{"id":"F2006L02839","name":"AD/B747/351 - Engine Pylon Internal Structure","slug":"ad-b747-351-engine-pylon-internal-structure","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":60071,"registerId":"commonwealth-F2006L02839-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Boeing 747 Series Aeroplanes","sectionType":"division","heading":"Boeing 747 Series Aeroplanes","content":"### Boeing 747 Series Aeroplanes\n\n| AD/B747/351 | Engine Pylon Internal Structure | 10/2006 |\n| ----------- | ------------------------------- | ------- |\n\n| Applicability: | Model 747-200B, -200C, -200F, -300, and 747SR series aircraft; as identified in Boeing Special Attention Service Bulletin 747-54-2223 original issue, or later FAA approved revision.                                                                                                                                                                                                                            |\n| -------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | Action in accordance with the technical requirements of FAA AD 2006-16-10 Amdt 39-14710.                                                                                                                                                                                                                                                                                                                         |\n| Compliance:    | As specified in the Requirement document, with a revised effective date of28 September 2006.                                                                                                                                                                                                                                                                                                                     |\n|                | This Airworthiness Directive becomes effective on 28 September 2006.                                                                                                                                                                                                                                                                                                                                             |\n| Background:    | The FAA received reports of heat damage and cracking of the skin and internal structure adjacent to and aft of the pre-cooler exhaust vent on several engine struts. Undetected cracking, buckling, wrinkling, or heat damage of the skin and internal structure of the engine struts could result in extensive damage to the engine struts, and consequent possible in-flight separation of an affected engine. |\n\n![](image.001.png)  \nDavid Villiers  \nDelegate of the Civil Aviation Safety Authority\n\n17 August 2006","sortOrder":0},{"sectionNumber":"AD/B747/351","sectionType":"part","heading":"AD/B747/351","content":"## AD/B747/351","sortOrder":1},{"sectionNumber":"Engine Pylon Internal Structure","sectionType":"part","heading":"Engine Pylon Internal Structure","content":"## Engine Pylon Internal Structure","sortOrder":2},{"sectionNumber":"10/2006","sectionType":"part","heading":"10/2006","content":"## 10/2006","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"This AD remains tightly focused on the original safety problem (heat damage/cracking adjacent to the pre-cooler exhaust vent on certain 747 engine struts). It does not broaden the regulatory reach beyond inspecting and repairing that specific structure; instead it adopts the FAA’s technical requirements by reference. There is no indication in the text that the AD’s substantive scope has been expanded beyond that original safety purpose."},"complexity_factors":["Single corrective action but cross-references external FAA AD 2006-16-10 (requires reading another document for full requirements)","Reference to Boeing Special Attention Service Bulletin 747-54-2223 for applicability details (external document dependence)","Safety-critical inspections and possible repairs — technical complexity lies in the external documents rather than the AD text itself","Limited number of affected models but conditional applicability (“as identified in … Service Bulletin”) adds administrative filtering","Effective-date revision noted, introducing an administrative change to timing"],"plain_english_summary":"**What this instrument does (mechanics)**\n\n- Requires operators of certain Boeing 747 series aeroplanes to carry out the technical actions specified in FAA Airworthiness Directive (AD) 2006-16-10.  The Australian AD adopts the FAA AD requirements and sets the Australian effective date as 28 September 2006 (see “Requirement” and “Compliance”).\n- The AD applies to Model 747-200B, -200C, -200F, -300, and 747SR series aircraft, but only those identified in Boeing Special Attention Service Bulletin 747-54-2223 (original issue or a later FAA-approved revision) (see “Applicability”).\n\n**Why it matters (stated purpose and risk)**\n\n- The stated safety concern is reports of heat damage and cracking of the skin and internal structure next to and aft of the pre-cooler exhaust vent on some engine struts.  