Important Scaling Parameters for Testing Model-Scale Helicopter Rotors

Abstract

An investigation into the effects of aerodynamic and aeroelastic scaling parameters on model scale helicopter rotors has been conducted in the NASA Langley Transonic Dynamics Tunnel. The effect of varying Reynolds number, blade Lock number, and structural elasticity on rotor performance has been studied and the performance results are discussed herein for two different rotor blade sets at two rotor advance ratios. One set of rotor blades were rigid and the other set of blades were dynamically scaled to be representative of a main rotor design for a utility class helicopter. The investigation was conducted in forward ight at rotor advance ratios of 0.15 and 0.35. Additionally, the rotors were tested over a range of nominal test medium densities from 0.00382slugs/ft³ to 0.009slugs/ft³. This range of densities permits the acquisition of data for several Reynolds and Lock number combinations.