Increased design gross weight and the Western Electric K-5 bombing system were the most significant new features of the conventional sweptback wing, all-metal B-66B. Like the RB-66B, the B-66B carried a 3-man crew.
The bomber configuration, endorsed by the Air Staff in August 1952, occasioned further changes to the initial Air Force version of the experimental A3D. The airplane's design gross weight was raised to 78,000 pounds (8,000 pounds more than the RB-66B's), the bomb bay was lengthened 17.5 inches, the capacity of the aft fuselage fuel tanks was increased, and pylons were provided to support extra 500-gallon fuel tanks. The approved B-66B configuration also involved the installation of a bombing system and of bomb dropping devices. Finally, a detachable probe-drogue in-flight refueling system was added, and a further revision of the XA3D's hydraulic system was directed out of necessity, since every effort was to be made to keep the bomber and reconnaissance versions as close to each other as possible, most B-66B requirements were incorporated into the RB-66As. Ensuing problems, resulting modifications, and reduction of the B-66B procurement did not alter the program's policy on interchangeability.
The B-66B procurement was initiated in August 1952, when Letter Contract AF 33(600)-16341 was amended to cover the purchase of 26 B-66Bs. The amendment in addition changed the terms of the letter contract of April 1952, which reverted to the cost-plus-fixed-fee type of agreement endorsed for the RB-MA's. The amended contract of August 1952, like the initial RB-66A document, assured Douglas of a profit amounting to 6 percent of the aggregate contract cost. A similar contract, AF 33(600)-25669, started by an October 1953 letter contract, called for 75 B-66Bs, but was amended many times as a result of a program reduction in mid-1955. For the same reason, contract AF 33(600)-28368, the fourth and last procurement order signed on 24 September 1954 also underwent many changes. By the end of 1955, only 55 B-66Bs were to be bought, but General Twining agreed in early 1956 that the single authorized wing of B-66Bs should acquire more planes to take care of normal attrition. The Air Force held the B/RB-66 program on a tight financial rein. The program's ceiling had been settled once and for all. Hence, the approved extra 17 B-66Bs were diverted from the RB-66B total. The Air Force also specified that any cost increases generated by the directed substitution would have to be absorbed by deleting additional RB-66Bs.
The first official B-66B flight was accomplished on 4 January 1955, 7 other B-66Bs being accepted by the Air Force before the new tactical bomber was cleared for operational assignment. Besides participating in the usual testing program, the early B-66Bs were involved from the start in the crucial development of their future sophisticated components. For instance, flight testing of a prototype K-5 bombing system, tailored for the B-66B, was pursued actively during the early part of 1955. These tests entered a new phase in March 1955, when high-altitude and high-speed trials began. The functional testing of a production model of the bombing system soon followed. As fully expected by the Air Research and Development Command's Armament Laboratory in mid-1955, the K-5 promised to give the Air Force ". . . an all-weather tactical bombing capability compatible with the mission requirements of the B-66."
The B-66Bs began reaching the tactical Air Command in March 1956, about 1 year later than originally scheduled. However, once under way, deliveries were reasonably steady, 64 of the 72 B-66Bs on order being accepted by mid-1957. The Ninth Air Force's 17th Light Bombardment Wing, at Hurlburt Field, Florida, remained sole recipient of the B-66Bs until September 1957, when TAC began to transfer its total contingent to the United States Air Forces in Europe.
Despite the importance of the electronic countermeasures program, nothing could be done about it when the B/RB-66 configuration started taking shape. Electronic countermeasures components were in early developmental stages, and technological incertitudes prevented the establishment of firm operational requirements. Nevertheless, after many tentative plans, the Air Force in October 1954 decided the process should be accelerated to acquire at least an interim electronic countermeasures capability. Hence, a multi-phase interim ECM program was set up early in 1955. Briefly stated, the program called for installation (during the aircraft production) of available parts of the APS-54 radar warning receiver and ALE-2 chaff dispensers. Three interchangeable types of jamming equipment were ordered, and interchangeable ECM tail cones were to be fashioned to carry some of the chaff equipment and antennas. Finally, provisions for ECM cradles were to be made in the bomb bay of the B-66B. Yet, even though some B-66Bs had already begun to reach TAC, configuration changes were still under consideration in the fall of 1956. Procurement of the B-66B had been reduced in mid-1955, but the aircraft had not been exempted from the ambitious electronic countermeasures program planned for the entire B/RB-66B fleet. During the second half of 1956, 2 development engineering inspections were held a few weeks apart. The first, in late September, covered all-chaff and half-chaff electronic countermeasures cradle configurations of the B-66B. The second, held in early October, was concerned with the B-66B's entire electronic countermeasures installation. The 2 development engineering inspections were successful, the Air Force being satisfied by the apparent completeness and flexibility of the selected arrangements. However, the whole project was soon to encounter problems.
Soon after the development engineering inspections of September and October 1956, the electronic countermeasures program ran into trouble. Major alterations would be needed to fit the required pieces of ECM equipment into the B/RB-66 airframes. Even if the Douglas production lines expedited the necessary modifications, full transfer of the B-66Bs to Europe and deployment of the several RB-66Bs destined for the Far East would have to be postponed. By the end of the year, it became clear that more unexpected changes would be needed, all of which affected tail cones and cradles. Included were substitution of various components, addition of some kind of apparatus to permit selective switching among jammers (a requirement previously overlooked), more powerful jamming signals, and new tail cone antennas.28 Moreover, just the interim ECM program proposed in March 1955 would be extremely costly-$40 million for a partial installation. In July 1957, Headquarters USAF decided that no B/RB-66Bs would be ECM-equipped during production. The Air Staff also cut down the procurement of cradles by one-third, to a total of 12, and reduced the tail cone purchase to 113, a decrease of 25. At the same time, the Air Force indicated that a modernization/IRAN program would catch the B/RB-66Bs that had not been modified to accommodate needed ECM equipment. In late 1957, 13 B-66Bs and 31 RB-66Bs were scheduled for such preparation.
