HMS ''M2'' was a

Royal Navy The Royal Navy (RN) is the naval warfare force of the United Kingdom. It is a component of His Majesty's Naval Service, and its officers hold their commissions from the King of the United Kingdom, King. Although warships were used by Kingdom ...

submarine A submarine (often shortened to sub) is a watercraft capable of independent operation underwater. (It differs from a submersible, which has more limited underwater capability.) The term "submarine" is also sometimes used historically or infor ...

monitor completed in 1919, converted in 1927 into a submarine aircraft carrier. She was wrecked in Lyme Bay,

Dorset Dorset ( ; Archaism, archaically: Dorsetshire , ) is a Ceremonial counties of England, ceremonial county in South West England. It is bordered by Somerset to the north-west, Wiltshire to the north and the north-east, Hampshire to the east, t ...

, Britain, on 26 January 1932. She was one of three M-class boats completed.

Design and career

Four M-class submarines replaced the order for the last four K-class submarines, ''K17''-''K21''. Although they were similar in size, the M class was an entirely different design from the K class, although it is possible that some material ordered for the K-boats went into them. In any event, the end of the

First World War World War I or the First World War (28 July 1914 – 11 November 1918), also known as the Great War, was a World war, global conflict between two coalitions: the Allies of World War I, Allies (or Entente) and the Central Powers. Fighting to ...

meant that only three were completed. ''M2'' was laid down at

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shipyard at Barrow in Furness in 1916, and launched in 1918. Like the other members of her class, she was armed with a single fixed 12-inch (305mm) gun as well as torpedo tubes. The Mark IX gun was taken from spares held for the ''Formidable''-class

battleship A battleship is a large, heavily naval armour, armored warship with a main battery consisting of large naval gun, guns, designed to serve as a capital ship. From their advent in the late 1880s, battleships were among the largest and most form ...

The M-class submarines were very large for the time at long. They were designed to operate as submarine monitors or cruisers. They displaced on the surface and when submerged. Two 12-cylinder

diesel engine The diesel engine, named after the German engineer Rudolf Diesel, is an internal combustion engine in which Combustion, ignition of diesel fuel is caused by the elevated temperature of the air in the cylinder due to Mechanics, mechanical Compr ...

s producing drove them on the surface; underwater, they were driven by electric motors producing . After the accidental sinking of in 1925, ''M2'' and her sister were taken out of service and reassigned for experimental use. Her 12-inch gun was removed, replaced by a small aircraft hangar, the work being completed in 1927. This could carry a small Parnall Peto seaplane, specially designed for the ''M2'', which, once its wings had been unfolded, could be lowered onto the sea alongside by a

derrick A derrick is a lifting device composed at minimum of one guyed mast, as in a gin pole, which may be articulated over a load by adjusting its Guy-wire, guys. Most derricks have at least two components, either a guyed mast or self-supporting tower ...

for take off. On landing, the aircraft was hoisted back onto the deck and replaced into the hangar. In October 1928, a hydraulic aircraft catapult was fitted, to enable the seaplane to take off directly from the deck. The submarine was intended to operate ahead of the battle fleet in a

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role, flying off her unarmed seaplane as a scout. The concept of a submarine cruiser was pursued with , but was not a success and was later abandoned.

Accident

''M2'' left her base at Portland on 26 January 1932, for an exercise in West Bay, Dorset, carrying Parnall Peto serial N255. Her last communication was a radio message at 10:11 to her submarine depot ship, , to announce that she would dive at 10:30. The captain of a passing merchant ship, the Newcastle coaster ''Tynesider'', mentioned that he had seen a large submarine dive stern first at around 11:15. Unaware of the significance of this, he only reported it in passing once he reached port.Treadwell 1999, pp. 45–46. Her entire crew of 60 was killed in the accident.Treadwell 1999, p. 52. The submarine was found on 3 February, eight days after her loss.Treadwell 1999, pp. 47, 50. Ernest Cox, the salvage expert who had raised the German battleships at Scapa Flow, was hired to salvage the ''M2''. In an operation lasting nearly a year and 1,500 dives, on 8 December 1932, she was lifted to within of the surface before a gale sprang up, sending her down to her final resting place. The hangar door was found open and the aircraft still in it. The accident was believed to be due to water entering the submarine through the hangar door, which had been opened to launch the aircraft shortly after surfacing. Two explanations have been advanced; The first is that since the crew were always trying to beat their record time for launching the aircraft, they had opened the hangar door on surfacing while the deck was still awash. The other theory is that the flooding of the hangar was due to failure of the stern hydroplanes. High pressure air tanks were used to bring the boat to the surface in an awash condition, but to conserve compressed air, compressors were then started to completely clear the ballast tanks of water by blowing air into them. This could take as long as 15 minutes to complete. The normal procedure for launching the aircraft was therefore to hold the boat on the surface using the hydroplanes whilst the hangar door was opened and the aircraft launched. Failure of the stern hydroplanes would have sent the stern down as observed by the merchant officers and water would have eventually entered the hangar. On 25 February 1932, a help message from ''M2'', written in pencil on a small piece of wood, was discovered by a fisherman on the shore at Hallsands, south

Devon Devon ( ; historically also known as Devonshire , ) is a ceremonial county in South West England. It is bordered by the Bristol Channel to the north, Somerset and Dorset to the east, the English Channel to the south, and Cornwall to the west ...

. It read: "Help. ''M2'' gone down. No. 2 hatch open.", with "Help. Lieut." on the back. It was handed over to the naval authorities and is now on display at the Royal Navy Submarine Museum in Gosport.

Aftermath

The submarine currently lies upright on the sea bed at (). Her keel is about below the surface at low tide, and her highest point at the top of the conning tower at around . She is a popular dive for scuba divers. The wreck is designated as a "protected place" under the Protection of Military Remains Act 1986. After the loss of ''M2'', the Royal Navy abandoned submarine-launched aircraft, although other navies experimented with the concept in the inter-war years and with Japan producing some 42 submarine aircraft carriers both before and during the Second World War.Dorr Carpenter, Dorr B. & Polmar, Norman. ''Submarines of the Imperial Japanese Navy'', Conway Maritime Press, 1986.

References

Bibliography

* * Brown, D.K. (2003) ''The Grand Fleet: Warship Design and Development 1906-1922'', London: Caxton Editions, * Treadwell, T.C. (1999) ''Strike from beneath the Sea: a history of aircraft-carrying submarines'', Stroud, UK: Tempus Publishing.
SI 2008/0950
Designation under the Protection of Military Remains Act

External links