11.4 Air Con & Cabin Pressure Flashcards
(206 cards)
1
Q
What is the main source of pressurised air in an aircraft?
a) Engines
b) Auxiliary Power Unit (APU)
c) Ground source (Air Cart)
A
a) Engines
2
Q
What is the primary function of outflow valves in an aircraft?
a) Control engine temperature
b) Regulate cabin temperature
c) Control the amount of air exiting the aircraft to maintain cabin pressure
A
c) Control the amount of air exiting the aircraft to maintain cabin pressure
3
Q
How do most pressurisation systems keep the air cool?
a) Using a heat exchanger or a full-air-cycle air conditioning system
b) Using a cooling fan in the cockpit
c) By passing air through a refrigeration unit
A
a) Using a heat exchanger or a full-air-cycle air conditioning system
4
Q
What stage of the engine compressor typically provides bleed air for pressurisation in turbine engines?
a) First stage
b) Fifth and ninth stages
c) Tenth stage
A
b) Fifth and ninth stages
5
Q
Which type of air is used during takeoff and climb?
a) Low-pressure air
b) High-pressure air
c) Both low and high-pressure air
A
a) Low-pressure air
6
Q
What happens when a bleed air leak occurs?
a) The engine becomes more efficient
b) The air may become contaminated with oils or fuel
c) The engine fails to start
A
b) The air may become contaminated with oils or fuel
7
Q
Which valve adjusts the pressure of bleed air in the system?
a) Temperature Regulating Valve (TRV)
b) Pressure Regulating Valve (PRV)
c) Bleed Air Valve (BAV)
A
b) Pressure Regulating Valve (PRV)
8
Q
What is a major disadvantage of using engine-driven compressors for cabin pressurisation?
a) Increased fuel consumption due to reduced engine power output
b) It increases engine efficiency
c) It makes the engine quieter
A
a) Increased fuel consumption due to reduced engine power output
9
Q
How are independent cabin compressors powered?
a) By the aircraft’s battery
b) By bleed air from the engine compressor
c) By electric motors only
A
b) By bleed air from the engine compressor
10
Q
What does a Roots-type blower do in the pressurisation system?
a) Compresses and delivers air to the cabin
b) Cools the air entering the engine
c) Filters the air entering the aircraft
A
a) Compresses and delivers air to the cabin
11
Q
What is a feature of the Roots-type blower?
a) It has a turbocharger
b) It compresses a fixed volume of air and delivers it under pressure
c) It has a variable-speed fan
A
b) It compresses a fixed volume of air and delivers it under pressure
12
Q
How does a centrifugal cabin compressor operate?
a) By expanding air to increase its pressure
b) By using an impeller to compress air
c) By cooling air using liquid nitrogen
A
b) By using an impeller to compress air
13
Q
Where is the centrifugal cabin compressor usually located?
a) Inside the cockpit
b) In the engine nacelle
c) In the aircraft’s tail section
A
b) In the engine nacelle
14
Q
What type of compressor is commonly used in smaller aircraft applications for pressurisation?
a) Positive displacement blower
b) Centrifugal cabin compressor
c) Turbo compressor
A
c) Turbo compressor
15
Q
What does a turbo compressor do to cabin air?
a) Heats the air for the cabin
b) Compresses the air and blends it with cooled, decompressed air
c) Filters the air to remove dust
A
b) Compresses the air and blends it with cooled, decompressed air
16
Q
How is the Cabin Air Compressor (CAC) on a B787 powered?
a) By the aircraft’s main engine
b) By a three-phase electric motor
c) By bleed air from the APU
A
b) By a three-phase electric motor
17
Q
What does an Auxiliary Power Unit (APU) provide on the ground?
a) Electrical power for navigation
b) Bleed air for engine starting and air conditioning
c) Water for the air conditioning system
A
b) Bleed air for engine starting and air conditioning
18
Q
What happens if an APU is designed for bleed air extraction in flight?
a) It can operate at any altitude
b) The bleed air extraction is limited to a specific altitude, usually around 22,000 feet
c) It stops functioning at altitudes higher than 20,000 feet
A
b) The bleed air extraction is limited to a specific altitude, usually around 22,000 feet
19
Q
Where is the APU typically located in an aircraft?
a) In the nose section
b) In the fuselage near the wings
c) In the tail section
A
c) In the tail section
20
Q
What happens when a ground air cart is connected to an aircraft?
a) It provides fuel to the engine
b) It supplies conditioned air to the aircraft’s cabin and air conditioning packs
c) It starts the aircraft’s engines
A
b) It supplies conditioned air to the aircraft’s cabin and air conditioning packs
21
Q
What is the primary function of the Air Conditioning System (ACS) in an aircraft?
a) To provide comfortable cabin temperatures
b) To regulate cabin air pressure
c) To supply oxygen to passengers
A
a) To provide comfortable cabin temperatures
22
Q
What is the typical temperature range that most ACS systems can maintain inside the aircraft?
a) 10 °C to 15 °C (50 °F to 59 °F)
b) 21 °C to 27 °C (70 °F to 80 °F)
c) 30 °C to 35 °C (86 °F to 95 °F)
A
b) 21 °C to 27 °C (70 °F to 80 °F)
23
Q
What term describes the heat transfer process caused by the physical contact of two objects?
a) Convection
b) Radiation
c) Conduction
A
c) Conduction
24
Q
Which of the following heat transfer processes involves the bulk movement of a fluid?
a) Convection
b) Adiabatic
c) Sensible Heat
A
a) Convection
25
Which term refers to the heat that causes a substance to change its state with no change in temperature?
a) Latent Heat
b) Sensible Heat
c) Super Heat
a) Latent Heat
26
What is sensible heat?
a) Heat that changes the temperature of a substance
b) Heat that changes a substance’s state
c) Heat that does not change the temperature of the substance
a) Heat that changes the temperature of a substance
27
What happens to air as it passes over a turbine in an aircraft's air conditioning system?
