Airbus A320 N462UA incident near Newark, New Jersey

Probable cause

a fault in the airplane's AC 1 electrical bus that caused a number of other electrical busses on the aircraft to lose power.

NTSB analysis

This incident occurred when United Airlines flight 731 experienced a fault in the airplane's AC 1 electrical bus, one of the two primary electrical distribution systems for the airplane, which in turn caused a number of other electrical busses on the aircraft to lose power. The loss of this electrical power led to the loss of a number of aircraft displays and systems. During the flights return to the airport, multiple messages on the electronic centralized aircraft monitoring (ECAM) system, which provides information to the crew regarding failures that have occurred on the aircraft along with recommended corrective actions, were being displayed then removed by the ECAM system, making it difficult for the flight crew to interpret and address the error messages. There were no faults found in the airplane wiring and the testing and teardown found don faults in the #1 integrated drive generator (IDG), bus tie contactor (BTC), and generator control unit (GCU).

Text from the NTSB. Open the NTSB docket for DCA08IA033 for the full record.