When do you know when to start descending?

In an A320 or 777-300ER When would you know when to start desending, it’s been a question that I have wanted answers for a while now. If anyone could help, it would be much appreciated.

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I am falling around a hundred nautical miles.

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Check out some of these topics :). Or if you want to take the easy way out, you can always use this tool ;)

http://www.freedomair.us/DescentCalc/descentdistance.php

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Take the first 2 numbers in your height, add 100. Subtract height of airport. Has never failed me, and is quite simple. Descend at -2000vs

Ex:
Airport is 3,000 ft in height and your cruise is at 30,000. 30,000-3,000=27,000 and take the first 2 numbers and add 100 which gets you 127. Hope this helps! Ask me if you have questions about this

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At around 190nm I start my descent with a VS of 1400 usually. I’m not looking to be realistic but it’s the general set up I have most of the time. 3 x your current alt will roughly give the distance at which you need. So 330 is your alt = 33*3= 99nm but this will require a VS of around 2000 so keep it safe and start 150nm away for example with a less steep descent.

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Thank you for the help

So you start to descend 127 nm away from the airport?

How do I find out the runway elevation?

If you click the airport dot then it should tell you the elevation.

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ah yes
Thank you

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No no, depends on your altitude and airport altitude. That was just an example I gave 😊

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So where did you get the 127 from? Did you just add 1 to the 27? Sorry for the questions, just a bit confused.

I added 100. And it is totally fine! Keep asking away I am glad to help a fellow pilot!

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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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