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Jerec
02-18-2014, 11:54 AM
Hey everybody,

in my flights i wonder every time, when i start descend, if im doing something wrong. When im at cruise alt (e.g. FL350) i set the next alt to 200 and press alt button for managed descent. After pushing, the engines go to idle as expected, but the aircraft "dives" into heavy descend with -4000 or more. So my question is, is this behaviour due to the uncompleted VNAV-implementation or do i have to descend via "selected alt" and V/S e.g. -2500 to control descent? Or is the SOP for the descent completely different?

Regards Henrik

Stephan Schwarz
02-19-2014, 03:04 AM
As far as I understood the VNAV is not working 100% exactly. I also select -2500 and activate the selected descent to avoid my XPAX passengers screaming :)

asessa
02-19-2014, 05:38 AM
Hi Jerec, in my last flight (B32) i started descent in management mode without problems and without -4000 f/m ...
My question is : which Cost Index value did you insert into for descent?

Regards

jeehell
02-19-2014, 04:36 PM
Hi

-4000fpm is not an excessive value when high and light weight...

Regards,
JL

Jerec
02-24-2014, 04:53 AM
Hello together,

yesterday i made i flight again to check your tips. Indeed, as asessa mentioned, the cost index was the same as for whole flight (60), which produces at a weight of about 60 tons a descent with ~300 kts. In idle, this would cause the "dive" into descent. In the next flights i will check the descent with other values and corresponding speeds to get best results and keep you informed. Yesterday i had to break up the flight because my 3rd PC for FO PFD/ND/MCDU failed with the PSU and i had to look after it.
Thanks for your comments!

Regards Henrik

asessa
02-24-2014, 05:07 AM
Hi Jerec, you can try a CI value about 25 to have a good descent speed.

I also made a flight yesterday ,with a CI of 45 , and never i had a speed of 4000 ft/m to descent.
Many airliners use a CI value between 15 and 40 .


Regards

staju
04-25-2014, 03:11 PM
I have the same porblem with more than 4000ft when the descent starts. With that problem I am not able to follow the descent profile and an RNAV-profile Approach