What happened
On the afternoon of 14 October 2023, a Robinson R44 Raven II helicopter, registration ZT-RLP, was engaged in a private livestock culling operation near Lephalale, Limpopo. The flight, which involved a pilot and two passengers, was intended to monitor and cull zebra and antelope species on Dwarsfontein Farm.
During the maneuvers required to position the aircraft for a shooter, the pilot experienced a decay in main rotor RPM, triggering an audible warning and an instrument light. This forced the pilot into an autorotative descent at approximately 200 feet. The helicopter struck dense bush and rocky terrain heavily, resulting in substantial damage to the airframe, including the main and tail rotor blades. Despite the impact, there were 0 fatalities and no injuries were reported.
The investigation
SACAA AIID investigators examined the aircraft's configuration and the pilot's credentials. The investigation revealed that the aircraft was operating with the right aft door removed. Furthermore, the investigation found that the pilot was flying with an invalid medical certificate, which effectively rendered his private pilot licence invalid at the time of the accident. Additionally, the pilot lacked the specific helicopter cull or livestock rating required for such operations.
Findings
Several critical factors contributed to the loss of rotor RPM and the subsequent crash:
- Improper Weight and Balance: The aircraft was operating with a substantial forward and lateral center of gravity (CG) condition, placing the longitudinal CG outside of the permitted forward limit.
- Environmental Conditions: High density altitude, caused by a temperature of 35°C, significantly impacted engine performance.
- Operational Errors: The pilot allowed the main rotor RPM to decay while maneuvering for the shooter.
- Regulatory Non-compliance: The pilot was operating without a valid medical certificate and without the necessary livestock culling rating.