Type 61 frigate

Class overview
HMS Lincoln, 1972
Name:	Salisbury class
Operators:	Royal Navy Bangladesh Navy
Succeeded by:	Leander class
Built:	1952–1959
In commission:	1957–1985 (British service) 1978–2016 (Bangladesh service)
Planned:	7
Completed:	4
Cancelled:	3
Retired:	4
General characteristics
Type:	Frigate
Displacement:	2,170 tons standard 2,400 tons full load
Length:	340 ft (100 m) o/a
Beam:	40 ft (12 m)
Draught:	15 ft 6 in (4.72 m)
Propulsion:	8 × Admiralty Standard Range ASR1 diesels, 14,400 shp (10,738 kW), 2 shafts 220 tons fuel oil
Speed:	24 kn (44 km/h)
Range:	7,500 nmi (13,900 km) at 16 kn (30 km/h)
Complement:	235
Sensors and processing systems:	Type 960 air search radar, later Type 965 AKE-2 Type 293Q target indication radar, later Type 993n Type 982 aircraft direction radar, later Type 986 Type 277Q height finding radar, later Type 278 Type 974 navigation radar, later Type 978 Type 285 fire control radar on director Mark 6M Type 262 fire control on STAAG mount Type 1010 Cossor Mark 10 IFF Type 174 search sonar Type 170 attack sonar
Armament:	1 × twin 4.5-inch (113 mm) gun Mark 6 1 × twin 40 mm Bofors gun STAAG Mark 2, later; 1 × twin 40 mm Bofors gun Mk.5; Llandaff & Chichester 1 × Sea Cat GWS-20 SAM; Lincoln & Salisbury 1 × Squid A/S mortar

The Type 61 Salisbury class were a class of four British aircraft direction (AD) (or radar picket) frigates built for the Royal Navy in the 1950s.

These ships were related to the Type 41 Leopard-class frigates, but with reduced armament (one twin 4.5 inch mount versus two) to make way for more aircraft direction equipment, particularly the four-ton radar antenna of the Type 965 (AKE-2). Unlike the four Battle-class AD conversions, the primary role of the Type 61 was not operations with fast carrier groups, for which their diesel power plant lacked the speed. The role of the Type 61 was as a seaworthy air ocean surveillance ship and air control ship to escort slow task forces, such as amphibious task forces. By the end of 1978 all had been relegated to non-combat roles, with one sold to Bangladesh.

The primary aircraft direction equipment fitted to the Type 61s was initially Type 960 (rapidly updated to Type 965 (AKE-2)) radar for aircraft warning and Type 982M radar for a degree of 3D cover and better air control over land. The Type 965 (AKE-2) had a large "double bedstead" antenna and the Type 982M radar had a smaller "hayrake" antenna. The Seacat missile system was fitted to Lincoln in a long refit from 1966–68 and in Salisbury from 1967-70. It was the same GWS 20 optically guided system being refitted at the time to the Rothesay-class frigates. Llandaff continued to carry the twin MK 5 Bofors until sold to Bangladesh. In the late 1960s Lincoln, Salisbury, Llandaff and the aircraft carriers Ark Royal and Bulwark were all refitted with the new Type 986 radar using the 982 antenna, as a partial substitute for the 984 3D radar capability lost with the phase out of the RN strike carriers. 986 radar was intended to partially replace one of the roles of 984 in giving more accurate, short range definition of closing air targets out to about 120 kilometres (75 mi), than 965 radar could provide. It was only a partial replacement as it lacked the 984 system's ability to rank and prioritise large numbers of targets for interrogation and air interception. The 965 twin array radar was limited and obsolete by the 1970s; the 986 was a clearer radar with more than the minimal MTI, and capability for tracking air targets over land compared with the solid state 966 version of 965M. 986's usefulness was limited by the slow speed of the Salisbury-class ships, and a policy decision was made in 1974 that only anti-submarine frigates would be operational in the frigate fleet from then on. Therefore, for the rest of the decade Salisbury and Lincoln alternated between the standby squadron and lengthy re-activations, under a number of pretexts.

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