Staff Writer (Updated: 4/5/2016):
The curvy, low profile YF-23 was a stark contrast from the sharp-angled YF-22, and featured a wide, almost pancake-like superstructure. The pilot sat in the extreme forward section of the fuselage in a completely digital and ultra-modern cockpit. Jet intakes were positioned on the underside of the fuselage with the sharp angled wing elements dividing the aircraft in half if viewed from the front. Rudder systems were held outwards at extreme angles on either side of the thrust-vectoring engine outlets.
The aircraft changed powerplants between the only flight-ready models ever built. Part of the design competition was to also test the two experimental engines in question - the Pratt & Whitney YF119 and the General Electric YF120. Designated as the PAV-1, this variant of the YF-23 utilized two YF119 engines in a side-by-side arrangement at aircraft's rear. The second YF-23 prototype - designated as the PAV-2 - contained the General Electric YF120 powerplant. The YF119 would eventually win bragging rights between the two competing engines, unfortunately only when married to the YF-22 Lightning II aircraft airframe.
The designation of Black Widow II for the YF-23 prototypes is not an official designation used by the USAF nor Northrop Grumman but in fact is believed to stem from a contest the YF-23 team held to name the aircraft. To follow up with this "unofficial" designation, future test flights of the YF-23 were seen with a red hourglass insignia on the underside of the craft, synonymous with the deadly North American spider known as the Black Widow.
The YF-23, with its thrust vectoring, was a highly nimble machine. But more importantly, the system was designed with the burgeoning "supercruise" technology in mind (as was the YF-22 Lightning II). Supercruise was the new concept of achieving supersonic flight without the use of afterburning by the powerplants or specialized engine augmentation. This would help the YF-23 achieve a stealth-like ability whilst still maintaining basic fighter interceptor capability. Couple the supercruise asset with the still-classified body material and the next generation aircraft could avoid nearly 100% detection on almost any radar system to date.
When all was said and done, the YF-22 Lightning II was selected as the ATF winner and went on to become a full production model as the F-22A Raptor. The two YF-23 Black Widow II's were relegated to becoming artifacts in the Parthenon of American aviation, with one becoming a fixture at the Western Museum of Flight. None-the-less, lessons learned throughout the development process by Northrop Grumman will most likely resurface in a new contract opportunity down the road.