AD/DHC-8/128 - Wing Root Electrical Wire Chafing

This AD rests on a small set of operational and technical concepts that structure the requirements.

• Targeted hardware and locations. The AD identifies precise part numbers for left and right electrical harness assemblies (82440073-001/301 and 82440074-001/301) and the aft seal assemblies they interface with (85350712-001 and 85350711-001), located at station Yw43.00 on the wing root to fuselage aft seal assembly. The specificity confines the directive to particular assemblies and a known geometric interface.

• Failure mode and consequence. The background records that chafing of wiring against the aft seal assemblies can abrade insulation or conductor, causing chafing and possible grounding. The reported consequence in an actual incident was un-commanded propeller feathering during climb, which resulted in an emergency landing. The AD identifies potential interruptions to multiple systems, explicitly including propeller feather control, AC electrical power, and standby hydraulic power.

• Two-step mitigation approach. The AD imposes two distinct but related actions. Requirement 1 calls for visual inspection and repair as necessary of the harnesses, following the detailed instructions in Bombardier SB 8-24-83, Revision A (or later approved revisions). Requirement 2 calls for a physical modification of the seal assemblies by installing ModSum 8Y122031 to rework the seal and create clearance between wiring and panel edge,this is a design/airframe modification to change the contact geometry that caused chafing.

• Equivalence and prior compliance. The AD recognises prior compliance where operators have already implemented the original SB 8-24-83 or have installed Bombardier ModSum IS8Q2400005 before the effective date. The AD treats those prior actions as satisfying its requirements.

• Regulatory approval of later revisions. The instructions in the SB may be revised over time; however the AD conditions compliance to later revisions only if they are approved by the Chief, Continuing Airworthiness, Transport Canada. That approval is the regulatory checkpoint for substitution of later SB revisions.

• Temporal compliance metric. The AD uses aircraft time-in-service hours as the compliance metric. Operators must carry out both the inspection/repairs and installation of the ModSum within 6 000 hours time in service after 31 August 2006, rather than using calendar days or cycles.

• Inter-regulatory reference. The AD explicitly cross-references a Transport Canada AD, CF-2006-15, indicating alignment or correspondence with the Canadian regulator’s action.

These concepts determine who must act, what they must do, by when, and which documents set the technical procedures. The AD thus combines prescriptive inspection and repair tasks with a mandatory structural modification to remove the geometric cause of chafing, anchored to approved manufacturer service instructions and subject to the approving authority for later changes.

The AD applies narrowly by aircraft make, model and serial number range, and therefore affects a defined set of economic actors with direct legal and practical obligations.

• Aircraft operators and owners. Operators and owners of Bombardier DHC-8 Models 102, 103, 106, 201, 202, 301, 311, 314 and 315 with serial numbers 003 through 606 are within the AD’s applicability. Those entities are the primary parties who must perform the inspection, repairs and ModSum installation specified in the AD within the stated compliance window.

• Maintenance organisations and authorised engineers. Persons or organisations that perform maintenance must follow Bombardier SB 8-24-83 Revision A or later revisions as approved by the Chief, Continuing Airworthiness, Transport Canada. The AD makes these SB instructions the technical standard for executing required inspections and repairs, so licensed maintenance providers will be engaged to carry out the work.

• Regulators and certifying authorities. The Civil Aviation Safety Authority (CASA) is the Australian regulator represented by the AD’s delegate signature (James Coyne). The AD also explicitly involves Transport Canada: later SB revisions must be approved by the Chief, Continuing Airworthiness, Transport Canada, and the AD refers to Transport Canada AD CF-2006-15. This places both CASA (for enforceability in Australia) and Transport Canada (for approval of revised SB material and cross-reference) as relevant decision-makers.

• Manufacturers and service bulletin authors. Bombardier (Boeing Canada/De Havilland) as the manufacturer and the author of SB 8-24-83 is implicated. The SB contains the approved instructions for inspection, repair and ModSum incorporation referenced as the technical method to meet the AD requirements.

• Lessors and financiers. Any party with a legal interest in affected serial-numbered aircraft, such as lessors or financiers, is indirectly affected because compliance work and associated downtime and costs attach to the aircraft asset until the AD requirements are met.

