The Lockheed S-3 Viking is a four-crew, twin-engine turbofan-powered subsonic anti-submarine jet aircraft designed and produced by the American aerospace manufacturer Lockheed Corporation. Because of its characteristic sound, it was nicknamed the "War Hoover" after the vacuum cleaner brand.
The S-3 was developed in response to the VSX program conducted by the U.S. Navy (USN) to procure a successor anti-submarine warfare (ASW) aircraft to the Grumman S-2 Tracker. It was designed, with assistance from Ling-Temco-Vought (LTV), to be a carrier-based, subsonic, all-weather, long-range, multi-mission aircraft.
On 21 January 1972, the prototype YS-3A performed the type's maiden flight. Upon entering regular service during February 1974, it proved to be a reliable workhorse. In the ASW role, the S-3 carried automated weapons and in-flight refueling gear. Further variants, such as the ES-3A Shadow carrier-based electronic intelligence (ELINT) platform, and the US-3A carrier-based utility and cargo transport, arrived during the 1980s and 1990s. In the late 1990s, the S-3B's mission focus shifted to surface warfare and aerial refueling a carrier battle group. It saw combat during the Gulf War of the early 1990s, the Yugoslav Wars of the mid-to-late 1990s, and the War in Afghanistan during the 2000s.
The S-3 was removed from front-line fleet service aboard aircraft carriers in January 2009, its missions having been taken over by the P-3C Orion, P-8 Poseidon, SH-60 Seahawk, and F/A-18E/F Super Hornet. For more than a decade after that, some S-3s were flown by Air Test and Evaluation Squadron Thirty (VX-30) at Naval Base Ventura County / NAS Point Mugu, California, for range clearance and surveillance operations at the NAVAIR Point Mugu Range. These final examples in U.S. Navy service were retired in early 2016. The last operational S-3 was used by the National Aeronautics and Space Administration (NASA) at its Glenn Research Center until NASA retired it in mid-2021. Most retired S-3s were placed into storage while options for their future were investigated. During the 2010s, Lockheed Martin proposed to refurbish them for carrier onboard delivery. The Republic of Korea Navy also had plans to operate revived S-3s for ASW; these plans were cancelled in 2017.
Development
In the mid-1960s, the United States Navy (USN) formulated the VSX (Heavier-than-air, Anti-submarine, Experimental) requirement, which sought a dedicated anti-submarine aircraft capable of flying off of its aircraft carriers as a replacement for its existing inventory of piston-engined Grumman S-2 Trackers. The service issued a request for proposals to industry. 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.Francillon 1982, pp. 455–456.
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.Godfrey 1974, p. 6.Goebel, Greg. Air Vectors, 1 May 2005. Retrieved: 21 April 2010.
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.Francillon 1982, p. 457. On 21 January 1972, the first prototype performed its maiden flight in the hands of military test pilot John Christiansen.Francillon 1987, p. 467. 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,Taylor, John W. R.: Jane's All The World's Aircraft, 1977–78. Jane's Yearbooks, London 1977, p. 329. 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,Elward 1998, pp. 54–55. while also maintaining relatively docile engine-out characteristics.Elward 1998, p. 69.
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. 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.Taylor 1976, pp. 315–316.
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 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 of the front seats ejects the entire crew in sequence, with the back seats ejecting 0.5 seconds before the front in order to provide safe separation (this was to prevent the pilots, who were more aware of what was happening outside the aircraft from ejecting without the rest of the crew, or being forced to delay ejection to order the crew to eject in an emergency; ejection from either rear seat would not eject the pilots, who had to initiate their own ejections, to prevent loss of the aircraft if a rear crewmember ejected prematurely. If a pilot ejected prematurely, the plane was lost anyway, and automatic ejection prevented the crew from crashing with a pilot-less aircraft before they were aware of what had happened). 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.
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, the co-pilot/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. As a consequence of this integration, the four-crew S-3 was considered roughly equivalent in terms of capability to the much larger P-3, operated by 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 sonobuoys are carried, 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). As a consequence of this role change, the MAD Boom was removed, along with several hundred pounds of submarine detection electronics. As there was no remaining sonobuoy processing capability, most of the sonobuoy chutes were faired over with a blanking plate.
Operational history
On 20 February 1974, the S-3A officially became operational with the Air Antisubmarine Squadron FORTY-ONE (VS-41), the "Shamrocks," at NAS North Island, California, which served as the initial S-3 Fleet Replacement Squadron (FRS) for both the Atlantic and Pacific Fleets until a separate Atlantic Fleet FRS, VS-27, was established in the 1980s. The first operational cruise of the S-3A took place in 1975 with the VS-21 "Fighting Redtails" aboard .
Initial operations of the Viking were somewhat troubled in the carrier environment, its sophisticated mission systems were largely dependent on the mission computer, which would often "dump" during the stress of a catapult-assisted take-off, requiring the crew to restart it and reload the software. The U.S. Navy had also purchased an insufficient number of spare parts, which negatively impacted the aircraft's mission readiness. Performance improved considerably once an ample supply of spares was provisioned, allowing the S-3 to become a valuable ASW asset as well as a good surface-surveillance platform.
Starting in 1987, the majority of S-3As were progressively upgraded to the improved S-3B standard; this involved the addition of several new sensors, avionics, and weapons systems, which included the capability to launch the AGM-84 Harpoon anti-ship missile. The S-3B could also be fitted with "buddy stores", external fuel tanks that allowed the Viking to refuel other aircraft. During July 1988, VS-30 became the first fleet squadron to receive the enhanced capability Harpoon/ISAR equipped S-3B, based at NAS Cecil Field in Jacksonville, Florida.