H-8 / H-10

The Kellett R-8 [later redesignated the XH-8] had a small egg-shaped fuselage which tapered into a very deep tail structure. It had two-bladed intermeshing rotors. It first flew in 1944, but only two were built.

The Kellett R-10 [later redesignated the XH-10] was a prototype utility helicopter which first flew in 1947. Based on the R-8, the two engines were installed in nacelles on the sides of a compact, box-like fuselage. It retained the intermeshing rotors and intermeshing two-bladed rotors. It was at the time the largest helicopter under development for the USAF, but it did not enter production.