{"id":"F2006B04005","name":"AD/BEECH 55/61 Amdt 2 - Wing Fatigue Life Limitation","slug":"ad-beech-55-61-amdt-2-wing-fatigue-life-limitation","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":43614,"registerId":"commonwealth-F2006B04005-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BEECH 55/61 Amdt 2 - Wing Fatigue Life Limitation","content":"![](image.001.png)\n\n![](image.001.png)  \nAIRWORTHINESS DIRECTIVE\n\nFor the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/BEECH 55/61 Amdt 1 and issues the following AD under subregulation 39.1 (1) of CAR 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\n![](image.001.png)\n\nBeechcraft 55, 58 & 95-55 (Baron) Series Aeroplanes\n\nAD/BEECH 55/61\n\nAmdt 2\n\n  \nWing Fatigue Life Limitation 3/2003\n\nApplicability: All models 58, 58A, 58TC, 58P and 58PA series.\n\nRequirement: Retire the wing spar and wing centre section spar low cap (and associated structural fittings) together with the wing rear spar upper and lower attachment fitting assemblies.\n\nThe model 58TC and 58P life limitation assumes an average mean cruise weight of 2490kg and one landing every 40 minutes. Should the mean cruise weight be greater than 2540kg or should the landings occur at a greater frequency than one landing every 30 minutes the Authority must be advised as it will be necessary to reassess the life limitation.\n\nNote 1: The wing rear spar attachment fitting assembly includes both fuselage and wing fitting components.\n\nNote 2: On the basis of currently available fatigue substantiating data, only one spar cap replacement is permitted. This will allow a single lifetime extension from spar cap replacement.\n\nNote 3: For aircraft which have had winglets fitted subsequent to manufacture, the retirement life, in hours, is to be calculated using the formula;\n\nRetirement Life Formula: RL = A + RLW ( 1 - A )\n\nRLW/O\n\nWhere:\n\nRL \\= Retirement Life (Hours)\n\nA \\= Hours flown before winglets were fitted\n\nRLW = Retirement Life (Hours) with winglets fitted RLW/O\\= Retirement Life (Hours) without winglets fitted\n\nBeechcraft 55, 58 & 95-55 (Baron) Series Aeroplanes\n\nAD/BEECH 55/61 Amdt 2 (Continued)\n\nThe Value for RLW will need to be specified based on approved data from the Supplemental Type Certificate Holder or, in the absence of such data, the value selected shall be approved by the Civil Aviation Safety Authority.\n\nCompliance: 1. For models 58 and 58A series: before exceeding 16,000 hours’ time in service or if winglets were installed, retirement life is in accordance with the Retirement Life Formula specified in this AD.\n\n    2. For model 58TC series: before exceeding 10,000 hours’ time in service, or if winglets were installed, retirement life is in accordance with the Retirement Life Formula specified in this AD.\n\n    3. For models 58P and 58PA series: before exceeding 13,250 hours’ time in service, or if winglets were installed, retirement life is in accordance with the Retirement Life Formula specified in this AD.\n\nThis Amendment becomes effective on 20 March 2003.\n\nBackground: Analysis and fatigue tests by the manufacturer have established the above retirement lives for the wing main spar and associated structure. Amendment 1 clarified the intent that the applicability includes all pressurised Baron aircraft.\n\nThis Amendment adds a formula to calculate the wing structure retirement life for aircraft that have had winglets installed since the aircraft was manufactured.\n\nAmendment 1 of this Airworthiness Directive became effective on 30 November 2000.\n\nThis original issue of this Airworthiness Directive became effective on 31 March 1981.\n\n![](image.002.png)  \n\nDavid Alan Villiers\n\nDelegate of the Civil Aviation Safety Authority 14 January 2003\n\n![](image.001.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 26 February 2003.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"This amendment does not broaden the AD's safety purpose; it refines and clarifies technical application. The original AD set retirement lives for wing structure. Amendment 1 clarified applicability to pressurised Barons; Amendment 2 adds a specific calculation method for aircraft fitted with winglets and confirms the one-time spar-cap replacement limit. The change is technical and procedural rather than a substantive expansion of scope beyond the original safety-limitation objective."