Did turbofan engine explosions become more frequent in last years in commercial aviation? There are many incidents with turbofan engine failures during last years. I can list:

2010-11-04 - Qantas_Flight_32
2015-09-08 - British Airways Flight 2276
2016-05-27 - Korean Air Flight 2708
2016-06-27 - Singapore Airlines Flight 368
2016-10-28 - American Airlines Flight 383
2017-09-30 - Air France 66
2018-04-17 - Southwest Airlines Flight 1380

This list is not exhaustive.

Question: did turbofan incidents indeed become more frequent in recent years?

If yes, is there a reason of this suggested?

May depend on the time period of interest and what you count as an incident, but in general over the time span of decades, turbo fan engines are significantly more reliable now than they were previously. You only have to count the engines to see this trend. Many years ago all jets had 4 engines, then 3, and now virtually all new planes have only 2. The reason of this is the increasing reliability of engines. Decades ago planes had 4 engines because the possibility of 2 engines failing during a single flight, while uncommon, was not unheard of. Now days, planes have only 2 engines because reliability of engines is very good. Failure of 2 engines during the same flight is very very rare (maybe not zero, but very rare)


What is a good plane for aerial photography? I'm a bit of a photographer and I keep thinking it would be fun to try and do some shots aloft.  Only trick is, I'm not sure what kind of plane I would want to use to get those pictures done.  I'd have to rent the plane and the pilot and I'd like to keep the price down as best as possible...  So a purpose built plane isn't such a big deal.

Other considerations

Good view of the ground, though it doesn't have to be straight down (I'm not doing surveying
Stable while banking so I can more easily track shots when the plane is at an angle.
Ability to be held stably at a bank without actually turning the craft, again to help me track my shots.
Low vibration, for the same reason as stated over the last two.
Big windows
Can fly low and slow for if I want to get close to things (within reason.)

Also, a high wing is probably preferred.  Though, if it's exceptionally good at holding a bank, it may not matter.

If you think of anything else that I should consider to keep my camera from being jangled about, and to allow me to have a good view so I can get some shots...  Please feel free to leave them in the comments.

So, what plane would work best for this mission?

I used to work at a sport parachuting center - we occasionally had photographers rent one of our Cessna 182 airplanes for the same purpose. An advantage of jump planes is the pilots are quite used to odd attitudes (and even odder requests) so a 60 degree bank angle with the door open and you leaning out of it will get a reply of "no problem".

Our conditions were the photographer wears a parachute, a seatbelt, and if the camera goes for a jump that's just too bad for your wallet. 30 minute lecture on what to do if you fall out. Short form: drop camera, grab this handle, pull. And the trip's over if you do anything silly.

You would sit on the floor where the co-pilot's seat would normally be, the pilot will open the door as needed, and you have a clear view out the right rear quarter of the plane. Obstacles are the wheel (front half of the door looking down) and wing strut (forward) - the tail is well out of the way. It's very noisy, but unless your camera is actually outside the fuselage the wind blast is not an issue. Don't change lenses though, and your clip-on lens hood will probably disappear rather quickly.

You can sit on the door ledge with your feet outside and have an excellent, stable field of view with both hands free to operate your camera. I've sat there hundreds of times without a seatbelt, it's no problem even in steep turns. Just a bit odd seeing the ground above the wingtip. Difference is, I don't care if I fall out.


Can the A380 ferry an extra engine, like the 747? A useful little quirk about the 747 is that it can ferry a fifth engine on the wing, for when another aircraft is stranded somewhere in the world.

Does the A380 have the same capability? If not, how would an airline manage an aircraft needing a new engine whilst away from a maintenance base?

One of the main reasons the 747 was given the ability to ferry an engine was due to the lack of large cargo aircraft available at the time.

Don't forget the 747 was a major game changer when it came out, it was designed to replace the 707/DC-8, and was almost twice the size of these aircraft. As a result, there just wasn't anything available to transport a 747 engine by air if needed.

This was a major problem that had the potential to affect sales of the aircraft, and so they had to find a solution to this. It wasn't until the 747 began to be introduced as a cargo carrier that it was possible to transport these engines by air, in the hold of an aircraft.

With the introduction of the A380, there was no need to add engine ferry capabilities, as large cargo aircraft were common enough to transport them.


How did the Boeing 777X's main landing gear lift before the nose on its first takeoff? Source: Boeing 777X Takeoff for its First Flight

Is this from a low payload and the configuration of flaps? Or perhaps a pilot pushing the yoke forward while the plane wants to lift?

Correct on both guesses to some extent I would say.  The airplane is pretty light, and with flaps down the flapped area of the wing is operating at a positive AOA (remember that the chord line is from the LE of the slat to the TE of the flap, so with flap down there is positive AOA even while 3 point).

Also as it's an initial test flight I wouldn't be surprised if the pilot delayed rotation past normal Vr 5 or 10 kts just to have some extra energy margin if something went amiss, so not necessarily holding the nose down, but delaying pulling it up.

Added together, maybe helped by a bit of crosswind coming from that side, you get the truck starting to come off before rotation.


What is a Polar airplane? I stumbled on a new chinese one here: The "Snow Eagle 601".

Can someone expand a little?

At first sight, I can't make any relevant difference from a regular one (It just looks like a stock DC3 fitted with new turboprop engines + snow skis for the purpose).

Anything to do with the plane's performance required by the toughness of elements in the poles?

The aircraft is a Basler BT-67, which is a retractable wheeled ski equipped undercarriage STOL aircraft. It is a remanufactured DC-3 with Pratt & Whitney Canada PT6A-67R turboprop engine. The modifications include lengthened fuselage, increased MTOW, new avionics, redesigned wingtips etc. The skis are added in Canada.

Reports indicate that the aircraft includes an ice radar system, airborne gravimeter, airborne magnetometer and onboard laser radar system.

It is called a 'polar' airplane because it is owned by the Chinese Arctic and Antarctic_Administration. The aircraft is used by quite a few other missions in Antarctica, like Australia and the US, all operated by the Kenn Borek Air.


When is a procedure turn not required? If you are not being radar vectored to the FAF or on a “no PT” transition, are there any other circumstances where a procedure turn that is depicted on an approach chart is not required?

First, I don't believe you need to be vectored to the FAF, just the final approach course, in order to forego a published procedure turn.

Also, you could be cleared "straight-in" when ATC gives you the clearance for the approach.  It may seem subtle, but it makes a difference. Here is the definition in the pilot-controller glossary:

  "STRAIGHT-IN APPROACH IFR. An instrument approach wherein final approach is begun without first having executed a procedure turn, not necessarily completed with a straight-in landing or made to straight-in landing minimums."

Also, don't take it literally.  If you approach at a 45 degree angle to the final approach course and are cleared "straight-in", you still approach at a 45 degree angle; there's just no procedure turn.

Using the below approach as an example here the difference would be, "Cleared 0M3 RNAV RWY 2" (Must do the PT) vs. "Cleared straight-in 0M3 RNAV RWY 2" (Shall not do the PT).

Another indicator I know of is notation on the MSA ring that declares a range of radials of approach as "No PT" such as this one.  Note that the MSA and radius on both halves is the same, so the only reason it is split is to declare no PT on the southwest approaching side.


Can this vane prevent/delay wing stall? Given that a stall results from the airflow over the top of the wing separating from the wing at high angles of attack, would it be possible to prevent, or at least ameliorate, a stall by deflecting the airflow downwards into the "dead zone" behind the wing using a curved/angled vane located just above the leading edge of the wing?

A rough illustration of what I'm thinking about:

This is a very good idea and has already been done. It is called a slat and is positioned ahead of the wing where it will do a better job of turning the airflow and not causing the slat to stall, as shown on your diagram. Slats allow a 10-12 degree higher angle of attack before the wing stalls. Fixed versions in this more forward position have lower drag in cruise.

source

The reason a more forward placement is superior can be seen in the streamlines of the airfoil at high AoA. The inlet gap between the slat and wing is located right at the airstream stagnation point. This is where air pressure is greatest, enhancing the operation of the slat.

source


Has there ever been a seaplane with retractable pontoons? I would like to know if there's ever been a seaplane in which all of its pontoons or sponsoons are retractable after takeoff.

This could be a seaplane with 1 or 2 main pontoons that somehow retract. Or more likely, this could be a flying boat (bouyant hull) whose under-wing pontoons retract into the wing. I will also count a flying boat with only sponsoons that can retract somehow.

There have been a couple of examples- the Blackburn B-20, for example, had a retractable pontoon below the hull (and retractable wing floats), though it was an one-off experimental aircraft with a single flight to its credit.

Blackburn B20, image from dinger.byethost5.com

As a more widespread example, the Consolidated PBY Catalina's wing floats were retracted electrically after takeoff.

Catalina's retractable wing float; image from navy.memorieshop.com

Retractable floats have been used in other aircraft too- like the Grumman G21A Goose and the SL-12C amphibian. Some designs like the Kawanishi E15K featured retractable floats, which were later removed due to issues.

A little more digging reveals that the German Ursinus Gotha WD 10 Fighter Seaplane had retractable floats quite early- during WWI!. However, I doubt it counts as the aircraft never went past taxiing stage.

Ursinus WD 10 fighter seaplane, image from 1000aircraftphotos.com


Why is London City getting a virtual tower? (Source)

London City is not a remote-low-traffic airport. Staffing a remote airport is like having lighthouse keepers. That I understand.

And yet the tower will be closed, and moved off-airport to become a virtual tower.

All those working on the project are very happy apparently, and the press releases (and videos) don't reveal much. I don't get it. The only thing that I saw as a positive, was an augmented reality overlay on the screens that highlights nearby drones.

  (...) a critical new safety feature means the cameras will be able to pick out rogue drones near the airport, as well as light the runway at night.

Why would a major airport undergo such change? What problems are being solved?

London City is severely space-constrained, being on an island in the Thames. Moving the tower means more space for functions that cannot be moved.

