THE EXPERIMENTAL AND ANALYTICAL DEFINITION OF HELICOPTER MODELING EFFECTS

This paper describes the results of an analytical and experimental investigation into helicopter model configuration effects. In this effort, a single helicopter model was analyzed and tested at two different scales to determine the effects of full and partial fuselage representation, full and partial main rotor wake representation, hub rotational advance ratio, and engine air flow/ exhaust simulation. The helicopter model used was the YAH-64. The analysis was conducted using program DRAG which is a fully interactive viscous wing/body computer code. The testing was conducted at the NASA/Langley V/STOL tunnel and the data recorded include surface pressure data as well as forces and moments for the isolated main rotor hub, pylon and fuselage. The data presented and discussed indicate that a larger than predicted tunnel correction should be applied to the large scale model. Using this correction, the analysis, small scale, and large scale surface pressure data correlate well. In addition, the data indicate a model scale Reynolds number of 300, 000 is needed to measure full-scale forces accurately. Also, model airflow simulation significantly influences model forces and should be included. The effect of main rotor wake and hub rotation are also discussed.