What is the typical temperature of an airliner's hull during flight?

There are two primary factors that affect the skin temperature of an aircraft in flight: the air temperature, and the speed of the aircraft.

The air temperature where airliners cruise is relatively cold, around -54 °C at 35,000 feet.

As a body like an aircraft moves through air, it compresses the air, which causes the air temperature to rise. The maximum temperature rise will be if the air is completely stopped, such as at a leading edge. This is called the total air temperature, and the amount that the temperature rises is called the ram rise.

Using a simple formula to find the ram rise:

$$RR = \frac{V^2}{87^2}$$

… where $RR$ is in Kelvin, and $V$ is the true airspeed in knots.

Using a typical airliner cruising speed of 500 knots gives a temperature of 33 degrees. This brings the total air temperature to -22 °C, which is still quite cold. At places other than the leading edge, the temperature rise will be less. This is why cargo holds will need heaters to be safe for live animals, even being insulated and pressurized. Airliners just don't fly fast enough to produce a significant amount of heating.

On the other hand, the SR-71 could fly at over 1,910 kts, which gives a ram rise of 482 °C. The air doesn't get much colder as you climb to the altitudes where the SR-71 flew, so this gives a total air temperature of over 400 °C. Speed makes a huge difference.


Is gascolator and fuel strainer the same thing?

Yes in practice they are the same thing (it's surprisingly difficult to find the origin of the term "gascolator") and most definitions will mention both terms, although I tend to think of the gascolator part as the gravity water separator bowl/quick drain component, and the strainer as the filter screen covering the outlet.
Back when cars had them (up to the early 60s) they were called "filter bowls" with the bowl part made of glass and without the quick drain.  You just removed the bowl to get rid of any water you saw when checking under the hood (airplane gascolators from the 40s also used glass bowls, although most have been replaced by metal ones).
Most aircraft gascolators use a 75 micron mesh screen (the strainer part - about like the screen on those plunger coffee makers) at the top of the housing to keep particles from passing to the carb.  On my homebuilt I improved on that by using a 30 micron sintered bronze filter made for the filter bowl of a late 50s Chev Impala, which fits perfectly in the standard gascolator bowl.


When was the last time the US Standard Atmosphere 1976 was updated?

No, this model was last updated in 1976, and only differs from the 1966 model above 51km in altitude, where aircraft rarely fly anyway. There are no newer versions of this atmospheric model.
There are other models though, some of which may be newer.


What aircraft are parked in this naval air station?

At the right end of the row of eight fighters, the two delta wings look like Dassault Mirages.  Trailing edge with a slight reverse sweep.  Ordnance just visible mid-span.  Upper fuselage flared towards the engine inlets.
The six fighters at left look very much like Hawker Hunters, but those are now flown only at air shows.  That guess led me to discover that they were stationed at Point Mugu AFB for a 2015 air show.
A video of the maybe-Hunter taxiing at Point Mugu in 2015 also
shows that one of the delta wings has registration N401AX,
which identifies it as a 1980 variant of the Dassault Mirage 5,
an Israel Aircraft Industries KFIR-C2.
Later, the video also shows the maybe-Hunter's registration, N330AX, confirming it as a 1959 Hawker Hunter Mk.58.


Professional airline pilots are paid by the airline for their flight hours, similarly to other transportation workers.  Time spent in preparation for flight or even preflighting the plane itself is not usually compensated.  This pay varies by the company and the position (first officer, captain, etc.), and sometimes there are signing bonuses on top.  Pilots are given a monthly minimum of hours pay that they'll receive, even if they fly less than that. This is often as little as 65 hours guaranteed pay.

Regional jets, e.g. Republic, are typically contracted by another company like American Airlines. The regional airline, not the major airline, would pay the pilots for their flight hours.  This is even true if the regional jet has the livery of the major airline or the tickets are sold by the major airline.

Private/charter pilots get paid by the company (or person) managing the plane.  This can be either a per-day wage, a yearly salary, or a mix of both.  (Source)

Flight instructors are paid an hourly wage by their flight school.  This hourly wage does not include things like weather delays, your own education, and planning.   Flight instructors can also work independently and then they'd be paid directly by the student.

Except where noted, the source for this information is The Truth About The Profession.


Are there any airliners capable of vertical climb with engine thrust only by pointing the nose up?

No, there are few planes that can do this at all. In order to be able to climb out straight up you need a thrust-to-weight ratio greater than 1. In other words you need enough thrust to propel the full weight of the aircraft up without the wings generating lift.

Wiki provides a brief list of aircraft and associated thrust to weight ratios, the Concorde comes in on top at 0.372 with full afterburner but this is at max weight. Although at its empty weight it was pushing a 0.877 ratio. Even running on fumes would not have done it at full afterburner in the Concorde. For comparison the 757-33 has a ratio of 0.6 at Operational Empty Weight assuming a maximum thrust of 42,600 lbf per engine.


Why is the initial short-field climb below Vₓ in a Cessna 172?

The published Vx is in the clean condition (no flaps): 62.

With the flaps down, for a short-field takeoff, Vx is 56.

This is the same reason why the stall speed (bottom of the white arc) is lower with flaps than without (bottom of the green arc)


How is horsepower measured for aviation piston engines?

Like anything else a Dynamometer is used except the engine is bolted directly to it (most likely on a test bench). In a car a rolling road is simply a way to couple the tires to the dyno without having to have any custom fittings. For what its worth cars lose a bit of horse power in the transmission/drive shaft/differential so shaft horse power and wheel horsepower are not always the same. However in a plane the prop is bolted more or less to the end of the crank (with the exception of some planes with stepper gear boxes). In any case shaft horsepower on a plane engine is more or less whats available at the prop.

Here is a lycoming engine on a dyno

(source)


What are these spinning discs next to the throttle of the Boeing P-8 Poseidon?

Those spinning discs on either side of the throttle quadrant are the stabilizer (stab) trim wheels.

The stab trim system can be actuated by electric trim switches on either the left or right control yoke, the autopilot (AP), or by manually turning the stab trim wheels. The yoke mounted electric trim switches "spin" the trim wheels at the high speed seen in the GIF above, while the AP turns the wheels at a relatively slower rate. A stowable handle in the trim wheel can be pulled out to allow for faster manual turning.

I've heard that this handle can be very painful to the knees if left unstowed and either the AP or especially the electric trim turns the wheels.

See "Why I hate the Boeing 737" for more info on the system, including photos of the trim wheel and stowable handle:


Let's continue with you example of France DGAC.

National body: DGAC

DGAC is in charge of French ATC, in airports and enroute, manages ATC education and training (ENAC, École Nationale de l’Aviation Civile), is the spokesperson for operators, crews and industrials.

DGAC in general is the operational safety people you can see at the airport, EASA is not present. They are reporting to French authorities (e.g. Ministère de la transition écologique) who are still responsible for overseeing aviation activities in France.

Regarding safety, the domain of EASA:

  DGAC is responsible for ensuring the safety and security of French air
  transport. On one hand it is a regulatory authority, but it also
  supervises security and safety [...]

  DSAC, The Civil Aviation Safety Directorate is the department of DGAC
  in charge of safety. Its task is to ensure safety for everyone
  involved in air transport. It is in charge of monitoring the
  application of the regulations, which are primarily developed by the
  European Aviation Safety Agency (EASA).

(Source)

STAC (Services Technique de l'Aviation Civile) is a branch of DGAC in charge of planning navaids and airports and designing airports systems.

EU body: EASA

The actual domain of EASA, as name implies, is safety. While EASA doesn't replace local authorities, it is the main regulatory body in EU for civil aviation.

DGAC (actually DSAC) on the other hand is participating to safety regulation preparation as do other national agencies in EU. Remember EASA was only 400 people a few years ago, maybe twice today.

EASA has issued a number of "regulations". Regulations don't have to be implemented locally contrary to "directives", they are binding per se. An analysis of the regulations structure is available here:

Some activities have logically shifted from DGAC to EASA, in particular the ICAO role to issue airworthiness directives for commercial aviation:

  From 15th February 2006, DGAC France stops issuing Consignes de
  Navigabilité (= Airworthiness Directives) on behalf of EASA

However ULMs or gliders topics (among other) are still under DGAC responsibility.

EASA vs FAA

Contrary to FAA which encompasses nearly every aspect of civil aviation in the US, EASA has a limited, though critical and expanding, role around security, safety and airworthiness.

Contrary to FAA, EASA is not an ANSP. Eurocontrol itself has not to be compared (yet) with FAA ANSP role, they actually cover only a very small part of the EU sky (Maastricht UAC), even if the long term idea is to standardize ANSP tools in EU and allow a true single sky ATM to cope with the increasing traffic. DGAC (DSNA branch) has still full authority for this aspect in France, and probably for some time since ATC means also coordinating with national air force.


Where is the taxiway between the Boeing factory and Paine Field airport?

That "road" is in fact a taxilane, and marked as such on the Paine Field side (note the yellow lead lines marked at the bottom of the image below, you would find on a taxiway). It connects the Boeing plant to Paine Field's "Boeing Ramp" where final prep can be completed before the aircraft are flown off to wherever they're going.

The terminology is important here: The bridge acts as a taxilane (a non-movement area not under the control of ATC which connects various aircraft parking areas to the taxiways). Boeing coordinates their own movements between the main plant (north) and Paine Field's Boeing Ramp (south). (The bridge is also not depicted on the airport diagram and may not even have "taxilane" status - as far as ATC is concerned. It's just sort of "there".)


May I fly an aircraft registered in an EASA member with an EASA licence (NOT same country as airplane) outside Europe?

Under ICAO rules, if Germany 'validates' your Italian license then yes, you can fly the German aircraft in other countries:

Use of flight crew licences on foreign-registered aircraft
Any pilot
who wishes to fly on an aircraft registered in a State other than the
one that has issued the licence, needs to obtain an authorization from
the State of Registry. This authorization is generally given by the
State of Registry through a validation or a conversion of the foreign
licence. In general, the validation process is used for short-term
authorization while the conversion process is used for longer-term
authorization.

