The F-16XL is perhaps one of the more interesting variants of the Fighting Falcon series, showing the ingenuity of General Dynamics and some of the oddities involved in military purchasing. First developed in the early 1980s, the F-16XL was a fierce competitor in the European Two-seater Fighter program for the U.S. Air Force, which was a design looking to replace the F-111 Aardvark. It lost the competition to the McDonnell Douglas F-15E Strike Eagle.
The F-16XL followed the advanced wing design program for future generations of supersonic airliners directly from the SCAMP project. It sported the cranked-arrow delta wing—which was much larger than that of the standard F-16—for 25% better maximum lift-to-drag ratio in supersonic flight and 11% in subsonic flight. The new design made the F-16XL able to carry twice as much load as the regular F-16 and to travel 44% further without external fuel tanks.
Harry J. Hillaker, chief project engineer of the F-16XL, said that while it retained the basic features of the Fighting Falcon, the new variant provided more range and payload. So, in addition to a pair of Sidewinder AIM-9 infrared-guided missiles, the F-16XL was designed to lug four AMRAAMs, making it a much more efficient fighter.
Apart from this, the F-16XL’s advanced design involved a lengthened fuselage and the wide use of carbon composite materials, saving weight and increasing internal fuel capacity by 82 percent. In the aircraft, enhancement was made in the wing planform and camber enablers, which helped in providing efficient supersonic cruise without a loss of low-speed maneuverability.
These enhancements aside, the F-16XL was ultimately passed over in favor of the dual-fan-engine-equipped F-15E which offered features such as more thrust, a higher operating speed, and an increased ceiling at less cost. The two developed F-16XL fighters were mothballed to Edwards Air Force Base but had a new life serving NASA.
In 1988, both F-16XL prototypes went to NASA for aeronautical research. One received an active titanium glove on its left wing to study laminar flow in its campaign to reduce drag. The glove, developed by North American Aviation, has millions of tiny laser-cut holes to remove turbulent surface air. The second aircraft was a two-seater. During its testing when fitted with a General Electric F110-129, it became the first aircraft to fly at Mach 1.1 at 20,000 feet without afterburner.
The work NASA has accomplished using the F-16XL has furthered the state of knowledge concerning supersonic flight and aided in the development of the F-22 Raptor’s supercruise capability. Studies with the aircraft have been conducted in such areas as sonic boom characteristics, take-off performance, and engine noise to further the knowledge of high-speed aerodynamics.
Although it never saw duty with the Air Force, the legacy of the F-16XL serves well in aeronautical research and left its mark on later fighter-bomber designs. The F-16XL holds an interesting place in the history of military aviation—the power of ingenious engineering and proving that aerospace engineering is an ever-changing art.