Hypoxia-induced engine control error leads to uncontrolled descent in Cessna 404

Casualties unknown • En-route from San Pedro Airport, Cape Verde Islands, to Dakar Airport, Senegal, GB

A pilot's failure to use continuous oxygen above 10,000 feet resulted in a period of hypoxia, leading to an engine control error and a high-speed spiral descent.

What happened

On 16 December 2006, a Cessna 404 aircraft, registration G-OOSI, was conducting a private survey flight from San Pedro Airport, Cape Verde Islands, to Dakar Airport, Senegal. During the climb, the commander instructed the passenger to move to the rear of the cabin to optimize the aircraft's center of gravity and to activate the oxygen system.

As the aircraft climbed through 10,000 feet, the commander used his oxygen mask only intermittently. While cruising at FL210, the commander removed his mask to adjust the engine controls. This action, combined with the lack of continuous oxygen, led to the pilot suffering from hypoxia. While attempting to adjust the controls, the pilot inadvertently caused engine vibration and triggered an uncontrolled, high-speed spiral descent. The passenger, noticing the change in engine noise and the aircraft's descent, prepared for a possible ditching by opening the emergency escape hatch. However, the commander eventually regained control at a lower altitude and diverted to Amilcar Cabral Airport, where the aircraft landed safely with no injuries to the crew or passenger.

The investigation

The AAIB examined the aircraft's oxygen system and the cockpit configuration. The investigation established that the aircraft's cabin had been modified for survey work, with an oxygen cylinder installed at the rear of the fuselage. Because the oxygen control knob was located at the rear of the cabin, the commander had to activate the system during the flight. Additionally, the passenger's oxygen mask had a broken strap held by adhesive tape, and at least one mask had a defective microphone, which necessitated removing the mask to communicate with air traffic control.

Findings

  • The primary cause of the incident was the commander's failure to use his oxygen mask continuously while flying above 10,000 feet.
  • The pilot's attempt to adjust engine controls while in a hypoxic state resulted in the engine vibration and subsequent uncontrolled descent.
  • The modified cabin layout, which placed the oxygen control knob at the rear of the aircraft, contributed to the difficulty in managing the system.
  • The passenger's ability to communicate was hindered by a defective microphone on at least one mask.

Probable cause

The incident was caused by the pilot's failure to maintain continuous oxygen use above 10,000 feet, leading to hypoxia and subsequent improper adjustment of engine controls.

Frequently asked questions

What happened in the 2006-12-16 Cessna 404 Titan accident near En-route from San Pedro Airport, Cape Verde Islands, to Dakar Airport, Senegal, GB?

A pilot's failure to use continuous oxygen above 10,000 feet resulted in a period of hypoxia, leading to an engine control error and a high-speed spiral descent.

What aircraft was involved and where did it happen?

The accident on 2006-12-16 involved a Cessna 404 Titan, registration G-OOSI, at En-route from San Pedro Airport, Cape Verde Islands, to Dakar Airport, Senegal, GB.

What was the probable cause of the accident?

The incident was caused by the pilot's failure to maintain continuous oxygen use above 10,000 feet, leading to hypoxia and subsequent improper adjustment of engine controls.

Loading the flight search…