{"id":"F2009L01698","name":"AD/MAKILA/14 - Engine Control Unit - Comparator/Selector Boards","slug":"ad-makila-14-engine-control-unit-comparator-selector-boards","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":78558,"registerId":"commonwealth-F2009L01698-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/14 | Engine Control Unit - Comparator/Selector Boards | 7/2009 DM |\n| ------------ | ------------------------------------------------ | --------- |\n\n| Applicability: | Makila 1A and 1A1 turboshaft engines, all serial numbers, having Engine Control Units (ECU) equipped with TU250 Comparator / Selector (CS) boards with serial numbers (S/N) in the range 241 EL to 1192 EL.                                                                                                                                                                                  |\n| -------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n|                | Note 1: CS boards with S/N in the above range are hereafter referred to as the suspect batch.                                                                                                                                                                                                                                                                                                |\n|                | Note 2: Makila 1A and 1A1 engines are installed in, but not limited to, Eurocopter AS 332 C, C1, L and L1 helicopters.                                                                                                                                                                                                                                                                       |\n| Requirement:   | 1. If both TU250 CS boards on the same helicopter are from the suspect batch and if both have an operating time since new of less than 200 hours, unless previously accomplished, replace at least one of the boards with a board not from the suspect batch in accordance with the instructions of Turboméca Mandatory Service Bulletin (MSB) 298 73 0809 Version A dated 12 February 2008. |\n|                | 2. Unless accomplished previously, replace all TU250 CS boards from the suspect batch with boards not from the suspect batch in accordance with the instructions of Turboméca MSB 298 73 0810 Version B dated 27 April 2009.                                                                                                                                                                 |\n|                | Replacement of all TU250 CS boards, accomplished prior to the effective date of this Directive, in accordance with Turboméca MSB 298 73 0810 Version A dated12 February 2008 is acceptable for compliance with Requirement 2.                                                                                                                                                                |\n|                | The use of later Versions of the above MSBs, approved by the European Aviation Safety Agency (EASA), are acceptable for compliance with the requirements of this Directive.                                                                                                                                                                                                                  |\n|                | Note 3: EASA AD 2009-0090 refers.                                                                                                                                                                                                                                                                                                                                                            |\n| Compliance:    | For Requirement 1 - Within 50 hours time in service from the effective date of this Directive.                                                                                                                                                                                                                                                                                               |\n|                | For Requirement 2 - During the next 500-hour routine inspection, or before30 November 2009, whichever occurs first.                                                                                                                                                                                                                                                                          |\n|                | This Airworthiness Directive becomes effective on 12 May 2009.                                                                                                                                                                                                                                                                                                                               |\n\n| Background: | Makila 1A and 1A1 ECUs incorporate a backup control 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.Several occurrences of 65% N1 backup activation remain unexplained despite detailed investigation. It is postulated that the events may have been due to corruption of the engine N2 speed signals by short perturbations, for example by electromagnetic interference. The potential therefore existed for a hazardous condition in which both engines on the same helicopter were simultaneously affected.To address this risk, Turboméca introduced modification TU250, which affects the CS board in the ECU and allows recovery from the 65% backup mode if the loss of N2 speed signals is determined to be temporary. Incorporation of modification TU250 was mandated by AD/MAKILA/9 (EASA AD 2007-0144).The installation of TU250 CS boards, however, has resulted in a few occurrences of erratic engine behaviour, in the form of unexpected N1 variations and/or illumination of the “GOV” warning light. The conclusions from an investigation by Turboméca are that these malfunctions are due to a lapse of