Lockheed S-3 Viking

Variants

S-3A: First production version, 187 built.
S-3B: Upgraded avionics, AN/APS-137 inverse synthetic aperture radar, Joint Tactical Information Distribution System, AGM-84 Harpoon launch capability, first flight 13 September 1984, 119 converted from S-3As.
ES-3A Shadow: ELINT aircraft, AN/APS-137 inverse synthetic aperture radar, first flight 15 May 1991, 16 converted from S-3A.
KS-3A: Proposed dedicated air tanker with fuel capacity of 4,382 US gal (16,600 l), one converted from YS-3A, later converted to US-3A.
KS-3B: Proposed air tanker based on S-3B and utilizing the buddy refueling system, not built.
US-3A: S-3A modified for carrier onboard delivery, capacity for six passengers or 4,680 lb (2,120 kg) of cargo, retired in 1998.
Aladdin Viking: Conversion of six aircraft for overland surveillance and Elint missions. May have dropped ground sensors in the Bosnian War.
Beartrap Viking: S-3Bs fitted with still-classified modifications.
Calypso Viking: Proposed anti-smuggling variant, not built.
Gray Wolf Viking: One aircraft fitted with AN/APG-76 radar in a modified cargo pod under the wing. Also dubbed SeaSTARS in reference to E-8 Joint STARS.
Orca Viking: Avionics testbed.
Outlaw Viking: One S-3B fitted with Over-the-horizon Airborne Sensor Information System (OASIS III), returned to regular S-3B in 1998. This particular Viking is now on display at the USS Midway Museum, located on the decommissioned USS Midway (CV-41).
NASA Viking: One aircraft was transformed into a state-of-the-art NASA research aircraft. The Navy's Fleet Readiness Center - Southeast and a Boeing facility in Fla. enhanced the plane by adding commercial satellite communications, global positioning navigation and weather radar systems. They installed research equipment racks in what was once the plane's bomb bay. NASA's S-3B Viking is equipped to conduct science and aeronautics missions, such as environmental monitoring, satellite communications testing and aviation safety research.