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

The story repeatedly refers to "oxygen bottles" for the pax O2 systems. Does the 787 not have O2 generators for the pax system? Or is the reference just the result of confusion on the part of the reporter and editors?

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.

Presumably a number of bottles from each batch are destructively tested to confirm - at least statistically - that they work?

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.

A very good combination of words in one sentence. A prone to failure pyrotechnic device to open a bottle of Oxygen in an aircraft ?
Is this for real ?

O2 bottles triggered by faulty pyrotechnic devices. What could possibly go wrong?

the valves are triggered by pyrotechnics. not the bottles.

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.

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!

No system based on single use chemical oxygen generators or pyrotechnic valves will undergo a 'functional check', meaning an actual check of delivering oxygen in an emergency situation. By functional check they mean the mask is still in one piece, not dried out, the bulkhead hinge opens, and the hoses haven't fallen off. This does not constitute a 'functional check', if so, every test would require a full replacement of the whole SINGLE USE emergency oxygen system, certainly a multi million dollar cost item. That is the reason they are NEVER tested. 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, but there are regimes of flight where an emergency descent would be impossible for extended periods, like most of the Chinese highlands. And you're still surprised Boeing would under-report a major safety issue, after MCAS, 777X doors, pickle forks, trim wheel etc etc. ad nauseum? Really get ahold of yourself.

Thanks for the information.

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

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.

Flight Alloy:
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.

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...

Humans are variable creatures, of course, but three minutes is the generally-accepted period after which hypoxic/anoxic brain damage is of serious concern. The FAA tables show TUC at FL300, with rapid decompression, as 30-60 seconds:

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!

I would prefer that my cockpit crew test their oxygen supply to assure it works.

Oh I think you misunderstood my intention with that statement. I just wanted to illustrate why deleterious effects from non functioning O2 masks seam quite rare, and why airlines aren't 'up in arms' because of possible faulty equipment, because (luckily) flight regimes where masks save lives are quite rare, but still occur (any time you're flying over mountains basically). I certainly advocate for plenty of emergency equipment, I was just highlighting why we might not have seen many injuries related to these failures, specifically because most depressurizations occur in regimes where quick emergency descent is possible, so even not using a mask should not cause serious injury. Unfortunately it is almost always media pressure and 'learning from mistakes' that drive (aviation) improvements, and not an inherent drive for safety from the airlines, so presumably they would only insist on improvements if incidents were to occur with more frequency.

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

Thanks for the link!

I thought there were more drop down passenger masks than seats, to allow for infants sitting on laps

These people are not walking along at sea-level (or whatever the cabin altitude is at the time of the depressurisation) one second, and the next they are at 39,000 feet. They spend many weeks and sometimes months acclimatising, where the number of red cells in their blood gradually increases to a level where the amount of oxygen scavenged from the atmosphere is greatly increased.

Even then, survival at that altitude is only for a matter of hours even with supplementary oxygen, which is why it’s called the ‘death zone’

My previous post was done tongue in cheek. I do know what happens with a sudden decompression and the max ROD. A significant proportion of paxs would die. Others would have long term hypoxic effects - dont worry about the medicine, just be assured any good lawyer would be after $$$ £££s for loss of job attainment, failure of relationships, mood swings and potential early cognitive degeneration

Luckily I normally fly below 2000 feet so I am not effected but I am surprised at the laisse faire attitude to yet another Boeing issue. The fact that nobody has come to harm is a matter of luck not judgement. Surely this should be an issue to be sorted immediately with interim measures such as free standing oxygen??? If it had been cc oxygen......

I was going to ask about this. Presumably there is some over-provision to allow for failures: does it get near to 25% (assuming that figure for failures is true/typical)? I'd also like to ask if this is a Boeing problem, or more widespread (assuming this equipment is supplied by a third party).

The FAA, being data-driven, came to the same conclusion: there is four masks per row of three, plus a couple extra in the toilet, so if 25% don't work everyone should still have a working mask, statistically speaking. Really don't see what the problem you people have.





