Why do older airplanes have a wing on both the top and the bottom of the aircraft?

Mainly for strength. Up to about 1920, wings used very thin airfoils and were mainly made of fabric stretched over a wooden frame. The main spar was too thin and would have been prone to bending if it had had to support the whole weight of the aircraft in a single span. Only by using two wings, the upper as the compression member and the other as the tension member of a truss, the needed strength was possible.

Airfoil thickness comparison by D.R. Kirk, Florida Institute of Technology (picture source)

In your photo, you can just about see the wires running from the top wing (near the outboard struts) to where the bottom wing joins the fuselage. These wires take most of the strain in flight, spreading the load on the wings. It's the same principle as using triangles in the construction of electricity pylons or bridges.

Monoplanes of that time needed even more wire bracing. Look at the picture of a replica of the Etrich Taube, a very popular plane of the pre-WW I period.

Etrich Taube in flight. Note the truss below the wing and the many wires keeping it in shape (picture source).

The shorter wingspan of a biplane also reduces the load on the wings. Biplanes tend to have a lot of lift (for their size) because of the large wing area, but also a lot of drag, so they're quite inefficient overall. There were also triplanes, with three mainplanes for even more lift in the same wingspan. WW I pilots demanded the highest rate of roll, which could best be achieved with biplanes.

In the time between the World Wars, the use of high-strength aluminium for aircraft and the monocoque airframe both allowed airframes to become stronger. This meant that monoplane designs became more practical, even though the older aviators didn't believe a monoplane could be strong enough. As soon as monoplanes were practical, the improvements in efficiency and flight performance saw them replace bi- and tri-planes.


What would be the effects of installing pitot tubes on the engine covers?

There is a very good reason to install pitot tubes in a place with relatively constant environmental circumstances: calibration.

Image source

When installed at around the nose of the aircraft, the pitot always have a good view of the airflow, at all angles of attack and of sideslip. These parameters do distort the pressure reading, that is why during aircraft development the prototype tows a flying pitot tube and compares measurements. These measurement sets are used for calibration.

If it was installed on the engine covers, not only the aircraft state but also the engine state would have influence on the reading. A nightmare to calibrate, and prone to unforeseen errors for instance if a fan blade breaks off and the wobbling fan causes an airstream situation that was not accounted for.

Best to use the prime location: the nose.


On a ducted propeller, how does duct length affect thrust?

Generally, there are losses due to friction drag in any tube carrying a fluid; therefore, the longer the duct, the more energy is lost from the air stream (this loss appears as back pressure against the fan, so the same power is absorbed at the reduced flow rate).

The higher the flow velocity, the greater these losses, but in a high bypass turbofan, there are other considerations.  Extending the bypass duct past the engine core allows the cool, relatively slow bypass air to mix with the hot, high velocity turbine exhaust, with the main effect of reducing exhaust noise.  The loss with a duct 2-3 meters long rather than half a meter is small; the gain in noise reduction can be large, and mixing the bypass exhaust with the turbine exhaust inside the duct may also give enough augmentation effect to offset the duct losses.


Is military grade jet fuel more expensive than civilian grade?

Prices

Relative prices depend on what military fuel you compare to what civilian fuel. The current US Defense Logistics Agency pricing for jet fuels is as follows:

    Fuel type     $/gallon $/barrel
    JP8 & JA1     2.15     90.30
    JAA           2.13     89.46
    JP5           2.18     91.56

JA1 is "Jet A1"--normal, internationally available civilian jet fuel.
JAA is "Jet A with Additives". It's Jet A (which is slightly less expensive than Jet A1, but available primarily in the US) with some additives added to improve lubrication, reduce corrosion, icing, etc.
JP8 is the jet fuel the US military used for years before (semi-recently) switching to mostly using civilian grades. Basically Jet A1 plus some additives.
JP5 is used primarily aboard aircraft carriers. It has slightly higher density than the others, and a substantially higher flash point (>= 60C, vs. >= 47C for Jet A1/JP8).

Summary

The military designations are mostly slightly more expensive than their purely civilian-grade counterparts. The prices given above are also somewhat higher than the IATA shows for pricing on jet fuels in the general market, at least at this moment1.

Why

Part of the reason for moving to civilian fuels is to reduce costs. Along with that, using something that's widely used and available makes it much easier to manage the supply chain, ensure an adequate supply, etc.

References

Defense Logistics Agency FY 2018 Fuel Prices
JP-8 and other Military Fuels (Warning: PDF)
IATA Jet Fuel Price Monitor

1. At least as I read things, the price given by the DLA is intended to be used for budget estimates, so it presumably reflects their worst-case estimate of the average price during the coming year.


Am I required to report entering the hold in lieu, persuant to the IFR mandatory reporting points?

If you're in radar contact with ATC, the answer is no, you will not need to report it unless requested to.  If you are not in radar contact (which would be unusual as that is in Class E airspace) you would not have to report your position entering the hold at YAYUB unless you were instructed to hold at this point with an EFC time.  From the AIM 5-4-9

  When a holding pattern replaces a procedure turn, the holding pattern must be followed, except when radar vectoring is provided or when NoPT is shown on the approach course. The recommended entry procedures will ensure the aircraft remains within the holding pattern’s protected airspace. As in the procedure turn, the descent from the minimum holding pattern altitude to the final approach fix altitude (when lower) may not commence until the aircraft is established on the inbound course. Where a holding pattern is established in-lieu-of a procedure turn, the maximum holding pattern airspeeds apply.

But 5-4-9 also states that

  If cleared for the approach prior to returning to the holding fix, and the aircraft is at the prescribed altitude, additional circuits of the holding pattern are not necessary nor expected by ATC. If pilots elect to make additional circuits to lose excessive altitude or to become better established on course, it is their responsibility to so advise ATC upon receipt of their approach clearance.

You would have to report leaving YAYUB inbound and to report crossing WIKUV FAF inbound as well.


Is it possible to reload Electric Aircraft in mid-air from a tanker aircraft?

This would certainly be possible, but the current status (pun intended) of the battery technology makes it pretty much pointless.

The charging would simply take too long: for example, Eviation Alice has a battery capacity of 900kWh. If we were to charge, say, 75% of this (because you would need to have some reserve capacity in case charging does not work out) it would take about 10 hours to charge if the charge time was comparable to Tesla Superchager (85kWh battery charges in about 75minutes =1.13 kwh/minute). Even if the battery was charged in ten parallel segments, charging would still take an hour.

Alice has an endurance of about two hours, so to double that, you'd have to spend at least an hour, most probably more charging.

Then, there's of course the sillyness of charging an electric aircraft with electricity made from jet fuel (or diesel)... it would be far more efficient to use that fuel to propel the aircraft without the engine-alternator-charger-battery-motor -detour.

For further reading, please see this Aviation Stack Exchange question regarding aerial refueling, many of the points raised in the answers also apply to aerial recharge.


What is the IATA code for the A320neo family?

The IATA three letter code for the Neo will likely be the same as for the regular model.
Unfortunately the IATA code list is copyrighted, and I can't find a public document that confirms it.

The more commonly used ICAO type designator, a four letter code can be found in  ICAO doc 8643. It contains a list of all common aircraft and their codes.

The ICAO type designator for the neo will be the same as for the regular versions. So A319, A320 and A321. Only if the performance of the Neo aircraft significantly differs from the originals, then a dedicated designator will be created.


If both propellers and wings are airfoils, then why do propellers deflect air perpendicularly to the rotor, but wings not?

Don't let wind tunnels fool with your perception of reality. In the real world, it's the wing that moves while the air remains stationary.

Consider a video just like the one you posted, but filmed with a stationary camera. (The one in your video is attached to the wing and moves along with it.) You'd see the folowing scenes:

The field of view is filled with stationary air.
A wing quickly passes through the video from right to left.
The air now moves downward more or less vertically.


The part looks injection-molded. The choice of transparent, moldable polymers available in the 1950s is manageable. The most likely candidates are:

PVC (back then the most widely used polymer, but normally not used in injection molding)
Celluloid (unlikely due to its high flammability)
PMMA (plexiglass)
Polystyrene

PVC can be detected when a heated copper wire is pressed into it and then again held into a gas flame. The copper will react with the chlorine of the PVC and color the flame greenish (Beilstein test). The last two candidates can be easily identified by the smell they produce when molten. Styrene in the case of polystyrene and derivates of benzene in case of PMMA. Since PMMA is rather soft, it can easily be notched but also has low mechanical strength. When dropped on a table, PMMA parts will create a more muffled, lower frequency sound than parts made of polystyrene.
Both are similarly well suited for being painted. Some plastics like polypropylene and polyethylene are unsuitable for painting because of their low surface energy. But while already known in the early Fifties, those materials were not yet used for parts production. The best substrate for painting would be ABS, but similarly while being known back then, transparent ABS types suitable for molding were not yet used.
My guess would be polystyrene, but given the few hints I am not really sure.


Yes in general it's accurate to say that lower wing loading is safer, especially in the hands of a pilot with low experience flying in calm weather with an unreliable engine.  Flying in gusty winds and strong turbulence, there would be safety advantages to a higher wing loading.

The basic idea of limiting the wing loading is to limit the stall speed and thus the destructive energy involved in a forced landing.  As the question suggests, perhaps it would be wiser to limit the stall speed, or to allow deviations from the prescribed minimum wing loading in the case of a demonstrated low stall speed.

However the Canadian regs may also be written with the idea of limiting the top speed too.  Exactly why that's a good thing is not completely clear, but in the US at least an ultralight must not be able to exceed 55 knots in sustained level flight.


How is an ILS approach conducted when following a heavy aircraft?

Other bodies may advise differently but I will answer for the FAA.

The FAA covers this in their wake turbulence handbook as well as many other scenarios you can look over.

Basically you can fly above the glide slope as you have assumed but you should always take precaution as it cant be known if the leading aircraft is at or above slope.

As in similar situations, separation services may be provided, load permitting.

  2.10.5.1 Air Traffic Control Assist

  Air traffic controllers are able to provide sepa- ration  distance
  information to  pilots  when workload  permits  and  they  have  radar
  dis- plays in the control tower.  They can provide airspeed
  differential between aircraft and may advise pilots following another
  aircraft when they are overtaking the preceding aircraft.

