Bad repairs caused plane fire

Poor quality repair jobs and an ineffective inspection contributed to an engine fire aboard a passenger flight spotted ablaze over Perth, a safety report has found.

An engine on the Cobham Aviation AVRO 146-RJ100 aircraft, packed with workers bound for Barrow Island in the state's Pilbara, caught fire shortly after takeoff from Perth Airport in April, 2014.

The Australian Transport Safety Bureau (ATSB) report found a crack in a welded boss allowed high-pressure fuel to escape and catch fire.

The flight was photographed by stunned onlookers as it streaked over Perth on fire.

The report found grinding within the engine housing, which increased stresses and the likelihood of a crack forming.

"It is likely that the grinding was associated with a weld repair conducted during a combustor turbine module heavy maintenance visit," the report said.

The report found the grinding repair was not of an acceptable manufacture standard to return it to original design strength.

The welded boss had been weld-repaired on three separate occasions while the grinding repair to the combustor housing was not part of the manufacturer's approved repair scheme.

Aboard the flight, the engine fire detection and suppression system worked effectively, according to the ATSB report, which said the crew were able to put out the fire using normal procedures.

Cobham undertook a fleet-wide inspection of the specific engine and while no more cracks were found to the specific part, one more engine with grinding was uncovered and seven ignition boss cracks were also found.

The engine manufacturers, Honeywell, also amended their LF507 engine maintenance manuals to address crack limits and well repair specifications.

While the investigation is continuing, the ATSB said it had not found any organisational or systemic issues that would affect the future safety of Cobham's aviation operations.