FAULT MAN EMER DEPRESS PRESS CONT LDG ELEV CABIN PRESS MAN ALT MAN RATE + INCR UP DOWN − DECR + INCR − DECR ECS CPAM PRESS CONT 2 CALT  600 600 FT RATE  0 0 FRM ∆P  4.3 4.3 PSI LOG ELEV  100 FT 21° C RAM AIR 28° C 74 PSI 75 PSI PACK 1 30 PSI PACK 2 30 PSI APU CABIN TEMP 22° C COCKPIT CABIN MAN ALT Controls pressurization in manual mode UP/DOWN—commands cabin altitude to climb/descend PRESS CONT When pressed, selects manual pressurization FAULT—indicates both controllers failed MAN—indicates manual mode selected MAN RATE Controls the rate of change of the cabin altitude in manual mode Figure 16-58.  The pressurization panel and environmental control system page on a Bombardier CRJ200 50 passenger jet have no  gauges. Traditional pressurization data is presented in digital format at the bottom of the page. gradually initiates pressurization during rollout. At takeoff,  the rate of climb and the pressurization schedule require the  outflow valve(s) to fully close. Passengers do not experience  a harsh sensation from the fully closed valves because the  cabin has already begun to pressurize slightly. all components of the air distribution system. Temperature  sensors, overheat switches, and check valves are also common.  On turbine-powered aircraft, temperature-controlled air  from the air conditioning system is the air that is used to  pressurize the cabin. The final regulation of the temperature  of that air is sometimes considered part of the distribution  system. Mixing air-conditioned air with bleed air in a duct  or a mixing chamber allows the crew to select the exact  temperature desired for the cabin. The valve for mixing is  controlled in the cockpit or cabin by a temperature selector.  Centralized manifolds from which air can be distributed are  common.  [Figure 16-59] Once in flight, the pressurization controller automatically  controls the sequence of operation of the pressurization  components until the aircraft lands. When the WOW switch  closes again at landing, it opens the safety valve(s) and,  in some aircraft, the outflow valve(s) makes pressurizing  impossible on the ground in the automatic pressurization  mode. Maintenance testing of the system is done in manual mode. This allows the technician to control the position of  all valves from the cockpit panel.  Distribution of cabin air on pressurized aircraft is managed  with a system of air ducts leading from the pressurization  source into and throughout the cabin. Typically, air is ducted  to and released from ceiling vents, where it circulates and  flows out floor-level vents. The air then flows aft through  the baggage compartments and under the floor area. It exits  the pressure vessel through the outflow valve(s) mounted  low, on, or near the aft pressure bulkhead. The flow of air is  nearly imperceptible. Ducting is hidden below the cabin floor  and behind walls and ceiling panels depending on the aircraft  and system design. Valves to select pressurization air source,  ventilating air, temperature trim air, as well as in line fans and  jet pumps to increase flow in certain areas of the cabin, are  Large aircraft may be divided into zones for air distribution.  Each zone has its own temperature selector and associated  valve to mix conditioned and bleed air so that each zone  can be maintain at a temperature independent of the others.  The air distribution system on most aircraft makes provisions  for ducting and circulating cooling air to electronics  equipment bays. It also contains a gasper air system. This is  air ducted from the cold air manifold or duct to an overhead  adjustable delivery nozzle at each passenger station. An inline  fan controlled from the cockpit supplies a steady stream of  gasper air that can be regulated or shut off with the delivery  nozzle(s).  [Figure 16-60] When an aircraft is on the ground, operating the engines or  the APU to provide air for air conditioning is expensive. It  Air Distribution 16-34