Why not tow aircraft instead of single-engine taxi? To save costs, budget airlines could potentially eliminate the single-engine taxi that is standard.

Companies are looking into things like electric motors on the wheels of airliners for taxi, which could be powered by the APU, using much less fuel than even a single-engine taxi.

But why not just tow all of them using existing towing equipment?

The related post 'Does it make sense towing airplanes to the head of airstrip by electric means?' asks for electric technology (internal or external), this one asks about using existing technology.

Single-engine taxi is used for taxiing out (to the runway) and taxiing in (after landing) when the aircraft/operator allows it.

It is usually done when the taxi time is big, which means at big and busy airports. Use Google Earth to see how complicated big airports are in case you're not familiar with the airport layouts. But for the purposes of your question, let's consider a simple airport.

(wikimedia.org)

As shown, there is a single runway and one major parallel taxiway. Typically airplanes land and takeoff in the same direction.

First off too many tow trucks is too much traffic, too much money, and an increased chance of accidents on the ground.

Let's say in the above picture the plane is towed to where it says (11) for takeoff, the tow truck will detach, then what? It will have to occupy the runway and exit (delaying departures and arrivals).

Same thing for arrivals, tow trucks will need to wait by the exits, and with the time it takes to attach, the exit will be occupied. If not the exit but farther down, then you're already almost at the gate.

So the why not is basically: more traffic that doubles when the tow truck detaches, expenses (trucks, drivers, maintenance), reduced runway capacity, bigger chance for ground accidents, and a very complicated coordination task.


Is there a way for pilots to report difficulties and challenges experienced during a flight, to the next flight crew? My question is reflected in the title - is there an official, international system for commercial pilots to report difficulties and challenges faced during a flight to the next and future crew? Ideally, such a system should also require the next crew to review recent entries into it. Does something like it exist and if so, how strictly is it followed?

"Difficulties" are hard to quantify. And it's questionable whether a difficulty experienced by one flight is even relevant to the next. Many difficulties are transient in nature (eg: weather, crew, cargo loading).

However, there is what is known as an Acceptable Defered Defect:

  An identified aircraft defect which has been assessed as being within the requirements of the Minimum Equipment List (MEL) or Configuration Deviation List and has had rectification deferred within a specified limit. Also referred to as a CFD (Carried Forward Defect)

This is used to notify future aircrew of a specific aircraft of any defects which, although does not require the aircraft to be removed from service, may be relevant to its operation.

Pilots absolutely check this before every flight.


What's the difference between the "100 above" and "100" GPWS above callout? Not all aircraft have both; this one does and can be heard at 1:12:

"100 above" refers to being 100 ft above the decision height, which is the height at which the pilot must initiate a missed approach if they do not have the required visual reference. The equivalent call on a Boeing is ‘approaching minimums’. The decision height or minimums will commonly be around 200 or 300 feet, but it is airport specific, so when you hear the "100 above" call, you are 100 ft above 200 or 300 ft (300 ft or 400 ft above the ground respectively) - or whatever the decision height is for your specific approach.
The "100" call means that you are 100 ft above the ground.
The audio clip in your video is a bit confusing, and probably not taken from a real flight. During a real approach, you would expect to first hear "100 above" followed by "minimums", since "minimums" is the call made at the decision height.


How to balance the cargo on a plane with the wings further aft? For example on an MD-88, is the center of gravity on the back of the plane because the empennage, wings and engines are located there? So they would have to put most of the cargo on the back of the plane?

Yes, the wing is positioned so that the center of lift is near the center of gravity. The MD-80 is very tail heavy due to the aft mounting of the engines. I have actually personally seen the nose of an MD-80 lifted off the ground by a jet bridge, and it didn't even hurt the door that was supporting the weight.

This chart is from the MD-80 weight and balance manual, which can be found on google. You can see that the center of gravity (CG) must be within -2.8% to 33.4% of the Mean Aerodynamic Chord (MAC) which is an approximation of average wing chord. So basically the CG must be in the forward 1/3 of the average wing chord, typically the center of lift is around 25% of chord. On the MD-80 the leading edge of the MAC is at body station 885.547, which is behind the actual LE of the wing at the fuselage.

The reason you want to place the CG near the center of lift is to create the smallest pitch moment possible between the CG and CL. The pitching moment created by the difference in the CG and CL location must be reacted out by the horizontal stabilizer. The more moment, the larger the stabilizer must be and the more inefficient the aircraft. Here is an illustration (stolen from this question How does a commercial airliner measure its weight/mass?):

Here is the picture of the MD-80 doing the wheelie:


Is there a significant difference between the jet blast from Airbus and Boeing? I am looking up for jet blast data and there are not much information in the net.

One of the main references I can found are the Airport Planning of each aircraft.
From these can be obtained that the jet blast contours from Boeing's aircraft are quite longer than the Airbus's ones at idle and breakaway conditions (the double in length of the jet blast print).

According to this, simulations carried out using specific software (AeroTurn, in this case) show that the jet blast affected area by a breakaway run of a B737-800, for example, would affect stands in a 100 m backwards zone, which is far from the truth.

Some researches can be find Googling a little, but they show comparison between simulations and experimental jet blast data from a JFK test campaign, besides the own JFK data.

Could anyone confirm if the difference is real? A mapping study, an experimental analysis or other similar evidence would be useful.

Thank you everyone for your help, and thanks for all your work in the community.

Probably not.

Airbus and Boeing aircraft may even have the same model of the engine. For instance,  2.4 m diameter Pratt & Whitney PW4000 is used on Airbus A310-300, A300-600 and also Boeing 747-400, 767-200/300. General Electric CF6-50 is used on both Airbus A300 and Boeing 747.

I would expect much more differences between jet blast from of Airbus A380 versus Airbus A220. A220 is near ten times lighter (575 vs 60 t).


How long to clear the 'suck zone' of a turbofan after start is initiated? I recently found this (IMO funny) picture. All funny and all. But let's make this a real situation.

Let's suppose I see my crush and his BF doing this, and I come with this 'genius' idea (alright, it's anything but a genius idea, but still) to start the engine they are sitting on. And no, I am not nice enough to turn the beacon lights on.

How likely is it that the engine gains enough suction to suck them in without they noticing it in time (considering the fact they need to standup and run for their lives)?

How long does it take for the engine to spool up enough suck a person in?

A start on a TF all the way to idle is about 20-40 seconds depending on the engine, and the fan itself won't do more than creep a bit until the core actually lights off which is 5-10 seconds, so they'll have lots of time to get down and get away as per @ymb1's diagram, once the wheeEEEEEEEEEEtickticktickticktickticktick starts.


What is the difference between Assumed Temperature and Derate takeoff thrust? Airlines like to avoid a full thrust takeoff as it increases the wear on the engine. There are two methods to achieve this: Assumed Temperature and Derate.

In the Assumed Temperature method, the takeoff performance is calculated by commanding the engine to mimic the thrust produced if the outside temperature is higher. Derated takeoff thrust basically tells the engine to pretend it is a weaker engine.

Both methods result in a takeoff thrust setting that is lower than 100% power. What are the differences between these methods, and how do the flight crew choose between the two?

The difference is in the minimum control speeds ($V_{mcg}$ and $V_{mca}$).

In Assumed Temperature takeoff thrust, the pilots are allowed to advance the thrust levers to full rated takeoff thrust. However, in Derated takeoff thrust, the levers should not be increased beyond the fixed decate limit, otherwise a engine failure may result in loss of directional control.

From Boeing 737 FCTM (my emphasis):

  The fixed derate is considered a limitation for takeoff. Takeoff speeds consider ground and in-air minimum control speeds (VMCG and VMCA) at the fixed derate level of thrust. Thrust levers should not be advanced beyond the fixed derate limit unless conditions are encountered during the takeoff where additional thrust is needed on both engines, such as windshear. A thrust increase, following an engine failure could result in loss of directional control.

The minimum control speeds are calculated based on the full rated takeoff thrust. The rated thrust is lowered in Derated takeoff but not in Assumed Temperature takeoff. Therefore, by calculating the minimum speeds based on a lower engine rating, the pilots can be ensured that sufficient directional control can be maintained on a slippery runway, whereas there is no such guarantee for Assumed Temperature takeoff.

On a dry and long runway, there is no operational difference between Assumed Temperature and Derated takeoff.

From the Boeing 777 FCTM (my emphasis):

  Reduced takeoff thrust (ATM) may be used for takeoff on a wet runway if
  approved takeoff performance data for a wet runway is used. However,
  reduced takeoff thrust (ATM) is not permitted for takeoff on a runway
  contaminated with standing water, slush, snow, or ice.

And:

  Derated takeoff thrust (fixed derate) may be used for takeoff on a wet
  runway and on a runway contaminated with standing water, slush, snow, or
  ice.

The Boeing 737 FCTM has a nearly identical description.

The A330/A340 FCTM explains that the slower $V_{mcg}$ / $V_1$ can also allow increased MTOW on short runways:

  When taking off from short or contaminated runways where ASDA [Accelerate-Stop Distance Available] is the limiting factor, a reduction in the minimum control speeds may generate a take-off performance benefit and a higher MTOW.


Where to download a specific flight route before the flight? Is it possible to download the flight route before the flight?

I'm interested in a table (or something similar) containing the following data:

Timestamp | Coordinates | Human readable location
————————-—+————————————-+—————————————————————————
                       ...

This would be quite helpful, so I can follow the airplane progress during the flight, without having internet connection.

Where can I get that from?

From what I know, you can "decode" certain routes on flightaware.com which will bring up this which may be the closest thing possible to what you want.


How does a flap load relief system work? I recently read about flap load relief systems in some aircraft that attempt to prevent flap overspeeds by automatically retracting flaps under certain conditions.

Are these systems common on all large aircraft or are they specific to just a few?
How do they work (i.e. under what conditions will they retract flaps)?
Do they prevent the possibility of overspeeding flaps altogether, or do they just make it less likely to happen?

I'm not sure how common flap load relief systems are - I know the Airbus A330 has them and I believe all the Airbus A3xx series do. I've also found at least one post that seems to imply it's common on most "large commercial" aircraft, which I assume encompasses most transport category aircraft.

