McDonnell F-101 Voodoo
The McDonnell F-101 Voodoo is a supersonic jet fighter designed and produced by the American McDonnell Aircraft Corporation.
Development of the F-101 began in the late 1940s as a long-range bomber escort for the United States Air Force's Strategic Air Command. It was also adapted as a nuclear-armed fighter-bomber for the USAF's Tactical Air Command, and as a photo reconnaissance aircraft. On 29 September 1954, it performed its maiden flight. The F-101A set world speed records for jet-powered aircraft, including airspeed, attaining per hour on 12 December 1957.
Delays in the 1954 interceptor project led to demands for an interim interceptor aircraft design, a role that was eventually won by the F-101B Voodoo. This role required extensive modifications to add a large radar to the nose of the aircraft, a second crew member to operate it, and a new weapons bay using a rotating door that held its four AIM-4 Falcon missiles or two AIR-2 Genie rockets hidden within the airframe until it was time to be fired. The F-101B entered service with USAF Air Defense Command in 1959 and the Royal Canadian Air Force in 1961. While the Voodoo was a moderate success, it may have been more important as an evolutionary step towards its replacement in most roles, the F-4 Phantom II, one of the most successful Western fighter designs of the 1950s; the Phantom would retain the twin engines, twin crew for interception duties, and a tail mounted well above and behind the jet exhaust, although it was an evolution of the F3H Demon while the Voodoo was developed from the earlier XF-88 Voodoo.
The Voodoo's career as a fighter-bomber was relatively brief, but the reconnaissance versions served for some time. Along with the USAF's Lockheed U-2 and US Navy's Vought RF-8 Crusaders, the RF-101 reconnaissance variant of the Voodoo was instrumental during the Cuban Missile Crisis and saw extensive service during the Vietnam War. Interceptor versions served with the Air National Guard until 1982, and in Canadian service, they were a front line part of NORAD until their replacement with the CF-18 Hornet in the 1980s. The type was operated in the reconnaissance role until 1979. The US Air National Guard operated former USAF Voodoos until 1982. The RCAF Voodoos were in service until 1984.
Design and development
Background and XF-88
Initial design on what would eventually become the Voodoo began in June 1946 in response to a USAAF Penetration Fighter Competition launched just after World War II. This competition called for a long-range, high-performance fighter to escort a new generation of bombers, similar to the wartime role of the North American P-51 Mustang in escorting the Boeing B-17 Flying Fortresses and Consolidated B-24 Liberators across contested airspace. McDonnell was among several companies to respond to the competition; their design benefitted from recently captured German research into high-speed jet aircraft.On 14 February 1947, McDonnell was awarded a contract to produce a pair of prototypes, designated XF-88 Voodoo. The first prototype, which was powered by two 3,000 lbf Westinghouse XJ34-WE-13 turbojets, flew from Muroc on 20 October 1948. Preliminary testing revealed that while handling and range were adequate, the top speed was a disappointing 641 mph at sea level. After fitting McDonnell-designed afterburners to the second prototype, thrust was increased to 3,600 lbf with corresponding performance increases in top speed, initial rate of climb, and reduced takeoff distance. Fuel consumption also increased, reducing range.
The XF-88 won the "fly-off" competition against the competing Lockheed XF-90 and North American YF-93. But the detonation of the first nuclear weapon by the Soviet Union led the United States Air Force to raise the priority of interceptors and reduce that of bomber escorts, and it terminated the Penetration Fighter program in 1950. Another factor in the termination was budgetary limitations. Analysis of Korean War missions, however, revealed that contemporary USAF strategic bombers were vulnerable to fighter interception. In early 1951, the USAF issued a new requirement for a bomber escort, to which all major US manufacturers submitted designs. The McDonnell design, a larger and higher-powered version of the XF-88, won the bid in May 1951. Six months later, the redesigned F-88 was designated F-101 Voodoo.
