Tail Rotor Failure Leads to Helicopter Crash in Alberta

Casualties unknown • Bell B205A-1 (Helicopter) C-FJTF, CA

A Bell 205A-1 helicopter crashed near Edson, Alberta, after a mechanical failure caused a sudden loss of tail rotor authority during a heavy-lift operation.

What happened

On 24 September 1993, a Bell 205A-1 helicopter, registered as C-FJTF, was conducting heli-slinging operations near Edson, Alberta. The aircraft was supporting a seismic drilling project, transporting a 2,500-pound basket of equipment via a 110-foot longline.

As the basket cleared the tops of 60-foot pine trees, the aircraft experienced intense vibrations. The pilot attempted to land the load, but the helicopter began to rotate and pitch violently. During the descent, the pilot was thrown within his seatbelt and was unable to trigger the cargo release mechanism. The helicopter struck tall trees on its left side, resulting in substantial damage to the aircraft. The pilot sustained serious chest injuries.

The investigation

The investigation focused on the sudden loss of directional control and the mechanical state of the tail rotor drive train. Investigators examined the flight parameters, noting that the aircraft was operating at a low height and low speed. While this flight profile fell within the shaded area of the manufacturer's height-velocity curve—a zone where safe autorotative landings are difficult—the operation was being conducted according to an approved external load supplement.

Technical analysis of the 42-degree intermediate gearbox revealed that the input bevel gear had fractured. This failure effectively severed the power connection between the main transmission and the tail rotor. Additionally, investigators noted that the pilot was not wearing a helmet or using the shoulder harness at the time of the impact.

Findings

  • The pilot lost tail rotor authority because the input bevel gear of the 42-degree intermediate gearbox fractured due to a high-cycle, low-stress fatigue mode of progressive cracking.
  • This fracture disconnected the drive shaft power from the main transmission to the tail rotor.
  • The loss of authority occurred while the helicopter was flying at a low height and low speed over a forested area, which prevented the execution of a safe autorotative landing.
  • The pilot was unable to release the external cargo due to the violent movements of the aircraft following the mechanical failure.

Probable cause

The primary cause of the accident was the fracture of the input bevel gear within the 42-degree intermediate gearbox due to fatigue cracking, which resulted in a total loss of tail rotor authority.

Frequently asked questions

What happened in the 1993-09-24 Campbell Helicopters Ltd. accident near Bell B205A-1 (Helicopter) C-FJTF, CA?

A Bell 205A-1 helicopter crashed near Edson, Alberta, after a mechanical failure caused a sudden loss of tail rotor authority during a heavy-lift operation.

What aircraft was involved and where did it happen?

The accident on 1993-09-24 involved a Campbell Helicopters Ltd., operated by Tail Rotor Drive Train Failure, at Bell B205A-1 (Helicopter) C-FJTF, CA.

What was the probable cause of the accident?

The primary cause of the accident was the fracture of the input bevel gear within the 42-degree intermediate gearbox due to fatigue cracking, which resulted in a total loss of tail rotor authority.

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