Can you turn a large airliner using only rudder input?

Yes you can, and this is the backup mode for turning the A320 when the Fly By Wire has failed. It is not very comfortable though:

Changing direction using only the rudder creates sideways acceleration, not good for passengers with drinks in front of them
Since the rudder is located above the center of gravity, the aircraft leans the wrong way when rudder only is used, amplifying the sideways acceleration. A ship has the rudder below the center of buoyancy and leans into the turn when rudder is deflected.


Is there simpler way than scraping flightradar to determine Number of Flights between Two Countries?

ADS-B Exchange could be an alternative to FlightRadar24. They have (free if you host a feeder station) APIs so you wouldn't need to go through the headache of scraping. The data should be comparable and with ADS-B becoming mandatory in more and more regions (US since the beginning of the year and an EU mandate covering pretty much all business flights coming in June) you should be able to track anything but small VFR only aircraft.


How does the fuselage handle the different loads?

Not sure this is what you're looking for, but if you're looking for a simple big picture analogy, try this:

Think of the fuselage as a very thin walled compressed air cylinder resting on an airbag at about it's mid point, filled with sandbags that are offset toward one end, enough so that the cylinder wants to tip over on that end.  All the way at the other end you add more sandbags (to represent the tail pushing down) until the tube balances out.  Your fuselage will be basically a tubular beam balancing on the air bag with the bottom half in compression and the top half in tension, and the largest compression load will be just on each side of the air bag, but mostly on the "tail" side because the moment arm is longer.

Almost all of the loads of the fuselage pass through the skin, the surface of the cylinder.  The frames and stringers are mostly to keep the "paper thin" tube from buckling or collapsing.

As a compressed air cylinder, pressurization loads are also absorbed by the skin in tension, like a balloon.  Usually at the aft end there is a spherical bulkhead to absorb the pressure while keeping the skins of the bulkhead (mostly) in tension.  Sometimes this bulkhead is flat, usually when there are tail mounted engines that require a support beam running across, which can cause many headaches crack wise (on the RJs, a long sad story).  The front end of the cylinder narrows down to a small flat bulkhead at the front of the cockpit, which being small isn't too much of a problem being flat.

The fuselage usually has a big cutout on bottom to accommodate the wing box
and landing gear, which puts this great big notch in the structure right at the point in the cylinder where the compression buckling loads are highest.  The wing box itself may form part of the fuselage structure there, but farther back the cutout usually continues, to make space for the landing gear.  There is usually a massive beam, called a keel beam, to bridge the cutout aft of the wing box and absorb the compression loads along that section.

As a tube that is trying to sag forward and aft of the wing, there is also a force that wants to squash the tube flat at the peak bending point, resisted by the frames.  There are usually several very heavy frames at this mid section to support the tube where this force is highest, and to tie the wing box into the fuselage structure.

The highest loads on the fuselage are usually compression buckling stress just aft of the rear spar wing attachments when in flight, or the gear attachments when on the ground, and are highest on landing touchdown.  When aircraft have broken fuselages on hard landings (Boeing did it on their company 717 -formerly DC-9 - on hard landing testing and an Embraer 145 broke its back on landing in Brazil about 15 years ago - they did an excellent job keeping it out of the media) they fail in compression buckling right at that stress peak point.

I don't want to oversimplify, and there are lots of other stresses, like from the floor beams and such, but that's kind of the big picture.


When is pre-heating a piston engine important, and how does one pre-heat correctly?

I'm going to be referring to an old AvWeb article by Mike Busch with my links in this post.
As with most of what Mike writes, it's worth a good read.
Why is Pre-Heating Important?
Pre-heating your engine in the winter is important for a bunch of reasons, but there are two main ones that should get your attention - the first is preventing metal-on-metal wear by ensuring all parts have adequate clearances to function, and the second is improving lubrication by making sure your oil is ready to flow, and the spaces it's going to flow in to are opened up enough to let the oil in.
Metal-on-Metal Wear
Starting a piston engine is responsible for most of the wear the engine sees in its life - surfaces which have long since had their protective coatings of oil drip off are banging together while you crank the engine, and for a few seconds after startup until the oil pump can build up pressure and splash lubrication in the crank case can thoroughly coat the other moving parts.
In the case of a truly cold start there's an additional complication: like 2NinerRomeo points out, different metals in your engine have different coefficients of thermal expansion, and you have steel (probably several alloys), aluminum, brass, and a few others in your powerplant. When cold the clearances between these metals can be so tight that the additional wear is substantial, and at a certain point you may even damage the engine by attempting a start, shaving or spinning bearings and scuffing cylinder walls with the rapidly expanding pistons once the engine fires.
Lubrication
The other factor to consider in a cold start is lubrication - both the oil doing the lubricating, and the spaces into which it needs to flow.
Take the dipstick out of a cold engine and you will marvel at how the oil just clings there in a thick layer (this is especially true of heavy single-grade oil like 100W, but even 15W50 starts getting very sticky down in the 30°F-35°F range).  Oil that has thickened up from the cold doesn't pump very well - your engine may take a longer than normal time to develop oil pressure, and narrow spaces may get little to no lubrication until the oil has heated (and thinned) enough to get through the narrower oil galleys and tight spaces between some components.
Those tight spaces, as I mentioned under Metal-on-Metal Wear, tend to be tighter when it's cold, which means it's even harder for oil to work its way in and build up a good film of fluid. Until that film is built up and doing its job your engine is really inadequately lubricated, even if it's running. (Check out the webinar video in 2NinerRomeo's answer where Mike Busch goes into a lot of detail on how oil works, he has a nice explanation of the fluid film lubrication process.)

How do I make sure I do my preheat right?
The best preheat possible is spending the night in a nice, warm, heated hangar. It basically guarantees that every part of your aircraft has been brought up to the same temperature, and even affords you a nice place to preflight as opposed to doing it out on the ramp in the 6-but-feels-like-60 knot winter winds.
A hangar preheat isn't just the best for your engine -- your gyro instruments get brought up to a nice warm temperature (remember, mechanical gyros have to spin up, and they have the same issues as your engine did in terms of clearances being reduced by the cold), and the ship's battery gets warmed up too so it's ready to provide its best possible cranking current.
I don't have a hangar you insensitive clod!
Unfortunately some of us (like ME) don't have hangars - heated or otherwise - or our local FBO charges a hefty sum to spend the night in the warm. Those of us without hangars have to make due with a ramp pre-heat of some kind.  I'm going to assume you're in the same boat as me (no hangar, no electricity), and have to use some other technique.
Most ramp pre-heats where you have neither a hangar nor electricity take the form of a "forced hot air" system - either one wheeled around by the FBO, or portable ones powered by propane. There are even ones built around a camp stove which are deceptively good at the job (and in a pinch can burn the avgas you drained checking your tanks for water).
The general procedure for a forced-hot-air preheat is to point the heat into the cowl's cooling inlets, letting the warm air flow over and around the engine and out the cooling outlets. Start the heater up before your preflight, and with a little luck by the time you're done with the walk-around your engine will be ready to start.
If it's extremely cold you may want to block part of the inlets and put a blanket over the cowling during the pre-heat to help keep the heat trapped on the engine, and as 2NinerRomeo points out, when using a high-intensity heat source like a propane heater make sure you don't pump so much heat into the cowling that you blister your paint.  A gradual warm-up is what you want - we're slow-roasting the engine, not broiling it.
How do I know the preheat is "done"?
There are three common ways to tell if your preheat has had enough time to adequately warm your engine - each technique works pretty well, and you can use whichever makes the most sense for your situation.
Testing by feel
This is classic if you have a cowling that can be easily opened like most Piper aircraft, just feel all of your cylinders and the crankcase. They should, if your preheat was thorough enough, all be slightly warm to the touch. It's low-tech, but it works well if you can use it.
As a practical matter it's usually easier to tell if the "top end" (cylinders) are ready this way than it is the "bottom end" crank case / crankshaft / bearings), but with some cowlings (many Cessnas, or my Cherokee 180) you're simply not getting your hand in there to feel the engine: you can reach the front cylinders and a bit of the case, but the aft half of the engine is basically inaccessible without taking the cowling apart (and losing all that trapped heat).
Testing with the dipstick
Another good indicator is that when you take the dipstick out of the engine the oil flows off nicely -- compare with how thick and syrupy the oil was in the cold engine and is should be obvious when it's "ready".
This works for pretty much every engine, even if the only access you have is the little oil door, but it's also one of the slowest & most conservative indicators: pretty much all the thermal mass of the engine needs to heat up before the oil in the sump is going to get warmed up and start to loosen up.
Checking with your instruments
The final way to check the status of your preheat is to check your engine instruments: If your cylinder head temperatures are all reading something reasonable (say 60-70F) and your oil temperature is at least "off the peg" your engine has been thoroughly heated.
This technique is a little instrumentation-dependent though -- some engines may not show an oil temperature indication until you get your oil up into the 90 degree range (which would be great for start-up, but lousy for sitting on the ramp waiting). For those engines you probably want to use the dip stick test to check if the oil is "ready".
This technique also works best if you have individual cylinder probes, as you can determine if your engine has been evenly heated (this is especially true of longer engines, like a 6-cylinder powerplant: if the front cylinders have been getting blasted with warm air and are in the 90s, but the rear cylinders are still reading 30 degrees you may need to adjust your preheat procedure to warm those rear cylinders!)

Parting Thoughts - Stuff outside the engine compartment?
I've concentrated mostly on pre-heating the engine, which is what most people think about when they think about pre-heating aircraft, but as I mentioned briefly it's worth noting that other parts of the aircraft benefit from pre-heating too.
For example, a warm battery (60-70°F) will crank better than a cold one. If your battery is in the engine compartment it will get warmed up during your preheat, otherwise you should be aware that cold starting puts a pretty heavy demand on the battery, and your battery will appreciate if you limit cranking as much as practical.
Similarly, your gyro instruments (turn & bank, directional gyro, attitude indicator) will all need to spin up - that happens in a hurry (as soon as you hit the master for the electric ones, as soon as the engine catches and the vacuum pump starts really spinning for the vacuum driven ones).
If you can direct some warm air into the cabin your gyro instruments will thank you (and you'll probably thank yourself - those control yokes are COLD!). The gyros take less of a beating than your engine, and certainly cost less to replace when they wear out, but keeping them happy is worth a little effort.


