{"id":"F2006B04743","name":"AD/BN-2/31 Amdt 1 - Engine Mounting Frames - Inspection","slug":"ad-bn-2-31-amdt-1-engine-mounting-frames-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44507,"registerId":"commonwealth-F2006B04743-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BN-2/31 Amdt 1 - Engine Mounting Frames - 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-2/31\n\nAmdt 1\n\n\nEngine Mounting Frames - Inspection 5/74\n\n \n\nApplicability: All models with engine mounting frames P/Nos. NB-20-G- 1901, NB-20-G-5231, NB-51-H-1021 and NB-20-D-5209.\n\n \n\nDocument: Britten Norman SB BN-2/SB.72.\n\n \n\nCompliance: Unless already accomplished, within 10 hours time in service after 31 May 1974.\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":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive focused specifically on engine mounting frame inspections for one aircraft type. It has not expanded beyond its original purpose; it remains a narrow technical airworthiness requirement."},"complexity_factors":["Very short document (approximately 150 words of substantive content)","Only 4 specific part numbers to identify applicability","Single compliance requirement with clear deadline (10 hours time in service after fixed date)","No defined terms section, no cross-references to other legislation beyond the parent Civil Aviation Regulations 1998","No conditional logic or nested exceptions — straightforward 'do this by this date' instruction","References only one technical document (Service Bulletin BN-2/SB.72)"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It applies to specific **Pilatus Britten-Norman BN-2 aircraft** (small twin-engine planes often used for regional transport and skydiving).\n\n**What it requires:**\nOwners and operators must inspect the **engine mounting frames** (the metal structures that attach the engines to the aircraft wing) on affected planes. The specific part numbers covered are NB-20-G-1901, NB-20-G-5231, NB-51-H-1021, and NB-20-D-5209.\n\n**Why it matters:**\nEngine mounting frames are critical structural components. If they crack or fail, an engine could detach from the wing in flight — obviously catastrophic. This AD was issued after the manufacturer (Britten-Norman) identified a safety issue requiring inspection.\n\n**The deadline:**\nThe inspection had to be completed within **10 hours of flying time** after 31 May 1974, unless it was already done.\n\n**Who needs to follow this:**\nAnyone operating or maintaining a BN-2 aircraft with the specified engine mount part numbers. Non-compliance means the aircraft cannot legally fly in Australian airspace."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The supplied text is labelled as Amendment 1 (Amdt 1) but contains only the amended directive text; it does not include the original AD text or a comparison showing how the scope was altered. Based on the material provided, there is no explicit indication within this excerpt that the scope (the set of affected part numbers or the required action) differs from the original intent."},"complexity_factors":["Narrow technical scope — applies only to BN‑2 series with four specified engine mounting frame part numbers (Applicability)","Single, short compliance action — one inspection required within a fixed 10‑hour time‑in‑service window (Compliance)","Dependency on an external technical document (Britten Norman SB BN‑2/SB.72) for the inspection procedure (Document)","Operational scheduling impact — tight deadline can create logistical complexity despite technical simplicity (Compliance)","Limited procedural detail in the supplied text — technicians must consult the referenced service bulletin for specific inspection steps (Document)"],"plain_english_summary":"What this instrument does (mechanically)\n\n- It requires an inspection of the engine mounting frames on certain Pilatus Britten‑Norman BN‑2 series aeroplanes. (Applicability)\n- The inspection must be carried out in accordance with the specified service document: Britten Norman SB BN‑2/SB.72. (Document)\n- If the inspection has not already been done, it must be completed within 10 hours time in service after 31 May 1974. (Compliance)\n\nWho is affected\n\n- Owners and operators of BN‑2 series aeroplanes that have engine mounting frames with part numbers NB‑20‑G‑1901, NB‑20‑G‑5231, NB‑51‑H‑1021 or NB‑20‑D‑5209. (Applicability)\n- The Civil Aviation Safety Authority (identified in the heading) is the issuing authority for the directive and enforces compliance through the airworthiness directive framework.\n\nWhy it matters (source statements and operational implications)\n\n- The supplied text does not state an explicit rationale for the inspection. The instrument is an airworthiness directive that creates a mandatory inspection requirement for the listed parts. (Document; Compliance)\n\nPractical effects, who pays, and what changes in behaviour\n\n- Who pays: The immediate financial and labour cost of performing the inspection falls on the aircraft owner or operator, since they must arrange for and carry out the inspection within the stated 10‑hour window. (Compliance)\n- What operators must do: Identify whether their aircraft have any of the listed engine mounting frame part numbers, obtain and follow Britten Norman SB BN‑2/SB.72, and record/complete the inspection within the time limit. (Applicability; Document; Compliance)\n- Timing and operational impact: The requirement creates a short, defined compliance window (10 hours time in service after 31 May 1974), which can force near‑term scheduling of maintenance and potential downtime for affected aircraft. (Compliance)\n- Downstream actions: If the inspection identifies defects, operators will incur additional costs and decisions about repair or grounding; those possible outcomes are implied by the inspection requirement but are not detailed in the supplied text. (Document)\n\nImplementation, compliance burden, discretion and trade‑offs\n\n- Compliance burden: The directive imposes a one‑off inspection obligation with a tight deadline; the burden includes labour, possible parts/repairs, and administrative records. (Compliance; Document)\n- Dependence on an external procedure: The inspection is to be performed according to the referenced service bulletin; operators must obtain and apply that bulletin to comply. (Document)\n- Administrative discretion: The AD sets a mandatory requirement and a deadline; the supplied text does not describe any discretion, exemption process, or follow‑up enforcement steps. (Heading; Compliance)\n- Opportunity costs and incentives: Operators must allocate maintenance resources and aircraft availability to meet the deadline; larger operators with in‑house maintenance may absorb the task differently than smaller operators who must contract it out. The text does not quantify costs or provide mitigation measures. (Applicability; Compliance)\n\nConcrete citation points\n\n- Applicability: lists affected aircraft and part numbers.\n- Document: references Britten Norman SB BN‑2/SB.72 as the procedural source for the inspection.\n- Compliance: sets the deadline (within 10 hours time in service after 31 May 1974) and the conditional clause (unless already accomplished)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bn-2-31-amdt-1-engine-mounting-frames-inspection","history":"/api/acts/ad-bn-2-31-amdt-1-engine-mounting-frames-inspection/history","analysis":"/api/acts/ad-bn-2-31-amdt-1-engine-mounting-frames-inspection/analysis","conflicts":"/api/acts/ad-bn-2-31-amdt-1-engine-mounting-frames-inspection/conflicts","importantCases":"/api/acts/ad-bn-2-31-amdt-1-engine-mounting-frames-inspection/important-cases","documents":"/api/acts/ad-bn-2-31-amdt-1-engine-mounting-frames-inspection/documents"}}