Guys, on the 737NG with the asprirated TAT probe option:
Is the logic for pitot heat through air/gnd?
Does it get it's air from the packs or from the pneumatic system?
I only ask because on our 757s which have the asiprated probe, it gets air from the pneumatic system. And on our 737NGs, pitot heat has no interface with air/gnd. It is manual only.