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| Army-Lockheed YO-3A "Quiet Star" | |
|---|---|
 NASA's YO-3A departingArmstrong Flight Research Center | |
| General information | |
| Type | Night reconnaissance |
| National origin | United States |
| Manufacturer | Lockheed Missiles and Space Company |
| Primary user | United States Army |
| Number built | 11 |
| History | |
| Manufactured | 1969–1970 |
| Introduction date | 1969 |
| First flight | 1969 |
| Retired | 1971 |
| Developed from | Schweizer SGS 2-32 |
TheArmy-Lockheed YO-3A "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.
The YO-3A was designed to aUnited States Army specification of 1968, which called for anobservation 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 inSunnyvale, California was contracted to produce twoprototype aircraft. In 1966, the company built two QT-2 "Quiet Thrusters", using modifiedSchweizer SGS 2-32gliders. The prototype QT-2s were then modified to theQT-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 theYO-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 intandem. The observer is located at the front of the cockpit. The YO-3A is an all-metal low-wing monoplane ofsemi-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 offiberglass. 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 byOle Fahlin. The engine cowling andfirewall 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 resonatingmuffler 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.
Following combat evaluation of the QT-2s in Vietnam by the Army, nine production YO-3As were sent toLong Thanh North, Vietnam, in 1970. Shortly after, three were sent tothe 220th Aviation Company, Phu Bai and two toBinh Thuy Air Base. Observations were initially made visually (80%), later followed on with aNight Vision AerialPeriscope developed by Xerox Electro-Optical of Pasadena, California. The mission equipment on the YO-3A was a Night Vision Aerial Periscope withinfrared illuminator. One YO-3A was equipped with alaser target designator. The laser designator system was never used.
The YO-3A operated silently at 1,000 feet (300 m), or lower, depending on terrestrial background noise. Some pilots were known to have gone unobserved over the enemy at 200 feet (61 m). 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 (150 m) 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, whereduct tape and other measures were employed to quiet noticeable sounds.[4]
After Vietnam, two YO-3As, 69-18006 and 69–18007, were used by theLouisiana Department of Fish and Game. The aircraft was effective at catchingpoachers. The FBI eventually acquired the aircraft, and operated the type for several years, assisting the apprehension of kidnappers and extortionists.
NASA took possession of one YO-3A, 69–18010. Following service with the U.S. Army this aircraft was transferred to anairframe and powerplant mechanics school. NASA'sAmes Research Center located atMoffett Federal Airfield inCalifornia acquired the YO-3A from the school in 1977. NASA equipped the aircraft with wing-tip and tail-mounted microphones. These microphones were used to record the in-flight acoustic signatures of a variety of U.S. Armyhelicopters andTiltrotor aircraft. The YO-3 was also used to measure sonic booms from theLockheed SR-71 Blackbird. In 1997, the NASA YO-3A was transferred to theDryden Flight Research Center (now Armstrong Flight Research Center) atEdwards Air Force Base, inCalifornia. The YO-3A remained in a flyable storage state until October 2004. Then the YO-3A was flown back to Ames to supportrotorcraft research again for nearly two years before once again returning to Dryden. In 2015, the aircraft was retired by NASA and sold by theGeneral Services Administration at auction to the Vietnam Helicopters Museum.[5]
General characteristics
Performance
Related development