• Operational partners. Airworthiness and dispatch partners, such as scheduling, operations control, and insurance underwriters, will be affected operationally because required maintenance may affect aircraft availability and risk profiles.

The AD excludes aircraft outside the stated serial-number range and models. The AD also explicitly recognises that certain prior actions (original SB issue compliance or prior ModSum IS8Q2400005 installation) already satisfy its requirements; owners/operators who have undertaken those works before the effective date are treated as compliant, which affects who actually needs to carry out new work.

Who pays. The source sets no allocation of cost, so the economic burden will fall on the legal operator or owner responsible for maintaining the aircraft in an airworthy condition in accordance with regulatory obligations. That includes costs of inspection, any required repairs, parts and labour for ModSum installation, and aircraft downtime during works.

Who decides. Technical decisions about acceptable repair methods and SB revisions are subject to approval by the Chief, Continuing Airworthiness, Transport Canada, while enforceability and regulatory oversight in Australia flow from CASA, by the signature and issuance of the AD.

The AD establishes a set of prescriptive duties and recognises limited equivalence rights. The source text provides the legal duties in the form of mandatory requirements, and it identifies who has authority to approve deviations.

Duties

• Inspect and repair. Requirement 1 imposes a duty to visually inspect specified left and right electrical cable harness assemblies for damage and to repair as required. The scope of the duty is confined to the identified harness part numbers and their location at station Yw43.00, and the inspection and repair must be carried out in accordance with the instructions in Bombardier Service Bulletin SB 8-24-83, Revision A, dated 2 August 2005, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada.

• Modify seal assemblies. Requirement 2 imposes a duty to install Bombardier ModSum 8Y122031 to rework the aft seal assemblies so that a clearance exists between the electrical cable assemblies and the edge of the fairing panel. The AD states that Bombardier SB 8-24-83 Revision A contains the approved instructions for incorporating ModSum 8Y122031.

• Compliance timeframe. Both duties are subject to one compliance deadline, expressly "For Requirements 1 and 2 - Within 6 000 hours time in service after the effective date of this Directive." The AD becomes effective on 31 August 2006; that fixes the start of the compliance clock.

• Prior work equivalence. The AD imposes no new work on aircraft where prior inspections and modifications were performed before the effective date "in accordance with the original issue of Bombardier SB 8-24-83" , the AD accepts those prior actions as satisfying its requirements. Similarly, incorporation of Bombardier ModSum IS8Q2400005 prior to the AD’s effective date is treated as equivalent to ModSum 8Y122031 and satisfies the AD.

• Use of approved SB revisions only. The AD conditions the use of any later SB revisions on approval by the Chief, Continuing Airworthiness, Transport Canada. This gives an administrative gatekeeper role to that official and limits operators from relying on unapproved SB edits.

Rights and discretion

• Right to rely on prior compliance. An owner or operator who can demonstrate that the original SB work or the earlier ModSum was installed before 31 August 2006 may treat their aircraft as compliant under this AD without repeating the work.

• Right to follow later approved SB revisions. Operators may follow later revisions of Bombardier SB 8-24-83 if those later revisions are approved by the Chief, Continuing Airworthiness, Transport Canada. The AD does not authorise non-approved alternative procedures; those would require separate approval.

• Delegated enforcement subject to regulator. The AD is issued by CASA (signed by a delegate). The AD contains no express mechanism for variations, exemptions or tolerances within the text, so any official discretion to grant relief would be exercised by the relevant regulator under its general powers, though the AD text itself does not specify those powers.

What the AD does not provide within its text

• The AD text does not specify permissible repair tolerances, replacement part sources, authorised maintenance providers, record-keeping procedures, or sanctions for non-compliance. The technical method is tied to Bombardier SB 8-24-83 Revision A or later approved revisions, so technical content beyond that reference is not in the AD itself.

• The AD does not specify whether the inspections are recurring or one-time; the requirement is framed as an inspection and repair, with no repeat interval stated. The installation of ModSum is a modification requirement and, by its nature, is a one-time incorporation unless further regulatory action is taken, but the AD does not enumerate recurring inspection intervals.

