Can you have an AME also sign off on your FAA BasicMed paperwork? It seems that you should be able to have an AME sign off on your First, Second, or Third Medical and also do the BasicMed exam at the same time.

If you are older, like me, the Third Class Medical would be in effect for two years and when it expires, I can take the course to extend the Basic Med for two more years. I could exercise the privileges of the Third Class Medical (e.g. fly to Mexico) for two years and then continue to fly under the restricted privileges of BasicMed for two more years.

As far as I can tell, getting the BasicMed paperwork doesn’t invalidate the other certificates and getting a Third Class (or higher) Medical doesn’t invalidate your BasicMed.

Is anyone aware of any FAA (or AOPA, EAA, etc,) guidance on the issue?

From the FAA's FAQ:

  Q35: Can my AME provide the medical examinations under BasicMed?

  A:
  All AMEs are state-licensed physicians and may elect to conduct
  physical examinations required under BasicMed. But the FAA does not
  require AMEs to provide medical examinations under BasicMed. It is up
  to the individual AMEs to decide whether to offer BasicMed medical
  examinations based on medical practice considerations

The key words in there are "may elect to". There have been several discussions about this on AOPA's forums (members only) and people's experience so far is that most AMEs won't do BasicMed. The only specific reason I've heard is liability: one explanation I read is that when acting as an AME, the physician is representing the federal government and is therefore more or less immune from liability. But if he does a BasicMed exam he's acting as a regular state physician, and his liability insurance may or may not allow it. So you just have to ask your AME if he'll do BasicMed or not.

As for whether BasicMed affects a third-class medical or vice versa, this is from the same FAQ:

  Q2: How does BasicMed affect FAA medical certificates? Does FAA still
  offer the third class medical?

  A: BasicMed does not affect medical
  certificates at all and did not do away with third-class medical
  certification. In fact, third-class medical certification is still
  required for GA aircraft and flights that do not meet the criteria for
  BasicMed. Nothing about the FAA’s medical certificate program has
  changed with BasicMed, and you can still apply for a first, second, or
  third class medical the way you always have. BasicMed is merely an
  additional qualification you can use to fly, in lieu of holding a
  medical certificate.

And this:

  Q6: Can I exercise BasicMed and hold a medical certificate at the same
  time?

  A: Yes. If you are operating under BasicMed, then you must comply with
  the BasicMed operating limitations (e.g. flying only within the U.S.
  and at or less than 250 knots). When operating under BasicMed, you are
  not exercising the privileges of your medical certificate.

Simply put, there is no link or dependency at all between an FAA medical and BasicMed. Your AME might do one physical exam and sign off both at the same time for the sake of efficiency, but that doesn't change anything about the renewal dates.


Is a braking rotation immediately after touching down a known maneuver? In this video the airliner landing on grass rotates high up after touching down, looks like more than it would do during take off. Is it a known possible way to drop the speed or it was more for the show? Is this maneuver ever used during more conventional landings?

There was a bit of a bounce and skip at touchdown along with the nosewheel bouncing due to the uneven ground and aggressive landing.  He was probably doing it to hold the nosewheel off after the bounce, to reduce the main wheel contact force somewhat (the normal soft field landing technique) but it looks to me like he overcontrolled with the pitch a bit.
There will be relatively little braking friction so initially you would get better deceleration with the high pitch attitude, but that benefit declines quickly as you slow down and you quickly become reliant on braking and reversers (If the grass is wet, you have about as much braking as compacted, glazed snow, that is, not much; they would have to makes sure the ground was dry or he would have slid into the next field).
If you're on pavement, you want maximum braking as soon as possible, which means you want the lift dumpers out as soon as possible, so you wouldn't use that sort of technique; it's just get the mains on, then fly the nosewheel on, then hard on the brakes right away.  You'd have a longer landing run on pavement trying to land like that, plus there's too much risk of bouncing the whole thing back in the air just as the lift dumpers are extending or about to extend, which results in follow-on touchdown that will rattle teeth and blow tires.


Why is a higher bypass ratio more efficient at lower speeds? Why is it that a larger volume of air moving slower is a more efficient means of propulsion than a smaller volume of air moving faster?  (This is true up to a given speed, obviously, as supersonic aircraft use lower BPR engines).

Because bigger reaction mass with lower speed carries away less energy for the same momentum.

To produce thrust the engine applies force to the exhaust gasses and air. This force accelerates the air. To produce thrust $F$, the engine has to impart momentum $p = \frac{F}{t}$ per unit of time on the air. Momentum is proportional to mass and first order of speed. $p = mv$ where $m$ is mass of the gasses (reaction mass) affected by the engine per unit of time and $v$ is speed of those gasses.

The gasses however also take away some kinetic energy. Kinetic energy is also proportional to mass, but also to second order of speed. $E_k = \frac12mv^2$.

This energy has to be provided by the engine. Since the fuel can only provide so much energy (it's heating value) per unit of mass, an engine that needs less energy needs less fuel. And that is achieved by moving more air. Which means higher bypass ratio for jet and bigger propeller for engines with propellers.

Note, that this does not say high-bypass engine would be more efficient at slow speed than at high speed. Because it isn't. All jet engines are more efficient at high speed. This is because the power the engine produces is $P = Fv$. So at high speed, larger part of the power output is the useful work moving the aircraft.

In high-bypass engine the maximum power output of the fan is limited though (similar to propeller), so compared to a turbojet the difference in efficiency is higher at low speed.


What is this type of aircraft? In this picture, could anyone describe what type of aircraft and which airline it is?

That's a US Airways Embraer E190

Here is another view of the E190 wing for comparison.


How is the F-22's nacelle/engine bay ventilated? How is the aircraft skin around the engine bay in the F-22 cooled?

As in the F-35, there are scoops below the wings, which provide ram air around the engine bay, but you don't see any scoop around in the F-22 for the same purpose.

Location of F-35 scoops according to codeonemagazine.com

The exact details of the F22 are classified. But the more likely scenario is the engine has a cold bypass air gap between the afterburner inner wall and its exterior shroud. From all the close-up shot of its nozzle, the thrust vectoring nozzle and the emergency arrestment hook fairing is lined with some sort of refractory materials and need no special cooling and the serrated nozzle fairings on either side of the nozzle seem airtight and have no place for a cooling air stream outlet. Plus, we see no scoop on the front of the aircraft as an inlet for engine cooling, and the scoop, should it exist, must be quite large. I say this is the most likely scenario because it's the least heavy and complex solution to engine cooling. And let us do not forget small cavities with a diameter in the range of millimeters is the most effective radar wave reflector/scatterer.

A less likely scenario is the engine is cooled by fuel, just like the avionics, the radar and the AC for the pilot. The fuel is then cooled first by the sheer amount of wing area as a radiator and second by a pair of hidden air-cooled fuel cooler. (I won't tell you where :))


What do airlines do with planes at the end of a multi-stop route? The question's kind of broad and simple, so let me be a little more specific. Take Southwest Airlines flight WN3223. This is a multi-stop, trans-continental route that starts at LGA in the morning, flies to DAL, then PHX, LAX, OAK and finally SEA with expected arrival times usually around 10:00 PM. This route runs daily.

Now, according to Flight24, sometimes the same tail number is used for the flight on consecutive days, more often there's a rotation. So the question is, what does the airline normally do with the plane between 10:00 PM one day and 6:00 AM the next (when a plane, if not the plane, is expected to be back in the gate at LGA)? Does Southwest just deadhead it all the way back to LGA? Do freight companies subcontract with airlines like Southwest to move boxes overnight on otherwise deadhead flights? Does the plane stay in Sea-Tac and is used for another flight number (possibly the reverse route)? Does the crew deadhead to a maintenance hub? All of the above?

EDIT: This question might be similar to the mentioned duplicate but I think it's more specific. I'm asking, more or less, how an aircraft used to operate a route that takes it across the country during daylight hours is typically "reset" so that it can fly that route again.

The assumption, of course, is that the plane does fly that route again on some cyclic schedule, which may itself be wrong; a look at the tail numbers available for WN3223 shows that none of the aircraft used for that route in the past 4 days have flown it again in that same time period, despite the planes used for older flights having ample opportunity to make it back to LGA for another run. So, I think my answer, at least for Southwest's routing model, is "the plane spends the night at SEA, then is sent on a new route number the next day, which may have nothing in common with WN3223 nor get the plane back in a situation to run WN3223 again".

Airlines running non-stop long-hauls probably have a more static schedule; an A380 might fly from Dubai to DFW, then turn around and fly right back, and that one route may be the only thing the plane is scheduled to do for weeks at a time.

Deadheading is rarely done because it is a non-revenue movement.

The most common use of deadheading (that is, flying the aircraft empty) is done for maintenance runs.

At the end of a scheduled route, the plane is parked at the last destination.  Sometimes, the next flight around uses the plane (if the route can be serviced by the aircraft).

Typically, airlines try to "park" their planes at their hub locations (where they have favorable landing and parking fees) rather than leave the aircraft at another airport.

Flight operations and planning make sure the aircrafts are maximized on revenue movements.

To give you an example - the shortest scheduled commercial flight for the A380 is Dubai - Kuwait (EK857); and the return flight Kuwait - Dubai (EK858).

The inbound aircraft on the flight yesterday (A6-EOH) was inbound from Perth to Dubai; and then flew to Kuwait and then back to Dubai. The next day (July 1st), the same aircraft is scheduled for SFO. (See the flight log at flightradar24).


How do the oxygen masks deploy after a cabin decompression? Is there any sensor incorporated on the Passenger Service Unit that tells the masks to deploy when a cabin decompression occurs?

