08/15/2008. Remarks by Ray Watkins: "The Kellett Autogiro Corp was one of two American companies (together with Pitcairn-Larsen) to hold a sub-license for the use of Cierva autogiro technology. The company produced a number of autogiros before moving into helicopter design with the XR-8, which first flew on August 7, 1944.
It had a three-blade intermeshing rotor system of the type first used by Anton Flettner for his Fl 265 in 1939, and the better-known Fl 282 Kolibri (Hummingbird), which flew in 1940. The rotor system lead to the type being popularly referred to as an 'egg beater', it was also known as a 'Synchropter'. The aircraft had a crew of two and was powered by a 245 hp Franklin air-cooled engine.
A second prototype fitted with a two-blade intermeshing rotor system was ordered, designated XR-8A and assigned s/n 44-21908, it was flown in March 1945. Both the XR-8 and XR-8A (later re-fitted with the three-blade rotor system) were tested by the USAAF but no production orders followed."