This SAE Aerospace Information Report (AIR) examines the need for and the application of a power train usage metric that can be used to more accurately determine the TBO for helicopter transmissions. It provides a formula for the translation of the recorded torque history into mechanical usage. It provides examples of this process and recommends a way forward. This document of the SAE HM-1 IVHM Committee is not intended as a legal document and does not provide detailed implementation steps, but does address general implementation concerns and potential benefits.
Operators of large transport helicopters equipped with a Health and Usage Monitoring System need to have the ability to track the power usage of the main rotor transmission and tail rotor drive system so as to concomitantly track health and usage for the purpose of accurately determining the times between overhauls for each major assembly.