Air Tractor AT-502B Landing Gear Spring Failure During Takeoff Roll (PRSRL)

Occurrence Overview and Flight History On 15 January 2022 at 09:05 UTC, an Air Tractor AT-502B agricultural aircraft, registration PR-SRL, operated by Aeroterra Aviação Agrícola Ltda., began a takeoff roll from Aeródromo Serra Branca Agrícola (SDZS) in Uruçuí, Piauí, Brazil. The aircraft was conducting a local agricultural spraying flight with one pilot aboard. During the initial takeoff roll, the spring of the right main landing gear broke. The aircraft yawed to the right and came to a stop within the runway limits, 90 m from the departure threshold. The aircraft sustained substantial damage, and the pilot exited uninjured. ## Aircraft, Maintenance, and Operational Findings The pilot held a valid commercial pilot license with appropriate ratings and a valid medical certificate. The aircraft was registered in the specialized public air services category and had a valid airworthiness certificate. At the time of the accident, it was 110 kg above the manufacturer’s maximum takeoff weight of 3,690 kg; the investigation could not establish a relationship between this condition and the accident. The aircraft had 3,488 hours and 25 minutes of total flight time. Its last 300-hour airworthiness inspection was performed on 19 January 2021 by DPA Aviação in Cachoeira do Sul, RS, after which it had accumulated 95 hours and 5 minutes. The right main landing gear spring had been replaced on 8 November 2019 under maintenance order 0501/19 by ABA Manutenção de Aeronaves. At the time of the occurrence, the spring had 610 hours of operation since new. The damaged landing gear was not made available for laboratory examination, so the root cause of the rupture could not be identified. Visual inspection, however, showed that the collapsed area was weakened by pre-existing cracks and corrosion, which could have been associated with the component’s failure. ## Service Life, Maintenance Program, and Safety Context Air Tractor Service Letter No. 104 defined service categories for main landing gear springs, including light, medium, and severe service based on landing rates and runway conditions. The aircraft’s component control map, updated on 19 November 2021, used a 3,000-hour time limit for the right-hand main landing gear spring, consistent with light service. However, the aircraft’s logbook and operational characteristics indicated medium service, which would have reduced the spring’s time limit to 2,000 hours. Because the failed spring had only 610 hours, this discrepancy was not directly related to the accident, but it indicated an inadequate systematic approach to the aircraft’s maintenance program, particularly regarding the landing gear spring time limit. Air Tractor Service Letter No. 334 emphasized that corrosion, damage, and environmental conditions can reduce landing gear spring life and accelerate crack formation and growth. It recommended 100-hour visual inspections of the main gear springs for nicks, scratches, stains, corrosion, and paint condition, with particular attention to the high-stress lower area near the attachment block. Any crack in a landing gear spring was stated to be a reason for replacement. The investigation was conducted by Brazil’s SIPAER under CENIPA case A-005/CENIPA/2022. Its purpose was prevention of future accidents, not the determination of fault or liability.