Compliance obligations thus are concrete in their aims and municipal in scope: a one-time visual inspection and repair where necessary, plus a one-time structural modification, both to be completed within a specified time-in-service window, using the Bombardier SB as the procedural standard unless a later revision is approved by the Canadian Chief of Continuing Airworthiness.

The AD text itself specifies mandatory actions and a compliance timeframe, but it does not set out penalties or an enforcement regime within the text supplied. The AD was issued by a delegate of the Civil Aviation Safety Authority (James Coyne) and references approval functions vested in the Chief, Continuing Airworthiness, Transport Canada for subsequent service bulletin revisions. From the source material the following enforcement-related facts and limits can be stated.

What the AD requires to be done and when. The AD makes two substantive demands: inspect and repair specified harnesses in accordance with Bombardier SB 8-24-83 Revision A (or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada), and install Bombardier ModSum 8Y122031 to rework seal assemblies. Both actions must be completed within 6 000 hours time in service after the AD’s effective date, which is 31 August 2006.

Regulatory issuing authority. The directive is issued under the authority of the Civil Aviation Safety Authority, a regulatory agency; the signature line shows the AD was issued by a CASA delegate. The AD also cross-references Transport Canada for approval of later SB revisions and references Transport Canada AD CF-2006-15, reflecting inter-jurisdictional coordination.

Penalty provisions not stated. The AD text contains no express penalty provisions, fines, or criminal sanctions. The source does not identify what sanctions, if any, attach to non‑compliance, nor the means by which CASA will detect or enforce non-compliance. The AD likewise does not set out inspection or reporting obligations directly to CASA as part of the AD text.

Enforcement mechanisms implicit in regulatory practice. While the AD does not enumerate enforcement procedures, the presence of a mandatory AD and a compliance deadline indicates a regulatory expectation of compliance; enforcement action, oversight and any penalties would be administered under the general powers and enforcement rules of the regulator in question (CASA) rather than under text within this AD. The AD also conditions acceptance of later SB revisions on approval by the Chief, Continuing Airworthiness, Transport Canada, creating an approval gate for alternative procedural approaches.

Equivalence acceptance and compliance avoidance. The AD explicitly accepts prior inspections and modifications performed before the AD’s effective date in accordance with the original SB as satisfying the AD. It also accepts prior incorporation of ModSum IS8Q2400005 as equivalent to ModSum 8Y122031. These equivalence clauses limit the regulator’s need to enforce action where compliant work is already complete.

Operational consequence. The AD identifies the safety deficiency that led to the directive,a reported incident of un-commanded propeller feathering during climb caused by chafing through the auto-feather wiring. This factual basis frames the AD as a risk-mitigation instrument, and the compliance deadline is set so operators have a finite window in which to complete the mitigations.

In sum, the AD establishes mandatory work and a deadline, names the regulating authority that issued it and the foreign regulator that must approve later SB revisions, and acknowledges certain prior actions as satisfying its requirements. The AD text itself does not specify penalties or enforcement mechanisms; enforcement modalities would arise from the regulator’s general statutory enforcement powers and procedures, which are outside the content of this AD as provided.

The AD explicitly references, and thereby interacts with, regulatory instruments and approval processes outside its own text. The source establishes the following interdependencies.

• Cross-reference to Transport Canada AD CF-2006-15. The AD contains a note that "Transport Canada AD CF-2006-15 refers." That indicates the Australian AD is aligned with a parallel Canadian airworthiness directive. The cross-reference implies that the technical issue has been addressed by at least one other national regulator and that the Australian AD is part of an internationally coordinated regulatory response.

• Approval by the Chief, Continuing Airworthiness, Transport Canada. The AD conditions reliance on any later revisions of Bombardier SB 8-24-83 on approval by the Chief, Continuing Airworthiness, Transport Canada. That creates an inter-regulatory approval link: CASA’s AD binds Australian operators to procedures in a Bombardier SB, but it allows later SB revisions to be used only after approval by the named Canadian official. This ties procedural flexibility to a foreign regulator’s approval authority for later SB revisions.

