AD/DHC-3/30 Amdt 1 - Elevator Connecting Rod

The directive rests on a small number of concrete technical and regulatory concepts described in the source.

• Applicability. The measure applies to all Model DHC-3 aircraft. The directive does not limit applicability by serial number, modification status, operator type or base location. This is explicit in the Applicability line: "All Model DHC-3 aircraft" (Applicability).

• Target components. The components specified are the elevator pushrod identified as part number C3-CF-167 (or replacement part C3-CF-633-1), and the elevator pushrod to rear quadrant attachment bolt identified as AN174-16 (or replacement NAS1954-24D), plus associated hardware. The rudder pushrod to rear quadrant attachment bolt and its hardware are implicated when NAS1954-24D is fitted to the elevator arrangement (Requirement 1 and Requirement 2).

• Inspection focus. The visual inspection called for in Requirement 1 concentrates on three failure modes: bowing of the pushrod, cracking of the pushrod threaded ends, and bending of the attachment bolt. The directive directs the inspector to detect those specific conditions as the basis for remedial replacement actions (Requirement 1).

• Remedial standard and approved data. Replacement and inspection actions must be carried out in accordance with de Havilland Service Bulletin No.3/35 Revision A and SB No.3/43 original issue, or later Transport Canada approved revisions. The directive therefore ties both inspection technique and replacement specifications to the SBs and to Transport Canada approvals quoted in the text (Requirement 1 and Requirement 2).

• Staged compliance window. The directive uses flight-hour based compliance windows counted from an effective date. Requirement 1 is a short window: within 50 flight hours after 15 January 2009, unless already accomplished. Requirement 2 is a longer window: within 100 flight hours after 15 January 2009, unless already accomplished. Separately, Requirement 3 is an operational trigger requiring inspection before further flight after a specified exposure (Compliance).

• Conditional substitution of parts. The directive allows the older bolt AN174-16 to be used temporarily "in lieu of bolt part number NAS1954-24D until Requirement 2 of this Directive comes into effect." That creates an interim permitted substitution before the full replacement requirement takes effect (Requirement 1).

• Operational safety trigger. The directive establishes an immediate operational safety requirement: if the aircraft has been parked and exposed to jet/propeller/helicopter blast or winds with estimated mean velocity of 55 km/h and gusts to 100 km/h, the inspection under Requirement 1 must be performed before further flight, irrespective of whether the replacement parts have been installed (Requirement 3). The directive also requires inspection of the remainder of the elevator control circuit in that event (Requirement 3).

• Regulatory provenance. The Background states that the Amendment 1 was issued to introduce the requirements of Transport Canada AD CF-85-04, which supersedes the original requirements of this Directive. The directive therefore represents an amendment to an existing CASA directive to align with Transport Canada’s action (Background; Amendment 1).

These concepts define the directive’s mechanics: who it covers, what parts and failure modes it targets, what approved data must be followed, what timelines apply, and what immediate post-event inspections are required.

The directive affects a narrow but clearly defined set of parties.

• Aircraft owners and operators of Model DHC-3 aircraft. The Applicability line states "All Model DHC-3 aircraft." That imposes obligations on the entity responsible for the airworthiness of those aircraft at the time the directive applies. Practically, that will be registered owners, operators, or maintenance organisations contracted by them. The directive’s requirements (inspections, replacements and immediate preflight checks after specified exposures) are operational and maintenance obligations that fall on those responsible for the aircraft’s continuing airworthiness (Applicability; Requirement 1-3).

• Maintenance organisations and technicians. Implementation requires visual inspection and parts replacement "in accordance with de Havilland Service Bulletin No.3/35 Revision A and SB No.3/43 original issue, or later Transport Canada approved revisions" (Requirement 1 and Requirement 2). That assigns the technical content to the SBs; workshop personnel and certificated maintenance organisations will carry out the inspections and replace hardware in accordance with the SBs and any Transport Canada approved revisions, and will be responsible for ensuring conformity to those documents (Requirement 1; Requirement 2).

• Parts suppliers and logistics. The directive specifies part numbers (C3-CF-167, C3-CF-633-1, AN174-16, NAS1954-24D). Suppliers and logistics chains that support DHC-3 operators will be implicated, because replacement bolts and pushrods must be procured to comply with the specified SBs. The directive also allows a temporary substitution (AN174-16 in lieu of NAS1954-24D until Requirement 2 takes effect), which affects procurement timing and inventories (Requirement 1).

