Enhancing the Royal Navy’s batch II OPVs

Speaking at DSEI in September 2019, RN Commander Operations, Rear Admiral Paul Halton said: “We are thinking about how we might enhance the lethality of the Batch II OPVs”. In this article, we consider some of the options and implications for upgrading these vessels.

A frequent criticism of the new Batch II OPVs that are entering service with the RN is that they are under-armed. They are lightly armed for their size but are designed and built with potential future upgrades in mind. A substantial number of mostly hidden changes were made to the baseline design (The 3 OPVs in now service with the Brazilian navy were built to the original specification). Upgrades to survivability include fire safety and fire-fighting enhancements, watertight integrity improvements, better emergency lighting and full ballistic protection of the magazine. These apparently mundane features are difficult to add to a vessel after construction and have resulted in a more combat-survivable platform than the average OPV. Additionally, the OPVs have a small operations room fitted with the BAES CMS-1 combat management system and ‘Shared Infrastructure’ using a common console system. This CMS backbone which is now common to most RN warships (except the Thales TACTICOS-based Type 31) should ease the installation of new sensors and weapons. This is rounded off with a full military communications fit, military GPS and Warship Electronic Chart Display and Information System (WECDIS).

Even if you have a ready-made platform, it must be recognised that the addition of new weapons and sensors is not a simple as some assume. Firstly the benefits of upgrading the OPVs may have to be balanced against other needs in the fleet. Then before the decision to add new capability is taken, there are a series of questions consider. What is the initial cost of the new item and what will be the total cost of ownership through its life in service? Is this already in the UK inventory or will a completely new support chain have to be established to maintain it and supply it with spares and ammunition? Will this capability require increasing the size of the ship’s company and do how do we generate a stream of trained operators and maintainers? What impact will the new equipment have on the ship itself? Can it be easily integrated with the existing combat management system and are the power supplies adequate? Is there sufficient top weight margin available and will its affect the handling of the ship or impact the operation, maintenance and safety of existing equipment?

HMS Forth newly arrived in the Falklands Islands where she will be forward-deployed for many years. Is heavy investment in upgrading her weaponry the best use of resources when her light armament is appropriate to her role as a patrol ship? The military threat to the Falklands from Argentina is now almost nil.

Bespoke tailoring

The Batch I OPVs are only armed with a single, manually-aimed 20mm cannon and a few GMPGs. Although it might be nice for them to be armed to the teeth in case of all eventualities, this would be a poor use of resources as they spend most of their time policing fishing boats. When tasked primarily to provide surveillance, conduct boarding operations and provide a presence in UK waters, having additional heavy weapons would be almost pointless.

As the RN complies with the defence secretary’s directive to maximise the use of the assets it already has, it is beginning to consider if the Batch II OPVs may be able to operate in the higher threat areas that are normally considered appropriate for frigates and destroyers. HMS Forth and HMS Medway have now been forward deployed in “low-threat” environments but HMS Trent, Tamar or Spey might be candidates to be forward-deployed either in the Arabian Gulf or Singapore. When operating in the Gulf, the most obvious threats are from gunboat swarms and land-based anti-ship missiles. To be of much use, the OPV must protect not just itself, but either merchant ships or mine warfare vessels it may be called on to escort. This will require more firepower than a single 30mm, although not necessarily expensive guided missiles. In the Asia-Pacific region where the mission may be to join a coalition to face down the might of the Chinese, a greater level of weaponry might be needed in order to be taken seriously both by allies and adversaries. Although slightly reducing the flexibility of the fleet as a whole, having ships forward-deployed permanently offers the advantage of being able to tailor the individual ship’s equipment fit more precisely to the threat level.

Upgrade options

If the RN decides to go ahead with some form of enhancement, the Batch 2 OPV’s are large enough to be equipped with a considerably heavier weapons fit (eg. German Braunschweig class corvettes are 1,700 tonnes compared to a Batch 2 OPV at 2,000 tonnes). This is technically much more complex than this paper exercise may suggest but there is spare capacity available within the vessels. Below are some outline suggestions for enhancing the OPVs.


