Air Conditioning Flashcards
What position is the APU bleed air switch normally in?
ENgine bleed air switches?
On- air con logic automatically opens and closes the valve
On- will indícate closed if other bleed sources are powering AC (APU or ground air)
Also will show off until pressure is available to open the valve.
Which section does bleed air normally come from?
IP - Intermediate section
During start what do the bleed valve AND PRV valves do on the starting engine?
When you pull the start switch on the overhead:
The Bleed valve opens to allow air to pass through the start valve to get to the engine to turn it.
The PRV VALVE closes to prevent flow into the compressor section
When you put the FUEL CONTROL SWITCH on the CENTER pedestal to RUN that opens the START VALVE turning the engine.
At 50%N2 the start valve closes again, the PRV valve then opens allowing the engine to supply bleeds to the packs once again.
Do the lower cargo lines receive air conditioned by trim air?
No, it’s straight from the bleed air duct
Thus if the master trim air valve is closed it does not affect the lower cargo heat.
What is meant by the master trim valve?
It is the valve that allows the hot bleed air to flow to 3 other trim air modulating valves that supply the different zones.
The modulating valve that serves the coldest zone remains closed to allow maximum cooling.
What is the temp range for cargo and main deck?
4-29C
Which packs supply air directly to the fwd and aft cargo?
Fwd- pack 3
Aft - pack 2
In LOW positions the associated pack provide 2/3 flow to cargo and 1/3 to ac manifold
OFF- they provide no air to the cargo. 100% to the AC manifold.
HIGH - all of the associated pack conditions the assoc cargo compartment.
Basically OFF and HIGH are opposites. One or the other manifold or cargo
On the ground, before having at least two engines started where does the equipment cooling air exhaust to?
After the second engine is started where does the air go?
Before the second engine is started it exhausts into the fwd cargo. If the temp is high then it flows outside through the GROUND EXHAUST VALVE.
After the second engine start, the GROUND EXHAUST VALVE closes.
You can force this by turning the equip cooling switch to STANDBY
If in NORM OR STBY modes for equip cooling and 1 supply fan fails, what does the system automatically do?
Goes into a closed loop mode by closing the GROUND EXHAUST VALVE, INBOARD SUPPLY VALVE and the INBOARD EXHAUST VALVE.
(Basically shuts off incoming and outgoing air)
Explain how the aft cargo heat works?
When you turn the switch on it opens two valves: TEMP CONTR VALVE AND OVERHEAT SHUTOFF VALVE. These allow air to flow into the compartment from pack 2.
The heat control is in the cargo compartment (HI/LO)
If using the LLCAFR switch it will close the TEMP CONTROL VALVE. However if the temp in the floor of the aft cargo that valve reopens heating the compartment.
