# When should I start my descent

Hey everybody. I have a few questions. First, I am in an A320, and at FL340 at M0.78. How many nm away should I start my descent? And the other question, what fpm should I do? And also I’m flying into EGLL.

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That would depend on whether you’re using a STAR (Standard Terminal Arrival). If you are, take the flight level of the first waypoint and subtract it from your Flight Level, then divide that by 3. That’s your NM. If you’re not using a STAR, you need to begin at around 113nm away.

Both methods will be initially at -2300fpm, and decrease with time.

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You can use this website:
http://aerotexas.com/desplan/desplan.php

@sebi-ue I looked it up and it said I start at 113 nm (I put that in because @DiamondGaming4 said around there. So I will be descending at -1800 fpm. Is that right?

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Yeah. But keep in mind that it isn‘t always 113nm. If you‘re cruising at FL380 you should start the descend earlier than if you‘re cruising at FL320. And also, if your KIAS changes, you have to change your VS too. When I used this website to calculate my descent rates, I checked the needed VS like 4 times during descend since my KIAS changed.
Meanwhile I don‘t need it anymore. If I‘m cruising at FL320-340 I start the descend when I‘m 120-130nm away from my destination, descending with ~1600fpm. I aim to be at FL180 when 60nm out. I figured that passing FL100 when 30nm away is good. If I continue descending with around -1500fpm I‘m always good.

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Hey! I was looking for this too! But found a legendary topic that actually helped me find the (literally) right spot to start descending!

Right here is the topic: (Please bookmark! 📖)

From 50nm at -1700 because u’ll be reducing speed so it will make up

Top of descent (TOD) is how far out you should start descent for a desired rate of descent (TOD)
TOD= (Alt/Rod)*(Gs/60)
Pick a rate of descent you like
Alt= Altitude
Rod= Rate of descent
Gs= Ground speed

If you want to know how fast to descend from a certain distance then;
Rod= (Gs/60)*(Ft/Nm)
Ft/Nm= Altitude loss needed divided by the distance to destination.

I either use a Descent calculator, time or a STAR for my descent. If I’m using time to calculate then I start about 20-30 minutes before ETA (depends on my altitude)

The calculations are:
Distance = flight level diffrence * 3
Descent VS = GS/2
I tend to descend earlier and with less VS so I don’t have to change it all the time to avoid an accidental overspeed.

I’d say about 140nm out at a decent rate of -1800vs (-1800vs) and then adjust accordingly.

I usually start decent at 130-140 NM away from the airport at -1800 FPM speed 290 then at FL100 speed 250 then 70NM out 7000 ft and when you are aligned with the runway always go 3000 ft but look at the airport elevation

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Same that’s what I do to

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Start to descend when you are 25-40 minutes away from your destination. Works well for me. Sometimes, forget to check the time, so i have to circle around to descend.

Start your descent 100-150 nm(depending your altitude) away from your destination. Use this formula: devide your altitude in hundreds of feet by 3 and you will get your rough TOD. From that point its very simple: just times your distance by 3 and times that by 100(This gives you a 3 deg descent path all way down so ajust your vs).
Eg: 340÷3= 113nm ~115nm =TOD.
Then every couple of thousand feet times the distance by 3 and 100 to check your on the descent path.
Eg: 50nm × 3 = 150 ~15000 feet at 50nm
20nm × 3 = 60 ~ 6000 feet at 20nm
Also dont forget to add your dest airports altitude for more accurate results.

Thank you everybody! Sorry I wasn’t responding as it was night in my time. I have look at how to calculate top of descent topic and I understand it. Thank you all for your help 😉

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