{"id":"F2006B04966","name":"AD/CESSNA 170/34 Amdt 1 - Engine Mounting Bracket Bolts","slug":"ad-cessna-170-34-amdt-1-engine-mounting-bracket-bolts","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44846,"registerId":"commonwealth-F2006B04966-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/CESSNA 170/34 Amdt 1 - Engine Mounting Bracket 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 170/34\n\nAmdt 1\n\n  \nEngine Mounting Bracket Bolts 9/80\n\nApplicability: All Cessna Model 172N fitted with Lycoming 0-320-H2AD series engines with S/Nos L-101-76 to L-5707-76 or any engine remanufactured prior to 4 January 1979.\n\nRequirement: To prevent loss of integrity of the engine to aircraft mounting due to loosening of the engine mounting bracket attaching bolts, accomplish the following:\n\n    Inspect the eight P/N LW 38-2.75 mounting bolts for tightness. Mounting bolts found to have less than 200 inch-pounds of torque when measured in the tightening direction must be replaced and the new bolts torqued to 360 inch-pounds.\n\n    2. Those bolts found with less than 360 inch-pounds torque but more than 200 inch- pounds must be re-torqued to 360 inch-pounds.\n\nNote: Lycoming SI No 1380 and FAA AD 79-10-03 R2 Amendment 39-3628 refers.\n\nCompliance: Unless already accomplished, within 10 hours time in service after 1 August 1980 and thereafter at intervals not exceeding 100 hours time in service.\n\nBackground: The engine mounting bracket bolts may lose torque during service. This amendment references affected engines by serial number and adds certain remanufactured engines.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"The amendment expands the scope by explicitly listing affected Lycoming engine serial numbers and including engines remanufactured before 4 January 1979, thereby increasing the population of aircraft and operators subject to the inspection and torque/replacement requirements (Background)."},"complexity_factors":["Precision technical requirements: two specific torque thresholds (200 in‑lb and 360 in‑lb) require calibrated torque tools and measurement in the tightening direction.","Dichotomous remedies: measured torque determines either re‑torque or replacement, creating parts and labour cost variability.","Applicability by engine serial number and remanufacture status requires document/records checks to determine if an aircraft is affected.","Tight compliance timing: an initial 10‑hour window after the stated date and recurring 100‑hour intervals imposes scheduling on operators.","Dependence on external guidance: references to Lycoming SI No. 1380 and FAA AD 79-10-03 R2 for methods increase reliance on external documents for implementation."],"plain_english_summary":"This directive requires owners/operators of certain Cessna 172N aeroplanes with Lycoming 0-320-H2AD engines to inspect eight engine-mounting bolts, re-torque them to 360 in‑lb or replace any measuring under 200 in‑lb. Checks must be done within 10 hours after the effective date and then every 100 hours; authorised maintenance personnel perform the checks and decide replacements (Requirement; Compliance). The amendment widens applicability by listing engine serial numbers and adding engines remanufactured before 4 January 1979 (Background)."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is an amendment (Amdt 1) to an existing directive, but it does not represent scope creep. The amendment simply clarifies which engines are affected by adding serial number specificity and including remanufactured engines. This is a precision refinement rather than an expansion beyond the original safety purpose of preventing engine mount bolt failures."},"complexity_factors":["Very short document (under 300 words)","Only 4 defined elements: specific aircraft model, engine type, serial number range, and bolt part number","Simple conditional logic: two-tier torque threshold (under 200 vs 200-360) with corresponding actions","No cross-references to other legislation (only informational references to manufacturer service instructions and FAA directive)","Single compliance pathway with clear timeframes","No exceptions or exemptions stated"],"plain_english_summary":"This Civil Aviation Safety Authority Airworthiness Directive targets owners/operators of Cessna 172N aircraft fitted with certain Lycoming O-320-H2AD engines (specific serials or remanufactured before 4 Jan 1979). It mandates inspecting the eight engine-mount bolts (part LW 38-2.75) because they may work loose in flight.\n\nBolts found under 200 in·lb must be replaced and torqued to 360 in·lb; bolts 200–360 in·lb must be retorqued to 360 in·lb. Inspections are due within 10 flight hours after 1 Aug 1980 and every 100 hours thereafter."}},"importantCases":[],"_links":{"self":"/api/acts/ad-cessna-170-34-amdt-1-engine-mounting-bracket-bolts","history":"/api/acts/ad-cessna-170-34-amdt-1-engine-mounting-bracket-bolts/history","analysis":"/api/acts/ad-cessna-170-34-amdt-1-engine-mounting-bracket-bolts/analysis","conflicts":"/api/acts/ad-cessna-170-34-amdt-1-engine-mounting-bracket-bolts/conflicts","importantCases":"/api/acts/ad-cessna-170-34-amdt-1-engine-mounting-bracket-bolts/important-cases","documents":"/api/acts/ad-cessna-170-34-amdt-1-engine-mounting-bracket-bolts/documents"}}