Why did the CL-400 Suntan have engines on the ends of its wings? I've been reading more about the development of the A-12, which in turn referenced the CL-400 Suntan. I noticed that the engines are located at the end of the wing, rather than integrated with the fuselage or on the midpoint, which is not something I've seen (or at least noticed) on any other aircraft (the closest thing I'm aware of is tip jets on helicopters). What is the design rationale behind locating engines on the end of the wing, and indeed for other locations?

The Suntan project needed all fuselage space to hold three tanks for liquid hydrogen, so the engines had to be placed somewhere else. Placing them near the fuselage would put them in the range of the fuselage's shock waves. Putting them out on the wing would help with wing bending relief and ensure a clean intake flow. Once they are so far out, you can as well put them on the wingtips, so that they do not cause a pitch-up moment. On the SR-71, the engines were also placed outside the fuselage and into the wing's plane, much for the same reasons.

Keeping the intake flow uniform is paramount for the undisturbed operation of supersonic intakes, and I assume that Kelly Johnson wanted to make sure that the engines would not suffer an unstart when flying reconnaissance missions over hostile territory. With the little experience in supersonic flight in 1955 it was prudent to avoid built-in pitching moments - after all, the supersonic L/D likely was in the single digits, so an out-of-plane engine placement would had produced more moment than on subsonic aircraft.

Hydrogen was selected to achieve the highest possible flight altitude, so the aircraft would be safe from surface-to-air missiles for as long as possible. I initially thought that the wingtip location would enable to cool the hot wing structure by heating up the hydrogen on its way to the engine, but heating was planned to be done with bleed air in a special heat exchanger. Quoting www.history.NASA.gov:

  The CL-400 design divided the hydrogen tankage into three sections;
  the forward tank had a capacity of 67 000 liters; aft, 54 000; and
  center (sump), 15 000. The two main tanks were kept at 2.3 atmospheres
  pressure and the sump tank slightly lower for fuel transfer. In the
  sump was a booster pump, built by Pesco Products, that supplied liquid
  hydrogen to the engines at a pressure of 4.4 atmospheres. The engines
  were mounted at the wing tips, which meant that the liquid hydrogen
  had to pass through a hot wing with surface temperatures up to 436 K.
  The design provided a vacuum-jacketed, insulated line for this
  purpose.

Regarding the perceived danger of using hydrogen, www.history.NASA.gov says:

  Tests were devised in which tanks containing liquid hydrogen under
  pressure were ruptured. In many cases, the hydrogen quickly escaped
  without ignition. The experimenters then provided a rocket squib (a
  small powder charge) to ignite the escaping, hydrogen. The resulting
  fireball quickly dissipated because of the rapid flame speed of
  hydrogen and its low density. Containers of hydrogen and gasoline were
  placed side by side and ruptured. When the hydrogen can was ruptured
  and ignited, the flame quickly dissipated -, but when the same thing
  was done with gasoline, the gasoline and flame stayed near the
  container and did much more damage. The gasoline fire was an order of
  magnitude more severe than the hydrogen fire. The experimenters tried
  to induce hydrogen to explode, with limited success. In 61 attempts,
  only two explosions occurred and in both, they had to mix oxygen with
  the hydrogen. Their largest explosion was produced by mixing a half
  liter of liquid oxygen with a similar volume of liquid hydrogen.
  Johnson and Rich were convinced that, with proper care, liquid
  hydrogen could be handled quite safely and was a practical fuel-a
  conclusion that was amply verified by the space program in the 1960s.
  At the time, however, Johnson and Rich filmed their fire and explosion
  experiments to convince doubters.

When work on Suntan started, liquid hydrogen was a laboratory curiosity. Preparing the infrastructure needed for operating the CL-400, the Suntan project led to the building of large-scale liquid hydrogen plants. Their availability paved the way for the cryogenic rockets of the Apollo program!

Interestingly, a similar engine location was selected by the Russian design bureaus Tsybin for their NM-1 and Myasishchyev for their M-50 supersonic bomber in the mid-50s. It was started after news of the US Weapon System 110 (which later led to the XB-70) reached Russia and was similarly cancelled after two prototypes had been built and only one aircraft had flown.

M-50 during display in 1961 at Tushino airshow (picture source). Note the similarity of the Mig-21 and M-50 planform - both originated from the same work done at TsAGI.

Placing the outer engines below the wing would had caused ground contact on rotation. Speaking of rotation: The M-50 had two central gears and the bomb bay between them, and the main gear had to be placed so far aft that the M-50 could not be rotated the usual way with the elevator. So the engineers devised what they called the "galloping bicycle". When the aircraft reached 300 km/h, the forward gear rapidly extended to rotate it to 10°. Placing the outer engines B-58-like below the wing would had required an even longer gear.


First airplane to use a flight simulator? Icarus, Pegasus, da Vinci's flying machine and Wright brothers airplane probably didn't have a flight simulator, since computer science was not yet developed enough (Antikythera ancient analogue computer in 70BC, Wright brothes until 1948, ENIAC introduced in 1946).

So, which bird was the lucky one, to first be accompanied by a flight simulator?

According to the Oakland Aviation Museum the first known was a simulator to learn to fly the Antoinette monoplane, although they don't provide any references for this, so I can't say that is entirely true.

The link trainer is the best known trainer and they were built in 1927 by Edwin Albert Link. They were used to train Army Air Corp pilots for instrument training in all weather conditions. The link trainer continued to be the sought after training device in WWII as well training almost all US Air Force Pilots.Link

If I find more information I will update my answer as best as possible.

I know typically answers on Wikipedia aren't the best but this one is littered with references that would take entirely to long to search out for ones self.


What is this tube along the right side of a Blue Angel? I was at the Museum of Flight in Seattle, WA, yesterday, and came across a Blue Angel aircraft, pictured below.

Along the right front of the plane, there is a small tube that is capped with a silver cap.

I thought at first that this might be a refuelling point, but (A) I didn't see any real purpose to have mid-air refuelling on a Blue Angel, and (B) it doesn't seem like a great place to refuel (since it seems like it could easily obstruct the pilot's view).

(I looked online at some images of Blue Angel aircraft and realized there are several makes. However, I didn't find this particular tube and cap on any of the other makes. (example) In fact, I don't even recall what make of Blue Angel this craft actually is.)

What is this tube at the front of the jet, and what is it used for? Why does it only appear on some makes of the jet?

The aircraft is the A4 Skyhawk and the probe is for air-to-air refueling.

As you can see, it doesn't really impede the pilot's view which in any case, is concentrated on the refueller.

You can always spot a refuelling probe. For NATO aircraft, and most others, they always have the same tip and are the only appendages which look like this.

The Blue Angels used it since transits to various air shows exceeded the range and air-air refuelling is cheaper and more effective than landing, refuelling and taking off again.


How does fuel flow and altitude affect the compression ratio of jets? Does the compression ratio of jet engines change with altitude and/or with the rate of fuel flow?

the compression ratio of a conventional gas turbine is a strong function of the rotating speed of the engine; note that at near-zero speed, the compression ratio of a gas turbine is essentially 1:1 and the engine will not run- even if some means is provided to alter the pitch of the compressor stage fan wheels.

density altitude also enters into the picture, inasmuch as beyond a certain altitude, there is not enough oxygen available to allow the engine to develop full rated power- and beyond that point the engine's power rating falls off with increasing altitude.


Do Jeppesen SIDs have top altitude? FAA SID charts show the top altitude, the maximum altitude you can climb to when cleared for the SID. Do Jeppesen SID charts also show the top altitude? I checked some of them but couldn't find it. If Jeppesen charts do not show it, how do you know the maximum altitude for SIDs?

You ask about Jeppesen in the title, but you mention ICAO in the body.

Does Jeppesen show top altitude? Yes.

Top image is FAA chart, bottom is Jeppesen. Both for the LOOP SID.

Does ICAO show top altitude? The ICAO charts are produced by NAAs based on ICAO's style if they don't have their own. The FAA has its own format. But the answer is also yes if the top altitude is used.

The top altitude was added for the climb-via instruction, which is a recent addition. Not all states (nations) follow the climb-via and descend-via system just yet. But those who do, will have that information.


What makes flight recorders harder to find than tagged sharks? It really bothers me that we can't find planes that weigh tons with black boxes (AFAIK) technology that's almost obsolete, on the other hand shark tags (AFAIK) work great for long time and we can monitor shark movement, depth, temperature, etc., all the time. So, why?

They're different usage cases, and have to be engineered differently. Three major points:

A shark tag doesn't have to survive a 500mph impact (#7 on the list) with the ground, and a flight recorder has to be able to do so. It adds a lot of padding and weight, and limits the kind of battery that can be used.

Sharks also don't dive to a depth much greater than 3000 feet on most occasions. A planes flight recorder is designed to survive to a much lower depth, under much larger amounts of pressure. Not to mention being designed to survive all sorts of other things.
Another point regarding depth, it is much harder to search for a signal at a depth of 15,000 ft, than it is even at a depth of 5000 ft. This article shows how big of a difference you get between even 20 meters and hundreds of meters (not thousands), it gives a good idea of what I mean.

If a shark tag fails, nobody cares. If you tag 100 sharks and 30 of the tags survive, you still have some pretty good data. But if one airplane crashes and its black box fails, it's considered unacceptable. They are required to survive 100% of the time.

All of these differences combined mean that black boxes are manufactured to much higher standards, and as a result they are bulkier, have different sorts of radios and require much more battery life (to support the larger systems) than a shark tag. All this conspires with the difficulty of getting a receiver deep into the ocean to make finding FDRs/CVRs really difficult.
That's not to say they couldn't design one that is much better, it just becomes extremely expensive (as all things are on airplanes). And you have to determine if these edge cases (like flight MH370) are worth making an airplane a few million dollars more expensive (between R&D and certification, the later being quite expensive).
I think the theory was they should be able to find any one of these within a month, and that may take some rethinking (maybe 3 months, or a year perhaps?) But they'll never be as successful as shark tags just because the requirements to be able to find one at that depth 100% of the time are quite different from the needs of a shark tag.


