Are TI graphing calculators permitted on the FAA knowledge exams? I know it's a bit odd, but I like using my TI-89 graphing calculator in addition to an E6B when doing calculations. It helps me avoid dumb arithmetic errors.

I read the section "Use of Test Aids and Materials" of  Recreational Pilot and Private Pilot Knowledge Test Guide (FAA-G_8082-17). It seems to meet all of the requirements except (d), which I don't really understand:

  The use of magnetic cards, magnetic tapes, modules, computer chips, or
  any other device upon  which pre-written programs or information
  related to the test can be stored and retrieved is  prohibited.

Does anyone have a definitive answer on whether these types of calculators are permitted?

The document you cite actually goes on to explain what the procedure is for calculators, and when testing centers can prevent you from using your own (you'll be provided a loaner):

  Testing centers may provide a calculator to you and/or deny use of your personal calculator based on the following limitations:

    a. Prior to, and upon completion of the test, while in the presence of the Unit Member (formerly referred to as proctor), you must actuate the ON/OFF switch and perform any other function that ensures erasure of any data stored in memory circuits.

    b. The use of electronic calculators incorporating permanent or continuous type memory circuits without erasure capability is prohibited. The Unit Member may refuse the use of your calculator when unable to determine the calculator’s erasure capability.

    [...]

Basically, you can bring a graphing calculator and wipe it, but unless the center is able to confirm that you've removed all stored memory, they're probably just gonna say "nah" and hand you a basic calculator. There's a pretty good chance that your graphing calculator falls under the "permanent or continuous type memory circuits" category anyway.


Who checks that pilots have their licenses? One weird thing came to my head In the ground, Every time you drive an 91 CRX SIR/Civic Si EM1 or ride an Honda Dirtbike There is an possibility of getting busted by the cops waiting in the temporary checkpoints But what about the air? Who will check (Non existent) licenses of DC-3/Bell 47GH pilots?

Who will check (Non existent) licenses of C208B Grand Caravan Amphibian pilots on the sea? Who will check people that flies alone in a Learjet 35 during IFR conditions? (I know, there are countries that you can do IFR flights alone)

Do you tell your license information to the ATC before the takeoff or there is an another way like authorities requesting flight logs of an C208B etc?

Just as people can go for quite a while driving without a license before they get caught, there is no certain way to catch somebody who goes flying without a license.  There are various ways that it can happen, but none of them are certain.

There was a quip quoted elsewhere referring to the high proportion of unlicensed pilots in Alaska, that supposedly the FAA had a goal of getting at least half of them licensed.  I have no idea how much, if any, truth is behind that statement.

On the other hand, just as having a license can make various things you might do with a car easier or possible, there are plenty of instances where having a pilot license is necessary:

Renting a plane
Buying insurance for a plane you own (without a convincing story of who else would be flying it, at least)
A "ramp check" by an FAA inspector
Getting a job (from a reputable company, at least) as a pilot

If you file a flight plan for your flight (required for IFR -- mostly, not required but very highly recommended for VFR), part of that is to provide a name for the pilot.  But that's it, just a name, not a license number.  (Phone number, yes -- so they have somebody to call in case you're overdue so they can see if you simply forgot to close your flight plan.)  I don't know how often that info would be checked against any database of current pilots, but the potential would be there.  But the ways the FBI would find people in an investigation is wildly different from what's routinely done by Flight Service.

So if Farmer Joe (licensed) owns an airplane & his (unlicensed) brother Fred flies it every now and then from their private dirt strip, the chances of Fred getting caught are probably pretty slight, unless something goes pretty badly wrong.  And, depending on Joe and Fred's tolerance for risk, they might be entirely okay with that scenario.

Me personally, there's no *%#@ing way I'd be party to any such arrangement, but I'm probably more cautious than some Alaska bush pilots that way!  This thread discusses the consequences for flying without a license.


Was the airframe involved in the LOT Flight 16 accident repaired? The belly landing of LOT Flight 16 is known by many:

Wikimedia
YouTube

My impression is that a lot of aluminum was ground off by the runway. Maybe too much?

Question: What is the status of that aircraft today? Was it economically and safely repairable? Is it still flying?

And any general comments about the "repair or retire" decision after a costly breakdown or accident are welcome.

(I am impressed by the airmanship on that flight)

From Wikipedia:

  The damage to the plane was so extensive that the airline chose not to make repairs. The aircraft was scrapped in November 2013.

I can't find information on the figures, but for Qantas Flight 32 the figure to repair it was ~$145 million.

Nowadays you can buy a used 777 for 2% of its list price. A fraction of the $145m figure above to fix an A380.

New 777 is 277.3 million, used is 7.7 million.

I hope that helps.

So cost of repair, age of aircraft, cost of adding a used plane to the fleet instead, etc.


Where can I ask questions (career advice) about jobs in Aviation Management? I am thinking of changing my career. I have a physics degree and I want to do a masters in aviation management.Is there any sites where can I get an idea about my chances at getting a job in the aviation management sector, if I do a masters? (with no prior experience).

There is a huge demand for aviation professionals. However, how that demand is looks like is very difficult to answer, since it's a pretty fragmented market and getting an overview is very difficult.

As such, you're best chances of understanding it are:

Going to recruitment fairs that major airlines attend.
Attending events that airlines hold themselves.
Trying to get in touch with human resources in an appropriate way directly.

From this you should be to gauge how interesting a candidate you will be. As with most things, this is hardly an exact science. Getting a program with a placement/internship as part of the course for instance might be quite beneficial. As for the no previous experience, I think this is the case for most people heading into this area.


What does "Last Call" mean on CTAF frequency? At non-towered airports I sometimes hear pilot's using the CTAF use the term “last call” as they depart the traffic pattern. This is not listed in the AIM.

What information is this suppose to convey and should I care?

Does this have some meaning internationally that I don't know about?

It means they are changing frequency and will not be making any more CTAF calls. As far as I know its not required although something along those lines is pretty common place. Personally I call:

  Departing the pattern to the [north|east|south|west]

Its the self announce version of "frequency change approved"


Why can't the A320's computer-imposed limits be overridden? Under the investigation section of US Airways Flight 1549, it is noted that

[The pilot] asserted that insufficient credit was given to the A320's fly-by-wire design, by which the pilot uses a side-stick to make control inputs to the flight control computers.
The computers then impose adjustments and limits of their own to keep the plane stable, which the pilot cannot override even in an emergency. This design allowed the pilots of Flight 1549 to concentrate on engine restart and deciding the course, without the burden of manually adjusting the glidepath to reduce the plane's rate of descent.
Sullenberger said that these computer-imposed limits also prevented him from achieving the optimum landing flare for the ditching, which would have softened the impact.

Although this design aids pilots most of the time, why is there not a 'last resort' option to override the computer-imposed limits? It could have been that in this incident, it was the difference between life and death / a 'hard landing' vs a complete hull loss.

Disabling the protections can technically be achieved. I say technically because there is not one scenario that Airbus has envisioned that would require the pilots to deliberately go into direct-law.

The imposed limit in the question is something called alpha-protection -- a protection against pulling back too much that the plane stalls. Stalling is bad. The system was receiving the correct information and functioning as designed, so what did Captain Sullenberger mean?

  Sullenberger said that these computer-imposed limits also prevented him from achieving the optimum landing flare for the ditching, which would have softened the impact.

This is what Wikipedia says. The reference is a Talks at Google lecture (around the 40-minute mark). What is left out from Wikipedia, which Captain Sullenberger covers in the talk right away -- and is present in the accident report -- is that the issue was not with the protection, but with the innards of the protection that Airbus did not cover in the training material. Below is the relevant section from YouTube's transcript:

  I was commanding for more, pulling back full aft on the stick and the flight control computers prevented me from getting more lift therefore we hit harder than we would have (...) It turns out there's a little-known software feature known only then to a few Airbus software engineers, and to no pilots to no airlines that was the case. It's called a phugoid mode. And it was not the way we were trained the airplane should work, apparently it is the way the airplane does work. But that was not apparent to us.

This was addressed as a recommendation in the final report:

  Require Airbus operators to expand the angle-of-attack-protection envelope limitations ground-school training to inform pilots about alpha-protection mode features while in normal law that can affect the pitch response of the airplane.

Providing training on the innards of the 'good' system, is far better than taking out a vital protection. Vital because of one thing the report points out (which is in no way a disparagement of the crew):

  The NTSB concludes the captain’s difficulty maintaining his intended airspeed during the final approach resulted, in part, from high workload, stress, and task saturation.

Protections are good for such high workload, stressful, and task saturated situations.


Do any airports have a steeper standard approach than London City? Watching the CS100 certification of the 5.5deg steep approach into London City, I wondered if there were any airports with steeper standard approaches. By standard I mean published.

I have seen very steep non-standard approaches, but this is not the point of this question.

I found the RNAV approach to Steamboat Springs at 7.75°


Are there standard visual cues or other methods for flaring in a B737-800? Just a newbie in the 737. I've flown 100 hours - in real life - in this lovely beast and found the landing to be very confusing: my main problem is every time just from 50 feet, the sink feels too much. I don’t understand the right time to flare, almost every time it’s early or late. Also that I can’t flare at one go. Very very frustrating. Maybe a lot to do with seating position? Can you suggest the right visual cues or other techniques to use?

I'm not sure I understand what you're asking, but proceeding from what I think you may be asking, consider the following.

Are you flaring from a stabilized approach? Until a pilot internalizes things for any large aircraft, using a stabilized approach on speed appropriate to your landing weight gives a common, starting reference to work from.

From such an approach you should have been given in training the altitude from which to start the flare. For purposes of discussion, let's say that's the 50 feet you mentioned. Thus, the first problem is determining when you're at that point. Assuming you have a radar altimeter, are you using the call outs from the altimeter to consistently start the flare at the same altitude?