The document outlines some other methods and is worth a read.


What is the reasoning behind this question about the correct altitude to avoid clear icing?

As John K already said in the comments, the definition for icing conditions is visible moisture at a TAT of less than 10°C. From the Boeing 737 NG FCOMv1 (SP.16.1 Supplementary Procedures - Adverse Weather):

  Icing conditions exist when OAT (on the ground) or TAT (in-flight) is 10°C
  or below and any of the following exist:

  visible moisture (clouds, fog with visibility less than one statute
  mile (1600m), rain, snow, sleet, ice crystals, and so on) is present,
  or
  ice, snow, slush or standing water is present on the ramps,
  taxiways, or runways.

To avoid icing, you should descend to an altitude where the temperature is above 10°C. The standard lapse rate of the atmosphere according to the International Standard Atmosphere (ISA) is 2°C per 1,000 ft:

  As an average, the International Civil Aviation Organization (ICAO) defines an international standard atmosphere (ISA) with a temperature lapse rate of 6.49 K/km (3.56 °F or 1.98 °C/1,000 ft) from sea level to 11 km (36,090 ft or 6.8 mi).

This would result in the following expected temperatures at the given altitudes:

A) 14,000 ft: -2°C
B) 12,000 ft: 2°C
C) 6,000 ft: 14°C
D) 9,000 ft: 8°C

This only leaves answer C) with a temperature above 10°C and therefore outside of icing conditions.

Note: The lapse rate of 2°C per 1,000 ft is only an average, the actual lapse rate could be somewhat different. Wikipedia says:

  A typical value is around 5 °C/km, (9 °F/km, 2.7 °F/1,000 ft, 1.5 °C/1,000 ft).

Maybe the question assumes a lower lapse rate of 1°C per 1,000 ft, where an altitude of 6,000 ft is exactly where you would get 10°C.


What are the exact dimensions of a B-2 Spirit?

I doubt you will find an official source for these. Luckily, we have google maps.

Using this example from Whiteman AFB (https://www.google.com/maps/@38.7250446,-93.5602627,145m/data=!3m1!1e3?hl=en) and distance measuring tool we get the following lengths:

1 - ~4.65 m (~15.24 ft)

2 - ~3.69 m (~12.10 ft)

3 - ~7.83 m (~25.69 ft)

4 - ~10.71 m (~35.13 ft)

5 - ~4.58 m (~15.04 ft)

6 - ~31.52 m (~103.40 ft)

The rest you can get from the published dimensions (height, length, wingspan), as an example.


Was a point system implemented to train pilots to land on aircraft carriers?

Early on in US Naval Aviation, the system began to assign a series of grades for landing performance and set minimum grade requirements to carrier qual and manintain proficiency for naval aviators assigned to carrier based fixed wing squadrons.  The reasoning was to weed out aviators who could not maintain these standards, thus preventing a lot of accidents aboard ship.

A fixed wing carrier pattern and landing has quite a bit in common with that found in terrestrial flying.  However due to the small landing area aboard the ship, the tolerances are considerably tighter and the procedure is more demanding on the aviator.  The Navy found that unless strict standards were adhered to, pilots would begin to lax in their performance and begin to develop bad habits with their flying which could degenerate into dangerous situations.  Therefore all landings aboard ship are now graded by a team of Landing Signal Officers (LSOs).  LSOs are experienced naval aviators who have undergone additional training and experience to become an LSO.  The LSO observes the aviator in the pattern and monitors the pilot’s progress to make sure they’re in the correct position, altitude, airspeed and AoA.  Specific position in the pattern and final approach are graded:

Abeam the platform: the Jet should be abeam the LSO platform on the downwind leg of the pattern, approx 1 mile offset from the port side of the ship, at 600 ft ASL, at a target pattern airspeed, in the landing configuration.
At the 90: the jet should be halfway through the left turn to final approach, perpendicular to the direction the carrier is steaming, about 1 1/2 miles behind the ship, 450 ft AGL, at optimal AoA.
A
Crossing the Wake:  the jet should cross the ship’s wake about a mile behind the ship, 450 ft AGL, at optimal AoA
At the Start: the jet should be lined up in the groove - landing area centerline - and on glideslope - call the ball - about 3/4 mile behind the ship at 450 ft ASL, at optimal AoA.  Major deviations from AoA, lineup and glideslope should be corrected at this point or a go-around should be executed.
In the Middle: in the groove, on glideslope, on AoA.  Any minor deviations should be corrected here. Overshoots and worsening deviations from these targets should require a waveoff.
In close: the jet is 1/4 mile from touchdown, on glideslope, in the groove and very very small corrections being made to maintain these metrics.  Probably the last safe chance for a waveoff, if needed.
At the Ramp:  jet is over the roundout, on glideslope, on groove.  LSO may give the cut signal for the pilot to pull power to idle, if high, but not unsaveable high.
In the Wires: jet touches down (impacts) the deck on the main gear between the #2 and #3 cross deck pendants.  Hook snags the #3 cross deck pendant.  Pilot goes to full power in case of bolter or hook skip and makes ready to go around.
Final Stop: jet comes to a halt in the LA on centerline.  Power to idle.  Disengage the hook from the cross deck pendant.

These positions and metrics are graded and a composite score is released by the LSOs on the platform.  Grades are as follows.

OK Underline:  Superlative pass at the boat conducted with additional complications eg engine failure, barricade landing, etc.  Worth 5 points.
OK “Oh-Kay”: The highest score achievable under standard conditions.  Jet flew pattern and approach with minimal deviations, all promptly corrected for.  Hook snagged the 3-wire.  Good pass worth 4 points.
(OK) “Fair”: A fair pass.  Flying was good but there were a few deviations.  But overall, solid and safe.  Worth 3 points.
OK-Bolter:  a solid and safe pass but hook did not snag a cross deck pendant.  Worth 2.5 points.
No Grade: Too many deviations.  Described by LSOs as “ugly but safe ugly”.  Ironically worth 2 points.
Cut Pass: Unsafe attempt.  Gross deviations outside of the safe margain for flying.  Consider yourself lucky to walk away from this one with only the LSO’s teeth marks in your hinder.  Worth zero points.

A typical review of a pass may read something like.

202 (Jar-Jar): Slightly wide abeam, High at the 90, high and left at the start, slightly high in close, OK.

Squadrons have certain minimum landing GPAs and boarding rates (ratio of traps to total landing passes).  An F-18 squadron might require a GPA of 2.75 with a 60% boarding rate, etc. to remain carrier qualed.

PERSONAL OPINION

I think that grading began as a means of leveraging the competitive nature of the aircrews to motivate better performance.  Again the tolerance between an OK pass and a No Grade are pretty tight compared with landing on terrestrial runways.  Sloppiness can start to creep in unless drilled out.  3-wires start to become 2-wires, then 1-wires, then taxi 1-wires and finally rampstrikes happen and people get killed.  Landing grades are posted in the squadron ready rooms and everyone wants top spot.  If you screw up, everyone’s gonna see it - and it has a serious meaning.


Broadly speaking, radiation exposure can be mitigated in three ways: Time, Distance, and Shielding.  Two of these mitigating factors can't really be improved: Distance and Time.

For distance, the radiation exposure concern for commercial jet pilots (and travelers)is generally related to cosmic radiation and ultraviolet radiation from the sun. The sources are already quite distant, and the practical distances we can achieve on Earth won't make any appreciable difference here, so we can neglect distance.

Time (duration of exposure) is already somewhat limited by the duration of flights, but the cumulative effect over multiple flights is what we're generally concerned about when we discuss "pilot's radiation exposure".
As their career requires them to fly, and the nature of jets means they'll be flying at high altitude there's not much that can be done with time, except perhaps having a very short career or not accepting a large number of flights. These options are not economically attractive if flying is your career.

That leaves shielding. Pilots sacrifice the benefit of shielding (from the Earth's atmosphere) as they climb: The atmosphere is less dense and there is less of it between the pilot and the background radiation, therefore their exposure is increased.
It's here that improvements can at least theoretically be made: The pilots and passengers already gain some shielding from the structure of the aircraft, but not nearly as much as 30,000 feet of atmosphere provides. The aircraft could be constructed with additional radiation-shielding materials (lead foil for example, and UV-attenuating tints in the windows) but doing so would add a significant amount of weight.

As with most radiation shielding situations it ultimately becomes an economic trade-off: You implement shielding to bring the exposure (dose) down to an acceptable level given the time and distance constraints you're working within.
The additional dose received by pilots is already extremely low, and adding shielding to reduce it further would not give a huge increase in safety. The costs (in terms of aircraft design, construction, and operating cost to carry the additional weight) would exceed the cost of treating the relatively minor complications such as skin cancer which may result from the additional exposure over a lifetime career of flying.

If all of that was too much to read, the short answer to your question is "The best way to mitigate increased radiation exposure from flying is to remain at low altitudes." (Similar to how the best way to mitigate the increased radiation from living in Denver, Colorado at ~5,000 feet above MSL is to move to New Orleans, LA at 7 feet below MSL.)

The next best thing would be to fly less frequently or on shorter legs (to reduce the duration of exposure).


What is the comparative roughness of fabric surfaces?

It varies with the level of finishing effort, and depends mostly on how much the weave of the fabric was filled in.  If the weave shows in the fabric, you can expect the surface roughness to be similar to lacquered wood.  If there are enough dope coats to fully fill the fabric, you'd have something similar to commercial metal painted finish.  But if you really go to town you can get to the filled and polished glass surface finish.  You'll see some award winning homebuilts at Oshkosh with a fabric finish that looks like shiny mylar plastic, but is actually regular fabric and dope.   Many many coats, and many many hours of sanding and rubbing.

Some of the latest finishing systems can produce that finish without zillions of coats and hours of rubbing.

This is all notwithstanding all the surface irregularities you have with fabric due to the use of reinforcing tapes etc., which may make the whole issue of surface smoothness moot anyway.


Can a pilot over the age of 65 exercise the privileges of a commercial pilot license under FAA Part 91 in the Bahamas?

