High Speed Gears Overheating Due To Lubrication

Abstract

Rotorcraft gearboxes are quite unique in the industry as they generally deal with high power, high overall gear ratio, low available space and a strong push towards weight reduction. The main functional components (gears and bearings) typically require pressurized lubrication when for any reason oil is not effectively drained away it can lead to overheating, especially on high-speed gears. Two cases are shown here to exemplify the issue and its solution the first example represents an MGB where one of the Input Modules got entirely filled with oil until the issue was understood and then easily solved the second example shows a Nose Gearbox where an unexpected windage phenomenon prevented oil drainage to the scavenge pump, thus leading to extreme and almost instantaneous overheating of the module.