{"id":"F2006B03062","name":"AD/B747/16 Amdt 3 - Nacelle Strut Midspar Fuse Pins","slug":"ad-b747-16-amdt-3-nacelle-strut-midspar-fuse-pins","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42421,"registerId":"commonwealth-F2006B03062-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B747/16 Amdt 3 - Nacelle Strut Midspar Fuse Pins","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/B747/16\n\nAmdt 3\n\n  \n\nNacelle Strut Midspar Fuse Pins 1/93 TX\n\nApplicability: All Model 747 series aircraft.\n\nRequirement: Action in accordance with the technical requirements of Telex FAA AD T92-24-51.\n\nNote: Boeing Service Bulletins 747-54-2063 and 747-54A2150 refer.\n\nCompliance: As specified in the Requirement Document with a revised effective date of\n\n18 November 1992 for Australian registered aircraft. The compliance of the previous issue of this Directive was:\n\nAs specified in the Requirement Document with a revised effective date of 14 October 1992.\n\nThis Amendment is effective from 18 November 1992.\n\nBackground: The manufacturer has received reports of fatigue failures of the older style fuse pins.\n\nAmdt 1 of this Directive referenced R5 of the Service Bulletin (which detailed an improved inspection procedure) and a revision of the FAA AD. Amendment 2 of this Directive is issued to reflect the requirements of the above referenced FAA AD, which supersedes two previous FAA Directives. Since the issuance of the previous Directives, the FAA has received several reports of fatigue cracks initiating at corrosion sites in the new style fuse pins on aircraft equipped with Pratt and Whitney or Rolls Royce series engines. Amendment 3 is issued in response to the latest FAA Directive which is issued as a result of the reports required by the previous Directive (AD 92-21-51 R1). The FAA received numerous reports of corrosion and 13 additional reports of fatigue cracking in the new style fuse pins. As a consequence, this Directive requires the removal of all old style fuse pins from service and revised inspection procedures for the new style fuse pins.","sortOrder":0}],"analysis":{"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":3,"scope_assessment":{"changed":true,"description":"The directive has expanded significantly from its original scope. Initially (Amendment 1), it required inspections of old-style pins using improved procedures. Amendment 2 incorporated a revised FAA directive. Amendment 3 now mandates complete removal of all old-style pins from service (not just inspection) and adds new inspection requirements for the 'new style' pins that were previously considered acceptable. The scope shifted from 'inspect and monitor' to 'replace all old parts and inspect the new ones too' as field data revealed the new pins were also failing."},"complexity_factors":["Short, single-purpose directive (approximately 250 words)","Only 1 defined term implicitly used ('Applicability')","Minimal cross-referencing: references one FAA AD (T92-24-51) and two Boeing Service Bulletins","Simple conditional structure: all aircraft in the series must comply, no exceptions or nested conditions","Clear compliance deadline (single date: 18 November 1992)","Background narrative explains evolution through three amendments but does not complicate the operative requirements"],"plain_english_summary":"This CASA Airworthiness Directive requires owners and operators of Australian-registered Boeing 747s to remove old-style nacelle strut midspar fuse pins from service and apply revised inspection procedures to the new-style pins. It responds to discovered fatigue cracking and corrosion—failures that have already occurred and could lead to engine separation in flight. This is the third, progressively stricter amendment following additional FAA reports."},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"Yes. The Directive's scope broadened across its amendments. The original measures focused on improved inspection procedures for older fuse pins; later amendments (including this one) require the removal of all old‑style fuse pins from service and add revised inspection requirements for the new‑style pins because corrosion and cracking were reported in the replacement parts (Background). Concretely, the instrument moved from prescribing upgraded inspections to mandating component removal plus continuing inspections of replacements, increasing the regulatory reach and ongoing maintenance burden on operators."