FUEL IMBALANCE.

Narrative

AFTER TKOF THE L WING DIPPED NOTICEABLY. THE CAPT AND I HEARD AND FELT A LOUD VIBRATION. THE CAPT INFORMED ATC THAT WE WOULD NEED TO RETURN TO THE ARPT FOR LNDG. UPON AN UNEVENTFUL RETURN TO OUR TERMINAL; THE CAPT INSPECTED THE EXTERIOR OF THE ACFT AND FOUND 1 NOSE GEAR DOOR OPEN. ALSO; BEFORE THE CAPT LEFT THE COCKPIT HE DISCOVERED A LARGE FUEL IMBALANCE (APPROX 1800 LBS). THE CAPT UNLATCHED THE FUEL DOOR AND FOUND THAT BOTH OF THE REFUEL SWITCHES WERE ON INCLUDING THE DE-FUEL SWITCH FOR THE R WING FUEL TANK. THERE IS A GANG BAR ON THE INSIDE OF THE FUEL DOOR THAT WOULD NORMALLY CLOSE ALL OF THESE SWITCHES IN THE EVENT THAT THE FUELER FORGETS TO CLOSE ANY OR ALL OF THE SWITCHES. THIS BAR WAS FOUND TO BE BENT JUST ENOUGH SO THAT IT WOULD NOT MAKE CONTACT WITH THE SWITCHES TO CLOSE THEM. OUR MAINT STAFF CHKED THE FUEL DOOR AND CONFIRMED THIS. BOTH FUEL DOORS AND NOSE GEAR DOORS WERE CHKED AND CONFIRMED CLOSED PRIOR TO DEP. THERE WERE NO MAJOR CTL PROBS NOTED AND NO EMER WAS DECLARED. CALLBACK CONVERSATION WITH RPTR FROM ACN #286726 REVEALED THE FOLLOWING INFO: THE RPTRS FLY THE EMB-120 FOR A REGIONAL ACR. THERE IS NO EFFECT ON THE ACFT IF THE REFUEL SWITCHES ARE LEFT 'ON.' WHEN A DE-FUEL SWITCH IS LEFT 'ON' AFTER THE FUEL HOSE HAS BEEN DISCONNECTED; THE ENG DRIVEN FUEL PUMP WILL TRANSFER FUEL IMMEDIATELY; AT A VERY HIGH RATE; TO THE OPPOSITE FUEL TANK; CAUSING AN IMBALANCE. THE BRASILIA HAS 2 FUEL TANKS WITH NO DUMP SYS; THE RPTR IS AWARE OF OTHER PLTS HAVING A SIMILAR PROB. THE FUELING DOOR IS EASILY REACHABLE FROM THE GND AND THE RPTR IS NOW OPENING IT TO SEE THAT ALL OF THE SWITCHES ARE 'OFF.' THE DOOR OPENS TO FAIR WITH THE WIND STREAM. SEVERAL HAVE BEEN TWISTED OR RIPPED OFF IN THE PAST. THE RPTR NOW UNLATCHES BOTH NOSE GEAR DOORS SO THAT HE WILL KNOW IF THEY ARE ATTACHED TO THEIR ACTUATORS. THERE SEEMS TO BE NO OTHER WAY TO DETERMINE IF THE DOORS ARE IN PROPER ORDER.