FL510 and above

[wabower]

I have ridden in many 121 jumpseats (prior to 9-11) and haven't seen any masks so far . . . .

Lance F;383312]Suppose the plane in question has no LOA for RVSM operations? FL280 would be it, and the masks wouldn't come into question. I suppose the POI could ask for a climb from 280 to 430 to see what the pilots do.

Also, I think you're right. The mask usage requirements are often "forgotten". (Can't speak for 121 ops. They may play this one more by the book, and may have more comfortable masks .)

[/QUOTE]

 

[Trapper John]

Actually, as the folks who designed the Comet found out, the metal fatigue cause by flexing due to repeated pressurization/depressurization cycles (that causes airplanes to expand/contract just like a balloon, although not as nearly much) can be more of a problem than the simple stress due to pressure differential. The stresses can be dealt with by brute force structural engineering, but the metal fatigue is a more complex metallurgical problem. I think you'll find most commercial airliners hit their cycle limits before they hit their hour limits unless they're used only on very long range flights (which are easier on planes that RJ-style pogo-sticking around).

The Aloha Airlines 737 is another example. But I think corrosion was also a contributing factor with that one, IIRC.


Trapper John

 

[poadeleted20]

The Aloha Airlines 737 is another example. But I think corrosion was also a contributing factor with that one, IIRC.

Yes -- a combination of corrosion due to the constant sea air exposure, and the extreme ratio of cycles per flight hour. Their flights last an average of like 20 minutes -- real short for a 737, and not anticipated by Boeing's engineering staff.

 

[TMetzinger]

I have ridden in many 121 jumpseats (prior to 9-11) and haven't seen any masks so far . . . .

[/quote]


The mask only needs to be donned between FL350 and FL410 if someone leaves the cockpit - the remaining pilot must be masked.

As long as neither pilot leaves the cockpit, quick-dons are acceptable up to FL410.

That's how I interpret what Ron posted, anyway.

 

[poadeleted20]

The mask only needs to be donned between FL350 and FL410 if someone leaves the cockpit - the remaining pilot must be masked.

You got it. And not a lot of airliners go above FL410 in normal operations.

As long as neither pilot leaves the cockpit, quick-dons are acceptable up to FL410.

I think "quick-dons at the ready are acceptable up to FL410" might be more precise -- they need not be on unless one pilot leaves the cockpit.

 

[gismo]

Thanks Ron, good to know info about commercial ops!

Doesn't higher altitude put more stress on the pressure bulkheads of the plane, since there is greater pressure differential? It seems airframe life would be degraded the more time you spend at very high FLs in a pressurized bird.

AFaIK all civilian airplanes have a limit on the pressure differential that's typically reached well below FL510. Once the limit is reached the cabin pressure must drop at the same rate as the exterior ambient pressure. IOW the cabin is exposed to the same differential pressure at FL350 as it sees at FL510 unless the pilot choses to use higher cabin altitude than necessary at FL350 (unlikely IME).