system operates the same as the automatic
mode, however, a manual rate can be selected
on the ground and the CPCS will follow that
rate after becoming airborne. In flight, the
manual control selector knob becomes effec-
tive in selecting the rate of change in cabin al-
titude. It will be necessary for the crew to
manage the cabin vertical speed and level the
cabin at the desired altitude.
Prior to landing the crew should manually de-
scend the cabin until it reaches the landing field
elevation. Upon touchdown, the system auto-
matically enters the landing mode, just as in
the automatic mode, and rates to the actual
field pressure.
HIGH ALTITUDE AIRPORT
OPERATION
When discussing the pressurization system,
airports above 8,000 feet are considered high
altitude airports. There are several unique
high altitude flight profiles for controlling
cabin pressure:
• Takeoff and landing field elevations are
both > 8,000 feet.
• Takeoff elevation > 8,000 feet and land-
ing elevation
≤
8,000 feet.
• Takeoff elevation
≤
8,000 feet and the
landing elevation > 8,000 feet.
In the first case both the takeoff and landing
field elevations are greater than 8,000 feet.
Upon lift-off the cabin altitude initially de-
scends at a rate of 600 fpm until it reaches the
maximum cabin schedule of 8,000 feet (Figure
12-10).Once the airplane has descended 1,000
feet and the airplane altitude is below 24,500
feet, the cabin altitude begins to rise, main-
taining an ascent rate of approximately 600
fpm, until the landing field elevation has been
reached. Once the airplane has landed, the
squat switches signal the pressurization sys-
tem to enter the ground mode.
The second situation, that takes off from an el-
evation above 8,000 feet, but lands at an ele-
vation below 8,000 feet, is illustrated in Figure
12-11. After takeoff, as the airplane estab-
lishes a climb, the cabin altitude begins a de-
scent to the maximum cabin altitude of 8,000
feet. After the enroute or the cruise portion of
the flight has been accomplished, as the de-
scent for landing is initiated, the cabin altitude
then descends to the landing altitude that was
preset by the crew.
The third scenario is applicable when the take-
off elevation is less than 8,000 feet, but the
landing elevation is above 8,000 feet (Figure
12-12). In this case the climb schedule for the
cabin altitude is normal during the climb and
enroute portion of the flight. As the descent
is established for landing, the cabin altitude
rates upward, not to exceed 600 fpm, to a max-
imum of 8,000 feet. When the airplane altitude
is below 24,500 feet the cabin altitude rates up
to selected landing altitude.
12-18
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
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