a) The air is compressed and heated
b) The air expands, creating a temperature drop
c) The air absorbs more energy from the engine
b) The air expands, creating a temperature drop
28
What is the role of the turbine in an air conditioning system?
a) It compresses air to increase temperature
b) It extracts air energy to drive the compressor
c) It filters the air before distribution
b) It extracts air energy to drive the compressor
29
What is the purpose of humidity control in an aircraft’s ACS?
a) To prevent fogging of windows
b) To add moisture to dry air
c) To regulate the temperature of the cabin
a) To prevent fogging of windows
30
What is a common feature of the majority of air conditioning systems on aircraft?
a) They supply air at a constant pressure
b) They control the humidity and prevent window misting
c) They do not regulate temperature, only air quality
b) They control the humidity and prevent window misting
31
What is the difference between an Air Cycle Machine and a Vapour Cycle machine in ACS?
a) Air Cycle Machines are used in smaller aircraft; Vapour Cycle machines in larger aircraft
b) Vapour Cycle machines are used in small and medium aircraft, while Air Cycle Machines are used in larger aircraft
c) Both types are used interchangeably in all aircraft sizes
b) Vapour Cycle machines are used in small and medium aircraft, while Air Cycle Machines are used in larger aircraft
32
Which type of ACS system is used in larger passenger aircraft?
a) Vapour Cycle Machines
b) Air Cycle Machines
c) Combined Cycle Systems
b) Air Cycle Machines
33
What is the effect of adiabatic cooling in air conditioning systems?
a) It raises the temperature of the air
b) It causes the temperature of the air to drop without adding or removing heat
c) It lowers the humidity of the air
b) It causes the temperature of the air to drop without adding or removing heat
34
What happens to air during compression in the air conditioning system?
a) The air expands and cools
b) The air is compressed and its temperature increases
c) The air is cooled and filtered
b) The air is compressed and its temperature increases
35
How does the ACS maintain a comfortable cabin environment during flight?
a) By supplying only heated air
b) By adjusting temperature and humidity
c) By purifying the air and removing contaminants
b) By adjusting temperature and humidity
36
What is the role of air conditioning packs in the ACS?
a) They supply power to the cabin lighting
b) They provide cool or warm air to the cabin
c) They filter the air in the cabin
b) They provide cool or warm air to the cabin
37
Which of the following statements is true about the operation of ACS systems?
a) They are capable of cooling the cabin only during descent
b) They use the surrounding ambient air to condition the cabin air
c) They continually measure and adjust air temperature based on preset settings
c) They continually measure and adjust air temperature based on preset settings
38
What is the function of an air conditioning system's sensors?
a) To measure air pressure only
b) To measure and regulate air temperature and humidity
c) To monitor fuel levels for air conditioning operation
b) To measure and regulate air temperature and humidity
39
Which of the following is a potential issue that air conditioning systems need to prevent?
a) Overheating of the aircraft engines
b) Contamination of cabin air with fumes, contaminants, and odors
c) High air pressure causing damage to the fuselage
b) Contamination of cabin air with fumes, contaminants, and odors
40
How does the ACS system handle both cooling and heating of the cabin air?
a) By using a combination of electrical heating elements and cooling compressors
b) By using the engine bleed air for both heating and cooling
c) By adjusting the flow of external air based on altitude
a) By using a combination of electrical heating elements and cooling compressors
41
What is the primary purpose of the air cycle air conditioning system in turbine-powered aircraft?
A) To cool the cabin with air from the Auxiliary Power Unit (APU)
B) To pressurize the aircraft cabin using engine bleed air
C) To filter external air before it enters the cabin
B) To pressurize the aircraft cabin using engine bleed air
42
Where is the air conditioning pack typically located in turbine-powered aircraft?
A) Wing sections
B) Lower fuselage or tail section
C) Near the cockpit
B) Lower fuselage or tail section
43
What happens to the temperature of the bleed air after passing through the primary heat exchanger?
A) It increases by 60 to 70 ºC
B) It decreases by about 100 ºC
C) It stays the same
B) It decreases by about 100 ºC
44
What component in the air conditioning system separates water particles from the air?
A) Compressor
B) Water extractor duct
C) Air cycle machine
B) Water extractor duct
45
What role does the re-heater play in the air conditioning system?
A) It cools the air for the cabin
B) It warms the air to improve turbine efficiency
C) It filters moisture from the air
B) It warms the air to improve turbine efficiency
46
At cruising altitude, why is the need for cooling minimal in the air conditioning system?
A) Due to high external temperatures
B) Because of the low ambient temperature at that altitude
C) The air cycle machine turns off automatically
B) Because of the low ambient temperature at that altitude
47
How does the pack or flow control valve regulate the airflow to the air conditioning system?
A) By using an electric fan
B) By modulating the temperature of the bleed air
C) By regulating the volume of hot, pressurized air from the pneumatic manifold
C) By regulating the volume of hot, pressurized air from the pneumatic manifold
48
What happens when the pack flow selector is in the LO position?
A) The airflow to the cabin is increased by 20%
B) The airflow to the cabin is reduced to 80%
C) The air conditioning system shuts down
B) The airflow to the cabin is reduced to 80%
49
What is the purpose of the primary and secondary heat exchangers?
A) To generate electricity
B) To cool the hot bleed air before it enters the compressor
C) To pressurize the cabin air
B) To cool the hot bleed air before it enters the compressor
50
What type of air cycle machine (ACM) uses air bearings and does not require oil?
A) Oil Lubricated ACM
B) Air Lubricated ACM
C) Hybrid ACM
B) Air Lubricated ACM
51
What does the condenser/reheater do in the air conditioning system?
A) It cools the air and removes moisture
B) It cools the air and adds energy to the air
C) It removes water particles from the air
B) It cools the air and adds energy to the air
52
How does the water separator function in the air conditioning system?
