AD/CL-600/109 - Nose Landing Gear Selector Valve

The directive revolves around four key concepts: (1) the affected part, (2) the S/N and identification markers, (3) the physical failure mechanism, and (4) the compliance actions. The affected part is the nose landing gear (NLG) selector valve and the NLG door selector valve, both designated by Bombardier part number 601R75146-1, which is functionally equivalent to Kaiser Fluid Technologies part number 750006000. The directive focuses exclusively on valves with S/N in the range 0001 through 2126. This is the batch that may have been assembled with incorrect lock-wire and/or incorrect torque on the end caps. The two markers that signify a valve is not affected are: (a) the suffix “T” after the S/N, which indicates manufacture by Tactair Fluid Controls Inc. (a different supplier with no known defect), and (b) an ink stamp reading “SB750006000-1”, which indicates that the valve has already been inspected and reworked in accordance with an earlier Service Bulletin. A valve bearing either marker (or both) requires no further action. The failure mechanism is straightforward: if the end cap backs off due to improper assembly, a seal is damaged, causing internal leakage within the valve. That leakage, combined with residual or applied hydraulic pressure in the No. 3 system, can cause the NLG to retract uncommanded - that is, without the pilot’s input - or the NLG doors to open uncommanded. This can happen any time electrical power is transferred or removed from the aircraft before the NLG safety pin is installed. The risk is particularly acute on the ground, as the six reported incidents and one collapse at a departure gate illustrate. The compliance action is tiered: first, an inspection to determine if the valve is in the suspect S/N range and lacks the two markers. If both conditions are met (S/N 0001-2126, no “T”, no ink stamp), then the operator must perform a detailed inspection and corrective action in accordance with Bombardier Service Bulletin 601R-32-104. That Service Bulletin gives instructions for checking the valve, replacing it if necessary, reworking the end cap assembly, and/or applying the ink stamp “SB750006000-1” to identify it as reworked. The directive also refers to the Illustrated Parts Catalogue (CSP A-006), which already gives instructions not to install a Kaiser Fluid Technologies valve with P/N 750006000 and S/N 0001 through 2126 unless it is ink stamped with “SB750006000-1”. That note reinforces the mandatory nature of the AD but also highlights that the IPC itself, prior to the AD, was advisory only. The AD elevates the IPC warning to a regulatory requirement. Finally, the directive cross-references Transport Canada AD CF-2009-19 dated 29 April 2009, indicating that the CASA AD is harmonised with the Canadian airworthiness authority’s action. This is common because the aircraft is type-certificated in Canada and the original manufacturer (Bombardier) is Canadian.

The primary group affected are the registered operators of Bombardier Inc. Model CL-600-2B19 aeroplanes with serial numbers 7003 and subsequent. Those are the aircraft covered by the applicability statement. The fleet includes Challenger 601 and Challenger 604 variants (the CL-600-2B19 type certificate covers the Challenger 604), though the directive applies specifically to that model and S/N range. Operators of earlier Challenger 600-series aircraft (e.g., CL-600-2A12, CL-600-2B16) are not affected unless they have a bespoke AD of their own. For the affected aircraft, the AD imposes a direct compliance obligation on the “operator” as defined in the Civil Aviation Act 1988 (usually the entity responsible for the continuing airworthiness of the aircraft). That operator must ensure the inspection is performed and any required corrective action is taken within the 1600 flight hours or 18 months from 2 July 2009. This has immediate financial and operational consequences: the operator must schedule the aircraft for maintenance, procure any necessary parts (if replacement is required), and absorb the costs of labour, downtime, and potential delays. The directive also affects maintenance organisations and engineers who perform the work. They must have access to the Bombardier Service Bulletin and must follow its accomplishment instructions exactly. They must also be able to correctly identify the valve S/N and markings. The AD places no direct obligation on the manufacturer, Bombardier, or the component supplier, Kaiser Fluid Technologies, but the referenced Service Bulletin is the approved method of compliance. Parts suppliers and distributors are indirectly affected because they must ensure that any valve they supply for these aircraft is either outside the suspect S/N range or carries the “T” suffix or “SB750006000-1” ink stamp. Anyone selling a Kaiser Fluid Technologies valve with S/N 0001 through 2126 without the ink stamp would be supplying a part that cannot lawfully be installed under this AD. Passengers, ground crew, and airport operators are the ultimate beneficiaries - in the sense that the AD aims to prevent the type of uncommanded NLG retraction that could cause a structural collapse at the gate. However, they bear none of the compliance costs. Insurers of the aircraft may also take an interest, as non-compliance with an airworthiness directive can void insurance coverage for related incidents. In Australia, the CASA surveillance network can target operators of these aircraft for spot checks. The AD also affects the residual value of aircraft that have not yet complied, because any buyer will demand proof of compliance before purchase.

