Airframe Systems & Components: Cabin Atmosphere Control Systems 🔊 Flashcards
What is the principal control element in a cabin pressurization system?
The cabin overflow valve
What is the purpose of the negative pressure relief valve in the pressurization system?
It prevents accidentally obtaining a cabin altitude which is higher than the altitude of the aircraft
What control changes the position of the overflow valve?
The pressurization controller
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 the engine compressor
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
Where does the warm air for cabin heating come from in most small reciprocating engine aircraft?
From the shroud around the engine muffler
What are three methods of supplying heat to the conditioned air when the “heat of compression” is not sufficient for this purpose?
Fuel burning combustion heaters, electric heaters, and exhaust gas air-to-air heat exchangers
What is the function of ventilating air in a combustion heater?
It is used to carry the heat to the places where it is needed
Where does the fuel used in an aircraft combustion heater come from?
The aircraft fuel tanks
What controls the temperature in an aircraft cabin that is heated with a combustion heater?
A thermostat
What are the sources for ventilation air in a combustion heater?
For air circulation and heater operation on the ground a blower is used. Inflight, ram-air inlets, or cabin compressors on pressurized aircraft.
What are the components of an air cycle cooling system?
An expansion turbine (cooling system), 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, condenser, receiver/dryer, expansion valve, and evaporator
How do you determine the liquid level in a vapor cycle cooling system?
Operate the system for about 5 minutes until it stabilizes, then observe the flow of Freon through the sight glass. If Freon is low, bubbles will be visible.
How is the vapor-cycle cooling system compressor lubricated?
Specialized refrigerant oil
What are the components of a continuous flow oxygen system?
High pressure cylinder, high pressure line, pressure regulation reducing valve, calibrated orifice in the outlet, rebreathing 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
What safety considerations must be observed when filling oxygen cylinders?
Oxygen cylinders should be filled in an oil free environment. Mechanics who fill them should not have any petroleum products on their clothes, hands, or in their hair.
What is the main chemical agent inside of an oxygen generator?
Sodium chlorate
How are high and low pressure oxygen cylinders identified?
High pressure (1800-1850 psi) are green and have “Aviator’s Breathing Oxygen” stenciled lengthwise in white, one inch letters. Low pressure (400-425 psi) are painted light yellow.
What are the three ways supplemental oxygen can be carried in an aircraft?
Liquid oxygen, high pressure gas, or chemical candle
What is an acceptable lubricant for installing oxygen system fittings?
Teflon, or water based lubricants
What type or grade of oxygen must be used in aircraft?
Aviator’s grade breathing oxygen
What is a roots blower?
A type of engine driven compressor
What is a British Thermal Unit (BTU)?
A unit of heat; the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit
How does a water separator work in an air cycle air conditioning system?
It operates using centrifugal force to spin water out of air