},"complexity_factors":["Multiple labelled aircraft sub-models with different hour limits (58/58A, 58TC, 58P/58PA)","A special conditional formula for aircraft with winglets requiring external data (STC holder) or CASA approval (Note 3)","Operational caveat requiring reassessment if mean cruise weight or landing frequency exceed specified bounds","Single permitted spar-cap replacement (Note 2) — creates a lifecycle exception to simple retirement","Relatively short text and few cross-legislative references (mostly self-contained within AD)"],"plain_english_summary":"**What this instrument does (mechanically)\n\n- Revokes the previous Airworthiness Directive (AD/BEECH 55/61 Amdt 1) and replaces it with Amendment 2.  The AD imposes a mandatory retirement life for specific wing structure components on Beechcraft Baron aeroplanes and prescribes how to calculate retirement life where winglets have been fitted.\n\nWho it applies to\n\n- Applies to Beechcraft Baron models: 58, 58A, 58TC, 58P and 58PA (all pressurised Barons are included).  (See \"Applicability\" and the clarification in the Background.)\n\nWhat operators must do\n\n- Requirement (what must be retired): the wing spar and wing centre-section spar low cap (and associated structural fittings) and the wing rear spar upper and lower attachment fitting assemblies must be retired (taken out of service) and replaced as required by this AD. (Requirement section and Note 1.)\n\n- Time limits (when to retire):\n  - Models 58 and 58A: retire before exceeding 16,000 hours time in service (TIS), unless winglets are fitted, in which case use the winglet retirement-life formula. (Compliance 1.)\n  - Model 58TC: retire before exceeding 10,000 hours TIS or use the winglet formula if winglets are fitted. (Compliance 2.)\n  - Models 58P and 58PA: retire before exceeding 13,250 hours TIS or use the winglet formula if winglets are fitted. (Compliance 3.)\n\n- One permitted life-extension by spar-cap replacement only: Note 2 specifies that only one spar-cap replacement is permitted for an aircraft’s life — this allows a single lifetime extension after replacement, based on the available fatigue data.\n\n- Winglets: when winglets have been fitted after manufacture, retirement life (in hours) must be calculated using a formula set out in the AD (\"Retirement Life Formula\"). The value for the retirement life with winglets (RLW) must be taken from approved data supplied by the Supplemental Type Certificate (STC) holder for the winglet modification or, if such data is not available, the RLW must be approved by the Civil Aviation Safety Authority (CASA). (Note 3 and Retirement Life Formula.)\n\n- Operating condition caveat: the life limits assumed underlying the 58TC and 58P figures are based on an average mean cruise weight of 2,490 kg and one landing every 40 minutes. If the mean cruise weight exceeds 2,540 kg or landings occur more frequently than one every 30 minutes, operators must notify CASA because the life limits need reassessment. (Requirement paragraph about mean cruise weight and landing frequency.)\n\nWhy the rule exists (as stated by the regulator) and how that compares to practical effects\n\n- Official rationale: manufacturer analysis and fatigue testing established finite retirement lives for the wing main spar and associated structure; the AD enforces those retirement lives to address an unsafe condition. Amendment 2 adds the special calculation method where winglets were later fitted. (Background.)\n\n- Practical effects and who bears costs and choices:\n  - Who pays: aircraft owners/operators pay for inspections, records, replacement of spar caps and associated fittings, downtime and any engineering/approval work. (Requirement; Note 2; Note 3.)\n  - Who decides: CASA enforces the AD, approves any RLW where STC data is absent, and must be advised where operating conditions differ from the assumptions used in life calculations. The STC holder supplies approved RLW data where available. (Note 3; requirement paragraph on advising the Authority.)\n  - Behaviour changes required: operators must track hours TIS precisely, record hours before/after any winglet installation, limit component use to the specified hours (or calculated RL), replace parts once the limit is reached, and notify/seek approvals from CASA when operating outside the assumptions or when STC data is unavailable.\n\nCosts, incentives, trade-offs and implementation risks\n\n- Direct costs and incentives: mandatory retirement reduces remaining economic life of the airframe and generates direct maintenance and parts costs. Because only one spar-cap replacement is allowed (Note 2), the operator faces a constrained option set for life extension; that concentrates replacement demand on maintenance/parts suppliers when replacements are required.