AD/DHC-6/16 Amdt 5 - Wing Front Spar Attachment Fittings

Overview

The Civil Aviation Regulations 1998, under Part 39 - 105, mandate the Civil Aviation Safety Authority’s (CASA) Schedule of Airworthiness Directives for various aircraft types, including the DHC-6 (Twin Otter) series aeroplanes. Specifically, AD/DHC-6/16 Amendment 5 pertains to the wing front spar attachment fittings and was enacted to address the identified issue of stress corrosion cracks in these fittings, which have been discovered during service. This amendment implements Revision D of de Havilland of Canada Service Bulletin No 6/174, requiring inspections and re-torquing of the wing attach bolts, and aims to ensure the continued airworthiness and safety of these aircraft by mandating regular inspections and necessary maintenance actions. The policy objective is to mitigate the risk of structural failure due to corrosion, thereby maintaining high safety standards in civil aviation. The Australian Civil Aviation Regulations 1998, overseen by CASA, were established to regulate the safety of civil aviation within Australia. The specific amendment AD/DHC-6/16 Amendment 5, introduced in 1987, targets the DHC-6 (Twin Otter) series aeroplanes, specifically those with serial numbers 1 to 210 inclusive, to ensure they comply with the updated service bulletin requirements. This amendment responds to the identified problem of stress corrosion cracks in the wing front spar attachment fittings, requiring periodic inspections and maintenance actions as outlined in the de Havilland of Canada Service Bulletin No 6/174 Revision D. The overarching goal is to maintain the structural integrity and safety of these aircraft through stringent regulatory oversight and compliance measures.

Scope and Application

The Civil Aviation Regulations 1998, specifically Part 39 - 105, governs the airworthiness directives for aircraft operating within Australia, ensuring that all commercial and non-commercial aircraft meet the required safety standards. The scope of AD/DHC-6/16 Amendment 5 pertains to the DHC-6 (Twin Otter) series aeroplanes with serial numbers ranging from 1 to 210 inclusive. This directive applies to all entities operating these aircraft, mandating specific actions to address the issue of stress corrosion cracks in the wing front spar attachment fittings. Compliance with the directive requires adherence to de Havilland of Canada Service Bulletin No 6/174 Revision D, which includes detailed inspection and maintenance procedures. For Part A of SB 6/174, inspections must be conducted at intervals not exceeding 500 hours of time in service or 3 months, whichever comes first, while Part B requires action within 100 hours of time in service after 31 July 1974, unless already completed. The repetitive inspections of Part A may be discontinued upon installation of the specified de Havilland fittings. This directive applies nationally and is enforced by the Civil Aviation Safety Authority (CASA) to ensure the safety and airworthiness of these aircraft within Australian airspace.

Key Provisions

The key operative sections of this legislative instrument, AD/DHC-6/16 Amendment 5, pertain specifically to the inspection and maintenance of the wing front spar attachment fittings of DHC-6 (Twin Otter) series aeroplanes with serial numbers 1 to 210 inclusive. Section 1 outlines the applicability, ensuring that all specified models are subject to the directive. Section 2 details the requirement, stipulating that the actions must comply with de Havilland of Canada Service Bulletin No 6/174 Revision D, Part A or Part B as applicable. The compliance criteria, outlined in Section 3, mandate that for Part A of SB 6/174, inspections must be conducted at intervals not exceeding 500 hours of time in service or 3 months, whichever comes first. For Part B, inspections must be performed within 100 hours of time in service after 31 July 1974, unless already completed. Furthermore, Section 4 notes that repetitive inspections under Part A may cease upon the installation of unused de Havilland fittings P/N C6WM 1133-1 and -2. The obligations imposed by this legislation are primarily centred around ensuring the airworthiness and safety of the DHC-6 series aeroplanes. Operators and maintenance personnel must adhere to the strict timelines and procedures outlined in the Service Bulletin, ensuring regular inspections and maintenance of the wing front spar attachment fittings to prevent the occurrence of stress corrosion cracks. Compliance with the directive involves thorough inspections and necessary re-torquing of wing attach bolts, as mandated by the Service Bulletin. Operators must maintain accurate records of inspections and maintenance actions, ensuring traceability and accountability. Failure to comply with the provisions of AD/DHC-6/16 Amendment 5 can result in significant consequences. Civil Aviation Safety Authority (CASA) regulations may impose civil penalties for non-compliance, including fines up to a specified amount. Additionally, failure to adhere to the airworthiness directives can lead to the grounding of the aircraft, preventing it from operating until the necessary inspections and repairs are completed. In severe cases, non-compliance may also result in criminal charges, particularly if the non-compliance is found to have contributed to an aviation accident or incident. Operators and maintenance personnel must, therefore, ensure strict adherence to the legislative requirements to avoid any potential penalties or safety risks.