Is there a NOTAM code for solar eclipse?

For the solar eclipse of March 20, 2015, I found this example below, seems like it's the opposite of a warning.

  E) A SOLAR ECLIPSE WILL TAKE PLACE ON THE 20TH OF MARCH.
  SPECIAL ROUTES HAVE BEEN DEFINED FOR FLIGHTS PLANNING TO VIEW THE ECLIPSE.
  THE ROUTES ARE DEFINED AS FOLLOWS:

  (...)

  ANY ADDITIONAL REQUESTS FOR A SOLAR ECLIPSE PROFILE SHALL BE SENT TO REYKJAVIK OACC SHIFT MANAGER, SEE CONTACT INFO BELOW. SOLAR ECLIPSE FLIGHTS WILL BE GIVEN PRIORITY DURING THE ECLIPSE.
  OTHER FLIGHTS MAY EXPECT A REROUTE AND OR LEVEL CHANGE FOR SEPARATION PURPOSES.

Regarding the temperature drop, from NASA:

  Because the patch of the shadow travels faster than the speed of sound, weather systems will only be affected very locally directly under the instantaneous footprint of the eclipse. The main effect is in the "radiant heating" component which goes away suddenly at the moment of eclipse and produces a very fast temperature decrease. If the wind is blowing, your body probably exaggerates, by evaporative cooling, how large the actual temperature swing actually is.

Due to the Earth's geometry, the shadow's speed differs from location to location, the slowest equates to Mach 2.2 at 50,000 feet for an F-15 to fly along.

Even for that F-15 in constant complete darkness, every instance is a new darkness. Some sources mention the drop at the surface being 3°C (5°F), but it looks like it's not a thoroughly studied field (impact of solar eclipses on local weather).


What is the best prop location for distributed propulsion - pusher, tractor or blown flap for an ultralight?

You are not wrong to go with tractor config.

In my opinion the best location of the propeller is pusher. The reason is that there is no airframe behind to interact with a heavily turbulent propeller wash. The thrust is developed on propeller blades alone and the airflow on the wing is the result of wing being thrusted forward in stationary air. It has nothing to do with propeller wash. The wing benefits from the most undisturbed air possible but the propeller gets the wash off the wing and airframe. For ultralight it may not be a big deal because of good thrust to weight ratio.

The tractor solution puts the engine ahead of the wing and is more common. The propeller gets the soft air and the wing gets the propeller wash. Maximum thrust, but not the best lift or drag.

Distributed propulsion means you have more contributors to propulsion.

15mph stall is similar to paramotor. You may go even lower if you’ll consider a gyro plane.


What regulations surround fitting aftermarket fuel tanks inside the cabin?

This is covered by 14 CFR 91.203:

  §91.203   Civil aircraft: Certifications required.

  ...

  (c) No person may operate an aircraft with a fuel tank installed
  within the passenger compartment or a baggage compartment unless the
  installation was accomplished pursuant to part 43 of this chapter, and
  a copy of FAA Form 337 authorizing that installation is on board the
  aircraft.

14 CFR 43 covers MAINTENANCE, PREVENTIVE MAINTENANCE, REBUILDING, AND ALTERATION.

Basically, it needs to be an approved installation that is signed off and approved by the FAA using a Form 337 - MAJOR REPAIR AND ALTERATION (Airframe, Powerplant, Propeller, or Appliance).  The maintenance shop will take care of that aspect for you.

It is pretty common for delivering aircraft that need to cross the ocean, and there are even companies that specialize in it.  Really, your only option is to purchase an already approved kit because certification costs are so high.

NBAA actually has a nice article which goes into more details, with lots of helpful links.


Does every device/software, developed for use in the cockpit, need to be certified?

The answer depends on the functionality and capability of the app. Some basic apps do not need to be certified, whilst more complicated ones will (either by the airline or by the regulator).

Tablets are split into 3 categories (these are the US FAA definitions):
1) Portable devices not mounted to the aircraft with read-only access to aircraft data.
2) Portable devices that can be mounted and can share information with aircraft systems.
3) Permanently mounted devices with access to the flight management computer.

There are also 3 classes of app:
A) Basic apps providing info such as aircraft manuals and procedures.
B) More complex apps providing some navigation info, weather info or exterior views of the aircraft.
C) More complex apps that can provide navigation information and can include 'own ship' position via GPS or the aircraft navigation platform.

Class 1 and 2 tablets can only host type A or B apps. Type A and B apps can be 'self certified' by the airline, providing that documentation on failure modes and usability is available. Some restrictions are in place for type B apps displaying, for example, weather info. Type C apps require regulator approval.

That's a brief summary, but it's very complex. Full details available
in this FAA document. Regulations worldwide vary, but most are broadly similar to those specified by the FAA.


What is the purpose of a retracting cowl?

You have seen one type of the possible thrust reversal systems in action. In the following image is the bottom one.

Image source

They deploy surfaces that deflect the bypass air and aid the brakes in slowing down the aircraft after touchdown.


I have a European EASA license - what do I need to do to be allowed to fly in the US?

From a private pilot's perspective, there are two possible options: a foreign-based license or a 'full' FAA pilot's license.

The first type is defined in 14 CFR 61.75, which starts like this:

  §61.75   Private pilot certificate issued on the basis of a foreign
  pilot license.

  (a) General. A person who holds a foreign pilot license at the private
  pilot level or higher that was issued by a contracting State to the
  Convention on International Civil Aviation may apply for and be issued
  a U.S. private pilot certificate with the appropriate ratings if the
  foreign pilot license meets the requirements of this section.

You apply to the FAA and they check with Germany (or wherever) that your foreign license is valid. If it is, they'll issue a foreign-based license "with the appropriate ratings" with no flight or theory test of any kind required. That's for VFR only; if you're instrument rated then you also have to do a theory test as well if you want to fly IFR.

That sounds great - and I suppose it is - but there are two big practical concerns. First, any limitations on the foreign license are applied, e.g. if your license is for daytime VFR only then you're still restricted to that, even if a regular FAA license would allow night VFR. And if your foreign license expires or becomes invalid for any reason, the FAA one does too.

Second, you won't have been required to learn anything about US regulations or flying practices. So you might not fly safely or legally because you simply don't know the rules or even what services are available to you as a pilot (FSS, Flight Following, TRSA etc.). One way to handle this is to get some general orientation or introductory training from a US instructor or school, but as a foreigner that will require TSA approval unless you can do it as ground school only (which is not defined as "flight training"). But you might find - as I did - that some instructors will not work with a foreign student at all until they have TSA approval, whether or not it's just ground work.

The other option is to get a normal, full FAA license. You have to pass the same FAA medical, written and flight tests as US pilots to the same standards. You can count your previous flight time towards the required hours but you do need to be able to pass the tests so you will certainly need some instruction. And as a foreigner you will need TSA approval before you can receive any flight training.

The big advantage of getting a full license is that it never expires. If you really want to get one and you have the time and money then you could look into spending a month somewhere suitable in the US (Florida? Arizona?) at a flight school to get it as quickly and cheaply as possible.


Why don't we have allocated cabin baggage space just like seats?

Passengers do usually have some allocated space - under the seat in front of them. No-one else is going to claim that...

For the overhead lockers, a quick calculation (as @mins suggests) - seat pitch averages about 30", so there is going to be approximately a 30" slot above each row for "its" locker. On a 3-4-3 widebody, this would be ten seats sharing 4x30" of locker space, equivalent to a 12" slot each. On a 3-3 narrowbody, the six seats would share 2x30" of locker space, or 10" each. Not all seats have an accessible locker above them - eg emergency equipment storage - and there is some space taken up by the opening/closing mechanisms, so in practice it would be an inch or two less than this overall.

Meanwhile, almost all airlines give a maximum smallest dimension of their cabin bags - ie narrowest width they can fit into - of 20-25cm, or 8-10". So one standard-sized bag per person approximately fills the space given, assuming they can all stack neatly on their sides.

So, in theory, yes, you could try allocating space, one ~8-10" bag slot per person, and the overall space is available. But this would almost certainly mean putting in dividers to avoid disputes (you can imagine the disputes, right? "That man's bag is taking up some of my space!").

The dividers would mean that you couldn't put anything weirdly shaped in there - say, a walking stick - and would mean there would be problems with bags that don't quite fit the limits. At the moment, they can bulge a bit and be squashed in with everything else, so the passenger in seat 11A with a slightly outsize or awkwardly shaped bag can benefit from the fact that 12C's is quite slim, and everyone is happy, but once you have rigid dividers that becomes impossible. 12C's would rattle around, while 11A's doesn't go in, and overall the space is used less efficiently.


What is the maths behind the descent rate calculation?

From Gypaets' answer
$$DescentRate = 0.0524 \cdot GroundSpeed$$
But the Ground speed is in nautical miles per hour [NM/h], and the descent rate is in ft/min.
So we have
$$DescentRate \left[\frac{ft}{min}\right] = 0.0524 \cdot GroundSpeed\left[\frac{NM}{h}\right]   $$
With $6076.12 \left[ft\right]$ in 1 $[NM]$ (yay for imperial units) and $60$ $[minutes]$ in 1 $[h]$ we get a conversion factor:
$$ 1 \left[\frac{NM}{h}\right]= \left[\frac{6076.12~ft}{60~min}\right] = \frac{6076.12}{60}\left[\frac{ft}{min}\right] \approx  100\left[\frac{ft}{min}\right]$$
This leaves:
$$DescentRate \left[\frac{ft}{min}\right]  \approx 0.0524    \cdot GroundSpeed \left[\frac{NM}{h}\right] \cdot 100_{(NM/h~to~ft/min)} $$
Further approximating it to:
$$DescentRate \left[\frac{ft}{min}\right]  \approx 5 \cdot GroundSpeed \left[\frac{NM}{h}\right]  $$


Which is better a push fan, a pull fan or both

I would say pull fan, as that is what most engines use.

https://en.wikipedia.org/wiki/Turbofan

  Modern turbofans have either a large single-stage fan or a smaller fan with several stages. An early configuration combined a low-pressure turbine and fan in a single rear-mounted unit.

