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KotlaSheetal

Engine data simulation variables

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Hello

 

I am trying to read the engine data out of the PMDG 737 NGX aircraft via SimConnect. The application is running, I am reading the data using the following variables:

 

simConnect.AddToDataDefinition(DEFINITIONS.EngineData, "TURB ENG N1:1", "Percent", SIMCONNECT_DATATYPE.FLOAT64, 0.0f, SimConnect.SIMCONNECT_UNUSED);

simConnect.AddToDataDefinition(DEFINITIONS.EngineData, "TURB ENG N2:1", "Percent", SIMCONNECT_DATATYPE.FLOAT64, 0.0f, SimConnect.SIMCONNECT_UNUSED);
simConnect.AddToDataDefinition(DEFINITIONS.EngineData, "TURB ENG CORRECTED FF:1", "Percent", SIMCONNECT_DATATYPE.FLOAT64, 0.0f, SimConnect.SIMCONNECT_UNUSED);
simConnect.AddToDataDefinition(DEFINITIONS.EngineData, "TURB ENG MAX TORQUE PERCENT:1", "Percent", SIMCONNECT_DATATYPE.FLOAT64, 0.0f, SimConnect.SIMCONNECT_UNUSED);
simConnect.AddToDataDefinition(DEFINITIONS.EngineData, "TURB ENG PRESSURE RATIO:1", "Percent", SIMCONNECT_DATATYPE.FLOAT64, 0.0f, SimConnect.SIMCONNECT_UNUSED);
simConnect.AddToDataDefinition(DEFINITIONS.EngineData, "TURB ENG JET THRUST:1", "Percent", SIMCONNECT_DATATYPE.FLOAT64, 0.0f, SimConnect.SIMCONNECT_UNUSED);
simConnect.AddToDataDefinition(DEFINITIONS.EngineData, "TURB ENG FUEL FLOW PPH:1", "Percent", SIMCONNECT_DATATYPE.FLOAT64, 0.0f, SimConnect.SIMCONNECT_UNUSED);
simConnect.AddToDataDefinition(DEFINITIONS.EngineData, "TURB ENG N1:2", "Percent", SIMCONNECT_DATATYPE.FLOAT64, 0.0f, SimConnect.SIMCONNECT_UNUSED);
simConnect.AddToDataDefinition(DEFINITIONS.EngineData, "TURB ENG N2:2", "Percent", SIMCONNECT_DATATYPE.FLOAT64, 0.0f, SimConnect.SIMCONNECT_UNUSED);
simConnect.AddToDataDefinition(DEFINITIONS.EngineData, "TURB ENG CORRECTED FF:2", "Percent", SIMCONNECT_DATATYPE.FLOAT64, 0.0f, SimConnect.SIMCONNECT_UNUSED);
simConnect.AddToDataDefinition(DEFINITIONS.EngineData, "TURB ENG MAX TORQUE PERCENT:2", "Percent", SIMCONNECT_DATATYPE.FLOAT64, 0.0f, SimConnect.SIMCONNECT_UNUSED);
simConnect.AddToDataDefinition(DEFINITIONS.EngineData, "TURB ENG PRESSURE RATIO:2", "Percent", SIMCONNECT_DATATYPE.FLOAT64, 0.0f, SimConnect.SIMCONNECT_UNUSED);
simConnect.AddToDataDefinition(DEFINITIONS.EngineData, "TURB ENG JET THRUST:2", "Percent", SIMCONNECT_DATATYPE.FLOAT64, 0.0f, SimConnect.SIMCONNECT_UNUSED);
simConnect.AddToDataDefinition(DEFINITIONS.EngineData, "TURB ENG FUEL FLOW PPH:2", "Percent", SIMCONNECT_DATATYPE.FLOAT64, 0.0f, SimConnect.SIMCONNECT_UNUSED);
 
Actually I am particularly interested in the fuel flow data. the figures I get from these variables do not match the fuel flow figure displayed on the PMDG engine display. Also the figure for TURB ENG CORRECTED FF:1 and TURB ENG CORRECTED FF:2 are much larger than the values read from TURB ENG FUEL FLOW PPH:1 and TURB ENG FUEL FLOW PPH:2 (e.g. FF PPH = 12.95, FF corrected = 218.92). The FF displayed on the engine display is 0.69, the value I get from the simvar is 12.72. I tried to find out if there is a kind of factor or function which relates these values, but did not succeed so far. I also already searched in the offset lists and PMDG SDK files, but there are no offsets or variables available.
Does anybody know of some coefficient, function or something else I can use to get the values displayed in the 737 engine display? 
 
Thanks a lot
Peter

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Careful with your data types and units.

 

Documentation says, that the correct unit for "TURB ENG FUEL FLOW PPH:x" is "Pounds per Hour" (and not "Percent") so that is the one I would use. Using different units may force the API to do some sort of conversion, which might not deliver what you expect.

 

Furthermore, be aware of the data types. If you get funny values with float or double, try if the simulator variable prefers to return integers. For example I had "Percent" usually work better with long = INT64 variables - if the variable actually returns a percent value, like for example the throttle lever position or combustion.

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Hi Oliver

 

Thank you very much for your answer, much appreciated. Perhaps it could be some kind of type issue, I will make a few tests using other datatypes and post the result here.

 

Cheers

Peter

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Part of the problem could be solved after changing the units from "Percent" to "Pounds per hour", as Oliver wrote. After this change the fuel flow figures are correct for all aircraft I tested, except the PMDG 737 (I have not checked the 777 yet). So there seems to be some kind of factor or function used by PMDG to get the FF figures displayed on the 737 engine displays.

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