AD/CL-600/93 - Fuel Quantity Gauging System Wiring

The AD is organised around a few discrete legal and technical concepts drawn from the text.

• Applicability. The AD applies only to Model CL-600-2B19 aircraft carrying specified serial numbers: "serial numbers 7003 through 7067, 7069 through 7982." The express listing creates a clear scope boundary; aircraft outside that serial-number range are not captured by this directive as written. The serial-number list therefore determines which operators are obliged to act.

• Mandatory modification. The core obligation is to "Modify the Fuel Quantity Gauging System (FQGS) harness routing" using Bombardier SB 601R-28-059 Revision E, 29 October 2007, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada. The AD ties method of compliance to a manufacturer's service bulletin, with a residual approval gate held by the named official at Transport Canada for any later SB revisions.

• Acceptance of prior work. Note 1 states that "Modification of FQGS harness routing prior to the effective date of this directive according to the original issue, Revision A, Revision B, Revision C or Revision D of the above noted SB satisfies the requirements of this Directive." That creates a retroactive acceptance pathway and removes the need for repeat work where earlier SB-compliant modification has already been installed.

• Compliance metric. The Directive uses an aircraft utilisation metric rather than calendar time: compliance must occur "Within 10 000 hours time in service after the effective date of this Directive." This focuses operational scheduling and maintenance planning on flight hours, not dates.

• Safety rationale. The Background section links the AD to regulatory changes in fuel tank safety standards (Chapter 525 of the Airworthiness Manual introduced through NPA2002-043) and to a Transport Canada policy letter, 525-001. The identified hazard is chafing between the FQGS harness and other higher-voltage harnesses, with the causal chain described as chafing leading to increased surface temperature of fuel probes and high-level sensors located inside the fuel tank, which could generate an ignition source and a fuel tank explosion.

• Cross-reference and approval. Note 2 states "Transport Canada AD CF-2007-36 refers." The AD also specifies that "later revisions" of the Bombardier SB are acceptable only if approved by the "Chief, Continuing Airworthiness, Transport Canada." That assigns an approval role to a named Transport Canada official rather than CASA. The AD itself is issued by the Civil Aviation Safety Authority, signed by its delegate.

These concepts determine the legal obligations, acceptable compliance routes, the scheduling metric, and the technical justification underpinning the mandatory action. The AD thus links a manufacturer’s service instructions, a foreign regulator’s approval gate, and an Australian regulator’s enforceable mandate.

This AD affects parties in several distinct roles, as shown in the text.

• Aircraft operators and owners of the listed models and serial numbers. The Applicability section identifies the class of aircraft that must comply: "Model CL-600-2B19 aircraft, serial numbers 7003 through 7067, 7069 through 7982." Those operators and owners are the primary obligation-bearers; they must ensure the required modification is carried out within the stated time-in-service interval.

• Maintenance organisations and aircraft engineers. The Directive prescribes a physical modification "according to the Accomplishment Instructions of Bombardier Service Bulletin (SB) 601R-28-059, Revision E, dated 29 October 2007." Maintenance providers, licensed engineers and workshops will therefore be those executing the modification work and certifying it, using the manufacturer’s instructions as the technical basis.

• The Civil Aviation Safety Authority (CASA). CASA is the issuing authority; the AD is signed by "Charles Lenarcic, Delegate of the Civil Aviation Safety Authority." CASA is therefore the enforcing regulator in Australia for compliance with the AD.

• Transport Canada, specifically the Chief, Continuing Airworthiness. The AD states that "later revisions" of the Bombardier SB must be "approved by the Chief, Continuing Airworthiness, Transport Canada" to be acceptable for compliance. Thus Transport Canada retains a gatekeeping role for future SB revisions, and its prior AD CF-2007-36 is cited as a related instrument. This creates a cross-jurisdictional oversight link: an Australian AD referencing Canadian approval processes.

• Bombardier Aerospace. The manufacturer is the source of the SB that defines the technical method for compliance. Bombardier's SB content and revision history determine acceptable methods of modification and, via Notes, earlier revisions can be accepted where previously applied.

• Compliance auditors and record-keepers. Organisations responsible for airworthiness records must reflect the modification in maintenance logs to demonstrate compliance within the 10,000 hours time-in-service window and to rely on the Note 1 acceptance where prior modifications were done.

The directive therefore assigns obligations primarily to operators and maintenance organisations while recognising the technical role of the manufacturer and an approval role to Transport Canada. CASA enforces the requirement in Australia.

