Abstract: To meet the requirements of the advanced helicopter transmission system, a type of helicopter transmission lubricating oil was developed with reference to specification issued by the U.S. Department of Defense DOD-PRF-85734A, using polyol ester as a base oil, the self-synthesized oligomer antioxidant and extreme pressure antiwear agent. The properties of the synthesized lubricating oil are similar with a foreign reference sample in viscosity, acid number, rubber compatibility and thermal oxidative stability, but better in extreme pressure antiwear property. The bench test and flight test proved that the developed lubricating oil can be used in advanced types of helicopters.

Key words: helicopter, transmission system, lubricating oil, extreme pressure and antiwear performance, oxidation stability