What happened
On the afternoon of 2 June 2021, a Tecnam P92 Echo, registration ZU-BJY, was conducting a routine circuit-and-landing training flight at Grand Central Airport. The flight, operated by Appelo Aviation, included an instructor and a student pilot. During the sixth circuit, following touchdown on Runway 17, the aircraft began to veer uncontrollably toward the left side of the runway.
The instructor attempted to regain directional control by applying right rudder, but the maneuver was unsuccessful. The aircraft eventually exited the paved surface and came to a rest on the grass adjacent to the runway. While the aircraft sustained substantial damage to its left landing gear, both occupants escaped the incident without injury.
The investigation
An investigation by the SACAA AIID established that the deviation from the runway was caused by the mechanical failure of two bolts and nuts securing the left main landing gear. Upon inspection of the aircraft after the event, the crew noted the left gear was loose and the attachment hardware was missing.
Investigators examined the maintenance history and found that the aircraft had flown 52.8 hours since its last 50-hour inspection. This meant the required inspection of the undercarriage bolts, as mandated by the aircraft maintenance manual (AMM), was overdue. There was no documented evidence that the necessary inspection had been performed to check for cracks or proper torque.
Findings
- The primary cause of the runway excursion was the failure of two left landing gear attachment bolts and nuts.
- This failure was likely the result of a fatigue crack that progressed undetected due to a lack of proper inspection as required by the AMM.
- A contributing factor was the manufacturer's requirement for only a visual inspection of the bolts, rather than a more rigorous non-destructive testing (NDT) method.
- The aircraft had exceeded its 50-hour inspection interval without the required maintenance being recorded.