AD/DHC-8/113 - Fuel & Hydraulic Tubes Chafing

The directive rests on a small set of technical and administrative concepts that determine scope, required work, and timing.

Applicability. The AD applies only to Bombardier DHC-8 Series 400 aeroplanes, serial numbers 4003 through 4089. This is an explicit scope limitation in the "Applicability" line. That confines the directive to a defined production range rather than the entire DHC-8 family.

Unsafe condition and root cause. The background states the unsafe condition and its mechanical cause: "Service difficulty reports indicate there is a potential for chafing of fuel and hydraulic tubes with the fairlead plate where the tubes pass through the firewall." The mechanism is described: titanium plates attached to the fairleads have close tolerance holes; "If the tubes are not centred in the fairlead plate, nacelle flexing can cause a fouling condition, which may cause chafing of the tubes, leading to leakage of fluid creating an unsafe condition." The hazard is fluid leakage (fuel and hydraulic fluid) originating from chafed tubes at firewall fairleads.

Corrective action. The AD prescribes installation of Bombardier Modsum 4-113438 , modified fairlead plate assemblies , as the required remedial measure. The specified method of compliance is Bombardier Service Bulletin 84-54-09 dated 23 January 2004, with allowance for "later revisions approved by Transport Canada." Thus the SB provides the approved technical procedure and parts list to accomplish the Modsum installation.

Interplay with existing modifications and temporary rework. The AD explicitly recognises that prior temporary rework and production modifications exist. Bombardier issued System Drawings SYD 84-28-002 and SYD 84-29-006 as temporary rework instructions to enlarge tolerance holes, and production Modsum 4-184079 and Modsum 4-184081 were issued to introduce the intent of those SYDs for production aircraft. The AD treats aircraft differently depending on whether these drawings or Modsum production modifications have already been incorporated.

Two-tier compliance timing. The AD sets two discrete time-in-service (TIS) windows for compliance. For aircraft without the SYDs or production Modsum incorporations, the required action must be completed within 500 hours TIS after the AD effective date. For aircraft with those incorporations, the required action must be completed within 4,000 hours TIS after the effective date. The two-tier schedule recognises existing mitigations but still requires the Modsum installation within a longer timeframe when temporary or production rework is already present.

Regulatory linkage. The AD references Transport Canada by name: the SB must be "or later revisions approved by Transport Canada," and the directive includes the line "Note: Transport Canada AD CF-2004-07 refers." The AD therefore links its approved compliance method and the applicable precedent AD to Transport Canada approvals.

Administrative form and effective date. The AD is presented as an official CASA instrument, signed by "Jayaprakashan Ambali, Delegate of the Civil Aviation Safety Authority" on 21 February 2006, and it specifies "This Airworthiness Directive becomes effective on 13 April 2006." These administrative elements set the legal operational timeline for operators.

Together, those concepts determine which aircraft must comply, what physical modification must be performed, what documentation controls the method, and the time allowed for completing the work based on prior modification status.

The directive identifies a narrow set of actors who are directly affected and a broader set of practical stakeholders.

Primary addressees. The direct, named addressees are the operators and maintainers of Bombardier DHC-8 Series 400 aeroplanes with serial numbers 4003 through 4089. The "Applicability" clause explicitly limits the AD to those serial numbers. Those operators are legally obliged to meet the AD requirements for any aircraft they operate within that serial range.

Maintenance providers and repair stations. Any maintenance organisation contracted to perform the Modsum 4-113438 installation will be affected, because they must perform the work to the Bombardier Service Bulletin SB 84-54-09 referenced in the AD, or to a later revision approved by Transport Canada. That requires access to the SB, the Modsum kit or parts, and competency to carry out the prescribed alterations.

Aircraft lessors and owners. Owners and lessors of the affected serial-numbered aircraft are stakeholders because the AD requires a physical modification to the aircraft. They will need to ensure that lessees or operators schedule and fund the modification within the AD-prescribed timelines. The AD does not distinguish between owner and operator obligations; instead it sets mandatory technical work tied to the aircraft serial numbers.

