{"id":"F2006B11215","name":"AD/LYC/97 - Connecting Rod Bolt Inspection","slug":"ad-lyc-97-connecting-rod-bolt-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56933,"registerId":"commonwealth-F2006B11215-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/LYC/97 - Connecting Rod Bolt Inspection","content":"![](image.001.png)  \nLycoming Piston Engines\n\nAD/LYC/97 Connecting Rod Bolt Inspection 6/95 DM\n\nApplicability: The following Textron Lycoming reciprocating engine models, assembled on or after 15 February 1994, and that contain connecting rod bolts shipped directly or indirectly from Superior Air Parts, Inc., on or after 15 February 1994:\n\nO-360-A1A, \\-A1AD, \\-A1C, \\-A1D, \\-A1F6, \\-A1F6D, \\-A1G6, \\-A1G6D, \\-A1LD, \\-A2A,\n\n\\-A2D, \\-A2E, \\-A2F, \\-A2G, \\-A3A, \\-A3AD, \\-A4A, \\-A4G, \\-A4J, \\-A4K, \\-A4M, \\-A4N,\n\n\\-A5AD, \\-B2A, \\-C1A, \\-C1C, \\-C1E, \\-C1F, \\-C1G, \\-C2A, \\-C2C, \\-C2D, \\-C2E, \\-D2A,\n\n\\-D2B, and \\-F1A6;\n\nIO-360-A1A, \\-A1B, \\-A1B6, \\-A1B6D, \\-A1C, \\-A1D, \\-A1D6, \\-A2A, \\-A2B, \\-A3B6D,\n\n\\-B1A, \\-B1B, \\-B1D, \\-B1E, \\-B1F, \\-B2F, \\-B2F6, \\-B4A, \\-C1A, \\-C1B, \\-C1C6, \\-C1D6,\n\n\\-C1E6, \\-C1F, and \\-J1A6D;\n\nAIO-360-A1A, \\-A1B, and \\-B1B; LO-360-A1G6D;\n\nHO-360-B1A, and \\-B1B;\n\nHIO-360-A1A, \\-B1A, \\-C1A, \\-C1B, \\-E1AD, and \\-E1BD; LIO-360-C1E6;\n\nTIO-360-A1B;\n\nAEIO-360-A1E, \\-B1G6, and \\-H1A;\n\nO-540-A1A, \\-A1A5, \\-A1B5, A1C5, \\-A1D, \\-A1D5, \\-A2B, \\-A3D5, \\-B1A5, \\-B1B5,\n\n\\-B2B5, \\-B2C5, \\-B4B5, \\-E4A5, \\-E4B5, \\-E4C5, \\-F1A5, \\-F1B5, \\-G1A5, \\-G2A5,\n\n\\-H1B5D, \\-H2B5D, J1A5D, \\-J3A5D, \\-J3C5D, and \\-L3C5D;\n\nIO-540-A1A5, \\-B1A5, \\-B1C5, \\-C1B5, \\-C4B5, \\-C4C5, \\-C4D5D, \\-D4A5, \\-E1A5,\n\n\\-E1B5, \\-G1A5, \\-G1B5, \\-G1C5, \\-G1D5, \\-G1E5, \\-G1F5, \\-J4A5, \\-K1A5, \\-K1A5D,\n\n\\-K1B5, \\-K1C5, \\-K1D5, \\-K1E5, \\-K1K5, \\-M1A5, \\-N1A5, \\-P1A5, \\-R1A5, \\-T4C5D,\n\n\\-K1F5, \\-K1F5D, \\-K1G5, \\-K1G5D, \\-K1J5D, \\-K1K5, \\-M1QA5, \\-M1B5D, \\-N1A5,\n\n\\-P1A5, \\-R1A5, \\-S1A5, \\-T4A5D, \\-T4B5D, \\-T4CTD, \\-V4A5D, \\-W1A5D, \\-W3A5D, and -AA1A5;\n\nTIO-540-A1A, \\-A1B, \\-A2A, \\-A2B, \\-A2C, \\-C1A, \\-E1A, \\-G1A, \\-H1A, \\-J2B, \\-F2BD,\n\n\\-J2BD, \\-N2BD, \\-R2AD, \\-S1AD, \\-AA1AD, and \\-AB1AD; LTIO-540-J2B, -F2BD, -J2BD, -N2BD, and -R2AD; IVO-540-A1A;\n\nAEIO-540-D4B5;\n\nTIO-541-A1A, E1A4, \\-E1B4, and \\-E1C4;\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 106 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\nIO-720-A1A, \\-A1B, \\-B1B, \\-B1BD, \\-C1B, and \\-D1B.\n\nRequirement: 1. Review engine records to determine if:-\n\n    (a) The engine was last assembled prior to 15 February 1994, or\n\n    (b) The engine is a first-run engine, or a remanufactured engine from Textron Lycoming, or\n\n    (c) It can be positively established that, for engines assembled on or after 15 February 1994, the engine contains only connecting rod bolts:\n\n    (i) that were purchased from Superior Air Parts prior to 15 February 1994 or after 20 December 1994, or\n\n    (ii) that were purchased directly from Textron Lycoming, or Aircraft Technologies, Inc., or\n\n    (iii) that have not been replaced since 14 February 1994.\n\nFor engines that meet the criteria specified in Requirement 1a, 1b, or 1c, no further action is required. Ensure an appropriate statement is entered into the engine log book.\n\n    2. For engines that do not meet the criteria specified in Requirement 1, remove cylinders as required and visually inspect each connecting rod bolt to determine if the bolt head is clearly identified with:\n\n    (a) raised letters \"SPS\", \"S\", \"C\", or \"FC\", identifying them as Textron Lycoming parts, or\n\n    (b) SL75060 etched on the head, identifying them as satisfactory PMA parts manufactured by Superior Air Parts, Inc., or\n\n    (c) AL75060 forged into the head, identifying them as PMA parts manufactured by Aircraft Technologies, Inc.\n\nIf the connecting rod bolts can be positively identified as satisfying the criteria specified in Requirement 2 no further action is required. Ensure an appropriate statement is entered into the engine log book.\n\n    3. If the connecting rod bolts cannot be positively identified as specified in Requirements 1 or 2 of this Directive, remove unapproved connecting rod bolts and replace with serviceable parts.\n\nNote 1: FAA Priority Letter Airworthiness Directive 95-07-1 also refers.\n\nNote 2: Further information is contained in Superior Air Parts Service Bulletin No. 95-002, dated 3 March 1995, which may be obtained by contacting the local Superior Air Parts representative on (07) 274 4288.\n\nCompliance: Effective 31 March 1995, prior to further flight.