Tapi-class corvette

Tapi-class corvettes are a class of two corvettes that were built for the Royal Thai Navy in the early 1970s.

HTMS Tapi (5) in 1983
Class overview
Name	Tapi class
Builders	American Shipbuilding Co / Norfolk Shipbuilding & Drydock Co, both USA
Operators	Royal Thai Navy
Built	1970–1974
In commission	1971–present
Completed	2
Active	1
Retired	1
General characteristics Following 1980s refit and rearmament[1]
Type	Corvette
Displacement	885 long tons (899 t) standard 1,172 long tons (1,191 t) full load
Length	275 ft (83.8 m)
Beam	33 ft (10.1 m)
Draft	14 ft 1 in (4.3 m) (sonar dome)
Propulsion	2× Fairbanks-Morse 38TD8-1/8-9 diesel engines, 2 shafts 5,250 hp (3,910 kW)
Speed	20 kn (23 mph; 37 km/h)
Range	2,400 nmi (2,800 mi; 4,400 km) at 18 knots (21 mph; 33 km/h)
Complement	15 officers, 120 enlisted
Sensors & processing systems	Radar: Signaal LW04 Air/surface search Raytheon SPS-53E surface search Signaal WM-22-61 fire control Sonar: Atlas Elektronik DSQS-21C hull-mounted, medium frequency active search/attack
Armament	1 × OTO Melara 76 mm/62 compact gun 1× Bofors 40mm/70 gun 2× Oerlikon 20 mm 2× 12.7 mm machine guns 2× triple Mark 32 Anti-submarine warfare torpedo tubes, Mark 46 torpedoes Depth charges

Design and construction

In 1969, Thailand ordered from the United States a single small PF 103-class frigate, of which four examples, the Bayandor class, had been built for Iran in the 1960s, with a second example being ordered in 1971. For procurement purposes, they were allocated the US Navy hull numbers PF 107 and PF 108.^[2]

As built, single 3 inch/50 calibre Mk 34 automatic anti-aircraft guns were mounted fore and aft,^[2] each capable of firing 6.8 kg (15 lb) shells to a range of 13,400 m (14,600 yd) at a rate of 45 rounds per minute,^[3] backed up by a twin Bofors 40mm/L60 mount. Two triple Mark 32 torpedo tubes for anti-submarine torpedoes and a Hedgehog anti-submarine mortar comprised the ships' anti-submarine armament.^[2] AN/SPS-6 air-search radar and SQS-17 sonar comprised the ships' sensor suite.^[2]

Operational history

The first ship, Tapi, was commissioned on 19 November 1971, with the second ship, Khirirat, following on 10 August 1974.^[1] Both ships were modernised during the 1980s, with the US 3-inch guns being replaced by a rapid fire OTO Melara 76 mm gun forward, and a Bofors 40mm/70 gun aft, with two single 20 mm cannon replaced the existing twin Bofors mount. The obsolete Hedgehog was removed, and the ships were fitted with new radar and sonar systems.^[2][1]

As of 2002, they were used for patrolling Thailand's Exclusive economic zone.^[1]

Units

Pennant number	Name	Builder	Laid Down[4]	Launched[4]	Commissioned[4]
5 (later 431)	Tapi	American SB Co, Toledo, Ohio	1 April 1970	17 October 1970	1 November 1971
6 (later 432)	Khirirat	Norfolk SB	18 February 1972	2 June 1973	10 August 1974