AD/B747/129 - Fuselage Lower Frames at Body Stations 2200 and 2220

Overview

The Civil Aviation Regulations 1998, enacted by the Australian Parliament, play a pivotal role in ensuring the safety of civil aviation in the country. This legislation includes specific provisions such as Part 39 - 105, which outlines the Civil Aviation Safety Authority's schedule of airworthiness directives for various aircraft models, including the Boeing 747 Series. One such directive, AD/B747/129, addresses the critical issue of cracks in the fuselage lower frames at specific body stations of Boeing 747 aircraft, particularly those in Line Numbers 1 to 757. The directive aims to mitigate the risk of frame failure and sudden decompression by mandating detailed visual inspections in accordance with Boeing Service Bulletin 747-53-2302. The policy objective is to maintain the structural integrity of the aircraft, thereby enhancing overall flight safety.

Scope and Application

The Civil Aviation Regulations 1998, specifically Part 39 - 105, which pertains to the Civil Aviation Safety Authority's Schedule of Airworthiness Directives, applies to Boeing Model 747 aircraft, specifically those with Line Numbers ranging from 1 to 757 inclusive, excluding SP versions. This regulation mandates detailed visual inspections of the fuselage lower frames at body stations 2200 and 2220 for cracks, in accordance with Boeing Service Bulletin 747-53-2302. The purpose of this directive is to ensure the safety of the aircraft by preventing frame failure and sudden decompression of the fuselage. Compliance with the inspection requirements is critical, with specific intervals prescribed based on the aircraft's flight history and any frame replacements that may have been performed. The inspection must occur before the aircraft reaches 10,000 flights or within 1,000 flights, whichever is later, for aircraft with less than 10,000 flights as at 18 August 1994. For aircraft with replaced frames, inspections must occur within 10,000 flights from the date of replacement, with subsequent inspections at intervals not exceeding 2,000 flights. If cracks are detected, the inspection area must be extended to include adjacent frames, stringers, skin, skin lap joints, and skin adjacent to the outflow valve. This directive ensures that all Boeing 747 aircraft, within the specified range and conditions, adhere to stringent safety standards to mitigate risks associated with structural integrity.

Key Provisions

The Civil Aviation Regulations 1998, specifically Part 39 - 105, which governs the Civil Aviation Safety Authority's Schedule of Airworthiness Directives, includes the directive AD/B747/129 (paragraph 1). This directive mandates a detailed visual inspection of the fuselage lower frames at body stations 2200 and 2220 for cracks in Boeing 747 series aeroplanes, excluding SP versions, with line numbers 1 to 757 inclusive (paragraph 2). The directive references Boeing Service Bulletin 747-53-2302 and FAA AD 91-18-04 for the inspection procedure (paragraph 2). Compliance with this directive requires several specific actions. For Boeing 747 aircraft with fewer than 10,000 flights as at 18 August 1994, a visual inspection must be conducted before reaching 10,000 flights or within 1,000 flights, whichever comes later (paragraph 3.1). If the lower frames have been replaced in accordance with Boeing Service Bulletin 747-53-2302, an inspection must be performed within 10,000 flights from the date of frame replacement (paragraph 3.2). In all cases, the inspection must be repeated at intervals not exceeding 2,000 flights (paragraph 3.3). If any cracks are detected during these inspections, the inspection area must be extended to include adjacent frames (BS 2180 and 2240), stringers, skin, skin lap joints, and skin adjacent to the outflow valve (paragraph 3.4). Failure to comply with these inspection requirements can result in serious consequences. While the specific penalties or legal consequences for non-compliance are not detailed within the directive itself, breaches of the Civil Aviation Regulations 1998 can generally lead to civil or criminal penalties, including fines and imprisonment, depending on the severity of the breach and the discretion of the court. The potential severity of the consequences underscores the importance of adhering to the detailed inspection schedule mandated by AD/B747/129 to ensure the continued airworthiness and safety of Boeing 747 aircraft.