Now, in a stabilized approach, you don't feel a change in sink rate in the seat of your pants until you actually start the flare, so when you say "the sink feels too much", I'm assuming that you're having trouble with the rate of your flare. In other words, how much back pressure you should be exerting on the yoke. My thought would be that you could try focusing on how much to raise the nose at the 50 foot call rather than trying for a given amount of feel in the seat of your pants. I never flew the 737, but on the 747, at the 50 foot call, I would would raise the nose to 5° higher than it was during the stabilized approach. Then at the 10 foot call, I would raise it 2° higher yet. There would, of course, be an appropriate power reduction each time.

The 737 will have different numbers than the 747, but what I'm suggesting is to try doing it by the numbers, consistently, every time. Any 737 instructor should be able to tell you what those numbers are. You might even try posting a question here asking specifically what those numbers are. Perhaps a 737 pilot will see this answer and provide them.

Finally, an advantage of doing things by the numbers is that it really doesn't matter what your seat position is, although you should certainly go for a seat position that will eventually allow you to best internalize what the numbers mean insofar as the view out the windshield. When I transitioned from the F-27 to the SA-227, I found the view out the front confusing, but no matter since they taught us to simply do it by the numbers at first.

My apologies if my answer has been too pedantic or if I have misunderstood the question. If so, let me know in a comment and I'll be happy to delete the answer.


What should be the relative positions of a wing's aerodynamic center and center of gravity? A positively cambered wing with finite length L has its aerodynamic center AC located 25% from the wing's leading edge. What about the CG of the wing itself (not the CG of the whole plane)? Is there any recommendation for the wing's CG position along the chord?

What about the position of the AC along the wing's span axis? Should the AC be ideally located halfway at L/2 on the wing? What about the position of the wing's CG relative to AC? Should the CG also be at L/2? Why?

1) It doesn't matter much. AC is relevant mostly for aircraft stability, so it is its relationship to the CG of the whole aircraft that matters. Only when the wing is the aircraft (flying wing), the distinction disappears.

Mass distribution (and thus CG) of the wing matters for aeroelastic effects, but then AC is not very relevant.

2) There is little sense in trying to determine spanwise location of AC. AC is related to the lift changes over angle of attack (AoA). When AoA changes, lift (CP) moves forwards and backwards but not sideways. Theoretically, if you consider a half-wing, you might be able to determine spanwise lift movement, esp. on a swept wing. But again, for stability analysis (where AC is relevant), you never need to do that, so you consider the whole wing and relate everything to its mean aerodynamic chord (MAC). L/2, by the way, happens to be on the airplane's plane of symmetry (L is normally the whole wingspan).


What stops Germanwings 9525 happening again — a suicidal pilot crashing the plane? I'm unpersuaded and still afraid, after reading What safety rule replaced the now-rescinded two-person rule (after Germanwings 9525)?. What's to stop or prevent another lone suicidal pilot from crashing the plane by suicide? Pilots and people can easily lie about whether they have psychiatric illness. They can readily fake and lie through medical exams and psychological evaluations. Psychiatrists’ experiences of suicide assessment

One of the respondents, however, argued that it was not up to the doctor to question the narrative of the patient.

” It is not the least difficult to lie to one’s psychiatrist, it is rather easy, it is very easy. It isn’t our job to unveil the patient’s untruths.”

The truth about lies

"It’s not just common, it’s ubiquitous," notes Barry Farber, PhD, a professor in the clinical psychology program at Columbia University’s Teachers College and the editor of the Journal of Clinical Psychology: In Session. "Lying is inevitable in psychotherapy," he says.

Farber isn’t just speculating—he’s studied this topic for decades. In a survey of 547 psychotherapy clients, 93 percent said they consciously lied at least once to their therapist (Counselling Psychology Quarterly, Vol. 29, No. 1, 2016). In a second survey, 84 percent said this dishonesty continued on a regular basis.
And while therapists might suspect that they can tell when patients are being less than truthful, research shows this is not the case. In Farber’s study, 73 percent of respondents reported that "the truth about their lies had never been acknowledged in therapy." Only 3.5 percent of patients owned up to the lies voluntarily, and in another 9 percent of cases the therapists uncovered the untruth, notes Farber, who reports on this and related research in a new book, "Secrets and Lies in Psychotherapy," with co-authors Matt Blanchard, PhD, and Melanie Love, MS. "It seems therapists aren’t particularly good at detecting lies," Farber says.

So, in other words, what measures are currently available to prevent unstable pilots from causing harm, given that the psychiatric tests are evidently unreliable?

Any security precaution will be shared with the pilots. Therefore, a determined pilot will know those and be able to find ways to circumvent them beforehand.
What are some of the possible precautions?

Give both pilots their individual key? Easy - disable the lock before the other pilot leaves the cockpit, maybe by breaking off your own key when it is stuck into the lock.
Use a numeric keypad for unlocking the cockpit door which can only be reset on the ground? After the first terrorist attack where this system is abused, this will be disabled. And it is easy to figure out scenarios where the terrorists will learn the passcode from an unwitting pilot.
Similarly to military ground collision avoidance: Don't let the FCS allow too low flight levels outside of terminal areas? Disable the system by pulling the appropriate circuit breakers.
Let traffic control take over the plane by remote control when limits are exceeded? Easy again - just jam the radio signal. Again, it is easy to imagine scenarios where such a system is abused.

Also, what works for rail-based systems cannot be transferred to aviation. Stopping an airplane in mid-flight does not work as it does with trains.
The pilots have to be able to control the airplane exactly because in an unforeseen emergency they are the last resort which can bring it down in one piece. Taking away this ability does not enhance safety but would be the only basis of really stopping a suicidal pilot.


Why would a PAPI and ILS glide slope for the same runway not coincide? Some pilots are reporting the glide slope on our PAPI is not coinciding with the glide slope on our ILS even though FAA did a flight check of our PAPI's. Are there any reasons why a PAPI and ILS would indicate different approach glide slopes?

From the FAA AIM (section 2-1-2(b) Visual Glideslope Indicators): PAPI angles are based on obstruction clearance +/- 10 degrees from the runway centerline, up to 4 miles from the threshold. The ILS provides for obstruction clearance in a 3-6 degree angle on a 3 degree glide path. Therefore, if there are obstructions in the PAPI clearance area (e.g. a tower off to the side of the rwy) that don't exist in the narrower ILS clearance area, the PAPI will have to be a steeper angle.


Why didn’t the 757 have manual-reversion capability? The Boeing 757 was the highest-capacity and latest-designed narrowbody Boeing ever produced (and, in the case of the 757-300, the highest-capacity narrowbody anyone ever produced); it was also the only Boeing narrowbody lacking any form of manual-reversion capability for its flight controls in the event of a total hydraulic failure.

Now, I can sort of see why Boeing didn’t bother to give their widebodies manual-reversion capability (even if I don’t agree with their reasoning on that point), but the 757 is just a large narrowbody, and not even Boeing's largest; the 707 was even heavier (123,830 kg MTOW for the 757-300, versus 151,500 kg for the 707-320B/C), and it had full manual backups for its flight controls.  Also, in the time since they decided to leave manual reversion out of the 757, they’ve grown the 737 to near-757 size, and yet haven’t had any trouble at all keeping its manual-reversion system working!

Besides, if our friends beyond the Iron Curtain could do it all the way back in the 1960s (MTOW 165,000 kg)...

The only reason I can see that would sort of make even a bit of sense (if you scrunch up your eyes and look at it in a certain very-specific sort of way) would be if they left it out in order to avoid introducing excessive differences between the piloting skills required for the 757 and those required for the (widebody, and, thus, reversion-free) 767, and thereby possibly jeopardising the common type rating pilots can obtain for the two - but how can operational convenience possibly justify skimping on safety?

Why did Boeing leave manual-reversion capability out of the 757?

When you have controls designed to be operated manually, in an airplane that heavy and that fast, you have to include things to provide aerodynamic force compensation like servo tabs and offset hinge lines (look at the IL-82's rudder hinges; like a B-29's...the most obvious tell-tail of manual controls on a large aircraft) to make the control forces reasonably manageable, and even there, I can say with pretty much total certainty the IL-82 required muscles the size of fence posts to operate comfortably.  A jet like that with B-29 flight controls is hardly a leap forward.  You also have to mass balance the surfaces because there are is no flutter damping capability afforded by the mechanical control linkages.  All rather heavy.

When you have hydraulic controls, you can get away without mass balancing the surfaces, without servo tabs, and without offset hinges, because the hydraulic actuators (plus flutter dampers in some cases) provide all the required force, AND the required flutter resistance.

So, if you are going to design a hydraulically boosted system with manual reversion, you have to incorporate some of those aerodynamic force aids to be able to operate the controls manually.  But once you have a design that is sufficiently robust from a design/risk/failure tolerance perspective to operate with hydraulics only, there is no point in including manual reversion.  It's a step backwards, adding all kinds of complexity and weight for no benefit.


What is the air/fuel mixture ratio in a turbojet engine? How does it relates to stoichiometry ? What are the possible extinction accidents related to air/fuel mixture ratio ?

This cannot be answered specifically, the stoichiometric fuel/air ratio (FAR) is based on burning all oxygen, while for cooling purposes the airflow is generally much higher; therefore the FAR will be lower than the stoichiometric FAR. Note that you do not want to burn fuel at stoichiometric conditions as this produces the most nitrogen oxides. Fuel is being burnt rich and then quickly burnt lean.

