Flashmeister From United States of America, joined Apr 2000, 2917 posts, RR: 6
Reply 6, posted (6 years 9 months 1 week 4 days 6 hours ago) and read 5358 times:
Well, they could open the door during climb before the pressure differential is at its highest, couldn't they? Particularly on power-assisted doors?
Quoting Ag92 (Reply 5): That's true actually but many don't know that so if you don't help to restrain the passenger, they could arrest your for helping the guy open the door
This is an interesting claim... using the same logic, though, if I don't tackle a guy with a gun robbing a convenience store that I'm in, then I'm guilty of helping him too? That could be a tough claim to make in court.
Glom From United Kingdom, joined Apr 2005, 2823 posts, RR: 9
Reply 7, posted (6 years 9 months 1 week 3 days 15 hours ago) and read 5008 times:
Quoting Flashmeister (Reply 6): Well, they could open the door during climb before the pressure differential is at its highest, couldn't they?
Well the easiest way to settle this is... QUACKULATION!
How much force do we believe the average punter could apply to the door? Let's be very generous and suggest they could bench press 150kg, aka 1.5kN. Let's then also assume an airplane door has a size of 2m³?
Okay then, so the differential pressure of the air must exert a force of no less than 1.5kN, which means that the door 750Pa to keep it secure. Even at first glance, this is already looking like a lost battle for the distressed passenger.
The pressure gradient of the atmosphere is 4Pa/ft. So the difference between cabin altitude and pressure altitude must be no less than around 200ft in order to generate sufficient pressure to keep the door closed.
The big question is, how the cabin altitude is varied with pressure altitude. If it's a case of equalisation up to cruise cabin altitude, then that means in the early stages of the climb, there is a clear threat*. If the cabin altitude is gently increased above pressure altitude from the beginning, then the window of opportunity I would saw is minimal.
*One factor I haven't included is the effect of dynamic pressure. As dynamic pressure increases with speed, static pressure drops. This means that the static pressure on the door from the outside would actually be lower than static pressure from the inside when airbourne even without cabin pressurisation. This can only work against the distressed passenger.
Ag92 From India, joined Jul 2006, 1317 posts, RR: 0
Reply 9, posted (6 years 9 months 1 week 3 days 7 hours ago) and read 4704 times:
Quoting Flashmeister (Reply 6): This is an interesting claim... using the same logic, though, if I don't tackle a guy with a gun robbing a convenience store that I'm in, then I'm guilty of helping him too? That could be a tough claim to make in court.
Sorry I just got that idea from watching United 93, where in the movie they showed that the crew only thought there were three hijackers but in the movie there were four cause the fourth one was actually sitting down waiting for the events to unfold