Theory about F-22 OBOGS solution

Unread postPosted: 03 Jun 2012, 20:34
by spazsinbad
Saw this 'how to fix F-22 OBOGS' theory and thought it might be useful here - other than that I have no clue - and good luck.

causes of F-22 oxygen problem have been found JameLi1986

http://www.defencetalk.com/forums/air-f ... und-11978/

causes of F-22 oxygen problem have been found

http://www.youtube.com/watch?v=zvUFm9SLM_I

"Published on May 29, 2012 by orion198606
causes of F-22 oxygen problem is discovered"

Unread postPosted: 03 Jun 2012, 20:42
by papakaz
I thought they solved that problem when they stopped wearing chem gear on every flight.

Unread postPosted: 04 Jun 2012, 00:22
by discofishing
I can't understand a damn thing this guy is saying. Sounds like one of my engineering professors. Is there a written version of this?

Unread postPosted: 04 Jun 2012, 00:32
by popcorn
Is it possible that we are seeing different physiological maladies arising from multiple and possibly unrelated fators being attributed to some single enigmatic cause? This is beginning to look like the physicists searching for the unified theory of everything.

Unread postPosted: 04 Jun 2012, 00:40
by f22spec
I'm pretty much seeing that this whole thing is based off of the fact that the F-22 does high altitude violent maneuvers? After Capt. Haney's crash, all F-22 flights were restricted below 25,000 ft. However, there were still plenty more incidents (including the pilot who hit a few trees on approach for his landing), after this flight level restriction. While it might have some affect on the OBOGS system, it's not the root cause.

I can't really understand what the guy in the video is saying, though so I'm just assuming this is what he's talking about.

Unread postPosted: 04 Jun 2012, 02:01
by spazsinbad
'f22spec' said: "...I can't really understand what the guy in the video is saying, though so I'm just assuming this is what he's talking about." I did not realise the video had bad English. I have no sound on this computer and assumed sound was OK. Sorry about that. I'm guessing that the text is sufficient (and also explains video?). Probably explains why the text came online later?

causes of F-22 oxygen problem have been found JameLi1986

http://www.defencetalk.com/forums/air-f ... und-11978/

Unread postPosted: 04 Jun 2012, 02:02
by river_otter
f22spec wrote:I'm pretty much seeing that this whole thing is based off of the fact that the F-22 does high altitude violent maneuvers? After Capt. Haney's crash, all F-22 flights were restricted below 25,000 ft. However, there were still plenty more incidents (including the pilot who hit a few trees on approach for his landing), after this flight level restriction. While it might have some affect on the OBOGS system, it's not the root cause.

I can't really understand what the guy in the video is saying, though so I'm just assuming this is what he's talking about.


Strikes me as an interesting amateur theory, not complete ignorance but it doesn't entirely fit the observed incidents. I don't think it could be correct.

Oh, and Discofishing and f22spec, what he's saying is basically exactly what the text of the defensetalk.com forum post is. He's just saying it slowly in a French Canadian(?) accent.

Unread postPosted: 04 Jun 2012, 04:58
by neurotech
f22spec wrote:I'm pretty much seeing that this whole thing is based off of the fact that the F-22 does high altitude violent maneuvers? After Capt. Haney's crash, all F-22 flights were restricted below 25,000 ft. However, there were still plenty more incidents (including the pilot who hit a few trees on approach for his landing), after this flight level restriction. While it might have some affect on the OBOGS system, it's not the root cause.

I can't really understand what the guy in the video is saying, though so I'm just assuming this is what he's talking about.

I don't buy the explanation either. Better monitoring isn't a real solution either, or swapping to primary LOX tanks.

If disrupted/insufficient airflow to both engines from aggressive maneuvering caused the OBOGS to malfunction, there would be other indications, including a probable double engine flameout. There is a few reports of F-14s having compressor stalls & flameouts during high altitude/low-speed maneuvers. This was very obvious to the pilot/RIO however.

If physiological issues originated in the OBOGS, then switching to emergency oxygen should quickly resolve the physiological issues, but it doesn't seem to. The F/A-18 can show an OBOGS warning at high altitude if there is low outflow pressure from a leak or something. I'm not certain if the F-22 has a OBOGS low outflow pressure warning or not.

My personal opinion is that its not actually the OBOGS at all causing these issues, as they are more consistent with decompression sickness. Improved cockpit pressurization might help avoid the problems. Another option is lightweight pressure suits.

Unread postPosted: 04 Jun 2012, 05:05
by munny
If pilots had experienced symptoms after merely flying straight and level at high altitude and high speed then theory = wrong

You can't really work out the cause unless you know all the conditions that were common for all pilots affected (and all pilots NOT affected too). At the moment, the public have only been told one factor ... aircraft flown was the F-22

I'm sure a good ol Kepner Tregoe analysis would sort it out if they had sufficient information on the nature of the incidents.

Re: Theory about F-22 OBOGS solution

Unread postPosted: 04 Jun 2012, 06:49
by Raptor_claw
causes of F-22 oxygen problem have been found JameLi1986
http://www.defencetalk.com/forums/air-f ... und-11978/

"Published on May 29, 2012 by orion198606
causes of F-22 oxygen problem is discovered"
He's wrong from the very beginning:

"Since the crash of F-22 in Alaska in November 2010. The mysterious oxygen supply problem is so far still a mystery. No one know what the real causes is. "

As has been discussed here before (extensively), the Alaska crash is well understood and involved an actual mechanical failure. ( http://www.f-16.net/f-16_forum_viewtopic-t-16562.html ). That event is unrelated to the hypoxia studies that have been ongoing for so long.

RE: Re: Theory about F-22 OBOGS solution

Unread postPosted: 06 Jun 2012, 12:50
by jamesli
Hi. I am JamesLi. I been read from news that the pressure suit they wear might be the problem . And neurotech says:
The F/A-18 can show an OBOGS warning at high altitude if there is low outflow pressure from a leak or something. I'm not certain if the F-22 has a OBOGS low outflow pressure warning or not.
---
If this is true. Then I believe my theory is wrong. The OBOGS of F/A-18 is also produced by honeywell. So they must also have such a warning mechanism.

