Optimizing Maintenance and Flight Safety with In-Service Grease Analysis Rich Wurzbach, MRG Labs, York, PA, USA Michael Johnson, AMRRI, Franklin, TN, USA
Abstract Rotary-wing aircraft such as helicopters rely on flight controls and drivetrains that contain multiple grease-lubricated components including bearings, swashplates, and splines. Periodic relubrication of these components during established maintenance intervals is the primary method for replenishment of grease prior to degradation, to ensure reliable and safe operation of assets. A project was completed to develop techniques for sampling and analyzing grease from the drivetrain components of rotarywing aircraft. The project was developed to evaluate the effectiveness of existing maintenance intervals, and to develop engineering data sets to propose interval adjustments. Such adjustments could be made to enhance safety and performance, while finding opportunities to reduce manpower and operational costs. This project incorporates new technologies including the use of sampling tools outlined in ASTM D7718, and new analysis methods that allow for small sample volume evaluation of component wear, as well as grease contamination, oxidation, and consistency changes. This paper will present the progress that has been made: 1) development of means to obtain representative samples from bearings, swashplates and splines; 2) data analysis methods that combine maintenance and operating histories with grease analysis results; and 3) findings that may lead to safer and more economical operation of critical assets. Background Continuous evaluation and enhancement of flight safety, reliability, and cost-effectiveness are at the core of aircraft operations and maintenance. This applies both to newly designed and developed platforms, and those that have been in operation for many years. Some designs, particularly in military applications, have been utilized effectively for decades. New technologies have emerged that can aid in this continuous evaluation to find applications to ensure the continued safe and reliable operation of these assets. Grease analysis has lagged significantly behind oil analysis for many years, not only in aerospace assets, but for lubricated machinery of all types. Over the last 10 years, advancements have been made to address the two main barriers to effective grease monitoring: obtaining representative samples, and having a meaningful test slate that can be applied to very small sample sizes. The purpose of this study is to reinforce the engineering basis for grease replenishment and servicing intervals for deployed aircraft. This study has produced significant findings related to the consistency, oxidation state, and contamination of in-service greases as well as levels of wear, thus providing a basis for data-driven decisions related to reliability, flight safety, and cost of operation of helicopters.
-6NLGI Spokesman | VOLUME 84, NUMBER 3 | July/August 2020
