<p>When World War II came to an explosive end in 1945, the USAAF was the most powerful war machine on the planet. It had built its success on a triumvirate of heavy bombers, light bombers and fighters, and, despite the massive cutbacks which ensued after VJ-day, invested heavily in new technology, especially nuclear weapons. However, the development effort was not pursued with the same vigor across the whole spectrum of its operations. In 1950, the young US Air Force found itself fighting the bitter Korean War, and while it had jet-powered heavy bombers and fighters entering service in numbers, the principal light bomber was still the Douglas A-26 Invader, one of the types that had been responsible for the US triumph in World War II. A modern jet-powered light bomber became a matter of considerable urgency, the result being the swift purchase of the British Canberra.
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<p>Notwithstanding the considerable capabilities of the Canberra, a new light bomber was still needed in fairly short order, and so was born the RBL-X requirement for a fast, agile, all-weather light bomber with reconnaissance capabilities, able to operate at both high and low altitudes and from short runways, and able to carry one of the then-large nuclear weapons and defensive electronic equipment. By far the most stringent requirement was that it should be in service by 1954, which ruled out any clean-sheet designs. There were modified versions of five existing bombers entered (North American B-45, Martin B-51 and B-57 Canberra, Boeing B-47 and the British Vickers Valiant), and a single unflown aircraft type, the Douglas A3D Skywarrior, which was in the final design stage. This dedicated naval attack aircraft suited admirably the Air Force's requirements, and was given the go-ahead on 12 January 1952, even though it was 28 October that year before the naval aircraft flew.
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<p>On 4 February 1952, Douglas received a contract for five RB-66A photo-reconnaissance aircraft, although the whole program was intended to use much commonality between variants with differing roles, beginning with reconnaissance and bombing, and followed by electronic and weather reconnaissance. To render the bomber more attractive to the USAF, its development was entrusted to a design team led by John Buckwalter (rather than Ed 'Mr Carrier Aviation' Heinemann, who had created the A-3), and production was intended to take place at Long Beach rather than the Navy-controlled El Segundo plant.
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<p>Based closely on the A3D, the RB-66A emerged as quite a different aircraft. The wing was redesigned with a different planform and larger flap area. The wing incidence was altered and spoilers were fitted to aid roll control (later fitted to the A3D also). A new fuel system was fitted, with provision for a nose-mounted refueling probe, larger capacity and optional underwing pylons for external tanks. The undercarriage was revised with lower-pressure tires and the bomb bay lengthened to accommodate Air Force weapons. The nose was completely revised, with reprofiled contours to house a much larger radar antenna and to provide the crew with better visibility. The cockpit layout was revised, with the pilot sitting at the front to port with navigator (starboard) and gunner/EWO (port) sitting behind him facing forward. Each had ejection seats, unlike the A3D crews who had to make do with an escape slide which was useless at low altitudes (the Skywarrior's official designation was often quoted by disgruntled crew as 'All Three Dead').
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<p>Apart from the new flight deck glazing and nose shape, the main distinguishing features were the rear gun turret and engines. The turret was remotely controlled from the flight deck using the MD-1 fire control system. The guns were twin M24A-1 20-mm cannon, armed with a total of 1,000 rounds. Powering the B-66 was a pair of Allison J71 turbojets, this engine having been chosen after the initial Westinghouse J40 had been rejected. The Navy chose the Pratt & Whitney J57 for its Skywarriors, but this was in too great a demand for other aircraft types to be adopted for the B-66. Throughout its history the J71 did not distinguish itself, although was available in three versions of increasing power and reliability levels throughout the B-66 production run. The last version, the J71-A-13, did something to alleviate the maintenance and operational difficulties of the earlier engines, but it was never an ideal choice. Indeed, the disparity between service careers of the B-66 and A3D/A-3 is largely attributable to the qualities of the poor J71 and remarkable J57.
