AD/B737/345 - Fuel Tank Safety

The directive organises around several technical and regulatory concepts set out in the text: applicability, actions to be accomplished, compliance timing, AMOCs, and related airworthiness documentation changes.

Applicability: The AD applies to Boeing 737-600, -700, -800 and -900 series aeroplanes "as identified in Boeing Alert Service Bulletin (ASB) 737-28A1221, Revision 1, dated 9 November 2007" (Applicability). That is a document-driven scope: only aeroplanes listed in that ASB are captured.

Actions and conformity: The core physical action is the installation of the hot short protector (HSP) support brackets and densitometer equipment for the FQIS, plus any "other specified actions" in the Accomplishment Instructions of the ASB (Requirement 1). The AD explicitly allows previously accomplished actions that followed an earlier ASB dated 14 January 2007 to count for compliance (Requirement 1, second paragraph), so the AD recognises work already performed under a prior service bulletin revision.

Airworthiness Limitations and Instructions for Continued Airworthiness: The AD requires revision of the AWL section of the ICA by incorporation of a specific AWL (28-AWL-07) from the Boeing MPD (Requirement 2). AWLs are maintenance/inspection limitations that, once incorporated into the ICA, become part of the continued airworthiness regime for that aeroplane.

CDCCLs and AMOCs: The AD bars the use of alternative Critical Design Configuration Control Limitations unless they are approved as an AMOC by the Manager, Seattle Aircraft Certification Office, FAA (Requirement 3). It further accepts later revisions of the ASB if those revisions have been approved by the FAA as AMOCs to the FAA AD 2008-17-15 (Requirement 3, last sentence). The AD thus ties any permitted deviation from the mandated CDCCLs to FAA managerial approval and to FAA-approved ASB revisions.

Timing structure: The AD sets a 60-month compliance window for the retrofit in Requirement 1 and requires the AWL revision to be done concurrently with the retrofit; Requirement 3 is framed as a post-Requirement 2 constraint (Compliance section). The AD's effective date fixes the calendar anchor for these windows (effective date line).

Cross-references to other ADs: The AD references FAA AD 2008-17-15 and AD/B737/329 (which in turn references FAA AD 2008-10-10) to explain termination of actions and to link acceptance of prior compliance actions. That creates a chain of interlocking directives and compliance pathways based on prior ADs and service bulletins.

Safety rationale: The Background states the safety trigger: fuel-system reviews by the manufacturer revealed the densitometer could overheat and become a potential ignition source inside the centre fuel tank; if flammable vapours were present that could, "in combination," lead to an explosion and loss of the aeroplane (Background). The AD therefore prescribes equipment installation and AWL changes to prevent that ignition source and to manage continued airworthiness.

Governance and signatory: The AD is signed by James Coyne, Delegate of the Civil Aviation Safety Authority, and dated 6 November 2008 (signature block). The AD becomes effective 18 December 2008 (effective date line).

These are the principal legal and technical building blocks: defined applicability tied to an ASB, mandated physical retrofit and documentation amendment, constrained options for alternate CDCCLs unless FAA-approved, acceptance of prior compliant work under an earlier ASB, a 60-month compliance period, and cross-reference to FAA ADs as the source of accepted AMOCs and termination routes.

The AD's textual scope and actions identify the affected parties directly and indirectly.

Aircraft types and their operators: The primary affected parties are operators and owners of Boeing 737-600, -700, -800 and -900 series aeroplanes specifically identified in ASB 737-28A1221, Revision 1 (Applicability). In practice, any legal or commercial entity that owns, operates, leases, or maintains those model aeroplanes listed in the ASB will be required to comply with the AD's requirements within the stated timeframes.

Maintenance organisations and certifying staff: The installation work and the AWL incorporation are maintenance and airworthiness tasks. The AD requires accomplishment "by accomplishing all of the applicable actions specified in the Accomplishment Instructions of ASB 737-28A1221, Revision 1" (Requirement 1). That places responsibility on the organisation that performs maintenance to follow the ASB's work instructions and to document compliance in ICA/AWL records.

Engineers and continuing airworthiness managers: Requirement 2 requires revision of the AWL section of the ICA by incorporating a specific AWL (28-AWL-07) from the Boeing MPD. Those document-keeping and continued-airworthiness functions fall to the organisation responsible for the ICA and to the continuing airworthiness manager or authorised person within the operator's compliance structure.

