<p>In answer to a USAF requirement issued in September 1985 for an ATF (Advanced Tactical Fighter), Northrop teamed with McDonnell Douglas to develop a new fighter which was intended to replace the F-15 Eagle as the service's prime air defense weapon. The ATF had to be more maneuverable than the F-15, with greater range, and also had to be stealthy. Northrop had been involved in stealth research since the 1960s, and was well placed to design a fighter with low observability, as indeed was Lockheed, who had teamed with General Dynamics and Boeing to offer the other ATF competitor, the F-22. Dem/Val contracts were awarded to the two teams, each covering two aircraft which would be powered by competing powerplants.
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<p>Northrop drew heavily on its high-technology base to design the YF-23, the aircraft emerging unlike any aircraft seen before or since. The forward fuselage was flat-bottomed and chined, the chine blending into the trapezoidal wing, whose leading and trailing edges were set at 40-degree sweep. Intakes slung under the wing aspirated the rear-set engines via a serpentine duct which shielded the compressor faces from prying radars. The engines were situated in blended bodies, and exhausted through deep slots which had a much extended lower lip to shield the exhausts from infra-red detection. The exhaust slots formed a sawtooth rear end to defeat radars, outboard of which were fixed large splayed tails.
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<p>As well as the cockpit, the forebody contained the missile armament, housed in two bays one behind each other. A complex fly-by-wire control system provided maneuverability through leading-edge flaps, trailing-edge flaps, drooping ailerons and the all-moving tails. Avionics included an advanced radar, and the entire system was tested aboard a modified BAC One-Eleven owned by avionics supplier Westinghouse.
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<p>Prototype Air Vehicle (PAV) No. 1 was serialled 87-800, and first flew on 27 August 1990 with Paul Metz at the controls, powered by Pratt & Whitney YF119 turbofans. PAV 2 (87-801) was fitted with the more powerful General Electric YF120, and took to the air on 26 October 1990. Throughout Dem/Val flying the pair of YF-23s demonstrated outstanding performance, 'supercruising' (i.e. flying supersonically without afterburner) with ease. Unlike the Lockheed team, Northrop did not demonstrate missile launches, although they were not required to do so. During the Dem/Val stage, the YF-23 picked up the nicknames 'Gray Ghost' and 'Black Widow II'.
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<p>On 23 April 1991 the USAF announced the Lockheed team's F-22 and the Pratt & Whitney F119 engine as the winners of the competition. This represented the lowest-risk route and was something of a blow to the Northrop team. The terms of the requirement allowed considerable latitude in the designs, and whereas the Lockheed aircraft was considered to be far more maneuverable, the YF-23 was undoubtedly faster, and probably stealthier.
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<p>Following the loss of the competition, the YF-23s were put into storage at Edwards AFB. In 1993 they were transferred to NASA Dryden where they would be used on ground tests of aircraft employing state-of-the-art construction techniques. Rumors circulating in 1994 concerning the continued highly-classified development of the F-23 for the defense suppression role cannot be ignored, considering the merits the aircraft displayed during its brief flying career.
<item><hi format=bold>Powerplant:</hi> two Pratt & Whitney YF119 or general Electric YF120 turbofans, each rated at approximately 35,000 lb thrust with afterburning
<item><hi format=bold>Performance:</hi> maximum speed Mach 2 with afterburning, approximately Mach 1.6 in military power; service ceiling 65,000 ft; unrefueled combat radius over 800 miles
<item><hi format=bold>Weights:</hi> operating empty 29,000 lb; normal take-off 54,000 lb
<item><hi format=bold>Dimensions:</hi> wing span 43 ft 7 in; length 67 ft 5 in; height 13 ft 11 in; wing area 900 sq ft
