*
Start/ignition selector in START
*
EEC maintenance switch in TEST.
The PMA starts to supply power at approximately five percent N2. The PMA has two windings, one for each channel of the EEC. The PMA has priority over airplane power.
Computer
The EEC has two channels with these main sections:
*
Processor
*
Cross-talk logic
*
Input/Output (I/O)
*
Memory
EFFECTIVITY
BEJ ALL
* Pressure transducers.
The processor does all of the control calculations. It supplies all the data for the I/O section and control signals for the torque motors and solenoids.
The cross-talk logic compares data from channels A and B. The EEC uses the cross-talk logic to find which EEC channel is the best to control an output driver for a torque motor or solenoid bank. The primary channel controls all of the output drivers. If the cross-talk logic finds that the other channel is better for control of a specific bank, the EEC changes control of that one bank to the other channel.
The I/O section receives and transmits digital and analog data.
The EEC has both non-volatile and volatile memory to store performance and maintenance data.
Each channel has three pressure transducers. They supply signals that are in proportion to the pressure input. The transducers also send the signals to the other channel.
Output Driver Banks
The EEC has output driver banks that supply the control signals to engine components. Each channel of the EEC supplies the driver banks with control signals. There are three torque motor banks and seven solenoid banks.
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ENGINE FUEL CONTROL -EEC -FUNCTIONAL DESCRIPTION
Each torque motor bank has four, two-channel drivers. Both channels of the EEC connect to each driver.
Each solenoid bank has a different number of solenoid drivers.
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ENGINE FUEL CONTROL -EEC -FUNCTIONAL DESCRIPTION
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ENGINE FUEL CONTROL -EEC SENSOR INPUTS
Engine Pressures
Pamb is the ambient static pressure. A Pamb pressure sense line goes from the fan cowl to the EEC. The EEC uses the pressure signal to calculate altitude.
P2 is the fan inlet pressure. The P2/T2 probe supplies the pressure to the EEC. The EEC uses P2 and P4.95 to calculate EPR.
P2.5 is the LPC exit pressure. A line from the N1 speed probe supplies the pressure to the EEC. This pressure signal is only for engine condition monitoring.
Pb (PS3) is HPC exit pressure. A tap on the HPC case supplies the pressure to the EEC. The EEC uses Pb for fuel flow limiting and surge detection.
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