Experimental Measurement Techniques for Full-Scale Helicopters

Abstract

The wake of its main rotor plays a key role in the overall performance and operational safety of a helicopter. The flow is governed by complex and unsteady features, such as the blade shear layers and blade tip vortices. In recent years, experimental measurement techniques have been developed and refined for this application, to keep up with an increasing level of detail in numerical simulations, and to provide reference validation data. In particular, the talk will address "out-of-the-lab" problems encountered during fullscale helicopter tests in an airfield environment. This includes long viewing distances combined with a limited sensitivity and resolution for optical camera systems, wind and temperature influence, short measurement intervals and inferior reproducibility, limited access to the sensors etc. It will also be shown how a careful selection and time-synchronous application of multiple measurement techniques can remedy the individual disadvantages, providing a better overall picture of the wake aerodynamics.