This is a classic example of fallback to INS. Most of the track data is coming from GPS. For some reason the GPS signal is lost momentarily causing a fall back to INS. The INS is offset by about 1km to the Northeast, which appears as a jump. Next position report is from the GPS again, in line with the original track. This happens several times.

In the transmitted data these spikes will be flagged as data of low integrity. This allows for filtering them out.


Is the IOSA useful even if not all airliners are IATA members?

IOSA is basically an audit program under IATA. It is not a regulatory regime and as such is different from the FAA, EASA etc, which have force of law. In fact, IOSA is only one of the various audits offered by IATA, which include:

IATA Operational Safety Audit (IOSA)
IATA Safety Audit for Ground Operations (ISAGO)
IATA Standard Safety Assessment (ISSA)
IATA Fuel Quality Pool (IFQP)
IATA Drinking-Water Quality Pool (IDQP)
IATA De-Icing/Anti-Icing Quality Control Pool (DAQCP)

IOSA deals with the operational management and control systems of an airline. The IOSA standards and recommended practices are derived from the ICAO recommendations. From the IOSA  Standards Manual

Sources for IOSA Standards and Recommended Practices (ISARPs)
The safety and security requirements published in the Annexes to the Convention on International Civil Aviation (ICAO Annexes) are the primary source for specifications contained in the ISARPs. Safety and security requirements in the ICAO Annexes used as the basis for ISARPs are those that
are applicable either directly or indirectly to the air operator.

However, these standards are not regulations (as are those defined by FAA etc.):

ISARPs contained in this manual have been developed solely for use under the IOSA program and contain the operational criteria upon which the audits are based. ISARPs are not regulations. (emphasis original).

The usefulness of the IOSA to airlines if from the fact that it is a standard recognized by most other airlines- instead of going to different auditors to ensure compliance of standards, they can agree on a common standard (also IOSA is required for IATA membership).


Did the F-8 have a stall speed of 1.6x its landing speed?

The stall speed your source is referring to may be the speed for a clean stall which means with the flaps are in flight position (= 0°).

Flaps on powered planes usually increase lift as well as drag. This means basically that you can fly slower and stall happens at a lower speed.

Here are the speeds from the F-8D flight manual (big pdf):

From the chart, in landing configuration with 19,000 lbs gross weight, the stall speed is ~113 knots.

  does ground effect come in to play for landing scenarios? – Owen

Ground effect reduces the touch down speed by reducing the stall speed below the value mentioned in the manuals.

The strength of the ground effect depends on the construction of the plane. Low wing planes have stronger ground effect then high wing planes.
This means that the difference of landing speed and touch down speed is grater for a Low wing plane. On the other  hand the ground effect increases the flare phase of the landing for a   Low wing plane.


The stall, for the most part, was not detected by the pilots: That was the entire problem.
There were many alarms and indications in the cockpit and that caused crew confusion, they neither knew which data to believe nor understood the situation that they were in. For much of the descent they could have recovered from the stall if they had been fully aware of the problem and had worked together. One pilot did try to recover the situation (by telling the other pilot to push the nose of the aircraft down) but he was not successful.

That answers the second part of your question too: The crew was able to recover from the stall but did not, due to their own confusion.


What spacing is needed between aircraft parking stands?

The Aerodrome Standards manual, which is based on ICAO Annex 14, gives the following values:

Clearance distances on aircraft stands
3.12.6 An aircraft stand shall provide the following minimum clearances between an aircraft using the stand and any adjacent building, aircraft on another stand and other objects:
Code Letter | Clearance
A | 3 m
B | 3 m
C | 4.5 m
D | 7.5 m
E | 7.5 m
F | 7.5 m

A references for the ICAO code letter categories is available here: http://www.skybrary.aero/index.php/ICAO_Aerodrome_Reference_Code


What are these long tubes under the wings?

They are flap track fairings which contain the flap mechanism.

They are called Küchemann carrots (also called anti-shock or Whitcomb body) and are used to reduce wave drag in transonic speeds.


Can commercial air traffic operate from uncontrolled airport, airspace?

I will answer your question with what we can see in Brazilian Airspace and its rules.

In Brazil, there are some airports - non towered, operated by radio stations - which give information such as wind direction/intensity and temperature and QNH. Based on this information, the pilot decides on which runway they will land or take off, and relays this message to the radio operator. The operator will only relay these pieces of information to pilots monitoring the radio frequency.

Those airports are not controlled, then, if there is any strike, flying visually, no control will be effective.

For example, ARU/SBAU is a non towered airport, and TAM Airlines operates the A320F there.


Is it feasible to replace brakes on airplanes with electric motor/generator?

On a hybrid or all-electric car, the motors on the wheels supplement or replace the engine, and by regenerating electricity from the braking, it extends the range of the battery.

On an aircraft, the engines would still be needed for the major part of the working life of the aircraft -- the time while it is in flight.  So unlike the case of a car, you don't get any advantage with the motors themselves by adding the motor/generators to the wheels.

Beyond this, on a large aircraft, electricity is in ample supply when you have jet engines turning, so what's gained by regenerating the electricity from the wheels, during the 60-90 seconds of heavy braking on landing, isn't all that significant when compared to the electricity used and produced over the course of a whole flight.  Not nearly as significant as a drive in the city with many cycles of accellerating to speed then decelerating to a stop, over and over.

Beyond this, the major players then are the added weight and complexity of the motor/generators, vs the gains in terms of (a) tire life, from spinning them up prior to landing, and (b) fuel saved by maneuvering on the ground from the wheel motors instead of the jet engines.  When you consider that the costs of jet fuel are on the order of $1000 to multi-thousands of dollars per flight hour, the costs savings of longer tire life will lose out if the extra weight of the motor generators over conventional brakes means that you're spending more money over the course of the flight to carry the extra weight.  Likewise, the fuel burn during taxi in & taxi our on the motors isn't all that great compared to an hour or many of high-power cruise... power settings for taxi are close to or at idle, so fuel consumption isn't all that high.  Plus, it's common to taxi without all engines running, further reducing fuel burn on the ground.

The big killer for this idea is the weight penalty.  Motor generators are significantly heavier than conventional brakes, and when you consider the amount of energy that brakes have to be able to absorb during a high-speed stop, you'd need some seriously beefy generators to accomplish what aircraft brakes can do.  Or else, you'd have conventional brakes installed to supplement the generators, and the weight goes up further.

As a ballpark, on an hour flight in a 737, an extra 1000 lbs of weight increases the fuel burn by about 10 lbs, or about 1.5 gallons.  Doesn't sound like much, but when you multiply the added weight times every flight hour that the aircraft is operated over the course of a year, it really adds up.  Beyond that, motor/generators are a lot more complex than simple brakes, so they'd be more expensive initially and require more maintenance throughout their service life.  Plus, I suspect, they'd need to be supplemented by conventional brakes that would be used in the event of a high-speed max-effort stop (rejected takeoff, landing on a short runway).

The end result of all of this is, no manufacturer I'm aware of has found that the tradeoffs make this sort of project worthwhile.

The best case is probably one of really long taxi times, but in that case a pushback tug could tow the aircraft to a point close to the runway, saving the fuel burn on the aircraft engines until it was time to start them.  I'm sure this has been considered as well, and again, I'm not aware of any carrier that uses this approach (although outside the U.S., somebody might be).

It's an interesting question, but the costs & the math behind the engineering haven't worked out in its favor, at least thus far.


Why would helicopters not have black boxes?

Airline and commuter type aircraft are required to have cockpit voice recorders and flight data recorders. There are no requirements for any other type of aircraft to have them.

Most helicopters are actually small or light aircraft. The helicopter in which Kobe Bryant and others died would be considered a medium sized helicopter, but a small aircraft.

You will find VERY few non-airliner or non-commuter aircraft have any type of “black boxes” as they’re commonly (and erroneously) called. They are not required to, either. Expense, weight, complexity, and maintenance are all reasons. The smaller number of lives at risk might be another. After all, they carry the same number of people as between a sports car and a passenger van. School and passenger buses carry more people.

Saying that, technology has become cheaper and more compact in order to provide de facto recorders. Some modern avionics have that function built in. With the proper app, iPhones and iPads have that function. Some pilots will go the extra step and buy their own sensors to provide more accurate data on Attitude, Heading, Position, Altitude, Ground Speed, Carbon Monoxide presence, and Traffic Data. Add-on apps will even record voice transmissions picked up by the headsets and audio system. This is not mandated by the FAA. It is more for the pilots Situational Awareness and review for training purposes. ForeFlight, CloudAhoy, Stratus, Sentry, and Lightspeed are some common devices and apps used to record data.


How are this helicopter's blades perfectly timed with the camera shutter?

If the rotor is spinning at 360 RPM, typical of helicopters, that's 6 revolutions per second, and 5 blades go by each revolution.  6 x 5 is 30, so you have 30 blades passing point X in any 1 second period of time.  Unlike film at 25fps, video is shot at 30 fps, in perfect sync with the blade passage, so the blades look stopped.  If the rotor was going a little faster or slower, the blades would start to move.

The video camera is in effect working like a stop action strobe camera.


In a dogfight, can a pilot shoot down a parachute?

You question is a question of rules of engagement. Shooting down a downed pilot in a dogfight is not only not OK, but also illegal.

According to Article 42 of Geneva Conventions,

  No person parachuting from an aircraft in distress shall be made the object of attack during his descent.

Of course, war is war and this kind of attacks have been practiced by pilots of almost all air forces, though it should be noted that in most cases, this practice was specifically prohibited by their high commands.


Could I build an airship (rigid dirigible) that used a vacuum rather than lifting gas?

what are the technical or mechanical limitations to doing so?

