<p>Development of the McDonnell Voodoo was particularly long, and subjected to more changes in policy and planning than that of any of its contemporaries in the so-called 'Century' series. If the initial proposal of the late 1940s for a penetration/escort fighter had gone ahead, the Voodoo would not even have been part of this remarkable collection of fighters, for it was originally known by the designation XP-88, two prototypes of which were ordered by the US Army Air Force during July 1946.
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<p>Even at this early stage the project was affected by an apparent inability to finalize the design, the prototype's first flight coming some six months later than scheduled as a result of revisions to the wing and intake ducts. Eventually, however, the first prototype did take to the air for a successful maiden flight on 20 October 1948. Nearly two years were to elapse before it was joined by the second machine, which had considerably better performance as a result of the installation of Westinghouse J43-WE-22 engines complete with afterburners. In the end, this aircraft was to enjoy only a brief flying career, for the whole project was cancelled during August 1950, largely for lack of mission range, and changes in defense plans which called for greater emphasis to be placed on atomic weapons.
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<p>As a stop-gap measure, the Republic F-84E Thunderjet assumed responsibility for strategic penetration, and it was proposed to replace this type with the swept-wing F-84F Thunderstreak, a course of action which was followed, although SAC was less than enthusiastic, reiterating its demands for a fighter with truly 'long legs'. Accordingly, on 12 January 1951 SAC laid down the criteria for a more suitable escort fighter type and USAF headquarters agreed to examine several proposals from industry to meet this need under the collective heading of General Operational Requirement 101 (GOR.101), which was published at the beginning of February 1951.
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<p>Industry response was extensive and prompt, proposals being submitted in May by Lockheed, McDonnell, North American, Northrop and Republic. It was McDonnell's concept, based on the now-defunct F-88, which found favor, although even then some months were to pass before the USAF decided to proceed, finally releasing funds in October 1951 in order that work might begin.
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<p>A few weeks later it was announced that the Cook-Craigie policy would be adopted for the new fighter, this being a concept whereby the initial production run would be kept to the minimum number needed for testing, subsequent changes being incorporated in time for full-scale production, planning for which went ahead during the course of the trials program. At a later date, test specimens would be retrospectively brought to the definitive configuration and issued to operational units. (In the event, none of the pre-production Voodoos reached the combat inventory.)
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<p>Four days later, on 3 November 1951, it was revealed that McDonnell's new fighter would henceforth be known as the F-101, the designation change arising from the fact that in its present guise the Voodoo was significantly different from the original F-88 proposal of 1946.
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<p>Events moved fairly swiftly thereafter, McDonnell acceptance of an initial letter contract occurring on 15 January 1952 and a definitive fixed-price plus incentive contract being signed during June of the same year. Mock-up inspection took place on 21 July, this being the first of several such meetings, but the project's rapid impetus was slowed somewhat by the Korean War armistice and the USAF's decision to delay the release of fiscal year 1954 appropriations until the completion of Category II flight testing. Despite this setback, 1954 brought its share of excitement, one of the undoubted highlights being the maiden flight of the prototype F-101A on 29 September, an event which took place at Edwards AFB, California, and which was particularly notable in that Mach 1 was exceeded during the course of the sortie, albeit in a slight dive. Further good news came in October, when the production-hold order was rescinded; by the end of the year an additional three F-101s had joined the flight test program, the USAF at this time specifying that operational capability should be achieved by early 1957.
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<p>All was not plain sailing, however, for the early trials revealed a number of quite serious deficiencies. Perhaps the hardest to fix centered around the Pratt & WhitneyJ57-P-13 turbojet engines which were prone to compressor stalls; the F-101 also displayed poor longitudinal stability qualities, having a disturbing tendency to pitch up, often with disastrous results for both man and machine. Repeated attempts to eradicate these and other snags met with little success, so it was hardly surprising that yet another production-hold order came into effect in May 1956. By that time no fewer than 29 aircraft were engaged in various aspects of test work, but this stoppage was of relatively short duration, although the production tempo was limited to a maximum of eight aircraft per month until the end of October 1956.
