{"id":"F2006B08834","name":"AD/DC4/28 - Fire Protection Modifications","slug":"ad-dc4-28-fire-protection-modifications","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52285,"registerId":"commonwealth-F2006B08834-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DC4/28 - Fire Protection Modifications","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nDouglas DC4 Series Aeroplanes\n\nAD/DC4/28 Fire Protection Modifications NK\n\nApplicability: All models.\n\nRequirement: 1. Modify the aeroplane to provide a level of protection against fire in flight equivalent to that called for in Section 101.1.3.1 of Air Navigation Orders.\n\n    2. Incorporation of all Douglas SBs listed in para. 3 of this Order together with the incorporation of the modifications detailed in para. 4 of this Order constitutes an acceptable means of meeting the above requirements.\n\n    3. DC4 Service Bulletins:\n\nNo. Title\n\n47 Install Firewall-Cabin Forward Bulkhead, Ceiling Panels and Reworkable Floor Panel.\n\n49 Oil Cooler Fairing and Inner Ring Seal.\n\n55 Replace Micarta Fairleads for Engine Controls through Nacelle Firewall and Inner Ring.\n\n61 Replacement of Generator Current Control Relay.\n\n    64 Installation of Cabin and Nose Heater Fire Extinguisher and Fuel System.\n\n    65 Firewall Junction Box Steel Cover Plate attached to Firewall.\n\n    66 Fire Prevention \\- Engine Section. Piping and Fitting Revision.\n\nNote: This Bulletin calls for the replacement of existing electrical disconnect plugs on the fire- wall by stainless steel plugs. It will be sufficient for the purpose of this Order if only that component of the plug actually attached to the firewall be made of fire-proof material.\n\n    67 Addition of Fire Extinguisher Lines Aft of Firewall and CO2 Bottles in Nose Wheel Well.\n\n    68 Installation of “Y” Outlet Stiffener Flange on Exhaust Collector Rings.\n\n70 Installation \\- Generator Blast Tube Shut-off System.\n\n85 Revision of Engine Section Surface De-icer Pressure Line-Vacuum Pump to Separator.\n\nIn addition to the requirements of para. 3 of this Order, modify aeroplanes as follows:-\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n    4.1. Fit fireproof seals around the cowl flap jack shafts where they pass through the fire seal baffles.\n\n    4.2. Seal with fireproof material all holes and gaps in the fire seal baffles.\n\n    4.3. Seal with fireproof material the gaps around the engine integral oil sump lines at the bottom of the fire seal baffles.\n\n    4.4. Seal with fireproof material the gaps between the bottom of the fire seal baffles and inner diaphragms in the area of the engine integral sump lines.\n\n    4.5. Using fireproof material, seal the fire seal baffles around the engine crankcase bosses, including the two bosses used for magneto vent line passage.\n\n    4.6. Fit fireproof seals over holes in inner diaphragm cup shrouds around the pre- heat controls.\n\n    4.7. Provide shut-off means in propeller feathering lines in those installations which utilise the combination starter and feathering pump unit.\n\n    4.8. Install an approved fire detector system in Zone 1.\n\n    4.9. Install an approved fire detector system in Zone 2 and approved fire detectors aft of the firewall in nacelle Zone 3. OR\n\n2. ANO 105.1.16.2.5.27, Issue 2.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"This directive stays within the original safety objective: improving in‑flight fire protection for the DC‑4. It does not materially broaden scope beyond that purpose; it specifies particular means (a set of SBs plus detailed sealing and equipment tasks) and records an alternative compliance route to an existing Air Navigation Order. In short, the instrument clarifies and prescribes methods to achieve an existing safety standard rather than expanding the legal or operational scope of regulation."},"complexity_factors":["Applies to all DC‑4 models (broad applicability)","11 Douglas Service Bulletins listed (SB Nos. 47, 49, 55, 61, 64, 65, 66, 67, 68, 70, 85) (para. 3)","Nine distinct, technical additional modification requirements in paras. 4.1–4.9 (detailed sealing and installation work)","Note with a partial exception about electrical disconnect plugs (para. 3, Note)","Acceptable‑means clause allowing SB package as compliance route (para. 2) and an explicit alternative reference to an Air Navigation Order (ANO 105.1.16.2.5.27)","Several instances requiring ‘‘approved’’ detectors/systems (paras. 4.8–4.9), which imports regulator discretion","Technical specificity (fireproof seals, exact locations: cowl flap jack shafts, crankcase bosses, sump lines, inner diaphragms) increases practical implementation complexity"],"plain_english_summary":"**What this instrument requires (mechanically)**\n\n- This Airworthiness Directive applies to all Douglas DC‑4 series aeroplanes and requires the aeroplane to be modified so it has in‑flight fire protection at least equal to the standard in Air Navigation Orders Section 101.1.3.1 (Requirement, para. 1).\n\n- The directive says one acceptable way to comply is to incorporate a package of Douglas Service Bulletins (SBs) listed in the Order (paras. 2–3). Those SBs cover firewall installation, seals, fairings, fire extinguishers, generator and electrical parts, exhaust modifications, and related items. The SB numbers are: 47, 49, 55, 61, 64, 65, 66, 67, 68, 70 and 85 (para. 3).\n\n- In addition to those SBs, the directive mandates a set of specific sealing, installation and equipment actions (paras. 4.1–4.9). Examples include: fitting fireproof seals around cowl flap jack shafts; sealing holes and gaps in fire seal baffles with fireproof material; sealing around engine sump lines and crankcase bosses; fitting seals over holes in inner diaphragms; providing shut‑off means in propeller feathering lines where certain pumps are used; and installing approved fire detector systems in specified engine/nacelle zones (Zone 1, Zone 2 and Zone 3 aft of the firewall) (paras. 4.1–4.9).\n\n- The directive also records one exception/note about replacing electrical disconnect plugs at the firewall: it is sufficient that only the firewall‑attached component of the plug be made of fire‑proof material (para. 3, Note).