Could some kind of impact absorbing gels be introduced into the aircraft fuselage, to minimize impact damage on passengers & cargo? There are a lot of impact absorbing gels, one example here.

Could some kind of more advanced gel be introduced into aircraft cabins, which expand rapidly on impact (like air bags) and fill the entire cabin, thus protecting the occupants from injury or death?

Unfortunately, not to any great advantage.

An airliner travels at several hundred kilometres per hour; even when landing and flying at its slowest (which it does only for a very short time) it will still be travelling at a considerable speed.

At such speeds, any impact in a crash is likely to be characterised by two things (I've left aside fire, to concentrate on the matter of impact alone):

a very significant change in velocity (deceleration)
a release of a great deal of energy

The deceleration of an aircraft in flight that hits something will be tremendous. If you have 30 metres in which to decelerate from (say) 500 km/hr to 0, padding won't make any difference to the bodies being decelerated.

If the padding is resistant enough to prevent an object experiencing such a deceleration from simply continuing on its way and smashing through everything in its path, then the padding may as well be a block of concrete for all the softness it could offer.

On the other hand, if the padding not so hard as to smash the bodies that crash into it into pieces, then they will go straight through it and smash themselves to bits on the first harder thing they encounter.

In fact, at such decelerations, not only is there no middle way between too hard and too soft, any padding aiming for the middle ground would be simultaneously too hard (it would certainly cause catastrophic injuries to the bodies encountering it) and too soft (it wouldn't prevent them smashing into other objects).

Then, an impact of the kind you describe releases a huge amount of energy. The things involved in such impacts aren't so much as damaged as cease to exist. Everything stops being what it was. You might as well wish for padding to protect you when you're on the inside of an exploding bomb.

Perhaps you were referring to lesser impacts that would be survivable with some protection, which is reasonable. Indeed, an aircraft can readily survive turbulence that breaks the bones and heads of passengers not wearing seatbelts.

But in this case, the idea sadly fails as not very practical.

How much damage would 300 or so exploding gel pods, or airbags, do to passengers? Once again, that's a release of quite a lot of energy.
How much damage would they prevent, compared to say, just wearing seatbelts?
How much would they interfere with the subsequent evacuation?

They simply wouldn't procure any advantage, or at least, only at the cost of a much greater disadvantage.


How do I use the GNS 620 Trainer provided by Garmin? I downloaded the Trainer for the Garmin GNS 620 here.

I installed and now have a few programs. I can open the GNS 620, the touchscreen GPS and boot it up, plan a route and so on.

There's also a program to open the G600, the PFD and MFD. However, when I open this program, it just says it can't connect to a simulator and exits.

My questions is: How can I use those trainers properly? How can I simulate the flight? How do I control the virtual plane? Do I need a simulator for this?

I would really appreciate answers, as I have no idea what to do.

Thanks!

I found all the information needed in the "Trainer's User Guide.pdf" that was installed with the software.

In short, launch ONLY the GTN - G600 Trainer.  Do not have any other components started.

3 windows should launch: GTN Trainer, G600 Trainer and Navigation Control.

Give it a good 30 seconds to load up, then on the GTN Trainer window, click "Power On".
All windows should come up and be active.


How are disabled passengers evacuated during emergency? Basically the title. However, I would request if someone can throw some light on how FAA or the airlines train the crew to handle emergency evacuations with a disabled person on board. Are the ramps and slides accessible to persons with disabilities?

You can find the full text of the FAA's recommendations in this AC

But the flight attendant is responsible for discussing with them whats best.

  ASSISTING DISABLED PERSONS. The handicapped person knows best . the
  manner in wbch he can be assisted, and flight attendants should not
  hesitate to discuss this with the individual. Keep in mind that
  different disabilities have different needs, and injury can result if
  a person with a disability is improperly assisted.

The AC goes on to describe most major scenarios and common instances.


Can a pilot rated in one category solo in another category without a current flight review? Scenario:

A pilot is rated to fly gliders in the United States.
The pilot allows his glider flight review to lapse.
That pilot now decides he wants to get a type rating for the airplane category, single engine land.

Question:

Does the pilot have to be flight review current in order to solo in a powered airplane?
(Secondary question, as long as we are at it) Does the pilot have to be flight review current in order to take the FAA practical (check ride) in a powered airplane?

Note: I'm most interested in the answer under US FAA regulations, though the answer in other countries would be of interest as well.

I have spent some time looking over the FARs, specifically 14 CFR 61.56 and I cannot find anything conclusive either way.

I should mention that I suspect the answer to this question to be no, though I am not prepared to offer evidence to back this up.

I've already seen this related question asking whether a biennial flight review is valid for any airplane category, but I don't believe it's a duplicate because that only covers the situation where the pilot is rated in both catagories. This question refers to the situation where the pilot is rated in one category, but not the other.

You do require a flight review, per the Beard (2013) interpretation:

  Finally, you have also asked whether a person operating in solo flight
  under a § 61.31(d) endorsement must comply with the flight review
  requirements in § 61.56(c). With a few listed exceptions, no person
  make act as pilot in command of an aircraft unless within the previous
  24 calendar months that person completed a flight review with an
  authorized  instructor. 14 C.F.R. § 61.56(c). Section 61.56(g)
  provides an exception for student pilots provided the student pilot is
  undergoing training for a certificate and has a current solo flight
  endorsement as required under § 61.87. Because this exception applies
  to student pilots, a pilot who holds a higher level pilot certificate
  and has an endorsement for solo flight under § 61.31(d) must comply
  with the flight review requirements in § 61.56 before acting as pilot
  in command of any aircraft.

Regarding the student pilot exception, others have suggested in comments that you are in fact a student pilot because you're new to the category/class. However, the interpretation says you are not:

  Section 61.81 states that subpart C "prescribes the requirements for
  the issuance of student pilot certificates, the conditions under which
  those certificates are necessary, and the general operating rules and
  limitations for the holders of those certificates." As such, by its
  express language, subpart C to part 61 applies only to those persons
  who are seeking or hold a student pilot certificate.

So, since you will be acting as PIC and none of the exceptions in 61.56 apply, you need a flight review. As for a checkride, the person taking the checkride is acting as PIC (61.47(b)) so again, you would need a valid flight review.


May I fly from the right seat due to a temporary disability? I am a student pilot with, and I have had carpal tunnel for years now. It has progressed to a point where my left hand is frequently weak and/or achy.  I do have use of the hand, and it is quite uncomfortable in the landing flare since I have to control the yoke left-handed when flying in the left seat to leave my right hand free for the lighter-duty tasks of operating the throttle and other equipment.

I am very close to my check-ride and I am scheduled to have surgery on my left hand next month.  I don't want to suspend my training and get rusty.  Also, after the surgery, I suspect that my left hand may not be 100% for some time, and I don't want to miss out on these great flying months.

I have seen articles about pilots with disabilities far greater than a case of carpal tunnel, so I'm wondering if there is a way I can avoid putting my training on hold.

Is it permissible to fly from the right seat so that my weak hand only needs to operate the throttle, flaps, etc. while letting my stronger hand handle the yoke?

Is this simply a request to my instructor/examiner or does this trigger an avalanche of FAA medical paperwork to make it legal?

I realize I would have to adjust to a slightly different sight picture in the right seat but I think that is a relatively minor transition in the grand scheme of things.

Generally speaking if your carpal tunnel syndrome is so bad as to preclude normal operation of an aircraft you probably shouldn't be flying from either seat: If something goes wrong you may well need both hands to operate the aircraft (we do have one-armed, and even no-armed pilots, but they generally have medical exceptions, and possibly additional restrictions).

If you cannot complete your training before your surgery your best bet would probably be to defer your checkride until after the surgery - yes this will probably mean additional training time after your surgery to knock off the rust, but you will likely need this anyway (you're going to get rusty during your recovery whether you're a certificated pilot or a student).
Additionally it's probably a good idea to have a safety pilot with you for your first few flights after recovery to ensure you're physically able to perform all the tasks required to safely fly an airplane, and an instructor accustomed to flying from the right seat makes an excellent safety pilot so you could knock off the rust and do your checkride prep at the same time you're making sure you can safely operate an airplane.

Re: FAA paperwork, I'm not an AME but looking at the FAA's Guide for AMEs carpal tunnel syndrome doesn't appear to be disqualifying unless it presents a "medical deficiency" (broadly "interferes with you operating the flight safely").

When you have your surgery you'll be effectively grounded until you recover adequate normal function in your hand to operate the flight controls without risk to the safety of the flight, and more importantly without risk of doing further damage and hindering your recovery.

Having had surgery is something you'll need to report on your next medical application (Question 18, item x: "Other illness, disability, or surgery "). Speak to your AME for details on what you may need to bring to the exam, if anything: Some may want a note from your treating physician stating you've regained normal grip and sensation, others might be OK just checking out your hand during the exam per 67.313 and saying "Your hand seems fine to me."
If you're enrolled in AOPA's Pilot Protection Services you can contact them for information on what you should have available for the exam.


What is the procedure for an engine fire in the 737-800? If there is a fire in one of the engines of the 737-800, what is the procedure to be followed in the following situations?

Climb
Cruising altitude
Approach

What should the pilot do in the cabin in these three situations? In the climb stage, should the plane return to the airport of origin or continue the flight?

