{"id":"F2006B08841","name":"AD/DC4/34 Amdt 1 - Electrical Distribution Bus","slug":"ad-dc4-34-amdt-1-electrical-distribution-bus","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52317,"registerId":"commonwealth-F2006B08841-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DC4/34 Amdt 1 - Electrical Distribution Bus","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/DC4/34\n\nAmdt 1\n\n  \nElectrical Distribution Bus 4/97\n\nApplicability: All DC-4 and C-54 aeroplanes.\n\nRequirement: 1. Inspect the electrical distribution bus to ensure that at least 12.7mm (0.5 inch) clearance is maintained between the bus and protuberances likely to “ground” the bus in the nacelle areas.\n\nNote 1: Particular attention should be given to the areas around the engine control pulleys and the pulley guide brackets.\n\n    2. Remove the large gauge nacelle-to-bus feeder cables, that are run in metallic conduits, from the conduits and inspect them for chafing or mechanical deterioration of the insulation.\n\nNote 2: Oil-soaked insulation alone is not considered as sufficient cause to require the replacement of the cables.\n\n    3. If any cables are found to be damaged during the Requirement 2 inspection, replace the cables with cables conforming to Douglas Aircraft Company (DAC) specification BXS7008, per MIL-L-22759 or DAC specification DMS2426, per MIL-W-81381/12.\n\n    4. If not previously accomplished, inspect the electrical distribution bus to ensure that the supporting brackets are of an approved DAC standard quality and that cushioned non grounding cable clamps are used for clamping the bus onto the brackets. Replace any substandard brackets or clamps.\n\nNote 3: FAA AD 48-09-02 and Douglas Service Letter A214TS-1245/SRD-530 dated 10 October 1947 refer.\n\nCompliance: For Requirement 1 \\- Prior to 22 May 1997 and thereafter at intervals not to exceed 400 hours time in service.\n\nFor Requirement 2 \\- Prior to 22 July 1997 and thereafter at intervals not to exceed 8000 hours time in service.\n\nFor Requirement 3 \\- Prior to further flight. For Requirement 4 \\- Prior to 22 July 1997.\n\nThis Amendment becomes effective on 27 March 1997.\n\nBackground: Actions mandated by this Directive are designed to preclude the possibility of short circuits occurring in the electrical distribution bus running from nacelles number one to four, which is impractical to protect by circuit protection devices.\n\nThis Directive was originally issued in 1948, this amendment both amplifies the requirements and clarifies the compliance intervals.\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\nThe original issue date of this Airworthiness Directive is unknown.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This amendment remains tightly focused on its original purpose: preventing electrical short circuits in DC-4/C-54 engine nacelles. The 1997 amendment amplifies inspection requirements and clarifies compliance intervals compared to the 1948 original, but does not expand to cover other aircraft systems, other aircraft types, or unrelated safety issues. The scope is appropriately narrow for a vintage aircraft-specific airworthiness directive."},"complexity_factors":["Very short document (approximately 300 words)","Only 4 substantive requirements with clear sequential numbering","Minimal defined terms — only standard aviation abbreviations (DAC, FAA, MIL-spec)","No cross-references to other legislation or complex conditional logic","Simple compliance structure with specific dates and hour-intervals","Straightforward applicability statement covering only two aircraft models","Background section provides clear rationale without legal caveats"],"plain_english_summary":"This safety rule requires owners/operators of Douglas DC-4/C-54 aircraft in Australia to inspect and, where necessary, repair or replace electrical wiring and buswork routed through engine nacelles to prevent short circuits, fire, or system failure. It mandates clearance checks, cable inspections and replacement with approved parts, and secure cushioned mounting. It updates a 1948 requirement with clearer deadlines because these circuits lack circuit-breaker protection."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"This amendment amplifies and clarifies inspection and compliance intervals for an existing 1948 Airworthiness Directive but does not expand the fundamental scope of the original requirement. It retains the same safety objective—preventing short circuits in the nacelle-to-bus electrical runs—while specifying clear inspection frequencies, a minimum physical clearance, and acceptable replacement cable specifications."},"complexity_factors":["Short document with 4 principal requirements (Requirements 1–4)","Two recurring inspection intervals with different periodicities (400 hours and 8,000 hours)","Specific numeric technical requirement (12.7 mm clearance)","Mandatory replacement tied to external technical specifications (DAC BXS7008 / MIL-L-22759 and DAC DMS2426 / MIL-W-81381/12)","One operational exception: oil-soaked insulation alone does not mandate replacement (Note 2)","References to external materials (FAA AD and Douglas Service Letter) rather than full technical detail","Some administrative ambiguity over what counts as \"approved DAC standard quality\" for brackets and clamps"],"plain_english_summary":"**What this directive does (mechanically)\n\n- Applies to: all Douglas DC-4 and military C-54 aeroplanes.