There should not be a problem as long as you are flying under Part 91 because the age restriction which you refer to does not apply to all commercial pilot operations.

14 CFR 61.3 is consistent with the ICAO rule which you refer to and covers a US pilot, flying a US registered aircraft internationally and states:

  (j) Age limitation for certain operations

  (1) Age limitation. No person who holds a pilot certificate issued
  under this part may serve as a pilot on a civil airplane of U.S.
  registry in the following operations if the person has reached his or
  her 60th birthday or, in the case of operations with more than one
  pilot, his or her 65th birthday:

  (i) Scheduled international air services carrying passengers in
  turbojet-powered airplanes;

  (ii) Scheduled international air services carrying passengers in
  airplanes having a passenger-seat configuration of more than nine
  passenger seats, excluding each crewmember seat;

  (iii) Nonscheduled international air transportation for compensation
  or hire in airplanes having a passenger-seat configuration of more
  than 30 passenger seats, excluding each crewmember seat; or

  (iv) Scheduled international air services, or nonscheduled
  international air transportation for compensation or hire, in
  airplanes having a payload capacity of more than 7,500 pounds.

  (2) Definitions.

  (i) "International air service," as used in this paragraph (j), means
  scheduled air service performed in airplanes for the public transport
  of passengers, mail, or cargo, in which the service passes through the
  airspace over the territory of more than one country.

  (ii) "International air transportation," as used in this paragraph
  (j), means air transportation performed in airplanes for the public
  transport of passengers, mail, or cargo, in which the service passes
  through the airspace over the territory of more than one country.

Each of the bolded sections (added by me) show how each part is ruled out for a Part 91 operation as you describe.

Along the same lines, the ICAO SARP that you are referring to governs "commercial air transport operations," and not all commercial operations.  Part 91 flights do not fall under the annex with these requirements.

That being said, it is a foreign country and they can make their own laws which do not necessarily have to agree with any of this.  To be sure, you can always contact the FBO that you intend to use and ask them, or obtain a copy of the Bahamas AIP (I wasn't able to find a free copy) and see what it says.

Being based in South Florida and doing lots of flying to the Bahamas, I haven't heard of a problem with this (although I haven't specifically been looking for it either).


What is the function of this small hole on the B737's hydraulic reservoir line?

Answering based on ATA 49 system, B757/767 APU Surge Control Valve muscle air plumbing.

Some pneumatic sensing and pressure systems have a moisture bleed hole to prevent icing in the system.  They are typically located at a low point or bend in the line to allow water to escape the system while maintaining pressure.  If the hole gets plugged it can prevent moisture from escaping and ice to form in the line.


What is the name of the previous Air Traffic Management System (ATMS) of Hong Kong International Airport?


This quote is from Barry Schiff, a retired pilot from TWA and aviation consultant (but this is only the beginning of the story, I invite everybody to read the article on Wikipedia):

Photo stolen from AOPA

Your recollection is accurate! This is indeed in One Six Right.

Landing on 16R at Van Nuys, Youtube

He says that at the beginning (3:06) of the documentary. The video is not available online, but the first sentence of this quote is often taken up, e.g. on page 39 of this Midwest Flyer issue.

The quote in its context:

  “Asking someone why they love to fly is almost like asking someone why
  they like Picasso. The beauty is the fact that you can’t really
  describe it, it’s something that you have to behold. Flying takes you
  into another dimension, literally. We see, feel, and experience things
  that people who don’t fly will never know.”

  Barry Schiff, Aviation Safety Expert / Pilot (source)


Does a nuclear weapon (B-61) equipped F-35 have the same nuclear confirmation failsafes as other nuclear device delivery aircraft?

Traditionally many single seater aircraft have had nuclear weapons capabilities.

To name a few:

A-4
F-104
F-105
F-84
F-16
A-7 (I think)
F-102
F-106
F-88
F-101

This list isn't exhaustive. The release of the weapon will typically be authorised before takeoff, the pilot then having the electronics on board to enter the final arming codes that will bring the weapon life. I'm not in the know about the exact procedures here, but my guess is someone on the ground acts as the first of the two keys before the flight starts, and the pilot entering his codes into the arming console during the flight acts as the second. This is far more reliable and less error prone than having the code transmitted to the weapon during flight over a radio link which may be jammed, detected, or simply not work in a nuclear war scenario.


Why are contrails not visible from the cabin?

The distance between the engine and the start of the contrail depends on:

the engine type
the temperature of the outside air
the moisture content of the outside air.

Usually the contrails don't form before the tail of the aircraft, but in extreme cold or humid air contrails can be seen forming just behind the wing.

On larger aircraft you have a better change of seeing the contrail from inside the aircraft. On the 747 you can often spot them for the window of the rear passenger door.


Why is there really only one basic design for passenger airplanes?

For most transport aircraft, aerodynamic efficiency is the key parameter as it allows lower fuel consumption. The layouts you see most often are the most efficient known:

For jets low swept wings with engines mounted under and ahead of the wings and conventional tail is most efficient known layout. Tail-mounted engines used to be common on smaller jets, but as that puts lot of bulk far aft, they are worse with respect to Whitcomb area rule, worse for weight and balance, and wing-mounted engines also help damp flutter. So new regiojets are switching to engines under wing too.
Propeller aircraft fly slower, so they have straight wings. Low mounted wings are slightly more efficient, but then the plane has to have long gear to maintain sufficient ground clearance for the propellers, so high wings are more common. T-tail is then simply used to put the elevator above the most turbulent wake of wing and engines.

The only deviations from these three basic layouts are on special-purpose plane that have other more important concern. The most notable is military cargo planes are generally high-wing so they can sit low on the ground for easy loading and unloading using built-in ramp. Their marked anhedral is to avoid overstabilizing the aircraft in roll as both high wing and wing sweep increase roll stability. Earlier regiojet designs used tail-mounted engines for the same reason; to sit lower on the ground so they can be easily loaded via built-in airstairs and these are not too heavy and bulky.


For most people, the answer is yes—you need an instrument rating to be a CFI or CFII for the categories that are listed.

It is possible to become an ATP by using military experience. In that specific case a person has instrument privileges but may not have an instrument rating.


What is this delta wing aircraft parked at NASA Ames Research Center at Moffett Field?

It is a STOVL E-7 Model.. It is not an actual aircraft.
https://artsandculture.google.com/asset/e-7-stovl-fighter-model-testing-in-ames-40x80ft-wind-tunnel-tom-trower/RQEHhSh_zF3TuQ?ms=%7B%22x%22%3A0.5%2C%22y%22%3A0.5%2C%22z%22%3A9.425586796493714%2C%22size%22%3A%7B%22width%22%3A1.2166568742655705%2C%22height%22%3A1.2375000000000007%7D%7D

The enlarged photo shows the inlet duct covers. It looks like they left the lifting cables just laying on top. This is a model that never flew.


No, a drone will normally not be visible on an aircraft TCAS. The TCAS system is based entirely on direct communication between aircraft transponders, so both parties (aircraft and drone) must have a transponder in order for TCAS to work. Normal drones do not have transponders, so they will not be visible on TCAS.

If a pilot reports a drone near the aircraft, what he means is that he (visually) has seen a drone out the window, not that it is indicated on an instrument anywhere. Besides, TCAS does not know different aircraft types, so even if a drone had a transponder and it was presented on a TCAS, the pilot would have no way of knowing that it was a drone (as opposed to any other aircraft).

  Or just primary radar target pick up by TCAS.

TCAS is NOT a radar. It is not able to display anything without a transponder. And even ground based primary radars will not necessarily pick up a small drone.


The terms you are looking for are Decision Altitude (DA) and Decision Height (DH). If no visual reference to the runway is established at the DA or DH, a missed approach has to be initiated. So based on the weather and the certification of the airport (CAT I / CAT II / CAT III), the pilot will make the decision to land or not land at the DA/DH.

(Image Source: SKYbrary)

Decision altitude (DA) is referenced to mean sea level and decision height (DH) is referenced to the threshold elevation.
The DH for Category II and III approaches is invariably assessed by reference to a radio altimeter and never a barometric altimeter; therefore the minima can only be expressed as DH and not DA. For approaches with DH of 200ft or higher, radio altimeter reading would be unreliable due to the unevenness of the terrain; therfore a barometric altimeter is always used and the minima may be expressed as DH or DA.
The required visual reference means that section of the visual aids or of the approach area which should have been in view for sufficient time for the pilot to have made an assessment of the aircraft position and rate of change of position, in relation to the desired flight path. In Category III operations, the required visual reference is that specified for the particular procedure and operation.
For convenience where both expressions are used they may be written in the form "decision altitude/height" and abbreviated "DA/H"

Related Videos:
CAT II ILS Approach LGTS
Related Questions:
Is it legal to land in bad visibility conditions without ILS?
Are zero visibility landings practical and desirable for commercial aviation?
How can landing in zero visibility be safe?


Wind correction on downwind during circling

Yes, they need to be corrected, mainly for two reasons:

1) Legally, the horizontal criteria for circling is the distance from the threshold of each usable runway (search for TERPS circling criteria if you are interested in US rules, or PANS-OPS circling criteria for the rest of the world). In other words: you need to stay within a given distance of the runway. If you have a very strong tailwind, without correcting for it, you might leave the circling domain.

2) In order to facilitate the base/final. If you have a very strong headwind (which is indeed not very likely, as it means you will land in a very strong tailwind), you will drift towards the runway during your entire base/final-turn. This means you will roll out on the final course a lot closer to the runway than you would in zero wind. This could be a problem, since your stable approach criteria usually requires you to be "wings level" at some altitude (typically 300 ft for circling).

Now, for the how, this will depend on aircraft and operator. One example is however to add/subtract half the wind component in knots from your timing in seconds. Example: Zero-wind outbound: 30 s, Tailwind component: 20 kt. Wind-corrected outbound: 30 - 0.5*20 = 20 s.

(In addition, outbound timing is usually also determined by circling height, since the higher you are, the longer you will need for your descent. A typical SOP here is to take the circling height in hundreds of feet, and multiply it by 3, to get your zero wind outbound timing. Example: Circling height: 1000 ft. 1000/100 * 3 = 30 s.)


