HELINOVI Aeroacoustic Main/Tail Rotor Test in DNW: Test Documentation and Representative Results

Abstract

A comprehensive wind tunnel study was conducted in DNW to investigate technologies for reducing noise, especially tail rotor noise and vibration of rotary wing aircraft. The test is performed under the umbrella of EU HeliNOVI project. HeliNOVI is the acronym of Helicopter Noise/Vibration Reduction research project. The research goal of HeliNOVI is to provide new design codes and technologies for reducing noise and vibration of rotary wing aircraft. The project combines 11 EU partners including two airframe manufacturers. The test model is a 40% scaled BO105 helicopter model with instrumented main/tail rotor and fuselage. The importance of tail rotor and of main / tail rotor interference noise as well as of tail rotor noise reduction potentials is investigated in detail. The tested configuration involved in the test are BO105 main rotor (MR) and tail rotor (TR) in combined and isolated conditions, TR sense of rotation, variation of position between MR and TR and variation of rotor rotational speed. The present report will contain some technique detail of the test and data reduction as well as data analysis of aeroacoustic test results. The measurement in acoustic test comprise of acoustic inflow and outflow microphones, blade pressure and Particle Image Velocimetry (PIV). The changing TR rotational direction from Advancing Side Down to Advancing Side Up shows a noise reduction of more than 6 dBA for the climb and level flight conditions. Reducing tip speed is effect way to reduce MR/TR noise. There is no change for 6° descent flight condition because the MR BVI noise is dominated. Interactions of TR and MR tip vortex are demonstrated in both PIV and leading edge blade pressure data. The splitting of MR tip vortex cutting by TR blade is observed.