In general, you always follow the steps in the Quick Reference Handbook (QRH) after any failure or other problem. An engine fire is serious enough that it requires Memory Items, which are performed immediately before getting the QRH. In this case, the memory items are the first 5 steps of the QRH checklist:

ENGINE FIRE or Engine Severe Damage or Separation

Autothrottle (if engaged) . . . . . . . . . . .Disengage
Thrust lever (affected engine) . . . . . . . . Confirm . . . . . Close
Engine start lever (affected engine) . . . . . . . . Confirm . . . CUTOFF
Engine fire switch (affected engine) . . . . . . . . Confirm . . . . . . Pull
To manually unlock the engine fire switch, press
the override and pull.
If the engine fire switch or ENG OVERHEAT light
stays illuminated:
Engine fire switch . . . . . Rotate to the stop and
hold for 1 second
If after 30 seconds the engine fire switch or ENG
OVERHEAT light stays illuminated:
Engine fire switch. . . . . . . .Rotate to the
other stop and
hold for 1 second
If high airframe vibration occurs and continues
after the engine is shut down:
Without delay, reduce airspeed and descend to
a safe altitude which results in an acceptable
vibration level.
If high vibration returns and further airspeed
reduction and descent are not practicable,
increasing airspeed may reduce vibration.
ISOLATION VALVE switch . . . . . . . . . . . . CLOSE
PACK switch (affected side) . . . . . . . . . . . . . OFF
This causes the operating pack to regulate to
high flow in flight with the flaps up.
APU BLEED air switch . . . . . . . . . . . . . . . . . OFF
Choose one:

APU is available for start:
APU . . . . . . . . . . . . . . . . . . . . . . START
When APU is running:
APU GEN switch (affected side) . . . . . . . . . . . . . ON
APU is not available:
Go to step 11

Balance fuel as needed.
Transponder mode selector . . . . . . . . . . TA ONLY
This prevents climb commands which can
exceed single engine performance capability.
If wing anti–ice is needed:
ISOLATION VALVE switch (after fire has been extinguished). . . . . . AUTO
Plan to land at the nearest suitable airport.

(Boeing 737NG QRH 8.2)
You can see that the items 2 to 4 have a Confirm written before the actual action. This means that the Pilot Flying (PF) will put their hand on the respective lever, then the Pilot Monitoring (PM) confirms that this is indeed the correct one for the engine that has a fire and says "Confirm" and only then the PF will actually perform the action. This is to make sure that you don't accidentally shut down the operating engine. After step 5, the engine with the fire indication is shut off and the fire should be extinguished.
After performing the memory items, the PM would get the QRH out and the pilots will work through the checklist (including verifying that steps 1-5 have been performed correctly).
The steps do not depend on the situation (climb, cruise or approach). You always follow the above procedure. The general order of importance is Aviate, Navigate, Communicate: first you keep the aircraft flying, then you figure out where you are going and where you want to go, then you communicate with ATC.

What should the pilot do in the cabin in these three situations?

I'm not sure what you mean by this. The pilots are in the cockpit and after figuring out what to do next, they will communicate with the cabin crew and the captain will probably make a PA to the passengers.
If you refer to pilots flying as passengers in the cabin: They would probably do nothing. A single engine fire is trained regularly by the flight crew and the two pilots in the cockpit should have no trouble handling the situation without help of a third pilot.

And at the climb stage, should the plane return to the airport of origin or continue the flight?

You can see in the checklist that step 14 says: "land at the nearest suitable airport". This is not as strict as "land as soon as possible", where you should get the aircraft on the ground without any delay (smaller airport, military airport, whatever). The nearest suitable airport should be a civilian airport within normal descent range where a landing can be performed without further risk. In the initial climb stage, this would typically be the departure airport.
Continuing the flight to the destination should only be done when the aircraft is already close to the destination anyway (e.g. during descent). An engine fire during cruise may require diverting to a different suitable airport.


Why do we see many more 5th and 8th freedom cargo flights than passenger flights? Usually, we can see many cargo flights operating between 2 foreign countries (and even as domestic flights within a foreign country in some cases). There are passenger flights that operate in the same way, but they are much fewer in number.
For example, this is an image of Fedex planes flying over Asia, and none of them originate/terminate at US:

But if you take any passenger airline, then it is very unlikely that they will have so many 5th and 8th freedom flights. Why do more cargo flights than passenger flights enjoy these freedoms?
So, what's happening here? Are cargo airlines awarded 5th and 8th freedom rights more easily, or do passenger carriers simply don't apply for them, frequently, or something else?

I think the answer is simply that Cargo is far less picky about how it gets to its destination, as compared to People. A pallet can easily take three different flights to arrive at it's recipient, whereas most passengers wouldn't tolerate so many transfers.
Fifth freedom cargo flights are also often irregularly scheduled. For example, Atlanta Hartsfield-Jackson Airport receives the occasional cargo flight from Turkish Airlines and Singapore Airlines. It frequently receives flights from Korean Air Cargo and Cargolux, but these often originate at a variety of cities, such as Chicago, Dallas, or Anchorage.
In short, cargo is more flexible, which allows cargo airlines to be more flexible.


What is maximum displacement for aircraft engine? Is there any standards or at least typical values of aircraft engine displacement and rotation relatively to the wing in flight? Actually I'm looking for that values at Boeing 747-400 RF or ERF.

There is no standard.  Even for a single plane and a single engine, there will be literally hundreds of different possible displacements depending on the condition. The engine manufacturer will split these into several categories.

First would be static versus dynamic loads. Static loads are the loads (or displacements) caused by gravity, thrust load, maneuvers or wind.  Dynamic loads are transient events caused by rotor unbalance, bird impacts, blade loss, etc.

The second category is the severity of the load.  There are several levels here.  First is a fatigue load.  The engine will experience this level of load (or displacement) on virtually every flight.  Therefore, all parts must be able to withstand this load and not have a fatigue failure.  The second level is a "limit" load.  This would be experienced by the engine say once every 4000 or 5000 flights.  E.g. a very rapid maneuver or a particularly hard landing. For this level, fatigue is not a concern, because the engine won't experience it very often.  Just have to make sure no parts yield.  Final level is "ultimate" load.  This is the highest load that will ever be experienced by any engine in the lifetime of the entire fleet (e.g. a fan blade out condition).  Yielding may be allowed here, as long as nothing breaks.

Depending on what you are looking for, the answers could vary between 0.001 inch and several inches. I'm not sure that you will be able to find exact values, as the airframer and engine manufacturers will regard this as proprietary information.


Do flight simulators imitate turbulence effectively? I know that flight simulators (which are used to train the pilots for commercial airlines) try to simulate almost all kind of weather conditions, but how effectively and realistically are they able to reproduce turbulence in the simulated environment?

No, simulators cannot realistically simulate turbulence. Turbulence is characterized by significant changes in altitude that happen very quickly, and even full motion simulators aren't going to be able to re-create that. They can bump you around a bit, but not really prepare you for the real thing.


What is the difference between flaps and slats? I have heard pilots talk about flaps and slats, seemingly interchangeably.

Is there a difference between a flap and a slat or they are the same thing?

Flaps are at the back of the wing, slats are at the front.

Easy! :)

If you want it more technical: They both help to generate more lift. See these diagrams with angle of attack and lift coefficient:

As the lift coefficient is inversely proportional to the minimum airspeed, a higher CL will allow a lower Vmin.


What is the effect of power extraction on turbofan compressor and turbine maps? Effects of Power Extraction on Turbofan Compressor and Turbine Maps

The two diagrams below show the effects of shaft power extraction (shaft power offtake / shaft power off-take for the propulsion of accessories such as fuel-/hydraulic-/oil-pumps, generators etc.) on a high-bypass turbofan engine at a flight altitude of $H = 11km$ and a speed of $Ma = 0.8$, calculated with GasTurb 12:

Effects of Power Extraction on the Operating Line (Blue)

Why are the operating lines (blue) of both the compressor and turbine shifted to the left towards the surge line?
In particular, why does the non-dimensional corrected mass flow decrease, while the pressure ratio stays approximately constant?
The same question from a different angle: Why does the pressure ratio not decrease at a constant mass flow?

Scholz, D. et al.: "Fuel Consumption due to Shaft Power Off-Takes from the Engine", AST 2013 - Workshop on Aircraft System Technologies, 23-24 April 2013, Hamburg, Germany
Shaft power extraction, no matter if taken from the High-Pressure (HP) shaft or the Low-Pressure (LP) shaft, will reduce the speed of this shaft. This reduces the mass flow [...] and the thrust [...]. Constant thrust regulation applied to the engine (achieved today by the Full Authority Digital Engine Control, FADEC) will primarily result in an increase of fuel flow, increasing the Turbine Entry Temperature, TET. Higher pressure in the combustion chamber and higher turbine load together with a reduced shaft speed will enlarge the angle of attack at the compressor blades and therewith slightly lift the pressure rise achieved at each stage. In this way, shaft power off-takes also result in closer operation to the surge line. [...]
If shaft power is taken from the LP shaft, its speed will reduce. Also, the fan speed is reduced, which decreases the thrust considerably. With the engine controls increasing the TET, the HP shaft (in this case not affected by power off-takes) will even increase its speed and mass flow through the LP turbine and compressor compared to the original situation. [...]
If shaft power is taken from the HP shaft, its speed will reduce and so also the mass flow through the LP compressor and turbine. With the engine controls increasing the TET, the situation is rectified.
Low thrust ratings always mean a high relative power extraction P/T [shaft power off-take P, jet engine thrust T] and high relative specific fuel consumption. At high thrust ratings, the relative power extraction P/T is smaller and the relative specific fuel consumption is less.


Why can't we see the downwash/wake roll-up behind 2D/wall-to-wall airfoil tests? Why we can't see the downwash/wake roll-up behind any wall to wall airfoil wind tunnel video?
To make that happen, the air behind the center of the airfoil must go down and the air at the side walls must go up, producing two roll-up vortices. Could you upload video of that if it exists (which I doubt)?
DOWNWASH BEHIND WING VIDEO
here is how downwash and wake roll-up vortex looks at finite wing in wind tunnel:

Who says we can't? It just needs open eyes and an open mind.
To understand the picture below, keep these things in mind:

If the streamlines are packed together, the flow speed is higher while pressure is lower than ambient.
Conversely, when the streamlines are spaced wide apart, flow speed is lower but pressure is higher.
Converging stream lines mean accelerating flow.
Diverging streamlines mean the flow slows down.

