# Top of Descent Calculation

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Hey again,

No TOD or TOC in this Hawker. Is it possibily time for some DC-9 influences of calculating this on our own?

EX:

FL310 --> FL150 | 16,000ft down....then 16*3 = 48nm

So...start your descent 48nm out...round if needed, so 50nm.

Next, what is your GS? For me...440. In that case, 440/2 *10 = 2,200fpm 50nm from the desired point.

Any corrections? Am I flying this right haha? That's have I been doing it, works pretty fine...sad that there is not T/D calculation though!

MD

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Hey again,

No TOD or TOC in this Hawker. Is it possibily time for some DC-9 influences of calculating this on our own?

EX:

FL310 --> FL150 | 16,000ft down....then 16*3 = 48nm

So...start your descent 48nm out...round if needed, so 50nm.

Next, what is your GS? For me...440. In that case, 440/2 *10 = 2,200fpm 50nm from the desired point.

Any corrections? Am I flying this right haha? That's have I been doing it, works pretty fine...sad that there is not T/D calculation though!

MD

Yep, you're doing it right! It's unfortunate that Carenado did not program any VNAV perf functionality into their FMS - and I doubt that they will ever add that feature. The only option is to hand calculate your own TOD the old fashioned way.

Open skies,

MD

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That seems right but why not just multiply ground speed by 5. Its just a bit less math.

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To get a three to one descent I take ground speed, drop the last digit and divide by half for FPM in hundreds...

440 kt 44 22 2200 FPM with less math

Or, VNAV with Bert PIeke's F1 GTN 750 mods works great!!!

Donald

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There is a descent calculator in the the GTN 750 under utilities tab from memory

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