Thrust control in Vertical Speed Mode
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When the aircraft is descending in Vertical Speed Mode, the PATH window of the FMA correctly shows "V/S" and the vertical speed is controlled by the autopilot. The THR window is showing "LL", and the SPD window shows "IAS(E)". As a result of this unusal autopilot behavior, the speed can not be maintained. In my opinion this is not correct. The THR window should be blank unless the thrust needs to be set to the lower limit "LL" to maintain the selected speed. The SPD window should be showing "IAS(T)". The selected speed should be controlled by the autothrottle system, not by the elevator.
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When the aircraft is descending in Vertical Speed Mode, the PATH window of the FMA correctly shows "V/S" and the vertical speed is controlled by the autopilot. The THR window is showing "LL", and the SPD window shows "IAS(E)". As a result of this unusal autopilot behavior, the speed can not be maintained. In my opinion this is not correct. The THR window should be blank unless the thrust needs to be set to the lower limit "LL" to maintain the selected speed. The SPD window should be showing "IAS(T)". The selected speed should be controlled by the autothrottle system, not by the elevator.
@Photonenbremse looking at your STATUS MFDS. The system is definitely confused on what you want it to do. This is one of the many old autopilot logic bugs you have found that the Fokker has in real life.
Best recommendation is autopilot disconnect, FDs off, FD back on. Autopilot re-engage, then speed knob pull and VS again.
