Forum: General F-22A Raptor forum

I have a theory that the issue with the F-22 has nothing to do with the OBOGS system at all. I think that it may be an issue with the ECS package. Being that ground crews are now experiencing some of the same issues on the ground, we need to assume that there is a flaw with the system that provide ambient air and pressure into the cockpit while closed.

This could be caused by the system not getting enough airflow from the bleed air route which in turn could affect not only the cockpit ambient air but also the avionic bays where all the equipment that controls enviromental conditions are kept. If the bay is not receiving a sufficient amount of air, the electronics may be overheating and affecting its operation. It may be relaying faulty signals. I suggest putting thermal paste on all the equipment for one flight to determine what type of temperatures we are dealing with when aircraft is at altitude.

The situation could be fixed by increasing the diameter of the openings of the bleed air inlets which would increase airflow and provide sufficient cooling and venting. My only question is how would the air at crusing altitude affect this change.

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BlueFoxGuitar wrote:

I have a theory that the issue with the F-22 has nothing to do with the OBOGS system at all. I think that it may be an issue with the ECS package. Being that ground crews are now experiencing some of the same issues on the ground, we need to assume that there is a flaw with the system that provide ambient air and pressure into the cockpit while closed.

Yes, the ECS/Cockpit pressurization is a more likely culprit than the OBOGS itself. The pilot symptoms sound more like decompression sickness than mild hypoxia.

BlueFoxGuitar wrote:

This could be caused by the system not getting enough airflow from the bleed air route which in turn could affect not only the cockpit ambient air but also the avionic bays where all the equipment that controls enviromental conditions are kept.

That is unlikely because the if something goes wrong with the cooling system, there are definite warnings to the pilot. The Alaska F-22 AIB report explained this.

BlueFoxGuitar wrote:

If the bay is not receiving a sufficient amount of air, the electronics may be overheating and affecting its operation. It may be relaying faulty signals. I suggest putting thermal paste on all the equipment for one flight to determine what type of temperatures we are dealing with when aircraft is at altitude.

Thermal paste? It's not a gaming PC, its a jet fighter.

Aerospace grade components have a higher thermal tolerance than consumer equipment. If a particular component was getting too hot in operation, the module would fail or go offline and it would show up in the data recorder. The F-22 Crash Survivable Memory Unit and the Integrated Maintenance Information System would reveal problems with the avionics. Sensors are usually digitally networked,and fail in obvious ways. An F-22 pilot at Nellis didn't do a correct pre-flight test of his flight controls, using the IBIT function. The rate sensors producted bad digital data due to a glitch in power availability. The pilot tried to take off and had to eject from a $140m jet. The CSMU revealed most of the answers for the AIB/SIB, and the cause was identified and a fix implemented. Lack of a cheap pull-up resistor on the rate sensors, crashed the jet.

BlueFoxGuitar wrote:

The situation could be fixed by increasing the diameter of the openings of the bleed air inlets which would increase airflow and provide sufficient cooling and venting. My only question is how would the air at crusing altitude affect this change.

Loss of thrust from the engines and questionable benefit. Avionics are not cooled with a chip-mounted fan. They use liquid cooling and heat exchangers to keep everything running cool.

neurotech wrote:

An F-22 pilot at Nellis didn't do a correct pre-flight test of his flight controls, using the IBIT function. The rate sensors producted bad digital data due to a glitch in power availability. The pilot tried to take off and had to eject from a $140m jet.

Point in fact the pilot DID do a correct pre-flight test. The technical order was to blame. The pilot was NOT found at fault. I suggest a read of the AIB report prior to talking about a particular accident.

checksixx wrote:

neurotech wrote:

An F-22 pilot at Nellis didn't do a correct pre-flight test of his flight controls, using the IBIT function. The rate sensors producted bad digital data due to a glitch in power availability. The pilot tried to take off and had to eject from a $140m jet.

Point in fact the pilot DID do a correct pre-flight test. The technical order was to blame. The pilot was NOT found at fault. I suggest a read of the AIB report prior to talking about a particular accident.

I may have phrased it poorly, but I had definitely read the AIB report.

I did not specifically say the pilot was at fault, only that he didn't do a correct pre-flight. The AIB stated that every jet with RSA problems, failed on the IBIT and ground-aborted.

According to the AIB report, there was no consensus prior to the mishap on precisely when a IBIT is required. A unique set of circumstances contributed to the mishap, but ultimately running the IBIT would have detected the problem.

Here is a copy of the AIB
http://www.f-22raptor.com/pdf/af.exsum_f22crash.pdf

BlueFoxGuitar wrote:

thermal paste

I'm going to venture to guess that a $100+ million dollar aircraft has a far superior thermal cooling system than your home PC. That is not a concern of the Air Force I do not think. It would be quite humorous to imagine an LM employee walking into their nearest Fry's Electronics to purchase some off-the-shelf thermal paste for F-22 avionics.

pants3204 wrote:

BlueFoxGuitar wrote:

thermal paste

I'm going to venture to guess that a $100+ million dollar aircraft has a far superior thermal cooling system than your home PC. That is not a concern of the Air Force I do not think. It would be quite humorous to imagine an LM employee walking into their nearest Fry's Electronics to purchase some off-the-shelf thermal paste for F-22 avionics.

