11.4 B Air Conditioning

Question 1

What does ‘adiabatic’ mean in terms of heat transfer?

A) Temperature change without adding or removing heat
B) Heat transfer through physical contact
C) Heat transfer by radiation

Answer 1

A) Temperature change without adding or removing heat

Question 2

How is heat transferred through direct physical contact?

A) Convection
B) Radiation
C) Conduction

Answer 2

C) Conduction

Question 3

What is the term for heat transfer through bulk movement of a fluid?

A) Convection
B) Conduction
C) Radiation

Answer 3

A) Convection

Question 4

Which heat transfer method does not require a medium?

A) Conduction
B) Convection
C) Radiation

Answer 4

C) Radiation

Question 5

What is latent heat?

A) Heat that changes the state of a substance without a temperature change
B) Heat that causes a temperature change that can be sensed
C) Heat added to a gas after complete evaporation

Answer 5

A) Heat that changes the state of a substance without a temperature change

Question 6

What is sensible heat?

A) Heat causing a temperature change that can be felt or measured
B) Heat causing a change of state without a temperature change
C) Heat transferred without a medium

Answer 6

A) Heat causing a temperature change that can be felt or measured

Question 7

What is superheat?

A) Heat transferred by radiation
B) Heat energy added to a gas after complete evaporation
C) Heat that changes the state of a substance

Answer 7

B) Heat energy added to a gas after complete evaporation

Question 8

What does humidity measure?

A) The heat energy in the air
B) The amount of water vapour in a volume of air
C) The temperature of the air

Answer 8

B) The amount of water vapour in a volume of air

Question 9

Why does air temperature drop as it expands in the turbine?

A) Because the turbine adds heat to the air
B) Because energy is removed from the air during expansion
C) Because the compressor stops working

Answer 9

B) Because energy is removed from the air during expansion

Question 10

What happens to air when it is compressed in the compressor?

A) It cools down
B) It gains energy
C) It loses energy

Answer 10

B) It gains energy

Question 11

What happens to air when it is expanded in the turbine?

A) It heats up
B) It loses energy
C) It gains energy

Answer 11

B) It loses energy

Question 12

What does the ACS system prevent from happening to the aircraft windows?

A) Scratching
B) Mist formation
C) Cracking

Answer 12

B) Mist formation

Question 13

Which of the following are primary functions of the aircraft’s Air Conditioning System (ACS)?

A) Supply ventilation air, heat air, cool air, and pressurise the cabin
B) Increase engine efficiency and reduce fuel consumption
C) Supply oxygen for passengers and flight crew

Answer 13

A) Supply ventilation air, heat air, cool air, and pressurise the cabin

Question 14

What is the primary purpose of the Air Cycle Air Conditioning System?
A) To power the aircraft’s engines during emergencies
B) To condition and pressurize bleed air for passenger comfort
C) To reduce the weight of the aircraft by removing auxiliary components

Answer 14

B) To condition and pressurize bleed air for passenger comfort

Question 15

What happens when the pack flow selector is set to “HI” flow?
A) Airflow to the cabin is reduced to 80%
B) The cabin receives more than 100% of the normal airflow
C) Air conditioning is turned off for efficiency

Answer 15

B) The cabin receives more than 100% of the normal airflow

Question 16

What percentage of air supply is used when the aircraft is not fully loaded and the pack flow selector is set to “Low Flow”?
A) 120% airflow
B) 80% airflow
C) 100% airflow

Answer 16

B) 80% airflow

Question 17

What percentage of air supply is used when the pack flow selector is in the “Normal” position?
A) 50% airflow
B) 100% airflow
C) 200% airflow

Answer 17

B) 100% airflow

Question 18

When the pack flow selector is in the “HI” position, how much airflow does the cabin receive?
A) 120% airflow
B) 80% airflow
C) 100% airflow

Answer 18

A) 120% airflow

Question 19

What components make up the Air Cycle Machine (ACM)?
A) Centrifugal compressor and expansion turbine
B) Centrifugal compressor and heat exchangers
C) Expansion turbine and oil seals

Answer 19

A) Centrifugal compressor and expansion turbine

Question 20

What is a primary advantage of an air-lubricated Air Cycle Machine?
A) It reduces noise during operation
B) It eliminates oil contamination of the air conditioning system
C) It requires less power to drive the turbine

Answer 20

B) It eliminates oil contamination of the air conditioning system

Question 21

What are the two types of Air Cycle Machines (ACMs)?
A) Turbocharged and Supercharged ACMs
B) Oil Lubricated and Air Lubricated ACMs
C) Electric and Hydraulic ACMs

Answer 21

B) Oil Lubricated and Air Lubricated ACMs

Question 22

Why is a water separator used in an air conditioning system?

A) To prevent water droplets from freezing in lines and valves.
B) To increase the cabin air pressure.
C) To stop the air cycle machine from operating.

Answer 22

A) To prevent water droplets from freezing in lines and valves.

Question 23

What happens to the air temperature as it passes through the heat exchangers in the condenser/reheater?

