AD/CL-600/123 - Wing Anti-Ice System - Outboard Low-Heat Detection Switches

This Airworthiness Directive (AD/CL-600/123, dated 21/2009) requires a set of immediate and staged changes to the wing anti-ice system (WAIS) on Bombardier CL-600-2B19 aeroplanes with serial numbers 7003 through 8101. Mechanically, the Directive mandates five discrete actions:

• Amend the Aircraft Flight Manual (AFM) CSP A-012 by inserting Temporary Revision (TR) No RJ/164-2 dated 12 May 2009, or later approved changes, and advise flight crews of the changes (Requirement 1). The AD text states this must be done "within 30 days after the effective date of this Directive" (Compliance).
• Revise the approved maintenance schedule by incorporating inspection requirements contained in TR 2A-46, dated 24 July 2009, of the Maintenance Requirements Manual, CSP A-053, Part 2, Appendix A, Certification Maintenance Requirements (Requirement 2). This is also due within 30 days (Compliance).
• Replace existing Data Concentrator Units (DCUs) P/N 622-9820-007 and/or -008 and/or -009 with modified DCUs P/N 622-9820-010 and, where applicable, modify Configuration Strapping Units (CSUs) in accordance with Bombardier Service Bulletin (SB) 601R-31-034 Revision A dated 10 April 2008, or earlier SB dated 19 November 2007, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada (Requirement 3). The AD requires this "prior to accomplishment Requirement 5" but no later than 1 November 2010 (Compliance).
• Install outboard low-heat detection switches, the wing A/ICE box assembly and associated wiring in accordance with Parts A, C, D and E of Bombardier SB 601R-30-031 Revision A dated 8 September 2009, or earlier Part A dated 15 May 2009, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada (Requirement 4). This must be completed prior to Requirement 5 but no later than 1 November 2010 (Compliance).
• Activate the outboard low-heat detection switches per Part F of Bombardier SB 601R-30-031 Revision A dated 8 September 2009, or earlier Part B dated 15 May 2009, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada (Requirement 5). Activation is to follow completion of Requirements 3 and 4, and no later than 1 November 2010 (Compliance).

The AD becomes effective 16 October 2009 and is signed by David Villiers, Delegate of the Civil Aviation Safety Authority (9 October 2009). The text contains multiple notes that qualify compliance and method: it allows accomplishment in accordance with original SB issues where expressly stated (Notes 2, 4, 6), specifies production aircraft S/N 8096 and subsequent already have modified DCUs (Note 1), flags a specific maintenance check for correct piccolo duct alignment (Note 5), and cross-references Transport Canada AD CF-2009-0037 (Note 8). The Directive also explains that the DCU software update fixes FDR sampling rate non‑compliances for normal acceleration and pitch attitude (Note 9). The AFM amendment carries an operational advisory that certain WAIS mode selection changes may result in a two-minute inhibition of the wing anti-ice message once the new outboard low-heat switches are installed and activated (Background; Requirement 1).

In short, the AD imposes combined operational, hardware, software and maintenance-program changes on affected aircraft to introduce outboard low-heat detection capability and associated signalling to flight crews, with staged compliance deadlines and prescribed manufacturer SBs as the means of compliance.

The Directive targets a specific safety gap: insufficient detection of low-heat conditions on the wing outboard leading edge. The AD explains that the existing WAIS heat sensors are located at the inboard wing ends and require a simultaneous low-pressure signal from both wings to generate an amber L or R WING A/ICE caution. That architecture can fail to detect an outboard low-heat condition, producing a scenario of unannunciated asymmetric ice build-up on the wing leading edge (Background). The identified in-service occurrences included partial failure of piccolo ducts and partial failure of a modulating and shut-off valve. The AD links these failures to the hazard that, in combination with manoeuvres close to stick shaker activation, may reduce aircraft controllability (Background).

