Current & Future Escorts - General Discussion

[Poiuytrewq]

Major cop out.

Not at all.

We don't have enough information available about the three contenders to come to any firm conclusions at present. We could compare the Khareef to Iver Huitfeldt to Valor but is it relevant? At this stage there is no way to tell.

If you want to post detailed plans of the three contenders I would happy to go to through the levels of compartmentalisation, blast proof doors/bulkheads, survivability and resistance to shock etc in minute detail.

Up until then I don't feel like entering into one of your manufactured arguments.

Have a nice day

[NickC]

Reading the following two quotes, I interpreted the 'towed array' to mean the LFAPS VDS ?

"The defence of a task group, or a single platform, heavily depends on underwater Situational Awareness (SA) through the individual and combined use of both the current and new underwater sensors. The new sensors are the Low-Frequency Active-Passive Sonar (LFAPS) on the M-frigate and the Helicopter Long-Range Sonar (HELRAS) on the NH90."

"We only take active acoustic detection of the threat into account. The considered sensors are hull-mounted sonar, towed array and the dipping sonar of the helicopter"

LFAPS is a combination of VDS fish and passive TASS, not VDS fish only, to my understanding. For example, the admiral says "HMNS Van Amstel now has LFAPS", not LFAPS and passive-TASS.

Thanks for info

Translated in google the Dutch to English of first tweet.
"Trials with Low Frequency Active Passive Sonar (LFAPS) a / b from ZrMs Van Amstel. Quantum Leap in the area of submarine control!"

[ArmChairCivvy]

submarine control!"

It is more than control as "bestrijding" is the W in "ASW"

[donald_of_tokyo]

I strongly believe that it will not be possible to build a truly viable "Escort" with the T-31e within the programmes current budget. Either the platforms should be build a gold plated for less money or the budget need to be increased so that a viable platform can be designed and built.

The idea of exports is a red herring regarding the programme. Unless the platform ends up being a wholly UK design that is high innovative, able to be easily adapted to need the needs of customers whilst be competitively priced.

The market for the class of vessel the would include the T-31e is pretty crowded. The T-31e design will have to stand out from other vessels and to support UK infrastructure and manufacturing must be wholly built in the UK using UK sources components. The UKs potential order for five T-31e vessels will not and cannot support any increase in our manufacturing capacity.

Agreed. We need to decide among 3 options:

1: really try hard to make T31e attractive for export: Reduced range (5000nm?) and endurance (30 days), (capability for) carrying heavier weapon loads, choice between two hull-standard options (OPV-standard and Frigate-standard), and some "UK" uniqueness" = mission bay, using a space/weight which can also be used for "conventional" weapon/equipments. (industry oriented)

2: Forget about export, leave the ship yards significantly shrink (at least for "escort building) or even die right after T31e program ends, and just focus on RN requirement. (RN oriented)

3: Stop T31e and relocate all the resources to other projects. (RN oriented)

Where investment and resources should be focused is the T-26, which has already shown its ability to generate export orders. The political brake applies to he speed at which the T-26 will be built must be released. The supply train for the T-26 must be expanded to include those yards involved in the construction of the Carriers. Rosyth should be retained as the final assembly location but workshare both in construction and fitting out needs to be spread around the country. This would give a steady workload to a number of manufacturers and allow them to consider investing in their facilities and capacity enabling them to bid for and build other vessels required by the RN....

I do not buy the idea of using many ship yards in UK. All UK ship yards are too small to be competitive. Keeping the ship yards as it is, is just keeping the current inefficient industry. On the other hand, just closing a ship yard is also not good, because it is the know-how and well-trained engineer/labors which is the core of the "ship building industry".

Why not form a third "center of excellence" in one place (the other 2 is Barrow and Clyde), candidate will be Cammell Laird, to make it all modern efficient yard. For example, why not Babcock buy Cammell Laird, move all the ship building workers from Appledore to Cammell Laird, and invest a lot there?

To sum up the historical stop/start mature of naval shipbuilding needs to be halted. A steady stream of orders needs to be placed across the UKs possible manufacturing capacity. This will require long term secure funding by the Treasury, to provide confidence to that Manufacturers that they can invest in both themselves and their sub-contractors. We have to reach a critical mass of shipbuilding capacity, from where it can stand on its own in the world market.

I agree here. What is not clear for me is, in many case Treasury is supporting the fund available, while the hull number decreases because of development/initial cost and unit-cost rises. For example, T45 program saw no money cut. I also think T26 is not.

