Feasibility Of An Acoustic Liner Applied To A Fenestron

Abstract

A helicopter anti-torque system significantly contributes to radiated noise. The Fenestron anti-torque system used on Airbus helicopters, reduces this noise through masking effects and blade distribution modulation. This paper explores integrating acoustic treatments into the Fenestron, similar to those used in aircraft engine nacelles, to further decrease the anti-torque system noise. Numerical simulations are performed to identify the optimal acoustic impedance for these liners, followed by proposing and assessing several liner designs on small-scale experimental benches. Finally, a larger-scale, more representative measurement campaign on a Fenestron mock-up with integrated liners demonstrates that a likely significant noise reduction can be attained.