The primary duty imposed by AD/CL-600/109 is on the operator of any aircraft within the applicability: the operator must, within 1600 flight hours or 18 months after 2 July 2009 (whichever is earlier), inspect the NLG selector valve and NLG door selector valve to determine their S/N and identification markings. If either or both valves meet the suspect criteria (S/N 0001 through 2126, no suffix “T”, no ink stamp “SB750006000-1”), the operator must then perform a detailed inspection and either replace, rework, identify the valve, or otherwise comply with the Accomplishment Instructions of Bombardier Service Bulletin 601R-32-104, dated 3 March 2009, or any later revision approved by the Chief, Continuing Airworthiness, Transport Canada. This duty is non-delegable in the sense that the operator remains legally responsible for compliance, even if the physical work is contracted out to a maintenance organisation. The operator also has a duty to record the compliance action in the aircraft’s continuing airworthiness records, typically by a logbook entry referencing the AD and the Service Bulletin. The AD confers certain rights on operators. First, if the inspection reveals that both valves fall outside the suspect S/N range, or are marked with a “T” suffix or the ink stamp, the operator has a right to treat the AD as complied with immediately, with no further action. Second, the operator is entitled to use a later revision of the Service Bulletin, provided that revision has been approved by Transport Canada. This allows the operator to incorporate any procedural improvements that Bombardier may issue. Third, the operator has the right to rely on previous rework: if a valve carries the ink stamp “SB750006000-1”, the operator need not repeat the inspection or rework. The AD does not grant operators any right to extend the compliance time beyond 1600 hours or 18 months, nor does it provide any alternative method of compliance (AMOC) procedure within the text. (In practice, operators can apply to CASA for an alternative means of compliance under CASR Part 39, but that is a separate process not addressed in the AD itself.) The AD also implicitly confers a duty on maintenance personnel to properly identify and handle affected valves. There is no explicit duty on the manufacturer to supply replacement parts or rework kits, but Bombardier’s Service Bulletin is the source of the required procedures. Finally, the AD does not create any private right of action in tort or contract, though failure to comply may be used as evidence of negligence in a civil claim.

Failure to comply with AD/CL-600/109 is a breach of the Civil Aviation Act 1988 and the Civil Aviation Regulations 1988. Under the Australian regulatory framework, an airworthiness directive issued by a CASA delegate (here, James Coyne) is a direction having the force of law. Operating an aircraft that does not comply with an applicable AD is an offence. The primary enforcement mechanism is the power of CASA to suspend or cancel the aircraft’s certificate of airworthiness, grounding the aircraft until compliance is achieved. In addition, the operator may be prosecuted for a strict liability offence under regulation 200 of the Civil Aviation Regulations 1988, which provides that a person must not operate an aircraft unless it is airworthy and complies with all applicable airworthiness directives. The maximum penalty for an individual is 50 penalty units (currently $8,250) and for a body corporate 250 penalty units ($41,250). However, where the non-compliance results in a serious safety risk or actual incident, CASA may escalate to prosecution under section 20A of the Civil Aviation Act for reckless conduct endangering the safety of an aircraft, which carries penalties of up to five years imprisonment for individuals and substantial fines for corporations. Enforcement is not limited to prosecution. CASA may issue a written direction requiring the operator to rectify the non-compliance by a certain date, and may impose a civil penalty for each day the direction is breached. The AD itself does not specify penalty provisions, but the general law applies. Importantly, the AD states its effective date as 2 July 2009. Any flight hours accumulated or calendar time elapsed after that date count toward the compliance limit. If the 1600-hour or 18-month period expires without compliance, the aircraft is immediately non-compliant and must be grounded. The background notes mention that six cases of the defect had already been reported, and one led to a collapse at a gate. This suggests that CASA viewed the risk as high, and enforcement action against operators who ignore the AD is likely to be robust. Operators who fail to keep records of compliance may face additional administrative penalties for inadequate maintenance records under CASR Part 42. The AD does not create a bounty or whistleblower provision, but any person aware of non-compliance may report it to CASA. In practice, CASA inspectors may request evidence of compliance during routine surveillance of operators of Challenger 604 aircraft. The directive is also enforceable under the bilateral safety agreements between Australia and Canada; Transport Canada would likely be notified of any enforcement action that affects aircraft that may travel internationally.