According to this Airliners.net forum post,

  The masks are deployed automatically (typically when cabin altitude exceeds 14,000 feet), or can be deployed manually from the flight deck. In addition, if a passenger service unit oxygen door should fail to open, cabin crew can open the PSU door (either inserting a flat object or a special tool depending on the aircraft type) manually.

So basically, the masks are deployed automatically based on sensors, with manual deployment as a primary failsafe and physical access as a secondary failsafe.


How to handle vacuum and turn coordinator failure in IMC? I just earned my FAA instrument rating and a considerable amount of time was spent training partial panel. This meant flying with no vacuum gyro instruments - attitude indicator and directional gyro. After my check ride the examiner said "you fly better without those instruments" which I considered a nice compliment to both myself and my instructor.

In reflecting upon this, I started thinking, what if I had an additional failure of something - how would I handle it? I launched X-Plane and set up an LNAV+V GPS approach on a windy, bumpy low IMC day and gave it a shot. Unsurprisingly, this was HARD.

I used the instruments as follows:

Altimeter / VSI and on the final approach the VNAV glide slope for altitude control. Not too bad.
GPS track and a bit of magnetic compass checking, along with the CDI needle. This is a very poor way to navigate. The magnetic compass obviously has lagging/leading errors and the GPS track is what I'd call a rate instrument - it lags a little.

The main problems I faced were that you can't time turns with no turn coordinator and the bumpy/windy air made constant corrections required. There appears to be no way to identify wings level. You can tell when you're no longer turning but you might be starting a turn the other way.

My strategy as I worked through this was to slow the plane (C172) down with 10 degrees of flaps throughout the procedure to make heading changes have the least effect. In the end, I tried to keep the track as close to the DTK and the CDI as centered as possible - effectively chasing two needles. This resulted in a sinusoidal course when I looked back at it on the X-Plane instructor console.

(By the way, I did land the plane safely but I'm not sure I'd be able to do this in the real world - the workload I experienced in my comfy chair was EXTREME.)

I know the scenario is unlikely but it's certainly possible. There appears to be no guidance that I can find on the Internet about it.

My question: is there a better way to do this? If so, what's the procedure?

This isn't exactly your scenario but at my last instrument checkride the DPE asked me how I would descend from VFR-on-top through a solid cloud layer following complete electrical and vacuum failure (in a C172 or something similar). No avionics meant no help from ATC (vectors, or even a PAR approach) and we also assumed that I had no tablet, phone or other external systems that could help me.

The question came at the end of a discussion about aircraft systems and failures and the DPE didn't expect me to have a ready answer because it isn't something you train for. But he suggested this procedure:

Set up the aircraft on an east or west heading to minimize compass turning errors
Use the rudder only to fly a constant heading on the compass; once you have the aircraft going straight, do not move your feet again
Set power and trim for a stable descent at a little above Va and a little less than your usual descent rate, e.g. 300fpm
Sit back, cross your arms and wait to break out. Resist the temptation to touch the ailerons or power.

His reasoning was that by avoiding using the ailerons and power you can avoid going into a graveyard spiral quickly. You may still do it, but you'll do it a lot more gradually and hopefully by that point you'll have broken out anyway. I've never tried it myself, but I'll have to do it sometime with a safety pilot.

In real life, if you can't get to VMC easily then a tablet app with a portable AHRS unit would be a good backup. Although personally, if I ever lost the complete panel my first thought would be to get to VMC, not to shoot an approach. I suspect that for most people, landing in a field is likely to be the much better choice. But like all 'what if' scenarios, it depends.


What is the difference between an air carrier and a commercial operator? I am currently studying for my commercial and I've been seeing both of these terms used interchangeably. Is there a difference?

From 14 CFR 1:

Air carrier means a person who undertakes directly by lease, or other arrangement, to engage in air transportation.

Commercial operator means a person who, for compensation or hire, engages in the carriage by aircraft in air commerce of persons or property, other than as an air carrier or foreign air carrier or under the authority of Part 375 of this title. Where it is doubtful that an operation is for “compensation or hire”, the test applied is whether the carriage by air is merely incidental to the person's other business or is, in itself, a major enterprise for profit.

To make this more clear FAA Order 8900.1, Volume 2, Chapter 2, section 2 says:

2-128    TYPES OF CERTIFICATES UNDER PART 119. There are two, basic types of air operator certificates (AOC) issued to U.S. applicants who will conduct operations in common carriage. See Table 2-4, Certification for a summary of certificate requirements.
A.    An Air Carrier Certificate. This certificate is issued to applicants that plan to conduct interstate, foreign, or overseas transportation, or to carry mail.
B.    An Operating Certificate. This certificate is issued to applicants that plan to conduct intrastate transportation.

From your perspective it isn't a too important distinction.  As a commercial pilot all that matters to you is that both air carriers and commercial operators need to have operating certificates.  As a commercial pilot you can be hired by someone who has an operating certificate but you cannot provide the same services on your own unless you yourself have an operating certificate (e.g. a charter operator can hire you, but you cannot operate a charter service).
As a commercial pilot you can be paid to act as PIC and can engage in the commercial operations that are excepted from operating certificates in 14 CFR 119.1(e).  You cannot act as either an air carrier or a commercial operator without complying with 14 CFR 119, which requires that you have an operating certificate.


What is the purpose of a wing Yehudi? Apart from covering the landing gear leg, the Yehudi also increases the wing root cord which allows the build height for the root to increase for the same wing relative thickness. This is useful as the wing has its highest stresses in this area, it is where the wings bending moment is at its highest (leehamnews.com).

I don't understand the text in bold. Apart from landing gear 'packaging'. What are the advantages of the Yehudi? Aerodynamic or otherwise.

(commons.wikimedia.org) An early jetliner without the Yehudi.

I'm also interested in the etymology.

Mitteneffekt
The pressure fields of the left and right part of a swept wing interfere at the center, causing a drop in lift. The Horten brothers called this "Mitteneffekt", and it was never properly translated into English, so the German term is used. The Hortens increased chord at the center trailing edge of the wing, reducing local sweep and increasing the area for lift creation. This helped to fill the "hole" at the center and at the same time allowed them to better enclose the pilot.

Lift distribution over unswept and swept wing (picture source)
The same is achieved with the reduced trailing edge sweep, airfoil change and change in incidence at the wing center of airliners. Since this part is occupied by slotted flaps, the rounded trailing edge contour of the Horten planforms is not possible there, so a straight line is the best solution.
Structural Efficiency
Large wings need heavy spars, and saving some spar weight goes a long way in reducing lift requirement and, consequently, drag. While smaller airplanes do not profit much from an increased wing root thickness, larger ones can save hundreds of kilograms by increasing their root thickness. Since the flight Mach number must not suffer from this thicker root, the simplest solution is to extend the wing chord at the center. (Sorry, the link leads only to a library, but the thesis gives extensive proof.)
A nice side effect is the increased space for housing the landing gear.
Separation Control
Interference between fuselage and wing will cause separation there to start earlier than on the clean wing. Also, the superposition of the flow fields of fuselage and wing will cause shocks at a lower flight Mach number. Therefore, aerodynamic efficiency both at low and high speed is increased when the local lift coefficient drops near the wing root, so the flow has more margin before shocks or separation start. By increasing root chord over what is required for an elliptic lift distribution, the local lift coefficient can be lowered while the circulation distribution stays elliptic.
Flap Effectiveness
With an unchanged leading edge sweep, Mach tolerance is not much affected, but the lower trailing edge sweep is very helpful for increasing the effectiveness of the trailing edge flaps.
Regarding the word "Yehudi": This is the first name of a famous violinist, but I do not connect it with a wing planform.


What does ATC do during "slow" times? I know at larger airports, it's NEVER a slow time. But what about at smaller airports that are large enough to rate manned ATC, but things aren't always fast-paced, high-traffic like at JFK or DFW, etc. (say an airport like JLN (Joplin Regional))?

What other duties do ATC personnel do when the traffic is light? Do they just sit and stare all day at the readouts, waiting for any one aircraft to appear and call in? Or are there other "busy work" items they do when things are 'slow' and they are listening for air traffic to call in for instructions?

Admin stuff, emails, chat with a colleague if you are not alone on shift, read up on (ever changing) procedures, eat, read a book, make sure the coffee machine works, meditate, watch TV. Anything goes, really, as long as you keep an eye on the radar and stay close enough to hear the radio and answer the phone. Of course, this is all assuming that there are literally no aircraft in the sector at that time (which happens regularily at smaller airports). Whenever you have any active aircraft, you obviously need to stay quite focused on that.


How does the line of thrust affect longitudinal stability? I’ve been studying Pilots Handbook of Aeronautical Knowledge FAA-H-8083-25B and on p 5-17 they talk about thrust line and stability. Can someone explain why the moment changes when thrust is applied?

  Power or thrust can also have a destabilizing effect in that an
  increase of power may tend to make the nose rise. The aircraft
  designer can offset this by establishing a “high thrust line” wherein
  the line of thrust passes above the CG. [Figures 5-26 and 5-27] In
  this case, as power or thrust is increased a moment is produced to
  counteract the down load on the tail. On the other hand, a very “low
  thrust line” would tend to add to the nose-up effect of the horizontal
  tail surface. Conclusion: with CG forward of the CL and with an aerodynamic tail-down force, the aircraft usually tries to return to a safe flying attitude.

There is a general rule: don't trust "Pilot's Handbooks" when they talk about aerodynamics. More often than not, they are full of misconceptions and, at best, oversimplifications. In your quote, for example, the conclusion has nothing to do with the preceding text.

But the question is fair. Thrust line can affect stability, but we need to define what exactly we understand by that.

Stability as such is a negative reaction to a disturbance: a disturbance of a particular defined kind must cause a reaction which negates the original disturbance. Usually, we restrict the analysis to relatively small disturbances, when reactions are more or less linear.

