{"id":"F2006B09979","name":"AD/FU24/17 - Aileron Mass Balance Arms - Modification","slug":"ad-fu24-17-aileron-mass-balance-arms-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":55277,"registerId":"commonwealth-F2006B09979-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/FU24/17 - Aileron Mass Balance Arms - 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\nAD/FU24/17 Aileron Mass Balance Arms - Modification 6/68\n\nApplicability: All models prior to S/No. 120 not incorporating Fletcher Aviation EO No. 698. Document:               Fletcher Aviation EO 698.\n\nCompliance: Forthwith.\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\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD text defines a specific and narrow scope: FU 24 series aeroplanes with serial numbers prior to S/No. 120 that have not incorporated Fletcher Aviation EO No. 698. The document does not indicate any change to that scope from an earlier instrument or intention; it simply mandates compliance with EO 698 for that defined population (see: \"Applicability\" and \"Document\")."},"complexity_factors":["Reliance on an external technical document (Fletcher Aviation EO 698) for the substantive technical instructions rather than including those steps in the AD text.","Immediate compliance requirement (\"Forthwith\") increases logistical complexity for owners/operators.","Applicability limited by serial-number cutoff (models prior to S/No. 120) requires record checks and verification of incorporation of EO 698.","Technical nature of the mod (aileron mass balance arms) requires specialised maintenance skills and parts, creating operational and supply constraints.","AD text provides no explicit rationale or estimated impact, which raises information gaps for cost–benefit assessment and implementation planning."],"plain_english_summary":"This AD mandates an immediate modification to the aileron mass‑balance arms on Airparts (NZ) FU 24 aeroplanes (serial numbers before S/No. 120) by requiring compliance with Fletcher Aviation Engineering Order No. 698. Owners/operators must arrange and pay for the work forthwith; the AD makes EO 698 mandatory but does not state a rationale, so affected operators must consult that EO for technical steps and the safety basis."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical defect in a specific aircraft type. It has not expanded beyond its original purpose of mandating a single engineering modification to prevent aileron flutter."},"complexity_factors":["Extremely short document (approximately 150 words)","Only 4 operative provisions: applicability, document reference, compliance timing, and the modification requirement","No defined terms section — uses plain aviation terminology","No cross-references to other legislation or regulations beyond the parent Civil Aviation Regulations 1998 citation","Single condition: serial number threshold (prior to S/No. 120) and exclusion for already-modified aircraft","No nested exceptions or conditional logic"],"plain_english_summary":"**What this is:** This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by the Civil Aviation Safety Authority (CASA) that requires aircraft owners to fix a specific mechanical problem.\n\n**What it does:** It orders owners of certain **Airparts (NZ) Ltd FU-24 series aeroplanes** to modify their **aileron mass balance arms** (small weighted components on the wing control surfaces that prevent dangerous vibrations). The modification must follow **Fletcher Aviation Engineering Order No. 698**.\n\n**Who it affects:** \n- All FU-24 models with **serial numbers below 120**\n- Aircraft that **haven't already** had Fletcher Aviation EO No. 698 incorporated\n\n**When it must be done:** **Immediately** (\"Forthwith\") — meaning before the aircraft flies again.\n\n**Why it matters:** Mass balance arms are critical for flight safety. If they fail or are improperly designed, they can cause **flutter** (rapid, destructive vibration of control surfaces) that could break the wings or tail off in flight. This AD prevents that catastrophic failure mode."}},"importantCases":[],"_links":{"self":"/api/acts/ad-fu24-17-aileron-mass-balance-arms-modification","history":"/api/acts/ad-fu24-17-aileron-mass-balance-arms-modification/history","analysis":"/api/acts/ad-fu24-17-aileron-mass-balance-arms-modification/analysis","conflicts":"/api/acts/ad-fu24-17-aileron-mass-balance-arms-modification/conflicts","importantCases":"/api/acts/ad-fu24-17-aileron-mass-balance-arms-modification/important-cases","documents":"/api/acts/ad-fu24-17-aileron-mass-balance-arms-modification/documents"}}