Cabin Atmosphere Control Systems Flashcards
Which section of a turbine engine provides high pressure bleed air to an air cycle machine for pressurization and air conditioning?
Low or high pressure compressor.
At which component in an air-cycle cooling system does air undergo a pressure and temperature drop?
Expansion turbine.
In a freon vapor-cycle cooling system, where is cooling air obtained for the condenser?
Ambient air.
What is ventilating air used for on a combustion heater?
Carries heat to the places where needed.
Turbine engine air used for air conditioning and pressurization is generally called…
bleed air.
In the combustion heater, combustion air system, what prevents too much air from entering the heaters as pressure increase?
Either a combustion air relief valve or a differential pressure regulator.
How is the cabin pressure of an aircraft maintained in flight?
By controlling the rate of the air flowing out of the cabin.
What controls the operation of the cabin pressure regulator?
Cabin altitude.
The basic air-cycle cooling system consists of…
a source of compressed air, heat exchangers, and a turbine.
The purpose of the dump valve in a pressurized aircraft is to relieve…
all positive pressure from the cabin.
What component might possibly be damaged if liquid refrigerant is introduced into the low side of a vapor-cycle cooling system when the pressure is too high or the outside air temperature is too low?
Compressor.
How can it be determined that a vapor-cycle cooling system is charged with the proper amount of freon?
Air bubbles in the sight glass disappear.
When charging a vapor-cycle cooling system after evacuation, the low-pressure gauge fails to come out of a vacuum. What is indicated?
Blockage in the system.
What component in a vapor-cycle cooling system would most likely be at fault if a system would not take a freon charge?
Expansion valve.
Frost or ice buildup on a vapor-cycle cooling system evaporator would most likely be caused by…
inadequate airflow through the evaporator.
What test is used to determine the serviceability of an oxygen cylinder?
Pressure test with water.
How often should standard weight high-pressure oxygen cylinders be hydrostatically tested?
Every 5 years.
To be eligible for recharging, a DOT 3HT oxygen cylinder must have been hydrostatically tested every three years and be retired from service after…
24 years or 4,380 filling cycles.
Which oxygen system employs a regulator that operates only when the user inhales?
Demand-flow system.
The component that determines the pressure level in the cabin is the cabin air pressure…
outflow valve.
Hot compressor bleed air operates the conditioned air system on some turbine aircraft, cold air supplied by the…
air cycle air conditioning.
For use in pressurized aircraft, which is generally the least complicated and requires the least maintenance?
Chemical oxygen generator systems.
What is the main cause of contamination in a gaseous oxygen system?
Moisture.
Where does the last stage of cooling in an air-cycle air conditioning system occur?
Expansion turbine.
The point at which freon flowing through a vapor-cycle cooling system gives up heat and changes from a gas to a liquid is the…
condensor.
The point at which freon flowing through a vapor-cycle cooling system absorbs heat and changes from a liquid to a gas is the…
evaporator.
How is the cabin pressure of a pressurized aircraft usually controlled?
By an automatic outflow valve that dumps all the pressure in excess of the amount for which it is set.
Which is considered a good practice concerning the inspection of heating and exhaust systems of aircraft utilizing a jacket around the engine exhaust as a heat source?
Supplement physical inspections with periodic operational carbon monoxide detection tests.
On some cabin pressurization systems, pressurization on the ground is restricted by the…
main landing gear operated switch.
The cabin pressure control setting has a direct influence upon the…
outflow valve opening.
The function of the evaporator in a freon cooling system is to…
lower the temperature of the cabin air.
What is the purpose of a mixing valve in a compressor bleed air air-conditioning system?
Control the supply of hot, cool, and cold air.
What component of a pressurization system prevents the cabin altitude from becoming higher than airplane altitude?
Negative pressure relief valve.
If the liquid level gauge in a vapor-cycle cooling system indicates a low freon charge, the system should…
be operated for a period of time to reach a stable condition and then the freon level rechecked.
If the cabin rate of climb too great, the control should be adjusted to cause the…
outflow valve to close faster.
The position of the thermostatic expansion valve in a vapor-cycle cooling system is determined by temperature and pressure of the…
freon in the outlet of the evaporator.
The function of the condenser in a freon cooling system is to…
transfer heat from the freon gas to ambient air.
The function of an expansion valve in a freon cooling system is to act as a metering device and to…
reduce the pressure of the liquid freon.
Which prevents a sudden loss of pressurization in the event that there is a loss of the pressurization source?
Delivery air duct check valve.
When servicing an air conditioning system that has lost all of its freon, it is necessary to…
check oil and add as necessary, evacuate the system, and add freon.
The primary function of the cabin pressurization system outflow valve is to…
maintain the desired cabin pressure.
One purpose of a jet pump in a pressurization and air conditioning system is to…
provide for augmentation of airflow in some areas of the aircraft.
After cleaning or replacing the filtering element in a combustion heater fuel system, the system should be pressurized and…
all connections checked for leaks.
The operation of an aircraft combustion heater is usually controlled by a thermostat circuit which…
alternately turns the fuel on and off, a process known as cycling.
The air-cycle cooling system produces cold air by…
extracting heat energy across an expansion turbine.
(Refer to Figure 13.) Determine what unit is located immediately downstream of the expansion valve in a freon refrigeration system.