  Aft-fan turbofan.
  One of the earliest turbofans was a derivative of the General Electric J79 turbojet, known as the CJ805-23, which featured an integrated aft fan/low-pressure (LP) turbine unit located in the turbojet exhaust jetpipe. Hot gas from the turbojet turbine exhaust expanded through the LP turbine, the fan blades being a radial extension of the turbine blades. This aft-fan configuration was later exploited in the General Electric GE36 UDF (propfan) demonstrator of the early 80s. One of the problems with the aft fan configuration is hot gas leakage from the LP turbine to the fan.

So perhaps fans in front can use less expensive material since they don't have to contend with hot exhause temperatures.


How can I find out if the government paid to build a runway?

The FAA gives funds to airports through the Airport Improvement Program (AIP) and that could include runway improvements. It's public money so the information is also public and should be in the Excel files on that page. If that isn't what you need, you can always submit an FOIA request to the FAA for all information they have about the airport.

It's also possible that you could get more information from the state or county. They usually have at least some input into airport construction, because of local zoning laws, easements and so on. Even if the rumor is false and the runway is built on private land and paid for with private money, there may be county planning or landowner records. But that's definitely beyond the scope of this site.


Would this mechanical apparatus be a new means of creating aerodynamic lift?

Yes, this device would produce some thrust. If oriented properly, this thrust could be used to lift a weight. But it would be extremely inefficient when compared to a standard airfoil, such as a wing or helicopter blade.
What you've basically created is a centrifugal pump without a case. Air would enter the "front" of the device (assuming the motor is the "back") just like a regular centrifugal pump, but without a case, it would be sprayed in all directions, including at an angle out of the "front". The curved panel would partially block the radial flow of air upward, creating a net upward force. But the fact that air exits at all angles, not just straight down, means that the various flows would partially cancel each other. What's worse, a lot of the air mass that emerges from the "front" would be drawn back into the incoming air stream, which would consume some of the motor's power but wouldn't contribute to the net thrust at all.
In short, I would be very surprised if this device could match even 1% of the performance of a simple ducted fan of the same power rating.
It's kind of hard to explain what I mean in words, so, here, have some bad, hastily-created images instead:


Why does Boeing use two different door-types (B757 hinge vs. B767 slide)?

Outward swinging doors require a great deal of effort to open and close, and can require the operator to potentially lean outside of the aircraft and risk a fall to close.  The 757 door originally had an issue where shorter operators could not get enough leverage to open (see: Making It Fly in the Seattle Times.  Upward doors were used for a while but they are finicky to operate and maintain and if the opening mechanism fails can be very difficult to open in an emergency.

The translating "gooseneck" door was originally designed by Airbus.  The design is simple, reliable and easy to operate.  It has more or less become standard on all new aircraft designs.


Is there a minimum separation between a landing aircraft and another crossing its runway?

When an aircraft has been given a clearance to land on a runway, that runway is exclusively reserved for the landing aircraft. (Except for LAHSO and "land after" operations, where only part of the runway is reserved for the landing aircraft).

That means that no other aircraft or vehicle should be on that runway. In this case, clearly something went unplanned. Either the crossing aircraft was not given permission to cross, the landing aircraft no clearance to land, or ATC mistakenly cleared both the landing aircraft and the crossing aircraft to access the runway.

Pilots should always check if the runway they are accessing is safe, and in this case the crew of the landing aircraft did apparently observe the incursion and aborted their landing. The crew of the crossing aircraft noticed the landing aircraft a bit late, but you hear their engines spool up as well as they cross. The sound of the go-around thrust arrives second later due to the difference in distance.

The crossing aircraft seems to be taxiing toward the rising sun so they may have been blinded and missed the fact that they were crossing a runway.


Autofeather is an automated feathering feature, common in a lot of turboprops, which automatically feathers the propeller on an engine if it loses power without having to either pull the power or propeller lever to feather the prop.

It reduces crew workload in the event of an engine failure and, as a feathered propeller greatly reduces parasite drag on the side of the dead engine, reduces the asymmetrical thrust yaw moment about the vertical axis of the airplane.

It is particularly useful during takeoff and landing operations where airspeed may be very close to minimum controllable airspeed on one engine.


What are those trucks towing around, and why?

They are called "Jersey barriers" and are temporary barriers used to alter the layout and to introduce defined lanes for vehicles, passengers etc.

For the bonus, they are not fun to tow.  If that line starts snaking, you have to stop until they all settle down before moving off again. Try drifting with those, and the weight would get so far outside your turn radius in no time flat that you'll spin the vehicle and jack-knife the lot.

Border Barriers UK©

RentPlasticJerseyBarriers.com©


How do I explain what makes an airplane fly to a non-technical person?

The simplest explanation is the "hand out of the window" one:

  Hold your hand out of the window while in a moving car and hold your hand at an angle. It gets pushed upwards. Your hand represents the wing of an airplane. The plane's engine simply makes sure the "hand" keeps moving forward against the force of the wind.

Even a 4-year old understands the concept using this explanation.


When is Minimum Safe Altitude Warning triggered?

The system projects the altitude that an aircraft will be at based on recent track and a calibrated "look ahead time" and an expected controller response time.  That value is then compared to a calibrated altitude floor.  If the aircraft is projected to be below the floor, then the controller will be alerted.

The specific values for all those things are calculated to minimize false alarms, accommodate the type of operation and local operational needs.  The values are specific to that facility and that area and so a straight answer isn't exactly possible.

Here are a few interesting resources in case they help.
Minimum Safe Altitude Warning
EUROCONTROL MSAW Guide


What is the flight time limitation for commercial air transport operation in Europe?

For EASA, flight times and duty periods are limited (PDF p.25) to:

(a) The total duty periods to which a crew member is assigned shall not exceed:
  (1) 60 duty hours in any 7 consecutive days;
  (2) 190 duty hours in any 28 consecutive days.
(b) The total flight time of the flights on which an individual crew member
    is assigned as an operating crew member shall not exceed:
  (1) 100 flight hours in any 28 consecutive days;
  (2) 900 flight hours in any calendar year;
  (3) 1000 flight hours in any 12 consecutive calendar months.


Why is air traffic control done manually by humans?

Having it explained to me briefly what exactly the tower does that cannot be handled by such a system would probably enlighten me somewhat.

Fair warning, that's my job you're trying to replace with a computer, so I'm probably biased. Still though, hear me out:

What do we do?

Handle a large amount of non-standard requests and communication between the cockpit, the airport, the airlines, flight schools, fire and rescue, authorities and many other parties
Deal with vehicles or even individual persons moving on the maneuvering area, where the only available communication is an (analogue) handheld radio
Identify obstructions or animals (such as birds) on and around the airport
Deal with smaller general aviation aircraft with no sort of digital communication, only a radio. Sport aircraft, gliders, hot air balloons.
Deal with individual aircraft without transponder (not visible on radar). A digital system would have no way of knowing where the aircraft are.
Handle traffic at entire airports without radar coverage. A digital system would have no way of knowing where any aircraft are.
Deal with aircraft with no flightplan (only way to know what the pilot wants is to talk on the radio)
Make decisions not only based on what is said, but also how it is said. It's quite easy to notice an inexperienced trainee pilot on the radio, and they need a bit more space and might not always do what they're told
Setting the runway lights to an appropriate level based on a number of factors (darkness, visibility), some of which are not easily measured digitally
See, visibly, when an aircraft enters or leaves the runway (most airports don't have ground surveillance, so the only way to determine the position of aircraft is to look out the window)

Could these things be solved/handled by a computer? In theory, sure. You could:

Invent some sort of artificial intelligence that intuitively knows exactly what someone means as they say it, and know who to forward the message to.
Replace all aircraft vehicles worldwide with fully autonomous, self-driving Teslas that can communicate with a central control system.
Install a number of high definition cameras on every airport worldwide, and use artificial intelligence to classify visible objects. Then alert the self-driving Teslas to go and scare the birds away.
Force millions of hobby pilots and flight schools worldwide to invest thousands of dollars in new equipment that can communicate with a new digital ATC system (before that: actually invent that equipment, and get it certified worldwide)
Force millions of hobby pilots and flights schools worldwide to invest thousands of dollars in transponders. Invent new light-weight batteries that enable the installation of transponders in light weight aircraft, gliders and hot air balloons.
Install thousands of new radar stations worldwide. Invent a way to deal with garbling and FRUIT caused by all the new radars.
Force all pilots to file a flightplan prior to flying. Change the flightplan format so that it is much more accurate than it is today, and teach all pilots worldwide the new format. Force all small, single-engine planes to always be flown by two pilots: one will fly the plane, the other will be busy on the iPad, changing the flightplan in real time as the flight progresses, since a short message over the radio is not an option (a digital system wouldn't understand it)
Assume the worst case scenario for all flights. Add extra separation between all aircraft. Reduce capacity at many airports by 50%, thus increasing delay by millions of hours worldwide.
Install a light control panel in the cockpit of every aircraft in the world. Teach all the pilots to use it, install redundancy systems in case it fails.
Since we've already made everyone buy transponders, why not install ground radar in every airport in the world? Will probably only cost a few million dollars per airport.

Last but not least, invent the system that actually processes all this data, to replace the decision making that is today done by air traffic controllers. Have it work in every single edge case, in every airport, in every type of climate and weather conditions, with every aircraft type, with every type of flight - and have it certified by aviation authorities worldwide.

Anyway, I think you see where I'm going with this. Is training air traffic controllers expensive? Yes. Do humans make mistakes? Yes. Would creating and getting certified a new digital system be cheaper? Absolutely not. Would it be safer? In the long term, maybe marginally. In the short term - most likely the opposite.


What's the reasoning for full-stop landings at night but touch-and-gos during the day for passenger currency?

There are three really convincing arguments I've heard for this - I'm not sure which is "correct" and explains the FAA's logic, but personally I suspect it's a little bit of each.

