How do planes descend for landing? I fly occasionally  on a pretty short route on a turboprop (DHC-8). When the airplane descends for landing, I can look through the window and see the ground below getting closer over time. However I can't really tell what the pilots do to achieve that. I know that turns make you lose altitude, but it's very clear to me when the airplane makes a turn, so let's count that one out. So we're basically left with:

Slight nose-down attitude
Reduction of engine power
Combination of both

The reason I'm asking this is that during descent I do get this sensation of going down. However, during that time I cannot really see what the pilot did to achieve it. The nose-down attitude might be too minor for me to actually notice (I do not notice a slight nose-up cruising attitude to be honest). I hear a slight reduction in engine power a few times during a descent, but the feeling of going down and the audible noise reduction are separated in time. Is it that it takes time for an airplane to reduce speed (and as a result, descend) when you reduce engine power?

One additional question: I guess that with all the electronics in the cockpit pilots just set a target altitude or rate of descent, and then the airplane systems apply the correct measures to achieve this. How does the airplane know how much to reduce engine power and/or pitch to achieve this exact rate of descent?

If the pilot reduces the airspeed while he increases the rate of descent, you will not notice any change in pitch attitude when the aircraft descends. With jets you should be able to hear a change in engine pitch when thrust is reduced. Turboprops run their engines at constant speed, and a reduction in power here means a reduction in propeller pitch. This causes the propeller noise to change, but this change is harder to discern. With a little practice you should be able to hear the slight drop in propeller noise which signals the begin of the descent, though.

Gliders control their sink rate by flying in rising or sinking air, and additionally by flying slow (and near their minimum sink rate) or fast. To descend quickly, they can open speed brakes and/or sideslip. My favorite for a fast descent is to spin the aircraft, but airliners do not use this option.

In order to produce the necessary lift to keep the aircraft in the air, the pilot picks a combination of speed and angle of attack at which lift equals weight. Other combinations would result in an accelerating vertical speed and are only used in transitions from one flight state to the next.

To arrive at the aircraft's pitch attitude, you need to add the flight path angle to this angle of attack. If the plane descends with a flight path angle of -3° and the pilot reduces speed such that he needs to increase the angle of attack by the same 3° to produce the same lift, the resulting pitch angle of the aircraft would stay the same.

Normally, the correct answer to your question is 2. Reduction of engine power. But the other answers are also correct: If the speed is held constant, the attitude has to be reduced by the desired flight path angle change. Note that this is achieved by reducing thrust alone. If the pilot wishes to descend really fast, he might move to answer 3. Combination of both as in this answer.


What's the reasoning for full-stop landings at night but touch-and-gos during the day for passenger currency? FAR 61.57 says that you need to have completed three takeoffs and landings to a full stop in order to carry passengers at night. However, you only need three touch-and-gos in order to carry passengers during the day.

Why the difference?

Is there some rationale for this?  Are full-stop landings considered safer during the night?

There are three really convincing arguments I've heard for this - I'm not sure which is "correct" and explains the FAA's logic, but personally I suspect it's a little bit of each.

Argument 1: Night landings are "special".

A night landing is definitely different from a day landing - there's much less of a sight picture in the flare unless your airport is in a really bright area or you have a bright moon (and even then it's "different").
If all you're doing is tapping your wheels on the ground and quickly accelerating back to takeoff speed you're missing a lot of what a landing is - bringing the nose down, decelerating to a safe taxi speed, and leaving the runway under control.

Which conveniently brings us to...

Argument 2: "You gotta learn how to taxi all over again!"

That's something my instructor told me, and I didn't really understand what he meant until I was in the plane. Airports are really dark and it's hard to find your way around the taxiways at night. Personally I think a big part of this requirement is the intent that you taxi off the runway and make your way back to the end to shoot another circuit. The hardest thing about my night training - aside from finding the darn airports was taxiing around without getting lost.

(Of course the regs don't say anything about "Taxi off the runway" - they just say "full stop". You can satisfy the legal requirement with "stop-and-go" landings, but there's a nagging voice in my head that says you're not really "getting current" if that's all you do...)

Argument 3: It slows your procedures down, which makes you safer.

Touch-and-Go landings are kinda dangerous if you think about them - Bring the plane in for a landing (which is already a lot of work). Now as soon as all your wheels are on the ground make a mental judgment as to whether you have enough runway to take off from given your current position & rolling start, if so retract your flaps to an appropriate takeoff setting, cram the throttle back in, and take off again..
When you look at them that way it's a bit odd that we have students do them (and there's more than one CFI around on the internet who says it's a lousy teaching tool).

Adding "Oh yeah, and it's dark out!" to that already difficult and dangerous procedure above is just begging for an accident - especially in a retractable gear aircraft (gear lever, flaps lever, and what happens if you miss in the dark cockpit?).


How to fly a parabolic arc? The title says it all, how do you fly a parabolic arc? Me and my friend Ben, are starting a research lab. We want to learn how to fly a parabolic arc.

Get lots of airspeed,pitch up within ac flight envelope limits and as you approach stall speed for your configuration, push forward so that 0 G is shown on the g meter, and keep it there.
As you come over the top pull out again within it's so you neo not exceed Vne,Vmo or Mmo or g limit's for your planes . A parabola for a few minutes or second depending on the plane.


Why don't we get more user-friendly weather reports than METARs? This question is not about how to decode METARs or what software or tools can be used to decode METARs. It is about why we are still using METARs today.

Given that we have smartphones with video messaging capability, cloud services with machine learning today, I struggle to understand why we are still reading METARs:

It is difficult to read. Sure it is not hard to learn, but the fact that you have to learn it means it's not intuitive
It is designed at an age when text are transmitted by telegraph and every character counts
It is trivial to program a parser and render more friendly messages

For me I always feel that METARs are meant for machines; there has got to be something better for pilots which happens to be human. Instead of having this on my flight plan:

  KSFO 111456Z 16015KT 9SM RA FEW012 SCT030 OVC070...

Why not just:

  Station: KSFO

  Time: Mar 11 14:56 UTC

  Wind: 160 degrees, 15 knots

  Visibility: 9 statue miles

  Weather condition: rain

  Clouds: few at 1,200 feet; scattered at 3,000 feet; overcast at 7,000
  feet

  ...

The problem is not about decoding them. Most pilots can read them, and by the time a new pilot completes his PPL training he should have no trouble reading either. The point is everybody around the world is reading them, today, in the 21st century!

I don't know if I'm the only one, but processing the METAR string during flight prep takes a couple of instruction cycles away from my brain (and I have a tendency to check whether the software got it right if I happen to be using one, so I will be processing it anyway, which is a good habit I suppose). I am sure some of that brain power can be better spent somewhere else: reading section charts, route planning, picking an alternate, etc. Scaling this to the global scale? It means every pilot is paying more attention to other things, as opposed to reading coded weather strings which really is the job of a machine. The result? Better flight safely.

So, why haven't we began the move?

One use case where the compact METAR format is tough to beat is rapidly scanning meteorological trends. For that purpose, METARs are user friendly in the sense that they are expert friendly.

For example, a friend invited me to fly with him today on an Angel Flight mission that would have required a landing at Nashville. We had to scrub because the weather is unfavorable and not getting any better according to the TAF and ADDS METAR Data:

Data at: 1616 UTC 11 Mar 2016
KBNA 111553Z 36006KT 1SM R02L/4000V6000FT -DZ BR OVC005 14/12 A3024 RMK AO2 DZB51 SLP239 P0000 T01390122 $
KBNA 111541Z 35005KT 1SM BR OVC005 14/12 A3024 RMK AO2 SFC VIS 1 1/2 $
KBNA 111527Z 01006KT 2SM BR OVC005 14/12 A3022 RMK AO2 SFC VIS 2 1/2 $
KBNA 111453Z 02008KT 3SM BR OVC005 14/12 A3021 RMK AO2 SLP227 T01390122 53015 $
KBNA 111451Z 02007KT 3SM BR OVC005 14/12 A3021 RMK AO2 $
KBNA 111434Z 01007KT 2SM BR OVC004 14/12 A3020 RMK AO2 $
KBNA 111353Z 02007KT 5SM BR OVC004 14/12 A3019 RMK AO2 SLP219 T01390122 $

A subsecond scan confirms that the low overcast ceiling is stuck at four to five hundred feet AGL for the past several hours. Try outdoing that using the same information in decoded METAR format.


Does the dihedral effect happen during coordinated flight? I have researched some about dihedral effect due to a question that I had, and I discovered that my question is essentially already answered, here and here, collectively.

This has led me to a new question because the information talks about slips.

If an airplane is flown in perfect coordination during a turn, does the dihedral effect still work to level the wings?

No.

The dihedral effect depends on a flow asymmetry between left and right wing. Coordinated flight means that both wings have the same flow conditions, and the only asymmetry between both is caused by control deflections.

You do have a flow asymmetry during a turn (coordinated or not) from the speed difference between the inner and the outer wing which grows with the turn rate and wing span. This does indeed cause more lift on the outer wing, but due to the difference in dynamic pressure, not due to dihedral. Since dihedral causes a side force component of lift, you can argue that the outer wing creates more side force which pushes the plane into the turn. But the pilot will compensate the difference in dynamic pressure with the ailerons to stop any rolling motion once the desired turn rate is stabilized. This will also equal the lift on both wings.

Another asymmetry is caused by the location of the vertical tail aft of the center of gravity. Essentially, the tail swings around during the turn, which causes a sideslip condition at the vertical tail. The result is a side force which grows with turn rate and tail lever arm, and due to the high location of most vertical tails also causes a small rolling moment. But again the wing's dihedral has nothing to do with that.

Dihedral only comes into play if you build up a sideslip, and then the turn is not coordinated any longer. @Zeus is right with his point that dihedral stabilizes the aircraft and makes it easier to keep the turn a coordinated one. Now we can split hairs all day if flying in turbulence makes a perfectly coordinated turn impossible. When it comes to dynamic stability, a moderate dihedral effect is highly recommended.


What is the airplane in this video? What is the airplane in this video?

