{"id":"F2006B09789","name":"AD/F28/54 - Horizontal Stabilizer Control Unit Bolts","slug":"ad-f28-54-horizontal-stabilizer-control-unit-bolts","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":54709,"registerId":"commonwealth-F2006B09789-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F28/54 - Horizontal Stabilizer Control Unit Bolts","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/F28/54 Horizontal Stabilizer Control Unit Bolts 4/88\n\nApplicability: All aircraft.\n\nRequirement: Ensure that the horizontal stabilizer control unit has been modified to incorporate the NAS 1303 bolts required by Menasco Service Bulletin No 27-76 Rev 3, rather than AN 3 bolts.\n\nNote: Fokker F28 S B No 27-168 Rev 1, RLD AD 86-08, DGAC AD 86-111-IMP(B)\n\nand FAA AD 87-18-01 all refer.\n\nCompliance: Not later than 7 October 1988 and on each occasion on which the lock washer P/No 25011-1 is disturbed.\n\nNote: Aircraft equipped with horizontal Stabilizer control units P/No 11100 (all dash numbers) which do not have S B 27-76 stamped on the nameplate are most likely to be affected. At delivery this included aircraft S/Nos 1003 to 11195, 11991 and 11992.\n\nBackground: Fatigue failures of certain bolts in the horizontal stabilizer control unit have occurred in service. This condition, combined with an in-flight hydraulic system failure, could add to uncontrolled movement of the horizontal stabilizer. Therefore a modification has been introduced which replaces the affected AN 3H3A bolts with stronger NAS 1303-2H bolt.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"The instrument heading and background target Fokker F28 series aeroplanes but the text states 'Applicability: All aircraft'. That language change expands who is formally covered beyond the apparent technical target, potentially requiring non-Fokker operators to assess applicability. Source: header 'Fokker F28 Series Aeroplanes' and 'Applicability: All aircraft.'"},"complexity_factors":["Technical specificity of parts: exact bolt types (AN 3H3A v NAS 1303-2H) and lock washer P/No 25011-1 increase technical and supply-chain attention.","Compliance triggers: fixed deadline (7 October 1988) plus event-driven rework whenever the lock washer is disturbed adds recurring compliance events.","Identification burden: reliance on nameplate stamping (SB 27-76) and listed serial numbers to determine affected units creates record-checking work for operators.","Cross-references: multiple external documents cited (Menasco SB No 27-76 Rev 3, Fokker SB 27-168 Rev 1, RLD AD 86-08, DGAC AD 86-111-IMP(B), FAA AD 87-18-01) require operators to consult outside materials.","Apparent applicability mismatch: header references Fokker F28 series but the instrument states 'Applicability: All aircraft', creating potential scope ambiguity."],"plain_english_summary":"This directive requires operators to replace AN 3H3A bolts in the Fokker F28 horizontal stabilizer control unit with stronger NAS 1303-2H bolts per Menasco Service Bulletin No 27-76 Rev 3. Compliance is mandated by the Civil Aviation Safety Authority by 7 October 1988 and whenever lock washer P/No 25011-1 is disturbed.\n\nAircraft owners/operators pay for the modification and inspections; identification relies on the unit nameplate and listed serial numbers. The change substitutes ongoing fatigue risk for a one-off modification and recurring inspection trigger."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, original airworthiness directive with a narrow, specific safety purpose. It has not expanded beyond its original intent of mandating a specific bolt replacement to address a known fatigue failure risk."},"complexity_factors":["Single, specific mechanical modification requirement","Only 2 defined compliance triggers (deadline date + lock washer disturbance)","No nested exceptions or conditional logic","Clear applicability criteria (aircraft serial numbers and part numbers)","Short document (approximately 200 words)","Single cross-reference to manufacturer service bulletin and related foreign airworthiness directives"],"plain_english_summary":"This AD orders owners/operators of Fokker F28 aircraft to replace identified AN3 bolts in the horizontal stabilizer control unit (P/N 11100 without “SB 27‑76” on the nameplate) with NAS1303 bolts per the manufacturer’s service bulletin. The change, required by 7 October 1988 and whenever a specified lock washer is removed, addresses metal‑fatigue failures that could, combined with a hydraulic failure, lead to loss of horizontal‑stabilizer control (affects mainly serials 1003–11195, 11991–11992)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f28-54-horizontal-stabilizer-control-unit-bolts","history":"/api/acts/ad-f28-54-horizontal-stabilizer-control-unit-bolts/history","analysis":"/api/acts/ad-f28-54-horizontal-stabilizer-control-unit-bolts/analysis","conflicts":"/api/acts/ad-f28-54-horizontal-stabilizer-control-unit-bolts/conflicts","importantCases":"/api/acts/ad-f28-54-horizontal-stabilizer-control-unit-bolts/important-cases","documents":"/api/acts/ad-f28-54-horizontal-stabilizer-control-unit-bolts/documents"}}