Design authorities and certifiers: Requirement 3 limits the use of alternative Critical Design Configuration Control Limitations (CDCCLs) unless the CDCCLs are approved as an AMOC by the Manager, Seattle Aircraft Certification Office, FAA. That gives a direct decision role to that FAA manager with respect to acceptability of alternative CDCCLs. It also places a requirement on operators/designers who might wish to rely on alternate CDCCLs to seek FAA approval.

Boeing and the ASB publisher: Boeing as the manufacturer is the source of the ASB and the MPD AWL cited. The AD ties compliance methods to Boeing's published ASB and MPD documents. The AD also allows "later revisions of ASB 737-28A1221, approved by the FAA as an AMOC to FAA AD 2008-17-15" to be acceptable (Requirement 3, last sentence), so Boeing's subsequent ASB revisions , if FAA-approved as AMOCs , affect compliance options.

Civil Aviation Safety Authority (CASA) and delegates: The AD is issued by CASA (delegate signature) and sets national regulatory obligations. CASA enforces the AD in that it issued the instrument. The AD itself, as provided here, does not list explicit penalties, but it is an instrument that prescribes mandatory actions and compliance dates.

Cross-jurisdictional actors: The FAA Manager, Seattle Aircraft Certification Office, has an approval role for AMOCs (Requirement 3). The AD also references FAA ADs (FAA AD 2008-17-15; FAA AD 2008-10-10) and a prior CASA AD (AD/B737/329) in relation to termination of Requirement 2. Therefore, FAA approvals and prior FAA/CASA directives determine some compliance pathways.

Less-direct affected groups: Less directly, aircraft lessors, insurers, and operators' customers may be affected because the AD requires modifications that can influence aircraft availability and maintenance scheduling. The AD does not directly address leasing or insurance relationships, but the mandated changes and the incorporation of AWLs into the ICA will be relevant to ongoing aircraft airworthiness records and lease-return conditions.

In sum, the AD assigns affirmative obligations to aeroplane operators/owners and to maintenance/continuing-airworthiness personnel, constrains design/alternative configurations without FAA AMOC approval, incorporates manufacturer documents as normative compliance sources, and delegates approvals for AMOCs to an FAA office. The AD's reliance on specific ASB and MPD documents makes the manufacturer and FAA approvals upstream determinants of compliance options.

The AD imposes clear duties and establishes constrained rights in respect of alternative compliance methods.

Duty to perform the retrofit and related actions (Requirement 1): Operators of applicable Boeing 737-600/700/800/900 aeroplanes must "install the hot short protector (HSP) support brackets and equipment for the fuel quantity indicating system (FQIS) fuel densitometer and do all the other specified actions as applicable, by accomplishing all of the applicable actions specified in the Accomplishment Instructions of ASB 737-28A1221, Revision 1" (Requirement 1; Applicability). The duty is both prescriptive (install HSP support brackets and densitometer equipment) and procedural (follow the ASB's Accomplishment Instructions).

Duty to update airworthiness documentation (Requirement 2): Operators must "revise the Airworthiness Limitations (AWL) section of the Instructions for Continued Airworthiness (ICA) by incorporating AWL No. 28-AWL-07 of Subsection F ... of Section 9 of the Boeing 737-600/700/800/900 Maintenance Planning Data (MPD) Document" (Requirement 2). This is a document-control duty that changes the aircraft's required maintenance limitations and inspection tasks as part of its continuing airworthiness obligations.

Restriction on alternative CDCCLs and duty to seek approval for alternatives (Requirement 3): The AD bars the use of alternative Critical Design Configuration Control Limitations "unless the CDCCLs are approved as an alternative method of compliance (AMOC) by the Manager, Seattle Aircraft Certification Office, FAA" (Requirement 3). That is both a negative duty (do not use alternatives) and a procedural right to seek an AMOC from the specified FAA manager. The AD also provides a route for operators to rely upon later revisions of ASB 737-28A1221 if those revisions are "approved by the FAA as an AMOC to FAA AD 2008-17-15" (Requirement 3, last sentence).

