What happened
On 25 September 2006, a Thunderbird MK VI float plane, registered ZU-GCW, was involved in an accident at Hartebeespoort Dam in Gauteng. The aircraft was being operated for private purposes during a pre-flight takeoff procedure. During these maneuvers, a sudden whirlwind struck the aircraft, lifting the right wing to an angle of approximately 90 degrees. This aerodynamic disturbance caused the aircraft to overturn into the water.
There were two people on board the aircraft at the time of the incident. Despite the aircraft capsizing, there were 0 fatalities and 0 injuries reported. The impact resulted in water damage to the airframe, but no occupants were harmed.
The investigation
Investigators examined the circumstances surrounding the takeoff attempt and the meteorological conditions at the time. The weather was reported as CAVOK (ceiling and visibility OK) with a northeast wind of 12 to 15 knots and a temperature of 24°C. The investigation confirmed that the pilot was performing standard pre-flight takeoff procedures when the localized wind event occurred. Maintenance records indicated that the aircraft's last annual inspection was completed on 23 November 2005, after which it had accumulated an additional 46.4 flying hours.