{"id":"F2006B08792","name":"AD/DC3/15 Amdt 2 - Engine Nacelle Fire Protection - Modifications","slug":"ad-dc3-15-amdt-2-engine-nacelle-fire-protection-modifications","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52140,"registerId":"commonwealth-F2006B08792-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DC3/15 Amdt 2 - Engine Nacelle Fire Protection - Modifications","content":"![](image.001.png)  \nDouglas DC3 Series Aeroplanes\n\nAD/DC3/15\n\nAmdt 2\n\n  \nEngine Nacelle Fire Protection \\- Modifications 4/84\n\nApplicability: All models.\n\nRequirement: 1. Install a fire detection system for each engine nacelle as follows:- Fire Detectors:\n\n    (a) Install a continuous type detector or a minimum of six (6) unit detectors in the accessory compartment. Mount unit detectors or portion of the continuous type detector at suitable locations on or near the forward face of the firewall and dispose as evenly as possible about the nacelle axis. In installations where the airstream from the oil cooler is discharged into the accessory compartment, mount at least one unit detector or portion of a continuous detector in the path of the airstream.\n\n    (b) All detectors used shall be of an approved type. Detector Circuits:\n    (a) Provide separate independent detector circuits for each nacelle.\n\n    (b) Provide a test switch in the cockpit in each detector circuit and arrange the circuit so that the operation of the test switch checks the circuit protection, the indicator lamps, and the continuity of the detector wiring.\n\nIndicators:\n\n    (a) Provide separate indicators in the cockpit for each nacelle; each indicator shall consist of two red lamps connected in parallel.\n\n    (b) Ensure that the indicating lights are in the field of vision of the pilot and co- pilot and are separated sufficiently to prevent confusion as to the source of the fire.\n\n    (c) In addition to indicating lights, install an audible warning device, which is capable of being silenced and common to all detector circuits, in the cockpit. Ensure that the noise emitted by such device is distinctive from that emitted by any other audible warning device in the cockpit.\n\nFire Extinguisher System:\n\nModify the existing fire extinguisher installation to comply with the following requirements:-\n\n    (a) Ensure that two separate charges of extinguishant are available to each nacelle. Each extinguishant charge shall consist of at least seven (7) pounds of carbon dioxode or six (6) pounds of methyl bromide.\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n    (b) Plumb the extinguishant to an accessory compartment spray ring. Where the airstream from the oil cooler discharges into the accessory compartment, arrange the extinguisher spray line so that an adequate amount of extinguishant is discharged into the oil cooler honeycomb.\n\nNote: Existing installations, where portion of the extinguishant is discharged into the carburettor air intake, may be retained if not more than 25 per cent of the extinguishant, by weight, enters the intake.\n\n    (c) Ensure that extinguisher lines and spray rings forward of the firewall are of fireproof construction, except that short flexible lengths may consist of fire- resistant coupled hose assemblies.\n\n    (d) Where the extinguisher bottles are electrically operated, arrange the firing circuit so that the failure of the wiring to any one bottle will not affect the operation of the remaining bottles.\n\nFluid Shut-off Valves:\n\nInstall shut-off valves in the fuel, oil and hydraulic fluid systems, as follows:-\n\n    (a) Mount valves immediately to the rear of each nacelle firewall and insert in the lines conveying fluid to the appropriate engine-driven pump.\n\n    (b) Install valves so that they are capable of being operated rapidly while the aeroplane is in flight.\n\nVentilation of Electrical Accessories:\n\n    (a) Modify the ventilation systems for the generator and magnetos so that the source of their air intake is not within the accessory compartment or adjacent to the exhaust stack.\n\n    (b) Replace with appropriate fire-proof components, ventilating tubes and ducts in cases where their burning through or collapse could permit the spread of fire from the engine compartment to the accessory compartment.\n\nFluid Lines:\n\n    (a) Replace, with approved flexible fire-resistant hose assemblies, all lines which carry flammable fluids or gases within the accessory compartment. Alternatively, fire-proof rigid lines may be used, connected to fire-resistant coupled flexible hose assemblies.\n\n    (b) Replace, with a fire-proof line, the line from the oil tank to the propeller feathering pump and the oil tank drain line where these lines lie forward of the firewall.