APUs
Just a gut feeling:
I think the efficiency loss of turbine:electric:mechanical is too great. APU on a dash8 is 200kW = 175hp, and able to drive a "150hp" electric powerplant. I guess the cost is a couple of hundred thousand USD, and I don't want to count on it as the only power (IAS) source! Oh! for a good 100kWh battery in a forced landing!
Mind you, even 40kWh would work wonders then.
OJ