CH47D Forward Transmission Input Pinion Seeded Fault Test

This paper summarizes the Forward Transmission Input Pinion Seeded Fault Test that was accomplished as a portion of the validation process for the Boeing Rotorcraft Transmission Vibration Diagnostic System (TVDS) Analyzer. The test specimen was a CH47D forward transmission input pinion with a known defect machined into one of its tooth roots. The specimen was operated at typical CH47D operational load and speed conditions in order to initiate and propagate a fatigue crack from the defective tooth root. During the testing, the TVDS analyzer monitored the specimen real time and successfully provided sufficient warning time of the impending failure. Following testing, the TVDS data (acquired real time) was evaluated along with a post-test fractographic evaluation of the pinion’s fatigue crack. During the post-test fractographic evaluation, beach marks and striation spacing of the fatigue surface were analyzed. This data was correlated with the TVDS analysis technique output data and detailed test data recorded in the engineering log books to define the initiation and rate of propagation of the fatigue crack during the test.