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The ability to complete a mission after loss of drive system lubrication has emerged as an important design consideration. Loss-of-lubrication operalion has become a basic military requirement to improve survivability after eombal damage; it is also applicable to commercial offshore oil rig operations, where an unscheduled landing would he hszsrdaus. This paper lraces the developmentsl test hislory of loss-of-lube operation condueled on current production helicopler drive systems. The key resulls of several test programs conducled on the UlTAS and AAH drive syslems are presented. The influences of gear and bearing malerials and processes on loss-of-lube operation are also presented. The techniques that were used to achieve successful loss-of-lube operation are defined along wilh important design eonsiderstions. Conclusions reached from experimental testing indicate that successful loss-of-lube operation is dependenl an the ability of the gear, bearing, and housing materials lo sustain thermal loading, increased gear backlash and internal bearing clearances, small reservoirs of residual oil inside the transmission, and use of emergency lubrication systems.

Long before the legendary Queen Dido cleverly maximised the area of future Carthage by choosing the optimum perimeter shape, man probably consciously or subconsciously tried to optimise his designs as well as his actions. In a more modern time, the post Renaissance period witnessed development of the principles of optimisation on a rigorous mathematical basis, as exemplified in works of Newton, Leibniz, Euler and many others. Eventually, those optimisation ideas were even transplanted by Leibniz and his school to the field of general philosophy, providing an attractive target for the merciless satire of Voltaire in Candide.

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