{"id":"F2009L02773","name":"AD/CL-600/114 - Landing Gear Alternate Extension System","slug":"ad-cl-600-114-landing-gear-alternate-extension-system","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":79933,"registerId":"commonwealth-F2009L02773-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Bombardier (Canadair) CL-600 (Challenger","sectionType":"division","heading":"Bombardier (Canadair) CL-600 (Challenger) Series Aeroplanes","content":"### Bombardier (Canadair) CL-600 (Challenger) Series Aeroplanes\n\n| AD/CL-600/114 | Landing Gear Alternate Extension System | 8/2009 |\n| ------------- | --------------------------------------- | ------ |\n\n| Applicability: | Bombardier Inc. Models CL-600-2C10 (Regional Jet Series 700 and 701) - Serial Numbers 10003 through 10216 CL-600-2D15 (Regional Jet Series 705) andCL-600-2D24 (Regional Jet Series 900) - Serial Numbers 15001 through 15039. |\n| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |\n| Requirement: | 1. Bypass Valve - Clevis Replacement:Replace the existing clevis with a new clevis, P/N 2323H037, in accordance with Part A of the Accomplishment Instructions in Alert Service Bulletin (ASB) A670BA-32-022, Revision A, dated 1 May 2009, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada.Replacement of the existing clevis in accordance with Part A of the original issue, dated 8 November 2007, of ASB A670BA-32-022 also meets the intent of Requirement 1 of this AD.It is not necessary to replace the clevis if Part III of this AD has already been accomplished.2. Downlock Assist Valve - Clevis Replacement:Replace the existing clevis with a new clevis, Part Number 2323H037, in accordance with Part B of the Accomplishment Instructions in ASBA670BA-32-022, Revision A, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada.Replacement of the existing clevis in accordance with Part B of the original issue, dated 8 November 2007, of ASB A670BA-32-022 also meets the intent of Requirement 2 of this AD.It is not necessary to replace the clevis if Part III of this AD has already been accomplished.3. Installation of Support Brackets:Install new support brackets for the bypass valve and downlock assist valve in accordance with Part C of the Accomplishment Instructions in ASBA670BA-32-022, Revision A, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada. |\n\n| | Note: Transport Canada AD CF-2009-22 dated 14 May 2009 refers. |\n| ----------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |\n| Compliance: | For Requirement 1:If, at the effective date of this AD, the bypass valve, Part Number (P/N) 53342-3, has accumulated 9,400 flight cycles (FC) or less, replace the clevis before the valve has accumulated 10,000 FC.If, at the effective date of this AD, the bypass valve has accumulated more than 9,400 FC, replace the clevis within 550 flight hours (FH) after the effective date of this AD.If it is not possible to determine the flight cycles accumulated by the bypass valve, replace the clevis within 550 FH after the effective date of this AD.For Requirement 2:If, at the effective date of this AD, the downlock assist valve, P/N 53341-5, has accumulated 9,400 FC or less, replace the clevis before the valve has accumulated 10,000 FC.If, at the effective date of this AD, the downlock assist valve has accumulated more than 9,400 FC, replace the clevis within 550 FH after the effective date of this AD.If it is not possible to determine the FC accumulated by the downlock assist valve, replace the clevis within 550 FH after the effective date of this AD.For Requirement 3:Within 4,500 FH after the effective date of this AD; orWithin 6000 FH after the accomplishment of Requirement 1 of this AD; orWithin 6000 flight cycles after the accomplishment of Requirement 2 of this AD,whichever comes first. |\n| | This Airworthiness Directive becomes effective on 30 July 2009. |\n| Background: | Investigation into a landing gear retraction problem on a production test flight revealed that, during aircraft pressurization and depressurization cycles, the pressure floor in the main landing gear bay deflects to a small extent. This causes relative misalignment between the AES bypass valve, the downlock assist valve and the summing lever which, in turn, can result in damage to and potential failure of the respective clevis attached to one or both of the valves. Such a clevis failure could remain dormant and, in the subsequent event that use of the AES was required, full landing gear extension may not be achievable. |\n| | This AD gives instructions to replace the clevis, with a new part, for both the bypass and the downlock assist valves. It also gives instructions to install new support brackets for both valves, in order to increase the stiffness of the installations and thus prevent future relative misalignment and potential clevis failure. |\n\n![](image.001.png) \nJames Coyne \nDelegate of the Civil Aviation Safety Authority\n\n19 June 2009","sortOrder":0},{"sectionNumber":"AD/CL-600/114","sectionType":"part","heading":"AD/CL-600/114","content":"## AD/CL-600/114","sortOrder":1},{"sectionNumber":"Landing Gear Alternate Extension System","sectionType":"part","heading":"Landing Gear Alternate Extension System","content":"## Landing Gear Alternate Extension System","sortOrder":2},{"sectionNumber":"8/2009","sectionType":"part","heading":"8/2009","content":"## 8/2009","sortOrder":3}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope — addressing a specific mechanical defect in the landing gear alternate extension system of specific Bombardier aircraft models. The document does not show evidence of scope creep beyond the original safety issue identified in the background."