But why the ASU automatically disconnected ?
Because that's probably the way PMDG(?) programmed it. In reality, the ground staff/engineers would disconnect the external air supply with their gloved hands. The aircraft would then be pushed back from the gate and the second engine started (with the running engine at higher-than-idle rpms).
it is a flight simulator issue, but the aircraft's behavior is the same like the reality.
So you're saying a $100 simulator program is 100% like the real aircraft?
I don't think even PMDG would claim that
