COM/GPS breakers - info

In my “C” config airplane, I have a COM1 and GPS1 breaker on the Essential Avionics buss associated with the top Garmin 430, and a COM2 and GPS2 breaker on the Non-essential Avionics buss associated with the bottom Garmin 430.

I got to wondering - does that mean that there is an independent COM function in the Garmin, that would continue to function if, say, the GPS portion died? If so, would the display still work? If not, how would I set the frequency?

Normally, I’d sit in the airplane and experiment, but since we’re in the middle of some unpleasant weather, I thought I would ask the folks at Cirrus, instead. I got a very quick response - interesting, too. In the interests of better system knowledge for all, I am posting the reply below.

  • Mike.

"-----Original Message-----

Sent: Tuesday, March 06, 2001 3:13 PM


Subject: RE: Question


Good question.

The 5A GPS breaker powers everything (GPS, NAV, the COM board, & the display), except the COM transmit.

The 7.5A COM breaker powers the COM transmitter, the single largest load in the radio.

If you lose the GPS breaker, you lose everything, since the transmitter will not function without the COM board.

If you lose the COM breaker, you lose the ability to transmit only, but you will retain the ability to receive. GPS, NAV, & display still operate.

Sorry we were not more clear about this in the manuals."