How are aircraft separated at high altitude?

First of all, there is no such thing as a stall speed, but that is a topic of its own.

The ATC system has numerous ways of dealing with keeping aircraft separated, even at high levels. Let me try to summarize some of the most important ones, starting with the planning that happens when planes are still at the ground at their departure airport, working our way towards what happens when they do get (too) close.

Aircraft flying en-route will follow pre-defined routes (known as airways or RNAV-routes). Airways are like highways in the sky, and ensure that air traffic will fly in predictable patterns. This makes it a relatively simple task of predicting potential conflicts (a conflict in this denotes a situation where two or more aircraft get closer than the prescribed separation minima), because every flight will send a flight plan in advance, detailing the planner route, level and speed to fly.

In addition to just specifying lateral paths, airways also have vertical restrictions. This means that, when following a certain airways, you have to be flying in a certain range of vertical levels. It is quite typical for airways to limit traffic to fly at either “even” or “odd” levels. An even level in this case could be 34,000 feet, 36,000 feet, 38,000 feet and so on, while an odd level could be 33,000 feet, 35,000 feet etc. The general rule in most parts of the world is that airways going east will force traffic to fly odd levels, while airways going west will force traffic to fly even levels. This acts as a fall back procedures, which in principle means that two aircraft flying in opposite directions (one heading west, the other east) will never fly at the same level. Of course, it is easy to realise that this rule cannot cover every potential conflict.

We have now looked at some of the permanent infrastructure in the sky, but let’s zoom in further and look at the tactical aspect of flight planning, specifically, air traffic control.

Air traffic controllers, whose job is it to “maintain a safe and expeditious flow of air traffic”, use various means of technology to keep aircraft in the sky separated. In many parts of the world, their job is achieved by processing large amounts of information received in real time about air traffic using radar technology, and communicating with planes using radio. In places where no radar coverage exists, such as over large oceans, only radio is used. If no radar is available, pilots have to periodically call up on the radio and make a detailed position report, stating the location, level, speed and planned route of the aircraft.

Using either radar or pilot position reports, air traffic controllers will predict potential conflicts and try to solve them. (This is really where the essence of your question will be answered).

There are a few different separation minima. For the sake of simplifying the answer slightly, let’s assume we are working with only three:

vertical separation (the vertical space required between two aircraft who pass each other at (almost) the same position
horizontal separation (the horizontal distance required between two aircraft passing each other at the same, or near the same level)
time based separation (the minimum time required between aircraft following the same route, at the same level)

The vertical separation minima is generally 2,000 feet, however, as aircraft altimeters and radars have gotten more accurate, this has been reduced to 1,000 feet in many areas of the world (called RVSM airspace). Considering the fact that most commercial aircraft cruise in a level band between 30,000 feet and 40,000 feet, this gives you 10 different levels to work with (30,000, 31,000, 32,000 and so on). That actually means, that using vertical separation alone, it is possible to have 10 different aircraft at the same position, at the same time, while they are still separated.

Of course, forcing an aircraft to fly at a non-optimum level is not the perfect solution in terms of fuel efficiency, but it can often be the lesser evil (as opposed to forcing speed changes etc.)

Horizontal separation is achieved by (temporarily) changing aircraft routes. This might sound like a big deal, but in fact, potential conflicts are usually detected early enough that only very small adjustments are required. For two aircraft on intersecting tracks, if you detect the conflict between them 10-15 minutes in advance, it will often be enough to instruct either of the aircraft to adjust their heading by as little as 5 degrees to prevent the conflict. Once they are passed, you simply instruct them to return to their planned routes. This will only result in marginally longer flight paths, and so will only cause a small impact on fuel consumption.

Time based separation using speed control is probably the last resort in most cases. Instructing an aircraft to change it speed for a long period can have a serious impact on fuel efficiency. However, there is no need to worry about aircraft being forced to slow down enough to risk a stall (or speed up enough to risk damage to the aircraft). For starters, the pilot would never accept such instructions from air traffic control, and ATC would have to come up with another plan. In addition, air traffic controllers have been trained thoroughly, and are well aware of the performance limitations of different aircraft.

As with heading adjustments however, it might surprise you how little it takes to ensure separation using speed control. This is because most modern airliners actually fly at very similar speeds (usually between 75% and 85% the speed of sound). Changing the speed of an aircraft by just 1% will have a huge impact over a long distance, such as a flight across the North Atlantic Ocean. And so, as with levels, where in principle you have around 10 usable levels, considering 1,000 feet minimum vertical separation, you might also have about 10 different speeds to work with.

Overall, speed control is a very efficient way of maintaining separation that already exists (e.g. two aircraft following each other on the same route, at the same level), because instructing them to fly at the same speed will ensure that the latter aircraft never catches up with the former. Horizontal and vertical separation can be applied when separation needs to be established, for example between aircraft on intersecting or opposite routes.

Finally, let’s briefly discuss what happens if the system fails. That is, if air traffic control, for one reason or the other, fails to provide the required separation between two aircraft.

All modern commercial aircraft are equipped with airborne collision avoidance systems (ACAS), the most common form being the TCAS. TCAS equipment of two different aircraft in proximity to each other communicate directly to determine a) if there is going to be a conflict and b) how to best solve it. I won’t go into details here, but basically, if two aircraft are predicted to get too close, the TCAS systems will work out how to solve the conflict, typically by instructing one aircrew to descend while instructing the other one to climb. The fact that the TCAS systems communicate ensures that the same instruction is not issues to both different aircrews (imagine the airplanes flying toward each other at the same level, both being instructed to climb …). If the TCAS goes off, all instructions received from the TCAS system takes precedence over air traffic control instructions (much like air traffic control instructions take precedence over the general airways rules we covered earlier).

So to sum it all up – aircraft separation comes down to planning. If it is predicted, based on flight plans received from hundreds of different aircraft, that a certain route or level will be very busy for a certain period of time, then the system will simply not allow more aircraft to fly this way. They will be re-routed or their planned level changed, even before they leave the gate (allowing them to bring extra fuel, if required, to fly a slightly longer route or at a non-optimum level). Once in the air, air traffic control will make use of vertical, horizontal and time based separation, and, if all else fails, on-board computer systems will ensure that no collisions actually occur.

Edit:

A few references for further reading:

Mid-Air Collision - On the consequences of losses of separation, and how to prevent them

Conflict Detection - On detecting potential conflicts in the ATC system

ATM Sector Management - On predicting capacity and responding to demand in the ATC infrastructure

Flight Plan Filling - On ATC flight plans and their content

Guidelines for providing Radar Separation - A few example calculations

Airborne Collision Avoidance System (ACAS) - On ACAS, the last resort, when all else fails

Reduced Vertical Separation Minima (RVSM) - On the parts of airspace where the minimum vertical separation is reduced from 2,000 feet to 1,000 feet


Is 'cost sharing' different between jet and prop powered aircraft?

I give up.  I have searched and can find no reference in the FARs concerning this question - just the current one about pr0-rate sharing that we all know and love.

Perhaps the 91F and 91K parts have replaced the vaguely remembered item from the 1980s.

Thank you for the opportunity to ask.


May airlines cancel unprofitable flights?

Yes, airlines may cancel any flight. There is no obligation to execute a specific flight.

Their obligations towards the passengers depend on the local legislation. For instance:

International Flights: Airlines may cancel international flights, but passengers on flights between countries that honor the Montreal Convention are entitled to damage compensation if a cancellation cannot be justified.
European Union: According to Flight Compensation Regulation 261/2004,
 airlines are obliged to transport their passengers within a certain time frame. They will have to compensate passengers after a certain amount of delay is exceeded.
USA: There are no federal laws requiring airlines to provide passengers with money or other compensation when their flights are delayed. Airlines may book passengers on a flight of a later day. (Source)

Yes, airlines will cancel a flight if it is not profitable, but they will take into account all operational and commercial implications, and not just the profit on this particular flight. For instance the plane and/or the crew might be needed at the destination, or the plane has to park in a different place.

It depends on the airline if they will use a pretext. It is fraud if they use a pretext and avoid paying compensations to their customers.

I am convinced that most airlines are honest, but many
   are not.

In a charter flight all seats are booked through a travel company. The legal obligations of the airline should be the same.


What FAA regulations govern a US International Airport name change, such as McCarran International to Harry Reed International?

The owner of the airport determines the name.  If there is a dispute, courts have settled naming rights.

Whether the airport offers customs determines the "International" designation.  Some airports have no international flights, yet have the "International" in their name. They will have customs available, at least part time.

Side story: At one time, using a grass strip a couple of farms over, I asked a neighbor who worked for US Customs if I could fly directly to the grass strip (which did not even have a FAA Airport Identifier assigned) and clear customs there.  He said I could, and had me notify customs inbound, so they would notify him to meet me at the grass strip for inspection.  Doing that made trips from Canada to back home free of the hassles of dealing with a big airport.


How can this kind of confusion about taxi instructions occur?

I continue my series of "not actually an answer but I got to say this":

The most valuable lesson you can learn from this is not figuring out afterwards what was said, but getting into a habit of always asking "Say again..." when you miss even a slightest part of a transmission. Ron stated it in the comments: no shame in that, not even a bit.

Whenever you allow yourself to guess the missing parts, you put yourself, and probably others in danger. Requesting repetition, every now and then you'll catch the grumpy controller that'll bitch at you for not paying attention, but never mind them. You don't want extra holes in your Swiss cheese.


What is that building in Suvarnabhumi Airport?

On page 5 of current airport chart states it is Transfer Baggage Terminal

It was officially opened on 1 November 2014 and reduce baggage transfer time from 75 minutes to 60 minutes. It was constructed above South Airside Tunnel between gate C, D and E and has usable space of about 12,550 sq.m.

Source (Sorry source is in Thai. My own translation.)
Another source in English. Similar to my original source.