The FAA’s stated hazard is that undetected cracking, buckling, wrinkling or heat damage could cause extensive damage to the engine strut and could lead to possible in-flight separation of an affected engine (see “Background”).\n\n**Who it affects**\n\n- Aircraft owners and operators of the specified Boeing 747 models listed above, where the individual aeroplane is identified in the referenced Boeing Service Bulletin.\n- Maintenance organisations and licensed engineers who must carry out inspections, repairs or modifications in accordance with the FAA AD and the Boeing Service Bulletin.\n\n**How it works in practice**\n\n- Operators must follow the technical instructions in FAA AD 2006-16-10. In practice that means performing the inspections and any required repairs or modifications described in the FAA AD/Boeing Service Bulletin within the intervals and to the standards those documents set out. The Australian AD does not restate the detailed technical steps; it adopts them by reference (see “Requirement”).\n- The effective date for compliance under Australian regulation is 28 September 2006.\n\n**Practical consequences, incentives and trade-offs**\n\n- Who pays: aircraft operators pay for inspections, labour, parts and any corrective work. Those costs include direct maintenance expense and indirect costs from aircraft downtime.\n- Who decides and enforces: the Civil Aviation Safety Authority (CASA) enforces compliance via the AD; maintenance providers and operators decide how and when to schedule the required work within the AD’s intervals, subject to any approval processes for alternative methods of compliance.\n- Behaviour changes: operators are incentivised to inspect and, where required, repair or modify engine pylon internal structure near the pre-cooler exhaust vent to remain airworthy. They may also change maintenance cycles or keep spare aircraft to cover downtime.\n- Trade-offs and opportunity costs: safety-driven maintenance increases operating costs and can reduce fleet availability while reducing the risk of structural failure and in-flight engine separation. Operators must allocate maintenance resources and may prioritise affected aircraft over other work.\n- Implementation risks: the AD relies on external technical documents (the FAA AD and the Boeing Service Bulletin). Risks include availability of approved parts or repair processes, the difficulty of detecting hidden or progressive damage, and scheduling complexity for heavy maintenance.\n- Compliance burden: the AD cross-references FAA requirements and a Boeing Service Bulletin rather than reproducing steps; this reduces repetition but adds administrative overhead for operators to obtain, interpret and act on those external documents.\n\n**Market and operational effects**\n\n- Effects on private enterprise: the measure imposes additional safety-driven maintenance costs on airlines and freight operators operating the affected 747s. Maintenance organisations will receive work for inspections and repairs; specialist repair parts or approved repair procedures may give an advantage to certain suppliers if they are the only approved source.\n- Competition and prices: increased maintenance costs can raise the operating cost of affected aircraft, which may influence choices about deploying those aircraft or replacing them with other types. The AD does not itself set prices or subsidies.\n\n**Scope and limits of this AD**\n\n- The AD is narrowly targeted: it applies only to specified 747 variants and only to aircraft identified in the referenced Boeing Service Bulletin. It does not impose generic rules on other aircraft types.\n\n(References: Applicability, Requirement, Compliance and Background sections of AD/B747/351.)"},"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a standard, narrow airworthiness directive addressing a specific safety defect in specific aircraft models. It has not expanded beyond its original purpose of mandating inspection/repair of engine pylon structures."},"complexity_factors":["Very short document (under 300 words)","Only 1 defined applicability criterion (specific aircraft models)","Single cross-reference to external technical document (FAA AD 2006-16-10)","No nested conditions or exceptions","Straightforward compliance requirement: follow the external standard","Clear, single effective date with no alternative compliance timelines"],"plain_english_summary":"This AD requires owners/operators of certain Boeing 747-200/300/SR series (as covered by the referenced Boeing service bulletin) to inspect and repair engine pylon internal structure for heat damage and cracking near the pre-cooler exhaust vent.  \n\nUnchecked damage could lead to engine strut failure and an in-flight engine separation; compliance follows FAA AD 2006-16-10 and was due by 28 September 2006."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b747-351-engine-pylon-internal-structure","history":"/api/acts/ad-b747-351-engine-pylon-internal-structure/history","analysis":"/api/acts/ad-b747-351-engine-pylon-internal-structure/analysis","conflicts":"/api/acts/ad-b747-351-engine-pylon-internal-structure/conflicts","importantCases":"/api/acts/ad-b747-351-engine-pylon-internal-structure/important-cases","documents":"/api/acts/ad-b747-351-engine-pylon-internal-structure/documents"}}