The XB-43 was essentially a jet version of the unconventional XB-42, officially developed by Douglas in early 1943. The XB-43 did not reach the drawing board before 1944, but the project's development started in September 1943.
General requirements for a jet bomber of the XB-43 type arose during World War II, as a result of the development of German jet fighters. Also, the Air Corps needed an aircraft that could destroy military targets on land and sea in support of air, ground, or naval forces. Specific requirements were defined in 1944. The Army Air Forces (AAF) wanted the XB-43 to have a gross weight of 40,000 pounds; a maximum speed of 420 miles per hour at an altitude of 40,700 feet; and a range of 1,445 miles, at the same high altitude, with an 8,000-pound bomb load.
A letter supplement to the XB-42 contract (W535 ac-40188) authorized on 14 January 1944 the initial procurement of 2 XB-43s. A formal supplemental agreement, approved on 31 March, set the estimated cost of the 2 experimental planes at $2.7 million and the contractor's fixed fee at about $107,000. The reason for such hurried transactions was to introduce tactical jet bombers swiftly into the operational inventory. As early as December 1944, the AAF seriously considered placing the XB-42 in production. Accordingly, the Air Technical Service Command asked Douglas on 30 December to submit a production proposal without delay.
The XB-43 was the first American bombardment airplane to be powered exclusively by jet engines: TG-180 turbojets (later J35s), designed by the General Electric Company. Otherwise, except for the absence of the dual-rotating propeller at the rear of the empennage, the XB-43 had retained the XB-42's appearance and structural design.
Early engineering problems with the pioneer J35 power plan hampered the XB-43's development. To begin with, General Electric only shipped the first J35 engine to Douglas in December 1944. Then, numerous changes in piping, wiring, and sheet metal work were necessary to make the engine suitable for flight. By March 1945, and in spite of the assistance of General Electric technicians, Douglas had spent more than 3,000 manhours to solve problems connected with the first engine. Moreover, subsequent engine deliveries, due since October 1944, were delayed until July 1945.
While the B-43 experimental program was assured from the start, the production program, which once appeared very promising, did not materialize. The Air Technical Service Command recommended in March 1945 the immediate procurement of 50 B-43s, but the Douglas production schedule for a preliminary lot of 13 test service airplanes proved unsatisfactory. Contrary to expectation, the planes would not be available for testing ahead of the B-45 and the B-46 prototypes. In addition, and notably of greater import, the proposed B-43 test aircraft would not meet the performance requirements that had been previously established. The AAF therefore opted to cancel all B-43 production plans. The Air Technical Service Command notified Douglas of the AAF decision on 18 August 945, specifying that the projected procurement of the 13 test aircraft was also nullified.
The XB-43 made its first flight on 17 May 1946. As in the XB-42's case, because of the experimental status of the aircraft, the 8-minute flight was made from a military installation. The XB-43 had been dismantled at the contractor's plant in Santa Monica, California, and moved to Muroc Army Airfield, where it was reassembled. The AAF had invoked the War Powers Act to override the state's objections to having the disassembled airplane trucked over the public highway.
The first official flight of the second XB-43, on 15 May 1947, lasted 20 minutes and took place between Hughes Field in Culver City, California, and Muroc. After being fitted with special instrument, the second XB-43 had been trucked to Hughes Field where Douglas tested its ground handling and flight characteristics. To control costs, the AAF had informed Douglas that the second XB-43's flight test time was not to exceed 5 hours, without special authorization.
General Electric's labor difficulties and similar problems at the General Motors Corporation's Chevrolet Division, where most J35 engines were being built, continued to slow Douglas's progress. For example, in January 1946, no one knew with any certainty when the J35s earmarked for the second XB-43 would be available.
However, Douglas's engineering setbacks were not confined to the XB-43s power plant. One early problem, stemming form the difficulty encountered in obtaining positive nose wheel door operation, involved the pressurization of the entire nose section and nose wheel well. This problem was solved, but only by default. In January 1946 Douglas requested, and the AAF granted, permission to eliminate this pressurized area because the original requirement which called for the installation of a nose code had been deleted. A second serious engineering problem was the tendency of the XB-43's Plexiglas nose to crack under temperature extremes. The substitution of costly metal units, $5,000 each, was first considered. In November 1947, however, the Air Force decided that the difficulty could be corrected by installing wooden noses, much cheaper and adequate for a plane earmarked for testing, but no longer due to reach production.
While both XB-43s were used extensively for testing purposes, flight testing of each aircraft was relatively short. Douglas test-flew the first XB-43 for over 9 hours, accumulated in 28 flights; the AAF only test-flew it for about 4 hours, reached in 3 flights. Testing of the second XB-43 was even shorter. Douglas flew it for less than 8 hours, gained in 17 flights; the Air Force test-flew it once, for 1 hour.
The first XB-43 was accepted on 27 February 1947; the second, on 27 April 1948.
The Air Force Contract Audit Office on 30 November 1947 recorded the cost of the XB-42, XB-42A, and the XB-43 programs at $13.7 million, and did not provide a breakdown of the amount spent on each program. However, retained data on the XB-43 project set the program's tentative cost at $6.5 million. Although estimated, the figure appeared credible.
ARDC used the first XB-43 for a variety of tests until February 1951, when an accident ended the aircraft's testing career, which by then had reached almost 400 hours in flight. The second XB-43, after being assigned to the Air Materiel Command's Power Plant Laboratory, went to Muroc where it served as a test-bed for the General Electric J47 (TG-190) engine. Supported by the spare parts retrieved from the first XB-43, the second model also paid back its investment, totaling more than 300 hours of flight time before leaving the Air Force inventory in December 1953. The second XB-43 then went to the National Air Museum of the Smithsonian Institution.
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