Rights to rely on prior compliant work: The AD expressly preserves the right to rely on actions accomplished before the effective date if those actions were done in accordance with ASB 737-28A1221 dated 14 January 2007: "Actions accomplished before the effective date of this Directive in accordance with ASB 737-28A1221, dated 14 January 2007, are acceptable for compliance with the Requirement 1" (Requirement 1, second paragraph). That is a forward-recognition right for earlier compliant modifications.

Conditional termination of a requirement: The AD provides a conditional termination for Requirement 2 where incorporation of AWL No. 28-AWL-07 into the AWLs section of the ICA "in accordance with Requirement 1.c. of AD/B737/329 (paragraph (g)(3) of United States Federal Aviation Administration (FAA) AD 2008-10-10), terminates the action required by Requirement 2" (Requirement 2). That means compliance with a specified prior AD/requirement (AD/B737/329 per the text) can negate the need to separately perform Requirement 2 under this AD, subject to the exact conformity set out in the referenced documents.

Compliance timing duties: The AD sets timing duties. For Requirement 1 the duty is to comply "Within 60 months after the effective date of this Directive." For Requirement 2 compliance is "Concurrently with accomplishing the Requirement 1 actions." For Requirement 3 the timing is "After accomplishing the action specified in Requirement 2." These timing provisions structure when duties must be completed and define the sequence (Compliance section).

No explicit penalty provisions stated: The AD text supplied does not set out civil or criminal penalties or enforcement mechanisms in this instrument. It prescribes mandatory actions and timing, identifies acceptable compliance means, and references FAA AMOC approvals, but it does not specify sanctions within the text provided (no penalty section appears in the supplied text).

Procedural rights and approvals: The AD affords procedural rights to seek AMOC approval from the FAA Manager, Seattle Aircraft Certification Office, for alternative CDCCLs. The AD also recognises later revisions of the ASB if those revisions carry FAA-approved AMOCs to the corresponding FAA AD. These are discrete procedural rights that allow constrained alternatives subject to FAA approval.

To summarise, the AD establishes affirmative physical retrofit and documentation-change duties, a prohibition on use of alternative CDCCLs except where an FAA AMOC exists, conditional reliance on prior compliant work and on FAA-approved ASB revisions, and explicit timing and sequencing for those duties. It does not itself specify penalties in the supplied text, but it sets out the compliance regime and the approval pathway for permitted alternatives.

The text of the AD provided contains no express penalty clauses, monetary fines, or criminal sanctions. The instrument is framed as a mandatory set of airworthiness requirements with specified compliance dates and methods, but the supplied text does not include an enforcement or penalty section.

What the AD does show that is relevant to enforcement is its effectivity and procedural constraints. The AD "becomes effective on 18 December 2008" (effective date line). It prescribes what actions are "acceptable for compliance" (for example, prior actions accomplished in accordance with ASB 737-28A1221 dated 14 January 2007 are acceptable for Requirement 1). It also sets a specific compliance deadline for Requirement 1 ("Within 60 months after the effective date of this Directive") and specifies sequencing and concurrency requirements for Requirements 2 and 3 (Compliance section). These elements,an effective date, regulatoryly-prescribed actions, and compliance deadlines,are the structural elements that enforcement authorities use to evaluate compliance, although the AD text itself does not specify enforcement measures.

The AD also channels alternative-compliance approvals through a named FAA official: "No alternative Critical Design Configuration Control Limitations (CDCCL) may be used unless the CDCCLs are approved as an alternative method of compliance (AMOC) by the Manager, Seattle Aircraft Certification Office, FAA" (Requirement 3). That creates an approval gate relevant to enforcement: use of an alternative without FAA AMOC is not permitted by the AD text.

The AD provides pathways that affect enforcement discretion indirectly. For example:

• Acceptance of prior work: "Actions accomplished before the effective date of this Directive in accordance with ASB 737-28A1221, dated 14 January 2007, are acceptable for compliance with the Requirement 1" (Requirement 1, second paragraph). That provides an evidentiary path to show compliance for enforcement purposes: operators can point to prior ASB-compliant work as meeting the AD.

• Conditional termination: Incorporation of AWL No. 28-AWL-07 "in accordance with Requirement 1.c. of AD/B737/329 (paragraph (g)(3) of United States Federal Aviation Administration (FAA) AD 2008-10-10), terminates the action required by Requirement 2" (Requirement 2). This creates a termination route which, if satisfied, means the operator need not perform a separate Requirement 2 action for enforcement purposes.

