AN ACR WDB CREW ADMITS THAT IT OVERSHOT ITS CLB ALT BECAUSE THEY FORGOT TO ARM THE ALT SELECT.

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WE WERE LEVEL AT FL320 APCHING ONEIL ON NOPAC RTE R580. WE HAD REQUESTED FL340 AND WERE WAITING FOR ATC CLRNC. JUST PRIOR TO ONEIL WE WERE GIVEN OUR CLRNC TO CLB TO FL340. THIS WAS A BUSY TIME PREPARING A POS RPT; VERIFYING NEXT POS COORDS; VERIFYING PRESENT POS; CHKING DISTANCE TO NEXT WAYPOINT; ETC. THE ACFT WAS ON AUTOPLT. THE ALT WAS SET IN THE ALT SELECT WINDOW AND A CLB WAS STARTED. BOTH PLTS ACKNOWLEDGED THE ALT IN THE WINDOW. WE REACHED ONEIL MIDWAY THROUGH OUR CLB. THE ACFT TURNED ON COURSE. THE PF FORGOT TO ARM ALT CAPTURE AND THE PNF FORGOT TO VERIFY IT ON THE FMS PANEL. AS A RESULT; WE DID NOT CATCH THE DEV UNTIL THE ALT WARNING SOUNDED. BY THE TIME WE REVERSED OUR CLB; WE HAD DEVED 800 FT HIGH. WE DID NOT FOLLOW SOP'S BECAUSE WE WERE BUSY. WE SHOULD HAVE WAITED UNTIL WE WERE ESTABLISHED ON THE NEXT LEG BEFORE CHANGING ALT. SUPPLEMENTAL INFO FROM ACN 339492: MAYBE CARELESSNESS AND A LITTLE FATIGUE ON MY PART; WE WERE RESCHEDULED TO LEAVE AT XA30 INSTEAD OF XH00 AND I WAS PLANNING ON TIMING MY SLEEP TO WAKE UP ACCORDINGLY.