AD/BAe 146/134 - Horizontal Stabiliser Lower Skin & Joint Plates

The AD rests on a small set of interlocking concepts: applicability, mandated inspection procedure, conditional corrective action, terminating repair option, and compliance timing. Each concept is defined by reference to the manufacturer’s service documents (the ISB and the Repair Information Leaflet), which the AD incorporates by reference.

Applicability: The AD applies only to BAe 146 Series 100 and 200 aeroplanes, limited to the serial numbers specified in ISB.55-020. That means the AD does not purport to apply to all BAe 146 aircraft, but only to those serial numbers identified by the manufacturer in the ISB (Applicability clause).

Mandatory inspections: The AD requires inspection of the horizontal stabiliser lower skin and joint plates in the rib 1 area, following the sequences set out in paragraphs 2.C.(1) through 2.C.(3) of the ISB (Requirement paragraph 1). The ISB is quoted as the operative inspection procedure; the AD explicitly allows later approved revisions of that ISB to be used: "Initial issue, dated 11 December 2007 or later approved revision" (Requirement).

Conditional drill/ream and rivet installation: If no damage is found in the initial ISB inspection, operators must drill and ream four holes in accordance with paragraph 2.C.(4)(a) and then inspect those holes per paragraph 2.C.(4)(b). If those holes show distortion or corrosion, operators must contact BAE Systems for approved repair instructions to be carried out prior to fitting rivets (Requirement 1.a). If no distortion or corrosion is found, the operator must install the four rivets per paragraph 2.C.(4)(c) before further flight (Requirement 1.b).

Repetitive inspection cadence: The AD requires repeating the inspection in accordance with paragraphs 2.C.(1)-2.C.(3) repeatedly at intervals not to exceed 24 months (Requirement 2; Compliance). If damage is found during any inspection, the AD requires contact with BAe Systems in accordance with paragraph 2.C.(5) and accomplishment of an approved repair per paragraph 2.C.(6) before further flight (Requirement 2).

Terminating action: The AD names a specific repair document , BAE Systems Repair Information Leaflet HC551H9061 (issue 2, dated 16 November 2007 or later revision) , and states that accomplishment of that approved repair on both left and right sides of the horizontal stabiliser is terminating action for the repetitive inspection requirement (Requirement Note).

Temporal anchors: The AD fixes an initial compliance window , "no later than 6 months after 16 September 2008" , and an inspection interval of 24 months for repeats (Compliance). The AD itself becomes effective on 23 October 2008 (Compliance).

Regulatory cross-reference: The AD explicitly notes that EASA AD 2008-0167 (dated 2 September 2008) refers, indicating alignment or correspondence with a European Aviation Safety Agency directive (Background).

Mechanically, then, the AD converts the manufacturer’s diagnostic and repair instructions into compulsory action for affected aircraft and links continued operation ("before further flight") to completion of the required inspections, repairs or rivet installations. The AD also delegates to the manufacturer (BAE Systems) the role of provider of approved repair instructions: operators must contact the manufacturer for approved repair instructions in the event of distortion, corrosion or damage.

The AD affects a narrow set of stakeholders defined by aircraft type and serial number, plus maintenance organisations that service those aircraft. The primary parties directly affected are the operators and owners of BAe 146 Series 100 and 200 aeroplanes whose serial numbers are identified in BAE Systems ISB.55-020 (Applicability). The ISB determines the exact population; the AD does not list serial numbers in the text supplied, but ties applicability to those serial numbers as set out in the ISB.

Maintenance organisations and maintenance personnel authorised to perform the specified inspections and structural repairs are directly affected because the AD requires specific inspection and repair procedures as set out in ISB.55-020 (Requirement paragraphs 2.C.(1)-2.C.(4) and others) and in Repair Information Leaflet HC551H9061 (Requirement Note). Organisers of scheduled maintenance (operators’ maintenance planners) are also affected because the AD fixes an initial compliance deadline ("No later than 6 months after 16 September 2008") and mandates repeat inspections at intervals not exceeding 24 months (Compliance). These timing constraints will feed into maintenance scheduling, aircraft utilisation planning and spare capacity.

BAE Systems (Operations) Limited plays a central role: the AD incorporates the BAE Systems ISB and the RIL as the operative technical source. The AD requires contact with BAE Systems for approved repair instructions where distortion or corrosion or damage is discovered (Requirement 1.a and Requirement 2); it also designates BAE Systems’ RIL HC551H9061 as the terminating repair. That allocates technical decision-making and repair-method authority to the manufacturer for these defects.

