{"id":"F2006B09995","name":"AD/FU24/48 - Tailplane Mass Balance Weight and Control Horn - Inspection and Modification","slug":"ad-fu24-48-tailplane-mass-balance-weight-and-control-horn-inspection-and-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":55341,"registerId":"commonwealth-F2006B09995-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/FU24/48 - Tailplane Mass Balance Weight and Control Horn - Inspection and Modification","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)  Airparts (NZ) Ltd. FU 24 Series Aeroplanes\n\n \n\n# AD/FU24/48 Tailplane Mass Balance Weight and Control\n\nHorn - Inspection and Modification\n\nApplicability: All models fitted with piston engines. Document: Aerospace SB ASB/FU/005.\n\n# 5/75\n\nCompliance: Inspect before 30 April 1975. Modify, where necessary, before 31 May 1975.\n\n \n\nNote: Aircraft with an incorrectly balanced tailplane may continue in service until modified.\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 presented directly in the text: it applies to all FU 24 series aeroplanes fitted with piston engines, requires inspection by 30 April 1975, and requires modification where necessary by 31 May 1975, following Aerospace Service Bulletin ASB/FU/005. The instrument does not, in its own text, broaden or narrow that scope beyond those stated applicability and deadlines. (AD/FU24/48, “Applicability”; “Compliance”; “Document: Aerospace SB ASB/FU/005”)."},"complexity_factors":["Short, prescriptive text with clear deadlines (inspect by 30 April 1975; modify where necessary by 31 May 1975) (AD/FU24/48, “Compliance”)","Applicability limited to FU 24 series with piston engines, which narrows but technically delineates the affected fleet (AD/FU24/48, “Applicability”)","Dependency on an external technical document (Aerospace SB ASB/FU/005) for inspection and modification procedures introduces procedural complexity and potential for implementation variability (AD/FU24/48, “Document”)","Technical work requires qualified maintenance resources and creates operational downtime for aircraft owners/operators (implied by inspection/modification requirements and reference to service bulletin) (AD/FU24/48, “Document”; “Compliance”)","The Note allowing continued operation until modification introduces an enforcement/discretion element that can complicate practical application (AD/FU24/48, “Note”)"],"plain_english_summary":"What this instrument changes, mechanically:\n\n- It requires inspection of the tailplane mass balance weight and the tailplane control horn on Airparts (NZ) Ltd. FU 24 series aeroplanes that are fitted with piston engines. The inspection must follow the referenced technical document (Aerospace Service Bulletin ASB/FU/005). (AD/FU24/48, “Applicability”; “Document: Aerospace SB ASB/FU/005”)\n- The inspection must be completed before 30 April 1975. If the inspection shows modification is necessary, that modification must be carried out before 31 May 1975. (AD/FU24/48, “Compliance”)\n- The directive includes a procedural note that aircraft found to have an incorrectly balanced tailplane may remain in service until the required modification is completed. (AD/FU24/48, “Note”)\n\nWho this affects and who decides:\n\n- Owners and operators of FU 24 series aeroplanes with piston engines are required to have the inspection performed and to arrange any necessary modification. (AD/FU24/48, “Applicability”; “Compliance”)\n- The Civil Aviation Safety Authority issued the airworthiness directive as part of the Schedule of Airworthiness Directives; the technical steps for inspection/modification are set out in the referenced Aerospace Service Bulletin (ASB/FU/005). (AD/FU24/48, header and “Document”)\n\nWhy it matters (stated purpose and practical implications):\n\n- The directive’s title and requirements indicate it is intended to address the condition of the tailplane mass balance weight and the control horn by forcing inspection and correction where needed. The directive prescribes when the inspection must be done and when any corrective modification must be completed. (AD/FU24/48, title; “Compliance”)\n\nPractical consequences, trade-offs and implementation considerations:\n\n- Direct costs and who pays: aircraft owners/operators pay for the inspection and for any modification found to be necessary (the directive places the action on the operator; see “Compliance”). (AD/FU24/48, “Compliance”)\n- Compliance burden and expertise: the work is technical and will typically require qualified maintenance personnel and use of the Aerospace Service Bulletin procedures, creating demand on maintenance resources and downtime for affected