Learjet 60 - Auxiliary Heating System; Cabin Auxiliary Heat; Cockpit Floorboard Heaters

Pilot's Manual
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Lewdet60
AUXILIARY
HEATING
SYSTEM
An auxiliary heating system is installed to provide additional cabin and
cockpit heating when desired . The COOL-OFF switch mustbe set to the
OFF position in order to operate the cabin auxiliary heater . Power must
be supplied by an
engine
generator, APU, or ground power unit . The
AUX HT switch, on the copilot's switch panel, is used to
control the
system . The auxiliary heater control circuit is wired through the start
cutout relay ; therefore, the system is inoperable during engine start .
CABIN AUXILIARY HEAT
The cabin auxiliary heat is provided by two heater assemblies located
in the cabin left and right overhead diffusers . The system utilizes the
cabin blower to provide air circulation .
The heater assemblies incorpo-
rate-several thermostatic controls to cycle the heaters at
approximately
170' F . The thermostatic controls of each heater are connected in series
to each other ; therefore, cycling of each heater occurs simultaneously .
The cabin blower will start when either heater warms to approximately
75' R An overheat monitor is installed to monitor the temperature of
both heaters . If either heater exceeds approximately 300' F or a switch-
ing failure occurs, both
heaters will be disabled . Maintenance action is
required when the overheat monitor disables the system . Each heater
incorporates a thermofuse which will melt and disconnect electrical
power to that heater should an overheat condition occur . The system
control circuit operates on 28 VDC supplied through the 75-amp AUX
CABIN-CREW HEAT circuit breaker on the copilot's circuit breaker
panel . The heater assemblies are supplied 28 VDC through two 50-amp
current limners . Operation of the cabin heaters is only available if the
CAB AIR switch is OFF . During pressurized flight (CAB AIR switch
ON), cabin heating is accomplished by pressurization airflow .
COCKPIT FLOORBOARD HEATERS
(Aircraft 60-067 &
Subsequent
and Prior Aircraft Modified by SB 60-21-5)
The cockpit floorboard heater system provides direct contact heat for
crew foot warming
. There are
four
heaters, one
located beneath each
rudder pedal . Each beater contains two heater blankets and a tempera-
ture limiting circuit which controls temperature between 100'F and
130'F independently of the other three heaters . When the temperature
of a heater reaches
103'F,
a relay will
remove power to the two heater
blankets causing them to cool . The cockpit floorboard heater is con-
trolled through the use of the AUX HT switch . The system control cir-
cuit operates on 28 VDC supplied through the 7 .5 amp AUX CABIN-
CREW HEAT circuit breaker on the copilot's
circuit breaker panel .
640
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PM-123
Change 4