{"id":"F2005L00855","name":"AD/TURMO/5 Amdt 4 - Centrifugal Compressor","slug":"ad-turmo-5-amdt-4-centrifugal-compressor","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":34237,"registerId":"commonwealth-F2005L00855-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Turbomeca Turbine Engines - Turmo Series","sectionType":"division","heading":"Turbomeca Turbine Engines - Turmo Series","content":"### Turbomeca Turbine Engines - Turmo Series\n\n| AD/TURMO/5 Amdt 4 | Centrifugal Compressor | 5/2005 |\n| ----------------- | ---------------------- | ------ |\n\n| Applicability: | Turmo IV A and IV C model turboshaft engines installed in Aerospatiale SA 330 F, G and J “Puma” helicopters.                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |\n| -------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | Inspect the centrifugal compressor in accordance with Turbomeca Mandatory Service Bulletin No. A249 72 0100.Note 1: DGAC AD F-2005-037 EASA approval No. 2005-1910 dated 22 February 2005 refers, which supersedes DGAC AD 1997-122R3.                                                                                                                                                                                                                                                                                                                                                  |\n| Compliance:    | Within 50 hours or within 6 months (whichever occurs first) from the effective date with the following frequency:At intervals not to exceed 200 flight hours if the engine has no TU 191, TU 197, TU 215 and TU224 modifications; orAt intervals not to exceed 750/K flight hours if the engine is equipped with TU 197 or TU 215 modifications; orAt intervals not to exceed 1,000 flight hours if the engine is equipped with TU 191 or TU 224 modifications.Note 2: The value of K is determined by the calculations given in Turbomeca Mandatory Service Bulletin No. A249 72 0100. |\n|                | This Amendment becomes effective on 12 May 2005.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |\n| Background:    | This Directive is in response to reports of engine power loss and in-flight shut down events resulting from the release of compressor wheel fragments. This Directive requires the inspection of the centrifugal compressor.This amendment requires different inspection intervals to be followed based upon the modification status of the engine.Amendment 3 was issued in response to the latest revision of the reference document and became effective 10 August 2000.                                                                                                             |\n\n|     | Amendment 2 was issued to amend the inspection frequency of this Directive became effective 17 June 1999.Amendment 1 was issued to reflect the latest revision to the reference document and became effective 25 February 1999.The original issue of this Directive became effective 14 August 1997. |\n| --- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n\n![](image.001.png)  \nJames Coyne  \nDelegate of the Civil Aviation Safety Authority\n\n31 March 2005","sortOrder":0},{"sectionNumber":"AD/TURMO/5 Amdt 4","sectionType":"part","heading":"AD/TURMO/5 Amdt 4","content":"## AD/TURMO/5 Amdt 4","sortOrder":1},{"sectionNumber":"Centrifugal Compressor","sectionType":"part","heading":"Centrifugal Compressor","content":"## Centrifugal Compressor","sortOrder":2},{"sectionNumber":"5/2005","sectionType":"part","heading":"5/2005","content":"## 5/2005","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"This amendment refines inspection intervals and ties them to specific engine modification statuses; it does not extend the AD to additional engine types or aircraft beyond the original Applicability (Turmo IV A and IV C on SA 330 F/G/J). The primary purpose—preventing failures from released compressor wheel fragments by mandating inspections—remains the original intent. The change is a technical refinement of compliance frequency, not a substantive expansion of scope."},"complexity_factors":["Short, single-issue directive focused on one engine component","3 conditional inspection-interval branches based on modification status (no mod / TU197 or TU215 / TU191 or TU224)","Dependence on an external technical document (Turbomeca Mandatory Service Bulletin No. A249 72 0100) for inspection procedure and for the K calculation","Presence of a parameter (K) that must be calculated using methods in the Service Bulletin (adds engineering calculation step)","Cross-references to prior ADs and manufacturer approvals (historical amendments noted)"],"plain_english_summary":"**What this instrument does (mechanical change)**\n\n- Requires operators of Turbomeca Turmo IV A and IV C turboshaft engines installed in Aerospatiale SA 330 F, G and J “Puma” helicopters to carry out inspections of the engine’s centrifugal compressor in accordance with Turbomeca Mandatory Service Bulletin No. A249 72 0100 (the manufacturer’s inspection procedure). (See: Applicability; Requirement.)\n- Establishes an initial compliance window: carry out the inspection within 50 flight hours or within 6 months from the effective date of this amendment, whichever occurs first. (See: Compliance.)\n- Sets repeat inspection intervals that depend on which Turbomeca modifications the engine has: \n  - If the engine has none of TU191, TU197, TU215 or TU224: inspect at intervals not to exceed 200 flight hours.\n  - If the engine has TU197 or TU215: inspect at intervals not to exceed 750/K flight hours (the value K is calculated using the method in the Turbomeca Service Bulletin).\n  - If the engine has TU191 or TU224: inspect at intervals not to exceed 1,000 flight hours.\n  - The directive points operators to the manufacturer’s Service Bulletin for the precise inspection method and for the K calculation. (See: Compliance; Note 2.)\n- Becomes effective 12 May 2005. Operators must follow the inspection procedure and any corrective actions specified by the Service Bulletin.