What happened
On 26 July 2002, a Robinson R-22 Beta helicopter, registration ZS-RGI, was conducting a private flight from Wonderboom Aerodrome toward the Gravelotte area. The aircraft had recently undergone a mandatory periodic inspection and a successful test flight with no defects noted. After refueling to its full capacity of 76 litres, the pilot departed Wonderboom and cruised at an altitude of roughly 4,000 feet.
Approximately 30 minutes into the flight, the helicopter experienced a sudden and violent yaw to the right. The pilot struggled to maintain directional control as the aircraft began oscillating between left and right yawing motions, accompanied by intense vibrations transmitted through the anti-torque pedals. In response to the instability, the pilot lowered the collective to initiate an autorotational descent. While the aircraft became more manageable during the descent, it continued to fish-tail. During the final flare for landing, a final violent yaw to the right caused the helicopter to strike the ground hard at a forward speed of 20 to 30 knots. The impact caused the right-hand skid gear to collapse, and the aircraft slid 35 meters before coming to rest on its side.
The investigation
Investigators examined the wreckage and the mechanical state of the aircraft following the impact. The investigation focused on the sudden loss of tail rotor effectiveness and the physical vibrations reported by the pilot. The aircraft sustained extensive damage during the landing sequence. The pilot survived the accident but sustained a cut to the face and injuries to the right shoulder.
Findings
- The primary cause of the loss of control was that one of the tail rotor pitch link bolts came adrift during the flight.
- This mechanical failure resulted in a loss of tail rotor control, leading to the violent yawing and subsequent emergency landing.
- Meteorological conditions at the time of the accident were fine, with no wind and zero cloud cover.
- A metallurgical analysis of the remaining three bolts showed they were in serviceable condition and showed no signs of impending failure.