A Survey of Aircraft Engine Health Monitoring Systems

This paper presents a survey of engine health monitoring systems for commercial aircraft. The state of practice is explored first, with the purpose of identifying the shortcomings of current systems. The state of the research to address these shortcomings is them surveyed to explore the alternatives. Research and monitoring applications for various other types of engines provide a good basis for further exploring the topic. This survey is meant to serve as a precursor to engine health and monitoring research at the NASA Ames Research Center. ENGINE MONITORING SYSTEMS Aircraft engines constitute a complex system, requiring adequate monitoring to ensure flight safety and timely maintenance [28]. Cockpit displays indicate engine performance through vital information such as rotational speeds, engine pressure ratios, exhaust gas temCopyright 1999 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. peratures, etc. Oil supply to critical parts, such as bearings, is vital for safe operation. For monitoring fuel and oil status, indicators for quantity, pressure, and temperature are used. In addition to these crucial parameters, vibration is constantly monitored during engine operation to detect possible unbalance from failure of rotating parts, or loss of a blade. Any of these parameters can serve as an early indicator to prevent costly component damage and/or catastrophic failure, and thus help reduce the number of incidents and the cost of maintaining aircraft engines [55]. To accomplish this demanding task, engine monitoring systems (EMS) have become increasingly standard in the last two decades, in step with advances in aircraft engines and computer technology. The first Aircraft Gas Turbine Engine Monitoring System guide was published by the SAE in 1981 [1]. It provided guidelines to airlines and engine manufacturers in their design and implementation of EMS. The current state of practice focuses on using some form of EMS on all aircraft, especially on military aircraft. For commercial aircraft, routine use of EMS for Engine Health Monitoring (EHM) poses challenges, mainly due to the abun-