AD/DHC-8/133 Amdt 2 - Main Landing Gear System

The AD rests on three interlocking regulatory mechanisms: (1) prescriptive inspection requirements with staged compliance windows tied to actuator part numbers, landing counts and time-in-service; (2) mandatory reporting of discrepancies to the manufacturer; and (3) mandated modification or recurring maintenance tasks that can terminate the inspection regime.

Inspection typology and hierarchy

• General visual inspections: Requirement 1 and Requirement 2a define "general visual inspection" steps. Requirement 1 calls for a once-only general visual inspection of the left and right main landing gear system per the manufacturer's maintenance tasks Z700-03E/Z700-04E. Requirement 2a focuses on ensuring the retract actuator jam nut wire lock is present and the nut is secured.
• Detailed visual inspections: Requirement 3 elevates the inspection standard to a "detailed visual inspection" of the retract actuator per Bombardier RD 8/4-32-059 Issue 5 or later, with specific repeat intervals (2,000 landings or one calendar year) and staged initial compliance times based on accumulated landings or time-in-service for actors with part numbers p/n 46550-7/-9/-11.

Staged compliance and part-number differentiation

• The detailed inspection initial deadlines differ by accumulated landings and years in service as of the original AD effective date, for actuators p/n 46550-7 or 46550-9: 8,000+ landings or >4 years, before further flight after 14 September 2007; 4,000-7,999 landings or 2-4 years, within 500 flight hours or 3 months; <4,000 landings or <2 years, prior to reaching 4,500 landings or 27 months in service. For p/n 46550-11, the initial requirement is prior to reaching 4,500 landings or 27 months in service. This creates a staged compliance burden reliant on accurate landing counts and service records.

Terminating actions

• Two terminating routes are specified. Incorporation of Modsum 4-901603 (replacement actuator p/n 46550-13) via Bombardier SB 84-32-55 Rev A or later is Terminating Action 1 for Requirement 3. Incorporation of maintenance tasks 320100-211 and 320100-212 into the approved maintenance schedule is Terminating Action 2 for Requirement 2. Note 2 indicates that Modsum 4-901610 replacing actuator with p/n 46550-15 also satisfies Requirement 5.

Reporting and manufacturer engagement

• Requirement 4 mandates reporting any discrepancies found during inspections to the Bombardier Technical Help Desk within seven days. The AD also permits earlier repair drawings to be acceptable: "Respective inspections performed in accordance with earlier issues of RD 8/4-32-059 satisfy the actions detailed in Requirements 2 and 3 of this AD."

Operational exception: ferry flight

• The AD contains a controlled exception to its "before further flight" language to permit ferrying an aircraft to a suitable location subject to prescriptive flight crew and maintenance limitations (gear pinned, minimum descent rate, minimized braking, essential crew only, no known/forecast icing, and inspector checks and installation of ground lock pins/lockwire).

Regulatory cross-reference

• The AD references Bombardier maintenance manuals, Repair Drawings, Service Bulletins and Temporary Revisions, and specifically names Transport Canada approval of maintenance schedule changes. The AD is issued by the Civil Aviation Safety Authority (CASA) and references Transport Canada AD CF-2007-20 R2 dated 6 February 2009 (Note 3), indicating parallel regulatory activity in another jurisdiction.

The core risk the AD targets is main landing gear collapse; the measures are designed to detect and correct corrosion, loose jam nuts/wire-locks, actuator thread/piston issues and to replace suspect actuator designs with a new design claimed to obviate recurring inspections.

Primary affected parties

• Registered owners and operators of Bombardier DHC‑8 Series 400 aeroplanes with the listed serial numbers (4001, 4003, 4004, 4006 and 4008 through 4208). The AD explicitly limits applicability to these serial numbers and models in the opening Applicability clause and repeated throughout each Requirement.

Maintenance organisations and engineers

• Any Part 145 or approved maintenance organisation performing inspections or modifications on these aircraft will be directly affected. The AD prescribes specific maintenance tasks (Z700-03E/Z700-04E; RD 8/4-32-059 Issue 5; SB 84-32-55 Rev A) and MRB task numbers (320100-211/320100-212) that must be followed or incorporated into an approved maintenance schedule.

