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 737 Series Aeroplanes
AD/B737/227 Electrical Bonding 8/2004
Applicability: Model 737-100, -200, -200C, -300, -400 and -500 series aeroplanes as listed in Boeing Alert Service Bulletin (ASB) 737-29A1096 Revision 1 dated 31 July 2003.
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 737-29A1096 Revision 1.
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 737-29A1096 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 737-29A1096 Revision 1 (Figure 8 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 737-29A1096 Revision 1.
5. Repair any leaks found, during the Requirement 4 examination, in accordance with ASB 737-29A1096 Revision 1.
Actions accomplished before the effective date of this Directive in accordance with Boeing ASB 737-29A1096, dated 7 June 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 737 Series Aeroplanes
AD/B737/227 (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 (CASA) introduced the Airworthiness Directive (AD) B737/227 in 2004 to address a critical safety concern related to electrical bonding in Boeing 737 series aeroplanes. This directive was enacted to correct an unsafe condition identified in the electrical bonding of the hydraulic heat exchanger within the fuel tanks of these aircraft. The potential for inadequate bonding to cause electrical arcing and subsequent ignition of fuel vapour during a lightning strike posed a significant risk of fuel tank explosions. The AD mandates specific actions, including the preparation of electrical bonding surfaces, measurement of bonding resistances, application of fillet sealant, and inspection for hydraulic and fuel leaks, all to be carried out within specified timeframes. This legislative instrument aims to ensure the airworthiness of the affected aircraft by mitigating the risk of fuel tank explosions due to inadequate electrical bonding.
Scope and Application
The Airworthiness Directive (AD) pertains to the Boeing 737 series aeroplanes, specifically the models 737-100, -200, -200C, -300, -400, and -500, which are subject to the directive as referenced in Boeing Alert Service Bulletin (ASB) 737-29A1096 Revision 1 dated 31 July 2003. This AD applies to aircraft registered within the jurisdiction of the Civil Aviation Safety Authority (CASA) in Australia, aligning with the requirements set forth by the Civil Aviation Safety Regulations (CASR) 1998. The directive mandates specific actions to address electrical bonding issues in the hydraulic heat exchangers of the aircraft's fuel tanks to mitigate the risk of fuel tank explosions due to inadequate electrical bonding, which could occur following a lightning strike. Compliance with this AD is required within stipulated timeframes, with particular actions to be completed before further flight following specified inspections and repairs. The AD is applicable nationally within Australia and is issued under the authority delegated by CASA, effective from 5 August 2004.
Key Provisions
This Airworthiness Directive (AD) issued under subregulation 39.1(1) of the Civil Aviation Safety Regulations 1998 (CASR) applies to specific Boeing 737 series aeroplanes, as detailed in Boeing Alert Service Bulletin (ASB) 737-29A1096 Revision 1 dated 31 July 2003. The directive mandates that certain actions be taken to address an unsafe condition related to the electrical bonding of the hydraulic heat exchanger on the rear spars of the fuel tanks in the left and right wings of the specified aircraft models. These actions include preparing the electrical bonding faying surfaces, measuring the bonding resistances, and applying fillet sealant and protective finishes. The directive specifies a timeline for compliance, with certain actions required within 60 months of the directive's effective date, and others needing to be completed before further flight after specific preceding actions have been undertaken.
Operators of the affected Boeing 737 series aeroplanes are obligated to follow the detailed instructions outlined in the directive, ensuring that the electrical bonding faying surfaces are properly prepared and that the bonding resistances are within the specified thresholds. They must also apply fillet sealant and protective finishes around the penetration fittings of the hydraulic heat exchanger. Additionally, operators are required to service and pressurize the hydraulic systems and examine for leaks, service the fuel tank and examine for fuel leaks, and repair any leaks found. The directive allows for actions taken in accordance with an earlier Boeing ASB dated 7 June 2001 to be considered acceptable for compliance with the corresponding actions specified in this directive.
Failure to comply with the AD may result in civil or criminal penalties, depending on the severity and intent of the breach. Under the Civil Aviation Act 1988, non-compliance with an airworthiness directive can lead to civil penalties, including fines and potential legal action. For example, an operator failing to adhere to the specified requirements could face fines as stipulated by the CASR. In cases where non-compliance is deemed to have caused or contributed to an accident or incident, the operator could also face more severe criminal penalties, including imprisonment. The maximum penalties for breaches of the CASR can include fines up to several hundred thousand dollars and imprisonment for individuals found guilty of serious violations.