo}$ is $0.82$. This is primarily due to the buffet (and ultimately high-speed stall/shock stall) and (or) flutter occurrence. Exceeding normal speed range may cause flutter to appear. It also may put the aircraft in grave danger if shock stall occurs. Shock stall will occur if the shockwave formed on the airfoil is too powerful and separates the boundary layer. In this case, the airfoil pressure distribution changes and introduces an intensive nose-down pitching moment. To avoid such scenarios, the aircraft are limited with Mach number as well. There might be some corrections on the $M_{mo}$ from the divergence Mach number standpoint, but $M_{dd}$ is not the primary reason why such aircraft are limited with respect to Mach number.


is it possible that setting a lower airspeed makes a steeper climb?

I think you have it backwards, it is not that a slower airspeed produces a steeper climb, it it that a steeper climb, given the same power, will cause a slower airspeed.
If the only constraint you're setting the FMS is the airspeed to maintain for a constant thrust, then it will pitch up more, increasing the rate of climb, which will slow the airspeed.


Are the discrete I/O considered to be part of the ARINC interface?

It depends on which ARINC document you're talking about. ARINC 429 is a digital serial bus standard. Discrete data may be sent in ARINC 429 data words, but that's just bits in a word not the physical discretes you're asking about.

ARINC also has documents that cover standards for other interfaces as well as 'Characteristics' that define specific LRUs such as ARINC 735A for TCAS II.  In these documents ARINC does specify discrete interfaces.  There are two types, open/ground and 28V/open and are defined for both input and output.

So yes, there are discrete interfaces that are part of ARINC standards, just not part of ARINC 429.


How does the autopilot act when it receives an obviously bad temperature value?

The autopilot does not receive information about the outside temperature, it has no (direct) relation to what the autopilot controls.

The autopilot receives aircraft state inputs like airspeed, Mach number, vertical speed, attitude, accelerations etc.


How does headwind influence the results of a pitot tube and therefore the airspeed indicator?

The pitot-static system (and the airspeed indicator) doesn't care about the speed of the aircraft with respect to the ground. It is concerned only with the speed of air with respect to the aircraft (that is why it is called airspeed and not groundspeed indicator).

So, if your aircraft is on ground and experiences a headwind of 60 kt, the airspeed indicator will show an airspeed of 60 kt, in an ideal case.

This is important because the wing generates lift depending on the airspeed, not the ground speed (forgetting about stuff like ground effect, etc.). This means that if an aircraft is parked on the ground and there is a headwind of sufficient velocity, it will try to lift the aircraft up.


Based on what concept/strategy is a new aircraft ICAO code assigned?

The downloadable comprehensive PDF (icao.int) only has one listing for the 747-8.

Compared to the website search function:

My speculation is that the website search accommodates someone searching for "BBJ" in different ways (why, I don't know), or the database needs cleaning up. As you can see, two of the three are the same. And judging by the actual designator, they are all the same.

As for the rules:

They are to be found in ICAO DOC 8643, Aircraft Type Designators; or FAA JO 7360.1B - Aircraft Type Designators. The FAA Job Order is 2 months old and also contains the full list.

The relevant part to this question:

  A different designator for an alternate or subtype version of the aircraft will only be allocated when there is a significant difference in performance for ATS or no shared designator can be assigned.

(Emphasis mine.)

That means the A320neo has significant performance change (A20N vs. A320). A plane like the Boeing 777-200 with three engine options doesn't need different designators. The A330neo is yet to fly, but A339 comes up on the website search. Nothing came up for the A330-800neo.

Related: What will the 737 MAX 7, 8, and 9 ICAO IDs be?