• Regulatory overseers. The instrument is issued by the Civil Aviation Safety Authority (signature by David Villiers, Delegate of the CASA). Transport Canada is referenced as the origin of the underlying measures (AD CF-85-04) and as the approving authority for later revisions to the SBs (Background; Requirement 1 and Requirement 2). CASA as issuer and Transport Canada as the referenced certifying authority are the named authorities in the source.

• Flight crews and operators who may need to ground an aircraft. Requirement 3 places an operational duty to inspect before further flight after specified exposure to gusts or blast; that affects pilots on overnight or parked aircraft and operations staff who assess aircraft movement after exposure to strong winds or blast environments (Requirement 3).

Who pays. The source does not expressly state funding or cost allocation. From the directive’s mechanics it follows that aircraft owners/operators and their maintenance providers will incur costs for inspections, parts and labour because they must perform the inspections and replacements under the SBs within the stated flight-hour windows. The directive does not identify any subsidies, reimbursements, or exemptions in the source text (Applicability; Compliance).

The directive does not identify exemptions for particular operators or aircraft configurations, nor does it carve out categories of owners. The applicability language and the mandatory framing of requirements indicate that all parties responsible for Model DHC-3 aircraft must comply.

The directive defines precise duties for operators and maintenance providers, and identifies operational triggers that convert inspection duties into pre-flight obligations.

Duties

• Visual inspection duty (Requirement 1). Within 50 flight hours after 15 January 2009, unless already accomplished, operators must visually inspect the elevator pushrod and the elevator pushrod to rear quadrant attachment bolt and associated hardware, concentrating on bowing of the pushrod, cracking of threaded ends, and bending of the attachment bolt. If evidence of component damage is found, replacement of damaged parts before further flight is mandatory, using de Havilland SB No.3/35 Revision A and SB No.3/43 original issue, or later Transport Canada approved revisions (Requirement 1; Compliance).

• Replacement duty (Requirement 2). Within 100 flight hours after 15 January 2009, unless already accomplished, operators must replace the elevator pushrod to rear quadrant attachment bolt and associated hardware in accordance with SB No.3/43; simultaneously the rudder pushrod to rear quadrant attachment bolt must be replaced unless already accomplished (Requirement 2; Compliance).

• Event-triggered pre-flight inspection duty (Requirement 3). Whenever a parked aircraft has been exposed to jet, propeller, or helicopter blast or winds with estimated mean velocity of 55 km/h and gusts to 100 km/h, operators must comply with Requirement 1 before further flight, irrespective of whether replacement parts required by Requirement 2 have been installed. Following such exposure the remainder of the elevator control circuit must also be visually inspected as specified in de Havilland SB No.3/35 Revision A, or later Transport Canada approved revision (Requirement 3).

• Conformity to SBs and approved revisions. All inspection and replacement work is to be done in accordance with de Havilland SB No.3/35 Revision A and SB No.3/43 original issue, or later Transport Canada approved revisions. The SBs provide the technical specification that the directive references (Requirement 1; Requirement 2; Requirement 3).

• Part substitution rule. Until Requirement 2 takes effect, AN174-16 may be used in lieu of NAS1954-24D. However, when AN174-16 is replaced with NAS1954-24D, the rudder pushrod to rear quadrant attachment bolt and associated hardware must be replaced simultaneously as specified in SB No.3/43 original issue or later Transport Canada approved revision (Requirement 1).

Rights and margins in the source text

• No express derogations or exemptions. The source contains no exemptions from the requirements for any subset of owners or operators. Compliance timing is qualified only by the "unless already accomplished" caveat; if the action is already done before the effective date, the operator has no further obligation under that particular requirement.

• Use of approved revision language. The directive allows reliance on "later Transport Canada approved revisions" of the de Havilland Service Bulletins. That creates an explicit right to implement the actions using later Transport Canada approved revisions of the SBs, rather than being locked to a specific SB revision. The authority for what counts as an acceptable revision, according to the text, rests with Transport Canada approvals referenced in the SBs (Requirement 1; Requirement 2; Requirement 3).

