{"id":"F2006B05938","name":"AD/PA-36/21 - Rudder Cable and Seat Belt Attachment Shackles - Inspection","slug":"ad-pa-36-21-rudder-cable-and-seat-belt-attachment-shackles-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":136068,"registerId":"commonwealth-F2006B05938-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/PA-36/21 - Rudder Cable and Seat Belt Attachment Shackles - Inspection","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  Piper PA-36 (Pawnee Brave) Series Aeroplanes\n\n \n\nAD/PA-36/21  Rudder Cable and Seat Belt Attachment Shackles - Inspection\n\n\n12/81\n\n \n\nApplicability: All models PA-36-285/300 and PA-36-375 with S/Nos. referenced in Piper SB No.\n\n729 or with S/Nos. referenced in subsequent issues or revisions of that service bulletin.\n\n \n\nDocument: Piper SB No. 729.\n\n \n\nCompliance: Within 25 hours time in service after 10 November 1981.\n\n \n\nBackground: Some shackles P/N 486-566 (MS 20115-5) installed for rudder cable/horn attachment and the upper seat belt/cable attachment may have cracks.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive's scope is the same as its stated purpose: it applies to PA-36-285/300 and PA-36-375 aeroplanes with serial numbers listed in Piper Service Bulletin No. 729 (or later revisions) and mandates an inspection within 25 hours after 10 November 1981 to detect possible cracks in shackles P/N 486-566 (MS 20115-5). There is no indication in the text supplied that the scope has been expanded or narrowed from that original statement."},"complexity_factors":["Narrow and clearly‑stated applicability (specific models and serial numbers referenced in a particular service bulletin). (Applicability; Document)","Single specified action (inspection) with a short, explicit compliance deadline (25 hours after 10 November 1981). (Compliance)","Relying on an external document (Piper SB No. 729) for serial number identification increases a small procedural step to determine whether an aircraft is in scope. (Document; Applicability)","Limited technical ambiguity in the directive text—it does not specify inspection technique or follow-up corrective action in this text, leaving some operational detail to the service bulletin or maintenance practice. (Document; Background)"],"plain_english_summary":"What this directive does (mechanical change)\n\n- Requires operators of certain Piper PA-36 (Pawnee Brave) aeroplanes to inspect specific shackles used for rudder cable/horn attachment and the upper seat belt/cable attachment. (Applicability; Document; Compliance)\n- The required inspection must be carried out within 25 hours time in service after 10 November 1981. (Compliance)\n\nWho it affects\n\n- Owners and operators of PA-36-285/300 and PA-36-375 aeroplanes that have serial numbers listed in Piper Service Bulletin No. 729 (or in later issues/revisions of that service bulletin). (Applicability; Document)\n- Maintenance personnel who perform inspections on those aircraft.\n\nWhy it matters (official rationale and practical implications)\n\n- The directive is issued because some shackles with part number 486-566 (MS 20115-5) installed in the specified locations may have cracks. The stated purpose is to detect any such cracking before it leads to a component failure. (Background)\n\nPractical mechanics, who pays, and who decides\n\n- The Civil Aviation Safety Authority (via this airworthiness directive) requires the inspection; aircraft owners/operators must comply. (Applicability; Compliance)\n- Owners/operators (or their contracted maintenance organisations) pay for the inspection work and any follow-up actions if cracks are found. (Compliance; Background)\n\nIncentives, costs, trade-offs and implementation risks\n\n- Incentives: Operators gain reduced risk of in-service failure if inspections find and rectify cracked shackles. (Background)\n- Direct compliance cost: time and labour to perform the inspection within the 25 hour window. The compliance window may force short-term grounding or schedule disruption. (Compliance)\n- Detection vs disruption trade-off: a short mandatory inspection window increases the chance inspectors find faults before failure, but concentrates downtime and repair demand into a narrow period. (Compliance; Background)\n- Implementation risk: the AD refers to Piper SB No. 729 for