Model tests on unsteady rotor wake effects.

A qualitative model of unsteady asymmetric wake effects is considered, taking into account a progressing blade flapping mode in which each blade flaps in a rotating frame of reference. The rotor model used for the tests is two bladed. The experimental data are compared with an analytical flapping response. It is found that the steady wake effects are largest at zero advance ratio and low collective pitch. The effects remain significant at higher advance ratios and collective pitch settings.