Longitudinal stability, in a broad sense, describes any longitudinal motion. For airplanes this involves pitch or speed. (Altitude is a different axis and even a different frame, although we'll need to consider it in some cases). These are linked but different motions, and we can talk about them separately to some extent. It just happens that for most airplanes, the characteristic times of these angular vs linear motion is so different that we can very well analyse them independently. The heavier the airplane (and/or higher its wing loading), the better it holds. Even for GA airplanes it's still largely true.

In a strict sense, when aircraft designers (but not pilots) talk about "longitudinal stability", they mean the short-period pitch stability, or more accurately, angle of attack (AoA) stability. This means that when AoA is disturbed (by a gust or control input), a moment immediately arises that counteracts this AoA change (which is done via pitch change).

The mechanism behind AoA stability involves purely aerodynamic moments/forces. (The explanation involves the concepts of neutral point and moment derivatives). Notably, it does not involve thrust nor airspeed. Both of them change too slowly compared to AoA/pitch and so play practically no role in longitudinal stability per se.

But when it comes to airspeed stability, with which pilots are more intuitively familiar, the situation is different. Airspeed stability is linked to AoA stability via an indirect mechanism that Robert already roughly described in his answer: "increased thrust, increased speed, increased lift, plane rises vertically, vertical "up" pushes tail down, pitch changes". The important result is that a statically stable (read: AoA stable) aircraft will also be stable in speed. But even that holds only if drag doesn't grow faster than lift; that is, on the front side of the power curve. (Pilots know it very well). At high (but pre-stall) AoAs, the airplane will remain stable in AoA but will become unstable by speed.

Technically, this is still speed stability, not thrust stability. We are not concerned how airspeed changed: thrust, gust, dive, whatever. A statically stable airplane will try to pitch up and climb as a response to increased airspeed, slowing down as a result.

But when we analyse speed changes as a specific result of thrust changes, other factors come into play. Namely, apart from speed, changing thrust can disturb the moment balance of the airplane. In general, multiple effects can be important here, not only the location of line of thrust with respect to CG, but also with respect to 'centre of drag'; and the changed slipstream may cause aerodynamic changes. Either way, it may happen that these extra moments may augment or negate the natural tendency that comes from AoA stability.

For simplicity, let's analyse a few obvious cases of reaction to increased thrust (leaving everything else unchanged, particularly trim).

Thrust is in line with CG. The airplane will start to climb (or reduce descent) and will settle on the same AoA and roughly the same speed.
Thrust line below CG (the case of most airliners with underwing engines). This will produce an added pitch-up moment, which will cause the airplane to slow down more than necessary, despite the added thrust! This is an unstable condition. It can be particularly nasty in go-around situations. How do we fly it? Luckily, unlike AoA, the changes are slow enough for pilots (let alone autopilots) to react with active trim changes.
Thrust line above CG. This is the opposite of the above and, in moderate amounts, can have stabilising effect and easier trim changes. The airplane will settle at a higher speed, which is presumably what the pilot wants (despite the "power controls altitude" mantra). When the line is too high, the airplane may even descend and accelerate more than necessary, until the aerodynamic moment balances out the thrust moment, but overall the condition is stable. (Note that in most cases thrust starts to fall with increased speed, which helps to find the balance).

As a conclusion:

In a strict sense, line of thrust (and thrust as such) does not affect longitudinal stability per se; that is, the AoA stability.
However, it does affect airspeed stability, which many pilots understand as longitudinal stability.
It certainly affects trim changes, which, again, pilots perceive as a measure of longitudinal stability (not entirely without reason).


Why are "Follow Me" cars painted yellow and black? Why are "Follow Me" cars painted black and yellow, and use square shapes in their design?

Yellow and black together are highly visible in any light, especially if there are sharp, straight lines between them; our eyes are drawn to that combo and our brains are evolved to recognize it as a danger. Think of bumblebees.

Stationary objects tend to be painted white and red for similar reasons.


Can having an incorrect hair color on my FAA medical certificate get me in trouble? I just got a new FAA medical certificate, and I accidentally put down that my hair color is blonde when in reality it is dark brown. Also, my hair is listed as brown on my pilot certificate.

I bleach my hair in the summer, which makes it blonde.

Would such a small detail cause any sort of trouble?

This probably won't cause you any practical trouble unless you go for a new certificate or rating (the data on your medical needs to match the data on your IACRA form which needs to match your existing certificates - an examiner may refuse to conduct a test if there are discrepancies).

It's something you should correct though: It's presumed your hair color on the medical is your natural hair color, and if you get ramp checked you don't want to have to explain the discrepancy.

Counterintuitively the answer for "How do I fix this?" is buried in the IACRA FAQ:

  Q:    The data on my medical certificate does not match what is in the FAA Airman Registry database, what should I do?

  A:    If it is less than 60 days since the date of issue of your certificate, contact your AME (Aeromedical Examiner) for resolution of this issue. If it is 60 days or more since the date of issue of your certificate, contact the FAA Aerospace Medical Certification Division for resolution of this issue. The contact info is below.

Aerospace Medical Certification Division, AAM-300
Federal Aviation Administration Civil Aerospace Medical Institute
P.O. Box 25082 Oklahoma City, OK 73125
Tel: (405) 954-4821


What is the purpose of logo lights on airliners? Why do modern airliners use lights to illuminate the sides of their tails and illuminate the airline's logo?  Is this just done to give ground and tower controllers an easy way to differentiate between multiple jets on the ground during night ops or direct them to the appropriate gates e.g. Delta flights to Delta terminal, Qantas flight to Qantas gates, etc.?

There are multiple reasons.

First of all: Of course promotion for the airline.
Another reason is the visibility. Airliners have several lights and strobes (Nav lights, rotating beacon, ...) but this can be overseen. The logo light is used to see if there are any other aircraft crossing the taxiway or apron. It's just better to have a big, bright illuminated area, instead of a few small lights.
And ATC has also something to do with it. Many phrases regarding taxiing include airline names. For example:

  AFA739, give way to an Air Berlin A320 moving from left to right on taxiway Bravo

ATC and the pilot can visually identify the companies name thanks to the logo lights.


Why does Airbus suppress stall warnings in certain situations? I was reading about Air France 447 and came across the line:

  The stall warnings stopped, as all airspeed indications were now considered invalid by the aircraft's computer due to the high angle of attack.

In short, due to pilot error, the aircraft (A330) reached a 40 degree angle of attack while under Alternative Law (due to icing conditions) and stalled at 52 kts. Further confusion came from the stall warning suppressing itself after some period of time.

  Roughly 20 seconds later, at 02:12 UTC, the pilot decreased the aircraft's pitch slightly, airspeed indications became valid and the stall warning sounded again and sounded intermittently for the remaining duration of the flight, but stopped when the pilot increased the aircraft's nose-up pitch.

It would seem, if the aircraft was stalled, and the computers knew the angle of attack was still far greater than normal, that it's most reasonable to assume the aircraft would still be in a stall even after other sensor data became unreliable. Also, if no airspeed sensors are reading valid data... seems it's most reasonable to assume the aircraft is in a stall... or on the ground (but wheel load sensors can corroborate when that's the case) - not just give up and assume everything is fine.

It seems to me, that perhaps this stall warning is at least partly at fault for this accident.

Why did Airbus design the stall warning system to suppress warnings in this situation?

Stall warning was inhibited below 60 knots airspeed, in order to eliminate nuisance warnings during taxi and other situations. It is well below the stall speed of an A330 in cruise configuration:

landing speed with flaps extended is in order of 135 knots;
stall speed in landing configuration would be in order of magnitude of 120 knots;
stall speed in cruise configuration way above that.

It was indeed a very tragic circumstance, one of the factors preventing the flight crew from recovering from their situation. The solution however, perhaps in addition to enabling stall warnings for very low speeds in cruise configuration, is to train flight crews in recovering from a fully developed stall. During recovery, the load factor must remain under 2.5 g, the structural limit for an airliner.

This is now mandated by regulation authorities, and the first systems have been certified for training use at airlines. FAA has published 14 CFR part 60 Change 2 for upset recovery training. Alaska Airlines had the first Part 121 simulator certified for Full Stall Training under Part 60 Change 2, in April 2016. The simulator is a B737-800.


What's this sound? - Dogfight between F14 & MiG23 The following video features real-life audio of a CAP "dogfight" between two F14 Tomcats and two Libyan MiG23's in 1989.

(YouTube uploader: TopGunMilitary)

The audio isn't the clearest but between 6.29 and 6.34 during the fight a electronic interference kind of sound can be heard.

I have heard similar noises to this in other videos cockpit videos, what is it? My current suspicion is that it is some kind of "jamming" signal from the F14's as I believe the pilots in the recordings talk about one of the MiG's firing a missile.

Any opinions would be more than welcome

EDIT:

This is another video displaying the same noise at 1.37:

(YouTube uploader: BongHitBrian)

That is the aural conversion of the input of an AIM-9 missile's infrared seeker head.  The missile allows the shooter to operate it in either a caged mode, that is where the seeker head is slaved to the angle and azimuth of the radar antenna, or uncaged mode, where the seeker head can freely seek out and track a bright infrared source like a jet engine on a fighter.

When the AIM-9 missile made its debut, the aural lock on cues were the only means a pilot had to know that the missile had acquired the target.  Today, pilots can often select this engagement mode if they wish to keep their fire control radars off in order to avoid detection.  When the missile seeker head is searching for a target, it makes a mechanical, raspy growling sound.  Once the seeker head acquires a heat source, the tempo of this growl picks up in conjunction with a steady mid to high-pitch tone.  You will often hear pilots acquiring a lock on an enemy aircraft refer to it as "getting a tone"; this is what they are talking about.


