Narrative:

During preflight I noticed circuit breakers aa 7 and 8; 'ext power egiu 1' and 'APU gen egiu 2' popped open without collars. Since the aircraft had been written up for APU problems I told the captain we should talk to the station operations to see if the mechanics who worked the previous issue had forgotten to collar them as part of the previous troubleshooting; or had simply left them pulled unintentionally. When the mechanic arrived; he noted the circuit breaker for 'APU gen egiu 2' (aa 9) was physically broken.he called maintenance control to advise the circuit breaker must be repaired prior to flight. After the replacement circuit breaker arrived the power was removed from the aircraft by selecting the 'ext power southwest' off and de-selecting the aircraft batteries. The ground power unit was not disconnected and the mechanic began opening the circuit breaker panel and removing the bad circuit breaker. Immediately the circuit breaker panel arced loudly as an electrical short occurred and smoke filled the cockpit. It was not a small amount; it was smelled all the way in the first class cabin. Visibly upset about the error; the mechanic immediately physically unplugged the ground power.my primary concern follows the arching and smoke. While talking to maintenance control; the controller asked the contract mechanic to take cell phone pictures of the damage so they could determine if the aircraft was still 'good to go.' I voiced my concern to the captain and the mechanic that a full check and test of the entire electrical panel should be accomplished; not simply having maintenance control look at cell phone pictures. The amount of smoke generated by the arcing event indicated that much greater damage to the electrical panel could have occurred.based on the overheard conversations I was very concerned the aircraft would be returned to revenue service without a full inspection of the panel being accomplished. Unless the degree of the arcing event and resultant smoking was made clear it could simply be written off as a non event. I refused to fly the aircraft without a complete inspection. The flight was canceled and the aircraft parked on the service ramp.

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Original NASA ASRS Text

Title: An A320 flight crew refused an aircraft for service when a maintenance operation resulted in significant electrical arcing and smoke from the involved circuit breaker panel.

Narrative: During preflight I noticed circuit breakers AA 7 and 8; 'EXT PWR EGIU 1' and 'APU GEN EGIU 2' popped open without collars. Since the aircraft had been written up for APU problems I told the Captain we should talk to the station operations to see if the mechanics who worked the previous issue had forgotten to collar them as part of the previous troubleshooting; or had simply left them pulled unintentionally. When the Mechanic arrived; he noted the circuit breaker for 'APU GEN EGIU 2' (AA 9) was physically broken.He called Maintenance Control to advise the circuit breaker must be repaired prior to flight. After the replacement circuit breaker arrived the power was removed from the aircraft by selecting the 'EXT PWR SW' off and de-selecting the aircraft batteries. The ground power unit was not disconnected and the Mechanic began opening the circuit breaker panel and removing the bad circuit breaker. Immediately the circuit breaker panel arced loudly as an electrical short occurred and smoke filled the cockpit. It was not a small amount; it was smelled all the way in the first class cabin. Visibly upset about the error; the Mechanic immediately physically unplugged the ground power.My primary concern follows the arching and smoke. While talking to Maintenance Control; the Controller asked the Contract Mechanic to take cell phone pictures of the damage so they could determine if the aircraft was still 'good to go.' I voiced my concern to the Captain and the Mechanic that a full check and test of the entire electrical panel should be accomplished; not simply having Maintenance Control look at cell phone pictures. The amount of smoke generated by the arcing event indicated that much greater damage to the electrical panel could have occurred.Based on the overheard conversations I was very concerned the aircraft would be returned to revenue service without a full inspection of the panel being accomplished. Unless the degree of the arcing event and resultant smoking was made clear it could simply be written off as a non event. I refused to fly the aircraft without a complete inspection. The flight was canceled and the aircraft parked on the service ramp.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.