(Video is intentionally set to start at 1:27; that is shortly before the first appearance of the airplane in the video.  After 1:50 there are no clear views of the exterior of the airplane, and only extremely limited views of the interior, so there is little need to watch beyond that point, unless you are into the music.  At 2:12-2:15 there is a brief low-resolution shot that includes a good portion of the control panel; nothing of significance after that.)


Are grass strips more dangerous than tarmac? There are a couple of flight schools near me. One is at a large airport, they use Piper Tomahawks primarily to teach. Naturally, they use well maintained, tarmac runways to takeoff and land. This school has had no accidents in the last few years and no fatal accidents for much longer than that.

The other school often use grass strips in fields and use Ikarus C42s and Cirrus SR22T models. This school has had 3 accidents in the past 2 years, one of which involved a fatality and all of which wrote off the air-frames.

I'm pretty sure this isn't due to the type of aircraft (as globally, they all have similar safety records) nor the instructors (both schools use very experienced instructors).

So are grass strips more dangerous to use as a runway and if so, why?

Cloud, you are making a huge inference from a few small data points.  But in any case, to the basic question, which is actually a very good one:

In terms of the chance of getting killed, (what you seem to be looking for), maybe, marginally, but not enough to rule out operating from grass.  If you know what you are doing, and make allowances, I would say zero.  In terms of non-fatal incidents, maybe a bit higher, depending.

On the plus side: A grass surface is more compliant than a paved one because the tires have less traction.  Grass is much easier to handle flying taildraggers because there is some lateral give with respect to tire side loading.  A tailwheel airplane on pavement is much more skittish and easier to ground loop.  This is also true of tri-gears but much less so because they are already naturally stable while rolling. In both cases however, most people will find it easier to maintain directional control while on grass because of the traction compliance.

On the down side: Somewhat less braking dry, quite a bit less braking wet (wet grass is quite slippery, as anyone who tries to run on it without spiked shoes quickly discovers).  Rolling resistance is higher so take-off distance can be longer than published numbers, which are based on a dry paved runway, and in marginal conditions this has to be accounted for and this varies with how long the grass is at the time.

Bottom line: If I'm in a taildragger I'll much prefer a grass runway. In a tricycle airplane I'll prefer a paved one.  Overall I would expect to see more runway excursion incidents on grass, like landings in rain or in morning dew where pilots slide off into a fence when they discover, surprise surprise, they can't stop, that kind of thing.

That being said, I would never say that a grass runway surface is inherently more dangerous IF the pilot is properly trained in what to expect (especially landing on wet) and makes allowances for it.  The only kind of fatality I would directly attribute to grass would be a takeoff fatality where the airplane's take-off run was extended and it struggled into the air at the far end and stalled out.

In the end though, regardless of this factor or that factor, these things really come down to that old standby, BAD AIRMANSHIP.

More than boating, aviation is fraught with hidden hazards waiting to trip you up.  But if you are educated and trained, they are neutralized and can't get you unless you let your guard down.  You have to approach things in flying this way, or you will worry yourself out of the activity before you ever really get to enjoy it.  On the other hand, you are asking the right kind of questions so this is good.


What do they use to de-ice aircraft and runways on snowy days? One of the answers to this question mentions how runways are usually in need of de-icing on cold days (which makes sense), and as anyone who has ridden an airplane on a cold day knows, planes need de-icing too.

What I'm wondering is a few things:

What is used to de-ice a commercial aircraft?
What is used to de-ice a runway at a large airport?
Do the two fluids effect each other at all?  Meaning, when an aircraft drips de-icing fluid onto the runway, does it cause any interactions or problems?

What is used to de-ice a commercial aircraft?

De-icing fluids are used which are made of ethylene glycol (EG) or propylene glycol (PG) in addition to other ingredients.

What is used to de-ice a runway at a large airport?

Airports use different types of materials, e.g. potassium acetate. Safegrip ECO2 is a brand which is popular.

Runways can also be deiced using normal techniques like salt and snowplows etc.

Do the two fluids effect each other at all? Meaning, when an aircraft drips de-icing fluid onto the runway, does it cause any interactions or problems?

I do not think that there is much or any damage to a runway from the de-icing fluid. If something is bad for solid concrete, how it can be good for fragile aluminium?

Research shows that the residuals left on the airplanes cause some issues. Those are described below.

Effect of runway de-icing fluid residuals on airplanes

There are some studies that show the runway fluid having some adverse effects when combined with de-icing fluid residuals on airplanes. They state:

  Runway deicing fluids contain potassium acetateor potassium
  formate-based fluids (deionizing salts). When these fluids combine,
  the separation of the anti-icing fluid thickeners may be enhanced,
  leading to a more rapid formation of the residue.

Effect of airplane de-icing fluid residuals on airplanes

However, de-icing fluid residuals on airplanes can freeze and cause damages to flight controls. More information is here.


Do interceptor squawk codes suppress TCAS RAs? Some parts of the world reserve a discrete squawk code for use by military interceptor operations (in the NBCAP, code 7777 is used for this).  Does this squawk code, or some equivalent value, suppress TCAS RAs from other aircraft, or is turning off their Mode A/C/S transponder replies the only way an interceptor can avoid triggering a TCAS RA from a TCAS-equipped aircraft?  Is some sort of Letter of Agreement used to keep track of interceptors in areas where transponding is mandatory but interceptors cannot squawk during intercepts, or during intercepts outside of primary radar coverage where the interceptor is unable to squawk?

To avoid an RA, the interceptor would almost certainly turn off at least his Mode C, and to avoid a TA and the concern in the intercepted aircraft of "what is this no-altitude traffic doing closing rapidly on me???" he will probably turn off his squawk altogether before he gets to the last few miles of the intercept.  (There were cases years ago when TCAS was pretty new of intercepted aircraft getting a series of RA's as interceptors -- squawking everything -- closed on them, maneuvering to continue the intercept even as the target climbed and dived all over the sky in response to the RA's. That scenario is undesirable for all sorts of reasons!)

A wingman may well hold a squawk and park himself some miles in trail of the target, monitoring both the interceptor and the target with his own air-to-air radar.  ATC can see the wingman and the target, and knows that there is an interceptor somewhere between them -- which is probably enough for their purposes.

Each specific case probably has letters of agreement between the ATC facility and the specific interceptors, so they'll all know in advance who's where, doing what, squawking or not squawking what, and who's talking on which frequencies.  Those sorts of specifics probably aren't available in the public domain.


How do I estimate how much air flows through the intake due to engine suction? I read that the intake mass flow ratio (not sure its translated to correct lingo) can be expressed as:

$C_A = \frac{\textrm{airflow through air intake}}{\textrm{air density } \times \textrm{ speed of free flow }\times \textrm{ intake area}}$

A graph of this could look like:

Now my question is two fold:

What is the correct english term for this factor?
How do I estimate how much air flows through the intake due to engine suction.

Okay, to solve this I assumed the atmospahere is ISA and flying at 0ft.
Also that air suction vary linear proportional to mil thrust.

So that airflowThroughAirIntake = factor*thrust

I then did some flight tests to estimate what that factor would be, getting the ratio from the graph at full mil thrust.


Why do aircraft leave the cruising altitude long before landing just to circle? Often flights will leave the cruising altitude long before the actual landing. They will go down to a couple of thousand feet and stay at that altitude and  circle for quite a while in waiting loops before it's actually their turn to land. It can be seen basically all the time at Heathrow Airport (LHR). But also for example in Munich Airport (MUC), where flights often come far down over the city and then make wide turns towards the airport.

So I'm wondering: if it's already clear ahead of time (and I'm sure mostly it is) that it's not their time to land yet, why not circle at higher altitudes? Often those waiting loops occur over dense populations and thus create quite some noise on the ground.

It's better to be low(-ish) and ready for a spot to open, than high and far from that spot. As to why, for busy international airports the answer is really simple:

► There isn't a way to manage it near perfectly (yet).

To understand that statement, requires some prerequisites, so I'll try to simplify and summarize the basics:

There is the concertina effect: it's when fast vehicles slow down, the spacing between them go down. So the nearer the airport for landing, the more squeezing happens.
Add to that that the arriving planes come from all or most directions, and the same low-ish airspace is being used by departures as well.
The trajectory of each plane depends on each plane's load and performance, and the wind it experiences. While wind is forecast, the forecasts aren't perfect.

A solution to that is for all planes to send their estimated trajectories to the air traffic management (ATM). That is one of the projects being worked on in Europe, but it's at least a decade from full deployment. One part of it is the extended arrival management (E-AMAN).

Why wasn't it worked on decades ago has to do with the history of data communication in aviation. And it boils down to money and return of investment. Initially some of the users, like the airlines, didn't see a benefit of the high cost of the high tech solutions they'd have to add to their planes.

Seasonal adverse weather en route or in the terminal area complicates matters even more.
Busy international airports with multiple runways land planes every 30 seconds or so, so you can imagine the impact of the slightest delay one plane headed to that airport experiences. So arrival management is first come, first served.

Related: What are the negative associations with Continuous Descent Approach?


How many people can stand on airliner's wings? This photo of Allegiant Air flight 331 got me wondering: how much weight would a typical airliner's wings be able to hold?

Aside: Apparently these folks didn't realise that if they smell gas in the cabin, they probably shouldn't decide to go out of the emergency exits and stand ON TOP OF ITS TANKS! God forbid one of them gets nervous and lights a smoke!

My question is basically: how much weight are airliner wings required to hold $\div$ the average passenger weight? Theoretically how many people? :)

Disregarding the fact that the wing load vector on a passenger jet usually points up, not down, the wings will usually bear most of the load for the entire aircraft. The MTOW for an MD-80 is 63,500 kg. If an "average" passenger is 80 kg, then that is 800 passengers. Obviously that is going to be greater than the number of passengers on the flight, because those wings had already lifted those passengers (and the rest of the plane) into the air in the first place.


