During August 1968, a team led by Lockheed, as well as a rival team comprising Convair and Grumman, were requested to further develop their proposals to meet this requirement. At this stage, Lockheed recognised that it had little experience in designing carrier based aircraft, thus the company reached out to the industrial conglomerate Ling-Temco-Vought (LTV), which joined the team. LTV assumed responsibility for the design of various elements of the airframe, such as the folding wings and tail, the engine nacelles, and the landing gear, some of which had been derived from the earlier LTV A-7 Corsair II and Vought F-8 Crusader. Sperry Univac Federal Systems was assigned the task of developing the aircraft's onboard computers which integrated input from sensors and sonobuoys. On 4 August 1969, Lockheed's design was selected as the winner of the VSX contest; an order for eight prototypes, designated YS-3A, was promptly received by the company. On 21 January 1972, the first prototype performed its maiden flight in the hands of military test pilot John Christiansen. Flight testing proceeded quickly with no major issues; two years later, the S-3 entered operational service with the U.S. Navy. During the type's production run, which ran from 1974 to 1978, a total of 186 S-3As were constructed. The majority of the surviving S-3As were later upgraded to the improved S-3B variant, while 16 aircraft were also converted into ES-3A Shadow electronic intelligence (ELINT) collection aircraft. Design The Lockheed S-3 Viking is a conventional monoplane with a cantilever shoulder wing, very slightly swept with a leading edge angle of 15° and an almost straight trailing edge. Its twin GE TF-34 high-bypass turbofan engines mounted in nacelles under the wings provide excellent fuel efficiency, providing the Viking with the required long range and endurance, while also maintaining relatively docile engine-out characteristics. The aircraft can seat four crew members (three officers and one enlisted) with pilot and copilot/tactical coordinator (COTAC) in the front of the cockpit and the tactical coordinator (TACCO) and sensor operator (SENSO) in the back. Entry is via a hatch/ladder folding down out of the lower starboard side of the fuselage behind the cockpit, in between the rear and front seats on the starboard side. When the aircraft's anti-submarine warfare (ASW) role ended in the late 1990s, the enlisted SENSOs were removed from the crew. In tanker crew configuration, the S-3B typically flew with a pilot and co-pilot/COTAC.