Enough Oxygen?

[737superace]

I recently travelled from LHR to HKG on an NZ 777.

I was more than a little surprised to see that we followed the Y1 route to the south of Urumqi.

An area with MSA's in excess of 20,000. I know the 777 can maintain that engine out, but what about the oxygen requirements.

Looking at a map there must be a position along that route where it would take longer than 15-20 minutes (chemical oxygen) to get to a 14,000 MSA.

What's the deal

[rudderrudderrat]

Are you sure it's chemical oxygen - and not supplied from large bottles of O2 held in the hold giving the legal duration required?

[mcdhu]

It's all part of performance planning.

mcdhu

[Checkboard]

The 737-300 and up uses generators, 20 mins is standard, 40 mins is an option for operations in high terrain areas.

The 737-1/200 and 747 uses bottles, and I wouldn't be surprised if the 777 was the same.

[INLAK]

The 777 uses standard 22 minute chemical generators.

[FE Hoppy]

Piece of cake. Thats what escape routes are for.

[a.mandon]

737superace said: "An area with MSA's in excess of 20,000. I know the 777 can maintain that engine out, but what about the oxygen requirements.
"

It also has something to do about the extend of that 20K ft MSA.

[cribble]

Inlak
Your 777 may use chemical generators, Air NZ's use gaseous (ANZ FCOM 1.40.8)

[heavy.airbourne]

As far as I know, L888 is the most critical airway. All others are within O2 generator certification limits, but that is a fake. Check the flow rate and you will find, that after one half to two thirds of the flow time the rate is insufficient to maintain a healthy adult. :hmm:

[c100driver]

Air NZ's use gaseous

Yes the Air NZ B772 and also the B773 have the gaseous O2 system.

[ghw78]

A check is done prior to each flight over the sector. The total Pax and F/D Oxygen pressure, which are contained in two separate bottle systems, has the pressure recorded and then corrected for local OAT temperature. This corrected pressure is then compared with the amount needed for
flight over the Y1 Route depending on the passenger cabin payload and flight deck complement. There are 304 seats plus up to 11 cabin crew (normal complement of 10) and the infants equates to depending on the number of passengers on the day to x amount of pressure required. Similarly for the F/D there needs to be y amount of pressure depending on whether there are 2, 3 or 4 occupants on the flight deck. If the pressure is below that required there are two choices, either a top up or alternatively it is the long way around.

[mutt]

Check the flow rate and you will find, that after one half to two thirds of the flow time the rate is insufficient to maintain a healthy adult.

Would you care to expand on this statement? Is this the reason our 180 minutes ETOPS was reduced to 159 minutes?

Mutt

[737superace]

That's all great
So when when all the x's and y's etc are all lined up, bottom line . . . . .how many minutes oxygen do you have?