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fsxswissflyer

When do I have to descend?

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Hi there,

 

First of all thank you very much to all the developers for this really nice product. I really enjoy flying the CRJ.

So I've done some flights in the past couple of days and there's one thing that I still don't get. When do I have to descend? I mean I've watched streams and videos, read the tutorial but I still don't know when to descent because the TOD point on the ND is always too late which means I have to descend at a VS of about -3000fpm and more, which is kinda fast in my opinion. So is this a bug that the TOD is not displayed correctly or am I just incapable of flying the aircraft ? ;)

 

Thank you very much and have a nice evening.

 

Alex

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You can use a simple method. Calculate the difference between your current CRZ ALT/Level and the first Restriction, share this value 1000 and multiply this value with 3.

In this NM distance you beginns with the Descend.

At beginn you read the Ground Speed and share this value 2 and multiply this value with 10. This is the vertical speed, you needed.

 

Example

 

Current altitude/Level = 37000

next/first restriction = 11000

difference = 26000

26000 / 1000 = 26

26 * 3 = 78 NM

 

Current ground speed  486 Kts

486 / 2 = 243

243 * 10 = 2430 ft/min vertical speed

 

78 NM before the waypoint with the restriction you start the descend with an vertical speed 2430 ft/min.

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Hi Alex,

 

to answer your question from the header:
Whenever you pass the TOD, ATC asks you to descend or when you feel it makes sense to descend now.

 

We could do it more complicated (I am sure someone will give the detailled answer), but 3000fpm does sound reasonable.

Going down with a normal 3° your V/S will be about 5 times your groundspeed. That makes up for around 2500fpm. A little bit more or less is totally normal.

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28 minutes ago, FraPre said:

You can use a simple method. Calculate the difference between your current CRZ ALT/Level and the first Restriction, share this value 1000 and multiply this value with 3.

In this NM distance you beginns with the Descend.

At beginn you read the Ground Speed and share this value 2 and multiply this value with 10. This is the vertical speed, you needed.

 

Example

 

Current altitude/Level = 37000

next/first restriction = 11000

difference = 26000

26000 / 1000 = 26

26 * 3 = 78 NM

 

Current ground speed  486 Kts

486 / 2 = 243

243 * 10 = 2430 ft/min vertical speed

 

78 NM before the waypoint with the restriction you start the descend with an vertical speed 2430 ft/min.

   

   ...and if you want to further fool-proof this valuable method above, my instructor taught me:

if Talwind > 75kts = multiply altitude to lose by FOUR instead of three .

 

and for even more safety, add 10% to required V/S    

GS = 486
486/2=243

243*10 =2430
2430*1.10 2700 (2673)

 

Off course this is just a numbers game of academic interest and usually you can make up for errors by deploying speedbrake and faster airspeed during descents if ATC permits (maybe these actions is frowned upon in a CRJ :) )

But with some very basic tools you can come a long way...

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15 hours ago, fsxswissflyer said:

Hi there,

 

First of all thank you very much to all the developers for this really nice product. I really enjoy flying the CRJ.

So I've done some flights in the past couple of days and there's one thing that I still don't get. When do I have to descend? I mean I've watched streams and videos, read the tutorial but I still don't know when to descent because the TOD point on the ND is always too late which means I have to descend at a VS of about -3000fpm and more, which is kinda fast in my opinion. So is this a bug that the TOD is not displayed correctly or am I just incapable of flying the aircraft ? ;)

 

Thank you very much and have a nice evening.

 

Alex

 

also you can configure the the vnav angle of descente (and so the TOD) in the mcdu vnav perf pages.

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Just now, david.hilker said:

Can I actually see the deviation from the glidepath somewhere?

yes on the pfd

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I follow the charts for the STARs usually. But I use vox atc so most of the time they are on the TOD by a few miles. 

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TBH the aircraft should tell you what descent rate to use in the MFD when you have a lower alt input at a waypoint, as you approach it. but it hasn't worked for me.

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