Cabin Atmosphere Control Systems Flashcards
In a typical high pressure-pneumatic system, if the moisture separator does not vent accumulated water when the compressor shut down, a likely cause is a
malfunctioning solenoid dump valve
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 machine cooling system does air undergo a pressure and temp drop?
Expansion turbine
In a freon vapor-cycle cooling system, where is cooling air obtained for the condensor?
Ambient air
What is ventilating air used for an combustion heater?
Carries heat to the places where it is 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 air pressure increases?
Either a combustion air relief valve or differential pressure regulator
How is the cabin pressure of an aircraft maintained in flight?
By controlling the rate of air flowing out the cabin
What control 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 vapour cycle cooling system when the pressure is too high or the outside air temp 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 vapour 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 vapour 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 4380 filing cycles
Which type of oxygen system uses the rebreather bag-type mask?
Continuous flow
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 of gaseous oxygen systems?
Mositure
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 vapour-cycle cooling system gives up heat and changes from a gas to a liquid is the
condenser
The point at which Freon flowing through a vapour-cycle cooling system gives up 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 temp 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 is too high, 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 temp and pressure of the
freon in the outlet of the evaporator
The function of the condenser in a freon cooling system is to
transfer the heat from the freon gas to ambient air
The function of the condenser in a freon cooling system is to
transfer heat from the freon gas to ambient air
The function of the 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 pressurization source?
Delivery air duct check valve
When servicing an air conditioning system that has lost all 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
What does a steady stream of bubbles indicate when servicing a vapor cycle air condition 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 filing cycles which ever occur first
The cabin pressurization modes of operations are
differential, unpressurized and isobaric
- Usually bleed air from a gas-turbine engine compressor can be safely used for cabin pressurization.
- Independent cabin condition air machines (air cycle machine) can be powered by bleed air from an aircraft turbine engine compressor
Both No.1 and No. 2 is true
A pressurization controller uses
Barometric pressure, cabin altitude, and cabin rate of change
What unit in a vapour cycle cooling system serves as a reservoir for the refrigerant?
Reciever-dryer
What is the condition of the refrigerant as it enters the evaporator of a vapour cycle cooling system?
Low-pressure liquid
What is the condition of the refrigerant as it enters the condensor of a vapour cycle cooling system?
High pressure vapor
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 vapour cycle cooling system?
Low pressure vapor
What is the condition of the refrigerant as it enters the condensor of a vapour cycle cooling system?
High pressure liquid
In what position should the bottle be placed when adding liquid freon to a vapour 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
When refrigerant is leaking from a vapor cycle system, what is the preferred method of finding the leak?
Electronic leak detection
In an operating vapor cycle cooling system, if two lines connected to the expansion valve are essentially the same temp, what does it indicate?
The expansion valve is not metering freon properly
The purpose of a subcooler in a vapour-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 system operation
No.2 Water in a vapour cycle cooling system will react with refrigerant to form hydrochloric acid which is highly corrosive to the metal in the system
No.2 is only true
When refrigerant-12 is passed over an open flame, it
changes to phosgene gas
What type of oil is suitable for use in vapor cycle cooling system?
Special high grade refrigerant oil
When an aircraft oxygen system has developed a leak, the lines and fittings should be
bubble tested with special soap solution manufactured specially 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 vapour 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 valves
High-pressure cylinders containing oxygen for aviation use can be identified by their
green color and the words - ‘AVIATORS BREATHING OXYGEN’ stenciled in 1” white letters
An oxygen bottle may be considered airworthy if it has been hydrostatically tested and identified
with a 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 at hostile environment of the upper atmosphere
Oxygen used in aircraft systems
is atleast 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 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 Transport
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 in the cylinder
What may be used as a lubricant on oxygen system tapered pipe thread connections
Teflon tape
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
Which of the following are characteristics of a chemical or solid state oxygen system?
A volume storage capacity about three times that of compressed oxygen and the system generators are inert below 400F even under severe impact
An aircraft magnetic compass is swung to up-date the compass correction card when
equipment is added that could affect compass deviation