\n\n- Inspections and physical clearances:\n  - Require an inspection to confirm the electrical distribution bus in each nacelle has at least 12.7 mm (0.5 in) clearance from any protuberances that could cause an electrical ground (Requirement 1).\n  - Pay particular attention to areas around the engine control pulleys and pulley guide brackets (Note 1).\n\n- Feeder cable checks and replacement:\n  - Remove the large-gauge nacelle-to-bus feeder cables from their metallic conduits and inspect them for chafing or mechanical damage to the insulation (Requirement 2). Oil-soaked insulation alone does not automatically require replacement (Note 2).\n  - If any feeder cables are found damaged, they must be replaced before the next flight, using cables that meet Douglas Aircraft Company (DAC) specification BXS7008 (MIL-L-22759) or DAC specification DMS2426 (MIL-W-81381/12) (Requirement 3).\n\n- Support hardware standard:\n  - Inspect the bus-supporting brackets and ensure they meet an approved DAC standard and that cushioned, non-grounding cable clamps secure the bus to the brackets. Replace substandard brackets or clamps (Requirement 4).\n\n- Timing (compliance intervals):\n  - Requirement 1 (clearance checks): complete the first inspection prior to 22 May 1997 and then every 400 hours time in service.\n  - Requirement 2 (feeder cable removal and inspection): complete the first inspection prior to 22 July 1997 and then every 8,000 hours time in service.\n  - Requirement 3 (replacement of damaged cables): replace before further flight if damage is found.\n  - Requirement 4 (brackets and clamps): complete the inspection prior to 22 July 1997.\n\n- Standards referenced: FAA AD 48-09-02 and Douglas Service Letter A214TS-1245/SRD-530 (dated 10 October 1947) are cited as related material.\n\nWhy the directive says it matters\n\n- The stated purpose is to prevent short circuits on the electrical distribution bus that runs from nacelles 1–4. The directive notes that those bus runs are impractical to protect with conventional circuit-protection devices, so physical separation, correct supports, and undamaged insulation are required instead.\n\nWho this affects and who pays\n\n- Aircraft owners/operators of DC-4/C-54 type aeroplanes must perform the inspections and fixes. Costs fall on those operators: labour for inspections (including removal of cables from conduits), parts if clamps/brackets or cables must be replaced, and potential downtime for the aircraft.\n\nHow it changes operator behaviour (incentives and compliance burden)\n\n- Operators must schedule recurring inspections (400-hour and 8,000-hour cycles) and act immediately to replace any damaged feeder cables before further flight. They must also verify that mounting hardware meets an approved DAC standard and use cushioned, non-grounding clamps.\n\nPractical implementation issues, trade-offs and risks\n\n- Parts availability: the directive requires replacement cables to meet DAC/MIL specifications. For vintage aircraft, sourcing compliant cables and approved-quality brackets or clamps may be difficult or costly, which can increase downtime and maintenance expense.\n- Ambiguity in approval: the text requires \"approved DAC standard quality\" brackets. The directive does not specify the approving authority or detailed acceptance criteria, which creates some administrative discretion (airworthiness authority or approved maintenance organisation will need to interpret and document acceptance criteria).\n- Inspection work scope: removing large-gauge feeder cables from metallic conduits for inspection is labour-intensive and may require scheduled downtime; operators may bundle these inspections with other maintenance to reduce operational impact.\n- Safety vs cost trade-off: the directive enforces physical mitigations (clearance, clamps, new cables) because circuit protection is impractical for these bus runs. That shifts the mitigation burden to preventative inspection and replacement, concentrating costs on operators of older airframes.\n\nConcentrated benefits and diffuse costs\n\n- Benefits (reduced short-circuit risk) are concentrated on the aircraft operator and their passengers/crew through reduced electrical-failure risk. Costs (inspection labour and replacement parts) are also concentrated on operators of DC-4/C-54 types; the broader aviation system bears little direct cost.\n\nNotes and limits of the source\n\n- The directive clarifies compliance intervals and amplifies inspection/replacement requirements from an original 1948 issue. It references external standards (DAC and MIL specifications) and an FAA AD and Douglas service letter; those external documents will govern technical detail in replacements and approvals."},"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-dc4-34-amdt-1-electrical-distribution-bus","history":"/api/acts/ad-dc4-34-amdt-1-electrical-distribution-bus/history","analysis":"/api/acts/ad-dc4-34-amdt-1-electrical-distribution-bus/analysis","conflicts":"/api/acts/ad-dc4-34-amdt-1-electrical-distribution-bus/conflicts","importantCases":"/api/acts/ad-dc4-34-amdt-1-electrical-distribution-bus/important-cases","documents":"/api/acts/ad-dc4-34-amdt-1-electrical-distribution-bus/documents"}}