Integrated health monitoring of gas turbine engine wire harnesses and connectors

Modem aircraft contain miles of wiring and hundreds of wire connectors that must function properly to avoid high maintenance costs and safety hazards. This research investigates health monitoring techniques applied to a gas turbine engine wire harness in order to, first, detect severe operation and service loads on the harness, and, second, identify any faults induced by these loads. The work presented will focus on three passive health monitoring techniques: 1) an inverse frequency response function (FRF) approach for sensing loads on the connector; 2) phase plane diagrams which detect changes in system parameters; and 3) transmissibility functions which also identify variations in system properties. The inverse frequency response method estimates the magnitude and direction of abnormal loads that could be experienced during a hard landing, or when connectors are jerked or stepped upon. An iterative estimation approach is presented that is able to monitor multiple force locations with minimal sensors. When a system is subject to harmonic oscillations and different levels of induced damage in the form a loose wire harness connection, the area enclosed by the data on a velocity-versus-displacement phase plane diagram changes and is most indicative of damage near resonant frequencies. Variations in the transmissibility functions of the system, which make use of random operational excitations, are shown to be accurate indicators of a loose wire harness connection. To minimize the required hardware for a health monitoring system, only one miniature, tri-axial accelerometer is used for the experimental validation.