AD/CL-600/103 - Refuel/Defuel Valve Electrical Bonding

Airworthiness Directive (AD). An AD is a legally enforceable notice issued by a national aviation authority, here CASA, requiring corrective action on an aircraft or component when an unsafe condition is identified and likely to exist or develop in other aircraft of the same type. ADs are the primary regulatory tool for addressing in-service safety defects outside the original type certification process. This AD is designated AD/CL-600/103 and is referenced as issue 11/2008, indicating it is the eleventh AD issued in 2008 for this aircraft type series.

Electrical bonding. This refers to the intentional connection of metallic parts to the aircraft structure to provide a low-impedance path for electrical current. In fuel systems, adequate bonding ensures that any static discharge or lightning-induced current is safely conducted away without creating a spark. The AD identifies two distinct bonding deficiencies: a non-conductive Gask-O-Seal gasket and an anodic coating on the conduit connection fitting. Both interrupt the electrical path. The mandated modification likely replaces or treats these components to restore conductive continuity.

Refuel/defuel shutoff valves. These valves control the flow of fuel into and out of the centre wing fuel tank during ground fuelling and defuelling operations. They are located inside the fuel tank and are therefore exposed to fuel vapour, making any electrical arcing particularly hazardous. The AD requires modification of these valves to ensure that the valve body and its actuating components are electrically bonded to the aircraft structure.

Gask-O-Seal. This is a type of gasket that integrates sealing elements with a metal or composite carrier. In its original configuration, the gasket apparently was not electrically conductive, thereby insulating the valve from the structure. The modification presumably replaces or supplements the gasket with a conductive alternative or ensures a metallic contact path is established.

Anodic coating. Anodic coating is an electrochemical process used to increase corrosion resistance and paint adhesion on aluminium parts. The coating is typically electrically non-conductive. The anodic coating on the shutoff valve electrical conduit connection fitting was found to impede electrical bonding. The modification would require removing or masking the coating on contact surfaces or installing a conductive bridge.

Unsafe condition. The background text states that the assessment showed that the bonding deficiencies could result in arcing and a potential ignition source during lightning strikes, leading to a fuel tank explosion. This is the ‘unsafe condition’ that the AD aims to correct. The concept of an unsafe condition is central to AD issuance: an authority cannot mandate a modification without first identifying a condition that is likely to exist in other aircraft of the same type and that, if not corrected, could cause a serious safety event.

Effective date and compliance time. The AD becomes effective on 23 October 2008. Compliance is required within 5000 hours time in service after that date. ‘Time in service’ refers to the total flight hours accumulated by the aircraft from the effective date onward, not from the aircraft’s entry into service. This gives operators a period during which they must schedule the modification.

The AD directly applies to operators and owners of Bombardier CL-600-2B19 (Challenger) series aeroplanes within the listed serial number ranges. The applicability is not a blanket type-wide directive; it is limited to two groups. The first group comprises serial numbers 7003 through 7067 and 7069 through 7939, but only if those aircraft have not already had the refuel/defuel shutoff valves modified according to the original issue of Bombardier SB 601R-28-053. The second group includes serial numbers 7989, 7990, and 8000 through 8034, with no exclusion for prior modification. Therefore, any aircraft in that second group must comply regardless of any earlier work. Aircraft outside these serial ranges, or within the first group but already incorporating the original SB, are not subject to this AD. This selective applicability reflects Bombardier’s production configuration changes and the fact that some aircraft were built after the bonding issue was corrected in manufacturing.

The AD also affects maintenance organisations, repair stations, and engineering departments that perform work on these aircraft. They must obtain the correct revision of Bombardier SB 601R-28-053 (Revision C or later approved version), obtain necessary parts and tooling, and carry out the modification in accordance with the service bulletin. The AD does not specify a particular type of maintenance organisation, but under the Civil Aviation Act 1988 and the Civil Aviation Safety Regulations, only appropriately authorised persons (such as licensed aircraft maintenance engineers or approved maintenance organisations) may perform the work. The compliance timeline of 5000 hours time in service requires careful tracking of each aircraft’s utilisation to ensure the modification is completed before the deadline. Operators with fleets heavily utilised may need to schedule the modification during a routine heavy maintenance check to minimise aircraft downtime.

