B747-400
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Workload; Troubleshooting; Distraction; Confusion
Aircraft Equipment Problem Critical; Inflight Event / Encounter Fuel Issue
Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Returned To Departure Airport; Flight Crew Landed in Emergency Condition; General Maintenance Action
Aircraft
Normal departure preparations were completed; engines started and we taxied to Runway XX for departure. Take off was normal and as we were climbing out with an autopilot engaged the master caution/beeper activated with the autopilot disconnecting and numerous EICAS messages populating the upper screen and associated status messages on the lower screen. We continued the climb out; now getting vectors and using FLCH/HDG SEL as LNAV/VNAV was no longer working. We coordinated an intermediate level off with ATC and advised of an electrical issue and requested vectors to stay away from air corridors. It was determined upon inspection of the P6 panel that the #4 AC distribution BUS CB (Circuit Breaker) had tripped. A call via satcom was placed to Ground Control and a three way call with Dispatch and [Maintenance Control] was initiated. [Maintenance Control] has us disconnect the #4 IDG and reset the CB. It worked momentarily but once again tripped. As a result the flight could no longer continue to ZZZZ1 with degraded systems from the malfunctioning BUS feed and a return to ZZZZ was coordinated with ATC. Fuel jettison was initiated (45 minutes) and upon completion of all QRH items and checklists and re-assessing the aircraft systems; an approach back into ZZZZ was prepared. The approach was normal and after rollout and taxi in the aircraft was shut down and secured. Maintenance was briefed after the appropriate log book entries made and the crew was subsequently released to rest.SOPs were followed and good crew coordination/ATC coordination allowed us to complete the task at hand with a positive outcome.
On takeoff from ZZZZ; passing approximately 500 ft. the AC BUS 4 distribution circuit breaker popped along with numerous EICAS messages. ATC was advised and radar vectors were requested. We continued the climb to FL250 under vectors while working the checklist.On completion of the checklist and in consultation with Dispatch; Maintenance and the Chief Pilot a decision was reached to return to ZZZZ. We advised ATC we would need to return and would need to dump fuel. Permission was granted and on completion of dumping we returned to ZZZZ for an uneventful landing.
A B747 flight crew reported observing numerous caution messages associated with a failed AC electric system bus; resulting in a return to the departure airport.