Does the PA-44's squat switch disable the stall warning?

Are you sure you're talking about the stall warning? I believe you're talking about the horn that activates when in the landing configuration with no gear down(e.g throttle retarded, flaps down).

The 44 has 2 electric stall warning tabs that won't be actuated on the ground.


Is the Cirrus Vision SF50 the only civilian monojet currently on production?

Multiple VLJ kitplanes have been on the market for several decades now; probably the most famous of which was the Bede BD-5J which gained fame in the 007 film Octopussy.  BD-5Js flew in airshows with the Coors Light Silver Bullet aerobatic team.
A supersonic VLJ kit called the Bede BD-10 was planned and flyable prototypes were produced.
And multiple companies have come and gone, offering everything from VLJ kits to wishful thoughts such as the ViperJet to MaverickJets to Stratos.
But near as I know the Cirrus SF-50 is the only certified single engine civilian aircraft for sale today.  Eclipse came close with its E-400, but it only remained a technology demonstrator.
The only other single engine jet airplanes on the market are military.  Aero Vodochody's L-29 and L-39 jet trainers are popular with civilians and air race teams as are MiG-15s -17s, -21s and even a few MiG-23s.  Western fighters like the F-86 Sabre, the Folland Gnat, the De Havilland Vampire, and the BAe Hawk are also popular.


Are all tires on an aircraft replaced at the same time?

Nope.. they are replaced 'on condition'. Exception is when one tyre has deflated before landing (cockpit indication and later confirmed) then the good tyre on the same axle has to be replaced irrespective of condition.

Tyres have a hard life and get damaged by rubbish on the runway and stand. Also airplanes don't always hit the ground straight .. when they come in at an angle  it wears the side of the thread more on that tyre.


How to calculate optimal prop diameter, pitch, torque and power coefficient given required thrust?

How would I be able to calculate the optimal prop diameter, pitch, Kp (power coefficient), Kt (torque coefficient), as well as optimal number of blades and optimal manufacturing material? Or, would a turbofan be more optimal?

Optimal prop diameter is simple: the largest you can accommodate = 30 cm. Disk area A = 0.07 m$^2$
Optimum number of blades: as few as possible, let's start with 2.
Use ducted rotors for a more vertical alignment of the rotor tips.
The quadcopter has horizontal rotors. Tip speed should not exceed 0.8M = 270 m/s which equates to $\Omega$ = 570 rad/s = 5,520 RPM
We have a prop diameter, RPM and thrust, now we need to determine power P and torque Q to drive the prop. We'll do so using expanded momentum theory for the hover, like in this answer.

For a rotor with solidity ratio $\sigma$ = 0.1, the thrust coefficient $C_T$  is maximum 0.01, let's use a safety margin of 20% and take 0.008. Then the maximum thrust for this rotor becomes:

$$T = C_T \cdot \rho A (\Omega R)^2 = 0.008 \cdot 1.225 \cdot 0.07 \cdot 270^2 = 50N$$

We need 15 times this thrust! In order to verify the value of $C_T$ there is another graph in Leishman that relates $C_T$ with blade-pitch angle. It turns out that $\sigma$ = 0.01 is at a blade-pitch angle of about 12 degrees, we cannot go much higher than that. Neither can we increase tip speed, our only choice is disk area.

$$A = \frac{T}{ \rho \cdot C_T \cdot (\Omega R)^2} = \frac {750}{1.225 \cdot 0.008 \cdot 270^2} = 1.05 m^2$$

You need four rotors of 1.2 m in diameter, with a solidity ratio of 0.1. With the $C_T$ of 0.008, we find a corresponding $C_P$ of 0.0007, which results in

$$P = C_P \cdot \rho A (\Omega R)^3 = 0.0007 \cdot 1.225 \cdot 1.05 \cdot 270^3 = 17.7 kW$$


With current technology, why is there still increased separation between aircraft and delays in low visibility conditions?

In good weather, airports can move lots of aircraft because the ATC separation standards are much less than the bad weather, poor visibility ATC separation standards.

“Current technology” really hasn’t changed much over the years as ground based ILS CAT II and CAT III are still the most accurate ways to get get aircraft on the ground in bad weather.

Most of the increased separation is due to the requirements to have uninterrupted ILS ground signals reaching the aircraft on approach. Aircraft waiting to take off must wait behind hold lines farther from the runway, and aircraft on final must be spaced farther apart so as to not interfere with the ILS signals.

Once on the ground, aircraft will often experience delays getting to the gate due to the difficulty of taxiing in near zero visibility. Even parking at the gate can often require special standards and procedures.


What qualifications or training allow a test pilot to fly a new aircraft?

All commercial or military test pilots attend either a DoD or ABET approved test pilot school.  The military has two said achools: the USAFTPS at Edwards AFB in Muroc, CA and the USNTPS out at NAS Pax River in MD.  There are at least two test pilot schools who train civilian pilots that I know of: The National Test Pilots School in Muroc, CA and Empire Test Pilot School in the UK.

Qualified applicants need to possess at least a commercial pilot's certificate and at least 750 hours TT, plus possess at least a bachelor's degree in engineering, physics, or related technical discipline.  Military programs are very competitive and sought after; TPS slots can pretty much guarantee a job with major aircraft OEMs doing test pilot work after their military service ends.  Outside of the military you will probably need some kind of corporate sponsorship to attend as it is very expensive. The NTPS Masters of Science in Test piloting in an 11-month course costing a whopping $960,000 to attend!

The courses in a TPS are graduate level type classes.  The NTPS curriculum can be found here.

Hollywood portrays test pilots as these outlandish, devil-may-care guys with brass balls and ice water running in their veins, but the truth about most test pilots and flight test work is pretty boring by comparison to the movie image. Test pilots are first good system engineers, second skilled aviators and third calm and collected under pressure. Test flying itself is much more about planning - and planning for contingencies and contingencies for those contingencies  - than the actual flying itself.  Test flying is conducted according to more or less a rigid schedule developed by a flight test department.  A test pilot will fly the aircraft through specific test points and is expected to maneuver the aircraft in a very precise way - precise control inputs, precise altitudes, air speeds, angle of attack, flight maneuvers, etc. In order to collect test data for the flight test team.  The test pilot is also expected to be able to correctly evaluate how the aircraft or systems handled.  Also needed is an ability to accurately describe discrepancies in performance and handling to design engineer teams to correctly determine the root cause of these issues and address these problems correctly.

Safety is also paramount for doing flight test work.  Long gone are the days of strapping your little pink fanny into a crate, pushing it off a cliff and hoping for the best on the way down.  Test plans are thoroughly evaluated prior to flight for risks, mitigating factors and means to minimize those risks - and contingency plans should something go wrong.  I once heard a USN test pilot put it "we try to make the process as boring as possible."  Many test points will be attempted in simulators prior to the actual flight test and test pilots will have flown them many times, complete with conducting emergency procedures there.

Most test pilots don't even do experimental work; often times they are involved with manufacture flight test work.  This is usually involves simply testing all the systems of an existing production sample aircraft.  Other jobs test pilots are involved with are testing of new avionics, weapons, or mission systems aboard existing aircraft as part of the approval process for its use.


What is the use of this jet aircraft with tanks between biplane wings?

It is the Polish PZL M-15, as you can read in the image if you zoom in. From Wikipedia:

  The aircraft was designed in Poland in response to a Soviet
  requirement for a new agricultural plane.

Agricultural airplanes fly slow and having a shorter span increases the number of (air)fields you can land on. That's probably why they decided using a biplane design.

The two tanks outside the fuselage could have several reasons:

Placing the chemicals further away from the turbine and pilot
Reduce the bending moment at the wing root
Shorter pipes between the tank and the spray nozzles

All this, of course, at the cost of a lot of drag. As explained in the image source page, fuel consumption was three times larger than other agricultural airplanes and it had a really bad maneuverability.

The jet engine was a requirement dictated by Aeroflot, who wanted to use the same type of fuel for their passenger and agricultural airplanes.


The number of drone sightings near airports is increasing (apart from last year), and frequently this results in temporary interruption of operations at airports, with enormous economic consequences. Most famous example is the December 2018 drone incident at Gatwick  which affected the airport operations for more than one day.

source: EASA Drone Incident Management at Aerodromes(pdf)
I live in Germany, where there have been over 500 sightings near airports since 2015, including several high-impact cases that resulted in the interruption of air traffic at major airports such as Frankfurt airport. Last year, the German Air Traffic Control (DFS) tested a number of drone detection systems  (press release, video link, article in German)  at Frankfurt and Munich airport as part of a market evaluation. Over 600 drone flights were performed, at distances up to 10 NM from the airport. I was involved in the design and execution of those tests and I can share a few observations.
At most airports in the world, drone detection still primarily relies on humans that happen to see a drone fly and inform the police, airport security or control tower by phone or radio.  There are a number of severe limitations to that approach, for example:

Drones are typically small and difficult to see at distances of more than 100 meters. At the scale of a major airport, it is plausible that drones can fly in safety critical areas for a prolonged time without being seen.
Position reporting to those that need to act upon the information (air traffic control, police, security staff) is delayed (phone call, relay of info) and inaccurate ("near the terminal", while the terminal building stretches over more than a kilometre).
Independent verification of the reports is difficult. This opens up the possibility to falsely report drones in an attempt to shutdown the airport.

To address these limitations, drone detection systems are under development, and some airports have deployed them with varying levels of success.
Ideally, a Drone Detection System (DDS) meets these high level requirements:

it detects all drones in the vicinity of the airport
it locates these drone(s) accurately
it does so without delay
it has a very low false alert rate (preferably no false alarms are raised at all)
it locates the position of the remote control (not needed for safety of air traffic, but helps the police in finding the drone pilot)
it does not interfere with aviation communication, navigation and surveillance systems.
preferably the system does not need any supervision; having staff 24/7 dedicated to drone detection is very expensive.

