AD/DHC-8/114 - Pitch Trim Control

The AD is built around a small set of interlocking technical and administrative concepts.

Applicability: The AD applies to a defined population , DHC-8 Models 400, 401 and 402 aeroplanes, serial numbers 4001 through 4065. The AD sets different corrective scopes inside that population: one Modsum is limited to S/N 4001-4058 (Modsum 4-113405), while the other covers S/N 4001-4065 (Modsum 4-113392). The AD thus creates overlapping but non-identical applicability bands; operators must check each airframe against serial numbers and Modsum applicability in the Requirement table.

Modsum-driven hardware/software change: The required rectifications are expressed as incorporation of Modsums. For Modsum 4-113405 the AD specifies changing FGM hardware/software from P/N C12429AA06 to C12429AA07 and performing a Return to Service Procedure. For Modsum 4-113392 the AD requires replacing specific FCECU P/Ns (398500-1001 or 398500-1003) with FCECU P/N 398500-1005. The AD therefore prescribes discrete parts swaps and demands the completion of defined service-bulletin procedures.

Approved technical documentation and foreign authority approvals: Each Modsum is implemented via Bombardier Service Bulletins (SB 84-22-04 for the FGM change; SB 84-27-14 for the FCECU change). The AD explicitly recognises those SBs “or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada” as the approved instructions for compliance. The AD further cross-references a Transport Canada AD (CF-2002-25) and identifies Transport Canada’s Chief, Continuing Airworthiness as the approval authority for referenced SB revisions. This embeds cross-jurisdictional technical approvals into the compliance framework.

Interim maintenance procedures: Until the Modsums are incorporated, the AD permits use of specified Bombardier Service Letters as “approved maintenance procedure[s]” to confirm serviceability or restore function after a failure. These interim procedures are explicitly identified and dated: SL DH8-400-SL-22-001D (8 November 2001) for autopilot pitch trim failures and SL DH8-400-SL-27-003 (22 May 2001) for manual pitch trim loss.

Operational symptom definitions for diagnosis: The AD offers operational signatures for the two malfunctions. The autopilot pitch trim failure is characterised by display messages “AP PITCH TRIM FAIL” followed by “AUTO TRIM FAIL” after manual disengagement of the autopilot. The manual pitch trim failure is characterised by illumination of the “PITCH TRIM” Caution Light and concurrent loss of pitch trim function during manual input. These diagnostic markers inform maintenance triage and choice between interim procedure or Modsum incorporation.

Time-bound compliance: The AD fixes a uniform compliance interval: both Requirements 1 and 2 must be complied with “within 30 days after the effective date of this Directive.” The AD provides a single effective date: 13 April 2006.

Authority and signature: The AD is issued under CASA authority, signed by James Coyne, Delegate of the Civil Aviation Safety Authority, dated 2 March 2006. The document carries the AD identification AD/DHC-8/114 and the heading “Pitch Trim Control 4/2006.”

Taken together, the AD sets a defined operator population, prescribes physical part replacements and a Return to Service action for one Modsum, recognises specified interim maintenance measures, issues an externally referenced approval mechanism (Transport Canada), and imposes a 30-day compliance deadline from a stated effective date.

The AD directly affects operators and maintenance providers responsible for DHC-8 Models 400, 401 and 402 aeroplanes with serial numbers in the ranges specified. The Applicability line expressly limits the AD to “DHC-8 Models 400, 401 and 402 aeroplanes, serial numbers (S/N) 4001 through 4065.” That identifies a bounded fleet for which the Requirements apply.

Operators: The operator of each affected aeroplane is the immediate obliged party, because the Requirements prescribe replacement of equipment (FGM units and FCECUs) and performance of a Return to Service Procedure. Compliance tasks (parts procurement, scheduling downtime, applying SB procedures and associated paperwork) fall on the operator and their contracted maintenance organisations, because the AD uses imperative language (“incorporate Modsum...”, “removing... and replacing with...”, “perform a Return to Service Procedure”).

Maintenance organisations and certifying staff: The AD refers to Bombardier SBs and Service Letters as the approved means of compliance and requires performance of particular maintenance steps. That places responsibility on mechanics and certifying engineers to implement the prescribed parts changes and procedures in accordance with the service documentation referenced in the AD. The requirement to “perform a Return to Service Procedure” for Modsum 4-113405 is an explicit maintenance action that triggers the need for competent certifying personnel to sign release-to-service paperwork.