On the Airbus the system is based on airspeed - When the maximum flap extension speed (VFE) is exceeded by a certain threshold the ship's computer automatically retracts the flaps.
My understanding is the retraction is staged, so if you've got full flaps selected and exceed VFE for that flap setting the system takes out one notch -- presumably it would continue doing so if you're still exceeding the operating limitations of the flap system until it reaches a point where it's convinced you're not going to damage the airframe.

When the overspeed condition is corrected (the speed has reduced to below Vfe by a set threshold) the flaps are returned to the selected position.


Can we fly in Japan and/or Australia with EASA approved training and licences? Disclaimer: I'm not a pilot, and seem to be lost with all the jargon and complexities around this matter despite trying to do adequate amount of research.

I am considering taking on my PPL in Hungary and it is all EASA approved training. Thereby the licence will be up to a standard of EASAs approval. Therefore with this licence, would I be able to fly in a foreign country such as Japan, Australia, etc. or other countries with whom EASA has a working arrangement?

If not how would I be able to switch over my PPL to be accepted in Japan and Australia?

Generally speaking, you need to hold a licence issued by the same country that the aircraft is registered in. There may be exceptions but you cannot fly an Australian aircraft on your EASA licence.

Luckily, converting a PPL between countries is generally straightforward when it has been issued by an ICAO-contracted state (which is most advanced countries and EASA).

For Australia, no additional tests are required (for PPL only, exams and flight tests are required for higher levels). You just need a medical, to pass a security check, and pay a fee. I believe EASA licences come with English Language Proficiency (ELP) level 4 to 6 so an English test is not required. Side note, the US does not have the ICAO ELP scheme so even native English speakers from there need to pass an English test when they convert to Australia.

I'm less familiar with Japan but according to AOPA Japan you need to sit a law exam and obtain a radio operator certificate.


Why would a glider have water ballast? If it is trying to stay aloft without an engine, wouldn't it be better to be as light as possible? So I was looking at the description of a ASW 27 B glider and ran across this statement:

  Two water tanks in the wing plus a further 35 liter tank in the
  fuselage enable the ASW 27 B to carry more water ballast than any
  other 15 m glider and also give it the widest range of wing loadings

If a glider is trying to stay aloft as long as possible, wouldn't it be better to be light?  Why would you add ballast and be able to dump it?

Mass doesn't affect the maximum distance, only the maximum endurance.

For example, image two identical planes A and B: A weights 50kg less than B. Assuming no wind (horizontal / vertical) and speed of best glide, both gliders will land at the exact same spot.

The lighter airplane A however will arrive later than B, as the speed of best glide is less than for B. In conclusion you can say, that additional mass only increases cruise speed, but not the travel distance.

Glider competitions are most of the time a route you have to fly in the shortest time possible. So that means, if you have a higher speed of best glide, you can fly faster in competitions.

The only downside to having a higher weight is, that your liftrate in thermals will be decreased and due to the higher speed it is harder to center the thermals.

It is to some extend also possible to shift the Centre of Gravity (CG) with the added load. The further it is to the aft limit, the higher your maximum distance is. This is because you will have less down-force from the stabilizer required. (If the CG is at the front limit, you will need to pull the control stick in order to fly level, therefore you have more drag). However I think this is rather a positive side effect and most of the time the water is used for flying faster.

Source: I am a glider pilot and currently doing my ATPL training.


Bernoulli Principle -- Reversed The Bernoulli Principle states that as the velocity of a fluid increases, the pressure of that fluid decreases. However what if it were to be reversed: As the velocity of the fluid decreases, the pressure increases; is this possible?
I am looking at pressure differentials and how pressure is 'high' on the lower surface of the aerofoil. But is the pressure truly 'higher' or is it of normal pressure of the surroundings of the aerofoil?
So this is where the question comes in: If the pressure of the airflow is greater ont the lower surface of an aerofoil, then doesn't that mean that the airflow is slower? Or is the 'high pressure differential' just a word to help differenciate the concept of pressure on an aerofoil, and truly the pressure on the lower surface of the wing is normal?

As said on Wikipedia, the principle says:
$$\frac{v^2}{2} + gz + \frac{p}{\rho} = \text{constant}$$
i.e., assuming no changes in the gravity potential energy or density:

an increase in velocity comes with a decrease in pressure
a decrease in velocity comes with an increase in pressure

It's all part of the same principle, there is no "reverse" needed.


What is the white pattern on trim wheel for? On a A320, there are white patterns spread regularly on the trim wheel (highlighted on the right of the picture). First I though it was to have visual feedback about THS (trimable horizontal plane) position. But looking closely, this role seems to be played by the graduations (highlighted on the left of the picture).

(photo #0393544 from airliners.net)

Why are there those white patterns on the trim wheel? What is their role?

The white marks make it easy to see if the trim wheel is moving, which would be tricky if it was entirely black.

But wouldn't the pilot always know if they was spinning the trim wheel? Remember that the autopilot can also adjust the trim, which might not be obvious to the pilot. The visual marks make it easy for the pilots to see what the autopilot is doing.

Example video (not an Airbus, but very similar):


What is the purpose of a walled area in the vicinity of Heathrow Airport? Looking at a satellite map to the East of Heathrow Airport, there is a small passenger jet parked in a walled off area. Looking at the aerodrome chart the entire area is listed as Bealine Base, which I assume is used for BA operations. What it the purpose of this walled off area?

It allows them to do a run-up test of the engines without blowing debris at other parked aircraft, people, or things on the ground.

[Credit to Ralph J]
The walls have a structure that allows the noise of engine run-ups to be absorbed as well. Engine run-ups, especially multi-engine run ups, can be very loud.

You can read more about IAC-Acoustics ground run-up enclosures here.


What is an Aircraft Overhaul? While reading the FAA presentation on Part 135 Airworthiness Requirements, on slide 7 where it discusses maintenance, the list includes

  inspection, overhaul, repair, preservation, and the replacement of parts, but excluding preventive maintenance

I am sure that the other regulatory bodies have their own, similar lists.

I know that an aircraft overhaul is one of the major processes involved in (especially commercial) aircraft maintenance. What exactly is meant by overhaul? What is done to an aircraft when it is overhauled? And finally, why is it so important for an aircraft?

Briefly, "overhaul" isn't a strictly defined term but it's generally used to refer to the intensive inspection, maintenance and repair of an aircraft component, frequently - but not exclusively - the engines.

The word overhaul by itself is a general term that's used in all sorts of places but it's not defined in 14 CFR 1.1, for example. The most specific definition I could find is in this agreement between the FAA and EASA:

  "Overhaul" means a process that ensures the aeronautical article is
  in complete conformity  with the applicable service tolerances
  specified  in the type certificate  holder's, or equipment
  manufacturer's instructions for  continued airworthiness, or in  the
  data which is approved or  accepted by the Authority.

  No person may
  describe an article as being overhauled unless it  has been at least
  disassembled, cleaned, inspected, repaired as necessary, reassembled
  and tested in accordance  with the above-specified data.

Note that that definition only mentions "aeronautical articles", which is very broad indeed and not limited to just engines, airframes or anything else.

In the general aviation world, a very common usage of "overhaul" is in the context of piston engines, which have a Time Between Overhaul (TBO or TBOH) set by the manufacturer. Once an engine reaches that number of hours, it needs to be overhauled. But even there, the term isn't precise and the FAA has a circular called Reciprocating Engine Overhaul Terminology and Standards that explains what it usually means:

  c. Overhaul.  In the general aviation industry, the term engine
  overhaul has two  identifications that make a  distinction between the
  degrees of work on an engine:

  (1) Major Overhaul.  A major overhaul
  consists of the complete disassembly of an  engine. The overhaul
  facility inspects the engine, repairs it as necessary, reassembles,
  tests, and  approves it for return to service within the  fits and
  limits specified by the manufacturer’s  overhaul data. This could be
  to new fits and limits or serviceable limits. The engine owner  should
  clearly understand what fits and limits should be used when  the
  engine is presented for  overhaul. The owner should also be aware of
  any replaced parts, regardless of condition, as a  result of a
  manufacturer’s overhaul data,  SB, or an Airworthiness Directive (AD).

  (2) Top Overhaul.  Top overhaul consists of repair to  parts outside
  of the crankcase, and  can be accomplished without completely
  disassembling the entire engine. It can include the  removal of
  cylinders, inspection and repair to cylinders, inspection and repair
  to cylinder walls,  pistons, valve-operation mechanisms, valve guides,
  valve seats, and the replacement of piston  and piston rings. All
  manufacturers do not recommend a top overhaul. Some manufacturers
  indicate that a powerplant requiring work to this extent  should
  receive a complete overhaul.

Apart from that usage, the term MRO (Maintenance, Repair and Overhaul) seems to be used in the airline industry to describe maintenance facilities, but there isn't any specific definition that I could find.

So there's no single definition of "overhaul". It just means that you've very thoroughly inspected and tested something on an aircraft, whether it's an engine or a wheel, and you've verified that it's fit to be used in flight, i.e. it's airworthy. The reasons why it's important are probably obvious; they're the same reasons that your car needs regular servicing to run safely, efficiently and reliably.


What are these protuberances on the north edge of runway 10/28 at Mataveri? The single runway (10/28) at Mataveri International Airport (IPC/SCIP) on Rapa Nui1 has (at least according to Google Maps) a few paved protuberances emanating from partway down its northern edge which serve no obvious purpose:

I wondered if at least some of them might be the old turnaround pads from before the runway was lengthened in the early 1980s, but:

if that were the case, one would not expect them to still exist in what at least appears to be good condition a third of a century later, and
they look far too small to be turnaround pads emeritus - compare, for instance, the turnaround pad at the approach end of runway 28:

Does anyone know what these appendages are, and what purpose they serve?

EDIT: As @MikeSowsun points out, the runway would not only have been shorter then, but narrower as well (not having needed to serve widebody jets or distressed spacecraft), meaning that the turnaround pads themselves could be smaller, and that they'd have been at least partly paved over when the runway was widened (leaving only the outboardmost portions visible); this still doesn't address the issue of "how come they're still visible a third of a century after being abandoned", though.