Bombardier (manufacturer)

• The manufacturer is implicated as the addressee of reports (Requirement 4: report discrepancies to Bombardier Technical Help Desk) and as the source of Repair Drawings, Service Bulletins and Modsum instructions that the AD requires or accepts. The AD thereby creates a compulsory reporting channel to Bombardier and makes certain manufacturer documents the mandatory method for compliance.

Regulators and approvals authorities

• The Civil Aviation Safety Authority (CASA) is the issuer. The AD expressly mandates changes to the "Transport Canada approved maintenance schedule" (Requirement 6), indicating interplay with foreign certificating authority documents. The AD also references Transport Canada AD CF-2007-20 R2, so operators who are subject to multiple regulators must reconcile overlapping requirements.

Operators’ flight crew and scheduling

• The ferry flight limitations (Ferry Flight: Flight Crew Limitations and Procedures A-F) affect flight crew and operational planning by prescribing how a ferry flight can be conducted to reach a maintenance facility. These limitations can restrict commercial operations, passenger carriage (essential crew only), and weather exposure (no known/forecast icing).

Who pays and who decides

• The document places the direct compliance costs and operational constraints on owners/operators and maintenance providers. Owners/operators must fund inspections, potential deferral logistics, reporting, and the cost of replacing actuators (Modsum) or incorporating additional maintenance tasks into the approved schedule. The AD itself makes CASA the decision-maker issuing the requirements, but compliance must be implemented using Bombardier documents and, for maintenance schedule changes, through the Transport Canada approved schedule framework. The AD designates Bombardier RD and SB documents as the prescriptive means of compliance.

Indirectly affected parties

• Aeroplane lessors, insurers and commercial operators will be indirectly affected because mandatory inspections and modifications can take aircraft out of service, affect availability, and influence contractual maintenance covenants and insurance exposure. The AD does not discuss these contractual or insurance mechanisms; it only prescribes technical and procedural steps.

Geographic scope

• This AD is issued by CASA and references Transport Canada documents; it applies to the listed aircraft irrespective of where they operate, to the extent CASA's regulatory reach covers a given operator. The document does not list cross-jurisdictional enforcement mechanisms, but it does indicate that the same safety concern prompted a Transport Canada AD.

Mandatory duties imposed by the AD

• Perform inspections and rectifications: Operators must perform the specific inspections and rectify discrepancies per the Bombardier maintenance tasks and repair drawings cited. Requirement 1 requires a general visual inspection "before further flight" after the original AD effective date in the cases specified. Requirement 2a requires an immediate general visual inspection of the jam nut wire lock "before further flight", with Requirement 2b requiring repetition at 250 landings or one month intervals. Requirement 3a mandates detailed inspection timing tied to landing counts/service time and Requirement 3b requires repetition at 2,000 landings or one calendar year.
• Reporting: Any discrepancy found "during any of the above inspections" must be reported to the Bombardier Technical Help Desk (Requirement 4) within seven days after each inspection.
• Modification: Operators must incorporate Modsum 4-901603 (or Modsum 4-901610 alternative) to replace affected retract actuators as prescribed by Bombardier SB 84-32-55 Rev A or later revisions (Requirement 5). The AD specifies compliance deadlines for the Modsum replacement dependent on landing counts and time-in-service as of the effective date.
• Maintenance schedule amendment: Operators (or the entity controlling the approved maintenance schedule) must amend the Transport Canada approved maintenance schedule to include MRB tasks 320100-211 and 320100-212 as introduced by Temporary Revision MRB-35 (Requirement 6), within 30 days of the AD's effective date.

Rights, permissible alternatives and flexibility

• Use of earlier approved materials: The AD states that inspections performed in accordance with earlier issues of RD 8/4-32-059 satisfy Requirements 2 and 3, giving operators some latitude if those earlier RD inspections were correctly carried out.
• Deferral allowance: A one-time deferral of up to 500 landings is permissible for the piston inspection where an earlier inspection lacked borescope or 10X magnification mirror, allowing limited operational flexibility.
• Terminating actions: Completion of Modsum 4-901603 or incorporation of MRB task numbers both provide terminating action to certain inspection requirements, giving operators a choice between recurring inspections or a one-time modification/maintenance schedule change.
• Acceptable alternatives: Note 2 explicitly states that Modsum 4-901610 replacing the retract actuator with p/n 46550-15 also satisfies Requirement 5, which provides an alternative design solution recognised by the AD.

