Technical Note: Twin Rotor Hover Performance

During 1947, Mr. Wieslaw Z. Stepniewski conducted a milestone model test that determined the influence on hover performance when co‐planar, twin rotors are overlapped. The original thrust and power data was, however, given very limited distribution in 1948. This data, in tabulated form, has been recovered from the archives and included in this technical note. The experimental results provide a valid data base for future theory versus test correlation. In addition, the “psuedo ideal” performance of co‐planar, twin rotors is given using blade element‐momentum theory and assuming constant chord blades twisted as θ_(x) = θ_tip/x. An engineering approximation to rapidly calculate co‐planar, twin rotor hover performance for any overlap ratio and at practical rotor loading is offered.