Douglas XB-42 Mixmaster

XB-42 Mixmaster

Picture - XB-42

Role: Medium and Pusher-prop Bomber
Manufacturer: Douglas Aircraft Company
Designed by: Edward F. Burton
First flight: 6 May 1944
Status: Cancelled in 1948
Primary users: United States Army Air Forces (intended) United States Air Force (intended)
Number built: 2
Unit cost: US$13.7 million for the program, including B-43
Developed into: XB-43 Jetmaster DC-8 (piston airliner)

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 drag-inducing 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

The XB-42 was 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 Boeing 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 propellers. Air intakes were in the wing leading edge. The undercarriage was tricycle and there was a long fin under the tail to prevent the propellers from striking the ground. The pilot and co-pilot sat under twin bubble canopies, and the bombardier sat in the extreme front behind a plexiglass nose. Defensive armament was two 0.50 in (12.7 mm) 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 aircraft'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. Initially ordered as attack aircraft (XA-42) in the summer of 1943, this variant would have been armed with 16 machine guns or a 75 mm (2.95 in) cannon and two machine guns.

Operational history

The first XB-42 was delivered to the Army Air Force and flew at Palm Springs, California 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. Due to the vertical stabilizer and rudder located underneath the fuselage, careful handling during taxiing, takeoff and landing was required on account of the limited ground clearance.

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.

Picture - View of the contraprop and cruciform tail.

In December 1945, Captain Glen Edwards and Lt. Col. Henry E. Warden set a new transcontinental speed record when they flew the XB-42 from Long Beach, California to Bolling Air Force Base in Washington DC (c. 2,300 miles) and in just 5 hours, 17 minutes, the XB-42 set a speed record of 433.6 mph (697.8 km/h).

The record-breaking XB-42 prototype had been destroyed in a crash at Bolling Field attributed to a failure of the landing gear, but the other was used in flight test programs, including fulfilling a December 1943 proposal by Douglas to fit uprated engines and underwing Westinghouse 19XB-2A axial-flow turbojets of 1,600 lbf (7.1 kN) thrust each, making it the XB-42A. In this configuration, it first flew at Muroc (now Edwards Air Force Base) on 27 May 1947. In testing, it reached 488 mph (785 km/h). After 22 flights, the lower vertical stabilizer and rudder were damaged in a hard landing in 1947. The XB-42A was repaired but never flew again, and was taken off the AAF inventory on 30 June 1949.

Picture - XB-42A with podded 19XB-2 jets.[6]

Survivors

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. In late 2010 the fuselage was transferred, along with the Douglas XB-43 Jetmaster, to the National Museum of the United States Air Force in Dayton, Ohio where they are awaiting restoration in the Restoration Hangars. Once completed, they will be displayed in the Museum's Experimental Aircraft Hangar.

Specifications (XB-42)

Picture - XB-42A

Data from McDonnell Douglas Aircraft since 1920

General characteristics

Crew: Three (pilot, copilot/gunner and bombardier)
Length: 53 ft 8 in (16.36 m)
Wingspan: 70 ft 6 in (21.49 m)
Height: 18 ft 10 in (5.74 m)
Wing area: 555 ft² (51.6 m²)
Empty weight: 20,888 lb (9,475 kg)
Max takeoff weight: 35,702 lb (16,194 kg)
Powerplant: 2x— Allison V-1710-125 V12 engines, (988 kW each) each

Performance

Maximum speed: 410 mph (357 knots, 660 km/h) at 23,440 ft (7,145 m)
Cruise speed: 312 mph
Range: 1,800 mi with 6.000 Lbs of bombs (1565 nmi, 2,895 km with 8,000 lbs of bombs.)
Ferry range: 5,400 mi (4,696 nmi (8,690 km))
Service ceiling: 29,400 ft (8,960 m)

Armament

Guns: 6 x— .50 in (12.7 mm) machine guns, two twin rear-firing turrets and two fixed forward-firing
Bombs: 8,000 lb (3,629 kg)

Pusher configuration

Related development

Douglas XB-43 Jetmaster
DC-8

Bibliography

Francillon, René J. McDonnell Douglas Aircraft since 1920. London: Putnam, 1979. ISBN 0-370-00050-1.
O'Leary, Michael, ed. "Elegant Failure." America's Forgotten Wings, Volume 1, 1994, pp. 4-11.
Winchester, Jim. The World's Worst Aircraft: From Pioneering Failures to Multimillion Dollar Disasters. London: Amber Books Ltd., 2005. ISBN 1-904687-34-2.

Douglas XB-42 Mixmaster Pictures

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Source: WikiPedia