Jet engines: are they owned by the airline or just rented? For commercial jets, the engines are complex parts of the aircraft, are the most expensive components, and must be carefully maintained.

Source

When a company buys an aircraft, do they also own the engines, or are they still the property of the engine manufacturer? What happens when an engine must be exchanged?

These days, engine manufacturers are not any more in the business of selling engines, but selling thrust.

Rolls-Royce were the first to offer this, and today most Rolls-Royce engines send telemetry data to four centers, the biggest one in Derby, in Great Britain, where every engine is under surveillance. An inspection can be scheduled at or spare parts can be directed to the right destination even before the pilots or the airline know that one of their engines has a problem.

By now, 80% of Rolls-Royce engines are sold at a loss which is recouped by a hourly fee paid under the TotalCare (.pdf!) program, and that center in Derby is monitoring maybe 4000 of them at the same time. Rolls-Royce has accumulated a treasure of engine operations data, which enables it to consult airlines on best practices. This makes it very hard for a third party to steal maintenance business from Rolls-Royce. All maintenance cost is covered by the TotalCare fee which now accounts for more than half of Rolls-Royce's revenue.

GE and Pratt&Whitney have similar programs. In GE's case, it is called OnPoint, sold as "Power by the Hour". The airline does not pay for the engines, but for the time they are flying. Now the engine manufacturer has a strong incentive to improve the reliability of its engines, but also a strong lever to push out third-party maintenance providers.


Why does flight training usually start with (unsafe?) propeller planes and not with (safer?) jets? I live in the UK and would like to learn flying jets, but most courses seem to start with propeller planes.
Not sure if this might be a misconception about the safety of different aircraft types, but I remember having read or heard somewhere that small propeller planes are, well, less safe than jets; maybe because they are more fragile and less powerful than jets when it comes to bad weather and are also difficult to recover from dangerous situations... not sure and cannot find the reference for now.

But also doing a quick search for popular aircraft types, the propellers like Cessna seem to have huge numbers of crashes/incidents compared to jet engine aircraft.

So the question is - why are propeller planes favored in training e.g. for the Private Pilot License? Is it simply because they are cheaper and wouldn't be such a huge loss of they crash?

Are there any alternatives where I could start with a jet engine?

Light Propeller Aircraft, if flown within their design limits, are just as safe as jets. If you do a proper and thorough daily inspection, you are far less likely to suffer any form of mechanical failure in the air. In saying this, the majority of all crashes, be it in a Jet Powered Airliner or a Propeller Driven Light Aircraft are caused due to pilot error.

You start out learning in a light single as:

They are lighter, and slower and can usually take the beating handed out by inexperienced pilots, this being:

Hard landings
Slipping onto the runway
Just hammering the day lights out of the engine.

Jet Aircraft are extremely expensive, and generally fairly heavy. Inexperienced pilots generally pay AU$80,000 for a Commercial Pilot License (In Australia) which qualifies you to fly single engine aircraft not over 5,700kg under the VFR by day. This is an absolute, level entry qualification looking for a job (most people will find that they at least also need a night VFR rating or a MECIR), so to add the cost of doing training in a jet on top of that, even if it is just for PPL, will be massive.
Jet Aircraft will be insured to be flown by pilots who have an amount of total experience and experience on aircraft/engine type. So, again, unless you're willing to pay the massive excess and premiums to be put on the insurance, you're going to have to fly a prop.

Now, you have identified that a lot of crashes are light singles (i.e. Cessna). This is because generally, these aircraft are not flown with the same discipline as a Jet Aircraft. Also, the pilots flying them are generally lower hour pilots who do not have as much experience (again, this is a generalisation, not an exact figure of the total community).

As for starting in a Jet, I honestly doubt that there is any flight school on the planet that will allow you to start training in a Jet (Even Fighter Jet pilots start out flying tiny little single engine aircraft).


Why do helicopters crash in low visibility (IMC)? There are no known direct eyewitnesses of the crash of helicopter flight Sikorsky S-76B N72EX with 9 people on board, including Kobe Bryant. However, there are many earwitnesses who heard the helicopter flying over their heads, but weren't able to see it due to extreme fog at the site, shortly before it crashed into a hill. Therefore, extremely low visibility was the probable cause of this helicopter crash. By assuming that, here's the question:

Why do helicopters crash in low visibility (instrument meteorological conditions IMC)?

For instance, what are current theories about the sequence of events of the helicopter crash of flight N72EX, assumed the crash happened due to the low visibility on site? Why did the pilot suddenly increase altitude above Ventura Freeway 101? And why didn't he follow freeway 101 by GPS (on this high altitude), although he was a certified IFR pilot flying under special VFR? And after his ascent, why the slow turn to the left followed by a sudden increase in speed while diving into the hill at about 4000 feet per minute? (Primary source: Flightradar24) (Note: ATC recording doesn't provide much useful information...)

[Note: I'm not interested in the many different theories or speculations about the crash of flight N72EX, just what are the most probable events that lead to the crash, if it was indeed caused by low visibility? Btw the crash flight N72EX was just used as an example. Actually, any other helicopter crashes caused by low visibility could be described in details as well, if they contribute to answering the main question. Please answer by using primary and secondary sources as well as some logic, physics/aerodynamics and psychology, thanks.]

The only flight rule that will completely eliminate human error is to ban people from flying planes or programming UAVs.

More regulations won't solve this.  Aviation is already strictly regulated.

As for why the pilot did not climb, well, you will have to ask him.

Keep in mind that a mechanical failure could be to blame.

We just don't know.

Answer to the previous question:
The risks of continued visual flight into poor conditions are already pretty well documented.  It is a serious hazard for all flying machines, not just helicopters.  We don't know if that is what caused the crash or is even a contributing factor, though some of the makings of a CFIT accident are present (bad weather, possible perceived pressure to go, and possible complacency due to familiarity with the area).  Anything we say here, including what I just typed, is pure speculation.

We don't know why the helicopter crashed and we will likely never know for sure.  It was not equipped wIth a CVR or FDR nor was it required to be so equipped.

This is a tragic accident and that's all we know.


The F/A-18 Hornet and MiG-29 ailerons from the external parts of the wings go up some degrees in flight. Why? In some parts of the flying envelope of the F/A-18 Hornet and MiG-29  the ailerons from the external parts of the wings go up in sync. They're made to go one up one down in order to get rolls, not up/up .

https://m.facebook.com/story.php?story_fbid=548605942390983&id=148530445855064

The pictures in the question show the normal position of the MiG-29 ailerons. That's how they are unless a roll is commanded.

According to Mikoyan Mig-29 Fulcrum Pilot's Flight Operating Manual (google books) the slight upward position is set to improve yaw stability during roll meneuvers:

As for whether this angle (neutral position of ailerons) changes in accordance with flight envelope: it does not. Check out this and this Youtube video for an example. Climb, dive, straight and level, no change. The position of the ailerons is not affected by load factor either, as you can see below, 1g (straight & level flight):

... and a pull of 3g's:

(Source: the second Youtube video posted above)

Whenever you see the ailerons move, it is always accompanied by roll.

As for the F-18, I'll investigate and be back later.
(edit: as a preliminary claim I'd say the F-18 drops flaps a few degrees on high g maneuvers to increase camber, but the flaperons only move when roll is comanded or flaps are lowered. So no flaperon up with high g)


Can a CFI give training outside the US in a non-N registered aircraft? My question is if a US CFI can give instruction in other countries with an airplane that's not registered in the US (N) (as long as he has certifications to fly those airplanes in other countries)?
Must he be a flight instructor as well in those other countries where the airplane is registered?
The perfect example would be a US CFI who is also rated as a CFI in Argentina.
Can he give a Flight Review or training required towards a US PPL certificate in Argentina (with an airplane registered in Argentina)?

I can not find any prohibition against a US FAA certificated flight instructor giving instruction in a foreign country for a US FAA issued pilot certificate or endorsements. Title 14 of the Code of Federal Regulations Part 61.51 specifically allows a CFI to give instruction in a foreign aircraft registered in a country that is a member state of ICAO. Part 61.41 specifically allows a foreign CFI from a country that is a member state of ICAO to give instruction.
So, this implies that a US CFI can give instruction in a foreign country for a US FAA issued pilot certificate or endorsements. Just as long as the CFI has authorization to fly the foreign registered aircraft in the country of question. Depending on the country, they may need authorization to fly for hire. Depending on the country, they may need authorization to instruct as well. This may only apply to instructing for the issuance of a certificate or endorsement for that country.
So, at the very least, instructing in an aircraft of foreign registry in a foreign country for a US certificate may only require foreign validation of the CFI’s pilot certificate. But, maybe not their instructor certificate.

