What happened
On 19 November 2018, a Robinson R44 helicopter, registration ZS-RPV, was performing a commercial operation to transport technicians and equipment to Geelhoutboom Mountain in the Western Cape. The mission involved repairing radio repeaters that had been damaged by a recent fire. After successfully completing an initial flight, the pilot returned to Witfontein to collect a second technician and several solar panels.
During the second approach to the mountain peak, the pilot encountered an updraft on the southern side of the terrain, which necessitated an aborted landing attempt. While orbiting to reposition for a second attempt, the aircraft encountered a sudden downdraft. In an effort to manage the rate of descent, the pilot increased the collective slightly; however, this triggered the low RPM warning horn. The pilot responded by lowering the collective and increasing the throttle, but the aircraft was already at an altitude too low to permit a safe recovery. The helicopter struck the ground with significant force and tilted backward. In an attempt to move away from the slope and avoid the tail boom striking the terrain, the pilot pulled the collective to regain altitude and turned the aircraft to the right. During this maneuver, the helicopter struck a protruding rock, causing the aircraft to roll onto its right side.
The investigation
The investigation examined the flight conditions, aircraft maintenance, and the sequence of aerodynamic events leading to the impact. The aircraft was found to be within its maximum takeoff weight, weighing 2,120 lbs against a limit of 2,500 lbs. Maintenance records indicated the aircraft was airworthy, with its last mandatory periodic inspection completed approximately 45 hours prior to the accident. Meteorological data confirmed visibility was excellent, though the terrain was subject to variable winds.
Findings
- The primary cause of the accident was a sudden downdraft at low altitude, which resulted in the loss of translational lift during the landing phase.
- The aircraft's proximity to the ground during the encounter with the downdraft left insufficient margin for a safe recovery.
- The impact with a protruding rock during the subsequent maneuvering led to the aircraft rolling onto its side.
- The aircraft sustained substantial damage to several critical components, including the main rotor blades, gearbox, fuel tanks, tail boom, and skids.
- There were no injuries to the pilot or the passenger.