Supply chain and parts manufacturers. Bombardier is identified as the originator of the Modsum and the SB. The directive implicitly affects Bombardier's supply chain, since Modsum 4-113438 and any associated parts will be procured and installed; Bombardier Service Bulletin 84-54-09 is the method of compliance. The AD also refers to previously issued System Drawings and production Modsum numbers (SYD 84-28-002, SYD 84-29-006, Modsum 4-184079, Modsum 4-184081), so production tooling and historic supplier actions are relevant.

Regulatory authorities. The Civil Aviation Safety Authority is the issuing authority, as shown by the signature block and effective date. Transport Canada is referenced as the approving authority for SB revisions and as the source of a related AD (Transport Canada AD CF-2004-07). Those two regulators are implicated , CASA as issuer and Transport Canada as approver for the SB revisions and as the source AD referred to.

Operational personnel. Flight crews and engineers are indirectly affected because the AD addresses fuel and hydraulic system integrity. The maintenance requirement reduces the risk of in-service fluid leaks that could affect aircraft safety and dispatch reliability. The AD’s compliance windows may require aircraft downtime and scheduling changes.

Insurance and risk managers. While not mentioned in the directive text, any parties responsible for operational risk or insurance underwriting for affected aircraft will be impacted by the need to meet the AD’s compliance dates, because non-compliance could expose the operator or owner to uninsurable or uninsured operational risk. The AD itself, however, contains no explicit discussion of insurance.

In summary, the mandatory range of aircraft serials defines who pays for and arranges the work: operators and owners of DHC-8-400 serials 4003-4089, maintenance organisations who carry out the SB, Bombardier as supplier of the Modsum and SB, and CASA and Transport Canada as the issuing and approving authorities respectively.

The directive imposes a single clear duty and supplies limited procedural choices.

Primary duty: install Modsum 4-113438. The fundamental obligation is stated in Requirement: irrespective of prior work status, the AD requires installation of Bombardier Modsum 4-113438 (modified fairlead plate assemblies). The AD gives the procedural vehicle for that installation as Bombardier Service Bulletin 84-54-09 dated 23 January 2004, or later revisions "approved by Transport Canada."

Timing duties tied to prior modification status. The AD divides the fleet into two groups for compliance timing:

• Aircraft without Bombardier Systems Drawings SYD 84-28-002 and SYD 84-29-006 incorporated, or without Modsum 4-184079 and Modsum 4-184081 incorporated, must have Modsum 4-113438 installed "within 500 hours time in service after the effective date of this directive."

• Aircraft with those SYDs or Modsum 4-184079 and 4-184081 already incorporated must have Modsum 4-113438 installed "within 4,000 hours time in service after the effective date of this directive."

Therefore the duty is conditional on an operator’s record of prior incorporation of the specified temporary or production rework.

Method of work: SB and approvals. The AD delegates the technical compliance method to Bombardier’s SB 84-54-09, but restricts acceptable SB revisions to those "approved by Transport Canada." That creates a constraint on acceptable procedures: operators must use either the stated SB date or a later SB revision only if Transport Canada has approved it. The AD does not itself list alternative methods of compliance or equivalent procedures; none are included in the text supplied.

Record and scheduling duty implicit. While the AD text specifies hours-in-service windows, it does not explicitly set record-keeping rules or require specific forms. However, compliance with the AD requires operators to track aircraft time-in-service and the incorporation status of the cited SYDs and Modsum numbers to determine which compliance period applies. That is an operational duty implied by the time-based compliance schedule.

Rights or choices. The directive offers limited choice: operators can use a later revision of SB 84-54-09 only if it is "approved by Transport Canada." The AD itself does not provide alternative corrective actions, nor does it offer an extended compliance timeframe, exemptions, or delegation of compliance to third parties. The only procedural discretion evident in the text is the choice of which SB revision to use, constrained by Transport Canada approval.

