#1 - Divide groundspeed by 2, then add a zero.
example: 120kts / 2 = 60, add '0': 600 fpm
#2 - To maintain a 3 degree glideslope (eg. ILS) multiply your groundspeed
by 5. The resulting number is the rate of descent to fly.
example: Groundspeed = 110 kts x 5 = 550 fpm rate of descent
to maintain a 3 degree glideslope
#3 - With glideslope out on an ILS approach with DME, multiply the distance
to go by 300. That should give you the height in feet you should be above the
example: 4 nm to the threshold. Multiply by 300 = 1200ft
#4 - Add a zero to your indicated speed, divide by two. This should keep you
stabilized on the approach.
example: 150 knots on the GS. 150(0) / 2 = 750fpm descent. 120(0) / 2 =600fpm descent,
#5 - Take your AGL height and divide it by three hundred. This is the distance
from the threshold you need to start your three degree glidepath.
example: 600ft AGL / 300 = 2 nm