What happened
On 18 May 2009, a Robinson R22 Beta II helicopter, registration ZS-RRO, was engaged in a private wildlife management operation at Grootfontein Farm in Vaalwater, Limpopo Province. The pilot had flown from Polokwane to Thabazimbi to assist a veterinarian with the darting of a buffalo. After picking up the passenger and removing the aircraft doors, the pilot began guiding the buffalo from a forested area toward an open clearing.
During the operation, the pilot approached the animal from behind, flying into the wind. As the pilot executed a right-hand turn to keep the buffalo within the clearing, the engine and rotor RPM began to decay. The pilot attempted to recover the rotor RPM by applying throttle and lowering the collective, a technique known as "milking the collective," but the recovery was unsuccessful. As the aircraft descended, the tail rotor struck a tree approximately 6 meters high, causing the tail boom to break. The main rotor blades subsequently struck another tree in front of the aircraft, resulting in a crash. There were no injuries to the pilot or the passenger.
The investigation
SACAA AIID investigators examined the wreckage and the aircraft's mechanical state. Post-accident testing of the engine at a maintenance organization revealed that the engine was functioning normally. The investigation also confirmed that the aircraft had sufficient fuel for the flight and was within its weight and balance limits. The pilot held a valid commercial helicopter license and was properly rated for the aircraft type.
Findings
- The primary cause of the accident was the tail rotor impacting a tree during the descent.
- A significant contributing factor was the low rotor RPM experienced during the turn.
- The pilot's attention was divided between monitoring the buffalo, communicating with ground crews, and managing the aircraft during low-level flight in a forested area, which may have hindered regular monitoring of the RPM gauge.
- The pilot had a documented history of several previous aviation accidents involving R22 helicopters.