What happened
During flight operations, a critical mechanical failure occurred involving the helicopter's tail rotor system. The retaining pin located at the aft end of the ballast bar disconnected unexpectedly. This failure allowed the ballast bar to disengage from its aft bolt attachment point.
Once detached, the ballast bar swung freely into the plane of rotation for the tail rotor blades. The moving ballast bar struck both tail rotor blades, causing them to separate from the assembly. This impact resulted in an immediate and total loss of directional control over the rotorcraft.
The pilot attempted to maintain control but was unable to do so due to the mechanical failure. Unable to sustain flight stability, the pilot executed an autorotation maneuver. The aircraft completed the autorotation and landed hard on the ground.
The investigation
Examination of the accident site and remaining components revealed that the ballast bar had physically struck the tail rotor blades. The separation of both tail rotor blades was consistent with impact from a foreign object within the rotation plane, specifically the disengaged ballast bar.
Findings
The primary factor in this accident was the disconnection of the ballast bar aft retaining pin. This mechanical failure allowed the ballast bar to enter the tail rotor's path, leading to blade separation and loss of control. Loss of directional control was the direct result of the tail rotor damage.
Safety message
Regular inspection of retaining pins and fasteners on rotating components is essential to prevent similar disengagements during flight.