{"id":"F2006B09293","name":"AD/DO-27/1 - Steel Band Tensioners - Replacement","slug":"ad-do-27-1-steel-band-tensioners-replacement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":53367,"registerId":"commonwealth-F2006B09293-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DO-27/1 - Steel Band Tensioners - Replacement","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)  Dornier DO-27 Series Aeroplanes\n\n \n\nAD/DO-27/1 Steel Band Tensioners - Replacement 8/61\n\nApplicability: All models Q-1, Q-3, Q-4 and H2.\n\n \n\nRequirement: 1. Replace the steel band tensioners (Drawing No. 27-404-01 H02) with tension chains (Drawing No. 27-416-01 H02).\n\n \n\n2.    SB No. 27/11 dated 22 February 1961, issued by Dornier-Merke G.m.b.H Munchen-Neuaubing, Federal Republic of Germany, covers the modification work required. or\n\n \n\n3.    LBA AD 6.27. Compliance: Before 1 September 1971.\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":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive focused on one specific mechanical component replacement. It has not expanded beyond its original narrow technical scope."},"complexity_factors":["Very short document (under 200 words)","Only 4 defined model variants in applicability","Single mechanical modification requirement with clear part numbers","No nested exceptions or conditional logic","Simple compliance deadline structure","References external technical documents (service bulletin and German AD) rather than incorporating complex internal cross-references"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order — issued by Australia's Civil Aviation Safety Authority (CASA) for specific Dornier DO-27 aircraft models.\n\n**What it does:**\n- Requires owners/operators of certain Dornier DO-27 planes (models Q-1, Q-3, Q-4 and H2) to replace old \"steel band tensioners\" with newer \"tension chains\" in the aircraft.\n- The steel band tensioners are identified by drawing number 27-404-01 H02; they must be swapped for tension chains (drawing number 27-416-01 H02).\n\n**Who it affects:**\n- Anyone operating or maintaining Dornier DO-27 aircraft in Australia, specifically the Q-1, Q-3, Q-4 and H2 variants.\n\n**Why it matters:**\n- Airworthiness Directives are legally binding safety instructions. If you don't comply, your aircraft cannot legally fly.\n- This particular directive references a 1961 service bulletin from the German manufacturer (Dornier) and a German aviation authority directive (LBA AD 6.27), indicating this addresses a known safety defect or wear issue with the original steel band tensioners.\n- The deadline for compliance was 1 September 1971 — meaning this is a historical directive that would have been complied with decades ago for any aircraft still in service."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive applies to the explicitly listed Dornier DO-27 models (Q-1, Q-3, Q-4 and H2) and mandates the replacement specified by drawing numbers. The text contains no indication that the scope has been expanded or narrowed relative to the directive's operative instructions; it remains focused on the stated models and parts. (Applicability; Requirement 1)"},"complexity_factors":["Single clear technical action required (replace part A with part B) (Requirement 1)","Limited number of affected aircraft models specified (Applicability)","Single, fixed compliance deadline (Compliance)","References to external technical documents (Dornier Service Bulletin No. 27/11 and LBA AD 6.27) increase administrative steps to obtain procedures (Requirement 2–3)","Specific drawing numbers required for removed and replacement parts, requiring correct parts procurement (Requirement 1)"],"plain_english_summary":"What this instrument does, mechanically\n\n- It requires that on Dornier DO-27 aeroplanes of models Q-1, Q-3, Q-4 and H2 the existing steel band tensioners (Drawing No. 27-404-01 H02) be removed and replaced with tension chains (Drawing No. 27-416-01 H02). (Applicability; Requirement 1)\n\n- The replacement work is to be performed in accordance with Dornier Service Bulletin No. 27/11 dated 22 February 1961, or by complying with LBA AD 6.27. (Requirement 2 and 3)\n\n- The deadline for completing the replacement is before 1 September 1971. (Compliance)\n\nWho this affects\n\n- Owners and operators of Dornier DO-27 models Q-1, Q-3, Q-4 and H2 must ensure the part replacement is done by the stated deadline. (Applicability; Requirement 1; Compliance)\n\n- Maintenance organisations and technicians who perform structural or control-system modifications will