No penalties or enforcement mechanism stated in the text. The AD specifies mandatory actions and effective date but does not include explicit penalties, sanctions, or enforcement procedures in the supplied text. Rights to seek exemptions, extensions, or alternative methods are not contained within the text provided.

In practice, the key duties are: determine applicability by serial number, determine which compliance window applies by checking incorporation of specified SYDs or Modsum numbers, and install Modsum 4-113438 per Bombardier SB 84-54-09 (or later Transport Canada-approved revision) within the prescribed TIS window. The AD does not elaborate rights to vary those duties within its own text.

The text of AD/DHC-8/113 itself contains no express penalties, fines, or administrative sanction provisions. The directive sets mandatory technical actions, specifies the method of compliance (Bombardier SB 84-54-09 or later revisions approved by Transport Canada), and sets effective and compliance dates. It does not, within the supplied material, include a clause that details enforcement procedures, civil or criminal penalties, or remedial enforcement mechanisms for non-compliance.

What the document does specify for enforcement context is administrative identification and timing: the AD is signed by "Jayaprakashan Ambali, Delegate of the Civil Aviation Safety Authority" on 21 February 2006, and states "This Airworthiness Directive becomes effective on 13 April 2006." Those administrative facts locate responsibility for issuing the directive with CASA and establish the date from which the compliance windows (500 hours or 4,000 hours time in service) are to be measured.

The directive includes a note referring to "Transport Canada AD CF-2004-07" and requires the SB or later revisions to be "approved by Transport Canada." This creates an inter-authority compliance link, but the AD text does not itself describe enforcement steps or identify enforcement authorities beyond the issuing delegate.

Absent explicit penalty language in the supplied AD, the text leaves unspecified the remedies or enforcement processes for failure to comply. The AD does impose time-limited mandatory technical work; the document makes that mandate clear, but it does not spell out enforcement consequences, inspection regimes, or certificate actions. Any enforcement action, sanctions, or administrative penalties that may result from non-compliance are not set out in the text provided and would need to be identified from other regulatory instruments or CASA enforcement policies that are not part of the supplied document.

Therefore, from the AD as supplied: it is an instrument that imposes mandatory obligations with specified timelines and an effective date, while not listing penalties or enforcement mechanisms in the body of the directive text.

The AD text explicitly references a linked overseas authority and Bombardier's own documentation, and it recognises prior design reworks and production Modsum incorporations. Those references define the interaction points between this AD and other normative instruments and technical documents.

Reference to Transport Canada. The AD requires use of Bombardier Service Bulletin 84-54-09 "or later revisions approved by Transport Canada." It also contains the note "Transport Canada AD CF-2004-07 refers." That indicates two interactions: first, procedural interaction with Transport Canada’s SB revision approvals; second, substantive linkage to a Transport Canada AD (CF-2004-07) as a related instrument. The AD thereby incorporates an external regulator’s approvals as the gating mechanism for acceptable SB revisions.

Interaction with Bombardier system drawings and Modsum history. The AD describes Bombardier System Drawings SYD 84-28-002 and SYD 84-29-006 which were issued as temporary rework instructions to enlarge tolerance holes, and production Modsum 4-184079 and Modsum 4-184081 which implemented the SYD intent for production aircraft. The AD distinguishes compliance timing based on whether an aircraft already has the SYDs or those Modsum production incorporations. Thus, prior compliance with Bombardier-issued engineering drawings and Modsum production reworks affects the AD compliance timeline. The AD thereby treats manufacturer engineering documentation as relevant to regulatory compliance timing.

Service Bulletin as regulatory method. The AD delegates detailed technical procedures to Bombardier SB 84-54-09 (dated 23 January 2004). The AD does not itself contain step-by-step instructions; instead it prescribes the SB as the means of compliance, and it conditions acceptable alternative SB revisions on Transport Canada approval. That creates a direct interaction between the AD and Bombardier’s technical publications, with an external regulator’s approval filter.

