From the Planes You’ve (Probably) Never Heard Of Department of Wingspan, we bring you the Douglas XB-42 Mixmaster and Douglas XB-43 Jetmaster.


The XB-42 Mixmaster. Douglas envisioned the aircraft as a ground attacker, but the US Army Air Forces saw instead a fast and potent bomber. (US Air Force)

In 1943, the Douglas Aircraft Company approached the US Army Air Forces with a radical new aircraft design, a large, heavily armed pusher-propeller aircraft envisioned as a potent ground attacker. But the USAAF didn’t see an attack aircraft. Instead, they saw a bomber that could rival the massive four-engine Boeing B-29 Superfortress in range and payload while doing so at a fraction of the cost and complexity. What was originally designated as the XA-42 was now the XB-42, and the USAAF requested two prototypes along with one static test airframe.

An artist’s impression of XA-42 attack aircraft destroying Japanese aircraft (Author unknown)

At a time of wing-mounted radial-engined bombers, the XB-42 was a radical design in a number of ways. It was powered by a pair Allison V-1710 liquid-cooled V-12 engines mounted side by side behind the cockpit each producing 1,800 horsepower. These two engines turned contra-rotating propellers at the rear of the aircraft behind a cruciform tail. With a top speed of more than 450 mph, the XB-42, dubbed Mixmaster for obvious reasons, was faster than any other contemporary American bomber, and it could cover 5,400 miles with an 8,000 pound bomb load, or a single 10,000 pound bomb, both of which far outperformed the B-29.

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Communication between the pilot and copilot in their individual bubble canopies proved difficult, so one Mixmaster was modified to use traditional side-by-side seating. Cooling air for the two Allison V-12 engines entered through the air intakes on the leading edge of the wing roots. (US Air Force)

For defensive armament, Douglas mounted two rear-firing .50 caliber machine guns in the trailing edges of the wings which were operated by the copilot, who faced backward while firing. Two more .50 caliber machine guns were fixed forward. And even though the Mixmaster was the fastest bomber of its day, Douglas sought to increase the speed of the Mixmaster by supplementing the Allison engines with a pair of Westinghouse axial flow turbojets mounted under the wings. The added jet power increased top speed to 488 mph.

The XB-42A, with two bubble canopies and additional jet engines mounted under the wings (US Air Force)

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By the time the Mixmaster was took its maiden flight on May 6, 1944, the end of the war was approaching, and the USAAF no longer had a need for the innovative bomber, despite its capabilities. Plus, the age of the jet engine was dawning, and piston engines were increasingly seen as the power plant of an earlier age. But the program’s cancellation didn’t mean the end of the Mixmaster concept. With its propulsion already coming from the back, XB-42 was a perfect candidate for modification into a jet-powered bomber.

The jet-powered Jetmaster, America’s first purely jet-powered bomber, takes off from Muroc Air Force Base (US Air Force)

To transform the Mixmaster into the Jetmaster, Douglas began by replacing the cruciform tail with a traditional tail, albeit with a substantially enlarged rudder. The XB-42's leading edge air inlets were removed, and two larger air intakes were placed on the side of the fuselage. These fed two Allison J35 engines, America’s first operational axial-flow compressor engine, mounted inside the fuselage. The 4,000 pounds of thrust from each of the early turbojet engines gave the XB-43 a top speed of 507 mph. At 8,000 pounds, the Jetmaster’s payload matched that of its predecessor, but the thirsty turbojets dramatically reduced the XB-43's range to 2,500 miles.

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The Jetmaster makes a low pass over Muroc Air Force Base (US Air Force)

When the Jetmaster took to the skies over Muroc Air Force Base in California on May 17, 1946 after two years of development, it became the United States’ first purely jet-powered bomber. Douglas planned to develop the Jetmaster into both a bomber and an attack aircraft, with the bomber having a glazed nose and remotely controlled rear-firing machine guns, while the attack version would have a solid nose housing eight .50 caliber machine guns.

The exhausts of the twin turbojet engines are visible here, as well as the greatly enlarged vertical stabilizer (US Air Force)

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Douglas built two Jetmasters, an XB-43 prototype and a preproduction YB-43, and the Air Force initially indicated plans for production of 50 bombers, while Douglas was preparing to build as many as 200. But with newer, purpose-built aircraft in development, such as the North American B-45 Tornado, the contract for the Jetmaster was canceled before any more could be built. Nevertheless, the dual-engine arrangement of the XB-43 made it ideal for engine testing, and one Jetmaster, nicknamed Versatile II for its utility and relative ease of swapping test engines, carried out more than 300 hours of testing, while the other XB-43 was cannibalized for parts to keep Versatile II flying. The stripped Jetmaster was eventually used for target practice and destroyed, but the second awaits restoration at the National Museum of the United States Air Force, along with the sole remaining XB-42.

The Jetmaster retained the side-by-side bubble canopy arrangement. The original glazed nose of this test aircraft had cracked from the heat of the desert heat the cold of high altitude, so mechanics fashioned a plywood nose to keep the Jetmaster flying. (US Air Force)

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