What 'validation' means here is up to the country where the aircraft is registered. ICAO itself doesn't define what they should do:

When a State validates a foreign licence, it recognizes it as valid
for use on aircraft on its own registry. The Convention on
International Civil Aviation and its Annex 1 do not contain specific
requirements for the validation of licences beyond establishing the
principle and the fact that the validity of a validation, cannot be
extended beyond the validity of the supporting licence.

In the US specifically, these ICAO rules are implemented in 14 CFR 61.3 (emphasis mine):

(b) Required pilot certificate for operating a foreign-registered
aircraft within the United States. No person may serve as a required
pilot flight crewmember of a civil aircraft of foreign registry within
the United States, unless—
(1) That person's pilot certificate or document issued under §61.29(e)
is in that person's physical possession or readily accessible in the
aircraft when exercising the privileges of that pilot certificate; and
(2) Has been issued in accordance with this part, or has been issued
or validated by the country in which the aircraft is registered.

Practically speaking, I would say that if you have some official piece of paper from the German authorities confirming that you are authorized to operate German aircraft - or at least this German aircraft - then you're good to go. The piece of paper may even be unnecessary as far as Germany is concerned, but if you plan on flying internationally then I think the more pieces of official paper that you have, the better.


What is the nominal frequency of the satellite communications terminal on MH370?

I looked through the report about the flight path analysis that is available from this page.

In Appendix G they explain in more detail how the analysis was done. On page 56, they provide the details about the frequencies (emphasis added):

  The uplink and downlink Doppler may be calculated from the relative movement of the aircraft, satellite and GES using the signal frequencies of 1646.6525 MHz (uplink) and 3615.1525 MHz (downlink).

This means the aircraft terminal transmits (uplink) on 1646.6525 MHz and receives (downlink) on 3615.1525 MHz. However, it is not that simple.

  The aircraft terminal adjusts its’ transmit frequency to compensate for the Doppler induced on the uplink signals by the aircraft velocity. Aircraft heading and ground speed are used to calculate the Doppler shift the signal would experience if the satellite was at its nominal location over the equator.

This is called Automatic Frequency Control (AFC) and Appendix G goes into more detail about all the factors involved, and provides tables with example calculations.


Were early military planes not pressurized?

There were a few problems:

Pressurization (while not impossible) was difficult requiring extra effort. It also increased weight and complexity.
Pressurization was still a relatively new technology at the time. For reference, the first pressurized commercial aircraft, the Boeing 307 Stratoliner, made its first flight later the same year (1938) as the B17. Note that it was developed from the B17.
There was an incredible amount of openings on early planes for gun turrets, bomb bays, etc. Sealing these off airtight would have been a impractical nightmare. You would traverse the bomb bay move to the back and front of the plane.
It's also better from a reliability standpoint- it's pretty easy to damage and make a hole in the fuselage, but everybody having their own oxygen masks removes that single point of failure.
While perhaps (I imagine) not incredibly comfortable for long duration missions oxygen masks worked fine.

30,000ft corresponds to around 9,200m, although that altitude is a ceiling defined by Boeing. With full load, they never achieved those altitude and hung around a lot lower. While I can't verify it, these forum posters appears to suggest that 19,000ft-28000ft with bombs was more common.

To do the math, the partial pressure of oxygen at sea level is around 0.21 bar. If you're being fed 100% oxygen through your mask, this is the same pressure as at 11,000m.

Photo by Margaret Bourke-White, Sept. 1942, from the LIFE Archives.


Flying from right seat of Socata TB9 - confused about Pilot manual limitation (US regulations)

Most airplanes are designed for the pilot to be in the left hand position, so some have controls on the left side that are inaccessible (or very hard to reach) in the right hand position, like parking brakes, fuel tank selectors, nosewheel tillers (on big jets), sometimes the key is hard to reach. On the TB9 the circuit breaker panel is by the LH pilot's leg, it would be extremely challenging for someone in the RH seat to reach those, and they could be important if one blows in flight or there's a fire.

The important things is that the person in the left seat is capable of and has been briefed on how to operate any controls required during the flight.

Personally I don't see why you need to let people sit in the left seat to give them a taste of flying, the right seat is just as good for that and it is less risky.


What is the difference between P208 and P209 base runway materials?

From the FAA Airports Construction Standards Part 3 ('flexible base courses');

Just a side note that these are just little introductions to the materials. Download the word document from the linked page and just read that if you want.

  P208: This item shall consist of a base course composed of course aggregate bonded with fine aggregate base. It shall be constructed on a prepared subgrade or subbase course per these specifications and shall conform to the dimensions and typical cross-section shown on the plans.
  The aggregate base material shall consist of both fine and coarse aggregate.  Material shall be clean, sound, durable particles and fragments of stone or gravel, crushed stone, [   crushed slag,   ] or crushed gravel mixed or blended with sand, screenings, or other similar materials produced from approved sources. The aggregate shall be free from lumps of clay, organic matter, and other objectionable materials or coatings.

And for P-209

  This item consists of a base course composed of crushed aggregate base constructed on a prepared course in accordance with these specifications and in conformity to the dimensions and typical cross-sections shown on the plans.
  Crushed aggregate shall consist of clean, sound, durable particles of crushed stone, crushed gravel, [   or crushed slag   ] and shall be free from coatings of clay, silt, organic material, or other objectionable materials. Aggregates shall contain no clay lumps or balls. Fine aggregate passing the No. 4 (4.75 mm) sieve shall consist of fines from the coarse aggregate crushing operation. If necessary, fine aggregate may be added to produce the correct gradation. The fine aggregate shall be produced by crushing stone, gravel, [   or slag   ] that meet the coarse aggregate requirements for wear and soundness.

You can download the Word file for more info on this, if you want to.


How would we calculate the load factor on an aerial vehicle while landing due to sudden gust loads?

You need at least the stroke of the tire-gear combination to calculate a load. If the airship contacts the ground with a velocity of $w$ and a mass of $m$, the impulse $m\cdot w$ needs to be absorbed by a force $F$ acting along the stroke $s$, as in $m\cdot w = F\cdot s$. Adding airship flexibility will greatly improve the accuracy of the result, because I suspect the hull will deform easily and add to the stroke.

If you need an example of how this is calculated for a Boeing 747, please click here.


What's the functional difference between PAPI and VASI?

A PAPI and a VASI are very similar in the the information they provide. The only functional differences between the VASI and PAPI is that the VASI has the red over the white, the PAPI the white actually goes to the right of the red, and the PAPI offers higher precision (or more glideslopes depending how you look at it a larger airliner with a high cockpit may elect to fly a slightly higher glidepath). The concept is the same though.

A VASI looks like this:

Usage:

As the saying goes,

  Red over White, you're alright. (on glidepath)

  Red over Red, you're dead. (too low)

  White over White, you're out-of-sight (too high)

A PAPI like this:

A regular VASI only offers one glide slope and is designed for an aircraft where the cockpit isn't so high up. However, there is a such thing as two-light PAPI, and a three-bar VASI. So either of them can really be tailored to fit the costs and types of aircraft flying to that airport.

In the case of a four-bar PAPI it is higher precision. Since the PAPI systems uses a narrower beam of light you must fly the glide path more precisely than the VASI to stay on the beam. The PAPI, with its extra lights, forewarns you when you are drifting from the desired glide path.

(source: airportlightingcompany.com)

So one red light would indicate slightly above glide slope, two and two would indicate the normal glide slope, and three red lights would indicate slightly below the glide slope on a 4-bar PAPI. A Three bar VASI works in similar fashion except there are only two glide paths with two reds being the lower, two whites the higher.


Do all the engines/propellers of a VTOL UAV need to be identical?

MIT CSAIL has researched apparently quite thoroughly on this and the end result it would seem is that you can have ANY different size of motors be able to fly given that it satisfies certain conditions such as thrustep etc. For this I would recommend following developments in two areas (as far as my knowledge goes)
First of ckurse MIT CSAIL's video demo of their custom software to simulate all combos of motor thrust and positioning

The next 'guy' you want to follow is ofcourse
Raffaello D'Andrea  and his research team. His TED talk explores drones at mechanical disadvantages, here you go

https://www.ted.com/talks/raffaello_d_andrea_meet_the_dazzling_flying_machines_of_the_future

That's as far as my enthusiast knowledge could help


How can a hang glider take off from flat ground?

If you were an avid hang glider pilot at the time you posted your question, you no doubt have long since connected into the local hang gliding community and found the answers to your questions, and have spent many joyful hours soaring under the beautiful cumulus clouds over the Texas flatlands.

Aerotow (towing up behind a slow-flying ultralight or lightsport aircraft) is one way to launch hang gliders from flat ground.  A typical tow will be to around 2500' or 3000' up.  You'll start with the glider on a three-wheeled dolly so your own legs don't have to be involved.  If you've never done it before you'll get training in a "tandem" hang glider, flying with an instructor.  There is an active hang gliding business very near Houston that offers aerotow launches, and I hope you have made contact with them since you posted your question.  (Google "Cowboy Up Hang Gliding".)

Another method is called "platform launch".  The glider is placed on a platform on the bed of a pick-up truck.  The truck has a reel of line that pays out under constant pressure, regulated by a disk brake.  The truck starts driving down a long little-used road or on a dry lakebed or an airport runway.  When sufficient airspeed is reached to ensure a strong positive launch with a strong vertical climb rate, the  pilot pulls a trigger to release the glider from the truck and the line starts spooling out.  I've gained as much as 4000' of altitude during this type of launch, using a reel of lightweight spectra line, and a 3-mile-long road.

This type of launch is a very technical procedure and unless you are a willing to take high risks as a test pilot, you must use the exact equipment that other experienced flyers have carefully developed over the years.  You must get training in the techniques, use a  detailed checklist, etc.  I'm not sure if this is currently being done anywhere near you.  Aerotow would be the easier route in most cases.

Yet another method uses a stationary winch that reels the line in.  Often such a winch is made from a motor scooter, mounted on a trailer, with the back wheel replaced by a drum (reel).  This method can be good for beginner training via ground-skimming flights, but also can be used to launch to several thousand feet of altitude.

