AD/CFM56/12 - Accessory and Transfer Gearbox Replacement

Overview

The Civil Aviation Regulations 1998, enacted by the Commonwealth of Australia, address the critical issue of ensuring the airworthiness of aircraft engines, particularly the CFM International CFM56 Series engines. These regulations, established by the Australian Parliament, aim to maintain safety standards and mitigate risks associated with engine failures, which could potentially lead to in-flight shutdowns. The regulations focus on the replacement and inspection of specific components in the accessory and transfer gearboxes of certain CFM56-3 engines, as identified by their serial numbers. Compliance with these directives is mandatory to ensure that the identified risks are effectively managed and to maintain the safety of aviation operations. The Civil Aviation Safety Authority issued this directive in response to reported incidents of in-flight shutdowns due to failures in the starter gearshafts of the accessory gearbox and potential failures in the conical gearshafts of the transfer gearbox. The directive mandates specific inspections and replacements for engines listed in designated batches, ensuring that these critical components are examined and replaced as necessary to prevent future incidents. Compliance requirements vary, with some inspections needing to be completed before specific dates and others before the next flight. This directive underscores the importance of regular maintenance and adherence to safety protocols to enhance aviation safety.

Scope and Application

The Civil Aviation Regulations 1998, as amended, under the authority of the Civil Aviation Safety Authority, specifically addresses the airworthiness of CFM International CFM56 Series turbofan engines through the AD/CFM56/12 directive. This regulation applies to all turbofan engines manufactured by CFM International, specifically the CFM56-3 series, which must comply with the requirements outlined in this directive if their serial numbers fall within the specified lists detailing engines with suspect components in the accessory gearbox (AGB) and transfer gearbox (TGB). The directive mandates inspections and, if necessary, the replacement of specific gearshafts and bevel gears identified in the lists, to prevent in-flight shutdowns caused by gearbox failures. The directive's geographic reach is nationwide, applying to all aircraft registered in Australia that use these engines. Compliance with this directive is mandatory, with specific timelines for inspections and repairs, and it overrides previous directives concerning these engines. The directive does not specify exclusions or exemptions, indicating that all applicable engines must comply with the outlined procedures. The directive's application may be further detailed or extended through subordinate instruments issued by the Civil Aviation Safety Authority.

Key Provisions

The Civil Aviation Regulations 1998, specifically Part 39 - 106 under the Civil Aviation Safety Authority Schedule of Airworthiness Directives, addresses the issue of CFM International Turbine Engines - CFM56 Series through Airworthiness Directive AD/CFM56/12. This directive concerns the replacement of accessory and transfer gearboxes in certain CFM56-3 series engines. The directive identifies specific engines by serial numbers, categorising them into several lists based on the components suspected of failure, such as the starter gearshaft, input bevel gear, output bevel gear, and intermediate gearshaft cluster. The directive requires the removal of these suspect components from service if magnetic particles are detected during checks, in accordance with relevant service bulletins. The obligations imposed by this directive are quite specific. Operators of the affected CFM56-3 engines must ensure that daily checks are conducted on the magnetic chip detectors in the accessory and transfer gearboxes. For engines listed in Lists 1A and 1B, the starter gearshaft must be removed before specified deadlines. Similarly, for engines in Lists 2A and 2B, the input and output bevel gearshafts must be removed before specified dates. For engines in List 3, the intermediate gearshaft cluster must be removed. If a twin-engined aircraft has both engines listed in one or more of these categories, all suspect gearshafts on one engine must be replaced before the next flight. Failure to comply with the provisions of this airworthiness directive can result in significant civil and criminal consequences. The directive mandates compliance on specified dates and before subsequent flights, underscoring the importance of timely action. Non-compliance could potentially lead to in-flight shut downs, compromising safety and potentially resulting in severe penalties. The directive specifies particular deadlines for compliance, highlighting the urgency and critical nature of these requirements. The penalties for non-compliance are not explicitly stated in the directive, but they can include fines, grounding of aircraft, and other regulatory actions by the Civil Aviation Safety Authority. Given the potential safety risks associated with in-flight shut downs due to gearbox failures, the consequences of not adhering to this directive could be severe, both in terms of regulatory action and the potential for harm to passengers and crew.