AD/M20/51 - Main Landing Gear Side Brace Bolt

Overview

The Civil Aviation Regulations 1998, introduced by the Parliament of Australia, aim to establish safety standards and regulations for civil aviation in the country. Part 39 - 105 of the Civil Aviation Regulations 1998, specifically the Schedule of Airworthiness Directives, contains safety measures that are mandated to ensure aircraft remain airworthy. One such directive, AD/M20/51, pertains to Mooney M20 Series aeroplanes and was enacted to address the risk of failure of the main landing gear side brace bolt due to cracks in the main landing gear leg bracket. This issue arose from the manufacturing process of these brackets, which used laser pattern cutting, leading to minor cracks at the bends that could propagate over time. The directive requires specific maintenance actions to be taken to mitigate this risk, ensuring the safety of the aircraft and its passengers. The Mooney M20 Series AD/M20/51, which became effective on 28 January 1999, mandates that certain Mooney M20 models undergo inspection and maintenance of the main landing gear leg brackets. This is to prevent potential failure of the main landing gear side brace bolt caused by cracks in the brackets, which could lead to a collapse of the landing gear. The directive applies to specific models and serial numbers of the Mooney M20 aeroplanes and requires the grinding of the surface of the main landing gear leg bracket, inspection for cracks, and replacement of any cracked brackets with new ones. The objective is to ensure the continued airworthiness of these aircraft and maintain safety standards in civil aviation.

Scope and Application

The Civil Aviation Regulations 1998, under Part 39 - 105, specifically within the Civil Aviation Safety Authority Schedule of Airworthiness Directives, governs the maintenance and safety standards of aircraft operating within Australia. This legislation applies to certain Mooney M20 Series aeroplanes, specifically those with the identified model types and serial numbers, to ensure their continued airworthiness and safety. The geographic and jurisdictional reach of these regulations is national, applying to all aircraft registered within the Commonwealth of Australia. The directive mandates that specific models of Mooney M20 aeroplanes undergo inspections and maintenance procedures concerning the main landing gear side brace bolt, as detailed in Mooney Service Bulletin M20-265. Compliance with these requirements is essential within 100 hours of the aeroplane’s time in service post the directive’s effective date of 28 January 1999, and before any further flight, to mitigate the risk of landing gear failure due to potential cracks in the main landing gear leg bracket. This Airworthiness Directive extends its application through references to FAA AD 98-21-26 Amdt 39-10834, aligning with international safety standards.

Key Provisions

The Civil Aviation Regulations 1998, specifically under Part 39 - 105, include an Airworthiness Directive (AD) that applies to certain Mooney M20 series aeroplanes. This directive, AD/M20/51, pertains to the main landing gear side brace bolt and is applicable to specific models and serial numbers of Mooney M20J, M20K, M20M, and M20R. The directive mandates the grinding of the surface of the main landing gear (MLG) leg bracket, part number 510010, and the inspection of this area for cracks (section 1). If any cracks are found, the affected MLG leg bracket must be replaced with a new one, in accordance with the instructions provided in Mooney Service Bulletin M20-265 and the applicable maintenance manual (section 2). The directive references FAA AD 98-21-26 Amdt 39-10834 for additional context. Under this directive, the operators of the specified Mooney M20 series aeroplanes are required to ensure that the actions specified are completed within 100 hours of time in service after 28 January 1999 and before any further flight. The directive came into effect on 28 January 1999, establishing the compliance timeline and conditions for the maintenance actions. The directive was issued due to the manufacturing process of the MLG leg brackets, which involved laser pattern cutting and led to the development of minor cracks at the bends that could propagate over time. These actions are necessary to prevent the failure of the MLG side brace bolt caused by cracking of the MLG leg bracket and to avoid potential collapse of the landing gear. Failure to comply with the requirements set out in this Airworthiness Directive could result in serious safety implications, potentially leading to catastrophic failure of the landing gear. Although specific offences, penalties, or civil/criminal consequences are not detailed in the directive itself, non-compliance could result in the aircraft being deemed unairworthy, leading to grounding until the required actions are completed. Additionally, there could be civil or criminal liability for operators who fail to adhere to the regulatory requirements, depending on the jurisdiction and the extent of the non-compliance. The potential for accidents or incidents arising from non-compliance could also result in severe consequences for the operator, including financial penalties, reputational damage, and legal action.