Date: 201602
Local time of day: 1201-1800
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Aircraft: B767 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: AC Generation
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Check Pilot; Instructor; Pilot Not Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Flight Instructor; Flight Crew Air Transport Pilot (ATP)
Human factors: Distraction; Workload; Troubleshooting
Anomaly: Aircraft Equipment Problem Less Severe
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance; Flight Crew Landed As Precaution; Flight Crew Returned To Departure Airport; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: I was giving a Target Of Evaluation to a new Captain. This is a 4 crew 12 hour flight. We departed the gate on time with everything normal. I was in the right seat and the [new Captain] was the PF. The [other] Captain and First Officer (FO) were the relief crew.Approximately 25 minutes after takeoff cruising at FL300 the autopilot disconnected and the aircraft rolled slightly feeling initially like an engine failure. The Captain took control of the aircraft as many multiple electronic failures were occurring. After identifying the problem the relief crew started running the checklist. ATC queried us for a loss of transponder. I told them to standby as we were working an issue. He asked if we needed assistance and I stated not at this time. I took control of hand flying the aircraft as the Captain's side had lost navigation; autopilot; auto throttles; top EICAS screen amongst the many messages. The checklist allowed for a generator reset. All systems came back normal. As soon as I attempted a SATCOM call to the dispatcher/maintenance for flight continuance and or concerns the AC bus dropped off line again. The APU was on line but did not cover the bus. We told ATC we would need to return to [destination airport]. He asked if it would be ok for a vector in order for us to sequence back. He then tried to sequence us on an arrival. I told him that we needed a vector as multiple navigation/autopilot issues were again being an issue. I was able to get the FMS programmed for the arrival and flew the magenta line in heading select as there was no LNAV/VNAV.Once we were headed back we [advised ATC] due to the overweight landing and asked for permission to dump fuel. We were maxed out at takeoff of 411k with a landing max landing weight of 320k. Meanwhile [the other] Captain was diligently coordinating the remaining TTSR with the flight attendants; passengers and calling local OPS. ACARS and SATCOM were inoperative for Dispatch and maintenance calls but the QRH had a land at the nearest suitable alternate. We consulted several manuals for max landing weight (ODM) and overweight landing considerations. We elected to dump as much as possible and an extended downwind. The Captains side recovered some of the navigation with the Alternate selector switches. The Captain suggested I might be more comfortable in the left seat for landing. I agreed and switched and the FO in to the right seat for landing. We landed at approximately 361k; flaps 25; ref161 and Max auto brake. The landing was smooth and uneventful probably because I had no landing lights. We had the trucks do a hot temp inspection. The right side got 2 brakes to 9 and the left 2 to 8. We crossed 25 left and was without a gate so ATC kept us taxiing to cool the brakes. They dropped to 4/5 by the time we shut down and towed in to the gate.This was a very busy event. This would have been very difficult without the extra help from the additional pilots. Their input and coordination was a great help in the success of this flight. The flight attendants were exceptional as well.I am not sure we could have done anymore at this time. However; every ATC frequency check in required souls on board and fuel. I felt one time was enough and provided additional distractions.




Synopsis: A Boeing 767 check airman reported an inflight AC electrical bus power failure which affected several significant aircraft electronic components. After an unsuccessful attempt to reset the affected generator; a decision was made to dump fuel and return to the departure airport; where a successful overweight landing was accomplished.