What happened
On 26 August 2005, a student pilot departed Ballito Aerodrome for a solo training flight in a Windlass Aquilla, registration ZU-MRB. The flight followed a brief dual instruction session earlier that day, and weather conditions were reported as fine. During the flight, the aircraft experienced a catastrophic structural failure that caused the wing to detach from the cart.
Witnesses on the ground observed the aircraft flying over blue gum trees. One observer noted the engine RPM increasing and witnessed the wing separating from the cart and gliding backward, while the cart dropped toward the ground. The aircraft's wreckage was located the following morning, approximately 3.37 km from Ballito Aerodrome. The pilot sustained fatal injuries due to the high-impact forces of the cart's descent.
The investigation
SACAA AIID investigators examined the wreckage and the structural components of the Windlass Aquilla. The investigation focused on the separation of the wing from the cart and the physical evidence left on the airframe. Metallurgical analysis of the pylon, strut, and safety cables showed no manufacturing defects or prior deficiencies; the components were found to be adequate for their intended purpose and likely failed only upon impact with the ground.
Investigators analyzed the wreckage to determine if the separation was caused by external factors, such as contact with high-tension wires or clear air turbulence (CAT). While the cart was found near high-tension wires, there was no evidence of wire contact. Furthermore, the structural damage patterns did not support a failure caused by turbulence, as the damage indicated a specific type of rapid deceleration and longitudinal force rather than vertical gust loads.
Findings
- The primary event was the separation of the wing from the cart during flight.
- The aircraft's maintenance records were in order, and the aircraft had undergone an annual inspection 25 hours prior to the accident.
- The pilot was properly licensed for the solo training operation.
- The investigation established that the cart was subjected to rapid deceleration and a downward pitching motion, which caused the trapeze base bar to strike and sever the profile tube.
- This structural failure led to a sequence where the wing became unrestrained in pitch, eventually causing the pylon to break and the wing to separate entirely.