\n\nBackground: The FAA has advised that a substantial number of connecting rod bolts have been shipped. At least two engine failures have occurred due to fracture of these bolts.\n\nLaboratory examination of these unapproved bolts has determined that the bolts do not meet material or design specifications. The nature of the discrepancies is such that failure is unpredictable and it is impossible to determine analytically how long the bolts may remain intact.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"There is no evidence in the text provided that this instrument departs from or expands beyond its original safety-focused purpose. The directive is narrowly targeted: it addresses a specific suspected non‑conforming part (connecting rod bolts) in a defined population of Lycoming engines and prescribes inspection/replacement before further flight. No broader powers, additional subject matter, or new obligations outside that technical safety remediation are introduced in this text."},"complexity_factors":["Extensive engine-model list (many variants) increases applicability mapping effort","Date-based conditions (assembled on/after 15 Feb 1994; purchase before 15 Feb 1994 or after 20 Dec 1994; bolts not replaced since 14 Feb 1994)","Requirement 1 contains multiple alternative clearing criteria (1a, 1b, 1c with subclauses i–iii)","Requirement 2 relies on visual identification of multiple alternative markings (four Lycoming marks, one Superior PMA mark, one Aircraft Technologies PMA mark)","Practical inspection may require cylinder removal (operational complexity and variable labour effort)","Recordkeeping/logbook entry obligations are mandatory on successful clearance or inspection","Cross-references to FAA Priority Letter AD and a manufacturer service bulletin (external documents required to fully implement)","Binary outcome logic (cleared by records or markings → no action; not cleared → replacement) but with diagnostic steps that create operational branches"],"plain_english_summary":"**What this instrument does (mechanically)**\n\n- It orders operators/owners of specific Textron Lycoming piston engines to check whether their engines contain potentially unsafe connecting rod bolts and, if they cannot positively identify the bolts as acceptable, to replace them before the aircraft next flies.\n\n- Applicability is limited to a long list of Lycoming engine model variants when the engine was assembled on or after 15 February 1994 and the connecting rod bolts were shipped (directly or indirectly) from Superior Air Parts on or after 15 February 1994. (See the model list at the start of the directive.)\n\n- The required steps are:\n  - Review engine records to establish whether the engine is outside the suspect population (Requirement 1). If records show the engine was assembled before 15 February 1994, or is a first-run or remanufactured Lycoming engine, or if records prove the bolts were purchased before 15 February 1994, purchased from Lycoming or Aircraft Technologies, or have not been replaced since 14 February 1994, then no further action is required but an entry must be made in the engine logbook (Requirement 1).\n  - If records do not positively clear the engine, remove cylinders as necessary and visually inspect each connecting rod bolt head for approved identifying marks: raised letters \"SPS\", \"S\", \"C\" or \"FC\" (Lycoming parts); \"SL75060\" etched (Superior Air Parts PMA part); or \"AL75060\" forged (Aircraft Technologies PMA part). If the bolts can be positively identified as acceptable, make a logbook entry and no further action is required (Requirement 2).\n  - If the bolts cannot be positively identified by records or head markings, remove the unapproved connecting rod bolts and replace them with serviceable parts (Requirement 3).\n\n- Compliance is mandatory before further flight from the effective date (effective 31 March 1995).\n\n**Why the action was ordered (official rationale)**\n\n- The FAA reported that a substantial number of connecting rod bolts had been shipped and at least two engine failures occurred because of bolt fracture. Laboratory testing found those suspect bolts did not meet material or design specifications and that failure is unpredictable. The directive cites that safety risk as the reason for inspection and removal where identification is not possible.\n\n**Who it affects and who pays**\n\n- Directly affects aircraft owners/operators, maintenance organisations and certificated mechanics who operate or maintain the listed Lycoming engine models assembled on or after 15 February 1994 and which may contain suspect Superior Air Parts bolts.