HMS D6
HMS "D6" was one of eight D-class submarine built for the Royal Navy during the first decade of the 20th century. Description. The D-class submarines were designed as improved and enlarged versions of the preceding C class, with diesel engines replacing the dangerous petrol engines used earlier. "D3" and subsequent boats were slightly larger than the earlier boats. They had a length of overall, a beam of and a mean draught of . They displaced on the surface and submerged. The D-class submarines had a crew of 25 officers and ratings and were the first to  adopt saddle tanks. For surface running, the boats were powered by two diesels, each driving one propeller shaft. When submerged each propeller was driven by a electric motor. They could reach on the surface and underwater. On the surface, the D class had a range of at . The boats were armed with three 18-inch (45 cm) torpedo tubes, two in the bow and one in the stern. They carried one reload for each tube, a total of six torpedoes. Construction and career. "D6" was laid down on 24 February 1910 by Vickers at their Barrow shipyard, launched 23 October  1911 and was commissioned on 19 April 1912. She was the first British submarine to be equipped with a deck gun when built, a 12-pounder (3-inch/76mm) gun. "D6" was sunk by "UB-73" 73 miles north of Inishtrahull Island off the west coast of Ireland on 24 or 28 June 1918. There were two survivors who were taken prisoner. Their post-war report apparently led the British to conclude that the torpedo that sank her had employed a magnetic pistol.