Design of a Cruise Efficient Compound Helicopter

A slowed-rotor compound helicopter is conceptually designed using a multi-fidelity approach, showing the potential for significant efficiency improvements above conventional helicopters. The cruise tip speed and bi-linear twist distribution are optimized using the comprehensive rotorcraft analysis, CAMRAD II. System level metrics are computed using the NASA Design and Analysis of RotorCraft (NDARC) program to show top-level payoffs. An aero-performance map is generated using comprehensive analysis for the optimum twist distribution, providing calibration data for the main rotor model within NDARC. Weight and performance models are developed for a high efficiency propeller. Effects of disk loading and wing loading on the size of the slowed-rotor compound helicopter are analyzed and off-design performance is computed. Rotor-wing interference effects are analyzed using CAMRAD II for several wing vertical locations.