What happened
On 15 July 1999, a Robinson R22 helicopter, registration ZS-HUB, was engaged in aerial work near the Baltimore Game Farm. The pilot had flown from Vaalwater to the site to assist in locating a buffalo trapped in a snare. After landing in an open field, the pilot removed the aircraft doors to facilitate the pickup of a veterinarian. Following the mission, the pilot flew back to the original landing spot to retrieve the doors.
Upon landing, the pilot secured the cyclic and collective friction mechanisms but left the engine running at 75% RPM. While the pilot exited the aircraft to collect the doors, the helicopter unexpectedly lifted vertically to an altitude of roughly 200 feet. The aircraft drifted approximately 100 meters from its position before beginning a slow descent. During the descent, the tail section struck the ground, resulting in extensive damage to the airframe. No injuries or fatalities were reported as the aircraft was unoccupied at the time of the incident.
The investigation
The investigation focused on the sequence of events leading to the unplanned flight and the state of the aircraft's controls. Investigators examined the engine settings and the mechanical state of the friction locks. It was established that the engine was left idling at a high power setting while the pilot was outside the cockpit. The investigation also reviewed the manufacturer's guidelines regarding engine idling temperatures and RPM limits.