• Use of manufacturer service bulletin as technical standard. The AD incorporates Bombardier SB 8-24-83 Revision A, dated 2 August 2005, by reference as the procedural mechanism for inspections, repairs and ModSum incorporation. The AD therefore interacts with the legal status of manufacturer service documents in aviation regulation: the SB becomes the technical standard for compliance under this AD.

• Equivalent prior modification recognition. The AD recognises prior incorporation of Bombardier ModSum IS8Q2400005 and prior compliance with the original SB as satisfying its requirements. The AD thus interacts with prior maintenance and modification records and with the legal recognition of equivalent modifications carried out before the AD’s effective date.

• Regulatory enforcement and airworthiness frameworks. The AD is issued by a CASA delegate and thus interacts with CASA’s statutory powers in the wider air safety regulatory framework. While the AD itself does not state enforcement mechanisms or penalties, it sits within the body of law and regulation that empowers CASA to determine airworthiness, require corrective action, and enforce compliance.

• Interaction with operational maintenance standards. The AD’s requirements must be satisfied in particular by maintenance organisations and licensed engineers operating under national maintenance and airworthiness rules. The AD therefore interacts with licensing, maintenance approval, and record-keeping regimes governing how maintenance is authorised and documented. The AD’s reference to the SB and approval of later SB revisions signals that the procedural elements of compliance are determined by a mix of manufacturer guidance and regulator approval.

• Jurisdictional implications for aircraft registered or operated outside Australia. The AD limits its applicability by aircraft model/serial number but does not state registration jurisdiction. Where the affected aircraft are registered in other jurisdictions, operators will need to consider corresponding national ADs (e.g. the referenced Transport Canada AD) and how compliance with one regulator’s ADs influences compliance with another. The AD text itself does not resolve cross-jurisdictional compliance mechanisms, but it explicitly references the Canadian AD and the Canadian Chief’s approval role, showing a practical regulatory overlap.

In short, the AD interacts with manufacturer service documents, with Transport Canada’s approval authority for SB revisions, and with CASA’s regulatory issuance and oversight. It recognises prior approved work as compliant and references an equivalent Canadian AD, embedding the Australian measure within an international regulatory dialogue over the same technical hazard.

The source provides limited explicit amendment history, but it does include specific textual references that constrain permissible changes and note prior compliance equivalences.

• AD effective date. The AD becomes effective on 31 August 2006. The compliance clock for the 6 000 hours time in service starts from that effective date.

• Service Bulletin revisions. The AD requires compliance with Bombardier SB 8-24-83, Revision A, dated 2 August 2005, as the operative technical document. It expressly allows "later revisions approved by the Chief, Continuing Airworthiness, Transport Canada." That language establishes the mechanism for amendment: the technical procedure can be updated only by a later SB revision if it receives the named regulatory approval.

• Prior compliance equivalence. The AD recognises two categories of prior actions as satisfying the AD: (1) prior inspections and seal assembly modifications done before the effective date in accordance with the original issue of Bombardier SB 8-24-83, and (2) prior incorporation of Bombardier ModSum IS8Q2400005 before the effective date, which the AD treats as equivalent to ModSum 8Y122031. These equivalence clauses operate like retroactive approval for specific earlier actions, limiting the need for rework where certain prior work has already been done.

• Cross-reference to Transport Canada AD. The AD contains a note that Transport Canada AD CF-2006-15 "refers." That indicates Transport Canada issued a corresponding or related AD. The source does not present amendments to this Australian AD in response to the Canadian AD, other than the cross-reference.

• No internal amendment log in the AD text. The supplied AD does not contain an internal amendment table showing earlier or later amendments to the AD itself. It contains no notation of superseding ADs, revocations, or post-issuance changes within this text.

• Technical amendment mechanism. The only explicit amendment pathway described in the AD is approval of later Bombardier SB revisions by the Chief, Continuing Airworthiness, Transport Canada. The AD does not describe any procedure by which CASA would issue an amendment to the AD text itself, nor does it specify procedures for exemptions, deferments, or alternative means of compliance beyond the approval clause for later SB revisions.

