Hey guys, today I just want to share a really easy and quick way to calculate your rate of descent. It works every time for me.
First, you want to note your cruising altitude and speed. Let’s say it’s 30,000 feet at Mach 0.80. The perfect way to capture your ILS is around 3000 feet, so add your arrival airport’s height to 3000 feet. For this example, the airport’s height will be 0 to make it simple.
Next, subtract the 3000 from your cruising altitude of 30,000 feet. You will get 27,000. Divide 27,000 by the vertical speed you want to descend at. I usually descend at -2200 fpm, but you can do whatever you want. 27,000 divided by 2200 is ~12.3.
12.3 is the amount of minutes you should start descending at. I play it safe and go for 12.5 (12 minutes and 30 seconds). As soon as it hits that, start descending!
To work in compliance with the 250 knots and under under 10,000 feet I would suggest 270 KIAS under 20,000, 260 KIAS under 15,000, and 240 KIAS under 12,000. Remember to use your speed brakes!
I know there are many tutorials on calculating your Top of Descent, usually resulting in too high or too low descents, but this one aligns perfectly. If you have any questions, please feel free to ask me below. Thank you!