  ... will also include an extended terminal building, enabling it to serve two million more passengers a year by 2025.

A high tower means substantial foundations, so you can't just stick the tower on top of another building. You have to build around it.


If a passenger steps in for the crew, are they eligible for a reward as in maritime law? Purely hypothetical question on aviation law.

In maritime salvage if your craft rescues/tows/supplies crew to a stricken vessel then you can claim a reward based on the value of the craft and cargo.

Let's assume that you are flying off somewhere warm for a few weeks in a commercial airliner and hear the call "Is there a pilot on board"... and let's all be honest every pilot has fantasised about it.

If you manage to take control of the aircraft and land it safely, does salvage law apply similar to maritime salvage laws? I cannot find anything online that covers it but it must have happened at some point in history.

The short answer is no but it really depends on what kind of "pilot" is on board.

  "Is there a pilot on board"

If the pilot in question is a Private Pilot as per FAA licensing (although its often similar elsewhere in the world). They would be legally prevented from receiving compensation for flight time as per the FAR's.

  § 61.113 Private pilot privileges and limitations:

  (a) Except as provided in paragraphs (b) through (h) of this section,
  no person who holds a private pilot certificate may act as pilot in
  command of an aircraft that is carrying passengers or property for
  compensation or hire; nor may that person, for compensation or hire,
  act as pilot in command of an aircraft...

If the pilot in question was a commercial rated pilot they could in theory receive compensation for the flight time but as far as I know there is no aviation law like the maritime law.

Furthermore maritime law generally allows you a portion or all of the recovered cargo value (think treasure salvage) in the case of a hull loss. Here in the US if an aircraft were to go down be it over land or water it becomes an accident scene which the NTSB would have jurisdiction over and is generally in charge of finding and salvaging for their investigation. If you were to recover a piece of an aircraft that was part of an ongoing investigation you may be required to turn it over to the authorities.

The closest scenario that I know of like this, was when a bomber pilot helped land a plane after one of the crew members had an issue. However he was not pilot in command and was only providing support.

All things considered you will probably get a book deal out of the whole thing if it were to happen...


Can air-superiority radar function as weather radar? Can the big, fat, sophisticated air-superiority radar in a modern fighter aircraft's nose serve as a weather radar for navigation in stormy conditions?

Alternatively would a datalink from somebody else (perhaps a tanker assigned to the deployment flight) be used to provide weather radar imagery into the cockpit?

Modern airborne fire-control radars seem to have a weather mode.

GRIFO-346, VixEn 1000E, and ELM-2032 (brochure PDF links).

This page suggests a "weather observation" capability in modern combat planes:

  Digital capabilities allow a radar to change its functionality at will, resulting in the modern "multimode radars" carried by combat aircraft.


Can a pilot act as cabin crew member? If several standby cabin crew members called in sick and there are no more available can standby pilot called to perform cabin crew member duties? Probably it would be more economical than postpone flight let say with 200 passengers...

For the U.S., can a non-cabin crew act as a cabin crew? Yes, except for safety duties.

  U.S. air carriers periodically use company employees in the cabins of its aircraft for the purpose of conducting certain passenger service activities, such as serving beverages, conducting customer relations, or acting as translators. These persons are not assigned to flights to perform safety duties. These company employees are not acting in the capacity of an F/A nor are they, in general, trained or qualified to act as a F/A. The regulations do not prohibit the use of non-F/A personnel by an air carrier. However, their presence could conceivably interfere with the F/As if they were not properly instructed.

Source: FAA

My interpretation is technically yes, especially that pilots are trained in safety duties.

But that's not to say there wouldn't be a union rule against it.


How to calculate the wing chord of the aircraft Aero A.10? Can anyone explain how to find the wing chord of the aircraft Aero A.10? Given Wing Span = 46.6 ft and Wing Area = 549 sqft. Thanks

how to calculate [...] the wing chord?

Given the data you provided you can only compute the SMC (Standard Mean Chord), that is equal to:

$$SMC = \frac{S}{b}$$

where $S$ is the wing surface and $b$ is the wingspan.


Why don't light-up runway numbers similar to runway lights? I know that some airports have lights on the runway that can be controlled with the mic transmit button. Additionally, during night flight, runway lights help the pilot determine where the runway is located on the ground.

However, the runway numbers/letters are always indicated on the end of the runway, but do not light up. Why aren't the runway numbers made to light up? I'd think that at busy airports, this would help pilots determine the correct runway at night (ex. in the case of a "left"/"right" runway for a busy airport).

Because it is fairly easy to determine which runway is the correct one by other means.

Runways are numbered based on their compass direction. The runway number will be the compass direction divided by 10 - for example, a runway with a direction of 150 degrees would be numbered 15.
This makes it possible to verify that you are using the correct runway by simply looking at your compass, to make sure the runway is pointing in the right direction. Even during day time in nice weather, this check is routinely performed before taking off by most pilots.

Runway identifiers for parallel runways are suffixed with an 'L' for the left runway and an 'R' for the right runway (from the pilot perspective). At airports with three parallel runways, the identifier of the middle one will be suffixed with 'C' for center.
When approaching an airport at night, the runways will - as you point out - be clearly lit. It is easy for the pilot to spot any parallel runways and make sure they are approaching the correct one, simply by observing the relative position of the runways.

During night or periods with degraded visibility, most traffic will make use of precision instrument approach systems, such as ILS, which will guide the plane precisely to the correct runway, without much risk for confusion.

On the ground, clear airport signage make it nearly impossible to mistake which runway you are on.

In addition, at busy airports with multiple runways, air traffic control service is likely to be provided. Air traffic controllers will monitor all aircraft movements on the maneuvering area and in the vicinity of the aerodrome, and will quickly be able to notify any pilot who is about to use a wrong runway.

Another point is that lighted runway numbers would probably be pretty ineffecient, as the relatively small size of runway numbers would make it impossible to read them from a distance, even if they were lit. A pilot approaching a wrong runway would notice this too late to be able to make corrections, and would have to perform a missed approach. Granted, doing so would in many cases be better than landing on the wrong runway.


What is the rationale behind "One engine - Two propellers" configuration? I stumbled upon a very unusual Russian amateur built ultralight:

One engine, two propellers configuration

My first impression is that it adds another useless layer of complexity and moreover it may involve some safety issue: I particularly think of the entry into a spin in case of one propeller failure.

What is the rationale behind it? The pros and cons?

It looks as if they rotate in opposite directions. This eliminates prop torque, which should improve handling, especially at low speeds.

On the other hand, you are right with your impression that it adds complexity, but at least it is not completely useless.

Asymmetric prop failure is indeed an issue and will markedly reduce handling qualities, and for that reason both props are close together, so if one is left, the yawing moment should be manageable if the craft flies fast enough.

Putting a single prop in the center would present it the messy flow coming from the unfaired cockpit and engine, so placing them left and right should improve inflow conditions. They are still close enough so the tail is in the prop wake and will have improved effectiveness at slow speed and on the ground. On the other hand, the outriggers will create additional drag, and it is hard to say if this arrangement will have performance benefits.


Why is training regarding the loss of RAIM given so much more emphasis than training regarding the loss of SBAS? I've noticed a lack of subject matter on the loss of SBAS as compared to RAIM.
In the ACS there is mention of RNP, SBAS (WAAS), and RAIM, which are all related, but the available content for RAIM and WAAS is much heavier on losses of RAIM than losses of WAAS.
This really became apparent to me when I was searching Garmin G1000 documentation to find annunciations regarding the loss of SBAS, and I noticed that there essentially isn't one other than "APR DWNGRADE" which loosely translates in the manual to, "you lost WAAS capability".
However, the loss of RAIM has a much more clear and direct annunciation, "RAIM UNAVAIL": that needs no translation and is immediately clear that you've lost RAIM.
Why would Garmin not have an "SBAS UNAVAIL" or "WAAS UNAVAIL" annunciation in the same manner as they do for RAIM?  It's almost as if the industry as a whole largely discounts the possibility of SBAS failures.

Here's a list of G1000 NAVIII Annunciations
Here is where WAAS is mentioned in the annunciation list.  Note that the column on the left is the annunciation displayed on the flight deck, but the column on the right is the manual's referenceable extrapolation:

Notice above that neither of the flight-deck-displayed texts on the left which have extended explanations on the right that include "WAAS" also contain "WAAS" or "SBAS" in their in-flight annunciation messages' texts.

Here is where RAIM is mentioned in the annunciation list:

Notice above that the flight-deck-displayed text does contain "RAIM" (twice) for a RAIM loss.

I included the above information to demonstrate my point, and I essentially have three closely-related questions:
Why is Garmin so indirect about the loss of SBAS in their annunciations?
Why do pilots not also perform SBAS predictions like they do for RAIM?
Why is the loss of RAIM given so much more emphasis in training than the loss of SBAS?

From a safety perspective RAIM is more critical than SBAS.
If you are flying using GPS, you always rely on RAIM to keep you safe, sometimes you need SBAS too.
Receiver Autonomous Integrity Monitor is a function within an aviation grade GPS receiver that monitors the integrity of the GPS system. Without RAIM, a malfunction in the GPS system can cause large position errors that go unnoticed. These position errors can lead to nuisances such as controlled flight into terrain that really ruin the day.
SBAS on the other hand is (merely) an augmentation to GPS. It improves the vertical accuracy by a few feet, improves the RAIM function so that it is quicker to detect position errors and can detect smaller position errors. But basically, GPS without SBAS is safely usable for the vast majority of applications.
So, if you loose SBAS, you may not be able to perform certain approaches or use certain routes, but RAIM is still there guarding the system integrity.
But if you loose RAIM, the GPS position shown may be correct, or it may be 5 miles off, or 10 miles, or more; it's anybody's guess. The GPS receiver simply has no way to determine whether the calculated position is correct if RAIM is not available.

