Subject: Re: Hybrid-Electric Aircraft?
...next-generation hybrid-electric regional aircraft ...

One could safely ignore this post, as I haven't looked into their technology.

But taking a step back...a hybrid, any hybrid, ultimately gets all of its energy from the fuel pumped into it. Fossil fuel, as a rule.

The only gains come from (a) increased efficiency, notably regenerative braking for cars, but otherwise generally being stuff you could do with or without hybridization (aerodynamics, that sort of thing); and (b) the amount of charge the batteries had when you left home.

For a hybrid aircraft, regenerative braking isn't a thing, and efficiency improvements are available without a change in propulsion. And, compared to the energy use during a flight, the amount of energy in batteries at take-off is negligible.

So, again forgiving my ignorance, where is there a gain?
The ability to use a greener fuel than a fuel-driven mechanical engine is nice, but jet kerosene could in principle be synthesized without fossil fuels too.

Is the putative gain purely from the greater energy conversion efficiency of (say) fuel-fuelcell-electricmotor or fuel-turbinegenerator-electric, versus fuel-jetturbine? And is it greater?

Jim