{"id":"F2006B04763","name":"AD/BN-2/51 Amdt 3 - Main Landing Gear Upper Torque Link Attachment Lug","slug":"ad-bn-2-51-amdt-3-main-landing-gear-upper-torque-link-attachment-lug","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44527,"registerId":"commonwealth-F2006B04763-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BN-2/51 Amdt 3 - Main Landing Gear Upper Torque Link Attachment Lug","content":"![](image.001.png)\n\n![](image.001.png)  \nAIRWORTHINESS DIRECTIVE\n\nFor the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/BN-2/51 Amdt 2 and issues the following AD under subregulation 39.1 (1) of CAR 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-2/51\n\nAmdt 3\n\n  \n\nMain Landing Gear Upper Torque Link Attachment Lug\n\n  \n10/2002\n\nApplicability: All BN2, BN2A, BN2B, and BN2T Series Islander aircraft.\n\nRequirement: 1. Inspect in accordance with FHL Service Bulletin 32-4 Issue 5, Revision 2, dated 15 June 2002.\n\n2. Replace Main Undercarriage Assembly Part Number 3499H1 with Assembly Part Number 3499H2, in accordance with FHL Service Bulletin (SB) 32-4 Issue 5, SB 32-4 Issue 5 Revision 1, or SB 32-4 Issue 5 Revision 2.\n\nNote: B-N Group Ltd Mandatory Service Bulletin SB 170 Issue 6 refers.\n\nCompliance: 1. As specified in the Requirement document.\n\n2. Within 1,000 landings after 9 January 2002, or before 30 September 2002, whichever occurs first.\n\nThe compliance times remain unchanged by this issue. This Amendment becomes effe ctive on 3 October 2002.\n\nBackground: There have been occurrences of main leg cylinders exhibiting fatigue cracks at the torque link lugs, which could result in detachment of the torque links under subsequent heavy static loads. In addition, a recent occurrence of detachment of the torque link showed no such evidence of cracking prior to failure under heavy static load.\n\nAmendment 3 is issued in response to a revision of the Requirement document, which corrects Figure 7 part numbers.\n\nPilatus Britten-Norman BN-2 Series Aeroplanes\n\nAD/BN-2/51 Amdt 3 (continued)\n\nAmendment 2 of this Airworthiness Directive became effective on 24 January 2002\\. Amendment 1 of this Airworthiness Directive became effective on 31 August 1986. The original issue of this Airworthiness Directive became effective on 31 July 1985.\n\n![](image.002.jpeg)\n\nDavid Alan Villiers\n\nDelegate of the Civil Aviation Safety Authority 22 August 2002\n\n![](image.001.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 11 September 2002.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"This Amendment 3 does not expand the subject matter or impose new categories of obligation beyond the prior amendment. It keeps the same inspection and replacement requirements and the same compliance times, and its stated purpose is to correct figure part numbers in the Requirement document. Therefore the scope of the AD (targeted corrective action on the BN‑2 landing gear) remains aligned with the original safety objective rather than being broadened."},"complexity_factors":["Single focused safety issue (main landing gear torque link lug)","Short, narrowly targeted AD (few operative clauses: inspect and replace)","References to multiple external documents (FHL Service Bulletin 32‑4 Issue 5 plus Revisions 1 and 2; B‑N Group SB 170 Issue 6)","One conditional compliance window (within 1,000 landings after 9 Jan 2002 or before 30 Sep 2002, whichever is earlier)","Cross‑reference to and revocation of earlier amendment (AD/BN‑2/51 Amdt 2), but no broad new powers or ongoing reporting requirements","Correction of figure part numbers in Requirement document (amendment limited to clerical/technical correction)"],"plain_english_summary":"**What this instrument does (mechanics)**\n\n- This Airworthiness Directive (AD) requires operators of Pilatus Britten‑Norman BN‑2 series Islander aeroplanes to inspect the main landing‑gear upper torque‑link attachment area and to replace the main undercarriage assembly where specified. (See: Applicability; Requirement.)\n- The inspection must be carried out in accordance with FHL Service Bulletin 32‑4 Issue 5, Revision 2 (dated 15 June 2002). (Requirement 1.)\n- Where fitted with Main Undercarriage Assembly part number 3499H1, that assembly must be replaced with part number 3499H2 in accordance with FHL Service Bulletin 32‑4 (Issue 5, Revision 1 or 2 also acceptable). (Requirement 2.)\n- Compliance timing: inspections as specified in the service bulletin; replacement must occur within 1,000 landings after 9 January 2002 or before 30 September 2002, whichever is earlier. (Compliance.)\n\n**Who is affected**\n\n- All owners and operators of BN2, BN2A, BN2B and BN2T series Islander aeroplanes (Applicability).\n- Maintenance organisations or workshops that perform structural inspections and undercarriage replacements for these aircraft.\n\n**Why it matters (official rationale and operational effect)**\n\n- The AD is issued because fatigue cracks have been found in main leg cylinders at the torque‑link lugs and because at least one separation of the torque link has occurred without prior visible cracking. The risk, if unaddressed, is detachment of torque links under heavy static loads, which could impair landing‑gear function. (Background.)