4 ms·

This explanation makes a lot of sense--I agree that not having the hole removed redundancy--but I'm not sure some of your details are exactly right. > If the t

This explanation makes a lot of sense--I agree that not having the hole removed redundancy--but I'm not sure some of your details are exactly right. > If the two panes would be sealed absolutely tightly the pressure between them would stay at normal level in any case. I think higher pressure inside the plane would push out on the inner pane, pushing it closer to the outer window, so the pressure between would go up compared to the outside. That is to say, cabin pressure would be highest, pressure between the panes would be in the middle, and pressure outside the plane the lowest. But ALL THREE pressures would be lower than air pressure on the ground. > Without the hole and with perfect seal if the pressurization fails for some reason you'd have maximum pressure gradient on both panes. The redundancy of the second pane would be lost. The air in between the panes would provide some "padding" so the outer pane would receive less pressure than the inner pane, but there's not much air between the panes so the padding, and difference in pressure, would likely be small, so yes, redundancy would be lost.

moioci 11y ago
"That is to say, cabin pressure would be highest, pressure between the panes would be in the middle, and pressure outside the plane the lowest. But ALL THREE pressures would be lower than air pressure on the ground." I think this is incorrect. Assuming the windows are sealed at ground level, the pressure between the panes would be slightly below ground level at altitude, due to flexion of both inner and outer panes; the pressure in the cabin is substantially lower than ground level; and outside pressure is the lowest of all. Thus the pressure between the two layers is the highest of the three compartments at altitude, subjecting both layers to considerable stresses with every pressurization/depressurization cycle. Now if you sealed a near-vacuum inbetween, that could help with thermal insulation and prevent condensation, but would cause more stress on the ground.
- copsarebastards 11y ago
  You're right, good catch. :)

moioci 11y ago

"That is to say, cabin pressure would be highest, pressure between the panes would be in the middle, and pressure outside the plane the lowest. But ALL THREE pressures would be lower than air pressure on the ground." I think this is incorrect. Assuming the windows are sealed at ground level, the pressure between the panes would be slightly below ground level at altitude, due to flexion of both inner and outer panes; the pressure in the cabin is substantially lower than ground level; and outside pressure is the lowest of all. Thus the pressure between the two layers is the highest of the three compartments at altitude, subjecting both layers to considerable stresses with every pressurization/depressurization cycle. Now if you sealed a near-vacuum inbetween, that could help with thermal insulation and prevent condensation, but would cause more stress on the ground.

copsarebastards 11y ago
You're right, good catch. :)