What are these protruding things on this Russian military aircraft (MiG-31BM)?

The upper thing is a mirror for the WSO's (rear seater's) periscope.  It gives that position some forward visibility when extended.  Without it, I doubt that position could see the runway.  There are several other Russian aircraft with periscopes.
The lower ones are speedbrakes.
Looking at the underside of the vehicle my speculation is that they interfere with the landing gear retraction, so are extended until that point.  But if that's true, do they have to extend when the gear come down for landing?  No idea.  I can't think of another good reason for them to be open on takeoff.
A comment from ymb1 showed a very nice image of the doors/speedbrakes on wikimedia
This shows that they need to be extended until the gear is retracted.


Why were there passengers allowed on Concorde's route proving flights?

Bear in mind that these tests weren't to prove the safety of the aircraft per se, just to show that it would work as an airliner. It had to be loaded up with an appropriate complement of passengers and luggage to prove this.

However proving flights may not generate revenue from passengers - they are either selected through an application process or chosen at random, and take part in the proceedings free of charge.

CAA AIRWORTHINESS INSPECTOR‘S HANDBOOK (Page 2, point 3)


How does supercruise thrust compare with static thrust ASL?

For Concorde, takeoff thrust:weight was 1:0.373. At cruise, the Concorde had a lift:drag ratio of 7:1. At cruise, thrust = drag. So cruise thrust is 1/7 = 0.1429
So, cruise:ASL is 0.14(rounded down for climb fuel burn):0.373 = around  1:3.8
For the SR-71, takeoff thrust:weight is 0.44:1. Using the Kuchemann supersonic L/D formula, we get
4(Mach(=3)+3)/Mach(=3)
=1:8
Now this looks too high. And running this formula for Concorde gave 10:1. So, having no better option (yet), I simply took 1:6 as the value. This would give us a cruise thrust:weight of around 1/6:1 = 0.167:1
0.167/0.44 = around 1:3.8 (again?)
The figures for the SR-71 may well be wrong.


What is the name of the figure consisting of a slow revolution around longitudinal axis?

What is an Aileron Roll?

You are correct, but should we really expect that level of precision from the entertainment business or the media?


How is the D8 Double Bubble aircraft by NASA so efficient?

The main advantage is its lower flight Mach number of 0.74. This allows it to use minimum sweep, which in turn reduces wing area, structural masses and thrust requirements. Now pick the right definition for efficiency (one that neglects speed), add the engine fuel consumption expected in 20 years, and the concept looks like a winner. If fuel prices go to \$200 or \$300 a barrel, this type of aircraft will lower the cost of flying substantially. The double-bubble fuselage will contribute only a little to the overall savings, though. Most will come from the (hypothetical!) engines and the high aspect ratio wings with little sweep.

Note that the lower flight speed is compensated by the claim of much shorter boarding times, so the double bubble comes out ahead in block times. The only reasoning is that passengers will board more quickly because they can choose between two aisles to get to their seats. Very questionable!

Below is page 105 from this report which shows the fuel consumption improvement of the separate steps from a Boeing 737 reference design to the D8.1 concept. The biggest contribution is from lowering cruise Mach (and increasing cruise lift coefficient, which allows to reduce wing area) and from engine optimization.

As it looks now, the marginal cost of fracking will keep oil prices below $70 for the next years, and airlines will keep ordering planes which look like those they operate today.

Looking through the proposals in the PDF linked in your comment, most of them make me cringe. Since the Seventies we see the same concepts for supersonic travel, and here they are again, only presented in different colors. Some subsonic designs are sound, but again we see hopeless concepts like the boxed wing which is kept alive by a stream of NASA grants, only because it looks so different. I am equally skeptical of those blended wing concepts which pop up with every new generation of aircraft designers.


What is this thing on a FDX MD11 (MD10?)?

It's the infrared sensor for the Enhanced Flight Vision System (EFVS).
From FedEx Newsroom June 23, 2008:

FedEx Express is the first major commercial carrier in the airline
industry to receive a Supplemental Type Certificate from the FAA for
the advanced system, authorizing its installation in the company’s
fleet of Boeing MD-10 freighters. The company’s goal for the system is
to improve the level of flight safety by increasing visibility of
pilots during adverse weather conditions and darkness.
A unique application of Honeywell International “Head Up Display”
(HUD) technology combined with infrared “Enhanced Flight Vision
System” (EFVS) technology of Elbit Systems of America Commercial
Aviation-Kollsman Business Unit, positions the system as the leader in
the avionic visual technologies market.
The Honeywell HUD interfaces with aircraft navigational and flight
data systems in presenting a high resolution liquid crystal display of
critical flight guidance information. This is overlaid with real-time
EFVS infrared video of the outside world that is displayed in an
overhead unit in the captain’s forward field of view using
state-of-the-art HUD “combiner” technology. Elbit Systems Ltd.,
Electro-Optics-Elop manufactures the combiner glass.

The combined image appears like this:

Source: FedEx


Will I fail a check-ride if I do a go-around for a short-field landing?

In general, you get one free go-around.

First of all, any checkride which involves short-field landings probably also involves demonstrating go-arounds.  If you don't do one on your own, your examiner will have to ask to see one later.

Going around when it's obvious you're not going to make your point demonstrates good judgment.  It shows that you're not going to try to force the airplane into an unsafe situation just to hit your mark.  If the runway you're landing on really is a short field, continuing the landing attempt would not only be a bad idea, it would be unsafe, and the examiner would be correct in taking the controls from you, as well as failing you.  If the runway is long and you're simulating a short field landing, the same applies.

If you go around on a short-field landing and then go around on the next one as well, the examiner is going to start to wonder whether you really know what you're doing.  Let's face it, it should not take you three tries to get properly set up for a short field landing, unless perhaps if the day is remarkably turbulent or there is a strong gusty crosswind.  If that's the case, though, why in the world did you decide to take your checkride in those conditions?


Are there any aircraft where minimum-V1 is limited by Vmcg?

Yes

Almost any transport category jet will reach its Vmcg V1 limit in favorable conditions.

The rationale is quite easy: When fully loaded with heavy fuel load (ie. at maximum takeoff weight) some 20% of weight is payload and about 20% is fuel. When the same jet is taking off with light passenger load for a short hop with low fuel load, there is massive surplus of thrust available so there is some acceleration available in case of engine failure on ground. This is especially true for twins.


For taking-off and landing in a DHC-7, what elements can be used in writing a novel?

(wikipedia.org) Viewing the full resolution image from the link might help you notice things to use.

Steering the yoke right and left controls the aircraft's roll. Pulling/pushing the control column controls the aircraft's pitch (nose up/down).
Radio altimeter is used in landing, it offers precise measurement of height above ground.
Landing gear lever, down is wheels down.
Airspeed indicator shows how fast the plane is going. 12 o'clock position, not going anywhere. Moves clockwise with speed increase.
Flaps lever: fully down for take-off/landing from short field.
Power levers: push away from you, full power. Pull all the way back, full reverse, which is useful in stopping the plane especially on ice. Don't use the brakes in your novel if the runway is icy.
Trim wheel: pilot will use it to fine tune the approach. And after take-off to make pulling the control column easier. You can watch it on YouTube (head-mounted GoPro).


How much snow can cover a runway while still allowing commercial airliners to land safely?

There is no set legal limit (ultimately it is up to the PIC to decide) but condition reports are available to pilots at many airports to assist in assessing takeoff and landing performance.   The FAA has recently created a standardized way of reporting runway conditions through their TALPA (takeoff and landing performance assessment) initiative.

TALPA is an improved way of assessing runway conditions, based on contaminant type
and depth, which provides an aircraft operator effective means to anticipate airplane
braking performance.

The RCAM (shown below) is the tool airport operators use to report a runway surface assessment when contaminants such as water, ice, snow, slush, and others are present on runways, taxiways, and aprons.   To find an updated RCAM look in Chapter 5 of Advisory Circular 150/5200-30, Airport Field
Condition Assessments and Winter Operation Safety.

The RwyCC is the runway condition code -- as you can see a code of 0 yields minimal to non-existant braking and/or directional control.


What are the requirement for electrical grounding of aircraft in hangar storage?

In general any aircraft parked in hangar should be electrically grounded. The grounding should be done from basic aircraft structure to a low resistance ground.

Grounding of the aircraft is usually done to,

Protect aircraft and personnel against hazards from lightning discharge.
Provide current return paths
Protect personnel from shock hazard
Prevent accumulation of static charge

During de-fueling or refueling, the aircraft is grounded to the fuel truck.

In general, the aircraft are grounded to a point where the impedance is less than 10,000 ohms referenced to earth for static grounding. For power grounding, it should be less than 10 ohms to power systems neutral.

Aircraft are not grounded to the hangar structure as the external power supply, when connected, is grounded to that.

The best reference, if you ask me, would MIL- HDBK-274(AS)- Electrical Grounding for Aircraft Safety.


What is the relation of AIR BLEED IN message with the pack system on an Airbus A320?

On A320, if the BLEED P/B are still pushed ON, it will not be a reason from the FWC to get a an error message on the ECAM in phase 1, 2 or 10 (Elec power, 1st Eng Start and 2nd eng shutdown) But you definitely will have the FAULT in amber on the P/B itself until there is bleed from APU or Engine coming up.


Could a kerosene fueled jet engine run on methanol without significant modifications?

You couldn't have any aluminum components in the fuel system because methanol dissolves aluminum (F1 race cars remove and purge their fuel systems right after racing).  Ethanol would be much better in that regard.

It would take changes to the fuel controller to change the air/fuel ratios used with less energy density.

Other than that, I don't think it would be a big problem.  I've been told that the Honeywell/Lycoming turboshaft in the M1 Abrams tank will run just about on any liquid hydrocarbon.. gasoline, kerosene, diesel, booze, rubbing alcohol...


According to the keel effect page on Wikipedia it is the rolling moment created by the fuselage and vertical surfaces in a sideslip if the center of pressure is vertically offset from the center of gravity.

