Air Conditioning/Packs CBT's Flashcards
How many packs?
3
How high can the APU run pack (s)?
It can run only 1 pack up to 15,000’
What is a PTC?
Pack Temperature Controller
What does OFF, NORM, A, and B mean on a pack selector?
Off: Turns off the pack
NORM: Automatically alternates between pack controller A or B on alternate flights.
A and B: Can select individual PTC channels. (Switches to the other if selected controller fails)
What does trim air do?
It allows independent temperature control for all 7 zones.
(Only 3 packs, but 7 temp zones. How do all 7 have independent temp control? Trim air)
What does the high flow switch do?
Allows you to toggle between normal flow and high flow.
Normal flow provides improved fuel efficiency, but high flow provides better cooling and ventilation.
How many zones are on the Freighter B747 Aircraft?
7
With the trim air switch OFF, can you manually select either PTC A or B?
No, it is inhibited. Trim air must be ON to manually select a PTC. With the trim air switch OFF, PTC A is selected. Only if A fails will it switch to B
How much does fuel consumption go up by when you use HI FLOW on the packs?
Each pack that operates in HI FLOW will increase the total fuel consumption by approximately 0.3% per operating pack.
When would a pack automatically shut down? What would happen?
When a PTC fault or a pack overheat is detected.
It would close the respective pack valve.
Hot air that is vented out of the flight deck electrical equipment and electrical equipment (EE) compartments is blown where?
4 basic configurations:
Normal 1: On the ground, engines off, with moderate or higher ambient temp- Air is vented overboard.
Normal 2: On ground with no engines and cold ambient temp, on ground w/ 1+ engines running, or temp goal is 10C or higher in FWD LL, or STBY mode -Vents into FWD LL.
Closed loop: Temp goal lower than 10C in FWD LL, or single internal fault, or main CARGO fire switch armed - Air just goes in circles.
Smoke override: Inflight with both internal fans failed, or FWD or AFT LL cargo fire arm switches armed, or OVRD mode selected,
On the EQUIP COOLING selector, what does STBY do?
Closes the ground exhaust valve and configures the cooling for flight. All other automatic system operation is the same as NORM
On the EQUIP COOLING selector, what does NORM do?
Ground operation is based on ambient temperature. Configuration of the system is automatic based on system logic.
On the EQUIP COOLING selector, what does OVRD do?
-Used only if the fans fail.
1.) Closes external and internal exhaust valves and closes the air supply valve.
2.) Cooling air is sucked in from the flight panels by the negative pressure caused by the fans
3.) Opens the smoke exhaust valve and the hot air gets exhausted out that valve.
What dictates the pack outlet temperature?
The temperature zone requiring the coolest temperature
What is a ZTC?
Zone temperature controller
How do you control the temperature of all the different areas of the airplane?
By setting the cold pack outlet
temperature and then adding trim
air to selected zones as required.
What determines the pack flow rate?
- the phase of flight,
- the number of packs operating, and
- the position of the Lower Lobe Cargo Conditioned Air Flow Rate selector.
On a temperature control rheostat, there is a 6 o’ clock MAN position. What does this do?
You can take manual control of the trim air valve. Turn it left towards C to close the valve and right towards W to open it. When you let go, the valve stays where it is at.
What does the flight deck FAN button do?
Its used when on the ground. With no packs on, it just increases air circulation. With a pack on, it increases conditioned air.
What is the normal position of the master trim air button?
ON
What happens if the master trim air button is OFF?
· Master trim air valve closes
· Pack output temperature in the backup mode.
· Cabin temperature panel control of the crew rest area and upper
deck zone temperatures inhibited.
· PTC A selected (automatic and manual selection of PTC B inhibited)
· If PTC A fails, PTC B controller automatically selected.
What causes the ZONE RST button to display a FAULT light?
· A temperature zone duct overheat or ZTC fault has occurred OR
· The master trim air valve has failed closed OR
· The Trim Air switch is OFF OR
· The master trim air valve is closed and pack air continues to flow.
Why is there an aft cargo heat switch and not a forward cargo heat switch?
Because aft cargo heat is provided from the center bleed air manifold as opposed to the forward which is heated by the flight deck electrical and EE compartments.
