AD/B747/183 - Nacelle Strut Structure

Overview

The Civil Aviation Regulations 1998, specifically Part 39 - 105, includes an airworthiness directive (AD/B747/183) aimed at addressing structural integrity concerns identified in certain Boeing 747 series aeroplanes. This directive was enacted to ensure the safety of the aircraft by addressing reports of cracking in critical components such as the vertical chords, midspar webs, and canted closure webs of the inboard and outboard struts, which could lead to severe safety issues if left unaddressed. The directive applies to specified models of Boeing 747 aeroplanes, excluding those that have already undergone relevant modifications or have been identified in specific Boeing alerts. Compliance with the directive is mandatory and requires adherence to the technical requirements outlined in the FAA AD 98-08-15 Amendment 39-10464, with revised inspection timelines. This legislative measure was introduced by the Commonwealth of Australia through the Civil Aviation Authority to mitigate risks associated with structural failure due to fatigue and stress corrosion, thereby ensuring the continued airworthiness and safety of the affected aircraft.

Scope and Application

The Civil Aviation Regulations 1998, specifically Part 39 - 105, apply to the Boeing 747 series aeroplanes, including models 747-100, -200, and -300, that are in specific line positions ranging from 1 through 886. However, the directive does not apply to aircraft that have already undergone the wing/strut modification as per the Federal Aviation Administration's (FAA) AD 95-13-07, nor does it apply to aircraft that are designated as Group 5 in Boeing Alert Service Bulletin 747-54A2179 Revision 2. This regulation is intended to address reports of cracking on the vertical chords, midspar webs, and canted closure webs of the inboard and outboard struts, which were found to be due to fatigue and stress corrosion. Compliance with the directive mandates adherence to the technical requirements set out in FAA AD 98-08-15 Amendment 39-10464, with a specified effective date for initial and repeat inspection requirements of 16 July 1998. The directive itself becomes effective on the same date, aiming to prevent potential failures at the strut-to-wing interface that could lead to the separation of the engine and strut from the aircraft.

Key Provisions

The Civil Aviation Regulations 1998, particularly Part 39 - 105 concerning the Civil Aviation Safety Authority (CASA) Schedule of Airworthiness Directives, contains specific provisions for ensuring the safety of Boeing 747 series aeroplanes. Section AD/B747/183 addresses issues related to the nacelle strut structure (paragraphs 1 and 2). This directive applies to Boeing 747-100, -200, and -300 models with specific line positions, excluding those that have undergone certain modifications or are designated as Group 5 in Boeing Alert Service Bulletin 747-54A2179 Revision 2 (paragraph 3). The directive mandates compliance with the technical requirements of FAA AD 98-08-15 Amendment 39-10464 (paragraph 4). Compliance is to be achieved as outlined in the Requirement document, with a revised effective date of 16 July 1998 for both initial and repeat inspection requirements (paragraph 5). The directive became effective on 16 July 1998 (paragraph 6). Under this directive, operators and maintenance providers of the specified Boeing 747 series aeroplanes must ensure that the nacelle strut structure is inspected and, if necessary, repaired or replaced to meet the technical requirements outlined in FAA AD 98-08-15 Amendment 39-10464. This involves conducting inspections at specified intervals, documenting findings, and implementing corrective actions as required. Operators must maintain detailed records of all inspections and maintenance activities to demonstrate compliance with the directive (paragraphs 7 and 8). Additionally, any modifications or repairs must be performed by qualified personnel in accordance with the approved procedures (paragraph 9). Failure to comply with the airworthiness directive can result in serious safety risks, including potential structural failure of the strut-to-wing interface, leading to engine separation and catastrophic consequences. The Civil Aviation Regulations 1998 impose significant obligations on aircraft operators and maintenance providers to ensure that these directives are strictly followed. Non-compliance may lead to enforcement actions by CASA, including fines, suspension or revocation of airworthiness certificates, and other regulatory sanctions (paragraphs 10 and 11). The specific penalties for non-compliance are determined by CASA and can include substantial financial penalties and other enforcement measures (paragraph 12).