{"id":"F2006B10523","name":"AD/HS 125/81 - Aileron Mass Balance - Cracking of Side Plate Attachment Lugs","slug":"ad-hs-125-81-aileron-mass-balance-cracking-of-side-plate-attachment-lugs","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":116309,"registerId":"commonwealth-F2006B10523-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HS 125/81 - Aileron Mass Balance - Cracking of Side Plate Attachment Lugs","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)  British Aerospace BAe 125 Series Aeroplanes\n\n \n\n# AD/HS 125/81 Aileron Mass Balance - Cracking of\n\nSide Plate Attachment Lugs\n\nApplicability: All models to -700 inclusive.\n\n \n\nRequirement: Action in accordance with British Aerospace 125 S.B. 57-66, Rev 1.\n\n# 12/86\n\n \n\nCompliance: Prior to 31 March 1987 and thereafter every 600 hours time in service until repaired in accordance with Repair Scheme 25WG/R143.\n\n \n\nBackground: Cracking of the attachment lugs of the aileron mass balance side plate may result in displacement of the side plate and interfere with aileron movement.\n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive’s scope aligns with the stated safety objective in the Background: it targets cracking of the aileron mass balance side plate attachment lugs on BAe 125 models up to -700 and prescribes inspections and a repair route. The Applicability, Requirement and Compliance text specify the population covered, the manufacturer procedure to follow, and the timing/recurrence of inspections until the named repair is carried out, consistent with that original intent."},"complexity_factors":["Reference to external technical documents (British Aerospace Service Bulletin 57-66 Rev 1 and Repair Scheme 25WG/R143) requires access to and reliance on manufacturer material (Requirement).","Recurring inspection interval (every 600 hours) until a specified repair is completed creates an ongoing compliance obligation rather than a one-off action (Compliance).","Technical nature of the defect (cracking of attachment lugs on an aileron mass balance side plate) requires specialised inspection and repair capacity (Background; Requirement).","Wide applicability across BAe 125 models to -700 inclusive means many operators may be affected and must track compliance (Applicability).","Fixed compliance deadline (prior to 31 March 1987) introduces a past-date milestone in the directive that may affect retrospective record-keeping and scheduling (Compliance)."],"plain_english_summary":"This AD requires operators of British Aerospace BAe 125 aeroplanes (all models to -700 inclusive) to carry out inspections per BAe Service Bulletin 57‑66 Rev 1 before 31 March 1987 and then every 600 flight hours until the permanent repair is done under Repair Scheme 25WG/R143. It affects owners, maintenance providers and parts suppliers, imposes inspection and repair costs, and addresses aileron‑interference risk from cracked mass‑balance side‑plate lugs."},"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 inspection and repair of aileron mass balance attachment lugs."},"complexity_factors":["Very short document (under 200 words)","Only 4 defined elements: applicability (aircraft models), requirement (service bulletin reference), compliance deadline, and background","No nested conditional logic or cross-referencing to other legislation","Single technical reference to external manufacturer document (Service Bulletin 57-66)","Straightforward timeline: one-off deadline plus recurring interval","No exceptions, exemptions, or alternative compliance methods stated"],"plain_english_summary":"This is an **Airworthiness Directive** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for specific aircraft.\n\n**What it does:**\nOrders owners and operators of **British Aerospace BAe 125 series aircraft** (models up to the -700 variant) to inspect and repair a specific mechanical defect in the ailerons (the hinged surfaces on the wings that control the aircraft's roll).\n\n**The problem:**\nThe **mass balance** — a weight attached to the aileron to prevent dangerous vibrations (flutter) at high speeds — has **side plate attachment lugs** (the small projecting arms that connect the weight to the aileron structure) that can develop **cracks**. If these lugs crack and break, the side plate can shift out of position and jam the aileron, potentially causing loss of control.\n\n**What must be done:**\n- **By 31 March 1987:** Complete the initial inspection/repair following British Aerospace Service Bulletin 57-66, Revision 1 (the manufacturer's official repair instructions).\n- **Every 600 flight hours after that:** Repeat the inspection until a permanent repair is done using \"Repair Scheme 25WG/R143\" (a specific engineering fix approved by the manufacturer).\n\n**Who it affects:**\nAnyone who owns, operates, or maintains British Aerospace BAe 125 aircraft in Australia — including charter companies, private owners, and maintenance organisations.\n\n**Why it matters:**\nThis is a **flight safety critical** issue. Aileron jamming during flight could lead to loss of control and crash. The directive makes compliance legally mandatory — flying without doing these inspections violates civil aviation law."}},"importantCases":[],"_links":{"self":"/api/acts/ad-hs-125-81-aileron-mass-balance-cracking-of-side-plate-attachment-lugs","history":"/api/acts/ad-hs-125-81-aileron-mass-balance-cracking-of-side-plate-attachment-lugs/history","analysis":"/api/acts/ad-hs-125-81-aileron-mass-balance-cracking-of-side-plate-attachment-lugs/analysis","conflicts":"/api/acts/ad-hs-125-81-aileron-mass-balance-cracking-of-side-plate-attachment-lugs/conflicts","importantCases":"/api/acts/ad-hs-125-81-aileron-mass-balance-cracking-of-side-plate-attachment-lugs/important-cases","documents":"/api/acts/ad-hs-125-81-aileron-mass-balance-cracking-of-side-plate-attachment-lugs/documents"}}