AD/CL-600/109 sits within a layered regulatory framework. The primary law is the Civil Aviation Act 1988 (Cth), which gives CASA the power to issue airworthiness directives under section 98 (powers of CASA) and regulation 198 (airworthiness directives) of the Civil Aviation Regulations 1988 (CAR 1988). The AD itself is a legislative instrument, though it is typically not registered on the Federal Register of Legislation; it is published by CASA. The AD must be read in conjunction with the aircraft’s type certificate data sheet, the maintenance manual, and the illustrated parts catalogue (IPC). The IPC for the CL-600-2B19 (CSP A-006) already contains a note warning against installing a Kaiser Fluid Technologies valve with P/N 750006000, S/N 0001 through 2126, without the ink stamp. The AD effectively makes that advisory warning mandatory. The AD also references Bombardier Service Bulletin 601R-32-104, dated 3 March 2009. That Service Bulletin is not itself law, but the AD incorporates it by reference, giving it regulatory force. Operators who follow a later revision of the Service Bulletin must ensure it is approved by the Chief, Continuing Airworthiness, Transport Canada. That introduces a foreign regulatory element: the AD harmonises with Transport Canada AD CF-2009-19 dated 29 April 2009. Because the CL-600-2B19 is a Canadian type-certificated aircraft, CASA typically adopts or mirrors Canadian ADs. This AD is a direct adoption. Under the Bilateral Aviation Safety Agreement between Australia and Canada, each party generally recognises the other’s ADs; however, operators in Australia must comply with the CASA version, not the Canadian version, unless the CASA version specifically allows otherwise. The AD does not directly interact with the Competition and Consumer Act 2010 or fair trading laws, but if a replacement valve is sold as airworthy when it is not, the vendor could face liability under the Australian Consumer Law for misleading conduct or breach of guarantee as to acceptable quality. The AD may also interact with state or territory occupiers’ liability laws if an uncommanded retraction causes injury to a ground handler. The failure to comply with an AD would likely be strong evidence of breach of duty of care in a negligence claim. The AD does not affect the operation of the Work Health and Safety Act in any direct way, but an employer (operator) who exposes workers to an unaddressed risk could face prosecution under that Act. Insurance policies typically contain a condition requiring compliance with all airworthiness directives. Non-compliance with this AD could allow an insurer to deny cover for any NLG-related incident, leaving the operator to bear the cost of hull damage and third-party liability. Finally, if the aircraft is leased or subject to a financing agreement, the lessor or financier may have the right to require compliance as a condition of the lease or loan.

AD/CL-600/109 (issued by CASA on 22 May 2009, effective 2 July 2009) is a single directive with no amendment history recorded in the source text. The directive is presented as a standalone document. The text indicates it is numbered AD/CL-600/109 with a reference “7/2009”. This notation likely means it is the seventh AD issued for the CL-600 series in 2009 (or the 109th in a continuous sequence). The source does not mention any superseding or amending ADs. In practice, airworthiness directives can be superseded by later directives, or amended via a separate CASA instrument, but no such information is contained in the source. The cross-reference to Transport Canada AD CF-2009-19 dated 29 April 2009 suggests that CASA issued this AD approximately one month after the Canadian authority. The Bombardier Service Bulletin 601R-32-104, dated 3 March 2009, is the underlying technical document. The note in Requirement 2 states that later revisions of that Service Bulletin may be used, provided they are approved by Transport Canada. That effectively allows the operator to rely on any future amendment to the Service Bulletin without needing a new AD, as long as Transport Canada has approved it. However, the AD itself does not automatically update; the operator must check whether a later revision has been approved. Over time, CASA may have issued a termination AD or a revision that removes the 1600 hour/18 month compliance time for valves that were subsequently reworked or replaced in service. However, given the source is the original 2009 text, no such later amendment is apparent. The absence of amendment history in the source means that for this deep dive, we must assume no amendments have been made to the directive itself. Practitioners should verify whether any later AD has superseded or terminated AD/CL-600/109. CASA’s online AD database should be consulted. The directive does not contain a sunset clause or expiry date; it remains in force until explicitly superseded. Similarly, the background regarding the six reported cases and the one NLG collapse is historical information from 2009; it may have been updated by later service information, but the source does not provide that.

