Engine trend monitoring limits

Safety issue

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.
Issue number	AO-2012-150-SI-02
Issue owner	Engine Alliance
Transport function	Aviation: Air transport
Date issue released	09/09/2013
Issue 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.

Action type	Proactive action
Action number	AO-2012-150-NSA-012
Organisation	Engine Alliance
Action date	09/09/2013
Action description	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.
Action status	Closed