Photography > Aerial Reconnaissance and Imagery Analysis > Airplanes

YO-3A (Yo-Yo)
The U.S. Army developed this little publicized surveillance aircraft for use in Vietnam. Night was the domain of the Viet Cong and NVA, whether within South Viet Nam or along the Ho Chi Minh trail, so the means to locate and target the enemy at night was high on the list of priorities for all services. The U.S. had many aircraft in service in Viet Nam in 1965-66, but they proved of little help in finding the nocturnal enemy. The DoD turned to DARPA, who in turned assigned the project to Lockheed. The Air Force opted not to participate due other programs, but the Army was enthusiastic (as were the Navy and Marine Corps) but insisted on a two-man crew – pilot and observer.

In April 1967, Lockheed was selected to build two experimental, low-aural signature aircraft to serve as a platform for different kinds of sensors. Lockheed selected the Schweizer model SGS 2-32 sailplane, a large – two-place, 57-foot wingspan – well-tested design. A Continental 4-cylinder engine powered the aircraft, fitted with a reduction gear to keep propeller rpm low (for noise). A large automobile exhaust muffler was used to quiet the exhaust. The initial design was designated the QT-1 (Quiet Thrust), soon followed by an enhanced design dubbed the QT-2. Even with these improvements, the fact remains, this platform was really nothing more than a modified glider, powered by a 100-horsepower engine with a wooden propeller. However, the aircraft could fly slow, linger over the target area, and it was quiet.

Test versions of the aircraft deployed to Viet Nam in January 1968. On January 31st, the Communists launched their much-publicized Tet Offensive, a massive campaign against installations in cities and towns throughout the South. Every asset had to be mustered to counter this offensive. Despite their test status, the QT-2s took off nightly, sometimes during rocket or mortar bombardment of the airfield, to find enemy targets; the enemy never knew what lurked only a few hundred feet above their heads. As for targets and intelligence, the QT-2 observers reported more than could possibly be dealt with. Their greatest coup was a sighting the fleets of supply sampans making their way along the Mekong River’s network from VC sanctuaries upriver in Cambodia. The test airplanes conducted reconnaissance missions before and after air and artillery strikes, surveillance operations over selected areas, and monitored canals, rivers, roads, and the coastline. At the conclusion of the test, the aircraft was accepted, but the Army wanted improvements.

Lockheed undertook the requirements the Army mandated, producing the YO-3A. The YO-3A (Yo-Yo) was a more sturdy aircraft, powered by a muffled 210-horsepower (Lycoming) engine, and ultimately carried a real time imaging sensor system (forward-looking infrared). It flew at altitudes adequate to allow the sensor operator to acquire targets (500-2000 feet), with missions lasting from 3-6 hours. The canopy was enlarged for better observation, with the observer seated forward and pilot aft. The Army deployed 13 YO-3As to Viet Nam late in 1969, assigning them to 1st ASA Company and operating from Long Binh. In mid-1970, at least three YO-3As were detached to Phu Bai, just south of Hue. These aircraft, operating from this northern airfield, conducted night reconnaissance and surveillance operations in I Corps and along the Ho Chi Minh Trail. The aircraft proved very effective in its mission operations, providing a unique night, real time target acquisition capability that allowed much more effective targeting of a deceptive enemy.

The YO-3A served in Viet Nam until April 1972.