One of two Grumman XF6F-6 prototypes (converted F6F-5s U.S. Navy BuNos 70188, 70913) fitted with a 2,100 hp Pratt & Whitney R-2800-18W engine at the Naval Air Test Center in Patuxent River, Maryland (USA), on 20 December 1944. The first XF6F-6 flew on 6 July 1944.