(b) Motive flow modulation The HMU contains 5 additional torque motors/pilot valves that modulate hydraulic signals to the following: 1 - Low Pressure Turbine Clearance Control Valve 2 - High Pressure Turbine Clearance Control Valve 3 - Rotor Active Clearance Start Bleed System 4 - Variable Stator Vane Actuators 5 - Variable Bleed Valve Actuators. Each torque motor contains two electrically isolated, independent coils. One is dedicated to channel A, the other to channel B, of the ECU. They provide flow and pressure at an HMU pressure port in response to electrical commands from the ECU.
(c) Fuel shut-off valve
1 General
_ The fuel shutoff valve shuts off fuel flow to the engine in response to an electrical signal commanded by the ENG MASTER SWITCH supplied electrical signal. The valve is driven by a solenoid. Valve position is indicated to the ECU by two electrical limit switches.
2 Description
_ R (Ref. Fig. 028)
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Pressurizing and Shut-off Valve Layout showing Switch Actuator
Figure 028
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3 Operation
_ The fuel shut off valve shuts off fuel flow to the engine in response to an electrical signal commanded by the ENG MASTER SWITCH.
R (Ref. Fig. 028) The fuel shut off solenoid is energized by aircraft 28VDC. It has to be noted that the HP fuel shut off valve shut off signal also closes the LP fuel valve.
R (Ref. Fig. 029) The HP fuel shut off valve is open when all three following conditions are met:
- command to open (ENG MASTER SWITCH ON position) (solenoid de-energized)
- engine rotation speed above 15 percent N2
- fuel flow requested by the ECU.
(d) Overspeed governor The overspeed governor is of the fly-ball type. It is designed to prevent the engine from exceeding a steady state speed in excess of 105.8 percent N2.
P. Electrical Harnesses.
(1) General. The electrical connections between the various electrical, electronic and electromechanical engine-mounted components or accessories are provided by 2 types of harnesses, as follows:
(a) The harnesses which run on the core engine and on the low pressure turbine assembly. These harnesses have a special design to withstand the high temperature environment of the engine hot section.
(b) The harnesses which run on the fan inlet case and on the fan frame (engine cold section). Such harnesses have a more conventional design.
NOTE : All the harnesses running on the core engine and on the
____ low pressure turbine and turbine frame assembly converge toward the 6 o'clock tube bundle and harness junction box (6 o'clock box). This box provide an interface between the 2 designs of harness, depending on whether the signals to be conveyed initiate from the core engine or from the low pressure turbine and turbine frame assembly.
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Power Supply HP Fuel Shut-off Valve Figure 029
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(2) Description.
(a) Harnesses which have their routing on the Core Engine (HPC, Combustor Case and HPT) and on the Low Pressure Turbine. These harnesses are designated: CJ11L, CJ11R, CJ12L, CJ12R and CJ13.
1 Harness CJ11L consists of:
_ R (Ref. Fig. 030)
a One bulkhead connector (CL111) for passage through, and
_ attachment to the L-H inner wall of the 6 o'clock tube bundle junction box (ALF) with a nut.
b One stainless steel connection box, integral with connector
_
CL111.
c Two branches identified RACSB-A and VBV-A.
_
d Two mobile connectors: CL112 and CL113.
_
- CL112 connects to connector A of VBV position sensor.
- CL113 connects to the connector A of the RACSB valve position sensor.
2 Harness CJ11R consits of:
_ R (Ref. Fig. 031)
a One bulkhead connector (CR111) for passage through the RH
_ wall of the 6 o'clock tube bundle junction box (ALF).
b One round-shaped connection box with a flange for
_ attachment to the R-H outer wall of tube bundle junction box. Internally, this connection box provides for attachment of bulkhead connector (CR111).
c Five branches identified BSV-A, T25-A, LPTCC-A, HPTCC-A and
_ VSV-A. The LPTCC-A and HPTCC-A branches have each a T-shaped metal fitting with one mounting lug for attachment to the engine. The T25-A branch has an angled metal fitting with one mounting lug for attachment to the engine.
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