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Monday 27 February 2017

Naresuan class frigates of the Royal Thai Navy

Written by D-Mitch

The lead ship in the class, Naresuan (421), after the upgrade.
Via Fb Combat-Zones
The most advanced and heavily armed surface combatants of the Royal Thai Navy (Thai: กองทัพเรือไทย; rtgsKong Thap Ruea Thai) are two (2) Naresuan class frigates, cooperatively designed by the Royal Thai Navy and China but built by the China State Shipbuilding Corporation in Shanghai the period 1991-94. The two vessels in the class, Naresuan (421) and Taksin (422), were commissioned in December 1994 and October 1995 respectively. The Naresuan class is considered a modified version of the Chinese-made Type 053 frigate. When Thailand ordered four new 053 frigates in 1990, China built them to the (then) latest 053H2 (Jianghu III) standard. Two were modified with helicopter decks in the back. Although the price was excellent, the Thai Navy complained of quality issues. The interior wiring was exposed and had to be re-wired. The ship's battle damage control system was very limited, with poor fire-suppression system and water-tight locks. It's said that if the ship's hull was breached, rapid flooding would lead to loss of ship. The Thai Navy had to spend considerable time and effort to correct some of these issues. The harsh criticisms lead to many improvements in China's shipbuilding industry. By the mid-1990s, the Thai Navy was confident enough to order two enlarged 053 hulls (F25T), later named HTMS Naresuan and HTMS Taksin, to be fitted with western engines and weapon systems. The ships were purchased at "friendship prices" of 2 billion baht each, compared to the 8 billion baht price tag for Western-built frigates.

The two Naresuan class frigates, after their upgrade, in formation

The general characteristics of the vessels is a displacement of approximately 3,000tons at full load, length of 120.5m while the speed is +32knots and the range is 4,000n.m. with 18knots cruising speed. The complement is 150.  The vessels carry one medium helicopter and two Rigid-Hulled Inflatable boats (RHIB), one at each side of the ships.

HTMS Taksin prior the upgrade.
Photo: tncon
HTMS Taksin before the upgrade.

HTMS Taksin prior the upgrade.
Photo: tncon


On 3 June 2011, Saab announced that it was awarded a contract for the upgrading of the two Naresuan class frigates with new electronics and new weapons. The extensive midlife upgrade program (MLU)  included a Vertical Launching System (VLS), new secondary guns, Saab's 9LV MK4 combat management system, Sea Giraffe AMB 3D long range air surveillance radar, CEROS 200 fire control systems, EOS 500 electro-optical system, Tactical Data Links (TDL’s) for communications with the newly acquired Royal Thai Air Force Erieye surveillance aircraft, a new sonar system, a new ESM system and other improvements The upgrade programme was finally concluded in 2016, after five years of work, and delivered almost complete new warships to the Royal Thai Navy.

Modified photo of Naresuan class frigate of the Royal Thai Navy. For a high resolution image click here.

Mk45 gun and VLS
The Mk45 gun of Naresuan frigates
The ships are equipped with a single BAE Systems Mark 45 Mod 2 5in (127mm) fully automatic lightweight gun (L54 Mk 19) in a bow unmanned turret (Mk 45) with a maximum range of 24 kilometers (effective range close to 15km) for surface targets, 7km for aerial targets, and a rate of fire of 20 rounds per minute. The gun has excellent performance in anti-surface and shore bombardment role and limited performance in anti-aircraft and anti-missile role due to the low rate of fire. The weapon has many different kinds of ammunition with a mean projectile weight of 30kg with a warhead of 3.5kg. The gun mount features an automatic loader with a capacity of 20 rounds. These can be fired under full automatic control, taking a little over a minute to exhaust those rounds at maximum fire rate. For sustained use, the gun mount would be occupied by a six-man crew (gun captain, panel operator, and four ammunition loaders) below deck to keep the gun continuously supplied with ammunition.

