Who runs the Air Navigation System (air traffic control) in Canada?

No. Unlike the United States where the Federal Aviation Administration (FAA) is both the operator and regulator of the air navigation system (ANS), these roles are separated in Canada and performed by two different parties. They are:

The regulator: Tranport Canada - Government of Canada
The operator: NAV CANADA

The Government of Canada passed the Civil Air Navigation Services Commercialization Act of 1996, which effectively sold the ANS to a newly-formed corporation, "NAV CANADA" for the price of $1.5 billion dollars. Since 1996, Transport Canada's role has changed to regulation and enforcement; they introduce, amend, revoke, and enforce the Canadian Aviation Regulations.

NAV CANADA become the sole operator of the civil ANS and is a private company whose revenues come from aviation customers and technology sales, not Government of Canada.

NAV CANADA operates the civil ANS using 7 Area Control Centres, 41 Control Towers, 56 Flight Service Stations, and 8 Flight Information Centres; military aerodromes and terminal control areas remained the responsibility of the Department of National Defence.


How can I scale down a propeller for wind tunnel testing?

The airfoil of the propeller should not change with size if you are scaling it up and down. As long as the airfoil is the same and the proportions are correct relative to both propellers (length, chord, pitch, etc.) that should be all you need to pay attention to.


Why is the IRST not centered on the Eurofighter Typhoon?

The Thales UK PIRATE IRST system is located here in order to allocate space on the starboard nose for the retractable in flight refueling probe.  The port space was the only available real estate for this avionics to fit.  Other aircraft like the MiG-29 have similar restrictions in space availability.

The asymmetric location does not affect functionality; the IRST seeker head does maintain full field of view without blockage from the nose or fuselage.


Why did Boeing choose to give the Boeing 720 such a designation?

Because the launch customer, United Airlines wanted it. From Boeing frontiers:

  The 720 was a ... first marketed to the airlines as the model 707-020. United Airlines was very interested in the 707-020 but had previously decided to go with Douglas and the DC-8. To help United avoid any negative public relations for going back to the 707, Boeing changed the name of the 707-020 to the 720.

According to aviationweek, the name change was at the behest of William ‘Pat’ Patterson, the president of launch customer United Airlines.


Is platinum present in a combustion chamber?

To elaborate on mins comment: platinum right now is selling for around \$1000 / troy ounce, which is ~\$14,500 / pound.  Nickel is selling for around \$4 / pound and cobalt is \$25/pound. Nickel and cobalt super alloys have sufficient temperature capability for jet engine applications.  So the choice is clear. Platinum is not mentioned because it is not used.


How can I consider a UAV thrust power for wind effects?

As i understand your image:

$V_{uav}$ is the velocity of the plane relative to the air.
$V_{wind}$ is the velocity of the air relative to the ground.
$V_{ground}$ is the velocity of the plane relative to the ground.

If the UAV velocity is 10 m/s and the stall speed is 10 m/s the plane is at its limit of flying no matter what the wind speed is (neglecting turbulences). The relative speed of the plane and the air is crucial, this speed is mandatory for the physics beyond the lift.

There is simple equation how to calculate sum velocities. Note that they are vectors (speed and direction) not just numbers. $V_{wind}$ can be named as drift velocity.

$$\overrightarrow V_{ground}=\overrightarrow V_{uav}+\overrightarrow V_{wind}$$

If the wind direction is opposite to the plane direction its ground speed, at the stall limit, is smaller than the UAV limit. It can be zero (the plane seems stand still) or even negative (plane seems to reverse).

Side notes: $V_{uav}$ is The velocity a pilot cares the most, $V_{ground}$ is the velocity his manager cares. This wind effect is also the reason why flying wit tailwind is preferred by airlines - they spare fuel - and it is also the reason why takeoff and landing is preferred in headwind - you need shorter runway to start/land sucesfully. With tailwind the runway may not be long enough.


What are the differences in aircraft performance between tractor and pusher propeller designs?

Well one major difference is the blade pitch, pusher props will seem to be backwards.

You must also modify the engine's bearings to be able to support the propeller mounting and crankshaft in compression, rather than tension.

A pusher prop's engine also has to be cooled differently than a tractor, because the propeller is not blowing air over the engine. Therefore some ducting and ram air magic has to be done, or some other system of cooling implemented. Many pusher-type planes have had severe issues with cooling.

Note: some of the next few might not necessarily apply to pusher-type planes where the engine is mounted above the fuselage, like the Lake Amphibian and many other seaplanes, or some other oddities like the B-36. I am talking about more conventional pushers like the Velocity, Beech Starship, or Cessna 337.

Another issue is FOD. A pusher prop will likely be mounted behind at least one of the wheels, which can kick dirt and rocks up into the propeller. Now imagine a prop that is very close to one of the mains. Even on paved runways you encounter rocks and debris occasionally, and it only takes one hit in the right place to produce a failure-causing nick.

Compounding on that last one, when a tractor-type plane takes off, beacause the prop is forward of the center of mass, the propeller will rotate up, away from the ground. But a pusher prop is usually just the opposite: it will rotate down a bit, increasing the chances of a prop-strike. This is one that is heavily considered and worked-around while building pusher-type planes, but while you can mitigate the danger by placing the prop closer to the CM, or making the landing gear taller, you can't completely remove it as far as I know.


Is there a rule of thumb to choose an aircraft for long-haul operations?

Because airplanes are incredibly expensive, using a "rule of thumb" would be extremely foolhardy.

A detailed analysis, likely laid out on a spreadsheet, would be much more appropriate.  You did hit on many of the major points, which also include:

Aircraft Range
Passenger Capacity
Speed
Crew Costs
Fuel Consumption
Cost per hour
Other costs: Insurance, Maintenance, and Leasing
Runway and Weight limitations
FBO services available

Obviously, if a candidate plane cannot fly the desired distance (perhaps limited by range, ETOPS, altitude or runway at takeoff or arrival), then you can't use that plane.  If a candidate plane cannot carry enough pax or cargo, then cross that off.

But once you have planes that can actually complete the mission, then its down to a complex matrix of costs, speed, time, and other benefits, and is a maximization problem without a precise answer.  (Some people will value speed above all else.  Some will value comfort and amenities.)


In quotable literature, I recommend „Aerodynamic Design of Transport Aircraft“ by Obert. In other useful stuff, there is a very useable (but not proven by Boeing) aerodynamic model of a 787 available on the Piano X website.

I‘d add that for any really useful analysis other than level flight, getting hold of a decent engine model giving maximum and minimum (net) thrust as well as fuel flows throughout the operating range will, in my experience, prove much harder than the aerodynamics...


How do rocket engines produce more thrust than aircraft jet engines?

For one, don't only look at the engine, but at the whole propulsion system. This includes tanks, piping, controls, pumps and the actual engine. Now the rocket looks much less favorable, especially if you size the tanks for equal running times.

The rocket does not need any of the parts which are ahead of the combustion chamber of a jet and also does not need the turbine. Also, being designed for full thrust only, it does not need an adjustable nozzle. Please look below at the engine installation of a typical airliner (I tried but could not find a fitting cross section of a turbojet plus intake):

Jet engine and nacelle cutaway drawing (picture source). As @Talisker correctly observed in the comments, the labels "high speed jet" and "low speed jet" have to be swapped in order to be correct.

Only the part labeled "combustor" and the section aft of the turbine are actually comparable to a rocket engine - all else is needed to condition and compress air or drive the turbo machinery in front. A rocket enjoys the luxury of being fed propellant and oxidizer at just the right ratio, condition and at high pressure, and since the oxidizer is mostly pure liquid oxygen, the turbo pumps for compressing it can be much smaller than the turbo machinery of a jet which works with an 80% nitrogen - 20% oxygen mixture of gasses.


Why does the A320’s maximum allowable aileron deflection decrease, rather than increase, when the flaps are extended?

You assume that

  the lower attack angle of the unflapped, aileron-containing portion of the wing should allow the ailerons to deflect further without stalling.

but that only looks at the geometric angle of attack. What counts, however, is the induced angle of attack. Since the flaps on the inner wing create much more lift, the induced angle of attack is much higher than for the clean configuration at the same geometric angle of attack. Consequently, the outer wing will stall at a much lower geometric angle of attack, and adding trailing-edge-down aileron deflection will stall the outer wing with only a medium angle.

Add to this that the spoilers are much more effective for creating rolling moments once the flaps are deployed and will avoid the adverse yaw of an aileron deflection due to their high drag on the down-going wing, and the spoilers are a much safer option for roll control that the ailerons are in landing configuration.


What dictates the aspect ratio of an aircraft's wing?

Now I am going to commit a heresy, but keep reading to get an explanation:

Increasing the aspect ratio of a wing will not change its induced drag. Increasing the span will.

The induced drag coefficient of a wing is $c_{Di} = \frac{c_L^2}{\pi\cdot AR\cdot\epsilon}$, and this seems to indicate that a bigger aspect ratio AR would lower the induced drag coefficient $c_{Di}$. But only at the same lift coefficient $c_L$!

Now let's look at the real numbers and compare two wings of the same span, but different aspect ratios. For simplicity, wing 1 has an AR of 5 and wing 2 has an AR of 10. Let's further assume that both wings have the same mass. Since both wings have the same span, wing 1 has twice the wing area of wing 2. To create the same lift, wing 1 needs only half the lift per area than wing 2! This means its $c_L$ is only half as big as that of wing 2, and now lets look at the induced drag again: $D_i = q_\infty\cdot S\cdot c_{Di}$

Wing 1: $D_{i_1} = q_\infty\cdot S_1\cdot\frac{c_{L_1}^2}{\pi\cdot AR_1\cdot\epsilon}$

Wing 2: $D_{i_2} = q_\infty\cdot S_2\cdot\frac{c_{L_2}^2}{\pi\cdot AR_2\cdot\epsilon} = q_\infty\cdot 0.5\cdot S_1\cdot\frac{4\cdot c_{L_1}^2}{\pi\cdot 2\cdot AR_1\cdot\epsilon} = D_{i_1}$

If both have the same span efficiency $\epsilon$, both have the same induced drag at the same lift. To reduce induced drag requires a span increase, regardless of aspect ratio.

