Cessna 182Q, VH-LMH

The pilot reported that while in cruise flight over water, the C182 aircraft was subjected to a strong downdraft. The pilot immediately reduced engine power to slow the aircraft in anticipation of further turbulence. Having established the desired airspeed, the pilot attempted to re-apply power but the engine did not respond. He selected carburettor heat and attempted several times to start the engine.

As there was no suitable landing area on nearby Huon Island, the pilot ditched the aircraft 1 km from the mainland shore. Three of the four occupants exited the aircraft unassisted; the fourth had to be pulled free by the pilot. All then made their way to the shoreline.

Subsequent salvage attempts were unable to locate the wreckage. Consequently, to assess the airworthiness of the aircraft, the investigation could examine only the aircraft documentation. No deficiencies that might have contributed to the accident were identified.

Information provided by the Bureau of Meteorology indicated that atmospheric conditions at the time of the engine failure were conducive to the formation of moderate to severe carburettor icing. The formation of ice in the carburettor venturi can result in partial or complete loss of power. Contamination of the fuel system was also considered. However, the aircraft operator said that the aircraft had not been fuelled from known contaminated batches.

The investigation could not determine why the engine failed. However, it is possible that carburettor icing formed after the pilot reduced power in response to the turbulent conditions.