Somehow, the air has to flow around the obstacle that the airfoil represents in a closed wind tunnel. It does so by speeding up (at least in subsonic flow). Conversely, when the airfoil tapers towards the trailing edge and an angle of attack makes the cross section downstream become wider, the air slows down in order to fill the available space. In the end, the mass flow near the suction peak where the cross section left open by the airfoil is narrowest is equal to that near the trailing edge when the cross section has become much larger. The same happens on the lower side: All the air passing below the stagnation line has to squeeze through the gap left between trailing edge and tunnel wall. This is only possible by a large change in speed.
Now have a look at stream lines in a windtunnel. Note that the lines near the upper and lower edge of the picture are almost straight and nearly follow the wall contour of the tunnel (picture source):

The downwash is the downward-pointing part of the streamlines over the rear part of the upper airfoil contour. Due to tunnel wall interference, the flow on the lower side near and especially past the trailing edge is very different from free flow and the air has to speed up to flow through the gap left between the airfoil and the tunnel wall.
You also see the smoke lines past the trailing edge fan out: The flow near the center section of the tunnel is still fast and stays near the bottom while the flow near the wall slows down and bends upwards, causing the lines to spread out. The lines near the wall even intersect the ones near the center! Clearly, this is a 3D effect which resembles the wake rollup past a wing in free flow, but crippled by the proximity of the tunnel wall.
While the air coming off a wing in free flight with attached flow has approximately the same speed over the whole height, here tunnel wall blockage means that the air coming off the lower side is much faster than air coming off the upper side. This is necessary to let the air shift downwards past the airfoil, as it does in the wake of a wing. Of course, the tunnel wall and friction will limit that downward movement, but by adjusting flow speed the tunnel airfoil is able to create a downwash, too.
Another way to look at it: The slow, high pressure air coming off the upper side of the airfoil squeezes the fast, low pressure air coming off the lower side down. Either way, downwash is the result.
The downwash is right there and hard to overlook: The streamlines coming off the airfoil clearly have a downward direction. Wake rollup is also happening, albeit near the right edge of the picture and less pronounced than in free flight. If that is not evidence enough, I don't know what ever will be.
The picture has to be sufficient. Sorry, no movie.


Do you say prefix K for airport codes in the US when talking with ATC? I'm a new student, and I see the US airport codes on charts with the K prefix, e.g. KORD for Chicago O'Hare.

I have always seen on commercial flight booking sites, only the last three, letters such as "ORD" are displayed.

Are pilots meant to pronounce the full code or just the letters after the prefix, assuming the K prefix, 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?


Why are the exhaust pipes design on the Ilyushin Il-2 not very popular? This is a piece of this image from Wikipedia

Note the circled region. Movies often show exhaust fumes coming from those pipes when the engine is started. So I assume these are actual exhaust pipes.
This design doesn't appear very often, especially in modern piston engine airplanes. Why is this the case?

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)


What is the typical procedure if an engine fails during a vertical takeoff? My understanding of VTOL aircraft (correct me if I am mistaken) is that the plane accelerates vertically until it's a bit off the ground, at which point the thrust is slowly vectored horizontally, and when it's finished, the plane has enough speed to produce sufficient lift. So, what happens if an engine fails before the plane has enough speed to lift itself? I'm asking about both single and double engine planes, for example the F-35, Harrier Jump Jet, or Yak 36.

F35 and Harrier are both single engined. Both  had a forward fan providing lift through this fan, and in case of Harrier forward nozzles turn aft for thrust. F35 it provided lift only.  Aft nozzles in both types vector to give lift or thrust. In Harrier all nozzles are synchronised,

So silence from the engine means it's time for the black and yellow handle.. If a twin engine e VTOL aircraft where lift is provided by both engines and one has a failure, then again until you transition to sufficient aerodynamic lift you are going down... But also probably rolling away due to non symmetric thust. Look at design of DornierDo31. You can climb I side on at the Deutches  Museum at Oberschleissheim near Munich.( I was Senior Systems Engineer on Harrier, Sea Harrier. )


What does BLU+ mean in a METAR? I know that BLU is military code and means "Ceiling at or above 2,500 feet; Visibility at or above 8,000 meters".

ETSH 241320Z 19007KT 9999 SCT048 SCT160 BKN200 08/03 Q1008 BLU+

ETSH 241220Z 20005KT 9999 FEW050 SCT160 BKN240 08/03 Q1009 BLU+

But what does + at the end signify?

Per the German Meteorological Service, the + means a ceiling 20,000 feet or higher.

  BLU: visibility>=8000m, ceiling 2500 - <20000 ft

  BLU+: visibility>=8000m, ceiling >=20000 ft


How are taxi to and hold instructions given on an airport without taxiways to the runway end? In a smaller airport which still handles large commercial aircraft (i.e. Princess Juliana Int. Airport (TNCM), Robert L. Bradshaw Int. Airport (TKPK), etc.), what are the taxi instructions given? I don't want to just assume that an airliner would be given a taxi and hold short, but that is what I would expect.

Here is a diagram of Bradshaw Airport,

Copyright, Acronautic

Let's say our commercial airliner is taking off from Runway 07. They get a Taxi To and Hold Short instruction preparatory to Cleared To Takeoff. Do they taxi to the end of ramp A and hold short? or do they go all the way to the turn around at the end of 07?

If it's the end of A, what instruction allows then to enter and use the runway as a taxiway?

A is a taxiway, not the ramp. It will have stop bars and signs at the end. Here, the double solid lines are on the taxiway side and must not be crossed without clearance.

If the instruction is hold short, you hold at the end of Alpha.

NB.  An active runway is never a taxiway.  The clearances and instructions are for runways, even when backtracking.

The initial clearance will likely be:

  Taxi via Alpha, hold short runway 07.

Followed by

  Line up runway 07 via backtrack and wait.

Then finally:

  cleared for take-off runway 07

The initial clearance might combine the first 2.

  Taxi via alpha, line up runway 07 via backtrack and wait

Note that the runway designator is always the departure runway so enter 25 and backtrack would not be used.


Do you get separate certificates for CFI and CFII? I passed my CFII checkride the same month my CFI was to expire. So far I have only received a new CFI card in the mail. Shouldn’t I be receiving a card that says CFII on it as well, or should the card I received have read CFII? Are there two separate cards?

No.  Under ratings on the backside of the Flight Instructor certificate, it should say:

FLIGHT INSTRUCTOR

AIRPLANE SINGLE ENGINE, INSTRUMENT AIRPLANE.

This is a CFI, CFII Flight Instructor Certificate, assuming you did your training in the United States under the FAA’s system.

You should see the same ratings on your temp certificate as well.


How to arrive and depart surface class E airspace I fly VFR. I found all the information about the airspaces and I believe I understood everything. What I'm still struggling to find is how to properly arrive and depart surface class E airspace surrounding certain airports. I never practiced that before and non of my instructors ever mentioned how to do that. What I understood from class E descriptions, I have to get authorization to enter surface class E airspace. How to do that? What frequency to use? Where to find it? What exactly should I say? What to expect in reply? Can I do touch an goes there? Is it possible that my request will be declined? Does anybody have a youtube URL showing an example how to do that?

Class E airspace has no requirements for communication when flying VFR. You only have to maintain two-way communication in Class E airspace when flying IFR. All airports where there is an operating control tower requires two-way communication within 4 Nautical Miles of the airport housing the control tower at and below 2500 feet AGL at a minimum, regardless of airspace. You basically treat all airports with an operating control tower like a Class D airport. A, B and C airspace rules are even more strict. You maintain that communication either through radio or light gun signals.

§91.127 Operating on or in the vicinity of an airport in Class E airspace.
(a) Unless otherwise required by part 93 of this chapter or unless otherwise authorized or required by the ATC facility having jurisdiction over the Class E airspace area, each person operating an aircraft on or in the vicinity of an airport in a Class E airspace area must comply with the requirements of §91.126.
(b) Departures. Each pilot of an aircraft must comply with any traffic patterns established for that airport in part 93 of this chapter.
(c) Communications with control towers. Unless otherwise authorized or required by ATC, no person may operate an aircraft to, from, through, or on an airport having an operational control tower unless two-way radio communications are maintained between that aircraft and the control tower. Communications must be established prior to 4 nautical miles from the airport, up to and including 2,500 feet AGL. However, if the aircraft radio fails in flight, the pilot in command may operate that aircraft and land if weather conditions are at or above basic VFR weather minimums, visual contact with the tower is maintained, and a clearance to land is received. If the aircraft radio fails while in flight under IFR, the pilot must comply with §91.185.

§91.126 Operating on or in the vicinity of an airport in Class G airspace.
(a) General. Unless otherwise authorized or required, each person operating an aircraft on or in the vicinity of an airport in a Class G airspace area must comply with the requirements of this section.
(b) Direction of turns. When approaching to land at an airport without an operating control tower in Class G airspace—
(1) Each pilot of an airplane must make all turns of that airplane to the left unless the airport displays approved light signals or visual markings indicating that turns should be made to the right, in which case the pilot must make all turns to the right; and
(2) Each pilot of a helicopter or a powered parachute must avoid the flow of fixed-wing aircraft.
(c) Flap settings. Except when necessary for training or certification, the pilot in command of a civil turbojet-powered aircraft must use, as a final flap setting, the minimum certificated landing flap setting set forth in the approved performance information in the Airplane Flight Manual for the applicable conditions. However, each pilot in command has the final authority and responsibility for the safe operation of the pilot’s airplane, and may use a different flap setting for that airplane if the pilot determines that it is necessary in the interest of safety.
(d) Communications with control towers. Unless otherwise authorized or required by ATC, no person may operate an aircraft to, from, through, or on an airport having an operational control tower unless two-way radio communications are maintained between that aircraft and the control tower. Communications must be established prior to 4 nautical miles from the airport, up to and including 2,500 feet AGL. However, if the aircraft radio fails in flight, the pilot in command may operate that aircraft and land if weather conditions are at or above basic VFR weather minimums, visual contact with the tower is maintained, and a clearance to land is received. If the aircraft radio fails while in flight under IFR, the pilot must comply with §91.185.


