Sikorsky Composite Rotor Hub Development

The current production S-76 and BLACK HAWK main rotor hubs are a combination aluminum and titanium structure with two elastomeric bearings per blade. The advanced composite hubs under development at Sikorsky Aircraft are a combination fiberglass and graphite structure with a single elastomeric bearing per blade. The hubs are designed to be interchangeable with existing fully articulated hubs. Presented will be the composite structure development of the hubs in the prototype phase of the programs. The designs have beendeveloped through a combined effort of rotor design engineering and composite manufacturing to yield a damage tolerant/safe life concept with demonstrated manufacturing producibility. Damage tolerance is obtained through a combination of isotropic material coupled with unidirectional fiberglass to yield a redundant structure with an infinite life and very high resistance to cross structure cracking. In addition, the single elastomeric bearing per blade will have a fatigue life in excess of 4000 hours and is relatively simple to replace. The progression of the S-76 design from the initial concept through the frozen prototype concept will be explored. The development testing effect on the design is integrally woven through this progression along with the manufacturing considerations. The result is an optimum design through an extensive use of composite material which is lighter, has a higher strength and is more easily inspectable than the existing S-76 rotor head.