Note that the FAR is depending on the speed, altitude and power setting (and the type of engine). To quantify the FAR, you would need to model the engine and simulate the performance. As an example (very simple to show the effect) a turbine exit temperature sweep for different altitudes and Mach numbers is shown below for a simple turbojet engine (the engine linked in the comments of the question is practically a turbojet engine considering the very low bypass ratio). You see that the FAR is variable (top graph is the burner exit FAR, bottom is the stoichiometric FAR):

I cannot address the second part of the question regarding the accident rate, that does not seem to be relevant.


Is ATC clearance or permission required to fly helicopter routes and transitions in the Los Angeles area? Skyvector has Los Angeles helicopter charts here and here.

Are pilots required to obtain ATC clearance or permission to fly helicopter routes and transitions?

According to the FAA's JO7210.3AA Facility Operation and Administration (chapter 11, section 5):

  Pilot adherence to charted helicopter routes and the recommended
  altitudes or flight ceilings associated with them will normally be
  voluntary. However, controllers may assign charted routes and
  altitudes and expect or request pilot compliance with them, provided
  such procedures are called for in specific FAA−operator Letters of
  Agreement, or are necessitated by traffic density and/or safety
  considerations; controllers also may restrict operations within
  designated operating zones when requested by local law enforcement
  officials and the restriction would not adversely affect other
  aircraft operations.

In other words, it's mostly a voluntary thing but pilots should still be aware of them and prepared to follow them if instructed.

And you have to consider the airspace as well: large parts of some routes are in uncontrolled class G airspace, e.g. the PALISADES coastal route, west of Santa Monica. ATC doesn't control traffic in class G, so asking for permission wouldn't make sense.


How far can a passenger plane taxi? Most commercial flights will have to taxi a short distance to the end of the runway, before actually taking off. But in an absurd, absolutely extreme case, what if that passenger plane could only taxi, not fly? How far would the plane be able to taxi before it runs out of fuel?

I imagine that the answer is in the ballpark of "many times around the world", given that passenger planes like a Boeing 777 or Airbus A380 hold tremendous amounts of fuel. However, since no plane has ever taxied until it has run out of fuel, I ask this question from a theoretical standpoint. I certainly wouldn't want to be on a plane taxiing the entire route from Los Angeles to New York!

The number will vary depending on the aircraft type & installed engines (how much fuel it holds, and how much fuel it burns per hour at taxi speed), but the ballpark figure is "Much less than the range in flight", because the specific fuel consumption figures (how much power, and thus distance, you get per unit of fuel burned) are less favorable during taxi than at cruise.

To work an example I used the numbers for an A320 taken from here and not checked it burns 270-330kg/hr (depending on the engines installed) so let's split the difference and say 300kg/hr as an average.

The A320 can hold around 15,000kg of fuel, so doing the division it could run its engines at taxi power for around 45 hours.

If we assume a taxi speed of 20kts for 45 hours the aircraft could theoretically taxi 900 nautical miles (1036 statute miles, or 1667km), a little less than one-third of the range in flight.


What's this fuel line for? Cessna 414 ram conversion

What's this fuel line for that is coming to injector , other then the one from fuel disturbutor  ?

It's a boost reference line which carries supercharged (Upper Deck) air to the injector for mixture atomization. Naturally aspirated engines don't need this as there is no positive pressure differential between intake manifold and the ambient atmosphere.


Can an airliner land safely using only propulsion control? In this amazing story ,after losing all hydraulic power of the aircraft , Captain Al Haynes guided the plane to the Sioux city, crashed but saved 185 of the 296 lives (United Airlines Flight 232-Sioux City, 1989). After this incident, NASA started to work on PCA systems.

Gordon Fullerton landed an F-15, using only engine power. How did the F-15 land while the airliner crashed? Since an airliner and a fighter jet have different engine positions honestly it would make more sense to me if the airliner made it to the ground but fighter couldn't because it has relatively greater distance between engines, so better capability of yawing and as a result of having a shorter wingspan a fighter needs to fly faster to stay airborne. I understand the weight difference, i understand the possibility of adverse weather conditions during 232 flight, but i still don't get how a fighter is more capable than an airliner.

Some airliners have in fact landed more or less successfully using only engine power for control. The 2003 DHL attempted shootdown incident is an example.

A major difference between United 232 and Fullerton's landings you cite is that Fullerton was working for NASA testing a system designed specifically for the purpose of assisting pilots in controlling an aircraft with power alone. United 232 had no such system. See https://www.nasa.gov/centers/armstrong/news/FactSheets/FS-041-DFRC.html


How to build a 2 mile long runway on a 1 mile square island? On Puzzling.SE I found this question:

  You have a 1 mile long x 1 mile wide private island that you wish to
  turn into a resort. A plane requires a 2-miles long runway to take
  off. What do you do?

There are plenty of answers, among them some irrational ones, but also some good approaches to solving this puzzle.

From an aeronautical point of view, what would be a reasonable solution?

I am thinking about a vertically curved runway. To meet the 2 mile requirement it would need to have an angle of (estimated) 25° at the edges of the curved runway. It would go diagonally across the island and by its curvature add the extra length needed to the √ 2 length of the diagonal length.

I am sure there must be a better solution though (extensions of the island shouldn't count!)

Anyone who has ever flown at Zar (EPZR) in Poland knows how much a runway slope can reduce the needed field length. For aircraft which need a 2 miles long level runway, a 1 mile long one with a 15% slope at its end will do just fine. Make the slope shallow at the bottom and increase it the further up the runway goes, just like the hillside runway at Zar. If the end point is 183.5 m higher than the touch-down point, the height difference is equivalent to a speed reduction from 60 m/s to zero.

Take-offs work in the opposite way, giving the same speed boost on the way down. A 1 mile long runway will do just fine. You do not even need to run it diagonally across the island.

Yes, this does not exactly answer the riddle, but is an engineering solution to a simple problem.


Are there any restrictions on long overwater flights by private aircraft? It is talked about in many questions here that (with the exception of older 3+ engine aircraft) airlines and their planes must be ETOPS certified if they are going to fly more than 60 minutes away from a suitable diversion airport.

Are there any similar restrictions for private flights?

If regulations differ, assume the flight is between the US and Europe in a US or European registered plane.

I am unable to find any ETOPS restrictions for private aircraft in the FAA FAR/AIM Part 91. The FAA Advisory Circular AC 91-70B is applicable for commercial aircraft operators. Anecdotally, general Aviation single-engine aircraft (Including helicopters) make oceanic journeys on a regular basis.


Why is the centre of pressure for a real wing with low aspect ratio more forward than that in two-dimensional flow? Why is the centre of pressure of a finite wing ahead of the quarter chord point predicted by 2D flow over the airfoil? Also what is a "LOW" aspect ratio in terms of numbers. The literature has terms like "very low A.R" "low A.R" "Moderate A.R" and "High A.R", but the actual ratios in terms of numbers are not given.

The center of pressure is defined as the point on the wing/airfoil where there is a zero net moment. This definition means that it is a function of the lift and subsequently of the lift coefficient. Airfoil theory overestimates the slope of the lift curve due to the absence of wing tip effects. With regards to the second question - I think the answer is rather subjective. Mathematically the limit of a very low aspect ratio is a 2D airfoil moving through unconstrained medium. How high an AR can go is mainly dictated by structural soundness of the wing. For real aircraft, have a look at the classic example of a low aspect ratio wing - F-104. Typical high aspect ratio aircraft are most gliders. I would point you to the exceptionally interesting read that is Theory of wing Sections by Abbott and Doenhoff and also any book on aerodynamics, e.g. Anderson


How much does pilot technique affect brake life? Anecdotally I have heard of various things that I can do to make steel brakes last longer before they have to be replaced, and they make sense but how much does it really help?

Things that I have heard:

Land at the minimum recommend speed
Use maximum reverse thrust (if you have it)
Delay braking after landing (if on a sufficiently long runway) to allow slowing before brake application
Various taxi techniques (taxi on one engine, don't ride the brakes, but instead build up speed and then brake to slow down.  Rinse and repeat.)

Are there any studies that have been done to show how much these things help and whether or not it makes a measurable difference?

I can't speak to techniques for for larger aircraft like the ones you're describing (reverse thrust, etc.), but for light GA aircraft one of the best things you can do to extend the life of your brakes is to not use them for directional or speed control during taxi1.

Most aircraft brake linings are "heat glazed" as part of their initial conditioning, and the heat from normal use (slowing down after a landing) maintains that glaze, but light brake use wears away the glaze on the surface of the brake linings, which reduces brake effectiveness and increases wear.

As far as landings go, I was always taught to use "aerodynamic braking" as much as possible (keeping the yoke back on the landing rollout). I don't know how much it helps with brake wear, but I find I don't need to be on the brakes as long, and anything that reduces the amount of time the linings and discs are rubbing on each other is probably saving a few millimeters of wear.

1 – Obviously safety is paramount here - if you're on a downhill taxiway you might have to ride your brakes unless you can get reverse thrust from your engine(s). Also on planes where differential braking is your sole means of directional control while taxiing just try not to drag the brakes the whole time you're moving.


How is the the turning error of an aircraft magnetic compass calculated? I have a major exam in school tomorrow and I still don't get how to get the turning error of an aircraft magnetic compass. For example, if given an initial heading of 120 degrees and final heading of the Northern and Southern hemisphere, how to calculate the overshoot and the level off? I know the UNOS and ONUS but still don't get the concept of it. Please help me.

First of all, in real life the overshoot will depend on the bank angle, so it is not really practical to do calculations unless you are doing some kind of special, precision flying or acrobatics. Normally you just get a feel for the overshoot and compensate intuitively. Exact calculations can be useful if you are doing precise figure-8's or something like that.

