Martin B-57 Canberra
|B-57A in flight over Chesapeake Bay, Maryland|
|First flight||20 July 1953|
|Status||Retired from military service; 3 in use by |
US$1.26 million (B-57B)
The Martin B-57 Canberra is an American-built,
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
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. The three remaining flightworthy WB-57Fs are technically assigned to the
At the outbreak of the
On 16 September 1950, the USAF formally issued a request for a jet-powered bomber; the sought aircraft had to possess a top speed of 630 mph (1,020 km/h), ceiling of 40,000 feet (12,190 m), and range of 1,150 miles (1,850 km). Full all-weather capability and a secondary reconnaissance role also had to be included in the design. The American contenders included the
As part of the USAF evaluation's process, all five aircraft were submitted to a series of fly-offs to determine their performance. On 21 February 1951, a British Canberra B.2 (WD932), flown by
That the Canberra was a foreign aircraft 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
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
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
In place of the curtailed B-57A, a more refined bomber variant, the B-57B, was developed. Having a more lengthy development time, this model incorporated the structural and system changes that had been recommended by WADC, which resulted in the aircraft being more adaptable than its B-57A predecessor. Of the external changes, the most significant was the adoption of a fighter-style
The B-57B introduced several other major changes. In terms of armaments, a total of four
The substantial design changes between the B-57A and B-57B models resulted in delays to the overall program, as well as incurring substantial costs on the fixed-price contract. Gunston and Gilchrist stated of the consequences to the program: "This was clearly not the manufacturer's fault, but the money effectively ran out after 177 of the planned 250-aircraft order had been completed". In 1954, in response to the sound performance offered by the B-57B, the USAF elected to place a large second order; this included a further 100 B-57B bombers, 38 B-57C trainers, and 20 RB-57D high-altitude reconnaissance aircraft. In 1955, a final batch of 68 B-57E
In 1969, in response to demands for a capable night interdiction aircraft for combat operations in the Vietnam theatre, a total of 16 B-57B Canberras were substantially rebuilt during a lengthy upgrade program. These aircraft received an entirely new nose section containing an AN/ANQ-139 forward-looking radar, a low-light television system, and an AN/AAS-26