The Lockheed YO-3 Quiet Star is an American single-engined, propeller-driven aircraft that was developed for battlefield observation during the Vietnam War. Designed to be as quiet as possible, it was intended to observe troop movements in near-silence during the hours of darkness.
Design and development
The YO-3A was designed to a United States Army specification of 1968, which called for an observation aircraft that would be acoustically undetectable from the ground when flying at an altitude of 1,500 feet (457 m) at night.
Lockheed Missiles and Space Company located in Sunnyvale, California was contracted to produce two prototype aircraft. In 1966, the company built two QT-2 "Quiet Thrusters", using modified Schweizer SGS 2-32gliders. The prototype QT-2s were then modified to the QT-2PC "PRIZE CREW" configuration. The QT-2PC had a silenced engine and a slow-turning propeller for quiet operation.[1]
Following operational trials with the QT-2PC in Vietnam, a production aircraft, designated the YO-3A was ordered. This aircraft's design was also based on the Schweizer SGS 2-32 glider. Like the QT-2PC, the YO-3A has a large wingspan and a larger canopy area for observation. Two crew members (a pilot and an observer) are seated in tandem. The observer is located at the front of the cockpit. The YO-3A is an all-metal low-wing monoplane of semi-monocoque construction. The control surfaces of the YO-3A including the ailerons and rudder are fabric-covered. The engine cover, canopy, engine exhaust shroud, wing-root fairings, and wheel-well fairings were constructed of fiberglass. The YO-3A has retractable tailwheel-type landing gear.[2]
The YO-3A was powered by an air-cooled, six-cylinder, horizontally opposed, fuel-injected, Continental Model No. IO-360D engine. The engine is coupled to a slow-turning propeller through a belt pulley-drive system. The propeller reduction ratio is 3.33:1. Originally equipped with a six-bladed ground-adjustable-pitch propeller, this was replaced in March 1971 with a three-bladed laminated constant-speed wooden propeller designed by Ole Fahlin. The engine cowling and firewall were lined with fiberglass material to dampen and contain engine noise.[2]
The YO-3A is equipped with an Asymmetrical Exhaust System. A crossover exhaust pipe is used to remove exhaust from the left bank of engine cylinders to the right side of the engine compartment. This crossover joins the right bank exhaust pipe and exits along the lower right side of the engine compartment. The exhaust gases are then moved through an acoustical fairing into a dissipating and resonating muffler continuing to the aft end of the fuselage.[2]
Nine of the eleven YO-3As produced operated in South Vietnam, at night, from 1970 to 1971 (Late June 1970 to September 1971) and, although three were destroyed in crashes, none were damaged by enemy fire or shot down.[3] The YO-3A was very successful in spotting movement by the Viet Cong and North Vietnam Army (NVA) operating in South Vietnam.
Operational history
Vietnam War
The YO-3 saw limited service in Vietnam.
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. Shortly after, three were sent to the 220th Aviation Company, Phu Bai and two to Binh Thuy Air Base. Observations were initially made visually (80%), later followed on with a Night Vision Aerial Periscope developed by Xerox Electro-Optical of Pasadena, California. The mission equipment on the YO-3A was a Night Vision Aerial Periscope with infrared illuminator. One YO-3A was equipped with a laser target designator. The laser designator system was never used.
The YO-3A operated silently at 1,000 feet, or lower, depending on terrestrial background noise. Some pilots were known to have gone unobserved over the enemy at 200 feet. Occasionally, daylight flights were made over the rivers. Crew chiefs would monitor the YO-3A flying over the maintenance section prior to deployment, listening for rattles, whistles or other noises. The propeller, even at 500 feet over the maintenance area, made only a light flutter, heard just as it approached. This was followed by a light rushing of wind over the wings. There was no audible sound once the aircraft had passed over. If any abnormal noises were heard, the aircraft returned to the runway, where duct tape and other measures were employed to quiet noticeable sounds.[4]
Postwar usage
After Vietnam, two YO-3As, 69-18006 and 69–18007, were used by the Louisiana Department of Fish and Game. The aircraft was effective at catching poachers. The FBI eventually acquired the aircraft, and operated the type for several years, assisting the apprehension of kidnappers and extortionists.
Two modified Schweizer X-26 two-seat sailplanes for evaluation, later modified with sensor packages as the QT-2PC.[6]
QT-2PC PRIZE CREW
Two QT-2s with combat sensor packages for evaluation in Vietnam theatre, one reduced to spares and the other returned to the United States Navy as the Schweizer X-26B.[6]
Andrade, John. U.S. Military Aircraft Designations and Serials since 1909. Hinckley, UK: Midland Counties Publications, 1979. ISBN0-904597-22-9.
Francillon, René J. (1982). Lockheed Aircraft since 1913. London: Putnam & Company. ISBN0-370-30329-6.
The Illustrated Encyclopedia of Aircraft (Part Work 1982-1985). London: Orbis Publishing, 1985.
Munson, Kenneth. Bombers in Service, Patrol and Transport Aircraft Since 1960. London: The Macmillan Co., 1972. ISBN978-0-71370-586-7.
Schnebly, F. David. A Greenhouse Anthology, Chapter 5: Taking The Night Away From Charlie (Development of the YO-3A). Xlibris Corporation, 2000 (ISBN 0-7388-3086-0)
External links
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