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N1 (LPC rotor speed)
*
N2 (HPC rotor speed)
*
EGT (T4.95)
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Engine vibration
*
P2.5 (LPC exit pressure)
*
T2.5 (LPC exit temperature).
Engine Pressure Ratio (EPR)
EPR is the main indication for engine thrust. EPR is the ratio of LPT exhaust pressure (P4.95) to fan inlet pressure (P2). The EEC calculates EPR and sends it to the AIMS for display.
Engine Tachometer
The shaft speed indicating system monitors N1 and N2. The N1 signal comes from the N1 speed (P2.5/T2.5) probe. The N2 signal comes from the permanent magnet alternator (PMA).
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The EEC sends digital N1 and N2 signals to the AIMS. The EEC sends an analog N1 signal to the EDIU and the AVM signal conditioner unit. The EEC sends an analog N2 signal to the AIMS and AVM signal conditioner unit.
Exhaust Gas Temperature (EGT) Indicating
The EEC uses four EGT T4.95 thermocouple probes to measure the temperature at the LPT exit.
Airborne Vibration Monitoring (AVM)
The AVM system measures engine vibration. The three engine accelerometers send electrical charges to the remote charge converter (RCC). The RCC changes the accelerometer electrical charges to voltage signals and sends them to the AVM signal conditioner unit. The signal conditioner unit uses the voltage signals and engine speed signals to calculate engine vibration.
The AVM signal conditioner unit also contains engine balancing system (EBS) functions. It uses speed and vibration signals to calculate a balance solution. You use the EBS to correct high engine vibration caused by the fan or the LPT. The signal conditioner sends the EBS data to the AIMS.
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ENGINE INDICATING -SUMMARY
Airplane Condition Monitoring System (ACMS)
The N1 speed (T2.5/P2.5) probe also sends the temperature (T2.5) and pressure (P2.5) at the LPC exit to the EEC. This data goes to the ACMS function in the AIMS. You can get reports from the ACMS for engine condition monitoring.
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PW4000 SERIES ENGINES
777 AIRCRAFT MAINTENANCE MANUAL
ENGINE INDICATING -SUMMARY
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PW4000 SERIES ENGINES
777 AIRCRAFT MAINTENANCE MANUAL
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BOEING PROPRIETARY -Copyright # -Unpublished Work -See title page for details.
ENGINE INDICATING -EPR -GENERAL DESCRIPTION
Purpose
The EPR indicating system supplies the main indication for engine thrust. EPR is the ratio of turbine exhaust pressure to fan inlet pressure.
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