Title: Impact of Aerodynamics and Structures Technology on Heavy Lift Tiltrotors
Abstract: Rotor performance and aeroelastic stability are presented for a 124,000-lb Large Civil Tilt Rotor (LCTR) design.It was designed to carry 120 passengers for 1200 nm, with performance of 350 knots at 30,000 ft altitude.Design features include a low-mounted wing and hingeless rotors, with a very low cruise tip speed of 350 ft/sec.The rotor and wing design processes are described, including rotor optimization methods and wing/rotor aeroelastic stability analyses.New rotor airfoils were designed specifically for the LCTR; the resulting performance improvements are compared to current technology airfoils.Twist, taper and precone optimization are presented, along with the effects of blade flexibility on performance.A new wing airfoil was designed and a composite structure was developed to meet the wing load requirements for certification.Predictions of aeroelastic stability are presented for the optimized rotor and wing, along with summaries of the effects of rotor design parameters on stability. NotationA rotor disk area c.g. center of gravity c l section lift coefficient c m section pitching moment coefficient C T rotor thrust coefficient, T/( AV 2 tip ) D drag F c fuel consumed FM figure of merit M Mach number q dynamic pressure R rotor radius Re Reynolds number t/c thickness to chord ratio T rotor thrust V tip rotor tip speed propulsive efficiency air density rotor solidity (ratio blade area to disk area) ISA international standard atmosphere LCTR Large Civil Tilt Rotor OEI one engine inoperative SFC specific fuel consumption SNI simultaneous non-interfering SOA state of the art VTOL vertical takeoff and landing