Lockheed YO-3A

Quiet Star

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The Lockheed YO-3A "Quiet Star" is a 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. The YO-3A was not armed

The YO-3A was designed to a U.S. Army specification of 1968, which called for an observation aircraft that would be acoustically undetectable from the ground when flying at an altitude of 1,200 feet at night. Lockheed was approached to produce such a design. In 1966 the company built a prototype QT1 "Quiet Thrust", AKA X-26B using a modified Schweizer SGS 2-32 glider. This was abandoned for 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 in Vietnam, 1968, a production version, designated the YO-3A was ordered by the Army. Based on the QT2's SGS 2-32 platform, the YO-3A was highly modified. It had a low-mounted wing, retractable main-wheel landing gear and a modified fuselage with tandem seating for a pilot in back and an observer in the front seat using a NVAP (Night Vision Aerial Periscope) and infrared illuminator. The YO-3A was powered by a 210 hp IO-360D engine driving a six-bladed fixed-pitch propeller; the propeller was later changed to a wooden three-bladed constant-speed version and was found to be as quiet at slow cruise speeds as the six-bladed unit, but much more efficient at higher speeds.

Nine of the eleven YO-3As in production by LMSC operated in South Vietnam, at night, 1970-71 (14 months) and never took a round or were shot down. The YO-3A was very successful in spotting movement by the North Vietnamese, but its deployment late in the American involvement in Vietnam reduced its value in that war. By 1975 all American troops were out of 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. three were sent to Phu Bai and two to Binh Thuy. The aircraft were used at night, at low altitudes. Observations were made visually (80%) and with followed on 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 12 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. One YO-3A was equipped with a laser target designator. The laser 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 listen to 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 the maintenance area. This was followed by a light rushing of wind over the wings. Once the plane had passed over, there was no audible sound. If any noises were heard, the plane returned to the runway and duct tape and other measures were taken to quiet noticeable sounds.

After Vietnam, two YO-3As, 69-18006 and 69-18007, were used by the Louisiana Department of Wildlife and Fisheries. 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, 69-18010, in the late 1970s. The plane was used in various noise measurement test, and was based at Moffett Field, California. (This aircraft was later used at the NASA's Dryden research facility at Edwards AFB, California in 1997.)


QT-1 Quiet Thrust Prototype single-seat glider conversion
QT-2 Two-seat version, two built for combat evaluation
Q-Star One-aircraft for propeller development
YO-3A Production aircraft for the United States Army, 11 built


Military operators, United States Army
Other operators: Louisiana Department of Wildlife and Fisheries, FBI and NASA.

YO-3A Aircraft History:

69-18000 is on display at the Army Collection at Fort Rucker. 1st production aircraft which remained in the USA for flight testing.
69-18001 is on display at the Hiller Museum. Vietnam operations 1970-72.
69-18002 Crash landed at Long Thanh November 1970. Vietnam operations 1970.
69-18003 Obtained by Mr. Richard Osborne as of 14 Feb 1977, currently stored awaiting restoration. Vietnam operations 1970-72.
69-18004 Crashed near Bien Boa SVN 6 June 1971, both crew members killed CW2 M. Loving and CW2 C. Borchers 73rd SAC. Vietnam operations 1970-71.
69-18005 was parked at Skagit Regional Airport, Washington. Donated to the Seattle Museum of Flight. Vietnam operations1970-72.
69-18006 is at the Pima Air and Space Museum, Arizona. Vietnam operations 1970-72. Operated by (LDWF), later FBI.
69-18007 is at the Western Museum of Flight in storage. Vietnam operations 1970-72. Operated by Louisana Dept of Wildlife and Fisheries, later FBI. Western Museum of Flight.
69-18008 Destroyed in Crash in South Vietnam. Pilot and Observer survived.
69-18009 Crashed near Hunter Ligget AAF/Ft. Ord in 1970. Two USAF personel aboard. One significantly injured.
69-18010 Acquired by NASA in 1978 and was based at Moffett Field, California. Later used at NASA's Dryden research facility at Edwards AFB, California in 1997. Vietnam operations 1970-72.

Wing span: 57 feet 1 inch.
Empty weight: Approx. 3,129 pounds.
Maximum speed: 138 MPH.
Cruising speed: 110 MPH, or as slow as 70 mph for maximum noise reduction.
Endurance: Approx. 5 hours.

Link to: www.yo-3a.com



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