C.
Control
_______
(1)
Cabin Pressurization System - Automode (Fig. 6, 7)
(a)
115 Vac powers both controllers, through the mode selector switch. Each controller is powered from independent sources.
(b)
Each controller contains a central processing unit (CPU). The CPU provides two major functions. It receives signals from the ADC and selector panel, and constantly samples cabin pressure. The CPU also tests the entire controller system operation.
(c)
An analog to digital converter (A/D) changes analog input signals to digital signals for CPU use. Analog inputs to the CPU through the A/D include selected autorate, selected landing field altitude, and cabin pressure signals. The ADC, air/ground relay and door status signals provide direct digital inputs to the CPU. The ADC provides ambient pressure and barometric correction signals. The air/ground signal determines the controller's mode of operation (ground mode, flight mode, etc.). Takeoff mode is initiated when the throttles are advanced.
(d)
The CPU collects the above signals and determines cabin pressure. Maximum cabin-to-ambient differential pressure, selected landing (field) altitude pressure and the autoschedule, limit the cabin pressure.
(e)
After determining existing cabin pressure, the CPU determines a cabin pressurization rate command. The cabin pressurization rate command depends on: 1) The error between the cabin pressure and the selected
autorate command (P = Pc Actual - Pc command). 2) The selected autorate limit. 3) The maximum cabin-to-ambient differential pressure.
(f)
The CPU compares the cabin pressurization rate command with the cabin pressure. The difference produces a digital error signal. A digital to analog (D/A) converter changes the digital signal to an analog signal. The signal goes through the controller's motor drive logic and solid state relays. The relays energize the outflow valve actuator. The actuator controls the outflow valve. A tachometer monitors the actuator speed, and sends a feedback signal to the controller motor drive logic, to improve the speed response of the actuator.
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MAINTENANCE MANUAL
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MAINTENANCE MANUAL
PRESS TEST
A
LDG GEARLIGHT ALL LAMPSSW FAULT
GROUND OPERATION A/P ALT >15000 FT FAULT
WOW=ON=1 CONTROLLERLDG GEAR SW
FLT/GND
POWER UP: GROUND MODE LANDED:
STORAGE
THROTTLE
DRIVE VALVE FULL OPEN
AND
DRIVE VALVESWITCH TO STANDBY CONT.
LOW INFLOWCONTROLLER
PROCESSOR
ADVANCED
FULL OPENCONDUCT SELF TEST (30KEEP PC CONSTANT
SEC.) AUTO SWITCH OVER
TILL TAKE OFF
VALVE POSITION
TO RETURN TO PRIMARY
SELECTOR
LOW INFLOWRATE OF
COMPARE CHANGE CMD AC POWER OFFSELECTORAUTO-HI
~(A/P ALT) >1000 FT
D SCHEDULE
CABIN ACTUAL ALT
WINSAC MOTOR
AC POWERALT
T/O ALT
WOW=OFF=1LDG ALT
OFF PA
~P ERROR
D/A
AC MOTORLEVEL FLIGHT
BITDISPLAYVERIFY
Pc A/D
MODERESET
~P STORED FAULTSAUTO SCHEDULE
~P í8.75 PSI
ERASE STOREDNO FAULT
PC RATE OF CHANGE >
CONTROLLER
RATE SELECT LIMIT
FAULTSSOFTWARE
FAULT
VERIFY VERIFYDISPLAY~(CABIN ALT) >100 FT
MODEROUTINE
FAULTS DETECTED BY VERIFYOUTFLOW VALVE CLOSED
RATE OF CHANGE (ACTUAL)
CABIN CABIN ALT >AUTOSCHEDULE
D PRESSURE Pc LOW FLOWSENSOR
A/D HARDWARECABIN ALT >8400 FT
AC MOTOR
FAULTCABINPRESSRATE
OFLDG ALT <8400 FT
LEVEL
CHANGE
ERROR
AUTO ENABLE
SELECTOR
DETECTOR (+)DRIVER/ENABLE
MOTOR/VALVE DRIVE OPEN
AUTO 2
X CHANNEL IN
SELECTOR
=1 IF VW 1, 2í 9.85V
OR VW 1, 2. 0.15V
