Example:
FL400
GS 450
FL: 40 X 3 = 120 nm
GS 45 - 15 = 30 nm
TOTAL: 150 nm
Easy to check as you descend...
As you approach FL300 at GS 400 you figure out that you need 115 nm. If reaching FL300 you are closer then that then just increase your ROD a bit or vice versa if you're further out.
I do this quite frequently during descent to ensure I stay on profile... Normal requires very few corrections.
Works for the CL604 as well as for the Airbus family...
Will