Key technical responses the AD mandates:

• Outboard low-heat detection switches: Installation of dedicated switches in the outboard leading edge (Requirement 4) widens the detection envelope so that a low-heat condition inboard-only detection cannot mask outboard low-heat conditions. The AD requires activation of those switches (Requirement 5).
• DCU replacement and software update: Replacing the DCU with P/N 622-9820-010 and modifying CSUs as necessary (Requirement 3) equips the aircraft electronics with software logic that accounts for the additional outboard detection switches and generates appropriate flight-deck messages. The AD explicitly states the software update also corrects the sampling rate of two previously non‑compliant Flight Data Recorder (FDR) parameters, normal acceleration and pitch attitude (Note 9).
• AFM and maintenance documentation changes: The AD requires an AFM temporary revision and revision of the maintenance schedule to add functional checks arising from the new hardware and activation (Requirements 1 and 2). The AFM TR specifically notifies flight crews that after installation and activation of the low-heat detection switches, certain WAIS mode selection changes may result in a two-minute inhibition of the wing anti-ice message (Background).
• Staged implementation: The AD prescribes sequencing: AFM and maintenance schedule changes within 30 days; DCU replacement and physical installation no later than 1 November 2010 and prior to activation; activation no later than 1 November 2010 and following the installations (Compliance). Note 7 allows each Requirement to be accomplished separately within the compliance constraints.

Mechanically and legally, the AD achieves change by mandating incorporation of manufacturer service documents as the means of compliance (Bombardier SBs and TRs). The Directive recognises alternative compliance paths only insofar as subsequent revisions of the stated TRs and SBs are "approved by the Chief, Continuing Airworthiness, Transport Canada" or as specified when original SB issues "also meet the intent" (Notes 2, 4, 6, and SB references in Requirements 3, 4 and 5). The Directive therefore relies on a mix of prescriptive parts replacement (specified P/Ns), installation and activation procedures in SBs, and administrative changes to operator manuals and maintenance programs.

The Directive limits applicability to Model CL-600-2B19 aeroplanes, serial numbers 7003 through 8101 (Applicability). The primary affected parties are therefore:

• Aircraft operators and owners of CL-600-2B19 aeroplanes within the serial number range. These parties must undertake the AFM and maintenance schedule revisions (Requirements 1 and 2), arrange DCU replacements and possible CSU modifications (Requirement 3), install the outboard switches and wiring (Requirement 4), and perform activation (Requirement 5). The compliance timetable imposes near-term action for documentation and staged deadlines for hardware and activation.
• Flight crews: They must be advised of the AFM TR changes (Requirement 1). The AFM TR warns that activation of the low-heat detection switches may create a two-minute inhibition of the wing anti-ice message for certain WAIS mode selection changes (Background). That changes the crew‑facing annunciation logic and affects in-flight decision-making and normal procedures when anti-ice modes are changed.
• Maintenance organisations, licensed engineers and maintenance schedulers: Maintenance providers must revise approved maintenance schedules to include the inspection requirements from TR 2A-46 (Requirement 2) and must perform the DCU replacement, CSU modification if applicable, outboard switch installation, wiring and activation per the Bombardier SBs referenced (Requirements 3-5). Note 5 draws attention to a specific maintenance task for correct piccolo duct alignment (Aircraft Maintenance Manual Task 30-11-41-820-801), which is a discrete maintenance quality risk during the reinstallation of piccolo ducts and leading edge assemblies.
• Parts and avionics suppliers: Supply of DCUs P/N 622-9820-010 and any required CSUs, A/ICE box assemblies and associated wiring will be in demand. Operators may find lead times and pricing affected by required part numbers and the need to source SB‑compliant kits.
• Certifying authorities and regulators: The AD interacts with Transport Canada approvals; several requirements allow compliance with earlier or later SB revisions "approved by the Chief, Continuing Airworthiness, Transport Canada" (Requirements 3-5 and Notes). The AD itself is issued by the Civil Aviation Safety Authority, with the Delegate signature of David Villiers. For international operators or cross‑registered aircraft, the cross-reference to Transport Canada AD CF-2009-0037 (Note 8) will be material.
• Flight data and accident investigators: The DCU software update corrects FDR parameter sampling rates for normal acceleration and pitch attitude (Note 9). This affects the integrity and regulatory compliance of recorded flight data and could change historical comparability of datasets before and after modification.

