{"id":"F2006B05453","name":"AD/PA-23/20 - Stabilator Tab Horn - Modification","slug":"ad-pa-23-20-stabilator-tab-horn-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"repealed","isInForce":false,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":46203,"registerId":"commonwealth-F2006B05453-current","compilationNumber":null,"startDate":"2026-04-02","status":"Repealed","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/PA-23/20 - Stabilator Tab Horn - Modification","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-23 (Apache and Aztec) Series Aeroplanes\n\n \n\nAD/PA-23/20 Stabilator Tab Horn - Modification 8/60\n\nApplicability: Model PA-23-250 with S/Nos. 27-2 to 27-5, 27-7 to 27-60 27-62 to 27-215. Document:               Piper SB No. 189.\n\nCompliance: Within 60 hours time in service after 19 August 1960.\n\n \n","sortOrder":0}],"analysis":{"kimi_summary":{"_metrics":{"model":"kimi-k2.5","source":"moonshot-batch","completionTokens":1875},"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a narrow, targeted airworthiness directive focused solely on a specific mechanical modification for a limited fleet of aircraft. The scope has not expanded beyond the original stabilator tab horn safety issue."},"complexity_factors":["Incorporation of external technical document (Piper Service Bulletin 189) by reference without reproducing the actual modification steps","Highly fragmented applicability limited to specific aircraft serial numbers rather than all models","Technical aviation terminology requiring specialized knowledge (stabilator, tab horn, time in service)"],"plain_english_summary":"**What it does:** Requires owners and operators of specific Piper Apache and Aztec aircraft to modify the \"stabilator tab horn\" — a structural component that helps control the aircraft's pitch (up and down movement).\n\n**Who it affects:** Only applies to Piper PA-23-250 aircraft with specific serial numbers: 27-2 through 27-5, 27-7 through 27-60, and 27-62 through 27-215.\n\n**Key requirements:** Operators must complete the modification described in **Piper Service Bulletin No. 189** within 60 hours of flight time (called \"time in service\") counted from 19 August 1960.\n\n**Why it matters:** This addresses a safety defect in the stabilator control system. If the tab horn fails, the pilot could lose the ability to control the aircraft's altitude, potentially causing a crash."}},"importantCases":[],"_links":{"self":"/api/acts/ad-pa-23-20-stabilator-tab-horn-modification","history":"/api/acts/ad-pa-23-20-stabilator-tab-horn-modification/history","analysis":"/api/acts/ad-pa-23-20-stabilator-tab-horn-modification/analysis","conflicts":"/api/acts/ad-pa-23-20-stabilator-tab-horn-modification/conflicts","importantCases":"/api/acts/ad-pa-23-20-stabilator-tab-horn-modification/important-cases","documents":"/api/acts/ad-pa-23-20-stabilator-tab-horn-modification/documents"}}