Few thoughts:

Label font does look British/Commonwealth in some way.
Flat bottom- unlikely to be cockpit canopy that curve down on the sides.
Not compatible with weapons- Search and Rescue aircraft?
Large curvature: Slow aircraft?

At some point I was considering the rear window of the Consolidated Catalina but it doesn't quite seem to fit the bill.

Tony Hisgett on Wikicommons/Source


Could the S.H.I.E.L.D. C-17 actually have a sensible center of gravity?

Might have been better as a canard design.  Yes, you can have two wings bearing weight with the CG in between.  But the fore wing must stall first.  This C17 would have problems unless there was a lot of weight up front, or if the rear wing(s) stalled first.  But note that the extra engines could go on the main wing, or the second wing could be mounted above or below the first, or even in front, making it an Avanti Piaggio from hell.  This design actually might have a chance if the T tail was removed as the transport version of the B-58 Hustler.

But for the movies, this design will certainly do.


Why is a rectangular wing with winglets not better than an elliptical wing?

If using Prandtl's lifting line theory, then mathematically/analytically, ignoring issues of wing weight that lead to bell shaped lift distributions and other sorts of intrusions of reality (e.g., stall behavior) the elliptical wing with the elliptical lift distribution is optimal for minimizing induced drag given a fixed wing area.

You can get an elliptical distribution of lift from a rectangular wing via twist, winglets, or other mechanisms, but it will only be elliptical at one cL value. At other values, it will not be elliptical, and thus suboptimal.


What would be the advantages and drawbacks of a single-propeller tiltrotor?

Such an aircraft can't exist.

Helicopters don't work with a single rotor, they need at least two of them to counter torque. There are several popular designs, including conventional, coaxial, intermeshing and tandem rotors.

All tiltrotors operate as tandems in helicopter mode. It's the only setup where both rotors can be placed at the nose, tail or wings. In all other designs, at least one of the rotors needs to be mounted in the middle, above the center of gravity, where it can't be tilted without crashing it into something.


Do I have to follow airways to meet the IFR cross country 250 NM flight requirement in 61.65?

14 CFR 61.65(d)(2) says:

  (ii) Instrument flight training on cross country flight procedures,
  including one cross country flight in an airplane with an authorized
  instructor, that is performed under instrument flight rules, when a
  flight plan has been filed with an air traffic control facility, and
  that involves—

  (A) A flight of 250 nautical miles along airways or by directed
  routing from an air traffic control facility;

  (B) An instrument approach at each airport; and

  (C) Three different kinds of approaches with the use of navigation
  systems.

The wording is saying that you must follow airways or a route given by ATC. But since the flight must be under IFR, you'll get a route from ATC in your clearance anyway so I don't know why the FAA has the airways reference in there.

(As a complete guess it may be left over from a time when there was less radar coverage and the FAA wanted to make sure that instructors weren't taking any shortcuts.)

I don't know what flight following has to do with this because that's VFR, and the flight must be IFR.


Do pilots ever intentionally takeoff or land downwind?

It's perfectly legal, but check the Chart Supplement (or AFD, or instrument approaches) to see if there are special exceptions for that airport.

If it is a non-towered airport and you aren't assigned a runway, you should of course try to use the prevailing runway that is already in use by other traffic in the pattern when it makes sense.

Some airports have obstructions in one direction of their runways that make it necessary (or safer) to always land or depart in a certain direction.

Some runways have a steep incline in one direction, making it preferable to land upslope and depart downslope.  (For example Lukla, Nepal: YouTube)

It's also common for larger airports to have preferred directions for arrival or departures in order to keep the flight volume high, even when the wind prefers other runways.

However, that usually relates to operating with intentional crosswinds at an airport that has parallel runways in a primary direction (allowing them to conduct more simultaneous flight operations), but not in the intersecting direction.


Why do airliners have to file delays through their handlers?

Since you mention Dublin, I am going to give an answer that describes the situation in Europe. Other parts of the world may have different procedures, although I believe they will be similar.

Usually a flight plan must be activated within a given time window to ensure that there is enough capacity (airspace, ATC staffing, departure & arrival airport constraints) along the route to handle the flight. If the flight is not departing with this 'slot' a new flight plan needs to be requested and approved by the Network Manager Operations Centre (NMOC) (Previously called Central Flow Management Unit (CFMU)).

The controller is not responsible for filing flight plans and cannot be tasked with doing the paperwork for the crew. The crew therefore needs to contact their handler or flight operation centre to refile a flight plan.

The NMOC will reassess the flight plan and verify that there is capacity along the planned route to handle the flight. If there isn't, the flight may need to be planned along another route or an additional slot delay will be given.


Where can I find good data on volume of air traffic?

For $799 you can buy IATA's World Air Transport Statistics (WATS)

IATA publish a few summary data values in various reports

Scheduled Passenger - Kilometres Flown
Scheduled Passengers Carried
IATA Annual Review 2013
IATA Annual Review 2014
IATA Statistics

Note that I think this is data is only collected from IATA members and much of the data is for western-built jets (figures for other manufacturers are much worse, according to comments in IATA reports)

Passenger Km
Total (International + Domestic)

Rank  Airline                   Millions
1     United Airlines           286,802
2     Delta Air Lines           277,560
3     Emirates                  209,377
4     American Airlines         206,551
5     China Southern Airlines   147,841
6     Southwest Airlines        145,124
7     Lufthansa                 144,236
8     Air France                136,405
9     British Airways           130,129
10    Qantas Airways            110,203


What's the difference between 'modification' and 'corrective action' in an AD or SB?

A modification is a change to the airplane's physical configuration from the standpoint of fit/form/function.  Think Service Bulletin with a parts kit. Or an SB that has instructions for a physical rework of a part that makes it different from non-reworked parts, and the part is re-identified.

A corrective action is any action required by the AD to mitigate the risk associated with it.  Usually it's something less than a mod, like a inspection, change to a maintenance program, crew procedural change, de-escalation of a check or procedure's interval, an operational limitation, or any other action as required by the AD.

Terminating action is some activity that completely resolves the AD and restores the airplane's original airworthiness state, as opposed to something that temporarily mitigates risk so you keep on flying.  Incorporation of a Mod, or permanent incorporation of a inspection regime that previously wasn't mandatory.

On a side note, one thing about FAA ADs that makes them a total pain from the OEM's standpoint is that the FAA will not issue revisions to ADs like other authorities do.  If there is a change to the AD's terms they will only issue a new AD that supercedes the old one. Makes getting minor changes to ADs very difficult because it has to be worth issuing a new one.


Where can I find/download infos about Special Use Airpsace (SUA) around the world?

EU: aixm.aero

France: sia.aviation-civile.gouv.fr

Upper space
RTBA map (military, low altitude)

USA: sua.faa.gov

AIXM Data: nfdc.faa.gov

Diverse locations: soaringweb.org

This is a community wiki, just add to it.


Can having an incorrect hair color on my FAA medical certificate get me in trouble?

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

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

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

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

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

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


What are these ribbons on the wing of an MD-83?

These are Ice Detection Tufts that check for ice. If they are stuck, it indicates there's a layer of ice on the wing, disturbing airflow and presenting a danger for the engines when it detaches. They are focused around the rear root side since this is most likely to be the spot with the most buildup, as remaining cold fuel below flows to this corner.

SAS had an incident with ice a few years ago in the Gottröra Accident (SAS Flight 751) that thankfully ended relatively well.


What can I do if I cancel IFR when I shouldn't have?

Since you used the term MOA, I assume you're in the US.

Within the FAA ATC software (not sure about DOD's), the only data difference between IFR and VFR Flight Following is the flight plan altitude. For instance, IFR might have a filed altitude of "060" (6000ft) while VFR FF might have a "filed" altitude of "VFR/065" (6500ft). When you cancel IFR, the controller amends your altitude and leaves the rest of the data unchanged. They don't actually delete your flight plan unless you cancel radar service. Therefore, to resume IFR, all they have to do is amend your altitude again.

Obviously, IFR and VFR are very different procedurally. When you canceled IFR, your existing clearance was invalidated, so you'll need to get a new one. However, since they should still have all your previous data available, it'll probably be similar. But it's less work for them than a normal pop-up IFR.


Do you say prefix K for airport codes in the US when talking with ATC?

There are actually two separate coding systems in play here.

IATA (International Air Transport Association) codes are 3 letters and are used for commercial bookings etc. They are assigned only to commercial airports throughout the world. ORD is the IATA code for Chicago O'Hare.

Pilots and ATC use the four letter ICAO (International Civil Aviation Authority) codes, which are assigned to every public-accessible airfield in the world. These are systematically allocated with the first one or two letters indicating the country. K is used as the first letter of airfields in the continental US (with separate codes for Alaska, Hawaii & territories in the Pacific/Caribbean matching regional standards).

Commercial airports in the continental US tend to have the two codes in matching pairs such as ORD/KORD, LAX/KLAX etc but this is not the case in other countries. Manchester, UK has IATA code MAN but ICAO code EGCC.

Meanwhile smaller airfields in the US may only have an ICAO code, where the corresponding IATA code (minus the K) could belong to an international airport elsewhere in the world (for instance KPRG is Edgar County Airport, Illinois and PRG is Prague Václav Havel Airport, Czech Rep.).

Finally, the very smallest airfields in the US (typically private/restricted access fields, in any case not large enough to warrant an ICAO code) are given a 3- or 4-character code by the FAA which extends the ICAO system by allowing digits as well as letters. Small public fields have a 3 character code (eg 9S2 or C97) while private fields have 4 characters which typically include the state abbreviation eg TX05.

For more details of the exact determination of which code type a US airfield is assigned by the FAA, see reirab's excellent self-answered question: How does the FAA determine which format of location identifier to assign to an airport?


What is the thick, dashed, magenta line on a sectional chart?

