What happened
On 27 August 2011, a BN2T Islander, registration G-LEAP, was conducting aerial work for parachuting operations approximately 5 nautical miles south of Swansea Airport. The aircraft was climbing through clear air when the pilot initiated a wide turn at approximately 8,000 feet to position the aircraft for a parachute drop. During this maneuver, the aircraft passed through a cloud layer described as a sleet storm.
As the aircraft entered the cloud, the pilot attempted to activate the engine anti-ice system. However, before the selection could be made, both Allison 2TR engines experienced a simultaneous flameout. The pilot observed a decrease in engine torque and fuel flow, accompanied by a drop in turbine RPM and a significant increase in Turbine Gas Temperature. The pilot immediately established a glide at 120 knots and continued the turn toward the airfield.
Upon descending to approximately 7,000 feet and exiting the cloud, the pilot engaged the igniters and set the power levers to idle. Both engines restarted immediately. After descending a further 500 feet and confirming stable engine operation, the pilot increased power. The parachuting mission was aborted, and the aircraft returned to Swansea without further incident.
The investigation
The AAIB investigation examined the aircraft's systems and the environmental conditions at the time of the incident. The investigation reviewed the Turbine Islander Flight Manual, which mandates that the power plant anti-icing system must be active when temperatures are below 5°C in the presence of visible moisture. The manual warns that ice accumulation in the air intake can lead to rapid power loss.
Meteorological data from the Met Office confirmed that the weather in the area was consistent with the pilot's report, featuring showery conditions with cloud layers between 6,000 and 10,000 feet and a freezing level near 6,500 feet. This confirmed that the aircraft had entered conditions where engine icing was a significant risk.
Findings
- The aircraft entered engine icing conditions while the Power Plant Anti-Icing was not selected.
- The failure to activate the engine anti-ice system prior to entering icing conditions caused the dual engine flameout.