{"id":"F2006B04903","name":"AD/CESSNA 120/3 - Elevator Spar Web Hinges","slug":"ad-cessna-120-3-elevator-spar-web-hinges","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44747,"registerId":"commonwealth-F2006B04903-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# AIRWORTHINESS DIRECTIVE\n\n![](image.001.png)\n\n![](image.001.png)  \nFor the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CASR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.\n\nCessna 120 and 140 Series Aeroplanes","sortOrder":0},{"sectionNumber":"AD/CESSNA 120/3 Elevator Spar Web Hinges","sectionType":"part","heading":"AD/CESSNA 120/3 Elevator Spar Web Hinges 5/2003","content":"# AD/CESSNA 120/3 Elevator Spar Web Hinges 5/2003\n\nApplicability: Model 120 and 140 aircraft, serial numbers 8001 through 13780.\n\nRequirement: Inspect the elevator spar web at the hinges for fatigue cracks. The cracks start either at the rivets or at an edge of the fitting and progress around the fitting, until the elevator breaks loose from the hinge fitting.\n\nIf cracks are less than 0.5-inch in length, install a reinforcing channel, Cessna part number 0434151 (outboard hinge) or 0434152 (inboard hinge), on the aft side of the spar with the flanges riveted between the spar flanges and the skin with two\n\nAN 455AD3 rivets per flange. Use four AN 442AD4 to attach each fitting to the spar web and reinforcing channel.\n\nIf cracks are more than 0.5-inch in length, replace the spar and add reinforcing channels.\n\nNote: FAA AD 47-43-05 and Cessna Service Letter No.46 refer.\n\nCompliance: Within 100 hours time in service or 12 months after 15 May 2003, whichever occurs first, and thereafter at intervals not to exceed 100 hours time in service; until reinforcing channels are ins talled at all hinge fittings.\n\nThis Airworthiness Directive becomes effective on 15 May 2003.\n\nBackground: The FAA requires inspections of the elevator spar webs for fatigue cracks.\n\n![](image.002.jpeg)  \n\nDavid Alan Villiers\n\nDelegate of the Civil Aviation Safety Authority 4 April 2003\n\n![](image.001.png)","sortOrder":1}],"analysis":{"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive maintains its original narrow scope. It addresses a specific mechanical defect in specific aircraft models with precise serial number ranges. There is no evidence of scope creep; the directive remains tightly focused on elevator spar web hinge integrity for Cessna 120/140 series aircraft."},"complexity_factors":["Single, specific mechanical issue addressed","Only 2 defined part numbers (0434151, 0434152)","Simple binary decision tree (cracks <0.5 inch vs >0.5 inch)","No cross-references to other legislation (only references to FAA AD and Cessna Service Letter as background)","Clear, single applicability criterion (specific models and serial numbers)","Straightforward compliance timeline (100 hours/12 months, then recurring)","No nested exceptions or conditional sub-clauses"],"plain_english_summary":"This CASA safety order addresses fatigue cracking in the elevator spar web of certain Cessna 120/140 aircraft (serials 8001–13780, built 1946–1951). Owners must inspect hinge areas and, depending on crack size, install reinforcing channels or replace the spar, with work due within 100 flight hours or 12 months from 15 May 2003 and repeated inspections every 100 hours until reinforcement is complete. The measure prevents loss of pitch control and potential crash."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"This AD remains narrowly focused on the single safety issue identified — fatigue cracks in the elevator spar web at hinge fittings for specified Cessna 120/140 serial numbers. It prescribes inspection, reinforcement or replacement actions and recurring inspections until modification is completed. The directive does not broaden into unrelated areas or add additional aircraft types or systems beyond its original safety remit."},"complexity_factors":["Short, single-issue airworthiness directive (focused on elevator spar web hinges)","Clear applicability limited to Model 120/140 serial numbers 8001–13780","Simple conditional repair rule with one clear numeric threshold (0.5 inch)","Specific parts and rivet types named (Cessna P/Ns 0434151/0434152; AN 455AD3; AN 442AD4)","Recurring compliance interval (every 100 hours) until reinforcing channels are installed","Cross-references to FAA AD 47-43-05 and Cessna Service Letter No.46 (external documents required for fuller context)"],"plain_english_summary":"**What this directive requires**\n\n- **Applies to:** Cessna Model 120 and 140 aeroplanes with serial numbers 8001 through 13780 (see \"Applicability\").