{"id":"F2006B09838","name":"AD/F50/13 - Accessory Bay Ventilation Air Outlet","slug":"ad-f50-13-accessory-bay-ventilation-air-outlet","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":54877,"registerId":"commonwealth-F2006B09838-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F50/13 - Accessory Bay Ventilation Air Outlet","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/F50/13 Accessory Bay Ventilation Air Outlet 5/89\n\nDM\n\n \n\nApplicability: S/No. 20103 to 20108 and 20110 to 20134 inclusive. Requirement:  Action in accordance with Fokker S.B. F50-54-004.\n\nNote: RLD AD 89-021 refers.\n\n \n\nCompliance: Prior to 31 May 1989.\n\n \n\nBackground:  Cold air moisture and rainwater can enter the aircraft through the ventilation air outlet. This has caused ice buildup on control cable systems at high altitude, low OAT and during high humidity conditions.\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":{"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 model. It has not expanded beyond its original purpose of mandating a ventilation outlet modification."},"complexity_factors":["Very short document — approximately 150 words of substantive content","Only 1 defined term implicitly referenced (S.B. = Service Bulletin)","No nested conditional logic or exceptions","Single straightforward requirement: comply with external technical document","Simple applicability criteria based on serial number ranges","No cross-references to other legislation sections — only a note about related foreign directive"],"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) for specific aircraft.\n\n**What it does:** It requires owners or operators of certain Fokker F50 aeroplanes to take corrective action on the accessory bay ventilation air outlet. The specific fix is detailed in a Fokker Service Bulletin (S.B. F50-54-004), which is a technical instruction document from the manufacturer.\n\n**Who it affects:** Only Fokker F50 aircraft with serial numbers 20103 to 20108 and 20110 to 20134 — a specific batch of 31 planes.\n\n**Why it matters:** Cold air, moisture, and rainwater were getting into the aircraft through this ventilation outlet. At high altitudes with low outside air temperatures and high humidity, this moisture was freezing on control cable systems — a serious flight safety risk because control cables are what pilots use to steer the aircraft.\n\n**The deadline:** The fix had to be completed before 31 May 1989.\n\n**Cross-reference:** This aligns with a Dutch aviation authority directive (RLD AD 89-021), showing international coordination on this safety issue."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive’s scope remains consistent with its stated intent in the text provided: it targets a specific set of Fokker F50 serial numbers and mandates action per Fokker Service Bulletin F50-54-004 to prevent moisture/rainwater ingress causing ice buildup on control cable systems (Applicability; Requirement; Background). The document sets a clear compliance deadline and does not expand or narrow obligations beyond the serial-number list and the single prescribed compliance method."},"complexity_factors":["Narrow applicability: specific list of serial numbers reduces scope complexity (Applicability).","Single-prescribed method of compliance: points to one Fokker service bulletin rather than multiple options (Requirement).","Fixed compliance date simplifies timing but imposes a deadline (Compliance).","Technical detail is delegated to the manufacturer’s service bulletin, so the AD itself is short and procedural (Requirement).","Reference to an external AD (RLD AD 89-021) requires cross-checking for full compliance context (Note)."],"plain_english_summary":"This directive requires operators of specific Fokker F50 (F27 Mk 50) aircraft (serials 20103–20108 and 20110–20134) to carry out the modification/inspection of the accessory-bay ventilation air outlet per Fokker Service Bulletin F50-54-004 by 31 May 1989. It aims to prevent moisture/ice ingress that can freeze control cables. Compliance costs and scheduling fall to the affected owners/operators; the SB is cited as the mandatory means of compliance."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f50-13-accessory-bay-ventilation-air-outlet","history":"/api/acts/ad-f50-13-accessory-bay-ventilation-air-outlet/history","analysis":"/api/acts/ad-f50-13-accessory-bay-ventilation-air-outlet/analysis","conflicts":"/api/acts/ad-f50-13-accessory-bay-ventilation-air-outlet/conflicts","importantCases":"/api/acts/ad-f50-13-accessory-bay-ventilation-air-outlet/important-cases","documents":"/api/acts/ad-f50-13-accessory-bay-ventilation-air-outlet/documents"}}