Study Aid Questions
Fill in the Blanks
1. Oxygen is a _________________________, __________________________, and _________________________ gas at normal atmospheric temperatures and pressures.
2. The words ____________________________________________ should be marked clearly on any cylinder containing oxygen for aircraft use.
3. Oxygen cylinders are considered empty when the pressure inside drops below _______________ psi. This ensures that air containing ___________________________________ has not entered the cylinder.
4. When oxygen is delivered only as the user inhales, it is known as a ______________________________ system.
5. There are two types of individual oxygen demand regulators: they are:
_____________________________________________ _____________________________________________
6. The main cause of contamination in an oxygen system is _______________________________________.
7. The cabin pressurization system must be capable of maintaining a cabin pressure attitude of _______________. or lower regardless of _______________________________.
8. Metal fatigue from repeated ___________________________, and ____________________________ weakens the aircraft structure.
9. There are three typical sources of air used to pressurize reciprocating aircraft. They are:
______________________________ ______________________________ ______________________________
10. Aircraft equipped with turbine engines typically use ______________________________________ as a source for cabin pressurization.
11. Aircraft cabin pressurization systems work in two different modes of operation. They are:
_____________________________________________ ______________________________________________
12. The flight crew can select and control _____________________________, ____________________________, and ____________________________________ on the cabin pressure controller.
13. The cabin pressure controller controls the position of the ___________________________________ located normally at the rear of the aircraft.
14. Many transport category aircraft have an outflow valve that operates ___________________________ , using signals sent from a remotely located ________________________________ that act as the pressure regulator.
15. Pressurization safety relieve valves are used to prevent __________________________________ of the cabin.
16. ____________________________________ are used to ensure that air pressure outside the aircraft does not exceed cabin air pressure.
17. Aircraft with reciprocating engines often use a _________________________ cooling system, and turbine powered aircraft use a __________________________ cooling system.
18. The air cycle cooling system is supplied with air from either ___________________________ or ____________
19. The heart of the air cycle cooling system is the _______________________________________, also known as the ________________________________________
20. The duct temperature sensors used in the temperature control system are ____________________________. Their ______________________________________ changes as temperature changes.
21. The temperature at which a substance changes from a _____________________ into a ___________________ when heat is added is known as the boiling point.
22. R134a refrigerant is filtered and stored under pressure in a reservoir known as __________________________
23. Most evaporators are constructed of ___________________________ or _____________________________ tubing coiled into a compact unit.
24. A concern of exhaust shroud heat system is that __________________________ could contaminate the cabin.
25. Maintenance of combustion heaters consists of routine items such as _________________________, checking ____________________________________ wear, and ensuring inlets are not plugged.
TRUE or FALSE
1. Gaseous oxygen systems are used in commercial aircraft and LOX oxygen systems are primarily used in military aircraft. TRUE/FALSE
2. Most oxygen storage cylinders are painted blue, but yellow and white may be used as well. TRUE/FALSE
3. Demand‐flow systems are used most frequently by the crew on high performance and air transport category aircraft. TRUE/FALSE
4. A blown out green disk in the side of fuselage indicates that the oxygen supply is low and this should be investigated before flight. TRUE/FALSE
5. The solid chemical oxygen generators used in most airliners are activated automatically by depressurization or manually by a switch operated by the flight crew. TRUE/FALSE
6. Petroleum products such as grease and oil should never be used for oxygen system maintenance because an explosion could be the result. TRUE/FALSE
7. The cabin pressurization system must maintain the cabin pressure altitude below 10,000 ft. TRUE/FALSE
8. Metal fatigue can result from repeated pressurization cycles and can weaken the airframe structure. TRUE/FALSE
9. Superchargers are the common source of pressurization on modern reciprocating engine aircraft. TRUE/FALSE
10. Turbochargers are driven by a shaft or a drive belt. TRUE/FALSE
11. Large turbine powered aircraft use bleed air from the engine compressor section as a source of air for cabin pressurization. TRUE/FALSE
12. The isobaric control mode of a cabin pressurization system controls cabin pressure to maintain a constant pressure between the air pressure outside the cabin and the ambient air pressure. TRUE/FALSE
13. Small aircraft often use a pneumatically controlled outflow valve while transport category aircraft use electrically/electronically controlled outflow valves. TRUE/FALSE
14. Pressurization safety relieve valves are used to prevent negative cabin pressure. TRUE/FALSE
15. Many pack valves used in air conditioning systems are electrically controlled and pneumatically operated. TRUE/FALSE
16. The primary heat exchanger is cooled by an electric fan during stationary ground operations and ram air is used in flight. TRUE/FALSE
17. The water separator has a fiberglass bag (sock) that condenses and coalesces the mist into larger water droplets. Gravity will drain the water droplets from the water separator. TRUE/FALSE
18. The function of the refrigeration by‐pass valve is to regulate the temperature of the air cycle machine so it does not freeze when passing through the water separator. TRUE/FALSE
19. A vapor cycle air conditioning system is an open system in which a refrigerant is circulated through tubing and a variety of components. TRUE/FALSE
20. Most modern vapor cycle cooling systems on aircraft use R12 refrigerant which has replaced the R134a refrigerant. TRUE/FALSE
21. During a feel test components and lines in the high side (from the compressor to the expansion valve) should warm or hot to the touch. TRUE/FALSE
