COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
Boeing 747 Series Aeroplanes
AD/B747/160 Fuselage Skin Above Main Entry Doors - 2 8/96
Applicability: B747 aircraft, line numbers 207 to 1088.
Note. AD/B747/149 refers to a similar problem for line numbers 1 to 206.
Requirement: 1. Remove stringers S-15, S-14E, S-14 between STA 460 and 480, and move STA 460 frame aft to gain internal access to the skin and doublers above main entry door 1. Perform an internal visual inspection for cracking of doublers along fastener holes up to stringer S-14E. Perform open-hole High Frequency Eddy Current (HFEC) inspections of skin and doublers up to stringer S-14 for cracking. Gain access and conduct inspections in accordance with Boeing Service Bulletin (SB) 747-53A2396, Revision 1.
2. If cracks are found, repair and reinforce the skin joint in accordance with the Structural Repair Manual, or if no cracks are found, install an external doubler in accordance with Boeing SB 747-53A2396, Revision 1.
3. After modification or repair in accordance with Requirement 2, reinspect the affected area using internal High Frequency Eddy Current (HFEC) or external Low Frequency Eddy Current (LFEC) inspections, in accordance with Boeing Service Bulletin 747-53A2396, Revision 1.
Note: For the purposes of this AD, a flight-cycle may be taken as only those flights which achieve a cabin pressure differential of 2.0 psi or greater.
Compliance: Inspect, and reinforce the skin joint by repair or modification, before 10000 flight cycles or within 3000 flight cycles after 18 July 1996, whichever occurs last.
Initially reinspect within 15000 flight cycles after modification or repair, and thereafter reinspect at intervals not to exceed 6000 flight cycles if using internal HFEC, or at intervals not to exceed 3000 flight cycles if using external LFEC inspectors.
Background: An operator has reported numerous skin cracks found in internal skin doublers under the outer flange of STA 460 frame above main entry door 1. Boeing's subsequent inspection of 747-100SR fuselage and 747-400 section 41 and 42 fatigue test articles also revealed multiple cracking. Further inspection of 5 in-service aircraft revealed 4 aircraft with multiple cracking at times as low as 15,000 flights. Skin cracks that are not found and reinforced may lead to sudden loss of cabin pressurisation.
Overview
The Civil Aviation Regulations 1998, enacted by the Parliament of Australia, include provisions aimed at ensuring the safety of civil aviation. One such provision, detailed in PART 39 - 105, addresses specific maintenance requirements for the Boeing 747 Series Aeroplanes to mitigate risks associated with fuselage skin integrity. This directive, AD/B747/160, targets Boeing 747 aircraft within line numbers 207 to 1088, focusing on preventing structural failures that could lead to sudden loss of cabin pressurisation. The policy objective is to enhance the safety of air travel by mandating rigorous inspections and necessary repairs to identified structural weaknesses. Compliance with these directives is critical to maintaining the airworthiness of the aircraft and ensuring passenger safety.
Scope and Application
The Civil Aviation Regulations 1998, specifically Part 39 - 105, includes Airworthiness Directives (AD) that govern the safety standards for aircraft within Australian airspace. AD/B747/160 pertains to Boeing 747 series aeroplanes, particularly those with line numbers ranging from 207 to 1088, and mandates inspections and repairs to address cracking issues found in the fuselage skin above the main entry door. The directive applies to all relevant aircraft operators and requires them to conduct detailed inspections, repairs, and reinforcement of the specified fuselage area to ensure continued airworthiness and safety. The directive outlines specific inspection procedures, repair requirements, and re-inspection intervals, ensuring that the affected area is maintained to prevent sudden loss of cabin pressurisation. Additionally, AD/B747/149 addresses a similar issue for line numbers 1 to 206. Compliance with these directives is crucial for maintaining the safety standards required by the Civil Aviation Safety Authority.
Key Provisions
The Civil Aviation Regulations 1998, Part 39, 105, through the Civil Aviation Safety Authority's Schedule of Airworthiness Directives, mandates specific actions for Boeing 747 Series Aeroplanes with line numbers 207 to 1088 (AD/B747/160). This directive addresses fuselage skin and doubler cracking above the main entry door 1. The main requirements (AD/B747/160) include the removal of certain stringers to access and inspect the skin and doublers for cracks, and conducting inspections using specified methods. If cracks are found, the skin joint must be repaired or reinforced; if no cracks are present, an external doubler must be installed. Reinspection is required after any modification or repair, with specific intervals based on the inspection method used.
Operators of affected Boeing 747 aircraft must comply with these requirements to ensure the airworthiness and safety of the aircraft. This includes performing the necessary inspections and repairs within specified timeframes. The initial inspection must occur before the aircraft reaches 10,000 flight cycles or within 3,000 flight cycles after 18 July 1996, whichever is later. Following any modification or repair, a reinspection is required within 15,000 flight cycles, with subsequent reinspections at intervals not exceeding 6,000 flight cycles for internal HFEC inspections or 3,000 flight cycles for external LFEC inspections.
Failure to comply with the provisions of this Airworthiness Directive may result in serious safety issues, including the potential for sudden loss of cabin pressurisation. While the specific regulatory consequences for non-compliance are not detailed in this text, it is reasonable to infer that such non-compliance could lead to enforcement actions by the Civil Aviation Safety Authority, including potential civil or criminal penalties for operators who fail to adhere to the mandated inspection and repair procedures.