Unryū-class aircraft carrier

The Unryū class aircraft carriers (雲龍型航空母艦) were World War II Japanese aircraft carriers. 16 carriers were planned under the Maru Kyū Programme (Ship #302 in 1941) and the Kai-Maru 5 Programme (#5001–5015 in 1942). However, only 3 carriers were completed.

Design
In the lead-up to the Pacific War the Imperial Japanese Navy (IJN) attempted to build a large number of fleet carriers. So that they could be built quickly, the design for these ships was based on that of the aircraft carrier Hiryū rather than the newer and more sophisticated Taihō or the Shōkaku class.

The Unryū class aircraft carrier design was very similar to that of Hiryū. The ships were lightly built, and the main difference from Hiryū was that the carriers' island was placed on the starboard side of the ships. The carriers were capable of carrying 63 aircraft in two hangars, and were fitted with two elevators. The Unryū class carried a smaller quantity of aviation fuel than Hiryū and the fuel tanks were protected by concrete. The ships were to be fitted with the same propulsion system as had been used in the aircraft carrier Sōryū and were capable of reaching 34 kn, though Katsuragi was instead fitted with two turbines of the same type as were used in destroyers and had a maximum speed of 33 kn. The carriers also had a similar armament to that fitted on Hiryū and were equipped with two Type 21 radars and two Type 13 radars.

Construction
The first three Unryū class aircraft carriers were laid down in 1942 and construction of a further three began the next year. In the event, only three (Unryū, Amagi, and Katsuragi) were completed and construction of the other three carriers (Kasagi, Aso and Ikoma) was abandoned in 1945.

Unryū class
Project number was G16. General production model of the Unryū-class. 3 carriers were completed. The IJN unofficial designation for Unryū and Amagi were Modified Hiryū-class (改飛龍型), Ship Number 5002–5006 were Modified Unryū-class (改雲龍型) also.
 * Amagi and Kasagi (built by Mitsubishi, Nagasaki Shipyard) were equipped with surplus stock of the Ibuki-class cruiser machinery.
 * Katsuragi and Aso (built by Kure Naval Arsenal) were equipped with two sets of the Kagerō-class destroyer machinery, because Japanese industry power became scarce. Dead space was replaced by fuel tanks.
 * Ship Number 5002 and 5005 (built by Yokosuka Naval Arsenal) were used Shinano's dock and was going to build 2 carriers at the same time, however, they were cancelled because Shinano was continued.

Ikoma class
Simplified and sped-up construction model of the Unryū-class. They fitted shift-arrangement machinery (four sets of parallel two boilers and one turbine). Therefore, as for their chimneys, those space intended to spread out. The IJN unofficial designation for this class was Modified Ship Number 302-class (改第302号艦型).