GTX 327 switching to ALT spontaneously

[prkaye]

I've noticed that sometimes when I check my xpnder in flight, or at the end of a flight, it has switched itself over the "ALT" mode on its own (i select "STNDBY" for my local flights over my home airport). Is this normal?

[Lionclaw]

I believe the 327 will automatically switch to alt based on either NMEA data from a connected GPS or air data (pins 19 or 22 if I remember right?).

Maybe Stein or someone else here will know how to disable it...

[647jc]

That's a configurable option, check your manual. It knows you have taken off by the change in the altitude provided it by the blind encoder output of the EFIS. The 327 can also switch back from ALT to Standby if you have it connected to a GPS and that option configured.