One question. If anyway the money spent on ship building is kept, why are RN committing to "number of hulls"? If RN just commit to money, not hull number, Treasury will be much more friendly. (They usually pay for what they promised to pay.) Then, why not industry can survive with it?

[Ron5]

We don't have enough information available about the three contenders to come to any firm conclusions at present. We could compare the Khareef to Iver Huitfeldt to Valor but is it relevant? At this stage there is no way to tell.

So stop making statements as if you did know.

You're sole argument to date is that the T31's will cost so much less, they must have lower standards in every area. That's bull.

[Lord Jim]

The problem there is if the MoD as a whole just commits to the money which the Treasury makes available then all three of the services are going to continue to shrink or more accurately atrophy to a point where you might as well disband them as they will be in most cases operationally ineffective.

The Government needs to accept that Defence Reviews should be driven by policy needs rather then budgetary ones. If the cost of meeting the former is too high the policy needs to change. At present the Government is asking the Military to do far more that it is equipped and manned to do effectively. It either needs to publicly accept that the Navy for example cannot do what it is committed to and withdraw from one or more of these or the budget needs to rise to provide the tools and personnel to do so.

This was one of the key points expressed during the above debate, yet the Minister simple repeated the same old mantra, quoting the same old buzz words. The words we need to hear are MASS, not capability, not transformational or fusion.

[tomuk]

Rosyth had never built a ship before the QEC carriers it was just a refit yard. The carriers should have been built at Harland and Wolf or Cammel Laird.

[Poiuytrewq]

Rosyth had never built a ship before the QEC carriers it was just a refit yard. The carriers should have been built at Harland and Wolf or Cammel Laird.

Personally I would like to see it stay that way. Non Frigate/Destroyer refit repair work at Rosyth and all RFA and Amphibious vessels built at Cammell Laird and H&W. I think the CL/H&W combination could be particularly efficient.

why not Babcock buy Cammell Laird

Not sure about Cammell Laird but H&W might be a possibility however I would like to see them work together ideally.

[Repulse]

I strongly believe that it will not be possible to build a truly viable "Escort" with the T-31e within the programmes current budget

Agreed, anyone who thinks that the sums involved will do anything but deliver a paper half arsed Frigate and there is a mass market for UK built warships is deluded. Selling UK designs and support services to support local ship builders (or maybe specific specialist modules) is the best hope there is.

Investing in a Frigate factory and getting BAE to deliver on a 9 T26s for the price of 8 is the best long term option for the RN and U.K. shipbuilding.

Having a second yard building 100m/2,500t ASW/MHPC Sloops is what is needed to compliment this, starting with 4 extended B3 Rivers.

A third yard focusing on building RFAs is an option but not one I’d see specifically in the national interest.

[Ron5]

Lord Jim wrote:
I strongly believe that it will not be possible to build a truly viable "Escort" with the T-31e within the programmes current budget. Either the platforms should be build a gold plated for less money or the budget need to be increased so that a viable platform can be designed and built.

The idea of exports is a red herring regarding the programme. Unless the platform ends up being a wholly UK design that is high innovative, able to be easily adapted to need the needs of customers whilst be competitively priced.

The market for the class of vessel the would include the T-31e is pretty crowded. The T-31e design will have to stand out from other vessels and to support UK infrastructure and manufacturing must be wholly built in the UK using UK sources components. The UKs potential order for five T-31e vessels will not and cannot support any increase in our manufacturing capacity.

Agreed. We need to decide among 3 options:

1: really try hard to make T31e attractive for export: Reduced range (5000nm?) and endurance (30 days), (capability for) carrying heavier weapon loads, choice between two hull-standard options (OPV-standard and Frigate-standard), and some "UK" uniqueness" = mission bay, using a space/weight which can also be used for "conventional" weapon/equipments. (industry oriented)

The Type 31 has 3 competitive advantages: 1. It is cheap, 2. It will be used by the Royal Navy 3. It will be built with a high degree of commercial practices and is therefore suitable for local country build.

However, the overwhelming first priority in all warship sales is politics. Countries will only do business with countries they want to do business with.

2: Forget about export, leave the ship yards significantly shrink (at least for "escort building) or even die right after T31e program ends, and just focus on RN requirement. (RN oriented)

I think, regardless of exports, whatever CL or Babcocks Type 31 build capability is created, it will eventually whither and die. The NSS offers no realistic solution to the biggest underlying flaw: there is not sufficient long term work for more than one frigate/destroyer shipyard. Its only idea is to build ships with shorter RN lives. An idea that quite clearly would cost a shed load more money to implement. Money which could actually be better spent on having a bigger fleet.

