Limbo, or Anti Submarine Mortar Mark 10 (A/S Mk.10), was the final British

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 development of a forward-throwing anti-submarine

Submarine

A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...

 weapon originally designed during the Second World War. Limbo, a three-barreled mortar similar to the earlier Squid

Squid (weapon)

Squid was a British World War II ship-mounted anti-submarine weapon. It consisted of a three-barrelled mortar which launched depth charges. It replaced the Hedgehog system, and was in turn replaced by the Limbo system....

 that it superseded, was developed by the Admiralty Underwater Weapons Establishment in the 1950s. Squid was loaded manually, which was difficult on a pitching deck in heavy seas with no protection from the elements; in contrast Limbo was loaded and fired automatically, with all the crew under cover. It was widely fitted on the quarterdeck

Quarterdeck

The quarterdeck is that part of a warship designated by the commanding officer for official and ceremonial functions. In port, the quarterdeck is the most important place on the ship, and is the central control point for all its major activities. Underway, its importance diminishes as control of...

 of Royal Navy

Royal Navy

The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...

 escort ships on a mounting stabilized for pitch and roll from 1955 to the mid–1980s. Limbo was also widely employed by the Royal Canadian Navy

Royal Canadian Navy

The history of the Royal Canadian Navy goes back to 1910, when the naval force was created as the Naval Service of Canada and renamed a year later by King George V. The Royal Canadian Navy is one of the three environmental commands of the Canadian Forces...

, being incorporated into all destroyer designs from the late 1950s to the early 1970s, including the St. Laurent

St. Laurent class destroyer

The St. Laurent class destroyer was a class of destroyers that served the Royal Canadian Navy and later the Canadian Forces from the mid-1950s to the mid-1990s....

, Restigouche

Restigouche class destroyer

The Restigouche class destroyer was a class of destroyers that served the Royal Canadian Navy and later the Canadian Forces from the late-1950s to the late-1990s....

, Mackenzie

Mackenzie class destroyer

The Mackenzie-class destroyer was a class of warship used by the Royal Canadian Navy and Canadian Forces from the 1960s-1990s. Six such ships were envisioned, of which four were completed to this specification...

, Annapolis

Annapolis class destroyer

The Annapolis class destroyer escort was a class of ships that saw service with the Royal Canadian Navy and Canadian Forces from the 1960s-1990s....

 and Iroquois

Iroquois class destroyer

Iroquois-class destroyers, also known as Tribal class, are a class of four helicopter-carrying, guided missile destroyers of the Canadian Forces. Launched in the 1970s, they were originally fitted out for anti-submarine warfare, but a major upgrade programme in the 1990s overhauled them for...

 classes.

The range of the mortars was controlled by opening gas vents from 400 to a maximum of 1,000 yards (366 and 910 m). The weapon was linked to the sonar

Sonar

Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...

 system of the ship, firing on command when the target was in range. The rounds were projected so that they fell in a triangular pattern around the target. Limbo could fire in any direction around the ship and is reported to have been very accurate. The weapon was used in the 1982 Falklands War

Falklands War

The Falklands War , also called the Falklands Conflict or Falklands Crisis, was fought in 1982 between Argentina and the United Kingdom over the disputed Falkland Islands and South Georgia and the South Sandwich Islands...

, and remained in service in the Royal Navy and Commonwealth navies until the 1990s when it was superseded by the Mark 44 torpedo

Mark 44 torpedo

The Mark 44 torpedo is an obsolete air-launched and ship-launched lightweight torpedo manufactured in the U.S., and under licence in Canada, France, Italy, Japan and the United Kingdom with 10,500 being produced for U.S. service. It was superseded by the Mark 46 torpedo...

Sonar control of the A/S Mortar Mk 10

The firing of the Mortar Mk 10 was controlled by the Type 170 (and later the 502) attack sonar from the Sonar Control Room (SCR), which was generally located next to the operations room in the warship.

The 170 sonar had 3 operators who maintained sonar contact with the target and effectively aimed the weapon in bearing, range and depth. The operators were controlled by the SCO (Sonar Control Officer) who was in charge of the SCR.

When a contact had been confirmed as a hostile submarine, the SCO manually fired the Mortar Mk 10 from the SCR upon receiving the order from the captain in the operations room. The firing was done by means of a pistol grip and trigger mounted to the deckhead immediately behind the operators.

General characteristics

• Total system weight: 35 tons including 51 projectiles (17 salvos).