What happened
The pilot and crew were operating an air ambulance helicopter while participating with the local fire department in a simulated disaster drill. During the exercise, the helicopter took off carrying two volunteers who were acting as immobilized patients. Because of this load configuration, it was necessary to keep the right cargo door open during flight.
While climbing through approximately 600 feet above ground level (AGL), the aircraft experienced a sudden loss of directional control. The pilot suspected that the tail rotor had failed and immediately initiated an autorotation. Despite these efforts, the helicopter impacted the terrain at a high rate of sink, resulting in substantial damage to the airframe.
The investigation
A physical examination of the wreckage revealed the cause of the failure. A strap, which is normally used to secure cargo and patients within the cabin, had departed from its secured position. The strap had exited the cabin area through the open right cargo door during flight.
Once outside, the strap became entangled on the tail rotor assembly. This entanglement resulted in one tail rotor blade being torn off approximately four inches from the hub. The loss of this blade component led directly to the loss of directional control observed during the climb phase.
Findings
The primary contributing factor was the improper securing of cargo equipment. The strap that caused the mechanical failure had not been adequately fastened inside the cabin. Its departure through the open door and subsequent entanglement with the tail rotor demonstrates the critical importance of securing all loose items, especially when external doors must remain open for operational reasons.
The incident highlights the risks associated with modified load configurations during emergency operations. Even in a simulated environment, standard safety protocols regarding cargo restraint must be strictly followed to prevent foreign object damage to critical flight control components.