The F-16XL's unusual cranked-arrow double delta wing platform is apparent in this 1997 photo. (NASA Photo)
NASA's Dryden Flight Research Center flew two prototype F-16XL aircraft in a variety of aeronautical research projects in the early and mid 1990s.
The two aircraft, a single-seat version with tail number 849 and a two-seat version bearing tail number 848, featured an unusual cranked-arrow double-delta wing. They were modified from F-16A and F-16B fighters by their manufacturer, General Dynamics Corp., for a U.S. Air Force strike fighter competition in the early 1980s that was one by the McDonnell Douglas F-15E. The two aircraft were loaned to NASA for aeronautical research in the late 1980s.
The single-seat F-16XL aircraft, tail number 849, arrived at the center in 1989 and supported several flight research projects during the 1990s. The aircraft was upgraded with a new Digital Flight Control System (DFCS) in 1997. The DFCS utilized an electronic flight control system coupled with a digital computer, replacing the F-16XL-1's original analog computer. The DFCS modification was equivalent to the U.S. Air Force F-16 upgrade known as Block 40. The aircraft's fly-by-wire flight control system remained intact.
The DFCS upgrade allowed NASA's F-16XL-1 the flexibility needed to perform experiments which required major new flight control functions or capabilities. The initial flight test objectives for the modified aircraft verified that the DFCS functioned properly and that the performance and handling qualities were acceptable throughout the flight envelope.
The added flexibility of the DFCS increased the versatility of this aircraft as a test bed for aerodynamic research and investigation of other advanced technologies. The aircraft's instrumentation system monitored control system operations, and was capable of supporting additional measurements.
The digital flight control system was compatible with a Research Flight Control System (RFCS) that could be installed when necessary. RFCS capability provided a flexible, reliable, and safe means to modify the aircraft control system. The RFCS computer significantly increased computational speed and computer memory.
NASA's F-16XL 849 deploys its drag parachute to aid braking following touchdown on the main runway at Edwards Air Force Base. (NASA photo) The F-16XL #849 was previously flown in NASA's Cranked-Arrow Wing Aerodynamics Project, or CAWAP, which provided aerodynamic boundary layer pressures and distribution data for NASA's High Speed Civil Transport (HSCT) research program in the early 1990s. The unique cranked-arrow wing shape provided better low-speed lift and handling characteristics than the modified "double-delta" wing used on the Concorde supersonic transport (SST).
It also participated in NASA's 1995 sonic boom study, in which the aircraft flew 200 feet behind a NASA SR-71 to probe the boundary of the SR-71's supersonic shock wave. These tests measured and recorded the shape and intensity of the shock waves. The studies helped HSCT engineers to better understand supersonic shock waves in order to reduce sonic boom intensity near populated areas.
NASA's F-16XL #849, which had been on loan to NASA by the U.S. Air Force, last flew in 1999 and last moved under its own power during a taxi test in 2007. It was turned over to the Air Force Flight Test Museum at Edwards in August 2013 for display.
The two-seat F-16XL was extensively modified by NASA Dryden for the Supersonic Boundary Layer Control research project in the mid-1990s. A turbine-driven suction system installed in the fuselage and a modified, thickened left wing pulled in boundary layer air flowing over the wing to enable laminar, or smooth, airflow over the wing. The aircraft last flew in 1996 and is no longer airworthy. The aircraft was recently transferred to the National Museum of the Air Force.