4 ms·
Just to put a number on it, the cabin pressure at high altitudes is given by Wikipedia as around 0.75 atm. (It varies by aircraft model.) If the inner cavity
by mturmon 11y ago
Just to put a number on it, the cabin pressure at high altitudes is given by Wikipedia as around 0.75 atm. (It varies by aircraft model.)
If the inner cavity between the two windows did not have a hole, the full sea level pressure would be pressing outward against the outer window. But with the hole, only about 75% of that pressure is present.
Additionally, if there were no hole, the inner cavity between the windows would be positively pressurized with respect to the cabin. This means the force on the inner window would be backwards from what it would have to bear if the outer window failed.
- beachstartup 11y ago> But with the hole, only about 75% of that pressure is present. wait, what? this isn't how pressure works... am i missing something here?
- mbrameld 11y agoI think it's saying if the two panes were sealed without a hole at ambient pressure when the plane is manufactured then the outer pane at elevation would have ~1atm of pressure pushing out on it and the middle pane would have ~1atm pushing in on it. With the hole the outer pane only has cabin pressure pushing out on it, which is ~75% of 1atm.
- mturmon 11y agoYes. This whole exchange could have benefited from a simple diagram (numbers approximately correct for 35K feet): | | [cabin] | [gap] | [outside] 0.75atm | X atm | 0.23 atm | | If "what to make X" is your design choice, you would not want to have it always pegged at 1 atm, as it would be if it was/could be completely sealed at sea level. It's simplest to have it equalize with the cabin pressure.
- weinzierl 11y agoThe ASCII diagram is very helpful. I wish I had thought of including something like this in my original comment. Thanks a lot.