Overview

The Civil Aviation Regulations 1998, enacted by the Australian Government, provide comprehensive regulations governing civil aviation operations within Australia. Part 39 of these regulations pertains to airworthiness directives, which are mandatory orders issued by the Civil Aviation Safety Authority (CASA) to address safety issues in aircraft operations. Specifically, AD/B747/140 was introduced to address the issue of fatigue cracks found in the lap joints of Boeing 747 series aeroplanes, which could potentially compromise the structural integrity of the fuselage. This airworthiness directive mandates detailed inspections and, if necessary, modifications to ensure the continued airworthiness and safety of Boeing 747 aircraft, particularly those in the ageing fleet. The policy objective is to mitigate the risk of in-flight structural failures by enforcing regular and rigorous inspections of specified components.

Scope and Application

The Civil Aviation Regulations 1998, specifically Part 39 - 105, pertains to airworthiness directives governing the maintenance and safety of aircraft. The regulation in focus, AD/B747/140, applies exclusively to Boeing 747 series aeroplanes with line numbers 001 to 628 inclusive, addressing the structural integrity of the fuselage's lap joint upper nose section between BS 400 and BS 520. The requirement is to conduct a close visual and high-frequency eddy current inspection at the stringer 6L and 6R lap splice, adhering to Boeing Service Bulletin 747-53A2303 Revision 1. This inspection is mandatory and is referenced in FAA AD 90-21-17, and it also falls under the 747 Ageing Fleet Modification Programme (AD/B747/79) at 23000 flights. Compliance with this directive necessitates an initial inspection before the aircraft accumulates 13000 flights, with specific timelines depending on the aircraft's flight history as of 27 April 1995, and subsequent re-inspections at intervals not exceeding 5000 flights. Notably, for aircraft modified to the stretched upper deck configuration or those already modified in accordance with Boeing SB 747-53A2303, the inspection thresholds differ, providing a tailored approach based on the aircraft's modification status.

Key Provisions

The Civil Aviation Regulations 1998, specifically Part 39 - 105, detail the Civil Aviation Safety Authority’s Schedule of Airworthiness Directives (ADs) for various aircraft types. Within this, AD/B747/140 pertains to Boeing 747 series aeroplanes, focusing on the fuselage lap joint upper nose section between beam stations (BS) 400 and 520. This directive mandates a close visual and high-frequency eddy current inspection of the specified area at the stringer 6L and 6R lap splice (Section 5/95). The requirement is to adhere to Boeing Service Bulletin 747-53A2303 Revision 1, with references to FAA AD 90-21-17 and the Boeing 747 Ageing Fleet Modification Programme (AD/B747/79) at 23,000 flights. The obligations under AD/B747/140 are stringent and vary based on the aircraft’s flight history and modifications. Initially, inspections must be conducted before the aircraft accumulates 13,000 flights, unless an inspection has already been performed within the last 5,000 flights. For aircraft that have exceeded 12,000 flights as of 27 April 1995, specific timelines apply: aircraft with more than 16,000 flights must be inspected within 100 flights post-date, while those between 12,000 and 16,000 flights must be inspected within 1,000 flights. The inspection threshold can also be measured from the time of any stretched upper deck configuration modifications, and aircraft modified according to Boeing SB 747-53A2303 need not be inspected until 10,000 flights post-modification. Non-compliance with the specified inspection requirements could lead to significant consequences. While the regulations do not explicitly state penalties or offences, the potential implications of failing to adhere to these airworthiness directives can be severe. Non-compliance may result in the grounding of the aircraft, denial of airworthiness certification, and potential legal actions against the operators or airlines for failing to meet safety standards. The safety and operational integrity of the aircraft depend on strict adherence to these inspection protocols, underscoring the importance of timely and accurate compliance.