{"id":"F2006B11034","name":"AD/JT9D/5 - Replacement of Main Gearbox Assembly Face Seals","slug":"ad-jt9d-5-replacement-of-main-gearbox-assembly-face-seals","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56645,"registerId":"commonwealth-F2006B11034-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/JT9D/5 - Replacement of Main Gearbox Assembly Face Seals","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  Pratt and Whitney Turbine Engines - JT9D Series\n\n \n\nAD/JT9D/5 Replacement of Main Gearbox Assembly Face Seals\n\nApplicability: JT9D-3A and JT9D-7 series.\n\n \n\nDocument: 1. Pratt & Whitney TE SB 3902, Rev. 6; or 2. FAA AD 74-10-04; or\n\n3. AD/PW-T/32.\n\n \n\nCompliance: 1 February 1975.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n\n6/74\n","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive from 1974/1975 focused specifically on gearbox face seal replacement. It has not expanded beyond its original narrow technical scope. The document appears complete and unamended in this version."},"complexity_factors":["Extremely short document (approximately 150 words)","Only 2 defined applicability criteria (engine model series)","Single compliance action with 3 alternative reference documents","No nested conditions, exceptions, or cross-references to other legislation","No interpretation section or defined terms","Straightforward command structure: 'do X by Y date'"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It requires owners and operators of specific Pratt & Whitney jet engines (the JT9D-3A and JT9D-7 series, commonly used on Boeing 747 aircraft) to replace the face seals in the main gearbox assembly.\n\n**What it does:**\n- **Mandates a specific maintenance action**: Replacing face seals in the main gearbox assembly to prevent potential engine failures.\n- **Cites technical sources**: Operators must follow Pratt & Whitney Service Bulletin 3902 (Revision 6), or an equivalent FAA directive, or an earlier Australian directive (AD/PW-T/32).\n\n**Who it affects:**\n- Airlines and aircraft operators in Australia using Pratt & Whitney JT9D-3A or JT9D-7 engines.\n- Maintenance organisations servicing these engines.\n\n**Why it matters:**\n- Face seal failures in main gearboxes can lead to loss of engine oil pressure, potentially causing catastrophic engine failure or in-flight shutdowns. This directive prevents that safety risk by ensuring worn or defective seals are replaced before they fail.\n- **Compliance deadline**: 1 February 1975 (historical — this AD is from the 1970s).\n\nThis is a **safety-critical maintenance requirement** — non-compliance would mean an aircraft cannot legally fly in Australian airspace."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The document sets a single, specific mandatory action for a defined set of engine models and prescribes which technical documents may be used, with a fixed compliance date. The text contains no indication that the scope has been expanded or narrowed from an earlier or different intent; it states the action, applicable models and deadline explicitly (Applicability; Document; Compliance)."},"complexity_factors":["Narrow applicability: applies only to JT9D-3A and JT9D-7 series engines (Applicability).","Single, clear mandated action: replacement of main gearbox assembly face seals (title and Document).","Fixed compliance date reduces procedural uncertainty but imposes scheduling constraints (Compliance).","Reliance on external technical documents (three specified documents) requires operators to obtain and follow those materials accurately (Document).","Technical execution requires certified maintenance personnel and parts, adding operational and logistical complexity despite regulatory simplicity (Document; Applicability)."],"plain_english_summary":"This AD mandates replacement of the main gearbox assembly face seals on Pratt & Whitney JT9D-3A and JT9D-7 series engines by 1 February 1975, using one of three specified technical documents. It affects aircraft owners, operators, and maintenance organisations, who must schedule, fund and carry out the work—incurring parts, labour and downtime—to address the identified airworthiness concern."}},"importantCases":[],"_links":{"self":"/api/acts/ad-jt9d-5-replacement-of-main-gearbox-assembly-face-seals","history":"/api/acts/ad-jt9d-5-replacement-of-main-gearbox-assembly-face-seals/history","analysis":"/api/acts/ad-jt9d-5-replacement-of-main-gearbox-assembly-face-seals/analysis","conflicts":"/api/acts/ad-jt9d-5-replacement-of-main-gearbox-assembly-face-seals/conflicts","importantCases":"/api/acts/ad-jt9d-5-replacement-of-main-gearbox-assembly-face-seals/important-cases","documents":"/api/acts/ad-jt9d-5-replacement-of-main-gearbox-assembly-face-seals/documents"}}