What happened
On 3 August 2011, a Robinson R44 Raven II helicopter, registration ZS-HTY, departed from Cape Town International Airport for a private aerial photography flight. The aircraft was carrying a pilot and three passengers, including a photographer, with the intent to capture images of the University of Cape Town campus.
During an approach toward the campus from a north-easterly direction, the helicopter entered a sudden, uncontrolled descent. The pilot attempted to increase forward speed and altitude to recover, but the aircraft began to sink rapidly. While attempting to maneuver, the helicopter's right-hand skid struck a large tree. The aircraft then impacted the ground and a perimeter fence, eventually rolling onto its left side. The pilot sustained minor head injuries, while the three passengers escaped without injury.
The investigation
SACAA AIID investigators examined the aircraft's maintenance, the pilot's training records, and the flight's weight and balance. The investigation revealed that the pilot had not flown this specific helicopter type as pilot-in-command for 33 months, failing to meet the required competency standards for carrying passengers. Furthermore, the pilot had disregarded specific instructions from his training organization to fly only under instructor supervision.
Technical analysis showed that the aircraft's takeoff weight had been manipulated on official documents to appear within limits, when in reality, the maximum gross weight was exceeded during the flight. Additionally, the right-hand rear door had been removed to accommodate the photographer without any recorded maintenance documentation or authorized procedure.
Findings
- The primary cause of the accident was vortex ring state (settling with power), which made the ground impact unavoidable.
- The pilot lacked recent proficiency and experience on the aircraft type.
- The aircraft was operating in an overweight condition, which reduced the margin between power available and power required.
- A tailwind component during the approach increased the power demand, contributing to the aerodynamic instability.
- The pilot was not flying within the required competency parameters for passenger-carrying operations.