{"id":"F2006B09790","name":"AD/F28/55 Amdt 1 - Generator Control Units","slug":"ad-f28-55-amdt-1-generator-control-units","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":54710,"registerId":"commonwealth-F2006B09790-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F28/55 Amdt 1 - Generator Control Units","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)  \nFokker F28 Series Aeroplanes\n\nAD/F28/55\n\nAmdt 1\n\n  \n\nGenerator Control Units 8/88 DM\n\nApplicability: All models fitted with generator control units P/N 914F569-4, \\-5 and \\-6.\n\nRequirement: 1. Replace all relays P/N 938D848-1 in accordance with Westinghouse service Bulletin 86-401 Revision 1.\n\n2. Install spacer P/N 935A376-1 between all TO5 case style transistors and printed circuit board in accordance with Westinghouse service Bulletin 86-401 Revision 1.\n\nCompliance: Requirement 1: Generator control panels fitted to Aircraft: Prior to 14 November 1988.\n\nGenerator control panels held as spares: Prior to fitment to an aircraft after 14 November 1988.\n\nRequirement 2: Whenever any TO5 case style transistor is replaced.\n\nBackground: Based on data provided by Fokker and various F28 operators it has been determined that a serious reliability problem exists with these control panels. The nature of the problem is intermittent and cannot be detected during normal testing, and the possibility of multiple simultaneous failures cannot be discounted. Amendment 1 to this Directive is issued to clarify the applicability and requirement.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"Amendment 1 clarifies the directive's applicability and requirements but does not expand or narrow the technical scope of mandated actions. The text expressly states the amendment's purpose is clarification rather than a change in substantive scope."},"complexity_factors":["Technical specificity: obligations reference precise part numbers (914F569‑4/‑5/‑6; 938D848‑1; 935A376‑1) and a specific Westinghouse service bulletin (86‑401 Rev 1).","Conditional requirement: spacer installation is triggered only when a TO5 case style transistor is replaced, creating a maintenance‑event linkage.","Multiple compliance timelines: deadlines differ for panels fitted to aircraft versus panels held as spares (prior to 14 Nov 1988 or prior to fitment).","Safety‑critical diagnostic difficulty: the defect is described as intermittent and not detectable in normal testing, increasing reliance on preventive parts change rather than inspection.","Operational logistics: operators must schedule parts replacement and stock control (spares) to meet the deadlines and fitment conditions."],"plain_english_summary":"This directive requires operators of Fokker F28 aeroplanes fitted with generator control units P/N 914F569‑4, ‑5 or ‑6 to replace relays P/N 938D848‑1 and, when a TO5 case transistor is replaced, fit spacer P/N 935A376‑1 in accordance with Westinghouse Service Bulletin 86‑401 Rev 1. Installed panels and spares have specified compliance deadlines. The cost and work fall to aircraft operators/maintainers. The action responds to reported intermittent, hard‑to‑detect failures and the risk of simultaneous malfunctions."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This amendment is minor and clarifying only. Amendment 1 explicitly states it was issued 'to clarify the applicability and requirement' of the original AD/F28/55. The scope remains tightly focused on the specific generator control unit reliability issue for Fokker F28 aircraft. No expansion of scope beyond the original safety-critical electrical system problem."},"complexity_factors":["Very short document (approximately 200 words)","Only 2 substantive requirements with clear part number references","Simple conditional logic (applicability limited to specific part numbers)","Straightforward compliance dates with minimal exceptions","No nested definitions or extensive cross-referencing to other legislation","Single amendment (Amendment 1) with limited scope — only clarifies applicability and requirement"],"plain_english_summary":"This Airworthiness Directive from CASA mandates repairs to generator control units on Fokker F28 aircraft, affecting operators and maintenance organisations with units P/N 914F569-4/-5/-6. It requires replacement of relays (P/N 938D848-1) per Westinghouse Service Bulletin 86‑401 Rev 1 and installation of spacers when certain transistors are replaced.\n\nThe AD responds to an intermittent fault that can cause multiple simultaneous failures and possible total electrical loss; panels in service must be fixed before 14 November 1988, and spares modified before installation after that date."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f28-55-amdt-1-generator-control-units","history":"/api/acts/ad-f28-55-amdt-1-generator-control-units/history","analysis":"/api/acts/ad-f28-55-amdt-1-generator-control-units/analysis","conflicts":"/api/acts/ad-f28-55-amdt-1-generator-control-units/conflicts","importantCases":"/api/acts/ad-f28-55-amdt-1-generator-control-units/important-cases","documents":"/api/acts/ad-f28-55-amdt-1-generator-control-units/documents"}}