Good Descent Calculator.

Hello!

To achieve a 3º descent rate you must multiply your ground speed by 5.2. Eg. You’re travelling at 500knots (ground speed). 500 x 5.2 = 2600. You should descend at 2600 feet per minute to achieve a 3º descent speed.

Note: as IF does not have a Flight Path Angle (FPA) option, you must monitor your ground speed and change vertical speeds as required. See the below table to assist in this.

Ground Speed (knots) 3º Descent angle (ft/min)
96 500
115 600
134 700
153 800
173 900
192 1000
211 1100
230 1200
250 1300
269 1400
288 1500
307 1600
326 1700
346 1800
365 1900
384 2000
403 2100
423 2200
442 2300
461 2400
480 2500
500 2600
519 2700
538 2800
557 2900
576 3000
596 3100
615 3200

Knowing when to commence decent for a 3º descent angle is very easy to work out! Take your current flight level, subtract the flight level you wish to end at and divide by 3. For example, to descend from FL410 to FL30, (410-30) = 380. 380 / 3 = 126.667. That means you’ll require 126.667 nautical miles to descend to FL30 from FL410.

Ensure you take into consideration the altitude of the destination airport and ensure you take into consideration the final 3000 ft. Eg. To descend from FL410 to FL30, you must allow an additional 10 nm to depend from 3000’ to 0. It is always a good practice to add a few extra nm on to the descent rate to ensure you’re at the desired altitude on time.

Hope this trick was helpful.

Regards,
@Transport_Hub

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