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<p>Despite engine troubles and other developmental problems, the first RB-66A (there being no prototype as such) eventually got air under its wheels on 28 June 1954, with George Jansen in the pilot's seat for the short flight from Long Beach to Edwards AFB. This flight, and those that followed, highlighted numerous shortcomings, the most severe of which was a buffet problem which had to be solved by stiffening key areas of the structure. Landing run was excessive, so anti-skid brakes and a landing chute were added. Cockpit visibility was found to be poor, so the glazing arrangement was revised.
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<p>Although bearing an operational designation, the five RB-66As were never intended for anything other than test purposes, so the RB-66B became the first service type. Designed for the night photo-reconnaissance role, the RB-66B featured a large reconnaissance pack in its weapons bay, which mounted four cameras and provision for 48 M120 or 40 M123 photo-flash bombs. The principal difference between it and the A model was the installation of the refueling probe, which was used in conjunction with Boeing KB-50 tankers. In fact, B/RB-66s demonstrated outstanding rapid deployment capabilities within a short time of entering service. Provision was also made for the attachment of 12 1,000-lb (4.45-kN) thrust -jet RATO bottles on the fuselage sides. All reconnaissance versions of the Destroyer were fitted with the APS-27 search radar.
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<p>In service, the RB-66B replaced RB-26Cs, RB-45Cs and RB-57As. The first recipient was the 363rd Tactical Reconnaissance Wing at Shaw AFB, South Carolina, beginning in January 1956, which equipped three squadrons (16th, 41st and 43rd TRS) with the type. Subsequent deliveries went to Europe (1st TRS/10th TRW at Spangdahlem, 19th TRS/66th TRW at RAF Sculthorpe and 30th TRS/66th TRW at Sembach) and Japan (12th TRS/67th TRW at Yokota). After a round of deactivations halved the force in 1959/60, the 1st, 16th and 30th TRS soldiered on in the photo-reconnaissance role until 1965, when the McDonnell RF-4C relieved them of their duties. The USAFE squadrons were moved many times during this short period.
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<p>The electronic warfare specialist 19th TRS fared a little better, flying ECM missions in Europe until 1966, when it was posted to Shaw as the 19th Tactical Electronic Warfare Squadron. This unit sent a detachment of EB-66Es to Osan AB in 1968 under Operation Combat Fox, the air power build-up in Korea which responded to the Pueblo crisis. In December it was transferred to the 18th TFW at Kadena, where it disbanded in 1970. During its European sojourn, the operations of the 19th had gained the Destroyer some notoriety, for it was the squadron which lost an RB-66B on 10 March 1964, shot down over Stendal by MiGs some 20 miles (32 km) inside East Germany after launching on a 'routine navigational training flight' from Toul-Rosi_res AB in France. The crew ejected safely, were held in captivity for a few weeks and subsequently released.
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<p>Development of the bomber version ran virtually concurrently with the photo-reconnaissance ship. The resultant B-66B was fitted with the Western Electric K-5 bombing system, which unfortunately did not provide sufficient accuracy for loft bombing, restricting the B-66B to lay-down or dive attacks. The large bomb bay could accommodate the massive nuclear bombs of the day (Mks 5 and 6) and up to 15,000 lb (6,800 kg) of conventional weapons. To improve bomb release characteristics, a perforated baffle was fitted to deploy forward of the bay prior to bomb-drop.
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<p>Bomber Destroyers entered service in March 1956, assigned to the 17th Bomb Wing (34th, 37th and 95th BS) at Hurlburt Field, Florida. After a short period of service they were reassigned to USAFE in June 1958, with the 47th BW (84th, 85th and 86th BS) at RAF Alconbury and RAF Sculthorpe. Their service there was short, too, the wing deactivating in June 1962. Many factors hastened the demise of the bomber version, not least the unsatisfactory performance of the K-5 system. In a very short period, the rampant US technology machine had decreased the size of the nuclear bomb markedly, while raising aircraft performance to Mach 2 levels. The tactical nuclear role passed to the Republic F-105 Thunderchief. However, the B-66 did get to drop a nuclear weapon, at least one B28 H-bomb being live-dropped at Bikini Atoll in 1956 during Operation Redwing, the first round of thermonuclear tests.
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<p>Electronic and weather reconnaissance were the next objectives of the design team after the initial photo-reconnaissance and bomber requirements had been met. For the former role, the RB-66C was produced, with the weapons bay reworked as a pressurized compartment for four forward-facing systems operators. The antennas for the sophisticated passive receiver suite were housed along the fuselage and, in the case of the APD-4 direction-finder, in large wingtip pods, which remained the principal distinguishing feature of this variant. Under the belly were canoe fairings, one covering antennas for the ALA-6 direction-finder and another which covered three bell-shaped steerable antennas for the ALA-32.
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<p>WB-66D weather reconnaissance aircraft also featured the central compartment, this time for just two operators, the extra space being devoted to meteorological equipment. RB-66Cs entered service in 1956 with the 9th (Shaw), 11th (Yokota) and 42nd (Spangdahlem) TRS in TAC, PACAF and USAFE, respectively, the WB-66Ds being assigned to the same units shortly after. Both types (along with RB-66Bs) flew regular reconnaissance missions around the periphery of (and probably over) the Communist Bloc. While the RB-66Cs regularly monitored Soviet radars and communications, the WB-66Ds mapped weather systems to aid the overall US attack plan against the USSR and its allies.
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<p>One of the original RBL-X requirements, namely that of defensive electronic countermeasures equipment, had been ignored during the early production run of the aircraft. In 1957, however, the Air Force ordered 113 ECM tailcones which could be interchanged with the gun turret. Initially these lengthened tailcones housed an ALE-1 chaff dispenser and various receivers/jammers, but were subsequently upgraded throughout the aircraft's life, notably with 'horn' antennas for the ALR-18 receiver. Additional chaff dispensers (ALE-2) and jammers could be carried under the wing pylons for further protection. Late in the B-66's career some aircraft (EB-66Cs and Es) were fitted with the Mod 2259 tailcone, which added an AAQ-4 infra-red countermeasures system. This was distinguished by a circular plate at the top of the tailcone, cooling intakes and the relocation of the ALR-18 'horns' to the sides.
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<p>ECM tailcones were fitted to 13 lucky B-66Bs which escaped the retirement of the bomber fleet. Under the 1959 program Brown Cradle, they were fitted with a package of receivers and jammers mounted on a pallet which fitted into the bomb bay. Jamming equipment could only be programmed on the ground to meet expected threats, so the electronic warfare officer had little more than an on-off switch in the cockpit to control the jammers. This was to be the start of a new career for the Destroyer, one which was to be far more important than any of its original roles. Brown Cradle aircraft initially served with USAFE.
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<p>As the US Air Force became embroiled in the Vietnam War, strike aircraft came up against SAM and gun-laying radars in growing numbers. In early 1965 the 363rd TRW dispatched six RB-66Cs to Takhli AFB to provide EW support, offering both limited jamming coverage and electronic reconnaissance. Two Destroyers would be launched to operate in a semi-escort role protecting F-105 strike forces over North Vietnam. During the course of these early missions, RB-66Cs brought back the first data on the Fan Song track-while-scan radar for the SA-2 missile. Three more RB-66Cs arrived at Takhli in September 1965 to form the 41st TRS, followed by five B-66B Brown Cradle jammers.
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<p>The latter arrivals were much better equipped for jamming, so the RB-66Cs were moved away to a stand-off role, while the B-66Bs escorted attackers almost to the target. This move depleted the overall escort jamming assets, so the remaining eight Brown Cradle aircraft were sent to Southeast Asia in June 1966, by which time the force had moved to Tan Son Nhut. In September they shifted back to Thailand, setting up base at Udorn, where the 6460th and 6461st TRS were formed under the 432nd TRW banner. During the year the aircraft were redesignated as EB-66B and EB-66C, and the units became tactical electronic warfare squadrons.