Regulators and certifying authorities are affected in the sense that they will need to ensure compliance for the affected aircraft in their registers. The AD bears the signature of a Delegate of the Civil Aviation Safety Authority (David Villiers), and states its effective date, indicating CASA issued the AD (signature and Compliance). The AD also references EASA AD 2008-0167, which may require coordination where aircraft operate across jurisdictions.

Passengers and third parties are not directly named in the AD, but safety-related actions that restrict aircraft operations pending inspections or repairs could affect service provision, scheduling and availability of flights operated by affected aircraft. Where the AD requires repairs or contact with the manufacturer "before further flight," this creates a direct operational constraint on the operator’s ability to use affected aircraft until the required action is completed.

Finally, there are commercial implications for suppliers of rivets and maintenance consumables; while the AD does not address supply chains, the specified drilling, reaming and rivet installation steps will require those consumables and the appropriate tooling, and operators must ensure availability.

Duties

• Inspect per ISB: Operators must inspect the horizontal stabiliser lower skin and joint plates in accordance with paragraphs 2.C.(1)-2.C.(3) of BAE Systems ISB.55-020 (Initial issue, dated 11 December 2007 or later approved revision). This is the primary duty and forms the baseline of compliance (Requirement 1).

• Follow conditional procedures: If no damage is found during the ISB inspection, operators must drill and ream four holes per paragraph 2.C.(4)(a) and then inspect those holes per paragraph 2.C.(4)(b). If distortion or corrosion appears in the rivet holes, the operator must contact BAE Systems for approved repair instructions and accomplish the repair before further flight (Requirement 1.a). If no distortion or corrosion is present, the operator must install four rivets per paragraph 2.C.(4)(c) before further flight (Requirement 1.b).

• Repeat inspections: Operators must repeat the inspection in accordance with paragraphs 2.C.(1)-2.C.(3) of ISB.55-020 at intervals not exceeding 24 months (Requirement 2; Compliance).

• Repair when damage found: If damage is detected during any inspection, the operator must contact BAe Systems in accordance with paragraph 2.C.(5) of ISB.55-020 and accomplish an approved repair per paragraph 2.C.(6) before further flight (Requirement 2).

• Apply terminating repair if chosen: Operators who elect to accomplish the approved repair described in BAE Systems Repair Information Leaflet HC551H9061 (issue 2, dated 16 November 2007 or later revision) on both left and right sides of the horizontal stabiliser will have performed the action that terminates the repetitive inspection requirement (Requirement Note).

• Timing obligations: The initial inspection must be completed no later than six months after 16 September 2008, and thereafter the inspections repeated at intervals not exceeding 24 months (Compliance).

Rights / Permitted options

• Use of later approved revisions: The AD allows the operator to use the ISB initial issue or "later approved revision" to satisfy the inspection procedures (Requirement). This preserves the ability to use updated or amended ISBs provided they are an approved revision.

• Optional terminating action: The operator has a choice between continuing with the repetitive inspection regime or performing the approved repair (RIL HC551H9061) as terminating action. The RIL is presented as an optional but definitive alternative to periodic inspections (Requirement Note).

• Manufacturer-provided repair instructions: If distortion, corrosion or damage is found, the operator is required to contact BAE Systems for approved repair instructions (Requirement 1.a and Requirement 2). This channels the repair decision and approved method through the manufacturer rather than leaving it to the operator or maintenance organisation alone.

Procedural constraints implicit in duties

• "Before further flight" constraint: Several required actions are mandated to be completed before further flight if particular findings arise (install rivets if no distortion/corrosion; accomplish repair if distortion/corrosion or damage is found). The AD thereby imposes immediate operational conditions on affected aircraft pending compliance (Requirement 1.a-1.b; Requirement 2).

• Serial-number limitation: The AD applies only to aircraft listed in ISB.55-020; operators must check the ISB to determine whether their aircraft are within the affected population (Applicability).

The AD text does not state rights to appeal, waiver or derogation within its body; it does, however, permit use of later approved revisions of the ISB and RIL, and allows operators to choose the terminating repair as an alternative to repeating inspections. The manifest duties are technical and time-bound and are predicated on use of the manufacturer’s service documents and instructions.