However, a higher aspect ratio wing does have advantages:

Lower surface area means less friction drag
Lower surface area also means less mass, at least at moderate aspect ratios.
Smaller pitching moments, requiring a smaller tailplane

but also disadvantages:

Less internal volume for fuel or the landing gear
Needs more complex high lift devices for the same landing speed

In the end, the wing chord is chosen to minimize wing mass and to yield the minimum required fuel volume, and the aspect ratio is just a consequence of the selected wing span. Driving wing mass down is also reducing induced drag, and the $\epsilon$ of modern airliner wings is only 0.75 to 0.8, which shows how little importance the induced drag coefficient has for finding an overall optimum.


Do you have to explain what your emergency is?

The order is "Aviate, Navigate, Communicate".

As a pilot, your first responsibility is to keep the plane flying. After that it is to avoid hitting something or to avoid getting lost. After that comes communication. There are many instances of in-flight emergencies where the pilots never talked to anybody about it, because they were busy flying the plane...

  According to FAA, is it required to detail/explain (maybe file some kind of official document) your emergency to some kind of authority?

The FAA has many procedures on reporting accidents, incidents, and emergencies. Whether or not you report it depends on what the emergency was. If its a very sick passenger, there may be no reporting required. If your control cables failed, you are required to report it. I'll update this answer with the regulations as soon as I find them all. Quick answer is any time you declare an emergency or "PAN-PAN", call the FSDO and let them know. Also depending on the nature of the accident/incident, you may be required to immediately notify the NTSB. See CFR 49 830.5

  If you do have to file an explanation, what information do you have to supply?

This depends again on the nature of the emergency, and the FSDO/NTSB will ask you for the proper information when you file the report. At the very least they are probably going to want a narrative of what happened, and depending on what took place, you may want to contact your lawyer first. (Note: You may have to contact the NTSB immediately but it doesn't say you need to provide details, just that there was an incident, so the NTSB would be your first call "I had an incident", short and sweet, and the lawyer second.)

  Also what would happen if they "didn't believe" that situation was an emergency?

Its not ATC's responsibility to determine if you are lying or not. When you as a pilot say "emergency" you have their full attention. After you get on the ground and the emergency turns out to be you forgot to call your girlfriend/wife and wanted to get ahead of other traffic, then the FAA will get involved. Until you are on the ground, an emergency is handled as priority, regardless of the reason.

Here you can read a good story about a stupid pilot who abused the "emergency" system by landing on a public beach in New York because of an airsick passenger and an engine that was "running a teensy bit rough". He didn't officially declare an emergency, and I can't find any record of official enforcement action against him for doing that. Note the NTSB did not investigate this "incident".


When flying VFR without GPS, how do pilots know if they are inside controlled airspace or not?

VFR aviation maps called "sectionals" (and now GPS map displays) depict the types of airspace through borders with different colors and dashed lines. You can buy or download the maps for free from this FAA site.

It is always the responsibility of a pilot to know where they are and follow all applicable laws. In the US, a pilot that breaks a rule because they didn't check NOTAM's can expect certificate action. NOTAM's will inform the pilot of TFR's, "hot" military zones, and other important regional and local (i.e. airport) regulatory information.

I got my PPL in 1975 and still carry maps with me. I plot an "X" along my route every 10min of flight time (20-30mi). As I reach each checkpoint, I follow a very old axiom, "Never.. Ever.. EVER!.. proceed to the next checkpoint until you identify where you are and what corrections are needed for the next checkpoint". In this manner, you can never be further than 1 or 2min and 1-2 mi from where you should be.

Even when sightseeing with no particular route, I routinely mark a map about every 10min with my location. In my 2500hrs of flying, the most I have ever been off  in my navigation was 10mi (even when flying 1500mi x-country). So, knowing where you are is not difficult if you practice the skill.

The front of the map has a legend to remind pilots what the coloring stands for.

Sectional map (US Gov public domain)

Front map legend (US Gov public domain)


How much thrust was provided by a typical Meredith Effect radiator?

Here they give a calculation for the thrust generated by a Meredith effect cooler. They do this for the P51 Mustang. It is also mentioned that in Aeroplane monthly, May 1999 (not accessible to me), the designer Atwood claims that the Meredith effects cooler generates 300 lbs of force.

They perform some calculations based on geometry obtained from  Gruenhagen's "Mustang. The story of the P51 fighter", 1969. These calculations also lead to number around 300 lbs (it calculates 270 lbs of thrust).
However, the calculations do not included the effects of the heating of the air whilst passing through the cooler (which is -according to me- a vital component of the way in which these coolers generate thrust).


What type of airspace is an Atlantic Low Control Area?

The Atlantic Low Control Area is a Class E area in international airspace, where domestic ATC procedures may be used for separation procedures.

Here are the relevant excerpts from FAA Chapter 19. Other Airspace Areas
Section 1. General

  Offshore/Control Airspace Areas are locations designated in international airspace (between the U.S. 12-mile territorial limit and the CTA/FIR boundary, and within areas of domestic radio navigational signal or ATC radar coverage) wherein domestic ATC procedures may be used for separation purposes.

and

  Class A Offshore/Control Airspace Areas are identified as “High" (e.g., Atlantic High; Control 1154H). Class E areas are identified as “Low" (e.g., Gulf of Mexico Low, Control 1141L)

The two parallel lines differentiate floors of class E airspace that is neither 700 feet nor 1200 feet AGL (Above Ground Level).


Where can I find the standards for airborne systems software design? Is there a central repository for this information?

Many of these are Radio Technical Commission for Aeronautics (RTCA) standards.
You can get these documents from the RTCA website. They are provided free of charge to RTCA members, non-members have to pay.

Alternatively you can acquire the European equivalents from EUROCAE (RTCA DO-178B is ED-12B in the EUROCAE eShop).

If you want to be up-to-date (for example if you're building a new avionics system), you should buy the latest version of the standard, such as DO-178C / ED-12C, which is the latest edition of your example above (published in 2012).


What could cause the APU on a Boeing 777 to fail and also trip the GPU?

Dispatching an aircraft with an inoperative APU, regardless of whether it's a passenger aircraft or a freighter, is a normal procedure. While an APU may be started inflight preparatory to it's use after landing, it is not needed inflight, so it's not a safety issue. In my experience (retired in 1999), dispatch of freighters with inoperative APUs is more common than dispatching passenger aircraft that way due to the passenger comfort aspect. Keeping passengers cool while unloading/loading is a priority. Keeping a freighter's crew comfortable is not.

An APU failing while in use is not unusual. GPU failure is also not unusual. If the APU tripped (as opposed to just quit) and the GPU tripped as well, a natural suspect is an electrical problem in the airplane. What is needed, of course, is a competent mechanic to troubleshoot.

APUs can fail for a number of reasons. They're just small turbine engines. In fact, for 747-100 and -200 aircraft, the APUs were often the same as the engines used for SA-226 and -227 Metroliners (with the addition of propellers of course) that I flew prior to flying 747s. Common causes of APU failure include overheating, loss of oil pressure, excessive load, and just plain mechanical breakdown.

The decision as to whether to dispatch a large airplane without an APU would be an economic one primarily. If you're sending the airplane to an airport that is known to have GPU power, it wouldn't make financial sense to delay the flight because of an inoperative APU. If, however, you're dispatching to an airport that doesn't have such, that would be unwise unless such an airport does have a huffer and you want to risk a battery start (never a good idea in my opinion).


You can find this information in the Airport Facility Directory which is published in print by the FAA and is available for free from them online here. REIL will be listed for the specific runway for the airport in question. For example I fly out of KDYL and if we take a look at the page in the AFD for KDYL you will see REIL listed for RWY 23

(source)


How can lift be less than thrust that is less than weight?

Your misunderstanding lies in your thought that lift is smaller than thrust, while in fact, lift is much larger than thrust.

The lift is provided by the wings. Their purpose is exactly to create a lift force (upwards force) while requiring relatively little thrust (forwards force). How well they do this is expressed by their lift-to-drag ratio (L/D ratio). A modern airplane can have an L/D of 20 or more. This means that for every newton of thrust, you can lift 20 newtons of weight!

You can think of wings the same way you think of an inclined plane: you need a lot less force to push a car up a gentle hill than up a steep hill. Indeed, if the hill is gentle, most people can push the car up the hill, while most people cannot single-handedly lift a car up. Wings work by pushing air down, and by pushing the air down at a relatively shallow angle (by going forwards real fast), you need less force to go forwards than to lift the plane.

If you want to know more than this 'intuitive' explanation, perhaps I can recommend you this answer of mine. I will present a terse derivation below, with the aim to calculate the L/D (neglection parasitic drag) purely from first principles.

Lift is due to a certain mass flow $\dot{m}$ being given a certain velocity $v$ downwards: $$L=\dot{m}v.$$ This mass flow is due to the wings encountering a certain amount of air; as an approximation, you can think that the airplane only affects a circular 'tube' of air with the diameter equal to its wingspan. The energy per unit of time (power) necessary to impart this downwards momentum equals $$P=\frac{1}{2}\dot{m}v^2.$$

This power is provided by the combination of thrust $T$ and forwards velocity, $$P=Tu.$$ This gives us an expression for the thrust: $$T=\frac{P}{u} = \frac{1}{2}\dot{m}\frac{v^2}{u}.$$ Note that the thrust $T$ equals drag force $D$, so we can now calculate the L/D:

$$\frac{L}{D}=\frac{L}{T} = \frac{\dot{m}v}{\frac{1}{2}\dot{m}\frac{v^2}{u}} = 2\frac{u}{v}. $$

In other words, like I said before, the L/D ratio is exactly how 'shallow' the relative velocity vector of the affected airflow is. It follows that the forwards speed $u$ should be as large as possible to maximize the L/D. However, I only took into account the so-called "lift induced drag" which is purely the horizontal force it takes to create a vertical lift force. In reality, there is also parasitic drag, which scales with $u^2$ and will at some point dominate over the reduction in L/D.


Can airlines choose whether or not to enable MCAS on their fleets, and if so, have US airlines chosen to do so?

No, MCAS was required for the 737 MAX to be certified by the FAA. It cannot be deactivated by any airline, including airlines in the U.S.

