{"id":"F2006B11149","name":"AD/LEARJET/31 - Handling Qualities and Aerodynamic Stall Characteristics - Modification","slug":"ad-learjet-31-handling-qualities-and-aerodynamic-stall-characteristics-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56838,"registerId":"commonwealth-F2006B11149-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/LEARJET/31 - Handling Qualities and Aerodynamic Stall Characteristics - Modification","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  Gates Learjet 24 & 25 Series Aeroplanes\n\n \n\n# AD/LEARJET/31 Handling Qualities and Aerodynamic Stall\n\nCharacteristics - Modification\n\nApplicability: All model 23 with S/Nos 23-003 to 23-099.\n\nAll model 24 with S/Nos 24-100 and subsequent. All model 25 with S/Nos 25-003 to 25-061.\n\n25-067 to 25-201.\n\n25-204 and subsequent.\n\n# 7/85\n\n \n\nWith unmodified wings.\n\n \n\nRequirement: 1. Install modification kit AMK 83-4, or\n\n \n\n2. Install modification kit AMK 84-5.\n\n \n\nNote: FAA AD No 80-19-11 R1 refers.\n\n \n\nCompliance: Before 1st October, 1986.\n\n \n\nBackground: GLC and the FAA have recently found evidence of undesirable handling characteristics at the limits of the flight envelope.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive focused specifically on correcting stall characteristics and handling qualities in specific Learjet models. It has not expanded beyond its original safety purpose."},"complexity_factors":["Very short document (approximately 250 words)","Only 2 defined modification kits (AMK 83-4 and AMK 84-5)","Simple binary compliance requirement (install one kit OR the other)","Single, absolute deadline (1 October 1986)","No nested exceptions or conditional logic","Minimal cross-referencing (only one reference to FAA AD No 80-19-11 R1 for context)","Clear applicability criteria based on aircraft model and serial number ranges"],"plain_english_summary":"**What this is:** This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) that requires specific repairs or modifications to aircraft.\n\n**What it does:** It orders owners and operators of certain **Gates Learjet 24 and 25 series aircraft** to install one of two specific modification kits to fix dangerous flight handling problems.\n\n**Who it affects:**\n- Owners and operators of specific Learjet Model 23, 24, and 25 aircraft with particular serial numbers (listed in the \"Applicability\" section)\n- Only applies to aircraft with **unmodified wings**\n\n**The safety problem:** Testing by the manufacturer (Gates Learjet Corporation or GLC) and the US Federal Aviation Administration (FAA) found these planes have **\"undesirable handling characteristics at the limits of the flight envelope\"** — meaning the aircraft behave unpredictably or dangerously when flown at slow speeds near stall conditions or at the edges of their safe operating range.\n\n**What must be done:**\n- **Option 1:** Install modification kit **AMK 83-4**, OR\n- **Option 2:** Install modification kit **AMK 84-5**\n\n**Deadline:** The modification **must be completed before 1 October 1986**.\n\n**Why it matters:** This is a **flight safety critical** directive. The \"undesirable handling characteristics\" could lead to loss of control during flight, particularly during approach, landing, or other low-speed operations. Compliance is mandatory — you cannot legally fly these aircraft in Australia without making this modification."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The instrument, as presented, sets out a targeted corrective requirement for specific serial-numbered Learjet models with unmodified wings and prescribes two alternative modification kits with a fixed compliance date. The text does not indicate any change in scope from an earlier statement of intent within this document; it defines its own applicability and required action without showing that those boundaries were altered from a prior version."},"complexity_factors":["Narrow applicability by specific model and serial-number ranges requiring record checks (Applicability).","Conditional applicability limited to aeroplanes “with unmodified wings,” requiring assessment of modification status (Applicability).","Two alternative approved modification kits are permitted, requiring operator choice without further selection criteria in the text (Requirement).","Fixed compliance deadline constrains scheduling and creates a time-bound compliance obligation (Compliance).","Cross-reference to an FAA Airworthiness Directive for related information creates dependency on external documentation (Note).","Limited explanatory detail in the background leaves technical implementation details to external sources or service documents (Background)."],"plain_english_summary":"This Directive requires operators of certain Gates Learjet Model 23/24/25 aircraft (specified serial-number ranges) with unmodified wings to install one of two approved wing modification kits (AMK 83-4 or AMK 84-5) by 1 October 1986. Issued to address undesirable handling near flight-envelope limits, it leaves kit choice, costs, scheduling and verification to the aircraft owner/operator and cross-references a related FAA AD for additional information."}},"importantCases":[],"_links":{"self":"/api/acts/ad-learjet-31-handling-qualities-and-aerodynamic-stall-characteristics-modification","history":"/api/acts/ad-learjet-31-handling-qualities-and-aerodynamic-stall-characteristics-modification/history","analysis":"/api/acts/ad-learjet-31-handling-qualities-and-aerodynamic-stall-characteristics-modification/analysis","conflicts":"/api/acts/ad-learjet-31-handling-qualities-and-aerodynamic-stall-characteristics-modification/conflicts","importantCases":"/api/acts/ad-learjet-31-handling-qualities-and-aerodynamic-stall-characteristics-modification/important-cases","documents":"/api/acts/ad-learjet-31-handling-qualities-and-aerodynamic-stall-characteristics-modification/documents"}}