\n\nNote: For the purpose of this Directive a fire-resistant hose assembly wrapped in asbestos lagging enclosed in a synthetic rubber or P.V.C. sheath may be regarded as fireproof.\n\nElectric cables:\n\n    (a) Ensure that wiring forward of the firewall is P.V.C. insulated glass braided cable to Specification AN-J-C-48a or other cable approved as fire-resistant Class II for the following circuits:-\n\n    (I) Fire detectors\n\n    (II) Propeller feathering\n\n    (III) Those portions of the starter circuit in which a fault could adversely affect the propeller feathering.\n\n    (b) Protect cables with glass outer braiding from abrasion by wrapping with\n\nP.V.C. tape, shrouding with P.V.C. tubing, or by other approved means.\n\n    (c) Sleeve cables in electrically unprotected circuits either individually, in P.V.C. tubing, or enclose in metal conduit. Before enclosing in metal conduit protect glass outer braided cables from abrasion in accordance with subparagraph (b) above.\n\n    (d) Install cables and cable runs forward of the firewall in the cooler parts of the engine nacelle. Arrange cable runs so that they are not exposed to mechanical damage during normal engine operation or during maintenance. Cables and cable conduits shall not be directly clipped to the engine diaphragm.\n\nSealing of Firewall Diaphragm:\n\nRework the firewall and diaphragm to ensure that they will provide a complete seal against the passage of flame and hot gas from one nacelle compartment to another. In particular, the following modifications are required:-\n\n    (a) Seal all gaps and holes in firewall and diaphragm with fire-proof material.\n\n    (b) Replace with fire-proof components, all existing light alloy fittings, connections, disconnect plates, etc., on firewall and diaphragm. Alternatively, shroud existing light alloy parts with adequate fire-proof shields so that, in event of an engine nacelle fire, they will not be subjected to flame or their failure will not allow flame to penetrate the firewall.\n\n    (c) Replace a sufficient number of the existing light alloy rivets on the firewall with steel rivets or bolts to ensure that, in the event of an accessory compartment fire hot enough to melt light alloy, the firewall will remain intact and impervious to flame.\n\nCompliance: Unless already accomplished, within 100 hours time in service after 31 March 1984.\n\nBackground: This Directive is raised in issue to remove the prohibition imposed on the use of free hose and clamps assemblies in Amdt. 1 of this directive. The prohibition is unnecessary for these large diameter low pressure applications considering their long satisfactory history.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":6,"scope_assessment":{"changed":true,"description":"This amendment narrows the scope of a prior prohibition in Amendment 1 by removing a blanket ban on the use of free hose and clamp assemblies for certain large‑diameter, low‑pressure applications. The AD retains extensive fire‑protection upgrade requirements but explicitly allows continued use of some hose/clamp assemblies where historically acceptable. In other words, the instrument modifies an earlier, stricter material prohibition rather than expanding the AD into new functional areas."},"complexity_factors":["Multiple distinct technical domains: detectors, wiring, indicators, extinguisher systems, fluid shut-offs, ventilation, fluid lines, firewall sealing (9 substantive areas).","Numerous nested subrequirements and options (e.g. choice between continuous detector or >=6 unit detectors; flexible fire‑resistant hoses or fire‑proof rigid lines).","Special conditional exceptions and tolerances (e.g. existing installations discharging into carburettor intake may be retained if ≤25% by weight).","Material and specification cross‑references (e.g. PVC insulated glass‑braided cable to Specification AN‑J‑C‑48a or other CASA‑approved Class II fire‑resistant cable).","Operational/procedural requirements combined with hardware changes (cockpit test switches that check lamps, circuit protection and wiring continuity; electrical redundancy for extinguisher bottles).","Technical vagueness in some performance standards (e.g. \"install…at suitable locations\", \"sufficient number of rivets\"), requiring engineering judgement and regulator interaction.","Multiple safety‑critical routing and protection requirements for cables and hoses (abrasion protection, routing to cooler parts, prohibitions on clipping to diaphragm).","Compatibility and certification constraints (approved types only for detectors and components) increasing procurement and compliance complexity.","Compliance timing requirement tied to flight hours creates programmatic planning needs for operators."],"plain_english_summary":"**What this instrument does (mechanically)\n\n- Requires owners/operators of all Douglas DC‑3 series aeroplanes to modify engine nacelle fire protection systems so each engine nacelle has its own working detection and extinguisher system and related protections.