§61.41 Flight training received from flight instructors not certificated by the FAA.   (a) A person may credit flight training
toward the requirements of a pilot certificate or rating issued under
this part, if that person received the training from:
(1) A flight instructor of an Armed Force in a program for training
military pilots of either—
(i) The United States; or
(ii) A foreign contracting State to the Convention on International
Civil Aviation.
(2) A flight instructor who is authorized to give such training by the
licensing authority of a foreign contracting State to the Convention
on International Civil Aviation, and the flight training is given
outside the United States.
(b) A flight instructor described in paragraph (a) of this section is
only authorized to give endorsements to show training given.
§61.51 Pilot logbooks.   (j) Aircraft requirements for logging flight time. For a person to log flight time, the time must be
acquired in an aircraft that is identified as an aircraft under
§61.5(b), and is—
(1) An aircraft of U.S. registry with either a standard or special
airworthiness certificate;
(2) An aircraft of foreign registry with an airworthiness certificate
that is approved by the aviation authority of a foreign country that
is a Member State to the Convention on International Civil Aviation
Organization;
(3) A military aircraft under the direct operational control of the
U.S. Armed Forces; or
(4) A public aircraft under the direct operational control of a
Federal, State, county, or municipal law enforcement agency, if the
flight time was acquired by the pilot while engaged on an official law
enforcement flight for a Federal, State, County, or Municipal law
enforcement agency.
§61.195 Flight instructor limitations and qualifications.   A person who holds a flight instructor certificate is subject to the
following limitations:
(a) Hours of training. In any 24-consecutive-hour period, a flight
instructor may not conduct more than 8 hours of flight training.
(b) Aircraft Ratings. Except as provided in paragraph (c) of this
section, a flight instructor may not conduct flight training in any
aircraft unless the flight instructor:
(1) Holds a flight instructor certificate with the applicable category
and class rating;
(2) Holds a pilot certificate with the applicable category and class
rating; and


What is the optimal sequence of departures and arrivals on a single runway? When in a peak load scenario with plenty of departing & arriving aircraft to keep the ATC pipeline full, are there considerations that make a certain sequence of Departures / Arrivals that optimizes throughput?

For specificity, let us assume a single runway in use and no general aviation aircraft with predominantly jet traffic and multiple runway entry & exit taxiways available. Including high speed exit turnoffs.

I typically see a sequence something like:

 Dep-Dep-Arr-Dep-Dep-Arr

But an alternative optimum might turn out to be:

Dep-Arr-Dep-Arr-Dep-Arr

etc.

I realize that the specifics will depend on the exact aircraft etc. but just to use an idealized model what would result from typical operating constraints. e.g. You need to allow a certain separation during approach but you can have multiple aircraft lined up for take off. So is the potential to squeeze departures into the "holes" higher? Also, you can clear a second departure after a first far more rapidly, than the landing-to-landing interval right?

Just wondering, if you had to set up a formal optimization model what sort of parameters & constraints should go into the model as inputs.

A follow up question: Say you had two runways available in parallel & widely spaced apart. Does it make sense (for throughput) to dedicate one to landings & another to takeoffs or is it more efficient to mix landings & takeoffs on both runways?

R18L: Dep-Dep-Dep-Dep-Dep-Dep-Dep-Dep-Dep
R18R: Arr-Arr-Arr-Arr-Arr-Arr-Arr-Arr-Arr

vs

R18L: Dep-Dep-Arr-Dep-Dep-Arr-Dep-Dep-Arr
R18R: Dep-Dep-Arr-Dep-Dep-Arr-Dep-Dep-Arr

PS. If further simplifying assumptions are necessary, let's imagine a hypothetical airport serving a single aircraft type, say A320 only. Or assume any type you will to be representative of a wide class of aircraft just to get the modelling started.

Usually a mixed usage runway is more efficient than a dedicated arrival runway(s). Arrivals are harder to get closer together than departures as well. Running a final with 5 mile gaps(for wake and all departures) is a good way to do dep-arr-dep-arr.

With dedicated Dep-Arr runways, and assuming you have aircraft ready to go, your expected hourly rate for Arrival only runways is usually around 30, whereas with a departure only runway the rate is about 45 or so(assuming minimal spacing, and have decent fan headings, and the departure routes are split decently to allow good separation heading to the center).


What do "azimuth window" and "compass switch" refer to in this accident report? I recently read the accident report on BEA 548, but I'm unsure of some technical terms used on p. 4 of the report (p. 14 of the linked PDF):

  Apart from the probability that in the particular conditions he would
  have elected to handle the aircraft himself, an examination of the
  lamp filaments in the P1 'azimuth' window showed that at the time of
  the crash the compass switch was turned to port, thus indicating that
  P1 was flying.

My question is:  What are the "azimuth window" and "compass switch" in this context?  Was the HSA Trident equipped with some sort of flight control transfer system between the P1 (captain) and P2 (flight officer) seats?

They are autopilot controls are visible in this clip from the Wikipedia cockpit picture:

Source: Wikipedia

Airliner avionics have independent left and right systems for the captain and first officer. But, in many aircraft, there's only one autopilot. It's not a critical system and the crew can hand fly the plane.

The autopilot controls allow it to be set to receive data from either side. Standard procedure is for it to be set to the side of the pilot flying so it follows what the pilot flying sees. The pilot not flying can monitor the flight on their displays and detect any deviations.

Note the switch at bottom center with the option to select Port or Stbd.


Is there a website with a list of all commercial airline incidents? I am looking for a website that contains a listing of all commercial airline incidents (under a sufficiently large definition of "incident"), by airline company.
I assume that incidents that happen are logged automatically somewhere, and I presume that this information may be further relayed to a public website.

Here's my finding so far:

I know of the ASRS database, https://asrs.arc.nasa.gov/search/dbol/strategies.html, but this doesn't list airline names, as far as I could see (and is also tricky to navigate).

The 3 other more usable website, that don't report just accidents, but also incidents (whatever they define as "incident"... meaning sites like http://aviation.globalincidentmap.com/ are excluded) are

https://aviation-safety.net/

http://avherald.com/

https://www.aeroinside.com/

Are these sources credible?

E.g. http://avherald.com/ states in their FAQ that they compile their report based on "own sources". https://www.aeroinside.com/ says, after some looking, that it's information is compiled from multiple other databases, but doesn't specify which. https://aviation-safety.net/ seems the most legit of these (excepting ASRS), but again, official assurances are missing.

I'm asking this, because I'd like to compile for myself some flights statistics (I'm a statistician by profession) and I'd like some site sthat are easier to navigate than ASRS (recompiling their data in a form amenable to statistics would be very time-consuming).

Each jurisdiction or organization will have its own reporting system, not all will provide that information to the public. News, social media, and websites provide information but more research is required to determine which parts are accurate.
https://aviation-safety.net/
The Aviation Safety Network is probably your best bet for both completeness and accuracy. The database is fairly comprehensive, contains events as far back as 1919, and lists sources. You can browse by date, location, and aircraft type. The Wikibase allows users to add incidents, providing coverage of many more small aircraft incidents but may be less accurate.
https://avherald.com/
Avherald strives for accuracy but is far from complete. Information is not reported without reasonable verification, sources are provided when possible. The team sometimes even has access to the radar data to provide more insight. Many news outlets use this as a source. Entries go as far back as 1999, but the items are intended to provide information on accidents and an overview of the types of incidents occurring worldwide. This will make any statistical analysis hard.
https://www.aeroinside.com/
AeroInside appears to just copy from Avherald and put the entries in a fancier format with ads and make them a bit more searchable.


At what speeds can an airplane land? I have read people's stories that they landed their small planes (e.g. C172) on bigger airports. They strongly recommended landing at a higher speed and without flaps as the runways are quite long, and there is traffic behind them.

Hence, if I want to land an airplane at higher than recommended landing speed (e.g. VS0):

How fast can I go?
What is the procedure to do this?
What consequences are there (good or bad)?

Note: Much of this material, and more, is also covered in answers to the question:
Can you fly a light GA airplane into a major hub? (Didn't know that at the time I wrote this answer.)

Landing at higher than normal speed is not recommended.

Tricycle gear airplanes require a nose-high attitude on touchdown in order to ensure the main gear touch down first. The nose gear is not designed to support initial touchdown forces. In many typical small planes, forcing the plane onto the ground at too high a speed will strike the nose wheel first, risking a collapse or prop strike.
At high speed, the control surfaces and wings are still capable of producing significant aerodynamic forces. If you've forced your wheels onto the ground, you may be producing a lot of torque with the elevator, again, risking gear collapse.
Kinetic energy is proportional to the square of your velocity. And crash damage -- both to the airplane and to its passengers -- is proportional to energy. If you do collapse the gear or lose control, you're going to have a lot more energy to dissipate. And if that energy is dissipated by your body, it's going to hurt. A lot.
You might overheat your brakes, causing brake pad/rotor damage or even a fire (I'm aware of at least one instance of a Piper Cherokee catching on fire because the pilot attempted to take off with a half-stuck parking brake.)

It is true that you will sometimes be pressured by controllers at large airports to keep your speed up as much as possible on approach. It's hard for them to sequence you when you're only flying half as fast as the guys in front of and behind you. The important thing to remember is that this is their problem, not yours. There's no FAR that says you must hot dog your airplane in order to fit in with the big boys.

Here are some things you can do safely to make everyone's job easier when operating at large/busy airports:

Practice your controlled-airport/airspace proficiency.

Know, and use, standard ATC phraseology.
Listen carefully for your callsign. Don't make them repeat themseleves.
Have a plan in advance, know what you want, and make sure you communicate that to them clearly.

Have the airport diagram handy, and study it before the flight so you know where you'll be taxiing and won't mess up ground operations. Ideally you should be able to taxi on your own, but if you're not comfortable when you get your taxi instructions, request a progressive taxi.
Know your airplane and its capabilities. Fly your approach at the highest practical speed, but no faster. Know how fast you can go on a 3 mile final in order to be able to decelerate to normal short-final and touchdown speeds.

If you're not comfortable with your proficiency in these areas, consider getting some more practice before attempting a flight to a "major" airport. Or, bring a CFI along with you who can help you out and give you pointers.

The bottom line is under no circumstances should you compromise safety in order to please ATC or the airline pilot behind you. As long as you are proficient and do your best to accomodate ATC's requests within the safe capabilities of your airplane, you'll do just fine. (In fact, I've found controllers at major airports to often be very pleasant to work with.)


Where does the oxygen come from in the deployable breathing masks? I don't know what they are called. In case of emergency like smoke they deploy, but where do this oxygen come from.

The oxygen is provided through Chemical Oxygen Generators. Oxygen masks are triggered either automatically given certain conditions or by the flight crew.

