{"id":"F2006B11118","name":"AD/LEARJET 35/39 - Forward Engine Beam Shear Web","slug":"ad-learjet-35-39-forward-engine-beam-shear-web","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56786,"registerId":"commonwealth-F2006B11118-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# AIRWORTHINESS DIRECTIVE\n\n![](image.001.png)  \n\nFor the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CASR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.\n\n![](image.001.png)  \n\nGates Learjet 35 and 36 Series Aeroplanes","sortOrder":0},{"sectionNumber":"AD/LEARJET 35/39 Forward Engine Beam She","sectionType":"part","heading":"AD/LEARJET 35/39 Forward Engine Beam Shear Web 5/2004","content":"# AD/LEARJET 35/39 Forward Engine Beam Shear Web 5/2004\n\nApplicability: Model 35, 35A, 36, and 36A aircraft, with serial numbers listed in Bombardier Service Bulletins 35/36-51-3, and 35/36-51-4 Revision 1 or Revision 2.\n\nRequirement: 1. Accomplish a detailed inspection (using a probe) and a general visual inspection of the shear webs of the forward engine beams (including modification of the drag angles) for cracking in accordance with the Accomplishment Instructions of Bombardier Service Bulletin (SB) 35/36-51-3, dated 1 February 2001.\n\n    2. Following detailed probe inspection required by Requirement 1, accomplish the follow-on actions specified in following Requirements 2.a., 2.b., or 2.c., as applicable, in accordance with Accomplishment Instructions of SB 35/36-51-3.\n\n    If the resistance measured during the inspection is less than 0.110 milliohm, repeat the inspections required by Requirement 1.\n\n    b. If the resistance measured during the inspection is 0.110 milliohm or more, but less than 0.150 milliohm, repair and modify the forward engine beam shear web in accordance with the Accomplishment Instructions of SB 35/36- 51-4 Revision 1, dated 2 August 2001, or Revision 2, dated 6 December 2001.\n\n    c. If the resistance measured during the inspection is 0.150 milliohm or more, repair and modify the forward engine beam shear web in accordance with the Accomplishment Instructions of SB 35/36-51-4 Revision 1 or Revision 2.\n\n    3. Following the general visual inspection required by Requirement 1, accomplish all of the applicable follow-on actions as specified in the Accomplishment Instructions of SB 35/36-51-3; except as specified as follows:\n\n    If any crack opening is found that is more than 0.030-inch during the general inspection required by Requirement 1, accomplish the actions specified in paragraphs 2.C.(16)(a) and 2.C.(16)(b) of SB 35/36-51-3; repair per a method approved by the Manager, Wichita Aircraft Certification Office (ACO), FAA; and accomplish the terminating action specified in Requirement 4.","sortOrder":1}],"analysis":{"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":false,"description":"The AD remains focused on detecting and correcting cracking in the forward engine beam shear web for specified Learjet 35/36 serial numbers. The text consolidates inspection procedures, numeric acceptance/rejection thresholds and prescribed repair/modification actions via Bombardier service bulletins, and it requires FAA ACO approval for certain repairs. Those are procedural refinements within the original safety-focused scope rather than a substantial expansion of purpose."},"complexity_factors":["Cross-reference to multiple external documents: Bombardier SB 35/36-51-3 and SB 35/36-51-4 Revision 1 and Revision 2","Conditional logic based on measured numeric thresholds (three resistance bands: <0.110, 0.110–<0.150, >=0.150 milliohm)","Combination of inspection methods: detailed probe (technical measurement) and general visual inspection","Follow-on actions that depend on inspection outcomes, including repeat inspections and different repair paths","Reference to additional SB paragraph content (e.g. 2.C.(16)(a)/(b)) and a terminating action in an unquoted Requirement 4","External approval required from the FAA Wichita ACO Manager for certain repairs (introduces administrative dependency and potential delay)","Applicability limited to specific serial numbers listed in the SBs (requires cross-checking those SB lists)","Technical measurement units and small tolerances (milliohm, 0.030-inch crack opening) increase precision and tooling requirements"],"plain_english_summary":"**What this directive does (mechanics)\n\n- Applies to: Gates Learjet Model 35, 35A, 36 and 36A aeroplanes that have the serial numbers listed in Bombardier Service Bulletins (SB) 35/36-51-3 and 35/36-51-4 Revision 1 or Revision 2 (see \"Applicability\").