Argument 1: Night landings are "special".

A night landing is definitely different from a day landing - there's much less of a sight picture in the flare unless your airport is in a really bright area or you have a bright moon (and even then it's "different").
If all you're doing is tapping your wheels on the ground and quickly accelerating back to takeoff speed you're missing a lot of what a landing is - bringing the nose down, decelerating to a safe taxi speed, and leaving the runway under control.

Which conveniently brings us to...

Argument 2: "You gotta learn how to taxi all over again!"

That's something my instructor told me, and I didn't really understand what he meant until I was in the plane. Airports are really dark and it's hard to find your way around the taxiways at night. Personally I think a big part of this requirement is the intent that you taxi off the runway and make your way back to the end to shoot another circuit. The hardest thing about my night training - aside from finding the darn airports was taxiing around without getting lost.

(Of course the regs don't say anything about "Taxi off the runway" - they just say "full stop". You can satisfy the legal requirement with "stop-and-go" landings, but there's a nagging voice in my head that says you're not really "getting current" if that's all you do...)

Argument 3: It slows your procedures down, which makes you safer.

Touch-and-Go landings are kinda dangerous if you think about them - Bring the plane in for a landing (which is already a lot of work). Now as soon as all your wheels are on the ground make a mental judgment as to whether you have enough runway to take off from given your current position & rolling start, if so retract your flaps to an appropriate takeoff setting, cram the throttle back in, and take off again..
When you look at them that way it's a bit odd that we have students do them (and there's more than one CFI around on the internet who says it's a lousy teaching tool).

Adding "Oh yeah, and it's dark out!" to that already difficult and dangerous procedure above is just begging for an accident - especially in a retractable gear aircraft (gear lever, flaps lever, and what happens if you miss in the dark cockpit?).


How do you avoid power of 10 or order of magnitude errors when using an E6B calculator?

It's not a problem you'll ever have in practice, as it will always be obvious to you whether that "2" on your wizz wheel is 0.2, 2, 20 or 200. It is not a problem you'll have with time/endurance etc issues as the inner scale of time is unmistakable.
But lets take some practical examples:
Conversion Nautical to statute miles

Set 90 next to the "NAUT" marking
Read the value next to the "STAT" marking. it is somewhere about 10.5.
You know that nautical miles and statute miles are fairly similar
You therefore know this cannot be 10 Statute miles, nor 0.1 so must be around 100
The answer is 103.5

Calculate speed from distance and time

Distance is 26NM and time is 13 minutes
Set 13 on the inner scale opposite 26 on the outer scale
The rate arrow points at the speed. It says 12.
I'm flying a standard single engine prop. Can it fly at 12 Knots? Can it fly at 1200 Knots?
The answer can only possibly be 120Knots

Fuel burn rate

You took 32 gallons of fuel and flew 4 hours 20 minutes
Set 4:20 on the inner time scale against 32 on the outer scale
Rate arrow points at 74.
Did I burn 74 Gallons per hour? My Cessna only holds 40! Did I burn 0.74? That seems awfully low - with that my endurance would be measured in days when I know its roughly 4 hours.
The answer can clearly only ever be 7.2 Gals/hour burn rate

The thing with being out by a factor of 10, is that it is always obvious you're out by a factor of 10. 2x, 3x even 4x you might get confused. But I don't think you ever will with 10x
The even shorter answer is that once you've gained your PPL you'll only ever pull out your E6B to answer these such questions, and any other time you'll use modern, electronic tools to answer these questions. Slide rules; gone from the classroom in the 1970's but still used to teach people to fly.


Does ATC handle non-regular widebody flights differently?

No, ATC does not handle these flights differently from regularly scheduled ops
ATC isn't concerned with why an airplane wants to go to an airport or whether they regularly operate there or even if there are ground services available for them at the destination.
Whether the flight is regularly scheduled or not may fall under different regulations but ATC services do not vary.  The charter flight will be operated under instrument flight rules (IFR) and will have a flight plan filed with ATC prior to departure.  The controllers at the departure airport will receive information about the flight prior to that planes departure and will service the flight to its filed destination.  This works exactly the same way as normal scheduled service by that same (or any other) airline.


What is required to 'upgrade' software from DAL C to DAL A?

The main difference in effort is in the amount of verification required.

Design Assurance Level (DAL) C only requires statement coverage whereas DAL A requires MC/DC coverage.

Some of the DO-178C objectives have to be meet with independence where they didn't need to be previously, and some life cycle data goes from CC2 to CC1.

I would suggest looking at the objective tables A1-A10 in DO-178C


Is a certificated pilot considered to be a student pilot when training in a new category or class?

No.  The regulations that apply to a student pilot do not apply to the private pilot working on a new category or class rating.

§61.81   Applicability.
This subpart prescribes the requirements for the issuance of student pilot certificates, the conditions under which those certificates are necessary, and the general operating rules and limitations for the holders of those certificates.

The required endorsements for a private pilot working on a new category or class rating are also different.  Student pilots are required to have endorsements for pre-solo flight training, a solo endorsement each 90 days and an endorsement for each cross country.  The student pilot must also abide by all the limitations placed on those endorsements by the recommending instructor.
A private / commercial / ATP pilot working on a new category or class rating is required to have one endorsement.  Again, any limitations placed on the endorsement by the recommending instructor must be followed.

To act as pilot in command of an aircraft in solo operations when the pilot does not hold an appropriate category/class rating.
I certify that (First name, MI, Last name) has received the training as required by § 61.31(d)(2) to serve as a PIC in a (specific category and class of aircraft). I have determined that he/she is prepared to serve as PIC in that (make and model) aircraft. Limitations: (optional). /s/ [date] J. J. Jones 987654321CFI Exp. 12-31-19

Required endorsements for FAA certificated pilots are found in AC 61-65.


Is there a brightness switch for the AOA gauge on the F-16?

The F-16's manual is declassified since it's in service in many countries.
AOA Indexer
The answer is yes, the switch (lever) is conveniently located on the gauge. From said manual:

AOA Indexer
(...)
A dimming lever, located on the left side of the indexer, controls the intensity of the lighted symbols.

And here's a photo from airliners.net (red arrow):

AOA Indicator
In case you mean the AOA indicator on the instrument panel (yellow arrow above), then no, it doesn't have its own separate lighting. It will be the instrument panel light switches aft of the flight stick.

Source: airman.dodlive.mil; click here for the switches schematic (first two rows)


What happens to #2 if a formation flight violates a FAR?

In the eyes of the FAA, the wingmen are individually responsible if they violate an FAR, even if they are led into it by lead.

The controlling NTSB decision is:

3 N.T.S.B. 3302, NTSB ORDER NO. EA-1560, 1981 WL 40208
Administrator
v.
MERRELL R. GOSSMAN, EDWARD J. MODES, AND HOWARD MORGAN, JR., RESPONDENTS
Docket No. SE-4591, SE-4592, SE-4593
Adopted February 13, 1981

  As the law judge stressed, each pilot-in-command of an aircraft “is
  directly responsible for, and is the final authority as to, the
  operation of that aircraft” and each pilot has the affirmative duty
  to comply with the minimum altitudes prescribed by section 91.79,
  which contains no exception for aircraft in formation following a
  leader.


PRIM 1 FAULT prior to ETOPS entry, Reroute or Continue?

Since you are already airborne, the MMEL doesn't come into it. The system was normal when you dispatched.  What applies is the QRH (Quick Reference Handbook).  You should look for that particular message in the QRH in the section on status messages (I assume that fault messages are white status messages in Airbus-land).
If there are any restrictions on ETOPS operations with a fault that comes on while airborne, there will be a notation of some kind to that effect, referenced or attached to that message in the QRH, that you have to divert or take some sort of mitigating action before or after entering ETOPS conditions.  If not, you're good to go.
The MMEL is based on an analysis of risk exposure related to potential follow-on effects following a departure with a degraded system (that is, a second failure of the remaining component of the system in flight that renders the entire system inoperative or operationally compromised).  The risk level prior to departure is higher than the risk level while airborne, because as a general rule, double failures on the same flight are assumed to be extremely improbable.
And, obviously, you should consult with someone in authority at your airline instead of going on the statements of anonymous nobodies on the intertubes...


Why did the manifold pressure gauge on the Ki-61 have negative values?

Disclaimer: I do not know if my answer is correct, but I think it is plausible.

The Ki-61 engine was the Kawasaki Ha-40, a Japanese version of the Daimler-Benz DB 601 Aa turbocharged inverted-V inline engine, so I would assume that the engine instrumentation was inspired by what was used in Germany at that time. Manifold pressure was measured in ata (Atmosphäre absolut, close to 1 bar), which is multiples of the standard atmospheric pressure. The picture below shows the manifold pressure gauge of the Me-109 G, which used the DB 605 A. This was derived from the DB 601, and the manifold pressure gauge has a range from 0.6 ata to 1.8 ata.

The DB 601 A had a maximum manifold pressure at sea level of 1.35 ata. This lets me assume that the Ha-40 was also turbocharged to 1.35 ata, which is 1.368 bar. The critical altitude was probably only 3700 m. The regular DB 601 A had a critical altitude of 4500 m, which was reduced in the DB 601 Aa export version to 3700 m. I could not find a direct reference for the critical altitude of the Ha-40.

At the 11,600 m service ceiling of the Ki-61, the atmospheric pressure is 206.6 mbar. Now we need to factor in the ram pressure gain of approx. 20% at 300 kts TAS, and with the 2.14 compression ratio needed for a critical altitude of 3700 m, this would translate to a manifold pressure of 530 mbar or 0.522 ata. If the Kawasaki engineers raised that to the 2.37 compression ratio of the original DB 601 A, the manifold pressure at 11,600 m could even had been 578 mbar or 0.570 ata.

The most plausible explanation for the numbers on the manifold pressure gauge now would be percentage over rsp. below 1 ata, the static pressure at sea level. Since it is more important to not overstress the engine at low level, the +40 upper limit fits well to the maximum 1.35 ata setting. This fits also well with the static value of 0, meaning 1 atmosphere. At high altitude the compressor would run at maximum setting anyway, and the scale here is for informing the pilot about available power, and would not cover the lowest values close to maximum altitude.

