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Posted: 2/7/2017 11:29:25 PM EDT
Saw this 2012 video tonight for the first time.

Has this been fixed?

Also, correct me if I'm wrong, but even though fighter pilots wear O2 masks over 10,000 feet, isn't the cocopit pressurized just like in an airliner, and the mask is really there as a backup?

https://www.youtube.com/watch?v=RTuJ9Lk1a-Q

Link Posted: 2/8/2017 12:09:06 AM EDT
[#1]
Cockpits are pressurized, but sometimes aren't pressurized to an altitude low enough to prevent hypoxia.  Depends on how the plane was designed - service ceiling, max cabin differential, etc.

In ejection seat planes regulations often dictate mask on always for protection during ejection and to prevent hypoxia once you leave the aircraft.  But all services and airplanes are different.
Link Posted: 2/8/2017 10:33:19 AM EDT
[#2]
airline cabins are pressurized at a max of 8000 feet

fighters are pressurized at a differential pressure schedule. At 50,000 feet the cockpit is at 25,000 feet.

at 30,000 feet the cockpit is about 12,000 feet

above 10,000 feet cockpit pressure the O2 regulator automatically starts supplementing cockpit air with oxygen through the mask and continues doing so  until it is 100%.

Combat edge increases that and supplies positive pressure 100% O2 under G.

So, the mask is not a backup. It is absolutely required for life support.

It also holds the microphone for comm, So you need it all the time. Very rarely does anybody ever drop the mask, to eat, drink on long missions, and then only to take a bite, then chew with the mask on. but that is about it. Fighter pilots dropping the mask like in the movies simply does not happen.
Link Posted: 2/8/2017 12:38:57 PM EDT
[#3]
Oxygen has been fixed for awhile now. I seem to remember a maintenance guy fixed one himself.....or something like that
Link Posted: 2/10/2017 3:43:31 PM EDT
[#4]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
airline cabins are pressurized at a max of 8000 feet

fighters are pressurized at a differential pressure schedule. At 50,000 feet the cockpit is at 25,000 feet.

at 30,000 feet the cockpit is about 12,000 feet

above 10,000 feet cockpit pressure the O2 regulator automatically starts supplementing cockpit air with oxygen through the mask and continues doing so  until it is 100%.

Combat edge increases that and supplies positive pressure 100% O2 under G.

So, the mask is not a backup. It is absolutely required for life support.

It also holds the microphone for comm, So you need it all the time. Very rarely does anybody ever drop the mask, to eat, drink on long missions, and then only to take a bite, then chew with the mask on. but that is about it. Fighter pilots dropping the mask like in the movies simply does not happen.
View Quote


So when you are at 30,000 feet in an airline, it's like being up at 12,000 without pressure?
Link Posted: 2/10/2017 3:47:39 PM EDT
[#5]
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Quoted:
Oxygen has been fixed for awhile now. I seem to remember a maintenance guy fixed one himself.....or something like that
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Cool.  Got any details on how they fixed it?
Link Posted: 2/10/2017 4:04:09 PM EDT
[#6]
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Quoted:


Cool.  Got any details on how they fixed it?
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Here is the article on how a guy fixed a recurring problem on a F-22 Link

Link on oxygen fix
Link Posted: 2/10/2017 4:37:58 PM EDT
[#7]
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Quoted:


So when you are at 30,000 feet in an airline, it's like being up at 12,000 without pressure?
View Quote
No. 8K.
Link Posted: 2/10/2017 5:06:01 PM EDT
[#8]
They have a presurization similar to modern day airlines, just smaller outflow and safety valves. If the plane is at 51,000 feet the cockpit is usually around 6000 to 9000 feet pressure altitude depending on where the pilot sets the cockpit presurization. I don't know where people get their information in the above posts. This is done so incase of an oxygen system failure, the pilots can breath normally. O2 is supposed to help with black outs at high g manuvers, like I said, supposed....along with a g suit and grunting/ breathing technique
Link Posted: 2/10/2017 10:39:30 PM EDT
[#9]
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Quoted:
They have a presurization similar to modern day airlines, just smaller outflow and safety valves. If the plane is at 51,000 feet the cockpit is usually around 6000 to 9000 feet pressure altitude depending on where the pilot sets the cockpit presurization. I don't know where people get their information in the above posts. This is done so incase of an oxygen system failure, the pilots can breath normally. O2 is supposed to help with black outs at high g manuvers, like I said, supposed....along with a g suit and grunting/ breathing technique
View Quote


