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This regulates cabin pressure outflow (see
Figure 12-1). The regulating valves include:
• Dive solenoid valve (with dive pump)
• Climb solenoid valve (with climb pump)
• Maximum differential pressure limiter
(maximum Delta-P) valve on each outflow
valve
• Maximum cabin altitude safety limiter
valve on each outflow valve
Climb and Dive Solenoid Valves
The two solenoid valves (dive solenoid valve
and climb solenoid valve) open or close on
command of the pressurization controller. This
regulates the control-chamber pressure and
diaphragm position on the outflow valves,
which control cabin air outflow.
Dive Solenoid Valve
When the pressurization controller energizes
the dive solenoid valve open, it allows cabin
air to enter the outflow valve control chamber,
inflating the chamber and causing the diaphragm
to expand, which restricts the cabin
opening (see Figure 12-2). If bleed air entering
the cabin cannot escape as fast as it enters,
then the cabin pressurizes (dives).
Climb Solenoid Valve
When the pressurization controller opens the
climb solenoid, air escapes from the outflow
valve control chamber to an ambient static
pressure line. As air is drawn out of the control
chamber, the outflow valve diaphragm
contracts. This exposes the cabin opening, allowing
increased airflow between the cabin and
the outside, which reduces cabin pressure
(cabin altitude climbs).
CITATION MUSTANG OPERATING MANUAL
12-4 510OM-00
CITATION MUSTANG OPERATING MANUAL
510OM-00 12-5
Electrical Failure Mode
If all DC power is lost, the dive and climb solenoid
valves fail in a closed position.
Pressurization is then limited automatically
by the maximum Delta-P valve and maximum
cabin altitude limit valve (which are
not affected by electrical power). Under these
conditions, if the aircraft descends to an actual
altitude equal to cabin pressure altitude,
the outflow valves are forced open by outside
air, which enters the cabin, equalizing the
pressure and maintaining the cabin at actual
aircraft altitude.
If normal DC power is lost and emergency
power is available, both solenoids fail closed;
however, the climb solenoid can still be operated
manually with the CABIN DUMP switch.
Maximum Cabin Altitude Limit
Valves
The maximum cabin altitude limit valves (one
in each outflow valve) automatically prevent
cabin pressure altitude from exceeding 14,300
± 300 feet.
Inside the valve, a sealed bellows, similar to
the aneroid chamber in an altimeter, maintains
a constant reference pressure, related to
the cabin altitude ceiling of approximately
14,300 feet. The bellows puts pressure on the
valve to open it. A spring pushes in the opposite
direction to hold the valve shut with help
from cabin air pressure.
However, if cabin altitude rises above 14,300
feet, cabin pressure drops, and is not enough to
hold the valve closed. The sealed bellows expands
and pushes the maximum cabin limit
valve open. This allows cabin pressure into the
outflow valve control chamber, increasing pressure
in the control chamber, which causes its diaphragm
to expand and restrict the outflow
valve cabin opening. Restricting the cabin opening
limits outflow. If adequate pressurization
source air is still available (as selected by AIR
SOURCE SELECT knob set to BOTH, L or R),
cabin inflow is greater than cabin outflow, and
cabin pressure altitude drops to 14,300 ± 300
feet or lower, and stays below that limit.
This valve is not dependent upon electrical
power, and overrides all other pressurization
system controls.
Maximum Differential Pressure
(Maximum Delta-P) Limiter Valves
If cabin pressure exceeds 8.6 psid, the maximum
differential pressure valves (one on each
outflow valve) open automatically, which releases
pressure from each outflow valve control
chamber. The diaphragm contracts, which
releases pressure from the cabin. As a result,
cabin altitude climbs, reducing cabin pressure
differential until reaching a differential
pressure of 8.6 psid.
The maximum differential pressure limiter
valves override all other pressurization system
Figure 12-2. Outflow Valve Positions
CABIN AIR FREELY
FLOWS TO TAIL CONE
DIAPHRAGM
RELAXED OPEN;
NO PRESSURIZATION
CABIN AIRFLOW TO
TAIL CONE RESTRICTED
DIAPHRAGM INFLATED;
SOME DIFFERENTIAL
PRESSURE DEVELOPING
DIAPHRAGM
VACUUMED OPEN;
NO PRESSURIZATION
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Cessna塞斯纳公务机飞行手册(66)
