What happened
On 24 August 2010, an Airbus A3/21-231, registration G-MEDJ, was conducting a scheduled commercial passenger flight from Khartoum, Sudan, to Beirut, Lebanon. While cruising at Flight Level 360 over northern Sudan under night instrument meteorological conditions, the aircraft experienced a series of electrical malfunctions.
The flight crew first observed the captain's primary flight display, navigation display, and upper ECAM unit flickering and eventually going blank. During this period, a continuous chattering sound was heard from the circuit breaker panels. The aircraft's flight control system transitioned to Alternate Law, and the autothrust system entered thrust lock mode. The aircraft also experienced an uncommanded left rudder trim application, causing a left-wing-low attitude and a deviation of approximately 20 nm from its planned track.
Following an 'ELEC GEN 1 FAULT' message, the crew selected the No 1 generator to OFF, which temporarily restored normal display operations. However, when the generator was re-engaged, the symptoms returned. The crew eventually utilized the APU generator to power the systems. After resetting the rudder trim to neutral, the aircraft returned to a wings-level attitude and landed safely in Beirut with no injuries to the 7 crew members or 42 passengers.
The investigation
Investigators examined the aircraft's performance data via the operator's Flight Data Monitoring programme. The investigation focused on why both the captain's and co-pilot's electronic displays were affected and the impact of electrical power interruptions on the flight control system. The investigation also looked into the source of the electrical power generation system fault.
Findings
- The incident was caused by an electrical power generation system fault.
- Multiple electrical power interruptions caused the Flight Augmentation Computer (FAC) to reset, resulting in an incremental offset in the rudder trim.
- The aircraft's ECAM did not clearly announce the root cause of the malfunction, leaving the crew without specific procedures to diagnose the issue.
- The crew's primary challenge was the lack of identifiable symptoms or procedures to address the simultaneous display failures and flight control changes.
Safety action
- Safety Recommendation 2010-092: It is recommended that Airbus alert all operators of A320-series aircraft that an electrical power generation system fault may not be clearly annunciated on the ECAM and could lead to uncommanded rudder trim operation.