Oxygen generators are usually installed in above each seat row. If the cabin altitude reaches a predetermined height (14,000' is standard) or if the system is activated by the flight crew, overhead panels open and oxygen masks drop out. To put the mask on, it is necessary for the intending user to pull it down and this action releases the firing pin and activates the generator.
The oxidizer core of an oxygen generator usually consists mainly of Sodium Chlorate (NaClO3) mixed with <5% Barium Peroxide (BaO2) and <1% Potassium Perchlorate (KClO4). This core is activated by the application of heat generated usually generated by a mixture of lead styphnate and tetracene which itself is activated by a small explosive charge in a percussion cap are a mixture. This explosive charge is set off by the release of a spring-loaded initiation mechanism which is restrained until released by a pull on the lanyard which is visible when oxygen masks are released from overhead panels. Once activated, the chemical reaction and production of oxygen will continue until the generator has been exhausted which is typically in the range 12 to 20 minutes.


Why are the Boeing 747-8 engines on the wings spread apart? I ask this because the Boeing 747-236 had the engines close together while the 747's have them spread apart. Does it have anything to do with the amount of thrust of the aircraft?

Look at how spread apart the engines are:

Now look at how close together those engines are on the Boeing 747-236:

That picture of the 747-200 you have with the engines in a pod together like a B-52 is a movie prop. http://www.airliners.net/photo/Boeing-747-236B/1070481/

All real 747s from the -100 through the -8 have their engines positioned like the first picture.

EDIT - Federico's response reminded me of another aspect of the engine position, and to answer your original question of why they're spread apart. Spacing between the 747s engines is important due to the need to maintain sufficiently clean airflow into the inlet. If the engines are too close together, they're essentially competing for the same amount of air, and at high power settings, the interaction between the two fans will disrupt their operation, potentially causing engine stall/surge. Additionally, the 747 uses thrust reversers, and the spacing between the engines helps ensure that the reverse flow from each engine doesn't impact an adjacent engine, for the same inlet distortion reason.

I assume, though I don't know the details of this, that the B-52 can have them that close together because they've shown that the inlet geometry, airflow required by each engine, whatever other magic of fluid dynamics that I know nothing about, prevents the engines from distorting each other's airflow enough to cause an issue. The 747 engines require a lot more air, and generate a lot more thrust, and are potentially more sensitive to inlet disruption than the engines on the B-52. This last paragraph is mostly a guess on my part as I'm not an aerodynamicist, but it's inferred from issues we've had to deal with on the 747 and other related airplanes.


What is the legal situation if a passenger dies in mid-flight? Reading this question, a new one came to my mind. That question is explaining how an airline behaves in that unfortunate situation. However, what are the legal consequences?

Concretely I would like to understand the following situations?:

Only a doctor can certify the death of a person. If no doctor is present in the flight (or all doctors have been dragged off due to overbooking), how is the death certified? On the ground I guess.
Can the passengers leave the airplane or they will need to wait until the authorities get inside?
Which country will be liable for any potential criminal investigation (if applicable)

Unfortunately, having been on board in this situation I can tell you what happened on board my flight:

The deceased was covered and secured in the seat.
The passenger sitting next to the deceased were relocated.

Needless to say, it was a very somber flight. No announcements were made to the effect, but for the people sitting around the rows, it was very sobering.

The aircraft landed and everyone was told to remain in their seats. ER staff along with a bunch of other personnel came onboard.

The body was removed.

Passengers were deplaned.

Years later, I was watching an episode of Ultimate Airport Dubai where an Emirates flight suffers a similar tragedy where a business class passenger is found unconcious.

In addition to the normal scenario on board that I faced, the documentary revealed that:

The crew was changed
The person was pronounced dead by the local authorities


Can the Apache detect infrared (IR) lock? Can the Apache, regardless if it's the AH-64E/D (US) or AH1 Longbow (UK), detect IR lock?

I am aware that the Wildcat AH1, Merlin HC3/4 and AH1 Longbow share the same defensive systems that can detect IR missile launch. However, I have yet to find any information suggesting any of these aircraft can detect an IR lock from a fire control system of another aircraft.

I think I have answered my own question from a little bit of research.

Warfare systems such as Laser and Radar are detectable because they are active emissions (i.e. They have to make their own emission, wait for it to reflect back, then lock onto it).

Visual and Infrared are not easily detectable because they are passive. The IR Launcher or TV-Guided missile only requires the targets emission to lock onto, not its own in the example above, so there is no way you can detect being locked onto.


Why does the elliptical wing planform have two different types of curves? Generally, I have seen that the planform of an elliptical wing consists of two different types of elliptical curves
The elliptical curve towards the leading edge has a lower value for semi-minor axis and the curve towards the trailing edge has a higher value of semi-minor axis
What is the reason for such a geometry?
(Image is attached for reference)

It's because the center axis for the ellipses has to be along the thickest section of the wing, because there is also a taper in thickness that must be accommodated as the ribs get smaller and smaller toward the tip.  In your sketch, the thickest section is at 40% of chord and the taper in both planform and thickness must be oriented to that 40% chord line, hence the asymmetrical curves.
The placement of the axis of maximum thickness is a function of the particular airfoil selected, that is, the point of maximum thickness of the airfoil section itself.  For structural efficiency, this is normally also the location for the main spar. In the sketch, which resembles a Spitfire wing planform, the broken line will be more or less the main spar location, with the nose ribs on the left and the main ribs on the right, with the ellipse curves placed to maintain the 40% forward/60% aft ratio out to the tip.
If the thickest section of the wing was at 50% of chord, then the ellipses would be symmetrical.


Doppler shift in appendix G of ATSB report for the MH370 incident Two people provided answers to my previous questions:

What is the nominal frequency of the satellite communications terminal on MH370?
How does one interpret the satellite data on flight MH370?

And they referred me to Appendix G. "Explanatory Notes on BTO and BFO Analysis".

Now I have questions about Appendix G.

The report (Appendix G) says that the Doppler shift from the satellite (down-link) to GES depends on the satellite movement with respect to GES, since the satellite is not exactly stationary.  But in Table 6. the Down-link Doppler frequency varies, from the satellite to GES depending on the aircraft Latitude. Why should the Aircraft Latitude affect the DeltaFdown Doppler frequency shift?
And another question is about the Down-link doppler-shifts, from the Satellite to GES, given in Table 5. The listed Doppler-shift in frequency is -75.1 Hz for UTC time 17:07. However, I can only derive this frequency using the satellite velocity for UTC time 16:55:00?  The calculated frequency differs slightly from the one in the report.

1. Why should the Aircraft Latitude affect the Doppler frequency shift?

It seems to me that table 6 is a check to test whether the equation on page 55 can reliably be used to predict the possible locations of an aircraft from a measured BFO. It does this by using the equation to predict what the BFO should be for a given set of inputs and comparing that with the measured BFO. To see how reliable this is they vary one of the parameters, latitude in this example, to show that the predicted BFO is considerably different for different latitudes and that the best match of predicted BFO to the measured BFO is for the known location of the aircraft. Therefore you know that the BFO is useful - it can be used to rule out some locations.

If you hold constant all the other factors and vary latitude why should that affect BFO?

I guess it's because for the same aircraft heading (with respect to true north), different latitudes but same headings mean different angles of flight with respect to the satellite. That means that there are different magnitudes of component of velocity that is parallel to the line from satellite to aircraft - those different magnitudes represent different speeds in a line directly away-from or directly towards the satellite. This affects doppler.

Note: The above doesn't explain why ΔFdown varies with aircraft latitude.

Other independent analyses of this data

Dr Richard E Cole, University College London
Dr Duncan Steele (who asks the same question)

I'm pretty sure Duncan Steele is smarter than me, so you may be on to something.

  2. However, I can only derive this exact frequency using the satellite velocity for UTC time 16:55:00?

That's more of a statement than a question. I guess your question is:

  why do my calculations give a different answer?

I see two possibilities

you made a mistake.
the ATSB made a mistake†.

In order for readers to help you with the first or confirm the second, you'd really have to share your calculations with us.

† And presumably Inmarsat, the NTSB, the AAIB and others.


What did the controller say during my approach to land (audio clip)? I recorded this ATC audio clip during a recent flight.

I'm not sure but he may be saying,

  6CP, cancel lining clearance......(missing)....traffic will be in position.

Can you complete this transcript? And I don't understand what "cancel lining clearance" is...

I think this is what the controller is saying:

  November Six Charlie Papa, cancel landing clearance. I'll have it back for you in a mile or so, traffic will be in position.

We can infer from this that the aircraft he's talking to (shortened callsign N6CP) has previously been cleared to land. But sometime since the controller decided to have another aircraft to line up and wait "in position" on the runway. The controller is now canceling that landing clearance, because he can't clear an aircraft to land while that aircraft is waiting for departure. And he's letting N6CP know that by the time they get 1 mile closer to the runway, he's anticipating that the waiting aircraft will get cleared for takeoff and N6CP will be cleared to land (again).


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

In the video it is clear that the jet takes off and lands with all these 3 things "open/stretching out" (so it seems to fly just like that - not retracting them).

Here is Wiki on that model.

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


Why have converging runways? This is Ramstein air base in Germany,

Why would you want to have runways converging (or diverging) like that, doesn't seem to do you much good in terms of parallel usage (either the approach, or the go-around would be exciting).

The only reason I can think of is that it gives you more separation when launching aircraft in rapid succession, but then again only in one direction. And it's not like the military would bother much with separation anyway when there's a – shall we say – pressing reason to get in the air fast.

Ramstein is a major US logistics airbase in Germany. Originally Ramstein used to have only one runway. The runway was built with fighter aircraft in mind and could also host C-130 Hercules aircraft. Bigger freight aircraft and passenger aircraft could not use Ramstein and were handled at Rhein-Main base, which was at Frankfurt's international airport.

