at which these changes in pressure take place.Safety features prevent the cabin from exceeding the maximum pressurization limit and from maintaining a negative pressure. A safety dump valve is used to manually dump cabin pressure. The entire fuselage, with exception of the nose baggage compartment, is pressurized. The outflow valve is located on the aft pressure bulkhead. The emergency dump valve is located on the forward pressure bulkhead. Normal airflow through the aircraft is rearward and out the outflow valve.HEATINGThe heating and cooling air conditioning system, the pressurization control system, and the fresh air system comprise the environmental control system (ECS).Bleed air supplied from the engines, mixed with cold air from the cooling turbines, is used for heating the cabin and cockpit. The heating system consists of two hot air mixing valves controlled by the temperature control system. Each valve controls the introduction of hot air into the cold air duct.An orifice plate is installed on all later model aircraft at the hot air entry side of the Hot Air Mixing Valve, between the hot air line flange and the valve gasket. The orifice reduces noise by restricting airflow.By reducing the airflow, the cabin will take longer to get warm. If you need to heat the cabin faster during the winter months, remove the orifice plate and reinstall it during the warmer months. The orifice plate may be removed permanently.COOLINGA cooling turbine is installed in each wing. Bleed air from the flow control valve drives the turbine. Cooled bleed air is used to cool and pressurize the cabin. Other systems remove moisture from the cooled air and help prevent ice accumulation in the system. Air enters the turbines and passes through an air-to-air heat exchanger. The cooling turbine inlet and outlet are located in the wing near the turbine. RAM air enters the heat exchanger and cools the bleed air. The inlet transition duct feature...
