{"id":"F2006B03071","name":"AD/B747/169 Amdt 1 - Midspar Fuse Pin","slug":"ad-b747-169-amdt-1-midspar-fuse-pin","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42430,"registerId":"commonwealth-F2006B03071-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B747/169 Amdt 1 - Midspar Fuse Pin","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/B747/169\n\nAmdt 1\n\n  \nMidspar Fuse Pin 9/97\n\nApplicability: Model 747 series aircraft with line numbers 1 through 1046, equipped with Pratt and Whitney model PW4000 series engines, or General Electric model CF6-80C2 series engines, or Rolls Royce model RB211 series engines; on which fuse pins having part numbers 310U2301-101, -116, -117, or -120 ( “third generation “ fuse pins ) are installed at the midspar / spring beam fittings of the engine pylon; and on which modification of the nacelle strut and wing structure in accordance with Boeing ASB 747- 54A2156 or Boeing ASB 747-54A2157, as applicable, has not been accomplished.\n\nRequirement: Inspect in accordance with the technical requirements of FAA AD 96-26-52 R1 Amdt 39-1002.\n\nCompliance: Unless the initial inspection has already been accomplished, within 15 days after 15 January 1997; thereafter as specified in the requirement document.\n\nThe compliance of the initial issue of this directive remains unchanged, while the repetitive inspection frequency as specified in the new requirement document, is changed by this issue.\n\nThis amendment becomes effective on 14 August 1997.\n\nBackground: The FAA received a report of a fuse pin which had migrated out of an inboard spring beam fitting on the number 1 engine pylon of a model 747-400 aircraft. In addition, the mating nut to this pin had backed off from full engagement with the pin.\n\nAmendment 1 is issued in response to the issue of a new FAA AD which decreases the frequency of inspections, as a result of new data provided by the manufacturer.\n\nThe original issue of this airworthiness directive became effective on 15 January 1997.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"The amendment does not expand applicability or add new inspection obligations; it alters only the repetitive inspection frequency. The initial inspection deadline and the requirement to inspect per FAA AD 96-26-52 R1 remain in place. The change is described as a reduction in inspection frequency based on manufacturer data and the new FAA AD (see 'The compliance...' and 'Amendment 1 is issued...')."},"complexity_factors":["Cross-reference to an external FAA airworthiness directive (FAA AD 96-26-52 R1 Amdt 39-1002) for technical requirements ('Requirement' clause).","Applicability defined by multiple technical criteria: airframe line numbers (1–1046), specific engine models (PW4000, CF6-80C2, RB211) and particular part numbers for fuse pins (310U2301-101, -116, -117, -120) ('Applicability' clause).","Reference to whether Boeing structural modifications (ASB 747-54A2156 or 747-54A2157) have been accomplished, creating a conditional applicability test ('Applicability' clause).","Change limited to repetitive inspection frequency while retaining the initial inspection requirement (explicit acknowledgement in the amendment text).","Short compliance timing for initial inspection (within 15 days after 15 January 1997 unless already done) and a later amendment effective date (14 August 1997) which affect scheduling and logistics ('Compliance', 'This amendment becomes effective').","Technical safety history in background (reported pin migration and nut backing off) informs the inspection focus and possible corrective actions ('Background')."],"plain_english_summary":"This amendment requires operators of Boeing 747s (line numbers 1–1046) with specified PW4000, CF6-80C2 or RB211 engines and certain “third generation” midspar fuse pins to carry out the FAA-prescribed inspection of the midspar/spring-beam fuse pin and nut. CASA adopts FAA AD 96-26-52 R1 for inspection procedures and sets a short initial compliance window. Operators pay for inspections and any repairs; the amendment reduces the required repeat-inspection frequency (per new FAA data), changing maintenance scheduling but not the initial inspection obligation."},"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This amendment stays within the original scope of the airworthiness directive. It modifies only the inspection frequency (making it less burdensome) based on new manufacturer data, without expanding the types of aircraft covered or adding new requirements."},"complexity_factors":["Multiple nested applicability conditions (aircraft line numbers, engine types, specific part numbers, and exclusion for modified aircraft)","Cross-reference to external technical document (FAA AD 96-26-52 R1) without reproducing its contents","Conditional compliance language ('Unless the initial inspection has already been accomplished')","Technical aviation terminology requiring specialized knowledge (fuse pins, midspar fittings, spring beam, nacelle strut, ASB — Alert Service Bulletin)","Amendment structure creates dual compliance tracks (original issue vs. amended requirements)"],"plain_english_summary":"This CASA Airworthiness Directive mandates inspections of the midspar fuse pin on certain Boeing 747s (serials 1–1046) with PW4000, CF6-80C2 or RB211 engines that have third‑generation fuse pins and no Boeing ASB 747‑54A2156/2157 modification. It stems from a nut‑backing failure that could allow engine separation. Amendment 1 eases recurring inspection intervals based on Boeing data but keeps the original initial inspection deadline."},"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"}},"importantCases":[],"_links":{"self":"/api/acts/ad-b747-169-amdt-1-midspar-fuse-pin","history":"/api/acts/ad-b747-169-amdt-1-midspar-fuse-pin/history","analysis":"/api/acts/ad-b747-169-amdt-1-midspar-fuse-pin/analysis","conflicts":"/api/acts/ad-b747-169-amdt-1-midspar-fuse-pin/conflicts","importantCases":"/api/acts/ad-b747-169-amdt-1-midspar-fuse-pin/important-cases","documents":"/api/acts/ad-b747-169-amdt-1-midspar-fuse-pin/documents"}}