Military Wiki
HMS Trenchant (S91)
Career (UK)
Ordered: 22 March 1983
Builder: Vickers Shipbuilding, Barrow-in-Furness
Laid down: 28 October 1985
Launched: 3 November 1986
Commissioned: 14 January 1989
Homeport: HMNB Devonport, Plymouth
Fate: in active service, as of 2022
Badge: File:HMS Trenchant crest.jpg
General characteristics [1]
Class & type: Trafalgar class submarine
Displacement: 4,800 tonnes, surfaced
5,300 tonnes, dived
Length: 85.4 m (280 ft)
Beam: 9.8 m (32 ft)
Draught: 9.5 m (31 ft)
Installed power: 15,000 shp (11 MW)
  • 1 x Rolls Royce PWR1 nuclear reactor
  • 2 x GEC steam turbines
  • 2 x WH Allen turbo generators; 3.2 MW
  • 2 x Paxman diesel alternators 2,800 shp (2.1 MW)
  • 1 x pump jet propulsor[Note 1]
  • 1 x motor for emergency drive
  • 1 x auxiliary retractable prop
Speed: 32 knots (59 km/h) dived
Range: Unlimited, except by food supplies and maintenance requirements.
Complement: 130 (18 officers)
Sensors and
processing systems:
Ferranti/Gresham Dowty DCB/DCG or BAE Systems SMCS data system, Type 2072 hull-mounted flank array passive sonar, Plessey Type 2020 or Marconi/Plessey Type 2074 hull-mounted active and passive search and attack sonar, Ferranti Type 2046 or TUS 2076 towed array passive search sonar, Thomson Sintra Type 2019 PARIS or Thorn EMI 2082 passive intercept and ranging sonar, Marconi Type 2077 short range active classification sonar, Kelvin Hughes Type 1007 I band navigation radar, Pilkington Optronics CK34 search periscope, Pilkington Optronics CH84/CM010 attack periscope
Electronic warfare
& decoys:
  • 2 × SSE Mk 8 launchers for Type 2066 and Type 2071 torpedo decoys
  • RESM Racal UAP passive intercept
  • CESM Outfit CXA
  • SAWCS decoys carried from 2002
  • 5 × 21-inch (533 mm) torpedo tubes with stowage for up to 30 weapons:
  • HMS Trenchant is a Trafalgar-class nuclear-powered fleet submarine of the Royal Navy built by Vickers Shipbuilding, Barrow-in-Furness. Trenchant is in service and is based at HMNB Devonport. She is the third vessel and the second submarine of the Royal Navy to be named for the characteristic of vigour and incisiveness. The submarine was ordered on 22 March 1983. She was laid down by Vickers Shipbuilding on 28 October 1985, and was launched on 3 November 1986 in the presence of Vice Admiral Sir Arthur Hezlet, who had commanded the World War II T-class submarine Trenchant.[3] She was commissioned into the Royal Navy on 14 January 1989.[4]

    Trenchant is scheduled to be decommissioned in 2017.[5]

    Operational history


    On 22 November 1990, the nets of the fishing vessel Antares were snagged by Trenchant in the Bute Sound in Scotland. At the time the submarine was conducting a 'Perisher' Submarine Command Course exercise in company with the frigate HMS Charybdis. Antares was pulled under with the loss of all four members of the crew.[6][7][8]

    In July 1997, the submarine ran aground off the western coast of Australia.[9] While approaching Fremantle, Western Australia, the submarine remained at a depth of 200 metres (660 ft) and grounded when she made contact with the continental shelf, coming to rest on a sloping patch of seafloor.[9] Trenchant was able to free herself, and an inspection by divers reported no significant damage.[9]

    Trenchant tested the non-hull-penetrating optronic mast in 1998. She also trialled a camouflage paint scheme comprising jagged shapes of various colours, including pale blue.[citation needed]

    2000-present day

    On 21 June 2007, the submarine became the first Royal Navy vessel to fire the new Block IV Tomahawk cruise missile in a live-firing trial in the Gulf of Mexico off the United States coast.[10]

    In late 2009, Trenchant entered the Devonport submarine refit complex to undertake a 2-year refit and upgrade programme. Upon completion of the programme, the submarine underwent a rededication service on 6 June 2011 to welcome the boat back to active service.[11]

    On 22 May 2013, HMS Trenchant completed the longest patrol ever carried out by a Royal Navy SSN. The patrol lasted 335 days (11 months) during which the submarine sailed 38,800nm.[12] During this time the vessel has visited six different ports: Fujairah, UAE; the British Indian Ocean Territory – Diego Garcia; the Kingdom of Bahrain; Aqaba, Jordan; Souda Bay, Crete; and Gibraltar.[13]


    Trenchant is affiliated with the following military and civilian organisations, bodies & individuals:[11]

    • Sea Cadet unit TS St David’s
    • Sea Cadet unit TS Echo (Llanelli)
    • Town of Llanelli
    • Lady Meriel Hunt (sponsor)


    1. All boats have a pump jet propulsor with the exception of Trafalgar which was fitted with a 7-bladed conventional propeller.[2]
    • Submarines, War Beneath The Waves, From 1776 To The Present Day, by Robert Hutchinson

    External links

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