When do you know when to start descending?

This what I usually do I got it from a topic somewhere on here I forgot where it was or what I searched but you take your current altitude say your cruising at 34,000 and you wanna descend to 3,000 subtract 34,000-3,000 you get 31,000 divide that by 1,000 or 1 and you get 34 times that by 3 31+31+31 you get 93 So you should start descending That far from your destination or what I do I usually add 10 miles so I descend like 110 or 120 if I feel like I’m too fast I usually slow down for descend around like 130 miles then begin my descend at like 115 or 120 with a vs of 1800 make sure to descend at vs of 1500-2500 but yea that’s usuallly what I do hope it helps

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No need to calculate that much, just use http://aerotexas.com/desplan/desplan.php

Its pretty accurate and I never had any issues with it.

Some tips:

FL300-350: 130nm, -1800fpm
FL350-380: 140nm, -1800fpm
FL380+: 150-155nm, -1800fpm

This is also quite accurate, however you need to monitor your distance/height and change the V/S if needed. (Oh and don’t forget to distract the airport elevation from your initial climb)

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How to get the answer

Several good threads already on this if you search ( already linked above)

Rule of thumb take your Flight level (ie 35,000 ft =FL350) then devide by 3. Then add about 20nm for slowing down, especially in the B777!

Ie FL350 = 350/3 = 116nm + 20nm = 136nm DTG.

REMEMBER to make alterations for height of airport above sea level.

PS this is similar to what professional pilots do IRL

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o as an example would this be right

my altitude is 35000 and the airport is 2,000 ft height. It would be 3500-2000 which is 33,000 and add 100 to the first two numbers which would be 133. So I would be descending 133 nm away from the airport?

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Thank you for all the help

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Thank you :)

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Yep that’s correct!

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Thank you for helping me

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Of course!

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For me, I usually start descend based on my altitude.
example: if I am cruising at 35,000, I would start my descend about 120 nautical miles away from airport.
Hopefully some helpful info.

  • IFS
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Thanks, I’ll be sure to try it! 😀

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Below 10000 feet it’s quite difficult to descend at a rate of -2000fpm without gaining speed. You should rethink your theory by making a slow down to maximum -1500fpm under 10000 feet.

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It depends, on the aircraft just alter the VS after 10,000 as you near the point where you want to enter the glide slope


This works the best:

Your crusing alt. (Ex. 32,000)- perfect alt to go on ils (3,000) : V/S (-1800) you are decending = 16,1111 mins to your destenation you start decending with v/s - 1800

32000-3000: 1800 = 16,1111

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Wow that dosnt give you a lot of tine to descend and lose speed. No need to overcomplecate the operation. Professional pilots ( see the link in my post higher up) which is FL/3.

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That would probably work out fine if you sold roller coaster tickets to your passengers and descended between 2500 and 3000 fpm

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