{"id":"F2006B10862","name":"AD/JBK 117/13 - Engine Mount Truss Supports","slug":"ad-jbk-117-13-engine-mount-truss-supports","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56358,"registerId":"commonwealth-F2006B10862-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/JBK 117/13 - Engine Mount Truss Supports","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)  \nKawasaki BK 117 Series Helicopters\n\nAD/JBK 117/13 Engine Mount Truss Supports 4/99\n\nApplicability: Kawasaki model BK-117, BK-117A-3, BK-117A-4, BK-117B-1, and BK-117B2 helicopters.\n\nRequirement: Action in accordance with Kawasaki Service Bulletin KSB \\-117-127.\n\nNote: JCAB AD TCD-4930-99 refers.\n\nCompliance: For helicopters with less than 1,200 total flight hours: Unless already accomplished, at the first 1,200 inspection. For helicopters with more than 1,200 total flight hours:\n\nUnless already accomplished, at the next 600 hour inspection or next engine removal after 22 April 1999, whichever occurs first.\n\nThis Airworthiness Directive becomes effective on 22 April 1999.\n\nBackground: Cracks caused by grain boundary corrosion were detected on the engine mounting sideward link. This Directive requires an inspection for corrosion on the engine truss supports which are fabricated with an identical material and installed in the same environment as the sideward link.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a standard, narrow Airworthiness Directive addressing a specific safety-of-flight issue (corrosion in engine mounts). It has not expanded beyond its original purpose of mandating inspections for a known defect pattern."},"complexity_factors":["Single, specific mechanical issue (corrosion inspection)","Only 2 applicability criteria (flight hours threshold)","Clear compliance timeline with binary logic (less than vs. more than 1,200 hours)","No defined terms section — uses plain aviation terminology","Single cross-reference to manufacturer service bulletin","No nested exceptions or conditional sub-clauses"],"plain_english_summary":"**What this is:** An Airworthiness Directive (AD) — essentially a mandatory safety notice issued by Australia's Civil Aviation Safety Authority (CASA) for specific helicopters.\n\n**Who it affects:** Owners and operators of Kawasaki BK-117 series helicopters (including models A-3, A-4, B-1, and B-2).\n\n**What it requires:**\n- **Inspection for corrosion** on engine mount truss supports — metal framework that holds the engine in place.\n- **When to do it:**\n  - If your helicopter has flown **less than 1,200 hours**: inspect by the time it reaches 1,200 total flight hours (unless already done).\n  - If your helicopter has flown **more than 1,200 hours**: inspect at the next 600-hour check or next engine removal after 22 April 1999 — whichever comes first.\n\n**Why it matters:** Cracks from corrosion were found on a related engine part (the \"sideward link\"). Because the truss supports are made of the same material and sit in the same harsh environment (engine heat, vibration, potential moisture), regulators want them checked before they fail. A broken engine mount could cause catastrophic engine separation in flight.\n\n**Key reference:** Operators must follow the specific inspection steps in **Kawasaki Service Bulletin KSB-117-127** (the manufacturer's official repair notice)."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The Directive confines action to the listed BK‑117 models and adds inspections of truss supports that share material and environment with an already‑identified corroded component. This aligns with the original safety aim (identify and inspect parts at comparable corrosion risk) and does not broaden the regulated population or impose requirements beyond the specified inspection regime (see Applicability, Requirement, Background, Compliance)."},"complexity_factors":["Applicability: limited to specific Kawasaki BK‑117 variants (clear but narrow scope).","Requirement references an external Kawasaki Service Bulletin (KSB‑117‑127) — implementers must obtain and follow that document.","Compliance timing uses flight‑hour thresholds and an event trigger (engine removal), which requires tracking logbooks and maintenance schedules.","Technical nature of inspection (inspection for grain‑boundary corrosion) may require specialist maintenance personnel or teardown.","Effective date constraint (becomes effective 22 April 1999) creates an immediate compliance deadline for affected aircraft."],"plain_english_summary":"This Airworthiness Directive requires operators of Kawasaki BK‑117 series helicopters (the listed BK‑117 variants) to inspect the engine mount truss supports for corrosion in accordance with Kawasaki Service Bulletin KSB‑117‑127. \n\nInspections must follow the stated flight‑hour schedule (first inspection at 1,200 hours if below that; otherwise at the next 600‑hour inspection or next engine removal after 22 April 1999). The measure responds to grain‑boundary corrosion found on a related engine mounting link made from the same material and exposed to the same environment."}},"importantCases":[],"_links":{"self":"/api/acts/ad-jbk-117-13-engine-mount-truss-supports","history":"/api/acts/ad-jbk-117-13-engine-mount-truss-supports/history","analysis":"/api/acts/ad-jbk-117-13-engine-mount-truss-supports/analysis","conflicts":"/api/acts/ad-jbk-117-13-engine-mount-truss-supports/conflicts","importantCases":"/api/acts/ad-jbk-117-13-engine-mount-truss-supports/important-cases","documents":"/api/acts/ad-jbk-117-13-engine-mount-truss-supports/documents"}}