3: Stop T31e and relocate all the resources to other projects. (RN oriented)

Where investment and resources should be focused is the T-26, which has already shown its ability to generate export orders. The political brake applies to he speed at which the T-26 will be built must be released. The supply train for the T-26 must be expanded to include those yards involved in the construction of the Carriers. Rosyth should be retained as the final assembly location but workshare both in construction and fitting out needs to be spread around the country. This would give a steady workload to a number of manufacturers and allow them to consider investing in their facilities and capacity enabling them to bid for and build other vessels required by the RN....

I do not buy the idea of using many ship yards in UK. All UK ship yards are too small to be competitive. Keeping the ship yards as it is, is just keeping the current inefficient industry. On the other hand, just closing a ship yard is also not good, because it is the know-how and well-trained engineer/labors which is the core of the "ship building industry".

Why not form a third "center of excellence" in one place (the other 2 is Barrow and Clyde), candidate will be Cammell Laird, to make it all modern efficient yard. For example, why not Babcock buy Cammell Laird, move all the ship building workers from Appledore to Cammell Laird, and invest a lot there?

That was the UK shipbuilding strategy put in place by Drayson i.e. force the shipyards to merge in order to create one national champion into which all investment could be focused. That strategy didn't survive one change of government but it did set up the Bae "monopoly" that is so disliked on this board. Boy George & Spreadsheet Phil delighted on stomping the idea further into the ground.

To sum up the historical stop/start mature of naval shipbuilding needs to be halted. A steady stream of orders needs to be placed across the UKs possible manufacturing capacity. This will require long term secure funding by the Treasury, to provide confidence to that Manufacturers that they can invest in both themselves and their sub-contractors. We have to reach a critical mass of shipbuilding capacity, from where it can stand on its own in the world market.

I agree here. What is not clear for me is, in many case Treasury is supporting the fund available, while the hull number decreases because of development/initial cost and unit-cost rises. For example, T45 program saw no money cut. I also think T26 is not.

I don't understand your point here. No UK government is going to commit to a long term defense spending plan. It's an idle dream to think they will.

The Type 45 program was cut from 14 ships to 12 to 8 then 6. Some were due to increasing costs, some were due to Treasury cuts.

One question. If anyway the money spent on ship building is kept, why are RN committing to "number of hulls"? If RN just commit to money, not hull number, Treasury will be much more friendly. (They usually pay for what they promised to pay.) Then, why not industry can survive with it?

I fear you have an unworldly view of how the UK government operates.

[serge750]

We all know the main driving force behind the T31 is lack of dosh to commit to increase hull numbers of T26 so the gov can say the haven't reduced hull numbers past the 2010 sdsr, but I actually think the T31 may be good for the RN as a light/frigate/corvette but hey will have to compromise somewhere, personally I would prefer a shorter range ship with a reasonable weapons/sensor fit, ( IMO I think they should build 3 or maybe 4 for the same budget to add capability ) ok they will definatly not be as good as the T26, but, look at the harrier when she first appeared - it was a poor second choice to the P1154 but it filled a niche nobody thought was there...

I think if there is a second batch it will be more directed towards ASW with better silent running qualitys & would be more useful for a ASW inner screen for the carriers

[Tempest414]

I think if we take a baseline Leander as the T-31 blueprint at a cost of 250 million with

Artisan radar
BAE CMS
wildcat capable hangar
Merlin capable flight deck
1 x 57mm , 2 x 30mm , 12 CAMM, FFBNW Phalanx ( weapon would come from the pool )

What can we add to this ship and at what cost

8 cell Mk-41 baseline VII strike length VLS - 11 million pounds each ( based on Finland buy of 4 for $70 million or 13 million pounds full package ) I have set the UK price lower due to the fact we are already buying 24 unit for T-26

CAPTAS-4CI say 30 million pounds each

2 x quad harpoon launcher (taken from T-23 ) say 2 million each

So if we were to buy 5 xMk-41 VLS systems , 2 x CAPTAS-4CI and fit the Harpoon systems from the T-23's this would work out to a extra 125 million on top of the 1.25 billion program budget meaning average cost per ship would be 275 million

[serge750]

Allowing for the usual cost overruns etc just build 4 for now, then hopefully if they turn out to be useful ships a second batch might be justified to keep the magic 19 figure & maybe a small increase in the long run, another 2 or 3 quieter versions for ASW ( quieter + TAS ) if the sub threat is deemed to be addressed...hopefully that would help with the short term crew deficit also

Maybe that might allow the T26 to be the GCS they are designed for.

