11.4 Air Conditioning Flashcards
Does atmospheric pressure increase or deafness with increase in altitude?
Atmospheric pressure decreases
What altitude do modern aircraft operate at?
40,000ft
What’s the maximum cabin altitude during flight?
8,000ft
What is the positive cabin rate?
Don’t exceed 500ft per minute
What is the negative cabin rate?
Don’t exceed 300ft per minute
What happens when cabin pressure increases to 10,000ft?
Crew put oxygen masks on
What happens when cabin pressure increases to 14,000ft?
Oxygen masks come down from passenger cabin ceiling
What happens when cabin pressure increases to 15,000ft?
Outflow valves close automatically
To prevent differential pressure what happens?
Two saftey valves
- positive and negative pressure relief valves
What three modes does the cabin pressurisation system have?
Automatic
Semi- Automatic
Manual
What does the ditching push button do?
Isolates the cabin from any water entering during an emergency landing (closes all valves)
An outflow valve normally has…?
3 motors
2 AC
1 DC
When cabin pressurisation system is switches to manual mode, what motor is used?
DC motor
During pressure leakage test what is cabin pressurised to?
4 psi above ambient pressure
What is the minimum number of sensors you can have in a pack?
3
What system reduces the operational costs of air conditioning?
Recirculation system
What is required to compensate for different cooling and heating effects?
A zone temperature control system
In an emergency how do you use air conditioning?
Emergency ram air inlet
What is the purpose of the trim air valve ?
Controls the amount of hot air that is mixed with cold supply air
Where is a separate ventilation system used?
Galleys and lavatories
What is the main air source?
Engine compressor
What temperature do the electrical heaters automatically switch in?
Below 7 degrees C
What are the 4 different cargo ventilation types?
- non ventilation
- ventilation and heated
- ventilation and unheated
- air conditioned cargo
What does HP mean?
Hugh pressure
What does IP mean?
Intermediate pressure
When is HP compressor used?
When low engine RPM
When is IP compressor used?
When high engine RPM
What does the bleed air valve do?
It regulates pressure to maintain a constant level of pressure
What can source air supply?
- engine
- APU
- external air supply
- high pressure ground connection
Why do we need air conditioning?
- provide temperature control
- ventilation
- pressurisation of the cabin
What are the air ducts monitored by?
Leak detection system
What temperature must the air be under when coming from the engine?
200 degrees c
What do you use to cool down air at bleed valve?
Precooler from fan air
How are non pressurised areas separated?
Pressure bulkheads
What areas aren’t pressurised?
- radome
- landing gear
- tailcone
What is ideal cabin altitude?
2500- 8000ft
What does pressure differential mean?
The difference between cabin and ambient pressure
What’s a disadvantage of a heat exchanger?
Not enough power to cool all of cabin air
How does a heat exchanger work?
One fluid passes through a tube while another fluid circulates around the partitions
- allows for heat exchanges without fluids mixing together
How do we clean the air in the cabin?
Air filters
What is the allowable temperature within the cabin?
18- 30 degree C
What does the regulation sauna single person needs to be supplied with fresh air?
0.283 cubic meters per minute per person
What 5 things must you ensure about the air in the cabin?
- fresh
- clean
- comfortable temperature
- correct humidity
- correct pressure
What are 2 characterises of air going to an air cycle machine?
High pressure and hot
What is the function of a cooling pack?
Cool hot bleed air to a valve given by the pack controller
What are air cycle machines driven by?
Turbines
What is a basic cycle for an air cycle machine?
- Hot air flows to compressor
- Then hot, high pressure air flows to heat exchanger
- ambient air flows across, decreasing the temperature, but pressure stays the same.
- Then flows to the turbine, where it expands and cools again
- Then cold air goes into the cabin
What is the basic series for a vapour system?
- An expansion valve expands a special pressurised cooling fluid
- Resulting in fluid becoming cold
- This cold fluid flows through an evaporator which is heated by cabin air, which flows across the evaporator
- Therefore reducing cabin air temperature
What is the purpose of the pack valve
Determines the amount of air going into the cabin
What is the purpose of the check valve?
Prevents back flow into the pack
What is the purpose of the water separator?
Remove moister from bleed air and anti - ice valve
What is the purpose of the ozone converter?
- Helps maintain a health cabin and provide comfort for passengers and crew
- prevent jet lag or air sickness
What is the reason for a fan in the ram air?
For when on the ground as there is no ram effect
What are the 3 primary components of an air cycle system?
Compressor, turbine and fan
What type of inlet is the ram air inlet?
NACA type air inlet
What type of valve is the bypass valve?
Butterfly valve
What is the purpose of the bypass valve?
Adjust the temperature in the pack
What is the normally temperature and PSI of the air that goes into the pack valve?
200 degrees c
45 PSI
What type of bearings are used in an air cycle machine?
Air bearings
What 4 things does a vapour cycle system pass through?
- Expansion valve
- Evaporator
- Compressor
- Condenser
