{"id":"F2006B05743","name":"AD/PA-31/39 - Propeller Feather Assist Spring - Installation","slug":"ad-pa-31-39-propeller-feather-assist-spring-installation","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"repealed","isInForce":false,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":135568,"registerId":"commonwealth-F2006B05743-current","compilationNumber":null,"startDate":"2026-04-03","status":"Repealed","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/PA-31/39 - Propeller Feather Assist Spring - Installation","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-31/39 Propeller Feather Assist Spring - Installation 12/75\n\nApplicability: All model PA-31P fitted with Hartzell propellers HC-C3YN-2L, HC-C3YN-2LF, HC-C2YN-2LA, or HC-C3YN-2LAF.\n\n \n\nRequirement: Install propeller feather assist springs in accordance with Piper SB No. 470.\n\n \n\nNote: Operators are advised to refer to Piper SB No. 458, which recommended operational procedures to be observed in the event of a propeller overspeed.\n\n \n\nCompliance: Within 100 hours time in service after 31 December 1975.\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":1970},"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This directive maintains its original, narrow scope: a targeted safety modification for specific Piper PA-31P aircraft with identified Hartzell propellers. It has not expanded beyond this technical remedy."},"complexity_factors":["Single operational requirement with no exceptions or conditional clauses","Applicability limited to four specific propeller models on one aircraft type","Minimal cross-referencing (only to two external manufacturer service bulletins)","Straightforward compliance metric (flight hours)"],"plain_english_summary":"This airworthiness directive requires operators of Piper PA‑31P Navajo aircraft fitted with certain Hartzell propellers to install propeller “feather assist” springs to improve feathering in an engine failure. Compliance must follow Piper Service Bulletin No. 470 within 100 hours’ time after 31 December 1975. The directive also references Service Bulletin No. 458 for propeller overspeed emergency procedures."}},"importantCases":[],"_links":{"self":"/api/acts/ad-pa-31-39-propeller-feather-assist-spring-installation","history":"/api/acts/ad-pa-31-39-propeller-feather-assist-spring-installation/history","analysis":"/api/acts/ad-pa-31-39-propeller-feather-assist-spring-installation/analysis","conflicts":"/api/acts/ad-pa-31-39-propeller-feather-assist-spring-installation/conflicts","importantCases":"/api/acts/ad-pa-31-39-propeller-feather-assist-spring-installation/important-cases","documents":"/api/acts/ad-pa-31-39-propeller-feather-assist-spring-installation/documents"}}