Ep.6 – Oxygen use in the flight levels

Author: Brent Fishlock

Today’s topic is oxygen use in the flight levels. According to some research, business aviation has a poor record when it comes to oxygen mask use and compliance.

A 2010 study by Embrey Riddle University in Florida found that more than 60% of business jet pilots do not use oxygen masks when required to by FAA regulations.

Hundreds of pilots were surveyed, and here is some of the data collected:

• Only 21% of Part 91 respondents “indicated they always use oxygen when one crew member leaves the cockpit above 35,000 feet”, 10% reported occasional use; 25% said “rarely”; and a full one third responded “never”.
• Above 41,000 feet, 18% of Part 91 respondents indicated that they always use oxygen; less than 1% said that they used oxygen occasionally; 8% said rarely; and 28% responded “never”.

Part 121 respondents used oxygen more frequently, with 39% reporting always using oxygen when required above 25,000 feet and 50% above 41,000 feet.

21% of Part 135 pilots surveyed always use supplemental oxygen when only one crew member is at the controls above 25,000 feet, and 18% continuously using oxygen when flying above 35,000 feet.

In every category, the respondents’ percentage of compliance with the rules is less than half, and in many categories, the compliance level is less than one quarter.

So, according to this survey, it’s pretty safe to say there is a culture of non-compliance with regards to oxygen use.

What are some reasons why pilots don’t wear an oxygen mask when they should?

• The mask itself can be uncomfortable, especially for long flights.
• Communication with the other crew member and ATC is more difficult.
• The oxygen bottle must be monitored for quantity level and refilled as necessary
• Oxygen toxicity could be a concern. Oxygen toxicity occurs after prolonged flights at high altitudes using a high oxygen concentration, which can produce lung infection or bronchial irritation.
• A less severe health concern could be oxygen mask hygiene.
• Some aircraft have automatic descent capability:
  • The Gulfstream G450 and 550 have a system where if the aircraft is operating at or above FL400 with the AUTOPILOT ENGAGED and a “CABIN PRESSURE LOW” message is displayed, The A/T will GOTOIDLE and set a SPEED of 340KTS, the AP will turn 90 degrees LEFT, and the aircraft will set a level off altitude level of 15000. At 15,000 feet, the aircraft will maintain 250KTS. Pretty impressive.

Although extremely rare, cabin decompression occurs probably more than you think. According to the Aviation Medical Society of Australia and New Zealand, about 40–50 rapid decompression events occur annually worldwide. So that accounts for the rapid decompression events, and explosive and gradual types of decompression add to that total. Obviously, chances are low on any individual flight however they do occur.

A fast decompression at high altitude can provide challenges in that crew members have to get their masks on in a certain amount of time. I said in the last podcast that Human Factors research indicates that response time is longer for unexpected events than for expected events. When a flight crew is confronted with a sudden, abnormal event, responses are more likely to be delayed or inappropriate, and a reaction time of 8 to 10 seconds may not be unusual.

If you fly at 43,000 feet or above, you have no margin for error. Time of useful consciousness is 9 to 15 seconds.

No slip ups, no mask webbing snags, no extra debris distraction. If the rupture is a window in the cockpit, this is probably going to be a very challenging situation. The assumption is that if you are required to wear the mask while at the controls at the high flight levels, you are. This is the professional thing to do.

It’s hard to argue with science, and the science says that by 10,000 feet ASL, the partial pressure of oxygen is low enough that all pilots will experience mild hypoxia, and some will become symptomatic.

What are some strategies to give yourself the best shot at survival?

• Wear the mask when required to do so, which goes without saying.
• Ask for theatrical smoke in the simulator. This was a great training experience for me to get used to the mask.
• Operate the simulator with the mask on. My experience is that there are communication challenges, to say the least.
• What is your oxygen mask pre-flight? Do you do it every time? It is believed that the Payne Stewart Lear 35 Accident aircraft had little or no oxygen on board.
• Does anything sit around your mask such as a glasses case or food items that could get in the way of the mask deployment? Some masks have doors that open upwards to allow the mask to come out of it as storage housing. This area must be clear of objects.
• If you wear glasses, this may slow down your mask deployment. Wear the mask in the simulator with your glasses to see how it fits.

The NTSB says that investigations of accidents in which flight crews attempted to diagnose a pressurization problem or initiate emergency pressurization instead of immediately donning oxygen masks following a cabin altitude alert have revealed that, even with a relatively gradual rate of depressurization, pilots have rapidly lost cognitive or motor abilities to effectively troubleshoot the problem.

Aviation professionals, please recall that this podcast is brought to you by the leader in online training for business aviation, TrainingPort.net.

“In the News”

(A segment of the podcast where I talk about other happenings in aviation.)

The FAA is changing the METAR coding for Snow Pellets and Small Hail, both of which use the code “GS”. According to the FAA, the reason for the change is to clarify each precipitation type, which will allow flight crews to apply the appropriate Allowance Times or Holdover Times.

Going forward, “GR” will refer to ALL hail of all sizes. Therefore, all reports of hail must include hailstone diameter size in the remarks section of the METAR or SPECI in increments of 1⁄4 inch. For example, when small hail less than 1⁄4 inch in size is occurring, the hailstone size will be reported in the remarks as, “GR LESS THAN 1⁄4 inch.” Small hail will also result in the issuance of a SPECI.

Aircraft are not permitted to operate in LARGE hail; however, many can operate in small hail with deicing and anti-icing procedures.

Snow pellets will be coded as “GS”. Holdover times for snow pellets can be found in Table 28 of the 2018-2019 FAA Holdover Time Guidelines document.

This new information can be found in the FAA’s Information for Operators, or InFO number 18011 dated October 10, 2018.

2014 TBM 900 Accident Brief

FAA InFO 18011

Altitude chamber video

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Brent Fishlock is a technical advisor for TrainingPort.net. Currently an airline pilot, he also has an extensive background in corporate aviation.

Brian Laird has over 10 years of sales and marketing experience.  He has dedicated the last six years to the training market within business aviation, helping flight departments of all sizes throughout the world with their training needs.  A thought leader on sales strategy and approach, Brian is currently focused on new client acquisitions within the United States.