Podcast
Questions and Answers
What is the basic system of cabin pressurization?
What is the basic system of cabin pressurization?
- Arrange a constant inlet and vary the outlet (correct)
- Arrange a constant outlet and vary the inlet
- Arrange both the inlet and outlet
- None of the above
What is the purpose of the differential capsule in a pressure controller?
What is the purpose of the differential capsule in a pressure controller?
- To control cabin differential pressure (correct)
- To maintain a constant cabin pressure
- To control the rate of pressurization
- To control cabin air flow
When is control of the rate of change of cabin pressure more important?
When is control of the rate of change of cabin pressure more important?
- It is not important to control the rate of change
- During ascent
- Equally important during ascent and descent
- During descent (correct)
What happens if the cabin pressure increases with the aircraft at maximum differential pressure?
What happens if the cabin pressure increases with the aircraft at maximum differential pressure?
What happens if the cabin altitude increases above the normal maximum?
What happens if the cabin altitude increases above the normal maximum?
Where is the water separator located?
Where is the water separator located?
What is a comfortable rate of cabin altitude climb for passengers?
What is a comfortable rate of cabin altitude climb for passengers?
What should be checked before carrying out a ground pressure check?
What should be checked before carrying out a ground pressure check?
What happens to the outflow valve on touch-down of the aircraft?
What happens to the outflow valve on touch-down of the aircraft?
What is the maximum velocity of air from the cabin ventilation system?
What is the maximum velocity of air from the cabin ventilation system?
As an aircraft descends from cruising altitude, the cabin altitude will:
As an aircraft descends from cruising altitude, the cabin altitude will:
Which of the following systems utilizes a refrigerant?
Which of the following systems utilizes a refrigerant?
If the signal line between the controller and discharge valve is leaking, the cabin pressure will:
If the signal line between the controller and discharge valve is leaking, the cabin pressure will:
The primary function of a spill valve is to:
The primary function of a spill valve is to:
Which component is responsible for protecting the cabin altitude from reaching an altitude of 13,000 ft?
Which component is responsible for protecting the cabin altitude from reaching an altitude of 13,000 ft?
If the cabin over-pressure relief valve opens, it indicates that:
If the cabin over-pressure relief valve opens, it indicates that:
What is the correct procedure for manually controlling the pressurization system?
What is the correct procedure for manually controlling the pressurization system?
What is the purpose of a sub-cooler in a typical vapor cycle system?
What is the purpose of a sub-cooler in a typical vapor cycle system?
How is heat added to the air in an air conditioning system?
How is heat added to the air in an air conditioning system?
Which component can be used on the ground to supply air in an air conditioning system?
Which component can be used on the ground to supply air in an air conditioning system?
What is the primary function of an air conditioning system?
What is the primary function of an air conditioning system?
What does an air cycle machine turbine do?
What does an air cycle machine turbine do?
What does the cabin differential pressure gauge in a pressurized aircraft measure?
What does the cabin differential pressure gauge in a pressurized aircraft measure?
What happens when the pressure controller is set to 0 ft?
What happens when the pressure controller is set to 0 ft?
During a pressurization check at maximum differential pressure, if the engines are shut down, what happens?
During a pressurization check at maximum differential pressure, if the engines are shut down, what happens?
Where is the water trap located in a bootstrap compressor?
Where is the water trap located in a bootstrap compressor?
What happens to the cabin rate of climb (R.O.C.) during a normal pressurized climb after takeoff?
What happens to the cabin rate of climb (R.O.C.) during a normal pressurized climb after takeoff?
When do the inward vent valves operate in a pressurized aircraft?
When do the inward vent valves operate in a pressurized aircraft?
What is cabin differential pressure?
What is cabin differential pressure?
What does cabin altitude represent in pressurized flight?
What does cabin altitude represent in pressurized flight?
How is temperature conditioning mainly achieved in pressurized aircraft?
How is temperature conditioning mainly achieved in pressurized aircraft?