A) It increases.
B) It decreases.
C) It stays the same.

Answer 23

B) It decreases.

Question 24

What is the fail-safe position for bypass valves in the system?

A) Fully open.
B) Fully closed.
C) Partially open.

Answer 24

B) Fully closed.

Question 25

Why is dry air at high altitudes beneficial for the aircraft? A) It reduces the chance of freezing. B) It increases the aircraft’s speed. C) It improves the air cycle machine efficiency.

Answer 25

A) It reduces the chance of freezing.

Question 26

What is the purpose of trim air valves in an air conditioning system? A. To control cabin air pressure. B. To mix conditioned air for accurate temperature control. C. To increase airflow speed in the cabin.

Answer 26

B. To mix conditioned air for accurate temperature control.

Question 27

Where is the ram air inlet typically located on an aircraft? A. On the top of the fuselage. B. On the underside or wing to body fairing. C. In the tail section.

Answer 27

B. On the underside or wing to body fairing.

Question 28

What happens when the pressure on a liquid is increased in terms of its boiling point? A. Its boiling point decreases. B. Its boiling point remains the same. C. Its boiling point increases.

Answer 28

C. Its boiling point increases.

Question 29

What is the boiling point of water affected by? A. The color of the substance. B. The pressure applied to the liquid. C. The speed of the air around it.

Answer 29

B. The pressure applied to the liquid.

Question 30

What are the five main components of a Vapour Cycle Machine? A. Compressor, Condenser, Expansion Valve, Evaporator, Refrigerant. B. Air Filter, Compressor, Heat Exchanger, Evaporator, Water Separator. C. Bleed Air, Compressor, Heat Exchanger, Expansion Valve, Evaporator.

Answer 30

A. Compressor, Condenser, Expansion Valve, Evaporator, Refrigerant.

Question 31

What happens in Step 1: Compression of the refrigeration process? A. The refrigerant is cooled and condensed. B. The refrigerant is compressed, increasing its pressure and temperature. C. The refrigerant absorbs heat from the cabin air.

Answer 31

B. The refrigerant is compressed, increasing its pressure and temperature.

Question 32

In Step 2: Condensation, what happens to the refrigerant? A. It evaporates and absorbs heat. B. It releases heat and changes from a gas to a high-pressure liquid. C. It cools and condenses into solid form.

Answer 32

B. It releases heat and changes from a gas to a high-pressure liquid.

Question 33

What is the role of the receiver-dryer in the refrigeration cycle? A. To store refrigerant and replace any lost from the system. B. To compress the refrigerant into a high-pressure gas. C. To release heat to the surrounding environment.

Answer 33

A. To store refrigerant and replace any lost from the system.

Question 34

What happens during Step 4: Expansion in the refrigeration cycle? A. The refrigerant is compressed and heated. B. The refrigerant expands rapidly, causing its pressure and temperature to drop. C. The refrigerant is stored in the receiver-dryer.

Answer 34

B. The refrigerant expands rapidly, causing its pressure and temperature to drop.

Question 35

In Step 5: Evaporation, what happens to the refrigerant? A. It releases heat into the cabin. B. It absorbs heat from the cabin air and evaporates into a vapour. C. It condenses into a high-pressure liquid.

Answer 35

B. It absorbs heat from the cabin air and evaporates into a vapour.

Question 36

What happens if any refrigerant is lost from the system in the vapour cycle machine? A. It is replaced by the receiver-dryer. B. It is replaced by additional air from the cabin. C. It is replaced by new refrigerant from an external source.

Answer 36

A. It is replaced by the receiver-dryer.

Question 37

What is the role of the receiver-dryer in the vapour cycle system? A. To store liquid refrigerant that is not passing through the system. B. To compress the refrigerant gas. C. To absorb heat from the cabin air.

Answer 37

A. To store liquid refrigerant that is not passing through the system.

Question 38

Which refrigerant is commonly used in vapour cycle systems due to its low global warming potential and lower impact on the ozone layer compared to earlier refrigerants? A. R12 B. R134a C. R123a

Answer 38

C. R123a

Question 39

What happens when refrigerant and water combine in the system? A. They form an acid that can deteriorate the materials inside the components and tubing. B. They create a stable mixture that improves system performance. C. They enhance the refrigerant's ability to absorb heat.

Answer 39

A. They form an acid that can deteriorate the materials inside the components and tubing.

Question 40

What issue does ice formation in the refrigerant system cause? A. It helps cool the system more efficiently. B. It blocks the flow of refrigerant, causing the system to become inoperative. C. It increases the pressure, improving refrigerant flow.

Answer 40

B. It blocks the flow of refrigerant, causing the system to become inoperative.

Question 41

Where does ice formation cause a problem in the refrigerant system? A. At the compressor, where the refrigerant is compressed. B. At the orifice in the expansion valve, the coldest point in the cycle. C. In the condenser, where the refrigerant releases heat.

