What happened
On August 21, 2018, a Piper PA-28-140, registration PT-JJM, was conducting a local flight instruction mission at the Aeroclube de Eldorado do Sul (SIXE) in Rio Grande do Sul, Brazil. The flight, which involved an instructor and a student pilot, was performing touch-and-go maneuvers. During the 17th landing of the flight, the right main landing gear wheel detached upon touchdown. The aircraft subsequently traveled 354 meters along the runway before coming to a stop on the right side of the pavement. The impact resulted in substantial damage to the right main landing gear, fuselage, right wing, right flap, and right aileron. Both occupants of the aircraft were uninjured.
The investigation
The investigation focused on the mechanical failure of the landing gear assembly. Laboratory analysis conducted by the Department of Science and Technology of the Air Force (DCTA) revealed that the bolt responsible for securing the main gear torque links had failed because the associated nut was stripped from the threads. Metallographic examinations confirmed that the components had suffered damage due to overload. Specifically, the threads of both the bolt and the nut experienced plastic deformation caused by axial tensile stresses that exceeded the yield strength of the materials.
Investigators also reviewed the maintenance history of PT-JHM. The aircraft's maintenance records showed that the operator was compliant with all required inspections, including the 50-hour inspection and the annual maintenance inspection. The aircraft was also in compliance with relevant Airworthiness Directives (AD) and Service Bulletins (SB) regarding the torque link models installed. The investigation determined that the mechanical failure was not due to improper maintenance, but rather the physical stresses applied to the components during operation.
Findings
- The primary cause of the component failure was an overload resulting from hard landings during flight instruction.
- The instructor's history of complacency, specifically failing to intervene during student errors, contributed to the repetitive application of excessive forces on the landing gear.
- A lack of managerial oversight at the aeroclube allowed for instruction techniques that permitted students to perform repeated hard landings without corrective intervention.
- The student pilot, being in the early stages of training, likely committed errors in judgment and control during the touch-and-go maneuver.