Understanding UH-60L Helicopter Main Generator Vibration Signatures

摘要

The main generators on the UH-60L helicopter provide power to on-board electrical and avionic equipment. Generator condition has traditionally been based upon a built-in sensor to provide detection of an internal bearing fault, as well as an aircraft system that detects the loss of electrical power. These sensors are effective in the detection of a generator failure, but the detection is normally too late to avoid unscheduled maintenance or to prevent avoidable generator and drive system degradation. Early detection and timely maintenance intervention was made possible during a two year demonstration of the IMD HUMS vibration diagnostics capability. This paper reports the results of this demonstration which tracked the condition of over 80 generators, as well as the condition of the power train driving and influencing the condition of these generators. The data has shown that many generator failures are in some measure caused by significant wear of bearings in the accessory module. This bearing defect in the power train is thought to be the result of normal wear which subsequently causes the spline adapter and generator to follow one of three primary degradation scenarios. Examples of these scenarios are presented to support this finding of probable cause and effect. In addition, the lessons learned reported in the paper will enable the Army to achieve early automated detections of generator related defects. These early detections will enable appropriate maintenance actions to be ordered to coincide with major inspections and prevent unnecessary damage and unnecessary removals while improving readiness and responding to the tenants of Condition Based Maintenance.