Duties imposed by the Directive are explicit and prescriptive. Principal duties include:

• AFM amendment and crew notification: Operators must insert TR RJ/164-2 dated 12 May 2009 into AFM CSP A-012 or later approved changes and "advise all flight crews" of the introduced changes (Requirement 1; Compliance: within 30 days). The duty is administrative and operational because it alters crew information and, indirectly, in‑flight behaviour due to a two‑minute WAIS message inhibition effect (Background).
• Maintenance schedule revision: Operators must revise their approved maintenance schedule to incorporate inspection requirements contained in TR 2A-46 dated 24 July 2009 of the Maintenance Requirements Manual CSP A-053 (Requirement 2; Compliance: within 30 days). This duty modifies the certified maintenance program and creates additional inspection obligations.
• Hardware replacement and modification: Operators must replace DCUs to P/N 622-9820-010 and modify CSUs where applicable in accordance with Bombardier SB 601R-31-034 Rev A (or specified alternatives) (Requirement 3; Compliance: prior to Requirement 5, no later than 1 November 2010). This imposes physical parts change and software update duties on the operator/maintainer.
• Installation of outboard switches and wiring: Operators must install the low-heat detection switches, wing A/ICE box assembly and associated wires per specified SB parts (Requirement 4; Compliance: prior to Requirement 5, no later than 1 November 2010). This is an installation duty requiring adherence to manufacturer instructions.
• Activation: Operators must activate the outboard low-heat detection switches per SB Part F (Requirement 5; Compliance: after 3 and 4, no later than 1 November 2010). Activation is a discrete software/procedural task.

Rights and permitted flexibilities in the Directive are limited but present and are expressed in the AD’s notes and references:

• Use of later approved revisions: The Directive allows compliance using the listed TRs and SBs "or later approved changes" or "later revisions approved by the Chief, Continuing Airworthiness, Transport Canada" (Requirements 1, 3, 4, 5). That gives operators and maintainers the right to use subsequent manufacturer revisions provided those revisions obtain the specified regulatory approval.
• Acceptance of original SB issues: The AD expressly states that accomplishment in accordance with original issues of certain Bombardier SBs "also meets the intent of" the relevant Requirements (Notes 2, 4, 6). This permits operators to rely on earlier SB releases where applicable.

The AD itself sets out the effective date (16 October 2009) and compliance deadlines, but it does not specify fines, sanctions or explicit enforcement instruments within its text. It is signed by David Villiers, Delegate of the Civil Aviation Safety Authority (9 October 2009), which establishes the Directive as a regulatory instrument issued by CASA with binding compliance obligations for affected operators (signature and effective date). Beyond that, the AD relies on the regulatory authority of CASA and cross-reference to Transport Canada approvals but does not list administratively imposed penalties in this document.

Absent penalty text in the AD, several practical enforcement mechanisms are implicated by the Directive’s structure and customary practices in civil aviation regulation:

• Operations limitation: Non-compliant aircraft would not meet the continuing airworthiness requirements set out by the AD and associated AFM/maintenance revisions. Regulators typically rely on certificates of airworthiness, maintenance release records and operator compliance with ADs to determine whether an aircraft is legally fit for flight. The AD’s documentation and installation requirements (Requirements 1-5, Compliance) imply that operators must certify compliance in their maintenance records and AFM contents before dispatch.
• Regulatory oversight: CASA, as issuer of the AD, would be the enforcing authority in Australia and may exercise its regulatory powers under relevant aviation legislation and regulations (not set out in this AD text) to ensure compliance. The AD’s text signals that later SB revisions must be "approved by the Chief, Continuing Airworthiness, Transport Canada" where specified, creating an approval requirement that a regulator would validate.
• Continued airworthiness audits and ramp checks: While not detailed in the AD, compliance with ADs is routinely verified through periodic audits, surveillance activities and ramp inspections in the aviation regulatory environment. The AD’s requirement to alter certified maintenance programmes and AFMs provides documentary evidence that auditors and inspectors can check.

The AD does not identify civil or criminal penalties, administrative infringement notices, suspension of an air operator certificate, or other sanctions within its content. If a reader requires the specific statutory penalty regime or procedural steps for enforcement, consultation of the Civil Aviation Safety Authority’s enforcement framework and the Civil Aviation Act and Civil Aviation Safety Regulations is necessary, because that material is outside the AD text. The AD does, however, make compliance mandatory by prescribing exact technical and administrative steps, compliance windows and regulatory approvals required to meet the Directive.

