Evaluation and Implementation of Low Core Hardness Gears in the SB>1 DEFIANT JMR Technology Demonstrator Aircraft

Abstract The Sikorsky Boeing SB>1 DEFIANT is a technology demonstrator aircraft that was built under the Joint Multi-Role Technology Demonstrator (JMR TD) program to address the next generation performance requirements of the US Army Future Vertical Lift (FVL) initiative. During the development of the SB>1 DEFIANT technology demonstrator aircraft several manufacturing lots of gears were produced with a core hardness that was 10-30% below the minimum engineering requirement. The defect was not detected until a large population of gears was near completion. To prevent significant program cost and schedule impacts, a safe load capacity for the discrepant gears was determined via test and dynamically loaded ground test articles for SB>1 DEFIANT technology demonstrator aircraft began qualification testing with the low hardness gears. The low hardness issue, root cause, and test method to establish a safe operating load limit are discussed.