{"id":"F2006B11166","name":"AD/LJ45/5 - Horizontal Stabiliser Actuator Assembly","slug":"ad-lj45-5-horizontal-stabiliser-actuator-assembly","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56863,"registerId":"commonwealth-F2006B11166-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\n![](image.001.png)  \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 CAR 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\nLearjet 45 Series Aeroplanes","sortOrder":0},{"sectionNumber":"AD/LJ45/5 Horizontal Stabiliser Actuator","sectionType":"part","heading":"AD/LJ45/5 Horizontal Stabiliser Actuator Assembly 5/2003","content":"# AD/LJ45/5 Horizontal Stabiliser Actuator Assembly 5/2003\n\nTX\n\nApplicability: Learjet Model 45 aeroplanes with serial numbers 45-001 through 45-232 inclusive.\n\nRequirement: 1. Carry out an inspection to determine the part number (P/N) of the horizontal stabiliser actuator assembly (A66) in accordance with Paragraph 2 of the Accomplishment Instruction of Bombardier Learjet Alert Service Bulletin (ASB) A45-27-15 dated 20 March 2003.\n\n    2. If, as a result of the Requirement 1 inspection, an horizontal stabiliser actuator assembly (A66) with either P/N 6627401000-001 or 2A9200F is found to be installed, replace the actuator assembly with a new actuator assembly P/N 6627401000-005 in accordance with Paragraph 2 of the Accomplishment Instruction of ASB A45-27-15.\n    3. Horizontal stabiliser actuator assembly (A66) with either P/N 6627401000-001 or 2A9200F may not be installed on any aeroplane as a replacement part.\n\nNote: FAA Emergency AD 2003-06-51 refers.\n\nCompliance: For Requirements 1 and 2 \\- Before further flight after the effective date of this Directive.\n\nFor Requirement 3 \\- As of the effective date of this Directive.\n\nThis Airworthiness Directive becomes effective on 21 March 2003.\n\nBackground: Learjet has received a report of an horizontal stabiliser actuator assembly (A66) internal structural failure which has resulted in excessive linear free play. This free play could result in possible loss of control of the aeroplane.\n\nThis Directive requires an inspection to determine the part number of the installed actuator assembly and, if necessary, replacement of the actuator.\n\n![Signature of James Coyne Delegate of the Civil Aviation Safety Authority](image.002.png)  \n\nJames Coyne\n\nDelegate of the Civil Aviation Safety Authority 21 March 2003\n\n![](image.001.png)","sortOrder":1}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope — addressing a specific safety defect in a specific aircraft component for a defined fleet. There is no evidence of scope creep; the directive precisely targets the identified unsafe condition without expanding into broader operational or maintenance requirements."},"complexity_factors":["Single, clearly defined applicability (specific aircraft serial numbers)","Three straightforward requirements with no nested conditions or exceptions","Only 2 part numbers to identify and 1 replacement part number specified","No defined terms section — all technical terms are explained in context or self-explanatory","Single cross-reference to a manufacturer service bulletin (ASB A45-27-15) and a related FAA directive","Clear, immediate compliance deadlines with no conditional timing","Short document (approximately 300 words) with linear structure"],"plain_english_summary":"This Airworthiness Directive requires owners/operators of Learjet Model 45 aircraft (serials 45‑001 through 45‑232) to immediately inspect the horizontal stabiliser actuator assembly and, if it is part number 6627401000‑001 or 2A9200F, replace it before the next flight.  \n\nThe faulty actuators can develop internal structural failure causing dangerous looseness and possible loss of control; those parts are banned from installation effective 21 March 2003."},"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"},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive stays within the original safety-focused scope: it addresses a reported actuator internal structural failure on specific Learjet 45 serial numbers by identifying and removing suspect part numbers. It does not expand beyond correcting that unsafe condition (inspection, replacement, and prohibition of certain part numbers) and therefore has not grown beyond its original purpose."