The Atlanta sectional near KANB, KASN, and KPLR gives a hint:

FOR REASONS OF NATIONAL SECURITY
PILOTS ARE REQUESTED TO AVOID FLIGHT
AT AND BELOW 5000’ AGL IN THIS AREA

It is called a National Security Area, which FAA’s training ALC-42: Airspace, Special Use Airspace and TFRs describes as follows.

National Security Areas
National Security Areas consist of airspace of defined vertical and lateral dimensions established at locations where there is a requirement for increased security and safety of ground facilities. Pilots are requested to voluntarily avoid flying through the depicted NSA. When it is necessary to provide a greater level of security and safety, flight in NSAs may be temporarily prohibited by regulation under the provisions of 14 CFR Section 99.7. Regulatory prohibitions will be issued by System Operations, System Operations Airspace and AIM Office, Airspace and Rules, and disseminated via NOTAM. Inquiries about NSAs Inquiries should be directed to Airspace and Rules.
Example — National Security Area near Pueblo, Co. and request to avoid flight at and below 3000’ AGL.

Wikipedia gives a brief description.

In United States aviation, a National Security Area is a designated airspace through which flight is discouraged for reasons of national security.
Flight through NSAs is not prohibited and no special advance clearance or authorization need be obtained to enter them. However, pilots of aircraft are strongly encouraged to either stay clear of NSAs or obtain prior authorization to pass through them in order to reassure the controlling agency that no threat to national security exists.
NSAs are a compromise between normal airspace and restricted or prohibited airspace. NSAs can be temporarily converted into restricted airspace by NOTAMs.
On VFR sectional charts, NSAs are delimited by a heavy dashed magenta border and a special notation.


How do civilian pilots and ATC verify that other people on the radio are who they claim to be?

This is a reasonable question, and to an outside the simple answer of We don't / can't might seem a little bit jarring.

After-all, we live in a time of hacking, terrorism and so on and I can certainly see how this looks like a simple vector to create some havoc.

So, what's to stop somebody from setting themselves up with a Radio Transmitter and deciding to be Air Traffic Control for the day? Absolutely nothing. In fact, lower power handheld air-band transceivers can be purchased legally and cheaply by anyone. I have one near me - I could literally turn it on now and declare myself [Local Airport Tower]

However - the thing about Airband radio is that it's wonderful in its simplicity. At its core is AM radio which is basically unchanged since the early 1900's. This means a few things:

The strongest signal doesn't simply "win". Multiple medium strength signals will simply merge into a garbled mess. This means you don't simply get to "take over" ATC's transmissions - all you can do is ruin them.
Similiar to the above, there's no way (from outside) to stop the ATC signal. All you can do is stomp all over it - something which is totally noticeable.
Even if you do "win over" air traffic control for some aircraft, communications is a two way process, and airband radio is simplex. This means only one person can speak at a time - at some point ATC are going to key in.
Pilots aren't automatons. We listen and build up a picture, we learn normal procedures and can hear stress in somebodies voice. We also know who we were speaking to. Combined with a decent situational awareness, we don't just do things without thinking - you can't just pipe up on the radio and ask an aircraft to fly into the ground.
And even if you did, and they initially believe you, real ATC is going to hear your readback and ask what the hell is going on.

By way of analogy, imagine you've  snuck in on a conference call between an employee and a boss. And you start trying to speak on behalf of the boss - it's going to last all of 1 second before somebody realises something is going on. I think people tend to think of ATC as somewhat robotic, but it's still a human interaction and any good pilot will understand why they're being given instructions.

To attempt to interfere in Air Traffic Control in a way that is believable by the pilots is going to be incredibly difficult. You won't be able to use normal phraseology and cadence if you're attempting to step on real ATC, and that will concern the pilot. To do that for more than a few seconds and to to cause some kind of conflict with multiple aircraft is verging on the impossible.

The most likely outcome is more a denial of service, rather than some kind of spoof. It's not really a great vector to cause any damage. A nuisance, certainly and absolutely dangerous (and there's a reason it's very illegal!) but there are well established procedures for disruption in communications.

I've focused primarily on somebody trying to be ATC here, which is the way in which somebody on the ground would likely go about trying to make a mess. As for pretending to be a plane - firstly there are more technical difficulties because you'll be transmitting Ground -> Ground. I live within 2 miles of my local airport and often struggle to receive their transmissions when I'm at home.

Pretending to be a real plane that currently exists in the sky poses the same problems as above and any facility with RADAR is going to know something isn't right. Again, it might cause some initial confusion but you're unlikely to persuade somebody of something.

You could, in theory, pretend to be a light aircraft with no (or a faulty) transponder but really to what end? I guess you could cause a little disruption before somebody realises you're having a laugh but we're more into the realm of 'pranks' (Not that it's funny) now rather than serious risk.


Is it enough for crossing/ascending/descending IFR-flights to adhere to the separation minima?

This might not be the answer to your question, but maybe it will help you understand separation.

Your question specifically asks for how separation is ensured between climbing, descending and crossing traffic over navigational fixes (NAVAIDs).

Flight routes are planned for traffic to use certain flight levels en-route, which follow the semicircular/hemispherical rule in effect in that country or are bound to the airway being used. In my example picture below I will use the German semicircular rule of eastbound flights using odd flightlevels.

(Image Source: Own Work - Program used: Aircraft Situation Editor (ASE))

Both aircraft will cross the HMM VOR roughly at the same time, based on the ground speed displayed. The westbound aircraft (DLH123) is at FL200 (even FL), the eastbound aircraft (BER456) is at FL210 (odd FL). The separation between both aircraft overhead HMM VOR will reduce to 0nm lateral separation, but 1.000ft of vertical separation, and thus, the separation criteria are met.

(Image Source: Own Work - Program used: Aircraft Situation Editor (ASE))

In this example, I need BER456 to descend to FL100, but I have crossing traffic from the right which would cause a cleared conflict, if I issue a descent clearance directly to FL100 without any conditional instructions. I can use a bit of mathematics here to ensure separation however and issue a clearance nevertheless.

Both aircraft are travelling at 420kt GS. An aircraft will also descend 1.000ft in 3nm, rule of thumb from every flight instruction book available. To ensure 5nm of lateral separation, I would need a buffer of 2.000ft during descent to the crossing traffic, not factoring in that the other traffic will be on a divergent track anyway. Let's just measure the distance to the HMM for simplicity.

My instruction to BER456 would be:

  R: BER456, when ready descend FL100, cross HMM VOR at FL230 or above (rate of descend 2.000ft/min or less)

With this instruction, I can issue a clearance to BER456 that will allow the aircraft a continuous descent to FL100, while ensuring minimum separation is kept to the other traffic. Overhead HMM VOR, both aircraft will have 3.000ft of separation. After BER456 has descended a further 2.000ft, it will have 6nm and 1.000ft of separation, making it well clear of a conflict, especially since the traffic is divergent.

The dirty solution would have been to clear BER456 to FL210 and after 5nm issue another clearance to FL100, but this doubles the frequency time and also interrupts the descent for BER456.


Which compressor is more like to surge and stall - axial or centrifugal?

Axial for sure.  Its blades are wings subject to aerodynamic stall within the blade array.

Centrifugal compressors just throw air outward; they don't really "stall" if in-flow is restricted, but will surge due to the pressure drop and resulting load reduction on the compressor.  Centrifugal compressor surge is what is happening when you block a vacuum cleaner and it goes vwwwwwweeeeeeeeeeeeeeeeeeeeee.

Axial compressors, being an array of little spinning wings, depend on a controlled angle of attack on the blades and are much more sensitive to flow disruptions.  And once they do stall, the surge and flow disruptions throughout the engine are more severe (those whomp whomp sounds and flames coming out the front of the engine as reverse pressure waves are induced, that sort of thing).

So if you want efficiency and high compression ratios, you go with axial and live with the sensitivity, the high cost and complexity.  If you want insensitivity to inflow disturbances and can live with a larger diameter engine and less efficiency, and want to make the engine cheaper, you go with centrifugal.


Why don't small planes use turbine (turboprop) engines?

First, piston engines are more efficient than turboprops, so their operational cost are lower. This also means that the system mass (engine plus fuel) for a trip is lower once you go beyond small ranges. In a helicopter, the engine mass is more important, because average flight times are much shorter, so you find many helicopters with turbo engines and only few with pistons.

Next, there is a well developed infrastructure for maintenance on those pistons, and new turboprops would need new, expensive infrastructure (trained people, tools, spare parts ...)

And then there is simply no incentive to develop a new GA engine. The expense to get it certified is too large for the rather small market. This is the same as for Diesel engines.


Basically, it's a combination of historical significance, passenger comfort, and ease of mental calculation.

Historically, before aircraft were pressurized a rapid descent would be uncomfortable for passengers. At the speeds typically flown, a 300ft/min descent was deemed to be comfortable enough for the typical passenger.

  Many aircraft had a cruising speed between 100–120 miles per hour (160–190 km/h). Three miles would be traveled in about 1.5–1.8 minutes, resulting in a rate of descent of about 550–660 feet per minute. That was about as fast as passengers could comfortably adapt to the changing pressure on their eardrums. However, many pilots used a 300-feet-per-minute descent rate because doing so is almost unnoticed by passengers. A pilot cruising at 10,500 feet would calculate that in order to be at 1,000 feet at his destination, he would have to descend 9,500 feet. Dividing 9,500 feet by 300 feet per minute, that descent would require about 32 minutes. If his ground speed was 120 miles per hour (190 km/h), he would begin his descent about 64 miles (103 km) from his destination (traffic permitting).

As you can see, there is a reasonably simple mental calculation that can be done there. This is commonly referred to as the rule of three which is in part quoted above.

That covers descent from cruising altitude, however you are right that flight in IFR will depend on procedures, and scenario. An example is London City Airport which uses a much steeper descent profile of 5.5 degrees on approach to land.


