A DHC-6 CREW; ON APCH TO PAHO; AK; ONCE CLRED FOR THE APCH STARTED TO PROCEED DIRECT TO THE IAF; CONTRARY TO THE PUBLISHED PROC. ATC THWARTED THE ATTEMPT.

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WE WERE OPERATING FLT XXXX. AT 8000 FT ENRTE DIRECT TO HOME; WE REQUESTED AND WERE CLRED FOR THE GPS APCH TO RWY 21 AT THE HOMER ARPT; TOLD TO DSND AND MAINTAIN 5000 FT UNTIL ESTABLISHED ON A PUBLISHED SEGMENT OF THE APCH. WE READ BACK THE CLRNC AND STARTED DSCNT TO 5000 FT. AS WE DSNDED; WE STARTED DIRECT TO THE IAF (OGLOQ). THROUGH ABOUT 6600 FT; THE CTR CTLR ASKED IF WE WERE ON A PUBLISHED PORTION OF THE APCH. I SAID 'NEGATIVE; WE ARE PROCEEDING DIRECT OSCAR; GOLF; LIMA; OSCAR; QUEBEC.' I REQUEST DIRECT OSCAR; GOLF; LIMA; OSCAR; QUEBEC. THE CTLR SAID THE MINIMUM SECTOR ALT WAS 8600 FT. I ASKED AGAIN FOR CLRNC TO OSCAR; GOLF; LIMA; OSCAR; QUEBEC; AND WILL CLB AND MAINTAIN 8600 FT. WE WERE CLRED AS REQUESTED. WE MAINTAINED 8600 FT UNTIL OGLOQ AND CONTINUED THE APCH. SHORTLY AFTER OGLOQ WE BROKE OUT OF THE CLOUDS; CANCELED IFR; AND THE REST OF THE FLT WAS UNEVENTFUL. THIS WAS THE FIRST TIME EITHER CREW MEMBER HAD COMPLETED THIS APCH. I BELIEVE CLOSER EXAMINATION OF THE APCH COULD HAVE PREVENTED THIS OCCURRENCE. THE APCH IS IN A SIMILAR AREA WITH THE LOC BACK COURSE TO RWY 21. WE USE THIS APCH REGULARLY AND WERE LOOKING FOR A DIFFERENT APCH TO USE THAT DID NOT TAKE US ANY FARTHER OUT OF THE WAY. AT NO TIME WERE WE WITHIN 2000 FT VERTLY OR HORIZLY FROM ANY OBSTRUCTION.