The AD explicitly cross-references and coordinates with other regulatory and manufacturer instruments. The most concrete interactions in the text are:

• Transport Canada linkage: The AD repeatedly allows or requires the use of SB revisions and changes "approved by the Chief, Continuing Airworthiness, Transport Canada" (Requirements 3-5). Note 8 explicitly says "Transport Canada AD CF-2009-0037 refers." This indicates that the AD has been aligned with corresponding Transport Canada regulatory action and that certain approvals and acceptance of alternative SB revisions depend on Transport Canada’s Continuing Airworthiness authority. For operators outside Australia, or for aircraft that are originally type-certificated in Canada, this coordination ties CASA’s directive to Transport Canada processes.
• Manufacturer documentation: The AD mandates insertion of an AFM Temporary Revision (TR RJ/164-2 dated 12 May 2009) into AFM CSP A-012 and incorporation of TR 2A-46 dated 24 July 2009 into the Maintenance Requirements Manual CSP A-053 (Requirements 1 and 2). It also prescribes adherence to Bombardier Service Bulletins SB 601R-31-034 and SB 601R-30-031 (Requirements 3-5). Those manufacturer documents are incorporated by reference into the AD as the method of compliance. Legally, that makes the contents of the TRs and SBs enforceable when they are identified in the AD, subject to any later revisions the regulator approves.
• Flight Data Recorder standards: Note 9 states that the DCU software update corrects sampling rates of two previously non‑compliant FDR parameters, normal acceleration and pitch attitude. The AD therefore interacts with FDR regulatory compliance requirements. While the AD does not reproduce the FDR standards, it creates an operational interaction between WAIS/avionics software changes and regulators' FDR performance expectations.
• Aircraft Maintenance Manual (AMM): Note 5 explicitly refers to Aircraft Maintenance Manual Task 30-11-41-820-801 for correct alignment of piccolo ducts. The AD therefore intersects with the AMM, which is typically part of the approved maintenance data for continued airworthiness.
• Compliance timelines and continuing airworthiness: The AD modifies the operator's approved maintenance schedule and AFM, both of which are components of the continuing airworthiness regulatory framework. The changes must be approved and documented as per regulatory requirements for maintenance programs and AFMs, integrating the AD into the broader statutory compliance regime for airworthiness.

The Directive text itself contains explicit internal references to revisions and previous versions of the manufacturer service bulletins and technical revisions that can be used to meet the Requirements:

• AFM TR: Requirement 1 specifies insertion of Temporary Revision (TR) No RJ/164-2 dated 12 May 2009, "or later approved changes to this TR."
• Maintenance TR: Requirement 2 references TR 2A-46 dated 24 July 2009 to the Maintenance Requirements Manual CSP A-053, Part 2, Appendix A.
• DCU replacement SB: Requirement 3 cites Bombardier SB 601R-31-034, Revision A dated 10 April 2008, and Note 2 confirms that "Accomplishment in accordance with the original issue of Bombardier SB 601R-31-034 dated 19 November 2007 also meets the intent of Requirement 3."
• Outboard switches SB: Requirement 4 cites Bombardier SB 601R-30-031, Revision A dated 8 September 2009, and Note 4 confirms that "Accomplishment in accordance with Part A of the original issue of Bombardier SB 601R-30-031 dated 15 May 2009 also meets the intent of Requirement 4." Note 6 indicates that "Accomplishment in accordance with Part B of the original issue of Bombardier SB 601R-30-031 dated 15 May 2009 also meets the intent of Requirement 5."
• Transport Canada AD cross-reference: Note 8 states that Transport Canada AD CF-2009-0037 refers, showing that the AD aligns with an earlier Transport Canada action.

The AD itself became effective 16 October 2009 and is dated 9 October 2009 (Delegate signature). The only amendment history present within the AD is the acceptance of original SB issues as meeting the AD intent in certain cases, and the permission to use later revisions if approved by the Chief, Continuing Airworthiness, Transport Canada. There is no record within this AD text of subsequent modifications to the AD after its issue, nor of superseding ADs or revocations. The AD does, however, identify specific dates for TRs and SB revisions that are acceptable for compliance and leaves open the pathway of later revisions subject to the stated approvals.