RE: Re: Theory about F-22 OBOGS solution

Unread postPosted: 07 Jun 2012, 06:25
by neurotech
Thats just it, operational F-22 pilots don't currently wear full pressure suits. Neither do operational fleet F/A-18 pilots. That said, even the U-2/SR-71 pilots are not immune from decompression sickness (DCS). A F-22 pilot does not breath 100% oxygen during pre-flight or during all phases of the flight, so could (theoretically) be at a higher risk of DCS. A full pressure suit isn't a 'magic' solution because it all depends on the suit design. A higher internal pressure restricts movement but requires less pre-breathing. This was readily apparent on the ISS where crew had both Russian & American suits for spacewalks. The Russians had lower pressure suits, and were easier to work in.

As for the warning mechanism, I haven't heard of a OBOGS outflow leak occurring in a F-22 during flight to know for sure how the system would handle it. The F-22 Panel Mounted BRAG system is more advanced than the F/A-18 "chest" mounted regulator. The F/A-18 does not warn a pilot of a malfunctioning regulator with avionics.

The F/A-18 uses a Cobham OBOGS unit, whereas the F-22 has a Honeywell OBOGS. The F-15E Strike Eagle uses a Cobham OBOGS unit as well. The thing that is interesting is that the F-15E can fly high-altitude/high-G profiles when not heavily loaded down with stores, and has done so without 'physiological incidents' matching the F-22 pilot issues.

The problem is that they are not getting enough of a pattern to say if a pilot flies this profile in a F-22 that they'll duplicate the issue.

I think part of the issue with the Combat Edge flight suit is that it restricts breathing, especially at high altitudes, but not in a way that results in an immediate decrease in blood oxygen saturation. It is possible to have an increase in exhale CO2 without the noticeable decrease in O2 stats when breathing 100% oxygen. The Combat Edge system requires different techniques at high altitude/high-G profiles, which is not demonstrated during standard centrifuge AGSM training. Monitoring pilot respiration/exhale stats would give a clearer picture of a physiological cause.

Re: RE: Re: Theory about F-22 OBOGS solution

Unread postPosted: 16 Jun 2012, 04:22
by jamesli
neurotech wrote:Thats just it, operational F-22 pilots don't currently wear full pressure suits. Neither do operational fleet F/A-18 pilots. That said, even the U-2/SR-71 pilots are not immune from decompression sickness (DCS). A F-22 pilot does not breath 100% oxygen during pre-flight or during all phases of the flight, so could (theoretically) be at a higher risk of DCS. A full pressure suit isn't a 'magic' solution because it all depends on the suit design. A higher internal pressure restricts movement but requires less pre-breathing. This was readily apparent on the ISS where crew had both Russian & American suits for spacewalks. The Russians had lower pressure suits, and were easier to work in.

As for the warning mechanism, I haven't heard of a OBOGS outflow leak occurring in a F-22 during flight to know for sure how the system would handle it. The F-22 Panel Mounted BRAG system is more advanced than the F/A-18 "chest" mounted regulator. The F/A-18 does not warn a pilot of a malfunctioning regulator with avionics.

The F/A-18 uses a Cobham OBOGS unit, whereas the F-22 has a Honeywell OBOGS. The F-15E Strike Eagle uses a Cobham OBOGS unit as well. The thing that is interesting is that the F-15E can fly high-altitude/high-G profiles when not heavily loaded down with stores, and has done so without 'physiological incidents' matching the F-22 pilot issues.

The problem is that they are not getting enough of a pattern to say if a pilot flies this profile in a F-22 that they'll duplicate the issue.

I think part of the issue with the Combat Edge flight suit is that it restricts breathing, especially at high altitudes, but not in a way that results in an immediate decrease in blood oxygen saturation. It is possible to have an increase in exhale CO2 without the noticeable decrease in O2 stats when breathing 100% oxygen. The Combat Edge system requires different techniques at high altitude/high-G profiles, which is not demonstrated during standard centrifuge AGSM training. Monitoring pilot respiration/exhale stats would give a clearer picture of a physiological cause.



Thanks for the very useful post!
Right now I believe in 2 possible causes:

1. The high altitude low cabin pressure + pure oxygen + high G maneuver = Alveolar collapsing / Atelectasis This have 70% possibility
2. The high altitude low air speed cause the OBOGS to malfunction. This have 30% possibility

Within 1 to 2 months we will see the report from airforce.

You say that F-15 also do high G maneuver at high altitude. That's a puzzling facts. Maybe the F-22 pilots do maneuver more frequent and more violent. I guess at high altitude(30000 feet+) the F-15 can't go beyond 6 G at most. This is my experience in combat SIMS
Any way we will wait and see the final report.
Thanks again for your profession information. :D

Re: RE: Re: Theory about F-22 OBOGS solution

Unread postPosted: 16 Jun 2012, 05:24
by neurotech
jamesli wrote:Thanks for the very useful post!

Your welcome. For the record my background is in neuro-physiology and EEG technology. I did previously fly various aircraft, mainly in the back seat.

jamesli wrote:Right now I believe in 2 possible causes:

1. The high altitude low cabin pressure + pure oxygen + high G maneuver = / Atelectasis This have 70% possibility

Right reasons, wrong conclusion. High Altitude + High O2 + High Gs can also cause neurophysiological issues. The Combat Edge suit under these conditions could conceivable result in BP or ICP (Intracranial Pressure) spike in the pilot, resulting in neurological effects after the flight. The "Alveolar Collapsing" idea would have been more obvious because it would result in a drop in SpO2 during the event.

jamesli wrote:2. The high altitude low air speed cause the OBOGS to malfunction. This have 30% possibility

I still doubt the OBOGS is involved.

jamesli wrote:You say that F-15 also do high G maneuver at high altitude. That's a puzzling facts. Maybe the F-22 pilots do maneuver more frequent and more violent. I guess at high altitude(30000 feet+) the F-15 can't go beyond 6 G at most. This is my experience in combat SIMS
Any way we will wait and see the final report.
Thanks again for your profession information. :D


The F-15 can do high altitude/high-G maneuvers, but not with the same energy as a F-22. The pilot can still trade energy (altitude) for additional g-force.

