Submarine aircraft carrier
One of the first U-boats to arrive at the Zeebrugge base was Kapitänleutnant Walther Forstmann's SM U-12, which was to play the role of a submarine aircraft carrier.
On 25 December 1915,[1] one of the newly modified aircraft flew across the English Channel and up the River Thames, dropping bombs on the outskirts of London, although they caused only minor damage.
Although the aircraft had been carried out to sea and had safely floated off the submarine's deck, it was obvious improvements were needed in the procedure and setup.
The plans were reinvestigated in 1917 in the hope that they would increase the striking power of new German subs such as the long-range cruiser-type Unterseeboote, which were to be equipped with small scouting seaplanes that could be assembled and dismantled onboard and stored in special compartments on deck – but the idea was abandoned as the war came to an end.
The guns were fed from a magazine holding 60 rounds and controlled by a director with a 16 ft 6 in (5.03 m) rangefinder, mounted high enough to view a 7 mi (11 km) horizon.
The Regia Marina (Italian Navy) ordered Ettore Fieramosca, a submarine with a waterproof hangar for a small reconnaissance seaplane in the late-1920s.
After the loss of the heavy gun-carrying HMS M1 and the Washington Naval Treaty which restricted the armament of vessels that were not capital ships, the remaining M-class submarines were converted to other uses.
By 1927, HMS M2 had entered service with a waterproof hangar for a Parnall Peto seaplane with folding wings, which could be launched and recovered with the aid of a derrick.
The United States began studying the concept in 1922 when two Caspar U.1 seaplanes were purchased from Germany for evaluation at Anacostia Naval Station.
[4][5] Problems with launching and recovering the aircraft, and the limited military value caused interest in the concept to wane, and news that the British submarine M2 had sunk during trials in 1933, plus damage to the XSL[6] during testings on the sheltered waters of the Anacostia River ended further U.S. Navy development.
The Kriegsmarine (German navy) also started development of submarines capable of launching aircraft and ordered four very large "cruiser" U-boats in early 1939.
These boats were to be twice as large as any existing U-boat and were to have had a crew of 110 while carrying a single Arado Ar 231 floatplane, but were cancelled at the outbreak of war later that year.
Another German long range U-boat was the Type IX D2 "Monsun", used in the Indian Ocean and Far East Area based in Penang (Occupied Malaya).
These submarines were fast, had a very long range, and carried a single Yokosuka E14Y seaplane, located in a hangar in front of the conning tower, which was launched by a catapult.
The range and speed of these submarines was remarkable (21,000 nmi (39,000 km) at 16 kn (30 km/h)), but their underwater performance was compromised, making them easy targets.
It had a figure-eight hull shape for additional strength to handle the on-deck hangar for housing the three Aichi M6A Seiran aircraft.
The 1946 study had a projected hull classification symbol of SSV, and was initially envisioned to carry two XA2J Super Savage bombers for strategic nuclear strike, or four F2H Banshee fighters.
This would still be a large submarine, projected at 460 ft (140 m) long and 9,000 tons submerged, with a 70,000 hp (52,000 kW) nuclear power plant to achieve 28 knots (52 km/h).
A more economical plan was also conceived to convert World War II fleet submarines to carry a seaplane version of the A4D Skyhawk in a similar manner to the Regulus missile-equipped SSGs, using hydro-skis for takeoff as the Sea Dart did.
