Advanced Technology Applied to the CH-47D Drive System

The U.S. Army CH-47D helicopter modernization program incorporates improvements in all major subsystems. The drive train has been redesigned to incorporate evolutionary improvements which will increase reliability, survivability, and maintainability. This paper describes the background experience that led to the selection of VASCO X-2 high-hot-hardness gear steel; it also discusses design improvements in the integration of components, in lubrication and diagnostic systems, in overrunning clutches, and in noise reduction. New capabilities to predict and measure gear bending stresses and resonant frequencies have been developed and are described as part of a systems design approach.