Studies made by Douglas in early 1943 marked the start of the official development of the XB-42, first known as the XA-42. (In 1939, the "attack aviation" category was replaced by a "light bombardment" one, even though the "A" designation was kept throughout the war. One reason for the change came from Gen. H. H. Arnold's belief that it was more efficient and safer to fight the enemy with light bombers, and their carefully selected bombloads, than to rely on the machine guns of the attack type aircraft.)
The radically new design was another example of the evolutionary process, although it incorporated features of the slightly smaller A 20 and A 26 airplanes, also manufactured by Douglas.
Requirements for the XA-42 (formally redesignated as the XB-42 on 25 November) stemmed from the Army Air Forces's recurring need during the war years for smaller, more efficient, more economical, speedier, and longer range tactical bombardment aircraft. Acquisition of the XA-42 was related to that of the B-29. The Army Air Forces (AAF) wanted modern light bombers to avoid using costly strategic bombers in strictly tactical applications.
The design proposal, submitted by Douglas in April 1943, impressed the AAF favorably, and Letter Contract W535-ac-40188 was approved on 25 June. This document, calling for 2 experimental models and a static test article, was logged by the Materiel Command (soon to be discontinued, as AAF Air Technical Service Command came into being) under Project MX-392 as a purely experimental endeavor. And, as it turned out, plans for manufacturing production models of the airplane did not go beyond the discussion stage.
In September 1943, just a few months after approval of the XB-42 project, the AAF asked if jet engines could be added to 1 of the experimental aircraft covered by the contract of June 25th. In October, the Materiel Command recommended that jet engines be installed in the XB-42 static test article, if the contractor thought that a satisfactory all jet airplane would result. Douglas quickly pointed out that development of a practically new aircraft would take time and that modifying 1 of the XB-42s would be much faster. But the AAF's interest in jet propulsion was increasing, and the development and production of new jet bombers were strongly favored. Hence, the XB-42 modification devised by Douglas, although approved by the AAF in December 1943, would not get underway before 1945, 1 year after the aircraft's first flight.
Clean aeronautical lines and the novel engine propeller arrangement were the most striking features of the all metal, cantilever, mid wing XB-42 monoplane. The 2 Allison liquid cooled, reciprocating engines were mounted inside the fuselage in order to eliminate the drag of large nacelles. Pusher type propellers were located in the empennage to do away with thrust disturbances. Win shafts, similar to those in the Bell P-39 fighter, connected the propellers to the forward located engines.
Designed and constructed in the record time of less than a year, the XB-42 was first flown by Douglas on 6 May 1944. As a safety measure, the aircraft's initial flight originated from and was conducted over Palm Springs Army Air Base, California. Even though the XB-42 was the first AAF bomber during World War II to substitute pusher for the conventional tractor propulsion, a change requiring the development of radically different propellers,(Built by Curtiss Wright, the 13 foot propellers needed perfecting. However, further development was stopped when it became obvious that production of the XH-42 was out of the question.) the 22 minute flight proved uneventful.
In routine fashion, the letter contract of June 1943 was replaced on 11 February 1944 by a definitive contract carrying the same identification (W535-ac-40188). The definitive contract, however, included a new provision covering the development of an all jet version of the XB-42, later identified as the XB-43. On the other hand, no official mention was made of the approved XB-42 modification until 23 April 1945, when a contract change notification authorized conversion of the first XB-42 to the XB-42A configuration.
Flight testing of the first XB-42 proved, on the whole, disappointing. In test flights, conducted between May 1944 and March 1946, stability of the airplane was satisfactory, but controls were inadequate. During development, the XB-42 had taken on considerable extra weight over that foreseen in the design proposal and, as a result, did not meet the Douglas guarantees either for maximum speed at altitude, or for range. Even more frustrating was the excessive vibration from the engines and propellers and from the bomb bay doors when open.