To actually do the calculation (which is based on a shallow turn 15-degrees to 20-degrees):

Target heading:

270 or 090 no correction necessary
northerly -- need to overshoot
southerly -- need to undershoot

Amount of correction (as variation from East/West parallel):

90-degree difference (eg heading 000) -- use 30-degree correction
60-degree difference (eg heading 330 or 030) -- use 20-degree correction
30-degree difference (eg heading 300 or 060) -- use 10-degree correction

Example 1:

You are on a 110 heading and want to turn to 030. You need a 20-degree overshoot. Turn left and roll out when you reach heading 010.

Example 2:

You are on a 335 heading and want to turn to 240. You need a 10-degree undershoot. Turn left and roll out when you reach heading 250.


Do aircraft performance figures include corrections for areas with especially strong or weak gravity? The strength of gravity at the Earth's surface is not constant, but varies from place to place by as much as a few percent:

(Image by NASA.)

As a result, an identically-loaded aircraft weighs less in (for instance) southern India, Uyghurstan, the eastern Caribbean, or the Hudson Bay area than it does in (for instance) Indonesia, Greenland, Liberia, or the Russian Far East, which should (in theory, at least) affect its operations in several different ways:1

An aircraft in a lower-gravity region won't need to generate as much lift in order to become, or remain, airborne, allowing it to take off and land at slightly lower speeds, to climb slightly more steeply, and to cruise at slightly higher altitudes.
An aircraft in a lower-gravity region can be loaded slightly fuller without exceeding its maximum allowable takeoff weight (potentially giving it a range advantage over an aircraft launched from a higher-gravity region, if the extra capacity is used to carry more fuel), and can land slightly fuller without exceeding its maximum landing weight and risking structural damage.
An aircraft landing in a lower-gravity region will have less weight on its wheels, slightly reducing the maximum braking force available from the wheelbrakes (which might well cancel out the landing-weight advantage mentioned in the previous bulletpoint), and, thus, requiring a slightly longer runway.

Do aircraft performance figures and calculations include corrections for local and/or regional variations in the strength of gravity, or are these variations simply considered too small to bother accounting with?

1: This is by no means meant to be an exhaustive list.

No they don’t. Any variations in gravity are swamped by variations in temperature, pressure, density, winds, runway surface, runway slope, runway conditions (wet?) etc. that all have a major impact on performance.

But it is an interesting question, and I learned something by following the link. Thanks!

I know it does have an impact on navigation for submarines, which use variations in gravitational fields in their inertial nav algorithms.


Why buy an new plane or an helicopter? This really keeps coming to my head.

A brand new 172SP costs a quarter million while a older one (10 years older or a little bit older) costs for less than 100.000 Dollars and the only visible difference is the G1000 NXI and a AoA indexer next to the compass.

Its maybe my ignorancy on the specifications but with the price difference I could:

Buy a brand new avionics suite turning the plane to a spaceship. everything from a autopilot to the Class S transponder.
AUX tanks
And maybe a brand new, upper model engine by selling the original one!

And I would STILL have surplus money!

Things is... As long as the owner of the second hand plane treats the engine good and doesnt abuse the airframe for aerobatics I dont see a SINGLE reason to NOT buy that plane.

So why waste so much money for a factory installed AOA Indexer that can be bought for less?

I am not acquinted with helicopters but the same "250K Brand New vs 100K Owned" thing applies to them too, I see. (Robinson R22)

Because some people like new things... Thats how salesmen stay in business.

There are however some practical aspects to this question and on the tail end of my instrument rating I've been getting serious about buying something, here is what I have found. For the purposes of this answer I'm only going to talk about aircraft that are still in production like the 172 and have been for some time. The only other comparable aircraft is the Piper Archer. Mooney no longer makes the lower power stuff, the early low power PA-28 variants have been out of production for some time and are thus out of scope. In the end it depend s on what you, the pilot/owner/operator really wants out of the aircraft.

While a 1956 172 will share a lot in common with ones rolling off the line now a G1000 cockpit is not a steam gauge cockpit. A G1000 unit, or any of the various glass options for retrofit are NOT cheap to buy and install. Thus if you get a decent, low time 172SP and replace the panel to make it just like a new one, you have already spend about what a new one costs and there may very well be 2000 hours on the airframe already.
The older the plane (generally), the more engines its been through. A well flown early era 172 may very well be on its 2nd, 3rd or 4th engine. These engines could have been overhauled, rebuilt, swapped by various different entities in various ways. There may or may not be a warranty on them anymore and you may have little protection against it blowing out on you. Meanwhile a new plane may come with a warranty which represents real tangible value especially considering the first hundred hours or so of an engines life are quite critical. You can find all of Textron/Cessna warranty info here.
You are buying effectively a 0 time engine (or as low as practical) again you can buy a nice 172 then go spend another 20K, 30K, 40K... putting a fresh engine in it to get a "new" airplane.
The paint and interior are new and clean. There is nothing quite like the tired velour interiors of rental aircraft but even second hand planes often have tired 80's fabric that have seen a lot in their time. A fresh paint job and new interior is not cheap, especially when you realize you need fireproof fabric, may need to take a lot of the plane apart to paint it and dealing with the downtime. We come back to the 80's 172 that needs paint and a costly interior example...
Finally, old planes are just tired. Even planes that look to be in good shape, pass inspections, and fly great dont last forever. Some times you are just taxing along and your gear gives out...

Buying an old plane and making it a new plane may just cost as much as a new plane.


What happens when changing the throttle on a PT-6 engine? Imagine a PT-6 in cruise flight. What would pushing the throttle forward for increased power show on the engine instruments? We know (I assume!) the prop RPM remains constant by varying the pitch, but what goes higher? Torque or TIT?

And what does the pilot do in descent for landing? Does pulling the throttle back for a long descent decrease the fuel flow to a point where it may not sustain combustion and cause flame out?

Pushing the power lever forward will command more power. Fuel flow will increase, so will the TIT and torque.

To maintain the same RPM, more torque is needed as the prop blades will increase their angle.

Pulling all the way back does not cut the fuel flow (FF). The minimum FF required to sustain operation will be managed by the fuel control unit (FCU).

Sidenote on terminology: throttle, power, and thrust levers are the controls for piston, turbine, and jet engines respectively.

RE: Torque limits

It depends on the engine, but generally:

  In cold weather conditions, torque limits can be exceeded while temperature limits are still within acceptable range. While in hot weather conditions, temperature limits may be exceeded without exceeding torque limits. In any weather, the maximum power setting of a turbine engine is usually obtained with the throttles positioned somewhat aft of the full forward position.

Related: Is turboshaft fuel efficiency affected by N2 loading?


Should I fly if conditions are VFR but the flight briefer says "VFR Flight Not Recommended"? I contacted a flight briefer this morning in the San Francisco Bay Area in California. At the time, ceilings at my airport (Palo Alto) had just hit 1000 ft, so the field was (barely) VFR. It is a very common pattern in this area for the ceiling to burn off, become broken, scattered, and then disappear.

The briefer told me there was an Airmet Sierra for IFR conditions and mountain obscuration in force, and that VFR flight was not recommended. When I talked with an instructor at the club, we talked about the specific location of the clouds and decided the whole area would soon be VFR.

Question: should I fly if conditions are clearly VFR but the flight briefer is telling me “VFR flight not recommended”? How should I think through the risk assessment here?

"VFR Flight Not Recommended" is a judgement call made by the flight briefer. It means, as you noted from the AIM, that the briefer doesn't think flying around VFR is a smart idea based on what they're seeing.

The usual reasons for a briefer using this phrase are:

The weather is currently below VFR minimums somewhere along your intended route.
The weather is currently "Marginal VFR" somewhere along your intended route.
The weather is forecast to be marginal VFR or below somewhere along your intended route.
Some other adverse condition (like mountain obscuration) exists along your route or in the area you intend to fly.

The briefer's recommendation is just that: a recommendation -- it is not binding. How you evaluate the flight to make a Go/No-Go decision when the briefer provides this recommendation is your choice as pilot in command. You will need to consider why the briefer is telling you VFR flight is not recommended, and apply your own knowledge and judgment.

A couple of examples:

If the briefer is telling you this because Airmet Sierra is active for mountain obscuration and you intend to fly through some mountain passes prudence suggests that proceeding VFR into mountains that may be obscured by clouds would be a Bad Idea.
If the briefer is telling you this because the weather is currently marginal VFR, but it's forecast to improve and you only plan to shoot a few touch-and-go landings at your home airport you might proceed with the flight anyway.

For evaluating the huge swath of conditions in between those two extremes consider your familiarity with the area (typical weather patterns, topography, obstacles, etc.) and the conditions of flight (especially day-vs-night). Thomas P. Turner's site has a nice set of guidelines which I happen to broadly agree with, but each flight needs to be carefully evaluated to determine if you believe you can complete it safely under the conditions reported to you by the briefer.

The safest approach is obviously to cancel the flight (or complete it under instrument flight rules) if you have any doubt.


Can a flight instructor without instrument rating legally provide instrument training? In the US the FAA requires student pilots to receive at least 3hrs of instrument flight training.

Can a flight instructor that does not hold an instrument rating legally provide a private pilot student the 3hrs of instrument training?

Long story short, a CFI without an instrument rating can provide training on the instrument flying required for a private certificate only. To provide instruction on the use of instruments for an instrument rating, a commercial certificate or an ATP certificate, the CFI must have an instrument rating.

You can read all the details in the Grayson (2010) legal interpretation and the FAA apparently revised 61.195 in 2009 to make this whole topic 'clearer':

  §61.195   Flight instructor limitations and qualifications.

  A person who holds a flight instructor certificate is subject to the
  following limitations:

  [...]

  (c) Instrument rating. A flight instructor may conduct instrument
  training for the issuance of an instrument rating, a type rating not
  limited to VFR, or the instrument training required for commercial
  pilot and airline transport pilot certificates if the following
  requirements are met:

  (1) Except as provided in paragraph (c)(2) of this section, the flight
  instructor must hold an instrument rating appropriate to the aircraft
  used for the instrument training on his or her flight instructor
  certificate [...]