the serial numbers to which it applies. That creates reliance on the service bulletin for exact scope; if the bulletin is updated (later issues/revisions are referenced), operators must determine whether their aircraft serial numbers are included. (Applicability; Document)\n\nCompliance burden and discretion\n\n- The directive is prescriptive about timing (25 hours after 10 November 1981) and about which aircraft are covered, leaving little regulatory discretion about whether to inspect once the aircraft is in scope. (Compliance; Applicability)\n- Operational discretion remains with owners/operators about when exactly to schedule the inspection within the 25 hours and which maintenance provider to use, but they must meet the time limit. (Compliance)\n\nConcentrated benefits and costs\n\n- Beneficiaries (reduced risk of shackle failure) mainly attach to operators and occupants of the affected aircraft; the costs (inspection and any remedial work) fall directly on those owners/operators. The applicability is limited to aircraft with serial numbers listed in the referenced service bulletin, so the affected population is narrow. (Applicability; Background; Document)\n\nSummary statement\n\n- The directive requires a one-time inspection within a short, specified time window for particular shackles on PA-36-285/300 and PA-36-375 aeroplanes identified by serial number in Piper SB No. 729 (or later revisions). It is aimed at finding cracks in part P/N 486-566 (MS 20115-5). The primary effects are a mandatory inspection task for affected operators, the associated inspection cost and possible downtime, and reliance on the service bulletin to determine applicability. (Applicability; Document; Compliance; Background)"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive focused on a specific mechanical defect in a specific aircraft model. It has not expanded beyond its original purpose of mandating inspection of cracked shackles."},"complexity_factors":["Single, specific aircraft type and limited serial number range","Only one part number to identify (P/N 486-566 / MS 20115-5)","Simple compliance deadline: 25 hours time in service after a fixed date","No conditional logic, exceptions, or alternative compliance methods","References only one external document (Piper Service Bulletin 729)","Extremely short — essentially a one-page safety notice","No defined terms section, no cross-references to other regulations"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It requires owners and operators of specific Piper PA-36 \"Pawnee Brave\" agricultural aircraft to inspect certain metal shackles (small U-shaped connectors) that attach the rudder cables and seat belts.\n\n**What the problem is:** Some shackles with part number 486-566 (also known as MS 20115-5) may have developed cracks. These shackles are critical — they connect the rudder control cables to the rudder horn (the moving part that steers the plane) and also attach the upper seat belt. If a cracked shackle fails in flight, the pilot could lose rudder control or have their seat belt detach.\n\n**Who must comply:** Owners of PA-36-285, PA-36-300, and PA-36-375 model aircraft with specific serial numbers listed in Piper Service Bulletin No. 729.\n\n**What must be done:** Inspect these shackles within 25 flight hours after 10 November 1981.\n\n**Why it matters:** This is a classic \"crack detection\" AD typical of agricultural aviation safety. The Pawnee Brave is a crop-dusting workhorse that operates in high-vibration, high-stress conditions. Fatigue cracks in critical hardware can cause catastrophic failure. The directive forces operators to check for cracks before they cause an accident."}},"importantCases":[],"_links":{"self":"/api/acts/ad-pa-36-21-rudder-cable-and-seat-belt-attachment-shackles-inspection","history":"/api/acts/ad-pa-36-21-rudder-cable-and-seat-belt-attachment-shackles-inspection/history","analysis":"/api/acts/ad-pa-36-21-rudder-cable-and-seat-belt-attachment-shackles-inspection/analysis","conflicts":"/api/acts/ad-pa-36-21-rudder-cable-and-seat-belt-attachment-shackles-inspection/conflicts","importantCases":"/api/acts/ad-pa-36-21-rudder-cable-and-seat-belt-attachment-shackles-inspection/important-cases","documents":"/api/acts/ad-pa-36-21-rudder-cable-and-seat-belt-attachment-shackles-inspection/documents"}}