# When is the best time to start descending?

What time should I descend?

My favourite flight attitude is FL350

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Its diffrent for each flight level.

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Probably before you land 😉

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The top of descent (Tod) is never a constant number. It changes from flight to flight. However, using the variables from each flight, you can figure out when to descend using a simple mathematical equation:

TOD (in nm from the airport) = Flight Level Of Cruise - Desired Flight Level / 3

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If you don’t wanna do all the maths, just start descending with around 30 minutes ETA.

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This is how i do it:

cruise flight level -( airport elevation + 3000) : V/S= minutes before i have to descent

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Too early. Just take the ALT of the airfield and subtract that from your cruise. And then half your cruise then start decent at that time.
Example

Cruise: FL350
Airfield ATL: 2000
35,000-2000 = 33,000
33/2 = 16.5
So in that case you’d start descent around 16 minutes out.
The 2 is VS speed of 2000:)
I use it every time and works pretty well, just remember the lower you get you should slow down:)

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This is a very unrealistic way of doing it.

What do you mean is not realistic its just diffrent way… What would be the realistic way?

Enlighten me on a “Realistic” Way:) Always open to new ideas/advice👍 and i know it’s not realistic. But it works and is probably one of the easiest and safest ways on IF

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Here’s another way https://fpltoif.com/ make a FLP using this website, i believe it’s gives you a descent profile and a climbing profile as well

It’s long to explain but in short :

1. Throttle idle
2. VS down
3. Monitor speed and keep it inside a window (m. 78 - m.70 later 300ias - 250ias)
4. Adjust VS and keep throttle to idle or low power.
5. If over 250 at FL100, stop at it and continue (you should be around 30nm of your destination)

you should be much lower the FL100 when 30 NM from your destination.

That’s with a lot of calculations. If you descend from FL300 and have the nose level constantly level then you’ll be at 3500ft close to the airport.

Stil doesnt explain when to descent

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It’s pretty basic, takes less time then most of the other ways to find TOD. And like i’ve stated already

I don’t go deep in calculations

Let’s say I’m at FL350

35×3 = TOD (105nm)
35×3.5 on heavys

What makes you say that?

And thats the realistic way?