Originally Posted by
tdracer
Not specifically familiar with the 787 APU, but I suspect the APU auto-start would commence at the same time as the RAT deployed.
The 787 APU has a dedicated battery, so there is no reason to wait until the RAT is 'on-line' to commence the start sequence.
What is the first item in the APU auto-start sequence, then?
I'm surprised it's not the opening of the inlet, is there an outlet that needs to be opened first? Fuel to be pumped?