• Practical implication. For operators and maintainers, the AD’s effective and operative technical versions are the Revision A of the SB dated 2 August 2005, unless and until Bombardier issues later SB revisions that the Chief, Continuing Airworthiness, Transport Canada approves. The AD’s recognition of specific prior ModSum work as equivalent means that some aircraft may be out of scope for new work due to earlier compliance.

Because the source contains no subsequent or earlier versions of the AD text besides the effective date and the SB revision references, the AD’s amendment history within this text is limited to the initial issuance effective 31 August 2006, the identification of Revision A of SB 8-24-83 as the operative technical standard, and the clause allowing later SB revisions only if approved by the named Canadian official. No other amendments or versioning are recorded in the supplied material.

The supplied AD text contains no record of litigation, appeals, judicial review, or administrative disputes arising from the AD. It does not cite any court or tribunal decisions, nor does it mention any challenges, enforcement actions, or legal determinations in relation to AD/DHC-8/128. The only legal or regulatory instruments identified are the AD itself and a reference to Transport Canada AD CF-2006-15.

What can be stated from the source

• No litigated cases named or summarised. The AD does not name, summarise, or reference any legal proceedings. There are no identified cases, regulatory adjudications or judicial determinations in the document.

• Administrative signature. The AD is signed by James Coyne, identified as a Delegate of the Civil Aviation Safety Authority, dated 21 July 2006. The signing indicates administrative issuance but does not reflect any adversarial or judicial process.

• Implication for practitioners. Because the AD text contains no litigation history, counsel and compliance officers reading the AD must rely on the directive’s text, related service bulletins and any administrative guidance from CASA and Transport Canada for interpretation and dispute resolution. Any litigation history, enforcement actions or interpretive guidance not contained in this AD would need to be located in external sources, which are not part of this supplied material.

Absent any litigation or administrative challenge recorded in the AD, the document operates as a regulator-issued safety mandate with the technical references and compliance deadlines described elsewhere in this note. Any record of litigation or regulatory adjudication arising after issuance would not be reflected in the AD text provided.

The AD contains several specific, potentially overlooked details and conditional clauses that can affect compliance planning, record-keeping and maintenance choices. These are concrete traps for the unwary and procedural items that materially affect whether an operator must act, how, and by when.

• Narrow applicability by serial number and model. The AD applies only to DHC-8 Models 102, 103, 106, 201, 202, 301, 311, 314 and 315 with serial numbers 003 through 606. Aircraft outside these serial numbers or models are not covered by this AD as written. Verify the serial number range carefully; clerical mistakes in identifying serial numbers can lead to unnecessary work or failure to act on covered aircraft.

• Specific parts and station location. The AD identifies precise part numbers for the harness assemblies and seal assemblies and locates them at station Yw43.00. The inspections and repairs must target harnesses 82440073-001/301 and 82440074-001/301 and the aft seal assemblies 85350712-001 and 85350711-001. Worker familiarity with these part numbers and station markings is necessary to ensure inspections cover the correct hardware.

• Service Bulletin revision gating. The AD requires adherence to Bombardier SB 8-24-83, Revision A, dated 2 August 2005, but allows later SB revisions only if approved by the Chief, Continuing Airworthiness, Transport Canada. That approval step creates an administrative dependency: operators who prefer to use a later SB revision must obtain or verify the named Chief’s approval. Relying on an unapproved later SB revision would not meet the AD’s stated condition.

• Equivalence clauses are strictly limited and time-bound. The AD accepts prior inspections and seal modifications that were completed before the AD’s effective date in accordance with the original issue of SB 8-24-83. It also accepts prior incorporation of ModSum IS8Q2400005 as equivalent to ModSum 8Y122031 if done before the effective date. These equivalencies do not apply if the prior work was not performed in accordance with the original SB or was completed after the effective date. Documentation proving the timing and compliance with the original SB will be necessary to rely on these equivalences.

• Visual inspection only; hidden damage risk. Requirement 1 specifies a visual inspection for damage and repair "as required." Visual inspection may fail to detect internal conductor damage beneath insulation or under routing grommets; the AD does not mandate intrusive or electrical testing. The AD’s reliance on visual inspection means repair obligations may occur when visible damage is seen, but the AD does not specify additional non-visual tests, so operators must consider whether the SB prescribes more thorough checks.

