I am curious to see if this is feasible or not. The main step in figuring this out is finding the energy density of a battery and it's associated electronics, compared to the energy density of an engine and it's associated hardware. There will be a point where it will be better to use an engine versus batteries (i.e. real life Aircraft) but where exactly is the point?
There are obviously disadvantages to having an IC engine, with only a few advantages (such as higher energy density, faster re-fueling, possibility for in-air re-fueling, etc). This is definitely not a question of whether it's possible or not, it's more a question of the size/cost/other feasibility constraints that would be required to answer. Which means a very detailed engineering study on this.
I am working on a quad-rotor project, (www.icarusuav.com) and one of our capabilities we plan to implement in the future is in-air refueling, so this question is of importance to me.
Air to air refuelling you say http://www.suasnews.com/2010/11/2676/ultra-slow-air-to-air-refuelin...
Fuel cells would be the way to extend range, better buy expensive ESCs to make sure they keep running under the strain.
LOL. Maybe in another 25 years electric systems will hold a candle to IC.
Right now the energy density of batteries is around 1/100th that of gas.
We've discussed the whole hybrid multicopter idea before. The calculations seem to show that you could *probably* get one to fly. It would have to be around the size of a golf cart, cost several hundred thousand dollars, would fly terribly, and be horribly inefficient.
That was my recommendation a while back during a lengthy discussion on the potential for fuel cell power supply. Gas/electric has been around a long time powering trains (diesel/electric) and hybrid cars. I think it's the way to go for long-duration multirotor flights. I imagine it all boils down to weight.
Not quite that simple you need feedback to know rotor rpm. But I'd love to see a weedwacker quad powered by 4 weedeater motors. That would be a hoot! With a 2 hour flight time.
I'm not willing to prove it but I'm sure you can get fast enough response from a 2-stroke to make it work if you operate in the power band of a specific motor.