Cabin Atmosphere Control Systems Flashcards
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.
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.
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
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 temperature is too low?
Compressor
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.
What is the condition of the refrigerant as it leaves the condenser of a vapor-cycle cooling system?
High pressure liquid.
In a gaseous oxygen system, which of the following are vented to blowout plugs in the fuselage skin?
Pressure relief valves
What is ventilating air used for on a combustion heater?
Carries heat to the places where needed.
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.
Frost or ice buildup on a vapor cycle cooling system evaporator would most likely be caused by
Inadequate airflow through the evaporator.
Which selection of a turbine engine provides high pressure bleed air to an air cycle machine for pressurization and air-conditioning?
Low or high pressure compressor.
What controls the amount of oxygen delivered to a mask in a continuous-flow oxygen systems?
Calibrated orifice
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.
At which component in an air-cycle cooling system does air undergo a pressure and temperature drop?
Expansion turbine
For use in pressurized, which is generally the least complicated and requires the least maintenance?
Chemical oxygen generator systmes.
Composite oxygen bottles that conform to DOT-E-8162 have a service life of
15 years or 10,000 filling cycles whichever occurs first.
In a freon vapor-cycle cooling system, where is cool air obtained for the condenser?
Ambient air
What does a steady stream of bubbles indicate when servicing a vapor cycle air conditioning system?
The system is under charged.
What is used in some oxygen systems to change high cylinder pressure to low system pressure?
Pressure reducer valve
The function of the evaporator in a freon cooling system is to
Lower the temperature of the cabin air.
If a high-pressure oxygen cylinder is to be installed in an airplane, it must meet the specifications of the
Department of transportation
What type of oxygen system uses the rebreather bag-type mask?
Continuous flow.
The purpose of the airflow metering aneroid assembly found ing oxygen diluter demand regulators is to
Regulate airflow in relation to cabin altitude when in driver demand position.
What is the main cause of contamination in a gaseous oxygen system?
Moisture
If oxygen bottle pressure is allowed to drop below a specified minimum, it may cause
Moisture to collect in the bottle.
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.
Which is considered a good practice concerning the inspection of heating and exhaust systems of aircraft utilizing a jacket around in the engine exhaust as a heat source?
Supplement physical inspections with periodic operational carbon monoxide detection tests.
Where does the last stage of cooling in an air-cycle air-conditioning system occur?
Expansion turbine
On transport category aircraft what might be an indication of an over pressure event of the aircraft oxygen system?
The green thermal expansion disk missing.
A contaminated oxygen system is normally purged with
Oxygen
The operation of an aircraft combustion heater is usually controlled by a thermostat circuit which
Alternatively turns the fuel on and off, a process known as cycling.
What is the purpose of a mixing valve in a compressor bleed air air conditioning system?
Control the supply of hot, cool, cool and cold air
What type of oil is suitable for use in vapor-cycle cooling systems?
Special high grade refrigeration oil.
Which of the following are characteristic of a chemical or solid state oxygen system?
1) An adjustable oxygen release rate.
2) A volume storage capacity about three ties that of compressed oxygen.
3) The system generators are inert below 400 degrees F even under sever impact.
4) A distribution and regulating system similar to gaseous oxygen systems.
2&3
The basic-air cycle cooling system consists of
A source of compressed air, heat exchangers, and a turbine.
Which prevents a sudden loss of pressurization in the event that there is a loss of pressurization source?
Delivery air duct check valve.
1) A small amount of water in a vapor-cycle cooling system can freeze in the receiver-dryer and stop the entire system operation.
2)Water in a vapor-cycle cooling system will react with refrigerant to form hydrochloric acid which is highly corrosive to the metal in the system.
Regarding the above statements,
Only no.2 is true
Before a high-pressure oxygen cylinder is serviced, it must be the correct type and have been
Hydrostatically tested within the proper time interval.
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
Condenser
What may be used as a lubricant on oxygen system tapered pipe thread connections?
