Sunday, 7 December 2014

pressure - Movie airplanes and suction


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?



Answer



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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