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P3D v4 Jet fuel flow when using Afterburner in stages

Roy Holmes

Roy Holmes

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A jet with afterburner has two Thrust Specific Fuel Consumption (TSFC) settings in the Aircraft.cfg file.
The sim calculates fuel rate based on thrust and TSFC
One setting relates to TSFC without Afterburner the other relates to Afterburner.
Typically the first value would be 0.7 and the second could be 1.7.
Also it may have say 5 Afterburner stages where each stage calls up an increasing amount of AB thrust augmentation and the last stage is full afterburner.
The value for full afterburner thrust scalar is set in the .air file according to Mach in a table.
So you would think that at full dry thrust setting you would have X fuel flow and as you enter each AB stage that would increase so that the fuel flow variable was the sum of the dry thrust times dry TSFC and the added afterburner thrust times AB TSFC.
But it is not so. Once you enter AB the fuel flow rate is AB fuel only. So if you go from full dry into AB stage 1 the fuel rate typically drops by half even though the thrust value is correctly increased.

Has anyone else noticed this and if so what did you do?
Roy
 
I think I have a method that should work.
Record 1524 gives Afterburner (AB) scalars vs Mach. this is a 2 column table.
At Mach 1.3 the scalar might be1.5
Lets also assume the AB has stages 0 through 5, and we are considering Stage 5.
This means that the full 1.5 scalar is applied to the dry thrust so the 5th stage adds 50% more thrust to the dry thrust total.
With 5 stages, stage 1 would add 10%, stage 2 20%, etc.
At this stage we can apply the dry thrust TSFC to the the first 2/3 of the total thrust output as (A:TURB ENG JET THRUST:1,pounds) and the AB TSFC to 1/3 of it.
That would give us a fuel consumption rate which would need to be written to (C:SIMVARS; ENG FUEL FLOW PPH:1, pounds per hour)
I now need to learn how to read Record 1524 and would appreciate any offerings.
Roy
 
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