737 MAX Flight Crew Operations Manual
Air Systems -
Pressurization System Description
MN-FLT-OH-201
2.40.3
Outflow Valve
The outflow valve is the overboard exhaust exit for the majority of the air
circulated through the passenger cabin. Passenger cabin air is drawn through foot
level grills, down around the aft cargo compartment, where it provides heating,
and is discharged overboard through the outflow valve.
Overboard Exhaust Valve
On the ground and in flight with low differential pressure, the overboard exhaust
valve is open and warm air from the E & E bay is discharged overboard. In flight,
at higher cabin differential pressures, the overboard exhaust valve is normally
closed and exhaust air is diffused to the lining of the forward cargo compartment.
However, the overboard exhaust valve is driven open if either pack switch is in
high and the right recirculation fan is off. This allows for increased ventilation in
the smoke removal configuration.
Note:
During pressurized flight, the overboard exhaust valve will be commanded
to a smoke mode upon a Forward Cargo Fire Alarm.
Pressurization Outflow Schematic
AFT LOOKING FORWARD
OUTFLOW VALVE
MANUAL
AUTO
FLT ALT
LAND ALT
MAN
AUTO
ALTN
E
S
O
L
C
N
E
P
O
E
V
L
A
V
DIFFUSER, OVERHEAD
AIRFLOW
CARGO
LINING
DIFFUSER
OUTLET
pressurization system.
FWD CARGO
COMPARTMENT
AFT CARGO
COMPARTMENT
- Exhausts E & E cooling air while
on ground, and in flight at low
- Controlled by the
OUTLETS AND CARGO
COMPARTMENT
EXHAUST PORT FOR
EXHAUST PORT FOR
OVERBOARD EXHAUST VALVE
OVERBOARD EXHAUST VALVE
OUTFLOW
VALVE
differential pressure.
COMPARTMENT
March 1, 2021
