What happened
On January 15, 2024, a Thrush Aircraft LLC S2R-T660 (710P), operating under a Chilean air operator certificate with Spanish registration, was engaged in aerial firefighting operations near Panguilemo Aerodrome (SCTL) in the Maule Region. The aircraft, designated as AC-13, was part of a coordinated effort by the National Forestry Corporation (CONAF) to contain the "San Juan" forest fire.
During a low-altitude water drop maneuver, the aircraft's right wing struck electrical cables and subsequently two utility poles. The impact caused the pilot to lose control of the aircraft, which caught fire in flight. The aircraft then crashed onto the Ruta 5 Sur highway, striking a passenger vehicle and a parked commercial truck. The accident resulted in the death of the pilot and caused minor injuries to three people traveling in the vehicle.
The investigation
The DGAC Chile investigation examined the flight history, aircraft maintenance records, and the operational procedures used during the fire suppression mission. Investigators reviewed the aircraft's airworthiness status, noting it was maintained by an approved foreign maintenance organization and was within its inspection intervals.
The investigation also analyzed the mission planning provided by CONAF and the operator. While the mission was intended to create a wet barrier to protect nearby infrastructure, the investigation focused on the specific flight path and altitude used during the water release. Investigators also examined the physical evidence from the crash site, including the damaged propeller, the missing right aileron, and the state of the electrical poles.
Findings
- The primary cause of the accident was the inadvertent impact of the right wing against electrical cables and poles during a water drop maneuver.
- The aircraft was performing the water release at an altitude of approximately 3 to 4 meters above the power lines, which was significantly lower than the 50-foot (15.2-meter) minimum altitude required by the operator's manual.
- The impact with the utility poles caused the right aileron to become embedded in a pole, leading to a total loss of control and an in-flight fire.
- Meteorological conditions were favorable and did not contribute to the accident.
- The aircraft's mechanical systems and maintenance records were found to be in compliance with regulatory requirements.
Safety action
- The operator should evaluate safety measures during firefighting operations, with a specific emphasis on adhering to established altitude minimums in the operations manual.
- It is recommended that safety evaluations regarding water drop altitudes be integrated into pre-season and post-season briefings for aerial firefighting operators.