Now to your questions:
1) Why is Garmin so indirect about the loss of SBAS in their annunciations?
I can't speak for Garmin as to why they emphasize RAIM more than SBAS in their annunciations.
In case of case of the SBAS loss, the annunciation focuses on the operational effect (Approach Downgrade). In case of the RAIM loss, the annunciation focuses on the cause / technical description (RAIM UNAVAIL and LOI).
My guess is that SBAS was added later to their product line as RAIM, and their interface design philosophy had changed from focusing on the technical cause to focusing on the operational effect. For system commonality reasons they did not update their pre-existing RAIM annunciations when adding SBAS.
2) Why do pilots not also perform SBAS predictions like they do for RAIM?
SBAS depends mainly on the availability of a healthy SBAS satellite. The SBAS satellites are predicted to be healthy, and they cover a fixed area of airspace (they are geostationary satellites). The availability status of SBAS in not dynamic; SBAS is predicted to be available.
RAIM depends mainly on the number of GPS satellites visible from the GPS receiver, and how the GPS satellites are distributed over the sky (from the GPS receiver's viewpoint). This is very dynamic, depends on the  total number of GPS satellites in orbit, their health status, their distribution in orbit, the position of the GPS receiver etc. etc. For RAIM to work, the GPS receiver needs at least GPS 5 satellites to be visible (a few degrees above the horizon) and they need to be nicely distributed over the sky. So for RAIM, the situation is very dynamic, but it is predictable. That is why RAIM prediction is done.
3) Why is the loss of RAIM given so much more emphasis in training than the loss of SBAS?
Because, if not properly handled, the loss of RAIM has a much higher probability of killing you than the loss of SBAS.


What are these autonomous, shape-shifting indoor neutral-density craft I read about? This may be on the edge of off-topic. I am trying to read more about a technology where generally autonomous (though could be sent commands), neutral-buoyancy craft were navigating indoors, in large spaces. The image I have in mind - vaguely - is of huge, transparent whales swimming around in the air in a giant atrium, never colliding with each other or the walls or floor or ceiling.

I'm trying to read more about how the sensing was done and the algorithms used, and how it was made to be so light weight, and what kind of propulsion they used that was also so light weight.

I seem to remember that they were possibly even changing shape in order to change direction.

But all I have is this image in mind from roughly 3 to 6 years ago, and so far I can't find search terms that give me anything even close. There were several articles and videos about this at the time.

The comment by @Andy suggesting they were Festo Air Rays almost nailed it.
They were Festo Air Penguins!

They can be seen maneuvering in these videos:

The article http://www.robaid.com/bionics/airpenguin-flying-robot-penguins-whats-next.htm describes the mechanism:

A strut to which the two wings are attached passes through the helium-filled balloon. This new type of wing design can produce either forward or reverse thrust. Each wing is controlled by two actuators: a flapping actuator for the up-and-down movement of the wings, and a further unit that displaces the wing strut to alter the pressure point of the wings. There is also a central rotational actuator for the two flapping wings that direct their thrust upwards or downwards, thus making the AirPenguins rise or descend.
The wing strut, which is supported at the pivot point of the torso, can be moved either towards the front or rear edge of the wing. Displacing the strut towards the front, for example, causes the wing’s pressure point to migrate forwards. The air-stream pressure bends the cross-section of the wing in such a way as to produce a profile that generates forward thrust. If the wing strut is moved towards the rear edge of the wing, the pressure point is likewise moved to the rear and the AirPenguin flies backwards. With this design a self-regulating, wing pressure-controlled, passively twisting adaptive wing has been realized for the first time.
The AirPenguins are also equipped with complex navigation and communication facilities that allow them to explore the space they float in on their own initiative, either autonomously or in accordance with fixed rules.

While they can be autonomous, and fly in formation, they can also maintain a "ground link."

By means of XBee, based on ZigBee, large volumes of data can be transmitted between the penguins and the transmitting stations by 2.4-GHz band radio. The penguins recognize each other on the basis of their distances to the transmitting stations. The rapid, precise control allows the AirPenguins to fly in a group without colliding, while also mastering height control and positional stability. As an alternative, they can act synchronously as a group. A comprehensive central surveillance system provides security in case of sensor failure. When AirPenguins are on low energy supply it prompts the penguins to return to the charging station.
The ongoing development of sensor and control technology is thus also being promoted along the road to decentralized, autonomously self-controlling and self-organizing systems thanks to the inspiration from nature.

While searching for information I found this even more advanced, articulated light (but not neutral buoyant) craft, the BoiniCopter, also http://www.robaid.com/bionics/festo-bionicopter-robot-dragonfly.htm which states a mass of 175 grams and wingspan of 70cm :

note: I have no affiliation with these sites or companies. This answer is a bit long I know, but the material is a bit unique. I felt that in this particular case the extra background may be helpful.


Why do cruise missiles look different than subsonic jet aircraft? They both fly. They both carry loads.

Why do cruise missiles look too different from subsonic jet aircraft?

They are designed to fly at one Mach-altitude combination only. Regular aircraft have to take off and land (low Mach, low altitude) and cruise (high Mach, high altitude). Cruise missiles are launched either from aircraft or accelerated by a booster rocket so their flight starts at a high Mach number already. Next, their nap-of-the-earth flight means they never go high, but stay low for the whole duration of the flight.

To minimize wing surface and, consequently, drag, the cruise missile has a higher wing loading than any aircraft. The published data only gives mass and wing span, so I needed to guess the wing area:

BGM-109 Tomahawk: 1192.5 kg, 2.67 m wing span. If I assume an aspect ratio of 6, the wing area is 1.188 m² for a wing loading of 1004 kg/m².
Boeing AGM-86: 1430 kg, 3.7 m wing span. This one has an aspect ratio of maybe 10, so the wing area is around 1.37 m² for a wing loading of 1044 kg/m².

For comparison, a typical airliner wing loading is around 600 kg/m², which is also the maximum wing loading of the B-52. Using Wikipedia data, the maximum wing loading of the B-1B is even almost 1200 kg/m², but the published area is for the outer wing only, linearly extended to the center. If the large delta is added, the wing loading drops below 1000.

At the other end of the scale, typical glider wing loadings range from 30 kg/m² (without water ballast) to 55 kg/m² (with full water ballast). A typical GA airplane with a stall speed below 61 knots has 60 kg/m² to 70 kg/m², a TBM-700 can reach up to 180 kg/m² while jet fighters range between 300 kg/m² and 500 kg/m².

Next, the cruise missile needs to be stored, so it must be compact. In case of the Tomahawk, it is designed for the 21 inch torpedo diameter standard. The AGM-86 is mounted on a rotary launcher, and the trapezoidal fuselage cross section makes most use of the available space. Since it never needs a runway, the foldable fins can be arranged symmetrically for best control effectivity and to avoid cross coupling between yaw and roll. For maximum range the cruise missile stays out of the transsonic speed regime, so little to no wing sweep is needed. In the end, cruise missiles have a very straightforward and functional design.

AGM-86 on rotary launcher (picture source)


How to improve manual flight skill? I've got a question quite specific, and directed to expert pilots:
How to improve a manual skill during solo flights?
I understand that take an instructor with me would probably be the best way, but I need to save money for the incoming CPL course.
So any suggestions?

Don't use the autopilot, use the trim, and look outside!  Fixating on the instruments will not make you better.  Know the sight picture out the windshield and what wing looks like in relation to the horizon.  Set 25' altitude brackets and 2° heading brackets and hold yourself to them.  It'll seem impossible but you'll get better.  Set those brackets with the intent to hold them by looking outside, not chasing needles in the cockpit.

Fly using the actual horizon as your reference, which is safer anyway, and make minor adjustments based on a periodic instrument scan that should become less and less frequent as you get better (think 10-15sec between scans to start).  Hold heading based on distant objects, not the compass or DG.

Finally, use the trim.  If it takes more than two fingers to adjust pitch, you are not trimmed.  If you fly a plane with a trim wheel between the seats get used to resting your hand on it.  Every time you change the power setting, retrim.  In an updraft?  Retrim.  Down draft?  Retrim. It'll become second nature in no time.


What are the differences between Cat I, Cat II, and Cat III as concerns aircraft requirements? I understand that Cat I, II, and III ILS approaches have progressively smaller weather minimums. However, I am asking about the aircraft themselves. What are the differences between Cat levels as concerns aircraft equipment requirements and approvals?

The differences are in the demonstrated accuracy of the ILS or RNAV equipment. Not sure if the question can be properly answered without writing a book, but digging into the documents linked by Jonathan Walters I extracted the tables below. The document is very long and full of caveats, exceptions and specifics on testing requirements, etc. and frequently refers to parameters set forth in other documents.

CAT I

Source

CAT II

Source

CAT III

  Landing System Performance.   All types of low  visibility  landings systems, including  automatic flight control, guidance for manual control, and hybrid, shall be demonstrated to achieve  the performance accuracy  with the probabilities prescribed in this section.  The performance values may  vary  where justified by  the characteristics of the airplane.

  The performance criteria and probabilities are as follows:

  (a)  Longitudinal touch down earlier than a point on the runway  200 ft. (60m) from  the threshold to a probability  of 1 x 10-6;
  (b)  Longitudinal touch down beyond 2700 ft.(823m) from  threshold to a probability  of 1 x 10-6;
  (c)  Lateral touch down with the outboard landing  gear more than 70 ft. (21.3m) from  runway  centerline to a probability  of 1 x 10-6.
  (d)  Structural limit load, to a probability  of 1 x 10-6.  An  acceptable means of establishing  that the structural limit load is not exceeded is to show  separately  and independently  that:

  (i)  The limit load that results from  a sink  rate at touch down not greater than 10 f.p.s. or the limit rate of descent used for certification under 14 CFR part 25 subpart C (see section 25.473), whichever is the greater.
  (ii)  The lateral side load does not exceed the limit value determined for the lateral drift landing condition defined in part 25, section 25.479(d)(2).

