PIC OF A B727 USED THE AUTOPLT WHEN IT HADN'T BEEN SIGNED OFF. HE HAD USED IT ALL DAY; TESTING IT AT MAINT REQUEST. DURING THE LAST LEG A CHK PLT AND AN FAA ACI GOT ON BOARD TO PERFORM A CHK RIDE. DURING HIS MIND SET AND PERSONAL HABIT HE FORGOT THE TECHNICALITIES AND ENGAGED THE AUTOPLT.

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I RECENTLY CHKED OUT AS CAPT ON THE B727 WITH ACR X. THE FOLLOWING OCCURRED ON MY FIRST PAIRING AS A PART 121 LINE CAPT. ON THE SECOND DAY OF A 2-DAY PAIRING: XA45 LCL WAKE-UP AFTER A MINIMUM REST LAYOVER IN SAIPAN TO BEGIN A 7 LEG DAY TO FINISH UP THE SHUTTLE BTWN GUAM AND SAIPAN (110 MI). THE B727 WE MANNED WAS DIFFERENT FROM THE ONE WE HAD FLOWN IN THE NIGHT BEFORE. THIS HAD NO AUTOPLT. FLEW TO GUAM. MAINT SWAPPED OUT AN AUTOPLT PITCH CTLR AND PERFORMED A GND TEST SATISFACTORILY; BUT WAS TOO RUSHED TO SIGN IT OFF. MAINT REQUESTED I FLT CHK THE EQUIP ENRTE TO SAIPAN. BECAUSE OF THE SATISFACTORY GND CHK (WITH WHICH I TOOK PART); I AGREED TO LATCH UP THE AUTOPLT ENRTE TO SAIPAN AND SYS CHKED OUT OK IN 'A' MODE; BUT DID NOT HAVE TIME TO TRY 'B' MODE. ON LATER LEG; CHKED OUT 'B' MODE AND IT WAS OK; BUT BACK IN GUAM WHERE I HOPED THE AUTOPLT WOULD BE SIGNED OFF; WE WERE PUSHED FOR TIME. (DURING THE COURSE OF THE DAY WE REJECTED A TKOF; AT LOW SPD -- 5 KTS; BECAUSE OF A TKOF WARNING HORN: STICKY SPD BRAKE NOT FULLY SEATED IN ITS DETENT; AND WE REJECTED A LNDG WHEN; IN THE COURSE OF AN ARPT DISASTER DRILL A RENEGADE AMBULANCE WITH NO COMS WITH TWR RACED ACROSS THE APCH END OF THE ACTIVE RWY WHILE I WAS ON FINAL. BY THE END OF THE DAY; I WAS A BIT TIRED.) ON THE LAST 2 LEGS (GUM-SPN-GUM); MY FO WAS REPLACED BY A CHK AIRMAN WHO WAS GOING TO BE OBSERVED BY THE FAA GIVING ME A 'NO NOTICE' LINE CHK. DETERMINED TO DO A COMPLETE AND THOROUGH JOB; I BRIEFED EVERY PHASE OF FLT THOROUGHLY. ATIS IN SAIPAN RPTED LNDGS ON A RWY WITH NO GS; AND I WANTED TO STUDY WHAT AVAILABLE LNDG AIDS THERE WERE. BECAUSE I WAS FATIGUED AND INVOLVED WITH A NEW COPLT; FAA; DIFFERENT RWY AND LINE CHK; I INADVERTENTLY LATCHED UP A PLACARDED AUTOPLT WHEN I LEVELED OFF AND USED IT UNTIL THE BEGINNING OF MY DSCNT. 1) I SHOULD NOT FLT CHK ANY INOP EQUIP WHILE CARRYING PAX AND NOT BE TALKED INTO IT BY MAINT. 2) IF I'M FATIGUED; I SHOULD NOT FLY.