What does it mean when pitch numbers move all over the HUD screen? In this video from an F-16:

You can see pitch angle move out of screen or be on the side at the end.

Updated answer based on F-16 specifics.

The top arrow shows the nose position—pitch angle, in the F-16 it is based on the Gun Cross (Boresight Cross), which also indicates the fuselage reference line.

The middle arrow shows the position of the flight path marker (FPM, also known as FPV), it shows where the aircraft is going. The vertical distance (angle) between both symbols is the angle of attack.

The bottom arrow is an air-to-air attack mode called a missile diamond. Don't focus on it.

The FPM can go sideways in crosswind and/or with rudder input, as the plane would be slipping, skidding, or flying sideways. That's the horizontal distance (angle).

The pitch angle numbers/lines—scale—moves with the FPM centered on it, unless the pilot wants it to be centered around the nose. The latter is called caged mode.

The rotation of the scale indicates the bank angle.

Now that we know all this, a direct answer is: the plane's nose relative to where it was going was all over the place, and so was the pitch scale.


Why are listed times of useful consciousness so low? I've been reading about Time of Useful Consciousness (TUC), and it says that at FL 180, the time of useful consciousness is 20 to 30 minutes at rest.

But I've been to a trip to Tibet, and we went on a bus trip around the places, and at one point the bus came to a mountain pass around 18,500 feet, and we all got off the bus, walked around, took pictures, and even ate lunch, so it was definitely not at rest. It was about 40 minutes to 1 hour, and I only felt slightly uncomfortable/out of breath.

According to the chart, I should have passed out, or at least become "useless". Why didn't this happen? Are the charts simply very conservative and apply to, say, unfit, crumbling, old pilots?

In short: acclimatization, both chronic and acute.

During your Tibet-trip, you had probably spent days at high altitudes, allowing your body to acclimatize to the lower oxygen partial pressure (similar to how some elite endurance athletes prepare themselves for competition), by increasing your hemoglobin count (and other mechanisms), making you better prepared for the walk at 18,500 ft. This is an example of chronic acclimatization.

A normal sea-level dweller will not have had the benefit of the same acclimatization phase in a depressurization situation (albeit a pilot could probably have some degree of acclimatization from continuously being exposed to higher than sea-level cabin altitudes), and will hence have a shorter TUC. The onset of the depressurization will also play a big part in determining your TUC. A slow depressurization will allow for some acute acclimatization, whilst a rapid depressurization will allow for none. The shock of a rapid depressurization will also decrease your TUC.

The table on the Wikipedia page you quoted is the same (or very similar) to what you'll find in most Human Performance literature for airmen, and is, according the same Wikipedia page "average TUC for healthy, young military pilots".


Is the user interface design of ATC equipment generic across countries? Are the computer screens used by ATC generic across different countries? I.e., do ATCs around the world simply purchase the same software from a few companies, or do each of them develop their own system and end up with different user interfaces?

For an analogy of aircrafts, most of the controls and instruments are universal across pretty much all aircrafts, be it Cessna, Piper, Airbus, Boeing, CRJ etc. Any trained pilot would likely recognize the important controls (e.g. throttle, flap lever, attitude indicator) right away; certain colors and symbols are also expected.

Is this the same for the computer systems used by ATC? E.g. if a controller from the US goes to Australia, is he expected to understand and know how to operate the equipment right away?

Most ATC software systems are developed by a few large companies. Companies that produce such software include Lockheed Martin, Thales, Raytheon, Indra, Comsoft, Adacel (and maybe a few others). It's not a big market since there are only a limited number of customers (countries) and safety critical software is very expensive to develop.

One interesting offering is the Albatross open source ATC software. This isn't a complete system (yet?) but some parts are available now. I'm not sure whether this software is actually used in operations anywhere at this point.

Most ATC providers (which are usually run or owned by their government, though not always) do not do their own software development. They buy a system from one of the established vendors, who may do some amount of customisation work ranging from none to extensive, perhaps with a support contract for future fixes or enhancements. There are a few exceptions though, for example Airways New Zealand uses software originally developed by a large vendor but also has an in-house software development group who maintains, enhances, and extends the existing software.

Each system has the same general operating concept - an ASD (Air Situation Display) which shows the locations of aircraft, plus auxiliary windows that may contain all kinds of other things used for communication and coordination. Like any sophisticated computer software, the general idea of two different systems might appear the same, but be completely different to actually operate (think of Photoshop vs. Gimp, or Microsoft Word vs. Apple Pages).

A qualified controller from the US would not be expected to be able to operate in Australia straight away. Not only will the software be different (different mouse clicks, or different key commands), but also the rules of air traffic control can be different between countries. Furthermore, a controller must become familiar with the local airspace and operating procedures.

Having said that, the general skills of air traffic controllers are portable between countries. On moving from one country to another, a controller would be expected to go through a certain amount of training in their new country, which could range from brief familiarisation to more rigorous retraining.


Why is one of two parallel runways sometimes closed in foggy weather? A few times, when flying into SFO, me and my fellow passengers were informed that due to foggy weather one of two parallel runways there is closed, causing delays. So, a few questions:

Why can only one runway be used during fog? During an instrument landing, if the instruments are precise enough to land the plane exactly in the middle of one runway, then surely they are precise enough to differentiate between two runways?
Is this standard practice in all airports or something specific to SFO? Is there some minimum distance between parallel runways above which it is safe to keep them both open in foggy weather?

SFO makes use of simultaneous close parallel approach operations.  This allows higher density operations than would otherwise be possible for runways spaced so close, but to make use of these ops, in SFOs case, requires 1600 ft ceilings and 4 sm visibility due to the requirement that aircraft maintain visual contact during close parallel operations.

It does look like SFO can run the ILS approaches simultaneously outside of close parallel operations, but is possible the required spacing makes its pointless to use both runways.  If weather was bad enough that cat II ops were in effect, I don't see any verbiage on the cat II charts indicating simultaneous ops are approved.

Regardless of how precise your instruments are, there are strict requirements on how close you can be to another airplane in the approach phase and that separation be maintained if both parallel aircraft perform the missed approach.

The ability to run parallel approaches in low visibility depends on how far apart the runways are laterally.  Airports like IAH and ATL can run triple parallel ops and if you take a look at their runway layout you will find they are spaced quite far apart and may be displaced relative to one another.


How do ATC radars know where to position a primary target? Primary target: An aircraft not reporting mode-C, the only thing the controller has is the return on the radar.

When a controller reports a primary target as traffic to other aircraft, the controller does not have the altitude of the target. Given this, I conclude that ATC radar does not have the altitude (angle-up) to the target, and only provides azimuth.

So then without the altitude, how does the radar-system know where to put the target laterally on the screen?

Example, a radar picks up a target that is 10 miles from the station. If the target is 0 AGL, the proper position would be 10 miles out. However, if the target is at 15,000ft, the proper position would be 9.5 miles out.

Since the difference is so small, does the radar just put the target at 10 miles, and the FAA separation guidelines factor in the discrepancy?

Primary radar, even modern digital systems, do not give any possibility to the controller to determine altitude.  The digital system has that capability, but civil ATC does not.

In primary radar displays usually just the azimuth and range are plotted. So an aircraft at 15.000 ft 9.5 NM away will be plotted on 10 NM distance, just like an aircraft at 0 ft 10NM away. Usually the secondary radar is collocated with the primary so secondary targets can be displayed using the same projection (disregarding the altitude).

If you now apply horizontal separation based on this projection, you will never bust the separation minima. It is a conservative way of providing separation, but when there is no altitude information it is the best possible way.

Note that this does not only apply to primary targets, but also to Mode-A only targets


Where can I find a list of rules of thumb formulas for navigation? Is there any list of formulas for quick counting navigational parameters of the flight, if navigational computer is malfunctioned.

For example, I need to recalculate how long can I fly, if the wind is changed.

There is no short list but almost all the navigation information you could ever want can be found in this handbook published by the FAA. If you are worried about your nav computer failing you can always get an E6B which is about as close to failure proof as you can get. An E6B will expedite most most nav related calculations in the air (like headwind component). My E6B has some common nav calculations written on the back of it actually.


Dropping an object from really high, landing at 0 velocity due to 'free' reverse thrust So a friend had an 'idea' where you could make an object land with 0 velocity.

Basically the idea is that you drop an object (like a rocket shape) from some altitude. To the object you attach fins (fixed propeller blades so to speak.) as it falls it starts rotating, due to the attached fins.

Now at some altitude above the ground you either:

1) You rotate the fins to get reverse 'thrust' (you don't really have thrust, but you would slow down rotation.)
2) Retract the fins and expand new ones that face the opposite way (so they counter spin)
3) something along those lines (like extending flaps)

Now one of the arguments he had as to why this works is because you could expand larger fins for the counter rotation, therefore getting more drag and generating more 'lift'.

It feels like you cannot do this, but I cannot give a (good enough) reasonable explanation as to why it would or would not work (I'm a noob in this area.) So let's ask the people in the know... that's you.

I would love to see some 'proof' more so than speculation.

Thank you in advance.

What you are describing is similar to a helicopter autorotation.  That is something that does work.  The rotors both generate drag and store rotational momentum.  Then, some of the momentum is converted to lift for landing.


What are the concerns and consequences of an overweight landing? If a 777 ER has to immediately land after takeoff on a planned 14,594 km trip (in the case of a fire, e.g.), the landing will be executed with a very heavy aircraft.

What are the major concerns of doing such a landing?
What will, on average, be the consequences of this overweight landing?

