What does "pulling" the speed selector and heading selector knobs on the FCU do?

[Saint Broseph]

Greetings everyone,

I apologize if this is in the wrong section and/or a stupid question. What does "pulling" the speed selector and heading selector knobs on the FCU do in the A300/A310?

[Saint Broseph]

I forgot to mention the vertical speed selector.

Edited August 10, 2021 by Saint Broseph

[AntonBunk]

Pulling knobs generally lets you select your desired value for e.g. Speed, overriding FMC calculated values or route constraints. For instance when in profile mode you might be given a ATC speed restriction and can pull the speed knob to tell the aircraft to maintain that speed.

Pushing, on the other hand, does different things:

• Speed: Preselect mode; doesn't change the speed that is presently dialed in but sets a speed target that will be selected if changing the vertical navigation mode (for instance you might set your V2 speed before takeoff, then pressing the speed knob and dial in the green dot speed after flap retraction. After takeoff, even though green dot is displayed on the FCU with the PreSel light illuminated, the aircraft will fly the V2 speed until you select Level Change, at which point it will accelerate to green dot speed, so you can retract the flaps
• Heading: Your present heading will be dialed in, so when you press heading select it will maintain your present heading. Very handy.

[tallen74]

How would you pull the knob. I can push it no danger but can't pull a knob