What happened
On July 5, 2016, at approximately 18:00 LMT, a private owner was conducting a second test flight following a specialized engine repair in a Zenair CH-601HD at Lublin-Radawiec airport (EPLR). During the takeoff roll, as the aircraft reached a speed of approximately 80 km/h just prior to liftoff, the right main landing gear fork and wheel separated from the aircraft.
The pilot first noticed a tendency for the aircraft to veer to the right. Upon reducing engine power, the aircraft settled onto its right wing and came to a stop on the runway, having deviated approximately 120 degrees from the original takeoff heading.
The investigation
The PKBWL investigation focused on the structural failure of the right main landing gear. The examination revealed that the connection between the landing gear strut and its lower plate, which holds the bolts for the wheel fork, had failed. The failure occurred specifically around the weld seam connecting these components.
Physical inspection of the landing gear strut showed evidence of advanced pitting corrosion. Crucially, the investigation established that corrosion had penetrated more than 25% of the length of the weld seam. The fracture lines were located just beyond the heat-affected zone created during the welding process. The investigation also noted that the separation of the wheel fork caused it to move toward the fuselage, resulting in minor structural damage to the rear right longeron and small punctures to the center section skin.