A) It separates ice from the bleed air
B) It removes water droplets from the air to prevent freezing and discomfort
C) It collects air for use in the turbine
B) It removes water droplets from the air to prevent freezing and discomfort
53
What is the main purpose of the air cycle machine bypass air?
A) To increase the pressure of the air
B) To maintain the air temperature around 35°F to prevent ice formation
C) To filter contaminants from the air
B) To maintain the air temperature around 35°F to prevent ice formation
54
What does the trim air valve do in some air conditioning systems?
A) It filters out contaminants from the outside air
B) It mixes conditioned air with engine bleed air to maintain temperature
C) It controls airflow through the primary heat exchanger
B) It mixes conditioned air with engine bleed air to maintain temperature
55
Where is the ram air door typically located on an aircraft?
A) Near the cockpit
B) On the underside of the aircraft or wing-body fairing
C) On the tail section
B) On the underside of the aircraft or wing-body fairing
56
What type of aircraft typically uses a vapor cycle air conditioning system?
a) Only turbine-powered aircraft
b) Only aircraft with reciprocating engines
c) Both reciprocating and turbine-powered aircraft
c) Both reciprocating and turbine-powered aircraft
57
What is the main purpose of the vapor cycle air conditioning system?
a) To heat the cabin
b) To cool the cabin by transferring heat to the outside
c) To increase cabin humidity
b) To cool the cabin by transferring heat to the outside
58
What is the refrigeration cycle based on?
a) Absorption refrigeration
b) Thermodynamic principles, particularly vapor compression refrigeration
c) Direct air cooling
b) Thermodynamic principles, particularly vapor compression refrigeration
59
What happens when pressure is increased on a liquid?
a) Its freezing point decreases
b) Its boiling point increases
c) It evaporates more easily
b) Its boiling point increases
60
What is the boiling point of water when pressure is decreased to 10 psi?
a) 212 °F (100 °C)
b) 194 °F (90 °C)
c) 226 °F (107.8 °C)
b) 194 °F (90 °C)
61
Which of the following describes how refrigerants work in the refrigeration cycle?
a) They are compressed and condensed into a gas before entering the system
b) They evaporate at much lower temperatures than water and extract heat rapidly
c) They absorb heat by increasing their boiling point
b) They evaporate at much lower temperatures than water and extract heat rapidly
62
Which component in a vapor cycle system compresses the refrigerant, increasing its temperature?
a) Condenser
b) Compressor
c) Expansion valve
b) Compressor
63
What is the role of the condenser in a vapor cycle system?
a) To release heat from the refrigerant to the surrounding air
b) To compress the refrigerant gas
c) To evaporate the refrigerant inside the cabin
a) To release heat from the refrigerant to the surrounding air
64
What happens when the refrigerant passes through the expansion valve?
a) It increases in temperature
b) Its pressure and temperature drop
c) It turns from a liquid to a gas without a temperature change
b) Its pressure and temperature drop
65
What is the function of the evaporator in the vapor cycle system?
a) To release heat into the surrounding air
b) To absorb heat from the cabin air and evaporate the refrigerant
c) To compress the refrigerant
b) To absorb heat from the cabin air and evaporate the refrigerant
66
What does the receiver-dryer do in the vapor cycle system?
a) Stores excess refrigerant and removes water and particles
b) Compresses the refrigerant gas
c) Increases the boiling point of the refrigerant
a) Stores excess refrigerant and removes water and particles
67
What is the main function of the thermal expansion valve?
a) To compress the refrigerant
b) To release refrigerant into the evaporator at the correct rate
c) To store excess refrigerant
b) To release refrigerant into the evaporator at the correct rate
68
What could happen if too much refrigerant is released by the expansion valve?
a) The compressor may break because liquids are incompressible
b) The system would stop absorbing heat
c) The temperature inside the cabin would drop excessively
a) The compressor may break because liquids are incompressible
69
What is the purpose of the externally equalized expansion valve?
a) To increase the pressure of the refrigerant
b) To ensure better control of refrigerant flow by considering both temperature and pressure
c) To store excess refrigerant
b) To ensure better control of refrigerant flow by considering both temperature and pressure
70
What happens if ice forms on the evaporator fins?
a) It improves heat exchange efficiency
b) It reduces the efficiency of heat exchange
c) It increases the cooling capacity of the system
b) It reduces the efficiency of heat exchange
71
What does the compressor do in the vapor cycle air conditioning system?
a) It circulates the refrigerant and compresses it to increase its temperature
b) It evaporates the refrigerant to cool the cabin
c) It stores refrigerant for future use
a) It circulates the refrigerant and compresses it to increase its temperature
72
What is the function of the service valves in the vapor cycle system?
a) To control the flow of refrigerant to the compressor
b) To allow access for system servicing and refrigerant charging
c) To cool the refrigerant before entering the compressor
b) To allow access for system servicing and refrigerant charging
73
What type of valve is commonly used on systems that operate with R12 refrigerant?
a) Schrader valve
b) Expansion valve
c) Compressor isolation valve
a) Schrader valve
74
What does the compressor isolation valve allow for in aircraft systems?
a) Servicing the system with refrigerant while the compressor is operational
b) Isolating the compressor for oil checks or replacement without losing refrigerant
c) Controlling the temperature of the refrigerant
b) Isolating the compressor for oil checks or replacement without losing refrigerant
75
How is conditioned air distributed in the cabin of an aircraft?
A) Through ceiling vents and floor level vents
B) Through floor vents only
C) Through overhead panels only
A) Through ceiling vents and floor level vents
76
Where does the conditioned air exit the aircraft?
A) Through the front of the aircraft
B) Through the outflow valve(s) near the aft pressure bulkhead
C) Through emergency exits
B) Through the outflow valve(s) near the aft pressure bulkhead
77
What material are distribution ducts typically made of?
A) Stainless steel
B) Light fibreglass material coated to prevent moisture damage
C) Rubber
B) Light fibreglass material coated to prevent moisture damage
78
What allows the flight crew to control the temperature of the conditioned air in the cabin?
