Passive Sonar Detection

[jimbo]

Hello,

Page 20 passive example.

When consulting Table 5.5.2.1, I don't understand the index of Target Noise Signature and passive PDR. I see the top horizontal row is

the Target Noise Signature, yet the left vertical side column states Sonar Range. Where is the PDR rating?

thanks

Jim

[williammiller]

Nov 28, 2017 19:53:14 GMT -6 jimbo said:

Hello,

Page 20 passive example.

When consulting Table 5.5.2.1, I don't understand the index of Target Noise Signature and passive PDR. I see the top horizontal row is

the Target Noise Signature, yet the left vertical side column states Sonar Range. Where is the PDR rating?

thanks

Jim

A units PDR (Passive Detection Range) is the second sonar rating listed on the units data sheet; for example the 'US FFG OH Perry' class has a sonar listing of  T1/T1+3~  ; value to the left of the slash (T1) is the active sonar range, the value to the right of the slash (T1+3~) is the passive sonar range (or PDR) value. In this case the passive sonar has a T1 range, while the sonar has some special characteristics of " +3~ " (which means it can detect up to 3 CZs away and is a towed sonar array).

[jimbo]

Thanks for the reply, yet I still don't understand table 5.5.2.1. The example states "indexing the Swiftsures PDR of T1 with Kotlins Noise Signature rating of a 1 on

table 5.5.2.1 we obtain a BDR of "T2". I see the top horizontal row on the table is Target Noise Signature (Kotlin 1), yet "indexing PDR of T1 is not on the left

vertical side of the table. I only have "Sonar Range 0 to 5". Am I missing the big picture? lol.

thanks,

Jim

[williammiller]

Nov 29, 2017 19:10:50 GMT -6 jimbo said:

Thanks for the reply, yet I still don't understand table 5.5.2.1. The example states "indexing the Swiftsures PDR of T1 with Kotlins Noise Signature rating of a 1 on

table 5.5.2.1 we obtain a BDR of "T2". I see the top horizontal row on the table is Target Noise Signature (Kotlin 1), yet "indexing PDR of T1 is not on the left

vertical side of the table. I only have "Sonar Range 0 to 5". Am I missing the big picture? lol.

thanks,

Jim

Sonar ranges are given in Tactical (the "T" part) ranges, so T1 is 1 range, T2 is 2 range, T2.5 is a 2.5 range, etc...the 'T' part is simply a reminder that we are talking about the 5nm tactical squares on the Tactical Display sheet, *not* the 25nm hexes on the strategic map. So in this case a "T1" ranges would be a "1" on the Sonar Range column on Table 5.5.2.1.

[jimbo]

Thanks, but the passive scenario states "2 (25nm) hex distant". The active scenario does state "2 holding boxes (10nm or T2)distant".
Via Table 2.1, 2 25nm hex equals 9-13nm for 5nm Tactical scale. I apologize for the many questions, I just want a thorough understanding.

thx
Jim

[williammiller]

Dec 2, 2017 7:09:14 GMT -6 jimbo said:

Thanks, but the passive scenario states "2 (25nm) hex distant". The active scenario does state "2 holding boxes (10nm or T2)distant".
Via Table 2.1, 2 25nm hex equals 9-13nm for 5nm Tactical scale. I apologize for the many questions, I just want a thorough understanding.

thx
Jim

Jim,

Table 2.1 lists how many Tactical (5nm) holding boxes it takes to equal so many Operational Hexes, not how many nautical miles (nm)...the example you cite shows that 9-13 Holding boxes equal 2 Operation hexes, not "9-13 nm equals 2 operational hexes". This is so you can easily convert holding box ranges (T1, T4, T15, etc) to operational hexes without having to do the math and rounding of fractions yourself.

I'll address the active sonar example in more detail tonight as I will not be back home for a few more hours.

Thanks!

[williammiller]

The below is the Passive Sonar example from the v1.04 Rules Manual:

Example: A Swiftsure SSN traveling at “VSlow” speed in “Good” weather is attempting to detect (using its passive sonar) a Koltin DDG that is two (25nm) hexes distant traveling at “Fast” speed.

The Swiftsure has a passive sonar rating of T1 so its PDR is T1 and the Koltin has a Noise Signature rating of “1”. Indexing the Swiftsure’s PDR of T1 with the Koltin’s Noise Signature rating of a 1 on Table 5.2.2.1 we obtain a BDR of “T2”. Rolling 1d10 on Table 5.5 we roll a “5”, indexing the 5 roll with the BDR of T2 we obtain an Adjusted Range of T2.

Consulting Table 5.5.2.2 we have the following modifiers: Target speed “Fast” = +6, own speed “VSlow” = -2, and Good weather = +1, for a total modifier of +5. Indexing the Adjusted Range of T2 with the Total Modifier of +5 on the appropriate section of Table 5.10 we obtain a final detection range of 2 hexes (50nm); since the Koltin is 2 hexes away the Spruance detects it!

It might be best to let me know at what part of the example you are lost at, then I can better help you with it.