The Type 76 twin 37mm of the ships

The Type 76 twin 37mm of the ships

The new MSI guns that replaced the old Type 76s

The Type 76 twin 37mm of the ships
with the
Type 347G  FCS atop hangar

Via Combat-Zones

MSI Defense Systems 30mm gun firing
MSI Defense Systems 30mm gun

The two secondary Chinese-built Type 76 twin 37mm dual-purpose gun systems that were equipping originally the ships, were removed and replaced by the MSI Defense Systems 30mm DS30M Mark 2 (Seahawk A2) gun systems consisting of a 30mm Mark 44 Bushmaster II cannon on a fully automated mount with an off-mount electro-optical director (EOD) and with below deck control console. The gun has a rate of fire of approximately 650 rounds per minute in a maximum range of less than 3km in anti-aircraft role. Except the main naval gun, the ships are equipped with 2-4 MH2B heavy machine guns. The M2 has a maximum (effective) range of around 1,830m and a cyclical rate of fire of approximately 600 rounds per minute.

Overview of Naresuan. Via
M2HB heavy machine gun
M2HB of HTMS Taksin

Harpoon launcher of HTMS Taksin
Harpoon launcher of HTMS Taksin
Each frigate carries four (usually) to eight (8) Boeing RGM-84D/G Harpoon anti-ship missiles in two Mk141 quad launchers amidships. These missiles have a range greater than 120km, a sub-sonic of speed of 860km/h (Mach 0.9) while they carry a warhead of 221kg. Harpoon missile has a low-level, sea-skimming cruise trajectory, active radar guidance and it is capable to perform pop-up manoeuver which it is a rapid climb of the missile to about 1,800m before diving on the locked target.

HTMS Taksin before the upgrade with the old sensors

Installing the Mk41 VLS on the ships
Installing the Mk41 VLS on the ships
The most important weapon addition during the MLU, was the installation of a (VLS), the Raytheon Mark 41 (Mk 41) for RIM-162 Evolved Sea Sparrow Missile (ESSM) surface-to-air missiles (SAM), as the vessels till that time did not have anti-aircraft missile system. On August 8, 2012, the Defense Security Cooperation Agency (DSCA) announced that it has received a letter of intent for Thailand to purchase vertical ESSM air defense missiles and associated equipment to upgrade the frigates, including the first nine ESSM air defense missiles and three Mk25 four-in-one missile launch box (loaded in the Mk41 vertical launcher) and four MK-783 marine missile containers, related components, training and logistical support, totaling $18 million. On January 14, 2013, DSCA signed the letter of Offer and Acceptance with Lei Song. On July 1, 2013, the Thai Navy and the US Navy formally finalized the military shipments of the Mk41 vertical launchers and ESSM missiles at a total value of $ 40.3 million.

Naresuan launching ESSM
Ready to launch ESSM for first time

Naresuan launching ESSM

Naresuan launching ESSM

ESSM launch
Naresuan launching an ESSM. Via
Two years later, on 30 August 2015, ESSM was fired from HTMS Naresuan during Exercise CARAT 2015. This launching system is located forward of the bridge of the ships and behind the main gun, and consists of one 8-cell module. The eight cells are equipped the RIM-162 ESSM. The ESSM are loaded in guad-packs per cell thus the total amount of ESSM each vessel can carry is 32 missiles. The ESSM can reach 50 km range with a speed of Mach 4 while its  maneuvering capability reaches the 50G (!) giving an excellent capability to the missile to counter supersonic maneuvering anti-ship missiles. The warhead of ESSM is of 39kg. The missiles are dependent on the ship's fire control systems for target illumination on final approach, since they are guided by semi-active radar homing.

