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Having watched a recent action movie (with zombies in it) I wondered whether the suction from a hole in the airplane's hull would really be able to rip out luggage, persons and even seating benches.

To my understanding, "suction" is nothing but the lack of pressure, i.e. the suction in the airplanes cabin can only be proportional to the pressure in there. Bernoulli principle would quickly void the plane of breathable air, justifying the oxygen masks that drop from the cealing. In this short period things would get pushed towards the hole by the air leaving the cabin.

Afterwards though, once the pressure in the cabin has dropped significantly, suction would cease, as there is no more air that can exert force onto objects.

The question now is: Is the above a correct description of the circumstances? And if yes, how large could the forces be? Would they be strong enough to rip people out of their seats or even the whole seat out of the airplane, or is this another cinematic exaggeration?

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I guess this depends on the size of the hole and the altitude of the plane. You are right that the suction effect will last only as long as there exists a pressure differential between the cabin and the outside. The hole's size determines the rate of equilibration. For example, in the James Bond movie Goldfinger, a firearm is triggered in an airplane. Goldfinger flies out the window making some funny noises, too. This is certain to be highly exaggerated and is addressed in German physics professor Metin Tolan's book. In reality, even with a whole window gone, there would be no danger to the passengers from suction. (Lack of oxygen is compensated for by masks, freezing is not a problem as long as the pilot enters descent after the incident.)

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    $\begingroup$ One thing not addressed is the flow of air through the plane. If the hole is large enough, or there is more than one hole, there could be a powerful wind that pulls things through. $\endgroup$ – Paddy Landau Jul 10 '13 at 15:56
  • $\begingroup$ That's true. A somewhat crude estimate could be given in terms of the above mentioned Bernoulli principle. Entering something like 1/2*(density of air at 10000 ft)*(300 m/s)^2 into Wolfram|Alpha gives 400 mbar. This would be comparable to the pressure difference due to the height only. $\endgroup$ – Jonas Greitemann Jul 10 '13 at 17:34
  • $\begingroup$ Well, that still does not cover the dynamic effects of having actually air flowing in the cabin (a.k.a. wind) $\endgroup$ – Jonas Greitemann Jul 10 '13 at 17:36
  • $\begingroup$ — Air flowing over the top of the cabin reduces its air pressure further (in exactly the same way as the wings work). If that reduction in air pressure is sufficient to lift the wings and plane, surely it is sufficient to lift luggage — and people? $\endgroup$ – Paddy Landau Jul 11 '13 at 12:37
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Mythbusters did the experiment in episode 10. This blog summarises the results.

The experiment was really to see if firing a bullet through the skin of the plane would cause the whole plane to burst like a balloon, and they conclusively proved that this wasn't the case. However the effects of losing a window or of major damage to the fuselage were indeed quite spectactular. The decompression didn't rip out seats, but a unbelted passenger in the seat next to a failed window would probably be seriously injured.

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