AD/B737/296 - Auxiliary Fuel System

Narrow applicability and incorporation by reference. The AD operates by two principal mechanisms: (1) defining a narrow class of aircraft by model, STC and serial number; (2) mandating compliance with an external, referenced FAA AD (FAA AD 2006-18-11 Amendment 39-14750). The CASA AD therefore functions as an adopting instrument: it makes foreign-sourced mandatory corrective measures applicable in Australia for the listed aeroplanes.

Identification by serial number and by PATS service bulletin. The Table 1 in the AD lists specific airframe serial numbers and, for each, the PATS Aircraft Service Bulletin that identifies that aeroplane. For example, S/Ns 22431 and 22628 on 737-200 series aeroplanes are listed with PATS service bulletin SA83NE-28-SB-002_IR dated 7 June 2006. The Table therefore serves as the primary identification tool for determining whether a particular aeroplane falls within the scope of the AD.

Source of the corrective action. The AD does not set out procedural detail; instead it instructs operators to "Action in accordance with FAA AD 2006-18-11 Amendment 39-14750." The FAA AD is therefore the operative technical document: inspections, modifications, compliance intervals and corrective work are those contained in that FAA AD. The CASA instrument changes Australian compliance obligations by importing the FAA AD's requirements for the listed aircraft.

Stated safety hazards. The AD’s background explicitly links the AD to a re-evaluation by the STC holder of the floor structure and cargo barriers. The concrete hazards the AD identifies are: overload of the auxiliary fuel tank support structure causing floor beam failure; consequential damage to primary flight controls and to APU fuel lines passing through the beams; and potential loss of control. Separately, cargo barrier overload could lead to cargo shift, damage to auxiliary fuel tanks, residual fuel leakage and an increased fire risk. The AD therefore ties structural and fire risk to the auxiliary fuel system installation and its interaction with floor beams and cargo barriers.

Delegation and effective date. The AD is signed by "James Coyne, Delegate of the Civil Aviation Safety Authority" and states an effective date for compliance: 23 November 2006. The instrument therefore indicates decision-making occurred at delegate level within CASA and fixes the date from which the mandated obligation applies.

Concentrated scope and technical reliance. The combination of specific serial numbers (14 listed) and STC identifiers concentrates the AD’s effects on a small, clearly defined subset of aeroplanes. At the same time, the instrument relies on technical materials produced outside the CASA document (FAA AD and PATS Aircraft Service Bulletins) for the actual work to be performed.

Aircraft owners/operators of the listed aeroplanes. The AD applies directly to operators and owners of Boeing Model 737-200, -300, -400 and -500 series aeroplanes that are equipped with the auxiliary fuel system installed under the listed STCs and that have one of the serial numbers recorded in Table 1. The Table lists 14 serial numbers in total: 22431, 22628, 22600, 23800, 22620, 23124, 23468, 26333, 26307, 27456, 27426, 27906, 24970 and 28866. Those 14 airframes are the only aircraft explicitly captured by the text of this AD.

STC holders and maintenance organisations. The AD results from a "re-evaluation of the floor structure and cargo barriers conducted by the STC holder." Although the AD's operative requirement is to implement the FAA AD, the STC holder’s re-evaluation is the triggering information. Therefore the STC holder (holders of SA83NE, SA1078NE, SA725NE, ST00040NY or ST01337NY) and the organisations that perform work under those STCs will have practical obligations: they will need to assist identification, deliver service bulletins (PATS Aircraft Service Bulletins are cited in Table 1), and may directly perform or certify corrective work.

Maintenance, repair and overhaul providers. Because the AD prescribes actions that are "in accordance with FAA AD 2006-18-11" and references specific Aircraft Service Bulletins, maintenance organisations, approved maintenance providers and engineers who carry out structural inspections, modifications or repairs will be directly involved. They must be able to read and implement the FAA AD and the PATS service bulletins for the specified serial numbers.

Operators of non-listed aircraft. Operators of Boeing 737s that either do not carry the listed STCs or do not have a serial number in Table 1 are not captured by the AD as written. The AD’s narrow textual scope means that aircraft with similar STCs but different serial numbers are outside its mandatory scope, at least until CASA or another authority expands applicability. That creates a clear boundary: only the serial numbers recorded in Table 1 are subject to this CASA AD.

Regulatory actors. CASA is identified as the issuing authority, and the AD is signed by a CASA delegate. The FAA is the source of the technical corrective action: the AD requires adherence to FAA AD 2006-18-11 Amendment 39-14750. The PATS Aircraft Service Bulletins listed in the Table are the technical identification documents linked to each serial number.

Who pays. The AD places the operational and compliance burden on the owners and operators of the 14 listed airframes and on those who perform the work (maintenance organisations or the STC holder if they have contractual obligations). The AD does not allocate costs or financial assistance; the source text contains no mention of funding, subsidies or cost recovery.

Primary duty: comply with the FAA AD. The CASA instrument imposes a single operative duty: perform "Action in accordance with FAA AD 2006-18-11 Amendment 39-14750." The CASA AD does not reproduce the corrective steps; it makes those steps mandatory by reference. Operators of affected aeroplanes must therefore obtain and follow the FAA AD’s procedures for inspection, modification and any corrective action it prescribes.

Duty to identify applicability. The AD identifies affected aeroplanes by model, STC and serial number in Table 1. An immediate duty for owners and operators is to determine whether their aeroplane appears in Table 1. The Table cross-references serial numbers with specific PATS Aircraft Service Bulletins that identify the aircraft: for example, SA725NE-28-SB-007_B Revision B dated 27 July 2006 is cited for a set of serial numbers. Ensuring accurate identification is therefore a necessary step before any compliance action.

Duty to follow PATS Aircraft Service Bulletins for identification. The Table instructs identification "As identified in PATS Aircraft Service Bulletin." That means operators must refer to the specified PATS service bulletin when confirming that the aircraft listed corresponds to the serial number and STC combination in question. The AD places a de facto duty on operators to obtain and consult the cited PATS documents to confirm applicability before implementing FAA AD actions.

Effective-date duty. The CASA AD fixes 23 November 2006 as the revised effective date. From that date, operators must have complied with the requirements as detailed in the FAA AD. The AD text creates a temporal obligation: actions must be completed in accordance with the compliance schedule contained in the FAA AD and by the effective date established by CASA, where the FAA AD sets the timelines.

Duty to address specific hazards identified by the AD. The AD states the reason for the action: to prevent structural overload of the auxiliary fuel tank support structure and the cargo barriers, and the consequent hazards (floor beam failure, damage to primary flight controls and APU fuel lines, loss of control, cargo shift, residual fuel leakage and increased fire risk). The duty to address these hazards translates into the duty to implement the FAA AD’s prescribed inspections and modifications, whatever they are.

Rights and scope limitations. The AD is explicit and narrow. If an aeroplane is not listed in Table 1, the CASA AD does not, by its terms, impose obligations on that aeroplane. The AD does not create rights or exemptions; it imposes an obligation on the subset of aeroplanes it names. The text does not provide an appeal procedure or an exemption mechanism within the AD itself; any dispute or request for relief would need to be addressed through CASA processes outside the text of this AD, but the AD does not specify such processes.

Delegatory decision-making. The AD is signed by a CASA delegate. The document therefore reflects delegate-level decision-making within CASA. The AD does not state whether CASA will provide additional guidance, whether the STC holder will reimburse costs, or whether operators may obtain alternative means of compliance; none of those mechanisms are contained within the document.

The AD text itself does not specify monetary penalties, enforcement mechanisms, or administrative sanction procedures. The instrument mandates compliance by stating that the listed aircraft must carry out "Action in accordance with FAA AD 2006-18-11 Amendment 39-14750" and fixes an effective date of 23 November 2006. The document therefore sets an obligation, but it contains no enforcement schedule, penalty figures or description of infringement procedures within the text provided.

What the AD does make enforceable is the obligation to implement the FAA AD’s requirements for the specified serial numbers and STC installations as of the effective date. The AD constitutes CASA’s formal direction that the FAA AD’s corrective actions are the standard to be met for the listed aeroplanes. Operationally, the AD establishes a compliance expectation: from 23 November 2006 operators of the listed airframes must have implemented the FAA AD actions as required. The CASA AD does not, however, include any language in the text provided here about how non-compliance will be detected, how CASA will verify compliance, or what penalties will follow persistent non‑compliance.

Absence of enforcement detail increases reliance on broader regulatory frameworks. Because the AD does not itself set out enforcement steps or penalties, enforcement in practice must rely on the broader regulatory regime and CASA’s operational procedures to determine compliance, to audit aircraft records, and to take action in the event of non-compliance. The AD does not describe those procedures and does not identify an enforcement authority beyond the signature by a CASA delegate.

Practical consequence for operators. For operators of the listed serial numbers the AD creates a straightforward legal obligation to implement the referenced FAA AD. The absence of explicit penalty language in the AD does not negate that obligation; it simply means the AD itself should be read alongside CASA’s general enforcement powers and operational practice (not included in the AD text) to understand the consequences of failing to comply.

No mention of exemptions, alternatives or delegations of cost. The AD does not provide text about exemptions, alternative means of compliance, timelines beyond the FAA AD’s content, or cost-sharing arrangements. Operators seeking relief or variation from the requirements would therefore need to rely on channels outside this AD (no such channels are described in the text).

Direct incorporation of a foreign AD. The CASA AD's principal interaction is with the FAA AD it incorporates by reference: "Action in accordance with FAA AD 2006-18-11 Amendment 39-14750." The CASA instrument therefore imports the FAA AD's substantive technical requirements into Australian compliance obligations for the listed aeroplanes. The CASA text does not reproduce the FAA AD, so the detailed interaction is one of mandatory adoption by reference: the FAA AD's inspections, modification instructions and compliance intervals become the operative standard for the listed aircraft in Australia.

Reference to manufacturer/STC service bulletins. The Table in the AD specifically ties serial numbers to PATS Aircraft Service Bulletins (for example SA83NE-28-SB-002_IR dated 7 June 2006; SA725NE-28-SB-007_B Revision B, dated 27 July 2006). That means the AD interacts with technical documents produced by the STC holder and by PATS. Those service bulletins serve as identification and technical support documents and are incorporated as the explanatory material identifying which specific aircraft the AD targets.

Linkage between STC-holder activity and regulatory action. The AD attributes its origin to "a re-evaluation of the floor structure and cargo barriers conducted by the STC holder." The CASA AD therefore evidences a causal chain: STC holder analysis leading to FAA AD issuance, which CASA then adopts for Australian-registered aeroplanes identified in the AD. The interaction here is procedural and evidentiary: regulatory adoption informed by a technical re-evaluation conducted by a private STC holder.

No direct text on interaction with Australian statutory enforcement provisions. The AD itself does not set out how it interacts with the broader Australian aviation safety statutes or administrative enforcement pathways; it does not name specific Australian Acts, regulations or penalty provisions. It should therefore be read as a CASA direction that must be implemented, with enforcement and remedies to be located in CASA’s wider regulatory toolkit rather than in the AD text itself.

Operational interaction with operator manuals and maintenance records. Because the AD refers operators to external technical documents (FAA AD and PATS service bulletins), compliance will require changes to maintenance workflows, the input of new inspection points into maintenance programmes for the affected airframes, and the creation or amendment of work orders and maintenance records to show the required action has been taken. Those interactions will occur in standard operational documentation even though the AD does not itself amend manuals or maintenance schedules in-line.

No mention of cross-jurisdictional reciprocal enforcement. The AD adopts FAA AD requirements for specific aircraft in Australia; the text does not address reciprocal recognition, enforcement actions taken by foreign authorities, or coordination with other national regulators. The interaction is one-way in the AD text: CASA requires Australian compliance with the FAA AD for the listed aeroplanes.

Dates and document identifiers. The AD references FAA AD 2006-18-11 Amendment 39-14750 as the technical document to be implemented and gives an explicit revised effective date of 23 November 2006. The CASA instrument itself is dated 12 October 2006 and is signed by "James Coyne, Delegate of the Civil Aviation Safety Authority."

No subsequent amendments recorded in the provided text. The document as supplied contains only the original CASA AD issuance information: CASA AD identifier AD/B737/296, title "Auxiliary Fuel System," and the date code 12/2006. There is no language within the AD text supplied here indicating that the CASA AD has been amended, superseded or extended after the stated effective date. The only temporal details set out by the AD are the signing date (12 October 2006) and the revised effective date (23 November 2006).

PATS and FAA documents dates. The Table lists specific PATS Aircraft Service Bulletin references with their own dates, which function as part of the documentary history tied to each serial number. Examples include SA83NE-28-SB-002_IR dated 7 June 2006, SA1078NE-28-SB-005_A, Revision A, dated 21 June 2006, SA725NE-28-SB-007_B, Revision B, dated 27 July 2006, ST00040NY-28-SB-003_IR dated 7 June 2006, and ST01337NY-28-SB-002_IR dated 7 June 2006. Those PATS dates show the underlying service bulletins were issued in mid‑2006 and are contemporaneous with the FAA/ CASA actions in October-November 2006.

No administrative history of internal CASA decisions cited. The supplied CASA AD does not include a record of internal CASA amendments, prior drafts, consultation statements or cost-benefit analyses. It contains the essential formal elements of an AD: identification of affected aircraft, the requirement to implement the FAA AD, the compliance effective date, a short background identifying the hazard and the signature of a CASA delegate. Beyond that, there is no text in this document to show amendment iterations or a revision log for the CASA AD itself.

Relation to the FAA amendment number. The CASA AD cites the FAA AD by number and by the FAA Amendment number (39-14750). The FAA amendment identifier forms part of the documentary trail: it tells the reader which FAA AD issuance CASA had in view and provides a way to locate the exact FAA text the CASA AD requires be implemented. No later CASA amendments or revocations are recorded on the face of the instrument provided.

No litigation or judicial decisions are recorded in the AD text provided. The document contains no references to court cases, appeals, administrative reviews, or any legal proceedings arising from the AD or its implementation. The AD text is purely a regulatory instrument giving effect to FAA AD 2006-18-11 for specific Australian-registered airframes; it contains no mention of contested proceedings, judicial review or legal challenges.

Absence of documented disputes in the instrument itself. Because the AD does not record any litigation, there is no source-based evidence here of contested compliance, injunctions or declaratory proceedings relating to the AD. The AD does not note any stay, suspension or interim order affecting its effective date. It thus appears, from the document itself, to have been issued as an unchallenged regulatory direction at the time of signature and to have taken effect on the date stated (23 November 2006) subject to compliance with the FAA AD.

Implication for practitioners. Because no litigation history is set out, practitioners seeking any case law or administrative determinations that interpret this specific CASA AD will not find such material inside the AD text. Any legal disputes or enforcement actions would need to be traced in external case law repositories or CASA records; none are referenced or summarised herein.

Very narrow textual scope. The AD applies only to the serial numbers listed in Table 1 and to aeroplanes equipped with the specified STCs. Operators who assume that a similar STC installation or the same auxiliary fuel system on a different serial number is covered by this AD will be mistaken. The AD’s obligation is precisely limited to the listed serial numbers: 14 airframes in total. Misidentification could lead an owner either to undertake unnecessary work or, conversely, to fail to comply when they are in fact subject to the AD. The Table explicitly instructs identification "As identified in PATS Aircraft Service Bulletin" for each serial number; operators must therefore consult those PATS documents to ensure they match the aircraft.

Import-by-reference creates an extra document burden. The CASA AD does not include the FAA AD’s substantive procedures. The operative duty is to implement FAA AD 2006-18-11 Amendment 39-14750. Practitioners must therefore obtain the FAA AD and the PATS service bulletins cited. Failing to obtain or correctly interpret the FAA AD could produce non-compliance, since the CASA AD does not itself repeat the FAA AD text.

Timing and effective date. The AD fixes a revised effective date of 23 November 2006. If the FAA AD contained compliance intervals measured from its own effective date, operators must reconcile those intervals with the CASA AD's stated revised effective date. The CASA text does not reproduce the FAA AD’s compliance schedule, so ambiguity can arise unless practitioners cross-check dates and intervals in the FAA document.

STC holder is the origin of the safety finding. The AD expressly states it "results from a re-evaluation of the floor structure and cargo barriers conducted by the STC holder." That means the STC holder initiated the assessment that led to the FAA AD and CASA adoption. In practice, this can lead to scenarios where responsibility for technical support or for remedial action coordination may rest with the STC holder in the first instance; the AD itself does not assign cost responsibility, but practitioners should be alert to contractual or warranty relationships between the owner/operator and the STC holder.

Multiple technical documents for identification and remedy. Each serial number in Table 1 is paired with a specific PATS Aircraft Service Bulletin; those PATS documents are identification tools and may contain different revisions. For the grouped serial numbers assigned to SA725NE, for example, the cited PATS SB is SA725NE-28-SB-007_B Revision B dated 27 July 2006. Practitioners must ensure they use the exact revision listed in the Table for the identification step; using the wrong revision could lead to a mismatch in applicability.

No procedural text for record-keeping or alternative compliance. The AD does not state whether alternative means of compliance are acceptable, how operators should document compliance, or whether CASA will accept equivalent inspections or repairs. This silence is a practical "gotcha": operators cannot rely on the AD for procedural direction about approvals of alternative methods or proof of compliance and must therefore proactively seek the FAA AD text and follow any procedural steps it contains.

