Pressurisation

[Daisy]

Can you explain to me exactly what is meant by the cabin being pressurised to so many thousand feet. I dont really understand the concept. Is it something to do with the body of the areoplane being squashed if the air pressure inside the plane is lower than outside? How do they pressurise the plane and what effect does this have on the body?

I know some of these questions may be outside your expertise - so anyone can jump in and answer!

Im getting nervous now, I fly a week on tuesday. The dreams have come back and I watched an aircrash investigation docu last night {yes, i know that was stupid - i couldnt help myself} Pilot error was the cause.

Daisy x

[Falcon]

Without knowing which incident you are refering to I can't comment but would advise you to be careful of bandying "Pilot error"around. It is a quick media term that can be used to label a complex issue.

Right pressurisation 101. As you gain altitude the air thins. There is still the same balance of gasses so we don't have to take oxygen just increase the thickness of the air to render it breathable. We do this by increasing its pressure. Aircraft don't pressurise to ground level because the pressure would require thicker walls and a stronger airframe which would need more fuel to lift, so a compromise was reached. The aircraft pressurises typicly to 8000ft. This is a handy way to measure the pressure nothing more. If you were at 8000 ft up a mountain say you would fine it perfectly easy to breath. Heavy exercise might prove more tiring due to the thinner air but as we are sitting on a seat sipping gin and tonic there is more than enough air to sustain us through this activity. For the effects, you may find you swell up a little, you will feel a little tired. The body may be fine at 8000ft (Equivalent hieght might be an easier way of thinking of it) but that is not your normal air pressure and after nine hours it will take a small toll. You will be a bit dehydrated throughout the flight, this is more to do with the dryness of the air. You will be fine as you are doing this once. My average day my body "Climbs" and "descends" four times a day, the body finds the change in pressure more tiring than the sustained 8000ft.

[spleisher]

Daisy... Just to add one more thing... it's not an issue of the plane being squashed or anything. Don't think of it the same way you would think of pressure undersea for a submarine. Think of it as Royd described it as an issue of your ability to breathe the air and your comfort. That's why you are given the spiel about oxygen masks on a plane. If the plane should lose pressurization, the oxygen masks would give you breathable air. Don't get caught up worrying about that though, 'cause I can almost guarantee you it ain't going to happen!!

Scott

[Daisy]

I didnt mean to offend you Royd with the 'pilot error remark'. You are competely right, there could be many other factors involved in that crash. The documentary was about the American Airlines flight 965 to Columbia. It was in this docu that they mentioned it was due to the fact the pilots tried to descend too fast to make a runway that was offered to them at the last minute.

Thanks for the info on the pressurisation.

Daisy x

[Falcon]

No offence taken I assure you. Like I said these documentries should only be watched with your friendly neighbourhood pilot. Florida is flatter than a billiard table any way.