There are many drone detection systems available in the market, at various levels of maturity and some more suitable for airport use than others.  Most, if not all drone detection systems, make use of various sensor types.
There are four categories of drone detection sensors:

Optical / infrared cameras
Radars
Radio detection systems
Acoustic detection systems

Optical / Infrared cameras
One way to detect drones is by cameras. But at the size of a major airport, you are almost always far away from the drone. This means that the camera must be able to zoom, zoom a lot. Some of the best cameras are able to show a clear picture of a 40 cm size drone at 2 kilometres, and a recognisable dot (distinguishable from birds) at several kilometres more. The problem is that with such zoom levels you have a very narrow field of view and so you are never going to detect a drone that you didn't know about before. Therefore cameras are not a good choice as primary sensor, they need to be pointed in the right direction by another sensor.
Once they are pointed at the object of interest, image recognition is often able to classify the object as drone or something else. Some camera systems do a great job optically tracking moving drones, others need manual input.
There are systems that use the camera subsystem for locating the drone, by combining the view angle of several cameras to calculate where the lines-of-sight cross. Laser range finders can also be used in combination with cameras to determine the distance of objects from the camera. Other systems just use the camera as means of classification of an unknown object, not for determining the position.
Having a combination of Infrared (IR) and visible light is beneficial. For one, because at night there is not enough visible light to see the drone, but also the contrast of the drone against the background is often much better in IR than in visible light.
Radars
Radars are an obvious choice of detecting flying objects near the airport. Unfortunately, air traffic control radars and surface movement radars are not able to detect objects of the size of a drone.
There are dedicated drone detection radars on the market, some with a background in military, border control or bird tracking, that are specifically tuned for drones. The maximum distance at which these radars detect a drone of course depends on the size of the drone, but also its shape and the manoeuvring it is doing. There are significant performance differences between radars, and even a good radar may perform badly if it is not properly tuned or sited.
Since these radars have to be very sensitive to pick up a radio reflection from a drone, they see almost everything: planes, cars, cyclists, birds, wildlife, trees moving in the wind etc. One of the biggest challenges for drone detection radars is to distinguish drones from other objects.
False alarms need to be balance with missed detections, which is a delicate process. In the end, a radar will occasionally classify something as drone while it is actually something else.
Radars transmit radio waves that potentially interfere with CNS systems at the airport. Most systems I have seen were operating at frequencies far away from aviation systems, and those that were operating at similar frequencies did not cause interference. (After doing a paper analysis first, the systems were switched on to see if there was interference. This was done at night when air traffic levels were low, and with all relevant people made aware before the system was powered up)
Radio detection
Radio detection systems work by detecting the radio signals transmitted by the drone or their remote control. These systems contain a library of signal properties and they recognise which signals belong to drones. Most systems I have seen cover vast frequency ranges.
The location of the drone (or its remote control) can be found by triangulation or multilateration. Some systems can decode data packages from specific drone models and read the GPS location directly from the drone and the remote control.
Since there are many radio signals transmitted at the airport, the background radio noise is quite high. Also radio signals reflect of large buildings such as hangars and terminals. This has an effect on the performance of radio detection systems. Some systems are severely impacted by the airport environment while other systems are less affected.
Of course these sensors only work if the drone transmits a signal, does so on a supported frequency, and with a protocol known in to the signal library. None of the systems I've seen was able to detect all drones in the test.
Acoustic
Finally there are acoustic detection and location systems, operating in the acoustic frequencies band.
These are passive systems that rely on detecting the noise characteristics of drones (specifically their propellers). They have a very limited range (up to ± 300 m) and are  susceptible to background noise, which degrades their performance.
Due to these characteristics the use of acoustic detection systems in airport environments is very limited. If there is any use at all, they could perhaps be used as a coverage gap-filler, for example between hangars.

A good drone detection system will make use of various sensors types and integrate their outputs using a multi-sensor data fusion and tracking system to a single, reliable situation picture. In every class of sensors there are some really promising products, but a  strong integration of a range of good sensors is hard to find. This market is developing quickly and I expect that the situation will be very different in a few years.


How does radius of a propeller affect its performance?

Would the propeller hub in the middle be the same size? You did say all things being equal, which I read as "unchanged".

Example, 86" total diameter prop, 12" diameter hub, leaving 2 blades that are (86 -12)/2 = 37" from edge of hub to tip of blade, and 74" of working blade length.

Then you reduce the radius to 43" with same 12" hub, so you have (43 - 12)/2 = 15.5" blade from hub to tip, and 31" of working blade length. 31" is less then 1/2 of 74", so you've lost more than 50%.

Assuming the engine can't spin any faster due to the engine governor limiting the RPMs, you're not getting off the ground.


How often are turbine blades in jet engines replaced?

So this article, says that the average brand new CFM56-7 will go 18,000 cycles (i.e. flights) before its first shop visit.  You can't replace the turbine blade on-wing, only in the overhaul shop.  So we could say that the blades would last at least 18,000 flights, potentially longer.


What is the maximum lateral deviation allowed on an RNAV route?

4 nm from centerline or 8nm total width of airway.
You are not required to instantly turn when transitioning between airways.  Required navigational precision for most enroute segments is 2 nm.  Being conservative and always assuming an operational error of 2nd means any observed deviation of more than 2 nm is a red flag.

Intentionally deviating within the course width is not prescribed within the regulations, but then there's no regulation prohibiting or allowing fly by (fly over is sometimes mandated).


Why do airlines require passengers to return to their allocated seats for landing?

Its a matter of legal requirement (under the FAA, and I presume the EASA has a similar reg). Strictly speaking its really more important that the passenger returns to a seat. Generally you are asked to return to your seat as it can be assured its empty and available for you. Under FAA regulations you are required to be wearing a seatbelt for landing and thus must be in a seat

  14 CFR 121.311 - Seats, safety belts, and shoulder harnesses.

  (b) Except as provided in this paragraph, each person on board an
  airplane operated under this part shall occupy an approved seat or
  berth with a separate safety belt properly secured about him or her
  during movement on the surface, takeoff, and landing. A safety belt
  provided for the occupant of a seat may not be used by more than one
  person who has reached his or her second birthday.

Weight and balance is important but not on a single passenger level i.e. on an airliner of decent size if a single passenger moved around it would be ok. If half the plane was empty and the passengers rearranged them selves there might be an issue.

  How do airlines which do not allocate seats to passengers satisfy the
  same requirement when there is no published seating manifest in
  advance of passengers entering the aircraft, or why are they exempt
  from such requirements?

They are not exempt from the requirements but there are enough seats for everyone on the plane and as noted above its really important that you are belted in so taking an available seat will do in this case. On these flights generally speaking, you take a seat prior to takeoff and that somewhat becomes your seat for the flight. In my experience there is little if any mid-flight seat swapping.

  Furthermore, in the event, only one member of the couple returned; the
  other remained in the non-allocated seats (an example of
  non-enforcement).

As noted above the policy is to be belted in, so the regulation was indeed enforced. The other member of the couple may have remained in the seat if they were the only person capable of preforming the exit row duties.


Do transoceanic airliners monitor marine VHF emergency frequencies?

156.8 MHz

Crews don't listen to channel 16 of the marine band.

Channel 16 is used by marine with FM, while a VHF aviation receiver demodulates only AM, and the upper limit of the VHF band for aviation is 137 MHz.

Channel 16 is monitored by local marine agencies -- coast guards -- e.g. CROSS in France and USCG in the US.

Aircraft are only required to carry an equipment able to receive and transmit on emergency frequencies used by aviation.

Emergency frequencies other than channel 16 are also used in marine, including 121.5 MHz, e.g. by EPIRBs. The use of 121.5 MHz for marine EPIRBs was to allow monitoring by aircraft.

Air regulation for listening 121.5 MHz

EPIRBs monitoring by aircraft is not relevant any more as EPIRBs are now efficiently monitored by satellite (COSPAS-SARSAT). However 121.5 MHz is still monitored ("guarded") by aircraft, in particular for interception response purposes. The requirement is specified in ICAO Annex 10 (volume II) to the Chicago Convention:

  5.2.2.1.1.1 Aircraft on long over-water flights, or on flights over designated areas over which the carriage of an emergency locator
  transmitter (ELT) is required, shall

  continuously guard the VHF emergency frequency 121.5 MHz , except for those periods when aircraft are carrying out communications on
  other VHF channels or when airborne equipment limitations or cockpit
  duties do not permit simultaneous guarding of two channels.

  5.2.2.1.1.2 Aircraft shall continuously guard the VHF emergency frequency 121.5 MHz in areas or over routes where the possibility of
  interception of aircraft or other hazardous situations exist, and a
  requirement has been established by the appropriate authority.

  5.2.2.1.3 Aeronautical stations shall maintain a continuous listening watch on VHF emergency channel 121.5 MHz during the hours of
  service of the units at which it is installed.

ICAO standard and recommended practices ("SARPs") for international aviation activity are recommendations, but they are generally implemented in the national regulations by the member states.

406 MHz

121.5 MHz is being replaced by 406 MHz, as this is the frequency of the COSPAS-SARSAT organization. This organization provides a permanent monitoring worldwide through the use of polar orbit satellites augmented by geostationary satellite relays.


Why are magnetic headings used for designating runways?

There are two parts to the question:

Why number runways based on their direction?

The runways have to be identified somehow and the identification has to be directional. So the, rounded, heading offers itself and it has advantage that:

The pilot can verify they are approaching the intended runway by looking at the compass, which

works at night, in bad visibility or early on the approach when the numbers on the ground are not visible yet and
serves as cross-check for verifying the instruments are set correctly during instrument approaches.

Since the pilot needs to know the runway heading for navigation and for checking the wind anyway, it makes it easier to remember.

Why use magnetic heading instead of true?

In the early days of aviation, magnetic compass was the only tool available for determining direction. It is simple and reliable and well tested in naval navigation. So magnetic headings became the obvious standard.

Later gyrocompass was introduced to overcome the limitation of magnetic compass that it is biased in turns and requires some time to stabilize. However gyrocompass precesses, so it has to be periodically corrected, which was, and is, still done by reference to the magnetic compass.

