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Schwarzgruber

Packs OFF on A320Neo

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I have a doubt about the packs before and during takeoff. Should they be disabled during take off and "ON" after take off once the "THR" has been returned to "CLB"?

I have seen videos that he leaves the "APU BLEED" and the "APU" "ON"? I don't think this is the right procedure.


fca-a320-banner.png

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Disclaimer: I am not a real world A320 pilot, but normally the APU gets turned off before taxi (after engines are on).

PAX are OFF for takeoff, ON after LVL CLB as far as I know.

Anti Ice 'ON' for takeoff, when temperature/moisture air content calls for it, but then FLEX temp needs to be calculated different.

Hope this helps. It seems different airlines have different procedures for this....

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Some of this is dependent on a particular airline's procedures, and some of these procedures vary with the conditions too. This is true for quite a few things with airliners and it is why you might see someone who is an airline pilot on the real thing tell you one thing, but then see information which contradicts that from someone else, who is also an airline pilot; it can sometimes be the case that they're both right even though they are saying different things. You should bear in mind too that some airliners have different equipment specs than others too, which can occasionally have a bearing on this stuff as well.

By way of example, here is a pic of the take off section of some standard operating procedures for the A320/321. This particular set of S.O.P.s is a book which I produced for use by two different airlines (which I've blacked out the names of for obvious reasons). Because it was used by two different airlines who used slightly different procedures and slightly differently-equipped variants of the A320 and 321, the book has numerous sections where the different procedure is noted for each particular airline, for example, see the last entry on this page, which lists a different procedure for cabin crew release for the two different airlines:

LIUJept.jpg

 

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Alan Bradbury

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According to the FCTM

"PACKS
If the take-off has to be achieved without air bleed fed from the engines for
performance reasons, but air conditioning desired, the APU bleed may be used
with packs ON, thus maintaining engine performance level and passenger
comfort. In case of APU auto shut down during take-off, the engine thrust is
frozen till the thrust is manually reduced. The packs revert to engine bleed which
causes an increase of EGT to keep N1/EPR.
If the take-off is performed with one pack unserviceable, the procedure states to
set the failed pack to OFF. The take-off may be performed with the other pack
ON (if performances permit) with TOGA or FLEX thrust, the pack being supplied
by the onside bleed. In this asymmetric bleed configuration, the N1 take-off value
is limited to the value corresponding to the bleed ON configuration and take-off
performances must be computed accordingly."

 

So the answer is they are usually on unless required takeoff perfomance cannot suffer the slight loss of power of having the bleed on during takeoff. Hope this helps

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8 hours ago, Schwarzgruber said:

I have a doubt about the packs before and during takeoff. Should they be disabled during take off and "ON" after take off once the "THR" has been returned to "CLB"?

Like everything in aviation... it depends...

Bleeding air from the engines reduces the thrust they produce (for a given N1 or EGT or Fuel flow) so if you need the thrust (i.e. the aircraft performance calculations suggest it simply won't take off without it) then you need to perform a 'bleeds off' take off. This is often referred to as a 'packs off' take off because the packs (air conditioning) are the main consumers of the engine bleed air.

If you need to perform a 'packs off' take off then you have 2 options.

1 - Turn the packs off as you enter the runway, take off and when you bring the engines back to climb power, turn them on again (one at a time with a gap between each one to let the pressurisation controllers handle the sudden change in air coming into the cabin).

2 - If you think the cabin environment will be adversely affected by the lack of conditioned air then you can run the packs from the APU (leaving the APU on for take off obviously).

All three of these options can be used at any time (packs on, or the 2 packs off methods). They are all 'right', although some companies will require the use of them at different times. Some companies use a 'packs off' take off as standard to reduce fuel usage and engine wear. These policies change, sometimes weekly depending on who you fly for, sigh.

So the answer to your question is that both the methods you allude to can be considered correct and would be used at different times by different airlines. Unfortunately for us, exactly which policy each airline uses is usually not publicly available.

I feel like I've answered your question and not helped whatsoever...

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