There is no known material that has a sufficient combination of lightness and strength to support a vacuum that would support the weight of the container on Earth at sea-level.

There was a similar question with a good answer on Physics.se

Beryllium Vacuum Sphere Boat/Aircraft

  Is it possible to make a solid rigid evacuated "balloon" out of Beryllium or other elements or alloys?

The currently first answer runs through the maths

  calculated it over a database of almost 3700 materials including all common aerospace composites, metals and alloys.

and concludes

  So in short, the best materials fall short of achieving our aim by a factor of just over 2. It is conceivable we might push up the stiffness / density ratio by perhaps developing some kind of Beryllium foam. For example, a closed cell foam of this Beryllium with a relative density of 0,041 would give a value of about 920 at the expense of lowering the Young's modulus to about 600MPa - however, I have no idea if such a foam is even possible. Alternatively it might be possible to come up with some clever engineering of the envelope geometry to overcome the buckling constraint. However, I suspect the effort is unlikely to pay off with a better boyancy ratio than is already achievable by conventional balloons.

Other related questions

Is it possible to create a vacuum ballon using concentric partially pressured spheres?


For airliners, what prevents wing strikes on landing in bad weather?

It's not how high the wing is off the ground, but the angle between the main landing gear when compressed and the tip of the wing, which with the wing dihedral makes it even higher off the ground – on the MD-80 that's 2.6 m (8'7"). This will be the roll angle limit.

It's for that reason, unlike smaller high-wing general aviation planes, big jet-liners don't decrab as much in a crosswind landing, whereas decrabbing (going one-wing-low) would be a problem. From an MD-80 flight manual:

Crosswind Landing
On final approach, establish a crab angle into the wind to hold the aircraft on the extended centerline of the runway. Maintain the crab angle until just before touchdown, then use the rudder to align the aircraft with the runway. The touchdown is made with cross-controls as necessary to track straight down the runway. Keep wings as level as possible as the wingtip will touch at an 8° bank angle. Do not hold off downwind wheels; prompt and firm runway contact will greatly assist in rollout stabilization.

So the prevention is respecting the limits, good training, and knowing when the weather is too gusty to just abort the landing.
It does remain a concern though. Wikipedia has an article on it, and the issue would also affect the engine when wing mounted, but with the engine typically forward of the wing, it's given better clearance when the nose is still higher for flaring. The A320 accident mentioned on Wikipedia seems to have been the result of both pilots controlling the plane during landing.
In 1997 a 747 hit the runway with the outer engine when landing in Kai Tak:

(flickr.com)
A more recent one is a Bombardier Global 6000 in 2014.


Why does fuel consumption decrease with increasing aircraft altitude?

I can't provide the math, but yes, this is correct. Fuel flow decreases as air density decreases. The engine becomes more efficient because of the greater temperature differential between inlet and exhaust gases combined with the lower fuel flow.


Is Qantas holder of the world’s longest commercial non-stop flight?

I assume you are referring to the recent Qantas flight from New York to Sydney:

Australian carrier Qantas has completed a test of the longest non-stop commercial passenger flight as part of research on how the journey could affect pilots, crew and passengers.
The Boeing 787-9 with 49 people on board took 19 hours and 16 minutes to fly from New York to Sydney, a 16,200-km (10,066-mile) route.

(BBC)
This flight was primarily a test flight to study impacts of ultra-long haul flights on passengers:

Qantas has announced three ultra long-haul research flights to gather new data about inflight passenger and crew health and wellbeing.

(Qantas News Room)
Because it was just a test flight, this does not count as regular service, which would not make sense with the current aircraft anyway:

No commercial aircraft yet has the range to fly such an ultra-long haul route with a full passenger and cargo load, Reuters news agency reports.
To give the plane sufficient fuel range to avoid re-fuelling, the Qantas flight took off with maximum fuel, restricted baggage load and no cargo.

(BBC)

The current record for longest regularly scheduled flight is indeed Singapore Airlines flight SQ21 between Newark and Singapore according to the Wikipedia List of longest non-stop flights (retrieved 2 Nov 2019, based on great circle distance, thanks to Michael Seifert for pointing this out).

The record for the longest ever flight with a commercial airliner however is still held by a Boeing 777-200LR:

In a trip that included two sunrises, a new long-range Boeing 777 flew more than halfway around the world nonstop on Thursday, breaking an aviation distance record set by a B-52 bomber 43 years ago.

New York Times
This flight was primarily a publicity stunt resulting in a Guinness World Record. It was never meant to be used commercially since they intentionally flew a longer route.


During a touch and go (C150) should I first raise flaps or set full throttle?

Flaps in a C150 (and pretty much any type) take a few seconds to move. Throttle change is more-or-less instantaneous. If you were to throttle up first, and then change the flap position there is a good chance that you are lifting off while the position of your flaps are changing. This is not a good idea, changing the amount of lift generated by the wings in this crucial stage of flight can lead to a take off stall. You could (and probably will) be too low to recover.

To minimise the chance of this happening, I would say that on touchdown, one of the first things I would do is to set flaps for takeoff ( giving the actuators a second or two to change flap position) before immediately setting take off throttle.

So, yes, your instructor was right. They usually are. In your specific case, I suspect that as soon as you floated too far down the runway, you should have initiated a go-around before touching down. You did not leave yourself enough runway to safely perform a touch-and-go. You dont assess take off distance available once you touch down, you asses it while still flying - you had ~10 seconds to make that call (approach, float, oh shit, go around!)


How can I tell if an aircraft is equipped with fly-by-wire or with a FADEC?

Only an aircraft model can be fly-by-wire or not, not an individual airframe of the same model.

Designing FAA/EASA certifiable fly-by-wire systems is extremely expensive, so only expensive aircraft, produced in large numbers, are going to have it. All Airbus since the A320 and Boeing 777 and 787 airliners are fly-by-wire, so are high-end Dassault bizjets. Recently the club has been joined by Bombardier, Embraer, Sukhoi, Irkut (Yakovlev) and Mitsubishi.

This doesn't include military aircraft, though you'll largely see the same players there with the addition of Lockheed, Northrop, MiG, BAE and a few other all-military contractors. Air forces have more need for fly-by-wire and are more risk-tolerant than airlines.

The SA227 is not fly-by wire. For the most part, if you have to ask, or if it's affordable below corporate level, it's probably not fly-by-wire.

EEC (of which FADEC is the most advanced subtype) versus hydromechanical engine control choice is specific to the engine and the airframe. It's not readily visible. An airframe will either have cables and hydraulic lines or sensors and wires. The majority of jet airliners currently flying use EEC or FADEC engines.


Are there any helicopter blades that fold in the middle?

Bending a helicopter blade in the middle is of course possible, but poses many serious problems and risks. The designers would look for different solutions first, like they did for the UH-60.

The blade loads are lift, centrifugal force, and twist. Manufacture the blade with modern composite technology, mount it with the fully articulated hinges that are usually a requirement anyway, and trust the blades with your life because a breakage would be catastrophic.

Any repeated action poses additional risk. Mounting a hinge and lock that operates every time, is not open to human error, and never fails - that is would be the quest for the folding blade designer.

Of course a folding blade can be designed, like the folding wings on navy fighter aircraft. But not for some arbitrary reason. Only for a vital reason that cannot be solved in any other way.


Where can I find that video of a college built blown wing aircraft?

FINALLY found it! IT was named using the technical name for blown flaps, 'Circulation Control'. I found it using the search 'state name' stol aircraft. Just so happened I chose the nearly right name first off, 'Virginia'.


What is the benefit or motivation for having Class G airspace?

You can also fly Ifr without a clearance in G.

Remember that the entire purpose of airspace is to keep us from hitting airliners. It is not about keeping GA planes apart. When you look at wx mins that is clear. The FAA gives us the freedom to fly around in low vis so long as we stay out of the areas you'd find airliners.

-Robert CFII


How does a weak shock-wave boundary-layer interaction create wave drag (other than through direct shock losses)?

As you know, wall shear stress $\tau_w$ (and thus friction drag) can be described as:
$$ \tau_w = \mu \frac{\partial u}{\partial y} \vert_{y=0} $$
where $\mu$ is the dynamic viscosity of the fluid and $\frac{\partial u}{\partial y} \vert_{y=0}$ is the fluid velocity gradient at the wall.

The shock-wave boundary-layer interaction (SBLI) can change these two factors through several mechanisms:

A change in boundary-layer thickness: As you noted correctly, an increase in boundary-layer (BL) thickness will decrease the velocity gradient, compared to an otherwise similar BL velocity profile.
However, my conclusion after reading several publications is that the increase in BL thickness doesn't always occur. BL thickness seams to scale with shock strength and very weak shocks actually produce a thinner BL.
A decrease in fluid velocity: The shock-wave will obviously result in a decreased velocity outside of the boundary layer, which decreases the velocity gradient. This will also decrease wall shear stress, so it cannot be the dominant mechanism either, since it contradicts our experience of increased friction.
An increase in turbulence: The turbulence of the BL is significantly amplified by the shock-wave through different mechanisms.
The image below visualises the distribution of reynolds shear stresses, which are a measure for turbulence. A high magnitude (positive or negative) of reynolds stresses means high turbulence:

 Reynolds shear stress distribution of a SBLI. Notice the strong negative values in the lower BL behind the SBLI. Negative values indicate slow fluid moving upwards and fast fluid moving downwards. Also notice the value is zero very close to the wall, because the wall prevents vertical fluctuations. Image Source (I added the white markings)
The increased turbulence causes an increased momentum exchange between the lower and slower part of the BL with the higher and faster part. This momentum exchange changes the velocity profile of the BL. There are higher velocities closer to the wall. This results in a higher velocity gradient at the wall.
I believe this must be the main cause of increased wall shear stress. The stronger turbulence will probably decay downstream, so the velocity profile will slowly change back to the normal turbulent flat plate type.
Increase in pressure and temperature by the shock-wave: The rising temperature and rising pressure (not so much) increase the dynamic viscosity of the fluid and thus increase shear stress.

