Recent Advances In Helicopter Aerodynamics

This paper deals mainly with the aerodyrrnmics of isolated rotors and fuselages although some topics in interactional aerodynamics are also discussed. We describe shortly the new theoretical and experimental approaches presently used by helicopter designers and those which are being developed. We limit the scope of the paper to phenomena having a significant influence on helicopter performance. We discuss computational methods of global rotor performance prediction and show the possibiIities offered by more elaborate methods which take into account dynamic stall, three-dimensional unsteady transonic flow and fuselage interference effects. The case of the rotor in hover is also outlined. Some typical wind tunnel and flight test results are shown and the problems related to their analysis are discussed. We end this section by rotor design considerations emphasizing airfoil selection criteria and the optimization of blade twist, planform and tip shape.