P-51D Mustang: Conic Formula in Excel
A quick technote on entering a conic formula in MS Excel spreadsheets. Getting the correct syntax is critical to achieving correct results.
I am updating the ordinate datasheets for the P-51 B/C and D models to incorporate new information using the various conic formula according to the curve type. Typically with these equations, there are a number of constants to be established to input to the final quadratic formula.
The original formula for one of the constants “P” is given as shown (1). If we enter the formula as prescribed in a hand calculator it will evaluate correctly but will not work correctly in Excel in this format. So we need to tell Excel to essentially divide everything in the top line by everything in the bottom by adding parenthesis as shown (2).
The bottom line shows the actual input in the excel formula bar (3).
We are continually working on updates to the Ordinate and Cad package so watch this space for new articles. There will also be in-depth tutorials on interrogating ordinate information to find max-width, tangents and matched second-degree curves as well as updates on detail drawings.
Aviation CAD TechNotes 
I modified some lisp routines for AutoCAD to plot those curves. Writing the equations in Autolisp is somewhat tedious.
Sent from my iPhone
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