Speed dropping below Selected Speed on final approach

[gvert]

On final approach, the speed dropped below the selected speed (VAPP in the FMS 131 - Selected VREF 137) and stayed there for the whole approach.

[Agent_Wurst]

I can only tell you from my experience that this is a "normal" A300 behavior to a certain extend 😅
Speed drops 2-3kt below the selected VAPP, but then the ATS regains VAPP within 5-10 seconds.

[Crabby]

Servos from the 60s and 70s.  

[gvert]

11 hours ago, Agent_Wurst said:

I can only tell you from my experience that this is a "normal" A300 behavior to a certain extend 😅
Speed drops 2-3kt below the selected VAPP, but then the ATS regains VAPP within 5-10 seconds.

Yeah, slightly dropping below and regaining is kinda expected. But it stayed there, about 5-7kts below, for the entrie approach.

[Alexair]

Did you middle-mouse-button clic the speed selector rotary knob after selecting 137 ?

[gvert]

13 minutes ago, Alexair said:

Did you middle-mouse-button clic the speed selector rotary knob after selecting 137 ?

Nope. Middle-Mouse Button clic enters free camera mode for me. So that doesn't do anything to the knob.

Edited December 29, 2023 by gvert

[Alexair]

Ok, different biding than mine. I believe that you need to find a way to push the speed selector knob after selecting the APP speed you want (might be wrong though, anyone to confirm?)

[gvert]

8 hours ago, Alexair said:

Ok, different biding than mine. I believe that you need to find a way to push the speed selector knob after selecting the APP speed you want (might be wrong though, anyone to confirm?)

Nah, thats only PRE SET, normally to fly Selected you need to pull the knob, which I did.

[Alexair]

Nope, I'm not talking about the PRE SET, there is another function (1 of them is push the other is pull, don't remember is PRE SET is push or pull).

[Agent_Wurst]

You have to push for a preset. But for the approach we don't use the preset function. In case of go around, we preset the speed to 250kts (or as required) to allow aircraft acceleration by pushing LVL/CH or at ALT* engagement, whichever is first

[Agent_Wurst]

During an ILS approach you are in selected speed, so pulling the speed knob has no effect. During a 3D RNP approach, flown in NAV/P.DES, the speed window is blank and you only can select the VAPP in the FMS. But my company has a newer FMS, so I don't know how the 3D RNP works with the old FMS