Naresuan with her original equipment moored in Hong Kong. Image: Kazec
HTMS Naresuan after the upgrade with new sensors and armament

Mk32 torpedo launcher of Naresuan.
Mk32 torpedo launcher of Naresuan.
Finally, the ships carry two triple Mk 32 Mod 5 torpedo launchers capable of launching Mk46 and Mk54 torpedoes for anti-submarine purposes. The Honeywell Mk46 Mod 5 active or passive/active acoustic homing lightweight torpedoes have a range of approximately 8,500-11,000m at 45 knots (maximum speed) and they carry a very powerful warhead of 44.5kg for this category of lightweight torpedoes. They are designed to attack fast submarines and to engage them even over 400m below sea level as well as surface targets (latest variants such as Mod 5). In August 26, 2016, the U.S. Navy was awarded Raytheon a $37.7 million contract for the procurement of MK 54 lightweight torpedo support parts. Under the contract, Raytheon will provide lightweight torpedo common parts kits and MK 54 Mod 0 lightweight torpedo kits. Additionally, the company will provide MK 54 exercise fuel tanks, spares, production support material, engineering support, and hardware repair support. This contract, combines purchases for the U.S. Navy and the Government of Thailand. The Mk54 torpedo is the next generation of Mk46 torpedo as it combines the expensive Mk50 search and homing system with the propulsion system of the Mk46 torpedo for optimized performance in the most challenging littoral scenarios.  It incorporates a guidance and control (G&C) section employing COTS processing technologies and tactical software improvements to significantly increase shallow water counter-countermeasure capability at reduced lifecycle costs. It has a speed over than 40 knots and it carries the same warhead as the Mk46.

Terma SKWS (Soft Kill Weapon System) C-Guard. Image: Terma

The old Chinese decoy launchers.
Details of Naresuan's decoy launchers
Terma SKWS (Soft Kill Weapon System) C-Guard is the decoy launching system of the ships that replaced the obsolete Chinese ones. The system is integrated with the Combat Managment System, that can fire all existing 130 mm decoys – also known as SeaGnat decoys, made to defeat stream attack with multiple missiles and torpedoes from multiple directions. The system is based on two Terma DL-12T launchers (12 firing tubes each) on each side of the ship and four Terma Mk137 SRBOC launchers (6 firing tubes each) atop the bridge. The total number of decoy launchers is 48 (!), which is the maximum system configuration supporting the 48 launchers, three Control Units and uses two Launcher Interface Units providing a dual network. This configuration and the dual voltage power supply in each LIU secure a high MTBCF and graceful degradation in case of any malfunction.
Terma SKWS maximum system configuration with 48 (!) launchers
DL-6T, DL-12T and Mk137
The plethora of decoy launders of
HTMS Naresuan frigate
The Terma launcher is designed to provide 360 degrees coverage against attacking anti-ship missiles and torpedoes. The DL-12T launchers are fitted with 12 tubes, 3 in each of the firing angles 10°, 40°, 60° and 135° in the azimuth plane in relation to the sailing direction. The DL-12T launcher tubes are fitted with a Round Identification System (RIS) in order to provide correct loading information to the SKWS operators and thus to avoid completely the delay in communicating the tube content and potential misunderstandings between loaders on deck and operators in CIC or on the bridge. The Mk137 launchers are fitted with 6 tubes, acting mainly as additional launchers for anti-torpedo decoys such as the Launched Expendable Acoustic Decoys (LEAD). The LEADs are available in two basic versions. The payload is in principle the same, but the decoy is either mortar or rocket propelled for deployment close to the ship or further away.C-Guard can operate in three different modes: Manual, Semi-Automatic, or Full-Automatic mode. In Full-Automatic mode, C-Guard automatically evaluates and executes the most effective countermeasures for defense by seducing incoming threats – greatly reducing stress load on the operator under multi-threat attacks. In Semi-Automatic mode C-Guard provides two firing scenarios for the operator to choose from – for the most effective countermeasures to layer the defense by distracting and/or seducing incoming missile threats. The two firing scenarios are automatically reevaluated as the engagement progresses.

The lead ship in the class with new sensors and weapon systems.
Photo via

Thales LW08 radar of Naresuan
Thales LW08 radar of Naresuan
The Thales LW08 is a 2D radar system for long-range air surveillance in D-band (L band), providing target indication to weapon control systems. LW08 presents a clear picture of the environment; it does so, reliably, under any circumstances. LW08 performs with great frequency agility over a wide band, due to its synthesizer-driven TWT transmitter. Excellent performance under various clutter conditions is ensured by the wide dynamic range receiver with application of digital video processing, supported by circular polarization. The LW08 antenna has a low side-lobe level, which assists the system in operating under ECM conditions. The radar can detect a small missile from 100km or a fighter aircraft from 230km flying with Mach 4 while the tracking capacity is 400 tracks. Minimum range is 2km.