The AD creates discrete duties and limited rights, as expressed in the instrument.

Duties

• Modify FQGS harness routing. The express duty is to "Modify the Fuel Quantity Gauging System (FQGS) harness routing according to the Accomplishment Instructions of Bombardier Service Bulletin (SB) 601R-28-059, Revision E, dated 29 October 2007, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada." That sets the mandatory action and the required technical standard.

• Meet the compliance interval. The modification must be completed "Within 10 000 hours time in service after the effective date of this Directive." Operators must schedule maintenance to meet that utilisation-limited deadline. The use of flight hours as the compliance metric is a specific scheduling duty.

• Maintain or produce compliance evidence. While the AD does not explicitly prescribe documentation language, compliance with an Airworthiness Directive necessarily implies that maintenance records will be updated to show the Bombardier SB Accomplishment Instructions were followed (or that prior work per Revisions A-D was already done). The operator must therefore be prepared to demonstrate compliance to CASA inspectors.

• Follow approval process for later SB revisions. If an operator proposes to comply using a later SB revision, that later revision must be "approved by the Chief, Continuing Airworthiness, Transport Canada." Operators and maintenance organisations therefore have a duty to obtain or confirm any required approval from the named Transport Canada official before relying on later SB content as compliance.

Rights and permitted pathways

• Retroactive acceptance of earlier SB compliance. Note 1 grants a right to count prior compliant modifications as satisfying the AD: "Modification of FQGS harness routing prior to the effective date of this directive according to the original issue, Revision A, Revision B, Revision C or Revision D of the above noted SB satisfies the requirements of this Directive." This means operators who already undertook the modification to those earlier specific SB revisions prior to 13 March 2008 need not repeat the work.

• Use of approved later SB revisions. The AD leaves open the possibility of complying with later Bombardier SB revisions, but only once those later revisions are approved by the Chief, Continuing Airworthiness, Transport Canada. That is a conditional right to adopt a later manufacturer's revision as the compliance means, subject to approval.

• Cross-reference to Transport Canada AD. Note 2 "Transport Canada AD CF-2007-36 refers" gives operators a right to consult the referenced Transport Canada AD for additional context or allowable alternative compliance measures if any are described there. The AD therefore points to a related foreign instrument but does not itself incorporate alternative methods from that AD.

Who decides

• CASA issues and enforces the AD, as signatory of the Directive. The approval authority for later SB revisions rests with Transport Canada, via the named Chief, Continuing Airworthiness. Maintenance and compliance decisions in practice will be executed by the operator and certified maintenance organisations, using the Bombardier Accomplishment Instructions.

The duties therefore combine a mandatory technical modification with a defined deadline, while the rights include acceptance of specific earlier work and conditional acceptance of later revisions once approved by Transport Canada.

The AD itself is an enforceable regulatory instrument issued by the Civil Aviation Safety Authority. While the text provided does not set out a schedule of monetary fines or criminal penalties inside the instrument, it establishes a mandatory maintenance requirement that CASA is empowered to oversee and enforce under the general civil aviation regulatory framework.

Enforcement mechanisms implied by the document

• Regulatory compliance expectation. The AD sets an explicit compliance obligation and a fixed compliance metric: the modification must be completed "Within 10 000 hours time in service after the effective date of this Directive." Operators who fail to comply within that timeframe will be out of step with an express CASA airworthiness requirement and therefore exposed to enforcement action under CASA’s regulatory powers.

• Inspection and airworthiness certification. Operators must maintain maintenance and logbook records showing compliance. CASA’s typical oversight role includes inspections and checks during continued airworthiness reviews, ramp inspections, or certification activities. The AD’s existence creates a specific item that CASA inspectors can verify on affected aircraft.

• Operational limitations in absence of compliance. Although the AD does not itself state that operation of a non-compliant aircraft is prohibited, CASA may use existing regulatory mechanisms to impose operational limitations, grounding, or grounding until rectification if a known unsafe condition exists and is not corrected in a required time. The AD’s Background identifies an unsafe condition (potential ignition source and fuel tank explosion), which is the factual basis CASA would rely upon in enforcing restrictions on non-compliant aircraft.

• Cross-jurisdictional reference. The AD refers to "Transport Canada AD CF-2007-36" and places approval authority for later SB revisions with the "Chief, Continuing Airworthiness, Transport Canada." Any enforcement or oversight involving later revisions therefore may engage Transport Canada’s determinations in dealing with equivalence or alternate compliance pathways. CASA retains enforcement authority in Australia but looks to Transport Canada for approval of later SB revisions.

