The Douglas XB-42 began as a private venture by the manufacturer, and was not originally conceived in response to any official requirement. In early 1943, Douglas designer Ed F. Burton began a company-funded study to determine the feasibility of designing a twin-engined bomber having a maximum speed in excess of 400 mph and capable of carrying a bombload of 2000 pounds to targets within a 2000-mile radius. Burton's team came up with the idea of mounting the engines entirely within the fuselage and using a completely clean wing.
An unsolicited proposal was submitted to the USAAF in May of 1943. The proposal attracted the attention of the Bombardment Branch of the Engineering Division of the Air Technical Service Command, and on June 25, 1943 a contract was issued for two flying prototypes and one static test airframe. The aircraft was considered as an attack aircraft at the time, and was assigned the designation XA-42. Almost immediately thereafter, the USAAF began to consider the Douglas proposal as a possible high speed bomber which could match the range of the B-29 at only a fraction of the cost. On November 26, 1943, the designation of the Douglas design was changed to XB-42.
Progress on the XA-42/XB-42 was quite rapid under the supervision of Ed Burton and Carlos C. Wood, Chief of the Preliminary Design Division, and the mockup was inspected and approved in September of 1943.
The aircraft that finally emerged was powered by a pair of 1325 hp Allison V-1710-125 liquid-cooled V-12 engines installed completely inside the fuselage immediately aft of the pilot's cabin. Air for the cooling radiators was provided by narrow slots cut into the leading edges of the inner wings. The centerline of each engine was about 20 degrees to the vertical and the engines were toed in a few degrees to the vertical. The power was transmitted via five lengths of shafting to a pair of contra-rotating propellers installed in the extreme tail cone. Each of the three-bladed contra-rotating propellers was driven by its own engines, the left powerplant driving the forward propeller and the right the aft. A lower fin and rudder was fitted underneath the tail to prevent the propellers from striking the ground during nose-high takeoffs and landings.
The tricycle undercarriage had main members which retracted aft into large wells in the fuselage sides. The extremely-clean laminar-flow wing was mounted at middle fuselage. It had double-slotted flaps on the inboard trailing edge, with ailerons on the outboard trailing edge.
A remotely-controlled General Electric turret with a pair of 0.50-inch machine guns was to be installed in the trailing edge of the wing between the ailerons and flaps. The guns were normally housed inside the wing underneath snap-action doors, but when extended into firing position, they could cover an area extending 25 degrees to either side, 30 degrees above, and 15 degrees below. They were controlled remotely by the copilot, who had a sighting station at the rear of his cockpit. It was true that this field of fire was rather limited, but it was assumed that the bomber's high speed would prevent any enemy fighter attacks except from the extreme rear. A gun were mounted in a fixed position on each side of the forward fuselage for head-on defense.
The crew consisted of three, with a navigator/bomb-aimer in the glazed nose section, and a pilot and copilot/gunner in a side-by-side cockpit with small separate canopies.
The first XB-42 aircraft (43-50224) was completed in May of 1944. The XB-42 took off for the first time on May 6, 1944, with test pilot Bob Brush at the controls. As a safety measure, the initial flight was carried out entirely over Palm Springs Army Air Base. The performance of the XB-42 was outstanding. Speed was within a percent of that predicted, and range and rate of climb exceeded expectations. The XB-42 was as fast as the Mosquito B.XVI but carried twice the maximum bombload (8000 pounds versus 4000 pounds over short ranges or a bombload of 3750 pounds versus 1000 pounds over a range of 1850 miles). Moreover, the XB-42 carried a defensive armament of four 0.50-inch machine guns in two remotely-controlled turrets whereas the Mosquito was unarmed. However, the twin "bug-eye" canopies of the XB-42 were found to interfere with pilot/co-pilot communication, and the aircraft suffered from yaw, excessive propeller vibration (especially when the bomb-bay doors were open), poor harmonization of control forces, and from poor efficiency of the cooling ducts.
The second XB-42 prototype (43-50225) flew on August 1, 1944. It was powered by V-1710-129 engines. Shortly after its first flight, the twin bug-eye canopies were replaced with a single canopy as was proposed for production versions of the aircraft. In early December of 1945, 43-50225 was flown from Long Beach, California to Bolling Field near Washington, D.C. at an average speed of 433.6 mph. However, on the 16th of December, the aircraft crashed near Bolling Field and was destroyed. Fortunately, the crew managed to parachute to safety.
By this time, the USAAF had decided that the XB-42 would not be put into production, since the end of the war had made it possible to wait for the more advanced, higher-performance jet-powered bombers that should soon be forthcoming. The surviving XB-42 (43-50224) was allocated to various test purposes.
One of these modifications resulted in the replacement of the -125 Allisons by a pair of 1375 hp Allison V-1710-133 engines. In addition, two 1600 lb.s.t. Westinghouse 19XB-2A axial-flow turbojets were installed underneath the wings. With these changes, the aircraft was redesignated XB-42A, and flew for the first time at Muroc Dry Lake, California on May 27, 1947. A total of 22 flights with the XB-42A were carried out by Douglas flight test crews, accounting for a total of 17 hours in the air. A maximum speed of 488 mph was achieved during the tests. On August 15, 1947, the XB-42A made a hard landing in the tail-low position, damaging the lower vertical stabilizer and lower rudder, and the aircraft was returned to Santa Monica late in 1947 for modifications of the jet nacelles.
The remainder of the XB-42 modification program was cancelled in August of 1948, and the XB-42A was struck off charge on June 30, 1949. It was turned over to the National Air and Space Museum. For several years thereafter, it was kept at the National Air Museum Storage Facility in Park Ridge, Illinois. In April of 1959, the fuselage of the XB-42A was moved to the Paul Garber restoration facility at Suitland, Maryland, where it was stored awaiting a possible future restoration. The XB-42A is now in the restoration hangar of the National Museum of the United States Air Force at Wright-Patterson Air Force Base in Dayton, Ohio, having been transported to the museum from the Paul Garber restoration facility in 2010. it?
Two Allison V-1710-125 liquid-cooled V-12 engines, each rated at 1325 hp for takeoff and 1800 hp war emergency. Performance: Maximum speed 410 mph at 23,440 feet, 344 mph at sea level. Cruising speed 312 mph. Service ceiling 29,400 feet. Normal range 1800 miles, maximum range 5400 miles. Dimensions: Wingspan 70 feet 6 inches, length 53 feet 8 inches, height 18 feet 10 inches, wing area 555 square feet. Weights: 20,888 pounds empty, 33,208 pounds gross, 35,702 pounds maximum loaded. Armament: Four 0.50-inch machine guns installed in remotely-controlled turrets on the trailing edges of the wings. The bomb bay could carry a maximum load of four 2000-pound bombs.