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DESCRIPTION
Cabin pressurization is achieved by controlling the leakage rate, or outflow of cabin air through an outflow valve.
The pressurization system has three independent modes of operation:
-Two automatic modes are available from two digital controllers within the Integrated Air System Controllers (IASC). Each IASC drives the outflow valve through the AUTO drive mechanism of its actuator -One manual mode is operated from the cabin pressure control panel through IASC 1 analog circuitry which drives the out flow valve through the manual drive mechanism of its actuator
Two safety valves are pneumatically operated to prevent cabin overpressure and negative pressure conditions. The safety valves operate independently of the automatic and manual pressurization modes to provide an additional level of protec-tion.
Normal operation of the pressurization system is automatic when the destination airport is programed into the FMS and the FMS sends the correct landing altitude to the IASC. The crew has the option of manually setting the landing altitude using the SOURCE SELECT to MAN and setting the landing altitude using the ALT switch.
Pressurization system control indications are displayed on the ECS and SUMMARY synoptic displays. CAB ALT and CAB RATE are displayed on the captain’s MFD.
COMPONENTS AND OPERATION
INTEGRATED AIR SYSTEM CONTROLLERS (IASC)
Two IASCs control all automatic phases of pressurization. Only one controller is active at a time, with the other controller in standby. If the operating controller fails, the standby controller automatically takes the active role.
Unless a failure is detected in IASC 1, it becomes the active controller after power up tests are complete. IASC 2 is operated as a standby mode.
OUTFLOW VALVE
The electrical outflow valve consists of a composite flow body, butterfly plate and electrical double actuator. The actuator has two motors, one for manual operation and the other for automatic operation.
The outflow valve is located on the bottom of the fuselage. An access panel in front of the wing allows access to the outflow valve.
In the manual mode, the outflow valve is controlled electrically by the MAN RATE switch on the PRESSURIZATION con-trol panel. From the control panel, the pilot can manually control the rate at which the cabin altitude climbs (UP) or de-scends (DN). To hold a particular cabin altitude, the pilot can command a zero cabin rate of climb.
SAFETY VALVE
Two safety valves located on the aft pressure bulkhead provide overpressure and negative pressure relief.
The safety valves are pneumatically operated and are spring-loaded closed. When cabin differential pressure exceeds nor-mal limits the safety valves automatically open to relieve excess cabin pressure.
If a negative pressure condition develops (ambient pressure is greater than cabin pressure), the safety valves automatically open to equalize cabin pressure.
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本文链接地址：庞巴迪挑战者300公务机机组操作手册 Bombardier Challenger-空调和增压 Air Cond and Press(12)
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