The, also called were a trio of aircraft-carrying cruiser submarines built for the Imperial Japanese Navy (IJN) during the 1930s. All three participated in the Pacific War and were lost.
The submarines of the A1 type were versions of the preceding J3 class with superior range, improved aircraft installation. Unlike the earlier boats, they were equipped with extensive communication facilities to allow them to serve as squadron flagships. They displaced 2919LT surfaced and submerged. The submarines were 113.70NaN0 long, had a beam of 9.5m (31.2feet) and a draft of 5.3m (17.4feet). They had a diving depth of 100m (300feet).[1]
For surface running, the boats were powered by two 62000NaN0 diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a 1200hp electric motor. They could reach 19kn on the surface[2] and underwater. On the surface, the A1s had a range of 16000nmi at ; submerged, they had a range of 90nmi at .
The boats were armed with six internal bow 53.3cm (21inches) torpedo tubes and carried a total of 18 torpedoes. They were also armed with a single 40-caliber 140mm deck gun and two twin 250NaN0 Type 96 anti-aircraft guns.[3]
Unlike the J3 class, the aircraft hangar was integrated into the conning tower and faces forward; the positions of the deck gun and the catapult were exchanged so the aircraft could use the forward motion of the ship to supplement the speed imparted by the catapult. The hangar could be accessed from inside the pressure hull and the floatplane was stowed with its wings folded.[3]
Two more boats were ordered under the 1942 Naval Program, but were later cancelled.[1]