What happened
On November 19, 2004, an Iberia Airbus A340-600, registration EC-IZX, was operating a flight from Madrid to Mexico City with 289 passengers and 15 crew members. During the cruise phase, the flight crew began receiving intermittent and spurious smoke warnings on the ECAM, including indications for the In-Flight Entertainment (IFE) system and the avionics compartment.
As the flight progressed, a persistent "FWD Cargo Smoke" warning appeared. The crew noted an acidic smell and eye irritation within the cockpit, prompting them to don oxygen masks and discharge the cargo compartment fire extinguishers. Due to the uncertainty of the situation, the flight was diverted to Lisbon Airport.
While the aircraft landed without incident, the situation escalated during taxiing. As the aircraft exited the runway onto taxiway S1, the crew detected a smell of smoke, and the Chief Cabin Attendant reported a smoke odor throughout the cabin. The commander immediately ordered an emergency evacuation. The evacuation was completed within approximately 50 seconds; however, the process resulted in one serious injury (a broken ankle) and four minor injuries among the passengers.
The investigation
The GPIAAF investigation focused on the origin of the intermittent smoke warnings and the cause of the reported odor in the cabin. Technical examinations of the Smoke Detection Control Unit (SDCU) and the aircraft's systems were conducted. Investigators examined the electrical connections of the smoke detectors and performed tests on the air conditioning and galley systems. The investigation also reviewed the flight recorders (FDR and CVR) and analyzed the maintenance history of the aircraft, specifically regarding a known issue with the SDCU hardware.
Findings
- The primary cause of the intermittent smoke warnings was the desynchronization of the Smoke Detection Control Unit (SDCU), triggered by an electrical disconnection of a smoke detector in the control loop during engine start.
- The aircraft was scheduled for a hardware retrofit to a newer version of the SDCU (P/N RA12811M0104) on November 22, 2004, but the incident occurred three days prior to the scheduled maintenance.
- Although the crew reported an acidic smell and eye irritation, post-flight inspections found no physical evidence of fire, smoke, or contamination in the cargo or avionics compartments.
- The flight and cabin crews performed their emergency duties effectively, managing the diversion and the rapid evacuation of all occupants safely.