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-boats of the Second World War, particularly FRENCH SUBMARINE Roland Morillot which were brought into French service.

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

The hulls of the Narvals were assembled from seven 10 m sections welded together.

The engine were two-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 Narvals underwent extensive modernisation, where their engines were replaced by a diesel-electrical design based on the SEMT-Pielstick 12PA4-185. The two stern torpedo tubes were deleted, electronics were replaced, and the conning tower was replaced by a more modern sail plan from the Daphné-class submarine.

Service history
The Narvals were used to explore limits of submarines performances in several ways.

In 1958, FRENCH SUBMARINE Dauphin and FRENCH SUBMARINE Requin broke the 30-day world record of the longest underwater cruise held jointly by the nuclear-powered USS Skate (SSN-578) and USS Seawolf (SSN-575), with 32 and 42 days submerged respectively.

In 1964, FRENCH SUBMARINE Espadon and FRENCH SUBMARINE 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 FRENCH SUBMARINE 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 decommissioned 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.