ATA 21 AIR CONDITIONING SYSTEM

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ATA 21 - AIR CONDITIONING SYSTEM 1. General The
air conditioning system keeps the air in the
pressurized fuselage compartments at the correct
pressure, temperature and freshness. In normal
conditions, the pneumatic system supplies air to
the air conditioning system from - the main
engine compressors, - the APU compressor, - a
high-pressure ground-air supply-unit. The hot
compressed air is cooled, conditioned and
supplied to the fuselage compartments and then
discharged overboard through the outflow
valves. You can also supply conditioned air to
the distribution system through a low pressure
ground-connection.
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ATA 21 - AIR CONDITIONING SYSTEM 2. System
Description The air conditioning system gives
satisfactory values of pressure, temperature and
freshness of the air in the pressurized fuselage.
It has the subsequent subsystems -
distribution, (21-20) - pressurization control,
(21-30) - heating, (21-40) - air cooling,
(21-50) - temperature control. (21-60)
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ATA 21 - AIR CONDITIONING SYSTEM 21-20.
Distribution System The distribution system
permits temperature controlled and conditioned
air from the air conditioning packs to flow
through the pressurized fuselage. 21-30.
Pressurization Control System The pressurization
control system controls the pressure in the
fuselage. It operates fully automatically and has
a manual backup. The pressure change rate is
controlled to give satisfactory pressure values
of safety and comfort for the passengers and
crew. 21-40. Heating System The heating system
increases the temperature of the air in the lower
fuselage.
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ATA 21 - AIR CONDITIONING SYSTEM 21-50. Air
Cooling System The air cooling system decreases
the temperature of the hot bleed air from the
pneumatic system. It also reduces the quantity of
water in the hot bleed air. Emergency air is
supplied if there is a failure in the two air
conditioning packs. 21-60. Temperature Control
System The temperature control system controls
the temperature of the air supplied to the
cockpit and cabin. You can adjust the temperature
in the cockpit and the cabin.
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Air Conditioning Packs
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Air Cycle Machine
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Water Extractor
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ATA 36 - Pneumatic system 1. General The
pneumatic system gets compressed air from the
pneumatic air sources and supplies the compressed
air through ducts to the user systems. The ducts
are installed in the fuselage, the belly fairing
and the wings. The control of the pneumatic
system is usually automatic. You can also control
the system manually. The pushbutton and selector
switches on the overhead panel in the cockpit,
control the manual function. You can monitor the
operation of the pneumatic system on the System
Display. The switches on the overhead panel have
no indication when the system operates correctly.
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ATA 36 - Pneumatic system A. Pneumatic Air
Sources The aircraft engines, the APU or a ground
air source can supply compressed air to the
pneumatic system. The distribution system
supplies the compressed air from the different
sources to the user systems. (1) The aircraft
engines are the primary source of compressed air
in flight. The air is bled from the 5th or 9th
stage of the engine High Pressure (HP)
compressor. The engine bleed air is temperature
and pressure controlled. (2) The Auxiliary Power
Unit (APU) is the primary source of compressed
air on the ground. The air is bled from the APU
load-compressor module. You can also use the APU
to supply bleed air to the user systems during
flight. The APU can supply bleed air - during
the climb, from the ground until the aircraft
reaches 23000 ft. (7010 m), - during the descent,
from 21000 ft. (6400 m). (3) A ground air source
is an alternative to the APU for the supply of
compressed air on the ground. There are two High
Pressure (HP) ground connectors installed on the
aircraft. You can use them to let the ground air
source supply compressed air to the pneumatic
system.
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ATA 36 - Pneumatic system B. User Systems The
pneumatic system supplies the subsequent aircraft
systems - the air conditioning system, - the ice
and rain protection system, - the engine starting
system, - the water/waste system, - the
hydraulic-reservoir pressurizing system (high
pressure from engine 2, regulated from the
crossfeed duct), - the trim air valve, - the
air-conditioning compartment ventilation-system, -
the nacelle anti-ice system , - rain repellent
pressurization through the air conditioning
system.