• Operational discretion limited by "before further flight". The wording "before further flight" in Requirement 1 and Requirement 3 imposes a strict operational constraint: if damage is found, or if the aircraft has been exposed to specified winds/blast conditions, no further flight is permitted until the mandated inspection and any required replacements are completed. The directive therefore converts inspection findings and environmental exposures into direct constraints on airworthiness and flight operations (Requirement 1; Requirement 3).

• Timing rights. The Compliance section sets out maximum windows (50 and 100 flight hours) rather than absolute calendar deadlines. Operators retain discretion to schedule inspections and replacements within those flight-hour windows, provided they are completed within the stated flight hours counted after 15 January 2009 (Compliance).

Areas the directive does not address in the source

• Record-keeping and certification. The text does not set out specific record-keeping or logbook entry requirements for the inspections or replacements. It also does not specify who must sign compliance statements or how compliance is to be documented in maintenance records. The requirement to use SBs for the technical particulars is the only documented linkage to standard maintenance practice (Requirement 1; Requirement 2).

• Penalties, enforcement procedures or oversight steps. The source does not specify penalties, sanctions or the enforcement process for non-compliance; those elements are not addressed in the directive text itself (see Penalties and enforcement section below).

These duties and limited rights define the practical compliance obligations that operators and maintenance providers must follow under the directive.

The source text of AD/DHC-3/30 Amendment 1 sets out mandatory technical and operational requirements, but it does not contain express provisions specifying penalties, sanctions or an enforcement regime in the directive itself. The directive records the effective date (15 January 2009), the compliance windows (50 and 100 flight hours), and the operational "before further flight" constraints, but it does not enumerate statutory fines, suspension mechanisms, or civil or criminal penalties for non-compliance in the text provided.

What the directive does make enforceable within its own wording

• Operational prohibition "before further flight." Requirement 1 binds operators to replace damaged parts "before further flight" if inspections reveal damage. Requirement 3 requires inspection before further flight after specified exposure even if replacement parts have not yet been installed. In practical terms, those commands are operationally enforceable: the aircraft is not permitted to continue to fly until the stated inspections or replacements are completed (Requirement 1; Requirement 3).

• Specified compliance windows. The Compliance table sets explicit flight-hour limits for performing Requirement 1 (within 50 flight hours after 15 January 2009) and Requirement 2 (within 100 flight hours after 15 January 2009). Missing those times would leave the operator non-conforming with the directive as issued (Compliance).

What the source omits on enforcement

• No explicit penalties or enforcement steps. The source does not define enforcement tools, monetary penalties, or administrative actions that CASA will take for non-compliance. It does not specify inspection, audit, mandatory reporting, or notice requirements tied to enforcement.

• No procedural guidance on non-compliance. The directive does not set out procedural steps such as reporting of non-compliance, rectification timelines after enforcement notices, or appeals processes.

Consequences that are implied by the directive’s mechanics

• Operational limitation as a compliance lever. Because the directive ties remedial action to the ability to conduct further flight (Requirement 1 and Requirement 3), failure to comply in the face of identified damage or specified environmental exposure would leave an aircraft not compliant with the directive’s airworthiness condition as stated. The practical consequence is grounding until the mandated maintenance is done.

• Interaction with referenced SBs. The directive requires replacement and inspection "in accordance with" specified de Havilland SBs and "later Transport Canada approved revisions." That creates a technical standard for acceptable corrective actions. Failure to adhere to those SB-prescribed procedures would, in the terms of the directive, mean a failure to comply with the AD. The text itself does not set out how CASA or other authorities will assess or record that non-compliance.

• Reference to Transport Canada AD. The Background notes that Amendment 1 introduces the requirements of Transport Canada AD CF-85-04, and that the Transport Canada AD refers. The source does not elaborate enforcement mechanisms within Transport Canada AD CF-85-04, but it establishes the instrument’s provenance and cross-reference (Background).

In sum, the directive establishes operationally binding inspection and replacement duties and timeframes but does not, within the text provided, set out an explicit civil or criminal penalty regime or enforcement procedure. The operative compliance obligations (including the "before further flight" constraints and the SB-referenced technical specifications) are the practical instruments by which airworthiness is maintained under the directive as presented in the source.

The directive references and integrates technical material from manufacturer service bulletins and a Transport Canada airworthiness directive. The source frames these interactions but does not provide a full map of legal cross-references beyond those elements cited.

