Reducing helicopter 1/rev vibration using extendable trailing-edge plate

Abstract

Due to manufacturing errors and wear, helicopter rotor blades are not completely similar resulting in significant 1/rev fuselage vibration. In practice, rotor track and balance (RTB) based on neural network is used to eliminate the 1/rev vibration. This greatly increases the maintenance workload and cannot adjust the 1/rev vibration in flight. In view of this, a new RTB approach, namely, extendable trailing-edge plate (TEP), is studied in the present paper. Since TEP extension changes the profile of the baseline airfoil, the computational fluid dynamics (CFD) calculation is performed to study the aerodynamic characteristics of the airfoil with the extendable TEP under different extension amounts. Combined with the aerodynamic characteristics of the extendable TEP airfoil, a comprehensive helicopter aeromechanic analysis program adapted to the extendable TEP mechanism is used to explore the effects of the extendable TEP on the 1/rev fuselage vibration and hub loads. In addition, by analyzing the hub loads and the acceleration of the fuselage caused by the extendable TEP device, the mechanism of action is studied. Results show that the adjustment method based on extendable TEP is able to reduce the 1/rev acceleration of the fuselage by up to 85%–95%, which is about 8% higher than that of neural network-based algorithm. Therefore, the extendable TEP has great potential in RTB (i.e., eliminating rotor inherent dissimilarity). In addition, the factors that affect the 1/rev vertical vibration level of the airframe under different flight conditions are different.