Can pilots REALLY concentrate at 35,000 feet?
korral
Instinctively I'm so not sure that AtoB is right about his assertion that
most airliners are usually being pressurised to 6500 feet. I would bet that they're not - but would be more than happy to look at any evidence that this is the case.
Instinctively I'm so not sure that AtoB is right about his assertion that
most airliners are usually being pressurised to 6500 feet. I would bet that they're not - but would be more than happy to look at any evidence that this is the case.
Apart from the Dreamliner - which we've already mentioned here - it must cost more to crank up the pressure above the "accepted" 8000 level - not just in power but in ensuring the aircraft will remain robust enough, over its long service life, to withstand the repeated pressurisation cycles to contain a 6500 ft pressure at - say 35,000 feet.
We all know about the incidents in which the skins of high-cycle aircraft have failed . 8000 ft pressure was enough to peel back the roof of that Aloha airlines 737 in 1988. ......Just imagine what the pressure equivalent of 6500 feet would have done.
Another factor in crew (and passenger) alertness - or lack of it after, say, 4 hours at 35,000 feet (pressurised to the equivalent of 8000feet) is something that hasn't been discussed here so far - the temperature of the air. When cold rarified air is drawn in at 35,000 feet AND heated to 70 degrees F (to say nothing of its subsequently being recycled) it must further reduce the concentration of oxygen molecules. Ergo - there may well be less oxygen available in this heated rarified air than people might think.
In summary I think we need some hard evidence to prove the often-made but totally unproven assertion that the performance of pilots and passengers is NOT degraded after sustained (3 hours or more) flight at 35,000 feet.
The way to establish what's really going on here is for the CAA to carry out cognitive ability tests of pilots (and passengers) . Test them on the ground at sea level - and then see how they perform after flying for at least three hours at 35,000 feet in an aircraft pressurised to 8000 feet. It would be a safe bet that performance would be worse at 35,000 feet.
.......Such tests would settle the issue once and for all - and may well
result in far reaching changes and safer flying.
result in far reaching changes and safer flying.
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When cold rarified air is drawn in at 35,000 feet AND heated to 70 degrees F (to say nothing of its subsequently being recycled) it must further reduce the concentration of oxygen molecules.
Carry on the good work, PD.
Paxing All Over The World
PD
Is this what they mean when they say that global warming has gone to local warming? 
It is STILL the case that I am more likely to die on the roads. When driving to an appointment this morning (a funeral as it happens) on the motorway, I was overtaken by a car who then realised that they wanted the next exit. They went from the outside (3rd) lane, across the 2nd and the 1st and went up the exit road at 70mph with no signal, or indication. Just swerved across all the lanes. THAT driver was drinking air at only a few hundred feet above sea level
and could have killed and maimed several of us. 
Fortunately, everone else - consuming the same air - was being watchful and we all avoided that twit. That's the job of driving.
Perhaps the drinking of rarefied air helps pilots concentrate better.
heating that cold, 35,000' air to 70 degrees .... it's heated to 100s of degrees by compression inside the engines, then COOLED DOWN AGAIN to cold, but then WARMED UP again to only 70.
It is STILL the case that I am more likely to die on the roads. When driving to an appointment this morning (a funeral as it happens) on the motorway, I was overtaken by a car who then realised that they wanted the next exit. They went from the outside (3rd) lane, across the 2nd and the 1st and went up the exit road at 70mph with no signal, or indication. Just swerved across all the lanes. THAT driver was drinking air at only a few hundred feet above sea level
and could have killed and maimed several of us. Fortunately, everone else - consuming the same air - was being watchful and we all avoided that twit. That's the job of driving.
Perhaps the drinking of rarefied air helps pilots concentrate better.
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OK - fair enough . Some very funny comments here . When you have PD, TightSlot and Paxboy on your tail you know you are in trouble....... But I really wasn't looking for a fight with anyone. All I'm suggesting is that maybe the "universally adopted" cabin pressure of the equivalent of 8000ft altitude isn't enough - and that's why it's no longer "universal".
Here's a quote from Boeing test pilot Heather Ross who's logged 1000 hours in the , 787 which has, as we know, a minimum cabin altitude of 6000ft (and has higher humidity than aluminium aircraft). After a 14 hour flight to India she said "You don't feel like you've been beaten up.You're not dry and thirsty all the time."
At 38,000 feet the 787 had a cabin pressure of equivalent of 5,400 feet (about the equivalent of living in Denver) .When the aircraft climbed to 43,000 feet the cabin altitude was at the 787 comfortable minimum of 6,000 feet.
So why has Boeing gone to all the trouble to rock the boat and increase cabin pressure on the 787 when passengers and aircrew are (to judge from this thread) apparently so happy to fly at a cabin-altitude of 8000ft? The simple answer is that they aren't.