1: Also known by its colonial names of Easter Island and Isla de Pascua.

It isn't a change in the runway length.* It was last lengthened in the 80s to serve as a Space Shuttle emergency landing site (latimes.com), and the length hasn't changed since.
Between c. 2007 and 2011 (sorry clouds got in the way) the runway was resurfaced in stages. In one stage, the runway was shortened and given a temporary (small; cheap) turnaround pad (with centerline markings as well). When this happens, the declared distances are amended.
When the work was done, a new proper one was built, and the temporary small one became vestigial. Note the X marking in the second image, and note that many runways utilize mid-runway turnaround pads to shorten the taxi time back to the terminal (on the west end).
* well, in a sense, it was


Can I still take the knowledge test with the US government shutdown? Non-Essential employees at the FAA are out of work due to the US Government shutdown.  I am nearing the end of my Private Pilot Training and am almost ready to take the Knowledge test.  With the US Government shutdown, can I still take the knowledge test or do I have to wait for the government to reopen?

Looks like private testing centers can conduct the tests now.

Full details here, from 22 Sept 2017.

https://www.faa.gov/documentLibrary/media/Order/FAA_Order_8080.6H.pdf


What determines the "acceleration" and "thrust reduction" heights? Thrust reduction height is the height at which automatic thrust reduction from takeoff thrust to climb thrust happens. And acceleration height is the height at which you start accelerating the plane from takeoff config to clean config.

But is the acceleration height always the same as the thrust reduction height, just sometimes, or will it depend on the company's SOP (standard operating procedure)?

(Highlight mine.)

Short answer: airport briefing.

If no restrictions, then company SOP.

Thrust reduction is usually set to activate once the plane clears the noise abatement and/or MSA (Minimum Sector Altitude).

VNAV takes care of acceleration when activated as long as the SID is programmed. It also warns the crew if constraints will not be met.

Boeing 737NG VNAV. (Highlight mine.)

From Skybrary:

  Thrust Reduction and Acceleration Procedures

  On take-off, in order to position the aircraft to a safe height away from terrain and obstacles (i.e. a flight path of maximum height and minimum ground distance desired), the engine thrust is set to a high ‘take-off power’ setting (although this is not necessarily full power) and the aircraft attitude is pitched up to maintain a specific speed (usually in the region of V2 + 15kts). Once the ‘safe height’ is reached the engine thrust can therefore be reduced to a more appropriate (i.e. efficient) setting and the aircraft flight path can be changed to a more appropriate (i.e. efficient) flight path.

  In order to achieve that described above and also to provide minimum noise disturbance to the area surrounding the airport, regulatory procedures require aircraft to fly one of the two profiles given below during every departure. The aerodrome briefing pages will state which one of the two profiles is to be flown at each particular airport:

    At 1,500ft aal reduce thrust to climb power and accelerate the aircraft towards 250 knots, retracting flaps and slats.
    At 1,500ft aal reduce thrust to climb power maintaining V2 + 15kts. At 3,000ft accelerate the aircraft.

  Operator’s SOPs must therefore enable the above procedures to be flown.

Typical Boeing 737 climb profile:

Acceleration here would happen at (2) when VNAV is engaged. Default acceleration height depends on the airline, manual entry is possible from 400 to 9999 feet.

The default thrust reduction height is 1500 feet (lowest manual entry is 800).


Procedure turn/hold required on this approach? I am an instrument student nearing my checkride. I recently flew the VOR-A approach into KLOL as a practice approach, using ROBUD as the IAF. I was wondering if the charted hold at MOBOH is required by this procedure?

I had a few thoughts:

It seems like AIM 5-4-9 (a) would say yes, since there is no "PT NA" on the plate. Flying a real IFR flight in this case, it seems likely that ATC would clear for a straight-in approach, in which case the hold would not be necessary.
If I was flying this approach on a real IFR flight and didn't hear "cleared for the straight in approach", I would ask ATC to clarify.

HOWEVER, I'm curious if, in the absence of specifically being cleared for a straight in approach, I would be expected to fly a circuit in the holding pattern on this approach starting from ROBUD, even though I'm already inbound on the final approach course?

If you start the procedure at ROBUD and your clearance does not include "cleared for straight in approach", then you are expected to do a procedure turn in the hold. In real life the first thing to do in such situation would be to query the controller "confirm we are cleared for straight in approach", they are very likely to forget it also.

In my opinion, this is an example of an error on the FAA chart, which is missing noPT annotation on the leg from ROBUD to MOFTE. That annotation is present on a Jepp chart. I've seen these kind of errors in the past and FAA is usually pretty good in correcting them, so go ahead and ask them at Aeronautical Inquires.

.


How did this Boeing 787 perform this near vertical takeoff? At angles of attack like this an airliner would stall very easily. The 787 wing would stall at an angle of 30 degrees. The plane would have been flying at speeds of around 200mph(more likely less) at this angle and speed the aircraft would be very susceptible to stalling? How is this even possible to perform this without stalling? Source:youtube The a380 also performed this near vertical takeoff.Source:Youtube

First of all, it was nowhere near vertical. It is basically an optical illusion created by the camera angle.

Second, and most importantly, what you are seeing is the pitch angle and not angle of attack.

As it can be readily seen from the following image, the angle of attack and pitch angle can be significantly different.

Image from What is Angle of Attack? by Boeing

Angle of attack (AOA) is the angle between the oncoming air or relative wind and a reference line (usually fuselage centerline or longitudinal axis in commercial aircraft) on the airplane or wing.

Pitch angle (attitude) is the angle between the longitudinal axis (where the airplane is pointed) and the horizon.

Flight path angle is the angle between the flight path vector (where the airplane is going) and the local atmosphere. In other words, it is the angle
between the flight path vector and the horizon, as far as a commercial airliner is concerned.

When referenced to the atmosphere, the angle of attack (AOA) is the difference between pitch angle and flight path angle. Depending on the aircraft atitude, they can be very different. During climb, usually the pitch is increased at constant angle of attack.

For example, in a steep descent, an aircraft could reach very high angle of attack if the nose is below horizon. While flying upside down (not something that happens in an airliner, I might add) , both differ by around 180 $^{\circ}$.

So, the angle of attack in this takeoff is surely well below the stalling angle of 787.


What does "redatum" means? I was doing a question about a fully hydraulic elevator and it's position in relation to the trimmable horizontal stabiliser and the explanation of the answer contained the word "redatum". What does it mean?
Full question, answer and explanation:

Q: What is the position of the elevator in relation to the trimmable horizontal stabiliser of an aeroplane with fully hydraulically operated flight controls that is in trim?
A: Elevator deflection is zero
A fully hydraulically operated flight controls is an irreversible system, and the trim is a redatum, as there is no physical connection between the stick and control. Therefore there will be no elevator deflection when trimmed.

I've never heard of the term, but from the context of the explanation it appears that they refer to a situation where the elevator neutral position is relative to the stabiliser, not to the aircraft. So stick moves elevator relative to aircraft and stabiliser, trim moves elevator relative to aircraft only because the elevator neutral position follows the stab position. Like the stabiliser/elevator arrangement on the B737.

Image source


Are control inputs different during autorotation? My understanding is that during power-off autorotation the main rotor is still coupled to the tail rotor, and the flight controls execute the same functions as during power-on flight.  Two questions:

Do any (heavy) helicopters have power-assisted controls?  If so are those difficult to handle in the event of total power failure?
How is the input during autorotation different from the input for the same attitude under power?  E.g., during a given glide and flare to land are the rotor blade angles of attack and swashplate orientation identical to when the a rotors are powered?

Yes and yes.

A certification requirement of helicopters with powered controls is that they have a manual reversion so that control can be maintained in the event of a power failure.  However, the controls can be really heavy with no power and accidents have occurred when hydraulics have failed at critical moments or pilots have lifted off with hydraulics off and have been caught by suprise with the effort needed to maintain control.

The control inputs during autorotation are the same.  For any given glide, or flare, the lift required is the same powered or unpowered.  Lift is proportional to the speed of the blades, which is independent of powered or unpowered, and the angle of attack.

During autorotation, the energy (power) going into the rotors is derived from the airflow coming up through the disc. In this sense, an autorotation is still powered but the power comes from the airflow rather than the engine.

During autorotation, since the airflow is from below, rather than above, the pitch required is lower for the same angle of attack to generate the same amount of lift.  So, the swashplate is lower in autorotation but lowering collective still decreases lift and raising it increases lift.  The primary difference is that rather than controlling lift and power, the collective controls rotor speed since increasing pitch increases the angle of attack which increases lift and therefore increases drag, slowing down the rotor.  Lowering the collective has the opposite affect.

The cyclic control is the same in all respects (you tilt the rotor thrust in the direction you want to go) since it increases, or decreases the pitch, and therefore the angle of attack, cyclically.  The movement of the swashplate about the X and Y axis is independent of the position of the swashplate in the Z axis.

The pedals work in the same way too.

In summary, the only difference in the controls is the vertical position of the swashplate.


Does an engine that combines an air-breathing rocket and non-air-breathing rocket exist? Does a rocket engine that combines air-breathing and non-air-breathing modes exist?

The advantage would be it would have to carry a smaller tank and less oxygen, leaving more room for payload on a weight basis.

There's a very recent claim for an engine called Fenris, which claims to be a no-moving-parts "rocket" that uses ambient air for its oxidizer.

On the face, that sounds like a ramjet, but the claims made by the inventors appear (to me) to be investor bait, rather than anything that could actually be true.  Video on the entry page at the inventor's web site shows a burn more like that of a poorly designed torch, than a rocket or jet.

As noted in comments, there is also the SABRE engine concept -- this is not yet a working engine, as far as I know, but will/would be a hydrogen-fueled turbo-ramjet which uses the liquid hydrogen to liquefy intake air while in jet mod, for use as oxidizer when it switches to rocket mode.  The intent is for use as a spaceplane-to-orbit.


Do all aircraft carry depleted uranium as counterweights? I was told that most aircraft had depleted uranium on board as counterweights. I have not seen one myself. Do all current modern aircraft have depleted uranium on board?

