At about 0815 Western Standard Time on 28 April 2012, a Gippsland Aeronautics GA8-TC 320 aircraft, registered VH-WOV, took off from runway 12 at Kununurra airport, Western Australia, for a sightseeing flight over the Bungle Bungle ranges. On board were the pilot and six passengers.

Despite the application of full throttle during the takeoff, the engine manifold pressure was lower than expected. The manifold pressure decreased further soon after the aircraft became airborne, to the point that level flight could not be maintained. The pilot initially prepared for a forced landing, but after finding that sufficient power was available to remain airborne, and assessing the surface of the selected field as unsuitable, the pilot elected to return to the departure airport. The pilot landed on the grass surface of the airport adjacent to the parallel taxiway, with no injuries reported and no damage to the aircraft. The low and decreasing manifold pressure was the result of an engine turbocharger system malfunction.

This incident highlights the importance of understanding the complexities of engine turbocharger systems. A turbocharger system malfunction may result in unpredictable engine power and aircraft performance. Furthermore, a turbocharger system malfunction does not necessarily mean that the engine will behave like a normally aspirated engine. Although this incident was the result of a turbocharger system malfunction, pilots are reminded that abnormal manifold pressure indications may be symptomatic of a serious problem, such as an engine exhaust system leak.

This incident also highlights the importance of pre-flight preparation. Self-briefing may help pilots respond to abnormal takeoff indications more effectively, and help manage the influence of perceived pressure when confronted with a time-critical decision.

Aviation Short Investigation Bulletin - Issue 12