\n\n**Why it matters (official rationale and practical effect)**\n\n- The directive is issued in response to reports that compressor wheel fragments were released in service, causing engine power loss and in‑flight shutdowns. The stated purpose is to reduce the risk of similar failures by ensuring regular inspection of the centrifugal compressor. (See: Background.)\n\n**Who it affects and who decides**\n\n- Affected parties: owners and operators of Aerospatiale SA 330 F, G and J “Puma” helicopters that use Turbomeca Turmo IV A or IV C engines. Maintenance organisations that service those engines will also be affected.\n- Decision-maker / enforcing authority: the Civil Aviation Safety Authority (CASA) via this Airworthiness Directive (signed by a CASA delegate), backed by the manufacturer’s mandatory Service Bulletin for inspection technique and calculations.\n\n**Costs, incentives and trade-offs (practical consequences)**\n\n- Direct costs: operators bear the cost of the inspections (labour, downtime, possible replacement parts or repairs if defects are found) and any recurring costs according to the required interval. The initial inspection must be done within 50 flight hours or six months, which may compress maintenance scheduling.\n- Incentives created: engines that carry certain Turbomeca modifications (TU191 or TU224, or TU197/TU215 with a K adjustment) qualify for longer inspection intervals. That creates a financial incentive for operators to install those modifications if the modification cost is lower than the expected ongoing inspection and downtime cost.\n- Compliance complexity and administrative cost: the TU197/TU215 branch requires operators to compute a K value using the Service Bulletin’s method. That adds an engineering/calculation step and reliance on the manufacturer’s procedures.\n- Risk and opportunity cost: operators face the choice of increased recurring inspection cost versus investing in the modification(s) to extend intervals. There is also a risk that incorrectly following the Service Bulletin or miscalculating K undermines the safety intent.\n\n**Implementation and enforcement considerations**\n\n- The directive delegates the detailed inspection method and any follow‑up actions to the manufacturer’s Service Bulletin. That concentrates technical discretion with the manufacturer’s documented procedure (the Service Bulletin must be followed precisely to meet the AD).\n- The AD’s effectiveness depends on operators performing inspections at the stated intervals and on maintenance organisations applying the correct K calculation where required.\n\n**Net effect (behavioural summary)**\n\n- Operators must inspect the centrifugal compressor to reduce the chance of in‑flight engine power loss from released compressor fragments.\n- Operators may choose to install certain Turbomeca modifications to reduce inspection frequency; otherwise they must accept more frequent inspections and associated downtime and maintenance costs.\n\n(References: Applicability; Requirement; Compliance; Background sections of AD/TURMO/5 Amdt 4.)"},"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":true,"description":"Originally issued in 1997 as a straightforward compressor inspection requirement, the directive has evolved through four amendments to become a more nuanced, risk-based system. The scope has expanded from a single inspection interval to a differentiated approach with three distinct compliance pathways based on engine modification history. This reflects a shift from blanket requirements to tailored safety management based on technical data about which modifications reduce failure risk."},"complexity_factors":["Multiple amendment history (4 versions since 1997) creating layered context","Conditional compliance intervals with three mutually exclusive branches based on modification status","External reference dependency — requires cross-referencing Turbomeca Mandatory Service Bulletin No. A249 72 0100 for inspection procedures and K-value calculation","Dual trigger for initial compliance (50 hours OR 6 months — whichever first)","Nested applicability: engine model → helicopter model → modification status","French DGAC (Direction Générale de l'Aviation Civile) and EASA approval references creating international regulatory cross-references"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It requires specific helicopter engines to be inspected for a dangerous fault.\n\n**What it does:**\n- Orders owners and operators of certain **Turbomeca Turmo IV A and IV C turboshaft engines** (used in Aerospatiale SA 330 \"Puma\" helicopters) to inspect the **centrifugal compressor** — a key engine component that compresses air for combustion.\n\n**Why it matters:**\n- The compressor wheel can break apart during flight, causing **engine power loss or in-flight shutdown** — a serious safety risk.\n\n**Who must comply:**\n- Anyone operating the affected helicopter engines in Australia.\n\n**What must be done:**\n- Inspect the compressor following a specific Turbomeca service bulletin.\n- **When:** Within 50 flight hours or 6 months (whichever comes first) from 12 May 2005.\n- **How often after that:** Depends on which engine modifications are installed:\n  - **Every 200 hours** — if no specific modifications (TU 191, 197, 215, 224)\n  - **Every 750/K hours** — if TU 197 or TU 215 modifications fitted (K is a calculated value from the service bulletin)\n  - **Every 1,000 hours** — if TU 191 or TU 224 modifications fitted\n\nThis is the **fourth amendment** to the original 1997 directive, adjusting inspection intervals based on newer engine modification data."},"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-turmo-5-amdt-4-centrifugal-compressor","history":"/api/acts/ad-turmo-5-amdt-4-centrifugal-compressor/history","analysis":"/api/acts/ad-turmo-5-amdt-4-centrifugal-compressor/analysis","conflicts":"/api/acts/ad-turmo-5-amdt-4-centrifugal-compressor/conflicts","importantCases":"/api/acts/ad-turmo-5-amdt-4-centrifugal-compressor/important-cases","documents":"/api/acts/ad-turmo-5-amdt-4-centrifugal-compressor/documents"}}