When Frankfurt needed to expand their civil operations, Rhein-Main base was closed and all the US military tranport operations were transfered to Ramstein. In order to accomodate the big transport aircraft at Ramstein, the airport needed an upgrade. To keep the base open during construction works it was elected to convert the old India taxiway into a runway (08-26) which was made longer, wider and thicker that the original 09-27 runway. Also new aprons were added to the North and South of the runways. When the work was completed in 2005, the old runway was closed for reconstruction. It was then resurfaced and extended so that since 2008 there are two operational runways at the airport, so that in case of maintenance or an incident the operations can continue.

There is no relation to launching fighter aircraft in rapid succession.


Is special equipment required to perform high-voltage line inspections? I was watching a youtube video about high voltage cable inspections performed with helicopters. It can be seen how the helicopter has to reach the same electric potential as the wire, something that normally does not occur to other crafts.

I was wondering, is there any kind of special instrumentation/equipment that must be installed on the helicopters to perform such operations?

Are the pilots aided in any special way to maintain a stable hover or it boils down to skill and training?

I work in this area and, to my knowledge, I never heard about any special aid to help the pilot. They know precisely which are the wind speed limitations to do the work safely, the rest is basically skill.

What they do install in helicopters, is the so called Wire Strike Protection System (WSPS), which should cut the cable if the helicopter strikes it, avoiding damages on the main rotor (see the picture https://upload.wikimedia.org/wikipedia/commons/b/bf/Ntsp-oh58-N170FR-070205-01cr.jpg that Bell has two WSPS, one over the cabin another underneath the avionics bay). But this is more important on power line inspection, which is made at around 60-80 km/h with cameras and LiDARs. When the helicopter is hovering by the cables this doesn't bring much aid.

But this is a risky job anyway and if you search, you will find plenty of accidents which happened with helicopters and power lines.


What is this pattern on this runway? What is this pattern on this runway? What is its function?

Location on Google Maps

It is not a runway that you see there. It is the US Navy's Radar Cross Section Range at Junction Ranch. From what I know, that is the platform on which they put the object which they want to see the Radar Cross Section of on. There is a radar at the other end of the "runway".

This is what it looks like:

Image Source


What does "mission mixing" mean for long-range aircraft? I know very little, like long-range aircraft will be used for short-range and medium-range operations. But what is the purpose of using them like that? Also I want to get complete details of "mission mixing" in layman's terms.

Mission mixing appears to be running computer simulations (or other probabilistic analyses) to assess aircraft engine components' reliability also under non-typical or non-designated use. All for the purpose of design or maintenance/inspection strategies, I would assume.

So, mission mixing is not something you would purposely do with actual aircraft. (Or maybe you would, but then it is not called mission mixing.)

Here are a few articles mentioning it:

https://arc.aiaa.org/doi/pdf/10.2514/1.13142
https://asmedigitalcollection.asme.org/GT/proceedings-abstract/GT2012/44731/439/247656

http://en.cnki.com.cn/Article_en/CJFDTotal-HKXB902.017.htm
https://www.astm.org/DIGITAL_LIBRARY/STP/PAGES/STP14812S.htm


What is the production status of the Pipistrel Panthera as of March 2017? What is the production status of the Pipistrel Panthera? They had plans to start production in 2016/2017 but nothing new has been published in the last two years.

I may have more news on that next week from Sun 'n Fun 2017.  Pipistrel will be an exhibitor at the show and may have a Panthera prototype on display.

Currently the Panthera is planned to be released as an experimental kit and may be type certified at some point in the future.

I know the program has suffered some setbacks, including an increase of empty weight by some 200 lbs.  New aircraft development is never fast nor without complications.

The Panthera does look intriguing - 200 KIAS on 10 GPH with good, stable flight characteristics and modern avionics, BRS parachute, etc.  I want to take it for a demo flight when production examples become available.


How bad is the efficiency of jet engines under low loads? VTOL operations need 4-5 times more thrust than a conventional take-off of an aircraft.

If you don't want to install additional lift-engines into a hypothetical aircraft and use thrust vectoring to turn the thrust towards the ground, you naturally end up with largely oversized engines for the cruise flight.

But how bad does the fuel efficiency (thrust per amount of burned fuel) get, when the engines run at their minimal self-sustaining throttle setting during cruise?

Current jet engines are actually not built for efficiency rather than performance.

If you consider efficiency, you don't build a VTOL aircraft. This is why the F35 has multiple versions with and without VTOL capabilities.

Also, jet engines even during flight have to be able to sustain fast speed change, fast altitude increase and high load factors, all combined with lightweight designs. Therefore, I wouldn't consider takeoff as the most demanding phase of flight for such engines, but I may be mistaken on that point.

All these conditions make it difficult to reach the efficiency of say turbofan or turboprop engines.


Can we use MAYDAY or PAN PAN on ground? Usually we read, on reports, aircraft reporting urgency or emergency during the flight, while airborne. But, is it correct to use these "words" on ground?

Yes, it is correct to use MAYDAY or PAN PAN PAN on the ground.

In recurrent training we are often reminded that in the case of a rejected takeoff in a foreign country it is important to use MAYDAY or PAN PAN PAN on the ground to avoid any confusion due to language difficulties.

It's probably a good idea at any airport as a disabled aircraft on a busy runway could be a major hazard to other aircraft landing and taking off.


Can an orienteering compass be used in place of a protractor? First off, please forgive me if this is a stupid question.

I was given a protractor during flight training, learnt to use it and obviously works quite well.

However, I've started using my old maps for sim use and used an orienteering compass which also works quite well

In fact, I found it easier to get bearings using the compass than the protractor.

So for my question, has a protractor always been issued and used, or do some schools prefer to use other orientation tools?

From your description you are using the orienteering compass to measure course lines by aligning the side of the compass to the grid lines and using the dial to align with the course. There's no thing inherently wrong with this method, if done properly it will give you an accurate course. Personally I like the protractor better, but it is personal choice. You may have to explain what you're doing to an examiner later, I wouldn't imagine it would be disqualifying though, although you never know, some examiners are sticklers for that kind of thing.

However, before you throw away the protractor I suggest you put one hand behind your back and try to use your orienteering compass to measure a course. You see, at least in the UK you will be tested on your ability to divert, measuring a course using a map while also flying the airplane. That's where that kind of protractor comes into its own, and why I'd recommend you stick with it.


Are there any aircraft designed to operate between an altitude of 50-80km? Aircrafts operating at high altitude falls into several categories:

Wings with high aspect ratio (Global Hawk, TR-1, Scaled Composite Proteus,...)
High velocity aircraft (Concorde, A-12, X-51,...)

Aircraft falling into those two categories cruise between 15km and 30km high.

Balloons (up to 50km high)
Suborbital aircraft (X-15, Space Ship Two), performing their mission between 80 and 120km high.
higher resides low earth orbit, and thus satellites which can hardly be qualified as aircraft.

I cannot find any aircraft designed to perform its mission at an altitude between 50km and 80km, which corresponds more or less to the mesosphere. Is there any aircraft designed to perform its mission into this 30km wide slice of atmosphere? What is the usefulness of this slice for aviation?

Is there any aircraft designed to perform its mission into this 30km wide slice of atmosphere?

(between 50km and 80km) - apart from some experimental rocket planes and so on, I can't think of any. The main problem is there's so little air - very little opportunity to generate lift, and very little air to run a jet engine.

In theory it should be possible for a winged aircraft to fly up there (it is below the Kármán line) but the engineering difficulties would seem to make this impractical.  For more detail I'd recommend the top answer for this question: What determines the maximum altitude a plane can reach?

  What is the usefulness of this slice for aviation?

If it were possible, it would be useful for futuristic or military things like:

spy planes like the SR-71 but higher and faster
super-fast suborbital transport
passing through on getting into orbit - single stage to orbit
vehicles for example.

(All of these examples are pipe dreams at the moment of course.)


What material is used for the skin of a modern fighter jet? Modern passenger jets/airliners use aluminum 2 to 3 mm thick as their skin, their maximum speed is 900 km/h give or take. Modern fighter jets travel at twice that speed on average.
What material is used to make their skin. If it's aluminum, is it thicker and why? Is it because of the extra cruising speed?
If specifics are required, I ask about the F-35.

The F35's skin consists of a/several composite(s). Although it's obviously classified, I suspect the main reason it's chosen has something to do with stealth rather than strength. Interestingly, there seem to be more information about the F22 than F35, which is supposed to be, err, more secretive? For example, the F22's airframe bulkheads and twin booms are known to be constructed from titanium, and there are aluminum elements in its wings, and its skin is composite as well. That's pretty much all that's let on.

If you are asking for some not-so-secretive fighters, they are made from more mundane materials, not that these are any less expensive:


Why is the Airbus A320 permitted to carry 180 passengers, instead of the maximum 179 allowed? The EASA regulations give the following requirement for number of emergency exits:

If then the Airbus A320 is certified to carry 180 passengers, it seems to me that it falls just outside the minimum bracket of 2x Type I exits and 2x Type III exits and it should then have a pair of additional Type III exits to be able to accommodate 180 passengers.

However, various sources give the emergency exits as (link):

This configuration, in my opinion only allows 179 passengers, not 180.

Is there some clause I am missing?

See Page 9 of TCDS A.064 ANNEX - Airbus A318, A319, A320, A321 - Special Conditions

  TCDS A.064 ANNEX - Airbus A318, A319, A320, A321 - Special Conditions

EQUIVALENT SAFETY FINDING         E-2107: Passenger Extension to 180
APPLICABILITY:                    A320
REQUIREMENTS:                     JAR 25.807
ADVISORY MATERIAL:                N/A

  Statement of Issue:

  An application was made on September 30, 1992 to JAA for certification of maximum number of passengers of 180.

  Paragraph 25.807(c)(1) of JAR specifies for passenger seating configuration, the number and
  types of Emergency Exits for each side of the fuselage.
  The maximum seating capacity allowable under JAR 25.807(c)(1) for A320 exit configuration is
  179 (2 Type I and 2 Type III).

  However, the exits size for front and rear doors on the A320 is such (32x73 inches) that they
  are oversized Type I and therefore can be considered as a non standard exit arrangement.