quality control in the varnishing process applied to the boards, and that only boards in a specific serial number range, as defined under “Applicability” and referred to below as the “suspect batch”, are affected.Turboméca has addressed this latest concern in two steps which provide first a near-term and then a long-term solution. The two steps are described in the referenced mandatory service bulletins (MSB).The first step, described in MSB 298 73 0809, recommends that no helicopter has CS boards from the suspect batch in both engines. Boards with more than 200 hours of trouble-free operation are exempt because service experience has shown that the malfunctions potentially induced by this manufacturing discrepancy are most likely to occur early in the lives of the boards.The second step, described in MSB 298 73 0810, recommends that ultimately all TU250 CS boards in the suspect batch, regardless of time in operation, be replaced with TU250 boards not from the suspect batch. |\n| ----------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n\n|     | This Directive makes the replacement of TU250 CS boards in the suspect batch mandatory. |\n| --- | --------------------------------------------------------------------------------------- |\n\n![](image.001.png)  \nJames Coyne  \nDelegate of the Civil Aviation Safety Authority\n\n4 May 2009","sortOrder":0},{"sectionNumber":"AD/MAKILA/14","sectionType":"part","heading":"AD/MAKILA/14","content":"## AD/MAKILA/14","sortOrder":1},{"sectionNumber":"Engine Control Unit - Comparator/Selecto","sectionType":"part","heading":"Engine Control Unit - Comparator/Selector Boards","content":"## Engine Control Unit - Comparator/Selector Boards","sortOrder":2},{"sectionNumber":"7/2009 DM","sectionType":"part","heading":"7/2009 DM","content":"## 7/2009 DM","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"Yes. While TU250 modification had been previously mandated (see AD/MAKILA/9) to address N2 signal loss, this Directive targets a specific \"suspect batch\" of TU250 CS boards and mandates their removal/replacement with defined time‑in‑service conditions and deadlines. The Directive therefore adds corrective obligations for certain previously installed TU250 boards rather than simply requiring the TU250 modification."},"complexity_factors":["Applicability tied to specific engine models (Makila 1A/1A1) and a narrow CS board serial‑number range (241 EL–1192 EL).","Two-tiered requirements: immediate conditional action if both engines have suspect boards <200 hours, plus a universal replacement deadline.","Multiple compliance deadlines (50 hours for Requirement 1; next 500‑hour inspection or fixed date for Requirement 2).","Dependence on external documents (Turboméca MSB 298 73 0809/0810) and acceptance of later EASA‑approved MSB versions.","Acceptance of prior compliance under an earlier MSB version as satisfying the Directive (introduces retrospective compliance checks).","Operational impacts: parts replacement, aircraft downtime and inspection scheduling burdens for operators."],"plain_english_summary":"Mandates replacement of TU250 Comparator/Selector (CS) boards with serial numbers 241 EL–1192 EL in Makila 1A/1A1 engine ECUs: if both engines’ suspect boards have under 200 hours, replace at least one within 50 hours; replace all suspect boards by the next 500‑hour inspection or by 30 Nov 2009. Affects operators of Makila‑equipped helicopters (e.g. Eurocopter AS332 variants).\n\nTurboméca attributes the action to varnish defects that produced erratic N1 behaviour and GOV warnings; operators bear parts, downtime and compliance costs and must follow Turboméca MSBs approved by EASA."},"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"},"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This is a standard airworthiness directive addressing a specific manufacturing defect in a defined component. The scope remains tightly focused on the TU250 Comparator/Selector boards within the specified serial number range. There is no evidence of scope creep beyond the original safety purpose of addressing the varnishing process defect."},"complexity_factors":["Multiple conditional requirements with nested logic (e.g., Requirement 1 applies only if both boards are from suspect batch AND both have <200 hours operating time)","Cross-references to external technical documents (Turboméca Mandatory Service Bulletins 298 73 0809 and 298 73 0810, plus EASA AD 2009-0090)","Version tracking of referenced documents (accepts Version A or B of specific MSBs, plus 'later Versions' approved by EASA)","Dual compliance timelines with 'whichever occurs first' logic (500-hour inspection vs. calendar date)","Specific serial number range applicability (241 EL to 1192 EL) requiring physical inspection of installed components","Grandfathering clause allowing prior compliance under earlier document version to satisfy current requirement"],"plain_english_summary":"This AD mandates replacing defective Comparator/Selector (CS) circuit boards in Turbomeca Makila 1A/1A1 engine control systems — used on Eurocopter AS332 (Super Puma) helicopters — because a varnish coating fault on boards serial 241 EL–1192 EL can cause erratic engine speed and warnings. Affected operators and maintenance organisations must carry out near-term replacement (one board within 50 flight hours if both engines have faulty, low-hour boards) and complete full replacement at the next 500‑hour inspection or by 30 Nov 2009."}},"importantCases":[],"_links":{"self":"/api/acts/ad-makila-14-engine-control-unit-comparator-selector-boards","history":"/api/acts/ad-makila-14-engine-control-unit-comparator-selector-boards/history","analysis":"/api/acts/ad-makila-14-engine-control-unit-comparator-selector-boards/analysis","conflicts":"/api/acts/ad-makila-14-engine-control-unit-comparator-selector-boards/conflicts","importantCases":"/api/acts/ad-makila-14-engine-control-unit-comparator-selector-boards/important-cases","documents":"/api/acts/ad-makila-14-engine-control-unit-comparator-selector-boards/documents"}}