Enlarged design
The new design was considerably larger, carrying three times the initial fuel load and designed around larger, more powerful Pratt & Whitney J57 turbojets. The greater dimensions of the J57 engines required modifications to the engine bays, and modification to the intakes to allow a larger amount of airflow to the engine. The new intakes were also designed to be more efficient at higher Mach numbers. In order to increase aerodynamic efficiency, reduce structural weight and alleviate pitch-up phenomena recently identified during flight testing of the Douglas D-558-2 Skyrocket, an aircraft with a control surface configuration similar to the XF-88, the horizontal tail was relocated to the top of the vertical stabilizer, giving the F-101 its signature "T-tail". In late 1952, the mission of the F-101 was changed from "penetration fighter" to "strategic fighter", which entailed equal emphasis on both the bomber escort mission and on nuclear weapons delivery. The new Voodoo mock-up with the reconfigured inlets, tail surfaces, landing gear, and dummy nuclear weapon was inspected by Air Force officials in March 1953. The design was approved, leading to an initial production order for 29 F-101As being placed on 28 May 1953. No prototypes were required as the F-101 was considered to be a straightforward development of the XF-88, with the Cook-Cragie production policy, in which initial low-rate production would be used for testing without the use of separate prototypes, chosen instead.Changing roles and into production
Despite securing an order for the type, McDonnell received a stop order for production on 16 April 1954; this was due to a substantial cutback in funding for the USAF in general. Meaningful production activity was not resumed until a favourable instruction was received by the company on 2 November 1954. At this point, the USAF gave McDonnell an operational deadline of early 1957.The first production aircraft, F-101A serial number 53-2418, performed its maiden flight on 29 September 1954 from Edwards AFB; during this flight, it attained a maximum speed of at an altitude of. This aircraft, which is privately owned, has been moved to the Evergreen Maintenance Center in Marana, Arizona, restored, and now on display at the Evergreen Aviation & Space Museum in McMinnville, Oregon. It was previously on display at the Pueblo Weisbrod Aircraft Museum.
The end of the Korean War and the development of the jet-powered Boeing B-52 Stratofortress negated the need for fighter escort and Strategic Air Command opted to withdraw from the program. Despite SAC's loss of interest, the F-101A had attracted the attention of Tactical Air Command, leading to the F-101 being reconfigured as a fighter bomber. In this capacity, it was intended to carry a single nuclear weapon for use against tactical targets such as airfields. TAC requested numerous alterations to the F-101 to suit the new role, including additional apparatus to permit air-to-ground communication, provisions to carry external pods, and structural strengthening.
Through the support of TAC, testing of the F-101 was resumed, with Category II flight tests beginning in early 1955. A number of problems were identified and were mostly resolved during this phase of development. Issues were found with the autopilot, hydraulics, viewfinder, and control system; McDonnell typically replaced unsatisfactory parts with redesigned counterparts. One particular issue was the aircraft's dangerous tendency towards severe pitch-up when flown at a high angle of attack; this would never be entirely rectified. However, the USAF was satisfied with the installation of an active inhibitor system to deter such instances. Around 2,300 improvements were made to the F-101 between 1955 and 1956 ahead of full-rate production commencing in November 1956.
Operational history
F-101A / RF-101G
On 2 May 1957, the first F-101A was delivered to the 27th Strategic Fighter Wing, which transferred to TAC in July that year, replacing their F-84F Thunderstreak. The F-101A was powered by two Pratt & Whitney J57-P-13 turbojets, allowing good acceleration, a high rate of climb, ease in penetrating the sound barrier in level flight, and a maximum performance of Mach 1.52. The F-101's large internal fuel capacity allowed a range of approximately nonstop. The aircraft was fitted with an MA-7 fire-control radar for both air-to-air and air-to-ground use, augmented by a Low Altitude Bombing System for delivering nuclear weapons, and was designed to carry a Mk 28 nuclear bomb. The original intended payload for the F-101A was the McDonnell Model 96 store, a large fuel/weapons pod similar in concept to that of the Convair B-58 Hustler, but was cancelled in March 1956 before the F-101 entered service. Other operational nuclear payloads included the Mk 7, Mk 43, and Mk 57 weapons. While theoretically capable of carrying conventional bombs, rockets, or Falcon air-to-air missiles, the Voodoo never used such weapons operationally. It was fitted with four 20 mm M39 cannon, with one cannon often removed in service to make room for a TACAN beacon-receiver.The F-101 set a number of speed records, including: a JF-101A setting a world speed record of 1,207.6 mph on 12 December 1957 during "Operation Firewall", beating the previous record of 1,132 mph set by the Fairey Delta 2 in March the previous year. The record was then subsequently taken in May 1958 by a Lockheed F-104 Starfighter. On 27 November 1957, during "Operation Sun Run," an RF-101C set the Los Angeles-New York City-Los Angeles record in 6 hours and 46 minutes, the New York to Los Angeles record in 3 hours and 36 minutes, and the Los Angeles to New York record in 3 hours and 7 minutes.
A total of 77 F-101As were built, only 50 of which were ever used operationally while the remainder were used exclusively for experimental work. They were gradually withdrawn from USAF service starting in 1966. Twenty-nine survivors were converted to RF-101G specifications with a modified nose, housing reconnaissance cameras in place of cannons and radar. These served with the Air National Guard through 1972.