DSTO-HUMS2001 CDROM
Paper 5-14 page - 1
Vibration-Based Helicopter Gearbox Health Monitoring - An Overview of the
Research Program in DSTO
A.K. Wong
Airframes & Engines Division
Aeronautical & Maritime Research Laboratory
Defence Science & Technology Organisation
Melbourne, Victoria, AUSTRALIA
Abstract
The Defence Science and Technology Organisation (DSTO) has a long and respected
association with vibration-based health monitoring technologies, and this paper
presents an overview of the DSTO’s program of work in this area. The paper briefly
charts through more than two decades of research and development, arriving at the
current work program of advanced algorithm development, experimental validation,
field deployment, and commercialisation. The presentation concludes with glimpses
of the future directions that DSTO will embark on.
1. Introduction
DSTO has been active in the development and application of vibration-based health
monitoring technology for over two decades. Early investigations included the use of
spectral analysis for the condition assessment of gearboxes used in aircraft operated
by the Royal Australian Air Force, covering both gears (McFadden, 1980a, McFadden
and Edwards, 1981, McFadden, 1981) and bearings (Swansson and Favaloro, 1984,
McFadden and Smith, 1984). In 1977, the Royal Australian Navy (RAN) had the
foresight to establish a program of vibration analysis (VA) to assist with the health
assessment of the main rotor gearboxes (MRGB) of its fleets of Sea King and Wessex
helicopters, and DSTO was called upon to serve as technical adviser (McFadden
1980b). The system selected for this program was based on "off-the-shelf"
equipment, and included a single accelerometer mounted on the MRGB, a battery-
powered portable FM tape recorder, and a high resolution spectrum analyser.
Vibration recordings of each gearbox were made at intervals of 25 to 50 flying hours,
each consisted of five records of approx. 30 seconds duration, covering a range of
torque settings. The spectral results were then examined by an experienced analyst
and compared with the previous spectra for the same and other gearboxes. By 1979,
this program was well established, and one of its first successes was in the detection
of two damaged bearings in the MRGB of a Sea King shortly after overhaul. Whilst
none of the other monitoring techniques used at the time could reveal any anomaly,
McFadden (1980b) was able to deduce the type and locations of the fault, which were
subsequently confirmed by physical examination of the gearbox during overhaul.
Unfortunately, this early success was quickly overshadowed by a more serious fault
that slipped through the net.
In December 1983, an RAN Wessex crashed into the Bass Strait due to a catastrophic
fatigue failure of the input bevel pinion in the MRGB (WAK143) resulting in the loss
of two lives. As this particular aircraft had been a candidate of the then existing VA
program, it became clear that the analyses employed were simply not able to provide
