C525 CROSSED RWY WHILE TAXIING FOR DEP AT TMB.

Narrative

THIS FLT WAS TO REPOS OUR ACFT FROM TMB TO MIA AFTER A WK LONG TOUR OF DUTY. BECAUSE OF THE PROX OF THE ARPTS; THE FLT WAS EXPECTED TO BE LESS THAN 10 MINS IN DURATION. WHEN I BOARDED THE ACFT; THE SIC (PNF) ALREADY HAD THE R ENG RUNNING. THE SECOND ENG WAS RUNNING BY THE TIME I HAD SECURED AND CHKED THE DOOR AND WAS GETTING SEATED. HE COMPLETED THE BEFORE TAXI CHKLIST WHILE I WAS FASTENING MY SEATBELT. I COMPLIMENTED HIS READINESS AND ANNOUNCED THAT IF THE CHKLIST HAD BEEN COMPLETED; THAT I WAS READY TO TAXI. AS I ROLLED FORWARD ON THE RAMP; HE CALLED GND CTL FOR OUR TAXI CLRNC. I HEARD THE CTLR'S RESPONSE TO TAXI TO RWY 9. I WAS NOT PAYING ENOUGH ATTN TO DISTINGUISH WHETHER HE HAD STATED RWY 9L OR RWY 9R. I ONLY ASSUMED THAT IT WAS THE CLOSER OF THE 2 RWYS TO OUR CURRENT POS. THE ARPT DID NOT APPEAR TO BE BUSY AND I WAS IN THE MIND SET THAT WE WOULD BE TAXIING TO THE CLOSEST SUITABLE RWY -- THE ONE THAT WE HAD USED FOR TKOF EARLIER THAT MORNING AND HAD LANDED ON JUST A SHORT TIME AGO. AS WE TAXIED ONTO THE TXWY; I HAD AN EXCHANGE WITH THE SIC AS TO OUR TAXI RTE AND WE BOTH AGREED THAT IT WAS BACK TO THE RWY WE HAD LANDED ON. AS WE TAXIED THERE; I REMARKED THAT WE WERE GIVEN AN UNRESTR TAXI TO THE RWY SO THAT A SPECIFIC CLRNC TO CROSS RWY 13/31 WAS NOT REQUIRED. AS WE APCHED RWY 13/31; WHILE COMPLETING THE TAXI CHKLIST; WE BOTH ANNOUNCED THAT OUR RESPECTIVE SIDE WAS CLR OF ANY LNDG OR DEPARTING TFC. IN HINDSIGHT; THIS ANNOUNCEMENT THAT WE USE AS MATTER OF HABIT; COULD SAVE US FROM A COLLISION WITH ANOTHER ACFT. I HAVE ALWAYS FELT THAT WE USE THIS ANNOUNCEMENT TO PROTECT OURSELVES SHOULD THE CTLR MAKE SOME MISTAKE AND CLR US ACROSS A RWY THAT IS IN USE. I NEVER FELT THAT THIS PRACTICE WAS USED TO PROTECT US AGAINST OUR OWN MISTAKES -- UNTIL TODAY! AS WE EXITED RWY 13/31 ON THE OTHER SIDE TAXIING TOWARD RWY 9R; THE GND CTLR ANNOUNCED THAT WE HAD MISSED OUR TURN TOWARDS RWY 9L. WE QUESTIONED AMONGST OURSELVES AS TO THE RWY WE HAD BEEN CLRED TO. I DON'T THINK EITHER OF US HAD ACTUALLY TRULY DETERMINED THE RWY THAT WE WERE TAXIING TOWARD; OTHER THAN IT WAS THE CLOSEST OF THE 9'S. IN OUR MISUNDERSTANDING AND COMPLACENCY; WE HAD TAXIED ACROSS AN ACTIVE RWY WITHOUT CLRNC. I CAN ONLY ASSUME THAT NO TFC CONFLICT TOOK PLACE BOTH THROUGH OUR VISUAL CHK BEFORE XING THE RWY AND THROUGH OUR EXCHANGE WITH THE GND CTLR AFTER WE HAD BEEN CORRECTED. WE WERE ISSUED A REVISED RWY FOR DEP AND THE FLT CONTINUED WITHOUT FURTHER INCIDENT. I CAN'T HELP BUT THINK THAT THE FACT THAT THIS WAS TO BE THE LAST FLT OF OUR TOUR OF DUTY WAS A FACTOR. ALSO; WE HAD A FAIRLY BUSY WK AND A FAIRLY BUSY MORNING; WE MAY HAVE BEEN TIRED AND NOT RECOGNIZED IT. WITHOUT ANY DOUBT; WE HAD BEEN COMPLACENT IN NOT REVIEWING OUR TAXI RTE PRIOR TO AND AFTER RECEIVING CLRNC FROM GND CTL. THE COMPLIANCE WITH GOOD OPERATING HABITS SUCH AS CLRING THE RWY PRIOR TO XING AND REVIEW OF TAXI PRIOR TO MOVEMENT ON THE RAMP ARE ESSENTIAL; AND YET IN OUR HASTE WE DROPPED OUR GUARD.