A) A temperature selector that mixes conditioned air with bleed air
B) A thermostat in each passenger seat
C) A manual valve operated by cabin crew
A) A temperature selector that mixes conditioned air with bleed air
79
How are large aircraft divided for air distribution?
A) By size of the passengers
B) By zones, each with its own temperature selector
C) By the number of engines
B) By zones, each with its own temperature selector
80
What additional function do air distribution systems serve in large aircraft?
A) To circulate cooling air to the flight crew
B) To circulate cooling air to electronics equipment bays
C) To deliver fuel to the engines
B) To circulate cooling air to electronics equipment bays
81
What is a gasper air system?
A) A ventilation system in the cockpit
B) Air ducted from the cold air manifold to an adjustable nozzle at each passenger station
C) A system that provides emergency air supply
B) Air ducted from the cold air manifold to an adjustable nozzle at each passenger station
82
How can the cabin be conditioned when the aircraft is on the ground?
A) Using the aircraft's air conditioning system
B) By using ground-conditioned air connected to the cabin’s air distribution system
C) By opening the windows
B) By using ground-conditioned air connected to the cabin’s air distribution system
83
What is the purpose of the check valve in the air distribution system?
A) To increase air flow
B) To prevent ground source air from flowing into the air conditioning system
C) To reduce the temperature of the air
B) To prevent ground source air from flowing into the air conditioning system
84
What is the purpose of temperature sensors, overheat switches, and check valves in the air distribution system?
A) To monitor the flow of conditioned air through the system
B) To regulate the air pressure
C) To control the cabin lighting
A) To monitor the flow of conditioned air through the system
85
Where is the temperature control regulator typically located?
A) In the flight deck
B) In the electronics compartment
C) Near the passenger seats
B) In the electronics compartment
86
What is the role of the temperature controller in the cabin temperature control system?
A) To control cabin lights
B) To compare actual temperatures with the desired set temperature
C) To regulate oxygen levels in the cabin
B) To compare actual temperatures with the desired set temperature
87
How does the temperature control system adjust the temperature in the cabin?
A) By increasing or decreasing the airflow
B) By modulating a valve that mixes warm bleed air with cold air
C) By adjusting the power of the engines
B) By modulating a valve that mixes warm bleed air with cold air
88
What type of sensor is used to monitor temperature in the cabin and ducts?
A) Thermistor
B) Thermocouple
C) Pressure gauge
A) Thermistor
89
What is the purpose of the trim air modulating valves in large aircraft?
A) To adjust the pressure in the cabin
B) To mix hot and cold air to match the selected temperature for each zone
C) To filter out airborne particles
B) To mix hot and cold air to match the selected temperature for each zone
90
What is the role of onboard humidifiers on long-distance flights?
A) To cool down the cabin
B) To help passengers stay hydrated and reduce jetlag
C) To increase cabin pressure
B) To help passengers stay hydrated and reduce jetlag
91
How much of the cabin air is typically recirculated on an aircraft?
A) 10%
B) 30%
C) Up to 50%
C) Up to 50%
92
What is one of the benefits of recirculating cabin air?
A) It saves fuel by reducing engine bleed air usage
B) It decreases cabin pressure
C) It reduces the amount of oxygen in the cabin
A) It saves fuel by reducing engine bleed air usage
93
How is exhaust air extracted from the cabin in most aircraft?
A) By fans located near the ceiling
B) By outflow valves located forward of the wings
C) By recirculation fans and return air grilles near the floor
C) By recirculation fans and return air grilles near the floor
94
What is the main function of the cabin ventilation system in controlling airflow?
A) To maintain a continuous flow of air without pressure fluctuations
B) To minimize airflow between seat rows, preventing the spread of contaminants
C) To regulate the humidity level
B) To minimize airflow between seat rows, preventing the spread of contaminants
95
Why is the interior of an aircraft pressurised when flying at high altitude?
A) To maintain structural integrity of the fuselage
B) To allow passengers and flight crew to function normally without additional oxygen
C) To reduce engine fuel consumption
B) To allow passengers and flight crew to function normally without additional oxygen
96
What is the cabin altitude in a pressurised aircraft generally maintained at for passenger safety and comfort?
A) 10,000 ft
B) 12,000 ft
C) 8,000 ft
C) 8,000 ft
97
At what cabin altitude must the flight crew be on oxygen?
A) 12,000 ft
B) 15,000 ft
C) 10,000 ft
C) 10,000 ft
98
What is the maximum cabin altitude allowed in commercial aircraft?
A) 8,000 ft
B) 10,000 ft
C) 12,000 ft
A) 8,000 ft
99
What is the term for the pressure difference between the inside of the cabin and the outside atmosphere?
A) Differential Pressure (ΔP)
B) Cabin Pressure
C) Atmospheric Pressure
A) Differential Pressure (ΔP)
100
What unit is used to measure differential pressure in aircraft pressurisation systems?
A) Hectopascal (hPa)
B) Pounds per square inch (psi)
C) Inches of mercury (inHg)
B) Pounds per square inch (psi)
101
At an altitude of 40,000 ft, what is the actual cabin differential pressure when the cabin is pressurised to the equivalent of 8,000 ft?
A) 6.5 psi
B) 8.2 psi
C) 12.0 psi
B) 8.2 psi
102
What is the equivalent force acting on 1m² of fuselage when differential pressure is 8.2 psi?
A) 10,000 N
B) 56,500 N
C) 100,000 N
B) 56,500 N
103
What happens to atmospheric pressure as altitude increases?
A) It increases slowly
B) It decreases rapidly
C) It remains constant
B) It decreases rapidly
104
At sea level, what is the weight of a 1-inch column of air?
A) 29.92 lbs
B) 14.7 lbs
C) 10.0 lbs
B) 14.7 lbs
105
In which layer of the atmosphere does temperature decrease as altitude increases?
A) Troposphere
B) Stratosphere
C) Mesosphere
A) Troposphere
106
What is the temperature range at the tropopause?
