What happened
On 28 February 2015, a Robinson R44 Raven II, registration ZS-RUN, was conducting a private flight near Thabimbi, Limpopo. Following a commercial game-transfer operation, the pilot was flying two passengers at a very low altitude—approximately 50ft AGL—to observe wildlife on a neighboring farm. While executing a 90-degree right turn while flying downwind, the helicopter lost altitude rapidly and struck the ground at a 15-degree nose-down attitude. The impact was severe, causing the main rotor hub to break from its attachment and the aircraft to land on its belly. The pilot and one passenger sustained serious injuries, while the second passenger suffered minor injuries.
The investigation
An investigation by the SACAA AIID examined the wreckage and the pilot's flight profile. The aircraft was found to have been well-maintained, with all service bulletins and inspections up to date. Investigators noted that the helicopter was operating at a slow forward speed of about 16 knots, placing it in a near-hover condition that requires precise collective control. While the pilot did not report hearing any unusual sounds or seeing RPM split indications, the physical evidence and flight dynamics pointed to a critical loss of rotor speed. The investigation also considered the pilot's attention, noting that the intense focus on observing the game may have diverted attention from essential flight instruments.
Findings
- The primary cause of the accident was the pilot's failure to maintain main rotor RPM during the maneuver.
- The helicopter was operating at a low altitude, leaving insufficient height for the pilot to execute recovery procedures like engaging autorotation.
- The pilot's focus was diverted by the task of observing wildlife, which likely led to a lack of monitoring of the manifold pressure and rotor RPM instruments.
- The aircraft was flying in a near-hover state with a tailwind component, increasing the difficulty of maintaining stable rotor speed.