Then you would be doubled over guffawing at some of the things done in the labs. Ever see an extension cord with a MALE plug at each end?
fisk

fiskerwad wrote:

pants3204 wrote:

BlueFoxGuitar wrote:

thermal paste

I'm going to venture to guess that a $100+ million dollar aircraft has a far superior thermal cooling system than your home PC. That is not a concern of the Air Force I do not think. It would be quite humorous to imagine an LM employee walking into their nearest Fry's Electronics to purchase some off-the-shelf thermal paste for F-22 avionics.

Then you would be doubled over guffawing at some of the things done in the labs. Ever see an extension cord with a MALE plug at each end?
fisk

What would even be the purpose of that?

pants3204 wrote:

fiskerwad wrote:

pants3204 wrote:

BlueFoxGuitar wrote:

thermal paste

I'm going to venture to guess that a $100+ million dollar aircraft has a far superior thermal cooling system than your home PC. That is not a concern of the Air Force I do not think. It would be quite humorous to imagine an LM employee walking into their nearest Fry's Electronics to purchase some off-the-shelf thermal paste for F-22 avionics.

Then you would be doubled over guffawing at some of the things done in the labs. Ever see an extension cord with a MALE plug at each end?
fisk

What would even be the purpose of that?

Hmm, how to stay out of jail?
OK, let's say the power lines to your neighbor's house fell off the pole. To help out, you build an extension cord but since you are lazy, you decide to just plug it into an existing outlet at your neighbor's house? Sort of a REALLY dangerous jumper cable.
That's not what happened ... except for the lazy part. Smile

fisk

Hey !!!!

I remember something from the past ! ! ! Do not know what aircraft any more but I see some similarities.
it was the paint..

I am sure it was the paint,do not know any more if it was paint used in the cockpit or in the ECS tubing, but when hot air got throught the system, the paint started to poison the pilots...and ground crews when they where doing long checks in the cockpit..

LM?? Check the paints used in the ECS system.

vilters wrote:

Hey !!!!

I remember something from the past ! ! ! Do not know what aircraft any more but I see some similarities.
it was the paint..

I am sure it was the paint,do not know any more if it was paint used in the cockpit or in the ECS tubing, but when hot air got throught the system, the paint started to poison the pilots...and ground crews when they where doing long checks in the cockpit..

LM?? Check the paints used in the ECS system.

They'd want to check a potential source of outgassing unique to the F-22.

pants3204 wrote:

BlueFoxGuitar wrote:

thermal paste

I'm going to venture to guess that a $100+ million dollar aircraft has a far superior thermal cooling system than your home PC. That is not a concern of the Air Force I do not think. It would be quite humorous to imagine an LM employee walking into their nearest Fry's Electronics to purchase some off-the-shelf thermal paste for F-22 avionics.

I think *you* might be surprised. There are always going to be air gaps under heatsinks that need to be filled (even if you're water, fuel, or even LN cooling). What do you use? That's right, thermal paste.

sferrin wrote:

vilters wrote:

Hey !!!!

I remember something from the past ! ! ! Do not know what aircraft any more but I see some similarities.
it was the paint..

I am sure it was the paint,do not know any more if it was paint used in the cockpit or in the ECS tubing, but when hot air got throught the system, the paint started to poison the pilots...and ground crews when they where doing long checks in the cockpit..

LM?? Check the paints used in the ECS system.

They'd want to check a potential source of outgassing unique to the F-22.

For what it's worth my money was also on some weird sort of outgassing from (possibly quite exotic) materials making up the ECS. Many materials, especially the newer ones, can act quite strangely when they aren't in standard atmospheric pressure conditions.

But the investigations into what was causing the problems included adding filters to the system to see if they could catch any toxins such as those that you might find coming out of paint or exotic materials; those tests all came up empty. ie. no toxins were identified.

I think their main line of inquiry now is that it's some sort of physiological effect which is occurring as a result of the F-22s altitude/maneuver regime. There has been a lot of research done over the years into the physiological effects of high altitude flight but I don't think that you could describe it as exhaustive. They may well have to think about going back to pressure suits although given the space restrictions in the cockpit and the impact that would have on the pilots ability to withstand hard maneuvering may mean that it isn't a short term fix.

I imagine that they'll have to try replacing the obogs system completely in a couple of jets, if they haven't already, or at least swapping it out temporarily, to see if the problem still occurs on bottled air.

vilters wrote:

Hey !!!!

I remember something from the past ! ! ! Do not know what aircraft any more but I see some similarities.
it was the paint..

I am sure it was the paint,do not know any more if it was paint used in the cockpit or in the ECS tubing, but when hot air got throught the system, the paint started to poison the pilots...and ground crews when they where doing long checks in the cockpit..

LM?? Check the paints used in the ECS system.

Guess you're talking about the F-16I problems with formaldehyde.

http://www.f-16.net/f-16_forum_viewtopic-t-10157.html

Is it possible that the extreme low pressure at the F-22's higher than normal operating ceiling is causing some of it's exotic materials to sublimate and work their way into the cockpit/OBOGS, even leaving residual effects for the ground crews?

That might explain the reluctance we're seeing from the USAF and LM. Such a problem would be extremely difficult (and expensive) to track down, and might even be impossible to fix.

my question is why did it take so long to surface? Raptors have been flying at their operating point for years an only now (last year or so) having the issue? That just sounds to me like something is wearing out that shouldn't be.

Forum: General F-22A Raptor forum

Possible Fix for F-22 problem