INTRODUCTION
The Learjet 45 air-conditioning system consists of a bleed-air temperature control sys-
tem and independent distribution systems to the cockpit and cabin for pressurization and
ventilation. Prior to engine start, the system can also be operated during ground opera-
tions using the auxiliary power unit (APU), if installed.
Primary heating and cooling is accomplished
by controlling the temperature of the bleed-
air entering the cockpit and cabin distribu-
t i o n s y s t e m s . Te m p e r a t u r e c o n t r o l i s
accomplished by mixing pressurized hot com-
pressed air and cooled compressed air as pro-
vided through the onboard environmental
control unit (ECU). Cooling is accomplished
by two methods; heat transfer within the pre-
cooler and primary/secondary heat exchanger
and compression with rapid expansion through
the air cycle machine (ACM).
The pressurization and air conditioning sys-
tem distributes conditioned bleed-air through-
out the cabin and cockpit. A portion of the
CHAPTER 11
AIR CONDITIONING
11-1
FOR TRAINING PURPOSES ONLY
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
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