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YF-93A

XF-88

XF-90

The YF-93A was originally the F-86C, but was redesignated after extensive design changes needed to prepare the aircraft for the USAF 'Penetration Fighter' competition. The McDonnell XF-88 and Lockheed XF-90 were also evaluated, but the USAF never acquired a 'Penetration Fighter'. A contract for 118 production F-93A's was signed, but canceled before any aircraft were built.

The standard F-86 engine air inlet was changed on the first prototype (S/N 48-317) to two flush mounted fuselage inlets to make room for avionics and to further streamline the aircraft for increased range. The second aircraft (S/N 48-318); however, was completed with conventional engine air intakes. Both aircraft had unusual two-wheel main landing gear struts to support the increased weight caused by the large fuel load carried. Both prototype aircraft were used as test platforms by NACA before being declared surplus and scrapped.

 

 

TYPE YF-93A

Number built/Converted 2

Remarks Penetration Ftr.; F-86C; 118 canc.

 

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Cut-away View

SPECIFICATIONS
Span: 38 ft. 9 in.
Length: 44 ft. 1 in.
Height: 15 ft. 8 in.
Weight: 25,500 lbs. maximum
Armament: Designed for six .50-cal. machine guns
Engines: Pratt & Whitney J48 of 8,750 lbs. thrust with afterburner

PERFORMANCE
Maximum speed: 708 mph at sea level
Range: 1,967 miles
Service ceiling: 46,800 ft.

 

 

XF-86C / YF-93A Penetration Fighter

 

 While the Sabre was engaged in heavy combat across the Pacific, the design was being updated back in the States. Design work on the "NA-157" or "XP-86C" was begun in late 1947, in response to a USAF requirement for a "deep penetration" fighter. North American's XF-86C, as it was redesignated in 1948, won the competition against the Lockheed "XF-90" and the McDonnell "XF-88" (which would eventually evolve into the F-101 Voodoo), with the Air Force ordering two prototypes.

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The XF-86C had a bigger and longer fuselage than the F-86A. The increased size was to accommodate 5,909 liters (1,561 gallons) of internal fuel to meet the range requirements, while the the increased length was to allow fit of an afterburning Pratt & Whitney J48-P-6 engine with 2,800 kilograms (4,500 pounds) thrust.

The J48 was an improved, afterburning version of the Rolls-Royce Nene centrifugal-flow turbojet, manufactured in Britain as the Tay, providing 2,835 kilograms (6,250 pounds) dry thrust and 3,625 kilograms (8,000 pounds) afterburning thrust. The J48's exhaust had a two-piece clamshell variable-size outlet.

The fuselage was designed using the new "area ruling" concept developed by NACA engineers, which specified that changes in an aircraft's cross-sectional area should be minimized to ensure smooth airflow at high speeds. As a result, the fuselage was "pinched" slightly along the wing roots. The result of all the changes was a somewhat inelegant machine compared to the F-86A, with a porpoise-like body and fat appearance. In fact, the aircraft was so clearly different that the USAF re-designated the type the "XF-93A" in 1948. 

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The nose intake was replaced with air intakes at the sides, leaving the nose available for SCR-720 radar, and the new aircraft was armed with six 20-millimeter cannon instead of six 12.7-millimeter guns, with 225 rounds per gun. The XF-86C's greater weight required reinforced landing gear, with dual wheels on the main gear. The twin air brakes of the Sabre were replaced with a single large air brake under the fuselage.

   NORTH AMERICAN F-86C / XF-93A:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                11.86 meters        38 feet 11 inches
   length                  13.43 meters        44 feet 1 inch
   height                  4.77 meters         15 feet 8 inches

   empty weight            6,370 kilograms     14,035 pounds
   loaded weight           9,800 kilograms     21,610 pounds

   max speed at altitude   1,000 KPH           620 MPH / 540 KT
   service ceiling         14,630 meters       48,000 feet
   range, no drop tanks    3,165 kilometers    1,970 MI / 1,710 NMI
   _____________________   _________________   _______________________

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The XF-93A had excellent performance and range, and it could be fitted with stores pylons for external tanks to give even greater range, or to carry up to 900 kilograms (2,000 pounds) of bombs, rockets, or other stores. The Air Force ordered 118 production F-93As in 1948.

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The first XF-93A prototype performed its initial flight in January 1950, again with George Welch at the controls. Only two were built, the contract having been cancelled a year earlier, since the USAF's new Boeing B-47 bomber was so fast that it didn't really need fighter escort, and money was tight anyway. Mid-air refueling would soon kill the "penetration fighter" concept completely.

The two XF-93A prototypes were completed as test articles, and flown in this role by NAA, the USAF, and NACA, eventually ending up as NACA property. They were used in various experiments into the late 1950s, in one case fitted with scoop-type air intakes instead of the original flush intakes, and then scrapped.

 

 

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