{"id":"F2006B02443","name":"AD/ARRIEL/11 - Gas Generator Rear Bearing Chip Detector","slug":"ad-arriel-11-gas-generator-rear-bearing-chip-detector","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41699,"registerId":"commonwealth-F2006B02443-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/ARRIEL/11 - Gas Generator Rear Bearing Chip Detector","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 106 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nTurbomeca Turbine Engines \\- Arriel Series\n\nAD/ARRIEL/11 Gas Generator Rear Bearing Chip Detector 5/99\n\nApplicability: All Arriel 1 series engines.\n\nRequirement: Install Turbomeca Modification TU 208 in accordance with Turbomeca Service Bulletin No. 292 72 0163 Updating 1.\n\nNote: DGAC Airworthiness Directive 98-394(A) refers.\n\nCompliance: At next engine shop visit, regardless of the purpose of the visit, or prior to 31 December 1999, whichever occurs first.\n\nThis Airworthiness Directive becomes effective on 20 May 1999.\n\nBackground: This directive has been issued to add a gas generator rear bearing chip detector to the main chip detector warning system. The requirement follows reports of 6 gas generator rear bearing rupture events. The additional chip detector will provide the pilot with an in-flight warning of rear bearing chip detector contamination.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical failure mode in a specific engine series. It has not expanded beyond its original purpose of mandating a chip detector installation."},"complexity_factors":["Single, unambiguous applicability clause ('All Arriel 1 series engines')","One clear mechanical modification requirement with specific part reference","Simple binary compliance trigger (next shop visit OR fixed date deadline)","No defined terms section, no cross-references to other legislation beyond a single note","No conditional exceptions or nested logic","Total length: approximately 150 words"],"plain_english_summary":"**What this is:** This is an Airworthiness Directive (AD) — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). Think of it as a \"recall notice\" for aircraft engines, but with legal force. Owners and operators must comply or the aircraft cannot legally fly.\n\n**What it does:** It requires all operators of Turbomeca Arriel 1 series helicopter engines to install an extra safety sensor — specifically, a chip detector for the gas generator's rear bearing. A chip detector is a magnetic plug that catches tiny metal particles; if it finds chips, it triggers a warning light in the cockpit, alerting the pilot to potential engine damage before catastrophic failure occurs.\n\n**Why it matters:** Six engines had suffered rear bearing ruptures — a serious failure that can cause engine destruction and potential crashes. The existing warning system didn't monitor this specific bearing. This modification adds that missing safety net, giving pilots early warning of trouble.\n\n**Who must act:** Anyone operating a helicopter with an Arriel 1 series engine (commonly used in helicopters like the Eurocopter AS350 Squirrel and similar types).\n\n**When to comply:** Either at the next scheduled engine overhaul/repair (\"shop visit\"), or before 31 December 1999 — whichever comes first.\n\n**Key details:**\n- **Modification required:** Turbomeca Modification TU 208 (installed per Service Bulletin 292 72 0163)\n- **Effective date:** 20 May 1999\n- **Based on:** French aviation authority (DGAC) directive 98-394(A)"},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":true,"description":"This directive changes the in‑service configuration of Arriel 1 series engines by mandating a retrofit: the addition of a gas generator rear bearing chip detector (Requirement; Background). Prior to the AD, engines in the fleet could be without this specific detector; the AD requires all affected engines to be modified to include it, implemented at the next engine shop visit or by 31 December 1999 (Compliance)."},"complexity_factors":["Scope limited to a single engine family (Arriel 1 series) — straightforward applicability (Applicability).","Single, specific technical action required (install Modification TU 208) following a single manufacturer service bulletin — lowers legal complexity but raises technical/operational requirements (Requirement).","Fixed compliance window with an operationally flexible trigger (next engine shop visit OR by a calendar date) — simple but requires maintenance scheduling (Compliance).","Dependence on external technical documentation (Turbomeca Service Bulletin No. 292 72 0163 Updating 1) introduces implementation dependency on manufacturer instructions and parts availability (Requirement).","No exemptions, alternatives or staged implementation detailed in the text — reduces procedural complexity but concentrates decision on operator/maintenance provider to comply (Requirement; Compliance)."],"plain_english_summary":"This directive requires Turbomeca Arriel 1 series engines to be retrofitted with a gas‑generator rear bearing chip detector per the manufacturer’s modification and service bulletin, to be done at the next engine shop visit or by 31 Dec 1999. It affects aircraft owners/operators and maintenance shops, who must arrange and fund the work. The retrofit—prompted by bearing ruptures—gives pilots an in‑flight warning but shifts costs and scheduling demands onto operators and MRO providers."}},"importantCases":[],"_links":{"self":"/api/acts/ad-arriel-11-gas-generator-rear-bearing-chip-detector","history":"/api/acts/ad-arriel-11-gas-generator-rear-bearing-chip-detector/history","analysis":"/api/acts/ad-arriel-11-gas-generator-rear-bearing-chip-detector/analysis","conflicts":"/api/acts/ad-arriel-11-gas-generator-rear-bearing-chip-detector/conflicts","importantCases":"/api/acts/ad-arriel-11-gas-generator-rear-bearing-chip-detector/important-cases","documents":"/api/acts/ad-arriel-11-gas-generator-rear-bearing-chip-detector/documents"}}