B744/748 Running 3 PACKs off the APU
Hello, I am wondering if it is a bad idea to run more than 2 packs simultaneously off the APU in the 744 or 748. If it is a bad idea, could you explain why. I can find no reference for this but it is widely accepted practice where I work to only run 2 of the 3 packs at once using APU bleed air. Thanks.