It is also possible to tow a hang glider from a car or truck using a fixed length of rope.  This is not as simple as it sounds-- for example a line tension gauge is essential.  Read on for more safety tips.

To safely tow a hang glider, you must avail yourself of community knowledge and training.  With many methods, it is vital to have some way to actively control the towline tension, and with all methods, a weak link of appropriate strength is essential.  Reliable release mechanisms that route the towline's pull to the appropriate points on the pilot's harness (and sometimes to a point on the glider as well) are also essential.  Simply tying one end of a strong rope to the glider and the other end to a fixed point on the ground and trying to launch yourself like a kite on a windy day would be extremely dangerous.  Several fatalities occurred this way back in the early days of hang gliding, before the community gained expertise in safer methods, and also developed a strong culture of safety-consciousness.  A phenomenon called a "lockout" is waiting to bite you if things go wrong.  If you've ever seen a tethered kite dive into the ground at high speed with the string under high tension, you'll have some idea of what this might be.

Generally speaking, hang gliders have less control authority than sailplanes, especially in the roll axis, so towing hang gliders is more complicated than towing sailplanes, and more care is needed to maximize the odds of a safe outcome.  However, if due caution is taken, towing can be a very effective way to get a hang glider up into the sky.

There are also motor units available for hang gliders.  The modern method is to incorporate the motor into the pilot's harness, not to attach it to the glider itself.  Using your own feet as landing gear while launching with a motor can be somewhat challenging and also dilutes the joy of pure soaring flight; you'll probably have a more enjoyable experience if you go the aerotow route.  But google "mosquito harness" or "hang glider powered harness" for more on the motor option.

A related concept is the "light trike", where there are wheels and a seat as well as a motor, all connected to a hang glider wing, but everything is kept light enough in relation to the wing size to allow a low sink rate in unpowered flight.  The motor is used to get some altitude, and then you shut it off and have a nice soaring flight.  The control "feel" may be a little awkward compared to a pure hang glider flown from a prone position-- most hang glider pilots would prefer to let the motor fly away with the towplane at the end of the tow, as long as the soaring conditions are good and a towplane is available.

I can't answer a question about hang gliding in Texas without referencing the famous flights originating from Zapata TX on July 8 2012-- one pilot flew 764 km (475 miles), and a second pilot flew just a few miles short of that distance.  Read more about it -- and see video of their aerotow launches-- here: https://xcmag.com/news/dustin-martin-and-jonny-durand-break-hang-gliding-world-record-in-zapata-4/

And yes of course it is also possible to run into the wind as fast as you can and then increase the angle of attack of the wing to do a little hop.  In terms of peak altitude gain, this is particularly effective on a beach, where the wind gradient tends to be especially pronounced-- the wind gradient will help you out as you start to climb-- but then will work against you as you come back down.  You'll never get more than a few seconds of flight time this way, but it can be a fun thing to  do a few times after you touch down on the beach after a nice long ridge-soaring or dune-soaring flight on a windy day.


How do the fighter jets in air shows color their smoke trails?

For example for the Patrouille de France under the Alpha Jet there is a tank called the smoke pod. Inside, two tanks contain oil with a colorant if you want color, or without colorant if you want white. When the pilot opens one of the valves, the oil flows through a small pipe and exits only at the left reactor. With the heat, around 700°C, it immediately turns into gas and gives this thick smoke. See this (in French):

Source: pilote-virtuel.com


Can air-to-air refueling be done in compliance with the FAR's?

I can't provide a definite yes or no, but I can discuss some of the FARs that will need to be considered. In most cases you have to consider three groups of FARs; covering aircraft, aircrew, and operations.
For the aircraft, they have to have an airworthiness certificate.
The Kodiak is certificated, but you have to address operating without the cargo door (may be approved) and if the temporary installation of your refueling equipment needs any approvals. Many temporary installations don't but since your refueling equipment will connect to another aircraft's fuel system it may need a 337 or STC.
You say the receiving aircraft will be custom built. That implies an experimental certificate. There are two, maybe three, different experimental certificates that you could theoretically apply. The first is Experimental-Amateur Built (E-AB). This could work if you are not a business and this effort is for personal educational purposes. It's the least restrictive, but is in a gray area of applicability. The second is Experimental-R&D. It would be applicable, but it's the most restrictive certificate as it limits you to just R&D flights and crew proficiency flights and it requires annual renewal. Experimental-Exhibition might apply, but it's usually limited exhibition flying of existing, non-certificated (typically ex-military) aircraft. In any of these, I would expect that you would need to include aerial refueling within the operating limitations and that means getting an FAA inspector to buy off on it.
For the aircrew, I expect the one potential issue is one of compensation. If everyone holds at least a Commercial certificate that would avoid any gotchas. The other issue may be meeting the FAA training guidelines for formation flying.
Flight operations would be subject to Part 91 and the operating limitations of the aircraft. I would expect that refueling operations would be limited to airspace 'not over populated areas.'
So, I expect it would be possible but it could be difficult getting the necessary approvals.


Where is the 36 month ATPL theory exam validity before CPL/IR test listed and described?

I don't know much about EASA regulations, but this seems to be a reference to Part FCL.025(c)(1):

  (1) The successful completion of the theoretical knowledge
  examinations will be valid:
  [...]
  (ii) for the issue of a commercial
  pilot licence, instrument rating (IR) or en route instrument rating
  (EIR), for a period of 36 months;
  (iii) the periods in (i) and (ii)
  shall be counted from the day when the pilot successfully completes
  the theoretical knowledge examination, in accordance with (b)(2).

Having said that, (c)(2) gives a much longer validity period for the ATPL exams:

  (2) The completion of the airline transport pilot licence (ATPL)
  theoretical knowledge examinations will remain valid for the issue of
  an ATPL for a period of 7 years from the last validity date of:
  (i) an
  IR entered in the licence;
  or (ii) in the case of helicopters, a
  helicopter’s type rating entered in that licence.

My understanding of that is:

Your IR theory exam is valid for 36 months from the date of the exam
Your ATPL exams are valid for 7 years from the date you receive your IR (although the wording is ambiguous, in my opinion)

It's possible that your provider is combining those two points somehow. The easy thing to do here is simply ask them to explain their statement in more detail and include a reference to the regulations.


Good catch! You are right, the center of gravity will be too much forward for a canard. If they put the prop on the sting behind the wing and the cockpit a bit ahead of the wing, things would look more credible.

The size of the foreplane is not obviously wrong, but the booms at the tips of the foreplane look strange. They serve no obvious purpose, like the sting, and the tailbooms look too thin for transmitting the loads from the vertical surfaces into the wing.

One third thing that looks odd are the control surfaces: The ailerons look too small to allow maneuvering in gusty weather at low speed. I guess the flaps on the inboard wing are for pitch control. Why are they not on the canard, where they would be more effective? Maybe because the center of gravity is so close to the foreplane, the designer decided to put them on the wing.

I agree with your assessment: This thing will remain an artist concept.

For comparison, see below a picture of a solar aircraft that actually flies and got most things right: The Icaré II:

Icaré II in flight (picture source)


From this reference:

$$c_f=K_1\cdot \frac {t}{c} + K_2(\frac {t}{c})^2 +  K_3(\frac {t}{c})^3 + K_4(\frac {t}{c})^4$$

For the 64A series:

$K_1$ = 8.2125018
$K_2$ = 0.7685596
$K_3$ = 1.4922345
$K_4$ = 3.6130133

$c_f$ is the particular scale factor for this profile. And then the reference continues with this head spinning further explanation:

  Now, for a specified family and thickness, the thickness distribution may be determined without iteration. From the thickness, the scale factor is computed from the polynomial function shown above. Then, the scale factor is used to multiply the basic values of the psi and epsilon functions for this airfoil family. These scaled psi and epsilon functions are used in mapping the z-plane to the z'-plane shown in Figure 1. The Joukowski function zeta = z' + 1/z' then maps the z'-plane into the zeta-plane and these results are normalized so that the leading edge is at x=0 and the trailing edge is at x=1.

Hope this helps, my head hurts after reading that.


Documentation about "drag stabilized flying wings using non-reflex airfoils"?

If you’re going attach a boom and surface, why are you comparing to a reflexed airfoil?  Attach the boom and surface conventionally and you get far better LD than either. The effective trim drag is lower. And you can get it thru the door of the hangar.
  Planks are cool, but applying the restoring force without much lever is the basic problem. The required force and resulting drag is much higher.
  The new config exposes the whole boom to flow and the vane is 100% drag. A conventional surface generates force with the L/D of the tail surface, only 20% drag if the LD of the tail is 5.
    Conventional boom or even a swept tailless is far superior to this config or reflexed plank. I don’t think anyone will spend time calculating the diff between two poor config. Sorry.


Is an aircraft's maximum landing weight really weight, or is it mass?

The maximum landing weight given here is actually the mass, not weight.

In general, the various 'weights' given for aircraft are masses, not weights. i.e. they are in kilograms, not Newtons.

This is simply an extension of our everyday usage. As @mins pointed out, if someone asks your weight, you tell your mass (70 kg or whatever), not the weight itself (~686N).


From the Code of Federal Regulations CFR 14

§21.613   Duration.
(a) A TSO authorization or letter of TSO design approval is effective until surrendered, withdrawn, or otherwise terminated by the FAA.
(b) If a TSO is revised or canceled, the holder of an affected FAA letter of acceptance of a statement of conformance, TSO authorization, or letter of TSO design approval may continue to manufacture articles that meet the original TSO without obtaining a new acceptance, authorization, or approval but must comply with the requirements of this chapter.

From the FAA's page on TSO Cancellation/Withdrawal:

What is the difference between a "Canceled TSO" and "Withdrawal of a TSO authorization"?
A "Canceled TSO" means that the TSO has been rendered inactive and the FAA will no longer issue new TSO authorizations against that particular TSO. However, any existing TSO Authorizations obtained prior to the cancellation of the TSO are still valid and may continue to be manufactured and marked in accordance with that authorization.
The "Withdrawal of a TSO authorization" means that a specific authorization letter is withdrawn by the FAA and the approval to manufacture that particular article is terminated.
In summary, if the TSO is canceled, you can still make the article but you can't apply for a new authorization to that particular TSO revision level. If the TSO is withdrawn, you can't even manufacture the article under the TSO system (i.e. the FAA won't let you put a TSO label on it).

