What do these do?

[Bigbluss 304]

Hey all,

These are in the Black Square Bonanza: https://imgur.com/a/VBw1rJE At the top left of the dash. It looks as though the left button is the same as the CDI button on the GPS - so presume its a remnant from before a more advanced GPS with built in CDI button existed? Is this wrong?

 

How about the GPS/APR button on the right with 'ATM' and ACTV'? This doesn't seem coupled to the autopilot, but I could be wrong.

 

I've skimmed the manual for the aircraft and could find a reference to almost everything except these!

[sd_flyer 6,042]

Normally you have CDI button on GNS (gps) unit that switched between GPS and LOC mode . Like you said, this panel is convenient “wiring” to bring autopilot approach arm in front of the pilot . When you fly solo IFR it’s nice to have a shortcut

[Bert Pieke 7,585]

Not sure the buttons are wired up, but the readouts are handy as visual confirmation.

[Bert Pieke 7,585]

2 hours ago, Bigbluss said:

so presume its a remnant from before a more advanced GPS with built in CDI button existed

That is likely the case.  As a matter of fact.. is there not another GPS option in the panel?

[Bigbluss 304]

Thanks guys :) yup there's another gps option across the cockpit!

[Stearmandriver 2,296]

In older IFR GPS units, the CDI source select was often not built into the GPS and required a separate physical switch in the cockpit.  Usually it was over by the HSI or nav head, vs on the radio stack.  This was one style of selector that was used.