As the interpretation explains, the instrument training requirements for a private certificate are very general (61.107 and 61.109): "basic instrument maneuvers", " control and maneuvering of an airplane solely by reference to instruments". But the commercial and ATP requirements are much more specific (this is from 61.129): "attitude instrument flying, partial panel skills, recovery from unusual flight attitudes, and intercepting and tracking navigational systems". For that reason, CFIs who provide instruction for the private requirements only do not need an instrument rating.

Practically speaking, I've never met a CFI who didn't have an instrument rating. I'm guessing that a CFI without one would have limited value for employers and might even have issues with insurance.


How frequent are touch-and-gos? Other questions on this site say that go-arounds are roughly 1-3 per 1,000 landings. But in many of them, as described by passengers, the wheels don't actually touch the ground. Recently I had a touch-and-go (at Nuka Hiva, a small airstrip on a cliffy island in the Pacific) where our wheels most definitely touched the ground but we immediately accelerated and went around. The brief announcement said it was due to wind shear - we were safely on the ground on the second try so all's well that ends well.

I'm curious as to whether a true touch-and-go when a pilot is not practicing touch-and-go, on a commercial flight, is a significant rarity. By coincidence, this very same flight started with my first ever aborted takeoff, because a fuel overfill on one side had left us unbalanced; we returned to the gate and span one prop for 10-15 minutes then took off without incident. Am I in lottery-ticket territory?

In larger aircraft you may not be able to execute a go around once you have touched down but its not always because of weather. This mainly has to do with the fact that once a plane touches down (situation depending) it may have already committed to the landing and will no longer be able to get airborne with the remaining runway. There is a discussion here on the topic and an article here that covers it as well.

It generally takes more distance to take off than land and a considerable amount of speed is bleed off during the flair and subsequent touch down. If a plane touches down at the proper touch down point on a runway it may not have enough distance to accelerate and become airborne again by the other end of the runway. Further more you can complicate the situation with things like thrust reversers which, once deployed force you to commit to the landing.

The airport in question has a 5578 x 98 feet runway which is a solid size but chances are you were flying a plane on the smaller side. Generally the smaller the plane the less runway you need to land and take off so go arounds after touchdown are possible.

To directly answer your question, in some instances they do happen but they will be recorded as an aborted landing. In other cases (heavy crosswinds) you may have only one side of the mains touch (does that count as a touch down?). The runway length and aircraft size/performance are the main factors and there are so many combinations of that.

--Edit--

Since you have provided the make and model of the plane we can extrapolate a bit more. You can find the full specs here but lets take the the At TOW for 300 Nm - Max pax - 3,000 ft - ISA +10 - situation which is quoted at 4,626 ft. Take off speed at max load is 116 Kts (and you were landing so you were on the lower end of the fuel which means you were below max load even with full passengers). Likewise approach speed is 113 Kts. Some of this depends on the pilots precision but It should be (and obviously was) possible to touch down, full power, and get airborne again in enough distance on the strip. Sine you would only need to make up 3 Kts assuming he came in on the mark at 113. They would lose speed in the touch down but if they were on the throttles fast enough it would work.


Do two of the same model of aircraft feel different to fly? How does it feel when you change from an aircraft to another but of the same model?

Sometimes when you change a car and drive another one of exactly the same model you do feel differences due to various factors like wear and tear, mileage, different service schedules etc.

Does this apply also to aircraft or are they exactly the same?

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

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


Do aircraft manufacturers like Airbus or Boeing charge the airline, when they assist in aircraft accident investigations? Most of the time, when an aircraft crashes or has an accident, the manufacturer also assists in the investigation. Is this a pro-bono kind of effort on part of the manufacturers, or do they charge the airline for it?

Investigating agencies are in charge of most air accident investigations not involving criminal acts. In the US this is the NTSB, which is required to investigate air accidents per US Code Title 49, Chapter 11. These agencies exist to provide independent investigation of accidents and provide recommendations to regulators.

The investigating agents will do their best to understand the circumstances and causes of an accident. Agents of the NTSB have authority under §1134 of the above mentioned law to gather information about an accident.

  (a) Entry and Inspection.—An officer or employee of the National Transportation Safety Board—
  (1) on display of appropriate credentials and written notice of inspection authority, may enter property where a transportation accident has occurred or wreckage from the accident is located and do anything necessary to conduct an investigation; and
  (2) during reasonable hours, may inspect any record, process, control, or facility related to an accident investigation under this chapter.

Investigations can also benefit from working with people that are already familiar with the critical elements. As part of the investigation, the agency may invite various parties. This could include airlines, manufacturers, air traffic control, workers unions, other agencies, or anyone else with information or expertise that could be helpful. If these parties do not abide by terms for participation, this status can be revoked. The resources spent by parties during an investigation can in some cases be fairly intensive. For example, while supporting the investigation of the crash of British Airways Flight 38, Rolls-Royce and Boeing ran full-scale tests of the engine and the fuel system designs.

Investigating agencies are funded by their governments. The Aviation Safety department of the NTSB has an annual budget of about $50 million. Parties to the investigation represent their respective parties and are paid by their party to do so. Part of the party agreement acknowledges this:

  Participation as a party to an NTSB investigation is a privilege and confers no rights or benefits.

They "pay" that parties get is good press for assisting in the investigation, and helping to both prove and improve the safety of their products and services.


Can the pilot stop airflow between cockpit and cabin? During normal operation the entire fuselage is pressurized equally:

  An aircraft fuselage does not contain separate compartments with different pressure values in each. The entire vessel is pressurized equally from the forward pressure bulkhead to the aft pressure bulkhead. This normally includes the cabin, cockpit, and lower-deck cargo holds. (source)

If my understanding of physics is correct, this means that there must be airflow between the cockpit and the cabin (otherwise a pressure difference would occur). The airflow equalizes the atmospheric pressure in the cockpit and cabin.

Question: Can the pilot completely stop the airflow between cockpit and cabin, i.e. hermetically sealing off the cockpit from the cabin ?

3 scenarios for which this question is interesting:

fire
If there is smoke in the cabin, the pilot would need to prevent the smoke from entering the cockpit.
hull breach
Does cabin depressurization (due to a hull breach for example) directly lead to cockpit depressurization? Or can the pilot prevent this by stopping the air outflow from the cockpit to the cabin?
MH370
One working hypothesis in the MH370 mystery is accidental or deliberate cabin depressurization. Assuming the latter, is there any way the perpetrator in the cockpit could prevent the cockpit depressurization ?

I would appreciate if your answers included these 3 scenarios. Since the third scenario deals with a B777, please use this type as an example. Technical airflow diagrams very welcome!

Concerning scenario 1 (fire), my research into this question seems to suggest, that the cockpit is indeed designed to be sealed off in case of fire. I could not find the relevant information for a Boeing-777, but here is a description of how smoke entered the MD-11 cockpit in the Swissair 111 crash and how it was supposed to be prevented (smoke barrier, etc):

SR 111 Investigation Report:

  Airflow patterns in the MD-11 are affected by the aircraft configuration. In the forward portion of the aircraft, this configuration includes the valve position of individual air outlets in the cockpit and throughout the cabin, and the position of the louvres in the bottom part of the cockpit door. Also, all MD-11s are equipped with a smoke barrier installed laterally across the aircraft in the attic area above the cockpit aft wall (see figure 3). Inspection of Swissair MD-11s showed that the smoke barrier was sealed relatively tightly in some aircraft, while in others there were gaps in the barrier at the edges and at the seams where conditioned air ducts pass through the barrier. These gaps allowed air to flow past the smoke barrier. The holes in the barrier, designed to permit the engine fire shut-off cables to pass through the barrier, would also be a path for smoke to pass between the cabin and cockpit.

fire If there is smoke in the cabin, the pilot would need to prevent
  the smoke from entering the cockpit.

This is a bit more complex as the cockpit door by its own nature will slow the flow of smoke but will not stop it all together. Smoke flow is also dependent on the movement of air within the aircraft. In your example of SR-111 the smoke was not in the cabin but in the overhead section so closing the cabin door would not have accomplished much. While smoke barriers are installed ultimately in a fire situation its only a matter of time before another hole is burned through. This is why early identification and extinguishing is so key. By the nature of cockpits things like wire bundles, cable chases, and at one time in history control cables must come and go so you cant truly seal a cockpit anyway.

  hull breach Does cabin depressurization (due to a hull breach for
  example) directly lead to cockpit depressurization? Or can the pilot
  prevent this by stopping the air outflow from the cockpit to the
  cabin?

  MH370 One working hypothesis in the MH370 mystery is accidental or
  deliberate cabin depressurization. Assuming the latter, is there any
  way the perpetrator in the cockpit could prevent the cockpit
  depressurization ?

You can generally lump these into the more general question of "can the cockpit be pressurized separately from the rest of the aircraft" to which the broad answer is no. Simplly put the cockpit door is not capable of serving as a bulkhead and cant withstand the pressure differential, as far as I know they also lack any sort of sealing, bracketing or joints for such a task. The only aircraft I can really think of that ever had a feature like this was the B29 Super fortress which had independent fore and aft sections that were independently pressurized. This allowed an unpressurized bomb bay in the center. To make this possible both sections had small pressure doors to allow entry.

(source)

The only thing a flight crew could do, is potentially depressurize the whole aircraft and use the pilot and co-pilot 02 system to outlast the cabin 02 masks, then decent below FL100 and breathe normally.


