page_title: French submarine Prométhée (1930)
section_title: Causes of the sinking
hierarchical_section_title: French submarine Prométhée (1930) / Causes of the sinking
caption_attribution_description: Français&#160;: Le ministre de la marine Georges Leygues avec les rescapés du sous-marin Prométhée en juillet 1932
context_page_description: Prométhée was a Redoutable-class submarine of the French Navy, launched in 1930 at Cherbourg. On 7 July 1932, while sailing on the surface during sea trials, she suddenly sank off Cape Lévi, Manche.
  62 of her 69 crew were lost with her, causing an outpouring of grief in France. The wreck was located the following day, but attempts to rescue any survivors and refloat the vessel were in vain. Survivors' statements indicated that the sinking was likely due to a sudden opening of the diving purges.
context_section_description: In the evening of 8 July Vice-admiral Le Dô, maritime prefect of Cherbourg, established an investigative commission to discover the causes of the sudden sinking. Unable to examine the wreck, the commission was unable to use physical evidence, and had to rely on interviews with the survivors, including the commander of Prométhée, Lieutenant de vaisseau Couespel du Mesnil, and conducting similar trial simulations on Prométhée's sister ship Archimède.
  Engineers studied how the Archimède submerged in as orderly and quick a manner as possible, to compare with what had happened to Prométhée. The Redoutable-class submarines were able to fully submerge in thirty seconds. Prométhée was still undergoing trials, and it was one of the boat's first voyages at sea. As the commander had not seen anyone at the command post, and the accident occurred when the order was given to start the diesel motors, the commission concluded on 13 July that an "unexpected, rapid and general opening of the purges" had flooded the ballast tanks with water, which rendered the submarine heavy and sank her. This unexpected opening could have been due to an error, or connectivity in the oleo-pneumatic section valve systems. This design flaw was well known prior to the loss of Prométhée: a similar incident had occurred within gravity on Redoutable and Vengeur. The incident aboard the Vengeur had been reported by her commander in a verbal-process hearing on November 1929, and had been confirmed by the testimony of the commander of the Surcouf in 1930. However no official instructions had been issued to commanders of French submarines. Following the loss of Prométhée, all related section valves were modified on French submarines.
  Deep sea navy divers examined the hatches around the bridge and observed that all of those they could see were closed. It was not possible to inspect all the hatches, as the steep angle at which the Prométhée had sunk at suggested that one hatch could have been left open, allowing water to enter the submarine, and sink her.
  Lieutenant de vaisseau Amaury Couespel du Mesnil was summoned before the war council on 3 November 1932, in order to answer for the loss of his boat. He was unanimously acquitted the following day. His career stalled however, and he ended up leaving the naval service a couple of years after the wreck. Enseigne Bienvenue was killed on 23 September 1940, during the Battle of Dakar.
caption: The survivors of the wreck with naval minister Georges Leygues.
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