Parts suppliers and supply chains: The AD identifies specific part numbers (FGM P/N C12429AA06 to C12429AA07; FCECU P/Ns 398500-1001/1003 to replacement 398500-1005). Suppliers who stock, manufacture or distribute those parts will see demand from affected operators. The AD also implicitly affects logistics and spare holdings because operators must source the specified P/N replacements within the 30‑day compliance window.

Regulatory authorities and approvals: Two regulatory actors appear in the AD. CASA is the issuing authority; the AD is signed by a CASA delegate, James Coyne, dated 2 March 2006, and gives an effective date of 13 April 2006. The AD also references Transport Canada: the Bombardier SBs are accepted “or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada,” and Note 3 explicitly refers to Transport Canada AD CF-2002-25. Thus, both CASA and Transport Canada are part of the compliance and approval framework the AD sets out.

Flight crew and operational planners: The Background section states the malfunctions “can, under adverse conditions, significantly increase flight crew workload.” Flight crews of affected aeroplanes are stakeholders because the operational symptoms (display messages and caution lights) affect cockpit indications and determine whether interim procedures or limitations apply prior to completion of the Modsums.

Insurance and lessors: The AD does not mention insurers or lessors specifically. However, any party with an interest in airworthiness and regulatory compliance of affected aeroplanes , including lessors and insurers , would be attentive to the AD’s requirements because they affect the aircraft’s maintenance status and approved configuration. The AD does not instruct how contractual parties must allocate costs; it mandates technical compliance by operators.

Geographical and jurisdictional scope: Although issued by CASA, the AD explicitly relies on Bombardier documents and Transport Canada approvals. Note 3 states “Transport Canada AD CF-2002-25 refers.” That indicates the AD is situated in a cross-jurisdictional regulatory environment where Transport Canada actions and approvals are relevant to compliance.

In short, the direct burden attaches to operators and the maintenance ecosystem supporting the specified DHC-8 airframes; regulatory oversight is shared implicitly between CASA and Transport Canada as signalled in the AD text.

Key duties under the AD are specific, time-bound and technical. The AD places obligations on operators and maintenance organisations to perform the defined replacements and procedures within the prescribed time.

Mandatory duties

• Identify affected aeroplanes: Operators must determine whether their aeroplanes fall within the applicability band, i.e. DHC-8 Models 400, 401 and 402 S/N 4001 through 4065. The Applicability section sets the universe to which the subsequent Requirements apply.

• Incorporate Modsum 4-113405 for S/N 4001-4058: For aeroplanes in that serial-number band, the AD requires incorporation of Modsum 4-113405 by replacing/reworking FGM1 and FGM2 P/N C12429AA06 with/to FGM P/N C12429AA07 and performing a Return to Service Procedure. The AD directs operators to Bombardier Service Bulletin 84-22-04 dated 29 November 2001 (or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada) for approved instructions. This is expressed as Requirement 1.

• Incorporate Modsum 4-113392 for S/N 4001-4065: For aeroplanes S/N 4001 through 4065, the AD requires removal of FCECUs P/N 398500-1001 or P/N 398500-1003 and replacement with FCECU P/N 398500-1005. Bombardier SB 84-27-14 dated 16 January 2002 (or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada) is the approved procedure. This is Requirement 2.

• Comply within 30 days of effective date: The Compliance section states “For Requirements 1 and 2 - Within 30 days after the effective date of this Directive.” The AD becomes effective on 13 April 2006; therefore the duties are time-bound to that effective date.

• Use approved interim procedures where applicable: The AD explicitly allows specified Bombardier Service Letters as “approved maintenance procedure[s]” until the corresponding Modsum is incorporated. Note 1 allows SL DH8-400-SL-22-001D (8 November 2001) as an interim procedure for autopilot pitch trim failure; Note 2 allows SL DH8-400-SL-27-003 (22 May 2001) for manual pitch trim loss.

Rights and administrative contours

• Approved revisions: The AD permits compliance using the Bombardier SBs “or later revisions, approved by the Chief, Continuing Airworthiness, Transport Canada.” That gives operators a right to rely on later SB revisions so long as the Chief, Continuing Airworthiness (Transport Canada) approves those revisions. This creates a defined approval pathway for updated technical instructions.