A) –2 °C to –3.5 °C
B) –57 °C to –69 °F
C) Constant at –57 °C
C) Constant at –57 °C
107
What is the primary reason aircraft burn less fuel at high altitudes?
A) Increased air density
B) Decreased drag due to lower air density
C) More efficient engines at higher pressure
B) Decreased drag due to lower air density
108
What does the pressurisation system in an aircraft do to manage extreme temperature and pressure levels?
A) Maintain a constant internal temperature at high altitudes
B) Ensure proper fuel consumption
C) Provide oxygen and heating/cooling to the cabin
C) Provide oxygen and heating/cooling to the cabin
109
What is the purpose of the cabin pressurisation system’s compressed door seals and grommets?
A) To improve aerodynamics
B) To ensure the cabin remains airtight
C) To support airflow to the engines
B) To ensure the cabin remains airtight
110
What is a major challenge for engineers when designing aircraft to withstand pressurisation?
A) Minimising the weight of the aircraft
B) Preventing metal fatigue from pressurisation cycles
C) Maintaining the colour of the fuselage
B) Preventing metal fatigue from pressurisation cycles
111
What is the function of the manual mode in the pressurisation system?
A) Automatically adjusts cabin altitude
B) Allows the flight crew to control pressurisation manually in case of failure
C) Ensures fuel efficiency during flight
B) Allows the flight crew to control pressurisation manually in case of failure
112
What happens when the cabin altitude exceeds the aircraft’s maximum differential pressure?
A) The aircraft will automatically descend
B) The system switches from isobaric to differential mode to maintain pressure
C) The cabin pressurisation system shuts down
B) The system switches from isobaric to differential mode to maintain pressure
113
What is the typical rate of descent for an aircraft during a controlled descent?
A) 500 fpm
B) 300 fpm
C) 2000 fpm
B) 300 fpm
114
Which of the following modes maintains cabin pressure to a constant pressure difference between the inside and outside air, regardless of altitude?
A) Manual Mode
B) Differential Mode
C) Isobaric Mode
B) Differential Mode
115
How is cabin pressurisation controlled in modern aircraft?
A) By varying the amount of air entering the cabin and adjusting the rate of discharge through the outflow valves
B) By adjusting the aircraft's altitude and engine power
C) By manually adjusting the cabin temperature and airflow
A) By varying the amount of air entering the cabin and adjusting the rate of discharge through the outflow valves
116
What role do the outflow valves play in cabin pressurisation?
A) They regulate the air entering the cabin
B) They control the amount of air leaving the cabin to maintain the correct pressure
C) They filter the air entering the cabin
B) They control the amount of air leaving the cabin to maintain the correct pressure
117
How do outflow valves typically operate?
A) By using electrical signals to regulate air flow
B) By pneumatically responding to the settings on the flight deck pressurisation panel
C) By manually adjusting the valve positions from the cabin
B) By pneumatically responding to the settings on the flight deck pressurisation panel
118
What is a key feature of some outflow valves in aircraft?
A) They use only electrical motors to adjust valve positions
B) They combine pneumatic operation with electrical backup for manual control
C) They only operate during the cruise phase of flight
B) They combine pneumatic operation with electrical backup for manual control
119
What type of valve is used to prevent excessive positive pressure inside the cabin?
A) Negative safety valve
B) Excessive differential pressure relief valve (Positive safety valve)
C) Dump valve
B) Excessive differential pressure relief valve (Positive safety valve)
120
What does a negative safety valve prevent in the cabin?
A) Excessive positive pressure
B) Excessive negative pressure
C) Excessive airflow
B) Excessive negative pressure
121
What is the purpose of a dump valve in an aircraft's pressurisation system?
A) To increase the cabin pressure during flight
B) To quickly remove air from the cabin during emergencies or maintenance
C) To regulate the air entering the cabin from the engines
B) To quickly remove air from the cabin during emergencies or maintenance
122
Which of the following is a typical pressurisation gauge or indicator found on the flight deck?
A) Engine power gauge
B) Cabin differential pressure indicator
C) Fuel consumption gauge
B) Cabin differential pressure indicator
123
What does the 'ground/flight' switch control during taxi?
A) It adjusts the cabin pressure to 0.1 psi for a gradual transition
B) It increases the cabin pressure to match ambient conditions
C) It switches the aircraft's air conditioning to high mode
A) It adjusts the cabin pressure to 0.1 psi for a gradual transition
124
During takeoff, how does the pressurisation system control the cabin pressure?
A) By switching to proportional control based on the aircraft's climb rate
B) By maintaining a constant cabin pressure, regardless of altitude changes
C) By automatically closing the outflow valve to prevent air leakage
A) By switching to proportional control based on the aircraft's climb rate
125
When is the pressurisation system switched to isobaric control?
A) During the descent phase
B) Once the aircraft reaches cruise altitude
C) When the cabin pressure needs to be adjusted for maintenance
B) Once the aircraft reaches cruise altitude
126
What happens to cabin pressure during the descent phase?
A) The pressurisation system switches to proportional control to maintain a gradual descent rate
B) The outflow valves are closed to maintain cabin pressure
C) The cabin pressure increases to accommodate for a change in altitude
A) The pressurisation system switches to proportional control to maintain a gradual descent rate
127
How does the pressurisation system respond during landing?
A) The outflow valves remain closed to maintain the cabin pressure
B) The outflow valves are fully opened to equalise cabin and ambient pressures
C) The pressurisation system switches to manual mode to adjust cabin pressure
B) The outflow valves are fully opened to equalise cabin and ambient pressures
128
What is the maximum permissible rate of change for cabin pressure during flight?
A) 0.16 psi per minute
B) 500 ft per minute
C) 1500 ft per minute
A) 0.16 psi per minute
129
During rapid changes in altitude, what is typically monitored to avoid discomfort for passengers?
