Experimental Study on the Effect of a Rapid Blade-Pitch Variation on the Performance of a Helicopter Rotor Model in Hover

In this paper are presented the results of an experimental study on the performance of a helicopter rotor model in hover during transient operation. The aim of this study is to quantitatively evaluate the variations of the aerodynamic forces, resulting from the rapid change of the pitch angle of the blades. The measurements are performed for two different rates of change of the pitch angle and for three rotor configurations with respectively 2, 3 and 4 blades. A brief description of the test stand is provided. The test stand allows for thrust and torque measurements of model helicopter rotors with diameters up to 1 meter, pitch angle settings from -12deg to + 24deg and rotational speeds up to 3000 RPM. Conclusions are drawn on the variations of the aerodynamic performance and efficiency caused by the rapid blade-pitch changes. A significant database was obtained during this experimental study, which will serve for validation purposes.