AN ACR B757 CREW FAILED TO DO THE PARKING CHKLIST. THE L ENG WAS LEFT RUNNING. ERROR ADMITTED. NIGHT OP. GATE OP.

Narrative

OURS WAS A MULTI-LEG TRIP. ON THIS DAY WE WERE TO FLY EWR-ORD-DCA-ORD-DSM. THE LOUSY WX AT ORD CAUSED EXTENSIVE DELAYS ON THE GND AND IN THE AIR ALL DAY AND NIGHT. ON THE DCA-ORD LEG; THESE DELAYS GAVE US A 4:44 LEG WITH AN 8:46 FLT TIME AND 14:30 DUTY DAY SO FAR; WITH AN ORD-DSM LEG YET TO GO. A PLANE FULL OF PEOPLE WAS WAITING FOR US AT ANOTHER GATE. FINALLY WE PARKED AT THE GATE AT ORD AND WAITED WITH 1 ENG (L) RUNNING FOR EXTERNAL PWR TO BE PLUGGED IN. THE SHUTDOWN SOP WAS DONE AND I LEFT THE COCKPIT. THE COPLT STARTED LEAVING THE COCKPIT WHEN A JUMP SEATER; HWO HAD BEEN RIDING IN THE CABIN; QUESTIONED WHY THE L ENG WAS STILL RUNNING. THE COPLT RETURNED AND SELECTED EXTERNAL PWR AND SHUT DOWN THE ENG. I RETURNED AND THE PARKING CHKLIST WAS DONE. NO DAMAGE DONE; BUT THE DANGEROUS POSSIBILITIES ARE ENDLESS! FATIGUE; STRESS; PRESSURE TO GET TO THE NEXT FLT ALL HELP EXPLAIN THIS LAPSE BUT DON'T EXCUSE IT. WORSE; I CAN THINK OF NO FAILSAFE PROC TO PREVENT IT IN THE FUTURE OTHER THAN RE- EMPHASIZE CONSTANT AWARENESS; ESPECIALLY WHEN FATIGUED AND PRESSURED.