CASA is the enforcing authority. The AD was signed by a delegate, meaning CASA retains oversight and can audit compliance. Transport Canada is indirectly affected because the AD references Transport Canada AD CF-2008-20 and requires any later revision of the service bulletin to be approved by the Chief, Continuing Airworthiness of Transport Canada. This creates a cross-border dependency: if Bombardier issues a later revision, CASA operators must use only the version approved by Transport Canada; CASA does not independently approve the service bulletin.

Passengers and crew of affected aircraft are not directly named, but they are the ultimate beneficiaries of the safety improvement. Insurers may also take an interest: failure to comply with an AD can void hull and liability insurance coverage or affect claims. Additionally, if an aircraft is sold or registered in another country, the AD obligation transfers to the new operator, and compliance must be demonstrated to the new authority.

Duty to modify. The primary duty is on the aircraft operator (or the person responsible for continuing airworthiness) to carry out the modification to the refuel/defuel system in the centre wing fuel tank. The modification must be performed according to the Accomplishment Instructions of Bombardier SB 601R-28-053, Revision C, dated 14 March 2006, or any later revision approved by the Chief, Continuing Airworthiness of Transport Canada. There is no duty to use an earlier revision; the AD only recognises Revision A and Revision B as satisfying the requirement if the work was done before the effective date. After the effective date, only Revision C or later approved revisions are acceptable.

Right to use prior modifications. Note 1 within the requirement text explicitly states that modification accomplished prior to the effective date of this AD according to Revision A or Revision B of the SB satisfies the requirement of this Directive. This is a grandfathering provision that prevents imposing a new compliance burden on operators who have already completed an earlier version of the same service bulletin. It does not, however, excuse operators who performed a non-standard repair or some other modification; only the two explicitly named revisions are recognised.

Compliance timeline duty. The duty to complete the modification arises within 5000 hours time in service after the effective date of 23 October 2008. This means the operator must track cumulative flight hours from that date for each affected aircraft and ensure the modification is done before the 5000-hour threshold is crossed. There is no provision for extension, and the AD does not mention any alternative means of compliance. Operators who cannot schedule the work within 5000 hours, for example because the aircraft is in a remote location, would need to seek special approval from CASA.

Right to use later approved revisions. The AD permits compliance using a later revision of the service bulletin that is approved by the Chief, Continuing Airworthiness of Transport Canada. This right is important: if Bombardier discovers an improvement or a correction to the modification instructions, operators can adopt the updated version without needing a separate CASA AD revision. However, they must verify that the revision approval has been granted by Transport Canada. If the later revision is not approved by Transport Canada, the AD still requires the Revision C version.

No right to defer or substitute. The AD does not grant any right to defer compliance beyond 5000 hours, nor does it permit the use of alternative methods (such as a different bonding technique, a different gasket, or an engineering analysis to show the condition does not exist on a particular airframe). This is typical of ADs: they are prescriptive. Any alternative would require a separate rule change or an exemption from CASA, which is not addressed in this document.

Right of review. Although not mentioned in the AD text, the general regulatory framework under the Civil Aviation Act 1988 provides a right for an affected person to apply for review of an AD or to seek an exemption. The AD itself does not mention such rights, but they exist in law. The delegate’s decision to issue the AD could theoretically be challenged in the Administrative Appeals Tribunal, though in practice such challenges are rare for safety-critical ADs.

