A B747-400 RETURNED TO FIELD AFTER DUMPING FUEL WITH DOOR #4L FALSE LATCHED.

Narrative

ON AUG/THU/96 FLT RETURNED TO FIELD WITH DOOR #4 LEFT OPEN WITH A FALSE LATCH. THIS DOOR WAS CLOSED BY DDDD CATERING PERSONNEL. THE ACFT HAD TO DUMP 100000 LBS OF FUEL; AT A COST OF ABOUT $75000 FOR FUEL AND CREW FLT TIME. 4 PAX DEPLANED ON RETURN. WE FOUND THE TOP PORTION OF THE DOOR WAS FALSE LATCHED. RECYCLED AND INSPECTED DOOR FOUND OK. PLEASE WHEN WE ACCOMPLISH A CIRCLE CHK THAT WE PAY SPECIAL ATTN TO THE TOP PART OF THE DOOR. THIS DOOR WAS ABOUT 2 INCHES INSIDE OF BEING FAIRED WHICH COULD BE SEEN FROM THE GND. I WAS THE DISPATCHING MECH RESPONSIBLE FOR THE EXTERIOR DOOR-PANEL CHK. I COMPLETED A PREDEP WALK AROUND OR 'CIRCLE CHK' AND VERIFIED THAT ALL DOORS AND PANELS WERE FAIRED WITH THE FUSELAGE. IN ADDITION; I ALSO COMPLETED THE REQUIRED B747 MAIN CARGO DOOR CLOSING LOG. PRIOR TO PUSHING BACK THE ACFT I INFORMED THE CAPT THAT 'ALL DOORS ARE CLOSED AND CIRCUIT BREAKERS ARE PULLED VIEW-PORT ALIGNMENT MARKS ARE VISIBLE' AND THE CAPT CONCURRED THAT 'ALL LIGHTS INDICATED OUT' (CLOSED). I PUSHED BACK AND DISPATCHED THE ACFT. AFTER TKOF AND CLBOUT CREW STATED THAT DOOR WARNING FOR DOOR #4L APPEARED. SUSPECT ACFT PRESSURIZATION POPPED THE FALSELY LATCHED DOOR AJAR; THE CREW DUMPED FUEL AND RETURNED TO ZZZ. INSPECTION REVEALED THAT THE DOOR WAS LATCHED AT THE BOTTOM BUT NOT AT THE TOP CORNER. FLT ATTENDANTS MADE MENTION THAT THE FOOD CATERING PERSONNEL HAD DIFFICULTY WITH THE DOOR BUT NEITHER PARTY HAD RPTED IT TO MAINT.