Originally Posted by
Fursty Ferret
Many reasons. If you ditch bleed air from your engines, you need cabin air compressors; huge generators; increased electrical redundancy; big inverters + cooling; alternative engine starting; alternative wing anti-icing technology; bigger APU (potentially), and a few other things.
All these have a weight penalty.
Bleed air cabin pressurisation is a proven technology, although it has the risk that an engine issue in the compressor section can contaminate the cabin air supply.
The question was only about packs, not about ditching the whole bleed system. All the other systems except pressurization would be conventional, you would just replace the packs with a system that would pressurize and cool outside air as opposed to bleed air. I think getting rid of all the fume events might make it worth looking into.