Evaporator coils.
What does a steady stream of bubbles indicate when servicing a vapor cycle air conditioning system?
The system is under charged.
An aircraft pressurization cycle is normally considered to be…
one complete series of events or operations that recur regularly.
Which best describes cabin differential pressure?
Difference between the ambient and internal air pressure.
Composite oxygen bottles that conform to DOT-E-8162 have a service life of…
15 years or 10,000 filling cycles whichever occurs first.
The cabin pressurization modes of operation are…
differential, unpressurized, and isobaric.
A pressurization controller uses…
barometric pressure, cabin altitude, and cabin rate of change.
What unit in a vapor-cycle cooling system serves as a reservoir for the refrigerant?
Receiver-dryer.
What is the condition of the refrigerant as it enters the condenser of a vapor-cycle cooling system?
High-pressure vapor.
What is the condition of the refrigerant as it enters the evaporator of a vapor-cycle cooling system?
Low-pressure liquid.
The evacuation of a vapor-cycle cooling system removes any water that may be present by…
lowering the boiling point of the water and drawing out the vapor.
What is the condition of the refrigerant as it leaves the evaporator of a vapor-cycle cooling system?
Low-pressure vapor.
What is the condition of the refrigerant as it leaves the condenser of a vapor-cycle cooling system?
High-pressure liquid.
In what position should the bottle be placed when adding liquid freon to a vapor-cycle cooling system?
Vertical with the outlet at the bottom.
When purging a freon air conditioning system, it is important to release the charge at a slow rate. What is the reason for the slow-rate discharge?
Prevent excessive loss of refrigerant oil.
When a vapor-cycle cooling system is not in operation, what is an indication that the system is leaking freon?
Oil seepage.
In an operating vapor-cycle cooling system, if the two lines connected to the expansion valve are essentially the same temperature, what does this indicate?
The expansion valve is not metering freon properly.
The purpose of a sub cooler in a vapor-cycle cooling system is to…
cool the freon to prevent premature vaporization.
A small amount of water in a vapor cycle cooling system can freeze…
in the expansion valve and stop the entire system operation.
When Refrigerant-12 is passed over an open flame, it…
changes to phosgene gas.
What type of oil is suitable for use in a vapor-cycle cooling system?
Special high grade refrigeration oil.
When an aircraft’s oxygen system has developed a leak, the lines and fittings should be…
bubble tested with a special soap solution manufactured specifically for this purpose.
If oxygen bottle pressure is allowed to drop below a specified minimum, it may cause…
moisture to collect in the bottle.
What controls the amount of oxygen delivered to a mask in a continuous-flow oxygen system?
Calibrated orifice.
When does the diluter-demand regulator operate?
When the user inhales.
The primary difference between aviation breathing oxygen and other types of commercially available compressed oxygen is that…
aviation breathing oxygen has had all the water vapor removed.
What is used in some oxygen systems to change high cylinder pressure to low system pressure?
Pressure reducer valve.
In a high-pressure oxygen system, if the pressure reducer fails, what prevents high-pressure oxygen from entering the system downstream?
Pressure relief valve.
High-pressure cylinders containing oxygen for aviation use can identified by their…
green color and the words AVIATOR’S BREATHING OXYGEN stenciled in 1-inch white letters.
(Refer to Figure 14.) One hour after an oxygen system was charged for a leakage check, the oxygen pressure gauge read 460 psi at 63 Degrees Fahrenheit; 6 hours later the temperature was 51 Degrees Fahrenheit. (A 5 psi change is the maximum allowable in a 6-hour period.) What pressure gauge reading would be acceptable to remain within the allowable limits?
445-450 psi.
An aircraft oxygen bottle may be considered airworthy if it has been hydrostatically tested and identified…
with the test date, DOT number, and serial number stamped on the cylinder near the neck.
In a gaseous oxygen system, which of the following are vented to blow out plugs in the fuselage skin?
Pressure relief valves.
What is the purpose of pressurizing the aircraft cabin?
To make human flight possible in the hostile environment of the upper atmosphere.
Oxygen used in aircraft systems…
is at least 99.5% pure and is practically water free.
Oxygen systems in unpressurized aircraft are generally of the…
continuous-flow and pressure-demand types.
The purpose of the airflow metering aneroid assembly found in oxygen diluter demand regulators is to…
regulate airflow in relation to cabin altitude when in diluter demand position.
If a high-pressure oxygen cylinder is to be installed in an airplane, it must meet the specifications of the…
Department of Transportation.
Before a high-pressure oxygen cylinder is serviced, it must be the correct type and have been…
hydrostatically tested within the proper time interval.
A contaminated oxygen system is normally purged with…
oxygen.
How should you determine the amount of oxygen in a portable, high-pressure cylinder?
Read the pressure gauge mounted on the cylinder.
What may be used as a lubricant on oxygen system tapered pipe thread connections?
Teflon tape.
On a transport category aircraft what might be an indication of an over pressure event of the aircraft oxygen system?
The green thermal expansion disk missing.
Which of the following are characteristics a chemical or solid-state oxygen system?
A volume storage capacity about three times that of compressed oxygen and system generators that are inert below 400 Degrees Fahrenheit, even under severe impact.
