054/A FFG Thread II

[sealordlawrence]

¦^ÂÃ: 054 Series Frigate Thread 2

The minute you have the ability to set the operating depth of a sonar it is a variable depth sonar.

The reason why submarines have towed sonars whose depth can not be manipulated is because the submarine itself can vary its depth, something a frigate can obviously not do.

If there is a picture of an 054A with anything like a TAS/VDS could someone please post it here.

 

[tphuang]

Re: ¦^ÂÃ: 054 Series Frigate Thread 2

thpuang,

Wrong. TAS/VDS are the same device, towed behind the vessel with VDS being set to operate at different depths in order to get round the problems caused by different layers in the water, check the specifications of any western ASW ship and you will not find seperate TAS/VDS. A hull mounted sonar can never provide anywhere close to the range of a TAS/VDS, it is not a matter of opinion but a fact. That is just the way the laws of physics work. If 054A does have a TAS, it almost certainly has VDS as the TAS used by the PLAN (ESS-1) are based on the French DUBV-43 VDS which is a VDS. However, if these ships only have a TAS without VDS capability, then first it is very strange, and secondly it is pathetic and makes PLAN ASW capability look lame. What is the evidence that the 054A has a towed array?

A UK example:

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Helicopters, submarines etc, you just repeated what I said. With one exception, you can not use a submarine as an example for a frigate. A submarine is a giant VDS, it can vary its own depth. You can not do this with a frigate so it has to vary the depth of the sonar. Hence why submarines have what you call a TAS which in itself can not be varied, but the submarine towing it can vary its depth.

Working with some half-knowledge here maybe ...
Isn't it that, technicly, a VDS is a small, sub-surface vehicle (an unmanned mini sub basicly) that is trailed on a cable and can be depth controlled, while a TAS is a really long cable that has an array of hydrophones attached to it's length (and that in modern versions can also be brought to a specified depth)?
But today the terms may have become less resoluble.
So the TAS would be a (passive) low frequency system, while the VDS more likely works in a med-frequency range (smaller array size) and might more easily be used in an active role as well.

The minute you have the ability to set the operating depth of a sonar it is a variable depth sonar.

The reason why submarines have towed sonars whose depth can not be manipulated is because the submarine itself can vary its depth, something a frigate can obviously not do.

If there is a picture of an 054A with anything like a TAS/VDS could someone please post it here.

you can do a search on TAS for this thread. But I just added it here. You can also check which holes coming out of the back of the ship is for TAS. I also attached a couple of 053s with a visible TAS for example. That way, it seems to indicate 052B/C have it too.

Your description of TAS/VDS seems to just be my definition of TAS (which is an array of hydrophone trailing). While my image of VDS is similar to what Scratch described. Of something that's almost like a dipping sonar, except that it's lowered from a ship. To me, there is a clear difference between the two. Now, if your definition of VDS is any sonar that can be lowered to different depth, then I'd think all modern TAS are VDS.

As for your argument about the range of TAS vs hull mounted sonar, that's probably true. But that doesn't change the fact that you have to operate at a certain speed and maneuver pattern to detect submarines. At the same time, you also need other assets like helicopter with dipping sonar and sonobuoys to establish accurate position of the target. And if you get closer to the target, you can use the HMS to find its location. I'm not that familiar on submarine hunting tactics, so I can only guess what a modern ASW team would try. Regardless, you would want to use every sonar suite you have to find the targets.

 

[sealordlawrence]

¦^ÂÃ: Re: ¦^ÂÃ: 054 Series Frigate Thread 2

you can do a search on TAS for this thread. But I just added it here. You can also check which holes coming out of the back of the ship is for TAS. I also attached a couple of 053s with a visible TAS for example. That way, it seems to indicate 052B/C have it too.

I did, and none of those are definitive, holes in the back of ships do not mean that a VDS is installed, even the one with the cable coming out of the back is less than decisive. What we need is the picture of the "fish".

Your description of TAS/VDS seems to just be my definition of TAS (which is an array of hydrophone trailing). While my image of VDS is similar to what Scratch described. Of something that's almost like a dipping sonar, except that it's lowered from a ship. To me, there is a clear difference between the two. Now, if your definition of VDS is any sonar that can be lowered to different depth, then I'd think all modern TAS are VDS.

VDS is not a dipping sonar, it is lowered out of the back of the ship and then towed behind at a set depths, depending on water layers. Your final sentence is correct. The clue is in the name, a variable depth sonar is a sonar that can have its operating depth varied.

As for your argument about the range of TAS vs hull mounted sonar, that's probably true. But that doesn't change the fact that you have to operate at a certain speed and maneuver pattern to detect submarines. At the same time, you also need other assets like helicopter with dipping sonar and sonobuoys to establish accurate position of the target. And if you get closer to the target, you can use the HMS to find its location. I'm not that familiar on submarine hunting tactics, so I can only guess what a modern ASW team would try. Regardless, you would want to use every sonar suite you have to find the targets.