What are the effects of different seasons on flight training? What effect will the time of year a student starts their flight training have on the difficulty of their training?

What particular problems will each season cause a student pilot?
What advantages does each season have?
Are there any studies showing how the time of year effects the duration or success rate of training?

Different latitudes will have different, or at least more extreme, effects so please note if an effect is only valid for a specific geographic area.

Pretty much the only thing that is going to change season to season is the weather. Depending on where you are, there may be more aircraft traffic around a particular time of year, but I can't answer that for sure.

Obviously, the further from the equator, the more extreme the seasons. If you are close to the equator, it probably doesn't matter what time of year you start, since the weather is pretty much the same year-round.

If you are not at the equator, you need to consider the pros and cons of each weather season. Additionally, at extremes from the equator (near the poles), summer and winter months have extremely long days and long nights, respectively, which can make night and day flying difficult.

In the winter, the aircraft has better performance (airplanes like colder weather). However:

You have to deal with ice and snow, which is especially dangerous to light airplanes, which are often not as prepared to deal with them. It is dangerous in some degree to all airplanes
You have to be careful of low temperatures when starting the airplane before you take off

In the summer, the aircraft has worse performance (they don't like hot weather).

Many small airplanes have poor airflow inside the cockpit, which means they can get rather hot (it is easier to run a heater inside a small cockpit than cool it)
You have to be more careful to avoid overheating the engine
Some places may form thunderstorms constantly

In the rainy season, which is often in the spring, you will have degraded performance. Even if it is not rainy, the air will likely be more humid, which decreases aircraft performance

Depending on your latitude, other weather conditions may be more prevelant at a certain time of year (hurricanes/cyclones, high winds, tornados, sudden storms). This paper discusses wind differences based on season and latitude. In particular, page 7 of the document shows that summer months had slightly stronger winds at southern latitudes (southern hemisphere), and winter months had significantly stronger winds at northern latitudes. Some geographical areas may have changes in prevailing wind directions, which could also affect training depending on routes and runways too.

TL;DR: It's mainly a weather concern, which can affect your comfort (temperature inside, possibly air turbulence), aircraft performance, as well as grounding weather. Additionally, the most obvious concern is also length of the day - summer months will have more daylight, a particular concern if you can only fly in VFR conditions/do not hold a night rating.


Who legally owns the Flight Data Recorder? Who legally owns the Flight Data Recorder after an aircrash?  Who is responsible for retrieving it and/or allowed to retrieve it?

And how is it decided who carries out the crash investigation?

Who legally owns the Flight Data Recorder after an aircrash?

Whoever owned it before the crash!

I'd guess this might be the aircraft owner (e.g. an airline or a leasing company) or an aircraft operator (e.g. an airline).

Ownership is less important than the obligations imposed by the relevant regulatory authorities, and probably by international treaties and agreements, effective in the area where the FDR is located after an accident.

For relevant discussion see NTSB FDR Handbook

  And how is it decided who carries out the crash investigation?

There are a complicated set of rules agreed internationally. From memory I think it goes something like this:

The government appointed body in whose territory(airspace?) the accident occurred. Or
The government appointed body in whose country the aircraft was registered.

EMSA state

  5.1 The State of Occurrence shall institute an investigation into the circumstances of the accident and be
  responsible for the conduct of the investigation, but it may delegate the whole or any part of the conducting of such
  investigation to another State by mutual arrangement and consent. In any event the State of Occurrence shall use
  every means to facilitate the investigation.

  5.3 When the location of the accident or the serious incident cannot definitely be established as being in the
  territory of any State, the State of Registry shall institute and conduct any necessary investigation of the accident or
  serious incident. However, it may delegate the whole or any part of the investigation to another State by mutual arrangement and consent.

Example 1

  The UK Air Accidents Investigation Branch (AAIB) is part of the Department for Transport and is responsible for the investigation of civil aircraft accidents and serious incidents within the UK and its overseas territories.

Example 2

  The NTSB is an independent Federal agency charged by Congress with investigating every civil aviation accident in the U.S.

Normally an air accident investigation organisation takes the lead role but co-opts experts from the airline, the manufacturer and other air-accident organisations with an interest in the incident or with special expertise. Involvement of interested parties (airline, ATC, manufacturer) obviously has to be handled very carefully to avoid detracting from the independence of the investigation.

Most investigations focus almost exclusively on determining facts and recommending actions to prevent recurrences. They generally are not mainly concerned with assigning blame, that may be the focus of a separate legal inquiry.


What is a "flare-out" and why does auto-thrust reduce thrust during flare-out? The functions of auto-thrust include thrust reduction during a flare-out. What is flare out and why during flare out will the auto-thrust reduce thrust?

The proper term is "flare" not "flare-out".

"Flare" is a term used to describe the act of raising the nose of an aircraft in order to increase lift and stop descending in order to land on a runway smoothly.

Whether the pilot, or Auto Thrust does it, a reduction of power to idle is needed in order to bleed off the excess speed that is used during the approach phase.  If the thrust is not reduced to idle, the aircraft will take longer to land, and use up more runway.

If you don't flare enough, the rate of descent will be too high and the aircraft will land hard.

Too much flare will make the aircraft climb back up.


How to extract the interrogator ID from a DF11 message? I've written a class which decodes raw Mode S messages.  Whilst browsing the ICAO specs the other day I noticed that the Interrogator ID is sent back in the DF11 message.

I thought that it would be a fun exercise to determine where in my coverage area interrogations from particular radar installations can be seen.

But I'm having a really hard time figuring out how to extract the interrogator ID.

For this DF11 message:

5D406FDB0D62DD

I've got the following:

Binary: 01011101010000000110111111011011000011010110001011011101
Integer Words:
    [0] => 93
    [1] => 64
    [2] => 111
    [3] => 219
    [4] => 13
    [5] => 98
    [6] => 221

 CA: 5
 AA: 4222939
 Address: 406FDB
 Parity: 255
 Residual: 0

As the Residual value is 0 I know that this is a valid DF11 message and the address checks out as well.

From the ICAO spec:

"The code used in downlink PI field generation shall be formed by a sequence of 24 bits (a1, a2,..., a24), where the first 17 bits are ZEROs, the next three bits are a replica of the code label (CL) field (3.1.2.5.2.1.3) and the last four bits are a replica of the interrogator code (IC) field (3.1.2.5.2.1.2)."

In that case I would expect the end of the last three integer words (4,5 and 6) to be mostly 0's but they aren't.

I've gone through the documentation numerous times but just can't see how to get the II and SL codes out of Parity value ?

I'm calculating the Parity value by doing the following:

$this->_pi = $this->_int[4] | $this->_int[5] | $this->_int[6];

where | in PHP is the OR operator.  Is this my mistake ?

Your calculation of $this->_pi just ORs the three parity bytes together,
which certainly doesn't make any sense.  I'm not sure what you hope to get out of that. Even XORing them together wouldn't seem to serve any purpose.

Addressing and checksumming in the Mode S protocol work in a funky way, in order to save bits. The last 3 bytes of a message are constructed as a CRC checksum (which Annex 10 calls "parity") of the first 4/11 bytes, XORed with an address for the "conversation" the message is part of. When you receive a message you're supposed to calculate the raw CRC on your own and then XOR it out of the bytes. What is left is the address, and by comparing it to addresses you're interested in you can see if the message was for you, or alternatively either garbled or for someone else.

In the basic Mode S interrogation protocol, this "address" is just the airframe address, and the checksum-xor-address field is named AP.  For uplink messages, transponders know what their own address are, of course -- and for downlink, radars know which addresses they have interrogated recently.

In a few other cases, the "address" is the "interrogator identifier", and the checksum-xor-address field is named PI.

For DF11, the transponder knows which II to put into its replies because it gets them out of the all-call message, and the radar knows which II corresponds to its own all-calls, so it can recognize those responses.

Finally, in squitter where the transponder sends a downlink message without being prompted by an uplink message, it sets the "address" to 0.

If you have been decoding ADS-B broadcasts, you're listening for squitter -- so you can identify them as the ones where the CRC you compute equals the PI field in the message (because XORing 0 into the CRC doesn't change it). Everything with a different address will look like checksum failures to your code.

Since the DF11 message you're showing does match the cheksum, it must be DF11 squitter. There are plenty of those to hear; TCAS depends on everyone sending them continually.

In order to find DF11 messages with a nonzero interrogator identifier you should look for messages where the last three bytes after you've XORed out the CRC do begin with 17 zeros but then have at least some of the remaining 7 bits nonzero.


How did the AAIB assist in locating MH370? I saw on news that the AAIB helped to locate the missing MH370 flight, saying that it ended up in Indian Ocean, with the help of a whole new technology.

I was wondering what kind of "new technology" it was?

The following statement has just been released today by the Prime Minister of Malaysia, in relation to the AAIB:

This evening I was briefed by representatives from the UK Air Accidents Investigation Branch (AAIB). They informed me that Inmarsat, the UK company that provided the satellite data which indicated the northern and southern corridors, has been performing further calculations on the data. Using a type of analysis never before used in an investigation of this sort, they have been able to shed more light on MH370's flight path.
Based on their new analysis, Inmarsat and the AAIB have concluded that MH370 flew along the southern corridor, and that its last position was in the middle of the Indian Ocean, west of Perth.
This is a remote location, far from any possible landing sites. It is therefore with deep sadness and regret that I must inform you that, according to this new data, flight MH370 ended in the southern Indian Ocean.
We will be holding a press conference tomorrow with further details. In the meantime, we wanted to inform you of this new development at the earliest opportunity. We share this information out of a commitment to openness and respect for the families, two principles which have guided this investigation.
Malaysia Airlines have already spoken to the families of the passengers and crew to inform them of this development. For them, the past few weeks have been heartbreaking; I know this news must be harder still. I urge the media to respect their privacy, and to allow them the space they need at this difficult time.