Are canards actually more efficient? Another post here triggers this question;
Since I was a kid I have read endless articles about how canards are more efficient because both wing-like surfaces are lifting, whereas a tail surface is adding weight.
Yet the most efficient aircraft, gliders, almost never use this layout. A few have, Solitare for instance, but obviously this claim is oversold given the complete dominance of conventional layouts.
So what’s the story here? Is it that they are more efficient but some other effect makes them unsuited for most roles? Or is it simply not true in practice?

No. It's not true in practice.

While the conventional layout puts the whole tail into the downwash of the wing, a canard will add downwash to the center wing and upwash to the outer wing. This means that while the tail of a conventional layout sees less angle of attack variation than the wing (which is good to prevent tailplane stalls), the up- and downwash variations with varying angle of attack will spoil the lateral lift distribution on the main wing of a canard airplane and increase its induced drag.
Since the canard surface needs to fly at a higher lift coefficient than the wing for natural stability, it will have less margin for control. It is no coincidence that successful canard designs are unstable. Also, this means the big wing surface cannot be fully used for lift, which is wasteful and increases take-off and landing speeds.

More on this can be found here.

Since I was a kid I have read endless articles about how canards are more efficient …

The reason for this is simple. It is much more exciting for authors to claim they know better than all the experts than to humbly admit that the state of the art is really the best under the circumstances. The incentive to laud canards above all else is much too enticing, and human psychology tends to prefer the sources which confirm a preconceived opinion. In the end the authors really think they have found a better solution and become evangelists for a better world, especially when their own understanding of the matter is limited.


What is the difference Between Minimum fuel and Mayday Fuel? what  is the difference Between Minimum fuel and Mayday Fuel ?

The term Minimum Fuel should be used when you currently expect to land with more than the minimum fuel reserves (so everything is OK right now), but any further delay would result in being below minimum reserves when landing. This situation is not yet an emergency and ATC does not need to give you any priority, but they know that keeping you in a holding pattern could result in you declaring an emergency.

The term Mayday Fuel should be used when it is clear that you will land with less than the minimum fuel reserves. This constitutes an emergency and requires ATC to act immediately (this could be priority for landing or diverting you to a different airport, if available).

The ICAO defined both terms in Amendment 36 to ICAO Annex 6 Part I:

  4.3.7.2.2 The pilot-in-command shall advise ATC of a minimum fuel state by declaring MINIMUM FUEL when, having
  committed to land at a specific aerodrome, the pilot calculates that any change to the existing clearance to that aerodrome may
  result in landing with less than planned final reserve fuel.

  [...]

  4.3.7.2.3 The pilot-in-command shall declare a situation of fuel emergency by broadcasting MAYDAY, MAYDAY, MAYDAY,
  FUEL, when the calculated usable fuel predicted to be available upon landing at the nearest aerodrome where a safe landing
  can be made is less than the planned final reserve fuel.


Can anyone identify what appears to be a crashed WWII German plane? This photograph is in my family's photo collection.  The only information with the photo is, "Cousin Bud Kohl - aircraft wreck."   If anyone can identify the make and model it is greatly appreciated.

It's a P-47 Thunderbolt, the original "razorback" version (not the later ones with the bubble canopy and cut-down rear fuselage).  The instant giveaway is the V shaped windshield, which had the armour glass as a separate panel behind it (removed in the pic). The bubble canopy versions have the armour glass as the windshield itself, like most other fighters.
The German rudder/fin looks to be a piece of a the right tail boom of a Focke-Wulf FW 189.
My guess is that Bud is probably at a forward P-47 base that was an ex-Luftwaffe base (the brick wall behind suggests a large base with permanent buildings, possibly within Germany or Eastern France, in early 1945) and therefore still strewn with German wrecks.  The Jug in the picture has had what looks to have been a gear up landing and was dragged away to a bone yard area, and is being cannibalized for parts as required.


Is there a speed needed to achieve flight? Is there a minimum speed needed for flight (universally)? For example, if something was going 10 miles per hour, could it achieve flight? And by flight I don’t mean throwing a paper airplane, I’m talking about the item going to that speed, then flying.

Is there a formula for calculating the speed needed for flight?

There may be an ultimate lower bound, about where the ratio of random air motion to forward motion is near 1:1. But that is an extremely slow speed.

I've seen competitive balsa-wood gliders, weighing just a few ounces, achieve flight from a rubber band, going less than 1 mph, or a slow walking speed.

If the craft is light enough, the wings are big enough, and a little air is moving over them, lift is generated.


Is the waves and signal dangerous for human at the airports? Waved like VHF , UHF and other themes like radio or something ....

No. To people at the airport, the electromagnetic radiation from various sources relating to aviation (or anything else) is not dangerous.

Any electromagnetic radiation is, with enough intensity, possibly dangerous, even instantly lethal, but you can rest assured, that such intensities are not present anywhere a normal person has access to.


Is the in flight emergency manual of a Boeing 737 Max 8 available to read online? I frequently read about pilots going through manuals/checklists/procedures  in an emergency situation in an airliner while in flight. Is there an online resource where the public can actually read it, for e.g. for Boeing 737 Max 8?

The in flight emergency manual is called the Quick Reference Handbook (QRH) and is in general not made publicly available by the manufacturer or airlines.

It is however possible to find quite a few online. Pages like smartcockpit.com have a lot of resources available. The Boeing 737 MAX is not mentioned on their page. A Google search for "737 max qrh" may help you find something.


What about a Plane-Train? The Shanghai Maglev Train's max speed is 267 mph. Could a plane be made to follow a rail, surface area provided, if not an existing rail to travel along? How much faster could the heavily modified train/plane travel?
The plane is "on rail, not touching the track while following it, not over water but over a track made of concrete" or less.
Another way to ask, is how much would a very large cruise missile shaped vehicle benefit from using ground effect (possibly using curved surface area or rail to follow) verses not? Because the the rail is not directly supporting the wight of the vehicle, at least directly, how sturdy would that rail need to be? When done over water, the water is displaced by the air pressure under the ground effect plane.

The first issue with airplanes is they are stupendously, freakishly light.  Any random American freight diesel locomotive weighs more than a 747-400.  Trains rely on this mass to provide the downforce to keep them engaged to the railhead.
So your vehicle would need to do something to replace this downforce; for instance have a tubular or I-beam rail which allows the train to grab the bottom of the rail; expect switches and special work to be complicated at that point, shifting an entire track instead of just small parts of it.
So while unloading weight off the rail only makes matters worse for track design, you're also paying for that lift with induced drag. In other words you're using a great deal more fuel (or electricity) to unload weight off the rail, when the rail really doesn't mind bearing weight.
In fact from an aviation perspective, the "induced drag" on a train can be approximated to zero, thanks to Mr. Babbitt (Mr. Timken's idea is worse for drag but better for reliability).
That's why good ole fashioned railroad just keeps winning the high-speed race (or coming too close to matter). The exact TGV train that ran 357 mph could be dropped onto a NYC subway branch in Brooklyn, interchange onto LIRR, come into Penn Station and the Amtrak Corridor, through the freight rail system to Detroit and run on Woodward Avenue Q-line, then to Long Beach CA and run on the Blue Line.  The only thing I'm arm-waving is power supply, and curve and platform clearances on NYCTA.  In fact, in 1993 Amtrak dragged an X2000 and ICE high-speed trainset all over America behind diesels. No wheel modification needed.
So while your idea has merit... once you get out the sharp pencil and really start optimizing for performance, you will find it best to forget wings and load full weight on the rail, and further, to optimize for Plain Old Railroad Track so you can just use existing rails to get downtown.  Going with a wack-a-doodle guideway doesn't buy you much, and makes getting downtown a mega-project of biblical proportion  all its own. Here:

The city of Victorville was selected as the location for the westernmost terminal since extending the train line farther into the Los Angeles basin through the Cajon Pass would be prohibitively expensive.

/facepalm... Cajon Pass is not a challenging hill for HSR. If they can't even handle that, they sure aren't getting into L.A. proper where all the connecting trains are.  And L.A. is a piece of cake compared to a dense, old city like Paris or even Boston.  This: This is the folly of a wack-a-doodle guideway.  They finally retreated from that to a standard railroad design, so they could come downtown on shared rails.


Can pilots use PAN PAN Medical, even if they were not on MedEvac mission? If there is a medical emergency on board, on a passenger or crew member, will the crew be cleared to use PAN PAN/MAYDAY MEDICAL on their R/T?

Is there any DOC in which regulates these phraseology?

The UK CAA Radiotelephony Manual (CAP 413) has the following to say about it:

  PAN PAN MEDICAL is not used in the UK but refers to a Geneva
  Convention term associated with medical transportation by parties
  involved in a conflict.

  Use of this term is not appropriate in the UK.

Which seems to be a pretty definitive no. Personally, I'd not heard of the term but assuming the CAA's interpretation of the ICAO's definition (i.e., for use during war) then I can't imagine it ever being appropriate outside of that use.

That said, why would you need to? Using a normal MAYDAY or PAN call and describing the emergency as a medical one is perfectly acceptable and would be fully understood by all parties.


Where does the 35 feet screen height come from? When taking off, why are we required to climb at least 35 feet over the departure end of runway? Why not other numbers? This comes from the FAA regulations. I believe there must a clear explanation for this but can't find one. Is there any historical or mathematical reason?

The best explanation I've seen for the logic behind the 35 foot crossing height requirement can be found in the FAA Instrument Procedures Handbook (IPH). It's available from the FAA website at this link: https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/instrument_procedures_handbook/
In Chapter 1, Departure Procedures, under Design Criteria on page 1-16: "The aircraft climb path assumption provides a minimum of 35 feet of additional obstacle clearance above the required obstacle clearance (ROC), from the DER outward, to absorb variations ranging from the distance of the static source to the landing gear, to differences in establishing the minimum 200 FPNM climb gradient, etc."
So, the 35 feet is in place to account for a multitude of variables. The phrase "differences in establishing the minimum 200 FPNM (Feet Per Nautical Mile) climb gradient" covers a whole host of potential errors such as variations in individual aircraft performance, early rotation, late rotation, under rotation, over rotation, poor airspeed control, etc. This error proofing is important since the 35 foot requirement is used when building all performance data for go and no-go decisions. That performance data is all based on set assumptions. Reasonable deviations from the assumptions are mitigated (somewhat) by the 35 foot margin.
As with most safety margins, there isn't necessarily a precise reason for the size of the buffer. However, even increasing the crossing height a slight amount, say to 50 feet can have significant effect on performance calculations. At a minimum climb gradient of 200 FPNM, the difference between a screen height of 35 feet and 50 feet is just over 450 feet of required horizontal distance. In a tight performance situation such as high pressure elevation or short runways, a 50 foot crossing height could be too much for some large commercial aircraft.
Of note, the regulation that created the 35 foot crossing height, SR422, came about in the late 50s during the beginning of jet-powered commercial aviation. The aircraft being designed and fielded back then, the Boeing 707 for example, would have had a hard time making a higher restriction. That likely had influence on the required crossing height.