The AD itself does not specify any penalty for non-compliance. However, airworthiness directives issued by CASA have the force of law under the Civil Aviation Act 1988 and the Civil Aviation Safety Regulations. Specifically, regulation 42 of the Civil Aviation Regulations 1988 (CAR) makes it an offence to operate an aircraft that does not meet the requirements of an applicable AD. The penalty for contravening a CAR provision is typically up to 200 penalty units for an individual (where one penalty unit is currently $313) and higher for a body corporate. In addition, operating an aircraft that does not comply with an AD voids any applicable certificate of airworthiness, meaning the aircraft is unairworthy. Continuing to fly such an aircraft could also attract offences for operating an aircraft without a valid certificate of airworthiness, which carries potential imprisonment under the Act in serious cases.

CASA may enforce the AD by grounding the aircraft, issuing a direction to rectify, or taking administrative action such as suspension or cancellation of an operator’s Air Operator’s Certificate (AOC). The AD can also be enforced retrospectively through investigations and prosecutions. The compliance deadline of 5000 hours time in service is not a grace period; it is the absolute limit. Operators who exceed that limit without completing the modification are in breach from the moment the 5000-hour threshold is crossed.

The AD does not include any reporting requirement, but if an operator discovers an incident of arcing or lightning strike damage before the modification is done, that may trigger a mandatory occurrence report under the Transport Safety Investigation Act 2003. Additionally, if an operator chooses not to comply, they might attempt to avoid detection by not reporting the non-compliance. However, during future maintenance or sale, the non-compliance will typically be discovered during an audit or transfer inspection. CASA conducts periodic surveillance of aircraft, and any non-compliance found is likely to result in enforcement action.

Insurance consequences are also significant. Most aviation insurance policies exclude liability cover if the aircraft is operated in violation of an AD. A non-compliant operator could be personally liable for any damage or injury resulting from a fuel tank explosion that the AD was designed to prevent.

The AD explicitly references Transport Canada AD CF-2008-20, stating that the directive refers to it. This means that the Canadian authority has issued a substantively identical requirement for the same aircraft. Since the CL-600-2B19 is a Canadian type-certificated aircraft, Transport Canada is the primary certifying authority. CASA, as the Australian authority, adopts the same AD to maintain consistent airworthiness standards across jurisdictions. If an Australian-registered aircraft operates into Canada or another country that recognises Canadian ADs, the operator must comply with the Canadian AD as well. The AD provision allowing use of later revisions approved by the Chief, Continuing Airworthiness of Transport Canada ensures that Australian operators can adopt improvements without waiting for a CASA amendment.

The AD sits within a hierarchy of laws. The Civil Aviation Act 1988 provides the overarching legal framework for safety regulation. The Civil Aviation Safety Regulations (CASR) contain detailed requirements for maintenance and AD compliance. Under CASR Part 42 (continuing airworthiness), the operator is responsible for ensuring that all applicable ADs are complied with and for maintaining a record of compliance. The AD must be entered into the aircraft’s continuing airworthiness records. Additionally, the Civil Aviation Regulations 1988 (CAR) 42 requires that no person operate an aircraft unless every applicable AD has been complied with. The AD interacts with these regulations by specifying the particular corrective action needed.

The AD also interacts with the design approval system. The service bulletin (SB 601R-28-053) is a Bombardier document approved by Transport Canada. The AD mandates the use of that specific SB. Any deviation from the SB’s instructions would require an alternative method of compliance approved by CASA. In the absence of such approval, following a different maintenance manual procedure or a different service bulletin would not satisfy the AD.

There is potential interaction with other ADs affecting the same aircraft type. For example, if a subsequent AD requires modification of the same area, operators would need to ensure that the work sequences are compatible. The AD does not mention any pre-existing ADs, so it is likely the first mandatory directive addressing this bonding issue.

The AD also interacts with the law concerning lightning strike protection under the airworthiness standards (Chapter 525 of the Transport Canada Airworthiness Manual, equivalent to US FAR Part 25 and EASA CS-25). The AD results from a system safety review against those standards, indicating that the original type certification did not meet updated requirements. This is a common scenario: as safety standards evolve, ADs are used to retroactively impose current requirements on in-service aircraft.