• Cross-acceptance of FAA-approved ASB revisions and AMOCs: "Later revisions of ASB 737-28A1221, approved by the FAA as an AMOC to FAA AD 2008-17-15, are considered acceptable for compliance with the equivalent Requirements of this Directive" (Requirement 3). That allows operators to rely upon FAA approvals where available, which will be material if an enforcement authority reviews compliance.

Because the AD text supplied does not itself spell out sanctions, a reader should not infer specific penalties from this instrument alone. The AD sets out mandatory actions, deadlines, documentation requirements and approval gates , all the normative features an enforcing authority requires to determine compliance , but the instrument as given must be read together with the broader statutory and regulatory enforcement machinery that the issuing authority uses, which is not contained in the supplied text. The AD thus defines duties and permissible compliance means and leaves the formal statement of enforcement tools outside the text supplied.

The AD is explicitly cross-referential and anchored to other airworthiness directives and manufacturer documents; it relies on interlocking ADs and FAA approvals to define acceptable compliance methods. The supplied text establishes these interactions.

Interplay with FAA ADs: The directive refers to FAA AD 2008-17-15 (Amdt 39-15653) in a note and in the context of acceptable ASB revisions and AMOCs (Requirement 3; Note). It also refers to FAA AD 2008-10-10 through the link to AD/B737/329: the AD states that "Incorporating AWL No. 28-AWL-07 into the AWLs section of the ICA in accordance with Requirement 1.c. of AD/B737/329 (paragraph (g)(3) of United States Federal Aviation Administration (FAA) AD 2008-10-10), terminates the action required by Requirement 2" (Requirement 2). These cross-references create conditional interactions: compliance with certain FAA-anchored requirements or approvals can be used to satisfy or to terminate obligations under this CASA AD.

Relationship to previous CASA ADs: The AD refers to AD/B737/329 and explicitly ties the termination of Requirement 2 to compliance with a provision of that earlier AD (Requirement 2). This shows that CASA ADs are intended to be read in sequence where prior ADs may already have required overlapping steps, and compliance with a prior AD may alter the obligations of a later AD.

Normative incorporation of manufacturer documents: The AD prescribes actions "by accomplishing all of the applicable actions specified in the Accomplishment Instructions of ASB 737-28A1221, Revision 1" and requires incorporation of an AWL from the Boeing MPD Document D626A001-CMR, Revision March 2007 R2 (Requirement 1 and Requirement 2). Those manufacturer documents are therefore given normative force within the AD: operators comply with the AD by following those documents' instructions or by relying on FAA-approved revisions/AMOCs.

AMOC approval and foreign authority recognition: The AD delegates authority for approval of alternative CDCCLs and for acceptance of later ASB revisions to an FAA office: "No alternative Critical Design Configuration Control Limitations (CDCCL) may be used unless the CDCCLs are approved as an alternative method of compliance (AMOC) by the Manager, Seattle Aircraft Certification Office, FAA" and "Later revisions of ASB 737-28A1221, approved by the FAA as an AMOC to FAA AD 2008-17-15, are considered acceptable for compliance with the equivalent Requirements of this Directive" (Requirement 3). That establishes a mechanism whereby an FAA approval can operate to satisfy CASA's AD. The AD thus coordinates national regulatory obligations with FAA certification decisions.

Conditional termination and duplication avoidance: By referring to previous ADs and FAA AD paragraphs, the AD avoids duplicative mandates where prior compliant actions already cover the safety objective. The conditional termination clause in Requirement 2 demonstrates this: if an operator has incorporated the AWL in the precise manner referred to in AD/B737/329 and the relevant FAA AD paragraph, then performing Requirement 2 under this AD is unnecessary.

Sequencing of documentation and physical modifications: The AD ties physical modification (install HSP support brackets) to concurrent changes in the ICA/AWL (Requirement 1 and Requirement 2), and it ties the validity of alternative configurations to FAA AMOC approvals obtained after incorporation of AWL changes (Requirement 3). This sequencing creates an interaction between maintenance execution, continuing-airworthiness documentation, and design-configuration control systems, all governed by manufacturer documents and cross-referenced ADs.