[donald_of_tokyo]

The Type 31 has 3 competitive advantages: 1. It is cheap, 2. It will be used by the Royal Navy 3. It will be built with a high degree of commercial practices and is therefore suitable for local country build.
However, the overwhelming first priority in all warship sales is politics. Countries will only do business with countries they want to do business with...

Overall, I agree to your point. What UK now need is, "a so-so competitive" UK based light frigate design, to be proposed to nations within a package of a political deal.

But, I'm not sure if T31e will be "cheap" = "compared to contenders". We know its total cost will be 1.25B GBP for 5 hulls, but no information yet for its capability. We need to at least make it "comparable cost to contenders". It is clear British ship building industry is inefficient, so "comparable to" is a big challenge. Keeping a few small yards across the UK is never going to make it efficient, never.

I think, regardless of exports, whatever CL or Babcocks Type 31 build capability is created, it will eventually whither and die. The NSS offers no realistic solution to the biggest underlying flaw: there is not sufficient long term work for more than one frigate/destroyer shipyard.

Umm, so what is your proposal? Just stop T31e and invest the money into T26 program?

... What is not clear for me is, in many case Treasury is supporting the fund available, while the hull number decreases because of development/initial cost and unit-cost rises. For example, T45 program saw no money cut. I also think T26 is not.

I don't understand your point here. No UK government is going to commit to a long term defense spending plan. It's an idle dream to think they will.

My point is, which is much important for industry, hull number or total budget?

UK has 10 years equipment budget program, coupled with "2% GDP" defense budget. The items within the list should show the industry how much money they will be able to bid. What is NOT clear is how much hulls they can build, because of cost inflation. For industry, money shall be more important than hull number, I guess. Isn't building three 333M GBP hull and one 1B GBP hull the same for the industry?

The Type 45 program was cut from 14 ships to 12 to 8 then 6. Some were due to increasing costs, some were due to Treasury cuts.

Thanks. I was re-checking the document.

Referring to "Ministry of Defence: Providing Anti-Air Warfare Capability: The Type 45 Destroyer":
In July 2000 Defence Ministers approved expenditure of £5 billion (with a maximum acceptable cost of £5.47 billion) to procure six (out of a planned class of 12) , but finally £6.46 billion was used for the 6 hulls.

So, it looks like 4 (12 --> 8) was cut from Treasury first, and then ~2 hulls (8 --> 6) were lost by cost overrun.

I fear you have an unworldly view of how the UK government operates.

As I stated, I am talking about 10 years equipment program. I understand this is a (certain level of) commitment. My point is, why industry cannot base their investment plan on this numbers. (But I agree the current optimistic (e.g. efficiency saving) listing always causing 5-10% shortage of money is a big risk for industry, because MOD will surely cut some of the items on the list, which might be related to the ship yards future...)

[Poiuytrewq]

Artisan radar
BAE CMS
wildcat capable hangar
Merlin capable flight deck
1 x 57mm , 2 x 30mm , 12 CAMM, FFBNW Phalanx ( weapon would come from the pool )

A vessel such as you describe would undoubtedly have a role within most Navies but my view is that we shouldn't be replacing T23's with them. They might possibly be a good idea to increase the size of the fleet above 19 escorts but that's all.

A 57mm/76mm looks increasingly unlikley but time will tell.

The part I struggle with is the idea that if we just stick a Captas 4 Compact on Leander we will have a ASW 'escort'. If so why are spending so much on the Type 26's?

I think if Leander has anything going for it, it is as a cost effective long range patrol vessel. A similar role that River Class OPV's would normally undertake outside the EEZ. Perfect for the Falklands and Caribbean etc. They would be a bit 'gold plated' for the OPV tasks but maybe in the 21st century a T31 type vessel is now more suitable for those tasks.

Personally I believe if Leander is to win the T31 competition it will need to go a little bit further for the £250m.