An example of the FAA suspending a TSO Authorization NavWorx ADS-B


Will the frequency 122.000 MHz no longer be used for Flight Watch after October 1st 2015?

Below 18,000 feet MSL, En Route Flight Advisory Service (EFAS) (a.k.a. Flight Watch) is provided on 122.0 MHz. Above this altitude, it is provided on discrete frequencies, with each one serving a specific ARTCC area (see AIM 7-1-5, FAA JO 7210.3Y Section 3).  These discrete frequencies are listed in the margin of IFR Enroute High Altitude charts:

To answer your original question, the FAA plans to consolidate EFAS onto existing Flight Service Station (FSS) frequencies on October 1, 2015. Because Lockheed Martin (the FSS contractor) has consolidated flight service stations, the EFAS weather briefers are now co-located with Flight Service personnel (they physically sit next to each other in the same room), making it possible to obtain both services on the same frequency.

At the same time, the FAA will phase out legacy Remote Airport Advisory Services and more significantly, require the ICAO format for all flight plans (international AND DOMESTIC), see Flight Service Program change announcement.


Will the pilot in a plane be able to tell if people are jumping up and down?

If an aircraft is large enough to have a “bedroom”, it will be too large for the movement of an average sized person in the bedroom to be noticed in the cockpit.


Normally not; details depend on the control system and by how much the aircraft is out of trim. The force produced by the empennage will be the same in the trimmed state and when out of trim, only the control forces are different.

Let's examine the different possibilities:

Adjustable spring (as used on some light aircraft and gliders): The elevator deflection will be identical to the trim position, so there is no difference at all.
Trim or servo tab on the elevator: The tab deflection will be different, but the elevator position will be practically identical. For tab angles of less than 10° relative to the elevator there should not be any difference in drag.
Adjustable stabilizer: Now the elevator deflection will be different, and depending on the trimmed state the deflection angle might cause higher airfoil drag. If the elevator deflection relative to the stabilizer is more than 10°, a slight drag increase can be expected.

If the power consumption of the autopilot is higher in the out of trim case, this might cause higher generator loads and more engine power is needed to keep it powered. But this effect should be very small.


Would a slower and larger rotor blade be practical?

Indeed a relatively large rotor has advantages:

Low induced velocities: less sand and bushes that are swept up by the rotor airstream.
Low autorotational rate of descent.
Low power required in the hover.

However, there are some disadvantages as well:

The size of the helicopter is less practical at landing, take-off, clearance of buildings etc.
The empty weight is higher, a very important factor in VTOL aircraft.
The hub drag is higher.

A smaller rotor will have a smaller and lighter hub and a lower overall parasitic drag: more efficient for cruising flight. There is a practical limit to blade radius of about 12 m due to static rotor droop when not spinning. From J. Gordon Leishman:

  The static droop can increase quickly for larger rotor diameters and may cause problems when starting and stopping the rotor, especially in gusty wind conditions where the low centrifugal forces on the blades may lead to "blade sailing,"causing the rotor blades to flap and flex and perhaps impact the airframe.

The rotational speed of the rotor is determined by the tip speed, and is set such that at cruise speed the advancing blade tip stays below the drag divergence Mach number. Reducing the tip speed permits a higher flight speed to be achieved.

Image source

There is a design optimum for rotor disk size, determined by weight. The weight over disk area ratio is the disk loading and the analogy with wing loading of fixed wing aircraft is very strong: a large wing area creates more drag and construction weight. The relationship between disk loading and operating weight is partly governed by the square-cube law, and a clear trend can be observed when the two parameters are plotted against each other: there is an optimum governed by weight, and the optimum is not the largest rotor diameter.


The atmosphere approximates an ideal gas, and as such you can relate pressure and density through the ideal gas equation.  The form we use in meteorology uses mass density and is given by:

$$p={\rho}RT$$

where $P$ is pressure in units of Pa, $\rho$ is density in units of kg m-3, $R$ is the gas constant for dry air (287 J kg-1 K-1) and $T$ is temperature in Kelvin.  This assumes a dry atmosphere and humidity will decrease density for a given pressure.  Consideration for water vapor is usually brought in by changing temperature into virtual temperature $T_V$ where $T_V=T(1+0.61q)$ and $q$ is the mixing ratio of water vapor (units $kg~ kg^{-1}$).

Pressure increases with temperature because the particles have more kinetic energy (which is proportional to $T$).  Imagine a box full of bouncing balls, if these balls start moving faster the balls will hit the walls of the box harder, imparting more force on the box.  Pressure is merely force per area, so if the force increases but the box stays the same size, the pressure has increased.

Air density can decrease with temperature if pressure is also decreasing.  If pressure is constant, this cannot happen (they would be inversely related).  Any time you specify a relation between any two of pressure, density or temperature you must hold the third constant or specify its behavior.

For example, hot air rises, but why then is it cold on top of a mountain.  The answer is that hot air is less dense than the cold air surrounding it for a constant pressure, and being less dense it rises.  With a mountain, the pressure is decreasing, and we likewise find in the atmosphere that temperature decreases with decreasing pressure.

On a hot day what tends to happen is that the surface, which is being warmed by the sun, heats the lowest level of the atmosphere, reducing its density (it is at the same pressure as its surroundings and its T rises).  This will eventually drive convection and mix this warmer air vertically.  Given enough time, this will reduce the mass in the column of air and therefore reduce the pressure at the surface.  These are called "heat lows" and you can see them forming in the desert areas and they play roles in sea breeze formation and the monsoons.

To address the expanded question:

The point in the FAA written is best understood by forgetting that we fly at constant altitudes -- we don't.  In level flight we fly on constant pressure surfaces which we then translate to an altitude.  In any given column of atmosphere, if it is warmer than standard a given pressure surface will be higher and when colder than standard the pressure surface will be lower.

To illustrate, let's consider you are flying at 3000 ft or roughly 900 mb.  Everywhere on this pressure surface will indicate 3000 ft on our altimeter for its current setting.  If we go somewhere hot, this pressure surface rises, and so we climb (though we think we are level) with this pressure surface but because the pressure has not changed, we still indicate 3000 ft.  However, we are higher than 3000 ft in reality.

This follows into your next question.  Aneroid wafers detect pressure changes and your altimeter displays an altitude not corrected for temperature.  This is why your true altitude can vary with temperature for a constant indicated altitude.  When you correct the altitude for temperature we call this "density altitude".

So back to my example above, your are flying along at 900 mb and indicating 3000 ft, and heading into warmer air.  The pressure surface starts to gently rise and as it does you are not yet following that rise and your altimeter will indicate a descent.  In true level flight you will begin to fly into higher pressure in this case as the 900 mb surface rises above you and the aneroid wafer in your altimeter will indicate a lower altitude and a descent.  You correct this and climb back up to the 900 mb pressure level so that your altimeter will once again indicate 3000', all the while actually gently climbing on this pressure surface.  You won't really be cognizant of this while flying however, and will just minimize vertical speed and maintain altitude blissfully unaware that you are really flying on a sloping constant pressure surface.

To better illustrate this, consider the following figure:

In this figure the reds signify a warmer than average column of air and the blues a cooler then average column.  The whitish area in the middle is a column at average temperatures.  The black solid lines are isobars (lines of constant pressure).  The dashed black line is a true altitude above the surface. Finally, the bold black line is the pressure level that corresponds to the true altitude of the dashed line at ISA conditions.

What you should notice is that the pressure levels in the warm column are spaced further apart because the air is less dense and more of it is needed to produce the same pressure (as pressure is just the weight of all the air above it).  Likewise in the cool column the pressure levels are spaced closer together because the air is more dense than standard.

To tie this into the discussions above, consider yourself in the standard column (white background) at the true altitude above ground represented by the dashed line.  Your altimeter does not sense this true altitude but instead senses the pressure outside of the airplane.  This will be roughly calibrated to your true altitude (uncorrected for temperature) but using the local altimeter setting.  Now as you fly either to the left or to the right and maintain a constant indicated altitude, you will track along the bold line, as this is the pressure that corresponds to your true altitude at standard temps.  As you fly toward a colder column you will in reality descend, and you will climb as you fly into the warmer column.


Where can I listen to the actual cockpit voice recorder audio from US Airways Flight 1549?

You can't, because it is in fact forbidden to release CVR audio under US law. From the NTSB:

  The CVR recordings are treated differently than the other factual information obtained in an accident investigation. Due to the highly sensitive nature of the verbal communications inside the cockpit, Congress has required that the Safety Board not release any part of a CVR audio recording.

Other countries may have different rules.

This rule came about after the crash of Delta Air Lines flight 1141, (commented by @MichaelK)

  [...] where the crew — in extremely cruel irony — were bantering on the flight deck about what to say that would get captured on the CVR in case of a crash. That irony was then squared in that the bantering was a directly contributing cause of the crash, in that they forgot to deploy flaps and slats


Does Global Entry give you any benefits when flying GA?

CBP has a lot of programs. Government programs are confusing. Regarding the two you mention...

Global Entry basically expedites the Customs process for pre-approved travelers, making use of an automated kiosk. The service is available at approved locations, generally major aiports. ClearlyNormally, this program is meant for the commercial traveler. However, large international GA destinations can have this service as well. Example: FLL, one of the nation's busiest international GA airports. They have a global entry kiosk at their GA facility.

Preclearance means that traveler processing/aircraft inspection are handled before the flight, rather than upon arrival in the US. But, this isn't very widespread yet. Private aircraft preclearance processing is only available at Shannon, Ireland and Oranjestad, Aruba. And the list of airports you can fly to, from what I have seen, is smaller than the list of Ports of Entry.

So no, neither of these programs really helps you out as a Canada/US travelling GA pilot. They aren't for small airports. You have to deal with Customs, APIS, and Ports of Entry, and everything else :)


What is the maximum allowed intensity for light beams pointing at the sky for non-aviation purposes?