I could not find a performance chart for the Ha-40 or the DB 601 A, and the nearest Google dug out for me is the performance chart of the DB 601 E below. Please note that this engine had more performance (2700 RPM and 1.42 ata manifold pressure for takeoff; the DB 601 A used 2400 RPM and 1.35 ata) and a higher critical altitude of 4800 m:


Why do airliners on autopilot climb during cruise?

Climbing further while cruising is saving fuel, not wasting it.

First, every airplane has an optimum angle of attack for most economical cruise. If it loses mass (due to fuel consumed), it needs to adjust either its altitude or its speed to keep that angle of attack. The goal is to keep dynamic pressure, the product of air density and the square of airspeed, constant. Since you want to reach your destination in the shortest time, climbing into less dense air is the better option.

Secondly, gas turbines need less fuel per unit of thrust when flying in colder air. As long as the plane stays in the troposphere, it will fly more economically when it flies in colder air.


The plane takes off vertically, with the prop wash blowing over conventional control surfaces. To tilt forwards the pilot pushes the stick forward in the usual way to "lower" the elevators and tip the nose "down". As the plane tips progressively over, it progressively gains flying speed and lift transfers to the delta wings. At the same time, the elevators are brought back to the level for conventional flight. Landing is the same thing in reverse, with the elevators being raised.

Manoeuvring in vertical mode is again just the same, but only a small control movement is needed for a gentle tip in the right direction: elevators in one axis, rudders in the other. The elevators also act as ailerons, which allow the pilot to gently spin the plane round even when vertical.


Should I have one hand on the throttle during engine ignition?

Yes hand on throttle when starting, always, except on engines with fuel injection where you have to have it on the mixture because you start on idle cutoff and move it up as the engine catches.  In any case, you shouldn't be reading checklist items during the start; you just learn what to do and do it so you can be in total control.  Back to the checklist after the engine is running and you are satisfied it's running properly on its own and you can divert your attention to other things.  Whoever was telling you to hold the checklist during the start is... well... an idiot.

I don't think you'll fail a checkride, but will probably get marked down a bit for that item.  Most checkride fails are because a series of screw-ups accumulates and drops your overall score, not because of a single item, unless the single item is something critical and screwing it up is dangerous, like taxing onto a runway with an airplane on final or making a really bad judgement call or leaving out a critical item.

When you do your check ride, you will probably be convinced at the end you failed, if you made this little mistake and that little mistake, and will be shocked to hear "you passed".  Because unless you do something that shows the examiner you're dangerous, it's the overall scoring that counts.


What is the visual difference between turbine fans and compressor fans?

Assuming we are speaking of axial compressors/turbines

Compressor blades are generally thin and straight, and resemble a tiny rectangular wing with low camber thickness.

Image source

Turbine blades are more curved, often in almost "U" shapes (like the ones seen here). In particularly large and recent engines, where efficiency is critical, turbine blades will often be full of tiny holes:

Image source

To distinguish between high pressure and low pressure stages (compressor or turbine does not matter), the length of the blade and its torsion (i.e. how much the aerodynamic profile turns around the axis of the blade going from the root to the tip) are key: shorter and more twisted blades will be high pressure ones, longer and straighter blades will be low pressure.

Note that two blades of the same length could come one from a high pressure stage and the other from a low pressure one of a different engine: "short" and "long" are relative to the engine size.

On the other hand, radial compressors and radial turbines are more difficult to distinguish.


Which air stream pressure / speed is measured by the pitot?

The first thing to have in mind is that a pitot tube is NOT measuring speed: the pitot tube measures pressure and later on the airplane (flight management system in a modern airplane) calculates the speed based on pressure.

More specifically the pitot tube calculates the stagnation pressure which is the sum of static pressure (what you show in your picture) and the dynamic pressure (pressure obtained by stopping the air).

The total pressure remains constant in the external free flow in normal airplane operations BUT will not remain constant in the boundary layer, which is a small region close to the wall. The boundary layer grows with the distance downwash along the airplane.

What I explained here justifies the following design solutions:

Pitot tubes are usually installed with an small distance to the walls "like floating" in order to be outside the boundary layer and free of loses on the stagnation pressure.
Pitot tubes are never installed at the tail of the airplane, in order to avoid high thickness of boundary layer (could reach 1 meter).


What is the term for an aileron that’s also used as a ground spoiler?

The action of a ground spoiler is essentially that of a lift dumper, which also acts as an airbrake.

As far as I am aware there is no special term for an aileron which also performs this function. Several Airbus types use the technique but their literature just calls them ailerons. On the A380 at least the spoiler action is initiated by the Speed Brake lever.

Of course, "spoilerons" are not quite the same, as these are spoilers used differentially for roll control during flight.

It is not too uncommon for a device named for one function to do double duty in another. For example "landing flaps" are often also (partially) deployed for takeoff - as of course is "landing gear" - and on some older types the servo tabs also double as trim tabs.


What is a jet engine's fuel flow at constant IAS?

The most obvious difference is due to the temperature of the air.

Both turbine and piston engines are heat engines. They work by converting thermal power into mechanical power. The theoretical absolute maximum efficiency you can achieve is called the Carnot efficiency, $$\eta = 1-\dfrac{T_C}{T_H}$$

This is the efficiency of an ideal engine using the Carnot cycle, that works by transferring heat from a hot reservoir with temperature $T_H$ to a cold reservoir with temperature $T_C$. A typical jet engine is approximated by the Brayton cycle, and a piston engine the Otto or Diesel cycle, but neither can ever by more efficient than the efficiency noted above. The efficiency of a Brayton cycle is $$\eta = 1-\dfrac{T_C}{T_E}$$ with $T_E$ the EGT.

When flying higher, the temperature of the cold reservoir (the atmosphere) drops lower. You can see that the maximum efficiency of the engine will also increase (even if $T_H$ or $T_E$ respectively drop simultaneously with $T_C$). This means that, even if the required power would stay constant for constant thrust, the fuel flow changes, because a single unit of energy from a drop of fuel can be converted into more mechanical power.


First time passenger flight by two pilots?

It is never “the first time”. What he is really saying is that after many hours of flying the aircraft (or an approved simulator) this is the first time doing a revenue flight with passengers. Previous flights would have been training flights.
When a new aircraft type is first introduced to an airline, it can be expected that the entire crew is doing their first revenue flight after training.
What is not expected is that the pilots announce it to the passengers. I would not advise doing that because the passengers might not understand, and it would put doubts in their minds, as it did for you.


What are the requirements for a foreigner to become an Air Traffic Controller in Sweden?

Sweden currently has a surplus of controllers, so you are unlikely to find open positions. However, since you are a qualified controller and speak Swedish, you should be qualified to apply for any position that might come up. I suggest you have a look at LFV, which is the largest Swedish ANSP: www.lfv.se/en


Is it practical to become an airline pilot in order to travel internationally?

No, this is not a good idea, and No, it is not possible finish your education at 23, and then get employed as an intercontinental airline pilot.

It seems you have a distorted idea of what an airline pilot actually does. An intercontinental airline pilot usually spends just 24 hours at the layover destination. Much of that time is spent sleeping to recover from the fatigue of the long haul flight and sleeping to prepare for the next long haul flight. Not much time for sight-seeing.

The first requirement for becoming an airline pilot is a love of aviation and aircraft.  Most airline pilots today have been passionate about aviation since an early age.

You will never be successful unless you are passionate about aviation due to all the roadblocks and hardships you will have to overcome in order to reach your goal.

To say that you only want to do it for 1-2 years is proof enough that you don't have what it takes.


Can the measured thrust of a propeller be greater than the max thrust predicted by Froude's theory?

No.

The actuator disc theory for Propellers uses some simplifications, which are grouped into a propeller efficiency factor which normally is between 0.7 and 0.9. This accounts for friction and swirl losses, which are both neglected but very real. Also, the theory assumes equal speed over the stream tube and an infinitesimally small hub, both of which increases efficiency over that of real propellers.

If the propeller uses a large duct, Froude's actuator disc theory would be insufficient to explain all thrust. You might want to explain your measurements in more detail to get a better answer.


Do any aircraft systems give spoken warnings in a language other than English?

I am quite sure that the systems that provide audio warnings for commercial aircraft, such as enhanced ground proximity warning computers, provide English Only. I am pretty sure because on the wiring diagrams there are no kind of dip-switches for language selection and for loadable software it is tightly regulated without any 'language selection' options.  One could imagine that separate part numbers are created for different languages but I know this is also not case case as international carriers share/pool spare black boxes. Basically aviation language is English.

I also see no future provision for other languages as it was only recently in 2008 that ICAO mandated English for all international flights (Amendment 164 to Annex 1 ). Under this ruling Air Traffic Controllers and Flight Crew Members engaged in or in contact with international flights must be proficient in the English language as a general spoken medium.

Regarding Airbus (and the love that the French have of their language) we might do well to know that actual official language of the Airbus company is surprisingly to some 'English.'

Of course I can't comment on military applications much. Actually, I was previously slightly involved in supporting a military aircraft and from what I can tell they use many modified versions of the same components commercial aircraft do. At least for US, British or French allies, who are allowed to import the technology. However, they are modified directly by the customer to be more security tolerant. For example, a military aircraft might not be transmitting its location around the globe unless the receiver has a decoding ability to a secure military key. So even in the small exposure I have encountered with military applications, I have not encountered or heard of 'language options.'  This is not to say that some Chinese or Russian might be heard in some remote aviation system somewhere but that if it does outside their aerospace industries it must be rare and still a 'one language' only feature. Possibly there are missile guidance systems in Russian, Chinese, or Korean but certainly not in international commercial aviation.


Will there be dynamic or variable separation minima in future?

There already is, to some extend.

Firstly, there is a big difference between separation in surveillance environments and non-radar environments. In non-radar environments, the separation minima are much larger, because separation is based on position reports provided by the aircraft, which is deemed less accurate than radar data.

