FULL-SCALE INVESTIGATION OF AERODYNAMIC INTERACTIONS BETWEEN A ROTOR AND FUSELAGE

A wind tunnel program has been conducted in the NASA Ames National Full-Scale Aerodynamics Complex (NFAC) to investigate the aerodynamic interactions between a full-scale helicopter main rotor and simple fuselage. This program provides the first complete, quantitative data base detailing the effects of a rotor on a full-scale fuselage. Steady fuselage and rotor loads were obtained as well as steady and unsteady fuselage pressures. Data were acquired over a range of rotor thrusts, advance ratios, and shaft tilts. As expected, results indicate that the largest effects on mean fuselage forces, moments, and surface pressures occur at low speeds and high rotor thrusts. Quantitative comparisons were made to determine the ability of small-scale tests to simulate the effect of the rotor on mean fuselage forces and pressures. The results were inconclusive. Additional small-scale data are needed at lower speeds where rotor/fuselage interactions are larger. The rotor and rotor wake caused large unsteady pressure fluctuations on the top of the fuselage which were similar in character to small-scale results. This supports the idea that the basic phenomena which cause unsteady loading on a full-scale fuselage can be studied, at least qualitatively, in small-scale. The magnitude of this unsteady loading was dependent on its source. Pressure fluctuations caused by blade passage were dependent on rotor thrust while fluctuations caused by close wake interaction were dependent on advance ratio.