Originally Posted by abelenky

Actually quite a lot changes when the power plant switches from combustion to electro-chemical energy.

A few things:
TOW == LW: Empty batteries weigh the same as full batteries, so you always land with the same weight you take off at.
This has consequences down to the landing gear design.
Electric planes won't trim to balance fuel that has been burned off.
Useful load no longer includes fuel weight.

You might then think that a plane should always take off with batteries at 100%, but that's not true.
Cycling lithium-ion batteries to 100% shortens their lifespan considerably.
If the planned flight does not require the last 20%, you're better off charging to only the needed energy (ideally below 80%) to increase the lifespan of the batteries.

Out of fuel emergencies end up very different with Li batteries.
With traditional fuel, when the tank is dry, the plane just glides.
With Li, gliding at Vbg can actually recharge the batteries and get you another couple minutes of power.
If the battery ends up empty at 15,000 feet, the motor can suddenly come alive again at 2,000 and help power in to a safe landing.
That is definitely not in the current POHs.


(me: Only a PPL pilot; Lithium-Ion BMS engineer)