On Jan. 28, the National Institute of Scientific Investigation (NISI) released an investigation result indicating that the fire that broke out on the AIR BUSAN flight BX391 (to Hong Kong) preparing for takeoff at Gimhae International Airport was likely caused by a short circuit inside the auxiliary battery.
The Ministry of Land, Infrastructure and Transport’s Aviation Rail Accident Investigation Committee (ARIC) disclosed on the 14th that the preliminary analysis results from NISI suggest that there is a high likelihood the initial ignition occurred due to internal insulation breakdown of the auxiliary battery (when the anode and cathode are short-circuited).
NISI explained that upon analyzing the debris of the auxiliary battery found in the cabin where the fire occurred, multiple electrical melting traces were confirmed. Such traces are a characteristic phenomenon that occurs when heat is generated due to a short circuit inside the battery.
NISI stated that although it is difficult to pinpoint the exact cause of the short circuit due to severe damage to the battery, it assessed that the likelihood of fire originating from other facilities within the aircraft is extremely low. The response report also noted, "No particularities related to ignition were found in the internal electrical wiring, lighting fixtures, or circuit board debris of the aircraft," concluding that it is highly likely that the fire started from the auxiliary battery.
The location where the fire first occurred is presumed to be the overhead compartment above seat 30 on the left side. Video footage captured by passengers during the incident shows flames starting from the overhead compartment above row 30, and debris from the burnt auxiliary battery was found on the floor at seat 31 after the fire was extinguished.
Previously, ARIC, along with NISI, the police scientific investigation team, and the fire department, conducted a joint fire investigation at the location where the aircraft was stored on the 3rd of last month. During the investigation, electrical wiring from rows 28 to 32 on the left side of the cabin, lighting fixtures, and debris from the auxiliary battery were secured for analysis.
The evidence secured was subsequently transferred to NISI for detailed analysis, including CT scans and microscopic examinations, resulting in the conclusion that the fire most likely originated from the auxiliary battery.
ARIC stated that based on the investigation results thus far, it plans to focus further inquiries on the possibility that the auxiliary battery was the cause of the fire. Additionally, if safety measures are deemed necessary during the accident investigation, safety recommendations will be issued to the respective airline.
An ARIC official stated, "We will do our best to determine the precise cause of the accident" and noted that the decision on whether to disclose additional investigation results will be made depending on the progress of the accident investigation.