Is a FAA certified plane allowed to fly everywhere in the world?

It's valid in countries that choose to accept it as de-facto valid but sovereign nations are free to require local certification if they like. The reality is that the FAA has a huge amount of resources at its disposal and for smaller nations is advantageous to simply say we agree that those people know what they are doing and we can't afford to do it any better.

However Boeing does hold an EASA Type Certificate for the 737 as well as the FAA issued one but if you dig into it you will find a lot of "see FAA TCDS" notes. With that said the 737 is certified by European agencies currently. A good chunk of regulations even stem from the FAA work, the best example of this is in the EASA TCDS where EASA changed some regulations to the FAA spec.

  However, to harmonize with the FAA, the same requirement was moved to JAR 25.810(a)(1)(ii) at Change 14 which is now in
  CS25.810(a)(1)(ii).


Why do IFR charts show TACAN paired frequencies when there is no collocated VOR?

Your supposition is correct. Tuning the paired frequency will allow you to receive DME information from the TACAN.
If your DME tuning is through your VOR/ILS receiver, the VOR output will be flagged no computed data (NCD) as there's no VOR signal to receive.
The DME will tune the appropriate paired frequency and the DME should display normal data.
Having DME data alone is not all that helpful. However, if you have an FMS and a multi-channel DME, the FMS will tune the DMEs independent of (or in conjunction with) the VORs. This will allow the FMS to perform DME/DME navigation. That was the primary FMS navigation method until GPS came along. These days, DME/DME is a backup to GPS or GPS/IRS navigation.


What does shimmy in nose landing gear mean?

the nose gear support strut contains a bearing which allows the nose wheel to swivel like a caster so the plane can turn on the ground. the nose wheel assembly itself is turned either via a hydraulic cylinder or a mechanical linkage connected to pads on the upper tips of the rudder pedals, or in some cases it freely turns on its own during the application of asymmetrical braking to the main gear.

But whatever the details of the nosewheel design are, "shimmy" occurs when the wheel assembly wobbles rapidly back and forth (left-right-left-right) as the plane is rolling down the runway at speed. this is called castering instability and occurs when there is excessive play or looseness in the caster bearing or the support strut or the wheel bearings, or slop in the steering control circuit, or improper inflation of the nose wheel.

The shimmy action sets up strong vibrations in the airframe that the pilot can feel and if strong enough can hear as well. Those vibratory stresses are acting to wiggle loose any bolted connections in the entire nosewheel assembly and can also seek out and activate any fatigue stress raisers present there- in addition to making the airplane difficult to accurately steer.


How will a damaged logbook affect pursuing a career as a professional pilot?

Well, you've already covered the "What to do if you've lost your logbook" bit.  The remaining bit of your question is a little trickier to answer, but not as bad as you might think.

The good part about renting is that as you've noted you can get the rental records & that gives you a good start on at least the hours portion of reconstructing your logs. The Day/Night, Instrument/Simulated Instrument, and destinations (Cross-Country) times may be a bit harder to reconstruct, but with a little luck you'll be able to piece that together too.

Will you have trouble with additional ratings? No.
This is the tricky bit though: You will need logs that prove that you meet the aeronautical experience requirements for any new rating you're pursuing, so if you're working through your instrument/commercial/multi and you just washed the records of that training time, cross-country time, etc. you're going to need to either reconstruct that (from rental records & landing fee receipts), fly the hours over again, or some combination of the two.
The same goes for any endorsements you have (tailwheel, high-performance, etc.) - you'll need to get re-endorsed to have a record of those (and if you show up to your next practical test in an aircraft that requires an endorsement the examiner may ask to see that endorsement).
Will you have trouble with employment? I doubt it.
Your certificates are your major qualification, and you'll have those (subject to reconstructing the requisite aeronautical experience entries like I mentioned above).
You'll want to reconstruct as much of your logs as possible because all that experience should count when you go sit down with an employer, but if you've "only" washed ~50 hours you'll make up most or all of that experience in your future training.

A few related questions you might want to look at:

What is the best way to keep logbook entries backed up?
(For my part: I scan each page once I've filled it.)
Are there any best practices for transitioning from paper logbooks to electronic logbooks?
(if you decide to go that route)


Can the TSA require supplemental screening AFTER a flight has landed?

TSA staff actually have very little authority - they can prevent you boarding an airplane, they can stop the airplane from leaving. For everything else, they call the local police (the phone is their Big Stick - they can call in some serious assistance, like SWAT or some loaded F-22s).

This sounds like a classic bureaucratic whoopsie - someone missed the initial screening note, someone else noticed that the box wasn't ticked in the system, and protecting the monthly performance statistics prevailed over common sense. Since the passenger declined the search they can prevent said passenger from boarding a flight, but since he did not wish to board a flight (and has not done anything illegal) all they can do is ask him to leave the secure area. As that is exactly what the passenger wanted to do anyway.....


What special training is required to fly in the Washington DC area?

There is a training course on FAASafety.gov that all pilots operating VFR flight within 60nmi of Washington DC must take.

Since I assume you are flying IFR, you would not be required to take it.

From AOPA:

  All of the following operations are exempt from the training
  requirement:

  Pilots operating under instrument flight rules (IFR);
  Law enforcement, military, and aeromedical operations; and
  A pilot who must deviate to the extent necessary to address an emergency situation.


Why do winglets reduce maneuverability (of fighter jets)?

Your observation about roll inertia is correct: Winglets add proportionally more roll inertia for their small increase in L/D, and this increase exists only for the higher range of lift coefficients. At low lift coefficients (think cruise), when the induced drag is low, they add more friction drag and reduce the L/D overall.

There are three aspects to maneuverability:

How quickly can you accelerate into a roll? Here the added inertia of winglets reduces roll acceleration
How high is the maximum sustained turn rate? This is determined by the maximum lift at zero sink rate, and here winglets are helping. Especially when mounted to low aspect ratio wings.
How high is the maximum turn rate? Now only lift counts, and the increased drag is compensated by an increased sink rate. Again, winglets help a little, but less than with the sustained turn rate.

Now look at the time any fighter will spend around 1g (hint: Something close to 100%) and how much is spent at high lift coefficients, like when turning tightly in air combat. Winglets would help in the turn (and I think Ethan's opinion is wrong), but be a source of drag for the rest of the mission. Adding winglets would require to increase the fuel volume to prevent a reduction in flight time and range.

Normally, winglets are only used on highly loaded, high-aspect ratio wings when their L/D at a rather high lift coefficient needs to be pushed up even more. Highly maneuverable configurations are less concerned with single-percentage increases in L/D for a small part of the flight, and in order to improve turn performance, increasing wing span is much more effective. But that increases roll inertia and roll damping, so fighters use low-aspect ratio wings and compensate their higher drag in a turn with more powerful engines. Note that the trend in fighter aspect ratios went down with the improving thrust-to-weight ratio of jet engines.

Now that is the reason why you don't see winglets on fighter jets: They would lower L/D for most of the flight. To perform the same mission, the fighter without winglets can be made smaller.

But let's make no mistake: Low aspect ratio configurations gain the most from winglets: They were essential on the Hermes re-entry vehicle project to give it enough L/D for a successful flare.


Where do flaps and elevators get input from?

Let's take the two most prolific airliners as examples, the A320 and the B737.

A320

For aircraft pitch control, the A320 has a horizontal stabiliser which can be trimmed, and an elevator.

The elevator can deflect very rapidly, and is actuated via hydraulic actuators. They receive their inputs from the digital flight computers, which compute appropriate inputs depending on pilot side stick input and aircraft flight state.
The horizontal tail can be trimmed: moved relatively slowly via a screw jack driven by two hydraulic motors. The hydraulic motors receive their inputs from the flight computers, which provide commands for auto-trim of the stabiliser. Direct mechanical control can also be used: the trim wheels have a mechanical cable connection with the hydraulic motors, rotating the trim wheels directly commands the hydraulic motors to run. The trim wheels are situated on either side of the thrust levers.

Flaps get their input from the flap lever. The A320 simply has settings 0,1,2,3,Full, and the pilot selects the proper number in the appropriate flight phase. From A320_Briefing_For_Pilots:

B737

The B737 has the same arrangement as the A320: a moveable horizontal stabiliser, and an elevator.

Again, the elevator makes the rapid deflections, actuated by hydraulic actuators. They receive their inputs from mechanical cables, connected directly to the columns in the cockpit. A feel spring provides artificial entering forces, proportional to the airspeed (q-feel).
The stabiliser is actuated via a screw jack, which can be rotated via electrical motors (by flipping the trim switch on the control wheel) or directly via the trim wheels, which are connected to the stabiliser via mechanical cables. From this link:

  Trim can be applied by electric trim switches, autopilot or a manual trim wheel. Electric and autopilot trim may be disengaged by cutout switches on the control stand in the event of a runaway or other malfunction.

  Moving the control column in the opposite direction to electric trim will stop the trim, unless the STAB TRIM switch is set to OVERRIDE. This function could be used to control the pitch of the aircraft with trim say in the event of a jammed elevator.

  The trim authority varies according to aircraft series and method of trim. The full range is only available with the manual trim wheel, but if at an extreme setting, electric trim can be used to return to the normal range. There are two electric trim switches on each control column, the right is for the direction and the left is an earth return for protection against spurious electrical signals.

Flaps again get their inputs from the flap lever, next to the thrust levers. There are slots for the lever to be situated at the appropriate flap setting, noted in degrees deflection.

Image source


Why do UCAV/UAV designs mostly use lambda wings instead of pure delta wings?

Aspect ratio.

Look at your two images: both wings offer the same wingspan, but the former requires a lot more wing area for it. Wing area is weight. More wingspan for less wing area means better fuel efficiency and thus better range.