This is the more affordable and more likely type of solution that could be adopted. The Bofors 40mm Mk 4 gun is being introduced into the RN inventory and will go to sea on the Type 31 frigates. This modern weapon weighs just 2.3-tonnes and is non-deck penetrating. It can deliver 5 rounds per second to a range of 12.5km and can act both as a close-in weapons systems for air and missile defence or against surface targets such as small boat swarms. 100 rounds are held in the gun ready to fire and there is a range of sophisticated target-optimised 40mm ammunition types available. The Terma Scanter 2D air and surface search radar that currently equips the OPVs is advertised as having fire-control capability but it is possible it may need to be replaced with something more capable for use with the Mk4. The existing 30mm cannon could be moved from the foredeck to one of the waist positions abaft of the bridge and another 30mm added on the other side.

A pair of rotary-wing UAVs that could be housed in TEU containers would be a very cost-effective way to extend the reach and range of the ship. Surveillance and intelligence gathering is an important aspect of any warship capability. There are several small-medium sized RWUAVs already in service with other navies. A good example is the Scheibel Camcopter 100 which has an operating range of up to 180km from its control station and is capable of mission durations up to 6 hours. This could effectively extend an OPV’s surveillance ‘reach’ to an area in excess of 100,000 km2. They can also be weaponised by adding a pair of LMM Martlet missiles which could be used against small craft at distance if needed.

The Long Range Acoustic Device (LRAD) is in service with several navies and law enforcement agencies worldwide and is a non-lethal weapon. Ideal for use against potential threats whose identity and intentions may be uncertain. LRAD can emit painfully loud noise out to 3.5km and can either be used to deliver instructions or deafen and confuse those manning hostile craft.


Adding a medium calibre gun and helicopter hangar would bring the river class more in line with many foreign OPV designs. The Bofors 57mm Mk 110 Mod 0 gun is also going to be introduced to the RN onboard the Type 31. The OPVs have the capacity and a magazine below to accept a deck-penetrating gun such as this. The Mk 110 has a high rate of fire for its size and can lay down 4 rounds per second out to about 17km. This would add significantly to the anti-surface vessel hitting power of the OPV and can also serve as an effective anti-air weapon. It can also fire the ORKA self-guided round which is a highly accurate one-shot-one-kill round for use against air and surface threats. A dedicated fire-control radar would also maximise the effectiveness of the Mk 110.

The RN recently tested a 30mm cannon with a 5-cell missile pannier added to launch the Lightweight Multirole Missile (LMM), known as Martlet and up to 20 will soon be carried by the Wildcat helicopter. The laser-based guidance of the LMM can track targets at up to 5km, although the missile can reach as far as 8km. The LMM is a low-cost and effective solution to small boat or UAV swarms and the addition of these mounts should become standard for deploying frigates and destroyers. Adding LMM to the OPVs would be one of the quickest and simplest ways to enhance their lethality.

The lack of a hangar capable of supporting indigenous helicopter operations has been the subject of much criticism. An embarked Wildcat helicopter would very significantly enhance the capability of the OPV. Its ability to monitor large areas as well as the weapons it carrier makes it a very desirable asset. To keep a helicopter at sea in all demands shelter to protect it from the weather and to allow it to be maintained. Telescopic hangars are a compromise solution that makes good use of limited space. Maintenance may be slightly restricted, lacking a gantry crane used for changing engines but at least the helicopter can remain sustained on board for much longer than if lashed to an open flight deck. To make this change, some structural work would be required to delete the built-in Flyco, re-route air intakes for the generators and the some of the deck landing aids would have to be re-sited. Fuelling arrangements for the helicopter are already in place but adding arrangements for air weapons storage and handling may be more challenging. With more major work it might just be possible to add a permanent hangar. Owning just 28 Wildcat helicopters, it is questionable whether the RN has numbers to allocate to OPV’s on a permanent basis. A helicopter also requires an additional air compliment of around 12 crew to be found and accommodated.


The RN has not had a vessel designated as a corvette in commission since 1950 and has been resistant to the concept since. Despite their adoption by many second-tier navies, they are seen as having much of the cost associated with high-end vessels but lack the protection and full spectrum capability of frigates. They are an expensive way to conduct maritime security but could a liability in combat. The RN is unlikely to go down this route, but the OPVs have the capacity for these modifications and the merits are worthy of some consideration.

