Oxygen irregularities

Flying Safety, March, 2002

Courtesy ASRS Callback #247, Jan 00

NASA's Aviation Safety Reporting System

Both pilots and controllers are educated to recognize the effects of oxygen deprivation and hypoxia. This training can be vital in safely resolving oxygen-related pilot incapacitation. Several ASRS reports illustrate:

While at FL250 on an IFR flight plan, my oxygen line became disconnected from the regulator. I could hear the oxygen escaping and thought the regulator had not sealed on the portable tank behind the passenger seat. As I had changed tanks within the past 15 minutes, I attempted to tighten the regulator, but to no avail. I recognized hypoxia coming on, pulled power back, disconnected the autopilot, and lost consciousness. I became conscious at 17,000 fret. The plane was descending and in a bank. I had lost my oxygen supply and had lost consciousness. I landed at the nearest airport. Upon landing, I saw the line to the regulator had come off. I have since found that if the oxygen line is kinked the line will pop off the barbed fitting on the regulator, so in the future I will secure a clamp at this attachment.

Portable oxygen tanks and lines should be inspected and secured during preflight to prevent potentially lethal "kinks" in the oxygen supply.

In another oxygen-related emergency reported to ASRS by an air traffic controller, ATC gave a superlative flight assist to the incapacitated pilot of a high-performance twin-engine aircraft.

Aircraft experienced oxygen problems and [pilot] was disoriented with hypoxia requesting descent from FL250 to 13,000 feet. I issued the clearance but [pilot] couldn't descend the aircraft due to his inability to focus. A flight instructor came to the sector and talked the aircraft into a descent and the pilot recovered, changed his destination to a closer airport, and landed safely.

In a callback to the reporter, ASRS learned that the controller kept the pilot conscious by talking to him and asking questions until a supervisor could locate another controller who was qualified and type-rated in the aircraft involved. This second controller instructed the pilot to disengage his autopilot, which started the aircraft down.

FAA Advisory Circular 61-107 alerts pilots who are transitioning to complex, high-performance aircraft capable of operating at high altitudes and high airspeeds "of the need to be knowledgeable of the special physiological and aerodynamic considerations involved within this realm of operation."

In addition to the guidance provided by AC 61-107, pilots who fly at altitudes requiring supplemental oxygen may want to consider equipping portable oxygen tanks with flow indicators that can be easily monitored within the instrument scan range. Flow indicators can provide an early warning of oxygen system problems--before the onset of debilitating hypoxia.