  The same exit size is being used on a derivative of the A320, for which Latin Square Tests
  have been conducted in order to establish an appropriate rating for that kind of exits. These
  tests have shown that, when associated with the performance of the slide installed at these
  exits, a rating of 55 passengers is appropriate.

  It should also be noted that the full scale emergency evacuation demonstration of the A320
  with 179 passengers has demonstrated compliance with JAR 25.803(c) with sufficient margin
  to justify 180 passengers.

  Under those conditions, a maximum capacity of 180 passengers is requested for the A320.

  JAA Conclusion:
  Based upon the demonstrated higher rating for the floor level exits and the adequate margins
  for 179 passengers shown in the 90 seconds demonstration, and used as a basis to show
  compliance to JAR 25.803(c), the JAA accept 180 passengers as the maximum capacity for the
  A320 on the basis of an Equivalent Safety Finding.


Which antenna on an commercial airline airplane is used for the transponder (SSR)? On the 767-200 image I see no SSR antenna, but since that TCAS uses the transponder I guess that are sharing the same antenna. Am I right ?]1

Short answer

The SSR antennas are labeled ATC L and ATC R (two at the top, two at the bottom).

Source

Both SSR and TCAS systems use the same communication protocol and use the same frequencies (1030 and 1090 MHz). They could well use the same antennas. However for best performance, SSR antennas are omnidirectional and TCAS antennas favor some sector, usually by beam forming.

On this B767-200 picture, TCAS antenna is the flat one at the front, and the yellow SSR antenna is a bit behind (only one):

See the full and higher quality photo by Ramon Jordi

Another airframe with two SSR antennas:

See the full and higher quality photo by Temo Madrigal

I was not able to find a good view of the SSR antenna on a B767-200, but on this A320, the two side yellow SSR antennas are more visible (as well as the single DME antenna behind):

A320 SSR antennas, source

Use and needs are different

  I guess that are sharing the same antenna. Am I right?

As said, you could be right as SSR and TCAS operate on the same L-band frequencies, and can't time overlap. But they have actually dedicated antennas, because they need different radiation patterns:

Transponder initial function consists in responding to SSR interrogators on the ground, and now in broadcasting ADS-B squitters in addition. The bottom SSR antenna is of some omnidirectional type, commonly a quarter wavelength monopole), Because the fuselage is not a perfect ground plane, the radiation pattern doesn't peak at the horizontal as one would expect, but has a privileged direction at 30° (source) below the aircraft plane, a low gain in the horizontal plane, and is nearly blind on its nadir.
TCAS on the contrary need to have a good reception in or close to the horizontal plane and around the nadir. They are the directions where the most immediate threats are coming from.

This is why the TCAS antenna is designed differently. Let's see the backside of the TCAS antenna shown earlier:

Source

Hum... not one antenna connectors, but four!

The flat shape of the TCAS radome (sometimes round) contains a 4-element phased array antenna which can be set to cover an hemisphere, but which can also focus on a quarter of this hemisphere. Example of design using a switched beam-forming network (SBFN):

Source: Microwaves & RF

The four outputs labeled A1..A4 are connected to the four individual connectors under the radome.

TCAS uses the steering obtained with the array to select which direction to send interrogations and to listen to responses, in order to reduce synchronous garble from close mode C transponders responding simultaneously to the aircraft (1.7 NM radius), and FRUIT from all aircraft responding to a ground ATCRBS interrogation.

TCAS reverts the bottom antenna to the omnidirectional mode (same phase on the four antennas) and decreases RF power in landing and takeoff phases, to prevent radio spectrum overload.

For a Mode S transponder aircraft, we would have this kind of configuration:

ACAS II Guide

Note there is a connection between TCAS and SSR to inhibit each other when they are using the frequencies and protect their RF input. If I remember well, SSR mode has the priority (at least when the TCAS is not in a TA/RA phase).


What is the difference between a forward slip and a side slip? I am having a hard time understanding what differentiates the two types of slip. I understand that in a forward slip, the longitudinal axis is tilted with respect to the flight path, whereas in a side slip it is not. In a forward slip your track stays the same, whereas in a side slip it would (in the absence of wind) cause you to track toward the down wing.

My difficulty comes from the fact that the control inputs needed to enter both are the same: banking with opposite rudder.

Why then is the heading of the aircraft with respect to the flight path different, if the control inputs are the same? Is it just a question of degree, which is to say, the forward slip just requires more rudder?

There is no difference aerodynamically. The only difference is in intention and presence of the wind. The airplane does not care about the ground track, all it feels is the movement through the air. Both side- and forward-slip make the airplane fly slightly sideways through the air, somewhere in the direction between nose and downwards pointing wing.

If there is no wind, your ground track will be exactly the same, between wing and nose, and you will feel that the nose points away from your track and call it forward-slip. If the wind is blowing and you manage the right amount of slip, you are moving sideways through the air, but the ground track (combination of wind- and slip- movement) can be aligned exactly with the nose and you call it side-slip.

There is really no difference aerodynamically and thus no difference in applied controls either.


What do all the indicators on a HUD mean? Every Jet Fighter these days seems to have a Head Up Display.  What do all of these indicators mean?

Some things are fairly obvious:

there is a compass
there is an artificial horizon

Other things are less obvious, i.e. what is this _ / \ / \ _ ?

HUD symbology varies depending on flight mode and aircraft configuration so you will find a wide variety of symbols capable of being displayed.  Some basic ones from the F/A-18 E/F aircraft are.

To your original question the ‘W’ symbol is called the Waterline symbol and represents the point at infinity where the longitudinal axis of the aircraft points toward.  It is analogous to the miniature airplane symbol on an attitude indicator.  A similar symbol called the Gun Cross is used on the F-16 HUD.

On high performance aircraft capable of high AoA operations, the waterline symbol is not as useful as the Flight Path Marker or Velocity Vector symbol which indicates the point at infinity the aircraft is currently trending towards.


How many controllers are there per frequency? Imagine multiple controllers talking on the same frequency would be a nightmare for pilots and other controllers.

So in real life how many controllers are there for each frequency? If there are more than one, how do they split the work load?

There is one frequency per sector and there can be two controllers per sector, one working the scope / talking to aircraft and one assisting with flight strips and coordination with adjacent sectors. If the sector does not require a second controller to coordinate and assist with flight strips, there will only be one controller doing all tasks single-handedly.

In some cases, two sectors are combined and both frequencies are manned by the same controller, but this is only done in low-traffic times, where overlapping transmissions have a low probability.

A good and well-written source to understand how ATC sectors and split workload works is the AVWeb Series of Say Again? by Don Brown.

See this related question for more information:
What is the maximum number of planes a controller can control?


Why do aircraft of the same model get progressively larger engines as they mature? For example, the Cessna 172 started production with the Continental O-300 145hp engine but today sells with the IO-360. Granted that engine is more "modern" but 145hp with the O-300 still feels too little for such an airplane.
The Robinson R22 started with the O-320 and eventually jumped up to O-360.
Do the designers not feel the lack of power when test flying the aircraft? Are we getting fatter?

The Cessna 172 first flew in 1955.
The Continental IO-360 was FAA certified in 1962.
The math is pretty simple.
Yes, we (Americans, at least) are getting fatter, but that still doesn't allow for use of an engine that isn't yet certified.
It's the same for GA as well as commercial aviation. Improvements in fuel efficiency and power tend to lead the manufacturers to want to certify existing airframes for new power plants because that's less expensive (testing, certification, pilot training, etc.) than building a whole new aircraft around a new engine.


How is an air accident's probable cause determined? I constantly hear that air accidents are caused by a range of shortcomings. However, most accident reports declare a main "probable cause". You can see below a bar-chart with the causes of fatal accidents by decade (data source):

Does anyone know which criteria are used to determine the main accident cause?

I participated in a tiny supporting role in a few crash investigations involving CRJs, so I'll give it a shot, and I would say that when a main cause is listed, especially for something mechanical, it's what you might call a "primary trigger", without which, follow-on supporting factors  and events that led to the crash would never have occurred.  Or an event in a chain that can be considered the "point of no return".

Pilot with poor training takes off in an overloaded airplane, and engine quits after V1/VR and it crashes.  The engine failure will be the main cause, with poor training and overloading added as contributing factors.  Without the engine failure, the poorly trained pilot in his overloaded airplane would've carried on his merry way, so the engine failure can be considered the main cause.

For pure "pilot error" events, it can be more nuanced, with a roughly equal-in-impact chain of events and if you took out any element in the chain, the other elements may have still happened, but just not leading to a fatality.  These reports will often list a series of accident causes without giving critical weight to any one, except to say that the cause was ultimately the crew and not the plane.  Running out of gas is a typical one.

On the other hand, sometimes a crew action is as much a triggering event as a major mechanical failure.  Colgan Flight 3407 is a classic example of this.  The Capt had the Mother of All Brain Farts and pulled when he should have pushed when the shaker went off and this is listed at the main cause.  Now, the shaker went off in the first place because they weren't paying attention to power when the A/P leveled off, but it was the response to the shaker that sealed their fate, and becomes the main cause.

There was a CRJ crash in China caused by taking off with frost on the wings on a cold clear morning.  Frost on the wings was the main cause.  Lack of understanding of the effects of frost, and maybe a bit of normally benign over-rotation-on-takeoff contributed, but without the frost, nothing would have happened.


How can Ryanair offer flights for a penny? Of course, we all know that you're not exactly treated like a rockstar on Ryanair, and their CEO wants to charge us £1 to use the toilet; but still, how can they offer flights for a penny?!

Looking at flights with budget airlines, they usually end up costing more, with taxes etc added on, but I've seen Ryanair offering flights for literally a penny, all in.

Besides @Sebass van Boxel's answer, I'd like to add the following:

I was talking to a Fastjet pilot (ex easyJet) and he was telling me that obviously not all seats are available for a cheap price.

