Now, i'm no expert on engines or anything else for that matter but don't those hybrid cars have big sets of (heavy) batteries in them to hold the charge? Using the heat from the brakes to recharge them works well on cars because around town people use the brakes quite alot, but if they were fitted to a light aircraft then the brakes would only charge the battery during taxi and landing. Assuming the manufacturers used cables to run from the brakes to the battery, that could cause a few maintenance problems in terms of worn wires from flexing when the gear's retracted (unless it's fixed gear), plus i'm sure it would add a bit of extra weight but not much. So with a gas engine either up front or on each wing, plus an electric motor supplying supplemental power, PLUS a battery/battries somewhere else i'm guessing you'd need a powerful engine/s to get the thing in the air. So, increase in weight = bigger engines = more fuel burn!!!
I'm curious as to how the electric motor would help out. Would it be used just for taxying, or would it supply some power in flight so that the gas engine could be throttled back a little to let the electric motor take some of the work? It's a nice concept, i'm just not sure if it'd work, but like i said i'm no expert.
Btw, i've been reading over the past year about diesel engines being considered for light aircraft....i think that would be interesting to see/hear.
In the dark you can't see ugly, but you can feel fat