• Diagnostic clarity: The AD provides the operational signatures for failures (“AP PITCH TRIM FAIL”, followed by “AUTO TRIM FAIL” after AP disengagement; illumination of the “PITCH TRIM” Caution Light with concurrent loss of pitch trim function). Operators and maintenance personnel have the right to use these symptom descriptions to identify which interim procedure or Modsum is applicable.

• Use of interim measures: Until the permanent Modsums are incorporated, operators may use the identified Service Letters as an “approved maintenance procedure” to confirm serviceability or to restore autopilot/pitch trim use after failure. The AD therefore recognises and authorises limited short-term mitigations.

Delegated authority and approvals

• CASA issuance: The AD is issued under CASA authority and signed by a CASA delegate (James Coyne), which establishes the directive’s regulatory provenance.

• Transport Canada approval role: The AD places a practical approval gate with Transport Canada’s Chief, Continuing Airworthiness , revisions to Bombardier SBs must be approved by that office to be acceptable under the AD. The AD therefore locates a specific external approval right and gate with Transport Canada.

What the AD does not state

• The AD does not set out a penalty regime or enforcement measures in the text. It also does not allocate financial responsibility between operators and other commercial parties. It is a technical airworthiness instrument requiring corrective action and specifying approved procedures and timescales; it leaves contractual and cost questions to the parties involved, and leaves enforcement details outside the AD text.

In short, the AD creates clear technical duties (identified aeroplanes, replace or rework specified parts, perform Return to Service Procedure) with a 30-day compliance deadline, while recognising interim authorised measures and an approval pathway for later service-bulletin revisions through Transport Canada.

The AD text itself does not enumerate monetary fines, licence suspensions, or criminal sanctions. The document sets mandatory maintenance actions and a compliance date, but it does not include express penalty provisions or describe enforcement mechanisms within its wording.

What the AD contains

• Mandatory actions and timeframe: The AD prescribes two mandatory technical actions and fixes a compliance interval “within 30 days after the effective date of this Directive.” The AD becomes effective on 13 April 2006. Those actions are stated as Requirements 1 and 2 in the body of the AD, and the directive is presented as a regulatory instrument signed by James Coyne, Delegate of the Civil Aviation Safety Authority.

• Regulatory provenance: The AD is issued by CASA and signed by its delegate, which gives the document regulatory authority. The signature block reads “James Coyne, Delegate of the Civil Aviation Safety Authority, 2 March 2006.” The document carries a formal AD identifier AD/DHC-8/114 and an effective date.

What the AD does not specify

• No penalties within the AD text: The AD does not mention specific statutory provisions that prescribe penalties for non-compliance, nor does it include an explicit enforcement process, notice regime, or appeal pathway. The AD does not provide information about consequences such as grounding, fines or licence actions in its own text.

• Enforcement implied by regulatory context: Because the AD is presented as a Civil Aviation Safety Authority directive, compliance is framed as a regulatory requirement. The AD’s mandatory tone and formal issuance imply that non-compliance would be inconsistent with maintaining an approved airworthiness configuration. However, the AD text itself does not describe the mechanics by which CASA would enforce the direction, or any administrative process connected to enforcement, inspection, or penalties.

Cross-reference to other authorities

• Transport Canada references: The AD directs operators to Bombardier SBs “or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada,” and Note 3 references Transport Canada AD CF-2002-25. These cross-references indicate a regulatory dialogue and technical reliance between CASA and Transport Canada but do not, within the AD text, modify or add penalties.

Operational consequences

• Implicit operational consequences: The AD requires equipment replacement and a Return to Service Procedure within 30 days. Practically, failure to comply would leave an aeroplane outside the configuration mandated by the AD. The AD does not state what paperwork or approvals demonstrate compliance; it references Bombardier SBs and Service Letters as the approved procedural sources. The AD does not specify who certifies completion for regulatory purposes in its own words.

In summary, the AD imposes time-limited mandatory maintenance actions and identifies approved technical documentation, but it does not include explicit penalty provisions or a described enforcement mechanism in the text provided. The AD’s regulatory status and signature indicate it operates within CASA’s enforcement apparatus, but details of penalties or administrative enforcement are not supplied in this document.

The AD explicitly interacts with technical approvals and a foreign regulator’s AD; beyond that the text is limited to cross-references and approved procedural dependencies. The AD integrates Bombardier service documentation and Transport Canada approvals into its compliance framework.