On the other hand GPS is still a rather recent technology. It is only precise enough to determine heading (or rather tracking) for last 15 years. It requires a complex electronic device that can fail in a myriad of ways and it is affected by many external factors including the state of ionosphere and the selective availability not being turned on again.

And not all aircraft have GPS anyway. So if you wanted to switch the ones that use GPS to true headings, there would still be some that would need to use the magnetic and it would be a mess. On the other hand when you have GPS, you have a computer already and it can contain and use the magnetic declination tables to give you magnetic heading as well.


How frequently are avionics on large commercial aircraft updated?

Infrequently. Large fleets, lots of down time, lot of equipment to buy.

The fleets are cycled thru at a refittng center where the panels are disassembled and re-assembled. Here is one example


Does the coriolis force have an effect on the direction in which an aircraft travels?

Yes, the effect is there, and (auto-) pilots have to compensate for it, but the direct impact of the Coriolis force is insignificant compared to the impact of any wind forces.

This has been discussed on Physics SE: Coriolis force on bullet vs airplane

On the other hand side, the Coriolis force (seemingly) deflects moving air masses and causes the global wind patterns as we now them. Through the resulting wind forces on aircrafts, the Coriolis force has a very significant indirect impact on aircraft travel.


What sort of sensors are used for sensing the positions of the control surfaces for the ECAM F/CTL page on Airbus aircraft?

No, they are not proximity switches, which are suitable olny to detect when a moving part has reached one of few predetermined positions (as in a landing gear, in which only two predetermined positions – up and down – are of interest; any other intermediate position is transient and undesirable).

For those moving parts that are required to be positioned anywhere within a given range, such as the control surfaces of an aircraft, you need a sensor (aka transducer) that can accurately measure the position of the part at any point within that range, not just at the ends. As already mentioned, the device of choice is the linear variable differential transformer (LVDT), or its rotary variant RVDT.

For example, this is the schematic of a yaw damper servo actuator of an Airbus A320:

Element No. 4 is an LVDT that measures the displacement of the actuating rod attached to the rudder. Similar devices are used for ailerons and elevators. The elevators also have an additional RVDT fitted directly onto the elevator's torque tube, in addition to the LVDT part of the servo control.


What is the breakout by service branch for FAA ATC specialists with military backgrounds?

All military services in the US have Air Traffic Control MOS codes and training, except the Coast Guard. Army, Navy, Air Force and Marines all have it.

I don't know of any source of data that tells me if an ATC controller is a veteran, and of what branch of service. As far as I know, the FAA does not discriminate on the basis of which branch you were in when you were awarded the ATC MOS upon completion of training.


Why should AKE LD3s not be used in the A380?

Emirates uses multiple kinds of ULDs.

The AKE with "DO NOT USE WITH A380" are made out of aluminum metal. The tare weight is 80 kg. Contrasted with the AKE (light weight) 66 kg tare weight and the AKL (ultra light weight) 56 kg tare weight, the difference may seem small, but multiplied over the large number of AKEs can reduce the payload and therefore fuel burn considerably.

Emirates Skycargo website.


Do we artificially add a smell to jet fuel?

Aviation fuels are all hydrocarbons that have fairly strong natural odors, so no additives are necessary to give them a noticeable smell. Jet-A1 is refined kerosene, which has a distinctive smell which some find unpleasant and others not. Aviation Gasoline (AVGAS) has many "aromatic" hydrocarbons to boost octane which are called aromatic because of their distinctive odors.

So you can smell a fuel spill or leak pretty easily, for at least AVGAS I know this from experience. I once had a fuel leak which filled the cockpit with avgas fumes, I got a lungful before I managed to ventilate the cockpit and it was very unpleasant!


What is the proper procedure when a passenger seat belt becomes inoperable during flight?

The flight crew should have given you a seatbelt extension to fix the connection. And if that did not work, then you should have been instructed to hold on and ask other passengers to hold you down for landing.
Also, if you were wondering why the flight attendant did not move you to an empty the jump seat, is because FAA regulations don’t permit.


What coming changes might render current IFR equipment worthless in the foreseeable future?

At the moment the answer is "None" - with two exceptions:

LORAN receivers
These are already worthless because the US has shut down our LORAN chains.
They are jokingly referred to as "IFR-Certified Lead Bricks".
ADFs
The FAA is killing off NDBs one by one - an ADF is basically an expensive, drag-producing AM Radio in many parts of the country, and its utility is in steady decline.

Other than that the core IFR technologies are pretty much sticking around:

VOR/LOC/ILS isn't going anywhere.
Some VORs are getting decommissioned, but even the bleakest plans call for the FAA to maintain a "minimal operational network" of VORs as a backup in the event of trouble with the GPS satellites..
DME is sticking around.
Lots of planes flying around use DME still, and there are lots of DME approaches which serve as good backups for GPS approaches.
(WAAS) GPS is the current "best technology" & isn't going away soon.
The FAA LOVES WAAS GPS. It lets them get ILS-type approaches to pretty much any runway without expensive ground equipment to install/maintain/test. If you have an IFR-Certified WAAS GPS in your aircraft you're on the cutting edge of IFR navigation equipment, even if the GPS itself is older-generation technology (such as the popular Garmin 430W).
If your GPS is not WAAS capable it's still going to be usable, but it's much more limited. It may also pose some problems for you down the road (see below).

Some equipment regulations are changing (as part of the ADS-B Out mandate coming in 2020), but that's not an IFR-specific thing.

The crux of the ADS-B Out mandate is if you want to fly in airspace where a Mode C transponder is currently required you will need two things in your aircraft (if they're not already installed):

An ADS-B Out transmitter to broadcast your position.
This can be achieved in two ways:
A Mode S transponder with Extended Squitter (1090ES); or
A 987MHz Universal Access Transceiver (UAT)
A suitably accurate position source to talk to the transmitter.
Currently that means a WAAS GPS - either a panel-mounted device or a separate "blind" box.

The cost of complying with this mandate falls somewhere within a wide range: If you want a modern WAAS GPS with a touchscreen interface that will let you fly GPS approaches and a new transponder to do the broadcasting part you're going to spend a lot more money than if you install a Universal Access Transceiver and blind GPS source that do the absolute minimum required to comply.


Winglets don't have some mysterious magical wing tip extending property.  They don't add to the total lift of the wing (except to the extent they are canted).

The best way to conceptualize them is they extract energy from the tip flow and convert it to THRUST which can be deducted from the induced drag.  They are little wings making lift (wing..let, see?), except the lift isn't up (unless they are canted, where there is a small vertical lift component).  They work the way boat sails propel a boat forward and were originally called "tip sails".

The flow striking the winget on top is curling inboard toward the fuselage so that there is an outboard angle of attack at the winglet's leading edge that creates a lift vector (being 90 degrees to the local AOA) inboard and slightly forward.

The split scimitar doohicky just flips the effect over to take advantage of unexploited flow below and behind. The flow striking the winglet on the bottom is angling outboard, causing a lift vector to be applied outboard and slightly forward (again at 90 deg to the local AOA).

If you examine most winglets you will see that they aren't just fins that "block" the flow. They have an airfoil cross section because, as I said, they are wings making lift... just not up.

The benefit of the lift being created at the winglet is only sufficient to exceed the thrust and weight penalty of the winglet itself at lower indicated airspeeds where the vortices are stronger.  For this reason you (almost) only see them on high altitude aircraft that cruise at low indicated airspeeds.


In what ways is color blindness an issue in modern jet airliners?

There are lots of problems.

Sight is just generally important when flying. Even in airliners, most approaches are still flown manually and often visually. Any significant degradation of sight is going to be a problem when flying any type of airplane.
Red/Green/White light signals are used by air traffic control in the event of a radio failure. The inability to differentiate red from green in this case would be an enormous safety hazard (e.g. did tower just clear me to land or tell me to keep circling?)
PAPI/VASI lights use colors to indicate whether you're above, below, or on the proper glide slope for a runway. While it's possible to land without them, it's a significant reduction in safety.
Lights at airports are color-coded to indicate whether a particular road is a runway or taxiway, how close you are to the end of the runway, that a runway is in use, etc. Landing on a taxiway is usually a bad idea, so it's best if you can tell the difference.
The navigation lights on airplanes themselves are color-coded. The right wingtip has a green light, the left wingtip has a red light, and the back has a white light. This lets other pilots easily determine which way you're going and, in case of conflict, who should yield (seeing a red light on another aircraft means that they're to your right and, therefore, you should yield to [i.e. divert around] them.)
Colors are used on aviation charts to indicate all kinds of things, including class of airspace, type of special-use airspace, whether a field is controlled or not, type of route, elevation of terrain, where you should expect to see city lights at night, etc. You need to be able to distinguish these things quickly and accurately, even in low-light conditions.
Some cockpit instruments use colors to indicate various things. These include color bands on airspeed indicators, color of annunciator lights or their on-screen equivalents (i.e. red for warning, amber for caution, green for gear down, etc.,) echo intensity on a weather radar display, etc.


There is no hard answer to this and it should always be looked at carefully as its dangerous to compare these things. The factors vary widely and a clear cut comparison is generally hard. Twin Turbo-Props may have a lower celling than your average regional jet, they often fly shorter routes and see more cycles compared to their total hourly lifetime, some turbo-props are even in reach of private pilots which puts them in a different operational situation all together but will be lumped in on the statistics.

The most comprehensive study I can find on the topic, and one I feel breaks it down nicely, is this one from NASA

  Differences in Characteristics of Aviation Accidents during 1993-2012
  Based on Aircraft Type

Im going to refrain from quoting to much directly as its all relevant and a fairly short 20 page read. The table that seems to sum it up best is the following (refer to study for table explanation):

A bit of a tangent but related, here is a nice article from AOPA comparing the data for Small Jets VS Turbo Props operated under part 91


Fuel dumping is almost always an emergency maneuver, and it is never good for the environment.  So the alleged danger from the dumping must be balanced with the imminent danger to the 200–400 passengers involved.  It is never an easy decision but that's why the Captain gets paid the big bucks...

