{"id":"F2006B03055","name":"AD/B747/153 - Nacelle Strut and Wing Structure - P & W JT9D Series Engine","slug":"ad-b747-153-nacelle-strut-and-wing-structure-p-w-jt9d-series-engine","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42414,"registerId":"commonwealth-F2006B03055-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B747/153 - Nacelle Strut and Wing Structure - P & W JT9D Series Engine","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nBoeing 747 Series Aeroplanes\n\nAD/B747/153 Nacelle Strut and Wing Structure \\- P & W JT9D Series Engine\n\n  \n9/95\n\nApplicability: Model 747 series aircraft with line positions 001 through 814, equipped with Pratt & Whitney JT9D series engine (excluding JT9D-70 engines).\n\nRequirement: Action in accordance with the technical requirements of FAA AD 95-10-16 Amdt 39- 9233.\n\nNote: Boeing Alert Service Bulletin 747-54A2159 refers.\n\nCompliance: As specified in the Requirement Document with a revised effective date of 17 August 1995.\n\nBackground: The FAA requires the incorporation of a modification of the strut and wing structure, that has been developed by the manufacturer to improve the damage tolerance capability and durability of the strut-to-wing attachments, and reduce reliance on inspections of those attachments.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope: a specific structural modification for a defined subset of Boeing 747 aircraft. It has not expanded beyond its original safety purpose."},"complexity_factors":["Very short document (under 300 words)","Only 1 defined term implicitly used ('line positions' — production sequence numbers)","Single compliance requirement with external reference to FAA AD and Boeing Service Bulletin","No nested exceptions or conditional logic — applicability is straightforward (model range + engine type, with one exclusion)","No cross-references to other Australian legislation beyond Civil Aviation Regulations 1998 Part 39"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for specific aircraft.\n\n**What it does:**\n- Requires owners and operators of certain Boeing 747 aircraft to carry out structural modifications to the **nacelle strut** (the structure that holds the engine to the wing) and the **wing structure** itself.\n- The modification improves how well these parts resist damage and wear over time, specifically where the engine strut attaches to the wing.\n- It reduces how often inspectors need to check these attachment points because the new design is more durable.\n\n**Who it affects:**\n- Operators of **Boeing 747 aircraft** with production line numbers 001 through 814 (roughly early to mid-production models).\n- Only those fitted with **Pratt & Whitney JT9D engines** (but **not** the JT9D-70 variant).\n\n**Why it matters:**\n- The strut-to-wing attachment is critical — if it fails, the engine could separate from the wing in flight.\n- The FAA (American aviation regulator) identified a safety issue and mandated this fix. Australia is adopting the same requirement to keep our skies safe.\n- Compliance is mandatory by **17 August 1995**.\n\n**Key reference:** Operators must follow the technical instructions in **FAA AD 95-10-16** and **Boeing Alert Service Bulletin 747-54A2159** to complete the work."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD’s scope is not expanded beyond the original technical intent described in the background: it applies specifically to Model 747 airframes within line positions 001–814 fitted with JT9D series engines (excluding JT9D-70) and requires incorporation of the manufacturer-developed modification as set out in the FAA AD and related Boeing service bulletin. The instrument adopts that modification requirement and its applicability without adding broader or different categories of aircraft or additional tasks beyond those referenced. (Applicability; Requirement; Background)"},"complexity_factors":["Cross-reference to an external FAA Airworthiness Directive (FAA AD 95-10-16 Amdt 39-9233) means operators must obtain and follow another document for technical detail (Requirement).","Reference to a manufacturer service bulletin (Boeing Alert Service Bulletin 747-54A2159) adds another external technical source to consult (Note).","Applicability is precise (limited to Model 747 line positions 001–814 and JT9D series engines excluding JT9D-70), which simplifies scope determination but requires verification of individual airframe/engine fit (Applicability).","The AD mandates a structural modification rather than a simple inspection, which typically