AN ACR E120 FLC NOTICES A FUEL LOSS FROM THE R MAIN TANK JUST AFTER TKOF. THEY DECLARE AN EMER AND RETURN. THE LEAK WAS FROM A LOWER R WING INSPECTION PANEL ON THE BOTTOM OF THE FUEL TANK THAT HAD SOME FASTENERS MISSING.

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SHORTLY AFTER TKOF I NOTICED A FUEL IMBALANCE AND QUESTIONED THE FO ABOUT THE FUEL LOAD. I THEN SAW THE IMBALANCE WAS INCREASING; AT THAT POINT WE WENT TO XFEED. WE NOTICED FUEL WAS DECREASING FROM THE R TANK AND DETERMINED WE HAD A SEVERE LEAK OF APPROX 100 LBS A MIN. WE THEN TOLD ATC WE NEEDED TO RETURN TO THE FIELD; AS THE IMBALANCE PASSED 600 LBS WE DECLARED AN EMER AND NOTIFIED THE FLT ATTENDANT. AFTER TOUCHDOWN WE SECURED #2 ENG ON RWY 36R WITH APPROX 1100 LBS IMBALANCE. WE TAXIED CLR FOR FIRE RESCUE TO LOOK FOR FIRE AND ADVISE US OF THE SEVERITY. WE WERE INSTRUCTED TO TAXI ONTO RWY 5/23 AND EVAC THE PAX. THE EVAC WAS THROUGH THE MAIN CABIN DOOR; NO INJURY TO PAX OR CREW AND NO DAMAGE TO ACFT OTHER THAN FUEL LEAK. THE LEAK WAS THROUGH ACCESS PANEL JUST INBOARD OF THE R ENG NACELLE. 9 SCREWS WERE GONE AND THE PANEL WAS HANGING DOWN. EVERYONE INVOLVED PERFORMED THEIR TASK EFFICIENTLY AND EFFECTIVELY. THE ONLY THING I WOULD HAVE LIKED TO HAVE DONE QUICKER; WAS TRANSPORTATION FOR THE PAX OFF THE RWY AND OUT OF THE ELEMENTS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR SAID THAT THE ACFT'S FUEL IMBALANCE DIFFERENTIAL LIMITATION IS 600 LBS BTWN WING TANKS ON THE EMB120RT. THEY WERE AT 1100 LBS AFTER TOUCHDOWN. THE CAPT SAID THAT THIS ACFT HAD COMPLETED A 'D' MAINT CHK APPROX 1 MONTH AGO AND; HE WAS TOLD BY A MAINT SUPVR; THIS INSPECTION PLATE WAS REMOVED AND REINSTALLED DURING THAT PROC. HE ALSO WAS; ALLEGEDLY; TOLD THAT THE FASTENERS ON THESE INSPECTION PLATES TEND TO 'BACK OFF' AND MUST BE RETORQUED PERIODICALLY. THE PLATES REFERRED TO BY THE RPTR ARE ON THE UNDERSIDE OF THE WING BTWN THE FUSELAGE OF THE ACFT AND THE ENG NACELLE. THE RPTR SAID THAT THERE ARE 3 PLATES ON EACH WING AND THIS PARTICULAR PLATE WAS ON THE R WING NEAREST THE ENG NACELLE.