Can winglets be used to compensate the high induced drag created by a low aspect ratio wing? I have read in some articles that the major advantage of having a high aspect ratio (AR) wing is to reduce the induced drag. If winglets main job is also to reduce the induced drag, how much drag does it reduces? Would it be possible for a low AR wing with well-designed winglets to have the same induced drag as a high AR wing?

In the lens of potential theory, we can explain and predict the efficacy of winglet through how much it dilutes the trailing vortices strength. Just like we can show that the Elliptical lift distribution produces the least induced drag for a given span length on a flat planform, we can equally derive the optimal lift distribution for any wing+winglet combination of arbitrary winglet height and cant angle.
The graph below, collected from Drela, Flight Vehicle Aerodynamics, shows parametrically how the most optimal induced drag of various winglet extensions and cant angles compare against the flat Elliptical drag, if the total lift on the wing is fixed. $h_{winglet}$ is the vertical height of the winglet above the planform plane, and $\theta_{winglet}$ is the cant angle measured from the planform plane (0 means a simple span extension, while 90 means a perpendicular winglet).

Image from Drela, Flight Vehicle Aerodynamics
As you can see, a simple span extension ($\theta_{winglet}=0$) is always better. For example, to achieve the same induced drag reduction as a span extension of 20%, we must have a vertical winglet whose combined height is 40% span (assuming we don't allow span extension whatsoever).
I must stress that the results above are a comparison between the most optimal planform + winglet combinations. Optimality means that when the winglets are attached, the wing itself is modified to achieve optimality. In practice, with the wing itself fixed, you could only do worse.


What is the practical usefulness of a small home made wind tunnel? Is a small wind tunnel, like in the video, of any value for building planes able to carry a man?

Can the lift and drag, corresponding to a scaled down wing (or segment of a wing) introduced in such a tunnel, be scaled up to obtain the lift and drag of the full size wing?

See this video

There are some things about this wind tunnel that are not as good as the best wind tunnel experiments for actual aircraft.
Obvious concerns are that the wing is very close to the bottom of the wind tunnel (relative to the size of the wing), which means there will be a kind of "ground effect."
(Notice how at the high level of attack shown in your photo, the airflow underneath the wing is almost completely pinched off.)
The relative nearness of the top of the tunnel could have an effect too.
The setup shown will not tell much about what happens at the wingtips of an aircraft--an airplane with huge vertical plates attached to the end of each wing (which is what this setup models, with its wing tip practically flush to the side wall of the tunnel) will fly differently than an otherwise identical aircraft without those vertical plates.
Merely testing the wing also doesn't tell us anything about the aerodynamics of the fuselage, which will affect how well the aircraft flies.

There are also scaling issues having to do with things such as
Reynolds numbers and (for jet aircraft) Mach numbers.
Practically all wind tunnels have these kinds of scaling issues.
The "aircraft" that are tested in them are generally scaled-down models.
This is something that wind-tunnel experts have learned to deal with
(see Peter Schilling's answer).

But while those are things of concern to people building the latest passenger jets and fighter aircraft, where flying just a little better than the competition is very valuable, I think a wind tunnel experiment like this is meant to investigate more basic properties of wings.
When the Wright Brothers were building their first aircraft, for example, the aerodynamics of wings was not very well understood at all.
Even a few years ago, incorrect notions about wings were widespread
(there are whole pages of the NASA website debunking them).
If a wind tunnel like this gives you information about the forces on the wings that is 30 percent more or less than the "true" values,
you're still way ahead of someone who is basically just guessing about the forces by combining naïve intuitions about the dynamics of the airstream with calculations based on actual speed, density, and so forth.

My biggest complaint about the design of this apparatus is that the arrow attached to the wing, pointing to the angle scale on the back wall, cannot measure negative angles of attack. This could be fixed by mounting the angle scale with the straight edge of the scale vertical instead of horizontal.


Are there any English speaking flight schools to get a PPL in continental Europe? I'm a UK citizen, planning on getting my PPL this year. My goal was to train intensively, taking lessons several times a week. Unfortunately the UK weather means that even if you have the time and money to train that often, it's easier said than done since lessons are called off more often than not due to a low cloud base or rain.

I was thinking I might be able to get it done faster if I went somewhere like Spain or Italy where the weather is better, but obviously for this to work I'd need to find somewhere with English instruction. I'm assuming if I could find such a place, then as long as the school was EASA certified then the hours would count towards a UK PPL and I could just return home at the end to take my checkride and written exams.

Does my plan make sense, or is there a flaw I've overlooked? If it would work, can anyone recommend a good school that meets these criteria?

Some years ago there were a couple of flight schools on Malta, I'm not sure if they are still operating, DuckDuckGo could probably tell you

The most common way of getting a JAR (pre-EASA) PPL (for UK trainees) outside the UK used to be to go to a JAR accredited school in the USA. Florida was very popular.  I expect there are schools in the US that are allowed to train to the EASA syllabus these days.  I think you need to travel on a training visa to do this and I'm not sure what is involved in getting one

I think I'm right in saying your flight test can be taken by an EASA examiner anywhere, no need to come home to do it (and anyway you'd want to do it over familiar territory)

A big warning to anyone learning to fly is not to pay upfront.  Pay lesson by lesson.  Flying schools can go bust very quickly, many students have lost a lot of money this way

Personally, I would be wary of training outside the UK, the weather conditions and procedures will be very different from what you are used to, and a low-hours pilot could easily get caught out.  Marginal conditions can go bad on you very quickly.  If you do do this, try to get some supplementary lessons in poorish weather and get some time fly through UK CAS to get used to ATC procedures


What are the structural differences between short- and long-haul airplanes? As I understand it, pressurization cycles introduce the most stress on an airframe so maintenance intervals are tied to it. However, not all planes are equal in that regard, a long haul flight in a 747 might easily take 10 hours counting for one pressurization cycle while a 737 can do 6 trips in that time. Are short-haul planes build "sturdier" in this regard than their long-haul counterparts so that they are able to better cope with the amount of stress? And/or do they have to go into maintenance more often?

Yes, short range airliners are designed for up to 90.000 cycles whereas long range airliners can be designed for 40.000 cycles or less. And it is not only the pressurized cabin that needs to be designed for more load cycles, also the landing gear has a lot more work to do. This should become clear when you calculate how many miles/kilometers an airplane will taxi in its life and compare that to the design life of a regular car.

Your average short range airliner will easily taxi 5 times more miles in its life than your average car will drive.


Is there any country that requires window blinds to be open for takeoff and landing? Does any country legally require the window blinds to be open for takeoff and landing? I'm asking about legal regulations that specifically mention window blinds, not airline procedures or general 'follow the crew instructions' regulations.

I only need one example, whether it's FAA, EASA, a national CAA or some other regulator, or an ICAO standard or recommendation.

There is a regulation which indirectly covers it. Certainly in the UK and I'm pretty sure in the US and EASA land, it is an offence to not comply with the lawful instruction of a member of the crew. Therefore, if you are asked to raise the blinds, it is a legal requirement for you to do so.

Failing to comply with an instruction which is not itself illegal is an offence. Rarely used but it has been. Usually, the cabin crew will just mark you down as "idiot" and do it themselves. But, if it is clear that you understand and that you are able to comply, you might be removed from the flight and prosecuted. Generic laws like this, e.g. "dangerous driving" are there to provide for reasonable action when a specific law does not apply.

A valid defence would be to demonstrate that you were unable to comply to the extent that the prosecution is unable to convince a jury of your peers to find you guilty "beyond reasonable doubt".

So, in summary, albeit indirectly, it is a legal requirement for you to raise the blind when asked to do so in the UK.


Are there any guidelines or regulations for seat legroom on airlines? I am over 6' 2" and endured an extremely unpleasant 9-hour flight last year.  Shorter folk were just fine. Are there any guidelines or regulations for seat legroom on airlines?

The short answer is no, beyond the need for an aircraft to satisfy the emergency evacuation requirements set by the FAA and other regulators. There must also be room for an approved seat cushion and seatbelts. So there is a point where a lack of legroom would impede evacuation to the extent that an aircraft couldn't pass the 90 second evacuation requirement, but there's generally no specific minimum legroom requirement.

The main exception is in the UK, which does have a form of minimum requirement (according to that link, the UK is the only country with one). The requirement is given as a different form of measurement from how airline seat pitch is normally defined, but the above link indicates that it basically translates to a 28-inch seat pitch. That's about as low as any airline goes, namely Spirit in the US. Most airlines draw the line at 30", with a few low cost carriers doing 29"


When should I notify ATC when I notice that I may have conflicting traffic? Let us say I am flying at FL100 with heading 360 and I noticed that ATC just cleared another aircraft to climb to FL100 with heading 270, and we may have a converging path if we proceed with our current flight paths; so, if, from then on, neither aircraft has gotten any further instructions from the controller, at what point should I remind ATC that I may have conflicting traffic based on my current flight profile and the clearance given to the other aircraft? For instance, would I have to wait until ADS-B alerted me of a loss of separation between me and the other traffic (say, coming within 3 nm of each other)? Or I could report the possible conflict earlier?

I think you will find there isn't a correct answer for this, and that answers will primarily be opinion based.  That said, my opinion is that if you have ADS-B, be patient and let ATC do their job.

Speak up eventually, of course.  Especially if you see a clear converging path on your scope.  The 3nm you suggested seems like as good a point as any to mention it.

It's a little different if you are VMC.  In that case I might wait even longer and attempt to acquire a visual first.  That way your reminder to them can consist of your assessment of the need to deviate, or declare that you can maintain visual separation.


How does passenger unloading order prevent plane tipping? This answer to the question about an emergency landing very early in a trans-continental flight indicated that the fuel in the aft auxiliary tanks could cause the plane to tip on its tail if the passengers weren't unloaded carefully. The cabin crew seems to have kept everyone calm and orderly, and they deplaned with no further incident.

