Can pilots REALLY concentrate at 35,000 feet?

[korrol]

OK - We all know we need oxygen to think.
And - we all know airliners are pressurised to 8,000 feet .
And - we're told that the percentage of oxygen in the air remains the same at sea level as it is at 8,000 feet and it's still the supposed to be the same at 35,000 feet
And - like me - I bet you've lost the will to concentrate on that paperback you bought at the airport once you're a few hours into the flight at cruise altitude..and like me you're starting to doze off.
...So, I just wondered, if you and I are feeling like this - how are the pilots feeling? And if they're feeling anything like me - are they fit to fly the plane? .

......So what's the problem?. Indeed - IS there a problem? .......Well, maybe - just maybe- there might be.

Depending on which science paper you read, the actual percentage of oxygen in the atmosphere seems to vary between 21% and 23% - but let's assume it's 23%.- and let's assume that the scientists are right and that the proportion of oxygen really is the same at all altitudes

The snag is that none of this takes into account that what the pilots and passengers are breathing isn't outside air - it's partly recycled air - which has already been breathed in and breathed out a couple of times - with some of the oxygen being absorbed by someone else's lungs before it got to yours.

So does anyone know what the ACTUAL proportion of oxygen is on a plane say four hours into a flight at 35,000 feet? ........I guess it's probably not 23% or even 21% and that's why everyone feels so woozy.. Of course it doesn't matter so much about the passengers. Unconscious is probably the best way to fly. But what's the oxygen percentage up front, on the flight deck?

I'd like to think the pilots were breathing the right stuff and getting their full 23% - but I worry that they may just be breathing the same recycled second-hand / third-hand air as the rest of us. And if so, I think they deserve better than that - for all our sakes..

[FlyingGoggles]

I don't think it's an issue tbh. If it was, wouldn't the media have got hold of it before now and predicted scores of aircraft falling from the skies, or being involved in near misses, because the pilots couldn't concentrate?

Put it this way, I am a nervous flyer, but this isn't one of the things that is going through my mind when I board a flight.

I also don't think the cabin altitude/amount of oxygen affects everyone the same. I can concentrate fine on a flight, what gets to me is tiredness. But I also get tired on long car, bus and train journeys so can't really put that down to the altitude, so I'm guessing it doesn't affect me much.

[XiRho]

It has to be noted surely that the air in the cabin is not sealed in at the start of the flight, pressurised and then set to remain stag net for the duration of the flight.

The air being used to pressurise the cabin is taken from a section of the engine normally, which is treated (for pressure, temperature and humidity) before being used to pressurise the cabin. Because this is an ongoing process, there are also outflow valves on the aircraft which air flows out of continuously, which is how the cabin altitude is controlled. An outflow valve allow more air to escape than is coming in will depressurise the cabin and vice versa.

Apologies if I have missed the mark here, I just don't feel it is a problem and my (non expert) understanding leads me to believe that there isn't one to be found.

[Radix]

Indeed - IS there a problem?
Of course not. Your assumption that every phase of flight requires the same level of concentration is wrong. Try correlating to workload.

[KBPsen]

I would suggest, Korrol, that you buy a more interesting book so you won't get bored so easily and let your mind wander off in silly directions armed with nothing but misconceptions and assumptions.

[Hartington]

I'm not supporting either side in this debate.

A quick Google scholar for "effect of altitude on cognitive ability" shows that some research has shown that altitude can have an effect on some people. The effect varies considerably by person and I can't (yet) find a paper which determines who is most likely to suffer.

Effects of Altitude and Heat on Complex Cognitive Tasks (http://hfs.sagepub.com/content/20/1/115.short)

I suspect the referenced paper took the participants to a higher altitude than 8000ft but given the spread of impairment suggested by the abstract I can't help wonder if 8000ft might restrict the cognitive ability of some people.

Can anyone point at research which is more aviation oriented?

[dwshimoda]

1) Most modern types provide fresh air to the flight deck, it does not come from the re-circulation manifold
2) Air crew develop higher levels of red blood cells due to working long periods of time in a hypoxic atmosphere. Red blood cells carry oxygen around the body, and so the increased oxygen percentage compensates for the outside air.

35,000ft is only a problem when the pressurisation goes pop - at 35,000 feet you have 30 - 60 seconds, but just 5,000 feet higher at 40,000 feet that figure drops to about 15 - 30 seconds...

