F-89 to F-94
All Weather Fighters
Shortly after the war with Japan ended, the Air Technical Service Command (ATSC) issued requirements for three kinds of specialized fighters, described as All-weather, Penetration, and Interceptor types. The largest of these would be the “all-weather fighter” with room for radar and an electronics operator to operate in darkness or any bad flying weather.
Tentative characteristics issued November 23, 1945, included a 550-mph top speed, 1,000-mile radius of action, heavy weapons, and ground attack capability. Curtiss received authorization on December 26 to go ahead with its Model 29A night fighter design by using funds remaining from an aborted XA-43 contract. An amended contract for two XP-87 prototypes was issued March 22, 1946.
The mockup officially inspected July 16, 1946, provided for four Westinghouse J34 jets paired under the wings, double-wheels for the tricycle gear, 600-gallon wingtip tanks, and side-by-side seats for the pilot and radar operator. Armament was to include four 20-mm guns in
a Martin conical nose turret that could swing the barrels
in a 60-degree arc around the nose, and was aimed by a periscope sight or by APG-3 radar. A planned remote-
control tail turret with two .50-caliber guns was eliminated to save weight.
When it was realized that the Martin turret would not be available until 1949, the prototype was completed without any guns at the Columbus, Ohio, factory in October 1947. Shipment by road to the Muroc test base met with accidents and flight tests were delayed until March 1, 1948.
Although the overweight Curtiss XP-87 Blackhawk (soon redesignated XF-87) did not reach the 600-mph speed promised, a contract for 58 F-87s and 30 RF-87As was authorized June 1, 1948. They were to use the two 6,000-pound thrust J47 engines planned for the uncompleted second prototype, but on October 19, 1948, that contract was canceled to free funds for other projects, and the famous Curtiss name was never again used on a new combat plane.
The first Scorpions
The Curtiss design was defeated by the more successful F-89 long-range all-weather fighter. Responding to the same November 23, 1945, requirement, Northrop offered four different proposals, of which the Air Force chose the most conventional, avoiding more problematic tailless layouts.
Northrop received a letter contract approved on June 13, 1946, for two prototypes of its NS-24 specification, and the mockup was inspected in September. That contract was formalized December 18 and approved on May 21, 1947. On August 16, 1948, the first XF-89 prototype was flown at Muroc by Fred Bretcher.
Powered by two 4,000-pound thrust J35-A-9 jets tucked against the fuselage under the thin wing, the XF-89 had split-edge full-span flaps lining the trailing edge out to 600-gallon wingtip fuel tanks. The outer panels of these flaps acted as both ailerons and speed brakes. Pilot and radar man sat in tandem ejection seats. A high tail and the black finish inspired the name Scorpion.
Originally, the rounded nose was designed for four 20-mm guns in a turret that could swing the barrels in a 30-degree arc, but in August 1947 that Northrop design had been replaced by the Martin conical nose turret planned for the XP-87. By September, it was decided to complete the XF-89 without guns and fit the second prototype and production aircraft with six 20-mm fixed guns.
That second aircraft became the pre-production prototype, YF-89A, flown on June 27, 1950. It introduced a pointed nose, 5,200-pound thrust J35-A-21s with afterburners added, fixed 306-gallon wingtip fuel tanks and dispensed with the solid black paint previously the night owl’s uniform.
A contract approved July 14, 1949, had ordered 48 similar F-89As and deliveries began in September 1950. When a new autopilot and instrument landing system was installed, beginning with the 12th aircraft in February 1951, they became F-89Bs. Powered with J35-A-21 engines, these Northrops had APG-33 radar in the nose with six 20-mm guns and 200 rpg, and under wing fittings could accommodate two 1,600-pound bombs or 16 5-inch rockets. Northrop Scorpions first went into service with the 78th Fighter-Interceptor Group at Hamilton AFB in June 1951, but the high-performance fighters were so complex that they would take a long time to become fully operational.
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