SA-JET From South Africa, joined May 2000, 297 posts, RR: 1 Posted (13 years 1 month 2 days 19 hours ago) and read 1132 times:
VC10-By now you must be bloody sick and tired of door questions (judging by your many responses re. the AA F/A) so I'm sorry to do this to you! (The burden of being an authority!!!)
Maybe I'm a tad daft today, but these questions still bug me.
1) Does all this mean that Airbus doors can be opened at any altitude? (hence the warning klaxon at the door stations)
2) If they can, what meassure is in place to prevent some deranged passenger from trying to do so in mid-flight (this has happened)
3) I understand (I think) the principle behind plug-doors, and how cabin pressure acts as a seal, so does this mean Airbus doors are not plug? I'm trying to visualise an Airbus door-and if I am correct, the interior portion does close inward, and then up, as the door handle is depressed-does this act as some kind of plug?
VC-10 From United Kingdom, joined Oct 1999, 3693 posts, RR: 35 Reply 1, posted (13 years 1 month 1 day 20 hours ago) and read 1091 times:
I have seen the post (otherwise I wouldn't be replying !!!!!) but don't have time to answer it tonight, but I will give it a go tomorrow.
But to answer the last question :- Airbus doors are plug type. To open one, when you lift the door handle you also lift the door. This lifting action takes the door out of the fuselage profile, the door can then be pushed out.
VC-10 From United Kingdom, joined Oct 1999, 3693 posts, RR: 35 Reply 2, posted (13 years 1 month 19 hours ago) and read 1070 times:
Assume the door is open parallel to the a/c fuse'. The interior door handle, which moves vertically, is in its up position about 20 degs from the vertical.
You now pull the door towards its frame, as the door enters the frame a lever on the door hits a plate in the door frame, this unlocks the lifting mechanism that has been holding the door in its current position. At the same time two lifting arms, one on each side of the door enter their guide channels in the door frame. The door now in the 'hole' but higher than its closed position. You push the handle down, this lowers the door into the fuselage profile by rotating the lifting arms in the channels. The last inch or two of handle movement moves the mechanism of rods & tubes that operate the lifting arms into an over centre postion. At the same time at the top of the door two locking latches contact their mating halfs in the door frame. This mechanism also goes over centre. The door is now locked shut.
An Airbus main pax door is 92 in x 52 in which gives a total area of 4784 sq inches. Now lets be conservative and pressurise the a/c to a diff press of 5 psi (it can be up to 8 psi). This means at that diff press there is 10.7 tons pressing on the door. So to open it in flight you would have overcome the 10.7 tons.The pressurisation loads are taken by about eight stops on each side of the door that butt up against stops on the door frame when the door is lowered into position.
Incidentally the door is sealed by a hollow rubber seal around the edge of the outer door skin. The seal has holes in it on its inboard side that allow cabin air in and expand the seal thus sealing the gap.
Having dug out my manufactures course notes ( the last time I worked an A300 in 1984) I found I was wrong about the klaxon. That is for when you try to open the door with the slide armed. However there is a warning light on the door that operates when the diff press is greater than 0.4 psi, the engines are not running and the door is not armed for slide operation.