aircraft. (AD/FU24/48, “Document: Aerospace SB ASB/FU/005”)\n- Timing and operational impact: fixed compliance dates create a short window to schedule inspections and modifications; the directive explicitly permits continued operation of aircraft with an incorrectly balanced tailplane until modification is completed, which changes the immediate operational consequence of a failing inspection. This introduces a choice for operators between carrying on in service pending modification or grounding until modification is complete. (AD/FU24/48, “Compliance”; “Note”)\n- Enforcement and discretion: the directive is prescriptive about deadlines but the Note creates a specific allowance (continued operation until modified) that narrows the immediate enforcement consequence; how that allowance is applied in practice will depend on regulatory follow-up and oversight. (AD/FU24/48, “Note”)\n- Effects on market participants: maintenance organisations able to perform the work may see increased demand; owners face direct maintenance expense and potential short-term loss of aircraft availability. The directive constrains owner choice insofar as required inspections and modifications must be completed in accordance with the referenced service bulletin. (AD/FU24/48, “Document”; “Compliance”)\n\nImplementation risks and opportunity costs:\n\n- If the referenced service bulletin is technically unclear, operators may experience delays or inconsistent repairs; the directive relies on that external document for the technical method. (AD/FU24/48, “Document: Aerospace SB ASB/FU/005”)\n- Owners incur opportunity costs from aircraft downtime and maintenance spend that could otherwise have been used elsewhere. (AD/FU24/48, “Compliance”)\n\nSummary sentence:\n\n- The directive mandates a time-limited inspection and, where required, modification of the FU 24 tailplane mass balance weight and control horn for piston‑engined models, tasks carried out under the referenced Aerospace service bulletin, with owners/operators bearing the costs and a specified allowance that aircraft may continue in service until modification is completed. (AD/FU24/48, all cited parts.)"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-bound safety directive targeting a specific aircraft type and component. It has not expanded beyond its original purpose of ensuring tailplane integrity on FU 24 series aircraft."},"complexity_factors":["Very short document (approximately 150 words)","Only 2 defined terms implicitly referenced (Document, Applicability)","No cross-references to other legislation or regulations beyond the parent Civil Aviation Regulations 1998","Simple conditional logic: inspect by date X, modify if necessary by date Y","Single exception/clarification note regarding continued service","Clear, prescriptive language with minimal legal drafting complexity"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It applies to specific small aircraft made by Airparts (NZ) Ltd, known as the FU 24 series, which are fitted with piston engines.\n\n**What it requires:**\n- **Inspection:** Owners or operators must check the tailplane (the small horizontal wing at the back of the aircraft) for problems with its **mass balance weight** and **control horn** by 30 April 1975.\n- **Modification:** If the inspection finds issues, the aircraft must be modified by 31 May 1975.\n\n**Why it matters:**\nThe mass balance weight helps prevent dangerous vibrations or flutter in the tailplane during flight. The control horn is part of the mechanism that moves the tailplane. If these are faulty, the aircraft could become uncontrollable.\n\n**Important exception:**\nEven if an aircraft fails the inspection, it can keep flying until the modification is done — but the fix must still happen by the deadline.\n\n**Key document reference:**\nThe technical details for the inspection and modification are found in **Aerospace Service Bulletin ASB/FU/005**."}},"importantCases":[],"_links":{"self":"/api/acts/ad-fu24-48-tailplane-mass-balance-weight-and-control-horn-inspection-and-modification","history":"/api/acts/ad-fu24-48-tailplane-mass-balance-weight-and-control-horn-inspection-and-modification/history","analysis":"/api/acts/ad-fu24-48-tailplane-mass-balance-weight-and-control-horn-inspection-and-modification/analysis","conflicts":"/api/acts/ad-fu24-48-tailplane-mass-balance-weight-and-control-horn-inspection-and-modification/conflicts","importantCases":"/api/acts/ad-fu24-48-tailplane-mass-balance-weight-and-control-horn-inspection-and-modification/important-cases","documents":"/api/acts/ad-fu24-48-tailplane-mass-balance-weight-and-control-horn-inspection-and-modification/documents"}}