\n\n- Effect on modification choices: fitting winglets changes how retirement life is calculated and requires approved data from the STC holder (Note 3). That gives the STC holder a technical influence over the allowable life after modification; operators may need to weigh the aerodynamic/operational benefits of winglets against any impact on structural life calculations and the administrative cost of securing CASA approval.\n\n- Record-keeping and compliance burden: precise tracking of hours before/after winglet installation (A in the formula), documentation for any spar-cap replacement, notifications to CASA if operating outside assumed weights/landing rates, and reliance on STC data or CASA approvals all add administrative and engineering workload.\n\n- Implementation risks and uncertainty: life limits depend on fatigue substantiation by the manufacturer and on assumptions (mean cruise weight, landing rates). If actual operations differ materially, the safety margin and remaining life estimates may change, and CASA must reassess (Requirement paragraph). There is also some dependency risk where RLW must come from the STC holder or CASA approval — absence of approved data delays calculation and compliance.\n\nConcentrated benefits, diffuse costs, and market effects to note\n\n- Concentrated benefits: the AD targets prevention of a specific structural failure risk (benefit concentrated in reduced accident risk for each affected airframe).\n- Diffuse costs: many smaller operators incur proportionate maintenance and downtime costs across the fleet.\n- Market effects: maintenance organisations, replacement-parts suppliers and STC holders see concentrated demand for replacements and for providing RLW substantiation/approvals; aircraft values and operating costs may be affected by the enforced finite-life limits.\n\nKey cross-references within the AD you may need to consult\n\n- Requirement (retirement and operational caveats), Notes 1–3 (definition of fitting assembly, limitation on spar-cap replacement, and winglet formula/approval), and Compliance paragraphs 1–3 (model-specific retirement hours and winglet handling)."},"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":true,"description":"The original 1981 AD established basic wing spar life limits. Amendment 1 (2000) expanded applicability to clarify pressurised variants were included. This Amendment 2 (2003) significantly expanded scope by introducing a complex mathematical formula to handle aftermarket winglet modifications — a specific equipment change not contemplated in the original safety analysis. The formula requires external data sources (STC holders) and creates a calculation burden that didn't exist in the original directive."},"complexity_factors":["Mathematical formula required for winglet-modified aircraft (RL = A + RLW(1 - A/RLW/O))","Three different compliance hour thresholds depending on specific model variant (10,000; 13,250; 16,000 hours)","Conditional logic for operational parameters (cruise weight >2540kg or landing frequency >1 per 30 minutes triggers reassessment requirement)","Cross-reference to external approval requirements (Supplemental Type Certificate Holder data or CASA approval needed for winglet calculations)","Nested applicability (covers 'all models' of specific series but with variant-specific limits)","Historical amendment tracking (references Amendment 1 and original 1981 issue for context)"],"plain_english_summary":"This CASA Airworthiness Directive mandates permanent retirement and replacement of critical wing spar and attachment fittings on Beechcraft Baron 58-series aircraft at specified flight-hour limits (varies by model), preventing further flight beyond those hard life limits. It affects owners/operators of Barons used in charter, training, and private operations across Australia.\n\nFatigue testing shows dangerous cracking risk; special reduced lives apply if winglets were fitted, and operators with heavier use or high landing rates must notify CASA because safe lives may be shorter."}},"importantCases":[],"_links":{"self":"/api/acts/ad-beech-55-61-amdt-2-wing-fatigue-life-limitation","history":"/api/acts/ad-beech-55-61-amdt-2-wing-fatigue-life-limitation/history","analysis":"/api/acts/ad-beech-55-61-amdt-2-wing-fatigue-life-limitation/analysis","conflicts":"/api/acts/ad-beech-55-61-amdt-2-wing-fatigue-life-limitation/conflicts","importantCases":"/api/acts/ad-beech-55-61-amdt-2-wing-fatigue-life-limitation/important-cases","documents":"/api/acts/ad-beech-55-61-amdt-2-wing-fatigue-life-limitation/documents"}}