AD/DHC-6/67 - Lower Skin and L/E Rivets at Front Spar

Overview

The Civil Aviation Regulations 1998, amended by the Legislative Instrument F2006B09155, specifically addresses the maintenance and airworthiness of DHC-6 (Twin Otter) series aeroplanes. This legislative instrument was enacted to address a critical safety concern identified in these aircraft models, particularly focusing on the structural integrity of rivets connecting the wing lower and leading edge skins to the front spar flanges. The problem was the corrosion of these rivets, which, if left unaddressed, could lead to catastrophic failure of the aircraft's structural components. The Civil Aviation Safety Authority (CASA) mandated these directives to ensure the ongoing safety and airworthiness of these aircraft by requiring specific modifications and inspections. The overarching policy objective is to maintain high safety standards in civil aviation, ensuring that all aircraft operating within Australian airspace meet stringent maintenance and safety criteria.

Scope and Application

The Civil Aviation Regulations 1998, specifically Part 39 - 105, addresses the airworthiness directives for DHC-6 (Twin Otter) series aeroplanes, including a directive concerning the lower skin and leading edge rivets at the front spar. This legislation applies to DHC-6 aircraft that have not yet incorporated the specified modifications 6/1645 and 6/1893. The regulation mandates that a detailed visual inspection be performed in accordance with de Havilland Service Bulletin 6/517, and further action be taken if unserviceable rivets are discovered. Specifically, if four or more rivets in the joint are missing or defective, additional steps outlined in Service Bulletin 6/517 must be followed. Furthermore, the directive requires the incorporation of specific modifications to ensure compliance, with different requirements for aircraft based on their serial numbers. Compliance with these directives must be achieved within certain timeframes post the directive’s issuance. The scope of this regulation is national, applying across Australia and ensuring safety standards are upheld in the civil aviation industry.

Key Provisions

The Civil Aviation Regulations 1998, specifically under Part 39, contain provisions that mandate the airworthiness of DHC-6 (Twin Otter) series aeroplanes. The regulation AD/DHC-6/67, which applies to Model DHC-6 aircraft that do not have Modifications 6/1645 and 6/1893 incorporated, stipulates detailed inspections and modifications to ensure safety. The primary requirement of section 1 is that a detailed visual inspection must be carried out in accordance with Part A of de Havilland Service Bulletin 6/517. If any unserviceable rivets are found during this inspection, the procedures outlined in Part C of the same service bulletin must be followed. Moreover, if four or more rivets in the joint are missing or defective, Part B of Service Bulletin 6/517 must be implemented. The second requirement involves modifications, where Part C of Service Bulletin 6/517 must be adhered to for aircraft up to and including serial number 580 by incorporating Modification 6/1645, and all aircraft must incorporate Modification 6/1893. The obligations imposed by this legislation on the parties or entities it governs include conducting thorough and timely inspections and making the necessary modifications to the aircraft. The inspection must be conducted within a specific timeframe: within 500 hours of time in service after 6 January 1994, or before 6 April 1994, whichever comes first. Additionally, the modifications must be completed prior to 6 July 1994. These requirements are critical to maintaining the structural integrity of the aircraft and preventing potential hazards due to corrosion or loss of rivets, which could compromise the safety of the flight. Failure to comply with the provisions outlined in this regulation can result in serious consequences. Although the specific civil or criminal penalties are not detailed in the provided text, it is evident that non-compliance could lead to significant safety risks. In general, breaches of airworthiness directives under the Civil Aviation Regulations 1998 can result in enforcement actions by the Civil Aviation Safety Authority (CASA). Potential penalties may include fines, legal action, or even the grounding of the aircraft, which can have severe implications for both the operator and the passengers. The severity of the penalties would depend on the nature and extent of the non-compliance, but it is clear that adhering to these directives is essential to avoid any adverse outcomes.