{"id":"F2006B08802","name":"AD/DC3/27 - Crew Compartment Acoustic Treatment - Restoration","slug":"ad-dc3-27-crew-compartment-acoustic-treatment-restoration","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52167,"registerId":"commonwealth-F2006B08802-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DC3/27 - Crew Compartment Acoustic Treatment - Restoration","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# Douglas DC3 Series Aeroplanes\n\n \n\nAD/DC3/27 Crew Compartment Acoustic NK Treatment - Restoration\n\n# Applicability: All models operating in Papua New Guinea.\n\n \n\nRequirement: Carry out suitable sound attenuating treatment of the crew compartment to achieve a sound pressure level not greater than that experienced in DC3 aeroplanes in their original condition.\n\n \n\nNote: Measurements of the sound pressure level in a number of DC3 aeroplanes in their original condition show that 90 db (re 0.0002 dyne/sq.cm.) is not exceeded in any of four octave bands 300-600, 600-1200, 1200-2400 and 2400-4800 cycles/second when in flight at normal cruise power settings, the measurements being at a point midway between the pilots’ heads.\n\n \n\n# Compliance: Forthwith.\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":{"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":false,"description":"The instrument states its applicability clearly as 'All models operating in Papua New Guinea' and sets a technical noise‑limit requirement to be met 'forthwith.' The text provides no indication that it alters or narrows a prior stated scope; based on this instrument alone, the scope does not appear to have changed from its stated applicability."},"complexity_factors":["Applicability: 'All models operating in Papua New Guinea' — affects all DC‑3 operators in that territory but not elsewhere (Applicability).","Prescriptive noise limit: 90 dB maximum in any of four specified octave bands, measured at a point midway between the pilots’ heads — requires technical acoustic measurement and equipment (Note).","Vague performance language: terms like 'suitable sound attenuating treatment' and 'original condition' are not precisely defined and create discretion for operators and certifiers (Requirement; Note).","Immediate compliance: 'Forthwith' gives no staged timetable, increasing short‑term compliance burden and potential operational disruption (Compliance).","Partial measurement specification: octave bands and measurement point are given, but procedural details (instrumentation, averaging, flight conditions beyond 'normal cruise power settings', acceptance testing protocol) are not specified (Note; Requirement).","Enforcement and approval path not stated: directive does not specify which authority verifies compliance, what records must be kept, or how alternative means of compliance are approved (absent from text).","Cost allocation: operators explicitly bear cost and must implement modifications to aircraft structure/interior; potential engineering, maintenance and downtime costs are implied (Requirement; Compliance).","Cross‑jurisdiction operational complexity: applying only in Papua New Guinea may require different configurations or record‑keeping for aircraft operating in multiple regulatory jurisdictions (Applicability).","No exemption or derogation mechanism: text offers no explicit exemption, transitional relief or equivalence clause, limiting flexibility for operators (absent from text)."],"plain_english_summary":"This directive requires operators of all Douglas DC‑3 models operating in Papua New Guinea to install sound‑attenuating treatment in the crew compartment so in‑flight noise does not exceed levels measured in original-condition DC‑3s (no more than 90 dB in any of the four octave bands 300–600, 600–1200, 1200–2400 and 2400–4800 Hz at a point midway between the pilots’ heads). Compliance is required forthwith; operators pay for and choose a “suitable” treatment and must demonstrate compliance by measurement."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-purpose safety directive focused specifically on cockpit noise levels for one aircraft type in one geographic region. It has not expanded beyond its original occupational health and safety purpose for flight crew."},"complexity_factors":["Extremely short document (under 200 words)","Only one substantive requirement with a clear technical standard","Single applicability criterion (all DC-3 models in PNG)","No defined terms section, no cross-references to other legislation","Simple compliance trigger ('forthwith' — meaning immediately)","Contains only one explanatory note with technical measurement details"],"plain_english_summary":"**What this is:** This is an Airworthiness Directive (AD) — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for specific aircraft.\n\n**What it does:** It requires all Douglas DC-3 aircraft operating in Papua New Guinea to have soundproofing (acoustic treatment) installed or restored in the cockpit (crew compartment). The goal is to reduce noise levels so they don't exceed what pilots experienced when these planes were new.\n\n**The technical standard:** The cockpit noise must not go above 90 decibels across four specific frequency ranges during normal flight. This measurement is taken between where the two pilots sit.\n\n**Who it affects:** Anyone operating DC-3 aircraft in Papua New Guinea — these are vintage propeller planes (mostly from the 1930s-40s) still used for cargo and remote area transport.\n\n**When it must be done:** Immediately (\"forthwith\"). There's no grace period.\n\n**Why it matters:** Prolonged exposure to high noise levels causes permanent hearing damage. This rule protects pilots' hearing and ensures they can communicate clearly during flight — critical for safety in challenging terrain like Papua New Guinea's mountains and jungles."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dc3-27-crew-compartment-acoustic-treatment-restoration","history":"/api/acts/ad-dc3-27-crew-compartment-acoustic-treatment-restoration/history","analysis":"/api/acts/ad-dc3-27-crew-compartment-acoustic-treatment-restoration/analysis","conflicts":"/api/acts/ad-dc3-27-crew-compartment-acoustic-treatment-restoration/conflicts","importantCases":"/api/acts/ad-dc3-27-crew-compartment-acoustic-treatment-restoration/important-cases","documents":"/api/acts/ad-dc3-27-crew-compartment-acoustic-treatment-restoration/documents"}}