When I started climbing the Fenix A320 learning curve, I had assumed that packs had to be turned-off prior to engines start so that there would be sufficient bleed air to start the engines so I kept turning them OFF and then ON after engines start.  In one of my earlier flights, I forgot to turn them off but the engines started fine anyway so the questions are:

• In normal procedures, are the packs supposed to be OFF or ON prior to engines start ?
• If ON, are they being turned-off and then turned-on behind the scenes automatically or are they ON all the time ? IRL flights with A320s, the cabin gets awfully quiet after pushback and back to the usual air rushing sounds after engines start.

I would appreciate some feedback on this issue.

The airbus when you go ignition start it closes the packs valve. Then they come on after 2nd engine start I believe Normally both packs are on till departure depending on company procedures. I believe EasyJet for instance keep pack 2 off then for departure they turn the other pack off unless this has changed recently.

You don't have to switch them off manually. Once you flick the switch to IGN/Start, the Packs are turned off, for 90 Seconds I believe. If you don't start the engines in that time window they will come back on again.

 

You can hear this happening as well, it does get quiet, just as you described, once you flick the switch.

12 hours ago, carlanthony24 said:

Normally both packs are on till departure depending on company procedures. I believe EasyJet for instance keep pack 2 off then for departure they turn the other pack off unless this has changed recently.

Can confirm. Many airlines keep both packs on until just before departure, then turn both packs off for take-off. Pack 2 comes back on upon thrust reduction, pack 1 when selecting flaps zero. They should not be turned on again simultaneously. It should be noted that a pack off departure is non-standard according to Airbus philosophy. 

28 minutes ago, thepilot said:

Can confirm. Many airlines keep both packs on until just before departure, then turn both packs off for take-off. Pack 2 comes back on upon thrust reduction, pack 1 when selecting flaps zero. They should not be turned on again simultaneously. It should be noted that a pack off departure is non-standard according to Airbus philosophy. 

On the EFB Takeoff page, it gives the option for packs on or off. 

34 minutes ago, Bobsk8 said:

On the EFB Takeoff page, it gives the option for packs on or off. 

'Non-standard' is not the same as 'forbidden' or 'impossible' 

Airbus distinguishes two types of start: automatic or manual

FCOM says: "Use the automatic engine start procedure in most circumstances. However, if the start aborts due to insufficient starter inlet air pressure (e.g. on high airfields, or in case of low pressure from an external pneumatic power group), it is recommended to use the manual start procedure, instead the automatic procedure."

For automatic engine starting, unlike the Boeing 737-800, packs 1 and 2 must not be set to OFF, the FADEC manages this alone
FCTM says:

Engines usually start using the Automatic Starting function. The Full Authority
Digital Engine Control (FADEC) systems control this engine Automatic Starting
function, and takes appropriate action, if engine parameters are exceeded. This
function significantly extends the duration of engine life.
The thrust levers must be confirmed at "idle" before engine-start. If the thrust
levers are not at "idle", the thrust increases above idle after engine-start, and can
result in a hazardous situation. However, an ENG START FAULT ECAM warning
triggers, to indicate that the flight crew must set the thrust levers to "idle".
The engines are started in sequence, preferably engine 2 first, in order to
pressurize yellow hydraulic system, which supplies the parking brake accumulator.
When the ENG START selector is set to "START", the FADECs are
electrically-supplied. When there is sufficient BLEED PRESS, the PF begins the
start sequence by setting the ENG MASTER switch to ON. The flight crew
should monitor the start sequence:
. Start valve opens
. N2 increases
. IGN A(B)
. Fuel flow
. EGT
. N1
. Oil pressure increases
. Start valve closed.
After reaching the peak EGT, or when AVAIL is displayed, the PF can start
engine 1.
The flight crew should check the relative engine vibration level.
When the ENG START selector is set to NORM, the packs return to the OPEN
position. APU Bleed should immediately be turned off, to avoid engine ingestion
of exhaust gas.
If the start is not successful, the flight crew must use the ECAM as usually
done, and avoid instinctively selecting the ENG MASTER switch to OFF. This
would interrupt the FADEC protective actions (e.g. cranking after hot start).

 

Edited February 28, 20242 yr by Area

1 hour ago, thepilot said:

Non-standard' is not the same as 'forbidden' or 'impossible'

In fact, it is not considered a non-standard procedure, it is rather recommended by Airbus and implemented at the discretion of each operator.

1 hour ago, Area said:

Airbus distinguishes two types of start: automatic or manual

To avoid confusion, regarding the question asked by the OP, in neither of the two scenarios (automatic or manual start) it is necessary to switch to PACKS to OFF position.

Le 28/02/2024 à 15h52, polosim a dit :

Le 28/02/2024 à 14h25, Area a déclaré :

Airbus distingue deux types de démarrage : automatique ou manuel

FCOM indique : "  Utilisez la procédure de démarrage automatique du moteur dans la plupart des circonstances. Cependant, si le démarrage est interrompu en raison d'une pression d'air d'entrée du démarreur insuffisante (par exemple sur des aérodromes élevés, ou en cas de basse pression provenant d'un groupe de puissance pneumatique externe), il est recommandé d'utiliser la procédure de démarrage manuel au lieu de la procédure automatique. "

....

Pour éviter toute confusion, concernant la question posée par l'OP, dans aucun des deux scénarios (démarrage automatique ou manuel), il n'est nécessaire de passer de PACKS en position OFF.

I think you are forgetting this case: booting without APU and with ASU, FCOM says  :

 

 

 

Edited March 6, 20242 yr by Area

7 minutes ago, Area said:

I think you are forgetting this case: booting without APU and with ASU, FCOM says  :

You have a valid point, we could add to my sentence: "At least the supplementary procedure orders to do it". 🙂