What happened
On August 2, 2009, a British Airways Boeing 757-236, registration G-CPEM, was performing a scheduled international flight from London Heathrow to Barcelona. During the approach to Barcelona Airport, the crew observed a "STANDBY INVERTER" status message on the EICAS. Shortly thereafter, an acrid odor began to permeate both the cockpit and the passenger cabin.
As the aircraft continued its descent, the situation escalated rapidly. Smoke became visible in the passenger cabin and emerged from the left side of the captain's seat in the cockpit. At 09:39 local time, while at 4,500 feet, the crew declared a MAYDAY due to the smoke and deployed oxygen masks as a precaution. During the final stages of the approach, several additional EICAS messages appeared, including warnings for the yaw damper and spoilers, resulting from the failure of the standby AC bus. The captain opted for a manual landing at 09:44 on runway 25R to avoid relying on automated systems that might be compromised by the electrical fault.
Upon landing, the crew ordered an immediate evacuation. While seven of the eight available slides were successfully deployed, the evacuation of the 176 passengers and the crew was complicated by the fact that the door 2R opening mechanism failed to assist, requiring significant physical effort to open. All passengers were evacuated, though eight passengers required medical attention for various minor injuries and anxiety.
The investigation
The CIAIAC examined the technical failure of the aircraft's electrical components and the functionality of the emergency exit mechanisms. Investigators analyzed the damaged static inverter and found that the fire was localized to the component's housing. The investigation also reviewed airport emergency procedures, specifically the management of evacuated passengers in the terminal.
Technical analysis of the static inverter revealed that the fire originated from the overheating of a specific carbon composition resistor (R170). This overheating subsequently caused adjacent capacitors to catch fire. Furthermore, the investigation into the failed evacuation of door 2R determined that while the door's activation mechanism was functional, a loss of gas from the reservoir—likely due to a defect in the frangible disc—prevented the pneumatic open-assist system from functioning correctly.
Findings
- The primary cause of the smoke and fire was the overheating of resistor R170 within the static inverter, which led to the combustion of nearby capacitors.
- The fire was contained within the static inverter's protective housing and did not spread to other aircraft systems.
- The failure of the door 2R open-assist mechanism was caused by insufficient gas pressure in the actuator, likely due to a leak through the frangible disc.
- The crew's decision to prioritize a manual landing and skip the "Smoke, Fire or Fumes" checklist was considered a calculated risk taken to manage the increasing workload and smoke density.
- At the airport, the designated holding area for uninjured passengers was occupied by other flight operations, resulting in the evacuation survivors being mixed with other passengers in a crowded boarding lounge.