Poor aspect ratio, leading to excess induced drag, is a major disadvantage of delta wings. Much of modern stealth design is an effort to mitigate the poor flight characteristics of early "stealth-only" solutions.

Neither UAV nor UCAV get meaningful benefit from supersonic flight, since they can't realistically oppose manned fighters. Large UAV and UCAV are meant for long-range predictable stealth missions, where slow and steady wins the race. Better fuel efficiency means more payload or longer-range missions, both directly improving the vehicle's usefulness.


Is there an online source of active flight plans?

It seems you are looking for domestic flights in the US. The FAA database is not public.

You can use ADS-B tracking sites to look at the route. Remember instructions after takeoff (departure and transition) and before landing (transition and approach) are determined late and can be changed, depending on winds and other parameters.

E.g. on Flight Aware, for JBU124 between LAX and JFK, the route is mentioned:

and can be decoded:

These sites also create route history records. After a certain number of days, it's paying.


Can a harbor freight predator 212 cc engine be enough for an ultralight

6.5 hp is enough to get a person off the ground - but it would require an extremely aerodynamically- and structurally- efficient airframe to do so. A first-time builder without experience or training is not going to build such an airframe on the cheap from wood and foam and fiberglass with "bits and pieces of aluminum for strength". Either the wings will break and you'll kill yourself, or more likely it just won't get airborne.

You should scrap this idea and instead find a good set of plans and follow them exactly.


How do aviation GPS navigation systems report GPS accuracy?

The required GPS accuracy depends mainly on the application. En-route requirements are more lenient than the accuracy requirements for non precision approaches.

The GPS accuracy is the result of inaccuracies in the signal combined with a factor based on the geometry of the satellites. Within the receiver the position error is thus estimated by looking at

The geometry of the satellites contributing to the position fix
The estimated user equivalent ranging error (UERE) caused by various disturbances

From the geometry of the satellites, the (Geometric) Dilution of Precision (DOP) is calculated. This is a number that expresses how the geometry of the satellites used to calculate the position influences the accuracy of the position solution. In an ideal situation, $DOP=1$, any value less than $4$ is considered good.

The DOP can be split up in three components, the horizontal (HDOP), the vertical (VDOP) and the time (TDOP). For horizontal position accuracy HDOP is used.

The second factor in the accuracy estimation is the User Equivalent Ranging Error (UERE). In the illustration above, this is the width of ranging bands.
UERE is composed of various factors:

Ephemeris data - Errors in the transmitted location of the satellite
Satellite clock - Errors in the transmitted clock.
Ionosphere - Errors in pseudorange measurements caused by ionospheric effects
Troposphere - Errors in pseudorange measurements caused by tropospheric effects
Multipath - Errors caused by reflected signals entering the receiver antenna
Receiver- Errors in the receiver's measurement of range caused by various internal factors.

The effect of the ephemeris data error is in the order of 2 meters (standard deviation).

The accuracy of the satellite clock used to be intentionally degraded under the Selective Availability programme. SA was turned of in May 2000, drastically improving the GPS accuracy. Receivers developed before that date are unaware of this change and will estimate a worse accuracy than they actually achieve.
. The residual clock error after SA was turned of is equivalent to about 2.5 meters (standard deviation).

The GPS signal includes parameters for an ionospheric model which can be used to correct ionospheric effects. The residual error cause by signal delay in the ionosphere is in the order of 5 meter (standard deviation).  It is the most significant contribution to the UERE.

Tropospheric effects are much less than the ionospheric effect. The effect is about 0.5 m (standard deviation).

Multipath effects (caused by reflections of signals) are very much depending on the environment. In a city the effects are worse than in the air. For airborne applications multipath can be cause by reflections of the signal from the wings. The effect is very limited. On the airport surface there can be significant effects especially near buildings.

Receiver errors caused by unstable oscillators (thermal noise), quantization and rounding errors, software errors etc. This contribution can be reduced by improving the design of the antenna and receiver; which all comes at cost.
Let's estimate the contributions to UERE about 3 meters.

The UERE is the root mean square of all these contributions.

$$UERE=\sqrt{2^2+2.5^2+5^2+0.5^2+1^2+3^2}\approx6.75meters$$

The 95% accuracy is then estimated by $2\times{UERE}\times{HDOP}$. For a HDOP of $2$, the position would be estimated to be within 27 meters 95% of the time. Typical accuracy is better, because the UERE factors are estimated quite conservatively.

Augmentation systems such as WAAS and GBAS can improve the GPS accuracy by sending correction signals. The GNS 430 (without the 'W') does not use these signals.

If the DOP is greater than $4$, the GNS 430 will display a message "Degraded accuracy". You can find the DOP on the Satellite status page. This page also shows the estimated position error.

Note that all the calculations to estimate the position error assume that GPS is working as it should, i.e. a fault free condition. Faults can occur in the satellites, in the transmission of data to the receiver and in the receiver itself. Fault detection is part of the RAIM function.


Why are the exhaust pipes design on the Ilyushin Il-2 not very popular?

This engine is about 10 times more powerful than a modern average piston engine. With such power you get some useful thrust from exhaust power directly. This design helps to recover it. With a small SEP, noise and keeping exhaust smoke away from the cabin probably is more important. And it's not true that it's not popular. It's popular with single engine turbines. Source: Wikimedia (click for link)


How do I calculate density altitude by hand?

Density altitude is a value that directly correlates aircraft performance to atmospheric conditions.

  Density altitude is pressure altitude corrected for non-standard temperature.

Almost all temperatures in aviation is Celsius including this formula.

You will notice that all aircraft performance calculations require pressure altitude and temperature and in effect is calculating density altitude.

To calculate pressure altitude you will calculate
$$ \left( 29.92 - \frac{\mathrm{current~altimeter~setting}}{\mathrm{inHg}} \right) \cdot 1000 \, \mathrm{ft} + \mathrm{current~field~elevation}$$

For example if the current altimeter is $30.12 \, \mathrm{inHg}$ and you are $ 6,400 \, \mathrm{ft} $ MSL, the pressure altitude is
$$ \left( 29.92 - 30.12 \right) \cdot 1000 \, \mathrm{ft} + 6,400 \, \mathrm{ft} = 6,200 \, \mathrm{ft}$$
pressure altitude.

Your formula to calculate density altitude is correct but is never required to be known to calculate aircraft performance as the "calculation" is being done in the background of the performance charts.

To calculate density altitude, you must first calculate pressure altitude and then apply it to your formula.

If you are at 10°C at $6400 \, \mathrm{ft}$ MSL with an altimeter setting of $30.12 \, \mathrm{inHg}$:
$$(10-2.6) \cdot 120 \, \mathrm{ft} + 6,200 \, \mathrm{ft} = 7,088 \, \mathrm{ft}$$ density altitude

I have never calculated density altitude once I got into the air.  I have calculated density altitude while determining if its a good idea to takeoff.  In higher elevation airports on a warm day, the airplane may not get out of ground effect due to the density altitude.

The formula for density altitude above is correct for any altitude, albeit a more simplistic formula.  Humidity also has an effect of density altitude and there are formulas that take humidity into account when calculating density altitude.


On a larger airplane, how do they manage balance?

Before the main cabin door is closed, the ramp personnel will deliver a cargo sheet that lists

number of checked bags
number of gate checked bags
number of heavy checked bags
pounds of commercial cargo
pounds of company cargo

With numbers broken down by cargo bin where accurate.

The flight attendant will deliver a sheet with passenger count in zones.

The FMS or EICAS screens can tell you how much fuel is on board.

From there, some airline have ACARS programs that you plug those numbers into and it will give you weight information (to turn #bags and #people into pounds). Other have worksheets to calculate the weights.  In the EMB-145 we then had to spin a special wheel with the weight information to get the balance info.  This can vary by operator.

Some operators will have the W&B calculated by dispatch and all of the numbers I mention above are put into the computer system by various people and the dispatcher will deliver the W&B and takeoff reference data to the pilots via ACARS.

What if there is a problem?

Problems can be overweight overall, overweight in the cabin, overweight in the bag compartments or out of balance.

For overweight, remove people or bags as necessary.  If fuel has not arrived and you can do without some, call dispatch to revise the numbers and load less fuel.

If you are out of balance, you move people or bags around.  This was rarely an issue and if it does happen you just ask a passenger from zone X to sit in zone Y for takeoff.


What does a reduction gearbox do in a turbofan engine?

The problem is that in bypass engines, the fan blades are much longer than the turbine blades that drive them. Both compressors and turbines should rotate as fast as possible, without shock waves occurring at the tip - so linear tip speed has an upper limit, meaning the compressor with longer blades must turn much slower than the turbine driving it.

This is what the geared turbofan does, reduces the rotational velocity relative to that of the turbine so that both can rotate at their optimum angular velocity. The forces involved and the required reliability make it not an easy design task, as noted in this answer,

  Does it improve fuel efficiency?

It does, when both the fan and the compressor can rotate at their optimum speed, and when the gearbox does not add much friction.


How long does it take for pilots to become unconscious after an uncontrolled depressurization at FL 340?


From which aircraft are these parts (plane crash on "Dallas" TV series)?

I think, based on that tail section, that it looks a lot like a Stinson 108-3.  They had large metal tails with horizontal corrugation.
The position of the rear nav light and trim tab (just above the light) allows for enough room below the light for the six rows of corrugation that I count in photos of other 108-3s.
The position of the tail wheel fits, too.  It is not too long but it is easily noticable and not buried in, or up close to, the tail.
The wings are metal with fabric covering.  108s were all metal and covered with fabric, except the tails.
The only thing that does not seem to match is the wing rib.  The Univair website images for 108 wing root ribs have a very similar outline but do not have what appear to be four holes near the rear edge.  They have a single large hole instead.  Univair may be selling improved parts, however, and the rib in the video may be a factory original -or- a field manufactured piece as part of a repair that does not match the original.


