{"id":"F2006B04788","name":"AD/BN-2/75 Amdt 2 - Turbine Engine Mounting Frame NB-20-6853","slug":"ad-bn-2-75-amdt-2-turbine-engine-mounting-frame-nb-20-6853","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44572,"registerId":"commonwealth-F2006B04788-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BN-2/75 Amdt 2 - Turbine Engine Mounting Frame NB-20-6853","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Safety Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \n\nAIRWORTHINESS DIRECTIVE\n\n![](image.001.png)\n\nFor the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/BN-2/75 Amdt 1 and issues the following AD under subregulation 39.1 (1) of CASR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.\n\n![](image.001.png)  \n\nPilatus Britten-Norman BN-2 Series Aeroplanes\n\nAD/BN-2/75\n\nAmdt 2\n\n  \nTurbine Engine Mounting Frame NB-20-6853 7/2004\n\nApplicability: Model BN2T, BN2T-4R, and BN2T-4S aircraft, which have accumulated 1,000 total flight hours.\n\nRequirement: Inspect in accordance with B-N Group Ltd. Service Bulletin SB 282 Issue 4.\n\nNote: UK CAA AD 002-05-2002 refers.\n\nCompliance: Unless the initial inspection is already accomplished, within 25 landings after 2 October 2003. Thereafter inspect as specified in the Requirement document.\n\nThe compliance time remains unchanged by this issue. This Amendment becomes effective on 8 July 2004.\n\nBackground: Cracking has been detected in the engine-mounting frame, in the welded area, where the diagonal beam attaches to the forward frame.\n\nAmendment 1 introduced Modification NB/M/1741, mounting frame NB-20-9309. Amendment 2 introduces the latest revision of the Requirement document.\n\nThe original issue of the Airworthiness Directive became effective on 8 August 2002.\n\n![](image.002.png)  \n\nDavid Villiers\n\nDelegate of the Civil Aviation Safety Authority 26 May 2004\n\n![](image.001.png)\n\nThe above AD is notified in the Commonwealth of Australia Gazette on 16 June 2004.\n\n  \n\nPage 1 of 1","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"Amendment 2 does not broaden the set of affected aircraft or add new mandatory modification requirements; it updates (revises) the referenced inspection document (Service Bulletin SB 282 Issue 4). Amendment 1 had previously introduced an approved modification (NB/M/1741). The directive’s core purpose — detect and correct cracking at the specified welded joint — remains the same, so the scope has not significantly changed beyond updating the technical instructions."},"complexity_factors":["Short, single‑issue AD focused on one component (engine‑mounting frame)","Applicability limited to three model variants and a 1,000 flight‑hour threshold","Single external technical reference: B‑N Group Ltd Service Bulletin SB 282 Issue 4 (adds dependence on an external document)","One short compliance window (initial inspection within 25 landings after 2 Oct 2003) plus recurring inspections per the SB","Cross‑reference to prior Amendments and a UK CAA AD (historical cross‑references increase traceability needs)","Amendment history (original AD, Amendment 1 with a modification option, Amendment 2 updating the requirement document) creates a small degree of documentary complexity"],"plain_english_summary":"**What this directive does (mechanics)\n\n- This is an Airworthiness Directive (AD) that requires specified Pilatus Britten‑Norman BN‑2 turbine‑engined aeroplanes to be inspected for cracking in the engine‑mounting frame.\n- Applicability: Model BN2T, BN2T‑4R and BN2T‑4S aircraft that have accumulated 1,000 total flight hours.\n- Required action: Carry out the inspection in accordance with B‑N Group Ltd. Service Bulletin SB 282 Issue 4 (the manufacturer’s inspection instructions).\n- Timing (compliance): If the inspection has not already been done, complete the initial inspection within 25 landings after 2 October 2003. After that, continue to inspect at the intervals and in the manner specified in the Service Bulletin.\n- History: This Amendment 2 revokes the earlier Amendment 1 and updates the referenced Requirement document to its latest revision. Amendment 1 previously introduced a modification option (NB/M/1741, mounting frame NB‑20‑9309).\n\n**Who is affected\n\n- Aircraft owners and operators of the specified BN‑2 turbine models (BN2T, BN2T‑4R, BN2T‑4S) that have reached the 1,000 flight‑hour threshold.\n- Maintenance organisations and engineers who perform inspections and corrective work following the Service Bulletin.\n\n**Why the rule exists (official rationale) and a practical test of that rationale\n\n- Official reason: Cracking was detected in the welded area where the diagonal beam attaches to the forward engine‑mounting frame. The AD’s stated purpose is to detect and correct that unsafe condition.