Embraer EMB145 - Page 2095

PNEUMATICS
AIR CONDITIONING
AND PRESSURIZATION
AIRPLANE
OPERATIONS
MANUAL
2-14-15
Page
2
Code
01
JUNE 29, 2001
OPERATION IN AUTOMATIC MODE
The automatic mode maintains minimum cabin altitude according to
the airplane operating altitude, imposing minimum cabin altitude rate of
change.
The automatic mode is controlled by the digital controller and requires
a landing altitude to be entered prior to takeoff. According to the
landing altitude, the measured cabin pressure, ADC inputs (airplane
altitude, altitude rate of change and barometric correction), air/ground
position, and thrust lever position, the digital controller determines the
adequate opening of the electropneumatic outflow valve. The
pneumatic outflow valve is slaved to the electropneumatic outflow
valve and both operate simultaneously, maintaining the same position
while in the automatic mode
Different operation sequences are automatically initiated by the Digital
Controller following the received inputs.
The Digital Controller schedules a cabin altitude that is the value that
the measured cabin altitude must be equal to.
Cabin altitude rate of change varies according to the different operation
sequences.
Proper operation of the pressurization system in the automatic mode
requires that the following conditions be met:
− Automatic mode is selected on the Digital Controller (button not
pressed and MAN inscription not illuminated). The pressurization
system is in the automatic mode when electrical power is first
applied.
− Landing altitude is entered in the Digital Controller prior to the
takeoff. Should the landing altitude not be entered, the system will
automatically consider 8000 ft as the landing altitude.
− Manual Controller is set to DN position (full counterclockwise). If the
Manual Controller is out of the DN position, the pneumatic valve
tends to open causing inappropriate automatic mode operation.
DETERMINATION OF THE THEORETICAL CABIN ALTITUDE
The theoretical cabin altitude is a function of the airplane operating
altitude. It is calculated in such a way that the maximum cabin
differential pressure (7.8 psi) is reached at the lowest possible airplane
altitude considering a minimum cabin altitude rate of climb and a
maximum airplane rate of climb.