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lization and to the fuel quantity computer. If
AHRS #2 fails, heading information to the
RMU backup navigation displays will be lost.
If either AHRS has failed the autopilot is in-
operative.
If neither AHRS has completely failed, but
there is a disagreement between them on atti-
tude or heading, the comparator monitor sys-
t e m w i l l a n n u n c i a t e t h e m i s m a t c h b y
displaying an amber "ATT", “PIT” or “ROL”
in the upper left corner of the ADI and/or an
amber "HDG" above and to the right of the HSI
lubber line (Figure 16-32).
AHRU COOLING FAN
The AHRUs are equipped with cooling fans
which operate automatically to keep the
AHRUs within proper temperature limits. If
the fan should fail and the temperature ex-
ceeds predefined limits, an "AHRS 1 or 2
OVHT" message will appear on the CAS (Table
16-2). Equipment damage may result if the
AHRU is operated outside of normal temper-
ature limits.
ELECTRONIC DISPLAY
SYSTEM (EDS)
GENERAL
The Learjet 45 electronic display system (EDS)
provides the flightcrew with complete flight-
path, navigation, engine and systems infor-
mation (Figure 16-25). Aircraft attitude,
heading, course orientation, air data, and nav-
igation information are formatted together on
a single dedicated display unit for each pilot,
t h e p r i m a r y f l i g h t d i s p l a y s ( P F D s ) .
Annunciators signal selected flight modes,
AP and YD engagement, altitude alert, mini-
mum altitude (MIN), go-around mode en-
gagement, and a number of additional events
or modes. Pitch and roll steering commands,
from the flight director assist the pilot in reach-
ing and/or maintaining the required flight-
path or altitude.
Two additional display units provide annun-
ciated engine instruments and systems infor-
mation and navigational displays. The EICAS
display consists of engine indications, CAS
messages and airplane system status pages.
The multi-function display (MFD) is capable
of supporting heading data, navigation, plan
map, weather radar, TCAS information and
checklists (optional). In addition, backup dis-
plays are available on the radio management
units (RMUs) for navigation and critical en-
gine instruments and data.
EDS information is displayed on four display
units (DUs) (Figure 16-1). The DUs are driven
by symbol generators, housed within the IC-
600s, and controlled through display con-
t r o l l e r p a n e l s , l o c a t e d a b o v e t h e D U s .
Additional EDS components include rever-
sion control panels that provide control of the
backup display modes, and a comparison mon-
itor system that alerts the operator should in-
valid or erroneous data be processed by the
integrated computer system (dual IC-600s).
DISPLAY UNITS (DU
S
)
The four display units are large format 7 x 8
inch, 16 color high resolution, cathode ray
tubes (CRTs). The display units are identical
and interchangeable, except for the bezel con-
trollers attached to the front of the units (Figure
16-25). The bezel controllers for the outboard
DUs are the same and the bezel controllers for
the inboard DUs are the same.
The brightness of the display units is con-
trolled through dimming knobs located on
the display controllers. There are two con-
centric dim knobs on each display controller
(Figure 16-29). The smaller knob controls
the inboard DU and the larger knob controls
the outboard DU. The photo sensors, located
on the DUs, are designed to modulate the
brightness for changing ambient light condi-
tions, but they are disabled in the LR 45.
The display units require forced-air circula-
tion for cooling which is provided by two fans
mounted on the rear of each DU. If a DU fan
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
16-36
FOR TRAINING PURPOSES ONLY
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