From my research, it looks like about 0.1% of all aircraft carry depleted uranium counterweights.

The Systematic Radiological Assessment of Exemptions for Source and Byproduct Materials (NUREG-1717), on page 3–260, gives a table showing that 430 domestic United States aircraft were delivered with depleted uranium counterweights, and says that "A reasonable estimate is that 50% of these aircraft still contain DU counterweights." So there are about 200 aircraft in the United States which contain depleted uranium counterweights.

Meanwhile, the FAA's "Air Traffic by the Numbers" publication says that there are over 200,000 aircraft in the United States currently.

So no, very few aircraft use depleted uranium counterweights.


Did Boeing subcontract the manufacturing of the wings on the B757 series? If Boeing did subcontract, which company took over the manufacturing of the wings? Where were the wings made?

The 757 Wing and Center Body Section was manufactured at the Renton plant at KBFI.


What is the difference between autopilot and autoflight? Can you please give me some explanations about autopilot and autoflight system?

Autoflight is the general term describing all of the following:

Flight Director: A guidance system for the pilot and autopilot with various modes. See What is a "Flight Director"? for details.
Autopilot: A system controlling the flight control surfaces to follow the flight director.
Autothrottle / Autothrust: A system setting engine thrust automatically depending on the selected mode. See also What is Auto-thrust?.

For example, the Boeing 737 NG FCOM describes it as follows (Vol. 2, Chapter 4 - Automatic Flight):

  The automatic flight system (AFS) consists of the autopilot flight director system
  (AFDS) and the autothrottle (A/T). The flight management computer (FMC)
  provides N1 limits and target N1 for the A/T and command airspeeds for the A/T
  and AFDS.

  The AFDS and A/T are controlled using the AFDS mode control panel (MCP) and
  the FMC. Normally, the AFDS and A/T are controlled automatically by the FMC
  to fly an optimized lateral and vertical flight path through climb, cruise and
  descent.

  AFS mode status is displayed on the flight mode annunciation on each pilot’s
  primary display.

Related: What is the relationship between "automatic flight control system AFCS", "autopilot", "flight director" and "flight management system FMS"?


Can a flight attendant have only one eye? I have only had one eye for many years and was a flight attendant before it happened now have received a one on one interview with airline. I just wonder if my eye will be a problem.

Let me refer you to the answer of this other question, that says a pilot may be considered for any class of medical (including First Class) with only one functional eye.

I think its fair to conclude that if a pilot can get a First Class medical with one functional eye, then you can be a flight attendant with one functional eye, assuming that you can fulfill all of the duties required.

Good luck.


Are civilian/GA pilots expected to "see and avoid" fast military jets in VMC? I don't know if this also applies to the U.S. or just to Europe, but in Europe the civilian airspace is frequently used by military jets. On numerous occasions I've seen F-16's and other fighter jets using the same airspace I was flying in (both controlled and uncontrolled)

According to the regulations, we should "see and avoid" other traffic but does that rule apply when encountering these fast military jets? Let's face it: there's no way you can see and avoid a fighter jet approaching at +400kts.

Are there specific regulations covering this? Who's at fault when a midair collision occurs? (sadly it has happened in the past)

EDIT

It happened again last week: https://en.wikipedia.org/wiki/2015_Moncks_Corner_mid-air_collision

How can something like this happen? Don't F16's have their own radar?

It is both parties responsibility to see-and-avoid, but it does help to know where you are more likely to find high speed military activity and high performance maneuvering to aid you in seeing and avoiding.

Military operations in the US are typically confined to military training routes (MTR), military operations areas (MOA), restricted airspace and prohibited airspace.

The MTRs are low altitude, high speed routes and are charted on sectional charts so you know to be extra vigilant around them or to just avoid them altogether.

Military operation areas or MOAs are charted and are big boxes with ceiling and floor altitudes.  GA aircraft can query ATC if these are active and in any case they can fly into them.  If a GA aircraft penetrates and active MOA, the military activity is typically stopped until you leave.  General rule of thumb is to just not go there.

Restricted areas are only accessible to you when cold, so there will not be military activity there if you allowed to be there.

Prohibited airspace may not have military activity before you show up, but certainly will after you do, and you might get to watch an F16 attempt slow flight and form up on your wing.  Remember your intercept procedures for this one.

Any military activity outside of this will generally be typical enroute flying at altitude.  You will occasionally hear ATC coordinating mid-air refueling but that won't be something you have to worry about.


What can I do to save my life if oxygen masks fail to drop down? Is it possible? What is the safest and fastest solution (method) in this situation?

If you are asking about all or some of the masks as your title suggests, it has happened before.

One such example from 2008 is Qantas Flight 30.

  After the accident, numerous passengers said that some oxygen masks did not deploy, whilst others had deteriorated elastic. Consequently, it was reported that one passenger smashed a panel of the ceiling to attempt to gain access to the masks. It was stated that these passengers were deprived of oxygen until the plane was lowered to a breathable altitude.

Best thing to do is to stay clam, and to breathe slowly/normally (deep calm breaths).

Worst case scenario if a person is a smoker and obese, they'll pass out but will regain consciousness when the pilots reach a lower altitude. In a rapid depressurization emergency, the pilots act quickly to descend, it will be a matter of few minutes until the air would have sufficient oxygen again.

Pilots have different mask systems that should be tested routinely.

Related:

How long will one remain conscious in the event of a sudden cabin depressurization?
Is it possible to suffer barotrauma during decompression?


What is the name of the figure consisting of a slow revolution around longitudinal axis? "An airplane performing one slow revolution around its longitudinal axis is performing one of these..."

This was a clue on Jeopardy today. The contestant responded with, "What is a barrel roll?" which I contend is incorrect. But he earned $2000 for it.

My response would have been: "What is an aileron roll?" Is he correct, am I correct, or are we both correct?

What is an Aileron Roll?

You are correct, but should we really expect that level of precision from the entertainment business or the media?


Why do jet engine fan blades have a twisted shape? is this a good answer. the blades rotate, the tip moves faster than the hub. So to make the blades efficient, the blades are usually twisted. The angle of attack of the blades at the tip is lower than at the hub because it is moving at a higher velocity than the hub. the amount of thrust generated is higher near the tips than at the root. Engineers want the thrust to be equivalent on every part of the blade.

I don't think it's accurate to say that the desired thrust is the same along the entire blade. For a large turbofan blade like the one in your image, the outer part is designed to act more like a propeller (efficient for the bypass air) while the inner part is designed to act more like a compressor (efficient for the core). You're not incorrect in stating that the twist does help optimize the angle of attack with the speed of the section, but that's more about not breaking the speed of sound at the tip than keeping thrust constant along the blade.

For any specific engine, though, the blades are highly optimized based on an incredible amount of complex CFD and wind-tunnel analysis for which there is no simple or intuitive summary. The design of a turbofan blade is driven by several factors, mainly

aerodynamic efficiency,
structural efficiency,
noise,
temperature,
vibrations, and
bird-strike resistance.

All of these go into the resultant shape, but you're unlikely to find specifics that are non-proprietary to the manufacturer and available for anyone to analyze. The twist specifically is just another parameter in the extensive, complicated optimization.


How does Propeller windmilling work? I’ve got a problem with understanding propeller windmilling. What I know is that when rpm are low and tas is high the blade aoa goes „over” the blade and is some kind of negative now, producing thrust in opposite direction than usual. But I don’t understand what really happens there. Is prop rotating in opposite direction or sth? I also read somewhere in the atpl book that when prop is windmilling the prop is driving the engine. How is that possible? Can somebody clarify that to me?

You can think of the propeller as a screw. Take a screw, a screwdriver, and starts screwing. The threads of the screw drive the screw into the block of wood.

The propeller works in a same way: the engine drives the propeller that "screws" through the air.

It also works the other way around. Well kind of, with the screw, because of the high friction btw the block of wood and the threads of the screw, but forget about the friction for a while, if you can.

If you stop twisting the handle of the screwdriver, and instead push the block of wood against the screw + screwdriver combo, what should happen? The screw should rotate just as if you were screwing it with the screwdriver, as the threads are still sinking deeper into the block of wood.  The screwdriver would of course rotate with it.

Again, it's the same with propellers (and engines). If you have speed, and you shut down the engine, the airflow will push against the propeller just as the (magically frictionless) wood against the screw. The propeller will keep rotating in the same direction, and as it does so, it keeps the engine turning also.

Now, in the case of you no longer twisting the screwdriver handle or the engine driving the propeller, there is no longer a force driving the screw or the propeller through the medium they are engulfed in. Instead, the medium (wood or air) is imposing a force on the screw & the screwdriver, or the propeller & engine to keep them turning.

If you do a google image search with words "propeller tip contrail" you'll find pictures displaying nicely how the propellers are actually screwing their path through the air.


Are there any known incidents of ejections by capsule? What are the survival chances? One hears of many stories of ejection seats but rarely of ejection by capsule. Probably because seats are so much more common.

So are there any known incidents of ejections by capsule? F-111 was one such aircraft that had an ejection capsule I recall.

While the F-111 had a custom build escape capsule integrated with the cockpit, escape capsule designs have been used in the past.  One notable type was the Stanley Corp. Ejection Capsule.  It was a special type of ejection seat which used a pressurized clamshell-type enclosure which could be deployed rapidly once the ejection process had been initiated.  It was designed specifically to protect a pilot against a supersonic, high altitude ejection which would have almost certainly been fatal using a conventional ejection seat.  The system was used on both the B-58 and XB-70 aircraft.

The system was pressurized allowing a flight crew to use standard life support equipment as opposed to a full body pressure suit for high altitude flight.

One notable ejection involving the Stanley capsules was the loss of XB-70 prototype No 2 on 8 June, 1966 near Barstow, CA.  During a formation flight of several other aircraft with the XB-70 for a General Electric photo shoot, an NF-104 collided with the starboard wing and tailfin of the XB-70 and disintegrated in flames, killing NASA test pilot Joe Walker in the process.  The Valkyrie continued on straight and level, then waltzed out of control and began tumbling toward the desert, spilling plumes of fuel vapor as it went.  Commander Al White initiated the ejection process using his Stanley capsule and egressed the aircraft but was seriously injured by failing to clear his arm from the clamshell enclosure during deployment.  The copilot, Carl Cross, failed to initiate ejection and rode the crippled Valkyrie to the desert floor, killing him in the process.