How might one obtain aircraft registration numbers for past flights (months ago)?

If you come up blank on the various open sources that have been suggested, which wouldn't surprise me, your best bet may be a personal letter to Air Canada and another as well to whatever headquarters address you can find for Jazz, explaining what you are attempting to do, and asking if they'd be willing to look up the aircraft ID for those flights for you.

For the right person, it's probably about 2 minutes of work total to look them up, although getting the request TO that person may take considerably longer.  Many airlines have customer relations departments whose job it is to address whatever issues people write in about, and a pleasant "we flew with you, flight was great, love you guys, silly us, forgot to get the tail #, baby's logbook, dedicated customers, please help, really love you guys, thanks millions..." letter may well get pointed to the right department and get you an answer.

You could also try calling and/or e-mailing; you're actually NOT looking for the standard front-line Reservations agent or "let me help you with your flight" type of person, but rather somebody in the Dispatch or Maintenance records section, as those are the people who have the big database of everything that the airline has ever done.  That said, it may be difficult to get past the usual barriers that airlines have in place to keep worried passengers in an airport from trying to talk to dispatchers about "why isn't my flight here yet???"  So I'd expect that the pleasant letter to a Customer Relations department may be your best bet.


What is the risk of leaving the MAN START PB 'ON' on the A320?

Well, documentation is a bit vague about this, and I suppose a technician would know more about the different things the ENG MAN START bp is doing, but from a quick glance at the FCOM there is one major difference that I can spot:

  [The FADEC durring a manual start]  (...) Closes the engine start valve, and cuts off the ignition when N2 reaches 43 %.

Bold emphasis is mine, no other conditions except N2>43%.

Leaving the ENG MAN START pb on means FADEC keeps assuming we are trying a manual start, and will cut off ignition anytime the N2 is above 43%. No prob as long as engines are running, right?

But that means (I assume) when you then enter turbulent/stormy weather in flight and turn on  IGN/START to prevent a flameout, nothing happens as FADEC is happy that N2 is above 43% and you manual start has been ‘succesfull’.

I don’t really know if it will even attempt an auto restart when you get a flameout, as the N2 will probably keep windmilling for some time depending on your airspeed, so you could end up with a big problem.


Do airlines use a software to calculate center of gravity?

Most airlines of any size use software to calculate the c.g., either their own software or vendor software.

Passenger aircraft weight & balance is relatively trivial compared to cargo aircraft w&b, where such things as floor loading, lateral imbalance, and monocoque limits can come into play.

http://www.champ.aero/ is one provider of that service and software for cargo aircraft for those companies not wishing to program their own.

Fuel efficiency is one advantage of loading to given c.g. An oft-used method is to load to a specified zero fuel weight c.g. For example, on 747 aircraft through the -400 models, a zfw c.g. of 26.6% mac is a typical target.

If you want to see and play with a free, online, open-source w&b system for cargo aircraft, go to http://terryliittschwager.com/WB/index.php.


How much does the swirl of engine exhaust affect aircraft performance?

More of a comment than a complete answer, but  the losses caused by swirl are not really on drag, stability, and turning performance. The swirl represents is a loss in total pressure in the axial direction, and so is a loss in shaft power extracted by the power turbine, or thrust provided by the engine if it’s a turbofan. This won’t reduce drag at the same aircraft velocity one iota, but does enable you to go faster if you reduce the swirl, due to the higher power (in a turboshaft) or thrust (in a turbofan). How much effect swirl has, I am not sure. I think it’s pretty small, because some engines have vanes at the turbine exit to remove, and others don’t bother, and instead choose to save the weight of these vanes.

Fairly obviously, extra power or thrust will help the vehicles turning performance, but I think it’s clearer to state this is due to extra power or thrust, rather than imply it’s a direct effect.


What are these things on the A350's instrument panel?

These are the EFIS CP (EFIS Control Panels) for the captain's and First Officer ND's (respectively). For example, clicking on the ARPT button will display airports on the relevant ND (Navigation Display, the right part of the left screen, or the left part of the right screen in the image you provided).

It's pretty clear in this close-up photo.

You can see the mentioned controls in the top left corner and the ND display in the PLAN mode (which shows the entire flight plan).

The barometric pressure setting can also be changed using the EFIS CP.

Opposing your comment regarding the A320, The EFIS CP in the A32X (A318-A321)  is also in a very similar location.


What are the options for installing ADS-B OUT in a Cessna Citation to meet the regulations?

It depends on what kind of Citation you are talking about.

I found a presentation by Textron(ppt) that discusses ADS-B installation for various models. Textron is focussing on creating Service Bulletins (SB) for installation of ADS-B on recent models (up to 15-20 years old).

For the Cessna Citation a SB is available for the following models:

Pro Line 21

CJ1+: SB525A-34-90
CJ2+: SB525A-34-41
CJ3: SB525B-34-26
CJ4: SB525C-34-09 R1
Encore+: SB560-34-163
XLS+: SB560XL-34-76

Sovereign

Primus EPIC: SB680-34-33 R1

Citation X

Primus 2000: SB750-34-58

For the following
Cessna Citation SB's are under development (when the presentation was given)

Ultra, Encore, XL, XLS

Primus 1000; expected Q2 2016; Prerequisite: Universal FMS with SBAS LPV

Mustang

G1000; expected Q2 2016

It is possible to install another transponder than advised by Cessna. However if it hasn't been done already, you have to go through a Supplemental Type Certificate (STC) process for that which makes it rather expensive. It also wouldn't be supported by Cessna, which will impact the resale value of the aircraft. You may offset the cost of the STC by offering it to other Citation operators, but then you are suddenly in a whole different kind of business.

Other considerations to take into account are support of future operations, mainly LPV approaches using the same GPS receiver.

Since all offers seem to prefer the Garmin GTX, I assume the aircraft is a Cessna Citation CJ1 or CJ2 with a non-Collins FMS. Cessna has a STC for this aircraft that is based on the Garmin GTX.


Can a bird strike destroy the stealth capability of F-35?

The F-35 is a plane that relies on safety via stealth, rather than armor. The F-35 fuselage can be dented much like any other plane. The F-35 uses a variety of methods to reduce the its radar signature, most of which revolve around the "skin" of the fuselage - the way the fuselage is physically shaped is meant to reduce the reflection of radar, and there are various paint and material considerations as well.

When at any considerable speed, a bird strike will tear right into the fuselage. Take for example the following picture of a bird strike on a separate military fighter.

When the fuselage is damaged in this way, the radar waves are no longer being strategically reflected or absorbed, and the aircraft becomes suddenly very visible on radar.


How much does it cost the airline if an aircraft misses its take-off slot?

A slot time is issued for aircraft flying through busy airspaces or to busy airports where the demand (number of flights) exceeds the capacity. If 50 flights are planned to arrive at an airport in 1 hour, but the airport can only handle 40 flights per hour, then the flow of traffic needs to be regulated.

Many years ago, everyone would simply depart, and then traffic would enter airborne holdings (circling in the air) along their route as they approached their destination, until there was room to land. Obviously, this is very inefficient, since planes would use a huge amount of fuel while waiting in the air.

Air traffic flow management was introduced to reduce this. Computer systems now calculate how many flights are planned to arrive at a certain airport in a certain time span. This calculation is done many hours in advance - so early, in fact, that the majority of the affected flights have not left their departure airport yet. This has the advantage that aircraft can wait on the ground, at their departure airport, soaking up the delay they will inevitable face. They will simply not be allowed to takeoff until a time where it can be assured that there is room for them when they reach their destination.

To achieve this, aircraft are issued a takeoff slot time (CTOT - Calculated TakeOff Time), at which time the flight must depart. If the flight misses this slot time, for one reason or the other, they are not allowed to depart - instead, they must request a new slot time. If flying to a very busy airport, the new slot time could be far in the future - sometimes several hours. This means that the plane must hold on the departure airport for several hours before being able to depart.

How these CTOT times are calculated is very complex, and deserves another question if you are interested.

While there are no direct costs from missing a slot time, getting delayed will cause many indirect costs for an airline - passenger compensation for delayed and missed flights, extra pay for crew (on the plane and at the airports) and so on. So the "thousands" it may cost an airline to miss a slot time come from these indirect costs of being delayed. Obviously, the exact amount will vary greatly from flight to flight.


What kind of flight termination measures are taken for supersonic aircraft?

Aircraft like the B-58 and XB-70 Valkyrie were equipped with escape pods to aid in super sonic ejection. The pod its self came down around the seat when activated the only movement that appears to have been required was bringing you legs up a bit. Heres some video of the capsule in testing.

(source)

You can find some more info on the only XB-70 capsule ejection in the answer here. There is also some interesting info on the topic in this Physics.SE answer.

Ultimately getting lower and slower may be your only option as was the case during an SR-71 ejection.

  Since the chances to survive an ejection at Mach 3.18 and 78,000 feet
  weren’t very good, Weaver and Zwayer decided to stay with the aircraft
  to restore control until they reached a lower speed and altitude, but
  the cumulative effects of system malfunctions exceeded flight control
  authority. Everything seemed to unfold in slow motion, even if the
  time from event onset to catastrophic departure from controlled flight
  was only two to three seconds.

  It was at that point that the pressure suit proved to be very effective protection for Weaver. In fact, once it was inflated, an emergency oxygen cylinder in the seat kit attached to the parachute harness was functioning. It not only supplied breathing oxygen, but also pressurized the suit, preventing Weaver’s blood from boiling at the extremely high altitude. In this way the suit’s pressurization had also provided physical protection from intense buffeting and g-forces. That inflated suit had become like a tiny escape capsule.

