What happened
On 20 April 2016, a Robinson R44 II helicopter, registration ZS-OWT, was conducting a commercial game darting operation in the Rooiberg area of Limpopo Province. The flight, operated by True North Aviation, included the pilot, a veterinarian, and a game lodge owner. To facilitate the operation, all four doors of the aircraft had been removed prior to departure.
The mission involved herding animals from high ground to flatter terrain for darting and subsequent collection by ground teams. While maneuvering the aircraft to assist the veterinarian in darting an animal, the pilot performed a tight right-hand turn. During this maneuver, the pilot received a low main rotor RPM audio warning. Due to the low altitude and insufficient height to recover the rotor speed, the pilot initiated a forced landing straight ahead.
Before reaching the ground, the main rotor blades struck several trees. The subsequent hard landing caused the skid gear to collapse and the lower vertical fin to strike the rocky terrain. While there were no injuries to the occupants, the aircraft suffered substantial damage.
The investigation
SACAA AIID investigators confirmed that the pilot held a valid commercial license with the appropriate type rating. The aircraft was airworthy and the weight and balance calculations showed the helicopter was 222 pounds below its maximum takeoff weight at the start of the flight.
At the time of the incident, the density altitude was 6,200 feet, and weather conditions were clear with light winds. The investigation also noted that the aircraft had been involved in two previous incidents in 2007 and 2010, both involving tail boom damage during landings.
Findings
- The primary cause of the accident was an unsuccessful forced landing caused by unsuitable terrain.
- The pilot encountered a low main rotor RPM condition during a tight turn.
- The low altitude prevented an effective recovery of the rotor RPM, necessitating the emergency descent.