Friday 28 May 2021

Pilot falls asleep and goes off course for 110 kilometres before waking

An experienced Queensland pilot suffering from fatigue fell asleep for 40 minutes mid-air, an investigation by the Australian Transport Safety Bureau (ATSB) has found. The pilot had been travelling in a Cessna 208B on a ferry flight from Cairns (CNS/YBCS) to Redcliffe (YRED), north of Brisbane, in July last year when the emergency incident unfolded. An ATSB report said on the day, Air Traffic Control (ATC) tried to make contact with the pilot when the plane was close to the Sunshine Coast, but there was no response. "At that time, and for next 40 minutes," the report said.

When further attempts to reach the pilot failed, the ATC asked a nearby Royal Flying Doctor Service (RFDS) pilot to try and intercept the light plane, but this also failed to get the pilot's attention. It was not until the plane had flown more than 110 kilometres past its intended destination that the pilot woke up and made contact.

'Not really with it'

The report said the pilot sounded "groggy" and "not really with it" when the pilot first came to, and had later reported feeling "confused" when first starting their descent. However the pilot had gone on to land the plane at Gold Coast Airport with no issues, the report said. It also said the pilot, who had 20,000 hours of flying experience and had ferried flights for 12 years, reported having "disturbed sleep" the night before the flight, which was a regular occurrence.

"The pilot reported feeling a little tired on the day of the incident, but was OK to fly," the report said.

The pilot also reported having the heater on and the cockpit being "reasonably warm", which they believed may have contributed to falling asleep.

Disrupted sleep and 'mild hypoxia'

But the ATSB determined the pilot's incapacitation was most likely caused by fatigue from prolonged disrupted sleep, paired with a condition called "mild hypoxia. It also determined the pilot suffered the condition because they had not used the supplemental oxygen system "appropriately" when starting to fly at a higher altitude.

"While cruising at 10,000 feet, the pilot encountered unforecast icing conditions and poor visibility due to cloud and climbed to 11,000 feet," the report said.

Pilots must continuously use supplemental oxygen when flying unpressurised aircraft above 10,000 feet, the report said. "This likely exacerbated the pilot's existing fatigue and contributed to the pilot falling asleep," it said.

Aircraft Details
Aircraft: Cessna 208B
Aircraft Registration: VH-DQP
Serial Number: 208B2069

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