In radar environments, the separation needed is generally 5 NM. However, in many terminal areas this is reduced to 3 NM - but only for aircraft going 250 KIAS or less (so, reduced relative speed). Moreover, on final approach, separation is commonly reduced to 2,5 NM - again, since the planes are going slow and pointing in the same direction (the runway), the relative speed is low.

Note that the navigation capabilities of individual aircraft does not matter, since separation is based on ground based equipment (radar), NOT on position information provided by the aircraft.


The answer will differ a bit from airfield to airfield but here is a typical inspection procedure for East Midlands in the UK(EGNX).

The inspection is carried out first thing in the morning and last thing at night, then at 2 hour intervals throughout the day.

It is carried out by a vehicle in co-ordination with ATC who might shut the runway down for a few minutes.  The vehicle must get permission from ATC to enter the runway and must report on leaving.

Approach will co-ordinate the arrivals, by extending them slightly, so that no-one has to hold or go around (hopefully).  It is also possible to do half the runway as a departing aircraft lines up, leave the runway at a turn off, wait for the departing aircraft, then complete the inspection before the next departure.  There are several ways to do it without causing disruption.

The vehicle enters the runway and drives the complete length visually checking the items on the inspection list.

The document gives you a complete list of items to check but essentially it is:

Clear of FOD.
Markings and signs in good condition and visible.
Lighting working and undamaged.
Runway surface not damaged.
Oil and fuel spills.


Can only victor way be used for route in cross country?

You just use (starting waypoint)  DCT  (ending waypoint) in your flight plan (DCT = Direct) and submit that.  It's up to ATC to approve that routing and you'll find out when you are issued your clearance.

Especially at lower altitudes it's likely you'll be cleared as filed, but there's always a chance they'll shift your route a bit to improve traffic flow for whatever reason, adding waypoints or moving you to an adjacent V airway, doing their best to minimize any increase in your distance.


What's the maximum range an A350-900 can reach at TOW of 250,606 kg and full payload?

Since Airbus does not publish this in the charts, we have to calculate it ourselves. You are asking about an Airbus A350-900 with a TOW (TakeOff Weight) of 250,606 kg. This weight would then consist of:

$$ \text{TOW} = \text{OEW} + \text{Payload} + \text{Fuel} = 142 \, 400 \, \text{kg} + 53 \, 300 \, \text{kg} + 54 \, 906 \, \text{kg} $$

based on typical OEW (Operating Empty Weight) and max. payload from Wikipedia. This leaves us with about 54.9 tons of total fuel. Not all of this fuel will be usable however, since the aircraft still needs some fuel reserves: $ \text{Fuel} = \text{Trip Fuel} + \text{Reserves} $.

To calculate the range of the aircraft, we can use the Breguet range equation (see e.g. this answer):

$$ \frac{\text{TOW}}{\text{LW}} = \exp \left( \frac{R \cdot g \cdot b_f}{v \cdot L/D} \right) = \exp(f \cdot R) $$

We are only interested in the TOW, LW (Landing Weight) and the range $R$, so I combined all the other aircraft specific factors into one factor $f$. The landing weight can be calculated via the fuel use:

$$ \text{LW} = \text{TOW} - \text{Trip Fuel} = \text{TOW} - (\text{Fuel} - \text{Reserves}) $$

We now have to solve for the two unknowns $f$ and the reserve fuel. For this, I read off two values from the plot you provided:

We now have two given ranges for known masses:

At MTOW and max. payload (resulting in 84.3t of total fuel) the range is about 5800NM.
At MTOW and max. fuel (about 112.6t based on about 25t of payload) the range is 8600NM.

By plugging these values into the Breguet equation, one can numerically solve for the unknowns:

$$ f \approx 5.2711 \times 10^{-5} \; \text{NM}^{-1} \;\;\; \text{and} \;\;\; \text{Reserves} \approx 10\,545 \, \text{kg} $$

We can test, if these parameters make sense, by plugging in no payload at maximum fuel:

$$ R = \ln \left( \frac{\text{TOW}}{\text{LW}} \right) / f \approx 9698 \, \text{NM} $$

This range is consistent with the value where the magenta line crosses the range axis.

Now moving back to your numbers. We can now plug in a TOW of 250,606 kg at maximum payload. The trip fuel will then be:

$$ \text{Trip Fuel} = 54 \, 906 \, \text{kg} - 10 \, 545 \, \text{kg} = 44 \, 361 \, \text{kg} $$

This gives the final answer:

$$ R = \ln \left( \frac{\text{TOW}}{\text{TOW} - \text{Trip Fuel}} \right) / f \approx 3696 \, \text{NM} $$


Can you turn off the instrument panel lights?

It depends.

On my Cherokee, when you turn the navigation lights on you can push the switch up or down. Up gives you bright lights on the panel and down gives you dim lights. There is also an overhead red light that has a sliding door that you can open or close for more or less light. There is one rheostat that controls the lighting in the VOR/LOC indicator.

On my Cessna 210 there are lights in some of the instruments, post lights next to the instruments, and overhead lights. The lights are controlled with two switches and several rheostats. The GPS has independent lighting controls.

The Piper Arrow has two rheostats—one for navigation and radios and one for instrument panel lights. If you turn the navigation lights on there is always some lighting on the radios. The GPS has its own lighting controls.

My friends Piper Dakota has lights for the instruments as well as a light strip along the base of the glare shield that illuminates the entire panel. Controlled by a combination of switches and rheostats.

Older general aviation aircraft have widely varying approaches to nighttime lighting so before you fly at night you need to become familiar with the idiosyncrasies of each one.


Do military pilots have flight & rest hours regulation?

Yes, they do. My experience is with the U.S. Air Force, so my answer will be from that perspective, but other air arms have similar regulations.

USAF

From the 11-202V3, Chapter 9, Crew Rest, Fatigue Management and Flight Duty Limitations:

9.4.3 Augmented Aircrew

  A basic aircrew supplemented by additional aircrew members to permit in-flight rest periods IAW paragraph 9.4.8. If the basic aircrew requires only one pilot and a second qualified pilot (includes pilots enrolled in an AETC formal aircrew
  training course) is designated an aircrew member to augment pilot duties, the crew can be considered augmented.

9.4.6 Flight Duty Period

  FDP begins when an aircrew member reports for a mission, briefing, or other official duty and ends when engines are shut down at the end of the mission, mission leg, or a series of missions. FDP for UAS ends at final engine shut down, final in-flight handover briefing, or final crew swap, whichever occurs last.

Table 9.1 (Maximum Flight Duty Period in hours by aircraft type)

9.8 Crew Rest

  Aircrew require at least 10 continuous hours of restful activities (including an
  opportunity for at least 8 hours of uninterrupted sleep) during the 12 hours immediately prior to the FDP. To ensure individual accountability and mission reliability, crewmembers should be officially notified prior to entering a crew rest period. A crew rest period cannot begin until after the completion of official duties.

So you can see from the chart that it depends on the type of aircraft, and the number of qualified pilots on board. But there are of course exceptions (e.g. the B-2 Spirit has been known to fly missions up to 44.3 hours), especially in wartime. All Air Force flights' risk is determined prior to the mission, and in training things like crew rest are instant no-flys, but when the needs of the mission dictate, pilots may have to overfly when they are the only or best option, or when exceptional circumstances dictate.

Also, from the Navy (I searched for other regulatory publications from other countries, but couldn't find any):

US Navy

From the OPNAVINST 3710.7T Chapter 8:

8.3.2.1.2 Flight Crew

  Ground time between flight operations should be sufficient to allow flight crew to eat and obtain at least 8 hours of uninterrupted rest. Flight crew should not be scheduled for continuous alert and/or flight duty (required awake) in excess of 18 hours. If it becomes necessary to exceed the 18-hour rule, 15 hours of continuous off-duty time shall be provided.

8.3.2.2.a Flight Time

  Daily flight time should not normally exceed three flights or 6-1/2 total hours flight time for flight personnel of single-piloted aircraft. Individual flight time for flight personnel of other aircraft should not normally exceed 12 hours. The limitations assume an average requirement of 4 hours ground time for briefing and debriefing


When is the logo light on the tail turned on?

There can be several lights on the empennage (tail section) of an airplane. There are two as shown here:

Image Source

The red light is called aircraft beacon. The white light is called strobe.

When to turn them on is explained here:

  All aircraft built after 11 March 1996 must have an anti-collision
  light system (strobe lights or rotating beacon) turned on for all
  flight activities in poor visibility. The anti-collision system is
  recommended in good visibility, where only strobes and beacon are
  required.

Another one is logo light:

This light illuminates the livery design on the vertical stabilizer.

For more details, please see this question:
When to use Beacon, Anti Collision, Strobe, Logo and Navigation lights?


Is it safe to fly ultralights at 6-7 weeks pregnancy?

Ultimately the decision of whether or not a pregnant woman should be piloting an aircraft is between her and her doctor, and you shouldn't take the commentary of strangers on the internet as medical advice ("I am not a doctor, and even if I were I am not your doctor").

That said while I'm not sure what EASA has to say on the subject I know the FAA does not consider pregnancy to be a "disqualifying medical condition" for operations requiring a medical certificate, so it would logically not be disqualifying for operations which do not require a medical certificate (gliders, balloons, or ultralights) either.

Ultimately much of the advice out there comes down to "you can fly through the second trimester, and shouldn't fly in the third trimester" - assuming a normal and uncomplicated pregnancy, with the arguments against flying in the third trimester largely focusing on the onset of labor, obstruction of the flight controls, or difficulty with the aircraft's restraints (seatbelts).

