What happened
On February 23, 2008, an EVA Airways Boeing 747-400, registration B-16410, arrived at Bangkok Suvarnabhumi International Airport from Taoyuan International Airport. After the aircraft parked and disembarkation began, passengers noticed smoke emanating from the left dado panel beneath seats 64A and 65A.
In response to the smoke, cabin crew directed passengers to evacuate the aircraft via the aerobridge. During the process, some passengers opened the L4 and R5 emergency exits. A maintenance representative from EVA Bangkok subsequently accessed the aft cargo waste tank compartment, where they identified the source of the smoke. The representative used a fire extinguisher to suppress the smoke and deactivated the electrical power. All passengers and crew members were unharmed.
The investigation
The investigation focused on the electrical components within the aft cargo section. Investigators examined the waste tank compartment and discovered that the rivets securing an aluminum standoff for wiring had failed.
Technical analysis revealed that one of the three-phase APU power supply cables from the No. 1 APU generator had chafed against a bolt on the waste tank tube fixture. This abrasion wore through the cable's insulation, allowing the exposed conductor to ground against the aircraft structure. This created a short circuit, leading to arcing that ignited contaminants on nearby insulation blankets.
Findings
- The primary cause of the incident was improper routing and installation of the APU cables, which created excessive loading and complex stress conditions. This led to the fatigue and breakage of the STA 2060 standoff.
- The failure of the standoff allowed the APU power cable to move, resulting in the insulation jacket chafing against a fastener.
- The resulting electrical arcing ignited accumulated contaminants (including lint, hair, and fibers) on the insulation blankets.
- The investigation also noted that the accumulation of contaminants on the blankets increased the fire's potential spread, and that the existing maintenance program did not sufficiently address the cleaning of such contaminants.
- During the evacuation, the investigation noted that the class divider curtains remained closed, which hindered smoke visibility and passenger movement, and that some passengers opened exit doors without crew authorization.