From CAO 20.4:
[b]Supplemental oxygen for flight crew members[/b]
6.1 A flight crew member who is on flight deck duty in an unpressurised aircraft must be provided with, and continuously use, supplemental oxygen at all times during which the aircraft flies above 10 000 feet altitude.
6.2 A flight crew member must, in respect of any period during which the member is not on flight deck duty, be provided with the amount of supplemental oxygen that is provided to a crew member in accordance with paragraph 6.3.
[b]Supplemental oxygen for other crew members[/b]
6.3 A crew member (not being a flight crew member on flight deck duty) in an unpressurised aircraft must be provided with supplemental oxygen:
(a) in respect of any period exceeding 30 minutes during which the aircraft flies between 10 000 feet altitude and Flight Level 120 (both inclusive); and
(b) at all times during which the aircraft flies above Flight Level 120;
and must use supplemental oxygen at all times during which the aircraft flies above Flight Level 140.

Hi Andrew,

They are giving you a guide to how much oxygen you need to carry onboard. In an unpressurised aircraft, if you are operating between 10000 ft and FL120 you do not need to carry supplemental oxygen for non-flying crew members as long as the flight time in that altitude band does not exceed 30 minutes. Or, in other words, when calculating the amount of oxygen to carry, you can ignore the first 30 minutes of time operating in that altitude band. However, you must carry oxygen for them for all the time expected beyond that 30 minutes between 10000 ft and FL120.

On top of that. you must also provide enough oxygen for them to cover all flight time above FL120. The reg then goes on to say, it is not enough to just carry that oxygen, the non-flying crew member must actually be using it at all times when operating above FL140.

This of course only relates to the non-flying crew member. Compare that to the pilot flying: they must actually be on oxygen from 10000 ft no matter what the duration.

Cheers,

Rich

So what if the aircraft is flying at FL 130?
I might be missing something but does it address that band between FL120 and FL140?

Hi Andrew, sorry cross-posted. I just finished editing my original answer.

If you were operating at FL130, you would need to provide supplemental oxygen the whole time you expect to be that high. In fact you need to carry enough for the whole time you expect to be above FL120.

Remember, this reg refers to the amount of oxygen that needs to be carried i.e. "made available". The actual regulation for using that oxygen is:
- [b]pilot-flying:[/b] all times above 10000 ft and
- [b]non-flying crew:[/b] all times above FL140 (but there needs to be enough oxygen available for them to use from FL120 and for any time beyond 30 minutes when between 10000 ft and FL120).

Cheers,

Rich

Great, thanks for that Rich, cleared that up.

Andrew

No worries 🙂