Originally Posted by
Sunfish
A quick look at the manual shows 2X2 ECU, 2 X ECU backup batteries plus battery and two generators so it’s difficult to, but of course not impossible to imagine a total electric failure as the cause.
That is a lot of batteries. I think some of them were added after a double engine failure on take off accident, though I don't know if they were added retrospectively or just to new builds.
In this accident both engines had been started off ground power (contrary to the POH, which stated the second engine must be started of the internal batteries - meaning they need to have suffficient charge to do this) and the engine failures occurred when the gear was selected up. There wasn't enough residual juice in the batteries to keep the ECU's running and the engines shut down.