CTHIn ForceLegislation
AD/MAKILA/9 Amdt 1 - Engine Control Unit - Comparator/Selection Board
Turbomeca Turbine Engines - Makila SerieTurbomeca Turbine Engines - Makila Series
Start here
Get a plain-English read of Turbomeca Turbine Engines - Makila Serie
Turn the raw legal text into a practical explanation grounded in AD/MAKILA/9 Amdt 1 - Engine Control Unit - Comparator/Selection Board.
Turbomeca Turbine Engines - Makila Series
| AD/MAKILA/9 Amdt 1 | Engine Control Unit - Comparator/Selection Board | 8/2008 DM |
|---|
| Applicability: | Makila 1A and Makila 1A1 turbo-shaft engines. |
|---|---|
| Note 1: These engines are known to be installed in, but not limited to, EurocopterAS 332 C, C1, L and L1 helicopters. | |
| 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). |
| 2. An ECU Selector-Comparator board incorporating Turbomeca modification TU250 must be installed on at least one engine of each helicopter. | |
| Note 2: A post-TU250 ECU and a pre-TU250 ECU can be installed in the same helicopter until 30 November 2009. | |
| Note 3: EASA AD 2007-0144R1 refers. | |
| Compliance: | For Requirement 1 - Not later than 30 November 2009. |
| For Requirement 2 - After 30 November 2008. | |
| This Amendment becomes effective on 20 June 2008. | |
| 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. |
| 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. |
|---|