Lockheed S-3 Viking

The Lockheed S-3 Viking is a four-seat twin-engine jet aircraft that was used by the U.S. Navy to identify and track enemy submarines. In the late 1990s, the S-3B's mission focus shifted to surface warfare and aerial refueling. The Viking also provided electronic warfare and surface surveillance capabilities to the carrier battle group. A carrier-based, subsonic, all-weather, multi-mission aircraft with long range, it carried automated weapon systems, and was capable of extended missions with in-flight refueling. Because of the engines’ low-pitched sound, it was nicknamed the "Hoover" after the vacuum cleaner brand. The aircraft would also see service in the Republic of Korea Navy, Royal Australian Navy, and Royal Navy.

Development
In the mid-1960s, the U.S. Navy developed the VSX (Heavier-than-air, Anti-submarine, Experimental) requirement for a replacement for the piston-engined Grumman S-2 Tracker as an anti-submarine aircraft to fly off the Navy's aircraft carriers. In August 1968, a team led by Lockheed and a Convair/Grumman team were asked to further develop their proposals to meet this requirement. Lockheed recognised that it had little recent experience in designing carrier based aircraft, so Ling-Temco-Vought (LTV) was brought into the team, being responsible for the folding wings and tail, the engine nacelles, and the landing gear, which was derived from A-7 Corsair II (nose) and F-8 Crusader (main). Sperry Univac Federal Systems was assigned the task of developing the aircraft's onboard computers which integrated input from sensors and sonobuoys. On August 4th 1969, Lockheed's design was selected as the winner of the contest, and eight prototypes, designated YS-3A were ordered. The first prototype flew on 21 January 1972 and the S-3 entered service in 1974. During the production run from 1974 to 1978, a total of 186 S-3As were built. The majority of the surviving S-3As were later upgraded to the S-3B variant, with sixteen aircraft converted into ES-3A Shadow electronic intelligence (ELINT) collection aircraft.

ES-3A Shadow
The ES-3A Shadow was designed as a carrier-based, subsonic, all-weather, long-range, electronic reconnaissance (ELINT) aircraft. All 16 aircraft were modified S-3 Viking airframes, which were modified with numerous additional antennas and antenna housings. The Shadow replaced the EA-3B Skywarrior, and entered fleet service in 1993. The ES-3A carried an extensive suite of electronic sensors and communications gear, replacing the S-3’s submarine detection, armament, and maritime surveillance equipment with avionics racks accommodating the ES-3A’s sensors. These modifications had minor impact on airspeed, reducing its top rated speed from 450 KTAS to 405 KTAS but had no noticeable impact on the aircraft's range and actually increased its rated loiter time. Because these aircraft were standoff indications and warnings platforms and were never intended to be part of an ingress strike package, this new speed limitation was considered insignificant.

Design
The S-3 is a conventional monoplane with a high-mounted cantilever wing, swept at an angle of 15°. The two GE TF-34 high-bypass turbofan engines mounted in nacelles under the wings provide excellent fuel efficiency, giving the Viking the required long range and endurance, while maintaining docile engine-out characteristics.

The aircraft can seat four crew members, three officers and one enlisted aircrewman, with the pilot and the copilot/tactical coordinator (COTAC) in the front of the cockpit and the tactical coordinator (TACCO) and sensor operator (SENSO) in the back. Entry is by an entry door / ladder which folds out of the side of the fuselage.[8] When the aircraft's anti-submarine warfare (ASW) role ended in the late 1990s, the enlisted SENSOs were removed from the crew. In the tanking crew configuration, the S-3B typically flew with only a crew of two (pilot and COTAC).[citation needed] The wing is fitted with leading edge and Fowler flaps. Spoilers are fitted to both the upper and the lower surfaces of the wings. All control surfaces are actuated by dual hydraulically boosted irreversible systems. In the event of dual hydraulic failures, an Emergency Flight Control System (EFCS) permits manual control with greatly increased stick forces and reduced control authority.

Unlike many tactical jets which required ground service equipment, the S-3 was equipped with an auxiliary power unit (APU) and capable of unassisted starts. The aircraft's original APU could provide only minimal electric power and pressurized air for both aircraft cooling and for the engines' pneumatic starters. A newer, more powerful APU could provide full electrical service to the aircraft. The APU itself was started from a hydraulic accumulator by pulling a mechanical handle in the cockpit. The APU accumulator was fed from the primary hydraulic system, but could also be pumped up manually (with much effort) from the cockpit.

All crew members sit on forward-facing, upward-firing Douglas Escapac zero-zero ejection seats. In "group eject" mode, initiating ejection from either front seat ejects the entire crew in sequence, with the back seats ejecting 0.5 seconds before the front in order to provide safe separation. The rear seats are capable of self ejection, and the ejection sequence includes a pyrotechnic charge that stows the rear keyboard trays out of the occupants' way immediately before ejection. Safe ejection requires the seats to be weighted in pairs, and when flying with a single crewman in the back the unoccupied seat is fitted with ballast blocks.

At the time it entered the fleet, the S-3 introduced an unprecedented level of systems integration. Previous ASW aircraft like the Lockheed P-3 Orion and S-3's predecessor, the Grumman S-2 Tracker, featured separate instrumentation and controls for each sensor system. Sensor operators often monitored paper traces, using mechanical calipers to make precise measurements and annotating data by writing on the scrolling paper. Beginning with the S-3, all sensor systems were integrated through a single General Purpose Digital Computer (GPDC). Each crew station had its own display, and the COTAC, TACCO and SENSO displays were Multi-Purpose Displays (MPD), capable of displaying data from any of a number of systems. This new level of integration allowed the crew to consult with each other by examining the same data at multiple stations simultaneously, to manage workload by assigning responsibility for a given sensor from one station to another, and to easily combine clues from each sensor to classify faint targets. Because of this, the four-man S-3 was considered roughly equivalent in capability to the much larger P-3 with a crew of 12. The aircraft has two underwing hardpoints that can be used to carry fuel tanks, general purpose and cluster bombs, missiles, rockets, and storage pods. It also has four internal bomb bay stations that can be used to carry general purpose bombs, aerial torpedoes, and special stores (B57 and B61 nuclear weapons). Fifty-nine sonobuoy chutes are fitted, as well as a dedicated Search and Rescue (SAR) chute. The S-3 is fitted with the ALE-39 countermeasure system and can carry up to 90 rounds of chaff, flares, and expendable jammers (or a combination of all) in three dispensers. A retractable magnetic anomaly detector (MAD) Boom is fitted in the tail. In the late 1990s, the S-3B's role was changed from anti-submarine warfare (ASW) to anti-surface warfare (ASuW). At that time, the MAD Boom was removed, along with several hundred pounds of submarine detection electronics. With no remaining sonobuoy processing capability, most of the sonobuoy chutes were faired over with a blanking plate.

Users

 * Australian Defence Force
 * Royal Australian Navy
 * 816 Squadron RAN (S-3AU)
 * 817 Squadron RAN (S-3AU)
 * 822 Squadron RAN (S-3AU)
 * 837 Squadron RAN (S-3AU)
 * 851 Squadron RAN (S-3AU)
 * British Armed Forces
 * Royal Navy
 * 700 Naval Air Squadron
 * 719 Naval Air Squadron
 * 724 Naval Air Squadron
 * 725 Naval Air Squadron
 * 737 Naval Air Squadron
 * 744 Naval Air Squadron
 * 796 Naval Air Squadron
 * United States Armed Forces
 * United States Navy
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