A B747-400 captain reported during maintenance repair at preflight the mechanic found a circuit brea...

Attributes
ACN	985136
Time
Date	201112
Local Time Of Day	0001-0600
Place
Locale Reference	ZZZ.Airport
State Reference	US
Aircraft 1
Make Model Name	B747-400
Operating Under FAR Part	Part 121
Flight Phase	Parked
Component
Aircraft Component	Circuit Breaker / Fuse / Thermocouple
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 240 Flight Crew Total 19000 Flight Crew Type 6000
Events
Anomaly	Aircraft Equipment Problem Critical

Narrative:

During preflight we had a problem with TR3 (EICAS status message). During the repair; the mechanics could not open the circuit breaker; located in the cockpit below and behind the copilot's seat. They ended up damaging the breaker in an attempt to open it with pliers. They still could not open it; and it had to be replaced. It was frozen. I am very concerned that the flight crew would not have been able to open this circuit breaker in flight; had the need arisen. The inability to open a circuit breaker; or its inability to open automatically; could cause an in-flight fire and a potential loss of the aircraft. The circuit breakers should be exercised once in awhile to ensure that they are serviceable. The primary maintenance inspector should be advised of this problem.

Original NASA ASRS Text

Title: A B747-400 Captain reported during maintenance repair at preflight the mechanic found a circuit breaker that was frozen closed and had to be replaced. Captain expressed his concerns with the possibility of inflight fire if a circuit breaker fails to operate.

Narrative: During preflight we had a problem with TR3 (EICAS status message). During the repair; the mechanics could not open the circuit breaker; located in the cockpit below and behind the copilot's seat. They ended up damaging the breaker in an attempt to open it with pliers. They still could not open it; and it had to be replaced. It was frozen. I am very concerned that the flight crew would not have been able to open this circuit breaker in flight; had the need arisen. The inability to open a circuit breaker; or its inability to open automatically; could cause an in-flight fire and a potential loss of the aircraft. The circuit breakers should be exercised once in awhile to ensure that they are serviceable. The Primary Maintenance Inspector should be advised of this problem.

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.

A B747-400 captain reported during maintenance repair at preflight the mechanic found a circuit breaker that was frozen closed and had to be replaced. Captain expressed his concerns with the possibility of inflight fire if a circuit breaker fails to operate.