AD/B717/21 - Fuel System Lightning Protection

The Directive is organised around a small set of technical and administrative concepts drawn from aviation maintenance practice. Applicability: the AD applies only to Model 717‑200 aeroplanes identified in a specific Boeing service bulletin (SB 717‑28‑0004, Revision 3, dated 21 June 2006). The technical fault addressed is a potential failure of the aluminium foil strip on the nylon base of certain ground clamps used in the fuel tank vent system; the Directive records that this foil strip can fracture or separate from the base and thereby risk improper electrical bonding. The safety mechanism targeted is electrical bonding of fuel pipes to the aeroplane structure, intended to provide a conductive path to dissipate lightning energy to structure so that energy does not remain in tank components where ignition risk could arise.

The compliance framework is prescriptive and time‑bounded. The Directive prescribes a parts replacement (improved clamp bases) and then immediate testing (electrical bond check) and repair if testing fails. Timing is split: the replacement must occur within a set calendar interval , 68 months after the AD’s effective date , while the post‑replacement check and any consequent repair must be completed before the aeroplane’s next flight. The AD recognises alternative compliance pathways: actions already accomplished in accordance with SB Revision 2 are accepted; later revisions of the SB may be acceptable where the FAA has approved them as an AMOC to a related FAA AD. The Manager, Los Angeles ACO, FAA, is the delegated decision maker for approving alternative repair methods under Requirement 3, and the AD identifies Boeing maintenance manuals as one approved repair method. The Directive cross‑references FAA AD 2006‑20‑12, signalling coordination with the FAA’s airworthiness directives.

Key administrative points are the AD’s effective date (2 August 2007) and the signature by a CASA delegate (David Punshon) dated 19 June 2007. The AD is framed as corrective maintenance: replace, verify, and repair where necessary. The logic is sequential , replacement first, test second, repair third , with the second and third steps gating the ability to continue flight operations. The AD therefore combines a deferred compliance window for replacement with immediate post‑work operational constraints enforced by the “before further flight” requirement.

The Directive affects owners, operators and maintenance organisations that operate Model 717‑200 aeroplanes specified in Boeing SB 717‑28‑0004 Revision 3 (21 June 2006). The AD’s applicability language confines the obligation to those aeroplanes identified in that specific service bulletin: only aircraft matching that identification are within scope. The primary obliged parties are the aircraft operators who are responsible for accomplishing the maintenance actions and ensuring compliance with the stated compliance times. Maintenance providers and engineers who perform the replacements, electrical bonding checks and repairs are operationally engaged by the owners/operators to meet the Directive’s prescriptions.

Because the Directive requires repair according to the service bulletin or a method approved by the Manager, Los Angeles ACO, FAA, the FAA’s Los Angeles Aircraft Certification Office staff are named decision makers for any non‑standard repair approach. Boeing, as the design authority producing the service bulletin and as proprietor of the maintenance manuals referenced, is also a practical actor: the AD lists Boeing manuals as an approved repair method and cross‑references the Boeing service bulletin for detailed instructions and parts identification. The Civil Aviation Safety Authority is the issuing authority: the instrument bears the name of the CASA delegate who issued it (David Punshon), and provides the effective date. The AD also references the FAA AD 2006‑20‑12 Amdt 39‑14782, indicating bilateral interaction so that FAA approvals and AMOCs have legal relevance under this Directive.

Who pays: the Directive imposes on operators the burden of replacing the clamp bases within 68 months, performing the mandated checks, and effecting repairs if checks fail. Those activities involve procurement of parts (improved clamp bases), labour, and downtime for the aircraft. The AD does not specify cost‑recovery mechanisms or financial assistance; it simply places the operational and execution obligation on parties responsible for the aircraft. Where operators propose an alternative repair method, they must secure approval from the Manager, Los Angeles ACO, which imposes administrative work to obtain that approval.

Who decides: the AD delegates certain approvals to the FAA Manager, Los Angeles ACO, for alternative repair methods, and indicates FAA approval of later SB revisions as AMOCs will be accepted. The CASA delegate issued the Directive, thereby setting the compliance deadline and the binding national requirement. The practical decisions an operator must make are sequencing and scheduling the replacement within the 68‑month window, ensuring the post‑replacement check before flight, and arranging approved repairs where checks fail.

Duties specified by the Directive are expressed as three core requirements. Requirement 1: replace the lightning‑critical clamp bases of the fuel tank vent system with improved clamp bases, following the parts and procedures set out in Table 1 of Figure 1 of the Accomplishment Instructions of SB 717‑28‑0004 Revision 3. The AD fixes a compliance deadline for that duty: within 68 months after the Directive’s effective date. Requirement 2: after the replacement, conduct an electrical bond check of the modified self‑bonding mounting clamps in accordance with the service bulletin’s Accomplishment Instructions, with the temporal constraint “before further flight” after the replacement. Requirement 3: if any electrical bond fails the check in Requirement 2, repair the electrical bond of the mounting clamp either in accordance with SB 717‑28‑0004 Revision 3 or by a method approved by the Manager, Los Angeles ACO, FAA, with the repair also to be completed “before further flight” after the check.

Rights and recognitions built into the AD create limited flexibility. Actions completed before the effective date in accordance with Boeing SB 717‑28‑0004 Revision 2, dated 11 March 2005, are explicitly accepted as compliant with the Directive. Additionally, later revisions of the SB that the FAA has approved as an Alternate Method of Compliance to FAA AD 2006‑20‑12 are considered acceptable for compliance with the equivalent requirements of this Directive. The AD explicitly identifies one approved repair method: Chapter 28‑00‑00 of the Boeing 717 Aircraft Maintenance Manual and Chapter 20‑50‑01 of the Boeing DC, MD, and 717 Standard Wiring Practices Manual. The AD also names the Manager, Los Angeles ACO, FAA, as the approving authority for any other alternative repair method sought under Requirement 3.

Operationally important duties are the “before further flight” constraints attached to the check and repair steps. Those phrases function as immediate operational gates: after the replacement, an aircraft must have the electrical bond check completed before it may be flown further; if the check fails, the repair must be completed before further flight. The AD therefore imposes not only a calendar deadline for the initial replacement but also immediate, flight‑critical constraints on post‑work testing and rectification, shifting the locus of decision‑making to maintenance planning and flight dispatch to ensure safe continuation of operations.

The Directive sets compliance obligations and explicit timing, including an effective date of 2 August 2007 and the temporal requirements for each numbered action: Requirement 1 within 68 months of the effective date, Requirement 2 before further flight after replacement, and Requirement 3 before further flight after any failed check. The AD itself contains no express statement of civil or criminal penalties, nor does it specify the administrative enforcement mechanisms used to compel compliance within the text included in this instrument. The document is signed by a CASA delegate, indicating the issuing regulator and the date of signature (19 June 2007), but the text of the Directive does not detail enforcement procedures, inspection rights, or specific sanctions for non‑compliance.

Operationally, the AD’s “before further flight” wording creates an immediate constraint on aircraft operations: the Directive requires that certain checks and repairs be completed prior to the aircraft being flown after the relevant maintenance step. That operational constraint functions as a de facto enforcement mechanism because it ties airworthiness to completion of the listed work. The AD also embeds a reliance on FAA approvals (AMOCs and repair method approvals by the Manager, Los Angeles ACO), which introduces an administrative control point: non‑standard repair methods must obtain FAA approval to be considered compliant with the Directive. The AD acknowledges acceptability of certain prior actions (SB Revision 2) and of later SB revisions if approved by the FAA as AMOCs; those acceptances provide compliance pathways that can be checked and verified.

Because the Directive text does not itself set out penalties or enforcement processes, parties seeking clarity on statutory sanctions, regulatory penalties, or inspection and audit powers will need to consult broader regulatory materials or CASA enforcement policies that are not contained in the AD text. The AD does, however, define obligations and dates which can be used as objective compliance measures by inspectors or auditors; failure to satisfy those obligations would be identified against the AD’s requirements.

The Directive explicitly cross‑references external regulatory and technical instruments. It notes FAA AD 2006‑20‑12 Amdt 39‑14782, indicating that this CASA AD is coordinated with an FAA airworthiness directive on the same technical issue. The AD accepts compliance pathways premised on FAA action: later revisions of Boeing SB 717‑28‑0004 that the FAA approves as an Alternate Method of Compliance (AMOC) to FAA AD 2006‑20‑12 are stated to be acceptable for compliance with equivalent requirements of this Directive. The AD therefore creates an interoperability relationship: FAA approvals and AMOCs have legal relevance to compliance under this CASA AD.

