Aerodynamic Design of Helicopters
We built the first helicopter by what we hoped was intelligent guess. It was time of crystal ball.
Igor Alexis Sikorsky (1957)
There are many fundamental issues, some of them conflicting, in the aerodynamic design of the modern helicopter. Helicopter designers are concerned with overall aircraft performance, rotor and airframe loads, vibration levels, external and internal noise, stability and control characteristics, and aircraft handling qualities. Specific emphasis in this chapter is placed on the general elements and features contributing to the aerodynamic design of helicopter main rotors and related components. However, many of the issues and arguments are applicable to other types of rotorcraft as well. The first part of this chapter outlines the basic sizing and overall optimization methodology of helicopter main rotors. This ultimately leads to the further consideration of rotor airfoil sections and the need for good airfoil designs, the trade-offs in blade planform design, and the role of tip shape in the efficient design of the modem rotor. While helicopter design is often synonymous with rotor aerodynamics, the aerodynamics of the fuselage has received considerable attention in recent years and now constitutes an important part in the overall design process of the modem helicopter. The general issues associated with the selection of anti-torque producing devices such as conventional tail rotors and other concepts are also discussed. Finally, some significant aerodynamic design issues associated with human powered helicopters and micro air vehicles are outlined.