DESIGNING SAFETY INTO HELICOPTER TRANSMISSIONS

The Boeing Model 234 helicopter is a commercial derivative of the U.S. Army CH-47C helicopter. Although the Chinook has an excellent safety record, features have been incorporated in the 234 that further enhance the design and provide additional safety. Specific items discussed are the use of double-vacuum-melt steels; shotpeening of all critical components; nital etching of all machined and ground surfaces; ultrasonic inspection of the gear steel at the mill; fatigue testing and qualification procedures; overload testing of all the main drive gears and shafting; and auxiliary oil capability.