[Basil]

Stirring the pot a bit, it gets worse:

Although the partial pressure of O2 is 21% of air pressure, due to expired CO2 and H2O vapour, the alveolar PPO is only 14%.
At sea level the alveolar PPO will be about 106 mmHg. at 8000ft: 79 mmHg and, at 4300m: 62mmHg (The research referred to used 4300m 14,100ft)

I've skied at 12,000ft but wouldn't want to hang about at 14,000ft for an extended period.

The mechanics of oxygenation are not linear. As the pressure reduces above 20,000ft then the ability of haemoglobin to transport O2 is diminished introducing a further problem. Like most RAF pilots I've had a demo of hypoxia at 25,000ft. It is insidious and one goes bye-byes with no warning (well, not to the subject who thinks he's doing just fine).

Anyway, getting back to 8000ft:
I can't help wonder if 8000ft might restrict the cognitive ability of some people
Perhaps, but professional pilots are closely monitored with regular medical checks. Back in the day, we were made aware that smoking could have an adverse effect upon oxygenation. I don't know whether that effect is significant or not.
everyone feels so woozy..
Could be the glass or three of wine with lunch :)

[Agaricus bisporus]

You'd kinda figure that something as basic as this would have occurred to someone other than the OP at some time previously in the 100 years of the most researched industry ever...As if the percentage of O2 could vary with altitude and as if the pressure wasn't the critical thing? Don't they teach science.... no, sorry..

Where do people get these bizarre ideas about recirculated air being somehow inferior? The Daily Wail I suppose. Well, that's proof then.

When Stevenson said his Rocket could do 30mph there was a belief that people couldn't breathe at such prodigious speed and would suffocate. We haven't progressed much when it comes to swallowing baseless mythology, have we?

:ugh:

[Load Toad]

Some people clearly can't function well at sea level and fortunately - they don't get to become pilots.

[TightSlot]

Can pilots REALLY concentrate at 35,000 feet?

No, they have great difficulty performing the simplest tasks - and that's when they are awake. I'm constantly having to enter the flight deck on my portable oxygen bottle and either wake them up or help them fly the aircraft. If you ask me, this is an accident waiting to happen...

[Gulfstreamaviator]

I always use mine above 45,000 ft, as it helps me concentrate on the Times crossword.
Impossible without the extra O2.
I also try to get the high O2 water from First Class.

[Mr Optimistic]

Anyway they only have to do anything on climb out and descent so don't see the issue providing coffee is on hand. As long as they can follow some magenta coloured thing I am assured the plane flies itself.

[PAXboy]

When weboard a flight, we know that we don't have to work, We may have just finished a day's work. The crew (flight and cabin) get on boar knowing they have to work. So they tend not to doze whilst reading their books. Of course, fatigue is another issue.

I'm self employed and some days, like everyone, I feel rather disinterested in going to work. But I know that the moment I start the car to drive to my client and do what they are paying me to do? I'm wide awake.

[In_Transit]

As someone that's spent some time in the cockpit at FL410, I don't think the wooziness is related to the air circulation at all. The air always seems fine up there. No mid-flight sleepiness. Keep in mind that what you experienced could be related to a lot of different things, including fatigue, boredom, dehydration (I drink sooooo much water on planes because of this). I'd suggest getting a good book, drinking a lot of water, and taking a nap if you feel tired.

[Sunnyjohn]

How many accidents happen at 35,000 feet? How many happen during take off and landing where oxygen is normal?

[Load Toad]

You may be onto something John - why can't all flights be at 35000 feet with abnormal oxygen?

[CelticRambler]

You'd kinda figure that something as basic as this would have occurred to someone other than the OP at some time previously in the 100 years of the most researched industry ever...

Indeed one might think that, but many's the time a new insight into an age-old problem has been accompanied by the phrase "Why did no-one ever think of this before?"

[Load Toad]

Because in this case it's obviously not a problem?

[CelticRambler]

In this case, maybe - but it does no harm to ask a thought-out question, even if some relevant information was missing from the thought process.

[Hartington]

There's an aricle in Flight International this week about "Hypoxia like" incidents when flying the F-22 Raptor. Now, there is simply no way that anything that happens to an F-22 pilot could be likened to a civilian air transport pilot but I found one paragraph interesting in relation to this discussion.

