{"id":"F2006B08543","name":"AD/CHA/17 - Wing Strut and Spar Attachment Bolt","slug":"ad-cha-17-wing-strut-and-spar-attachment-bolt","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":51327,"registerId":"commonwealth-F2006B08543-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/CHA/17 - Wing Strut and Spar Attachment Bolt","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)  \nAmerican Champion (Aeronca, Bellanca) Series Aeroplanes\n\n| AD/CHA/17      | Wing Strut and Spar Attachment Bolt | 11/77 |\n| -------------- | ----------------------------------- | ----- |\n| Applicability: | All model 8GCBC and 8KCAB.          |       |\n| Requirement:   | Retire from service:                |       |\n\n    The front and rear wing strut upper and lower attachment bolts.\n\n    2. The front and rear wing spar to fuselage attachment bolts.\n\nCompliance: 1. For aircraft which have achieved 1000 hours time in service: within 200 hours time in service after 30 November 1977 and thereafter at intervals not exceeding 1200 hours time in service.\n\n2. For all other Aircraft: at intervals not exceeding 1200 hours time in service.\n\nNote: For 8KCAB aircraft each hour engaged in aerobatics shall be counted as equivalent to 10 hours normal flight.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive, as presented, sets mandatory retirement intervals for specified bolts on models 8GCBC and 8KCAB. The excerpt does not indicate any expansion, narrowing, or amendment of scope from an earlier intent; it simply prescribes the components, applicability, schedules and the aerobatic counting rule. There is no text in the excerpt showing a change from an original scope."},"complexity_factors":["Different compliance timing depending on whether the aircraft had ≥1000 hours TIS at the baseline (initial 200‑hour action then 1200‑hour intervals) (Compliance).","Uniform recurring interval (1200 hours) coupled with an initial accelerated deadline for older aircraft introduces a two-tier schedule (Compliance).","A special counting rule for aerobatic hours on model 8KCAB (each aerobatic hour = 10 normal hours) alters effective maintenance frequency (Note).","Multiple distinct bolt locations covered (front and rear; strut upper/lower; spar-to-fuselage) requiring precise parts/maintenance actions (Requirement).","No alternate means of compliance or exceptions are stated in the excerpt, so compliance is rigidly defined (Requirement/Compliance)."],"plain_english_summary":"What this directive does (mechanical change)\n\n- It requires the removal from service (retirement) of specific wing attachment bolts on certain American Champion aeroplane models. The parts named are: the front and rear wing strut upper and lower attachment bolts, and the front and rear wing spar-to-fuselage attachment bolts (Requirement).\n\nWho it applies to\n\n- It applies to all American Champion model 8GCBC and 8KCAB aircraft (Applicability).\n\nHow compliance is required (schedule and counting rules)\n\n- For aircraft that already have 1000 or more hours time in service (TIS): those bolts must be retired within 200 hours TIS after 30 November 1977, and after that they must be retired at intervals not exceeding 1200 hours TIS (Compliance).\n- For all other aircraft: retirement must occur at intervals not exceeding 1200 hours TIS (Compliance).\n- For model 8KCAB only, each hour spent doing aerobatics is to be counted as 10 hours of normal flight time when calculating those intervals (Note).\n\nWhat the document says about purpose\n\n- The excerpt sets mandatory retirement intervals for the listed bolts but does not include an explanatory statement of the reason in the text shown. The directive is issued under the Civil Aviation Regulations framework and prescribes the mandatory maintenance action and schedule (header and Requirement/Compliance).\n\nWho pays, who decides, and what behaviours change (practical mechanics)\n\n- Who pays: aircraft owners/operators must arrange and pay for the removal and replacement of the specified bolts (Requirement/Compliance). They also incur labour and downtime costs while the aircraft is grounded for the work.\n- Who decides/enforces: the directive is issued under the Civil Aviation Regulations (Part 39) and is a mandatory airworthiness directive for the named models (header, Applicability). The operator is responsible for meeting the specified retirement schedule.