{"id":"F2006B09850","name":"AD/F50/24 - Engine Control Rod Clearance","slug":"ad-f50-24-engine-control-rod-clearance","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":54917,"registerId":"commonwealth-F2006B09850-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F50/24 - Engine Control Rod Clearance","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/F50/24 Engine Control Rod Clearance 13/89\n\nDM\n\nApplicability: F27 MK50 aircraft with serial numbers 20103 through 20108 and 20110 through 20167.\n\n \n\nRequirement: Action in accordance with Fokker SB F50-54-006.\n\n \n\nNote: Netherlands AD 89-100 refers.\n\n \n\nCompliance: Prior to 31 December 1989.\n\n \n\nBackground: Country of origin AD. Freezing of water on control rod at feedthrough hole could cause jamming.\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":2,"scope_assessment":{"changed":false,"description":"The directive’s scope remains as stated in the instrument: it applies only to the listed serial numbers and requires the specific corrective action in Fokker SB F50-54-006 to be completed before 31 December 1989 (Applicability; Requirement; Compliance). There is no text in the instrument indicating an expansion or narrowing of that scope from its original stated purpose (Background; Note)."},"complexity_factors":["Narrow applicability limited to a defined range of serial numbers (Applicability).","Mandates a single referenced technical document for the corrective action (Fokker SB F50-54-006) rather than multiple compliance options (Requirement).","Fixed compliance deadline (Compliance) creating scheduling and operational considerations.","Cross-reference to a foreign AD (Netherlands AD) that may require operators to consult non‑Australian material (Note).","Technical issue (freezing of water causing jamming) is specific but requires hands‑on maintenance access (Background)."],"plain_english_summary":"What this instrument does mechanically\n\n- This Airworthiness Directive (AD/F50/24) requires operators of certain Fokker F50 (F27 Mk 50) aeroplanes to carry out the specific maintenance action set out in Fokker Service Bulletin F50-54-006 (Requirement).  \n- The AD applies only to aircraft with serial numbers 20103–20108 and 20110–20167 (Applicability).  \n- The work must be done before 31 December 1989 (Compliance).\n\nWhy the requirement exists (stated purpose)\n\n- The background to the directive states that water can freeze on a control rod at a feedthrough hole and cause the rod to jam (Background).  \n- The AD notes a related Netherlands airworthiness directive (Note).  \n\nWho pays and who decides\n\n- Aircraft owners/operators of the affected serial-numbered aeroplanes bear the cost and must arrange the maintenance. The AD prescribes the action and the Civil Aviation Safety Authority publishes the directive (header: Part 39 - 105 Civil Aviation Safety Authority; Schedule of Airworthiness Directives).\n- The required technical method is specified by the manufacturer’s service bulletin, so operators rely on the Fokker SB to describe the corrective steps (Requirement).  \n\nImmediate effects on behaviour and operations\n\n- Operators must schedule and perform the service-bulletin action on each affected airframe before the stated date. That may require removing an aircraft from service temporarily to complete the work and could involve parts, labour time, and inspection access.  \n- Because the AD cites a foreign (Netherlands) AD and a Fokker service bulletin, compliance depends on access to that bulletin and any parts or tooling it requires (Requirement; Note).\n\nCosts, incentives and trade-offs\n\n- Direct costs fall on the owners/operators in the form of maintenance labour, possible replacement parts, and aircraft downtime (implicit in Requirement and Compliance).  \n- The immediate benefit is reduced risk of a control-rod jam caused by freezing water at the feedthrough hole, per the Background statement.  \n- There may be limited flexibility for operators: the AD mandates conformity with the Fokker service bulletin rather than permitting a range of alternative fixes, so operators are incentivised to follow the manufacturer-prescribed method (Requirement).  \n\nImplementation, compliance burden and risks\n\n- Implementation risk arises if operators lack timely access to the service bulletin, parts, or qualified maintenance capacity; until work is done, the hazard described in Background remains.  \n- Enforcement is administrative: the AD is part of the Civil Aviation Safety Authority’s schedule of directives, so compliance is an airworthiness requirement (header; Schedule of Airworthiness Directives).  \n\nConcentrated benefits and diffuse costs\n\n- The safety benefit is mainly concentrated on operators and their passengers/crew on the specific affected aircraft. The compliance cost is concentrated on the owners/operators of those serial-numbered aeroplanes (Applicability; Requirement)."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-bound safety directive addressing a specific mechanical defect in a specific aircraft type. It has not expanded beyond its original purpose of mandating a single technical fix."},"complexity_factors":["Extremely short document (under 150 words)","Only 4 substantive sections: Applicability, Requirement, Note, and Compliance","Single cross-reference to external technical document (Fokker SB F50-54-006)","No defined terms section — all language is plain technical English","No conditional logic, exceptions, or nested provisions","Simple date-based compliance deadline with no alternatives or escalations"],"plain_english_summary":"**What this is:** This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). Think of it like a compulsory recall notice, but for aircraft instead of cars.\n\n**What it does:** It requires owners and operators of specific Fokker F50 aeroplanes to carry out a safety fix. The problem? Water could freeze on an engine control rod where it passes through a hole (the \"feedthrough hole\"), causing the rod to jam. A jammed engine control is obviously catastrophic — you don't want the throttle stuck when you're trying to land.\n\n**Who must act:** Anyone operating Fokker F50 aircraft with serial numbers 20103–20108 and 20110–20167. That's a specific batch of 64 aircraft.\n\n**What they must do:** Follow the instructions in **Fokker Service Bulletin F50-54-006** — a technical repair notice from the manufacturer. The directive itself doesn't spell out the mechanical steps; it simply points to that document.\n\n**When:** The fix had to be completed before 31 December 1989.\n\n**Why it matters:** This is about preventing engine control failures in freezing conditions. The directive originated from the Netherlands (where Fokker was based), showing how aviation safety relies on international information sharing. Ignoring an AD is illegal — you cannot fly the aircraft until compliance is proven."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f50-24-engine-control-rod-clearance","history":"/api/acts/ad-f50-24-engine-control-rod-clearance/history","analysis":"/api/acts/ad-f50-24-engine-control-rod-clearance/analysis","conflicts":"/api/acts/ad-f50-24-engine-control-rod-clearance/conflicts","importantCases":"/api/acts/ad-f50-24-engine-control-rod-clearance/important-cases","documents":"/api/acts/ad-f50-24-engine-control-rod-clearance/documents"}}