For battery start procedure, there is a NOTE as follows;
If engine N°2 is to be started first, set BUS TIE switch to ON and confirm MAIN BUS 2 voltage is not below 23V.
I thought ENG 2 Starter/Generator was powered by DC MAIN BUS 2, so we got to set BUS TIE SW to ON to start No.2 ENG first, but it is described in RFM 3-51 that ENG 2 IGNITER & START is powered by DC ESS BUS 2.
I wonder if we can start No.2 ENG first with BUS TIE SW in AUTO position in battery start.