Introduction
On 21 February 2023 at 0620Z, a Robinson R44 Raven II helicopter, registration ZS-RTH, was involved in an accident during an aerial work operation (game darting, Part 137) near Brisbane Farm, Pomfret, North West Province. The helicopter was substantially damaged, but the pilot and veterinarian on board sustained no injuries.
Sequence of Events
The pilot and veterinarian took off from Brisbane Farm for a game darting operation. While flying at approximately 40 feet above ground level (AGL), the pilot positioned the helicopter for the veterinarian to dart buffalo. After the darting was completed, the pilot turned downwind. During the turn, the main rotor RPM low audio warning sounded. Due to the low altitude, the pilot could not recover, and the helicopter impacted bushy terrain. The main rotor blades, rotating below normal speed, flapped down and severed the aft tail boom. The helicopter rolled over to the right and came to rest.
Weather Conditions
At the time of the accident, weather was: wind 045° at 10 kt, visibility 9999 m, temperature 18°C, no cloud, CAVOK, dew point 10°C, QNH 1019 hPa.
Probable Cause
The probable cause, as determined by the investigation, was: "During a game darting operation whilst the pilot manipulated the flight controls, the main rotor RPM decayed, which resulted in the helicopter losing height, followed by a crash-landing as there was insufficient height available to restore the main rotor RPM to cushion the landing."