Can an ultralight aircraft fly with a 18hp engine? I have some questions - I'm planning on building single seat UL aircraft with this plan sketch (I have more), I drew this based on real plain and some research. Empty weight is between 50-70kg with engine

The power plant I will use this engine. 4 stroke, OHV, single cylinder, 440cc, power 18hp/3600 RPM, torque 3.0 kgm/2500 RPM (21.7 lb ft), ignition TCI, gross weight 37 Kg.

My questions:

Is this engine enough to make it fly?
Do I need belt reduction or gear reduction for a 1 meter propeller?
What propeller size to fit with this engine?
Do you see any problems with this design?

https://en.wikipedia.org/wiki/AmEagle_American_Eaglet

I found this on Wikipedia, it use a McCulloch MC101 15HP engine with 9000 RPM, that's make me doubt to use SFE 460 because the RPM far bellow. I can't find McCulloch MC101 here

It's possible to arrive at a rough estimate by assuming that the L/D ratio is 9. Now, the empty mass is 70 kg. Let's add 45 kg for the engine, transmission and propeller. And we must not forget the mass of the pilot (85 kg) and 20 kg of fuel. It's a total mass of 220 kg. Let's round it to 250 kg in order to be on the safe side.

If we imagine the plane gliding at L/D = 9 and 25 m/s, the sink speed will be 25/9 = 2,78 m/s. As the mass of the plane is 250 kg, its weight is 2450 N. Thus, the 'gravitational power' involved in the glide is 2,78 x 2450 = 6805 W.

The plane, for straight and level flight, will need exactly that power. If we assume that the transmission and propeller losses are 50%, you'd need twice that power, that is, 13,6 kW. Besides, some extra power is needed, (in order to climb, for example...) so let's increase the figure by 30%. 13,6 x 1,3 = 17,68 kW = 24 hp. That's the engine power that, in theory, and according to this simplified estimation, would be needed for that plane...


What is a seal in aeronautics? I've read phrases like "All gas turbine engines use pressurized seals for their shaft bearing compartments to keep [...]" but I do not understand what "seals" means. In spanish we haven't a word for it.

Translation

Seal means sello mecánico.

While the answer could stop here, we wouldn't know what seal types are used in turbine engines, and how some are pressurized to prevent contaminants entering the aircraft pressure vessel.

Need for bearing compartments and seals

  I've read phrases like "All gas turbine engines use pressurized seals
  for their shaft bearing compartments..."

In turbine engines, there are one or more shafts holding the rotating parts of the compressors and turbines (rotors). Bearings are inserted between a shaft and its stationary supports to limit destructive and heat-generating friction. Bearings also bear the large axial load transferred by compressor and turbine rotors to the shafts.

In turbine engine bearings, solid friction is replaced by fluid friction using an oil film between balls or rollers and races. Bearings are enclosed in a cavity and oil is injected into the cavity. This cavity is known as a sump.

The following drawing is taken from  an answer to In a turbofan what holds the spinning axis?. You can see the five bearings within their sumps:

(Source)

Oil must be circulated from the oil tank to the sumps and back, and cooled before being reused. As oil quantity is limited, oil must be prevented from leaving the oil system. This is where seals enter into action. In particular, seals are used to prevent leakage between a rotating shaft and stationary sump apertures.

High speed seals

Turbo engines' oil seals are specially selected to bear the high rotation speed of the shafts (wear), and the high operating temperature of the engine core (adjustment and bending). They are of two main types: Carbon or labyrinth. Both reduce oil pressure while it travels in the interstice between the shaft and the sump wall.

Carbon (source) and labyrinth (source) seals

Air sealing

  All gas turbine engines use pressurized seals

As one would think, these seals are not perfect: a small quantity of oil will be able to make its way across the seal, and this quantity will increase with seal wear. Unfortunately, burnt oil releases hazardous fumes which could enter the aircraft air conditioning system as cabin air is tapped most of the time into the engine compressor.

To limit the leakage further and to recover leaked oil, a second cavity is built around the first seal and pressurized air is injected into it. This has two effects:

Air pushes oil back into the sump.
The second cavity being also sealed, any leaked oil can be drained and dumped overboard.

For example, the forward sump (on the left of the first picture) encloses 3 bearings (from left to right: #1, #2 and #3). Oil must be contained within the sump near bearings #1 and #3. Let's look at a CFM56-7B engine mounted on Boeing 737 NG. This is the lower half of the forward sump:

CFM56-7B forward sump, based on drawing from CFM56-7B Familiarization Manual

Oil enters the sump and is directed to bearing races using tubes and oil nozzles.
An oil seal prevents oil from escaping the sump in large quantity.
As some oil would nevertheless cross the seal, compressed air is injected on the other side of the seal, to counter oil leakage. Air entering the sump is then dumped overboard by the centrifugal air-oil separators.
The space where air is injected is closed by a cap on the sump with a air seal on the shaft.
Air and a small quantity of oil able to cross the oil seal are eventually drained and released overboard.
Oil crossing the bearing is scavenged and returns to the oil tank after air has been removed.

Metal particles in scavenged oil are captured by magnets to detect abnormal wearing of bearings. From time to time oil is added to the oil tank to compensate for small leakages in the bearing sumps (and in the gearboxes).

See on Youtube: Carbon Seals - Turbine Engines: A Closer Look.


How do I calculate FPNM for standard take-off minimums? I have trouble understanding and calculating FPNM for standard take-off minimums.

As I understand, the formula is: (Ground speed)/60 * FPNM = FPM

Let's say the ODP says:

  565' per NM to 2800, or 1000-3 with minimum climb of 370' per NM to
  2800, or 1500-3 for climb in visual conditions

With a Cessna 172S, could you let me know whether the aircraft is able to meet this requirement? Here is the rate of climb chart:

You don’t specify an altitude in your question, so let’s start with 2000' and the requirement to climb at 565' per NM and assume you have the airspeed at 73 kts. Then the performance table says

-20°   0°   20°    40°

760   695   555   560

So you meet the requirement for all temperatures up to almost 40°.

At 4000' you will make it at 20° but to see what the maximum temperature would be you need to interpolate.

-20°   0°   20°   ?°   40°

685   620   625  565  496

There are lots of ways to do the arithmetic, one way is with percentages.
The difference between 625 and 496 is 129. The difference between 625 and 565 is 60. So 565 is 60/129 (47%) of the way between the two. Our unknown temperature is also 47% of the way between 20° and 40°.

The difference in temperature is 20°. 47% of that difference is 9.4°. We went from left to right in calculating the percent difference so we do the same thing for temperature and add 9.4° to 20° to get 29.4°.

So as long as the temperature is less than 29.4° and you maintain an airspeed of 73 kts indicated, you can meet the climb gradient.

If you are at an altitude in between one on the table then you would need to do two interpolations. One at the lower altitude and one at the higher.

In the real world, and not on an FAA test, just use the next higher altitude and temperature.

Note that the table is based on pressure altitude, so set your altimeter to 29.92 to get the pressure altitude of the field.

Also note that if your airspeed is faster than in the table, you will be climbing too slow to make the numbers. This is also a no wind table. If you are climbing with a tail wind you will not meet the climb rate per nautical mile.

And finally, the climb can be to an altitude that is fairly high above the field elevation. If you look at the chart you will see that performance drops off with altitude. In your example if the field is sea level, then you will need to climb 2800' at 565 fpnm. Don’t use the sea level numbers since you are climbing through the 2000' level. Use the 2000' numbers to be safe.

My home field is at 212' MSL and one of the departures has a minimum climb of 320' per NM to 3000'. I’d use the 4000' row to decide whether I could make the departure.


What part of an aircraft design process is governed by mathematics? I am well aquainted with the six steps of the engineering process, but what is the six steps of design specifically for aircrafts (if there is one)?
I'm very mathematical, so I would appreciate it if you could include equations that are necessary for each step.
Also, does anyone have a CFD that they would recommend? I'm building models in AutoCad, and am currently working with a CFD called Anasys.

Right now, I understand how the different components of a plane affect its flight, but I am really more interested in understanding how to design a plane using math.  I do a lot of work with rockets, which is governed by a pretty good set of written equations, but I was hoping I could do similar in the field of airplanes.

Maths have their place in pre-design of aircraft, but it is still a design process so creativity has a place as well. Designing a plane is an iterative process, that also includes steps like determining what the plane is used for, what the payload will be, what the range should be, is it allowed to use a runway etc.

Once these factors are determined and honed down, there is a lot of math to be applied to check if the wing can support the weight, if the engines can propel the plane, if the structures can take the static and fatigue load, if the hydraulic pumps are dimensioned correctly, if the control surfaces are dimensioned correctly...

Rockets are relatively easy in that respect. Not taking anything away from the achievement of putting men on the moon, but a rocket has a single mission type, has very little bother with aerodynamics, and does not need to be optimised for decades of safe, economical or mission ready use.

One aspect of aeroplane design where maths & physics rule is aerodynamics, but what's great for aerodynamics is usually not great for structural engineering for instance. So if you would like to focus on maths only, aerodynamics would be a good place to start. Please realise that it is only one aspect of aeroplane design though.

The complete process of aeroplane design is really a lengthy process that does not fit within one answer on this site. I can recommend my goto book for design aspects, Torenbeek. It has 600 pages. Check out Appendix C. on a mathematical method for weight prediction of the wing structure for instance.


