C172 INVOLVED IN NMAC WITH EMS HELI IN VICINITY OF RHV ARPT.

Narrative

AT ABOUT XA30 AT RHV; I WAS CLRED FOR TKOF ON RWY 31L FOR A R TURNOUT DEP. AT ABOUT 600 FT AND LESS THAN 1 MI FROM THE ARPT; I SAW SOMETHING AT MY 10 O'CLOCK POS. SHOCKED BY WHAT I SAW; I STARED FOR A MOMENT OR TWO UNTIL I REALIZED IT WAS SOMETHING COMING RIGHT AT US. I INITIATED A SHARP TURN TO THE L JUST IN TIME TO SEE THE TAIL ROTOR FROM A HELI GO ACROSS OUR WINDSHIELD. I BELIEVE THAT WE WERE WITHIN ABOUT 15 FT FROM THE ACFT; AND SLIGHTLY LOWER; MAYBE A FOOT OR TWO. I BELIEVE THAT HAD I NOT TAKEN ACTION; WE WOULD HAVE COLLIDED. A COUPLE DAYS LATER; I FOUND OUT THAT THE HELI HAD ORIGINATED FROM A HOSPITAL N OF THE ARPT; AND HAD FAILED TO CALL THE TWR UNTIL IT HAD REACHED 900 FT; WHICH WAS AFTER IT HAD PASSED ME. I FAILED TO RPT THE INCIDENT TO THE TWR DUE TO SHOCK OF THE CLOSE CALL I HAD. I JUST WANTED TO GET TO A SAFE ALT FAR AWAY FROM THERE. I AM RPTING THIS BECAUSE; FROM WHAT I HAVE HEARD; THIS IS NOT THE FIRST TIME THE HELIS HAVE FAILED TO FOLLOW PROC; AND I AM AFRAID THE NEXT TIME THEY DO THIS; IT MAY BE FATAL FOR ALL INVOLVED. RHV TWR NEEDS TO MAKE THE MEDICAL FLTS AWARE OF THE CLASS D COM REQUIREMENTS. CALLING THE TWR AT 900 FT MSL IS WAY TOO LATE!