Testing of the second XB-42, first flown on 1 August 1944, was another disappointment, mainly because its combat capability was no better than that of the first model. The plane did have slightly improved speed and range, however, as demonstrated in a coast to coast flight in November 1945 in which it covered 2,295 miles in 5 hours and 17 minutes. In any case, testing ended abruptly. The second XB-42 was completely destroyed on 16 December 1945, in an accident near Bolling Field, D.C. Failure of the landing gear and fuel starvation were the accident's major causes.
The XB-42 flight testing program was extensive, but the second aircraft's premature loss prevented completion of a number of special tests. Douglas tested the first XB-42 for some 129 hours, accumulated in 154 flights. The contractor test flew the second, short lived aircraft for more than 65 hours, accrued in 57 flights. The Air Force put in 14 hours of flight tests on the first XB-42, and 51 hours on the second one. The modified XB-42 (XB-42A) was flight tested by Douglas for approximately 17 hours that were reached in 22 flights. The Air Force test flew the XB-42A only once, for 1 hour. The flight met the contractual acceptance requirements.
Douglas was authorized to begin work on the XB-42 conversion in April 1945, but the modifications were immediately postponed because the Bureau of Aeronautics could not speed delivery of the Westinghouse 19XB-2A Navy type jets due to be fitted on the aircraft (1 unit under each wing). Testing therefore went on until March 1946, when the aircraft's left engine failed in flight. The XB-42 was then returned to the Douglas plant in Santa Monica, California, where a new landing gear, plus internal and external fuel tanks were to be installed in addition to the auxiliary turbojet engines.
During the latter part of 1946 and early in 1947, after the forging problems of the Westinghouse turbojets were solved, Douglas advanced the factory completion date of the programmed modifications several times, consequently delaying the important vibration tests.
The first flight of the XB-42A on 27 May 1947, from Santa Monica to Muroc Army Airfield, California, was marred by the obvious drag of the XB-42A's new turbojets. In ensuing flight tests at Muroc, both the Allison engines and added jets proved unsatisfactory. To make matters worse, the vibration tests, only started in mid 1947, were stopped on 15 August, when the XB-42A made a hard landing in the tail low position, damaging the lower vertical stabilizer and lower rudder. The contractor wanted to resume testing as soon as possible, but the Air Materiel Command (The Air Materiel Command replaced the Air Technical Service Command on 9 March 1946) decided that the new jet nacelles also needed modifications, and the aircraft was flown back to Santa Monica late in 1947. In the ensuing months, although it appeared that the Air Force still wanted a perfected XB-42A, Douglas became increasingly convinced that further studies and engineering to reduce weight, eliminate vibration, and bring the modified plane up to guaranteed performance would not be economical.
Convinced by the Douglas argument, the Air Force in August 1948 decided to cancel the remainder of the XB-42A modification program, and to accept the aircraft "as is." The decision also marked the end of the entire B-42 experimental project.
The first XB-42, after being conditionally accepted on 24 September 1946, became the XB-42A which was finally accepted on 19 August 1948. The second, ill fated XB-42 was accepted and delivered on 8 December 1945.
Both the XB-42 and XB-43 (also developed by Douglas) were procured under the same contract (W535-ac-40188) at a total cost of $13,682,095, including the contractor's fixed fee of $227,775. The $13.7 million settlement figure, recorded by the Air Force Contract Audit Office on 30 November 1947, did not provide a breakdown of the amount expended on each project. A portion of the XB-42A modifications was the object of another contract (W33-038-ac-14525), signed on 31 March 1947. The contract's relatively small amount (about $300,000) was most likely covered by the audit of November 1947.
The Air Force thought the modified XB-42A, with its clean aeronautical lines and other novel features, was a true museum piece and kept it at the National Air Museum Storage Activity in Park Ridge, Illinois, pending completion of additional space at the Smithsonian Institution in Washington, D.C. In April 1959, the fuselage of the XB-42A was moved to the Smithsonian's Suitland Annex, in Silver Hill, Maryland.
|Join the GlobalSecurity.org mailing list|