|Manufacturer||Douglas Aircraft Company|
|Designed by||Edward F. Burton|
|Maiden flight||6 May 1944|
|Status||Cancelled in 1948|
|Primary users||United States Army Air Forces (intended)|
United States Air Force (intended)
|Unit cost||US$13.7 million for the program, including B-43|
The Douglas XB-42 Mixmaster was an experimental bomber aircraft, designed for a high top speed. The unconventional approach was to mount the two engines within the fuselage driving a pair of contra-rotating propellers mounted at the tail, leaving the wing and fuselage clean and free of aerodynamics-reducing protrusions. Two prototype aircraft were built, but the end of World War II changed priorities and the advent of the jet engine gave an alternative way toward achieving high speed.
Design and development
Developed initially as a private venture, an unsolicited proposal was presented to the United States Army Air Forces in May 1943. This resulted in an Air Force contract for two prototypes and one static test airframe, the USAAF seeing an intriguing possibility of finding a bomber capable of the B-29 Superfortress' range without its size or cost.
The aircraft mounted a pair of Allison V-1710-125 liquid-cooled V-12 engines behind the crew's cabin, each driving one of the twin propellors. Air intakes were in the wing leading edge. The undercarriage was tricycle and there was a long fin under the tail to prevent the propeller from striking the ground. The pilot and co-pilot sat under twin bubble canopies, and the bombardier sat in the extreme front behind a glass nose. Defensive armament was two 0.50 inch machine guns each side in the trailing edge of the wing, which retracted into the wing when not in use. These guns were aimed by the copilot through a sighting station at the rear of his cockpit, The guns had a limited field of fire and could only cover the rear, but with the plane's high speed it was thought unlikely that intercepting fighters would be attacking from any other angle. Two more guns were fitted to fire directly forward. A proposed attack variant would have been armed with 16 machine guns or a 75 mm cannon and two machine guns. 
The first XB-42 prototype flew on 6 May 1944. Performance was excellent, being basically as described in the original proposal; as fast or faster than the de Havilland Mosquito but with defensive armament and twice the bombload. The twin bubble canopies proved a bad idea as communications were adversely affected and a single bubble canopy was substituted after the first flight. Testing revealed the XB-42 suffered from some instability as excessive yaw was encountered , vibrations and poor engine cooling - all problems that could probably have been dealt with.
The end of World War II, though, allowed the Air Force to consider possibilities in a little more leisure and it was decided to wait for the development of better jet bombers rather than continue with the B-42 program.
One of the XB-42 aircraft had been destroyed in a crash, but the other was used in flight test programs, including fitting uprated engines and underwing turbojets (1600 lb/7.1kN thrust), making it the XB-42A. In this configuration, it reached 488 mph (785 km/h). Damaged in a hard landing in 1947 after 22 flights, it was repaired but never flew again.
The prototype was struck off charge in 1949 and was given to the National Air and Space Museum, in whose care it remains although it has never been placed on display. The wings were removed for transport but have since been inadvertently lost. 
- Length: 53 ft 8 in (16.4 m)
- Wingspan: 70 ft 6 in (21.5 m)
- Height: 18 ft 10 in (5.7 m)
- Wing area: 555 ft² (51.6 m²)
- Empty weight: 20,888 lb (9,475 kg)
- Loaded weight: 33,200 lb (15,060 kg)
- Max takeoff weight: 35,702 lb (16,194 kg)
- Powerplant: 2× Allison V-1710-125 V12 engines, 1,800 hp (1,300 kW each) each
- Maximum speed: 410 mph (660 km/h)
- Combat range: 1,800 mi (2,900 km)
- Ferry range: 5,400 mi (8,700 km)
- Service ceiling: 29,400 ft (8,960 m)
- Rate of climb: ft/min (m/s)
- Wing loading: 59.8 lb/ft² (292 kg/m²)
- Power/mass: 0.11 hp/lb (0.18 kW/kg)
- Guns: 4× .50 in (12.7 mm) machine guns
- Bombs: 8,000 lb (3,600 kg)
- Knaack, Marcelle Size. Post-World War II bombers, 1945-1973. Washington, DC: Office of Air Force History, 1988. ISBN 0-16-002260-6.
- Winchester 2005, p. 27.
- Winchester 2005, p. 26.
- Winchester 2005, p. 27.
- Winchester, Jim. The World's Worst Aircraft: From Pioneering Failures to Multimillion Dollar Disasters. London: Amber Books Ltd., 2005. ISBN 1-904687-34-2.
- B- sequence: XB-39 - YB-40 - XB-41 - XB-42 - XB-43 - XB-44 - B-45
- A- sequence: A-39 - A-40 - A-41 - XA-42 - XA-43 - A-44 - XA-45
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