What happened
On 19 July 2012, a Robinson R44 Raven II helicopter, registration ZS-RUI, was preparing for a private flight from the Witfontein Fire Base in the George area of the Western Cape. After two passengers disembarked, the pilot attempted to lift off for the final leg of the journey to Botlierskop Private Game Reserve.
As the aircraft reached a hover approximately 4 to 6 feet above the ground, it became unstable, exhibiting significant pitching and yawing motions. The pilot attempted to stabilize the helicopter by increasing power; however, this action led to the aircraft entering two consecutive 360-degree clockwise turns. During this uncontrolled sequence, the helicopter struck a wire mesh perimeter fence before impacting the ground. The pilot sustained minor injuries during the accident.
The investigation
SACAA AIID investigators examined the wreckage and the mechanical state of the aircraft. While the pilot reported that the controls felt stiff during the initial hover, post-accident testing confirmed that the hydraulic system was fully functional and the friction adjustments were correctly set. Maintenance records indicated that the airframe and engine had been properly maintained, with the last periodic inspection completed earlier that year.
Physical evidence revealed that the tail rotor skid had made contact with the soft ground during the takeoff sequence. This contact caused damage to the tail boom structure, which subsequently led to the failure of the flexible coupling plate attachment assembly. This failure disconnected the tail rotor drive shaft from the gearbox drive assembly, rendering the tail rotor ineffective and causing the uncommanded turns observed by witnesses.
Findings
- The pilot was properly licensed and the aircraft held a valid Certificate of Airworthiness.
- The primary cause of the loss of control was gusty wind conditions at the takeoff site.
- The initial contact between the tail rotor skid and the ground damaged the tail boom, causing the tail rotor drive shaft to fail.
- The lack of a windsock at the fire base prevented the pilot from accurately assessing the wind strength and direction, as the pilot had relied on ground references from a previous landing.
Safety action
- It is recommended that the authorities engage with the owners of the Witfontein Fire Base to request the installation of a windsock to assist pilots in determining wind conditions at this frequent landing site.