The Type A Kai 2 (A Modified 2) submarine (巡潜甲型改二潜水艦), also called I-13-class submarine (伊一三型潜水艦) was a pair of large, aircraft-carrying cruiser submarines built for the Imperial Japanese Navy (IJN) during World War II.

Design and description

The Type A Mod.2 submarines were versions of the preceding A2 class with the command facilities replaced by an enlarged aircraft hangar, which was fitted for a pair of Aichi M6A1 floatplane bombers. They displaced 3603 LT surfaced and 4762 LT submerged. The submarines were 113.7 m long, had a beam of 11.7 m and a draft of 5.9 m. They had a diving depth of 100 m. The machinery was reduced in power from the A2-class boats. For surface running, the boats were powered by two 2200 bhp diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a 300 hp electric motor. They could reach 16.75 kn on the surface and 5.5 kn underwater. On the surface, the AMs had a range of 21000 nmi at 16 kn; submerged, they had a range of 60 nmi at 3 kn. The boats were armed with six internal bow 53.3 cm torpedo tubes and carried a total of a dozen torpedoes. They were also armed with a single 140 mm/40 deck gun and two triple and one single mount for 25 mm Type 96 anti-aircraft guns. In comparison to the A2 class, the aircraft hangar was enlarged to accommodate two aircraft. It was offset to the right of, and was faired into the base of, the conning tower which protruded over the left side of the hull. A single catapult was positioned on the forward deck. Two folding cranes on the forward deck were used to recover the floatplanes.

Name Translation

Sources also refer to this class of ships as the "Type AM" (standing for the "Type A Modified"), or "Type AM2" (for "Type A Modified 2"), contrasting with two other sub-classes of the type, the I-9-class (Type A/A1) and I-12-class (Type AM1/A2). As the I-12 submarine was only a minor evolution of the I-9-class as well as being the sole ship of its class, it may also be considered as part of the I-9-class, making the I-13-class the only sub-class of the type, hence the I-9-class "Type A" and the I-13-class of the "Type AM". "Type AM" might also be a miss-translation of Kai Ni (改二) (equivalent to 2nd remodel/modification) being interpreted as "Mark 2" in the sense of the 1st remodel/modification. As the original Japanese name (Junsen kō-gata kai-ni sensuikan (巡潜甲型改二潜水艦)) is better translated as either "Type A Mod.2 Submarine Cruiser" or "Junsen Type A Kai 2 Submarine ", the "Type A Mod.2" designation is used here.

Boats

Seven units were ordered, but only two were completed, while construction of two more was abandoned in March 1945. Construction of the remaining three submarines never started.