What the instrument does not specify

• The directive text does not list specific penalties or infringement notice amounts for non-compliance; those are handled through CASA’s broader statutory powers and enforcement regimes under the Civil Aviation Safety Act and associated regulations. The AD itself is the compliance instrument that CASA will use as a basis for enforcement actions, including administrative or sanctioning processes available under the wider regulatory framework.

In practice, operators facing enforcement risk must treat the AD as a binding maintenance imperative and ensure documentary evidence of compliance exists to avoid CASA enforcement measures.

This Airworthiness Directive explicitly situates itself within an international and regulatory ecosystem by referencing other instruments and standards, thereby shaping cross-instrument interactions.

• Interaction with manufacturer service documentation. The AD prescribes compliance with Bombardier Service Bulletin 601R-28-059, Revision E, or later approved revisions. That makes the manufacturer’s SB a de facto incorporated technical standard for the purposes of compliance with the AD. Operators must follow the Accomplishment Instructions in the SB, which are not reproduced in the AD but are mandated by reference.

• Interaction with Transport Canada’s oversight. The AD makes Transport Canada the approval authority for any "later revisions" of the Bombardier SB that an operator might wish to rely on for compliance. Specifically, the AD requires later SB revisions to be "approved by the Chief, Continuing Airworthiness, Transport Canada." Thus, while CASA enforces the AD in Australia, it defers to a nominated Transport Canada official for approval of subsequent SB revisions, producing a formal cross-jurisdictional dependency for changes to compliance methodology.

• Reference to Transport Canada AD CF-2007-36. Note 2 states "Transport Canada AD CF-2007-36 refers." Where that Transport Canada AD contains related requirements or alternate compliance methods, operators may have to reconcile the two instruments to establish compliance. The AD does not incorporate the Transport Canada AD by text, but it directs attention to it as relevant.

• Alignment with Airworthiness Manual changes and policy. The Background explains that Bombardier completed a system safety review against "new fuel tank safety standards, introduced in Chapter 525 of the Airworthiness Manual through Notice of Proposed Amendment (NPA)2002-043" and that the non-compliances were assessed using "Transport Canada Policy Letter No. 525-001." The AD therefore implements corrective action that traces back to changes in the Airworthiness Manual and a Transport Canada policy document, indicating an interplay between technical standards updates and mandatory corrective measures. This situates the AD within the broader regulatory reform that produced the updated fuel tank safety standards.

• Implications for maintenance regulation and certifications. Compliance will necessarily affect maintenance records, sign-offs by authorised personnel, and potential certification of airworthiness. The AD obliges maintenance action that will be logged and relied upon by CASA during airworthiness checks, consistent with statutory maintenance and record-keeping requirements under the general aviation safety regulatory regime.

• No express change to operational rules. The AD mandates a maintenance modification rather than altering flight operations rules or airworthiness regulations text. However, because the Background identifies a safety hazard that could lead to catastrophic failure, absence of compliance could trigger CASA action under other regulatory provisions, which is an interaction by enforcement rather than a direct textual amendment.

In short, the AD interacts with Bombardier’s SBs, Transport Canada’s ADs and approval functions, and with Airworthiness Manual changes and policy letters, creating a web of technical and approval dependencies spanning CASA and Transport Canada while leaving enforcement and record-keeping within CASA’s Australian remit.

The AD text itself contains a limited amendment and revision history as follows.

• Service Bulletin revisions. The AD mandates compliance with Bombardier SB 601R-28-059 Revision E, dated 29 October 2007, and explicitly recognises earlier revisions. Note 1 records that "Modification of FQGS harness routing prior to the effective date of this directive according to the original issue, Revision A, Revision B, Revision C or Revision D of the above noted SB satisfies the requirements of this Directive." This provision accepts work done under the original SB and Revisions A through D if completed before the AD became effective. The AD therefore acknowledges a sequence of SB revisions from original through Revision E and provides a cutoff rule for earlier compliance.

• Transport Canada reference. Note 2 states "Transport Canada AD CF-2007-36 refers." That citation signals that a related Transport Canada AD existed prior to, or contemporaneously with, the CASA AD. The CASA AD therefore lines up with a Canadian corrective action sequence, with the SB revision timetable evident in the dates provided (Revision E dated 29 October 2007) and the AD effective date of 13 March 2008.

