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North American YF-93

Escort / Penetration Fighter Prototype Aircraft

At the close of World War 2 (1939-1945), with the jet age dawning on engineers and military warplanners, it became apparent to the United States Army Air Forces (USAAF) that it required a "penetration fighter" of considerable performance to escort accompanying bomber formations deep into enemy territory and back. Such an aircraft would have to exhibit inherent agility and speed while packing enough firepower to bring down any intercepting enemy threat. The USAAF requirement was officially announced on August 28th, 1945 and called for a twin jet engine layout with swept-back wings and large-caliber armament. Performance specifications included a maximum speed of 600 mph, a combat radius of 900 miles, and a service ceiling of up to 50,000 feet.

Several prominent players entered the ring including Consolidated Vultee, Curtiss, Goodyear, Lockheed, McDonnell, North American, and Northrop. Of these, a McDonnell, Lockheed, and North American design made it through.

North American helped to win the war for the Allies by its excellent offerings in the B-25 Mitchell medium bomber and P-51 Mustang fighter - the latter perhaps the best in all of the war. The company was also working on another legendary fighter which would become a star in the upcoming Korean War (1950-1953) - the jet-powered F-86 Sabre. Their entry into the USAAF penetration fighter competition became NA-157 which was originally offered in 1947 as an offshoot of the F-86 - the F-86C day fighter carrying a radar. Considerable changes were imparted onto the F-86C to beget an all new designation as the "YF-93A" for 1948.

Unlike the F-86 and its nose-mounted intake, the YF-93A incorporated a nose cone housing the radar system. To aspirate the single engine fitting, the slim, flush intakes were fitted to the sides of the fuselage for a more modern design approach. The wings were swept as in the F-86 and the sole pilot had good vision out of his elevated cockpit position. The empennage used a single vertical fin with mid-mounted horizontal tail planes. The wing mainplanes along the sides of the fuselage were low-mounted and a tricycle undercarriage was utilized (as in the F-86). Power for the airframe was through a single Pratt & Whitney J48-P-6 engine which was nothing more than a licensed, locally-built American version of the British Rolls-Royce RB.44 "Tay" engine series. The engine provided an output of 8,750 lbf. Commonality of parts between the YF-93A and the F-86 would be a chief selling point of the new North American fighter.

Proposed armament was 6 x 20mm cannons - outmatching the 6 x 12.7mm heavy machine guns seen in the F-86 Sabre line considerably. These guns were to reside along the sides of the nose (as was the case with the F-86's machine guns).

Interested enough in the North American submission, the USAAF - now the USAF - commissioned for a pair of prototypes to begin an evaluation phase. Consistent with other promising aviation ventures of the period, a production order for some 118 aircraft also followed in June of 1948 even before development work had completed - these aircraft to be designated in service as "F-93A".

First flight of a YF-93A prototype occurred on January 24th, 1950. Due to budget constraints, the USAF nullified the production order in 1948 though development of the two prototypes was allowed to continue. The YF-93A design failed to impress against the competing McDonnell XF-88 and the Lockheed XF-90 penetration fighter submissions - the XF-88 going on to win the competition. However, the USAF need for a penetration fighter was over by then and even the XF-88 lost out in this way - though it did evolve along other lines to become the famous F-101 "Voodoo" fighter.

The Lockheed XF-90 met a similar fate as the YF-93A - its two flyable prototypes were passed on to NACA for military flight testing before ending their days in various ways. The pair of YF-93A prototypes were passed on to NACA and operated as chase plane aircraft until 1956 before being given up in full. One major issue encountered with NACA operation of the YF-93A was insufficient airflow to the engine from the small, flush intakes - eventually explained as "low net thrust" brought about by primary and secondary air flow. The proposed armament of 6 x 20mm cannons was also never fitted to the airframe.

As finalized, the YF-93A featured an overall length of 13.4 meters, a wingspan of 11.8 meters, and a height of 4.8 meters. Empty weight was listed at 14,035 lb with a Maximum Take-Off Weight (MTOW) of 21,610 lb. Maximum speed was 708 mph with a range out to 2,000 miles, a service ceiling of 46,800 feet, and a rate-of-climb of 11,960 feet per minute.

YF-93A managed to reach Mach 1.05 though only in a dive. Both prototypes were eventually scrapped after their service to NACA.

Specifications

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