Will an Airbus A320 plane go into an unrecoverable nosedive and crash if a single angle of attack sensor fails, like on Lion Air JT610?

if a single angle of attack sensor fails

No.

An A320 has three AoA sensors. If one reports a different value to the other two, the avionics will ignore values from that AoA sensor and use the values from the other two.

If two of the three fail and report consistent values - the avionics will believe the third is the odd-one out and unreliable.

If those two both both report a consistent and  overly high AoA then the flight protections will apply a nose-down input in an attempt to restore the AoA to normal values and prevent a stall. this input is averaged with the pilot's inputs.

As I understand it all the following conditions must be met for the AoA protections to be erroneously invoked and cause a nose-down input:

Two AoA sensors fail and
Both report the same value and
The value is one that would cause a stall if true.

According to Airbus' Safety-First magazine:

  In normal law, on a protected aircraft, exceeding the AOA value of the
   α PROT threshold would immediately trigger the
  high AOA protection, thus resulting in a nose down pitch rate ordered by the
  flight control laws. Further increasing the AOA by maintaining full back stick
  would eventually result in reaching the α MAX threshold.

  are there any cases of an AOA sensor failing on an Airbus, and the plane not crashing?

I expect there are many.

There are even cases of two AoA sensors simultaneously failing and the aircraft continuing, after some control problems.

For example this incident  reported by Aviation Week

  German investigators studying the cause of an uncommanded pitch-down of a Lufthansa Airbus A321-200 near Pamplona, Spain, in November 2014, hope to discover the probability of similar events linked to frozen angle-of-attack (AOA) sensors as the investigation continues. In the interim, both the European Aviation Safety Agency (EASA) and Airbus have published directives alerting pilots of the issue and the workarounds.

...

  The captain continued to hold “more than 50%” rearward stick in stable flight for a period, but with help from technicians on the ground, the crew was able to reconfigure the automation into the aircraft’s alternate control law, rather than its normal “direct” law. The action removed the alpha-protection checks and canceled the nose-down input. The aircraft then continued to its destination.

...

  Airbus in early December issued a Flight Operations Transmission and Operations Engineering Bulletin to all A320-family aircraft operators noting that “if two or three AOA probes are blocked at the same angle, an increase of the Mach number may activate high-angle-of-attack protection,” which results in “continuous nose-down pitch rate that may not be stopped with backward sidestick inputs, even in the full backward position.” The recommended fix is to turn off two of the three ADRs, which puts the aircraft in alternative control law, deactivating the high AOA protection.


What effect would an air-to-air GPS jamming system have?

Jamming GPS means that the GPS receiver is unable to lock-on to the signal from any satellite.

Presumably, pilots of small aircraft would have to revert to more traditional forms of navigation - assuming they have a GPS based navigational instrument or two.

Pilots of airliners would presumably see alerts and (as with most smaller aircraft?) their flight displays would include non GPS sources such as gyrocompasses or magnetic compasses.

I imagine redundant systems would include other sources of position information such as reception of radio-based omnidirectional navigation beacons, inertial navigation systems and looking out the window.


Why are only captains allowed to taxi the aircraft?

Taxiing can sometimes be one of the more difficult tasks required on a flight, and affords one of the few opportunities to run into something.

Historically, in the earlier days of crewed flying, a captain may have done most or all of the flying. A captain might have let the copilot fly some of the tedious cruise portion of the flight, and a nice captain might have even let a copilot land or takeoff. As CRM developed, the concept of both pilots sharing the flying duties was eventually standardized.

Most larger aircraft are steered in taxi primarily by means of a steering tiller. When installed, a steering tiller is always installed at least on the left side of the cockpit. In the past, aircraft did not offer an option for a second steering tiller on the right side, likely reflecting the norms of the day. Updated aircraft and newer designs commonly include as standard—or offer the option of—a steering tiller on the right side as well. Some companies choose to omit this option as a weight and cost saving measure.

Some companies allow either pilot to taxi the airplane unless the aircraft is not properly equipped to allow this. I do not have personal knowledge of any companies that forbid the first officer from taxiing, but such policies may well still be in place. In many cases it is still not an option since the aircraft is not properly equipped to be taxied from the right seat.


Is it safe to fly with a B737-800? Is it different from a B737 Max 8?

All B737 Max, as of today 19-Sept-2019, are still grounded and will be for the foreseeable future. So if you are flying in an aircraft, you are guaranteed that it will not be one of those.

As for the underlying question "is it safe to fly in airplane model "X"?" the answer always is that if authorities are allowing it to fly, it is safe to the best of our knowledge.


Where can you find symbols (like these) that aren't on the legend?

You can find this symbol in the  "FAA Aeronautical Chart User Guide"

on page 30.

It shows as "Swamps, Marshes, Bogs"


Is there a minimum weight requirement for flying manned aircraft in controlled airspace (B, C, D, E)?

If there were any minimum weight requirement for manned aircraft in controlled airspace, the requirement would probably be in 14 CFR Part 91, Section 126 through Section 135. These are the sections which describe the operating rules for various types of airspace. I looked through those sections, and there are no weight requirements.

I also can't imagine why there would be a minimum weight requirement for any class of airspace.

Like most aircraft, the Colomban Cri-Cri must have an airworthiness certificate and a registration certificate (14 CFR 91.203). The regulations describing getting an airworthiness certificate are in 14 CFR 21, Subpart H.

Some aircraft weighing less than about 254 pounds are "Part 103 ultralights" and do not need to be registered. However, this doesn't apply to the Colomban Cri-Cri, because Wikipedia says that it has a cruise speed of 100 knots; Part 103 ultralights must be "not capable of more than 55 knots calibrated airspeed at full power in level flight".


What is the difference between a wing station and wing buttock line?

The wing stations are perpendicular to the leading edge. Wing station zero is typically where the leading edge meets the fuselage. Wing ribs are typically parallel to the wing station. On swept wing aircraft, this won't match the flow direction, but it makes design and construction easier.

The wing buttlines are parallel to the airplane buttlines, which run down the length of the aircraft. Wing buttline zero is typically where the wing meets the fuselage.

This means that, unlike with other sections like the fuselage, the wing stations and buttlines are not perpendicular if the wing has sweep.

Rough illustration of the wing vs. fuselage BL and STA. Not to scale.


When buying airliners what is the difference between "orders", "options" and "purchase rights"?

Manufacturers typically plan their aircraft production well into the future, which includes having a buyer lined up for each aircraft, so they will know their position in the production line and have an anticipated date for delivery.

An order means that the buyer has agreed to purchase a certain aircraft in the production line, at a certain price. The buyer may cancel, but there will probably be a substantial penalty for doing so.

An option means that the manufacturer has reserved a certain aircraft in the production line for the buyer, usually at a certain price. However, the buyer will make the decision on whether to convert this to an "order" at a later date. There is less commitment than with an "order".

A purchase option is even less of a commitment than an "option." This just means that the buyer has agreed to purchase aircraft at a certain price, but it's not tied to a specific aircraft at that time.

It is becoming more common for buyers to mix these three types of orders, which allows them to have a balance of locking in an aircraft and price with orders, and less risk and commitment with options and purchase options.

These can all be canceled, though of course there will be more penalties for breaking a more firm commitment. Buyers may also change their order, either for their own or the manufacturer's business reasons.

The detailed finances of how much is actually paid for aircraft, and how much it costs to make or break any of these contracts, is generally not disclosed. Negotiations can be very specific to each order. For a rough estimate, this book considers that for 6 aircraft worth 45 million per unit, options would be worth 2.3 million each to the airline, or about 5%. This book estimates the down payment on a firm order at 10 to 15 percent, but notes that at least in the case of business and commuter aircraft, depending on market conditions, this may not always be required.


Why don't pilots parachute from small planes that are in distress?

Mainly because in the situation that you describe, the airplane is perfectly capable of flying.  You don't need an engine to fly as airplanes are designed to glide without it. Part of every pilots training is how to land the airplane when this happens.

Many of the same issues also apply in the smaller airplanes.  Unless the pilot and the passengers fly around with their parachutes on, it would be quite difficult to put them on in the confined space, in a high stress situation, and with the very limited time available.  Even if they did, untrained people are going to be hurt (probably quite badly) during the landing even if everything else with the jump goes well. (See my answer on your linked question for some of the things that can go wrong during the jump.)

You are also creating a hazard with the aircraft not being piloted and crashing into a random place on the ground.  All of this when the airplane could have just glided in for a landing in a field or on a road.  Most of these types of emergencies end quite well, and even a lot of the accidents will have fewer injuries and deaths than if people were jumping out all of the time. As an added bonus, the airplane can even be used again!

On the other hand, a major structural failure that makes the aircraft incapable of flight could be a reason to jump.  This is extremely rare however, and even if one has a parachute in this situation it may be impossible to exit the airplane safely because of high G forces and the possibility of hitting the airplane as you are both tumbling through the sky.

Some manufacturers are now building ballistic parachutes into the airplane which can bring the entire airplane down safely in these situations.  This is much more safer, reliable, and does  have a positive impact on safety in these extremely bad situations.  For just an engine failure though, I doubt that most pilots would even fire the ballistic parachute if there were suitable landing spots within gliding distance.

My view is that you would have a far greater safety impact by requiring everybody in a moving car to wear a helmet.  Would it improve safety?  Absolutely.  Would people want to do it?  A few would (and perhaps a few do), but the general population doesn't want to be inconvenienced by something that is only a remote possibility.  The odds of a parachute helping you in a typical GA airplane is far more remote than the odds of the helmet helping you in a car.


What are the unusually-enlarged wing sections on this P-38 Lightning?

It was a test bed that was looking into laminar flow on the wings.

  was converted in 1942 as a two-seater, with an elongated central
  nacelle extending aft of the wing trailing edge, intended as a
  research vehicle to find ways of reducing drag, and was the only P-38
  to have have a full dual set of flight controls. Later it was modified
  with enlarged laminar-flow wing sections outboard of the engine booms,
  complete with slots and boundary layer control by means of exhaust
  bleed air.

There is some discussion on it here as well.


Why is the Tu-95 so efficient despite having propellers that spin faster than the speed of sound?

