Optimising Aircraft Engine Shop Visit Rate

Sofema Aviation Services (SAS)?www.sassofia.com?– considers best practices related to optimisation and generating improvements in the Aircraft Engine Shop Visit Rate

Introduction

By focusing on operational practices to reduce stress on engines, and implementing stringent maintenance protocols, operators can significantly lower the shop visit rate of their engines.

These measures not only extend the operational life of the engines but also lead to substantial cost savings in maintenance and spare parts management.

• Adopting these best practices ensures that operators can maintain high levels of reliability and efficiency while minimizing unnecessary expenditure.

Implement Rigorous Maintenance Protocols

• Effective LLP Management:?Keeping a close track of the life cycles of LLPs and scheduling timely replacements can prevent unexpected failures and reduce unplanned shop visits.

>> Effective LLP management involves accurate tracking and forecasting based on usage patterns.

• Workscope Optimization:?Tailoring the scope of maintenance works to address specific needs rather than performing unnecessary full overhauls can reduce both time and cost.

>> An optimized work scope should focus on critical components and known issues.

• Incorporate Reliability Improvement Modifications:?Constantly updating engines with the latest reliability improvements and modifications can prevent common failures.

>> Operators should stay informed about manufacturer recommendations and industry best practices to ensure their engines incorporate the latest advancements.

• Engine Health Monitoring: Employing advanced engine health monitoring systems allows for real-time tracking of engine performance and early detection of potential issues.

>> Proactive health monitoring can preempt major failures and schedule maintenance activities more effectively.

?Factors Influencing the Shop Visit Rate

• High EGT margin – EGT Margin is a parameter used to evaluate and track engine time on-wing and health. An engine’s EGT Margin is the difference between the peak EGT incurred during take-off and the certified redline.

>> The level of EGT margin of an engine is a function of an engine’s inherent design.

• Engines with high EGT margins remain on the on-wing longer and thus tend to have lower shop visit rates.
• EGT margin deterioration typically results from hardware distress as a result of the gradual increase in clearance between the turbine blade tips & surrounding static seals or shrouds.
• Combustor Distress – As the gas path of an engine deteriorates, it becomes necessary to adjust the engine power to a higher setting to obtain the required thrust.
• Higher power settings contribute to increased fuel flow, which creates higher EGT and reduced EGT margins.

Note – EGT margin deterioration is often the primary driver of engine removals, particularly for engines operating on short-haul flights.

• Stub Life Considerations

>> The term LLP stub-life is used to represent the shortest life remaining of all LLPs installed in an engine.

>> Engines whose inherent design includes LLPs with high stub-lives will tend to experience lower rates of engine removals compared to engines with lower LLP stub-lives.

>> Engines designed with high LLP stub lives have overall operational advantages, particularly if operating on short-haul routes.

Cost Implications and Spares Management

• Control SVR to manage costs:?Since the shop visit rate directly influences maintenance costs, reducing the SVR can result in significant cost savings.

>> Lower SVRs reduce the need for spare engines, maintenance man-hours, and associated operational disruptions.

• Optimize spare provisioning:?By maintaining a lower SVR, operators can reduce the need for a large inventory of spare engines.

>> This not only saves on the cost of spares but also reduces the capital tied up in holding these spares.

>> Optimizing spares management involves balancing the shop repair turn-time with available spares to ensure operational efficiency without overstocking.

Operational Reliability

• Higher thrust levels generate greater thermal stress, accelerating wear. Utilizing thrust derate options where possible can significantly reduce engine stress, especially on shorter flights.
• Implementing a policy of using derate settings can help in managing and prolonging engine life.

Next Steps

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