Pressurization; Auto Schedule; Isobaric Mode - Citation Encore 560 Operating Manual

MODEL 560
ENVIRONMENTAL
The pressurization and air conditioning systems utilize engine bleed air to pressurize and air condition
the cabin and defog the cabin and cockpit windows.
automatic. The only manual adjustments required are for individual comfort, such as cabin rate-of-climb
and temperature. Ram air for cabin ventilation is available when the pressurization system is not in use.

PRESSURIZATION

The cabin is pressurized by engine bleed air which has been conditioned (cooled) by the
environmental control system. This inflow of conditioned air remains constant through a wide range of
engine power settings.
controlled by the Cabin Pressure Control System, a microprocessor-controlled pneumatic/electrical system
linked to outflow valves.
feet/minute rate and decrease cabin altitude at a 500 feet/minute rate. When in the high altitude mode,
these rates may increase to a climb rate of 2,500 feet/minute and a dive rate of 1,500 feet/minute.
Ultimately, cabin pressurization is also controlled by limiters installed on the outflow valves. These limiters
prevent the cabin altitude from exceeding 8.9 PSI, ±0.1 PSI, higher than ambient (Max Delta-P Limiters)
and prevent cabin altitude from exceeding 14,500 feet (Max Altitude Limiters). Primary components of the
system include the digital cabin pressure controller, the primary and secondary outflow valves, a MANUAL
TOGGLE VALVE, an AUTO/MANUAL switch and an EMER DUMP switch.
AUTOMATIC OPERATION
The system has two methods of automatic operation. The primary (and default) method is the Auto
Schedule Control Mode, which is used during all normal flight operations.
schedules the cabin altitude as a function of airplane altitude, cabin altitude, throttle position and whether
the airplane is on the ground or in flight. In the auto schedule mode, the cabin will be depressurized by an
altitude of 1500 feet above the set destination field elevation before landing.
A secondary method of automatic operation is called the Isobaric mode. This is a reversionary mode
which can be used only if the Air Data Computer (ADC) altitude signal becomes invalid.
Neither Auto Schedule nor Isobaric modes are available in case of DC electrical power
failure, since the controller does not receive power from the emergency bus. The
manual control system functions without electrical power and is used to directly control
the outflow valves in case of electrical failure or failure of the automatic controller.

AUTO SCHEDULE

In Auto Schedule, the controller maintains the lowest practical cabin altitude for the airplane throughout
its flight envelope. This is done by electrical signals sent from the microprocessor to solenoids located on
the primary outflow valve. These solenoid valves add or remove air in the outflow valve chambers, thus
affecting the rate at which conditioned air is allowed to exit the pressure vessel. The controller has five
sub-level modes of operation when in auto schedule: Ground Mode, Take-off (pre-pressurization) Mode,
Flight Mode, Descent Mode and High Altitude Mode. When in auto schedule, the only crew action is to
program in the Set Landing Altitude (SLA) prior to landing.

ISOBARIC MODE

The isobaric mode is a standby mode that can not be entered directly while in flight. The controller
will switch from auto schedule to isobaric mode anytime the altitude signal (generated through the ADC)
becomes disabled. Isobaric mode is indicated by a yellow warning indicator on the pressurization controller
display face. If the air data sensor information resumes, the controller will automatically switch back to the
auto schedule mode and the yellow warning indicator will extinguish.
If the controller switches to isobaric mode, the SLA on the controller display is replaced with the
selected Flight Level, allowing the pilot to set the desired airplane cruising altitude. This altitude is selected
by rotating the SET ALT knob to the desired flight level. The controller then uses the selected flight level to
control the cabin pressure rate of change and the cabin pressure altitude to maintain near-maximum
differential pressure.
I
56OMB-01
The level of pressurization (cabin altitude) and rate of cabin change is then
Under most conditions, the controller will increase cabin altitude at a 600
NOTE
Configuration AA
During normal operation, most functions are
This method of operation
SECTION II
AIRPLANE AND SYSTEMS
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