Yes, propellers have problems at high speed, but if done right, they still have an advantage over turbofans at speeds up to Mach 0.8. Look at the inner engine gondolas of the Tu-95: They are elongated and thicker aft of the trailing edge. This was done to stow the landing gear in them, but also to area-rule the aircraft. The Tu-95 applies knowledge that was gained only in the early jet age. This, of course, also explains the swept wing.

Next, it uses contra-rotating propellers which spin very slowly (just 750 RPM). By having two coaxial propellers spinning in opposite direction, the efficiency at high speed is improved. The first propeller pre-swirls the flow so the flow conditions on the second propeller are more favorable for thrust creation.

The tips of the fan blades of a modern turbofan also move at supersonic speed, so the supersonic propellers on the Tu-95 do not create a direct disadvantage. By keeping the relative thickness of the blade near the tip low, the drag increase can be kept at tolerable levels. But make no mistake: Supersonic flow adds wave drag, and especially around Mach 1 the zero-lift drag coefficient of everything which moves through air has a maximum. It would make the Tu-95 even more efficient if it would fly at a lower cruise speed where the propeller tips are still subsonic, but Tupolev wanted to push the design to the highest useable cruise Mach number.

What you learned about propellers and jets is not wrong, but it is not a black and white world, either. Airliners use jet engines to fly at the highest cruise speed possible, but at the cost of higher fuel consumption. If they would restrict themselves to lower speeds, plenty of fuel could be saved. But too few people would book these flights, because on intercontinental routes they will take noticeably longer. Note that turboprops are still used in regional air traffic, and even the regional jets have lower flight speeds than the intercontinental jets.

Now to the efficiencies of engine types:

Piston engines are the most fuel efficient aviation engines. Their drawback is a constant power output over speed, so that thrust is inverse to speed. This helps for acceleration at take-off, but limits maximum speed. A modern piston engine uses 240 g of fuel for providing 1 kW of power over one hour: 240 g/kW-h. Diesel engines use as little as 220 g/kW-h. This number is already true for the old Jumo 205, among the first aviation diesel engines in operation 80 years ago.
Turboprop engines are next, and their power increases a little over speed due to ram pressure (which will raise the internal pressure in the engine by approx. 30% at Mach 0.8). Their power-specific consumption is about 300 g/kW-h but goes down with increasing size, so the biggest turboprops approach piston engine levels of efficiency.
Jet engines are less efficient than both, but are better for flying fast and high. Their thrust drops even less with speed, so the better basis for expressing consumption is thrust, not power. The typical fuel consumption of a modern jet engine (GE-90) is 30 grams of fuel per Newton of thrust over one hour (30 g/N-h) when run stationary, and twice that in cruise at Mach 0.85. Modern Military jet engines achieve 80 g/N-h at take-off and have roughly constant thrust and specific consumption over speed. Since most innovation happens on turbofans these days, the most modern turbofans again approach piston engine levels of efficiency, but if you compare the same technological standard, they are less efficient than their piston and turboprop contemporaries.

In all cases, thrust is created by accelerating a mass of air backwards. The general equation for propulsive efficiency $\eta$ is $$\eta = \frac{v_{\infty}}{v_{\infty}+\frac{\Delta V}{2}},$$ where $\Delta v$ is the speed increase of the mass of air due to that acceleration. This formula shows that it is better to accelerate a big mass of air only a little than a smaller mass by a lot. Propellers do this and for that reason offer the best efficiency. Turboprops use less efficient, but lighter gas turbines for creating power, but retain the efficient propeller. Civilian turbofans try to increase the mass of air by increasing their bypass ratio, and only the military is using the least efficient types with bypass ratios below 1, because they are the best choice at supersonic speed.

Below you see a plot of the thrust-specific fuel consumption in cruise condition of different engine types over their bypass ratio. The inverse relation is easily visible.

Plot of the thrust specific fuel consumption in lb of fuel per lb of thrust per hour of different engines over the logarithm of their bypass ratio (picture source).

To make a comparison between piston and turbofan engines possible, let's compare fuel consumption at take-off. The formula for static thrust of a propeller is $$T_0 = \sqrt[3]{P^2\cdot\eta_{Prop}^2\cdot\pi\cdot d_P^2\cdot\rho},$$ where $P$ is the shaft power, $d_p$ the propeller diameter and $\rho$ the air density. For our example, we use a four-bladed prop of 3.4 m diameter and an engine with 1111 kW power. Its static thrust is 10.727 kN when we assume standard atmospheric conditions and a prop efficiency of 85%. The fuel flow will be 266.6 kg per hour, and relative to thrust this is 24.8 g/N-h or just 80% of that of a modern turbofan.

I wonder if even the enthusiasts could guess what airplane I used, because I obfuscated it by using those unfamiliar metric units. I guess nobody will argue that it is not optimized for fast flight, so this comparison should also hold for the Tu-95, for which I have less data available.

Here follows the requested expansion on propeller tip speeds. Thanks to the excellent comment by @JanHudec not much is left to say: The propeller diameter is 5.6 m and their speed is 750 RPM, so the circumferential component is $5.6 \cdot \pi \cdot 750 / 60 = 220 m/s$. Add to this the cruise speed of Mach 0.67 (taken from this site — others list quite incredible numbers) at altitude, where the speed of sound is 295 m/s. Mach 0.67 equates there to 197.65 m/s, and vector addition gives 295 m/s for the propeller tips, exactly Mach 1.0. This means that the propeller is subsonic over its whole span.

But the top speed is quite a bit higher. Thanks to the excellent work of Ferdinand Brandner and his team back in the Fifties the NK-12 engines developed already 12,000 horsepower back then, and their power output has since been raised to 14,795 HP. This allows a top speed of Mach 0.82, and now the tip speed comes out at 327 m/s or Mach 1.08 — mildly supersonic. This means that the outer 30% of the propeller experience supersonic flow.

I fail to find a source for the range figures you list in your question. Again I refer to this site: It is 7,800 miles or 12,552 km at a cruise speed of 400 knots or 179 m/s which equals Mach 0.606 at altitude, resulting in Mach 0.96 for the propeller tips. Therefore, it seems the best range is reached with subsonic propeller tips.


Can we borrow Formula One's ground effect for airplanes?

The reduced pressure on the car not only exerts a downward force on the car, but an equal upward force on the ground. Mythbusters did an episode where they drove an Indy car over a manhole to show that it does lift the manhole cover slightly.

The force on the ground is irrelevant because it doesn't move and is not attached to the car. But in your drawing the same thing is happening. The reduced pressure exerts an upward force on the bottom of the channel and an equal downward force on thing top of it. They cancel each other.


Who is the woman that famously survived a light-plane crash in the arctic in the 1950s?

I'm guessing that this is "Hey, I'm Alive" by Helen Klaben (the female survivor).

From one of the reviews:

  [...] Flores's Howard five-seater crashed in a heavily wooded region, which no doubt saved their lives. The treetops softened the crash landing yet left the plane listing at an angle, making an uncomfortable shelter for either of them to lie down. Both Klaben and Flores were injured with various broken bones, and each had limited mobility. They were not prepared for an emergency and thus had no winter supplies or extra food. Their scant supply of food ran out after being stretched to siege-of-Leningrad proportions over ten days. I recall a dramatic scene from the movie where Sally Struthers, who played Klaben, discovers a tube of toothpaste which she shows Flores, played by Ed Asner. The two treat the toothpaste as a precious meal, which is exactly how Klaben described it.
  [...]
  Once all food ran out, including the toothpaste, the pair took to re-chewing their gum and by drinking melted snow. I am amazed that they could have survived on only water for five weeks. Flores, hearing a mysterious buzzing in the distance, was determined to find out what it was. I won't spoil the story by revealing if he found out the source of the buzzing or not, but when he returned to the crash site he and Klaben moved camp to a clearing, miles away from the trees. Klaben, who could not walk because her gangrenous toes were decaying, with bone pushing through the skin, was towed along on a toboggan made from the fuselage.

National Post Article on her story

People article

Quote from People:

  When Ralph Flores and Helen Klaben were found alive on March 25, 1963 near the wreckage of his single-engine plane in the Yukon, their names became synonymous with “miracle.” For seven weeks the 42-year-old electrician and the 21-year-old Brooklyn girl had endured pain from crash injuries and temperatures 42° below zero while subsisting on little more than melted snow and a few biscuits.

  Flores was flying home to California from Fairbanks and Klaben had accepted his offer of an inexpensive ride to San Francisco. During their ordeal he lost 51 pounds. She dropped 45 and after their rescue had the toes of her right foot amputated because of frostbite. Still, they survived on guts and ingenuity.

They didn't actually "walk-out", they moved the camp to a clearing and were found. Klaben couldn't walk (due to the condition of her toes/feet).


Well, let's tackle the second question first: What keeps the fan spinning? It is connected by a shaft to the low pressure turbine and the gasses expanding from the high pressure turbine towards the outside keep it spinning. Look at a good diagram and you'll see two (or three) concentric shafts that connect the low pressure turbine and the fan and the high pressure turbine and the compressor.

As for why bypass, pure jet engines where all the air goes through the combustors are really fuel hungry. You have to have a certain air/fuel ratio to get combustion. You can't lean it beyond a certain point or the fire goes out. Using all the air would use really a lot of fuel. The high-bypass ratio turbofan only takes some of the air through the combustors and just sucks the rest in with the fan and blows is out the back. The difference between that and a turbo-prop is mostly the cowling around the fan.


Military aircraft rarely have any sort of keys or any sort of authentication systems, they rely on physical security measures to prevent people from getting to the airplanes in the first place, like fences, dogs, cameras, guards, and of course guns.

