interconnects the control chambers of the out-
flow valves (Figure 12-3).
When power is applied to the airplane elec-
trical system, the CPC performs a functional
check. Once the functional check is success-
fully completed, the system is in the auto-
matic mode. The left channel will normally
control the pressurization in the automatic
mode but will relinquish command to the right
channel if a fault is detected in the left chan-
nel. Selection of the channel to be active is not
a crew option; however, manual can be se-
lected on the currently active channel.
The CPC utilizes crew input from the control
panel along with airplane altitude and baro-
metric correction and true airspeed from the
air data computers, cabin pressure, left thrust
lever position (MCR), landing gear switch po-
sition and squat switches along with internal
program logic to perform its functions.
In the automatic mode, the controller uses ei-
ther the climb or descent schedule to maintain
the appropriate cabin altitude inflight. When
the airplane is level, the CPC holds the cabin
altitude at the climb schedule value. The air-
plane has to deviate by + 200 feet from the es-
tablished altitude before the system allows
changes in cabin pressure. When the airplane
descends 1,000 feet, the CPC initiates the de-
scent schedule.
The rate-of-climb and descent is non-se-
lectable in the automatic mode. The controller
12-5
FOR TRAINING PURPOSES ONLY
L E A R J E T 4 5
P I L O T T R A I N I N G M A N U A L
FlightSafety
international
EMER PRESSURE
9,500 FT.
OR
14,500 FT.
CABIN ALTITUDE
VOICE MESSAGE
10,000 FT
OR
14,500 FT
CABIN
OXYGEN ON
14,500 FT.
EICAS
PRIMARY
(LEFT)
CHANNEL
SECONDARY
(RIGHT)
CHANNEL
CABIN PRESSURE
ADC1/ADC2
LDG GEAR SW
THROTTLE SW (MCR)
EMER BATT BUS
R PRESS
CABIN PRESSURE
ADC1/ADC2
LDG GEAR SW
THROTTLE SW (MCR)
L MAIN BUS
L PRESS
ACM BYPASS
RELAY (40,000 FT.)
CABIN
AIR
DISCHARGE
JET PUMP
ENGINE SERVO
BLEED-AIR
FORWARD PRESSURE BULKHEAD
SEC
OUTFLOW
VALVE
PRI
OUTFLOW
VALVE
DELTA P
LIMITERS
(9.7 PSID)
CABIN ALT
LIMITER
(13,700 FT.)
CABIN ALT
LIMITER
(13,700 FT.)
TORQUE
MOTOR
TORQUE
MOTOR
ON
DEPLOY
OFF
PAX
OXY/AUTO
PAX OXYGEN
ON
MANUAL
PRESS
ON
EMER
DEPRESS
OFF
L BLEED
ON
EMER PRESS
OFF
R BLEED
ON
HI FLOW
OFF
PACK
ON
APU BLEED
3 5 0
I . 2
I 3 0 0
CABIN PRESSURE CONTROL
CAB RATE
DELTA P
CAB ALT
FPM
PSID
FT
LDG ALT
DN
UP
MANUAL
DN
UP
PRESSURIZATION
CABIN PRESSURE CONTROLLER
Figure 12-3. Cabin Pressure Control Diagram