RE: Re: RE: Re: Theory about F-22 OBOGS solution

Unread postPosted: 16 Jun 2012, 05:29
by That_Engine_Guy
I'd say it's not the fault of the motors providing insufficient air flow or pressure. If the engines were running out of air like that at high altitude and high AOA, they would likely compressor stall/stagnate long before bleed-air pressure/flow dropped below specification.

The pilot would know this from the loud BANG, or the loss of power in the motor(s). If anything, a condition like this would be indicated in the CSFDR or in the remaining engine control component memory. (Yes, if still somewhat intact, they can retrieve data from the engine control system chips after a crash!) It would have been obvious with any mishap that the engines had surged/stalled/flamed-out and contributed to situation.

I don't know much about the bleed-air system of the F119/Raptor, but I'm going to assume that both motors feed the common OBOGS? So that a single engine out situation would not affect Oxygen supply? This further reduces the possibilities that the Raptor's propulsion system 'slow/high' would ever be insufficient to supply the OBOGS - feeding from BOTH engines equally.

:shrug: TEG

Re: RE: Re: RE: Re: Theory about F-22 OBOGS solution

Unread postPosted: 16 Jun 2012, 09:31
by neurotech
That_Engine_Guy wrote:I'd say it's not the fault of the motors providing insufficient air flow or pressure. If the engines were running out of air like that at high altitude and high AOA, they would likely compressor stall/stagnate long before bleed-air pressure/flow dropped below specification.

The pilot would know this from the loud BANG, or the loss of power in the motor(s).

That's what I thought. It would be an unusual "physiological incident" for a pilot to not notice a loud BANG from the engines.

That_Engine_Guy wrote:I don't know much about the bleed-air system of the F119/Raptor, but I'm going to assume that both motors feed the common OBOGS? So that a single engine out situation would not affect Oxygen supply? This further reduces the possibilities that the Raptor's propulsion system 'slow/high' would ever be insufficient to supply the OBOGS - feeding from BOTH engines equally.

:shrug: TEG

According to the AIB, What happen in the Alaska crash was an indicated DUAL BLEED AIR failure, that shut down the supply to the OBOGS, and the OBOGS itself shut down and caused a suffocating feeling by the pilot before he crashed.

The OBOGS shutoff, with ICAWS, is different to the physiological incidents which came to light after the crash, that are a different cause, and apparently have not resulted in any ICAWS faults being recorded. These ICAWS are recorded to the CSFDR.

Thanks for your insight TEG

Re: RE: Re: RE: Re: Theory about F-22 OBOGS solution

Unread postPosted: 23 Jun 2012, 11:30
by jamesli
That_Engine_Guy wrote:I'd say it's not the fault of the motors providing insufficient air flow or pressure. If the engines were running out of air like that at high altitude and high AOA, they would likely compressor stall/stagnate long before bleed-air pressure/flow dropped below specification.

The pilot would know this from the loud BANG, or the loss of power in the motor(s). If anything, a condition like this would be indicated in the CSFDR or in the remaining engine control component memory. (Yes, if still somewhat intact, they can retrieve data from the engine control system chips after a crash!) It would have been obvious with any mishap that the engines had surged/stalled/flamed-out and contributed to situation.

I don't know much about the bleed-air system of the F119/Raptor, but I'm going to assume that both motors feed the common OBOGS? So that a single engine out situation would not affect Oxygen supply? This further reduces the possibilities that the Raptor's propulsion system 'slow/high' would ever be insufficient to supply the OBOGS - feeding from BOTH engines equally.

:shrug: TEG


Hi pale. I am saying not the compressor stall. let's say if the f-119 ENGINE have a compression ratio of 20. and subject to low or still air speed with only 10% of sea level air pressure. Then the bleed air can reach only 200% or 300% of sea level air pressure.
But this still enough to make the engine run normally.(Provide much much less thrust of course)

Re: RE: Re: RE: Re: Theory about F-22 OBOGS solution

Unread postPosted: 24 Jun 2012, 08:13
by neurotech
jamesli wrote:Hi pale. I am saying not the compressor stall. let's say if the f-119 ENGINE have a compression ratio of 20. and subject to low or still air speed with only 10% of sea level air pressure. Then the bleed air can reach only 200% or 300% of sea level air pressure.


James,
I was the one who posted that I doubted that it was insufficient airflow into the engines causing problems with the OBOGS, because in a case of insufficient airflow to the engines, there would be a compressor stall well before the loss of bleed air would cause the OBOGS to fail. If bleed air supply is compromised, a very noticeable "BLEED AIR" caution warns the pilot before OBOGS failure. The Crash Survivable Fight Data Recorder would record both the BLEED AIR & OBOGS failure. This is what happened in the Alaska crash.
jamesli wrote:But this still enough to make the engine run normally.(Provide much much less thrust of course)

The engines wouldn't run normally. When an engine has a reduction in thrust due to disrupted airflow(or malfunction, low fuel flow) it is called a "roll back" and engine RPM is reduced. If the disrupted airflow is not corrected quickly it will result in a compressor stall and flameout. The F119 engine has excellent airflow characteristics compared to earlier engines (eg. TF-30 in the F14A) so even high altitude/slow flight wouldn't cause a rollback, much less bleed air problems.

As posted previously, I think the theory about the Combat Edge flight gear being improperly fitted is quite possible.