\n\n- **Action required (\"Requirement\"):** Inspect the elevator spar web at each hinge fitting for fatigue cracks. (The spar web is the vertical plate in the elevator structure; hinge fittings attach the elevator to the horizontal stabiliser.)\n  - If a crack is **less than 0.5 inch** long: install a reinforcing channel (Cessna part 0434151 for the outboard hinge, or 0434152 for the inboard hinge) on the aft side of the spar. The instruction specifies how the channel and fittings must be riveted: two AN 455AD3 rivets per flange, and four AN 442AD4 rivets to attach each fitting to the spar web and reinforcing channel.\n  - If a crack is **more than 0.5 inch** long: replace the spar and then add the reinforcing channels.\n  - The directive refers to FAA AD 47-43-05 and Cessna Service Letter No. 46 for related information.\n\n- **When to do it (\"Compliance\"):** Carry out the first inspection within 100 hours time in service or within 12 months after 15 May 2003, whichever comes first. Repeat inspections at intervals not exceeding 100 hours time in service until reinforcing channels have been fitted at all hinge locations. The AD took effect on 15 May 2003.\n\n- **Why it matters (\"Background\"):** The FAA identified fatigue cracking in the elevator spar web that can start at rivets or the fitting edge and grow around the fitting until the elevator can separate from the hinge. The AD is issued to detect and correct that unsafe condition.\n\n**Who is responsible and what changes in behaviour**\n\n- Aircraft owners/operators are responsible for having the inspections and repairs carried out and for paying the costs of parts and labour (see \"Requirement\" and \"Compliance\").\n- A maintenance organisation or appropriately authorised engineer will decide whether a crack is below or above the 0.5-inch threshold and perform the reinforcement or spar replacement to the rivet and part specifications given in the AD.\n- Until reinforcing channels are installed at all hinge fittings, operators must perform recurring inspections every 100 hours time in service.\n\n**Costs, incentives, and practical effects**\n\n- Immediate compliance creates direct costs: inspection labour, possible downtime while awaiting inspection/repair, and parts and labour for either reinforcement (moderate cost) or spar replacement (substantially higher cost and downtime).\n- The directive concentrates costs on owners/operators of the specified serial-numbered aircraft; the safety benefit is concentrated on preventing a specific catastrophic mechanical failure (elevator separation).\n- The mechanical instructions (part numbers, rivet types and counts) reduce discretionary variation in repair method, which favours consistent installations but requires access to specified parts and rivet types.\n- Maintenance markets (independent shops and Cessna-authorised facilities) can provide the required work; availability of parts and skilled labour will affect the time and price to comply.\n- Requiring recurring inspections until modification is completed creates an operational incentive to fit the reinforcing channels promptly to avoid ongoing inspection costs and repeated aircraft downtime.\n\n**Implementation and compliance risks**\n\n- The AD depends on correct detection of small fatigue cracks; inadequate inspection technique or missed cracks could defeat the safety objective (see \"Requirement\").\n- Improper installation (wrong rivet type, incorrect riveting) could undermine structural strength; following the specified rivet types and counts is part of the directive.\n- If replacement spars are required, lead times for parts or specialised labour could extend aircraft out-of-service time and increase costs.\n\n**Reference to source claims**\n\n- The AD itself states the unsafe condition (cracks progressing until the elevator detaches) in the \"Requirement\" and \"Background\" and references the FAA AD and Cessna service information as related guidance.\n\nOverall, the AD is a targeted, technically prescriptive requirement for inspection and repair of a known fatigue problem on a defined fleet. It shifts inspection and repair costs to owners/operators, reduces repair-method variation by specifying parts and rivets, and creates an operational incentive to complete the reinforcing modification to avoid repeated inspections (Applicability; Requirement; Compliance; Background)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-cessna-120-3-elevator-spar-web-hinges","history":"/api/acts/ad-cessna-120-3-elevator-spar-web-hinges/history","analysis":"/api/acts/ad-cessna-120-3-elevator-spar-web-hinges/analysis","conflicts":"/api/acts/ad-cessna-120-3-elevator-spar-web-hinges/conflicts","importantCases":"/api/acts/ad-cessna-120-3-elevator-spar-web-hinges/important-cases","documents":"/api/acts/ad-cessna-120-3-elevator-spar-web-hinges/documents"}}