USAF pinpoints root cause of F-22 Raptor (http://www.flightglobal.com/news/articles/usaf-pinpoints-root-cause-of-f-22-raptors-oxygen-woes-374690/) is the whole article. The paragraph that I find interesting is towards the end:

In the early days of jet aviation, Schwartz says, the aerospace physiology community played a very large role. But in recent years, that base of expertise has atrophied. "The engineering know how that's associated with that has diminished, I think, even on a national basis."

Now, again, I am not trying to make a direct correlation here that would be silly. But I find it intresting the there seems to have been no real research into the effects of working at altitude (unless someone knows different.....)

[korrol]

Well - of course I'm not a doctor. ...And indeed I'm not much of a pilot either. But I did once manage to get a Victa Airtourer to climb to over 9000 feet - at which - point both plane and pilor were struggling.

But really, what we're doing to passengers (and pilots) in airliners, is asking them to ascend from not much above sea level to 8000 feet very quickly.

There's really not much difference between people in a plane and people climbing mountains. ....And we know altitude sickness can begin to affect otherwise healthy people at just 5000 feet after just a few hours ( maybe over three or four) at that level.


Acute Mountain Sickness (AMS) apparently starts to manifest itself at anything above 6,500 ft.. Symptoms include headache, fatigue, stomach illness, dizziness.
..........So, if it can happen to fit people like climbers - what's so special about pilots - or, come to that, passengers?


Frankly I have to confess I don't feel all that great after a long flight - like one of those bone-crackers from Los Angeles to London.. And I guess that goes for a fair proportion of the other passengers.......... But we knew what we were getting into when we booked - and if our performance is poorer than normal it probably won't matter.that much ...As for the pilots though - Well that's a different matter..



Air France 447 had been in the air for around 4 hours when the pilots (at cabin pressurre of 8000 feet) were overwhelmed by the emergency and clearly weren't able to think straight. The Captain had been off-watch asleep - but how many pilots - let alone passengers - when roused from a relatively low-oxygen slumber at 8000 feet would be sharp enough to deal logically with a multi faceted emergency like that?

[11Fan]

No, they have great difficulty performing the simplest tasks - and that's when they are awake. I'm constantly having to enter the flight deck on my portable oxygen bottle and either wake them up or help them fly the aircraft. If you ask me, this is an accident waiting to happen...

TightSlot....... :D

[crippen]

To digress a little


Do the flight simulators have reduced pressure in them? Asked by a simple SLF. If not,why not?:confused:

[Hokulea]

Hartington,
Now, again, I am not trying to make a direct correlation here that would be silly. But I find it intresting the there seems to have been no real research into the effects of working at altitude (unless someone knows different.....) There certainly have been studies although I can't point to an example of one online at the moment. I know there have been because I have read one or two and have actually been a guinea pig for another couple over the years!

I often work at 14,000 feet (on Mauna Kea, unpressurised) and I don't know anyone working at that altitude that doesn't suffer at least one sympton of high altitude sickness, although it's usually very minor (e.g., slight headache). I can count the number of people whose mental performance is not degraded in some way on the fingers of one hand (there's one remarkable individual I know whose mental performance actually seems to improve at altitude!).

As someone mentioned, it's the partial pressure of oxygen that's the important thing, not the actual percentage of oxygen in the atmosphere (which is essentially unchanged at these altitudes). What I can tell you is that most if not all altitude related problems seem to go away when we stay at the accommodation at 9,000 feet (again unpressurised). Although most people find it hard to sleep at that altitude, at least initially, mental performance is rarely degraded.

Given my own experience I don't think working at an altitude of 8,000 feet is much of an issue for most especially if it's not particularly physical work, but you don't need to go much higher to start having problems, especially if you are not acclimated.

[Sunnyjohn]

You may be onto something John - why can't all flights be at 35000 feet with abnormal oxygen? Statistically it would be a lot safer. A bit boring for the crew though.http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/wink2.gif

[PAXboy]

If the pax had abnormal air, it would make the work of the CC easier! They could sit with their O2 masks on and giggle as we sat goggle eyed, unable to reach the call button!

[deltahotel]

Recollections from military training! At 10000', the partial pressure of O2 is 1/2 that at sea level which is the point at which you start needing to increase the level of O2, so a military mask will start to give an O2 airmix to solve this problem. More clever stuff happens higher up.

It is ok to operate at this 10000 level indefinitely but above that not so, which is why the CABIN ALT warning goes off at 10000' cabin alt.

