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 attitude of the aircraft.
What pressurization control unit will change the position of an outflow valve?
The cabin pressure controller, located in the cockpit is used to set the cabin air pressure to a desired
altitude, normally between six and eight thousand feet.
What are the two groups of independent cabin compressors?
They are positive displacement, and centrifugal compressors.
What method is used by turbine powered aircraft for pressurization?
Bleed air from the turbine 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 the air that is warmed and sent into the cabin.
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?
A blower/fan or ram-air.
What are the components of an air cycle cooling system?
An expansion turbine (cooling system), an air-to-air heat exchanger, and various valves.
What causes a temperature drop in an air cycle cooling system?
The compressed air performs the work of turning the turbine and it undergoes a pressure and temperature drop.
What are the components in a vapor cycle (Freon) cooling system?
The compressor, condenser, a 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 to reach a stabilized condition, and then watch the flow of
Freon through the sight glass. A steady flow indicates enough charge. If the Freon is low,
bubbles will appear in the sight glass.
what is the vapor-cycle cooling?
Specialized refrigerant oil. (a closed system in which a refrigerant is circulated through tubing and a variety of components to remove heat from the aircraft).
how does a continuous flow oxygen system operate?
Oxygen flows from a high-pressure cylinder through a high pressure line to a reducing valve and to mask outlets.
What must be accomplished if an oxygen system has been open to atmosphere for 2 hours or more?
The system must be purged to remove moisture.
What safety considerations must be observed when filling oxygen cylinders?
Oxygen cylinders should be filled in an oil free environment. The mechanic who fills the cylinders
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 is the main chemical agent used in aviation oxygen generators. The chemical is
ignited by a spark-emitting cap, and when it burns, O2 is generated. These systems are lighter and
less complex than oxygen storage based systems. The main drawback of oxygen generators is that
once the burning of the sodium chlorate begins, it cannot be stopped until the chemical is consumed.
How are high and low pressure oxygen cylinders identified?
High pressure (1800-1850 psi) oxygen cylinders are green in color and have the words “Aviator’s
Breathing Oxygen” stenciled lengthwise in white, one inch letters. Low pressure (400-425 psi)
cylinders are painted light yellow.
What are the three ways supplemental oxygen can be carried in an aircraft?
As liquid oxygen, a high pressure gas, or a chemical candle.
What is an acceptable lubricant for installing oxygen system fittings?
Teflon, or water based lubricants.
Why is oil added to a vapor-cycle freon system?
To seal and lubricate the compressor.
What is a roots blower?
An engine-driven compressor.
How does water separator remove moisture from the air?
The moist air passes through vanes that swirl the air, and the droplets are collected and drained.
What safety precautions should be observed when servicing oxygen system?
Clean, grease free tools, clothing, hands, no smoking or open flames within 50 feet, do not use adhesive tape of any kind.
What is used to purge oxygen lines of moisture?
Dry nitrogen, dry air, or oxygen.
What type of oxygen must be used in aircraft?
Aviators breathing oxygen.