Source:

  "M.C.A.S. was necessary then for the airplane [737 MAX] to be
  certified by the F.A.A. to have met all of the regulatory design
  requirements for stability and control."

  https://www.nytimes.com/2019/02/03/world/asia/lion-air-plane-crash-pilots.html


Why is the A400M APU on the side of the fuselage instead of the back?

The A400M is designed to operate from unpaved surfaces.

With the RAT on top, this avoids FOD issues, and provides ground clearance.

For the APU, it's space and proximity. You've got the wing box above the fuselage, plenty of space to add things there. Also easier maintenance access. Proximity as in less wiring and tubing to run inside the airframe, saves on weight and complexity. And again FOD. The inlet would be away from the debris and dust the wheels kick up.

Source: gizmodo.com


What is the type of a SID that is neither RNAV nor RNP?

That SID is not an RNAV SID since it uses VOR/DME and headings for navigation. The FAA Aeronautical Chart User’s Guide simply refers to them as “non-RNAV SID’s”


How can I easily keep track of my landing count during pattern work?

The trick my CFI taught me is to use your Course Deviation Indicator or ADF to keep track of landings. After your first landing, bug a course of 010. After your second landing, bug 020. You can reach over and adjust the knob after every landing without having to juggle a pen and a notebook. It's still a manual step, though.
You could also use a product like Foreflight or CloudAhoy or even a service like ADSBExchange to count the number of approaches you made after the fact.


The fuel used by civilian airlines, fueled in the USA, is Jet A. To acquire some, go to a nearby airport which can handle operations by Turboprop or Turbofan aircraft. Some of the smaller airports, only supporting piston aircraft operations, may not be able to help you, but anything which can handle a Lear Jet should be able to supply you with examples of it.

There's no specific chemical formula for this. It is a mixture of a variety of compounds. And no, you can't isolate just one particular compound and use it as a representative sample. There are reasons for the various additives, and all of them will have SOME effect on the burn characteristics.

Try not to breathe the fumes, before or after combustion. Do not operate any kind of radio transmitter (including a cellphone) within 50 feet of the vapors of it (when the fuel is exposed to air, before or during combustion). Make sure that whatever vessel you're going to burn it in is metal (plastic doesn't respond well to burning petrochemicals :-) and make sure there is good electrical conductivity between the vessel and the ground. Have a large, CO2- or Halon-based (NOT water or dry chemical) fire extinguisher nearby.

When I was refueling F-16s in the Air Force:

no radio transmitters (walkie talkies, at the time) were allowed with 50 feet of refueling operation
the aircraft and the refueling vehicle BOTH had to be grounded and connected to each other BEFORE connecting the refueling line
no refueling ops were permitted if there was lightning within 5 miles
no refuelings ops were permitted without a 50-pound halon-based fire extinguisher and a dedicated person (fire guard) to man it

This should give you some idea of proper safety around this stuff.


At Airbus, the Natural Flight Loop is the set of the models that simulate the Natural
Aircraft behaviour: kinematics, mass, fuel, center of gravity, inertia, thrust, ground handling, ground reaction, slat/flap, aerodynamics.

Let me know if you need more info.


From a biological point of view, flapping wings is a viable means of flight. However, this presents some problems when scaled up for human flight.

One issue is the square-cube law: as the wings are scaled up, the area scales as a square (relating to lift), but the volume scales as a cube (relating to weight). This means the wings increase in weight faster than they increase in lift, resulting in less effective wings. The higher weight presents issues in making them flap.

ratchet freak pointed out that we do have such machines, and they are called ornithopters. Although there is some potential at smaller sizes (for small UAV's), the weight and force issue prevents them from being very useful at larger scales. Ornithopters were some of the first unsuccessful designs for heavier than air flight.

The best solution we have found is propellers. This doesn't work as well as biological propulsion, but it's much easier to spin a prop than flap the whole wing, and works much better for the larger scales we need to move humans. Flapping is also not effective for reaching higher speeds.

You can also see from the biological side that there is a size limitation. The largest birds are much smaller than our airplanes.


In regions and weather conditions where this is likely to be a problem, other fuels are used instead of Jet-A.

For example, Jet-B has a freezing point of -60C and is used during the winter in some parts of Russia and other very cold places.

For information about fuel freezing in flight, see this previous question/answer.


During the early design stages, what parameters are considered in determining the weight of an aircraft?

Any design starts with a mission profile. As a design engineer, you get the payload, range and speed, and maybe constraints like the maximum runway, and then have to come up with a configuration.

With that in hand, you look what others have achieved before. There are collections of weight data for different designs and their parts, and formulas which combine the main parameters in a way that the weights line up more or less nicely when plotted over the result of this equation. Plug in your new design's number, and you get something wich will be within ±10% of what is realistic. This is called parametric weight estimation (PDF!).

Since you can only consider what you have, you start with the boundaries of the sizing mission:

Payload
Range or endurance
Desired cruise speed and altitude
Operational constraints like runway length, operation from unprepared fields, threat scenario.

EDIT:

@Peter is right: Cost per kilo of airframe and per seat-mile (where applicable) is also a starting requirement, and cost minimization is taken care of by designing the smallest possible airframe which can satisfy all requirements while using proven technology. And parametric sizing only works when based on proven technology.


Are there any regulations about the distance between destination and alternate airports?

On an IFR flight plan, 14 CFR 135.233 requires

§ 135.223 IFR: Alternate airport requirements.
(a) Except as provided in paragraph (b) of this section, no person may operate an aircraft in IFR conditions unless it carries enough fuel (considering weather reports or forecasts or any combination of them) to—
    (1) Complete the flight to the first airport of intended landing;
    (2) Fly from that airport to the alternate airport; and
    (3) Fly after that for 45 minutes at normal cruising speed or, for helicopters, fly after that for 30 minutes at normal cruising speed.

Constraining from the other side, 14 CFR 91.169 requires

(c) IFR alternate airport weather minima. Unless otherwise authorized by the Administrator, no person may include an alternate airport in an IFR flight plan unless appropriate weather reports or weather forecasts, or a combination of them, indicate that, at the estimated time of arrival at the alternate airport, the ceiling and visibility at that airport will be at or above the following weather minima:
    (1) If an instrument approach procedure has been published inpart 97 of this chapter, or a special instrument approach procedure has been issued by the Administrator to the operator, for that airport, the following minima:
        (i) For aircraft other than helicopters: The alternate airport minima specified in that procedure, or if none are specified the following standard approach minima:
            (A) For a precision approach procedure. Ceiling 600 feet and visibility 2 statute miles.
            (B) For a nonprecision approach procedure. Ceiling 800 feet and visibility 2 statute miles.
        (ii) For helicopters: Ceiling 200 feet above the minimum for the approach to be flown, and visibility at least 1 statute mile but never less than the minimum visibility for the approach to be flown, and

The maximum distance for an alternate airport is limited by your aircraft’s fuel range, but practicality (not losing the purpose of the trip) will tend to be more constraining than math. The minimum distance depends on the weather.
Considering it from this perspective, given that the objective is safety, stipulating “at least X but no more than Y units of distance” would be inappropriate for similar reasons as to why we tend to think of fuel in terms of time rather than length.


Why does the 1090 ES use the same frequency for both uplink and downlink?

It's a broadcast protocol - devices spontaneously announce themselves for listeners to hear. There are no interrogations to put on a different channel.


Why are the boundary layer suction holes placed far forward from the engine?

Ideally, the engine inlet supplies the engine with appropriate air-flow across the operating range of the aircraft while incurring a minimal loss in total pressure. Under supersonic operation, shocks form near the inlet lip. The shock wave boundary layer interaction (SWBLI) thickens the boundary layer around the shock, develops an adverse pressure gradient, and increases total pressure loss. Boundary layer suction is used to prevent further pressure losses from flow separation due to the adverse pressure gradient. So, suction removes low-energy air to help control SWBLI near the lip and subsequently improve inlet pressure recovery.

From (Titchener 2013) specifically relevant to the SR-71:

  In inlets where there are multiple SWBLIs distributed suction is often employed. Fukuda et al. (1977) suggest that a major reason for this lies in the complexity of these inlets which leads to a heavily iterative bleed system design. In such a case, a model with a large number of distributed holes that can be easily switched on and off helps to lead the design to optimal solution more quickly. Consequently, the complex mixed compression inlet system on the SR-71 (see Smeltzer et al. (1975)) and the Boeing/NASA SST inlet (see Tjonneland (1971)) both utilize substantial areas of distributed suction. As do the F-4, F-14, and F-15 which have multiple compression ramps on which distributed suction was deemed necessary.

The following are good references for further reading (included the thesis since the first link requires access to AIAA papers):

R.K. Scharnhorst, An Overview of Military Aircraft Supersonic Inlet Aerodynamics, AIAA 2012-0013, 2012.
N. Titchener, An Experimental Investigation of Flow Control for Supersonic Inlets, Ph.D. thesis, University of Cambridge, 2013.


What does "Controlling Object" mean in FAA documentation?

'Controlling object' is, as far as I can tell, the old term for 'controlling obstacle'.

From the TERPS manual (Appendix B):

  Controlling Obstacle. The obstacle on which the design of a procedure or establishment of a minimum altitude or angle is based on. See also Order 8260.19, Flight Procedures and Airspace.

Controlling object is mentioned as a field in the Public Use Airport Runways database:

Attribute_Label: BE_CTL_OBJ
Attribute_Definition:
Description of the controlling object at the base end of the runway
(e.g., trees, bldg, fence, none).
Attribute_Definition_Source: FAA
Attribute_Domain_Values:

And as you can see, it can be trees, a building, and so on.


What happens when the velocity of the lower surface of the airfoil is lower than the velocity of the free stream?

Local pressure will rise above the freestream pressure. Speed and pressure are linked, as expressed in Bernouilli's principle. Also the local temperature will rise, as expressed in the ideal gas law.

Note that at all angles of attack there is one point where the local flow speed will decrease to zero in 2D flow: This is the stagnation point. On wings in three dimensional flow this becomes a stagnation line, and swept stagnation lines still have some residual flow speed, but in all cases the local speed is below the free flow speed at and around the stagnation line.

Since lift is proportional to the pressure difference between the upper and lower side of the wing, this slowing down is welcome. Another beneficial effect is the lower wall friction of the slower flow. However, the thicker an airfoil is, the higher will be the flow speed on both sides, due to the displacement effect of the thicker airfoil. Thinner airfoils are structurally less efficient, so a compromise needs to be found which allows enough internal structure while keeping thickness reasonably low.