No other domestic statutes or regulations are cited. The supplied AD text does not reference other Australian Acts, Civil Aviation Regulations, or enforcement provisions. The document’s cross-reference to Transport Canada is the only inter-jurisdictional or inter-instrumentary linkage present in the text provided.

Implication for records and maintenance data. The AD’s reliance on prior incorporation of certain Modsum and SYD work means that maintenance records and historical compliance with manufacturer drawings are functionally relevant to satisfying the AD. Operators will need to reference their maintenance logs to establish which compliance window applies. While the AD does not specify record-keeping requirements, the interaction with prior modification history is explicit.

In sum, the AD interacts with other instruments principally by: (a) requiring compliance per a named Bombardier SB and conditioning later revisions on Transport Canada approval; (b) referencing and differentiating aircraft by prior incorporation of Bombardier SYDs and production Modsum numbers; and (c) referring to a Transport Canada AD as related material. No other statutory or regulatory dependencies are stated in the supplied text.

The AD’s own amendment history within the supplied text is limited and must be stated as presented.

Dates and issuance. The directive is identified as AD/DHC-8/113 dated 4/2006. The signature block records the issuer and date: "Jayaprakashan Ambali, Delegate of the Civil Aviation Safety Authority" with the date 21 February 2006. The AD specifies an effective date: "This Airworthiness Directive becomes effective on 13 April 2006."

Service Bulletin date and approval pathway. The AD bases the required modification on Bombardier Service Bulletin 84-54-09 dated 23 January 2004, or "later revisions approved by Transport Canada." By including that phrase, the AD allows for later revisions of the SB to be used for compliance, provided Transport Canada approval exists. The AD text thus contemplates future, Transport Canada-approved revisions to the Bombardier SB as acceptable compliance vehicles. The AD itself does not list any revisions or amendments beyond the initial SB date; it leaves the avenue open for subsequent SB revisions subject to Transport Canada approval.

Prior Bombardier temporary drawings and production Modsum issuance. The AD summarises Bombardier’s prior technical issuances that are relevant to aircraft configuration and AD applicability: System Drawings SYD 84-28-002 and SYD 84-29-006 (temporary rework instructions), and Modsum 4-184079 (hydraulic) and 4-184081 (fuel) as production rework. These pre-existing documents are part of the historical change path to which the AD responds. The AD itself does not amend these earlier documents; instead it acknowledges them and sets compliance timeframes depending on whether they have been incorporated.

Reference to Transport Canada AD CF-2004-07. The AD contains a short note: "Note: Transport Canada AD CF-2004-07 refers." That records a linkage to an earlier Transport Canada AD, which in effect is part of the regulatory history relevant to the same technical issue. The AD does not reproduce or summarise the Transport Canada AD in the text provided.

No subsequent amendments recorded in the supplied text. The document as supplied does not include any later revisions or amending instruments to AD/DHC-8/113 itself. The AD allows for later revisions of the Bombardier SB to be used but does not show any later amendments to the AD directive text, nor any revocations or extensions. Any amendment history beyond the issuance and effective dates, or any changes made after 21 February 2006, is not present in the supplied material.

Therefore, within the text provided, the amendment history is limited to: SB 84-54-09 exists dated 23 January 2004; the AD was issued 21 February 2006; and the AD became effective 13 April 2006. The AD permits later, Transport Canada-approved SB revisions to be used for compliance, but no specific subsequent revisions are listed in the directive text supplied.

The supplied AD text contains no litigation history. It does not reference any court proceedings, administrative appeals, judicial review, or disputes related to AD/DHC-8/113. There is no mention of any legal challenges to the AD, nor any enforcement actions, settlements, or cases arising from non-compliance recorded in the document.

The only legal-regulatory cross-reference in the document is to a Transport Canada AD (CF-2004-07) and to Transport Canada approval of Service Bulletin revisions, neither of which the AD characterises as having associated litigation. The AD’s background and technical narrative are framed around service difficulty reports and Bombardier-issued drawings and Modsum actions, not adjudicated disputes.

