Aeroelastic scaling for rotary-wing aircraft with applications

This paper presents a new treatment of the aeroelastic scaling problem for rotary-wing vehicles (i.e. helicopters and tiltrotors). It is shown that the offset hinged spring restrained blade model is the rotary-wing equivalent of the typical cross section that has been used during the last 50 years to obtain aeroelastic scaling laws for fixed wing vehicles. A new two-pronged approach for developing refined aeroelastic scaling laws for rotary-wing aeroelastic and aeroservoelastic applications is presented. It combines the classical approach with computer simulations to obtain new refined aeroelastic scaling relations. The rotary-wing scaling laws are applied to the vibration reduction problem in helicopter rotors using an actively controlled, partial span, and trailing edge flap. The results obtained for a Mach scaled rotor are compared with those obtained for a Froude scaled rotor. The results indicate that the Mach scaled rotor is needed so as to obtain the correct actuation requirements for vibration reduction.