{"id":"F2006B10540","name":"AD/HS 125/97 Amdt 1 - Auxiliary Bracket Rear Engine Mount","slug":"ad-hs-125-97-amdt-1-auxiliary-bracket-rear-engine-mount","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":116343,"registerId":"commonwealth-F2006B10540-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HS 125/97 Amdt 1 - Auxiliary Bracket Rear Engine Mount","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)  \nBritish Aerospace BAe 125 Series Aeroplanes\n\nAD/HS 125/97\n\nAmdt 1\n\n  \nAuxiliary Bracket Rear Engine Mount 7/89\n\nApplicability: All models fitted with Garrett TFE 731-3 engines. Requirement: 1. Action in accordance with BAe SB 72-1-2844A Rev 2.\n\n2. Retire from service auxiliary mounting bracket engine attachment bolt P/N 3073361-1.\n\nNote: BAe 125 SB 72-4 refers.\n\nCompliance: 1. Prior to 28 February 1989.\n\n2. Prior to accumulating 750 hours component time in service or within 50 hours component time in service after 13 July 1989, which ever is later.\n\nBackground: Weld failures subsequent to inspection in accordance with Garrett SBs TFE 731-72- 3159 and TFE 731-72-3309 have occurred without any report of contributing incident and/or any indication that a failure has occurred. The engine manufacturer has indicated that the failure mechanism appears to be one that has not previously been encountered.\n\nGarrett have now imposed a retirement life on the affected bolt.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"Scope shifted from inspection-based responses to a mandatory retirement life for the affected bolt. The directive now requires action per BAe SB 72‑1‑2844A Rev 2 and retirement of bolt P/N 3073361‑1 by specified hours or dates, responding to weld failures that occurred after prior inspections and reflecting Garrett's imposed retirement life (Requirement 1–2; Compliance; Background)."},"complexity_factors":["Narrow technical applicability: applies only to BAe 125 models fitted with Garrett TFE 731‑3 engines (Applicability).","Mandated action references an external manufacturer service bulletin: BAe SB 72‑1‑2844A Rev 2 (Requirement 1), adding reliance on that document for procedural detail.","Mandatory retirement of a specific part number (bolt P/N 3073361‑1) rather than ongoing inspection (Requirement 2).","Dual compliance triggers: an absolute calendar deadline for SB action and an hours‑in‑service limit or short hours window after a specified date for bolt retirement (Compliance).","Safety rationale limited by technical uncertainty: weld failures occurred despite prior inspections and with no reported precursor, increasing precautionary measures (Background).","Operational and logistical impacts on operators: scheduling replacements, locating part P/N, and recording component-time for compliance (implied by Compliance and Requirement)."],"plain_english_summary":"This airworthiness directive requires operators of BAe 125 aircraft fitted with Garrett TFE 731-3 engines to follow BAe Service Bulletin 72‑1‑2844A Rev 2 and to remove (retire) the auxiliary engine‑mount bracket attachment bolt P/N 3073361‑1 by specified hours or dates. It was issued after weld failures were found without prior indication; the engine maker has imposed a retirement life for the affected bolt, so operators must replace the part and comply with the bulletin by the stated deadlines."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a standard, narrow Airworthiness Directive targeting a specific safety-critical defect in a specific aircraft/engine combination. It has not expanded beyond its original purpose of addressing the auxiliary bracket rear engine mount weld failure issue."},"complexity_factors":["Single, specific aircraft type and engine combination (BAe 125 with Garrett TFE 731-3)","Only 2 discrete compliance actions required","Straightforward time-based compliance deadlines","Minimal cross-referencing (only 3 external documents: BAe SB 72-1-2844A Rev 2, BAe SB 72-4, and Garrett SBs TFE 731-72-3159/3309 mentioned in background)","No defined terms section","No conditional logic or nested exceptions","Single page document with clear applicability and requirements sections"],"plain_english_summary":"This is an **Airworthiness Directive** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) that requires specific maintenance actions on certain aircraft.\n\n**What it does:**\nThis directive orders owners and operators of **British Aerospace BAe 125 series aircraft** fitted with **Garrett TFE 731-3 engines** to:\n- **Inspect and modify** the auxiliary bracket rear engine mount following specific instructions in British Aerospace Service Bulletin 72-1-2844A (Revision 2)\n- **Permanently remove from service** a specific bolt (part number 3073361-1) used in the engine mounting bracket after it reaches a certain number of flight hours\n\n**Why it matters:**\nThe bolt and mounting bracket were experiencing **weld failures** — cracks in the welded joints — even after previous inspections. These failures were happening unexpectedly, without warning signs or prior incidents. The engine manufacturer (Garrett) identified this as a new type of failure mechanism they hadn't seen before and imposed a **mandatory retirement life** on the bolt to prevent catastrophic engine mount failure in flight.\n\n**Who must comply:**\n- Operators of affected BAe 125 aircraft\n- Maintenance organisations servicing these aircraft\n\n**Deadlines:**\n- The inspection/modification had to be done before 28 February 1989\n- The bolt had to be retired before reaching 750 hours of use, or within 50 hours after 13 July 1989 (whichever came later)"}},"importantCases":[],"_links":{"self":"/api/acts/ad-hs-125-97-amdt-1-auxiliary-bracket-rear-engine-mount","history":"/api/acts/ad-hs-125-97-amdt-1-auxiliary-bracket-rear-engine-mount/history","analysis":"/api/acts/ad-hs-125-97-amdt-1-auxiliary-bracket-rear-engine-mount/analysis","conflicts":"/api/acts/ad-hs-125-97-amdt-1-auxiliary-bracket-rear-engine-mount/conflicts","importantCases":"/api/acts/ad-hs-125-97-amdt-1-auxiliary-bracket-rear-engine-mount/important-cases","documents":"/api/acts/ad-hs-125-97-amdt-1-auxiliary-bracket-rear-engine-mount/documents"}}