NASA’s Subsonic Research Aircraft Testbed, or SCRAT, is a modified Gulfstream III that operates out of Armstrong Flight Research Center in Edwards, California. SCRAT the test bed aircraft for the ACTE flexible-flap research project, which examines flexible wing flap technology’s benefits to aerodynamic efficiency.

Claudia Sales, NASA’s acting X-59 deputy chief engineer and airworthiness certification lead for the quiet supersonic research aircraft, stands in front of a Gulfstream G-III, also known as Subsonic Research Aircraft Testbed (SCRAT). Sales supported ground testing as test conductor for Acoustics Research Measurements (ARM) flights at NASA’s Armstrong Research Flight Center in Edwards, California, in 2018.

Initial flight-testing of the ACTE followed extensive wind tunnel experiments. For the first phase of ACTE flights, the experimental control surfaces were locked at a specified setting. Varied flap settings on subsequent tests are now demonstrating the capability of the flexible surfaces under actual flight conditions.

The National Advisory Committee for Aeronautics (NACA) Lewis Flight Propulsion Laboratory obtained a Northrop P-61 Black Widow in October 1945 and modified it to serve as a subsonic testbed for ramjet engines and swept-wing aircraft models. The P-61 was developed during World War II specifically for nighttime attacks. It was the largest and heaviest US fighter in the war. The P-61’s unique design included an abbreviated fuselage and twin booms that were joined by a single tail. To facilitate its nighttime missions, the P-61 was painted black and carried a radar system in its nose. It was designed so the crew could perform their flight and tracking tasks in complete darkness. NACA Lewis was in the midst of a massive research effort on ramjets when it acquired the Black Widow. Researchers used the aircraft to accelerate the ramjet until it reached a velocity at which it could be ignited. A ramjet can be seen being fired underneath the aircraft in this photograph. Sensors and instrumentation fed data from the ramjet to the pilot and researchers on the ground. The NACA researchers created a rectangular ramjet with a V-shaped gutter flameholder. The researchers installed the ramjet on the P-61 and flew it at subsonic speeds over a range of altitudes up to 29,000 feet. The ramjet had been previously tested at low speeds on a test stand on the hangar apron. The rectangular ramjet was also used to study different types of flameholders and nozzles used to spray fuel into the combustion chamber. The Black Widow was transferred from Lewis in October 1948.