Links to manufacturer data and foreign regulatory action

• De Havilland Service Bulletins. The directive requires inspection and replacement actions "in accordance with de Havilland Service Bulletin No.3/35 Revision A and SB No.3/43 original issue, or later Transport Canada approved revisions" (Requirement 1; Requirement 2; Requirement 3). That means the directive’s technical instructions are explicitly anchored to the details in those SBs. The SBs supply the methods, parts, and sequence for inspection and replacement. The AD thereby makes those SBs the referenced technical standard for compliance, within the limits set by CASA’s directive text.

• Transport Canada AD CF-85-04. The Background states that Amendment 1 introduces the requirements of Transport Canada AD CF-85-04 and that the Transport Canada AD is referred to in the note. The directive thus aligns CASA’s measure with an existing Transport Canada airworthiness directive, adopting the same or similar technical measures (Background). The directive also allows adoption of "later Transport Canada approved revisions" of the SBs, which creates an explicit link to Transport Canada’s approvals as acceptable updates to the technical standards.

Implications for domestic regulatory framework

• Harmonisation with foreign authority. The source shows a deliberate alignment with Transport Canada’s action by introducing Transport Canada’s requirements into a CASA directive. The directive therefore operates as a domestic instrument that mirrors or implements measures from a foreign regulator. The AD’s text does not elaborate how CASA treats Transport Canada approvals beyond permitting the use of later Transport Canada approved revisions to the referenced SBs (Requirement 1; Requirement 2; Requirement 3).

• No explicit interaction with Australian statutory provisions in the text. The directive itself does not cite specific Australian legislative provisions, regulations, or penalties. The source is administrative: it sets technical maintenance and inspection obligations but does not, within the text provided, invoke particular sections of the Civil Aviation Act or Civil Aviation Safety Regulations, or detail enforcement powers in statutory terms. The directive is issued by CASA and signed by a CASA delegate; however, the text does not set out the statutory authority being exercised (signature and effective date).

• Interface with operating certificates and maintenance approvals. The directive’s reliance on SBs and the pre-flight constraint imposed by Requirement 3 imply an interface with the practical obligations of operators operating under their air operator certificates and maintenance organisations carrying out work under approved maintenance arrangements. The source does not set out the administrative steps to notify CASA, amend maintenance programmes, or update operations manuals , those interactions are not described in the directive’s wording.

Parts and standards substitution effect

• Temporary part substitution. The directive permits the continued use of AN174-16 in lieu of NAS1954-24D until Requirement 2 comes into effect. That creates an interim permissible configuration that is consistent with the directive but will require subsequent replacement to the NAS1954-24D standard once Requirement 2 is complied with. The directive further requires co-ordinated replacement of rudder pushrod hardware when NAS1954-24D is fitted to the elevator arrangement (Requirement 1; Requirement 2).

In short, the instrument integrates manufacturer SBs and a Transport Canada AD into a CASA AD. It references but does not expand upon enforcement or statutory mechanisms in the text provided. It establishes technical compliance routes by reference to SBs and allows Transport Canada approved SB revisions to be used as the operative technical standard.

The source includes an explicit amendment history entry and a background note summarising why Amendment 1 was issued.

• Original directive and Amendment 1. The document presented is AD/DHC-3/30 Amendment 1, relating to the elevator connecting rod for DHC-3 Otter aeroplanes. The text records that "Amendment 1 is issued to introduce the requirements of Transport Canada AD CF-85-04, which supersedes the original requirements of this Directive" (Background; Amendment 1). The directive thus replaces or modifies the original AD/DHC-3/30 requirements with those reflecting Transport Canada’s AD CF-85-04.

• Effective date. The amendment entry in the Compliance section states that "This Amendment becomes effective on 15 January 2009" and the signature block is dated 27 November 2008 under the name David Villiers, Delegate of the Civil Aviation Safety Authority (Compliance; signature block).

• Text of amendment. Amendment 1 introduces three explicit Requirements for inspection, replacement and event-triggered inspection. The first Requirement clarifies immediate inspection protocols and interim part substitution allowances (AN174-16 permitted until replacement by NAS1954-24D mandated by Requirement 2). The second Requirement imposes a replacement timetable for the rear quadrant attachment bolt and associated hardware and requires simultaneous replacement of the rudder pushrod to rear quadrant attachment bolt, unless already accomplished. The third Requirement creates a pre-flight inspection obligation prompted by environmental exposure (Requirement 1; Requirement 2; Requirement 3).

