Stopped and Slow Rotor Aircraft Configuration

Fundamental limitations on the forward flight speed of compound helicopters are of such a nature as to suggest that further increases in forward flight speed may be obtained by reducing main rotor RPM and altering basic rotor geometry.

Reducing rotor RPM to a fraction of normal operating RPM allows higher flight speeds as a “slowed-rotor” configuration. Complete stopping of the rotor allows higher flight speeds as a “stopped-lifting rotor” configuration. And finally, complete stopping of the rotor with subsequent in flight blade folding allows higher flight speeds as a “folded-rotor” configuration. All configurations exhibit common aeroelastic design criteria which require additional rotor structural weight to provide higher forward velocities. Each configuration has mechanical and aerodynamic requirements peculiar to the type which also result in empty weight and fuel weight differences.

By assessing the several empty weight and fuel weight differences which are exhibited by the three subject configurations, the optimum speed range for each configuration may be identified.