What happened
On 25 February 2007, a microlight aircraft, registration ZU-EIR, was conducting a performance test flight as part of a Proving Flight Authority near Empangeni. The flight, which included the pilot and the aircraft owner, had been flying locally for approximately twenty minutes when a mechanical failure occurred while the aircraft was on the base leg for runway 35.
A retaining bolt from the throttle torque tube detached and fell, causing the tube to drop onto the airframe's structural components. Due to uncertainty regarding throttle response and control, the pilot elected to land on runway 35 rather than diverting to the more suitable runway 09.
While the touchdown itself was smooth, the aircraft began to veer sharply to the right once the tail wheel settled at a walking pace. Despite the pilot's attempts to correct the veer using full left rudder and left braking, the aircraft could not be stabilized. The aircraft departed the runway at a 90-degree angle toward the east, striking a sandy verge. The impact caused the main undercarriage to collapse, leaving the aircraft resting on its belly. There were 0 fatalities and 0 injuries resulting from the incident.
The investigation
Investigators examined the mechanical failure and the assembly of the throttle system. The manufacturer's inspection revealed that a bolt intended to hold the throttle bell-crank in place had loosened during standard operation. This was identified as an assembly and installation error rather than a fundamental design defect. The manufacturer noted that no other owners had reported similar issues prior to this event.
Findings
- The primary cause of the mechanical failure was an assembly/installation fault involving a loose bolt.
- The pilot lost directional control of the aircraft following touchdown.
- The aircraft sustained damage to the propeller, fuselage, cowlings, right wing, and undercarriage.