how do the descent calculations work when slope is NOT 3.0 degrees down

[Rebrecs]

I have a flight plan software application that sets up a TOD followed by a 4.4 degree descent (slope). It switches to 3.0 degrees at the approach fix. HENCE, (what a word) -- Im looking for the right math book?

 

Internet search returns hundreds of docs and papers, every rule-of-thumb one would ever need - for 3.0 slopes.

 

I figure the 3.0 degree rules-of-thumb were derived from a more general formula. Might anyone have seen such a thing?

 

TIA

 

 

 

[PhrogPhlyer]

Here is the FAA's Decent Table.

It covers from 2 to 12 degrees and 30 to 180 kts (GS). You can interpolate if the slope is between those presented.

https://www.touringmachine.com/images/Climb_Descent_Rates.pdf

[lnuss]

Check out this site, the Aviation Formulary:
 

http://www.edwilliams.org/avform147.htm