{"id":"F2006B10513","name":"AD/HS 125/72 - Engine Mounting Cowling Damage","slug":"ad-hs-125-72-engine-mounting-cowling-damage","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":116289,"registerId":"commonwealth-F2006B10513-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HS 125/72 - Engine Mounting Cowling Damage","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)  British Aerospace BAe 125 Series Aeroplanes\n\n \n\nAD/HS 125/72 Engine Mounting Cowling Damage 10/85\n\nApplicability: All models fitted with Garrett TFE 731-3R-1H engines.\n\n \n\nRequirement: Inspect and repair in accordance with British Aerospace 125 S.B. 71-38.\n\n \n\nNote: If engine mounts are found to be damaged on aircraft fitted with thrust reversers, their fatigue life is limited. Refer AD/HS 125/45 at latest amendment.\n\n \n\nCompliance: Prior to 30 November 1985.\n\n \n\nBackground: Several cases of damage to the forward engine mounting caused by fouling with the cowling have been reported. This damage could result in reduction of fatigue life.\n\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The AD’s expressed scope is limited to BAe 125 aeroplanes fitted with Garrett TFE 731-3R-1H engines and requires inspection/repair per a specific service bulletin to address forward engine-mount damage from cowling fouling (\"Applicability\", \"Requirement\", \"Background\"). The text contains no indication that the scope has been broadened or narrowed from the directive’s stated purpose; it remains focused on that specific aircraft/engine combination and the stated defect."},"complexity_factors":["Narrow, well-defined applicability (specific aircraft models with Garrett TFE 731-3R-1H engines) (\"Applicability\").","Single principal mandatory action: inspect and repair per a named service bulletin (\"Requirement\").","Reliance on an external technical document (British Aerospace 125 S.B. 71-38) increases procedural dependence on that bulletin’s content (\"Requirement\").","Fixed compliance deadline introduces scheduling and operational constraints (\"Compliance\").","Cross-reference to another AD (AD/HS 125/45) for cases involving thrust reversers adds a secondary compliance pathway for some aircraft (\"Note\").","Technical judgement and repair execution rest with maintenance providers following the service bulletin, creating modest interpretive/implementation discretion (\"Requirement\")."],"plain_english_summary":"This Airworthiness Directive (AD) requires owners/operators of certain British Aerospace BAe 125 aircraft to inspect and, if necessary, repair engine mountings because of reported damage from the engine cowling fouling the forward mounting.\n\n- What the instrument requires mechanically: Inspect and repair the forward engine mounting in accordance with British Aerospace 125 Service Bulletin 71-38 (\"Requirement\"). If damage is found on aircraft fitted with thrust reversers, the AD notes that the mounting's fatigue life is limited and refers to AD/HS 125/45 for additional direction (\"Note\"). The inspection/repair must be completed by the compliance deadline (\"Compliance\").\n\n- Who it applies to: All BAe 125 models that are fitted with Garrett TFE 731-3R-1H engines (\"Applicability\").\n\n- Who decides and who pays: The directive is issued under the Civil Aviation safety framework and prescribes mandatory action for affected aircraft. Practically, aircraft owners/operators must arrange the inspection and any required repairs and will therefore bear the direct costs and operational consequences (see \"Requirement\" and \"Compliance\").\n\n- Why it matters (stated purpose and technical mechanism): The AD cites several reported cases where the cowling fouled the forward engine mounting, causing damage that could reduce the mounting’s fatigue life (\"Background\"). The AD’s mechanical aim is to detect that damage and restore or preserve mounting integrity by following the manufacturer’s repair instructions (British Aerospace 125 S.B. 71-38) (\"Requirement\").\n\n- Implementation and compliance trade-offs to note: The AD mandates use of a specific service bulletin as the repair standard, creating a dependency on that external technical document for method and scope of work (\"Requirement\"). The operator-directed compliance deadline (completion prior to 30 November 1985) creates a fixed time window to perform inspections and repairs, which can impose scheduling and aircraft-availability costs (\"Compliance\"). If damage is found, affected aircraft—especially those with thrust reversers—may face additional operational limits or follow-up requirements under AD/HS 125/45 (\"Note\").\n\n- Practical effects on behaviour: Operators must schedule an inspection consistent with the AD, follow the specified service bulletin for any repairs, and address any fatigue-life limitations flagged by further ADs if relevant. Those actions change operator maintenance planning, short-term aircraft availability and maintenance expenditure (\"Applicability\", \"Requirement\", \"Compliance\", \"Note\")."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-bound safety directive addressing a specific technical defect in a specific aircraft/engine combination. It has not expanded beyond its original purpose of mandating inspection and repair of engine mounting cowling damage."},"complexity_factors":["Extremely short document (under 200 words)","Only 1 defined applicability criterion (engine type)","Single straightforward requirement referencing an external technical standard (Service Bulletin 71-38)","One cross-reference to another directive (AD/HS 125/45) for related but distinct issue","No nested conditions, exceptions, or legislative interpretation sections","Binary compliance deadline with no phased or conditional implementation"],"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). Think of it as a \"recall notice\" for aircraft, but legally binding.\n\n**What it does:** It requires owners and operators of specific British Aerospace BAe 125 business jets to inspect and repair damage to the forward engine mounting. The damage occurs when the engine cowling (the removable cover around the engine) rubs against or \"fouls\" the mounting structure.\n\n**Who it affects:**\n- **Aircraft:** All BAe 125 series planes fitted with Garrett TFE 731-3R-1H engines\n- **People:** Aircraft owners, operators, and maintenance engineers responsible for these planes\n\n**Why it matters:**\n- **Safety risk:** The rubbing damage reduces the \"fatigue life\" of the engine mounts — meaning the metal weakens over time and could eventually fail, potentially causing engine separation or other catastrophic failures\n- **Special warning for thrust reverser models:** If damage is found on planes with thrust reversers (equipment that helps slow the plane after landing), those mounts have a strictly limited remaining lifespan and must be managed under a separate directive (AD/HS 125/45)\n\n**What had to happen:** The inspection and any necessary repairs had to be completed before 30 November 1985, following the specific technical instructions in British Aerospace Service Bulletin 71-38."}},"importantCases":[],"_links":{"self":"/api/acts/ad-hs-125-72-engine-mounting-cowling-damage","history":"/api/acts/ad-hs-125-72-engine-mounting-cowling-damage/history","analysis":"/api/acts/ad-hs-125-72-engine-mounting-cowling-damage/analysis","conflicts":"/api/acts/ad-hs-125-72-engine-mounting-cowling-damage/conflicts","importantCases":"/api/acts/ad-hs-125-72-engine-mounting-cowling-damage/important-cases","documents":"/api/acts/ad-hs-125-72-engine-mounting-cowling-damage/documents"}}