Cabin Atmosphere Control Systems Flashcards
What is the principle control element in a cabin pressurization system?
The cabin outflow valve.
What is the purpose of the negative pressure relief valve in the pressurization system?
The negative pressure relief valve prevents accidentally obtaining a cabin altitude which is higher than the altitude of the aircraft.
What control changes the position of the outflow valve?
The pressurization controller is the source of control signals for the pressurization system.
What are the two groups of independent cabin compressors?
They are positive displacement compressors and centrifugal compressors.
What method is used by turbine-powered aircraft for pressurization?
Bleed-air from the engine compressor is used for pressurization.
What limits the degree of cabin pressurization?
The structural design features of the fuselage, and by the capacity of the superchargers to maintain a constant volume of airflow to the fuselage.
What are three methods of supplying heat to the conditioned air when the “heat of compression” is not sufficient for this purpose?
Gasoline 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 for ventilating air?
A blower for air circulation and heater operation on the ground, and a ran-air inlet, or the cabin compressors on pressurized aircraft.
What are the components of an air cycle cooling system?
An expansion turbine (cooling turbine), an air-to-air heat exchanger, and various valves which control airflow through 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 (freon) cooling system?
The compressor, the condenser, the expansion valve, and the evaporator.
How do you determine the liquid level in a vapor cycle cooling system?
Operate the system for approximately 5 minutes to reach a stable condition and then observe the flow of freon through the sight glass. A steady flow indicates that a sufficient charge is present. If the freon charge is low, bubbles will appear in the sight glass
What is a continuous flow oxygen system?
When the line valve is turned on, oxygen will flow continuously from the charged cylinder through a highpressure line to the pressure-reducing valve, which reduces the pressure to that required at the mask outlets. A calibrated orifice in the outlets will control the amount of oxygen delivered to the mask.
What must be done if an oxygen system has been depleted and not recharged within two hours?
It must be purged with dry nitrogen or dry air and oxygen.
