{"id":"F2006B02098","name":"AD/AC/4 - Main Landing Gear Upper Retaining Pins - Replacement","slug":"ad-ac-4-main-landing-gear-upper-retaining-pins-replacement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41328,"registerId":"commonwealth-F2006B02098-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AC/4 - Main Landing Gear Upper Retaining Pins - Replacement","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-description: CASA Airworthiness Directive\nmeta-generator: Aspose.Words for .NET 22.10.0\nmeta-keywords: Issue NK,Aircraft below 5700 kg,Twin Commander (Gulfstream/Rockwell/ Aerocommander 500, 600 and 700) Series Aeroplanes,Main Landing Gear Upper Retaining Pins - Replacement,4\ntitle: Airworthiness Directive - AD/AC/4 - Main Landing Gear Upper Retaining Pins - Replacement\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)  Twin Commander (Gulfstream/Rockwell/ Aerocommander 500, 600 and 700) Series Aeroplanes\n\n \n\nAD/AC/4  Main Landing Gear Upper NK Retaining Pins - Replacement\n\nApplicability: Models 560A, 560E and 680: S/Nos. 231 to 559. Document:  1. Aero Commander SB No. 43; or\n\n2. FAA AD 57-15-1.\n\n \n\nCompliance: Forthwith.\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, targeted safety directive focused on a specific mechanical component in a narrow aircraft fleet. It has not expanded beyond its original purpose of mandating immediate replacement of defective landing gear pins."},"complexity_factors":["Extremely short document (under 200 words)","Only 3 defined applicability criteria (specific models and serial number range)","Single, unambiguous compliance requirement ('Forthwith')","No nested exceptions, conditional logic, or cross-references to other legislation beyond two referenced technical documents","No interpretation section or defined terms"],"plain_english_summary":"**What this is:** This is an Airworthiness Directive (AD) — a mandatory safety order issued by the Civil Aviation Safety Authority (CASA). Think of it as a \"recall notice\" for aircraft, but legally binding.\n\n**What it requires:** Owners and operators of specific Twin Commander aircraft (models 560A, 560E, and 680 with serial numbers 231–559) must **immediately replace the upper retaining pins on the main landing gear**. These pins are critical components that help hold the landing gear in place.\n\n**Why it matters:** Faulty or worn retaining pins could cause the main landing gear to fail — potentially leading to a collapse during landing, taxiing, or takeoff. The directive uses the word \"Forthwith,\" which means **do it now** — not at the next scheduled maintenance check.\n\n**Who must comply:** Anyone operating the affected aircraft models in Australia. The directive references an Aero Commander Service Bulletin and an older FAA directive, meaning this safety issue has been recognized internationally.\n\n**The bottom line:** If you own or fly one of these specific Twin Commander planes, you cannot legally operate it until those pins are replaced."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The provided AD text identifies a specific, fixed applicability (models 560A, 560E and 680; S/Nos. 231–559) and a single required action (replacement of main landing gear upper retaining pins) to be done 'Forthwith'. The document includes no amendments, expansions, or historical notes indicating a change of scope from an earlier instrument."},"complexity_factors":["Narrow and specific applicability (limited models and serial number range).","Immediate compliance requirement ('Forthwith') increasing urgency of implementation.","Technical procedure and details are not contained in the AD but referenced to external documents (Aero Commander SB No. 43 or FAA AD 57-15-1).","No procedural timelines, exception rules, or funding/compensation provisions included in the AD text.","Simple one-action requirement (replacement of a specific component) reducing multi-step regulatory complexity."],"plain_english_summary":"This AD requires owners/operators to replace the main landing gear upper retaining pins on Twin Commander 560A, 560E and 680 aircraft with serial numbers 231–559, with compliance required \"forthwith.\" It delegates the technical procedure to Aero Commander Service Bulletin No. 43 or FAA AD 57‑15‑1. Issued by CASA under the Civil Aviation Regulations 1998 Part 39‑105, it aims to address an airworthiness/safety concern and may cause immediate maintenance downtime and costs for operators."}},"importantCases":[],"_links":{"self":"/api/acts/ad-ac-4-main-landing-gear-upper-retaining-pins-replacement","history":"/api/acts/ad-ac-4-main-landing-gear-upper-retaining-pins-replacement/history","analysis":"/api/acts/ad-ac-4-main-landing-gear-upper-retaining-pins-replacement/analysis","conflicts":"/api/acts/ad-ac-4-main-landing-gear-upper-retaining-pins-replacement/conflicts","importantCases":"/api/acts/ad-ac-4-main-landing-gear-upper-retaining-pins-replacement/important-cases","documents":"/api/acts/ad-ac-4-main-landing-gear-upper-retaining-pins-replacement/documents"}}