RE: Re: RE: Re: Theory about F-22 OBOGS solution

Unread postPosted: 06 Nov 2012, 17:56
by jamesli
Hey guys. It's jamesLi here again. After so many months and the F-22's oxygen problem is still no totally addressed. You know why is this? Because I just don't have the phone No. of the F-22 project manager or some generals of USAF. If Give me 2 minutes to talk to some of these guys. I can make them get it right in minutes. any way the reason I am here back again to post is there is news came out saying I made it very right. Almost proved my theory in someway.
here it is go ahead and read this please:

http://www.military.com/daily-news/2012 ... ckpit.html

"As the aircraft descends and the pilot puts eight Gs on the aircraft, the percentage of oxygen produced by the Obogs is reduced," the report says. "As the pilot reduces the G load, the Obogs begins to recover and then the percentage of oxygen produced by the Obogs is reduced again when the pilot reapplies the Gs."

The report says, "The amount of oxygen being produced does decrease to between 60 percent and 70 percent."

I am not an arrogant man. BUT I JUST WANT TO SAY A BARE TRUTH HERE: FOR THE f-22 oxygen problem. ONE CHINESE GUY HAD JUST BEAT THE ENTIRE LOCKHEED ENGINEERING TEAM in 3 minutes.

RE: Re: RE: Re: Theory about F-22 OBOGS solution

Unread postPosted: 06 Nov 2012, 20:55
by neurotech
I'm sure Gen. Mike Hostage, USAF, Commander of Air Combat Command who is qualified to fly a F-22, also checks his email. A smart guy can often figure out what email address is for even senior USAF personnel are :D If the Gen. responds, thats another story in itself.

I see a flaw in your comment. It was not HIGH and SLOW flight that induced the OBOGS output deficit. A F-22 can manoever at high altitude and not bleed airspeed like other jets. This is due to having thrust vectoring engines. The problem wasn't technically "extreme" altitude related, but related to the OBOGS "oxygen" output under high G loads.

Saying "Use LOX bottles would solve the problem" is technically correct except that operationally, when a F-22 (Or any fighter pilot) goes to emergency Oxygen supply, that is a knock-it-off event except for real combat emergencies. The pilot at that point ceases pulling High-Gs

The short version is something like this. Air contains a mixture of primarily nitrogen and oxygen. OBOGS enhances the oxygen concentration in the bleed air by filtering mechanism. If the oxygen concentration into the oxygen mask is reduced, the effect is difficult for humans to handle. The pilot(human) will become hypoxic. It is fatal for a human to inhale 100% nitrogen for any length of time. Due to the lack of inhaled CO2, the human doesn't feel breathless, they pass out. An SpO2 alarm will alert the pilot, in time to switch to 100% [emergency] oxygen and recover the jet.

In the F-22 case, some smart people decided NOT to mix the OBOGS air. The report says. "Unlike most other aircraft oxygen generation systems, the breathing air to the F-22 pilot is not diluted with cockpit air to obtain the appropriate oxygen partial pressure (PPO2) necessary to maintain physiological function at a particular altitude". That is fine, except that it places additional demands on the OBOGS, compared to previous jets. What the problem is that under medium altitude, high G conditions, the OBOGS is still cycled to maintain software scheduled PPO2 but isn't matching the demanded PPO2 at the pilots mask, after the regulator. That is a combination of software regulating PPO2 and the design used.

I suspect that your confusing two major issues here;
1) The "raptor cough" etc. was substantially caused by the Breathing regulator/anti-g (BRAG) valve. This has been addressed with replacement valves and education on Combat Edge vest fitting instructions.
2) Neuro-physiological issues that remain. This is what I commented on above.

Re: RE: Re: RE: Re: Theory about F-22 OBOGS solution

Unread postPosted: 07 Nov 2012, 02:15
by jamesli
neurotech wrote:I'm sure Gen. Mike Hostage, USAF, Commander of Air Combat Command who is qualified to fly a F-22, also checks his email. A smart guy can often figure out what email address is for even senior USAF personnel are :D If the Gen. responds, thats another story in itself.

I see a flaw in your comment. It was not HIGH and SLOW flight that induced the OBOGS output deficit. A F-22 can manoever at high altitude and not bleed airspeed like other jets. This is due to having thrust vectoring engines. The problem wasn't technically "extreme" altitude related, but related to the OBOGS "oxygen" output under high G loads.

Saying "Use LOX bottles would solve the problem" is technically correct except that operationally, when a F-22 (Or any fighter pilot) goes to emergency Oxygen supply, that is a knock-it-off event except for real combat emergencies. The pilot at that point ceases pulling High-Gs

The short version is something like this. Air contains a mixture of primarily nitrogen and oxygen. OBOGS enhances the oxygen concentration in the bleed air by filtering mechanism. If the oxygen concentration into the oxygen mask is reduced, the effect is difficult for humans to handle. The pilot(human) will become hypoxic. It is fatal for a human to inhale 100% nitrogen for any length of time. Due to the lack of inhaled CO2, the human doesn't feel breathless, they pass out. An SpO2 alarm will alert the pilot, in time to switch to 100% [emergency] oxygen and recover the jet.

In the F-22 case, some smart people decided NOT to mix the OBOGS air. The report says. "Unlike most other aircraft oxygen generation systems, the breathing air to the F-22 pilot is not diluted with cockpit air to obtain the appropriate oxygen partial pressure (PPO2) necessary to maintain physiological function at a particular altitude". That is fine, except that it places additional demands on the OBOGS, compared to previous jets. What the problem is that under medium altitude, high G conditions, the OBOGS is still cycled to maintain software scheduled PPO2 but isn't matching the demanded PPO2 at the pilots mask, after the regulator. That is a combination of software regulating PPO2 and the design used.

I suspect that your confusing two major issues here;
1) The "raptor cough" etc. was substantially caused by the Breathing regulator/anti-g (BRAG) valve. This has been addressed with replacement valves and education on Combat Edge vest fitting instructions.
2) Neuro-physiological issues that remain. This is what I commented on above.


