FAR 135 pilot oxygen requirements

[METARMan]

If above FL350 operating FAR 135 in a pressurized aircraft, must at least one pilot wear an oxygen mask? I don't remember doing that in FAR 121 flying.

Sec. 135.89

Pilot requirements: Use of oxygen.

(a) Unpressurized aircraft. Each pilot of an unpressurized aircraft shall use oxygen continuously when flying--
(1) At altitudes above 10,000 feet through 12,000 feet MSL for that part of the flight at those altitudes that is of more than 30 minutes duration; and
(2) Above 12,000 feet MSL.
(b) Pressurized aircraft. (1) Whenever a pressurized aircraft is operated with the cabin pressure altitude more than 10,000 feet MSL, each pilot shall comply with paragraph (a) of this section.
(2) Whenever a pressurized aircraft is operated at altitudes above 25,000 feet through 35,000 feet MSL, unless each pilot has an approved quick-donning type oxygen mask--
(i) At least one pilot at the controls shall wear, secured and sealed, an oxygen mask that either supplies oxygen at all times or automatically supplies oxygen whenever the cabin pressure altitude exceeds 12,000 feet MSL; and
(ii) During that flight, each other pilot on flight deck duty shall have an oxygen mask, connected to an oxygen supply, located so as to allow immediate placing of the mask on the pilot's face sealed and secured for use.
(3) Whenever a pressurized aircraft is operated at altitudes above 35,000 feet MSL, at least one pilot at the controls shall wear, secured and sealed, an oxygen mask required by paragraph (b)(2)(i) of this section.
(4) If one pilot leaves a pilot duty station of an aircraft when operating at altitudes above 25,000 feet MSL, the remaining pilot at the controls shall put on and use an approved oxygen mask until the other pilot returns to the pilot duty station of the aircraft.

 

[FlyFlyFly]

Yes, they must. Be careful landing after a flight at 360 or 370 with a full O2 Tank. I have heard of guys getting ramped and dinged for not having used any oxygen.

 

[HMR]

Yes, they must. Be careful landing after a flight at 360 or 370 with a full O2 Tank. I have heard of guys getting ramped and dinged for not having used any oxygen.

Ummm.... Why would the O2 level decrease if you're using the mask in a pressurized airplane?

 

[Otter]

I assume that is a sarcastic and rhetorical question.

 

[transpac]

Ummm.... Why would the O2 level decrease if you're using the mask in a pressurized airplane?

Ummm....Care to explain this?

 

[Lead Sled]

I assume that is a sarcastic and rhetorical question.

Hey, it's a legitimate question. Assuming you're in a typical jet, say at FL430, and you had the mask on and everything was functioning normally would you be consuming any of your oxygen stores? Why or why not? If so, how much would you be using?

'Sled

 

[User546]

I would assume that you wouldn't, and if you were it would be very minor amounts.

On the Citation, the oxygen masks we use don't actually start flowing oxygen until you pinch a clamp on the line which then opens the tubes allowing the oxygen to flow.

But with that in mind also, we have to periodically replinish our oxygen supply despite never using the masks. So....?

 

[FlyFlyFly]

If you put the mask on and it is a demand type mask, every time you breath it will supplement with oxygen, regardless of cabin pressure, unless of course one is the forgetful sort and did not turn the oxygen on. If it is dialed to 100%, then it will draw down at a fairly good rate, see your aircraft's operating manual for the numbers.

 

[Otter]

Fly is right on, same concept with a scuba diving rig. Doesnt matter if you are under water or above, if you breath with it the level of source air (oxygen or compressed) the level in the bottle will go down. Assumption here is a demand mask.

 

[Lead Sled]

If you put the mask on and it is a demand type mask, every time you breath it will supplement with oxygen, regardless of cabin pressure, unless of course you are the forgetful sort and did not turn the oxygen on. If it is dialed to 100%, then it will draw down at a fairly good rate, see your aircraft's operating manual for the numbers. You must have never worn a mask for any length of time, or you would know the answer to this question from practical experience instead of hypothetical hoohah...

I assure you that I have worn my share of masks for my share of the time. A couple of things to point out first.

Metarman...
Many (most) airline crews don't have to don a mask above FL350 because they have waivers that allow them to operate up to FL410 without them.

FlyFlyFly...
You are absolutely correct - if the mask is set to 100% O2. Perhaps the most common crew mask out there is the Scott Eros. It is a diluter demand mask and unless it is set to 100%, it won't provide 100% O2 until you have a cabin altitude of 35,000. User997 pretty much it the nail one the head. If you leave the mask in Normal and your cabin altitude is around 6,000 to 7,000 feet you won't be using a lot of oxygen at all. If you run around with the mask set on 100% then you'll use 4 or 5 times as much.

'Sled