The submarines of the A1 type were versions of the preceding J3 class with superior range, improved aircraft installation, and were fitted as squadron flagships. 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 A1s had a range of at ; submerged, they had a range of at. The boats were armed with four internal bow torpedo tubes and carried a total of 18 torpedoes. They were also armed with a single /40deck gun and two twin Type 96anti-aircraft guns. Unlike the J3 class, the aircraft hangar is integrated into the conning tower and faces forward; the positions of the deck gun and the catapult were exchanged so the aircraft can use the forward motion of the ship to supplement the speed imparted by the catapult.
Construction and career
On 30 November 1941, I-10, patrolling in the South Sea region in advance of the attack on Pearl Harbor, launched a Yokosuka E14Y floatplane on a night air sortie of Suva Bay in the Fiji Islands. It reported sighting no enemy in the harbor but then failed to return to the sub. The I-10 searched for three days but failed to find the seaplane or its crew. During 1942, I-10 conducted long-range operations in the Indian Ocean and the Pacific, using her seaplane to carry out reconnaissance on the harbours of Durban and Port Elizabeth and other locales, including Madagascar. In late May 1942, a force comprising I-10, I-20 and I-16, carried out an attack on Allied warships at Madagascar. After the seaplane crew from I-10 spotted the battleship HMS Ramillies at anchor in Diego Suarez harbour, I-20 and I-16 both launched midget submarines; one of these managed to enter the harbour, fired two torpedoes. One torpedo seriously damaged Ramillies, while the second sank the 6,993-ton oil tankerBritish Loyalty. Ramillies required repairs in South Africa and England. The crew of one of the midget submarines, beached their craft at Nosy Antalikely and moved inland towards a pre-arranged pick-up point near Cape Amber, but were both killed in a firefight with British Marines three days later. One marine was killed in the action as well. The second midget submarine was lost at sea and the body of a crewman was found washed ashore a day later. On 12 June 1944, I-10 assembled and launched her Yokosuka E14Y to reconnoiter Majuro. "Since the Americanexpeditionary force had departed six days earlier, the aviator saw nothing important, and his plane, crashing on landing, had to be abandoned." I-10 was sunk on 4 July 1944 by US warships David W Taylor and Riddle while operating in the Pacific east of Saipan, in the Mariana Islands.