If there were no physical barriers then you have 3 major barriers to being able to steal a fighter jet:

Support: just about every military fighter aircraft has an assigned crew to prepare it for flight and help the pilot(s) get in it. Without this crew you'd have to get the airplane powered up, fueled up, and then you'd have to figure out how to get into it and get the ladder removed. There's a lot of knowledge you'd need to do all this, just knowing how to open the canopy isn't going to be immediately obvious
Starting: starting up a fighter isn't like starting a car, you don't hit a button and everything happens for you, there's fuel tanks and pumps, hydraulic systems, electrical systems, and engine management. You'd have to know where to find all of the switches, dials and levers, and the sequence in which to use them. This isn't something you'd be able to guess, you'd need knowledge of the particular airplane
Flying: high performance jets are challenging to fly, and by flying I mean aviating, navigating, and communicating. Although modern fighters have a lot of computers to help out with this the systems require a great deal of training to use, and if you don't know exactly what you are doing you are most likely going to dig a big hole in the ground

If you know how to start and fly the airplane there's nothing stopping you from doing it, provided you can solve the problems of prepping and getting in the airplane. In fact, it's been done when pilots defect with their airplanes, see the comments below for some great examples.


Do autopilots in non-glass cockpits feed off of the gyro instruments?

Yes, they do. Also for glass cockpit, the autopilot uses the sensors that are used for the displays (ADC, AHRS, etc).
Here are some extracts from the FLM of the SA 365N Dolphin, describing the autopilot and coupler (I selected only parts relevant to the question):


What is the definition of "occupant" in 14 CFR 91.307?

If you're solo you don't need a parachute (emphasis mine):

  Unless each occupant of the aircraft is wearing an approved parachute,
  no pilot of a civil aircraft carrying any person (other than a
  crewmember) may execute any intentional maneuver that exceeds [...]

Incidentally, 91.307 says nothing about aerobatics; that's in 91.303.

And this question is closely related.


Why limit the bank angle to 10° when passing through FL300 on a B737-800?

One reason that comes to mind is as you get closer to the coffin corner, the extra G force due to maneuvering could cause a stall.  Quoting from "Stall the Pig",

  In the thin air at altitude, jets operate within a very narrow
  airspeed band between MMO (redline) and the low-speed limit, typically
  a yellow arc that provides a warning zone prior to a stall, indicated
  by a lower red line. At high altitudes and high weights, this
  band—known as “coffin corner”—can be quite narrow, leaving you a mere
  10 knots of usable airspeed range, for example. Load up the wing in a
  turn and that lower redline will quickly move upward toward your
  airspeed.

By limiting the bank angle, you also limit the G forces, and stay farther away from an accelerated stall.


Are there any supersonic aircraft with strictly mechanical controls?

There's one I can think of immediately, and that's the granddaddy of them all, the X-1. The X-1's control system was unassisted and it had no hydraulic system. The only part of the control system that was assisted was the horizontal stabilizer, which was operated using high-pressure nitrogen gas.

I think most of the early supersonic test airplanes were mechanically operated .


Why do ATC instructions to change level include the words "climb" or "descend"?

Adding the instruction "climb/descend" to the flight level is an example of linguistic redundancy offering a very rudimentary form of error detection for voice communication (which is inherently "unreliable", as it can be misheard by the receiver – on top of the sometimes poor ATC radio channel quality):

  In […] telecommunication, error detection [is a] technique that
  enables reliable delivery of […] data over unreliable communication
  channels. Many communication channels are subject to channel noise,
  and thus errors may be introduced during transmission from the source
  to a receiver. Error detection techniques allow detecting such errors.
  (source)

Therefore adding the instruction "climb/descend" offers an additional layer of security, because

the pilot would never descend when instructed to climb (and vice versa)
and the pilot is able to detect an instruction mismatching the flight level, i.e. "climb to FL240" when already at FL320 (taking the example in your question)

... but not perfect security (because the pilot at FL320 would not detect an error if ATC mistakenly instructs him to "climb to FL420" instead of "climb do FL400"). Therefore ATC instructions are repeated on the receiving end by the pilot.

(For a non-aviation analogy, the same technique is applied when dates are agreed upon on the phone as "Friday, 4 January 2019", although the day of the week is already implied by the date itself.)

In essence, your question "Why do ATC instructions to change level include the words 'climb' or 'descend'?" can be best answered by the (limited) added information transmission security these instructions provide. Therefore for me the real question is why instructions concerning speed and heading don't obligatorily require this sort of disambiguating instruction – especially so as this unspecificity can demonstrably lead to confusion. I hope someone else will be able to answer this part of your question, as I don't have specific knowledge about this aspect of it.


What regulations in the US exist for jetpacks?

This depends on what you mean by a "jetpack". If you mean the classic James Bond-style rocket pack, then according to an FAA spokesman quoted in the Wall Street Journal they just don't fly long enough for the FAA to be interested:

  Once aloft, a jetpack pilot is preoccupied with getting down quickly:
  A typical pack holds about 10 gallons of fuel, only enough to fly for
  about half a minute. The Federal Aviation Administration doesn't
  regulate jetpacks. "Thirty seconds is not sufficient to be considered
  a flight," says FAA spokesman Les Dorr. He adds that it's up to the
  individual to assess the risks.

On the other hand if you're referring to the Martin Jetpack, which uses fans instead of rockets, then several sources (e.g. Wikipedia) say that it's considered an ultralight by the FAA, in which case all the usual ultralight regulations would apply. But I couldn't find any direct confirmation of that on Martin's site.


When do I have to hold during an instrument procedure?

I suspect you are thinking of AIM 5-4-8 (b)(2) [page 5-4-31], which states:

  When a teardrop procedure turn is depicted and a course reversal is required, this type turn must be executed.

If so, have a look at the Instrument Flying Handbook, page 7-31.  The teardrop procedure turn is not referring to the same thing as a teardrop entry into a hold-in-lieu-of-procedure turn, it's something different entirely.


Does a vortex/wake turbulence reach ground level nearby?

According to the FAA vortices from the very largest planes generally do not drop vertically below 1000ft of the flight path. So, large aircraft flying less than 1000ft (300 meters) overhead have the potential of being felt on the ground.

This YouTube video shows a fatal aircraft accident after a medium sized prop airplane flew about 100ft above, and 40secs before the takeoff of a small plane.

The FAA addresses vortex generation and avoidance in AC_90-23G.pdf and the following information encompasses some of that information. In general, pilots are told to be weary of vortexes for 5min, 5mi, and 1000ft below. The following diagram supports this generalized rule...

Flight tests have shown that at higher altitude the vortices from large  aircraft sink at a rate of several hundred feet per minute (upto 300 fpm), slowing their descent and diminishing in strength with time and distance behind the wake-generating aircraft.

6 things determining vortex strength and behavior

1) Aircraft Speed - As the velocity of an aircraft increases, the strength of the vortices is typically reduced. That's because flying faster typically requires a lower angle-of-attack. It's also why takeoff and landing are critical times to pay attention to the flight path of large aircraft around you, because they're going relatively slow and creating large vortices.

2) Aircraft Weight - The heavier the aircraft, the more lift must be produced to sustain flight. Increased lift also increases vortex strength. The A380 below is a great example of this.

3) Angle of Attack - Higher angles of attack result in stronger vortices. You have a stronger difference between low and high pressure around the wing with a high angle of attack.

4) Wing Configuration - Clean configurations result in stronger vortices, because higher angles of attack are typically needed.

5) Proximity to Ground - When your wing is close the ground, wingtip vortices can't get as big, because as they spin around your wingtip, they impact the ground and dissipate. This is a major part of ground effect.

6) Wind - While wind doesn't change the strength of vortices produced, it does impact the way vortices affect you. Wind speed and direction determines how vortices travel and dissipate. For instance, if you have a strong crosswind, the vortices produced by airplanes will float in the direction of the wind.

The aircraft was likely flying near 250-275ft altitude
most approaches are 3deg
1.5km=4920ft
.0524 = tan(3deg)
height(ft) = dist(ft) * tan(deg)
257(ft) = 4920ft(dist) * .0524 (tan(3deg))


What is the maximum amount of flight hours an aircraft can have a month?

I don't think there is any regulation on max flying hours, just regulations on maintenance intervals.

The "A" check is the most frequent check, and according to Wikipedia:

  This is performed approximately every 125 flight hours or 200–400
  cycles. It needs about 20–50 man-hours and is usually performed
  overnight at an airport gate or hangar. The actual occurrence of this
  check varies by aircraft type, the cycle count (takeoff and landing is
  considered an aircraft "cycle"), or the number of hours flown since
  the last check. The occurrence can be delayed by the airline if
  certain predetermined conditions are met.

The other checks include:

B check - every 4–6 months, requiring about 150 man-hours and is usually performed within 1–3 days at an airport hangar
C check -  every 20–24 months, requiring about 6000 man-hours, taking 1 to 2 weeks to complete
D check - major maintenance check, occuring about every 6 years, requiring 50,000 man hours, generally spanning a couple months.

Note that all of these times are approximate, depending on the exact maintenance plan filed by the airline and the aircraft type. Also cycle count may be factored into the maintenance intervals in addition to flight hours so aircraft that do many short-haul flights may have more frequent maintenance.

So in any case, only looking at the A checks, if you can land, refuel, service, and get back in the air in 2 hours between 10 hour flights, the plane could stay in the air for 20 hours/day. Every 6 days, it will need some downtime for the A checks, let's say the airline puts enough  people on it to get the check done in 5 hours. So that's 125 hours per cycle: 120 hours flying, 5 hours in maintenance. They can fit 4.83 of these cycles in a 30 day month so the aircraft could be flying up to 580 hours in any given month (but that last A check gets deferred to the next month, so that means less time in the air that month.

With longer flights (which reduces the overhead from turnaround times) and tighter turnaround times, the flight hours per month could be higher. If you really want the maximum for a month, then if you assume 125 hours per maintenance inverval and that the plane is kept in the air as long as possible with 0 turnaround time, that's around 690 flying hours out of 720 total hours in a month.

Of course, this makes a big assumption that the A check interval really is 120 hours, and that the time to do the maintenance is 5 hours, in the real world both numbers will vary based on aircraft, airline, and maintenance staffing levels.

Plus, over the longer term, you need to factor the other, less frequent but also more time consuming maintenance checks (B through D checks), as well as allow downtime for unexpected repairs.


Why is there a difference between nosegear retraction directions?

For both main and nose landing gear the main and really only consideration is where they can make space for the gear (there is no standard direction for retracting the main landing gear either; the Tu-154 retracts main gear rearwards into the anti-shock body).