\n\n- Requires inspections: operators must perform a detailed probe inspection (using a probe) and a general visual inspection of the shear webs of the forward engine beams, including modified drag angles, following the Accomplishment Instructions in Bombardier SB 35/36-51-3 (Requirement 1).\n\n- Uses a measured resistance test to decide next steps: after the probe inspection, the measured resistance determines required follow-up (Requirement 2):\n  - If resistance is less than 0.110 milliohm: repeat the inspections required by Requirement 1;\n  - If resistance is 0.110 milliohm or more but less than 0.150 milliohm: repair and modify the forward engine beam shear web per Bombardier SB 35/36-51-4 Revision 1 or Revision 2 (Requirement 2.b);\n  - If resistance is 0.150 milliohm or more: repair and modify per SB 35/36-51-4 Revision 1 or Revision 2 (Requirement 2.c).\n\n- Visual-inspection follow-up: after the general visual inspection, follow the applicable follow-on actions in SB 35/36-51-3 (Requirement 3). If a crack opening greater than 0.030 inch is found on the general inspection, do the specified SB actions (paragraphs 2.C.(16)(a) and (b) of SB 35/36-51-3), repair using a method approved by the Manager, Wichita Aircraft Certification Office (ACO), FAA, and carry out the terminating action specified in Requirement 4.\n\n**Who this affects\n\n- Aircraft operators and owners of the affected Learjet 35/36 serial numbers — they must arrange inspections and any required repairs or modifications.\n- Maintenance organisations and licensed maintenance engineers — they must perform the probe, general visual and repair/modification work to the SB instructions and document compliance.\n- The Wichita ACO (FAA) manager — has authority to approve repair methods in certain cases (Requirement 3).\n\n**Why it matters (safety and operational effect)\n\n- The directive addresses potential cracking in the shear web of the forward engine beam, a structural element that supports the engine attachment loads. The inspections and required repairs or modifications are intended to detect and correct cracking before it degrades structural integrity.\n\n**Costs, incentives and practical effects (implementation, who pays, who decides)\n\n- Who pays: aircraft owners/operators bear the direct costs — inspection labour, downtime, and any repair/modification parts and labour.\n- Who decides: maintenance organisations decide timing and execution of inspections and repairs within the AD/SB instructions; the FAA Wichita ACO manager can approve alternate repair methods when the SB prescribes a particular fix (Requirement 3).\n- Incentives: operators will face a trade-off between inspection frequency and repair/retirement of airframes; repeated inspections are required if low resistance is measured (<0.110 milliohm), potentially increasing ongoing maintenance time and cost (Requirement 2.a).\n- Concentrated services: repair and modification work must follow Bombardier SB instructions; that creates demand for maintenance providers able to perform those SB-prescribed repairs and to document compliance.\n\n**Implementation risks and compliance burden\n\n- Measurement and access: the directive relies on a specific resistance measurement threshold (milliohm values). Accurate measurement, correct probing technique, and access to the shear web areas are required; operator training, tooling and calibration are necessary to apply the thresholds reliably (Requirement 2).\n- Downtime and parts supply: repair/modification per SB 35/36-51-4 may require parts and skilled labour, producing aircraft downtime and logistics costs.\n- Decision points requiring third-party approval: where a crack >0.030 inch is found, repairs must be done to a method approved by the Wichita ACO manager, which may introduce approval delays (Requirement 3).\n\n**What the AD does not say here (for implementers to check)\n\n- Exact compliance times and intervals are not reproduced in the excerpt; operators must consult the full AD text and the referenced Bombardier SBs for specific compliance windows, detailed steps, and terminating actions (Requirement 4 is referenced but not shown in full here).