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H4 Sonar Buoy Employment


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In layman's terms what would be the sequence of action for a MH-60B dropping sonar buoys in search of an anticipated, not necessarily suspected diesel electric sub.

 

I'm solo'ing part of that HNR03 LCS scenario again. Right now, the convoy is reaching a choke point and Red diesel electic boat is missing from the port it was last seen. An MH-60B has been punched out. Scale at the moment is 1"=1nm. I have set up a 10x10 square inch box (using 1" square graph paper, with 10 sub-divisions per "box"). I roll a D10 to come up with which box the DE boat is in, then roll 2D10 to come up with a four digit grid coordinate for its exact location. I then do the same for the MH-60B. This gives me arbitrary start points.

 

The MH-60B will then drop one of its SB's at the start point. It would be a Passive SB at this point - correct? Once they detect something, I assume that the helo would then drop an active one to try and bracket the sub. Are there some general search patterns - like a lazy figure 8 or something like that? How often, or far apart from the previous, would the helo drop a passive SB while it is still drawing straws?

 

Finally, rules indicate that SB's can be dropped into Shallow or Intermediate I depth. Would it be correct to assume that an SB would only be able to detect contacts within its current depth level only.

 

Thanks,

 

Pete

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The MH-60B will then drop one of its SB's at the start point. It would be a Passive SB at this point - correct? Once they detect something, I assume that the helo would then drop an active one to try and bracket the sub. Are there some general search patterns - like a lazy figure 8 or something like that? How often, or far apart from the previous, would the helo drop a passive SB while it is still drawing straws?

 

I going to assume you actually mean an MH-60R.

 

And yes, typically, you start the search with a pattern of passive sonobuoys (like an SSQ-53D/F DIFAR). The pattern is typically a grid of some sort. I do vaguely recall a discussion one time about what these grid patterns might typically look like, but in any event, you're trying to maximize the area covered given the range of your sonobuoys. I believe the SSQ-53 has a passive range of 0.9 nm. So certainly no more than 1 nm apart, and probably a lot less.

 

And while passive sonobuoys are typically the initial tool, and ASW aircraft and helicopters usually carry more of these than the active kind, keep in mind that they are probably going to be of limited utility against a small diesel sub operating in shallow waters. A modern diesel-electric submarine moving slowly (2-3 kt) is probably undetectable by passive means beyond 1,000 yards. This will obviously influence the size and shape of your search pattern and your use of passive sonobuoys. (The SSQ-77C VLAD might be a better performer overall but I can't see it being terribly better in shallow water; I could be wrong).

 

If and when your contact is detected by passive means, your helo might then drop a line of active sonobuoys (eg. SSQ-62D/E DICASS) to develop the contact, and to try to determine course and speed while working on a positive ID. I believe H4.1 assigns an active range of 1.7 nm to the SSQ-62. And again, while active sonobuoys might be the way to flush out a quiet diesel, you typically don't have many of them and their performance might be attenuated by local conditions (shallow water, rocky bottoms, wrecks, etc).

 

Finally, rules indicate that SB's can be dropped into Shallow or Intermediate I depth. Would it be correct to assume that an SB would only be able to detect contacts within its current depth level only.

 

Hmm, good question. Offhand, I would say so. I don't have my copy of the rules in front of me, but I don't recall any of them having a depth capability greater than 1,000 ft (at least as far as public sources go). The SSQ-53 series, for example, has three depth options (90, 400 and 1,000 ft) and 5 endurance options (0.5, 1, 2, 4 and 8 hours).

 

Hope this helps.

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I going to assume you actually mean an MH-60R.
yep MH-60R, my bad.

 

Hmm, good question. Offhand, I would say so.

Thanks, maybe I'll post to Yahoo AT, see if we can get a Bond edict...sounds worthy enough.

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Peter Grining chimed in over on the Yahoo AT Group. I will plug in his ideas, continuing a change I made earlier, making a using a Type 212 which is rated "Very Quiet".

 

I'll be sure to post what I find out. Tony's Combat Plotter mod will be credited with an "assist" (think hockey).

 

Birthday Boy...out.

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Peter Grining chimed in over on the Yahoo AT Group. I will plug in his ideas, continuing a change I made earlier, making a using a Type 212 which is rated "Very Quiet". I'll be sure to post what I find out. Tony's Combat Plotter mod will be credited with an "assist" (think hockey).

Birthday Boy...out.

 

Since you're likely occupied with all that celebrating, :lol: I'll post what Peter Grining had to say...

 

Take the MH-60R sonobuoy - HNT 2003, pg 25 says DICASS - 25 carried. The

MH-60R has a UYS-2 sonobuoy processor - this can handle 99 channels of which

61 are search, 32 localisation and 6 active.

A DICASS buoys requires 2 localisation channels or 16 buoys can be monitored

at once

25% range is 1.3 nm in passive mode

Each DICASS sonobuoy can cover a square 1.3 x 1.4 = 1.8 nm wide (ignoring

the fact a sonobuoy coverage is a circle, not a square - this coverage is

swiss cheese in any case). The 1.4 comes from 1/ sin 45

 

The area the submarine is in is 10 x 10 nm - a total of 5 buoys cover 9 nm.

