How did this guy open the plane door at 23,000 feet?

[chappachula]

According to this newspaper article, a man committed suicide by opening the door of a plane at 23,000 feet and jumping out. How is this physically possible?.
The aircraft was a small 13-seat propeller plane,called a King Air 200, flying to a remote area of Canada.

A pilot said “This door has four big steel pins that lock the main cabin door to the fuselage. So while the aircraft is pressurized, it’s not possible to open the door…It would take huge force and you’d have to have a failure of that safety feature”
Help me with the physics here:
At 23,000 feet, air pressure is 5.7 psi

Regular air pressure on the ground is 14.7 psi, but I know that planes reduce air pressure in the cabin (that’s why my ears pop).So I’m guessing that at 23,000 feeet the cabin was pressurized to , say, 10 or 11 psi. Am I right?

So 10 (or 11) minus 5.7 is about 4 or 5 pounds of pressure (on each sq. inch) that the suicidal guy had to overcome in order to open the door. And the door is, say 3 feet high and 2 feet wide for 6 sq feet. Which is 6x144 = 864 square inches.

And multiplying 4 (or 5)psi, times 864, is about 3500 (or 4300) pounds.
So the man would have had to use about four TONS of muscle power to open that door.

So where’s my mistake?

[ivn1188]

From a comment to the article:

@internets

As a former King Air pilot, the door can be opened in flight, albeit difficult. Most airliners have plug type doors, meaning as the plane pressurizes it seals the door closed. To open this type of door on a plane that is pressurized is nearly impossible since you must overcome the force of the pressurization to open the door. The King Air door is not a plug type door, and is only locked by pins. Usually, an inflatable seal around the door seals it shut and allows the aircraft to be pressurized. Doors like these have opened (usually because of improper locking) in flight before, so it isnt impossible. Once the pressure equalizes the door could be closed, provided someone wanted to go back and try, but it is not necessary for landing.

[wisernow]

Also, how could two pilots not overpower one 20 year old!?

[The_Hamster_King]

@wisernow

Also, how could two pilots not overpower one 20 year old!?

Presumably at least one of them was occupied with flying the plane … .

[Mk_VII]

Downside of a bathplug type door, which the differential pressure forces into the frame, is that it has to open into the inside of the a/c and in a small airframe there isn’t much room to do that.

[Santo_Rugger]

@chappachula

… is about 3500 (or 4300) pounds.
So the man would have had to use about four TONS of muscle power to open that door.

So where’s my mistake?

Keep in mind that although there are 3500 or 4200 pounds of force on the door, what’s important when you’re trying to swing it open is going to be the moment. For a symmetric door, the moment is going to be equal to half the distance from the hinges times the total force. Using your numbers, this will give us a moment arm of one foot*, necessitating 3500 or 4200 foot-pounds. If we apply the force at the edge of the door farthest away from the hinges, our moment arm will be 2 feet, requiring “only” 1725 or 2100 pounds of force. While that’s still a huge number, it’s still something that should probably be accounted for if we’re talking about a plug type door.

*That seems like a really small door.

Also, I live at 7,000 feet, and the pressure here is around 11.5 psi. I’d imagine they pressurize the cabin to at least that, because people are known to get altitude sickness at that level of oxygen. Does anybody know for sure, I’m interested now.

[sailor]

@Santo_Rugger

Keep in mind that although there are 3500 or 4200 pounds of force on the door, what’s important when you’re trying to swing it open is going to be the moment. For a symmetric door, the moment is going to be equal to half the distance from the hinges times the total force. Using your numbers, this will give us a moment arm of one foot*, necessitating 3500 or 4200 foot-pounds. If we apply the force at the edge of the door farthest away from the hinges, our moment arm will be 2 feet, requiring “only” 1725 or 2100 pounds of force. While that’s still a huge number, it’s still something that should probably be accounted for if we’re talking about a plug type door.

We are missing a really important point here and that is that the pressure wants to push the door out, which, in this case is what the guy wanted to do, so he did not have to overcome that force at all, rather, that pressure was helping him. He only had to overcome the friction of the locking mechanism.

[Magiver]

I don’t know about a King Air but I’ve been in a number of small planes where the door WANTS to open. Found that out the hard way as a student (tried to relock a door that was leaking on a Piper Arrow). The air stream will keep it pushed back but the door will be almost impossible to latch closed.

[Richard_Pearse]

@chappachula

At 23,000 feet, air pressure is 5.7 psi

Regular air pressure on the ground is 14.7 psi, but I know that planes reduce air pressure in the cabin (that’s why my ears pop).So I’m guessing that at 23,000 feeet the cabin was pressurized to , say, 10 or 11 psi. Am I right?

@Santo_Rugger

Also, I live at 7,000 feet, and the pressure here is around 11.5 psi. I’d imagine they pressurize the cabin to at least that, because people are known to get altitude sickness at that level of oxygen. Does anybody know for sure, I’m interested now.

chappachula is about right with his 10-11 psi. Aircraft cabins are typically pressurised to 8000 feet pressure altitude at their max cruising altitude, with the pressure gradually increasing the lower they fly. 7000 feet seems very low to be getting altitude sickness, but of course it depends a lot on the individual.

@sailor

We are missing a really important point here and that is that the pressure wants to push the door out, which, in this case is what the guy wanted to do, so he did not have to overcome that force at all, rather, that pressure was helping him. He only had to overcome the friction of the locking mechanism.

You are right. The King Air door opens outward. It is possible, through clever engineering, to make a plug type door open outward though but it still takes internal room as the door must open inward at first.