AN EMBRAER 120 PARKED ON GATE WITH GPU POWERING ACFT THE GND PWR PLUG CAUGHT FIRE. LATER IN THE DAY GND PWR PLUG AGAIN CAUGHT FIRE INCURRING MAJOR ACFT DAMAGE. CAUSE A SUSPECT GND PWR CTL PANEL.

Narrative

ON MAY/FRI/00; WE ARRIVED AT OUR GATE AND GND PWR WAS PLUGGED IN. WE HAD A GOOD GPU AVAILABLE LIGHT; THE PWR SELECT SWITCH WAS SELECTED FROM BATTERY TO EXTERNAL PWR. THE SYS DEPOWERED AND THE GPU AVAILABLE LIGHT WENT OUT. THE PWR SELECT SWITCH WAS SELECTED BACK TO BATTERY. THE AIRPLANE WAS SHUT DOWN PER OUR SHUTDOWN CHKLIST (PWR SELECT SWITCH OFF). STATION PERSONNEL SAID THE GPU HAD PROBS AND WAS JUST FIXED. THE CREW LEFT THE AIRPLANE. ON MAY/SAT/00; DURING PREFLT INSPECTION WE NOTED THE AREA AROUND THE GPU RECEPTACLE HAD BEEN SCORCHED. GND PERSONNEL SAID THE GPU PLUG CAUGHT ON FIRE. APPARENTLY THE GPU WAS LEFT ON AND PLUGGED IN. A CONTRACT MECH CHKED THE SYS AND SIGNED IT OFF. WE FLEW TO ZZZ. ARRIVING AT THE GATE IN ZZZ; GND PWR AS PLUGGED IN. WE HAD A GOOD GPU AVAILABLE LIGHT AND A NORMAL 28 VOLT READING. WE SET BRAKES AND SHUT DOWN THE AIRPLANE PER THE CHKLIST AND LEFT THE PWR SELECT SWITCH ON EXTERNAL PWR (NORMAL PRACTICE). WE NOTIFIED OUR MAINT CTLR OF ANOTHER MINOR DISCREPANCY AND SUGGESTED THE MECH ALSO TAKE A LOOK AT THE GPU RECEPTACLE. WE LEFT THE AIRPLANE. LATER ON I WAS NOTIFIED THAT THE AIRPLANE CAUGHT FIRE AGAIN AT THE GPU PLUG. SIGNIFICANT DAMAGE WAS RPTED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE EXACT CAUSE OF THE GND PWR FAULT IS UNKNOWN BUT MAINT SUSPECTS THE GND PWR CTL UNIT. THE RPTR SAID THE CONTRACT TECHNICIAN AT XXX WHO INVESTIGATED THE FIRST RPT DID NOT APPEAR TO HAVE THE KNOWLEDGE OF THE EMBRAER 120 ELECTRICAL SYS. THE RPTR SAID THE TECHNICIAN CLEANED THE PLUG AND INSPECTED THE BACK OF THE EXTERNAL PWR PANEL AND CLRED THE LOGBOOK. THE RPTR STATED THE AIRPLANE SHOULD HAVE BEEN GROUNDED AT THIS TIME.