{"id":"F2006B03249","name":"AD/B747/70 Amdt 2 - Nacelles/Pylons - Diagonal Brace Lugs","slug":"ad-b747-70-amdt-2-nacelles-pylons-diagonal-brace-lugs","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42673,"registerId":"commonwealth-F2006B03249-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B747/70 Amdt 2 - Nacelles/Pylons - Diagonal Brace Lugs","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/B747/70\n\nAmdt 2\n\n  \nNacelles/Pylons \\- Diagonal Brace Lugs 2/99\n\nApplicability: Model 747 series aircraft with line positions 1 through 1046; equipped with Pratt & Whitney JT9D series engines, General Electric Model CF6-45 and \\-50 series engines, or Rolls Royce Model RB211 series engines; excluding those aircraft on which modifications of the strut/wing structure have been accomplished in accordance with FAA AD 95-10-16 (AD/B747/153), FAA AD 95-13-05 (AD/B747/154 Amdt 1), or\n\nFAA AD 95-13-07, as applicable.\n\nRequirement: Action in accordance with the technical requirements of FAA AD 99-01-10 Amdt 39- 10976.\n\nNote: Boeing Alert Service Bulletin 747-54A2126 Revision 5, Revision 6, and Revision 7 refer.\n\nCompliance: As specified in the Requirement Document with a revised effective date of 25 February 1999.\n\nThis Amendment becomes effective on 25 February 1999.\n\nBackground: Operators have reported ten diagonal brace lug cracks which are believed to initiate at lug bore corrosion pits and propagate by fatigue.\n\nAmendment 1 required new repetitive inspections to detect discrepancies of the diagonal brace lugs, and rework of the diagonal brace lug, if necessary. Since issuance of AD 89-07-15, the FAA received several reports of six additional diagonal braces with cracks in one lug of the aft clevis on the affected aircraft.\n\nAmendment 2 is issued in response to a new FAA AD which adds a requirement to repetitively inspect a new area of the diagonal brace, and for certain aircraft, adds new repetitive inspections of the subject area, while requiring that certain previously required repetitive inspections be accomplished at reduced intervals.\n\nAmendment 1 of this Airworthiness Directive became effective on 4 December 1997.\n\nThe original issue of this Airworthiness Directive became effective on 10 August 1989.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":true,"description":"Amendment 2 expands and tightens the original directive: it adds a new inspection area on the diagonal brace, requires additional repetitive inspections for certain aircraft, and shortens intervals for some previously required inspections. It implements the technical requirements of FAA AD 99-01-10 and updates the effective date to 25 February 1999."},"complexity_factors":["Cross-reference to an external FAA AD (FAA AD 99-01-10) as the substantive Requirement, creating dependency on another instrument for detail.","Multiple applicability constraints: specific line positions (1–1046), three engine families, and explicit exclusions where prior FAA AD-based modifications have been done.","Repetitive inspection regime with some intervals reduced compared to earlier ADs, increasing scheduling and ongoing compliance burden.","Multiple referenced Boeing Alert Service Bulletin revisions (Revision 5, 6, 7) introduce version-tracking and potential ambiguity about the correct technical procedure.","Amendment history (original AD, Amendment 1, Amendment 2) changes scope over time, requiring operators to track which requirements apply to each aircraft.","Effective date specification (revised effective date of 25 February 1999) imposes time-bound compliance obligations."],"plain_english_summary":"This Airworthiness Directive requires operators of Boeing 747s (line positions 1–1046) fitted with JT9D, CF6-45/-50 or RB211 engines—unless previously modified under specified FAA ADs—to carry out repetitive inspections and any required rework of diagonal brace lugs per FAA AD 99-01-10, effective 25 February 1999. CASA enforces the inspections because cracks have been found that start at corrosion pits and propagate by fatigue; operators must schedule, perform and fund the inspections and remedial work."},"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":4,"scope_assessment":{"changed":true,"description":"The original 1989 directive addressed diagonal brace lug cracks with initial inspection requirements. Amendment 1 (1997) expanded this to require new repetitive inspections and rework. Amendment 2 (1999) further expanded the scope significantly: adding inspections of entirely new areas, increasing inspection frequency for certain aircraft, and reducing intervals for existing inspections. The directive has evolved from a targeted crack-inspection order to a comprehensive, multi-area, frequency-adjusted maintenance regime based on accumulating incident data."},"complexity_factors":["Multiple amendment layers (original 1989, Amendment 1 1997, Amendment 2 1999) with cumulative requirements","Cross-reference to external FAA technical document (AD 99-01-10) without reproducing its full content","Conditional applicability based on: aircraft line position numbers, engine types, AND exclusion of aircraft with prior modifications","Three specific FAA AD exclusions referenced by number (AD 95-10-16, AD 95-13-05, AD 95-13-07)","Reference to multiple Boeing Service Bulletin revisions (Rev 5, 6, and 7) without specifying which applies when","Nested compliance structure: 'As specified in the Requirement Document' delegates timing details to external source"],"plain_english_summary":"This CASA Airworthiness Directive mandates operators of specified Boeing 747s (serials 1–1046) with certain Pratt & Whitney, GE or Rolls‑Royce engines to follow FAA AD 99‑01‑10 and perform repetitive inspections of diagonal brace lugs that attach engine nacelles to wings, due to corrosion‑initiated cracking.\n\nAmendment 2 expands the inspected area, shortens inspection intervals for some aircraft, and increases inspection frequency to prevent possible engine‑mount structural failure."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b747-70-amdt-2-nacelles-pylons-diagonal-brace-lugs","history":"/api/acts/ad-b747-70-amdt-2-nacelles-pylons-diagonal-brace-lugs/history","analysis":"/api/acts/ad-b747-70-amdt-2-nacelles-pylons-diagonal-brace-lugs/analysis","conflicts":"/api/acts/ad-b747-70-amdt-2-nacelles-pylons-diagonal-brace-lugs/conflicts","importantCases":"/api/acts/ad-b747-70-amdt-2-nacelles-pylons-diagonal-brace-lugs/important-cases","documents":"/api/acts/ad-b747-70-amdt-2-nacelles-pylons-diagonal-brace-lugs/documents"}}