Lockheed F-94 Starfire - Design and Development

Design and Development

Built to a 1948 USAF specification for a radar-equipped interceptor to replace the aging F-61 Black Widow and North American F-82 Twin Mustang, it was specifically designed to counter the threat of the USSR's new Tupolev Tu-4 bombers (reverse-engineered Boeing B-29). The Curtiss-Wright XF-87 Blackhawk had been designated to be the USAF first jet night fighter, but its performance was sub par, and Lockheed was asked to design a jet night fighter on a crash program basis. The F-94 was derived from the TF-80C (later T-33A Shooting Star]) which was a two-seat trainer version of the F-80 Shooting Star. A lengthened nose area with guns, radar and automatic fire control system was added. Since the conversion seemed so simple, a contract was awarded to Lockheed in early 1949, with the first flight on 16 April 1949. The early test YF-94s used seventy-five percent of the parts used in the earlier F-80 and T-33As.

The fire control system was the Hughes E-1, which incorporated an AN/APG-33 radar (derived from the AN/APG-3 which directed the Convair B-36's tail guns) and a Sperry A-1C computing gunsight. This short-range radar system was useful only in the terminal phases of the interception, most of the operation would be directed using ground-controlled interception as was the case with the earlier aircraft it replaced.

The added weight of the electronic equipment soon dictated that a more powerful engine be fitted, the afterburning Allison J33-A-33 centrifugal-type turbojet replacing the standard J-33 fitted to the T-33A. The F-94 was to be the first US production jet with an afterburner. The J33-A-33 had standard thrust of 4,000 pounds-force (18 kN), and with water injection this was increased to 5,400 pounds-force (24 kN) and with afterburning a maximum of 6,000 pounds-force (27 kN) thrust. The combination of the new, larger engine and the electronics gear reduced the internal fuel capacity. The YF-94A's afterburner had many teething problems with its igniter and the flame stabilization system.

The initial model was the F-94A. Its armament was four .50 in (12.7 mm) M3 Browning machine guns mounted in the fuselage with the muzzles exiting just behind the radome. Two 165 US Gallon (1,204 litre) drop tanks, as carried by the F-80 and T-33, could be carried under the wingtips. Alternatively, these could be replaced by 1,000 lb (454 kg) bombs, giving the aircraft a secondary fighter bomber role. 109 were produced. The subsequent F-94B, which entered service in January 1951, had upgraded and more reliable electronics and engines, as well as a new ILS. 356 of these were built.

The F-94C Starfire was significantly modified from the early F-94 variants; in fact, it was initially designated F-97, but it was decided to treat it as just a new version of F-94. Initially, USAF interest was lukewarm, so Lockheed funded development themselves by converting two F-94B airframes to YF-94C types for evaluation. To improve performance, a totally new wing was fitted, much thinner than the previous one and a swept tail surface. The J33 engine was replaced by a more powerful Pratt & Whitney J48, a license-built version of the afterburning Rolls-Royce Tay which dramatically increased power, giving a dry thrust of 6,350 pounds-force (28.2 kN) and with afterburning approximately 8,750 pounds-force (38.9 kN) of thrust. The fire control system was upgraded to the new Hughes E-5 with AN/APG-40 radar in a much larger nose. The guns were removed, replaced with an all-rocket armament mounted in a ring around the nose radome. The rockets were loaded into flip-up panels on the sides of the nose, and fired by opening four panels just behind the radome. According to test pilot Tony LeVier, the F-94C was capable of supersonic flight.

The F-94C was the only variant to be officially named Starfire. With time, the entire F-94 family has adopted the name.

An F-94D model was proposed as a single-seat fighter bomber, with bombs and rockets under the wings. A single prototype was built, but the model was not accepted for production. The prototype was later used as a testbed for the 20 mm (.79 in) M61 Vulcan cannon subsequently used on the F-104 Starfighter and many others.