Trends for Optimum Flying Crane Design

Five helicopter configurations possible suitable for use as Flying Cranes are discussed, Relative gross weights and direct operating costs are compared for designs of various disc loadings and cruise speeds, The configurations include the shaft-turbine-powered single, tandem, and quadrotor configurations and the single rotor pressure jet, and tip turbojet configurations. It is shown that, in general, for the high lift, short range mission low empty weight rather than maxirmun fuel economy is of primary importance for reducing operating costs, With the light turbine engines now available, this is best obtained with design disc loadings of about 10 psf. However, consideration of downwash velocity and autorot ation capability will probably establish a practical rmmaum disc loading of about 7 psf for this mission. In the very high payload category, the shaft turbine quadrotor promises to have a lower operating cost and gross weight than the pressure jet for ranges of 50 miles and over. Development costs can be minimized for large~ special purpose, flying cranes by using rotor systems and drive components which are within the present state-of-the-art, and combining them into a quadrotor configuration. In this manner~ dynamic components for a moderate-range tandem rotor transport helicopter can be applied to a short-range quadrotor Flying Crane,