In sum, the AD functions as a node in an interlocking network of manufacturer documents (ASBs, MPD), CASA ADs (including AD/B737/329), and FAA ADs (FAA AD 2008-17-15 and FAA AD 2008-10-10), using FAA AMOC approvals as the pathway for acceptable alternatives and subsequent ASB revisions. The AD itself does not set out the underlying legal basis for CASA's power to issue ADs or the enforcement framework; those are not in the supplied text. What the AD does provide is a clear set of references and procedural gates that make FAA approvals and prior AD compliance material to compliance under this instrument.

The AD gives limited internal amendment history and links to prior manufacturer documents and ADs rather than setting out a standalone amendment log in the supplied text. The document contains these references that together form the effective amendment history relevant to compliance.

Service bulletin revisions: The AD makes compliant use of ASB 737-28A1221 revisions central. It identifies ASB 737-28A1221, Revision 1, dated 9 November 2007, as the operative service bulletin for the actions required (Applicability; Requirement 1). It also recognises the earlier ASB dated 14 January 2007 for the purpose of accepting actions done under that earlier revision: "Actions accomplished before the effective date of this Directive in accordance with ASB 737-28A1221, dated 14 January 2007, are acceptable for compliance with the Requirement 1" (Requirement 1, second paragraph). That reflects an internal amendment recognition: work performed under an earlier service bulletin revision is grandfathered for compliance.

CASA AD links: The AD refers back to AD/B737/329 and ties the incorporation of AWL No. 28-AWL-07 in accordance with a specific requirement of AD/B737/329 (Requirement 1.c) to termination of Requirement 2 in this AD: "Incorporating AWL No. 28-AWL-07 into the AWLs section of the ICA in accordance with Requirement 1.c. of AD/B737/329 (paragraph (g)(3) of United States Federal Aviation Administration (FAA) AD 2008-10-10), terminates the action required by Requirement 2" (Requirement 2). That creates an amendment-effect relationship between the earlier CASA AD and this AD.

FAA AD references and amendments: The AD refers to FAA AD 2008-17-15 (Amdt 39-15653) and FAA AD 2008-10-10. It treats FAA approvals and FAA AMOCs as controlling for acceptance of later ASB revisions: "Later revisions of ASB 737-28A1221, approved by the FAA as an AMOC to FAA AD 2008-17-15, are considered acceptable for compliance with the equivalent Requirements of this Directive" (Requirement 3). Thus, the AD's operational amendment history is partly determined by whether the FAA later approves ASB revisions as AMOCs.

Effective date and signature: The AD was signed by James Coyne, Delegate of the Civil Aviation Safety Authority, on 6 November 2008, and the AD "becomes effective on 18 December 2008" (signature block; effective date line). Those dates are the instrument's formal issuance and operative amendment point.

Absence of explicit versioning within the AD text: The supplied text does not itself include an internal amendment log (for example, prior versions of AD/B737/345) or indicate that the AD amends any prior CASA AD other than by reference (AD/B737/329 is referenced in relation to termination effects). The AD relies on references to earlier ASB revisions and to prior ADs rather than on internal revision history.

Practical implication of the amendment links: The AD's amendment history is therefore best understood as a chain of document-level changes: Boeing ASB revisions and MPD AWL revisions; prior CASA ADs (AD/B737/329); and FAA ADs and AMOC approvals. The AD explicitly recognises an earlier ASB revision dated 14 January 2007 as giving acceptable prior compliance, and it leaves room for later ASB revisions approved by FAA AMOCs to be acceptable. That means the AD's effective obligations can be satisfied by conforming actions taken under earlier or later ASB versions, subject to the FAA approvals and the linkage to prior CASA ADs referenced in the text.

The supplied AD text contains no litigation history, court challenges, judicial interpretations, or references to legal proceedings. There are no cases, judgments, or litigation outcomes mentioned in the instrument. The AD is an administrative directive; the text provided records its technical requirements, effective date, cross-references to other directives, and the signatory, but it does not report any past or pending litigation.

Accordingly, there is no litigation history to summarise within the scope of the provided text. Any inquiry into judicial treatment, review of AD validity, or disputes over compliance, approvals, or enforcement would require sources beyond this AD. The AD itself simply establishes obligations, timeframes, and approval pathways (FAA AMOCs), without documenting any legal challenges to its contents in the supplied material.

