What happened
On September 22, 2011, a Eurocopter AS350B3, registered JA6522, departed Takamatsu Airport for a scheduled power transmission line inspection. The flight, operated by Shikoku Air Service Co., Ltd., included the pilot and two passengers. During the mission, the occupants began to notice a burnt odor inside the cabin, followed by the appearance of white smoke rising from the floor area near the rear seats.
As the smoke intensified, the pilot attempted to return to the airport but found the cabin filling with thick smoke, which eventually obscured the flight instruments. Seeking the nearest safe area, the pilot executed a forced landing at a baseball field in Hiketa, Higashikagawa City. While the pilot and both passengers escaped the aircraft without injury, the helicopter caught fire upon landing and was subsequently destroyed by the flames.
The investigation
The Japan Transport Safety Board (JTSB) examined the aircraft' and interviewed the pilot, passengers, and eyewitnesses. Investigators analyzed GPS data from the aircraft's route mapping system and reviewed maintenance and flight manual procedures. The investigation focused on the origin of the smoke in the rear hold and the pilot's ability to execute emergency protocols during the crisis.
Findings
- The investigation could not pinpoint the exact ignition source, but it identified a high probability that the fire originated in the rear hold.
- It is possible that the wiring connected to the strobe light power supply ignited and spread to nearby flammable materials.
- The wiring was not sufficiently protected by a rigid housing or cage, leaving it vulnerable to damage.
- The movement of passengers or baggage in the rear hold, which was not secured with a net, may have damaged the electrical components.
- The pilot was unable to immediately execute critical emergency procedures, such as turning off the electrical master switch, because the necessary steps were not clearly identified as "memory items" in the flight manual.
Safety action
Following the accident, the operator implemented several measures, including prohibiting the use of certain strobe lights and banning baggage loading in the rear hold. The JTSB also issued safety recommendations to the European Aviation Safety Agency (EASA), urging a mandatory design modification to ensure all electrical wiring in the baggage compartment is fully protected from physical damage.