During the 1980s NASA built the High Angle-of-Attack Technology Program or HATP. It chose the F-18 Hornet to be used in the program. However, throughout the years, it was severely cannibalized for parts, so mangled that the Navy thought it will never fly again.
Still, engineers remembered it as a legendary High Angle-of-Attack Research Vehicle, giving the important foundations for handling all future American fighter aircraft.
In the 1980s NASA started the High Angle-of-Attack Technology Program or HATP. It aimed to give flight-validated aircraft design tools aside from enhancing the handling of aircraft, especially fighters at high angles of attack.
F-18 High Angle-of-Attack Research Vehicle
NASA then chose a pre-production McDonnell Douglas single-seat F-18 fighter. The plane would come to be known as the F-18 High Angle-of-Attack Research Vehicle.
This particular F-18 has been severely dismantled for spare parts by the Navy, and they never expected it to fly again. But it would prove them wrong.
Research flights started in 1991 with successful trials. During the following years, the plane was constantly modified with additional instrumentation.
The HARV project featured three different flight modes, providing researchers with enhanced flexibility, and getting more detailed information. In September 1996, the project ended after 385 flights.
Ultimately, the combined technologies that resulted from years-long investigation helped in upgrades to handle fighter aircraft enhancing conditions that were a previously dangerous flight regime. It also enhanced the understanding of flight at high alpha.
As a result, designers and developers of US fighter aircraft were now allowed to build planes that could safely execute maneuvers in portions of the flight envelope that were avoided previously.