Dependence of Vibration Characteristics on Grease Service Levels in an AH-64D Intermediate Gearbox

The purpose of this experiment is to determine if the intermediate gearbox (IGB) grease service level can be characterized through existing condition-based maintenance (CBM) practices, which include vibration monitoring sensors and analysis algorithms, in the IGB of the AH-64D. A secondary objective is to quantify a common phenomenon in the gearbox–the expulsion of lubrication during different times of operation. If both goals are achieved then common maintenance practices on the aircraft can be changed to reduce workload. Three different gearboxes of similar condition were used for this experiment. Each gearbox was run in a two hour test under different loading conditions five separate times. In each iteration, the gearbox contained a different volume of grease that increased in 25% increments of the standard service level (0%, 25%, 50%, 75%, and 100%). The vibration data analyzed was collected through the modern signal processing unit (MSPU) to find a trend against the different amounts of grease. To complete the secondary goal, the amount of grease ejected during the initial parts of the runs was captured and weighed. This will be used to obtain a constant number at which to service the IGB and prevent the "burping" of grease during operation. . More research should be conducted to discover whether higher-order vibrations analysis will allow this fault to be detected.