What are the specifications of the General Electric J85 engine compressor?

That's probably going to be beyond the scope of most on this board.  If you really want an answer to this, I'd contact Thornton Aircraft Company in Van Nuys, CA (http://www.thorntonaircraft.com).  They deal in sales and maintenance on old T-38s and F-5s as well as do type ratings in the jets.  They are intimately familiar with the J-85 power plant and could probably supply you with that info.


Are there roll control devices other than ailerons?

Yes, that will work. If the entire wing tip pivots, it simply acts as an aileron that takes up the entire chord of the wing.

Other alternatives to ailerons include:

Weight shifting. If you can shift the aircraft's center of mass left and right a significant amount, thus will cause the aircraft to roll in the same direction. This is how hang gliders turn.
Wing warping. Essentially the same thing as ailerons, but accomplished by bending or warping the wing rather than by pivoting a hinged piece of the wing. Early Wright aircraft did this, but I don't know of any modern aircraft that do. (Birds probably do this, too.)
Roll spoilers. By deploying a spoiler on just one wing, you'll cause the aircraft to roll in the same direction. Some airliners do this some of the time.
Sliding the wings left and right. Okay, I admit that I don't actually know of any aircraft whatsoever that do this. But if you were to slide an aircraft's wings left or right, that would cause it to roll in the opposite direction.
Cyclic pitch control. Only rotary-wing aircraft (such as helicopters) can do this. The rotor blades can be configured to change pitch depending on where they are in the cycle, and this can produce a roll. Cyclic pitch control is the main way that helicopters are controlled.
Yawing and using the dihedral effect. An aircraft doesn't actually need any roll controls at all if the wings have a significant dihedral angle. Instead, you can roll the aircraft by yawing it into a sideslip; the dihedral effect responds to the sideslip by rolling the aircraft. A lot of RC aircraft use this method, as does at least one ultralight aircraft, but it's not a great way to go, because sideslips produce drag, and they can produce a "snap roll" in the event of a stall.


Why do extra flight crew members sit in the cockpit during takeoff/landing?

There'a a few reasons for this:

Safety:
During takeoff and landing, everyone should be buckled into a secure seat. They have these seats in the cockpit, and in large aircraft, they're actually very comfortable. Laying down in a crew bed would not be allowed during takeoff or landing (though it happens, off the record). Do note that these beds do indeed have belts that are similar to those on rolling hospital beds, but it's not intended that these be used during takeoff or landing. It would be very difficult to escape the small confined space of the crew bunks during an emergency. Though some crew areas have seats, these are typically not "safe" seats, and they are only meant for resting on while in level flight.

Redundancy:
If something goes wrong with one, or both, of the pilots flying, you would really regret letting the other two qualified pilots go lay down in the back of the plane. Safety comes first in aviation, and the pilots are there to support each other.

Extra Help:
Extra crew sometimes helps the flying crew, whether that be by looking up information, radio frequencies, airport identifiers, and so forth.

Socializing:
Pilots are (usually) pretty friendly to each other. They all share a common interest, and while some of the older pilots may be a bit grizzled, they all got into aviation for their love of aircraft. There's typically some pretty lively conversations in the cockpit. As noted in the comments, this is while on the ground, pre/post taxi. Even during flight operations, additional pilots may be in the cockpit assisting with spotting traffic, birds, and so forth. Conversation is limited somewhat during taxi, takeoff, landing, and all other flying activity below 10,000ft (or until at cruising altitude, if cruising altitude is <10,000ft),


Can a helicopter like the R44 be lifted up by his rotor head?

Yes, but you better know what the heck you are doing. :) Whether an individual helicopter can be lifted this way is a different question. You'd have to look at the maintenance manual for the individual aircraft for the answer.


What is a "Land And Hold Short Of" light?

It's an in-pavement (flush) light bar that indicates the hold-short for the LAHSO operations. See: What is a land and hold short clearance (LAHSO)? For the FAA they are:

  FLASHING L-850A OR L-850F LIGHT FIXTURE (Source: AC No: 150/5345-54B)

A single L-850F unit in the light bar looks like this:

(adbsafegate.com)

(FAA AIM) The light bars are located as indicated by the blue arrows.

I tried to find a video to show the pulsating white light at night when in use, but I couldn't find any. By checking Boston Logan (KBOS) on Google Earth, and zooming in at where the LAHSO hold-short lines are, the flush light fixtures can be barely seen:


How can the Cirrus Vision jet be cheaper than its competition?

I read an article on the SF-50 recently published in AOPA Pilot and, to be honest the Cirrus Jet is not even in the same league as the other aircraft mentioned.  People think 'oh it's a jet for $2 mil - I want one' but remain fairly ignorant of exactly what that means compared with other jet aircraft.

The primary differences in performance between the Cirrus and other light jet aircraft is that it's much slower and suffers from 'short legs'.  Depending on payload, the Vision has about at 600 NM range at its max cruising speed of 300 KTAS, burning a stiff 84 gallons/hr.  It sounds enticing to an SR-22T owner looking to upgrade, but consider that high end turboprops like the TBM-9XX are leaving you in the dust by at least 20 knots and using 40% less fuel to do so.  Ranges of approx 1200 NM are possible, depending on payload, but at an economy cruise of 240 KTAS, making it faster than the owner's old SR-22T but slower that nearly all turbobprops and probably more expensive to operate.  The Vision is also not RVSM certified, limiting operations to 28,000 ft.  As a yardstick for comparison, an Embraeer Phenom 100 with a similar sized cabin, at roughly twice the cost of a Vision is capable of over 400 KTAS (Mach 0.70) at FL410 with an 1100 NM range with alternate and IFR fuel reserves.

Ther are other items that aren't immediately visible but play an important factor in the cost difference, chiefly cabin environment.  The Vision's pressurization isn't on par with similar jets, probably being limited to a 5-6 psi cabin differential, yielding around an 8,000 ft cabin altitude at 28000 ft.  The Cirrus is spacious compared with an SR-22 but it's nothing impressive when it comes to light jets and it's not even in the same league as larger jets.  Many of the systems do not have the creature comforts of the big boys e.g. The Cirrus still uses a castering nosewheel as opposed to NWS equippped on most jets, etc.

The Cirrus represents a solid, if somewhat expensive, upgrade from the SR-2X aircraft.  Just don't expect it to be a personal 747; it's not and you do get what you pay for.


Approximately what percentage of aircraft are equipped with RNAV?

Use of RNAV began in late 1960’s . Some airlines began exploring RNAV systems

KLM/SwissAir/SAS/UTA had a cooperative effort
Swissair became responsible for the development of a database to
support this effort

In June 1973, National Air DC-10 equipped with Collins ANS-70 conducted RNAV operation, including approaches in VMC, with database.

In January 1983, the Federal Aviation Administration revoked all RNAV routes in the contiguous United States due to findings that aircraft were using inertial navigation systems rather than the ground-based beacons, and so cost-benefit analysis was not in favor of maintaining the RNAV routes system.

RNAV was reintroduced after the large-scale introduction of satellite navigation.And, since 1990 it is there in almost all the planes you see.
So, as a rough estimate it would be more than 90%. Because, most of the pre-1990 planes have either been upgraded or grounded.

Sources: Wikipedia, Federal Register, This Article.


Can pilots change the callsign shown on tracking websites mid-flight?

Yes, a pilot can change this in-flight, just as they would have entered the data when on the ground before the flight.

On the A320, this is done from the FMGS (Flight Management and Guidance System). To do this, the pilot presses the DATA key on the MDCU (Multipurpose Display and Control Unit) keyboard. This brings up the following display:

And then selects the A/C STATUS page, which allows them to change the code (call sign/flight number):

This can be changed in flight by the pilots at any time. This information is sent to the ADS-B and other data-link systems that show up on radars and ultimately sites like FlightRadar24.


Why did the DC-3 have a much higher cruise speed than the HP.42, despite their similar weight and power?

Struts every which way, uncowled engines, wheels with fenders hanging out, wires, bits sticking out here, bits sticking out there, corrugated skins, fabric wings and tail... it's a mess; a flying Truss Bridge.  There's just too much to try to quantify it like that.

You could probably take a DC-3 and start adding all those things one at a time, and each item would knock off 10-20 kt, and eventually you'd end up down at 87 kt, but the slower you get the smaller each accumulative penalty would be.


Is there a way to code Minimum Enroute Altitude using ARINC 424 file format?

As the name suggests, MEA is coded for enroute segments lik ethe airways (ARINC permits this).  In so far as Instrument Approaches are concerned, the templates takes into account vertical clearances in Primary and secondary areas and then arrives at safe heights at each segment. Geometry of primary and secondary areas and the clearance therein depends on types of approach. For example, in ILS approach, half full scale deviation is considered safe. Also, it stems from this, obstacle clearance at different segments of the approach would be differen, so, specifying a minimum altitude may not be applicable. Secondly, in emergency, Minimum Sector altitude (MSA) centered 25 nm around airport/nav aid provides requisite obstacle clearance..


Are there planes that can fly without wings? How would a plane be able to fly without wings?

There is a certain class of aircraft that are lifting bodies, which do not have wings but instead rely on airflow over a peculiarly-shaped fuselage to generate lift. However, this method is very inefficient and requires high airspeeds to make enough lift to support the plane. This means that the plane would have to carry an enormous engine to propel it, and its takeoff and landing speeds would be very high.

Several experimental lifting-body planes were built and flown as gliders ~50 years ago for research purposes, and a search on lifting body will furnish you with more information on them.


How do changes in flight affect L/D max and the speed at which I must travel to maintain it?

The best way to fly a constant L/D max is to have an angle of attack indicator.  Otherwise you would be constantly re-calculating the best speed as you burned fuel and changed weight.  Because most most GA aircraft don't have AOA, and are not too dramatically affected by changes in weight, max range and max endurance are generally expressed as an airspeed.

For a constant L/D max AOA, airspeed would actually decrease as the plane got lighter.  Think about the fundamental forces acting on the aircraft - lift is produced by a combination of airspeed and AOA.  If AOA remains constant, less airspeed will be required to produce the lift needed to counter the weight as the airplane gets lighter.

