Design and test evaluation of FBR bearingless main rotor

A new main rotor system has been developed and tested in flight at Fuji Hea vy Industries Ltd. (FHI). The rotor system, designated the FBR (Fuji Bearin gless Rotor), is an all composite, four-bladed, soft-inplane bearingless ma in rotor for a 10,000 to 12,000 lb gross weight helicopters. The FBR was te sted on a Bell Model 412 helicopter. Based on the advanced composite techno logy at FHI along with the extensive research on aerodynamics, noise, and v ibration, the rotor system was designed and developed for new generation he licopters with challenging design objectives. The paper begins by providing a description of the FBR rotor system, the overviews of the aerodynamic/lo w noise and low vibration/dynamics design are presented. The flight test re sults with respect to performance, handling qualities, noise emission, and vibration levels are discussed. Overviews of structural features, strength substantiation, and ground test results are also presented. The rotor syste m has shown an improvement in high speed performance, a significant reducti on in noise emission and a remarkable reduction in vibration levels. Remark able reductions in hover noise and cabin noise were observed which were une xpected given that the low noise design was concentrated mostly on a high s peed condition, and no intentional design effort was made for cabin noise. In conclusion, it was confirmed that the design objectives have been achiev ed or surpassed for the FBR rotor system.