Photo during the installation of the new sensors. Photo: Saab

Photo during the upgrade
The main mast with the new sensors.
Photo via

The Saab Sea Giraffe AMB is a medium range, multi-role surveillance radar optimized for detecting small air and surface targets with high tracking accuracy and high update rate in all kinds of environments, including the littorals. The Sea Giraffe replaced the Chinese-built Type 360 E/F 2D radar. The new radar will assist the commander in all kind of naval warfare and give the operators maximum time to react to incoming threats. It can detect air and surface targets from the horizon up to a range of 120km and height of 20,000m at elevations up to 70°, and can simultaneously handle multiple threats approaching from different directions and altitudes, including diving anti-ship missiles. Also, it is specialized for rapidly detecting small, fast moving targets at all altitudes and small surface targets in severe clutter.

Kelvin Hughes SharpEye X-band and S-band radars

Details of SharpEye hatch. Image: Kelvin Hughes
The ships are also equipped with one Furuno navigation radar (replaced Raytheon AN/SPS-64) and two Kelvin Hughes SharpEye I-Band and E/F-Band (X & S-Band) radars that replaced other Chinese-built radars in the class. SharpEye transmits a low power patented pulse sequence, which enables short, medium and long range radar returns to be detected simultaneously, allowing the radar operator to maintain situational awareness regardless of the range scale setting of the radar display. Other users of the radar can select their own radar display range scale. A low peak transmission power (less than 300W) equivalent to a 25kW magnetron reduces the probability of intercept by ESM systems. Doppler processing of radar returns provides coherent information concerning a target's velocity (radial) and enable the detection of very small and slow moving objects and targets with a low RCS (Radar Cross Section) and through a series of electronic filters is able to distinguish between the targets of interest and sea, rain and land clutter. SharpEye I-Band (X-Band) transmitters are the first in their class to employ Gallium Nitride GaN power transistor technology. The significant performance benefits of GaN transistors have been harnessed to directly improve the performance of the radar. Other differentiating technologies include Moving Target Detection (MTD) providing enhanced clutter suppression at the Doppler processing stage and pulse compression of the return signal, enabling a low transmit power, providing efficient use of the radar and reducing the probability of detection by ESM equipment. SharpEye is a truly multipurpose naval radar transceiver and is/can be used for navigation, surface search and helicopter control and recovery.

Naresuan prior the upgrade and modernization with S70 helicopter

CEROS 200 with sensors uncovered
Photo: Saab
The aft CEROS200 of HTMS Naresuan
Saab CEROS 200 is a radar and optronic tracking fire control director, that replaced the Thales STIR 180 director aboard the frigates, designed for automatic target detection and lock-on, high acquisition speed and great tracking precision combined with the ability to track any target in any weather situation. The versatile CEROS 200 can track multiple supersonic missiles including advanced sea skimming missiles as well as surface targets extremely close to the ship such as asymmetric surface threats in littoral environments, and enables fast target switching. Moreover, CEROS 200 design incorporates many Electronic Counter-Countermeasures (ECCM). The CEROS 200 incorporates CHASE, a patented method for processing of the complex radar target return signal from a very low flying target such as sea skimming missiles, to eliminate multi-path effects. A prerequisite for the CHASE algorithm is the very wide RF-bandwidth of the tracking radar on the CEROS 200. The CHASE algorithm has been thoroughly tested in a wide range of sea states. The extensive testing proves that the radar tracking accuracy of the CHASE method against sea skimming targets is better than 0.2 mrad in calm sea and better than 0.4 mrad in rough sea. Combined with Saab’s gun fire control CEROS 200 provides unparalleled accuracy for gun engagements

