One thing is certain about the planned Type 31 Frigate for the Royal Navy – there is no consensus on what it should be or what it should do.
This article was submitted to the UK Defence Journal by Alex Matthews, Alex has undertaken some strategic consulting whilst at university and has twice in recent years directed the University of Birmingham Model United Nations Society’s annual political crisis and war games simulation, one of the largest of its type in Europe not run by a government or armed forces. His approach to the subject comes from professional training in engineering and his passion as an amateur historian.
The role of the large, air defence escort is taken by the Type 45 destroyer, the anti-submarine frigate role is to be passed from the Type 23 to the Type 26, constabulary duties are the domain of the River class offshore patrol vessels. The only common type of smaller surface vessel not operated by the RN is the corvette, a term nobody wants to talk about.
Two schools of thought exist on corvette design. The first of which is a smaller, more affordable frigate design suitable for countries that want to project their interests at sea without the capital costs associated with maintaining a proper navy. The second option is a fast missile boat intended for swarming enemy defences in large numbers and drowning their fleet through volume of fire. European navies favour the former. Russia, Iran and China favour the latter. The Royal Navy appears afraid of wanting a corvette in the from of the Type 31, as such a designation would carry connotations of a small vessel with limited defensive capabilities, hardly desirable descriptions of a vessel seemingly conceived with the export market in mind. Another key factor in the Type 31 is cost, allowing the treasury to spend less on defence whilst convincing the public that they’re spending more.
This is not the first time a navy has found itself afraid of a particular word. During the Second World War, the United States Navy ordered a sextet of ‘Large Cruisers’ called the Alaska Class. A common description of these vessels was through the word the US Navy were eager to avoid; battlecruiser. The original idea behind the battlecruiser was a large ship armed with the guns of a battleship, but the armour of a cruiser. This would give such a vessel the speed to chase a fleeing enemy battlefleet and destroy any damaged battleships before they could escape. Their heavy armament ultimately lead many naval commanders to view them as conventional battleships until their limited armour protection, combined with unsafe ammunition handling procedures and the gung ho command style of Admiral Beatty resulted in the loss of three British battlecruisers at Jutland in 1916.
In a Second World War context, a battlecruiser would be invaluable for hunting down enemy cruisers, as battleship on battleship actions were now by far the exception of naval combat. The Alaska class was designed with the intention of being a ‘cruiser killer’ capable of hunting down and destroying the large fleets of Japanese cruisers that could inflict heavy disruption on allied supply convoys in a protracted war in the Pacific. By the time the first two ships had been completed, the Japanese cruiser fleets had been broken and the Alaska class never saw action in their intended role, with ships 3-6 being cancelled and the two completed vessels being decommissioned after less than three years service.
The success of the Alaska was that naval planners thought of it not as a light battleship, but as a very heavy cruiser. This definition allowed them to avoid the stigma associated with battlecruiser whilst building a ship that took the concept to its logical conclusion. The lesson for the Royal Navy would be to build the Type 31 not as a light frigate, but as a ‘corvette killer’.
So what would a corvette hunter or heavy corvette feature? To fulfil the role it would need to be fast enough to catch up with the corvettes and missile boats it is likely to face, with an armament suitable for engaging a large number of small vessels. As such a vessel might be expected to last 20-25 years in service the inclusion of active stealth design should be considered as well. Corvettes and missile boats typically carry a single main gun, 8-16 anti-ship missiles, 4-10 air defence missiles and a point defence system. To counter this system it must be possible to overwhelm the defences and survive a response.
An aluminium hull would lighten the draft, increasing speed and acceleration whilst reducing capacity for detection by sonar, as compared with a steel hull. However as the Royal Navy knows all too well from the Falklands War, aluminium ships burn faster and hotter than steel ships reducing their survivability. Gas turbine engines common to frigates and destroyers will be of use in this design as well, as the Type 31 will need the speed to engage fast travelling corvettes, and the reliability to ensure that the ship can safely outrun anything larger.
Offensive measures should be built around missile and gun options. Although missiles carry advantages of range and payload, gunfire shells cannot be intercepted by air defence missiles or point defence systems. A heavy gun of either 4.5” or 5” calibre is a staple of modern escorts. Such a weapon has proven value not only in providing naval fire support for amphibious operations but also in engaging small and medium sized targets. A single turret could be incorporated simply into any design from existing developments. Two of these turrets, with one mounted on the front and another on the rear could increase the capacity of the ship to engage small surface ships whilst reducing the chance of a misfire disabling the ship’s offensive capacity. Another option would be for the ship to carry a pair of 30mm autocannons located amidships, as is the case with the Type 45 destroyer. Whilst these weapons are less effective at engaging larger vessels, their higher rate of fire than the main gun make them a better choice than a second large gun. A large gun at the rear would also preclude the presence of a shipborne helicopter.
The extent to which a missile armament should be provided is more difficult. Major NATO anti-ship options take the form of the Boeing Harpoon and the MBDA Exocet, neither of which compare favourably with the Russian P-800 Oniks and P-1000 Vulkan entering service. Current options for an anti-ship missile appear focused on Marlet and Sea Venom for maritime helicopters, with Harpoon being phased out without replacement. The MBDA SCALP missile could provide a viable long term solution, with either extended service of Harpoon or Exocet being used in the interim. The standard practise of equipping ships with 8 Harpoon missiles is also a serious limitation in a protracted engagement with corvettes. As this design of the Type 31 would not be intended for supporting ground operations, there is no need for land attack cruise missiles, allowing for an increased load of anti-ship missiles, either in VLS tubes or in angled silos.
Survivability measures for such a ship would be twofold. Passive defences would include a stealthy hull configuration, and decoy launchers. For more active measures, a VLS with 8 missile tubes would be capable of long distance air defence, especially given that the new generation ‘Sea Ceptor’ Anti-aircraft missiles are designed to be ‘quad packed’ into a single tube. A point defence system, most likely in the form of a single superstructure mounted Phalanx CIWS would be needed to provide a second layer of defence against anti-ship missiles.
Finally the ship should have a flight deck and hangar capable of supporting a single helicopter, presumably a helicopter in the weight class of a Wildcat as opposed to the larger Merlin. A helicopter is essential for target scouting and aerial fire support with torpedoes and missiles. A helicopter capacity also includes the potential for the Type 31 conducting anti-submarine operations in support of the more dedicated Type 26. The capacity to support a helicopter fills the naval aviation requirement that the River class OPV critically lacks, which may have been a factor behind the limited international interest in the design.
A vessel in this configuration would have the teeth to fight against corvettes, whilst providing planners with a ship that can be produced more cheaply than larger frigates. Overseas deployments could involve maritime security and counter-piracy in peacetime, and patrol escorts for battlegroups in war operations. It should also be possible for such a vessel to be constructed under a specification of £200 million, suitable for the constrained budget of the British Armed Forces as well as filling a niche role in the export market.