Incorrect engine repairs led to an engine failure and in-flight fuel-fed engine fire of a Cobham Avro RJ.100 aircraft in Australia, according to an ATSB investigation.
On 29 April 2014 an Avro RJ.100 aircraft, registered VH-NJI and operated by Cobham Aviation Services Australia, was on a charter flight to Barrow Island Airport from Perth Airport, Australia. The aircraft sustained a mechanical failure of the no. 2 engine shortly after take-off that resulted in an in-flight fuel-fed engine fire. The flight crew extinguished the engine fire by shutting down the no. 2 engine and activating the fire suppression system. The aircraft was flown back to Perth Airport, having sustained significant damage to the no. 2 engine and cowling. There were no injuries.
The ATSB made the following findings:
– A repair to the two o’clock combustion liner retention boss of the no. 2 engine combustor turbine module housing was not performed in accordance with the manufacturer’s repair specification, resulting in a thin-walled housing that increased local stresses in that location.
– As a result of fatigue, the no. 2 engine combustor turbine module housing cracked, then fractured adjacent to the two o’clock combustion liner retention boss weld, propagating at an unpredictable rate as a result of the non-approved repair.
– High-temperature combusting fuel and gases escaped radially from the fracture in the no. 2 engine combustor turbine module housing, leading to an in-flight engine fire.
Other factors that increased risk:
– The Honeywell International Inc documentation for blending did not limit the amount of material that could be removed from the combustor housing.
– The Honeywell International Inc LF507-1F heavy maintenance schedule was adequate to identify and repair cracks in the combustor turbine module housing combustion liner retention boss weld.
In response to this occurrence Cobham proactively inspected all of their LF507 engines, focusing on the welded bosses. Of those engines, one spare engine had grinding at one of the welded bosses, similar to the occurrence engine, and was withdrawn from the availability pool. Although no cracking was found at the combustion liner location pin welded bosses, Cobham did find seven cracks at the location of the ignition bosses that had not been previously identified. These cracks were managed in accordance with the Honeywell maintenance manual.
Honeywell also instigated several actions in response to this occurrence. These included amendment of the LF507 engine maintenance and overhaul manuals to address crack limits and weld repair specifications, and the issue of a Service Bulletin to alert operators of possible welded boss cracking.