What happened
On 8 March 2008, a Robinson R44 II helicopter, registration ZS-RJL, was conducting a private pleasure flight from Rand Aerodrome to the Sun City heliport. The flight, which included the pilot and three passengers, proceeded without incident until the final approach stages.
As the pilot prepared to land at the Sun City heliport, the airspeed was reduced to 10 knots with a descent rate of 400 feet per minute. During the attempt to cushion the landing using collective pitch, the aircraft entered a state of settling with power. This resulted in a hard landing on an incline approximately 27 meters short of the helipad, causing damage to the helicopter's skids and striking a nearby shrub.
Following the initial impact, the pilot attempted to reposition the aircraft onto the level surface of the helipad without first inspecting the damage. During this maneuver, the tail rotor made contact with a perimeter fence, leading to substantial damage to the tail rotor blades, the gearbox, and the main rotor blades.
The investigation
An investigation by the SACAA AIID established that the aircraft was properly maintained, and all required documentation and certifications were in order. The engine and airframe showed no signs of mechanical failure, and the fuel system was found to be free of contamination.
The investigation focused on the flight dynamics during the approach. It was determined that the combination of low forward airspeed and a high rate of descent created the aerodynamic conditions necessary for the aircraft to enter a vortex ring state. Furthermore, the investigation noted that the pilot's decision to attempt a repositioning maneuver without verifying the extent of the initial landing damage led to the secondary impact with the perimeter fence.
Findings
- The primary cause of the hard landing was the aircraft entering a vortex ring state due to an incorrect approach technique.
- The secondary damage to the tail rotor and gearbox was caused by a tail strike against the perimeter fence during a repositioning attempt.
- The pilot did not exit the aircraft to inspect the skids for damage following the initial impact on the incline.