Many Category A helicopters fly sectors which are over one hour and in the event of a main gearbox loss of oil could require a forced landing over hostile terrain. The purpose of this research was to evaluate methods of improving both the reliability of pressurized lubrication systems and the ability to continue powered operation for an extended period having suffered loss of oil. Therefor the objective of this project was a survey of different gearbox lubrication system architectures, options for minimising occurrences of loss of oil events, and investigation of possible design solutions to increase the capability of continued operation after loss of oil.
Possible design features were identified which may have the potential to increase the duration in which a gearbox can continue to operate having suffered loss of oil. The findings were demonstrated by performing a test using representative hardware which adequately simulated the relevant parts of an actual rotorcraft main gearbox under typical operating conditions, i.e. speed (RPM), torque and temperature for continued flight.