},"complexity_factors":["Short document (single-airworthiness directive, three explicit requirements)","Applies to a single aircraft model and a limited serial-number range (45-001 through 45-232)","Three actions only: inspect part number, replace if specific P/Ns found, ban two P/Ns from future installation","Single external technical reference: Bombardier Learjet ASB A45-27-15 (Paragraph 2)","Single cross-reference to FAA Emergency AD 2003-06-51","Simple timing rules: inspection/replacement before next flight; installation prohibition effective immediately"],"plain_english_summary":"**What this directive changes (mechanically)**\n\n- Applies to: Learjet Model 45 aircraft serial numbers 45-001 through 45-232 inclusive.\n- Requires an inspection to read the part number (P/N) of the horizontal stabiliser actuator assembly (A66) (Requirement 1).\n- If the installed actuator is P/N 6627401000-001 or P/N 2A9200F, it must be replaced with P/N 6627401000-005 (Requirement 2).\n- From the effective date, P/N 6627401000-001 and P/N 2A9200F are prohibited from being installed as replacement parts (Requirement 3).\n- The inspection and any required replacement must be done in accordance with Paragraph 2 of the Accomplishment Instruction of Bombardier Learjet Alert Service Bulletin A45-27-15 dated 20 March 2003 (Requirements 1–2).\n- Timing: the inspection and any replacement must be completed before the next flight after the AD becomes effective; the installation prohibition applies immediately on the effective date (Compliance).\n\n**Why the rule exists (official rationale)**\n\n- The stated reason is a reported internal structural failure of an A66 actuator that produced excessive linear free play; that free play could lead to loss of control of the aeroplane (Background).\n\n**Who is affected and who decides/acts**\n\n- Primary duty-bearers: aircraft owners/operators of the listed Learjet 45 serial numbers and the maintenance organisations that service them. They must perform the inspection and do any replacement in accordance with the Bombardier service bulletin (Requirements 1–2).\n- Parts suppliers and installers are affected by the installation ban on the two older part numbers (Requirement 3).\n- The Civil Aviation Safety Authority (CASA) delegate is the issuing authority under CAR 1998 subregulation 39.1(1) and enforces compliance.\n\n**Practical effects, costs and implementation issues**\n\n- Direct costs to operators: time and labour for the inspection; if a disallowed part is present, the cost of a replacement actuator (P/N 6627401000-005) and installation. Aircraft downtime while awaiting parts or maintenance is an opportunity cost.\n- Compliance burden is concentrated: only operators of the affected serial-numbered fleet must act. Maintenance shops must follow the referenced Bombardier procedure (Accomplishment Instruction, Paragraph 2).\n- Supply risk: if replacement assemblies are scarce, operators may face grounding or schedule disruption because the AD requires replacement before further flight (Compliance).\n- Behaviour change: operators must inspect immediately and must not fit the two older P/Ns after the effective date; maintenance providers must source the specified P/N 6627401000-005 when replacing an affected unit.\n\n**Where the AD looks externally**\n\n- It references Bombardier Learjet Alert Service Bulletin A45-27-15 (for how to inspect and replace) and cites the FAA Emergency AD 2003-06-51 as related material.\n\n**Assessment of the stated purpose against trade-offs**\n\n- The AD’s stated safety objective is to remove actuator assemblies that may have an internal structural defect and thereby reduce the risk of loss of control (Background). Mechanically, the AD achieves this by identifying suspect part numbers and mandating their replacement and prohibition (Requirements 1–3).\n- Trade-offs: the safety gain is achieved at the expense of immediate inspection and possible replacement costs and aircraft downtime. The instruction-to-replace mechanism concentrates costs on the affected operators and relies on timely availability of replacement parts and competent maintenance to implement the remedy (Requirements 1–2; Compliance).\n- Enforcement and compliance are straightforward (inspection → replace if certain P/Ns found → ban on those P/Ns), but implementation risk (parts availability, maintenance scheduling) is the main operational constraint.\n\n(References: Requirement 1–3; Compliance; Background; Bombardier ASB A45-27-15.)"}},"importantCases":[],"_links":{"self":"/api/acts/ad-lj45-5-horizontal-stabiliser-actuator-assembly","history":"/api/acts/ad-lj45-5-horizontal-stabiliser-actuator-assembly/history","analysis":"/api/acts/ad-lj45-5-horizontal-stabiliser-actuator-assembly/analysis","conflicts":"/api/acts/ad-lj45-5-horizontal-stabiliser-actuator-assembly/conflicts","importantCases":"/api/acts/ad-lj45-5-horizontal-stabiliser-actuator-assembly/important-cases","documents":"/api/acts/ad-lj45-5-horizontal-stabiliser-actuator-assembly/documents"}}