\n\n- The financial cost falls on the aircraft owner/operator: time to review records, labour and hangar time to remove cylinders and inspect, and the price of replacement bolts and fitting if replacement is required. There is also an administrative cost of making engine logbook entries.\n\n**Practical effects on behaviour and markets**\n\n- Operators will check logbooks and parts records more carefully and may choose to replace bolts pre-emptively to avoid downtime or inspection uncertainty.\n\n- The directive raises demand for serviceable replacement bolts (from Lycoming, Aircraft Technologies or other approved suppliers) and reduces the practical usability of bolts from the suspect Superior shipments unless they can be visually identified as acceptable.\n\n- Independent maintenance businesses must allocate labour and facility time to perform inspections and any necessary removals and replacements; this imposes a short-term operational cost and potential aircraft downtime.\n\n**Trade-offs, incentives and implementation risks**\n\n- Benefit claimed: reduces risk of engine failure from fractured bolts by removing unidentified/suspect bolts (as stated in the background).\n\n- Costs and trade-offs: owners/operators pay inspection and replacement costs and suffer aircraft downtime. There is also a risk of false negatives or positives because the visual identification method may not always be definitive if markings are worn, leading to potentially unnecessary replacements or, conversely, missed unsafe bolts.\n\n- Incentives: manufacturers of approved parts and authorised repair stations gain demand for replacements; suppliers of suspect parts bear reputational and commercial costs.\n\n- Implementation risk: the inspection requires cylinder removal in some cases (increasing labour and downtime). The AD relies on physical markings and documentation; missing or ambiguous records/markings create enforcement and compliance friction.\n\n**Administrative and legal mechanics**\n\n- Compliance is enforced by the civil aviation safety regulator under the airworthiness directive mechanism. Operators must record actions in the engine logbook when the engine is cleared or when bolts are inspected/replaced (Requirements 1 and 2).\n\n**Cross-references and supporting material**\n\n- The directive notes a related FAA Priority Letter AD and refers to a Superior Air Parts service bulletin for additional information.\n\n(References in text: Requirement 1, Requirement 2, Requirement 3; Compliance date: effective 31 March 1995.)"},"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"},"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive maintains a focused, targeted scope addressing a specific safety-critical defect in a defined population of aircraft engines. The scope is appropriately narrow — limited to specific engine models, specific assembly dates, and specific supplier batches — reflecting the precise nature of the safety risk rather than mission creep."},"complexity_factors":["Extensive applicability list with 100+ specific engine model variants requiring careful cross-checking","Nested conditional logic in Requirement 1 with three alternative exclusion criteria (1a, 1b, 1c) that must be evaluated before proceeding to physical inspection","Date-based eligibility thresholds (15 February 1994, 20 December 1994, 14 February 1994) that create overlapping time windows","Multi-source supply chain verification required (Superior Air Parts, Textron Lycoming, Aircraft Technologies, Inc.)","Visual inspection criteria requiring identification of six different manufacturer markings on bolt heads","Cross-reference to external documents (FAA AD 95-07-1 and Superior Air Parts Service Bulletin No. 95-002) for complete compliance understanding"],"plain_english_summary":"This AD orders owners/operators of certain Lycoming piston engines assembled on/after 15 Feb 1994 to verify whether connecting rod bolts supplied by Superior Air Parts between 15 Feb–20 Dec 1994 are installed. If records don’t prove acceptable bolts, remove cylinders to inspect bolt markings or remove and replace suspect bolts.\n\nIt matters because those bolts may be substandard and have fractured in service, causing catastrophic engine failure; action is required before next flight."}},"importantCases":[],"_links":{"self":"/api/acts/ad-lyc-97-connecting-rod-bolt-inspection","history":"/api/acts/ad-lyc-97-connecting-rod-bolt-inspection/history","analysis":"/api/acts/ad-lyc-97-connecting-rod-bolt-inspection/analysis","conflicts":"/api/acts/ad-lyc-97-connecting-rod-bolt-inspection/conflicts","importantCases":"/api/acts/ad-lyc-97-connecting-rod-bolt-inspection/important-cases","documents":"/api/acts/ad-lyc-97-connecting-rod-bolt-inspection/documents"}}