Pilot may have turned off plane's engine before crash: watchdog

Australia's transport safety watchdog is investigating whether a pilot inadvertently turned a plane's engine off before it crashed in Western Australia's north earlier this year.

The plane, operated by Skippers Aviation, was carrying two pilots and five passengers when it crashed shortly after take-off from Broome airport on March 19, about 2,000 kilometres north of Perth.

One passenger was seriously injured.

The Australian Transport Safety Bureau (ATSB) released its preliminary report into the crash on Tuesday, outlining what it said was "factual information established in the investigation's early evidence gathering phase".

While the report does not contain any official findings, the aviation watchdog said a previously logged defect required both of the plane's engines to be started manually.

The report said the flying pilot was "unsure" after take-off whether they had pressed the engine's stop or start buttons.

In 'manual mode'

The control computers responsible for enriching the plane's engines with fuel were not working, according to the report.

"This was logged … meaning the aircraft could still operate, subject to specific conditions," ATSB chief commissioner Angus Mitchell said.

"The aircraft's engines had to be started in manual mode, with the pilots planning to use the left and right START buttons to enrich each engine with fuel."

The Cessna 441 engine start buttons are located next to the stop buttons, on the same panel.

The plane was being operated by two pilots at the time of the incident — a pilot flying from the left seat, and a training captain on the right.

The ATSB said the pilot flying pressed "what they believed to be the left and right start buttons, without looking at the panel" after take-off.

After noticing a change in engine sound, the training captain asked the pilot flying if they "had pressed the stop buttons".

The pilot flying was unsure, according to the report.

With "limited time available to restart the engines", the training captain made the call to land the aircraft in the mangroves.

One passenger was seriously injured, with the remaining four passengers and two pilots receiving minor injuries.

The aircraft was "substantially damaged".

Investigations continue

Mr Mitchell said the focus of further investigations would include operational procedures and training, in addition to aircraft design features such as the stop and start buttons.

The ATSB is also set to investigate safety considerations, with the preliminary report noting two passenger seats detached from their seat tracks during the forced landing, and a third partially detached.

The commissioner said information from the preliminary reports may be subject to change should new evidence become available to the investigation.