{"id":"F2006B05960","name":"AD/PA-38/21 - Vertical Fin Forward Spar Attachment Plate Replacement Life Limits","slug":"ad-pa-38-21-vertical-fin-forward-spar-attachment-plate-replacement-life-limits","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"repealed","isInForce":false,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":136128,"registerId":"commonwealth-F2006B05960-current","compilationNumber":null,"startDate":"2026-04-03","status":"Repealed","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/PA-38/21 - Vertical Fin Forward Spar Attachment Plate Replacement Life Limits","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-38 (Tomahawk) Series Aeroplanes\n\n \n\n# AD/PA-38/21 Vertical Fin Forward Spar Attachment\n\nPlate Replacement Life Limits Applicability: All model PA-38-112 with S/Nos. 38-81A0001 to 38-82A0101. Document:               Piper Service Bulletin No. 710.\n\n# 3/83\n\nCompliance: At 3000 hours time in service install forward fin spar attachment plate and support brackets kit, Piper P/N 764 421, and thereafter at intervals not exceeding 5000 hours time in service replace forward fin spar attachment plate, Piper P/N 77553-05.\n\n \n\nBackground: Fatigue testing of the empennage structure has established replacement life limits.\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\n \n","sortOrder":0}],"analysis":{"kimi_summary":{"_metrics":{"model":"kimi-k2.5","source":"moonshot-batch","completionTokens":1316},"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This directive establishes original equipment life limits based on fatigue testing for a specific structural component. It remains tightly focused on its original safety purpose and has not expanded beyond addressing the identified airworthiness risk in the specified aircraft fleet."},"complexity_factors":["Single specific compliance action with clear time-based trigger","Limited applicability (one aircraft model with defined serial number range)","Direct reference to manufacturer part numbers without alternative compliance methods","No conditional exceptions or cross-references to other instruments"],"plain_english_summary":"**What this does:** This is a mandatory safety directive (called an Airworthiness Directive) issued by the aviation regulator that requires owners and operators of specific Piper Tomahawk aircraft to replace a critical tail section part at set flight-hour intervals.\n\n**Who it affects:** Owners and operators of Piper PA-38-112 model aircraft with serial numbers between 38-81A0001 and 38-82A0101.\n\n**What you must do:**\n- **At 3,000 flight hours:** Install a new forward fin spar attachment plate and support brackets kit (manufacturer part number 764 421)\n- **Every 5,000 flight hours after that:** Replace the forward fin spar attachment plate (part number 77553-05)\n\n**Why this matters:** Fatigue testing showed this attachment plate wears out over time and could fail, potentially causing the vertical fin (tail) to separate from the aircraft. This rule prevents catastrophic accidents by ensuring the part is replaced before it reaches a dangerous level of wear."}},"importantCases":[],"_links":{"self":"/api/acts/ad-pa-38-21-vertical-fin-forward-spar-attachment-plate-replacement-life-limits","history":"/api/acts/ad-pa-38-21-vertical-fin-forward-spar-attachment-plate-replacement-life-limits/history","analysis":"/api/acts/ad-pa-38-21-vertical-fin-forward-spar-attachment-plate-replacement-life-limits/analysis","conflicts":"/api/acts/ad-pa-38-21-vertical-fin-forward-spar-attachment-plate-replacement-life-limits/conflicts","importantCases":"/api/acts/ad-pa-38-21-vertical-fin-forward-spar-attachment-plate-replacement-life-limits/important-cases","documents":"/api/acts/ad-pa-38-21-vertical-fin-forward-spar-attachment-plate-replacement-life-limits/documents"}}