{"id":"F2006B08803","name":"AD/DC3/28 Reissue - Hydraulic System - Modification","slug":"ad-dc3-28-reissue-hydraulic-system-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52170,"registerId":"commonwealth-F2006B08803-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DC3/28 Reissue - Hydraulic 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 DC3 Series Aeroplanes\n\n \n\n# AD/DC3/28\n\nReissue\n\nApplicability: All models.\n\n# Hydraulic System - Modification 1/84\n\n \n\nDocument: Douglas SB No 239.\n\n \n\nCompliance: Unless already accomplished within 100 hours time in service after 31 May 1984.\n\n \n\nBackground: This Directive is reissued with no changes to the requirement. In the event of an engine failure during the take-off phase, this modification ensures the availability of hydraulic pressure to raise the undercarriage if required.\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\n \n\n \n\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive explicitly states it is reissued with no changes to the requirement (Background: This Directive is reissued with no changes to the requirement.), so the scope of required action remains the same as the prior version: perform the hydraulic modification per Douglas SB No 239 on all DC‑3 models within the stated flight‑hour window unless already accomplished."},"complexity_factors":["Single prescriptive action: requires one specific modification (Document: Douglas SB No 239).","Clear applicability: applies to all DC‑3 models (Applicability: All models.).","Fixed compliance metric: deadline given as 100 hours time in service after a specified date (Compliance: ...within 100 hours time in service after 31 May 1984.).","Reissue without technical change reduces interpretive complexity (Background: This Directive is reissued with no changes to the requirement.).","Dependency on an external technical document (Douglas SB No 239) for procedural detail creates a secondary source to consult.","Practical complexity from parts, qualified labour, and scheduling availability despite legal simplicity."],"plain_english_summary":"What this directive does mechanically\n\n- Requires installation of a specific hydraulic-system modification on Douglas DC‑3 series aeroplanes by following Douglas Service Bulletin No. 239 (Document: Douglas SB No 239). (Document: Douglas SB No 239.)\n- Applies to all DC‑3 models. (Applicability: All models.)\n- The work must be completed within 100 hours time in service after 31 May 1984 unless the modification has already been done. (Compliance: Unless already accomplished within 100 hours time in service after 31 May 1984.)\n- The Civil Aviation Safety Authority (CASA) has reissued the airworthiness directive but has not changed its technical requirement. (Background: This Directive is reissued with no changes to the requirement.)\n\nWhy the rule exists (official rationale and how it operates)\n\n- The stated purpose is to ensure that, if an engine fails during take‑off, hydraulic pressure will still be available to raise the undercarriage if needed. That is the safety objective described by the issuing text. (Background: In the event of an engine failure during the take-off phase, this modification ensures the availability of hydraulic pressure to raise the undercarriage if required.)\n\nWho pays, who decides, and what changes in behaviour\n\n- Who pays: Aircraft owners or operators must pay for the modification and any associated labour, parts and downtime because the Compliance clause mandates the work unless it is already done. (Compliance: ...within 100 hours time in service after 31 May 1984.)\n- Who decides / enforces: CASA issues and enforces the airworthiness directive under Part 39 (header: Civil Aviation Safety Authority — Schedule of Airworthiness Directives). Compliance is mandatory for affected aircraft. (COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - CIVIL AVIATION SAFETY AUTHORITY — SCHEDULE OF AIRWORTHINESS DIRECTIVES.)\n- Behavioural change: Operators must schedule and perform the modification in their maintenance programme; maintenance facilities must be able to carry out the work to Douglas SB No 239.\n\nCosts, incentives, and trade‑offs (testing the stated purpose against practical impacts)\n\n- Direct costs: Purchase of parts, labour and aircraft downtime to perform Douglas SB No 239. (Document: Douglas SB No 239; Compliance: ...100 hours time in service.)\n- Incentives: Operators are incentivised to complete the modification promptly to meet the mandatory deadline and to avoid regulatory non‑compliance or grounding risk.\n- Compliance burden: The deadline expressed as \"100 hours time in service after 31 May 1984\" creates a short, measurable compliance window tied to flight hours rather than calendar time; recordkeeping and accurate time‑in‑service tracking will be required. (Compliance: Unless already accomplished within 100 hours time in service after 31 May 1984.)\n- Implementation risks and practical constraints: Availability of parts or qualified maintenance personnel and scheduling of aircraft downtime could delay compliance in practice; the directive text does not describe exemptions, staging or supply arrangements. (Document: Douglas SB No 239; Compliance: ...)\n- Effects on private enterprise: Independent maintenance organisations that can perform SB No 239 may receive additional business; operators incur higher short‑term maintenance costs that affect operating budgets and scheduling. (Document: Douglas SB No 239.)\n\nTrade‑offs and opportunity costs\n\n- The directive imposes an immediate maintenance expense and downtime in exchange for the operational effect the authority describes (availability of hydraulic pressure for undercarriage operation after an engine failure during take‑off). (Background: ...ensures the availability of hydraulic pressure to raise the undercarriage...) \n- The reissue statement indicates no technical change to the requirement, so the directive preserves prior obligations rather than expanding them. (Background: This Directive is reissued with no changes to the requirement.)\n\nDiscretion and scope of the rule\n\n- The directive specifies a single technical action (modification per SB No 239) and a fixed compliance window; there is little operational discretion for owners beyond timing and selection of maintenance provider. (Document: Douglas SB No 239; Compliance: ...100 hours time in service.)\n\nNotes on interpretation\n\n- The document supplied is brief and refers to Douglas SB No 239 for technical details; the SB will contain the specific steps, parts and certification records required to demonstrate compliance. (Document: Douglas SB No 239.)"},"kimi_summary":{"content_quality":"ok","complexity_score":1,"scope_assessment":{"changed":false,"description":"This is a straightforward reissue of an existing airworthiness directive with no changes to requirements. The scope remains exactly as originally intended: a specific safety modification for DC-3 hydraulic systems."},"complexity_factors":["Extremely short document (approximately 150 words)","No defined terms section","No cross-references to other legislation beyond a single service bulletin citation","Single, unconditional compliance requirement with one simple exception ('unless already accomplished')","No nested conditions or exceptions","Clear, plain language throughout with minimal aviation jargon ('undercarriage' is explained by context)"],"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 aircraft.\n\n**What it does:** It requires owners and operators of **Douglas DC-3 aircraft** (all models) to modify the hydraulic system according to **Douglas Service Bulletin No. 239**. This modification ensures that if an engine fails during take-off, there will still be enough hydraulic pressure available to raise the landing gear (undercarriage) if the pilot needs to.\n\n**Who it affects:** Anyone who owns, operates, or maintains a Douglas DC-3 aeroplane in Australia.\n\n**When it had to be done:** The modification must have been completed within **100 hours of flying time** after 31 May 1984 — unless it was already done before that deadline.\n\n**Why it matters:** Engine failure during take-off is a critical emergency. Without this modification, a failed engine could deprive the hydraulic system of pressure, leaving the landing gear stuck down. This would prevent the pilot from retracting the gear to improve climb performance and safety during a critical phase of flight."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dc3-28-reissue-hydraulic-system-modification","history":"/api/acts/ad-dc3-28-reissue-hydraulic-system-modification/history","analysis":"/api/acts/ad-dc3-28-reissue-hydraulic-system-modification/analysis","conflicts":"/api/acts/ad-dc3-28-reissue-hydraulic-system-modification/conflicts","importantCases":"/api/acts/ad-dc3-28-reissue-hydraulic-system-modification/important-cases","documents":"/api/acts/ad-dc3-28-reissue-hydraulic-system-modification/documents"}}