{"id":"F2006B04806","name":"AD/BO 105/3 - Tail Rotor Gearbox Attachment","slug":"ad-bo-105-3-tail-rotor-gearbox-attachment","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44594,"registerId":"commonwealth-F2006B04806-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BO 105/3 - Tail Rotor Gearbox Attachment","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)  Eurocopter BO 105 Series Helicopters\n\n \n\nAD/BO 105/3 Tail Rotor Gearbox Attachment 7/86\n\nDM\n\n \n\nApplicability: All model BO 105 up to and including S/No 780. Requirement:  Action in accordance with MBB Alert Bulletin No. 28.\n\nCompliance: Within 100 hours time in service after 20 June 1986 but no later than 31 July 1986.\n\n \n\nBackground:  Inspection of bolts supplied to the manufacturer has revealed flaws necessitating the replacement of the existing bolts.\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":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-bound safety directive issued in 1986. It has not grown beyond its original purpose of addressing a specific manufacturing defect in a specific helicopter component. The scope remains precisely limited to the bolt replacement requirement for the affected serial numbers."},"complexity_factors":["Single, specific technical requirement (bolt replacement per manufacturer bulletin)","Clear applicability criteria (specific helicopter model and serial number range)","Simple compliance deadline (dual trigger: hours flown or calendar date, whichever first)","No defined terms section, no cross-references to other legislation beyond the manufacturer bulletin","Short document (approximately 150 words of substantive content)","No conditional logic or nested exceptions"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for specific helicopters.\n\n**What it does:**\n- Orders the inspection and replacement of certain bolts on the **tail rotor gearbox attachment** of **Eurocopter BO 105 helicopters** (specifically those with serial numbers up to 780).\n- The bolts were found to have manufacturing flaws that could compromise safety.\n\n**Who it affects:**\n- Owners and operators of BO 105 helicopters with serial numbers 780 and below.\n- Maintenance organisations servicing these aircraft.\n\n**What must be done:**\n- Follow the instructions in **MBB Alert Bulletin No. 28** (the manufacturer's safety notice).\n- Complete the work within **100 hours of flight time** after 20 June 1986, but **no later than 31 July 1986** — whichever comes first.\n\n**Why it matters:**\nThe tail rotor keeps the helicopter stable and prevents it from spinning. If the gearbox attachment bolts fail, the tail rotor could detach, causing catastrophic loss of control. This directive forces a fix before a dangerous failure can occur."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive’s scope is limited to BO 105 helicopters with serial numbers up to and including 780 and requires bolt replacement per the manufacturer’s bulletin. The text does not indicate any amendment or expansion of that original scope; it defines a one-time corrective action for the identified subset of aircraft (Applicability; Requirement; Compliance; Background)."},"complexity_factors":["Reference to an external technical document (MBB Alert Bulletin No. 28) for the required procedures rather than containing procedural detail in the AD (Requirement).","Tight, dual-form compliance window (100 hours TIS after 20 June 1986 or by 31 July 1986), requiring prompt scheduling (Compliance).","Applicability limited by serial-number cutoff (all BO 105 up to and including S/No 780), requiring fleet-specific identification (Applicability).","Logistical and cost implications for operators to replace bolts and obtain specified parts within the deadline (implied by Requirement and Compliance)."],"plain_english_summary":"This directive requires operators of BO 105 helicopters serial number ≤780 to replace tail‑rotor gearbox bolts per MBB Alert Bulletin No. 28 because inspections found flaws in supplied bolts. Work must be done within 100 flight hours after 20 June 1986 or by 31 July 1986. It compels operators/maintenance organisations to schedule and bear the cost to mitigate a detected hardware defect."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bo-105-3-tail-rotor-gearbox-attachment","history":"/api/acts/ad-bo-105-3-tail-rotor-gearbox-attachment/history","analysis":"/api/acts/ad-bo-105-3-tail-rotor-gearbox-attachment/analysis","conflicts":"/api/acts/ad-bo-105-3-tail-rotor-gearbox-attachment/conflicts","importantCases":"/api/acts/ad-bo-105-3-tail-rotor-gearbox-attachment/important-cases","documents":"/api/acts/ad-bo-105-3-tail-rotor-gearbox-attachment/documents"}}