Prescribed methods and documentation

• The AD prescribes Bombardier RD 8/4-32-059 Issue 5 or later approved revision and Bombardier SB 84-32-55 Rev A or later as the technical documents that define how inspections and modifications must be executed. It also refers to specific MRB tasks and Temporary Revision MRB-35 of the Maintenance Requirements Manual (PSM1-84-7) for maintenance schedule changes. This makes manufacturer documentation the de facto method for compliance.

Operational constraints and exceptions

• The AD provides a narrowly defined ferry-flight regime with explicit crew and maintenance procedures to permit transit to a maintenance facility. The ferry flight conditions (A-F and maintenance procedures i-iv) are prescriptive, not discretionary.

Timing and recordkeeping implications

• The AD creates multiple timing obligations tied to landings, flight hours, or calendar periods, which require accurate recordkeeping of landings, accumulated cycles, and service time for each actuator. For example, initial compliance for certain actuators is staged by accumulated landings (e.g. before 4,500 landings or prior to reaching 8,000) or by months in service. Operators must have systems to monitor these metrics and document compliance, including filing reports to Bombardier within seven days if discrepancies are found.

What the AD does not provide

• The instrument does not set out enforcement penalties or administrative sanction processes within its text. It likewise does not offer funding, transition assistance, or specific contractual guidance for lessors or insurers. It does not provide alternative technical solutions other than the two Modsum options and the acknowledged earlier RD versions.

What the AD explicitly states

• The text of AD/DHC-8/133 Amdt 2 does not include specific penalty provisions, monetary fines, or an administrative enforcement schedule within its content. It sets out mandatory actions, compliance timings, permissible deferrals, and terminating actions, but does not itself enumerate sanctions for non-compliance.

Practical enforcement implications (source-grounded)

• The AD is a regulatory instrument issued by the Civil Aviation Safety Authority, with prescriptive, mandatory requirements and effective dates. Those features imply that the AD is an enforceable safety obligation for affected operators within CASA’s regulatory domain. The AD’s language uses mandatory phrasing,"Perform", "Incorporate", "Report",and sets compliance deadlines for inspections, reporting and modifications. The presence of explicit "before further flight" provisions and detailed ferry-flight exceptions creates binary operational requirements: either comply with the inspection/modification, or operate under the tightly constrained ferry conditions.

Limits of the source

• Because the AD itself does not specify penalties or the administrative route for enforcement, the AD as provided does not state the exact nature of CASA’s enforcement actions, such as grounding orders, fines, or certificate suspensions. It also does not describe appeals or review processes for disputing CASA’s action.

Enforcement risks and operator exposure (analysis tied to AD content)

• Operational non-compliance with "before further flight" requirements could expose an aircraft to required grounding until the mandated inspections or modifications are completed, given that the AD conditions the aircraft’s continuing airworthiness on those steps.
• Failure to report discrepancies within the seven-day window to Bombardier could mean that the manufacturer lacks information potentially relevant to fleet-wide safety responses; the AD makes reporting compulsory but does not state the immediate regulatory consequence of delayed or missing reports.
• Choosing to operate under the ferry-flight provisions imposes strict limitations (gear pinned, minimal descent, essential crew only, no icing), which reduce the aircraft’s operational utility and may not be acceptable for commercial revenue flights. If these limitations are breached during a ferry, the operator would be operating contrary to the AD’s allowed exception and could face regulatory scrutiny.
• Replacing retract actuators per Modsum carries procurement and maintenance execution timelines; failure to meet the staged Modsum deadlines leaves the operator subject to the recurring inspection regime, with attendant maintenance operational impacts.

Recordkeeping and audit exposure

• The AD creates specific recordkeeping duties by its timing language (landings, calendar months, service time) and the reporting requirement. In an audit or safety investigation, absence of records documenting compliance with the inspection intervals, reports to Bombardier, or incorporation of Modsum/SB work would be material.