The most common configuration is retracting nose gear forward, because it's easy to make space for it there leaving more space for the cargo hold. I don't think the air pressure during gravity extension plays any role in the decision.

Most older Russian planes were however originally designed with glass nose seating navigator, so they did not have the room there. It was no longer the case with Tu-154 though. So they either had other equipment there or were simply used to making it retract rearward and didn't think about the advantage of changing it.

The most common configuration for main gear is retracting it inward into the wing box, but note that the Tu-154 is exception there as well retracting the main gear into the rather large anti-shock bodies. Because they needed the anti-shock bodies they thought how to use them and there were not that many options.


Why does wake turbulence seem to move upward on touchdown?

(YouTube)

This is not wake turbulence. This is a hard landing. The smoke from the tires is hot, it rises, hits the fuselage, curls away from it, and then curls back on itself due to the Rayleigh–Taylor instability.

(YouTube) A more persistent example. Note the still rising column of smoke.


Can a closed Airworthines directive get reopened by a new revision?

ADs aren't 'closed', they are 'complied with'. If the AD has been revised and the new compliance criteria are not met, then you would need to perform whatever measures are required by the revised AD.

There are a number of reasons that the AD may have been revised but in the example that you allude to, the proposed action does not appear to be sufficient to remedy the problem. Therefore a new or revised AD has been issued.

If the revision is mostly a clarification or change in affected aircraft, the identifier usually remains the same e.g. 2018-03-03 R1

If the revision makes a substantial change to the method of compliance, they usually rescind the original AD and issue a new one. e.g.

  SUMMARY: We are rescinding an airworthiness directive (AD) for Lycoming Engines model TIO- 540-A series reciprocating engines. The existing AD, AD 71-13-01, was prompted by a report of a failed fuel injector tube assembly. Since we issued AD 71-13-01, we became aware that Lycoming Engines no longer supports Service Bulletin (SB) No. 335A, which was incorporated by reference in AD 71-13-01. The intent of the requirements of that SB is now in Lycoming Engines Mandatory SB No. 342F, which we have incorporated by reference into AD 2008-14-07. The FAA determined, therefore, that this requirement is duplicated by another AD.

I had my A&P comply with a fuel selector AD 2018-02-05 so it was noted as complied with in my logbook. The AD was superseded by AD 2018-07-03 which allows a pilot to comply with the AD, so I made an entry in the logbook to indicate that I had complied with the new AD. This example is the same as the one in your question, though in my case the only additional action required was a logbook entry.

  SUMMARY: We are superseding Airworthiness Directive (AD) 2018-02-05 for certain Piper Aircraft, Inc. Models PA-28-140, PA-28-150, PA-28-151, PA-28-160, PA-28-161, PA-28-180, PA- 28-181, PA-28-236, PA-28-201T, PA-28R-180, PA-28R-200, PA-28R-201, PA-28R-201T, PA- 28RT-201, and PA-28RT-201T airplanes. AD 2018-02-05 required inspecting the fuel tank selector cover to verify the left and right fuel tank selector placards are located at the proper positions and replacing those that are improperly located with new placards. This AD addresses the same unsafe condition and requires the same actions as AD 2018-02-05, but changes the inspection of the fuel tank selector cover to a preflight check and allows for various fuel selector clocking configurations. This AD was prompted by our determination to allow the owner/operator (pilot) holding at least a private pilot certificate to perform the preflight check. We are issuing this AD to allow the pilot to do a preflight check of the fuel selector placards.


Where is fuel metered in continuous flow fuel injection system?

Just in front of the engine. It makes most sense to measure fuel flow as close to the engine as possible: any leaks between meter and engine will distort the measurement. Here is an example of the B737 arrangement.

As to the how, airborne fuel flow meters work in the same way that turbines do: the mass flow of the fuel causes an impeller to spin, rotational speed is then a measure of fuel flow. Note that it is a measure of fuel mass flow, not fuel volume flow: mass flow is not subject to variations due to temperature etc.


You will need to find a US CFI-AI who can perform a competency check for you.  It can be done in the US or in Canada (in a US registered aircraft unless that CFI holds TC and FAA credentials).

If you are within 6 months of being current, you can do approaches with a safety pilot in Canada. If you are flying a US registered plane, then you will most likely need a US certificated safety pilot.  If you are flying a Canadian plane, then your safety pilot should be a Canadian pilot, acting as PIC for the flight.  You could still log the approaches and simulated instrument time.

In my experience, it will be far easier to find a US CFI in Canada than it is to find a Canadian CFI in the US.  Ask around.  Consider contacting an organization like AOPA if you are a member, or COPA, and asking them for help locating US CFIs.  I would also ask if they have additional guidance because they may have letters from Transport Canada and the FAA which may have policy considerations which might be good to know.


What are airline "flag" and "supplemental" operations?

Part 121 certificated carriers are given specific permission within their Operations Specifications (OpSpecs) to conduct one or more of those three types of operations -- Domestic, Flag, and Supplemental.

The OP asked: how are these different than "normal" Part 121 operations. The answer is: they're not. A "normal" 121 operation must be operated under one of those three types, with slightly different rule requirements for each.

Each is defined in Part 110.2. (the previous reference to 119.3 is out of date) The gist of it is as Shawn said: US-to-US location is a domestic operation, US-to-nonUS location is a flag operation, and all-cargo or "large aircraft charters" are a supplemental operation. These are not exact, and there are exceptions and legalese within the 110.2 page-long definitions for each one. Please read the FAR for the complete definition.

Each individual flight needs to be released and operated according to the rules of the operation type that is applicable to that specific flight.

Airline themselves are not "domestic" or "flag" or "supplemental" (per definition), but it is common to call an airline a "domestic airline" who only has OpsSpecs approval to conduct domestic operations. But that is not a legal term.  Most (I suspect all?) of the majors are OpsSpec'd to conduct all three types of operations.

Let's take an example of Alaska Airlines. An aircraft is scheduled for (important) and operated on a flight from Seattle to LAX. This flight meets the definition of a domestic operation, so all of the "domestic" rules would apply to this flight. That same aircraft is then operated on a flight to Mexico City. This would be a "flag" operation, and so some slightly different rules would apply to how this flight is dispatched, released, and operated. (alternate airport requirements, fuel requirements, and how much crew rest was required prior to the flight, etc. are slightly different)

Finally, the Washington State Huskys football team charters an Alaska Airlines aircraft to transport them to the Rose Bowl. The flight from Seattle to Los Angeles would be operated under "supplemental" rules. The previous paragraph's example domestic flight might have used the same exact routing, the same exact crew, and the same exact aircraft. But the rules for this specific flight were slightly different, due to the different type of operation being conducted.

The air carrier, "Alaska Airlines", is not a "Domestic Airline", nor a "Flag Airline", nor a "Supplemental Airline"... rather, the company's certificate grants them permission to conduct all three types of operation.


Why do passenger jet manufacturers design their planes with stall prevention systems?

Why do car manufacturers install seat belts? Shouldn't licensed drivers be well aware that they should slow down when it's raining or snowing and that they shouldn't run through red lights or stop signs?

A better analogy:

Why do car manufacturers install anti-lock break systems? Shouldn't drivers know that when their brakes lock up they should release brake pressure and/or pump the brakes quickly to slow the car down?*

*To be fair, I don't think this is actually taught in driver's education (at least in the US) anymore - my kids learned this from me, but never reported being taught and/or practicing when they took driver's ed. One of the many reasons flying is safer than driving.

Because accidents happen.
Because pilots are human and make mistakes.
Because when you're flying in the clouds with no visual references, it's easy to get confused.
Because even with stall warning & prevention systems in place, confused pilots will fight the system. AF 447


Has a pilot ever been disciplined for taking a guest for a flight in a single-seat fighter aircraft?

According to the book "A Spitfire Girl" the pilot's name was Flight Lieutenant Edward Gordon Brettell DFC of "Great Escape" fame, among other things, and he was court-martialed for flying his Spitfire Mark Vb of 92 Squadron to a dance with a WAAF on his lap. Squadron Leader Tony Bartley DFC helped defend him during the court-martial.
The man was a colorful character, to say the least. In one of the many references to him on the Internet I found this:

He had flown his girlfriend, a WAAF based at Tangmere, in his single
seat Spitfire to RAF Biggin Hill for a squadron party. Unfortunately
for him, the station commander who was there when they landed took a
dim view of his actions and reported him. Among the charges at his
later court martial was endangering the King's aircraft (King George
VI was then on the throne). He called upon his friend, a Battle of
Britain ace with a Hatfield-link, Anthony Charles Bartley (41816) for
help.
Tony Bartley was acting as a test pilot for Supermarine at the time.
He later revealed in his autobiography that he asked Jeffrey Quill
(Supermarine's chief test pilot) and Joseph Smith (Supermarine's chief
designer after Reginald Mitchell's death) for their help. Joe Smith
even went so far as to draw up some mathematical equations alleged to
prove the aircraft wasn't in any danger, which Bartley presented at
the court martial. Although the clinching argument was when asked by
the prosecution how he could prove it, Bartley admitted to having
committed an identical offence previously. Now faced with the prospect
of having to prosecute two badly needed officers with a war on, the
charge was dismissed. Although Gordon Brettell was transferred away
from the squadron.


What are the "Static Ports" in a Boeing 767?

One of the standard instruments of an aircraft is a "Pitot tube". This instrument allows measurement of the forward air pressure as the aircraft moves through the air. By this measurement the instrument can estimate the relative air speed of the aircraft.

In order to make the measurement, the forward air pressure is compared to the side air pressure and the difference between the two is presumed to be due to the force of the aircraft moving through the air. Thus, the measurement is a relative one, comparing the forward air pressure to the air pressure on the side of the plane.

The "static ports" allow air into the instrument to provide the input for the air pressure on the side of the aircraft. They are called "static" ports because in general they take in air at the ambient pressure which does not change very much as compared to the pitot tube which takes in air as the plane rushes through it, thus frequently changing according to the speed of the plane. The pitot tube is usually located on the bottom of the plane and is pointed forwards.


How does the A350 variable camber system decrease drag?

Henning Strüber, one of the Airbus engineers behind this system, has written a paper on it.

