The overview of KARI bearingless main rotor hub system

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Kim, D.K.
Kim, S.
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The new composite bearingless main rotor hub system had been developed and tested on the whirl tower at Korea Aerospace Research Institute (hereinafter KARI). The purpose of this program is to prepare future helicopter development program and to study the advanced core technologies in helicopter composite rotor hub system. KARI bearingless main rotor hub system (hereinafter KARI BMR) is an all composite, four bladed, soft-in-plane, crucial cross attachment concept for a 7,000lb gross weight helicopters. The KARI BMR was developed for 7,000lb class but tested with BO-105 blades (5,000lbs class) on the whirl tower since the available blade is the only BO-105 blade in KARI. Based on the KARI experience on composite rotor system for research and development, KARI could start to launch the national research program on bearingless rotor hub system development. In Korea, there had been no research activities on full-scale bearingless rotor hub system until 2010. But through many experiences on the previous several rotor research projects, KARI could have confidence in the opportunity of the advanced rotor hub system research such as a full-scale composite bearingless rotor hub system. The KARI BMR has several core composite parts such as flexbeam, torque tube and damper system. The primary part is the flexbeam to give elastic hinges for flapping, lagging and feathering. The sectional shape and construction design of flexbeam are complicated to give these hinges as one part. The secondary part is the torque tube to give pitch change of blade with appropriate stiffness. The sectional shape and construction design of torque tube are also complicated to give appropriate lag stiffness and torsional stiffness with a low aerodynamic drag. The shear restrainer and damper system is other’s parts. The overview program of KARI BMR was introduced in this paper. The general development procedure and activities were also described. The overview of design and analysis were explained generally. In consequence, the basic qualification tests such as sectional property test, structural test and whirl test were conducted and the brief results were described in this paper. Consequently, KARI BMR Program showed the improvement of weight advantages, aerodynamic drag reduction and the reduction of the total number of rotor hub parts. In conclusion, it was convinced that the development object have been achieved or the core technology of BMR have been achieved in KARI.