What happened
On January 24, 2019, an Airbus AS350-B3e operated by Hélilagon was engaged in firefighting operations near the Piton de la Fournaise volcano on Réunion Island. While transiting from a water drop site to a freshwater replenishment point at approximately 930 ft, the pilot heard a high-frequency noise and simultaneously lost tail rotor effectiveness. The pilot declared a "MAYDAY" and managed to perform an emergency landing on an uneven lava flow near the coast.
Upon inspection, the pilot discovered that the suspension cables of the Bambi Bucket had become entangled in the tail rotor, causing significant damage to the rotor blades and the tail gear box. The pilot successfully shut down the engine following standard procedures, and no injuries were reported.
The investigation
The BEA examined the wreckage, flight data from the Vision 1000 and Helisafe systems, and the pilot's recent work schedule. The investigation focused on the configuration of the external load, specifically the use of a five-meter sling connecting the Bambi Bucket to the helicopter's cargo hook. Investigators also analyzed the meteorological conditions, noting high winds and significant turbulence caused by the volcanic terrain and the heat from the active wildfire.
Findings
Several factors contributed to the collision between the external load and the tail rotor:
- The use of a short five-meter sling, which did not meet the manufacturer's recommendation to use a sling of at least 15 meters (50 ft) or to attach the bucket directly to the hook to maintain sufficient clearance.
- The aircraft was flying at an indicated airspeed of approximately 97 knots, which exceeded the maximum recommended speed of 80 knots for this specific equipment.
- The aircraft was in a descending flight path within highly turbulent air, which can cause the towed load to momentarily move at a different rate than the helicopter.
- The Bambi Bucket was empty, making it more susceptible to aerodynamic shifts.
Additionally, the investigation noted that the intense pressure of the ongoing wildfire and the pilot's heavy workload following a period of leave may have influenced the choice of speed and affected situational awareness. The pilot's significant experience was credited with preventing a more serious accident during the emergency landing.
Safety action
Following the accident, the operator's manual was updated to prohibit the use of slings shorter than eight meters, and a minimum sling length of 15 meters has been implemented for these operations.