89 terms


expansion valve is not metering Freon properly
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?
controlling the rate at which the air is allowed to leave the cabin
The cabin pressure of an aircraft in flight is maintained at the selected altitude by
either a combustion-air-relief valve or a differential-pressure regulator is provided.
In the combustion heater, combustion air system, what prevents too much air from entering the heaters as air pressure increases?
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
alternately turns on and off the fuel going to the burner.
This process is known as cycling.
The operation of an aircraft combustion heater is usually controlled by a thermostat circuit which
pressure reducer valve
In a high-pressure oxygen system, if the pressure reducer fails, what prevents high-pressure oxygen from entering the system downstream?
The green thermal expansion disk is missing
On transport category aircraft what might be an indication of an over pressure event of the aircraft oxygen system?
it produces phosgene, a deadly gas.
When Refrigerant-12 is passed over an open flame, it
Aviator's breathing oxygen has all of the water vapor removed from it.
The primary difference between aviation breathing oxygen and other types of commercially available compressed oxygen is that
oil seepage
When a vapor-cycle cooling system is not in operation, what is an indication that the system is leaking freon?
tested every five years.
How often should standard weight high-pressure oxygen cylinders be hydrostatically tested?
outflow valve should be made to close faster
If the cabin rate of climb is too great, the control should be adjusted to cause the
unpressurized mode, the isobaric mode, and the differential mode.
The cabin pressurization modes of operation are
Bleed air
Turbine engine air used for air-conditioning and pressurization is generally called
cabin altitude, barometric pressure, and cabin rate of change
A pressurization controller uses
What unit in a vapor-cycle cooling system serves as a reservoir for the refrigerant?
15 years or 10,000 filling cycles, whichever occurs first.
Composite oxygen bottles that conform to DOT-E-8162 have a service life of
absence of bubbles in the sight glass
How can it be determined that a vapor-cycle cooling system is charged with the proper amount of freon?
cool the refrigerant after it leaves the receiver. By cooling the refrigerant, premature vaporization (flash-off) is prevented.
The purpose of a subcooler in a vapor-cycle cooling system is to
landing gear safety, or squat, switch.
On some cabin pressurization systems, pressurization on the ground is restricted by the
continuous-flow system and pressure-demand system
Oxygen systems in unpressurized aircraft are generally of the
A leak in the plumbing of an oxygen system may be found by applying a solution of a special nonpetroleum-base soap to the suspected area. If a leak is present, bubbles will form.
When an aircraft's oxygen system has developed a leak, the lines and fittings should be
maintain the desired cabin pressure
The primary function of the cabin pressurization system outflow valve is to
control the supply of hot, cool and cold air
What is the purpose of a mixing valve in a compressor bleed air air-conditioning system?
low-pressure vapor
What is the condition of the refrigerant as it leaves the evaporator of a vapor-cycle cooling system?
expansion turbine
Where does the last stage of cooling in an air-cycle air-conditioning system occur?
evaporator coils
(Refer to Figure 13.) Determine what unit is located immediately downstream of the expansion valve in a freon refrigeration system.
Teflon tape
What may be used as a lubricant on oxygen system tapered pipe thread connections?
Both 1 and 2 true
(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,
regulator airflow in relation to the cabin altitude, when the regulator is in the diluter-demand position.
The purpose of the airflow metering aneroid assembly found in oxygen diluter demand regulators is to
cabin altitude.
What controls the operation of the cabin pressure regulator?
outflow valve.
The altitude controller maintains cabin altitude by modulation of the
Difference between ambient and internal air pressure
Which best describes cabin differential pressure?
By an automatic outflow valve that dumps from the cabin all pressure in excess of the amount for which it is set
How is the cabin pressure of a pressurized aircraft usually controlled?
1 is not true, 2 is true
(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,
moisture to collect inside the bottle
If oxygen bottle pressure is allowed to drop below a specified minimum, it may cause
vertical with the outlet at the bottom.
In what position should the bottle be placed when adding liquid freon to a vapor-cycle cooling system?
high-pressure liquid.
What is the condition of the refrigerant as it enters the condenser of a vapor-cycle cooling system?
checked and oil added if needed, The system is then evacuated, Freon is then put into the system while it is under vacuum
When servicing an air-conditioning system that has lost all of its freon, it is necessary to
one complete series of events or operations that recur regularly.
An aircraft pressurization cycle is normally considered to be
Pressure relief valves
In a gaseous oxygen system, which of the following are vented to blow out plugs in the fuselage skin?
The point at which freon flowing through a vapor-cycle cooling system absorbs heat and changes from a liquid to a gas is the
blockage in the system.
When charging a vapor-cycle cooling system after evacuation, the low-pressure gauge fails to come out of a vacuum. What is indicated?
hydrostatically tested within the proper time interval.
Before a high-pressure oxygen cylinder is serviced, it must be the correct type and have been
delivery air duct check valve
Which prevents a sudden loss of pressurization in the event that there is a loss of the pressurization source?
When the user breathes
In the diluter demand oxygen regulator, when does the demand valve operate?
low-pressure liquid
What is the condition of the refrigerant as it enters the evaporator of a vapor-cycle cooling system?
