micro alternator airborne / out runner balance charger for large scale rc aircraft

using the same concept as diesel trains. As they drive / pull on electric. The drive train is actually electric . The noise we hear are the generators charging the power banks. . Electric are far more efficient than diesel or gas engine direct  to the drive train.

That being said.
How can we set up micro scale generator on board 1/3 scale electric rc airplane.

concept :
connect 40 size os max rc nitro engine direct to 700 kv E. out runner shaft , rectifier bridge /  12 volt SMART lipoly charger, all this to enhance primary lipoy bank on large scale electric rc planes. ( increase flight time dramatically) sounds stupid I guess, but the concept apparently works in real world cargo trains.

Can anyone help wth the system set up of rectifier bridge components to give this a shot ? I have no electrical expertise. 

Thanks

Jeff