22. During a feel test low side lines and the evaporator should be warm. TRUE/FALSE
23. The charging capacity of a vapor cycle air conditioning system is measured by weight. TRUE/FALSE
24. Most single‐engine light aircraft use a bleed air system to heat the cabin. TRUE/FALSE
25. The fuel for the combustion heater is drawn from a dedicated small fuel tank inside the cabin. TRUE/FALSE
Knowledge Application Questions
1. What component in the pressurization system is the principal control of a pressurization system?
__________________________________________________________________________
2. What source of air supply is used by most turbine‐powered aircraft for pressurization?
__________________________________________________________________________
3. What pressurization control unit will change the position of an outflow valve?
__________________________________________________________________________
4. On reciprocating engine aircraft, what are some methods of supplying heat to the cabin?
__________________________________________________________________________
5. What is the function of ventilating air in a combustion heater?
__________________________________________________________________________
6. What are the typical components used in an air‐cycle cooling system?
__________________________________________________________________________
7. What causes a temperature drop in an air‐cycle cooling system?
__________________________________________________________________________
8. Describe how a water separator in an air cycle cooling system removes moisture from the air?
__________________________________________________________________________
9. Describe the theory of operation of a vapor‐cycle cooling system illustrated in textbook figure 16‐74?
__________________________________________________________________________
10. Describe the theory of operation of an air cycle cooling system illustrated in textbook figure 16‐63.
__________________________________________________________________________
11. What are the main components in a vapor‐cycle cooling system?
__________________________________________________________________________
12. How does a continuous‐flow oxygen system operate?
__________________________________________________________________________
13. What must be accomplished if an oxygen system has been open to atmosphere for 2 hours or more?
__________________________________________________________________________
14. What is used to purge oxygen lines of moisture?
__________________________________________________________________________
15. What type of oxygen must be used in aircraft?
__________________________________________________________________________
16 Why is oil added to a vapor‐cycle Freon system?
__________________________________________________________________________
17. What safety precautions should be observed when servicing oxygen systems?
__________________________________________________________________________
18. What sources of air are used by pressurized aircraft with a reciprocating engine?
__________________________________________________________________________
19. What is the main advantage of using LOX systems?
__________________________________________________________________________
20. What kind of adjustments can be made on a pressure controller?
__________________________________________________________________________
Multiple Choices Questions
1. The purpose of the dump valve in a pressurized aircraft is to relieve:
a. all positive pressure from the cabin
b. a negative pressure differential
c. pressure in excess of the maximum differential
2. The basic air cycle cooling system consists of:
a. a source of compressed air, heat exchangers, and an air cycle machine
b. heaters, coolers, and compressors
c. ram air source, compressors, and engine bleeds
3. Frost or ice buildup on a vapor cycle cooling system evaporator would most likely be caused by:
a. the mixing valve sticking closed
b. moisture in the evaporator
c. inadequate airflow through the evaporator
4. In a Freon vapor cycle cooling system, where is cooling air obtained for the condenser?
a. Turbine engine compressor
b. Ambient air
c. Pressurized cabin air
5. What component in a vapor cycle cooling system would most likely be at fault if a system would not take a Freon charge?
a. Expansion valve
b. Condenser
c. Receiver dryer
6. What controls the operation of the cabin pressure regulator?
a. Cabin altitude
b. Bleed air pressure
c. Compression air pressure
7. The cabin pressure of an aircraft in flight is maintained at the selected altitude by
a. controlling the air inflow rate
b. inflating door seals and recirculating conditioned cabin air
c. controlling the rate at which air leaves the cabin
8. What is ventilating air used for on a combustion heater?
a. Provides combustion air for ground blower
b. Carries heat to the places where needed
c. Provides air required to support the flame
9. At which component in an air cycle cooling system does air undergo a pressure and temperature drop?
a. Expansion turbine
b. Primary heat exchanger
c. Refrigeration bypass valve
10. How often should standard weight high pressure oxygen cylinders be hydrostatically tested?
a. Every 5 years
b. Every 4 years
c. Every 3 years
11. Turbine engine air used for air conditioning and pressurization is generally called:
a. compressed air
b. ram air
c. bleed air
12. 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?
