{"id":"F2006B08838","name":"AD/DC4/31 - Propeller Feathering System - Modification","slug":"ad-dc4-31-propeller-feathering-system-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52310,"registerId":"commonwealth-F2006B08838-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DC4/31 - Propeller Feathering System - 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)  Douglas DC4 Series Aeroplanes\n\n \n\nAD/DC4/31 Propeller Feathering System - Modification NK\n\nApplicability: All models.\n\n \n\nRequirement: Replace the existing flexible hose components of the propeller feathering lines forward of the firewall with hose assemblies having greater fire resistance. The following hose assemblies are acceptable for this application:\n\n \n\nResistoflex P/N SSFR-3800-10 Aeroquip P/N 304000 (680-10S with 304 sleeves over end fittings) Aeroquip P/N 309009-10S or -8S; or\n\n \n\nNote: Flexible hose assemblies located forward of the cylinders and connecting to the governor are not affected by this Order.\n\n \n\nFAA AD 55-15-3; or ANO 105.1.16.2.5.31.\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":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The instrument sets a specific replacement requirement and identifies affected components and acceptable replacement assemblies. The text does not indicate an amendment of an earlier directive that would broaden or narrow scope; it instead imposes the stated requirement and cross-references related AD/ANO material. There is no statement in the provided text that the directive changes an earlier scope."},"complexity_factors":["Narrow, single technical requirement (hose replacement forward of firewall) reduces legal complexity.","Specificity of acceptable part numbers requires technical matching and supply-chain checks (Resistoflex and Aeroquip P/Ns listed).","Exception for hoses forward of cylinders connecting to governor adds a limited scope nuance to interpret on individual aircraft.","Cross-references to FAA AD 55-15-3 and ANO 105.1.16.2.5.31 mean practitioners may need to consult other instruments for full compliance context.","No compliance timeframe or installation/test criteria stated in the provided text increases procedural ambiguity for implementers.","Potential operational complexity from sourcing parts and scheduling aircraft downtime (practical, not textual complexity)."],"plain_english_summary":"This AD requires all Douglas DC‑4 operators to replace flexible hoses in the propeller feathering lines forward of the firewall with specified, more fire‑resistant hose assemblies. It excludes hoses forward of the cylinders that connect to the governor.\n\nIt affects aircraft owners/operators and maintenance organisations (who pay for parts, labour and downtime), and matters for fire safety and maintaining airworthiness; approved part numbers are named in the AD."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical vulnerability in a specific aircraft type. It has not expanded beyond its original purpose of mandating fire-resistant hose replacement."},"complexity_factors":["Very short document (approximately 150 words of substantive content)","Only 3 defined part numbers for replacement hoses","Single clear applicability statement ('All models')","One explicit exemption (governor hoses forward of cylinders)","No cross-references to other legislation beyond citation of originating FAA AD and old ANO","No conditional logic or nested exceptions","Straightforward imperative requirement ('Replace...')"],"plain_english_summary":"**What this is:** This is an Airworthiness Directive (AD) — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for specific aircraft.\n\n**What it does:** It requires owners and operators of **Douglas DC-4 series aeroplanes** to replace certain flexible hoses in the propeller feathering system with more fire-resistant versions.\n\n**The safety problem:** The existing hoses run \"forward of the firewall\" (in the engine area where fire risk is highest) and apparently don't resist fire well enough. If these hoses fail in a fire, pilots might lose the ability to \"feather\" the propeller — a critical emergency procedure that stops a windmilling propeller from causing drag and vibration after an engine failure.\n\n**What must be done:** Replace the old flexible hoses with specific approved alternatives made by Resistoflex or Aeroquip (part numbers listed). Hoses connecting to the governor and located forward of the cylinders are **not** affected.\n\n**Who it affects:** Anyone operating or maintaining Douglas DC-4 aircraft in Australia.\n\n**Why it matters:** This prevents a potential catastrophic scenario where an engine fire destroys the feathering system hoses, leaving the crew unable to control the aircraft properly after engine failure."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dc4-31-propeller-feathering-system-modification","history":"/api/acts/ad-dc4-31-propeller-feathering-system-modification/history","analysis":"/api/acts/ad-dc4-31-propeller-feathering-system-modification/analysis","conflicts":"/api/acts/ad-dc4-31-propeller-feathering-system-modification/conflicts","importantCases":"/api/acts/ad-dc4-31-propeller-feathering-system-modification/important-cases","documents":"/api/acts/ad-dc4-31-propeller-feathering-system-modification/documents"}}