• Effective date and signature. The AD is signed by the CASA delegate on "21 January 2008" and became effective on "13 March 2008." This sequence indicates the internal administrative dates: signature preceded effectiveness by approximately seven weeks, giving operators notice time before the compliance clock (10,000 hours time-in-service from 13 March 2008) starts.

• No further amendments recorded in the instrument. The text supplied does not record subsequent amendments, supersessions, or revocations of the AD. There is no explicit amendment history beyond the relation to SB revision A-E and the Transport Canada AD reference. Any later amendments to this CASA AD, or further SB revisions, are not included in the supplied text.

Operators should therefore treat the AD’s internal history as: Bombardier issued multiple SB revisions culminating in Revision E (29 October 2007), CASA issued an AD signed 21 January 2008 and effective 13 March 2008, accepting earlier SB-compliant work done prior to effectiveness and allowing later SB revisions only with Transport Canada approval. Any post-AD amendments, if they exist, are not contained in the provided instrument.

The supplied text contains no litigation history. The instrument does not name any cases, nor does it reference court decisions, administrative appeals, or contested enforcement outcomes. It does not record any appeals against the AD, petitions for review, or judicial pronouncements concerning its validity or application.

What the AD does include relevant to dispute context

• Regulatory references that might feature in disputes. The AD cites Bombardier SB 601R-28-059 Revisions, Transport Canada AD CF-2007-36, and Transport Canada Policy Letter No. 525-001. These instruments could be relevant in any legal or administrative dispute about compliance scope, alternative methods, or approval for later SB revisions. However, no litigation is recorded in the AD itself.

• No appeal or review pathway stated in the AD text. The AD does not set out an internal appeal mechanism or a specific process for challenging CASA’s directive. That does not mean none exists under the broader civil aviation legal framework; it simply means the AD text does not document a litigation history or procedural review steps.

If practitioners require litigation or case law context for enforcement treatments of ADs or the interplay of foreign regulator approvals, they will need to consult other sources outside the provided instrument. The supplied AD contains no entries on legal challenges or judicial treatment.

The AD contains several concrete pitfalls and practical details that may surprise operators or maintenance planners if overlooked. These are drawn directly from the instrument text.

• Narrow serial-number applicability with unintended exclusions. The Applicability clause lists "serial numbers 7003 through 7067, 7069 through 7982." That sequence omits serial number 7068 and any serials below 7003 or above 7982. Operators of adjacent serial-numbered aircraft must not assume inclusion; compliance obligations attach only to the explicitly listed serials. Relying on proximity of serial numbering is not a permissible interpretation of the AD.

• Compliance measured in hours, not calendar time. The compliance window is "Within 10 000 hours time in service after the effective date of this Directive." This means the countdown is measured in aircraft time in service (flight hours), not days or months. Operators with high-utilisation aircraft must plan earlier; low-utilisation aircraft may have more calendar time available. Failing to track the hours metric accurately risks missing the compliance point.

• Earlier SB revisions are conditionally accepted but only if done before the effective date. Note 1 enables acceptance of modifications done to the "original issue, Revision A, Revision B, Revision C or Revision D" of the SB, but only if they were completed "prior to the effective date of this directive." If modifications were performed after the effective date using those earlier revisions, the AD does not state that they satisfy the Directive. The timing of prior work relative to 13 March 2008 is therefore critical.

• Later revisions require Transport Canada approval. The AD allows later Bombardier SB revisions to be used for compliance, but only when "approved by the Chief, Continuing Airworthiness, Transport Canada." Australian operators wishing to adopt a later SB revision must secure that Canadian approval or otherwise demonstrate equivalence; CASA’s AD does not unilaterally accept later revisions without that named approval.

• Cross-reference to Transport Canada AD. Note 2 "Transport Canada AD CF-2007-36 refers." Operators should consult that Transport Canada AD for technical context or alternative methods; assuming it is identical or optional without checking may be an error.

• The AD does not specify alternative methods of compliance within its text. While later SB revisions may be approved by Transport Canada, the AD itself does not enumerate alternative procedures, nor does it provide a local CASA approval route for deviations. Operators must therefore work through the specified SB or obtain the stated approval for alternate SB revisions.

• The unsafe condition described involves internal fuel-tank components. The Background defines the hazard as increased surface temperatures of "fuel quantity probes and high level sensors inside the fuel tank," creating a potential ignition source. Any work that does not materially change harness routing affecting these probe and sensor locations may not satisfy the safety objective. Compliance requires following the Accomplishment Instructions to address the specified hazard pathway.