Hey man. So nice to see you again. I am not a neuro scientist and not sure why you are saying is. But you know. The most direct and positive fact the news saying. Is when the aircraft dive (like from 26000feet)and pulling 8G maneuver. the output oxygen of the Obogs is reduced by 40% to 30%.

This is perfectly match to my theoretical prediction. which is : low speed high G high altitude all leads to engine core pressure drop. and leads to obogs output reduction.

(if the F-119 have max pressure ratio of 36. at full power. the core pressure is 36bar at sea level. but only 3.6bar at 30000 feet. yet another factor remains. only at high speed the engine can reach full power at 30000 feet. this is due to the effect of ram air intaking)

for the obogs. the higher the pressure differential. the better the air separation capacity. :D

RE: Re: RE: Re: RE: Re: Theory about F-22 OBOGS solution

Unread postPosted: 07 Nov 2012, 02:18
by jamesli
you can see. a medium altitude high G maneuver already causes 40% drop in oxygen output. what would it be for a high g maneuver or even stall in 30000 to 40000 feet.

RE: Re: RE: Re: RE: Re: Theory about F-22 OBOGS solution

Unread postPosted: 07 Nov 2012, 03:50
by neurotech
Can we separate "air show" F-22 from a "combat" F-22 please?

Pulling 8Gs in most jets for any length of time(2-30 seconds) seconds isn't a low-speed maneuver, this is true for the F-22 as well. The F-22 just can maintain the maneuver as it has a high t/w and thrust vectoring. Previous jets, like the F-16 in A/A config can do a 8G turn, and actually increase airspeed in certain parts of the flight envelope.

Secondly, they did NOT say that there was a reduction in bleed air output under G load that was the cause. They only said the "oxygen" concentration (Partial Pressure O2) from the OBOGS output was reduced under G load. They have the engine control computer's data recorder to confirm the engine bleed output. A F-22 pilot could be at zero airspeed(post stall thrust vectoring) and still get the full bleed air output at a high altitude.

Third, The neuro-physiological issues currently experienced are not an extreme high altitude (eg. at 60,000 ft) phenomenon, they can and do happen at 25,000 ft to 40,000 ft, which is a more typical fighter jet operating altitude.

RE: Re: RE: Re: RE: Re: Theory about F-22 OBOGS solution

Unread postPosted: 07 Nov 2012, 15:04
by jamesli
Hi there pale. @neurotech

You just didn't get it. What I said in my post is
----------
So why other aircraft have no oxygen problem and the F-22 does?

The answer is clear: They are all not designed to fly at high altitude. They can’t perform

violent maneuver at high altitude like F-22 dose. Especially the high AOA, low speed and post

stall maneuver.
----------
see, ofcourse I know to pull Gs a plane must have enough kinetic energy/air speed. and at

centain altitude a good steedy turn can be achieved without lossen air speed.
Let me explain my theory again.
How much pressure the engine can build inside the engine core is decided by engine RPM/ ambient

pressure/ air speed/ and AOA. This core pressure will decide the bleed air pressure which then

decide the OBOGS output capacity.

1: the higher the engine RPM. they higher pressure the compressor produce
2: if we say it's stall status and 0 airspeed. then no matter how much the engine RPM is. the

max air flow rate/core pressure is only decided by the ambient pressure. The engine is like a

black hole. it sucks in surrounding air. but this suction force is from by the surrounding air

pressure in fact.
3: for a certain low ambient pressure level. the air speed which is the amount of extra air

rushing into the intake channel. will decide the flow rate of the engine compressor/core

pressure
4: the angle of the intake channel to the incoming air. at high G. the AOA of the intake

channel to the incoming air is high. This will reduce the ramming effect by some level. and to

reduce the flow rate of the engine compressor/core pressure.
the other factor is the increased oxygen demand of the pilot during high G maneuver . for

example : the anti G mussel contraction act

To you second question.
They said the OBOGS's output oxygen is reduced by 40%. So if it isn't my theory to explain this

phenomenon. What would you suggest the causes to this phenomenon? they checked every mechanical

parts including the valves. That's not the causes.

And I need to ask that if you know it or not. That what is OBOGS's working principle?

Re: RE: Re: RE: Re: RE: Re: Theory about F-22 OBOGS solution

Unread postPosted: 07 Nov 2012, 15:16
by jamesli
neurotech wrote:Can we separate "air show" F-22 from a "combat" F-22 please?

Pulling 8Gs in most jets for any length of time(2-30 seconds) seconds isn't a low-speed maneuver, this is true for the F-22 as well. The F-22 just can maintain the maneuver as it has a high t/w and thrust vectoring. Previous jets, like the F-16 in A/A config can do a 8G turn, and actually increase airspeed in certain parts of the flight envelope.
....

And ofcourse the steedy turn can only achieved at certain altitude and condition. For most turns. the plane lose air speed.

Re: RE: Re: RE: Re: RE: Re: Theory about F-22 OBOGS solution

Unread postPosted: 09 Nov 2012, 10:01
by neurotech
jamesli wrote:So why other aircraft have no oxygen problem and the F-22 does?

The answer is clear: They are all not designed to fly at high altitude. They can’t perform violent maneuver at high altitude like F-22 dose. Especially the high AOA, low speed and post stall maneuver.

The F-22 can fly at high AoA, low speed and post-stall maneuver and the engines will keep running, and producing bleed air for the OBOGS. That is not the problem, although you originally suggested that it was a bleed air supply problem.

Other jets don't have the supersonic agility of the F-22, but they still do high altitude, high-G turns without any problems. They may have to trade some altitude to maintain speed.
jamesli wrote:----------
see, ofcourse I know to pull Gs a plane must have enough kinetic energy/air speed. and at

centain altitude a good steedy turn can be achieved without lossen air speed.
Let me explain my theory again.
How much pressure the engine can build inside the engine core is decided by engine RPM/ ambient pressure/ air speed/ and AOA. This core pressure will decide the bleed air pressure which then decide the OBOGS output capacity.

