{"id":"F2008L02100","name":"AD/MAKILA/9 Amdt 1 - Engine Control Unit - Comparator/Selection Board","slug":"ad-makila-9-amdt-1-engine-control-unit-comparator-selection-board","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":74320,"registerId":"commonwealth-F2008L02100-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Turbomeca Turbine Engines - Makila Serie","sectionType":"division","heading":"Turbomeca Turbine Engines - Makila Series","content":"### Turbomeca Turbine Engines - Makila Series\n\n| AD/MAKILA/9 Amdt 1 | Engine Control Unit - Comparator/Selection Board | 8/2008 DM |\n| ------------------ | ------------------------------------------------ | --------- |\n\n| Applicability: | Makila 1A and Makila 1A1 turbo-shaft engines.                                                                                                                                                                                                                                                                                                                                                                                                          |\n| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |\n|                | Note 1: These engines are known to be installed in, but not limited to, EurocopterAS 332 C, C1, L and L1 helicopters.                                                                                                                                                                                                                                                                                                                                  |\n| Requirement:   | 1. Replace the Engine Control Unit (ECU) Selector-Comparator board with one incorporating Turbomeca modification TU250. Replacement of the Selector-Comparator board and return of the Modification Compliance Certificate to Turbomeca must be performed in accordance with Turbomeca Mandatory Service Bulletin 298 73 0250 dated 23 March 2007 or later revision approved by the European Aviation Safety Agency (EASA).                            |\n|                | 2. An ECU Selector-Comparator board incorporating Turbomeca modification TU250 must be installed on at least one engine of each helicopter.                                                                                                                                                                                                                                                                                                            |\n|                | Note 2: A post-TU250 ECU and a pre-TU250 ECU can be installed in the same helicopter until 30 November 2009.                                                                                                                                                                                                                                                                                                                                           |\n|                | Note 3: EASA AD 2007-0144R1 refers.                                                                                                                                                                                                                                                                                                                                                                                                                    |\n| Compliance:    | For Requirement 1 - Not later than 30 November 2009.                                                                                                                                                                                                                                                                                                                                                                                                   |\n|                | For Requirement 2 - After 30 November 2008.                                                                                                                                                                                                                                                                                                                                                                                                            |\n|                | This Amendment becomes effective on 20 June 2008.                                                                                                                                                                                                                                                                                                                                                                                                      |\n| Background:    | Modification TU203, applicable to Makila 1A and Makila 1A1 engines, introduced a control system backup law that fixes N1 (gas generator speed) at 65% when at least two of the three N2 (power turbine speed) signals are lost. The intent is to limit the maximum speed attainable by the power turbine in the event of a failure of the shaft between the Engine and the Main Gearbox that could result in collateral damage to the N2 speed probes. |\n\n|     | Recent occurrences of 65% N1 backup activation remain unexplained despite detailed investigation. Although not substantiated, it is postulated that the events may have been due to corruption of the engine N2 speed signals by short perturbations, for example by EMI. The potential therefore exists for a hazardous condition in which both engines on the same helicopter are simultaneously affected. |\n| --- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |\n|     | The original issue of this Directive required a hardware modification to the ECU that allows recovery from the 65% backup mode if the loss of N2 speed signals is determined to be temporary. The modification applies to the Selector-Comparator board in the ECU.                                                                                                                                          |\n|     | This Amendment limits the applicability to civil helicopters and continues the requirement for ECU Selector-Comparator board to be modified, extending the compliance until 30 November 2009 for both engines. The Amendment also requires that at least one engine of each helicopter has a modified ECU Selector-Comparator board installed after 30 November 2008.                                        |\n|     | The original issue of this Directive became effective on 5 July 2007.                                                                                                                                                                                                                                                                                                                                        |\n\n![](image.001.png)  \nJames Coyne  \nDelegate of the Civil Aviation Safety Authority\n\n13 June 2008","sortOrder":0},{"sectionNumber":"AD/MAKILA/9 Amdt 1","sectionType":"part","heading":"AD/MAKILA/9 Amdt 1","content":"## AD/MAKILA/9 Amdt 1","sortOrder":1},{"sectionNumber":"Engine Control Unit - Comparator/Selecti","sectionType":"part","heading":"Engine Control Unit - Comparator/Selection Board","content":"## Engine Control Unit - Comparator/Selection Board","sortOrder":2},{"sectionNumber":"8/2008 DM","sectionType":"part","heading":"8/2008 DM","content":"## 8/2008 DM","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"The Amendment narrows applicability to civil helicopters and adjusts timing and transition rules: it continues the requirement to modify the ECU Selector‑Comparator board (original Directive) but requires at least one engine per helicopter to have the TU250 board after 30 November 2008 and extends the full‑replacement compliance date for both engines to not later than 30 November 2009. It also permits mixed pre‑ and post‑TU250 ECUs in the same helicopter until 30 November 2009 (see 'This Amendment limits the applicability to civil helicopters' and the Compliance dates)."},"complexity_factors":["Technical specificity: requirement targets a single ECU component (Selector‑Comparator board) and a specific manufacturer modification (TU250).","Regulatory cross‑reference: compliance requires following Turbomeca Mandatory Service Bulletin 298 73 0250 and any later EASA‑approved revision.","Deadlines and phased requirement: separate compliance dates for installation on at least one engine (after 30 Nov 2008) and for full replacement (not later than 30 Nov 2009).","Compatibility window: allows mixed post‑TU250 and pre‑TU250 ECUs in the same helicopter until 30 Nov 2009, adding transitional operational complexity.","Certification paperwork: mandatory return of the Modification Compliance Certificate to Turbomeca increases administrative burden.","Scope limitation: amendment restricts applicability to civil helicopters, requiring attention to operator category.","Dependence on external investigation: background safety rationale references unexplained EMI‑like perturbations, creating uncertainty about residual risk and mitigation sufficiency."],"plain_english_summary":"This directive requires operators of helicopters with Makila 1A/1A1 engines to replace the Engine Control Unit (ECU) selector‑comparator board with one incorporating Turbomeca modification TU250, installed and certified per Turbomeca Mandatory Service Bulletin 298 73 0250 (Requirement 1). It also requires at least one engine per helicopter to have the modified board after 30 November 2008 (Requirement 2). Operators pay for installation and certification; CASA enforces the deadlines. The change aims to reduce the risk of both engines entering a 65% N1 backup when N2 signals are corrupted (Background)."},"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This Amendment 1 maintains the original safety purpose of preventing dual-engine backup mode activation. It narrows applicability to civil helicopters (excluding military) and extends compliance deadlines, but does not expand beyond the original technical scope of ECU board replacement."},"complexity_factors":["Single, specific technical requirement with clear deadlines","Limited applicability (only two engine models, primarily one helicopter type)","Straightforward two-stage compliance schedule","References external technical documents (Turbomeca Service Bulletin, EASA AD) but does not incorporate them by full text","Minimal defined terms (only standard aviation abbreviations like ECU, N1, N2)","No nested exceptions or conditional logic beyond the phased compliance dates"],"plain_english_summary":"This AD requires owners/operators and maintenance organisations to install an updated Selector‑Comparator circuit board in the Engine Control Unit of Turbomeca Makila 1A/1A1 engines (used on certain Eurocopter AS332 models). The change prevents unintended activation of a backup engine mode—caused by electrical interference—that could, if both engines entered it, create a serious in‑flight hazard. Compliance: at least one engine by 30 Nov 2008; both engines by 30 Nov 2009."}},"importantCases":[],"_links":{"self":"/api/acts/ad-makila-9-amdt-1-engine-control-unit-comparator-selection-board","history":"/api/acts/ad-makila-9-amdt-1-engine-control-unit-comparator-selection-board/history","analysis":"/api/acts/ad-makila-9-amdt-1-engine-control-unit-comparator-selection-board/analysis","conflicts":"/api/acts/ad-makila-9-amdt-1-engine-control-unit-comparator-selection-board/conflicts","importantCases":"/api/acts/ad-makila-9-amdt-1-engine-control-unit-comparator-selection-board/important-cases","documents":"/api/acts/ad-makila-9-amdt-1-engine-control-unit-comparator-selection-board/documents"}}