What happened
On 17 December 2014, a solo pilot was conducting a private gliding flight departing from Welkom Aerodrome (FAWM) in the Free State province. The flight began with a successful aero-tow, where the ASW 2D7 glider was pulled to an altitude of 5,500 feet above mean sea level at approximately 110 kph. After reaching the target altitude, the pilot released the towline.
Shortly after separation, the aircraft encountered a significant loss of lift. The pilot attempted to maneuver the glider into a thermal to maintain altitude, but the aircraft continued to descend. In an effort to manage the descent, the pilot attempted to dump water ballast from the wing tanks; however, due to the urgency of the situation, only one minute of the required six-minute process could be completed, leaving the wings heavily weighted with water.
As the pilot initiated a forced landing into a nearby ploughed field, the aircraft performed a sharp left turn at an altitude of less than 400 feet. During this maneuver, the left wing tip struck the soft ground, causing the aircraft to ground loop. The impact resulted in the tail-boom breaking off and damage to the left wing.
The investigation
An investigation by the SACAA AIID examined the wreckage and the pilot's credentials. The investigation confirmed that the pilot held a valid gliding license and was medically fit for the flight. The aircraft, an ASW 27, was found to be in a serviceable condition with no evidence of mechanical defects or control malfunctions prior to the impact. All maintenance records and authorities to fly were found to be valid.
Witnesses at the scene observed the aircraft making a steep bank at low altitude, suggesting the pilot was attempting to establish a final approach track for the landing site. The investigation also noted that the aircraft's landing gear was in the down position, consistent with an intended landing.
Findings
- The primary cause of the accident was an unsuccessful forced landing following the loss of thermal activity in flight.
- Atmospheric conditions in the Welkom area likely provided very weak thermals or a localized descending air mass immediately after towline release.
- The aircraft's altitude during the final turn was likely too low to safely complete the maneuver.
- The presence of significant water ballast in the wings, due to the incomplete dumping process, may have influenced the aircraft's handling during the forced landing.