• Documentation and traceability. Because acceptance of prior SB revisions is conditional on timing and because later revisions require external approval, robust maintenance records that record the SB revision used and the date of accomplishment are essential. An incomplete log entry may render an operator unable to rely on Note 1 or to demonstrate correct application of a later approved revision.

These gotchas are drawn directly from the AD’s text and structure. They highlight precise interpretation risks around serial-number scope, compliance metrics, acceptable SB revisions, and documentary proof.

The AD prescribes a specific, narrowly-defined compliance pathway and a limited set of permissible alternatives. Compliance steps consistent with the instrument text are as follows.

1. Confirm applicability. Check the aircraft serial number against the Applicability clause: "serial numbers 7003 through 7067, 7069 through 7982." Only aircraft whose serial numbers fall in that range are subject to this AD.

2. Establish the compliance deadline in hours. The AD requires the modification "Within 10 000 hours time in service after the effective date of this Directive." The effective date is "13 March 2008." Calculate the aircraft’s accumulated hours from that effective date forward and schedule the modification before the aircraft reaches 10,000 hours in service relative to 13 March 2008.

3. Use the mandated technical standard. Perform the harness routing modification "according to the Accomplishment Instructions of Bombardier Service Bulletin (SB) 601R-28-059, Revision E, dated 29 October 2007." Obtain and use the Accomplishment Instructions verbatim for the physical work. If using documentation in a maintenance organisation, ensure the correct SB revision (Revision E) is the one cited and applied in the maintenance release.

4. If the work was done prior to the effective date, check whether it used an accepted earlier SB revision. Note 1 states that "Modification of FQGS harness routing prior to the effective date of this directive according to the original issue, Revision A, Revision B, Revision C or Revision D of the above noted SB satisfies the requirements of this Directive." If your aircraft was modified prior to 13 March 2008 under any of those revisions, retain the records as evidence and no further action under this AD is required for that aircraft.

5. If relying on a later SB revision. The AD permits "later revisions approved by the Chief, Continuing Airworthiness, Transport Canada." If Bombardier issues a revision after Revision E and you intend to comply using that later revision, obtain written approval from the Chief, Continuing Airworthiness, Transport Canada before relying on it for compliance. Retain the approval documentation with the maintenance records.

6. Record-keeping. Enter the modification into the aircraft maintenance logbook and other required airworthiness records, citing the SB (including revision and date), the AD identifier (AD/CL-600/93), the date of accomplishment, and the authorised signatory who released the aircraft back to service. If the modification relied on Note 1 or on Transport Canada approval of a later revision, document those facts expressly.

7. Coordinate with transport authority and Bombardier if questions arise. The AD cross-references "Transport Canada AD CF-2007-36" and places approval authority with a Transport Canada official. If there is uncertainty about whether a proposed routing satisfies the Accomplishment Instructions, whether a later SB revision is appropriate, or whether an alternative method of compliance could be acceptable, make enquiries to Transport Canada for approval or to CASA for guidance on enforcement expectations. Do not assume orally conveyed approvals; obtain written approvals where required.

8. Plan operational disruptions. Although the AD does not state the duration of the modification, treat the work as scheduled maintenance that may require aircraft downtime, parts, and certified maintenance personnel. Schedule the work to meet the 10,000 hours TIS deadline and to fit within existing maintenance checks where possible.

9. Compliance verification. Prior to returning the aircraft to service, confirm the harness routing change has been executed per the SB Accomplishment Instructions, that the routing addresses the chafing hazard described in the Background, and that all required inspections and tests included in the SB were completed and signed off.

10. Keep a watch on related instruments. Because the AD references Transport Canada AD CF-2007-36 and Transport Canada policy and Airworthiness Manual changes, monitor those instruments for any guidance or approvals that affect compliance pathways. If Bombardier issues clarification or revised instructions and those are approved by the Chief, Continuing Airworthiness, Transport Canada, maintain records of that approval.

Following these steps will align an operator’s actions with the precise text of the AD as supplied. The critical elements are verifying serial-number applicability, meeting the 10,000-hour time-in-service deadline from 13 March 2008, performing the work to Bombardier SB 601R-28-059 Revision E instructions (or using an approved later revision), and retaining documentary proof of the SB revision used and the date of accomplishment.