Oxygen requirements

[felixthecat]

Does anyone know of pilot O2 requirements at certain flight levels…ie above a certain level it has to be available at 100% full mask etc etc.

My thoughts are around a discussion that should you loose crew O2 pressure a good idea is to get a couple of O2 bottles from down the back. The argument that was put to me was that you should then negotiate a decent to FL 250. I don't see why though since O2 is available in our case for over an hour with a portable bottle and descending would burn much more fuel and may require a tech stop. My point was why descend at all since it is just a loss of O2 pressure and O2 is available in the portable bottles if it is subsequently required.

Any thoughts and references? Many thanks

[ImbracableCrunk]

You're at cruise, you're out of O2 , and you "should negotiate" a descent to FL250?

So what is your hypothetical scenario?

[felixthecat]

The O2 crew oxygen is out, a leak of some sort. There is no further problem at this stage ie pressurisation etc is normal. We get a couple of portable O2 bottles on the flight deck that give us O2 in our case for 1:17 -2:35 depending on Hi or Low flow. So we are not out of O2, and at this moment in time we do not actually need it….so why descend to FL250? And is so why 250 and not FL100?

If I descend to 250 I will burn a heap more fuel than at altitude and might now be fuel limited and need a tech stop, whereas if I stay at altitude I can make destination.

[FE Hoppy]

From a legal point of view you need quick donning masks above 25000'

EU OPS ref is 1.770 b
(iv) Oxygen masks for use by flight crew members in pressurised aeroplanes operating above 25 000 ft shall be a quick donning type of mask.

There will be a FAR equivalent.

[felixthecat]

Thanks Hoppy that will be the reason :O ….The quick donning bit

[Checkboard]

We get a couple of portable O2 bottles on the flight deck that give us O2 in our case for 1:17 -2:35 depending on Hi or Low flow.

Supplement therapeutic oxygen provided at 2 or 4 litres per minute doesn't give you sufficient oxygen for consciousness at high altitude, nor is it designed for that. :rolleyes:

You should also note that the crew O2 system is also the primary smoke inhalation protection - and the bottle therapeutic oxygen is useless for that scenario.

[FE Hoppy]

4 litres per minute would be more than enough if you could get it into your lungs.

TSO requirements for supplemental oxygen in litres per minute are roughly:
1.3 at 15000'
1.9 at 20000'
2.4 at 25000'
2.7 at 30000'
3.3 at 35000'
2.3 at 40000'

So a walk-round bottle with 4 lpm flow will give you enough O2. The trouble is getting the mask on in time and at high cabin alt getting the O2 into your lungs. Without an appropriate mask the oxygen will just be flowing into the cabin at 4 lpm.

I got the figures from a certifying document for a quick donning mask so they are pretty trustworthy :-)

[beaver34]

Whatever you do: stay a present level or descent at FL 250 you don't have any smoke inhalation protection.In case of fire with toxic fumes you're dead.

[FE Hoppy]

@Beaver.

That's a bit of an oversimplification there.

[lomapaseo]

The argument that was put to me was that you should then negotiate a decent to FL 250. I don't see why though since O2 is available in our case for over an hour with a portable bottle and descending would burn much more fuel and may require a tech stop. My point was why descend at all since it is just a loss of O2 pressure and O2 is available in the portable bottles if it is subsequently required.



Will the passengers be included in this negotiation :confused:

Then again they may just stay very quiet as you tool on

[stormyweathers]

No need for Oxygen bottles in the cockpit. Continue flight as planned. Do you really think you will have a depressurization the exact same time that you have an oxygen leak, assuming it really is a leak?

[9.G]

well, on the airbus the matter is very clearly stated in the limitations applicable both for dispatch and in flight. If my oxygen dropped to zero I'd try to verify the bottle pressure and if not able to simply divert. My primary concern is smoke protection. :ok: