{"id":"F2006B05474","name":"AD/PA-23/48 - Alternate Air Induction Hose - Modification","slug":"ad-pa-23-48-alternate-air-induction-hose-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":46268,"registerId":"commonwealth-F2006B05474-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/PA-23/48 - Alternate Air Induction Hose - 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-23/48 Alternate Air Induction Hose - Modification 11/71\n\nApplicability: Turbocharged model PA-23-250 with S/Nos. 27-4053, 27-4226 to 27-4563, 27-4565 to 27-4579, 27-4581 to 27-4617, 27-4619 to 27-4627 and 27-4630 to\n\n27-4636.\n\n \n\nDocument: 1. Piper SB No. 334; or 2. FAA AD 71-21-6.\n\nCompliance: Within 100 hours time in service after 30 November 1971.\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 from 1971. It has not expanded beyond its original narrow purpose of addressing a specific hose defect in specific aircraft. ADs are typically narrow instruments by design."},"complexity_factors":["Single, specific technical requirement (hose modification)","Limited applicability — only one aircraft model variant with explicitly listed serial numbers","Two alternative compliance documents referenced (Piper SB 334 or FAA AD 71-21-6)","Simple deadline structure (100 hours time in service after fixed date)","No nested exceptions, conditional logic, or extensive defined terms","Document is extremely short — essentially a safety notice format rather than legislative text"],"plain_english_summary":"**What this is:** This is an Airworthiness Directive (AD) issued by Australia's Civil Aviation Safety Authority (CASA) under the Civil Aviation Regulations 1998. An Airworthiness Directive is a mandatory safety notice that requires aircraft owners or operators to perform specific maintenance, inspections, or modifications to keep their aircraft safe to fly.\n\n**What it does:** This directive requires owners of specific Piper PA-23 Apache and Aztec aeroplanes (turbocharged model PA-23-250 with particular serial numbers) to modify the alternate air induction hose. The alternate air induction system is a backup air supply for the engine — if the main air intake gets blocked (by ice, debris, or a bird strike), this alternate system kicks in to keep the engine running. A faulty hose here could mean engine failure at a critical moment.\n\n**Who it affects:** Owners and operators of very specific Piper twin-engine aircraft:\n- Turbocharged PA-23-250 models\n- With serial numbers: 27-4053, 27-4226 through 27-4563, 27-4565 through 27-4579, 27-4581 through 27-4617, 27-4619 through 27-4627, and 27-4630 through 27-4636\n\n**What must be done:** The modification must be carried out following either:\n- Piper Service Bulletin No. 334 (the manufacturer's official repair notice), OR\n- FAA AD 71-21-6 (the equivalent American safety directive)\n\n**When:** Within 100 hours of flying time after 30 November 1971.\n\n**Why it matters:** This is a critical safety fix. If the alternate air induction hose fails, the pilot could lose engine power with no backup air supply — potentially catastrophic during flight, especially in icing conditions where the alternate air system is most needed."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The text of the AD itself sets out a single, targeted requirement for modification of the alternate air induction hose on the listed PA-23-250 serial numbers, and specifies the documents and a single compliance deadline. The instrument does not indicate any alteration to a previously stated scope or extend applicability beyond the enumerated aircraft; therefore there is no evidence in this text that the scope has changed from an earlier intent. (Applicability; Document; Compliance)"},"complexity_factors":["Narrow, explicit applicability limited to specific serial-number ranges (simple identification of affected aircraft). (Applicability)","Single, prescriptive technical action required (modification of alternate air induction hose) with two alternative reference documents to follow. (Document)","Clear, short compliance timeframe (100 hours after a fixed date) — definitive but potentially operationally urgent. (Compliance)","Dependence on external technical documents (Piper SB No. 334 or FAA AD 71-21-6) introduces small additional complexity for operators who must obtain and follow those texts. (Document)","No staged obligations, calculations, exemptions, or ongoing reporting requirements stated in the AD — reduces procedural complexity."],"plain_english_summary":"This AD requires a specific modification to the alternate air induction hose on certain turbocharged Piper PA-23-250 aeroplanes (only those serial numbers listed). Compliance must follow Piper Service Bulletin No. 334 or FAA AD 71-21-6 and be completed within 100 hours time-in-service after 30 November 1971.\n\nIt affects owners/operators of the listed aircraft and the maintenance organisations who carry out the work; owners pay parts, labour and downtime, and CASA enforces compliance to preserve airworthiness."}},"importantCases":[],"_links":{"self":"/api/acts/ad-pa-23-48-alternate-air-induction-hose-modification","history":"/api/acts/ad-pa-23-48-alternate-air-induction-hose-modification/history","analysis":"/api/acts/ad-pa-23-48-alternate-air-induction-hose-modification/analysis","conflicts":"/api/acts/ad-pa-23-48-alternate-air-induction-hose-modification/conflicts","importantCases":"/api/acts/ad-pa-23-48-alternate-air-induction-hose-modification/important-cases","documents":"/api/acts/ad-pa-23-48-alternate-air-induction-hose-modification/documents"}}