Why is an accident referred to by flight number instead of registration number of the airframe? Most accidents are referred to by flight number, for instance MH17 or MH370 to name a few recent ones.

Flight numbers are usually but not always retired after a crash. So why isn't referred to the registration number instead?

Most accidents are referred to by flight number

It depends who it is that is referring to the accident, and on who they are addressing.

News media and the general public

Newpapers and other media use flight numbers because that is the number known to friends and relatives of the individuals concerned and because most members of the public who have flown as passengers are very familiar with  the concept of flight numbers but not really familiar with aircraft registration numbers.

Investigators

Investigating authorities have their own numbering schemes for accidents they investigate.

Aircraft registration numbers change when an aircraft is sold to a purchaser based in another country.

The only number that stays with an aircraft for its entire life is the manufacturer's serial number.

All these numbers can appear in official accident investigations reports. The registration number is usually prominent.

AAIB

NTSB

BEA


How many 747-200 are still in service? I'm wondering how many 747-200's are still in service?
I know for sure Rolls Royce is using one for testing purposes.
And the one from the US Forces.

Are there any civilian operated ones left?
Does somebody have photos?

Running the numbers from RedGrittyBrick's answer, there appear to be 36 active 747-200s out of 393 built (according to Wikipedia). Of the 36, 9 are passenger planes, 22 freight (including 6 converted from passenger planes, marked *), 3 combi (passenger and freight), and the two VC-25As ("Air Force One").

The active aircraft are as follows, with tail numbers included so you can look for photos.

Aerospace One: 1 freight (SX-ASO), 1 combi (SX-ASC)
AHS Air International: 1 freight (AP-BIO)
Cargo Air Lines: 1 combi (4X-ICM)
Caspian Airlines: 1 freight (EP-CQA)
Iran Air: 3 passenger (EP-IAG, EP-IAH, EP-IAI), 1 combi (EP-ICD)
Jet Star: 1 freight (ER-BBS)
Kabo Air: 3 passenger (5N-DKB, 5N-JRM, 5N-MAD)
Kalitta Air: 2 passenger (N715CK, N793CK), 4 freight (N704CK, N746CK, N794CK,* N795CK*)
Kam Air: 1 freight (4L-TZS)
Midex Airlines: 3 freight (A6-MDG, A6-MDH, A6-MDI)
Orient Thai Airlines: 1 passenger (HS-UTC)
Rayyan Air**: 2 freight (AP-BKI, AP-BKS*)
Saha Airlines: 2 freight (EP-SHB, EP-SHH)
Saudi Arabian Airlines: 1 freight (HZ-AIU)
United States Air Force: 2 VC-25A (82-8000, 92-9000)
Uni-Top Airlines: 3 freight (B-2448,* B-2450,* B-2462)
Veteran Avia: 1 freight (EK74799*)
Vision Air International: 1 freight (AP-BIV)

* Built as passenger and converted to freight.
** Not to be confused with Ryanair! :-)

There are also several stored aircraft, including the Rolls-Royce test plane you mention in the question.

Thanks to fooot for explaining that BSF denotes "Boeing Special Freighter", a passenger plane converted to freight use.


What are the differences between battens and ribs? What are the differences between battens and ribs?

A flexible airfoil's battens have the same purpose on a sailboat, windsurfer, hang glider, iceboat, landsailer, 17th century windmill, or anything else.  The mast or spar adds stiffness to one dimension (transverse to  airflow), the battens to the other (parallel to airflow).
On a rigid airfoil covered by fabric or film, ribs have the same purpose.  (Some recent sailboats have such rigid airfoils instead of flexible sails, too.)
The main difference between ribs and battens is that battens usually stiffen only the aft part of the foil.  On something that sails on both port and starboard tack, that lets the front part of the foil flex appropriately.  (If you found a hang glider that dared to fly inverted, the same would apply.)  On a hang glider that doesn't fly inverted, leaving the front part unbattened avoids stress risers and, at any rate, it's only the aft part that would be prone to fluttering like a flag and contributing no lift, were it not stiffened.


First time passenger flight by two pilots? In this video, the captain proclaims after take-off:

We were nervous about this, but takeoff went smoothly

It was his first passenger flight in the A350, but still... not exactly what I would want to hear as a passenger. This got me thinking, does it ever happen that two pilots take their first passenger flight on a given type together, or will it always be the case that if it's someones first time, the other pilot will have X amount of hours on that type?

It is never “the first time”. What he is really saying is that after many hours of flying the aircraft (or an approved simulator) this is the first time doing a revenue flight with passengers. Previous flights would have been training flights.
When a new aircraft type is first introduced to an airline, it can be expected that the entire crew is doing their first revenue flight after training.
What is not expected is that the pilots announce it to the passengers. I would not advise doing that because the passengers might not understand, and it would put doubts in their minds, as it did for you.


What would happen if flaps are extended beyond 40 degrees? The angle of flaps is limited to a specific value. It's around 30° to 40° on most aircraft what I've seen.

Source

But what happens when they get extended even further? 50°, 80°, 90°, ...
Let's also say they don't break due to high load on them. I just want to know it theoretically.
What will happen to the plane?

Will drag be increased?
At which point will the aircraft loose it's lift due to the extreme deformation of the wing?
What about the slats?
Are there any aircraft that use a higher than usual angle of flaps?

Depends on the kinda of flaps installed on the aircraft; in the example above with fowler flaps, the design would begin to just create excessive drag without gainful lift and would require a pretty bulky structure to accommodate for the aerodynamic loads imposed upon them.

Now some other types of flaps like the split flaps or dive brakes like those found on the Spitfire fighter were designed to extend 90°.


At what point are the pilots allowed to communicate with the ground crew whilst they are still in the cockpit? The question comes from this comment by Federico

  you cannot be directly connected with the ground crew while the aircraft is autonomously moving (and pushbacks are not used for gate alignment)

Is he saying pilots aren't allowed to talk to the ground crew until the plane is no longer under their control?

no longer under their control

is a strange phrasing, the aircraft has to stop sooner or later, do you define a parked aircraft "not under the pilot's control"?

I'm saying that the ground crew does not generally connect the external "headphones" while the engine is used to power the aircraft, the connector is near the nose gear well and the cable is generally not overly long, to avoid the grond crew from being ingested by the engine, they generally wait until it is safe.


What plane is this, looks a lot like a BAe-146-100 or an Avro 146-RJ100, however with only 2 engines? I saw it and took a picture. It is flying out of Phoenix Sky Harbor International Airport. It landed at about 5:27 if that matters. It is a green tail livery that extends downward. The wings are above it like on a C172 however the engines are straight under the wings. The engines are fan engines, not props. It looks like the 146-RJ100 with only 2 engines total though.

Thanks for your help!


How do I get attention on a busy radio channel? As I understand it (I'm not a pilot), radio communications are a more-or-less first come first served proposition. If I'm in busy airspace with near constant communication between ATC & aircraft, how do I break in to make contact with the ATC for whatever purpose necessary (establishing comms to enter airspace, or whatever the situation may be)?

As Ron commented, the basic answer is that you try to anticipate when a short gap is going to be, and jump on before someone else does. It sounds a bit daunting, but it actually works out pretty well in practice.

That being said, it's not exactly first come first serve. ATC tends to prioritize talking to the aircraft which need the most immediate instructions. So, an aircraft on final is going to get more priority than one which hasn't even entered the airspace yet. Even if you manage to get your request in, if the controller has a more immediate issue to address, you may get completely ignored. Sometimes they'll come back with "calling approach, say again" or sometimes you just have to try again later.

Either way, it's usually not too difficult to stay out of trouble long enough to get someone's attention. If you're IFR or have already made initial contact, you can probably just continue on your path and you'll eventually become a big enough priority for them that they'll call you if you still haven't a chance to get a word in. If you're VFR and haven't made initial contact, you can probably just avoid the airspace for a few minutes.


Is there a standard on-board diagnostics protocol for FADEC aviation piston engines? Almost any car engine manufactured since 1997 will have on-board diagnostics, either the OBD1 or more recently the OBD2 standard which provides a standard for protocols, standard message codes and a standard connector which is universal across all engines (there are different pinouts used but newer readers can usually read them all), plus the ability for manufacturers to add their own fault codes where applicable. There is also telemetry available from the engine sensors which can be read to diagnose engine health, for example air flow and inlet air temperature, engine coolant temperature, etc.
I am well aware that the vast majority of aviation pistons are completely mechanical, but for the small percentage of electronically controlled engines that are out there is there any such standard? Do they use OBD2, another common standard, or are they all proprietary?

OBD systems were introduced by law in the 80s to reduce / control emissions, so it originated as a method to determine fault with emissions control systems. However, it was refined enough to monitor and control in real time engine and powertrains sytems in further iterations. Keep in mind that the OBDI / OBDII is a protocol that is run on the CANBUS network, which is important to remember that these two are separate entities  (CANBUS can run several different protocols, as Ron Beyer had stated). Other networks such as the LINbus for Audi/VW/BMW run different protocols but still work in a similar fashion.
From my military aircraft maintenance experience (from way back), our systems ran on the 1553 databus, which linked all systems together (nav, comms, AP/FD, etc) and is essentially the CANBUS equivalent. I believe Civil aircraft used the ARINC429 system, however I cannot confirm. For the protocol side, many aircraft (though mainly helicopters) use the Health Usage Monitoring System (HUMS), which provides the OBDII equivilant (more or less) to report back on engine condition, conditional maintenance, operation, etc.
So to make a short story long, there area a few standaridzed networks that aircraft use, however so far there is no standard protocol for all engines. Keep in mind that car manufacturers design and build the system as a whole in-house (chassis, powerplant and drivetrain), so it is not an issue to have all the systems integrate in a relatively simple manner), where airframes are generally designed by a company that will use a powerplant designed and built by a different manufacturer (or perhaps event the same airframe could have different engine variants from different companies), which makes standardization increasingly difficult.


