Start the APU on bat only?
In the QRH 1.01 Elec Emer Config Sys Remaining it says that the APU ECB-STARTER only is available when the RAT is running. It says INOP when on BAT ONLY in flight en is only restored ON THE GROUND when speed is below 100 knots.
Can you explain me how you can start the APU in flight on BAT ONLY?