Why don't jets fly higher?
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Gentlemen,
I'm a freelance rocket scientist.
An airliners maximum cruising altitude is determined by the lowest of the following three characteristics.
1) The max certified altitude which is usually determined by the pressure load limits on the fuselage.
2) The thrust limited altitude. This being the altitude at which sufficient thrust is available to provide a specific rate of climb...normally 100fpm
3) The manoeuvre limited altitude. This is the altitude at which a specific manoeuvre margin exists prior to the onset of buffet. This varied depending on the certification authority (CAA/FAA/JAA) but is normally between 1.2g and 1.4g giving between 33 and 44 degrees bank angle prior to buffet/stick shake.
Aircraft which can fly higher than the normal 40,000 foot approx ceiling are usually either very fast, (M0.85+) or capable of flying very slowly (U2)
I shall be doing a dissertation on particle physics and the origins of the universe next.
I'm a freelance rocket scientist.
An airliners maximum cruising altitude is determined by the lowest of the following three characteristics.
1) The max certified altitude which is usually determined by the pressure load limits on the fuselage.
2) The thrust limited altitude. This being the altitude at which sufficient thrust is available to provide a specific rate of climb...normally 100fpm
3) The manoeuvre limited altitude. This is the altitude at which a specific manoeuvre margin exists prior to the onset of buffet. This varied depending on the certification authority (CAA/FAA/JAA) but is normally between 1.2g and 1.4g giving between 33 and 44 degrees bank angle prior to buffet/stick shake.
Aircraft which can fly higher than the normal 40,000 foot approx ceiling are usually either very fast, (M0.85+) or capable of flying very slowly (U2)
I shall be doing a dissertation on particle physics and the origins of the universe next.
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Riverman
Only problem with that level was them catching up Islanders and the like though 
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PPRuNe Radar
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Can't find the specs on the Boeing site but I think the B747-SP (early 80's?) wud cruise at FL50.
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PPRuNe Radar
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Twistedenginestarter,
Wing design is also important - look at the wingspan of the A330 & 777. The A300-600, with its rather stubby wing, has the engine performance to achieve FL410, but generally is limited to FL290 for the first few hours of flight. The wing area is insufficient to produce required lift at higher levels (at med/high AUW) without running into coffin corner.
Wing design is also important - look at the wingspan of the A330 & 777. The A300-600, with its rather stubby wing, has the engine performance to achieve FL410, but generally is limited to FL290 for the first few hours of flight. The wing area is insufficient to produce required lift at higher levels (at med/high AUW) without running into coffin corner.
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Hey, Alex, don't you know you're supposed to be annonymous??
The Falcon 50 and 900 fly superbly at F470 - 45 degree banked turns no problem. I guess that's because of the superb wing design. Pity the engines lack the puff to get it up there till it was pretty light!
I've always understood that the airliners don't go much above 410 because it takes too long to get back down to more reasonable altitudes in the case of decompression - isn't there a CAA/JAA/FAA ruling that public transport aeroplanes have to be below F300 within 3 minutes, or something like that? (Don't know how Conc. gets away with it, though.)
The Falcon 50 and 900 fly superbly at F470 - 45 degree banked turns no problem. I guess that's because of the superb wing design. Pity the engines lack the puff to get it up there till it was pretty light!
I've always understood that the airliners don't go much above 410 because it takes too long to get back down to more reasonable altitudes in the case of decompression - isn't there a CAA/JAA/FAA ruling that public transport aeroplanes have to be below F300 within 3 minutes, or something like that? (Don't know how Conc. gets away with it, though.)
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Just to add my two cents, the American SST was killed not so much because of environmentalists (who also made a lot of noise) or size/design factors. Essentially, the American taxpayer didn't wish to foot the bill for development, especially when all the profits went to the a/c maker and the airlines. Government funding of private enterprises is just not the American way (usually).
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R. J. Emery
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R. J. Emery