In cruise:

  This can be applied in early cruise phases to shift the center of lift more inboard and by that reducing the wing root bending moment, which can be transferred into a structural weight saving.

A plane that can be built lighter will have lower drag [for the same payload].

For a heavy and/or a hot and high takeoff:

  In high-lift configuration a more outboard loaded lift distribution can be achieved to reduce induced drag during take-off.

For how that works, see here. The answer there by @PeterKämpf confirms that outboard loading requires a heavy wing relative to the whole mass (scaling laws work for an insect, but not for an albatross or an airplane). So those two regimes may appear to be contradictory: if the cruise system allows a lighter wing, then how can that lighter wing achieve more outboard lift for a heavy takeoff.

Accounting for the gust loads in cruise is the key here, which are smaller for takeoffs. (Thanks to @PeterKämpf for this insight; see comment posted below.)


What is the difference between experimental and amateur built aircraft in the US?

The FAA provides pretty clear definitions and/or explanations:

Amateur built:

  Title 14, Code of Federal Regulations (14 CFR), part 21, section
  21.191(g), defines an amateur-built aircraft as an aircraft "the major portion of which has been fabricated and assembled by person(s) who
  undertook the construction project solely for their own education or
  recreation."

They define Experimental as a category, since it has to do with how the airworthiness cert is issued:

  A special airworthiness certificate in the experimental category is
  issued to operate an aircraft that does not have a type certificate or
  does not conform to its type certificate and is in a condition for
  safe operation.  Additionally, this certificate is issued to operate a
  primary category kit-built aircraft that was assembled without the
  supervision and quality control of the production certificate holder.

And further

  Special airworthiness certificates may be issued in the experimental
  category for:

  Operating amateur-built aircraft: to operate an
  amateur-built aircraft in which the major portion has been fabricated
  and assembled by persons for their own recreation or education.
  Operating kit-built aircraft:  to operate a primary category aircraft
  that was assembled by a person from a kit manufactured by the holder
  of a production certificate for that kit, without the supervision and
  quality control of the production certificate holder.

So... All amateur built aircraft are experimental (flown under an experimental airworthy type certificate) but not all experimental's are amateur built, for example a pre-production aircraft may need to be registered as an experimental for test flights before a type certificate is received.


What is the force exerted by the catapult on aircraft carriers?

Takeoff

Steam/power settings are adjusted for each a/c type and T/O weight.

The EMALS stores 484 MJ in four 121 MJ alternators spinning at 6400 rpm. It delivers up to 122 MJ over 91 m. That averages out to 300,000 lbf. EMALS more finely controls launch forces (Max Peak-to-Mean Tow Force Ratio = 1.05), allowing it to launch smaller a/c (eg, smaller UAVs) and delivering a smoother ride that reduces airframe fatigue.

Current steam catapults deliver up to 95 MJ over 94 m. Each shot consumes up to 614 kg of steam piped from the reactor (NB: not the primary coolant loop). That averages out to 230,000 lbf.

Accelerations average around 3 g's, peak around 4 g's.

Landing

Landings are stressful (notice the fuselage skin wrinkling beneath the radome on this Hawkeye):

(Source: DoD photo by: PHAN KRISTOPHER WILSON, USN Date Shot: 11 Jan 2005.)

An F/A-18 touches down around 720 fpm (12 ft/s). It's rated to twice that. CTOL fighters typically do about half that. I believe airliners average under 200 fpm (3 ft/s).

Here an F/A-18 is dropped from 20ft (36 ft/s, 2200 fpm):

Service life

NATO fighters are typically designed for 30 year service lives (6,000 to 8,000 flight hours). Historically, Soviet/Russian fighters fly much less. The Su-27SK is rated for 2,000 flight hours over 20 years. [See table for cost and service life comparison.] F/A-18's were built for 20 year service lives, 30 years with service life extensions.

The fuselage and landing gear are much stronger to withstand carrier landings and launches. The nose gear regularly transfers 4x the takeoff weight of the a/c into the rest of the fuselage.

Compare the F-35A's CTOL nose gear:

(Source: USAF)

...to the F-35C's CATOBAR nose gear:

(Source: USN)

Here's an excerpt from a Naval Air Warfare Center paper on EMALS:

  Other drawbacks to the steam catapult include a high volume of 1133 m3
  , and a weight of 486 metric tons. Most of this is top-side weight
  that adversely impacts the ship's stability and righting moment. The
  large volume allocated to the steam catapult occupies "prime" real
  estate on the carrier. The steam catapults are also highly maintenance
  intensive, inefficient (4-6%), and their availability is low. Another
  major disadvantage is the present operational energy limit of the
  steam catapult, approximately 95 MJ. The need for higher payload
  energies will push the steam catapult to be a bigger, bulkier, and
  more complex system.

Endspeed:      28-103 m/s [54-200 knots]
Cycle time:    45 seconds
Weight       < 225,000 kg
Volume       < 425 m 3

  At max speed, the output of one of the disk alternators would be 81.6
  MW into a matched load... These magnets have a residual induction of
  1.05 T at 40 oC and create an average working air gap flux density of 0.976 T, with tooth flux densities approaching 1.7 T... Maximum output voltage is 1700 V (L-L) peak and current is 6400 A peak per phase. The
  disk alternator's overall efficiency is 89.3%, with total losses of
  127 KW per alternator. This heat transfers out of the disk alternator
  through a cold plate on the outside of each stator. The coolant is a
  WEG mixture with a flow rate of 151 liters/minute. The average
  temperature of the copper is 84oC, while the back iron temperature is
  61oC.

Sources:

EMALS/ AAG: Electro-Magnetic Launch & Recovery for Carriers
Electromagnetic Aircraft Launch System - EMALS
Steam catapult types
Electromagnetic Aircraft Launch System - EMALS - NAWC


At what intervals do planes land and take off from Chicago O'Hare?

As a general average, Chicago O'Hare (KORD) seems to do somewhere between 1.5 and 2 operations per minute (so roughly one takeoff or landing every 30-40 seconds).

I based this on data from the FAA's Air Traffic Activity Data System - Terminal Operations report, and specifically looked at November 23 through November 30 of 2014 (17835 operations, over 8 days works out to 1.55 operations per minute - I poked around randomly and found days as high as 1.7 operations per minute).

One of the limiting factors for number of operations at any airport is separation between aircraft, which is covered here

  Incidentally we were discussing airport/tower activity levels in chat earlier today, and Chicago O'Hare is the busiest airport in the United States overall - a title it recently stole back from ATL (which was #1 from 2004 to 2013).


How do I find out what happened on this flight?

Issues in flight are more common than we think: engine shutting down in flight, fumes in cabin, ... Aircraft are huge pieces of engineering with many parts and sensors that can fail. Aircraft have many redundancies which most of the time allows for a safe landing.

I tried to look on the avherald, a reliable and extensive source of aircraft reports, incidents and accidents, mainly fed by its owner and its users but the flight does not appear there. However you can appreciate the number of incidents occurring every day and this is a small part of them.


Why don't airliners carry radar jamming technology or missile counter measures?

Surface-to-air missile attacks on airliners at cruising altitude are vanishingly rare: there have only been three known attacks in the past half-century (MH-17, IR-655, and probably S7-1812).  Any protection system needs to take that into account -- any safety system needs to be justified in terms of cost, weight, and safety -- it needs to save more lives than it costs.

Direct jamming.  Suppose you stick an AN/ALQ-99 jamming pod on the airplane.  That's 6000 extra pounds, a good deal of drag, and a bunch of parts that can break off, catch fire, or otherwise be a hazard.
Active countermeasures.  Stick an AGM-88 HARM missile on the plane.  Now, your anti-radar missile isn't much faster than the radar-guided missile trying to shoot you down, so for reasonable safety, you need to launch as soon as you get painted by the tracking radar.  What do you suppose the odds are that a twitchy co-pilot acting as ECM/weapons officer is going to launch against an innocent control tower?  How many weather radars are you willing to destroy to save that one airplane every 20 years?  Are you sure that missile will never malfunction on the launching rack and destroy the airplane?
Stealth.  Hiding from radar-guided missiles means you're also hiding from traffic-control radar.  How often are crashes prevented by that radar?  I bet it's more than one every twenty years.

The benefit is roughly one less airplane crash every 20 years.  That means the cost, both in terms of money and in terms of risk, needs to be very, very low.


Does the FAA have a document that details each step found in a Component Maintenance Manual?

In general aviation and even working in FBOs, I have referenced AC43.13 to approve repairs that the CMM does not cover. These processes and techniques are approved by the Administrator. In general terms, the FAA tends not to tell you how to meet a requirement but rather gives the requirement then the organization has to meet that requirement through a FAA approved QMS. This process is applicable regardless if you are working with the MIDO, ACO, or FISO. In order to get down in the weeds, you would have to be very specific in your question.

Here is the link to FAA AC43.13 for everyone's review.
https://www.faa.gov/regulations_policies/advisory_circulars/index.cfm/go/document.information/documentid/99861

Best,
Mark


How can I estimate the minimum runway needed to take off with a hang glider?

What you need is enough lift to remain in the air. For that, the maximum lift of your hang glider needs to exceed the total weight.

When you know the total weight of the glider (you included), you can derive the theoretical minimum airspeed from the lift formula:

$$L_{max}=\frac12{\rho}V^2C_{max}S$$
$$V_{min}=\sqrt{\frac{2W}{{\rho}C_{max}S}}$$

Where:

$L$ = lift
$\rho$ = air density
$V$ = air speed
$C_{max}$ = maximum lift coefficient
$S$ = wing surface
$W$ = weight

Now you have to know your maximum lift coefficient. Suppose this is 1.2, and for safety and initial manoeuvring, let's add a margin of 40% to the weight.

Let's say your mass is 85 kg, and the glider has a mass of 35 kg. The total weight would be 120 kg — that is about 1,177N weight, which for the sake of safety margin is increased to 1,650N.

I'll estimate the surface of the wing to be $16m^2$. Assume a normal day, the air density will be about $1.225kg/m^3$.

Filling in the numbers is the formula:

$$V_{min}=\sqrt{\frac{2\times1650}{1.225\times1.2\times16}}\approx 12 \textrm{ m/s}$$

Any wind speed you get you can subtract from this figure: what is left you have to achieve by pushing, running or diving.


