Mk 11 Depht Charge

Type

Air-launched free-fall depth charge.

 Development

The Mk 11 depth charge was developed by British Aerospace (now BAE Systems) specifically for air delivery from maritime aircraft and helicopters for the UK services. Although primarily designed as a quick-reaction air-launched ASW weapon ideally suited for shallow water operations against submarines on the surface or at periscope depth, it can also be deployed against small- to medium-size surface vessels. Since entering service there have been several modification programmes to improve the overall performance of the weapon. The current in-service Mk 11 Mod 3 has a redesigned strengthened nose section and outer casing in order to withstand entry into the water at high velocities without distortion. It also has a modified fuzing system to withstand the harsh vibration environment associated with helicopter operations. In the early 1990s it was reported that a new polymer-bonded explosive (PBX) was being developed, which used long-chain molecules to bind the energetic materials together forming a relatively insensitive explosive matrix, thus making it more resistant to mishandling and attack than the current explosive used.
            The Mk 11's design allows it to be carried in a similar way to a high-drag general purpose bomb or torpedo and has been cleared for carriage on Lynx, Merlin, Sea King, Wessex and Wasp helicopters and Nimrod maritime patrol aircraft.

 Description

The Mk 11 depth charge is similar in appearance to early high-drag bombs, having a cylindrical steel body with a flat nose and an old fashioned four fin/ring stabilising fin combination. The tail assembly is designed to break off when the depth charge impacts with the water. This break-off capability is to facilitate the eventual hydro-pneumatic arming and subsequent detonation of the charge. The cylindrical body section of the depth charge is 0.97 m long and has a body diameter of 279 mm; with the break-off tail unit fitted to the weapon, it is 1.39 m long. Its overall launch weight with an 80 kg HE charge is 145 kg. The Mk 11 was initially filled with Torpex, however a polymer bonded explosive (PBX) is now offered as an alternative. The explosive charge is fitted with a fuze system, which is inserted at the rear of the body cylinder. It comprises a valve, pistol unit, detonator and primer assembly, which can withstand severe vibration and shock to ensure accurate detonation at the set depth. On impact with the sea the hydro-pneumatic arming system is activated.
            A training versions of the Mk 11 Mod 3 have also been produced, one being for use by aircrew in carriage and release practice.

 Operational status

The Mk 11 has been operational in the UK for a number of years and has been supplied to many other navies. It was successfully used in the 1982 Falklands campaign and has been evaluated by the US Navy. In 1989 a contract was signed to supply a number of Mk 11 depth charges to the French Navy.

 Specifications

Length: 1.39 m (with 0.42 m tail assembly)
Body diameter: 279 mm
Weight: 145 kg
Warhead: 80 kg HE
Operating depth: Preset   

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