{"id":"F2007L02369","name":"AD/CL-600/77 - Engine Exhaust Nozzle","slug":"ad-cl-600-77-engine-exhaust-nozzle","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":67724,"registerId":"commonwealth-F2007L02369-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-600/77 | Engine Exhaust Nozzle | 9/2007 |\n| ------------ | --------------------- | ------ |\n\n| Applicability: | Bombardier Inc. CL-600-2B19 Regional Jet (CRJ), aircraft serial numbers 7003 through 7067, and 7069 through 7947.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |\n| -------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | 1. Inspect both left and right exhaust nozzles in accordance with the Accomplishment Instructions, Part A of Bombardier SB 601R-78-021 dated2 June 2006 or later NAA approved revisions.a. If a bolt is missing or fractured on the engine exhaust nozzle, before further flight, replace the existing engine exhaust nozzle attachment hardware with new hardware in accordance with Requirement 3 of this AD.b. If no bolt is missing or fractured, no further action is required until the next inspection.2. Repeat Requirement 1 of this AD.3. Replace the existing engine exhaust nozzle attachment hardware with new hardware in accordance with the Accomplishment Instructions, Part B of Bombardier SB 601R-78-021 original issue or later NAA approved revisions.Completion of Requirement 3 of this AD constitutes terminating action for Requirements 1 and 2 of this AD for the applicable engine exhaust nozzle.Note: Transport Canada AD CF-2006-19 dated 28 July 2006 refers. |\n| Compliance:    | 1. Within 1500 flight hours after the effective date of this AD, unless previously accomplished.2. At intervals not to exceed 1500 flight hours.3. Within 4000 flight hours after the effective date of this AD.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |\n|                | This Airworthiness Directive becomes effective on 30 August 2007.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |\n\n| Background: | There have been three reported incidents of CL-600-2B19 (CRJ) aircraft engine exhaust nozzle and fairing departure in flight. Investigation on the failed retaining bolts revealed the bolts attaching the engine exhaust nozzle to the engine flange offered less than desirable stress margins. Loss of the engine exhaust nozzle during flight could result in damage to the aircraft and create a hazard to persons and property on the ground.In order to rectify this problem, Bombardier has issued service bulletin (SB)601R-78-021 to introduce an inspection and replacement of the hardware attaching the engine nozzle to the engine flange. |\n| ----------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n\n![](image.001.png)  \nDavid Punshon  \nDelegate of the Civil Aviation Safety Authority\n\n25 June 2007","sortOrder":0},{"sectionNumber":"AD/CL-600/77","sectionType":"part","heading":"AD/CL-600/77","content":"## AD/CL-600/77","sortOrder":1},{"sectionNumber":"Engine Exhaust Nozzle","sectionType":"part","heading":"Engine Exhaust Nozzle","content":"## Engine Exhaust Nozzle","sortOrder":2},{"sectionNumber":"9/2007","sectionType":"part","heading":"9/2007","content":"## 9/2007","sortOrder":3}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a standard, targeted airworthiness directive addressing a specific mechanical defect in a specific aircraft type. The scope remains precisely limited to exhaust nozzle hardware on the identified CRJ serial numbers, consistent with the original safety purpose."},"complexity_factors":["Single, clearly defined applicability (specific aircraft serial numbers)","Only 3 numbered requirements with straightforward conditional logic (if bolt missing/fractured → replace; if not → continue monitoring)","No defined terms section or interpretation provisions","Minimal cross-referencing (only references one Bombardier service bulletin and one Canadian AD)","Clear terminating action (Requirement 3 ends the need for Requirements 1-2)","Simple compliance table with three time-based triggers","Total length is approximately one page"],"plain_english_summary":"This CASA Airworthiness Directive orders operators of Bombardier CRJ aircraft (S/N 7003–7067 and 7069–7947) to inspect and replace weak bolts on engine exhaust nozzles after reports of nozzles detaching in flight. It mandates inspections every 1,500 flight hours and replacement of the bolt hardware within 4,000 flight hours (first inspection within 1,500 FH of 30 Aug 2007). Once new hardware is fitted, the recurring inspections for that engine are no longer required."},"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD remains tightly focused on the original safety problem: inadequate stress margins in the bolts that attach the engine exhaust nozzle to the engine flange on specified CL-600-2B19 (CRJ) serial numbers. The instrument prescribes inspection and replacement procedures and sets deadlines; it does not broaden the subject matter beyond that original purpose. Allowing compliance with later NAA-approved revisions of the Bombardier service bulletin introduces procedural flexibility but does not materially expand the AD’s substantive scope."},"complexity_factors":["Single-component focus (engine exhaust nozzle) reduces subject-matter breadth","Applicability limited to a specific model and serial-number range (narrow scope)","Three main operative requirements with simple conditional logic (inspect → if bolt missing/fractured replace before flight; otherwise repeat)","Fixed, small set of compliance intervals (1,500 and 4,000 flight hours) — low temporal complexity","References to Bombardier Service Bulletin SB 601R-78-021 and allowance for later NAA-approved revisions introduces cross-reference and minor jurisdictional variation","Termination provision where replacement ends repetitive inspections (single-layer exception)","References a related foreign AD (Transport Canada) but no deep cross-referencing to multiple legislative instruments"],"plain_english_summary":"**What this instrument does (mechanically)**\n\n- It orders operators of certain Bombardier CL-600-2B19 (CRJ) aircraft to inspect the left and right engine exhaust nozzles and, in some cases, replace the attachment hardware that secures the nozzle to the engine flange. (Applicability; Requirement 1–3.)