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Repair of Helicopter Gears

05FTM15

Authors: Suren Rao and Doug McPherson, The Pennsylvania State University and Gary
Sroka, REM Chemicals, Inc.
In order to reduce costs by extending the operational life of the sun and input pinion gears of a helicopter
transmission, scraped gears were subject to a superfinishing process. This process was found to remove
minor foreign object damage by uniformly removing a minimal amount of material on the gear teeth, while
meeting original manufacturing specifications for geometry. The process also resulted in enhanced surface
quality and did not exhibit detrimental metallurgical effects on the surface or sub--surface of the teeth. The
process was also found to eliminate gray staining, an early precursor to pitting. This paper describes the
results of the helicopter gear repair project and includes the geometry and metallurgical evaluations on the
repaired gear. Further effort to characterize the durability and strength characteristics of the repaired gear is
ongoing.
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