Most likely there are other factors that also play a role. I am no expert in SBLIs, I only read through a fair amount of literature to come to my conclusions.

Literature that I found especially helpful:

Anderson, J.: Fundamentals of Aerodynamics : My standard book for aerodynamics. Fairly easy to read. Section 9.10 briefly covers SBLI.
Schülein, E.: Skin-Friction and Heat Flux Measurements in Shock/Boundary-Layer Interaction Flows This paper shows the skin friction along an SBLI for different shock intensities. It provides schlieren images and figures that show the thickness of the boundary layer. It also discusses the causes for the observations.
Schülein, E.: Documentation of Two-Dimensional Impinging Shock/Turbulent Boundary Layer interaction Flow Here the velocity profile of the BL is measured at different locations for the same test setup as above. All the interesting data is presented in the appendix. You can see how the SBLI changes the velocity profile and BL thickness. It also explains how to calculate the skin friction from the velocity profile data (quite complicated)

Humble, R. Et al.: PIV Measurements of a Shock Wave/Turbulent Boundary Layer Interaction This is also the source of the image I used. They used Particle Image Velocimetry to measure the flow field of an SBLI. The part about turbulence is very interesting.
Anyiwo, J. and Bushnel, D.: Turbulence amplification in shock-wave boundary-layer interaction This paper investigates the mechanisms that amplify turbulences in an SBLI. Also very interesting.
Schlichting, H. and Gersten, K.: Boundary-Layer Theory Great book, every aspect of BLs. Detailed, long, harder to read than Anderson.


Where can the highest air density be found on Earth?

Any place in the arctic near sea level on a cold day would be much lower than the dead sea on a cool day.

Density Altitude Calculator


When are you allowed to use a call sign that is not the aircraft registration?

For the US, this is covered in AC120-26L, or in a more human-interpretable way from an NBAA article.

  When are you required to use your aircraft registration

By default unless you have a callsign

  Can anyone use whatever call sign they want or is it limited to airlines only?

What you use must be registered. For international flights if you fly frequently enough you can get a 3 letter ICAO designator (SWA, DAL, UAL, etc.)

There are national callsigns which are detailed in that letter, and local callsigns which may apply only to your tower, TRACON, or center depending on who you talk to and what their own rules for issuing a letter of agreement to use it are.


Can military aircraft send out false ADS-B tracking information?

It is certainly possible, and also happens with some regularity. Here is an article discussing a recent USAF RC-135 flight over the South China Sea in which the RC-135 changed it's Mode S identifier to that of some Malaysian-registered plane.

At some point, the plane’s Mode-S number suddenly changed, from AE01CE to 750548. That’s the ICAO number for an unknown Malaysian aircraft. The RC-135W, call sign RAINY51, then flew a racetrack pattern between Hainan Island and the Paracel Islands, an archipelago in the South China Sea that China claims, but whose ownership is in dispute.

https://ph.news.yahoo.com/u-spy-plane-impersonates-malaysian-130000120.html
Relevant twitter thread linked in the article, with ADSB Exchange screenshots
https://twitter.com/steffanwatkins/status/1303776525083381760


Are modern aircraft (fully loaded and fueled) able to operate from hot and high airports?

1. Thrust / FADEC
FADEC does not increase the thrust of jet engines. If anything it limits the thrust; the MD-11 has an emergency power overboost bar that disables the FADEC protections.
(YouTube) Instructor holding the aforementioned bar.

Whereas in crisis (for example, imminent terrain contact), a non-FADEC engine can produce significantly more than its rated thrust, a FADEC engine will always operate within its limits.
— Wikipedia

2. Lift
Aerodynamic advances sure help. But they can't make the air denser. Hot and high conditions still limit aircraft performance.
3. Tires
Tires are better now, but even with an extremely long runway, they can't withstand the speed needed to lift off fully fueled and loaded from a hot and high airport. (Higher speed is needed because of the thinner air and high takeoff weight.)
4. Number of engines
The more engines you have, the better performance you get, namely if an engine fails on takeoff, you'll have more power left on a quad-jet versus a twin-jet (3/4 vs. 1/2).

MD-11
In this answer, you see the MD-11F needs to stop for fuel mid-journey because it takes off from a hot and high airport.

The answer to the main question is no—the tires would burst at the required high takeoff roll speed given an adequate runway length and zero (hypothetical) climb limitations.

Boeing 787 (21 years later)
In this other answer, you see a not particularly high airport, but hot, limits the amount of passengers on the 787 headed from Vegas to Europe.

The first linked answer examines the physics behind hot and high, and the 787 answer examines a real life scenario with real numbers.


Does cargo heat failure require a diversion? What about if there are live animals in cargo?

Does cargo heat failure require diversion? It depends on the cargo being carried.
For your question about pets, then yes.
Council Regulation (EC) No 1/2005 regulates the protection of animals during transport in the EU, which itself is in accordance to IATA Live Animals Regulations. The guidelines based on that EU regulation say:

Commanders, and loadmasters and aircrew under their authority must ensure that the aircraft and equipment are suitable for carriage of the animals concerned in the manner intended. They must ensure that the animals are loaded, carried and unloaded in a way which will protect their welfare.
In particular they must ensure that the animals are accommodated in accordance with the IATA LAR, and that an appropriate environment of air quality and quantity, temperature and pressure is maintained whilst the animals are on the aircraft.

The ability to ventilate and regulate the temperature of an aircraft belly hold varies considerably. The arrangements vary between individual aircraft depending on the make and type, the compartment, and whether or not ‘standard’ or ‘special’ specifications have been fitted.
It is therefore essential that the aircraft operator, who should know the individual features of each of its aircraft, is satisfied that the belly hold to be used can be sufficiently ventilated and maintained at a satisfactory temperature during all stages of the proposed flight. This assessment should take into account the species, number, weight and size, and volume of the animals to be carried, and the heat and moisture that they will produce. Other cargo being carried at the same time will also need to be taken into account.

Even the Minimum Equipment List of aircraft takes that into consideration. For example, the aircraft can be dispatched with an inoperative cargo heater or ventilation fan, but not if there's an animal in that respective cargo hold.
All that confirms the pilot's action in the story you mention.


Is NOAA GFS winds aloft data available for applications?

See the following web page:

http://www.nws.noaa.gov/tg/general.php

This page describes getting started with the HTTP or FTP access to NOAA weather service APIs.


What should you do if you are forced to enter restricted or prohibited airspace?

Even if ATC can't legally give you permission to enter prohibited airspace (they sometimes can for restricted airspace by the way), if you declare an emergency they will still coordinate with the controlling agency which will help to keep you safe.

Squawk 7700, fly as high as possible, turn on all your lights, broadcast your intentions on 121.5 if you aren't talking to ATC, and don't make any sudden dives toward the ground/buildings, etc.  This will all help to show that you aren't trying to "sneak in under the radar" and can only improve your situation.

Don't be surprised if you get intercepted though, and make sure that you talk to them on 121.5 if you do.  Know your intercept procedures (section 5-6-2) and follow them exactly.  They will most likely try to help you as much as possible.  You will still face a lot of questions and probably even certificate action when you get on the ground though because, as you said, poor planning is no excuse....

Also, this applies in the US. Some other countries (possibly Cuba, Iran, etc.) tend to be far more sensitive to issues like this and may "shoot first and ask questions later".


How can I be US aircraft maintenance technician?

The FAA has a guide to becoming an aviation mechanic, and the related regulations are in 14 CFR 65 Subpart D. In summary:

Be at least 18 and be able to speak and write English
Have 18 months experience working on airframes or powerplants; or, 30 months experience working on both
Pass three tests: written, oral and practical

The experience requirements are in 65.77 and it doesn't say that you need to have worked in the US. So your experience in Pakistan should be valid, although I have no idea what documentation you need to provide.
If you're inside the US, there's no requirement to be a US citizen, although to work and/or study in the US you need an appropriate visa (or green card). Some employers might require citizenship for specific positions, for security or other reasons.
If you're outside the US, you have to be a citizen or permanent resident, or get special approval per 65.3:

§65.3   Certification of foreign airmen other than flight crewmembers.
A person who is neither a U.S. citizen nor a resident alien is issued
a certificate under subpart D of this part, outside the United States,
only when the Administrator finds that the certificate is needed for
the operation or continued airworthiness of a U.S.-registered civil
aircraft.


How are AOA sensors tested after working on them?

At the manufacturing facility, regulatory requirements mean you need a specialized wind tunnel to perform testing. The big part of the testing revolves around aerodynamics and icing. Testing is done at cold temperature and high altitude conditions and involves, among other things, subjecting the device to solid ice particles and supercooled liquid water droplets in high concentrations.

On the flight line and local maintenance facilities, AOA's are usually tested along with the rest of the pitot-static system with RVSM (Reduced Visual Separation Minimums) test sets such as this one.

This all applies to commercial airliners and private jets, as well as military aircraft. Most general aviation propeller-driven aircraft do not have AOA sensors or indicators, but you can buy third party systems and install them if you wish.


Is a fly-by tower legal for civilians not during a show?

No, that is not legal.

  4.6 Except when necessary for take-off or landing, or except by permission from the appropriate authority, a VFR flight shall not be flown: [...] at a height less than 150 m (500 ft) above the ground or water.

(ICAO Annex 2)

So unless you are taking off or landing (which you are obviously not, if you are right next to the tower), you are not allowed to fly below 500 feet - and control towers are not 500 feet high.

(The quoted rule is for VFR flights, which I consider to be on topic since you are asking about "a small plane, like a Cessna 172". Similar rules exist for IFR flights, but those are even stricter)


Is it legal to land aircraft in national parks and state forests in Australia?

The answer to your question, is yes and no.

CAR 92 (1) states that:

  An aircraft shall not land at, or take-off from, any place unless: ... (d) the place... is suitable for use as an aerodrome for the purposes of the landing and taking-off of an aircraft; and, having regard to all the circumstances of the proposed landing or take-off (including the prevailing weather conditions), the aircraft can land at, or take-off from, the place in safety.

