What happened
On 9 August 1998, a Turner Super T40A, registered ZS-VGF, was conducting a private flight departing from Springs Aerodrome. The pilot, accompanied by one passenger, had intended to fly a standard circuit. During the downwind leg of the flight, the pilot encountered a thermal updraft. Utilizing his experience as a glider pilot, the pilot maneuvered the aircraft to intercept the rising air, even notifying a contact on the ground via mobile radio about a climb rate of approximately 500 feet per minute.
Witnesses on the ground observed the aircraft performing various maneuvers. While accounts varied regarding the exact nature of the flight path—with some describing loops or barrel rolls—most observers noted the aircraft entered a steep, left-hand turn that transitioned into a spiral dive. During this high-speed descent, a portion of the aircraft, identified by one witness as the left-hand wing, separated from the airframe. The aircraft subsequently broke apart and crashed in Ebertson Park, Brakpan. The accident resulted in two fatalities and no injuries.
The investigation
SACAA AIID investigators examined witness testimonies and the sequence of events leading to the structural failure. While different observers provided conflicting descriptions of the aircraft's specific maneuvers, a consensus emerged regarding the catastrophic loss of a wing in mid-air. The investigation focused on the aerodynamic forces acting on the Turner Super T40A during the pilot's attempt to utilize the thermal updraft.
Findings
- The aircraft entered a stall and subsequently entered a spin while the pilot was attempting to exploit a thermal updraft.
- During the subsequent recovery attempt, the aircraft's airspeed exceeded the never-exceed speed (Vne).
- The resulting aerodynamic loads caused the aircraft to become over-stressed, leading to the structural failure of the wing.