\n- Behaviour changes and incentives: operators must track TIS and schedule bolt retirement. Operators of 8KCABs who do aerobatics accumulate “effective” hours faster (each aerobatic hour counts as 10 normal hours), which increases retirement frequency and maintenance costs per flown hour (Note). The fixed intervals and the aerobatic multiplier create incentives to reduce aerobatic time or accept higher maintenance frequency.\n\nCompliance burden, discretion and implementation risks\n\n- Compliance burden: periodic record-keeping of TIS, scheduling recurring maintenance events at the specified intervals, parts procurement and labour to retire/replace bolts (Requirement/Compliance). The initial deadline for aircraft with ≥1000 hours creates an upfront scheduling requirement (Compliance).\n- Discretion: the directive sets fixed retirement intervals and a counting rule for aerobatics; the text does not provide alternative methods of compliance, deferrals, or explicit discretionary exemptions (Requirement/Compliance).\n- Implementation risks and trade-offs: accurate hour-tracking is required to meet the intervals; failure to track or perform the retirements will leave the operator non-compliant. Increased maintenance frequency (especially for aerobatic 8KCABs) imposes direct costs and aircraft downtime, which are the principal opportunity costs to operators (Compliance/Note).\n\nNet mechanical effect (summary)\n\n- Operators of the two named models must periodically remove and replace the listed wing attachment bolts on a fixed-hours schedule; aerobatic usage of 8KCABs accelerates the replacement schedule via a 10:1 counting rule for aerobatic hours (Requirement/Compliance/Note)."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive focused specifically on bolt replacement for two aircraft models. It has not expanded beyond its original purpose of addressing a specific airworthiness concern with wing attachment hardware."},"complexity_factors":["Very short document (approximately 150 words)","Only 2 defined aircraft models in applicability section","Simple conditional structure: two compliance paths based on hours flown (1000+ hours vs under 1000 hours)","Single note regarding aerobatic hour equivalency","No cross-references to other legislation or regulations beyond the enabling authority (Civil Aviation Regulations 1998, Part 39)","Clear, imperative language ('Retire from service') with minimal legal drafting conventions"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for specific aircraft.\n\n**What it does:**\nIt requires owners and operators of certain American Champion aeroplanes (models 8GCBC and 8KCAB) to **permanently remove and replace** four critical bolts that attach the wings to the fuselage:\n- The front and rear wing strut attachment bolts (upper and lower)\n- The front and rear wing spar attachment bolts\n\nThese bolts are vital structural components. If they fail, the wing could detach from the aircraft.\n\n**Who it affects:**\nAnyone who owns or operates these specific American Champion aircraft models (also known as Aeronca or Bellanca aircraft).\n\n**When you must comply:**\n- If your aircraft has already flown **1,000 hours or more**: You must replace these bolts within **200 flight hours** after 30 November 1977, and then replace them again every **1,200 flight hours** thereafter.\n- If your aircraft has flown **less than 1,000 hours**: You must replace them every **1,200 flight hours**.\n\n**Special rule for aerobatic flying:**\nFor model 8KCAB aircraft, every hour spent doing aerobatics (loops, rolls, etc.) counts as **10 hours** of normal flight time. This accelerates the replacement schedule because aerobatic flying puts more stress on the airframe.\n\n**Why it matters:**\nThis directive was issued because these bolts were found to be at risk of fatigue failure — meaning they could crack and break after repeated stress cycles. The rule prevents catastrophic wing separation by forcing proactive replacement before the bolts reach a dangerous condition."}},"importantCases":[],"_links":{"self":"/api/acts/ad-cha-17-wing-strut-and-spar-attachment-bolt","history":"/api/acts/ad-cha-17-wing-strut-and-spar-attachment-bolt/history","analysis":"/api/acts/ad-cha-17-wing-strut-and-spar-attachment-bolt/analysis","conflicts":"/api/acts/ad-cha-17-wing-strut-and-spar-attachment-bolt/conflicts","importantCases":"/api/acts/ad-cha-17-wing-strut-and-spar-attachment-bolt/important-cases","documents":"/api/acts/ad-cha-17-wing-strut-and-spar-attachment-bolt/documents"}}