B787 O2 supply
Boeing whistleblower raises doubts over 787 oxygen system
By Theo Leggett Business correspondent, BBC Newscopyright BoeingA Boeing whistleblower has claimed that passengers flying on board the company's 787 Dreamliner could be left without life-saving oxygen if the cabin were to suffer a sudden decompression. John Barnett, a former quality control engineer at the company, says he organised tests which suggested that up to a quarter of the oxygen systems used on the aircraft could be faulty and might not operate when needed. https://www.bbc.com/news/business-50293927 |
Originally Posted by Longtimer
(Post 10611799)
Boeing whistleblower raises doubts over 787 oxygen system
By Theo Leggett Business correspondent, BBC Newscopyright BoeingA Boeing whistleblower has claimed that passengers flying on board the company's 787 Dreamliner could be left without life-saving oxygen if the cabin were to suffer a sudden decompression. John Barnett, a former quality control engineer at the company, says he organised tests which suggested that up to a quarter of the oxygen systems used on the aircraft could be faulty and might not operate when needed. https://www.bbc.com/news/business-50293927 |
Nope, 787 uses O2 bottles both for flight deck and cabin oxygen systems. Each 3 seat group shares one oxygen bottle in the bulkhead overhead, fired by a pyrotechnic valve when operated. These valves, by definition single use, can not be tested, and are the source of failures.
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Originally Posted by Flight Alloy
(Post 10611812)
Nope, 787 uses O2 bottles both for flight deck and cabin oxygen systems. Each 3 seat group shares one oxygen bottle in the bulkhead overhead, fired by a pyrotechnic valve when operated. These valves, by definition single use, can not be tested, and are the source of failures.
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Indeed they were, as per the article, and 25% were shown to fail. A problem which the whistleblower reported to the FAA after Boeing didn't do anything about it. And neither did the FAA. The plot thickens.
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Originally Posted by Flight Alloy
(Post 10611812)
787 uses O2 bottles both (....) , fired by a pyrotechnic valve when operated. These valves,(...) are the source of failures.
Is this for real ? |
Originally Posted by Flight Alloy
(Post 10611812)
Nope, 787 uses O2 bottles both for flight deck and cabin oxygen systems. Each 3 seat group shares one oxygen bottle in the bulkhead overhead, fired by a pyrotechnic valve when operated. These valves, by definition single use, can not be tested, and are the source of failures.
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Originally Posted by double_barrel
(Post 10611961)
O2 bottles triggered by faulty pyrotechnic devices. What could possibly go wrong?
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It's decades since worked with an airliner - VC10 in the RAF. But IIRC a functional check of all the passenger oxygen masks was an item of a periodic maintenance schedule. I assume that I still so with modern airliners? In which case, I would expect the airlines to be concerned at a high incidence of failure (25%) and to raise the issue with Boeing and the CAA / FAA. So it would not have needed a whistleblower to raise concern effectively. I can't see that the story adds up. That said, I accept that I am a long time away from the aircraft maintenance scene.
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The pyrotechnically activated O2 bottles would have a certified lifetime beyond which they need replaced, but they evidently wouldn't be tested in the mean time as they are single use by design. There are several far more dangerous pyrotechnic agents on board passenger aircraft - none of those ever caused a problem to my knowledge - such as flares in the survival kit, and some escape slides/rafts have chemical agents to inflate them. I wouldn't get too excited about the activation mode of the bottles. But the failure rate and subsequent cover up by Boeing management AND the regulator, well, that is an entirely different story!
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Originally Posted by kiwibrit
(Post 10612087)
It's decades since worked with an airliner - VC10 in the RAF. But IIRC a functional check of all the passenger oxygen masks was an item of a periodic maintenance schedule. I assume that I still so with modern airliners? In which case, I would expect the airlines to be concerned at a high incidence of failure (25%) and to raise the issue with Boeing and the CAA / FAA. So it would not have needed a whistleblower to raise concern effectively. I can't see that the story adds up. That said, I accept that I am a long time away from the aircraft maintenance scene.
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Originally Posted by Flight Alloy
(Post 10611812)
Nope, 787 uses O2 bottles both for flight deck and cabin oxygen systems. Each 3 seat group shares one oxygen bottle in the bulkhead overhead, fired by a pyrotechnic valve when operated. These valves, by definition single use, can not be tested, and are the source of failures.