As the supplied material contains no litigation record or references to judicial or administrative cases, no litigation history can be reported from this source. Any actual litigation or dispute history would have to be located in external records that are not part of the text provided.

Several practical and interpretive risks arise from the AD’s wording and structure that operators and maintainers should note. These are drawn strictly from the text provided.

Limited applicability window by serial number. The AD applies only to DHC-8 Series 400 aircraft serial numbers 4003 through 4089. Aircraft outside that serial range are not covered by the directive as written. An operator who overlooks the specific serial-number limitation may either overapply compliance requirements to unaffected aircraft or, conversely, fail to apply the AD to an in-range aircraft. The AD does not provide flexibility on applicability beyond those serial numbers.

Two different compliance windows contingent on prior modifications. The AD sets two different time-in-service deadlines: 500 hours for aircraft without SYD 84-28-002/SYD 84-29-006 or Modsum 4-184079/4-184081, and 4,000 hours for aircraft with those incorporations. Operators must verify historical incorporation of the specified SYDs or Modsum numbers to determine the correct compliance window. Ambiguity or gaps in maintenance records could cause misclassification, leading to missed deadlines or unnecessarily accelerated work.

The AD requires use of a Service Bulletin subject to Transport Canada approval. The directive prescribes Bombardier SB 84-54-09 dated 23 January 2004, or "later revisions approved by Transport Canada." That phrase creates a dependency: an operator cannot rely on a later SB revision unless it has been approved by Transport Canada. Using an unapproved revision could fail to meet the AD requirement as written. Operators must check the approval status of any later SB revision; the AD text itself does not provide the approval status, only the condition.

Overlap with temporary rework. Bombardier issued System Drawings SYD 84-28-002 and SYD 84-29-006 as temporary rework instructions to enlarge tolerance holes. The AD treats those as existing mitigations but still requires installation of Modsum 4-113438 within the AD-prescribed windows. An operator who relies on earlier SYD work must note that the AD nevertheless mandates the Modsum installation within 4,000 hours TIS. Temporary fixes are not treated as full compliance with the AD.

No enforcement or penalty specifics in text. The AD does not state penalties, so operators cannot find enforcement procedures or remedial paths within the document. If an operator seeks to understand consequences for non-compliance, that information is not in the supplied AD and must be sought in other regulatory materials.

Potential for confusion over numbering and wording. The Requirement section repeats closely similar phrasing for "For aircraft without..." and "For aircraft with..." and then lists the same Modsum and SB requirement for each. Readers may be tempted to read the first as the only requirement; careful reading is required to map each requirement to its corresponding compliance timeframe. The Compliance section separates two time windows numerically (1 and 2), but does not explicitly restate which window applies to which Requirement paragraph. The intended mapping appears to be: Requirement paragraph 1 corresponds to Compliance item 1 (500 hours) and Requirement paragraph 2 corresponds to Compliance item 2 (4,000 hours). Operators should confirm that mapping when planning.

Timing between issue and effective date. The AD was signed on 21 February 2006 and "becomes effective on 13 April 2006." That gap means that the compliance clock is measured from 13 April 2006; operators must schedule work in reference to that effective date. Misreading the effective date as the issue or sign date could lead to scheduling errors.

No alternative methods of compliance in the text. The AD does not list acceptable equivalent modifications or specific procedures for seeking alternative compliance; if an operator believes an alternative measure addresses the unsafe condition, the mechanism for approval is not included in the directive text. The only expressly permitted alternative is using a later SB revision if approved by Transport Canada.

Transport Canada linkage may create cross-jurisdictional steps. The AD conditions SB revision acceptability on Transport Canada approval and references a Transport Canada AD. Operators may need to consult or coordinate with Transport Canada records to confirm approved SB revisions. This cross-reference is a gotcha for those who assume CASA alone governs acceptable SB revisions.

In sum, the key operational traps are: precise serial-number applicability; the need to determine prior Modsum/SYD incorporation to select the correct compliance window; reliance on a Service Bulletin only when it is Transport Canada-approved for later revisions; potential record-keeping gaps; and absence of enforcement details in the AD text.