Article 80(1) of the Air Navigation (Hong Kong) Order 1995 stipulates that

  A person shall not exhibit in Hong Kong any light which —

  (a) by reason of its glare is liable to endanger aircraft taking off from or landing at an aerodrome; or

  (b) by reason of its liability to be mistaken for an aeronautical ground light is liable to endanger aircraft.

  Any such contravention is liable on summary conviction to a fine.

The full text of the regulation can be read here.

Given this text, if your show is going to be anywhere near the approach or departure path to/from the airport (anywhere on Lantau Island, or east/west of the Gold Coast) you should probably refrain from using such lighting. I would strongly suggest you get approval from the authorities well before the event using an experienced local consultant, and prepare for that approval to be given or denied based on subjective analysis.


Day and Night for Pilots

As pilots we often talk about night flying and daytime flying meaning when it is dark or light, but for logging time and for currency there are specific definitions that we must pay attention to.

FAR 1.1 General Definitions

Night means the time between the end of evening civil twilight and the beginning of morning civil twilight, as published by the American Air Almanac, converted to local time.

Day is not defined in the FARs but the definition of night implies that it is the time between the beginning of morning civil twilight and the end of evening civil twilight.

The Air Almanac is published annually on CD-ROM but you can find sunset, sunrise, and civil twilight times for specific locations at the US Naval Observatory website.

The time between sunrise/sunset and twilight is 26-30 minutes depending on the time of year. Since you can easily find sunrise/sunset information in newspapers, the weather channel, etc. you can estimate twilight fairly easily.

Currency
§61.57 (b) (1) … no person may act as pilot in command of an aircraft carrying passengers during the period beginning 1 hour after sunset and ending 1 hour before sunrise, unless within the preceding 90 days that person has made at least three takeoffs and three landings to a full stop during the period beginning 1 hour after sunset and ending 1 hour before sunrise, and…

VFR Weather Minimums
Only Class G airspace has different minimums depending on night and day and they use the standard night definition—end of evening twilight to the beginning of morning twilight.

Aircraft Lights
Aircraft lighting is required between sunset and sunrise.
§91.209 During the period between sunset and sunrise no person may 1. operate an aircraft unless it has lighted position lights, 2. park or move an aircraft in an area of an airport where night operations are being conducted unless it is clearly illuminated, has position lights, or is in an area marked by obstruction lights.

Aeronautical Experience Requirement
In order to obtain a private pilot certificate night training is required. The commercial pilot certificate requires solo night flights. In these cases the standard night definition—end of evening twilight to the beginning of morning twilight—applies.

Special VFR
AIM 4-4-6 g. Special VFR operations are prohibited between sunset and sunrise unless the pilot is instrument rated and the aircraft equipped for IFR flight.

Logging Night Flying Time
Logging of night flight should be made in accordance with Part 1 definitions, which is from the end of evening civil twilight to the start of morning civil twilight. This differs from the definition used for night currency.

Summary

Position lights – sunset to sunrise

Special VFR – sunrise to sunset unless instrument rated

Carry Passengers – 1 hour after sunset to 1 hour before

Everything else – twilight to twilight


What makes the loss of a flap track fairing strongly increase fuel consumption on Airbus planes?

The fairings double as anti-shock bodies (or Küchemann carrots) and help to reduce shocks on the lower side of the wing. Below you see a wind tunnel test from the Vickers VC10 development where flow visualization using oil was used at Mach 0.9:

Wing without (left) and with (right) anti-shock bodies at Mach 0.9 (picture source). The light line on the left side indicates a strong shock which increases drag substantially over the situation pictured on the right where the flap track fairings have been used to smooth out the sudden reduction in cross sectional area from the rear-loaded wing airfoil.

Please read this answer if you are unsure why aircraft experience more drag as they approach the speed of sound. By stretching the aircraft body over a larger length, the gradients in the cross sectional area distribution can be made more shallow such that the air has more opportunity to make way for the aircraft.


Is the Auxiliary Power Unit used after landing when ground power is available?

How do pilots know that the ground power is connected?
The ground crew hooks a headset to the plane to communicate with the flight deck.
Once the ground power is connected, they confirm it, also a light comes on in the flight deck confirming external power is now available.
(Source) Ground power switch and light on a Boeing 737.
In a twin-jet airliner, they usually (subject to company) taxi-in with one engine, the other being shut down after it had time to cool down after the reversers are stowed.
They usually shut down the number 2 engine, the starboard side, where the GPU and other ground crew members approach the plane as soon as it is parked.
Many airports have restrictions with regard to keeping the APU running at the gate, due to emissions and noise, unless the plane is pushing back.
Related: Do airliners have horns for use on the ground?


How do I pay fees if I don't even land at the airport?

I fly in France and I had the same question. Apparently they use the aircraft registration to identify the owner. If you rented the plane from a club or renting company, the bill is going directly to them, otherwise they are going to try contacting you. If for some reason they didn't get your registration or if the airport was uncontrolled then you don't pay the fee. That's how it works over here, however I can't say if the same would apply in the UK.


How does pilot know when to trim when flying an aircraft that have fly by wire flight control computer

Fly-by-wire just means that the control column is not connected to the control surfaces (hydro-)mechanically, but using digital (electrical or optical) signal wires. That says nothing about how the controls behave. There are two basic ways they can:

The Boeing way:

Force and position is transmitted in both directions, emulating
control with mechanical link. The pilot feels force on the control surfaces and trims as usual.
The Airbus way:

The position of the control column corresponds to wing loading in pitch and roll rate in roll axis. The computer manipulates the controls to achieve the target values. The control column is spring-loaded, so force always corresponds to position.

The trim is operated by the computer to balance the control surface for wing loading of 1 G (or is not a separate control at all as in case of FBW fighters with all moving stabilator).

But when the system is in direct law (during take-off or if degraded due to fault), the trim still works more or less normally. The centred position of control stick corresponds to the trimmed position of the control surface, so if the pilot feels force on the control stick, because it is displaced, they dial trim and reduce pressure on the stick until the plane flies straight with the stick centred.

The Airbus way is used on Airbus A320 and all newer models, Sukhoi Su100 and some fighters (since F16).

The Boeing way is used on Boeing 777, 787 and, IIRC, some regional jets.


Who else is using electro-thermal wing anti-/de-icing apart from the 787?

I fail to see what is exactly new in the B787 de-icing system, except for the way it is manufactured (spraying metallic layers onto the composite structure).

Electric heating is the most obvious and straightforward method of de-icing, and the least energetically efficient at that. It is much more efficient to break the ice rather than to melt it - in terms of the energy required. Even B787 with its sheer electric supply can't afford anti-icing (that is, constant heating to prevent ice formation), and de-icing power consumption is 45-75 kW.

Perhaps most Russian (larger) aircraft had electrical wing de-icing system: from Tu-95 (1952) to Il-18 (1957) to Tu-154 (1968) (I could give specific links but they are in Russian). Typically, they work in sections to reduce power demand, and consist of heating wires (rather than layers like on 787) that melt the ice.

Later aircraft such as Il-86 (1976) and -96 had a more advanced electric impulse system, which creates mechanical impulse on the leading edge with induction coils. This deforms the skin for a very brief moment to break the accumulated ice.


What is the name for a flap that increases the wing's area but not its camber?

Useless flap.

It is always the increase in camber that increases the lift. The reason to increase the chord is that if the curvature was increased too much, the flow would separate and the wing would stall, so the flaps move aft to be able to move down more while still maintain moderate curvature.

The Fowler flaps do move a bit down even in the first step, and the slats move forward and down with (or even before) them, so the camber increases even in the first step.


Could I issue clearances at a private airstrip without being a controller?

NO!

An uncontrolled field is just that - uncontrolled. No pilot will accept a clearance in uncontrolled airspace in the first place. Consider the legal consequences if two aircraft were to collide as a result of a "clearance" issued by you. Since the aircraft are in uncontrolled airspace, it is the responsibility of the pilots to make sure they do not get too close. However,  if you got on the radio and started issuing "clearances", you might trick pilots into thinking that you are in control. If something bad happens, you should not expect to just walk away from it.

Besides, what makes you think you are qualified to provide air traffic control? Becoming an air traffic controller takes years of intense training, and only the top few percent of applicants are admitted to the education in the first place. Even the fact that you have to ask this question makes it seem like you have a very poor understanding of air traffic control.

The issue of not wanting people to land on a private airstrip has nothing to do with air traffic control. Air traffic controllers do not exist to tell pilots what they can and can't do - they are there to provide a service to the pilots! As others have pointed out, this would be a matter of trespassing. Pilots are very well aware that private airfields are just that - private. No one will just randomly spot a private airfield from the air and decide to land there without having first done some research - unless in emergency situations, of course.


Why does the ACS forbid activation of the stall warning during slow flight?

I attended the ACS webinar on June 25th.  This is the response from Christopher Morris at the FAA.  You can also read the FAQ on the FAA website.