Some specific concerns that have been identified for pregnant pilots include:

Inability to get full range of movement on the flight controls
If the pilot's "baby bump" is large enough to obstruct the free movement of the flight controls they probably shouldn't be flying an airplane.
This is a concern for all pilots with larger-than-average abdomens, but as pregnant women tend to enlarge quickly it's something they need to be aware of on each flight.
Onset of labor
All the women I know who have given birth have lead me to believe it would be rather difficult to simultaneously fly an aircraft and give birth, so it would be sensible to avoid single-pilot operations (including ultralight flying) late in pregnancy where this might be an issue.
Blood Clots
Sitting in the same position for long periods of time increase the chance of blood clots. This is a problem for all pilots, but pregnant women can be more susceptible to blood clots so flights should be kept short if possible.
Hypoxia
Mom is breathing for two, and physiologically the fetus has a priority claim on oxygenated blood. As a result pregnant women may require oxygen at lower altitudes, but this is not likely to be a concern for ultralight pilots as you won't be climbing that high.


Why do some airports have more than 2 runways, when LHR can get by with 2?

Heathrow is somewhat of a standout when it comes to volume. Your wording, that LHR "gets by" with 2 runways is apt. By movements, it is the busiest 2-runway airport in the world. By passenger volume it is second only to Dubai Intl. (Note, though, that DXB is home to Emirates, who has the world's largest fleet of A380's. They are the only airport that averages over 200 passengers per movement!)

Aircraft movement is the best way to look at it from a runway usage standpoint. The following chart is sorted by aircraft movement.*

As you can see, the top 3 all have 5 or more runways. There are 7 large airports with 5 or more rwys and they all fall in the top 16. The top 16 is rounded out by 5 airports with 4 runways, three with 3 runways and... LHR. The next 2-rwy airport on the list is Benito Juarez Intl. in Mexico City clear down at 21st on the list.

Any busy airport with 2 runways has to make those runways work as tightly as possible with little room for error. Otherwise they end up with delays. If I sort the list by movements per rwy, all of those with 2 rwys rise to the top. 10 of the top 15 have 2 rwys.

So, how does LHR pull it off? How do they manage to pack all those flights in to just two runways?There's a downside to handling that kind of volume with so few runways. The following collage gives a clue as to what that is.

Those are just a random pick of arrivals at a couple of random times yesterday morning at LHR. There was no significant weather at the times. As you can see, you just don't arrive at LHR without being put in a holding stack. Every single flight I could find had to do at least one racetrack. At any point during the day, in places like Chesham, Effingham and Brentwood, if you look up there will be as many as 6 or 7 aircraft doing racetracks waiting to be cleared into Heathrow. That makes for very efficient runway usage when there are 20 planes waiting in line, but it's terribly inefficient for the airlines and passengers to have to spend so much time burning fuel circling around London.

On the flip side, building more runways has a down side too. It will get the planes out of the air quicker, but, as happens at Schipol - which has 6 runways - you can end up with a long taxi back to the terminal.

All data was taken from Wikipedia.


How do you calculate the maximum distance to communicate with tower control?

The formula for VHF range taught in flight schools1 is

$$ d = 1.25 * \sqrt{h} $$

where d is the range in nautical miles and h is the height in feet of the receiver above the transmitter.

So in your case it would be (spoiler: mouse-over to see hidden text):

   $$ 1.25 * \sqrt{(1981 - 335) * 3} \approx 87.84  $$

However, keep in mind that in some countries the range of Tower VHF radio tranmitters is limited so they only achieve a certain range. Uncontrolled airfields in Germany usually have a range of 30nm, which is achieved by limiting their power.

1: "Motorflug kompakt" - Winfried Kassera / 2012 - p. 296


How does afterburner efficiency vary with thrust?

Normally, what is throttled back is the afterburner. The principle of reheating an already hot gas is so inefficient that partial wet thrust is achieved by running the engine at full power and using less than full afterburner.
The efficiency of the afterburner is proportional to the ratio of gas temperatures (peak to entry temperature), but at partial jet thrust the pressure level and volume flow in the jet exhaust is also diminished, so the available thrust increase from the afterburner will also decline sharply. To produce the same thrust, it will be much more efficient to run the jet at full speed and to throttle the afterburner.
The Tornado attack aircraft, designed for nap-of-the-earth flight, was so inefficient at higher altitudes that during the Bosnian war of the mid-Nineties it had to run one engine in partial afterburner in order to keep up with the tanker aircraft. For inexperienced crews which used most of their allotted time for coupling with the tanker, the tank stop could result in a negative fuel gain because so much was needed to keep up with the tanker.


What forces air to move from lower to higher pressure?

In the compressor, the pressure continuously increases from first stage to last stage, that's the purpose of the whole thing. But your question is valid: Why would air move from the first stage to the second stage where the pressure is higher?
The reason is indeed the rotating blades of a stage push air to the next stage. Energy extracted by the turbines is used to rotate the compressor blades and create a relative wind. Air is accelerated over the blade and like for a wing, a downwash force is created. This accelerated air is then slowed down by the next stator vanes to convert the additional velocity into additional pressure, and maintain velocity nearly constant in the compressor (else efficiency would decrease), as visible in tsg's answer.
Stop the blades and air goes back until pressure equalizes in all stages.

I have heard seals are used to prevent leakage of air from compressor
to forward section of engine

Correct, there are seals. But while the air moves towards the combustor within the compressor annular duct, under the effect of blades rotation, seals are here to prevent it from getting back to previous stages by escaping the annular duct, and leaking below the stator vanes (between the rotor drums and the inner shrouds of the vanes).
The fixed vanes plane is actually the plane where pressure increase occurs. So air will try to return on the front side of the vanes, towards the rotor blades using the interstices (orange flow), but it will be blocked by seals.
The seals are highlighted in yellow on the picture below, they rub on the inner shroud of the stator vanes (actually for the engine shown, a honeycomb ring fixed inside the vanes shroud provides an abradable track to the labyrinth seal:

HP compressor interstage labyrinth seals (CFM56-7B), source
These seals are required because a small gap exists between the rotor and the stator platforms forming the inner wall of the duct.


How can a tug be referred to as company?

I just saw BowlOfRed's comment, and listened to it again and I could make it out this time as "Tug 1 and Company". So, basically, when used with vehicles, using "and company" will often indicate that there's more than one vehicle in the group(or possibly aircraft in tow), and whoever's being addressed is in charge of talking for them. Just like when a flight of aircraft is flying or taxing, whoever's talking for the flight, that callsign is used for the whole group.

For other examples of "and company": During snowplow operations, usually you'll just have 1 driver in a group talking to Ground/Tower for that group, and they're also in charge of reporting when all their group is clear of runways or other movement areas. Other times, it's when airport operations is escorting(via vehicle) other vehicles on the airport, from survey crews to construction crews.


Is a single-engine ferry flight allowed with a twin-engine plane?

Civilian aircraft are not designed for this - but some military aircraft are. The Antonov-70 can easily take off with one engine inoperational (it has four in total), but it has a limited capability to take off with two engines out on the same side! For that, it has to be empty and can carry only minimum fuel.

This capability is the consequence of the demand of the Soviet Air Force for the An-70 to operate for 6 months with minimum maintenance. The Antonov design bureau, well aware of the limited capabilities of front-line troops in aircraft maintenance, designed this transporter with lots of redundancy.

Edit:
With one engine inoperational, any twin-engined civilian aircraft would not be legal if it attempted a one-engine take-off. I would expect there is a way to do it, but it needs the agreement of the owner and some paperwork with the local authorities. If you can prove that this particular ferry flight is safe, I think you would be allowed to fly. But I am certain that without lengthy preparation and paperwork there is no way to legally take off on one engine only.

This is in contrast to military aviation where this kind of operation is planned for.


Why does a subsonic nacelle inlet have a throat before the diverging section?

The throat is a byproduct of trying to prevent flow separation at slow airspeeds or high angles of attack.

Below you can see a rudimentary sketch of the intake streamlines for different airflow conditions. As you can see in the first case, the air needs to curve around the tip of the lip at low airspeeds. Flow will separate, if the curvature is too strong. Flow separation can lead to all kinds of problems for the engine. In order to prevent flow separation, a thick and rounded lip is used. Superimposing such a rounded lip on the divergent geometry of the inlet results in a throat as you described.

Image by K. Aainsqatsi - self-made, CC BY-SA 3.0, https://en.wikipedia.org/w/index.php?curid=11098086


What are the implications of building a private airfield in the United States?

This has been somewhat covered in other questions here. You can find the legal requirements in the answer to this question (somewhat of a dupe to this question). There are some notes on security in this question.

  What would it cost to maintain this installation, above and beyond the
  cost of maintaining any piece of property of this size? What's
  included in these costs?

For a grass strip you will need a good ride on mower and possibly something to level/press the ground. Maybe some filler if there are any divots etc. But all in all the cost to maintain a strip of grass is pretty cheap.

  Are you required to pay to have an airfield listed on charts?

Im not sure of this one but there may be some requirements you need to meet which could cost you money.

  Do the parameters I've listed seem reasonable for the requirements
  I've mentioned?

Yes, 22-2500 is more than common, FWIW a bit on the short side but you should have no problem getting your common GA planes in and out of there. Keep in mind that with trees at the end and on either side this could get tight. In reality runways (at least nice paved ones) have a lot of clear space around the immediate area.


Where can I find information on the DC-9's turn radius in flight?

No different from any other jet.  Use this turn radius calculator http://www.csgnetwork.com/aircraftturninfocalc.html


Why is it advantageous to vary sweep angle with relative thickness?

Here's a high speed reason:

TL;DR: They counter each other's effect on the wave drag

Thickness versus wave drag

Basically, a thicker airfoil has a bigger curvature, and will accelerate the airflow around it more. This leads to more lift for the same speed. However, at cruise speed, closer to M=1, sonic effects will occur. This will lead to increased drag.

This can seen from the figure below, with increasing $t/c$, the value of $c_d$ is higher, and the rapid increase associated to wave drag starts earlier. The value of $M$ at which this occurs is called the Drag Divergence Mach number, $M_{DD}$.

Source: NASA supercritical airfoils: A matrix of family-related airfoils

Sweep versus wave drag

When a sweep angle is present, we can decompose the velocity in two components, of which only the one perpendicular to the chordline ($V_\bot$) is effecting lift (and thus wave drag).

