What happened
On 18 June 2018, a Piper PA-28R-200-2 Cherokee Arrow II, registration G-EDVL, was conducting a training flight at Redhill Aerodrome. The flight was intended to assist a student pilot in obtaining a complex aircraft rating. After completing start-up procedures, the crew taxied across the grass runway and onto Taxiway A.
As the aircraft approached the A2 holding point, the pilot moved onto a grass area to perform pre-takeoff power checks. During this maneuver, the pilot heard a loud thud, immediately followed by the right wing dropping toward the ground. Upon inspection, the instructor found that the right main landing gear leg had shifted from its standard position and that the top of the gear leg had pierced the upper surface of the wing skin. There were no injuries to the crew during the incident.
The investigation
Investigators examined the wreckage and identified that the forward trunnion of the right main landing gear leg had failed. This failure allowed the gear leg to rotate rearwards, which subsequently caused the wing to drop and the gear leg to puncture the wing skin.
Analysis of the fracture surfaces on the trunnion revealed evidence of mechanical damage and characteristics of failure due to overload. Additionally, investigators identified an area consistent with crack propagation caused by fatigue. While the specific site where the crack first began could not be determined due to surface damage, the presence of fatigue was confirmed.
Records from the maintenance organization showed that a visual inspection of the trunnions had been performed during the annual inspection in March 2018, with no cracks or deterioration noted at that time. It was noted that the physical location of the forward trunnion makes it impossible to inspect visually during standard pre-flight checks.
Findings
- The primary cause of the accident was the failure of the right main landing gear forward trunnion.
- The trunnion failure was the result of a fatigue crack progressing through the material, followed by a final failure under overload.
- The fatigue crack likely originated from an unreported heavy landing or an abnormal event, such as rapid taxiing over uneven ground.
- The aircraft's design allows for operations on unpaved surfaces, but the uneven nature of the grass area at the time of the incident contributed to the mechanical stress on the component.