Mission.Control wrote on Mar 1^st, 2019 at 3:10pm:

Colvale wrote on Mar 1st, 2019 at 8:57am: Is it any wonder, when you have selected a V/S speed of initially -800 fpm descent then all of a sudden you increase it to -2600fpm descent? Naturally the IAS will shoot up because the aircraft is pithing down at ridiculous  ::) I think you missed what I said...I intervened at the 0:14 mark. I turned VNAV off, which switches V/S mode on automatically. Whatever the current decent rate is at that moment is selected as the V/S fpm. At 0:48, I attempt to re-engage VNAV but it again blows through the speed restrictions. At 0:57, I intervene again because it's pushing the throttles all the way forward. Turning off VNAV switches V/S on again. On my next flight, I'll get a video of it's attempts to push through the sound barrier with VNAV on (without my intervention), if that's what you'd like.

No need for a video.

Let me try and get my head around this. Why did you intervene and switch off VNAV in the first place? Did you not trust it to bring your aircraft to the FL you wanted? Yes, I am aware that it switches to V/S, but even so, that rate can be set by the pilot.

I have never had issues selecting the SPD I want or letting VNAV descend to what I set as my ALT.

Kindly give me your routing and I will try this scenario out to see if it manifests itself.