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<p>Difficulties encountered in the test program also had a quite significant effect on production-configured aircraft for the USAAF, the original proposal calling for the construction of the first 33 machines with a stress factor of 6.33 g. Subsequent Voodoos were to have been capable of absorbing g-loadings of 7.33, but McDonnell now reported that it would not be able to produce a 7.33-g airframe until the 116th machine, adding that although the earlier specimens could be brought to the latter standard it would entail their virtual remanufacture. Eventually, the USAF opted to accept the 6.33-g aircraft, these henceforth being known as F-101As while the 7.33-g examples became F-101Cs.
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<p>Even allowing for the fact that the USAF chose to stay with the 6.33-g configuration, most of 1956 was occupied in incorporating design changes and engineering improvements in the production line. One of the most important of these modifications was the installation of an active inhibitor to solve the embarrassing pitch-up problem, and this cleared the way for the USAF to authorize production for the operational inventory, the final restraints being lifted on 26 November 1956.
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<p>By this time, changes in SAC philosophy (brought about largely by the advent of the Boeing B-52) had prompted the decision to dispose of its fighter force in 1957. Thus, Tactical Air Command (TAC) assumed responsibility for the F-101. Since TAC was more directly concerned with conventional air warfare, it was hardly surprising that it was less than enamored with the Voodoo, which was incapable of operating with 'iron' bombs. Despite this reluctance, production continued and the F-101A entered operational service with the 27th Strategic Fighter Wing at Bergstrom AFB, Texas, on 2 May 1957, this unit being redesignated as a tactical fighter wing on 1 July, when it transferred to TAC control. Ultimately, only 50 of the 77 F-101As produced saw service with front-line forces, but the problem of just what was the best use to make of the F-101As was solved in 1958-59 with their transfer to USAFE's 81st TFW at RAF Bentwaters and Woodbridge in the United Kingdom, the type's long range and nuclear capability providing a significant boost to the forces at the disposal of NATO.
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<p>The only other tactical fighter variant of the Voodoo was the F-101C, which more or less followed the F-101A and which featured the stronger 7.33-g structure. Production was initiated in early 1956, although doubts about the value of the Voodoo as a tactical fighter were confirmed in December 1956 when it was revealed that a combined total of only 124 F-101A and F-101C aircraft would be built. Like the F-101A, the new variant initially joined the 27th TFW with effect from September 1957, and soon found its way to Europe, where it also served with the 81st TFW, enjoying a front-line career which ended in 1966 when the 81st converted to F-4C Phantoms.
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<p>This did not quite mark the end of the line for the F-101A and F-101C, a substantial number of the surviving examples being reconfigured for reconnaissance duties with the Arkansas, Kentucky and Nevada ANG. Essentially, this involved the installation of a battery of cameras in a redesigned nose, modified F-101As henceforth being known as RF-101Gs, while F-101Cs became RF-101Hs, the two models remaining active until retired by Kentucky in 1973.
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<p>If the initial production models of the Voodoo received little acclaim for their operational exploits, the same was most certainly not true of the specialist reconnaissance-configured derivatives, in particular the RF-101C which racked up an impressive combat record in Southeast Asia between 1961 and 1970. Conforming to the original GOR of early 1951, and in spite of considerable company doubt concerning the type's suitability for this demanding mission, work on the reconnaissance model went ahead steadily and was rewarded by a letter contract in January 1953 to cover production of a brace of YRF-101A prototypes.
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<p>Mock-up inspection took place in January of the following year, while the first prototype was airborne just five months later, during May 1954. The decision to reassign this model from SAC to TAC control inevitably resulted in some delay in order to accommodate the somewhat different mission requirements of the latter command, and in particular the need for additional electronic devices.
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<p>Production-configured RF-101As began to appear during the summer of 1956 and, although similar in many ways to the F-101A, they were instantly recognizable by the elongated nose section which was intended to accommodate cameras. However, production of the aircraft had outstripped the development of mission-related equipment and many of the early specimens lacked much of the specialized apparatus they required to execute their task. Thus, in its initial form the RF-101A represented only a minimal improvement over the RF-84F Thunderflash it was supposed to replace.
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<p>The original reconnaissance fit was supposed to consist of a single long-focal-length Fairchild KA-1 framing camera, plus one vertical and two side oblique Fairchild KA-2 framing cameras and one CAI KA-18 strip camera, but limited availability of these items impaired operational capability for a considerable time. Nevertheless, the RF-101A entered service with the 363rd Tactical Reconnaissance Wing in May 1957, this unit initially receiving most of the 35 aircraft produced by October 1957. As far as is known, the RF-101A played no part in the Vietnam conflict, spending most of its service career on training tasks at Shaw AFB, South Carolina. Eight examples were supplied to the Chinese Nationalist air force between 1960 and 1970, and these almost certainly experienced a far more active operational career.
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<p>Built in greater numbers than the rest of the single-seat Voodoos combined, the RF-101C was eventually the definitive reconnaissance model, ultimately becoming the USAF's tactical reconnaissance maid-of-all-work. A machine far superior to the RF-101A, it benefited from the 7.33-g structure and was the subject of a March 1956 contract for a total of 70 aircraft, this figure being substantially increased by the December 1956 contract change which stipulated that a proposed batch of 96 F-101Cs be completed as reconnaissance aircraft.
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<p>Flying for the first time on 12 July 1957, the RF-101C underwent a test program by no means as lengthy as those of its predecessors, for the basic design was by now fairly well proven and the new model was therefore rapidly introduced to service with two squadrons of the 432nd TRW at Shaw during the last quarter of the year. Overseas deployment followed quickly, aircraft joining USAFE and PACAF (Pacific Air Forces) during the course of 1958, and by the end of that year close to half of the total production had found its way abroad.
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<p>Like many of the 'Century' series fighters, the early period of service was not a happy one. The RF-101C certainly suffered from its fair share of problems, these ranging from servicing difficulties to poor contractor support, which significantly impaired in-commission rates. Technical grounding orders also figured prominently at this time, 1959 being a particularly unhappy year with at least two such occurrences arising from main landing gear member failures and hydraulic problems, but extensive modifications gradually overcame the worst shortcomings. Skin cracks and corrosion proved to be the cause of some headaches in 1960, and necessitated the return of a large number of aircraft to rework centers in the USA for recertification.
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<p>It was not all gloom, for when the aircraft and its systems were working satisfactorily it became clear that the RF-101C was an excellent reconnaissance platform that very soon began to prove its worth in Southeast Asia, initial small detachments being active there as early as 1961. The type also performed sterling work in the Cuban missile crisis of October 1962. Improvements in reconnaissance-gathering equipment also enhanced the RF-101C's undoubted capability, especially at low level.
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<p>Although the type was engaged in combat for close to 10 years, the first RF-101C to be lost as a direct result of enemy action went down in late 1964 and attrition rates worsened in later years as North Vietnam's defensive network expanded in size. Attrition and the advent of the RF-4C Phantom conspired to bring about the RF-101C's withdrawal, a process which took place during 1969-70, most of the survivors being passed on to the Air National Guard (ANG), with which they served until 13 January 1979.
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<p>The final and most numerous variant of the Voodoo was the F-101B, a total of 480 being built. About one-quarter were fitted with dual controls, these aircraft being known initially as TF-101Bs, although they were subsequently redesignated as F-101Fs. A two-seater derivative optimized for air-defense duties, the F-101B was produced mainly as a form of insurance in case the so-called 'ultimate' Convair F-106 interceptor failed to satisfy the stringent USAF requirements, a situation which by no means seemed unlikely when one recalls the problems encountered with the Convair F-102A.
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<p>The initial proposal by Air Defense Command (ADC) was made during October 1952 but was quickly rejected by USAF headquarters, which opted instead to increase procurement of the North American F-86D Sabre. ADC raised the suggestion again some six months later, recommending its use as a long-range interceptor and in areas where existing radar coverage was poor. On this occasion, USAF headquarters was more enthusiastic, going so far as to request industry to examine those characteristics desirable in an interceptor aimed at bridging the chasm between the Northrop F-89 and the F-106.