The AD relies on Boeing technical publications to specify the work. Applicability and procedural detail are drawn from Boeing SB 717‑28‑0004 Revision 3, and the AD accepts work done per Revision 2 as compliant if accomplished prior to the effective date. The AD also identifies Boeing maintenance manuals (Chapter 28‑00‑00 of the Boeing 717 Aircraft Maintenance Manual and Chapter 20‑50‑01 of the Boeing DC, MD, and 717 Standard Wiring Practices Manual) as one approved repair method. In practice, this makes Boeing’s service bulletin and manuals the normative technical sources for execution and for any audit of compliance.

The AD assigns the Manager, Los Angeles ACO, FAA, the authority to approve alternative repair methods under Requirement 3. That delegation positions an FAA office as the approving authority for non‑standard repairs that will be accepted by CASA under this AD. The AD therefore integrates CASA’s regulatory requirement with FAA technical approval procedures, so that bilateral administrative action affects compliance status. The AD does not, in its text, reference any other Australian statutes, regulations, or standards by name; nor does it specify how CASA’s enforcement practices under Australian law will be applied. The AD’s interactions are thus with a foreign regulator (FAA) and with manufacturer documentation, and it formalises those interactions by accepting certain FAA approvals and Boeing documentation as satisfying the AD.

The Directive itself contains a limited amendment history within its operative text. It makes explicit that actions accomplished before the effective date in accordance with Boeing SB 717‑28‑0004, Revision 2, dated 11 March 2005, are acceptable for compliance with the requirements of this Directive. That clause recognises prior maintenance activity performed under an earlier revision of the service bulletin as a valid compliance pathway, thereby grandfathering certain earlier work.

The AD also contemplates later iterative changes to the Boeing service bulletin by accepting, as compliant, “later revisions of the above SB, approved by the FAA as an Alternate Method of Compliance (AMOC) to FAA AD 2006‑20‑12.” Thus the AD builds in a forward‑looking acceptance of FAA‑approved updates to the SB as they relate to the technically equivalent requirements of the related FAA AD. The Directive does not itself list a sequence of amendments to the AD instrument; instead, it references revisions of the Boeing SB and FAA AMOC approvals as the operative means by which technical practice may evolve while remaining compliant with the AD.

The AD’s effective date is recorded: it “becomes effective on 2 August 2007.” The signature block records the issuing CASA delegate and the directive’s issuance date, 19 June 2007. No other amendments or subsequent amendments to the AD are provided in the text supplied. The AD does not specify a process within its text for CASA to accept amendments to its own directive based on external approvals; rather it accepts, within the instrument, specific prior and later technical approvals issued by Boeing and the FAA as establishing compliance equivalence.

The text of the Directive contains no litigation history, no references to court proceedings, and no mention of legal challenges. The AD cites an FAA investigation as the factual basis for the Directive’s technical concern (that aluminium foil strips on the nylon base of the ground clamps can fracture or separate), but it does not reference any disputes, appeals, or judicial reviews concerning the AD’s issuance or substance. The instrument records administrative coordination points , notably the FAA Manager, Los Angeles ACO’s role in approving alternative repair methods, and acceptance of FAA AMOCs , but supplies no record of contested administrative decisions or litigation arising from those processes.

Where a reader requires information on any court or tribunal challenges to the AD, they will not find it within this text; the AD does not provide a register of appeals, judicial review outcomes, or enforcement litigation. The absence of litigation history in the Directive does not imply litigation has not occurred; it simply reflects that no such history is documented in the AD as provided. Any enquiries about litigated matters would therefore need to be pursued through external legal research in courts or administrative review records, which are beyond the AD’s content.

The Directive contains several technical and administrative details that may produce operational surprises if overlooked. Applicability is confined to Model 717‑200 aeroplanes “as identified in Boeing Service Bulletin (SB) 717‑28‑0004, Revision 3, dated 21 June 2006.” Operators must therefore verify that their fuselage/serial numbers or configuration are among those identified in the specified revision of the SB; an operator assuming broader applicability may either undertake unnecessary work or, conversely, may miss that an airframe is in scope because its identification is SB‑dependent.

