An Australian Transport Safety Bureau (ATSB) investigation was unable to determine why the engines on a Piper Seneca lost power, resulting in a fatal accident at Broome in July 2012.
Seneca VH-LCK was departing Broome on a night freight run to Port Hedland when it crashed into sand dunes shortly after take-off, killing the pilot.
"The take-off towards the ocean was conducted in dark night conditions with limited external visual cues," the ATSB investigation report states. "An on-board global positioning system (GPS) recorded a reducing ground speed as the aircraft approached and passed overhead the upwind runway threshold, but without a significant increase in climb performance.
"That reduction in ground speed occurred about the same time witnesses heard unusual noises from the aircraft’s engines. In the absence of any identified environmental, airframe or structural factors, the witness reports and GPS data were consistent with the aircraft’s performance being affected by a reduction in engine power.
"Following the likely loss of engine power, the aircraft speed reduced significantly, resulting in uncontrolled flight, a steep descent and collision with terrain."
Investigation showed the magneto switches for the left engine were shut off, but that impact damage to propellers was consistent with both engines running at low power at the time of impact.
Despite inspection and testing, the ATSB found no potential cause for loss of engine power.
The report also cites several precedent accidents in Piper Senecas where the pilot inadvertantly switched off magnetos instead of the landing lights on take-off.
The full report is on the ATSB website.