involves parts, certified maintenance organisations and aircraft downtime—logistical complexity for operators (Requirement; Compliance).","Compliance timing is tied to the referenced FAA AD with a specified effective date, so operators must align scheduling to that external compliance timetable (Compliance)."],"plain_english_summary":"Summary\n\n- What the rule does, mechanically: The Civil Aviation Safety Authority (CASA) requires certain Boeing 747 aeroplanes to have a physical modification made to the nacelle strut and wing structure at the engine attachment area. The AD directs operators to carry out the technical steps specified in FAA Airworthiness Directive 95-10-16 Amendment 39-9233, and notes Boeing Alert Service Bulletin 747-54A2159 as related information. (Requirement; Note)\n\n- Which aircraft are affected: The requirement applies to Model 747 series aeroplanes with line positions 001 through 814 that are fitted with Pratt & Whitney JT9D series engines, but it explicitly excludes aircraft fitted with JT9D-70 engines. (Applicability)\n\n- When it must be done: Compliance must follow the timing and procedures set out in the referenced FAA AD, with a revised effective date of 17 August 1995. (Compliance)\n\n- Why the change is required (official technical rationale): The FAA and the manufacturer developed a modification intended to improve damage tolerance and durability of the strut-to-wing attachments and to reduce reliance on repeated inspections of those attachments. CASA’s AD requires incorporation of that modification by reference to the FAA AD. (Background; Requirement)\n\nOperational and economic mechanics (who pays, who decides, what changes):\n- Who pays: Aircraft operators or owners are responsible for carrying out the modification and for any parts, labour and downtime associated with it, because the AD places the obligation on the operator to comply. (Requirement; Compliance)\n- Who decides and enforces: CASA enforces compliance by issuing this AD and by requiring action in accordance with the FAA AD it references. Aircraft maintenance organisations must follow the technical instructions in the FAA AD/Boeing service bulletin when performing the work. (Requirement; Note)\n- What behaviour changes: Operators must arrange and complete the structural modification instead of depending only on inspection regimes. Maintenance providers will perform the specified structural modification work per the referenced documents. (Background; Requirement)\n\nTrade-offs, implementation and compliance considerations:\n- Compliance requires obtaining and following external technical documents (the FAA AD and Boeing service bulletin), so operators must locate and apply those detailed instructions. (Requirement; Note)\n- There will be direct costs (parts, labour, aircraft out-of-service time) and administrative work to schedule and certify the modification. (Requirement; Compliance)\n- The stated technical effect is reduced need for recurring inspections; this alters ongoing maintenance workload and may shift costs from inspection labour to a one-time or limited modification expense. (Background)\n- Enforcement depends on CASA’s AD referencing another jurisdiction’s AD and a manufacturer bulletin, so interpretation and application rest on those external technical documents as well as CASA’s incorporation by reference. (Requirement; Note)\n\nImplementation risks and precise scope: The AD’s applicability is limited by airframe line numbers and engine model exclusions; operators must check those criteria to determine if an individual aeroplane is within scope. Failure to complete the required modification leaves an aircraft operating without the prescribed structural change and thus subject to the existing inspection regime the modification was intended to reduce. (Applicability; Background)\n\nReference sections: Applicability; Requirement; Note; Compliance; Background."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b747-153-nacelle-strut-and-wing-structure-p-w-jt9d-series-engine","history":"/api/acts/ad-b747-153-nacelle-strut-and-wing-structure-p-w-jt9d-series-engine/history","analysis":"/api/acts/ad-b747-153-nacelle-strut-and-wing-structure-p-w-jt9d-series-engine/analysis","conflicts":"/api/acts/ad-b747-153-nacelle-strut-and-wing-structure-p-w-jt9d-series-engine/conflicts","importantCases":"/api/acts/ad-b747-153-nacelle-strut-and-wing-structure-p-w-jt9d-series-engine/important-cases","documents":"/api/acts/ad-b747-153-nacelle-strut-and-wing-structure-p-w-jt9d-series-engine/documents"}}