Can you open a plane door in flight?
In case you needed some fresh air.
When you’re thirty-five thousand feet in the sky, the last thing you want is a hole in your plane, just like you wouldn’t want a hole in your boat in the middle of the ocean. For all intents and purposes, the only designed holes in an airplane are doors. After all, we need a way to get ourselves—and our baggage—onto the plane and to our destination. Like we’ve talked about here before, plane cabins are pressurized to a comfortable condition for us. So, when you’re up that high in the sky, the pressure outside is much less than the pressure inside. This means that any hole that connects the two to each other will be met with an extremely large suction force, pulling anything in the area through it as the cabin depressurizes.
That’s pretty scary, I agree, but if the implications of a hole while flying are so dire, they better do their due diligence when designing the doors. I think you’ll be very pleased to find out that they do.
When the doors are closed, they are latched tight enough to withstand pressurization on their own, with plenty of safety factors included. This means they can actually withstand a much higher pressure difference than they actually experience. The physics behind this is rather simple: the metal that latches the door closed is much stronger than the forces associated with the pressure difference. But what if someone purposefully tries to open it mid-flight? What if that latch was removed?
In comes the beauty of a robust design—one that can’t fail no matter how hard someone may try to make it. Airplane doors aggressively fall into this category. The door geometry is designed at an angle, unlike normal doors.
This rather simple diagram shows that, when the door latch is opened, the door will feel a large force towards the outside air. The geometry at the top and bottom (and also sides) of the door essentially wedge the door into the walls. This, funnily enough, actually makes a tighter seal. The pressure force on these doors at flight conditions is about 1,000 pounds per square foot. That’s about 3 Toyota Priuses pressed onto each door holding them shut. So, unfortunately, if you’re in need of some fresh air, you’ll get even less if you try to open the door.
But what if the plane is at a low altitude, where the pressure difference between the inside and outside air is zero? This would mean that there’s no suction force… right? This means that someone could theoretically open the door at a lower altitude, but still very dangerously up in the sky. The good news is that can’t happen either. The same physics applies—pressure difference leads to a force outward that keeps the seal in place. This pressure difference, however, comes from a different source: airspeed.
Like we’ve seen before, the faster the air moves, the lower pressure it has. In the case of planes, air moves past very, very quickly. As a result, the air outside the door is still at a much lower pressure—maintaining the force and the resulting seal.
So there you have it! Your airplane doors won’t open while you’re flying. Not because the flight attendants know not to open them, but because they literally couldn’t if they tried. I hope you enjoyed this week’s edition of It’s Not Rocket Science, see you next week!
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Cover Image: https://www.businessinsider.com/why-plane-doors-cant-open-mid-flight-2020-2
Such relief ! Thanks matthew for once again breaking a topic down into language we can all understand.