Operators should note:

• The AD explicitly authorises the use of certain earlier manufacturer documents to meet the AD intent where stated (Notes 2, 4, 6). That can reduce the need to procure particular SB revision A issues if the earlier documents are available and properly applied.
• The AD requires later SB revisions to be "approved by the Chief, Continuing Airworthiness, Transport Canada," effectively delegating to Transport Canada the function of approving later technical revisions that CASA will accept for compliance purposes. Tracking approvals and any later revisions from both Bombardier and Transport Canada therefore becomes part of an operator’s amendment control for demonstrating compliance.

The AD document provided does not record any litigation or case law arising from this Directive. It contains no references to legal challenges, judicial review, enforcement proceedings or administrative appeals. The only cross-jurisdictional regulatory reference is to Transport Canada AD CF-2009-0037 (Note 8), which is regulatory coordination rather than litigation.

What the absence of litigation detail in the text means for practitioners and researchers:

• The AD itself is an administrative regulatory instrument; such instruments are often subject to regulatory enforcement rather than courtroom litigation. The AD does not include any description of enforcement actions taken against specific operators or manufacturers for non-compliance in relation to this Directive.
• For proof of any litigation history (for example, if a party seeks to know whether compliance requirements were contested), a judicial or administrative law database search would be needed. The AD text does not authorise drawing conclusions about litigation prevalence or outcomes.
• The AD includes prescriptive obligations and references to manufacturer SBs and regulator approvals. If disputes arise about whether a maintenance action "meets the intent" of the AD (for example, whether an earlier SB issue legitimately satisfies the Requirement under Notes 2, 4 or 6), such disputes would typically be handled administratively by CASA or Transport Canada in the first instance, and possibly in judicial review forums if there is contention about approval decisions. None of these procedures are recorded in the AD text itself.

If a reader requires a complete litigation history, the recommended next steps are to consult CASA enforcement records, Transport Canada records, court and tribunal databases, and industry legal reporting covering the period after 2009 for any cases or enforcement actions that reference AD/CL-600/123 or Transport Canada AD CF-2009-0037. The AD text supplies the precise identifiers (AD/CL-600/123, Transport Canada AD CF-2009-0037, SB numbers and TR numbers) that should be used for targeted searches.

The Directive contains several concrete points that operators and maintainers can easily overlook, each with operational or technical risk if not addressed:

• AFM message inhibition: The AFM TR required by Requirement 1 warns that, after installation and activation of the outboard low-heat detection switches, "certain WAIS mode selection changes may result in a two-minute inhibition of the wing anti-ice message" (Background). The practical effect is that a newly installed detection system can cause the wing A/ICE message to be suppressed for a finite period after specific mode changes. Operators must consider the human factors and dispatch ramifications of this inhibition period and ensure crews understand the AFM TR wording and any interim procedures. Failure to properly brief crews could lead to misinterpretation of the absence of annunciation.
• Sequencing constraints: The AD requires DCU replacement (Requirement 3) and installation of outboard switches (Requirement 4) "prior to accomplishment Requirement 5" and sets a not-later-than date of 1 November 2010 for Requirements 3-5 (Compliance). Requirement 5 (activation) must occur after 3 and 4. Note 7, however, permits each Requirement to be accomplished separately within the compliance times. Operators must carefully schedule parts procurement, maintenance man-hours and flight availability to respect sequencing. Mis-sequencing could result in activation prior to a DCU software update, potentially producing inconsistent annunciation or degraded functionality.
• Parts numbering and production fit exceptions: The AD mandates replacement of DCUs P/Ns 622-9820-007/008/009 with P/N 622-9820-010 (Requirement 3). Note 1 states production aircraft S/N 8096 and subsequent already have modified DCUs. Owners of aircraft S/N 8096+ should verify records to avoid unnecessary retrofits; owners of earlier serial numbers must confirm part availability and compatibility with on-wing systems, including whether their CSUs require modification.
• Piccolo duct orientation: Note 5 reports a "small number of cases" where piccolo ducts were installed in the opposite wing, resulting in incorrect orientation of bleed holes. The AD emphasises careful alignment of piccolo ducts during reinstallation per AMM Task 30-11-41-820-801. If piccolo ducts are misoriented, the outboard heat distribution and detection could be compromised, creating safety risk despite compliance with switch installation and DCU updates.
• FDR parameter sampling rate changes: Note 9 states the DCU software update corrects sampling rates for normal acceleration and pitch attitude, which had previously been non‑compliant. This change affects recorded flight data. Investigators, operators and data analysts must be aware that FDR parameter histories differ before and after the DCU replacement. Operators should consider documenting the software change in FDR records and notifying any relevant oversight bodies to prevent misinterpretation of FDR data continuity.