As you can see, you are able to takeoff and land away from a proper aerodrome provided it is safe to do so. As you can see here, misjuding this level of safety can be fatal.

The Civil Aviation Advisory Publication (CAAP) 92-1(1) provides guidelines on what constitutes a safe landing/takeoff field other than an aerodrome. These safe areas are known as Aeroplane Landing Areas. Although the CAAP is only a guide, it is highly recommended that any area you choose to operate from meets these minimum standards.

So you are allowed to takeoff and land outside of an actual aerodrome. But your question includes national parks. The rules surrounding these are outside of my knowledge (and they vary from state to state) , but I do know that many parks carry restrictions on vehicle entry, and the types of activities permitted. I would therefore find it very surprising if you received permission to land a plane in their park (if you found a safe landing site in the first instance).

EDIT: Some commercial flying is permitted within national parks. For instance, they use helicopters and a person on a sling rope to collect crocodile eggs in Kakadu. Obviously then some activities can be approved in a national park. I'd say it all depends on the specific park and the activity being performed. Private flying away from an aerodrome? You would have to check. In any case, my answer to your question is you can land out bush somewhere but possibly not in a national park.


A cruise weight-climb is a climb segment during the cruise phase of the flight to achieve a higher flight level that was previously not reachable due the weight of the aircraft.

Long range aircraft cannot climb as high initially because of the weight of the fuel they carry. Their operating ceiling is power limited. As the aircraft burns off weight during the flight, the drag decreases and gradually excess power becomes available for climbing.

This recommendation is not to start climbing to the next level until a vertical climb speed of 500ft can be maintained at the new level, at the initial cruise speed after that weight-climb.

For example, if the the cruise starts at FL270, and one wants to climb to FL290 for a cruise at Mach 0.80, the weight-climb should not start before the aircraft can maintain a 500 ft/min climb at Mach 0.80 at FL290.


Can I log simulated instrument time in a simulator as a CFII?

A Level C or D Full Flight Simulator (FFS) can be used for all training required for an initial type rating, a 61.58 check, an IPC, landings required to maintain landing and instrument currency. In fact, so long as it is not (in most cases) your first type rating, you can fly a Level C or D sim, get certified and then walk out to the airplane, load it up with PAX and go flying, legally while having ZERO actual flight time in the actual aircraft.

So I would say yes you can log Dual given in a flight simulator, but you cannot log that time as flight time.


Is it practical to fly IFR into Hawthorne Airport (KHHR) in IMC?

Without pulling up the SOP/LoAs between HHR and LAX and SoCal Tracon, or working at those facilities to see if there's a better option, and just looking at the positions of the airports and their approaches, I'd say for an actual approach into HHR, you'd have to be vectored into the LAX arrival stream and sequenced like that.

From the approach plates, at the HHR Final approach fix you might have enough separation from LAX's 25L/R, vertically, but once you get to the end of the runway there isn't enough separation between the procedures.

Now if HHR tower can see the LAX traffic and apply visual separation that can change things as well, such that they are making sure you don't get too close, to the other final, as long as wake turbulence isn't involved.

Beyond the theoretical, just call the tower or SoCal Tracon and ask, or schedule a visit and ask.


How do investigators always know the logged flight time of the pilots?

The methods that Dan referred to in his answer are valid, and might be used by investigators—the NTSB for example.

However, generally speaking the NTSB will not spend a great deal of effort researching pilot time. Instead they will resort to one of two methods of determining pilot experience.

Firstly, if a logbook is readily available—either found at the scene or made available through the investigation—it will be used to determine pilot experience.

Secondly, if a logbook is not readily available, the NTSB can determine pilot experience based on the pilot's reported flight time on his or her last application for a medical certificate. Since an application for a current FAA third class medical can be several years old, private pilot experience determined by this means may not accurately reflect an accident pilot's actual level of experience. However, a professional pilot's application for an FAA first or second class medical will only be six to twelve months old, and will much more accurately reflect that pilot's actual level of experience.

Similarly, FAA certificated pilots report their flight time on some IACRA applications for pilot certificates. This reported time will have been independently verified as accurate (unlike times reported on medical certificates). However, in most cases, a pilot will have applied for a medical more recently than for a certificate.

For actual examples of these two scenarios, see NTSB report CEN16FA333, in which both are detailed.

For the first pilot involved:

  The [first] pilot's flight history was reconstructed using logbook documentation. His most recent pilot logbook entry was dated July 31, 2016, at which time he had accumulated 135.5 hours total flight time, of which 48.6 hours were listed as pilot-in-command. All of his flight time had been completed in a Cessna model 172N single-engine airplane. He had accumulated 5.0 hours in actual instrument meteorological conditions, 12.9 hours in simulated instrument meteorological conditions, and 3.4 hours at night. He had flown 24.7 hours during the prior 12 months, 4.4 hours in the previous 6 months, 2.4 hours during prior 90 days, and 1 hour in the 30 day period before the accident flight. The pilot's logbook did not contain any recorded flight time for the 24 hour period before the accident flight.

For the second pilot involved:

  According to FAA records, the [second pilot], age 60, held a private pilot certificate with a single engine land airplane rating. His last aviation medical examination was completed on November 6, 2014, when he was issued a third-class medical certificate with a limitation for corrective lenses. A search of FAA records showed no previous accidents, incidents, or enforcement proceedings. A pilot logbook was not recovered during the on-scene investigation; however, on the application for his current medical certificate, he reported having accumulated 120 hours of flight experience.


Why does enabling engine sync on the MD-80 series trigger the "Master Caution" light?

AFAIK The reason you aren't supposed to take off/land with prop or engine sync on is because if the leader engine fails, the follower engine will reduce power to match it, and that is really not ideal, especially low and slow, a la V1 cut or failure on short final. Try it out- fail the leader engine just after V1 and see what happens!


What is supposed to prevent a commercial crew from flying to the wrong airport?

According to the Wikipedia article on IFR:

  VFR is the most common mode of operation for small craft. However, it is only safe to fly VFR when these outside references can be clearly seen from a sufficient distance; when flying through or above clouds, or in fog, rain, dust or similar low-level weather conditions, these references can be obscured.

So basically, a pilot would land at a wrong airport due to one of the following conditions:

He/She did not have previous experience of landing at the said airport
He/She paid more attention to VFR that IFR (which is usually suggested), and the proximity of the airports confused him/her

  Any aircraft operating under VFR must have the required equipment on board, as described in FAR Part 91.205[5] (which includes some instruments necessary for IFR flight). VFR pilots may use cockpit instruments as secondary aids to navigation and orientation, but are not required to; the view outside of the aircraft is the primary source for keeping the aircraft straight and level (orientation), flying to the intended destination (navigation), and not hitting anything (separation).

This means that a pilor following VFR can get confused, and that would be a completely manual error. To prevent this from happening, he/she should raise a flag with the Control Tower before landing if his IFR shows a different destination, when compared to the place he is intending to land at following VFR.


Can Ospreys land without running engines?

Welcome to AviationStackExchange and to provide a short answer to your question, yes there are autorotation measures that are similar to those featured on helicopters. The basis for most of my answers pertain the unique drive shaft system, which allows for redundancy between proprotors, something other twin-engine fixed wing aircraft usually lack, so here's a diagram for some reference:

As for the detailed answer, I'll split it into three parts: One engine failure, total engine failure, and a stuck rotation mechanism.

The two RR T406 type engines of the V-22 are connected by a driveshaft, which means that if one engine loses power, the other, provided that it is in good working order can deliver power to both proprotors through said shaft. It lacks the power to actually hover on that one engine though, so it has to be glided down, and protocol presumably dictates a powered glide to somewhere safe.
When both engines fail, autorotation just as on a helicopter is instructed, however, due to the fact that the proprotors are about a third of the diameter of conventional rotors means its low rotational inertia results no autorotation will significantly reduce the impact from a total failure. In other words, it can't really glide like a plane and won't autorotate like a helicopter. It's getting the best and worst of both worlds.
As long as the engines are working, the V-22 can land and take off in both configurations. However, there's an approximately 18-20% (Wikipedia quotes 18, Boeing claims 20) increase in flight efficiency in the turboprop aircraft configuration over the VTOL setting. I can only imagine that number goes higher by 10-15% during takeoff and landing. Planes are simply more efficient this way.

So, yeah.


What are ATC-side procedures to handle a jammed frequency?

Honestly, there is no guarenteed way we can solve such a problem, and it is extremely frustrating when it happens. A few possible solutions:

The radio transmitter associated with the tower frequency is usually quite powerful, so (at least for nearby aircraft) it may be possible to override the other transmission by simply transmitting normally. AFAIK, the transmitter is actually designed to be more powerful than aircraft transmitters as a safety feature. Sounds like this is what happened in your situation. This is usually only the case for tower frequencies (not ground/approach etc.)

Sometimes there is an obvious alternative frequency you can use, and maybe some of the pilots will try tuning to that frequency. We could also do a call on 121.5 and ask everyone tuned to the tower frequency to check for stuck mic. This wouldn't help for small GA aircraft with only one radio, since they won't be listening to 121.5.

In CPDLC airspace (en-route environment), ATC can send a "CHECK STUCK MIC" message to relevant aircraft.

In the end, the pilot with a stuck mic will usually realise after a while of apparent silence on the frequency.

Here is a recording of a stuck mic causing issues at JFK:


What precautions are taken to avoid bird strikes?

Humans are more important than animals by "most" societal standards. Therefore, bird safety is secondary to human safety (pilots and passengers). However, there are certain areas (in US) that are designated as protected areas for certain types of birds, such as in California where I have seen protected areas for the California Condor which requires pilots to fly at a certain altitude above that area. On VFR Sectional Charts the special conservation areas are depicted as indicated here:

These conservation area restrictions are mostly to avoid disturbing the birds, but I assume it also reduces the risk of a bird strike by requiring the aircraft to fly higher over these areas.

One of the most important precautions is for pilots to remain vigilant and see and avoid, but that is not always possible when a flock of thousands of birds takes off near an airport when airplanes are landing and taking off.

