NASA Advanced Control Technology for Integrated Vehicles
In 1994, after the conclusion of Air Force S/MTD testing, the aircraft was transferred to NASA Dryden for the NASA Advanced Control Technology for Integrated Vehicles (ACTIVE) research project. ACTIVE was oriented to determining if axisymmetric vectored thrust could contribute to drag reduction and increased fuel economy and range compared with conventional aerodynamic controls. The project was a collaborative effort between NASA, the Air Force Research Laboratory, Pratt & Whitney,
and Boeing (formerly McDonnell-Douglas). An advanced digital flight fly-by-wire control system was integrated into the NF-15B, which was given NASA tail No. 837. Higher-thrust versions of the Pratt & Whitney F100 engine with newly developed axisymmetric thrust-vectoring engine exhaust nozzles were installed. The nozzles could deflect engine exhaust up to 20 degrees off centerline. This allowed variable thrust control in both pitch and yaw, or combinations of the two axes. An integrated propulsion and flight control system controlled both aerodynamic flight control surfaces and the engines. New cockpit controls and electronics from an F-15E aircraft were also installed in the NF-15B. The first supersonic flight using yaw vectoring occurred in early 1996. Pitch and yaw thrust vectoring were demonstrated at speeds up to Mach 2.0, and yaw vectoring was used at angles of attack up to 30 degrees. An adaptive performance software program was developed and successfully tested in the NF-15B flight control computer. It automatically determined the optimal setting or trim for the thrust-vectoring nozzles and the aerodynamic control surfaces to minimize aircraft drag. An improvement of Mach 0.1 in level flight was achieved at Mach 1.3 at 30,000 feet with no increase in engine thrust. The ACTIVE NF-15B continued investigations of integrated flight and propulsion control with thrust-vectoring during 1997 and 1998, including an experiment that combined thrust vectoring with aerodynamic controls during simulated ground attack missions. Following completion of the ACTIVE project, the NF-15B was used as a testbed for several other NASA Dryden research experiments, which included the efforts described below.