},"complexity_factors":["Multiple conditional compliance pathways based on flight hours vs flight cycles and current accumulated usage","Cross-references to external technical documents (Alert Service Bulletin A670BA-32-022, Revision A, and Transport Canada AD CF-2009-22)","Nested exceptions (e.g., clevis replacement not required if Part III already accomplished)","Specific part numbers and serial number ranges that limit applicability","Alternative compliance methods (original issue dated 8 November 2007 vs Revision A dated 1 May 2009)","Requires interpretation of 'effective date' and tracking of component-level flight cycles rather than just airframe hours"],"plain_english_summary":"This CASA Airworthiness Directive mandates safety modifications to certain Bombardier CL-600 series (Regional Jet 700/701/705/900) to prevent loss of alternate landing-gear extension. It requires replacing clevis fittings on two gear hydraulic valves and fitting new support brackets because cabin-floor flexing can misalign valves and break clevises, risking a wheels-up landing. Deadlines: clevis replacement within 550 flight hours (or before 10,000 cycles as applicable) and brackets within 4,500 flight hours (or 6,000 hours/cycles after clevis work). Non-compliance grounds the aircraft."},"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":false,"description":"The AD remains narrowly focused on remedying a specific mechanical risk: potential clevis damage and failure in the landing‑gear alternate extension system caused by relative misalignment during pressurisation cycles. It prescribes part replacement and bracket installation and accepts compliance performed to the original service bulletin. There is no indication the AD expanded beyond that technical fix (no added unrelated regulatory burdens or new operational restrictions); it primarily refines required parts, compliance windows, and approved service‑bulletin revisions."},"complexity_factors":["Applicability spans multiple models and two distinct serial‑number ranges","Three separate mandatory actions (Req 1, Req 2, Req 3) with distinct parts and SB parts (A, B, C)","Conditional compliance timing rules based on flight cycles (FC) and flight hours (FH) with multiple thresholds (≤9,400 FC; <10,000 FC; 550 FH default)","Multiple competing compliance time windows for Requirement 3 (4,500 FH after AD, or 6,000 FH after Req 1, or 6,000 FC after Req 2 — \"whichever comes first\")","References to external documents and approvals (Alert Service Bulletin A670BA‑32‑022 original and Revision A; later revisions require Chief approval; Transport Canada AD CF‑2009‑22)","Allowance that work done to an earlier SB issue satisfies the AD (multiple pathways to compliance increase branching)","Several part numbers referenced for valves and replacement clevises (P/N 53342‑3, 53341‑5, new clevis P/N 2323H037)","Dependence on operator records (FC/FH); unknown-record branch introduces a strict alternate deadline","Short textual notes (e.g. \"It is not necessary to replace the clevis if Part III of this AD has already been accomplished\") that refer to other AD parts not reproduced here, producing potential cross‑part ambiguity"],"plain_english_summary":"**What this instrument does (mechanically)**\n\n- It requires operators of certain Bombardier Challenger CL-600 series aeroplanes to change specific small parts on the landing-gear alternate extension system (AES) and fit new support brackets. Specifically:\n - Requirement 1: replace the clevis on the AES bypass valve with P/N 2323H037 (see Part A of the referenced Alert Service Bulletin).\n - Requirement 2: replace the clevis on the downlock assist valve with P/N 2323H037 (see Part B of the referenced Alert Service Bulletin).\n - Requirement 3: install new support brackets for both valves to stiffen the installation (see Part C of the Alert Service Bulletin).\n- The work must be done in accordance with Bombardier Alert Service Bulletin A670BA-32-022 (Revision A dated 1 May 2009, or later Transport Canada–approved revisions). Work already done to the original (8 Nov 2007) issue of the same SB also meets the requirements.