Throw out 3 lines of 5 buoys = 15 buoys - this leaves one spare. The lines

should be staggered:

x-x-x-x-x

-x-x-x-x-x

x-x-x-x-x

x = sonobuoy

 

You could also space the lines out further to cover all the 10 x 10 nm

x-x-x-x-x

 

-x-x-x-x-x

u

x-x-x-x-x

u = submarine.

 

Trouble here is the sub may parallel the lines and never pass into the

sonobuoy coverage.

 

According to rules 4.4.6.2 sonobuoys can set to Shallow or Intermediate I.

The scenario has Shallow depth only - in any case you'd use the Tgt

Cross-Layer modifier for targets on the other side of the layer.

 

Sounds good in theory, but: the Red submarine is either a Type 209, Kilo or

Foxtrot - I'll assume a Kilo (Quiet signature), speed is dependent on what

the Red sub us doing, but I'll assume 5 kts, from pg 4-11 of teh rules:

Quiet x 1

Tgt Speed x1

Ignore Own Ship Modifier

SS 2 x1

MF sonar x 1 (Shallow Water)

Scenarion says sonar conditions D6+5 x10% (60-110%) - I'll be lazy and

assume 100%

The only thing the sub can do is use the x0.5 for Ultra-Quiet submarines -

which means the nice neat coverage above now resembles swiss cheese. Thats

fine, if the sub is stationary it may never get picked up by the sonobuoys -

if he is moving he may run into the sonobuoy coverage.

 

If the sub snorts he ends up with a x 2 modifier. Each sonobuoy now covers

3.6 nm x 3.6 nm. Lets go with the 3 seperate lines, each line is 3.6 nm

apart. the sub will be detected if he snorts.

x-x-x-x-x

 

-x-x-x-x-x

u

x-x-x-x-x

 

 

The helo also has the excellent AQS-22 dipping sonar. The mission is

sanititise a 10 x 10 nm area to protect a transitting convoy - the helo

needs to either detect and attack the sub or drive the sub away.

Own ship speed x 1 (dipping sonar)

SS 2 x 1

Anechoic coating (Kilo) x 0.5

LF-MF sonar in shallow water x 0.5

Total x 0.25

 

The helo has time and speed, so each dip should be at least two tactical

turns in active mode (you want to either scare the sub away or herd him into

the sonobuoys). This link says 10 minute dips - which is close enough to 3

tactical turns: http://www.naval-technology.com/projects/nh90/

With 3 turns at 25% detection - this 58% for the three turns (pg 6-13, Stick

size 3)

3 turns at 50% detection is 88%

3 turns at 75% is 90%

 

Might as well stick with out 25% figure so the MH-60R needs to dip every 1.7

nm (4.8 m, sonar x 0.25 sonar mods x 1.4 for square size)- it'll take 6 dips

to cover each space between the buoys - trouble is could wipe out sonar

reception (4.4.5.1.4) - the MF sonobuoys can detect the active LF-MF

AQS-22 - The Quiet sub is then masked by the Loud active sonar (4.4.5.2)

 

 

APS-147 radar should be active - at the ranges we are talking about it will

detect any submarine mast. You might want to have the sub randomly snorting

if it hasn't detected the helo. This site says the standard indiscretion

ratio is 7-10 % whilst on patrol at 4 kts. From 4.4.3 you only want to snort

of 9 minutes max -assuming 70-100% battery charge (3.2.3) - you get a unit

every 6 minutes, at 5 kts or below one units is used an hour - so the boat

needs to snort 6 minutes for every hour on battery (indiscretion ratio 9%).

To avoid radars snort in

 

Also the helo must be at Low or Medium altitude when dropping the buoys

(4.4.2.6) and the sub has a chance of detecting the helo at Low altitude

(4.4.5.3)

 

I'll admit the above plan has enough holes in it - but I'm interested in how

your game goes. If I was the sub I'd bottom - Ultra-Quiet x 0.5 vs passive

and 0.5 x active - and try and bluff the dipping sonar out.....

 

Regards,

Peter Grining

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From the navel-technology website provided by PeterG, the take aways are:

 

"In a typical four-hour 'relocation on call' operation, the helicopter would take: 35 minutes to reach the area of operation; 20 minutes releasing sonobuoys; two hours on surveillance in the area of operations; 30 minutes releasing torpedoes; and 35 minutes to return to ship and land, with 20 minutes in reserve.

 

In a typical four-hour 'screening' operation, the helicopter would take: 15 minutes to reach the area of operation; three hours and 30 minutes in the operations zone carrying out 11 consecutive cycles of ten-minute sonar dipping; and 15 minutes to return to the ship and land, with 20 minutes reserve."

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  • 3 weeks later...

Peter,

 

As I progressed, I realized that I needed to concentrate more on getting comfortable with submarine operations, sonar, TMA, torpedo attacks, etc. so I did not yet implement the sonar bouys in a full bore scenario. With so many ideas it may a take a week or two.

 

Thanks for asking though, keeps me honest. B)

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