My question is how did the orderly disembarkation prevent the plane from tipping?

These are the thoughts that ran through my head as I read the story:

Were the pilots busy moving fuel out of those aft tanks while the pax were deplaning?

If so would they have started the rebalancing as soon as the firefighters cleared the plane to move?
Would that have taken the hour it took to get the plane to a gate for them to shift all the fuel?

What else would be involved?
If the fuel in the tail would cause the plane to tip, unloading the pax slowly would still leave it with an aft CG, and it would still tip once the critical number of people were off.

Apparently, there have been a number of incidents with 'tail tipping' in case of Boeing 737-900s and 900ERs. In these situations, the plane 'tipping' on its tail can be prevented by two methods:

Unloading the passengers starting from rear to front.
Unloading the (baggage from) aft cargo hold before passengers were allowed off the aircraft.

There is also some indication that the 737-900s are loaded in the front rows (1-17) first followed by aft rows, while the unloading takes place in the opposite way.


How frequently do aircraft get struck by lightning? We have several questions here about what happens to an aircraft when it gets struck by lightning (e.g. this question), and at least one answer from a former pilot who knows he was struck once and thinks he was struck other times. How frequently do aircraft get struck by lightning?

Additional commentary on how do you know you've been struck would be appreciated, but I'll make that a separate question if it's more appropriate.

It is estimated that on average, each airplane in the U.S. commercial fleet is struck lightly by lightning more than once each year.

Edward J. Rupke, via Scientific American.

  The Federal Aviation Administration estimates that on average, lightning hits each airliner in U.S. service once a year.

Washington Post

It looks like commercial airliners get struck about once a year. I was also able to find an FAA source, but it doesn't look like it's the original source.


Is there a manual which describes the algorithmic procedure on which the Vertical Navigation Guidance is based? I am interested in the methods implemented by Flight Management Systems in order to calculate a trajectory path of vertical navigation guidance (VNAV), which takes into consideration the legs of the instrument procedures used for a flight plan, among other things such as aircraft's performance characteristics, wind etc.

In other words, a manual or a guide from official sources (for example, FAA, ICAO or Eurocontrol), but other reliable third-party solutions would also suffice.

I am mainly interested in a way to determine the vertical profile of an instrument flight procedure (SID, STAR, IAP) based on its legs and any crossing altitude or speed constraints that are assigned to any of their waypoints.

Can someone point me in the right direction? I am aware that there is not one way of determining the vertical profile of a route, however my guess is that some universally accepted guidelines must exist.

EDIT: I will provide some more information about what I have in mind, based on Noah's contribution. Let's take for example FINNZ2 and HHERO3 departure procedures of KSNA airport. We can see that some of the waypoints have crossing altitudes assigned.

Can an acceptable implementation of vertical navigation be based on the aforementioned crossing altitudes, by considering them as mandatory altitudes that an aircraft must have while passing from them? This would mean that every such crossing altitude would be considered as "CROSS X AT Y ALTITUDE" restriction, even if it is At or Above, At or Below or Block.

Something like the following vertical profiles:

In other words, I am trying to figure out if this would be a useful or realistic information that an FMS would also provide.

My other idea would be to take a predefined climb gradient for the aircraft, let's say 500 feet per nautical miles and adjust the vertical path if any waypoint crossing altitude restrictions are violated.

For this answer:

Hard altitude requirement - a fixed altitide which an airplane must
be at. (eg. 7000ft)
Soft altitude requirement - a window of altitudes for the aircraft to
be at (eg. abv. 3500ft, between 9000ft and 12000ft)
Using a 757 for all examples unless specified otherwise.

A simple FMS may simply assume and use the minimum of a soft requirement as the desired altitude, as you correctly stated.

However, in airliners, it is much more common to use what is called a "Cost Index" (CI) to calculate speeds, climb rates and the like.
Cost index can be calculated as so:

CI = (Time cost/hr)/(Fuel cost/lb)

A CI of 9999 means that the FMC will aim for Velocity Maximum Operating (VMO) in every stage of flight. Whereas a CI of 0 will result in the FMS aiming for the following:

+=================================+===============+===============+
|              Climb              |    Cruise     |    Descent     |
+=================================+===============+===============+
| Minimum fuel to cruise altitude | Maximum Range | Max L/D ratio |

So that will lead to the following speeds:

+============+=======+========+========+
| Cost Index | Climb | Cruise | Descent|
+============+=======+========+========+
|          0 | 290kn | .778m  | 250kn  |
+------------+-------+--------+--------+
|       9999 | 345kn | .847m  | 334kn  |
+------------+-------+--------+--------+

Now we have climb speeds, we can work backwards to calculate the best climb or descent rate for this speed (I can't find a reliable source for this, so that's where the practical examples end). From here; TOD, TOC and TTC. As long as an FMS can remain at its best CI speed to meet an altitude requirement, it will. Otherwise it will alter best CI speed by the smallest amount possible to meet the requirements.

Some good (debatable) reading is this report by MITRE, an information security organisation. They found that most FMS' tested had very little variation in the time they began descents and climbs, as well as altitudes for a fixed CI. They also found that the RTCA standards for RNP - called RTCA DO-236 where generally adhered to in every tested FMS.
That means the following was met:

  ... tolerances for a
  flight along a specified vertical path is 160’ for 0’-
  5000’, 210’ for 5000’-29000’, and 260’ for 29000’-
  41,000

MITRE also says:

  If a preceding waypoint is encountered before the altitude of the
  constraint specified for that waypoint has been reached, then the
  constraint altitude of the waypoint is adopted for the reference path
  altitude at the waypoint.

Now, armed with our new CI based climb rates and speeds, my other answer can be used to finish our calculations and work out where (in the Z dimension) the aircraft will reach a soft requirement.


Why does a plane shake while passing through clouds? Why does a plane shake while passing through the clouds?

During my last journey all the other passengers started shouting when the plane was passing through clouds. It was the third time I was travelling by plane and was a fearful experience. Can someone explain what the reason is for the shaking? So the next time I can travel free of fear.

In a word, it's called "Turbulence" and in cloud, it is caused by differing air density.

Sciencey bit: The sun warms the earth and causes the air to rise. As warm air rises, it cools at the wet adiabatic lapse rate. Inside of a cloud, this rate is much slower than outside of it. Clouds are more dense than dry air, and the water vapour inside a cloud is not spread out evenly. Combined with the thermal turbulence (the movement of warm air) and the lower wet adiabatic lapse rate (rate of cooling) results in drafts of air through the cloud.

The result to the aircraft is pockets of more and less lift on the wings in somewhat unpredictable patterns. You feel this inside the aircraft as bumpiness and occasional feelings of rising or dropping. Sometimes this can be quite pronounced - this is why you will almost certainly be asked to remain seated with seatbelts fastened.

Very occasionally, outside of clouds, there can be more unpredicatable turbulence which may come as a surprise to the Pilot. This type of turbulence can cause injuries - usually from falling luggage or persons. This is why, even during cruise, the cabin crew and pilot usually suggest you keep your belt on while seated.

In almost no case does any kind of turbulence cause any damage to the aircraft or significantly affect its airworthiness.

Another answer here might be interesting reading for you How dangerous was the turbulence on this commercial flight?
as might What is turbulence, and how does it happen?


Why is a (jet) engine in flight shutdown so critical? EASA just announced an Emergency Airworthiness Directive grounding all A320neo planes with a certain type of engine. Reason is, that they have apparently the tendency to shut down in flight more often than acceptable.

I was wondering, why are IFSDs so critical? Can't a jet engine be just restarted? If not, is it something with the inherent design of jet engines? Or something that most engines are just designed for?

Having an engine shutdown during the flight is an engine failure. An engine failure is one of the procedures where every pilot is trained to deal with because it is easy to simulate. Engine failure is an emergency, meaning that the pilots must land the aircraft as soon as possible.

  Can't a jet engine be just restarted?

Maybe, maybe not. It depends on the diagnostics in the cockpit. You certainly do not want to restart a damaged engine. All jet engines are capable of being shut down and restarted in flight, provided that nothing is broken and proper procedures are followed.

Now, of course, if everything was working then the engine would not have shut down in the first place. It is an event which pilots are prepared for, but it should not have occurred. When it does, that means something is wrong. The decision of whether to attempt a restart is evaluated by the flight crew based on engine data, distance to nearest airport, weather, and possibly a discussion with ground support. In short, it is a risk management exercise.

  Why are in flight shutdowns so critical?

With one engine shut down, your chances of making it to the destination are virtually none. Aircraft performance is calculated assuming that all engines are working. With one engine shut down, the amount of thrust is reduced and the aircraft must descend to a lower altitude. At lower altitude, fuel consumption is higher, therefore you will not have enough fuel to reach your destination and you need to land somewhere closer.

Furthermore, you are now running on your last good engine. If that engine fails as well, the airplane will become a glider. ETOPS is designed so that an aircraft may limp to the nearest airport in no more than X minutes, and the presumption of ETOPS is that the engine failure rate is low enough. In other words, the aircraft failed to meet its certification standards.


Why is EGT decreasing on a jet engine when the generators cut in (take over)? Is the EGT decrease related to the generators cutting in or is it related to the fact that the fan is now providing enough ventilation air for the engine?

When I say cut in I mean that the engine driven generator has taken over in supplying the electrical load from the APU driven generator.

EGT on some engines is proportional to the engine developed power, cutting the generators reduces the needed power, thus reduces the EGT


Do afterburners use excessive amounts of fuel? The purpose of an afterburner is to provide additional thrust, and it is obvious that more fuel is needed for that.

But that is to be expected independent of an afterburner. That more thrust needs more than a proportional increase of fuel may be the case because the thrust increase needed per speed difference is not linear¹.

