AD/AC-SNOW/18 - Wing Front Spar Corrosion

Overview

The Civil Aviation Regulations 1998, enacted by the Australian Parliament, provide a comprehensive framework for ensuring the safety of civil aviation. Among these regulations is Part 39, which includes the Civil Aviation Safety Authority Schedule of Airworthiness Directives. Specifically, AD/AC-SNOW/18 addresses the issue of wing front spar corrosion in Ayres Thrush (Snow) Commander Series Aeroplanes. This legislation was introduced to address the safety concerns identified in an accident investigation where extensive corrosion was found on the upper and lower portions of the front spar. The policy objective behind this directive is to ensure that these aircraft are maintained in a safe condition by mandating regular inspections and repairs to prevent the recurrence of such incidents. The enacting body, the Australian Parliament, aims to mitigate the risks associated with corrosion in aircraft by enforcing mandatory checks and repairs. This directive applies to various models and serial numbers of the Ayres Thrush (Snow) Commander Series, requiring inspections and repairs to be conducted at specified intervals and before further flight if corrosion is detected. The directive references FAA AD 93-01-03 Amdt 39-8456, aligning Australian regulations with international safety standards to maintain high levels of safety in civil aviation.

Scope and Application

The Civil Aviation Safety Authority Schedule of Airworthiness Directives, specifically AD/AC-SNOW/18 concerning the Ayres Thrush (Snow) Commander Series Aeroplanes, applies to a specified range of models and serial numbers. This directive mandates inspections for corrosion on the wing front spar of the mentioned aircraft, a requirement necessitated by an accident investigation that revealed extensive corrosion on the upper and lower portions of the front spar. The directive is applicable to all serial numbers of the S2D model and specific serial number ranges for the S2R model, including various sub-models such as S2R-R1340, S2R-R3S, S2R-R1820, S2R-T11, S2R-T15, S2R-T34, S2R-T45, S2R-T65, S2RHG-T65, and S2R-G6. The inspections must be carried out in accordance with the instructions detailed in Ayres Service Bulletin SB-AG-29, with corrosion treatment and repair required if any is found. Compliance with these directives is mandatory, with inspections needed before 27 August 1993, and thereafter at intervals not exceeding 12 months, and before any further flight if corrosion is detected.

Key Provisions

The Civil Aviation Regulations 1998, specifically under PART 39 - 105, include detailed Airworthiness Directives (AD) for certain models of Ayres Thrush (Snow) Commander Series Aeroplanes, notably referencing AD/AC-SNOW/18 concerning wing front spar corrosion. This directive applies to various serial numbers, including S2D, S2R, and other specified variants (sections 6/93 and Applicability). The main requirement under this AD is to inspect the wing front spar for corrosion in accordance with the “Accomplishment Instructions: I. Inspection of Front Spar” section of Ayres Service Bulletin SB-AG-29. If corrosion is detected, it must be treated and repaired following the “Accomplishment Instructions: II. Repairs” section of the same bulletin (Requirement section). The directive references FAA AD 93-01-03 Amdt 39-8456 for further guidance. Compliance with these directives imposes specific obligations on the parties involved. The inspections and necessary repairs must be completed before 27 August 1993 for any aircraft that have not already undergone these procedures, and thereafter, the inspections must occur at intervals not exceeding 12 calendar months (Compliance section 1). Additionally, if corrosion is found during an inspection, further flight is not permissible until the corrosion is appropriately treated and repaired (Compliance section 2). These obligations are essential to ensure the airworthiness and safety of the affected aircraft, particularly in light of the investigation findings that revealed extensive corrosion on the front spar, which contributed to an accident (Background). Failure to comply with the AD/AC-SNOW/18 directive may result in significant legal consequences. While the specific penalties are not detailed in the text, breaches of airworthiness directives typically fall under the Civil Aviation Act 1988 and the Civil Aviation Regulations 1998. Penalties for non-compliance with these regulations can include substantial fines, enforcement actions by the Civil Aviation Safety Authority (CASA), and potentially criminal charges if the breach leads to safety incidents or accidents. The exact penalties would depend on the severity of the breach and the resulting impact on aviation safety. Ensuring adherence to these directives is crucial to avoid such adverse outcomes.