1: the higher the engine RPM. they higher pressure the compressor produce
2: if we say it's stall status and 0 airspeed. then no matter how much the engine RPM is. the

max air flow rate/core pressure is only decided by the ambient pressure. The engine is like a

black hole. it sucks in surrounding air. but this suction force is from by the surrounding air

pressure in fact.
3: for a certain low ambient pressure level. the air speed which is the amount of extra air

rushing into the intake channel. will decide the flow rate of the engine compressor/core

pressure
4: the angle of the intake channel to the incoming air. at high G. the AOA of the intake

channel to the incoming air is high. This will reduce the ramming effect by some level. and to reduce the flow rate of the engine compressor/core pressure.
the other factor is the increased oxygen demand of the pilot during high G maneuver . for example : the anti G mussel contraction act

Yes, intake airflow can affect the engine, but it would have to be a really bad disruption to cause ANY PROBLEM with bleed air. The engine will make a loud bang when intake airflow is insufficient, before bleed air output is effected.
jamesli wrote:To you second question.
They said the OBOGS's output oxygen is reduced by 40%. So if it isn't my theory to explain this phenomenon. What would you suggest the causes to this phenomenon? they checked every mechanical parts including the valves. That's not the causes.

And I need to ask that if you know it or not. That what is OBOGS's working principle?

Your theory said it was a problem with the engine bleed output at high altitude/low-speed. That is incorrect. From the USAF statements, the problem is with not with OBOGS input (bleed air) but with OBOGS output under G-load. The OBOGS warning would come on if it was a OBOGS bleed air supply problem.

OBOGS units use zeolite molecular sieve to filter nitrogen out of the supply (bleed) air, which is at a high pressure, and then supply it to the breathing regulator (aka BRAG valve)for the pilot. Part of the problem is the OBOG unit is allowing excessive nitrogen to seep through under high G-load, causing hypoxia in pilots.

The other problem is the software that controls how much oxygen the OBOGS unit produces, according to a programmed schedule based on altitude.

RE: Re: RE: Re: RE: Re: RE: Re: Theory about F-22 OBOGS solu

Unread postPosted: 09 Nov 2012, 12:43
by f22spec
@Neurotech

To clarify what you're saying, if the airflow is interrupted to the intakes, the jet will continue to output bleed air and supply the pilot with OBOGS? If that's correct, are you getting this information from your knowledge of engines, or is there a source somewhere saying this? I apologize if this sounds like an accusation because it isn't, I'm just curious.

RE: Re: RE: Re: RE: Re: RE: Re: Theory about F-22 OBOGS solu

Unread postPosted: 09 Nov 2012, 14:17
by cerberus
I think the APU automatically takes over if the engines go out. Wasn't the issue to do with G-suits and winter wear rather than the OBOGS anyway? Didn't they do centrifuge tests to prove this?

Re: RE: Re: RE: Re: RE: Re: RE: Re: Theory about F-22 OBOGS

Unread postPosted: 09 Nov 2012, 19:35
by neurotech
f22spec wrote:@Neurotech

To clarify what you're saying, if the airflow is interrupted to the intakes, the jet will continue to output bleed air and supply the pilot with OBOGS? If that's correct, are you getting this information from your knowledge of engines, or is there a source somewhere saying this? I apologize if this sounds like an accusation because it isn't, I'm just curious.

Not exactly. I'm saying that if the F-22 pulls high-alpha, the engines keep running, complete with bleed air. Disrupted (turbulent) airflow at high-alpha isn't going to induce a compressor stall in a F-22.

The above is not the same for older jets, like the F-14A. A VF-101 F-14A had an ACM mishap due to a dual compressor stall. I don't think the F-14A had OBOGS, but pilot & RIO were a little more concerned with the rapid loss of airspeed and altitude. They ejected safely. Loss of bleed air, preventing a cross-feed restart was a factor in the mishap.

IF the F-22 does have a compressor stall (Has there even been a documented compressor stall in a F-22?) It is obvious to the pilot, and thrust from the engines(s) will be lost. Bleed air supply from the affected engine will be lost. The pilot will get the appropriate ICAW warnings in the HUD if the engines fail, or if Bleed Air is lost, and if a dual bleed failure, within seconds OBOGS warning.

There has not been any evidence to suggest that engine issues is to blame for the F-22 physiological issues. There is a digital recorder in the engine & flight computer which would alerted the investigators if this was the cause.

Re: RE: Re: RE: Re: RE: Re: RE: Re: Theory about F-22 OBOGS

Unread postPosted: 09 Nov 2012, 19:59
by neurotech
cerberus wrote:I think the APU automatically takes over if the engines go out. Wasn't the issue to do with G-suits and winter wear rather than the OBOGS anyway? Didn't they do centrifuge tests to prove this?

I thought procedure in dual engine failure was to switch to emergency oxygen. APU Bleed Air would be primarily used to restart the engines first. I'm not sure if the APU supplies Bleed Air to OBOGS in that case.

The centrifuge tests confirmed a faulty BRAG valve. The replacement BRAG value solved the respiratory issues, such as "raptor cough" but not the neurological issues.

Re: RE: Re: RE: Re: RE: Re: RE: Re: Theory about F-22 OBOGS

Unread postPosted: 10 Nov 2012, 03:18
by jamesli
neurotech wrote:
cerberus wrote:I think the APU automatically takes over if the engines go out. Wasn't the issue to do with G-suits and winter wear rather than the OBOGS anyway? Didn't they do centrifuge tests to prove this?

I thought procedure in dual engine failure was to switch to emergency oxygen. APU Bleed Air would be primarily used to restart the engines first. I'm not sure if the APU supplies Bleed Air to OBOGS in that case.

