Japanese submarine I-31
The Japanese submarine "I-31" was one of 20 Type B cruiser submarines of the B1 sub-class built for the Imperial Japanese Navy (IJN) during the 1940s. Design and description. The Type B submarines were derived from the earlier KD6 sub-class of the and were equipped with an aircraft to enhance their scouting ability. They displaced surfaced and submerged. The submarines were long, had a beam of and a draft of . They had a diving depth of . For surface running, the boats were powered by two diesel engines, 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 "B1"s had a range of at ; submerged, they had a range of at . The boats were armed with six internal bow torpedo tubes and carried a total of 17 torpedoes. They were also armed with a single /40 deck gun and two single mounts for Type 96 anti-aircraft guns. In the Type Bs, the aircraft hangar was faired into the base of the conning tower. A single catapult was positioned on the forward deck. Construction and career. On 12 May  1943, near Holtz Bay, Attu, her periscope was sighted by American destroyers, and , who immediately opened fire. "I-31" dove quickly but not before "Edwards" scored hits. The destroyers quickly made sonar contact and began a series of depth charge attacks until, after surviving for 10 hours, she was sunk by "Frazier" on 13 May.