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<p>By 1967 the EB-66s were not performing any escort missions, the strikers relying on 'Wild Weasel' support and ECM pods for protection. The Destroyers concentrated on stand-off jamming of early warning and ground control radars. The need was immense, so the USAF instigated a hasty modification of redundant RB-66Bs into the EB-66E configuration, usually identified by a veritable forest of blade antennas protruding from the belly. Internally, the navigator and EWO stations were transposed, while the weapons bay was packed with racks of jammers and receivers, making the EB-66E the most capable in terms of jamming power and coverage.
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<p>Squadron and wing designations continued to change, the 6460th TEWS becoming the 42nd TEWS and the Destroyers moving back to Takhli, then finally to Korat (under the 388th TFW). EB-66s were involved in all phases of the air war, and were notable for their contributions during the 1972 Linebacker campaigns. Six were shot down, five falling to SAMs and one to a MiG-21. Nine more were lost in operational accidents. Throughout the conflict equipment and tactics were continually updated, including the carriage of double or triple loads of QRC160/ALQ-71 ECM pods from the underwing pylons. Much of the development work was undertaken by the 4416th Test Squadron at Shaw AFB (363rd TRW), which was activated to support the growing EW effort in Southeast Asia. Similarly, the 4417th Combat Crew Training Squadron was activated to handle the EW training effort, also at Shaw.
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<p>The end of the air war in Southeast Asia effectively signalled the end of the B-66's career, the last EB-66Es having already been withdrawn from USAFE's 39th TEWS at Spangdahlem in December 1972. The 42nd TEWS flew its last mission from Korat on 17 April 1973, and stayed in Thailand until January 1974. Back at Shaw, the 39th Tactical Electronic Warfare Training Squadron (formerly 4417th CCTS) was the last Destroyer unit, inactivating on 15 March. Whatever the questionable qualities of the aircraft, the B-66 had played a massive part in the development of the electronic jamming role which has become such a feature of modern air warfare. The EB-66s were sorely missed, for it was not until late 1981 before the USAF's next dedicated jamming platform, the Grumman/General Dynamics EF-111A Raven, entered squadron service.
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<p>Although not used in as great a number, the B-66 mirrored its naval cousin by becoming a useful testbed for a wide variety of projects. Most worthy of mention was the Northrop X-21A, a bold attempt to demonstrate the novel concept of laminar flow control. Using two surplus WB-66Ds as the basis, Northrop fitted an entirely new wing which incorporated nearly 17,000 ft (5,200 m) of very thin slots. These were connected to two turbines mounted in large fairings under the wings, which sucked the turbulent boundary layer of air next to the wing skin through the slots, thereby smoothing the air flow over the surface and dramatically improving the efficiency of the lifting surface. Two XJ79 jets were mounted in pods either side of the tail to provide power for flight and bleed air for the turbines. The pressurized compartment was retained to house the necessary flight test engineers. Initial tests showed much promise, but the program foundered as the huge area of tiny slots proved far too expensive in both effort and finances to be practical.
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<p>Perhaps the most ignominious end to befall any Destroyer was the hapless fate of three RB-66Bs handed over to the FAA for crashworthiness tests at Lakehurst, New Jersey. Mounted on a sled, they were hurled down a track to deliberately impact against barriers so that the damage could be analyzed to aid the design of future aircraft.
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<p>At best a workmanlike aircraft in its original roles, the Douglas B-66 Destoyer earned its place in the history books by being a true pioneer of the equipment and tactics of electronic warfare. Its efforts over the years in Southeast Asia saved an incalculable number of US airmen, while it laid the foundations for the next generations of EW aircraft to save countless more in following conflicts.
