John.Roo
Well-Known Member
Sorry, I know I will repeat myself...For aircraft that the mission flight time is under an hour, there are studies showing the electric propulsion system, even with current battery technology, could be even lighter than the piston internal combustion system. I agree, in current aviation that is a very small niche (some training perhaps, or short fun flying), but that can change as electric propulsion enables much easier development of VTOL configurations, and a personal VTOL aircraft could replace the car as commuting vehicle.
Electric propulsion actually makes sense in aerodynamically efficient airplanes (like gliders). We can also call it "short fun flying" - especially when weather is not perfect or pilot has no experience with gliding
"Short fun flying" = flight arround 1 hour. But in real life this means to have capacity of batteries for at least 80-90 min.
Why?
Because:
1) you don´t want to have 0% reserve when you landing = safety
2) you want to have as long as possible lifetime of your bateries = economy.
Small glider like looking airplane will need battery with capacity arround 12 kWh (approx. 50 kg weight). Max. power for takeoff 24-30 kW (32-40 hp) will keep discharge rate on reasonable value of 2-2,5C. This is also good for battery life and no need for battery active cooling systems. For horizontal flight you have to stay at +-8 kW power.
With this parameters you can make "affordable" nice small electric one-seater for fun flying.
I am not experience with VTOL airplanes, but I am sure you need MUCH more energy to achieve 60 min. endurance = MUCH bigger battery, probably more motors and controllers and props and active battery cooling (large discharge rates). I would also recommend reasonable safety reserve. During takeoff (when batteries are fully charged) is all OK, however during landing = lower battery voltage also lower available power = more stress and very limited time to repeat landing.
That is my actual point of view
Best regards!
Martin