\n\n(References to specific parts of the directive: \"Applicability\"; \"Requirement 1\" (detailed probe and general visual inspections per SB 35/36-51-3); \"Requirement 2\" and subparagraphs a–c (resistance thresholds and follow-on repairs per SB 35/36-51-4); \"Requirement 3\" (follow-on actions after visual inspection and FAA approval requirement for certain repairs).)"},"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"},"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This is a standard airworthiness directive with a narrow, specific scope targeting a known unsafe condition in particular aircraft models. It has not expanded beyond its original safety purpose."},"complexity_factors":["Multiple conditional branches (Requirements 2.a, 2.b, 2.c) based on precise electrical resistance measurements","Cross-references to external documents (Bombardier Service Bulletins 35/36-51-3 and 35/36-51-4 Revisions 1 and 2) that are not reproduced in the directive itself","Nested exceptions in Requirement 3 (general visual inspection follow-on actions with specific carve-out for cracks exceeding 0.030-inch)","Technical aviation terminology requiring specialized knowledge (shear webs, drag angles, milliohm measurements, terminating action)","Dual regulatory framework reference (CASA delegate issuing under CASR 1998, but requiring FAA approval for certain repairs)"],"plain_english_summary":"This is a **safety order for specific private jets** — the Gates Learjet 35 and 36 series. It requires owners and operators to inspect a critical structural part called the \"forward engine beam shear web\" (a metal component that helps hold the engine to the wing) for dangerous cracks.\n\n**Who it affects:**\n- Owners and operators of Learjet Model 35, 35A, 36, and 36A aircraft with specific serial numbers listed in two Bombardier service bulletins.\n\n**What must be done:**\n- **Inspect** the engine beam shear webs using a probe and visual check, following specific manufacturer instructions.\n- **Take action based on findings:**\n  - If electrical resistance is very low (under 0.110 milliohm), keep re-inspecting.\n  - If resistance is moderate (0.110–0.150 milliohm), repair and modify the part using specific service bulletin instructions.\n  - If resistance is high (0.150+ milliohm), repair and modify using updated instructions.\n  - If cracks wider than 0.030-inch are found, complete additional repairs and get FAA approval for the repair method.\n\n**Why it matters:**\nCracks in this structural component could lead to engine separation or wing failure — a catastrophic safety risk. This directive is legally binding; failure to comply grounds the aircraft."},"summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a stand-alone airworthiness directive issued under existing regulation 39.1 of CASR 1998; it imposes mandatory inspection and repair requirements on operators but does not amend any other legislative instrument."},"complexity_factors":["Multiple conditional thresholds (electrical resistance and crack opening size)","Requires reference to two service bulletins with different revision statuses","Inspection methods include detailed probe and general visual procedures","One repair pathway requires FAA engineering approval"],"plain_english_summary":"This CASA Airworthiness Directive requires operators of certain Gates Learjet 35/36 series (specific serials per Bombardier SBs) to inspect the forward engine beam shear web for cracking, because failure could lead to engine separation. Inspections use a probe and visual check; electrical-resistance findings and any crack larger than 0.030\" trigger repair/modify actions under Bombardier service bulletins and an FAA-approved repair pathway. Affected owners/operators must comply by the AD’s specified times to maintain airworthiness."}},"importantCases":[],"_links":{"self":"/api/acts/ad-learjet-35-39-forward-engine-beam-shear-web","history":"/api/acts/ad-learjet-35-39-forward-engine-beam-shear-web/history","analysis":"/api/acts/ad-learjet-35-39-forward-engine-beam-shear-web/analysis","conflicts":"/api/acts/ad-learjet-35-39-forward-engine-beam-shear-web/conflicts","importantCases":"/api/acts/ad-learjet-35-39-forward-engine-beam-shear-web/important-cases","documents":"/api/acts/ad-learjet-35-39-forward-engine-beam-shear-web/documents"}}