Is there a common template or mnemonic for a take-off briefing? I know that a take-off briefing is a good idea so that your actions are a bit "spring-loaded" should a unexpected event occur.  Is there a common template on mnemonic out there (something like CRAFT for instrument clearances)?

For example, I was talking to a flight instructor who broke down the altitudes based on the elevation of the airport and what he would do in the event of an engine failure at or below those altitudes (example, airport elevation is 427 ft MSL, then 900 ft MSL, land straight ahead, 1400 MSL, turn back to runway...) The notable thing in this case is that he pre-computed the altitudes so he wouldn't have to think about them if something happened and had a straight-ahead, and turn back to airport plan and altitude.

I have never used any checklist or Mnemonic for this, but I do use it as a sneaky way to make myself look professional to my passengers while really using it to remind myself what the hell I'm actually meant to be doing.

Typically it will contain the following

What will happen in the next 5 minutes ("We'll line up on the runway when told to.... we will begin rolling..... we will lift off at about [speed]")
What will happen immediately after take off ("We will climb until X, at which point I will turn [left|right] and head towards Y")
What the intention of the flight is ("We will continue via X & Y to Z")
Any quick emergency procedures which might be necessary (Much like your instructor demonstrated, along with briefly what the passenger should do in case of this emergency.)

I do this at the hold when with an instructor, or experienced pilot in the other seat. If its an inexperienced or nervous flyer I take longer about it, usually sitting in the aircraft prior to startup.


Why do flight attendants wear gloves during takeoff and landing? Last time I was flying the flight attendant put on black leather gloves during while she was seated during takeoff and landing. She took them of as soon as she got up from the seat.

This wasn't the first time I've seen this.

Is this a safety of flight issue?

Edit:
The airline I've seen this was Finnair.
There where three flight attendants on the flight, but only one was sitting near me, so I couldn't see what the others did.

From Finnair's Facebook page, it looks like Flight Attendancts wear gloves for safety reasons during takeoff/landing and galley preparation. Also it seems they do remove them when greeting passengers.

https://m.facebook.com/Finnair/posts/10151523242117911


What does runaway failure mean (position difference between APPU and FPPU) on A320? I've been reading the description and operation of Flap systems. WTBs will stop and hold the transmission whenever SFCCs receive some failures.

A runaway failure of an actuator is a situation where the actuator deflects maximally into one of its stops and stays there. Particularly hydraulic actuators can be subject to these: if the servo valve cannot close due to for instance dirt being stuck in the valve, oil flow will cause this type of failure. Electrical actuators commanded by a servo loop can fail in this mode as well.


What is the trim wheel behavior on the A320 family? The Trim Wheel in the A320s usually is moving by itself, representing the current stabilizer position (or rather command). Before takeoff I believe it is set by hand to set the takeoff trim.

During flight it is not touched unless the aircraft goes into direct law or "worse".

What happens though if the pilot touches the trim wheel in normal law?

Will the aircraft shift into another Law where manual trim can be used? Will it move the stabilizer to the position set by the pilot and then adjust back to where it would usually be, possibly turning off any AP that is engaged? Will the aircraft ignore the manual input?

Before takeoff I believe it is set by hand to set the takeoff trim.

Correct. And after landing the trim [wheels] auto-resets.

The trim wheels always have priority over the electrical trim. Moving them in-flight:

Bypasses the flight computers (an override mechanism with micro-switches).
Disconnects the autopilot when moved beyond a certain threshold.
Freezes the automatic trim.

The flight computers for normal stabilizer control (ELACs) remain active though, no change in laws would take place. They remain active to ensure they're synchronized with the manual action. Let go of the trim wheels, use the stick again in pitch, and auto trim will resume.

If you use the stick, while holding tight on the wheels, the flight computers will think the stabilizer is jammed, and the warning STABILIZER JAM will show, with it the associated procedure.

During flight it is not touched unless the aircraft goes into direct law or "worse".

There are two scenarios where you'd need them that are better (not worse) than direct law. That is the aforementioned [actual] stabilizer jam, or F/CTL STABILIZER JAM. The latter is when the flight computers lose contact (electrical signal) with the stabilizer (this scenario leads to alternate law with protections lost).

In both scenarios, if the pilot is able to move the trim wheels, they'll use the elevator position shown on the flight controls display to make trim inputs such that the elevator moves to the neutral position.

Source: A320 FCOM (don't use for flight).


How is the crew rest area on the A350 accessed? As per this image of the A350, the crew rest areas have been placed on the top of the fuselage. How can this be possible and how would the crew get into the rear one since it seems that it is placed above first class?

I understand that the front one is accessible from the cockpit, but the second one seems to be straight on top the first/business class section. Is this actually practical?

It looks like your image came from this article, since they have the exact same one.

According to Boeing, this is the most practical place, and Airbus has finally decided they agree.

  For the first time in Airbus aircraft –and after benchmarked[sic] Boeing´s configuration-, the A350 XWB’s crew rest compartments are in the aircraft crown.--All images and quotes from article linked above unless otherwise noted.

This image shows that the cabin crew's rest area is at the rear of the aircraft, while the flight crew's is up front. It also shows how they've shifted out of the basement and into the attic:

Image courteously, but unknowingly supplied by core77.com

Further down in that article they state why the crew rest areas are where they are:

  The A350 XWB crew rests, located overhead in the crown area, have no impact on revenues space – whether cargo or passenger – and contribute to the efficiency of the A350 XWB cabin.

It also explains how you get there:

  Entrances to these rest areas are located outside the passenger cabin, so they do not use up seat space. “This is the first time a crew rest area on an aircraft will have no revenue-generating impact,” A350 XWB Marketing Director Bausor said.

Unfortunately, I'm guessing that the crew rest areas do not actually have a skylight one might infer from this image:

I'm sure the day-shift crew would enjoy sleeping under the stars at night, though the night-shift crew probably wouldn't enjoy the bright sunlight while trying to sleep.


What is 0650// in the metar? I have this metar, I cannot find anywhere what does 0650// or 1600// or 0250// mean. I tested on multiple decoder websites. They call it unknown identifier.

ESCF 240220Z AUTO 00000KT 0800 0650// R01/P2000N R19/1900U BR OVC035/// 00/00 Q1005

ESCF 240250Z AUTO 10001KT 4100 1600// BR OVC033/// 01/01 Q1005

ESCF 240120Z AUTO 00000KT 0450 0250// BR OVC037/// 00/00 Q1005

This is most likely the minimum visibility (in metres), with the compass direction given as "//" (not possible to determine). A single slash is more common, i.e. 0650/. WMO Publication No. 306 - Manual On Codes - Volume I.1 - Part A, Section A, FM 15 METAR, FM 16 SPECI (emphasis added):

  15.6 Groups VVVV VNVNVNVNDv

  15.6.1 The group VVVV shall be used to report prevailing visibility.
  ...

  15.6.2 Directional variation in visibility
  VNVNVNVNDv

  When the horizontal visibility is not the same in different directions and when the minimum visibility is different from the prevailing visibility, and less than 1,500 metres or less than 50% of the prevailing visibility, and less than 5,000 metres, the group VNVNVNVNDv shall also be used to report the minimum visibility and, when possible, its general direction in relation to the aerodrome reference point indicated by reference to one of the eight points of the compass. If the minimum visibility is observed in more than one direction, the Dv shall represent the most operationally significant direction.


Are turboprops more efficient than piston engines (thrust per fuel consumption)? I want to compare two types of engines: Turboprops and piston engines. I want to know which one is more efficient. There are many types of efficiencies, so I will specify: thrust (in newtons) per fuel consumption (kg/second).

Right now I don't care about power/weight ratio or max speed or horsepower. Those are all valid concerns for aircraft design, but I'm trying to pick exactly one criteria and figure which engine is more efficient in its terms and its terms alone. I don't want to mix criteria. I want to focus on one aspect, get an answer to it, then move on to the others later.

A complication is that piston engines usually give their output in horsepower. I have no idea why this is. What's ultimately needed is thrust. I realize that a propeller engine's job is to create torque, and thrust will depend on blade length and airspeed. In that case, I can't understand why those engines don't specify their output in torque.

Citing engines that actually exist (and citing their specs) will answer this question as long as the choices are modern, good engines.

(I did not include turbojets or turbofans for fear of being too broad. I picked two propeller engines and don't want to mix them with jet engines.)

One more thing. I realize that engines are capable of varying levels of thrust. It's my understanding that max thrust is usually more inefficient than cruising thrust. Therefore, I will ask for thrust/fuel-consumption figures of an engine at typical cruise conditions.

No, piston engines are more efficient.

Their output is given in kilowatts or HP because this does not change much with speed, unlike the thrust of a propeller. By running a piston engine a few times on a dynamometer stand you can get reasonable numbers which are valid over the full operating range. If you want to characterize them by their thrust, you would need to look at an engine-propeller combination at one particular speed, which is not very helpful.

Now you ask for specs of contemporary engines. The funny thing is that the efficiency of aviation piston engines has not changed much over the last decades. If you assume 250 g of fuel per kWh at full power for gasoline engines, this figure holds already for good WW II-era engines like the Jumo 213 A which was run on 87 octane gasoline. The low octane number restricted compression to 6.93:1, while the higher octane number of contemporary AVGAS allows for an 8.5:1 compression ratio in engines like the Lycoming O-360, which consumes 280 g of fuel per kWh. Adding fuel injection enabled Lycoming to reduce fuel burn to 240 g per kWh in the IO-390, which was first run in 2002.

Diesel engines are even more efficient; they typically consume 220 g per kWh. This low value was already possible with the venerable Jumo 205 of the 1930s which consumed only 213 g per kWh at its most efficient speed. Modern aerodiesels run at similar efficiency: The Thielert range of engines which have been taken over by Continental consume 220 g per kWh.

Even the best turboprops rarely achieve less than 300 g per kWh. The most modern version of the venerable Pratt&Whitney PT6 consumes 308 g per kWh, and only very recent developments can close the gap to piston engines. The Progress D27 claims a specific fuel consumption of 231 g per kWh while the Europrop TP400 one of 237 g per kWh. Note that here the remaining thrust from the exhaust has been converted into an equivalent power rating to achieve such good values.


