SA226 PLT ASSUMES DSCNT AND HDG CHANGE IS FOR HIM; RECOGNIZING THE ATC XMISSION WAS CLIPPED INCOMPLETE.

Narrative

ATC; IN A XMISSION THAT WAS CLIPPED OFF AT THE BEGINNING; SAID '...TURN 10 DEGS L FOR TFC; I'LL HAVE DIRECT ROCHESTER FOR YOU SHORTLY; DSND AND MAINTAIN 11000 FT; ALTIMETER (BUF) 30.14.' I RESPONDED; '...10 DEGS L; DOWN TO 11000 FT AND SAY AGAIN THE ALTIMETER.' AFTER GETTING THE ALTIMETER I WAS TOLD TO TURN AN ADDITIONAL 15 DEGS (NO DIRECTION STATED; SO I ASSUMED L). THIS CHAIN OF INSTRUCTIONS WAS THE CAUSE OF THE LOSS OF SEPARATION WHICH OCCURRED WITHIN THE NEXT MIN. THE CTLR ASKED FOR MY NEW HDG AND I RESPONDED 050 DEGS. AFTER A PAUSE; THE CTLR ASKED IF I HAD TURNED L OR R. I SAID I HAD TURNED L. I WAS THEN GIVEN A R TURN TO A HDG OF 140 DEGS AND TOLD TO STOP MY DSCNT AT FL190. AFTER I RESPONDED; I HEARD THE LAST PART OF A XMISSION '...INSTEAD MAINTAIN FL180.' I ASKED IF THE FL180 WAS FOR MY ACFT AND GOT NO RESPONSE. AFTER APPROX 10 SECONDS; I ASKED WHAT ALT THEY WANTED ME AT. DURING ALL THIS; INSTRUCTIONS WERE ALSO BEING GIVEN TO 2 OTHER ACFT AND BOTH HAD TO ASK FOR VERIFICATION. THE BEGINNING OF EACH XMISSION WAS BEING CUT OUT; EITHER BECAUSE OF DEFECTIVE EQUIP OR THE CTLR NOT PRESSING HIS MIKE BUTTON BEFORE BEGINNING TO TALK. IF THE CTLR SAID TURN 10 DEGS R AND I IN FACT READ BACK 10 DEGS R; THEN I AM AT FAULT. I DO NOT BELIEVE THIS IS THE CASE. FATIGUE ON MY PART MAY HAVE PLAYED SOME PART IN THIS IF I DID REPLY TO A TURN TO THE R BUT INSTEAD TURNED L. I WAS UP FROM XA00 AM TO XD30 PM ON WEDNESDAY. I WAS CALLED OUT AT XA30 AM THURSDAY TO DO A RUN (UNSCHEDULED. BY THE TIME THIS EVENT OCCURRED; I HAD ONLY SLEPT 2 HRS IN THE PAST 32+ HRS AND WAS OPERATING SINGLE PLT. ATC IS IN THE HABIT OF GIVING HDG CHANGES AS '...TURN X DEGS L/R' INSTEAD OF GIVING A HDG. WHILE THIS DECREASES THEIR WORKLOAD; I FEEL THAT IT DETRACTS FROM THE PRECISION OF THE HDGS AND THE SAFETY FEEDBACK INHERENT IN THE READBACK. FOR MY PART; I AM NOT IN THE HABIT OF READING BACK 'ANOTHER 15 DEGS' AS I DID; AND IN THE FUTURE I INTEND ON VERIFYING THE DIRECTION OF THE TURN BY READING BACK '...TURN AN ADDITIONAL 15 DEGS L...THAT MAKES MY NEW HDG 050 DEGS.' THIS WILL NOT ONLY INGRAIN THE INSTRUCTION IN MY OWN MIND; IT WILL GIVE ATC ADDITIONAL INFO; AND; IF INCORRECT; WILL GIVE THE OPPORTUNITY TO CATCH THE ERROR BEFORE IT LEADS TO A PROB.