It's not a "new technology" per se, but a new form of analysis. You might have heard recently that the aircraft responded to hourly "pings" from a satellite:

British satellite company Inmarsat immediately began doing calculations based on a series of hourly "pings," as the plane and one of the company's satellites tried to communicate with each other.
Triangulating those pings seems to have given Inmarsat a pretty good idea of where the plane went, along one of two routes, to the north and to the south.

Here is some further information:

About three hours after Flight MH370 went missing, Inmarsat, a British-based satellite company, began tracking the Boeing 777 through an on-board data system called Aero Classic. Every hour, Inmarsat's satellites would try to communicate with the aircraft, pinging it with a computerized question asking, in effect, "Are you there?"
For several hours, Flight MH370 responded "Yes, I am," notifying engineers on the ground with a so-called handshake that the plane was still powered up.
Using that series of pings, Inmarsat engineers and other analysts were able to piece together two broad, arcing regions where the plane could have been located when it last communicated with the satellite.
"Our engineers looked at the time between the handshakes, and they realized that the object wasn't stationary under a satellite but moving away from it," Christopher McLaughlin, senior vice president of Inmarsat, said Thursday. "Over time, the engineers here recognized that there were a number of data points and that it had flown for several hours. We didn’t know if it was on the northern or southern corridor."

More information on how Inmarsat determined MH370 flew along the Southern corridor specifically, will likely be released tomorrow at the press conference (as mentioned in Najib Razak's statement), which I gather is the information you're looking for.


High altitude turbine efficiency question The simple reason turbine engines are more efficient at high altitudes is because as the air becomes less dense it requires less fuel as the ratio has to remain constant.  This holds true up to isothermal temperature which is usually at 40,000 feet.  The turbine compresses the colder air with less fuel required and you have a much lower fuel burn.

This isn't true. Less dense air at higher altitudes means less oxygen to burn with the fuel. Less burn means less thrust. In the limit of no oxygen, there is no burn, and no thrust at all.


Why do certain aircraft's landing gear tilt up? Why do the main landing gears of aircraft like the A330, 777, 787, etc tilt up? This does not happen with the 767. Interestingly, for the 747, the inner landing gear does not tilt up while the outer landing gear (under the wing) does. Why does that happen?

Pulling mostly from the answers provided here it seems that

The torque produced by the straightening gear helps to flatten the plane out.
The main gear tilt on the B747 also provides air/ground sensing. All four main gear bogeys tilt when the aircraft is airborne, so on touchdown any systems relying on air/ground logic can activate
The gear is tilted to fit into the wheel well

You can check the link for the rest of the explanations.


Can regular emergency exits not work after crashlanding? Live accounts of survivors of Bangla Air 211 mention getting out after breaking windows but not out of the emergency exits.

My question is can regular airline exits not work in such cases?

All regular exits are generally used in an emergency. This information would be included on the safety card and in the briefing by the crew before the flight.

Of course, during a crash, structure can deform and exits can become blocked. Regulations require evacuation within time limits using only half of the available exits. This must be demonstrated to be possible.

Here is a Q400 safety card, showing that two forward and two aft exits are used for evacuation. The forward right exit (called R1) is an emergency exit.

Source


For a 180 degree turn after takeoff, what is the normal turn radius for the A320 and 737? I'm looking for some rule-of-thumb guidance on this matter. It relates to route 4, the westerly take off from London Gatwick (LGW).

While in theory possibly a duplicate of the other question, and while the physics are very well explained there, the numbers to be used for takeoff and landing aren’t given in the other thread.

The following works as a rule of thumb for most commercial airliners: Maximum bank angle after takeoff with all engines would be around 25 degrees, with a failed engine it would be around 15 degrees until minimum clean speed is reached and the flaps are up and 25 degrees after that.

True air speed shortly after takeoff shouldn’t be much above 200 knots for most weights, airfield elevations and temperatures encountered except in extreme circumstances.

Plugging both these into the formula for turn radius explained elsewhere gives just above 2300m radius on all engines, and just above 4000m radius with a failed engine and before cleanup.

Brief answer, but I hope it helps!


What's the mechanical 'whoosh, whoosh' sound in this video? Sound in question comes right after the warning sound at 22:57.

It's the sound of the trim wheel rotating on the center console of the Boeing 737.

The trim wheel controls elevator trim. It can either be moved automatically by the autopilot, or manually by the pilot. The pilot can push the trim button on the yoke with their thumb (left for the captain, right for the copilot).

This is a photo of a B737 classic series, but this feature is unchanged on the NG series.

In this specific instance, it sounds like there were two small manual push on the trim button.


What is the average temperature in the luggage hold of a passenger plane? I am asking this seemingly odd question, as we'll have to transport some medicine in our luggage and it's supposed to be stored at temperatures between -8C and +2C. I'm not sure, if airport security will allow this to pass if this is in a cooling box as hand-luggage, although, in my opinion there shouldn't be a problem, as the ampules are 4 x 1 ml and I have a prescription (however, the cooling box will probably be treated as partially liquid containing).

Your advice will be much appreciated!

According to an A320 pilot quoted in this question on travel.SE (and see this one too), the temperature can be 7C at the low end but potentially above 18C if animals are being transported. Therefore, if you want to transport something in the hold that needs to be kept at a specific temperature range you would need to check with the airline about how to do that.


Why didn't Philippine Airlines Flight 113 dump fuel prior to forced landing? Philippine Airlines Flight 113 operated by a Boeing 777 bound for Manila suffered a compressor stall and engine fire.

I wonder why the pilot didn't dump fuel from the left-side prior to the landing to meet the maximum landing mass (MLM) required and to avoid damaging the undercarriage as seen in pictures?

I assume that, when I have an engine fire, I shut it down and crank the remaining fuel residual until it is put out. Any idea?

If you had an engine fire, even though it may be "out", you want your airplane on the ground as soon as you possibly can.  You don't know what structural damage is lurking as a result of the fire.  Dumping fuel would take a fair amount time to get rid of any significant amount.

So it's "Screw the landing gear.  We're landing overweight".


Why do airplanes start descending when we initiate a left turn? Today I watched a video about the Fly-by-Wire (FBW) system (see below) and at 3:20 there is a left turn initiated in a Cessna 152. Then it is shown that with a left turn (only by ailerons), in aircraft with a mechanical flight control system, it will start a descend (and a slip).
I understand why the aircraft starts flying a slipping turn, but I don't understand why it start descending. Because gyroscopic effect would make the aircraft to pitch up in a left turn.
It is also said that each aircraft with mechanical flight control system, either little Cessna or Boeing 737, will have that tendency. Can somebody explain that descending tendency?
My guess is that the turn is initiated without power increase, so to stay with the same indicated airspeed the aircraft must be pitched down, but I'm not sure of that.

This is because when you roll left (or right), the lift changes from pushing up to pushing up + left. This is what makes you turn. Since some of that lift is being used to the left, not as much is pushing up, causing the plane to lose a bit of altitude. On FlyByWire aircraft, since it is computer controlled, the computer automatically compensates for this by adjusting elevators to pitch up slightly.


Where can I find a catalogue or lists of realtime, streaming (major) airport cameras? I ask in the spirit of aircraft spotting and would also prefer those with live ATC feeds, like Osaka. As of now, the visual quality is blurry and hazy, but perhaps this is due to low visibility and bad weather?

On the side panel of that, I clicked on another for Narita, but this one doesn't capture the (active) runways.

Is there an efficacious, systematic method to find all such webcams for substantive airports worldwide? Do such manifests or records already exist? I tried a forum thread on FlightRadar24 which cites airportwebcams.net, but these are NOT streaming and realtime.

I don't have a website link with a list, but we can create a collaborative Community Wiki with all the webcams everyone knows — feel free to edit this answer to add any you know!

Americas

Brazil

FLN/SBFL - Hercílio Luz/Florianopolis
NVT/SBNF - Navegantes

Canada

NavCanada Weather Webcams (only available at some airports, updated every 10 minutes)

Chile

All airports and aerodromes

Europe

Germany

DUS/EDDL - Düsseldorf
CGN/EDDK - Cologne Bonn/Köln-Bonn


What airfoil is used on the MQ-1B Predator's wing? There are lot of UAV's in todays world to be re worked on. The General Atomics series of UCAVs is quite remarkable. I have selected MQ-1B Predator UAV, for an geometric analysis project(undergraduate).
Though the wing dimensions including root and tip chord's length are found at https://mq-1predator.weebly.com/design-and-specifications.html and the rest performance specifications for it is available at https://www.af.mil/About-Us/Fact-Sheets/Display/Article/104469/mq-1b-predator/.
Still it isn't mentioned anywhere at websites and in factsheet too, about its "Airfoil profile".
I have been trying to figure it out.
Can anyone please help me out to ascertain MQ-1B's airfoil profile?

The MQ-1B uses three different airfoils: Drela GW-19, GW-25 and GW-27, created by Dr. Mark Drela (one of the creators of the XFOIL software) and proprietary to General Atomics.

The airfoils used on the MQ-1B (Drela GW-19, GW-25, GW-27, created by Dr. Mark Drela) are proprietary material of General Atomics. Dr. Drela personally stated on a hobbyist remote-control drone forum that a scale model should use an SD7032 wing (similar shape to a NACA 3510), while the full-scale MQ-1B airfoils "...have LOTS of top surface camber."

"Fixed-Wing UAV Airframe Design and Validation", Bachelor's Thesis of Timothy Brown, University of Queensland


Why are Krueger flaps called flaps and not slats? I always thought that flaps are trailing edge high lift devices and slats are leading edge high lift devices. This is also confirmed by the accepted answer for What is the difference between flaps and slats?.

