I suggest reading the GSX manual, starting at Page 18, the "Airplanes using custom refueling systems" chapter, and the PMDG 737 surely is. With these airplanes, GSX is NOT fueling the airplane. The airplane is fueling itself, and the only thing the GSX Fuel Truck does, is to react with its animations to the fueling process performed by the aircraft, but it's not really "fueling" it.
On the manual, there's an example of using GSX with such airplanes, like the PMDG 737 or the PMDG 777. The key sentence is:
When the Fuel Truck arrives, it will wait for you to act on the Fuel menu in the FMC, to set a desired quantity. GSX will display the “Please use the refueling system of your airplane to refuel” message, to remind you it’s waiting for your action.
At THAT point,
after you saw that message from GSX, use the Fuel menu in the 737 to change the Fuel Quantity to the desired level ( either in percentage or in absolute lbs ) and, if that quantity is higher than the quantity you had before seeing that message, the GSX Fuel Truck will display its counter going up, but it will just be cosmetic, since it's the
airplane that has refueled itself, NOT GSX.
What might change, is the speed of the counter, depending on the GSX Settings:
- If the "Always Refuel Progressively" is ENABLED, the counter will go up according to the speed of the fuel pump as set in the GSX vehicle, so the GSX fuel truck will stay for more time.
- If the "Always Refuel Progressively" is DISABLED, the counter will go up very fast, so the GSX truck will go away way sooner.
Again, in BOTH cases, it's the
airplane that is refueling itself. GSX only reacts to that process.