Do unused parachutes need to be repacked? If so how often and why? I was reading some military fiction and saw a comment that army airborne operations were required to repack all parachutes every ninety days, allowing parachutes that were due to be repacked soon to be cheaply used for training. This got me thinking: do parachutes need to be repacked on a schedule? Is this uniform across all types of parachutes and use cases? (are there differences between military and civilian requirements?) How long is the repack cycle? Why is scheduled repacking needed?

Yes, parachutes need to be repacked regularly. The length of the interval depends on the material of the parachute and is between 60 and 180 days. Every parachute should have a small pocket with a piece of paper which lists the most recent repack date and the name of the packer (who needs to comply with FAR part 65, subpart F).

FAA part 91.307 says:

  (a) No pilot of a civil aircraft may allow a parachute that is
  available for emergency use to be carried in that aircraft unless it
  is an approved type and has been packed by a certificated and
  appropriately rated parachute rigger—

  (1) Within the preceding 180 days, if its canopy, shrouds, and harness
  are composed exclusively of nylon, rayon, or other similar synthetic
  fiber or materials that are substantially resistant to damage from
  mold, mildew, or other fungi and other rotting agents propagated in a
  moist environment; or

  (2) Within the preceding 60 days, if any part of the parachute is
  composed of silk, pongee, or other natural fiber or materials not
  specified in paragraph (a)(1) of this section.

The reason should be clear from the regulation: If moisture is present, the growth of mold may prevent the parachute from unfolding easily.

For the T-10D parachute, which is the standard US Army parachute for airborne assault operations, the repack period is 120 days.


In a Practice Forced Landing (PFL), what are Low Key and High Key and how are their locations determined? Please explain what are "low key" and "high key" in practice forced landings? Are they any particular locations with respect to the airfield? Are they the same for every aircraft? Will they change based on runway elevation?

Practice (or real) forced landings and (SFO) simulated flame out (or actual flame out - engine failure)  maneuvers are done often by the military in the fashion shown in the pictures below. Part of the reason for this type of maneuver is due to the characteristics of the aircraft involved.  For example, high speed fighter jet aircraft need to fly fast and they use this maneuver to dissipate speed and altitude in a relatively short space.

Regarding the SFO or actual Flame Out:

The High Key  position is generally when the aircraft is somewhere over the first third of the runway and is the point at which the pilot will begin his right/left turn and start his descent (if currently level). If it's an actual flame out, then the aircraft may be in a descent prior to reaching High Key but should be attempting to be at or near the altitude that was practiced during a simulated flame out (when training).

The Low Key position is generally abeam the approach end of the runway.

These "Key" positions serve as altitude and configuration reference points in order to ensure that the aircraft will be at the proper position, speed, and altitude over the end of the runway.

The altitudes (which may vary based on aircraft type) utilized for the SFO and forced landing maneuvers are based on above ground level (AGL) and the AGL altitudes won't change based on runway elevation.

The pictures below show how these maneuvers generally are done:

From: laartcc.org/stm/special-military-procedures


What is the function of the tail section on a fixed-wing aircraft? In a generic fixed-wing aircraft like a Cessna, what is the function of the tail section, i.e. the rudder and elevators?

First off lets be clear that a tail section does the same thing on small aircraft that it does on large aircraft.

Second off lets be clear that a tail section is not necessary for flight and there are planes like the Northrop Grumman B2 that dont have a tail section they are affectionally called "Flying Wings".

The short answer is that the rudder (vertical part) controls yaw and the elevator (horizontal part) controls pitch. A plane is capable of movement and similarly adjustment in all 3 dimensional axes. But lets dig in a bit:

The Elevator: This is usually located in the back but by no means has to be. Burt Rutan has implemented many designs that have forward mounted elevators. As to functionality they essentially allow you to alter the pitch of the plane which in turn alters the angle of attack of the wing which furthermore has a direct effect on the lift generated by the wing. In a simple world we could say that when you pitch up you climb and when you pitch down you descend. The reality is that the engines thrust plays a large factor in this. For example if you are flying at a level attitude and increase thrust your will increase speed (and the speed of air over the wing) which will generate greater lift and cause the plane to elevate with out a pitch increase (you will have to apply some force to keep the plane level though). The elevator provides a way to easily alter the pitch of the plane (and angle of attack) so you can climb when you want. Generally speaking you will also add power for the climb. For a more lengthy explanation check out the wikipeidea article.

The Rudder: The rudder is mainly to control the left-right yaw of the aircraft. In a single engine prop plane this can be used to help overcome the left turning tendencies created by uneven force of a spinning prop (P-Factor). In a more general case the rudder is often used to correct yaw when a heavy crosswind is present on landing. It is also used in flight to ensure your turns neither skid or slip (stay coordinated) remember "Step On The Ball". For more reading check out Wikipedia

This picture shows the axes of movement pretty well.


How is the quadrantal rule applied to VFR flights in Hungary? I'm looking for a clear explanation for this quadrantal rule question (it applies to Hungary):

  A VFR pilot is cruising, en-route in level flight, above the transition level of FL035. His magnetic heading is 355°, and he sees that by having allowed for 8° of starboard drift he is exactly on track. What would be an appropriate Flight Level for the pilot to choose in accordance with the Quadrantal Rule?

Since the question is about Hungary, the answer will be in Hungary's AIP.

ENR 1.2 says:

  2.6. VFR flights in level cruising flight, when operated above 3 500 FT (1 050 M) MSL, shall be conducted at a level appropriate to the track specified in the table of cruising levels (ENR 1.7 para 3.).

(Emphasis mine.)

And by referencing that table (PDF) in ENR 1.7, it becomes clear Hungary uses a semicircular/hemispheric, and not a quadrantal rule.

The pilot's starboard drift will make their actual track 355 + 8 = 003°. VFR flights use the IFR rule + 500 (see below), so for this "eastbound" flight the pilot should fly odd + 500, an example would be FL 55.

(Hungarian eAIP)


Where is the APU in the case of an S-duct (like the L-1011)? This question asks about the S-duct of the L-1011 Tristar. Fooot's answer shows a cut-out of the L-1011. Looking at this cut-out, I'm wondering:
If the engine is at the 'normal' location of the APU, where did the designers of the L-1011 put the APU?
I did a search, and found this site which mentions

The APU is located in a compartment in the aft fuselage.

Another site mentions

Its still in the "tail". Its mounted below the #2 engine. Just forward of the tail skid.

But I don't see how you could fit the APU in the small available space.

(Source via aircraft.wikia.com)

APU is number 134 on the cutaway, which you can find near root of left stabilator leading edge. It is ahead of the engine, below the intake duct, on the left side.

By Reedy (Own work) [CC BY-SA 3.0], via Wikimedia Commons

Its exhaust is on the right side close to the stabilator's leading edge.


Minimum distance required to turn at maximum speed of an F-16 What would be the minimum distance required for an F-16 to turn either sideways or upwards in order to avoid a collision (assume an infinitely long wall both length and breadth wise).

Also would it be better for such planes to turn sideways or upwards? Which is faster and requires less distance.

According to this F-16 turn performance chart, at the rated maximum airspeed of 800 knots, an F-16 can turn at about 10.5 degrees per second, so a 90° turn would take about 8.5 seconds. The turn radius would be 9,000 feet. Since you specified a 90° turn to avoid an infinite wall, the pilot would have to start their turn at or before 9,000 feet from the wall in order to avoid a collision.

However, this doesn't tell the whole story. The F-16 can't maintain speed in such a turn, and the reduced speed would in turn reduce the turning radius. If the plane, for whatever reason, absolutely had to maintain its maximum speed, then it would be limited to a turn rate of 3.5 degrees per second and a turning radius of 25,000 feet.


What is NH overspeed test and how it is preformed on DHC Q400 aircraft? In the Aeroplane Operating Manual of DHC Q400 aircraft it is written that, at the time of normal engine shutdown, the engine system tests the NH overspeed circuitry by using it to shutdown the engine.

I didn’t understand that, how the NH O/S circuit is used to shutdown the engine and how it is tested?
And what are the conditions that will ensure the correct operation of NH O/S circuit?

The same statement is made here in a document describing the PW150 turboprop engine, which powers the de Haviland Canada, now Bombardier,  Dash-8.

It gives a little more detail in section 12.23.14.4, NH overspeed protection.

It says:

  The PW150A Powerplant has an independent overspeed (O/S) protection circuitry (dual chan- nel) built into the FADEC which has the capability to cut off the fuel flow through the Fuel Shutoff Solenoid. Independent NH signals (from the FADEC) are used by the O/S circuitry. A fuel shutoff command is issued when the measured frequency of the NH input signals exceed a pre-pro- grammed threshold value of 108%. The O/S Protection circuitry is exercised on normal shut- downs by the FADEC.

So, it would appear that, when testing the overspeed protection in a normal shutdown, they do not actually allow the shaft speed to increase to 108%, but rather they electronically alter the speed sensor frequency signal, so it appears like the shaft speed is greater than 108%, which then cuts off the fuel flow.

NH is the term used to describe the high pressure shaft speed, measured in units such RPM.


Does an AD terminate by issuing new one? When an AD superseded by a new one, Does the operator still retain the instruction of superseded AD even though the AD include repetitive action?

That sounds like a typical US AD where as I mentioned in a previous post, they don't issue "revisions", like AD 2019-12, AD 2019-12 Rev A, Rev B, Rev C etc.   If the AD is basically the same but has some internal change, the FAA will not issue a "Rev A".  They will issue a superceding AD with a new number that is the same as the old one except for various changes which will be spelled out.  So AD 2019-23 will be replaced by AD 2019-32, which supercedes 2019-23, instead of 2010-23 Rev A, as would be done in Canada or elsewhere.

That language tells you that the new AD is issued with administrative changes and that the compliance requirements are the same as the superceded AD, including any repetitive instruction.  In fact the new AD should have all the compliance requirements of the old one included in it.


Where can I find information about post-WW2 airports in Saudi Arabia? Where can I find historical information about airports in Saudi Arabia since 1945?

