Accident Overview
On 16 September 2024 at 1520Z, a Robinson R44 Raven II helicopter (registration ZT-RBY) was involved in an accident at Doornhaag Farm near Vryburg in the North West Province, South Africa. The aircraft was on a private flight to Tswalu Nature Reserve in the Northern Cape Province. The pilot and one passenger were on board; no injuries were reported. The helicopter sustained substantial damage.
Sequence of Events
The pilot reported that while transitioning at approximately 20 feet above ground level and 20 knots, the low rotor RPM warning light and horn activated. The helicopter lost height rapidly. The pilot identified an area for a forced landing. During the forced landing, the tail rotor blades impacted a farm barrier fence, and the helicopter landed hard. Subsequently, the main rotor blades struck the tail boom. The tail boom was substantially damaged.
Findings
The pilot held a valid Commercial Pilot Licence and a Class 1 medical certificate. The helicopter had a valid Certificate of Airworthiness and had undergone a 100-hour/annual inspection on 8 August 2024 with no defects recorded. The loss of engine rotor RPM was attributed to excessive power demand exceeding available power at high-density altitude. The calculated density altitude at the time was 6700 feet, significantly higher than the actual elevation of 4167 feet. The total weight of the helicopter (1000 kg) was within design limits but at the high end of operational limitations, which may have exacerbated performance issues.
Probable Cause
The probable cause was an unsuccessful forced landing after take-off due to loss of engine rotor RPM as a result of high-density altitude. The helicopter landed hard, and the tail rotor struck the tail boom. A contributing factor was density altitude.