Fans of the video game Ace Combat 4: Shattered Skies will fondly remember flying their F-15 ACTIVE into the depths of Megalith to defeat the evil Erusians. Most gamers assumed the F-15 ACTIVE was nothing more than a fantasy aircraft developed by the minds at Namco. With its futuristic look and incredible performance, many assumed that no such aircraft could actually exist. However, the aircraft is indeed real and served as a flying laboratory with NASA and the US Air Force for two decades.
The F-15 ACTIVE began its life as the McDonnell Douglas F-15 STOL/MTD, a heavily modified F-15 Eagle. The aircraft was the first two-seater F-15 ever built and was the sixth F-15 to roll off of the assembly line at McDonnell Douglas (now Boeing), according to NASA. In the mid 80’s engineers at the US Air Force Flight Dynamics Laboratory were looking for a way to test new experimental thrust vectoring nozzles for application on Short Take Off and Landing (STOL) aircraft. They began taking bids for a test aircraft, named the STOL/MTD (Short Take OFF and Landing/ Maneuver Technology Demonstrator). McDonnell Douglas won the bid and work on the new aircraft began.
Operational checks of the flight control and instrumentation systems on the F-15B #837 ACTIVE project aircraft were conducted Sept. 18, 1995, in a test bay in the Integrated Test Facility at NASA’s Dryden Flight Research Center, Edwards, CA. A key feature of the ACTIVE research project was the evaluation of thrust vectoring nozzles, developed by Pratt and Whitney, that could enhance high angle of attack control and maneuverability on future aircraft.
In 1988, McDonnell Douglas delivered the F-15 STOL/MTD to the Air Force. The new plane had several experimental features, including thrust vectoring nozzles, reverse thrust engines, and nose canards (which were borrowed from the tail of the McDonnell Douglass F/A-18 Hornet). In the late eighties and early nineties, the STOL/MTD performed a series of tests involving short take-offs, take offs from wet and damaged runways, in-flight deceleration, and controlled flight in extreme angles of attack.
In 1993, the F-15 STOL/MTD left the Air Force and was acquired by NASA, which performed a series of additional modifications on the engine. It was also renamed the F-15 ACTIVE (Advanced Control Technology for Integrated VEhicles). NASA used the ACTIVE for testing new Pitch/Yaw Balance Beam Nozzles (P/YBBN) and advanced control-logic programming. It also served as a testbed for high altitude instrumentation.
Later in life, the ACTIVE was used to test the next-generation of flight control systems, specifically the Intelligent Flight Control System (IFCS), which is a made up of a network of control sensors that have the ability to “learn” and analyze the flight properties of the aircraft. In theory, the IFCS allows a pilot to control the aircraft during an emergency in ways which before would not have been possible.
Graphic depicting use of propulsion controls in place of aerodynamic controls/ NASA Illustration
The ACTIVE was finally retired from service on January 30, 2009. During its service, the F-15 STOL/MTD-ACTIVE tested new aircraft design and propulsion systems, flight control systems, high altitude sensors, and communication equipment. While it never fired a shot in anger, the F-15 STOL/MTD-ACTIVE helped test and discover new technology which today is invaluable to the United State’s national defense, as well as aviation as a whole.
This story was written by Joseph LaFave
Image courtesy of NASA