AN ACR CREW MEETS THE ALT RESTR BUT NOT THE DISTANCE REQUIRED FOR THE FIRST TURN ON THE SUMMA 6 DEP FROM SEATTLE; WA; RWY 34L-R.

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DURING CLBOUT ON SUMA 6 DEP WITH MYSELF FLYING; I INITIATED A TURN AT 6 DME TO A HDG OF 070 DEGS ABOVE A MINIMUM ALT OF 4000 FT. I BELIEVED AT THE TIME OF THE TURN THAT I WAS COMPLYING WITH THE DEP PROC. ATC CAME ON THE RADIO AND ADVISED THAT WE HAD TURNED TO OUR HDG EARLY AND THAT OUR TURN HAD SURPRISED ATC; BUT THAT NO HARM WAS DONE AND NO OTHER ACFT WERE INVOLVED. FLT CONTINUED TO BE UNEVENTFUL AFTER MAKING OUR APOLOGIES TO DEP. I BELIEVE PAYING CLOSER ATTN TO THE DEP PROC AS WELL AS MAYBE A WAY TO MAKE 5'S; 6'S; AND 8'S STAND OUT MORE WOULD HAVE HELPED IN PREVENTING THIS ERROR. BOTH CREW MEMBERS WERE WELL RESTED AND ALERT. SUPPLEMENTAL INFO FROM ACN 563819: WE WERE CLBING OUT ON THE SUMMA 6 DEP; HAD JUST ENTERED IMC AND BEGAN A TURN FO 070 DEGS ABOVE 4000 FT (I'M NOT SURE OF THE DME). ABOUT 30 SECONDS OR LESS LATER; THE DEP CTLR TOLD US WE TURNED EARLY AS IT WAS 8 DME AND ABOVE 4000 FT WHEN WE SHOULD TURN. SHE TOLD US IT WAS NOT A BIG PROB THIS TIME. I ONLY SAW 4000 FT ON THE SID. I HAD PUT IN THE ROUTING AS IT APPEARED ON OUR FLT PLAN. FIRST FIX SUMMA; ALONG WITH THE DEP RWY. IF WE WERE CLRED THE SUMMA 6; WOULDN'T IT MAKE MORE SENSE TO HAVE THE BOX REFLECT WHAT WE'RE GOING TO FLY AUTOMATICALLY? THAT IS; IF WE ALWAYS FLY THE SUMMA 6; IT SHOULD BE THE DEFAULT FLT PLAN. SAME IN PHX WITH THE ST JOHNS 2. THAT WOULD PROVIDE MOVING MAP GUIDANCE IMMEDIATELY.