Submarine Aircraft Carrier

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Submarine aircraft carriers are submarines equipped with fixed wing aircraft for observation or attack missions. These submarines saw their most extensive use during World War II, although their operational significance remained rather small.

The most famous of them were the Japanese I-400 class submarine and the French submarine Surcouf, although a few similar craft were built by other nations’ navies as well. Except for the I-400, submarine aircraft carriers used their aircraft in a supporting role (usually for reconnaissance), unlike the typical surface aircraft carrier, which describes a ship whose main function is serving as a base for combat aircraft.

Germany was the first nation to experiment with submarine aircraft carriers, inspired by the Imperial German Naval Air Service commander Oberleutnant zur See Lothar von Arnauld de la Perière. He commanded a unit of two reconnaissance seaplanes (Friedrichshafen FF.29s) in Zeebrugge which had been recently occupied by the Imperial German Army in the early months of World War I. One of the first U-Boats to arrive at the Zeebrugge base was Kapitänleutnant Walther Forstmann’s U-12, which was to play the role of submarine aircraft carrier.

Arnauld and Forstmann theorized that they could effectively increase the range of their seaplanes by taking the aircraft to the sea on the deck of submarine and placing it in a takeoff position, then launching the planes after the sub partially submerged, allowing the plane to float off. They proposed further development experiments to the German Naval Command, but were vetoed as their project was considered technically impracticable.

Surcouf was a French submarine launched in 1929 and commissioned in 1934. At 4,000 tons displacement submerged, Surcouf was the largest submarine in the world at the start of World War II. Her short wartime career is laced with controversy and conspiracy theories. Surcouf was designed as an ‘underwater cruiser,’ intended to seek and engage in surface combat.

The Japanese applied the concept of the submarine aircraft carrier extensively. Altogether 47 submarines were built with the capability to carry seaplanes. Most IJN submarine aircraft carriers could carry only one aircraft, though a few types could carry two, and the giant I-400 class submarines could carry three.

The I-400 class submarine displaced 6,500 tons and was over 400 ft long, three times the size of ordinary submarines. It had a figure-eight hull shape for additional strength to handle the on-deck hangar for housing the three Aichi M6A Seiran aircraft. In addition, it had three anti-aircraft guns and a large deck gun as well as eight torpedo tubes from which they could fire the Long Lance – the largest, longest ranged and most deadly torpedo in use at the time.

Each aircraft could transport a 1,760 lb (800 kg) bomb 650 mi (1,050 km) at 360 mph (580 km/h). Its name was combination of ‘sei’ (‘clear sky’) and ran (‘storm’), literally ‘storm out of a clear sky,’ because the Americans would not know they were coming. It had a wing span of 40 ft (12 m) and a length of 38 ft (11.6 m). To fit the aircraft into the hangar, the wings of the aircraft were folded back, the horizontal stabilizers folded down, and the top of the vertical stabilizer folded over so the overall profile of the aircraft was within the diameter of its propeller. A crew of four could prepare and get all three airborne in 45 minutes, launching them with a 120 ft (37 m) catapult on the fore deck of the giant submarine.

There are no known submarine carriers in use today; they are considered tactically very limited. There are, however, several projects to develop Unmanned Aerial Vehicle (UAV) launch and recovery capabilities. There are three known methods for doing so: launching out of a standard torpedo tube, out of an ICBM vertical launch tube, or from a custom designed unit.

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