Posted on 12/14/2011 3:26:55 PM PST by Yo-Yo
A US Air Force report says the regular oxygen system stopped working before a fatal Lockheed Martin F-22 crash in Alaska last November.
The accident investigation board still blames the accident on the pilot, Captain Jeffrey Haney, who failed to activate an emergency oxygen supply that could have saved his life and the aircraft.
But the failure of an engine bleed air system that feeds the Honeywell onboard oxygen generation system (OBOGS) in the moments before the crash is a new twist in the evolving story.
Only two months after the accident, the USAF internally acknowledged serious concerns about the F-22's oxygen system. In January, the USAF limited F-22s to flying below 25,000 feet. Starting on 3 May, the USAF grounded the entire fleet for more than four months, citing concerns about the pilot's oxygen system.
Although the F-22s resumed flying, the cause of dozens of reported oxygen system failures over several years was never pinpointed.
General Norton Schwartz announced the F-22 return-to-flight order in September. Speaking to reporters during the Air Force Association convention, Schwartz said investigators had "ruled out" the oxygen system as the cause of the F-22 crash last November.
The investigators instead blamed the accident on Haney, who failed to activate the EOS during the 31sec period after his normal oxygen supply became restricted.
The F-22's oxygen supply was automatically cut off after onboard computers detected bleed air was leaking out of the engine bay, which could cause a fire, the report says. The USAF investigators were unable to determine the cause of the bleed air leak.
Shutting down the bleed air system caused the OBOGS to fail, the report says. The OBOGS filters the bleed air through a molecular sieve and delivers the oxygen to the pilot's oxygen mask.
The report concluded that Haney inadvertently pointed the aircraft at the ground while trying to activate the EOS, a procedure that calls on the pilot to pull up on a small ring tucked into the side of his ejection seat.
Fifteen seconds before he crashed, Haney appeared to accidentally enter a sharp, descending right roll that turned the aircraft upside down, the report says.
A pilot assigned to the accident investigation tried to pull the EOS activation ring in a ground simulation, and also moved the stick and the rudder pedals by mistake trying to reach the device.
Haney's night vision goggles and cold weather gear also may have caused him to inadvertently veer off course. To look to the side or down without hitting the night vision goggles on the canopy, F-22 pilots have to brace themselves to shift their torso, the report says.
The investigators ruled out loss of consciousness as a possible cause despite possible oxygen deprivation.
Haney appeared to be conscious the entire flight. Only 3sec before the crash, Haney suddenly attempted a violent pull-up manoeuvre, but it was already too late.
Just a few days ago I read that John Denver was trying to switch fuel tanks which apparently caused the same rudder / roll-over / fatal crash problem. The switch was located in a difficult-to-reach place over the shoulder.
I vote for design flaw.
It is night, you are on instruments and using night vision goggles. You have a warning about your oxygen and know if not corrected you will soon be unconscious. At that point his main concern was remaining conscious.
Pilot error due to design fault and I would suspect proper training for this scenario.
How many pilots at $150 million dollars/loss due to . . . ?
We were told the platinum expensive F-22 was the answer to air dominance. It appears it is primarily a threat to its operators.
You don’t need an F-22 to kill a pilot with OBOGS. The Navy has been doing it for years with hornets and the F-14D.
In Denver's case, the problem was that the builder had moved the fuel selector from between the pilots legs, as Burt Rutan designed, to a location in the wing root. As a result, this required a complicated and difficult to operate linkage.
The new location for the fuel selector switch was above and behind the pilot's shoulders, as you note.
This was bad enough, but Denver also failed to verify how much fuel was on-board before taking off on the fatal flight. (a cardinal sin)
When the airplane ran out of gas, he tried to reach over his shoulder in an attempt to switch tanks and stepped on the rudder pedal in the process which caused the airplane to go out of control, as you also noted.
Lost in all of this was that Denver had been previously convicted of DUI, which prompted the FAA to order him to surrender his airman certificate. (pilot's license) This is standard practice and is usually the main reason why most pilots lose their license. They may lose their medical certificate due to failing health, but once issued, the airman certificate is usually kept for life.
Naturally, like most celebrities, Denver thought himself above the law and neither surrendered his license, nor stopped flying.
Had he complied with the FAA and the law, he would probably still be alive today.
I concur.
Yeah, who needs a pilot if there is a potential for a fire sometime soon!
...while trying to activate the EOS, a procedure that calls on the pilot to pull up on a small ring tucked into the side of his ejection seat.
Pilot is low on oxygen, and is having trouble thinking and operating his hands. Let's tuck a small metal ring on the side of the ejection seat, and give him seconds to find it!
...to look to the side or down without hitting the night vision goggles on the canopy, F-22 pilots have to brace themselves to shift their torso...
But lets not make it easy!
This plane control layout and pilot support system is a pile of crap. There might be a special place in Hell for the engineers who did this.
“There might be a special place in Hell for the engineers who did this.”
You mean non-engineering managers. Engineers know better. Aviation companies are run by incompetents.
EOS aka green apple
When it looks bad for the designers/test/evaluation group, blame the dead pilot !
Seems obvious the pilot was “mousetrapped” by a series of design flaws creating a hypoxic state was unable to overcome. No, you don’t have to “lose consciousness” to become “incompaciated”; particularly if oxygen deprivation occurs slowly over time.
IOW this is “just another cover-up” ! >PS
Don’t know as I’d put the ilk of Denver in the same class as an USAF pilot ! Recall he was flying sans a valid medical, (i.e. his “license” was void), it was also under suspension as I recall. >PS
Believe me, I was not doing that! I just thought it coincidental to read about two similar events with similar outcome in the same week. But by no stretch of the imagination would I put Denver anywhere near the class as a USAF pilot!
Well that’s a relief, POF !!
Oxygen deprivation is insideous in its effects. Strangely, in its early stages it can cause an euphoria akin to a couple of strong shots of alcohol. And, like alcohol, everyone’s response differs, even individually on a daily basis !
I know the USAF (and other military orgs as well) spend a good deal of effort/funds in making crew aware of these limitations. But what does that lone jock do when both his machine and its ergonomics betray them ? >PS
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