Inspired by this question, I learned that Krueger flaps are actually leading edge devices, despite being named flaps. The definition on SKYbrary is:

  Krueger flaps are high lift devices that are fitted to all or part of the leading edge of the wings of some aircraft types. The aerodynamic effect of Krueger flaps is similar to that of slats; however, they are deployed differently. Krueger flaps are mounted on the bottom surface of the wing and are hinged at their leading edges. Actuators extend the flap down and forwards from the under surface of the wing thus increasing the wing camber which, in turn, increases lift.

(image sources: Wikimedia and SKYbrary)

I understand that the deployment mechanism is different, but the Krueger flaps are still deployed differently than other (trailing edge) flaps:

(image source: SKYbrary)

So why are they called flaps and not Krueger slats instead?

A flap increases airfoil camber, and can be on the leading edge or trailing edge.  The Krueger Flap is a Leading Edge Flap, the actual generic term.

The Krueger dude developed the LE flap used on some airliners so his name is attached.

A slot increases stalling AOA, without necessarily increasing camber, as in the fixed slots used on a lot of light aircraft in the 40s to improve aileron control at the stall instead of wing washout, like Stinsons and Globe Swifts, etc.

Combine the slot function of injecting slightly higher velocity air along the top to keep flow attached at higher AOA, and the flap function of increasing wing chord, together on the leading edge, and you get SLAT.

Or you could say more correctly, Slotted Leading Edge Flap.

Without the slot part though, it's just a flap, as in Krueger Flap.


Can a passenger realistically replace suddenly incapacitated pilots? Yes, this is a question from the movies. Assume that the plane is in flight and in perfect mechanical conditions. However, all the pilots onboard are suddenly incapacitated.

Can a passenger without any previous flight experience realistically save the plane and take it to a safe landing only by remote radio help?

I guess this is a secret dream of many of you here: You sit on a scheduled flight, and hear in the PA system: "Both our pilots just passed out. Any volunteers to take over their duties?"

Won't happen.

Think of what would happen next: Panic! The volunteers won't even make it to the cockpit. All cabin crew are focussed to keep the cabin calm, so this announcement will never be made.

Instead, one of the cabin crew will take over. That is part of their duties, actually, and some airlines even give them basic training so they have a fair chance when they are in contact with someone on the ground who can talk them through all steps.

Edit: Thanks to some commenters for pointing out that the question also includes GA traffic. Yes, I did not cover this. Generally, I think a passenger should have an easier time to take over, when he/she is sitting already in the right seat. He/she could watch the pilot before and has a full set of controls available. GA planes move much more slowly, so things happen at a slower pace and much less kinetic energy is involved if the touchdown is not perfect. Much depends on the constitution of the new pilot: Some people will simply panic and not be able to follow even the best remote help. But if they keep their cool, a good landing (meaning one you can walk away from) should be possible.

I had been in the right seat of a Lancair once and the pilot turned the plane over to me on final. The Lancair was so sensitive in pitch that I porpoised the aircraft - I first had to get adjusted. So even a pilot in a new type might not be able to land it immediately when he gets to fly it first time on short final!


What is the difference between Cloud Ceiling and Cloud Base? By definition, Cloud ceiling is The height above the ground or water of the base of the lowest layer of cloud below 6000 meters (20,000 feet) covering more than half the sky.
So does, Cloud Ceiling become Cloud base if it is covering less than half of the sky.
Thank you for your time.

They are not the same thing.  Cloud base is simply the bottom "surface" level of the a cloud regardless of the sky coverage.  Where cloud coverage constitutes a ceiling, then the cloud base would be the same as the ceiling, but regardless, the bottom margin of any cloud is its base.


Why does the Trent XWB have intermediate compressor stages? I realized that the Rolls-Royce Trent XWB on the Airbus A350 has intermediate compressor stages. Why is that?

Other engines like the CFM56 or IAE V2500 that power most of the A320-family have low pressure compressor stages (including the fan), and not intermediate ones. And the Trent XWB doesn't have a low pressure compressor. Unless the fan counts as one.

Is the low pressure compressor just the fan on the A350 and they don't call it a fan?

Jet engine designers have to find compromises all the time, and the one that counts here is between lower complexity and higher efficiency.

In the 1960s, Rolls-Royce fell behind in large commercial jet engines as competitors introduced large bypass ratio fans such as the GE CF6 and the P&W JT9D, which powered the new generation of wide body jets being introduced at that time. All efforts on the British side came to nought, partially for lack of funding (source: Wikipedia):

  The company [Rolls-Royce] went ahead with the project and under the
  leadership of (Adrian) Lombard built the twin spool demonstrator.
  Overall development costs of the RB.178 was £2.6 million. As a
  comparison, the G.E. and P&W companies were awarded nearly $20 million
  by the U.S. DoD ( Department of Defense) to develop and build the TF39
  and STF200 technology demonstrators.

or for the preference of US aircraft manufacturers for US engines. Wikipedia again:

  There are perhaps many reasons why the RB.178 failed to take off and
  chief among them was the refusal of Boeing to accept the Rolls-Royce
  engine on the transatlantic 747.

Rolls-Royce realised that they had no chance to catch up by designing yet another two-spool fan and risked the company on a three-spool design, which would later become the RB 211. Wikipedia again:

  Meanwhile, Rolls-Royce was also working on a series of triple-spool
  designs as replacements for the Conway, which promised to deliver
  higher efficiencies. In this configuration, three groups of turbines
  spin three separate concentric shafts to power three sections of the
  compressor area running at different speeds. In addition to allowing
  each stage of the compressor to run at its optimal speed, the
  triple-spool design is also more compact and rigid, although more
  complex to build and maintain.

The advantages of using three spools is that the speed of each stage can be more finely optimized, so each stage operates at a higher efficiency. Another promised advantage was the use of carbon fiber for the first stage fan, which allowed considerable weight savings and offered Lockheed a distinct advantage in its L-1011 TriStar over the very similar Douglas DC-10.

However, the carbon fiber fan failed the bird strike test and the engine did not meet its development targets. In the end, Rolls-Royce had to be taken over by the British government and the TriStar entered the market with a one-year delay. But the RB211 went into production, albeit with a delay. The gamble did not pay off commercially, but technically it placed Rolls-Royce instantly ahead of its competitors. When a higher-performance version of the RB211 was added as an engine option to the Boeing 747, the direct comparison with the two-spool designs made the efficiency gains of the three-spool design obvious. FlightGlobal reported in 1980:

  The importance placed on fuel saving by airlines is emphasised by
  Qantas' adoption of RB.211-524 power for its new Boeing 747s - the
  only aircraft on which all big three fans are available. Qantas found
  that British Airways' Boeing 747s fitted with RB.211s burnt roughly 7
  per cent less fuel than its JT9D-equipped fleet, a saving of about $1
  million a year at today's prices.

The second oil crisis in 1979-1980 made those efficiency gains very relevant to the airline industry. But the three-spool design offers another advantage: By tailoring the number of stages and their diameter to the desired performance, the same basic design allowed Rolls-Royce to cover a much wider thrust spectrum with one basic engine design. The RR Trent is a direct development of the RB211 and covers a thrust range from 240 to 430 kN without compromising on efficiency. This enables Rolls-Royce to adapt the engine optimally to stretched or shortened versions of most airliners, so it is in an ideal position to offer the most efficient engine for the job. In fact, the successful development of a three-spool fan engine in combination with a better business model helped Rolls-Royce to gain an overall market share of 40%. Wikipedia again:

  Sales of the Trent family of engines have made Rolls-Royce the second
  biggest supplier of large civil turbofans after General Electric,
  relegating rival Pratt & Whitney to third position.

That is the reason for the intermediate compressor on the A350: It helps to give it the most efficient engine for the lowest development cost and risk. And yes, the fan is all what is left of the low pressure compressor stage on the Trent 1000. This way it can be run at a lower speed while the intermediate compressor can be built smaller since it runs at a higher speed.


Why does the Las Vegas Airport have three control towers? Why does the Las Vegas Airport have three control towers? I just noticed, and I find it a little weird. There should only be one... Does anybody know details on how this came about? And how they work like that?

EDIT: Not a duplicate, the question is specific to Las Vegas Airport, the other question is about another airport.

One of those is the old tower, built in 1983, and scheduled for demolition.
(in the bottom left of the picture)

The location and height of the old tower created blind spots, which were covered by the much shorter ground control tower attached to the D Gates. (upper right of the picture)

The new tower is in a better location, and tall enough that it doesn't have blind spots.  I couldn't find a reference to if the D-Gate mini-tower will continue, or be demolished.


Why is a turbofan engine less efficient when air leaks over fan blade tips? Image source

I understand part of the reasoning for minimal clearance between the casing and the fan blades, is to have the larger fan blade possible, which generates a larger low pressure area to increase air intake.

However I don't understand why, if leaking occurred, it would reduce the overall efficiency.

If it was to leak, it's still going through the intake to the compressor or bypass duct.

If it was to leak, it's still going through the intake to the compressor or bypass duct.

This is incorrect. A "leak" would cause the compressed air to circle around the fan and exit again from the front, reducing the efficiency of the fan, because part of the power would be used to compress air that does not do any useful work in the engine.

The circling around is a consequence of the work the fan itself does: after the fan the air is at a higher pressure than the air in front of the fan, this means that the air outside is pushed back by the air inside, and if there is a leak, the higher pressure air (inside) leaks out from the front.

Minimizing this "leak" helps maximising the efficiency of the fan, and of the engine as a consequence.


Are the IMU velocities equivalent to the GPS ground velocity, except for the coordinate reference system? If the velocities measured by the IMU in the body-fixed reference frame are converted into earth fixed frame, are they equivalent to the ground velocity measured using the GPS?

An IMU uses gyro and accelerometer measurements to calculate its velocity vector relative to the Earth.   Similarly, a GPS uses range, range-rate, doppler, and/or carrier phase shift measurements to several satellites to calculate the same velocity vector.  So, an IMU and a GPS calculate the same velocity vector, but use different measurements.

