03/31/2010. The Lockheed Missiles & Space Company (LMSC) of Lockheed ventured but once into the aeronautical field. It did so as the result of a unique requirement created by the Southeast Asia War, and the outgrowth of this venture was as far removed from its usual line of business as it could possibly be. Guerrilla operations by Viet Cong units, which quickly faded back into the jungle after striking, brought the need to devise means of more reliable tracking of enemy movements.
For this purpose a variety of sensors already existed, or were quickly developed, but their short detection range inhibited their effective use from conventional platforms. Accordingly, in its search for solutions, the Department of Defense (DoD) turned to industry. Various approaches were used and among those known to have seen actual use in Southeast Asia were the Pave Eagle (combining sensor-equipped Beech QU-22B drones and Lockheed EC-121R relay aircraft) and Prize Crew programs, the latter based on the LMSC-developed aircraft.
To bring sensors within effective range without the vehicle being detected by the enemy, engineers in the Advanced Programs Directorate of LMSC conceived in early 1966 the idea of mounting sensors on an aerodynamically-efficient aircraft powered by a muffler-equipped engine driving a slow-turning propeller. To demonstrate the feasibility of this concept, LMSC proposed to the DoD Advanced Research Projects Agency that a Schweizer SGS 2-32 two/three-seat glider be modified as the QT-1 (Quiet Thruster, single-seat) prototype powered by a 57 hp engine mounted in the fuselage aft of the pilot and driving a tractor propeller by means of a pylon-mounted extension shaft.
The Army was interested, but wanted the aircraft to be QT-2 two-seaters, and arranged for the transfer to Lockheed of two Schweizer X-26A sailplanes
(SGS 2-32s ordered by the Navy for use in the training program at the Naval Test Pilot School (NTPS), NAS Patuxent River, Maryland).
To produce the QT-2 demonstrators, modifications of the Schweizer sailplane were kept to a minimum and essentially centered on the powerplant installation. It consisted of placing aft of the cockpit a 100 hp Continental O-200-A four-cylinder air-cooled engine which was fitted with outsize mufflers and drove a four-blade wooden propeller by means of a long extension shaft running over the two-seat cockpit.
Built by personnel of Lockheed Aircraft Service Company under the direction of Stanley Hall and his LMSC project team, and bearing the civil registration N2471W, the first QT-2 was tested in great secrecy from the small agricultural airfield at Tracy, beginning in July 1967. Results were excellent, as the QT-2 proved outstandingly quiet, and the two aircraft were hurriedly fitted with their sensor packages to be airlifted to Vietnam for operational evaluation by the US Army.
Arriving in the war theatre in December 1967, the two QT-2PCs (the initials PC, Prize Crew, referring to the code name of the project) demonstrated their effectiveness during the January 1968 Tet offensive. After a few months they were brought back to the USA, where one of them was cannibalized to provide spares for the other which was used at the NTPS as the X-26B, in Navy markings. Later this aircraft returned to the Army and was further evaluated before being placed on display at the US Army Aviation Museum at Fort Rucker.
While the QT-2PCs were tested in Vietnam, Lockheed modified more extensively a third SGS 2-32 which was fitted with a conventional fixed undercarriage instead of the bicycle type used on the previously modified sailplanes. Designated Q-Star and registered N5713S, this demonstrator initially retained the Continental O-200-A engine installation of the QT-2s but was used to test at least nine different types of propellers, including three-blade constant-speed and four- and six-blade fixed-pitch units.
Later, in a program funded by Lockheed, the Curtiss-Wright Corporation, and the Navy, it was re-engined with a Wright RC2-60 liquid-cooled Wankel-type rotary combustion engine. The use of this powerplant, which was derated from 200 to 185 hp and cooled by an automobile radiator mounted in the nose, was the first aeronautical application of a Wankel-type engine and was first flown with its novel engine in September 1969. The Q-Star was put in store within less than two years and eventually donated to a private museum.
The successful operational evaluation of the QT-2PCs in Vietnam prompted the US Army Aviation Systems Command to award a contract to Lockheed in July 1968 for fourteen YO-3A production aircraft (s/n 69-18000 to 69-18013). Still retaining the basic Schweizer sailplane all-metal structure, the YO-3A had a conventional undercarriage-with its main legs retracting inwardly into the wing-and a single-piece, upward-hinged canopy and windshield.
The main difference between the production aircraft and the earlier demonstrators was in the powerplant, with the YO-3As being powered by a nose-mounted 210 hp Continental IO-360D six-cylinder air-cooled engine. Initially this engine drove a six-blade fixed-pitch propeller but this was later replaced by a three-blade variable-pitch unit. Wing area was also later increased by the addition of a trailing-edge extension over the inner half of the span.
After completing its manufacturer's trials, the first YO-3A was retained for further testing by the Army while the other thirteen aircraft were shipped to Vietnam in early 1970 and assigned to the 73rd Surveillance Aircraft Company, 1st Aviation Brigade at Long Binh. On 30 April, 1972, the operations were terminated and the YO-3As were returned to the USA. Subsequently two of these aircraft were acquired by the State of Louisiana Department of Wildlife and Fisheries and, registered N14425 to N14426, used to track down poachers.
In 1980 four other YO-3As were on the US civil register: one was privately-owned in Connecticut, two were operated by the Federal Bureau of Investigation from Oxnard, California, and one, registered N718NA, was used by NASA as a microphone-carrying vehicle to measure rotor-blade noise as part of the helicopter research program under-taken by the Ames Research Center.
The pictured aircraft was produced under the s/n 69-18005 (c/n 006) and served in Vietnam from 1970 to 1972. Struck off charge the aircraft was registered as N64495 to the Special School District of St. Louis County at Rock Hill, Missouri, on February 15, 1973. Subsequently the incomplete airframe was acquired by Harold and Vic Hansen of Seattle, Washington, rebuilt using spare parts, and was reregistered N33YQ (with the incorrect c/n 5, which was derived from the military serial no 69-18005). The aircraft was acquired by its present owner, Bruce Elliot of Skagit, on December 10, 1987.
For more information of the YO-3A Quiet Star see Kurt Olney's web site.