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In the 2012 film Flight, the cause of the mechanical failure is a sort of worm-screw that controls the rear tailplane. And I believe that in real life failures in those devices have been implicated in one or more crashes, with people shocked that there were no fail-safe mechanisms.

Do airline pilots feel or have a responsibility not to subject a machine to extreme mechanical stresses? Or is the assumption that nothing they can really do has not been foreseen by the designers?

Do some individual flying techniques, used by pilots, wear aircraft out quicker than others?


Full context:

This 2012 film, with Denzel Washington, aired last night on UK TV.

I think I have seen bits of it before... this time around for various reasons I also missed a small part of it.

If you haven't seen the film this question might not be of interest. If you have, and you're interested in flying, you probably remember it: it involves a "hero pilot" implausibly "inverting" a commercial airliner which is plummetting downwards, and eventually doing a crash landing where most people walk out alive.

One of the main "themes" of the film is that the pilot, played by Denzel Washington, is a "maverick": he is an alcoholic and cocaine-snorter, etc. He is drunk when he gets on the plane, and drinks more during the flight.

The thing that I'd like to ask about is this: the cause of the mechanical failure is a sort of worm-screw which controls the rear tail plane... and I believe that in real life failures in these devices have been implicated in one or more crashes, with people shocked that there was no failsafe mechanism, etc.

But another aspect of the film is the very "dramatic" take-off: the plane takes off in a very bad storm, and "Denzel" takes the plane through some very macho manoeuvres in order to get out of the "bad air" and find some "good air". The passengers are terrified and the plane is rolling all over the place, while the co-pilot is saying that the plane is flying too fast.

The "investigation" sequence of the film, which is the bulk of it, never seems to pose the question about the advisability of "macho" flying techniques and the possibly culpability of a pilot when taking a plane to its mechanical "limits". The clear position of the film is that the aircraft was simply "bad" (and recommended maintenance procedures hadn't been followed, etc. etc.).

Do pilots flying commercial airliners feel or have a responsibility not to subject a machine to extreme mechanical stresses, as far as is humanly possible, or is the assumption that nothing they can really do has not been foreseen by the designers? Do some individual flying techniques, used by commercial pilots of passenger aircraft, wear aircraft out quicker than others?

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    $\begingroup$ Practically speaking it's really hard to enforce any rules to the user, any product included. A lot of times the cost of such enforcement mechanism is so expensive that it's just not implemented, but only documented. E.g. the machine would not prevent certain operations but the manual says those operations should not be performed. Personally I believe for any product, not limited to aircraft, there are far more ways it could be used than it should be used. $\endgroup$ – user3528438 Dec 29 '17 at 21:31
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    $\begingroup$ So, first of all designer can not foresee all the possible uses, misuses, and abuses of the product, also for the things the did foresee, very often they lack the means to prevent them. $\endgroup$ – user3528438 Dec 29 '17 at 21:33
  • $\begingroup$ Aircraft failures used for training that suffer abnormal numbers of poorly handled takes offs & landings have been ruled not justifiable cause for several AD's. Float planes may cause specific wear or excessive corrosion that would otherwise be worthy of AD's. Pressurized commercial aircraft are required to track pressurization cycles and may be forced to retire early if they have been used for short trips. Hawaiian Air has been forced to retire jets early because most of their routes only last 30min with an abnormal number of T/O and landings. $\endgroup$ – jwzumwalt Jan 18 '18 at 1:50
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Let’s start out by agreeing that “Flight” got lots and LOTS of details very very wrong in more ways than 1 thread can list. Any pilot who did a tiny fraction of what the “hero” does in that movie would be reported, and drug/alcohol tested, and fired, in very very short order. Whoever decided to write a script with that sort of thing going on as its premise, has his head planted very firmly in an alternate reality to the one that the rest of us live, and fly, in.

That out of the way, let’s talk about the specific questions asked, starting with the “dramatic takeoff.” In the military, there can be missions where “you do have to go out, you don’t have to come back” — i.e. your chances of survival may not be very good, but this is war & you’re going to launch. In the airline world, the reverse is the case: takeoffs are optional, landings are mandatory. If you don’t see the path for the whole flight being completed safely, you don’t take off. Period, dot, end of story. There is no airline flight out there these days that is “the last flight out of Saigon” (where you’re going to attempt the takeoff because the alternative is just too awful). If the weather around your departure airport is dangerous, then you wait until it isn’t. If you think you’re going to need “macho maneuvers” to get out of town, you have no business taking off.

There will be times when what looked like a decent ride turns out not to be, or you knew that the ride would be somewhat bumpy & things turn out to be worse. That’s the limitation of how much information you have about the atmosphere. And yes, you will be working to find a better ride. However…

  • There is nothing particularly exciting about finding a better ride — it’s simply the same sort of climb or descent that’s used getting to and from cruise altitude. And changing course to find a better ride will be the same 20-30 degree bank turn that everything else is maneuvering the airplane. Nothing dramatic, nothing macho, nothing wild.

  • Also, if the unexpectedly bad ride scares the passengers, well, that’s the way things can go, but if what the PILOT is doing is scaring the passengers, then HE IS SCREWING UP! There is essentially no scenario you can come up with where doing something that scares the passengers is the right answer. If you got to the point where something “scary” is required to avert disaster, then either you’ve had the one-in-a-million combination of bad things happening to you, or else you screwed up by letting yourself get to that point. (Okay, rolling inverted in the movie to control the uncontrollable pitch is in that sort of category. Could that have actually worked for the Alaska flight? No idea. But that’s how creative you have to get to come up with any sort of scenario which such crazy behavior makes sense.)