Functions of a keel

The keel of a ship (besides shifting the center of gravity below the metacenter) provides a stabilizing side force when the ship rolls. The same is achieved by a tail surface, but in aviation this is called roll damping. The much larger wing tends to dominate roll damping, so the effect of the vertical surface is small.

The next task of the keel is to balance the side force and rolling moment from the sails in crosswind conditions. It does this by letting the boat build up a sideslip condition until the side force from the keel and hull balances the side force from the sails, and the rolling moment from the side force and from heeling balances the rolling moment from the sails. The keel effect is this rolling moment due to a sideslip condition.

A few aircraft with very small wings and large vertical surfaces do indeed suffer from excessive moments created by side loads on those vertical surfaces. The best known of those is probably the Lockheed F-104 Starfighter. The massive tail on the upswept rear fuselage made 10° anhedral necessary to get the sideslip-induced rolling moment right.

Pendulum effect

The Wikipedia page also mentions the pendulum effect and calls both the fuselage contribution to the dihedral effect. Man, if there is ever a competition for the most misleading name of an effect, this would be the winning entry.

A pendulum is a mass mounted below the pivot or the metacenter, so it will stabilize in the down position. It seems the adherents of the pendulum effect belief believe that the plane is somehow hinged at the center of the wing. This is so wrong! A flying aircraft is not hinged, so all motion is around the center of gravity.

This is different with airships: As @JanHudec points out in the comments, the buoyancy of the lifting gas always works against gravity whereas the lift of a wing acts perpendicular to its span and the airspeed. This does produce a moment when the airship rolls, and the heavy gondola is pulled down by the same effect which pulls down a pendulum. Also, due to an airship's low density (by definition very close to the density of the air it displaces) the aerodynamic side forces on an airship are much larger compared to the inertial forces. This lets the airship effectively pivot around a point near the center of the envelope. Note that airships have no means of roll control - it is just gravity which ensures that the gondola stays on the lower side of the hull.

Now you can argue that the same is true for aircraft, only with much smaller aerodynamic forces. Yes, but those side forces are vanishingly small in comparison to the wing's aerodynamic forces which, again by definition, are close to the weight of the aircraft. A small change there will completely dominate the picture, and the small loads on the fuselage are just a rounding error. By moving the control surfaces, the pilot can shift the lift vector around almost as he/she likes, and the forces on the fuselage are insignificant.

Note that knife edge flight, a situation when the side force on the fuselage really is close to the aircraft's weight, needs lots of fuselage area and a powerful engine. Fuselage loads in normal flight are a fraction of those in knife edge flight.


What 's the difference between Angle of Attack and Pitch?

The reference of pitch is the horizontal. The reference of AoA is the direction of the relative wind.


What prep work can I do before transitioning from SEL to SES?

If you already have a pilot license for single-engine land airplanes you've done a huge amount of prep work already - you know all the airspace, navigation, airwork, etc. that you need to know for your seaplane rating.
Brush up on all of that in the seaplane as you can be tested on it and the aerodynamics will be a bit different with floats hanging out there, but you're already well ahead of the game.
You need to learn how to take off, land, and taxi/sail all over again on water (which is arguably the hard part) but the bulk of your existing knowledge will transfer over.

For studying and prep I imagine the FAA Seaplane Operations Handbook (FAA-H-8083-23) would be the best place to look - it's pretty comprehensive.
Also if you can commandeer a seaplane pilot for some hangar flying (or better a pilot and aircraft for a few real-world touch-and-gos & some practice sailing the plane on water) that would obviously be a great advantage, but coming to your first lesson familiar with the Seaplane Operations Handbook would probably put you well ahead of the curve anyway.


A pilot faces a medium-term loss of their medical. What can they expect?

It will first and foremost depend on the carrier you are working for and if they have anything in place for such a case. There are personal insurance policies out there to cover this exact case, like this one and this one. Some carriers may offer policies like this in house for their employees as well.

If available to you it might be possible to spend some time in the sim without a medical or (if you are allowed to) instruct and work with other pilots at the company for ground based instruction.


What is the difference between a ground controller and an air traffic controller?

Ground controller is a "position" (role) carried out by an air traffic controller.  The role of an air traffic controller who is working the ground position is to coordinate traffic moving on taxiways and to and from runways.  The ground controller is in charge of the taxiways.  An air traffic controller may be certified to work multiple positions.

You can think of a ground controller as a type of air traffic controller.

Positions (roles)

There are many air traffic controller roles which an air traffic controller may perform.  Other air traffic controller positions are:

Clearance delivery: A clearance delivery controller gives the pilots their clearances, which details their route.

Ground controller: A ground controller is responsible for traffic moving on the ground along the taxiways.

Tower controller.  A tower controller is responsible for traffic landing and taking off or in the air in the immediate vicinity of the airport.  The tower controller is in charge of the runways.

Departure controller.  A departure controller controls traffic which is leaving the airport.

Enroute or "center" controller.  An enroute controller handles traffic which is flying between airports.

Approach controller.  An approach controller controls traffic which is approaching to land at the airport.

Some air traffic controllers work just one position.  Others work multiple positions.  For example, at a small airport, the same controller may be the ground controller and tower controller.  Or an airport that is busy enough in the daytime to need separate controllers for ground and tower may be need only one controller for both roles at night when there is less traffic.

Example flight

Let's take for our example a pilot who is departing from a large airport, flying under instrument rules, and land at a small airport.

The pilot might first contact clearance delivery.  Clearance delivery will give the pilot her route, which she will write down.  The pilot will then radio ground and ask for permission to taxi.  The ground controller will give the pilot permission to taxi, including the specific route along the taxiways to use to get to the departure runway.  On reaching the runway, the ground controller instructs the pilot to contact the tower controller.  The tower controller will then clear the pilot to take off.  The pilot enters the runway and takes off.  The tower controller instructs the pilot to contact the departure controller.  The departure controller gives the pilot instructions to control the route and altitude during departure.  The departure controller then instructs the pilot to contact an enroute controller.  As the plane moves along, the enroute controller instructs the pilot to contact a different enroute controller.  That controller gives the pilot instructions to descend and approach the destination.  The enroute controller instructs the pilot to contact the tower.  The tower gives the pilot instructions to approach the runway and land.  Since this is a very small airport, the tower and ground positions are handled by the same controller, and on the same frequency, so after the plane touches down, the same controller gives the pilot instructions to taxi to her destination.

Every person the pilot talked to was an air traffic controller.  Each of these air traffic controllers was working different positions (roles).

See also: Air Traffic Controller (wikipedia)


Commercial aircraft minimum and maximum climb angle and rate?

You are asking several different questions, but I can answer the first part easily enough.

First, let's distinguish between climb rate and climb gradient:  climb rate is expressed as feet per minute, climb gradient is expressed in feet per nautical mile.

The autopilot I am familiar with can be programmed for a target climb or descent rate, heading and altitude.  With ground speed and some math a FPM rate could be set that will achieve a desired gradient, but I am not aware of any systems where this can be actually set.

737 takeoff and climb performance will vary greatly depending on weight and other variables.


Why does the DC-10's horizontal stabilizer have such a pronounced dihedral?

In a general sense, there are multiple reasons for the horizontal stabilizer to have dihedral/anhedral.

To clear the tail from the downwash/propwash. A good example is the Cessna 425, which was developed from the Cessna 421. The 421 had a straight horizontal stabilizer. However, with the addition of dihedral, the tail is kept out of the propwash, improving ride quality. From a report citing Cessna engineers:

  Cessna engineers say the dihedral improves Dutch roll qualities and moves a major portion of the tail out of the prop wash, thus providing a smoother ride.

The Dassault Falcon 50 had anhedral so as to clear the tail from the wing's downwash. Another good example of this is the F-4 Phantom. The prototypes had a straight tail. However, the anhedral tail was adopted so as to keep it clear of the disturbed air from the wing at high angles of attack while at the same time keeping it out of engine exhaust.

The anhedral in BAE Hawk is explained by the same reason. From The Hawk Story:

  This model gave the first indications of high speed problems due to interference between the high intake and the low wing, and the
  position of the tail.

  This resulted in the adoption of a low intake, ... .The rear fuselage was cambered downwards  to bring the tail down, and the tailplane was
  given pronounced anhedral for the same purpose.

Stability- The dihedral/anhedral in the stabilizers affects the aircraft's stability. In short, for a conventional tail, an anhedral improves the yaw stability of the aircraft while reducing the pitch stability (slightly), while a dihedral will reduce the tail's contribution to both pitch and yaw stability.

However, the use of dihedral in the horizontal tail influences static roll stability in the same way as that of dihedral in the wing. Dihedral affects the roll response in the same way as that of the wing- it causes the lift on the right and left semispans to respond differently to downwash.

A good example of this is the Vickers Viscount, which had a dihedral horizontal stabilizer, which improved its stability.

Due to this, it is better for the designer to add a dihedral to the horizontal tail rather than wing especially if problems are found in later stages of design as the impact will be lesser.

From Roskam's Aircraft Design Vol III, Chapter 5.1:

  The overall lateral stability is usually dominated by the inherent lateral stability designed into the wing. Wing sweep, dihedral angle and (wing) location on the fuselage dominate the magnitude and the sign of the stability derivative. Since the wing is designed by performance and operational considerations, the empennage is often used to fine tune the lateral stability of the aircraft. Examples include the F-4 and the AV-8B.

It should be noted that, as with any other design consideration, the dihedral of the horizontal stabilizer depends on the design choices made and perfomance characteristics required; as a result, the configuration required will change from aircraft to aircraft.

In case of DC-10, the main reason appears to be to keep the stabiliser out of the wing influence, especially when high flap settings are used. The more pronounced dihedral (compared to, say Boeing 737) appears to be used as the stabilizer is mounted lower due to the presence of engine in the tail.


Are CO2 cartridges not considered explosive?

I had a cartridge in my bag when going through airline security.

These are not uncommon. They are also used in for instance:

Life Vests
Ski Airbags
Soft air guns

In other words, it's not an unusual object, especially for holidays which I guess both your two mentioned destinations might be for many travellers. I've checked in my bag with an automatic self-inflating life vests a few times and while it went in the  hold never had any problems or found it removed. I believe there may be some limitations though on the number you can pass through, and they might start asking questions if you have more than two.

