AVIONICS COOLING
The instrument panel cooling fan is located for-
ward of the throttle quadrant and is provided
to draw air from the center pedestal area and
directs it to the area behind the instrument
panel to prevent overheating of the avionics
displays and instruments. The system con-
sists of an avionics cooling fan, an ON/OFF
thermostat switch and an overtemperature
thermostat circuit.
If the temperature sensing switch reaches 90°
F (32° C) the avionics cooling fan is activated.
The fan automatically turns off when the tem-
perature has been reduced below 70° F (21° C).
If the temperature reaches an extreme of 135°
F (57° C) the overtemperature circuit is ener-
gized and the white advisory CAS message,
“INSTR PNL TEMP” is annunciated on
EICAS (Table 16-2). The CAS message re-
mains illuminated until the temperature has
been reduced to 125° F (51.7° C) and below.
The cooling system was designed primarily for
ground use and operations in high outside air
temperatures. It is unlikely that the cooling sys-
tem would activate inflight.
The system is powered from the left main bus
and protected by the INSTR FAN circuit
breaker located on the pilot circuit breaker
panel in the ENVIRONMENTAL group. Since
the on/off switch is remotely located and ther-
mostat controlled, the only crew action avail-
able to either enable or disable the system is
through the circuit breaker.
The temperature in the nose avionics bay is
monitored by a thermal switch. If the tem-
perature reaches 158° +
5° F, a white “NOSE
BAY TEMP” CAS message will be displayed.
This message will remain on until the tem-
perature decreases to below 148° +
5° F.
The nose section avionics bay is cooled in
flight by the air outflow from the pressurized
section and is exhausted into the nose wheel-
well.
COCKPIT VOICE
RECORDER (CVR)
A Sundstrand solid state cockpit voice recorder
is installed in the Learjet 45. The three chan-
nel CVR provides 30 minutes of recording.
Two of the channels are used to record pilot
and copilot audio. The third channel is used
for the area mic. A 2 hour CVR is available as
an option.
Located in the tailcone, the CVR is painted in-
ternational orange with reflective tape added
to aid in recovery. It also has an underwater
locator beacon installed on one end of the
unit. The recording is converted to a digital for-
mat and stored in crash protected memory.
The area mic is located in the upper center area
of the instrument panel. An erase button and
headphone jack are located on the CVR panel
just beneath the copilot audio control panel.
The CVR performs a self-test at power-up and
has a continuous self monitor. If a fault is de-
tected at any time, a “CVR FAIL” message is
displayed on the CAS.
The erase function is initiated by pressing the
erase button on the CVR panel. An interlock-
ing device only allows this function to work
when the airplane is on the ground and the
parking brake is set. When the erase function
is complete, a 3 second tone is output to the
headphone jack.
LEARJET 45 PILOT TRAINING MANUAL
16-105
FOR TRAINING PURPOSES ONLY
FlightSafety
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