I am referring to an Airbus A320. I have heard of Pack Flow but I don't understand it.

If you put it on High, does that mean that all the parts of the air conditioning system work faster and harder?

I have also heard that if you put it on High, that means the demand for air supply is high, and vice versa, i.e. if it's on low then the supply for air is low, but what about NORM, or Economy flow?


2 Answers 2


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Source: FCOM A320 familly

From the flight crew operating manual (FCOM) about the pack flow selector (4):

Permits the selection of pack valve flow, according to the number of passengers and ambient conditions (smoke removal, hot or wet conditions). LO (80 %) - NORM (100 %) - Hl (120 %).

Manual selection is irrelevant in single pack operation, or with APU bleed supply. ln these cases, Hl is automatically selected.

lf LO is selected, the pack flow can be automatically selected up to 100 % when the cooling demand cannot be satisfied.

So to answer your question directly:

  • The normal flow (100%) is when the selector is on position NORM.
  • Position HI adds 20% to the air flow, and LO removes 20%.

In addition:

  • In LO position, the flow can be increased by the controller up to 100% in case the temperature cannot be obtained with only 80%.

  • In case of single pack operation, the flow is automatically set by the controller to 120%.

  • $\begingroup$ "hat or wet conditions" - I presume that should be "hot or wet conditions". If not, could you clarify "hat conditions"? :) $\endgroup$
    – FreeMan
    Jun 12, 2017 at 20:10
  • $\begingroup$ @FreeMan: Hat off :-) $\endgroup$
    – mins
    Jun 12, 2017 at 23:23
  • $\begingroup$ A tip o' the hat to ya' $\endgroup$
    – FreeMan
    Jun 13, 2017 at 11:30

Pack flow is air flow through the air conditioning packs. There are two packs, one operated by each engine. Normally the system works on two packs, with some portion of the cabin air filtered and recirculated. The entire system can operate one one pack, which then must set to HIGH.

Yes if you put the pack on HIGH flow it means that that pack and all its connected parts work harder.

There is a lot of information on how exactly the system works and how to set it to what, for instance here.


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