The reverse is true of course, if you are flying a constant airspeed you would need to gradually trim nose down to a lesser AOA as the aircraft gets lighter to prevent it from climbing.

Regarding speedbrakes, they add drag so if you want to speed up you would not extend the speed brakes.  Speedbrakes are used to slow down, or to maintain a given airspeed at a higher power setting to improve throttle response and go around capability (upon retraction) during approaches.


Is this a wing-tip device on the A-10 "Warthog"?

The wingtip devices used in A-10 Warthogs are called drooped wingtips (also called Hoerner wingtips in some cases), which essentially increase the aspect ratio of the wing by forcing the vortices further out.

Source: zenithair.com

There are a few reasons for having this wingtip device:

The drooped wingtips act in a manner similar to the winglets and reduce the induced drag. As a result, the loiter capability of the aicraft, an important one for Close Air Support (CAS) aircraft, is improved. The A-X competition, that lead to the A-10 develpment, required the aircraft to have Two hour mission loiter time at max mission radius with 9,500 lbs payload
The drooped wingtip increases the local span loading near the wingtip, due to which the aileron response is improved, increasing the manuverability at low altitudes. The A-X competition required the aircraft to be Highly maneuverable below 1,000 ft
The drooped wingtips also improve the takeoff performance, an advantage as the aircraft is expected to be operated from short, forward fields. Infact, drooped wingtips are found in STOL kit of some aircraft, like DC-2 Beaver. One of the requiremens of the A-X competition was that the aircraft should have 4,000 ft takeoff distance at MTOW.

As can be seen, the drooped (down) wingtips wingtips serves these purposes.

There seems to be some confusion regarding the reason for these wingtip devices. One theory (@Peter Kämpf) is that they are there to protect the ailerons from ground contact. However, I think this is unlikely, given the ailerons, when extended, go well beyond the wingtips, as shown below:

Source: scienceforums.net

Dropped down wingtips do serve that purpose (sometimes) in gliders. However, there is no reason to believe that is the case here, considering the height above the ground and the aspect ratio. The drooped wingtips, on the other hand serve to hold the countermeasure system.

Source: rcgroups.net


Need some help with a seemingly simple question

Try this: (a small amount of rounding, not considering instrument error -basic)

Speed = Distance x 60/Time (in minutes)

Speed = 155 x 60/83(minutes)

Speed = 112 nmh

Speed of 112 nmh consists of 100 kts TAS and 12 kts Tailwind.

Then, TAS = 100 kts.


According to worldmilitair.com (.pdf), serial E8557 was assigned to an Airco DH.9A, a light bomber used by the newly formed Royal Air Force starting in the final months of World War 1.

Source: Wikimedia


Has anyone been able to verify ADS-B works without radar?

I can confirm that ADS-B works without radar. I have been involved in several ADS-B trials in areas where there was no or only partial radar coverage. It works. No surprise, it has been designed that way.


What information am I legally required to provide during a FAA ramp check?

AOPA has a good article on this topic:

You're required to present pilot and medical certificates (plus logbook if required for flight)
The inspector may not detain you
The inspector may not board the aircraft without informing you

But an inspector is authorized to check the following items:

The airworthiness certificate
The aircraft registration
The operating handbook
The weight and balance information
The minimum equipment list (if applicable)
Aeronautical charts (if applicable)
The general airworthiness of the aircraft
The ELT battery
A VOR check
The seats/safety belts.

In general, saying as little as possible seems to be a good plan:

  If the ramp check is due to a possible violation, anything you say or
  do may be used against you.

  If you have enrolled in AOPA's Legal Services Plan, call AOPA's Pilot
  Information Center at 800/USA-AOPA immediately. The consequences for
  even minor infractions can be far more serious than you might think.

As for a search warrant, a ramp check is an FAA administrative process, not a law enforcement action. The issue of law enforcement checking private aircraft is a hot topic currently and AOPA provides a checklist in case you are stopped for search. Their recommendation is to refuse the search (unless they have a warrant, of course) but not interfere if they go ahead and do it anyway.


Does the NTSB and other investigative agencies charge airlines for investigations?

In the United States, no, the airline does not pay the NTSB or the FAA for accident investigations. This is considered a public service and is paid for by tax funds.

That doesn't necessarily mean that they won't pay for anything. For example if the NTSB has to remove wreckage to examine it, they will often have the insurance company pay for the removal and transport. This is especially true in GA investigations where the responsibility for moving the wreckage (after the NTSB says so) is up to the owner/their insurance.

Whether or not Boeing/Airbus/XXX charges airlines would be another matter that is probably outlined in contracts between the airlines, the aircraft leasing company, and the manufacturers.

Note that NTSB may involve any number of parties, for example they would have Boeing for the airframe, GE for the engines, Honeywell for the avionics/sensors, and representatives from other companies/groups (like the Airline Pilots Association) as they see fit. NTSB has manufacturer representatives for the bigger parts, and may ask for additional help from other smaller providers. This is done under the NTSB "party system" which is by invitation and does not compensate the parties for participation.

So as far as accident investigation goes, no, airlines/manufacturers don't pay for that directly.


This answer is specifically for a fixed-wing airplane, not a helicopter or multicopter, although some aspects of it will apply to them too.

What is a turn?  A turn is a curvature in the flight path.  This means a turn is a form of acceleration.  Specifically, a centripetal acceleration-- the flight path is being continually "bent" toward the center of the turn, creating a circular path.

Newton's second law is force = mass * acceleration, or acceleration = force / mass.  You can't have an acceleration unless you are exerting a force to cause that acceleration.  You can't have a centripetal acceleration unless you are exerting a centripetal force-- a force vector pointing toward the center of the turn.

What part of an aircraft is designed to produce force as efficiently as possible?  The wing.  If you roll the aircraft into a bank, you tilt the wing's lift force to one side, and you've now a created a centripetal force as efficiently as possible-- i.e. with the least drag possible.

Instead of banking, you can also turn by yawing the fuselage sideways relative to the flight path to expose the side of the fuselage to the airflow.  Essentially this makes the fuselage act as a sideways wing, generating some sideways lift or "sideforce".  This method also points the thrust vector from the engine or engines sideways relative to the flight path.  So this method will create some centripetal force, but it is very inefficient-- drag will be very high.  It will also be uncomfortable for anyone in the plane as they will tend to be thrown against the "upwind" side of the fuselage.

Note the difference between causing or allowing just enough yaw rotation to let the nose track around the horizon and "keep up with" the changing the direction of the flight path as the flight path curves due to the centripetal force generated by the banked wing, and forcing the nose to yaw to point in a different direction than the aircraft is actually travelling through the air at any given instant, as would be required if you were trying to turn without banking at all.

A car on flat ground can turn without banking fairly efficiently but that's only because the tires usually grip the road quite well, so it only takes a very small sideways angle between the alignment of each wheel, and the instantaneous path of travel of that part of the car, to generate a strong sideways force.  So you don't scrub off a lot of energy due to excess drag.  Very different from dragging a fuselage sideways through the air at a large sideslip angle.

A good source for starting to learn about the basic physics of flight is John S. Denker's "See How It Flies" website .  On second thought, this website is not so much designed to introduce a complete novice to the basic principles of flight, as to help someone with some flying experience and training understand the "why" of it all on deeper lever than some pilots ever manage to reach in a whole lifetime of flying!


Is the Meredith effect utilized in the cowling design of air-cooled engines?

The Meredith effect is to recover radiator drag by using engine heat for thrust, just like a jet engine.  It worked very well in the P-51 Mustang, actually adding a few knots of airspeed.

It also would work well with any source of heat, including a nuclear reactor, so yes it would work with aircooled engines.

The issue is drag from the radiator.  Aircooled radials have much greater frontal drag, so it worked, just not as well.  Efforts to reduce drag in the B-36 bomber resulted in roasted engines, particularly the rearward banks of the "corncob" R-4360 radial.  Overheating is a major concern, as is drag.  Engineers try to find a good balance.


How long are modern variants of the F-16 expected to be in production?

An article last month in the Greenville News about the relocation of the F-16 production line provided this comment:

  The Trump administration fast-tracked a $1 billion F-16 deal with
  Bahrain, Navarro said. Deals closed or on the verge of closing since
  then guarantee the plant in Greenville will stay busy at least through
  2025 and likely much longer, he said.

The "likely much longer" will be based on future sales (and Government approval of those sales.) It's a good plane at a competitive price, but a change in the marketplace could mean it ends after this contract build.


What would non-potable water be used for on an airliner?

Aircraft travel in countries were pathogen bacteria or viruses are carried by insects which like to lay their eggs in stagnant water. Aircraft water systems must be designed carefully to prevent spreading diseases.

On a typical airliner like the Boeing 737NG, you won't find any non-potable water source that would contain chemically untreated water. Equipment is fed from the potable water tank. Used water is either dumped overboard or stored. From the aircraft familiarization manual, the water system:

and the toilet waste system:

Condensation water is a by-product of many systems cooling air (including by expanding it). This water is collected and drained overboard. Jet engines (including APU) are the main generators of water, as fuel combustion generates essentially water (in mass) and CO2.

It's worth noting that at cruise altitude, moisture in atmosphere can be insufficient for humans well-being. The water extractors present in air-conditioning packs then reincorporates a part of extracted water into conditioned air.


Why is FAC 1 cycled OFF to ON during a dual engine failure?

Resetting FAC 1 enables the recovery of characteristics speed displayed on the PFD.
  Resetting FAC 1 also enables rudder trim recovery, even if no indication is available.
  When the hydraulic power is lost, the right aileron is lost, and is in the upfloat position.
  Rudder trim may be used to compensate for this upfloating aileron.

This is from the QRH under 'ENG DUAL FAILURE'. That answers why FAC 1 is reset.

FAC 2 on the other hand (unlike FAC 1) is not powered by the emergency electric system, see § Flight Control System - Electrical Supply. And that's why you don't cycle FAC 2.

From the same section FAC 1 is not on a hot (stand by) supply, so after a power interruption it requires a reboot (my interpretation).

(Red highlight mine)

Do not use for flight.


How does the ADS-B compact position report NL() function work?

