An early Huey used by the US Army to test various armament configurations. In 1965 it was loaned to Bell Helicopters for test purposes with two Continental T72-T-2 turboshaft engines installed in a module driving a common gearbox under the Model 208 name. After proving the concept of dual engines in the 205 airframe, it was not pursued (until the Bell 212/UH-1N) and around 1966 the helicopter was returned to the Army in original configuration. Now preserved in a diorama depicting a well-publicised photograph from the Vietnam conflict of an air assault landing of the 9th Cavalry "Bravo Blues"

The first Model 205 stretched Hueys were seven YUH-1D prototypes, 60-6028 through 6034. Photo from: Wright State University