The RN is currently assessing which anti-ship missile to purchase for its Interim Surface-Surface Guided Weapon (I-SSGW) requirement. Mounting this type of weapon that put adversaries large combat vessels at risk makes a bigger strategic statement. Backed by a helicopter and a medium calibre gun the corvette at least becomes a complicating factor for enemy naval forces. Adding a more sophisticated radar, an enlarged operations room and soft-kill missile countermeasures start to make for a credible small combatant. Fitting I-SSGW would preclude carrying two TEU containers in their usual position which offer lots of flexible options. Containers could be placed on the flight deck instead but at the expense of helicopter capability. It might even be possible to go full-on “Type 31 Lite” and replace the 30mms with two 40mm Mk4s. Containerised Sea Ceptor missiles could also be mounted but this is all highly unlikely.

Inspiration from Thailand

With technical support from BAE Systems, the Royal Thai Navy has constructed two of its own batch II River-class OPVs. The first vessel, HTMS Krabi, was completed in 2013 and represents the “OPV plus” concept. Krabi is armed with the Oto Melara compact 76mm gun and two 30mm cannons. (There is a video here with good footage of Krabi’s construction in dry dock and entry into service which makes an interesting contrast with the methods used to build the RN vessels). Working on the principle of iterative development, a second and considerably upgraded vessel, HTMS Prachuap Khiri Khan was commissioned in 2019 armed with the improved Oto Melara 76/62 Super Rapid gun and mounts for up to 8 Harpoon Block II anti-ship missiles.

Despite their BAES heritage, the Thai vessels are equipped with the Thales TACTICOS combat management system integrated with Thales-made sensors and platform management system. The philosophy of using the same supplier for the CMS, sensors and integration work reduces costs and complications and the Type 31 will use a similar Thales-led model. The RN’s OPVs use the BAES CMS and selection of equipment where possible that is either supplied by BAES or they already have experience integrating would make sense.

What is most obviously lacking from the Thai vessels and the upgrade options for the RN’s OPVs is real anti-submarine capability. Propelled by noisy diesels and lacking the space even for a compact towed array sonar, adding ASW capability is complicated and probably the only realistic solution would be to utilise USV or UUV-based sensors. Unmanned platforms have range and endurance limitations and have yet to be developed to the stage where they are capable of sinking submarines. A hull-mounted sonar could probably be fitted but are also fairly limited in range and inhibited by the ship’s self-generated noise. At least an ASW Merlin Mk2 operating from a frigate, carrier or land base can theoretically land on the OPV’s flight deck where they might be refuelled or re-armed.

  • HTMS Krabi of the Royal Thai Navy.

  • HTMS Prachuap Khiri Khan. (Photo: Kawin Prayoonyuang)

  • Model of HTMS Prachuap Khiri Khan. The two Thai OPVs do not carry a crane abaft the funnel instead, the second ship has mounts for Harpoon AShM. Note the fire-control radar for the 76mm gun and the soft-kill decoy launchers forward of the bridge. Has the OPV become a corvette?

  • Two Seahawk DS30M A2 30mm cannons (British-made by MSI) are carried each side abaft of the bridge of the Thai river class OPVs. For now, the RN OPVs carry a single DS30M A1 (Referred to as the Automated Small Calibre Gun)

  • The Schiebel’s CAMCOPTER S-100 Rotary Wing Unmanned Air System has a range up to 200 km and can be used for surveillance or could be ‘weaponised’ with two Lightweight Multirole Missiles (LMM)

  • Five-pannier LMM launcher mounted on the 30mm ASCG – trialled on board HMS Sutherland in July 2019. Adding this would be the easiest available option for enhancing the lethality of the RN’s OPVs (and the Frigates and Destroyers) right now.

With five new platforms possessing good endurance, seakeeping and basic survivability features, the RN has the opportunity to significantly improve its order of battle without enormous expenditure. Alternatively, it is possible that the RN may select not to enhance the OPVs at all. There is a strong argument that if the RN has any ‘spare funds’ (looking increasingly unlikely again!) then it might be better invested in adding more capability to the Type 31 frigates which are more suited to going into harm’s way. In an ideal scenario, all vessels would be permanently equipped with a full spectrum of armament, allowing them to be rapidly redeployed at very short notice and able to cope with the highest level threats. With constrained resources, the RN already has to share some equipment between ships as they rotate in and out of high threat areas. Enhancing the OPVs in a modest way makes sense but equipping them to corvette standard would appear to be an unnecessary luxury.