\n- Practical test against costs and incentives:\n  - Who pays: The aircraft owner/operator pays for inspections, any required repairs, or installation of the modification. Inspection costs include labour, parts (if repairs are needed), and aircraft downtime.\n  - Incentives: Operators are incentivised to comply to keep the aircraft legally airworthy and avoid regulatory enforcement, and to reduce the risk of in‑flight structural failure. There is also an operational trade‑off: frequent inspections or corrective modifications increase maintenance cost and downtime but reduce the risk (and potential cost) of failure.\n  - Trade‑offs and opportunity cost: Choosing recurring inspections (per the SB) keeps the original structure but creates ongoing cost. Electing a one‑time modification (where permitted by the manufacturer/AD) may raise immediate cost but reduce or remove the need for repeated inspections.\n  - Implementation risk and compliance burden: The AD relies on an external document (SB 282 Issue 4). That places some burden on maintenance organisations to obtain and follow the current Service Bulletin and for CASA to accept compliance via that SB. If the SB lacks clarity, implementation risk (incorrect inspections/repairs) rises.\n  - Bureaucratic discretion: CASA (through a delegate) enforces the AD; the AD delegates technical detail to the manufacturer’s Service Bulletin rather than restating technical steps in the AD itself. That transfers technical judgment to the SB and to maintenance organisations interpreting it.\n\n**Concrete behavioural effects\n\n- Owners/operators must schedule and pay for the initial inspection within the short compliance window, then follow the recurring inspection intervals in the SB.\n- Maintenance providers must follow the SB’s inspection procedure and record compliance in the aircraft maintenance logbooks.\n- Operators may opt for the approved modification introduced in Amendment 1 (NB/M/1741) if that is available and permitted by the SB/AD; this can change the future inspection profile and costs.\n\n**Other references and cross‑checks\n\n- The AD refers to the UK CAA AD 002‑05‑2002 and to B‑N Group Service Bulletin SB 282 Issue 4 for the technical inspection procedure, so compliance requires consulting those documents.\n\n**Bottom line (neutral)\n\n- The AD mandates inspections to find and fix cracking found at a specific welded joint on certain BN‑2 turbine models. It shifts technical detail to the manufacturer’s Service Bulletin, requires a near‑term initial inspection if not already done, and then recurring inspections as specified. The direct costs fall on owners/operators; the expected benefit is reduced structural failure risk at that joint. The amendment updates the inspection instructions rather than broadening the set of affected aircraft."},"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This AD remains tightly focused on its original purpose: addressing cracking in the turbine engine mounting frame of specific BN-2 aircraft. Amendment 2 simply updates the referenced service bulletin to its latest revision (Issue 4) and revokes Amendment 1's alternative modification path. The scope has not expanded beyond the specific airworthiness issue identified in the original August 2002 directive."},"complexity_factors":["Single, specific mechanical component targeted (engine mounting frame NB-20-6853)","Clear applicability criteria (three specific aircraft models, 1,000+ flight hours)","Straightforward compliance timeline (25 landings after fixed date, or already done)","External reference to manufacturer service bulletin (SB 282 Issue 4) creates dependency on outside document","Brief amendment history (original issue, Amendment 1, Amendment 2) adds context but not operational complexity","No nested exceptions or conditional logic — inspection required or already completed exemption only","Single requirement section with one primary action"],"plain_english_summary":"This mandatory CASA Airworthiness Directive requires owners/operators of certain Pilatus Britten‑Norman Islander BN2T models (with ≥1,000 flight hours) to inspect the turbine engine mounting frame (PN NB‑20‑6853) for cracks at the welded diagonal beam connection, using Service Bulletin SB 282 Issue 4. Inspections must be done within 25 landings after 2 Oct 2003 and continued per the bulletin. Amendment 2 updates the SB reference, revokes Amendment 1, and took effect 8 July 2004."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bn-2-75-amdt-2-turbine-engine-mounting-frame-nb-20-6853","history":"/api/acts/ad-bn-2-75-amdt-2-turbine-engine-mounting-frame-nb-20-6853/history","analysis":"/api/acts/ad-bn-2-75-amdt-2-turbine-engine-mounting-frame-nb-20-6853/analysis","conflicts":"/api/acts/ad-bn-2-75-amdt-2-turbine-engine-mounting-frame-nb-20-6853/conflicts","importantCases":"/api/acts/ad-bn-2-75-amdt-2-turbine-engine-mounting-frame-nb-20-6853/important-cases","documents":"/api/acts/ad-bn-2-75-amdt-2-turbine-engine-mounting-frame-nb-20-6853/documents"}}