Helicopter Drive System On-Condition Maintenance Capability
UNITED TECHNOLOGIES CORP STRATFORD CT SIKORSKY AIRCRAFT DIV
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This report presents the results of a study that was conducted to determine the feasibility of operating CH-5354 gearboxes without any scheduled removals for overhaul, that is, being maintained on-condition. A reliability analysis technique was developed to establish gearbox hazard functions, which express the relationship between the equipment failure rate and its operating time. Furthermore, design concepts and procedures were identified which enhance on-condition maintenance for CH-5354 gearboxes. Concurrent with the initiation of an on-condition maintenance policy, it is recommended that field and depot maintenance of on-condition gearboxes be monitored. The fact that data for this study was obtained from aircraft that flew in Vietnam where they saw overtorque situations reinforces the practicality of an on-condition maintenance philosophy for the transmission system. The reliability analysis technique developed by this study used hazard functions of individual generic component failure modes as building blocks to construct the gearbox level hazard function for each category of failure mode. The method permits evaluation of current design practices. Its real benefit is that it will allow future gearbox reliability requirements to be evaluated by the designer so that reliability is understood and designed in.