What happened
On August 15, 2011, an Airbus A330-322 departed Düsseldorf International Airport carrying 383 passengers and 11 crew members. Shortly after takeoff, a flight attendant seated near door 2R observed a loud bang, followed by smoke and visible flames emanating from the service light integrated into the door panel.
The crew immediately notified the cabin lead and the flight deck. Flight attendants utilized a Halon fire extinguisher to spray the area through the door's openings. While visible flames were extinguished, smoke continued to emerge from the door panel. The flight crew declared an emergency and initiated a return to Düsseldorf, landing safely approximately 13 minutes after the initial departure.
The investigation
The BFU examined the electrical components of the service light, specifically the power supply unit (PSU) designed to convert 115V/400 Hz AC to 6V for the halogen lamp. The investigation focused on the environmental protection of the PSU and the structural integrity of door 2R.
Investigators found that the door structure allowed water to enter through openings on the upper side, and the insulation mats behind the panel were heavily saturated with water. Laboratory analysis of the PSU revealed evidence of high current flow along two traces on the circuit board. The BFU also reviewed the component's certification under RTCA/DO160C standards and the manufacturer's previous service information letters regarding moisture-related failures.
Findings
- The fire was caused by a short circuit within the power supply unit.
- The short circuit was triggered by the ingress of water, which reduced the insulation resistance on the circuit board.
- The door's design allowed for moisture accumulation through both external rain/weather exposure when the service door was opened and internal condensation.
- The environmental classification of the PSU (Category W) was insufficient for the actual installation conditions, as the component was not adequately sealed against moisture in its specific orientation.
- Previous manufacturer communications (OIT) failed to adequately communicate the risk of actual fire, focusing instead only on component failure and the smell of burning.