• Single compliance window measured in hours TIS. The AD sets a single compliance deadline of 6 000 hours time in service. Operators must translate that hours requirement into operational scheduling. For high-utilisation aircraft, the 6 000-hour window may be short; for low-utilisation aircraft, it may be a long calendar period. The AD does not provide an alternative calendar deadline, so accurate TIS accounting is essential.

• No explicit record-keeping or reporting clause in the AD text. The AD does not state that an operator must submit compliance reports to CASA or Transport Canada, nor does it specify records retention requirements. Nevertheless, because the AD accepts prior work as compliant only if performed under the original SB, operators should retain and be prepared to produce maintenance records proving the timing and content of relevant work.

• Interplay with Transport Canada approvals and a foreign regulator. The AD requires approval by the Chief, Continuing Airworthiness, Transport Canada for later SB revisions. This ties Australian compliance procedures to a Canadian approval process for technical content, which can create administrative friction if operators must seek confirmations from a foreign authority or await confirmation that a later SB revision has been approved.

• Multiple system impacts referenced. The background notes that chafing may interrupt propeller feather control, AC electrical power, and standby hydraulic power. The AD focuses on harness inspection and ModSum installation but does not lay out contingency plans if component replacement or broader system repairs are needed, nor does it address dispatch limitations prior to AD compliance. Operators should note that damage to the harnesses could involve systems critical to safe flight.

• Absence of stated penalties or enforcement process in the AD. The AD sets out mandatory tasks and a deadline but does not specify penalties or enforcement mechanisms in the supplied text. Operators should not infer the absence of enforcement; regulators may rely on general aviation safety laws for compliance and enforcement actions.

• Scope of repairs tied to SB instructions. Repairs must be carried out "in accordance with the instructions contained in Bombardier Service Bulletin (SB) 8-24-83, Revision A, dated 2 August 2005, or later revisions approved by the Chief..." That means alternative repair methods, different part numbers, or non-SB procedures will require explicit regulatory approval to be treated as compliant.

These points are concrete, verifiable from the AD text, and they show where operators must be careful in interpretation and scheduling. The AD’s precise part numbers, station reference, SB and ModSum identifiers, and the approval gate for SB revisions are the principal detailed compliance friction points.

The AD prescribes a clear two-step mitigation approach and sets an explicit compliance window. The following operational checklist synthesises the actions required by the AD and highlights the documentation and approval steps that the AD conditions.

1. Confirm applicability

• Verify aircraft identity. Confirm the aircraft model and serial number fall within those specified: DHC-8 Models 102, 103, 106, 201, 202, 301, 311, 314 and 315 with serial numbers 003 through 606. If the aircraft is outside this list or the serial number is not within the listed range, the AD does not apply to it as written.

2. Determine prior compliance equivalence

• Check maintenance records for prior SB work. Determine whether the original issue of Bombardier SB 8-24-83 was implemented before the AD’s effective date (31 August 2006). If the original SB work was done pre-effective date in accordance with the original SB, those actions "satisfy the requirements of this Directive" and no further action under this AD is required related to that work.
• Check for prior ModSum. Determine whether Bombardier ModSum IS8Q2400005 was incorporated before the AD’s effective date. The AD treats that ModSum as equivalent to ModSum 8Y122031 if installed prior to the effective date.

3. Plan inspection and repair work in accordance with Bombardier SB 8-24-83 Revision A

• Obtain the correct SB. The AD requires inspection and repair per Bombardier SB 8-24-83, Revision A, dated 2 August 2005, unless a later revision has been approved by the Chief, Continuing Airworthiness, Transport Canada. Obtain and review Revision A; if a later revision is preferred, verify it has the required approval from the Chief, Continuing Airworthiness, Transport Canada before using it as the compliance method.
• Identify the targets. The inspections must cover left electrical cable harness assembly 82440073-001 (Models 100/200) or 82440073-301 (Model 300) attached to aft seal assembly 85350712-001, and right electrical cable harness assembly 82440074-001 (Models 100/200) or 82440074-301 (Model 300) attached to aft seal assembly 85350711-001, located at station Yw43.00.
• Visual inspection. Perform a visual inspection for chafing and damage of the identified harness assemblies in accordance with the SB’s procedures. If the SB provides a detailed inspection sequence, follow it exactly. The AD text states "visually inspect for damage and repair as required" according to the SB.

