What happened
On 7 March 1999, a winch launch was being conducted by the Underberg Soaring Club at Underberg Airfield in KwaZulu-Natal. The pilot of the Phoebus C Glider, registration ZS-GGC, initiated a launch from Runway 14 under favorable meteorological conditions, characterized by good visibility and a light easterly crosswind.
During the ascent, once the aircraft reached an altitude of roughly 200 feet and an airspeed of 130 km/h, the winch driver observed the winch beginning to overspeed. This was caused by a lack of sufficient tension on the cable. To prevent equipment damage, the winch power was shut down. The pilot subsequently released the winch harness.
Following the release, the pilot attempted to return to the runway for a landing. While flying the base leg, a tailwind component caused the glider to drift toward the airfield's boundary fence at an altitude of approximately 50 to 75 feet. In an effort to clear the fence, the pilot executed a right-hand turn, during which the right wing struck the boundary structure. This impact induced a 360-degree spin, leading to a nose-down impact with the ground. There were no injuries reported, though the aircraft was heavily damaged.
The investigation
Investigators examined the mechanics of the winch launch and the flight path taken following the cable tension loss. The inquiry focused on the aircraft's attitude during the launch phase and the pilot's decision-making regarding the margin of safety during the subsequent go-around and landing attempt.
Findings
- The pilot maintained an excessively shallow nose-up attitude during the winch launch.
- This attitude resulted in insufficient cable tension, which triggered the winch overspeed and the subsequent emergency release at 200 feet.
- The pilot failed to maintain a sufficient margin between the altitude during the go-around and the ground, specifically failing to account for the glider's glide characteristics relative to the available runway length and the presence of the boundary fence.