- Control of engine power during reverser operation, engine idle setting during reverser transient

 - Control of maximum reverser power at full rearward throttle lever position

 - IDLE setting in case of non-commanded deployment

 (f) Engine parameters transmission for cockpit indication

 - Primary engine parameters

 - Starting system status

 - Thrust reverser system status

 - FADEC system status.

 (g) Engine condition monitoring parameters transmission (optional)

 (h) Detection, isolation, accommodation and memorization of its internal system faults

 (i) Fuel return valve control ECU controls the ON/OFF fuel return to the aircraft tank in relationship with :

 - Engine oil temperature

 - Aircraft fuel system configuration

 - Flight phases.

 (2) Hydromechanical Unit (Ref. Fig. 002) The hydromechanical unit (HMU) is attached to the aft section of the fuel pump unit housing. The HMU fuel pump package is installed on the aft side of the AGB, at the left side of the horizontal drive shaft housing. The HMU receives electrical signals from the engine electronic control unit (ECU) and converts these electrical input signals through torque motors/servo valves into the engine fuel flow and hydraulic signals to various external systems. Engine fuel is the hydraulic media.

 (3) Functional Interfaces
 (Ref. Fig. 003)

 (4) Additional Engine Sensing
 (Ref. Fig. 001)

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R R  Location of the Hydromechanical Unit (HMU) Figure 002
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 INTENTIONALLY BLANK

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 Functional Interfaces - Block Diagram R Figure 003
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 B. Gas Generator Control
 (1) Fuel Control

 (a) General The fuel is set by the ECU to hold the requested N1 as limited by : N2, PS3, WF, WF/PS3, dN2/dt, dWF/dt. (Ref. Fig. 004) The requested N1 is a function of the following logics : TLA & power management .... Sets N1 Auto Thrust A/C Signal .... Overrides TLA Landing configuration ..... Sets approach idle Alpha floor signal ........ Commands max T.O. Flex T.O. ................. Derates T.O. power Idle N2 ................... N2 set, N1 floats Min PS3 schedule .......... N1 and N2 float

 (b) Limitation description

 - Maximum and minimum N2 schedule. The ECU sets the fuel to hold the N1 provided N2 is within the limits shown in referenced illustration. (Ref. Fig. 005)

 - Accel and decel limitation schedules WF/PS3. The ECU sets the fuel to reach the N1 provided WF/PS3 is within limits shown in referenced illustration. (Ref. Fig. 006)

 - N2 and WF rate.

 - Maximum PS3, WF, N1, N2 limitations.

 - Minimum PS3, WF and N2 come from the idle schedules.

 (2) VSV Control The VSV position is controlled by the ECU. The steady state VSV schedules are more open that in transient and altitude bias allows different altitude schedules. (Ref. Fig. 007) The ECU uses the VSV feedback signal to adjust the actual VSV position. The VSV control loop is given on referenced illustration.

 (3) VBV Control The VBV position is controlled by the ECU. The VBV schedules are given on referenced figure (Ref. Fig. 008) The FADEC uses the VBV feedback signal to adjust the actual VBV position. The VBV control loop is given on referenced figure

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 Fuel Control Limits Figure 004
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 Max and Min N2 Limiting Curves
 Figure 005

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 Fuel Control Strategy Curves
 Figure 006

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