\n\nKey mechanical requirements (by component):\n\n- Fire detectors: install either a continuous detector or at least six unit detectors in each engine accessory compartment, positioned around the nacelle and in the oil‑cooler airstream when present; detectors must be an approved type and each nacelle must have its own independent detector circuit with a cockpit test switch that checks wiring continuity, lamp indicators and circuit protection. (Fire Detectors; Detector Circuits)\n\n- Indicators and warnings: provide separate cockpit indicators for each nacelle (two red lamps in parallel per nacelle) placed so both pilots can see them and clearly tell which nacelle is indicated; provide a distinctive, silencable audible warning common to all detector circuits. (Indicators)\n\n- Fire extinguisher system: provide two independent extinguisher charges per nacelle (minimum weights specified), plumb to spray into the accessory compartment (and into the oil‑cooler honeycomb if the oil‑cooler airstream discharges there); extinguisher lines and spray rings forward of the firewall must be fireproof (short flexible runs may be fire‑resistant hose assemblies); electrically operated bottles must be wired so one failure does not disable the others. An existing installation that discharges extinguisant partly into the carburettor intake may be retained only if no more than 25% by weight enters the intake. (Fire Extinguisher System)\n\n- Fluid shut‑off valves: install quickly operable shut‑off valves for fuel, oil and hydraulic lines immediately aft of each nacelle firewall, inserted in lines to the engine‑driven pump. (Fluid Shut‑off Valves)\n\n- Ventilation of electrical accessories: ensure generator and magneto intake air does not come from the accessory compartment or next to the exhaust; replace vulnerable ventilation components with fire‑proof ones where burning/collapse could let fire spread. (Ventilation of Electrical Accessories)\n\n- Fluid lines and hoses: replace all flammable fluid/gas lines in the accessory compartment with approved flexible fire‑resistant hose assemblies or fire‑proof rigid lines with fire‑resistant flexible connections; replace oil tank to feather pump and forward oil drain lines with fire‑proof lines where they lie forward of the firewall. (Fluid Lines)\n\n- Electrical cables forward of the firewall: use specified fire‑resistant PVC insulated glass‑braided cable (or approved Class II fire‑resistant cable) on fire detectors, propeller feathering and critical starter circuit sections; protect glass‑braided cables against abrasion and sleeve or enclose other forward‑firewall cables; route cables where cooler and protected from physical damage and do not clip them to the engine diaphragm. (Electric cables)\n\n- Firewall sealing: reseal firewalls/diaphragms to prevent flame/gas passage between nacelle compartments; seal gaps, replace or shroud light alloy fittings with fire‑proof components or shields, and replace a sufficient number of light alloy rivets with steel rivets/bolts so the firewall remains intact if light alloy melts. (Sealing of Firewall Diaphragm)\n\n- Compliance timing: these modifications must be done within 100 hours time in service after the specified date unless already accomplished.\n\n\nWhy the instrument was issued (official explanation and testing that claim)\n\n- Officially the amendment removes a previous blanket prohibition (in Amendment 1) on the use of free hose and clamp assemblies. The explanatory note says that prohibition was unnecessary for the large‑diameter, low‑pressure applications used on these aeroplanes given their satisfactory service history. The directive keeps substantive fire‑protection upgrades while restoring limited permissibility for certain hose/clamp assemblies.\n\nTesting that claim against trade‑offs and incentives:\n\n- Who pays: aircraft owners/operators pay for parts, labour, downtime, and any certification/inspection required to demonstrate compliance. (See requirements for new detectors, wiring, hoses, valves, extinguisher bottles and firewall work.)\n\n- Who decides/approves: components must be of an \"approved type\" and installations meet Civil Aviation Safety Authority (CASA) airworthiness / AD enforcement. That channels work to certificated suppliers and maintenance organisations.\n\n- Behaviour change: owners/operators must inspect, upgrade, or replace detectors, wiring, extinguisher systems, fluid lines, ventilation and firewall hardware. They must also adopt cockpit test routines and ensure extinguisher bottle wiring has required redundancy.