{"id":"F2006B03109","name":"AD/B747/21 Amdt 3 - Nacelle Strut Forward Engine Mount Bulkhead","slug":"ad-b747-21-amdt-3-nacelle-strut-forward-engine-mount-bulkhead","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42481,"registerId":"commonwealth-F2006B03109-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B747/21 Amdt 3 - Nacelle Strut Forward Engine Mount Bulkhead","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/B747/21\n\nAmdt 3\n\n  \nNacelle Strut Forward Engine Mount Bulkhead 6/98\n\nApplicability: Model 747 series aircraft; as listed in Boeing Alert Service Bulletin 747-54A2069, Revision 9.\n\nRequirement: Action in accordance with the technical requirements of FAA AD 98-02-02 Amdt 39- 10284.\n\nCompliance: As specified in the Requirement document for the repetitive inspection requirements, until terminating modification action is accomplished.\n\nThis amendment becomes effective on 21 May 1998.\n\nBackground: Service experience with aircraft previously repaired, has shown that the parts provided for the repair were incorrectly heat treated. Amendment 2 provided for on- going repetitive inspection, or, alternatively, accomplishment of a revised repair scheme.\n\nAmendment 3 is issued in response to a new FAA AD prompted by reports that fatigue cracking was found in an area adjacent to the inspection area specified in the existing FAA AD. This amendment adds repetitive inspections for certain aircraft, adds a one-time inspection for other aircraft, and adds an additional optional terminating action for the repetitive inspection requirement.\n\nAmendment 2 to this Airworthiness Directive became effective on 31 December 1982.\n\nAmendment 1 to this Airworthiness Directive became effective on 30 April 1980.\n\nThe original issue of this Airworthiness Directive became effective on 29 February 1980.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":true,"description":"The original directive (1980) addressed incorrectly heat-treated repair parts. Amendment 2 (1982) added repetitive inspections or revised repairs. Amendment 3 (1998) significantly expanded scope by adding inspections for newly discovered fatigue cracking in adjacent areas, creating a multi-tier inspection regime (repetitive for some, one-time for others, plus new terminating actions). The directive evolved from a simple repair verification to an ongoing structural integrity monitoring system."},"complexity_factors":["Short, single-purpose document (1 page)","Only 1 defined term implicitly referenced (FAA AD 98-02-02)","No nested conditional logic — requirements are straightforward (inspect per FAA document)","Cross-reference to external technical document (FAA AD) rather than internal complexity","Clear applicability statement limiting scope to specific aircraft models","Simple amendment structure tracking version history (Amendments 1-3)"],"plain_english_summary":"This AD orders operators of certain Boeing 747s to inspect and, if needed, repair the nacelle strut forward engine‑mount bulkhead after discovery that some replacement parts were incorrectly heat‑treated and prone to fatigue cracking. It mandates repetitive or one‑time inspections per Boeing guidance, with an optional terminating repair that ends recurring checks. The measure targets prevention of engine‑mount failure that could lead to catastrophic structural or in‑flight loss."},"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"},"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":true,"description":"Amendment 3 expands the scope of the directive relative to earlier issues by adding repetitive inspections for certain aircraft, adding a one-time inspection for others, and providing an additional optional terminating action. It explicitly responds to new reports of fatigue cracking adjacent to previously inspected areas and thus broadens inspection coverage and compliance options."},"complexity_factors":["Cross-reference to external FAA AD 98-02-02 and Boeing Alert Service Bulletin 747-54A2069 Revision 9 creates dependency on separate technical documents for full requirements.","Multiple compliance paths: repetitive inspections, one-time inspections for some aircraft, and an optional terminating modification increase procedural choices and recordkeeping.","Applicability is limited to aircraft listed in the referenced service bulletin, requiring operators to match fleet serials to the bulletin.","Historical layering: this AD is Amendment 3 with prior amendments and an original AD, producing potential legacy compliance and traceability issues.","Technical subject matter (fatigue cracking and heat treatment defects) implies need for specialised inspection techniques and repair capabilities.","Timing and recurrence: inspections are repetitive 'until terminating modification accomplished', requiring long‑term scheduling and potential operational disruption."],"plain_english_summary":"This directive requires operators of Boeing 747 aeroplanes listed in *Boeing Alert Service Bulletin 747-54A2069, Revision 9* to carry out inspections of the nacelle strut forward engine mount bulkhead as specified in FAA AD 98-02-02, including repetitive inspections until a terminating modification is done. It was issued after fatigue cracking (and earlier incorrect heat treatment in repairs) was reported. The directive affects aircraft operators, who must fund inspections, one-time or recurring repairs, or the optional terminating modification."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b747-21-amdt-3-nacelle-strut-forward-engine-mount-bulkhead","history":"/api/acts/ad-b747-21-amdt-3-nacelle-strut-forward-engine-mount-bulkhead/history","analysis":"/api/acts/ad-b747-21-amdt-3-nacelle-strut-forward-engine-mount-bulkhead/analysis","conflicts":"/api/acts/ad-b747-21-amdt-3-nacelle-strut-forward-engine-mount-bulkhead/conflicts","importantCases":"/api/acts/ad-b747-21-amdt-3-nacelle-strut-forward-engine-mount-bulkhead/important-cases","documents":"/api/acts/ad-b747-21-amdt-3-nacelle-strut-forward-engine-mount-bulkhead/documents"}}