Future helicopter transmission oils

For many years helicopter transmissions have shown low reliability relative to planned overhaul lives and to other comparable lubricated systems. Reasons for this include the extremely wide range of conditions encountered by the lubricant in helicopter transmissions and also the requirement that, in many cases, the oil be common to both transmission and gas turbine engines. Recently acquired understanding of lubrication mechanisms shows that potential exists both for improved performance and for the ability to cater for higher temperatures by the development of new helicopter transmission oils based on synthetic lubricants. This paper discusses the particular lubricating problems associated with helicopter transmission lubrication and describes test methods and formulation approaches to improving such lubricants.