Lockheed F-94 Starfire

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. 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. 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. Flight testing determined the test aircraft to possess adequate performance. 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. 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. 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. 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. 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. 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. Furthermore, the clearance for the ejection seats was too small, resulting in several tragic accidents during emergency ejections. F-94B During January 1951, the improved F-94B entered service; it was outwardly virtually identical to the F-94A. The Allison J33 engine had received several modifications to make it considerably more reliable. 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. 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. 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. These rockets were carried in four panels that could be hinged upwards and outwards for ground reloading. 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. The F-94C was the only variant to be officially named Starfire. 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. 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==