Answer 41

B. At the orifice in the expansion valve, the coldest point in the cycle.

Question 42

What does the presence of bubbles in the sight glass indicate? A. The system is overcharged with refrigerant. B. The refrigerant level is low and the system requires more refrigerant. C. The system is functioning at an optimal refrigerant level.

Answer 42

B. The refrigerant level is low and the system requires more refrigerant.

Question 43

What are the two primary purposes of a compressor isolation valve in an aircraft's air conditioning system? A. It isolates the compressor for oil level checking and replenishment without losing refrigerant. B. It allows for refrigerant servicing and can isolate the compressor for oil checks and replenishment. C. It prevents compressor damage by regulating air flow through the compressor.

Answer 43

B. It allows for refrigerant servicing and can isolate the compressor for oil checks and replenishment.

Question 44

Question 2: Which of the following is true about a compressor isolation valve? A. The valve is hard-mounted to the inlet and outlet of the compressor. B. The valve can only isolate the compressor for refrigerant servicing. C. It has two positions: fully open for normal operation, and fully closed for compressor replacement only.

Answer 44

A. The valve is hard-mounted to the inlet and outlet of the compressor.

Question 45

How does a compressor isolation valve help prevent refrigerant loss during system maintenance? A. By isolating the compressor, oil can be checked and replenished without opening the entire system and losing refrigerant. B. It controls the pressure of the refrigerant to keep it contained during maintenance. C. It acts as a fail-safe, ensuring refrigerant does not escape from any valve.

Answer 45

A. By isolating the compressor, oil can be checked and replenished without opening the entire system and losing refrigerant.

Question 46

What should be done after servicing a compressor isolation valve on an aircraft's air conditioning system? A. The valve handle and service port should be capped. B. The valve should be fully open to ensure proper refrigerant flow. C. The valve should remain in the intermediate position for maximum system efficiency.

Answer 46

A. The valve handle and service port should be capped.

Question 47

How does conditioned air exit and circulate through the cabin of an aircraft? A. It exits through floor-level vents and circulates through ceiling vents. B. It exits through ceiling vents, circulates, and flows out through floor-level vents. C. It only exits through ceiling vents and remains stagnant in the cabin.

Answer 47

B. It exits through ceiling vents, circulates, and flows out through floor-level vents.

Question 48

What material are the distribution ducts generally constructed of in an aircraft's air conditioning system? A. Heavy metal to ensure durability. B. Light fiberglass material coated to prevent damage from moisture. C. Plastic tubes to reduce weight.

Answer 48

B. Light fiberglass material coated to prevent damage from moisture.

Question 49

How is conditioned air distributed into the cabin of an aircraft? A. Through a series of ducts leading to ceiling and floor vents. B. By using only the air conditioning packs in the cabin. C. Through air vents directly from the cockpit.

Answer 49

A. Through a series of ducts leading to ceiling and floor vents.

Question 50

Where do the conditioned air exit vents typically get placed in an aircraft? A. Near the cockpit only. B. Near the passenger windows. C. Through ceiling vents, circulating to floor-level vents.

Answer 50

C. Through ceiling vents, circulating to floor-level vents.

Question 51

Where does the conditioned air exit the aircraft after circulating through the cabin? A. Through the ceiling vents. B. Through the outflow valve(s) mounted near the aft pressure bulkhead. C. Through the side windows for ventilation.

Answer 51

B. Through the outflow valve(s) mounted near the aft pressure bulkhead.

Question 52

Where is the temperature control regulator typically located in an aircraft's cabin temperature control system? A. In the flight deck B. In the electronics compartment C. Near the cabin air ducts

Answer 52

B. In the electronics compartment

Question 53

What is the primary purpose of onboard humidifiers in aircraft? A. To control the cabin temperature B. To help passengers stay hydrated and reduce the effects of jetlag C. To purify the air for better breathing

Answer 53

B. To help passengers stay hydrated and reduce the effects of jetlag

Question 54

What is the impact of recirculating up to 50% of cabin air on engine performance? A. It increases the engine's power output B. It decreases the amount of engine compressor bleed, saving fuel C. It causes the engines to consume more fuel

Answer 54

B. It decreases the amount of engine compressor bleed, saving fuel

Question 55

What is removed from the cabin air during the recirculation process? A. Oxygen B. Airborne particles, bacteria, and odours C. Heat

Answer 55

B. Airborne particles, bacteria, and odours

Question 56

What is the typical percentage of cabin air that is filtered and recirculated on an aircraft? A. 10% B. 25% C. 50%

Answer 56

C. 50%

Question 57

How does the airflow system in the cabin minimize the spread of passenger-generated contaminants? A. By controlling the airflow to move forward and backward along the cabin B. By ensuring air supplied at one seat row leaves at the same seat row C. By exhausting air directly from the front of the cabin

Answer 57

B. By ensuring air supplied at one seat row leaves at the same seat row

Question 58

Where are the return air grilles located in the aircraft cabin? A. On the ceiling near the overhead bins B. In the sidewalls near the floor, running the length of the cabin C. In the cockpit

Answer 58

B. In the sidewalls near the floor, running the length of the cabin