The F-16XL aircraft was externally different from other experimental F-16s. It had the shape of a wing in a plane, which can be defined as a “modified delta with a variable sweep.”
It was developed jointly with the NASA agency to study the problem of minimizing drag during subsonic and supersonic flight.
The fuselage was elongated with two inserts, the ventral carinae removed. The deltoid wing scheme was proposed by General Dynamics in 1980 and supported by NASA.
The F-16XL had seven pylons with 29 variants of external arms suspension, including four units for hanging the AIM-120 missiles, partially hidden in the root part of the wing, as well as sites for the AIM-9 or AIM-120 missiles at the end of the wing. The first F-16XL first took to the air on July 15, 1982, later the second, double F-16XL-2.
In the same year, the US Air Force held a competition for dual-purpose fighters to find a replacement for the F-4 and F-111 aircraft. F-16XL participated in the competition, but the F-15E Strike Eagle surpassed it in demonstration flights.
He became the winner, and a number of other factors were taken into account, among them – the high cost of development and construction of the F-16XL, its low modernization stock and a smaller resource.
In 1989, on a single F-16XL, the section of the left wing plane was replaced by an experimental – titanium, containing several million microscopic holes cut by a laser, to study the effect of the motion of the vortex flows along the wing.
Two F-16XL were used to study the take-off characteristics and the effect of engine noise. They also experimented with vortex flaps and control of the boundary flow of air.