Dumping fuel sounds dangerous but it is not.  It is not going to explode.  Jet-A can be compared to kerosene and I don't have that statistic so let's compare it to Diesel Fuel which is not dissimilar to Jet-A.  Diesel Fuel at 400°F(204°C) is as volatile as gasoline is at 70°F(21°C).  Obviously that is a big difference.  Jet-A also evaporates into the air, so little if any hits the ground.

The biggest danger I see is to the atmosphere.


What does the "DO NOT USE FOR NAVIGATION" indication mean?

Unless it's an obsoleted procedure chart, it usually means that it's not complete.  The example you show has only the features pertinent to that approach, and its missing (for clarity) the features needed for any other aviation in that area.

You must use a sufficiently complete chart for navigation; the approach diagram is supplementary to your navigation chart.


What is this aircraft with a big gun on its back?

That's a German WWII V-1 flying bomb.

  It was an early cruise missile and the first production aircraft to use a pulsejet for power.

The pulsejet being the tube on top.

(Source)


What is the type of nozzle used on the MiG-21 and MiG-27?

Mig-21F, the first version of Mig-21 to be called as such, used a Tumansky R-11F-300 engine, which had a (variable) convergent nozzle. Later versions used Tumansky R-13-300, which was similar to the R-11 and Tumansky R-25-300 which had variable convergent nozzles as well. The Mig-27 used the Tumansky R29B, which has a convergent-divergent nozzle according to the manufacturer's site.

In theory, the aircraft speed is not limited by the exit speed, but the extra speed imparted to a mass of air by the engine (more the $\Delta v$, more the thrust). Basically, there is nothing that prevents an aircraft with convergent nozzle from attaining supersonic speeds, albeit the system is very ineffecient.

If the designer is ready to accept a weight and fuel consumption penalty, he/she can use a supersonic convergent nozzle. Though this is ineffecient, for short duration, this would be acceptable.
Another point to note is that the high exit temperatures means that the sonic velocities in the exhaust are nuch higher than the freestream ones. This means that the difference in speed is there, though the mach number may be less.


Do two of the same model of aircraft feel different to fly?

In larger aircraft being flown by airlines that buy their airplanes from the carriers that originally bought them from the manufacturers, this can be a real problem. For example, Boeing used to allow considerable customization of 747 cockpits. For example, the forward cockpit overhead panel of 747-100 and -200 aircraft made for TWA had the switches reversed from all other purchasing airlines. The panel was at an angle, neither vertical nor horizontal. TWA treated it as a logically horizontal panel in that if you wanted a switch on, you moved it forward. All other airlines treated it as a logically vertical panel in that if you wanted a switch on, you moved it up. Thus, from the pilot's point of view, to turn on a switch on a TWA airplane, you moved the switch in the reverse direction of the other airplanes. Things got especially bad when switches from, say, an ex-Pan Am airplane were put in an ex-TWA airplane. Towards the end of my career (retired 1999), if I was in an ex-TWA airplane, I always looked directly at an overhead panel switch before throwing it. The differences section of the QRH (Quick Reference Handbook) of both 747 carriers I flew for was lengthy.

As I remember, the FAA finally stepped in and required Boeing to offer less cockpit customization.


Does it make sense having a MiG 19 fuselage 'area ruled'?

Maybe a little, but not really worth doing.
Area ruling is not a precise science. The exact cross-section used to calculate the area depends on the Mach number, so the best you can do is pick some problem speed and area-rule for that. Also, junctions and other features do not always blend smoothly, so the ideal area profile as you work along the plane is not achievable. You end up making compromises.
And even then, unless your design already has a problem, area ruling will not magically push your plane faster. For example the English Electric Lightning had a similar straight-through fuselage design yet was capable of Mach 2 plus.
The MiG-19 was one of the fastest "pre-area rule" types in large part because it had among the fewest problems with sharp changes in area. The kind of re-contouring that Convair undertook between the YF-102 and YF-102A would not need to be nearly so drastic on the MiG-19 and would not bring anything like the same benefits.
The Mig-21 is in some ways what you suggest, a developed MiG-19 with area ruling (and a few other little tweaks!). Prototypes were originally built with swept and delta wings, and the delta only then selected for production.


Is there anything extra required to spin a Cessna 172 in the Utility category?

Provided you meet ALL of the requirements for utility category operation as spelled out in the POH (within W&B limits for the utility envelope, no aft passengers, empty baggage compartment, and anything else you may find in the Limitations and W&B sections of your POH) a Cessna 172 is approved for intentional spins, and may be used for spin training.

As to the gyro instruments, spinning MAY cause the gyro instruments to tumble. This is not good for the instrument (it beats up the bearings - do it too much and you'll wind up with an early gyro overhaul).
Newer vacuum gyros tend to be more resilient than the old ones that birthed the "Don't let the gyros tumble" rule of thumb - they'll tolerate more extreme angles without tumbling - so there's less of a need to worry about damaging them in spin training.
(Solid-State gyros obviously won't suffer damage as they have no gimbals and bearings to beat up. They may however become "confused" and go offline if they sense something they're not designed for.)

As a note, I would not do spin training in a Cessna 172 (or any other typical trainer where spins are only authorized within the utility envelope) that hasn't had a recent physical weighing, unless your operating weight and balance range is squarely in the middle of the utility envelope.

A plane with many years of "computed" W&B updates may in fact weigh 100lbs more (or, rarely, less) than the weight and balance sheets indicate, and the empty center of gravity could vary by an inch or more.

If you are going to be performing intentional spins it behooves you to ensure that you're actually operating within the envelope for which recovery has been tested.


In case of transponder failure, can I use my ADS-B out (Stratus II) serve as a back-up?

The Stratus does not broadcast. It recieves only. So that is no help.

If you had a stand alone UAT ADS-B transmitter. It might continue to broadcast your altitude if your transponder failed. The UAT requires an altitude input and it must be from the same source that your transponder gets it. Sometimes that gets wired directly from a 2nd output of your altitude encoder (bypassing the transponder which gets it from the 1st output) in which case it would continue to broadcast altitude. Sometimes the altitude wiring goes from your encoder to your transponder, then the transponder has an output that sends it to your ADS-B UAT. In this case it might fail if the transponder fails.

It might be useful to know that the ADS-B transmitter must broadcast your current transponder code (1200 for vfr). The UAT generally senses it automatically as the transponder broasdcasts it so you don't need to set it in 2 different controls. But if your transponder fails, it won't sense the code and may go into a fail mode on it's own (not sure about this though).

The advent of ADS-B brings no relaxing of the regulations regarding the requirement of using transponders.


What's the refueling process like for a light aircraft?

The DHC-6 Twin Otter has two fuel tanks located in the belly of the fuselage, one forward (1235 lbs or 185 gal) and one aft (1341 lbs or 201 gal). There is a fuel fill port on the port side of the fuselage above each tank.

Refueling a plane is similar to refueling a car, except (a) planes can hold a lot more fuel than cars, (b) you rarely completely fill the tanks due to weight limitations, and (c) full service is fairly common.

However, with a very light load and a very long trip, you would completely fill the tanks to maximize range. That can mean 30+ minutes at the pump for a plane this size.

For self service, you taxi over to the self-serve pump, stop the engine(s), insert your credit card, attach the ground wire, insert nozzle, pump however much fuel you need, take the receipt, restart the engine(s), and taxi away.

For full service, typically you park on the ramp or at a terminal, call (on the radio) for a fuel truck, the driver does the fueling while you're parked, and you settle the bill before leaving.

Note: in less developed countries, you will likely have to pay cash (USD is accepted everywhere) before they will give you fuel, especially in large quantities. And a smuggler may not want bank records of their transaction anyway.

Normally, passengers will want to get out at fuel stops to stretch their legs, use the restrooms, get snacks, etc. But it wouldn't be unreasonable for passengers to remain aboard if the story has a reason for them to want to stay out of sight.


I think what the placard actually says is.

Lifeline
Extension Belt

(ie, its 2 things, not one!)
An A320 equipment specification indicates the narrow OHB you reference as number 16. Which is titled "Lifeline". This line is used to aid evacuation from the overwing exits and more details can be found in this answer
Extension belts are used for infants on their carers laps, an extra belt loops round the child and attaches to the carers lap belt.

(source: cabincrewsafety.com)


What are the reasons for this radial piston engine shut down procedure?

It could also be to remove lead deposits from the spark plugs. Some avgas has an agent added to remove lead deposits, this only works above a certain temperature which is achieved above a certain RPM. We had to do a similar procedure in the Cessna 152.

As you will know, Avgas 100LL contains a compound known as Tetra Ethyl
Lead (TEL) which acts as an octane booster for the fuel. This results
in a fuel which is commonly known as a 100 Octane lean mixture and 130
rich mixture Performance Number fuel.
In practice it is even better than this, with ratings more like 106
lean mixture & 130 rich mixture which are far in excess of the
comparable 85 - 87 octane of road fuels. To achieve this a lot of TEL
is used - around 5 times the quantity that was used in the old Leaded
automotive fuels.
This increase in octane allows aviation engines to produce more power
through increased compression ratios or alternatively by increasing
the inlet pressure by using a turbo or a supercharger. The problem
with using Leaded fuels is that they will always burn with more
deposits than unleaded fuels.
The Tetra Ethyl Lead used for octane boost in the fuel naturally
degrades to form Lead Oxide when it is burned. In reality it is this
oxide which gives the octane boost. The problem is that Lead Oxide is
a solid up to about 900 deg C which is well within the wall
temperatures inside a piston engine.
In order to prevent these deposits from forming, a Lead scavenging
compound is added to Avgas 100LL - this compound is Ethylene
Dibromide. This scavenger is designed to react with the Lead oxide to
form Lead Bromide which is more volatile - becoming a gas at around
200 - 250 oC. This is a low enough temperature to ensure that the Lead
is removed from the engine as a gas end it subsequently goes back to
the solid phase as the exhaust gas cools in the atmosphere.
As a point of interest the pale brown / ash coloured staining that is
often seen leading from the exhausts of high powered engines, such as
those found on the warbirds, is in fact Lead Bromide.
To enable this reaction between the Lead Oxide and the scavenger to
work, there needs to be a relatively high combustion temperature.....

