How lubricant formulations and properties influence the performance of rotorcraft transmissions under loss of lubrication conditions

Abstract

Loss of lubrication (LOL) in a rotorcraft transmission causes erratic degradation of drivetrain components due to direct surface contact thereby increasing the frictional heat in the system. This article studies the ability of synthetic and mineral-based lubricating oils typically used in the aviation industry regarding their physical properties, chemical composition, and detailed chemical structure to extend the longevity of the rotorcraft transmissions in the event of LOL. The lubricating oils were subjected to boundary lubrication tests using a FZG gear test rig and two lab-scale tribometers, cylinder-on-ring and ball-on-disc. The results provide an enhanced ranking of the selected lubricating oils based on their load-carrying capacity and scuffing resistance under LOL conditions complemented by the consideration of the oil chemistry.