Hi ross
We speak "wheel tug" yes? APU is power, the engine is in the truck (wheel) of the a/c. It will be electric, of course.
I see you are a partisan. Let me direct you to an electric motor that produces three hp per pound of engine weight.
You will need symmetrical motive power, so at least one engine per side, but better would be one engine per wheel, sixteen on a 747.
No problem, the wheel is the armature, the brake disc the rotor, easy peasy.
Old technology, proven, and expensive.
Where is it? The problem is not the technology.
Your problem is to demonstrate cost/benefit. No mean feat. Two 880 pound systems would cost an airline four thousand dollars a day.
All the best.
Last edited by Lyman; 12th Oct 2012 at 14:41.