\n\n- Costs vs benefits: the instrument concentrates costs on DC‑3 owners/operators (one identifiable group) while benefits (reduced risk of engine nacelle fire spread) are safety‑oriented and diffuse. It raises maintenance and parts procurement costs and may require limited grounding/downtime while work is done. Requiring approved parts and specific cable types increases demand for certified parts and maintenance services.\n\n- Compliance options and substitution effects: the AD allows alternatives in some places (e.g., fire‑proof rigid lines instead of flexible hose assemblies; retention of existing installations that only let up to 25% of extinguisant into carburettor intake). Those options reduce costs in some configurations and permit operators to choose among acceptable engineering approaches.\n\n- Implementation risks and administrative burden: operators must locate approved detectors and cables that meet the specified standards (including AN‑J‑C‑48a or CASA‑approved equivalents), ensure correct routing and abrasion protection of glass‑braided cables, and document compliance within the AD timeframe. That creates workload for maintenance organisations and requires technical judgement about what is \"sufficient\" (for example, how many rivets to replace) — this invites interaction with the regulator or delegated engineers for interpretation.\n\n- Market effects: demand for fire‑resistant hoses, specified cable types, extinguisher bottles and approved detectors will increase; small maintenance shops may need to subcontract to approved suppliers, concentrating work with certificated overhaul organisations.\n\n\nWho is affected\n\n- All operators and owners of Douglas DC‑3 series aeroplanes (the AD states applicability to all models). Maintenance organisations and suppliers of approved detectors, cables, hoses and extinguisher systems are also affected.\n\n\nNet mechanical effect in one sentence\n\n- The AD mandates physical upgrades to engine nacelle fire detection, warning, suppression, fluid shut‑offs, fire‑resistant wiring/hose installations and firewall sealing so each nacelle has an independent, testable detection circuit and at least two independent extinguisher charges with protected delivery and circuitry.\n\n(References to specific paragraph headings in the AD: Fire Detectors; Detector Circuits; Indicators; Fire Extinguisher System; Fluid Shut‑off Valves; Ventilation of Electrical Accessories; Fluid Lines; Electric cables; Sealing of Firewall Diaphragm.)"},"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"},"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive maintains its original scope: mandatory safety modifications for DC-3 engine fire protection. Amendment 2 makes a minor technical adjustment (removing the hose and clamp prohibition from Amendment 1) but does not expand beyond the original purpose of ensuring adequate fire detection, suppression, and containment systems."},"complexity_factors":["Technical aviation terminology throughout (e.g., 'nacelle', 'firewall diaphragm', 'propeller feathering', 'honeycomb')","Precise material specifications requiring cross-reference to external standards (e.g., 'Specification AN-J-C-48a', 'fire-resistant Class II')","Nested conditional requirements with alternatives (e.g., 'continuous type detector OR minimum of six unit detectors'; 'fire-proof rigid lines OR fire-resistant coupled flexible hose assemblies')","Multiple sub-paragraph hierarchies (Requirement 1 → Fire Detectors → (a), (b); Detector Circuits → (a), (b); etc.) creating dense structure","Specific quantitative thresholds (6 detectors, 7 pounds CO2, 6 pounds methyl bromide, 25% by weight, 100 hours)","Cross-references to previous amendments (Amdt 1) and external regulatory framework (Civil Aviation Regulations 1998, Part 39)"],"plain_english_summary":"This Airworthiness Directive requires all Douglas DC‑3 aircraft in Australia to have improved engine-nacelle fire protection: upgraded detectors and cockpit warnings, two extinguisher charges per engine, emergency shut‑off valves, fire‑resistant/ fire‑proof hoses and wiring, sealed firewalls, and safer ventilation routing. It affects every DC‑3 operator and was mandated to close serious engine‑fire safety gaps (compliance within 100 flying hours after 31 March 1984). Amendment 2 also rescinds a prior ban on certain hose-and-clamp assemblies."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dc3-15-amdt-2-engine-nacelle-fire-protection-modifications","history":"/api/acts/ad-dc3-15-amdt-2-engine-nacelle-fire-protection-modifications/history","analysis":"/api/acts/ad-dc3-15-amdt-2-engine-nacelle-fire-protection-modifications/analysis","conflicts":"/api/acts/ad-dc3-15-amdt-2-engine-nacelle-fire-protection-modifications/conflicts","importantCases":"/api/acts/ad-dc3-15-amdt-2-engine-nacelle-fire-protection-modifications/important-cases","documents":"/api/acts/ad-dc3-15-amdt-2-engine-nacelle-fire-protection-modifications/documents"}}