{"id":"F2007L02353","name":"AD/ARRIUS/11 Amdt 1 - Fuel Control Unit \"Delta P\" Diaphragm","slug":"ad-arrius-11-amdt-1-fuel-control-unit-delta-p-diaphragm","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":67678,"registerId":"commonwealth-F2007L02353-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Turbomeca Turbine Engines - Arrius Serie","sectionType":"division","heading":"Turbomeca Turbine Engines - Arrius Series","content":"### Turbomeca Turbine Engines - Arrius Series\n\n| AD/ARRIUS/11 Amdt 1 | Fuel Control Unit \"Delta P\" Diaphragm | 9/2007 |\n| ------------------- | ------------------------------------- | ------ |\n\n| Applicability: | TURBOMECA ARRIUS 2F turboshaft engines.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |\n| -------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | Incorporate modification Tf55 in accordance with paragraph 2 of Turbomeca Mandatory Service Bulletin No. 319 73 4055 or later NAA approved revisions.Note: EASA AD 2006-0237 dated 9 August 2006 refers.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |\n| Compliance:    | Before 30 September 2007, unless previously accomplished.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |\n|                | This Amendment becomes effective on 30 August 2007.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |\n| Background:    | This Directive is issued following the case of an increase in fuel flow resulting from deterioration of the constant delta pressure diaphragm.The increase in fuel flow led to an increase in gas generator rating which resulted in an increase in power turbine and helicopter rotor rating. This then led to an uncommanded in-flight engine shut-down following power turbine blade-shedding (blades contained) due to overspeed.This increase in fuel flow is attributed to the deterioration of the constant delta pressure diaphragm installed the wrong way round.The aim of this Directive is to replace the diaphragm potentially installed in the wrong way by one having two projections indicating proper direction.This amendment changes the applicability to include all ARRIUS 2F engines.The original issue of this AD became effective on 27 October 2005. |\n\n![](image.001.png)  \nDavid Punshon  \nDelegate of the Civil Aviation Safety Authority\n\n26 June 2007","sortOrder":0},{"sectionNumber":"AD/ARRIUS/11 Amdt 1","sectionType":"part","heading":"AD/ARRIUS/11 Amdt 1","content":"## AD/ARRIUS/11 Amdt 1","sortOrder":1},{"sectionNumber":"Fuel Control Unit \"Delta P\" Diaphragm","sectionType":"part","heading":"Fuel Control Unit \"Delta P\" Diaphragm","content":"## Fuel Control Unit \"Delta P\" Diaphragm","sortOrder":2},{"sectionNumber":"9/2007","sectionType":"part","heading":"9/2007","content":"## 9/2007","sortOrder":3}],"analysis":{"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"},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"This amendment broadened the AD’s applicability to include all ARRIUS 2F engines and mandates replacing any potentially incorrectly installed diaphragm with a redesigned part having two directional projections (Background). The original AD was effective 27 October 2005; this amendment became effective 30 August 2007 and set a compliance date of 30 September 2007 (Compliance; Background)."},"complexity_factors":["Narrow technical scope limited to TURBOMECA ARRIUS 2F engines (Applicability)","Requires a specific engine modification (Tf55) implemented per Turbomeca Mandatory Service Bulletin No. 319 73 4055 or later NAA‑approved revisions (Requirement)","Firm compliance deadline with retrospective effective date (Compliance)","Dependency on manufacturer service bulletin content and any later NAA approvals (Requirement)","Operational burden on operators: parts, labour, and scheduling to meet the directive (Compliance; Background)","Cross-reference to EASA AD 2006-0237 and prior AD history increases regulatory linkage (Background)"],"plain_english_summary":"Requires operators of Turbomeca Arrius 2F turboshaft engines to install modification Tf55 — following Turbomeca Mandatory Service Bulletin No. 319 73 4055 (or later NAA‑approved revisions) — to replace the fuel control unit “delta P” diaphragm by 30 September 2007. (Applicability; Requirement; Compliance)\n\nThis affects Arrius 2F engine owners/operators who must pay for parts and work and schedule the change. CASA issued it after reports that a backward‑installed diaphragm increased fuel flow and caused in‑flight shutdowns; the replacement diaphragm adds directional projections to prevent misinstallation. (Background)"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":true,"description":"The original 2005 directive covered a limited subset of engines. This 2007 amendment expands applicability to include ALL Arrius 2F engines, broadening the safety mandate significantly."},"complexity_factors":["Very short document (approximately 250 words)","Only 1 defined applicability (specific engine model)","Single mechanical modification required with clear reference to manufacturer bulletin","No nested exceptions or conditional logic — straightforward compliance deadline","Minimal cross-referencing (only references one EASA AD and one Turbomeca bulletin)","Plain language background explanation included"],"plain_english_summary":"This CASA Airworthiness Directive requires owners/operators and maintenance organisations of Turbomeca Arrius 2F turboshaft engines to replace the faulty “Delta P” diaphragm with a redesigned part (with installation markers) per Turbomeca’s service bulletin to prevent backward installation that caused fuel flow increases, engine overspeed, blade damage and in-flight shutdowns. The mandatory modification (expanded to cover all Arrius 2F engines) had to be completed by 30 September 2007."}},"importantCases":[],"_links":{"self":"/api/acts/ad-arrius-11-amdt-1-fuel-control-unit-delta-p-diaphragm","history":"/api/acts/ad-arrius-11-amdt-1-fuel-control-unit-delta-p-diaphragm/history","analysis":"/api/acts/ad-arrius-11-amdt-1-fuel-control-unit-delta-p-diaphragm/analysis","conflicts":"/api/acts/ad-arrius-11-amdt-1-fuel-control-unit-delta-p-diaphragm/conflicts","importantCases":"/api/acts/ad-arrius-11-amdt-1-fuel-control-unit-delta-p-diaphragm/important-cases","documents":"/api/acts/ad-arrius-11-amdt-1-fuel-control-unit-delta-p-diaphragm/documents"}}