Descend VS?

Hello IFC,
I am very troubled recently as to what on average should my descend VS be (-VS)? I usually descend at around -800VS and I’m not sure if that is correct. I also, just as a rule of thumb, start descend about 30 minutes away from the airport. Don’t know if that is correct?

Cheers and stay safe,
Jing

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My basic rule of thumb is any V/S under -1,500 and there are also ways to calculate your top of decent. Try out VirtualHub.

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Isn’t -1500VS a bit too much and your nose just goes below level?

I usually descend at 1800, on average 150nm out.

I count every 12,000ft as 50nm. It actually works very well.

At 12,000ft, about 50-60nm I slow down to 200-230knts on a 1200-1400 desent to the runway.

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Have a look at this
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=2ahUKEwiXtKyrx9voAhVG4aQKHR_5DyIQwqsBMAB6BAgKEAQ&url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3Dotn03svda1A&usg=AOvVaw3ZLcFJNdZ3zK30C1OicVSG

there are some different rule of thumb out there

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I do under -1,500, usually -1,200 for me. I was just saying anywhere under -1,500

Also another great source

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I see most people descend anywhere below -1000VS and I think it’s too deep a depression so I have kept it at -800VS. Just wanna know what is the most realistic VS to set for descend.

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I’ll normally use https://www.freedomair.us/DescentCalc/descentdistance.php to calculate my descent. It already comes with the descent rate

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VS -1800 is fine, its normal

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I looked it up. A normal airliner usually depends at a rate of -900 to -1,200. All up to you though. It is based on opinion.

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Exactly the same for me.

Another thing I use at times is also this descent calculator, its great.

http://aerotexas.com/desplan/desplan.php

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So there is no hard or fuss rule?

3 degree slope. Half your ground speed for V/S, triple your altitude for top of descent plus a buffer to lose energy

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It really depends on the pilot and some other things. Generally I aim to be at FL250 when I am 100nm out. I am usually descending anywhere between -2500 and -500 fpm, but you could descend in excess of -5000 fpm, if for example ATC had to delay your descent due to traffic or other factors.

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No, you can realistically descend with -2000+. At time IRL flights may also go below -3000 too.
Can’t find a better example, but this is a decent rate of more than -2000 and its very normal and fine:

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For VS, just multiply groundspeed*5, be sure to round up or down.

A formula that always works for me is current altitude-target altitude/100 then divide by 3. Just gotta change the descent rate for every 20kt loss or so, always gets me there accurately.

Here’s an example if you’re still confused. You’re at FL410 and want to get down to 3000 feet. 41000-3000=38000. 38000/100=380. 380/3=126.7, so you start your descent around 126.7nm from your target waypoint/fix. Lets say you’re at 551kts and nearing TOD. Well, 551*5=2755, and that’s closer to 2800 than 2700, so you round up and go for a descent rate of 2800fpm. Obviously you’re gonna start slowing down, so once you dip below 551kts you’re gonna round down to 2700fpm, because below 550 and (eventually) 540kts, whatever value you multiply 5 by, will be closer to 2700 than 2800. Basically you keep decreasing descent rate every every 20 knots. So your descent rate would be decrease to 2700fpm below 550kts, 2600fpm below 530kts, 2500fpm below 510kts, so on and so forth. Hope that helped.

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I start from -3200 and once I enter the denser part of the atmosphere I drop it down to 600 slowly to maintain a 250 knots glide.

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This topic has been discussed many many times, have a look in the search bar and have a read! Mean time check out this video by Captain Joe which will give you all some great tips.

PS as a rule of thumb I use following VS for descent: -2500 above FL250, -2000 above FL200 and various -1500 to -700 below that. Happy landings

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i generally descend at -1300, although if i have to expedite, or i started my descent late, ill go down to -1600 if necessary

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