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<p>Study of the various proposals resulted in the F-101 being judged most suitable in June 1954, but it was not until late February 1953 that McDonnell received the green light, an initial contract for 28 specimens (soon raised to 96) being awarded in March. Officially designated F-101B in August 1955, the new variant was a tandem two-seater with accommodation for a radar intercept officer in the rear cockpit. Almost inevitably, the new model was subjected to some of the frustrations experienced by its predecessors, but the first example made a successful maiden flight from Lambert Field, St Louis, on 27 March 1957, this marking the start of an intensive two-year test program which, at its peak, involved as many as 50 aircraft at Edwards AFB, California, Eglin AFB, Florida, and Otis AFB, Massachusetts.
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<p>Trials were formally completed in mid-March 1959, some two months after the F-101B had entered the operational inventory with the 60th Fighter-Interceptor Squadron at Otis. Problems abounded (most notably with the poor design of the radar officer's cockpit and the Hughes MG-13 fire-control system, which was by no means as advanced as the aircraft in which it was housed) but the pace of the re-equipment program was quite startling, and by December 1960 no fewer than 17 squadrons had converted to the Voodoo. Even more remarkably, almost all of these were operationally ready.
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<p>Subsequent modification programs went some way towards improving the type's capability, armament being upgraded through provision for the unguided MB-1 Genie nuclear-tipped air-to-air missile in the early 1960s, while operational effectiveness in an ECM environment was also enhanced, as was the low-flying tracking potential of the integral radar. Yet another later upgrade effort finally eradicated the pitch control problem which had plagued all variants of the Voodoo for years, but it is worth noting that in the first 10 years of service roughly one-fifth of the F-101B force fell victim to attrition, most of these losses resulting from uncontrollable spins.
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<p>Phase-out from the front-line ADC force, when it came, was also fairly swift, being accomplished between 1968 and 1971, although many of the aircraft continued to see service with the Air National Guard. It was not until 1982 that the last examples of the interceptor disappeared. In addition to the pure fighter models which saw service with the ANG, approximately 25 F-101Bs were reconfigured for reconnaissance duty, being fitted with camera noses and redesignated as RF-101Bs.
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<p>The last of these glorious aircraft in service were those of Nos 409, 410, 416 and 425 Squadrons, Canadian Armed Forces. They continued in their NORAD-dedicated air defense role until, one by one, the units began to hand in their CF-101s, pending the arrival of new CF-18s. In 1984/85, No. 425 'Alouettes' Squadron disbanded and exchanged its Voodoos for Hornets, the last Canadian fighter squadron to do so. Even then the story was not quite over, as a handful of aircraft survived as electronic warfare trainers. The last of these adopted an all-over black color scheme, but by the late 1980s its time had come. Withdrawn from use, it closed the account of the second and probably most versatile of the 'Century' series aircraft.
<item><hi format=bold>Powerplant:</hi> two Pratt & Whitney J57-13 turbojets each rated at 14,880 lb (66.2 kN) with maximum afterburner
<item><hi format=bold>Performance:</hi> maximum speed (clean, at height) Mach 1.7 (1,120 mph; 1,802 km/h); service ceiling 52,000 ft (15,850 m); range (with internal fuel at high altitude) 1,890 miles (3,040 km), with two 450-US gal (1,705-liter) drop tanks 2,400 miles (3,862 km)
<item><hi format=bold>Weights:</hi> empty, equipped 25,610 Ib (11,617 kg); loaded (clean) 42,550 Ib (19,300 kg); maximum (with two tanks) 48,720 lb (22,099 kg)
<item><hi format=bold>Dimensions:</hi> span 39 ft 8 in (12.09 m); length 69 ft 3 in (21.1 m); height 18 ft 0 in (5.49 m); wing area 368 sq ft (34.19 m<su>2</su>)
