Both B777's engine driven generators dropped off the line during climb; then were reset but both dri...

Narrative:

We departed on time and after completing our flight duties the other international relief officer and myself headed back to the main cabin to get ready for our break. While using the lavatory I noticed the lights going out. As I exited the lavatory I also noticed that all the cabin lights were out and the emergency lights were on. At that time we got a call from the cockpit requesting our return. When the other international relief officer and I returned to the cockpit we were informed of the dual generator failure. I noticed the right generator had the drive light on and the captain and first officer were running a checklist on the left generator. The checklist prompted a reset and after performing it; the generator came back online. After about 2 minutes the left generator went back offline and shortly after that a drive light also illuminated on the left generator switch. At that point; the captain and international relief officer started communicating with maintenance; dispatch and duty manager; while I assisted the first officer flying the airplane and communicating with ATC. Shortly after that the captain made the decision to return to the departure airport. We declared an emergency and started heading back to the airport. I made the flight attendants aware of the plan to return and the captain made a PA. After that we started getting ready for the air return. We talked to ATC and then started the fuel jettison checklist. We divide the tasks among the 4 of us to get everything accomplished before landing. The fuel dumping took about 25 minutes; time that we used to return back to the airport and get ready for the approach. The approach and landing were non eventful and after taxiing to the gate; we were met there by operations and maintenance.

Original NASA ASRS Text

Title: Both B777's engine driven generators dropped off the line during climb; then were reset but both DRIVE lights illuminated again so an emergency was declared; the QRH completed and the flight returned to the departure airport.

Narrative: We departed on time and after completing our flight duties the other IRO and myself headed back to the main cabin to get ready for our break. While using the lavatory I noticed the lights going out. As I exited the lavatory I also noticed that all the cabin lights were out and the emergency lights were on. At that time we got a call from the cockpit requesting our return. When the other IRO and I returned to the cockpit we were informed of the dual generator failure. I noticed the right generator had the DRIVE light ON and the Captain and First Officer were running a checklist on the left generator. The checklist prompted a reset and after performing it; the generator came back online. After about 2 minutes the left generator went back offline and shortly after that a DRIVE light also illuminated on the left generator switch. At that point; the Captain and IRO started communicating with maintenance; dispatch and Duty Manager; while I assisted the First Officer flying the airplane and communicating with ATC. Shortly after that the Captain made the decision to return to the departure airport. We declared an emergency and started heading back to the airport. I made the flight attendants aware of the plan to return and the Captain made a PA. After that we started getting ready for the air return. We talked to ATC and then started the fuel jettison checklist. We divide the tasks among the 4 of us to get everything accomplished before landing. The fuel dumping took about 25 minutes; time that we used to return back to the airport and get ready for the approach. The approach and landing were non eventful and after taxiing to the gate; we were met there by operations and maintenance.

Data retrieved from NASA's ASRS site 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	1192431
Time
Date	201407
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZZ.ARTCC
State Reference	FO
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Make Model Name	B777 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Climb
Flight Plan	IFR
Component
Aircraft Component	AC Generation
Person 1
Function	First Officer Pilot Not Flying
Experience	Flight Crew Last 90 Days 255 Flight Crew Type 940
Events
Anomaly	Aircraft Equipment Problem Less Severe Aircraft Equipment Problem Critical

Both B777's engine driven generators dropped off the line during climb; then were reset but both drive lights illuminated again so an emergency was declared; the QRH completed and the flight returned to the departure airport.