If BAE/CL Leander could come up with a slightly higher spec such as,

Artisan radar
BAE CMS
Wildcat capable hangar
Merlin capable flight deck
HMS, ideally 2050/2150 but probably something cheaper
1 x Mk8
2 x 30mm
12 CAMM
Phalanx FFBNW
4x Harpoon (or equivalent)

Leander really would be a bargain at £250m with this spec and very much in line with a 21st century La Fayette type vessel.

In my opinion if BAE/CL just go with a 117m Leander at baseline spec the Arrowhead 140 or Meko variant will win.

The crucial part remains in getting the T26 build above eight. Ten T26's plus a couple of dedicated TAPS vessels would be enough. Filling the remaining gaps with cost effective £250m Leander type vessel's would be fine in my opinion.

[Caribbean]

The part I struggle with is the idea that if we just stick a Captas 4 Compact on Leander we will have a ASW 'escort'. If so why are spending so much on the Type 26's?

Both Leander and the A140 are said to meet the NATO ASW URN standards, both can support capable HMS's, both support a helicopter capable of delivering LWT's or depth-charges and both claim to have the space to mount a 2087, so it's quite reasonable to regard them as "escorts" (when suitably equipped, of course). They meet the current standards, with a little bit of future-proofing in their ability to mount (future) offboard ASW systems. Properly exploited, they have great potential as littoral ASW platforms.
Why have we spent so much on the T26? Partly for reasons that are nothing to do with the ship itself and more to do with politics and industrial strategy, but mainly because it comfortably exceeds the current standards (perhaps even sets "THE standard" for the future). They will be extremely capable blue water and littoral ASW platforms

[ArmChairCivvy]

with a little bit of future-proofing in their ability to mount (future) offboard ASW systems. Properly exploited, they have great potential as littoral ASW platforms.

All of that agreed. But with the latter, littoral part, off-board MCM systems (interchangeable?) go better... we are, in the end, planning to do away with our dedicated fleet - which is not even self-deploying
- the French have already ordered (their) replacements

sets "THE standard" for the future

- exactly that
- we've seen the price tag, though
- the Canadians seemed to like the option of turning it "into a jack(capable)-of-all-trades" as changes in that direction bring on v little extra cost (and the size of their navy, split between two oceans, demands it, too)

[Repulse]

The T31 always comes back to where does it fit within a balanced fleet what do we need it to do.

IMO the peacetime role of the T45s and T26s are:
- to act as escorts for the RN CSGs rotating with the CVFs through readiness cycles: 4 T45s + 4 T26s
- to provide an escort for Kipion and an Far East deployment (with the new FLSS): 5 T26s
- to provide a FRE and give a level of BMD defence: 2 T45s

I’ve taken liberty to take BAE up on their free 9th T26 ( ).

By rejecting the concept of a global (light) Patrol Frigate (Flag Pole) as anything more than a joke, then by recognising we have 5 OPVs already for a low level of EEZ protection, the only real role I think is left is a ASW Sloop that either operates in or near UK/BOT ports capable of operations in the North Atlantic (acting as TAP) and Littoral wars, protected either by layered land based assets or the CSG.

I personally would go back to the Avenger Class design, change the gun for a 57mm one (no requirement for NGFS), add a 8 cell VLS amidships (initially for a mixture of CAMM and ASROC) and pay for super quiet diesel-electric engines and a TAS. No other bells or whistles (no RAS for example) and build 4 as cheaply as possible.

[Caribbean]

with the latter, littoral part, off-board MCM systems (interchangeable?) go better...

No argument with that. I think the key word is "interchangeable". Use different "modules" for different missions - though in our case, it looks like the "modules" will be standard sized offboard systems, rather than stanflex or LCS containers.

[Tempest414]

A 57mm/76mm looks increasingly unlikley but time will tell.

Right now I don't mind if T31 gets a Mk-8 so from now on I will just say a main gun

The part I struggle with is the idea that if we just stick a Captas 4 Compact on Leander we will have a ASW 'escort'. If so why are spending so much on the Type 26's?

I am not saying that just adding CAPTAS-4 CI will make T-31 a top end ASW like T-26 but if it could work with a P-8 to cover TAPS then this will be a big plus for RN

I think it will be possible to get 3 Leander's fitted with

Artisan Radar ( taken from T23)
BAE-CMS
Wildcat capable hangar
Merlin capable flight deck
1 x Main gun ( taken from RN stocks )
2 x 30mm ( taken from RN stocks )
12 CAMM
FFBNW Phalanx ( Weapon to come from RN pool )
1 x 8 cell Mk-41 VLS
4 to 8 Harpoon ( taken from RN stocks )

For 260 million and then build the last 2 for 290 to 300 million with CAPTAS-4 CI

[Poiuytrewq]

Thanks,

so it's quite reasonable to regard them as "escorts"

Of course but will they actually be properly equipped? In this day and age what do they need in terms of offensive/defensive capability to be regarded as credible. It really all depends on what they are going to be escorting and against what opposition.

