Supplemental oxygen

[need2AV8]

Perhaps one of you with the 'FAR's explained' book, or otherwise, can help with this one.

For flight above 12,500 MSL - must use supplemental oxygen for that portion of the flight that is more than 30 minutes. Some controversy at my flight school - is that cumulative 30 minutes throughout the flight, or 30 minutes at a time?

I'm pretty sure of what I think. How do YOU interpret this FAR?

 

[avbug]

Ordinarily you do not climb above 12,500 for 29 minutes and then descend. However, the intent of that regulation is that anytime you are above that altitude for more than 30 minutes, you should be on oxygen.

Under Parts 121 and 135, that altitude is lowered to 10,000.

Bear in mind that while one could get by the regulation by restricting time above 12,500 to 29 minutes at a time, one is still subject to 91.13, careless and reckless operation. That subparagraph was left open ended for a reason...don't be that reason.

Also bear in mind that hypoxia is very real, and it can and does affect you without your being aware. If you're going to spend any appreciable amount of time at altitude, consider strongly using oxygen.

I hear all the non-flatlanders saying that they grew up at these altitudes...so did I. Even as a nonsmoker who lived at density altitudes that commonly were greater than 10,000, for much of his life, I firmly believe that altitude and hypoxia are nothing to be fooled with.

I also understand that the FAA suggests oxygen at night above 5,000...though for many of us that would mean wearing it all the time we're sitting on the ground at home, too. A tad impractical, and pointless.

When I was flying air ambulance, I did a lot of experimentation with oxygen and altitude using a pulse oxymeter (before they became chic as a result of heavy advertising by Avweb). You might be surprised as to what your 02 blood sats are really doing, and how it's affecting you.

That long reply is simply to say, in answer to your question, that the regulation's intend is to have you on oxygen after a specific minimum time above 12,500; this time is continuous for the intent of the regulation.

Note the wording:

At cabin pressure altitudes above 12,500 feet (MSL) up to and including 14,000 feet (MSL) unless the required minimum flight crew is provided with and uses supplemental oxygen for that part of the flight at those altitudes that is of more than 30 minutes duration;

"for that part of the flight..." married to "at those altitudes." If you are above 12,500' on one leg of the flight for 36 minutes, then you must use oxygen for at least the last 6 minutes. If you then descend for 20 minutes and go back up for 31 minutes, you must use oxygen for the last minute of that 31 minute leg. For the 20 minutes you're below 12,500, you do not need oxygen.

If you have several excursions above 12,500, each is a separate part of the flight, and the time and oxygen requirements apply to each part.

The big however, applies to the time you have a reason for the FAA to become involved. While technically you can loophole the flight by reducing it to less than 30 minute segments above 12,500, you are still subject to the aforementioned 91.13, as well as the requirement to be in an airworthy medical condition yourself 61.53(a). The FAA will hold you certainly to the wording of the regulation, but because of the other parts of the regulation, you will also be held to the intent (and may be so, legally).

Use the oxygen.