{"id":"F2006B04751","name":"AD/BN-2/39 - Aileron Mass Balance Tube - Inspection","slug":"ad-bn-2-39-aileron-mass-balance-tube-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44515,"registerId":"commonwealth-F2006B04751-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BN-2/39 - Aileron Mass Balance Tube - Inspection","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)  Pilatus Britten-Norman BN-2 Series Aeroplanes\n\n \n\nAD/BN-2/39 Aileron Mass Balance Tube - Inspection NK\n\nApplicability: All models.\n\n \n\nDocument: Britten Norman SB No. BN-2/SB.98.\n\n \n\nCompliance: Within 100 hours time in service after 31 January 1977 or not later than 1 March 1977 whichever occurs first.\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":1,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive focused on one specific mechanical component on one aircraft type. It has not expanded beyond its original safety purpose."},"complexity_factors":["Extremely short document (approximately 150 words)","No defined terms section","No cross-references to other legislation beyond the enabling regulations","Simple, unambiguous compliance requirement with single deadline","No conditional logic or exceptions","Single applicability criterion ('All models')","Refers to external technical document (Service Bulletin) rather than embedding complex technical specifications"],"plain_english_summary":"**What this is:** This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) under the Civil Aviation Regulations 1998.\n\n**What it does:** It requires owners and operators of **Pilatus Britten-Norman BN-2 series aircraft** (commonly known as Islander or Trislander planes) to inspect the **aileron mass balance tube** — a component that helps keep the aircraft's ailerons (the hinged surfaces on the wings that control rolling) stable during flight.\n\n**Who must comply:** Anyone operating any model of BN-2 aircraft.\n\n**The requirement:** The inspection must be carried out following the instructions in **Britten-Norman Service Bulletin No. BN-2/SB.98**.\n\n**When it had to be done:** Within 100 hours of flying time after 31 January 1977, or by 1 March 1977 — whichever came first. (Note: This deadline has long passed; this is a historical directive.)\n\n**Why it matters:** Mass balance tubes prevent dangerous vibrations or flutter in the ailerons that could lead to loss of control. This AD was issued to catch potential failures before they caused accidents."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The supplied AD applies to all Pilatus Britten‑Norman BN‑2 models and requires an inspection per the manufacturer's service bulletin within the specified time window (Applicability: \"All models.\"; Document: \"Britten Norman SB No. BN-2/SB.98.\"; Compliance: \"Within 100 hours time in service after 31 January 1977 or not later than 1 March 1977 whichever occurs first.\"). The text contains no indication that the AD expanded or narrowed the applicability from an earlier intention; based on the supplied text, the scope remains a universal requirement for BN‑2 aircraft."},"complexity_factors":["Very short text with a single, clearly stated action (inspection) and clear applicability (\"All models.\")","Fixed, simple compliance timing (100 hours TIS after 31 January 1977 or by 1 March 1977) reduces interpretive complexity","Technical details and acceptance criteria are not contained in the AD but delegated to a referenced service bulletin (Britten Norman SB No. BN-2/SB.98), creating dependence on an external document","No explicit remedial actions, record‑keeping rules, or waiver/alternate compliance options in the supplied text introduce practical ambiguity for implementers","Historical/retroactive deadline elements (dates in 1977) may require interpretation for aircraft with differing hours records, but the AD itself does not elaborate"],"plain_english_summary":"This AD mandates inspection of the aileron mass balance tube on all Pilatus Britten‑Norman BN‑2 aeroplanes, to be done per Britten Norman SB No. BN‑2/SB.98 within 100 hours TIS after 31 Jan 1977 or by 1 Mar 1977, whichever comes first.  \n\nIt creates a short, mandatory compliance window that operators or their maintenance providers must meet and pay for, with technical procedure and criteria delegated to the referenced service bulletin."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bn-2-39-aileron-mass-balance-tube-inspection","history":"/api/acts/ad-bn-2-39-aileron-mass-balance-tube-inspection/history","analysis":"/api/acts/ad-bn-2-39-aileron-mass-balance-tube-inspection/analysis","conflicts":"/api/acts/ad-bn-2-39-aileron-mass-balance-tube-inspection/conflicts","importantCases":"/api/acts/ad-bn-2-39-aileron-mass-balance-tube-inspection/important-cases","documents":"/api/acts/ad-bn-2-39-aileron-mass-balance-tube-inspection/documents"}}