FLC OF AN MDT FAILED TO NOTICE ON PREFLT THAT THE FUEL SVC DOOR HAD BEEN LEFT OPEN RESULTING IN THE AFT ENG NACELLE DAMAGE DURING THE SUBSEQUENT FLT.

Narrative

PRIOR TO DEPARTING LAN TO DTW IN SCHEDULED ACR OPS THE ACFT WAS FUELED BY A LCL FUELING SVC WHILE THE ACFT WAS SIMULTANEOUSLY BOARDED BY PAX. BEFORE LEAVING THE GATE; AS PER THE ACFT PLT'S OPERATING MANUAL; A CREW MEMBER MUST VISUALLY CHK TO ENSURE THE FUEL PANEL ACCESS DOOR IS CLOSED; WHICH IS LOCATED ON THE AFT; R ENG NACELLE. IN ORDER TO COMPLY WITH THIS REQUIREMENT; THE CAPT ASKED THE FLT ATTENDANT TO CHK THE FUEL DOOR; WHICH SHE DID BY LOOKING OUT ONE OF THE AFT; R PAX WINDOWS. SHE RETURNED AND CONFIRMED THE DOOR WAS CLOSED. WE DEPARTED FOR DTW. DURING THE TERMINATION OF THE FLT; DURING THE CAPT'S POSTFLT WALKAROUND INSPECTION; IT WAS DISCOVERED THAT THE FUEL PANEL ACCESS DOOR WAS OPEN AND THAT THE ACTUAL FUEL CAP; NORMALLY ATTACHED TO THE ACFT WAS MISSING; ONLY THE CHAIN REMAINED. PRESUMABLY THE FUEL CAP WAS LOST IN FLT DUE TO AERODYNAMIC FORCES; BUT NOT BEFORE CAUSING DAMAGE TO THE AFT R ENG NACELLE; WHICH CAUSED THE ACFT TO BE GNDED FOR REPAIRS. IN MY PERSONAL OPINION; I ASSUMED THAT NOT ONLY DID THE ACFT REFUELER FORGET TO REPLACE THE FUEL CAP AND CLOSE THE ACCESS DOOR; BUT ALSO; THE FLT ATTENDANT FAILED TO OBSERVE THIS IN HER VISUAL CHK. A POSSIBLE COURSE OF CORRECTIVE ACTION MIGHT BE TO AMEND THE PLT'S OPERATING MANUAL TO REQUIRE A CREW MEMBER (POSSIBLY REQUIRE THIS CREW MEMBER TO BE EITHER THE CAPT OR FO ONLY) TO EXIT THE ACFT AND VISUALLY CHK THE FUEL PANEL ACCESS DOOR.