The Lockheed F-94 Starfire is a first-generation jet-powered all-weather day/night interceptor aircraft designed and produced by Lockheed Corporation. Put into production in 1949, it was the first operational United States Air Force (USAF) fighter equipped with an afterburner as well as being the first jet-powered all-weather fighter to enter combat during the Korean War.
The F-94 was developed to fulfil a specification issued by the USAF in 1948, seeking a new interceptor capable of day and night operations to replace its piston-engined types in light of recent military advances made by the Soviet Union. The F-94 was derived from the successful Lockheed T-33 Shooting Star trainer; being a relatively simple conversion from an established aircraft led to USAF officials viewing it as a low-risk option and opting to procure the type. Maintaining a high level of parts commonality with the preceding aircraft, the majority of the F-94's external changes were related to the adoption of a larger nose that accommodated multiple guns, radar, and an automatic fire-control system. Engine thrust was also bolstered by adding an afterburner to the Allison J33 powerplant used.
On 16 April 1949, the prototype YF-94 conducted its maiden flight. While teething problems were encountered, these were overcome relatively quickly. During May 1950, the F-94A reached operational service with Air Defense Command (ADC), its principal operator, where the type soon replaced the piston-engined North American F-82 Twin Mustang in the all-weather interceptor role. It was soon followed by the F-94B, a refined model that proved to have greater engine reliability and a more spacious cockpit; the F-94C equipped with a thinner wing, a more powerful Pratt & Whitney J48 engine, and a new Hughes E-5 fire-control system also followed. Further models, including a dedicated aerial reconnaissance variant, were proposed but ultimately not pursued.
In the interceptor role, the F-94 proved to have less endurance and greater reliance upon Ground Control Interception methods than some of its piston-engined predecessors. Beyond its use by ADC, it was also operated by the Far East Air Force, which used the type against various Soviet-supplied aircraft during the Korean War of the early 1950s. The Alaskan Air Command (AAC) and the Air National Guard (ANG) also operated the F-94. It had a relatively brief operational life, the replacement process commencing in the mid-1950s in favor of more advanced fighters such as the Northrop F-89 Scorpion and North American F-86D Sabre. The last aircraft was withdrawn from USAF service in 1958, while the ANG opted to retire its F-94s only one year later.
Design and development Background On 8 October 1948, the USAF issued a new general operating requirement that called for a radar-equipped interceptor to replace the aging Northrop F-61 Black Widow and North American F-82 Twin Mustang.Knaack 1982, p. 101.Pace 2016, p. 46. This new interceptor was specifically designed to counter the emergence of new Soviet aircraft such as the Tupolev Tu-4 bomber (reverse engineered from the Boeing B-29 Superfortress). The Curtiss-Wright XF-87 Blackhawk had been developed with the intention of becoming the USAF's first jet-powered night fighter, but its performance was subpar. Accordingly, Lockheed was approached by the service with a request to design a jet night fighter on a crash program basis.Coniglio, Serigio. "F-94 Starfire (Monopama Special File)." Aviation and Marine International, Issue 34, June 1976.
The resulting aircraft was derived from the TF-80C (later designated T-33A Shooting Star) which was a two-seat trainer version of the F-80 Shooting Star. Designated F-94 Starfire, it was redesigned with a lengthened nose area to accommodate the addition of guns, radar, and an automatic fire-control system. In November 1948, the P-94 was met with the approval of James Forrestal, United States Secretary of Defense. Having observed the conversion to be relatively straightforward, USAF officials chose to issue a letter contract to Lockheed during January 1949. Months later, a definitive contract for 150 production aircraft was received. By December 1949, the number on order had risen to 368 aircraft.
Into flight
On 16 April 1949, the first YF-94 prototype performed its maiden flight.Knaack 1982, pp. 101-102. To accelerate development, these early test aircraft were converted from existing T-33s; they maintained roughly 75% commonality in terms of components with those used in the earlier F-80 and T-33As.Pace 2016, p. 44. Flight testing determined the test aircraft to possess adequate performance.Pace 2016, p. 48. By the end of 1949, the program had been restructured to fulfil pressure from the USAF for more capable fighters; an more austere model, the F-94A, would be delivered quickest while a more capable and ambitious model, the F-94C, was produced.Knaack 1982, p. 102.Pace 2016, pp. 48-49.
The fire-control system selected for the F-94 was the Hughes E-1; this unit incorporated an AN/APG-33 radar (derived from the AN/APG-3, which directed the Convair B-36 Peacemaker's tail guns) and a Sperry A-1C computing gunsight.Hallion 1980, p. 17. Due to the short range of this onboard radar system, it was useful only during the terminal phases of the interception mission; instead, the F-94 would largely be directed through traditional ground-controlled interception, akin to the preceding aircraft that it would replace.
The additional electronic equipment increased the weight of the aircraft, thus it required a more powerful engine. The Allison J33A-35 centrifugal turbojet engine, which had been installed as standard on the T-33A, was replaced with a more powerful afterburner-equipped model, the J-33-A-33. The F-94 was to be the first US production jet with an afterburner. The J33-A-33 had standard thrust of , and with water injection this was increased to and with afterburning a maximum of thrust."Technical Gen". RAF Flying Review, September 1962, p. 59. The combination of added weight and the use of an afterburner considerably reduced the F-94's internal fuel capacity. The YF-94A's afterburner suffered numerous teething problems, typically related to its igniter and the flame stabilization system.