If the copilot is telling the captain that he’s flying too fast, then one of two things is going on: either the copilot doesn’t understand what is & isn’t “too fast” (which can happen), or else the captain is, in fact, flying too fast. And any captain that makes very many copilots uncomfortable like that is going to be having a talk with his Chief Pilot before very long.

“Do pilots flying commercial airliners feel or have a responsibility not to subject a machine to extreme mechanical stresses…?”

Yes, absolutely. And the Flight Data Recorder will record what happens. If you do something that grounds an airplane for an inspection and/or repairs, you’ll probably be explaining yourself to somebody before too long. More than that, you have a responsibility to your passengers to give them a safe flight, as comfortable as possible, with as little drama as possible. And sometimes that means that things won’t happen on schedule, because we’re going to wait out whatever adverse weather condition is out there.

“ … or is the assumption that nothing they can really do has not been foreseen by the designers?”

Airliners today are pretty tough, but a sufficiently negligent pilot can mishandle them to the point of catastrophic failure. (Fly-by-wire gives some protections in this regard, but also allows for failure modes that are easier to catch in non-FWB aircraft — Air France 447 as an example of the latter.) The designers known that somewhere in the aircraft’s lifespan, the flaps will be oversped, and there is ample safety margin there. But if you go pulling 9 G’s on a full airliner, the designers can’t help you, and you are absolutely beyond any margins they gave you.

In general, the range of techniques that 99.9% of airline pilots will use won’t greatly affect the service life of an aircraft. It will be limited (typically) by pressurization cycles more than by anything else. And that’s because the culture IS to keep things safe, and calm, and as smooth and as low-drama as possible.

Did I mention that “Flight” really is about an alternate universe mostly unrelated to our own?

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  • $\begingroup$ Haha... yes, you did. And I assumed it was: when Hollywood has a chance to take liberties with the facts, even if the plain facts are more interesting and would make for a better movie, it will always opt for juvenile comic-book nonsense. It's just that the concept of a "macho" manoeuvre to avoid "bad air" was one that intrigued me... I've now got a couple of great answers. $\endgroup$ – mike rodent Dec 31 '17 at 17:13
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This is a three-part answer (and probably will not be the most comprehensive):

Limitations

Each aircraft type comes with a limitations section in the aircraft manual (or Flight Crew Operating Manual—FCOM for short). That already answers that aircraft (jetliners or Cessnas) are not tanks.

For example, as the pilots configure the plane for takeoff and landing, the wing changes shape by the deployment of high-lift devices. The slow-speed config has a slower max speed.

There are indications that help maintain those speeds, and sometimes features such as load-relief mechanisms that would catch any error or any big gusts.

Pilots are trained to respect those limitations. Engineers put into those numbers a factor-of-safety, that they don't reveal to the airline pilot.

Wear and tear

This is why aircraft go through multiple checks. As the aircraft accumulates more time in the air and more takeoffs and landings, bigger checks are scheduled. The biggest check of them all, the D-check, can take up to 2 months to complete. This is when the aircraft is taken apart and put back together again.

There is also a Quick Access Recorder, or QAR, that logs the 'health', and it is checked regularly by the engineers (including the manufacturer). Some airports even have wireless (Wi-Fi) connections to the plane when it parks, so this data dump can go to the engineers more quickly.

Screws, etc., are checked for wear. If a certain manufacturer prescribed limit is reached, or about to, that part is replaced. A similar screw problem like the one you describe is Alaska Airlines Flight 261, which was "failure due to improper maintenance".

Macho flying

No, no. Even hard landings get reported. And big weather cells are avoided.

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I am a private pilot and fly small single engine airplanes like Cessna 172.

Cessna doesn't have any self correcting mechanisms, it just does what you command it to do by controls.

That's why you can put the structure under undue stress by not trimming or not distributing your passengers in a balanced way on the seats.

You can also help the plane's frame last longer by avoiding flying behind or ahead of power curve, meaning you don't want to hang from the propeller or fly too rich on high power.

I know the big planes have redundant systems of automatic correction, not small airplanes though. They can't afford extra cost nor weight.

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  • $\begingroup$ Not sure that most of the things you list put stress on the airframe. Trimming means that you don't hold pressure to keep the elevator where you want it, but it's there either from your force or aerodynamic force from the tab. W&B is important, but unless it leads to a crash, the "balance" part isn't about airframe life. Likewise flying behind the power curve -- bad, but for different reasons. Agree with too rich/lean -- that affects engine life. Hard landings & too many G's -- those would affect airframe life. $\endgroup$ – Ralph J Jan 18 '18 at 0:32
  • $\begingroup$ If you fly with all the weight on one side the frame acts as in a cantilever beam, in that case if you're flying in turbulence the stresses magnify. As for the benfit of trimming, when you use the yoke you apply force to the shaft at the base of elevator with large mechanical leverage and stresses, but trim tab is at the end with most effective impact. If you fly uncoordinated, you correct by counter rudder. Which is undue stress. I use an iPad for navigation which on stormy day's gets bumped around the cockpit, hence many scratches on it. It is not to expose the plane to unnecessary loads. $\endgroup$ – kamran Jan 18 '18 at 3:21

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