The centrifuge tests confirmed a faulty BRAG valve. The replacement BRAG value solved the respiratory issues, such as "raptor cough" but not the neurological issues.


I don't think it's the valve's problem or pressure vest or something. Since may until now. There have been the same type of incidents happens again. They have not yet find the problem.

and your are keep saying a compressor stall. Well it doesn't take a stall to fool the OBOGS. Just if the enough pressure differential is not maintained . The oxygen production capacity is going to be too low for what pilot needed.
______
(if the F-119 have max pressure ratio of 36. at full power. the core pressure is 36bar at sea level. but only 3.6bar at 30000 feet. yet another factor remains. only at high speed the engine can reach full power at 30000 feet. this is due to the effect of ram air intaking)
______
a 3.6bar core pressure at sea level is almost a compressor stall. but when ambient pressure is only 0.1bar. This make the engine look good running. Although the bleed air pressure is droped by 10 fold.
----------
I believe this is what you are still not make right.
And I really doubt if there is a bleed air pressure warning on the F-22. Or how much is the trigger value to send the warning.
So far I seems clear to me. my original guess is right.
The most advanced fighter jet ever. depending solely on an OBOGS that have no big enough buffer tank and no backup oxygen.

in my original post I suggested they use a backup/buffer oxygen tank(if they dont' have one) to make the F-22 safe to fly. Which is just what lockheed martin is doing right now.

Re: RE: Re: RE: Re: RE: Re: Theory about F-22 OBOGS solution

Unread postPosted: 10 Nov 2012, 03:42
by jamesli
neurotech wrote:

The F-22 can fly at high AoA, low speed and post-stall maneuver and the engines will keep running, and producing bleed air for the OBOGS. That is not the problem, although you originally suggested that it was a bleed air supply problem.

--------------The engine is running but infact the bleed air pressure is dropped by 10 fold at 30 Kft.-------------

Other jets don't have the supersonic agility of the F-22, but they still do high altitude, high-G turns without any problems. They may have to trade some altitude to maintain speed.

--------------but exact how much G, at what speed, and altitude? the flight envelope of F-22 is nothing an f-15 can look at even.--------------------

Your theory said it was a problem with the engine bleed output at high altitude/low-speed. That is incorrect. From the USAF statements, the problem is with not with OBOGS input (bleed air) but with OBOGS output under G-load. The OBOGS warning would come on if it was a OBOGS bleed air supply problem.
--------------------please read this: AF Still Reviewing Oxygen Levels for F-22 Cockpit

by defensetech on October 16, 2012
---------------------
---------------------They said " the report says the incidents “merit further analysis and testing.” Which they still believe it's some sort of G force acting on mechanical parts or some thing. From a mechanical point of view. This is just not a little possible. As the G force is not very big on small light weighted parts.
---------------------
---------------------They also said: "Oxygen concentration level fluctuations were noted in the Air Force Scientific Advisory Board (SAB) Report on Aircraft Oxygen Generation, which delved into the recent Raptor pilot breathing problems and was released last month."
Which is exactly what I suggested in my original post also. They are now aiming at the right direction but still blind on the target.
----------------------Please note the word "recent". after the replacement of BRAG valve. Things keeps happening. Just like the filter and contaminants claims. That's just so fuzzy to me.-----------------------

Re: RE: Re: RE: Re: RE: Re: RE: Re: Theory about F-22 OBOGS

Unread postPosted: 10 Nov 2012, 03:50
by jamesli
f22spec wrote:@Neurotech

To clarify what you're saying, if the airflow is interrupted to the intakes, the jet will continue to output bleed air and supply the pilot with OBOGS? If that's correct, are you getting this information from your knowledge of engines, or is there a source somewhere saying this? I apologize if this sounds like an accusation because it isn't, I'm just curious.


Well clearly Mr. Neurotech think that if only the engine is still spinning. The bleed air is not stopping. The OBOGS should works fine. Even if the bleed air pressure had dropped by 10 fold. :arrow:

Re: RE: Re: RE: Re: RE: Re: RE: Re: Theory about F-22 OBOGS

Unread postPosted: 10 Nov 2012, 05:03
by neurotech
jamesli wrote:Well clearly Mr. Neurotech think that if only the engine is still spinning. The bleed air is not stopping. The OBOGS should works fine. Even if the bleed air pressure had dropped by 10 fold. :arrow:

Actually Yes to the first part. If the engine is still "spinning" then some bleed air will be produced, at a lower pressure. I don't think the OBOGS keeps working during with the engine windmilling on the way down. Having said that, the pilot usually shuts off the bleed air supply valve if the engine flames out, as part of a restart procedure.

I didn't say "OBOGS should work fine", It doesn't work properly, thats the problem. What I had previously said there was no OBOGS ICAW in these incidents.

Do we have any confirmation that an actually "Bleed Air" pressure drop is actually occurring in these "physiological incidents"?? There has not been a "Bleed Air" ICAW displayed in these incidents, yet the pilot is experiencing problems. The recent DefenseTech article didn't mention "Bleed Air". What the DefenseTech article DID say was that the partial pressure Oxygen (PPO2) output from OBOGS was dropping.

The F-22 DOES have a backup Oxygen System. What the Alaska crash AIB determined was that Capt. Haney was unable to activate it. The bottle is now larger, and the activation handle is also larger, and easier for the pilot to access.

Your understanding of Engine Pressure is mistaken, it is typically expressed as a ratio. The Engine Pressure Ratio varies with altitude and thrust. Remember, Bleed Air comes from the first stage COMPRESSOR and even at high altitude (60,000 ft) there is enough airflow to provide more than enough pressure for the Bleed Air for the OBOGS and ECS.

And That_Engine_Guy has previously confirmed my comment about the airflow vs bleed air. Here it is again:
That_Engine_Guy wrote:I'd say it's not the fault of the motors providing insufficient air flow or pressure. If the engines were running out of air like that at high altitude and high AOA, they would likely compressor stall/stagnate long before bleed-air pressure/flow dropped below specification.

