{"id":"F2006B09863","name":"AD/F50/37 - Auto Flight Idle Stop Mechanism","slug":"ad-f50-37-auto-flight-idle-stop-mechanism","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":54957,"registerId":"commonwealth-F2006B09863-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F50/37 - Auto Flight Idle Stop Mechanism","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)  Fokker F50 (F27 Mk 50) Series Aeroplanes\n\n \n\nAD/F50/37 Auto Flight Idle Stop Mechanism 10/90\n\nApplicability: Model F50 series with serial numbers 20103 through 20192 with Service Bulletin F50-76-008 Revision 1 incorporated.\n\n \n\nRequirement: Action in accordance with Fokker Service Bulletin F50-76-009.\n\n \n\nNote: RLD AD 90-044 refers.\n\n \n\nCompliance: Within 250 hours time in service after incorporation of SB F50-76-008 Revision 1, and thereafter at intervals not exceeding 250 hours time in service.\n\n \n\nBackground:  This Directive requires repetitive inspection of the auto flight idle stop mechanism to ensure correct solenoid stroke, which is affected by the gradual wear of the parts.\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\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive's scope remains a targeted maintenance requirement for a defined set of Fokker F50 serial numbers with a specific service bulletin incorporated. It mandates repetitive inspections on a 250-hour cycle and directs compliance to a named Fokker service bulletin. There is no indication in the text that the directive expands or narrows its applicability beyond that stated intent (Applicability, Requirement, Compliance, Background)."},"complexity_factors":["Narrow, clearly defined applicability limited to F50 serial numbers 20103–20192 with SB F50-76-008 Rev 1 incorporated (Applicability).","Compliance depends on following an external technical document (Fokker Service Bulletin F50-76-009) rather than the AD stating detailed procedures (Requirement).","Recurring inspection interval fixed at 250 hours time in service creates an ongoing, periodic compliance obligation (Compliance).","Technical check concerns solenoid stroke and progressive wear, which requires skilled maintenance personnel and possible parts replacement (Background).","Cross-reference to another airworthiness directive (RLD AD 90-044) may require operators to check for related obligations (Note)."],"plain_english_summary":"This directive mandates repetitive inspections of the auto‑flight idle stop solenoid stroke on Fokker F50 aircraft (serials 20103–20192) that have incorporated Service Bulletin F50‑76‑008 Rev 1, using Fokker Service Bulletin F50‑76‑009. The first check is within 250 flight hours after SB incorporation and repeats every 250 hours.\n\nIt affects operators and their maintenance organisations (enforced under the Civil Aviation Safety Authority). Operators pay for inspections, downtime and any corrective work and must follow the referenced Fokker bulletin for technical procedures."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete airworthiness directive with a narrow, specific safety purpose (inspecting a single mechanical component on a specific aircraft type). It has not expanded beyond its original intent; it does exactly what it says on the tin."},"complexity_factors":["Single, specific technical requirement with clear cross-reference to manufacturer service bulletin","Narrow applicability limited to specific aircraft serial number range and prior modification status","Simple compliance timeline: initial inspection + recurring 250-hour intervals","No defined terms section, no nested exceptions, no conditional logic beyond the applicability criteria","Document is essentially a safety notice format — short, directive, and self-contained"],"plain_english_summary":"This is an **Airworthiness Directive** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for specific aircraft.\n\n**What it does:**\nRequires owners and operators of certain Fokker F50 aeroplanes to repeatedly inspect a specific mechanical component called the \"auto flight idle stop mechanism.\" This part controls how the aircraft's engines behave during flight (specifically, preventing them from going to idle when they shouldn't).\n\n**Who it affects:**\n- **Aircraft:** Fokker F50 series planes with serial numbers 20103 through 20192\n- **Only if:** These planes have already had a specific modification installed (Service Bulletin F50-76-008 Revision 1)\n- **People:** Airlines, charter operators, or anyone who owns or maintains these specific aircraft\n\n**What must be done:**\n- Inspect the mechanism within 250 hours of flying time after the modification was installed\n- Then re-inspect it every 250 hours of flying time thereafter (repetitively)\n- Follow the exact procedures in Fokker Service Bulletin F50-76-009\n\n**Why it matters:**\nThe mechanism's parts wear down gradually over time. If the \"solenoid stroke\" (the distance a magnetic switch moves) becomes incorrect due to this wear, the safety system could fail. This could potentially allow engines to go to idle unexpectedly during flight — a serious safety risk.\n\n**Key point:** This is a **recurring inspection** (not a one-off fix), meaning operators must keep checking this part for the life of the aircraft."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f50-37-auto-flight-idle-stop-mechanism","history":"/api/acts/ad-f50-37-auto-flight-idle-stop-mechanism/history","analysis":"/api/acts/ad-f50-37-auto-flight-idle-stop-mechanism/analysis","conflicts":"/api/acts/ad-f50-37-auto-flight-idle-stop-mechanism/conflicts","importantCases":"/api/acts/ad-f50-37-auto-flight-idle-stop-mechanism/important-cases","documents":"/api/acts/ad-f50-37-auto-flight-idle-stop-mechanism/documents"}}