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Engine trend monitoring limits

Issue number: AO-2012-150-SI-02
Who it affects: All operators of A380 aircraft with Engine Alliance GP7200 engines fitted
Issue owner: Engine Alliance
Operation affected: Aviation: Air transport
Background: Investigation Report AO-2012-150
Date: 09 September 2013

Safety issue description

The threshold limits for the engine trend monitoring program were not set at a level that provided sufficient opportunity for inspection of the engine before failure could occur from the effects of HPT stage-2 nozzle degradation.

Proactive Action

Action organisation: Engine Alliance
Action number: AO-2012-150-NSA-012
Date: 09 September 2013
Action status: Closed

As a result of the occurrence, the engine manufacturer enhanced the trend monitoring system to receive alerts earlier. Under the new process, the change in exhaust gas temperature on engine serial number P550121 would have issued an ‘Urgent – Prior to next flight’ notice two flights prior to the occurrence flight.

ATSB response:

The ATSB is satisfied that the action taken by Engine Alliance adequately addresses the safety issue.

The introduction of the new HPT stage-2 nozzles and repetitive inspections in place for both the new and old nozzle configurations will reduce the prevalence of HPT stage-2 nozzle distress and will identify nozzle distress before it progresses to a stage that would impact flight. The enhanced trend monitoring system that has been put in place provides additional assurance that an impending nozzle failure is identified in time for preventative maintenance action.

   
Current issue status: Adequately addressed
Status justification: The introduction of the new HPT stage 2 nozzles and repetitive inspections in place for both the new and old nozzle configurations will reduce the prevalence of HPT stage-2 nozzle distress and will identify nozzle distress before it progresses to a stage that would impact flight. The enhanced trend monitoring system that has been put in place provides additional assurance that an impending nozzle failure is identified in time for preventative maintenance action.
 
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Last update 08 January 2014