Investigation of Aerodynamic Interactions between a Rotor and a Fuselage in Forward Flight

A series of wind tunnel experiments were conducted to examine the interactional aerodynamic effects between a small-scale articulated helicopter rotor and an idealized, but realistic, helicopter fuselage. Tests were conducted on the isolated fuselage, isolated rotor and on the rotor and fuselage combination. Independent strain-gauge balance loads were obtained on the fuselage and rotor along with both steady and unsteady pressure measurements on the fuselage. Data were obtained for various combinations of advance ratio, shaft tilt and rotor thrust. The results indicate that while the rotor wake produces large changes in the mean loads on the fuselage, unsteady pressure fluctuations due to blade passage and wake impingement are the most dominant form of loading. The magnitude of the unsteady loads on the fuselage were found to be primarily a function of rotor thrust. Results also show that when operating at low advance ratio, the presence of the fuselage produces an increase in rotor thrust for a given collective pitch and a reduction in rotor power for a given thrust. The wake skew angle was found to be an effective parameter governing the magnitude of the time-averaged interactional loads on both the rotor and fuselage.