Potential for transient operational disruption. Although the AD does not specify the nature of the FAA AD’s actions, the hazards described (structural overload, potential floor beam failure, damage to primary flight controls or APU fuel lines, cargo shift and fuel leakage) imply that inspections could be structural and remedial work could be substantive. Operators should anticipate possible downtime, but the AD contains no schedule or cost guidance; operational planning will therefore require obtaining the FAA AD to assess the scope and timing of interventions.

No mention of follow-up or monitoring measures. The AD makes no provision for follow-up monitoring, reporting obligations to CASA, or post‑action inspections beyond whatever the FAA AD prescribes. Practitioners must therefore consult the FAA AD to determine whether the FAA AD contains continuing airworthiness instructions or recurring inspections.

Step 1 , Confirm whether your aeroplane is listed. Check the airframe serial number against Table 1 in the CASA AD. The AD applies only to the listed serial numbers and to aeroplanes equipped with one of the specified STCs (SA83NE, SA1078NE, SA725NE, ST00040NY or ST01337NY). The Table pairs serial numbers with PATS Aircraft Service Bulletins; use those PATS documents for positive identification (for example, SA83NE-28-SB-002_IR dated 7 June 2006 for S/Ns 22431 and 22628).

Step 2 , Obtain the referenced FAA AD and the cited PATS service bulletin. The CASA AD’s operative requirement is: "Action in accordance with FAA AD 2006-18-11 Amendment 39-14750." Obtain the full text of FAA AD 2006-18-11 Amendment 39-14750 and the PATS Aircraft Service Bulletin listed for your serial number to determine the precise inspections, modifications and corrective actions required.

Step 3 , Read the FAA AD for the compliance tasks and intervals. Because the CASA AD does not reproduce the FAA AD, compliance requires following the FAA AD’s inspection procedures, modification instructions and compliance timeframe exactly as written. Identify whether the FAA AD prescribes immediate inspections, specific modifications, or recurring checks, and map those into your maintenance schedule.

Step 4 , Plan and schedule the work. The CASA AD sets 23 November 2006 as the revised effective date. Ensure that the required action timelines in the FAA AD are reconciled with that effective date. Organise maintenance slots, appropriate qualified personnel and approved maintenance organisations capable of delivering the structural inspections or modifications required by the FAA AD and the PATS service bulletins.

Step 5 , Use the PATS Aircraft Service Bulletin for identification and for any SB-specific instructions. The Table in the CASA AD identifies the PATS Service Bulletin relevant to each serial number. Where the PATS bulletin contains model- or STC-specific instructions, use it for accurate identification and any STC-related technical steps. Confirm you are using the exact revision cited in Table 1.

Step 6 , Execute work with approved personnel and document completion. Carry out the inspections/modifications as mandated by the FAA AD using appropriately authorised maintenance providers, in accordance with applicable maintenance standards and licences. Because the CASA AD does not set out its own record-keeping requirements, retain maintenance records and certification evidence that demonstrate completion of the FAA AD actions for audit or verification purposes.

Step 7 , Reconcile with aircraft operational dispatch requirements. If the FAA AD work requires removal from service or temporary grounding, plan for operational impacts. The CASA AD does not provide mitigations or alternative compliance routes; therefore ensure all required work is completed before returning the aircraft to service in line with the FAA AD and any applicable maintenance release procedures.

Step 8 , Where uncertainty exists, seek clarification from CASA or the STC holder. The CASA AD does not specify how to obtain variations, appeals or alternative means of compliance. If an operator considers that an alternative method would be equivalent or if there is doubt about applicability (for example, if STC installation records are unclear), contact the STC holder for technical clarification and CASA for regulatory direction. The AD itself is silent on the procedures for seeking alternative compliance; any such process will be external to the AD and must follow CASA processes.

Step 9 , Keep records of the identification process. Because applicability turns on serial number and PATS service bulletin matching, keep the documentation used to identify the aeroplane as being within scope (for example, the PATS SB reference and its confirmation that the serial number is the same as the airframe in question). Maintain work orders, sign-offs and any FAA AD compliance statements to evidence that you have carried out the mandated actions.

Step 10 , Monitor for further directives. The CASA AD adopts a particular FAA AD at a point in time. After completing the immediate steps, monitor for any further FAA or CASA directives that amend, supersede or expand the scope of the required work, since the AD’s operational effect depends on those external documents and subsequent regulatory action.

Practical note: the AD’s obligations are narrowly framed but mandatory from the effective date. Implement the FAA AD text and follow the PATS service bulletin referenced for your serial number; keep contemporaneous, auditable records of identification and completion. If there is any doubt about whether your aeroplane is in scope, the Table and its PATS cross-references are the determinative starting point.