FlyCRJ.com

Thanks for coming back! I hope you are finding this information on flying and on the CRJ 200 useful. Be sure to sign up for email updates or my RSS feed.

I respect your email privacy. You can unsubscribe at any time!

Recent discussions on the flight deck and some company communications about oxygen use on the flight deck had me wondering about the oxygen (O₂) use on the flight deck. I basically understood the requirements, but wanted to know a little bit more. What I found was that there were a few misconceptions between Part 91 – General Operating and Flight Rules and the Part 121 – Operating Requirements concerning (crew) use of oxygen. This article will hopefully clarify some issues. There is even a legal interpretations from the FAA.

First of all, there is the Part 91 requirements. If you’ve been through your Commercial rating, you will be familiar with the following.

For Non-Pressurized Aircraft Operating under Part 91:

• At cabin pressure altitudes above 12,500 feet (MSL) up to and including 14,000 feet (MSL), if there for longer than 30 minutes, the crew must use supplemental oxygen
• At cabin pressure altitudes above 14,000 feet (MSL), the crew must use oxygen continuously
• At cabin pressure altitudes above 15,000 feet (MSL), each occupant is provided (but doesn’t have to use) supplemental oxygen. (Why wouldn’t they…I don’t know.) (Reference: FAR 91.211)

For Pressurized Turbine Aircraft Operating under Part 91:

• Above FL250, there must also be at least a 10-minute supply of supplemental oxygen available for each occupant
• Above FL350, one pilot must always wear an oxygen mask that is supplying oxygen or can automatically supply oxygen if the cabin pressure altitude exceeds 14,000 feet MSL (or Mean Sea Level); however, if the aircraft is below FL410 and there are two pilots at the controls and each pilot has a quick-donning mask (i.e., they can place it on their face within 5 seconds) available (which we do), then neither has to wear a mask while operating the airplane unless one of the pilots leaves their station. (Reference: FAR 91.211)

For pressurized turbine aircraft (like the CRJ) when operating under Part 121 regulations and when operating above 10,000 feet, here are the following requirements:

• Above 10,000 feet, the certificate holder of the airplane must first and foremost comply with FAR 121.329, Supplemental Oxygen for Sustenance.
• Above10,000 feet, there must be a two-hour supply of oxygen for each crewmember on-board which provides oxygen for a descent to 10,000 feet in 10 minutes and thereafter for 110 minutes (1 hour, 50 minutes) of flight at 10,000 feet if the cabin pressurization system fails.
• AboveFL250, each crewmember must be provided with an quick-donning oxygen mask that is in working condition and capable of providing communications between crewmembers and can be secured within 5 seconds with one hand.
• Above FL250, if both pilots have quick-donning masks, neither has to wear their mask unless the other pilot leave their station.
• If in the case of the CRJ, if the airplane is flown above FL410, then both pilots have to wear their oxygen masks. (Reference: FAR 121.233)

I know this all seems fairly straight forward once you break down the regulation into bit size chunks but the confusion comes when you start interpreting FAR 121.329 as well.

Free Pilot Tip-of-the-Week from PilotWorkshops.com For You! Click Here Now!

FAR 121.329 vs. FAR 121.333

If you fly Part 121, then this is where it can get a little confusing. FAR 121.329 discusses “Supplemental Oxygen for Sustenance“ whereas FAR 121.333 discusses “Supplemental Oxygen For Emergency Descent and For First Aid.” The differences hinge of the words “cabin pressure altitude” and actual flight levels, respectively.

FAR 121.329 states that ”at cabin pressure altitudes above 10,000 feet, up to and including 12,000 feet, oxygen must be used by each member of the flight crew on flight deck duty and must be providedfor other crewmembers for that part of the flight at those altitudes that is of more than 30 minutes duration.”