The AD itself does not contain any amendment history. It was issued as a single document on 9 September 2008, became effective on 23 October 2008, and appears not to have been amended since. However, the AD text references three revisions of Bombardier SB 601R-28-053: the original issue, Revision A, Revision B, and Revision C (dated 14 March 2006). The AD mandates Revision C or later revisions approved by Transport Canada. Therefore, the service bulletin has undergone at least four iterations (original, A, B, C). The AD does not specify when the original or revisions A and B were issued. Note 1 of the AD recognises that modifications accomplished using Revision A or B prior to the AD’s effective date satisfy the requirement. This suggests that earlier versions existed before March 2006, possibly dating back several years.

The AD’s own amendment record, if any, would be maintained in CASA’s AD system. A search of CASA’s website would reveal whether any subsequent ADs have superseded or amended AD/CL-600/103. Given that the AD is from 2008 and concerns a specific unsafe condition, it is likely that all affected aircraft have since complied, and the AD may have been closed out as no longer active for the fleet. However, for aircraft entering the Australian register after the AD was issued, the AD would still apply unless the aircraft had already been modified per the SB. The AD’s effect is ongoing until the modification is applied.

The AD does not refer to any earlier AD that it replaces or amends. It appears to be the first directive addressing this issue for the CL-600-2B19. The reference to Transport Canada AD CF-2008-20 indicates that the Canadian authority issued its AD in 2008 as well, presumably around the same time or earlier. The CASA AD likely mirrors the Canadian directive, as is common for foreign type-certificated aircraft.

The source text does not reference any litigation, court decisions, tribunal rulings, or enforcement actions related to AD/CL-600/103. No cases are mentioned, and no appeal history is provided. Given that the AD is a technical, safety-critical directive with a clear compliance timeline and a specific modification requirement, it is unlikely that it generated litigation. Operators typically comply with ADs to maintain airworthiness and avoid grounding. Any dispute would more likely arise over enforcement action for non-compliance, such as a prosecution under the Civil Aviation Act. No such cases appear in the source.

The lack of litigation history is not unusual. Airworthiness directives are generally accepted as necessary safety measures, and the cost of non-compliance (grounded aircraft, loss of airworthiness certificate) far outweighs the cost of compliance for most operators. Additionally, the legal avenues for challenging an AD are narrow: an operator would need to argue that the unsafe condition does not exist on their aircraft, that the AD is disproportionate, or that CASA failed to follow proper procedure. Such arguments are rarely successful given the breadth of authority delegated to CASA under the Act.

It is possible that the AD was the subject of an alternative means of compliance request from an operator, but that is an administrative process, not litigation. No information on such requests is in the source.

Selective applicability. The AD includes a large serial number range (7003 through 7067 and 7069 through 7939) but excludes any aircraft in that range that have already incorporated the modification per the original issue of the service bulletin. This means an operator who did the work using the original SB before the AD effective date is not affected. However, an operator who did the work using the original SB but after the effective date would not receive credit for it under the AD; they would still need to upgrade to Revision C. The distinction between the original issue and Revision A/B is critical. Many operators may assume that any prior service bulletin compliance suffices, but the AD only grandfathers Revision A and B work completed before the effective date. Work done after the effective date, even if using Revision A or B, does not satisfy the requirement unless it also meets Revision C or later.

Compliance time based on time in service. The AD requires compliance within 5000 hours time in service after the effective date. This is not 5000 hours total on the aircraft since new, but 5000 hours from 23 October 2008. An aircraft that had already accumulated, say, 4000 hours before that date would need to complete the modification within the next 1000 hours. Operators must carefully track flight hours with a start point of 23 October 2008. Failure to do so could result in inadvertent non-compliance. Also, an aircraft that was parked or in storage for an extended period after 2008 would still accrue no flight hours, so the compliance clock pauses. When the aircraft returns to service, the remaining hours start counting again.

Transport Canada approval for later revisions. The AD allows compliance with later revisions of the SB only if they are approved by the Chief, Continuing Airworthiness of Transport Canada. If Bombardier issues a Revision D that is not yet approved by Transport Canada, an operator using that revision would not be in compliance with the AD. The operator must verify the approval status before adopting any revision beyond Revision C. This creates a dependency on a foreign authority’s administrative process.

