HMS K13 was a steam-propelled First World War K class submarine of the Royal Navy. She sank in a fatal accident during sea trials in early 1917 and was salvaged and recommissioned as HMS K22. Design and construction In early 1915, a requirement arose for a new type of fast submarines capable of operating with the Grand Fleet, which would operate ahead of the fleet in conjunction with the fleet's cruisers and attack an enemy force before the battleships would engage. The submarines would need a speed of at least 21 knots on the surface in the rough waters of the North Sea, with this being beyond the capability of conventional diesel-powered submarines. To meet this requirement, a 1913 design for a steam-powered submarine by the Admiralty's Director of Naval Construction was passed to Vickers for detailed design. The submarines were long overall and between perpendiculars, with a beam of and a surfaced draught of . Displacement was on the surface and submerged. Two Yarrow water-tube boilers fed steam at to two sets of Brown-Curtis impulse steam turbines rated at which drove two propeller shafts. This gave a design speed on the surface of . Submerged, the submarine was propelled by four electric motors rated at which gave a design speed of which corresponded to a sea speed of about . An auxiliary diesel engine was fitted to power the submarine on the surface when the steam plant was unavailable (for example when the submarine had just surfaced and steam was being raised). This engine drove a dynamo which powered the electric motors or charged the batteries. The steam engines required large openings in the pressure hull, with two funnels and four air intakes, which had to be closed off and made watertight before the submarine submerged. The funnels hinged into the submarine's superstructure and the openings by the funnels and air intakes sealed by electrically operated valves. The submarine had a range on the surface of at (powered by the diesel engine) or at full power. The submerged endurance was much less than expected, at and at . Ten 18 inch (450 mm) torpedo tubes were fitted, with four bow tubes, four beam tubes and two on a revolving mount on the superstructure, A total of 18 torpedoes were carried. Gun armament consisted of two 4 inch (102 mm) guns and one 3-inch (76 mm) anti-aircraft gun. Once in