Two things:

Loads on the landing gear. This can be alleviated by carefully touching down, but you never know what exactly will happen in the next landing, so better don't count on it to be smooth
Deceleration distance: The higher mass requires a higher approach and touch down speed (higher by the square root of the mass ratio between your actual mass and the maximum certified landing mass). Now you have more mass and more speed, but the landing strip and the airliner's brakes are still the same. The risk is that you overshoot the runway with an airplane full of fuel or that you overheat the brakes (which will result in their failure, and again an overshoot). Since the kinetic energy is proportional to mass times speed squared, the energy which needs to be absorbed by the brake goes up with the square of the mass increase.

If the selected runway for your overweight landing is long enough and the weather is calm (so a smooth landing is easier), an overweight landing is not such a problem.

Now let's look at the 777-300ER in detail. I use the figures from Wikipedia, because the manufacturer's site is trying much harder to hide the relevant data. The MTOW (maximum take-off weight, which is actually a mass) is 351,534 kg, and the maximum landing weight is 251,290 kg, about 100 tons less. Now let's assume that taking off and returning to the airfield uses 5 tons of fuel, so the mass ratio is 1.379. Therefore, the approach speed has to be 17.4% higher and the total kinetic energy at touchdown is higher by a factor of 1.9 compared to the case at maximum allowable landing weight.

If we now assume that speed is reduced linearly during the landing run and that the wheel brakes will just absorb as much energy over time as in the case at maximum landing weight, the deceleration needs to be lower by the mass ratio, so the aircraft decelerates with only 72.5% of the deceleration at maximum landing weight. To shed its kinetic energy, the landing run will take longer by the increase in kinetic energy, i.e. 1.9. Since the average speed is also higher by 17.4%, the landing distance will be higher by a factor of 2.233 or 223% of the landing distance at maximum landing weight.

This neglects that the heating of the brakes is an instationary process, so you cannot simply brake with the same intensity for more than twice the time they were designed for. But this little estimation should illuminate what impact a higher landing mass has on the energy and distance involved.


Does a 4 bladed prop have almost twice the thrust of a 2 bladed prop? Does a 4 bladed prop have almost twice the thrust of a 2 bladed prop?

As a general rule, I'm told GA planes generate 4 lbs of thrust per horsepower. (Source: Zenith School of Airplane Design, Flying on your own Wings)

So if you use a 4 bladed prop, does it generate anything close to 8 lbs of thrust per hp?  In other words, say for an ultralight, where you're only flying 60 mph, and prop drag isn't an issue, can you use an engine with half the horsepower, or some other fraction thereof?

Will that shorten my takeoff roll? Conceptually, takeoff roll is just the distance to accelerate from zero to my minimum takeoff speed.

Since F=ma, then a=F/m, so if I want to accelerate twice as fast, I need twice the force, or thrust ( probably more than twice the thrust, to overcome rolling drag, etc.)

Is this correct, at least conceptually?

Just to summarize:

In the GA world, I'm told as a general rule, props develop 4 lbs of thrust per hp. So, for 160 hp, I get 640 lbs of thrust, or is this not correct?

In the STOL world, with 8' props, I'm told, they get 8 lbs of thrust per hp. So, for 160 hp, I get 1,280 lbs of thrust.

Well, I'd rather have a 160 HP engine and prop that produces 1,280 lbs of thrust than 640lbs of thrust.

So... if I take my 8 ft 2 bladed prop, chop it in half to get a 4' 4 bladed prop ( same overall "wing area"), I'll still get 1,280 lbs of thrust ( less a few % for inefficiency), instead of 640 lbs of thrust. Is this correct? If not, what value of thrust should I expect, roughly?

Or are these rough estimates incorrect?

At the same size and rpm, a 4-bladed prop will require twice the horsepower to drive, approximately.

Due to blade interference, it will always generate less than twice the thrust. So lbs thrust per hp will generally slightly decrease, as long as the propeller is in its optimal tip airspeed band.

If the propeller was overly fast initially, slowing it down and going with more blades to compensate can result in small thrust/hp gains (+X percent, not X times). This will generally apply to aircraft originally designed with much less power and later modified.

There are a few legitimate cases where design size is less than the aerodynamically optimal size. One is clearance to the ground or between the props (in quads). Another is turbofans: the drag of the nacelle overcomes the benefits of lower disc loading. Even for airliners there's a push for wider fans, but the "open fan" idea (basically a turboprop) was scaled down to geared fans and the Ultrafan for noise reasons.

In helicopters, at some point, the blades become so long and so far apart that adding more blades beats the weight and bulk of longer blades. The more blades, the worse, so going up to 4 is not such a big deal as doubling it again to 8. For small aircraft with low power/weight ratios, where 2 blades fit easily, that's generally the best configuration.


What's the shortest amount of time a commercial airplane will be on the ground in between flights? What's the shortest amount of time a commercial airplane will be on the ground in between flights?

After a commercial flight lands the passengers and luggage have to be unloaded, the airplane needs to be refueled and undergo mandatory inspections, etc.

With all of that going on between a commercial airplane's landing and takeoff, what's the shortest time it would take between flights?

I flew SA-226/227 Metroliners for two different commuters back in the 1980s. If we were behind schedule, station managers had the option of asking the pilots to do an engine-running turn. The passenger entry door and the cargo door were on the left side of the airplane, so that meant the right engine was left running.

Such turns, usually only requested if there were few passengers exiting and entering, and little baggage being unloaded and loaded, took as I remember less than 10 minutes. The Metroliner was very noisy even with only one engine running and you didn't want to do it if any kind of a line would form at the bottom of the entry stairs.

Captains had the option of refusing such turns, and some captains wouldn't do them.


Why B-52 was not re-engined as a more efficient 4-engine? Why B-52 was not re-engined as a more efficient (also for maintenance) 4-engine but is still an 8-engine aircraft?

In history, almost all others models were re-engined with new engines also quite different from original, some examples could be C5 Galaxy or also B737 that in latest geneations requires also to extend undercarriage or make bottom "flat" area of engines, to accomodate new bigger ones.

So why B-52 remains the original projects despite its long history? Did development cost be affordable in this very long period?

There were several proposals to do just that, none of them ever went beyond the proposal phase.

Part of the reason is almost certainly the large stockpile of spare engines the USAF had (and maybe still has), taken in part from re-engined KC-135s.

Part of the reason no doubt is also that there have been near constant plans to retire the B-52 "soon" and a major project like this was never deemed economical.


How can I calculate the optimum loiter airspeed for an aircraft? I am in the conceptual phase of designing a 10 seater amphibian aircraft. I have done the initial sizing using Raymer and Roskam's methods. I have got my design point. To do a constraint analysis as well as to find the fuel fraction for loiter phase I need to calculate the optimum loiter velocity for a loiter time of 60 minutes at 7000ft. Breguet's range equation doesn't help since I don't know the fuel fraction of loiter phase. How can I calculate the loiter airspeed?

The optimum cruise speed is the speed at which fuel consumption is minimized per unit of velocity. So, you need to compute the derivative (C/v)' where C is rate of fuel consumption and v is rate of travel (airspeed). (I assume you want this by "loiter". If you want to minimize fuel consumption, that is called "maximum endurance" and that is explained below on the chart.)

Since fuel consumption is proportional to power, and power divided by velocity is thrust, we can graphically determine this point by the thrust required curve. The diagram below shows the relevant relationships:

So, to compute the optimum cruise speed, first draw the thrust-required curve, as shown in the lower part of the diagram above, then you draw a line from the origin tangential to the thrust required curve. The point of tangency lies above the optimum cruise speed on the x-axis.

Maximum Endurance

If by "loiter" your goal is to minimize the fuel flow while maintaining a particular altitude, then you use the power required chart (the upper chart in the figure above). The fuel flow is proportional to power, so the maximum endurance speed is found by locating the lowest point on the power required curve. In the example above, that point is located at 80 CAS. Mathematically, the maximum endurance is found by solving the equation P'=0, where P is the power required function.


What is the busiest airport? What is the busiest airport in the world, and how is this measured?

Note: Since this answer was first written, updated statistics have been published. The original answer was written against 2015 figures, with the update from 2017 figures.

There is no one simple measure of "busiest" when it comes to airports, there are usually (at least) three.

Busiest by passenger traffic - defined as total passengers emplaned and deplaned, with transit passengers counted once
Busiest by cargo traffic - loaded and unloaded freight and mail measured in metric tonnes
Busiest by traffic movements - total number of landings and takeoffs of all aircraft

The most recent statistics produced by Airports Council International are from 2017.

By passenger traffic the top 3 are

2015

Hartsfield–Jackson Atlanta International Airport,  USA
Beijing Capital International Airport,  China
Dubai International Airport,  UAE

2017

Hartsfield–Jackson Atlanta International Airport,  USA
Beijing Capital International Airport,  China
Dubai International Airport,  UAE

By cargo traffic

2015

Hong Kong International Airport, Hong Kong
Memphis International Airport, USA
Shanghai Pudong International Airport, China

2017

Hong Kong International Airport, Hong Kong
Memphis International Airport, USA
Shanghai Pudong International Airport, China

By traffic movements

2015

Hartsfield-Jackson Atlanta International Airport, USA
O'Hare International Airport, USA
Dallas/Fort Worth International Airport, USA

2017

Hartsfield-Jackson Atlanta International Airport, USA
O'Hare International Airport, USA
Los Angeles International Airport, USA

(Aside: Wow, those Americans like their traffic movements - 8 of the top 10 are USA! | 2017 update: 7/10)

There are a few non-standard claims too. They are interesting, if not winners.

Memphis International is the Home of FedEx, and as such was the highest freight airport for a number of years.
Gatwick Airport is the busiest single-runway airport (There are actually two runways, but only one is ever in use)
Wittman Airport hosts an aviation event which temporarily raises it to one of  the busiest airport in the world for that short period.
The airports of London (Heathrow, Gatwick, City, Luton, Stanstead & Southend) host the most passengers annually for a single city's airports combined.