It is not probably true, it is completely true, again, laws of physics, if you can not get below the isothermic layer you are going to have a very short ranged sonar, and the only way you can do that is with a VDS. Other assets are useful but the real deep diving sub-hunting capability coming from VDS. It is plausible that the PLAN is simply draqqing a passive array behind them- if they are it is virtually unique and quite pointless. What is missing is at the moment is the fish.

 

[plawolf]

I always thought of towed sonar as a very advanced VDS.

With a TAS, the array of hydraphones can be hundreds of meters long if not longer. That means instead of dragging it along as a straight horizontal line behind the ship at differing depths, you can have the entire array 'droop' in a diagonal stance behind the ship, so you get a "/" effect instead of simply a "---" effect.

The significance of this characteristic is that a TAS can easily monitor several different lays at the same time, which would be a great improvement over a VDS which would only be able to monitor the lay it is in.

 

[tphuang]

Re: ¦^ÂÃ: Re: ¦^ÂÃ: 054 Series Frigate Thread 2

I did, and none of those are definitive, holes in the back of ships do not mean that a VDS is installed, even the one with the cable coming out of the back is less than decisive. What we need is the picture of the "fish".

on top of that, the captain of one of the Sov ships also said 054 has TAS in a TV interview. And if they put TAS on back of Jiangwei-I ships as you can see there. And 054A ship has a cable coming out of same hole as the one on Jiangwei-I, you make your own judgment. That is unless you don't think the ones on 540 and 542 are TAS. But if you are waiting for a picture of the actual tow cable or the hydropohone, that might be a while, since you are unlikely to see the deck under the helipad to be revealed on 054A as it is on Jiangwei-I. Just think about how many years 052 has existed and how many photos of its VDS we have seen.

VDS is not a dipping sonar, it is lowered out of the back of the ship and then towed behind at a set depths, depending on water layers. Your final sentence is correct. The clue is in the name, a variable depth sonar is a sonar that can have its operating depth varied.

did you look at my first diagram? Scratch and I both thought of VDS as having a cable lowering one small, sub-surface vehicle to different depth. What do you think dipping sonar is?

It is not probably true, it is completely true, again, laws of physics, if you can not get below the isothermic layer you are going to have a very short ranged sonar, and the only way you can do that is with a VDS. Other assets are useful but the real deep diving sub-hunting capability coming from VDS. It is plausible that the PLAN is simply draqqing a passive array behind them- if they are it is virtually unique and quite pointless. What is missing is at the moment is the fish.

actually, it's just as important to have a helicopter with good dipping sonar, because it can also get through those layers that you are talking about. At the same time, it can chase down the submarines much more easily, launch sonobuoys and carry torpedo at the same time.

As for seeing "the fish", you are not going to see it for a while. So you can either choose to believe the cable coming out of 054A is an operational TAS or PLAN just decided that it wants to put a trawler out there to catch fish.

 

[sealordlawrence]

¦^ÂÃ: Re: ¦^ÂÃ: Re: ¦^ÂÃ: 054 Series Frigate Thread 2

tphuang,

You are still confused, a dipping sonar is a sonar that you dip, it is a stationary device unlike a towed VDS. On a srface ship its primary use would be for in port defence against swimmer threats. A few companies are trying to sell such things but I am not aware of any in service with warships at this time.

A helicopter is a useful asset, but again you are getting carried a way. A helicopter can not carry a sinar as powerful as one that a ship can tow, a dipping sonar can not go as deep as a towed array and helicopters suffer from availability relating issues relating to fuel capacity, crew endurance, weather conditions and mechanical failure in a way that the parent ship does not.

The 054A also appears to lack any method of launching the fish, there is no hatch in the rear of the ship as would be required, particularly for a large active array.And those holes could be for anything. The 054A may well have a TAS, but we need more evidence.

 

[Scratch]

Re: ¦^ÂÃ: Re: ¦^ÂÃ: Re: ¦^ÂÃ: 054 Series Frigate Thread 2

To illustrate my, an I think also tphuang's understanding of those, I'll do a little illustration.

I think we do know that the term "dipping sonar" does mean a housing containing a sonar array hanging from, i.e., a helo via a cable. (pic-1)
The VDS, wich tphuang described using the key words "almost like a dipping sonar", as again being a sonar array in a container housing being dragged along at the end of a tow cable. (pic-2)
While in our understanding the term TAS is ment to describe a long cable with a lot of hydrophones attached to it, making the cable itself the sonar array. (pic-3)
That is irrespectiv of the fact that such an array may have the capability to be operated at different depths.
Now, I've also seen a slightly different classification. That uses "TAS" as a generic term wich can be further distinguished in "VDS" (pic-2) and "passive hydrophone array" (pic-3).

