Background
On 12 September 2013, Swiss International Airlines flight SWR2140, an Airbus A320 registered as HB-IJU, was en route approximately 60 nautical miles north of Marseille when the aircraft experienced a loss of cabin pressure during cruise flight. The crew performed an emergency descent to a lower altitude.
Flight Sequence
The flight had departed with only one of the two pneumatic systems operational due to a pre-existing malfunction. During the cruise, the operating pneumatic system exhibited characteristics that led to overheating, causing it to automatically shut down. This resulted in a loss of cabin pressure and triggered the emergency descent. After landing, maintenance personnel conducted troubleshooting, and the aircraft returned to Zurich following repairs.
System Condition
The aircraft's pneumatic system had an existing issue that limited its operation. The crew was managing the flight under the Minimum Equipment List (MEL) procedures, which allowed dispatch with one system inoperative. However, the procedures for operating the remaining system were found to be confusing, leading to suboptimal operation. Additionally, a manufacturer service bulletin that could have improved the system's performance had not yet been implemented on the aircraft. The manufacturer had also developed a revised MEL procedure, but it was not yet available to the airline at the time of the incident.
Contributing Factors
Investigation identified several factors that contributed to the serious incident:
- The flight began with only one pneumatic system operational.
- Confusing procedures led to that system not being operated optimally.
- The pneumatic system had characteristics that caused overheating, resulting in its automatic shutdown.
- A manufacturer service bulletin addressing the issue had not been executed.
- A revised MEL procedure from the aircraft manufacturer was not yet available to the airline.
- Information and procedures for managing an in-flight system failure were not clearly presented to the crew.
Injuries and Damage
There were no personal injuries and no damage to the aircraft.
Meteorological Conditions
Weather conditions at the time and location of the incident were not a factor.