Lockheed YO-3

Lockheed YO-3

The Lockheed YO-3A "Quiet Star" was an American single-engined, propeller-driven monoplane that was developed for battlefield observation during the Vietnam war. It was designed to be as quiet as possible, and was intended to observe troop movements in near-silence during hours of darkness.

Design and development

The YO-3A was designed to a US Army specification of 1965, which called for an observation aircraft that would be acoustically undetectable from the ground when flying at an altitude of 1,200 feet. Lockheed was approached to produce such a design. In 1966 the company built a prototype QT1 "Quiet Thrust" which was a modified Schweizer SGS 2-32 glider, and a further two prototypes of a two-seat version called the QT-2 PRIZE CREW. The QT had a silenced engine and a propeller operating at subsonic tip speed for quiet operation.

Following operation trials with the QT-2 a modified version, designated the YO-3A was ordered by the Army. Based on the QT2 but with a low-mounted wing, retractable main-wheel landing gear and a modified fuselage with tandem seating for a pilot and observer. The YO-3A was powered by a 210hp IO-360 engine driving a six-bladed fixed-pitch propeller, the propeller was later changed to a three-bladed constant-speed version.

Operational history

Vietnam War

Following combat evaluation of the QT-2s in Vietnam by the Army, nine production YO-3As were sent to Long Thanh North, Vietnam in 1970. The aircraft were used at night, at low altitudes. Observations were made visually and with a Night Vision Aerial Periscope developed by Xerox Electro-Optical, Pasadena California night vision devices. The YO-3A had a specially designed propeller operated by belts, an exhaust system that ran the length of the aircraft and other sound quieting technologies. The mission equipment on the YO-3A was a Night Vision Aerial Periscope with infrared illuminator. Some YO-3As were equipped with a laser target designator. The YO-3A operated silently at 1,000 feet and depending on terrestrial background noise, could be operated much lower. Some pilots were known to have gone unobserved over the enemy at 200 feet. Reportedly, the aircraft sounded like "a flock of birds" to those on the ground.

Post-war usage

After Vietnam, two YO-3As, 69-18006 and 007, were used by the Louisiana Department of Fish and Game. The plane was effective at catching poachers. The FBI eventually acquired the aircraft, and operated the planes for several years, assisting the apprehension of kidnappers and extortionists.

NASA took possession of one YO-3A in the late 70's. The plane was used in rotorcraft research. It is still in operation today at Moffett Field, California. (This aircraft is currently in use at Nasa's Dryden Research facility at Edwards, AFB, CA.)


QT-1 Quiet Thrust
Prototype single-seat glider conversionQT-2
Two-seat version, two built for combat evaluationQ-Star
One-aircraft for propeller developmentYO-3A
Production aircraft for the United States Army, 14 built


The following YO-3A aircraft and their last known status, all are in the United States:

  • 18000 is on display at the Army Collection at Fort Rucker.
  • 18001 is on display at the Hiller Museum.
  • 18003 is in storage in Florida.
  • 18005 is parked at Skagitt Airport, Washington.
  • 18006 is at the Pima Air and Space Museum, Arizona.
  • 18007 is at Cable Airport Upland California with the CAF 3rd Pursuit Squadron and is in the process of being restored to flight status.
  • 18010 belongs to NASA and is still flying. Currently based at Moffett Field, California.


Military operators

Civil operators


External links


  • John Andrade, U.S.Military Aircraft Designations and Serials since 1909, Midland Counties Publications, 1979, ISBN 0 904597 22 9 (Page 140)
  • The Illustrated Encyclopedia of Aircraft (Part Work 1982-1985), 1985, Orbis Publishing

See also

Search another word or see Lockheed YO-3on Dictionary | Thesaurus |Spanish
Copyright © 2015 Dictionary.com, LLC. All rights reserved.
  • Please Login or Sign Up to use the Recent Searches feature