Blake Emery - director of cabin design - says Boeing's research shows what's described as "passenger discomfort" on ordinary non-787 flights with cabin pressure at 8000ft . This shows up (according to Boeing) in the form of headaches, muscle cramps, and feelings of fatigue after three to five hours in the air - and there's no evidence that, on an ordinary airliner, the pilots are feeling any better than the passengers. (The FAA found that pilots' nighttime vision deteriorates once cabin altitude drops to 5000 feet - never mind 8000)
Lastly - just to return to the question of the lower amount of oxygen in heated rarified air which amused Magnus P . A cubic metre of warm air, as Magnus P will remember from his Form 1 Physics classes, contains fewer molecules of oxygen (and all other gases come to that) than does cold air. The proportion of oxygen is the same - 23% or thereabouts - but it's less dense..
........And, what's more, remember that 60% of cabin air has already been recycled (i.e. breathed). - but we won't go there.
Here's a quote from Boeing test pilot Heather Ross who's logged 1000 hours in the , 787 which has, as we know, a minimum cabin altitude of 6000ft (and has higher humidity than aluminium aircraft). After a 14 hour flight to India she said "You don't feel like you've been beaten up.You're not dry and thirsty all the time."
At 38,000 feet the 787 had a cabin pressure of equivalent of 5,400 feet (about the equivalent of living in Denver) .When the aircraft climbed to 43,000 feet the cabin altitude was at the 787 comfortable minimum of 6,000 feet.
So why has Boeing gone to all the trouble to rock the boat and increase cabin pressure on the 787 when passengers and aircrew are (to judge from this thread) apparently so happy to fly at a cabin-altitude of 8000ft? The simple answer is that they aren't.
Blake Emery - director of cabin design - says Boeing's research shows what's described as "passenger discomfort" on ordinary non-787 flights with cabin pressure at 8000ft . This shows up (according to Boeing) in the form of headaches, muscle cramps, and feelings of fatigue after three to five hours in the air - and there's no evidence that, on an ordinary airliner, the pilots are feeling any better than the passengers. (The FAA found that pilots' nighttime vision deteriorates once cabin altitude drops to 5000 feet - never mind 8000)
Lastly - just to return to the question of the lower amount of oxygen in heated rarified air which amused Magnus P . A cubic metre of warm air, as Magnus P will remember from his Form 1 Physics classes, contains fewer molecules of oxygen (and all other gases come to that) than does cold air. The proportion of oxygen is the same - 23% or thereabouts - but it's less dense..
........And, what's more, remember that 60% of cabin air has already been recycled (i.e. breathed). - but we won't go there.
Last edited by korrol; 10th Aug 2012 at 15:11.
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I spend a lot of time in the mountains. At heights below 10000 feet, all of the symptoms you describe are solved by drinking more water, ie its dehydration increasing with altitude, not the number of oxygen molecules.
By an amzing coincidence, drinking more water on long haul flights seems to have the same beneficial effects, as maintaining hydration in the mountains.
By an amzing coincidence, drinking more water on long haul flights seems to have the same beneficial effects, as maintaining hydration in the mountains.
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I'm afraid I can't contribute to this thread anymore because having to read it is causing blood to gush from my eyes and then I have lie down for a short nap. I'm beginning to wonder if this isn't some frightening new genetic mutation of trolling? We'd better count the Lab Rats and make sure.
There is a lot of 'informed' rubbish here.
Try putting breathing 100% oxygen after a couple of hours in cruise at night and look out of the window. From a black hole the scenery changes to millions of stars! Obviously the lack of oxygen affects the brain especially if the packs are on recirc.....
Used to suffer migraines but only on long high altitude flights - get stuck below Nat tracks and the symptoms disappear.
Even as SLF I can feel the effects.
Roll on the Dreamliner with fresh air.
Similar effects flying sailplanes over 10000 ft.
Try putting breathing 100% oxygen after a couple of hours in cruise at night and look out of the window. From a black hole the scenery changes to millions of stars! Obviously the lack of oxygen affects the brain especially if the packs are on recirc.....
Used to suffer migraines but only on long high altitude flights - get stuck below Nat tracks and the symptoms disappear.
Even as SLF I can feel the effects.
Roll on the Dreamliner with fresh air.
Similar effects flying sailplanes over 10000 ft.
Last edited by blind pew; 12th Aug 2012 at 09:53.
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This site would seem to offer a feast of reasoned scientific evidence on the subject. effects of air density on pilots
The various articles would seem to suggest there is indeed an adverse effect at 8000ft - but it is minimal and has no operational effect. A fact, I would suggest, born out by empirical evidence gained over the last sixty years or so.
The various articles would seem to suggest there is indeed an adverse effect at 8000ft - but it is minimal and has no operational effect. A fact, I would suggest, born out by empirical evidence gained over the last sixty years or so.
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Aren't we overlooking the mental stimulation caused by purer cosmic rays at 35000' that counteract oxygen deprivation? Empirically, it's clear that the real reason ground-level drivers are so much more accident prone is because the cosmic rays have been weakened, reflected and defracted all over the place and our human brains, originating as snippets of DNA on a meteor, can't function properly. 
Paxing All Over The World
One of the reasons that I think Boeing are making so much of the air-con for the 787 is simple publicity.
They have heard the complaints over the years and have claculated a way that they can increase fresh air without a penalty on fuel consumption. So they want everyone to know that is a big part of the 787.