Problems with concentration come not from the reduced O2 in a properly functioning cockpit but from a myriad of factors - time zone changes, sleep patterns, diet, temperature, vibration, noise, under arousal among others and some or all of which exist in aviation and other careers. Certainly in a short-term office based job poor eating habits, insufficient sleep, repetitive work, higher temperatures and others made concentration very difficult.

[korrol]

I hadn't planned to add any more to this thread - but the interesting comments made here prompted me to do a little more research.

The more I looked the more obvious it became - the scientists, the airlines, the CAA, BALPA and Parliament are all missing the point.

They've all tried to explain why pilots fall asleep on the flight deck, or why their performance -when awake - is so degraded it results in increased risk to the flight or even an accident. ....And they all blame pilot rosters, insufficient sleep, insufficient breaks and "flying around the backside of the clock".

However incontrovertible peer-reviewed studies like that by J H Goode (Journal of Safety Research "Are pilots at risk of accidents due to fatigue?" Issue 34: Pages 309–313) produce graphs show that the longer the flight, the greater the likelihood of accident - and again lack of sleep gets the blame:-.


Fly for 1 - 6 hours and you have fewer accidents than the average for all pilots.
Fly for 7 - 9 hours and you have slightly above average risk of accident (1.1 times the average)
Fly 10 - 12 hours and the risk rises to 1.7 times that of all pilots
Fly over 13 hours and the proportion is 5.62 times higher.....and that is a lot

The scientists consistently assume lack of sleep is the problem but they don't fully analyse WHY pilots are sleepy.

Loads of work has been done on the circadian rhythms (i.e. sleep/wake patterns) of flight crew. Books like "Lag: A Look at Circadian Rhythms" by Bill Ragan highlights the tactic of taking a "power nap" on the flight deck (one pilot at a time of course) - but we all know what happens then. A sleepy Air Canada pilot suddenly wakes up, totally disorientated, spots a bright light (the planet Venus), thinks it's an oncoming plane and cranks his aircraft into a nosedive. It would be funny if it wasn't for the fact that 16 passengers were injured and he nearly hit a real aircraft flying below him.

Mr Ragan says its not only airline pilots who "power nap" - so do military pilots - 94% of them. He also says military pilots also use drugs like dextroamphetamine to stay alert on 54% of missions.

BUT .... it doesn't seem to have occured to any of these researchers is that very probably the real reason airline and military pilots are nodding off is not so much because of lack of sleep and roster patterns. The real culprit is that recycled, rarified air - air which just has too few oxygen molecules in it. The longer pilots work at an equivalent atmospheric pressure of 8000 feet (or even higher) the worse they perform.

Astonishingly the CAA's 2007 weighty paper entitled “Aircrew Fatigue" -a learned treatise some 68 pages long - doesn't even mention cabin air pressure or oxygen levels once. Maybe they should take another look at this

What's the answer? Well clearly the ironically-named Boeing Dreamliner is, paradoxically, the one airliner which is the least likely to send you to sleep because it has a cabin pressure equivalent to 6000 feet. As for the rest of the world's airliners - they'd probably start rupturing their skins if the internal pressure was pumped up.

.....So I suppose we'll have to leave things the way they are until they all get scrapped - maybe 25 even 50 years from now....keep our fingers crossed...hope for the best .....and nod off.....

[Fredairstair]

Am really glad this issue has been raised, and good on you Korrol for sticking with it in the face of some less than encouraging posts.

I'm not a Doctor, but it's NOT NORMAL to spend your working day at 8000' breathing in stale farts and skin flakes. It must have an effect, what that is needs some proper analysis.

We, as a workforce are our own worst enemy in these and other issues, by that I mean we don't tend to 'make a fuss'. For example, when your mate down the pub asks you how your day was (eg ugly scenes at INN, SMI, JMK etc) the typical response is "fine".

There is an issue here, it should be investigated and the results made clear, not least to airline management, who think we sit in a comfy chair watching 'the computers' do the work!!

[R04stb33f]

Hi,

Just wanted to make sure that you understand the difference between PERCENTAGE of something and the AMOUNT of something....

Anyway, I had a little browse and found this (http://www.patricialipe.com/talk.htm) which you might find interesting (or take with a pinch of salt etc...)

[Basil]

crippen
Do the flight simulators have reduced pressure in them?
No, they don't.
The reason, I would guess: great additional cost for little increase in realism.
Most, but not all, simulator work is carried out close to airport level.
If simulating high level cruise or a high level airport at, say, 8000ft, the alteration in aircraft handling characteristics will be reproduced but not the physiological effect of the reduction in pp of O2.

