What happened
On 17 August 2024, a pilot operating a Bushbaby Explorer, registration ZU-IOU, was conducting a proving flight from Howick Airfield (FAHC) in KwaZulu-Natal. The flight, performed under visual meteorological conditions, was intended to be a short circuit returning to the same airfield.
While the takeoff and initial flight phases proceeded without incident, the aircraft encountered difficulties during the landing phase on Runway 16. As the pilot applied the brakes following touchdown at approximately 55 knots, the aircraft underwent a ground-loop and veered toward the left side of the runway. The impact of the maneuver caused the left main landing gear to collapse inward. The pilot, who was uninjured, disembarked to find the aircraft had sustained substantial damage.
The investigation
SACAA AIID investigators examined the mechanical state of the landing gear and the aircraft's maintenance records. The inquiry focused on the failure of the brake assembly and the validity of the aircraft's airworthiness documentation. The investigation scrutinized the physical condition of the brake caliper attachment bolts and the status of the aircraft's Certificate of Release to Service (CRS).
Findings
- The primary cause of the excursion was the failure of the brake caliper attachment bolts, which sheared under the load of braking.
- The investigation determined that the bolts had succumbed to corrosion and metal fatigue, a condition that was not externally detectable during the pilot's pre-flight inspection.
- The failure of these bolts caused the caliper to rotate with the wheel hub, effectively locking the wheel and inducing the sideways movement.
- The aircraft's Certificate of Release to Service had expired on 3 February 2024, meaning the required maintenance certification was not valid at the time of the accident.
- The aircraft was operating under an Authority-to-fly (ATF) certificate as part of a proving flight for non-type certificated aircraft.