A) The aircraft's fuel efficiency
B) The cabin's rate of climb or descent
C) The external temperature at different altitudes
B) The cabin's rate of climb or descent
130
When is a pressurisation system leak rate test performed?
A) Only after a major system malfunction
B) After aircraft repairs and modifications to the pressure hull
C) Annually, regardless of system performance
B) After aircraft repairs and modifications to the pressure hull
131
What does the operation of a pressurisation controller typically involve?
A) Adjusting the aircraft’s engine power to maintain altitude
B) Sensing ambient and cabin pressure to adjust the outflow valves
C) Maintaining a constant cabin temperature
B) Sensing ambient and cabin pressure to adjust the outflow valves
132
What occurs if the maximum differential pressure is reached during flight?
A) The cabin pressure will continue to rise
B) The controller will prevent further increase in differential pressure
C) The aircraft will descend automatically to reduce cabin pressure
B) The controller will prevent further increase in differential pressure
133
What is the typical rate of descent for the cabin pressure during landing?
A) 500 ft per minute
B) 300 ft per minute
C) 200 ft per minute
B) 300 ft per minute
134
How is a pressurisation system manually operated in case of emergency?
A) By adjusting the cabin temperature
B) By using a manual control switch to position the outflow valves
C) By adjusting the engine thrust levers
B) By using a manual control switch to position the outflow valves
135
What is the primary function of the cabin pressure controller in modern aircraft?
A) To regulate engine power during flight
B) To control the cabin air pressure
C) To monitor fuel efficiency
B) To control the cabin air pressure
136
How did earlier aircraft control cabin pressure?
A) Using electrical signals to adjust the outflow valve
B) By pneumatic means for controlling cabin pressure
C) Through manual control of airflow into the cabin
B) By pneumatic means for controlling cabin pressure
137
How do modern aircraft cabin pressure systems differ from earlier systems?
A) They use only pneumatic controls
B) They use a combination of pneumatic, electric, and electronic controls
C) They rely solely on manual adjustments by the flight crew
B) They use a combination of pneumatic, electric, and electronic controls
138
Where is the cabin pressure controller located on most modern aircraft?
A) In the flight deck
B) In the electronics equipment bay, near the pressurised portion of the aircraft
C) Underneath the aircraft
B) In the electronics equipment bay, near the pressurised portion of the aircraft
139
What information is input to the cabin pressure controller?
A) Only the cabin altitude
B) Cabin pressure, ambient pressure, and other parameters like rate of climb
C) Only the ambient pressure
B) Cabin pressure, ambient pressure, and other parameters like rate of climb
140
How does the cabin pressure controller regulate the outflow valve?
A) By directly adjusting the valve's mechanical components
B) By sending electric signals to a torque motor that modulates airflow through the valve
C) By manually adjusting the valve from the flight deck
B) By sending electric signals to a torque motor that modulates airflow through the valve
141
What is the role of the air data computer (ADC) and flight management system (FMS) in pressurisation?
A) They provide the cabin crew with the ability to override automatic pressurisation
B) They supply the pressurisation controller with parameters for the pressurisation schedule
C) They monitor the cabin temperature
B) They supply the pressurisation controller with parameters for the pressurisation schedule
142
How does the pressurisation system function during normal flight operations?
A) It requires constant input from the crew to maintain pressurisation
B) It is fully automatic once initial parameters are set on the pressurisation control panel
C) It operates manually until the aircraft reaches cruising altitude
B) It is fully automatic once initial parameters are set on the pressurisation control panel
143
What feature do all pressurisation systems have in addition to automatic control?
A) A manual mode to override automatic control
B) A temperature control system
C) A system to increase cabin humidity
A) A manual mode to override automatic control
144
What happens when the operator selects the manual mode on the pressurisation control panel?
A) The automatic pressurisation system is locked in a preset state
B) The operator can manually control the outflow valve and pressurisation settings
C) The pressurisation system is turned off
B) The operator can manually control the outflow valve and pressurisation settings
145
How does entering a flight plan into the FMS affect the pressurisation system on some aircraft?
A) It provides the necessary parameters for the pressurisation schedule throughout the flight
B) It overrides the cabin altitude settings for the entire flight
C) It adjusts the engine power for optimal cabin pressure
A) It provides the necessary parameters for the pressurisation schedule throughout the flight
146
In modern pressurisation systems, which of the following is typically automatic?
A) The selection of the cabin altitude and rate of change
B) The monitoring of engine temperature
C) The adjustment of cabin temperature for comfort
A) The selection of the cabin altitude and rate of change
147
How are the inputs from the pressurisation panel processed in the cabin pressure controller?
A) They are manually adjusted by the flight crew
B) The signals are converted into digital signals for use by the controller
C) The panel displays the pressurisation status without affecting the system
B) The signals are converted into digital signals for use by the controller
148
What is the purpose of the torque motor in smaller aircraft pressurisation systems?
A) It adjusts the cabin temperature
B) It controls the rate of climb
C) It modulates the outflow valve to maintain the pressurisation schedule
C) It modulates the outflow valve to maintain the pressurisation schedule
149
Why might an aircraft's pressurisation system need to be manually controlled?
A) To override automatic settings for specific flight conditions or during maintenance
B) To decrease cabin humidity during flight
C) To manually adjust the cabin temperature for passenger comfort
A) To override automatic settings for specific flight conditions or during maintenance
150
What does the pressurisation controller primarily rely on for managing the pressurisation logic during flight?
A) Input from the flight crew only
B) A combination of cabin altitude, rate of climb, and barometric pressure settings
C) Engine performance parameters
B) A combination of cabin altitude, rate of climb, and barometric pressure settings
151
How do modern cabin pressure controllers use electrical signals?
A) To communicate with the flight crew during emergencies
B) To drive the torque motor in the outflow valve for automatic pressure regulation
C) To control the aircraft's speed and altitude during flight
B) To drive the torque motor in the outflow valve for automatic pressure regulation
152
What is a key difference between older and modern cabin pressure control systems?