Compact Position Reporting (CPR) is a way of reducing the number of bits needed to transmit position whilst maintaining high position resolution (~5.1 meters for airborne encoding). Ordinary encoding would require 45 bits, but CPR uses 35 bits thus saving 10 bits. To do so, the world is divided up into a number of zones, both for latitude and for longitude and the position within the zone is encoded. Since transmitting the zone numbers would cost as many bits as that would have been saved a clever trick is used. Two types of encoding are used, each with a different number of zones. From the difference in zone coordinates between the two types of encoding one can determine which zone the aircraft is in. Therefore one needs to receive an even and an odd encoded message within 10 seconds from each other. Once the initial position decoding is successful every subsequent position message will give the updated position.

In CPR decoding, you first determine the latitude of the aircraft based on a pair of odd and even position messages received within 10 seconds from each other.

Latitude is always encoded in the same number of zones between the equator and the poles (15 for even encoding, 14.75 for odd encoding). Due to the roundness of the earth the numbers of zones used for longitude encoding depends on the latitude. Longitude even encoding uses 59 zones at the equator and only 1 at the poles. Odd encoding uses always 1 zone less, except near the pole where 1 zone is used like in even encoding. The number of longitude zones used for even encoding can be found by the $NL()$ function.

The transition latitudes, i.e. where the number of zones for longitude encoding change, can be calculated by the inverse $NL()$ function. This function can be used to create a lookup table of transition latitudes which is more efficient to use than the original $NL()$ function.

Without knowing anything about your implementation it is difficult to assist further, the formula is depicted correctly in your question. Note that input latitude is given in degrees, but the trigonometric function are assumed to work on radians hence the $\frac{\pi}{180}$ factor.

Edit: on further inspection I noticed a mistake in the formula: it should be :

$$
NL = int \left( 2 \pi \left[ arccos \left( 1 - { 1 - cos \left( {\pi \over 2NZ} \right) \over cos^2 \left( { \pi \over 180} \mid lat \mid \right) } \right) \right] ^{-1} \right)
$$

(note that the conversion from degrees to radians is corrected)

For those that really want to understand CPR coding and decoding in detail, you'll have to obtain a copy of RTCA document DO-260B or Eurocae document ED-102A (unfortunately they're expensive, I think about $700) and read Appendix A.1.7 and Appendix T.


What is the aircraft in the 'Be Altitude' album cover?

Its a Boeing 747 courtesy of Delta Airlines as per the album credits. Photo by Gerry Griffith. For the right amount of money its not that hard to take pictures in, on, or near jets.


Which country would employ foreign air traffic controllers?

As I know, Vietnam is one of the countries employing foreigners for the position of an air traffic controller.


Is it possible to overheat or damage the engine on an F-16?

Yes, you can overheat and damage an F100 or F110 engine just like any other jet engine.  It has mechanical and thermal limits that may not be exceeded.  And it often happens as part of high performance military flying, though it can make you very unpopular with your crew chiefs and inevitably with you commanding officers if you keep willfully exceeding the limits and damaging engines.

FADEC systems ie “power by wire” systems just use a computer to administer engine control commands based on pilot inputs.  They do not necessarily limit a flight crew from giving inputs that can exceed engine parameters.

Earlier engines were more finicky about this, in particular to exceeding hot section temperature limits or compressor stalls.  The F-14A with the TF-30 engines was particularly prone to compressor stalls and could be treacherous during critical phases of flight.  Improved intake diffuser, gas core aerodynamics, advancements in materials science and manufacturing plus improvements to fuel control units reduced the risks but did not eliminate them.


Is it normal to choose a left or right pattern based on the wind direction?

It is NOT normal to pick the pattern (right/left) based on crosswind.

As JScarry pointed out in a comment, "At a non-towered field you fly the published direction. If none is published, you fly left traffic. At a towered field you fly whichever direction they tell you."  That's how you pick the pattern.

  When you are flying into the wind you have more airspeed and if you suddenly turn out of the wind you lose airspeed and risk stalling

This is flat out wrong.

To prove this, find a day where the winds aloft are high, then practice flying constant bank angle circles at altitude while at Minimum Controllable Airspeed.  If your theory is correct, you should consistently stall whenever the nose of the plane is pointing downwind.  (Hint: it won't)

For a second experiment, on a day with a strong crosswind, watch your airspeed indicator as you make your first turn after take off.  Try turning both into the wind and away from the wind. (i.e., try both a left & right pattern).  The airspeed indicator shouldn't show any difference.

Once you are in the air, the only speed your wing cares about is airspeed.  The wing doesn't know if it's a headwind or a tailwind.


What are the minimum requirements for a student to solo a second make and model aircraft?

As long as your training has been done in the same category, class, and type as the aircraft you are switching into, the FARs aren't specific regarding repeat training required.  Instead, this will fall into the realm of flight school policy, and CFI judgement.

For example, if you are transitioning from a high wing to a low wing, or from manual to electric flaps, your instructor will need to ensure that you are safe and comfortable flying the new aircraft before signing you off to solo.  To the first question, it is almost a 100% certainty that you will at a minimum need to complete a presolo exam on the new aircraft to ensure that you know the systems, airspeeds, etc.

If the instrumentation and navigation equipment are similar enough you probably won't need to refly any cross country flights, but again this is at CFI/Owner's discretion.

You will, of course, need a new solo endorsement for the specific make and model.

And don't forget the most important piece, two weeks before your checkride YOU need to be comfortable in the aircraft you will take your practical exam in!  Don't short change yourself, push out the checkride if needed to make sure you are ready.

The best advice is to consult your CFI and/or the flight school chief pilot to put together a re-training/recovery plan to transition.  Good luck!

ADDENDUM:  I see in your profile that you are a CFI with 20 years of flying experience.  What gives?!  (downvote for what I perceive as deception...)


How much the Concorde secondary nozzle contribute to thrust?

This source suggests at subsonic speeds, the secondary reduces drag but doesn't contribute significantly to thrust.

  At all times below Mach 0.55 – on the ground, take-off and initial
  climb – the buckets are set to 21 deg., forming a ‘jet-pump’ gap at
  the nacelle trailing-edge. The high speed jet exiting from the primary
  nozzle draws-in atmosphere air from above and below the nacelle to
  eradicate a source of base drag that would otherwise exit between the
  nozzles.


DA40 fuselage static ports / G1000 not in AFM

I found the answer by further reading the AFM. On DA40's with an auto pilot installed, optional static ports may be added to the fuselage.


Why do some A320s have double-bogie landing gear?

Air India is the only carrier with that kind of landing gear in the A320 due to India's low pavement classification number back when those A320s were ordered. In other words, more tires distribute the load over a larger area.


What is the difference between ILS and VOR/DME?

Which one is better for carrying out approaches?
An ILS approach is more precise for two reasons:

The ILS localizer is more sensitive than a VOR radial, therefore providing more accurate lateral guidance.
The ILS has a glide slope providing vertical guidance. A VOR approach does not have any vertical guidance (although with a VOR/DME one can at least determine the exact point at which to start a CDFA (continuous descent final approach) and regularly crosscheck the altitude with the DME).

Why do pilots use VOR/DME when the ILS is a better option?
Pilots fly a VOR/DME approach when they are cleared for the VOR/DME approach by ATC. Why would ATC provide a VOR/DME approach clearance when the runway also has ILS? This is usually due to ongoing maintenance of one of the ILS antennas. When an antenna is not available, you obviously cannot fly the ILS approach (although it may be possible to fly a localizer approach, if only the glideslope antenna is unavailable).
A pilot can also request the VOR/DME approach for various reasons, e.g.:

It could also be that the aircraft is not equipped with an ILS receiver antenna and is therefore unable to fly an ILS approach, but at least for an airliner that would be quite unusual.

For training the specific approach type or to maintain proficiency (thank to StephenS for pointing this out).

Sometimes flying the VOR approach might actually be more convenient if the VOR approach has different approach transitions available compared to the ILS. In Jersey (EGJJ) for example, the VOR is not co-located with the aerodrome and therefore allows an IAF further to the east compared to the ILS approach, which begins at the NDB (which is co-located):


When a paraglider pilot applies brake on one side and maintains the brake pressure, why does the roll rate eventually come to zero?

In essence the question is "In a turn using brakes, when a paraglider pilot applies brake on one side and holds it indefinitely, why does the roll rate eventually come to zero?  Why must be substantial brake be applied just to maintain the bank angle in the turn?"

While turning using brakes1, to maintain the desired bank angle once it is established, paragliders do in fact typically require the pilot to maintain a substantial control input (brake pressure) in the same direction as was used to initiate the turn.  This is quite different from what we see in most conventional airplanes, and in modern hang gliders, but we do see similar dynamics in airplanes with lots of dihedral that lack ailerons and turn using the rudder or spoilers (examples-- "Gentle Lady" or "Radian" radio-controlled sailplane, Quicksilver MX Ultralight).  We also see similar dynamics in older hang gliders, where ample roll stability2 is created by  the highly swept shape of the delta or modified delta wing.  In many of these older hang gliders, additional factors contribute to roll stability.  These factors include a) some amount of dihedral, and b) a point of connection between the pilot's harness and the airframe that is well below the center of mass of the airframe, so that the resulting low CG contributes a strong stabilizing "pendulum effect" even when the pilot exerts zero force on the control bar.

For a basic description of paraglider turn dynamics, see this ASE answer -- How do paraglider controls work? . The answer explains how applying "brake" on one side modifies the lift vectors generated at various points along the arc of the wing in a way that generates a roll torque.

The present question is asking not what causes the roll torque into the turn when the brakes are applied, but rather why does the roll rate eventually drop to zero even with the brakes still applied. Clearly some aerodynamic force or torque is "trying" to roll the paraglider back toward wings-level.

The answer is that the turn involves some sideslip.  The aircraft is yawed to point slightly toward the outside or high side of the turn, relative to the direction of the flight path at any given instant. One cause of this sideslip is the simple fact that during turning flight, the outboard wingtip travels along a larger circumference and therefore must move through more air in a given unit time than the inboard wingtip, so it tends to experience more drag than the inboard wingtip.  The extra drag from the deployed brake on the inboard wingtip partly compensates for this, but not fully.  This makes the wing fly in an attitude where it is yawed to point slightly toward the outside of the turn relative to the actual direction of the flight path at any given instant.  In other words, the wing is constantly experiencing a sideways airflow component, toward the outside of the turn.

