Classic British Flight Sim

Well.. here's something for you. As noted.. my default flight always begins with the default Cessna. I've never touched the tank switch on it and it's 'Both' by default. I don't even have the parking brake or lights on.. it's just 'A' default model sitting at the end of the runway at Culdrose then saved and made my default flight.
This doesn't explain why the 748 isn't working for you again and neither does it explain why you have to physically select 'Both' on the Cessna. Are you using a saved flight using a different model then chopping to the Cessna then chopping to the 748? Just try creating a flight at the airfield of your choice, selecting the Cessna (or any other default model).. make sure it's not got any wild switch positions made then save it. It doesn't have to be your default flight if you don't want it to be but it will load the sim with a default model in a default state
ATB
DaveB

I've found the issue!

The updated HS.748 V6 has THREE engines, one is left, two is right and the third acts as the GPU, which is why I can't used the GPU with GSX as it thinks it's an engine. However, the HS.748 only has 2 fuel selectors; left and right, and changing these in the flight saves in documents/flightsimulatorfiles from Tankselector=left and TankSelector1=right to Tankselector=all and Tank Selector1=all just resets to left and right again when the flight is loaded. In the aircraft.cfg, because the right engine is the 'centre' engine and the GPU is the right, the right engine draws from the left tank instead and the GPU draws fuel from the right (even though it doesn't draw anything).

Therefore I had three options; Make fuel selectors=3 so that there is an all option, switch engine.2 to engine.3 and the GPU to engine.2 so the GPU is central and the right engine is right, or because the GPU doesn't work with GSX anyway, I deleted the GPU as an engine so now engine.2 is right, not centre. This works without messing up the HS's fuel systems.

I see said the blind man

Fraser has been known to 'trick' us behind the scenes before and without exception (in FS9 at least) he's got away with it. New sims and newer addons look for different things though. I'd have never thought of the 3rd engine so well done for spotting it
ATB
DaveB

Can't check until the weekend, but the fuel system programming is very basic, each engine fed by it's respective tank by default.

Will come back to you then.

Cheers

Fraser