What happened
On 10 October 2008, an Extra EA 230, registration G-CBUA, was taxiing at White Waltham Airfield in Berkshire during a private flight. After completing a daily inspection and starting the engine, the pilot began taxiing toward the holding point for Runway 21. During the taxi, the right landing gear leg fractured. This failure caused the right wing tip to strike the grass surface, which in turn caused the aircraft to pivot approximately 90 degrees to the right. The movement resulted in the propeller contacting the ground, which shattered the wooden blades. There were no injuries to the pilot during the incident.
The investigation
Investigators examined the fractured aluminium landing gear leg at a specialized laboratory. The metallurgical analysis revealed that the right leg had failed at the bend located at the top of the component. The examination of the fracture surface using a scanning electron microscope identified between 45 and 50 distinct growth bands. These bands suggested that the crack had been progressing through multiple cycles, potentially spanning up to 50 separate landings or various instances of taxiing over uneven ground. The investigation also noted that the left landing gear leg exhibited a second, similar crack originating from a small corrosion pit.
Findings
- The primary cause of the failure was a fatigue crack that began at a small corrosion pit on the inner surface of the gear leg's bend radius.
- The 2024 aluminium alloy used in the gear leg is susceptible to corrosion, and there was no evidence of effective protective measures, such as inhibited paint, being applied to the component.
- The failure occurred in an area covered by a composite fairing, which lacks specific maintenance requirements for crack inspection.
- The aircraft had flown 28 hours since its last annual maintenance check and approximately 1,743 hours since manufacture.