Am I the only one who's puzzled by the POH?
You have flat batteries
You start one engine using ground power
You disconnect the ground power
You now have flat batteries being charged by one alternator
You get enough charge into the batteries to crank the other engine, that depletes the charge, you have flat batteries again.
You take off.
Who's to say that the charge in the batteries is now sufficient to maintain voltage under load?
What happens to the 45 minutes ECU endurance mentioned by B2N2 following electrical failure in this situation?
For years boats have had a very simple system with a separate engine starting battery arranged using a blocking diode so that it is not depleted by the domestic load. As Vedeneyev suggests it's not difficult to set up a similar arrangement to provide a fully charged ECU battery permanently on-line.
I don't buy the arguments of moggiee et al. For years aircraft crashed because non-return valves were manufactured so that they could be inserted either way round. Writing documentation that said they had to be inserted the right way round didn't fix it. Making it mechanically impossible by having differing threads on each end did. If you follow the argument to its logical conclusion you wouldn't have squat switches or GPWS either because if the procedures were followed correctly the need for them would never arise.
