What was found
AFTER COMPLETING SB-328-28-598 FUEL – REPLACEMENT OF BONDING STRAPS INSIDE FUEL TANK ON D328 A/C 3016 DURING HEAVY CHECK, WE EXPERIENCED ADDITIONAL DELAYED FUEL LEAKS. FUEL TANK ACCESS PANELS WERE REMOVED, THE SB WAS ACCOMPLISHED, AND THE FUEL CELLS WERE CLOSED. THE AIRCRAFT WAS THEN FUELED TO APPROXIMATELY 7,000 LBS AND LEAK CHECKED FULL, WITH NO LEAKS NOTED ON 01-MAY-26. ON 04-MAY-26, A WALK-AROUND FOUND A LEAK AT THE LH FEED AFT FUEL PANEL. FUEL WAS TRANSFERRED FROM THE LH WING TO THE RH WING WHILE DEFUELING THE LH WING FOR REPAIR. NO RH WING LEAKS WERE NOTED AT THAT TIME. THE AIRCRAFT REMAINED RH HEAVY WITH THE RH FEEDER FULL WHILE THE LEAK ON THE LH SIDE WAS FIXED, AND NO LEAKS WERE OBSERVED MONDAY THROUGH THURSDAY MORNING. ON 07-MAY-26, THE AIRCRAFT WAS FUELED TO APPROXIMATELY 5,000 LBS FOR FCF, WITH NO LEAKS NOTED AFTER FUELING. AFTER THE AIRCREW RAN THE APU FOR APPROXIMATELY 30 MINUTES, A FUEL LEAK OCCURRED FROM 623-AT. THIS SUPPORTS THE CONCERN IDENTIFIED IN SPR A000109228, WHERE DEUTSCHE AIRCRAFT STATED THERE IS CURRENTLY NO ALTERNATE PROCEDURE TO LEAK CHECK WINGS AFTER FUEL TANK MAINTENANCE WITHOUT USING FUEL. LEAKS ARE NOT ALWAYS PRESENT IMMEDIATELY AFTER REFUELING AND MAY APPEAR DAYS LATER OR AFTER AIRCRAFT OPERATION. WE REQUEST DEUTSCHE AIRCRAFT PROVIDE GUIDANCE, A DEFINED SOLUTION, OR ADDITIONAL STEPS TO IMPROVE THE FULL WING LEAK-CHECK PROCESS FOLLOWING FUEL TANK MAINTENANCE.