Interplay with manufacturer documents and other regulatory ADs

• The AD makes Bombardier repair drawings, service bulletins, maintenance manual tasks and temporary revisions the prescribed means of compliance. It explicitly allows earlier issues of RD 8/4-32-059 to satisfy Requirements 2 and 3. This makes operator compliance dependent on manufacturer-supplied documentation and approvals.
• The AD references Transport Canada AD CF-2007-20 R2 dated 6 February 2009 (Note 3). That indicates coordinated action with another national regulator. Requirement 6 also mandates amendment of the "Transport Canada approved maintenance schedule," showing the AD is intended to align with or impose obligations that touch on foreign-approved maintenance documentation.

Regulatory hierarchy and approvals

• The AD is issued by CASA but references the Transport Canada approved maintenance schedule and Bombardier documents as the detailed technical method of compliance. This creates an interplay in which CASA mandates actions that operators must effect using documents and approvals produced by the manufacturer and documented within a maintenance schedule that in this case is described as "Transport Canada approved." Where an operator is subject to multiple jurisdictions, reconciling CASA’s AD with foreign regulator approvals and maintenance schedules will be necessary.

Contractual and commercial law interactions

• The AD imposes costs and out-of-service time on operators which will interact with lease agreements, maintenance control agreements and insurance policies. While the AD does not address contractual obligations, required actions (e.g. Modsum replacement) could trigger responsibilities under warranty, lease, or service contracts. The experimental text does not set any contractual default rules; operators must rely on their contracts and possibly seek manufacturer support for parts or labour.

Occupational health and safety and crew limitations

• The ferry-flight provisions limit crew and operational environment (no icing). These are operational constraints that interact with crew duty regulations, commercial passenger carriage rules and safety-of-flight obligations. The AD prescribes "essential crew only" for ferry; this will interact with regulations governing who may be carried and under what certification.

No statutory amendment power described

• The AD requires operators to amend a "Transport Canada approved maintenance schedule" by adding specified MRB tasks, but the AD itself does not amend primary legislation or directly change certification regulations. It prescribes maintenance manual changes as an operational compliance mechanism.

Areas the AD does not address legally

• The AD does not purport to adjudicate disputes between private parties (such as between lessor and lessee) and does not prescribe compensation or cost-sharing mechanisms. It does not provide penalty schedules or detailed enforcement routes; these will be found in CASA’s broader regulatory framework, not the AD text itself.

Documented amendments in the source

• Original issue: the original AD was effective 14 September 2007. The Background clause states the original AD responded to two reported cases of main landing gear collapse.
• Amendment 1: amended on 2 November 2007. The Background records that Amendment 1 changed compliance time by introducing calendar periods and repetitive inspections until a terminating action became available.
• Amendment 2: the current document (AD/DHC-8/133 Amdt 2) became effective 9 March 2009. The Background states that Amendment 2 amends the detailed visual inspection requirement and adds a requirement to mandate incorporation of main landing gear actuator p/n 46550-13 and adds additional maintenance requirements.

Content changes traced in the AD

• From the Background, the original AD required immediate action after 14 September 2007 in response to two gear collapse incidents. Amendment 1 introduced calendar-based compliance periods and repetitive inspections, creating staged inspection requirements. Amendment 2 introduced stricter technical prescriptions: it amended the detailed visual inspection requirement (Requirement 3) and added a modification requirement (Requirement 5) mandating incorporation of Modsum 4-901603 (actuator p/n 46550-13) and additional maintenance schedule obligations (Requirement 6).
• The AD’s text documents that incorporation of Modsum 4-901603 in accordance with Bombardier SB 84-32-55 Rev NC dated 14 January 2008 meets Requirement 5 (Note 1), and that Modsum 4-901610 with p/n 46550-15 is an alternative satisfying Requirement 5 (Note 2). The AD also records that earlier RD versions satisfy Requirements 2 and 3, preserving compliance options tied to historical documentation.

Effective dates and compliance deadlines

• The AD provides multiple effective/compliance dates linked to the original effective date (14 September 2007), Amendment 1 effective date (2 November 2007), and Amendment 2 effective date (9 March 2009). Where the AD references time-in-service and accumulated landings "at 14 September 2007," it preserves the original compliance reference point for staged deadlines. Requirement 6 imposes a narrow deadline: incorporate the new MRB tasks within 30 days after the effective date of this AD.

Notices and delegation

• The notice is signed by James Coyne, Delegate of the Civil Aviation Safety Authority, dated 19 February 2009; the effective date subsequently recorded is 9 March 2009.

