What happened
On 20 August 2022, an Alpi Pioneer 300, registration G-IPKA, was taxiing at Fenland Airfield in Lincolnshire following a private flight. During the taxi phase, the aircraft's left main landing gear suddenly collapsed. This failure caused the left wing to make contact with the ground. The pilot, who was the sole occupant of the aircraft, sustained no injuries during the incident.
The investigation
Investigators examined the aircraft's landing gear assembly, specifically focusing on the upper strut, damper, and swinging leg. The examination revealed that the swinging leg had failed completely around its circumference. The crack was found to have started near the weld connecting the swinging leg to the pivot tube.
Evidence suggested the fracture was caused by an overload, indicating a rapid failure. While the interior of the tube showed light corrosion, the investigators also noted that the weld between the swinging leg and the pivot tube appeared to have insufficient penetration into the parent material. The aircraft's maintenance history showed that the landing gear components had been in use for 725 hours and 837 landings since their installation in 2012. Although the pilot did not report any recent heavy landings, it was noted that the aircraft frequently operated from grass airfields which could be uneven.
Findings
- The failure originated at the interface between the swinging leg tube and the pivot tube.
- The weld quality at this junction was insufficient, creating a stress raiser that likely facilitated the crack.
- The fracture pattern was consistent with a sudden overload event.
- The location of the crack initiation is difficult to inspect because it is partially obscured by the landing gear's downtube.
Safety action
Following the investigation, the Light Aircraft Association (LAA) is currently reviewing the manufacturing and design of the landing gear for the Alpi Pioneer 300 to determine if new maintenance requirements are necessary.