If you book early you will get a special price but try booking a day before and you will see.

As has been said, a lot of money is made on all the extra services such as luggage, food, etc.

From what he told me, the profit on each flight for easyJet is minimum \$400 per flight at 96% full — which is not much, but consider that easyJet has something like 1,000 flights a day and that means \$400,000/day profit. Not bad...

That how the money is made.


Why does An-225 (Mriya) perform a low-pass on its landings? Today was a big event for aviation fans where I live (Warsaw, Poland, EPWA). We have had a visit of Antonov 225 (Mriya).

Today, but also as I saw in other videos, it often (always?) performs a low-pass first and only then lands. Why is that? I bet this is about safety, but...

is it mandated by some official rules?
or by some internal rules of the operating airline?

What kind of information does the pilot need which they wouldn't get by reading the maps, diagrams or by talking to ATC?

As of the time of writing this answer, this only appears to have happened in one out of the last 6 flights of the AN-225 (the same flight into Warsaw you mentioned, https://www.flightradar24.com/data/aircraft/ur-82060#245b19c0) so I can't say that this is an official "rule", a standard of any kind or any procedure regarding the AN-225.

There are 2 other videos of that particular landing on YouTube:

It is clear in both videos that the first approach is done with the landing gears up, most likely on purpose "for the show", of course with coordination with ATC.

If someone is fluent in Ukrainian they can confirm it quite easily since the communication between the pilots can be clearly heard in the video you provided.


As a drone hobbyist, is flying below the listed FAA UAS ceiling a violation of controlled airspace? FAA (emphasis mine):

  In Class B, Class C, or Class D airspace [controlled airspace] or within the lateral boundaries of the surface area of Class E airspace designated for an airport, the operator obtains prior authorization from the Administrator or designee before operating and complies with all airspace restrictions and prohibitions.

The FAA also has this interactive map showing where airspace restrictions on drones exist.

In the screenshot depicting class B airspace around PHX, it shows that there is a ceiling of 100 feet in the selected square.

Hobbyists cannot currently get permission to fly in controlled airspace due to the absence of LAANC. Is authorization required to fly a drone below 100 feet in this area, or can a hobbyist fly without authorization up to 100 feet since it's within class G airspace and the class B airspace doesn't start until 100 feet? Or, is this location "within the lateral boundaries of the surface area of Class E airspace designated for an airport," requiring authorization for that reason?

https://en.wikipedia.org/wiki/Airspace_class_(United_States)

As a drone hobbyist, is flying below the listed FAA UAS ceiling a violation of controlled airspace?

Short answer:
As of now, since the LAANC pre-authorization system is not yet up and running for recreational SUA flyers, any recreational sUAS operation below 9000' MSL in the lower left corner of the grid square highlighted in the question would be violating the applicable rules.  In the rest of the grid square highlighted in the question, recreational sUAS operation from the surface up to 400' AGL violates no rules.
Now read on for more:
In the particular grid square that is highlighted in the question, the LAANC pre-authorization system will only authorize a ceiling of 100'.  But the questioner is mistaken to believe that the floor of the Class B airspace is 100' anywhere in that grid square.
The lower left corner of the grid square highlighted in the question has Class B airspace extending from the surface upwards.  In that airspace, a recreational sUA flyer can not legally fly a drone without prior authorization.  Since the LAANC pre-authorization system is not even operational yet for recreational sUA flyers, to legally fly in any airspace that is Class B at the surface, a rec SUA flyer would have to fly at a "blue dot" fixed site.  "Blue dot" fixed sites are typically prescribed the same ceiling as the ceiling specified for the LAANC grid square in which they are located, which in this case would be 100 feet.  No "blue dot" fixed site currently exists anywhere in the Class-B-to-surface airspace around Phoenix.
Once the LAANC pre-authorization system is up and running for recreation sUA flyers, a rec SUA flyer will be able to use that system to get pre-authorization to fly from the surface up to 100' AGL anywhere in the grid square highlighted in the question.
But does this mean a recreational sUA flyer is limited to a ceiling of 100' AGL if he or she is flying in a part of the grid square highlighted in the question that does NOT have Class B airspace at the surface?
No it does not.
And does the fact that LAANC pre-authorization is not yet available to recreational SUA flyers have any impact on recreational sUA flight in any point within a LAANC grid square if the airspace at that particular point, from the surface up to 400', is NOT Class B, Class C, Class D, Class E airspace that extends down to the surface and is "designated for an airport", or some other kind of restriction such as those shown by the heavy red markings on the LAANC map?
No it does not.
In all but the lower-left corner of the grid square highlighted in the question, the Class B airspace has a floor of 5000' MSL.  Below that is Class E (E5) airspace down to 700' AGL and Class G airspace from 700' AGL down to the surface.  In that airspace, one can legally fly a drone (sUA) up to 400' AGL with no prior authorization of any kind, either as recreational flyer or as a non-recreational flyer, despite being in a LAANC grid square.
VFR sectional chart view, centered on Phoenix: http://vfrmap.com/?type=vfrc&lat=33.434&lon=-112.012&zoom=10
However, if a rec SUA flyer doesn't fully understand the airspace system or how to read a VFR sectional chart, he or she would be wise to stay on the safe side and avoid any operations within any LAANC grid square until the LAANC pre-authorization system becomes operational for sUA flyers, unless he or she is flying at a "blue dot" fixed site.
The phrase "within the lateral boundaries of the surface area of Class E airspace designated for an airport" refers to Class E airspace that extends down ALL THE WAY DOWN TO THE SURFACE.  More specifically, it refers to E2 airspace, but not E3/E3a/E4 airspace.  To read more about this, visit this outside link to a forum for rc flyers-- "Understanding E4 airspace-- prior authorization not required".
No Class E airspace is present at the surface anywhere in the region depicted in the illustration accompanying the question.


What is the name for the Mitsubishi A6M Zero's one-piece wing/fuselage? The Wikipedia article on Mitsubishi A6M Zero fighter cites an article from Life magazine published on Nov 4, 1942:

  The Zero's fuselage and wings were constructed in one piece, unlike the American method that built them separately and joined the two parts together. The Japanese method was much slower, but resulted in a very strong structure and improved close maneuverability.— Wikipedia

(Source)

This design is harder to implement but it allows for higher strengths for the same weight or lighter weight for the same required strength.

Is there a name for such fuselage design?

The construction of the Zero was slightly different from that of its western counterparts. The aircraft had three major sub-assemblies:

wing/center fuselage
forward fuselage, and
aft fuselage.

The construction of the first sub-assembly was such that the both the wings were constructed as one piece integral with the cockpit. This is (presumably) what the author means in the article in question. Otherwise the wing was a semi-monocoque structure with two main spars, which is quite common.

The image below shows the sub-assembly in question (the wing+cockpit section) from a recovered zero. It can be seen that there is no great difference in design, only in the choice of the sub-assembly (a wing+cockpit section, instead of wing + fuselage).

A6M Zero midsection; image from lasamurai.blogspot.in

The images below show the different sections of the aircraft (middle and rear sections) from a rebuilt Zero.

Cockpit+wing sub-assembly; image from j-aircraft.com

Rear fuselage assembly; image from j-aircraft.com

I'm not aware of any special name for this. It appears to be a normal semi-monocoque structure.


Do special procedures exist to limit pilot workload during pilot incapacitation? Although pilot incapacitation is rare, the website avherald.com lists several occurrances of flight crew incapacitation, alone two events reported yesterday.

FAA AC 25.1523-1 requires all aircraft to be capable of operation
by one pilot only from either seat, so just one pilot can safely fly the aircraft - albeit under increased workload.
In case of flight crew incapacitation, do airlines (or regulatory bodies?) have dedicated Standard Operating Procedures (SOPs) for the remaining pilot? Obviously, the pilot would declare PAN/Mayday and assess whether it is safer to land asap or continue. Or are there no special procedures because it happens so rarely?

Are there any procedures to limit pilot workload in these instances, such as shortened procedures, ask a cabin crew member for assistance such as reading checklists, any support from the ground / airline operation center...? The remaining pilot must execute all tasks of Pilot Flying and Pilot Monitoring, which means heavy workload during final approach.

Well, as a catch-all there is always FAR 91.3 which says he pilot in command can deviate from any regulation if they deem necessary in time of emergency in order to safely operate and land the aircraft. Obviously there's a reasonable limit to that and you'll be asked to give a report to the FAA on what happened, so be ready to defend your actions.

I can't comment on airline company procedures, but I have to assume there is a plan in place for this scenario since it is so realistically likely to happen at some point. I believe another crew member would be asked to help with simple tasks like reading checklists as you mentioned.


How do aircraft stall warning systems handle (or not) asymmetric-stall situations? Most, if not all, new airplanes are required to have stall warning systems to (as the name should make clear) provide the pilots with a warning when the airplane is about to stall.  Most stall warning systems work not by directly detecting the rapid increase in airflow separation near the stall point, but, rather, by measuring the airplane’s angle of attack and giving an alarm if it is greater than some threshold value.  However, as the attack angle at which the wing stalls can vary by a great deal, these older stall warning systems have multiple thresholds; for instance, a particular system might sound an alarm at 15º in a clean configuration, but lower the threshold to just 5º if icing is detected (as icing promotes airflow separation, and, thus, lowers the wing’s stall angle), while waiting until 30º if the slats are extended (as leading-edge devices, such as slats, delay airflow separation, and, thus, increase the allowable attack angle).

With all this in mind, how do stall warning systems handle situations in which one wing is stalled, or close to stalling, but the other wing is not?

I can think of a number of scenarios under which this might occur:

Category 1 - The two wings have different stall angles, such as could result from...