  I estimate roughly 15 airports (some duplicates) either didn't detect the cartridge or just ignored it.

It's not unjustified not checking them in. Onboard pressure changes, the cargo hold is cold and will shake during turbulence which just might trigger it to deploy if left screwed onto a life vest of similar.

  probably present more danger than other prohibited items, such as nail clippers

I can't see any real threat posed by these, except for the gun application, which of course requires a gun and not only a cartridge. Btw, TSA allows nail clippers.

Ryanair, the World’s favourite airline ;) states the following:

  Carriage of Self Inflating Lifejacket

  A self inflating lifejacket with 2 carbon dioxide cylinders (plus 2
  spares) can be included in either cabin or checked baggage.

In other words, they appear pretty liberal on the matter.


Is it possible to use reverse thrust while airborne?

Commercial jets are not designed to use reverse thrust in flight. With engines mounted under the wing, the turbulence can affect the lift over that section of wing. Tail mounted engines could interfere with the tail. This, in addition to the huge increase in drag, is what causes loss of control, as in the incidents that RedGrittyBrick mentions. Speed brakes are designed to provide the needed drag for emergency descents or otherwise slowing down faster. If the pilots find themselves too high/fast for an approach, and deploying spoilers/gear/flaps won't fix it, then they should go around for another approach.

The loss of control is more of a risk when a thrust reverser deploys only on one engine. Other risks are still there, since those thrust reversers are designed to deploy in landing conditions, not flight conditions. Notable exceptions listed on Wikipedia include the Hawker Siddeley Trident, though it also mentions that the capability was not often used.

Military aircraft, such as the C-17, can be different. They tend to make extremely steep descents more often (called a tactical descent/approach), so thrust reversers can be used in flight.

I did some testing with the stock 747-400 in X-Plane. Deploying the thrust reverser only changes the force applied by the engine, but doesn't seem to affect the air flow. So the loss of lift is not reflected by the model.


Is there a database of airport ceilometer raw data?

OGIMET looks like it goes back to 2005.

My favorite weather site Weather Underground has historical data.

It seems like you need to plug in dates one at a time but there are plenty of ways to skim a page and im sure you can ask them for a data dump if you know what you need.


How unusual is it for remotely piloted aircraft to fly through commercial or general aviation airspace?

In the US, the main operators of large UAS (i.e. non CFR Part 107 aircraft) are Air National Guard (MQ-9) and the Department of Homeland Security (Customs and Boarder Protection, also MQ-9). Here is a table from the Pentagon on how many missions UAS flew domestically in FY2018. (Note that these are "missions" and do not include other types of operations such as training or flight test, see below.)

A report from OIG published in 2014 lists a total of 5,102 flight hours by CBP in FY2013 (which is supposed to be closer to 26,000+, hence the OIGs investigation). Air National Guard also operates MQ-9 domestically for frequent training missions and contractors such as General Atomics Aeronautical Systems, Inc. and Northrop Grumman operate a fleet of capital aircraft at their respective training centers (e.g. Grand Forks). Lastly, of course, NASA also flies UAS. An example of how such missions are executed is described in this NASA report on the Western States Fire Missions starting on page 30.

So on your question about frequency: Assuming that the sum of all those aircraft result in ~5x number of flight hours, you'd be looking at something like 25,000 yearly flight hours in the US National Airspace System of large Remotely piloted aircraft. This is likely on the low side given the OIGs observation about the operational tempo of the CBP fleet.

So Why Is This Demonstration Relevant?

You may ask: if we're already operating these aircraft without chase planes, what was so special about this flight? It was the ability to fly a UAS without a chase plane without first having to climb to Class A airspace.

FAA Notice 8900.227 stipulates the requirements for how to obtain operational approval for an unmanned aircraft; specifically, it states:

  ... compliance with the see-and-avoid requirement [is a] primary concerns in UAS operational approvals leading to [...] the use of observers [to maintain] flight separation and collision avoidance or ‘segregation’;

In the case of a flight with a chase aircraft, that visual observer is onboard the chase aircraft. This is also where the "Visual Line of Sight Requirement" comes from - the observer/pilot must be able to see the aircraft during the operation.
There is one exception in N8900.227 for the visual observer (VO) requirement:

  VOs are not required in Class A airspace [...]

As a result, so far operations of the above-mentioned agencies occur almost exclusively in Class A airspace; i.e. above 18,000ft. Since those entities are either government agencies or contracting with a government agency, access to restricted airspace is straight forward where these aircraft can circle up or down to and from Class A airspace. In the case CBP and Global Hawk operations in Grand Forks there is a Temporary Flight Restriction that enables this access to Class A airspace without the need of a chase aircraft below 18,000ft.

This type of operation is incredibly inefficient though (imagine if manned aviation had to operate like that). As a result, and that is what makes this NASA flight unique, the ability to use an onboard system to detect and avoid other aircraft (i.e. a Detect and Avoid System) when operating in airspace other than Class A, in particular Class E below 10,000ft where "non-cooperative" aircraft operate removes a list of operational limitations. From N8900.227 again:

  b. Risk Mitigation. While considerable work is ongoing to develop a certifiable detect, sense, and avoid system as an AMOC with the see-and-avoid aspect of §§ 91.113 and 91.115, no current solution exists.

The "considerable work" mentioned refers to this NASA project - and the flight was the capstone demonstration to show equipment in fact can serve as an Alternate Means of Compliance (AMOC) when operating outside of Class A airspace.


Where to find comprehensive description of Special Use Airspaces (SUAs)?

The definition of Special Use Airspace according to Wikipedia are:

  Is an area designated for operations of a nature such that limitations may be imposed on aircraft not participating in those operations. Often these operations are of a military nature.

Types of SUA's

  restricted airspace, prohibited airspace, military operations areas (MOA) and temporary flight restriction.

Two relevant PDF documents:
https://www.faa.gov/documentLibrary/media/Order/7400.8SBasic.pdf

https://www.faasafety.gov/files/events/GL/GL05/2007/GL0515004/CH_3_Sec_4.pdf

Wikipedia link: https://en.wikipedia.org/wiki/Special_use_airspace


Amazon Atlas nose-down elevator deflection?

"Nose-down elevator deflection" is a long winded way to say the elevators moved in the direction that would push the aircraft into a dive.  It's phrased this way because it isn't always clear from flight data recorders whether this was a commanded (pilot input) movement, or uncommanded.

In either case, the elevators were deflected downward, which pushes the tail up and the nose down, and over a fairly long time (in terms of a crash in progress) the aircraft was nosed down by 49 degrees.


How is fuel stored and routed on a trijet with one engine at the tail?

(Own work based on MSFS)
On an MD-11 the tail mounted engine is fed from tank 2, which is two halves as shown above -- the two halves are connected via vent lines.
Sequence
The center tank on an MD-11 is called aux, and it feeds all the engines until it's empty -- the aux tank actually fills the other tanks and the other tanks do the feeding (systems display shown below). Tank 2 (being bigger than 1 or 3) then carries on filling tanks 1 and 3 plus feeding all the engines. Once tanks 1, 2, and 3 have the same fuel quantity, each tank then feeds the respective engine.

(Own work based on MSFS)
Stabilizer tank
Fuel is transferred to and from the stabilizer (tail tank) to manage the CG. It is fully consumed by the time the plane reaches its top of descent -- as a forward CG is more economical for descending. The exact sequence is managed by the fuel system controller. The tail tank also feeds the tail engine as part of the CG automation.
The sequence (and scheduling) is automated even with an engine, or even two, out.
Summary
The #2 engine is fed by the aux, tail, and #2 tanks. If an engine fails, then cross-feeding is involved.


Backup airspeed indicators (lack thereof)

In order to answer your question first we need to figure out what we're trying to accomplish with airspeed. For the most part the goal is "envelope protection" - keeping the pilots from either stalling the aircraft or overspeeding (and overstressing) it.

So the first thing to know is thaton modern transport category aircraft there are already backup systems to compensate for a failed airspeed indicator.

For starters there are usually at TWO (visible) airspeed indicators (one for each flight control station - pilot & co-pilot). The airspeed indicators are usually using two different pitot (ram air pressure) sources, so that if one pitot system or indicator fails the aircraft can still be flown on the others.
In addition to those two indicators there is often a third "tie-breaker" system on modern aircraft which is used to determine which system has failed (if two systems agree the third is declared insane and ignored).

In the unlikely event that all of the pitot-based airspeed indicators fail they aren't the only system providing envelope protection: Angle-of-Attack vanes are used to determine when the wing is approaching the critical angle of attack (and is in danger of stalling). These operate independently of the pitot system as a redundant form of stall protection, and as with the pitot system aircraft usually have more than one AoA vane installed.

Both the pitot-based airspeed indicators and the AoA vanes are critical systems, and are heated (to prevent ice from accumulating and interfering with their proper operation) and monitored (by onboard computers and/or the pilots).

Finally in the face of a failure of all of those systems there is the ultimate fallback method that others have described: Pitch + Power = Performance.
A pilot should be able to at the very least maintain level flight, descend, climb, and make standard-rate turns within a safe flight envelope by reference to engine power and aircraft attitude.
While that's far from an ideal situation it is one pilots are trained for.


Can glide ratio be increased with bi-wing configuration?

Glide ratio is determined by L/D. If we can increase lift without increasing drag, or decrease drag without decreasing lift, we have a better glide ratio.

Increasing the wing span (for a given wing area => reduce the chord) helps: the longer wing span spreads out the lift creation over a longer distance, thereby decreasing induced drag. Keeping the flow laminar for as long as possible also helps.

Your question is about adding a second wing to an airplane. The problem with biplanes is that they were mainly constructed decades ago, and we associate them with older construction methods and mainly lots of drag, such as addressed in this question. It seems that the classical biplane has no aerodynamic advantages, and always has a lower L/D ratio than a comparable mono wing.

