{"id":"F2006B11133","name":"AD/LEARJET/17 Amdt 1 - Cabin Altitude Pressure Limiter - Installation","slug":"ad-learjet-17-amdt-1-cabin-altitude-pressure-limiter-installation","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56816,"registerId":"commonwealth-F2006B11133-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/LEARJET/17 Amdt 1 - Cabin Altitude Pressure Limiter - Installation","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\nAD/LEARJET/17\n\nAmdt 1\n\n\nCabin Altitude Pressure Limiter - Installation 1/84\n\n \n\nApplicability: All model 24 with S/Nos. 24-100 to 24-349;\n\n \n\nAll model 25 with S/Nos. 25-003 to 25-226.\n\n \n\nDocument: Learjet Airplane Mod. Kit AMK 78-5 or AMK 83-1 as applicable.\n\n \n\nCompliance: For Learjet Airplane Mod. Kit AMK 78-5 - within 600 hours time in service after 31 January 1979. For Learjet Airplane Mod Kit AMK 83-1 - within 300 hours time in service after 31 January 1984.\n\n \n\nBackground:  This Directive is raised in issue to include additional Models 24 with S/Nos 24-100 to 24-229 except S/No 24-218 and models 25 with S/Nos 25-003 to 25-066 except S/No 25-061 per Learjet Airplane Mod Kit AMK 83-1.\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\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":true,"description":"The original AD covered a narrower range of aircraft. This amendment expands applicability to include additional Model 24 aircraft (serial numbers 24-100 to 24-229, except 24-218) and additional Model 25 aircraft (serial numbers 25-003 to 25-066, except 25-061) under the new modification kit AMK 83-1. The scope has grown from the original directive to capture more airframes requiring the safety modification."},"complexity_factors":["Very short document (approximately 200 words)","Only 2 defined modification kits referenced (AMK 78-5 and AMK 83-1)","Simple conditional structure: serial number ranges determine applicability","No nested exceptions or cross-references to other legislation","Clear, single compliance action with two alternative pathways based on modification kit type","Minimal regulatory jargon — uses standard aviation terminology (S/Nos, time in service)"],"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). Think of it like a compulsory recall notice, but for aircraft instead of cars.\n\n**What it requires:** Owners and operators of specific Gates Learjet 24 and 25 series aircraft must install a **cabin altitude pressure limiter** — a safety device that prevents the cabin from depressurizing (losing air pressure) too quickly or to dangerous levels at high altitudes.\n\n**Who it affects:**\n- **Learjet Model 24** aircraft with serial numbers 24-100 through 24-349\n- **Learjet Model 25** aircraft with serial numbers 25-003 through 25-226\n\n**The two compliance paths:**\n- **Older modification kit (AMK 78-5):** Must be installed within 600 flight hours after 31 January 1979\n- **Newer modification kit (AMK 83-1):** Must be installed within 300 flight hours after 31 January 1984\n\n**Why it matters:** This amendment (Amdt 1) expands the original directive to cover more aircraft than initially required. Without this device, a cabin pressure failure could cause hypoxia (lack of oxygen) for passengers and crew at high altitudes — a serious flight safety risk. Compliance is legally mandatory; you cannot fly these aircraft without making this modification."},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"The amendment broadened the Directive's applicability by adding additional Model 24 and Model 25 serial-number ranges while excluding specific serial numbers (per the 'Background' paragraph)."},"complexity_factors":["Multiple applicability bands: separate model/serial-number ranges for Model 24 (24‑100 to 24‑349) and Model 25 (25‑003 to 25‑226) increase administrative tracking.","Two different modification kits with different compliance windows: AMK 78‑5 requires installation within 600 hours TIS after 31 Jan 1979; AMK 83‑1 within 300 hours TIS after 31 Jan 1984 (source: Compliance paragraph).","Fixed reference dates plus hours‑in‑service metric require operators to calculate remaining compliance time from flight logs rather than calendar deadlines.","Background amendment: expands applicability to additional serial ranges and lists specific exclusions (e.g. S/No 24‑218, 25‑061), creating edge cases for inspectors and operators (source: Background paragraph).","Operational burden: sourcing and installing the specified Mod Kit per the Learjet Airplane Mod. Kit document creates costs, downtime and coordination with maintenance providers (source: Document/Compliance).","Traceability and recordkeeping obligations implicit in airworthiness directives — operators must demonstrate compliance for each affected serial number."],"plain_english_summary":"This Airworthiness Directive requires installation of a cabin altitude pressure limiter on specified Gates Learjet 24 and 25 aeroplanes by fitting Learjet Mod Kit AMK 78‑5 or AMK 83‑1 within set time-in-service limits. It affects owners/operators of the listed serial-numbered aircraft, who must schedule and pay for the modification, accept aircraft downtime, and keep compliance records. The amendment expands which serial ranges are covered."}},"importantCases":[],"_links":{"self":"/api/acts/ad-learjet-17-amdt-1-cabin-altitude-pressure-limiter-installation","history":"/api/acts/ad-learjet-17-amdt-1-cabin-altitude-pressure-limiter-installation/history","analysis":"/api/acts/ad-learjet-17-amdt-1-cabin-altitude-pressure-limiter-installation/analysis","conflicts":"/api/acts/ad-learjet-17-amdt-1-cabin-altitude-pressure-limiter-installation/conflicts","importantCases":"/api/acts/ad-learjet-17-amdt-1-cabin-altitude-pressure-limiter-installation/important-cases","documents":"/api/acts/ad-learjet-17-amdt-1-cabin-altitude-pressure-limiter-installation/documents"}}