Scenario 1: ...asymmetrical icing, or damage to the leading edge of one wing but not the other, which would increase the roughness of the damaged or more-iced wing, thereby increasing the tendency for the airflow to separate from said wing, and, therefore, cause it to stall at a lower attack angle than the undamaged or less-iced wing.
Scenario 2: ...asymmetrical leading-edge device (non)deployment, such as from failure during takeoff of the hydraulic system powering one wing’s outboard slats, resulting in the retraction of said slats, which would decrease the stall angle of the wing with non-extended or less-extended leading-edge devices.

Category 2 - The two wings are at different angles of attack relative to the airflow around them, such as could result from...

Scenario 3: ...violent, fine-grained turbulence, which could result in the airspeed of one wing being considerably lower than that of the other wing, thereby causing the horizontal component of the airflow around that wing to be considerably decreased while leaving the vertical component of said airflow unchanged, thus resulting in the lower-airspeed wing encountering the oncoming air at a much steeper angle than the higher-airspeed wing, and, as a result, possibly causing the lower-airspeed wing, but not the higher-airspeed wing, to exceed its stall angle; for instance, if an airplane is flying at an indicated airspeed 30 knots above its stall speed, and is hit by an asymmetric gust that causes the left wing to experience a 45-knot tailwind while the right wing sees a 15-knot headwind, the left wing will be 15 knots below its stall speed at the same time as the right wing is 45 knots above its stall speed, and, therefore, the left wing will stall, but not the right wing.
Scenario 4: ...a rapid yaw to one side, possibly as a result of overenthusiastic piloting or a mechanical failure, causing the airspeed of one wing to increase and that of the other to decrease, possibly causing an asymmetric stall via the same mechanism as in scenario 3 (for instance, a sudden rudder hardover would produce an extremely high yaw rate, and, thus, airspeed differential, before the pilot(s) had time to react, which could easily bring one wing, but not the other, below its stall speed).

They don't.  The Stall Protection Computer only considers overall body AOA as measured by vanes on the left and right side of the nose.  AOA is just one bit of data, and the SPC also is measuring G loads, yaw rates, speed wise acceleration or deceleration, pitch rates, etc. and also getting inputs on flap/slat position etc to allow for all those effects.  It computes a solution for presenting the barber pole on the speed tape, and the shaker and pusher (if installed) firing points based on the body AOA and all those other factors, not local wing AOA.

If you yaw a swept wing jet really hard with rudder, it will roll on its back, stalled or not, just from the asymmetric lift with the sweep (full aileron may or may not be enough to counteract it - you learn this the first time you do a V1 cut in training).

In any case you don't normally touch the rudder pedals on a jet except during takeoff and landing or if an engine quits.  Yawing the plane also makes the vanes show radically different angles because of the changes in airflow around the nose when skidding or slipping, and you will get some kind of mismatch related error message.

On a jet with heated leading edges, if you had ice on the wings, the SPC will be fooled and can't account for this, and the wing will stall at a lower AOA than the SPC's computed solution and the airplane may depart when the barber pole still shows good margin, and before the shaker goes off.  A nasty surprise.  Ice on one wing and not the other just means when it goes, before shaker, it will roll really hard.


Can I get a pilot's license following a vehicular homicide charge? I was wondering if a vehicular homicide charge that was not drug or alcohol related will prevent me from get a pilot's license?

I'm assuming you're asking about training in the US because "vehicular homicide" is an American term, at least as far as I know. If that assumption is wrong, please update your question to include the country. You also didn't mention if you were only charged, or actually convicted.

Anyway, if we assume the US then you need TSA approval before flying solo (for citizens) or before starting flight training (for non-citizens). I have no idea how the TSA would view a vehicular homicide charge (or conviction), but obviously it's a potential issue.

But assuming you get TSA approval, you'll also need a medical certificate. Criminal charges or convictions shouldn't really matter for that, unless they involve drugs and alcohol (as you mentioned) or if the incident led to you needing long-term drug treatment, a major operation or psychological/psychiatric treatment. The FAA views psychiatric treatment in particular (including most counselling) very negatively, so if you had any that would almost certainly result in a lot of extra paperwork and potentially denial of your application.

Alternatively, you could go for a sport pilot license and fly an LSA without any medical if you have a valid driver's license. But if the FAA has ever denied a medical application from you, you can't use that option, so research and plan accordingly.

But if there are no medical issues the only other thing I can think of right now would be insurance. There's no legal requirement in the US to have any insurance in order to fly but most people who rent aircraft (including students) will have renters' insurance in case they damage the aircraft or injure someone or whatever. If your homicide charge resulted in a conviction, that could be a problem for an insurance company. Even if you don't get your own insurance, you might have to sign something for the flight school's insurers stating that you've never been convicted of a felony or motor vehicle charge (I have no idea, by the way, if vehicular homicide is a felony or not). I'm not saying that it would be impossible to get insurance, just that it might come up when/if you apply for it.

Finally, if you eventually want to get an ATP license then a felony conviction is a potential concern: see this question for more information.

Disclaimer: I'm not a lawyer or a flight instructor so don't take my word on anything important (or unimportant, for that matter). Legal issues are always tricky and for a real answer you should consult an aviation attorney or join AOPA and ask them.


What does the FAA mean by "Make and Model" of aircraft? Short Version: How does the FAA define the terms "make" and "model" in regulatory documents, particularly in the context of referring to pilot experience in aircraft?

Long Version
In  14 CFR 135—and doubtless elsewhere in 14 CFR—the FAA occasionally uses the terms "make", "model", or some combination of these, such as "make and model".
Specifically, §135 gives requirements for pilot experience to be eligible for certain operations, such as to operate under "eligible on-demand" rules or to act as PIC.
See, for example, 14 CFR 135.4, "Applicability of rules for eligible on-demand operations":

(3) Pilot operating limitations. If the second in command of a fixed-wing aircraft has fewer than 100 hours of flight time as second in command flying in the aircraft make and model and, if a type rating is required, in the type aircraft being flown, and the pilot in command is not an appropriately qualified check pilot, the pilot in command shall make all takeoffs and landings in any of the following situations: [omitted for brevity]
(4) Crew pairing. Either the pilot in command or the second in command must have at least 75 hours of flight time in that aircraft make or model

See also, 14 CFR 135.105, "Exception to second in command requirement: Approval for use of autopilot system":

No certificate holder may use any person, nor may any person serve, as a pilot in command under this section of an aircraft operated in a commuter operation, as defined in part 119 of this chapter unless that person has at least 100 hours pilot in command flight time in the make and model of aircraft to be flown and has met all other applicable requirements of this part.

See also, 14 CFR 135.244

(a) No certificate holder may use any person, nor may any person serve, as a pilot in command of an aircraft operated in a commuter operation, as defined in part 119 of this chapter unless that person has completed, prior to designation as pilot in command, on that make and basic model aircraft and in that crewmember position, the following operating experience in each make and basic model of aircraft to be flown:

In contrast to the foregoing, the FAA often uses the term "type" to refer to the group of aircraft that the pilot must be experienced or trained on. An example of this would be §135.225 (e), where a pilot is required to have logged 100 hours as pilot in command in that type of airplane.

My question is, what does the FAA mean by these terms, and how should we apply them?
I would typically understand the term "make" to refer to the manufacturer: Cessna.
I would typically understand the term "model" to refer to the basic model, without reference to sub-model designations: 172 (but not 172M vs 172R). However, note where the FAA uses the phrase "make and basic model", to make this idea clear, perhaps in contrast to a separate meaning where the word "basic" is omitted.
Type, in reference to pilot certification, seems clearly to refer to all types encompassed by a type rating designation.
To apply this, would a pilot's time in a Cessna Citation 550 Bravo count toward the time required when operating a Cessna Citation 560 Encore? What about in a Cessna Citation 500 or a Cessna Citation 560 Ultra? All of these fall under the same type rating.
Does the FAA offer some guidance on this, or is there a letter of interpretation perhaps?

TL;DR: The make of an aircraft is the name of the designer (for example, Boeing) and the model of an aircraft (also called the type) is the designation for the general design of the aircraft (for example, 737).  It looks like "basic model" is just an older term for "model".
According to FAA Order 8000.71:

c. Aircraft Make. An aircraft make is the name assigned to the aircraft by the manufacturer when it was produced.  In most cases, the aircraft make is the organization common name of the aircraft manufacturer.  If the organization that holds rights to an aircraft design permits another organization to build that aircraft then the aircraft make would be the aircraft name assigned by the organization that holds rights to the aircraft design in most cases.  If an aircraft manufacturer is an amateur construction, then the aircraft make would be the name of the organization responsible for design in most cases.

and

c. Aircraft Model. An aircraft model is an aircraft manufacturer's designation for an aircraft grouping with similar design or style of structure.
(1) The aircraft model listed in the aircraft TC is the designation used by the aircraft manufacturer to distinguish a particular aircraft or is the designation used by a national military or armed force to distinguish a particular aircraft.
(2) If an aircraft manufacturer is amateur construction, then the aircraft model would be the name designated by the organization responsible for the design in most cases.

Also,

(7) Title 14 of the Code of Federal Regulations (14 CFR) 1.1 defines "type" and provides the basic classification for aircraft as follows:
"(2) As used with respect to the certification of aircraft, means those aircraft which are similar in design.  Examples include: DC-7 and DC-7C; 1049G and 1049H; and F-27 and F-27F."
Examples: 777
DC-9
Note: Historical policy and documentation may refer to type as "basic model."


How can I find information about the aircraft with registration / tail-number N58644? I am trying to find information on aircraft N58644 which doesn't show on the N number listing. This is a BT-13A converted to civilian use from the 40s or 50s. Any ideas where I can get any information since the FAA doesn't show it?

I have checked the 01 July 1965 FAA register, and it does not show there. My father had a BT-13A N61907, and it doesn't show either. The usual fate of postwar BT's was sale to crop duster companies; they were of value only for their R-985 engines and 2D30 props to be fitted on Stearman dusters or airshow planes. The airframes were scrapped.

If you can convince someone at FAA OKC, they could call up their archives (in Ft. Worth IIRC) and get the answer you seek.