CL65 CAPT QUESTIONED TWR CTLR RELATIVE TO THE TYS DEP OBSTACLE CLRNC NOTE VERSUS HIS ACTUAL DEP CLRNC INSTRUCTING A TURN AFTER TKOF WITH NO MINIMUM TURNING ALT.

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DAY VMC PREVAILED AS OUR FLT PREPARED TO DEPART TYS FOR CVG. OUR CLRNC WAS TO FLY HDG 020 DEGS AFTER TKOF; CLB AND MAINTAIN 6000 FT; EXPECT FL220 10 MINS AFTER DEP. WE WERE NOT CLRED VIA THE KNOXVILLE 4 SID. THE BACK SIDE OF OUR COMMERCIAL ARPT DIAGRAM SAYS UNDER THE HDG 'OBSTACLE DEP PROC' TO 'COMPLY WITH SID OR RADAR VECTORS; OR CLB RWY HDG TO 4000 FT BEFORE TURNING ON COURSE.' I ASKED THE TWR PRIOR TO REACHING THE RWY WHETHER THE INSTRUCTION TO FLY HDG 020 DEGS AFTER TKOF CONSTITUTED A RADAR VECTOR BECAUSE WE WERE NOT ISSUED A SID AND IT DID NOT SEEM THAT ATC WANTED US TO REMAIN ON RWY HDG UP TO 4000 FT. TWR ASSURED ME THE 020 DEG INSTRUCTION WAS INDEED A RADAR VECTOR. NEXT; I ASKED IF WE SHOULD THEREFORE COMMENCE THE TURN TO 020 DEGS UPON REACHING 400 FT AGL. THE TWR CTLR WAS VERY VAGUE IN HIS RESPONSE TO OUR QUESTION ABOUT AT WHAT ALT SHOULD THE TURN BE STARTED. SO; TO ENSURE THAT EVERYONE WAS ON THE SAME PAGE; IT WAS AGREED THAT WE WOULD MAINTAIN THE RWY HDG TO 4000 FT BEFORE TURNING ON COURSE.