11.4 Air Conditioning Flashcards
Air supply sources
Engine
APU
ground pneumatic cart
Emergency ram air system purpose
Ventilate cockpit and cabin if all packs fail
ATA 36
Pneumatics
ATA 21
Air con
HEPA
High efficiency perticulate air filter
Ideal temp
In cabin
Between 70 and 80f
Or 21 and 27c
Ideal humidity
30%
How many pounds of fresh air per minute in cabin
0.55lbs fresh air per person per minute
HEPA filter efficiency
85 to 99.995%
Aircraft cooling systems
- Vapour cycle cooling system( small aircraft)
* air cycle cooling system ( large aircraft)
Vapour cycle cooling system systems:
• compressor
When vapour compressed its pressure and temp increases
Vapour cycle cooling system systems:
• condenser
Condenses hot refrigerant gas from compressor
Vapour cycle cooling system systems:
• the reciever dryer
Serves as resevoir for liquid refrigerant
Vapour cycle cooling system systems:
• the theromostatic expansion valve
Regulates the amount of liquid flowing into evaporator
Vapour cycle cooling system systems:
• the evaporator
Absorbs the heat of aircraft cabin into refrerant . As heat abaorbed the refrigerant evaporates
Vapour cycle cooling system systems:
• refrigerant
You want a refrigerant with low boiling point so it turns to vapour quicker
Air cycle cooling system
AKA air conditioning packs , installed in newest aircraft
Air cycle cooling system ( systems )
• flow control valve
AKA pack valve
Air cycle cooling system ( systems )
• air cycle machine (ACM)
Consists of turbine which drives compressor , compressor increases pressure and temp
Air cycle cooling system ( systems )
• turbine by pass valve
Controls pack outlet temp
• AKA temp control valve
Air cycle cooling system ( systems )
• water seperator valve
Collects excess moisture before it enters the cabin
Air cycle cooling system ( systems )
• pack anti ice valve
Removes and prevents ice at turbine outlet and water seperator
Air cycle cooling system ( systems )
• ram air inlet and outlet doors
Used to control amount of cooling airflow across the heat exchanger
Air cycle cooling system ( systems )
• fan bypass check valve
It opens if amount of ram airflow is higher than the cooling fan delivers
Where is aircraft most efficient
High altitude
Cabin climb rate?
500 feet per minute (max)
Descent rate?
300 feet per minute (max)
How is cabin altitude measured
Adding ambient pressure to pressure inside aircraft
Where is outflow valve when plane is landed?
Fully open
Pressurisation control systems:
• outflow valve
• Modulates cabin air
Pressurisation control systems:
• pressure controller
Provides control signals to the outflow valve ac motors
Pressurisation control systems:
• control panel
Contains all necessary selectors and indicators for the fligjt crew to operate the pressurisation system.
Excessive rate of cabin altitude:
Greater than 3100 feet per minute or descend greater than 2000 feet per minute
Safety and warning devices:
• pressure relief valves
Designed to open if too much pressure difference
Safety and warning devices:
• negative relief valves
- AKA vacuum relief valves
* equalise a possible negative pressure difference duriny descent
Safety and warning devices:
• pressure system monitoring
- At 10,000 feet warning for cabin altitude
* at 14,000 oxygen masks drop
Purpose of emergency ram system
Ventillate cockpit if packs fail
Why cant air con packs be used at the same time
High cabin airflow may damage the air con ducts
What component extracts cabin air
Evaporator
Max pressure in aircraft is determined by?
Strength of cabin
To decrease cabin altitude:
Outflow valves must be closed
Purpose of pack valves
Allows certain amount of bleed air from engine through to the pack system and as trim air
% of air recirculated
30-55
How is temp in cabin controlled
Through a pack : vapour syetem, air cooling system
What is charge air
Bleed air from engine
What is ram air
Air used to cool packs
Boot strap system?
Pack system ( air cycle cooling system )
How is air distributed into cabin and cargo bays
Exit louvers
Location of trim air valve
Downstream of the packs
Components of air cycle machine (acm)
Turbine , compressor , cooling fan
Purpose of thermostatic expansion valve
Regulate liquid flowing into evaporator
What controls cabin pressure
Outflow valve
Purpose of dessicant in reciever dryer?
Absorbs moisture from refrigerant
Purpose of turbine
Drives compressor