I am in the middle of a research project about airports in KSA (Kingdom of Saudi Arabia) since 1945, especially the period from 1945 to 2008. Any information, books, documents or images will be helpful.

There have always been three primary airports, representing the commercial hubs of Saudi Arabia:

Dhahran International Airport / Dammam - King Fahad International Airport

This was a dual use, single runway airfield which was the primary international commercial airport for the Eastern province, until the new Dammam International was commissioned and opened for the first flight in November 1999; Dhahran has since been reverted back to military use and is still actively being used today.

Riyadh Airport / King Khalid International

As with Dhahran - Riyadh Airport is a military dual-use airport until the dedicated King Khalid was opened in 1982, and the old Riyadh airport (OERY) was reverted back to military use.

Jeddah Airport / King Abdulaziz International

This is busiest airport in the kingdom, also one of the largest terminal buildings in the world. It is also the hub of the state carrier Saudia. It opened for service in 1981.

There then the secondary airports which also service international flights:

Medina / Prince Mohammad Bin Abdulaziz International (OEMA) - Opened in 1950; new terminal opened in 2015.
Taif International - Opened in 1976, it gained importance as it is the closest airport to Makkah (the Holy City) - and it is one of the most popular summer destinations in Saudi Arabia.

There are a lot more regional and domestic airports is Saudi Arabia. You can find information on those from the General Authority for Civil Aviation (GACA) website.

Saudia (the flag carrier) has great information dating back to 1945 available on their website.

King Abdulaziz: His Plane and His Pilot is a great book that covers the history of Saudi aviation.


Does the weight of the battery count as "fuel" in a battery powered ultralight? 14 CFR 103 compliant powered aircraft should be less than 254 pounds (excluding fuel). Do the batteries account for fuel in case of electric engine?

The jury (i.e. FAA) is still out on this question as of early June 2014.  FAA has indicated it will not give a gasoline "fuel allowance" to be credited against weight for batteries.  Given that fuel weighs 6 lbs. per gallon, or 30 lbs. for the maximum legal gas an ultralight can carry, it would be a somewhat negligible, but certainly welcome, allowance for would-be electric manufacturers.

One company, Chip Erwin of AeroMarine, has imported a barebones ultralight motorglider based on the Goat towed ultralight glider.  It's called the Zigolo, and carries batteries enough for 30-40 mins. of flight, without exceeding the 254-lb. weight limit of the part 103 category.

In time the FAA may well decide to grant the allowance.  It's still not going to amount to much more time, maybe 10 minutes given current battery energy density, which is a fraction of the energy density of gasoline, but research into electric storage is at a feverish pace worldwide.

Look for sport, then commercial electric aircraft, within the next 5 to 10 years.  Several electric single and two-seat electrics are already flying.  The Airbus ducted fan, recently ballyhooed as the first electric aircraft, which it certainly isn't, is a promising look at one way commercial electric applications might come to market.


Why doesn't a single engine airplane rotate along the longitudinal axis? As far as I know, the tail rotor in helicopters prevents the aircraft from turning in the opposite direction that the main blades turn (due to Newton's third law). On the other hand, torque in single-engine airplanes makes them drift away from the center of the runway during take-off (which must be compensated by using the rudder). Now, my question is: once in the air, why doesn't this torque make the whole aircraft spin along the longitudinal axe? Perhaps the engine's power isn't enough to exceed the resistance of the wings against the air?

First, it's about torque, not power.  A helicopter rotor has a large amount of torque at a relatively low RPM.  A single engine airplane has much less torque at a higher RPM (Power = Torque X RPM).  On top of that, for a craft of similar size, the helicopter will have much more power (it has to lift the copter directly.)  So the helicopter has to deal with torque levels several multiples higher than that of a single engine aircraft.

As to the solution, most single engine aircraft have the vertical stab offset by a small amount to generate a counter force to the torque.  If you look at some high power aircraft such as the P-51, it's a noticeable offset. And that's set for cruise power.  Takeoff power requires additional rudder input.

It should also be noted that for smaller aircraft, P-factor is a bigger turning force during climb than engine torque.


How can pilot remember when or where to do tasks such as changing radio frequency and change fuel tank? As a student pilot, I sometime forget tasks such as changing radio frequency after reaching a location or switching fuel tank in long navigation.

  These tasks happen in specific time or location and may not be in checklists

Is it something experience will help or
Are there method that can help pilot remember these tasks?

Make your own checklists

While the manufacturer provided check lists are a good starting point and generally cover the operation of the aircraft well the FAA does not forbid you from extending them. If you have a few more steps you feel are worthy of a checklist write up and print your own.

If you are switching tanks it sounds like you are flying a piper. Are you starting a time right before takeoff? If not you should be and you should always be changing tanks around the 30 minute mark. Another good rule of thumb with tank changes is to always execute them when near or overflying a field. Waiting an extra 5 minutes or switching 3 minutes early if their is a field below you is always a bit safer (should the engine cut out). Remember, for the pilot, a flight is not a journey from point A to point B it’s a series of maneuvers from one potential emergency landing spot to the next.

As a student pilot you are also still deloping habits which will be honed over time. You should debrief either with an instructor or do a self review after every flight. What went well what didn’t, what can be improved and how. The next time you get in the plane work these things and eventually you will build a good cockpit workflow.


What data does ACARS send back to base? Can it be used to track a plane? An aircraft's Aircraft Communications Addressing and Reporting System uses line of sight HF via ground stations or satellites to communicate with its base station.

This system allows for three types of messages to be sent:

Air Traffic Control
Aeronautical Operational Control
Airline Administrative Control

  Aeronautical operational control and airline administrative control messages are used to communicate between the aircraft and its base. Various types of messages are possible, for example, relating to fuel consumption, engine performance data, aircraft position, in addition to free text.

So, questions:

Can ACARS be turned off? Would this generate a warning at the base station?
Can ACARS send postion, altitude and heading information automatically?
Can ACARS be repeatedly pinged to track an aircraft's position and heading? Would this require any intervention by the pilots? (posted separately)
Is this system standard on commercial airliners?
What data do Airlines collect from the ACARS, if any at all?

Can ACARS be turned off? Would this generate a warning at the base station?

Yes, ACARS can be turned off.  See another answer of mine for more details.  Typically other systems use ACARS to send reports on a regular basis to update position and track other information, plus on an "as-needed" basis for abnormal things.  It would be up to the individual airline to look for these reports and to generate a warning if one didn't check in at the expected time, but I don't believe that they do this.  There is a lot of variation in the communication systems and they aren't 100% reliable so a lot of false alarms would be triggered.

  Can ACARS send postion, altitude and heading information automatically?

ACARS itself can not, but other systems like the Flight Management Systems (FMS) or ADS-C on board the aircraft can use ACARS to send reports like this automatically, and in some cases they do.

  Can ACARS be pinged to track an aircraft's position and heading? Would this require any intervention by the pilots?

Again, ACARS is simply a communication system.  A message can be sent via ACARS which will forward to the appropriate system requesting this information and have it respond.

  Is this system standard on commercial airliners?

I believe that most airliners that travel over international waters have ACARS, but I'm not sure if it's a requirement or not.

  What data do Airlines collect from the ACARS, if any at all?

This varies from airline to airline, but messages at the beginning and end of the flight (used to track flight time, etc.) and periodically during the flight are typical.  Usually periodic position updates and abnormal system indications are included as well.


What do the levels stand for in French Air Traffic Service Levels? I am planning a flight to Le Touquet (LFAT) in France next week, I've been told that ATC is not open all days so I've checked the NOTAMS. This seems applicable but I'm not sure I'm interpreting it correctly:

  LFFA-B3753/14  A) LFAT  LE TOUQUET PARIS PLAGE B) 2014 Aug 01  07:00
  C) 2014 Aug 31  23:59 E) FIRE AND RESCUE HOURS OF SERVICE:
  0700-0900 1500-1800    : LEVEL 2
  0900-1500              : LEVEL 4
  SAUF 15,16,22,23,26-29 : LEVEL 2 ATS HOURS OF SERVICE LEVEL 5 O/R, PPR 24H
  TO OPR  PHONE: +33(0)3 21 05 03 99  FAX: +33(0)3 21 05 59 34 LEVEL 1
  OUTSIDE ATS HOURS OF SERVICE.

I think what this is saying is that it is operating at level 2 ATC hours of service except  (Sauf) on the 15,16,22,23,and 26-29th of August, but level 1 all other hours. I think what this means is that next week on weekdays it will be operating at level 2 hours of service. I also think that level 2 means 07-09:00Z and 15-18:00Z, and during this service level 5 will be offered, but all other times level 1 will be offered.

So I think that if I go on those days listed and times listed the tower will be open, otherwise it will be closed (I'm assuming that's what level 1 means), and that I will need to use French non-towered procedures, including French calls.

I'd like to know if I've made the right interpretation, and if there's a source of information about ATC levels in France. I've scoured the web for a couple of hours with no result.

So what are level 2 hours of service, and what service is provided? What is provided with level 1 ATS?

This NOTAM concerns the fire and rescue level not the ATS operating hours.

You can find the description of the fire and rescue levels here.

The reference of the ATS hours is to say the level is raised during the opening hours of the ATS.

The ATS opening hours are available on the Visual Access Chart from the SIA. (French service for aeronautical information)

Where you have on last page:

  SUMMER 0700 - 1800

Finally for the language, you have to speak French when the ATS is closed.


Would one fighter pilot know that another's mask is not on? I admit, this comes from the original “Independence Day” movie from 1996, but during the first dogfight scene one of the characters claims they can't breathe and takes their mask off.  Another character tries to order him to put the mask back on.  I assume that he couldn't just look into the other person's cockpit.  Is it possible in such a scenario to know that another pilot isn't wearing their mask?

No, there's no mechanism to check if a pilot has their mask on. It's sometimes possible to hear the difference in how muffled the sound is. Other than that, it might just be that that particular pilot has a reputation for taking his mask off when he's not supposed to, and the other pilot just assumed that's what happened.