A Guide to Extending Times Between Overhaul for Rotorcraft Power Train Transmissions Using Monitoring Data
|Publication Date:||1 June 2020|
Time in Service (TIS), or flight hours, logged in maintenance records against an installed rotorcraft transmission is normally used as the "official" time on wing metric for the transmission's component wear out inspection interval requirement and, in some instances, retirement change on life limited parts. This AIR addresses traditional methods of transmission TBO extensions and introduces rotorcraft transmission monitoring usage metrics that could be used to modify TIS inspections by tracking torque to determine both loads on life limited parts and component wear.
This is a document of the SAE HM-1 Committee intended to be used as a technical information source and is not intended as a legal document or standard. This AIR does not provide detailed implementation steps, but does address general implementation, past experience, concerns and potential benefits.
The purpose of this SAE Aerospace Information Report (AIR) is to provide information and guidance for use of monitoring data from transmissions in the rotorcraft power trains so as to enhance or replace the traditional TIS metric for inspection intervals and life limited component replacement. The scope of this document is limited to those inspections, analyses, and devices that can be considered appropriate for routine maintenance.
Some commercial helicopter operators such as those supporting the Oil and Gas Producers (OGP) community have helicopters equipped with HUMS and have trained HUMS data analysts. The addition of HUMS functionality has enhanced the flight safety of large transport helicopters supporting the OGP around the world (see Appendix A: , , , and ) and offer the opportunity to enable MSG-3 maintenance for rotorcraft. Operators recognize that more accurate monitored data than logbook Flight Time (FT also known as TIS) data offers them an opportunity to better manage aircraft inspections and life limited part replacement while potentially achieving both cost and safety benefits. As such, commercial helicopter operators desire to utilize the transmission monitoring data to improve operational efficiency and effectiveness.
All of the major rotorcraft OEMs in the UK, Europe and the USA are involved in the refinement and implementation of MSG-3, Volume 2 (for helicopters). The information provided herein provides a potential point of departure for the implementation of MSG-3 maintenance intervals for rotorcraft transmissions as the OEM engineering teams develop the details of MSG-3 Volume 2 (see Appendix A: , , and ).