AD/CL-600/114 - Landing Gear Alternate Extension System

The directive revolves around several technical and regulatory concepts. The Landing Gear Alternate Extension System (AES) is a backup system for extending the landing gear when the primary system fails. The bypass valve and downlock assist valve are components of the AES. The clevis is a connecting part shaped like a U with a pin or bolt, here used to link the valves to the summing lever. The summing lever is a mechanical linkage that combines inputs from different control mechanisms. The observed problem arises from relative misalignment between these components due to deflection of the pressure floor in the main landing gear bay during pressurization and depressurization cycles. This deflection is not a direct failure but a flexural movement that changes the geometry of the valve attachments. Over time, this misalignment can cause the clevis to wear improperly, crack, or fail. The AD characterises this as a latent failure: the clevis may break but the AES remains untested until an actual need for alternate extension arises. Thus the fault may only become apparent during an emergency when the system must function. The regulatory mechanism is an Airworthiness Directive, which is a mandatory instrument under the Civil Aviation Act 1988. ADs are issued when an unsafe condition is identified in a type design or in maintenance practices and the condition is likely to exist in other aircraft of the same type. Compliance is compulsory for the operator and the holder of the airworthiness certificate. The AD references Transport Canada AD CF-2009-22 dated 14 May 2009, indicating that CASA is adopting a foreign airworthiness directive from the state of design (Canada, where Bombardier is based). This is consistent with Australia's reliance on the design state for certification. The compliance thresholds use flight cycles and flight hours. A flight cycle is typically one takeoff and landing. Flight hours are simply hours of flight time. The distinction matters because the failure mechanism is linked to pressurization cycles (which occur each flight) rather than hours aloft. The AD uses both metrics for different thresholds, which creates a two-dimensional compliance matrix. The concept of a new part (clevis P/N 2323H037) and support brackets are prescribed modifications to increase stiffness of the valve installations and prevent future relative misalignment. The AD also introduces the concept of a later revision approved by Transport Canada, which gives a dynamic reference that allows future amendments to the ASB without needing a new AD from CASA.

This directive directly imposes obligations on operators and maintenance organisations responsible for the specific Bombardier models and serial numbers listed. Affected parties include airline operators who fly the Regional Jet Series 700, 701, 705, or 900 with serial numbers within the stated ranges. In Australia, this may cover a small number of aircraft operated by regional carriers or corporate flight departments. Also affected are maintenance, repair, and overhaul (MRO) facilities that conduct heavy maintenance or component replacements on these aircraft types. The AD requires availability of the Alert Service Bulletin and the hardware, including the clevis P/N 2323H037 and support brackets. Parts supply is a practical issue: if the parts are not readily available in Australia, operators face downtime and procurement delays. This may disproportionately impact smaller operators who do not carry inventory and rely on just-in-time ordering. Lessors and financiers with security interests in affected aircraft are indirectly affected because the AD may affect aircraft value and airworthiness status. Non-compliance can result in grounding, which impairs revenue and may trigger loan covenants. Insurers may adjust premiums or require evidence of compliance. End users (passengers and cargo shippers) are affected if the aircraft is removed from service or if compliance costs lead to fare increases or reduced service. The AD does not exempt aircraft used for private or business aviation. All affected aircraft must comply regardless of operational purpose. The AD also affects CASA itself as the regulator. CASA must monitor compliance and may take enforcement action. The AD references Transport Canada approval for later revisions of the ASB, which means Transport Canada staff also become necessary participants in the approval chain. Suppliers of the clevis and brackets, and Bombardier as the design approval holder, are also affected because the AD relies on their design data and parts availability. The compliance costs borne by operators include parts, labour, aircraft downtime, and administrative record-keeping. For an aircraft that generates revenue, downtime represents a direct revenue loss. The requirement to replace a clevis is relatively inexpensive as a part, but the labour and access to the landing gear bay may be substantial. The support bracket installation likely requires additional structural work, increasing the cost burden. The AD does not provide any compensation or tax relief for these costs, which is typical of prescriptive safety regulations.