Some airports use various methods (see links provided) to scare flocks of birds away such as using hawks, noise, and other methods.

I don't know of any aircraft that are designed for the safety of birds. I believe this is a very low priority in aircraft design.

Try checking the Audubon Society website, they have a lot of information on risk to birds and statistics on such risks.


Can I execute an ILS approach using a NAV CDI with LOC signal only?

No, you cannot execute an ILS approach without an ILS glide slope indication as the primary form of vertical guidance.

Even if you could supplement it with alternatives (WAAS, GPS software, etc), they are not recognized as the appropriate standard of vertical guidance required for an ILS approach.

Many airports that have an ILS also have LOC (localizer-only) approaches.  If such an approach is published, you could certainly fly it with only the use of the localizer, but then again, it is not an "ILS approach" it is a localizer approach.

The localizer -only approach will have different minimums which will be based on your altitude at a published minimum descent altitude rather than a decision height.

If no localizer approach is published, then you'd need to find another method or airport.


Are there any airports with multi-level taxiways?

If you allow taxiway to also mean a surface where an airplane rolls but not under its own power, then there's the lower decks of an aircraft carrier, and Schätz's carousel hangars.  Note that even Schätz prefers scissors lifts to multilevel tarmac.
Multilevel tarmac would means ramps between levels, which is commonplace for surface vehicles but rare for airplanes, both in airframe design and in pilot training.


What is an Inertial Navigation System? How does it work?

Inertial Navigation Systems, unlike other navigation systems, do not depend on external (radio) measurements. Instead an INS keeps track of its position by accurately measuring acceleration (accelerometers) and rotation (gyroscopes). It therefore works in remote areas where there are no ground based navaids available.

Initially, the INS gets its position from pilot input at the gate, or in more recent systems from GPS, sometimes even during flight. By measuring all the accelerations and rotations and integrating them into speed and direction the position is tracked. In doing this, the INS has to correct for the rotation of the earth and the related Coriolis force.

Due to small inaccuracies in the measurements the velocity error and, with that, the position errors grow over time.

Wikipedia has quite a detailed article about the history and working of the INS.

While raw INS position has mainly been replaced by GPS measurements on oceanic flights, the system is not being phased out. GPS is a sensitive systems and by crosschecking it with INS, errors can be detected in both systems. It is often used as a backup to GPS.

Integrated GPS / INS systems provide better systems integrity and allow the navigation system to coast through short GPS outages with high accuracies. In addition to that, the (laser) gyroscopes of the INS are often used to provide data to the digital artificial horizon displays in the cockpit and to the auto flight systems. In this case the term Inertial Reference Unit (IRU) is used, which acts as a basis for the INS.


How does the Harrier avoid engine damage when operating from dirt fields?

How does the Harrier avoid engine damage from dirt ingestion during rough-field operations?

The short answer is that they don't. They avoid using these FOD-laden strips if possible, but doesn't have any kind of active method for reducing FOD damage from debris ingestion.

This is supported by an RFP that NAVAIR put out asking for proposals to reduce FOD for the AV-8B:

  The AV-8B currently has the highest FOD damage rate in the U.S. DoD inventory which incurs a cost of more than $100M per year in engine removal, rebuild, and reinstallation, as well as decreased readiness and safety.

The method here is to just deal with it when it happens. The engine is removed, repaired, and replaced when a FOD incident occurs.

The document also says:

  To date, NAVAIR has experienced more than eight Class 'A' mishaps in the AV-8B due to FOD

Where mishaps are defined:


What is the meaing of the circuit breaker marking "Audio/Mkr" in a PA-28-181?

This circuit breaker is responsible for your Audio Control Panel. It's called Audio/Mkr. because the Audio Control Panel in most aircraft includes the Marker receiver and displays (maybe you noticed the three colored lamps on the left side reading O, I and M, colored white, blue and orange).

If the circuit breaker is out you loose your audio on the one hand side, on the other side you also loose your ability to identify Marker Beacons (functionality explained by Carlo).


Why will windshear inop illuminate after landing in an MD-83?

The WINDSHEAR INOP light tells the pilots that the Predictive Windshear System cannot work:

  System Annunciator Lights

  [...]

  An amber WINDSHEAR INOP annunciator is installed on the annunciator panel.
  This light illuminates any time the windshear systems detects a fault which
  renders the system inoperative.

(MD-80 FCOM Sec. 16 - Instrumentation / Navigation / Communication - Predictive Windshear System)

In order for this system to function, the radar system needs to be active, which is a hazard to the ground crew:

  RDR-4B Radar System Theory

  Like all modern radar systems, the RDR-4B operates by emitting short
  intense pulses of microwave energy which are reflected by objects having
  reflective characteristics within the range of the system. The reflected
  signals are processed to produce visual displays that are representative of the
  size, intensity, bearing and distance of the targets. The RDR-4B incorporates
  an advanced microprocessor design which utilizes the Doppler principle to
  identify areas of moderate and higher turbulence as well as low level
  windshear (microburst) activity. The RDR-4B system is designed to operate
  in the windshear mode automatically any time the aircraft is below 1500’
  AGL, at least one engine is running, and the transponder is not in OFF or
  STBY, REGARDLESS OF RADAR MODE SELECTED. The system also
  operates in the windshear mode below 1500’ AGL using an alternate scan
  technique if the radar is operating in any mode (WX / TURB, WX, MAP). The
  windshear mode is activated at 2300’ AGL. However, no alerts or displays
  are annunciated above 1500’ AGL.

  WARNING:
  Failure to return the transponder to STBY after landing or
  selecting any mode except STBY prior to leaving the ramp area
  allows the radar to operate in the windshear mode creating a
  radiation hazard to personnel on the ground. The RDR-4B
  radiation hazard area extends 13.4 feet from the radar antenna
  in a 120 degree arc left and right of the aircraft centerline.
  This hazard exists even if the radar mode is selected OFF or
  TEST.

(MD-80 FCOM Sec. 16 - Instrumentation / Navigation / Communication - Predictive Windshear System)

After landing, the pilots will switch the transponder to STBY in order to deactivate the radar system before reaching the apron (where ground crews are working). This will disable the Predictive Windshear System and causes the WINDSHEAR INOP light to illuminate.


What are the consequences of fouled spark plugs in flight, and how can I clean them?

You should read up here but generally speaking plugs are less likely to foul in flight (and is why its not talked about much). Plugs often foul due to the mix of low engine temps and high led content during warm up at full rich settings. This is why a leaned out warm up is advised for some planes, you should talk with your instructor about the plane you are flying and what the proper warm up procedures are.

Please consult your POH for any airframe specific emergency checklists that may apply to your aircraft. Generally speaking if you depart with a fouled plug and it is causing a rough running issue you should cycle the magnetos untill you are running on the good set of plugs and get the plane down safely. This is most likely the result of a poor or non-existant run up check. Unless you are sitting in line for a long time after your runup, you should generally be doing runup close to departure time.


Why do most airliners have underwing engines, while business jets have rear-mounted engines?

Underwing engines have more advantages for larger planes, but there must be enough room underneath the wing to mount them.

This was tested by Boeing in the 1960s, when they designed the B737 and had two competing teams pre-design both configurations. The underwing config won. When Airbus designed the A320 two decades later, the underwing config won again with engines that were a good amount wider.

Image source.

Advantages of underwing mount:

Engines mounted in pods underneath the wing reduce the upward bending moment of lift creation, and therefore allows for lighter construction.
If the pods stick out forward of the wing, the backwards aerodynamic twisting moment is also reduced: lighter construction.
The engines can be easily reached for maintenance.
All of the fuselage can be used for useful load - tail mounted engines have structural reinforcements in the fuselage between the engines.

Advantages of fuselage mount:

The yawing moment of a single engine fail is smaller, allowing for a smaller vertical tail.
Fuselage can be lower to the ground and allow for low door sill height.
Landing gear can therefore be shorter.
Clean wing configuration.
Lower trim change due to thrust.
Less noise in most of the cabin.

In smaller planes, the wing bending & twisting moment is a relatively smaller constructive issue than in larger planes. And indeed, being closer to the ground allows for easier boarding via air stairs.


What are the two blisters on F-35 upper wing surface?

Those are Luneberg Reflectors.

They enhance the radar cross section of the aircraft.

For two reasons; to be more safe around civilian traffic due to being easier spotted by traffic control radars, and where they do not want adversaries to train their radar systems on it to gain knowledge of its strengths and weaknesses.

Not sure if those on the picture is retractable, or has to be fitted/removed by mechanics.

There are many sources for this, here is one:
https://www.businessinsider.com/f-35-luneberg-radar-cross-section-russia-estonia-2017-5?r=US&IR=T


I presume you are asking about lights that are on the surface of the runway like centerline lights and touch down zone lights. The FAA has an AC that covers their design and installation which you can find here. Take a look at section 4.5 "In Pavement Light Fixture Testing". This section outlines some of the force requirements the light must be able to withstand. The FAA currently requires the light to be mounted in an L-868 base can which is imbedded in the runway during construction. There are also a bunch of size requirements laid out in section "3.4. Dimensional Requirements." that describe how the lights are to be built.


Is it safe to use a parallel runway's PAPI/VASI?

Per the AIM (2-1-2 - Visual Glideslope Indicators)

  The visual glide path of the PAPI typically provides safe obstruction clearance within plus or minus 10 degrees of the extended runway centerline and to 4 SM from the runway threshold.

(Deviations from that are supposed to be noted in the Airport/Facility Directory, for example if the clearance path is offset from the centerline, or theoretically if you could use a parallel PAPI...)

A few miles out you're probably within the 10 degree arc, so the PAPI will be useful, but as you get closer that arc narrows, and as Lnafziger mentioned there might be an obstacle in your way (like the FAA-Standard 50-foot tree right at the threshold line).
Also as abelenky pointed out you're not supposed to be using parallel PAPIs/VASIs for approach guidance - It's a good cross-check, but not a primary reference.


What is the suggested position for a canard?