By increasing the sweep, we can reduce the value of $V_\bot$, allowing the airfoil to experience a lower value of $M$, thus delaying the drag rise.

Source: Wing Shape Multidisciplinary Design
Optimization

Combined effects

As you can see, for wave drag, the two counteract eachother. If you have a certain value of $t/c$ and a certain $\Lambda$, this will lead to a certain $M_{DD}$. If for some reason, you want to increase the value of $t/c$, the wave drag increase will come earlier, leading to a lower $M_{DD}$. To maintain the same $M_{DD}$, you could counteract the effects of a larger $t/c$ by increasing $\Lambda$.

This is clearly shown by the emperic Korn-Lock-Mason method, which states:

$$ M_{DD} = \frac{K_A}{cos \Lambda} + \frac{t/c}{cos^2 \Lambda} +\frac{c_l}{cos ^3\Lambda} $$

This also shows the effects of lift on the value of $M_{DD}$.


Why do airline toilets delay for a few seconds before flushing?

Most passenger aircraft of today (747, A380, widebodies of any kind) use vacuum-flush toilets.  It takes time for that system to go through. It also has to coordinate lids into the waste storage container that is usually fireproofed.

Those 2 seconds took decades to develop and keeps the odor and fires out!


Can you mount a net between 2 helicopters for search and rescue?

Could you? Well - technically, yes. For a little while anyway... Would you actually do it to enact effective rescue operations? No.
There's countless issues with the idea that would make it rather impractical, but I had fun thinking of some of the challenges.
For starters, the net would end up being rather rectangular. The short edges would be as long as the arms on the helicopters could be (which couldn't get too long before they get in the way of landing, flying, etc.), but then you'd need to be able to keep good separation between the two craft so the net would be quite long and thin. The shorter the net was between the two craft, the more responsive it would be to changes in altitude, distance, etc. between the two craft, making the ride even worse. So you'd want it to be long.
You can try this at home - grab a scarf or something similar, and try and hold it out fairly flat between your outstretched arms, with a little action man or barbie doll sitting on it, while going for a walk around the house. You'll be constantly adjusting your arms to keep it flat while in motion and it's still going to be a bouncy ride for your passenger.
The longer the net is, the more drag it will experience, further exacerbating the ride as the drag would be tugging the helicopters around. It wouldn't be very long before the net is pulled tight, at which point the weakest link will fail - the net might tear, but lets pretend it's very strong - the net would be pulled off the arms, the arms might be pulled off the helicopter, or a helicopter might be pulled out of the air.
I did have an idea to help reduce drag... once you've got your passengers on the net (I'll come back to challenges with that), you could have one or both helicopters execute a series of rolls or loops (depending on whether the arms are mounted to a side, or to the front) in order to twist the net up to reduce its surface area! This would have the added benefit of snugly securing your passengers inside the twists of the net.
As for people boarding the net - you'd have to lay it carefully on a flat, open stretch of ground or water. The helicopters would need to either land or very carefully hover, coordinating the entire time in order to not tangle or crash. At which point the person boarding the net could just go for a short jog (or swim) over to one of the helicopters, and board that instead (winched up in the case of water). I'm a bit of a daredevil so I might actually still opt for the net, but in my final seconds (which began counting already when I made that decision) I'd feel pretty guilty about likely destroying two helicopters, the lives of the pilots and crew, and their families.
But oh boy it would be one heck of a ride!


Does the AOA and G-Force increase if a fighter uses the afterburner during a max G level turn?

TL;DR: Maybe.  Maybe not.  It depends on the particular fighter jet, and how it's loaded, and the effect will, in any case, be very small.

An increase in thrust causes an airplane to pitch up via two mechanisms (more details in this PDF):1

An increase in thrust causes an increase in speed; for airplanes with positive speed stability (which is true for all civil aircraft, but is often not true for newer fighter jets), this causes the airplane to pitch up and slow down.2  This changes the slope of the airplane's flightpath (making it point more up), but (at least at first approximation3) does not change its angle of attack.
If the thrust from the airplane's engines is not exactly aligned vertically with the airplane's center of mass, an increase in thrust will create a change in the airplane's pitching moment, which does change the airplane's attack angle; if the engines apply their thrust below the airplane's CoM (examples: 737, B-58), increasing thrust will pitch the airplane up to a higher AoA, whereas, if the engine thrust is applied above the CoM (examples: DC-9, Learjet 23) increasing thrust will pitch the airplane down, decreasing the AoA.  Most fighter jets have engines that are very close to the vertical location of the CoM, so the change in pitching moment from a thrust increase is very small, and its exact direction and magnitude will depend strongly on the specific aircraft and loading used (for instance, burning off fuel could change the vertical location of the airplane's center of mass - and, thus, the magnitude, and, possibly, even the direction, of the change in pitching moment caused by a thrust increase).

Thus, going from maximum dry thrust (no afterburners) to maximum thrust (with afterburners) could, depending on the aircraft, produce a slight increase in angle of attack and vertical4 load factor, but:

the effect would, at best, be quite small, and would depend strongly on the specifics of the aircraft and its loading;
with certain aircraft and/or under certain loading conditions, this effect could well be negative (in which case engaging afterburner would decrease the maximum achievable AoA and vertical load factor); and
the main effect would be (as you, in the latter part of your question, surmised could possibly be the case) to allow a high-G manoeuvre to be sustained for longer (due to the increased thrust helping to counter the high drag of a high-attack-angle manoeuvre).

1: For the purposes of this discussion, I am ignoring aircraft with thrust-vectoring capability.

2: Most airplanes will initially enter cyclic phugoid oscillations with anything other than a very slow, gradual thrust change, but the phugoid eventually damps out, and, even during the phugoid cycles, the "constant-attack-angle" part of the situation remains approximately true.

3: In practice, an airplane undergoing phugoid oscillations with a non-infinite period will undergo continual small changes in its attack angle, due to various damping effects, but the AoA does remain approximately constant.

4: Vertical from the aircraft's perspective, that is.


Would knowing the exact weight that has been loaded on a commercial plane and it's distribution be useful?

YES.

The obvious solution is to roll the plane over a scale.  Useful CG data can also be obtained by weighing the front wheel and comparing its torque to known values.  A light front wheel means an aft CG.  This could be corrected by moving fuel BEFORE the plane is airborne, as well as while in flight.

Of course, moving passengers and cargo are an option too.

For example the plane weighs in at 2200 lbs total on the ramp ready to go.  The nose wheel weight is 200 lbs.  The distance between the main and nose wheels is 11 feet.  The aft CG limit is 0.75 feet forward of the mains.

CG is calculated as follows:  200 lbs/2200 lbs = 1/11.
          CG is 1/11 * 11 feet = 1.00 feet forward of mains.
          CG is with in limits.

And how accurate weighing the nose wheel can be (due to long torque arm):

Nose wheel weight 100 lbs.  Total weight 2200 lbs.
        100 lbs/2200 lbs = 1/22.
         CG is 1/22 * 11 feet = 0.500 feet forward of mains.
         CG is NOT in limits.


Where can I download the coordinates of navigation fixes/intersections?

The closest I can think of would be the Navigraph FMS data, however this is provided in multiple formats. Otherwise you can use Skyvector to look at them graphically.


What would happen if a helicopters rotor hit the [in-air] refueling probe?

It would chop it right off.

Watch the video. It's fun. When the helicopter pitches up right after refueling, the rotor disc cannot follow the movement (its hinges allow the blades to pitch up and down, and inertia makes it change its plane of rotation only slowly). The refueling probe is cut cleanly in half.

However, I would not try this on purpose. The risk of damaging a blade is considerable. I am sure the rotor blades needed to be replaced after that incident.


What's This Cable Connecting Cockpit to Vertical Stabilizer in Air Tractor AT-401?

The wire shown is a cable deflector which is part of a Wire-Strike Protection System common on most agricultural aircraft.

Wire-strike protection systems
As a last resort, when pilot situational awareness and on-board systems fail to detect a wire in sufficient time to avoid contact, a passive wirestrike protection system (WSPS) may protect the aircraft from the consequences of a wire-strike. These are designed to cut or deflect wires away from an aircraft. The types of WSPS vary depending on whether the aircraft is fixed-wing or rotary-wing. They have proven to be an effective safeguard by extensive testing and over two decades of use by both military and non-military operators' worldwide (Jackson, Boitnott, Fasanella, Jones & Lyle, 2004; RAAF, 1 997). However, to enable the WSPS to operate effectively, the wire must contact the cutter at an appropriate angle and the aircraft must also have adequate forward speed. This combination of circumstances may not always be present during low-level aerial operations.
WSPS for fixed-wing aircraft are designed to cut wires that could pass under the aircraft, in order to prevent the wires from coming into contact with the landing gear, or pass over the aircraft, possibly contacting the tail section. Serrated deflection wires may also be fitted from the cabin to the tail section, with the purpose of cutting the wire or lifting it over the tail section. Fixed-wing aircraft used in aerial agriculture operations have had WSPS fitted as standard equipment for several years.
Fixed-wing aircraft used for other purposes rarely carry WSPS as fitment often requires reinforcing parts of the aircraft and may cost several thousand dollars. In general, they are not fitted unless it is expected that the aircraft will spend many hours in low-level flight.


Does the FAA prescribe radar cross-section requirements for civilian aircraft?

No. Primary radar isn't a universal tool to begin with. Secondary radar and thus transponders are more commonly used. So there are regulations as to where and which aircraft need to install transponders. Ultralights and some GA can get away without.

Related: Is it legal to make a non-military stealth plane?

No RCS requirement, but you'll need a transponder regardless.


This article states it pretty well (better than I can word it).

  When the angle of attack (AOA) of the wing increases, the point where
  the airflow separates will move forward and the streamlined airflow
  will become turbulent and separate from the wing. This turbulent wake
  then meets the aft fuselage and tail section of the aircraft. This
  will be felt by the occupants of the aircraft as a rumble or buffet.
  Not all aircraft have a pronounced buffet, this depends on the size
  and location of elevator.