Why was the F-22 designed with that "unlimited oxygen" system? Are LOX tanks, which have been use since the 50's, I would think, really that hard to deal with?  Also, is running out of LOX a common occurrence?
Link Posted: 2/11/2017 1:46:07 AM EDT
[#10]
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Quoted:
don't know where people get their information in the above posts.
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From the airplane manuals?  One I currently fly tops out at 19k cabin altitude at the service ceiling.  Most single seat planes do not have adjustable cabin pressure or cabin climb rate, in fact I do not know of one that does. The pressure differential is fixed at some value(a few psi), i.e. It keeps the cabin X psi above ambient.  So when you're below say 10k the cabin is not pressurized at all.  As you climb above that 10k the cabin is held at 10k until the pressure differential is maxed out.  Then the cabin alt climbs with the aircraft altitude.  Cabin altitudes commonly max out around 1/2 of the aircraft's service ceiling.

Single seat planes are not passenger planes, there is no need to keep the cabins around 8k feet.  Doing so would add much complexity, cost, and weight.
Link Posted: 2/11/2017 1:10:59 PM EDT
[#11]
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Quoted:


So when you are at 30,000 feet in an airline, it's like being up at 12,000 without pressure?
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Quoted:
airline cabins are pressurized at a max of 8000 feet

fighters are pressurized at a differential pressure schedule. At 50,000 feet the cockpit is at 25,000 feet.

at 30,000 feet the cockpit is about 12,000 feet

above 10,000 feet cockpit pressure the O2 regulator automatically starts supplementing cockpit air with oxygen through the mask and continues doing so  until it is 100%.

Combat edge increases that and supplies positive pressure 100% O2 under G.

So, the mask is not a backup. It is absolutely required for life support.

It also holds the microphone for comm, So you need it all the time. Very rarely does anybody ever drop the mask, to eat, drink on long missions, and then only to take a bite, then chew with the mask on. but that is about it. Fighter pilots dropping the mask like in the movies simply does not happen.


So when you are at 30,000 feet in an airline, it's like being up at 12,000 without pressure?


nope. 8000 feet
Link Posted: 2/11/2017 1:14:02 PM EDT
[#12]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
They have a presurization similar to modern day airlines, just smaller outflow and safety valves. If the plane is at 51,000 feet the cockpit is usually around 6000 to 9000 feet pressure altitude depending on where the pilot sets the cockpit presurization. I don't know where people get their information in the above posts. This is done so incase of an oxygen system failure, the pilots can breath normally. O2 is supposed to help with black outs at high g manuvers, like I said, supposed....along with a g suit and grunting/ breathing technique
View Quote


I find that hard to believe but I have no info on the F22. The info I posted above is from F15/F16/F18
Link Posted: 2/16/2017 4:21:37 AM EDT
[#13]
Quoted:
Saw this 2012 video tonight for the first time.

Has this been fixed?

Also, correct me if I'm wrong, but even though fighter pilots wear O2 masks over 10,000 feet, isn't the cocopit pressurized just like in an airliner, and the mask is really there as a backup?



View Quote


The cockpit is pressurized but the function of the mask is to "provides positive pressure breathing in the oxygen mask with concurrent inflation of the upper pressure garment in response to altitude and G force"....."The oxygen concentration is automatically controlled to approximately 60 percent at or below 11.0 cockpit altitude and approximately 90-94 percent above 11.0 cockpit altitude".


Basically the pilot receives air with an increased oxygen level during high G maneuvers to help combat blackouts.

There are a total of three oxygen bottles in the aircraft:

One emergency bottle that is mounted to the ejection seat and provides oxygen after a ejection.

Two oxygen bottles that are mounted behind the ejection seat and serve as the "Automatic Back-up Oxygen System". That system was put into place to combat any future issues with the On-Board Oxygen Generation System incase of a failure of that system or any other issues that arise (minus ejection). "Each ABOS oxygen bottle is designed to provide 15 to 35 minutes of oxygen depending on altitude, breathing rate and use of the pressure garment. ABOS can be either activated on command by the pilot or automatically".

The aircraft was without the two ABOS backup bottles for almost twenty years. So some think that was the fix for the hypoxia situations and some don't.
Link Posted: 2/16/2017 12:12:31 PM EDT
[#14]
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Quoted:
No. 8K.
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Quoted:
Quoted:


So when you are at 30,000 feet in an airline, it's like being up at 12,000 without pressure?
No. 8K.


Oh ok, that makes more sense, becuase I know at or around 10k the GA guys crack open the o2.

That would also explain why I can't sleep worth a shit on the airplane.
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