What happened
On 3 October 2001, a Robinson R22 Beta helicopter, registration ZS-RFO, was performing a ferry flight between two farms within the Groblersdal district. The flight was being conducted under fine meteorological conditions. While the aircraft was maintaining straight and level flight, the pilot experienced a sudden and violent loss of control. This was characterized by a steep left turn and erratic changes in the aircraft's attitude.
Upon identifying a failure in the cyclic control system, the pilot attempted to stabilize the aircraft using rudder control and side-slip techniques. Despite these efforts, the helicopter struck a field. As the aircraft skidded approximately 10 meters along the ground, the front of the skids dug into the earth and broke off. The sudden deceleration caused the main rotor to strike the tail boom, severing it from the fuselage. Both occupants of the two-person crew escaped the wreckage unharmed.
The investigation
SACAA AIID investigators examined the mechanical state of the aircraft and the circumstances surrounding the flight. The pilot held a valid commercial license and medical certificate, with 1,200 total flying hours and 137 hours on this specific type. Records indicated that the aircraft had been maintained according to requirements. The investigation focused on the mechanical failure of the control linkage and the physical forces acting on the airframe during the impact.
Findings
- The primary cause of the accident was a failure in the cyclic control system.
- Specifically, the left-to-right cyclic control rod flared and pulled out of its connection, leading to the loss of directional control.
- The investigation noted that current inspection procedures during Maintenance Period Inspections (MPI) are insufficient, as they do not require a detailed examination of the cyclic and collective control rods.
- There were concerns regarding the structural integrity of certain trailers used to transport these helicopters, suggesting that transport methods may contribute to component fatigue or damage.
Safety action
- The investigation highlighted a need to review and enhance inspection protocols during MPIs to ensure the detailed integrity of all control rods is verified.
- The construction and use of helicopter transport trailers require further scrutiny to prevent damage during transit.