page_title: Martin B-57 Canberra
section_title: Production arrangements
hierarchical_section_title: Martin B-57 Canberra / Development / Production arrangements
caption_attribution_description: English: English Electric-built Canberra B Mk2, WD940, shown here after its transatlantic flight, as 51-17352, the prototype Martin B-57.
context_page_description: The Martin B-57 Canberra is an American-built, twinjet tactical bomber and reconnaissance aircraft that entered service with the United States Air Force in 1953. The B-57 is a license-built version of the British English Electric Canberra, manufactured by the Glenn L. Martin Company. Initial Martin-build models were virtually identical to their British-built counterparts; Martin later modified the design to incorporate larger quantities of US-sourced components and produced the aircraft in several different variants.
  The B-57 Canberra holds the distinction of being the first jet bomber in U.S. service to drop bombs during combat. The Canberra was used extensively during the Vietnam War in a bombing capacity; dedicated versions of the type were also produced and served as high-altitude aerial reconnaissance platforms, and as electronic warfare aircraft. The B-57 Canberra was also sold to export customers abroad; further combat use was seen by the Pakistani Air Force during the Indo-Pakistani War of 1965 and the Indo-Pakistani War of 1971.
  In 1983, the USAF opted to retire the type; the B-57 Canberra's retirement marked the ending of the era of the tactical bomber.
context_section_description: The Canberra was a foreign aircraft, which meant its superiority in terms of performance did not guarantee political support in spite of the urgent need, particularly in light of there being several rival indigenous aircraft designs. There were also doubts about production availability with English Electric being able to mesh with USAF demands, as well as questions over continued spares support. In March 1951, many of these questions were answered; with production lines already at full capacity meeting Royal Air Force orders and those emerging from other export customers, English Electric entered into discussions with Glenn L. Martin Company. It was proposed that Martin would receive a license to domestically build the Canberra in the United States. According to Gunston and Gilchrist, the Americanization of the Canberra program proved effective at dismissing much of the political opposition to the project.
  On 23 March 1951, the USAF issued a contract to Martin, requesting the manufacturing of an initial quantity of 250 Canberras, which had received the USAF designation B-57A (Martin internally designated the type as the Model 272). On 3 April 1951, English Electric and Martin both signed a formal licensing agreement to cover the Canberra's production.
  During August 1951, a second British-built Canberra (WD940) was flown to the US to act as a pattern aircraft for Martin, as well as to perform assorted trials and to support performance validation of airframe changes. On 21 December 1951, one of the British pattern aircraft (WD932) was lost in accident; although this was subsequently discovered to be caused by incorrect fuel scheduling having led to the tail-heavy aircraft exceeding its design limits during a maneuver, the crash jeopardized the entire program and invigorated the anti-Canberra political opposition. The crash did lead to some design changes in the face of political pressure, but these were not implemented on the first 75 aircraft to be produced.
  Due to the great urgency placed on delivering the B-57A Canberra, the initial phase of manufacturing performed by Martin used a minimum-change formula to expedite production; thus the first B-57As to be produced were largely identical to the Canberra B.2. As such, more than 30 changes that had been requested by the Wright Air Development Center (WADC) were rejected on program schedule or cost grounds. One noticeable exception was the adoption of more powerful Armstrong Siddeley Sapphire engines capable of producing 7,200 lbf (32 kN) of thrust, which were license-built in the United States as the Wright J65. The Sapphire-based J65 powerplant had been selected in place of the British-built Canberra's Rolls-Royce Avons as the USAF had placed an emphasis on operations within hot climates and intended to fly at a slightly higher maximum gross weight than the RAF's operating practices.
  Several other minor differences were also present between early US-built and UK-built Canberras. These changes included the canopy and fuselage windows being slightly revised, the crew being reduced from three to two, the adoption of wingtip fuel tanks, engine nacelles were modified with additional cooling scoops, and the conventional "clamshell" bomb bay doors were replaced with a low-drag rotating door originally designed for the XB-51. As a result of these changes, the bomb bay of the US-built aircraft was slightly smaller than its UK-built counterparts in order to allow the American aircraft to carry more fuel; however, the overall external shape of the Canberra remained unchanged.
  In early July 1953, the first US-built production aircraft (52-1418) rolled out; it conducted its maiden flight on 20 July 1953. One month later, this initial production aircraft was accepted by the USAF, by which point a cessation of hostilities had come into effect in Korea. This was one of only eight B-57A Canberras to be manufactured; the remaining 67 aircraft from this first batch, deemed no longer to be required as bombers, were converted on the assembly line to serve as medium-altitude reconnaissance air
caption: The British-built Canberra B.2 that was used as a pattern and prototype for the B-57
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