B777 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Critical
Flight Crew Landed As Precaution; Flight Crew Returned To Departure Airport; General Declared Emergency; General Maintenance Action
Aircraft; Human Factors
Approximately 25 minutes after takeoff; R generator went offline. While running checklist and prior to complying with checklist-directed disconnection of the R IDG; the L generator also went offline. The 2 generator failures occurred within minutes of each other. Continued to work ECL for R generator failure; and disconnected R IDG. L and R sides of electrical system load was then assumed by the APU. An initial reset on the L generator was successful. It only lasted maybe a minute. L generator drive shortly disconnected on its own. After collaboration with Dispatch; decision was made to declare an emergency and return. Had to dump fuel. A normal landing was made. Maintenance later informed me that both drives had contaminated fluid.
B777 Captain experiences a dual IDG failure 25 minutes after takeoff. With the APU supplying the electrical system fuel is dumped and the flight returns to the departure airport. Maintenance determines that contaminated fluid was the cause of both failures.