Interestingly enough you can also induce a stall (and first high speed buffeting) by gong too high and too fast while trying to maintain level flight which will cause the center of lift to move aft along the wing. Basically your stall speed and your critical mach number eventually converge this is known as the coffin corner. There is a nice discussion on it here.


Why might an altimeter read incorrectly by 4000ft after sitting on the ground for some time?

This is how it works and I am surprised you switched the altimeter, unless I am missing something in your question. The altimeter reads the barometric pressure and should be set before you go flying. The airport will report the elevation and the knob on the altimeter can be turned till the altimeter is set to the correct altitude. You can confirm there is no blockage and the altimeter works correctly by getting the barometric pressure for the airport from the control tower or weather station, and it should match the barometric pressure numbers in the corner of the altimeter. Pressure changes on a daily basis and must be set each time. When we do a B check before flight, this is the exact procedure we do.

There is more information needed to properly diagnose this problem. With the lack of information I will continue on a couple of assumptions.

1) The altimeter has been bench tested and is serviceable
2) The altimeter system when installed in the plane does not match the local barometric pressure with the corresponding elevation

It was stated that the altimeter was replaced with a known good one. When this occurs the whole system must be pressure checked with a pitot-static test kit. This is a requirement since the system was opened up by replacing the altimeter. If this is not done the system is considered unserviceable. It appears this was not done.

To be complete I would check out the lowest point in the system for moisture and drain it if present.

Generally the procedures including connecting the tester to the pitot static system and taping (covering) all ports not connected. Then pressure is applied to the system, simulating different elevations. The airplane altimeter should match the testers simulated elevation within a certain + or -, for all specified elevations. Additionally, the rate of change of elevation is monitored for any abnormalities that may indicate a problem with any internal mechanisms.

Using the pitot-static tester is an absolute requirement in this situation.


How is a stator like a diverging passage?

If you take a look at the geometry of the path between two stator blades and compare the cross section of the path(relative to the direction of the traveling gas), you can see, that they form a divergent path.


What is the beeping occasionally heard in the background of ATC?

I can't identify the specific sound, but - just like in a cockpit - there are several different audible alerts in a control tower/control centre. Just to list a few:

Conflict alert, as suggested in the comments
Various other radar based safety nets (MSAW, MTCD, DUPE etc.)
Strip printer printing a strip (not an alert as such, but the sound is quite noticable)
Phone ringing (typically a tower has several different phones, possibly with different ringers)
Fault indication on a runway light/navigation aid
Change in status (on/off) of ILS equipment (localiser, glideslope, DME)
Crash alarm, when activated by the controller
Microwave/toaster timer! (at least in smaller towers without a separate kitchen or break room)
Several others, depending on the local equipment

It may be a bit startling when you hear something on the radio that sounds like some sort of alarm, but you shouldn't be worried. The sound can signify many different things and it does not necessarily indicate anything dangerous.


A QRH is a Quick Reference Handbook and is an approved (by some overseeing entity) document specific to an airplane and operator that contains checklists for just about anything the airplane can experience.  At my airline we had copies in the airplane and also in our company flight manual (CFM).

The entry point into a QRH checklist is one of a few things

Memory items
EICAS message
An abnormal event

For option 1, there are various checklists that must be memorized and performed at a moments notice with no reference to the checklist.  Some of these are things like trim runaways, engine fire/severe damage, emergency descent.  Once the memory part of the checklist is complete you refer to the printed version of the checklist in the QRH to verify and perform additional steps beyond the part you were required to memorize.

For the other options, any time anything abnormal happens or an EICAS message is presented, there are indices by procedure name and also by EICAS message into a specific procedure in the QRH to follow.  These procedures may reference other procedures.

For example, If I were to experience a dual engine failure, I would pick up my QRH and find the procedure "DUAL ENGINE FAILURE", this procedure says I should have the master warning light illuminated (and an aural triple chime) and I should see the EICAS message (in red) "ENG 1-2 OUT".  After verifying this presentation and verifying I am in the right procedure, I would perform:

Airspeed....................MINIMUM 260 KIAS
Altitude....................MAXIMUM FL250
Oxygen Mask (if required)...DON
APU.........................START
ENGINE AIRSTART procedure...PERFORM  (note, this is another QRH procedure)

CAUTION: IF THE APU HAS BEEN USED TO START THE ENGINES,
         DO NOT ALTERNATE THE FADECs AFTER START

Note: If the APU is not available, only equipment supplied by the
      Essential DC Bus 1 and 2 will be available.  Engine windmilling
      should drive engine driven hydraulic pumps and supply hydraulic
      pressure.

IF neither engine can be restarted:
    DITCHING or FORCED LANDING procedure......PERFORM


What do the partially filled circles on skyvector mean?

It's an indication of how much of the sky is under that weather condition: IMC, marginal VMC, VMC.


If a tail dragger is converted to a tricycle gear airplane, what will be the effect on weight distribution?

There are some planes out there that exist in both configurations. One of the more common and first that comes to mind is the popular Cessna 150, the Cessna 172 also has an available conversion.

As a taildragger

(source)

And with tricycle gear

(source)

Since the majority of the mass remains unmoved (the engine, fuel tanks etc) the CG will see a bit of a shift but will not be that drastic. The biggest weight shift will be moving the mains up front. However since your gear is located in a different place and thus is loaded differently your CG limits may change.


The system is highly impracticable for a number of reasons.

The referred paper acknowledges that the fuel savings due to existing tankers are negligible and a new design is required. I doubt anyone is going to develop this. Even the military uses modified civil airliners for its tankers needs. Development of the tanker as outlined in the paper will cost billions of dollars and no one is going to do that for a handful of tankers.
Even if such a tanker is built, the existing aircraft will require significant modifications for in flight refueling (assuming that the tanker is standardized from day one, which is practically not possible; even the US armed forces use two different type of tankers). Basically, the structural weight goes up,which reduces performance and increases fuel consumption.
Then the pilots have to be trained for operations of both the aircraft. In flight refuelling is potentially dangerous.See http://foxtrotalpha.jalopnik.com/aerial-refueling-hooking-up-is-hard-to-do-1559495801. Nobody's going to take that risk with civil operations.
The study is extremely simplistic. modern civil aircraft fly in a number of 'flight levels', separated by set altitude. So, for refueling, either the tanker or receiver should climb or descend the difference in altitude, and that burns up more fuel.
If carrying extra fuel in the aircraft is dead weight, it makes no sense to carry it in another aircraft and pay for its operations and maintenance.
It is not correct to compare the military and civil operations. Their priorities, methods and end goals are different. What looks good on paper may not work on real life. Remember Concorde?


How did SR-71 spy, flying at 80,000 ft and 3500 km/h?

The SR-71 Blackbird was equipped with specialized cameras. It would overfly the area of interest and take high-resolution pictures of the ground.

Of particular interest is the Technical Objective Camera (TEOC). It could shoot pictures with a 6'' resolution from the operational altitude of the SR-71. This task was not simple as the aircraft would have moved several hundred feet forwards during the exposure time of the picture which was (depending on the settings) around one or two tenths of a second. Without some kind of correction, this would have resulted in a picture that was blurry in the direction of motion of the aircraft.

To solve this, the velocity over height ratio number was fed to the camera, either manually as computed by the pilot or automatically as computed by the sensors and computer of the SR-71 (and it turns out that the machine did a better job at this than the pilot) and while the picture was taken, the high-precision mirror that directed the camera FOV downwards would rotate in the opposite direction towards which the airplane was moving, thus cancelling it out.


How much time does it takes to buy a landing slot?

I know that in the Netherlands this procedure is open and not obscured behind a login portal.

In the Netherlands the commercial airports are operated by the Schiphol Group, the number of flight movements or slots per airport is determined in collaboration with the government. For Schiphol this is now 500,000 per year. The allocation of the slots is governed by a second body which is set up to be non discriminating in the allocation of slots. Most of the answers to your questions can be found there: https://slotcoordination.nl (English website)

Who allocates slots?

  Under the European Union rules – (EC) Regulation 95/93, as amended -,
  a Member State of the EU needs to appoint an airport coordinator for
  each coordinated airport. The same coordinator can be appointed for
  more than one airport. SACN has been appointed for coordinating AMS,
  EIN and RTM. Coordinators are independent bodies to maximise
  transparency.

How often are slots allocated?

  Slots are allocated for each season, and slot coordination recognises
  two different ones. There is a Winter season and a Summer season. The
  mark of the change of season coincides in the EU with the change of
  summer/winter time. The difference is recognised to make sure we use
  daylight optimally.

How are slots allocated?

  The allocation planning process starts around six months before the
  start of each season. Slots are allocated free of charge from a pool
  of available slots. Allocation takes place according to certain
  priority rules in a neutral, non-discriminatory and in a transparent
  manner. The leading principle of distribution is based on historical
  precedence, the so-called grandfather rights. When an airline operates
  a series of slots in a season for 80% or more, it can hold on to the
  same series in the next same season. When it operates less than 80% it
  loses its historic rights (the so called ‘use-it-or-loose-it’ rule).
  Slots can be re-allocated until the day of operation.

What happens when the requested slot is not available?

  An airline can keep its request on the list of ‘outstanding requests’
  to see if during the allocation process slots become available over
  time. Airlines can freely exchange slots. Prior to each season a
  worldwide Scheduling Conference takes place enabling face to face
  meetings between airlines, airports and coordinators to improve the
  allocation process.

Apart from being assigned a slot, an airline also needs to file a request with the airport to request for the required services to handle the aircraft. Schiphol has a very informative website with a lot of publicly available information:

For passenger handling (gates, check-in, etc.)

https://www.schiphol.nl/en/operations/page/passenger-process/

For aircraft handling (gate assignment procedure etc.)

https://www.schiphol.nl/en/operations/page/aircraft-process/

If you want to know more about the trade in landing slots then I would suggest opening a new question since there is a lot to tell about that subject as there is a lively trade going on there.