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Lets say a monkey / snake interacts with 3 random controls inside the cockpit within less than 3 seconds until the PIC / SIC can take control of the aircraft again. Could such interactions result in a configuration leading to a crash that could not be reversed in time?

Assume the following:

  • small commercial aircraft (e.g. A319, CRJ900)
  • short distance flight (e.g. LEJ -> FRA)
  • appropriate cruising altitude for this distance

Edit: (for clarification)

  • It was mentioned I mixed the technical terms controls and instruments. I mean anything that does something when its pressed. So any buttons, switches, flight controls, etc.
  • This question is aiming at quick interactions with controls, no prolonged input.
  • Assume the pilots make no errors after the incident.

Background:
I was recently telling a post-9/11 flyer that I was generally allowed to visit the cockpit during the flight (as a child, pre-2000s). That person was surprised that this was allowed and asked what would've happened if a kid managed to interact with the cockpit.
Neglecting the fact that the pilots would probably intervene before any controls were touched it got me thinking if it would even be possible to doom a plane with a few quick interactions.

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    $\begingroup$ There have been several disasters caused by just one control being set wrong. In Helios Airways Flight 522, the crew became incapacitated because the cabin pressurization control was not set correctly. Korean Air Lines Flight 007 was shot down after accidentally entering Soviet airspace because its navigation system was set to the wrong mode. Multiple airplanes have crashed shortly after takeoff due to the flaps not being set correctly. $\endgroup$
    – Tanner Swett
    May 31, 2017 at 14:52
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    $\begingroup$ @Azor-Ahai The yoke and throttle are examples of controls. Control inputs directly manipulate the aircraft. The altimeter, radio, and transponder are examples of instruments. They are mainly informational, but fiddling with their settings could certainly cause dangerous confusion as well. $\endgroup$
    – 200_success
    Jun 1, 2017 at 0:05
  • $\begingroup$ Monkeys and snakes in the cockpit? Oh my! $\endgroup$
    – Todd Wilcox
    Jun 1, 2017 at 3:51
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    $\begingroup$ A kid crashing a plane was a Michael Chriton novel. One I bought in an airport, oddly enough. I wonder if plan-based books make for popular choices? $\endgroup$
    – JDługosz
    Jun 1, 2017 at 5:01
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    $\begingroup$ @TannerSwett Presumably (I'm guessing) those incidents were because the crew were unaware that the settings were wrong. In the scenario the OP's asking about -- a kid "twiddling knobs" for a few seconds -- I would hope the crew would double-check anything the kid might have touched. $\endgroup$
    – TripeHound
    Jun 1, 2017 at 12:01

5 Answers 5

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There's a real-life example that seems very similar: Aeroflot 593. The pilots let two children sit in the cockpit while the aircraft was on autopilot. One of the children pushed the control column for 30 seconds, which disengaged the autopilot and started a steep turn. The pilots tried to recover but the aircraft stalled and crashed, killing everyone on board.

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    $\begingroup$ Exactly the crash that came to mind when I read the question. $\endgroup$
    – Ron Beyer
    May 31, 2017 at 14:38
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    $\begingroup$ There are many factors which contributed to this accident; the pilots' unfamiliarity with the autopilot system is one of them. $\endgroup$
    – kevin
    May 31, 2017 at 14:49
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    $\begingroup$ I have zero flight hours, but an interest for flying. 2 years ago I saw a documentary about a new kind of tactic for pilots to save themselves from the situation Aeroflot 593 was in during the stall. Basically it says to not pull up to hard, but instead to pull up more mildly and let the plain fly better. Do you know which tactic that is about? And would that tactic indeed have been beneficial for Aeroflot 593's recovery from the stalling? $\endgroup$
    – Christiaan Westerbeek
    May 31, 2017 at 19:02
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    $\begingroup$ @ChristiaanWesterbeek That's not a "new kind of tactic", that has been the rule since the first airplane in 1903. Pulling up too hard, too fast can stall the plane. As Wikipedia notes, "Despite managing to level the aircraft off, the pilot over-corrected the attempt to pull up, causing the plane to stall and then crash into a hillside." $\endgroup$
    – ceejayoz
    May 31, 2017 at 20:02
  • $\begingroup$ Right, now I realize I remembered incorrectly. It was about somebody showing pilots the effect of resisting against the instinct of pulling up to hard. $\endgroup$
    – Christiaan Westerbeek
    May 31, 2017 at 20:07
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Random? Probably not. Deliberate? It's hard to say, but the pilots will certainly have a hard time landing.

There are many switches in a cockpit, and some are more important than others. If you don't know what you're touching, chances are you're manipulating a control that is not so important, for example the brightness of the LCD display panel, or the frequency of the VHF radio.

If you know which circuit breaker or engine control switch to hit however, you can attempt to deliberately sabotage. Such important controls are usually protected by a plastic cover to avoid accidental activation, because once it is activated, there is no turning back. To push one of these switches, the usual cockpit procedure is for one pilot to place his hand on the switch, then wait for the other pilot to say "confirm" to make sure there is no mistake.

