Two pilots who suffered hypoxia during high-altitude flight but survived to read about themselves in Aviation Safety Reporting System narratives had one thing in common: Both were saved by people who recognized their impairment, and took action.
Fortunately the pilots, flying alone in unpressurized oxygen-equipped airplanes, could still comply with suggestions from a companion aircraft’s pilot, and from an air traffic controller. The narratives demonstrate a well-known characteristic of hypoxia: “a euphoric sense of well-being that masks the associated lapse in judgment, memory, and coordination.”
A Turbine Legend kitplane pilot’s decision to execute an unauthorized climb into the flight levels tipped off ATC that impairment might be at issue. Because of prior communication problems and a delayed IFR clearance, the pilot had been holding beneath Class A airspace before odd occurrences began.
“After sometime at FL175, I climbed to FL250 believing I should follow my ‘as filed’ route and profile,” the pilot wrote. “Was finally able to contact Approach and explain my situation. They asked me to take a northerly heading and descend to FL130 then recommended I land, fix the comm and check my Oxygen System as he felt I was exhibiting hypoxia. I realized I was experiencing hypoxia.“
The pilot’s limited experience in the aircraft and with the oxygen mask, and transposed N numbers on a flight plan filed online, contributed to the confusion.
In the other case, two Cessna 337 Skymasters were cruising at 13,000 feet—only 500 feet above the altitudes at which oxygen rules kick in—when trouble began.
“The lead pilot recognized classic signs—noticeable slurring of speech, decreased cognitive/situational awareness, altitude/course deviation. Reduction of altitude and ‘keeping the pilot talking’ yielded a safe landing” with help from ATC, the ASRS report said.
An older, erratically serviced oxygen system may have been partly at fault. The lead pilot opined that the stricken aviator was “nearly 60 years old, somewhat ‘out of shape’ with little physical exercise, mainly desk work, and approximately 6 feet 4 inches, 220 pounds, so the delivered oxygen dosage was apparently inadequate.”
Both scenarios serve as a reminder to review your safeguards, especially if you rarely fly in higher portions of your unpressurized aircraft’s altitude capabilities and plan flight to a high-elevation destination, or along airways with high minimum altitudes. Keeping your communications lines open and heeding safety-related suggestions may be your best antidote for a masked state of impairment.