Aircraft that cross over between groups. The applicability is defined by serial numbers. However, if an aircraft in the first group (7003.7067, 7069.7939) is later modified per the original SB after the effective date (which is not possible if it was already modified before), that aircraft might fall into a gap? No, the AD applies to that aircraft regardless; the grandfathering only applies to pre-effective date work. So an aircraft in that range that had not been modified at all by the effective date is subject to the AD. Operators may be uncertain about whether their aircraft was modified during production; they must check the aircraft’s modification status.

The consequence of non-compliance is severe. Even though the AD itself does not state penalties, operating an aircraft past the 5000-hour deadline without the modification makes the aircraft unairworthy. Any subsequent flight is unlawful. If an incident occurs, the operator could face criminal liability, not just for the breach but potentially for any resultant damage.

Compliance with AD/CL-600/103 requires a sequence of steps, all derived from the text of the directive.

1. Identify affected aircraft. Determine whether the aircraft is a Model CL-600-2B19 and whether its serial number falls within either of the two defined groups. Serial numbers 7003 through 7067 and 7069 through 7939 are affected unless they have already been modified according to the original issue of SB 601R-28-053. Serial numbers 7989, 7990, and 8000 through 8034 are always affected regardless of prior modification. If the aircraft is not in these ranges, no action is needed under this AD.

2. Check existing modification status. For aircraft in the first group, review maintenance records to determine whether the refuel/defuel shutoff valves were modified per the original issue of SB 601R-28-053. If that modification was accomplished before the effective date of 23 October 2008, the aircraft is exempt from this AD. If the modification was accomplished after the effective date, or if not accomplished at all, the aircraft is subject to the AD. For aircraft in the second group, there is no exemption.

3. Obtain the correct service bulletin. The AD mandates compliance with Bombardier SB 601R-28-053, Revision C, dated 14 March 2006, or any later revision approved by the Chief, Continuing Airworthiness of Transport Canada. Contact Bombardier or its representative to obtain the latest approved revision. Do not rely on Revision A or B for work performed after the effective date.

4. Plan the work. The compliance time is 5000 hours time in service calculated from the effective date. Record the aircraft’s total flight hours as of 23 October 2008. Subtract that figure from 5000, or simply track the hours accrued after that date. When the aircraft approaches 5000 hours post-effective date, the modification must be completed before the next flight. Coordinate with a CASA-approved Part 145 maintenance organisation or a licensed aircraft maintenance engineer to schedule the modification during a convenient maintenance interval, such as a C check or overnight heavy check.

5. Perform the modification. Follow the Accomplishment Instructions precisely as written in the approved revision of the service bulletin. This likely involves removing the refuel/defuel shutoff valves, replacing or modifying the Gask-O-Seal gasket, treating or removing the anodic coating on the conduit connection fitting, and reassembling with adequate electrical bonding. Ensure that tooling and torque values are correct. The modification must be signed off by a certifying staff member with the appropriate ratings.

6. Record compliance. Enter the AD reference (AD/CL-600/103), the service bulletin revision used, the date of accomplishment, and the aircraft time in service at that date in the aircraft’s continuing airworthiness records (logbooks). A CASA Form AD compliance sticker or entry may be required. Keep proof of the service bulletin revision used and the Transport Canada approval if a later revision was used.

7. Verify continued compliance. If the aircraft is sold or transferred to a new operator, ensure the AD compliance record is transferred as well. If a later revision of the service bulletin is approved after the modification, no further action is required unless that later revision is declared mandatory by CASA through a new AD.

8. If compliance cannot be met within 5000 hours. Apply to CASA for an extension or an alternative means of compliance before the deadline. Provide evidence of scheduling constraints or lack of parts. CASA has discretion to grant relief, but there is no guarantee. Do not operate the aircraft beyond 5000 hours without a granted exemption.