Teflon tape
The primary function of the cabin pressurization system airflow valve is to
Maintain the desired cabin pressure
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
The purpose of the dump valve in a pressurized aircraft is to relieve
All positive pressure from the cabin.
The cabin pressure control setting has a direct influence upon the
Outflow valve opening
Turbine engine air used for air-conditioning and pressurization is generally called
Bleed air
An aircraft pressurization cycle is normally considered to be
One complete series of events or operations that recur regularly
How often should standard weight high-pressure oxygen cylinders be hydrostatically tested?
Every 5 years
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 cabin pressurization modes of operation are
differential, unpressurized, and isobaric.
What is the condition of the refrigerant as it leaves the evaporator of a vapor-cycle cooling system?
Low pressure vapor
On some cabin pressurization systems, pressurization on the ground is restricted by the
Main landing gear operated switch.
How is the cabin pressure of an aircraft maintained in flight?
By controlling the rate of the air flowing out of the cabin.
The component that determines the pressure level in the cabin is the cabin air pressure
Outflow valve
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
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 purpose of pressurizing aircraft cabins is to
1) Create the proper environment for prevention of hypoxia.
2) Permit operation at high altitudes.
Regarding the above statements,
Both no.1 and no.2 are true
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.
The air-cycle cooling system produces cold air by
Extracting heat energy across an expansion turbine.
Oxygen systems in unpressurized aircraft are generally of the
Continuous-flow and pressure-demand types.
In the diluter demand oxygen regulator, when does the demand valve operate?
When the user breathes.
What component of a pressurization system prevents the cabin altitude from becoming higher than airplane altitude?
Negative pressure relief valve.
(Refer to figure 13.) Determine what unit is located immediately downstream of the expansion valve in a freon refrigeration sysem.
Evaporator coils
1) Oxygen used in aircraft systems is at least 99.5% and is practically water free.
2) Oxygen used in aircraft systems is at least 99.5% and is hospital quality.
Regarding the above statements,
only no.1 is true
Hot compressor bleed air operates the conditioned air system on some turbine aircraft, cold air supplied by the
Air cycle air conditioning
A pressurization controller uses
Barometric pressure, cabin altitude, and cabin rate of change.
How should you determine the amount of oxygen in a portable, high-pressure cylinder?
Read the pressure gauge mounted on the cylinder.
The function of the condenser in a freon cooling system is to
Transfer heat from the freon gas to ambient air.
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.
If the cabin rate of climb is too great, the control should be adjusted to cause the
Outflow valve to close faster
Which best describes cabin differential pressure?
Difference between the ambient and internal air pressure.
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 test is used to determine the serviceability of an oxygen cylinder?
Pressure test with water.
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.
What is the condition of the refrigerant as it enters the condenser of a vapor-cycle cooling system?
High-pressure vapor
1) Usually bleed air from a gas-turbine engine compressor can be safely used for cabin pressurization.
2) Independent cabin condition air machines (air cycle machine) can be powered by bleed air from an aircraft turbine engine compressor.
Regarding the above statements,
Both no.1 and no.2 are true.
What is the condition of the refrigerant as it enters the evaporator of a vapor-cycle cooling system?
Low-pressure liquid
What unit in a vapor-cycle cooling system serves as a reservoir for the refrigerant?
Receiver-dryer
(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 F; 6 hours later the temperature was 51 degrees F. (A 5 PSI change is the maximum allowable in a 6-hour period.) What pressure gauge readings would be acceptable to remain within the allowable limits?
445 to 450 PSI
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.
The purpose of a subcooler in a vapor-cycle cooling system is to
Cool the freon to prevent premature vaporization.
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.
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.
When refrigerant-12 is passed over an open flame, it
Changes to phosgene gas
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.
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 be identified by their
Green color and words ‘Aviators Breathing Oxygen’ stenciled in 1-inch white letters.
In the combustion heater, combustion air system, what prevents too much air from entering the heaters as air pressure increases?
Either a combustion air relief valve or a differential pressure regulator.
What controls the operation of the cabin pressure regulator?
Cabin altitude
