No pre-crash defects have been identified in the structure or flight controls of an aircraft that nose-dived into the ground south of Perth in December, killing the pilot.
The Australian Transport Safety Bureau says it is continuing to examine the recovered components of the Dynaero light plane and analyse the downloaded flight data.
However, its preliminary report said witnesses heard an audible change in the aircraft's engine noise shortly after take-off from the Serpentine Airfield on December 28.
The aircraft was then observed to make a slow turn to the left and another change in engine noise was heard before the left wing dropped and it went into a steep, nose-down rotating descent.
ATSB transport safety director Mike Walker said the retrieved components included a damaged GPS unit, aircraft instrumentation, the engine, propeller and fuel system components including the fuel flow indicator.
"No pre-impact defects were identified with the aircraft's flight controls or structure," Dr Walker said.
As well as the analysis of data from the aircraft's fuel flow meter and other electronic devices, and considering witness information, the ATSB's investigation will examine the recovered aircraft components and review the aircraft's maintenance history and flight characteristics.
A final report will be released at a later date.
Australian Associated Press