A320 OXY Flow seletor
 

Isnt it required to switch to normal flow in order to get more than 15 minutes from the oxy bottle? i hanvt seen any procedure advising it.

If you leave with the minimum dispatch requirement on the O2 bottle pressure, you have 15 mins at 8000' at 100% oxygen for each pilot. Most of the time you will have more than that - but it is worth noting in the case of smoke in the cockpit (where you will be required to use 100%).

In terms of procedure - the QRH EMER DESCENT checklist has the step:

Thank you checkboard. :)

While on the subject Checks what would you do if yer cockpit
oxy bottle suddenly went to '0' on the SD in cruise at F380?

You had a suck on the masks and confirmed the loss of O2.

Case 1: Plenty of nearby airports

Case 2: 120 min ETOPS - nearest airport 100 min all engines

I know what I'd do, but just asking your opinion for discussion.

Yep it happened to me! :bored:

Without referring to any manuals (off the top of my head). ;)

Generally RPT operations require a guarantee that we can accept any major failure, and still continue operations to an airport. E.G.: if we lose an engine at any point in the flight, we calculate that we have the performance required to avoid terrain, and the fuel needed to reach a destination etc etc.

So - loss of the oxygen system requires a descent to 10,000 - in the same way that loss of an engine (in a twin) requires diversion to the first acceptable airport - as you no longer have redundancy for a failure.

Once you are at 10,000 - where you can motor to depends on how much fuel you have. There isn't any need to divert per se (in the sense that everything else is working), but your remaining range is obviously going to be curtailed (and you can't fly over high LSALTs).

Thanks for that Checks. I did it differently (descent to FL250
keeping an eye on pressurisation and had 2 bottles from the
back brought up to cater for any cockpit smoke), and got no
abuse from the office.

The pressurisation system was working fine, which gave me
no real cause to descend to 10,000ft but of course would've
done so had we lost it. It could be argued a sudden decomp
would have to fit into the equation, but with bugger-all and
nearest airport 100 mins away its debatable I suppose.

They wouldn't have helped if you had smoke in the cockpit, portable "constant flow" systems mix surrounding air with the oxy. as you breath in. The flight deck masks are "diluter demand" systems and do the same thing when they are in the normal position (unless you are very high) which is why they need to be set to 100% to protect you from smoke. Part of the de-press drill should be to set the flow to normal if there is no smoke.

In my opinion loss of flight crew oxygen means land at the nearest suitable airfield and range and terrain permitting descend to 10000ft.

I would not descend below 140.

The smoke scenario is the most concerning problem, though. It is a very common occurrence, so diverting is probably the best course of action.

The problem is that the managemen will not look at it in the same manner, They will say "oh come on, what are the chances you have smoke in the flight?"

therefore, in 99% of the cases, the crew would continue to destination.

I would reply "what are the chances of surviving smoke without oxygen"?