Read more at this link.


Why don't airliners use noise cancelling?

First, some airliners do use it - the Bombardier Q400 uses a NVS (Noise and Vibration Suppression) system to reduce cabin noise. Basically, it uses devices called Active Tuned Vibration Absorbers (ATVAs) mounted on the fuselage frames to 'cancel' the vibrations from propellers and outside noise, thereby quieting the cabin.

However, there are some issues with using active noise cancellation in aircraft:

The aircraft cabin is quite big and complex, and it would be very difficult to achieve noise cancellation over the entire volume; as active noise cancellation depends on the cancellation of sound waves using opposite phase, it works best in small, confined spaces. If the waves turn out to be in phase in a region, the sound would be doubled - not a good result.
A significant contributor to the noise inside the cabin is the wind outside; this is usually random and the frequency spectrum is also quite wide, resulting in difficulties in noise cancellation.
Noise cancellation is effective mostly when the frequency of the source is constant, which is not usually the case (the props are an exception - they lend themselves well to noise suppression)

Instead of active noise cancellation, aircraft manufacturers are putting more energy in reducing the noise itself:

Better engines, which has lesser noise through the use of chevrons, etc.
Better modelling of aircraft, so that the fuselage design minimizes the noise due to wind.
Better damping and cabin design, so the noise produced (for example, due to air conditioning and ventilation) is reduced.


FSX has lessons. See the Learning centre.
You have to scroll through the text, and then you can fly some lessons.


Does this web page really correctly depict the angle that is called "incidence" in the French language in the aviation context?

Yeah it's right if we consider that the relative wind is parallel to the ground.

In French, the "angle d'incidence" is the angle between the chord line and the relative wind, contrary to the US and UK which it's the angle between the chord line and the longitudinal axis.(fr="angle de calage")

  In french: In fluid mechanics, "l'angle d'incidence" is the angle formed by the chord of a profile and the relative wind speed vector. In English l'angle d'incidence" is called angle of attack (AOA).
  Attention, angle of incidence in English corresponds in French to the "angle de calage", the angle formed by the reference chord of a wing and the longitudinal axis of the aircraft.
  L'incidence (fr) notes : α

"Croisière" is cruise flight .the picture of the website is not clear because it confusing chord line and longitudinal axis(perhaps to simplify)... other important notion: RELATIVE WIND is the relative movement of air relative to the plane; it is ALWAYS PARALLEL AND SENSE OPPOSITE to the TRAJECTORY OF THE AIRPLANE(path)

Source: (the second link is french because the same page is different in French and in English)
https://fr.m.wikipedia.org/wiki/Incidence_(a%C3%A9rodynamique)
https://www.lavionnaire.fr/AerodynCPFoyer.php


A Pod-Pak is a aerodynamically shaped enclosure to transport an extra engine under the wing.

From 'Flying Magazine', Nov 1959:

  Spare engine in “Pod Pak” is the airlines' modern method of
  transporting extra engines to maintenance points. Nine major airlines
  flying Boeing 707s have ordered Pod-Paks. This spare suspended below
  the wing of a Qantas Airline's 707 shows the Pod Pak suspended from
  the airplane's front wing spar by means of two fittings and to the
  landing geard support rib by four bolts. Fairings streamline ends of
  the engine and normal engine cowls enclose the sides. No structural
  changes are required in the airplane's wing and, when not needed,
  Pod-Pak can be removed completely.

The exhaust pipes of the Pratt & Whitney JT3C turbojet engine on the left of the picture are an attempt to reduce the noise of the engine. They should aid in the mixing of the core exhaust stream and the freestream air which is quite a noisy process.

The successor to the JT3C, the JT3D, was a turbofan. In a turbofan there is a layer of bypass air between the core exhaust stream and the freestream which reduces the noise and increases the efficiency. Later B707s fitted with the JT3D engines did have not have the 20 pipes exhaust. Most of the aircraft which were originally fitted with the JT3C where later retrofitted with the JT3D.


How do police/ambulance helicopters communicate with ATC?

The exact procedures will vary locally but typically ATC will give priority to police and ambulance helicopters that operate emergency services.

If these helicopters are operating in controlled airspace, communication with ATC will be done by normal VHF radio. There is no need for a dedicated communications person, the pilot will be in contact with ATC.

Sudden manoeuvring of these flights is rarely a problem for ATC since these aircraft are operating under Visual Flight Rules.

When chasing a car, the pilot remains responsible for keeping clear of obstacles and other traffic, therefore this requires a second person to keep a look out (either on the car or the surroundings)


Why would a foreign military aircraft be parked at a US Air Force base?

It is actually fairly common for NATO aircraft to be at Eglin AFB.  When I was stationed there (a long time ago) we had two RAF Tornadoes on site for several months.

Eglin AFB is the home to the munitions development programs. Part of that development includes ensuring the weapons are compatible with the aircraft that will deploy them. Eglin also has a large test range to support that effort.

Since we sell the majority of our munitions throughout NATO (common weapons reduce the  size of stockpiles and increase flexibility), they also need to be tested on NATO aircraft. The Eurofighter is likely there for testing.


Is it an acceptable practice to take off in a microburst?

The airfield in the video is KAFF, the Air Force Academy air base. Everybody you see in the video are air force cadets or retired Air Force pilots (in the tows).

There is a credible thread about this over on Reddit where one commenter says:

  I'm very curious as to how you got this video, i was under the impression it never left the airfield.

  This happened in April 2014, this past year. The weather is absolute crap here, especially for soaring. Well... we get good weather sometimes. Anyway, it's not uncommon for those TG-16A's to go up with a 25 knot gust... But i digress.
  The cadets were pushing in because winds were out of limits and the weather was getting worse... and BAM! Microburst.

  This microburst hit right next to the airfield. The tower spotted it early, gave a verbal warning "look out..." and cadets are trained to do the following: grab a wing (glider) and turn broadside into the wind and put the spoilers out. The tows were not so easy... nor lucky. Their takeoff speed is about 50 knots, and none of them were powered up when they lifted off the ground, to give you an idea of how bad the wind was. Their only maneuver is to face into the wind and pray they dont actually take off. The tows that took off left for COS airport... it took another 30 minutes of holding gliders before the tower let the cadets start moving the gliders.

  As for taking off... 55 kt gusts are the highest the Academy has had in a long time. Considering there were a half-dozen other aircraft within 100 ft of the tows, along with people (i.e. cadets around/in the gliders) if he was moving too far from his position in the queue, the safest action is to get some altitude and try and leave the microburst. Or at the very least put some altitude and distance in between himself and the cadets and aircraft. You saw how slow the tows in the air were moving relative to the ground... those were HARSH winds.
  At about 0:20, you can see a cadet hanging onto the wing of a glider on the bottom of a screen. This wind was scary. I don't know if anyone was up at the time, but full tempo ops can be up to 5 tows and 8 gliders... on a standard afternoon training day 3 tows and 4 or 5 gliders is normal. It looks like they were already pushing the gliders to the hangar...

I believe the commenter is wrong in that the planes were not powered up, but everything else is accurate (relatively so, those Cub (?) tow planes can take off much less than 50kts).

From your question:

  Taking off against the wind seems impossible because where does it get its thrust? And with the wind also seems impossible because all the wind is traveling at the same speed as the airplane, which to me should make the airplane drop like a stone.

Taking off against (into) the wind is the most preferable way to get an airplane into the air. It reduces the amount of ground speed that you need in order to take off. Aircraft work according to the airflow over the wings, if the airflow is great enough and the angle of attack is right, then the aircraft flies.

Taking off with the wind is also possible, but it extends your ground roll since you need to get to the same relative speed with respect to the wind before the airplane will fly.

Look at it this way, lets say you have the wind at your back and you take off on a bike. As you gain speed there is a point at which there will feel like there is no wind since you have the same speed as the wind at your back. As you keep going faster you'll start to feel like the wind is blowing at you, but slower. The amount of wind blowing at you is your air speed, the speed you are actually going is your ground speed.

Airplanes work the same way, taking off down wind requires the aircraft to get a greater ground speed (but the same air speed) to take off. After the airplane starts moving the only thing that really matters is the speed of the relative air flowing over the wings. When somebody says they need 50 kts to take off, they mean 50kts of airspeed, or 50kts of air flowing over the wings.

Now, a little commentary. There are two aircraft that take off in the video, one goes to the left which is up wind and the other goes to the right which is down wind. The upwind pilot has a much easier time controlling the aircraft since they don't need as much ground speed to keep it in control.

The downwind pilot almost bought the farm, and I'm pretty sure when he got back on the ground he needed a change of pants and a new aircraft seat. He's having a lot more difficulty controlling the aircraft because of the low airspeed. It doesn't look like he had much of a choice to go in that direction though, so I'd buy that man a beer if I ever met him just to hear the story.

The thing to take away from this is those pilots are retired Air Force pilots with thousands of hours of experience in high performance aircraft. The average pilot would be a stain on the tarmac in similar conditions.

To answer your edited question:

  Is that standard practice to take off and fly to try to escape a burst? Is that even allowed and/or sensible?

No, it is not standard practice. Larger aircraft would probably not have this issue but the aircraft in the video all weigh less than 1000lbs, a little more with the pilots and fuel probably but not much. Pilots are trained specifically to avoid microbursts if possible because they are very dangerous things. A search of the NTSB accident database for the keyword "microburst" provides 73 accident reports with that mentioned, 21 with fatalities.

Is it allowed? No, airports will halt operations when low level wind shear is detected, however its not to say an aircraft isn't already in its takeoff run when the shear is detected. The highest priority is to stay on the ground. The aircraft in the video however don't have a choice, the wind speed they encountered is greater than their take-off speed, they were probably going to fly or tumbleweed.

CFR 91.3(b) gives a pilot full authority to deviate from any ATC instruction or rule in an emergency. An emergency does not need to be declared first, a pilots responsibility is Aviate, Navigate, Communicate. If all your attention is on flying (or keeping from flying) you can be in an emergency without telling ATC. I'm sure these pilots did not face any disciplinary or regulatory actions as the result of taking off from the parking ramp.


