{"id":"F2006B02956","name":"AD/B737/56 - Engine Control Cable","slug":"ad-b737-56-engine-control-cable","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42298,"registerId":"commonwealth-F2006B02956-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B737/56 - Engine Control Cable","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)  Boeing 737 Series Aeroplanes\n\n \n\nAD/B737/56 Engine Control Cable 5/91\n\nApplicability: Model 737 series.\n\n \n\nRequirement: Action in accordance with the technical requirements of FAA AD 91-05-08 Amdt 39- 6906.\n\n \n\nNote: Boeing Service Letters 737-SL-76-2 A and 737-SL-76-9 refer.\n\n \n\nCompliance: As specified in the requirement document but with a revised effectivity date of 16 May 1991 for Australian registered aircraft.\n\n \n\nBackground: The FAA has received reports of engine control cable strand separation due to cable corrosion. This condition, if not corrected, could result in engine control cable separation and subsequent loss of engine control.\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":3,"scope_assessment":{"changed":true,"description":"The AD does not change the applicability (Model 737 series) but revises the effectivity date for Australian-registered aircraft to 16 May 1991 (Compliance). The instrument adopts the technical requirements of FAA AD 91-05-08 rather than reproducing them locally (Requirement)."},"complexity_factors":["Cross-reference to FAA AD for all technical requirements (Requirement) — adds an extra document to consult","Reference to Boeing service letters as related guidance (Note) — introduces additional external material","Revised effectivity date limited to Australian-registered aircraft (Compliance) — a narrow jurisdictional modification","Technical subject matter (engine control cable corrosion/strand separation) is specialised though the AD itself is short (Background)","Lack of embedded technical detail in the instrument — operators must obtain and interpret external documents (Requirement)"],"plain_english_summary":"### What this instrument does\n\nThis Airworthiness Directive (AD) applies to Boeing 737 series aircraft registered in Australia (Applicability). It requires operators to carry out the technical actions set out in the US Federal Aviation Administration (FAA) AD 91-05-08 Amdt 39-6906 (Requirement). The directive also points to Boeing Service Letters 737-SL-76-2 A and 737-SL-76-9 for related guidance (Note). For Australian-registered aircraft the AD’s effective date is set to 16 May 1991 (Compliance).\n\n### Why it exists (official rationale)\n\nThe background states that the FAA received reports of engine control cable strand separation caused by corrosion, and that, if not corrected, this could lead to engine control cable separation and loss of engine control (Background). The AD therefore directs corrective action to address that specific risk.\n\n### How it works mechanically\n\n- The Civil Aviation Safety Authority (CASA) has issued an AD that adopts the technical content of an FAA AD; operators must follow the FAA AD’s technical requirements (Requirement). \n- The AD signals Boeing service letters as additional reference material for the corrective work (Note). \n- Australian-registered aircraft are required to comply by the revised effectivity date of 16 May 1991 (Compliance).\n\n### Who decides, who pays, and what changes in behaviour\n\n- Decision authority: the AD is issued by the Civil Aviation Safety Authority by reference to the FAA AD and specifies the required technical actions (Requirement; Compliance).\n- Who pays: the text requires operators of applicable 737 aircraft to perform the mandated actions; therefore aircraft owners/operators will bear the direct costs of inspections, corrosion remediation, repairs or cable replacements required by the FAA AD and any referenced Boeing service letters (Requirement; Note). The AD itself does not allocate funding or state cost-recovery mechanisms.\n- Behavioural change: operators must inspect and, if necessary, repair or replace engine control cables according to the FAA AD and Boeing service letters. This may impose additional maintenance planning, potential aircraft downtime, and parts/labour expenses (Requirement; Note).\n\n### Trade-offs, compliance burden and implementation points to note\n\n- Compliance burden: the directive does not reproduce the technical steps; it mandates compliance with an external FAA AD (Requirement). Operators must obtain and follow that FAA document and the referenced Boeing service letters, which adds a step compared with a self-contained domestic regulation.\n- Discretion and dependence: by adopting the FAA AD’s technical requirements, the CASA instrument delegates detailed technical specification to the FAA document rather than setting those details in the Australian text (Requirement). The AD itself only revises the effectivity date for Australian aircraft (Compliance).\n- Opportunity costs and operational impact: following the FAA AD can require inspection time, maintenance resources, and possible part replacement, which can take aircraft out of service temporarily. The AD does not quantify these costs or prescribe any financial support (Requirement; Note).\n- Implementation risk: successful mitigation depends on operators locating and applying the FAA AD and Boeing service letters correctly. The AD does not include additional Australian-specific procedures beyond the revised effectivity date (Requirement; Note; Compliance).\n\n### Concentrated benefits and diffuse costs (mechanism, not judgement)\n\n- The safety benefit (reduced risk of engine control cable separation) accrues to operators, passengers and the public if the required actions are carried out (Background). \n- The direct costs (inspections, repairs, replacements, downtime) are concentrated on the aircraft owners/operators because they must carry out the mandated work; the AD text does not provide for cost-sharing or compensation (Requirement; Note).\n\n(References in parentheses refer to the labeled parts of the AD: Applicability, Requirement, Note, Compliance, Background.)"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-limited safety directive addressing a specific mechanical defect in a specific aircraft type. It has not expanded beyond its original purpose of mandating cable corrosion inspections and repairs."},"complexity_factors":["Very short document (approximately 150 words)","Only 1 defined term implicitly ('Model 737 series' in applicability)","No cross-references to other legislation — only references to external FAA directive and Boeing service letters","Simple conditional structure: single requirement with single compliance date","No nested exceptions or complex logical operators","Incorporates external technical standard by reference (FAA AD 91-05-08) rather than reproducing it"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety notice issued by Australia's Civil Aviation Safety Authority (CASA) for specific aircraft.\n\n**What it does:**\nOrders owners and operators of **Boeing 737 series aircraft** to inspect and fix a specific safety problem with **engine control cables**. These cables connect the pilot's throttle controls to the engines. The directive requires compliance with a US Federal Aviation Administration (FAA) safety order (AD 91-05-08) that addresses corrosion causing cable strands to break apart.\n\n**Why it matters:**\nCorroded control cables can snap, causing **complete loss of engine control** — a potentially catastrophic failure. The directive mandates specific maintenance actions to prevent this.\n\n**Who it affects:**\n- Australian-registered Boeing 737 operators\n- Maintenance organisations servicing these aircraft\n\n**Key details:**\n- **Compliance deadline:** 16 May 1991 for Australian aircraft (different from the US date)\n- **Reference documents:** Boeing Service Letters 737-SL-76-2 A and 737-SL-76-9 provide additional guidance\n- **Nature of the defect:** Cable strand separation due to corrosion"}},"importantCases":[],"_links":{"self":"/api/acts/ad-b737-56-engine-control-cable","history":"/api/acts/ad-b737-56-engine-control-cable/history","analysis":"/api/acts/ad-b737-56-engine-control-cable/analysis","conflicts":"/api/acts/ad-b737-56-engine-control-cable/conflicts","importantCases":"/api/acts/ad-b737-56-engine-control-cable/important-cases","documents":"/api/acts/ad-b737-56-engine-control-cable/documents"}}