Transport Canada linkage

• Approved instructions by Transport Canada: For both Requirements 1 and 2, the AD states that Bombardier Service Bulletins (SB 84-22-04 and SB 84-27-14) dated 29 November 2001 and 16 January 2002 respectively, “or later revisions, approved by the Chief, Continuing Airworthiness, Transport Canada” provide the approved instructions for incorporating the Modsums. This expressly locates authority for approving SB revisions with the Chief, Continuing Airworthiness, Transport Canada. The AD therefore allows an operator to use later-service-bulletin revisions only if they have Transport Canada approval, embedding a foreign regulatory approval mechanism within an Australian AD.

• Reference to Transport Canada AD CF-2002-25: Note 3 states “Transport Canada AD CF-2002-25 refers.” By explicitly referring to that AD, the CASA AD recognises analogous foreign regulatory action on the same technical subject. The AD therefore cross‑references parallel regulatory instruments rather than functioning in isolation.

Interaction with manufacturer documentation

• Bombardier service publications as the means of compliance: The AD makes Bombardier Service Bulletins and Service Letters the prescribed instruments for performing the Modsums and for applying interim procedures. The AD therefore integrates manufacturer technical documents into the statutory compliance path, subject to the Transport Canada approval caveat for later revisions.

Gaps in legal cross-references

• No mention of domestic statutory enforcement clauses: The AD does not cite or quote domestic statutory sections (for example of the Civil Aviation Act or relevant regulations) that underpin the AD’s enforceability nor does it specify administrative penalties or enforcement procedures within the AD text itself. The AD does not set out how compliance is to be documented for regulatory records, or the effect of non-compliance in legal terms. Those matters lie outside the AD text provided.

Practical jurisdictional consequence

• Cross-jurisdiction approvals: By accepting later Bombardier SB revisions only if approved by Transport Canada’s Chief, Continuing Airworthiness, the AD effectively makes Transport Canada the technical approver for acceptable amendments to the SBs under this AD. This creates a functional interaction where Australian operators must follow Bombardier technical guidance and Transport Canada approvals to demonstrate compliance.

• Alignment of technical standards: The AD’s link to Transport Canada material and reference to an earlier Transport Canada AD suggests technical coordination between CASA and Transport Canada on the pitch trim safety issue. The AD thereby aligns CASA action with established manufacturer/foreign-regulator remedies for the identified malfunctions.

The AD, as written, therefore operates within a technical and regulatory network that includes Bombardier service documentation and Transport Canada approvals. The AD itself does not state how it interacts with other domestic legal instruments or enforcement mechanisms, and does not specify penalties or procedural detail about regulatory enforcement, but it does create a compliance pathway that depends on manufacturer documentation and a named Transport Canada approval authority.

The AD text contains a concise set of dated documents and references that collectively form its amendment and technical history; there is no separate legislative amendment log in the text. The AD itself is labelled AD/DHC-8/114 Pitch Trim Control 4/2006 and provides its own issuance and effective dates, and it lists the key Bombardier documents and Service Letters that underpin the remedies.

Dates and versions present in the AD

• AD issuance and effective dates: The AD is dated in the signature block as signed by James Coyne on 2 March 2006. The AD states that it “becomes effective on 13 April 2006.” The Compliance section requires actions to be completed within 30 days after the effective date.

• Bombardier Service Bulletin dates: Two Bombardier Service Bulletins are named with dates. SB 84-22-04 (Auto Pilot - Flight Guidance Module - Introduction of Software V666 - Modsum 4-113405) is dated 29 November 2001; SB 84-27-14 (Flight Controls - Flight Control Electronic Control Unit Upgrade - Modsum 4-113392) is dated 16 January 2002. The AD permits “later revisions, approved by the Chief, Continuing Airworthiness, Transport Canada” to be used in place of the dated SBs.

• Bombardier Service Letter dates (interim procedures): Two Service Letters are identified as interim approved maintenance procedures. SL DH8-400-SL-22-001D is dated 8 November 2001 and the AD permits it to be used to confirm AP pitch trim function and restore autopilot following the specific autopilot pitch trim failure. SL DH8-400-SL-27-003 is dated 22 May 2001 and the AD permits its use to confirm pitch trim serviceability after a manual pitch trim loss.

