DESIGN AND CERTIFICATION OF THE MODEL 429 SUPERCRITICAL TAIL ROTOR DRIVE SHAFT

This paper discusses the design and certification of the tail rotor drive shaft system under development for the Bell Model 429 Helicopter. The 429 tail rotor drive shaft differs from prior Bell Helicopter drive shafts in that it is a supercritical drive shaft, and differs from other rotorcraft supercritical drive shafts in that it uses composite material drive shaft tubes instead of conventional metallic tubes. The advantages and design challenges of the supercritical configuration are discussed and compared with those of a conventional subcritical design. Likewise, the benefits and challenges associated with the composite material construction will be discussed in relation to conventional metallic designs. Weight and cost metrics comparing supercritical composite, subcritical composite, and subcritical metallic designs are presented. Additionally, the certification methodology being used to demonstrate compliance with supercritical design and composite material requirements is discussed.