(Don't get me started on Southend being a "London" airport - it's at least 20 miles from what could sensibly be called London)

References:

ACI: busiest airports in 2015
ACI: busiest airports in 2017
Wikipedia: Busiest airports


How to start up a Lockwood-Hiller Valveless Pulse Jet? So me and my group mates in university got a lockwood hiller valveless pulsejet manufactured, and there was one error in manufacture. We are having trouble with trying to start the engine as demonstrated in the attached link. Is there an error in the engine you can see?
One manufacturing error we identified is that the exhaust cone is slightly at an angle and is not exactly parallel to the combustion chamber+intake which looks something like the attached. Could making it parallel solve it?
Also, would putting the gas cylinder upside down solve it?

The key to the operation of a valveless pulse jet is the oscillating shock wave created by repeated explosions in the combustion chamber. In this video they talk about using a spark plug to trigger these explosions initially, and once the engine is running the process is self sustaining.

Looking at your video I don't see any connections to the engine except the fuel pipe, and you seem to be attempting to start the engine by pushing some burning material into the combustion chamber. This will not create an explosion, so the shock wave that keeps the engine running won't be created either.


What is the status of a bravo airspace when the associated TRACON is evacuated? On 18 March 2020, an earthquake struck just south of KSLC, causing an evacuation of the control tower and TRACON facilities.  The airport was closed.  Later in the day, I found myself unable to contact approach control.  The control tower at KPVU informed me that the TRACON was still closed, making radar services unavailable.

What I want to know is, does the bravo airspace stop existing when this occurs?  There was nobody to give me a clearance into the airspace.  Could I enter anyway, or should the airspace essentially be sterile?

In cases where a given unit of airspace (for example, a Class D circle around an airport with a tower) is only in effect part time, there is always a note to this effect in the FAA's "Airspace Designations and Reporting Points" document.  The current (August 2019) edition of this document is FAA Order JO 7400.11D.  The Class B airspace for KSLC is listed on pages B-25-26 and there is no notation that it is only in effect part-time.  In fact this is true of all Class B airspace.  Some Class C airspace is only in effect part time-- an example is Lincoln Airport (KLNK) in Nebraska.  However in such a case the airspace opens and closes according to a set schedule that is published in the Airport Facility Directory or in NOTAMs.

The Class B airspace at KSLC definitely does not stop existing when an unexpected circumstance closes the associated air traffic control facility.  In the absence of authoritative information to the contrary, you need to assume that you should not enter the airspace without a clearance.  Checking for NOTAMS would be one way to check whether the FAA has temporarily authorized some unusual procedure for the special circumstance you describe.

In a NOTAM search via this link selecting an "archive" search (click on "location" tab for this option) and using "KSLC" as the search term, we see various NOTAMs for March 18 (ILS approaches unavailable, etc) but nothing indicating that any part of the Class B airspace was temporarily revoked.  Some of the NOTAMS key to messages that may be seen on this
Air Traffic Control System Command Center website.  It appears that none of the NOTAMs or messages pertain to alternative ways to get clearance to enter the Class B airspace.


why is rhumb line bearing for this question 270 as the answer? An aircraft leaves position "G" in lat 40 degree South and flies the following Rhumb Line tracks and distances:
G to H : 180 (true) 240 NM
H to J : 270 (true) 240 NM
J to K : 000 (true) 240 NM

what is the rhumb line bearing from G to K ??
According to me answer should be 090 but it is given as 270 ..
can someone please give the reason for the same

The only movement in the east-west direction is your 2nd leg, moving west. Therefore, from the starting point G to the ending point K, the bearing is west, 270 degrees. The answer 090 would describe the course from K to G to close the path.
K--->090--->G
^           |
|           V
J<---270<---H

All the legs are the same length, and the north/south aren't drawn to the same scale as the east/west, but it's just a square.  270 from H to J, so 090 from K to G.  And thus 270 from G to K.


What could I do to a give a plane an emergency boost of power for takeoff? For some reason the pilot has to take off in an emergency or is on a runway too short or maybe they just want more places they can land and takeoff. The single engine plane is already light on fuel and cargo. Could adding Nitrous oxide or richer fuel or something like an afterburner for a piston engine work?

That really depends how safely you want to get off the ground.
If you are looking to get in and out of tight airfields using STC'ed parts you may want to consider a STOL kit which can modify the plane such that you can utilize a shorter runway.
There are some airframes that do have horsepower increase modifications available but that takes actual mechanic work and wont really be feasible in your "pinch" scenario.
There are a few aircraft that can be operated with JATO rockets and it looks like it was done at least once on an ercoupe during testing
You could add Nos but then again most pilots prefer their engine to run for the duration of the flight... You would also have to contend with the fact that adding NOS may very well require a direct port bore, which is no small job.
Afterburners don't really apply to internal combustion engines, at least not ones that generate meaningful thrust...


What altitude to fly on a STAR when it reads "expect"? I just took the instrument knowledge test and one of the questions referred to this STAR. Like many of the questions, there were two right answers and you were supposed to pick the one that was most right.

(airnav)

The question stated that you were cleared for the STELA ONE arrival from the west and asked what altitude you should be at when crossing STELA. My understanding of a clearance for a STAR is that, unless otherwise instructed, you should use both the lateral and vertical guidance on the chart. So at STELA, you should be at 11000'. The notation for expect isn’t applicable unless you were told to fly at a higher altitude when given your clearance. Even then, you wouldn’t descend to 11000' until instructed.

Is my understanding correct, or am I missing something?

Terrible question (not your question, but the test question).

As far as I can tell, there are NO altitudes on the arrival that are mandatory; everything is an "expect" altitude only.

When you are "cleared for the STELA ONE arrival", you are cleared to (required to) fly the lateral ground track, and comply with any airspeeds stated on the chart ("cross at xxx knots", not "expect to cross at xxx knots" restrictions).  That clearance by itself doesn't clear you for any altitudes, even ones that are mandatory on the chart.

When you are cleared to "Descend Via the STELA ONE" arrival, then you are additionally cleared for all mandatory altitudes.  (Which I don't see any of on this chart, but I may have missed one -- NOS formatting isn't the best.)  Importantly, if the arrival has published altitudes to cross A at or above FL 230, cross B at or below FL 200, cross C at 12,000', and expect to cross D at 5000' (and no other altitudes after D), then you are ONLY cleared down to 12,000' -- you are NOT, in that case, cleared for the 5000' altitude.  You can expect it (i.e. load it in the FMC), but you can't depart 12,000' without explicit ATC clearance (i.e. don't spin  the 5000' into the altitude window on the mode control panel until ATC says "cross D at 5000").

Yeah, it's a "gotcha".  Really poor human factors design for an arrival to do that, IMHO, but there are a few of those out there.

Now, flying the STELA ONE, you're PROBABLY going to end up crossing STELA at 11,000', but until they assign you that altitude, you aren't cleared to do so.  "Expect" altitudes on an arrival have to be explicitly given by ATC -- "Descend Via" doesn't include those.

I don't know what other answers you had on the knowledge test besides 11,000', but my first guess would be that something along the lines of "not enough information given to know" or "cannot be determined" or "last assigned" would be better than "11,000" if the question asked something along the lines of, "having been assigned this arrival, at what altitude are you cleared to cross the STELA waypoint?"  With only clearance for the arrival itself, you haven't been cleared for ANY altitude change.

I don't much like that arrival since it has no mandatory altitudes at all, and I really don't like that question.  Have to love the FAA, sometimes!


When is an aircraft considered dispatched? When is an aircraft considered to be dispatched?
Before an aircraft is dispatched certain pieces of equipment must be operational on an aircraft.  If some equipment is found to be inoperative, a determination can be made of whether or not to dispatch based on the information found in the MEL or CDL.
After an aircraft has been dispatched, disposition of inoperative equipment would follow the guidance inside the AFM.
Simply put, at what point does the dispatcher / crew switch over from relying on the MEL / CDL to the AFM for guidance?  The pilot in command has the final authority to takeoff so I am not asking about equipment that are significant to the operation of the airplane.
I am interested in both FAA Part 121 airline operations, Part 135 charter operations and Part 91 flights.
Thanks

Technically, before the aircraft is dispatched / released, everything can be inoperative.
However, most everything needs to be in working order to be dispatched / released, with exceptions as per the MEL / CDL.
MEL / CDL procedures are followed until the takeoff is commenced.
If an item is discovered to be missing or inoperative,
A) prior to door close
B) after door closed but prior to block out
C) after block out but prior to flight
there are specific MEL procedures to follow in each of those three scenarios.
Taking the runway and setting takeoff thrust / power is the act of commencing a takeoff.
After that point, equipment failures are treated as an in flight emergency, and flight crew follow QRH / AFM guidance. At that point the MEL no longer applies.
Applicable US FARs for Airline ops:
121.687 Dispatch Release - Flag or Domestic Operations
121.689 Flight Release - Supplemental Operations
135 has a similar regulation.
91k (fractional) does as well.
Plain Jane 91 owners/operators/pilots don't normally operate with an MEL. If they do, they have a letter of authorization with the FAA.


Can a non-US citizen (or entity) own an N-registered aircraft? Distantly related to this question, but can a non-US citizen (or corporation) own an N-registered aircraft?

Nothing in the regulations seems to preclude it - but there are some conditions you have to meet per the FAA:

  An individual who is a United States citizen,
  A partnership each of whose partners is an individual who is a U.S. citizen,
  A corporation or association:

  organized under the laws of the U.S. or a State, the District of Columbia, or a U.S. territory or possession,
  of which the president and at least two-thirds of the board of directors and other managing officers are U.S citizens, and
  in which at least 75% of the voting interest is owned or controlled by persons that are U.S. citizens,

  An individual citizen of a foreign country lawfully admitted for permanent residence in the U.S.,
  A U.S. governmental unit or subdivision
  A non-U.S. citizen corporation organized and doing business under the laws of the U.S. or one of the States as long as the aircraft is
  based and primarily used in the U.S. (60% of all flight hours must be
  from flights starting and ending within the U.S.)