• Reference to Transport Canada AD: Note 3 states “Transport Canada AD CF-2002-25 refers.” No date is provided in the AD text for that Transport Canada AD, but the inclusion signals prior or parallel foreign regulatory action.

No explicit amendment history of the AD itself

• The AD text does not contain a record of amendments to this CASA AD. It lists the SBs and Service Letters with their historic dates and permits reliance on later revisions only if approved by Transport Canada. The AD thereby builds a limited amendment pathway for the technical instructions (SB revisions approved by Transport Canada), but it does not provide a timeline of changes to the AD document itself, nor does it include a consolidated history of prior versions of AD/DHC-8/114.

Implications for recordkeeping

• Operators relying on later SB revisions must ensure the revision has Transport Canada approval because the AD expressly allows “later revisions, approved by the Chief, Continuing Airworthiness, Transport Canada.” That creates a de facto amendment route for the technical means of compliance even while the AD text itself remains unchanged.

• The AD’s dated documents and the effective date provide a fixed compliance baseline. The AD’s Compliance clause (30 days after 13 April 2006) ties obligations to that effective date, and Service Bulletins or Letters dated after the SB dates listed would only be acceptable if the Chief, Continuing Airworthiness, Transport Canada approves them.

In short, the AD’s internal amendment history is limited to the dated Bombardier SBs and Service Letters it references and to the explicit permission to use later SB revisions once those revisions have Transport Canada approval. The AD itself is dated and has a single effective date; it does not present a formal amendment log of previous CASA AD versions within the text provided.

The AD text does not include any litigation history, judicial decisions, or case references. The document refers to regulatory and technical materials (Bombardier SBs and Service Letters, and a Transport Canada AD), but it does not mention legal proceedings or court decisions in relation to AD/DHC-8/114.

What the AD states

• No cases or legal disputes: The AD provides technical requirements, references to Bombardier documents, and a link to Transport Canada AD CF-2002-25, but it contains no mention of litigation, appeals, or prior adjudications.

• Administrative signature: The AD is issued and signed by a CASA delegate, James Coyne, on 2 March 2006. The AD itself is an administrative regulatory instrument; the text does not recount any judicial review or challenge.

Implications for legal research

• Absence of litigation in the text: Because the AD does not contain litigation references, any researcher seeking litigation or judicial treatment of AD/DHC-8/114 would need to consult external legal databases, court records or CASA enforcement records. The AD text alone provides no such entries or pointers.

• Cross-reference to Transport Canada AD: The AD’s Note 3 stating “Transport Canada AD CF-2002-25 refers” suggests there was prior or parallel regulatory action on the matter under Transport Canada’s authority. That may be a starting point for research into whether Transport Canada’s AD was litigated or otherwise contested in its jurisdiction. The CASA AD itself, however, contains no litigation trail.

• Administrative remedy or review: The AD does not describe internal review or appeal mechanisms available to an operator directed by the AD, nor does it include procedural language about seeking exemptions, variations, or equivalent means of compliance. Those processes, if available, would be governed by the broader regulatory framework authorising CASA to issue ADs, but they are not described in this instrument.

Summary

The supplied AD contains no litigation history or case references. It sets out technical directives and cross‑references other regulatory and technical documents, but it does not record any legal challenges or judicial decisions. Any inquiry into litigation connected to this AD would require searching outside the AD text for court or tribunal records, or CASA enforcement and administrative records.

Operators and maintenance organisations should note several practical traps and small but consequential details in the AD’s text that can lead to non-compliance, misdiagnosis, logistical problems, or improper reliance on unapproved documents.

Different applicability bands for the two Modsums: The two required Modsums do not cover identical serial-number ranges. Modsum 4-113405 applies only to S/N 4001 through 4058, while Modsum 4-113392 applies to S/N 4001 through 4065. That creates a subset of aeroplanes (S/N 4059-4065) that require only the FCECU replacement (Modsum 4-113392) and not the FGM replacement (Modsum 4-113405). Operators must check serial numbers carefully; applying the wrong Modsum to the wrong airframe would be a compliance risk.

Specific part-number changes: The AD specifies precise part numbers for removal and installation. For Modsum 4-113405 the change is FGM1 and FGM2 P/N C12429AA06 to FGM P/N C12429AA07. For Modsum 4-113392 the FCECU replacements are from P/N 398500-1001 or 398500-1003 to P/N 398500-1005. Using incorrect P/Ns, or assuming equivalence without documentary approval, risks non-compliance.

