# Ideal descent point?

How many miles outside the aerodrome is ideal to start descending between 220MN and 280MN from the destination, is there an application to calculate?
On my flights I always start to descend 120mn outside the destination.

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Here’s my math:

Take your cruising altitude and hack off the last three digits.

Multiply the number by 3.

Add 10 and round up or down.

For example: at 33,000, you take that to 33. 33x3 is 99. Round that to 100. Add 10 for 110. Start descent 110 nautical miles out with V/S between -1800 and -2000 feet per minute.

Hope this helps! I’ll be glad to answer questions.

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That looks cool! Thanks for your tip.

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No problem! Glad I could help :)

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Here is what I do, start your decent, when your cruise altitude matches you ETE to DEST and keep a stable decent all the way down

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When VNAV comes out with 20.1 this will be a lot easier

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Thanks for opination!

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Have shared this vid a couple of times, but it clearly shows best way to calculate your TOD. Good luck

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I have been using this tutorial since this video came out, (Swiss001)

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Hey mate, good question! An app that nobody else has mentioned yet is Virtual Hub. It’s an app where you can access charts for airports, and gate info, and there is even a TOD (Top of Descent) system in it! I recommend you check it out, as the descent distance is pretty accurate, I use it for every flight! If this isn’t for you, feel free to use any other technique here that fits you, there’s no right or wrong. ;)

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Good estimate that will work 9 times out of 10 for an altitude and speed of FL350 and M.84 respectively is about 20mins out from your destination, descend at a rate between -1200 and -1500fpm. Give this a try on your next flight and play with it. It’ll get you to about 10000 within 25 - 50nm of your airport. 🙂

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I start my descent when my “ETA to Dest” is in between 15m and 20m. Depends on what my altitude is o.o

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I use these formulas

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.

How do you know what V/S to have?

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Hey there Junior!

I strongly recommend you watch this video.

And use this a source:

As of VS: Use the link over here.

Happy flying! 👨‍✈️

Ace out! ✌️

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Here’s one it does TOD and your V/S

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This may sound weird but i start my descent 25 minutes out. It’s the same nautical miles because I always start at around the same time.

So once I’m 25 minutes out i start descending at -2000fpm. Once I hit below FL280 I slow my speed to 195 knots and change my descent rate to -800fpm to -1000fpm.

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I generally take an average descent profile of 3 degree. So i roughly add 3.5nm for every 1000ft i’ve to loose and add 20% to it for speed to loose and other stuff.
Works for me most of time. Sometimes on wide body i’ve to get my spoilers out but very rare. Hardly 1 out of 10 times. Rest 9 times i’m almost on my ideal approach.

Suppose cruise altitude fl350. Airport elevation 1100 ft.
Altitude to loose 34000ft.
34 x 3.5 119nm
Add 20% about 143nm out.

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I think thats a good point. Look at this

i hope this wil be clear off for you.

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yes it does sound weird :)

descents are usually calculated as a function of distance remaining rather than time remaining. Also slowing to 195knts at FL280 and having such a slow rate of descent is odd - you shouldn’t be that slow until you get somewhere near the airport.

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