There are two general configurations for canard wings, the long coupled and the short coupled canards. From Torenbeek:

Long coupled canard. This configuration is designed for minimal drag in cruise. The canard wing is placed far forward of the main wing in order to reduce interference drag. Vertical position is higher than the main wing to reduce adverse effects at high angle of attack.
Short coupled canard. The canard wing is again higher than the main wing: the interference is deliberately used to increase maximum lift (at the cost of high drag), achieved:

at large angles of attack;
on surfaces of low aspect ratio with highly swept back leading edges.

Quoting from Torenbeek:

  In short, the canard layout appears to be suitable for transonic or supersonic and highly maneuverable aircraft, in the latter case if sufficient thrust reserve is available


How can an all flying rudder be almost 100% more efficient than a vertical stabilator and rudder?

Because on the Zenith the massively slab sided fuselage is the vertical stabilizer, and the rudder is still the rudder.  The surface area of the all flying rudder is about the same as the rudder on a normal plane, and it depends on the fuselage for weathervaning tendency.   There's no free lunch.  If you build a Zenith with a skinny boom tail and the all flying rudder, it will be quite marginally stable in yaw, like a Fokker DR-1.


Do any propellers/propfans use stator vanes? Why is this not a commonplace feature?

When a compressor rotor stage speeds up the flow, the stator:

Slows it back down, turning kinetic energy into pressure (see image here from the book The Jet Engine)
Presents the flow at the correct angle for the next rotor stage.

A nozzle guide vanes stage (what a turbine stator stage likes to be called) comes before the turbine stage, and it does the same but in reverse (turns pressure into velocity) and adjusts the flow direction for the upcoming turbine stage.

The de-swirl function of the stator stage behind a fan in a turbofan (the outlet guide vanes – OGVs) is beneficial because of how much air the fan has acted on.

The number (and size) of blades tell the whole story. It's often said that propellers move air by a little, and jet engines by a lot. To put that into perspective, the typical pressure ratio rise behind a fan is 1.4–1.6, whereas behind a propeller it's less than 1.02.$^1$

This is where a turbofan's OGVs become beneficial. Adding a static stage of blades behind a propeller (with or without a case) that doesn't accelerate the air by that much to recover meaningful pressure (compared to a turbofan's fan, not much kinetic energy to begin with) in the axial direction won't help. On the contrary it will add drag (air hitting a static object), and weight.

    Actively contra-rotating both props adds a lot of complexity, and seems somewhat unnecessary if the goal is mostly to remove large part of the swirling motion. Cancelling all torque is not necessary for a plane.

A propeller is like a wing, it needs to act on (hit) air to create a normal force. If we substitute the second set of moving prop blades with static ones, we've just lost a lot of thrust.

$^1$: https://history.nasa.gov/SP-468/ch10-3.htm


What policies, technologies, equipment, etc is used to mitigate liquid spills in the cockpit especially during turbulence?

Keeping the cockpit clean is a major consideration for airlines. The inflight team will scheduled meal times accordingly with reports from ARTCC and other aircraft on a similar routes. They tend to stagger their eating times, so one pilot can be the PIC and the other can eat. Once he/she is done eating they will switch. Here you can find a link explaining Multi Crew Operations. Hope this helps!


Why is one of Madera Municipal's runways labelled with only "R" on both sides?

R is for Restricted. From the chart supplement (formerly AF/D) that runway (8-26) is restricted for agricultural use only.

It's non-standard, both internationally (ICAO) and on the FAA level for Part 139 airports (see AC 150/5340-1M). Note that the airport is neither international nor Part 139, so standards may not apply.

(via skyvector.com)

Beyond the meaning of the non-standard R, the Madera County's website offers this (PDF; Sep 2015):

  Future abandonment of Runway 8/26 when the agricultural aerial applicator lease expires in 2019.

This hints at a legal agreement with a local agricultural operation. Perhaps someone who is familiar with the local government there can offer more insight.


Why did America not build its own ekranoplan?

Best answer: the United States had no need for one.   These kinds of large wing-in-ground-effect craft, while impressive, really serve no military purpose and provide no major military advantage for the US Armed Forces to possess.

Aside from the internal Great Lakes, there are no major bodies of water within the United States of America where such a craft could be readily employed and no need to position strategic or tactical assets there.   Both the Atlantic and Pacific oceans are covered by the US Navy with the form of carrier battle groups and submarine fleets, which provide portable power projection for undersea, surface and air operations  virtually anywhere around the globe.

Large wing-in-ground-effect aircraft do not provide a significant increase in America’s  power projection when compared with that.


Are there rules about using the "Fasten seatbelt" sign outside of take-off/landing/turbulence?

You dont have a jurisdiction tagged (although it sounds like this is an EASA matter) your answer may vary depending on where you are asking for. I can answer for the US/FAA.

Here in the states you are technically in breach of an FAA FAR by not remaining seated. As per FAA FAR 121.317

  Sec. 121.317

  Passenger information requirements, smoking prohibitions, and additional seat belt requirements.

  ....

  (f) Each passenger required by Sec. 121.311(b) to occupy a seat or
  berth shall fasten his or her safety belt about him or her and keep it
  fastened while the "Fasten Seat Belt" sign is lighted.

  .....

  (k) Each passenger shall comply with instructions given him or her by a crewmember regarding compliance with paragraphs (f), (g), (h), and (l) of this section.

I cant find a regulation on using it in times its not otherwise required by FAA FAR 121.311 but this discussion seems to elude to the fact its at the "Captains Discretion".


What can a passenger do if (s)he objects to the flight route?

The passenger can in all likelihood do nothing that is going to change the route.

As you point out, there is always the option to not board.

On long range flights like this, the routing will (depending on winds aloft and other conditions) almost certainly require a fairly direct route to insure that additional fuel stops are not needed. In cases where routes go over warzones or other dangerous areas, they are often rerouted, but in the case of Ukraine the conflict has until now been isolated and military in nature.

Either you trust the flight crew to also be aware of these risks, or you don't. Get on board, or not. I'm sure you could raise the issue with a gate agent, and if you made enough noise or escalated it, you might be able to get a refund (note: I have no idea). However, you also might be perceived as the source of the risk and detained!


Why does an ADIRU 1 failure disable all functions of the A330/340’s GPWS - even those not requiring ADIRU data?

You wrote:

  (...) the GPWS's original functions (...) require only radioaltimeter data (...)

That's wrong. The basic GPWS needs barometric data alongside the RA.$^{[1][2]}$ (Not talking enhanced functions of EGPWS here, rather the most basic modes 1–3, and mode 4 needs airspeed/Mach with RA.)

The A340's GPWS computer (EGPWC) takes this barometric info (vertical speed) from ADIRS 1 (schematic), if that's failed, so would the basic GPWS.

$^1$: GPWS patent from 1970
$^2$: Aircraft Instrumentation and Systems (page 342 snippet below)

Note: Computing the height time derivative ($\dot h$) is not as easy as using V/S, you need high sampling rate and a perfect radar lock that won't be fooled by say trees or uneven ground reflecting the signal away. In France, some airports use radar reflectors on masts to fool the RA into thinking the ground is flat:

  Source: lustublog.com (in French)


Is there any theoretical problem powering the fan with an electric motor

Taking into account your wish to ignore all things that make electric aircraft unviable, like power-to-weight ratio of engines and battery capacity, the answer is yes.
You would, however, need to compensate the missing jet engine thrust by increasing the fan thrust.
Otherwise the answer is no.


You can see an example sketch of a heated pitot tube in the FAA Handbook of Aeronautical Knowledge:

As you can see, there are two heaters that heat the entire tube and (ideally) stop ice from forming in the first place (anti-ice, not de-ice).


On acquiring an aircraft for my own PPL training and later use

Is it possible? Sure. But there are pitfalls you need to be aware of...

First, you may find it difficult to find financing for a new(er) aircraft especially if you are still a student, and especially if you are intending to offer it as a lease-back.

Then there is insurance, which for a student purchaser is going to be expensive, and even more so if you are leasing back with the idea of it being used in a flight school as a primary trainer.

The AOPA has a good article on leasebacks:

Lenders Leery of Leasebacks
AIrcraft Owners Guide to Aircraft Leasing
Turning the tables on leasebacks

Along with any number of other articles.

Another thing you need to keep in mind is that when you put an aircraft on leaseback, you, even as the owner, are subject to the same scheduling issues as renters.

The biggest thing to remember is that buying an aircraft for use in training is not a way to save money, you would be surprised at what it costs to own an aircraft, even on leaseback. You have annuals, maintenance, insurance, etc.


What does the “test result indicator” indicate on a cockpit voice recorder?

I could not find the exact model you showed, but the A330 and A340 FCOM on SmartCockpit shows a similar one. Unfortunately the description of the test is rather short:

The Overhead Pushbutton explanation on SmartCockpit is equally short:

My best guess would be that it shows the recorded volume from low on the left to high on the right and it is considered OK (test passed) if it reaches into the green LEDs, therefore making sure the CVR can pick up voices clearly enough. I hope someone working with these CVRs can provide a more accurate answer!


What is the reason for the sudden increase of French published accident and incident investigation reports in 1997?

A related event could be the adoption by The European Community Council of:

Council Directive 94/56/EC of 21 November 1994 establishing the fundamental principles governing the investigation of civil aviation accidents and incidents [Official Journal L 319 of 12.12.1994].

European directives must be transposed in a country law and adopted by the country Parliament. This has been done for France in 1999, with the law "Loi n°99-243 du 29 mars 1999". This law actually modified the regulations related to civil aviation (Code de l'Aviation Civile, Livre VII).

Most of the articles added new obligations to the State and, from what I understand, no obligation for investigation or for releasing a public report existed before, so it may have been at the discretion of the Transport Ministry.

Two articles are of interest:

  Obligation to investigate every accident or serious incident with the
  aim of preventing any reoccurrence thereof.

and

  Obligation to publish an accident (or incident) report, containing
  safety recommendations where appropriate.

