! ! WARNING ! !
Above is Zulu Time!!
ATA 21 Air conditioning
The air conditioning system is provided to keep the environment which contain passengers or cargo as well as all other pressurized compartments at a pre-selected pressurization level, also the temperature, humidity and cleanliness is kept at a comfortable level for the passengers and crew. And this during the compete flight as well as on the ground. The air conditioning system also ventilates; the avionics compartment, the lavatories and galleys.
Where does the pneumatics come from?
The conditioning air is taken from the following possible sources :
What does the air conditioning system do?
The air conditioning blows the air into the cabin after it is checked on temperature and pressure. The air conditioning system is also known as “the packs” being “pack #1” and “pack#2” or left and right pack. Eventually the conditioned air gets dumped overboard after passed trough the cabin creating a continuous air flow so their always fresh air coming into the airplane.
But it also keeps the cabin pressure inside the plane at a certain level, think of your popping ears!
How does the crew keep it so nice in the cabin?
To supply the passengers the highest possible comfort during flight all variations are controlled within the system. This can be done automatically, or manually.
In this case the most airplanes have a device called a “RAM AIR INLET”, this is a little door somewhere in the fuselage, equipped with a actuator that will open/close the ram air door. Ram air is the air that due to the forward movement of the airplane will be “forced” into the intake. So in fact the ram air inlet can only be used during flight because of the movement required to “ram” the air inside the inlet. It will only be used in case of emergency.
Inside the electronic racks below the floor there is also ventilation provided to cool the electronic boxes. In case the plane is on the ground without any bleed supply from neither APU or engine or ground supply for that matter, the airplane is sometimes equipped with another device called a ground blower, like the A300 I worked on. This will take over from the air conditioning system to cool the electronic boxes, because else they will overheat and possibly cause a fire down below.
Article last modified on 10/06/2015