The AD text supplied sets out mandatory inspection and repair actions, timing, and "before further flight" constraints, but it does not itself specify penalties, fines or civil/criminal sanctions for non-compliance. The AD states the required actions and the effective date (23 October 2008) and identifies the authoritative technical materials (ISB.55-020 and RIL HC551H9061) and the signature of a Delegate of the Civil Aviation Safety Authority (David Villiers) (Compliance; signature). The AD therefore establishes regulatory obligations for the affected aircraft and operators, but the instrument as presented does not include express enforcement mechanisms or penalty schedules within its text.

Consequences that the AD text does specify, and that have enforcement implications, include:

• Operational prohibition until compliance for certain findings: The AD requires that where distortion, corrosion or damage is found, operators must contact BAE Systems and accomplish approved repairs "before further flight" (Requirement 1.a and Requirement 2). The "before further flight" language functions as a direct constraint on continued operation of the airframe until the mandated corrective action is completed. That operational prohibition is an enforcement lever because compliance is a precondition to returning the aircraft to service.

• Mandatory timing: The AD fixes a deadline for initial inspection ("No later than 6 months after 16 September 2008") and prescribes repeat intervals not exceeding 24 months (Compliance). Those timing requirements create a clear compliance schedule to be checked by regulators and maintenance oversight bodies.

What the AD does not contain

• No explicit penalty clause in the text: The AD does not set out explicit penalties, sanctions, or the process for enforcement action where an operator fails to comply. It also does not set out any administrative processes for exemptions, special flight permits, or urgent operational relief within this text.

• No administrative enforcement procedures: The AD does not itself describe how CASA will monitor, audit, or otherwise verify compliance, nor does it describe the mechanism by which non-compliance will be escalated to enforcement action.

Practical enforcement implication (source-based inference)

• Enforcement will operate through the regulatory status of an AD as a mandatory directive: The AD text, by setting required actions and "before further flight" conditions, creates obligations that must be met as a condition of continuing to operate the affected aeroplanes. In practice, regulatory authorities (here, CASA or its delegated inspectors) would be the bodies tasked with checking adherence to the AD through normal oversight activities, but the AD text supplied does not record those oversight practices or penalties.

Users of this AD should therefore note that while the instrument requires specified actions and fixes deadlines, it does not include a penalty schedule or enforcement procedures within the text provided. To determine specific sanctions, enforcement processes, or procedures for relief from the AD, operators would need to consult the broader regulatory framework governing Airworthiness Directives and aviation safety enforcement in the relevant jurisdiction (CASA rules and enforcement policies), which are not reproduced in this AD text.

The AD interacts primarily with manufacturer service documentation and with supra‑national aviation safety directives as referenced in its text. The AD explicitly incorporates BAE Systems ISB.55-020 and Repair Information Leaflet HC551H9061 as the technical instruments that set inspection procedures and the approved repair method. In that sense, the AD operationalises those manufacturer documents into regulatory obligations for the applicable fleet: operators must follow the procedures in the ISB and the RIL as specified by the AD (Requirement and Requirement Note).

The AD also notes that EASA AD 2008-0167, dated 2 September 2008, refers (Background). That reference indicates the AD is part of a set of parallel safety directives addressing the same technical issue across jurisdictions; it aligns the CASA AD with an EASA directive. The text does not elaborate whether the CASA AD is intended to mirror the EASA AD verbatim, nor does it set out cross-border mechanisms for enforcement, but the reference signals recognition of the EASA action on the same subject matter.

Beyond those explicit references, the AD text does not set out interaction with domestic aviation regulations, certification rules, or broader statutory enforcement regimes. It does not, within the supplied text, quote provisions of the Civil Aviation Safety Regulations or list how compliance with the AD affects certificates, continuing airworthiness records, or maintenance release obligations. The AD does, however, impose "before further flight" conditions and timing obligations that will intersect with operators’ continuing airworthiness obligations, maintenance release procedures, and flight authorisation processes established under local aviation law and regulation. Those interactions exist functionally because airworthiness directives form part of an operator’s regulatory obligations for continuing airworthiness even though the AD text itself does not reproduce the enabling statutory provisions.

The AD allows the use of "Initial issue, dated 11 December 2007 or later approved revision" of the ISB and permits RIL HC551H9061 "at issue 2, dated 16 November 2007 or later revision" as the approved repair (Requirement; Requirement Note). That means the AD anticipates the use of later approved revisions of both documents; it therefore interacts with the administrative processes for approving updates to manufacturer service documents. Operators who use later approved revisions must ensure the revisions are indeed "approved" under the relevant approval process, which lies outside the AD text.

Finally, the AD’s "before further flight" requirement will interact with any legal mechanism that allows special flight permits or exemptions for ferrying aircraft for repair. The AD does not address whether such exemptions are available or the process to obtain them; that interaction would be governed by separate provisions of the aviation regulatory framework and not by the AD text itself.

In short, the AD incorporates manufacturer technical material and cross-references a relevant EASA AD; it imposes obligations that will be implemented through operators’ existing maintenance and continuing airworthiness systems and will thus interact with broader aviation regulations, administrative approval processes for service document revisions, and any special flight permit regimes , interactions that are implicit in the AD but not spelled out in its text.

The AD records dates and document versions that form its amendment history and points to where later revisions are permissible. The textual evidence supplies the following documentary points:

• ISB reference: The AD mandates inspections "in accordance with paragraphs 2.C.(1) through 2.C.(3) of BAE Systems ISB.55-020 Initial issue, dated 11 December 2007 or later approved revision" (Requirement). The AD therefore incorporates the ISB initial issue dated 11 December 2007 and permits use of later approved revisions. The AD does not list any subsequent amendments to the AD itself in the supplied text.

• Repair Information Leaflet reference: The AD identifies BAE Systems Repair Information Leaflet HC551H9061 "at issue 2, dated 16 November 2007 or later revision" as the approved repair that serves as terminating action for the repetitive inspection requirement (Requirement Note). This establishes that issue 2 of the RIL is the reference document, but allows later approved revisions.

• Cross-reference to EASA AD: The AD notes that "EASA AD 2008-0167, dated 2 September 2008, refers" (Background). That indicates contemporaneous regulatory action by EASA; it does not itself alter the CASA AD but situates the AD in a broader regulatory timeline.

• Effective and signature dates: The AD records that it "becomes effective on 23 October 2008" (Compliance), and is signed by David Villiers, Delegate of the Civil Aviation Safety Authority, dated 8 September 2008 (signature block and date). The AD also specifies compliance timing relative to 16 September 2008 ("No later than 6 months after 16 September 2008") for the initial inspection (Compliance).

• Document issuance metadata: The AD is labelled AD/BAe 146/134 and dated 11/2008 in the header rows. The background commentary states the rationale and reiterates dates. The ISB and RIL reference dates show the manufacturer documents pre-date the AD, with the ISB initial issue on 11 December 2007 and the RIL issue 2 on 16 November 2007. The AD itself was signed on 8 September 2008 and became effective 23 October 2008.

The AD text does not contain any subsequent amendments, superseding directives, or revocation language. It does allow the use of later approved revisions of the incorporated manufacturer documents, meaning that the operative technical requirements can be met by following either the named issues or later approved versions. For tracking changes, users should monitor the status of ISB.55-020 and RIL HC551H9061 for later approved revisions and check CASA notices for any amendments to or superseding ADs, none of which are recorded inside the text provided.

The supplied AD text does not include any litigation history. It contains no references to court proceedings, administrative appeals or legal challenges related to this AD, nor does it cite cases or decisions. The text only records the manufacturer's determination of need, the technical documents (ISB and RIL), the related EASA AD reference, the signature of a CASA Delegate and the effective date.

Because the AD does not discuss litigation, there is no source-grounded record in this document of legal challenges, judicial review, or enforcement proceedings arising from implementation of the AD. If readers require litigation history,cases raising points such as interpretation of "before further flight," the sufficiency of manufacturer repair instructions, or enforcement actions for non-compliance,they will need to consult judicial or tribunal records, CASA enforcement records, or case law databases. Those materials are not part of the AD text supplied and thus are outside the scope of this document.

In short, within the text provided, there is no litigation history to summarise; the AD records only its technical and administrative content and cross-references to the related EASA AD.

The AD contains several precise procedural and timing elements that create potential pitfalls for operators and maintainers. Because the AD binds actions to specific paragraphs of manufacturer documents and to explicit timing, small oversights can produce compliance failures or operational disruptions. The following items are concrete, source-grounded "gotchas" drawn from the AD text.

Applicability is serial-number specific: The AD applies to "BAe 146 Series 100 and 200 aircraft, serial numbers as identified in BAE Systems (Operations) Limited Inspection Service Bulletin ISB.55-020" (Applicability). Operators cannot assume the AD applies to all BAe 146 Series aeroplanes. They must check the ISB to confirm whether a given airframe’s serial number is included. Failing to consult the ISB could lead to either unnecessary work or inadvertent non-compliance.

