As explained so many times, when the airplane uses custom refueling ( and the fenix surely is ):
- Simbrief doesn't have any effect on GSX. In fact, unless you changed the airplane configuration to not have custom refueling ( which you cannot do, since the fenix can't be refueled externally ), you are not even supposed to see the GSX Refueling menu with a Simbrief option. If you see it, reset the airplane config to default or, DISABLE the "show fuel/cargo" option in it, which is how the fenix is supposed to work.
- If the above option is set correctly, the correct procedure to refuel an airplane with a custom refueling is explained in this video:
It's with the PMDG 737, but the concept is not different with the Fenix, which is:
- Do not alter the fuel quantity from the airplane own menu while the GSX truck is coming
- Enter a quantity LARGER than the one you had on board before, otherwise the truck will just go away.