See for example, the overhead panel of a 747:

enter image description here

If let's say, you manage to very quickly turn off all IRS, or disengage the electricity generator of every engine (which cannot be re-engaged without mechanical maintenance), you can wreak havoc in the cockpit. If the pilots handle the emergency well, they can land safely - but not in a easy way at least.

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    $\begingroup$ Is there a "Dump Fuel" button? Accidentally hit that one over the pacific... $\endgroup$
    – Shane
    May 31, 2017 at 21:36
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    $\begingroup$ @Shane Yes, but you can just turn it back off to stop dumping fuel. It takes quite a long time to empty the tanks of an airliner with enough fuel to cross the Pacific. $\endgroup$
    – reirab
    May 31, 2017 at 21:38
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    $\begingroup$ @Shane On 747-100/200 aircraft (and I think it safe to assume on the -300 and -400 at least), there is a common manifold system for refueling, dumping, and transfer between tanks. How the manifold is used depends on valve positions and how the manifold is pressurized. The closest thing to a dump fuel button would be the two JETTISON NOZZLE VALVES switches, one for each side. If you threw one of those switches, whether anything would go overboard would depend on whether you positioned other valves and fuel pumps to put pressurized fuel into the manifold. $\endgroup$
    – Terry
    Jun 1, 2017 at 6:08
  • $\begingroup$ That's a great answer! I was thinking that randomly pressing things would not do much and was hoping that critical switches would be guarded. Is there a reason that flight critical systems can be turned off in flight other than 'the pilots should know better'? $\endgroup$
    – McFarlane
    Jun 1, 2017 at 7:51
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    $\begingroup$ @McFarlane Anything you put on an aeroplane could, in theory, malfunction in flight, requiring you to turn it off. For example, if you developed a fault that caused an electrical fire in a generator, you'd want to turn it off as fast as possible, regardless of the fact that you can't turn it back on without landing and getting the ground crew to assist. In fact, you wouldn't want to turn it back on, because it would make the fire harder to deal with, and increase the chances of it turning into a full-blown engine fire. Similar arguments apply to basically everything on the aircraft. $\endgroup$
    – anaximander
    Jun 1, 2017 at 8:54
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Yes and no, for most planes you'd have to be really unlucky to do some kind of unrecoverable damage in a few seconds.

Kids, would be told to not touch, or to put their hands in their pockets, or something. And a pilot would have plenty of time to smack the kid (something that they also did back then) if he reached for something that would crash the plane. Today of course that's like 9 law suites already, possibly from each of the passengers. But back to the question, could a "something" smash a "something" that could cause a crash. It would be rare but yes.

Some instant crash controls would be possibly (depends on conditions)

  • Flaps, gear, thrust reverses, speed brakes - Essentially anything that "flops out" when landing or taking off. They usually have much slower speed ratings then cruising speed, and if they got "pulled off" you would have one heck of a time flying. For example speed brakes aren't really a big deal, but they "could" really damage the aerodynamic profile of the wing as they are yanked off. The landing gear could in theory snap off and cause enough damage to the body of the aircraft as to make it difficult to fly; landing would be interesting too.
  • Auto pilot settings, like vertical speed or auto thrust. It wouldn't be too hard to recover from, but if a "snake" ran over the vertical speed dial and set the vertical speed to -4,500 ft/s, it could push you over your max speed and cause issues. Auto thrust would be the same, but would have to be over speed. Most modern aircraft autopilots cut off if you get close to a stall so slowing down (vs up, thrust down) wouldn't do much. Keep in mind, you would have to be really close to your speed limits anyway.
  • Fuel dump, fuel emergency cut-offs, and other system emergency cut-offs, like engine fire systems, could really cause a scare, but most can just be turned right back on (or off). I suppose if something was to dump fuel, and throw the fire suppression system on (that cuts fuel to the engine) the pilot may have a hard time, but even the huge planes can "glide" for a really long time while they try to get things restarted.
  • Bleed air, or other like systems. Well if you cut all the engines off and the plane doesn't have a APU, you're screwed. If the APU takes a huffier, you're screwed. But again you should still be able to glide a while and get something going. If you messed up the bleed air settings I suppose you could perhaps cause engines to turn off.

Your main problem is that almost all planes are designed so that they will "crash slowly" if there is a critical system failure. They should be able to "glide" down for a decent distance giving pilots the chance to fix most anything. So whatever damage that needed to happen would need to be something that takes a ground crew to fix (wings out of shape or missing; engines needing huffers; and so on). For that to happen, it would likely take longer than 3-4 seconds, unless you know exactly where to smash, turn, or poke.

Keep in mind, even for a trained pilot to smash the "insta-crash" button they would need to be really familiar with that model, maybe even that exact plane, or they will take a few seconds to "hunt" for the buttons. Every plane (model but some times every plane) has different controls in different areas. They are generally in the same "area", but not in the exact same spot.

