The Martin B-57 Canberra was a twin jet engine tactical bomber that has equipped the United States Air Force from the mid of 1950s. Its robust aerodynamic design and its great reliability made it ideal for the role of tactical bomber and reconnaissance aircraft. It was equipped with two Wright J65 turbojet engine and it was able to reach 960 km / h. Thanks to its bomb bay and its four external hardpoints it was able to carry an offensive load of 3,300 Kg. During its long operating activities, several versions had been developed. In particular the B-57G, derived from the B-57B, was developed as night intruder. Easily recognizable by the added “radome”, the B-57G played an important role during the Vietnam War to support combat along the Ho Chi Minh trail. It was equipped with a new radar, a more modern avionics and, in particular, a variety of sensors able of dropping laser guided bombs.
Night strike operational problems in Southeast Asia led to a major reconfiguration of the plane that had been ordered many years before for another conflict. The B-57 night intruder, too late for combat in Korea and never totally successful in Southeast Asia, at least demonstrated under fire the basic qualities justifying its original selection. In 1967, after several trial projects involving the special equipping of different planes were delayed or proved unsuccessful, the Air Force looked to the B-57 to begin satisfying increasingly tough requirements. As successively published in the late sixties, Southeast Asia Operational Requirements 35, 64, 77, and 117 called for a self-contained night attack jet aircraft. The plane had to carry every device needed to acquire and attack mobile ground targets and fixed anti-aircraft artillery sites, in any kind of weather and without any ground or airborne assistance.
The Air Force thought General Dynamics F-111D, as ordered in May 1967, would be the ultimate answer. Yet, production of such a high-performance, avionics-loaded weapon system would not be an easy task. For that matter, the less-ambitious reconfiguration of the already-proven B-57 would also be difficult, again because of the components earmarked for it. Pressed for time, the Air Force in March 1967 decided to equip 3 PACAF B-57Bs with an improved version of the Tropic Moon I low-light-level television already fitted in 1 A-lE. Referred to as Tropic Moon II, the new project was not allowed to linger. The Air Force notified all concerned commands on 12 April, and soon thereafter the Westinghouse Electric Corporation received the modification contract for the 3 aircraft that PACAF chose and ferried from Southeast Asia to Baltimore. Once modified, the Tropic Moon II planes were returned to Southeast Asia without delay. They actually reached Phan Rang AB in South Vietnam on 12 December 1967.
Meanwhile, the B-57’s final reconfiguration was approved. Initially labeled Night Rider, this project centered on a General Dynamics proposal to equip 15 B-57s with low-light-level television, forward-looking radar, and infrared sensors. The B-57 appeared well suited for the Night Rider role. The aircraft was available, had room for several sensors, and could carry 9,000 pounds of bombs at speeds of 160 to 500 knots. TAC and PACAF supported the Night Rider project, but in May 1967 the Air Staff rejected it as somewhat risky and far too costly. Rising difficulties in Southeast Asia, where enemy night movement of troops and supplies continued unabated, caused the Air Staff to reconsider its disapproval. In mid-year, the Air Force not only decided to endorse the Night Rider concept, but also to speed it up. This gave way to Tropic Moon III, the conversion of B-57s to self-contained night attack configuration. Tropic Moon III received added impetus in August, when the Air Staff told the Air Force Systems Command to skip usual managerial procedures, to develop a B-57G prototype “immediately,’ and to plan for simultaneous procurement of a full B-57G squadron. The Air Force wanted the Tropic Moon III prototype to be ready for testing by September 1968. It also wanted the 15 B-57Gs “to be deployed as soon as possible” to Southeast Asia.
Notwithstanding Tropic Moon Ill’s urgency, money had to be found before anything could be done about it. By late 1967, the skimpiest Air Force estimates showed that it would take some $50 million to accomplish the project. But in early 1968, the problem seemed to be solved. Funds from lower priority programs had been shifted, $25 million had been added to the overall budget for fleet modification, and the Air Force was ready to inform industry of its requirements. Hence, on 8 March, Air Force Systems Command’s Aeronautical Systems Division advertised for bids to modify government-furnished B-57Bs to a new “G” configuration by integrating government- and contractor-furnished equipment. The contractor guidelines, offered by the Aeronautical Systems Division, were quite explicit. Besides the basic airframe, the Air Force would furnish engines, electronic countermeasures equipment, and communications sets. The contractor would provide the weapons delivery and navigation systems as well as modify the airframes. Specific yardsticks were established for the B-57G’s avionics. The Tropic Moon III forward-looking radar had to be highly sophisticated, certainly as efficient as the ANI APQ-126 of the LingTemco-Vought A-7D (the Air Force’s forthcoming version of the Navy A-7 Corsair). The Tropic Moon III weapons delivery computer and navigation system were to be particularly accurate. Additional armor plate and new ejection seats had to be provided to increase crew protection. Also, other changes were required in order to enhance safety, including the mounting of self-sealing fuel tanks in the aircraft fuselage.
