Crab,
It is you who seem confused. TCAS gives you 360 degree coverage and it displayed on the pilots' screens so that they can see traffic at all times - it is not linked to the radar it is a separate system. With the Sea King's current arrangement you can only see I Bands when someone is in the "shack", so no cover when winching etc. TCAS also shows you when non SAR aircraft get in the way!
The world has moved on since the Sea King, wake up and smell the coffee.
RI