A LOW WING TURBOPROP FO PULLED THE ALTIMETER VIBRATOR CIRCUIT BREAKER AFTER SHUTDOWN IN VIOLATION OF COMPANY AND FAA PROCS.

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WE TAXIED FLT INTO THE GATE AND DID A NORMAL SHUTDOWN. I; OUT OF A HABIT STARTED WHILE I WAS A NEW HIRE; PULLED THE CIRCUIT BREAKER FOR THE ALTIMETER VIBRATOR. WE CONTINUED OUR SHUTDOWN PROCS WHILE THE PAX UNLOADED; THEN EACH OF US BEGAN OUR OWN ACTIVITIES TO PASS THE 1 HR 30 MINS WE HAD PRIOR TO OUR RETURN FLT TO ZZZ. I HAD PLANNED TO STAY IN THE COCKPIT. THE CAPT DID NOT KNOW I HAD PULLED THE CIRCUIT BREAKER AND DID NOT INSTRUCT ME TO DO SO. SOMETIME DURING THE 1 HR 30 MIN BREAK; I NOTICED THE CIRCUIT BREAKER WAS OUT AND RESET IT. ALL INSTS WERE NORMAL AND THE RETURN FLT TO ZZZ UNEVENTFUL. OVER THE PAST YR OR SO; OUR COMPANY HAS ISSUED AT LEAST 2 MEMOS REGARDING CIRCUIT BREAKERS AND PULLING THEM. IN SHORT; WE WERE TOLD NOT TO DO IT ANYMORE. I BELIEVE PLTS BEGAN THE PRACTICE OF PULLING THE ALTIMETER VIBRATOR CIRCUIT BREAKER AFTER THE ACFT ENGS AND AVIONICS WERE OFF DUE TO THE EXCESSIVE NOISE IT GENERATES. DURING 'BREAKS' BTWN FLTS; ESPECIALLY ON LONG (14+ HR) DAYS WITH OFTEN 7+ LEGS TO FLY; THIS ADDED NOISE IN THE COCKPIT IS VERY FATIGUING AND CREATES A DISTRACTING ENVIRONMENT. DURING MY FIRST YR AT COMPANY I WAS INSTRUCTED BY SEVERAL CAPTS TO PULL THE CIRCUIT BREAKER TO HAVE SOME 'PEACE' IN THE COCKPIT AND REDUCE FATIGUE BTWN FLTS. I USUALLY ONLY DID IT IF THEY WERE ADAMANT; AS PULLING CIRCUIT BREAKERS IS NOT NORMAL. SINCE THE MEMOS ISSUANCE; WE AS A GROUP HAVE DISCONTINUED THIS PRACTICE; AND NO ONE HAS INSTRUCTED ME TO DO IT. I FULLY RECOGNIZE AND RESPECT THE DANGERS OF AND NEED FOR STANDARD OPERATING PROCS. I UNDERSTAND THAT SINCE THE ISSUE HAS BEEN CLARIFIED BY THE COMPANY; IT IS NOT OKAY TO DO IT ANYMORE (OR EVER WAS?). IF IT GETS PULLED; I BELIEVE IT IS BECAUSE IT WAS COMMON PRACTICE FOR SO LONG; NOT DUE TO BLATANT DISREGARD AND DISRESPECT FOR OUR COMPANY POLICY. I AM NOW THAT MUCH MORE CAUTIOUS AND DELIBERATE IN MY ACTIONS; CHKLISTS; READING NUMBERS; AS I SEE HOW OLD HABITS CAN CREEP UP ON YOU; OR OLD OUT OF DATE PROCS MUST BE CONSCIOUSLY FORGOTTEN TO MAKE ROOM FOR THE NEW; EVER-CHANGING PROCS.