Can I safely plug something that draws 6 amps into the cigar lighter (power port) in my Piper Archer lll?

Yes, you can safely plug in a 6A load. Possibly a circuit breaker will pop out after some time. That depends on the rating of the circuit breaker serving the outlet and if there are any other loads on that circuit breaker. But it is completely safe to try it.


When you have a thin sheet that is put under a shearing load like a spar web as shown, the sheet, being flexible, has very little resistance to bending under compression out of its surface plane (or buckling) at which point its ability to resist the shear force is lost.  The stiffener just gives the flat web some resistance to compression buckling by making it less flexible; "stiffening" it in other words.


Is the separation distance between two aircraft approaching an airport the same under CDA and Non-CDA scenario?

Continuous descent operations do not warrant a change in separation minima. The same separation minima (wake turbulence, radar minima, lateral, horizontal and vertical minima) apply at CDA airports as they do at all other airports.

To answer 2, 4 and 5 at the same time: continuous descent approach means that an aicraft descending from cruise level (typically 10-11 km.) to the final approach procedure (typically about 1000 metres) will do so in one continuous motion - e.g. without levelling out and maintaining a certain intermediate level along the way.
Although it is possible, and widely utilised, crews are not required to use idle engine thrust for the descend. It may well be the case that an aircraft is required by air traffic control to maintain a certain speed during descend, in order to establish and maintain the separation requirements mentioned above. As such, you can see CDA operations where aircraft apply thrust during descend, but where the descend is still conducted as one continuous motion.
On the final approach, usually starting at an altitude of about 1000 metres, 20 or-so km. from the airport, there is no difference between CDA and non-CDA operations. Aircraft will fly completely normally, using engine thrust and lift augmentation devices (flaps, slats) to maintain an appropriate airspeed (actually, angle of attack) so that the aircraft descends at the correct rate to hit the runway. For a normal jet aircraft, it is not possible to fly the final 20-or-so km. of the approach with idle thrust - it simply wouldn't make it to the runway.

When talking about track miles, I will assume you are talking about the distane from the top of descend (TOD) until the runway threshold (THR). For an average jet airlines, descending from a level of 10-11 km., it will take somewhere between 100 and 120 nautical miles of distance to get from TOD to runway THR. For non-CDA airports, this distance will generally be longer, because the descend has to be initiated sooner, but you will also find examples where there is almost no difference.


Is an Airbus A319 allowed to fly with a missing flap track fairing?

Fully permitted according to this Configuration Deviation List for the A320:

  One fairing may be partly or completely missing.

There are more posts about this occurring. As Noah Krasser points out, it looks fairly dodgy to observant passengers. This is the "Master" list, i.e. the safe and approved baseline. Some airlines may have changes in their own internal documents not to dispatch aircraft in this condition at all.


Why do some Turbofan engines have multi-stage fans?

All three engines you show are for fighter jets flying at supersonic speeds. These engines need a low bypass ratio: Why do military turbofan engines use a low bypass ratio?
To achieve more thrust at lower bypass ratios, the bypass air needs to be accelerated more, which requires more than one fan stage because axial compressors can only add a limited pressure difference per stage:

Low bypass engines often have a multistage fan which generates a low volume but relatively high speed air stream whereas high bypass engines usually have a single stage fan which generates a high volume but relatively low speed air stream.

(SKYbrary - Turbofan Engine)
In principle, high bypass ratio engines where more air is accelerated less are more efficient and therefore used on modern airliners, but they are not suited for supersonic flight.


Can you help me identifying an A-4 Skyhawk-like jet?

They are A-4 Skyhawks all right. They are operated by Draken International and provide adversary training for USAF (among others); here's a closeup photo of them.

Image from edwards.af.mil


Could reduced-lift wingtips allow an airplane to generate less wake turbulence?

Lift already does taper off gradually towards the tips, even on rectangular wings without any washout. That effect becomes stronger with tapered wings, of course. The reason is the pressure equalization resulting from flow around the wingtips, like you show in the lower picture. And like in that picture, the wake is spread over span in reality. Your upper picture is unrealistic and a gross oversimplification.

However, the eventual strength of the wing wake will be little affected by this. The resulting vortices are caused by wake rollup and do not come directly from the tips. The tip vortices are only a small part of the overall wake.

Regarding efficiency: Tapering lift towards the tips will make the wing more efficient. Lift far away from the wing root causes high root bending moments and requires a heavier structure. Lift near the root costs less structural weight and the net lift of the wing (lift minus wing weight) will be higher with a near-triangular lift distribution. This insight was published as early as 1933 by Ludwig Prandtl and rediscovered by R. T. Jones in 1950.


How does compression ratio change, if at all, from sea level to higher altitudes?

The compression ratio of the turbo machinery will not change with altitude as long as the speed of the compressor does not change (excluding Reynolds number effects). This will lower the maximum pressure in parallel with the outside pressure.

However, to create the same lift at altitude, the aircraft has to fly faster. In 10 km, where the air density is roughly 1/4 of sea level density, the airplane has to fly twice as fast. Also, air temperature drops with altitude, so the flight Mach number increases even more. And this Mach number determines how much ram compression happens ahead of and in the intake. Flying fast will increase the intake pressure level, which partially compensates for the lower atmospheric pressure. Since the pressure rises with the square of the Mach number, fast airplanes have a clear advantage here.

Take the Concorde: Its Olympus 593 had a compression ratio of measly 12, but the precompression around the intake added another factor of 7 at Mach 2, so the total pressure ratio between the peak pressure in the engine and outside air was over 80! Admittedly, this air pressure was only 76 mbar at the cruising altitude of the Concorde, so the absolute peak pressure in the engine was a much less impressive 6 bar.

Typical compression ratios

To answer the question about typical compression ratios: This correlates strongly with the age of the design: The first operational turbojet, the Junkers Jumo 004 of 1943, had a compression ratio of just 3.2 using 7 compressor stages. The more recent Eurojet EJ200 of the Eurofighter achieves a compression ratio of around 26 with a similar size and weight using 8 compressed stages, but produces almost 7 times more thrust. The main difference is better aerodynamics.

The most recent civilian engines achieve a pressure ratio of around 50 using 15 compressor stages. They can afford to compress the air more because they try to heat and accelerate the air as little as necessary during the combustion process. Since the maximum heat inside the engine is limited by the materials used, a higher compression in military engines would leave less thermal margin for combustion heating. The higher nozzle velocities of supersonic-capable engines are best achieved with less compression and more combustion heating.

Here is a plot of the pressure ratio trends for commercial transport engines (Epstein, 1998)


How do airlines without assigned seating verify cargo balance?

The cabin crew simply counts the seated passengers (or alternatively empty seats) by zone (a block of rows), writes it down and hands the slip to the flight crew. It is common to do this on commuter planes even with assigned seating since passenger balance matters more on small aircraft and people may move.

As pointed out by SKYbrary:

  In practice, low cost airlines, which routinely offer free seating, also operate the majority of their flights with a high load factor, so that identifying any unoccupied seats will be a fairly simple matter.


Why would the runway separation for parallel triple simultaneous precision approaches be dependent on airport elevation?

What the text means is for triple simultaneous approaches for airports above 1,000 feet MSL, the FAA needs to conduct a case-by-case study. I.e. there is no automatic approval, yet.

Also, but not related, for airports below 1,000 feet MSL, reduction in separation from 5,000 feet also requires a case-by-case study.

  ... impractical or the...

I do think the paragraph you quoted can benefit from better punctuation.

Runway-to-runway separation does increase with elevation due to increased ground-speed and reduced reaction time.

The case-by-case study is usually done via numerous trials.

As for why 5000 feet, I was stuck in a loop between Annex 14 Volume I, PANS-ATM (Doc 4444), and the AC 150/5300-13A. Each quoting the other. Literally.

The Manual On Simultaneous Operations On Parallel Or Near-Parallel Instrument Runways does indeed discuss reaction times.

So, it's fair to deduce the increased separation is to give more time for ATC to notice any deviation and have time to react.

The FAA AIM does confirm the OFZ (Obstacle Free Zone) increases by 20 feet per 1000 feet elevation. The OFZ is in turn quoted as the reason for the runway separation increase the higher the airport is in the AC you quoted.

In short, increased elevation/ground speed requires case-by-case study to approve or bring down the separation. It's down to the reduced reaction time and airport equipment—e.g. radar accuracy, refresh rate, and so on.

The values themselves seem to be derived from trials plus added factor of safety plus rounding up. I can't find information on the trials.

Separation is not reduced with increased elevation, it's the opposite—if the airports (low and high) have the same exact equipment.


What is the white pattern on trim wheel for?

The white marks make it easy to see if the trim wheel is moving, which would be tricky if it was entirely black.

But wouldn't the pilot always know if they was spinning the trim wheel? Remember that the autopilot can also adjust the trim, which might not be obvious to the pilot. The visual marks make it easy for the pilots to see what the autopilot is doing.

Example video (not an Airbus, but very similar):


How does Pitot Heat influence airspeed indication (assuming no ice or moisture)?

No, there is no decrease or change with the use of pitot heat.

The pitot system measures pressure. There is no airflow through the system in normal operation. Any airflow through the system would be due to a system failure which led to leakage.


Can you bust a TFR while operating under IFR?

This is a letter from AOPA that was published in Aero News Network, based on a query made to the FAA on this very topic.

My interpretation of this is that there is no definitive answer, and that both the pilot and the controller have a responsibility, which may answer the question regarding why both parties were suspended in case described in the OP's post.