\n- If an inspection finds a missing or broken bolt, the operator must replace the nozzle attachment hardware before the aircraft flies again. (Requirement 1.a)\n- If no bolt is missing or broken, the operator must repeat the inspection at regular intervals until the nozzle attachment hardware has been replaced. (Requirement 1.b and 2)\n- Replacing the nozzle attachment hardware as specified in the Bombardier service bulletin is a terminating action: once replaced, the repetitive inspections are no longer required for that nozzle. (Requirement 3)\n- The inspections and replacement must be performed in accordance with Bombardier Service Bulletin SB 601R-78-021 (Part A for inspection; Part B for replacement), or later revisions approved by the relevant national aviation authority (NAA). (Requirement text)\n\n**Who this affects**\n\n- Aircraft operators/owners of Bombardier Inc. CL-600-2B19 Regional Jets with serial numbers 7003–7067 and 7069–7947 (Applicability). These are the aircraft required to comply with the directive.\n- Maintenance organisations and engineers who perform the inspections and replacements under the Bombardier service bulletin.\n- The regulator that enforces compliance (Civil Aviation Safety Authority delegate issued this instrument). The directive references Transport Canada’s corresponding AD as related background. (Background; Note)\n\n**Why it matters (official rationale and practical implications)**\n\n- The stated reason is that there were three reported in-flight departures of engine exhaust nozzles and fairings on this model. Investigations found the retaining bolts attaching the nozzle to the engine flange had lower-than-desired stress margins. A nozzle departing in flight could damage the aircraft and endanger people and property on the ground. The AD therefore mandates inspection and replacement of the attachment hardware to reduce that risk. (Background)\n\n**Key compliance timings (deadlines)**\n\n- Initial inspection: within 1,500 flight hours after the AD’s effective date, unless already done. (Compliance 1)\n- Repeat inspections: at intervals not exceeding 1,500 flight hours until terminating action is completed. (Compliance 2)\n- Mandatory replacement of attachment hardware (terminating action): within 4,000 flight hours after the AD’s effective date. (Compliance 3)\n- Effective date of the AD: 30 August 2007. (Compliance header)\n\n**Who pays and who decides**\n\n- Operators pay: costs include labour for inspections, parts for replacement hardware, potential aircraft downtime, and any administrative costs for regulatory compliance.\n- The regulator (Civil Aviation Safety Authority delegate) enforces the AD; the work must follow Bombardier’s service bulletin or later NAA-approved revisions, giving national aviation authorities discretion to accept future revisions. (Requirement text)\n\n**Incentives, trade-offs and practical effects**\n\n- Safety benefit vs. operating cost: The mandatory inspections and required replacement reduce the risk of nozzle departure (a concentrated safety benefit) while imposing direct maintenance costs and potential aircraft out-of-service time on operators (diffuse cost borne by many operators). (Background; Requirement; Compliance)\n- Scheduling incentives: Because replacement is a terminating action, operators may choose to perform the replacement earlier than required to avoid recurring inspections and associated operational disruption. (Requirement 3)\n- Supply and logistics risk: Compliance depends on parts availability and maintenance capacity. If replacement hardware or approved modification kits are constrained, operators may face scheduling delays or interim inspection burdens. (Implicit from Requirement/Compliance reliance on SB)\n- Regulatory discretion and variation: The AD requires compliance with the Bombardier service bulletin or later NAA-approved revisions. That allows national aviation authorities to approve changes to the instructions, which can produce minor variance in how the work is accomplished across jurisdictions. (Requirement text)\n\n**Implementation and enforcement considerations**\n\n- The AD provides clear conditional logic: inspect, and if a missing/fractured bolt is found replace before flight; otherwise repeat inspection until replacement is completed. (Requirement 1–2)\n- Enforcement is straightforward: inspectors check maintenance records for completed inspections and replacements within the specified flight-hour windows. Records should show conformity with SB 601R-78-021 or an NAA-approved revision. (Requirement/Compliance)\n\n**Source claim and testing that claim**\n\n- The directive’s stated purpose is to prevent in-flight loss of the engine exhaust nozzle after three reported incidents and bolt stress-margin findings (Background). This is a risk-reduction measure whose direct cost is maintenance time and parts for operators; the benefit is reduced risk of airframe damage and hazard to people/property on the ground. The trade-off is therefore increased maintenance expenditure and potential aircraft downtime in exchange for reduced risk of a hazardous component failure. (Background; Requirement; Compliance)\n\n"}},"importantCases":[],"_links":{"self":"/api/acts/ad-cl-600-77-engine-exhaust-nozzle","history":"/api/acts/ad-cl-600-77-engine-exhaust-nozzle/history","analysis":"/api/acts/ad-cl-600-77-engine-exhaust-nozzle/analysis","conflicts":"/api/acts/ad-cl-600-77-engine-exhaust-nozzle/conflicts","importantCases":"/api/acts/ad-cl-600-77-engine-exhaust-nozzle/important-cases","documents":"/api/acts/ad-cl-600-77-engine-exhaust-nozzle/documents"}}