wrote:
....
I don't think there are any computer based "FAA approved software".
...

I AM nit-picking here, no more....

The FAA offers for download to the people who need it, a PC application
which will compute the spherical geometry for the distance and angle
between two lat/lon coordinate pairs, or location of a point at a given
distance and bearing from a given lat/lon etc., etc.

If you need a standard computation for navaid siting etc., this is it.

It offers to even fewer people the data tables on which they base the
specifications for airfields and navaids, for checking and finding
corrections.

Brian W