Van Speijk class frigate

The Van Speijk class frigate were built for the Royal Netherlands Navy in the 1960s. They were versions of the British Leander class frigates with Dutch radars. The British design was chosen in order to enable rapid construction in order to replace elderly destroyer escorts and take up part of the NATO patrol duties of the decommissioned anti-submarine warfare carrier Karel Doorman. The ships were modernised in the late 1970s. All six ships were sold to the Indonesian Navy in 1986-89 and are still in service (as of 2010) as the Ahmad Yani class frigates.

For the most part the Dutch limited their changes to the Leander design to a wholesale replacement of the original British electronics and electrical equipment by those from Dutch manufacturers. Hollandse Signaalapparaten supplied the entire electronics suite. Specifically their LW-02 long-range air-surveillance radar, the DA-02 medium-range air/surface search radar and the M45 combined radar and optical fire control system for the 4.5 in (110 mm) guns. The Dutch HSA M44 radar/visual director for the Seacat anti-aircraft missiles could automatically target in elevation and bearing and allowed the single Seacat launcher on the British ships to be increased to two launchers on the Dutch ships, each with their own director.

Beginning in December 1976 each of the Dutch ships was given a mid-life modernization that took about two years to finish. The twin 4.5-inch turret was replaced by a single Otobreda 76 mm gun and two quadruple mounts for Harpoon anti-ship missiles were fitted abaft of the funnel. The Mk 10 Limbo ASW mortar was replaced by a pair of triple Mk 32 torpedo launchers, one mount on each side of the hangar, and its mount plated over so the flight deck could be increased to allow the ship to carry the larger Westland Lynx helicopter in lieu of the Wasp carried earlier. The removal of the variable-depth sonar from the quarterdeck to the interior of the stern also allowed more room for the flight deck.

The electronics were also upgraded, the LW-02 radar was exchanged for a LW-03 and the DA-02 was replaced by a DA-05 radar. Most importantly an automated combat management system, SEWACO V, was fitted to aid the ship's captain in decision making. Its power plant was also extensively automated. All told these changes allowed the crew to decrease in size from 254 to about 175 which allowed greatly increased standards of habitability.

General characteristics
Class and type:	Frigate
Displacement:	2,200 tons standard, 2,850 tons full load
Length:	113.4 m
Beam:	12.5 m
Draught:	5.8 m
Propulsion:	two geared steam turbines delivering 22,370kW (30,000shp) to two shafts. All 6 have now been re-engined with Caterpillar (5 ships) or SEMT-Pielstick Diesels (1 ship)
Speed:	28.5 knots. With new diesels - est max. 24 knots.
Range:	4500 nm at 12 knots
Complement:	180
Sensors and processing systems:	Radar: LW-03, DA-02, M45, M44 Sonar: Types 170B, 162 Combat system: SEWACO V
Armament:	(as designed) 1 x 2 - QF 4.5 inch Mk V (113 mm) guns 2 x 4 - Seacat surface to air missiles 1 x 3 - Mk 10 Limbo ASW mortar 1 Westland Wasp Helicopter (after modernisation) 1 x 1 - OTO-Melara 76mm gun 2 x 4 - Harpoon SSM (Dutch Navy) 4 x 1 - SS-N-26 SSM (On at least one ship) (Indonesian Navy) 2 x 2 - C-802 SSM (On two ships) (Indonesian Navy) 2 x 4 - Seacat surface to air missiles Seacat now removed. some of class may have 1 twin Sinbad Launcher for Mistral SAM's 2 x 3 - Mk 32 anti submarine torpedo tubes
Aircraft carried:	one NBO-105C
Aviation facilities:	Hangar