  (e)  Bank  angle resulting  in hazard to the airplane to a probability  of 1 x 10-7.  A hazard to the airplane is interpreted to mean a bank  angle resulting  in any  part of the wing, high  lift device, or engine nacelle touching  the ground. 6.3.2.  Speed Control Performance.   Airspeed must be controllable to within +/- five  knots of the approach speed*, except for momentary  gusts, up to the point where the throttles are retarded to idle for landing.  For operations flown with manual control of approach speed, the flightcrew must be able to control speed to within +/- five  knots of the approach speed.

Source


What are magnetrons installed on aircraft used for? I'm interested in characterizing the radio signatures of magnetrons that appear to be installed in most large aircraft, some examples appearing on this list:

http://www.mpdcomponents.com/pdfs/FAA-PMA.pdf

My understanding is that these magnetrons were the first form of radar, but other technologies have largely supplanted them. However, they still seem to appear in the parts lists of modern Boeing and Airbus jumbo jets.

My question is what are these magnetrons used for, and when they are used, how they are used? Do pilots still use these regularly?

The magnetron is a high-powered vacuum tube, that works as self-excited microwave oscillator. They are used mainly in radar transmitters as either pulsed or cw oscillators at frequencies. In (civil) aircraft, they are mostly used in weather radars.

They have relatively simple construction but have been replaced in almost all aircraft due to their disadvantages:

They can usually work only on a constructively fixed frequency.
They have poor reliability.
They have high power consumption and have noise issues.
They have finite life, considerably lesser than solid state devices.

Most of the aircraft operating today use solid state devices in their Radars. It may be still used in some older aircraft and helicopters, but they are becoming increasingly rare.

Weather radars are regularly used by pilots to detect the weather conditions in front of them. According to Airbus Flight Operations Briefing Notes: Optimum Use of the Weather Radar The weather radar only detects:

Rainfall
Wet hail and wet turbulence
Ice crystals, dry hail and dry snow. However, these three elements give small reflections compared to water droplets.

It does not detect clouds, fog or clear air turbulence.

Most of the aircraft in the list were designed 25+ years ago and have (mostly) switched over to solid state devices. Aircrafts are rarely used after 30 years as maintenance becomes expensive.

However magnetrons are still used in some aircraft due to their simple construction and high power output. For example, the WU-880 Radar Receiver Transmitter Antenna in Honeywell Primus 880 radar used in Falcon 2000EX uses magnetron.

Note: Almost all commercial aircraft use convection ovens to heat food (they won't have aluminum foils if they microwave ovens were being used); however, microwave ovens are available for aircraft and are used in some executive aircraft.


Effect of Low Vitamine B12 on Class 1 Medical Does anyone know what the effect of LOW Vitamin B12 is on an aviation medical class 1? My doctor did a blood test recently and put me on Vitamin B12 pills. Is this an issue for Aviation Medical doctors when they do a class 1 medical? i have to do mine shortly.

I am not a doctor, really the best way to get definitive answers is by talking to an AME.

Vitamin B12 deficiency isn't by itself any sort of issue, lots of people get less than they need because of diet, especially vegetarians and vegans. Vitamin B12 deficiency can lead to a form of anemia, which is potentially disqualifying, unless it can be kept below a certain level.

So, if your doctor hasn't found any sort of anemia or other condition due to lack of B12 then there's no consideration on your medical. Work on getting more in your diet or keep up on the supplements. However, if you have anemia or some other condition due to the deficiency then it is a consideration on a medical.


What is this plane shown on the 'Blended wing body' Wikipedia page? (wikimedia.org via wikipedia.org)

What is the second plane from left, between the 757 and the B-2?

Its a Rockwell B-1 Lancer a heavy bomber used by the USAF.

(source)


How are banners kept upright? Banners are towed with a single line trailing from the plane.

source: © Raimond Spekking / CC BY-SA 4.0 (via Wikimedia Commons)

How can they guarantee the banner is vertical and not upside down?

The tow line has the "Y" connection to a pipe/rod along the leading edge of the banner.  This keeps the leading edge perpendicular to the tow direction.  The bottom end of the pipe/rod is weighted so that once in the air gravity will rotate the banner to the vertical.


Is "passenger loading bridge" a synonym to "contact stand"? In a master plan of an international airport, which is already approved by the client, I face some confusion between the terminology of the PLB and the contact stand.

Sometimes they're mentioned just as the same component, not like other locations. I assumed a sort of a conflict in the master plan but I'd like to confirm this please.

Is there any  benchmark like ICAO or IATA that defines such components, e.g., the gate, rotunda, PLB, contact stand, etc.?

ICAO Annex 14, which deals with aerodrome design (not really terminals) uses the terms PLB and aerobridge.

Wikipedia lists many names for it, with the official being PBB (Passenger Boarding Bridge). The names listed are jet bridge, jetway ®, gangway, aerobridge/airbridge, air jetty, portal, and skybridge.

Official FAA documents use the term PBB. (Example.)

Contact stand most probably is used to distinguish it from a remote stand, it's not very popular according to Google. Rotunda or pivot describes that a PBB pivots, or perhaps the pivoting / telescoping part.

To answer the main question, yes they all mean the same thing, with PBB being an official name.


Have there been any studies on which fly-by-wire pilot interface is preferred; rate control or direct control? Provided an aircraft with a fly-by-wire system, there are basically two possible choices when it comes deciding how to let the pilots interface with it:

rate control / attitude hold: a deflection of the stick will command a certain rate, releasing it will make the system maintain the current attitude. See the Airbus Normal control law.
direct control: a deflection of the yoke will directly translate to a deflection of the surfaces, mimicking the "old" mechanical control setup. It is my understanding that this is the design choice of Boeing in its new aircrafts.

I do not wish to discuss how Airbus and Boeing made their design decisions, but rather see if there has been performed a study on what interface is preferred by pilots, eventually differentiating among private/commercial pilots or Airbus/Boeing certified pilots or even pure civil/(former) military pilots.

Does any of you have any reference?

I have no study to refer to, but I expect the results to differ very much from group to group.

For airline operations, I imagine the objective of the pilot is often to maintain a constant attitude, varied with a smooth transition to another attitude. This would be easy to achieve with the first option you describe.

For military operations, I think a rapid feedback is desired. This aligns better with the seconds option you describe.

When you would perform a study under pilots, the response you'll get will very likely be that they prefer whatever they are used to at the moment.


Why do aircraft have two brake pedals instead of one? Why do aircraft have two brake pedals instead of one?  If each pedal controls different sets of wheels e.g. the left wheels and the right wheels of the main gear, is that not a safety flaw given that at any point in time, it is impossible for the pilot to apply an equal amount of pressure to the brakes?

Isn't ABS enough to the point that only one pedal is enough?

Finally do both captain and pilot step on the brakes at landing? If not then why have two pedals?

In an aircraft the brake pedals control the respective side brakes. This allows for the pilot to turn the aircraft not only with the pivoting nose wheel (if it has one) but also with the brakes. This allows for a very tight turning radius.

(source)

  If each pedals controls different sets of wheels eg the left wheels
  and the right wheels of the main gear, is that not a safety flaw
  rather than measure given that at any point in time,

It is by design to allow for the tight turning. Some smaller aircraft also do not have a steerable nose wheel so differential braking is the only option.

  it is impossible for the pilot to apply an equal amount of pressure to
  the brakes?

Pushing equally on each toe pedal will result in equal brake operation.

  Isn't ABS enough to the point that only one pedal is enough.

The pedals allow for brake steering which a single pedal would prevent. Airplanes also do have ABS but that simply prevents the tires from skidding.

  Finally do both captain and pilot step on the brakes at landing. IF
  not then why have two pedals?

Im not sure, when I fly with an instructor or co-pilot in smaller planes only one person operates the brakes.


Why do all the rings of MH370's transmission locations have the same origin point? This question originates from the video "The Vanishing of Flight 370", by Lemmino.

At 6:00 he says

While these transmissions did not contain any information about the flight's position, investigators were able to measure the distance between the satellite and the aircraft at the time of each transmission, based on how long it took those transmissions to be sent and received. This generated seven rings of possible locations, from which seven of these transmissions are thought to have originated.

And this diagram is displayed:

But something about the visual strikes me as odd: don't satellites move? I thought they had to keep orbiting or they would crash. So why do these rings of transmission locations, taken over a roughly six-hour period, all show the satellite above the exact same place? Clearly something about my reasoning must be wrong if the investigators never considered it.
(I'll understand if this belongs more on Space Exploration stack exchange.)

Because the Inmarsat 3 series satellites that were used to transfer the ACARS system data are geostationary. They orbit at a speed and altitude that causes them to stay in the same location with reference to the earth. The signals were received specifically by the Inmarsat 3 F1 satellite which was, at the time, geostationary over the Indian Ocean.


Who sells aviation fuel to airports? I want to ask about the jet fuel purchasing cycle. Is it the airport that buys the jet fuel from refineries and then sells it to the airlines? Or do airlines buy fuel directly from refineries?

The airport is buying fuel and selling to airlines. And more over, they provide different types of fuel on prior request by the airliner. Reference : VCBI


Best Glide with Flaps T/O in DA20-A1 The Diamond Katana DA20-A1 Manual says that the best glide angle can be achieved with flaps in the t/o position at 72kn at maximum weight.

My naive understanding would be that a flaps up position would always provide a better glide angle, because of the lower drag. So why does the Katana apparently have a better glide with flaps t/o?

The best glide flap setting is a matter of definition. If the base airfoil was optimized for high lift (like, say, the Wortmann FX63-137), the cruise flap setting would be some trailing-edge up position. If that is defined as 0°, and the take-off setting is the one for which the airfoil has originally been optimized, then it should not be too surprising that it allows the best L/D.

