An Approach to Fault Diagnosis and Failure Prognosis of Spline Wear

The Bell 407 engine adapter spline, which transfers power from the engine to the main rotor gearbox (MRGB) and tail rotor gearbox (TRGB), is prone to wear slowly over time. Visually inspecting the spline periodically for tooth wear costs the operator time and money due to helicopter downtime. Bell Helicopter and Georgia Tech have teamed together and developed a method, which accurately detects and quantifies spline tooth wear without the need to visually inspect the spline. Using offthe- shelf sensors to detect spline wear modalities and in-house software to analyze test data from a spline with induced wear, Bell Helicopter and Georgia Tech have investigated spline whirling, vibration, and phase shift to successfully demonstrate that induced spline wear is detectable. The use of this data for determining spline remaining useful life is explored and a methodology is presented by Georgia Tech.