Return to Service Procedure requirement: For Modsum 4-113405 the AD requires not only the hardware/software change but also “perform a Return to Service Procedure.” That is a discrete action; it is not enough to swap the unit. The AD references Bombardier SB 84-22-04 for the approved instructions. Ensure the Return to Service Procedure is completed and documented as directed in the SB.

Interim procedures are limited and specific: The AD permits two Bombardier Service Letters as interim approved maintenance procedures. These are time‑limited insofar as they are only authorised “until such time as” the respective Modsums are implemented. Operators should not treat the Service Letters as a permanent substitute. The interim procedures cover specific failure symptoms: SL DH8-400-SL-22-001D (8 November 2001) for reinstating autopilot after an autopilot pitch trim failure characterised by “AP PITCH TRIM FAIL” followed by “AUTO TRIM FAIL” on the PFD; and SL DH8-400-SL-27-003 (22 May 2001) for confirming pitch trim system serviceability following loss of manual pitch trim indicated by illumination of the “PITCH TRIM” Caution Light and loss of manual input function.

Transport Canada approval gate for later SB revisions: The AD allows later revisions to the Bombardier SBs only if they are “approved by the Chief, Continuing Airworthiness, Transport Canada.” That introduces an external approval requirement; operators in Australia cannot unilaterally rely on later SB revisions unless they carry the specified Transport Canada approval. Treat any later SB revision as acceptable only if Transport Canada approval is documented.

Tight compliance window: The AD sets a 30-day compliance window measured from the effective date (13 April 2006). Short windows increase parts, scheduling and operational pressure. Operators must plan for procurement lead times, maintenance slots, and Return to Service validations within that period.

Symptom overlap and diagnosis risk: The AD describes two unrelated malfunctions but both involve pitch trim functionality. Maintenance staff and flight crews must correctly identify the presented symptom set: autopilot pitch trim failure is associated with specific PFD messages (“AP PITCH TRIM FAIL” and “AUTO TRIM FAIL”); manual pitch trim failure is associated with the “PITCH TRIM” caution light and loss of manual input. Misdiagnosis could lead to applying the wrong interim procedure or failing to capture the correct Modsum applicability.

Reference to Transport Canada AD CF-2002-25: Note 3 says “Transport Canada AD CF-2002-25 refers.” Operators should consult that AD for technical background or additional requirements; failing to consider the Transport Canada AD could omit relevant context referenced by CASA.

Documentation and audit trail: The AD requires the mods and Return to Service Procedure; it does not spell out required records in its own text. Operators should nonetheless document performance of SB steps, part numbers used, and Return to Service certification to demonstrate compliance should CASA or other oversight bodies audit compliance. The AD does not provide explicit paperwork instructions; absence of such direction is itself a operational gotcha.

Implicit fleet-level costs and downtime: The AD requires parts replacement on many aeroplanes in a bounded fleet. Operators with multiple affected aircraft need to coordinate parts and maintenance windows, taking account of the 30-day limit.

In summary, careful attention to serial-number applicability, exact part numbers, the required Return to Service Procedure, the limited scope of interim Service Letters, Transport Canada approval for SB revisions, and the compressed compliance timeframe are the principal practical gotchas embedded in the AD.

Compliance under this AD requires a sequence of technical and administrative steps strictly aligned to the Requirements and the approved documents named in the AD. The AD sets out the actions and the window: both Requirements must be complied with within 30 days after the effective date (effective date 13 April 2006).

Step 1 , Determine applicability

• Check each aeroplane’s model and serial number. The AD applies to DHC-8 Models 400, 401 and 402 aeroplanes S/N 4001 through 4065. Note carefully the different serial-number coverage for each Modsum: Modsum 4-113405 is required for S/N 4001-4058; Modsum 4-113392 is required for S/N 4001-4065.

Step 2 , Obtain the approved technical instructions

• For Modsum 4-113405 (FGM change): obtain Bombardier Service Bulletin SB 84-22-04 Auto Pilot - Flight Guidance Module (Introduction of Software V666 - Modsum 4-113405) dated 29 November 2001, or a later revision that has been approved by the Chief, Continuing Airworthiness, Transport Canada. The AD identifies this SB as providing the approved instructions to incorporate Modsum 4-113405.
• For Modsum 4-113392 (FCECU change): obtain Bombardier Service Bulletin SB 84-27-14 Flight Controls - Flight Control Electronic Control Unit Upgrade - Modsum 4-113392 dated 16 January 2002, or a later revision approved by the Chief, Continuing Airworthiness, Transport Canada.