There is some interesting footage of wind blast testing on flight gear and seats for the F-106 aircraft you can find here. According to some of this data the helmet and flight suits were capable of surviving wind forces in and around Mach 1.3 and the seat was capable of ejecting at those speeds. However in the case of the F-106 line of aircraft it was ultimately deemed that 0-0 ejections were more likely (and a higher priority) than high altitude high speed ejections. Since no seats were capable of both ejections the 0-0 seats were ultimately favored. (check out this for more info)


Where can I find glide ratios for commercial aircraft?

The glide ratio is closely related to the lift/drag ratio; as lift/drag ratio is closely related to aerodynamic performance, aircraft manufacturers are very restrictive on such data and little reliable information is publicly available.
Some guesses can be made from incidences like Air Transat Flight 236. For the A330 this results somewhere around 24.

I'm not aware of any data on BA146/RJ85. As BA146/RJ85 focusses on short haul it may have a slightly lower glide ratio; 4 engines are also not favourable for a sailing plane. Still anything below 20 would be a surprise to me.

Edit: Seems I sort of mixed up the numbers. The A330 should be somewhere over 20 (quite a time since I worked on that...). Fopr the RJ85 on this forum the glide ratio is estimated as 15:1.

P.S.: Keep in mind that all these values are maximum values that can be reached under optimal conditions. Real values may be lower.


Is potentially dangerous to select the take-off power on airliner lower that temperature at the moment on the airport?

No it's not dangerous.  Flex thrust simply exploits all of the runway available, taking advantage of any length that is surplus to the minimum required at max thrust, to allow takeoff with less than maximum thrust to save wear and tear and fuel (wear and tear is a big deal taking off in a sandy/dusty environment and use of flex has a significant effect on engine life).

The fact that you are using "just enough power" for a flex takeoff does not change the technical risks.  The balanced field length requirements (accelerate/stop and accelerate/go safely) are still met, so the extra length available in a non-flex takeoff does not technically speaking, reduce the risks of something going wrong following an engine failure on takeoff or following a reject.


Why are electric shavers specifically permitted under FAR §91.21

This is an educated guess, based on history:

Electric razors were once well known as prone to generating elctromagnetic interference -- the ones available in the 1940s could pretty well blanket a nearby AM broadcast radio receiver.

However, in similar time frames, it was very important for oxygen masks to fit closely on the face, and beard stubble, besides being reportedly very uncomfortable, would compromise the seal (either increasing consumption from the limited store of oxygen available for high altitude flight, or risking hypoxia for the wearer).  Therefore, on long flights, it wasn't at all uncommon for aircrew to shave one or more times before getting where they were going.

As noted in comments, shaving with a blade razor (even the safety razors available when this regulation has its roots) was a bit hazardous in an airplane that might, without any warning, encounter turbulence that could literally knock someone out of their seat if not belted in place.  Wind-up rotary razors existed before 1950, but they were rare, relatively delicate, and expensive.  Electric razors that ran on 115 V were available before 1940 and, with care, would do a good enough job to let an oxygen mask seal well (rechargeable types didn't appear until the late 1950s).

The regulation, then, is to recognize that even with the potential radio interference, an electric razor was specifically to be permitted during flight.


What does it mean for a plane to be aerodynamically stable?

Static stability

is the tendency of a system to return to its initial state after a disturbance. Typical disturbances in case of airplanes are:

Flying into a vertical or horizontal gust
A jerk on the stick

The classic explanation is with a ball sitting in a pit. Whenever its position is changed by a disturbance, it will roll back towards the center. This does not mean that it will stop there - in an ideal world free of friction it will keep moving back and forth like a pendulum.

This is static stability. Broadly speaking, static stability is achieved by placing the center of gravity ahead of the neutral point, the point in which all additional forces due to a change in angle of attack can be summarized. There are two neutral points, one for longitudinal stability and one for directional stability. In both cases the change in angle of attack or sideslip will create a correcting moment around the center of gravity, pulling the aircraft back on its old path.

Even altitude stability can be achieved, but here we take advantage of the fact that air becomes less dense the higher you climb. If the aircraft is trimmed for horizontal flight at a certain altitude, an altitude change will mean that the power setting does no longer match drag at this new altitude. The aircraft will either climb or sink, depending on the altitude change, until the old altitude has been reached again.

In all cases you will experience overshoots and oscillations around the trim point. It can even happen that these overshoots become worse the longer the oscillation lasts (the phugoid motion in a glider is a good example). To stop the oscillations, you need to add

Dynamic stability

which describes the behavior of the aircraft over time. In most cases, friction will ensure that motions die down, and sometimes aircraft need little helpers like yaw dampers to get those under control.

You mention stalls and dives: They can indeed occur in a statically stable airplane. Low drag means low damping, therefore many high performance gliders have a dynamically unstable phugoid motion. I know, Wikipedia spells this wrongly, but the explanation is OK, so I linked it nonetheless. If you wait long enough after an initial upset, the oscillations will become so severe that the aircraft stalls at the upmost point of the cycle.

If you keep enough altitude and have no traffic nearby, this is fun to try.

Spiral dive

Note that I omitted to say something about roll stability so far. The glider (and your Cessna 172) will also start to roll, and in many cases the roll motion will increase more quickly than the phugoid, so you might need to try several times before you get a phugoid-induced stall. Most aircraft have a weak tendency to increase roll angle and to eventually fall into a spiral dive.

There is no aerodynamic mechanism to right the aircraft up after a roll disturbance. Sorry, @kevin, but dihedral won't help - it only works in case of sideslip.


What is the first fighter jet which was built with twin engine and tail configuration?

One of the first was probably the unconventional XP-79.
https://en.wikipedia.org/wiki/Northrop_XP-79

It never entered service of course, but does meet your criteria.

Something that kinda meets your criteria would be the F7U Cutlass. Twin tails and twin rear mounted engines though the tails were in separate tail booms outboard of the engines, a similar configuration to that of the DH Sea Vixen and Venom of roughly the same period.

These did enter service.

Then there is the XF-90 which has twin rear mounted engines with a single vertical stabiliser over them.
The Soviet La250 and Tu28 had similar configuration but came later.

This also did not enter service.


Why do multiple planes arrive from the same airport at the same time?

This has to do with codesharing or codeshare. Two or more airlines can agree to share the same route and operate it with only one aircraft to reduce cost of operation.
See the WikiPedia article on codeshare
Here an excerpt:

A codeshare agreement, sometimes simply codeshare, is an aviation business arrangement where two or more airlines share the same flight. A seat can be purchased on one airline but is actually operated by a cooperating airline under a different flight number or code

In the case where multiple flights are listed arriving at the same time from the same departure airports, there will only be one physical airplane serving the connection but under different flight numbers and operators. The different flight numbers and operators are listed to make it easier for passengers to identify their flight if codeshares are being used.
On busy airports or where there is not enough space on the information displays to show all flights of a codeshare, the relation is only shown once with rotating flight numbers.


Can a bullet hit make the cockpit door open?

The FAA standards seem to anticipate the use of firearms by people attempting to gain unlawful access to the cockpit.

Opening locks with firearms is probably not as successful as TV would have you believe.

Cockpit Door Standards

  Press Release – FAA Sets New Standards for Cockpit Doors
  Release No. APA 01-02
  January 11, 2002
  Contact: Alison Duquette  Phone: 202-267-3462 WASHINGTON, DC
  In response to President Bush's call to strengthen aircraft security, the
  U.S. Department of Transportation's Federal Aviation Administration
  (FAA) today published new standards to protect cockpits from intrusion
  and small arms fire or fragmentation devices, such as grenades. The
  Aviation and Transportation Security Act authorizes the FAA to issue
  today's final rule that requires operators of more than 6,000
  airplanes to install reinforced doors by April 9, 2003.

From FAA Press Release

This press release doesn't actually say that the locks on the doors must resist being fired on using handguns but it is apparent that the scenarios envisaged included those where handguns were present. There are obviously other measures to prevent passengers carrying combat shotguns into the cabin surreptitiously.

Guns and Locks

  In movies and television, a locked door, or a padlock on a cage is never an impediment so long as the Hero has bullets to spare. One or two shots is generally enough to destroy the lock, allowing the door to open.
  Unfortunately, in real life — as shown by the MythBusters — this requires a high powered gun at close range, which causes lots of very dangerous shrapnel. Lesser firearms, especially handguns may harmlessly bury rounds in even standard padlocks to little effect. Only SWAT teams and soldiers ever do this in real life, and it involves a shotgun, Kevlar body armor, specialized ammunition (a powdered metal breaching round, often jokingly referred to as "Avon Calling"), and full face protection. Even then, the goal is not specifically to destroy the lock, but to destroy the surrounding door or the hinges.

From TvTropes Shoot out the lock

Other references

Mythbusters - shooting locks


Why might this trans-pacific flight not follow a more direct route?

Looks like they were avoiding a storm system from Oregon north into Canada.


Can it be determined from beyond visual range whether an unknown aircraft is armed or not?

Only if the airplane wants you to know it is armed.

It has several ways at its discretion:

If it has a powerful radar, it can switch it on at altitude and announce its presence to other aircraft up to 150 km away.
It can send IFF squawks which are reserved for military aircraft. Note that IFF is used by both military and civilian aircraft.

Both methods are only indirectly indicating whether an aircraft is armed. The armament itself will not show up at BVR distances. In the end, if you want to be sure, you have to move some sensors close to the aircraft if the weapons are carried externally, or even wait until they are deployed when they are carried internally. Especially many small aircraft are used both in a civilian and a military role.

A BVR radar is a dead giveaway for a military aircraft - such equipment is not fitted with civilian aircraft, and removed or disabled when an ex-military aircraft is converted to civilian use. Similarly, supersonic speed, which can reliably be detected with Doppler radars, is a telltale sign of military aircraft approaching.

Transport aircraft are much harder to distinguish from bombers on the basis of radar signals alone, and in the end you cannot exclude that the hostile aircraft tries to spoof your equipment into classifying it as a civilian aircraft.