},"complexity_factors":["Short stand‑alone directive text but relies heavily on external technical documents (FAA AD T92-24-51 and Boeing Service Bulletins)","Multiple previous amendments referenced (Amdt 1, Amdt 2, Amdt 3) and cross‑references to superseded FAA directives","Operational change from inspection procedures to mandatory removal of a component type (old style fuse pins) plus revised inspections for new style pins","Compliance is conditional on the content and compliance times stated in the Requirement Document rather than being self-contained","Some technical detail (inspection intervals, removal/replacement criteria) omitted and delegated to external documents, increasing implementation complexity for operators"],"plain_english_summary":"**What this instrument does (mechanics)\n\n- Applies to: All Boeing Model 747 series aircraft (Applicability).\n- Requires: Operators must carry out the technical actions set out in the referenced FAA telex (Telex FAA AD T92-24-51). The Boeing Service Bulletins 747-54-2063 and 747-54A2150 are relevant (Requirement / Note).\n- Key actions: Remove all *old‑style* nacelle strut midspar fuse pins from service and follow the revised inspection procedures for the *new‑style* fuse pins, as specified in the FAA requirement document (Background / Requirement).\n- Timing: The directive is effective for Australian-registered aircraft from 18 November 1992; compliance times are those stated in the Requirement Document (Compliance).\n\nWhy it was issued (stated purpose)\n\n- The manufacturer and FAA reported fatigue failures and corrosion-related cracking of fuse pins. Earlier inspections and procedures did not fully prevent cracking in the new‑style pins. This amendment requires removal of the older pins and imposes revised inspection procedures for the newer pins (Background).\n\nWho is affected and who decides\n\n- Who pays and must act: Aircraft owners/operators and their maintenance organisations. They must schedule the removals/inspections, source replacement parts, and absorb associated labour and downtime costs.\n- Who prescribes the technical detail: The Civil Aviation Safety Authority (through this directive) requires compliance with the FAA telex and the Boeing service bulletins — those external documents contain the step‑by‑step technical requirements (Requirement / Note).\n\nPractical effects and implementation mechanics\n\n- Operators cannot rely on in‑service operation of older style fuse pins; those pins must be taken out of service and replaced per the technical documents.\n- For aircraft fitted with the new style pins, operators must adopt more frequent or more detailed inspections as described in the FAA telex. The exact inspection intervals, methods and replacement criteria are defined in the referenced documents (Requirement / Compliance).\n- Compliance will impose direct maintenance costs: parts, labour, aircraft out‑of‑service time, and record‑keeping. It will also create demand for replacement pins and maintenance work (Background).\n\nTrade-offs, incentives and risks (analytic checklist)\n\n- Intended safety benefit: Reduced risk of in‑flight failure of the nacelle strut fuse pin by eliminating a known weak component and improving detection of cracks in its replacement.\n- Direct costs: Operators pay for removal, replacement parts, additional inspections and possible unscheduled repairs discovered by inspections.\n- Concentrated benefits: MROs and parts suppliers are likely to gain workload and sales; the cost burden is concentrated on 747 operators.\n- Implementation risk: The Directive delegates detailed methods to external FAA and Boeing documents. That reliance requires operators to obtain and correctly apply those documents; differences between editions or cross‑references create scope for misunderstanding or inconsistent implementation.\n- Compliance burden and discretion: The regulator mandates compliance with the Requirement Document; however, the AD itself does not reproduce procedural detail, so practical compliance depends on interpreting and following the referenced telex/service bulletins.\n\nWhere to look for the technical steps\n\n- The AD points operators to the FAA telex AD T92-24-51 and Boeing Service Bulletins 747-54-2063 / 747-54A2150 for the exact inspection, removal and replacement procedures (Requirement / Note). The AD sets the legal obligation to follow those documents but does not restate their procedures.\n\n(Sections referenced: Applicability; Requirement; Note; Compliance; Background.)"}},"importantCases":[],"_links":{"self":"/api/acts/ad-b747-16-amdt-3-nacelle-strut-midspar-fuse-pins","history":"/api/acts/ad-b747-16-amdt-3-nacelle-strut-midspar-fuse-pins/history","analysis":"/api/acts/ad-b747-16-amdt-3-nacelle-strut-midspar-fuse-pins/analysis","conflicts":"/api/acts/ad-b747-16-amdt-3-nacelle-strut-midspar-fuse-pins/conflicts","importantCases":"/api/acts/ad-b747-16-amdt-3-nacelle-strut-midspar-fuse-pins/important-cases","documents":"/api/acts/ad-b747-16-amdt-3-nacelle-strut-midspar-fuse-pins/documents"}}