Should the Type 31e frigate be reclassified as a corvette?

Plymouth MP, Luke Pollard, suggested last week in Parliament that “the debate around the Type 31e Frigate could be resolved simply if we renamed if from a frigate to a corvette“. This proposal is unlikely to be welcomed by the Navy, the MoD or industrial partners but does raises questions about the Type 31’s capabilities and results from the general confusion over how surface combatants are to be classified.

How are warships classified?

Unlike merchant ships, there are no internationally recognised standards for the way warships are classified. Over time conventions have evolved but are not applied consistently. There is enormous variation in size between vessels that have the same classification, even within NATO. A very crude classification scale in descending order of surface combatant capability would be (1) aircraft carriers and battleships, (2) cruisers, (3) destroyers and frigates, (4) corvettes and fast attack craft and (5) Offshore Patrol Vessels.

The main trend is that warships are much bigger than their equivalents in the past. The motivation to downgrade classifications may partly come from a wish to play down their cost and size from politicians and the Treasury. The RN and majority of NATO navies generally designate surface combatants optimised for anti-air warfare as destroyers, and those designed for anti-submarine warfare, as frigates. The Type 26 frigate will be almost as large as the Type 45 destroyer and at 8,000 tons will be nearly double the displacement of the Type 23 it replaces.

HMS Belfast (Type 26 frigate) and HMS Belfast (1938)

This is a mock up of how the future Type 26 Frigate, HMS Belfast might look alongside the museum ship HMS Belfast (1938). It demonstrates how classification of warships has changed. The Type 26 frigate of c2028 is 70% WWII Cruiser size. (The Type 26 actually has a broader beam than the cruiser). A typical frigate of WWII displaced just 1,400 tons.

Defining a corvette

Modern Corvettes are usually considered to be the smallest credible surface combatant. Larger and more capable than a fast attack or patrol vessel but smaller than a frigate. Some may have the weapons and sensors fit similar to a frigate but compromise on range and endurance to make them smaller and cheaper. Corvettes are normally operated by second-tier navies that may need to engage in full naval combat operations, but not for a sustained period or over long distances. (This excellent piece by Chuck Hill discusses the definition of a corvette in more depth).

Examples are the small 650-ton Swedish Visby class stealth corvette that has a range of just 2,550 nm and is designed to primarily to fight in the confined waters of the Baltic. A more typical mid-range corvette is the German Navy’s Braunschweig class that have a range of 4,000nm and 7-day endurance without support. Possibly the best all-round corvette design at sea today is the Russian Steregushchiy class which have balanced armament, genuine anti-submarine capability, 15-day endurance and 3,800nm range. 

At the top end of the endurance, scale is the British-built Khareef class of the Omani Navy that have a range of 4,500 nm and can operate for 21-days without support. An enlarged version of the Khareef design forms the basis of the BAE Systems/Cammel Laird Leander concept which is a contender for the Type 31e frigate.

The last vessel designated a corvette in service with the RN, HMS Oakham Castle, decommissioned in 1950. The castle class were simple 1,060 ton ships, evolved from the more famous flower class which were designed to be quickly mass produced for convoy escort work in WWII. The Type 31e is likely to displace around 3-4,000 tons, have little in common with its wartime ancestors and will be larger than any corvette in service with any of the world’s navies.

How will the Type 31e meet the Royal Navy’s requirements?

The outline specification issued for the Type 31e frigate states it should be “capable of global operations, in between the marginal ice zones and including the Gulf/Red Sea, with self-sustaining food and water for 28 days and a fuel range of 6,500 nm at economical speeds.” While the combat capability and survivability of Type 31 may be more limited than the typical frigate, the RN is very clear that the ship it wants must be able to serve around the globe. Type 23 frigate has a range of 7,500 nm and can stay at sea without replenishment for around 40 days. Type 31e is not expected to match this, but will have greater endurance than most corvettes.

The emerging concept of operations for the RN frigate force is that in the main, the high-end Type 26 will escort the aircraft carriers while the lower-end, general purpose Type 31e will conduct maritime security duties. (Whether this role could be done by cheaper OPVs instead is another discussion). Typically this might include deployments to the Caribbean, Indian Ocean or South Atlantic where endurance and sea-keeping are important factors.

Type 31e splits opinion

As the comments made in Parliament suggest, the Type 31e is becoming increasingly controversial. Supporters are keen to see a broad revival in UK shipbuilding and break the cycle of ever-fewer and more expensive warships. Off-board, unmanned systems may yet be able to mitigate the budget weapon and sensor fit and poor baseline anti-submarine capability. Opponents argue against the National Shipbuilding Strategy, saying it would be more efficient to cede all warship building to a single ‘super yard’ (BAE Systems) and see the Type 31e as a dangerously compromised “snatch Land Rover of the seas”. There is fierce debate about whether the RN would be better off abandoning Type 31e in favour of obtaining a further two Type 26s, or if it is better to maximise hull numbers and hold out for the chance of a warship export revival.

Growing awareness about of the state of the navy in Parliament

The four and a half hour defence debate in Parliament on the 11th January proved there are a growing number of MPs who have a real understanding of UK defence issues and even a few with a genuine grip on the specific problems faced by the RN. There was also an encouraging cross-party consensus against any government attempt to make further cuts. However, defence is still a relatively low priority in Parliament, only around 45 out of the UK’s 650 MPs attended the debate. The column inches and hand-wringing devoted to the similarly parlous state of the NHS will outnumber defence by a hundred to one.

Luke Pollard did make a substantive point about how the very low price tag will make the Type 31e such a big step down from the Type 26. However, the RN does not want limited-range corvettes and the export appeal of the Type 31e would be diminished by this classification. The designation of “light frigate” is a better fit, reflecting the global capability of the ship, even if its anti-submarine credentials are in doubt.