The source text does not mention any litigation specifically related to AD/CL-600/109. No court or tribunal decisions are referenced. However, the directive itself was precipitated by six reported cases on CL600-2B19 aircraft, one of which led to a collapse of the nose landing gear at a departure gate. That incident may have been the subject of a separate accident investigation (by the Transportation Safety Board of Canada, if it occurred in Canada, or by the ATSB if in Australia). The source does not name the incident or any party involved, so we cannot infer any litigation from the incident itself. In general, airworthiness directives are rarely challenged in court. They are administrative instruments issued under delegated powers, and judicial review is limited to grounds such as jurisdictional error, procedural unfairness, or unreasonableness. No record of a challenge to AD/CL-600/109 appears in the source. More commonly, litigation arises from the underlying defect. If an operator failed to comply with the AD and a subsequent NLG collapse caused damage or injury, the operator could face a civil lawsuit for negligence or breach of statutory duty. The non-compliance would be strong evidence of breach of duty. Conversely, if an operator complied but the defect still occurred (e.g., because the Service Bulletin was inadequate), the operator might have a claim against Bombardier or Kaiser Fluid Technologies for product liability or breach of contract. No such litigation is referenced. In the Australian context, an operator prosecuted by CASA for not complying with the AD might defend on the basis that the AD was invalidly issued, but that is rare. The source does not indicate any such prosecution. The directive itself includes a note that the Illustrated Parts Catalogue gives instructions not to install an unmarked valve. That note might be relevant in litigation to show that the defect was known before the AD, potentially affecting the standard of care in a negligence claim. Overall, the litigation history for this specific AD appears to be nil or unreported. The practical significance for this deep dive is that operators should not rely on any expected legal challenge to the AD; compliance is straightforward, and the risk of enforcement or civil liability for non-compliance far outweighs the cost of performing the inspection and any necessary rework.

Several features of AD/CL-600/109 may trap unwary operators or maintenance engineers. First, the applicability statement refers to “Bombardier Inc. Model CL-600-2B19, Serial Numbers (S/N) 7003 and subsequent.” An operator might mistakenly think that only aircraft with S/N 7003 exactly or above are affected. That is correct, but note that many Challenger 604 aircraft have S/N well above 7003. However, serial numbers below 7003 are not covered at all, even if they have the same valve. An operator of an older Challenger 604 or a pre-7003 aircraft is not required to comply, but should be aware that the valve may still be defective; the AD only covers a specific manufacturing range of the airframe. Second, the AD applies to two valves: the NLG selector valve and the NLG door selector valve. Some operators might inspect only the selector valve and ignore the door selector valve. The AD requires a check of both. Third, the compliance time is “within 1600 flight hours or within 18 months after the effective date of this AD, whichever comes first.” Because the effective date is 2 July 2009, the 18-month deadline is 2 January 2011. An operator that flies infrequently and accumulates hours slowly might focus on the 18-month date, but a high-utilisation operator could hit the 1600-hour threshold well before 18 months. The operator must track both. Fourth, the AD includes a note that valves with S/N outside the range 0001 through 2126 require no action. But note: the “T” suffix or the ink stamp only matters if the S/N is within that range. A valve with S/N 3000 cannot be identified by those markers; it is automatically compliant, regardless of markings. Operators might waste time looking for the ink stamp on a valve that is already out of range. Fifth, the AD does not explicitly state that the Bombardier Service Bulletin 601R-32-104 is the only approved means of compliance. It says to act “in accordance with” that SB. However, it also says “or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada.” If an operator uses a revision not yet approved, compliance is invalid. The operator must verify that Transport Canada has approved the specific revision. Sixth, the Illustrated Parts Catalogue note (Note 3) warns against installing a Kaiser Fluid Technologies valve with P/N 750006000, S/N 0001-2126, without the ink stamp. But the AD itself does not prohibit installation; it requires a check and rework. The IPC note is advisory, but the AD supersedes any advisory that is inconsistent. An operator might mistakenly think that if the valve is already installed and unmarked, it must be removed immediately under the IPC note; but the AD gives a compliance time of 1600 hours/18 months, so immediate removal is not required. Seventh, the AD uses the phrase “any pressure, including residual pressure, in the No. 3 hydraulic system can result in an uncommanded NLG retraction and/or uncommanded opening of the NLG doors.” This suggests that the risk exists even when the aircraft is unpowered but the hydraulics have residual pressure. The fix (rework/end cap torque) is meant to prevent internal leakage. But the AD does not mandate any interim precautions, such as always installing the safety pin before hydraulic power is applied. Operators may wish to adopt such precautions as a matter of good practice. Eighth, the AD was issued by a delegate of CASA, not by the full Authority. That is routine, but an operator challenging the AD might argue that the delegate lacked actual authority if the instrument’s scope went beyond what is allowed. The source shows the signature block of James Coyne as delegate. The AD’s validity is not in doubt, but it is a minor point for thorough legal analysis. Finally, the AD makes no mention of record-keeping beyond the typical aircraft maintenance records. However, failure to document the check of both valves, including those that were found to be compliant (e.g., S/N outside range), can cause problems during an audit. CASA may require proof that each valve was inspected, not just that the rework was done. Operators should document the S/N and markings for both valves, even if no corrective action is needed.