HTMS Naresuan; view from the stern with Saab EOS-500 and CEROS-200 visible

EOS-500 EO sensor. Photo: Saab
Naresuan class frigate together with
modernized CVL Chakri Naruebet
Saab EOS-500 is a lightweight stabilized electro-optical fire control director with high quality stabilization and advanced TV- and IR-cameras and Laser Range Finder for observation, gun fire, missile laser guidance and target identification. The new sensor replaced the Chinese-built Type 347G  I-band fire-control radar (Rice Bowl) above hangar, for the 37mm guns. The inherent video tracker provides automatic detection of up to four concurrent threats, enabling the operator to change target within fractions of a second. EOS-500 is capable of high accuracy 3-D tracking all types of threats, including sea skimming missiles. The advanced Saab video tracker uses simultaneous input from the TV- and the IR- cameras in a data fusion process. The two (2) Saab CEROS 200 radar and optronic tracking systems and the EOS 500 optronic tracking system are the core of the frigates fire control capability and are fully integrated with the small and large calibre guns as well as the Surface to Surface (SSM) and Surface to Air (SAM) Missile systems providing unprecedented self defence capabilities against all modern symmetric and asymmetric threats.

Naresuans' ES-3601S ESM. Image: Harris

The Harris (former Exelis) ES-3601S is a high-capability radar Electronic Support Measures (ESM) system that equips the ships. The ES-3601S uses an innovative monopulse direction-finding system for accurate bearing measurements, in the purposes of long range detection, intercept, DF (over 360°) and tracking, and has been integrated into the ship's combat system.

Saab 9LV Mk4 Combat Management System (CMS). Photo: Saab

The new Saab CMS of Naresuan.
Photo via
The new Saab CMS of Naresuan.
Photo via
The frigates Naresuan and Taksin are equipped with the latest generation Combat Management (CMS) of Saab, and one of the most advanced in the world today, the Saab 9LV Mk4. The Saab 9LV system integrates sensors, weapons and data links enabling the frigates to engage a variety of modern threats including sea-skimming missiles and small surface threats. The 9LV Mk4 CMS comprises a set of Multi-Function Consoles (MFC) providing display and input facilities for control of the system and the integrated sensors and weapons. The CMS is the core of the frigates CS and performs command and control, identification, tracking and weapon engagements. In addition to the modernization of the CMS the frigates are also equipped with Tactical Data Links (TDL’s) to enable them to share their tactical picture between them and to share information with the Royal Thai Air Force Gripen fighters and Airborne Early Warning radar aircraft which dramatically improves the effectiveness of both the naval and air force assets. In September of 2015, HTMS Naresuan frigate successfully tested a datalink with the Saab Gripen fighter and Saab 340 Airborne Early Warning aircraft.

RTN HTMS Naresuan with RTAF Gripen and Saab 340 AEW aircraft.
As it was mentioned already in the introduction the ships carry one medium helicopter, either a Sikorsky S-70/76 B Seahawk (only on flight deck) for SAR/ASW/ASuW/transport operations or an Agusta Westland Super Lynx 300 (advanced Super Lynx with CTS-800-4N engines) helicopter for ASW/ASuW operations (can fit also in the hangar) or a general utility/transport Bell 212. The ASW helicopters use the Mk46 torpedo with the capabilities described earlier in the paragraph about the ships' torpedo launchers.

The hangar of Naresuans can fit one Super Lynx 300
Super Lynx aboard Taksin

Super Lynx landing in Taksin
Bell 212 on the flight deck of Taksin. Via Fb Combat-Zones

Naresuan firing ESSM with S76 aboard

Among other equipment, the ships, after the upgrade have received the Atlas Elektronik DSQS-24D hull-mounted sonar that replaced the DE-1160, the Selex Communications SIT422 CI and M425 NGIFF, two Saab Bridge Pointer Target Designation Sights (TDS, INMARSAT-M, Saab Link E Link G (TIDLS), Saab Link 11 (TADIL-B) etc.

Beautiful photo of HTMS Naresuan, via



  1. Great at last RTN nice work.

    1. I am glad you enjoyed it. I have many Thai followers; it was my duty to write an article about Royal Thai Navy!