The AD specifies a concise path to compliance. The steps below are drawn from the AD text and reproduce the required decision points and actions.

1. Ascertain aircraft applicability by serial number. Confirm the aircraft's serial number is within the AD applicability range: DHC-8 Series 400, serial numbers 4003 through 4089. The AD's "Applicability" line is definitive.

2. Determine existing configuration status. Check maintenance and modification records to establish whether any of the following have been incorporated:

   • Bombardier Systems Drawing SYD 84-28-002, Issue 1 or later approved revisions; and
   • Bombardier Systems Drawing SYD 84-29-006, Issue 1 or later approved revisions; or
   • Modsum 4-184079 (hydraulic) and Modsum 4-184081 (fuel) production reworks.

   The AD differentiates compliance timing based on whether these SYDs or Modsum incorporations are present.

3. Identify the applicable compliance window. Use the AD’s two-tier timing scheme:

   • If the aircraft does not have SYD 84-28-002 and SYD 84-29-006 incorporated, or does not have Modsum 4-184079 and 4-184081 incorporated, the Modsum 4-113438 installation must be completed within 500 hours time in service after the AD effective date (13 April 2006).

   • If the aircraft already has SYD 84-28-002 and SYD 84-29-006 incorporated, or has Modsum 4-184079 and 4-184081 incorporated, the Modsum 4-113438 installation must be completed within 4,000 hours time in service after the AD effective date.

4. Obtain the required SB and parts. The AD mandates installation "using Bombardier Service Bulletin (SB) 84-54-09, dated 23 January 2004, or later revisions approved by Transport Canada." Obtain SB 84-54-09, the Modsum kit 4-113438 and any associated parts lists or tooling specified. If considering a later SB revision, confirm that Transport Canada has approved that revision; the AD permits only revisions "approved by Transport Canada."

5. Schedule and perform the Modsum 4-113438 installation. Arrange for maintenance personnel competent in the SB procedure to perform the modified fairlead plate assembly installation. The AD requires the installation of the Modsum; the AD text itself delegates the detailed method to the Bombardier SB.

6. Record completion. Although the AD text does not prescribe specific record-keeping forms, operators must retain evidence the Modsum has been installed and the SB has been complied with within the specified TIS window. Record entries should include the Modsum number installed, SB reference and revision, date and time-in-service at completion, and sign-off by authorised maintenance personnel to demonstrate compliance.

7. Verify related temporary measures. The AD notes that Bombardier issued System Drawings to provide temporary rework instructions to enlarge tolerance holes. If such temporary rework was performed, note that it does not eliminate the AD requirement; it only alters the time window applicable. Ensure the final Modsum 4-113438 installation is still completed within the applicable deadline.

8. Use approved procedures only. Do not substitute an unapproved SB revision or an alternative modification without documented approval from the relevant authority. The AD explicitly limits acceptable SB revisions to those approved by Transport Canada.

9. Plan for aircraft downtime and parts lead time. The AD does not specify how long the Modsum installation will take, but maintenance planning should account for parts availability and scheduled aircraft downtime within the required TIS window. This is necessary to meet the 500- or 4,000-hour deadline after the AD effective date.

10. Cross-reference regulatory documents as needed. The AD notes "Transport Canada AD CF-2004-07 refers." Operators may wish to consult that AD and Transport Canada approvals for context and to confirm SB revision approvals. The AD itself conditions SB revision acceptability on Transport Canada approval.

By following those steps derived from the AD text , confirm serial number applicability, establish prior SYD/Modsum incorporation status, obtain SB 84-54-09 or a Transport Canada-approved later revision, install Modsum 4-113438 within the applicable TIS window, and document the work , an operator conforms to the directive as written. The AD does not provide competing alternative compliance pathways or specified enforcement mechanisms in the text provided; compliance must therefore be achieved by the steps spelled out in the directive and its referenced SB.