{"id":"F2006B02444","name":"AD/ARRIEL/12 - Power Turbine Nozzle Inspection","slug":"ad-arriel-12-power-turbine-nozzle-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41700,"registerId":"commonwealth-F2006B02444-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/ARRIEL/12 - Power Turbine Nozzle Inspection","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/12 Power Turbine Nozzle Inspection 5/99\n\nApplicability: Arriel 1A, 1A1, 1A2 and 1B models not incorporating Turbomeca Modification TU 38.\n\nRequirement: To detect cracking of the power turbine nozzle vanes which may result in an in flight shutdown of the engine, carry out an ultrasonic inspection of the internal face of the gas generator module rear bearing support in accordance with the procedure detailed in Turbomeca Service Bulletin No. 292 72 0213.\n\nNote: DGAC Airworthiness Directive 98-493 (A) refers.\n\nCompliance: At next engine shop visit, regardless of the purpose of the visit, or prior to 30 June 1999, whichever occurs first.\n\nThis Airworthiness Directive becomes effective on 20 May 1999.\n\nBackground: This directive has been issued to require a once only inspection of the gas generator rear bearing support. The requirement follows advice from the manufacturer of cracks developing in the bearing support.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-bound airworthiness directive with a single, specific safety purpose. It has not expanded beyond its original intent of requiring a one-time inspection for crack detection in specific engine models."},"complexity_factors":["Very short document (under 200 words)","Only 4 defined applicability criteria (specific engine models plus one modification exclusion)","Single, clear compliance requirement with no nested conditions","No cross-references to other legislation or complex procedural rules","Straightforward deadline structure (next shop visit OR fixed date)","Background section provides clear rationale without legal caveats"],"plain_english_summary":"This is a **safety order for helicopter engines**. It requires owners and operators of specific Turbomeca Arriel engines (models 1A, 1A1, 1A2, and 1B without a specific factory modification) to get their engines inspected for cracks.\n\n**What the problem is:** Cracks can develop in the power turbine nozzle vanes (parts inside the engine). If these cracks aren't found, they can cause the engine to shut down unexpectedly during flight — obviously dangerous.\n\n**What must be done:** An **ultrasonic inspection** (a type of scan using sound waves to detect cracks invisible to the eye) must be performed on a specific part of the engine called the \"gas generator module rear bearing support.\" The inspection must follow the exact procedure in Turbomeca Service Bulletin No. 292 72 0213.\n\n**When it must be done:** Either at the next time the engine goes to the shop for any reason, or before 30 June 1999 — whichever comes first.\n\n**Who this affects:** Anyone operating helicopters with these specific Arriel engine models in Australia. This is a mandatory safety requirement — compliance is not optional."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The instrument implements a one‑off inspection for the specified engines as described in the Background and Requirement. It does not broaden to other models, establish recurring obligations, or otherwise expand the stated scope; the effect is limited to the listed applicability and the single inspection with the stated compliance deadline (Applicability; Requirement; Compliance; Background)."},"complexity_factors":["Narrow applicability — applies only to Arriel 1A, 1A1, 1A2 and 1B models not incorporating TU 38 (Applicability).","One‑off mandated action — single ultrasonic inspection rather than ongoing monitoring (Requirement; Background).","Technical procedure specified — inspection must follow Turbomeca Service Bulletin No. 292 72 0213, requiring appropriate shop capability (Requirement).","Fixed compliance timing — at next engine shop visit or by 30 June 1999, creating a short compliance window (Compliance).","Cost and scheduling burden on operators/maintenance organisations — operators must fund and arrange the inspection (Requirement; Compliance).","Limited administrative discretion — AD prescribes the action and deadline; little scope for alternative measures (Requirement; Compliance).","Safety‑critical focus increases operational impact despite procedural simplicity — detection aimed at preventing in‑flight shutdown (Background).","Exemption by modification — engines with Turbomeca Mod TU 38 are outside scope, so fleet segmentation matters (Applicability)."],"plain_english_summary":"This Airworthiness Directive requires operators of Turbomeca Arriel 1A, 1A1, 1A2 and 1B engines that do not have Turbomeca Modification TU 38 to carry out a one‑off ultrasonic inspection of the internal face of the gas‑generator rear bearing support, using Turbomeca Service Bulletin No. 292 72 0213. Compliance is required at the next engine shop visit or by 30 June 1999, whichever comes first. CASA issued the AD to detect cracks that could cause an in‑flight engine shutdown. Operators or their maintenance organisations pay for and schedule the inspection."}},"importantCases":[],"_links":{"self":"/api/acts/ad-arriel-12-power-turbine-nozzle-inspection","history":"/api/acts/ad-arriel-12-power-turbine-nozzle-inspection/history","analysis":"/api/acts/ad-arriel-12-power-turbine-nozzle-inspection/analysis","conflicts":"/api/acts/ad-arriel-12-power-turbine-nozzle-inspection/conflicts","importantCases":"/api/acts/ad-arriel-12-power-turbine-nozzle-inspection/important-cases","documents":"/api/acts/ad-arriel-12-power-turbine-nozzle-inspection/documents"}}