The full rules:

  2-2. How Designators are Formulated. The International Civil Aviation Organization (ICAO) has the role
  of creating standard aircraft type designators for aircraft that commonly request air traffic service. ICAO
  assigns an aircraft type designator using the following principles:

  a. Only one designator will be assigned per aircraft type.

  b. A designator will be derived from the manufacturer’s model number or name, or from a common
  military type.

  c. The designator will not be longer than four characters and will generally begin with a letter.

  d. An assigned designator will not be changed for license-built aircraft, when an aircraft model is sold to
  or manufactured by another company, when the manufacturer’s name changes, or when the aircraft type is
  derived or converted from another type.

  e. A different designator for an alternate or subtype version of the aircraft will only be allocated when
  there is a significant difference in performance for ATS or no shared designator can be assigned.

  f. “Homebuilt,” “amateur-built,” or “kit plane” aircraft that exist in operationally significant numbers will
  be assigned a designator; however, these aircraft will only be listed under the original designer or under the
  manufacturer that produces or produced the aircraft type in series.

  g. In general, an aircraft type designator will be assigned to all aircraft heavier than micro-/ultra-light. For
  the purpose of ICAO Document 8643:

    Micro-/ultra-light are those aircraft types with a maximum certified take-off weight of 1,000 pounds
    or less and a stall speed not greater than 35 knots.
    Micro-/ultra-light helicopters and gyrocopters are those helicopters or gyrocopters with a maximum
    certified take-off weight of 1,000 pounds.
    Micro-/ultra-light autonomous, optionally piloted, and remotely piloted aircraft are defined as
    having a maximum certified take-off weight of 330 pounds or less and a stall speed not greater than 35 knots.
    Micro-/ultra-light autonomous, optionally piloted, and remotely piloted helicopters are defined as
    having a maximum certified take-off weight of 330 pounds or less.

  h. Roman numerals used as part of aircraft model names or numbers will be replaced by Arabic numbers.


Is there any ATS into the Special Use Airpaces (SUA)?

In many cases, there are controllers dedicated to providing ATC services to the aircraft that are USING the SUA.  Callsigns such as "Nellis Range" or "Eglin Mission" are used for the controllers working with aircraft within the SUA, be it MOA or Restricted or Warning areas or whatever.  What looks like one big chunk of airspace on the chart may likely be divided into separate areas for training or testing purposes that the aircraft flying into it will know about, and it's useful (sometimes, vital) to have a controller monitoring the various missions and keeping the various aircraft apart.

These controllers may work in a dedicated facility that only deals with military aircraft, or they may work within a larger facility that includes "regular" ATC functions as well.  For instance, the controllers who work the off-shore warning areas south of Eglin AFB as well as the on-shore restricted areas east and west of Eglin are physically located in the same RAPCON that is Eglin approach.  So civilian aircraft inbound to Crestview or Destin or Eglin/Ft Walton Beach are talking to controllers working one set of scopes, but across the room are the controllers for Eglin Mission who are watching the various SUA.  An aircraft that departs Eglin (or Hurlburt, or Duke Field) would probably be talking to one of the former initially, then when they head into one of the restricted or warning areas, they'd be handed off from "Eglin Approach" to "Eglin Mission."  Essentially it's like being handed off from one Approach sector to another, just that the Mission controllers have slightly different roles in keeping the airspace safe.

It's far better to clear an aircraft transiting a particular sector of SUA to fly through it ABOVE the aircraft in it that is employing air-to-ground ordinance, for instance, than clearing him through the airspace BELOW the bomb-dropper!  Or, if necessary -- maybe it's a helo with an emergency that needs a straight line return to base and isn't going to climb up very high -- at least you have the bomb-dropper go cold and hold up high until the transiting aircraft is out of the way!  That's the sort of ATC that Eglin Mission does that Eglin Approach doesn't... along with confirming that this callsign is in fact scheduled for this range at this time, and the last aircraft has departed, so "you're cleared in to Range XYZ to work surface to 15,000', advise 5 minutes prior to departing."

Fun times!


Is there anything wrong with this more symmetric aircraft design, and why isn't it used?

The biggest single problem with this is the location of the main spar - across the middle of the fuselage. This might not be a problem for single seat military or sports aircraft but would be a major headache for almost any other design. Imagine trying to load 100+ passengers with 50% of them having to clamber over or under a major obstruction in the cabin.

Yes, you can engineer around this but the resultant solution is likely to be heavier and more complex than simply moving the wing up or down and out of the way.


Could atmospheric effects cause a PA-30 to break up?

Atmospheric conditions do not cause aircraft to break up in flight.

Improper aircraft handling in response to bad weather can cause an aircraft to be overstressed and then breakup.

So can improper handling due to disorientation.