Are two twin-jet flights more efficient than one quad-jet flight? Ignoring for this question the issue of flexibility for the airline, would it be more (fuel, cost) efficient to have a single flight with a 4 engine plane than to have two flights with 2 engine planes.

I imagine, that 2 flights of twin-engine planes move more dead mass than a single flight of a quad-engine plane with the same capacity.

As one concrete example, say one A-380 @ 15000 km and 650 passengers vs. two A-350 @ 15000 km and 325 passengers each.

Some further clarification

The two (full) twins carry the same number of passengers as the (full) quad
The two twins and the quad fly the same (long haul) distance
Efficiency can be either consumed fuel, the cost or any other interesting parameter.

The sales figures tell it all. The majority of airlines prefer twin-jets. From businessinsider.com:
Qantas CEO offers his insight on 2x 787 vs 1x A380:

According to [Qantas CEO], he can fly two 236-seat Dreamliners for less than the cost of a single 486-seat A380, which entered the Qantas fleet in 2008.
"If we were to fly two 787s tail-to-tail, the per-seat cost would be less than the A380," the Qantas CEO said.

Even though the 787 has a newer generation engines compared to the A380, the fact that the 747-8I (the passenger variant) didn't sell well confirms the above.

(wikipedia.org) Fuel per seat figures for a 7,200 NM sector.
A major issue in comparing is finding:

A twin whose ideal seating capacity is half that of a quad
And boosts the same range
And be of the same generation.

(DVB Bank SE)

See: Why are twin engine airliners more fuel efficient than three or four engine airliners?

RE edit and comments:

As one concrete example, say one A-380 @ 15000 km and 650 passengers vs. two A-350 @ 15000 km and 325 passengers each.

They fail one of the conditions above, the 350 and 380 have different engine generations. And it's like the Qantas 787/380 example above.

Would there be a twin & quad combination with roughly the same age?

The A330-300 (twin) and A340-300 (quad) are the same age, and even better they share the same fuselage, wing, and total thrust, but they too fail one of the conditions: the A330-300's range is shorter than the A340-300's.
The A340 has longer range because the outboard engines on the A340 increase the bending relief, allowing 30 tonnes more fuel (flightglobal.com):

Because of bending relief from the weight of its outboard engines, the bending moment of a four-engined aircraft is substantially lower than it is for a twin at the same maximum take-off weight. For the same fuselage weight, therefore, a twin needs a stronger, heavier wing than a quad.
It follows that, for the same wing, the payload carried in the fuselage must be less for a twin than a four, which is exactly what has happened with the A330/A340: the latter carries about 20% more payload. This translates to about 30t of extra fuel, giving the A340 its long-range capability and requiring the addition of a centre-fuselage undercarriage leg. Design strength required was "only 1% higher than the A330", says Jeff Jupp, BAe chief engineer, Airbus.

The A330-2/300 sold 5.87 times more than the A340-2/300 (now out of production) as of end of March 2018.

What about a 767 vs 747 limited to the 767's range?

Limiting the 747 to the 767's range is again not fair, because of the fuel the 767 will have to carry to reach its max range, while the 747 will breeze by because it won't carry its full fuel load. See this related post: How much fuel is burned to carry the trip fuel?


How can I consider a UAV thrust power for wind effects? Sorry that I can't write English well.

I was wondering how can I consider a UAV thrust power for wind effects.

Assuming a wind velocity of -7 m/s, uav velocity of 10m/s and the stall speed is 10 m/s.

Considering that the desired velocity of the uav must be close to the stall speed. And, assuming that the wind is opposite to the flight direction.

With this information the uav velocity should be 3m/s? And if that's the case, how can I calculate the thrust force.

I'll add a figure and clarifying question.
first, I desire minimize thrust power of UAV for flight.

Like a figure, If the wind speed is 7m/s and the UAV speed is 10 m/s, ground speed must be 3m/s.

however, I thought relative velocity for a UAV is 17m/s. And To minimize thrust, The UAV closed to the stall speed(stall speed is 10m/s).
I thought the UAV need only UAV speed over than 3m/s.

And if that's the case, how can I calculate the thrust force.

As i understand your image:

$V_{uav}$ is the velocity of the plane relative to the air.
$V_{wind}$ is the velocity of the air relative to the ground.
$V_{ground}$ is the velocity of the plane relative to the ground.

If the UAV velocity is 10 m/s and the stall speed is 10 m/s the plane is at its limit of flying no matter what the wind speed is (neglecting turbulences). The relative speed of the plane and the air is crucial, this speed is mandatory for the physics beyond the lift.

There is simple equation how to calculate sum velocities. Note that they are vectors (speed and direction) not just numbers. $V_{wind}$ can be named as drift velocity.

$$\overrightarrow V_{ground}=\overrightarrow V_{uav}+\overrightarrow V_{wind}$$

If the wind direction is opposite to the plane direction its ground speed, at the stall limit, is smaller than the UAV limit. It can be zero (the plane seems stand still) or even negative (plane seems to reverse).

Side notes: $V_{uav}$ is The velocity a pilot cares the most, $V_{ground}$ is the velocity his manager cares. This wind effect is also the reason why flying wit tailwind is preferred by airlines - they spare fuel - and it is also the reason why takeoff and landing is preferred in headwind - you need shorter runway to start/land sucesfully. With tailwind the runway may not be long enough.


Why are you required to commit to a full stop landing if reverse thrust is selected? According to Airbus:

  ‐ After the flight crew selects reverse thrust, they must perform a full stop landing.

Does it really make sense to have this limitation, and why? What happens if you realise there's not enough space to land, and you've still got adequate speed?

The biggest problem is that thrust reversers take time to move. During that time they are still producing reverse thrust (even if only at idle) and slowing you down. They must all completely close before you get forward thrust and can add power to start accelerating again.  Then, what happens if they don't stow, or only part of them stow?  Now you've used up valuable runway that could have been used to stop (or at least slow down more) and are no longer in a position to takeoff from. The consequences can be pretty severe.


Are there any Airworthiness Directives for the Boeing 777 that might explain MH370's disappearance? Are there currently any ADs for Boing 777s which would indicate the potential for catastrophic electronic system failures that might explain MH370's transponder failure and other issues?

Was the aircraft used for MH370 in compliance with all ADs?

Are there currently any ADs for Boing 777s which would indicate the potential for catastrophic electronic system failures that might explain MH370's transponder failure and other issues?

No one of the ADs issued for 777s can by itself fully explain all the facts of the final flight of MH370/MAS370.

Basic facts

The aircraft was a 777-2H6ER with 53460 flight-hours and 7525 take-offs and landings
A 777 has three VHF radios, two HF radios and two transponders.
Modern airliners have two main generators, an auxiliary power unit(APU) and a ram-air turbine(RAT) for emergency power. I think the 777 also has backup generators and two independent main power buses.
The aircraft left Kuala Lumpur for Beijing on 8 March 2014 at 00:14 local time with 239 passengers and crew on board.
Communications were normal up to and including 01:19 when someone on board (believed to be the co-pilot) said to ATC KL "Good night, Malaysian three seven zero". This was the point at which ATC control is handed to Vietnamese ATC. After there were no further communications from the transponder, the ACARS system or from the VHF radios.
Malaysian military reported that their primary radar system records do contain information on an unidentified aircraft to the northwest of Malaysia. The timing, position and heading of the unidentified aircraft in this report are consistent with MH370 changing course away from its intended flight path.
MH370 did not arrive at Beijing at 06:30 as scheduled.
A satellite communications system on the aircraft continued to respond  to routine hourly handshakes from an Inmarsat ground station via satellite 3-F1 located at 0.0°N (±1.59°), 64.5°E at a height of 35786 km. These normal handshakes ceased after 08:11, there was an unexplained incomplete handshake at 08:19.
Subsequent analysis of the handshakes is consistent with MH370 continuing into the southern Indian ocean (and somewhat inconsistent with other routes or it being stationary)
Countries within range of the plane's potential flight paths were asked to check their primary radar records for signs of MH370. No country reported finding anything.
No part of the aircraft or its contents have been located and firmly identified.
Many months later, some parts from the aircraft were washed ashore.
Investigators report that the condition, timing and location are consistent
with ocean currents from a point in the south Indian ocean.

Electrical failure hypothesis

Anyone speculating about the fate of MH370 needs to fit their hypothesis to the above facts.

They would have to explain how the failure incapacitated multiple systems within a few minutes and before any of them could be used.

In particular what did NOT happen:

The pilots did not make an emergency broadcast on VHF
The transponder did not squawk any emergency code
The ACARS system did not continue normal communication
The aircraft did not return to KL and follow procedures for loss of communication.
The aircraft did not continue on its planned route
The aircraft did not arrive at any of the airfields a pilot should divert to in emergency.

And what DID happen

The aircraft remained airborne for a further 7 hours.

Therefore the engines continued to run

Electricity was available to a satellite communications system on the aircraft.
The aircraft most likely deviated from its planned route.

AD 2014-05-03

This AD issued Feb 18th was reported on in March in connection with MH370.

But Reuters reports that Boeing stated this AD does not apply to the aircraft used for flight MH370.

If you ignore that and look at the consequences of a fuselage crack in the vicinity of the satellite antenna, you can see that this would not turn off the transponder, would not affect the VHF aerials and, if it caused a slow decompression - does not by itself explain why the crew would have failed to respond to the resulting low-pressure alerts by donning oxygen-masks, contacting ATC and descending to a safe altitude.

Occams razor

A shortage of facts always leads to speculation. Some of which can be very imaginative. The onus of proof is on those producing the hypothesis.

I'm sure there are thousands of hypotheses but, in my opinion, the simplest explanation I've read which is consistent with the known facts is deliberate action by a pilot or persons unknown. This doesn't mean it is the right explanation, just that it seems the most probable to me at the moment.

  Was the aircraft used for MH370 in compliance with all ADs?