Regarding your count on the BEA site, this info is lacking some important details, for instance:

The hang-glider or ultralight aircraft are relatively new, and we don't know how it has changed the number of incidents/accidents. It's well known that in France hang-glider accidents where not investigated by the BEA because hang-gliders are not subject to an airworthiness certificate. It seems this has changed, but it's not clear to me.
You don't provide a list of events, only a list of reports, which as demonstrated in the Rio-Paris accident can multiply by 4 the count because of the 3 interim reports (this is now mandatory to publish a preliminary report each 12 months if the final report cannot be completed within the first year).


How does auto-trim work on fly-by-wire aircraft?

In fly-by-wire aircraft (to fix things, let's consider an A320), there is no such effort to maintain as you use sidesticks.

Let's be clear: there is no such effort on the pilot side, but the forces on the surfaces are still there and are taken care of by the electro-hydraulic actuators.

  In flight in normal law, how and when does the computer decide it must trim the plane?
  What does it take into account to trim the plane?

I will answer these two together. And let's remember what written above: the actuators are taking care of the control surfaces loads, this means that part of the actuator authority is being used to control a static load.

In an ideal situation all the authority (coming from hydraulic pressure or coil current) can be dedicated to control transients: gusts, configuration changes, turn entering, turn leaving. If you are allocating part of this authority to keep level flight, a gust (for example) that otherwise would have been easily compensated for, will lead to a momentarily loss of coordination, reducing the comfort of the passengers.

That is what (mostly) you use to trim the aircraft: if your actuator is constantly (or on average over several seconds) applying a certain force in a certain direction, the system will use the trim functionality to remove said force while not altering the flight equilibrium.

  Does it anticipate the trim?

I have no public reference for this.

  What happen on the ground?

Usually you leave the aircraft with no trim.

  What happen if not in normal law (I guess auto-trim would be one of the feature unavailable in alternate law)?

Unless you are outside of normal law for actuator-related issues (power/hydraulic losses, for example) I see no reason why trimming would be unavailable, all that is required for trimming, as said above, is the average load on the actuators and trimming actuation capabilities.


On which point(s) in a jet engine does the reaction force act?

The thrust produced by the engine is due to the net resultant of various forces acting on various surfaces of the engine. The thrust produced is a function of mass flow rate and the change in velocity ($T = \dot{m} (V_{e}-V_{\inf})$). So, both of these have to be taken into account, rather than acceleration alone. The location of maximum thrust generated varies with the type of engine.

For high bypass jet engines like those used by the modern commercial airliners, most of the thrust is produced by the bypass fan. Though the acceleration is not the greatest here, mass x acceleration is- so this is where the thrust is maximum. The maximum reaction forces are applied there
In case of pure turbojets, the (almost all of the) thrust is produced by the core. For low bypass turbofans, its somewhere in the middle, with the lion's share of thrust produced by the core.

Note that most of the reactive force is applied on the diffuser and the compressor due to the high pressure and the forward facing area (due to cross sectional variation) in this region. This high pressure also acts on the combustion chamber, increasing the reaction force.

In the turbine and nozzle, the variation in the cross section creates a surface area facing the rearward direction, where the gas pressure acts, resulting in an force applied in direction opposite to the compressor. The net result of all these forces gives the thrust.

Image from Aircraft Performance and Design by John Anderson; taken from quora.com


What kind of delay does the A320's fly-by-wire system add?

Yes there will be a delay, but the delay caused by the control loop is really tiny. I've seen position control loops run successfully and stable at a couple of hundred Hz for simulator motion systems, and the time delay is just one iteration frame = less than 10 msec.

And as @ymb1 correctly points out, if we deflect any control surface the end position is subject to actuation forces, aerodynamic pushback forces, inertia of the surface, cable stretch and -friction, aero damping, maximum flow velocity through the servo valve etc etc. The total transfer function of stick input => surface position is such that an extra time delay of 10 msec in the total loop is not really noticeable. And control position is only the input of the aircraft response, with aircraft inertia playing a large role.

So my answer would be: a tiny time delay that can be totally disregarded.


Wing pitching moment decomposition into two terms

Interestingly, when $O=AC$ and $x_O=x_{AC}$, the moment does not change with changing $α$

Yes, but only if your lift is also applied at the AC! That's the whole point of the aerodynamic center. You replace the pressure distribution with a lift force (actually a resultant force, but let's neglect drag here) and a moment. If you place the lift force at the center of pressure, then the resultant moment about that point is zero. Then, the moment about any other point $O$ is only "created" by the resultant force. So in that case indeed:
$$M_O = (x_{CP} - x_O)L$$

If you now place the lift at your AC and also O=AC, then:

$$M_O = M_{AC}$$

This $M_{AC}$ is independent of $\alpha$. If you now move to any different O, you get:
$$M_O = M_{AC} + L (x_O - x_{AC})$$

The first term $M_{AC}$ is what you are calling "$M_{camber}$" and the second term is your "$M_{lift}$".


How do class E/G airfields charge for stops without refuel?

I have found this really varies by airport and even by FBO at a given airport. The only way to know is either to check their website or call in advance and find out. After a quick look I don't see any prices listed on their site.

Often times the price is related to the services they provide by default. If you land and there is a marshaler waiting for you, a golf cart ride from your spot to the FBO building and loads of free local snacks: you're likely to be paying. If you land and the airport manager lives next door but his cell phone number is written on a sign that says "call for assistance", the fuel is self serve, and the gate code is the CTAF frequency: you're likely not paying for parking.

The one thing that's worth noting is if there is a local (usually nominal) landing fee charged by the municipality the airport resides in.

AOPA's airport information site has some fee info on it. For example KLOM has some fairly high fees for a class E un-towered field. While I can confirm from experience that the $5 ramp/parking fee at KDDH is waved for buying fuel.


It is exactly the other way round:

$$ \alpha = \mathrm{arctan} \left( \frac{v_z}{v_x} \right) $$

You can simply derive it from the trigonometry in a triangle:

In this image the aircraft is moving to the right (along the arrow labelled v) and the $x$-axis is pointing along the aircraft body.

The resulting function looks like this:

For $ v_z = 0 $, you get $ \alpha = \arctan(0) = 0 $.
For $ v_x \to 0 $, you get $ \alpha \to \frac{\pi}{2} = 90^\circ $.


On which axis do we measure angle of attack and airspeed?

Airspeed is always the total magnitude of the free-stream incident on the wing/airplane. In zero sideslip, angle of attack is exactly the angle between free-stream and body x-axis (could be chord for an isolated wing). In non-zero sideslip, it's nuanced; see below.

By industry standard (Ref. Etkins, Dynamics of Flight; Stevens, Aircraft Control and Simulation), the angle of attack ($\alpha$) and the angle of sideslip ($\beta$) are defined as Euler rotation from the coordinate axis attached to the free-stream such that the speed vector is $\begin{bmatrix}V_a & 0 & 0\end{bmatrix}^T$, where $V_a$ is the airspeed magnitude, to the body frame (where x-axis aligns with the chord):

$$\begin{bmatrix}u_a \\ v_a \\ w_a\end{bmatrix} = \begin{bmatrix}\cos\alpha\cos\beta & -\cos\alpha\sin\beta & -\sin\alpha \\
\sin\beta & \cos\beta & 0 \\
\sin\alpha\cos\beta & -\sin\alpha\sin\beta & \cos\alpha
\end{bmatrix}\begin{bmatrix}V_a \\ 0 \\ 0\end{bmatrix}$$

where $u_a$, $v_a$, $w_a$ are the incident speeds in the body frame.

Simplify, and we have:

$$\alpha = \tan^{-1}\frac{w_a}{u_a}$$

$$\beta = \sin^{-1}\frac{v_a}{V_a}$$

(Image Ref. Etkins, Dynamics of Flight)

Note that when sideslip is small (whereby $\cos{\beta}\approx1$), we can reduce the above to:

$$\alpha \approx \sin^{-1}\frac{w_a}{V_a}$$

Therefore, taking angle of attack as the projected angle between chord and free-stream is pretty darn good.


Why do aircraft have an unusable amount of fuel?

Pilot here (with Cessna 152 hours) as well as an engineer who made it most of the way to an Airframe and Powerplant technician license at one point in life.

There are several reasons that conspire to produce 'unusable fuel':

Fuel tanks on airplanes have complex shapes - they include baffles and other walls (with holes in them) to prevent oscillations from building up during in-flight movement. Sometimes these baffles are even engineered into the tanks late in the design cycle as testing finds oscillation issues. These baffles result in 'geometric trapping' of fuel in nooks and crannies.
Drawing fuel from a fuel tank is more complicated in a plane - cars are pretty much flat with minor tilts while airframes can have all sorts of odd and sustained directions that the fuel wants to go due to acceleration. Imagine an extended tilted spiral while descending - that fuel experiences far more lateral acceleration over a longer time period that a car would have. Getting the fuel system to pull fuel out from these different angles is challenging (note that I've picked a non-aerobatic maneuver for which the Cessna 152 of your question is qualified here).
All of this is a cost/complexity tradeoff - solutions exist for 1 and 2 above - fighter jets use fuel bladders that have pressure bladders arranged to squeeze the fuel out so that they can get almost all the fuel even at high G-forces and unusual angles. Aerobatic planes have similarly more expensive and complicated systems than the old and cheap Cessna 152.

There are other considerations as well, but mostly it comes down to whether the plane in question can justify the cost and effort to get every last drop of fuel.

Things get even more complicated in rockets - the moon rockets (properly the Saturn 5 although it was an upper stage specifically) had special extra engines called ullage motors whose only job was to give the stage a little boost in space to push the fuel towards the rear of the rocket so that the main motors could draw fuel and start.

Addendum edit: @supercat below - the definition of unusable fuel is set by federal aviation regulation part 23, section 959 (FAR 23.959) and basically is the worst case under "intended operation" for the particular plane. Since the Cessna 152 is not aerobatically rated, for example, the unused fuel is defined as the fuel level where SOME intended maneuver would be capable of causing a fuel system error. In practice, especially in flat level flight, some of that unusable fuel would be available for use although you are not supposed to plan to use it in your flight planning.