NMAC BTWN EMS HELI AND LTT. HELI PROCEEDS THROUGH CTL ZONE WITHOUT SVFR CLRNC.

Narrative

I WAS THE PLT OF AN EMS HELI BASED AT THE HOSPITAL WHICH IS LOCATED 6 MI S OF ZZZ ARPT. I DEPARTED ON A FLT TO ANOTHER HOSPITAL FOR A PATIENT PICKUP. ZZZ WAS RPTING THE WX AS 1000 AND 3. AS I TOOK OFF I ESTIMATED THAT THE FLT VISIBILITY WAS APPROX 1 1/2-2 MI. I HELD A NW HDG TO KEEP CLR OF THEIR AIRSPACE AND IMMEDIATELY CALLED ZZZ TWR FOR CLRNC THROUGH THEIR AREA. THEY CLRED ME THROUGH AND ISSUED TFC TO ME AS AN LTT INBOUND FROM THE SW AT 1100 FT. I WAS JUST REACHING 1100 FT MSL; 500 AGL; AND WANTED TO BE BELOW THE TFC SO I STARTED A DSCNT; GLANCED AT MY ALTIMETER AND TURNED MY HEAD TO THE L TO LOOK FOR TFC. AS SOON AS I TURNED MY HEAD I SAW THE LTT AT MY 10 O'CLOCK POS; SLIGHTLY ABOVE ME AND ABOUT 300-400 FT AWAY. THE LTT WAS IN A STEEP R TURN; PRESUMABLY TO AVOID ME. I IMMEDIATELY NOSED THE ACFT OVER TO INCREASE MY DSCNT AND DSNDED TO ABOUT 900 FT MSL; 300 AGL. MY PAX SAW THE LTT AND WERE CONSIDERABLY UPSET. BECAUSE OF THE INCIDENT AND THE NECESSITY TO CALM MY PAX; I PROCEEDED THROUGH THE CTL ZONE AS CLRED WITHOUT REMEMBERING TO REQUEST A SVFR CLRNC SINCE THE FLT VISIBILITY WAS LOW AND THE CEILING WAS ACTUALLY ABOUT 700 FT AGL. THIS WAS PROBABLY WHY THE LTT WAS AT 500 FT AGL IN VIOLATION OF FAR 91.119.