{"id":"F2006B03046","name":"AD/B747/145 Amdt 1 - Outboard Engine Strut Spring Beam","slug":"ad-b747-145-amdt-1-outboard-engine-strut-spring-beam","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42405,"registerId":"commonwealth-F2006B03046-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B747/145 Amdt 1 - Outboard Engine Strut Spring Beam","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/B747/145\n\nAmdt 1\n\n  \nOutboard Engine Strut Spring Beam 1/99\n\nApplicability: Model 747 series aircraft, line numbers 202 through 396, equipped with Pratt & Whitney Model JT9D-70 engines.\n\nRequirement: Action in accordance with the technical requirements of FAA AD 98-21-17 Amdt 39- 10826.\n\nNote: Boeing Service Bulletins 747-54A2171 and 747-54-2177 refer.\n\nCompliance: As specified in the Requirement Document with a revised effective date of 28 January 1999.\n\nThis Amendment becomes effective on 28 January 1999.\n\nBackground: A failure of an outboard spring beam on a number 4 engine strut was reported. The failure was due to a material problem in the titanium spring beam which is only fitted to B747 aircraft with JT9D-70 engines. Continued operation with a damaged spring beam could result in loss of an engine.\n\nAmendment 1 is issued in response to a new FAA AD which was prompted by the development of an improved process for manufacturing titanium spring beams that will eliminate the embedded porosity flaws in the existing spring beams, from which fatigue cracking can originate.\n\nThe original issue of this Airworthiness Directive became effective on 25 June 1995.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"This amendment updates the earlier 1995 AD by adopting the newer FAA AD 98‑21‑17 and sets a revised effective date (28 January 1999). The applicability (B747 line numbers 202–396 with JT9D‑70 engines) remains the same, but the mandated technical actions are changed to those specified in the newer FAA AD to reflect an improved manufacturing process for titanium spring beams."},"complexity_factors":["Cross‑reference to an external FAA AD (98‑21‑17) — requires users to consult another legal/technical document","Narrow applicability (specific Boeing 747 line numbers and a single engine model) but safety‑critical consequences","Reliance on manufacturer service bulletins (Boeing 747‑54A2171 and 747‑54‑2177) for technical detail","Fixed compliance effective date (28 January 1999) imposes a clear timeline","Technical subject matter (titanium spring‑beam material and fatigue cracking) requires specialist maintenance actions","Amendment replaces an earlier AD (1995), so operators must track regulatory history to confirm current obligations"],"plain_english_summary":"**What this does:** Requires operators of Boeing 747 aircraft (line numbers 202–396) fitted with Pratt & Whitney JT9D‑70 engines to carry out the technical actions set out in FAA AD 98‑21‑17, effective 28 January 1999. \n\n**Who it affects and why it matters:** CASA enforces the directive; aircraft operators pay for compliance. The measure responds to titanium spring‑beam porosity that can cause fatigue cracking and possible engine loss, and updates the earlier 1995 directive to reflect an improved manufacturing process."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This amendment maintains the original scope of the 1995 Airworthiness Directive. It updates the technical requirements to reflect improved manufacturing processes for the titanium spring beam, but does not expand the applicability to new aircraft types, engine models, or additional components. The amendment remains tightly focused on the original safety issue."},"complexity_factors":["Very short document (approximately 200 words)","Only 2 defined applicability criteria (line number range and engine type)","Single technical requirement referencing external FAA document rather than spelling out detailed procedures","No nested exceptions or conditional logic — compliance is mandatory and straightforward","Minimal cross-referencing (only 2 Boeing service bulletins and 1 FAA AD mentioned)","Clear, single-purpose scope (one specific part on one specific aircraft/engine combination)"],"plain_english_summary":"This safety order requires Australian operators of Boeing 747s (line numbers 202–396) fitted with Pratt & Whitney JT9D‑70 engines to inspect or replace the number‑4 outboard engine strut spring beam per FAA AD 98‑21‑17 and Boeing service bulletins. It updates a 1995 directive after a spring‑beam failure caused by flawed titanium that can develop fatigue cracks and risk engine detachment; compliance is required by the new effective date, 28 January 1999."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b747-145-amdt-1-outboard-engine-strut-spring-beam","history":"/api/acts/ad-b747-145-amdt-1-outboard-engine-strut-spring-beam/history","analysis":"/api/acts/ad-b747-145-amdt-1-outboard-engine-strut-spring-beam/analysis","conflicts":"/api/acts/ad-b747-145-amdt-1-outboard-engine-strut-spring-beam/conflicts","importantCases":"/api/acts/ad-b747-145-amdt-1-outboard-engine-strut-spring-beam/important-cases","documents":"/api/acts/ad-b747-145-amdt-1-outboard-engine-strut-spring-beam/documents"}}