unreliable vs pitch switch

flyforever

Why is the VS switch so fluky. At times,on autopilot, no matter what I do, the aircraft will not commence pitch up or down. Can someone please provide me with the correct procedure. Currently, I turn off ALT Hold, then VS and then I press the pitch lever.
I know that the mouse cursor on the switch is more effective, but I am using a programmed switch.
thanks
tony

b3lt3r

@flyforever I find that for VS to kick-in the target new alt must be active via the ALT-ARM selector. If not it will not engage.

flyforever

@b3lt3r Thank you. Just to be sure I understand.

first engage ALT-ARM button
then use the pitch switch.

I will try it. Thank you again.
tony

b3lt3r

@flyforever what I do is set my new alt, press alt-arm, then VS and then use my controller bound to pitch trim to increase or decrease commanded fpm.

Good luck!

flyforever

I remember watching a tutorial in which the vs button was pressed only after achieving the desired vsi. I will try your method .
tony

plhought

Set AP on.

Set your pitch and desired V/S via Pitch Sync or the pitch switch on the AP controller.

Then select V/S on AP panel.

b3lt3r

@flyforever I believe both methods work - when I climb - I normally do it in IAS mode and will get to the climb rate then engage IAS and finally AP. If I want to change it then use the temp AP release and pitch to what I want then release.

On descent 99/100 I use use and will use the method I outlined first - new alt, VS, pitch control and down I go - normally around 2300fpm which holds around 250kts. That sequence does work equally well for climb (for me).