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Hello all,
With all of the stability and control derivatives of my 747 decided, it is now time to get thrust figured out. I am about 95% confident in my values of N1 and N2, and I have begun writing my own fuel flow system so I am not concerned with that.
I am using the method of setting table 1507 ram drag to all zeroes, and using 1506 for net thrust. Thankfully, NASA gives me corrected net thrust as a function of EPR and mach number, seen in the two below pages:
A later page gives CN1 vs. EPR, so I know exactly how to correlate CN1 to thrust by reading from the two tables, and I have formed a graph for Mach 0 and Mach 0.8 in table 1506 (others will come later).
It looks like this:
However, this graph results in far too much thrust at mach 0.8. I have been referencing this thread...
... And I noticed that jx's JT9D data gives 14600 lbs of net thrust at Mach 0.8 and CN1 of 102.4, whereas the NASA chart is showing around 41000 lbs.
What am I missing here?
With all of the stability and control derivatives of my 747 decided, it is now time to get thrust figured out. I am about 95% confident in my values of N1 and N2, and I have begun writing my own fuel flow system so I am not concerned with that.
I am using the method of setting table 1507 ram drag to all zeroes, and using 1506 for net thrust. Thankfully, NASA gives me corrected net thrust as a function of EPR and mach number, seen in the two below pages:
A later page gives CN1 vs. EPR, so I know exactly how to correlate CN1 to thrust by reading from the two tables, and I have formed a graph for Mach 0 and Mach 0.8 in table 1506 (others will come later).
It looks like this:
However, this graph results in far too much thrust at mach 0.8. I have been referencing this thread...
A discussion of how to correctly set up Corrected thrust table 1506
Go here for an explanation, http://fsdeveloper.com/forum/showpost.php?p=579052&postcount=24 then feel free to post questions in this thread. UPDATE: Here is a simpler explanation that may be easier to implement. http://fsdeveloper.com/forum/showpost.php?p=654582&postcount=5 It includes...
www.fsdeveloper.com
... And I noticed that jx's JT9D data gives 14600 lbs of net thrust at Mach 0.8 and CN1 of 102.4, whereas the NASA chart is showing around 41000 lbs.
What am I missing here?