Notice that the arched shape of a paraglider wing exposes a tremendous amount of surface area to any sideways component in the airflow.  Ordinarily when we give an aircraft an anhedral geometry by lowering the wingtips in relation to the wing root, this interacts with any sideways airflow to generate a de-stabilizing roll torque, in the "upwind" direction, which in a slipping turn, would be away from wings-level.  This destabilizing roll torque component exists in the paraglider case too, but it is dwarfed by the stabilizing "downwind" roll torque caused by the fact that the center of area of the wing is so high above the CG of the whole system.  Since the wing is so high above the CG of the whole system, any aerodynamic sideforce generated by sideways airflow against the wing during the (slipping) turn will contribute a strong dihedral-like roll torque in the "downwind" direction, toward wings-level.  So will the wing's drag vector, because the glider is "pointing" a different direction than it is actually flying, and the drag vector acts parallel to the flight path.  Since these effects are both related to the fact that the CG of the whole system is located far below the center of area, they are sometimes collectively described as a "pendulum" effect, though we need to be cautious not the invoke the idea that the aircraft is somehow directly "feeling" the direction of the weight vector in a way that is not dependent on sideslip.3

So the answer to your question of why the bank angle does not continue to increase even when the brake application is maintained, is essentially this:

Turning flight in paragliders, as in many other rudderless aircraft, always involves some sideslip.
 The resulting sideways component in the relative wind acts on the center of area of the wing, high above the CG of the whole system, to generate a roll torque towards wings-level.

Here's one more nuance to consider in closing: we should note that when we initially apply "brake" in wings-level flight, the increased drag on the "braked" wing initially will "steer" (yaw) the glider into a skid in the intended direction of turn, so that the glider is actually pointing slightly toward the inside of the turn relative to actual flight path at any instant.  At this point the glider is "feeling" a sideways component in the relative wind toward the inside of the turn.  So at this point the interaction between the sideways airflow and the wing surface area, high above the CG, is actually generating a torque to help roll the wing toward a steeper bank angle.  Only once we establish a significant roll rate, and/ or
 a significant bank angle and turn rate, do we see the glider adopt an attitude where it is yawed slightly toward the outside of the turn, so that is "slipping" rather than "skidding".  (This answer has focused on how turning tends to cause sideslip; to read about how rolling also tends to cause sideslip see this section on adverse yaw from the excellent "See How It Flies" website.)  All the same can be said of an airplane with lots of dihedral that has no ailerons but rather uses the rudder for roll control-- like many radio-controlled sailplanes-- when we first apply rudder to enter a turn, we know the aircraft must be skidding, but as the bank angle increases and we settle into a steady turn at constant bank angle, we know the aircraft must in fact be slipping, even though we are continuing to hold some rudder input into the turn.  If the aircraft were not slipping at this point, the net roll torque could not be zero, due to the fact that the wing on the outside of the turn is moving faster through the air, and tending to generating more lift, than the wing on the inside of the turn.

Highly related -- Does "pendulum effect" apply to hang gliders or any aircraft?

Footnotes --

1 -- It is not the intent of this answer to suggest that a turn in paragliders is always, or typically, or ideally, accomplished using brakes alone with no weight-shift.  Weight-shift, where the pilot leans in the harness to rock his body to one side and load up one side of the suspension system and unload the other side, is another way to turn.  Both methods may be used in combination.  However the original question was focused on a turn carried out with the brakes, so this answer is as well.

2 -- This answer uses "roll stability" to mean a tendency to roll toward wings-level.  Other alternative terms might be used to avoid suggesting that the aircraft is tending to maintain a given bank angle, but "roll stability" is the phrase we'll stick with for this answer.

3 -- "Keel effect" is another term that is sometimes used to describe the stabilizing effect of a low CG position, though this is also somewhat problematic, for two reasons.  A) It would be better to call it the "keel weight effect", because an unweighted keel (think of a lightweight centerboard that may be raised or lowered at will) actually contributes a net hydrodynamic roll torque in the opposite direction during sideslip (sideways drift), tending to roll the boat in the upstream direction.  B) The righting effect of a heavy keel weight is actually not dependent on sideslip at all-- buoyancy creates a righting moment even when total velocity, and therefore sideslip velocity, is zero-- so we still have the issue that we were trying to avoid by not using the term "pendulum effect", namely that we'd like to avoid suggesting that a (non-buoyant, e.g. heavier-than-air) aircraft in flight can somehow "feel" the direction of the gravity vector and therefore "sense" when the aircraft is tilted away from level, even if sideslip is somehow completely eliminated by appropriate rudder usage or by any other means.

Addendum--

This answer has referenced a "skid" as the turn is first initiated with brake, and a "slip" once the turn is established.  This begs the question, "what about the roll torque created as the pilot's body tends to swing to the left or the right, just as a slip-skid (inclinometer) ball would, due to the apparent forces created by the slip or the skid?  Doesn't this play a key role in the balance of roll torques on a paraglider?"

Or in other words, "Isn't there some additional sort of 'pendulum effect' that we have not yet fully considered?"

At least one answer to the related question "How do paraglider controls work?" has in fact focused on apparent inertial forces caused by the pilot's body "not want[ing] to turn (yet)", purportedly causing the pilot's body to "swing" against the intended direction of turn as the turn is being initiated, thus creating a roll torque.

The truth is that we can consider the paraglider and pilot to be a single, essentially rigid sytem.  The lines do not go slack in normal flight.  The pilot is fixed in position under the wing by the triangular geometry of the multiple suspension lines.  If we want to analyze the motion of the whole body, it is not necessary to take into account the fictitious "centrifugal force" created by turning, or any other apparent inertial force.  (An exception would arise if the aircraft were rotating very rapidly about one of its axes-- for example a very high rate of yaw rotation, somewhat similar to a flat spin in a conventional aircraft, might tend to flatten out the canopy into more of a horizontal line, due to "centrifugal force".  Similarly, very high rates of pitch rotation play a key role in the dynamics of certain aerobatic maneuvers, such as spiral dives, in paragliders.)

The apparent tendency of the pilot to "swing" toward the inside of the turn in a slip, and toward the "outside" of the turn in a skid, thus imparting a roll torque to the wing, is in fact already fully accounted for in this answer.  We account for that roll torque when we note that the sideforce created by the impact of the sideways airflow against wing acts high above the CG of the whole system and thus creates a roll torque.  The apparent sideways force experienced in the reference frame of the pilot in a slip or skid, is in fact simply the mirror image of the sideways component of the real aerodynamic force generated by the aircraft during the slip or skid.  If the aircraft could somehow slip or skid sideways through the air without generating any aerodynamic sideforce, then no roll torque would result.  Also, if the aircraft could somehow slip or skid sideways through the air without generating any aerodynamic sideforce, then the pilot would experience no apparent tendency to swing to one side.

After noting that during a slip or skid, the sideways airflow against the wing generates an aerodynamic sideforce that acts high above the CG of the whole aircraft-pilot system and thus generates a roll torque, it would be erroneous to suggest that the apparent tendency of the pilot's body to "swing to one side" in a slip or a skid somehow contributes an additional roll torque about the wing's center of lift or about any other point.

Additional content on ASE relating to the ideas in this addendum--

(Q) Forces "felt" by pilot, G-meter, inclinometer--are they the aerodynamic forces generated by the aircraft, or the sum of weight+centrifugal force?

(A) Forces "felt" by pilot, G-meter, inclinometer--are they the aerodynamic forces generated by the aircraft, or the sum of weight+centrifugal force?

(A) Forces "felt" by pilot, G-meter, inclinometer--are they the aerodynamic forces generated by the aircraft, or the sum of weight+centrifugal force?

(A) Forces in a slipping turn


What is this fighter aircraft parked in the South African desert?

According to the unofficial South African Air Force forum it is a fake Mirage F1, intended as a decoy. It seems it works as intended.

According to that forum, approximately 30 were built. They were constructed of metal tubing, metal plates and glass fibre. According to one post they even contained heating elements to give infrared sensors on satellites the impression that the "exhaust" was hot.


How does engine exhaust temperature affect contrail formation and why?

There are some building-blocks to the answer:

Part 1: Assumption/Simplification
Let's assume for a moment that the only difference between the two planes is the exhaust gas temperature (EGT). A less efficient engine will utilise less of the available (chemical) energy of the fuel. This means a less efficient engine will have a hotter and faster exhaust jet (wasting caloric and kinetic energy).

Part 2:
The water-content of the exhaust gas contains water from two sources: first the water (very low fraction) from the ambient air humidity and second from the combustion of the fuel (carbon-hydrates).

Part 3: Assumption
When humid air (from an engine exhaust) mixes with the atmosphere it is a reasonable assumption that the state of the atmosphere will not change measurably given enough time for the exhaust to mix out.

Part 4:
The mass of water vapour which can be contained in a given mass of air depends on pressure and temperature of the air. This dependency is often visualized in either the Mollier-Diagram or Psychometric-Chart. The following simplification of a Mollier-Diagram shows two areas or states humid air can have. For a given temperature and low water content the water is in its gaseous phase. If the water content is increased (over the saturation point) than part of the water will be condensed (fog, small water droplets).

Part 5: Answer-Part I
When hot humid air exits the engine it will cool down an partially/continuously mix with the atmosphere. This means temperature and water content/ratio (per a given volume) will decrease. The following sketch illustrates this for two starting points. At the end of this process the jet reaches the state of the atmosphere (see part 3). In the case of a lower EGT the cooling of the exhaust can cause the humid air to cross the saturation-line which will result in a contrail.

Part 6: Answer-PartII
A lower by-pass-ratio-engine is likely to have a higher velocity difference between the ambience/atmosphere and the jet from the engine. This will increase the mixing of the exhaust gases which suppresses the condensation as well.

The model used in the paper (Schumann 2000) also includes basic thermodynamic considerations for the jet-engine which do increase the predictive accuracy of the model. But the thermodynamic effect should be captured by the parts 1-6 given here.


Who closes an airline's IFR flight plan and when?

When landing at a controlled aerodrome, air traffic control will automatically close the flightplan once the flight has safely arrived. The pilot does not have to do anything in this case. The majority of commercial flights take place at controlled aerodromes, which is probably what makes you think that pilots never close their flightplans.