The Air Force’s 1968 financial bliss did not last long. Bids submitted in April by General Dynamics, Ling-Temco-Vought, North American Rockwell, and Westinghouse topped the highest USAF estimate by $30 million or more. In May and June, the extra money actually needed could not be secured. It therefore became clear that the Air Force had only 3 choices, one of which was to forget the whole project, a possibility considered for a while. Less drastic second and third alternatives were to reduce the number of B-57Gs, or to trim some of the weapon system’s costly requirements. Well acquainted with the state-of-the-art limits and the pitfalls of new components of the forward-looking radar type, the Aeronautical Systems Division fought for the third solution. The division won its case, as Wright Air Development Center had years before when challenging the wisdom of the B-57A production. Reconfiguration of 16 lower-performance Tropic Moon III B-57Gs (prototype included) was officially approved on 29 June. The selected prime contractor, the Westinghouse Defense and Space Center of Baltimore, agreed on 15 July to do the work for $78.3 million-an amount still higher than hoped for. The major subcontractors were involved. Westinghouse counted on Martin-Marietta to inspect and repair the elderly B-57Bs picked for reconfiguration. Texas Instruments was made responsible for the forward-looking infrared radar and laser ranger.
When dealing with new technology, the best plans could go astray. The Air Force wanted to put the Tropic Moon III B-57s into combat by April 1969, but this soon was changed to December. And this more realistic deployment date was not met, even though the modification at first proceeded smoothly. There were many reasons for every delay. In early 1969, Westinghouse category I tests fell behind schedule because the Air Force was late with the shipments of necessary ground equipment. To compound the problem, in August Texas Instruments’ deliveries of forward-looking infrared sensors began to slip significantly, and the Air Force failed to deliver the electronic countermeasures equipment on time. In late 1969 investigation of recent crash of a B-57G, still being tested by Martin pilots, indicated that the aircraft’s minimum speed was too slow for safety. Ensuing flying incidents, in February and May 1970, uncovered mechanical flaws which, although minor, had to be corrected.
Meanwhile, there were other setbacks. In 1968, the Tropic Moon II B-57’s performance had proved disappointing, mainly because the lowlight-level television system did not live up to expectations and the aircraft’s navigation system remained unreliable. In mid-1969, Westinghouse announced that the Tropic Moon III project would cost at least an extra $3.5 million. This additional expense was troublesome, but the Air Force was more disturbed by other events. Foremost were difficulties experienced with the weapon system’s most crucial components which, besides delaying the program further, affected crew training and testing of new devices and munitions. As a result, the Air Force no longer thought of Tropic Moon III as a partial solution to a most urgent Southeast Asian problem. Rather, it had begun to consider the B-57G and F-111D as evolutionary steps toward the development of a high-speed, fully integrated, self-contained night and all-weather weapon system of the future.
In line with its new Tropic Moon III appraisal, the Air Staff in early 1970 insisted that the latest September deployment date would be met. The B-57G’s category III tests, conducted by the Tactical Air Warfare Center between 29 April and 27 July, did not alter the Air Staff’s decision. Overall, the results of category III testing indicated that, except for the forward-looking infrared radar, the aircraft’s avionics equipment satisfied basic requirements. Concluding that the aircraft performance was nearing that originally specified, Gen. John D. Ryan, 20 Air Force Chief of Staff, ordered the 13th Bombardment Squadron to move to Ubon Air Base, Thailand, on 15 September. Only 11 of the remaining 15 B-57Gs were assigned to the squadron, leaving 3 aircraft at MacDill AFB to train replacement crews. A last B-57G also stayed behind to serve as a “test bed” for future improvements.
The Tropic Moon III B-57Gs were returned to the United States in April 1972. Despite the combined efforts of Texas Instruments and Westinghouse, the forward-looking radar proved deficient. Improved sets updated at a cost of $2 million and first combat tested in September 1971, also never worked completely well. But the B-57G airframe, with its new J65-W-5D engines, measured up to the planning criteria. The aircraft also got involved successfully in such projects as Pave Gat, which showed that sensor-slued guns could function effectively in a jet bomber.
B-57Gs: these planes stayed in Southeast Asia until 12 April 1972. Having been stripped of most of their Tropic Moon components, the B-57Gs went to the Air National Guard-like many of TAC’s B-57Bs in the late fifties.