Sonar Blindness Re: FT-Subs?

At 11:38 AM -0400 7/28/01, Richard and Emily Bell wrote:
> energy.
>
>Convoy escorts need a device like a k-gun (depth charge thrower). 
Escorts can
>detect subs passively at a range of six times the applied thrust (less
applied
>thrust of the escort) and can use a firecon to search a single arc for
a sub
>within 24 mu (only twelve when the sub is deep).  Passive does not 
>work aft, and
>active does not detect a sub within 12 in the forward arc [I do not
know why,
>just that for some historical and technical reason, subs fell off the
scope
>during attack runs in WWII].

This was because as the ship got closer to the sub (driving directly 
at it to pass over for a depth charge salvo off the fantail) the sub 
passed out of the sweep of the ASDIC/Sonar 'beam'. The subs could 
dash out of the way at the last instant if good.

Hedgehogs, K and Y guns and 2 ship tactics helped to counter this 
blind spot below the ship.

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