Vibration and Performance Analyses Using Individual Blade Pitch Controls for Lift-Offset Rotors

Jae-Sang Park,Sanghyun Chae,Jeong-In Go,Ye-Lin Lee,Do-Hyung Kim

doi:10.1155/2019/9589415

Abstract

This work attempts to reduce the hub vibratory loads of a lift-offset rotor using IBC (individual blade pitch control) in high-speed forward flight. As a lift-offset rotor for the present study, the rigid coaxial rotor of a XH-59A compound helicopter is considered and CAMRAD II is used to predict the hub vibration and rotor performance. Using the IBC with a single harmonic input at 200 knots, the vibration index of the XH-59A rotor is minimized by about 62% when the 3/rev actuation frequency is applied with the IBC amplitude of 1° and control phase angle of 270° (3P/1°/270°); however, the rotor effective lift-to-drag ratio decreases by 3.43%. When the 2/rev actuation frequency with the amplitude of 2° and control phase angle of 270° (2P/2°/270°) and the 3/rev actuation frequency using the magnitude of 1° and control phase angle of 210° (3P/1°/210°) are used in combination for the IBC with multiple harmonic inputs, the vibration index is reduced by about 62%, while the rotor effective lift-to-drag ratio increases by 0.37% at a flight speed of 200 knots. This study shows that the hub vibration of the lift-offset rotor in high-speed flight can be reduced significantly but the rotor performance increases slightly, using the IBC with multiple harmonic inputs.

Highlights

Lift-offset helicopters using ABCTM (Advancing Blade Concept, [1]) have been developed to solve the low-speed flight performance of conventional helicopters
The modeling and analysis techniques of CAMRAD II using the prescribed wake model are validated for the XH-59A rotor without IBC
The vibration and performance of the XH-59A lift-offset rotor using IBC were investigated by the rotorcraft comprehensive analysis code, CAMRAD II

Summary

Introduction

Lift-offset helicopters using ABCTM (Advancing Blade Concept, [1]) have been developed to solve the low-speed flight performance of conventional helicopters. Lift-offset compound helicopters have showed excellent high-speed flight performance, they have a serious vibration problem during high-speed flights. In flight tests of the XH-59A compound helicopter, significant 3/rev cockpit vibration was observed because of the use of a rigid coaxial rotor and the absence of a vibration control system [5]. To solve this vibration problem in high-speed flights, the X2

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