ters the pre-cooler, where it is initially cooled
by ram/fan air.
The bleed-air then enters the primary heat ex-
changer where it is cooled by ram air. The air
then travels to the compressor section of the
ACM before passing into the secondary heat
exchanger, where it is cooled by ram air as-
pirated with water drawn from the water sep-
arator. The air then flows into the turbine
section of the ACM.
AIR CYCLE MACHINE (ACM)
The air cycle machine (ACM) consists of a tur-
bine, a compressor and a fan. All three wheeled
components are mounted to a common drive
shaft.
Bleed-air from the primary heat exchanger
first passes through the ACM compressor
stage where the air is compressed and ducted
to the secondary heat exchanger for addi-
tional cooling. The air exits the secondary
heat exchanger outlet and is ducted into the
ACM turbine for expansion.
Bleed-air exiting the secondary heat exchanger
is ducted to the ACM turbine and the bypass
shutoff valve (Item 2 in Figure 11-5). ACM tur-
bine airflow is cooled to near freezing tem-
peratures through rapid expansion. At 40,000
feet the CPCS delivers a signal to open the by-
pass shutoff valve and allows some of the
bleed-air to bypass the turbine.
11-3
FOR TRAINING PURPOSES ONLY
LEARJET 45 PILOT TRAINING MANUAL
FlightSafety
international
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