This works fine for me,
Take your altitude and multiply it by 3. That equals your distance in miles to begin your descent. 2. Now take half your ground speed. This is your rate of descent in hundreds of feet.
Ex. If you are flying at 12000ft at a ground speed of 150kts and you need to descend to 2000ft, the difference is 10000ft. Multiply 10*3=30 miles out you must begin your descent. Half your ground speed is 75, add a zero, and 750 ft per minute is your rate of descent.
KW
