What happened
On April 9, 2021, a Bell 206L1 helicopter was performing passenger and cargo transport services for a telecommunications company in the Los Muermos area, specifically near Llico Bajo in the Los Lagos Region of Chile. Approximately five minutes after departing from the Río Pescado sector, the aircraft was in straight and level flight when the engine suddenly lost power.
In response to the power loss, the pilot initiated an emergency autorotation maneuver. The aircraft subsequently impacted a native forest area at a low vertical speed and overturned to the right. Despite the impact, the pilot and the four passengers on board escaped the wreckage without injuries. The aircraft sustained significant structural damage, including a fractured tail boom, deformed rotor blades, and a broken landing skid.
The investigation
DGAC Chile conducted an investigation into the mechanical and operational aspects of the flight. Investigators examined the aircraft's maintenance records, which showed that the operator was following the approved maintenance program and that the most recent 300-hour inspection had been completed in December 2020. The fuel, Jet A-1, was tested and found to meet all required standards.
Technical inspections of the engine, a Rolls-Royce 250-C30P, were performed by the manufacturer in the United States. The physical inspection and subsequent functional tests in a test cell revealed no evidence of fire, internal damage, or malfunctions. The engine was found to be capable of producing sufficient power and responding correctly to throttle inputs. Furthermore, the investigation ruled out meteorological conditions as a contributing factor, as the weather was clear at the time of the event.
Findings
- The loss of engine power in flight occurred for reasons that could not be determined through physical inspection or functional testing.
- The manufacturer, Rolls-Royce, noted that since 2007, there have been at least eight documented instances of similar power loss events where the cause remained undetermined.
- The pilot successfully executed the necessary emergency procedures, leading to a low-speed impact that prevented fatalities.
- The aircraft's structural damage was consistent with a vertical impact into trees followed by a rollover.
Safety action
Following the investigation, the DGAC recommended that the findings be shared with helicopter operators utilizing Rolls-Royce M250-C30 engines to alert them to the possibility of unexplained power loss. Additionally, the authority emphasized the importance of maintaining robust survival procedures for operators facing extreme emergency situations.