Step 3 , Prepare parts and personnel

• For Modsum 4-113405: ensure availability of FGM units P/N C12429AA07, and any tooling, software update media, or test equipment specified in SB 84-22-04. The AD requires replacing/reworking FGM1 and FGM2 P/N C12429AA06 with/to FGM P/N C12429AA07 and performing a Return to Service Procedure.
• For Modsum 4-113392: ensure availability of FCECU P/N 398500-1005 to replace FCECU P/N 398500-1001 or P/N 398500-1003. Verify compatibility and follow SB 84-27-14 instructions.

Step 4 , Schedule maintenance and Return to Service

• Schedule maintenance within the AD’s compliance window: the AD states compliance with Requirements 1 and 2 must be completed “within 30 days after the effective date of this Directive” (effective date 13 April 2006). Plan for aircraft downtime, parts procurement lead times, and certifying engineer availability.
• For Modsum 4-113405, complete the Return to Service Procedure as specified in SB 84-22-04 following the FGM replacement/rework.

Step 5 , Use interim procedures where applicable (if immediate permanent Modsum incorporation is not yet possible)

• If immediate incorporation of Modsums is not feasible, use the interim approved measures specified in the AD:
  • For autopilot pitch trim failure: use Bombardier Service Letter SL DH8-400-SL-22-001D dated 8 November 2001 as an approved maintenance procedure to confirm AP pitch trim function and restore use of the autopilot after the specific autopilot pitch trim failure characterised by an “AP PITCH TRIM FAIL” message on the PFD followed by “AUTO TRIM FAIL” after manual AP disengagement (Note 1).
  • For manual pitch trim loss: use Bombardier Service Letter SL DH8-400-SL-27-003 dated 22 May 2001 as an approved maintenance procedure to confirm the pitch trim system is serviceable following loss of manual pitch trim characterised by illumination of the “PITCH TRIM” Caution Light and concurrent loss of pitch trim function during manual input (Note 2).
• Treat these as interim measures only, valid “until such time as” the corresponding Modsum is implemented.

Step 6 , Document compliance

• Record the aircraft serial number, the parts removed (including part numbers), the parts installed (including serials and P/Ns), and the Bombardier Service Bulletin revision used. Document completion of the Return to Service Procedure where required by Modsum 4-113405. Maintain maintenance-release or release-to-service documentation consistent with operator procedures and regulatory expectations, referencing the relevant SB or Service Letter used for compliance.

Step 7 , Verify approvals for later SB revisions

• If using a later revision of SB 84-22-04 or SB 84-27-14 than those dated in the AD, obtain confirmation that the later revision has been approved by the Chief, Continuing Airworthiness, Transport Canada, because the AD permits “later revisions, approved by the Chief, Continuing Airworthiness, Transport Canada” as the approved instructions.

Step 8 , Ongoing monitoring and reporting

• The AD’s Background emphasises recurring malfunctions; after compliance, monitor aircraft for recurrence of the operational symptoms identified in the AD (“AP PITCH TRIM FAIL”, “AUTO TRIM FAIL”, “PITCH TRIM” caution light plus loss of manual input). If symptoms continue to occur post‑modification, follow applicable reporting or further maintenance procedures consistent with Bombardier instructions and CASA expectations.

Step 9 , Cross-reference Transport Canada AD if needed

• Note 3 in the AD directs readers to Transport Canada AD CF-2002-25. Operators should consult that AD for further technical or historical context that may be relevant to their compliance or to understand prior remedies.

Step 10 , Regulatory liaison

• Ensure that the maintenance release or other regulatory paperwork demonstrates compliance within the AD’s 30-day window. While the AD itself does not spell out enforcement mechanics, CASA issued the directive and may require documentary evidence of compliance.

By following these steps, closely adhering to the specified Bombardier SBs and Service Letters, and ensuring any later SB revisions used are approved by the Chief, Continuing Airworthiness, Transport Canada, operators will meet the AD’s technical requirements within the time limit the AD establishes.