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    $\begingroup$ "Your main problem is that almost all planes are designed so that they will "crash slowly" I wouldn't regard that as a problem (it might be a reason why kids playing with switches shouldn't be catastrophic, but not a problem!) $\endgroup$
    – TripeHound
    Jun 2, 2017 at 10:16
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    $\begingroup$ Though at least some flight simulators have something pretty close to an "insta-crash" button: It's called set random attitude. At least Flightgear has it, and I don't think I have ever managed to recover from it. Usually by the time I have figured out which way is up, I'm half way to ground. Thankfully I have yet to find that particular button in any real-life aircraft. $\endgroup$
    – user
    Jun 2, 2017 at 11:33
  • $\begingroup$ @TripeHound It is if your goal is to come up with some way a "creature" could randomly mash buttons to cause a plane crash. $\endgroup$
    – coteyr
    Jun 2, 2017 at 17:05
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Fly at max speed, deploy the flaps (one lever movement, the flaps take couple seconds to deploy to the first position). They are not built to withstand this, so there's quite a chance they'll rip off the plane, destroying the wing aerodynamics.

However, the lever movement would be accompanied by a loud overspeed warning in modern aircraft, which the pilots would have to ignore. Also, the correction is pretty simple: move the flaps lever back.

I don't think you can get much closer than this and reduce the required time. However, imagine that a snake actually pulled the lever. The lever is at the very back of the instrument panel between the pilots. When you cruise at max speed and suddenly hear the overspeed warning and feel a strong turbulence (as high speed flaps deployment would probably feel like a turbulence), would you think that the flaps got deployed?

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  • $\begingroup$ A minute is also far longer than the OP's specified allowed time of three seconds before PIC or SIC is able to react. Would the flaps even have time to move a sufficient distance during those three seconds for this to cause more than a slightly bumpy ride? $\endgroup$
    – user
    Jun 1, 2017 at 14:11
  • $\begingroup$ @MichaelKjörling Well, so was the time period in the real scenario in the top voted answer :-/ $\endgroup$
    – yo'
    Jun 1, 2017 at 14:14
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    $\begingroup$ @MichaelKjörling It's actually 9s to the first position: youtu.be/QQG-xU21VP4?t=14s This needed not be enough, but I suppose the next positions would not take much longer. $\endgroup$
    – yo'
    Jun 1, 2017 at 14:23
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When this happens, you will be much safer in a plane than when the same happens in a car

Chances are good that anything which someone will touch randomly is of very little importance for the aerodynamic stability of the airplane. I am 1.90m tall and once, upon entering a 737-400 cockpit, I moved several switches with my head. I survived the flight. Well, actually, nothing noticeable happened. It was a daytime flight and I probably turned on some spare lighting or such. Neither the pilots nor I did check.

Now, what would happen at a nighttime flight, when some cockpit visitor turned off the light? The plane might get visually invisible (but still is visible to RADAR). The pilots can still use ILS and whatever other navigation goodies they and the airport have their disposition.

What could be more dangerous? Well, lowering the landing gear in flight. However, this is not very accessible from outside the pilots' seats, and it needs to be operated quite deliberately. If someone wanted to be mischievous, it would be much, much easier to open the doors or the windows (yes, the 737-400 cockpit has small window sections which can be opened).

Next idea: braking. Reverse thrust can easily be employed, if you know how, and it will earn you more than just a blue eye from the pilot when you come close to this control. And the "handbrake" is not only inaccessible from outside the pilots' seats, but also useless in flight.

In contrast, surprisingly pulling the handbrake of a moving car send the car into a spin immediately, with a crash very short thereafter. Yes, car passengers have tried that, with lethal results.

Makes you wonder if a 737-400's cockpit is not a much safer place for children than your car!

Okay, no more stupid examples. I guess you can figure out enough possible and impossible ways of wrecking airplanes and cars. The point that if it is considered to be "safe" to have passengers in the passenger seats in a car, then it should be reasonably safe to allow untrained visitors in a cockpit.

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    $\begingroup$ For B737: 1) Both doors and cockpit windows are held closed by positive pressure, ie. the differential pressure from a pressurised cabin would keep them shut hard. 2) Landing gear can be safely extended up to MMO (if MMO > 270 kias, which is usually the case at cruise altitude). 3) Reverse thrust is mechanically (and hydraulically) locked out in cruise. (P.S, I bet you hit the service interphone switch, or the dome light switch, I do it all the time /Another 1.90m:er :)) $\endgroup$
    – Waked
    Jun 1, 2017 at 16:05
  • $\begingroup$ I got the sign wrong above, it should be IAS for MMO < 270 KIAS, but comments can apparently only be edited for 5 min. $\endgroup$
    – Waked
    Jun 1, 2017 at 16:12
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    $\begingroup$ I once pulled the handbrake on a car, as a passenger, when the car was going downhill on a gravel road, approaching a bend, and the driver told me that the brakes had failed. I did it gently though, you know, kept my thumb on the button so I could vary the amount of braking. $\endgroup$
    – ChrisW
    Jun 1, 2017 at 16:59

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