{"id":"F2006B05754","name":"AD/PA-31/50 - Horizontal Stabiliser Stringer Attachment - Inspection","slug":"ad-pa-31-50-horizontal-stabiliser-stringer-attachment-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":135602,"registerId":"commonwealth-F2006B05754-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/PA-31/50 - Horizontal Stabiliser Stringer Attachment - 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-31 Series Aeroplanes\n\n \n\nAD/PA-31/50 Horizontal Stabiliser Stringer Attachment - Inspection\n\n\n11/76\n\n \n\nApplicability: All model PA-31 and PA-31-325 with S/Nos. 31-7612060 to 31-7612080, 31- 7612082 to 31-7612089, 31-7612091, 31-7612096 and 31-7612099. All model PA-\n\n31-350 with S/Nos. 31-7652105 to 31-7652115, 31-7652117, 31-7652118, 31-\n\n7652120 to 31-7652146, 31-7652148 to 31-7652162, 31-7652164, 31-7652165 and\n\n31-7652168.\n\n \n\nDocument: Piper SB No. 521.\n\n \n\nCompliance: Within 100 hours time in service after 30 November 1976.\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":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive issued in 1976. It has not expanded beyond its original purpose of mandating a specific safety inspection for specific aircraft. The scope remains precisely targeted at the horizontal stabiliser stringer attachment issue for the identified Piper aircraft."},"complexity_factors":["Very short document (approximately 200 words)","Only 3 defined elements: applicability (specific aircraft models and serial numbers), reference document (Piper SB No. 521), and compliance deadline","No cross-references to other legislation or regulations beyond the enabling authority (Civil Aviation Regulations 1998, Part 39)","Single, clear obligation: inspect within specified timeframe","No conditional logic, exceptions, or nested provisions","Straightforward applicability test based on aircraft model and serial number"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It requires owners and operators of specific Piper PA-31 series aircraft to inspect a particular part of the plane's tail (the \"horizontal stabiliser stringer attachment\") for defects.\n\n**Who it affects:**\n- Owners and operators of specific Piper PA-31, PA-31-325, and PA-31-350 aircraft with particular serial numbers (listed in the document)\n\n**What they must do:**\n- Inspect the horizontal stabiliser stringer attachment (a structural component that helps hold the tail section together)\n- Follow the procedures in Piper Service Bulletin No. 521\n- Complete the inspection within 100 hours of flight time after 30 November 1976\n\n**Why it matters:**\nAirworthiness Directives are legally binding safety instructions. If the specified aircraft aren't inspected as directed, they cannot legally fly. This particular AD addresses potential structural failures in the tail section that could affect flight safety."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"Based on the text supplied, the instrument’s scope is the set of listed PA-31 and PA-31-350 aircraft by serial number and the single required action (inspection per Piper SB No. 521 within the stated 100-hour window). The directive’s stated applicability and compliance requirement align with that scope; there is no indication in the text that the scope has been changed from its original stated terms."},"complexity_factors":["Narrow, detailed applicability: multiple specific serial-number ranges increase administrative work to determine covered aircraft (Applicability).","External technical reliance: the directive delegates procedural detail and acceptance criteria to Piper SB No. 521 (Document).","Fixed retroactive compliance window: a single short compliance timeframe (100 hours after 30 November 1976) creates scheduling pressure (Compliance).","Lack of remedial detail: the directive mandates inspection but does not specify follow-up repairs or alternative compliance paths, requiring reliance on the service bulletin and maintenance judgement.","Record-keeping and verification requirements are implicit rather than specified, leaving discretion to operators/maintenance organisations on how to demonstrate compliance."],"plain_english_summary":"This Airworthiness Directive requires owners/operators of specified Piper PA‑31 and PA‑31‑350 aircraft (listed by serial number) to have the horizontal stabiliser stringer attachment inspected in accordance with Piper Service Bulletin No. 521. The mandatory inspection must be completed within 100 hours time in service after 30 November 1976, affecting maintenance organisations and certificated engineers who perform the work."}},"importantCases":[],"_links":{"self":"/api/acts/ad-pa-31-50-horizontal-stabiliser-stringer-attachment-inspection","history":"/api/acts/ad-pa-31-50-horizontal-stabiliser-stringer-attachment-inspection/history","analysis":"/api/acts/ad-pa-31-50-horizontal-stabiliser-stringer-attachment-inspection/analysis","conflicts":"/api/acts/ad-pa-31-50-horizontal-stabiliser-stringer-attachment-inspection/conflicts","importantCases":"/api/acts/ad-pa-31-50-horizontal-stabiliser-stringer-attachment-inspection/important-cases","documents":"/api/acts/ad-pa-31-50-horizontal-stabiliser-stringer-attachment-inspection/documents"}}