4. Repair as required

• Follow SB repair instructions. If the visual inspection reveals chafing or damage, carry out repairs "in accordance with the instructions contained in Bombardier Service Bulletin (SB) 8-24-83, Revision A, dated 2 August 2005, or later revisions approved..." Ensure all repair parts, routing, clamps, grommets or other remedies specified by the SB are installed per the SB’s methods.
• Document repairs. Maintain maintenance records that identify the work done, parts used, work order references and date/time in service when the repairs were completed. Although the AD does not explicitly mandate reporting, the AD recognises prior work as satisfying requirements only if performed as specified; documentation will be necessary to evidence compliance.

5. Incorporate ModSum 8Y122031

• Install ModSum 8Y122031. Rework the seal assemblies to create clearance between the electrical cable assemblies and the edge of the fairing panel by incorporating Bombardier ModSum 8Y122031 following the instructions contained in Bombardier SB 8-24-83, Revision A (or later approved revision). The AD treats incorporation of ModSum IS8Q2400005 prior to the effective date as equivalent to ModSum 8Y122031.
• Schedule for downtime. Plan for the hours and facilities necessary to perform the ModSum installation. The AD requires the ModSum to be installed within the same 6 000 hours time-in-service compliance window that applies to the inspection and repair.

6. Meet the compliance deadline

• Calculate compliance threshold. Both Requirement 1 (inspection/repair) and Requirement 2 (ModSum installation) must be completed "Within 6 000 hours time in service after the effective date" of 31 August 2006. Translate that into the aircraft’s TIS at the time of issuance and plan completion before the TIS reaches the 6 000-hour threshold.
• Avoid ambiguity. Ensure that all work is completed and logged before the TIS threshold to avoid operating a non-compliant aircraft beyond the AD-specified window.

7. Obtain approvals for any alternative procedures or later SB revisions

• Seek Chief approval for later SB revisions. If an operator intends to follow a later revision of Bombardier SB 8-24-83, confirm that the later revision has been explicitly approved by the Chief, Continuing Airworthiness, Transport Canada before relying on it for AD compliance.
• Seek regulatory approval for non-SB alternatives. If an operator wishes to use an alternative repair method or different parts than those in the SB, formal approval from the regulator would be required. The AD text does not provide a specific alternative means of compliance mechanism but conditions any variation on regulatory approval processes.

8. Record-keeping and evidence

• Retain maintenance records. Keep documentation that proves when the inspection, any repairs, and ModSum installation were completed, what procedures were followed (SB revision used), parts installed (part numbers and serials where applicable), and the aircraft’s time in service at the time of completion. Although the AD does not contain an express reporting requirement, proof of timing and conformity with the SB is necessary to rely on the AD’s equivalence clauses and to demonstrate compliance if audited.

9. Coordinate with regulators and manufacturer where appropriate

• Refer to Transport Canada AD CF-2006-15. Because the AD notes that the Transport Canada AD "refers," review that AD to confirm any technical alignments or differences and to verify whether the Chief, Continuing Airworthiness, Transport Canada has approved any later SB revisions.
• Liaise with CASA. If there is any uncertainty about interpretations of the AD, seek guidance or confirmation from CASA, particularly regarding documentation sufficiency or the acceptability of earlier ModSum incorporation.

10. Operational precautions pending compliance

• Avoid operating with known damage. The AD identifies the safety risk of chafing leading to loss of propeller feather control and other system interruptions. If chafing or damage is detected, carriage of the aircraft pending repair should be managed in accordance with safety and airworthiness rules and operator procedures. The AD does not set dispatch limitations; however, operators should manage the operational consequences consistent with accepted safety practices.

Following this checklist and strictly using Bombardier SB 8-24-83 Revision A (or later revisions only after the named regulatory approval) will implement the AD’s technical requirements. Documentation of prior SB work or prior ModSum installation is essential to establish equivalence and avoid unnecessary duplicative work.