However there are now Computed Fluid Dynamics. There has been work done on biplane configuration with low drag in recent years - many are behind a pay wall, this one is not. Their work found two configurations with high L/D ratios:

Upper wing AoA = 13º
Upper wing forward sweep = 30º
Lower wing AoA = -2.8º
Lower wing backward sweep = 3.5º
Wing profile of both wings = NACA 4412
Both wings 6 ft span and 6 inch chord
Computed L/D = 32.3

The other configuration they found with a high L/D was a canard configuration: one wing in front of the other. If you insist on using two wings, this may be your best bet: one wing mounted in front of the other, in such a way that the back wing is out of the way of the wake of the front wing, or mounted at the optimum AoA for the disturbed flow. Their canard configuration used two different wings, resulting in an L/D of 35.8:

Note that none of the configurations included a fuselage of any kind, so their CFD work would have to be repeated with the fuselage and with interference computations. Fortunately computing power has increased dramatically in recent years.


How to calculate the amount of weight my plane can takeoff with?

Yes, you can do your equations at OEM (Operating Empty Mass) and get your ground distance. Then you can calculate the same for different mass values (your OEM+your payload), and generate a distance vs mass. Since you know how much distance you have (including any safety factors), you can see what mass you can take off with. Or work backwards from the same equation, set the maximum distance you allow, and work back to your mass value.

Keep in mind this will not tell you whether the airplane is structurally strong enough to carry that weight, only if it can take-off with it. Structural calculations are a bit more complex than this. Also, you might want to do similar calcs for landing distane as well!


Can thrust reversers alone steer and stop an airliner?

Steer: No. Stop: Yes.

Thrust reversers are either in or out. They cannot be engaged proportionally to some control setting in the cockpit. Once they are unlocked, the airflow through them sucks them out completely. The only way to vary their braking effect would be to throttle the engine up or down, and airliner engines react rather sluggishly to control inputs. Their responsiveness will not suffice to steer the aircraft; only rudder inputs (and those only at higher speed), nose wheel steering and differential braking with the wheel brakes are suitable for directional control on the ground.

Their braking effect is biggest at high speed and tapers off as the aircraft decelerates. For the first third of the landing run they will help noticeably in slowing the aircraft, but you will need a long runway when you want to land without wheel brakes. Details depend on landing weight, airfield elevation and wind speed.


Is there an Instrument Flight Procedures database in digital format such as ARINC 424 for Germany?

Eurocontrol does offer the whole thing as well – albeit not for free as the FAA does. Check out https://www.eurocontrol.int/service/european-ais-database for more information.


What is a counseling session with the FSDO/FAA?

A "Counseling Session" is the lightest slap on the wrist the FAA can give you (aside from doing nothing).

Basically it means "you screwed up, you know you screwed up, and we (the FAA) know you know you screwed up" -- they just want to sit you down with someone from the FSDO (probably a FAA Safety Team representative) and have a conversation to make sure everyone is clear on what happened, how the violation happened and that you know how you can avoid this sort of thing happening in the future.

My understanding is that counseling sessions are "informal" (they're not an official "administrative action", so I'm pretty sure they don't go on your airman record) - the FSDO will note that they talked to you and bury that tidbit in their internal file, to be generally forgotten unless you decide to make a habit of busting airspace.

(The closest "official documentation" I can find on counseling sessions is in the FAA Safety Team's Representative Manual -- Page 12 if you're interested.)

Some things to bear in mind:

You're the kind of pilot the FAA isn't out to beat up on.
Yes, you screwed up - but you know that and you clearly want to make sure you don't do it again, which is really all they want too.
Make sure you're clear in your mind what happened & how to avoid similar incidents in the future.
Did you misread the chart? The altimeter? Get distracted looking up the frequency? Something else?
Don't admit to any other violations during the counseling session.
(Presumably you didn't commit any, you got a proper flight briefing, etc.)
Hang on to your ASRS strip.
You won't need it for a counseling session, though mentioning you've filed an ASRS report won't hurt anything. If the FAA opts for a more formal action that strip is going to be important.
If you have AOPA pilot protection services now would be a good time to chat with them too, just to cover all your bases.


What ground-based, airline job in the 1940s could have involved radio communications?

Perhaps she was a flight dispatcher?

A flight dispatcher (also known as an aircraft dispatcher, airline
dispatcher, flight follower or flight operations officer) assists in
planning flight paths, taking into account aircraft performance and
loading, enroute winds, thunderstorm and turbulence forecasts,
airspace restrictions, and airport conditions. Dispatchers also
provide a flight following service and advise pilots if conditions
change. They usually work in the operations center of the airline.

-Wikipedia


How does pulling back provide better steering during rollout for light GA planes?

Pulling back on the yoke does not improve nosewheel steering.  If there is enough elevator effectiveness to hold the nose off then there will be plenty of rudder authority for directional control.

Not all airplanes are the same of course, but the Cessna 172 you specifically mentioned has a tendency for the nosewheel to shimmy at high speeds.  Holding the nose off as long as possible reduces the annoying vibration and stress on the nose strut.  It also prevents the pilot from over controlling.

As the elevator looses effectiveness so too does the rudder, and once the nose falls through direction control is maintained through nosewheel steering.  Ideally this transition is smooth and virtually transparent to the pilot since rudder pedals are used for both.


Are you required to record flight hours of serialized parts?

Short answer: only for the airframe, engines, propellors and rotors (as applicable).

This legal interpretation is a response to someone who asked which records are required to identify when life-limited parts need to be replaced. It says that you're only required to keep flight time records of the airframe, engine(s), propellor(s) and rotor(s), as appropriate:

  Existing regulations, specifically 14 C.F.R. § 91.417(a)(2)(i), require
  each owner or operator to keep records containing the total time in
  service of the airframe, each engine, each propeller, and each rotor.
  This is accomplished by the owner or operator recording and tracking
  in some form and manner the time in service of the airframe,
  engines(s), propeller(s), and rotor(s) from the moment the aircraft
  leaves the surface of the earth until it touches it at the next point
  of landing, as referenced in 14 C.F.R. § 1.1. In addition, §
  91.417(a)(2)(ii), and similar provisions in 14 C.F.R. §§ 121.380(a)(2)(iii) and 135.439(a)(2)(ii), require owners or operators (certificate holders) to keep records that show the current status of
  life-limited parts of each airframe, engine, propeller, rotor, and
  appliance.

91.417 does indeed say - among other things - that owners and operators have to record the time in service and status for the airframe, engines, props and rotors, but only the status for life-limited "appliances":

  (2) Records containing the following information:

  (i) The total time in service of the airframe, each engine, each
  propeller, and each rotor.

  (ii) The current status of life-limited parts of each airframe,
  engine, propeller, rotor, and appliance.

1.1. defines "time in service":

  Time in service, with respect to maintenance time records, means the
  time from the moment an aircraft leaves the surface of the earth until
  it touches it at the next point of landing.

And 43.10 defines "life-limited parts":

  Life-limited part means any part for which a mandatory replacement
  limit is specified in the type design, the Instructions for Continued
  Airworthiness, or the maintenance manual.

To summarize:

You only need to record service time for the airframe, engine, props and rotors
For any other life-limited parts, you only need to record their status, i.e. you need to be able to say when it's time to replace them


How does ATC handle tv coverage of police pursuits in the US?

I know about the operations of police in South Pacific Area so I will answer from that point of view not the USA as is queried.

The Air Traffic Controllers have an agreement set up between the various Police Forces and themselves. This agreement allows them to operate in a covert capacity if required. When they do this special phrases and/or special call signs are used to give them higher priority.

When something like a chase or surveillance is being carried out the police helicopters are usually operating below the control steps. If not they will talking with ATC to obtain a clearance for either to operate in an area or for particular headings. I have seen clearances be issued that say Stay North of Road X Operate Below 1500 AGL.

If Police operations bring them near an airport, the Terminal Area Controllers or Tower Controllers will separate them from the other traffic. In fact this is very safe operations.

As to do with TV helicopters they have to follow the same rules as all the other helicopters. If in controlled airspace obtain a clearance and if not operate VFR under the VFR Rules. The TV choppers would be told to get lost if they were interfering with Police choppers (Yes I have heard it happen).


On old sectional charts, what was the purpose of the domestic ADIZ regions and what was the difference between a "Defense Area" and an "Open Area"?

Originally they were zones to protect Americas nuclear testing areas and other key military interests. The Albuquerque area was likely there to protect Los Alamos Laboratory and other related nuclear assets of the era.
This report prepared for congress (on a slightly different topic) has some notes on this in the "History" section.
They explain an ADIZ as:

An ADIZ is a designated area of airspace over land or water within
which a country requires the immediate and positive identification,
location, and air traffic control of aircraft in the interest of the
country’s national security.

Which does not necessarily limit it to border monitoring. The modern ADIZ is large a border related zone but that was not always the case.

In 1948, the U.S. Air Force designated several offshore areas as
“active defense areas” or “defense zones.”3  From these, the first
ADIZs in the world were established in 1950, under an Executive Order
directing the Secretary of Commerce to exercise security control over
aircraft.4 Various defense zones were redesignated as ADIZs.5  The
present-day U.S. ADIZs, including the contiguous U.S. ADIZ, the
Alaska ADIZ, the Guam ADIZ, and the Hawaii ADIZ, are codified in Title
14, Part 99, of the Code of Federal Regulations, along with the
procedural requirements for flights operating in these designated
areas. They are predominantly located over water and typically do not
extend to the shore, leaving a narrow strip of sovereign airspace
parallel to the coastline that is not within the ADIZ.

The citation for the above paragraph explains it better (bolded for emphisis)

At the time, U.S. ADIZs included offshore regions stretching from
Maine to North Carolina in the Atlantic, and from the U.S.-Canada
border to waters off the Baja California in the Pacific. Additionally,
several over-land areas were designated as ADIZs, mostly along the
west coast and south of the U.S.-Canada border, but also above
interior lands around Albuquerque, NM, and Knoxville, TN, as part of
national security efforts to protect key nuclear research facilities
in these regions. The over-land ADIZs no longer exist. For a time,
portions of the special flight rules area (SFRA) around Washington,
DC, established after the 9/11 attacks in 2001, were designated as an
ADIZ, but this airspace is no longer referred to as such.