A) Older systems used digital signals, while modern systems use pneumatic controls
B) Modern systems combine pneumatic, electric, and electronic controls, while older systems were purely pneumatic
C) Older systems were fully automatic, while modern systems require manual input
B) Modern systems combine pneumatic, electric, and electronic controls, while older systems were purely pneumatic
153
What is the primary benefit of having two cabin pressure controllers on modern aircraft?
A) To ensure redundancy, so one can take over if the other fails
B) To allow separate control of the cabin temperature and pressure
C) To allow for multiple pressurisation schedules during different flight phases
A) To ensure redundancy, so one can take over if the other fails
154
In what situation would the pressurisation system's manual mode be useful?
A) During normal cruise operations
B) During maintenance or if automatic control fails
C) During the aircraft's pre-flight inspection
B) During maintenance or if automatic control fails
155
What is the primary purpose of using leak detectors in vapour cycle air conditioning systems?
A) To detect excessive refrigerant pressure
B) To find leaks that could cause refrigerant loss
C) To monitor temperature changes within the system
B) To find leaks that could cause refrigerant loss
156
What type of alarms do electronic leak detectors typically trigger?
A) Audio-only alarms
B) Visual and audible alarms
C) Visual-only alarms
B) Visual and audible alarms
157
Which leak detection method involves applying a soapy solution to fittings?
A) Electronic leak detection
B) Dye injection detection
C) Bubbles forming to indicate leaks
C) Bubbles forming to indicate leaks
158
What is a common issue with old hoses in the vapour cycle system?
A) They may become too rigid to allow refrigerant to flow
B) They may become porous and leak refrigerant over time
C) They may develop corrosion from prolonged exposure to refrigerant
B) They may become porous and leak refrigerant over time
159
Which refrigerant was banned in the early 1980s due to its harmful effects on the Earth's ozone layer?
A) R134a
B) R12
C) R22
B) R12
160
What is required by government legislation when servicing vapour cycle air conditioning systems?
A) Release of refrigerant into the atmosphere
B) Capture and recycling of refrigerant
C) Use of only R12 refrigerant
B) Capture and recycling of refrigerant
161
What is the purpose of a manifold set in vapour cycle system servicing?
A) To monitor refrigerant temperature
B) To connect gauges, valves, and hoses for servicing the system
C) To generate refrigerant pressure
B) To connect gauges, valves, and hoses for servicing the system
162
What does the centre fitting on a manifold set connect to?
A) The refrigerant supply or vacuum pump
B) The high-pressure side of the system
C) The low-pressure side of the system
A) The refrigerant supply or vacuum pump
163
What does the low-pressure gauge on a manifold set typically measure?
A) Vacuum level
B) Temperature
C) Pressure in psi, usually ranging from 0 to 150 psi
C) Pressure in psi, usually ranging from 0 to 150 psi
164
How is refrigerant charged into a vapour cycle system using a manifold set?
A) By manually adjusting valves to control refrigerant flow
B) By turning the refrigerant container upside down
C) By using a vacuum to draw refrigerant into the system
A) By manually adjusting valves to control refrigerant flow
165
What type of equipment is now commonly used to collect refrigerant during servicing, rather than a manifold set?
A) A refrigeration service unit designed for refrigerant collection
B) A vacuum pump
C) A pressure relief valve
A) A refrigeration service unit designed for refrigerant collection
166
What is a key feature of high-quality vapour cycle servicing units?
A) They require manual operation for each function
B) They can perform all servicing functions automatically once hoses are connected
C) They can only evacuate the system but cannot charge it
B) They can perform all servicing functions automatically once hoses are connected
167
What is the typical size of refrigerant containers used for servicing vapour cycle systems?
A) 1 oz
B) 12 oz to 50 lbs
C) 1 lb to 10 lbs
B) 12 oz to 50 lbs
168
How does the vacuum pump function when servicing a vapour cycle air conditioning system?
A) It charges the system with refrigerant
B) It removes moisture from the system to prevent corrosion
C) It increases system pressure to facilitate cooling
B) It removes moisture from the system to prevent corrosion
169
What is the recommended vacuum holding time to ensure that all moisture is removed from the system?
A) 5-10 minutes
B) 15-30 minutes
C) 45-60 minutes
B) 15-30 minutes
170
What should be checked during a visual inspection of a vapour cycle system?
A) Only the refrigerant level
B) The condition of components, alignment, and leakage
C) The colour of refrigerant
B) The condition of components, alignment, and leakage
171
How can dirt in the evaporator or condenser fins affect the system?
A) It causes a system shutdown
B) It restricts airflow and prevents effective heat exchange
C) It increases refrigerant consumption
B) It restricts airflow and prevents effective heat exchange
172
What should be checked on the condenser during a visual inspection?
A) For ice formation
B) For the presence of debris obstructing airflow
C) For signs of refrigerant leakage
B) For the presence of debris obstructing airflow
173
What should be checked on the evaporator to ensure it functions correctly?
A) It should be ice-free to prevent ineffective heat exchange
B) It should be covered in a thin layer of frost for maximum cooling
C) It should be disconnected from the system for maintenance
A) It should be ice-free to prevent ineffective heat exchange
174
What is the correct procedure for adding oil to a vapour cycle system during servicing?
A) Add oil only when the refrigerant is low
B) Add 1/4 ounce of oil for each pound of refrigerant added to the system
C) Add oil every time a component is changed, regardless of refrigerant levels
B) Add 1/4 ounce of oil for each pound of refrigerant added to the system
175
What can cause ice formation on the evaporator in a vapour cycle system?
A) The system being overcharged with refrigerant
B) The presence of dirt on the evaporator
C) The system being low on refrigerant or a faulty expansion valve
C) The system being low on refrigerant or a faulty expansion valve
176
Why is it important to check the alignment and security of the compressor during inspection?