The AD contains specific drafting features and cross-references that can produce compliance pitfalls if read superficially.

Document-driven applicability: Applicability is not simply "Boeing 737-600/700/800/900" generically; it is "Model 737-600, -700, -800 and -900 series aeroplanes, as identified in Boeing Alert Service Bulletin (ASB) 737-28A1221, Revision 1, dated 9 November 2007" (Applicability). That means an aeroplane of the listed model will be subject to the AD only if it appears in the specified ASB revision. A reader who assumes broad model-level applicability without checking the ASB inclusion list risks misidentifying affected aircraft.

Grandfathering of earlier service bulletin work: The AD accepts actions done before the effective date "in accordance with ASB 737-28A1221, dated 14 January 2007" as acceptable for Requirement 1 (Requirement 1, second paragraph). It is therefore essential to document that any pre-effective-date work followed that precise earlier ASB, rather than another document or a partial adoption. Failure to show that the earlier ASB was followed precisely could leave an operator without the AD's compliance protection.

Interplay with AD/B737/329 and FAA AD 2008-10-10: The AD states that incorporation of AWL No. 28-AWL-07 "in accordance with Requirement 1.c. of AD/B737/329 (paragraph (g)(3) of ... FAA AD 2008-10-10), terminates the action required by Requirement 2" (Requirement 2). The gotcha is that termination of Requirement 2 depends on the precise manner of incorporation and the specific cross-referenced paragraph in a prior AD. Operators must verify that their incorporation aligns exactly with the referenced language in AD/B737/329 and FAA AD 2008-10-10 to claim the termination effect; otherwise, Requirement 2 remains live.

AMOC approval gate with named FAA office: The AD bars use of alternative CDCCLs unless approved by the Manager, Seattle Aircraft Certification Office, FAA (Requirement 3). That is a single named approval gate. Parties seeking to use an alternative CDCCL must secure an AMOC from that particular FAA manager. The AD further accepts later ASB revisions only if approved by the FAA as an AMOC to FAA AD 2008-17-15 (Requirement 3). The gotcha is that alternative approaches require FAA managerial approval rather than a CASA or local engineering authority sign-off; operators must ensure their AMOC request is routed appropriately and evidence of FAA approval is obtained.

Sequence and concurrency requirements: The AD requires Requirement 2 (AWL incorporation) "Concurrently with accomplishing the Requirement 1 actions" (Compliance section) and sequences Requirement 3 "After accomplishing the action specified in Requirement 2." Non-observance of the required sequencing could create technical non-compliance even where the physical work is done.

No penalty language in the AD text: The AD does not include explicit penalty provisions in the supplied text. The gotcha here is that absence of a penalty clause in the AD document does not mean there are no consequences for non‑compliance under broader regulatory frameworks. The instrument's silence on penalties requires operators to consult the wider regulatory enforcement regime for consequences, which the AD itself does not supply.

Reliance on FAA approvals and AMOCs: The AD allows later ASB revisions "approved by the FAA as an AMOC to FAA AD 2008-17-15" to be acceptable (Requirement 3). If an operator chooses to rely on such a later ASB revision, they must ensure the FAA approval explicitly states AMOC status to the FAA AD named; partial or informal FAA assurances may not satisfy the AD's language.

Documentation burden: The AD requires incorporation of a specific AWL into the ICA. The gotcha is that incorporation into the AWL section is a formal documentation act; casual or informal technical notes will not satisfy the AD's requirement. Operators must ensure the AWL is formally inserted into the ICA in the precise manner required.

In short, the main compliance pitfalls are: checking precise ASB applicability; documenting pre-effective-date compliance under the specified earlier ASB if relied upon; ensuring exact conformity to cross-referenced ADs to obtain any termination of obligations; obtaining the correct FAA AMOC approvals where alternatives are sought; observing the sequencing and concurrency requirements; and performing formal ICA/AWL revisions, not informal record-keeping.

The AD itself prescribes the compliance pathway and acceptable methods; following the AD text closely is the compliance strategy.

