737 MAX Flight Crew Operations Manual
Air Systems
Chapter 2
Air Conditioning System Description
Section 30
MN-FLT-OH-201
2.30.1
30 Air Conditioning System Description
Air Conditioning System Description
File Highlight
Introduction
The air conditioning system provides temperature controlled air by processing
bleed air from the engines, APU, or a ground air source in air conditioning packs.
Conditioned air from the left pack, upstream of the mix manifold, flows directly
to the flight deck. Excess air from the left pack, air from the right pack, and air
from the recirculation system is combined in the mix manifold. The mixed air is
then distributed through the left and right sidewall risers to the passenger cabin.
Conditioned air for the cabin comes from either the airplane air conditioning
system or a preconditioned ground source. Air from the preconditioned ground
source enters the air conditioning system through the mix manifold.
Air Conditioning Pack
The flow of bleed air from the main bleed air duct through each air conditioning
pack is controlled by the respective pack valve. It is pneumatically actuated and
electrically controlled by the Integrated Air Systems Controller (IASC).
Normally, the left pack uses bleed air from engine No. 1, and the right pack uses
bleed air from engine No. 2. A single pack in high flow is capable of maintaining
pressurization and acceptable temperatures throughout the airplane up to the
maximum certified ceiling.
The APU is capable of supplying bleed air for two packs on the ground, or one
pack in flight. Most external air carts are capable of supplying adequate bleed air
for two pack operation. In flight one engine bleed is capable of supplying bleed
air for two packs. On the ground do not operate more than one pack from one
engine.
Airflow Control
During normal flight, with both air conditioning pack switches set to AUTO, both
engines operating and both engine bleed switches set to ON, the packs provide
normal air flow to maintain necessary ventilation. If the air conditioning pack
switches are set to HIGH, the packs provide high air flow to increase ventilation.
When the aircraft is not on the ground and the flaps are up, and both air
conditioning pack switches are set to AUTO, and the engine bleed switches are
both set to ON, if one pack fails or one engine fails or a pack switch is selected to
OFF, the remaining pack automatically transfers to high air flow to increase
ventilation.
March 1, 2021