• Reference to Transport Canada. The Background notes in-service damage history and explains the causal mechanism: in-service damage has occurred to the elevator pushrod and attachment bolt to the elevator quadrant in the stub fin, typically manifesting as pushrod bowing and attachment bolt bending, caused by high external loads from strong gust loading while parked. It further notes that similar problems could develop with the rudder pushrod to rear quadrant attachment bolt. This is the factual justification recorded in the Amendment for importing Transport Canada’s requirements (Background).

• Record of origin and signature. The AD is signed by David Villiers, Delegate of the Civil Aviation Safety Authority, and dated 27 November 2008 (signature block).

• Cross-reference to Transport Canada AD. The directive includes a note "Transport Canada AD CF-85-04 refers." That records the connection between the CASA amendment and the Transport Canada AD; the note captures the provenance of the technical action incorporated into CASA’s AD (Background).

The source does not include a history of earlier amendments beyond indicating that Amendment 1 supersedes the original requirements. It does not set out the original AD/DHC-3/30 text in full; the Amendment 1 text as presented is the operative text in the source.

The source document contains no references to litigation, court decisions, enforcement actions or appeals related to AD/DHC-3/30 or Amendment 1. There are no cases, tribunal decisions, or judicial reviews cited in the text. The directive’s Background summarises in-service occurrences and the technical reasons for the AD, but it does not record any contested administrative proceedings, legal challenges or litigation outcomes.

Accordingly, within the bounds of the source provided, there is no litigation history to report. The directive contains:

• No mention of legal proceedings brought by affected owners or operators challenging the AD.

• No reference to judicial or administrative decisions interpreting, quashing, or upholding the directive.

• No mention of enforcement actions taken against operators for non-compliance.

If a user requires information on any subsequent litigation or legal challenges after the date of the directive, those matters are outside the text of the source and would require independent research beyond the AD/DHC-3/30 Amdt 1 document provided.

The directive contains several technical and procedural details that are easily overlooked but affect compliance cost, sequencing and operations. The following points are grounded directly in the source and identify practical pitfalls.

• "Before further flight" is an absolute operational trigger. Requirement 1 requires replacement of damaged parts "before further flight" if the inspection reveals damage. Requirement 3 requires the inspection of the specified parts before further flight after particular environmental exposure, regardless of whether replacement parts have been installed. Those phrases create an absolute operational stop: once damage is identified, or once the aircraft has been exposed to the specified wind/blast conditions, operators cannot lawfully proceed to fly until the prescribed inspection and any replacements are completed (Requirement 1; Requirement 3). Overlooking this language could lead to inadvertent non-compliance.

• Two-stage compliance with interim part substitution. The directive permits AN174-16 to be used in lieu of NAS1954-24D until Requirement 2 comes into effect. That means an operator may lawfully retain or install the older bolt up to the time Requirement 2 becomes due. However, when AN174-16 is later replaced with NAS1954-24D, the directive requires simultaneous replacement of the rudder pushrod to rear quadrant attachment bolt and associated hardware per SB No.3/43. Operators who plan staged maintenance across cycles need to account for the second-stage replacement of rudder hardware and associated costs when the elevator bolt is upgraded (Requirement 1; Requirement 2).

• Simultaneous replacement of rudder hardware. The simultaneous replacement requirement creates a cost cluster: fitting the NAS1954-24D elevator bolt triggers required replacement of the rudder pushrod attachment bolt and hardware at the same time. If an operator replaces the elevator bolt alone, that triggers an additional mandatory replacement to the rudder hardware; the directive does not allow piecemeal upgrading without the corresponding rudder work at the moment of fitting NAS1954-24D (Requirement 1; Requirement 2).

• Dependence on Service Bulletins and Transport Canada approvals. The directive repeatedly requires actions "in accordance with de Havilland Service Bulletin No.3/35 Revision A and SB No.3/43 original issue, or later Transport Canada approved revisions" (Requirement 1; Requirement 2; Requirement 3). Compliance therefore depends on access to the correct SB revisions and any later Transport Canada approved revisions. Operators must ensure they use the SB revision or a Transport Canada approved later revision; relying on other technical sources or older non-approved revisions would not meet the directive’s explicit standard.