Of course, my cynical mind says that they will tell everyone enough times so that folks believe it ... they HAVE to make a success of the 787 as they have bet the farm on it. They saw that the word Jumbo was theirs and then became public property as the 'Hoover' word as a generic for large pax aircraft.
You will have seen that, this time, they chose the word and branded it all over the place. All the publicity has this and lauch carriers are also splashing the name - just look at Thompson inviting you to name their Dreamliner not their 787.
Boeing hope that pax will want to travel on the Dreamliner and not the super-jumbo that could be a 744 or 748 or 787 or 380. In idle conversation with a friend yesterday about aircraft, they mentioned the Dreamliner - even though they had no idea what size/capacity it had or what duration it would operate. So Boeing appear to be succeeding and all strength to them for having found a new angle. Personally, I'll wait for it work through it's teething problems for a few years.
So, to return to the topic (
) if you tell folks you've fixed the air-con problem and the fix is called 'Dreamliner' you have a chance of getting your money back.
Whether there is a problem is another matter but I'm sure that Boeing could line up a 727 full of 'experts' to tell me all about it.
They have heard the complaints over the years and have claculated a way that they can increase fresh air without a penalty on fuel consumption. So they want everyone to know that is a big part of the 787.
Of course, my cynical mind says that they will tell everyone enough times so that folks believe it ... they HAVE to make a success of the 787 as they have bet the farm on it. They saw that the word Jumbo was theirs and then became public property as the 'Hoover' word as a generic for large pax aircraft.
You will have seen that, this time, they chose the word and branded it all over the place. All the publicity has this and lauch carriers are also splashing the name - just look at Thompson inviting you to name their Dreamliner not their 787.
Boeing hope that pax will want to travel on the Dreamliner and not the super-jumbo that could be a 744 or 748 or 787 or 380. In idle conversation with a friend yesterday about aircraft, they mentioned the Dreamliner - even though they had no idea what size/capacity it had or what duration it would operate. So Boeing appear to be succeeding and all strength to them for having found a new angle. Personally, I'll wait for it work through it's teething problems for a few years.
So, to return to the topic (
) if you tell folks you've fixed the air-con problem and the fix is called 'Dreamliner' you have a chance of getting your money back.Whether there is a problem is another matter but I'm sure that Boeing could line up a 727 full of 'experts' to tell me all about it.
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PAXboy is right of course - Boeing is using the 6000ft cabin altitude as a means of differentiating the Dreamliner from "ordinary" airliners (including - ironically - their own)
But let's also remember that Airbus - after a lot of hesitation - are now on the same path with the A350 XWB which will also offer 6000ft max cabin altitude - and 20% humidity..
Soon all airliners will be like this. It'll be like jets versus pistons. The 6000ft cabins will win. 8000ft airliners will collapse in value. The cosy assumption that a well-maintained 747 could fly for 30-40 years will be shown up as just plain wrong. Sure it'll still fly just fine - but no one will want to fly in it. Watch those 8000ft cabin seat-prices slide and those used aluminium aircraft residuals start to crumble.
The days when passengers had no option but to endure being reduced to a semi-comotose state of virtual anaesthesia at the fag-end of a long-haul could be coming to an end sooner than we all think.
Of course this is isn't going to be popular with traditionalists and knuckle-dragging neanderthals - and it's certainly going to be traumatic for the aviation industry. .....But it will be good for passengers and good for pilots.
But let's also remember that Airbus - after a lot of hesitation - are now on the same path with the A350 XWB which will also offer 6000ft max cabin altitude - and 20% humidity..
Soon all airliners will be like this. It'll be like jets versus pistons. The 6000ft cabins will win. 8000ft airliners will collapse in value. The cosy assumption that a well-maintained 747 could fly for 30-40 years will be shown up as just plain wrong. Sure it'll still fly just fine - but no one will want to fly in it. Watch those 8000ft cabin seat-prices slide and those used aluminium aircraft residuals start to crumble.
The days when passengers had no option but to endure being reduced to a semi-comotose state of virtual anaesthesia at the fag-end of a long-haul could be coming to an end sooner than we all think.
Of course this is isn't going to be popular with traditionalists and knuckle-dragging neanderthals - and it's certainly going to be traumatic for the aviation industry. .....But it will be good for passengers and good for pilots.
Paxing All Over The World
Well korrol ... my last post was because you mentioned the 787 and I put forward what I thought was a more realistic reason for the 6,000ft cabin NOT that they think there is a prob with flight deck air.
Since we used to have cigarette smoke and, I think, worse recirculation rates until it reached public discussion - we are already better than we were. When did they ban smoking on the flight deck? In the cabins?
If I had to list the things that make me anxious about commercial flight these days, flight deck air quality would not be in the top five.
Since we used to have cigarette smoke and, I think, worse recirculation rates until it reached public discussion - we are already better than we were. When did they ban smoking on the flight deck? In the cabins?
If I had to list the things that make me anxious about commercial flight these days, flight deck air quality would not be in the top five.
