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 Seacatanti-aircraft missiles could automatically target in elevation and bearing and because of its much lighter weight, allowed the single Seacat launcher on the British ships to be increased to two launchers on the Dutch ships, each with their own director.[1]
Mid-life modernization
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 OTO Melara 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.[2]
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.[2]
At least some, if not all, of the Indonesian ships have replaced their Seacat launchers with two twin Simbad launchers.[3] Recently, the two quadruple Harpoon launchers were also replaced by Yakhont missile (SS-N-26) launchers purchased from Russia, because the early version Harpoon missiles previously installed were nearing their obsolescence period. There are also some conflicting reports that the Harpoon missiles were replaced with Chinese-sourced C-802 rather than Russian Yakhont. There are some pictures circulating on the internet showing several vessels of the class carrying box launchers that look much too small to be Yakhont's launchers, but they are the right size for C-802.
Pictures released in March 2011 show that modifications were made to KRI Oswald Siahaan with 4 SS-26 Yakhont VLS cells located in the quarterdeck beside the helicopter hangar.[4]
Engine replacement
In Indonesian service, the Van Speijk class is known as the Ahmad Yani class after the lead ship. All were named after Indonesian Armed Forces heroes. Between 2003 and 2008, all vessels of the Ahmad Yani class had their existing steam turbine engines replaced with dieselpropulsion.[5]
Engine/Gearbox
Power
Replacement date
Shipyard
Ships
2 x Caterpillar CAT DITA 3616, Reintjes WAV 1000 P gearboxes
16,000 hp (12,000 kW)
2007–2008
PT Tesco
351, 352, 353, 355
2 x Caterpillar CAT DITA 3612, Reintjes WAF 4566 gearboxes
^Wertheim, Eric (2007). The Naval Institute Guide to Combat Fleets of the World: Their Ships, Aircraft, and Systems (15th ed.). Annapolis, MD: Naval Institute Press. p. 308. ISBN978-1-59114-955-2.
Adamsn, Thomas A. (1982). John Roberts (ed.). Dutch Leanders: The Van Speijk Class. Warship. Vol. VI. London: Conway Maritime Press. pp. 192–4. ISBN0-85177-265-X.
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