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conditions. When airborne with the flaps and
gear up, the reference will be set at the ap-
propriate value for the detent the thrust levers
are set at (i.e. APR, T/O, MCT, or MCR).
When the thrust levers are below MCR the
bug is removed from the N1 indicators. The
bug is also removed from view when the com-
puter is off. During the use of thrust reversers,
the bug will be set at maximum reverse thrust
for the airplane speed (Figure 7-29).
When engine synchronization is on, the N1 bug
will display N1 speed for the detent the power
lever is selected to, but in this case, the bug
will not be N1 compensated. The N1 gage nor-
mally displays physical (actual) N1 speed plus
or minus compensation, but during sync op-
eration, the compensation is identical on both
engines which is the average of the two engine
compensators.
Turbine Temperature (ITT)
Turbine temperature is sensed by ten parallel-
wired thermocouples located between the HP
and LP turbines. The averaged ITT provided
by the parallel circuits sends two output sig-
nals, one to the ITT indicator (Figure 7-6), and
the other to the DEEC.
Each ITT indicator on the EICAS 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 display is from 100
to approximately 1,000 degrees Celsius. The
precise limit of the scale varies depending on
operating conditions.
The ITT analog scale is normally white with
a red tick at the high end and has a white
pointer. If the pointer reaches the red tick, the
pointer and the digital display will turn red,
and a red exceedance arc will appear on the
scale from the tick up to 1,014 degrees C. An
amber caution band will appear prior to the red
tick under some conditions. See Table 7-2.
The engine has different maximum ITT lim-
its specified for different operating conditions
such as start, takeoff, computer off, etc. The
DEEC will automatically change the limit for
these conditions through an ITT limiter and ad-
just the markings on the ITT indicator to cor-
respond to the current limits.
There are four sets of conditions that will
determine the value the red tick represents on
the ITT scale. Condition #3 will also cause
an amber arc to appear on the ITT scale prior
to the red tick (Figure 7-7). The scale logic
is summarized as follows for conditions 1
thru 4:
1. With the DEEC on, after engine start,
during ground operations, prior to set-
ting T/O power and anytime after take-
off once the thrust levers have been
retarded from the T/O detent, the APR
is not on, and anti-ice is not on.
2. With the DEEC on during engine start,
when thrust levers are in T/O detent for
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
7-9
FOR TRAINING PURPOSES ONLY
FlightSafety
international
Color
Lower Limit
(% RPM)
Upper Limit
(% RPM)
White
Red
0
100.1
100.0
110.0
NOTE:
N1 limits the red tick at 100% N1.
When the analog pointer enters the red range,
the red arc distance doubles and the normally
white pointer and digital fan readout turn red.
Color
Lower Limit
(% RPM)
Upper Limit
(% RPM)
White
Amber
Red
0
100.1
100.0
102.5
102.6
115.0
NOTE:
If APR is activated, the N2 display does not
turn amber unless 101.1 is exceeded.
FAN (N1) SPEED DISPLAY
TURBINE (N2) SPEED DISPLAY
Table 7-1. ENGINE SPEED