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Also, how often do airlines suffer depressurization with extended high altitude flight, where some failed masks would result in detectable injury to passengers? Luckily very rarely, as most incidents result in immediate expeditious descent to breathable atmosphere, where in such an event a lack of functioning mask would almost be undetectable and its use practically unnecessary Not sure I would be happy without oxygen. Must pick one of the 75% of seats that has working oxygen. Ryannair would probably be charging a premium for them if they operated them |
Originally Posted by Radgirl
(Post 10612263)
Why bother to have slides? Or any other emergency equipment for 'rare events'? Would you care to tell us the duration of consciousness in the case of sudden depressurisation in the cruise for a healthy adult? And would you care to postulate on how long an elderly patient with heart disease would survive? And compare it with the time needed for an emergency descent to 10,000 feet?
Not sure I would be happy without oxygen. Must pick one of the 75% of seats that has working oxygen. Ryannair would probably be charging a premium for them if they operated them Emergency descent from FL400 to 10,000 ft: A lot longer. Flight Alloy: Also, how often do airlines suffer depressurization with extended high altitude flight, where some failed masks would result in detectable injury to passengers? |
Originally Posted by OldnGrounded
(Post 10612270)
Time of useful consciousness at FL400: 15-20 seconds. Probably less than that for me, with significant heart disease in my old age.
Emergency descent from FL400 to 10,000 ft: A lot longer. Probably good to note that the "detectable injuries" to pax with non-functioning masks would likely range from significant permanent brain damage to death. Always important to consider when establishing risk factors. But from 30.000ft you get back a bit of oxygen , there are lots of people that climb the Himalayas without oxygen and they do not suffer brain damage. But again I am not a brain specialist.. I just remember a decompression on a Spantax DC8 over the Netherlands from FL33 or 370 where half the O2 masks did bot deploy because stuck by nicotine tar .. Diverted to AMS. .. Nobody was injured, shocked yes, but most of the pax continued a few hours later to the Canaries... |
Originally Posted by ATC Watcher
(Post 10612300)
Not a medic but I think the critical part is from 400 to 300 , at 4000 ft/min (typical emergency descent on most types) say 2- 3 min deprivation ; like a long underwater scuba dive ., brain damage ?
But from 30.000ft you get back a bit of oxygen , there are lots of people that climb the Himalayas without oxygen and they do not suffer brain damage. But again I am not a brain specialist.. I just remember a decompression on a Spantax DC8 over the Netherlands from FL33 or 370 where half the O2 masks did bot deploy because stuck by nicotine tar .. Diverted to AMS. .. Nobody was injured, shocked yes, but most of the pax continued a few hours later to the Canaries... https://www.faa.gov/pilots/training/...%2061-107A.pdf Of course, that doesn't mean brain damage at that limit, but it does mean that few will be able to don those masks if they don't do so very quickly. I don't mean to suggest that serious or permanent injury is guaranteed, just that it's far too serious a risk to discount. You really, really want all the pax O2 systems to work when the cabin undergoes rapid decompression. |
Thanks for the tech briefing, including why the O2 supply is not tested, Flight Alloy. I think that the RAF VC10 C Mk1s I worked with in the late 60s had a manifold supply to the passenger emergency masks. Thereafter my aircraft experience was with military non passenger aircraft. I shall now retire back into my cave!
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I would prefer that my cockpit crew test their oxygen supply to assure it works.
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Originally Posted by Radgirl
(Post 10612263)
Why bother to have slides? Or any other emergency equipment for 'rare events'? Would you care to tell us the duration of consciousness in the case of sudden depressurisation in the cruise for a healthy adult? And would you care to postulate on how long an elderly patient with heart disease would survive? And compare it with the time needed for an emergency descent to 10,000 feet?
Not sure I would be happy without oxygen. Must pick one of the 75% of seats that has working oxygen. Ryannair would probably be charging a premium for them if they operated them |
Here is a link to the original STORY written by Gerald Eastman on his blog 'The Last Inspector' more than 1,5 years ago. The guy was a quality inspector for Boeing for many years and chronicles his battle for transparency and safety against the corporate machine of rushing jobs for profit. His blog is full of stories of his own and other colleagues experiences at both Boeing factories about corners cut, non conforming parts liberated from scrap cages and installed into production airframes to maintain production, and the pressures of management to bury any safety concerns and maintain tempo. He also goes into the complacency for the FAA in responding to whistleblower complaints and how the system worked to punish anyone with an ounce of integrity. Do head over and read if interested in the internal goings on by someone experienced in the business! Here's the main blog too for reference: The Last Inspector
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