[crippen]

Thanks! Just wondered.:)

[AtoBsafely]

There is some good info in this thread and some mis-information.

As has been stated, the percentage of oxygen in the air is the same at all levels (in and outside the cabin) but the partial pressure will reduce at altitude. At 10,000 ft the pressure is about 85% of sea level pressure and at 18,000 ft it is about half.

Cabin altitude in cruise is typically 6-7000 ft and never above 8000 ft unless something has gone wrong.

Your body - and the pilot's - won't have any significant drop in blood oxygen levels in spite of the reduced pressure, because the body's need for oxygen is quite low as we are mainly sitting. There is not any significant or measureable effect on mental performance.

This is also why altitude sickness is not a concern at these levels. Smokers handicap themselves with equivalent of a few thousand feet extra altitude, but that has never shown significant negative effects on mental performance at these altitudes.

Even at 14,000 ft most people are "fully functional", although they may be losing some mental performance. Back in the early days of aviation pilots regularly flew at these altitudes without oxygen.

For a healthy person on an airplane, your brain can get all the oxygen it needs during a normal flight.

The effects of fatigue are much more significant on pilot performance. The airline business with its industrial attitude to crew duty times and rest requirements is a thousand times more significant in putting a "slow" pilot in the seat.

[korrol]

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.

[TightSlot]

........Such tests would settle the issue once and for all - and may well result in far reaching changes and safer flying.
There is no issue, except in your belief that there is: You have created the issue, based on your own perceptions and understanding and are now creating potential solutions. Aircraft are not fluttering from the sky like discarded candy wrappers: Pilots are not regularly reporting themselves, or others hypoxic. A majority of accidents/incidents take place during the take-off/landing phases of flight, where pressurisation is unlikely to be a factor.
...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.
A value of approximately 7000 feet is the figure normally accepted: There is no need to produce "evidence" of this - It's what it is.
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.
You have simply failed to understand the nature of this incident and the facts. The aircraft never reached an altitude greater than 25,000ft meaning that the pressure differential was never as high as you believe. Corrosion, Airframe Cycles & Fatigue were the dominant causes of the event, with pressurisation being simply a contributor to the end result.
...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
There may, or may not be degradation of performance - that is not the question. The question should be as to whether any such degradation affects the actual performance of an individual to a point that it becomes a significant safety hazard.

[KBPsen]

Korrol,

As you obviously have no need for facts and summarily dismisses them and weighs "instinct" or what you "think" much higher, here's a few other things for you to ignore.

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. You require evidence to disprove your "instinct". How about you prove your "instinct".

As it happens AtoB is entirely correct. Also note that AtoB did not say "pressurised to..." as aircraft are not pressurised to an altitude, despite your "as we all know" claim. Aircraft are pressurised to a maintain a constant differential pressure, not a specific altitude. The resulting cabin altitude is a function of ambient pressure. Knowing that the differential pressure is between 8 and 9 PSI, depending on aircraft type, it is not difficult to calculate the resulting cabin altitude.

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.You appear somewhat confused here. "crank up the pressure to above...8000". It is again apparent that you do not understand how an aircraft pressurisation system works. The Aloha flight was a short one, so it was cruising at FL240. You do the math, it is not difficult.

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.Complete nonsense, is the kindest thing that can be said.

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. Not really. What we need is you providing some hard evidence to prove your often-made but totally unproven assertion that the performance of pilots and passengers is 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. Knowledgeable people already know what's going on. They have known for some time. The effects of altitude on physical and cognitive abilities have been examined numerous times by both military and civilian organisations.

........Such tests would settle the issue once and for all The only issue is your idèe fixe.

[PAXboy]

KorrolThe way to establish what's really going on here is for the CAA to carry out cognitive ability tests of pilots (and passengers) Why the Pax??


Pax are not working.
Pax may have BEEN working and be tired.
Pax may have delayed meals to hurry to the airport and have low blood sugars at the start and be less alert.
Etc.

It is well known that pax are not alert during the safety briefing but, if an emergency develops they wake up real fast! Adrenalin will do that to you.

If such a test were done (and I really don't care one way or the other) pax could not be a 'control group' for flight and cabin crew.

(yawn) The air pressure today is really high and it's made me very tired, so I'm off to have a snooze.