  Hello Mr. Ward,

  Your email was forwarded to us here in the Air Traffic department of
  AOPA. I contacted FAA headquarters for an official response to your
  question and received the following explanation:  Guess you could say
  it is the responsibility of both the pilot and air traffic controller:

  FAA Order 7110.65 states that ATC shall vector aircraft for separation
  and safety. This includes vectoring aircraft around TFRs as well as
  traffic. For the pilot, the applicable regulation is 14 CFR 91.103
  which pertains to preflight action and states that "Each pilot in
  command shall, before beginning a flight, become familiar with all
  available information concerning that flight," which includes TFRs.
  Additional regulations are covered in 14 CFR 91.13 and whichever CFR
  promulgated the TFR (e.g. 14 CFR 91.137; 14 CFR 91.138; 14 CFR 91.139;
  14 CFR 91.141; 14 CFR 91.143; 14 CFR 91.145)

  From a legal standpoint TFR avoidance is a joint responsibility. (This
  is in no way to be construed as a legal interpretation from FAA's
  legal staff). A pilot should not file an IFR flight through a TFR. If
  they did and that flight violated the TFR, they are subject to
  enforcement action.

  From an Air Traffic Quality Assurance standpoint, a controller should
  not allow an IFR or VFR flight that they are working to fly though a
  TFR. If they did, they would be subject to an Operational Deviation.
  However, looking at the totality of the circumstances: It is the
  pilot-in-command's (PIC's) duty to know exactly where the airspace is,
  just as it is ATC's responsibility to know where the airspace is. If
  ATC gave the pilot a vector that was going to take the aircraft right
  into the TFR and the pilot did not question the controller (just as if
  s/he would if being vectored into an area of known thunderstorms) then
  it is still the final responsibility of the pilot to question the
  clearance, just as it would be ATC's responsibility to question a
  pilot who wanted to fly directly through a TFR. Luckily, we are not
  aware of any instance where a controller let an IFR aircraft fly into
  a TFR. However, we are aware of many cases where pilots filed flights
  directly through TFRs and thought that ATC would vector them around,
  but instead, the pilot departed VFR expecting to pick up an IFR
  clearance in the air. While waiting for ATC to respond and issue a
  clearance the pilot flew through the TFR. In those cases, FAA
  suspended pilot certificates from 30 to 150 days.

  There is no question that it is bad operating practice to file an IFR
  flight through a TFR. During flight planning, pilots should avoid
  TFRs. Arguably, to deliberately file a flight plan through a known
  TFR, in and of itself, would be a violation of 14 CFR 91.103.

  Hope this helps!

  Heidi J. Williams

  Manager

  [emphasis mine]


How can an inexperienced pilot tell if the weather is good enough for flying?

I'm a UK PPL of 14 years, I fly out of North Weald which is on the opposite side on London to Farnborough, so I'm well placed to give you some tips here. First, use the Met Office aviation portal for your planning, most of the services a PPL will use are free. Metars are useless for planning as they only say how the weather is right now, TAFs are good for planning, however they only get you so far as they show you the forecast for one location. The Met Office portal gives you access to the low level forecast charts and spot wind charts, these give the big picture for the whole UK and Europe, including fronts, and forecasts in specific zones. These are published 4 times a day and are good for about 18 hours each.

The weather in the south east of England is very hard to predict accurately, it's getting better as they throw more computing power at it but it's still a challenge. When I do my weather planning I look at the low level chart and spot winds, then I look at the TAFs throughout the area. Heathrow and Gatwick both have 24 hour TAFs, and Farnborough is snuggled between them I'd look at them both and assume the worst from each.

Read the TAFs and look at the briefing charts every day you can until you get a feel for it, experience will give you confidence.

Next set limits. In the SE of England there ain't much topography but you don't want to cruise below 800ft in most places, back before I got an instrument rating I typically set a limit of 1000 ft ceiling, anything below and I wouldn't fly except for circuits, and even than that's pushing it. Wind-wise you need to know your crosswind limit for your airplane and yourself. It doesn't matter if your airplane's rated for 20 knots if you can't hack it, so don't put yourself in a bad position.

Lastly, UK TAFs have a funny quirk. You'll often see PROB for probability in a TAF. The only 2 figures you'll ever see in a UK TAF are PROB 30 and PROB 40, the numbers are for percentage likelihood. PROB 30 means it's unlikely to happen, whereas PROB 40 means it probably will happen. In other words a 40% probability does not mean 40%, but about 60-70%, don't ask me why. So if you see PROB 40 consider it likely.


Is there an aviation career where I would help design an entire aircraft and its systems?

You were born 100 years too late.
In order to be an improvement over existing designs, airplanes become ever more complex and every detail is optimised over years and years. The days when someone like Robert Hall or Kurt Tank would design and test fly their designs are long gone.
The best you can do is to design an experimental aircraft and maybe market it as a homebuilt or a kit plane. But forget about designing front-line fighters all by yourself: This by now involves thousands of engineers and the test pilots have very different careers from those of the lead engineers.


Can the Mexican presidential aircraft be sold?

Not sure about that specific aircraft, but the Dutch government recently sold its transport (a Fokker 70) for the royal family in anticipation of the arrival of its more capable replacement.

I've seen the aircraft many times before it was sold.

I've also seen President's Eisenhower's personal Beechcraft Twin Bonanza, which has been called the very first dedicated Air Force One, which is currently in a private collection in Canada. Not sure when it last flew, but the owner tries to keep his entire collection airworthy and once in a while takes one of them out.


What happens with the avionics if in midair there is loss of power or fuel flow interrupted?

This is somewhat dependent on the aircraft of course, so I will focus on the Boeing 737 NG series as an example of a typical airliner. Details will differ with other aircraft, but the general concept should be the same.

When there is loss of thrust on both engines, both engine driven generators will stop providing power. The battery will take over powering some of the systems immediately. If two batteries are installed, all emergency systems can be supplied for at least 60 minutes:

  Two 24 volt nickel–cadmium batteries, main and auxiliary, are located in the
  electronics compartment. The batteries can supply part of the DC system. The
  auxiliary battery operates in parallel with the main battery when the battery is
  powering the standby system. At all other times, the auxiliary battery is isolated
  from the power distribution system. Battery charging is automatically controlled.
  Two fully charged batteries have sufficient capacity to provide standby power for
  a minimum of 60 minutes. Battery voltage range is 22–30 volts.

(Boeing 737 NG FCOMv2 6.20.12 Electrical - System Description)

The batteries power some DC buses directly and the AC standby bus via a static inverter:

  Standby Power System - Normal Operation

  The standby system provides 115V AC and 24V DC power to essential systems
  in the event of loss of all engine or APU–driven AC power. The standby power
  system consists of:

  static inverter
  AC standby bus
  DC standby bus
  battery bus
  hot battery bus
  switched hot battery bus
  main battery
  auxiliary battery.

  [...]

  Static Inverter

  The static inverter converts 24 volt DC power from the battery to 115V AC power
  to supply the AC standby bus during the loss of normal electrical power. The
  power supply to the inverter is controlled by the standby power switch and the
  battery switch on the overhead panel.

(Boeing 737 NG FCOMv2 6.20.16 Electrical - System Description)

The FCOM contains a long list with all systems that are powered in this configuration. In general, only the captain's side instruments will be available. I will not quote the full list here, since you only asked about "cockpit display, flight plan". The relevant items are:

  All Generators Inoperative

  The following list identifies the significant equipment that operates when the main
  battery and the auxiliary battery are the only source of electrical power.

  emergency instrument flood lights
  Captain's pitot probe heat
  VHF No. 1
  upper display unit
  Captain's outboard and inboard display units (EFIS/MAP or PFD/ND)
  clocks
  left EFIS control panel
  Standby instruments
  FMC
  left CDU
  heading/track indications
  VHF NAV No. 1
  ILS No. 1
  left IRS
  left GPS

(Boeing 737 NG FCOMv2 6.20.19 Electrical - System Description)

This allows the Captain to continue flying the aircraft via manual reversion (no hydraulic pressure will be available, no autopilot is available). An emergency descent will have to be initiated without thrust. The checklist in the QRH will aim at restarting one or both engines. If that fails, the APU can be started in flight below 25,000 ft to provide more electrical power (all AC buses powered, all displays available again, electric hydraulic pumps available again).


Is there an alternative (more robust) operating law/setting for jet-engines? After one engine failed?

Aircrews regularly practice emergency procedures for engine out scenarios in their training and simulations.

Aircraft manufacturers and airlines provide procedural outlines for various possible emergency conditions specific to the type of aircraft.

During an in flight emergency, fuel efficiency is not a priority. The aircrew is to ensure safe flight of the aircraft and the priority becomes landing quickly and safely. This may require use of the engine in any fashion to keep the aircraft in flight.

In the report you reference, there is no real way to know what (if anything) caused what appeared to be a trail of smoke seen by another person in another aircraft waiting to take off.


Before the Soviet Union collapsed, what was Russia's official ATC language?

There's surprisingly little information on this to be found via Google, at least in English, but according to this academic paper from Embry-Riddle titled Air Traffic Control in Russia, Soviet controllers operated entirely in Russian, at least within the Soviet Union itself:

  Prior to 1991, Soviet air traffic controllers and pilots flying within
  Soviet airspace were not required to speak English and the majority of
  them spoke only Russian. After the KAL007 incident, translators were
  stationed at each of the three main control centers in order to
  assist with any controllers who encountered English-only pilots, though
  they weren’t used often (Taubman, 1987).

The cited source is a New York Times article which says that "80 percent of the civilian air controllers in the Soviet Far East speak some English" but translators (more correctly, interpreters) would be used "in an emergency", implying that the standard and/or availability of English was very limited.

If you consider the Warsaw Pact in general, then it looks like other languages may have been more common. This history of Hungarian ATC (you have to love the internet!) includes this information about the 1970s:

  The regular international cooperation between Air Traffic Controls
  commenced in the seventies under the aegis of ICAO, since Hungary
  became one of its regular members. It is more than interesting that
  the Hungarian controllers had to be able to speak not less than three
  languages with the flight crews and use not more than three units of
  measurement, namely the Flight Levels and metric systems of ICAO and
  the Soviet metric system. [...] Then at last, in 1975, Hungary applied
  the full ICAO system, but the Russian language as a medium of
  telecommunication remained in constant use until 1991 when the Soviet
  military forces left our country, after the 1989 political changes in
  Hungary.

It also confirms that Russian was a requirement for ATC controllers:

  Boys in their twenties with more than basic English and Russian
  language knowledge were the target as new trainee controllers.

