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Fuel-air ratio does not set

DragonflightDesign

DragonflightDesign

Resource contributor
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northernireland
Yet another complete failure on my part. I'm trying to set the fuel-air ratio on a reciprocating engine. Both the FSX and P3D SDK state that this can only be set through a simconnect action. I'm not interested in finding out what it currently is; I just want to set the ratio, so no REQUEST in the enumerations.

Global variables:
Code: 
double recip_engine = 0;            // The engine to be set (1 - 4)
double fuelair_ratio = 0;            // The ratio to be set (whatever)
double set_fuelair_ratio = 0;    // Tell simconnect to do the work ( = 1)
Enumeration for the engine:
Code: 
    DEFINE_FUELAIR_RATIO_ENG1,
    DEFINE_FUELAIR_RATIO_ENG2,
    DEFINE_FUELAIR_RATIO_ENG3,
    DEFINE_FUELAIR_RATIO_ENG4
Data definitions for the four engines:
Code: 
    hr = SimConnect_AddToDataDefinition(hSimConnect, DEFINE_FUELAIR_RATIO_ENG1, "RECIP MIXTURE RATIO:1", "ratio", SIMCONNECT_DATATYPE_FLOAT64);
    hr = SimConnect_AddToDataDefinition(hSimConnect, DEFINE_FUELAIR_RATIO_ENG2, "RECIP MIXTURE RATIO:2", "ratio", SIMCONNECT_DATATYPE_FLOAT64);
    hr = SimConnect_AddToDataDefinition(hSimConnect, DEFINE_FUELAIR_RATIO_ENG3, "RECIP MIXTURE RATIO:3", "ratio", SIMCONNECT_DATATYPE_FLOAT64);
    hr = SimConnect_AddToDataDefinition(hSimConnect, DEFINE_FUELAIR_RATIO_ENG4, "RECIP MIXTURE RATIO:4", "ratio", SIMCONNECT_DATATYPE_FLOAT64);
The event call:
Code: 
    case CLIENT_6HZ:
    {
        // Fuel-air ratio set
        if(set_fuelair_ratio)fuel_air_ratio(hSimConnect, recip_engine, fuelair_ratio);
    }
The function doing the work:
Code: 
void fuel_air_ratio(HANDLE hSimConnect, double engine, double ratio)
{
    HRESULT hRes;

    if (engine == 1)hRes = SimConnect_SetDataOnSimObject(hSimConnect, DEFINE_FUELAIR_RATIO_ENG1, SIMCONNECT_SIMOBJECT_TYPE_USER, NULL, NULL, sizeof(double), &ratio);
    if (engine == 2)hRes = SimConnect_SetDataOnSimObject(hSimConnect, DEFINE_FUELAIR_RATIO_ENG2, SIMCONNECT_SIMOBJECT_TYPE_USER, NULL, NULL, sizeof(double), &ratio);
    if (engine == 3)hRes = SimConnect_SetDataOnSimObject(hSimConnect, DEFINE_FUELAIR_RATIO_ENG3, SIMCONNECT_SIMOBJECT_TYPE_USER, NULL, NULL, sizeof(double), &ratio);
    if (engine == 4)hRes = SimConnect_SetDataOnSimObject(hSimConnect, DEFINE_FUELAIR_RATIO_ENG4, SIMCONNECT_SIMOBJECT_TYPE_USER, NULL, NULL, sizeof(double), &ratio);
    // Reset the call variable
    set_fuelair_ratio = 0;
    return;
}
and finally, the call as set by the mixture lever:
Code: 
    recip_engine = 1;                // Select the engine
    fuelair_ratio = 0.06;        // Set the F/A ratio to 0.06
    set_fuelair_ratio = 1;    // Tell simconnect to update
hres returns S_OK, but of course, the ratio is never set which is why I'm asking for help to figure out where I went wrong. Following through with the debugger shows the code path is being followed as I expect it.
 
Its another one of those sim vars which the SDK claims is settable but isn't. I mask mixture events from the sim and redirect them into my own code, while I control the mixture lever sim var instead and monitor the fuel air ratio to get it where I want it.
 
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