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Fan Speed (N1)
The low-pressure rotor (fan) N1 indicators
are the primary thrust indicating instruments.
Fan speed is measured by the dual element
N1 monopole which is located just below the
end of the low-pressure rotor. The monopole
senses the gear teeth on the low pressure rotor
cutting through a magnetic field around the
monopole tip. One element in the monopole
provides a speed signal to the DEEC (digital
electronic engine control) and the other pro-
vides a speed signal to the EICAS display.
Since no two engines are identical, the N1
signal is biased by an N1 compensator so that
the indicator shows rated rpm when rated
power is achieved. The bias required varies
from one engine to another and is set during
calibration of the engine.
Each N1 indicator on the EICAS display has
both an analog scale (arc) and pointer together
with a four digit readout within a cyan box
(Figure 7-6). The range of the arc is 0 - 110%
and the range of the digital display is far in ex-
cess of the engine capability. The digital dis-
play values will change in 0.1% increments.
The N1 analog scale (arc) is white with a white
pointer. The white scale has a horizontal red
tick that begins at 100.1%. The color of the
L E A R J E T 4 5
P I L O T T R A I N I N G M A N U A L
7-7
FOR TRAINING PURPOSES ONLY
FlightSafety
international
EICAS
(DU 2)
Normal circuit
for engine
indications to
EICAS on DU 2
MFD
(DU 3)
SG 1
L ESS
BUS
SG 2
RMU 2
RMU 1
EMER
BATT BUS
DAU 1
CH A
DAU 1
A
B
DAU 2
A
B
FUEL FLOW
CONVERTER
L ENG
R ENG
FMS
IC-600 #2
IC/SG
IC-600 #1
IC/SG
EMER
BATT BUS
DAU 2
CH A
DAU 1
CH B
R ESS
BUS
DAU 2
CH B
DISCRETES
AND ANALOG
INPUTS
AIRCRAFT SYSTEMS
Figure 7-5. EICAS Block Diagram