What happened
On 22 June 2024, a Piper PA-2-161, registration G-SACS, was conducting a training flight involving practice forced landings and touch-and-go maneuvers at Sherburn-in-Elmet Airfield. Immediately following the second touch-and-go takeoff, ground crew notified the pilot that the right main wheel and oleo assembly had detached from the landing gear cylinder, though it remained connected via the brake hose.
The pilot took control and performed several additional circuits to manage fuel levels and await emergency services. The aircraft subsequently landed on a grass runway. During the landing, the aircraft veered approximately 90 degrees to the right, at which point the wheel assembly finally detached from the brake hose. There were no injuries to the pilot or the student passenger, though the aircraft sustained significant damage to the fuselage, wing, and landing gear.
The investigation
Investigators examined the landing gear assembly and discovered that the torque link attachment lugs on the main landing gear cylinder had fractured. This failure allowed the wheel and oleo assembly to separate from the cylinder.
The investigation focused on the maintenance history and the applicability of manufacturer service bulletins. While a Service Bulletin (SB1131A) exists for inspecting these lugs, it is not a mandatory requirement in the UK. The aircraft had been subject to visual inspections at 100-hour intervals, but the failure occurred 339 hours after the last dye penetrant inspection, placing the event outside the recommended inspection window.
Findings
- The primary cause of the separation was fatigue cracking of the torque link attachment lugs.
- Visual inspections alone were insufficient to detect the cracks; the investigation highlighted that cracks may not be visible even under 10x magnification without the use of liquid dye penetrant.
- The failure occurred outside of the 100-hour inspection interval specified by the manufacturer's service bulletin.
- The investigation noted that training aircraft, which undergo high landing cycles, may be more susceptible to accelerated fatigue.
- A discrepancy was noted in parts catalogues, where some documentation recommended forged assemblies for training operations, a detail not explicitly included in the primary Service Bulletin.