{"id":"F2006B05005","name":"AD/CESSNA 170/9 Amdt 1 - Main Undercarriage U Bolts","slug":"ad-cessna-170-9-amdt-1-main-undercarriage-u-bolts","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44915,"registerId":"commonwealth-F2006B05005-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/CESSNA 170/9 Amdt 1 - Main Undercarriage U Bolts","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nCessna 170, 172, F172, FR172 and 175 Series Aeroplanes\n\nAD/CESSNA 170/9\n\nAmdt 1\n\n  \nMain Undercarriage “U” Bolts 11/67\n\nApplicability: All 172, F172, FR172 and 175 series fitted with “U” bolts P/N 0541153.\n\nRequirement: 1. Visual: Inspect the main undercarriage “U” bolts P/N 0541153 type in situ for cracks or other damage and check that the “U” bolt retaining nuts are torqued to the values specified in the Cessna Service Manual.\n\n2. Magnetic Particle: Remove the main undercarriage “U” bolts P/N 0541153 type and inspect by the magnetic particle method for cracks particularly in the radius of bends and in the root of the threads.\n\nCompliance: Visual: At intervals not exceeding 100 hours time in service.\n\nMagnetic Particle: At intervals not exceeding 500 hours time in service.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The document is labelled as Amendment 1 (Amdt 1), but the provided text contains only the current applicability, inspection requirements and compliance intervals. No prior text or explicit statement of what was changed from the original AD is included here, so the supplied material does not itself show a change of scope."},"complexity_factors":["Targeted applicability limited to specific airframe models and a single part number (Applicability).","Two inspection methods with different intervals: frequent in‑situ visual checks (≤100 hours) and less frequent removal plus magnetic particle NDT (≤500 hours) (Compliance).","Dependency on an external technical document (Cessna Service Manual) for required torque values rather than giving numeric values in the AD (Requirement: Visual).","Operational coordination required for removal/refitting of bolts and access to magnetic particle testing facilities (Requirement: Magnetic Particle).","AD specifies inspection requirements but does not prescribe remedial actions in the provided text, leaving operators to apply maintenance standards or other guidance (Requirement: Visual; Requirement: Magnetic Particle)."],"plain_english_summary":"This AD requires recurring inspections of main undercarriage U‑bolts (P/N 0541153) on Cessna 172/F172/FR172 and 175 series: in‑situ visual inspections and retaining‑nut torque checks every 100 hours, and removal for magnetic‑particle NDT every 500 hours, to detect cracks and reduce bolt‑failure risk.\n\nAircraft owners/operators and their maintenance providers must schedule and pay for the recurring visual checks, removal/refitting and any specialist NDT; torque values are taken from the Cessna Service Manual."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a standard Airworthiness Directive with a narrow, specific safety purpose: preventing U-bolt failures on particular Cessna models. The scope remains tightly focused on this single mechanical component and has not expanded beyond its original safety intent."},"complexity_factors":["Very short document (approximately 150 words)","Only 2 substantive requirements (visual and magnetic particle inspection)","Single defined term (P/N 0541153 — part number)","No cross-references to other legislation beyond generic 'Civil Aviation Regulations 1998' header","Simple conditional logic: if aircraft has specific part, inspections apply","Clear, unambiguous compliance intervals (100 hours and 500 hours)","No exceptions, exemptions, or nested conditions"],"plain_english_summary":"This is an **Airworthiness Directive** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It requires owners and operators of specific Cessna aircraft to inspect and maintain the U-bolts that hold the main landing gear (undercarriage) in place.\n\n**Who it affects:**\n- Owners and operators of Cessna 170, 172, F172, FR172, and 175 series aircraft\n- Specifically those fitted with U-bolts part number 0541153\n\n**What it requires:**\nTwo types of inspections on the main landing gear U-bolts:\n\n1. **Visual inspection** — Check for cracks or damage while the U-bolts are still installed, and verify the nuts are tightened to the correct torque (tightness) specified in the Cessna manual. Must be done **every 100 hours of flight time**.\n\n2. **Magnetic particle inspection** — Remove the U-bolts and use a special crack-detection method (magnetic particle testing) to find hidden cracks, especially in bent areas and at the base of screw threads. Must be done **every 500 hours of flight time**.\n\n**Why it matters:**\nU-bolts are critical structural components that attach the landing gear to the aircraft. If they fail due to cracks or improper installation, the landing gear could collapse during takeoff, landing, or taxiing — potentially causing serious accidents. This directive prevents catastrophic failures by mandating regular, thorough inspections."}},"importantCases":[],"_links":{"self":"/api/acts/ad-cessna-170-9-amdt-1-main-undercarriage-u-bolts","history":"/api/acts/ad-cessna-170-9-amdt-1-main-undercarriage-u-bolts/history","analysis":"/api/acts/ad-cessna-170-9-amdt-1-main-undercarriage-u-bolts/analysis","conflicts":"/api/acts/ad-cessna-170-9-amdt-1-main-undercarriage-u-bolts/conflicts","importantCases":"/api/acts/ad-cessna-170-9-amdt-1-main-undercarriage-u-bolts/important-cases","documents":"/api/acts/ad-cessna-170-9-amdt-1-main-undercarriage-u-bolts/documents"}}