An ATR-72-212, registered PR-TTI, was damaged in a runway excursion accident at Altamira Airport, PA (ATM), Brazil. The airplane operated on a domestic flight from Bel‚m/Val-de-C?es International Airport. The approach for landing was visual and stabilized. The touchdown on runway 25 was smooth, with gradual deceleration, in which only ground idle power was utilized. After the 70kt callout, a strong noise was heard, and the left main gear collapsed, with the aircraft veering off to the left. The aircraft exited the runway and came to a stop in a grass area. Contributing factors 1 Human Factor 1.1 Medical aspect Nil. 1.2 Psychological aspect Nil. 1.2.2 Psychosocial information Nil. 1.2.3 Organizational information a) Capacitation – a contributor The lack of capacitation and training of the subcontractors’ professionals for handling aircraft material hindered the execution of an efficient maintenance work as prescribed by the manufacturer’s manual, culminating in inadequate machining during the maintenance process. b) Organizational Processes – a contributor The lack of an effective process of supervision, both on the part of TRIP Linhas A‚reas and on the part of the other contractors and subcontractors allowed the existing maintenance services’ latent failures not to be checked and corrected, in a way capable of subsidizing, in an adequate and safe manner, the execution of the landing gear maintenance service The process of supervision of the TRIP Linhas A‚reas and the AV Ind£stria Aeron utica Ltda. companies by the Civil Aviation Authority, prescribed by specific legislation in force, was not enough to mitigate the latent conditions present in the accident in question. 2 Operational Factor 2.1 Concerning the operation of the aircraft a) Aircraft maintenance – a contributor According to the technical opinion issued by the DCTA, the AFT PIVOT PIN (D61000 and SN 25) presented fracture surfaces with ñ 45§ inclination, as well as a flat area with multiple initiations, indicative of a fracture mechanism related to fatigue. In examinations of the external surface of the pin, in a region close to the fatigue fracture, cracks were observed that had initiated from scratches created by an inadequate maintenance machining process. In the region where the overload-related fracture occurred, it was also possible to identify that the machining process had modified the profile of the part in the section transition region, by producing a depression. Thus, it can be said that the AFT PIVOT PIN (D61000 and SN 25) of the PR-TTI left main gear broke on account of fatigue, whose onset was facilitated by an inadequate machining process that had been performed in the section transition region of the pin. 3 Material Factor Not a contributor.