If the pilot recognizes the stall warning and promptly makes an appropriate correction or airspeed adjustment, a momentary activation of the stall warning horn does not constitute unsatisfactory performance on the maneuver. As with other standards, the problem would arise from continual deviation from the standard, lack of correction, and/or lack of acknowledgment. The goal is to ensure that the applicant does not perform the maneuver with the stall warning activated.
The certification standard in 23.207 states for airplane certification testing, the stall warning must “begin at a speed exceeding the stalling speed by a margin of not less than 5 knots and must continue until the stall occurs.” This is the primary reason the suggested range above stall speed has moved from “3-5 knots” to “5-10 knots without stall warning activation.” The certification standard for the stall warning does play a role in the airspeed selection for the maneuver, and stall warning activation will vary from one airplane to the next, so it is important for the applicant to select an airspeed where the stall warning should not activate except on a momentary basis (e.g., due to turbulence).
The PTS standard for maneuvering during slow flight was for the applicant to establish and maintain “an airspeed at which any further increase in angle of attack, increase in load factor, or reduction in power, would result in an immediate stall.”
The current version of the Airplane Flying Handbook says slow flight should be performed at “the slowest airspeed at which the airplane is capable of maintaining controlled flight without indications of a stall—usually 3 to 5 knots above stalling speed.” The guidance has always intended for there not to be a stall warning, and that is consistent with slow flight guidance published in AC 120-111. However, the 3-5 knot range given does not pair well with the part 23 requirement for a stall warning (§23.207). It is not practical to maneuver in that airspeed range and not have the stall warning, which is an indication of a stall.  The standard in the PTS also implies being right above the critical AOA, which means the stall warning would be activated. This result does not align with the guidance, or with what the FAA advocates. Specifically, the FAA does not advocate intentional disregard for a stall warning while maneuvering.
The purpose of teaching slow flight is to ensure that the pilot understands how the airplane responds with less airflow over the flight control surfaces. Since airplanes are operated at low airspeeds and high angles of attack during the takeoff/departure and approach/landing phases of flight, it is essential for pilots to learn the airplane cues and how to operate the airplane in this state. Regardless of airplane type, a pilot does not need to be just below the critical AOA to experience the desired characteristics and achieve the slow flight objectives. These objectives can be accomplished without deliberately activing the stall warning through flight just below the critical AOA. We want to influence the behavior and practices the pilot will follow outside the training environment. Therefore, with the exception of performing a full stall maneuver, a pilot should always perform the stall recovery procedure when the stall warning is activated.
With respect to guidance, the change to AC 61-67 published just prior to the final decision on the AFH wording change, which drove the FAA’s decision to modify this ACS Task element. We are working on another change to ensure the AC will align with the AFH and the ACS and be consistent with AC 120-111. To further explain these changes, we intend to publish a SAFO that is now in formal coordination.
Teaching what an airplane will do at the critical AOA is part of stall training and should be addressed in that context. You allow someone to ‘ignore’ the warning in one narrow instance – as part of stall training. The pilot can still learn what happens at that point – but as part of stall training and learning the proper recoveries – not as part of slow flight.


How to use a set of Pressure Transducer to mimic pitot static tube for VTOL vertical airspeed indicator?

You won't be measuring any static pressures because facing the transducers into the sense direction produces dynamic positive pressure which is not subject to temperature compensation or air density corrections at altitude. A Vertical Speed Indicator works by taking static pressure and a calibrated leak inside the instrument to show your climb rate. You can't replicate this using the system you describe.
Even using your suggestion of adding another transducer for static is not enough. You need a rate of change which, as stated above, is normally provided by a calibrated leak inside the VSI.
If you want to explore further options of measuring position in 3d space that don't involve pressure transducers, I suggest looking at gyros and accelerometers.


The runway ahead of you is useful to accelerate and - if needed - to decelerate.

If you enter (or touch down) the runway in the middle, you will not be able to benefit from the part of the runway behind your entering point. It is the same as if that part would not exist. Therefore it is useless.


Can an airplane on an SVFR clearance land when visibility is less than 1 mile?

If the pilot is on an SVFR clearance, the weather inside the surface area deteriorates below 1 mile visibility, and the pilot has the airport in sight, he can inform the controller that he has the field in sight and will be cleared to land. The pilot is responsible for continuing to the airport or exiting the surface area in order to remain visual.

  NOTE− Clear an aircraft to land at an airport with an operating
  control tower, traffic permitting, if the pilot reports the airport in
  sight. The pilot is responsible to continue to the airport or exit the
  surface area. 14 CFR Section 91.157 prohibits VFR aircraft (other than
  helicopters) from landing at any airport within a surface area when
  flight visibility is less than 1 mile. A pilot could inadvertently
  encounter conditions that are below SVFR minimums after entering a
  surface area due to rapidly changing weather. The pilot is best suited
  to determine the action to be taken since pilots operating under SVFR
  between sunrise and sunset are not required to be instrument rated,
  and the possibility exists that flight visibility may not be the same
  as ground visibility. 14 CFR Section 91.3 authorizes a pilot
  encountering an inflight emergency requiring immediate action to
  deviate from any rule of 14 CFR Part 91 to the extent required to meet
  that emergency. Flight into adverse weather conditions may require the
  pilot to execute the emergency authority granted in 14 CFR Section
  91.3 and continue inbound to land. Air Traffic Control Handbook, 7−5−4


At low speeds.  This is why you see them on jet airliners, which cruise a low "indicated" airspeeds, just low enough that the vortice strength is enough to get a decent lift vector out of the winglet from the flow.  An airliner cruising at M.78 say, at FL380, is only going about 2x its flaps up stall speed.  A straight wing airplane at 20000 ft cruising at 250 kt might be going 2 1/2 to 3x its flaps up stall.  The vortices aren't strong enough in that case and you see them on straight wing airplanes rarely, and if you do it'll be to improve rate of climb more than anything, or maybe simply "styling".


How to adjust time of useful consciousness for pilots acclimatised to high altitudes?

The simple answer is "they don't". Training will dictate that at altitude, they need to be able to don masks within a few seconds, regardless of an individuals tolerance to altitude. The problem isn't that you have X seconds of full-cognition and then you pass-out, your brain function degrades during that period. It's best to get your mask on and oxygen flowing before doing anything else, and this is how pilots train.

Euphoria and a false sense of ability is a side-effect of altitude sickness/hypoxia. There are numerous videos out there showing altitude chamber tests where individuals are given simple tasks as the oxygen saturation decreases. These tasks can be as simple as those infant "put the shape in the hole" boxes, and it is surprising to see how well the people think they are doing versus how poorly they are actually performing. These two things combine for a very dangerous situation and you, as a pilot, need to recognize that this can happen and to mitigate that as quickly as possible, without trying to take into account your own tolerance (which can change day-to-day) for altitude.

Check this one out, this is a military pilot getting cards wrong, this is a stark demonstration of the effects. These symptoms happen in seconds. Watch how fast his cognition comes back when given oxygen.

Or this one which demonstrates euphoria and the inability to follow directions or perform basic actions.


What are the evenly-spaced "bumps" on Bell X-1 tailplane?

This documentary is about the X-1 breaking the sound barrier. It shows that the bumps are indeed hinges, and that the horizontal tail was indeed originally designed as a trimmable stab and elevator. At 25:40 the control surfaces can be seen moving.

At 35:00 Chuck Yeager talks about losing control at M.94 with this configuration, and then having the tail config reworked into an all flying tail, directly connecting the stabiliser to the stick.

Update Aug 2019

The original clip has been removed, this is the new link. Starts at the movement of the all flying tail.


To which security domain does the Cabin Intercommunication Data System (CIDS) belong?

As the commentators above pointed out, there are some issues with your question due to the concepts involved.

As @Bluephoenix mentioned, the security domains are defined in ARINC 664 Part 5. These domains specifically apply to ARINC 664 networks, though the concepts can be applied to other networks.

You also reference a Cabin Intercommunication Data System (CIDS) which is an Airbus specific system in the A320 series -- which does not have an A664 network. But we can look at its functions to see which domain would apply if they were implemented on an A664 network.

The A664P5 descriptions are:

  Part 5 describes the objectives, characteristics, services and
  functions that should be satisfied and provided by the aircraft
  computing network as a whole. Their allocation to specific networks
  and devices is the responsibility of aircraft network designers and
  specified by other documents.

  The Aircraft Control Domain (ACD) and Airline Information Services
  Domains (AISD) can be divided into sub-domains.

  The ACD can be divided into two Sub-domains:
  • Flight and Embedded Control System Sub-domain, where the aircraft is
  controlled from the flight-deck
  • Cabin Core Sub-domain, which provides environmental functions
  dedicated to cabin operations, such as environmental control,
  passenger address, smoke detection, etc.

  The AISD can be subdivided into two sub-domains:
  • Administrative Sub-domain, which provides operational and airline
  administrative information to both the flight deck and cabin
  • Passenger Support Sub-domain, which provides information to support
  the passengers

  Subsystems within the Passenger Information and Entertainment Services
  Domain (PIESD) could be supplied by different suppliers.

  Passenger Owned Devices (POD) can be supported by onboard networks.
  The Passenger Owned Devices Domain (PODD) is constituted of only those
  devices that passengers may bring on board the aircraft.

Reviewing the CIDS documentation of functions and comparing it to the A664P5 definitions, it would appear that the CIDS has functions within the ACD Cabin Core Sub-domain (environmental control, passenger address, smoke detection, etc.) and AISD Administrative Sub-domain (operational and airline administrative information to both the flight deck and cabin.)

To your last question, ACARS is a legacy communications link designed to support Airline Operational Control (AOC) and Airline Administrative Control (AAC) messaging.  With advances in data link systems and applications, ACARS can refer to either the AOC messaging (most correctly) or the entire data link system (not so correct) which also includes Air Traffic Control (ATC) messaging.

The ATC portion of data link falls under the ACD. AOC and AAC messaging fall into the AISD. In the case of the A320, the CIDS does not have a direct interface to the AOC/AAC messaging. These messages (manifests, gate assignments, etc.) are printed out in the cockpit and passed to the cabin crew as needed. On some newer aircraft, this may be accessible by the cabin crew via a terminal.


Is it safe to roll an airplane that isn't approved for it?

There are a lot of good reasons not to roll such an airplane.

If the plane has gyroscopic instruments, you might tumble them (cause the spinning gyro to hit the inside of the instrument).  This can be expensive.

You might easily over-stress the air frame.  Normal category light aircraft are rated to -1.5 to +3.8Gs.  (That's for a new aircraft)  A botched roll can easily hit 4.5 or higher.

If you over stress the air frame, you might just put a lot of very expensive "wrinkles" in the skin that would be very hard to explain to the FBO, your boss, or the insurance company.  Trashing the gyros would be cheaper.
If you're not lucky, the wings fold up and you fall out of the sky.  It's a stupid way to die.

Non-aerobatic aircraft typically have limited elevator authority; once upside down, you might find it very difficult to keep the nose pushed up high enough to keep the roll going.  Turning a botched roll into a "split-S" is one of the worst "recovery" mistakes you can make, and you're setting yourself up for it.

Non-aerobatic aircraft often have gravity-feed fuel systems.  A little bit of 0 or negative "G" and it will get very very quiet in the plane.  Some people consider this silence detrimental to the continued safety of the flight.