Can a commercial airliner sink to the bottom of the ocean?

Can a large modern jet airliner plunge intact underwater from flight?

No.

Large airliners are not desgned for this and are not even strong enough to make a landing on water in less than perfect conditions.

E.g. 961

striking the surface at a larger angle would certainly lead to widespread disintegration.

Is it possible for a large modern jet airliner to sink intact?

Yes (as near as makes no difference)

Almost all large aircraft impacting the sea surface in an emergency or uncontrolled will break up immediately and catastrophically.

One notable exception was US1549, an A320, which was landed on water without breaking up. It was described as "still virtually intact though partially submerged and slowly sinking". The left engine detached and sank.

So a controlled landing on water is possible under extremely favourable circumstances. It would then be possible for the aircraft to sink in more-or-less one piece without creating a large amount of floating debris.


You should definitely not attempt flight if there is frost on the windows that would affect visibility, or on any of the wings or flight control surfaces.  Frost accumulation on such surfaces can reduce the lift generated by your wings, possibly causing a crash on takeoff.

According to the NTSB, frost the size of a grain of salt, distributed as sparsely as one per square centimeter over a wing's upper surface, can destroy enough lift to prevent a plane from taking off.

The cheapest solution is to try to re-position the plane on the ramp so that the sunlight has a chance to melt it away.

You can also temporarily move the plane into a heated hangar until it melts, or ask the FBO to do so for you.  If the forecast is predicting a chance of such conditions the night before, you can usually call the FBO on the night before and ask them to move your plane into their hangar just for the night, in advance of your morning flight.

If you're really anxious to go, you can ask the FBO to apply a heated deicing solution to your plane, but be prepared to pay for it (it's priced by the gallon and the amount needed will depend on the size and amount of frost of your plane).  Not all FBOs will have deicing capabilities, particularly if the region does not commonly experience such conditions.


What could cause a low-pressure compressor first stage blade of a turbofan engine to bend forward?

Forward bending of the first stage of the low pressure compressor is usually associated with (soft) Foreign Object Damage (FOD).

Ice and/or large quantities of snow in the engine intake will typically cause forward bending of the leading edge of the tip of the blades.

 Damage to GE CF680C2 turbine engine compressor fan blades after snow/ice ingestion
Source: Flight Safety Australia

 Damage to Turbomeca gas turbine Arriel 2B turbine engine compressor blades after snow/ice ingestion
Source: Transport Safety Board of Canada, aviation accident investigation report A12P0008


What is this item on the nosewheel of the Sukhoi PAK-FA?

It is a mud guard/FOD deflector, which is found in almost all Russian combat aircraft operating from land bases.

This is basically a reflection of the Russian philosophy of aircraft operations:

  The fact is that most Russian fighters and attack aircraft were built to operate in pretty horrific conditions, ones that would chew up and destroy their western counterparts. Features that allowed them to do this usually included twin tire nose gear and a mud and debris catcher located behind the nose wheels.

The nose debris deflector prevents debris being ingested by the air intakes (which are to the rear of nose wheel) and damage to the airframe. According to ausairpower.net, it also has:

  Alternate intakes for the propulsion system, as seen on earlier Flankers.

for rough field operations, similar to Mi-29. The image below shows the add-ons.

Detail of inlet and lower fuselage area (Sukhoi); image from ausairpower.net

The FOD deflector is similar to that of the Su-27's, as shown below:

Su-27 nose landing gear, from another answer; originally from maybach300c.blogspot.com


How much could human power add to the endurance of an electric gyrocopter?

According to the wikipedia page on "Human Power", a trained cyclist can produce about 400 watts of mechanical power for an hour or more, adults of good average fitness can produce between 50-150 watts for an hour of vigorous exercise, and a healthy laborer over the course of 8-hour shift can sustain about 75 watts per hour.

The Electric motor on the autogyro mentioned in the question has an 80kW (i.e. 80,000 Watt) motor. However, as you know most aircraft only use 100% power on takeoff and approximately 75% for fast cruise. For simplicity, I'll assume 75% power for cruise. That is 80kW * 75% = 65kW (i.e. 65,000 Watts). The information from the AutoGyro says the current endurance is 45 minutes.

So, if we assume the "trained cyclist" power output of 400 Watts, which is 0.62% of 65,000 Watts, then it would result in a 0.62% increase to the current endurance of 45 minutes. A 0.62% increase would result in an increased endurance of approximately 17 seconds of flight (45 min * 0.62% = 45.28 min or 45m 17s).

Its important to note that the human powered glider mentioned in the link was designed from the ground up to be powered by human power. It only weighs a fraction of the electric gyro. For example, a similar human powered glider the MIT Daedalus weighed just 69 lbs (31kg)! (https://en.wikipedia.org/wiki/MIT_Daedalus). The gyrocopter in the question appears to be a modified version of the Cavalon model by the company AutoGyro; on it's technical details page it says its empty weight is between 606-672 lbs (275-305kg).


Where is the airport in Disneyland Paris? (DLP)

IATA codes don't necessarily correspond to airports. Some non-airports have IATA codes to allow airlines to sell through tickets that might, for example, consist of travelling from A to B by plane and then onward from B to C by train. DLP isn't on Wikipedia's list of railway stations with IATA codes but I imagine something very similar is going on here.


What aircraft has the highest suggested landing speed?

Based on its fixed-wing hypersonic design and inordinately high wing loading, I would predict that the X-15 has the highest recommend landing speed of any earthbound aircraft, with a preliminary search seemingly bearing this hypothesis out. According to an ostensibly legitimate NASA source (link below), the X-15's normal landing speed was 200+mph (173.8kts=321.9kph),

http://www.nasa.gov/centers/armstrong/news/FactSheets/FS-052-DFRC.html

But if unofficial sources are to be believed, its actual landing speed was much higher, closer to 390kph=208kts (although these numbers are admittedly more dubious):

  “According to an early edition of 'the Guinness book of world records' the X15 also holds the record for fastest landing speed at 242 mph compared with 210 mph for the space shuttle.”

http://area51specialprojects.com/x15.html

If only powered aircraft are open to consideration, then the F-104 Starfighter would have to be up there as well. It needed a blown-flap flow control system just to be sane during landing...

  “To make landing speeds “reasonable,” The F-104 forced engine air through the wings to smooth the airflow and give more lift. With bleed air, the Zipper could land at the challenging but not extreme speed of 160 to 165 knots. If the air-bleed system was not working, landing speeds climbed to 240 knots.”

http://www.pacificaviationmuseum.org/pearl-harbor-blog/lockheed-f-104-starfighter

So, if mechanical failure scenarios are deemed admissible, then the F-104 without its crucial boundary layer control systems would be the clear winner for powered landing speed, weighing in at an absolutely terrifying 240 kts. Otherwise, it would appear that the X-15 (unofficially) reigns supreme.


Is pressure pattern navigation used in the real world? How effective is it really?

It is used in the real world, especially by airlines. The best example is the North Atlantic Track system. The tracks are tailored every day to maximize the tailwind on West to East crossings and minimize the headwind East to West crossings.


Operational control is defined in 8900.1 Volume 3, Chapter 25 as:

  Operational control functions include, but are not limited to:

  Preflight planning;
  For part 121 operations, preparation and dissemination of dispatch/flight releases;
  Canceling a flight due to potential hazardous or unsafe conditions;
  Ensuring that only those operations authorized by the OpSpecs are conducted;
  Ensuring that only crewmembers who are trained and qualified in accordance with the applicable regulations are assigned to conduct a flight;
  For part 121 operations, ensuring that no flight is started unless it has been authorized by a dispatcher or person authorized to exercise operational control in accordance with §§ 121.593, 121.595, or 121.597, as applicable;
  Ensuring that crewmembers are in compliance with flight and duty time limitations and rest requirements prior to departing on a flight;
  Designating a pilot in command (PIC) and, where applicable, a second in command (SIC) for each flight;
  Providing the personnel who perform operational control functions (PIC, dispatcher, etc.) with access to all necessary information for the safe conduct of the flight (for example, weather, Notices to Airmen (NOTAM), airport aeronautical data (analysis), and inoperable instruments and equipment);
  Specifying the conditions under which a flight may be dispatched or released (weather minimums, flight planning, airworthiness of aircraft, aircraft loading, and fuel requirements);
  For part 121 operations, ensuring that when the conditions, limitations, and authorizations specified in a dispatch or flight release cannot be met, the flight is either cancelled, delayed, rerouted, or diverted;
  For part 121 operations, ensuring that each flight is conducted in accordance with the conditions and limitations of the dispatch or flight release;
  Ensuring that each flight is operated in accordance with the limitations of the MEL and CDL;
  For part 121 operations, monitoring the progress of each flight and initiating timely actions when the flight cannot be completed as planned, including diverting or terminating a flight;
  For part 135 operations, locating a flight for which a Federal Aviation Administration (FAA) flight plan (FP) has not been filed;
  For part 121 operations, ensuring rapid and reliable communications in accordance with §§ 121.99 and 121.122, as applicable;
  Restricting or suspending operations in accordance with §§ 121.551, 121.553, or 135.69 as applicable; and
  Exercising the emergency authority described in §§ 121.557, 121.559, and 135.19, as applicable.

These functions are normally performed by a variety of people:

Dispatch
Crew Scheduling
Maintenance
Chief Pilots
Director of Operations
The PIC of the flight
Manager of SOCC (System Ops Control Center)
Director of Training

Operational control is implemented by the above people and must hit all of the bullets in the definition above.  This means that to exercise operational control you must always know where your planes are, you must determine who flies them, plan those flights, ensure the pilots and aircraft are legal, ensure everyone is trained for the operations performed and to always be able to communicate with your aircraft.

There is also mention of Operational Control Systems, which require that any flight operated by the carrier is dispatched, followed and can be located at all times.  These functions are normally carried out by the Dispatcher assigned to your flight.

Further reading beyond the 8900.1 can be found in AC 120-101 for 121 ops.


Why would this A-10 Thunderbolt be flown over rural New Hampshire?

Practice makes perfect!

