What happened
On July 31, 2020, at approximately 11:30 local time, an Airbus Helicopters AS 350 B3 was conducting a flight from the Santiago SpA helipad in Huechuraba toward Tuncahue. The mission involved transporting the aircraft to an agricultural site for frost control monitoring. While overflying the Independencia district in the Santiago Metropolitan Region, the pilot experienced an unannounced engine failure in flight.
According to the pilot, the engine shutdown occurred suddenly without any prior visual or audible warnings. The failure was accompanied by a rightward yaw and the activation of red "GOV" and "ENGINE P" warning lights on the instrument panel, alongside an aural warning. As the main rotor RPM began to decrease, the pilot initiated an emergency autorotation maneuver. Due to the densely populated urban environment, the pilot selected a parking lot at the Dr. Roberto del Río Children's Hospital as the landing site. The aircraft performed a hard landing, during which the tail rotor struck a tree, resulting in significant structural damage.
The investigation
The DGAC Chile investigation focused on the mechanical state of the Arriel 2B1 engine and the maintenance history of the aircraft. Investigators examined the wreckage, noting severe damage to the fuselage, including fractured windows and detached sliding doors. The main rotor assembly sustained heavy damage, with the Starflex head fractured and rotor blades deformed or delaminated. The landing gear was found deformed, consistent with a high-impact landing.
Technical analysis of the engine revealed that the unit was seized, with fractured internal bearings and obstructed oil injectors. Furthermore, the investigation reviewed the maintenance logs, noting that while the aircraft had undergone recent inspections, there were gaps in the recording of specific operational parameters. Specifically, the logs did not include data regarding "operating atmospheres" or the systematic recording of engine power check parameters, which are essential for trend monitoring.
Findings
- The primary cause of the accident was an unplanned engine shutdown during flight.
- The engine was found to be seized, with internal mechanical failure and contaminated oil.
- The landing was characterized by a high-impact force, causing the landing gear to deform and the tail section to strike a tree.
- Maintenance records lacked the systematic recording of engine power check parameters and specific operating environment data, which are necessary for effective trend monitoring and early detection of engine degradation.
- The aircraft was operating within its approved weight and center of gravity limits at the time of takeoff.