If pressurization air comes from an engine compressor and there is an internal oil leak, what will happen?
If pressurization air comes from an engine compressor and there is an internal oil leak, what will happen?
How does a cold air unit produce a drop in temperature?
How does a cold air unit produce a drop in temperature?
What is the primary source of heating for pressure cabins?
What is the primary source of heating for pressure cabins?
When an aircraft has reached maximum differential pressure and is at a constant altitude, what does the pressurization system allow?
When an aircraft has reached maximum differential pressure and is at a constant altitude, what does the pressurization system allow?
What combination of components controls the ventilating and pressurizing air released to the atmosphere?
What combination of components controls the ventilating and pressurizing air released to the atmosphere?
Where is the silencer located in a 'blower' air conditioning system?
Where is the silencer located in a 'blower' air conditioning system?
When does a 'blower' air conditioning system produce the most air?
When does a 'blower' air conditioning system produce the most air?
What is the function of an air mass flow control valve?
What is the function of an air mass flow control valve?
In a cabin air recirculation system, what proportions of fresh air and recirculated air are supplied?
In a cabin air recirculation system, what proportions of fresh air and recirculated air are supplied?
How is cabin pressure maintained in an air conditioning system?
How is cabin pressure maintained in an air conditioning system?
What controls the rate of change of cabin pressure during flight?
What controls the rate of change of cabin pressure during flight?
What is the purpose of an air-to-air heat exchanger in an aircraft?
What is the purpose of an air-to-air heat exchanger in an aircraft?
Study Notes
Cabin Pressurisation and Air Conditioning
- During normal pressurized climb, cabin rate of climb (ROC) is less than ambient ROC.
- Inward vent valves operate when cabin altitude exceeds aircraft altitude.
- Cabin differential pressure is the difference between cabin pressure and ambient pressure.
- Cabin altitude in pressurized flight is the altitude corresponding to cabin pressure, regardless of aircraft altitude.
Temperature Control
- Temperature conditioning is mainly achieved by extracting heat from the pressurizing air.
- Heating for pressurized cabins is obtained from air supply heated by the pressurizing process.
- A cold air unit produces a drop in temperature by reducing pressure and driving the unit's compressor.
- A cold air unit allows cabin temperatures to be a little more than ambient air temperature, despite compression heating.
Pressure Control
- Control of rate of change of cabin pressure is more important in descent.
- The purpose of the differential capsule in a pressure controller is to control cabin differential pressure.
- The basic system of cabin pressurization is to arrange a constant inlet and vary the outlet.
- Control of ventilating and pressurizing air released to the atmosphere is achieved by a pressure controller/dump valve combination.
Ventilation and Air Distribution
- The velocity of air from the cabin ventilation system should not exceed 120 feet per second.
- Air supplied for pressurization and conditioning is hottest from an engine compressor bleed.
- An air-to-air heat exchanger is provided to reduce the air supply temperature.
- Temperature control of cabin air is achieved by regulating the amount of air by-passing the cooling system.
Safety Features
- A warning light comes on in the cockpit if the cabin altitude increases above the normal maximum.
- On touch-down, the outflow valve will be fully open.
- Ditching control is used to close the outflow valves.
System Components
- A water separator is located downstream of the turbine.
- A spill valve opens to control the flow to the cabin.
- An air mass flow control valve is used to maintain a reasonably constant air mass flow into the cabin at all altitudes.
Testing and Maintenance
- Before carrying out a ground pressure check, all pitot and static lines must be fitted.
- On ground, internal doors, cupboards, etc. must be open during pressurization testing.
- Prior to conducting a ground pressurization test, it is necessary to set QFE.
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Description
Test your knowledge on aircraft altitude changes and refrigerants with this quiz. Questions cover topics such as cabin altitude adjustments during descent and the use of refrigerants in different systems. This quiz is based on information from the Jeppesen A&P Technician Airframe Textbook.
