Pressurised aircraft

[JonW]

Above what altitude does an aircraft need to be pressurised, and what exactly is involved in layman's terms? And below that altitude, what would happen if a door were to come open or a window to break - would you be sucked out? Hope this isn't too insensitive, but the disaster in the Congo the other day got me wondering.

[sddsddean]

This is the link http://www.casa.gov.au/avreg/fsa/download/00mar/pa
ge42-44.pdf You will need Adobe Acrobat to read it.

[tsproston]

Its about 10000 feet about 1/3 of a typical jet's flight height. that an aircraft must be pressurised. Its because above that height, air density decrease and so it becomes thinner and "harder" to breathe. Pressurisation involves pumping air in from outside into a volume inside- so pumping a set amount into a known space will give a known pressure - usually set to ground level in a jet.. Personally, I have no idea what a depressurisation below 10000ft would do, but as the air density always decreases with greater height, much the same will happen i guess.

[Ewood27]

As the article says, passenger jet aircraft are always pressurised. The pressurisation comes in just after take-off and only cuts out just before landing. So as the aircraft climbs to its cruising height of 35,000 - 40,000 ft, the cabin "climbs" to 6,000 - 8,000 ft, gradually achieving a differential pressure about 8.5 lbs psi. Having a door/window come open below 10,000 ft is most unlikely. For one thing they are nearly all "plug" fittings and have to be pulled inwards to open. Just picture the square inches in a window panel and multiply them by 8.5. That's the force needed to open them in pressurised flight. They could come open below 10,000 feet, I suppose. There would still be a depressurisation, but less violent, since the differential pressure is less, and those on board could breathe without oxygen at those heights. People/things could still be blown (not sucked) out, even when the inside pressure is reduced to the same as outside, just as if you open a car window at 70 mph you can lose your newspaper! And relax. You are in the hands of professional pilots who know how to deal with things like this. I know - I used to be one. I never had a decompression, but I practised the drill regularly in the flight simulator.

[JonW]

Thanks everyone. Pretty much answers my question. It's not something I worry about - just curious.