A COMMERCIAL RATED PLT FLYING A TWIN ENG TURBOPROP CHARTER FROM SFO DEPARTS VFR AND IS UNABLE TO MAINTAIN THE CLRNC THAT ATC ISSUED.

Narrative

I WAS DEPARTING SFO ON THE AFTERNOON OF JUL/XA/99. THE WX AT THE TKOF END WAS CLR; AND THE WX AT THE DEP END AND TO THE W WAS 1200 FT OVCST WITH 10 MI VISIBILITY. I WAS GIVEN A VFR CLRNC TO TURN R TO A 350 DEG HDG AND TO REMAIN AT OR BELOW 2000 FT. THAT HEADING WOULD KEEP ME CLR OF THE OVCST LAYER. SHORTLY AFTER TKOF AND THE TURN TOWARDS 350 DEGS; THE TWR TOLD ME TO 'KEEP THE HWY ON YOUR R.' I WAS CONFUSED BECAUSE THE FIRST HWY I SAW HAD A HILL TO ITS L THAT I WOULD HAVE HIT BECAUSE IT WAS COVERED BY THE STRATUS LAYER. I SAW ANOTHER HWY GOING W UNDER THE OVCST THAT I COULD KEEP ON MY R. I THEN ASKED THE TWR IF HE STILL WANTED ME ON A 350 DEG HDG AND HE SAID NO. I THEN FOLLOWED THE WBOUND HWY TO THE W. THE TWR HAD EXPECTED ME TO FOLLOW A DIFFERENT HWY AND CALLED WHEN HE SAW I WAS WBOUND. HE THEN HAD SOME DIFFICULTY ARRANGING A HDOF BECAUSE THE OVCST HAD ME AT 1000 FT AND BELOW HIS RADAR COVERAGE. BECAUSE OF AN AMBIGUOUS INSTRUCTION AND MY FAILURE TO ADEQUATELY CLARIFY IT; I DIDN'T DO WHAT THE TWR EXPECTED OF ME. I HAD DONE THIS PROC SCORES OF TIMES IN THE PAST AND HAD BEEN SWITCHED TO A WBOUND HEADING BEFORE BUT HAD NEVER BEEN ASKED TO FOLLOW A HWY; SO I WAS SOMEWHAT SURPRISED BY THE INSTRUCTION. I TRIED TO FOLLOW THE INSTRUCTION TO FOLLOW THE HWY WHILE ENSURING MY OWN SAFETY BY NOT COMING TOO CLOSE TO THE TERRAIN. MY RESPONSE WHEN I WAS CONFUSED SHOULD HAVE BEEN THAT I DIDN'T UNDERSTAND WHAT WAS EXPECTED OF ME AND THEN THAT I COULDN'T COMPLY BECAUSE OF THE CLOUD COVER.