CPR ACFT FAILS TO COMPLY WITH SID. HDG DEV.

Narrative

OUR FLT WAS TO LEAVE HPN (WHITE PLAINS NY) AND FLY TO BOS. WHEN WE ASKED FOR OUR CLRNC FROM HPN TWR WE RECEIVED THE FOLLOWING CLRNC. 'CLRED TO BOS BY THE WHITE PLAINS 9 DEP; VECTOR TO MERIT INTXN; DIRECT TO NORWICH VOR (ORW); NORWICH 2 ARR; MAINTAIN 3000 FT.' THIS WAS FOLLOWED BY EXPECT TO CLB TO A HIGHER ALT; THE DEP FREQ FOR NEW YORK DEPS AND A XPONDER CODE. ON RECEIVING THE WHITE PLAINS 9 DEP CHART IT SHOWED FOR DEPARTING ON WHITE PLAINS RWY 16 'MAINTAIN RWY HDG TO 800 FT; THEN TURN R TO A 320 DEG HDG; MAINTAIN 3000 FT.' THIS WAS FOLLOWED BY INSTRUCTIONS TO EXPECT RADAR VECTORS TO ASSIGNED RTE OR FIX. ON TAKING RWY 16 FOR TKOF; WE WERE CLRED FOR TKOF BY HPN TWR BUT WERE GIVEN NO HDG TO TURN TO AFTER DEP AS IS USUAL FOR MOST OF OUR PAST OPS. I DIDN'T QUESTION THIS AT THE TIME BUT I SHOULD HAVE. I GUESS THAT I WAS EXPECTING A TURN CLRNC IN THE AIR AFTER TKOF AND BEFORE BEING SET OVER TO THE NEW YORK DEP CTLR. SHORTLY AFTER LIFT OFF WE WERE REQUESTED BY THE HPN CTLR TO DO A MAX RATE OF CLB TO 3000 FT AND THEN SENT OVER TO THE DEP FREQ. WE CONTACTED NY DEP LEAVING 1800 FT STILL ON RWY HDG AND WERE ADVISED TO MAKE AN IMMEDIATE R TURN TO 320 DEGS AND CLB TO 4000 FT. WE WERE THEN ASKED BY NY DEP WHY WE HAD NOT TURNED TO 320 DEGS SOONER. WE REPLIED THAT WE HAD NOT RECEIVED ANY TURN INSTRUCTIONS FROM THE HPN TWR. NY DEP ADVISED THAT THE TURN CLRNC WAS ON THE WHITE PLAINS 9 SID IF WE WOULD HAVE READ IT. MY PAST EXPERIENCES HAS ALWAYS BEEN THAT THE ARPT TWR HAS ALWAYS GIVEN THE FIRST TURN AFTER DEP TO CLARIFY THAT BOTH THE CTLR AND THE PLT KNOW THE EXPECTED PROC TO EXPECT TO FOLLOW. IN RETROSPECT I SHOULD HAVE ASKED THE HPN TWR FOR A TURN HDG AFTER DEP WHEN WE WERE FIRST CLRED FOR TKOF. WE KNEW THAT THE WHITE PLAINS 9 SID STATED TO DO BUT IN THE PAST WE HAVE SOMETIMES BEEN GIVEN TURNS TO HDGS OTHER THAN WHAT THE SID HAS ON IT DUE TO TFC CONFLICTIONS; A SLOWER CLBING ACFT AHEAD OF US ON CLBOUT; ACFT DIVERTING AROUND WX; OR INBOUND ACFT TO THE ARPT.