Lower the temperature of the Cabin air
The function of the evaporator in a freon cooling system is to
Supplement physical inspections with periodic operational carbon monoxide detection test
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?
ram air cycle cooling unit
Hot compressor bleed air operates the conditioned air system on some turbine aircraft, cold air supplied by the
expansion turbine
At which component in an air-cycle cooling system does air undergo a pressure and temperature drop?
ambient air
In a freon vapor-cycle cooling system, where is cooling air obtained for the condenser?
inadequate airflow through the evaporator
Frost or ice buildup on a vapor-cycle cooling system evaporator would most likely be caused by
transfers heat from the Freon gas to the ambient air.
The function of the condenser in a freon cooling system is to
Both 1 and 2 are true
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,
calibrated orifice
What controls the amount of oxygen delivered to a mask in a continuous-flow oxygen system?
High-pressure oxygen cylinders used in aircraft should be painted green and should have the words AVIATOR'S BREATHING OXYGEN stenciled on them in 1-inch white letters.
High-pressure cylinders containing oxygen for aviation use can be identified by their
thermal expansion valve
What component in a vapor-cycle cooling system would most likely be at fault if a system would not take a freon charge?
high-pressure liquid.
What is the condition of the refrigerant as it leaves the condenser of a vapor-cycle cooling system?
filled with water and pressurized
What test is used to determine the serviceability of an oxygen cylinder?
negative-pressure relief valve
What component of a pressurization system prevents the cabin altitude from becoming higher than airplane altitude?
Department of Transportation (DOT).
If a high-pressure oxygen cylinder is to be installed in an airplane, it must meet the specifications of the
Freon is low.
When checking a freon system, a steady stream of bubbles in the sight gauge indicates the charge is
Chemical oxygen generator systems
For use in pressurized aircraft, which is generally the least complicated and requires the least maintenance?
extracting heat energy across an expansion turbine.
The air-cycle cooling system produces cold air by
What type of oxygen system uses the rebreather bag-type mask?
all connections checked for leaks.
After cleaning or replacing the filtering element in a combustion heater fuel system, the system should be pressurized and
prevent the excessive loss of refrigeration oil.
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?
a source of compressed air, a heat exchanger, and a turbine
The basic air-cycle cooling system consists of
low or high pressure stages of the turbine engine compressor.
Which section of a turbine engine provides high pressure bleed air to an air cycle machine for pressurization and air-conditioning?
after 24 years or 4,380 pressurizations, whichever occurs first.
To be eligible for recharging, a DOT 3HT oxygen cylinder must have been hydrostatically tested every three years and be retired from service after
Freon in the outlet of the evaporator
The position of the thermostatic expansion valve in a vapor-cycle cooling system is determined by temperature and pressure of the
A contaminated oxygen system is normally purged with
reduce the pressure of the liquid Freon
The function of an expansion valve in a freon cooling system is to act as a metering device and to
lowers the boiling point of the water and drawing out the vapor.
The evacuation of a vapor-cycle cooling system removes any water that may be present by
445 to 450 PSI
(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°F; 6 hours later the temperature was 51°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?
pressure reducer valve
What is used in some oxygen systems to change high cylinder pressure to low system pressure?
carries it to places in the aircraft where it is needed.
What is ventilating air used for on a combustion heater?
2 and 3
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 times that of compressed oxygen.
3. The system generators are inert below 400°F even under severe impact.
4. A distribution and regulating system similar to gaseous oxygen systems.
1 true and 2 not true
(1) Oxygen used in aircraft systems is at least 99.5 percent pure and is practically water free.
(2) Oxygen used in aircraft systems is 99.5 percent pure and is hospital quality.
Regarding the above statements
stamped on the cylinder, near the neck, with its DOT number, its serial number, and the date of its last hydrostatic test.
An aircraft oxygen bottle may be considered airworthy if it has been hydrostatically tested and identified
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?
special high-grade refrigeration oil
What type of oil is suitable for use in vapor-cycle cooling system?
special high-grade refrigeration oil
opening of the outflow valve.
The cabin pressure control setting has a direct influence upon the
Reading the pressure gauge mounted on the cylinder.
How should you determine the amount of oxygen in a portable, high-pressure cylinder?
the system should be operated for a period of time to allow the system to stabilize. The sight glass should be rechecked to see if it still indicates that the refrigerant charge is low.
If the liquid level gauge in a vapor-cycle cooling system indicates a low freon charge, the system should
A jet pump is essentially a special venturi in a line carrying air from certain areas in an aircraft that need an augmented airflow through them. Jet pumps are often used in the lines that pull air through galleys and toilet areas.
A nozzle blows a stream of high-velocity compressor bleed air into the throat of the venturi. This increases the velocity of the air flowing through the venturi and produces a low pressure that pulls air from the compartment to which it is connected.
One purpose of a jet pump in a pressurization and air-conditioning system is to
relieves all positive pressure from the cabin when the aircraft is on the ground.
The purpose of the dump valve in a pressurized aircraft is to relieve