I remember reading something about the ability to isolate a tank needed to be built into the model. I can't find those discussions here anymore (bad searching on my part, I know. *grin*). Can anyone re-shed some light on this?

Not sure what you mean by "isolating". If you avoid the biggest fuelproblem in FS, that of ALL tanks being set as default, and instead actually select the tank to be used, isolation shouldn't be necessary.Like, a check during initialization; if ALL tanks is selected, then switch to LEFT, RIGHT, CENTER, EXTERNAL or whatever. LEFT and RIGHT tanks will always be drained first no matter selection, so you could use TIP or AUX tanks instead for full control.Although, I haven't played much with this in the current version, so I could be wrong here...

That's pretty much what I wanted to avoid... having to do auto-feeding as based on continuous tank quantity testing, just to prevent use of fuel from/in a single tank.

Even my Crossfeeding is still done via switching to the tank on the other side automatically in my fuel panel gauge. The most interesting part is to automatically switch to the next tank in line after the first has run out of fuel without the engine dying. I have a special setup where an external fuel tank automatically pumps it's content into the main tank until the external tank is empty. The engine in real life always draws from the main tank but due to this automatic fuel transfer from the external tank I need to switch the engine in FS to the external tank until this is empty, and then back to the main tank before the enigne deciedes to quit.The fuel tank area is still one of the most messed-up areas of FS coding to this day, similar to the electrical stuff...

Actually, I'm just looking for a simple/easy way to leave fuel in a tank completely alone. I never want to use that fuel. (I just want the weight so I can dump it as necessary to simulate airdrops, bomb drops, jumpers, etc). I was hoping for an easy/simple solution that I could slap on a great many planes, rather than dig into each plane's fuel system and have to code for each plane. I was hoping for an understanding of the XML isolate tank command from the SDK. *grin*

If you can determine for sure which tank will be drawn on last, you could build a gauge that would close all the fuel valves when TOTAL_FUEL_QUANTITY reached value X, where X was equal to the capacity of that last tank. Such a gauge would effectively make this tank unusable. All you really need to do is determine for sure which tank FS will use last.Doug

Good food for thought there! Especially so when used in conjunction with your gauge!Thinking/rambling "out loud"...From old experiments, I think the last to be drawn from were the mains assuming ALL TANKS selection is left alone... lots of hours last year at 64x time scale rate watching. *grin* FS liked to use a tank a piece (experiments were using a four engine plane) for each engine until the end when it used any tank with fuel, so the last tanks used depend on the plane and what tanks were configured. Problem there is I don't want to lock the default mains, as it would cause problems when applied to planes that have existing fuel systems' logic created for them. I'm trying/hoping for a generic solution to slap on anything from a Handley Page 0/400 to a B-17F to a C-141B to a B-52G to a [insert civilian skydiving plane], so who's plane and their fuel system programming could determine how much problems would be caused by adding this ability to dump the weight suddenly.Optimum would be the ability to lockout the fuel in, say a center tank for any plane, then use your gauge to "drop" it when appropriate. Alternately, the use of the inherent external drop tanks command would do it as well (although your gauge is much more elegent! *grin*).