We won't know with any certainty until the investigations branch of the relevant regulatory authority publishes their report on the incident. In previous accidents over an ocean, it has, on at least one occasion, taken years before a final report could be written.

Currently, there have been no confirmed reports, that I can find, of an AD that warned of the potential for catastrophic failures and which should have been applied to 9M-MRO and wasn't.


What is this plane approaching an airport in Asia? (Also, what is the airport?) The airport is in Asia, that is all I know.

The airport is Lukla - Tenzing-Hillary in Nepal.

The aircraft is a Eurocopter AS350 Écureuil helicopter. I found a picture of one that has the same panel layout.


Is aerodynamic braking really effective? (YouTube)

In the frame above the pilot is pulling back, as evident by the stabilator's position, and this technique is usually cited as a means of slowing down.

But wouldn't the brakes have better effect if the struts are fully compressed as with jet-liners? What makes aerodynamic braking effective for jet-fighters then?

Clarification:

Presumably that fighter pilot is applying some brakes at least (otherwise they wouldn't have added a drogue chute).

My thinking is, if the nose gear was planted, the same braking force will have a better effect (reduced lift), even without spoilers present since the jet engines won't be contributing to the struts decompression. Also the nose tire will add to the rolling friction.

The aero brake in this picture is the chute! and yes, it works!

Your wiki source is mistaken in stating that this use of elevator increases load on the main gear. The wing angle of attack will increase wing lift in multiples of the tail download, as you observe in the extended gear struts.

Landing like this allows the aircraft to slow with less use of brakes. It is counter-intuitive to claim to both save brakes and increase main gear load, which is intended to allow greater use of brakes.

Military jets land at comparatively high speeds, making this more useful since aero drag is proportional to speed squared. It may even be more effective at high speed than brakes, saving brake capacity for later in the landing when aero braking becomes less effective. Brake capacity may be limited to keep brakes small and light.

Nose gear does not have brakes and adds negligible friction.


Is there anything extra required to spin a Cessna 172 in the Utility category? I'm trying to find a suitable aircraft to get my spin endorsement for my CFI rating but am running into trouble with most aerobatic aircraft due to my height (too tall).

My last thought is that I could use a 172 in the utility category (I already know I fit in one and can have full control authority - I can get my legs under the dash to reach the pedals and my knees don't block the yoke).

It looks like 14 CFR 91.307(d) says I wouldn't need a parachute since I'm doing this with a flight instructor for training for a certificate.

In Section 2 of the 1978 Cessna 172N POH under the heading Utility Category (page 2-7), it says

  This airplane is not designed for purely aerobatic flight. However,
  in the acquisition of various certificates such as commercial pilot
  and flight instructor, certain maneuvers are required by the FAA. All
  of these maneuvers are permitted in this airplane when operated in the
  utility category.

Provided I am operating the aircraft in the Utility category (CG within limits and Weight 2000 lbs. or less), is there any reason I couldn't use a Cessna 172 to obtain my spin endorsement?

(I know that the gyro in the Attitude Indicator can tumble - I'm not sure how to get around that if I can't cage it - but is it really harmful? I've heard this is one of those perpetual aviation myths - that it doesn't really cause damage, it just takes time to reset)

Provided you meet ALL of the requirements for utility category operation as spelled out in the POH (within W&B limits for the utility envelope, no aft passengers, empty baggage compartment, and anything else you may find in the Limitations and W&B sections of your POH) a Cessna 172 is approved for intentional spins, and may be used for spin training.

As to the gyro instruments, spinning MAY cause the gyro instruments to tumble. This is not good for the instrument (it beats up the bearings - do it too much and you'll wind up with an early gyro overhaul).
Newer vacuum gyros tend to be more resilient than the old ones that birthed the "Don't let the gyros tumble" rule of thumb - they'll tolerate more extreme angles without tumbling - so there's less of a need to worry about damaging them in spin training.
(Solid-State gyros obviously won't suffer damage as they have no gimbals and bearings to beat up. They may however become "confused" and go offline if they sense something they're not designed for.)

As a note, I would not do spin training in a Cessna 172 (or any other typical trainer where spins are only authorized within the utility envelope) that hasn't had a recent physical weighing, unless your operating weight and balance range is squarely in the middle of the utility envelope.

A plane with many years of "computed" W&B updates may in fact weigh 100lbs more (or, rarely, less) than the weight and balance sheets indicate, and the empty center of gravity could vary by an inch or more.

If you are going to be performing intentional spins it behooves you to ensure that you're actually operating within the envelope for which recovery has been tested.


How can I estimate Roll from Position? I have flight test data where the IMU is junk. The roll and yaw are obviously wrong, while the pitch seems to be correct. [I know the yaw is wrong because it doesn't match the changes in headings, and I know the roll is wrong because the it stays near 0° during horizontal loops where it should be closer to 20°.] The pitch seems ok because it is stays near 5° most of the time, which was the angle of attack for most of the flight.

I also have GPS data that gives me position at a high update rate.
I was able to use the position to compute the yaw values. With the position updates I can also estimate speed. With the position I can get a turn radius, and the change in position gives a velocity which can lead to a linear and/or angular momentum.

Now, I'd like to get an estimate of the roll (I say estimate because I figure the computation will require some simplifying assumptions).
The resolution for roll that I need is much less than the position data (by a factor of about 1000).

My question is this: given the position of the aircraft, how can I estimate the roll?

The purpose of this is for analysis of flight test data for a product that was tested on the aircraft. The product had (what turned out to be) a poor IMU, and we cannot do another flight test. I need the attitude and position to complete my analysis.

You can, but the accuracy is going to be somewhat poor.

Given the positions you can approximate the path with your favourite line approximation method. The important thing is that it can give you continuous evaluations (no jumps and no discontinuities) of at least the first and second derivative. Third order algebraic splines are a good approach.

Note that you will need to map Latitude and Longitude to some Cartesian representation. Depending on the length of the flight, a "flat earth" approximation might or might not be a good idea.

With these, assuming that each manoeuvre was mostly flat(*), you can compute your local curvature:

$$k = \frac{x'y'' - y'x''}{\sqrt{(x'^2 + y'^2)^3}}$$

Now you can estimate your bank angle $\phi$ with

$$\phi = atan\left( \frac{k \cdot V_{tas}^2}{g} \right)$$

where $g$ is Earth's gravity.

(*) the formula is for a manoeuvre in the x-y plane. You could turn your coordinates so to have a local x-y plane that is coincident with the plane where the aircraft was manoeuvering, but then you could not use the bank angle formula, that is correct only for turns in the horizontal plane (thanks Jan Hudec for correcting)


Why does an airliner fuselage have a constant section over its length rather than a tear drop shape? It is usually stated than a tear drop shape is a good shape for aerodynamic efficiency:

Adapted from Nasa

On the other hand, fuselage on an airliner has most of the time a long cylindrical section with round/tapered ends. I understand an aircraft has other constraints than just having the lowest possible drag. It comes to mind a cylindrical shape allows the same number of seats in most of the rows and also prevents to increase the section of the forward cabin.

Without further explanation, it seems curious the fuselage has not a shape between a rounded cylinder and a tear drop shape which is often seen for gliders:

Source

Without going into deep details, what are the most important reasons preventing such design?

On the other hand, fuselage on an airliner is most of time bullet shaped.

No, it is not. A “bullet shape” has a flat end, which is where most of the drag is generated (at subsonic speeds). But that shape is never used on flying vehicles except on rockets where the end is occupied by the rocket engines.

Instead, airliners always have a tapered “boat” tail, sloping gently enough to avoid separation (sometimes with help of strakes). The resulting shape is as if you split a droplet in the widest point and insert a piece of cylinder. And the difference in drag coefficient between pure droplet and droplet with cylinder section inserted is very small.

Still, a continuously varying shape is slightly better than the cylindrical section. And the early aircraft did have that. Likely the last one of those was the Lockheed Constellation. The shape was great aerodynamically, but it was expensive to build, it made it more difficult to ensure all elements have proper strength to withstand the pressurisation, every time they derived a larger version they had to redesign all frames and in operation it was not exactly convenient for loading either.

In contrast the tubular section is much easier to design, easier to make and when they want to make a bigger version of the plane, they just insert a couple more frames and mount stronger engines to match the increased weight—between A318 to A321 or between all variants of B737-MAX, vast majority of parts is the same and there is just different number of frames and different engines. And it's simple to load—seats are mounted on straight rails and containers simply slide in to the cargo bay. And the difference in drag is small enough that the cheaper manufacturing and practicality will easily offset the increase in consumption.


How are airliners secured on the ground during hurricanes? Say a major hurricane is expected to hit. Given that the weather is known beforehand, what can be done to avoid damage to the airliners sitting on the tarmac?

Fly every plane away - not very economical, considering that commercial operations cease at the last minute.

Move all planes into a hangar - a Boeing 747 takes a huge hangar to park. It may be possible to move all GA planes inside, but certainly not airliners.

Planes are designed to interact with winds; the wings is meant to generate lift, and the sideway forces on a vertical stabilizer is meant to swing a plane around. What procedures would minimize the stress put in the airframe by the 100+km/h winds?

Looking at the hurricane manuals for a few airports, evacuating flyable aircraft to a safer location tends to be the most common choice.
From the Boca Raton Airport:

Effective with the issuance of a Storm WARNING and/or Hurricane WARNING:
Relocate flyable aircraft to other geographical areas, place under suitable shelter, or secure as appropriate.

Also, from the Miami International Airport:

Upon receipt of a Hurricane Warning, Airside Operations will:

Initiate evacuation of all flyable aircraft and post Airfield Operations Senior Agents and Agents in detail to insure compliance and report results.


Why do planes sometimes make a touch-and-go? I have seen airplanes on YouTube and even in my country doing a touch-and-go.

I don't know why planes come down from thousands of feet just to touch the runway and then fly away:

Is it for show?
Is it to check the landing gear?
Is it because of a malfunction?
Does it increase the use of fuel?

Why do planes make a touch-and-go?