Documentation of terminators

• The AD explicitly documents the terminating actions that arose across amendments: incorporation of Modsum 4-901603 (Terminating Action 1) and incorporation of MRB tasks 320100-211/320100-212 (Terminating Action 2). The AD also documents the allowed deferral for certain piston inspections and the specific situations when earlier RD issues are accepted.

What the amendment history signals

• The recorded evolution from initial urgent inspections to staged calendarised inspections and to a mandated design modification plus maintenance schedule changes shows an escalation from reactive inspections to a prescriptive permanent remedy for the identified risk. The AD itself provides the historical record of that progression, which is the sole source for tracing regulatory choices here.

What the source records

• The AD text provided contains no references to litigation, court decisions or administrative appeals concerning AD/DHC-8/133 or its amendments. There are no cases, appeals, legal challenges or adjudications cited in the document.

Implications of the absence of litigation references

• The absence of litigation references in the source means there is no documented judicial interpretation of the AD contained in this material. The AD's enforceability, timing, scope and the technical instructions are presented as administrative mandates without accompanying judicial or tribunal commentary in this source.

Potential dispute vectors (grounded in the AD text)

• Interpretation of technical terms: disputes could arise over the interpretation of "general visual inspection" versus "detailed visual inspection" as those terms carry operational significance for the depth of inspection and tooling required (the AD allows borescope/10X magnification where required and permits a one-time deferral if earlier inspections were performed without those aids).
• Compliance timing calculations: the AD stages initial compliance by reference to accumulated landings and service time "at 14 September 2007" for certain actuator part numbers. Disagreements could arise over the accuracy of recorded landing counts/cycles or which service interval applies to a particular actuator.
• Acceptability of earlier RD issues: the AD permits inspections performed in accordance with earlier issues of RD 8/4-32-059 to satisfy Requirements 2 and 3. If a regulator or operator took a different view of the sufficiency of earlier RD inspections, that difference could lead to dispute pending administrative review, but the AD itself explicitly authorises earlier RD-based compliance, reducing risk of that particular conflict.
• Reporting adequacy and timeliness: Requirement 4 mandates reporting to Bombardier within seven days for any discrepancies found. Disputes might arise if an operator believes a discrepancy is not reportable or if a report's timeliness is contested.
• Acceptance of alternate terminating modifications: the AD explicitly accepts Modsum 4-901603 and Modsum 4-901610 as satisfying Requirement 5. A dispute could occur if an operator performed a different modification not listed, but the AD does not provide a mechanism within its own text for approving other alternatives; that approval process would likely involve CASA or the certificating authority and is not described here.

Practical note on litigation landscape

• While no litigation is recorded in the AD text, the enforcement of ADs commonly gives rise to administrative review processes or civil disputes between private parties (e.g. lessor/lessee) when costs or scheduling conflicts occur. Those processes are not discussed in the AD and would be governed by broader administrative law and contractual law frameworks outside the instrument itself.

Precise serial-number applicability

• The AD applies only to specified serial numbers (4001, 4003, 4004, 4006, and 4008 through 4208). Operators should verify serial numbers carefully. Misapplying the AD to non-applicable aircraft or failing to apply it to an applicable serial number risks unnecessary work or regulatory non-compliance.

Differences between "general visual" and "detailed visual"

• The AD requires both general visual inspections (Requirements 1 and 2) and a detailed visual inspection (Requirement 3 per RD 8/4-32-059 Issue 5). Operators must ensure maintenance personnel understand the required standard for each inspection. The AD explicitly links detailed inspection to a specific RD Issue and allows use of borescope or 10X magnification; failure to use the specified aids when required could invalidate compliance unless the limited deferral applies.

Staged compliance windows tied to landing counts and months in service

• The AD sets multiple thresholds: 250 landings/one month for general visual repeats; 2,000 landings/one calendar year for detailed inspection repeats; and initial detailed inspection windows tiered by accumulated landings and months in service. Operators must track landings and time-in-service precisely, as the AD references counts and service time "at 14 September 2007" for initial staging. Poor records can result in missed deadlines or disputes over which interval applies.

One-time deferral nuance

• If an inspection of the piston (p/n 46570-1/-3) was previously performed without borescope or 10X magnification mirror, a one-time deferral of up to 500 landings is permissible to complete the inspection with the specified tools. This is a narrow allowance and only available where the earlier inspection lacked the named tools. Relying on the deferral without documentary evidence of the earlier inspection method risks non-compliance.

