What happened
On the afternoon of 30 September 2023, a Robinson R44 Raven II helicopter, registration ZS-RXY, was involved in an accident in the Pine Ridge suburb of Emalahleni. The aircraft, operating a commercial charter flight, had departed from the One United sports ground with a pilot and two passengers, intending to fly to Burgersfort.
Shortly after takeoff, while the helicopter was approximately 30 feet above the ground and traveling at a forward speed of roughly 25 knots, the pilot observed the low main rotor RPM light and heard the audio warning buzzer. This sudden decay in engine and rotor RPM caused the aircraft to lose altitude, resulting in a crash-landing on Gazania Street. During the impact, the helicopter rolled onto its right side, causing the rotor blades to strike the ground. Despite the substantial damage to the aircraft, there were 0 fatalities and 0 injuries among the occupants, who were able to exit the aircraft through the door and windscreen.
The investigation
SACAA AIID examined the circumstances surrounding the flight and the technical state of the aircraft. The investigation confirmed that the pilot held a valid Commercial Pilot Licence and was medically fit for the operation. The aircraft was found to be airworthy, with a valid Certificate of Airworthiness and a recent 100-hour mandatory periodic inspection completed less than two weeks prior to the accident. The operator also held a valid Air Operating Certificate and had permission to use the sports ground for the flight.
Findings
- The primary cause of the accident was a decay in the main rotor RPM as the helicopter attempted to climb.
- The aircraft was operating at a low airspeed of approximately 25 knots, which was below the 50-knot threshold recommended in the Pilot's Operating Handbook height-velocity diagram for a safe climb.
- The flight was conducted within a high-risk area of the height-velocity diagram, where the aircraft lacked sufficient performance margin to recover from the RPM loss.