{"id":"F2006B09865","name":"AD/F50/39 - Elevator Torque Tube Bearing Plate Bolts","slug":"ad-f50-39-elevator-torque-tube-bearing-plate-bolts","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":54964,"registerId":"commonwealth-F2006B09865-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F50/39 - Elevator Torque Tube Bearing Plate Bolts","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/F50/39 Elevator Torque Tube Bearing Plate Bolts 2/91\n\nDM\n\n \n\nApplicability: F27 Mark 050 aircraft with S/Nos 20103 through 20184.\n\n \n\nRequirement: Action in accordance with the technical requirements of Netherlands AD BLA 90-104.\n\n \n\nNote: Fokker SB F50-55-004 refers.\n\n \n\nCompliance: Prior to accumulating 500 hours time in service after revised date of 4 December 1990, or prior to revised date of 1 June 1991, whichever occurs first.\n\n \n\nBackground: Country of origin AD. It was found that, during production, bolts were tightened to a torque load that was too high. To prevent failure, replacement of bolts 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","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"The directive's scope is consistent with its stated purpose in the text: it targets F27 Mark 050 aircraft with specified serial numbers to replace over-torqued bolts to prevent failure. The instrument delegates the technical method to Netherlands AD BLA 90-104 and references Fokker service bulletin F50-55-004; no change from the directive's stated purpose or applicability is indicated within the provided text. [Applicability] [Requirement] [Background]"},"complexity_factors":["Narrow applicability to a specific serial-number range (S/Nos 20103–20184) creates a precise but limited scope. [Applicability]","Mandates compliance with an external foreign airworthiness directive (Netherlands AD BLA 90-104) rather than containing full technical instructions, requiring operators to obtain and interpret additional documents. [Requirement]","References an aircraft manufacturer service bulletin (Fokker SB F50-55-004) as a related source, increasing cross-document dependency. [Note]","Dual compliance trigger (500 hours time-in-service after a revised date OR a calendar revised date) adds scheduling complexity for operators. [Compliance]","Operational and logistics implications (parts, labour, docking time) impose practical coordination burdens on operators and maintenance organisations. [Compliance] [Requirement]"],"plain_english_summary":"The directive requires operators of Fokker F27 Mark 050 aircraft (S/N 20103–20184) to replace elevator torque-tube bearing-plate bolts per Netherlands AD BLA 90-104 (and related Fokker service bulletin) because production bolts were over-torqued and could fail.  \n\nWork must be done within the specified hours-or-date window; operators must obtain the technical instructions, arrange and pay for parts, labour and downtime to comply."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific manufacturing defect in a specific aircraft type. It has not expanded beyond its original purpose of mandating bolt replacement to prevent mechanical failure."},"complexity_factors":["Single, specific mechanical issue (bolt replacement)","Only 82 aircraft affected (narrow serial number range)","Clear compliance deadline with simple 'whichever occurs first' logic","No defined terms section","No cross-references to other Australian legislation","Relies entirely on external technical document (Netherlands AD) for actual procedure","No exceptions, exemptions, or conditional provisions"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order for aircraft. It applies to specific **Fokker F50 aeroplanes** (serial numbers 20103 through 20184).\n\n**What it does:**\n- Requires owners/operators to replace certain **bolts** on the elevator torque tube bearing plate\n- These bolts were originally tightened too much during manufacturing, creating a risk of failure\n\n**Who must act:**\n- Anyone operating the affected Fokker F50 aircraft\n\n**When it must be done:**\n- Before the aircraft reaches 500 flight hours after 4 December 1990, **or** before 1 June 1991 — whichever comes first\n\n**Why it matters:**\n- The elevator controls the aircraft's pitch (up/down movement). If these bolts fail, the pilot could lose control of the elevator, potentially causing a crash. This directive prevents that by mandating replacement of the faulty bolts.\n\n**How to comply:**\n- Follow the technical instructions in **Netherlands AD BLA 90-104** (the Dutch aviation safety authority's equivalent directive)\n- Reference **Fokker Service Bulletin F50-55-004** for detailed procedures"}},"importantCases":[],"_links":{"self":"/api/acts/ad-f50-39-elevator-torque-tube-bearing-plate-bolts","history":"/api/acts/ad-f50-39-elevator-torque-tube-bearing-plate-bolts/history","analysis":"/api/acts/ad-f50-39-elevator-torque-tube-bearing-plate-bolts/analysis","conflicts":"/api/acts/ad-f50-39-elevator-torque-tube-bearing-plate-bolts/conflicts","importantCases":"/api/acts/ad-f50-39-elevator-torque-tube-bearing-plate-bolts/important-cases","documents":"/api/acts/ad-f50-39-elevator-torque-tube-bearing-plate-bolts/documents"}}