Initial compliance window anchored to a calendar date distinct from the effective date: The Compliance section requires the initial inspection "No later than 6 months after 16 September 2008", but the AD also states it "becomes effective on 23 October 2008" (Compliance). This creates an apparent sequencing distinction: the deadline is fixed relative to 16 September 2008, a date earlier than the AD effective date. Operators must treat the specified compliance window as the controlling provision and ensure they meet the "no later than" deadline, even if the AD’s effectivity date follows that anchor date.

Use of manufacturer paragraphs as the operative instruction: The AD requires inspections and corrective actions "in accordance with paragraphs 2.C.(1) through 2.C.(3)" and other paragraphs of ISB.55-020 (Requirement). That makes the ISB paragraphs the operative technical method. A gotcha arises where an operator uses a different section of the ISB, a different service bulletin, or an unapproved revision; the AD explicitly allows "later approved revision" but does not allow arbitrary deviations. Operators and maintenance organisations need to ensure they are following the precise paragraphs referenced or an approved later revision.

Drilling, reaming and rivet installation sequence: If no damage is found in the ISB inspection, the AD requires drilling and reaming four holes, then inspecting those holes (paragraphs 2.C.(4)(a) and 2.C.(4)(b)), and then either contacting BAE if distortion/corrosion is found or installing four rivets if no distortion/corrosion is found (Requirement 1 and 1.a-1.b). Mistiming or skipping the inspection of the drilled holes before rivet installation would contravene the AD; the AD mandates the sequence and conditions precisely.

"Before further flight" constraints create operational grounding risk: The AD requires certain repairs or rivet installations "before further flight" where distortion/corrosion or damage is found (Requirement 1.a and Requirement 2). This means an aircraft cannot legally fly until the conditions are rectified. Operators must plan for potential grounding and associated costs and logistics in their maintenance scheduling.

Manufacturer contact required where damage found: The AD mandates that operators "contact BAe Systems... and accomplish an approved repair in accordance with paragraph 2.C.(6)" whenever damage is found (Requirement 2). That channels repair approval and repair method decisions to the manufacturer. A potential gotcha is the time it may take to liaise with BAE and receive approved instructions; the AD requires the repair "before further flight", potentially creating delays while awaiting approved instructions.

Optional terminating action requires both sides to be done: The AD states that accomplishment of the approved repair RIL HC551H9061 on the left AND right sides of the horizontal stabiliser is terminating action for the repetitive inspection requirement (Requirement Note). A partial repair on only one side will not terminate the inspection requirement. Operators must ensure that both sides are repaired if they intend to retire the 24-month inspection cycle.

Reliance on "later approved revision" requires approval status confirmation: The AD permits later approved revisions of the ISB and RIL. However, the AD requires "approved" revisions; operators must confirm that any later revision used is indeed an approved revision and acceptable under the AD. Failure to verify approval status could lead to use of an unapproved revision and non-compliance.

Cross-reference to EASA AD does not itself modify obligations: The AD notes EASA AD 2008-0167 refers, but the AD does not explain whether EASA’s AD contains different procedures, deadlines, or affected serial numbers (Background). Operators should not assume equivalence in all respects; they must comply with the CASA AD as written for aircraft on the Australian register and check EASA AD where relevant for aircraft registered or operating under EASA jurisdiction.

Documentation and record-keeping implications: Although not stated expressly in the AD, compliance will necessarily create entries in maintenance records showing inspections, drillings, rivet installations or repairs, and whether the terminating repair was completed. Ensuring those records match the AD’s requirements and the referenced ISB/RIL paragraphs is essential for demonstrating compliance to regulators.

In sum, the AD’s precise references, sequencing, and "before further flight" triggers create narrow compliance pathways. Operators should pay attention to the serial-number applicability in the ISB, the precise ISB paragraphs referenced, the sequencing of drill/inspection/rivet actions, the need to contact the manufacturer for approved repairs where damage is found, and the requirement that terminating repairs be applied to both left and right sides if the operator wishes to retire the inspection requirement.

This section sets out a practical, source‑grounded compliance checklist based strictly on the AD text. It follows the AD’s own sequence and timing requirements, cross-referencing the specific paragraphs the AD invokes.

1. Confirm applicability

   • Obtain a copy of BAE Systems ISB.55-020 and check the serial-number list within the ISB to determine whether each BAe 146 Series 100 or 200 aeroplane in the operator’s fleet is included (Applicability). Only aircraft identified in the ISB are subject to this AD.

