{"id":"F2006B02144","name":"AD/AC/83 Amdt 8 - Corrosion of Wing Lower Spar Cap","slug":"ad-ac-83-amdt-8-corrosion-of-wing-lower-spar-cap","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41374,"registerId":"commonwealth-F2006B02144-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# AIRWORTHINESS DIRECTIVE\n\n![](image.001.png)  \n\nFor the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/AC/83 Amdt 7 and issues the following 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\n![](image.001.png)  \n\nTwin Commander (Gulfstream/Rockwell/ Aerocommander 500, 600 and 700) Series Aeroplanes","sortOrder":0},{"sectionNumber":"Corrosion of Wing Lower Spar Cap 11/2003","sectionType":"part","heading":"Corrosion of Wing Lower Spar Cap 11/2003","content":"AD/AC/83\n\nAmdt 8\n\n#   \nCorrosion of Wing Lower Spar Cap 11/2003","sortOrder":1}],"analysis":{"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":true,"description":"The instrument explicitly revokes AD/AC/83 Amdt 7 and replaces it with AD/AC/83 Amdt 8 (preamble). The supplied text does not include the detailed Requirement or Compliance provisions from either amendment, so while the legal scope has been altered by revocation and reissue, the exact technical or temporal changes in required actions cannot be determined from the material provided."},"complexity_factors":["Delegated decision-making: the CASA delegate determines what \"action...necessary\" (preamble: subregulation 39.1(1)), creating reliance on administrative judgement.","Cross-references and modular structure: substantive duties are placed in the Requirement and Compliance sections which are not reproduced here, requiring readers to consult multiple parts of the AD to know obligations (Requirement section; Compliance section).","Technical subject matter: addressing structural corrosion (wing lower spar cap) implies engineering inspection and repair procedures that add operational and technical complexity beyond legal text.","Operational impact: compliance may require aircraft downtime, parts and certified maintenance, which complicates scheduling and costs for operators.","Regulatory transition: the AD revokes a prior amendment and issues a new one (revocation of Amdt 7), obliging operators to determine what changed and whether previously completed work remains compliant.","Enforcement and legal consequence: ADs are mandatory under CASR s.39.1(1), so non-compliance carries regulatory risk; operators must interpret and implement mandatory requirements.","Limited information in supplied text: absence of the detailed Requirement and Compliance provisions increases interpretive workload for affected parties."],"plain_english_summary":"### What this instrument does\n\nThis Airworthiness Directive (AD) (AD/AC/83 Amdt 8) revokes the previous amendment (AD/AC/83 Amdt 7) and issues a new mandatory safety direction under subregulation 39.1(1) of the Civil Aviation Safety Regulations 1998 (CASR). The AD targets corrosion of the wing lower spar cap on specified Twin Commander (Gulfstream/Rockwell/Aerocommander) 500, 600 and 700 series aeroplanes (Applicability section).\n\nThe AD requires operators to carry out the specific corrective actions set out in the AD’s Requirement section. Those actions must be taken (a) in the circumstances the Requirement section specifies, (b) in accordance with the instructions in that section, and (c) at the times stated in the Compliance section (Requirement section (a)-(c)). The CASA delegate is the decision-maker who has revoked the prior AD and issued this AD (preamble invoking subregulation 39.1(1) of CASR 1998).\n\n### Who is affected\n\n- Aircraft owners and operators of Twin Commander 500, 600 and 700 series aeroplanes listed in the Applicability section.\n- Maintenance organisations and engineers who perform inspections and repairs on those aeroplanes.\n\n### Why it matters (mechanics, not motives)\n\n- The AD makes one or more actions mandatory to correct an identified unsafe condition described as \"Corrosion of Wing Lower Spar Cap.\" The AD is the legal instrument that requires compliance; failure to comply with an AD is a regulatory breach (subregulation 39.1(1) citation).\n\n### Who pays and who decides\n\n- Costs fall on the aircraft owners/operators who must arrange inspections, repairs, parts, and any associated downtime. Maintenance providers will perform the physical work and be paid by those operators.\n- The CASA delegate decides the content of the Requirement section and the timing in the Compliance section (preamble language: actions the delegate \"considers necessary\").\n\n### Incentives, burdens and likely behavioural effects\n\n- Operators face a direct compliance cost (labour, parts, possible aircraft downtime) and an incentive to perform the required work to restore legal airworthiness for the affected aircraft.