What % fuel load starts to fill the Robbie Tank?

[Nealius]

With 100% fuel, the Robbie Tank and internal tanks are obviously full, but let's say I want to have full internals with an empty Robbie. What percent should I set in the Mission Editor/Planner?

[FalcoGer]

From the manual

Quote

The AH-64D includes two internal self-sealing, crash-resistant fuel cells. The
forward fuel cell holds up to 156 gallons, and the aft fuel cell holds up to 220
gallons. Fuel is normally balanced between the two cells automatically by the
avionics.
A 230-gallon external fuel tank can be mounted on each of the four stub wing
pylons. An Internal Auxiliary Fuel System (IAFS) can be installed into the
ammunition.

And also density is 6.5-7 lb/gal. Considering it starts off at 660 lbs, I think it's 98 gallons internal.

As such I calculate that 98 * 100% / (156+220+98) = 20.67%. So full fuel without robbie should be 79.33%

[Raptor9]

5 hours ago, Nealius said:

With 100% fuel, the Robbie Tank and internal tanks are obviously full, but let's say I want to have full internals with an empty Robbie. What percent should I set in the Mission Editor/Planner?

Fuel is automatically place at the percent value in the main tanks and internal aux. So if set to 50%, all three tanks will fill to half. You'll just need to start pumping the center tank after starting.

I don't know how this affects the external wing tanks though. Each external holds 230 gallons, roughly 1500 pounds, so you might see the change in the editor fuel or gross weight to determine this.

Edited March 20, 2022 by Raptor9

[Nealius]

Through the Mission Editor 79% didn't seem to work. In-game, using the rearm/refuel menu, going down to 75 or 70% emptied the Robbie tank.

[Raptor9]

5 minutes ago, Nealius said:

Through the Mission Editor 79% didn't seem to work. In-game, using the rearm/refuel menu, going down to 75 or 70% emptied the Robbie tank.

Weird, I'm seeing different behavior. What kind of "start" are you using?

[Nealius]

1 hour ago, Raptor9 said:

Weird, I'm seeing different behavior. What kind of "start" are you using?

Cold start when I reduced fuel through the Mission Editor. Hot start when through rearm/refuel menu. 

[Parzival]

Fuel is always placed on the robbie tank as well as on the mains, but it is quickly auto transferred to the main tanks and those get balanced