AD/B747/142 - Fuselage Skin Lap Joints

Overview

The Civil Aviation Regulations 1998, amended by the Legislative instrument F2006B03043, was enacted to address specific safety concerns identified in the Boeing 747 series aeroplanes, particularly focusing on the integrity of the fuselage skin lap joints. The Australian Civil Aviation Safety Authority (CASA) introduced these regulations to mandate inspections and necessary repairs to mitigate the risk of fatigue cracking, thereby ensuring the continued safety and airworthiness of the aircraft. The regulations were developed in response to Boeing’s extended pressure tests that revealed susceptibility to fatigue cracking in certain areas of the B747 fuselage lap joints. The policy objective was to enforce mandatory periodic inspections and repairs, ensuring that any identified issues are promptly addressed to prevent potential safety hazards during flight operations.

Scope and Application

The Civil Aviation Safety Authority (CASA) has issued an airworthiness directive under the Civil Aviation Regulations 1998, specifically targeting Boeing 747 Series Aeroplanes, as outlined in AD/B747/142. This directive applies to all B747 aircraft identified in Boeing Service Bulletin 747-53-2367 revision 1 dated 27 January 1994. The primary requirement of this directive involves inspecting the upper fastener row of the specified fuselage skin lap joints using the surface high frequency eddy current method. If any cracks are detected, the directive mandates the removal of the upper row fasteners for one frame bay either side of the crack and further inspection of the open holes using the same high frequency eddy current inspection method. Compliance with this directive requires an initial inspection before reaching 22,000 full pressure cycles or within 1,000 full pressure cycles after 27 April 1995, whichever occurs last, followed by re-inspections at intervals not exceeding 3,000 full pressure cycles, and further inspection before any subsequent flight. The directive is grounded in extended pressure tests conducted by Boeing, which identified areas susceptible to fatigue cracking, thus necessitating these inspections and repairs to ensure the continued safety of B747 operations.

Key Provisions

The main operative sections of this legislation (AD/B747/142) pertain to the inspection and maintenance requirements for Boeing 747 Series Aeroplanes, specifically focusing on the fuselage skin lap joints (Section 1). This directive applies to all B747 aircraft listed in Boeing Service Bulletin 747-53-2367 revision 1 dated 27 January 1994. The requirement is to inspect the upper fastener row of the specified lap joints using a surface high frequency eddy current method. If any cracks are detected, the upper row fasteners must be removed for one frame bay either side of the crack, and the open holes inspected using the same high frequency eddy current inspection method as specified in the aforementioned bulletin. The obligations imposed by the Act on the parties governed by it include conducting an initial inspection before reaching 22,000 full pressure cycles or within 1,000 full pressure cycles after 27 April 1995, whichever is later (Section 1). Following this initial inspection, re-inspections must be carried out at intervals not exceeding 3,000 full pressure cycles. A full pressure cycle is defined as a period where the cabin differential pressure equals or exceeds 2.0 psi. Additionally, an inspection must be performed before each flight to ensure compliance with safety standards. Breach of these regulations can lead to civil or criminal consequences. While specific penalties are not detailed in this legislation, non-compliance with Civil Aviation Regulations in general can result in substantial fines and potential imprisonment. The Civil Aviation Safety Authority (CASA) has the authority to enforce these regulations, and failure to adhere to the prescribed inspection and maintenance protocols can lead to severe penalties under Australian aviation law. The exact nature and severity of these penalties would be determined by CASA in the context of the breach.