Maintenance Interval Adjustment

Abstract

How does an organization that is mainly used to conduct maintenance to its aircraft according to manufacturers prescriptions adapt a method with which they can change and optimize their maintenance policies? This thesis report describes the state of the art in maintenance- and related reliability engineering that is used to obtain a step-by-step method for ’in house’ Aircraft Maintenance Programme (AMP) alterations. A summary of the proposed method in a single figure can be found in fig. 5-1. The method first contains a business part where organizational alterations and regulations are mirrored against some common Maintenance Steering Group (MSG) and Reliability Centered Maintenance (RCM) approaches to combine into a Maintenance Review Board (MRB)-cycle that can be applied to the Royal Netherlands Airforce (RNLAF). Secondly, a reliability analysis part that uses RNLAF life data from all 8 types of aircraft is designed with use of Weibull and Failure Mode Effect and Criticality Analysis (FMECA) theory. This combines into a 11-step model that closely follows aviation regulations and that should give the associated reliability engineers within the RNLAF the necessary tools to start assessing the AMP of aircraft that fall under their responsibility. Finally, the model is tested with two cases. The 125hrs lead-lag link inspection of the AH-64 Apache and the hydraulic pumps of the CH-47 Chinook proved to be sufficient examples to apply and verify the method. Life data is analyzed and all the steps of the model are performed, which has resulted in advice to change the 125hrs interval to 250hrs and to apply an inspection/replacement interval to the hydraulic pumps in order to proactively monitor the wear and preventively replace the pumps to reduce corrective downtime.