in the engine shut down cl we see that if the eng 1 fire p/b is pushed we use apu bleed with xbleed at shut position.
what is the reason that we use apu bleed? What happens if I donīt use apu bleed
There is no checklist but ECAM which doesn't even tell you to start the APU leave alone using bleed. One live Engine is capable of all air-conditioning loads and also single bleed two pack operation. The APU is started for electrics so in case the only generator fails you don't land up in ELEC EMER. APU bleed is only used in case of overweight landing to provide better gradient, again not necessary you can just switch off the pack in approach.