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North American YF-93

1950 COLD WAR X-PLANE

History of the North American YF-93

At the end of World War II (1939-1945), as engineers and military war planners began to enter the jet era, the United States Army Air Forces (USAAF) realized they needed a lot of "penetrating fighter" performance to provide accompanying escort bomber formations deep into enemy territory and back. Such an aircraft would need to have inherent agility and speed, while also having sufficient firepower to eliminate any threat to intercept an enemy.

The USAF requirement, officially announced on August 28, 1945, called for a twin-engine layout with swept wings and large-caliber weapons. Performance specs include a top speed of 600 miles per hour, a combat radius of 900 miles and a service cap of up to 50,000 feet.

Several famous players have entered the ring including Consolidated Vultee, Curtiss, Goodyear, Lockheed, McDonnell, North American and Northrop. Of these, the McDonnell, Lockheed and North American designs succeeded.

North America helped the Allies win the war with its stellar offerings in the B-25 Mitchell medium bomber and P-51 Mustang fighterprobably the best of the war. The company is also developing another legendary fighter that will be the star of the upcoming Korean War (1950-1953) - the jet F-86 Saber.

Their entry into the USAAF penetration fighter race became the NA-157, originally offered in 1947 as an offshoot of the F-86, the radar-equipped F-86C day fighter. Considerable changes were made to the F-86C, which received a new designation "YF-93A" in 1948.

Unlike the F-86 and its nose air intake, the YF-93A includes a nose cone that houses the radar system. To appeal to the single-engine trim, sleek, flush air intakes were moved to the sides of the fuselage for a more modern approach to the design. The wings are swept over like an F-86, and the solo pilot has excellent visibility from his elevated cockpit position. The tail uses a vertical tail with a mid-mounted horizontal tail. The main-wing aircraft on the sides of the fuselage were low-mounted and used three-wheel landing gear (as on the F-86).

The fuselage is powered by a Pratt & Whitney J48-P-6 engine, a locally-built American version licensed from a British Rolls-Royce RB. 44 "Thai" engine series. The engine has an output of 8,750 lbf.

Shared parts between the YF-93A and the F-86 will be a key selling point for the new North American fighter.

The proposed weapon is a 6 x 20mm machine gun, significantly better than the 6 x 12.7mm machine gun seen in the F-86 Sabre series. These guns should be on either side of the nose (like the F-86's machine guns).

The United States Air Force (now USAF) was very interested in the North American submission and commissioned two prototypes to begin the evaluation phase. Like other promising aviation programs of the time, production orders for some 118 aircraft were received in June 1948, even before development work was completed - these would enter service as "F-93As".

The first flight of the YF-93A prototype took place on January 24, 1950. In 1948, due to budget constraints, the USAF cancelled production orders, although two prototypes were allowed to continue to be developed. The YF-93A design failed to compete with the rival McDonnell XF-88 and Lockheed XF-90 penetration fighters - the XF-88 won the competition.

By then, however, the USAF's need for penetration fighters was over, and even the XF-88 lost that way -- though it did evolve into the famous F-101 "Voodoo" fighter in other ways.

The Lockheed XF-90 suffered a similar fate to the YF-93Atwo of its airworthy prototypes were handed over to NACA for military flight testing before ending their days in various ways. The pair of YF-93A prototypes were turned over to NACA and used as pursuit aircraft until 1956 when they were completely scrapped.

A major problem encountered during NACA operations on the YF-93A was insufficient airflow into the engine from the small flush intake - which was ultimately explained as "low net thrust" caused by primary and secondary airflow. The proposed 6 x 20mm artillery armament was also never mounted on the fuselage.

When completed, the YF-93A has a total length of 13.4 meters, a wingspan of 11.8 meters and a height of 4.8 meters. Empty weight is listed at 14,035 lbs and maximum takeoff weight (MTOW) is 21,610 lbs.

Top speed is 708 mph, range is up to 2,000 miles, service is capped at 46,800 feet, and climb rate is 11,960 feet per minute.

The YF-93A managed to hit Mach 1.05, but only in a dive. Both prototypes were eventually scrapped after serving NACA.