Transponder AUTO ALT/GND Setting

[Drthomasd]

I have the transponder set to Auto alt/gnd in my RV-12.
On takeoff  the transponder cycles from GND to ON.

Alt does not come on automatically. Is this the correct?

Thanks,

Tom

 

[dynonsupport]

It should go to ALT, not ON.

When you manually press ALT, do you get ON at the top or ALT at the top? If you are only getting ON then you probably have something mis-configured and the transponder isn't getting an altitude source.

 

[Drthomasd]

Thanks for the reply!

When I manually press ALT, ALT will appear at the top of the skyview and mode c is received by the tower.

Presently when I take off GND goes to On.

Thanks,

 

[dynonsupport]

It should go to ALT. I honestly don't even know how it could not do this...

In your setup menu, do you see "GND ON ALT" or "AUTO ON ALT"?

 

[kalewis]

I noticed while practicing slow flight in my RV-12, GS was 38kts... My transponder switched from altitude into ground mode. I was at 3100 feet FYI. Thought that was interesting.

 

[Dynon]

When in AUTO mode, the transponder has an algorithm that it uses to determine whether it should be in ALT or GND mode. I don't know off the top of my head what the conditions for the switch are, but you may be able to fool it by doing some slow flight.