(emphasis added)

So Toyota could not buy an aircraft and register it to their main company in Japan  on the US registry, nor could they buy & register it under a US Subsidiary and subsequently fly it off to Japan to live out the rest of its days shuttling executives around Asia.
A Toyota executive with Permanent Resident status could buy themselves a nice Cirrus and register it on the US Registry though.


What is TAPS in this report? In researching for this question, I came across some reports from EASA referring to TAPS. What is the meaning of TAPS in this context?

TAPS means Twin Annular Premixing Swirler, a cyclone mixer / combuster designed to keep the NOx emissions of the General Electric GEnx engines low.

source: FAA report

AIAA report


Why don't all flights use the North Atlantic Tracks (NATs)? I had assumed that all flights between western Europe and North America would use the North Atlantic Tracks (NATs) but this answer says that, actually, only about half do.  What reasons might a flight have for not using the tracks?

Wikipedia says that Concorde didn't use the tracks because it flew above them but I'd expect all commercial transatlantic flights these days to be within the band covered by the tracks (FL290–410).

The answer doesn't state that half of the flights between western Europe and North America use the North Atlantic Oceanic Track System (OTS). It states that half of the flights over the North Atlantic use the OTS.

Part of the flights over the North Atlantic don't cross between western Europe and North America and they don't use the tracks. Examples are flights to/from Iceland or the Azores. Also flights crossing between Ireland and the North Western point of Spain are entering the North Atlantic Region.

Also part of the flights that do cross between western Europe and North America and vice versa may use random routing for various reason.

On some days the winds are such that favourable tracks to North America are within the Reykjavik control area, which allows for random routings.

Some combinations of origin / destination are better served by avoiding the OTS area at all. For example flights between the Iberian peninsula and Florida are generally South of the OTS.


If a helicopter's tail rotor fails, is it possible to perform an emergency landing? In the event of a total failure of the tail rotor, is it possible to maneuver a helicopter to an emergency landing spot that is within, say, 30 minutes flying time?

What are the maneuvers required for a pilot to fly reasonably straight, and how do the aerodynamics work?

Although I used to think this was impossible, I now believe this can be done using weathervaning.

At a fast enough forward speed, the airflow will naturally keep the helicopter facing in that direction. For an example of someone doing this in reality, for an almost identical time period that OP requested, see this link:

http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=10493099

According to the link, he needed to maintain 80 knots forward speed to prevent it from rotating out of control. Note whether this is possible may well depend on the weathervaning charactistics of the particular helicopter.


Why are Oscar, India, and X-Ray (O, I, and X) not used as taxiway identifiers? An old CAR "Licensing of Aerodromes" document indicated that taxiways may not be designated by O, I, or X.

Is this still in effect today?  Why were (or are) those not used as taxiway identifiers?

My guess is that the shapes of those letters could cause confusion such as an "X" meaning something like "closed" or I looking like a vertical line "|".

Because those symbols are easily confused with the number 0, the number 1 and the symbol for a closed runway/taxiway (✕) respectively.

(1) Numbers  by  themselves,  and  the  letters  "I"  and  "O"  must  not  be  used  because  they could be mistaken for a runway number.
(2) The letter "X" must not be used because a sign with an "X" could be misconstrued as indicating a closed taxiway or runway.

Source: FAA Engineering Brief No. 89 on Taxiway Nomenclature Convention (via SKYbrary.aero).
Most aerodromes do refrain from using these identifiers, but there are also examples of them being used. For example, Copenhagen (EKCH) has a taxiway I(ndia).


How does an operator change the engine thrust rating? If, for example, an operator has a Boeing 737-800 with CFM56-7B engines set at a 22K thrust rating, but the next operator wanted to operate the engines at 24K thrust rating, what would they need to physically do to the aircraft in order to change this?

Would it involve the engine going to the shop for certain components replacement, or is it as simple as a FADEC reprogram? I've noticed the life of certain engine components differ depending on the thrust rating used so I wondered how the engine is converted to these different configurations?

Please refer to the following website, it explains the plug programming.:

http://nandang-smart.blogspot.com/2014/09/cfm56-7b-identification-plug.html

You may read:

  WHEN ENGINES ARE MOVED BETWEEN AIRCRAFT AND MAY REQUIRE A DIFFERENT THRUST INSTALLATION THIS N1 MODIFIER IS USED IN CALCULATIONS TO UPRATE OR DERATE A GIVEN ENGINE AT AN APPROPRIATE LEVEL.

You may also read

  THE THRUST LEVEL OF AN ENGINE IS CHANGED (PERHAPS MORE ACCURATELY "PROGRAMMED") BY INSTALLING A "ID PLUG" THAT SCREWS ONTO THE EEC AND CONVEYS PROGRAM INFORMATION THAT SETS THE ENGINE THRUST OUTPUT TO THE LEVEL DESIRED BY THE OPERATOR.

With respect to the thrust limit, you may display on the CDUs ( MCDUs) the FMS thrust limit page that allows the pilots to derate the TO thrust.

The following website shows for the B777 how to get access to the «  thrust limit » page:

So the pilot may change the thrust limit from the CDU, while the rating is changed by pin programming on the plug, the value entered in the CDU by the pilot is transmitted to the FMS which will ask the FADEC to reduce the thrust whatsoever below the rated value chosen by the operator by pin programming.


Why does the Boeing 787 use Cabin Air Compressors (CACs)? What are the advantages of this new air conditioning system compared with the traditional engine bleed systems? More engine output power, or easier adaption to future aircraft design?

Boeing is moving to a bleedless system with the 787 Dreamliner and GEnx engines. In the past engine bleed air has been used extensively for ECS (Environment Control System) e.g. cabin pressurization and air conditioning, as well as anti and de-icing, ozone removal and many other uses.

Nevertheless Boeing firmly believes that the overall efficiencies and improved reliability are a large step forward. Moving to a bleedless system will reduce the mechanical complexity of the 787 by more than 50% compared to the 767. The new system is expected to be save about 3% in fuel and 15% more efficient overall.

The move to a bleedless architecture has been the subject of much enthusiast debate e.g. here because while many advantages are apparent it's not immediately obvious that the increased electrical loads to replace the pneumatic functions isn't a moot point. Additionally, Rolls Royce wasn't willing to commit to developing a bleedless system, so the Airbus A350 XWB will continue to use bleed air pneumatic systems.

Boeing summarizes the primary bleedless architecture benefits as being:

  Improved fuel consumption, due to a more efficient secondary power extraction, transfer, and usage.
  Reduced maintenance costs, due to elimination of the maintenance-intensive bleed system.
  Improved reliability due to the use of modern power electronics and fewer components in the engine installation.
  Expanded range and reduced fuel consumption due to lower overall weight.
  Reduced maintenance costs and improved reliability because the architecture uses fewer parts than previous systems.

787 No-Bleed Systems: Saving Fuel and Enhancing Operational Efficiencies

Pneumatics have long been one of the weakest links in modern airliners. Moving to an electric system should increase reliability of a number of sub-systems, portend reduced long term maintenance costs and aids in the improvement of many components.

One example of the advantage of moving to an "electric aircraft" is to facilitate the move from hydraulic to electric braking. I think it's a great move.


Are there any airports that require arriving/departing flights to fly under an obstruction? Are there any airports with approaches and/or departures that require pilots to fly under an obstruction at some point (thus meaning that, for at least a short segment of the approach or departure, there is not only a minimum safe altitude, but also a maximum safe altitude)?

I can imagine a few situations where this might occur, such as for an airport at the bottom of a deep, steep-sided valley with powerlines or a bridge across the top of the valley, but I don't know if any airports like this actually exist.

It would not surprise me if someone, somewhere had done it, maybe even for good reasons (for example, possibly during the barnstorming era, one of the world wars, or perhaps on an Air America / POW rescue mission or similar) but thinking about an airport doing it as standard procedure brings to my mind phrases like "outrageously dangerous", "criminally irresponsible", and "out of your mind".

So I'm going to go with no, there aren't.


In a hydrogen fueled plane, could part of the fuel load be allowed to become lighter than air to offset or trim for the load? This is inspired by How can adverse maneuverability due to a fuel tank behind the rear pressure bulkhead be mitigated in Airbus ZeroE hydrogen plane? .
I was thinking, with the cryogenically stored hydrogen (and required equipment) being heavy and so far away from the centre of lift of the craft in Airbus's design, it might be possible to trim the aircraft by releasing some of the hydrogen into a chamber where it can be lighter than air, reducing the nett weight of the tail, rather than trimming aerodynamically or with a movable weight.
I'm not good enough to do the math, but I suspect the size of the chamber would have to be colossal to make enough of a difference to matter - with the added bonus of being essentially an explosion waiting to happen.
Would there be a sweet spot for the average temperature of the stored hydrogen that balances the weight (including weight of corresponding equipment) against the volume of fuel stored, or is it going to be a case of coldest/most dense is the most efficient and trim needs to occur the traditional way?

The buoyancy of hydrogen is not as high as expected, and is even lower at high altitude due to the lower ratio of the density of hydrogen and air.
Just for comparison:
The tail tank of the A380 has a capacity of 23698 l.
When this tank is filled with kerosene / air / hydrogen, the content weights:
Substance           | Density [kg/l] | Weight of 23698 l [kg]
--------------------+----------------+-- -----------------
Kerosene            | 0.8            | 18958
Air (sealevel)      | 0.00122        | 28.91
Air (10km)          | 0.00041        | 9.72
Hydrogen (sealevel) | 0.00009        | 2.13
Hydrogen (10km)     | 0.00003        | 0.72

At sealevel, the lift of this tank filled with hydrogen is 28.91kg-2.13kg=26.78kg.
And at altitude, it's just 9.72kg-0.72kg=9.00kg
This is nothing compared to the 18958kg of kerosene, and shows that it makes no sense to fill any volume in an aircraft with hydrogen for trim.