• Triggered remainder-of-circuit inspection. Requirement 3 mandates that after a specified wind or blast exposure, operators must "visually inspect the remainder of the elevator control circuit for damage in accordance with de Havilland SB No.3/35 Revision A, or later Transport Canada approved revision." This extends the inspection beyond the pushrod and bolt to other elevator control circuit items and may reveal additional maintenance needs that require grounding until fixed (Requirement 3).

• Compliance windows counted from effective date. The Compliance section states specific flight-hour deadlines "after 15 January 2009" for the two staged requirements (50 and 100 flight hours). Operators must count flight hours from that effective date, and the "unless already accomplished" provision only removes an obligation if the specified action has already been completed prior to those deadlines. Failure to track flight hours accurately from the effective date could produce inadvertent late compliance (Compliance).

• No record-keeping guidance in the AD text. The directive does not require specific logbook entries or reporting of compliance to CASA in the text provided. Operators must nevertheless follow usual maintenance record practices and the SBs’ instructions, but the absence of explicit recordkeeping directions in the AD could be a trap if an operator assumes the AD supplies the means of demonstrating compliance; the AD relies on SBs for technical details but leaves documentary practice unspecified (Requirement 1; Requirement 2).

• Environmental exposure threshold specifics. The threshold that triggers Requirement 3 is an estimated mean wind velocity of 55 km/h with gusting up to 100 km/h, or exposure to jet/propeller/helicopter blast. Estimating mean wind velocity and gust conditions may be imprecise in practice; the directive does not provide an objective measurement standard beyond those figures, so the decision of whether the threshold has been met is operationally driven and should be treated conservatively in safety-critical judgement calls (Requirement 3).

• Transport Canada AD reference. The directive’s Background states that Amendment 1 introduces the requirements of Transport Canada AD CF-85-04. The AD text itself refers to Transport Canada approvals for SB revisions. Operators should not assume CASA has modified technical content beyond importing Transport Canada’s measures; the AD aligns CASA’s directive with the Transport Canada AD (Background).

These are operational "gotchas" that arise directly from the wording and sequencing of the directive in the source text.

The source sets out a small, specific set of actions and timeframes. Below are step-by-step, source-grounded actions an operator or maintenance organisation should follow to comply with the directive as written.

Step 1 , Identify affected airframes and schedule compliance

• Confirm applicability. Verify whether the aircraft is a Model DHC-3. The directive applies to "All Model DHC-3 aircraft" (Applicability). If so, the AD applies.
• Determine whether the inspection or replacement work has already been accomplished at the time of the effective date. The Compliance entries for Requirements 1 and 2 are qualified by "unless already accomplished" (Compliance). If the specified action was completed prior to the effective date, the operator may be able to rely on that completion to meet the AD.

Step 2 , Obtain the referenced technical data

• Acquire de Havilland Service Bulletin No.3/35 Revision A and SB No.3/43 original issue, and identify whether later Transport Canada approved revisions exist. The AD mandates work "in accordance with" those SBs or later Transport Canada approved revisions (Requirement 1; Requirement 2; Requirement 3). Use the SBs as the authoritative instruction set for inspections and replacement procedures.

Step 3 , Perform Inspection required by Requirement 1 (within 50 flight hours after 15 January 2009)

• Timing. Unless already accomplished, the visual inspection must be completed within 50 flight hours after 15 January 2009 (Compliance).
• Scope. Visually inspect the elevator pushrod (C3-CF-167 or replacement C3-CF-633-1), the elevator pushrod to rear quadrant attachment bolt (AN174-16 or NAS1954-24D) and associated hardware. The inspection should concentrate on detection of:
  • Bowing of the pushrod;
  • Cracking of the pushrod threaded ends;
  • Bending of the attachment bolt. (Requirement 1)
• Action on discovery. If evidence of component damage is found, replace the damaged parts before further flight, in accordance with de Havilland SB No.3/35 Revision A and SB No.3/43 original issue, or later Transport Canada approved revisions (Requirement 1).

