French Narval-class submarine

The Narval class (sous-marins d'escadre, "fleet submarines") were patrol submarines built for the French Navy in the 1950s.

Design
The Narval type was an offspring of the E-48 project, inspired by the German Type XXI U-boat of the Second World War, particularly the Roland Morillot brought into French service.

Compared to the Type XXI, the Narval introduced an entirely new schnorchel system and novel detection systems, gained 33% in operational range on electric power (400 nautical miles, compared to the 290 available to the type XXI), and doubled the test depth. The propellers were also particularly studied to minimise noise.

The hull of the Narvals was assembled from seven 10-metre sections wielded together.

The engine were 2-stroke diesels made by the French constructor Schneider, which proved unreliable and noisy to the point where the engine section became difficult to man at full power. From 1966 to 1970, the Narval underwent extensive modernisation, where their engines were replaced by a diesel-electrical design based on the SEMT-Pielstick 12PA4-185. The 4 stern tubes were deleted, electronics were replaced, and the conning tower was replaced by a more modern sail plan from the Daphné class.

Careers
The Narval were used to explore limits of submarines performances in several ways.

In 1958, Dauphin and Requin broke the 30-day world record of the longest underwater cruise held by the nuclear USS Skate and Seawolf, with 32 and 42 days submerged respectively.

In 1964, Espadon and Marsouin sailed up to the 70th parallel north to prepare the first French attempts at navigation under sea ice. These tests were carried out the next year by Dauphin and Narval when they spent a week and a half in the 72nd parallel north.

During her last years, from 1980, Requin was fitted with the sonar system planned for the M4 refit of the SNLE. Similarly, Dauphin was extensively modified from 1986 to be used as a test bed for equipment and sensors to be installed on the Triomphant-class submarines, then under design. When finally decommissionned in 1992, she was the oldest submarine in service. She was later expended as a target ship off Toulon.

In 1985, Espadon became the first French submarine used as a museum ship.