A high zero-lift drag coefficient, like from a fixed landing gear, will drive the optimum L/D to low speeds and a high lift coefficient. That is where the Wortmann FX63-137 excels and the reason why the optimum L/D of the Katana is at such a low speed. The Katana has inherited this airfoil from the H36 Dimona motorglider, and here it had been selected to meet the minimum sink speed requirement at that time for certification as a motorglider.

Airfoil trivia: The Wortmann FX63-137 has originally been designed for a human powered aircraft project. This explains its very high maximum lift at low Reynolds numbers.


How long can I use an FAA license in Colombia without having to validate it? What is the maximum range of time that an FAA certificated pilot can stay and fly in Colombia, without the need to validate his license there?

You could fly US-registered aircraft in Colombia with your FAA license, but if you want to fly Colombian aircraft then you need to either validate your FAA license or get a Colombian one.

You validate your FAA license (or any ICAO license) by getting a Colombian "provisional" license. It remains valid as long as your FAA certificate and medical are valid. See section 2.1.7 of the Colombian regulations:

  2.1.7. CONVALIDACIÓN

  Cuando la UAEAC convalide una licencia extranjera otorgada por un
  Estado contratante de la OACI, en vez de otorgar su propia licencia,
  hará constar la convalidación mediante autorización apropiada que
  constará en una licencia provisional la cual deberá acompañar a la
  licencia extranjera y reconocerá ésta como equivalente a las otorgadas
  por dicha autoridad aeronáutica colombiana. La validez de la
  autorización no podrá exceder el plazo de validez  de la licencia
  extranjera.

Note that the process of validation depends on your personal situation, especially whether or not you plan to become a Colombian resident (see 2.1.7.1).


On a procedure turn, do you make the turn on the inside or outside of the procedure turn? When flying a procedure turn like the one shown below, the first step is to fly outbound 039 degrees. When you turn inbound to 219 degrees, do you make that turn to the left or to the right? The left meaning to turn to the outside of the procedure turn (a greater distance from the FAF) and the right meaning to turn to the inside of the procedure turn (a shorter distance from the FAF).

If you look at these pictures, it looks like the procedure turn is made outwards from the course:

Section 5-4-9 of the AIM contains a lot of guidance on procedure turns, and says (in short):

If the procedure turn is charted as a teardrop or hold-in-lieu of procedure turn, then it must be flown as charted. (Does not apply in this case.)
If it is a standard procedure turn, the barbed arrow shows the maneuvering side (so the first turn should be flown as indicated), but the rest of the procedure is at the discretion of the pilot, as long as they stay within the distance specified on the chart.

I was taught (and see it as a "standard practice") to turn away from the fix defining the start of the procedure turn for the 180 degree turn, and in fact have never seen anyone fly it the other way.  That being said, there is nothing which prevents it if it can be done within the protected area and accomplishes the purpose of becoming established on the final approach course in time.

A small excerpt from the AIM (lots more information is available there):

  5−4−9. Procedure Turn and Hold−in−lieu of Procedure Turn

  ...

  On U.S. Government charts, a barbed arrow indicates the maneuvering side of the outbound course on which the procedure turn is made.
  Headings are provided for course reversal using the 45 degree type
  procedure turn. However, the point at which the turn may be commenced
  and the type and rate of turn is left to the discretion of the pilot
  (limited by the charted remain within xx NM distance). Some of the
  options are the 45 degree procedure turn, the racetrack pattern, the
  teardrop procedure turn, or the 80 degree  260 degree course
  reversal. Racetrack entries should be conducted on the maneuvering
  side where the majority of protected airspace resides. If an entry
  places the pilot on the non−maneuvering side of the PT, correction to
  intercept the outbound course ensures remaining within protected
  airspace. Some procedure turns are specified by procedural track.
  These turns must be flown exactly as depicted.

  ...


Why are the lights inside commercial airplanes turned off during take off and landing? Before landing and taking off, I notice the lights inside commercial aircraft are greatly reduced. I don't buy the explanation of power saving in case full thrust is needed as nowaday lights don't need a lot of energy and the crew says we can use the smaller reading lamp to continue reading. I suppose this is something to do with security but I don't understand what.

This is for safety reasons.

Take-off and landing are the two most critical phases of flight and thus, every additional step to ensure survivability, be it even just adjusting the light, is taken.

The interior lights or cabin lights are adjusted to match the exterior environment, so that in case of an emergency, especially if the interior lights fail, your eyes are already accustomed to the light setting and you do not require additional valuable seconds for adjustment to a possibly darker or brighter environment. The lights are usually adjusted at dusk, night or dawn to match the exterior environment.1

If the cabin lights do not fail during an emergency, the dimmed light also makes it easier to identify the "EXIT" signs which illuminate and make the guidance lighting on the floor easier to follow. The bright emergency lighting is more prominent to identify when the cabin light is dimmed, saving valuable seconds as the aircraft is evacuated.

This also ties in with having to raise the blinds on the windows. The blinds need to be raised during take-off and landing irrespective of the outside light situation, however, with a darker cabin, any outside light source, especially from fires or other hazards is easier to identify by the crew, making the decision process of whether one side could be inappropriate to use for evacuation faster, e.g. fire on port side --> no evacuation on that side.

The blinds are therefore raised to allow a better view for cabin crew of the outside area and external aircraft parts, such as engines, wings, etc.
See also this related question: Why open up the window shades before takeoff and landing?


Can you use a home built helicopter for solo hours? I'm curious to know if anyone has heard of or has any knowledge of using a kit helicopter for the FAA required minimum solo hours of flight training.

I assume that this is for a Private Pilot - Helicopter license. I also assume you mean something like larger kit aircraft, not ultra-light helicopters like the Mosquito.

You can do this, but there are other conditions that must be met:

The aircraft must have completed it's flight test phase (this is usually the first 25-40 hours of operation)
The CFI must be willing to provide instruction in the aircraft. It will be difficult because either the CFI is not familiar with the aircraft or insurance won't cover them, some just won't fly homebuilts.
Your aircraft insurance must allow primary flight training in the aircraft (not many do)
The aircraft must meet requirements such has having a radio, transponder, etc for being able to operate in required airspaces.

The big ones will be finding a CFI willing to do this, and getting insurance to cover you. The insurance alone may outweigh the cost of renting a certificated aircraft.


How does cultural difference impinge upon human factors in aviation industry safety? Safety through understanding of human factors

This question is based on https://aviation.stackexchange.com/questions/27814/ and related to:

How have deep-seated cultural human factors (particularly in east Asia) in the cockpit been successfully managed in the past 20 years?
To what extent have political (race, gender, social class) attitudes been implicated as human factors in the cockpit?

Aviation industry safety has improved as much through better understanding of human factors in the cockpit as it has through advances in science, technology and engineering, to the extent that practitioners in other sectors (from software development to surgery) are interested in how its principles might apply to their own disciplines.

Aviation practices of this kind that aim to manage or mitigate human factors include:

extensive use of checklists
strict rule-following
extensive cross-checking
health-checking
blameless incident analysis
eliminating authority gradients that make it hard for junior crew to question decisions

Aviation practices across different cultures

These practices and the ideas behind them have largely emerged from western social cultures, and largely in the civilian post-WWII industry, and to a certain extent exemplify aspects of western politics and culture.

Examples of incidents related to cultural human factors

There are many stories (and some are no doubt apocryphal) of how cultural human factors have been involved in incidents. In recent years:

steep cultural authority gradients:

a junior first officer reluctant to question an overbearing captain's decisions
a timid first officer who failed to realise his remote and taciturn captain had actually died

attitudes to regulation, and attitudes of family/VIP exceptionalism:

the pilot who allowed a teenaged family member to touch controls in the cockpit
the pilots who ignored ATC advice to divert in fog because the president and other VIPs were anxious to attend a ceremony

How does cultural difference impinge upon human factors in aviation industry safety?

For example:

How well have they worked (adoption, implementation, outcome) in very different cultures?
Has it been particularly hard for them to find acceptance in other cultures (this applies not just to non-western cultures, but also for example to military culture in the west, where levels of authority and hierarchy are very significant)?
Have different approaches been used or tried with better results, in different cultures?

What you are asking looks like a university assignment on Interface design and sociology. It is a very complex area and your question does not suggest a simple answer but here goes:

These cultural factors are covered by Hofstead's theory of Cultural dimensions. Specifically the Cultural factors of Power Distance, Individualism and Uncertainty Avoidance. I have studied Hofstead (and others) and its relation to Interaction Design and Interface Design for a computing degree.

Power Distance (PD). The higher the score then the more likely the culture is to vest  power in an elite and accept that their decisions. The lower the score the more power is devolved and people are more likely to question leaders.

Individualism (IND). The higher the score the the more loose the societal structure. The lower it is then the society tend to collectivism and rigid structure.

Uncertainty Avoidance (UA). The higher the score then the more the society prefers rigid rules and procedures for all events. The lower then the more relaxed the society is to rules unexpected events.

Note that these overlap considerably.

What this means is that cultures with high PD, UA or Low IND are more likely to follow instruction or even crave instruction and rule. Checklists and instructions are more likely to be followed. Cultures with the opposite may be inclined to be a little more relaxed and may be more of a risk to safety due to a laissez-faire attitude to checks.

However a high PD, low IND and high UA may result in a subordinate unquestioningly accepting instruction from the captain despite knowing that the order was wrong even to the point of crashing.

It is a massively complex subject and to get an answer you really need to be specific with scenarios and cultures.

To see the scores for various cultures then go to geert-hofstede.com/countries.html and try some countries


Can small airplanes be towed (or carried) as cargo to be dropped at some other location by air? Is there any present technology where a large plane can carry a small plane (or multiple small planes) and drop it midair where the small plane deploys itself? This would be very good from defense point of view, where small fighter jets with limited range could be dropped off by large airplanes with very long range.

If you are talking about externally carrying/deploying other aircraft, this has already been done with the B-52 (albeit for testing purposes) carrying the X-15.