The key duties are the three mandatory requirements. The duty holders are the operators and owners of the affected aircraft. For requirement 1, the duty is to replace the bypass valve clevis with a new part per the ASB. For requirement 2, the duty is to replace the downlock assist valve clevis with a new part per the ASB. For requirement 3, the duty is to install support brackets for both valves per the ASB. These duties are absolute, subject to the compliance deadlines specified. Operators have the right to choose the method of compliance within the bounds of the ASB. They may use original issue ASB for requirements 1 and 2, or Revision A, or later revisions approved by Transport Canada. For requirement 3, they must use Revision A or later; the original issue is not listed as acceptable. Operators also have the right to rely on an approved alternative means of compliance if CASA grants it, though the AD does not expressly mention this. The note that it is not necessary to replace the clevis if Part III of this AD has already been accomplished is a right to skip requirements 1 and 2 if the support brackets (Part III) are already installed. This implies that the support brackets alone address the clevis failure risk, making the standalone clevis replacement unnecessary if the brackets are already in place. Operators have the right to use flight cycles or flight hours for requirement 3 compliance: the deadlines are 4,500 FH after effective date, 6,000 FH after requirement 1, or 6,000 FC after requirement 2, whichever comes first. This gives operators some flexibility in scheduling. However, there is no discretion to extend deadlines beyond those specified unless CASA issues a variation. The AD imposes a duty to keep records of compliance, which is implicit from regulation but not stated in the AD. Operators also have the right to request a review of the AD from CASA, though such a review is unlikely to succeed given the safety basis. The duty to comply rests with the operator, regardless of whether a third party MRO performs the work. The operator must ensure that the MRO uses the correct ASB revision and that the parts are genuine. The duty is ongoing: even after compliance, the operator must ensure the modifications remain in serviceable condition.

The source does not specify penalties, but an Airworthiness Directive carries the full force of the Civil Aviation Act 1988. Contravening a condition of an airworthiness certificate or failing to comply with an AD can lead to civil penalty proceedings, imposition of infringement notices, suspension or revocation of airworthiness certificates, and even criminal prosecution in serious cases. Under section 20AA of the Civil Aviation Act, CASA can issue an AD and non-compliance may result in enforcement action including directions to ground the aircraft. The practical consequence is that an affected aircraft that does not meet the AD's requirements cannot lawfully be operated. CASA may issue a grounding order under regulation 37 of the Civil Aviation Regulations. Operators risk substantial financial losses from aircraft grounding, loss of revenue, and damage to reputation. Additionally, if an incident occurs involving the AES and the AD has not been complied with, the operator may face personal injury or wrongful death claims, and the non-compliance would be relevant evidence in any civil litigation. The AD is effective 30 July 2009. After that date, any affected aircraft flying without compliance is at risk. CASA inspectors may detect non-compliance during routine surveillance, ramp checks, or airworthiness reviews. Given that the AD applies to a small fleet, CASA may conduct targeted campaigns. The AD itself does not specify a penalty amount. The maximum civil penalty for a contravention of Part III of the Civil Aviation Act (which includes ADs) can be significant; for a body corporate, it was historically up to AUD 220,000 per contravention (indexed), and for individuals up to AUD 55,000 per contravention. Criminal penalties can be higher if the conduct is reckless. Judges may also consider the degree of departure from safety standards. Enforcement discretion lies with CASA, which may issue an infringement notice for lesser breaches or take court action for deliberate or repeated non-compliance. The cost of fighting an enforcement action is itself a penalty. Even if no fine is imposed, the legal costs and management time are substantial. The AD does not provide for a grace period after the effective date. Compliance must be achieved by the deadlines.

The AD references Transport Canada AD CF-2009-22 dated 14 May 2009, indicating that CASA is adopting the same corrective action that Transport Canada mandated for the state of design. This is common practice under bilateral airworthiness agreements, and it affirms that the design state's AD is the primary source. The AD also incorporates by reference the Alert Service Bulletin A670BA-32-022, both the original issue (for requirements 1 and 2) and Revision A (for all requirements). This incorporation gives legal effect to the private ASB. Any later revision must be approved by Transport Canada, and then by implication CASA would likely accept that approval. The AD sits under the Civil Aviation Act 1988 and the Civil Aviation Regulations 1988 (CAR), particularly regulation 37 which empowers CASA to issue ADs. Compliance with an AD is a condition of the aircraft's airworthiness certificate under CAR 1988 regulation 26 (now superseded by CASR parts but transitional provisions apply). The AD also interacts with the operator's maintenance control manual and approved maintenance schedule. The affected aircraft may have existing maintenance tasks for the landing gear system, and this AD adds a one-time modification plus possibly a recurring inspection element (though the AD does not specify recurring inspections). If the aircraft is operated under a continuing airworthiness management organisation (CAMO) under CASR Part 42 or Part M, the CAMO must ensure the AD is incorporated into the maintenance program and complied with. The AD may also interact with the aircraft's type certificate data sheet. No mention of interaction with other specific laws such as the Competition and Consumer Act or work health and safety legislation, but those could apply indirectly if a failure causes injury or damage. For aircraft that are maintained overseas, the operator must ensure that foreign maintenance providers comply with this AD even if acting under a foreign regulatory system. The interaction with insurance law is relevant: a policy may exclude cover for losses arising from non-compliance with an AD. This is a common condition in aviation insurance policies. If the AD is not complied with, the insurer may deny cover for a landing gear incident. The AD also interacts with aircraft leasing documentation: a lease will typically require the lessee to comply with all ADs. Non-compliance can constitute an event of default under the lease.

