Why The Finnish Navy has added ASW capability even in FACs? Does Towing a sonar at low speeds from fast attack craft with torpedoes sound reasonable while they already had compact commercial sonar? They did it for shallow water ASW.
The answer is hidden in the Finnish Navy Fleet composition.
There are 8 combatants in the fleet, there are no dedicated ASW ships in the fleet. Also no dedicated ASW helicopters or aircraft of any kind. Also, I remember that commercial sonar was used at first, and more or less it does the job as intended in littoral (shallow) waters, and after a point they added another sonar on some other ships (but I remember this weakly, so don't take my words for granted).
So all in all a solution becomes valid within a Navy's doctrinal approach.
LWT like Leonardo MU90, has an effective range of 12 to 25 km.
Tuzla Class are littoral patrol boats. Their range is no more than 1900km. So they are not going to take on the responsibilities of a Corvette or even a Fast Attack Boat. (Kilic Class has a range of 1900km too. But have a different purpose, even though it is essentially to be deployed for littoral waters like Tuzla Class)
Tuzla Class has a specific job of being an ASW vessel. Any submarine coming close to our harbours and littoral shipping lines will have to be detected and if necessary, targeted by it, without herself being a target. Also she has to be able to pluck out any submarine lurking at the bottom of the shallow waters close to our coasts.
How is a Tuzla class to defend herself against a submarine and against an AShM fired from a helicopter ?
It needs a better sonar and better self defence weaponry to be more versatile.
From this point of view, even the ocean-going ASW destroyers are not capable of countering or detecting submarines beyond the submarine's sensing capability. And launching a torpedo is not the primary strength of a submarine, it remains hidden until its functions are needed. Thus, ASW is mainly aimed at the submarines that are set for an infiltration, shadowing mission and when the submarine passes these blockades there may be not much to do but unleash all ASW capability of the fleet or the Navy.
In addition, AShM is not a valid target set for a 300 meter boat, I doubt anyone will fire a full fledged AShM at a 300 ton target as it is likely to miss or even if hit it might sink, here I will be more concerned about Hellfire, Spike-NLOS or loitering munitions that can definitely hit and render the ship immobile. The ultimate goal in naval warfare is to disable / render immobile a ship so that the enemy has to send a rescue team, a ship, and more to the area to make it vulnerable, etc.
To counter Hellfire, Spike and other NLOS I think instead of a CIWS we need some manpads, anti-UAV solutions and better sensors to detect carrier of these threats and a USV will work dearly for the case. I think the winning part of an upgrade will be the addition of a USV on NTPB.
USV (with sonar or Sungur depending on the mission), Sungur-Levent launcher, MAR-D or scaled down ARDA (CENK-300N)* and CENK-100 or AKREP-200N* for better target tracking and maybe ORKA/TORK torpedo could be the maximum of a possible MLU. Also i believe in a pure HAS mode Levent missile can attain longer ranges.
*These will be luxury if happens.
I think if TORK goes through and a miniature torpedo is introduced after the project, these can be used with UAVs similar to how Corvettes/Frigates use helicopters to deliver a dipping sonar and torpedo bundle to hunt and kill.