[Hipennine]

Well, as somebody who has been around long enough to remember travelling from the channel ports across europ in 2nd class sitty up trains, and who still occasionally does an overnight drive to the alps with friends, I can confirm that performance is degraded much more significantly during such ground level experiences, rather than a Europe-west coast americas hop at 35000 feet.

[AtoBsafely]

Korrol,

The lack of oxygen is not an issue at the slightly reduced pressures of an aircraft cabin.

People inside an aircraft tend to feel drowsy because:
- they are not moving about much (check out "stagnant hypoxia"),
- they don't have much to do, and
- the constant noise is actually quite fatiguing, and tends to put you to sleep.

[PukinDog]

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.


You're instincts are correct. But it's a major cover-up that you can only expose through infiltration followed by whistleblowing. So you must get yourself licensed and buy yourself a Boeing or Airbus type-rating. Then, you can check to see for yourself and log the results/readings. Don't worry, you'll undoubtedly recoup your $50,000+ investment when people are lining-up to buy your book instead of the next Harry Potter installment. Blow the cover off this thing. Go take out your loan today.

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.

It only stands to reason it must cost more to crank up the pressure. In a house it costs more to crank up the heat in winter or crank up the AirCond in summer, so why would an airpcraft be any different with air? An airplane has a kitchen, bathrooms, the cabin has chairs you sit on while you watch movies holding a thing you can switch channels with, and up front is an office with books and pens and stuff.

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.

It's too incredible to even imagine. You could almost say it's unimaginable.

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.

Ok, I can't maintain silence any longer now that you've gotten this close re the temperature thing, but it's much worse than you thought. If the ill- effects of heating that cold, 35,000' air to 70 degrees concern you, just how much does it scare the holy bejeezus crap out of you to find out that the rarified air is heated not from "cold to 70", but in fact is heated from cold to....HUNDREDS OF DEGREES! You didnt' read that wrong, 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. This may fool the unwary, but there is major abuse of the air happening that even liquid couldn't sustain. This information strengthens your case.

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.

Yes we do. I may as well feed you some evidence since I've said so much I'm probably marked for death anyway: Ask any pilot if he/she has ever shared a cockpit with a rambling idiot who droned-on for hours about something stupid while cruising at 35,000'. You'll find almost all of them will confirm they have. Coincidence? How could it be, when the common denominator in every instance is the existence of weak air in the cockpit? Feel free to use that information. You don't even have to pay me.

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.

The Powers behind the cover-up wouldn't allow objective testing, or would finesse the results to maintain it. You'll have to conduct tests on your own, I'm afraid. I'd suggest a fold-out Skinner Box maze disguised as a carry-on, with a live rat smuggled down your pants. Since you'll have already conducted sea level tests at home to establish the cognitive baseline, all you have to do is wait for 3 hrs to elapse at 35,000', then release the rat and observe the behavior of the rat and those around you and ask yourself; "is this normal"?


.......Such tests would settle the issue once and for all - and may well
result in far reaching changes and safer flying.


Indeed they would. So spend the money, get the ratings, use the rat, write the book, and my instincts tell me you're on your way to a real breakthrough.

[ThreadBaron]

Reserve a copy for me. Not his, Pukindog, yours! :ok:

[MagnusP]

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.

Gosh! Wonder where all these oxygen molecules go! :ugh: :ugh:

Carry on the good work, PD.

[PAXboy]

PDheating 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.Is this what they mean when they say that global warming has gone to local warming? :E


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 :uhoh: and could have killed and maimed several of us. :ouch:

Fortunately, everone else - consuming the same air - was being watchful and we all avoided that twit. That's the job of driving. :hmm:

Perhaps the drinking of rarefied air helps pilots concentrate better. :ok:

[WingSlinger]

Didn't you get the memo? You don't have to signal if you're crossing 3 lanes of traffic in an (self created) emergency.

[korrol]

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.

[Hipennine]

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.

[TightSlot]

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.

[blind pew]

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.

[strake]

This site would seem to offer a feast of reasoned scientific evidence on the subject. effects of air density on pilots (http://www.pilotfriend.com/aeromed/medical/pressure.htm)

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.:ok:

[CelticRambler]

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. :8

[PAXboy]

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. :p

[korrol]

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.

[PAXboy]

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.

[TightSlot]

Since korrol has kindly provided all of the answers I think I can now raise my knuckles from floor level to close this thread. Next week? "The Secret of Fire".