Whirl Flutter Investigation of Hingeless Proprotors
Hyeonsoo Yeo, Andrew Kreshock
Abstract
Hingeless proprotor whirl flutter in cruise flight is investigated using comprehensive rotorcraft analysis codes CAMRAD II and RCAS. Generic hingeless proprotor designs include conventional soft-in-plane and stiff-in-plane rotors operating at cruise tip speeds typical of existing tiltrotor systems and a rotor that exhibits higher frequencies and operates at much lower cruise tip speed than existing rotor designs. The effects of the blade elasticity, wing/pylon model, density, speed of sound, unsteady aerodynamics, and realistic airfoil tables on whirl flutter speed are examined. CAMRAD II and RCAS show consistently excellent agreement with each other for wide variations of design variables and operating conditions.