\n- The AD’s corrective steps (inspection and replacement) are intended to remove or mitigate the affected parts and thereby reduce the risk of torque‑link detachment.\n\n**Costs, incentives, and trade‑offs (practical effects)**\n\n- Who pays: aircraft owners/operators must fund inspections, the purchase of replacement undercarriage assemblies (P/N 3499H2), and labour and downtime costs. (Requirement; Compliance.)\n- Timing pressure: the replacement window (1,000 landings after 9 Jan 2002 or before 30 Sep 2002) forces operators to schedule work within a defined short term, which may increase maintenance scheduling costs or require out‑of‑sequence removals. (Compliance.)\n- Supply and downtime risk: if replacement assemblies (3499H2) are in limited supply, operators may face grounded aircraft or delays while waiting for parts; independent MROs must ensure they have access to the specified parts and the current service bulletin instructions to comply. (Requirement; Practical implication.)\n- Detection uncertainty: the Background notes that at least one failure occurred without prior evidence of cracking. That means inspection alone may not reliably predict all failures; replacement is therefore mandated as a more certain corrective action for assemblies with the older part number. (Background; Requirement 2.)\n- Administrative/implementation clarity: the AD references specific FHL Service Bulletin revisions and also notes a B‑N Group mandatory service bulletin (SB 170 Issue 6). Operators must follow the correct revision identified in the AD; Amendment 3 corrects figure part numbers in the Requirement document (Background), so operators must use the corrected figures to identify parts correctly.\n\n**Effects on market actors and choice**\n\n- Independent maintenance organisations can perform the work but must follow the specified service bulletin instructions; this preserves private MRO choice but requires they have the correct documentation and parts availability.\n- The directive imposes a relatively concentrated cost on the subset of operators flying BN‑2 family aircraft. Competing aircraft types or other operators are unaffected.\n\n**Implementation risk and regulatory discretion**\n\n- The AD is prescriptive: CASA (via its delegate) prescribes the inspection and replacement and sets compliance deadlines. The delegate also revoked the previous amendment and issued this updated amendment (mechanism of regulatory action). (Opening text; Background.)\n- The main practical risk is logistical: parts supply, accurate identification of assemblies (the amendment corrects figure part numbers), and scheduling the replacement within the short compliance window.\n\n**Net operational effect**\n\n- Operators must inspect per the specified service bulletin and, where older assemblies (3499H1) are fitted, replace them with 3499H2 within the stated landing/ date window. The directive keeps the compliance times unchanged from the prior amendment but corrects part‑number figures in the service instructions. (Compliance; Background.)"},"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 Amendment 3 is a technical correction only. The scope remains identical to Amendments 1 and 2 — addressing fatigue cracks in main landing gear torque link lugs on Islander aircraft. The only change is correcting Figure 7 part numbers in the referenced service bulletin."},"complexity_factors":["Short, single-purpose document (2 pages)","Only 4 defined aircraft model variants in applicability section","Clear, numbered requirements with specific part numbers and document references","Simple compliance formula: 'whichever occurs first' between two dates/landings count","Minimal cross-referencing (only to specific service bulletins and one related mandatory bulletin)","No nested exceptions or conditional logic — requirements apply to all applicable aircraft uniformly"],"plain_english_summary":"This CASA Airworthiness Directive mandates inspections and, where required, replacement of main landing gear components on Pilatus Britten‑Norman Islander aircraft (BN2, BN2A, BN2B, BN2T) to address fatigue cracking at the torque‑link attachment lugs that can lead to torque‑link detachment and landing‑gear failure.\n\nCompliance was required by the earlier deadlines (1,000 landings after 9 Jan 2002 or before 30 Sep 2002). Amendment 3 only corrects part numbers in Figure 7 and does not change required actions or dates."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bn-2-51-amdt-3-main-landing-gear-upper-torque-link-attachment-lug","history":"/api/acts/ad-bn-2-51-amdt-3-main-landing-gear-upper-torque-link-attachment-lug/history","analysis":"/api/acts/ad-bn-2-51-amdt-3-main-landing-gear-upper-torque-link-attachment-lug/analysis","conflicts":"/api/acts/ad-bn-2-51-amdt-3-main-landing-gear-upper-torque-link-attachment-lug/conflicts","importantCases":"/api/acts/ad-bn-2-51-amdt-3-main-landing-gear-upper-torque-link-attachment-lug/important-cases","documents":"/api/acts/ad-bn-2-51-amdt-3-main-landing-gear-upper-torque-link-attachment-lug/documents"}}