B737 FLC FAIL TO CORRECT AND VALIDATE LAS FMC RNAV DEP PROC; DRIFT OFF COURSE; RECOGNIZE THE PROB AS L30 CHALLENGES THE ERRANT RTE OF FLT.

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IDALE 1 DEP RWY 25R LAS. PRIOR TO DEP; WE WERE INVOLVED IN AN ACFT SWAP AND RUNNING LATE ON PREFLT. THE FO DIDN'T PROGRAM THE DEP RWY INTO THE FMC; AND THE CAPT DIDN'T REVIEW THE NAV ROUTING. (STRIKE 1) PUSH; START; AND TAXI OUT WENT NORMALLY. APCHING THE DEP END OF THE RWY; TWR CLRED US FOR TKOF WITH A 'RPT DEPARTING ACFT IN SIGHT.' WE THEN STARTED OUR DEP ROLL WITHOUT UPDATING THE RWY DATA. IF WE HAD TRIED TO UPDATE; WE WOULD HAVE MOST LIKELY FOUND OUR MISTAKE. (STRIKE 2) APPLIED RNAV PROCS ON DEP AND WHEN WE ENGAGED THE AUTOPLT; THE ACFT TURNED L TOWARDS POINT IDALE. AFTER ABOUT 20 DEGS OF TURN; I RECOGNIZED THE PROB AND CORRECTED BACK TOWARDS CTRLINE; BUT NOT BEFORE THE CALL FROM ATC ASKING WHERE WE WERE GOING. WE REPLIED UNABLE RNAV AND REQUESTED A HDG. WE RECEIVED A HDG AND PHONE NUMBER TO CALL. (STRIKE 3) REST OF THE FLT WENT NORMAL. I CALLED LAS WHEN I GOT TO BUR; AND THE SUPVR JUST WANTED TO KNOW WHAT HAPPENED. I EXPLAINED THE ABOVE; AND HE SAID NOT TO WORRY. CONSIDERATIONS: DO NOT RUSH YOURSELF. PUT RNAV CHK ITEM ON THE CHKLIST. NEED BACKUP RAW DATA WHEN THINGS GO WRONG.