What happened
On 1 June 2018, a private flight departed from Rustenburg Aerodrome with the intention of landing at Zebula Golf Estate & Spa Aerodrome. The Robinson R44 Raven II, registered ZS-MZS, was carrying a pilot and one passenger.
As the aircraft approached the destination, eyewitnesses observed the helicopter hovering at a very low altitude near the Quinta Domingo Farm gate. Shortly after, the helicopter began moving forward and descending. During this transition, the aircraft performed a left bank before rolling and impacting the ground at Lumarie Game Farm in a nose-down attitude. The impact destroyed the aircraft, and both occupants were fatally injured.
The investigation
SACAA AIID investigators examined the wreckage and interviewed witnesses at the scene. The investigation focused on the flight dynamics during the final moments of the descent and the mechanical condition of the main rotor blades. Metallurgical testing was conducted on the recovered blades to check for structural failures. The investigation also reviewed the aircraft's maintenance history, specifically regarding compliance with Airworthiness Directives related to blade skin integrity.
Findings
- The aircraft entered a transverse flow effect during its forward movement, which caused the helicopter to roll to the right.
- In an attempt to recover from this roll, the pilot applied left cyclic control but overcompensated, leading to a total loss of control.
- There was a possibility that the blade skin had debonded from the main rotor blade spar, which would have destabilized the rotor, though this could not be definitively proven.
- There was no evidence of pre- or post-impact fire.
- Weather conditions at the time of the accident were clear and did not contribute to the crash.
Safety action
- It is recommended that the SACAA ensures all operators of Robinson R22 and R44 helicopters strictly adhere to AD 2014-23-16, performing the required inspections before the first flight of every day.
- Compliance with these inspections must be documented in the aircraft records.
- Operators utilizing main rotor blades with part number C016-5 should include the daily inspection in their standard checklists until the blades are replaced.