A practical compliance checklist, derived from the AD text, follows. Each step cites the AD’s Requirement or Note where applicable. Operators should incorporate these items into their continuing airworthiness management plans with documented evidence of completion.

Immediate administrative steps (within 30 days of 16 October 2009):

1. Insert AFM TR: Amend AFM CSP A-012 by inserting Temporary Revision No RJ/164-2 dated 12 May 2009, or a later approved change that the regulator accepts (Requirement 1; Compliance: within 30 days). Record the TR insertion in the AFM revision history and ensure TR is available on all affected aircraft.
2. Crew notification: Advise all flight crews of the AFM TR changes, emphasizing that certain WAIS mode selection changes may result in a two-minute inhibition of the wing anti-ice message after activation of the outboard switches (Requirement 1; Background). Document the briefing and retain crew acknowledgement where applicable.
3. Maintenance schedule revision: Incorporate inspection requirements in TR 2A-46 dated 24 July 2009 into the approved maintenance schedule, Maintenance Requirements Manual CSP A-053 Part 2, Appendix A (Requirement 2; Compliance: within 30 days). Seek necessary approvals under the operator’s continuing airworthiness management system for the schedule change.

Hardware, software and installation steps (no later than 1 November 2010, and sequenced): 4. Plan parts procurement: Order DCU P/N 622-9820-010 units and any CSU modification kits required for the operator’s serial numbers (Requirement 3; Note 1 clarifies S/N 8096+ may already be compliant). Validate part numbers against airframe serial numbers and confirm availability with Bombardier or approved suppliers. 5. Arrange DCU replacement and CSU modification: Execute replacement of DCUs P/N 622-9820-007/008/009 with P/N 622-9820-010 and modify CSUs as applicable, following the Accomplishment Instructions in Bombardier SB 601R-31-034, Revision A dated 10 April 2008, or the original issue dated 19 November 2007 where Note 2 permits (Requirement 3; Compliance: prior to Requirement 5, no later than 1 November 2010). Record software version changes and maintain evidence of SB compliance in logbooks and maintenance release documentation. 6. Install outboard low-heat detection switches and A/ICE box assembly: Conduct installations and associated wiring per Parts A, C, D and E of Bombardier SB 601R-30-031, Revision A dated 8 September 2009, or the original Part A dated 15 May 2009 or later regulator-approved revisions (Requirement 4; Compliance: prior to Requirement 5, no later than 1 November 2010). Where installations are performed in separate sessions, ensure each SB Part’s instructions are fully implemented and documented, because Note 3 states Parts A, C, D and E may be performed separately. 7. Pay attention to piccolo duct alignment: During reinstallation of piccolo ducts and leading edge assemblies, verify correct alignment of piccolo ducts as incorrect installation has been reported (Note 5). Use AMM Task 30-11-41-820-801 as the reference for correct alignment and document the inspection and verification results. 8. Activate the outboard low-heat detection switches: After DCU replacement and physical installations are complete, perform activation in accordance with Part F of Bombardier SB 601R-30-031, Revision A dated 8 September 2009, or Part B of the original printed issue as allowed by Note 6 (Requirement 5; Compliance: following 3 and 4, no later than 1 November 2010). Record activation steps, software versions, and any test or functional check outcomes. 9. Perform required functional checks: Implement the revised and new functional checks introduced by TR 2A-46 and by the SBs during and after activation. These checks are required parts of the maintenance schedule amendment and provide evidence that the system is fully operational (Requirement 2). 10. Document FDR impacts: Record the DCU software update in maintenance records and FDR configuration logs, noting that the software corrects sampling rates for normal acceleration and pitch attitude (Note 9). Notify any relevant investigators or authorities if required by airworthiness reporting procedures.