X-26A Frigate (Schweizer SGS 2-32) / X-26B (Lockheed)

The X-26 program is among the smallest and more secretive of the X-plane programs, and comparatively little is known of its history or accomplishments. The X-26A was a stock Schweizer SGS 2-32 sailplane used by the Navy to expose novice pilots to the phenomenon of yaw/roll coupling. At least 3 of the X-26A's were destroyed in accidents, and one remaining X-26A is housed at the Army Aviation Museum, Fort Rucker, Alabama. The final example of this unpowered glider continues in use at the U.S. Naval Test Pilot School (TPS).

The powered X-26B was created in response to a requirement for a low-acoustical signature observation and reconnaissance platform for use in the Vietnam war. The X-26B was powered by a single Continental O-200A four-cylinder, horizontally-opposed air-cooled engine. A total of two X-26B's were built, though apparently no intact X-26B's survive. The X-26B was a Lockheed-modified Schweizer SGS.2-32 glider. The initial single seat QT-1 (Quiet Thrust) was never built, but it was the progenitor of three quiet-airplane designs. A pair of two-seat QT-2 aircraft were built, and underwent flight tests at a secret base in the Mojave Desert in August 1967. These were later modified to the QT-2PC Project Prize Crew configuration, which was tested in Vietnam combat beginning in January 1968.

The X-26B planes were prototypes of the YO-3A Quiet Star aircraft flown in Vietnam during the United States military action. The Lockheed "Q-Star" was a Schweizer sailplane, modified to a prototype silent reconnaissance aircraft with an engine behind the pilot. A long shaft was positioned above the cockpit, and a big propeller was fitted on top of the nose. The Q-Star used a Wankel-type rotary engine driving a slow-moving wooden propeller via a 10-foot shaft in an attempt to achieve audio stealth. One example of this direct follow-on to the QT-2 was built, which is currently on display at the Pima Air & Space Museum in California.