PPRuNe Forums - B787 O2 supply

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Quote:

Originally Posted by golfyankeesierra (Post 10614585)

Exactly! The whole point is that Boeing, instead of sticking to the proven system, applied some new technology which got certificated by the FAA.
But contrary to everything we do in aviation, this cannot checked or tested. It is a lifesaver! How could this have passed certification?
And now apparently it has been tested, only 75% works. Doesn’t exactly return my faith in Boeing and FAA..

Or mercury filled bulbs for logo lights, requiring a special tool and procedures to remove, store and dispose of bulbs. What the hell is wrong with the good old halogen or LED lamps? Nope, gotta use a unique and potentially dangerous mercury filled bulb.

Quote:

Originally Posted by Flight Alloy (Post 10615368)

The ring main system sounds like it has some controlability at every station, does it have extra plugs for medical masks and manual activation valves for such uses?

On the aircraft I have experience of there are indeed extra outlets for medical masks at most the Passenger service units. They can be set for a high or low rate of flow (FWIW there's also a check valve to prevent flow if a mask is not plugged in).

The actual "on/off"switch to pressurise the system is on the flight deck.....

After re-reading Collins' description of their PulsOx system I find myself a little confused by this:-

"Three duration options (small, medium and large) accommodate your aircraft’s descent profile – so you can choose the right size oxygen cylinder to get the aircraft to safety without carrying extra weight. Changing the descent profile is easy. Simply switch out the individual oxygen cylinder to the size that matches the new profile."

Can anyone with 787 experience translate this option into practical terms please? How does a flight crew know which money-saving option was adopted?

Quote:

Originally Posted by Viscount Way (Post 10616055)

why would you need to know that? An emergency descent is flown at the speed, and hence rate of descent, at maximum or max prudent depending on perceived airframe damage. What happens subsequently is the result of engineering and cost calculations made prior by others. You can only play the hand that you are dealt.

Quote:

Originally Posted by Viscount Way (Post 10616055)

FCOM?

I'm guessing it's for routine flights over high ground where a descent to a safe breathing altitude is not practical. Extended use of O2 would be required.

Not necessarily money saving, weight saving. Don't forget that Boeing promised performance and fuel savings which were difficult to meet when the structure required some redesign, which added a lot of weight.

As I said in an earlier post, this system uses smaller, lighter weight O2 bottles.
https://cimg2.ibsrv.net/gimg/pprune....2ff0c06923.jpg
This synoptic from the training manual may help understanding the system.

chemical vs bottles varies by operator.

As far as I encountered, only B747 and A380 still use bottles (for the carriers I operated with)

Our 777 had chemical generators, 22mins duration as they did many cross-Himalayas flights.

A380 used gaseous system, with separate system for flight deck. If inadvertent activiation took place, replacing the pins into the valves at each PSU would cease oxygen flow, or it stopped automatically at 10,000' cabin alt.

Anyone else around when the 310L bottles were around with the full face mask attached? Ah, brings back memories of my first few flights...

As givemewings pointed out some aircraft have more O2 capacity for diversions over higher terrain. AIrcraft without the large O2 capacity would have 'no fly' zones to avoid the higher terrain where O2 capacity, or s/e cruise capability, couldn't ensure clearance with high terrain in the event of a depressurization or engine failure. Parts of the Andes are an example of 'no fly' zones for different aircraft types.