{"id":"F2006B09592","name":"AD/ENST 28/35 - Inadvertent Trim Motor Operation","slug":"ad-enst-28-35-inadvertent-trim-motor-operation","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":54304,"registerId":"commonwealth-F2006B09592-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/ENST 28/35 - Inadvertent Trim Motor Operation","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)  \nEnstrom F-28 Series Helicopters\n\nAD/ENST 28/35 Inadvertent Trim Motor Operation 2/94\n\nTX\n\nApplicability: All F-28C, F-28C-2, F-28F, 280C, 280F and 280FX series helicopters equipped with a 24 volt DC electrical system.\n\nRequirement: 1. Inspect and modify the trim system in accordance with Enstrom Helicopter Corporation Service Directive Bulletin 0082 Revision A dated 18 March 1993.\n\n2. Inspect the trim system in accordance with Enstrom Helicopter Corporation Service Directive Bulletin 0082 Revision A dated 18 March 1993.\n\nNote: FAA Priority Letter AD 93-12-14 issued 6 December 1993.\n\nCompliance: 1. Within five hours time in service from 13 December 1993.\n\n2. At intervals not to exceed 100 hours time in service or at each annual inspection, whichever occurs first.\n\nBackground: There have been three reports of inadvertent trim motor operation as a result of sticking relays. A stuck relay causes the trim motor to rapidly deploy to the full trim position, resulting in high cyclic control forces that significantly reduce the controllability of the helicopter and possibly lead to total loss of control.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a standard, narrowly-targeted airworthiness directive addressing a specific mechanical defect in specific aircraft models. The scope remains tightly focused on the original safety issue (sticking trim motor relays) and has not expanded beyond this purpose."},"complexity_factors":["Very short document (under 300 words)","Only 2 defined applicability criteria (aircraft model and electrical system type)","Simple two-part compliance structure with clear timeframes","Single cross-reference to FAA directive for background context only","No nested exceptions or conditional logic — requirements apply uniformly to all affected aircraft","Plain language background section explaining the safety risk"],"plain_english_summary":"This CASA Airworthiness Directive mandates immediate inspection and modification of the trim system on specified Enstrom helicopters with 24‑volt electrical systems to fix sticking relays that can cause the trim motor to run to full deflection, producing uncontrollable cyclic forces. Owners, operators and maintenance engineers must comply within 5 flight hours (from 13 Dec 1993) and repeat inspections every 100 flight hours or at annual inspection to prevent loss of control."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive targets the same hazard described in the Background (sticking relays causing inadvertent trim motor deployment) and applies to the listed F‑28/280 models with 24V systems (Applicability). It mandates modification and recurring inspections (Requirement; Compliance) but does not expand the affected fleet or alter the underlying safety issue."},"complexity_factors":["Technical requirement to modify/inspect an aircraft trim system (airworthiness/maintenance knowledge needed).","Mandates compliance with an external document (Enstrom Service Directive Bulletin 0082 Rev A) rather than prescribing all technical steps in the AD.","Short initial compliance window (within five hours TIS) creates operational urgency and logistical complexity for operators.","Recurring inspection interval (every 100 hours or at annual inspection) imposes ongoing maintenance scheduling and cost.","Applicability limited to specific models and 24V electrical systems requires aircraft-by-aircraft applicability checks.","Cross-reference to FAA Priority Letter AD increases inter-jurisdictional coordination considerations."],"plain_english_summary":"Requires owners/operators of specified Enstrom F‑28 and 280 series helicopters with 24‑volt DC systems to modify and inspect the pitch trim system according to Enstrom Service Directive Bulletin 0082 Revision A. The modification must be done within five hours TIS and inspections repeated every 100 hours or at each annual inspection. The rule responds to reports of sticking relays that can drive the trim motor to full travel; operators pay for and schedule the work while the regulator mandates the safety action."}},"importantCases":[],"_links":{"self":"/api/acts/ad-enst-28-35-inadvertent-trim-motor-operation","history":"/api/acts/ad-enst-28-35-inadvertent-trim-motor-operation/history","analysis":"/api/acts/ad-enst-28-35-inadvertent-trim-motor-operation/analysis","conflicts":"/api/acts/ad-enst-28-35-inadvertent-trim-motor-operation/conflicts","importantCases":"/api/acts/ad-enst-28-35-inadvertent-trim-motor-operation/important-cases","documents":"/api/acts/ad-enst-28-35-inadvertent-trim-motor-operation/documents"}}