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[Spartan95]

Re: ¦^ÂÃ: Re: ¦^ÂÃ: Re: ¦^ÂÃ: 054 Series Frigate Thread 2

thpuang,

Wrong. TAS/VDS are the same device, towed behind the vessel with VDS being set to operate at different depths in order to get round the problems caused by different layers in the water, check the specifications of any western ASW ship and you will not find seperate TAS/VDS. A hull mounted sonar can never provide anywhere close to the range of a TAS/VDS, it is not a matter of opinion but a fact. That is just the way the laws of physics work. If 054A does have a TAS, it almost certainly has VDS as the TAS used by the PLAN (ESS-1) are based on the French DUBV-43 VDS which is a VDS. However, if these ships only have a TAS without VDS capability, then first it is very strange, and secondly it is pathetic and makes PLAN ASW capability look lame. What is the evidence that the 054A has a towed array?

A UK example:

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Helicopters, submarines etc, you just repeated what I said. With one exception, you can not use a submarine as an example for a frigate. A submarine is a giant VDS, it can vary its own depth. You can not do this with a frigate so it has to vary the depth of the sonar. Hence why submarines have what you call a TAS which in itself can not be varied, but the submarine towing it can vary its depth.

Pardon me for joining the discussion on sonars.

Traditionally, Towed Array Sonar (TAS) refers to a length of cable towed behind a ship with a series of hydrophones (passive and active) at the end of the cable. The length of the hydrophones can be hundreds of meters long (not including the length of cable towing it), hence making a TAS a very long tail behind a ship. Here's an example of a TAS used onboard a submarine that is reflective of what a ship uses:

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A Variable Depth Sonar (VDS) typically refers to a much shorter "tail" with a "fish" (as you have mentioned). The sensors are entirely within the "fish" and its depth is controlled by fins on the "fish" as well as varying the speed of the vessel towing it. Here's an example of a VDS used by the USN:

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The 2 systems are clearly distinct from each other. However, in recent times, there has been new "hybrid" systems that combine TAS with VDS. This is where a "fish" is used to reel out a TAS (instead of reeling it out from the ship). 1 example is the Thales Combined Active / Passive Towed Array Sonar (CAPTAS):

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From the looks of the hole at the stern of the 054, it is quite clear that is at most a TAS. It cannot be a VDS since it is not large enough for a "fish" to be deployed through it.

 

[sealordlawrence]

¦^ÂÃ: 054 Series Frigate Thread 2

Actually the AN/SQS-35 is frequently used as a fish to provide a VDS capability to generic arrays. Submarines are not comparable as the submarine itself is the fish.

 

[Spartan95]

Re: ¦^ÂÃ: 054 Series Frigate Thread 2

Actually the AN/SQS-35 is frequently used as a fish to provide a VDS capability to generic arrays. Submarines are not comparable as the submarine itself is the fish.

Surface warships uses TAS similar to the example that I quoted for submarine (i.e., cable + hydrophone only. No "fish" attached.). Hence, you will find that quite a few surface warships have a hole at the stern similar to that of the Type 054 through which a TAS is streamed.

For ships that uses a VDS or a hybrid (such as the CAPTAS), a much larger opening will be required to stream the equipment into the water.

--- EDIT ---

The length of TAS is often classified. However, this link provides an indication of just how long a TAS can be:

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AN/SQR-19 Tactical Towed Array SONAR (TACTAS)

The AN/SQR-19 Tactical Towed Array SONAR (TACTAS) provides very long-range passive detection of enemy submarines. TACTAS is a long cable full of microphones that is towed about a mile behind the ship. It is towed so far behind the ship so as to not let noise radiating from the shipitself interfere with the noise picked up from targets. Using that noise can determine exactly what ship or submarine is being tracked. The AN/SQR-19B Tactical Array SONAR (TACTAS) is a passive towed array system which provides the ability to detect, classify, and track a large number of submarine contacts at increased ranges. TACTAS is a component sensor of the AN/SQQ-89(V)6 ASW Combat System, and provides significant improvements in passive detection and localization, searching throughout 360 degrees at tactical ship speeds. Processing of complex TACTAS data is performed by the largest computer program assembly ever developed for surface ship anti-submarine warfare.

Meteorology and Oceanography Center Detachment TACTAS support products describe oceanographic and acoustic conditions (using range dependent models) in the prosecution area for towed array ships tasked by CTF-69 for ASW operations. This message is provided when own ship Sonar In-situ Mode Assessment System (SIMAS) or the Mobile Environmental Team�s Mobile Oceanographic Support System MOSS) are not available. It is tailored to the specific towed array carried onboard. The message is transmitted prior to the start of a prosecution and daily thereafter or as requested.

There is a useful diagram provided in the link illustrating the various sections of a TAS.