A) To ensure it is properly lubricated
B) To ensure it is functioning at optimal pressure
C) To ensure it operates smoothly and is not under stress due to improper alignment
C) To ensure it operates smoothly and is not under stress due to improper alignment
177
What is the purpose of the pressure sensor in a vapour cycle air conditioning system?
A) To regulate the amount of refrigerant in the system
B) To monitor the pressure and help control system operations
C) To measure the temperature of the refrigerant
B) To monitor the pressure and help control system operations
178
How should the compressor belts be checked during a system inspection?
A) For tension and wear
B) For contamination by refrigerant
C) For excessive heat buildup
A) For tension and wear
179
What is the typical oil addition rule when changing components in the vapour cycle system?
A) Add no oil unless the system is completely empty
B) Add additional oil to replace oil lost in the replaced component
C) Add oil only if the system shows signs of oil leaks
B) Add additional oil to replace oil lost in the replaced component
180
What is the most obvious sign of a possible leak in a vapour cycle air conditioning system?
a) High refrigerant levels
b) Low refrigerant levels
c) Presence of ice
b) Low refrigerant levels
181
What indicates that more refrigerant is needed in a vapour cycle system?
a) High temperature in the evaporator
b) Low refrigerant pressure
c) Bubbles in the sight glass
c) Bubbles in the sight glass
182
When all refrigerant escapes from the system, what should be done to locate the leak?
a) Visually inspect the system
b) Partially charge the system with refrigerant
c) Replace the compressor
b) Partially charge the system with refrigerant
183
How much refrigerant pressure is required in the high and low sides for a leak check?
a) 100 psi
b) 50 psi
c) 75 psi
b) 50 psi
184
What needs to be done if a vapour cycle air conditioning system loses all its refrigerant charge?
a) Add refrigerant immediately
b) Perform a full system evacuation
c) Replace the receiver dryer
b) Perform a full system evacuation
185
What should be checked to verify the performance of a vapour cycle air conditioning system?
a) The size of the system
b) The pressure in the system
c) The temperature of the air cooled by the evaporator
c) The temperature of the air cooled by the evaporator
186
What is the expected temperature range of air cooled by the evaporator?
a) 0-4 °C
b) 4-10 °C
c) 10-15 °C
b) 4-10 °C
187
What should be done if discrepancies are found during a feel test of the vapour cycle system?
a) Replace the compressor
b) Investigate further
c) Add more refrigerant
b) Investigate further
188
What does purging the system involve?
a) Removing air and moisture from the system
b) Adding more refrigerant
c) Replacing the receiver dryer
a) Removing air and moisture from the system
189
What should be used to recover refrigerant when purging a vapour cycle system?
a) A vacuum pump
b) A service cart with recovery capabilities
c) A nitrogen tank
b) A service cart with recovery capabilities
190
When should the oil quantity in the compressor be checked?
a) After each performance test
b) When the system is purged
c) During normal operation
b) When the system is purged
191
What should be used to check the oil level in the compressor?
a) A dipstick
b) A pressure gauge
c) A thermometer
a) A dipstick
192
What must be done if there are signs of contamination in the system during purging?
a) Flush the system clean
b) Replace the compressor
c) Recharge the system immediately
a) Flush the system clean
193
What must be done after purging the system if the compressor was removed for oil inspection?
a) Evacuate the system
b) Add new refrigerant
c) Replace the receiver dryer
a) Evacuate the system
194
What happens if the system refrigerant charge falls below atmospheric pressure?
a) The system must be recharged immediately
b) The system must be evacuated
c) The compressor will shut down
b) The system must be evacuated
195
How does the compressor draw refrigerant into the system during charging?
a) By opening the high side valve
b) By running the engine at high idle speed
c) By drawing refrigerant directly from the recovery tank
b) By running the engine at high idle speed
196
What is the standard amount of oil added to a system during charging?
a) 1/4 ounce per pound of refrigerant
b) 1/2 ounce per pound of refrigerant
c) 1 ounce per pound of refrigerant
a) 1/4 ounce per pound of refrigerant
197
What is the role of a bleed air leak in an aircraft pneumatic system?
a) To regulate cabin pressure
b) To prevent overheating of components
c) To control airspeed
b) To prevent overheating of components
198
What is used to monitor the function of the bleed air system?
a) Flight deck gauges
b) Cabin air pressure sensors
c) Fuel pressure gauges
a) Flight deck gauges
199
What is the function of the flow control valve in a bleed air system?
a) To regulate cabin humidity
b) To control the flow of air to the system
c) To measure refrigerant pressure
b) To control the flow of air to the system
200
What happens if an overheat condition occurs in the air conditioning pack?
a) The pack automatically shuts down
b) The temperature sensor resets the system
c) The pack continues to operate at high speed
a) The pack automatically shuts down
201
What is displayed on the flight deck if an overheat occurs in the air conditioning pack?
a) ‘FAULT’ warning
b) ‘OVERHEAT’ warning
c) ‘LOW PRESSURE’ warning
b) ‘OVERHEAT’ warning
202
What is the purpose of the Central Warning Panel (CWP)?
a) To provide flight crew with status information on all aircraft systems
b) To monitor the flight path
c) To indicate the temperature in the cabin
a) To provide flight crew with status information on all aircraft systems
203
What do red indicator lights on the CWP signify?
a) A system is in use
b) A system’s condition is critical and requires immediate attention
c) A system is under maintenance
b) A system’s condition is critical and requires immediate attention
204
What is an example of an attention getter in the warning system?
a) A flashing light on the CWP
b) A continuous tone from the speakers
c) A visual warning on the outside of the aircraft
a) A flashing light on the CWP
205
What happens when the cabin altitude exceeds 10,000 feet?
a) The flight crew is notified via the CWP
b) The air conditioning system automatically shuts down
c) Emergency oxygen is deployed
a) The flight crew is notified via the CWP
206
What altitude does the Boeing 737 pressurisation system typically maintain during normal operation?
a) 8,000 feet
b) 10,000 feet
c) 12,000 feet
a) 8,000 feet
