Helicopter drive system diagnostics through multivariate statistical process control

The Naval Air Warfare Center has developed a Helicopter Integrated Diagnostic System (HIDS) which performs mechanical diagnostics on a helicopter's drive system. Diagnostic indicators indicative of the mechanical health of the drive system components are derived from vibration data through a combination of statistical and signal processing methods. This paper discusses the application of a multivariate statistical process known as Hotelling's T2 analyysis to HIDS diagnostic indicators. Multivariate analysis uses a composite function of multiple quality indicators to produce a single, trendable indicator that characterizes the state of the monitored process. A statistically valid method of creating and adjusting an alarm threshold for the resultant composite indicator is inherent in the method. When applied to mechanical diagnostic indicators from helicopter drive system seeded fault tests, the method produced timely and unambiguous fault identification with a reduced number of false alarms as compared to current diagnostic methods.