Reporting timeline

• Any discrepancy found during the inspections must be reported to Bombardier Technical Help Desk within seven days. This is a short reporting window and requires administrative processes to ensure prompt reporting. Failure to report may not be explicitly penalised in the AD, but it inhibits manufacturer fleet-safety monitoring and could be relevant in any later inquiry.

Terminating action alternatives and version control

• The AD prescribes Modsum 4-901603 via SB 84-32-55 Rev A or later approved revisions; it also notes that Modsum 4-901610 with p/n 46550-15 satisfies Requirement 5. Operators must ensure they use the correct Modsum and the approved SB revision. Note 1 records that Revision NC of the SB dated 14 January 2008 meets Requirement 5 , operators should ensure the SB revision used is among those the AD accepts.

Maintenance schedule alignment across jurisdictions

• Requirement 6 requires amendment of "the Transport Canada approved maintenance schedule" by incorporating MRB tasks. Operators in jurisdictions where maintenance schedules are approved by other authorities must coordinate cross-acceptance. The AD references both CASA and Transport Canada documents; failure to align maintenance approval may create administrative friction or gaps in compliance.

Ferry flight caveats

• The ferry-flight provisions are tightly prescriptive: gear extended and pinned, minimum descent rate for landing, minimized braking, flight per AOM Section 4.8, essential crew only, and no known/forecast icing. Maintenance steps before ferry (inspection of jam nut wire lock, general visual inspections per BOM All Operators Message No. 236 Rev A, insertion of ground lock pins/lockwire, ensure nose landing gear ground lock) are mandatory. Any deviation risks invalidating the ferry exception and exposing the aircraft to being non-compliant with the AD.

Costs and resource planning implications

• Modsum incorporation is a hardware replacement likely requiring parts, downtime and qualified maintenance resources. The AD does not provide for supply lead times, so operators must plan for possible procurement delays. Recurrent inspections at short intervals (e.g. 250 landings or one month) can be resource-intensive for high-utilisation operators.

Documentation trail

• Operators must keep accurate records demonstrating inspections were performed in accordance with the specified RD, SB, MRB tasks and that discrepancies were reported to Bombardier within seven days. Absence of such records will complicate any subsequent regulatory oversight or proof of compliance.

Step-by-step compliance checklist tied to the AD

1. Identify applicability

   • Confirm each aircraft’s serial number. The AD applies to Bombardier DHC‑8 Models 400/401/402 with serial numbers 4001, 4003, 4004, 4006 and 4008 through 4208 (Applicability clause). Only aircraft with those serial numbers are subject to these requirements.

2. Perform Requirement 1

   • For aircraft within serial number scope 4001, 4003, 4004, 4006 and 4008 through 4182: perform a general visual inspection of left and right main landing gear in accordance with Bombardier PSM 1-84-7 Part 1 tasks Z700-03E and Z700-04E, and rectify any discrepancies (Requirement 1). This is required "before further flight after 14 September 2007" for instances when it remained outstanding.

3. Perform Requirement 2 (jam nut checks)

   • For all applicable serial-numbered aircraft (4001, 4003, 4004, 4006 and 4008 through 4208): a. Immediately perform a general visual inspection of the left and right main landing gear retract actuator jam nut to ensure the wire lock is present and the nut is secure (Requirement 2a). This is "before further flight after 14 September 2007" unless previously accomplished. b. Establish a recurring inspection schedule to repeat Requirement 2a at intervals not to exceed 250 landings or one month, whichever occurs first (Requirement 2b).

4. Perform Requirement 3 (detailed inspection)

   • For serial numbers 4001, 4003, 4004, 4006 and 4008 through 4182 that have actuators p/n 46550-7/-9/-11: a. Conduct a detailed visual inspection and any required actions in accordance with Bombardier RD 8/4-32-059 Issue 5 or later approved revision (Requirement 3a). b. Repeat detailed inspections at intervals not to exceed 2,000 landings or one calendar year, whichever occurs first (Requirement 3b).
   • Apply the staged initial compliance deadlines based on accumulated landings/service time recorded at 14 September 2007, as set out in the Compliance section. Ensure accurate records of accumulated landings and months in service to determine the correct deadline bracket.

