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Fatal Problems Continue To Plague F-22 Raptor
Hugh Pickens writes "The LA Times reports that even though the Air Force has used its F-22 Raptor planes only in test missions, pilots have experienced seven major crashes with two deaths, a grim reminder that the U.S. military's most expensive fighter jet, never called into combat despite conflicts in Iraq, Afghanistan and Libya, continues to experience equipment problems — notably with its oxygen systems. New details from an Air Force report last week drew attention to a crash in November 2010 that left Capt. Jeff Haney dead and raised debate over whether the Air Force turned Haney into a scapegoat to escape more criticism of the F-22. Haney 'most likely experienced a sense similar to suffocation,' the report said. 'This was likely [Haney's] first experience under such physiological duress.' According to the Air Force Accident Report, Haney should have leaned over and with a gloved hand pulled a silver-dollar-size green ring that was under his seat by his left thigh to engage the emergency system (PDF). It takes 40 pounds of pull to engage the emergency system. That's a tall order for a man who has gone nearly a minute without a breath of air, speeding faster than sound, while wearing bulky weather gear, says Michael Barr, a former Air Force fighter pilot and former accident investigation officer. 'It would've taken superhuman efforts on the pilot's behalf to save that aircraft,' says Barr. 'The initial cause of this accident was a malfunction with the aircraft — not the pilot.'"
The new systems are smaller and lighter. Also, at least from the original crash report, the oxygen system wasn't at fault. It shut down like it was supposed to (it was operated by bleed air from the engine, the ECS detected a hot bleed air leak and shut off the bleed air valves. If you don't check a hot bleed air leak, you can set the plane on fire or melt parts of it), but the pilot struggled to activate the emergency oxygen system and had significant difficulty with this due to the bulky gear he was wearing.
While struggling with activation of the EOS, he lost track of time and became disoriented, failed to notice that his aircraft attitude had changed, and attempted a dive recovery far too late to save himself.
No, that is not what this means.
"Air bleed" is the method by which the OBOGS generates breathable air. It's called "bleed" because it "bleeds" off a small amount of air from the engine's compressor system. (This air can also be used for deicing flight surfaces, generating power, and other purposes).
An "air bleed failure" means that either no air is getting into the system, or a sensor failed and it thinks no air is getting into the system.
To summarize, this wasn't a failure where air was bleeding, this was a failure of the system that bleeds air from the engine for the pilot to breathe. That's important to understand.
Touch everywhere, even when inappropriate.
No. Read the report:
http://usaf.aib.law.af.mil/ExecSum2011/F-22A_AK_16%20Nov%2010.pdf
This wasn't a case of extraordinary circumstances. This was calm, high altitude flight where a critical (but understood) subsystem failed.
The pilot then became distracted by the system failure possible because of oxygen deprivation, or because the emergency air control was in an ergonomically challenging location. While distracted, he became inverted (240 degree roll during descent) and didn't attempt to correct until 3 seconds prior to impact.
The ergonomic issue may be a contributing cause. but a pilot *must* be able to continue instrument scan while dealing with an emergency. Just because you're air doesn't work doesn't mean you can't still crash while dealing with that.
It's sad, but more or less understood what happened.
Touch everywhere, even when inappropriate.
You've mixed things up, it makes no sense. I've read the report. Here's what happened:
1. The fire control system (FCS) detected a bleed air duct leak and has closed the isolation valves, cutting off engine bleed air from reaching the bleed air manifold (or duct). Bleed air is hot air from the compressor, used to power other systems. This triggers the "C BLEED HOT" caution.
2. Loss of bleed air made the following systems inoperational: environmental control system (ECS), forced air cooling for avionics et al (ACS), oxygen generator (OBOGS), inert gas generator (OBIGGS), cabin pressurization.
3. About 5 seconds after the bleed air was cut off, a new caution appeared: "OBOGS FAIL". This means the oxygen generator is out and you have to activate emergency oxygen generator on your seat - soon. That one is on your seat because it has to supply you with oxygen when you eject.
4. About 14 seconds later, a sensor picks up loss of oxygen pressure to the mask (from failed OBOGS).
That's all there's to it. Apparently the pilot never managed to activate emergency oxygen, and while fumbling with that he also bumped the control stick and rudder, causing the aircraft to fly a "random" trajectory. The cabin is cramped, and with extra cold weather gear it's nigh impossible to activate that emergency oxygen without bumping into things. That is a design issue, as well as the awkward way of activating that emergency oxygen system (you have to pull a ring from a hip level about 2 in. forward (away from you) with 40lb or more of force.
The report is here.
A successful API design takes a mixture of software design and pedagogy.
Sigh. Mistake upon mistake in those comments. The computer didn't detect any oxygen leaks. It detected a leak of hot air (bleed air) that is used to power various things, including oxygen generator (OBOGS). Since an uncontained leak of bleed air is likely to start a fire, the bleed air was automatically cut off by closing isolation valves at the engines. Thus it was no more powering the oxygen generator. The pilot fumbled for about 30s trying to activate emergency oxygen, eventually failing to do so, but while he was fumbling he bumped the control stick and rudder pedals, sending the aircraft on an uncontrolled inverted dive.
The bleed air is really hot -- between 1200F to 2000F (650C to 1000C). PHX (primary heat exchanger) then cools it down to 400F (200C).
There was some maintenance done in the previous months that required disconnecting the bleed air ducts, the accident investigators didn't think that anything went wrong there.
The bleed air leak was survivable, but somehow the pilot couldn't get emergency oxygen going, and lost situational awareness. When he tried to recover from the dive, it was too late.
A successful API design takes a mixture of software design and pedagogy.
Laminar flow gave it range via low drag and therefore reduced fuel consumption. It was unsatisfactory for its mission until the British got a hold of it and in fact, initially failed to perform up to anticipation. With the US made engine, it could only perform down low and high altitude performance was a requirement for long distance bomber escort. Without the British's contribution to the P51, it would have been little more than a footnote in history. Period.