What happened
On December 17, 2007, an Airbus A320-232, registration PR-MBB, operated by TAM Linhas Aéreas, was performing a scheduled flight from Natal (SBNT) to Brasília (SBBR). The aircraft was carrying 68 passengers and 6 crew members.
While cruising at 38,000 feet (FL 380), the flight crew noticed an uncommanded reduction in airspeed, followed by a sudden loss of power in both engines. This loss of thrust was accompanied by a total loss of electrical power as both generators disconnected. The aircraft descended approximately 6,000 feet while the crew performed emergency procedures to relight the engines. Once power was recovered, the commander elected to return to Natal, where the aircraft landed safely. There were no injuries and no damage to the aircraft.
The investigation
CENIPA's investigation focused on the simultaneous failure of both engines and the subsequent loss of electrical systems. Investigators examined the aircraft's maintenance history, noting that the APU had experienced two automatic shutdowns earlier that day, which had necessitated using an external pressure source for the first engine start and a cross-bleed start for the second.
The investigation also involved international cooperation with the French BEA and the American NTSB. A technical challenge was identified regarding the flight data download: a mismatch between the Flight Data Interface Unit (FDIU) and the Digital Flight Data Recorder (DFDR) caused data to be recorded at a different rate than the recorder's capacity, complicating the retrieval of flight parameters.
Findings
- The primary cause of the dual engine flameout was fuel starvation due to the fuel pumps being left in the off position.
- The crew failed to notice the fuel pumps were inactive because the fuel pump alarm had been suppressed/canceled during the start of the first engine.
- The aircraft's architecture allowed the second engine to be started with fuel pumps off without triggering a new alarm, provided the initial alarm had been cleared during the first engine start.
- Human factors contributed to the event, specifically regarding checklist discipline and the lack of awareness regarding the pump status during the engine start sequence.