O-ring Failure Contributed To In-flight Fire Accident

Piston aircraft operators and maintainers are urged to proactively replace O-ring seals within fluid-carrying components of their aircraft before they naturally deteriorate from age, after a Mooney fatal in-flight fire near Luskintyre, NSW on 17 October 2022.

The ATSB has issued the safety advisory with the release of its investigation report from the accident where a pilot was fatally injured when the Mooney M20J they were flying caught fire in flight, and collided with terrain short of the runway at Luskintyre Airfield.

The Mooney had taken off from Maitland for a local flight, and flew to and around Cessnock, before heading north-east to Luskintyre.

“The Mooney had just completed a left orbit of the airfield when witnesses observed the aircraft descending to land, and reported seeing smoke and flames trailing the aircraft,” ATSB Chief Commissioner Angus Mitchell said.

The aircraft collided with terrain near the threshold of Luskintyre’s runway 30. While the pilot survived the collision, they later succumbed to injuries associated with an intense post-impact fire.

“The ATSB investigation determined fuel leaking from an age-affected O-ring seal of the engine-driven fuel pump ignited and caused an engine compartment fire,” Mr Mitchell said.

“A leak from the pump outlet fitting that supplied the engine fuel control unit was identified, and analysis indicated the O-ring sealing that fitting had deteriorated with age.”

Piston engines, and the components necessary for their operation, installed in aircraft operating in the private or airwork category are permitted to remain in service beyond their recommended calendar time overhaul interval, the investigation report notes.

Aircraft records indicated the pump had been in service for more than 29 years and had likely remained undisturbed for maintenance throughout that period.

“Inspect the uninspected,” Mr Mitchell said.

“If aircraft records identify elastomer – rubber-based – type components that have remained undisturbed for significant periods of time, take a proactive approach – replace components such as O-ring seals before they deteriorate to the point of failure.”

The ATSB’s final report also notes the finding that the aircraft had been recently refurbished.

“This refurbishment included repainting the aircraft, and replacing interior furnishings with alternate materials, but neither the refurbishment, nor the flammability assessment of the substituted materials, were recorded in the aircraft’s log books,” Mr Mitchell explained.

“While the effect this had on the in-flight fire or survivability in this case could not be determined, aircraft owners should be sure to document refurbishment action in the log book, and include details of materials if substituted, as well as their suitability for use in aircraft interiors.”

You can find here the report: In-flight fire and collision with terrain involving Mooney Aircraft Corporation M20J, VH-UDQ, near Luskintyre Airfield, NSW on 17 October 2022

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