Groton, NH (along with a large chunk of rural New Hampshire further off to the north) sits more or less under an area of military Special Use Airspace called the Yankee 1 and 2 Military Operating Area complex, or MOA for short:

(If you're wondering why Groton is not on the map, ask FAA/NACO -- it's about at the bend in the road WNW of Hebron, right under the southern edge of the Yankee 1 MOA.  The snippet was taken using vfrmap.org.)

These areas of airspace are used by US military tactical pilots to practice their tactical maneuvers (such as "dry" practice bomb and strafing runs, and air combat maneuvering) without getting in the way of other airspace users -- high-performance jets making sharp maneuvers don't mix well with slow little propeller planes or not-so-maneuverable airliners!

As to why the pilot was circling?  They were probably killing time, waiting for their practice partner to show up, or the MOA to free up so they could use it.  Also, the airplane in the picture looks to be unarmed -- on one side is an empty pair of Sidewinder rails, while the other side carries a pair of targeting and countermeasures pods.

So, what your mom saw was a small part of our military keeping their gun oiled and ready, so to speak -- practice makes perfect, after all, and the airspace over rural parts of the US is about the only place in this country non-busy enough to serve as a suitable practice area.


What determines the touchdown zone and aiming point markings on a runway?

There are actually several different indicators on the end of a runway. Here's a diagram of the most common ones during the day:

... and at night:

The first touchdown indicator, as shown, is usually placed a set distance (here 500') from the threshold of the usable runway. Then, there are additional markers at 500' increments. Which one the pilot will aim for on approach depends on the plane he's flying, its weight, and instructions from the tower such as to land "deep" or "shallow" (light craft, and sometimes even commercial airliners, are often given these instructions to help manage air and ground traffic more efficiently at peak times).

As you can also see from the night shot, the glide slope lights (here using a system called PAPI which is a more precise indicator of slope than the older and more well-known "white-over-red" VASI) are positioned smack in the middle of the touchdown zone; again, with an approach path aiming directly for that point from the pilot's perspective, the plane will touch down on full-strength runway pavement even if he's in a 747-800.

Of course, maintaining that glide slope all the way in is not the greatest idea, as a standard descent rate for an airliner on final approach is 400ft/min, which works out to more than 6 feet per second. Even the cushiest main gear struts are going to make that a pretty rough "smack" in the seats of the passengers and can cause very expensive damage to the airframe itself. To avoid that, pilots usually add a little throttle and/or pitch up a few more degrees in a maneuver called a "flare", which reduces the rate of descent, ideally zeroing the plane's descent rate just as the wheels touch. This means that during the last few seconds of approach, the glide slope decreases, moving the "aim point" further up the runway and causing the main gear to touch further down the runway.

You'll find that if you look at the touchdown marks on older, well-used runway surfaces, touchdown of the main gear (remember that's anywhere from 50 to 150' behind the pilot's perspective and up to 25' below it) actually ends up centered pretty close to the ideal spot, due to the leveling off of the flare maneuver:

You can see in this image the average touchdown point (the widest and blackest part of the runway) is right at the PAPI lights to the left.

You'll also notice a few significant tire marks just a little too close to the threshold for comfort. Clearly landing a plane is not an exact science, and this is why the touchdown zone and aiming point is further down the runway than you might think; a sudden downdraft or a thinning of the air due to surface heat at just the wrong time in these crucial final seconds, and if the pilot was aiming for the threshold, his main gear will touch down short of it, possibly doing millions of dollars of damage to his plane, the runway and approach lighting as well as likely closing the runway.


How can a crew be warned of "Clear Air Turbulence" during the flight?

Not on board the aircraft as of yet, no (unless, as @Gerry said, you count the radio that lets you hear about the person ahead of you running into CAT).

There are ways of detecting CAT, however, which could become standard aircraft equipment in the future.  LIDAR is one possibility, as both @Gerry and @mins mentioned; see also here and here.  Interestingly, the idea of using LIDAR to detect clear-air turbulence has been around since at least the late 60s, but, when it was first proposed, they couldn't get the sensitivity high enough; later, when this obstacle was overcome, they faced a different problem, which was that the equipment required was far too heavy, bulky, and power-hungry to be practical, which remained the case until very recently.  N-slit interferometry can also be used to detect clear-air turbulence (see here, for instance), and an interferometric (I think; the patent description is remarkable in its unintelligibility) CAT detector was patented in 1978, but the equipment required is far too large to fit on an aircraft; as a result, most work with interferometric CAT detection seems to have been in the area of developing a ground-based clear-air turbulence detector that could monitor runway approaches for dangerous CAT.


How can I know the manufacturer of the PFD (Primary Flight Display) of the current mainstream passenger aircraft?

The 737 does NOT use a G1000... Many of these devices are made by companies like honeywell or the makers of the airframe themselves although they may very well source the physical screen from another manufacturer.


Can an airplane engine fire be extinguished without shutting down the engine?

In most modern jets (e.g. Boeing 757/767) when you pull the fire handle the engine shuts down (fuel, hydraulic, etc., are cutoff). But pulling the fire handle only "arms" the extinguishing system.  You have to rotate the handle (left or right) to discharge a bottle. (there are other bottle configurations based on the airplane type, but this is the general scheme)

Usually, after pulling the fire handle (before rotating it left or right) you wait momentarily to determine if the overheat or fire warning lights have extinguished.  If not, you rotate the handle to discharge the extinguisher.

So, if you are asking about modern jets, the answer would be no, you can't discharge the extinguishing agent without shutting down the engine first.

I am not aware of a modern design that would allow the engine to continue operating after activating the fire extinguishing system.


Does skin friction drag decrease with velocity?

Your question is about friction drag while the text is mainly about aspect ratio. You seem to explain the choice of aspect ratio to be based on friction drag. This is not correct.

Here and here are some good answers to explain the choice of aspect ratio. You will see that it has mostly to do with structural strength and wing volume to pack enough fuel. For supersonic aircraft the delta wing provides a highly swept leading edge, a stiff, light wing and good low-speed characteristics even with the thin airfoils which are helpful in supersonic flight.

Generally, aspect ratio becomes less important the faster the aircraft flies, because it has more air flowing past per unit of time  for creating lift. At supersonic speed some of the drag is proportional to the local inclination of the surface, so the designers try to make the aircraft as sleek as possible. To put it bluntly, a subsonic aircraft likes to be as wide as possible to reduce induced drag, while a supersonic aircraft likes being longer to reduce wave drag.

Friction drag will go up with the square of velocity if all other parameters are constant. Since a higher velocity increases the Reynolds number (the ratio of inertial to viscous forces), in the real world the increase is slightly less than with the square of velocity. Since lift also goes up with velocity squared, the airplane can fly at higher altitude where the density is lower, which reduces both lift and drag.

Now you need to consider the change in temperature over altitude: Air gets cooler when it expands, and cooler air causes higher viscous forces. By flying higher, the Reynolds number goes down again and the viscous drag goes up. In total, flying faster and higher will result in a slight increase of the absolute friction drag at the same lift.

If you plot the drag coefficient over flow path length you will find that lengthening the flow path will generally increase drag less than proportionally. Only when the boundary layer is laminar and lengthening the flow path adds a turbulent transition will you find that friction drag briefly goes up more than proportionally. Sometimes it is helpful to force that transition, but mostly it comes sooner than the engineers like.

Please follow the links and read the linked answers, only then is this answer complete.


Why does propeller slip (efficiency) change during the flight (fixed-pitch)?

The reason that efficiency is reduced during phases of flight that are flown at high airspeeds is because the angle of attack between the propeller and relative wind is reduced. If an aircraft is stationary on the ground, its propeller is taking a larger "bite" of air because there is no relative wind. When there is more air moving past the prop, it takes a smaller "bite" of air, therefore producing less thrust and being less efficient. The advantage of a constant speed prop is that you can change the pitch of the prop depending on your airspeed, so it maintains a constant angle of attack, and is more efficient in every phase of flight. I'm not totally sure that's what you are asking, but that's what I got :)


The numerical method used by F.X Wortmann for inverse design

What is the $(t)$ in $\bar{y}_n^{(t)}$ in (A-2)

The text doesn't say. t in German normally denotes chord (Tiefe), but since we later see $\bar{y}_n^{(s)}$ for the camber line (Skelettlinie), it here stands for Tropfen, denoting the thickness distribution of the uncambered airfoil.

I would also interpret the long dash between $\bar{y}_n^{(t)}$ and the sum in A2 as a misprinted equal sign. Otherways the whole sequence will not add up.

  what is the $p^{th}$ approximation in (A-3)

You mean $p$th, don't you? p is used as the index of a stepwise approximation. $f_m^{(p)}$ is the $p$th iteration of $f_m$.

  What is the $(s)$ in $\bar{y}_n^{(s)}$ in (A-2)

That is only in A 6 and indicates that $\bar{y}_n$ this time denotes the ordinate values for the camber line (see above).

  Does (A-6) refer to the camber line calculation?

Yes.


Still using knots, nautical miles, inches of Hg. Is that impossible to switch to SI units?

For me metric or imperial is not the question, from my perspective the key is standardization. Having 2 different unit systems has only got drawbacks:

Customers: many airline's customers are living in a metric system, and they do not know what's is a mile or a feet. Is a matter of making flights more comfortable.
Cost reduction: units transformation is finally a cost. Engineer at manufacturers and airlines need to spend some time using a calculator to understand what is meant by other unit system. Maybe is only 30 minutes per month, but if we are talking about 2000 people, we are reaching a cost that is not adding value of 1000h per month. Finally this cost is somehow appearing in our airplane tickets.
Reduce human factor: we all are humans and exposed to errors. The less opportunity we have to make an error the best. Already there had been an issue with satellites with unit conversion. Reducing this difficulty is finally improving the safety of the air transport.
Increase competence in the sector: suppliers from, let's say, metric system have an slight competitive disadvantage when competing for a contract with imperial units. The more competition in airline services, airplane manufacturers suppliers, handling services the lower the price of our tickets.

Having 2 standards is a cost that is not producing any value and is actually a sector issue, moreover, a society issue. From my point of view the industry should try to move to a single standard. Metric or Imperial, I don't mind.

Next discussion will be which side of the road we should drive...


