AD/B747/141 - Pylon - Inboard and Outboard Strut Forward Lower Spar

Overview

The Civil Aviation Regulations 1998, as amended, form a key component of Australian civil aviation legislation. Among these amendments is F2006B03042, a legislative instrument that addresses specific safety concerns with Boeing 747 series aeroplanes. Enacted by the Commonwealth of Australia, this regulation was introduced to ensure the airworthiness of these aircraft by mandating detailed inspections of critical structural components, specifically the Inboard and Outboard Strut Forward Lower Spar Chords, Stiffeners, and Webs. The problem this legislation aims to resolve is the potential for structural failure due to undetected cracks and loose fasteners in the specified areas, which could lead to catastrophic engine separation and compromise flight safety. The policy objective of this directive is to enhance the safety and reliability of Boeing 747 operations by enforcing stringent and regular inspection protocols, thereby mitigating the risks associated with identified structural vulnerabilities. This legislative instrument is administered by the Civil Aviation Safety Authority and is aligned with international standards, referencing FAA AD 94-17-17 for consistency in safety practices. The regulations set forth specific timelines for initial and subsequent inspections based on the number of landings the aircraft has accumulated, ensuring that maintenance is performed in a timely manner to address the identified safety issues.

Scope and Application

The Civil Aviation Regulations 1998, specifically Part 39 - 105, under the Civil Aviation Safety Authority Schedule of Airworthiness Directives, applies to Boeing 747 series aeroplanes with line numbers 001 through 510 that are powered by JT9D-3 or -7 series engines, excluding those with JT9D-70 engines. The regulations mandate a detailed visual inspection of the Inboard and Outboard Strut Forward Lower Spar Chords, Stiffeners, and Web to detect any cracks or loose fasteners. This inspection must be conducted in accordance with Boeing Service Bulletin 747-54-2160, and references FAA AD 94-17-17. Compliance with these requirements involves initial inspections that must be performed before 2 February 1996 or before the aircraft exceed 6000 landings, whichever is later. For aircraft that have accumulated between 6000 and 15000 landings, inspections must be completed before 2 October 1995, while aircraft with more than 15000 landings must be inspected before 2 July 1995. Subsequent inspections are required at intervals not exceeding 2000 landings or 8000 hours of time in service, whichever comes first. These measures have been implemented in response to reports of cracks in the specified web and the suspicion that a web crack may have contributed to an engine separation incident.

Key Provisions

The Civil Aviation Regulations 1998 (Regulations), specifically Part 39, Section 105, includes an Airworthiness Directive (AD) for Boeing 747 series aeroplanes concerning the pylon inboard and outboard strut forward lower spar. The directive, identified as AD/B747/141, mandates a detailed visual inspection of the inboard and outboard strut forward lower spar chords, stiffeners, and web to detect cracks and loose fasteners. This inspection must be conducted in accordance with Boeing Service Bulletin 747-54-2160. This requirement is applicable to Boeing 747 aircraft with serial numbers between 001 and 510, powered by JT9D-3 or -7 series engines, excluding JT9D-70 engines. The directive references FAA AD 94-17-17 for further guidance. Under this directive, operators of the specified Boeing 747 aircraft must ensure that the required inspections are performed. The initial inspection must occur before 2 February 1996 or before the aircraft exceeds 6000 landings, whichever is later. For aircraft that have accumulated between 6000 and 15000 landings, the inspection must be completed before 2 October 1995. Aircraft with more than 15000 landings must have the inspection conducted before 2 July 1995. Subsequent inspections must be carried out at intervals not exceeding 2000 landings or 8000 hours of time in service, whichever occurs first. Failure to comply with the requirements of this Airworthiness Directive may result in serious safety issues, including the risk of structural failure of the strut, which could lead to catastrophic in-flight incidents. The Regulations do not specify civil or criminal penalties for non-compliance with this directive, but non-compliance could result in the aircraft being deemed unairworthy, leading to potential grounding and significant operational disruptions. Additionally, such non-compliance could lead to enforcement actions by the Civil Aviation Safety Authority, including the imposition of fines and other regulatory measures.