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Design of Helicopter Transmission for “On-Condition” Maintenance
ISSN: 0148-7191, e-ISSN: 2688-3627
Published February 01, 1970 by SAE International in United States
Annotation ability available
This paper considers the reduction of helicopter “cost of ownership” by the process of reducing the frequency of transmission overhaul. Reasons for time scheduled overhauls (TBO) and their validity to helicopter transmissions are explored. Failure functions for several transmissions are shown and individual failure modes explored for indications of failure function trends beyond the current operating regime.
The conclusion is reached that significant cost savings are possible with On-Condition maintenance.
The only valid reason for retaining a TBO in the mature transmission is the presence of wearout type non-detectable safety-affecting failure modes. These generally take the form of structural fatigue originating from fretted joints or surfaces or slow wear in internal spline and clutches. These modes may exist in some of today's transmissions and, if so, represent the limiting TBO. The full potential of On-Condition operation may not be realized without safety oriented changes.
These changes include concepts which minimize or eliminate fretting, provide fail safety via redundancy or are tolerant to damage. Further improvement in condition monitoring and early, concentrated, development testing are the necessary ingredients for On-Condition maintenance of tomorrow's helicopter transmissions.
CitationHarding, D. and Mack, J., "Design of Helicopter Transmission for “On-Condition” Maintenance," SAE Technical Paper 700587, 1970, https://doi.org/10.4271/700587.
- Casenia R. W. “Reliability Disciplines - Determine the Optimum Replacement Times for Major Helicopter Mechanical Components, of Helicopters” SAE Paper 855B April 1964
- Burroughs L. K. “Study of Helicopter Transmission System Development Testing, Final Report” Sikorsky Ser 50547 June 1968
- Coronato A. A. “Overhaul on Condition - Eliminates TBO’ AHS Forum May 1961
- Tallian Tibor “Weibull Distribution of Rolling Contact Fatigue Life and Derivations Therefrom” ASLE Transactions 5 1 April 1962