Japanese Type L submarine

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Class overview
Name	Type L submarines
Builders	Mitsubishi Heavy Industries-Kōbe Shipyard
Operators	Imperial Japanese Navy
Subclasses	Type L1 (Ro-51-class) Type L2 (Ro-53-class) Type L3 (Ro-57-class) Type L4 (Ro-60 -class)
Built	1918-1927
In commission	1920-1945

The Type L submarine (L型潜水艦, L-gata Sensuikan) submarines were medium-sized submarines of the Imperial Japanese Navy (IJN), serving during the 1920s and World War II. The Type L submarines were built with Vickers naval technical guidance. All boats were built in the Mitsubishi Heavy Industries-Kobe Shipyard by the contract with Vickers.

The Type L submarines were divided into four classes:

• Type L1 (L1型（呂五十一型）, Ro-go-jū-ichi-gata, Ro-51-class)
• Type L2 (L2型（呂五十三型）, Ro-go-jū-san-gata, Ro-53-class)
• Type L3 (L3型（呂五十七型）, Ro-go-jū-shichi-gata, Ro-57-class)
• Type L4 (L4型（呂六十型）, Ro-roku-jū-gata, Ro-60-class)

In 1916, the Mitsubishi Shipbuilding Corporation got the Vickers L class submarine informations. Mitsubishi which lost competition to the Kawasaki's Type F submarines (Fiat-Laurenti design, Ro-1 class and Ro-3 class), bought the license for the L class submarine from Vickers. The IJN hoped an improvement of submarine technologies will be achieved and ordered this submarine from Mitsubishi. Mitsubishi bought six submarine kits, and built two boats by semi-knock down. The submarine crews were satisfied with the Vickers diesels because they proved to be reliable. The IJN studied the diesel engines and made many variants of similar design, for example: Kampon Mk.24 diesel for the Ro-100 class.

• Boats in class

The Type L2 had minor changes from the Type L1. The changes were:

• The ship's side torpedo tubes were removed.
• Changed the batteries. (The L1 was equipped 3 groups, 336 small-sized batteries. The L2 was equipped 2 groups, 224 medium-sized batteries.)
• Boats in class

The Type L3 is a license production model of the British L class submarine Group 2.

• Boats in class

The Type L4 is a license production model of the British L class submarine Group 3. Their performance was good. The IJN was satisfied with them and stopped the development of Kaichū type submarines for a long time. Later the IJN was not able to regain the technical delay in development of the medium-sized submarines until the end of the Pacific War.

• Boats in class

• "Rekishi Gunzō"., History of Pacific War Extra, "Perfect guide, The submarines of the Imperial Japanese Forces", Gakken (Japan), March 2005, ISBN 4-05-603890-2
• The Maru Special, Japanese Naval Vessels No.43 Japanese Submarines III, Ushio Shobō (Japan), September 1980, Book code 68343-44
• The Maru Special, Japanese Naval Vessels No.132 Japanese Submarines I "Revised edition", Ushio Shobō (Japan), February 1988, Book code 68344-36
• The Maru Special, Japanese Naval Vessels No.133 Japanese Submarines II "Revised edition", Ushio Shobō (Japan), March 1988, Book code 68344-37