A320 Avionic cooling logic
 

Hi all

Regarding Avionic cooling on A320 fleet

The FCOMS says

CLOSED CONFIGURATION (Flight and ground)

Flight phase
The threshold is
+35c and increasing
+32c and decreasing

Ground phase
The threshold is
+12c and increasing
+9c and decreasing

INTERMEDIATE CONFIGURATION (Inflight only)

The threshold is
+35c and increasing
+32c and decreasing

OPEN CONFIGURATION (On ground only)

The threshold is

+12c and increasing
+9c and decreasing



I do understand that the 3 degrees split is for the computer not to go crazy.

I am trying to visualize the above logic, any idea to simplify this ?

Highly appreciate your knowledge sharing.

Open:
-This configuration is used if warm ambient conditions exist while the aircraft is on the ground.
-Outside air is drawn through the open inlet valve by the blower fan where it then passes around the avionics equipment.
-The extract fan then pulls the heated air and expels it out through the fully open extract valve.
-Avionics compartment air does not pass through the aircraft skin heat exchanger or the cargo under floor.

Intermediate:
-This configuration is used if warm ambient conditions exist during flight (airborne or thrust levers placed to a takeoff position while on the ground).
-The configuration is exactly the same as the closed configuration except that a small internal flap within the extract valve opens to expel some of the heated avionics compartment air overboard.


Closed:
-This configuration is used mostly during flight or if cold ambient conditions exist while the aircraft is on the ground.
-Avionics compartment air is cooled via an aircraft skin heat exchanger; air is circulated by the blower and extract fans.
-The inlet and extract valves remain closed.
-Air is expelled through the cargo under floor and out through the outflow valve.


A G00g1e search for "Quizlet A320 Air Systems mrdeerwood" found a text description, does my picture (incorporating a table of the thre possible heat sinks assist?http://i1007.photobucket.com/albums/...psf20d1d6e.png

Note that on the latest A320 the logic has changed slightly. Our last 3 aircraft delivered this year have a different setting for on the ground.
Before, on the ground, skin temp above 12deg and the inlet/outlet doors would open. On the new config they stay closed until the avionics cooling exhaust rises to 35 deg. So in European temps, the inlet/outlet flaps will not open normally on the ground.
The crew notice and ask questions.

The new behaviour comes with the new "comfort duct temperature sensor" (34HQ) in combination with an AEVC V07. Threshold is 40 °C.
See OIT 999.0042/14.