A B747-400 captain reported loss of an AC bus that produced a large number of failure messages. Usin...

Narrative:

Approximately one hour into flight; got multiple EICAS messages; five pages of failures in the cmc of mostly right side navigation and datalink systems. It appeared we had lost an entire bus as all generators and bus ties showed normal; also lost ACARS. Checked circuit breaker (circuit breaker) panel and found AC 2; dist P-7 popped. [We] called dispatch and maintenance for conference. Maintenance checked wiring schematics and said 3-phase breakers sometimes pop. Advised I could use captain's emergency authority to try one reset. We reset the circuit breaker and all systems returned to normal operations. All EICAS messages cleared except no land 3. [We] used cmc to clear all status messages at maintenance direction. Maintenance suggested we turn off and re-engage autopilot to reset no land 3 message and it worked as stated. [We] sent mrm code per maintenance request. The help we received from maintenance was superb! The following systems were lost: ATC right; stabilizer automatic trim; rudder ratio; DME; right ADF; right VOR; right ACARS; mu; radio altitude; right stabilizer; xfr sig; ILS right; flap system monitor; flap cont right; no land 3; transponder right; rudder ratio; sngl satcom; data datalink system. The use of captain's emergency authority was warranted to prevent a diversion. Had the system not reset; we would probably have ended up diverting rather than risk an ocean crossing and possible subsequent failures.

Original NASA ASRS Text

Title: A B747-400 Captain reported loss of an AC Bus that produced a large number of failure messages. Using his Captain's emergency authority; he re-set a circuit breaker and restored the affected systems.

Narrative: Approximately one hour into flight; got multiple EICAS messages; five pages of failures in the CMC of mostly right side navigation and datalink systems. It appeared we had lost an entire bus as all generators and bus ties showed normal; also lost ACARS. Checked Circuit Breaker (CB) panel and found AC 2; DIST P-7 popped. [We] called Dispatch and Maintenance for conference. Maintenance checked wiring schematics and said 3-phase breakers sometimes pop. Advised I could use Captain's emergency authority to try one reset. We reset the CB and all systems returned to normal operations. All EICAS messages cleared except No Land 3. [We] used CMC to clear all status messages at Maintenance direction. Maintenance suggested we turn off and re-engage autopilot to reset No Land 3 message and it worked as stated. [We] sent MRM code per Maintenance request. The help we received from Maintenance was superb! The following systems were lost: ATC RIGHT; STAB AUTO TRIM; RUDDER RATIO; DME; RIGHT ADF; RIGHT VOR; RIGHT ACARS; MU; RADIO ALT; RIGHT STAB; XFR SIG; ILS RIGHT; FLAP SYS MONITOR; FLAP CONT RIGHT; NO LAND 3; TRANSPONDER RIGHT; RUDDER RATIO; SNGL SATCOM; DATA DATALINK SYS. The use of Captain's Emergency Authority was warranted to prevent a diversion. Had the system not reset; we would probably have ended up diverting rather than risk an ocean crossing and possible subsequent failures.

Data retrieved from NASA's ASRS site as of July 2013 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.

Attributes
ACN	990889
Time
Date	201201
Aircraft 1
Make Model Name	B747-400
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Component
Aircraft Component	Electrical Distribution Busbar
Person 1
Function	Check Pilot Pilot Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 90 Flight Crew Total 13000 Flight Crew Type 2900
Events
Anomaly	Aircraft Equipment Problem Critical

A B747-400 captain reported loss of an AC bus that produced a large number of failure messages. Using his captain's emergency authority; he re-set a circuit breaker and restored the affected systems.