I'm not too sure about having an aircraft drop out of a cargo bay such as the C-130.

On a side note military gliders were used extensively during WW2 and some were capable of carrying light tanks. The gliders were usually towed behind larger bombers to give them the required altitude and speed. They were used because of their wooden construction allowing a stealthy approach due to the reduced radar signature.


What twinjet with rear-mounted engines and swept wings did I see in Savannah, GA? I saw this flying in Savannah, GA and need help identifying it. It looks like something military due to the color and lack of markings. Can anyone help?

Gulfstream G500. The G600 is longer. The angle is close, but look at the window just ahead of the wing fairing. The original is faint but clearly ahead of the fairing curve. The G600 window is in the middle of the curve. The G600 has a bigger wing.

G500 pinterest

G600 wikipedia


How many pilots are required in an Airbus A380? Is it possible for one single person to fly, maneuver and land an Airbus A380 by him/herself?

In general, it is perfectly possible for a single person to fly modern aircraft like A380. However, regulations require the presence of 2 pilots (PF and PNF). In other words, technically yes, legally no.

In long distance flights, the aircraft usually carries two sets of cockpit crew (4, each capable of flying the aircraft) as the flight hours may be more than the permitted flying hours.

FAA Advisory Circular 25.1523-1 deals with the minimum flight crew in transport category aircraft. According to Section 5 Certification Procedures, Subsection c, Testing (vi) Incapacitated Crew member,

  Whenever the applicable operating rule requires a minimum flightcrew of at least two pilots, the certification program should include a demonstration
  of operations during the total incapacitation of a crewmember at any point in a given flight. It must be shown that the airplane can be operated safely and landed safely with the remaining crew at a planned or unplanned destination.


Is there a procedure for landing on an aircraft carrier when the tailhook fails to deploy? When landing on aircraft carriers, a tailhook is used to snag one of the cables on the carrier deck, which slows the aircraft.

When the landing gear fails to deploy I have seen it is possible to make an emergency landing by landing on the belly - and I'm sure there are other options too.

However, what would a pilot do if the tailhook failed to deploy when landing on a carrier? Is the carrier deck long enough for a pilot to stop without the tailhook? What else could a pilot do in this situation?

The high landing speeds of modern jets mean that they cannot make anything but an arrested landing as the carrier flight deck is too small.The carriers usually have barricades to facilitate emergency landings. The following image shows a barricade.

Image source

The following image shows the barricade, raised.

Image source

The following image shows an aircraft using a barricade.The aircraft was unable to make a normal arrested recovery because of damaged landing gear.

"US Navy DN-SC-93-04867 to 04876 S-3A Viking emergency landing USS Abraham Lincoln (CVN-72) animation" by PH3 Eric Hayhurst - This Image was released by the United States Navy with the ID DN-SC-93-04867 to 04876 Commons.

See here for some other cases where barricades were used.


What prevents the use of an EMAS along the sides of a runway? The NTSB report about the crash of American Airlines Flight 1420 discusses whether an EMAS would have mitigated the severity of the accident, but concludes, based on testimony from a representative of an EMAS manufacturer, that

  ...the benefit of an EMAS in this accident would have been limited by the airplane traveling partly outside the runway edges; thus, the airplane would not have been able to use the full length of the EMAS. The report also concluded that an EMAS would have reduced the speed of the airplane by 15 knots but would not have enabled the airplane to stop within runway 4R’s runway safety area.  [report page 64/PDF page 78]

What I’m not seeing is any reason why an EMAS would have to be confined to the extended track of the runway; extending it from the ends up along the sides of the runway would provide additional protection for aircraft sliding off, or partly off, the sides of the runway (such as AA1420):

(Aircraft tracks shown in these images are merely examples of possible runway-excursion trajectories, and are not intended to represent any specific flights in particular.)

Am I missing something here?

I can think of a couple reasons why you might not want to expand EMAS all around the edges of the runway.  One is simply cost vs benefit:  If it is more likely that an airplane will run off the end of the runway than the edges it would make more sense to put the material there.

EMAS would seem most beneficial in stopping forward speed if the wheels were to make contact uniformly.  An aircraft departing the side of the runway already has directional control problems.  The situation would be amplified if the wheel on the side “pulling” the aircraft off the edge was to be dramatically decelerated.  It could even cause a ground loop.


Why were early AFRP A300/A310 rudders prone to delaminating? Reading the TSB report about that time an A310's rudder flew the coop, I came across this piece of background information (section 1.12.9.1, History of Earlier Design Aramid Fibre-Reinforced Plastic Rudders):

  In the earlier design of the rudder, GFRP [glass-fibre-reinforced plastic] was used as the bridging layer between honeycomb and CFRP [carbon-fibre-reinforced plastic] only in the reinforced region around the hydraulic actuators. Elsewhere, AFRP [aramid-fibre-reinforced plastic] was used. The AFRP system resulted in poor bond strength of the interior skin. Those rudders experienced large in-service disbonds of the inner skins.  [...]

What made A300/A310 rudders using AFRP so prone to the rudder skin delaminating from the underlying structual framework?

You'd have to find someone with access to the original Airbus failure analysis to know the details, but in general it's more difficult to get good bonds with Kevlar laminates compared to graphite or glass (something to do with helpful reactive compounds on the surface of glass and graphite fibres that Kevlar lacks), and special surface treatments and epoxies are required.

I'll hazard an educated guess that Airbus engineering at the time may not have had a lot of experience with Kevlar composites and didn't appreciate the bonding issues sufficiently, and it didn't show up in testing and took the stresses of service operation to uncover it.

Nothing new there as such screw ups go... on the CRJ200, the floors were carbon honeycomb set on floor beams of aluminum.   Somebody seemed to have missed their galvanic scale class in university and didn't realize that carbon and aluminum don't like to live side by side, and areas of the floor see significant moisture from people spilling stuff, rain coming in the doors, humidity, etc.  The company ended up replacing the floor beams on the first couple hundred airplanes with titanium ones.


Will a stalled aircraft fall down like a brick? Or how steep does the Lift-AoA curve fall off after stall? When an aircraft stalls, do all or most lift forces abruptly disappear or is this transition continuous?
Will the aircraft drop from the sky like a brick or can this (losing lift and altitude) happen so gradually that it will be entirely unnoticed from the crew and passengers?

I'm troubled by this sentence on Wikipedia referring to the AF447 disaster:
"The aircraft remained stalled during its entire 3 minute 30 second descent from 38,000 feet (12,000 m)"
(source: https://en.wikipedia.org/wiki/Air_France_Flight_447#Accident)
It seems the crew were unaware of the stall condition. (But let's not discuss the reasons here)

If lift abruptly disappears when entering a stall, wouldn't people notice a considerable loss in perceived body weight at least as long the aircraft accelerates downward and builds up vertical speed downward.
I expect that the airframe experiences enormous drag in the vertical direction once downward speed is being built up and it probably reaches an equilibrium condition limiting its fall rate.

But if lift disappears abruptly during the stall, then you should have a sensation of free fall (no weight) at least during a short time.
Is this the case or does lift diminish continiously during a stall?

PS: While writing the question i have searched and found those Lift-AoA diagrams (like this: https://www.grc.nasa.gov/www/k-12/airplane/incline.html) that should be able to answer the question.
Basically my question is: How quickly does Lift drop off to the right of the diagram. All diagrams i found did not in fact go much beyond the stall condition.

You make some valid observations: not all lift disappears after the stall, and at the event of stall there is a downward acceleration that may or may not be perceived.

Let's start with what happens after the stall. Measurements on airfoils have been taken over 180°, and they show that after the stall, lift drops back until flat plate lift is achieved at the same angle of attack. Increase AoA further, and lift increases again. An example for a relatively thin airfoil from this document:

Pull the aircraft back far enough to 45°, and the $C_L$ is even higher than when it stalled! Of course, the drag will be huge compared to normal operating circumstances, and any fixed wing other than a military jet fighter or a VTOL won't have enough power installed to fly at such angles of attack.
Isn't there a perceived loss of body weight during the acceleration to stall. Yes there is, but it does not last long, is not necessarily very powerful, and could be referenced to other factors than stall, such as turbulence. Once the $C_L$ - $\alpha$ curve hits the trough at 15°, the acceleration stops and weight perception returns to normal. And it's sensory perception, the body only really understands what is happening if all sensory organs are aligned (vision, motion, sound), and can only react in a composed manner if it anticipated the cues and is trained in how to respond. Otherwise we just fight or flee.

You mention the case of AF447. It was in a fully developed stall and descending with on average 10,000 ft/min, but the onset to stall was different. It was  very gradual, and it was a high speed high altitude stall: there simply is not enough air up there to provide enough lift for the weight of an airliner. It can stall at AoA of zero, then start to fall, as a result of which the AoA changes but the pitch attitude of the aircraft does not, and your body is still aligned with gravity in a dark cockpit where the horizon cannot be seen. No physical cues on what is happening whatsoever!


How is oil distributed through the engine in a wet sump system? A wet oil sump is within the engine crankcase. However, how is the oil distributed throughout the engine and all the other magical parts? I know for a dry oil sump, it's with a oil pump which holds the oil from a reservoir, but for wet oil sump, how?

The short answer is "The same way as in a dry sump system." – There is an oil pump which sucks oil out of the oil pan and forces it through the engine oil galleries under pressure.
Wet and dry sump oil systems only really differ in where they store "extra" oil.

Wet Sump Systems
In a wet sump system the oil is stored in the oil pan under the engine. The oil pan serves as both the oil tank (holding the supply of lubricating oil) and the oil sump (where oil eventually collects after making its way through the engine). The pressure pump sucks oil directly from the oil pan and circulates it through the engine's oil galleries.

Dry Sump Systems
Dry sump systems store their oil in a separate tank, which feeds the pressure pump. Dry sump engines have a smaller oil pan which only serves as a sump, and a "scavenger pump" that drains the sump back into the main oil tank. They are termed "dry sump" systems because under normal operating conditions very little oil remains in the sump.