If landing at an uncontrolled field (that is, one without a control tower), however, the pilot will either close the flightplan by contacting a nearby ATC station on the radio before landing, or via telephone after landing.

This applies equally to IFR and VFR flightplans, to big passenger jets and small one-person GA aircraft. If the destination airport — any airport of any size — has an operating control tower at the time of arrival, they will close your flight plan. If the airport does not have a control tower, or the tower is closed at the time, you have to contact another ATS unit to have it closed.

This is actually very logical when you think of it. When you are on a flightplan, you are automatically provided with alerting service. Meaning that if you do not arrive on time, people will start looking for you. If you are landing at an aerodrome with a control tower, the tower is responsible for your alerting service. They have your ETA (based on your FPL EET and ATD) and will initiate a search and rescue operation if you are late. If flying to an uncontrolled aerodrome, some other ATS unit (for example an area-wide flight information service) is responsible for your alerting service, so they are the ones who need to initiate search and rescue if you do not arrive on time.

Now think of this: if landing somewhere with a tower, the tower obviously knows when you land (they clear you to land, after all, and their job is to look at the runway). Thus, the tower knows that you have landed safely and that alerting service can be cancelled.

However, if landing somewhere without a tower, where another unit (not on-site) is responsible for making sure you land safely, how would they know that you have landed? The only way to be sure is for you to call them up on the radio or telephone to let them know that you have safely arrived. They will then file the arrival time to note that you have arrived safely and no search and rescue needs to be initiated.

And this is essentially what "closing a flightplan" is - it actually just means that your arrival time is sent to whichever unit is responsible for your alerting service. It's not that your flightplan is actually "closed" or "deleted" from some system, it just means that your arrival time is filed so that everyone knows the flight has landed.


Companies that currently manufacture aircraft with center stick controls?

Some of the lancair airplanes have it but those are kit built so Im not sure if you can count them as true production planes.

Vans aircraft
Most Variants of the Piper Cub like planes that are still made
Extra Aircraft
Pipistril Aircraft
Czech Sport (formally Piper Sport)

Its worth noting that Cessna did recently have a run trying to make the "Sky Catcher" which was quickly discontinued but center stick none the less.

A lot of light sport airplane and aerobatic planes tend to have center sticks.


If stealth aircraft are invisible to radar, then how does their own Air Force manage them or see them in flight?

Like most military aircraft, the F-22 has a military equivalent of a transponder, an IFF system (Wikipedia):

Identification, friend or foe (IFF) is a radar-based identification system designed for command and control. It uses a transponder that listens for an interrogation signal and then sends a response that identifies the broadcaster. It enables military and civilian air traffic control interrogation systems to identify aircraft, vehicles or forces as friendly and to determine their bearing and range from the interrogator.

Depending on mission profile the F-22 may also carry a radar cross section (RCS) enhancer to hide its stealth capabilities and make it more visible on radar.
Usually the main system for creating situational awareness during military operations and training is the Link 16 military tactical datalink. This system is carried by all modern NATO military aircraft, though F-22 will be getting the full feature Link 16 system including transmit functionality during 2021  . Link 16 also utilized by other branches of the military forces.


What is the Specific Fuel Consumption of CFM56-7B24/26/27 engines?

SFC for CFM56-7B is 0.5lb/lbf/hr. As an aside, the LeapX is 16% better at 0.42lb/lbf/hr.


Why aren’t there any lifting-canard airliners?

Sean I have no idea where you got the idea that the horizontal tail on a conventional aircraft lifts up, like a canard surface but at the opposite end, and can therefore stall and let the nose rise.  It's exactly backwards.

The tail lifts down.  When the airplane stalls, the center of lift of the main wing shifts sharply aft creating a strong nose down pitching moment that the horizontal tail lacks authority to counteract until the plane speeds up, and the nose drops.  If the down lifting tail surface itself stalls, that is a disastrous situation and is abnormal for any aircraft.

Canards generally suck because they have a host of limitations that negate most of the theoretical benefits and that's why they have been commercial failures. Otherwise, you'd see lots of them.


What work besides flying planes does an airline pilot regularly do?

There isn't much non-flying duty for airline pilots.
The most important is recurrent training. Pilots are required to attend a refresher course at least annually. This school covers regulations, aircraft systems, and performance. The performance part involves computing weight and balance, airfield/weather restrictions, fuel required, etc (basically the same thing as a Cessna 172, but with much bigger numbers). Additionally, full flight simulators are used to teach and/or evaluate normal and non-normal (we don't get emergencies anymore) procedure. This training is usually concurrent with the groundschool.
Pilots are required to maintain their approach charts and aircraft manuals; changes come frequently.
A junior First Officer will spend an eternity (at least it seems like it) doing standby duty. This involves being available to take the place of any pilot who calls in sick or is otherwise unavailable.
All pilots must pass a flight physical. The implication is that they must maintain themselves in at least minimal health.

I hope this at least partially answers your question.


When do pilots perform a CAT II/III autoland?

CAT II / III operations depend on DH and RVR, not cloud layer. It will be based on "the most demanding" of the two.*

Extreme low visibility, say due to dense fog (which is a cloud type), can actually be considered OVC000, hence the use of RVR. RVR tells you how bad the fog is and how far you can see inside it.

Here's an example of such METAR for Charles de Gaulle Airport:

  LFPG 051100Z 13005KT 090V180 0350 R27L/0900U R09R/1500D R26R/0800N R08L/0750N R26L/0800U R08R/0650N R27R/1000U R09L/0800U FG OVC000 00/00 Q1033 NOSIG

The airport also needs to enforce low visibility procedures (LVP) and broadcast it on the ATIS, so the ILS' safety area is protected. By planning ahead and by checking the ATIS, the pilots will know which approach to expect based on their operator's established 'operating minima'.

There's more to it however than DH, RVR, and LVP, for further reading check the Airbus publication, 'Getting to grips with CAT II / CAT III operations'.

* ICAO Manual of All-Weather Operations

Re: comment:

    Can cat II/III only be done, when airport announced (ex. via ATIS) that LVP are in force?

Yes, the alternative is for the pilot to request from the tower/approach a CAT II / III approach, so the tower can enforce the safety area and verify the ILS equipment is working up to the CAT II / III standards.

    If the weather was like in your METAR - RVR0800, the pilot would have to use CAT I minima if no LVP is enforced, but he could use use Cat II/III only if LVP is in force to make sure he won't have to go around - is that correct?

Without checking the French authority's specifics, the METAR visibility (350 m) is already below CAT I (>800 m), so the airport should be operating in LVP.

    (...) after choosing CAT II/III he must auto land - is that correct?

It will be based on their operator's established 'operating minima', i.e., the airline procedures, which adhere to the regulations set by its national authority. CAT III B must be flown using auto land to touchdown incl. roll-out. CAT II and III A not necessarily.


How do pilots maintain level flight after launching missile?

It's kind of a mix of the two. Flight controls on aircraft have what's known as trim. All (or nearly all) airplanes have elevator trim; many also have rudder trim and aileron trim. The trimmer for each control is used to balance constant forces needed on that control.

To take an example that's more widely applicable than launching missiles: when you increase power (to climb or to reach a faster airspeed), the airplane will have a tendency to pitch up, so you might find you need to push forward on the stick to maintain the right attitude. By moving the elevator trim forward, you eliminate the needed force, effectively changing the neutral position of the stick.

On early aircraft, the trim often worked by having springs connecting the control wires to a large lever. Working the lever pulls the spring in that direction, applying a force to the controls. On modern light aircraft, there is a trim tab on each control surface. The trim tab is like a tiny control surface on the control surface. Moving the trim tab to one side or the other provides a force on it, replacing the force the pilot would provide through the controls.

Fly-by-wire aircraft, such as military jets and large passenger airplanes, have electronic trim. Since the pilot doesn't have to put much force on the controls to work them anyway, trimming just resets the neutral position of the stick as you describe. Because it's electronic, there can be different ways to control it. Some aircraft still have small levers to set the trim; some have up/down buttons in reach of the stick (such as the Su-27); and yet others simply have a single button that trims to the current position of the controls (the A-10). As Mr Çetin points out, some very modern military jets take advantage of the possibility of computer control: the aircraft is aerodynamically unstable, but a flight control system manages keeping stable flight.

Returning to the particular case of the F-18, it doesn't re-trim itself. When heavy ordnance is launched, the aircraft will roll to one side as you suspect, and the pilot has to compensate with the stick and pedals. Once he has stablised the aircraft at the desired attitude and airspeed, he can adjust the trim using a hat switch on the stick.


What is the effect of airfoil thickness on aerodynamic lift?

In chapter 2 of his book Fluid Dynamic Lift, Sighard Hoerner discusses the influence of thickness by going to the extreme of an airfoil with a circular cross section:

  Assuming that we would manage by means of boundary layer control
  around the rear side, to displace the stagnation points from zero (at
  the forward side) and from 180° (at the rear side) both down toward 90°
  (at the lowest point), without losing any momentum, its lift curve
  slope would be dCL/dα =4π, rather than = 2π, as in thin foil sections.

Since you desire a mathematical expression: This is the linear approximation he gives:
$$c_{L\alpha} \approx 0.11 + 0.09\cdot\frac{t}{c}$$

Note that the lift curve slope is per degree. $\frac{t}{c}$ is the relative thickness of the airfoil.
In figure 21 of that chapter he uses the concept of the lift angle, the angle at which the lift coefficient reaches unity, to show how the lift curve slope varies over airfoil thickness. This plot should demonstrate how limited the applicability of the approximation is in reality.

The lift angle of airfoil sections as a function of their thickness ratio (picture source).

Stall is dominated by flow separation, and the displacement effect of an airfoil adds to the stresses on the boundary layer which determine when the flow separates. On the other hand, thickness is indirectly influenced by the nose radius of the airfoil, and this in turn determines the suction peak at the nose and at higher angles of attack. A higher suction peak also stresses the boundary layer. In consequence, both a too small nose radius (and too small airfoil thickness) and a too high thickness lower the maximum lift coefficient. The sweet spot is at a thickness of around 10%.

In chapter 4, Hoerner looks into that dependency in detail. The plot below does not include highly cambered, thin airfoils, and the straight limit for thin airfoils is misleading.

Maximum lift coefficient of various types of airfoils as a function of their thickness ratio (picture source).