Step 1 , Confirm applicability: Check whether the specific aeroplane serial/line number appears in Boeing Alert Service Bulletin (ASB) 737-28A1221, Revision 1, dated 9 November 2007. The AD applies only to "Model 737-600, -700, -800 and -900 series aeroplanes, as identified in" that ASB (Applicability). Only aeroplanes listed in that ASB are captured.

Step 2 , Prepare for the hardware installation per the ASB: For applicable aeroplanes, plan and schedule installation of the hot short protector (HSP) support brackets and the equipment for the FQIS fuel densitometer, plus every "other specified action" applicable to the aeroplane as set out in the Accomplishment Instructions of ASB 737-28A1221, Revision 1 (Requirement 1). The AD explicitly ties the required actions to the ASB's Accomplishment Instructions, so use that document as the technical compliance manual.

Step 3 , Evidence prior compliance if relevant: If the hardware actions were accomplished before the AD's effective date, assemble documentation showing the work was done "in accordance with ASB 737-28A1221, dated 14 January 2007" because the AD accepts such prior actions for Requirement 1 compliance (Requirement 1, second paragraph).

Step 4 , Incorporate the AWL into the ICA concurrently: The AD requires revision of the AWL section of the ICA by incorporating AWL No. 28-AWL-07 from the Boeing MPD (D626A001-CMR, Revision March 2007 R2) "Concurrently with accomplishing the Requirement 1 actions" (Requirement 2; Compliance section). Ensure the AWL insertion is a formal amendment to the ICA and that the revised ICA is dated and recorded.

Step 5 , Check whether Requirement 2 is terminated by prior AD compliance: If you have already incorporated AWL No. 28-AWL-07 "in accordance with Requirement 1.c. of AD/B737/329 (paragraph (g)(3) of United States FAA AD 2008-10-10)", that action "terminates the action required by Requirement 2" (Requirement 2). To rely on this, retain documentary evidence of the prior incorporation and ensure it matches the precise requirements and paragraph referenced.

Step 6 , Do not use alternative CDCCLs without FAA AMOC: If you contemplate using alternative Critical Design Configuration Control Limitations, obtain an AMOC from the Manager, Seattle Aircraft Certification Office, FAA before implementing the alternative (Requirement 3). The AD explicitly disallows alternative CDCCLs absent that FAA AMOC.

Step 7 , Consider later ASB revisions where appropriate: The AD accepts "later revisions of ASB 737-28A1221, approved by the FAA as an AMOC to FAA AD 2008-17-15" as acceptable for compliance with the equivalent Requirements of this Directive (Requirement 3). If a later ASB revision exists and has FAA AMOC approval to the FAA AD, confirm the FAA approval and use that revision for compliance, documenting the approval trail.

Step 8 , Meet the compliance timetable: For Requirement 1 the AD gives a compliance window of "Within 60 months after the effective date of this Directive." The AD's effective date is 18 December 2008 (effective date line). Requirement 2 must be completed concurrently with the Requirement 1 actions; Requirement 3 is effective after Requirement 2 (Compliance section). Plan maintenance scheduling and part procurement to meet these timing and sequencing constraints.

Step 9 , Maintain records: Keep contemporaneous maintenance records demonstrating that the ASB Accomplishment Instructions were followed, and retain formal ICA/AWL revisions showing incorporation of AWL No. 28-AWL-07. If relying on prior ASB compliance or on FAA AMOC approvals (for ASB revisions or alternative CDCCLs), retain the documents certifying those approvals and the applicable AD paragraphs used to claim termination or equivalence.

Step 10 , Liaise with the appropriate certification authority for alternatives: Any application for an AMOC to permit an alternate CDCCL must be directed to the Manager, Seattle Aircraft Certification Office, FAA. Document interactions and approvals. If relying on later ASB revisions, obtain and retain proof that those revisions were "approved by the FAA as an AMOC to FAA AD 2008-17-15" as the AD requires.

These steps are what the AD itself prescribes or authorises. The AD ties physical modification to specific ASB Accomplishment Instructions and requires formal AWL incorporation into the ICA. It also creates a strict pathway for permissible deviations through FAA AMOCs and explicitly recognises certain prior ASB-compliant work. To comply, operators must follow the ASB instructions, perform a formal ICA/AWL revision, meet the calendar timelines and sequence, and secure documented FAA approvals where alternative methods are proposed.