Why doesn't Concorde stall when passing Mach 1, where a normal airliner does?

The phenomena you are referring to is better known as "tuck".  This is caused by buildup of a supersonic shock wave on the upper surface of an airfoil when a plane enters the transsonic Mach region of flight (approaching Mach 1).  This leads to a disruption of airflow behind the shockwave, resulting in a pitching down even without excessive AOA.  Concorde actually did this too, and trimmed for it with the help of fuel transfer pumps.  Discovery of this effect in the 1940s also lead to the creation of the "all flying" horizontal stabilizer.

The designers gave Concorde a very long, pitch stable design, along with a delta wing.
That, and 4 powerful Rolls Royce/Snecma 593 Olympus engines, easily pushed it past transsonic, cruising along at Mach 2 up to 60,000 feet.

"Normal" airliners simply are not designed for supersonic flight.


USA: Why don't airports raise landing fees to make up for low passenger fees?

This depends on where you are in the country and more specifically who controls the airport. A lot of airports in the US are owned by cities (or local governments) in some capacity. As such changing the landing fees often requires a legislative change which is not always easy. For example here is the legislation that covers the landing fees at both major airports Philadelphia Controls

Changing these requires a policy change at the government level and it takes a long time to get just about anything through the Philadelphia government. In many cases these fees are paid to the municipality anyway and the airport never sees any of the money so the fees don't (directly) help the airport. In a lot of cases the fees do (or at least are presumed) to go back to the maintenance and upkeep of the airport.

Private airports (generally smaller GA ones) can levy fees as they see fit and sometimes do to help with the upkeep of the field.

What airports or more specifically FBO's and other on field operators do is raise operational costs to use their facilities. Rising FBO fees have been of concern lately and sometimes there is no way to escape them if someone has what amounts to all the parking space on the field. It may only cost $5 to land somewhere but keeping your plane there for a while, getting a pre-heat, maybe even using a terminal is by no means cheap.


It's not so much that thrust reversers (TRs) are more unreliable than other components of the plane. However, they have a very important impact on the airplane's performance. Hydraulics, flaps, and even engines fail regularly. But engines and hydraulics can be backed up by redundant systems, and an airplane can still land without flaps. But engineers learned from Lauda Air Flight 004 that an airplane may not be controllable if the TRs deploy in flight.

So in the interest of safety, the TRs have additional precautions. The reasons for not aborting a landing after they are deployed are discussed in your first linked question. Reliability is also not the only reason for having no TRs on the A380 outboard engines, as discussed in the second linked question.

So to answer your question, there is indeed a technical challenge in making the TRs reliable: they absolutely must not deploy in flight. This means many safeguards are put in place, and they are designed to fail by not deploying if there is any doubt about whether it is safe. A TR that won't deploy is more desirable than a TR that deploys when you don't want it to.


Is the pod on the right wing of the PC-12 and Cessna 208 a gyrocompass?

Its not the gyrocompass. Its where the weather radar unit is mounted since the prop prevents it from being mounted in the nose like on many larger aircraft. You can find a nice instructional video on how to use it here. The magnetometer used on many aircraft to provide magnetic heading information to the systems is much smaller than those domes.

(source)

If you are referencing the heading indicator when talking about a gyrocompass those are panel mounted. If you are referencing the wet compass (which is balanced in fluid) those are mounted on the column in the center of the windshield typically. A lost of the more modern aircraft in this class have glass panels which use AHARS units and may not have traditional gimbals anymore.


If airports with pilot controlled lighting share a CTAF frequency, could the lights be triggered at multiple airports?

In theory, this could happen.  The consequences may not be severe - wasted power, some light pollution, and a false impression from seeing the lights alone that an(other) aircraft is trying to use the airport when in fact it isn't.

However, it may be less likely than you think.

For one, an aircraft in the air, even at pattern altitude, is going to have a much better path of radio propagation to another aircraft in the air, than an aircraft over one airport may have to a ground antenna at another - in simplistic terms, the radio horizon has doubled.  Ideally (for example in planning towers for a cellular phone network) frequencies are not re-used within the range of expected propagation, but only beyond it - however, in the aircraft-to-aircraft case you have doubled that over the air-to-ground case.

For another, an aircraft receiver is designed to be able to pick up weak signals.  In contrast, the receiver and decider for pilot controlled lighting may have an intentionally high signal threshold, to only trigger on strong nearby transmissions, and not on distant ones, random radio noise, or weak harmonic interference from transmitters on non-aviation bands or unintended emissions from non-radio equipment.


How many controllers are there per frequency?

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

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

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

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


Why is a urine test performed during pilot medical examinations?

It's for diabetes and kidney disease. You can read the AME guidance here:

  Item 57. Urine Test
  Glycosuria or proteinuria is cause for deferral of medical
  certificate issuance until additional studies determine the status of
  the endocrine and/or urinary systems. If the glycosuria has been
  determined not to be due to carbohydrate intolerance, the Examiner may
  issue the certificate. Trace or 1+ proteinuria in the absence of a
  history of renal disease is not cause for denial.

Glycosuria is an indication of diabetes, and proteinuria is an indication of kidney disease (among dozens of other things, if Wikipedia is to be believed). And the AME can do other tests too, if he thinks they're necessary:

  The Examiner may request additional urinary tests when they are
  indicated by history or examination.

The regulatory reference (per the AME guide) is 14 CFR 67.113 for a first-class medical, but exactly the same regulation is there for second- and third-class too.


Thrust is needed to overcome drag, and a good airplane design can create a lot of lift for little drag. In the case of an A-320, the lift-to-drag ratio is 18 in cruise (a little less during take-off), so to lift those 78 tons needs only 4.33 tons of thrust. All it needs is the right amount of forward speed, and the engines only need to maintain this speed.

Gliders are even more efficient, their L/D can approach 60. A glider of maybe 450 kg mass (= 4412 N weight) will create a drag force of only 74 N, admittedly at a much slower speed than an A-320.

To be more precise, in a climb the thrust will actually compensate a little of the weight, in addition to the drag, depending on the climb angle. The thrust needs to grow by weight $\cdot$ sin($\gamma$), where $\gamma$ is the flight path angle. If the A-320 had enough thrust to lift all its weight, it could take off vertically, flying in a nose-up, vertical attitude. Modern fighter aircraft do really have that much thrust installed.

This drawing shows a climbing aircraft. There are four forces at work:

Lift L (blue arrow)
Drag D (red arrow)
Thrust T (green arrow), and
Weight m$\cdot$g (black arrow)

For a trimmed state, the concatenated arrows should form a closed trapezoid (lightly shaded arrows). Note that both thrust and drag are drawn longer here in relation to weight and lift than they are in reality.

To answer the why part needs a few more lines. Lift is created by deflecting the airstream over the wings downwards. This change in momentum is lift, and creating it would be free of drag if the wing's span would be infinite and the air inviscid. In reality, flying causes these drag components:

Lift creation incurs a small backwards-pointing component which is biggest at slow speed and decreases with speed. To be precise: This drag component is proportional to the aircraft's span loading (weight divided by wingspan) and the inverse square of airspeed. It is called induced drag because it could be successfully calculated first with the same equations that describe electric induction.
Flying through air causes friction. This friction drag grows almost with the square of airspeed and is proportional to air density and surface area.
In inviscid flow, the sum of pressures around a body would just cancel out. In reality, the pressure on the forward-facing sections is normally higher than that on the aft-facing sections. This drag component is called pressure drag and is also proportional to the square of airspeed at the same angle of attack.

At the speed of best L/D the sum of 2 and 3 is equal to 1, and 2 and 3 are of the same magnitude for a well-designed airplane. High subsonic and supersonic flight adds a fourth component, called wave drag, and it's onset is the reason why the A-320 prefers to fly not much faster than Mach 0.78.


There are multiple non-destructive methods to detect delamination in composite materials.

In case the delamination occurs on the surface, it can be easily found by visual inspection. This is the easiest method to detect delaminations; however, this is useful only if the delaminations are visible from the outside (i.e. they are on the surface), which is rarely the case, at-least in aircraft.
Ultrasonic testing- In this method, ultrasonic waves are passed through the surface of the material and the response is monitored. Depending on the condition of the material (whether it has defect or not), the ultrasonic waves behave differently.

Source: cnde.iastate.edu

The ultrasonic method used can be through scan (with the transmitter and reciever on the opposite sides of the part) or pulse echo method, where the transmitter/reciever 'listens' to the ultrasonic sound reflected back from the defect or the other end of the part. There are three main methods of ultrasonic scanning in use:

The A-scan presentation displays the amount of received ultrasonic energy as a function of time.
The B-scan presentations is a profile (cross-sectional) view of the part. Here, the travel time of the sound energy is displayed along the vertical axis and the linear position of the transducer is displayed along the horizontal axis.
The C-scan presentation provides a plan-type view of the location and size of defects.
Tap test, using a coin or an instrumented hammer- This is the most widely used method in the field as it requires minimal instrumentation. However, it requires a trained operator, who can distinguish between the normal and delaminated composite from the sound. Instrumented hammers are also available, where the frequency response of the part can be analyzed for identifying defects.

Source: amumagazine.com

Thermography- Here, an energy source is used to produce thermographic contrast between tthe defect on the part. This is useful in detecting shallow subsurface defects, but is rarely used in field operations.

Infrared thermography Source: seattleinfrared.com

X-Ray radiography (or CT scan in some cases)- This is a very accurate method for detecting internal defects; however, the equipment requirements mean that it is usually used in the place of the OEM, though some field equipment is available for military uses.

Fatigue crack under X-Ray, Source: vidisco.com

There are some other methods like the acoustic emission and lasers, which also can be used for detecting delamination. The table below gives some of the methods used for detecting defects in a manufacturing environment

Source: amumagazine.com