PROPULSION: 2 x SEMT-Pielstick diesel engines developing 3,600 horsepower with 1 x Electric motor generating 2,950 horsepower to 1 x Shaft.
The Agosta-class diesel-electric attack submarines were adopted by the French Navy specifically for patrol work along the crucial waterways of the Mediterranean Theater. The series was also adopted by the navies of Spain and Pakistan and continue in service with those two countries today (2016). The French Navy operated the class for about two decades before the line was retired in the early 2000s. A total of four Agosta-class boats were on hand with the French Navy - lead boat Agosta (S620) and her sisters Beveziers (S621), La Praya (S622) and Ouessant (S623).These marked the final diesel-electric driven boats servicing the French Navy prior to the move to an all-nuclear undersea force.
The series succeeded the outgoing Daphne-class boats and was itself succeeded by the newer, more modern and powerful Scorpene-class family.
The Agosta-class was born from the 1970-1975 French naval rearmament and modernization program and served collectively from the latter part of the decade until the new millennium. They showcased conventional profiles with their rounded bow sections, tapered sterns, and forward-set conning towers. Dimensions included a length of 219.9 feet, a beam of 19.7 feet and a draught of 17.8 feet. The vessels displaced 1,500 tons surfaced and 1,760 tons submerged. The crew numbered 54 men.
Power was from 2 x SEMT-Pielstick diesel engines developing 3,600 horsepower paired with 1 x Electric motor generating 2,950 horsepower. The diesel units propelled the boat during surfaced travel and the electric fit was used for underwater work. Either propulsion scheme drove a single shaft. Maximum speed while surfaced reached 12 knots and speeds in excess of 20 knots were reached when submerged. The boats could manage operations down to 980 feet. The boats were engineered for low-noise operation but able to perform at high-speed in deep waters. Sensors and processing systems included the Thomson CSF DRUA-33 series radar and several onboard sonar systems including the DSUV 62A series towed array.
Armament centered on 4 x 533mm (21") torpedo tubes (all fitted to the bow) and these featured pneumatic-rammed reloading for rapid response. The boats were also capable of engaging with torpedoes at any depth reachable and at any speed, offering considerable tactical flexibility. In the 1980s, the French boats were given capabilities to launch the SM-39 "Exocet" anti-ship missile from underwater.
Agosta, the lead ship of the French group, was completed in 1977 and saw service until decommissioned in 1997.