The T23's they are replacing should be the benchmark. How many other countries worldwide are replacing frigates with vessels that are less capable than the preceding class?

Properly exploited, they have great potential as littoral ASW platforms.

Absolutely but will that potential be exploited? At present are we even sure that they will receive a basic hull mounted sonar?

ACC's point about the overlap with the MH(P)C programme in terms of Littoral ASW is well made. If HMG would commit to funding 6 to 8 credible T31 escort Frigates then RN will be set up for decades and the MHC programme will be a lot more straightforward. Unfortunately, I'm not convinced the penny has dropped in Whitehall as of yet, at least partly due to Brexit blinkers.

We all know the problems but what is the solution? We are making bad decisions (again) due to another fiscal black hole. I believe there is money tied up in the T26 programme that can yet be released, but it may well require more money to be spent to release it. Overall, the UK needs a coherent Naval strategy including a clear and costed procurement plan that will deliver the vessels RN needs on time and on budget. A plan that Governments of all colours can support and whilst it should be ambitious enough to keep RN with the mass and capability it needs to fight and win it should not be overly ambitious thereby creating another black hole down the line.

RN needs 24 escorts, a way must be found to provide them.

[Lord Jim]

I think we need to give the discussion on the T-31e a rest until we have further information. We are going around in circles between what we think should happen to what we think will happen and everything in between.

[Ron5]

Donald-san, thank you for your replies. Here's some additional comments.

It is clear British ship building industry is inefficient, so "comparable to" is a big challenge.

Cammell Laird does not agree with you.

Umm, so what is your proposal? Just stop T31e and invest the money into T26 program?

Throw away the NSS which isn't a strategy but merely a thinly veiled excuse for building cheap frigates. In particular, throw away the absurd idea that there is enough warship building capacity in the UK to sustain meaningful competition.

Develop a proper long term strategy around creating and investing in single site surface warship shipbuilding. Just like the massive investment made at Barrow in order to produce excellent submarines at excellent prices. Enable a world class efficient frigate factory. Create a long term build plan, commit to it and invest and make orders accordingly i.e. if 8 T26 are to be acquired, order 8 so that the shipyard & Treasury can invest in creating modern infrastructure.

By all means open up international competition for RFA and other non-complex warships that commercial yards can reasonable be expected to successfully build. But add value to any UK bids commensurate with the taxes the shipbuilders & workers will pay back to the Treasury and add value for the social benefits of maintaining employment in the UK. Develop a black list of countries who will not be invited to bid. Start the black list with Russia, China and North Korea. Add Germany, Spain & France based on their actions toward the UK. Then decide a winner.

My point is, why industry cannot base their investment plan on this numbers.

Because they are not reliable. Industry can only base their investments on signed and sealed orders not subject to capricious delays and cancellation. Who doesn't believe that one or more of the carriers would have been cancelled if they had not been tied up with bullet proof contracts?

[Ron5]

The T23's they are replacing should be the benchmark. How many other countries worldwide are replacing frigates with vessels that are less capable than the preceding class?

Comparing the published equipment, sensor, comms, & CMS of the T31 contenders against the T23 GP, the only meaningful difference in favor of the T23GP would appear to be the HMS and lower T23 noise signature. On the plus side, the T31s offer mission bays, CIWS, smaller crew, lower running costs and probably a lower RCS.

[Caribbean]

Comparing the published equipment, sensor, comms, & CMS of the T31 contenders against the T23 GP, the only meaningful difference in favor of the T23GP would appear to be the HMS and lower T23 noise signature. On the plus side, the T31s offer mission bays, CIWS, smaller crew, lower running costs and probably a lower RCS.

I would just add that there is still the possibility that the Sonar 2050's may be ported over as well (and even upgraded to the 2050TR standard of the T23ASWs) - the cost per hull is not great.
With regard to the URN signature, I think that we tend to overlook the fact that what was cutting-edge hull and machinery design twenty years ago, is now pretty much standard MOTs (and, as the RSS has shown with it's DNV Silent-R rating, COTS) technology, certainly at lower speeds.