AIRWORTHINESS DIRECTIVE
For the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CASR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.
Boeing 747 Series Aeroplanes
AD/B747/309 Electrical Bonding 8/2004
Applicability: Model 747 series aeroplanes with line numbers 1 through 1271 inclusive.
Requirement: 1. Prepare the electrical bonding faying surfaces for the tubing penetrations of the hydraulic heat exchanger on the forward and aft surfaces of the rear spars of the fuel tanks of the left and right wings, together with carrying out a one-time measurement of the electrical bonding resistances between the penetration fittings of the hydraulic heat exchanger and the rear spars; and between the heat exchanger tube and the lower wing stringer surfaces, per the Accomplishment Instructions of ASB 747-29A2104 Revision 1 dated 7 March 2002.
2. If the bonding resistance is incorrect, repeat the preparation of the electrical bonding faying surface for the tubing penetrations of the hydraulic heat exchanger on the forward and aft surfaces of the rear spar of the fuel tanks of the left and right wings as necessary to achieve a bonding resistance below the threshold specified in the Accomplishment Instructions of ASB 747-29A2104 Revision 1.
3. Apply fillet sealant and protective finishes around the penetration fittings of the hydraulic heat exchanger in accordance with the Accomplishment Instructions of ASB 747-29A2104 Revision 1 (Figure 4 refers).
4. Service and pressurize the hydraulic systems and examine for signs of hydraulic fluid leakage. Service the fuel tank and examine for signs of fuel leakage. All these actions are to be accomplished in accordance with ASB 747-29A2104 Revision 1.
5. Repair any leaks found, during the Requirement 4 examination, in accordance with ASB 747-29A2104 Revision 1.
Actions accomplished before the effective date of this Directive in accordance with Boeing ASB 747-29A2104, dated 19 July 2001, are considered acceptable for compliance with the corresponding action specified in this Directive.
Note: FAA AD 2004-10-06 Amdt 39-13636 refers.
Compliance: For Requirement 1 - Within 60 months after the effective date of this Directive.
Boeing 747 Series Aeroplanes
AD/B747/309 (continued)
For Requirement 2 - Before further flight after the Requirement 1 bonding resistance check.
For Requirement 3 - Before further flight after completing Requirements 1 and 2. For Requirement 4 - Before further flight after completing Requirement 3.
For Requirement 5 - Before further flight after completing Requirement 4. This Airworthiness Directive becomes effective on 5 August 2004.
Background: This Directive requires, among other things, preparation of the electrical bonding faying surfaces for the tubing penetrations of the hydraulic heat exchanger on the forward and aft surfaces of the rear spars of the fuel tanks of the left and right wings, a one-time measurement of the electrical bonding resistances together with follow-on actions.
These actions are necessary to ensure adequate electrical bonding between the penetration fittings of the hydraulic heat exchanger and the rear spars of the fuel tanks. Inadequate electrical bonding, in the event of a lightning strike, could cause electrical arcing and ignition of fuel vapour in the wing fuel tank, which could result in a fuel tank explosion.
James Coyne
Delegate of the Civil Aviation Safety Authority 23 June 2004
The above AD is notified in the Commonwealth of Australia Gazette on 14 July 2004.
Overview
The Civil Aviation Safety Authority Airworthiness Directive (AD) AD/B747/309, enacted in 2004, addresses the problem of inadequate electrical bonding in Boeing 747 series aeroplanes, specifically those with line numbers 1 through 1271 inclusive. This issue was identified as a potential safety hazard due to the risk of electrical arcing and ignition of fuel vapour, which could lead to a fuel tank explosion in the event of a lightning strike. The AD was issued under subregulation 39.1 (1) of the Civil Aviation Safety Regulations 1998, by the delegate of the Civil Aviation Safety Authority, with the objective of ensuring the adequate electrical bonding between specified components of the aircraft. The directive mandates specific actions to be taken within certain timeframes to mitigate this safety risk, including the preparation of electrical bonding surfaces, measurement of bonding resistances, application of fillet sealant and protective finishes, and examination for leaks in the hydraulic and fuel systems.
Scope and Application
The Airworthiness Directive (AD) issued by the Civil Aviation Safety Authority (CASA) applies specifically to Boeing 747 series aeroplanes with line numbers ranging from 1 through 1271 inclusive. This legislation mandates specific safety measures to ensure the airworthiness of these aircraft, focusing on the electrical bonding of hydraulic heat exchangers in the fuel tanks. The AD necessitates the preparation of electrical bonding surfaces, measurement of bonding resistances, application of fillet sealant and protective finishes, and thorough checks for hydraulic and fuel leaks. These actions are to be carried out within specified timeframes and in accordance with the instructions provided in ASB 747-29A2104 Revision 1. The directive is applicable across the Commonwealth of Australia, ensuring a uniform standard of aircraft safety and maintenance throughout the country. Any actions completed before the directive's effective date that align with the requirements of Boeing ASB 747-29A2104, dated 19 July 2001, are deemed acceptable. The AD was officially published in the Commonwealth of Australia Gazette on 14 July 2004 and became effective on 5 August 2004, underscoring the urgency and importance of the mandated safety measures.
Key Provisions
This Airworthiness Directive (AD), issued under subregulation 39.1(1) of the Civil Aviation Safety Regulations 1998 (CASR 1998), applies to Boeing 747 series aeroplanes with line numbers 1 through 1271 inclusive. The directive mandates specific actions to address an identified unsafe condition concerning the electrical bonding of the hydraulic heat exchanger within the aircraft's fuel tanks. It is imperative that these actions are executed as per the detailed instructions provided in the Accomplishment Instructions of ASB 747-29A2104 Revision 1 dated 7 March 2002. The actions include preparing the electrical bonding faying surfaces, measuring the bonding resistances, applying fillet sealant and protective finishes, and conducting system checks for leakages, with subsequent repairs if any are detected. These actions must be completed within specified timeframes and before further flight following each respective requirement.
The obligations imposed by this AD on the relevant parties, including aircraft operators and maintenance organisations, are comprehensive. Firstly, they must ensure that the electrical bonding faying surfaces are adequately prepared for the hydraulic heat exchanger tubing penetrations. This involves meticulous attention to detail in the preparation process, as outlined in the referenced Accomplishment Instructions. Secondly, operators must conduct a one-time measurement of the electrical bonding resistances and, if necessary, repeat the preparation steps to meet the specified resistance thresholds. Thirdly, operators are required to apply fillet sealant and protective finishes to the penetration fittings, again following the detailed instructions provided. Lastly, operators must service and pressurize the hydraulic systems, inspect for leaks, and perform necessary repairs. These obligations are crucial to maintaining the airworthiness of the aircraft and preventing potential hazards such as fuel tank explosions.
Failure to comply with the AD's requirements can result in serious consequences. The AD outlines specific timeframes for completing each requirement, and non-compliance within these timeframes can lead to enforcement actions by the Civil Aviation Safety Authority (CASA). Although the AD does not explicitly state civil or criminal penalties for non-compliance, CASA has the authority to take enforcement actions under the Civil Aviation Act 1988 and CASR 1998, which can include fines and other sanctions. Additionally, non-compliance could potentially lead to aircraft being grounded or prohibited from flight, which can have significant operational and financial repercussions for the operators. Ensuring adherence to the AD is, therefore, not only a regulatory requirement but also a critical safety measure.