The source is a single AD document effective 30 July 2009. Within the document, it references the Alert Service Bulletin A670BA-32-022 which had an original issue dated 8 November 2007 and a Revision A dated 1 May 2009. The AD allows use of the original issue for requirements 1 and 2 but not for requirement 3. This means the ASB itself has been amended. The AD also states that later revisions approved by the Chief, Continuing Airworthiness, Transport Canada are acceptable. This is a dynamic reference that allows future amendments without necessitating a new AD. The AD itself has not been amended on the face of the source. However, in practice, ADs are sometimes superseded by later ADs for the same type design. No supersedure is referenced in this source. The AD is numbered AD/CL-600/114, indicating it is the 114th airworthiness directive for the Bombardier CL-600 series. The document also includes the signature of James Coyne, Delegate of the Civil Aviation Safety Authority, dated 19 June 2009. The AD becomes effective 30 July 2009, which is 41 days after signing, allowing a lead time for operators to obtain parts and schedule maintenance. The Transport Canada AD is dated 14 May 2009, approximately one month before the CASA AD. There is no evidence of any subsequent amendments to this AD. Over time, CASA may have issued a revision or a new AD superseding this one, but that is not disclosed in the source. The source as provided is the original issuance. For regulatory certainty, an operator should check the current CASA AD database to see if AD/CL-600/114 has been updated or replaced. The AD number format suggests it is part of a series that may have been superseded by a newer AD for the same type design, possibly AD/CL-600/115 or later. The operator should also check if the affected serial numbers have been extended by a later amendment. The absence of an amendment in the source does not guarantee the AD is still current.

The source does not mention any litigation. Airworthiness Directives are rarely litigated directly because they are based on safety findings and the regulator has broad discretion. In Australia, challenges to ADs under the Administrative Decisions (Judicial Review) Act 1977 are possible but uncommon. A successful challenge would require showing that the AD is not based on evidence of an unsafe condition, or that the decision was irrational. Given the technical evidence from the manufacturer and the Transport Canada basis, a challenge would face a high hurdle. There is no known reported case in Australia specifically concerning AD/CL-600/114. However, there have been a small number of cases in Australia and Canada involving ADs for landing gear components, generally where an accident occurred and the AD compliance was an issue. In Canada, Bombardier CL-600 operators have been involved in litigation about maintenance records and AD compliance, but that is not part of this source. The latent failure mechanism described background could potentially lead to litigation if a clevis fails and causes an accident. In such a scenario, the AD would be used as a standard of care in negligence or product liability claims against the operator, the maintenance organisation, or the manufacturer. The fact that the AD was issued well before the accident would make it more difficult for the operator to argue the failure was unforeseeable. For the purpose of this deep dive, it is sufficient to state that no litigation is referenced in the source material. The absence of litigation does not mean the AD is insignificant; rather it suggests operators have generally complied without legal contest. The AD is a prescriptive regulatory instrument that offers little room for interpretation, which reduces the grounds for litigation. If there were litigation, it would more likely arise from an accident caused by non-compliance rather than a challenge to the AD itself.