Timing is bifurcated and consequential. Requirement 1 has a long calendar window (68 months after the effective date); however Requirements 2 and 3 are gated by “before further flight” after the replacement and after any failed check. This sequencing means that while an operator can schedule replacement within the 68‑month window, once the replacement is installed the aircraft cannot be dispatched until the electrical bond check (Requirement 2) has been completed satisfactorily. If the check fails, a repair compliant with the SB or approved by the Manager, Los Angeles ACO, FAA, must be completed before further flight. Failure to understand the operational gating effect of the “before further flight” language could leave an aircraft unexpectedly grounded pending maintenance or approval of a repair method.

The AD accepts prior work done under SB Revision 2 as compliant if done before the effective date; that acceptance is narrow and time‑bound. Similarly, the acceptance of later SB revisions depends on FAA AMOC approval to FAA AD 2006‑20‑12. Relying on an unapproved SB revision, or on an FAA AMOC that is not applicable to FAA AD 2006‑20‑12, will not, under the AD’s terms, constitute acceptable compliance. Operators seeking to use alternative repair methods must obtain approval from the Manager, Los Angeles ACO, FAA; the AD identifies one approved repair method in Boeing manuals but does not authorise other methods absent FAA approval.

Finally, the safety rationale rests on a single technical failure mode recorded in the AD’s background: fracture or separation of the aluminium foil strip on the nylon base of ground clamps. The AD is narrowly focussed on the bonding of fuel pipes to structure to ensure lightning energy dissipation. Operators should be careful not to infer broader fuel system or lightning protection work beyond what the SB and AD specify without obtaining the necessary FAA approval or a separate regulatory directive.

Compliance follows the three numbered steps in the Directive, using the Boeing service bulletin where it is referenced and securing FAA approvals where needed. Step 1 (Requirement 1): within 68 months after 2 August 2007 (the Directive’s effective date), replace the lightning‑critical clamp bases of the fuel tank vent system with the improved clamp bases identified in Table 1 of Figure 1 of the Accomplishment Instructions of Boeing SB 717‑28‑0004, Revision 3, dated 21 June 2006. Operators must use the parts and procedural detail contained in that service bulletin to effect the replacement for aircraft that are within the SB’s applicability.

Step 2 (Requirement 2): after installing the improved clamp bases, perform the electrical bond check of the modified self‑bonding mounting clamps exactly as directed in the SB’s Accomplishment Instructions. The AD requires this check to be done “before further flight” after the replacement, which means the aircraft cannot be flown beyond its current movement authority until the check has been completed satisfactorily.

Step 3 (Requirement 3): if any electrical bond fails the check, carry out the repair of the electrical bond either in accordance with SB 717‑28‑0004 Revision 3 or by a repair method approved by the Manager, Los Angeles ACO, FAA. The AD specifies that Chapter 28‑00‑00 of the Boeing 717 Aircraft Maintenance Manual and Chapter 20‑50‑01 of the Boeing DC, MD, and 717 Standard Wiring Practices Manual are one approved repair method. Any repair needed as a consequence of a failed check must be completed before further flight.

If the work was done prior to the AD’s effective date in accordance with SB 717‑28‑0004 Revision 2 (11 March 2005), operators may treat that prior work as compliant with the Directive. If operators intend to use a later revision of the Boeing SB, ensure that the later revision has been approved by the FAA as an AMOC to FAA AD 2006‑20‑12; the AD expressly accepts such FAA‑approved later revisions for compliance with equivalent requirements. For any proposed alternative repair method not specified in the Boeing manuals or SB, an operator must obtain approval from the Manager, Los Angeles ACO, FAA before treating the repair as compliant under this Directive.

Administratively, operators should schedule the replacement work within the 68‑month window, but plan for immediate post‑installation testing and rapid availability of approved repair methods or FAA approvals to avoid unexpected aircraft grounding under the “before further flight” constraints. The AD does not stipulate documentation formats or record‑keeping procedures in its text; compliance practitioners should therefore follow the Boeing SB and applicable maintenance record practices to produce auditable evidence that the replacement, checks and any repairs were completed in accordance with the AD and any FAA approvals relied upon.