That is were sustenance applies and the operative words being “cabin pressure altitude.” Since most the time we fly the CRJ above 10,000 feet MSL, the airplane pressurizes the cabin to somewhere around 6,000 and 8,000 feet, or so, which is comfortable for the crew and most passengers, so it is kind of a mute point. But, if we were unpressurized, for some reason, then this regulation would apply. 

FAR 121.329 goes on to discuss the use of oxygen above 12,000 feet, cabin pressure altitude, and does not include any provision for “more than 30 minutes duration;” however it does state that oxygen must be provided for and used by each crew member on flight deck duty. Now some crew members have used that to mean that pilots can operate between 10,000 and 12,000 feet cabin pressure altitudes for 30 minutes or less without oxygen.

This is not true.

A Legal Interpretation

In a legal interpretation of the regulation dated March 20th, 1992, Mr. Donald P. Byrne, Assistant Chief Counsel in the Regulations and Enforcement Division of the FAA said:

“FAR 121.329(b)(1) requires oxygen to be provided for and usedby flight crew members on flight deck duty at altitudes above 10,000 feet, up to and including 12,000. Other crewmembers (those not on flight deck duty, or those who are not flight crewmembers) only need to have oxygen provided for that part of the flight at those altitudes of over 30 minutes duration.

Comparison with other oxygen requirements in the FAR [ed: from Parts 91 and 135 as provided in the letter of inquiry] will not yield the uniformity you were hoping for because Part 121 has higher safety standards than other parts.”

To look at it another way, let’s break up the sentence. It contains two compound verb forms, i.e., “must be used” and “must be provided” with their accompanying phrases separated by the conjunction “and.” (Are you getting all this?) The reference to “altitudes that is of more that 30 minutes duration” is contained in, and applies to, only the “must be provided” phrase, i.e., other crewmembers.

Note that only flight attendants would be authorized by this regulation to go without supplemental oxygen for the first 30 minutes between 10,000 and 12,000 feet. Interestingly, they are not required to use it but only that it be provided.

My Oxygen Mask and Smoke Goggles on the CRJ-700

So I know that these seems to be splitting hairs but it is still an interesting discussion.

In actual practice, it would have to be an extreme circumstances that I would fly a CRJ that couldn’t pressurize and I certainly wouldn’t do it with passengers on board, but if I did, I would have to wear an oxygen mask when above 10,000 feet cabin pressure altitude. It would be very uncomfortable and noisy.

And if ever during a flight, if I were to get a warning or caution message regarding my cabin pressurization, my quick-donning oxygen mask would come on FIRST, I would establish communications, then I’d evaluate what the problem is because depending on your altitude and health, your “time of useful consciousness” (TUC) may only be a few seconds. Think of the Paine Stewart accident if you need a reminder.

Anyway, I learned a lot and I hope this helped you too. Read it a few times if you didn’t get it the first time. I think that it will be much clearer with a second or third reading.

To Your Flying Success…

Jeffrey

Jeffrey is a captain at a regional airline and flies the CRJ200, CRJ700, and the CRJ900. He has over 4000 hrs of flying experience in many different airplanes and is a Gold Seal flight instructor to his credit. He has recently written “The CRJ200 Quicknote Study Guide” that simplifies the systems of the CRJ200 into a easy-to-understand, downloadable eBook. Click here to get your copy today!

Disclaimer: I am not a lawyer nor am I associated with the FAA in any way, shape, or form. This entry is based on what my understanding of the regulations are and should not be construed nor implied that I am providing legal advice, counsel, or otherwise. If there is any inaccuracies in this post please let me know and always refer to the appropriate FAR for compliance and as a definitive source.

Related posts:

• A Sick Flight Attendant and A Sick Passenger
• Domestic Reduced Vertical Separation Minimum (DRVSM) Explained
• CRJ-200 Recurrent Simulator Proficiency Check – Part 1
• CRJ-200 Recurrent Simulator Proficiency Check – Part 2
• Double Check Your FMS and the GPS Waypoints