To practice approaches, traffic patterns and landings without the added downtime of taxiing back for another takeoff.  Pilots have to maintain proficiency in these skills by practicing them on a regular basis and touch and gos are some of the best ways to do this.  It can also be used for meeting regulatory currency for carrying passengers depending on local time and landing gear configuration of the airplane.  In terms of gas consumption, it’s no less wasteful than a stop and go or a taxi back.  It’s not just for small aircraft either.   I’ve seen plenty of large military aircraft doing pattern work like that as well as there is no substitute for the real thing.  Airliners occasionally do touch and gos, but generally as part of a test flight after major maintenance; company pilots will fly approaches and landings in a level D full motion simulator simply because it’s cheaper and can simulate a wide range of conditions and emergency contingencies as well.


What is the proper procedure when a passenger seat belt becomes inoperable during flight? I was on a Delta flight in Business class on a 777 and during flight the motor of the seat caused the seat belt buckle to pop off the end of the seat belt causing the seat belt to be inoperable.

This was a completely full flight and the flight attendants were unable to fix the seat belt.  I ended up just tying the two ends of the seat belt together for landing and the crew found that acceptable.

What should the proper procedure be in this case?

The flight crew should have given you a seatbelt extension to fix the connection. And if that did not work, then you should have been instructed to hold on and ask other passengers to hold you down for landing.
Also, if you were wondering why the flight attendant did not move you to an empty the jump seat, is because FAA regulations don’t permit.


Where is the lateral position of the aerodynamic center? There is plenty of literature that describes how to find the aerodynamic centers (AC) longitudinal position.

But where would it be lateral?

My guess is somewhere near 1/3 out the wing from the fuselage, but I do not know..or would it maybe be close to the mean aerodynamic chord line?

For a simple tapered half wing the aerodynamic centre spanwise location is at:
$$
y_{ac} = {{b}\over{6}} \cdot {c_r + 2c_t\over c_r+c_t}
$$

where $b$ is the span, $c_r$ is the root chord and $c_t$ is the tip chord.

For a symmetric aircraft it should be at the centreline, since it's the combination of the two identical (but opposite sign) locations.

Source is a aicraft sizing code I wrote some years ago, I remember solving the integral for a simple tapered wing.
Looking quickly at design books I can find the following image in Raymer, hope this helps:


What is the relationship between centre of gravity, centre of pressure and pitch? Ok so I've got a couple of questions regarding CG, CP and pitch

1) When the aircraft is taking off, is the tail down force required to pitch up the aircraft high? Because the aircraft always has a natural tendency to pitch down.

2) When the aircraft increases its AoA, the CP moves forward (towards the leading edge). Does this mean it would go ahead of the CG or move closer
to the CG.

Reading the heated discussion between Robert and JZYL makes me sad. Both are right and still they cannot agree. Maybe a longer and more detailed description might help.

  1) When the aircraft is taking off, is the tail down force required to pitch up the aircraft high? Because the aircraft always has a natural tendency to pitch down.

The aircraft should always have a natural tendency to return to its trimmed state. This might be by pitching up or down, depending on the actual state. There are conditions where that is not true, therefore I say 'should'.

In a take-off, the aircraft is rolling on its wheels and needs to rotate around the main wheels in order to increase angle of attack for liftoff. This means either to decrease tail lift (say, on a taildragger where the pilot has lifted the tail off the runway earlier in order to reduce drag) or to increase tail downforce. In order to pitch up the aircraft, the center of pressure needs to move forward of the main wheel location and the center of gravity, which is done by pulling on the stick. So what is needed is not an absolute tail downforce but a decrease in tail lift. This might well be a downforce, but could also be a lower positive tail lift. Most likely, it is a change from around zero to negative lift on the tail.

As soon as the correct pitch attitude is reached, the pitch rotation has to be stopped by pushing briefly on the stick. This shifts the center of pressure briefly back, behind the center of gravity. After that, the aircraft is in the correct attitude for its initial climb and the center of pressure is at the same lengthwise location as the center of gravity. If it isn't, the aircraft accelerates into some pitching motion which is not desired in straight flight.

Disclaimer: This all assumes no pitch moment contribution from either engines or drag. Any additional moment from other than lift forces adds to the momentum equilibrium and requires the pilot to shift the center of pressure a bit fore or aft of the center of gravity for straight flight.

  2) When the aircraft increases its AoA, the CP moves forward (towards the leading edge). Does this mean it would go ahead of the CG or move closer to the CG.

When the angle of attack of an airfoil with positive camber is increased, its center of pressure moves forward.

In potential flow theory, lift can be calculated as the linear superposition of a contribution from camber and one from angle of attack. While the camber-related part of lift is constant, the angle-of-attack related part varies linearly with this parameter. The center of pressure of the camber part is somewhere at mid-chord (details depend on the camber line; with a Joukowski airfoil the center of pressure is precisely at mid chord). The center of pressure of the angle-of-attack dependent part is at the quarter chord (the center of the area below the chordwise Birnbaum distribution of lift). The important part is the self-similarity of Birnbaum distributions for different angles of attack: The center of pressure of the angle-of-attack dependent part is constant and at 25% of chord for 2D flow and wings of large aspect ratio. Since lift at zero angle of attack is solely from camber, the center of pressure is at around mid chord and moves forward towards the quarter chord point as angle of attack increases. But this would make an airplane with only a main wing using a positively cambered airfoil unstable in pitch.

Hence the addition of a tail surface with less loading than the main wing. Since it operates on a point of the lift curve slope that is lower than that of the wing, a change in angle of attack means a larger relative lift change on the tail which shifts the center of pressure of the whole aircraft back as angle of attack is increased. However, as this happens, the pilot will pull back on the stick, reducing some of the additional tail lift in order to keep the center of pressure close to the center of gravity.

In short: The center of pressure is always very close to the center of gravity unless the pilot commands some pitch acceleration.


How does altitude affect drag? Consider two aircraft. Aircraft A flying at sea level with weight (W) and Angle of attack (α). Aircraft B flying at altitude h in level flight at the same weight (W) and same angle of attack (α) (same configuration as Aircraft A). Will the drag experienced by both the aircraft be the same?

Approximately, yes.
Both lift and drag depend on the density of air, so in order to generate enough lift at the same angle of attack in thinner air, an aircraft has to fly faster. Thus the same number of air molecules hit the plane every second and the drag is approximately the same.
This is a bit of a simplification (especially the bit about drag being caused by air molecules hitting the plane) as the change in temperature causes a slight change in viscosity, which affects one type of drag (detailed Peter's linked question). However it's a good enough approximation for most pilots, who use 'Indicated Air Speed' as a air-density-independent guide to aerodynamic speed.


How critical is it if a pebble blows into a propeller? How critical is it if a pebble blows into a propeller while taxiing and leaves a small abrasion in the leading edge? It wasn't noticed during flight and there was no apparent change in performance of the airplane, it was only noticed after parking. This is on a single engine piston aircraft.

This sort of FOD is often not an immediate problem, however introducing any slight knick or gouge to a propeller could be the beginning of a stress fracture. The last thing you want is a catastrophic prop failure whilst flying!

The correct course of action, much like any minor damage to the airframe, is to note it in the logs, have a mechanic look at it, and make the call if a repair is necessary.


Why did the YF-23 never enter service? The YF-23 was one of the most stealthy aircraft of all time and had a range capability of 2,000 miles (that's more than some airliners can travel) but never entered service. The F-22, has high maneuverable, and is considered to be the second option compared the to YF-23 stealth and speed. So why did the YF-23 never enter service? Image source: NASA/DFRC

The YF-23 lost the Advanced Tactical Fighter program to the YF-22, however it has not been made public why. The ATF evaluation is still classified and details about the YF-23's performance are not easy to come by. They are both excellent aircraft, performed similarly, and there is much speculation why the YF-22 won.

Global Security states that...

  According to the Air Force, factors in the selection for production of the F-22 were a better designed for maintainability, greater potential for future development, and slightly lower cost. Secretary of the Air Force Donald B. Rice stated that the choice was based on confidence in the ability of the Lockheed team and Pratt & Whitney to produce the aircraft and its engine at projected costs. Emphasizing the importance of the Lockheed team's management and production plans, he denied that either prototype was significantly more maneuverable or stealthy. A popular view is that the decision reflected a preference for maneuverability over stealth

A derivative of the YF-23 was proposed for the 2018 Bomber, but that idea died when the program was cancelled in 2006.


What should I do with aileron reversal? During high speed flight, any aileron deflection may cause the wing to twist about its torsional axis (aileron reversal).
Is it dangerous?
In what kind of conditions this occurs, what have I do as a pilot to deal with it or prevent it?
What speed should be for aileron reversal in transport type of aircraft(average)

Yes, this is dangerous and must be avoided.

Consider this: Between the low speed range where the aileron works as intended and the high speed range where it works like a Flettner flap there is one speed point where the rolling moments of the aileron and the wing twist cancel each other out. There the aircraft is uncontrollable in roll. No sane pilot would fly such an aircraft voluntarily.

Set the speed at which full aileron deflection produces only a quarter of the rolling moment coefficient as the never exceed speed.


How much would it cost to fit and maintain every passenger life jacket with personal beacon? About a year ago one sailor showed his fancy life jacket. It included EPIRB or also known as personal beacon.

To date, the smallest personal beacon I managed to find is Fastnet 220, which weights 150 grams and has battery life of 6 years.

Given the scale of airline industry, how much would it cost in installation, maintenance and fuel, to fit each passenger life jacket with such device, excluding the device cost itself?

Edit: Total weight per 200 seat airplane is 30kg. Perhaps someone can translate to fuel/$ per year per whole industry?

From Thomas Cook PDF, I found that life jackets are audited every 12 weeks and takes up to 40 man-hours per aircraft although they've implemented RFID tags now.

Regarding points outside the original question scope:

The device cost can also decrease to few dollars if they are manufactured in mass scale.

Certification is also a factor. Feel free to estimate it as well if you are familiar with the industry.

The extra weight is roughly the weight saved by the introduction of iPads to replace paper. That's apparently saving close to $10K per plane, so you'd expect a similar cost for just flying all those beacons around.