The pilot would know this from the loud BANG, or the loss of power in the motor(s). If anything, a condition like this would be indicated in the CSFDR or in the remaining engine control component memory. (Yes, if still somewhat intact, they can retrieve data from the engine control system chips after a crash!) It would have been obvious with any mishap that the engines had surged/stalled/flamed-out and contributed to situation.

I don't know much about the bleed-air system of the F119/Raptor, but I'm going to assume that both motors feed the common OBOGS? So that a single engine out situation would not affect Oxygen supply? This further reduces the possibilities that the Raptor's propulsion system 'slow/high' would ever be insufficient to supply the OBOGS - feeding from BOTH engines equally.

:shrug: TEG

Am I missing something?

Re: RE: Re: RE: Re: RE: Re: RE: Re: Theory about F-22 OBOGS

Unread postPosted: 10 Nov 2012, 12:09
by jamesli
neurotech wrote:Do we have any confirmation that an actually "Bleed Air" pressure drop is actually occurring in these "physiological incidents"??


-------We don't have yet. What I think is this "Bleed Air pressure drop" is the only logical explanation.----------

neurotech wrote:There has not been a "Bleed Air" ICAW displayed in these incidents


-------I know very little about these detail desgin. I just now assure that there is no proper ICAW design.-----------

neurotech wrote:The Engine Pressure Ratio varies with altitude and thrust.

-------No. Technically, The pressure ratio of compressor is only decided by forward air speed/incoming air speed and engine RPM.---------

neurotech wrote:Bleed Air comes from the first stage COMPRESSOR and even at high altitude (60,000 ft) there is enough airflow to provide more than enough pressure for the Bleed Air for the OBOGS and ECS.

-------I didn't know whether the bleed air is from the LPC or HPC. If it does from the LPC. Then thank you for this lesson. But that doesn't change my theory as I think the pressure drop at the LPC or HPC is both the same situation. "low air speed. high AOA. low ambient air pressure. will reduce the bleed air pressure, No matter it's being taken from the end of LPC or HPC"

neurotech wrote:And That_Engine_Guy has previously confirmed my comment about the airflow vs bleed air. Here it is again:

-------Well I don't think the airflow have anything to do with air pressure. The OBOGS rely on the pressure to work. And from some point of view. for a fix sized air pipe. the pressure and flow rate is positively linked.

I think at this point the USAF will discover some linkage between the pulling Gs and oxygen drop. whether it's my theory is right or just some mechanical or software fault. What I really doubt is when they do find out. would they keep it secret or disclose it? This could be classified.

Re: RE: Re: RE: Re: RE: Re: RE: Re: Theory about F-22 OBOGS

Unread postPosted: 10 Nov 2012, 12:20
by cerberus
neurotech wrote:
cerberus wrote:I think the APU automatically takes over if the engines go out. Wasn't the issue to do with G-suits and winter wear rather than the OBOGS anyway? Didn't they do centrifuge tests to prove this?

I thought procedure in dual engine failure was to switch to emergency oxygen. APU Bleed Air would be primarily used to restart the engines first. I'm not sure if the APU supplies Bleed Air to OBOGS in that case.

The centrifuge tests confirmed a faulty BRAG valve. The replacement BRAG value solved the respiratory issues, such as "raptor cough" but not the neurological issues.

In that case, I'm not really sure. I know that airflows can be a pain for separating into several flows, each of similar properties.

Re: RE: Re: RE: Re: RE: Re: RE: Re: Theory about F-22 OBOGS

Unread postPosted: 10 Nov 2012, 17:46
by neurotech
jamesli wrote:
neurotech wrote:There has not been a "Bleed Air" ICAW displayed in these incidents

I know very little about these detail desgin. I just now assure that there is no proper ICAW design.


ICAW(S) = Integrated Caution And Warning (System). ICAWS, the System that is, works great, it prioritizes pilot attention to the most safety critical items first.

The Bleed Air pressure warning & leak detection system warning does work properly. The Bleed Air warning in the Alaska crash was resulting from a Center Bleed Air Duct leaking.

The OBOGS output pressure warning does work correctly. What does not work properly is that the OBOGS warning will not warn the pilot in case of a "Partial Pressure O2" drop at the OBOGS output.
jamesli wrote:
neurotech wrote:And That_Engine_Guy has previously confirmed my comment about the airflow vs bleed air. Here it is again:

-------Well I don't think the airflow have anything to do with air pressure. The OBOGS rely on the pressure to work. And from some point of view. for a fix sized air pipe. the pressure and flow rate is positively linked.

I think at this point the USAF will discover some linkage between the pulling Gs and oxygen drop. whether it's my theory is right or just some mechanical or software fault. What I really doubt is when they do find out. would they keep it secret or disclose it? This could be classified.

The USAF have pretty much confirmed the OBOGS PPO2 drop, they just don't know if it can be fixed in software, requires a OBOGS re-design or other changes to the pilot Oxygen system. I think they'll release a statement regarding the ongoing investigations and solutions. The precise operational details will not be released publicly, as that is either Classified and/or "For official Use Only"

Re: RE: Re: RE: Re: RE: Re: RE: Re: Theory about F-22 OBOGS

Unread postPosted: 11 Nov 2012, 12:19
by jamesli
neurotech wrote:The USAF have pretty much confirmed the OBOGS PPO2 drop, they just don't know if it can be fixed in software, requires a OBOGS re-design or other changes to the pilot Oxygen system.

Well I think the so called PP02 drop is in fact a result of insufficient oxygen production/lower than desired 02 concentration. Which is a result of input air pressure drop?
I really don't think it could a G force induced mechanical or software fault.
I should just wait to say what the air force investigation will find out next.

Hey, Mr. Neurotech. I had made another very important discovery about the crashed morpheus moon lander. Please check it out in the attachment.
The moepheus moon lander has inherent design flaw. It will never be a safe.