The difference between the IMU and GPS measurements are that, inherently, an IMU has very good short-term accuracy but drifts over longer periods of time;  a GPS has very good long-term accuracy, but is very noisy over short periods of time. Therefore, IMU and GPS measurements are usually combined to provide a navigation solution that is accurate over both the short-term and the long-term.

The components of the velocity vector are usually given in a local-level, local-north reference frame; for example, the north- east, and down components: $v_N$, $v_E$, $v_D$. The ground speed is $v_H=\sqrt{v^2_N+v^2_E}$.


What are the major hazards in operating a PT6 Turbine Engine? I am just in the process of doing a bit of study in the hope of doing my Basic Gas Turbine Endorsement in the next few months, and just wanted some feedback/comments/discussion on the major hazards associated with starting, managing and shutting down a PT6 Turbine Engine (PT6 as it is the most common used Turbine Engine on an aircraft I will touch for this endorsement).

Mainly, what I am looking at is during the start - If the EGT raises above the evil 700* mark, what is the best course of action to prevent "melting the turbine"?

During Climb/Cruise Operation - What are the most common failures, and their indications?

Maintenance/Shutdown - What are the most common methods of recording Cycles? By landing or by Start/Shutdowns?

You MUST NOT allow the EGT or ITT (whichever is applicable) temperature limit to be exceeded in any turbine engine. If it gets close to occurring during start on a PT-6, you need to abort the start by stopping fuel flow into the engine, then conduct the appropriate checklist for an aborted start. Unlike the Honeywell / Garrett TPE single-shaft engines, the PT-6 normally won't get close to the temperature limit on start. The Garretts I used to fly in Metroliners had to get right next to redline and stay there on every start. One reason that PT-6 engines are so much more relaxing to fly.
On takeoff / climb, just don't exceed the maximum temp limit; regulate the power lever(s) to keep below it. I've never had a failure of a Pratt except for bleed air leaks.
Airlines count cycles as a start, flight, and shutdown. If one of these did not occur, you did not have a cycle.


Have any operational aircraft ever used over wing fuel tanks? We are most familiar with under wing fuel tanks, has any operational aircraft ever used over wing fuel tanks?

Early aircraft designs used gravity feed to supply the engines with fuel. All those designs had their tanks located above the wing, and in biplanes in the center of the upper wing. The picture below (source) shows an Etrich Taube with the cylindric fuel tank mounted above the fuselage.

The next application of overwing tanks were "Doppelreiter" fuel tanks (slipper fuel tanks) which were used on some German fighter airplanes in WW II. They were mounted above and behind the wing, and to everyone's surprise they had little impact on the top speed of the airplanes, and in case of the Me-309 helped to increase it slightly. They were the first practical application of Küchemann carrots and worked much like the flap track fairings of today's airliners.

FW-190 A with Doppelreiter tanks.


How does a flex takeoff increase fuel consumption compared to a TOGA takeoff? I read this also in the FCTM green operating procedures that doing a flex takeoff increases fuel consumption as we have a longer takeoff phase

Fuel consumption for the flight will be slightly higher when carrying out a reduced thrust takeoff.

Simply put, the flight is operated at lower, less efficient altitudes for a tiny fraction longer, so less time is spent at more efficient altitudes. It’s a rather small amount, but nonetheless measurable.

From Airbus‘ Getting to Grips with Fuel Economy:

  Compared to a full thrust take-off, flex thrust will generally increase fuel burn. The increased time at low level offsets the slight reduction in fuel flow induced by the lower thrust.

The source goes on to list typical fuel burn increases, e.g. for an A320 it’s 1kg (!) when taking off in CONF 1+F and 5kg in CONF 2.


How do planes maintain constant speeds at cruise altitudes? I'm a noob so pardon my ignorance. So my understanding is that as the plane gets lighter during the flight, its mass reduces therefore reducing the lift needed to maintain the altitude. At those altitudes and speeds, my understanding is that we can't engage slats or flaps. As a result, we would have to reduce thrust to reduce the lift to account for the loss in fuel and maintain the same flight level

So what can one use to continually reduce lift coefficient at those altitudes to maintain constant airspeed and flight levels? I understand that ATC also clear aircraft to higher FL thereby reducing the air density and therefor reducing lift and enabling higher airspeed but that still leaves us with the problem of flying at constant airspeed at cruise altitudes.

The autopilot pitches to hold the flight level when it captures the level at the top of the climb, so later on as the aircraft gets lighter and wants to climb further, the A/P will lower the nose as required to hold the flight level (the A/P is able to move the elevator through its servo's link to the elevator controls; it can also work the trim if the servo has to hold too much out-of-trim force for too long, to avoid wearing out the servo - in effect it does what the human pilot does, more or less).  It happens very slowly and significant amount of pitch over is not apparent until some time has passed.

Effectively, AOA is being reduced by the A/P to compensate for the reduction in wing loading.  Because induced drag is being reduced, if thrust is not reduced to compensate for the drag reduction, the A/C will accelerate.  If your clearance requires you to maintain a certain Mach #, this is a problem.

If the jet has an autothrottle system that can be configured to hold a Mach # while the A/P holds the altitude, the thrust is adjusted automatically.  If not, the pilot monitoring at some point will notice the Mach # creeping up, and will reduce thrust in very small increments compensate and maintain the flight planned/cleared Mach #.


Is there a limit to a subsonic ramjet's pressure ratio? Subsonic ramjets have high specific fuel consumption. This indicates to me they must have a low pressure ratio.
Is there a limit to how high pressure ratio one can achieve with subsonic air? Why can't you just increase the area ratio between inlet and the diffuser exit?

Yes, they have a limit at around 2. And this can only be achieved at Mach 1, as Peter Kampf points out. Increasing the inlet to diffuser area ratio to extreme values will just lead to your engine being filled with slow moving air. The mass and volume of air in your engine will increase, but neither the pressure nor the rate of airflow will increase appreciably


How much of an airline's costs are labor costs? What percentage of a commercial airline's costs are labor costs? Can an airline run a low-cost operation without reducing the wages for crew and pilots, or subjecting them to long shifts? E.g. Southwest has a history of paying good wages; also personnel is unionized there.

Are there other ways that an airline can reduce costs? Simplified fleets, aircraft utilization, good revenue management, come to mind.

(Source) Direct Operating Costs

  What percentage of a commercial airline's costs are labor costs?

By labor I believe you mean flight- and cabin-crew, the percentage is roughly 12%.

  Can an airline run a low-cost operation without reducing the wages for crew and pilots, or subjecting them to long shifts?

Yes, but they won't make money. What Low Cost Carriers do is save in everything by making sure each expenditure runs more efficiently, so they can offer cheap tickets, which in turn enables them to fill all the seats.

Examples for saving:

Single-type fleet greatly reduces maintenance cost, which is 15% of an airline's operating costs.
Fuel hedging removes the risk of fuel price hikes, but when oil is cheap, it's offset by having to pay more.


Why are planes slower at higher altitudes? On many flight simulators, I have noticed that planes tends to get slower with increasing altitude. For example, I can reach 1100 knots just above the sea level in Google Earth flight simulator(F16), but only about 400 knots at 11km with the same plane.

This is because what you are looking at is the IAS indicator (Indicated Air Speed).
This represents the amount of relative air which flows over and under the wings of the plane. This is what creates lift and enables the plane to fly. This is why this instrument is so important and belongs to the primary flight instruments.

This is not to be confused with GS (Ground Speed), which can be sensed by IRS (Intertial Reference System), or by the GPS. Ground Speed is not relevant to pilot an aircraft, but it's still useful for example to determine the ETA (Estimated Time of Arrival), and for fuel estimation during flight.

The IAS indicator indicates a lower speed because the more you climb, the less air there is. So even the air flows faster, the global pressure feeling is lower.

So, actually planes are not slower at higher altitudes. They are faster (at least most planes whose flight envelope force them to fly faster when they are higher, otherwise they would stall, because they would have to increase their Angle of Attack too much to counterbalance the lack of air flowing above and under the wings). But when they reach their target Mach speed, their speed will decrease slowly as the outside air temperature is decreasing until end of climb.

Sorry for the picture being in French... But as you can see, the flight envelope of an airliner forces him to actually fly faster as it is climbing.

Different speeds

There are different speeds on an aircraft, and it can be quite confusing.

IAS (Indicated Airspeed) is what the instruments directly sense. It is computed by subtracting the static pressure (static ports are placed on the fuselage, vertically to relative airflow) from the total pressure (pitot tubes are placed parallel to relative airflow. This gives a measured dynamic pressure which is then displayed in knots, km/h or mp/h. This speed is showed on most general aviation aircrafts as the main speed indication (but it's actually not a speed and more a 'pressure of air feeling').
CAS (Calibrated Airspeed) is the same as IAS, but without instrument errors. It gives a speed related to the real dynamic pressure felt by the aircraft. This speed is showed on most airliners as the main speed indication (for pilot and autopilot).
TAS (True Airspeed) is the same as CAS when at 15°C, 0% humidity, 1013,25 hPa (29.92 inHg) (ISA, International Standard Atmosphere). This time it is literally the air speed (speed of the air): it is the real speed at which the relative air flows around the aircraft. It takes into account the fact that air density is not always the same. This speed is used when measuring or referring to an aircraft performance during cruise for example. It is also used during flight planning before the wind has been taken into account.
GS (Ground Speed) is the speed of the aircraft relative to the surface of the Earth (the equivalent of the speed showed in a car). In an airplane, we cannot use wheel speed to measure it because we are in the air, so we need GPS or IRS to do this. If there is no wind outside, TAS and GS are the same. If there is 30kt tailwind, GS is 30kt higher than TAS. This speed is used to know when you will arrive at your destination airport, and to know if you will have enough fuel (because the wind is taken into account). This speed is also used when the aircraft is on the ground (when taxiing, or more generally at low speeds when wheels are on the ground). Airlines or airports fix speed limitations when taxiing. The only way to know if you respect the limits is to look at the Ground Speed. Also, the airspeed indicator usually won't be active below a certain speed (45KIAS for the B737).

