AirWillie6475
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Flying At FL400+

Tue Jul 12, 2005 5:38 pm

The WN and FL 73Gs, I noticed, cruise at 39-40k altitude range during long flights . There are advantages to cruising at that altitude if you can manage to get there but is it safe to stay up there? Isn't there an issue of atmoshperic radiation above 40k that could affect the passengers?
 
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VirginFlyer
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RE: Flying At FL400+

Tue Jul 12, 2005 8:27 pm

I am not too sure what the exact radiation doses at altitude are. However, I did learn something interesting just yesterday - it is a requirement to carry a geiger counter if flying above FL490 (under Australian regulations anyway...)

V/F
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avioniker
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RE: Flying At FL400+

Tue Jul 12, 2005 9:57 pm

737NG's have a top cruise altitude of 410 while classics are limited to 370-380.
Radiation at those levels isn't high enough (according to current "wisdom") to be a factor in those aircraft. With fuel being the highest cost item as of last Thursday I'm certain you'll be seeing the airlines operating as high as ATC will allow.
One may educate the ignorance from the unknowing but stupid is forever. Boswell; ca: 1533
 
SlamClick
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RE: Flying At FL400+

Tue Jul 12, 2005 10:36 pm

Whatever happened to concerns about cabin ozone concentration in long east-west flights in northerly latitudes, especially in the spring and fall?

That was the safety issue about twenty years ago.

Then there was the safety of the potable water put onboard airliners.

All I know is that jet airliners kill bees.

I find dead bees on the ramp all the time. Ever see dead bees lying around in your neighborhood? Something must be done!
Happiness is not seeing another trite Ste. Maarten photo all week long.
 
B744F
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RE: Flying At FL400+

Wed Jul 13, 2005 4:33 am

Bees only live for a few weeks once they go out of the hive, so that explains why you see so many dead bees.

And according to a recent study, any radiation is harmful, no matter the amount. So who really knows?
 
ContnlEliteCMH
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RE: Flying At FL400+

Wed Jul 13, 2005 7:56 am

Quoting B744F (Reply 4):
And according to a recent study, any radiation is harmful, no matter the amount. So who really knows?

Uh huh. So will any thinking person listen when a person flying at 41,000 feet complains about radiation, on a trip to lie on the beach for 20 cumulative hours?
Christianity. Islam. Hinduism. Anthropogenic Global Warming. All are matters of faith!
 
pilotpip
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RE: Flying At FL400+

Wed Jul 13, 2005 12:25 pm

Quoting SlamClick (Reply 3):
Then there was the safety of the potable water put onboard airliners.

I won't drink it. Will you? I've heard about/seen the insides of those storage tanks and seen how the rampers care for that hose. I'll pass Big grin
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MADtoCAE
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RE: Flying At FL400+

Wed Jul 13, 2005 6:53 pm

Concorde cruised at FL600(I think).
Is radiation dangerous up there?
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bongo
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RE: Flying At FL400+

Thu Jul 14, 2005 5:04 am

Quoting MADtoCAE (Reply 7):
Concorde cruised at FL600(I think).

Yes, you are right. And BTW at that altitude you can see the Earth's curvature...such a nice thing  Wink
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QantasA330
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RE: Flying At FL400+

Thu Jul 14, 2005 8:37 pm

The risk associated with high altitude radiation is far less apparent than the risk involved in the unlikely event of a depressurisation.

At FL400, a passenger has a Time of Useful Consciousness of only 30 seconds, a pilot at that altitude has only 20 seconds. At FL450 this reduces to 20 seconds and 15 seconds, respectively. Factor into this the notion that passengers will only be using a 'continuous flow' oxygen mask, which isn't at all efficient at that altitude. At that altitude, one must breathe PURE oxygen... not recycled air from the lungs.

Furthermore, above 40,000ft even breathing PURE oxygen does not provide that blood with sufficient oxygen, due to the lower partial pressure at that altitude. Special 'pressure demand' masks are required to deliver 100% oxygen at an increased pressure... and only the pilots will/should have these. This isn't even considering the fact that during an emergency oxygen intake can increase by a factor of twenty or so.

While radiation is certainly an issue for pilots at those altitudes over the course of a lifetime, the effects on passengers are negligable. That said, the most serious risk at these altitudes remains to be the rather improbable likelihood of a depressurisation.
 
David L
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RE: Flying At FL400+

Thu Jul 14, 2005 9:08 pm

Quoting MADtoCAE (Reply 7):
Concorde cruised at FL600(I think).
Is radiation dangerous up there?

The radiation level was about double that of subsonic flights at FL350-ish but the flights took less than half the time so the net dosage was no worse. Crews carried some kind of dosimeter and, as far as I know, no-one ever received a dose that was considered to be worth worrying about.
 
vc10
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RE: Flying At FL400+

Thu Jul 14, 2005 9:38 pm

Concorde crews did not wear any radiation badge but the aircraft itself monitored both the instananeous and cumalative dose of radiation that it received.

little vc10
 
David L
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RE: Flying At FL400+

Fri Jul 15, 2005 7:22 am

I'd forgotten about the radiation meter but I'm sure I've read about individual meters. I'm not saying all crew wore them on all flights but I'm sure some were used, perhaps on earlier flights. However, until I can find positive proof, I'll have to concede that one.

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