This map just pre dates the deployment of the Distant Early Warning System in the north and various Nike Missile Sites that were put on either coast but you can see how the American costal strategy was shaping up in a post WWII country which is interesting.
As radar became more prevalent at local facilities (think class B/C/D approach control as well as regional centers) the need for specialized interior radar was far less and those duties could be off loaded to the local facilities


Could improper deplaning of a flight with full fuel tanks cause the plane to tip?

The 737-900ER has (two) auxiliary fuel tanks in the aft cargo compartment, behind the wing (and center of gravity) with ~3400l capacity for increasing range (from 2800nm to 3,200nm).

In usual conditions, unloading of passengers wouldn't be a problem as the fuel would've been used up; However, as this was an overweight landing with full fuel tanks (the auxiliary fuel tanks weigh ~ 3t), the crew are just being cautious to prevent any incidents.


How did the De Havilland Mosquito compete with contemporary jets?

The Mosquito was a great aircraft but it was not faster than Germany's Messerschmitt ME-109 and Focke-Wulf Fw 190 piston powered fighter aircraft.

It also did not successfully compete with the jet powered Messerschmitt Me 262. The limited numbers of ME-262 were probably the only reason the Mosquito could survive in the same airspace.

On 26 July 1944 the first aircraft to be shot down by a ME-262 was in fact a Mosquito: Mosquito Operational History

"a 262 A-1a, caught and severely damaged the Mosquito in a pursuit. The Mosquito, which managed to escape into cloud, later crashed at its destination airfield in Italy, and the airframe was written off"


In a flight plan, does it make any difference to write an increase of the flight level instead of writing a cruise climb?

They are different things. A cruise climb allows you to continually climb at your own rate to achieve maximum efficiency. This is what Concorde used to do. However this requires ATC to "give you" all of the levels from the bottom to the top of the climb, which is impractical with the volume of traffic.

Instead, we use set levels. We can "step climb" to another level when we become light enough to do it, and this way ATC only has to block off one level at a time for us.


Can climbing above RVSM airspace cause temporary loss of separation with an aircraft in RVSM airspace?

I think the way rules regarding RVSM are worded in ICAO documents leaves some room for interpretation. When RVSM was implemented, it was probably not very common for aircraft to be able to climb above FL400, so this specific problem was probably not considered when writing the rules. But I would say, when in doubt, use the more conservative interpretaion, which would be that: Yes, this would be a loss of separation.
It sounds weird that increasing the distance between two aircraft can cause a loss of separation, but RVSM airspace is not actually the only place where this can happen. I can think of a few other examples:

Two aircraft flying on parallel tracks with exactly 3 NM between. They are flying parallel to an airspace border. On one side of the border, the required separation is 3 NM, on the other side, the required separation is 5 NM (this is quite a common setup, actually). Imagine one of them is flying almost directly on the airspace border. If this aircraft now turns slightly away from the other one, increasing the distance between the two, it crosses the border into the airspace where 5 NM of separation is required. That's a loss of separation.

Losing lateral separation when no other separation exist. For example, imagine a visual reporting point 1.5 NM from the runway. In the local rules, it is defined that VFR traffic orbiting overhead this reporting point are separated from aircraft taking off and landing. When an aircraft takes off whild a VFR flight is orbiting over this point, that's all well and good. By definition, they are separation. But if the VFR flight now leaves the reporting point, separation may be lost - even if the VFR flight takes a heading directly away from the other aircraft, so the physical distance is increasing. As the VFR flight leveas the reporting point, the rule about lateral separation no longer applies, so if the flights are closer than the prescribed radar minima, that's a loss of separation.

Two aircraft taking off after each other. Initially, the tower controller can visually see both aircraft and ensure separation. When the controller can see both aircraft, normal minima do not apply - it is up to the controller to visually make sure there is no risk of collision. Now imagine the first aircraft climbs into a cloud, so the controller can no longer see it. Even if the higher aircraft is climbing faster than the lower one, so physical separation is increasing, if the required vertical separation does not exist when the controller loses visual contact with the first aircraft, that's a loss of separation.

Two aircraft flying on opposite, parallel tracks. The required radar separation is 3 NM for aircraft flying less than 250 knots, and 5 NM for aircraft flying faster than that. Both flying at 250 knots, they pass each other with exactly 3 NM in between, and are now flying away from each other. One aircraft now accelerates to 251 knots, while there is still less than 5 NM between them. Although they are rapidly moving away from each other, that would be a loss of separation.

These are all real examples that, although they shouldn't happen, could result in a loss of separation between two aircraft that were initially separated, while distance between them actually increases. I think the key point here is the fact that in each example, the rules regarding separation minima change, which is what causes the loss. A rule that allowed the aircraft to be relatively close together, for one reason or another, no longer applies, and so we have to fall back to another rule, which may require larger minima.
While this may not specifically answer your question regarding RVSM, I think the exact same logic can be applied. In your example, initially, one rule applies: RVSM, which allows 1000 ft vertical separation. As aircraft B leaves RVSM airspace, the RVSM rule no longer applies, so we have to fall back to the general rules for vertical separation, which says we need 2000 ft. Thus, your example would indeed be a loss of separation.


Is anti-icing a small area of the windscreen (hot-plates) adequate for the full flight or only an interim solution?

Those hot plates, in my experience, are useless.  The only reason we had one on our PA34 cargo plane was to make it legal for flight into known icing.  As far as I'm concerned, the whole and entire point of those external hot plates is to check a regulatory box to make the plane legal for FIKI if so certified.

It never once actually kept ice from accumulating and the entire windshield, hot plate included, frosted over on more than one occasion.  I recall hoping for strong right crosswinds so I could crab down to the runway using the side window.  We checked that the circuit was powered so we knew the plate had power, it was just totally ineffective.  Cutting a new pilot loose in that thing for their first low IFR icing encounter was a serious decision.

Now, proper heated windshields with integrated elements work wonders on ice.  They also cost $25k per side (twin Cessnas), so they'd better work.  The plates bonded to the windshields (on Barons, for example) seem to work OK too though I've never used one.  I think the cold air flowing over and under the stand-off hot plates simply overcomes the capabilities of the unit except in the most mild conditions.


Circulation does not mean that any fluid particular is traveling in a circuit around the airfoil. One way to look at circulation is that it's a description of how much a uniform flow has been turned asymmetrically by the body.

Another, slightly more technical way, is to consider the flow around a rotating cylinder (which produces lift) as a combinatory sum of a uniform flow (free-stream flow), a doublet flow (non-lifting) and a vortex flow (which produces circulation). See this illustration excerpt from Anderson, Fundamentals of Aerodynamics.

Therefore, circulation can be regarded as the path of the fluid when the symmetrical components have been taken out, which is indeed circuitous.


How did ICAO SARPS come to include the 250 knots speed limit for aircraft below 10,000 feet?

The tricky part is that a de facto rule is unlike a de jure rule, it's hard to pinpoint its origin as it is not based in law. The more I dig, the more it seems it is indeed a de facto rule that found its way to Annex 11.

It would take a team of aviation historians hunting through countless meeting points to get to the bottom of it.

However, I gathered some clues, mostly in reverse chronological order:

For the 250 knots during climb I found:

ICAO's REVIEW OF NOISE ABATEMENT PROCEDURE RESEARCH & DEVELOPMENT AND IMPLEMENTATION RESULTS

  Target climb speeds are given as V2 plus, no attempt was made to specify the actual target speed as it is accepted that the segment is flown to the manufacturer’s specified safety speed.

It just so happens 250 is a numerical rounding that matches most aircraft, except for heavies loaded up for long-haul flights.

Numerous parties were involved:

  ... various parties, including universities, regulatory agencies, manufacturers, air carriers and airports.

So everyone came together, and agreed to 250 knots. But that's recent and has to do with noise.

ICAO Journal TOWARDS A PERFORMANCE-BASED NAVIGATION SOLUTION

  Pilots should also avoid airspeeds of more than 250 knots below 10,000 feet above ground level (AGL), especially at times of the year when birds are migrating. Aircraft speed is more critical than bird size (body mass) in causing collision damage.

Someone should tell the geese to stop flying at FL400. (Related post.)

Activities of the European Office from 1954 to 1958 (link)

They discussed the advent of the jet age, and how the prop aircraft speeds of 250 knots are being exceeded leading to research into the consequences.

At that time, namely what affected the ATC and navigation systems because jet planes were relatively crossing sectors much faster.

It's not much but this section hints at the origin of 250 knots:

  ... significant increase in cruising speed of the jet-aircraft over the propeller-driven airline [...] around 400 knots = 750 km/h versus 250 knots = 450 km/h ...

REPORT OF THE EIGHTEENTH MEETING OF THE APANPIRG ATM/AIS/SAR SUB-GROUP

  Appendix 4 to Annex 11 speed limitations of 250 kt below 10 000 ft AMSL are required for certain airspace classes.

Annex 11 history:

  In October 1945, The Rules of the Air and Air Traffic Control (RAC) Division at its first session made recommendations for Standards, Practices and Procedures for Air Traffic Control. These were reviewed by the then Air Navigation Committee and approved by the Council on 25 February 1946. They were published as Recommendations for Standards, Practices and Procedures—Air Traffic Control in the second part of Doc 2010, published in February 1946.

Chapter 2

  2.6.3 The requirements for flights within each class of airspace shall be as shown in the table in Appendix 4.

Appendix 4 lists the now de facto limit.

It doesn't say why, so it's most likely it's what everyone agreed on at that convention and consequent meetings.

8 December 1959 is likely the date when an amendment was added to Annex 11 that detailed those figures in Appendix 4 we now know.

That's 8 years before the FAA. Check this post for the FAA's side of the story if interested.

Without access to meeting points, that's the most I could find.

Short version of the above:

At numerous conventions and meetings beginning in the 50's, many parties met again and again to discuss the jet-to-prop traffic separation, the noise impact of jet planes, and the dangers of bird strikes. They concluded V2 plus speeds should be used, but since civilian jet aircraft have the same performance more or less, the 250/10,000 rule found its way to the requirements of airspaces.

It's not hard evidence, but given what I found, it's not far fetched to assume the above is correct. Over to you.