There are also numerous aviation forum threads about Soviet and modern Russian ATC controllers, the overall picture seems to be that there was always some English spoken by ATC but it was often grudging, limited or just hard to understand. However most commenters (e.g. airline pilots) seem to agree that since the end of the Cold War, it's become much more widespread and the general level of ATC professionalism in Eastern Europe and Russia has improved significantly.


What's the purpose of partial autopilot disengagement after applying certain force to the control wheel?

The autopilot will disconnect on large control inputs because this is the most intuitive way to control the plane. On Boeing planes, the controls will physically move along with the autopilot. If the plane starts doing something you don't want it to do, the instinctive action is to grab the controls to correct it. While the autopilot button would normally be the way to disconnect the autopilot, it may not be the instinctive way in an emergency, and it can be helpful to already have both hands on the controls when the autopilot disconnects, rather than having one hand disconnecting the autopilot.

The reason for only disconnecting one part of the autopilot could be to help the pilot. Maybe there is a problem with the elevator controls, or an upset that affects the aircraft primarily in pitch. Maybe the TCAS gives a "climb" command. The pilot wants to take over pitch control to address this situation, but other controls are fine. While the pilot now has control of just pitch, the autopilot is still taking care of the other controls. The autopilot only gives the pilot control of the modes that are being overridden, instead of just turning off and requiring the pilot to deal with all control modes.


How do I simplify explanations for the drag formula?

Part 1:
As an aircraft travels faster, drag increases more in thicker air (usually lower to the ground) more than it does in thinner air (usually higher in the atmosphere).
Also, doubling speed quadruples drag.
Part 2:
Force of Drag (self-explanatory) =
Density (the thickness of air or how many molecules there are in a cubic meter) * Velocity^2 (the aircraft’s speed multiplied by its own value)
divide this value by 2
then multiply by Coefficient of Drag (basically, a value that shows how easily an object will slide through the air)
finally, multiply by Area (how much surface is actually in contact with the air. Obviously, a bigger object will interact with more air, increasing drag).
Hope this helps!


How feasible is it to use Smart Materials on aircraft?

Shape-memory alloys are only a small part of smart materials. Once deformed, they will change back to their old shape when heated or subjected to strong magnetic fields. Of the many alloys with this characteristic, only a few like nickel-titanium would be suitable for primary structures. They are extremely expensive to make and to process, so they have never been an economical alternative.

Also, heating and cooling would be required to switch between shapes, which is very energy intensive when the outer structure of an aircraft is involved. Airflow will ensure intense convective heat transfer, and to maintain the needed temperature will be very uneconomical. Please consider that an aircraft with shape-memory alloys would need to carry extra fuel for heating or cooling over much of the flight time. Hinges and electric or hydraulic actuators will have a clear mass advantage when you consider the system mass, including energy sources.

I guess you agree that creating strong magentical fields in parts of an aircraft is an exceedingly bad idea, so I will rule out magnetic shape-memory alloys.

Shape-memory alloys will only switch between two shapes, and intermediate shapes are easier to realize with hinges and actuators. Sure, a smooth shape is aerodynamically better than one with a contour break at the hinge line, but the small aerodynamic advantage of shape-memory structures is quickly lost when you look at the whole picture.

Another disadvantage is the accumulation of small cracks with every shape change. The low number of cycles will either require frequent replacement of the shape-memory parts or a very limited structural life of the aircraft.

In the end, much of what can be said about other smart materials also applies to shape-memory alloys. Their main function is to justify research grants and to keep the press occupied.


What kind of identification code is this format? (AAA0000)

That format is the flight id. The first three characters are the ICAO operator code which identifies the airline. The rest of the characters are unique to that flight. The first character after the ICAO operator code is always a number, after that both numbers and letters are allowed. The maximum length of the flight id is 7 characters.

The flight id is transmitted to Mode S radars by the transponder and also broadcast on ADS-B. It is used to correlate a flight to a flightplan.

The flight id is also the basis for the callsign used in radio communications. The ICAO three letter code represents the airline's callsign, the rest of the code is pronounced in the ICAO alphabet.


What does an absolute novice need to learn to make a successful emergency landing?

ATC has successfully talked down folks with zero experience in GA planes, and if there's one thing you need to learn, it's how to call ATC so they can give you that help.  Any pilot would be happy to teach you this, and it should only take a few minutes while you're sitting in the plane before departure.  Anything you know beyond that will make ATC's help a lot easier to understand and get you safely on the ground that much faster, but that's the bare minimum.

My recommendation is a "discovery flight" at a nearby flight school; that will teach you far more of the basic skills you'd need to survive than days of looking for tips online.  Flight sim time would save money if you're interested in becoming a pilot, but otherwise I wouldn't bother; you need to actually sit in a real plane, touch real buttons and knobs and levers, and feel how a real plane reacts--with someone at your side explaining the key points along the way.  I learned every one of the things on your list and more, plus made my first landing, in that one hour lesson.

FWIW, it doesn't matter if that discovery flight is in a Cessna and your emergency happens in a Mooney, or whatever.  For light planes, most of the differences border on cosmetic for emergency purposes.  Once you know what to look for and why, it shouldn't take much to recognize the important controls and instruments in any other light plane.  Again, any pilot you're flying with should be happy to explain the differences if you don't pick them up on your own; an instructor is only needed when you're starting from zero.

If you'll be flying GA a lot, particularly in the same plane and/or with the same pilot, look into "Pinch Hitter" courses; they'll cost quite a bit more than a simple discovery flight, but they're worth every penny if you'll be flying often enough for real concerns about emergencies.


Air-to-Air guided missiles are little airplanes. If there are only fins at the tail, it's a ballistic rocket, basically a fin stabilized artillery shell accelerated by a rocket motor instead of an explosion in a pipe.

On missile like AMRAAM, Sidewinder, or Sparrow, the vanes are wings and the missile is a rocket powered aircraft that can climb, descend and turn as required.  The vanes/wings don't have to be very big because the thing is going superdupersonic.  The X plan form means the wings can support and control the missile equally well in any axial position.

The front vanes are movable and do the controlling.  It's effectively a rocket powered robot canard aircraft on a suicide mission, really.

Since the missile accelerates to >Mach pretty quickly and operates supersonically, the wings/vanes use a supersonic airfoil profile, either biconvex (like the F-104's airfoil) or a diamond profile.  The vanes on the AIM-9M look like biconvex airfoils.

The missile descends when it is first launched because it's going too slowly for its teeny tiny supersonic wings to do enough lifting, and has to accelerate first.

Now, for a change of pace, slow something like an AMRAAM or Sidewinder down to subsonic speed, make the fins bigger and provide control surfaces on the rear ones, power it with a turbojet instead of a rocket except for boosting it into the air, and you have the CL-89 surveillance drone, basically a reconnaissance cruise missile that flies hither and yon at low level taking pictures.


Are there limitations in US legislation on a US citizen to own a MiG-15 in Europe?

With mere possession the only issue you might run into is any live, functional weapons on the aircraft. This is governed more by the nature of the device than the person owning it. Generally speaking, Europe is far less accommodating regarding private citizen ownership of military weapons than the US, especially nasty ones like automatic cannons. If they have been demilled to the specifications of the country in which they reside, then they're not guns any more, just decorations.

A couple of years ago, I saw a Soviet era MI-24 attack helicopter for sale in the US. Main and tail rotors present, no engines, no weapons, cockpit was pretty much gutted, airframe was past its useful life, for static display only. It looked intact from the outside... and also looked very sinister. For some odd reason, my wife balked at me spending $8k on this ultimate lawn decoration. But, there were no regulations regarding its ownership, other than maybe a neighborhood association getting huffy about someone parking an attack helicopter in their front yard.

Now, if you want to actually fly the MIG15, that's a different matter. But if you as a US citizen want to purchase a MIG15 as a static display, without functional weapons, the only thing the US government is going to care about is whether you paid their income tax on the money you use to buy it.


How to calculate the DC-4 landing distance with this graph?

Follow the arrows in the graph.

You start with the gross weight on the right X-axis and move straight upward until you intersect the correct field elevation. In the graph the line starts at 58,000 lbs and moves up to a field elevation of approx. 1700 ft.

From there move left into the left side of the graph. There, the X-axis is the effective headwind speed. Note the remark above the graph: This is 50% of the reported speed when the data for this graph was collected. Now you need to find the intersection of the line from the right half with the line vertically up from the headwind. Where both cross you take an interpolation of the landing distance lines. In the example the headwind is 18 knots, so the landing distance becomes 2000 ft.

Yes, temperature would have an effect, but for the landing distance that effect is small. A colder air is denser and reduces all speeds, so a shorter landing distance will be possible in colder air. But compared to a take-off where air density has a much stronger influence on engine performance, this effect can be neglected for a landing chart.


Why doesn't the U.S. Federal Government auction their retired but memorable aircraft?

There are a few reasons for this.

First off they may not want the public, or more importantly potentially enemy nations obtaining a large quantity (or any quantity for that matter) of military planes. Even old war birds can still do a lot of damage if equipped by a person with intent on doing damage.

Secondly, the boneyard you have pictured serves a few purposes. For one it houses aircraft that have reached their life time limit. To keep an airplane flying it takes not only money but a supply of parts (or the resources to make your own under certain FAA rules). Out of service planes may be tough if not impossible to keep flying for no other reason than you cant get airworthy parts for them.

Thirdly, some of the planes in these bone yards are scrapped (or kept there) for reserve parts for the planes still in service. Again airworthy parts are not as simple to get as going to your local car parts store. There are many more regulations around them. In this case you can pull parts from an airworthy plane (if you know the cycles its been through) and use them to fix another plane.

Lastly, and this is mainly speculation, maybe the government is hidings its back up planes in plane sight...

On the note about buying old war birds, rules have changed over time and its not as easy to get ahold of government property as in days past. Some military equipment that sees its way to the public hands actually left the US as a sale to another country then that country sold it into public trade as well. For what its worth Trade-a-Plane has a whole section just for war birds.