The Effect of Rotorcraft CG Offset on Aerodynamic Stability Aiming to Obtain Vibration Reduction

Abstract

Rotorcraft experiences high level of vibration as its cruise speed increases. When the number of main rotor blade is N, N/rev vibration dominates relative to vibrations at other frequencies. To reduce that vibration, CG offset in the x-y plane from the baseline position was introduced in the previous study. The authors have analytically examined the effect of CG positions on the vibration of SH-60K as an example helicopter. SH-60K is a mid-sized helicopter which has 4-bladed articulated rotor. It has been revealed that when the CG moves toward right and also backward from the baseline position, the 4/rev vibration reaches 40% of the baseline vibration. This article discusses about the effect of SH-60K CG positions on its inherent stability. This discussion about the inherent stability restricts the CG offset. By considering the limitation of the CG offset, the vibration decrease owing to the CG offset is limited up to 20%.