Helicopter crashes during external load operation after sudden yaw (N7915)

What happened

The accident occurred while the helicopter was in a hover configuration carrying an external load. During this phase of flight, the pilot reported hearing a loud bang followed immediately by an uncommanded yawing motion of the aircraft. In response to the sudden loss of directional control, the pilot released the external load and applied collective pitch to gain altitude while centering the cyclic controls. Despite these corrective inputs, the main rotor blades struck nearby trees, causing the aircraft to fall to the ground.

The investigation

A thorough examination of the engine and associated components was conducted following the accident. Mechanical inspection did not reveal any evidence of mechanical failure or malfunction that would explain the initial loud noise or the subsequent loss of control. No physical defects were found in the powerplant that could account for the event.