AD/B747/53 Amdt 3 - Longitudinal Skin Lap Joint and Body Frame Corrosion and Cracking

Overview

The Civil Aviation Regulations 1998, enacted by the Parliament of Australia, establish a comprehensive framework for the safety and regulation of civil aviation within the country. A specific legislative instrument, F2006B03234, was introduced to address the identified issue of corrosion and fatigue cracking in the fuselage skin lap joints of Boeing 747 series aeroplanes. This legislative measure aims to ensure the continued airworthiness of these aircraft by mandating rigorous inspection and maintenance protocols. The policy objective is to enhance aviation safety by preventing structural failures that could arise from undetected corrosion and cracking in the specified aircraft components.

Scope and Application

The Civil Aviation Regulations 1998, specifically Part 39 - 105, governs the airworthiness directives for Boeing 747 series aeroplanes, focusing on issues such as longitudinal skin lap joint and body frame corrosion and cracking. The AD/B747/53 Amendment 3 applies to Boeing 747 aircraft line numbers 1 to 200. This regulation mandates that operators conduct an external visual inspection of the lower fuselage lap joints for corrosion and high-frequency eddy current inspections on the upper fastener row of lap joints, in accordance with Boeing Service Bulletin 747-53A2267. The inspections must be performed before certain service thresholds and at regular intervals thereafter to ensure ongoing airworthiness. The regulation is consistent with similar directives issued by the Federal Aviation Administration (FAA), as noted in FAA ADs 94-17-01 and 86-09-07. Compliance is mandatory and includes initial inspections before a specific number of hours or flights in service, followed by re-inspections at prescribed intervals until the aircraft is modified according to the relevant Boeing service bulletin.

Key Provisions

The Civil Aviation Regulations 1998, under Part 39 - 105, include specific directives concerning the airworthiness of Boeing 747 Series aeroplanes. Of particular note is the Airworthiness Directive AD/B747/53 Amendment 3, which addresses the issue of longitudinal skin lap joint and body frame corrosion and cracking on B747 aircraft line numbers 1 to 200. The directive mandates two primary inspection requirements. Firstly, an external visual inspection of the lower fuselage lap joints must be conducted to identify any signs of corrosion, following the guidelines provided in Boeing Service Bulletin (SB) 747-53A2267 dated 28 March 1986. Secondly, the upper fastener row of lap joints, which have been modified in accordance with Boeing SB 747-53A2267, must be inspected using high frequency eddy current methods, as outlined in Boeing SB 747-53A2267, Revision 3, Fig 7. The obligations imposed by this directive require operators to adhere strictly to the inspection schedules and methodologies stipulated. For the initial inspection, operators must ensure that inspections are completed before the aircraft reaches 12,000 hours of time in service or before 100 hours of service after 30 October 1986, whichever is later. Subsequent inspections must occur at intervals not exceeding 4,000 hours of service or 15 months, whichever comes sooner, until the aircraft is modified in accordance with Boeing SB 747-53A2267 dated 28 March 1986. For aircraft that have been modified, initial inspections must occur before reaching specified flight thresholds, depending on the revision of the SB under which the modification was performed. Failure to comply with the requirements of this directive can result in significant consequences. The regulations do not explicitly state the penalties for non-compliance in the excerpt provided, but such breaches can generally lead to enforcement actions by the Civil Aviation Safety Authority. These actions may include fines, operational restrictions, or even the grounding of non-compliant aircraft, depending on the severity and impact of the non-compliance. Operators must therefore ensure rigorous adherence to the inspection requirements to avoid such penalties.