Production versions
F-94A The initial production model was the F-94A, which entered operational service in May 1950. Its armament was four 0.50 in (12.7 mm) M3 Browning machine guns mounted in the fuselage with the muzzles exiting just behind the radome. Two drop tanks, as carried by the F-80 and T-33, could be carried beneath the wingtips. Alternatively, these could be replaced by bombs, giving the aircraft a secondary fighter bomber role.Francillon 1982, p. 294. 109 F-94As were produced. This model was only in operational service for a brief time as it was originally built and was not received well by its aircrews. The main source of complaints was its somewhat unreliable J33 engine, which frequently necessitated ground aborts and had been deemed by many crews to be unsafe.Knaack 1982, pp. 102-103. In flight, the aircraft was often judged to be unstable and difficult to maneuver when flown at high altitude by its pilots. The pilot and radar operator commonly found that the cockpit was too narrow for them to be able to quickly enter and exit the aircraft, which was routinely expected during alerts and scrambles.Knaack 1982, p. 103. Furthermore, the clearance for the ejection seats was too small, resulting in several tragic accidents during emergency ejections.Isham and McLaren (1993) Lockheed F-94 Starfire, A Photo Chronicale, Schiffer Publishing, Ltd,
F-94B During January 1951, the improved F-94B entered service; it was outwardly virtually identical to the F-94A.Knaack 1982, p. 104. The Allison J33 engine had received several modifications to make it considerably more reliable. The pilot was also provided with a more roomy cockpit while the canopy was replaced by a redesigned unit with a bow frame in the center between the two crew members, along with a new Instrument Landing System (ILS).Knaack 1982, pp. 103-104. 356 F-94Bs were completed. It proved to be a fairly reliable aircraft, particularly in comparison to its predecessor, and encountered relatively few problems during its service life. This improved model quickly replaced the F-94As in service with the active-duty squadrons, after which these older aircraft were temporarily returned to Lockheed to be re-engined and rebuilt to F-94B standards. These upgraded F-94A/B aircraft were also modified with a twin-gun pod under each wing for two additional 0.50 in (12.7 mm) machine guns each, bringing the total to eight. These aircraft were then passed along to Air National Guard units where they served until the end of the 1950s.
F-94C The F-94C Starfire was extensively modified from the early F-94 variants. In fact, it was initially designated F-97 before officials decided that it would be treated as a new version of the F-94 instead.Knaack 1982, p. 106. At the time, USAF interest in the aircraft was allegedly lukewarm, thus Lockheed opted to fund development themselves, converting two F-94B airframes into YF-94C prototypes for evaluation. To improve performance, a completely new and much thinner wing was designed, along with a swept tail surface. The J33 engine was replaced with a more powerful Pratt & Whitney J48, a license-built version of the afterburning Rolls-Royce Tay, which dramatically increased power over the J33, producing a dry thrust of and approximately with afterburning.Pace 2016, p. 49. The fire control system was upgraded to the new Hughes E-5 with an AN/APG-40 radar, a change which required the use of a much larger nose. All of the guns were removed and replaced with all-rocket armament consisting of four groups of six rockets in a ring around the nose.Pace 2016, p. 51. These rockets were carried in four panels that could be hinged upwards and outwards for ground reloading.Knaack 1982, pp. 106-107. In flight, these rockets were normally hidden aft of four inwards-folding doors that surrounded the nose cone. According to Lockheed test pilot Tony LeVier, the F-94C was capable of supersonic flight in a steep dive with afterburner engaged.Schmidt 1997, p. 107.
The F-94C was the only variant to be officially named Starfire. With time, the entire F-94 family has adopted the name. The first production F-94C aircraft were delivered in July 1951, 387 examples being delivered before May 1954. The largest problem discovered in service was the nose-mounted rockets, which blinded the crew with their smoke and fire. The most severe problem associated with firing the nose-mounted rockets was that the exhaust could cause a flameout of the jet engine, which could lead to the loss of the aircraft.Knaack 1982, pp. 107-108. After the 100th aircraft, mid-wing rocket pods were added to the leading edges, similar in concept to the previous gun pods, holding 12 rockets apiece and fitted with a frangible aerodynamic nose cap which was discarded when firing the rockets.Modern Military Aircraft Anatomy, p. 100, Paul E. Eden ed., Aerospace Publishing Ltd, 2007 Most of the time, the nose rockets were not fitted, and the mid-wing pod rockets were the sole armament. This version of the aircraft was extensively used within the Semi Automatic Ground Environment (SAGE) air defense system.
F-94D An F-94D model was proposed as a single-seat fighter bomber, being armed with both bombs and rockets under the wings as well as eight nose-mounted machine guns. A single prototype was built, but the model was not ultimately accepted for production. The prototype was later used as a testbed for the 20 mm (0.79 in) M61 Vulcan cannon subsequently used on the Lockheed F-104 Starfighter and many other combat aircraft.
Operational history
Air Defense Command