For all practical purposes, flight testing of the B-66B ended in January 1957, for the few tests yet to be completed were of minor importance. Overall test results were satisfactory, and the engineering improvements prompted by the testing program either had been or were being incorporated into the aircraft. The B-66B nearly met the Air Force procurement specifications. Noted performance decreases (10 percent in altitude, 12 percent in range, and 7 percent in low-altitude speed) might not be correctable, but the aircraft's flying characteristics were good. Thorough testing had demonstrated that the B-66B was especially well-adapted to low-level flight, could handle a variety of special weapons, and could be aerially refueled to 96,000 pounds.
The positive qualities of the B-66B, flown by the 17th Bombardment Wing, were not in doubt, testing having ascertained the aircraft's basic soundness. Nevertheless, being practically identical to the RB-66B, the new tactical bomber shared the engine problems, Sta-Foam vicissitudes, and other early difficulties of the reconnaissance aircraft. The B-66B in addition had a few flaws of its own, which also remained uncorrected prior to the aircraft's overseas deployment.
Early in 1958, after a period of training, the squadrons of TAC's 17th Bombardment Wing were transferred to the 47th Bomb Wing (Tactical), a unit of USAFE's Third Air Force, with stations at Sculthorpe and Alconbury in the United Kingdom. While the 47th Wing's conversion from the obsolescent B-45 was a major operational gain, the B-66B's arrival was accompanied by serious maintenance difficulties. The flow of spare parts from the United States remained inadequate until August 1958, and shortages of electronic equipment and of such critical items as hydraulic pumps and oxygen regulators persisted throughout much of the year. In addition, the bomb shackles initially installed on the B-66B did not have a lock secure enough to prevent inadvertent bomb releases. This problem, though addressed from the start by TAC, was not being solved as fast as the Air Force would have liked. To save time, personnel of the 47th Wing installed the first new shackles developed by Douglas. Other B-66Bs were due to receive the improved shackles during the B/RB-66 overall modernization program. However, even the simplest plans could be affected by circumstances beyond USAF control. Although started as scheduled on 1 May 1958, the "Little Barney" overseas program taking place at the AMC's Air Depot at Chateauroux, France, was hindered significantly by French labor unrest. The B-66Bs shipped to Chateauroux for modernization (elimination of Sta-Foaming damages, engine retrofits, and the like) were often held for 52 days, almost twice the work time authorized for every aircraft. To speed up the B-66B's operational readiness, the Air Force decided to ship new shackles directly to the 47th Bomb Wing, which would enable the unit to install them promptly on the modified aircraft, finally back from Chateauroux.
The October 1957 delivery of the last B-66B marked the end of production.
The Air Staff finally agreed to let USAFE retain its B-66Bs beyond the FY 61 inactivation date that had been established originally. Still, except for 13 specially equipped B-66Bs, the entire contingent was out of the operational inventory by mid-1963.
From the start of the B/RB-66 program, the Air Force thought the B-66 light tactical bomber would also be used for ECM jamming. Hence, a pallet (or cradle), carrying jammers, chaff dispensers and other necessary gear, could be fitted in the aircraft's bomb bay, once the latter was stripped of its bombload and shackles. Nevertheless, retention of 13 ECM equipped B-66Bs would entail some work since the aircraft were not new. In April 1964, the Air Force Logistics Command began to develop a working agreement between USAFE's 42d Tactical Reconnaissance Squadron, the Mobile Air Materiel Area, and a Lear-Siegler contract team. The project, as settled, covered the IRAN program for each aircraft, including removal and inspection of all fuel cells and updating of the electronic countermeasures system of the aircraft, referred to as Brown Cradle. The Air Force estimated that to do the overall task properly would require some 3,400 man-hours for each of the 13 Brown Cradle B-66Bs. Since USAFE did not want to part with more than 2 of the aircraft at one time, the B-66B's renovation and Brown Cradle modification extended well into 1965.
USAFE retention of its updated Brown Cradle aircraft was short. In late 1965, 5 of the modernized B-66Bs were deployed to Southeast Asia. In May 1966, the 42d Tactical Reconnaissance Squadron's remaining 8 Brown Cradle aircraft also departed for the war theater.
Eleven B-66Bs were reactivated early in 1967 and, after modification, were sent to Southeast Asia. Meanwhile, on-going testing to determine the aircraft's life expectancy proved satisfactory enough. Even though the B-66B shared the engine problems of the entire RB-66 fleet, additional B-66Bs were soon withdrawn from storage and modified for war service. Reactivated and modernized B-66Bs followed the operational pattern of the RB-66Bs. Also known as EB-66s since early 1966, a few of the aircraft still lingered in the active inventory in mid-1973.
On 12 August 1956, one of the Air Force's new subsonic B-66 jet bombers flew from Hawaii to California in 4 hours and 27 minutes, covering a distance of 2,690 miles at an average speed of more than 600 miles per hour. In the fall of 1957, only 17 hours after being alerted in the United States, several B-66Bs, after crossing the Pacific as elements of a Composite Air Strike Force, were flying simulated bombing missions over the Philippines.
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