a. The system is functioning normally
b. The expansion valve is not metering Freon properly
c. The compressor is pumping too much refrigerant
13. In the diluter demand oxygen regulator, when does the demand valve operate?
a. When the diluter control is set at normal
b. When the user demands 100 percent oxygen
c. When the user breathes
14. If oxygen bottle pressure is allowed to drop below a specified minimum, it may cause:
a. the pressure reducer to fail
b. the automatic altitude control valve to open
c. moisture to collect in the bottle
15. In a high‐pressure oxygen system, if the pressure reducer fails, what prevents high pressure oxygen from entering the system downstream?
a. Check valve
b. Pressure relief valve
c. Manifold control valve
16. What is the condition of the refrigerant as it leaves the condenser of a vapor cycle cooling system?
a. Low pressure liquid
b. High pressure liquid
c. High pressure vapor
17. What is the condition of the refrigerant as it leaves the evaporator of a vapor cycle cooling system?
a. Low pressure liquid
b. Low pressure vapor
c. High pressure vapor
18. The primary difference between aviation breathing oxygen and other types of commercially available compressed oxygen is that:
a. the other types are usually somewhat less than 99.5 percent pure oxygen
b. aviation breathing oxygen has had all the water vapor removed
c. aviation breathing oxygen has a higher percentage of water vapor to help prevent drying of a person's breathing passages and possible dehydration
19. In a gaseous oxygen system, which of the following are vented to blow out plugs in the fuselage skin?
a. Pressure relief valves
b. Filler shutoff valves
c. Pressure reducer valves
20. High pressure cylinders containing oxygen for aviation use can be identified by their:
a. green color and the words 'BREATHING OXYGEN' stenciled in 1‐inch white letters
b. yellow color and the words 'AVIATOR'S BREATHING OXYGEN' stenciled in 1‐inch white letters
c. green color and the words 'AVIATOR'S BREATHING OXYGEN' stenciled in 1‐inch white letters
21. What part of a pressurization system prevents cabin altitude from becoming higher than airplane altitude?
a. Cabin rate of descent control
b. Negative pressure relief valve
c. Positive pressure relief valve
22. The cabin pressure control setting has a direct influence upon the:
a. outflow valve opening
b. pneumatic system pressure
c. inflow valve opening
23. If the cabin rate of climb is too great, the control should be adjusted to cause the:
a. outflow valve to close slower
b. outflow valve to close faster
c. cabin compressor speed to decrease
24. The main cause of contamination in gaseous oxygen systems is:
a. moisture
b. dust and other airborne particulates
c. other atmospheric gases
25. What may be used as a lubricant on oxygen system tapered pipe thread connections?
a. Silicone dielectric compound
b. Glycerin
c. Teflon tape
26. Which is considered a good practice concerning the inspection of heating and exhaust systems of aircraft utilizing a shroud around the engine exhaust as a heat source?
a. Supplement physical inspections with periodic operational carbon monoxide detection tests.
b. All exhaust system components should be removed periodically, and their condition determined by the magnetic particle inspection method.
c. All exhaust system components should be removed and replaced at each 100‐hour inspection period.
27. What unit in a vapor cycle cooling system serves as a reservoir for the refrigerant?
a. Receiver dryer
b. Evaporator
c. Condenser
28. Which best describes cabin differential pressure?
a. Difference between cabin flight altitude pressure and Mean Sea Level pressure
b. Difference between the ambient and internal air pressure
c. Difference between cabin pressure controller setting and actual cabin pressure
29. Regarding the statements below:
(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.
a. only No. 1 is true
b. only No. 2 is true
c. both No. 1 and No. 2 are true
30. The cabin pressurization modes of operation are:
a. isobaric, differential, and maximum differential
b. differential, unpressurized, and isobaric
c. ambient, unpressurized, and isobaric
SUPPORTING LESSONS
Physiology of FlightAircraft Oxygen Systems
Oxygen Systems and Components
Oxygen System Servicing
Prevention of Oxygen Fires or Explosions
Aircraft Heaters
Aircraft Pressurization Systems
Pressurization Issues
Sources of Pressurized Air
Control of Cabin Pressure
Pressurized Aircraft
Air Conditioning Systems
Vapor Cycle Air Conditioning System Servicing
Vapor Cycle Air Conditioning System Components