On 6 May 2023, an Airbus Helicopters AS350 B3 was conducting routine maintenance ground runs at Smithers Airport in Canada when a loss of control on the ground led to a fatal accident. The purpose of the operation was to balance the tail rotor drive shaft, requiring repeated short engine runs at flight idle while maintenance staff worked nearby.
During the third ground run, shortly after the engine power was increased, the helicopter suddenly began an un-commanded rotation to the right. The pilot reacted by reducing power, shutting off fuel, and applying the rotor brake, but the aircraft had already rotated approximately 540 degrees before coming to a stop. Two maintenance personnel working alongside the helicopter were struck by the tail rotor; one was fatally injured and the other seriously injured.
The investigation found no mechanical faults. Instead, the loss of control resulted from a combination of system conditions and human factors. Critical checklist items had been omitted during successive restarts, including hydraulic system checks and the yaw load compensator check. As a result, hydraulic pressure remained in the system, leaving the anti-torque pedals in an incorrect position. When power was applied, this created a strong yaw force that the pilot was unable to counter effectively.
The pilot had adapted procedures to expedite what was perceived as a routine task, relying on memory rather than full checklist use. Reduced vigilance, limited attention at the moment of the event, and the proximity of ground personnel to the rotating components further increased the consequences.
The accident highlights the importance of strict checklist discipline, effective hazard controls during ground operations, and maintaining awareness that even routine maintenance tasks remain safety-critical activities.
Photo from the official report