5. Apply the permitted deferral (if applicable)

   • Where an earlier inspection of the piston (p/n 46570-1/-3) threads and thread relief area was done without borescope or 10X magnification mirror, log that condition and use the one-time permissible deferral of up to 500 landings to complete the inspection using a borescope or 10X mirror (as per the deferral allowance stated).

6. Reporting (Requirement 4)

   • Establish an internal procedure to report any discrepancy found during any of the above inspections to the Bombardier Technical Help Desk within seven days after each inspection. Maintain copies of each report and acknowledgement records as part of maintenance records.

7. Implement modification (Requirement 5) or the terminating maintenance schedule (Requirement 6)

   • Decide whether to pursue terminating action via Modsum replacement or via incorporation of MRB tasks: a. Modsum option: procure and install the new design retract actuator p/n 46550-13 in accordance with Bombardier SB 84-32-55 Rev A dated 10 March 2008 (or later approved revision), completing Modsum 4-901603. Alternatively, Modsum 4-901610 with p/n 46550-15 is acceptable (Note 2). Observe the Modsum compliance deadlines provided in the AD, staged by accumulated landings/time in service at the AD effective date. b. Maintenance schedule option: amend the Transport Canada approved maintenance schedule to include tasks 320100-211 and 320100-212 as introduced by Temporary Revision MRB-35 of PSM1-84-7. Incorporation of these tasks provides terminating action to the Requirement 2 general visual inspection regime.
   • Record the incorporation of the Modsum or maintenance tasks and retain documentation of the SB workpack, parts installed, and certificate of release to service.

8. Ferry-flight procedures (if ferry is necessary)

   • If the aircraft must be ferried to a maintenance location before completing inspections/modification, comply strictly with the ferry-flight limitations:
     • Flight crew limitations: gear extended and pinned; landing conducted at minimum descent rate; minimise braking on landing; fly per AOM Section 4.8; essential crew only on board; no flight in known or forecast icing conditions.
     • Maintenance prerequisites: inspect jam nut wire lock; perform general visual inspections as per Bombardier All Operators Message No. 236 Rev A or later; if satisfactory, insert main landing gear ground lock pins and lockwire; ensure nose landing gear ground lock engaged.
   • Document all ferry-flight checks, maintenance actions and crew decisions.

9. Recordkeeping and tracking

   • Maintain accurate logs of landing counts, time-in-service, inspection dates, reports to Bombardier, parts installed, SB compliance documentation and Maintenance Release certifications. Track inspection intervals (250 landings/one month; 2,000 landings/one year) and Modsum deadlines tied to landing thresholds.

10. Use authorised documents and versions

• Execute inspections and modifications per Bombardier RD 8/4-32-059 Issue 5 or later approved revision, Bombardier SB 84-32-55 Rev A or later approved revision, PSM1-84-7 MRB-35 Temporary Revision and any earlier RD versions where the AD accepts them. Retain evidentiary documentation that the specific RD, SB or MRB revision used is the one approved for compliance with the AD.

11. Communicate with regulator and manufacturer

• If there is uncertainty about acceptable compliance methods, raise the issue with CASA and Bombardier, referencing the AD’s allowances (e.g. acceptance of earlier RD issues, alternative Modsum 4-901610). Ensure any deviations or approvals are recorded and, where required, formally approved by the appropriate authority.

12. Plan for resource impact

• Anticipate parts procurement, maintenance manhours and aircraft downtime for Modsum replacement and for recurring inspections at short intervals. Align scheduling with revenue operations to minimise commercial impact.

Documentation to retain for audit

• Completed inspection reports (general and detailed) showing tasks performed per RD/Z700 tasks.
• Discrepancy reports sent to Bombardier (Requirement 4) with date/time stamps and any manufacturer responses.
• Records of Modsum or SB incorporation (parts numbers installed, certificate of release to service, SB revision used).
• Records evidencing incorporation of MRB tasks into the approved maintenance schedule (Requirement 6).
• Ferry-flight checklists and maintenance verification documents where ferry is used.

By following the AD’s prescriptive methods, using the exact Bombardier documents and observing the timing thresholds, operators can demonstrate compliance and, where required, obtain terminating relief from recurring inspections by completing the prescribed modifications or maintenance schedule changes.