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ASW creeping attack


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#1 Last Mate

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Posted 05 August 2015 - 03:30 AM

The creeping attack allowed to the RN and USN says you shift down one on the depth charge attack table. However, shifting down one row rarely makes a difference and sometimes makes no sense (such as allowing early war depth charges to hit at deeper depths, if a strict rules lawyer applies the rule as written). Is this a holdover from an earlier version or am I missing something here? Should the rule maybe say deduct one from the DC attack dice roll(s)? (It does disallow evasive meneuvering by the sub, a major help if that rule is being used, and it should, but then so does S+ sonar.)



#2 Lonnie Gill

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Posted 10 August 2015 - 07:45 PM

G' Day Last Mate,

 

Hmmm, this hopping between centuries is a lot harder than it appears in the movies.  

 

The ASW adjustment for a creeping attack is to shift DOWN one row on the British or American ASW table. The benefit is reflected in deeper attacks, as an advantage of the creeping attack in actual operations is that it allowed for better placement of DC patterns to offset the additional distance submarines can move in the longer time required for depth charges to sink to lower depths. [This was somewhat minimized later when faster sinking, streamlined DCs were used,]   In fact, deeper attacks became the primary reason for employment of creeping attacks.  By contrast, shallow attacks are more like a regular DC attack: higher attack speeds have to be maintained to enable the attacking vessel to vacate the blast area in time, and the delay in DC sinking time is less .  As you correctly inferred, shifting down a row can increase the attack probability, but would not enable attacks to be made at depths deeper than listed in the basic row for the year of the scenario.  The maximum depth on each row of the ASW table reflects the DC fuse limits for the year being simulated.  Hence, a USN creeping DC attack at 400' in 1942 would increase the probability from "1" to "1 - 2" for each D12 rolled, but would not would enable a DC attack at 800'.  I will take a note that this is worth clarification in Rule Section 3.6.6 for any future updates.

 

Subtracting - 1 from the DC attack probability might seem like a good solution on the surface [who can resist a chance for such a bad pun] , but it turns out to be too large an adjustment as multiple D12s are rolled in an attack.  By 1942 and later, most British and American escorts have DC patterns of 3 or 4 DC (i.e., three or four D12s).  An adjustment of "- 1" would mean a probability increase of 8.33 % per D12 x three or four dice would result in a 25% - 33% increase in the probability of one hit. This, of course, would be too large an increase for an individual attack.

 

The primary benefit of a creeping attack was the elimination of evasion maneuvers by the target submarine as steaming slowly up her wake usually meant the sub didn't sense that an attack run was under way.  Use of advanced rule section 3.6.5 provides a more realistic simulation of DC attacks - and the ensuing frustration that the simplified basic procedure avoids. Use of the evasion rule in conjunction with a creeping attack reflects the true benefit of the creeping attack tactic.  Elimination of evasion is a major improvement in the probability of each individual DC attack.

 

Thus, elimination of evasion and some improvement in deep attacks  (partially minimized by the later streamlined DCs) reflects the effectiveness of the creeping attack.  As shown by the experience of Captain Walker's support group and others, individual attacks had low probability, but multiple attacks were deadly - when the escorts could loiter long enough to achieve success.  Use of multiple escorts also maximize the probability of regaining contact after a DC attack (rule Section 3.5.6).

 

LONNIE



#3 Last Mate

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Posted 11 August 2015 - 04:19 AM

Hey Lonnie,

 

Thanks, that clears it up. 






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