Compliance with AD/CL-600/109 requires a step-by-step process that can be integrated into normal scheduled maintenance. Step one: identify whether the aircraft is within applicability. The AD applies only to Bombardier Model CL-600-2B19 with serial numbers 7003 and subsequent. Check the aircraft’s type certificate data sheet or registration documents. If the aircraft is a different model or has a lower serial number, no further action is required, though operators should retain a record of the reason for exclusion. Step two: physically locate both the nose landing gear selector valve and the nose landing gear door selector valve on the aircraft. Their locations should be identified using the aircraft maintenance manual or the Bombardier Service Bulletin. The part numbers are 601R75146-1 (Bombardier) / 750006000 (Kaiser Fluid Technologies). Step three: record the serial number and any identification markings for both valves. Look for the S/N stamped or engraved on the valve body. Determine whether the S/N falls within the range 0001 through 2126. Also look for the suffix “T” after the S/N (indicating a Tactair-manufactured valve) and for the ink stamp marking “SB750006000-1” (indicating prior rework). Step four: evaluate the results. If both valves fall into any of these categories: S/N outside 0001-2126, or S/N inside 0001-2126 but with suffix “T”, or S/N inside 0001-2126 but with the ink stamp “SB750006000-1”, then no further action is required. Compliance is complete. Record the inspection in the aircraft logbook, stating the AD reference, the valves’ S/Ns, and the finding that they are compliant. Step five: if either valve (or both) has a S/N in the range 0001 through 2126 and lacks both the suffix “T” and the ink stamp, proceed to Requirement 2. Obtain a copy of Bombardier Service Bulletin 601R-32-104, dated 3 March 2009, or a later revision approved by Transport Canada. Follow the Accomplishment Instructions exactly. This will involve checking the valve end cap lockwire and torque, and either replacing the valve, reworking the end cap assembly, and/or applying the ink stamp. The Service Bulletin will detail the specific tools, torque values, and inspection criteria. Step six: after the corrective action, ensure the valve is re-identified with the ink stamp “SB750006000-1” (if required). Reinstall the valve and perform any necessary operational checks (e.g., function test of the NLG retraction system). Step seven: complete the aircraft maintenance records. Record the dates of the inspection and any corrective action, the S/Ns of the valves, the Service Bulletin revision used, the part numbers, and the statement that the AD has been complied with. Sign off in accordance with the operator’s approved maintenance organisation procedures. Step eight: monitor compliance time. The AD requires the work to be completed within 1600 flight hours or 18 months after 2 July 2009, whichever occurs first. For aircraft that already exceeded that time at the effective date (unlikely, but possible if the aircraft accumulates hours quickly), immediate grounding is required. Most operators will schedule the inspection at the next convenient maintenance check. Step nine: if a later revision of the Service Bulletin becomes available, verify that it has been approved by the Chief, Continuing Airworthiness, Transport Canada before using it. Contact Bombardier or Transport Canada for confirmation. Step ten: keep copies of all relevant documentation, including the AD text, the Service Bulletin, and the logbook entry, in the aircraft technical records for future reference, audits, and transfer of ownership. Note that some operators may choose to replace both valves with new valves from Tactair (S/N with suffix “T”) or with valves outside the suspect S/N range, as a more permanent solution. That is permissible, but the operator must still comply with the AD by the compliance time; replacement alone satisfies the requirement. If replacement is chosen, ensure the new valve is properly documented. Finally, if the operator has any doubt about the identification of the valves or the interpretation of the SB, they should contact Bombardier technical support or CASA’s airworthiness division for clarification, rather than delaying compliance.