Step 4 , Meet Replacement duty of Requirement 2 (within 100 flight hours after 15 January 2009)

• Timing. Unless already accomplished, perform replacement work within 100 flight hours after 15 January 2009 (Compliance).
• Work required. Replace the elevator pushrod to rear quadrant attachment bolt and associated hardware in accordance with SB No.3/43 original issue, or later Transport Canada approved revision. At the same time, unless already accomplished, replace the rudder pushrod to rear quadrant attachment bolt in accordance with SB No.3/43 original issue, or later Transport Canada approved revision (Requirement 2).

Step 5 , Manage part substitution and co-ordination

• Interim use of AN174-16. The directive permits the use of part number AN174-16 in lieu of NAS1954-24D until Requirement 2 comes into effect. If operators choose to retain or install AN174-16 temporarily, plan for the eventual replacement requirement under Requirement 2 (Requirement 1).
• Simultaneous rudder hardware replacement when NAS1954-24D is fitted. If AN174-16 is replaced with NAS1954-24D, replace the rudder pushrod to rear quadrant attachment bolt and associated hardware at the same time in accordance with SB No.3/43 (Requirement 1; Requirement 2). Schedule maintenance to ensure both elevator and rudder attachments are attended to without creating compliance gaps.

Step 6 , Comply with event-triggered Requirement 3 (before further flight after exposure)

• Trigger conditions. If a parked aircraft has been exposed to jet, propeller, or helicopter blast or winds with an estimated mean velocity of 55 km/h with gusting up to 100 km/h, comply with Requirement 1 before further flight (Requirement 3).
• Expanded inspection scope. After exposure to those wind velocities visually inspect the remainder of the elevator control circuit for damage in accordance with de Havilland SB No.3/35 Revision A, or later Transport Canada approved revision (Requirement 3).
• Action on discovery. If damage to any inspected component is found, replace as required in accordance with the SBs prior to further flight (Requirement 1; Requirement 3).

Step 7 , Technical conformity and documentation

• Follow the SBs. All inspections and replacements must be done "in accordance with" the specified de Havilland Service Bulletins, or later Transport Canada approved revisions (Requirement 1; Requirement 2; Requirement 3). Ensure the SB revision used is either the one cited or a Transport Canada approved later revision.
• Record the work. Although the AD text does not specify record-keeping, standard aviation practice requires maintenance entries in the aircraft logbook and maintenance release documentation consistent with the SBs and applicable maintenance regulations. Record the inspection results, parts replaced (including part numbers C3-CF-167/C3-CF-633-1 and AN174-16/NAS1954-24D where applicable), and the SB revision used.

Step 8 , Logistics and cost planning

• Parts procurement. Identify suppliers for the specified pushrod and bolt part numbers. The directive’s part references must be matched precisely when replacement is required by the SBs (Requirement 1; Requirement 2).
• Labour and scheduling. Plan for the labour time required to inspect and, where necessary, replace bolts and pushrods and to inspect the remainder of the elevator control circuit after gust exposure. If NAS1954-24D is being fitted, schedule simultaneous rudder hardware replacement to comply with the simultaneous replacement requirement (Requirement 2).

Step 9 , Operational practices

• Prompt pre-flight checks after storm exposure. Implement procedures to identify when parked aircraft have been exposed to blast or high winds so that Requirement 3 is applied before further flight (Requirement 3).
• Conservative judgement. Given the estimation component of wind speed thresholds, adopt a conservative approach when in doubt; treat potential exposures as triggers for Requirement 3 inspections.

Step 10 , Monitor for updated SB approvals

• Transport Canada approved revisions. The AD permits the use of later Transport Canada approved revisions of the referenced SBs. Monitor Transport Canada and the SB issuer for approved revisions and, when a Transport Canada approved revision supersedes the cited SB, adopt that revision for compliance (Requirement 1; Requirement 2; Requirement 3).

Who pays and who decides

• The source places the responsibilities operationally on the aircraft operator and maintenance organisations, which will incur costs for inspections, parts and labour. The directive does not provide funding or cost-sharing arrangements (Applicability; Compliance).
• Responsibility for technical conformity decisions (which SB revision to use, whether later Transport Canada approved revisions exist) rests with the operator and maintenance organisation, subject to the SBs and the Transport Canada approval caveat set out in the directive (Requirement 1; Requirement 2).

This stepwise approach mirrors the directive’s text and timing requirements and ties all technical actions to the de Havilland SBs and Transport Canada approved revisions as specified in the AD.