Firestone XR-9

The Firestone XR-9, also known by the company designation Model 45, was a 1940s American experimental helicopter built by the Firestone Aircraft Company for the United States Army Air Forces. Only two (the military XR-9B and one civil example) were built.

Read more about Firestone XR-9:  Development, Variants, Operators, Specifications (XR-9B)