{"id":"F2006B04988","name":"AD/CESSNA 170/6 Amdt 2 - Undercarriage Attachment Bolts","slug":"ad-cessna-170-6-amdt-2-undercarriage-attachment-bolts","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44885,"registerId":"commonwealth-F2006B04988-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/CESSNA 170/6 Amdt 2 - Undercarriage Attachment Bolts","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)  Cessna 170, 172, F172, FR172 and 175 Series Aeroplanes\n\n \n\nAD/CESSNA 170/6\n\nAmdt 2\n\n\nUndercarriage Attachment Bolts 11/71\n\n \n\nApplicability: Model 170, 170A and 170B.\n\n \n\nRequirement: Remove the AN7-20A bolts and the nuts attaching the inboard end of the undercarriage spring legs, and replace with new AN7-20A bolts and new nuts.\n\n \n\nCompliance: At intervals not exceeding 500 hours time in service. For aircraft which have exceeded 500 hours time in service since last bolt replacement - Within 100 hours time in service after 30 November 1971 and thereafter as above.\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\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 Amendment 2 of an existing Airworthiness Directive, but the scope remains tightly focused on its original purpose: mandating replacement of specific undercarriage bolts on specific Cessna 170 variants. The amendment appears to be a routine update (possibly to clarify compliance timing or incorporate prior amendments) rather than an expansion of scope. The directive has not grown beyond its original safety purpose of preventing undercarriage failure."},"complexity_factors":["Extremely short document (approximately 150 words of substantive content)","Only 3 defined elements: specific aircraft models (170, 170A, 170B), specific bolt part number (AN7-20A), and compliance intervals","Single operational requirement with straightforward replacement instruction","Simple temporal compliance structure with only two conditions (standard 500-hour interval vs. transitional 100-hour provision for high-time aircraft)","No cross-references to other legislation, regulations, or technical standards","No exceptions, exemptions, or conditional logic beyond the basic compliance timing"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It applies to specific older Cessna aircraft models (the 170, 170A, and 170B).\n\n**What it requires:**\n- Aircraft owners must **replace the bolts and nuts** that attach the undercarriage (landing gear) spring legs to the airframe\n- The specific parts involved are AN7-20A bolts and their matching nuts\n\n**When it must be done:**\n- **Every 500 hours of flight time** (\"time in service\")\n- For aircraft that had already flown more than 500 hours when this directive came out: they had **100 hours to comply** from 30 November 1971, then every 500 hours after that\n\n**Why it matters:**\nUndercarriage bolts are critical safety components. If they fail, the landing gear could collapse during takeoff or landing. This directive prevents catastrophic accidents by mandating regular replacement of these parts before they can wear out or fail from metal fatigue."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The supplied instrument (labelled Amendment 2) prescribes replacement of the inboard undercarriage attachment bolts and nuts for Cessna Model 170/170A/170B on a 500‑hour recurring schedule with a specified catch‑up interval. The text itself does not identify how this differs from any prior version or original intent, so no scope change can be identified from the supplied text alone."},"complexity_factors":["Narrow applicability limited to three aircraft models (Applicability).","Single, specific physical action required (remove and replace AN7-20A bolts and nuts) (Requirement).","Recurring compliance schedule with a clear interval (500 hours TIS) and a one‑time catch‑up window (100 hours after 30 Nov 1971) (Compliance).","Need for operators to track hours in service to determine compliance windows (Compliance).","Legacy date and retroactive catch‑up requirement introduce minor administrative complexity for historical records (Compliance).","Text omits procedural installation details and enforcement/inspection mechanics, requiring reliance on existing maintenance practices (Requirement)."],"plain_english_summary":"This Civil Aviation Safety Authority airworthiness directive requires owners/operators of Cessna Model 170, 170A and 170B aeroplanes to remove and replace the AN7-20A bolts and nuts at the inboard ends of the undercarriage spring legs. Replacements are mandatory every 500 hours TIS, with an overdue catch‑up requiring replacement within 100 hours after 30 November 1971. Operators bear parts, labour and downtime costs and must track hours to meet the recurring schedule."}},"importantCases":[],"_links":{"self":"/api/acts/ad-cessna-170-6-amdt-2-undercarriage-attachment-bolts","history":"/api/acts/ad-cessna-170-6-amdt-2-undercarriage-attachment-bolts/history","analysis":"/api/acts/ad-cessna-170-6-amdt-2-undercarriage-attachment-bolts/analysis","conflicts":"/api/acts/ad-cessna-170-6-amdt-2-undercarriage-attachment-bolts/conflicts","importantCases":"/api/acts/ad-cessna-170-6-amdt-2-undercarriage-attachment-bolts/important-cases","documents":"/api/acts/ad-cessna-170-6-amdt-2-undercarriage-attachment-bolts/documents"}}