The reason to build afterburners may be that stronger jet engines can not be build with the same mass or volume. Or that a stronger jet engine is not useful in standard use, for example because the fuselage would overheat.

Doubling the speed increases the fuel usage by more than double I would expect, purely based on aerodynamics, independent of the engine.

Is the fuel usage for increasing speed greater with an afterburner  than with a stronger jet engine? How much? Why?

¹ For spaceflight, that is true according to special relativity.

Yes the specific fuel consumption of the afterburner, lbs of fuel used per lb of thrust, is much higher than the core engine.  This is because the fuel is being added to a part of the engine where the air is less compressed, so the energy conversion is a lot less efficient. The bright orange flame coming out the tail pipe when in reheat is pretty much all that un-oxidized carbon fluorescing - wasted energy. See this article.

Fighters use reheat because all that extra power is available with minimal extra weight (the weight of the burner and additional fuel), but they can only exploit that power for short periods if they want to have decent range or endurance, so they are generally used for dashing somewhere, or to assist with maneuvering, or taking off with a heavy load.


Why are there so many aircraft designs which look generally profoundly similar? The F-86, mig-15, Dassault Ouragan
The b-1 and tu-160
Concorde, tu-144, 2707

The low wing and T tail with two engines at the back. (CRJ, dc9)

The 'standard' shape with the mid aircraft wings, and vertical and horizontal stabilizers at the back, used from the E170 to the a380.

And while many general aviation craft are low winged or differ from a high wing tricycle single engine design, most seem to stick with that formula as well.

For some of the odder shapes, the question is 'industrial espionage?' but in the greater context, is it simple convergent evolution in that there are only so many shapes which are functional and useful so most things take on that general shape?

It’s an interesting question.  Aviation historian Bill Sweetman wrote about just that in an Air & Space article called How the 747 Got Its Hump.  The answer to the question is quite long and specific to the aircraft type and use but the short and sweet answer is that airplanes are a great compromise between a number of factors, including mission profile, aerodynamics, structures, propulsion, avionics, manufacturability, realities and practicalities of product use, and on a few occasions customer insistence and industrial espionage.  See illustration below.

It just works out that, when all the factors above are taken into account, the designs you describe tend to be the best all around solutions for particular aircraft sizes, costs, payloads, mission profiles, safety, etc.  Like any other artifact made by humans, aircraft are but single answers to open ended design problems; a compromise between all of these competing requirements into a tangible product.  No one answer is 'correct' per se, but these kinds of aircraft designs seem to be the most optimal and every single design team when confronted with the requirements and design constraints create much the same thing.


What are these clip-like things? With me becoming an aviation enthusiast and AirBerlin becoming insolvent, my mom has gone on a hunt for deals on what I can best describe as AirBerlin merch (old uniforms, shirts, skirts, belts and many more).

In one of the packets that arrived recently she found items that neither her nor I knew the purpose of.

They are about 2cm * 2cm, yellow, have some kind of number on them and on most of them was the writing "Air-Berlin SEALED" or "airberlin group SEALED" and an engraved "PULL". It also looks like you can break off and bend a part in the plastic to the back and clip it there.

Below is a picture I took of a few of these:

Galley seal. It works like a cable tie, you can put one end inside a hole on the main body but you can't pull it out without destroying the seal.

The cabin crew will seal the galley carts containing alcohol and other duty-free items before landing and note the seal numbers in their report. This is required by law in a lot of countries.


How can I find out if the government paid to build a runway? I've heard rumors that the government paid to build a runway at a residential fly-in community in the mountains of North Carolina to have it available as an emergency landing strip.  I would appreciate suggestions of how to find out.  I tried calling the FAA but with the automated system, I found it impossible to reach a human being.

Thank you!

The FAA gives funds to airports through the Airport Improvement Program (AIP) and that could include runway improvements. It's public money so the information is also public and should be in the Excel files on that page. If that isn't what you need, you can always submit an FOIA request to the FAA for all information they have about the airport.

It's also possible that you could get more information from the state or county. They usually have at least some input into airport construction, because of local zoning laws, easements and so on. Even if the rumor is false and the runway is built on private land and paid for with private money, there may be county planning or landowner records. But that's definitely beyond the scope of this site.


What is the battery voltage for a Supermarine Spitfire? I am used to modern aircraft being 28V systems. I found an article saying that a trolley AC plug in battery used to start WWII aircraft was 12V. I'm trying to confirm or disprove this.

This aircraft museum says that the "Trolley Acc" (Trolley Accumulator) used for Spitfires and other aircraft supplied 12 volts. Lots of sources state that Spitfires had 12 volt electrical systems, including the Pilot's Manual.


Why are sidestep ILS minima not used in EASA-land? (specific example: EGKK) If you are not aware, London Gatwick (aka EGKK) has a setup with a primary air carrier runway and a backup runway immediately next to it, such that only one runway can be used at a time.

The main runway 8R/26L (South) has full HIALS (ALSF-2 in FAA parlance) with CAT III ILS as well as RNAV (LNAV/VNAV, no SBAS/LPV) and plated SRA non-precision approaches; however, the backup runway 8L/26R (North) only has RNAV and SRA approaches, and no ALS.

Similar runway configurations in the US (KEWR aka Newark Int'l is similar save for having a crosswind runway) allow what is called a sidestep ILS procedure, where the main ILS is flown to higher (nonprecision) minima and then a maneuver is executed on short final to "slide" over to the other runway after visual contact with both runways has been achieved. From AIM 5-4-19:

  5−4−19. Side−step Maneuver

  a. ATC may authorize a standard instrument
  approach procedure which serves either one of
  parallel runways that are separated by 1,200 feet or
  less followed by a straight−in landing on the adjacent
  runway.

  b. Aircraft that will execute a side−step maneuver
  will be cleared for a specified approach procedure
  and landing on the adjacent parallel runway.
  Example, “cleared ILS runway 7 left approach,
  side−step to runway 7 right.” Pilots are expected to
  commence the side−step maneuver as soon as
  possible after the runway or runway environment is
  in sight. Compliance with minimum altitudes
  associated with stepdown fixes is expected even after
  the side−step maneuver is initiated.
  NOTE−
  Side−step minima are flown to a Minimum Descent
  Altitude (MDA) regardless of the approach authorized.

  c. Landing minimums to the adjacent runway will
  be based on nonprecision criteria and therefore higher
  than the precision minimums to the primary runway,
  but will normally be lower than the published circling
  minimums.

Why has the UK not published similar minima for Gatwick's ILS?  The existing OCHs for the secondary runway RNAV approaches are in the 650' range -- if the Newark ILS sidestep minima are any indication, it'd be possible to obtain lower minima for a sidestep approach to the EGKK secondary runway than are currently available from the RNAV or SRA approaches, and it would require no new navaids to be put into service.

Are sidestep approaches verboten in JAR-land? Is there some terrain or obstacle factor that I'm not seeing that makes a sidestep ILS approach into EGKK problematic or not desirable relative to the current RNAV approaches to the secondary runway?  Or can the ICAO/CAA format for approach plates not represent sidestep minima?

You use circling minima for sidestep manoeuvres. While not commonly practiced, they may be requested by the pilot, have done so many times when LEMD (MAD) is in N config, saves 20min taxi-time...


Why do I hear the "real" engine noise only when the plane is on the runway? I understand that (from other answers) planes taxi using engines only. But, when I'm a passenger, then why do I hear the "real" engine noise only when the plane is on the runway?

So, if planes taxi till runway using engines only, then why don't I hear that much noise until the aircraft reaches the runway?

When you have the thrust levers of, say, a 747 all the way back to idle, the airplane still has enough power to move. In fact, you will have to use the brakes to keep it from taxiing too fast. If you didn't use the brakes, it would finally accelerate to somewhere around 45 knots or so, far too fast for taxiing, but much too slow to take off. At the idle power setting, relatively little noise is produced by the engines.

To take off, if the 747 were at max gross, you would have to accelerate to around 180 knots. That would require a power setting approaching the maximum, depending on the length of the runway. The noise produced by the engines is relative to the amount of power they're producing. Hence, taxiing at idle produces little noise relatively speaking, on the runway taking off a whole lot of noise.


What is the FAA's official outlet for informing the public of permanent, systemic changes? When the FAA changes a regulation or rule, such as the recent change in April that student pilot certificates will be a plastic pilot certificate without an expiration date... (This page)

  Student pilot and medical certificate are no longer the same document, therefore, refer to 14 CFR 61.23 for complete information on duration of a medical certificate.

  After April 1, 2016, Student pilot certificates do not expire; the certificate will be surrendered and superseded upon successful completion of the higher certification. Student pilot certificates issued prior to April 1, 2016, will expire according to their expiration date, either 24 or 60 months from the date of issuance.

... what is the standard, official, go-to document to keep abreast of the existence of these new changes?  How often is is released or how are we notified of its release if it is irregular?

This question is not about NOTAMS which cover temporary changes, or changes that will later be added to a document with regularly occurring updates at known intervals such as those for approach charts.

This question is also not asking about the contents of advisory circulars; however, I would view an update to an advisory circular or release of a new one as being a pertinent, permanent change considering many of them have been around since the 1970s and contain official FAA information on various topics.

So, to be totally clear, I am asking how we are notified when there are changes and where they are located not necessarily what the specific, full-text contents of the changes are.

The changes could be to such things as:

Handbooks and manuals
Federal Aviation Regulations
Advisory Circulars
Practical Test Standards
The Airman Information Manual
FAA knowledge exam contents

The FAA has multiple email groups you can subscribe to.

https://public.govdelivery.com/accounts/USAFAA/subscriber/new?topic_id=USAFAA

Click the link and you will be brought to a page where you can provide your email address.

You will then be brought to a page where you can select the email groups you want to subscribe to.