Non-aerobatic aircraft rarely have inverted oil systems.  As the engine gets quiet, it also loses most of its lubrication.  Bare metal on metal friction can be detrimental to achieving TBO.

Having said all that, in the hands of an expert, it is technically possible to barrel roll most aircraft.
A good way to tell if you're an expert is to call your insurance company and tell them exactly what you plan to do.  If they'll quote you affordable coverage, you might be an expert.
Obligatory links because if I don't include them someone else will:

Tex Johnson rolling a 707.  I'm pretty sure he'd never get away with this today.
Bob Hoover pouring iced tea.  Bob Hoover is beyond expert.  Way, way, beyond expert.

If you want to roll an airplane, contact your local aerobatic club.  In the US and some countries, it's the [International Aerobatic Club][5].  Get some competent dual instruction in a suitably rated airplane.


Can you be a monocular airline pilot in Europe?

UK CAA says

  EASA MED.B.070 (e) states that “Applicants for a Class 1 medical certificate shall be required to have normal fields of vision and normal binocular function”.

Therefore, you will unfortunately have to move out of the EU to become an airline pilot.


Why must one wait 48 hours to fly, after scuba diving?

Yes It's true. And yes it's related to pressure.

Have you heard of "The bends" or decompression sickness?

As divers go deeper the pressure increases. The longer you dive and deeper you go the more nitrogen is absorbed into your blood as a dissolved gas. As you return to the surface the pressure reduces and the nitrogen reverts to a gas.

This decompression needs to be done slowly so the nitrogen can pass back out through your lungs.  If you ascend too fast the nitrogen can form bubbles in your blood (Just like when you open a bottle of coke.) which can be painful and possibly fatal.

Even once you have finished diving you will still have residual nitrogen in your blood which will take time to release.

Air pressure reduces further when you fly. If you finished a dive and got in a plane the rapid climb in altitude would result in a drop in pressure similar to a rapid ascent while diving. So you would run the risk of getting the bends.

Small planes aren't pressurized. But even pressurized planes might not maintain atmospheric pressure when flying.

This topic should have been covered if you have taken a dive course.


Why would one want to slow to V2 following an engine failure during takeoff?

Simply put, V2 is the speed that guarantees the best angle of climb on one engine. Any slower or faster increases the risk of hitting an obstacle.

Drag

There are 2 main categories of drag - induced drag, and parasite drag. Induced drag is an unavoidable consequence from lift and largely shows itself in the form of wake vorticies. Induced drag is largest at high angles of attack - i.e low speed.

Parasite drag includes drag from things like skin friction, rough surfaces, wires, and so on. Parasite drag is largest at high speed.

If you plot both categories of drag together, you end up with a chart like this:

The aircraft must provide enough thrust to overcome the total drag, so this can be renamed the thrust required curve. If you picture a horizontal line across the top of the graph, that would represent the thrust available for a jet engine. The speed which provides the biggest gap between thrust required and thrust available, or excess thrust, is the speed at which the aircraft climbs at the steepest angle.

But if you lose 50% of the thrust available, then that horizontal line moves down a lot. If you are going too fast, the total drag might be more than the available thrust, forcing the aircraft to descend.

That's why V2 exists, to give the pilots a guarantee that at that speed, there will still be enough excess thrust to climb at the steepest possible angle.

It's true, slowing to V2 doomed this flight. But uncontained engine failures, especially ones that damage the wing, are extremely rare, and more rare than that is a dual engine failure for whatever reason. The powers that be decided it is safer to give pilots the V2 target so they don't mess up in an already high-workload scenario and hit a tree.


How do airlines replace a pilot at the last minute if they're unable to fly?

The airplanes can't depart without the minimum crew, which means 2 pilots, or 3 if there is a Flight Engineer.
The airlines have "Reserve" and "Ready Reserve" types of duty to cater to this, and pilots will be scheduled for one or the other at different times (depending on seniority and what they bid for).
Reserve is on-call at home, with the ability to show up at the airport within, say, 1 or 2 hours of being called.  This is for pilots who call in sick etc, a number of hours before departure.
Ready Reserve is you show up in uniform and with your gear at the operations dept of the airline and hang around in the crew lounge in case they need a crew right now. If they don't, you go home at the end of your shift without flying.
A pilot who is incapacitated just before a flight will be replaced with someone who is on Ready Reserve, and if none are available, then the flight takes a delay until a Reserve pilot can show up.


How do electric anti-icing systems work?

How do they work?

An electric current is passed through a heating element built into the device needed to be heated. For example, 115 VAC may be applied to a heating element of anywhere between 5-300 ohms (resistance values vary widely depending on the heating application). The voltage applied may be dependent on a controller that will dictate how much voltage is applied.

Using basic Ohm's Law, we can deduce that the current draw of 115 VAC across an example 60 ohms coil, would be approximately 1.9 A, and the power 220W. Keep in mind, this isn't a strict calculation as phase angle and other variables might be involved in an AC circuit - but close enough... That 220W is dissipated as heat which thus heats the device.

This is virtually the same in most GA and commercial applications.

Are they viable?

If by viable you mean "They work, but do have occasional failures that falls within a reasonable rate of expectation," then yes, they are viable.


What should the pilots do when fire is detected during the takeoff roll at high speed?

Before starting the takeoff, the pilots will have calculated at least 3 V speeds: V1, VR and V2. The important one for your question is V1, the takeoff decision speed. This is the critical speed that determines whether or not to reject the takeoff in case of a critical failure or other problems.
During the takeoff, there are 3 phases relevant for the decision of rejecting:

Until reaching 80 knots: At these relatively low speeds, you would reject the takeoff for any reason. Any caution message appearing or any failure you notice results in rejecting the takeoff.
Between 80 knots and V1: At these speeds, you would only reject for critical failures, like e.g. an engine failure or a fire warning.
At or after V1: At these speeds, you should never reject the takeoff unless the captain determines that the aircraft is unable to fly.

The details may depend on the exact aircraft, but here is the official list of reasons for rejecting for the Boeing 737 NG:

Prior to 80 knots, the takeoff should be rejected for any of the
following:

activation of the master caution system
system failure(s)
unusual noise or vibration
tire failure
abnormally slow acceleration
takeoff configuration warning
fire or fire warning
engine failure
predictive windshear warning
if a side window opens
if the airplane is unsafe or unable to fly.

Above 80 knots and prior to V1, the takeoff should be rejected for any
of the following:

fire or fire warning
engine failure
predictive windshear warning
if the airplane is unsafe or unable to fly.

(Boeing 737 NG QRH MAN 1.2 - Maneuvers - Non-Normal Maneuvers, emphasis mine)
As you can see, a fire or fire warning is serious enough that you want to reject up to V1. At or after V1, you should not reject for a fire warning. Rejecting a takeoff after V1 usually results in an accident, even if there is enough runway available, because the brakes may not be capable of stopping the aircraft any more:

Rejecting the takeoff after V1 is not recommended unless the captain judges the
airplane incapable of flight. Even if excess runway remains after V1, there is no
assurance that the brakes have the capacity to stop the airplane before the end of
the runway.

(Boeing 737 NG FCTM 3.23 - Takeoff and Initial Climb)


Has an airplane ever been launched from a train?

It's not a train, but Brendan O'Brien (with the O'Brien Flying Circus) has an act where he lands a Piper Cub on a moving trailer, towed by a car. There are some YouTube-clips showing this, including a take-off (around 1:50). Regarding your earlier comment on 'as close at it gets': I think this is it.


What do Air Traffic Controllers (tower supervisors) say to pilots before takeoff and landing?

ICAO document 4444 contains phraseology and pronounciation in chapter 12. It might however be a little bit difficult (but not impossible) to find online, as ICAO documents are rarely officially published online.

CAP 413: Radiotelephony Manual is published by the Civil Aviation Authority (CAA) in Britain, but is considered reference material for pilot training throughout Europe. CAP 413 is largely built on ICAO doc 4444.

Phraseology in the US differs somewhat from ICAO standard (but is getting more and more harmonized). The Pilot/Controller Glossary published by the FAA may be of some help.


As the US military primarily flies and trains in US airspace, they use the standard measures associated with the airspace. That is feet (or flight levels), nautical miles and knots, inHg, and °F. Though, using °C is fairly common in the US now since weather reports shifted to the ICAO format.

That said, the cockpit systems can be switched to HPa and meters for altitude and °C for temp for when they fly in airspace where that is the standard. Speed and distance are always in nm and kts.


What passenger airplane has the lowest fuel efficiency?

TU-144 =  9.78 passenger mpg

TU-144 figures found on another forum, from an official flight planning document:
https://www.airliners.net/forum/viewtopic.php?t=1355819#p19483811

--

By comparison the TU-104A = 15.88 passenger mpg

From an old Aviation Week story on the TU-104:
http://aviationweek.com/blog/tupolev-104-harsh-proof-rapid-soviet-progress-1956

Using that article and assuming 0.8 l per kg and 20% reserve, imperial gallons. These figures (especially TU-104A) are rough and would vary by loading and flight profile.


It's just making sure the rectangle formed by the spars, compression tubes and cross bracing is square.  It's done using a trammel bar, which is just a stick (which the guy in the picture is holding) with a metal point at each end that is used to make sure diagonal reference points along the spar beams are the same distance apart when set across one leg of the X formed by the cross bracing, then the other leg.  The effect on stability and performance is indirect insofar as you don't want a rectangular wing to be trapezoidal (swept - unless the sweep is part of the design like the upper wings of some biplanes, in which case you trammel to that requirement), as well as the fact that parts won't fit if things aren't square.


What are the most challenging taxi manoeuvres that a typical commercial airline pilot must execute?

"Most challenging" is a matter of opinion, but if I were to pick, it is probably the 180 degree turn.

The purpose of the maneuver is to turn the aircraft around and face the opposite direction. The technique is to position the aircraft to one side of the runway (taxiways are generally too narrow for this), then apply maximum steering angle, minimum thrust as well as differential braking (i.e. braking on the inner set of wheels only).

