The Royal Australian Navy commenced a regular program of vibration analysis of power train components for the Wessex and Sea King helicopters in the mid 1970's. This program, termed the RTVAP (Recorded Tape Vibration Analysis Program), continued through until the mid 1990's. The catastrophic failure of a RAN Wessex main transmission in 1983 accelerated the development of advanced diagnostics at DSTO, for immediate application to this program. This led to the refinement of algorithms, especially those related to gear faults, and the introduction of digital resampling for data processing. The digital re-sampling replaced the earlier procedure of phase-locked-loops, and has been used by DSTO through to the present day. During this period a number of laboratory experimental programs were carried out, to evaluate tooth crack detection effectiveness, and the early attempts at a prognostic capability. Construction of a 700 HP full-load test rig was completed, to test Bell 206B-1, and Squirrel AS350BA main rotor transmission, for fault detection. These test rigs also included in-line wear debris sensors. Later developments included the building and test of two in-flight advanced diagnostic systems. Algorithm development was assisted by access to seeded fault data from a variety of sources. The Sea King, Seahawk, Seasprite and Chinook fleet are currently equipped with integrated sensors and wiring, and the RAN and Australian Army are evaluating the options for replacement of these systems which may include on-board units. The use of vibration health monitoring is not mandated in the Australian fleet, although FDR's and CDR's are in most aircraft, and maintenance is still aligned with processes and procedures that were in place prior to the advent of the advanced capability. This paper reviews the key outcomes of the DSTO research programs, and describes recent benefits gained from the application of these techniques to a specific failure mode in the Sea King helicopter.
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