Apu use on ground
Hi, I have just a simple question for all pilots as a spectator.
On ground, in the airports where there's no particular restrictions I see the APU start (even with GPU and normal temperature) follows no rule. Somebody starts before boarding, others 20 mins or later.
When do you usually start? Do you look at the time and eobt or just start when see pax boarding?
I read fuel for APU is included in the flight plan, how much fuel for apu use is included in the OFP?
Cheers