(4)
The MANUAL light indicates that the pressurization control system is operating in the manual AC or DC mode.
C. The outflow valve position indicator is installed on the forward overhead panel and is powered from the precision 20-volt supply in the pressure controller.
D. The cabin altimeter and differential pressure indicator are combined in one instrument on the forward overhead panel, and powered directly by sensed pressure changes. The altimeter and differential pressure indicator registers cabin altitude and pressure difference between cabin and ambient.
E. The cabin rate of climb indicator is installed on the forward overhead panel and registers rate of pressure change in the airplane.
F. The cabin altitude warning system is activated by a pressure switch which is connected to the aural warning devices box (Ref 31-26-00). The system provides an intermittent sound signal when cabin altitude exceeds approximately 10,000 feet.
2. Operation_________
A. The pressurization control system is normally operated in the automatic mode. Any change in the operating mode causes illumination of one or more lights on the forward overhead panel. The operating mode may be selected by positioning the selector switch. The STANDBY or MANUAL lights will illuminate as applicable. A loss of power during operation in the AUTO mode will cause illumination of the AUTO FAIL light. An automatic transfer from automatic to standby mode causes illumination of the AUTO FAIL and STANDBY lights. The AUTO FAIL light will go out if the mode selector is switched to STBY.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 737-300/400/500MAINTENANCE MANUAL
B. The OFF SCHED DESCENT light illuminates if the airplane descends prior to reaching within 0.25 psi of FLT ALT selected with the pressurization mode selector in AUTO. The controller programs the cabin to land at the takeoff field elevation without further pilot inputs. If the FLT ALT is reselected or the FLT ALT reset is depressed during climb, the automatic cabin abort capability to the original takeoff field elevation will be lost. Selecting the present airplane altitude with the FLT ALT selector will extinguish the light.
C. There is an outflow VALVE position indicator below the MANUAL light on the pressurization control panel. During manual mode operation the outflow valve is positioned manually with the toggle switch.
D. The cabin altimeter and differential pressure indicator are combined in one instrument on the pressurization control panel. The cabin altimeter senses cabin pressure and displays equivalent altitude in FEET. The other scale indicates pressure differential from cabin to ambient in PSI.
E. The rate of cabin altitude change is sensed and indicated by the CLIMB indicator.
F. The aural warning system provides an intermittent horn signal if cabin altitude exceeds approximately 10,000 feet during flight (Ref 31-26-00). The ALTITUDE HORN CUTOUT switch may be used to stop the sound signal.
AUTO OFF SCHED STANDBY MANUALFAIL DESCENT
A A G G
0
ALT
110
HORN AUTO
MANUALSTANDBY
0
50
CUTOUT
V
9 2
CABIN40 ALT 5
A
35
00000 L
30
DECR INCRFLT ALT
8 3
V
X 1000 FEET 10
CABIN RATE
25
E 20
15
74
65
00 000
00 000
PRESS DIFF LIMIT:TAKE-
2
1
OFF & LDG .125 PSI 3 UP 0
4 DN 3 1
2
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Pressurization Panel
Figure 1
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
1.
2.
3.
A
737-300/400/500MAINTENANCE MANUAL
CABIN RATE OF CLIMB INDICATOR - REMOVAL/INSTALLATION
____________________________________________________General
_______
A. The cabin rate of climb indicator is located in the P5-16 module on the lower right part of the forward overhead panel.
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