be the parties doing the physical work and must follow the specified Service Bulletin or the LBA AD procedure. (Requirement 2)\n\nWhy it matters (stated and implied)\n\n- The document is an airworthiness directive titled “Steel Band Tensioners - Replacement,” and it prescribes a mandatory physical modification. The text itself gives no narrative justification for the change beyond the instruction to replace the specified parts. (Title; Requirement 1–3)\n\nPractical effects, costs and incentives (mechanical and market implications)\n\n- Who pays: aircraft owners/operators will incur the direct cost of parts (tension chains) and labour to carry out the modification, and will also bear any aircraft downtime while work is done. (Requirement 1; Compliance)\n\n- Procurement and supply: the modification specifies precise drawing numbers for both the removed item and its replacement (27-404-01 H02 and 27-416-01 H02). That channels demand to suppliers or parts inventories that can supply items conforming to those drawings; maintenance organisations must obtain the correct drawings or Service Bulletin to perform the work. (Requirement 1–2)\n\n- Compliance burden: operators must locate and apply the Dornier Service Bulletin dated 22 February 1961 or follow LBA AD 6.27 to perform the modification; this imposes administrative steps to obtain and follow the technical instructions and to schedule the work before the deadline. (Requirement 2; Compliance)\n\n- Behavioural effect on maintenance market: independent maintenance providers that can perform the SB or meet LBA AD procedures may capture the work; firms that cannot access the required instructions or parts may be excluded from supplying that service for these aircraft. (Requirement 2)\n\n- Timing and scheduling incentive: the fixed compliance date (before 1 September 1971) creates an operational deadline that will push owners to prioritise the work and allocate hangar time and funds accordingly. (Compliance)\n\nTrade-offs, implementation risk and opportunity costs\n\n- Opportunity cost: hours and funds used to perform this mandated modification cannot be used for other maintenance or upgrades during the same period. (Requirement 1; Compliance)\n\n- Implementation risk: if the specified replacement parts, drawings, or the Service Bulletin are hard to obtain, operators may face delays or higher costs to meet the deadline. The AD points to a specific Service Bulletin or an LBA AD as the authorised procedures, so authorised documentation is the path to compliance. (Requirement 2)\n\n- Discretion: the directive sets the required outcome (replacement to a part with a specified drawing number) and points to a Service Bulletin or LBA AD for the work instructions. It does not leave substantive technical discretion beyond following those referenced documents. (Requirement 1–3)\n\nConcentrated benefits and diffuse costs (mechanics only)\n\n- The demand created by the replacement is concentrated on suppliers of the tension chains that meet Drawing No. 27-416-01 H02 and on maintenance providers able to perform the SB procedure. The costs (parts, labour, downtime) are borne by the many owners/operators of the affected aircraft models. (Applicability; Requirement 1–2)\n\nSubstitution and contract effects\n\n- Operators will substitute the original steel band tensioners (27-404-01 H02) with tension chains (27-416-01 H02), changing which parts and suppliers are contracted for future maintenance. Contracts for ongoing support or spares that referenced the old part will need amendment to reflect the new drawing number. (Requirement 1)\n\nSummary of source citations\n\n- Applicability: specifies affected models. (Applicability)\n- Requirement 1: mandates replacement and gives drawing numbers. (Requirement 1)\n- Requirement 2: references Dornier Service Bulletin No. 27/11 dated 22 February 1961 for modification work. (Requirement 2)\n- Requirement 3: references LBA AD 6.27 as an alternative compliance path. (Requirement 3)\n- Compliance: sets the deadline of before 1 September 1971. (Compliance)\n\n"}},"importantCases":[],"_links":{"self":"/api/acts/ad-do-27-1-steel-band-tensioners-replacement","history":"/api/acts/ad-do-27-1-steel-band-tensioners-replacement/history","analysis":"/api/acts/ad-do-27-1-steel-band-tensioners-replacement/analysis","conflicts":"/api/acts/ad-do-27-1-steel-band-tensioners-replacement/conflicts","importantCases":"/api/acts/ad-do-27-1-steel-band-tensioners-replacement/important-cases","documents":"/api/acts/ad-do-27-1-steel-band-tensioners-replacement/documents"}}