\n\n**Who this affects**\n\n- Aircraft operators and owners of Bombardier Model CL-600-2C10 (Regional Jet Series 700/701) with serial numbers 10003–10216, and CL-600-2D15/2D24 (Series 705/900) with serial numbers 15001–15039.\n- Licensed maintenance organisations and engineers who will perform the replacements and install the brackets.\n- Parts suppliers who provide the clevis P/N 2323H037 and the new support brackets.\n\n**Why it matters (stated purpose and mechanistic effect)**\n\n- The stated purpose is to prevent clevis fatigue or failure caused by small deflections of the landing-gear bay pressure floor during pressurisation cycles. That relative movement can create misalignment between the bypass valve, downlock assist valve and summing lever, which can damage the clevis that links those items. A clevis failure could prevent full landing gear extension when the Alternate Extension System is used (Background text).\n- Mechanically, replacing the clevis with a new part and fitting stiffer support brackets reduces the chance of misalignment and subsequent clevis damage (Requirements 1–3).\n\n**Key compliance timings and conditional rules (what operators must do and when)**\n\n- For the bypass valve clevis (Req 1, P/N 53342-3):\n - If that valve has accumulated 9,400 flight cycles (FC) or less at the AD effective date, replace the clevis before it reaches 10,000 FC.\n - If it has already exceeded 9,400 FC, replace the clevis within 550 flight hours (FH) of the AD effective date.\n - If you cannot determine the valve’s FC, replace the clevis within 550 FH of the AD effective date.\n- For the downlock assist valve clevis (Req 2, P/N 53341-5): the same timing rules as for Requirement 1.\n- For the support brackets (Req 3): install within the earliest of the following:\n - 4,500 FH after the AD effective date; or\n - 6,000 FH after accomplishing Requirement 1; or\n - 6,000 FC after accomplishing Requirement 2.\n- The AD accepts compliance performed to the original (8 Nov 2007) Alert Service Bulletin as meeting the requirement; later revisions require Transport Canada/Chief approval.\n\n**Costs, incentives, trade‑offs and who pays**\n\n- Direct cost: parts (new clevises and brackets) plus labour and aircraft downtime. These costs are borne by aircraft operators (owners) under normal maintenance obligations.\n- Incentives: operators are compelled to schedule the work within the specified windows. There is an operational incentive to do the work earlier to avoid the shorter deadlines that apply once a part accumulates higher cycles or when flight-hour records are unavailable.\n- Trade‑offs and opportunity costs: time in maintenance facilities and replacement part lead times could affect aircraft availability and scheduling. Independent maintenance organisations (MROs) may perform the work if authorised; this can spread demand for services across the market but may also temporarily concentrate demand for the specific parts and approved procedures.\n\n**Implementation and compliance risks**\n\n- Recordkeeping dependence: the AD’s timing rules hinge on knowing the valve’s flight‑cycle count. If that count is unknown, the default is the shorter 550‑FH window, which could impose compressed scheduling.\n- Parts availability and MRO capacity: operators may face short-term bottlenecks for P/N 2323H037 and for technicians familiar with the SB procedure.\n- Administrative discretion: the AD requires compliance “in accordance with” a Transport Canada–approved SB revision; any later revisions must be approved by the Chief, Continuing Airworthiness (the AD ties acceptable work to regulator approval).\n\n**Market and regulatory effects (concise)**\n\n- Competition and private choice: the measure imposes a mandated maintenance task but does not limit who may perform the work provided regulatory approvals for the procedure/part are satisfied. That preserves choice among qualified MROs.\n- Prices and productivity: short-term maintenance demand may raise costs or produce scheduling delays; long-term effect is increased AES reliability which may reduce risk‑related costs.\n\n**Cross‑references and notes**\n\n- The AD references Transport Canada AD CF‑2009‑22 and accepts compliance with the original 8 Nov 2007 version of ASB A670BA‑32‑022. The AD became effective 30 July 2009.\n\n(Requirements cited: Requirement 1, Requirement 2, Requirement 3; Compliance section; Background.)"},"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"}},"importantCases":[],"_links":{"self":"/api/acts/ad-cl-600-114-landing-gear-alternate-extension-system","history":"/api/acts/ad-cl-600-114-landing-gear-alternate-extension-system/history","analysis":"/api/acts/ad-cl-600-114-landing-gear-alternate-extension-system/analysis","conflicts":"/api/acts/ad-cl-600-114-landing-gear-alternate-extension-system/conflicts","importantCases":"/api/acts/ad-cl-600-114-landing-gear-alternate-extension-system/important-cases","documents":"/api/acts/ad-cl-600-114-landing-gear-alternate-extension-system/documents"}}