Note that there are other engineering differences in dry-sump systems, but they're largely beyond the scope of your question.
Illustrations thieved from https://www.slideshare.net/jesscar/piston-engines-oil.


Were airworthiness certificates revoked for B737 Max? Following up from this question - or more specifically Brian Drummond's comment on the accepted answer:

  Or even revoked without modification, if something new is discovered about the existing components (e.g. failure modes)

When B737 Max were grounded due to suspected issues with MCAS, what happened to the Certificates of Airworthiness of individual aircraft?  Technically speaking,

  something new [has been] discovered about the existing component

Per the quoted comment, this could result in the certificates being revoked.  Did it actually happen? If not, what formal measures exist that prevent somebody flying a B737 Max? (Other than common sense of course.)

The grounding of the 737max is a Prohibition of Operation, not a revocation of Type Certificate. This is done by each jurisdiction around the world. China suspended flights two days before the FAA did.

Technically, if you could find a country that never prohibited its flight, the Max could still be used there. Repositioning flights of grounded aircraft, as to a storage location, are authorized on a case by case basis.


Is there independent evidence that the Wright brothers celebrated Roosvelt's election in 1904 by a flight of over 5 minutes? In a letter addressed to Octave Chanute, Wilbur Wright made the following statement:

Wilbur Wright, “Letter to Octave Chanute”, Dayton, November 15, 1904.
“On the 9th we went out to celebrate Roosevelt’s election by a long
flight and went around four times in 5 min. 4 sec. We unfortunately
failed to set the recording anemometer and so did not get a measure of
distance, but it was evidently a little over three miles. The trouble
in righting the machine after swinging a short circle is evidently
corrected. The machine landed without any injury and was put back on
the track for another trial, but the wind had been working more and
more to the south and we were unable to get another start.”

I guess, there should have been some witnesses, journalists, etc., present. Well then, who really saw the flight?

The short answer is No. The independent witnesses are missing. Only Wilbur, Orville, and possible their father, saw the Nov. 9, 1904, flight.
There exists a commented collection of old documents of the period 1903-1905 (most of them from 1904), over 200 letters and articles, all quoted in full, that studies, based on primary sources, whether the Wrights really flew a plane in 1904 (they claimed 105 landings for that year).
This book is titled: "The Wrights and their impossible 1904 flights"

The 1904 plane as imagined by C. Dienstbach in his March 1905 article in German (Source: "The Wrights and their impossible 1904 flights", page 62)
Regarding the existence of the Nov. 9, 1904, flight, besides the letter sent to Octave Chanute, this is the evidence I could find, in the above mentioned work:

November 9, 1904 - An entry in Bishop Milton Wright's diary reads: “… I go on 11:00 car to Sims. At 2:00, Wilbur flew three (lacking one-fourth) miles in 5 minutes and four seconds. The distance was only limited by failure of engine.” (col. 1, p.28)
November 9, 1904 - Wilbur recorded, in one of his notebooks, a flight of 5 minutes and 4 seconds as the 82nd trial of that year. Orville also mentioned the flight in his logbook. (p. 95)
December 17, 1904 - The Dayton Press published an anniversary article, stating: "Their work and trials have been carried on quietly. They have not made any public trial, and have no intention of making any in the near future. … The longest fights yet accomplished by the machine occurred on November 9 and December 1, when the flyer made almost three miles in five minutes.” (p. 36)
December 20, 1904 - Wilbur mentions, in a letter to G. A. Spratt (a fellow aviation enthusiast), that the longest flights of 1904 occurred on November 9th, 16th, and December 1st. (col. 1, p. 18)
December 21, 1904 - Orville Wright wrote to the German journalist Carl Dienstbach saying, amongst other things,: "The two longest flights of the season were made on the 9th of November and the 1st of December. In each of these flights we made almost four complete circles and covered a distance of a little over four and one half kilometers, at a speed of about 35 miles an hour. In the flight of November 9th a weight of 50 lbs. (iron bars) were carried in addition to the weight of the operator; in the flight of December 1st, 70 lbs." The letter of Orville was published in German under the heading: “Das erste Lebensjahr der praktischen Flugmaschine”, Illustrierte Aëronautische Mitteilungen, March 1905, pp. 91-93. (p. 19)
February 3, 1904 - The Holt County Sentinel (Oregon, Missouri) published a short text that quoted the father of the two inventors: " After years of unsuccessful efforts by some of the world’s greatest scientists, it appears that the Wright Brothers, of Dayton, O., have solved the problem of the flying machine. Accounts of a successful test made by them appeared in the papers last summer, and it seems that they are making rapid strides toward perfecting their invention. We quote the following from a letter from their father, Bishop Milton Wright, of Dayton, to his niece, Mrs Frank Petree. “Wilbur, on November 9th, celebrated Roosevelt’s election by a flight of nearly three miles, in five minutes, and Orville did the same December 1st. I was there. They are improving their engine and will put the experience of 1904 into a new machine by April.” " (col. 2, p. 89)

In conclusion, the Press states that nobody saw a powered flight performed by the Wrights before December 17, 1904. The only possible witness (not really independent) of the Nov. 9th long flight could have been Bishop Milton Wright. However his diary just implies he witnessed the performance of that day. The father of the two inventors does not explicitly use the words "I saw".
If somebody else finds new evidence, in the book or from other primary sources not quoted there, I would be happy to see it.


Is there a planned ADS-B update that would allow ATC to view an aircraft's traffic coverage? ADS-B allows a plane to broadcast its GPS location to other planes and ground stations used by ATC.

The range is 200nm for A/A and 180nm for A/G (source).

Same SSR coverage issues would still impact oceanic areas.

But what if a train of planes (crossing the Atlantic for example) communicated what they see to each other, until the one closest to a ground station relayed all that information to an ATC facility? Is it being planned as a future update?

No, this is not being planned as a future update. The current ADS-B mandates of USA and Europe foresee ADS-B version 2 (EUROCAE ED-102A / RTCA DO-260B for 1090ES) to be implemented in 2020. Work on the development of version 3 of the standard has started but the retransmission of received data is not foreseen currently. Because of 1090 MHz spectrum overload, integrity, security and latency issues I don't think it is a particular good idea either.

For oceanic areas ADS-B coverage will be provided by satellites equipped with ADS-B receivers. Aireon is a company that will use the next generation of Iridium satellites to provide oceanic ADS-B coverage for ADS-B.


How do I calculate the landing distance in a landing chart with tailwind? With the following chart I can calculate the landing distance with the headwind, gross weight and altitude. The charts uses headwind component, but how can I calculate the landing distance required if an aircraft is landing with tailwind? There is this rule of 50% for headwind and 150% for tailwind but how do i apply this with this chart?

Thanks in advance

You can’t use that chart with tailwinds - not without an expansion of the graph to include that information.  Without more information from the OEM on landing distance in a tailwind I would not risk my life on a calculation derived from that chart.


What were the U.S. Air Force's first 2-crew fighter planes? The Navy has had 2-crew planes since at least as early as 1944 with the Grumman F7F Tigercat but when did the U.S. Air Force adopt 2-seaters. Does the Navy prefer 2 crew and the Air Force prefers 1? Was the McDonnell F-101 Voodoo one of the first AF 2-crew?

The first two-crew fighter aircraft to enter service with the US Air Force was the Lockheed F-94 Starfire.

Source: Wikipedia Public Domain

The aircraft's first flight was on April 16, 1949 and entered service in May of 1950.


Is there a legal requirement for planes to start from the ground? If I could somehow store a plane inside another plane, would I be allowed to start the second plane somewhere in the air? Maybe different countries have different laws for this kind of aviation?
I know that this is technically at least challenging if not impossible, I was just wondering if I would even be allowed to do this.
Bonus Question: How would the pilot communicate this to the authorities?

At least in the US, this is perfectly legal. There have been quite a few such aircraft in history.
However, an aircraft docking and undocking from another is so rare that there's no standard way of communicating it with ATC. So you'd have to explain what you're doing in plain language. (And then you'd have to explain it again when the confused controller replies, "What?") If I were flying such a mission, I'd contact the local FSDO ahead of time to explain it, so that they can forward the information on to the local ATC facility to cut down on confusion.


What are the advantages of the Cri-Cri's tail and fuselage design? I have some questions regarding the Cri-Cri design. If some of them can't be answered directly, I would like to read what theory says about it.

Why is a T-tail used? What are its advantages for an LSA over a classic tail?
The plane has a polygon-shaped fuselage which is not streamlined. How much efficiency was traded for production simplicity?

The T-tail positions the horizontal stabilizer out of the turbulent "prop wash".  This reduces the strength and weight that would be required of the structure if it had to endure the aerodynamic stress behind the two propellers (which is terrific).

This simple shape has everything to do with parts and assembly simplicity and low cost for the homebuilder.  Drag increases exponentially with speed; so for slow aircraft, draggy shaped components are much less a problem.


Why do planes need a roll motion? Isn't only pitching up/down and yawing right/left enough for travelling from one location to another?

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

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

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

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

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

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

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

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


List of all FIR and their authorities Wikipedia has this page https://en.wikipedia.org/wiki/Flight_information_region containing a table of all FIR (with ICAO codes) and their respective authority countries.

Is there any place where I can download an updated list like this one as a CSV file (or XML)?

I need to do some automatic calculation of overflight costs. For that I have a set of calculation formulas from IATA, but they are based on authority country, and my input is based on the FIR, that the actual flight is passing through. Therefore I need some way to find the authority country for each specific FIR.

I would prefer somehow to be able to automatically download a fresh list once in a while. I'm not yet sure, how often these data might change.

For posterity, I found what I needed here: https://www.icao.int/safety/istars/pages/api-data-service.aspx

They currently have 58 datasets. The one satisfying my needs is "Flight Information Regions - Names".

