Experimental And Analytical Comparison Of Stiff And Flexible Rotor Blades For Tiltrotor Whirl-Flutter Stability

Abstract

The U.S. Army and NASA recently completed their second wind tunnel entry in the Transonic Dynamics Tunnel with the TiltRotor Aeroelastic Stability Testbed (TRAST). Parametric studies were conducted on important components of the wing semi-span testbed and 8-ft-diameter rotor system to assess their effect on whirl flutter. TRAST is a dynamically scaled testbed that is representative of the XV-15 and has adjustable pitch-flap coupling (?3), tuning springs, and two blade sets with different stiffnesses. The first blade set, made of fiberglass, is dynamically scaled to the XV-15 blade so that the frequencies are approximate to the aircraft. The second blade set replaces the fiberglass layup with carbon fiber and has approximately twice the stiffness. This paper will show how a dynamically tuned blade can increase the stability boundary.