Why is tailwind during final approach and landing so dangerous? I understand that tailwind is typically a good thing during your flight as it increases your ground speed and gets you to your destination faster.  Despite that I get a feeling that pilots typically get very uncomfortable when there is a significant tailwind present during landing.  Sadly, recent proof of this danger was in Aspen, Colorado accident

Questions:

Why are tailwinds bad during landing?
Given "extra long" runway for extended rollout, are there any dangers with landing at a higher ground speed?
How are tailwinds mitigated?  Would ATC just switch the landing direction?

It's not so much a matter of "pilots typically get very uncomfortable" as it is "pilots recognize that it is an inherently less safe situation", and pilots (at least the ones you want to fly with) tend to be somewhat safety obsessed.

So Why are tailwinds during landing "bad"?
The same reason tailwinds in cruise flight are good: you're moving over the ground at a higher speed.
The amount of energy the aircraft has (and thus its landing distance) is roughly proportional to the square of the groundspeed.

Let's consider the plane I fly as an example (a Piper Cherokee) because I know the numbers:
if I'm flying by the book then when the wheels of my plane hit the ground my indicated airspeed should be around 45 knots.

No Wind
If there's no wind my ground speed and my indicated airspeed will be about the same - my brakes will have to slow me from 45 knots to a stop before I run out of runway.
The brakes on the Cherokee aren't Porsche brakes (they're tiny little things), but they're up to the task and a book-perfect landing would have me stopped in 600 feet.
15-Knot Headwind
A 15 knot headwind reduces my groundspeed to 30 knots - at 2/3 the speed I can stop much sooner with the same braking force, which means less wear on the brakes and a greater safety margin of runway remaining.
A book-perfect landing in these conditions would have me stopped in about 270 feet.
15-knot Tailwind
A 15 knot tailwind increases my groundspeed to 60 knots. The tiny little brakes on the Cherokee CAN stop me, but they're going to take much longer to do so: A book-perfect landing would take over 1000 feet to stop (nearly twice the "normal" no-wind landing roll).

The big consideration above is landing distance -- as you noted in your question you can solve that with a longer runway (more pavement means more room to stop), but there are other dangers with tailwind landings, mainly in the fact that Landings don't always go according to plan.
The slower your groundspeed at landing the less energy you have to get rid of if something goes wrong

Consider the three landings I outlined above, but let's add a problem to the mix: One of my tires blows right at touchdown, and the plane veers off the runway into a ditch.
There is much less energy to dissipate with a 15-knot headwind (30kt groundspeed) than there is with a 15-knot tailwind (60kt groundspeed) - it's roughly the difference between crashing your car driving through a school zone versus speeding on a highway.

Fortunately it's really easy to avoid landing with a tailwind -- most runways are bidirectional (Aspen, which you mentioned in your question, is a notable exception due to geography).

ATC (or at uncontrolled fields, the pilots themselves) will "turn the airport around" once a certain tailwind limit is reached.  Precisely when that happens depends on the airport and the traffic mix (at my home field, with mostly small piston aircraft, ATC will typically switch the runway when the tailwind component exceeds 5 knots - at JFK they might land a jet with a 10-knot tailwind rather than messing up the arrivals).
Of course there's nothing that says a pilot has to accept a landing with a tailwind: If the pilot is not comfortable with the conditions they can request a runway aligned so the winds are more favorable. (There is a somewhat famous case of an airline pilot at JFK who ultimately decided to declare an emergency to ensure a landing on a favorable runway).


What was the airline attendants looking at in LED display before light off in A320 I was journeying on Indigo Pune-COK back and forth. At both the times, I noticed airline attedants looking at some LED display which seemed to be some sort of balance scale. At first, I thought they might be looking to check at some sort of weight distribution sensor to check whether things are distributed evenly all across the aircraft or something else. I am not sure now but would be glad if somebody could chime in. The plane is and was single class 180 Airbus A320. https://seatguru.com/airlines/IndiGo/IndiGo_Airbus_A320.php

Edit : Update - . Both times, it was before the takeoff procedure. The LED/LCD display was located above the flight attendants chair on the left . The chair on which they sit in the front during take off. The one which is located to left of the refreshments and just before the pilot cabin/cockpit.  The LED/LCD display was above the flight attendant's chair at eye-level.

While I'm sure it had to do with probably some sort of avionics controls they were looking at, I am not sure what.

The panel you have seen near the forward left door was most probably the Flight Attendant Panel of the CIDS (Cabin Intercommunication Data System). It looks like this: picture of the CIDS panel at jetphotos.com

In the lower part, it has two LED scales which can show the quantities in the fresh and waste water tanks of the aircraft. If I remember correctly, they will only light up while the IND ON pushbutton next to them is pressed.

The cabin crew will routinely check those water levels to ensure e.g. the lavatories can be used.


What are the certification requirements for software used at airports? If you develop software that is used at the airport and integrates into a departure control system (DCS), is it required to undergo some IATA certification processes?

When I search for IATA regulation on software used at airports, I can not find much. Actually I haven't found anything that states that, for example, a departure control system (DCS) must undergo some certification process.

I therefore ask, are there any certifications or validation requirements for software used at airports? For example if you develop a new DCS, would you be required to undergo IATA certification? What other hurdles (FAA, EASA, ...) are their for software used at airports?

Note, I explicitly want to exclude software that is used for air traffic control.

The short answer is yes, With larger airlines, they may own and manage their IT infrastructure at central hubs, so the airline will need to ensure their software works with their chosen peripherals. At smaller airports where this is not possible, many airports use a common use computer platform, managed by both the airport authority and commercial IT vendors. Ultra is one such example. Airline DCS software would need to undergo validation to ensure it will correctly interface with the various devices at the airport: bag tag, boarding pass, document printers, self-check-in kiosks, and gate scanners.

The Passenger and Airport Data Interchange Standards (PADIS) Board as well as the
Common Use Working Group (CUWG) provide direction to IATA for creating technical standards. CUPPS (Common Use Passenger Processing Systems), is the IATA standard recommended practice for such common use computer systems.

DCS systems also must be able to transmit advance passenger information to government agencies, for example TSA to verify the passenger is not on a terrorist watch lists. Requirements for transmitting such information is set by the UN EDIFACT PAXLST specification, but not all passenger information transmissions will be sent from a DCS system.

EASA and FAA are more focused on flight data (flight plans, ATC, and weather) and have specifications for receipt and transmission of that information, but the transmission is usually done by separate software.


Why does the Tu-22M3 nose have this peculiar shape? What is the reason behind this unusual nose shape? I am not referring only to the presence of the protuberance on the tip, but mainly to the asymmetry between the top and bottom side.

Image source

It can be seen better in the profile depiction here:

Image source

Nobody knows why except Andrei Nikolayevich Tupolev, and he is dead.

Andrei Tupolev was known to insist on the fast and adequate at the expense of the theoretically correct, leading to widespread technical debt in his designs. He may have raised the nose cone for no more profound reason than to get the refueling probe in line with the pilot's vision. Once he had energetically dictated where the probe was to go, no one at the design bureau would dare suggest moving it; they would just work the forward avionics into the resulting odd shape as best they could.

Tupolev died in 1972 leaving this and many other of his decisions unexplained.


Is it a flight violation to mishear ATC instructions for exiting the runway? I was on landing rollout and misheard a tower "turn off at xxx switch ground" call. We read back the incorrect taxi way and turned off there and switched to the ground frequency. After our incorrect read back we were not contacted again until ground told us to call tower. I was under the impression that the landing aircraft had the right of way over any traffic behind them, even on roll out. I was also under the impression that a tower cannot stop you from using the whole runway.

Is missing a directed turn off a runway a flight violation? If so what FAR/AIM or regulation did it violate? Is the fault with us for mishearing or with the controller for not correcting us? Does this count as a runway incursion? Does the controller maintain responsibility for maintaining separation until we taxi clear?

To answer a few of the questions from below:
when we contacted the ground controller, they gave us a phone number to contact tower then gave us a taxi clearance. When they told us to call i became concerned with receiving a flight violation. We were not corrected to my knowledge, we only heard radio traffic once we had turned off the runway. This was also not a LAHS operation.

another question: From the AIM 4-3-20 it says : "the following procedures must be followed..." "exit the runway without delay"
" is that at the discretion of the pilot?

also if tower gives you a taxiway instruction to leave the runway is that an instruction or a clearance?

Is it a good idea to call the local FAA office and see if they have opened an investigation?

I don't think you violated any regulations. It was an ATC instruction, not an ATC clearance.

It was an instruction you were unable to comply with. The instruction was badly timed and was obviously not clear since you did not correctly understand it.  In the busy time during the landing roll, you understood something different, and read back what you understood it to be.

The landing roll-out can be a busy time needing the attention of both pilots.  ATC issuing an instruction while you are basically still in the landing roll should not be expected to be complied with unless it is happens to be convenient for you to do so.

Many airlines SOP say that you do nothing until you are clear of the runway. Both pilots remain heads up and don't touch anything. The pilot in command alone will decide where it is safe to tun off the runway. If ATC makes a "Request", and it can be safely complied with, then the PIC may decide to deviate from SOP and comply.

If you ran off the side of the runway trying to comply with an ATC "request", who do you think will be held responsible? (I'll give you a hint, it won't be ATC)

This is a prime example of why ATC should not be doing this.