A fuel line fire is the most likely cause of a plane crash that killed a nurse and seriously injured a pilot in West Australia's far north, Australia's transport safety watchdog has found.
The West Australian Country Health Service flight took off from Broome on the morning of April 16 last year on a 'milk-run' flight, stopping at various remote towns in the Kimberley.
The Beechcraft B58 Baron aircraft carried a 29-year-old pilot, who had more than 2,400 hours of flying experience, and a nurse in his 50s.
As the plane neared Kununurra airport the pilot noticed unusual alerts from his instruments as he tried to put the landing gear down.
An electrical burning smell was quickly followed by smoke and then a fire, which he failed to put out with a fire extinguisher.
The flames intensified near the pilot's leg and black smoke filled the cockpit shortly before the plane crashed near the Ord River, just 800 metres from the runway at East Kimberley Regional Airport.
The pilot escaped and pulled the passenger to safety before he collapsed.
The nurse died at the scene, while the pilot was airlifted to Darwin Hospital with serious injuries.
Fire likely caused by landing gear fault
Australian Transport Safety Bureau (ATSB) Chief Commissioner Angus Mitchell said a breach of the cabin heater fuel line likely created a fuel source, and an electrical fault within the aircraft's landing gear wiring provided the ignition.
"The fuel line to the aircraft's cabin heater passes through the area where the pilot reported the fire initiated, and multiple looms of electrical wiring pass through that area as well," Mr Mitchell said.
The ATSB's review of the aircraft electrical wiring was not able to identify a single point of failure.
The ATSB could not completely examine the wreckage due to damage from the fire, but it found no evidence of pre-existing defects in the engines or flight control components that could have contributed to the accident.
Restraint types examined in crash probe
The ATSB report found the passenger may have suffered more serious injuries, which led to his death, because he wore a three-point restraint while the pilot had a four-point restraint.
"Four-point restraints, where available, provide increased survivability," Mr Mitchell said.
The ATSB said Kununurra-based aviation company Aviair had flagged it would install four-point restraints on the crew seats of all their B58 aircraft.
The report said the existing restraints either met or exceeded regulations.
The report said Aviair would also install another fire extinguisher in each of its B58 aircraft and conduct additional 100-hourly fuel line and wiring inspections in the vicinity of the heater fuel line and circuit breakers adjacent to the pilot's seat.
The investigation also mentioned a handful of other occurrences in Australia and the United States involving in-flight fires in Baron aircraft, with damaged wiring identified as a likely factor.
The ATSB has urged operators to thoroughly check fuel lines and wiring in the wake of the crash.
