{"id":"F2008L01906","name":"AD/ARRIEL/29 - Low Fuel Pressure Switch","slug":"ad-arriel-29-low-fuel-pressure-switch","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":74131,"registerId":"commonwealth-F2008L01906-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Turbomeca Turbine Engines - Arriel Serie","sectionType":"division","heading":"Turbomeca Turbine Engines - Arriel Series","content":"### Turbomeca Turbine Engines - Arriel Series\n\n| AD/ARRIEL/29 | Low Fuel Pressure Switch | 7/2008 |\n| ------------ | ------------------------ | ------ |\n\n| Applicability: | Turboméca S.A. ARRIEL 2B, 2B1 and 2B1A turboshaft engines.Note 1: These engines are known to be installed on, but not limited to EurocopterAS 350 B3 and EC 130 B4 helicopters. |\n| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement: | 1. Accomplish a one-time inspection of the Hydro Mechanical Unit (HMU) in accordance with paragraph 2 of Turboméca Mandatory Service Bulletin (MSB) 292 73 2826 to identify the low fuel pressure switch installed on adjusted HMU.2. If a Hydra-Electric low fuel pressure switch Part Number (P/N) 9 550 17 956 0 is installed:a. Inspect low fuel pressure switch and chamber of the HMU body.i. If any parts from the low fuel pressure switch are missing or found in the HMU chamber, replace the HMU with a new or overhauled HMU equipped with an IN-LHC low fuel pressure switch.ii. If not, replace only the low fuel pressure switch with an IN-LHC low fuel pressure switch.3. If an IN-LHC low fuel pressure switch P/N 9 550 17 199 0 or P/N 9 550 17 913 0 is installed:a. If an IN-LHC low fuel pressure switch has been installed since new, repair or overhaul, no further action is required.b. If a Hydra-Electric switch P/N 9 550 17 956 0 has been or may have been previously installed:i. Inspect the chamber of the HMU body.ii. If any parts are found in the HMU chamber, replace the HMU by a new or overhauled HMU equipped with an IN-LHC low fuel pressure switch.Note 2: EASA AD 2008-0077 dated 28 April 2008 refers. |\n| Compliance: | No later than 30 September 2009. |\n\n| | This Airworthiness Directive becomes effective on 3 July 2008. |\n| ----------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Background: | Several cases of loss of internal components from the HMU low fuel pressure switch Hydra-Electric Part number 9 550 17 956 0 into the fuel system, have been reported on Arriel 2 engines. The loss of internal components from the low fuel pressure switch into the fuel system may lead to a rupture of the HP-LP pumps drive shaft shear pin, and thus to a possible uncommanded In-Flight Shut-Down (IFSD). On a single-engine helicopter, an uncommanded IFSD results in an emergency autorotation landing and in certain conditions may lead to an accident. |\n\n![](image.001.png) \nJames Coyne \nDelegate of the Civil Aviation Safety Authority\n\n22 May 2008","sortOrder":0},{"sectionNumber":"AD/ARRIEL/29","sectionType":"part","heading":"AD/ARRIEL/29","content":"## AD/ARRIEL/29","sortOrder":1},{"sectionNumber":"Low Fuel Pressure Switch","sectionType":"part","heading":"Low Fuel Pressure Switch","content":"## Low Fuel Pressure Switch","sortOrder":2},{"sectionNumber":"7/2008","sectionType":"part","heading":"7/2008","content":"## 7/2008","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"Scope is narrowly focused on Turboméca Arriel 2B/2B1/2B1A engines fitted or possibly fitted with the specified low fuel pressure switch part numbers. The directive addresses the precise failure mode described (internal switch parts entering the fuel system) and does not broaden to other engine types or unrelated components (Applicability; Requirement; Background)."},"complexity_factors":["Targeted technical inspections tied to specific part numbers (Hydra‑Electric P/N 9 550 17 956 0 vs IN‑LHC P/Ns 9 550 17 199 0 and 9 550 17 913 0) (Requirement ¶2–3).","Conditional outcomes: inspection only, switch replacement, or full HMU replacement depending on findings (Requirement ¶2.a.i–ii; 3.b.ii).","Need to inspect the HMU chamber for loose parts, which may require disassembly skills, tooling and possible contamination control (Requirement ¶2.a.i; 3.b.i).","Record/history check whether IN‑LHC switch has been installed since new/repair/overhaul to determine further action (Requirement ¶3.a).","Compliance deadline creates a fixed operational window (Compliance: no later than 30 September 2009).","Applicability limited to specific engine models but notes broader installation on listed helicopter types, requiring operators to map affected airframes (Applicability).","Reference to an external regulator's AD (EASA AD 2008‑0077) for related context (Requirement Note 2).","Safety‑critical downstream consequence (possible HP‑LP pump drive shaft shear pin rupture and uncommanded IFSD) quoted in Background increases implementation urgency and regulatory scrutiny."],"plain_english_summary":"**What it does:** Requires a one‑time inspection of the Hydro Mechanical Unit (HMU) on Turboméca Arriel 2B/2B1/2B1A engines to identify the low fuel pressure switch fitted and, depending on the part‑number and inspection findings, to replace the switch or the whole HMU. **Who it affects and why it matters:** Helicopter operators using these engines (e.g. AS350 B3, EC130 B4) must act to prevent loose switch parts entering the fuel system, which the AD says can lead to pump drive failure and an uncommanded in‑flight shutdown."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a standard, narrow Airworthiness Directive addressing a specific known defect in a specific engine component. The scope remains tightly focused on the original safety issue — preventing uncommanded engine shutdowns due to a faulty fuel pressure switch. No scope creep or expansion beyond the immediate safety-critical maintenance action."},"complexity_factors":["Short, single-purpose directive with one specific mechanical defect to address","Only 3 main requirement paragraphs with clear conditional branching (if/then logic)","Minimal defined terms — only standard aviation abbreviations (HMU, P/N, IFSD) used without formal definitions section","No cross-references to other legislation or complex regulatory frameworks — only references to manufacturer's service bulletin and EASA AD for background","Straightforward applicability section listing specific engine models and example helicopter types","Single compliance date with no phased or conditional deadlines"],"plain_english_summary":"Owners and operators of helicopters fitted with Turboméca Arriel 2B-series engines (notably AS350 B3 and EC130 B4) must inspect the HMU to identify and, if necessary, replace a Hydra‑Electric fuel pressure switch whose internal parts can break off, contaminate the fuel system, jam the fuel pump and cause in‑flight engine shutdown. \n\nThis mandatory AD requires inspection and replacement (or HMU overhaul if debris is found) to prevent engine failure; compliance deadline: 30 September 2009."},"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"}},"importantCases":[],"_links":{"self":"/api/acts/ad-arriel-29-low-fuel-pressure-switch","history":"/api/acts/ad-arriel-29-low-fuel-pressure-switch/history","analysis":"/api/acts/ad-arriel-29-low-fuel-pressure-switch/analysis","conflicts":"/api/acts/ad-arriel-29-low-fuel-pressure-switch/conflicts","importantCases":"/api/acts/ad-arriel-29-low-fuel-pressure-switch/important-cases","documents":"/api/acts/ad-arriel-29-low-fuel-pressure-switch/documents"}}