Approximate methods for estimating the performance of conventional and unconventional helicopter designs

A set of equations with the necessary background information is presented to calculate the power required for the conventional single main rotor helicopter during hover and forward flight. The power required is a function of weight, parasite drag, speed over the ground, and rotor system design.

Alternative helicopter designs are evaluated using the "power required" analytical technique. Alternative helicopter designs include rotorcraft with auxiliary lift and thrust (compound helicopters), rotor airfoils with enhanced lift using active circulation control, rotor designs with reduced radius and increased solidity, and machines with coaxial, counterrotating main rotors.

Comparison of calculated performance with published helicopter data indicates that the approximate methods do provide a useful means of predicting power required for helicopter flight.

Alternative designs found to have merit include intermeshing rotor helicopters, helicopters with horizontal thrusters, and heavily loaded disk-loaded helicopters with wings.