Cabin Atmosphere Control Systems Flashcards
What is the principal control element in a cabin pressurization systems?
The cabin outflow value.
What is the purpose of the negative pressure relief value in the pressurization system?
To prevent a negative pressure condition where the cable altitude is higher than the aircraft altitude (less pressure in the cabin than outside).
What control changes the position of the outflow value?
Cabin altitude setting on pressure controller located in the cockpit (6 to 8 thousand feet).
What are the two groups of independent cabin compressors?
Positive displacement and centrifugal compressors.
What method is used by turbine powered aircraft for pressurization?
Bleed air from engine compressor.
What limits the degree of cabin pressurization?
The structural design of the fuselage and capacity of the superchargers to maintain constant volume of airflow.
What are the three methods of supplying heat to the conditioned air when the “heat of compression” is not sufficient for this purpose?
Combustion heaters, Electric heaters, and Exhaust gas air-to-air heat exchangers.
What is the function of ventilating air in a combustion heater?
Ventilating air is used to carry the heat to the places where it is needed.
What are the sources of ventilating air?
On the ground: a blower. In flight: ram-air inlet. On pressurized aircraft: cabin compressors.
What are the components of an air cycle cooling system?
Expansion turbine (cooling system), and air-to-air heat exchanger, and various valves to control airflow throughout the system.
What causes a temperature drop in an air cycle cooling system?
As the compressed air passes through the expansion turbine, it performs the work of turning the turbine and undergoes a pressure and temperature drop.
What are the components in a vapor cycle cooling system?
Compressor, condenser, receiver/dryer, expansion valve and evaporator.
How do you determine the liquid level in a vapor cycle cooling system?
Operate for 5 minutes to a stable condition, then observe Freon flow in sight window. If bubbles are visible, the Freon charge is low. If no bubbles, then sufficient charge is present.
What are the components of a continuous flow oxygen system?
From a high pressure cylinder into a high pressure line, then through a pressure regulating reducing valve. Then, through a calibrated orifice and finally to a rebreathing mask.
What must be done if an oxygen system has been depleted and not recharged with two hours?
The system must be purge using dry nitrogen or dry air and oxygen.
