{"id":"F2006B09883","name":"AD/F50/55 - Autoflight - Autopilot Computer - Replacement","slug":"ad-f50-55-autoflight-autopilot-computer-replacement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":55014,"registerId":"commonwealth-F2006B09883-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F50/55 - Autoflight - Autopilot Computer - Replacement","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/F50/55 Autoflight - Autopilot Computer - Replacement 6/92\n\nApplicability: All aircraft specified in the Requirement Document.\n\n \n\nRequirement: In accordance with the Requirement Document Fokker Service Bulletin F50-22-005. Compliance:               As specified in the Requirement Document\n\nBackground:  The autopilot engage button on the Flight Mode Panel apparently exhibits a tendency to stick in the `engage’ position. As a result the autopilot re-engages when either an autopilpot disconnect button on the control wheel or a `go-around’ button on the power levers is released. A modification to the autopilot computer is required.\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\n \n\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive’s scope is replacement/modification of the autopilot computer on the Fokker F50 series aircraft identified in the Requirement Document. The text shows no alteration from that stated purpose: it specifies applicability, the required action (per Fokker Service Bulletin F50-22-005), and defers compliance timing and technical detail to the Requirement Document (Applicability; Requirement; Compliance)."},"complexity_factors":["Technical avionics work: replacement/modification of an autopilot computer requires certified technicians and avionics capability (Requirement).","Dependence on an external Requirement Document and Service Bulletin for technical detail, parts, and timing (Requirement; Compliance).","Operational scheduling and aircraft downtime implications for operators (Compliance).","Potential parts availability and approved supplier constraints due to OEM-specified service bulletin (Requirement).","Regulatory record‑keeping and certification obligations following the mandatory modification (Requirement; Compliance)."],"plain_english_summary":"What this directive does, mechanically\n\n- Requires replacement or modification of the autopilot computer on the affected Fokker F50 (F27 Mk 50) series aeroplanes. The work must be carried out in accordance with the Requirement Document, specifically Fokker Service Bulletin F50-22-005 (Requirement). Compliance timing is: “As specified in the Requirement Document” (Compliance).\n\nWhy the requirement is stated\n\n- The directive says the autopilot engage button on the Flight Mode Panel can stick in the “engage” position. That behaviour can cause the autopilot to re-engage unexpectedly when either the control-wheel disconnect button or the go‑around button on the power levers is released. The stated remedy is a modification to the autopilot computer to prevent that re‑engagement (Background).\n\nWho it affects and who decides\n\n- Aircraft operators and owners of the Fokker F50 (F27 Mk 50) series listed in the Requirement Document must have the modification done (Applicability; Requirement). The Requirement Document sets both which specific aircraft are covered and the required compliance schedule (Applicability; Compliance). Qualified maintenance organisations or engineers must perform the replacement or modification in accordance with the Service Bulletin (Requirement).\n\nWho pays and what behaviour changes\n\n- Operators/owners pay for parts, labour and any associated aircraft downtime. The behaviour change required is that operators must schedule and carry out the specified autopilot computer modification to maintain the aircraft’s airworthiness status under this directive (Requirement; Compliance).\n\nTrade-offs, costs, and implementation considerations\n\n- Direct costs: purchase of the replacement computer or modification kit, labour for installation and testing, and aircraft out-of-service time. These costs are borne by the aircraft operator or owner (Requirement).\n\n- Incentives: operators have a regulatory incentive to comply to keep the aircraft certificated and to avoid continued exposure to the described autopilot fault (Compliance).\n\n- Supply and service considerations: the instruction ties work to a Fokker service bulletin. That concentrates the technical specification and parts sourcing to the OEM or approved suppliers and makes compliance dependent on availability of parts, approved procedures, and suitably certificated maintenance organisations (Requirement).\n\n- Operational substitution: operators may coordinate the change with scheduled heavy maintenance or other downtime to reduce incremental downtime cost. The directive does not itself prescribe the exact timing beyond deferring to the Requirement Document (Compliance).\n\n- Implementation risk and compliance burden: the directive delegates technical detail and timing to the Requirement Document. If that document lacks parts, or if parts are scarce, operators may face delays or additional costs. The directive imposes record‑keeping and certification obligations implicit in carrying out mandatory modifications to airworthiness-critical avionics (Requirement; Compliance).\n\nConcentrated benefits and diffuse costs\n\n- The immediate, concentrated benefit is reduced risk of unintended autopilot re‑engagement for each modified aircraft (Background). The costs (parts, labour, downtime) are concentrated on the aircraft owner/operator who must fund compliance (Requirement).\n\nExplicit limits in the instrument\n\n- The AD applies only to the aircraft listed in the Requirement Document and requires work “in accordance with the Requirement Document” and on the timetable set out there. The AD does not itself list serial numbers, parts, or a specific compliance date; those specifics are contained in the referenced Service Bulletin and Requirement Document (Applicability; Requirement; Compliance).\n\nSource citations: Applicability; Requirement (Fokker Service Bulletin F50-22-005); Compliance; Background. The directive is identified as AD/F50/55 dated 6/92."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical fault in a specific aircraft type. It has not expanded beyond its original purpose of mandating an autopilot computer modification."},"complexity_factors":["Very short document (approximately 150 words of substantive content)","Only 2 defined terms implicitly referenced (Requirement Document, Service Bulletin)","No nested conditional logic or exceptions","Single straightforward requirement with clear external reference","No cross-referencing to other legislation or regulations beyond the parent Civil Aviation Regulations 1998","Linear structure: applicability → requirement → compliance → background"],"plain_english_summary":"This is an **Airworthiness Directive** (a mandatory safety order) issued by Australia's Civil Aviation Safety Authority for **Fokker F50 aircraft**.\n\n**What it does:**\n- Requires owners and operators to replace or modify the **autopilot computer** on these planes.\n- The fix addresses a dangerous fault where the autopilot \"engage\" button on the Flight Mode Panel can get stuck in the \"on\" position.\n\n**Why this matters:**\n- If the button sticks, the autopilot can **re-engage unexpectedly** when pilots release either:\n  - The autopilot disconnect button on the control wheel, or\n  - The \"go-around\" button on the power levers (used during aborted landings)\n- This creates a serious flight safety risk during critical phases of flight.\n\n**Who must comply:**\n- All operators of Fokker F50 series aircraft (also known as F27 Mk 50).\n\n**How to comply:**\n- Follow the technical instructions in **Fokker Service Bulletin F50-22-005**.\n- The deadline for compliance is specified in that same document."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f50-55-autoflight-autopilot-computer-replacement","history":"/api/acts/ad-f50-55-autoflight-autopilot-computer-replacement/history","analysis":"/api/acts/ad-f50-55-autoflight-autopilot-computer-replacement/analysis","conflicts":"/api/acts/ad-f50-55-autoflight-autopilot-computer-replacement/conflicts","importantCases":"/api/acts/ad-f50-55-autoflight-autopilot-computer-replacement/important-cases","documents":"/api/acts/ad-f50-55-autoflight-autopilot-computer-replacement/documents"}}