What happened
On the morning of 26 October 2023, a Robinson R44, Raven II helicopter, registration ZT-RBU, was performing a private flight from a farm in Vaalwater to Marataba Mountain Lodge in the Limpopo province. The flight was conducted under clear weather conditions and visual meteorological rules.
As the pilot was completing the final approach to the landing zone at approximately 50 feet above the ground, the engine suddenly lost power. This triggered the low rotor RPM warning light and the cockpit warning horn. The loss of power led to an uncontrolled descent, during which the helicopter struck the ground heavily on its landing gear skids. The force of the impact was severe enough that the main rotor blades severed the tail boom. The aircraft subsequently rolled onto its right side, sustaining substantial damage to the fuselage, skids, and rotor components. Despite the severity of the impact, the pilot and passenger escaped without injury.
The investigation
SACAA AIID investigators examined the wreckage and the engine, a Lycoming IO-540-AE1A5, which had been transported to a maintenance facility in Gauteng for a teardown inspection. The investigation focused on the mechanical state of the engine and the circumstances leading to the power loss. Technical analysis of the engine components was also conducted by the manufacturer, Lycoming.
Findings
- The pilot was fully licensed and medically fit for the operation.
- The aircraft was airworthy, with all maintenance inspections and certificates up to date.
- The engine had completed 330 hours of operation since its last overhaul.
- The primary cause of the power loss was a mechanical failure within the engine.
- Microscopic analysis of the failed flange bolt revealed that the root cause was fatigue, though the specific origin of this fatigue remains unknown.