The challenge is that the nose wheel, outer set of wheels, outer wingtip and the tail each have their own turning radius. It is made even trickier when the nose wheel is a good 20~30 feet behind the cockpit. The pilots will be above the runway grass while the nose wheel is still on the pavement.

This maneuver is challenging enough that most aircraft manuals I've seen (e.g. B737, B777, A320) dedicate a good 10~20 pages just for this. Here is an example diagram for the B737-600:

B737 FCOM Volume 2, Section 1.10.7

This maneuver is mostly executed on small airports where there is no taxiway connecting to the end of the runway. For example, the only taxiway connection to the runway might be at the runway's middle length. A plane that wishes to use the full runway length to takeoff will have to turn onto the runway, taxi down half its length to the end, then execute a 180. On large airports this is rarely an issue, although a 180 might be useful when part of the taxiway / runway is blocked due to an incident.


To what extent can I deviate from the endorsement guidance given in AC 61-65?

Advisory Circulars by definition, are advisory and not regulatory in nature (Chapter 1, paragraph 3 of FAA Order 1320.46C). Therefore, AC 61-65 provides suggested language that will ensure compliance with the FARs.  You are free to word the endorsements differently, but if the examiner takes issue with your endorsement, the student may not have any recourse but to have the entries redone (by you, or another CFI).

Since you say your student is ready (I am assuming for their Private Pilot check ride), why not go ahead and endorse them right now? FAR 61.109(a)(4) requires the student to receive 3 hours of flight training within the two months prior to the test, this would cause your endorsement to automatically expire if they don't test (or receive additional training) within that window.

Alternatively, I would suggest contacting the local Flight Standards District Office and get guidance from them directly.


How many aircraft does an ATC controller usually handle at the same time?

Depends entirely on complexity, rather than sheer numbers. In ATL I can comfortably handle somewhere around 60-70 departures per hour from a ground control position. More than double that when you factor in arrivals. That’s a VERY low complexity situation, with everyone moving one direction.

On the flip side, I’ve worked TRACON radar positions with five aircraft dodging severe weather and worked my ass off. High complexity.

ARTCC sectors are different in that they have known numbers, and will go from green to yellow to red depending on saturation. These are based on routings, in trail restrictions and so on. Again, all complexity.


Are there any regulations on fueling aircraft inside hangars?

Your previous FBO is correct. According to FAA Advisory Circular 150/5230- 4B Aircraft Fuel Storage, Handling, Training and Dispensing on Airports:

Standards The FAA uses the standards contained in the most recent edition of National Fire Prevention Association (NFPA) 407, Standard for aircraft Fuel Servicing. NFPA 407 provides a standard for the storage and delivery of aviation fuel in an airport environment

NFPA 407, on the other hand requires outdoor fueling.

5.10 Aircraft Fuel Servicing Locations.
5.10.1 Aircraft fuel servicing hall be performed outdoors...
5.10.2* Aircraft being fueled shall be positioned so that aircraft fuel system vents or fuel tank openings are not closer than 7.6 m (25 ft) to any terminal building, hangar, service building, or enclosed passenger concourse other than a loading walkway.

A revision of the same standard also looks the same, with some differences in wording. So, the aircraft fueling should be done outdoors. Its doubly important if the hangar/airport where your aircraft is located also follows NFPA 407.


"Total time away from gate", "Longest time away from gate" - what does this mean?

The US regulations have the tarmac delay rules, which apply to extended delays where passengers are left sitting on the tarmac. This followed a variety of incidents where passengers were kept on board non-moving aircraft for long periods of time, sometimes without access to food and water. The rules are a bit complicated with various exceptions, but broadly:

  How long can an airline keep me on a DEPARTING flight before the
  airline is required to start moving the airplane to a location where
  passengers can safely get off?

  For flights departing from a U.S. airport, airlines are required to begin to move the airplane to a location where passengers can
  safely get off before 3 hours for domestic flights and 4 hours for
  international flights.

So yes, a flight can potentially have multiple tarmac delays. For example, a flight could potentially leave the gate on time, sit on the tarmac for 2.5 hours, return to the gate (to allow passengers a chance to get off, as is required), leave the gate, wait another hour, be cancelled, and return to the gate. The airline would report both all the time the plane was away from the gate (2.5 + 1 = 3.5 hours) and the longest period the plane was away from the gate (2.5 hours).

  What is a "single time"? A single time period out of multiple ones?

Yes. If the flight sits waiting on the tarmac for more than one period, the "single time" is whichever period was the longest.

  Why would a plane be away from the gate multiple times? i.e. leave the
  gate, return to the/a gate, leave again and return again?

It could happen for a number of reasons. One would be that the plane returned to the gate to comply with the rule and allow passengers an opportunity to get off after 3-4 hours delay. The plane might return to the gate for a maintenance issue. They could be waiting out bad weather or a situation where an airport is not accepting flights. Most airlines seek to avoid this, but it can happen, and the reporting requirement is intended to capture data about how long it takes when it does.

  Why would a diverted plane be on the tarmac multiple times at the same airport?

The same reasons. I had this happen once due to a tornado. The flight diverted, we went to a gate, we went back to the tarmac to wait for better weather, the flight was cancelled, so we went back to a gate again. It's an unusual situation, but it can happen.


Why does the C-2 left inboard stab not have a rudder?

The C-2 was developed from the E-2 Hawkeye (the one with the big radome).

The radome disrupts the airflow behind, hence the need for the inboard fins (source), they help stabilize the airflow and act as fences for the outboard fins.

Those inboard fins were not needed for the streamlined radome of the earlier E-1 (shown below).

Alternatively they could have extended the fuselage length, but they didn't go that way. The three rudders provide sufficient control in single engine operation, yet are overpowering when both engines are working, which caused early control problems and stability augmentation had to be implemented (source: University of Tennessee, MS thesis, 2002).

The E-2 and C-2 feature rudder authority limiter as part of that augmentation (C-2A flight manual).

And apparently the rudder authority is sufficient enough that the E-2 can turn (to remain in orbit) while keeping the radome fairly level (source).

As to why the right one is the one with the rudder, I don't know. The engines are not handed (video). But as far as I know, a normal force on a laterally placed fin does not change the moment arm around the yaw axis, but I'm happy to be corrected.

Development information on the E-2/C-2 is scarce, so I hope that's sufficient for the time being, I tried to find as good sources as possible.


What does it mean when ATC says climb maintain 7000, block 8000?

It means you've been allocated a block altitude - you can fly whatever altitude you want between 7000 ft and 8000 ft.

Typically this would be something you'd request, e.g. to practice unusual attitude recovery or to avoid having to hold a hard altitude in mountain wave.  It's unusual for ATC to volunteer a block altitude without the pilot asking for it, but maybe if previous aircraft along the same route reported difficulty maintaining altitude then ATC might offer it to you unprompted.


Why are holding patterns in an oval shape?

I don't have any definitive information on why the oval shape was chosen. However, it seems to me to be the most practical shape given the navigational equipment available when holding patterns first became necessary. VOR, DME, and GPS technology did not exist. Holding patterns were flown, often by single pilots hand flying, with reference to an ADF needle, maybe with a little marker beacon help.

I don't know if a square-like pattern was considered, but if it was I think it would have been rejected for at least the following;

a rectangular pattern would involve 4 turns, better to keep it simple with only 2 turns.
flying any kind of a leg perpendicular to the holding radial would mean getting farther away from the radial than necessary with no advantage to be gained, and it might involve more terrain clearance problems.

Flying a circular pattern makes it more difficult to keep track of where you are in your head (no glass cockpits, indeed no HSIs even, not even rotating ADF cards at first), than an oval. Worse, though, is what could occur in some wind conditions. For example, let's say you're supposed to hold north of a fix on the 360 radial (inbound course 180). Further, lets say there's a significant north wind. You're approaching the fix on a course of 180. You cross the fix and then fly a circle with respect to the air you're in. In a no-wind condition, you'll come back to the fix. However, with a north wind, you'll come back to the course south of the fix, and will have thus violated where you were supposed to hold.

With today's navigational technology, we can of course easily fly any kind of shape we want, but the disadvantages previously mentioned would still apply.


Is a forward slip considered a "normal maneuver" under 91.175(c)(1)?

I can't find any specific definition of "normal maneuvers", probably because it varies a lot by aircraft type and situation. But I did find AC 120-29A - Criteria for Approval of Category I and Category II Weather Minima for Approach that gives some indication of what the FAA considers not normal (section 4.3.1.6):

Part 91, section 91.175 requires that approach procedures should be
based on use of “normal maneuvers” before and after passing DA(H) or
MDA(H). Normal maneuvers typically do not involve use of bank angles
greater than 30 degrees, pitch attitudes in excess of 25 degrees nose
up or 10 degrees nose down, or sink rates in excess of 1100 ft. per
minute below 500 ft. HAT while maneuvering to land within the
touchdown zone, during go-around, or during a rejected landing. During
a missed approach, pitch attitudes in excess of +30 degrees or bank
angles greater than 30 degrees would typically be considered
excessive.

But even if there is a specific definition of normal maneuvers out there somewhere, I think the context is important too. 91.175 is about instrument approaches, not general flying. So I think you have to ask if slipping to land is a normal maneuver during an instrument approach and I'd say no.
The entire point of an instrument approach is to get you to the runway safely and predictably, and there's a lot of emphasis on stable approaches. I can't think of any obvious reason why you'd need a forward slip if you've flown an approach successfully. You might be able to come up with some scenarios (circling to land? shooting an approach with an MDA of more than 2000' AGL?) however I'm not convinced that it's a normal technique in the specific context of instrument approaches.
If you look at what the FAA says about forward slips in the Airplane Flying Handbook Chapter 8 it strongly suggests that slips are for limited and unusual situations:

Intentional slips are especially useful in forced landings and in
situations where obstacles must be cleared during approaches to
confined areas. A slip can also be used as an emergency means of
rapidly reducing airspeed in situations where wing flaps are
inoperative or not installed.

I find it hard to see how those examples fit with executing an instrument approach. But that's just my opinion. If you happen to know a DPE it would be a great question to ask them.