CAPT OF AN MD88 STARTED APCH DSCNT PRIOR TO BEING CLRED RESULTING IN ARTCC CTLR INTERVENTION TO REMIND RPTR THAT HE WAS INSTRUCTED TO ADVISE WHEN ESTABLISHED ON THE LOC.

Narrative

APCHING PWM ARPT OVER PARSO IAF; ZBW CLRED US TO DSND TO 4000 FT; INTERCEPT THE LOC FOR RWY 11; AND 'ADVISE WHEN ESTABLISHED.' WE DID SO; BUT AFTER INTERCEPTING THE LOC; ZBW WAS BUSY TALKING TO ANOTHER ACFT; AND MY FO WAS GIVING THE REQUIRED CALLS ON CTAF AS PWM TWR AND APCH WERE CLOSED. SOMEHOW; I THOUGHT WE WERE CLRED FOR THE APCH; AND I STARTED BY DSCNT TO CATCH UP TO THE STEP-DOWN ALTS AFTER PARSO. ZBW CALLED AND SAID WE HAD NOT BEEN CLRED TO DSND. THEN CTR CONFIRMED WE WERE ESTABLISHED ON LOC; AND IMMEDIATELY CLRED US FOR THE APCH. BY THEN THE RWY WAS IN SIGHT. WE REQUESTED AND WE WERE GIVEN A VISUAL APCH. THINKING BACK; I REALIZED WE HAD TALKED EARLIER TO ZBW ABOUT STARTING WITH THE ILS AND THEN GOING VISUAL. THEN WHEN CTR SAID 'RPT ESTABLISHED;' I ASSUMED WE HAD BEEN 'CLRED FOR THE APCH.' FATIGUE; NOT KEEPING MY FO IN THE LOOP; CLOSED TWR AND APCH; AND NOT WANTING TO BE HIGH ON APCH FOR A SHORT RWY; ALL ADDED TO THE PROB. TO MY KNOWLEDGE; NO OTHER ACFT WAS AFFECTED (NONE EVEN AROUND); AND WE WERE ALWAYS AT OR ABOVE THE ALTS ON THE APCH. BUT I LEARNED FROM THIS AND WILL BE MORE CAREFUL AS A RESULT.