What happened
On May 31, 2020, an AS350B3 helicopter, operated by Helibravo – Aviação Lda., was conducting a training session in preparation for the upcoming forest fire fighting season. The flight involved a pilot and an instructor pilot performing water scooping and release maneuvers using a Bambi Bucket in a mountainous area near Lousã, Portugal.
During the fifth cycle of the training, the instructor pilot took control of the aircraft to demonstrate the proper procedure for water scooping and takeoff. As the helicopter began its transition from a hover into translational flight, it initiated an uncommanded leftward rotation. The instructor attempted to counteract this movement by applying significant right pedal, but the aircraft failed to respond appropriately to the controls. The helicopter entered a circular descent of approximately 360 degrees, during which the bucket was dragged through vegetation. This forced the aircraft into a steep nose-down attitude, resulting in a high-energy impact with the ground. The aircraft was destroyed upon impact.
The investigation
The GPIAAF conducted a technical examination of the aircraft's hydraulic and electrical systems, coordinated with Airbus Helicopters and Safran Helicopter Engines. The investigation focused on the flight controls, engine, and the sequence of events leading to the loss of control. Investigators examined the wreckage, noting that the main rotor blades were destroyed upon ground contact and the tail rotor transmission system had decoupled due to impact inertia. The engine was found to have been delivering power at the moment of impact, and no pre-accident mechanical abnormalities were identified in the engine or the flight control assemblies.
Findings
- The aircraft experienced an uncommanded leftward rotation during the transition to translational flight.
- The instructor pilot applied unusual force to the flight controls, but the aircraft did not respond to the right pedal input.
- The pilot in the right seat did not utilize the emergency bucket release systems before the impact.
- The impact occurred with a significant nose-down attitude, causing the destruction of the cockpit and lower cabin area.
- The instructor pilot sustained minor head injuries during the crash, while the other crew member was uninjured.
- All dynamic components, including the engine and flight controls, were operating normally prior to the ground impact.