Helicopter Rotor Blade Aeroacoustics: A Comparison of Model-scale Wind Tunnel and Full-scale Flight Test Results

Abstract

Several major international-cooperative rotor-aeroacoustic research programmes have been conducted during the past decade, employing a 40% geometrically and dynamically scaled model of the main rotor of an ECD (MBB respectively) helicopter BO-105, most notably the European Brite/Euram HELINOISE project and the European/US HART-project. Among several other objectives, these projects served to simultaneous determine unsteady blade surface pressures and the resulting acoustic radiation and to provide a comprehensive data bench. A wealth of information was obtained to be used for both validating and furthering rotor noise prediction schemes but also to devise means to reduce noise at the source. Although the model scaling factor was large (namely 0.4) thus implying a good scalability towards the full-scale condition, the final proof was still lacking, in that no comparable aeroacoustics information form the full-scale.