Here is some further information on some of the developed versions of the X-26A that Walt included above and showed a photo of a NASA application. (Does that photo look like a mockup drawing?, Just wondering.)

The U.S. Army became interested in the X-26 program beyond the Navy's Test Pilot School training requirement and took two Schweizer SGS-2-32 sailplanes for Lockheed to modify under a then secret program called QT-2, for Quiet Thruster. The first QT-2 flew on 26 August 1967.

The QT-2 had a fiberglass enclosed "hush house" with Continental O-200 engine mounted behind and above the 2-32 canopy with a long aluminum drive shaft to a forward gear-reduction drive housing mounted on the thrust line. A bit weird-looking, perhaps. Various tractor propeller designs from three to six blade configurations were used to achieve a low acoustic signature at low rpm. A tail fairing and a propeller spinner were also added, and landing gear modified. Lockheed's nomenclature for the QT-2 became X-26B under the military contract.

The Army's purpose was to develop an observation and reconnaissance aircraft to use in the Vietnam War, having a long patrol endurance duration and low acoustic signature. Secret tests were done domestically and then two QT-2s were tested in Vietnam in 1968 combat conditions. They contained many sensors seeking enemy jungle movements. They operated at very low altitudes and could not be easily detected audibly unless the ground enemy was directly under their flight path. This led to the follow-on Q-Star and the YO-3A four seat observation aircraft developments.

Of interest, some Lockheed YO- quiet aircraft were owned by a tenant group at Point Mugu during the the late 1970s and early to mid-1980s, parked on the ramp behind the NAS Control Tower building together with some Piper large twin aircraft models that were apprehended and confiscated from drug smugglers. From 1983 on I parked my car near that ramp as my office then was upstairs in the adjacent Weapons Program Management Dept. hangar.

Lockheed X-26B SPECS

Crew: Two

Power: one 100 Hp Continental O-200 piston engine

Max speed: 115 mph

Max altitude: 13,000'

Wing span: 57' 2"

Length: 30' 9"

Height: 9' 3"

Gross weight: 2,128 lb