Flight crew O2 requirements

[Aztec Kid]

I don’t believe ETOPS regulations have any impact on the oxygen requirements.

To address oxygen requirements during a depressurization, the FAA requires a supplemental oxygen flow rate of 0.8 LPM at 10,000 feet. The mask on my aircraft supplies oxygen at about 2.4 LPM when at 10,000 feet.

Charts for oxygen duration for smoke protection (100 percent oxygen) are based on a consumption rate of 30 LPM per pilot. This is why the duration is so much shorter when using 100 percent oxygen. It is also the reason that the decompression drills include a reminder to ensure the mask regulator is set to normal rather than 100 percent.

Typically, the net result is that if you have enough oxygen for 15 minutes at 100 percent at 8,000 feet, you will have more than enough to meet the two hour requirement at 10,000 feet. However, if you are flying routes with very high MEAs that would preclude an immediate descent to 10,000 feet, an analysis would have to be performed to determine the additional oxygen requirements. In some cases, it could be greater than the 15 minute supply at 100 percent.

I believe duration for a full bottle is simply a linear relationship. So for a full 49 cubic ft cylinder and two pilots, I would estimate that you would have approximately 26 minutes at 100 percent and 8,000 feet.

Please keep in mind that I am definitely not an expert in this area. I am simply conveying what was told to me by the engineer.

Regardless if you are miles away from land or directly over a suitable airport, dealing with smoke in the aircraft would be an extremely challenging task for even the most proficient flight crew. Keep in mind; while the pilots may have a limited oxygen supply, other than a few PBEs, the cabin crew and passengers have nothing. This may be one of the reasons that regulators do not dwell on the limited crew oxygen for smoke protection.

The Kid