Vertical Speed (VS) issue with Boeing 747-8

Hello,
I have a vertical speed (VS) issue when flying the B747-8. I do fly that AC a lot and still having the problem, that when planning a decent (like 2.500’ out of FL 300), the AC does’nt accurately hold on that margin. It changes all kind of decend-rates. like 1.110’ but NOT those desired 2.500’. That way i can’t plan the time and distance that is needed for the decend. It drives me mad and I feel that I am doing something wrong here, also because it seems that nobody else seems to have that issue.

My procedure to decent is as follows:
While flying level at a given altitude and having changed the numbers to the desired Altitude, I press the VS-Button and then turn the VS-rate wheel. That should initiate the rate of decent, right? What the AC does is to decent but to a much lesser extend than planned. Is the FMC interfering here and choosing a somewhat “ideal” descend rate? :roll_eyes:

Can anybody here help me on that and tell me what I am doing wrong here? As I recall, the decent rates should always be nailed-accurate and precise.

P.S:: I don’t have any mods installed and fly the FS2020 in its original setup.

Is the airspeed staying the same and does the A/T system reduce thrust to maintain the selected speed when you are initiating the descent?

Thank you for your fast response!

Well yes, that speed should stay the same, and I don’t change the A/T. But I am going to focus on the speed next time I am flying

Thank you for giving me that hint with the A/T. I just did a long and thorough flight, testing all kind of settings and focusing on that A/T. And it could be that I just screwed up with the tiny at night somehow nearly invisible A/T knob or something else. At my testflight, the VS worked somehow fine again. Not perfect, but OK for the moment. I am going to observe this in my upcoming flights.

So thanks again for that hint. We have a saying in the german language: Sometime you just don’t see the wood with all that trees in front of you… :roll_eyes: