{"id":"F2006B09160","name":"AD/DHC-6/72 - Corrosion Prevention and Control - 2","slug":"ad-dhc-6-72-corrosion-prevention-and-control-2","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52871,"registerId":"commonwealth-F2006B09160-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DHC-6/72 - Corrosion Prevention and Control - 2","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)  \nDHC-6 (Twin Otter) Series Aeroplanes\n\nAD/DHC-6/72 Corrosion Prevention and Control \\- 2 13/99\n\nApplicability: Model DHC-6 aircraft that are in full compliance with Airworthiness Directives AD/DHC-6/69 (CF-94-12) or AD/DHC-6/69 Amdt 1 (CF-99-12R1).\n\nRequirement: Action in accordance with the technical requirements of Transport Canada (TC) AD CF-99-11.\n\nThe following is a substitution for the last paragraph of the Requirement document which states reporting requirements:\n\nCorrosion classified as Level 1 need not be reported.\n\nLevel 2 corrosion may be consolidated with a quarterly report of corrective action, and submitted to the Authority District (Airport) Office under cover of a single MDR.\n\nLevel 3 corrosion shall be reported by MDR.\n\nCompliance: As specified in the Requirement document with a revised effective date of 30 December 1999.\n\nThis Airworthiness Directive becomes effective on 30 December 1999.\n\nBackground: The Corrosion Prevention and Control Manual requirement for repetitive inspections after initial compliance was deleted by the issue of AD/DHC-6/69 Amdt 1. This Directive is issued in response to a new TC AD which requires Corrosion Tasks (CTs) to be performed on a repetitive basis and provides the option of performing the CTs during several maintenance visits in one year (Part A) or a specific group of CTs on an annual basis over a five year period (Part B).","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope — it applies only to DHC-6 Twin Otter aircraft and specifically addresses corrosion prevention. It does not expand beyond its original safety purpose."},"complexity_factors":["Short, single-purpose directive (approximately 250 words)","Only 4 defined/referenced terms (Level 1/2/3 corrosion, MDR, CTs, Part A/Part B)","Simple conditional structure: applicability limited to aircraft already compliant with specific prior ADs","Single cross-reference to Canadian Transport Canada AD CF-99-11","Clear tiered reporting structure with three distinct levels","No nested exceptions or complex procedural logic"],"plain_english_summary":"This CASA Airworthiness Directive requires owners/operators of DHC‑6 Twin Otter aircraft (already subject to AD/DHC‑6/69 or its revision) to carry out recurring corrosion inspections per new Canadian rules, restoring ongoing checks that had been removed earlier.\n\nInspections may be scheduled across multiple visits or as annual cycles; reporting tiers apply (no report for minor, quarterly for moderate, immediate MDR for serious). Effective 30 December 1999."},"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"This directive reverses the earlier deletion of repetitive inspection requirements by reinstating repetitive Corrosion Tasks and formalising reporting tiers and scheduling options. It replaces the prior manual requirement with mandatory compliance with TC AD CF-99-11 and specific MDR reporting rules (Background; Requirement). Operators now face recurring inspection and reporting obligations rather than a one-off compliance regime."},"complexity_factors":["Cross-reference to Transport Canada AD CF-99-11 imposes external technical requirements to be applied locally (Requirement).","Three-tiered corrosion reporting regime (Level 1/2/3) with differing submission methods increases administrative distinctions.","Two scheduling options for repetitive Corrosion Tasks (Part A multiple visits or Part B annual grouping over five years) create planning choices for operators (Background).","Applicability is conditional on prior compliance with AD/DHC-6/69, creating a dependency on historical maintenance status.","Mandatory use of Maintenance Defect Reports (MDRs) for certain findings imposes recurring recordkeeping and submission costs."],"plain_english_summary":"This directive requires DHC-6 (Twin Otter) aircraft already compliant with AD/DHC-6/69 to follow Transport Canada AD CF-99-11 for corrosion prevention tasks and reporting (Requirement). It sets reporting tiers: Level 1 need not be reported, Level 2 may be included in a quarterly corrective-action report under one MDR, and Level 3 must be reported by MDR. Effective date: 30 December 1999. The directive also restores repetitive corrosion-task schedules and allows either multiple maintenance visits in a year (Part A) or annual groups over five years (Part B) (Background)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-6-72-corrosion-prevention-and-control-2","history":"/api/acts/ad-dhc-6-72-corrosion-prevention-and-control-2/history","analysis":"/api/acts/ad-dhc-6-72-corrosion-prevention-and-control-2/analysis","conflicts":"/api/acts/ad-dhc-6-72-corrosion-prevention-and-control-2/conflicts","importantCases":"/api/acts/ad-dhc-6-72-corrosion-prevention-and-control-2/important-cases","documents":"/api/acts/ad-dhc-6-72-corrosion-prevention-and-control-2/documents"}}