What happened
On 11 October 2019, a private flight involving an Alpi Aviation SRL, Pioneer 330, registration ZU-MJB, was conducting touch-and-go landing exercises at Jack Taylor Krugersdorp Aerodrome (FAKR). During the landing roll on Runway 08, the left main undercarriage suddenly collapsed. This caused the left wing to strike the ground, forcing the aircraft to veer off the runway and come to rest approximately five metres from the paved surface. The aircraft sustained substantial damage to the left wing, the left-side undercarriage, and the underbelly, though the pilot escaped without injury.
The investigation
Investigators examined the aircraft's mechanical systems and maintenance history following the incident. The aircraft was found to be in a valid state of airworthiness, with a recent annual inspection completed only about two months prior to the accident. The investigation focused on the retractable tricycle landing gear system, which utilizes an electric motor and screw jacks to manage gear extension and retraction. While the landing gear was fully extended at the time of touchdown, the mechanism failed to secure the gear in the down position.
Findings
Technical analysis of the recovered main landing gear gearbox revealed that the center lock pin had broken, which prevented the over-center mechanism from locking the gear in place. This mechanical failure directly led to the collapse of the left main undercarriage upon touchdown. Furthermore, the investigation established that the existing manufacturer maintenance program for the Pioneer 330 did not include specific inspections or maintenance tasks for the undercarriage gearbox components.
Safety action
Following the discovery that the gearbox was not covered under standard inspection protocols, a recommendation was made for the aircraft manufacturer, the Italian agent, and the Italian Civil Aviation Authority to develop a revised maintenance program that includes explicit inspections of the landing gear gearbox.