I must say that I am ashamed to be posting this,(could not find an ashamed smile to put here) but how do you get FUEL_TANK_LEFT_MAIN_LEVEL to show gallons in C++ :-hmmmIn xml is was simple, but every way I try in C++ I either get compiler errors or it complies but does not work.:-zhelp

You didn't show exactly what you're doing... but, in C++ the normal variable for the left tank is FUEL_QUANTITY_LEFT. It returns the amount of fuel in gallons by default.The variable you're using is a bit "odd". It returns a value of 8388608.0 to represent 100%. To translate that into gallons or pounds of fuel you'd have to also reference the FUEL_TANK_LEFT_MAIN_CAPACITY variable which returns the total tank capacity in gallons.To convert from gallons to pounds you need to use the FUEL_WEGHT_PER_GALLON variable.

Hi EdI was going to use FUEL_QUANTITY_LEFT, but if I remember correctly that gives the combined total for Left Main as well as Left Aux, and I need seperate gauges for each tank.The code I am trying to get to work is using the variables FUEL_TANK_LEFT_MAIN_LEVEL and FUEL_TANK_LEFT_MAIN_CAPACITY, As you pointed out the first variable does give out a odd number, which is where I am getting confused. Some how I have got to use FUEL_TANK_LEFT_MAIN_CAPACITY to alter 8388608.0 to 62 gallons :-roll. Time to give it a rest tonight, my brain is just not working, will start again tomorrow, thanks for the help so far Ed, at least I now know I am using the right variables :-)

Russell,Declare a float variable:FLOAT64 LeftFuelQty;Then use:execute_calculator_code("(A:FUEL TANK LEFT MAIN QUANTITY, gallons)", &LeftFuelQty, NULL, NULL);Much easier than messing around with the native C variables.Doug

Ok... here's what you need to do:FLOAT64 fuel_pct = FUEL_TANK_LEFT_MAIN_LEVELvar.var_value.n/8388608.0;FLOAT64 fuel_amt_gal = FUEL_TANK_LEFT_MAIN_CAPACITYvar.var_value.n * fuel_pct;

Hi Russel,here is what I use for the rxpGNS WAAS (and for previous GNS as well):double rxpGNS::AcftFuelCapacity(){ module_var mvar; double value = 0.0; mvar.Init(FUEL_TANK_LEFT_MAIN_CAPACITY); value += mvar.Lookup(); mvar.Init(FUEL_TANK_LEFT_AUX_CAPACITY); value += mvar.Lookup(); mvar.Init(FUEL_TANK_LEFT_TIP_CAPACITY); value += mvar.Lookup(); mvar.Init(FUEL_TANK_CENTER_CAPACITY); value += mvar.Lookup(); mvar.Init(FUEL_TANK_CENTER2_CAPACITY); value += mvar.Lookup(); mvar.Init(FUEL_TANK_RIGHT_MAIN_CAPACITY); value += mvar.Lookup(); mvar.Init(FUEL_TANK_RIGHT_AUX_CAPACITY); value += mvar.Lookup(); mvar.Init(FUEL_TANK_RIGHT_TIP_CAPACITY); value += mvar.Lookup(); return (value * 3.7853); // convert gallons to liters}double rxpGNS::AcftFuelLevel(){ module_var mvar; double value = 0.0; mvar.Init(FUEL_QUANTITY_RIGHT); value += mvar.Lookup(); mvar.Init(FUEL_QUANTITY_LEFT); value += mvar.Lookup(); mvar.Init(FUEL_QUANTITY_CENTER); value += mvar.Lookup(); return (value * 3.7853); // convert gallons to liters}double rxpGNS::AcftFuelFlow(){ module_var mvar; double value = 0.0; mvar.Init(ENGINE1_FF_GPH); value += mvar.Lookup(); mvar.Init(ENGINE2_FF_GPH); value += mvar.Lookup(); mvar.Init(ENGINE3_FF_GPH); value += mvar.Lookup(); mvar.Init(ENGINE4_FF_GPH); value += mvar.Lookup(); return (value * 3.7853); // convert gallons to liters}class module_var : public MODULE_VAR{public: module_var() {id = MODULE_VAR_NONE; var_ptr = 0; var_type = VAR_TYPE_NONE; var_value.n = 0.0; var_old.n = 0.0;}; void Init(GAUGE_TOKEN tok){id = tok; initialize_var((PMODULE_VAR) this);}; void Update() {lookup_var((PMODULE_VAR) this);}; FLOAT64 Lookup() {lookup_var((PMODULE_VAR) this); return var_value.n;}; FLOAT64 Val() {return var_value.n;}; int ValInt() {return var_value.e; }; int ValFlag() {return var_value.f; }; bool ValBool() {return (var_value.:( ? true : false; }; void* ValPtr() {return var_value.p; }; long ValOctal() {return var_value.o; };};Hope this helps!

I should have checked this thread before I started. Brain is working today, came up with this:FLOAT64 FSAPI left_main_fuel_quantity_cb(PELEMENT_NEEDLE pelement){ lookup_var(&left_main_fuel); current_fuel_left_main = left_main_fuel.var_value.n; lookup_var(&left_main); left_main_capacity = left_main.var_value.n; current_fuel_left_main = current_fuel_left_main /8388608.0; current_fuel_left_main = left_main_capacity * current_fuel_left_main; return current_fuel_left_main;}Ed looks like your code is the same but with a lot less typing. Doug I have not tried using the execute_calculator_code before, so will give that a try. JeanLuc will add your code to the long list of bits of code I have for future reference.Thanks

As Doug said, "execute_calculator_code" is easy to use, especially if you need the Fuel-Quantity in lbs or kg:FLOAT64 FuelSys::GetCenterTankQuantityLbs() const{ FLOAT64 val; execute_calculator_code("(A:FUEL TANK CENTER QUANTITY, gallons)",&val,NULL,NULL); return val * FuelSys::GetFuelWeightPerGallonLbs();}FLOAT64 FuelSys::GetCenterTankQuantityKilograms() const{ FLOAT64 val; execute_calculator_code("(A:FUEL TANK CENTER QUANTITY, gallons)",&val,NULL,NULL); return val * FuelSys::GetFuelWeightPerGallonKilograms();}