That said, why do you need a full beacon for every vest? If your vests end up scattered over even 10 kilometers distance, you won't have survivors. What you need is a few beacons to locate the plane, and the medium-range active RFID tag on each vest. Such a tag only responds to queries originating nearby. This cuts down dramatically on the battery requirements, as the RFID tag is generally asleep and only woken up by the interrogation signal. Such RFID tags would cost about $20, and weigh a few grams. Battery life is similar (6 years) as that's just chemistry.


Why aren't requirements to use GNSS systems in the Regulations? I've been sorting through the publications outlining the proper use of GPS in IFR scenarios.  Looking at AIM 1-2-3 (dated 10/12/17), it appears that there is some regulatory language in (b) and (c).  To me it seems this information belongs in Part 91 somewhere between 91.167 and 91.299, along with VOR checks, ELT's and ADS-B.

Why isn't this information in the regulations rather than in the AIM?

There are formal rules required to make new federal regulations and it would be incredibly difficult and time-consuming to put every detailed point through committees, public feedback etc. (Some people might actually see that as a good thing, but that's a discussion for another site.)

As for your specific example, 14 CFR 1.1 defines "suitable RNAV system" as (emphasis mine):

  an RNAV system that meets the required performance established for a type of operation, e.g. IFR; and is suitable for operation over the route to be flown in terms of any performance criteria (including accuracy) established by the air navigation service provider for certain routes (e.g. oceanic, ATS routes, and IAPs). An RNAV system's suitability is dependent upon the availability of ground and/or satellite navigation aids that are needed to meet any route performance criteria that may be prescribed in route specifications to navigate the aircraft along the route to be flown. Information on suitable RNAV systems is published in FAA guidance material.

In other words, "there's far too much detail here to make this a regulation, and technology keeps changing anyway. So just go read our dedicated documentation on it".


Will IATA codes run out? Three letter combinations gives $26^3=17576$ possible codes. Some airports have multiple codes (ARN = STO, for example).

I’m just going to guess that there are more than 17576 airports in the world. Are we reusing these codes?

In short, the people sitting over the nose wheel use the ICAO codes, and the people in the back use the IATA codes.

The IATA is the International Airline Transport Association. The ICAO is the  International Civil Aviation Organization. While you are correct, the IATA does not have more than 17500 codes, their primary concern isn't creating codes for every airport including grass strips and private airfields. It is easy to think of IATA codes as being concerned essentially with identifiers that the passengers will need.

As far as ICAO is concerned, they contain a country identifier in their codes. They can even be more than 4 digits, as in the case of RU-2244 (Ukrainka Air Base). The vast majority are 4 digit or 5 digit, with the first 1 or 2 as the country code.

This allows ICAO to be available for every airport in the world. It is very common to refer to the IATA codes when flying locally, let's say within the USA, and refer to the ICAO if flying internationally.

I have a database structure of all airports in the world (or at least all known ones). This includes any grass/water/helipad/paved runways.

There are a total of: 46,465 airport/airfields including those that have been closed.

Source: http://ourairports.com/data/


What is the fan tip speed at maximum thrust? What is the fan tip speed at maximum thrust? Is it any different for a Rolls-Royce Trent 900 (powers the Airbus A380) and Pratt & Whitney PW6000 (powers the Airbus A318)?

Are they efficient at maximum thrust?

Second question first, the higher the jet engine thrust, the more efficient it is (in terms of thrust for fuel rate, bang for buck).
(Source: Boeing)
On to the Trent 900 and PW6000, the big one and small one. The bigger fan will have slower RPM. From the type certificates the max permissible RPM's are 2818 (takeoff) and 6350 (undefined), respectively.
The fan diameters are 2.95 m and 1.435 m, which translate to 435 and 477 m/s. Speed of sound in dry air at 20°C is 343 m/s.
Here's the caveat, the fan RPM (%N1) at takeoff does depend on the ambient air pressure and temperature (among other operational considerations). But as you can see, the smaller fan can rotate faster—read: max permissible—because it has less mass and the centrifugal forces are more manageable.
And since the 1960's or so, the fan RPM is rarely a limiting factor for the jet engine operation, so the engine manufacturer will have designed for the optimum blade tip speeds.

N1 RPM limit

It might be necessary to limit the engine RPM in order to avoid overloading the fan blades in centrifugal force, and to control the fan blade tip speeds. This is purely an N1 limit and is not a function of altitude.
The N1 limit is rarely more restrictive than the pressure and temperature limits.

(Emphasis mine; Jet Transport Performance Methods)
So much so—as you can see below from a 777 manual—the hotter and higher the airport up to about 40-45°C, the faster the takeoff N1 is to compensate.
(Click to view)
That answers the efficiency part, and the blade tip comparison as requested.

Related: Why does lower atmospheric pressure produce higher EPR (thrust)?


Do large airliners have a short-field landing technique? Other than extra braking and reverse thrust, is there a specific short-field landing technique for large jet airliners?

In discussions about the famous landings at St Maarten, it is sometimes said that part of the reason for the low passes is due to the relatively short runway, so the 747s try to land right on the numbers, rather than the usual technique of touching down within the first third of the runway.

Such a procedure is fine in a Cessna, but in a large passenger jet? I have my doubts.

Other than extra braking and reverse thrust, is there a specific short-field landing technique for large jet airliners?

Never heard of any. The required landing distance is calculated so that the plane can reliably stop (even if reversers fail) and landing at shorter runway is not allowed.

  so the 747s try to land right on the numbers, rather than the usual technique of touching down within the first third of the runway.

The usual technique is to aim for 1,000 ft down the runway and touch down with some flare somewhere around 1,500.

  In discussions about the famous landings at St Maarten, it is sometimes said that part of the reason for the low passes is due to the relatively short runway, so the 747s try to land right on the numbers

Actually the TNCM runway 10 has PAPI and TDZ marking a little beyond the usual 1,000 ft mark at around 1,250 ft. Ourairports says the threshold is displaced 162 ft (but it also says runway 9, so it is likely out of date), but according to the satellite images it is a bit over 300 ft plus some runway end safety area, placing the threshold around 500 ft past the fence and the touch-down zone around 1,750 ft past the fence.

Now the normal glide-slope is around 5%. That means the aircraft is supposed to cross the fence at around 90 ft, on average. That seems about right. Of course you can't expect every aircraft to be positioned precisely within a few feet, so now and then some crosses it at maybe 50 ft. That is not intention, but simply a deviation. But of course the photos of planes flying especially low are more likely to be picked for publishing.

Also, a short field landing normally calls for steep approach which make precise aim for landing spot easier. That would actually place the aircraft higher over the beach. But the glide-slope at TNCM is normal 3° (5%) one, so it is not a steep approach.

  Such a procedure is fine in a Cessna, but in a large passenger jet? I have my doubts.

In large jet it isn't. Air transport has stricter regulations than general aviation because more is at stake and larger aircraft have stricter limits because the higher energies involved mean errors are harder to fix and have more serious consequences.


What is the horizontal stabilizer failure procedure? During the final flight of Alaska Airlines Flight 261:

  The CVR transcript reveals the pilots' continuous attempts for the duration of the dive to regain control of the aircraft. At one point, unable to raise the nose, they attempted to fly the aircraft upside-down.

I was wondering what the actual procedure is, if the horizontal stabilizer has a complete failure like this? Do commercial pilots ever simulate such scenarios?

This would fall under catastrophic failure and theres not much that can be done. You may as well ask what will happen if a wing falls off.

but..

UA232 Sioux City. The #2 engine (in tail) blew up and took out the hydraulic lines rendering all tail control surfaces (horizontal and vertical) inoperative. The crew found they could regain limited control of the attitude of the aircraft by varying the thrust on the wing engines, increasing thrust gave some pitch up, decreasing thrust-pitch down. This was due to the line-of-thrust being below the wing. The crew did a great job of getting the airplane back to the airport and heading down the runway. Even though it cartwheeled and burned, a lot of passengers survived, thanks to the crew's action.


Is there any technical word to be used on Radio Telephony, to say that there is a "body air-shipped"? A great number of dead bodies are transported by airplanes everyday.
How will pilots report to ATC they are transporting it/them?

The crew needs to be advised primarily, usually via the NOTOC(Notice to Captain) as this falls under Dangerous Goods classified as HUM under IATA.
But indeed, the controllers are not made aware of it, nor is it mentioned in the flight plan( as far as I'm aware).


What is the fuel consumption per mile for a full CEO A320? I’m writing an essay as part of my GCSE HPQ and one of the statistics I need to base my research and answer on is the fuel consumption per mile or kilometre for a CEO A320.
It doesn’t have to take into account onboard weight like pax and luggage (however if there is someone with that knowledge it would be greatly appreciated) and it would be a normal flight, so both engines running around 50% or whatever cruise speed is and there are no faults with the engines.
Preferably I would like to know it on a plane with tip Fences on the wings but if someone knows the answer for blended winglets instead then it will still be greatly appreciated.

For some general numbers, you can look at the fuel economy tables on Wikipedia. They tell you an A320 flying a 1000 NM flight at typical payload will burn 3.13 kg/km (11.1 lb/mi) of fuel. For a 2151 NM flight, it will burn 2.91 kg/km (10.3 lb/mi) of fuel.
As already indicated in the comments, the fuel burn depends on the payload (and to some extend of course the route length). To get more realistic values, you can use the Breguet equation as shown in Peter Kämpf's answer. When plugging in different values for the payload and flight range (all at 3t fuel reserves), you get these fuel burns:

Since you asked about fuel consumption per distance, we can just divide by the trip distance and get this:

These numbers are somewhat smaller than the numbers from the Wikipedia table. The difference is likely caused by additional fuel burn for the takeoff and initial climb.


Why do older planes not have a middle hand luggage compartment? Why do older planes not have a middle hand luggage compartment?
Where are the oxygen masks for the people in the middle rows?

L-1011 Interior:

777 Interior:

Since the L-1011 was born prior to airlines charging for checked baggage, and passengers didn’t feel the need to bring massive carry-on items with them, the L-1011 featured compact overhead bins that were (to quote advertising of the day) “sized for a lady’s wig box.”

Source: airlinereporter.com

The link provides really good information on the L-1011.