Oh, the whole row wouldn't work if the valve doesn't open....

At my airline a functional check of all cockpit masks is required on the first flight of the crew day (i.e. not repeated at each turnaround). While the check is conducted "in container" i.e. the mask is not actually removed and donned, I have full confidence in the check other than it confirming that the gas being delivered is actually O2. I have to rely on ground servicing integrity for that.
To answer another poster's query, an additional pax mask is installed above every set of seats.

Regarding failure to use supplemental O2 in the case of depressurisation I'm going to go out on a limb and say that during even the worst case scenario, i.e. explosive depress at FL450 followed by a poorly flown emergency descent to an intermediate altitude due terrain followed by a further descent to 10000' within 30 minutes of initial depress, the risk of serious or lasting effects is very low except, perhaps, for physical injury due to unrestrained pax movements while unconscious, or rarer cases where an underlying medical condition is triggered by the resulting hypoxia.

My rationale:
While Time of Useful Consciousness at FL450 is quoted as 9-15 seconds (it may be less in affected people, think seriously unfit or heavy smokers) and is reduced by activity, think walking back to your seat, the time to actual unconsciousness is much longer. And the time to actual deleterious effects of hypoxia on brain or other cells is even longer still.
There are reports of passengers failing to refusing to don masks with no long-term or serious after-effects provided that the cabin altitude was reduced in the previously mentioned timely manner.

Now, I am not defending the position challenged by the OP. Safety-sensitive systems such as supplemental O2 systems should not be experiencing 25% failure rates and manufacturers and regulators should not be brushing aside genuine reports of such failures. O2 systems are installed for very good reasons but I get the feeling we are overstating the risk a little.

Ok, let the howling begin....

I wonder what the failure mode of the valve is. Open circuit in the squib (electric match)? Bad or weak pyrotechnic charge?

The squib circuit should be testable for continuity non-destructively. It's what demolition pyrotechnicians do prior to setting off a group of charges to bring a building down. The failure of some could result in the structure falling in an uncontrolled manner. I would be seriously surprised if the O2 system did not incorporate such a built-in-test (BITE).

Pyrotechnics themselves are pretty reliable, assuming that they are built with some quality control in mind. And if a suitable level of reliability can't be achieved, either redundant charges or a manual backup to open the O2 valve might be needed.

@ Speed of sound + @ easy Street : Good point . Agree . My point was about permanent brain damage and even death for being subject to single minutes of O2 deprivation. But you are right . Point taken.

At height say above 35,000 ft as the emergency oxygen masks are not pressurized they will not prevent loss of consciousness. However, the availability of higher percentage oxygen in the low pressure air being breathed means that the pax wearing masks will come round faster when back to 10,000ft and have less chance of brain damage. This is why an emergency descent to 10,000ft is required. Do not expect anyone in the cabin to be reliably responsive above that altitude.

4000’ per minute ? You ain’t even trying . 7500’ is achievable

For the 787 the answer is invariably, "to save weight". However, there are other considerations such as the difficulty in transporting O2 generators after the Valuejet tragedy.

Regarding BITE checks, from memory I think there's an LED indicator on each bottle/valve assembly that shows the go/nogo state of the unit. I think they are ' on demand' too which means less O2 is required and therefore a smaller bottle, which again saves weight.

At VMO, gear extended and in a side slip, maybe. So definitely not realistic in the real life. 4000 is a correct figure.

"At height say above 35,000 ft as the emergency oxygen masks are not pressurized they will not prevent loss of consciousness."
How are the flightdeck masks pressurised? ( Not a professional, but thinking that "pressurised" does not, in this sense, refer to oxygen pressure at the mask.)

No mask can work as a 'pressurized' mask, aka delivering more pressure to the lungs than ambient, as without a pressure suit, the lungs and their muscles have very little capacity to breathe/pump air, as they fight to deflate the lungs with every breath against the oncoming pressure (imagine a balloon and trying to deflate it against pumping). With this limited muscle 'overcapacity', pressurized breathing is only possible with suits that also pressurize the chest area to the same pressure as the breathed gas.