So, why is the primary airspeed indication (IAS or CAS) the wrong speed (not actual speed) of the air flowing around the aircraft?
This is because this wrong airspeed represents actually the real pressure feeling around the wings that is responsible for the lift. It is this parameter that we need as pilot and it is used in aircraft manuals to describe the V-speeds. It's perfect that IAS and CAS are not corrected with altitude and temperature, because if we know that our airplane stalls at 120kts for example, we won't need to care about altitude or temperature. Our airplane will stall at that same speed regardless of altitude and temperature. If we would use TAS, stall speed would be constantly changing and it would be more difficult to keep the aircraft in good and safe flying conditions.

Here is where you can find these speeds in the Boeing 737 NG cockpit:


What runway length and width is needed to land a G650 and take off? How long and how wide should the runway be to take off or land a Gulfstream 650 on private ranch property?

75-foot wide runway, and since you'll need to takeoff after landing, the takeoff distance at maximum takeoff weight at sea level is 5,858 feet.

Sources:

G650 spec sheet
Rocky Mountain Metropolitan Airport Facility Requirements


How do internally carried IR missiles acquire a lock? On aircraft that carry their IR missiles on external stores, like the F/A-18, an IR-missile acquires a lock by having its seeker being directed to the target heat source by whatever means and the missile then locking on the the heat contrast with its own seeker. The missile only gets fired once the seeker has a positive lock.

How would this work in an aircraft that carries its IR-missiles internally?

Would the weapons bay doors have to be open to let the missile acquire a target with its own seeker or would the missile just be given an approximate position where to search and it would then acquire a lock on its own once it's out of the weapons bay?

If you are referring to the Sidewinder missile, the first iteration AIM-9X did not have a requirement to be launched from internal stores, known as captive carry, but in testing it demonstrated that it could lock on after launch. This was deemed interesting enough that Raytheon got a contract for the Block II variant, which among other things adds a datalink capability so that an aircraft with the right equipment can direct the missile to where the target is located, after which it locks on with the IR sensor. This allows it to be used on the F-35, F-22 and even submarine platforms.$^1$

Block III has the same datalink capability (derived from tech developed for the AMRAAM missile) but also has increased range and an insensitive warhead that reduces possibility of accidental detonation on the ground, among other things.

A big reason why the AIM-9 series continues to be upgraded is because of its IR capability. Some countries have developed jamming technology that can interfere with the more modern AIM-120's radar tracking system.

$^1$: Raytheon AIM-9X Block II Missile Completes First Captive Carry Flight, spacewar.com, 2008


How dangerous can it be if something falls from a flying aircraft? How dangerous can it be if something falls from a flying aircraft?

The standard operating procedures state that before every flight, a thorough pre-flight inspection should be performed. Depending on the aircraft, minute and tiny details are not even omitted.

Things do not normally and occasionally fall off from a flying airplane, the same way as different objects do not fall from a driving car, although the pre-drive inspection of a car is no where nearly as comprehensive as the pre-flight inspection. Yet, how many times we have seen a bumper, guard, muffler or rear-view mirrors falling off?

How dangerous it would be when it happens? This depends on the part which has fallen. Some parts are not noticeable until landing or next inspection and some can cause disasters.

Baltimore Sun reports this:

  No deaths or injuries have been reported in such incidents, but the
  Federal Aviation Administration is not even 100 percent certain of
  that.

The proper term for this incident is Things Falling Off Aircraft (TFOA). The pilot must then submit a hazardous material report within 24 hours in case the material can cause further harm.

This site has listed some TFOA incidents:

  In August 2000, a KLM Royal Dutch Airlines Boeing 747 was forced to make an emergency landing when some engine pieces plummeted to the
  ground and landed on a crowded Los Angeles beach
  On March 10, 2005, a couple taking a stroll through woodlands near Gatwick airport had a lucky escape when a door from a passing British
  Airways jet, crashed to earth. A part of the 70-pound door from a
  Boeing 777 had become dislodged just after take off and missed the
  couple by only 20 feet!
  On August 11, 2006, a door fell off from a TAM Fokker 100 from Sao Paulo to Rio de Janeiro. It dropped off 18 minutes after departure but
  the plane was able to return to Sao Paulo without incident. Nobody was
  injured.
  An engine exploded on a Japan Airlines flight bound for Tokyo with pieces of the engine falling on a neighborhood in Jakarta. The falling
  debris hurt no one but 16 homes were damaged.
  The right wheel of a Blue Panorama Airlines Boeing 737 fell off after it departed from an airport in Spain and was forced to make an
  unscheduled landing amid emergency in Rome.
  A similar incident happened near Los Angeles where an American Airlines Boeing 757 lost its right nose gear but managed to land
  safely with 105 passengers on board.
  A landing gear door fell off a Delta Airlines Boeing 727 shortly after the plane took off from Boston*s Logan International Airport.
  The 30-pound metal door crashed into an empty street in a quiet
  residential neighborhood.


Can anyone identify this pusher biplane? This plane was probably built around 1912. I do not know by what company built this. Does anyone know what airplane this is?

It looks like a Farman Aviation Works design but many builders copied the Farman designs.

Most Farman aircraft had straight boxed struts but some had staggered wings and slanted struts:

Maurice Farman biplane

Source: http://flyingmachines.ru/Site2/Crafts/Craft28602.htm#tabs-1

Source:  ebay auction

Also similar to the MF.9

Source:http://flyingmachines.ru/Site2/Crafts/Craft28795.htm


Is this contrail from an airplane or a rocket? A relative of mine showed me the following picture that she took on the 11th of April, around 8 to 8:30 pm in the Netherlands somewhere near "Leiden" pretty close to Schiphol airport (unfortunately I do not know the direction she was looking at, or the exact location, nor does she remember).

This relative thinks that what is shown in this picture is a rocket ascending due to the steep vertical incline. I however doubt this and rather believe it is a plane flying towards the photographer. The illusion of it ascending steeply being caused by the shadow of the earth falling close to the "plane" while the distant contrail is still in sunlight due to the height at which a plane flies, creating a fake depth effect.

What makes me doubt my theory however is the (to me seemingly) irregularly shaped contrail at the end which look like the plane did some weird zigzagging (or a very strange wind blowing it like that), and it seemingly "just appearing" out of nowhere

Now we both don't know a lot about airplanes, so I was wondering if by looking at these contrails it is possible to confirm or deny that this is caused by an airplane.

Looking at the flightradar for that moment there appears to only have been one plane in the area, and even that appears to be quite far out. Could this plane possibly have left those contrails?

I am pretty sure it is an aircraft.

When aircraft fly straight towards you they can appear like rockets. The contrail is distorted by winds in the upper airspace. Yesterday there were a lot of cirrus fibratus and cirrus uncinus in the upper atmosphere (at least above Frankfurt, and we are in the same weather system at the moment), and when aircraft fly through them the contrails typically wobble like in your picture.

Now, which aircraft was it?

The aircraft visible on the picture is not flying in sunlight anymore, but most of its contrail still is. It also just made a turn.

On the eleventh of April, sunset in Leiden was at 20:33 local time (18:33 UTC), setting in a bearing of 285 degrees.

Flightradar24 show this DHL Airbus A330 descending from FL 390. I would estimate that this picture was taken at 20:36 local time, perhaps a bit later. The turn is clearly visible on the picture and on FR24. The contrail matches that of a large twin engine. (my first guess was a 777, an A330 has a similar contrail. It is definitely not a 747).

A comparison picture created by ymb1 shows the shadow/lighted parts of the contrail highlighted, contrasted with the terminator on the map.


Which military aircraft does this seem to be? [F-16 vs MiG-21] Can someone identify the aircraft based on the components, riveting style, or other technical details visible in these crash pictures?

a) Based on publicly available details, the chief suspects are MiG21-Bis or F-16. Are there US vs Soviet construction details, materials, etc that can enable identification based on these images?

b) There is a drop-tank in the images, which is claimed to be only compatible with one of these two aircraft. I'm looking for someone familiar with the MiG-21 or F-16 to comment.

Background:

Three aircraft crashed in the Kashmir region during hostilities on 27th Feb 2019. One was an Indian MiG-21bis, whose pilot ejected and was apprehended by Pakistani locals. Another was a Mi-17 helicopter, which crashed "due to technical reasons" killing six persons onboard, within Indian territory.

No information is available about the third aircraft; Indian sources claim they hit an F-16 while Pakistani spokespersons said they did not have F-16s in the area.

These are purportedly pictures of the downed third aircraft. This could be part of an F-16, JF-17, MiG-21, SU-30MKI, or Mirage in Pakistani or Indian service.

source: Photo/ANI

source: Photo/ANI

There is also a low-resolution video available via twitter, showing the droptank recovered from the site being loaded into a truck.

Link to low-resolution video on Youtube

source: @MdShafiKhatana/Twitter

Edit:

This is a recent incident. Some sources claim the image shows a part of an F-16 engine. Is this plausible?

source: Photo/ANI

Edit 2:

Is it plausible that this number "J0269" (from the above picture) can be used to identify the aircraft as an F-16B Block 20 MLU with tail number J-269 using this link?

It's a MiG21. There was another photo showing the front section area and the unmistakable nose cone of the MIG21.


Where exactly are the pitot tubes positioned on the A330/340? While going through a document for analysis I came across a statement saying the positions 1 and 2 of the pitot probes are symmetrical on long-range Airbus aircraft but not on their single-aisle aircraft.

Can any one please confirm it by giving suitable reference? I didn't find any clue on the internet.

Seems like they are under the cockpit for the A330

source

Couldn't really find anything for the A340 that helped with answering your question but I assume based on the A330 that they most likely are located somewhere in the same area.