\n- Maintenance and repair businesses may see increased demand for inspection and repair work on the listed aircraft.\n- The AD concentrates costs on the subset of operators who own the affected models; any safety benefit is distributed across users of the airspace and the public.\n- The AD’s language delegates substantive choice about the specific remedial steps and timing to the Requirement and Compliance sections; where those sections are technical or prescriptive, compliance will be straightforward; where they allow choice, operators will need to decide among compliant repair or replacement options (Requirement section; Compliance section).\n\n### Implementation and compliance risks, trade-offs and administrative discretion\n\n- Administrative discretion: the preamble explicitly frames required actions as those the CASA delegate \"considers necessary,\" which places substantive decision-making power with the delegate (preamble reference to subregulation 39.1(1)).\n- Implementation risk depends on the clarity and specificity of the Requirement and Compliance sections. The text provided does not reproduce the detailed steps or timings, so operators must consult the full AD text to know exact inspection intervals, allowable repairs, or record-keeping obligations (Requirement section; Compliance section).\n- Opportunity costs for operators include aircraft downtime and diversion of maintenance resources from other tasks. There may be substitution effects: operators can choose different approved repair methods or parts only if the Requirement section allows them.\n\n### What changed compared with the prior document\n\n- This instrument expressly revokes AD/AC/83 Amdt 7 and replaces it with AD/AC/83 Amdt 8 (preamble). The concrete technical or timing changes between Amdt 7 and Amdt 8 are not included in the supplied text; to assess those differences one must compare the Requirement and Compliance sections of both amendments."},"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This appears to be a routine amendment (8th revision) of a long-standing airworthiness directive originally issued in 1983 (AD/AC/83). The scope remains focused on the specific corrosion issue in Twin Commander wing spar caps. Amendment 8 likely updates inspection intervals, incorporates new service information, or refines compliance requirements based on operational experience, but does not represent scope creep beyond the original safety purpose."},"complexity_factors":["Cross-references to previous amendments (revokes AD/AC/83 Amdt 7)","Multiple manufacturer names for same aircraft type (Gulfstream/Rockwell/Aerocommander) due to corporate history","Technical aviation terminology requiring specialist knowledge (spar cap, airworthiness directive, CASR subregulations)","Conditional compliance structure (circumstances, instructions, and timeframes in separate sections)","Regulatory framework reference (Civil Aviation Safety Regulations 1998, subregulation 39.1(1))"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by the Civil Aviation Safety Authority (CASA) that requires aircraft owners and operators to take specific action to fix a known safety problem.\n\n**What it does:**\n- **Revokes** the previous version (Amendment 7) and replaces it with this updated version (Amendment 8)\n- **Requires inspection and maintenance** to address **corrosion (rust)** in the **wing lower spar cap** — a critical structural component that helps hold the wing together\n- Applies to **Twin Commander series aircraft** (models 500, 600, and 700 series), which are twin-engine propeller aircraft originally made by Gulfstream, Rockwell, and Aero Commander\n\n**Who it affects:**\n- Owners and operators of these specific aircraft types\n- Maintenance organisations that service these aircraft\n- Pilots who fly them\n\n**Why it matters:**\nCorrosion in a wing spar cap is extremely serious. The spar is essentially the \"backbone\" of the wing. If it corrodes and weakens, the wing could fail in flight, leading to catastrophic loss of the aircraft and lives. This AD ensures that this known defect is found and fixed before it becomes dangerous.\n\n**What must happen:**\nThe directive requires specific actions (inspections, repairs, or replacements) to be carried out according to set instructions and within specified timeframes (detailed in the compliance section, not fully shown here)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-ac-83-amdt-8-corrosion-of-wing-lower-spar-cap","history":"/api/acts/ad-ac-83-amdt-8-corrosion-of-wing-lower-spar-cap/history","analysis":"/api/acts/ad-ac-83-amdt-8-corrosion-of-wing-lower-spar-cap/analysis","conflicts":"/api/acts/ad-ac-83-amdt-8-corrosion-of-wing-lower-spar-cap/conflicts","importantCases":"/api/acts/ad-ac-83-amdt-8-corrosion-of-wing-lower-spar-cap/important-cases","documents":"/api/acts/ad-ac-83-amdt-8-corrosion-of-wing-lower-spar-cap/documents"}}