Several details could trap unwary operators. First, the use of flight cycles versus flight hours. The clevis replacement deadlines for requirements 1 and 2 are based on flight cycles for the valve, not aircraft flight cycles. The valve may have different cycle counts if it was replaced earlier. The AD says if at the effective date the bypass valve has accumulated 9,400 FC or less. The valve may have a different cycle count than the aircraft. Operators must track component cycles, not just airframe cycles. If the valve cycles are unknown, the AD defaults to 550 FH, which could be a much tighter deadline. Second, the default to flight hours if cycles cannot be determined. If the operator does not have accurate records of valve cycles, they must comply within 550 FH, which may be a very short window (maybe less than two months for high utilisation operators). Third, requirement 3 compliance triggers three separate deadlines that must be calculated independently. The operative deadline is the earliest of 4,500 FH after effective date, 6,000 FH after requirement 1, or 6,000 FC after requirement 2. An operator might complete requirement 1 on a specific date, but the 6,000 FH count starts from that date, not from the effective date. If requirement 1 is delayed, the 6,000 FH window may be deceptively long. However, the 4,500 FH from effective date is a hard deadline that is date-based. So an operator cannot postpone requirement 1 indefinitely without hitting the 4,500 FH deadline anyway. Fourth, the note that replacing the clevis is not necessary if Part III has already been accomplished. An operator may assume that if support brackets are already installed, they have no obligations. But they still need to verify that the support brackets are installed in accordance with the AD, not just as a previous modification. The AD does not grandfather previous installations unless they were done per Part III. Fifth, the AD allows use of the original issue of the ASB for requirements 1 and 2 but only Revision A for requirement 3. An operator may inadvertently use the original issue for requirement 3, which would not comply. Sixth, the AD requires that later revisions be approved by Transport Canada. If Bombardier issues Revision B and it is approved by Transport Canada, the operator must use that revision. But if Transport Canada approval is delayed, the operator may be stuck using Revision A even if Revision B is available. Seventh, the effective date is 30 July 2009. Any work done before that date does not count for compliance unless it meets the AD requirements. An operator who replaced a clevis on 15 July 2009 using the original ASB would need to check if that replacement is considered compliant for the specific valve. Finally, the AD does not address record keeping or tagging requirements. The operator must maintain records showing the date, cycles/hours at compliance, and details of parts and ASB used. The AD does not specify a threshold for support bracket installation if the operator has already done the clevis replacement. The deadlines for requirement 3 are linked to the effective date and the completion of requirement 1 or 2, which could create a moving target if the operator does requirement 1 and 2 at different times.

Compliance requires a systematic approach. First, the operator must identify all affected aircraft in their fleet against the serial numbers listed. Then, for each affected aircraft, the operator must determine the flight cycles and flight hours on the bypass valve (P/N 53342-3) and the downlock assist valve (P/N 53341-5) as at 30 July 2009. This may require accessing the component log cards, maintenance records, or electronic engine/component tracking system. If records are incomplete, the operator must assume the valve has more than 9,400 FC and follow the 550 FH deadline. For the bypass valve: if cycles are known and 9,400 or less, schedule clevis replacement before the valve reaches 10,000 FC. If cycles are known and more than 9,400, schedule replacement within 550 FH from 30 July 2009. If cycles unknown, replacement within 550 FH from 30 July 2009. For the downlock assist valve: identical logic using P/N 53341-5. Note that both valves may have different cycle counts, so separate calculations are needed. The clevis replacement parts (P/N 2323H037) must be procured. The work must be done in accordance with Part A and Part B of ASB A670BA-32-022 Revision A (or original issue for these requirements). Then, for requirement 3, the operator must install support brackets for both valves in accordance with Part C of ASB A670BA-32-022 Revision A (original issue not permitted). The deadline is the earliest of 4,500 FH after 30 July 2009; 6,000 FH after the completion of requirement 1; or 6,000 FC after the completion of requirement 2. The operator should record the date and FH/FC at each completion. If requirement 3 is done first, then requirements 1 and 2 are not needed (per the note). However, if requirement 3 is done after requirements 1 and 2, then the clevis replacement was already done and the support brackets if installed within the deadline still comply. But if the brackets are installed after the 4,500 FH deadline, the operator may be in breach even if the clevis was replaced early. The operator should engage an approved maintenance organisation (AMO) rated for the aircraft type. The AMO must have the current revision of the ASB and the approved parts. After the work, the maintenance release must reference the AD number and the ASB used. The operator must update the aircraft maintenance records and the airworthiness review process. For ongoing compliance, no recurring task is specified, but the operator should monitor for any future ADs superseding this one. Finally, the operator should retain records for the life of the aircraft, as CASA may audit compliance years later. The operator should also consider the cost of parts and labour and the downtime required when scheduling the work. If the operator has multiple aircraft, prioritising those with valves closer to the 10,000 FC threshold makes sense. The AD does not require reporting compliance to CASA unless CASA specifically requests it, but the records must be available on request. The operator should integrate this AD into their maintenance tracking system and set alerts for the deadlines based on the effective date and the completion dates of requirements 1 and 2. The operator should also check that the AMO uses the correct revision of the ASB. The AMO may have its own copy of the ASB, but the operator should verify the revision.