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[ReverseTrike]

I am an aerospace engineer and all these new electric motor developments are a complete game changer for General Aviation(GA) and I want to explore their use to replace the current 80 year old ICE. The batteries are bottleneck for range so let me go straight to the point:

For a Series hybrid (like here http://www.siemens.com/innovation/en/news/2013/e_inno_1318_1.htm) Firewall forward(FWF) for a GA aircraft(in range of~60HP-80HP) the power train is as follows assuming 90% best case efficiency of all components that are all off the shelf,

ICE->75-5motor@90%->Controller(size4)@90%->Battery@90%->Controller(Size6)@90%->75-7motor@90%----->Propeller

or
ICE--[blackbox @ 59%]----->Propeller

So, I have lost >40% of my engine efficiency even without seeing the prop 
   1. Is there a better path of doing this without going the way of parallel hybrid?
   2. I am looking at the Generac & Aixro (35hp continuous) as the engine choice so the motor/controller should be able to hold that much power for regen?
   3. Can I run the 75-5 motor in regen mode to recharge the batteries rather than redoing the controller? Basically I want to use the FX motor as an alternator for a geneset(range extender) that is directly connected to the PTO end of the ICE.
   4. Can I go around the batteries and directly power 75-7 motor rather than charging the batteries in cruise and use the batteries only for take off & climb?
   5. Again, using the FX motor+ controller allows me to use off the shelf available components rather than hooking up another motor that might do a better job. I know of a lot of other motors but this plug and play flexibility reduces the complexity (for me) many folds.

I would appreciate your expert opinion as for sure mine is flawed. I know I do not know
   

[emotofreak]

I think you pretty much have to go parallel hybrid to keep the efficiency up during cruise. Otherwise you're just tossing something like 20% of your energy away. So you either have to clutch between ice and electric drivetrain on a single prop, or run 2 completely independent drive systems, in a push-pull config for example. Or just live with the loss of efficiency in a serial system

For inspiration...



Claims 1800ft/min climb

[firepower]

Why not ice>alternator>controller>electric motor>prop. why need batteries?
Do it same as diesel electric trains / mineing equipment.

[ReverseTrike]

Claims 1800ft/min climb

I do not think that this is a claim. If you do the math for the Gull the rate of climb for the UL with the 54HP motor and Rotax gearbox comes out to that based on the ROC of the regular UL on 28HP.

The interesting part is the tremendous weight gain and weight in the nose and even then that high of the ROC 

Why not ice>alternator>controller>electric motor>prop. why need batteries?
Do it same as diesel electric trains / mineing equipment.

I dont know how this works as a separate controller will be required for each motor but I do not know for sure 

[trikester]

The need for batteries is to make the ICE size requirement smaller because the batteries provide the higher energy needed while climbing. It's the same principle used for hybrid cars. If the engine supplies all of the climbing energy then it is over-sized for cruising and not running it its best efficiency.

Trikester

PS - Wish I was younger, I'd be building one of these things. I was very active in the beginning years of modern sport hang gliding.

[NoiseBoy]

Why would you use a 75-5 motor and a controller as a generator?  It doesnt make sense to use a motor, which is designed to be driven efficiently and withstand rapid changes in torque, as an alternator.  Use a proper alternator and a rectifier to charge the battery properly. It will also be a lot lighter.