When registering for an API key, I am allowed to do 100 requests for free each month. Downloading the entire list counts as 1 request. So the way I read it, I am complying with their EULA. If I'm wrong, please comment.


How does ATC radar/ADS-B ground stations not get confused with signals sent from multiple aircraft? I understand that the radar sends a 1030 MHz interrogation signal to an aircraft and the aircraft's transpoder responds using 1090 MHz. When it comes to Mode S squitter, the transmissions are unsolicited (does not require interrogation). Considering that the airspace is highly populated, there would be multiple aircrafts transmitting data on the 1090 MHz to the radar. Won't these signals interfere with each other and become a huge mess at the radar side?
(Similar is the case of ADS-B, where data would be continuously broadcasted between aircraft-aircraft, aircraft-ATC and vice versa on the 1090 MHz Extended Squitter, how are the signals prevented from mixing up with each other?)

Also how is the interrogation signal transmitter from ATC to aircraft (and also back) sent? Is Frequency modulation used here? What is the bandwidth of the 1090 Mhz channel? Does it have sidebands?

The class of ATC radars that you are talking about is secondary radar.

Secondary radar works by transmitting an interrogation signal on 1030 MHz to which the transponder replies on 1090MHz. There are several modes of interrogation. For civil ATC, modes A,C and S are important.

The uplink signal (interrogation) is a simple pulse encoding (Mode A/C) or a Differential Phase Shift Key modulation (Mode S / TCAS) on 1030 MHz.

The downlink signal (replies, unsolicited squiters) is a simple pulse encoding (Mode A/C) or Pulse Position Modulation (Mode S / TCAS / ADS-B)

Originally only Mode A & C were available. Mode A and Mode C are unaddressed; every transponder receiving a Mode A or Mode C interrogation will reply*. This causes two problems,  garbling and FRUIT.

Garbling is caused by the overlap of replies from multiple transponders. A transponder replies on 1090 MHz in the from of a number of pulses. For Mode A & C, there are at most 12 pulses between a set of framing pulses. When multiple aircraft reply to the same interrogation, these pulses mix up and it becomes difficult to find out which transponder sent which pulse. This leads to false altitudes or false squawk codes.

FRUIT (False Replies Unsynchronised to Interrogator Transmission) is caused by replies that are triggered by other radars. When multiple radars operate in an area, transponders can be quite busy and the radar is easily mislead by a reply to another radar. In addition to the timing (range) being wrong, the reply can be Mode A (squawk code) while the radar interrogated Mode C (altitude). There is no way to see what kind (A or C) reply was sent.

To overcome these problems of Mode A/C, Mode S was introduced. Mode S is quite different from Mode A/C and requires a more sophisticated radar and transponder.

Most Mode S interrogations are addressed; the interrogation contains the unique 24 bit address of the aircraft it is interrogating. This reduces the probability of garbling since other aircraft will not reply
Unaddressed Mode S interrogations will solicit replies that contain the address of interrogator (radar). This prevents FRUIT since the radar can verify that the reply is correctly addressed.
Unlike Mode A/C which does not have any error checking, a Mode S reply contains a 24 bit CRC check code.
Mode S Altitude and identity (squawk) replies have their own identifier so they can be distinguished.
Mode S radars can be operated in clusters and coordinate between them  who is interrogating which aircraft at which time. This further reduces the message load and garbling / fruit probability.

Despite all the enhancements,  Mode S radars are still receiving garbled messages and FRUIT, but are much better equipped to cope with it than a Mode A/C radar due to the addressing and CRC checks.

Since TCAS works on the same frequency as secondary radar, radars will occasionally receive TCAS messages as well. But since these have another downlink format (DF 0, DF 16) they are ignored. The same holds for ADS-B (DF 17 / 18)

Garbling remains a concern. Modern Mode S radars are relatively resilient against garbling due to their narrow beamwidth and advanced degarbling processors. But other systems like TCAS, ADS-B in and Wide Area Multilateration systems with their omnidirectional antennas receive overlapping messages quite often. But when the signal strength of the messages differs the messages can be often untangled with modern digital signal processors.

In the Mode S (& TCAS) a reply can be either short (56 bit) or long (112) bit. ADS-B messages are 112 bit long. Every bits takes  1μs, and there is a preamble that takes 8μs. So a message takes either 64μs or 120μs.

Every second, a Mode S transponder sends 1 unsolicited short squitter, and at most 6.2 long squitters when ADS-B equipped.

*To reduce number of Mode A/C replies, Mode S radars will include an extra pulse when interrogating in Mode A or C, so that Mode S capable transponders will not reply to these A/C interrogations.


How do I have a gravel kit certified as an STC? Any idea how one certifies a gravel kit for an aircraft? I am interested in possibly developing and certifying a gravel kit as an STC.

I am looking for FAA regulations that would be involved in such a project.

The FAA has a nice checklist here.

You should read through the FAA's GUIDE FOR OBTAINING A SUPPLEMENTAL TYPE CERTIFICATE. I assume you are a civilian but,

  This advisory circular (AC) is a certification guide for obtaining a
  supplemental type certificate (STC). It is intended for civilian
  applicants only. We have written it to help designers, manufacturers
  and installers applying for STCs to better understand the STC process.
  The guidance in this AC is general in nature and intended to help an
  applicant gain a basic understanding of the STC process and our
  respective roles and responsibilities.

You will need to fill out this application form and submit it to the FAA ACO office in your area.


What are some unique engineering challenges in designing large, widebody aircraft that do not apply to regional/corporate jets? In terms of appearance, the Embraer 170/190 series aircraft look similar to their larger counterparts.Jets of all sizes have similar ceilings, airspeeds, and life support needs. If Embraer (or any RJ maker) were motivated to do so, could these smaller airframes be scaled up / elongated to fit 300+ pax? What new challenges would be faced in designing a widebody?

Technically, designing and manufacturing narrow-bodies does not differ much from designing wide-bodies. Sure, the scale is different, heavier jet engines, larger factories etc, but in principle the engineering issues to be solved are pretty much the same. Airbus' first design, the A300, was a wide-body. Sure, Embraer and others can utilise their experience for designing and manufacturing wide-bodies.

The real challenge is in the size of the market, and in conquering market share. Only Boeing and Airbus make successful wide-body aircraft. The combined deliveries per year for wide-bodies are a bit over 200 for all types, for narrow-bodies over 1,000, gearing up for > 1,100 in a couple of years.

Image source

Industrial issues to be tackled for starting a wide-body plant:

The investment for designing and starting a manufacturing plant are higher: harder to secure capital.
The market size is smaller: securing a number of unit sales equates to conquering a more sizeable portion of the market than with narrow-bodies.
There are two well-established manufacturers with multiple types each, in multiple variations, cornering all segments of the market.

Very hard to compete here. Much better to scale up the regionals into the narrow-body sector, like China did with the C-919.


Why is tape being applied to this jet engine? When I read this question asking for identification of the aircraft, my immediate question was:

What is that duck tape for?

Whether you call it duck tape or duct tape, why is it being applied to the nacelle?

It's not duct tape. It's speed tape.

  Speed tape is an aluminum pressure-sensitive tape used to do minor repairs on aircraft and racing cars. It is used as a temporary repair material until a more permanent repair can be carried out.

Probably just got a bit of a gap around the cowling or perhaps a loose fastener or two. It's common practice for sealing minor gaps and things until it's next in the hangar for work.

Whilst I was Googling for speed tape, I also found these:

http://www.askthepilot.com/duct-tape/

This is how the wonderful British "tabloid" press deal with aviation stories.  Top marks for getting the "shocked passenger" phrase in.


Does an AME's advertisement on the back of the medical certificate affect the document's validity under the FAA? I know a guy who has a medical certificate from an AME based in Dallas Fort Worth, and the front side of the paper has a side-by-side printing of the front and reverse of the FAA medical certificate (FAA form 8500-9) and the back side of the physical paper containing the front and reverse on one side has the AME's website, name and phone number with an airplane graphic.
In short, the back of the paper is a doctor's advertisement.  I have heard rumor that a local DPE says this would make the medical certificate invalid.
Does anyone know of a regulation, LOI, etc. that would confirm or deny this stance on the medical's validity.  Apparently, this AME is quite popular, so if this is true, then that would mean that many pilots currently hold an invalid medical certificate.
I personally find this hard to believe.

It's an interesting question...
The AME Guide gives the following "advice":

Medical Certificates – AME Completion
(Updated 07-26-2017)

Date the medical certificate to reflect the date the medical examination
was performed, NOT the date of import, issuance, or transmission.
Limitations must be selected from the list in the Aerospace Medical Certification
System (AMCS). Additional limitations may NOT be typed/written in.
Signatures: Each medical certificate must be fully completed prior to being
signed.

Both the AME and applicant must sign the medical certificate in ink.
The applicant must sign before leaving the AME’s office.

Give only ONE certificate to the airman
Use AMCS generated certificates only.
Transmit the exam electronically to the FAA using AMCS within 14 days.
The following are NOT valid:

Copies of medical Certificates;
Typewriter or handwritten certificates;
Obviously corrected certificates;
Paper 8500-8 certificates (any remaining paper forms should be destroyed
by the AME).

Replacement medical certificates must be issued by the FAA.

(Remember, the guide, like the Pilot Handbook, is a guide, not regulatory)
The AMCS also gives:

Certificates will be printed on standard printer paper as a single-sided document. Both the front and back sides will be printed on a single sheet of paper that can be folded.

But as far as I can tell in the FAR, the back side (inside when folded) does not have to be blank. As long as the medical certificate follows the 8500-9 and is in a "form prescribed by the Administrator", then it is a valid certificate.
Technically, even if it was against the rules, the medical certificate wouldn't be invalid, just the paper evidence of it would be. As long as the data was entered into AMCS, which it is required to be, the certificate can be reprinted in the proper format for showing anybody who asked.