Douglas XB-42 Mixmaster
Douglas designed and built two bomber prototypes and one static test airframe under a contract received from the US Army Air Force on 25 June 1943. This was based on two 1800-hp (1342-kw) Allison V-1710-25 inline engines located in tandem in the fuselage to drive a pair of contra-rotating propellers behind the cruciform tail unit. Named Mixmaster by the company, this aircraft had a mid-set cantilever monoplane wing, cruciform tail surfaces and tricycle landing gear, whose main units retracted aft to be housed in the sides of the fuselage.
A second prototype was flown for the first time on 1 August 1944, soon afterwards being modified by the addition of a single canopy over the pilot/copilot cockpit. This prototype was destroyed in a crash during December of that year, but by that time the USAAF had decided not to proceed with production of this design, awaiting instead the development of higher-performance turbojet-powered bombers. As an interim step to allow evaluation of turbine power, the first prototype was given a mixed powerplant comprising two 1025kW Allison V-1710-133 piston engines to drive the propellers, plus two 726kg thrust Westinghouse 19XB-2A turbojets mounted in underwing nacelles. Redesignated XB-42A, this aircraft was used for performance testing over several months before being retired at the end of June 1949. The XB-42A is now in storage for the National Air and Space Museum. Somewhere along the way its wings were removed for transport and haven't been seen since.