Does a sudden drop of the velocity of the headwind affect the airspeed by lowering it?

Your airspeed does not remain constant because of inertia: it takes more time for the airplane to adapt to the new relative wind, compared to the time it takes for the wind to change.

Example One: you're flying 80 knots and the headwind is 20 knots. Over a time of 3 minutes, the headwind gradually reduces from 20 knots to 10 knots. Since the change is gradual, you will notice the ground speed smoothly increases from 60 knots to 70 knots.

Example Two: you're flying 80 knots and the headwind is 20 knots. In 2 seconds, the wind drops from 20 knots to 10 knots. At the start (t = 0), you are moving 60 knots over the ground. However, 2 seconds later, the plane has not yet accelerated 10 knots faster (maybe only 61.5 knots), but the wind is now 10 knots. Therefore you experience an airspeed drop in 2 seconds from 80 knots to 71.5 knots.

Given sufficient altitude, the plane will eventually speed up to 70 knots ground speed (airspeed 80 knots again). When you are landing, you may end up touching down short of the runway if corrective actions are not taken in a timely manner.


Are ATC radar tracking records and audio recordings considered legally public?

The FAA is only authorized by congress to regulate FLIGHT, not radio communications.

Radio communications are regulated by the FCC.

Both of these agencies have no power to make laws. They can make only "regulations". In the United States, according to the Constitution, laws can only be made by Congress or the legislatures of the several states.

The position of the FCC is that it is legal for any person to monitor and record any radio transmission that they wish. The only exception to this is listening to private telephone conversations or encrypted military transmissions. The Federal law that prohibits this, explicitly exempts maritime and aeronautical transmissions. This is the language:

  18 USC § 2511 (2)(g.ii.IV) It shall not be unlawful under this chapter
  or chapter 121 of this title for any person to intercept any radio
  communication which is transmitted by any marine or aeronautical
  communications system;

Therefore, by United States federal law it is explicitly allowed and permitted for anyone to monitor and record maritime or aeronautical communications.


Do aviation intercoms have a standardized compatibility with radio stacks?

This is a good question - the comments above answer most of it, but here are some more details:

Short answer: yes, they are pretty much standardised. Any modern GA intercom will work with any modern GA radio.

Part of the job of the intercom is to tell the radio when to transmit, and to route the correct microphone signal through to it. This is almost always done using a single wire which signals "transmit now", and a pair of wires for the microphone signal from the headset corresponding to the PTT button that was pushed.

On more advanced integrated setups, the signals might be transmitted over a digital bus, but outside of fully integrated setups like the G1000 (and even then on some models), there are always ways to connect standard aircraft radios to the intercom.


Why don't all wind tunnels use magnets to suspend models?

Two reasons:

When a model is suspended in a magnetic field, and then the wind tunnel is switched on, you'll see a change in the force along 'y-axis' (The lift forces) and change in force along 'x-axis' (The drag forces). Hence, you'll need a complex mechanism for sensing this forces, and changing the magnetic field in such a way that the change in forces is compensated by the 'change in magnetic field' so that the model does not translate in any of these directions and stays static. Then you'd measure the change in magnetic field to measure the forces, and hence the system becomes expensive and cumbersome.
For pressure measurements, you'd have to use wireless sensors on the pitot ports, as you dont want tubes dangling form the suspended models. This makes the process more cumbersome and expensive

This is why the magnetic suspension is not used every where, as the cost to accuracy ratio in normal wind tunnels is much less than the ratio in magnetically suspended models of magnetic wind tunnels


How does an Airbus aircraft connect to the Internet?

There are three different ways that aircraft can give internet access to its passengers, which will most likely be on at around 38,000 feet. First off, to have Inflight wifi, there needs to be a ground-based internet server, a transmitting dish, or a satellite dish. There must also be a receiving and transmitting antenna on the aircraft and an onboard server and a Wi-Fi router.

The first system is the ATG system, which stands for Air-To-Ground transmission. It requires two antennas that are installed on the belly of an aircraft so that it can pick up signals from the ground-based cell towers. With this system, a passenger can receive at least 3 Mbps and one of the highest currently is 9.8 Mbps by gogo wifi.

The next system is the "Ku-Band" Service, which was formerly used by the military. K, short for Kurz (meaning short in German) and u for under the original NATO/K-band frequency range. This system works by a ground station sending signals to a satellite first, and then reflect off the satellite and send the signals to the aircraft. The signal is then decoded and then transferred to the router. This can deliver about 50 Mbps with this system, but you still have to consider that there will be more than a hundred passengers on the aircraft. Since this system has to send signals to a satellite first, there could also be delays on signals and could get slower as more aircrafts use this service. If you've seen aircraft with a pod on the top of its fuselage, you may not know that under it sits a satellite antenna, which rotates and can adjust itself to the nearest satellite.

The last system is the "Ka-Band" Service. K still stands for Kurz, and a stands for above since this is in the upper region of the native frequency band which is at 20–36 GHz. This service can deliver about 70 Mbps. Presently, there are two ViaSat (a satellite wireless service provider) Ka-Band satellites, one covering the US, and one covering Canada and parts of Europe.

Some aircraft even have a hybrid system, so they can use Ku-Band and Ka-Band service depending on which has a better signal at the time, so it would depend on the internet speed on which the A380 you are referring to is.

An onboard server will be required on the aircraft for an Inflight Entertainment system, which will run three services: a media server, a DRM (Digital Rights Management) license server, and a device provisioning server. The media server is for storing your content keys (but doesn't necessarily have to be on the media server, it can be on a separate onboard server). The device provisioning server will need to store a reserve of device personalities (unique device credentials) for distribution to onboard mobile devices (via your mobile app) upon request. The signals from the satellite (in a Ku/Ka-Band service) will be transmitted into the pod/antenna, then into the onboard server, which will be transmitted to several routers distributed throughout the aircraft. For example, an A320 or a B737 usually have two routers. The signal is sent to your phone, then signals will be sent back to the antenna, then to the satellite, which is passed back to the ground.

More about in-flight wifi at HOW does WIFI WORK on AIRPLANES? Explained by CAPTAIN JOE


How are pitching and rolling moments transferred from rotor to the body?

The impact of these effects depend on the rotor design.  E.g. a teetering rotor only includes the second effect you mentioned (tilted thrust vector), the 1st effect is absent.  The first effect you mentioned increases as the "flap hinge" is moved away from the hub, giving more control force utilizing CF.  You may be interested to know there's typically a 3rd effect - if the blades are restrained from flapping freely (in the simplest case a spring) that restraint creates a pitch moment about the hub which also pitches the aircraft.   Each of these is discussed here.


Why is the F-117A the only plane to use the fully faceted design?

The F-117 was designed at a critical point in aeronautical history where we didn't have enough computing power to analyze the radar cross section of more complicated geometry, but did have the computing power to provide artificial stability to unstable designs.

The faceted design is not ideal for stealth or aerodynamics. Obviously the corners are less aerodynamic than a smooth surface. But it also means that if the facets align with a radar source they will reflect a strong return. The compromise is that it's easy to calculate the reflecting angles of radar energy off of flat surfaces based on various locations of radar sources relative to the aircraft.

A curved surface means that only a small section of the surface is really reflecting directly back to a radar source, while the rest is scattered. Together with radar absorbing materials, this can provide effective stealth. It just takes more analysis to determine how different curves and features will reflect radar energy.

You can see the evolution of stealth designs from the Have Blue (prototype for the F-117) in the mid 70's, to the Tacit Blue prototype in the late 70's, to the B-2 in the early 80's.


How do pitch attitude, airspeed and sink rate come into play in a rapid descent or a dive?

Airspeed control is the difference. In a rapid descent, airspeed is controlled and the pilots will keep it below $v_D$, the maximum dive speed for which the aircraft is certified. For a modern airliner, this is somewhere around Mach 0.9.

In a dive with "nose down as far as they care to" (I read this as 90°), airspeed is not controlled, but an outcome of the situation. The airliner will go supersonic. It is possible to recover it from a short dive, but will incur damage to the aircraft (e.g. the pilots will need to lower the landing gear to increase drag, but lose the gear doors in the process).

If the pilots would only care to put the nose down to the point where they not exceed $v_D$, we are back at a rapid descent. They could lower the gear in order to increase the sink speed, and circle to increase drag further. Circling needs more lift (proportional to the inverse of the cosine of the bank angle), so more lift-induced drag is produced. To maximize drag, the pilots should fly at the maximum permissible load factor (which is rather low at maximum dive speed due to gust loads).

If we assume the L/D of the airliner to be 5 with gear and spoilers deployed, the pitch attitude would be between -11° and -12° and the sink speed would be between 50 and 60 m/s (10,000 to 12,000 ft/min). The bank angle would be between 45° and 60° and the plane would be violently shaken by buffeting.

Going any steeper than that would only be attempted by pilots with suicidal leanings. Flying like described above is scary enough already.


Typical airplane is not stable in roll. The outside wing flies a bit faster, which does indeed make it produce a bit more lift and that in turn will make it bank into the turn, tightening it and if left uncorrected, ending in a spiral dive.

In a coordinated turn, an aircraft even can't be made stable in roll. There is no way to create a restoring force without involving side-slip.
The only thing that can be provides is the yaw-roll coupling where a slip produced a rolling moment into the slipping turn. This rolling moment is affected by dihedral and sweep.

Fortunately as the turn tightens, if the rudder is held fixed, some slip does develop that can provide the restoring force reducing the bank. However, it causes another dynamic mode, the Dutch roll.

As the bank increases, the tendency changes from Dutch roll to spiral mode. If you wanted to avoid the spiral mode, the Dutch roll would be very strong, so practical aircraft are designed with moderate yaw-roll coupling and do require a bit of opposite aileron in turns.


Will portable Stratus ADS-B In receivers operate normally from the passenger cabin of a commercial airliner?

The receiver will work in the cabin but the reception is really poor. GPS will only work if it has enough satellites in view, so a window seat is best. The signal is severely attenuated by the windows.

I have brought ADS-B receivers with me on various flights but in my experience you will not get a proper ADS-B signal from aircraft further than about 20-30NM away.

Whether it is permitted or not depends on the airline and the country of operation.