Hi

How do we calculate ft/nm?

6080ft in a nautical mile

 

Or just rounded to 2000 yards per mile

At a ground speed of 60 knots, your VS in FPM equals ft/nm. You can compute the ft/nm FPM by taking the ratio of your ground speed to the 60 knot baseline.

 

400ft/nm at 60 knots ground speed equals 400fpm.

 

At 120 knots ground speed, you will require 800 fpm.