Flight Crew Air Transport Pilot (ATP)
Distraction; Situational Awareness; Time Pressure; Troubleshooting; Workload
Aircraft Equipment Problem Critical
Flight Crew Landed in Emergency Condition; Flight Crew Returned To Departure Airport; General Declared Emergency; General Maintenance Action
Aircraft
After takeoff; crew noticed all cockpit lights flickering. On inspection; found Number 3 generator with excessive kilowatt reading. Shortly after; Number 2 generator failed with an annunciation of 'over excitation' shortly after the AC bus suffered phase imbalance and tripped all three bus tie breaker. This was followed by numerous circuit breakers popping and the failure of the Number 3 generator with a three light trip. ATC was contacted and the decision was made to declare an emergency and return the aircraft to the departure airport for further inspection. On the subsequent approach and landing further breakers popped and accordingly further systems were lost. The decision to reengage the Number 1 bus tie breaker was made on final approach to facilitate sufficient systems to complete a safe approach and landing. No further incidents occurred. The apparent cause was a mechanical failure of the Number 3 generator system; accompanied by the mechanical failure of the remaining generators to protect themselves from the kilowatt spike caused by the Number 3 generator.
A B727's Number 3 Generator failed mechanically resulting in all three bus tie breakers opening and numerous other breakers popping. An emergency was declared while the flight returned to the departure airport.