# Time to decent planner

Can you all help me by telling me when to start are decent for airport or suggest any software for that Please?

This should be in #general :)

Yeah I’m stuck on that to when I fly to an airport that I never flew to I never know when to begin my decent

Hey! I actually made a tool for this just yesterday. Check it out at http://bit.ly/TODcalculator

I believe that this is the equation to calculate top of descent. I don’t think I’ve missed anything out but if I have then tell me.

``````         A - a
d =   ------------
tan(g)
-----------------
6076
``````

d = distance from destination (nautical miles)
a = altitude of destination (feet)
A = altitude of aircraft (feet)
g = descent angle (degrees)

The constant 6076 is there to convert between feet and nautical miles.

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It’s a very simple calculation. In order to be 10000ft AGL 25mm from your destination (giving you a good amount of time to descend to pattern altitude) simply take your Flight Level Of Cruise, and subtract the flight level of your destination airport, with 100 added to that. Then, divide that number by 3, add 25, and that’s your distance. Next, for VS, just take your Mach speed and multiply it by 1000 then by 3.

For example, I’m cruising 31000 ft at M.85 and I want to land at an airport with 2500ft elevation. Here’s my equation:

310-125=185/3=61.6+25=86.6

For my VS:
.85x1000x3=2550fpm

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A simple Speed, time distance triangle can get you vertical speed.

Sub out the distance for altitude in this case.

In your FPL page, you can see times to waypoints. If you’re descending from 36000’ to hit waypoint AAAAA at 11000’ and you’ve got 9:15 to go to waypoint AAAAA then take
25000/9.25=VS -2703

Another option is to use SIDS and STARS when creating a flight plan. These are real life approach patterns and they give detailed information including altitude, speed, etc…
I use them for every flight, so maybe give it a shot. :)

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We have dozens of topics like that. Please use search. :)

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@NeoPauliMittwoch you might be somewhat close when you said dozens. There are a ton of topics here on the forum regarding descent planning. Be sure to check out the interwebs too. Lots of good information out there too! 😐