\n\n- The Order identifies an alternative compliance route by reference to an Air Navigation Order (ANO 105.1.16.2.5.27, Issue 2) (closing line). That means operators may be able to comply by meeting that ANO requirement instead of the SB/modification package, subject to regulatory acceptance.\n\n**Who this affects**\n\n- Aircraft owners and operators of DC‑4 series aeroplanes: they must carry out the modifications or adopt an acceptable alternative to keep the aircraft airworthy under Australian rules (Applicability & Requirement paras). They pay for parts, labour and downtime.\n\n- Maintenance organisations and certificated engineers: they must perform the work to the standards required and use ‘‘approved’’ equipment where the Order requires it (paras. 4.7–4.9).\n\n- The Civil Aviation Safety Authority (CASA) or its delegate: enforces compliance and assesses alternative means of compliance or approval of supplied equipment (implicit in the ‘‘approved’’ language and the directive format).\n\n**Why it matters (stated purpose and practical implications)**\n\n- Stated purpose: to provide protection against in‑flight fire equivalent to a stated Air Navigation Order standard (Requirement, para. 1). The concrete mechanism is mandating defined structural, sealing, electrical and detection changes to reduce the likelihood of fire spreading from engine/nacelle areas into the cabin and to improve detection/extinguishing capability (paras. 3–4).\n\n- Costs and incentives: owners/operators bear the direct costs — parts, certified labour and aircraft downtime — and must choose either to install the listed SBs and the additional modifications or to demonstrate compliance via the alternative ANO route (paras. 2–4). Because the DC‑4 is an older type, sourcing parts and specialised labour may increase time and expense.\n\n- Trade‑offs and implementation risk: the directive prescribes many physical modifications (para. 4.1–4.9 and para. 3 SB list). That creates a non‑trivial maintenance workload and may require certification of substituted components or systems as ‘‘approved.’’ Operators face the choice of incurring retrofit costs or grounding/limiting operations until compliance is achieved. There is a practical risk of delays if components are scarce or if installers must secure approval for alternative methods.\n\n- Operational effects and behaviour change: to remain legally flyable, operators must schedule and pay for the retrofits, and maintenance organisations must adopt the specified procedures and use approved detectors/seals. The directive therefore shifts costs to DC‑4 operators and imposes a set of technical installation requirements on maintenance providers (paras. 1–4).\n\n**Notes on regulatory framing and options**\n\n- The Order treats the listed Service Bulletins plus the specific sealing and installation items as an ‘‘acceptable means’’ of compliance (para. 2). That wording normally allows other means if they are shown to provide equivalent protection and are accepted by the regulator, but any alternative will require regulatory agreement.\n\n- Several items require ‘‘approved’’ equipment or systems (paras. 4.8–4.9). That retains regulatory discretion about what counts as acceptable detection or extinguishing equipment and may necessitate paperwork or formal approvals for alternative components.\n\n**Who pays, who decides, and what changes**\n\n- Who pays: aircraft owners/operators pay for the modifications and any associated downtime (paras. 2–4).\n\n- Who decides: CASA (or its delegate) enforces the directive and approves alternative compliance methods or components described as ‘‘approved’’ (implicit in the directive structure and the ‘‘approved’’ language in paras. 4.8–4.9).\n\n- What behaviour changes: operators must retrofit DC‑4s with the listed SB modifications and do the additional sealing and equipment installs, or obtain regulator‑approved alternative compliance. Maintenance organisations must carry out the specified work to appropriate standards and use approved parts where required.\n\n"},"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This appears to be a standalone airworthiness directive with a clear, focused scope: fire protection modifications for DC-4 aircraft. The document maintains its original intent of specifying mandatory safety upgrades without significant expansion into unrelated operational areas."},"complexity_factors":["Multiple cross-references to external documents (Air Navigation Orders Section 101.1.3.1, ANO 105.1.16.2.5.27 Issue 2, and 10 specific Douglas Service Bulletins)","Technical aviation terminology requiring specialised knowledge (fire seal baffles, inner diaphragms, cowl flap jack shafts, magneto vent lines)","Alternative compliance pathways (the 'OR' option at the end referencing a different ANO issue)","Nested structure with paras 3 and 4 containing multiple sub-requirements (4.1 through 4.9)","Conditional language in Service Bulletin 66 allowing partial compliance (only the firewall-attached component needs to be fireproof)","Zone-based fire detection requirements (Zones 1, 2, and 3) requiring understanding of aircraft zoning conventions"],"plain_english_summary":"This mandatory Airworthiness Directive requires owners and operators of Douglas DC‑4 aircraft in Australia to upgrade onboard fire protection to modern safety levels. It compels physical modifications—improved engine fire prevention, detection, and suppression systems—to address known fire risks on this aging design.\n\nIt affects DC‑4 owners, operators and maintenance organisations; non‑compliant aircraft cannot legally operate in Australian airspace, making the work essential for continued airworthiness."},"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"}},"importantCases":[],"_links":{"self":"/api/acts/ad-dc4-28-fire-protection-modifications","history":"/api/acts/ad-dc4-28-fire-protection-modifications/history","analysis":"/api/acts/ad-dc4-28-fire-protection-modifications/analysis","conflicts":"/api/acts/ad-dc4-28-fire-protection-modifications/conflicts","importantCases":"/api/acts/ad-dc4-28-fire-protection-modifications/important-cases","documents":"/api/acts/ad-dc4-28-fire-protection-modifications/documents"}}