What happened
On 28 December 2003, two gliders, ZS-GRZ and ZS-GFE, were launched via winch from Howick Aerodrome for soaring activities. The first aircraft, a K6CR, departed at 1430Z, followed five minutes later by the KA6E at 1435Z.
After approximately 40 minutes of soaring, the pilot of ZS-GFE contacted the pilot of ZS-GRZ via radio to announce intentions to join the same thermal. While the pilot of ZS-GFE followed the lead aircraft, he widened his turn toward a straighter path to search for better lift. During this maneuver, the canopy of ZS-GFE was suddenly struck by debris, shattering the transparent cover. The pilot of ZS-GFE reported being unable to see ZS-GRZ at the time of the impact.
An eyewitness in a third glider observed ZS-GRZ entering a vertical dive with its tail section missing and wings still attached, before the aircraft disappeared from view. The K6CR struck the ground approximately 4nm from Howick Aerodrome, resulting in one fatality. The pilot of ZS-GFE landed safely at Howick Aerodrome with no injuries, though the aircraft sustained minor damage.
The investigation
SACAA AIID examined the flight paths and radio communications of the involved aircraft. The investigation confirmed that the weather conditions were clear with temperatures around 29°C and visibility exceeding 10km. Investigators reviewed the maintenance records for both gliders, noting that both had undergone annual inspections earlier in 2003. The investigation focused on the spatial relationship between the two aircraft during the thermal maneuvering process.