In March 1996, NASA initiated flight testing of a new thrust vectoring concept that could lead to significant increases in the performance of both civil and military aircraft flying at subsonic or supersonic speed.
The tests at Dryden Flight Research Center are part of a program known as ACTIVE (Advanced Controls Technology for Integrated Aircraft), a collaborative effort of NASA, the Air Force's Wright Laboratory, McDonnell Douglas Aerospace (MDA), and Pratt & Whitney Government Engines & Space Propulsion unit (P&W).
The F-15 ACTIVE is exploring a vectored thrust system that could replace conventional aerodynamic control surfaces.
The test aircraft is a twin-engine F-15 ACTIVE, a modified version of the Air Force F-15B fighter built by MDA and powered by F-100-PW-229 engines, each of which is equipped with a nozzle that can swivel 20 degrees in any direction, giving the aircraft thrust control in the pitch (up and down) and yaw (left-right) directions. This vectored (deflected) thrust system could replace conventional drag-inducing aerodynamic controls and thereby gain increased fuel economy or range.
The tests began with four flights in March/April, then progressed to the first supersonic flight on April 24. On that occasion, the F-15 ACTIVE successfully demonstrated both pitch and yaw deflections at speeds of Mach 1.2 to 1.5. The flight test plan contemplated about 60 flights totaling 100 hours at speeds up to Mach 1.85 and angles of attack (the angle between the aircraft's body/wings and its actual flight path) up to 30 degrees.
The F-15 ACTIVE program is representative of the type of flight research conducted by NASA to explore new technologies and new flight regimes. NASA conducts such programs independently or in cooperation with U.S. industry and the Department of Defense, sometimes in cooperation with international development teams.
Another example of a Dryden flight research program is NASA's High Alpha investigation. High Alpha refers to high angles of attack, a flight regime in which the airflow becomes extremely complex. To provide aircraft manufacturers with a technology base for designing high performance aircraft capable of "supermaneuverability" and of maintaining stability/controllability at high angles of attack, NASA conducted the decade-long High Alpha program that concluded on May 29, 1996 with the final flight of NASA's F-18 HARV (High Alpha Research Vehicle).
NASA's veteran F-18 HARV research aircraft concluded a decade-long flight test program that explored aircraft maneuverability and controllability at high angles of attack.
In the first phase of the program, initiated in 1987, the F-18 HARV explored angles of attack up to 55 degrees. In the second phase, NASA investigated thrust vectoring technology to determine the impact on aircraft maneuverability at high angles of attack. In the final phase, the F-18 HARV's handling qualities were evaluated by 14 different pilots representing NASA, the Department of Defense, and support contractors McDonnell Douglas Aerospace and Calspan Corporation.
Among other flight projects under way at Dryden are two examples of test programs intended to support NASA activities not directly connected with aeronautics advancement. One is a project involving airborne tests of an advanced thermal protection system (TPS) for use on the X-33 Reusable Launch Vehicle (see page 30). The project employs an F-15B Flight Test Fixture-II (FTF-II) aircraft for atmospheric testing (the ascent and landing phases of the launch vehicle's operation), where the potential threat to the TPS is impact with rain drops, cloud droplets or ice crystals. Test participants include Marshall Space Flight Center and Rockwell International.
Another new program involves testing the Theseus, a robot aircraft to be employed in NASA's Mission To Planet Earth program for research in such areas as stratospheric ozone depletion and the atmospheric effects of future high speed civil transport engines. Built by Aurora Flight Sciences Corporation, Fairmont, West Virginia, Theseus is a twin-engine propeller-driven craft with a 143-foot wingspan. Constructed largely of composite materials, it is capable of carrying 700 pounds of science instruments to altitudes above 60,000 feet for durations of more than 24 hours. The plane made its initial flight at Dryden in May 1996.