British 18-inch torpedo

18 inch Mark XII
A Mark XII torpedo fitted to a Bristol Beaufighter
Type	Torpedo
Place of origin	United Kingdom
Service history
In service	1937-1945
Production history
Designed	1935
Specifications
Weight	1,548 lb (702 kg)
Length	16 ft 3 in (4.95 m)
Diameter	17.72 in (450 mm)
Warhead	TNT
Warhead weight	388 lb (176 kg)
Engine	Burner cycle 140 hp (at 40 knots)
Speed	40 knots (74 km/h; 46 mph) for 1,500 yd (1,400 m) or 37 knots (69 km/h; 43 mph) for 3,500 yd (3,200 m)

There have been a number of 18 inch torpedoes in service with the United Kingdom.

These have been used on ships of the Royal Navy and aircraft of both the Fleet Air Arm and Royal Air Force, while Royal Navy surface ships and submarines use 21 inch torpedoes.

The British "18 inch" torpedoes were 17.72 inches (45.0 cm) in diameter, beginning with the "Fiume" Whitehead torpedo of 1890.

First introduced into British service in 1894.

Used on the River class and 1905 Tribal class destroyers.

Used on Destroyers of the early 1900s.

Introduced on the 1908 members of the 1905 Tribal class destroyers. Used by torpedo boats built before the First World War and destroyers. Used by RAF flying boats in the 1920s.

Aircraft launched, used by Fleet Air Arm and RAF Coastal Command.

The Mark XIV was an aircraft-launched torpedo. Stocks were lost with the fall of Singapore.

Electric torpedo project not completed.

An air-dropped passive acoustic homing torpedo known as "Dealer" and "Dealer B". "Dealer" did not see service use, but its successor, "Dealer B" (the Mark 30 Mod 0), was issued from June 1954. Considered very successful with approximately 1,200 being built, it served in both the Royal Navy and RAF until 1970. The Mark 30 Mod 1 had several improvements, but this program was cancelled in 1955 in favour of purchasing Mark 43 Mod 3 torpedoes from the USA.