Originally Posted by
elonmussk
meanwhile there was one instructor who says that we might want to reserve the battery power by not starting the apu,
because he said the Starting APU uses battery power..
If the APU fails to start, once the sequence is completed, the remaining GEN, will start changing again the batteries.
In addition in case of failure of one generator (FCOM):
The system automatically replaces the failed generator, with the :
‐APU GEN, if available, or
‐Other engine generator.
So according to the airbus logic, APU if available automatically takes priority to relieve the remaining generators (no action required to connect the APU to the failed side).
Originally Posted by
elonmussk
He was insisting that if the apu didnt start for some reason then it would end up using battery power.
The APU will use the battery power anyway as long as the start motor is activated (successful start or not).
Originally Posted by
elonmussk
Which means, if we get to lose remaining generator for some reason (I dont think so,. but...)
it would lead to electric emergency configuration,
if we had have used battery power with starting apu, saying that it would shorten the time with electricity .
The condition to be in Elec Emer configuration is :
Both AC BUS 1 and AC BUS 2 are lost.
Even with batteries fully charged you will be in the same condition.
The instructor is confusing/concerned of the situation “flight with batteries only” which is time limited to 30mins minimum(case of Elec emer configuration + RAT failure).
The batteries provide power to Hot BUS1,HOT BUS 2, DC ESS BUS and AC ESS bus through AC STAT INV.
In case of Elec Emer configuration, you are time limited as well as the batteries are not charging, being segregated from the part of the electrical system which is powered by the RAT.
But in this case the available time is much longer than 30 minutes as they only provide power the Hot Bus 1 and Hot bus 2
In that case you are mostly concerned by the lack of redundancy. (LAND ASAP Red)
So yes the instructor could be right If the APU fails to start, you immediately loose the second generator and the RAT fails to deploy.
He either misunderstood the redundancy of the system, or he is not trusting the certification of the A320 and he does not feel comfortable flying this Aircraft.