2. Identify the authoritative documents

   • Use BAE Systems ISB.55-020 Initial issue, dated 11 December 2007, or a later approved revision for the inspection procedures (Requirement).
   • Use BAE Systems Repair Information Leaflet HC551H9061 (issue 2, dated 16 November 2007) or a later approved revision for the approved repair that provides terminating action (Requirement Note).

3. Schedule the initial inspection within the AD window

   • Ensure the initial inspection is scheduled and completed no later than six months after 16 September 2008, as required by the AD (Compliance). Even though the AD became effective on 23 October 2008, the AD text sets the initial compliance deadline relative to 16 September 2008; plan accordingly.

4. Perform the ISB inspection steps

   • Execute the inspection of the horizontal stabiliser lower skin and joint plates in accordance with paragraphs 2.C.(1) through 2.C.(3) of ISB.55-020 (Requirement 1).
   • Ensure maintenance personnel performing the work are authorised and competent to carry out structural inspections as per the ISB.

5. If the ISB inspection finds no damage

   • Drill and ream four holes as required by paragraph 2.C.(4)(a) of ISB.55-020 (Requirement 1).
   • Inspect the drilled holes in accordance with paragraph 2.C.(4)(b) (Requirement 1).
   • If the inspection of the holes reveals distortion or corrosion, contact BAE Systems for approved repair instructions and accomplish the repair prior to fitting rivets or returning the aircraft to service (Requirement 1.a).
   • If no distortion or corrosion is found in the holes, install the four rivets in accordance with paragraph 2.C.(4)(c) of ISB.55-020 before further flight (Requirement 1.b).

6. If any inspection finds damage

   • If damage is discovered at any point during the inspections, contact BAe Systems in accordance with paragraph 2.C.(5) of ISB.55-020 and accomplish an approved repair in accordance with paragraph 2.C.(6) before further flight (Requirement 2).
   • Follow the manufacturer’s approved repair instructions and ensure documented authorisation for the repair.

7. Consider the terminating repair

   • If the operator prefers to remove the need for repetitive inspections, accomplish the approved repair contained in BAE Systems Repair Information Leaflet HC551H9061 (issue 2, 16 November 2007 or later approved revision) on both the left and right sides of the horizontal stabiliser. Accomplishment of that repair on both sides is specified as terminating action for the repetitive inspection requirement (Requirement Note).
   • Ensure the repair is carried out by appropriately authorised maintenance personnel and that both sides are completed if the operator intends to cease the 24‑month inspection cycle.

8. Establish the repeat inspection schedule

   • If not electing the terminating repair, set the inspection recurrence no later than every 24 months in accordance with the AD (Compliance). Incorporate this into the continuing airworthiness management programme and maintenance planning.

9. Documentation and record keeping

   • Record the inspections, drill/ream action, rivet installations, manufacturer contact and any repairs accomplished in the aircraft’s maintenance records in a manner that clearly demonstrates compliance with the AD and identifies the ISB or RIL paragraphs followed (the AD references explicit ISB paragraphs).
   • If the terminating repair is performed, file evidence that RIL HC551H9061 issue 2 (or later approved revision) has been carried out on both the left and right sides.

10. Manage operational constraints

    • Treat any requirement to accomplish repair "before further flight" as binding: an aircraft with distortion, corrosion or damage as described must not be operated until the mandated repair is completed (Requirement 1.a and Requirement 2).
    • Plan for potential down-time, parts procurement (e.g., rivets, tools), and liaison time with BAE Systems in the event manufacturer-approved instructions are required.

11. Use approved revisions only

    • If electing to use a later revision of ISB.55-020 or RIL HC551H9061, confirm that the later revision is an "approved revision" as permitted by the AD (Requirement and Requirement Note). Maintain documentary evidence of the revision used and its approval status.

12. Coordinate with regulators where necessary

    • While the AD does not state enforcement procedures or appeal routes within its text, operators should liaise with their regulatory authority (CASA delegate or inspectorate) as necessary to confirm compliance status and to understand any broader regulatory implications, including any required maintenance releases or certificates for return-to-service.

Following the steps above, as drawn directly from the AD’s Requirement and Compliance sections and the referenced ISB and RIL identification, will satisfy the AD’s technical and timing obligations. Operators must ensure that all actions are performed by authorised personnel and accurately documented against the specific ISB and RIL paragraphs the AD mandates.