737 Flight Crew Operations Manual
Air Systems -
Pressurization System Description
Boeing Proprietary. Copyright © Boeing. May be subject to export restrictions under EAR. See title page for details.
2.40.6 D6-27370-866-EGP
Flight Path Events – Auto Mode
Manual Mode Operation
A green MANUAL Light illuminates with the pressurization mode selector in the
MAN position.
Manual control of the cabin altitude is used if both the AUTO and ALTN modes
are inoperative. In the MAN mode, the outflow valve position switch is used to
modulate the outflow valve by monitoring the cabin altitude panel and valve
position on the outflow valve position indicator. A separate DC motor, powered
by the DC standby system, drives the outflow valve at a slower rate than the
automatic modes. Outflow valve full range of motion takes up to 20 seconds.
.25 psid
TAXI
CLIMB HOLD CLIMB CRUISE DESCENT TAXI
LAND
OFF ALTITUDE
CONSTANT FLT ALT SETTING
CRUISE MODE
ACTIVATES
DESCENT MODE
ACTIVATES
NORMAL
28,000 ft. to 37,000 ft.)
( P = 7.45 psid at or
( P = 7.80 psid above
( P = 8.35 psid above 37,000 ft.)
CABIN ALT
below 28,000 ft.)
T/O
AIRPLANE ALT
.25 psid
*Note
*Note: Deviations from cruise alt
can cause P to vary.
CABIN ALTITUDE VS. AIRPLANE ALTITUDE
March 28, 2013
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